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Palestine - Gaza - Alzahra City- Tel :0097282843433
Volume 3: issue 1ISSN: 2523-0522October, 2019
2019
Dr. Addel Fattah A. Qaraman
General Supervisor
Editor in Chief
Dr. Ahmed Alhussaina
Proof Reader
Design and Output
Prof. Adnan Hajar
Abed El Hammed El Derawi
Bessaan Al Mudalal
Editorial Team
Prof. Hikmat Hilal, An - Najah University - Palestine
Prof. Ahmad Harb, Jordan-German University - Jordan
Prof. Netham Al - Ashqar, Islamic University - Palestine
Prof. Hazem Abu Shawish, Al - Aqsa University - Palestine
Prof. Helmi Salem, SDRI - Bethlehem - Palestine
Prof. Nahed El Laham, Al-Azhar University - Palestine
Prof. Hala Al-Khazindar, Islamic University - Palestine
Dr. Akram Abu Eisha, Harford University - USA
Dr. Bassam Tawabini, (KFUPM) - Saudi Arabia
Dr. Pedro A. Garcia, University of Granada - Spain
Dr. Jamil Abdul Ati, Saybrok University – California - USA
Dr. Mohammed Al - Nahal, Al - Israa University - Palestine
Dr. Maher Al - Bayoumi, Al - Israa University - Palestine
Dr. Tamer Madi, Al - Israa University - Palestine
Dr. Ezzat Al - Askari, Al - Israa University - Palestine
Dr. Fadel Abu Hain, Al - Aqsa University - Palestine
Dr. Atef Masad, Al - Israa University - Palestine
Dr. Tariq Al - Bashiti, Islamic University - Palestine
Dr. Nabil Al - Eilah, Al - Aqsa University - Palestine
Dr. Saeb Al Awaini, Islamic University - Palestine
Dr. Jihad Adwan, University of manchester -UK
Improving the Performance of Children with Autism through an Adaptive Learning System 1 9
Attitudes of Obese Women Toward Group Therapy as A method of Increasing Compliance with TherapeuticProgram in Gaza Strip, Palestine
2 32
Study the formation of the deposit resulting from the sulfate-reducing bacteria on the steel surface of oil pipeN80
3 51
Improving Solar Power System's Efficiency Using Artificial Neural Network 4 64
The Activity of HYPR surfactant as Superplasticizer on fresh and hardened properties of concrete 5 89
Improvement of Steam Power Plants Performance Using a Heat Exchanger 7 116
Synthesis of pure Zinc Oxid (Semiconductor) and ZnO:Ga Nanostructure for Different Sensing Applications 8 133
Metal Oxide (Quantum Dots) for Gas Sensor Application 9 146
Rotavirus Gastroenteritis among Children Under five years of age in Gaza, Palestine 6 102
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It is my pleasure to write the editorial of the current issue of Israa University journal of Applied Sciences (IUJAS). I would like to thank the university administration, Department of Scientific Research and all those who contributed to this issue to come to light; essentially the editorial board and arbitrators who helped in selection of the valuable papers.This issue contained nine scientific papers that dealing with This issue contained nine scientific papers that dealing with important research topics including public health, physics, and chemistry. The editorial board has a very important responsibility, to not only The editorial board has a very important responsibility, to not only perform the editorial tasks of the journal, determine the rules of publication and attention to the comprehensive review on time, but also to include a great responsibility towards the readers of IUJAS. Therefore, they always required working on improving the quality besides the future planning of the journal.Finally yet importantly, the journal looking forward reaching a Finally yet importantly, the journal looking forward reaching a higher level of appreciation, as the editorial board and the advisory board have a great responsibility to assist the editors as well as to the promoters of the journal by encouraging their colleagues to publish their eminent experience and scientific papers.
Dr. Addel Fattah A. Qaraman
9
Improving the Performance of Children with Autism through an
Adaptive Learning System
Khaled Ismail*
*Faculty of Computer Science and Information Technology, University of Malaya, Malaysia
ABSTRACT
Children with autism experience significant impairments in social, behavioural
and communication skills. These impairment levels varies between children and that made
teaching autistics a challenge. Hence, assistive technology offers an alternative way to
attract autistics to learning using representational visual illustration as a learning method
instead of textual forms. The development of the ALS for children with autism is visually
customisable to suite the individuals needs taking in considerations the simplicity of the
interface based on the child computer interaction principles. This paper presents the ALS
evaluation throughout observations and autism treatment evaluation assessment of
traditional learning methods compared to the proposed intervention learning methods. The
evaluation results reflect the effectiveness and efficiency of the proposed prototype for
children and caregivers at home or at schools to influence children to improve their skills
and enhance their performance in their daily life activities.
Keywords: Children with autism, intervention, adaptive learning, design, learning styles
& principles
10
1. Introduction
The term ‘Autism Spectrum Disorders’ (ASD) refers to a cluster of developmental disorders
that present from birth or very early in development (Esposito and Venuti 2009, Tsai 2012),
with usually life-long effects on essential human behaviours such as social interaction,
communication, imagination, and relationships with others (National Research Council
2001). ASD has been characterized as a spectrum of difficulties in these areas that vary in
combination and severity, between and within individuals (Charman 2002). ASD includes
various conditions such as autistic disorder, Asperger syndrome, pervasive developmental
disorder not otherwise specified (PDD-NOS) and Rett syndrome based on American
Psychiatric Association reports (American Psychiatric Association 1994) and international
classification disease (ICD-10) and World Health Organization (1992). According to the
DSM-IV-TR, autism is a severe disorder characterized by the presence of at least 6 out of 12
symptoms concerning communication, joint social interaction, behaviour, and activities that
are present from the age of three years (American Psychiatric Association 2000).
While it is controversial whether the popularity rates of ASD are actually growing (Baird et
al. 2006, Charman 2002) or, because of factors such as changes in diagnostic conditions and
increasing awareness and recognition (Wing and Potter 2002), it appears to be growing,
significant occurrence rates are reported by a number of studies. For example, the Australian
Advisory Board on Autism Spectrum Disorders reported an estimated popularity rate for
ASD across Australia, based on the Commonwealth government’s Centreline data, of 62.5
per 10,000 for 6 to 12-year-old children (Williams et al. 2008).
Similar popularity rates have been found in other studies; Charman (2002) reviewed three
recent prevalence studies and suggested an average frequency rate of 60 per 10,000 for
children under 10 years old. (Wing and Potter 2002)Reviewed 39 studies conducted
internationally and reported occurrence rates of 60 per 10,000 for autism and higher rates for
the broader spectrum. A prevalence rate of 62.5 per 10,000 indicates there is an average of
one child with ASD for every 160 children between 6 and 12 years (Williams et al. 2008).
Significantly, ASD is like other disabilities, has considerable social impact, especially on
family and education. (Williams et al. 2008)Points out that, with a popularity rate of 62.5 per
11
10,000, ASD affects families containing half a million Australians. The families of
individuals with ASD experience demands in a variety of family life contexts, including the
needs of parents, both as individuals and as a couple (National Research Council 2001), and
of siblings.
Children with autism spend less time engaged in social and non-social activities compared
to a typical developed children that resulting in reduced learning opportunities for them
(Kishida and Kemp 2006, McWilliam and Bailey Jr 1995, Ruble and McGrew 2007).
Promoting and supporting engagement is considered as an effective learning intervention for
children with autism (Corsello 2005, National Research Council 2001), although certain
behavioural, educational, and pharmacological interventions have been demonstrated to be
helpful for many individuals with autism, there is currently no cure for the disorder (White,
Keonig, and Scahill 2007). Learning and behavioural interventions methods widely used
such as: Treatment and Education of Autistic and related Communication handicapped
Children (TEACCH) method and Applied Behavioural Analysis (ABA) method, these
methods will be explained in section 2.4. And according to Ruble and McGrew (2007)
parents admitted that behavioural and educational mixed methods are an effective and
productive method as an intervention technique. Additionally, an early intervention can
provide long-term improvements to a child’s ability to integrate with society (Wetherby and
Woods 2006, Matson and Smith 2008).
Education is extremely important for children with autism, and research continues on
developing educational goals appropriate for them with the aim of promoting personal
independence and social responsibility (National Research Council 2001). Educational
interventions have been characterized by active engagement in intensive instructional
programs accompanied by ongoing measurements of progress toward educational objectives
(National Research Council 2001). However, educational intervention is also used to enhance
the treatment of the behaviour impairments found in children with autism specially when
applied early and intensively (Matson and Smith 2008). The behavioural interventions are:
Treatment and Education of Autistic and related Communication handicapped Children
(TEACCH) method and Applied Behavioural Analysis (ABA) method.
12
Investigation of the subjective experiences of children with autism has the potential to make
educational interventions more effective by treating them as independent entities. It allows
for a more in-depth mediation between learners’ inner world of personal experience and the
public world of social knowledge within which they function (Pring 2000).
The educational interventions were admitted by families as a more successful intervention
with better outcomes compared to medical interventions (Ruble and McGrew 2007).
Therefore, many research studies are directed towards the educational intervention in order
to curb the stereotypical behaviour of these population. In addition, education intervention is
affordable if compared to the medication interventions, due to the reusability of the
educational materials whether manual or systematic form by many children.
Many tools are existed to diagnose children with autism such as Childhood Autism Rating
Scale (CARS) (Schopler, Reichler, and Renner 1986), Autism Diagnostic Observation
Schedule (ADOS) (Lord et al. 2000), Autism Diagnostic Interview-Revised (ADI-R) (Lord
and Schopler 1994), Autism Behaviour Checklist (ABC) (Krug, Arick, and Almond 1980)
and Gilliam Autism Rating Scale (GARS) (Gilliam 1995). However, Autism Treatment
Evaluation Checklist (ATEC) assessment was developed to provide a free and easily
accessible method for caregivers to track the changes of ASD symptoms over time (Rimland
and Edelson 1999). Importantly, ATEC was not designed for diagnostic purposes; only to
measure changes in ASD severity, making it useful in tracking the efficacy of a treatment
over time. Various studies have sought to confirm the validity of ATEC (Al Backer 2016,
Geier, Kern, and Geier 2013, Jarusiewicz 2002).
ATEC consists of four subscales: (1) Speech/Language/Communication, (2) Sociability, (3)
Sensory/Cognitive Awareness, and (4) Health/Physical/Behaviour. These four subscales are
used to calculate a total score that ranges from 0 to 179. A lower score indicates less severe
symptoms of ASD and a higher score indicates more severe symptoms of ASD (Rimland and
Edelson 1999). The subscales provide survey takers information about specific areas of
behaviour which may change over time.
13
2. Assistive technology intervention
Technology-based educative methods are increasingly regarded as playing a key role in the educating
children with autism (Konstantinidis et al. 2009). Educational technology can be used either as a
constant assistive tool or used temporarily as a teaching aid (Goldsmith and LeBlanc 2004). The use
of technology in educational interventions for children with autism, such as computer-aided learning,
has been shown to benefit areas such as literacy skills (Tjus, Heimann, and Nelson 2001, Williams et
al. 2002), facial recognition abilities (Tanaka et al. 2010) and social skills (Mitchell, Parsons, and
Leonard 2007, Piper et al. 2006). Pennington (2010) also suggests that computer-aided instruction
could be beneficial in other academic areas such as mathematics and science. Children with autism
frequently need one-to-one adult instruction, but even when this is available there can still be issues
with learning due to “non-compliance, lack of motivation, behavioural difficulties and engagement
in stereotypical or ritualistic behaviours” (Williams et al. 2002). Technology offers an alternative
provision of one-to-one instruction, but also the potential to overcome some of these additional issues.
Previous research has shown that children with autism often exhibit a strong interest and enjoyment
interacting with technology as well as a high level of ability in using it (Higgins and Boone 1996,
Goodwin 2008, Putnam and Chong 2008). Researchers have cited a number of benefits that
technology specifically offers children with autism:
The level of the child’s social skills does not affect the interaction with the technology as it
does with the class teacher (Bölte et al. 2010) and is particularly suitable for certain “domain-
specific” learning (Williams et al. 2002).
Technology can be used to teach and reinforce specific skills in which children with autism
can exhibit difficulties. It could be possible to use technology for a whole range of skills but
previous research has mainly concentrated on communication and social skills (Parsons et al.
2000, Rajendran and Mitchell 2000, Grynszpan, Martin, and Nadel 2008), which are the skills
children with autism typically struggle with, and has been shown to have a positive effect on
learning.
The same software can be used at both school and home, allowing the child to practice any
areas they are struggling with outside of school in a learning environment they are used to
and helping to provide training in generalisation (Panyan 1984).
A computer screen offers a smaller area of focus than a classroom setting, which means the
child is less affected by the external environment and increases concentration on the task
(Williams et al. 2002).
14
Technology offers a safe environment in which the child can make errors and learn from
them without any fear of the consequences, giving the child more confidence to try unfamiliar
things (Goldsmith and LeBlanc 2004, Konstantinidis et al. 2009).
The material can be delivered in a visual way, which is a preferred way of learning for many
children with autism (Williams et al. 2002).
The software can be designed to provide as much additional one-to-one individualized
support as required, the level of which can be varied between children adapting to their
specific learning and other needs e.g. visual/hearing sensitivities (Higgins and Boone 1996,
Williams et al. 2002, Goodwin 2008). This can potentially reduce the amount of one-to-one
teaching time the child requires (Panyan 1984).
Technology can give the child more control over their learning, allowing them to work at
their own pace and also are often appealing to children with autism, potentially increasing
their engagement in the task (Bölte et al. 2010, Konstantinidis et al. 2009).
Children with autism do not like change and technology can provide consistency across tasks,
as well as being predictable and familiar (Bölte et al. 2010, Konstantinidis et al. 2009).
Learning through technology has been shown to increase motivation and improve behaviour
in children with autism (Williams et al. 2002, Goldsmith and LeBlanc 2004, Konstantinidis
et al. 2009).
Although the use of technology in the education of children with autism can be beneficial, it is also
important to keep in mind the potential issues that the use of technology could present, which include:
Reducing the interaction time in class and replacing it with interaction with the technology could
further isolate children with autism, reducing their opportunities for social interaction with the
teacher and other children (Higgins and Boone 1996).
Children with autism often have obsessive-compulsive behaviours and the technology could
become a focus of one of these, particularly if their special interest is related to technology in
some way (Williams et al. 2002).
It can be hard to tailor technology for each individual child effectively and adapt to their changing
needs. When designing technology for this specific group it is difficult to generalise, as what
works for one child may not always work for another due the vast differences between children
on the autistic spectrum (Constantin et al. 2017).
Children with autism find it hard to transfer skills they have learnt in one environment into
another, and they might struggle applying skills they have learnt through interaction with the
technology into a real world scenario (Wood et al. 2017).
15
Not all skills are best taught using technology, it should be used to teach or reinforce appropriate
skills and not seen as the answer to all problems experienced in the classroom-learning
environment (Smith, Cowie, and Blades 2015)
Overall the use of technology in educational interventions offers great potential for this population,
and despite the concerns of some researchers there is mounting evidence that computers can provide
a wide range of benefits to children with autism. It is however important that this technology is
employed in appropriate situations and used to complement other successful teaching methods, to
ensure the children still have exposure to social learning situations. This technology also needs to be
appropriately designed ideally taking into consideration current theories of autism and structured
approaches to learning as well as input from the ASD children population as the system informant
which is the source of information, ideas and materials.
It is important for technology designers to be aware of the vast individual differences within autistics
and the difficulty in achieving a universal technological solution to educating these individuals. It is
also very challenging for neuro-typical adult designers to understand the needs and preferences of
children with autism. Suitable customisation and personalization options and the involvement of this
user group in the design process offer two potential solutions to these issues and are discussed in the
following sections and the literature review chapter as well.
Figure 1: Adaptive learning model design.
16
3. Adaptive learning approach
Adaptive learning method as seen in Figure 1 took in considerations Kerns (2013) list of many
benefits using adaptive learning approach for children with autism such as: it can be personalized
which adapts to all learning capabilities, also to provide a real-time feedback to users. Moreover, the
adaptive learning approach tends to balance between the face-to-face instructions and the online
instructions. It does not mean adaptive learning meant to replace the educators, it just help to initiate
a self-paced guidance system and build up the independence aspect into the learners. Nonetheless, it
is a motivation factor in the learner’s life. Consequently, children can become more engaged with the
educational materials or the tasks assigned to them via the system in order to achieve it aiming to a
better scores and understanding.
Nonetheless, adaptive learning method as seen in Figure 1 attempts to transform the students from
passive receptor of knowledge and information to a collaborator in the educational activity. It also
provides valuable information and feedback to teachers and parents as one of its key features in order
to use it in a more constructive way.
4. Adaptive learning process
Learning process as Figure 2 shows, teacher or the parent starts the process by identifying
the learning objectives such as mathematics, facial expressions and emotion or any desired
subject to be taught to the learners, identifying the learning objectives shall make the learning
process a goal oriented rather than deviating away from the main objective for starting this
process with learners. The learning styles such as video presentations, transitional images,
humanoid animations or decorative styles which are determined by the teacher or the parent
to assist in achieving the learning process objective. Followed by the learning strategies as a
presentational guidelines to the educational materials.
Specifying the materials or the contents which are required to educate the children and
applying the learning methods such as the variability of the contents to assist children
cognitive skills and learning progress, repetition and reinforcement of the contents to enhance
the child's memory, motivation after an achievement which contributes in attracting children
to the contents and gives the feel of progressive achievement while learning, and the final
learning method is the visualisation which is the contents presentation taking in
considerations that the targeted users are autistics with low cognitive abilities as compared
17
to typical children. Therefore, a simplified visual illustrations of the learning materials and
contents are highly recommended.
Figure 2: Adaptive learning process.
Learning process is a task that has to be accepted by the targeted learners, they should be
self-determined and willing to go through this process. The teacher or parents should observe
the learners in order to build the learning environment which aims to empower learners and
motivate them in the initial stages so that they could understand the learning process and
tasks in order for them to use the system independently. Assessments and quizzes are given
to the children at the end of each learning session to evaluate their learning progress.
18
Figure 3: ALS welcome page.
Figure 3 is showing the ALS welcome page which navigate the user between tutorial or quiz
modules, whereby Figure 4 shows a listing of the available tutorials in the system.
Figure 4: List of available tutorials in ALS application.
Figure 5: Facial emotions tutorial.
19
A sample of facial emotions tutorial is shown in figure 5, the text “Sad” is written in in
decorative style and different samples express the emotion targeted to teach autistics.
After conducting a tutorial session, a quiz module shall start to assess the children with autism
learning process, Figure 6 shows a quiz module of the facial emotions.
Figure 6: Facial emotions quiz.
Participants
Ten participants, four girls and six boys were contributed to evaluate the ALS prototype,
these participants are diagnosed with mild autism who exhibit low attention level from PRF
autism centre the Islamic centre for children with special needs as well as “Autism Café”
Centre in Kuala Lumpur, Malaysia. Table 1 shows the participating children demographics,
the age range of the ten participants was between 4 and 13 years old. The communication
skills for the participants are verbal or non-verbal by pointing.
All the ten participating children are familiar with computers and smart devices such as IPad
and android devices. However they’re from observations like to touch and point to the
computer screen instead of using the mouse and keyboard.
The educational classes are following the TEACCH approach in delivering knowledge to the
children in the PRF autism centre. Another two members of staff and two parents were
contributed to the study and assist in the settings as well as the system evaluation.
20
Table 1. Participants children with autism demographics
No Gender Age
(Y)
Familiarity with
computer and
smart devices
Communication
skills Learning style Motivation
P1 Female 7 Familiar Non-verbal
Visual, Auditory
& Kinaesthetic
Variability
P2 Female 5 Familiar Verbal Variability
P3 Female 4 Familiar Non-verbal Variability
P4 Female 9 Familiar Non-verbal Variability
P5 Male 8 Familiar Verbal Variability
P6 Male 6 Familiar Verbal Variability
P7 Male 9 Familiar Verbal Variability
P8 Male 13 Familiar Verbal Variability
P9 Male 11 Familiar Verbal Variability
P10 Male 10 Familiar Verbal Variability
Settings
The class setting was teacher to child and the teaching time is shortened to small slots, each slot is
between 20 to 25 minutes to make sure the children do not feel bored or to avoid any anxiety in the
class so a refreshment break of 5 to 10 minutes are given between learning slots.
The class setting was set with three personal computers (clients) connected via a network to another
computer (server) which is installed with the ALS system as Figure 7 shows, The client computers
access the server computer via its IP address in order to launch the ALS system.
Figure 7: Class setting with three clients and server.
21
Procedures
The ten participants were observed during the traditional learning style (baseline) as well as
the ALS learning style within a total period of 9 weeks (2 sessions per week and 20 minutes
for each session) in two centres. The first 4 weeks were mainly to observe the children as
well as the teacher’s traditional methods used to educate the children, data collection in the
first centre PRF autism centre for six participants and from the second centre (Autism Café)
for four participants. The ATEC is used to evaluate the children’s progress scoring.
The following five weeks are maintained to train the teachers/parents on how to use the
system and feed the system with educational materials either in the autism centre or at home.
The ten participants had the chance to use the ALS system at home as well as at both centres
as part of their activities.
Observations methodology
During the first eight session of this study; the observer recorded nearly everything that
children and teachers do during each session using field notes as a precaution against any
loss of data, video recording as well as teacher’s interviews and feedback in order to evaluate
the effectiveness of the traditional approach. The children behaviours observation aims to
assist in skills analytics of the current state of the traditional rehabilitation approach so that
can derive a deep analysis of the phenomenon and are associated to children behaviour.
The teachers were asked to complete the ATEC assessment for all children aiming to monitor
the children progress in different subscales such as: verbal and none verbal communication,
social, cognitive and the behaviour subscales. Those subscales are the main components of
the ATEC assessment. Table 2 shows the ATEC assessment subscales and its measurements,
the lower the score, the better the functioning.
22
Table 2. ATEC subscales and measurements
ATEC subscales Measurement
Verbal communication subscale 0 - 28
Social subscale 0 - 36
Cognitive awareness subscale 0 - 34
Behaviour subscale 0 - 45
Total 0 - 143
5. Results and analysis
ATEC assessment baseline
Participated teachers and parents were asked to fill up the ATEC assessment on the last session of
this study in order to evaluate the overall children progress. The children ATEC assessments readings
were calculated and the total accumulated result is presented in Table 3 and figure 8 is the graphical
presentation of the subscales for each participant. And as mentioned earlier the lower the total is the
better the functioning and the progress.
Table 3. ATEC assessment subscales readings - baseline
No
Particip
ants
Ag
e (Y)
Speech/
Language/
Communication
Subscale
Sociability
Subscale
Sensory/
Cognitive
Awareness
Subscale
Health/ Behaviour
Subscale
To
tal
1 P1 7 71.43 63.89 64.71 62.22 65.03
2 P2 5 57.14 69.44 73.53 53.33 62.94
3 P3 4 78.57 63.89 55.88 62.22 64.34
4 P4 9 89.29 72.22 64.71 71.11 73.43
5 P5 8 71.43 69.44 61.76 64.44 66.43
6 P6 6 50 41.67 58.82 46.67 48.95
7 P7 9 42.86 52.78 73.53 73.33 62.24
8 P8 13 50 58.33 67.65 68.89 62.24
9 P9 11 53.57 69.44 55.88 44.44 55.24
10 P10 10 39.29 58.33 67.65 55.56 55.94
23
Figure 8: Participants ATEC assessment subscales percentage – baseline.
ATEC assessment intervention
ATEC assessment was filled up after the intervention sessions to document the teachers at centres
and parents at home feedback after their observations to the children performance. Table 4 shows the
detailed ATEC results for each subscale and figure 9 is the graphical presentation of the subscales for
each participant.
Table 4. ATEC assessment subscales readings – ıntervention
No Participants Age
(Y)
Speech/
Language/
Communication
Subscale
Sociability
Subscale
Sensory/
Cognitive
Awareness
Subscale
Health/
Physical/
Behaviour
Subscale
Total
1 P1 7 50 63.89 61.76 60 59.44
2 P2 5 57.14 69.44 73.53 53.33 62.94
3 P3 4 46.43 63.89 52.94 53.33 54.55
4 P4 9 64.29 69.44 64.71 68.89 67.13
5 P5 8 57.14 69.44 58.82 71.11 65.03
6 P6 6 50 41.67 58.82 46.67 48.95
7 P7 9 42.86 52.78 73.53 73.33 62.24
8 P8 13 39.29 55.56 61.76 68.89 58.04
9 P9 11 53.57 69.44 55.88 44.44 55.24
10 P10 10 39.29 41.67 50 55.56 47.55
24
Figure 9: Participants ATEC assessment subscales percentage – Intervention.
Table 5. Baseline and intervention ATEC assessment readings
No Participants Baseline Intervention
1 P1 65.03 59.44
2 P2 62.94 62.94
3 P3 64.34 54.55
4 P4 73.43 67.13
5 P5 66.43 65.03
6 P6 48.95 48.95
7 P7 62.24 62.24
8 P8 62.24 58.04
9 P9 55.24 55.24
10 P10 55.94 47.55
25
Figure 10: A scatter chart of baseline and intervention.
6. Discussion
Learning application has been one of the interventions used by different studies for correcting
some of the impairments in children with autism. There has been quite a number of
technology interventions or applications to teach different skills. These interventions have
been implemented with different techniques in making them useful for these children because
of their learning disabilities which as a result led to difficulty in processing information like
the typical children (Happé 1999). Moreover, the “Theory of Mind” plays a vital role in their
way of thinking (Baron-Cohen and Wheelwright 2004). They perceive messages differently
and understand them best in visual form.
This study proposed an adaptive content management learning system for children with
autism as a new intervention tool whereby the parents at home and teachers at school can
collaborate to customise the overall look and feel to suite the individuals. The ALS was
designed according to Wise (2014) list of characteristics to be followed when the targeted
environment is children with autism.
The evaluation is based on the intervention observations which aims to test the prototype use
compared to the traditional approaches, and how the ALS model can change the participants’
behaviours. Noticeable results presented in Table 5 and Figure 10 which occurred on P1, P3,
P4, P5, P8 and P10 which the post study ATEC score is less than the baseline ATEC score.
26
On the other hand, P2, P6, P7 and P9 did not show any improvement with no significant
ATEC score change between using ALS and the traditional methods. However, the majority
of participants which is six participants show a noticed improvement when using ALS.
Therefore, these results show a higher effectiveness and efficiency of learning children with
autism using ALS compared to traditional methods. Thus, the ALS system can be considered
as a new and effective method to positively affect children with autism performance.
7. Conclusion
This paper presented the development and evaluation of ALS system as a new intervention
tool for children with autism and it is evaluated throughout teachers and parents observations
and the ATEC assessment. The results of the participants scoring showed the betterment of
the ALS system intervention over the traditional approach in improving the children with
autism learning. Moreover, the majority of participants showed an improvement results when
using ALS. Therefore, the ALS model is effective in providing a better learning medium for
the children with autism compared to traditional method.
27
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23
Attitudes of Obese Women Toward Group Therapy as A method of Increasing
Compliance with Therapeutic Program in Gaza Strip, Palestine
Mahmoud A. Al-Shaikh Ali*
* Ibn-Al Nafees Center, Gaza – Palestine,
Email: [email protected]
Abstract
This study aimed to examine the attitudes of overweight and obese women toward a group
therapy in Gaza Strip, and to identify if they prefer group therapy and willing to continue
participation in group therapy. The sample of the study consisted of 1004 overweight and obese
women who are registered at Ibn El Nafees Center for weight reduction from July 2016 to June 2017.
The researcher used descriptive, cross-sectional design, and for data collection constructed self-
administered questionnaire was used and prepared by the researcher, and validity and reliability of
the questionnaire were tested by a pilot study on 50 participants. The results showed that about half
of the study participants were from age group 26 – 45 years, and mean age was 34.43 years, and
87.5% had BMI of ≥ 30. The results also indicated that obese women have positive attitudes towards
group therapy with weighted percentage of 84%. Furthermore, the vast majority of obese women
(93.1%) preferred group therapy and willing to continue participation in group therapy during their
therapeutic program. In addition, women aged 36 – 45 years preferred group therapy compared to
women from other age groups, and are willing to continue participation in group therapy, while
women aged 46 years and more had higher positive attitudes toward group therapy. Also, there were
no significant differences in preference of group therapy and willingness to continue in group
therapy related to marital status. Moreover, women who were working preferred group therapy,
willing to continue participating in group therapy, and had more positive attitudes toward group
therapy. The study concluded that group therapy could be an integrated approach in addition to
individualized treatment that may enhance compliance to therapeutic program for weight reduction
and control.
Key words: Attitudes; Group therapy; Obesity; Therapeutic program; Gaza.
22
1. Introduction
Obesity is a complex, multifactorial, and largely preventable health problem, affecting over a third
of the world’s population (Ng et al. 2014; Stevens et al. 2012). Most of the therapeutic programs are
designed on individual basis and focusing on dietary regimes and medical treatments, but the idea
of group therapy focusing on behavioral weight loss interventions for obese persons started to gain
attention from some therapists. According to Perri & Fuller (1995) behavioral weight loss
interventions are typically delivered in a group treatment format with 8 to 12 members per group.
This approach typically produces body weight reduction of 8 to 10 kg over the course of 16 to 24
weeks. In addition, group therapy produced significantly greater reduction in weight and body mass
compared to individual therapy (Renjilian et al., 2001).
The researcher assumes that engagement of obese individuals in group therapy is thought to be
effective, as the psychological aspect of the problem and exchange of experience between group
members would act as a motivating factor that will increase compliance with therapeutic program
and enhance weight reduction. To the best of the researcher's knowledge, very few studies had been
conducted globally to highlight the effectiveness of group therapy for weight reduction, and no
studies had been conducted locally in the Gaza Strip (GS).
1.1 Research problem
Obesity and the related health risks have been noted to be an epidemic problem worldwide,
especially in developing countries (Popkin, 2002; McLaren, 2007). Within the Eastern
Mediterranean Region, an increasing prevalence of overweight has been recorded and has been
noted to be at an alarming level (Al-Riyami and Afifi, 2003; Alsaif et al., 2002; Bahrami et al.,
2006). In Palestine, obesity is a growing prevalent public health problem with prevalence of
overweight at national level was 16.5% (13.3% overweight; 3.2% obese); of these, 20.4% were
males and 13.0% were females (Al Sabbah et al., 2009). The growing rate of obesity puts
challenges for weight reduction for the obese individuals and their therapist. The effect of peers and
matched groups who are sharing the same problem of obesity could be a factor in motivating each
other and learning from individual experiences to enhance compliance to group therapy and weight
reduction during the course of treatment. So, having positive attitudes toward group therapy will
23
increase level of compliance for the long-term management of overweight and obesity and motivate
the individual to maintain the ideal weight.
1.2 Aim of the study
The aim of this study is to identify the attitudes toward group therapy among obese women in Gaza Strip.
1.3 Objectives of the study
- To examine if obese women prefer group therapy during therapeutic program.
- To determine the willingness of obese women to continue participating in group therapy.
- To compare attitudes toward group therapy in relation to selected factors (age, marital status,
work status, body mass index).
2. Literature review
In psychology, an attitude is a psychological construct, it is a mental and emotional entity that
inheres in, or characterizes a person. It is an individual's predisposed state of mind regarding a value
and it is precipitated through a responsive expression toward a person, place, thing, or event - which
in turn influences the individual's thought and action (Perloff, 2016).
Group therapy is a form of psychotherapy that involves one or more therapists working with several
people at the same time. This type of therapy is widely available at a variety of locations including
private therapeutic practices, hospitals, mental health clinics, and community centers. Group
therapy is sometimes used alone, but it is also commonly integrated into a comprehensive treatment
plan that also includes individual therapy and medication (Cherry, 2017).
Group therapy as a psychological approach of treatment used in treatment of many disorders, and
some studies suggested the use of group therapy in treatment programs of obese people. Perri &
Fuller (1995) emphasized that behavioral weight loss interventions are typically delivered in a
group treatment format with 8 to 12 members per group, and this approach typically produces body
weight reduction of 8 to 10 kg over a course of 16 to 24 weeks. At one year, 73% of participants
either lost or maintained their weight (Limwattananon, 2007). In addition, Minniti et al. (2007)
found that after 6 months, individual therapy members had a higher dropout rate than group
23
therapy, and after 6 months of treatment, those who completed the program lost 6.39% of initial
weight.
3. Methods and materials
3.1 Study design
The study utilized descriptive, cross sectional design.
3.2 Study population
The study population consisted of all overweight and obese women who are registered at Ibn El
Nafees Center for counselling and weight reduction therapeutic program.
3.3 Study sample
The sample of the study consisted of all the overweight and obese women (BMI ≥ 25) who are
participating in group therapy during their visits to Ibn El Nafees Center. The total number who
agreed to participate in the study and filled the questionnaire was 1004 women. The study has been
conducted from November 2017 to September 2018.
3.4 Instrument of the study
The researcher used constructed, self-administered questionnaire (developed by the researcher). The
questionnaire measures the attitudes of study participants toward group therapy. The questionnaire
was divided into three parts:
- Personal information.
- Attitudes toward group therapy (18 items).
- Preference and willingness to continue participation in group therapy.
23
3.5 Pilot study
For the purpose of pre-testing of the questionnaire, the researcher conducted the pilot study on a
sample of 50 participants, selected randomly from the target group.
3.6 Content validity
For the purpose of judging content validity, the researcher distributed the questionnaire to a panel of
experts (3 experts) in this field for face and judged content validity. Their suggestions were
considered in modifying the questionnaire.
3.7 Reliability
The researcher used split-half method to calculate the correlation coefficient between the total
scores of odd statements and the total score of even statements, the correlation value was (r =
0.723). In addition, the researcher used Cronbache alpha method and alpha coefficient was 0.765.
3.8 Data collection
The researcher collected data using self-administered questionnaires. The participants were asked
their voluntary participation in the study, and those who agreed to participate filled the
questionnaire during their therapeutic sessions. The researcher gave explanations and instructions as
requested to ensure proper filling of the questionnaires.
3.9 Data entry and statistical analysis
The researcher entered the data of appropriate questionnaires using the Statistical Package for
Social Sciences (SPSS version 20) and the steps were as follows:
- Over viewing of the questionnaires, coding of questions, designing data entry model, defining
and coding variables, data cleaning.
- For piloting, split half method and alpha coefficient were used.
- Perform frequency calculations and mean score and cross tabulations for study variables.
23
- Perform (T) test and One way ANOVA to examine differences in variables in relation to
selected variables.
3.10 Ethical considerations
Before conducting the study, the researcher obtained consent form from the participants confirming
their agreement to participate in the study and explanatory form was attached to each questionnaire
included the purpose of the study, the right of participants to withdraw from the study and assurance
of confidentiality of given information.
4. Results
4.1 Sample characteristics
Table 1: Characteristics of study participants
Variable Frequency Percent
Age (years)
25 and less 241 24.0
26 – 35 332 33.1
36 – 45 268 26.7
46 and more 163 16.2
Total 1004 100.0
Mean age = 34.43 SD = 10.684 Median age = 33.0 years
Marital status
Single 229 22.8
Married 696 69.3
Divorced / widow 79 7.9
Total 1004 100.0
The study participants included 1004 obese women who are registered at Ibn Al Nafees center for
treatment and consultation during the period from September 2016 to May 2017. Their mean age
was 34.43 years, of them 24% aged 25 years and less, 33.1% aged between 26 – 35 years, 26.7%
aged between 36 – 45 years, and 16.2% aged 46 years and more. More than two-thirds (69.3%)
were married, 22.8% were single, and 7.9% were divorced or widows.
23
Figure (1): Distribution of study participants by work status
The majority of study participants (86.5%) were not working (house wife), and only 13.5% were
working.
Figure (2): Distribution of study participants by BMI
Concerning body weight, the vast majority (87.5%) were obese with BMI ≥ 30 and 12.5% were
overweight with BMI 25 – 29.9.
23
4.2 Attitudes toward group therapy
Table (2): Attitudes of study participants about group therapy
N
o. Item
Dis
ag
ree
Neu
tra
l
Ag
ree
Mea
n
SD
%
1 Group therapy motivate me to follow the
dietary program better 4.1 6.0 89.9 2.86 0.451
9
5
.
3
3
2
My body weight decreased faster in
group therapy compared to individual
therapy
3.8 28.2 68.0 2.64 0.553
8
8
.
0
3 Group therapy did not help me reach my
ideal weight 77.7 19.0 3.3 1.26 0.506
4
2
.
0
4 Group therapy enhanced my ability to
continue the dietary program 3.1 7.2 89.7 2.87 0.421
9
5
.
6
6
5
Success stories in group therapy
increased my willingness to continue
dietary program
1.7 3.4 94.9 2.93 0.312
9
7
.
6
6
6 Group therapy offer psychological
support to me 2.7 11.3 86.1 2.83 0.439
9
4
.
3
3
34
7
I feel embarrassed of being within a
group of women during treatment
sessions
80.3 13.4 6.3 1.26 0.564
4
2
.
0
8 I feel embarrassed from my body shape
compared to other women in the group 74.2 17.2 8.6 1.34 0.630
4
4
.
6
6
9 I'm satisfied from the weight I lost
during group therapy 9.0 20.6 70.4 2.61 0.645
8
7
.
0
10 Being in a group therapy give me a
feeling of psychological ease 4.3 16.1 79.6 2.75 0.521
9
1
.
6
6
11 Group therapy decreased psychological
stress of being obese 3.5 15.7 80.8 2.77 0.495
9
2
.
3
3
12 Group therapy give me feeling of self-
esteem 3.0 19.2 77.8 2.75 0.498
9
1
.
6
6
13 Group therapy is a chance to know other
women 4.3 9.3 86.5 2.82 0.482
9
4
.
0
14 Group therapy is a chance to make new
friends 7.3 18.9 73.8 2.67 0.607
8
9
.
0
34
15 Group therapy is a chance to benefit
from others' experiences 1.9 3.8 94.3 2.92 0.329
9
7
.
3
3
16
Group therapy is a chance to talk with
other women about my own experience
with obesity and treatment
6.3 12.8 80.9 2.75 0.562
9
1
.
6
6
17 I gained new experiences during group
therapy 2.1 7.8 90.1 2.88 0.384
9
6
.
0
18
I feel lazy and unwilling to follow
dietary program when being a way from
group therapy
21.5 19.1 59.4 2.38 0.816
7
9
.
3
3
Overall mean 2.52 0.235
8
4
.
0
Table (2) showed that the overall mean score obtained from participants' response on the scale was
2.52 and weighted percentage was 84.0 which reflected that women have positive attitudes towards
group therapy at Ibn El Nafees center. The highest score was in the item "Success stories in group
therapy increased my willingness to continue dietary program" with mean score 2.93 and weighted
percentage 97.66, followed by "Group therapy is a chance to benefit from others' experiences" with
mean score 2.92 and weighted percentage 97.33, and "I gained new experiences during group
therapy" with mean score 2.88 and weighted percentage 96.0, while the lowest scores were in item
"Group therapy did not help me reach my ideal weight" with mean score 1.26 and weighted
percentage 42.0, and "I feel embarrassed of being within a group of women during treatment
sessions" with mean score 1.26 and weighted percentage 42.0, "I feel embarrassed from my body
33
shape compared to other women in the group" with mean score 1.34 and weighted percentage
44.66.
4.3 Willingness to participate in group therapy
0.00%
10.00%
20.00%
30.00%
40.00%
50.00%
60.00%
70.00%
80.00%
90.00%
100.00%
Prefer group therapy Willing to continue ingroup therapy
93.10% 93.10%
6.90% 6.90%
Yes
No
Figure (3): Prefer and willing to continue participate in group therapy
Figure (3) showed that the vast majority (93.1%) of women preferred group therapy and willing to
continue participation in group therapy during their visits to Ibn El Nafees Center. This result
revealed that group therapy was effective in enhancing weight reduction among obese women, and
that was strong motivation to continue participation in group therapy.
32
4.4 Attitudes toward group therapy related to selected variables
Table (3): Attitudes toward group therapy related to age
Variable Sum of
squares df
Mean
square F P
Preferred
group
therapy
Between Groups 0.949 3 0.316
4.99
7
0.002
*
Within Groups 63.309 100
0 0.063
Total 64.258 100
3
Will
continue
group
therapy
Between Groups 1.067 3 0.356
5.62
8
0.001
*
Within Groups 63.191 100
0 0.063
Total 64.258 100
3
Attitudes
toward
group
therapy
Between Groups 359.915 3 119.972
6.81
5
0.000
*
Within Groups 17604.0
4
100
0 17.604
Total 17963.9
6
100
3
*= significant at 0.05
Table (3) showed that there were statistically significant differences in preference of group therapy
(P= 0.002), willingness to continue in group therapy (P= 0.001), and attitudes toward group therapy
(P= 0.000) related to age of women. To identify these differences, the researcher used Post hoc
Scheffe test which indicated that women aged 36 – 45 years highly preferred group therapy
compared to women from other age groups (P= 0.026), and are more willing to continue
participation in group therapy (P= 0.017), while women aged 46 years and more had higher positive
attitudes toward group therapy compared to other age groups (P= 0.003).
33
Table (4): Attitudes toward group therapy related to marital status
Variable Sum of
squares df
Mean
square F P
Preferred
group
therapy
Between Groups 0.207 2 0.104
1.61
9
0.199
//
Within Groups 64.051 100
1 0.064
Total 64.258 100
3
Will
continue
group
therapy
Between Groups 0.207 2 0.104
1.61
9
0.199
//
Within Groups 64.051 100
1 0.064
Total 64.258 100
3
Attitudes
toward
group
therapy
Between Groups 225.156 2 112.578
6.35
3
0.002
*
Within Groups 17738.8
0
100
1 17.721
Total 17963.9
6
100
3
*= significant at 0.05 //= not significant
Table (4) showed that there were statistically no significant differences in preference of group
therapy (P= 0.199) and willingness to continue in group therapy (P= 0.199) related to marital status,
but significant differences existed in attitudes toward group therapy (P= 0.002). To determine these
differences, the researcher used Post hoc Scheffe test which indicated that single women had lower
attitudes toward group therapy compared to married women (P= 0.005) and widowed or divorced
women (P= 0.022).
33
Table (5): Attitudes toward group therapy related to working status
Variable Category N Mean SD T value P
value
Preferred
group therapy
Working 136 1.15 0.363
4.283 0.000
* Not
working 868 1.06 0.229
Will continue
group therapy
Working 136 1.16 0.370
4.658 0.000
* Not
working 868 1.05 0.226
Attitudes
toward group
therapy
Working 136 45.525 5.053
4.342 0.000
* Not
working 868 43.845 4.044
* = significant at 0.05
Table (5) showed that there were statistically significant differences in preference of group therapy
(P= 0.000), willingness to continue in group therapy (P= 0.000), and attitudes toward group therapy
(P= 0.000) related to work status of women. Women who were working preferred group therapy,
willing to continue participating in group therapy, and had more positive attitudes toward group
therapy compared to women who were not working.
Table (6): Attitudes toward group therapy related to BMI
Variable Category N Mean SD T value P
value
Preferred
group therapy
Overweight 126 1.08 0.271 0.504 0.614
Obese 878 1.07 0.251
Will continue
group therapy
Overweight 126 1.08 0.271 0.504 0.614
Obese 878 1.07 0.251
Attitudes
toward group
therapy
Overweight 126 44.809 4.390
1.386 0.166 Obese 878 45.367 4.206
33
Table (6) showed that there were statistically no significant differences in preference of group
therapy (P= 0.614) and willingness to continue in group therapy (P= 0.614) and attitudes toward
group therapy (P= 0.166) related to marital status.
5. Discussion
Obesity and its associated health problems is a worldwide public health problem especially in the
developing countries. This study aimed to examine the attitudes of overweight and obese women
toward group therapy, and to determine if these women prefer group therapy and willing to continue
participation in group therapy during the course of therapeutic program. The sample of the study
consisted of 1004 women from different ages (mean age was 34.43 years), and about half of them
aged between 26 – 45 years old. More than two thirds were married, the majority (86.5%) were not
working, and 87.5% were obese with BMI ≥ 30.
The results indicated that obese women have positive attitudes towards group therapy at Ibn El
Nafees Center with weighted percentage 84%. The results reflected that group therapy revealed
success stories which were motivators to continue therapeutic program, adding to that, group
members share and exchange their experiences, and learn from others' experiences.
Furthermore, the results indicated that the vast majority of obese women preferred group therapy
and willing to continue participation in group therapy during their therapeutic program at Ibn El
Nafees Center. Regarding preference and willingness to continue participation in group therapy, the
results showed that women aged 36 – 45 years preferred group therapy compared to women from
other age groups, and are willing to continue participation in group therapy, while women aged 46
years and more had higher positive attitudes toward group therapy compared to other age groups.
Also, there were no significant differences in preference of group therapy and willingness to
continue in group therapy related to marital status, while single women had lower attitudes toward
group therapy compared to married and widowed or divorced women. Moreover, the results
indicated that women who were working preferred group therapy, willing to continue participating
in group therapy, and had more positive attitudes toward group therapy. Also, overweight and obese
women had similar preferences and attitudes toward group therapy.
33
Comparing our results with other studies reflected similar results. A study included 132 overweight
and obese women with a mean age of 38.4 years and BMI of 28.9 kg/m2 were randomly assigned to
receive either group behavior therapy or individual behavior therapy showed that mean percentage
weight loss at month 6 of group behavior therapy was comparable to individual behavior therapy
5.9% versus 5.4%; P = 0.027. Other outcomes were attitude, subjective norm, and perceived
behavioral control improved slightly; whereas, intention, healthy dieting behavior, and dietary
intake improved significantly after interventions. At one year, 73% of participants either lost or
maintained their weight. Anthropometric outcomes and healthy dieting behavior were significantly
better than baseline. The study concluded that group behavior therapy was not inferior to individual
behavior therapy, and it should be used as the first line mode of behavior therapy for weight control
management (Limwattananon, 2007). Furthermore, Perri & Fuller (1995) reported that behavioral
weight loss interventions are typically delivered in a group treatment format with 8 to 12 members
per group, and this approach typically produces body weight reduction of 8 to 10 kg over a course
of 16 to 24 weeks.
Another study aimed to compare outcome and dropout rates of an individual nutritional counseling
and a cognitive behavioral group therapy. The study included 129 women aged 18–65 years, with
BMI 25 kg/m2 and more. The study results indicated that after 6 months, 37.2% of subjects
abandoned the treatment program, and those who completed the program were older and had a
worse body uneasiness symptoms. Individual therapy members had a higher dropout rate than group
therapy. After 6 months of treatment, those who completed the program lost 6.39% of initial weight
and obtained improvements in all studied variables. The study concluded that dropout rate of
individual therapy was higher than that of group therapy, suggesting that some characteristics of
group therapy can contribute to the reduction of attrition (Minniti et al., 2007). In addition, a post-
treatment group therapy showed greater reduction in weight and body mass compared to individual
therapy (Renjilian et al., 2001).
33
6. Recommendations
In the light of study results, the researcher recommends the following:
- Integrate group therapy as a complementary model with individual therapy for weight
reduction among obese people.
- Highlight the advantages of group therapy in increasing the clients' compliance to therapeutic
program and reduce the rate of drop out from weight reduction programs.
- Train the therapists on skills of carrying out group therapy sessions to achieve maximum
benefits to their customers.
33
References
1. Al-Riyami, A.A. & Afifi, M.M. “Prevalence and correlates of obesity and central obesity
among Omani adults”. Saudi Medical Journal 246 (2003): 641-646.
2. Alsaif, M.A., Hakim, I.A., Harris, R.B. “Prevalence and risk factors of obesity and overweight
in adult Saudi population”. Nutrition Research, 22, no.11 (2002): 1243-1252.
3. Al Sabbah, H., Vereecken, C., Abdeen, Z., Coats, E. & Maes, L. “Associations of overweight
and of weight dissatisfaction among Palestinian adolescents: Findings from the national study of
Palestinian schoolchildren (HBSC-WBG2004)”. Journal of Human Nutrition and Dietetics 22, no.
1 (2009): 40-49.
4. Bahrami, H., Sadatsafavi, M., Pourshams, A. et al. “Obesity and hypertension in an Iranian
cohort study; Iranian women experience higher rates of obesity and hypertension than American
women”. BMC Public Health 6, no. 158 (2006).
5. Cherry, k. “What is group therapy and how does it work”? (2017) (https://www.verywell.com).
Retrieved 29.6.2017.
6. Limwattananon, C. “Group behavior therapy versus individual behavior therapy for healthy
dieting and weight control management in overweight and obese women living in rural
community”. Obesity Research & Clinical practice 1, no. 4 (2007): 223-232.
7. McLaren, L. Socioeconomic status and obesity”. Epidemiologic Reviews 29, no. 1 (2007): 29-
48.
8. Minniti, A., Bissoli, L., Di Francesco, V., et al. “Individual versus group therapy for obesity:
Comparison of dropout rate and treatment outcome”. Eating and Weight Disorders - Studies on
Anorexia, Bulimia and Obesity 12, no. 4 (2007): 161-167.
9. Ng, M., Fleming, T., Robinson, M., Thomson, B., et al. “Global, regional, and national
prevalence of overweight and obesity in children and adults during 1980–2013: a systematic
analysis”. Lancet 384, no. 9945 (2014): 766-781.
10. Perloff, R.M. “The Dynamics of Persuasion: Communication and Attitudes in the Twenty-First
Century. 4th edition, Rutledge, 2016.
11. Perri, M.G. & Fuller, P.R. “Success and failure in the treatment of obesity: Where do we go
from here”? Medicine, Exercise, Nutrition & Health 4 (1995): 255-272.
34
12. Peters, R.M. & Templin, T.N. “Theory of planned behavior, self-care motivation, and blood
pressure self-care”. Res Theory Nurs Pract 24, no. 3 (2010): 172-186.
13. Popkin, B.M. “The shift in stages of the nutrition transition in the developing world differs
from past experiences”. Public Health Nutrition 5, no. 1 (2002): 205-214.
14. Renjilian, D., Perri, M., Nezu, A., McKelvey, W., Shermer, R., Anton, S. “Individual versus
group therapy for obesity: effects of matching participants to their treatment preferences”. Journal
of Consulting and Clinical Psychology 69, no.4 (2001): 717-721.
15. Stevens, GA., Singh, GM., Lu, Y., Danaei, G., et al. “National, regional, and global trends in
adult overweight and obesity prevalence”. Popul Health Metr 10 no. 1 (2012):22.
51
Study the formation of the deposit resulting from the sulfate-reducing
bacteria on the steel surface of oil pipe N80
Dekhili Nouerlhouda*
*Department of mechanics, University of Biskra, Algeria.
E-mail: [email protected]
ABSTRACT
This article examines the components of formed deposits on the surface of the petroleum
pipes by Sulfate-Reducing Bacteria in the region of Hassi Messaoud (south of Algeria). These
bacteria were found in the wells of water and oil. However, we find the problem of bacterial
corrosion in the circuits of production and injection when petroleum is extracted. This
bacterial corrosion occurs when petroleum which contains water touched the pipes for well
long enough to be able to start corrosion. This problem results to the formation of deposits on
the inner surface of pipes which lead to the risk of clogging. In this work, we study the deposit
resulting from bacterial corrosion on the surface of N80 steel samples and we have identified
the most important components of the deposits resulting from the phenomenon of bacterial
corrosion.
Keywords: Corrosion, Bacterial Corrosion, Sulfate-Reducing Bacteria (SRB), Steel N80.
52
1. Introduction
The oil industry is an important driving force of the Algerian economy. But there are a number
of problems, in particular bacterial corrosion. The Corrosion can be defined as a phenomenon of
degradation of materials whose annual cost represents between 3 and 5% of GNP (Gross National
Product) of an industrialized country (Marconnet et al., 2005 ; Maluckov & Biljana, 2012).
Whereas, bacterial corrosion brings together all the phenomena of corrosion or the bacteria act
directly, or through their metabolism, creating the favorable conditions for its establishment
(Chantereau & Bouffard, 1977 ; Videla & Herrera, 2005). That's why we'll talk about the main
bacterial types associated with this deterioration which are Sulphate-Reducing Bacteria or SRB.
They are anaerobes capable of synthesizing and accumulating large quantities of sulphates in
their natural habitat. Indeed, in a low oxygen environment and contains sulphate, SRB contribute
to the mineralization of the organic material by reduction of sulphate (Videla & Herrera, 2005;
Enning & Garrelfs, 2014). Microorganisms can be considered as formidable catalysts of a
phenomenon of electrochemical nature (corrosion). Among these microorganisms, bacteria are
feared for their extraordinary enzymatic potential that allows them to grow in very complex
environments and to adhere to various surfaces, including metallic materials 8 (Santegoeds et al.,
1998; Busscher et al., 2006).
The purpose of this paper was to study the deposit resulting from bacterial corrosion on the
surface of N80 steel samples and determine the elements contribute in the formation of this
deposit. In this work, we have prepared a culture environment adapted for living bacteria. First,
we place the N80 steel samples in this environment. Then, we added a natural water extracted
with petroleum which contains sulphate-reducing bacteria, then placed all the samples in the
incubator at temperature of 37 °C for a different time period (30, 60 and 90 days) for observe the
clearly formed deposits and to determine the most important components of the deposits.
This paper contains new results concerning the role of bacteria in corrosion by the formation of
Sulfur (S) which forms the FeS (Ferrous Sulfide or Iron Sulfide) deposits that cause blockage of
oil pipes using in the region of Hassi Messaoud (southern Algeria). The rest of this paper is
organized as follows: next section provides the needed materials and methods. However, last
section presents our results with discussions, and we conclude the paper by the conclusion.
53
2. Experimental materiel and techniques
This study was conducted on samples of oil pipe that carry crude oil during the extraction (steel
N 80) that having a high resistance to the pressure. Also, it can be used during the process of
drilling of oil wells and can withstand the wall of a well after the completion of the latter, in order
to ensure a normal operation in all the wells. The surface of the samples is rectifies, degreases
and dried, whose chemical composition (%) represent in the Table 1.
Table 1. The chemical composition of the base metal (weight %)
Componen Weight (%)
C (Carbon) 0.24
Si (Silicon) 0.22
Mn (Manganese) 1.19
P (Phosphorus) 0.013
S (Sulfur) 0.004
Cr (Chromium) 0.036
Mo (Molybdenum) 0.021
Ni (Nickel) 0.028
Nb (Niobium) 0.006
V (Vanadium) 0.017
Ti (Titanium) 0.011
Cu (Copper) 0.019
On the other hand, Table 2 represents a description about the situation of each sample of our
experimentations.
Table 2. Description of the samples
Sample number Description of situation
Sample 1 A steel N80 in a contaminated environment by
SRB after 30 days at 37°C.
Sample 2 A steel N80 in a contaminated environment by
SRB after 60 days at 37°C
Sample 3 A steel N80 in a contaminated environment by
SRB after 90 days at 37°C.
While, Table 3 gives the different amounts of chemical composition of the culture environment
of bacteria.
54
Table 3. The chemical composition of the culture environment of bacteria
The components The quantity
Magnesium Sulfate MgSO4, 7H2O 1.0g
Ammonium sulphate (NH4)2SO4 1.0g
Sodium citrate trisodium Na3C6H5O7, 2H2O 1.0g
DI-potassium Hydrogenophosphate K2HPO4 1.0g
Ascorbic acid 0.2g
Yeast extract 0.2g
Agar-agar 0.1g
Sodium Lactate 4.0ml
Distilled water for the manufacture of medium 1L
After the preparation of the culture environment, we measured the pH of the environment. Then,
we have filled 9 ml of environment prepared in vials penicillin’s, in order to add our metal
samples defatted prior to acetone in these vials. We have plugged the vials to using capsules of
rubber, capsuling then were blocked by the aluminum. After that, we have purged the vials with
nitrogen to create the anaerobic environment and sterilize by autoclaving under wet pressure at
120°C for 50 minutes. Then, using a syringe, we collected 1 ml of water contains bacteria, and
we eliminated the trapped air bubbles possibly in the syringe. Subsequently, we injected the
contents of the latter through the capsule in the rubber stopper of the vial containing 9 ml of
culture environment. Finally, we have labeled the vials. They have incubated in the incubator at
37°C for 30, 60 and 90 days.
55
3. Results and discussion
The pH measurements
The pH measurements of environment samples before and after incubation were calculated. It is
described in Table 4.
Table 4. pH in the environment of the samples
Environment pH (before incubation) pH (after incubation)
Environment of sample 1 7.10 8.54
Environment of sample 2 7.10 8.88
Environment of sample 3 7.10 9.01
The table 4 shows that pH of environments increases as incubation time increases, this
environment is suitable for the multiplication of bacteria and the formation a biofilm (the biofilms
have complex structures consisting of cells and clusters of bacteria, randomly distributed). This
biofilm develops or can develop under extreme conditions of: temperature (12° C to 115° C), pH
(0 to 13) and hydrostatic pressure (Normand, 2004).
Analysis of the surface of the samples by scanning electronic microscope (SEM)
The determination of the morphology of deposit that formed on the surface of the steel N80 has
been carried out by scanning electron microscopy (see Figure 1). We have achieved for each
sample an image with expansions of (500X).
Figure 1. The image of the surface of the sample 1 by SEM at 37 ° C for 30 days of incubation
The formation of the deposit in the form of colonies on the surface of the sample was noted as
specified in red in the image.
56
Figure 2. The image of the surface of the sample 2 by SEM at 37 ° C for 60 days of incubation
We observe an increase in the formation of the deposit in the form of colonies on the surface of
the sample as specified in red in the image.
Figure 3. The image of the surface of the sample 3 by SEM at 37 ° C for 90 days of incubation
For sample 3, we observe that the deposit is formed densely in the form of colonies on the surface
of the sample as indicated in red in the picture.
Clearly, the images (Figures 1, 2 and 3) of the surface samples show the existence of a stable
adherent deposit in the form of colonies. Where, the amount of deposits on the sample surface is
greatering whenever the incubation period for samples is longer. These samples contain active
bacteria owing to deposits formed on the surface of samples in colonies.
To justify the presence of the deposit, we give the theory of cathodic depolarization (or VWK
theory). The basis of this theory was originally formulated in 1934 by Von Wolzogen Kühr and
Van Der Vlugt (De Beer et al., 1994). It postulates the microbiological consumption of hydrogen
from the cathodic reaction by the following mechanism:
57
Ionisation of water:
𝟖 𝑯𝟐𝑶 ↔ 𝟖 𝑯∓ + 𝟖𝑶𝑯−
Equation 1
Anodic corrosion of iron:
𝟒𝑭𝒆 ↔ 𝟒𝑭𝒆𝟐+ + 𝟖𝒆−
Equation 2
The formation of hydrogen at the cathode:
𝟖𝑯+ + 𝟖𝒆− ↔ 𝟖𝑯°
Equation 3
The absorption of hydrogen by bacteria:
𝑺𝑶𝟒𝟐− + 𝟖𝑯°
𝐇𝐲𝐝𝐫𝐨𝐠𝐞𝐧𝐚𝐬𝐞→ 𝑺𝟐− + 𝟒𝑯𝟐𝐎
Equation 4
Anodic secondary reactions:
𝑭𝒆𝟐+ + 𝑺𝟐− → 𝐅𝐞𝐒
Equation 5
𝟑𝑭𝒆𝟐+ + 𝟔𝐎𝑯− → 𝟑𝐅𝐞(𝑶𝑯)𝟐
Equation 6
Global reaction:
𝟒𝑭𝒆 + 𝑺𝑶𝟒𝟐− + 𝟒𝑯𝟐𝐎
↔ 𝑭𝒆𝑺 + 𝟑𝐅𝐞(𝑶𝑯)𝟐 + 𝟐𝑶𝑯
−
Equation 7
58
Analysis of the surface of the samples by EDX
In order to know the chemical compositions of the layer are formed on the surface of the samples,
we observed the samples by EDX (Energy Dispersive X-ray spectrometry). The maps were
carried out for each sample to obtain a distribution of chemical elements with an allocation of
color for each element detected (see Figure 4 to 6). Whenever the color is shiny, it means that
the element is abundant; and in the case of the matte color, it means that the element exists in
the form of traces.
Figure 4. Mapping-chemistry of the surface of the sample 1 after 30 days of incubation at 37°C
We observe in figure (4) that the elements existed in the deposition layer are: Oxygen (O), Iron
(Fe), Carbon (C), Manganese (Mn), Magnesium (Mg), Phosphorus (P) and Sulfur (S).
59
Figure 5. Mapping-chemistry of the surface of the sample 2 after 60 days of incubation at 37°C
We observe in Figure (5) that the elements existed in the deposition layer are: Oxygen (O), Iron
(Fe), Carbon (C), Magnesium (Mg), Phosphorus (P) and Sulfur (S).
Figure 6. Mapping-chemistry of the surface of the sample 3 after 90 days of incubation at 37°C
60
We observe in figure (6) that the elements existed in the deposition layer are: Oxygen (O), Iron
(Fe), Sulfur (S), Magnesium (Mg), Phosphorus (P) and Carbon (C).
Through the results obtained by Mapping-Chemistry of our samples, we observe that the most
important elements existed in the deposit layer are: Oxygen that appeared water ionization, Iron
that appeared from iron oxidation, and the Sulfur that appeared from the conversion of
Magnesium Sulfate and Ammonium Sulphate.
Effectively, SRB use as electron acceptors compounds derived from the oxidation of
Sulfur such as: Sulphate (SO4-2), Sulphites (SO3
-2), Thiosulfates (S2O4-2), and elemental Sulfur
(S°). These compounds are reduced entirely to Sulfide (Marty et al., 1989). The basic metabolic
reaction of these bacteria is the reaction of the Sulfate ion. More precisely, the Sulphate is
produced entirely to Sulphide as follows (DEGRÉMONT, 1989):
𝐒𝑶𝟒−𝟐 + 𝟖𝑯+ → 𝑺− + 𝟒𝑯𝟐𝑶
Equation 8
In this reaction, Hydrogen is provided by organic materials such as alcohol, proteins, starch and
hydrocarbons. The overall reaction is as follows:
𝟒𝐅𝐞 + 𝑯𝟐𝑶+ 𝐒𝑶𝟒−𝟐 → 𝐅𝐞𝐒 + 𝟑𝐅𝐞 + (𝑶𝑯)𝟐 + 𝟐𝑶𝑯
−
Equation 9
Subsequently, the sulphide ions will react at the level of the anode with ferrous ions and iron ions
are formed [15].
𝑺− + 𝑭𝒆++ → 𝐅𝐞𝐒
Equation 10
However, other ferrous ions combine with the hydroxide ions to give the iron hydroxide:
𝑭𝒆++ + 𝟐𝑶𝑯− → 𝐅𝐞(𝑶𝑯)𝟐 and 𝟑𝑭𝒆++ + 𝟔𝑶𝑯− → 𝟑𝐅𝐞𝑶𝑯𝟐
Equation 12
61
Hence, the deposit formed on the surface of samples contains the iron oxide and iron Sulphide.
4. Conclusion
The present work is a contribution to understanding the phenomenon of bacterial corrosion by
knowing the chemical constituents of deposits formed on the surface of the N80 steel. For
confirmed the activation of bacterium, we measure the pH of environment and we study the
deposit on the surface of the sample using the SEM and the EDX machines. We concluded the
following results: The longer incubation period gives us a high pH. We found that deposit wide
stable in the form of colonies on the surface. The most important chemical components involved
in the composition of the deposits formed at the surface of the samples are the Oxygen, Sulfur,
and Iron, low concentration for Magnesium, Carbon, and Potassium. Through these results which
we obtained from studying the phenomenon of bacterial corrosion on steel N80 for oil pipes, we
found that the bacterial corrosion is divided into two main phases; oxidation of iron in the water,
and role of bacteria in the dismantling of the sulfate to sulfur. In the two phases, we find bacterial
corrosion resulting in the iron oxide (Fe(OH)2) and iron Sulphide (FeS) that we see in the form
of deposits on the surface of the samples.
As future work, we plan to develop solutions to eliminate the problem of bacterial
corrosion by extraction of organic biocides from plants and herbs widely available in
Algeria and used as a solution for the eradication of this propblem.
62
References
1. Busscher, H. J., & van der Mei, H. C. (2006). Microbial adhesion in flow displacement systems.
Clinical microbiology reviews, 19(1), 127-141.
2. Chantereau, J., & Bouffard, A. M. (1977). Corrosion bactérienne-bactéries de la corrosion (pp.
262-262).
3. Davey, M. E., & O'toole, G. A. (2000). Microbial biofilms: from ecology to molecular genetics.
Microbiol. Mol. Biol. Rev., 64(4), 847-867.
4. De Beer, D., Stoodley, P., Roe, F., & Lewandowski, Z. (1994). Effects of biofilm structures on
oxygen distribution and mass transport. Biotechnology and bioengineering, 43(11), 1131-1138.
5. DEGRÉMONT, S. (1989). Mémento technique de l’eau, édition du cinquantenaire, 9 e édition.
LAVOISIER (Éditeur), Paris, France, tomes, 1.
6. Enning, D., & Garrelfs, J. (2014). Corrosion of iron by sulfate-reducing bacteria: new views of
an old problem. Appl. Environ. Microbiol., 80(4), 1226-1236.
7. Karr, E. A., Sattley, W. M., Jung, D. O., Madigan, M. T., & Achenbach, L. A. (2003).
Remarkable diversity of phototrophic purple bacteria in a permanently frozen Antarctic
lake. Appl. Environ. Microbiol., 69(8), 4910-4914.
8. King, R. A., & Miller, J. D. A. (1971). Corrosion by the sulphate-reducing bacteria. Nature,
233(5320), 491-492.
9. Maluckov, Biljana S. (2012) "Corrosion of steels induced by microorganisms. " Metallurgical
and Materials Engineering 18, no. 3: 223-232.
10. Marconnet, C., Dagbert, C., Roy, M., & Féron, D. (2005). Comportement d’aciers inoxydables
en eaux naturelles. Matériaux & Techniques, 93, s-83.
11. Marty, D., Bertrand, J. C., & Caumette, P. (1989). Les métabolismes bactériens dans les
systèmes sédimentaires marins. Microorganismes dans les écosystèmes océaniques. Masson,
Paris, France, 101-151.
12. Normand, B. (2004). Prévention et lutte contre la corrosion: Une approche scientifique et
technique. PPUR presses polytechniques.
13. Santegoeds, C. M., Ferdelman, T. G., Muyzer, G., & de Beer, D. (1998). Structural and
functional dynamics of sulfate-reducing populations in bacterial biofilms. Appl. Environ.
Microbiol., 64(10), 3731-3739.
63
14. Videla, H. A., & Herrera, L. K. (2005). Microbiologically influenced corrosion: looking to the
future. International microbiology, 8(3), 169.
64
Improving Solar Power System's Efficiency Using Artificial Neural
Network
Mohammed I. A. ALFarra*1 and Hatem A. Elaydi 2
1 Gaza Community College for Tourism and Applied Studies, Gaza, Palestine.
2 Islamic University of Gaza, Gaza, Palestine.
E-mail: [email protected]
ABSTRACT
Renewable energy sources are the best solution to reduce dependence on conventional and non-
renewable sources that also cause environmental pollution. With the increase in the prices of
conventional fuels globally, the increase of gas emissions resulting from its use, and the impact on the
environment and the global climate; various renewable energy sources have emerged as an alternative
to traditional sources of energy. Ssolar energy is one of the most important renewable energy sources
used globally; The technology used is relatively simple and uncomplicated, compared to the technology
used in other renewable energy sources. Solar energy is the ideal alternative to conventional energy in
the Gaza Strip in Palestine, due to the relatively high solar radiation in the region, which makes its
application more practical and economical compared to other parts of the world. Palestine has higher
rates of total solar absorption, ranging from 4-8 kWh / m2 per day, which is high compared to other
countries. This paper offers a solution to the Gaza Strip, which has suffered from a severe power shortage
due to the Israeli blockade, by using solar PV as a backup system and a good alternative to diesel
generators. Photovoltaic cells convert the sunlight into DC electric power. Where the major problem of
the PV is that with the changing of atmospheric conditions, the voltage is changing, and so the maximum
power is changing. We know that PV systems are still very expensive; therefore, the Artificial Neural
Network controller is designed for the converter to secure the maximum power to the system to increase
the efficiency of it.
ANN controller is designed to bring out the maximum power from the solar panel. This paper uses a
controller that utilizes MPPT technique to increase the efficiency of converting solar energy into
electrical energy by modifying the duty cycle of Puls Width Modulation (PWM) for the boost converter
to obtain the MPP energy from solar cells at all times.
A solar panel applied and their components are individually modeled in the MATLAB / SIMULINK
program to simulate a real PV system behavior, then an MPPT technique, including DC/DC boost
converter was designed. Then an ANN controller is designed and then trained to get the maximum power
65
point from the solar panel at different atmospheric conditions. Also, this controller is compared with the
direct connected method without an MPPT controller. The system performance is measured by changing
solar radiation and temperature of the PV module.
The findings indicate that MPPT ANN has a fast response to the variability and is more efficient, which
means more power transfer to the system. The outcome shows that the photovoltaic module directly
associated without MPPT technique has less efficiency because of the mismatch between the photovoltaic
module and the load.
Keywords: ANN, MPPT, Gaza Strip Energy, PV, Solar Energy.
66
1. Introduction
This paper aims to design an ANN controller and applied it to MPPT technique to control the duty
cycle of the boost converter to get maximum power; thus, increasing the efficiency of PV cells.
This paper proposes using of solar power in Gaza in order to find alternative energy sources to
cover the shortage of electricity and the continuously increasing demand of power supply at Gaza
and to reduce the usage of normal grid electricity. Besieged Gaza Strip suffered for years from a
chronic lack of energy due to the Israeli blockade. The situation worsened after the Israeli attack
in 2014, which destroyed the only power station in Gaza, even before the war, the electricity
supplied from Israel was less than half of the estimated needs of the sector. A power outage stream
that lasts more than 16 hours a day, and when it is available electricity intermittently come for a
period of between four and eight hours during the intervals. Fortunately, the Gaza Strip is one of
the richest areas in the world in terms of sunshine. It delights in an average of 320 sunny days a
year, thus making solar power an attractive alternative source of energy.
The increment of the volume of irradiance delivered from the sun is the best, most accessible way
to improve the operation of solar energy. There are many techniques to increase and maximize
production of power from solar systems. These methods depend on controlling certain aspects;
thus, using control methodology such as intelligent methods is justified. Artificial Neural Network
controller (ANN), as an intelligent control, will be used in this study.
2. Mathematical modeling of solar cell
Sunlight turns directly into electricity using modules consisting of many photovoltaics, solar cells
manufactured from semiconductors such as silicon. The word photovoltaic comes from the Greek
meaning “light” (photo) and “electrical” (voltaic), The popular abbreviation for photovoltaic is
PV. The first solar cell was manufactured in 1954 around 5% efficient. The first solar cells were
constructed specifically for space applications, so the cost scale was not important. The efficiency
of solar cells has steadily increased while costs have declined significantly in recent decades.
Silicon is the main component of solar cell construction, but other components and compounds
have been developed to improve efficiency and reduce cost (Quaschning, 2016).
67
PV is mainly a PN junction manufactured from a thin wafer of semiconductor. The electromagnetic
irradiation of solar power falling on the solar cells immediately turns into electrical energy through
the PV technique. Photovoltaic model is based on the Shockley diode equation and modules
naturally exhibit a nonlinear I-V and P-V characteristics which change according to the
temperature and radiation.
Typically, solar cells produce less than 5 W at about 0.5 V DC. The circuit diagram of the PV solar
cell module consists of a photocurrent, diode, parallel resistor -leakage current - and a series
resistor as illustrated in figure 1 (Natsheh, 2013).
Figure 1. Equivalent circuit diagram of of PV solar cell.
The output power of a single diode is given by (Villalva, Gazoli, & Filho, 2009)
𝐏 = 𝐈𝐕 (1)
From the photovoltaic cell circuit diagram shown in Figure 1 and Kirchhoff’s laws, the PV current
is calculated as the following: (Kim & Youn, 2005)
𝑰 = 𝑰𝒈𝒄 − 𝑰𝒅𝒔[𝒆𝒙𝒑(𝒒
𝑲𝑩𝑭𝑻𝒄(𝑽 + 𝑰𝑹𝒔)) − 𝟏] −
𝑽+𝑰𝑹𝒔
𝑹𝒑 (2)
Where 𝐼𝑔𝑐 is the light generated current, 𝐼𝑑𝑠 is the dark saturation current depends on the cell
temperature, q is the electric charge 1.6 x 10-19 C, 𝐾𝐵 is the Boltzmann’s constant 1.38 x 10-23 J/K,
F is the ideal factor of the cell, Tc is the absolute temperature of the cell, Rs is the series resistance,
and Rp is the parallel resistance. The photocurrent 𝐼𝑔𝑐 which basicly rely on the solar irradiance
and cell temperature, is presented as follows: (Villalva et al., 2009)
𝑰𝒈𝒄 = [𝝁𝒔𝒄(𝑻𝒄 − 𝑻𝒓) + 𝑰𝒔𝒄]𝑮 (3)
68
Where 𝜇𝑠𝑐 is the temperature coefficient of the short circuit current of the solar cell, Tr is the
reference temperature of the solar cell, 𝐼𝑠𝑐 is the short circuit current of the solar cell at 25o C and
1000 W/m2 and G is the solar irradiation in kW/m2. Moreover, the saturation current 𝐼𝑑𝑠 of the
solar cell changes according to the cell temperature and can be obtained as follows: (Villalva et
al., 2009)
𝑰𝒅𝒔 = 𝑰𝒐𝜶 (𝑻𝒄
𝑻𝒓)
𝟑𝒆𝒙𝒑 (
𝒒𝑽𝒈
𝑲𝑩𝑭(
𝟏
𝑻𝒓−
𝟏
𝑻𝒄)) (4)
𝑰𝒐𝜶 =𝑰𝒔𝒄
𝒆𝒙𝒑(𝒒𝑽𝒐𝒄
𝑲𝑩𝑻𝒄𝑭)−𝟏
(5)
Where 𝐈𝐨𝛂is the reverse saturation current of the cell at solar irradiation and reference temperature, Vg is
the band gap energy of the semiconductor used in the solar PV cell, and Voc is the open circuit voltage of
the cell. F is depending on the material from which the cell is manufactured as illustrated in Table 1
(Natsheh, 2013).
Table 1. Idealizing factor (F) depending on the cell's technology.
Cell
Technology
F
Si-mono 1.2
Si-poly 1.3
a-Si:
tandem
3.3
a-Si-tripple 5
a-Si: H 1.8
CdTe 1.5
CIS 1.5
GaAs 1.3
Mathematical modeling of PV module and array
Output power of solar PV cell is low. To raise the power, the cells are connected in series and
parallel arrangement on a module. For PV systems, the PV array is the group of several PV
modules which are connected in series and parallel circuits to produce the desired voltage and
current. Figure 2 shows this configuration (Natsheh, 2013).
69
Figure 2. Configuration of photovoltaic cell, module, and array.
The equivalent circuit of the solar module is coordinated in NP and NS, it is illustrated in figure 3.
Figure 3. Equivalent circuit diagram of photovoltaic module.
The terminal equation for IPV, to solar cell module goes out as follows (Kim & Youn, 2005)
𝐈𝐏𝐕 = 𝐍𝐏𝐈𝐠𝐜 − 𝐍𝐏𝐈𝐝𝐬 [𝐞𝐱𝐩 (𝐪
𝐊𝐁𝐅𝐓𝐜(
𝐕
𝐍𝐬+ 𝐈
𝐑𝐬
𝐍𝐏)) − 𝟏] −
𝐍𝐏𝐍𝐬
⁄ 𝐕+𝐈𝐑𝐬
𝐑𝐏 (6)
Where NP: Number of parallel cells, NS: Number of series cells.
Photovoltaic characteristics
The PV modules are available in a range of sizes. Some are used in grid connected and others in
standalone systems. Both types range from 80W to 300W. The performance of photovoltaic
modules and arrays are generally assessed according to the maximum output of DC power
according to Standard Test Conditions (STC). STC is achieved when the module operating at
temperature (25º C) and the incident solar radiation level is 1 kW/m²; Since these conditions do
70
not always exist, PV modules and arrays operate with a performance of 85 to 90 % of STC (Kim
& Youn, 2005). Table 2 presents the PV module (KYOCERA_ KC200GT) specifications which
used in this thesis. All the data and numbers were taken from the data sheet (KYOCERA SOLAR).
Table 2. PV module specifications.
Solar Module Parameter KC200GT
Maximum power (PMPP) 200.143 W
Open circuit voltage (Voc) 32.9 V
Voltage at MPP (Vmax
power)
26.3 V
Short circuit current (Isc) 8.21 V
Current at MPP (Imax Power) 7.61 A
No. of cells (NS) 54
Diode ideality constant 1.3
Series resistance 0.221 Ω
I leakage 9.825x10-8
A
71
There are many factors that may affect the performance of photovoltaic panels, the changes in the
shape of the power characteristic function depend on electrical connection, position of the nearby
objects and of PV system, bypass diodes, time of the day, location, module mismatch, irradiance
level, temperatures and technology.
3. Maximum Power Point Tracking
The major problem facing researchers and manufacturers in the using solar energy is to increase its
efficiency, and meet the consumer's demand loads. The most efficient use of energy is one of the key options
for obtaining sustainable global development in the 21st century. The output power of solar cell systems
(PV) changes with the varying of solar irradiance and ambient temperature. Because of the nonlinear
current–voltage (I–V) characteristics of the PV, there is a unique MPP on the power–voltage (P–V) curve.
MPPT is an important technology to improve the overall efficiency of solar cell systems.
When generating power from solar cells, the output power must be produced with maximum efficiency by
working always at the highest point of power (peak power point), regardless of changes in weather
conditions and load. To apply this, MPPT technology is implemented to ensure maximum power
transmission during the operation of the solar module that traces the maximum power output from
differences in weather conditions. The MPPT is an electronic device that is mainly introduced between the
PV module and the load. This technique consists of two important parts, as shown in figure 4, a DC to DC
boost converter with MPPT control technique to operate the PV system, In a way that enables it to deliver
maximum power to the load.
Figure 4. PV with MPPT technique.
72
The maximum output power of the solar system is changed by varying in solar radiation and
temperature of the cell, and the electrical characteristic of the load may also change. So, the
photovoltaic module internal impedance rarely matches the load impedance. It is important to
operate the photovoltaic generation system at the maximum power point or near to it to guarantee
the optimal utilization of the available solar power. The primary aim of the MPPT is to match these
two parameters by adjusting the duty cycle of the converter. Because the maximum power point
changes in the I-V curve in an unexpected way, it cannot be defined in advance because of changes
in the temperature of the solar cells and the radiation changes. Therefore, MPPT technique or
calculation model should be used to determine this point (Cheikh, Larbes, Kebir, & Zerguerras,
2007; Enrique, 2009).
A characteristics curve of PV module I-V curves is illustrated in figure 5, and the P-V curve is
presented in figure 6.There exists a single maximum power corresponding to a particular voltage
and current (Cheikh et al., 2007).
Figure 5. I-V characteristics curve of PV module.
Figure 6. P-V characteristics curve of PV module.
73
The DC / DC boost converter is considered the most important component of an MPPT system.
The same converter is applied for an MPPT to provide load matching for the maximum power
transfer by regulating the input voltage at the PV module MPP by controlling the duty cycle. If the
PV module is joined to a load directly, its operating point will be determined by the intersection
of the load and PV generation curves as illustrated in figure 7. Thus, there is only one point where
both curves intersect each other at MPP. The generation curve nonlinearly varies with the variation
of the irradiation G and temperature T, while the load curve has a various characteristic according
to the type of load is joined to the PV module. And therefore, DC / DC converters are used to join
the PV module with the load, so as to guarantee the PV module is always working at the MPP.
This is achieved by controlling the converter duty cycle with MPPT technique (Mohan &
Undeland, 2007).
Figure 7. Intersection of the load characteristic with PV generation curve.
The output voltage of the boost converter is always larger than the input voltage, so the step up
converter can be applied with MPPT systems, where the output voltage must be larger than the
input voltage. Circuit diagram of the step up converter is shown in figure 8 (Messenger & Ventre,
2010).
74
Figure 8. DC-DC step up boost converter.
Therefore, the current passing through the inductor rises linearly due to the source of the input
voltage, in which case the output phase is isolated and the capacitor is partially discharged to
provide the current load. When the switch is off during the second period the diode is conducting,
and during this time the load receives energy from both the inductor and the input source. The
signal form of the inductor current during continuous conduction mode is illustrated in figure 9.
When the converter is running at steady state condition, the duty cycle, D, can be calculated as
follows (Kasat, 2004; Mohan & Undeland, 2007).
𝑫 = 𝟏 −𝑽𝒅
𝑽𝒐 (7)
Figure 9. Step-up converter signal form of the VL and IL in continuous conduction mode.
Where Vd input voltage and Vo output voltage of the converter. In addition the modification of
the duty ratio results in a change in the input and the output current of the boost converter.
The filter inductor and capacitor to operate the converter in the continuous conduction mode can
be calculated as follows (Kasat, 2004);
75
𝐋 =𝐕𝐝𝐃
𝟐∆𝐈𝐋𝐟𝐬 (8)
𝐂 =𝐈𝐨𝐃
∆𝐕𝐨𝐟𝐬 (9)
4. Artificial neural networks
You receive a highly interconnected set of some 1011 neurons to facilitate your reading, writing, movement,
breathing, thinking and so along. Each of your biological neurons, a rich assembly of tissue and chemistry,
has the complexity, if not the speed, of a microprocessor. Some of your neural structure was with you at
birth. Other parts have been shown by experience (Hagan, Demuth, & Beale, 1996).
It consists of a number of very simple and highly interconnected processors, called neurons, which are
correspondent to the biological neurons in the brain. The basic model of a single neuron is illustrated in
figure 10, which, p an input vector, w a connection weight vector, b a bias , f an activation function and a
an output (Haykin, 1998).
Figure 10. Basic model of single neuron.
The summation output, often mentioned to as the net input, goes into a transfer function f ( also
called activation function) 𝑎 = 𝑓(𝑊𝑃 + 𝑏):
𝒂 = 𝒇(𝑾𝑷 + 𝒃) = 𝒇(𝒘𝟏,𝟏𝒑𝟏 + 𝒘𝟏,𝟐𝒑𝟐+ . . . . . +𝒘𝟏,𝑹𝒑𝑹 + 𝒃) (10)
There are three main activation functions used commonly in neural networks, the activation
function f can be got from a set of activation functions as a hard limit function, piecewise-linear
function, sigmoid function (Hagan et al., 1996).
ANN may be one or more hidden layers, the structure is determined by experience and trial and
error. And there are two types of machine learning based on ANN, one is called supervised
learning where the other is called unsupervised learning (Scott, 2008).
76
There are many different algorithms are utilized to train the ANN, including Backpropagation,
Quasi-Newton, Conjugate Gradient, Kohonen training, Delta-bar-Delta and Levenberg Marquardt.
To train the multilayer feedforward network, the Levenberg Marquardt algorithm is generally
recommended due to its robustness, providing fast convergence and the user does not necessarily
to initialize parameters (Resende, 2012).
ANN technique is used with MPPT to optimize the response of the MPPT, in order to increase
the efficiency of PV module.
5. Model and Calculation
In this paper, KYOCERA – KC200GT PV module is taken as an example. PV model was
constructed and applied by using Matlab / Simulink to verify the nonlinear I-V and P-V output
characteristics. The schematic of the PV module is implemented and illustrated in figure 11.
Figure 11. Detailed schematic diagram (sub systems) for the PV module.
77
The PV model was simulated and illustrated in figure 12.
Figure 12. The schematic of PV module.
The P-V and I-V output characteristics of the produced PV module are illustrated in figure 13, also, from
this figure we can see the nonlinearity of the output power and the output current which depend on the
solar irradiance and the temperature of the cell, and the cell terminal operating voltage as well.
Figure 13. P-V and I-V output characteristics at 25°C.
It was found from figure 13 that, the voltage and current output both increases when the irradiations are
increasing, so the maximum power output of PV module are increasing.
Figure 14. P-V and I-V output of varying temperature and fixed irradiation.
78
As we observe from figure 14, increasing in the input temperature will cause the output current
increases while the voltage decline accordingly. This contributes to decrease the output power of
the PV module.
The design specifications of boost converter are shown in Table 3. The specifications are for a
variable value of the input voltage of the boost converter where the input voltage comes from the
renewable source and the output voltage of boost converter is fixed to 45V DC.
Table (3): Specification of Boost Controller.
Parameter Value
Input Voltage 26.3Vdc
Power Converter 200.143
w
Output Voltage 45Vdc
Output Current 4.5A
Switching frequency fS 20kHz
Percent of output
voltage 1
Efficiency n 0.9
𝐷 = 1 −𝑉𝑖𝑛 × 𝑛
𝑉𝑜𝑢𝑡
= 1 −26.3 × 0.9
45= 0.526 → 𝐷 = 52.6%
𝐼𝑜𝑢𝑡 =𝑃𝑜
𝑉𝑜
=200
45= 4.45 𝐴
𝑑𝑖 = 𝐼𝑟𝑖𝑝𝑝𝑙𝑒 × 𝐼𝑜𝑢𝑡 ×𝑉𝑜𝑢𝑡
𝑉𝑖𝑛
𝐼𝑟𝑖𝑝𝑝𝑙𝑒 a good estimation of the inductor ripple current is 20% to 40% of 𝐼𝑜𝑢𝑡
𝑑𝑖 = 0.4 × 4.45 ×45
26.3= 3.1
𝐿 =𝑉𝑖𝑛 × (𝑉𝑜 − 𝑉𝑖𝑛)
𝑑𝑖𝑓𝑠𝑉𝑜
=26.3 × (45 − 26.3)
3.1 × 20000 × 45= 1.763 × 10−4 𝐻
𝑑𝑣𝑜 = 𝑉𝑜 ×1
100= 45 ×
1
100= 0.45
𝐶𝑜𝑢𝑡 =𝐼𝑜𝑢𝑡 × 𝐷
𝑑𝑣𝑓𝑠𝑉𝑜
=4.45 × 0.526
20000 × 0.45= 2.6008 × 10−4 𝐹
𝐶𝑖𝑛 =𝐼𝑖𝑛 × (1 − 𝐷)
𝑑𝑣𝑖𝑛𝑓𝑠𝑉𝑖𝑛
=7.61 × (1 − 0.48)
20000 × 0.26= 693.681 × 10−6 𝐹
𝑅 =45
4.45= 10.11 Ω
D = 84 % , L = 17..1e-4 H, let ΔV = 0.45; so capacitance C = 2.373e-4 F, R = 10.11 Ω.
79
The output characteristics of the PV module are nonlinear. Moreover, the solar irradiance is
changed continuously and unpredictable, so the maximum power point varied continuously.
To design an ANN model, "nnstart" or "nntool" function is used to create the ANN model. The
proposed ANN in this thesis is a multilayer feed forward back propagation NN, which consist of
two layers which are hidden layer and output layer. Inputs on this design are irradiance and
temperature also the output of the ANN model is a voltage at maximum power.
Neurons number in each layer and structure of multilayer feed forward propagation NN are mostly
variable and thus determined by experience and trial and error. So many of the trials are
implemented until reaching the best design. And the final design consists of hidden layer
constructed of 5 neurons whose activation function is a tangent sigmoid and the output layer has
1 neuron which activation function is a pure linear transfer function. The building of the ANN is
illustrated in figure. 15.
Figure 15. The training network model in MATLAB.
The "trainlm" tool at Matlab is used to train the ANN using Levenberg-Marquardt, so the ANN is
trained to discover the relationship between inputs (irradiation and temperature) and the output
(maximum voltage) as shown in figure 16.
80
Figure 16. Training neural network.
MSE with different epochs, training state plot and the R plot are presented in figures. 17, 18, and
19 respectively.
Figure 17. Training result of ANN block.
81
Figure 18. The plot training state for ANN.
Figure 19. The regression plot performance analysis.
Then the trained NNs can get an optimum voltage for MPP under different atmospheric cases and the output
of the ANN model is applied to determine the duty ratio, as shown in the next sections. The trained ANN
model for MPPT is illustrated in figure 20.
Figure 20. Block diagram of ANN with two layers.
82
The complete system with the ANN MPPT controller was designed as shown in figure 21, the
system was tested with multi cases and the designed system is compared with the direct connected
System (DCS) wich is directly connected with load without using MPPT technique. the outcomes
are illustrated in figures. 22, 23, 24 and 25. The simulation results show that the output power of
a PV module is greater when the ANN technique is connected to the MPPT controller at all
variables radiation and temperature than the DCS as observed in figures 24 and 25. This yields an
indication that, the DCS is working far from the maximum power point all the time. Thus, when
the radiation varies the ANN model controller calibrates the duty cycle, to get the operating points
where the power is at the maximum value (MPP), and that happened by decreasing the PV current
operating point and increase the PV voltage operating.
Figure 21. The complete MPPT system with ANN network.
Figure 22. Output Power for MPPT system with ANN network with variable irradiation and constant
temperature (25˚C).
83
Figure 23. Output Power for MPPT system with ANN network with variable temperature and constant
irradiation 1000 W/m2.
Figure 24. PV system with (a) the direct connected system compared with (b) ANN MPPT controller with
variable irradiation and constant temperature.
(b)
(a)
84
Figure 25. PV system with (a) the direct connected system compared with (b) ANN MPPT controller with
variable irradiation and variable temperature.
From the diagrams and previous results the Artificial neural network technology shows a quick
and accurate response, according to sudden solar radiation change. Figs 22, 23, 24 and 25 show
that, the output power of the photovoltaic module changes as the solar irradiance varies at different
time periods, And thus results in a change in the maximum power value, so changes must be
detected and handled by the ANN MPPT controller technique by changing the value of the duty
cycle. The designed system ANN MPPT controller can increase the total efficiency of the system
by more than 14 % higher than the system without an MPPT controller.
At the direct connected system without ANN MPPT controller is working at a lower PowerPoint
than the MPP and has a slower response to solar radiation changes. On the other hand, the directly
associated without MPPT technique has less efficiency because of the mismatch between the
photovoltaic module and the load. These cause loss of energy so that the ANN MPPT technique is
better and saving energy.
Time (Sec)
(b)
(a)
85
In addition, the ANN MPPT technology shows the ability to adapt rapidly to the rapid change in
radiation and to avert the accompanying deviation from the maximum power point.
Finally, we can say in general that the ANN controller, which is applied to MPPT technique is
effective to track the maximum power point and this technique can increase the efficiency of the
PV module when rapid change in radiation and temperature occur.
6. Summary
Recently, solar energy has become increasingly and effectively used worldwide because of the
increasing demand for energy and fossil fuels begin to diminish, also the huge pollution resulting
from its use.
In particular, Gaza Strip suffers from a severe shortage of electricity, reaching a maximum at 2017,
where the power failure period from 12 hours to 14 hours continuous, while the link period is about
4 to 6 hours per day. Also lack of fuel, noise and pollution resulting from the use of electrical
generators, led to reduce the use of electrical generators, so residents resorted to using solar energy
as an alternative solution, effective and clean. Which it available all the time.
Because of the relatively high cost of the solar system, the overall efficiency of the solar cell
system should be increased to reduce the use of a large amount of solar panels; so MPPT
technology has been used to improve the efficiency of the solar cell system.
An artificial intelligent maximum power point tracking technique using neural networks is
proposed, which predicts the appropriate duty cycle for which the DC-DC converter can operate
with and thus the maximum power can be obtained from the PV system. The system comprises of
PV modules, DC-DC boost converter and ANN controller to get MPPT. Each component is
simulated and discussed in details using MATLAB/SIMULINK software. The PV model was
verified The ANN MPPT method is designed and developed and it is compared with the direct
method without MPPT system.
Also DC-DC boost converter model is simulated which is the key for changing the PV’s terminal
voltage to track the maximum power.
86
The system is tested by the artificial neural network MPPT method under the sudden irradiance
and variable temperature, and the ANN method gave very fast and accurate response. Where an
ANN MPPT controller has been designed and implemented; so the designed system increased the
overall efficiency of the solar system by more than 14%.
7. Future Directions
Using hybrid control consists of P&O technique with an ANN control to eliminate the oscillation
around the MPP in steady state. Also a good area of research to implement Fuzzy control and
compare it with ANN control. Another area which it is Implementation of a physical model for
MPPT controller with an artificial neural network technique using microcontrollers and applying
it on a real PV panel.
87
References
1. Cheikh, MS Aït, Larbes, C, Kebir, GF Tchoketch, & Zerguerras, A. (2007). Maximum power
point tracking using a Fuzzy logic control scheme. Revue des energies Renouvelables, 10(3), 387-
395.
2. Enrique, J.M., Andujar, J.M., & Bohorquez, M.A. (2009). A reliable, fast and low cost
maximum power point tracker for photovoltaic applications. Solar Energy, 84(1).
3. Hagan, M. T., Demuth, H. B, & Beale, M. (1996). Neural Network Design (2nd ed.). Boston,
MA, USA: PWS Publishing Co.
4. Haykin, S. (1998). Neural Networks: A Comprehensive Foundation (2nd ed.): Prentice Hall.
5. Kasat, S. (2004). Analysis, design and modeling of DC-DC converter using simulink.
(Master), Oklahoma State University, USA.
6. Kim, I-S, & Youn, M-J. (2005). Variable-structure observer for solar-array current estimation
in a photovoltaic power-generation system. IEE Proceedings-Electric Power Applications, 152(4),
953-959.
7. KYOCERA SOLAR. KC200GT High Efficiency Multicrystal Photovoltaic Module
Datasheet Kyocera. Japan.
8. Messenger, Roger A., & Ventre, Jerry. (2010). Photovoltaic systems engineering (3rd ed.):
CRC Press/Taylor & Francis, Boca Raton, FL.
9. Mohan, N., & Undeland, T. M. (2007). Power electronics: converters, applications, and
design. Daryaganj,India: Wiley.
10. Natsheh, E. M. (2013). Hybrid Power Systems Energy Management Based on Artificial
Intelligence. (Doctoral), Manchester Metropolitan University, Manchester, England. Retrieved
from http://e-space.mmu.ac.uk/id/eprint/314015
11. Quaschning, Volker. (2016). Understanding renewable energy systems (2nd ed.). London;
New York: Routledge, Earthscan.
12. Resende, F. d. O. (2012). Contributions for microgrids dynamic modelling and operation.
(Doctoral thesis), Porto University, Portugal
13. Scott, D. (2008). The discovery of new functional oxides using combinatorial techniques and
advanced data mining algorithms. ( Doctoral thesis), UCL (University College London). Retrieved
from http://discovery.ucl.ac.uk/id/eprint/15214
88
14. Villalva, M. G., Gazoli, J. R., & Filho, E. R. (2009). Comprehensive Approach to Modeling
and Simulation of Photovoltaic Arrays. IEEE Transactions on Power Electronics, 24(5), 1198-
1208. doi: 10.1109/TPEL.2009.2013862
89
The Activity of HYPR surfactant as Superplasticizer on fresh and
hardened properties of concrete
Abdel Fattah A. Qaraman*
* Energy and Environment Research Center - Israa University, Gaza, Palestine.
Email: [email protected]
ABSTRACT
Superplasticizers are a basic component in a today concretes, enhancing workability, which
leads to producing durable and sustainable concrete. This research aims to study the effect of Alkyl
dimethyl hydroxyl ethyl ammonium chloride (HYPR) cationic surfactant as superplasticizer on the
fresh and hardened properties of concrete to produce concrete with adequate workability. The
mechanical properties of fresh and hardened concrete first obtained for control mix, then for
different concentration of HYPR that added to the concrete, 0.10, 0.25, 0.50 and 0.75% by cement
weight. The slump tests, air content, compressive strength tests , microstructure and morphology
of the hardened concrete were conducted for all specimens with and without HYPR. The results
indicate that using HYPR admixture at their best ratios in the concrete mixes would improve the
slump loss problem from 70 mm to 230 mm. The use of HYPR admixture showed an adverse effect
on compressive strength. The scanning electron microscope (SEM) illistrates that the addition of
HYPR on concrete produces consistent bubble structure with a uniform small air voids system
(80.41 µm).
Keywords: Superplasticizer, compressive strength, air content, HYPR, surfactant, slump.
90
1. Introduction
Superplasticizers are chemical admixtures providing workability enhancement at low water to
cement ratios (W/C) which leads to producing durable and sustainable concrete.
The main action of the superplasticizers is to wrap themselves around the cement particles and
give them a highly negative charge so that they repel each other, by repelling action cement
particles are deflocculated and dispersed releasing water confined inside them.
The workability can be enhanced by using the exact required amount of superplasticizer
(Andersen, 1986) and (MacInnis and Racic, 1986). Usually, manufacturers indicate the effects
of such admixture; however, their action and performance should be checked before use
(Baalbaki, and Aitcin, 1994). When concrete is fresh, it is desirable to be malleable or workable.
However, sometimes, due to scorching conditions at the site, desirable workability cannot be
maintained. Then superplasticizer enhances the workability to a sufficient extent by lowering the
shear and flow resistance [Golaszewski, and Szwabowski, 2004]. Even in the case of self-
consolidating concrete, superplasticizer greatly enhances the workability of concrete (Felekoglu,
and Sarıkahya, 2008) and ( Sahmaran, et. al 2006). Normally, the chemical admixtures used
for reducing water are liquids and have less than 0.5 percent of cement weight. In these chemical
admixtures, solid's contribution ranges from 30 - 40% of total volume. In low range water
reducing admixtures, high retardation and bleeding may take place but, comparatively, high
range water reducing admixtures can be added from 0.7- 2.5% of cement weight [Hameed, 2012].
HYPR belong to a chemical family called surfactants, surfactants are amphipathic molecules,
which have two characteristics, polar head, and non-polar tail, in different parts of the same
molecule. Therefore, a surfactant molecule has both hydrophilic and hydrophobic characteristics.
Surfactants are classified, based on the charged groups present in their heads, into the following
four categories: [Qaraman, 2017) Anionic, cationic, non-ionic and amphoteric or zwitterionic.
HYPR is a cationic surfactant, which has an appositive charge in its head.
The main aim of research is to study the effect of (HYPR) as superplasticizer on the fresh and
hardened properties of concrete to produce concrete with adequate workability.
91
2. Experimental
2.1 Materials
2.1.a Surfactant
Different cooncentration 0.10, 0.25, 0.50 and 0.75% are used of the surfactant Alkyl dimethyl
hydroxyl ethyl ammonium chloride (HYPR) which supplied from Clariant, the HYPR surfactant
structure is:
Figure 1: Alkyl dimethyl hydroxyl ethyl ammonium chloride (HYPR) chemical structure
2.1.b Cement
The cement used is Portland cement of mark CEM I 52.5N obtained from El-Arish cement
factory. Its chemical composition is given in Table (1).
Table (1): Chemical composition of the used ordinary Portland cement (OPC). (Qaraman et al ,2016)
Ox
ide
(%
)
Si
O2
Al2
O3
Fe2
O3
Ca
O
Na
2O
K2
O
Cl- M
gO
SO
3
Fr
ee
Ca
O
Ig
nit
ion
Lo
ss
OP
C
22.
12
5.5
6
3.6
9
62.
87
0.2
9
0.1
1
0.0
2
2.3
6
0.9
1
0.9
2
1.2
2
The cement tested according to ASTM C109, C187, C191 and C204 and the result are accepted
according to the specification of ASTM C150. The results physical and a mechanical properties
92
and the specification requirement according to ASTM C150 of the cement was mentioned in
Table (2).
Table (2): Cement characteristic according to testing and (ASTM C150)
Type of test Related
ASTM
specification
Characteristic Result Cement
Type I
ASTM
C150
Setting time using Vicat test
( minutes)
C191 Initial 105 >60
Final 315 <600
Mortar compressive strength
(MPa)
C109 At age 3 days 13.5 Min 12
At age 7 days 29.6 Min 17
At age 28 days 47.3 No limit
Blain fineness (cm2/g) C204 - 3035 Min.
2800
Water demand (%) C187 - 27.5 No limit
2.1.c Aggregate
The physical property of fine and coarse aggregate are listed as below:
2.1.c.1 Sieve analysis
The sieve analysis of fine and coarse aggregate was made according to ASTM C136; the result
was listed in the Table (3).
Table (3): Sieve analysis results for fine and coarse aggregate
Sample Name
Sieve
#
Sieve
Size Type I Type II Type III Type IV
(FOOLIIA) (ADDASIA) (SOMSOIA) (Sand)
1.5" 37.5 100.00
1" 25 98.56
3/4" 19 59.80 100.00
1/2" 12.5 1.78 55.44 100.00
3/8" 9.5 0.00 8.95 95.20
93
#4 4.75 0.00 0.00 23.32
#8 2.36 0.00 0.00 0.20 100.00
#16 1.19
94.45
#30 0.6
76.77
#100 0.18
1.05
#200 0.075
0.00
3. Absorption and Specific Gravity
The Absorption and specific gravity of fine and coarse aggregate was made according to
ASTM C 128 & ASTM C 127 and the results are presented in Table (4).
Table (4): Absorption and specific gravity of fine and coarse aggregate
Sample
Name Absorption Specification
Apparent
specific
Bulk
specifi
c
Bulk specific
gravity in SSD
After 24
hour gravity
gravit
y
Type I 1.25% Max. 2% 2.654 2.549 2.588
Type II 1.23% Max. 2% 2.667 2.541 2.592
Type III 1.14% Max. 2% 2.538 2.505 2.590
Type IV
(Sand) 0.57% Max. 2% 2.664 2.577 2.638
3.1 Water:
Tape water is used for all mixing and curing of concrete.
3.1.a Techniques and Instrumentation:
3.1.a.1 Mix Design:
After finishing of all tests for concrete constituent and ensure that all material like water,
aggregate, sand and cement are according to specification, the concrete will design with strength
94
30 MPa at 28 days age. The job mix will be designed according to Standard Practice for Selecting
Proportions for Normal, Heavyweight, and Mass Concrete (ACI 211.1-91). The design criteria
that used in the current study is as:
1. Compressive strength: The most strength of normal concrete for general use is 30 MPa for
cubic strength and 25 MPa for cylinder strength so the mix will be design for that strength.
2. Slump: The most slump of normal concrete for general use is between 25 to 100 mm and the
mix is designed for slump around 75 to 100 mm.
3. Nominal maximum aggregate size: The nominal maximum aggregate size in the job mix is 25
mm.
4. Water cement ratio: The water cement ratio in the job mix is 0.57.
5. The final average weight for job mix: The final average weight for the job mix is list in
Table (5)
Table (5) : The final average weight for the job mix.
Material Weight (kg) Volume (m3)
Entrapped air 0 0.0150
Water 182 0.1650
Cement 320 0. 1016
Coarse aggregate 1161 0.4519
Fine aggregate 687 0.2665
Total 2350 1.000
3.1.b Preparation of concrete specimen:
3.1.b.1 Mixing procedure:
The concrete will mix according to Standard Method of Making and Curing Test Specimens in
the Laboratory ASTM C 192.
95
3.1.b.2 Curing of hardened concrete:
After 20-40 hour, the hardened concrete will be removed from the molds very carefully to prevent
any defect in the samples. After that, the samples will be placed in curing water tank at
temperature 21-25 C0 until the period of testing.
3.1.b.3 Fresh concrete test and sampling:
1. Slump Test according to ASTM C 143: the test was made to measure the workability of fresh
test according to the standard Test Method for Slump of Portland Cement Concrete ASTM C
143, the scope of this test is determination of the slump of hydraulic-cement concrete.
2. Sampling of fresh concrete in several molds according to ASTM C 192.
3. Compressive strength According to ASTM C 39 and BS 1881, Part 127.
4. Air content according ASTM C138.
5. The morphology and microstructure of the dried hydrated samples are studied using JEOL JXA
840 A electron Probe micro analyzer SEM. The specimens are coated with a thin film of gold
under a vacuum evaporator with cathode rays then analyzed.
4. Results and Discussion
4.1 Effect of HYPR on air content of the concrete
Air content is the controlling factor which affects other aspects of the concrete (i.e. density,
compressive strength and workability) (Qaraman,et al,2016). Dodson, 1990 believed that
adsorbed surfactant molecules at the surface of the bubble form a film, with their polar heads in
the water phase. If the molecule is charged, the bubble acquires this charge. The electrostatic
repulsion keeps bubbles separated and prevents coalescence. In addition, the ends of the
surfactants molecules that protrude into the water are attracted to cement grains. This allows for
a coating of calcium salts (the products of cement hydration) to be formed around each air bubble,
making it more stable than bubbles formed in plain water (Algurnon, 2013).
The results, which presented graphically on figure (1) shows that the entrained air is increased
gradually with the surfactant concentration until it reaches a maximum value at a fixed surfactant
96
content. However, the maximum air content is 11.31% on using 0.75 % of the HYPR surfactant
by weight of cement.
The efficiency of HYPR as air entraining agent may refer to the electrostatic repulsion between
the positive charges on the quaternary nitrogen of HYPR and those on the cement grains, which
may enhance the air bubbles separation and stabilize them due to the probable formation of
hydrogen bonding between the HYPR hydroxyl group and the silica network (CSH).
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8
0
1
2
3
4
5
6
7
8
9
10
11
12
13
air
co
nte
nt
concentration wt%
Figure (1): The air entrained by 0.10, 0.25, 0.50 and 0.75% HYPR
4.2 Effect of HYPR on the concrete slump
The concrete slump test is an essential test for measuring the workability of fresh concrete. The
test measures the consistency of concrete in that specific batch. It is performed to check the
consistency of freshly made concrete. Consistency refers to the ease with which concrete flows.
It is used to indicate the degree of wetness.
Consistency affects the workability of concrete. That is, wetter mixes are more workable than
drier mixes, but concrete of the same consistency may vary in workability. The test is also used
to determine consistency between individual batches.
97
The data are recorded and being shown to observe the relation between dosages of HYPR
admixture and slump loss. The values of slump loss for different dosages of HYPR admixture as
show in figure (2) the slump loss against the time for different dosages of HYPR. From the graph,
it is clear that slump reduces with time. It is acceptable since continuous hydration process will
produce calcium silicate hydrate to fill the pores between the cement particles and aggregate. As
a result, setting of the concrete will reduce the fluidity of concrete, hence, reduce the slump too.
When observation is done on the content of HYPR, increase in dosage of the chemical admixture
will decelerate the rate of setting of concrete, since HYPR will help to retain the concrete in
liquid state for a longer time, and hence, reduce the slump loss during the transportation of
concrete to the site. The optimum content of HYPR is 0.50 % by cement weight, however, over
dosage of HYPR will not lead to significant improvement of concrete slump. As a result,
conclusion is made that HYPR is more effective in retaining the slump of the concrete than the
normal concrete.
0 20 40 60 80 100 120
0
20
40
60
80
100
120
140
160
180
200
220
240
slu
mp
lo
ss (
mm
)
time (min)
0
0.1
0.25
0.5
0.75
Figure (2): Relations between the HYPR concentration and the slump loss values
98
4.3 Effect of HYPR on the concrete compressive strength
Compressive strength is an important criterion specified in the design of concrete. The
properties of concrete are time dependent, therefore, any test method performed on the concrete
should be done at a certain hydration age.
The values of the compressive strength of concrete with and without HYPR at different
concentrations and different hydration ages (7, 14 and 28 days) have been determined .Three
specimens of each mix at each hydration time are used for examining the compressive strength
of the pastes. The mean value of the compressive strength of the three specimens at each
hydration age is considered.
The 7, 14 and 28 days compressive strength of concrete mixes having 0.10, 0.25, 0.50, and 0.75%
of HYPR admixture by cement weight are shown in Figure (3). The results show that the 7 days
compressive strength is about 75% of 28 days compressive and the 14 days compressive strength
is about 90% of 28 days compressive strength for all contents.
All mixes show an increase in the values of the compressive strength with increasing hydration
time. This is believed to be due to progress of the cement hydration.
As mentioned above, the compressive strength of the concrete increases with the hydration
time both in absence and presence of HYPR regardless of their concentrations. The highest
compressive strength are achieved, in both cases, after 28 days of hydration.
In addition, Figure (3) shows that the compressive strength was decreasing by increasing the
dosages of HYPR admixture, the 7days compressive strength decreased linearly from 20.3 MPa
at 0.10% of HYPR to 14.9 MPa at 0.75% of HYPR. The 14 days compressive strength decreased
linearly from 25.3 MPa at 0.10% of HYPR to 18.5 MPa at 0.75 of HYPR. The 28 days
compressive strength decreased linearly from 28.4 MPa at 0.10 % of HYPR to 20.9 MPa at 0.75%
of HYPR.
99
The loss of strength was essentially due to the entrained air in the concrete mix, these air voids
weaken the strength of concrete. The air entraining increased as increased the content of HYPR.
(Qaraman & Zuhud, 2018).
0 3 6 9 12 15 18 21 24 27 30
0
3
6
9
12
15
18
21
24
27
30
33
co
mp
ressiv
e s
tre
ng
th (
MP
a)
time (days)
0
0.1
0.25
0.5
0.75
Figure (3): effect of HYPR concentration on the compressive strength
4.4 Effect of HYPR on the microstructure and morphology of the hardened concret.
The scanning electron microscope (SEM) is a powerful tool for imaging and chemical analysis
in concrete . With a high resolution and a large depth of focus, it enables a detailed study of
surface topography of the rough surfaces of e.g. the formed calcium silicate hydrate (CSH) and
calcium hydroxide (CH). The micrographs of the hardened concrete in absence and presence of
the HYPR after 28 days are shown in Figure 4 (a &b). Figure (4-a) illustrates the hydration
products formed in absence of surfactants. Calcium hydroxide appears as hexagonal plates and
the ettringite needles exist beside the fibrous CSH phase. Addition of HYPR (figure 4-b) shows
an increase in the amount of calcium hydroxide, which has a layered structure, appears beside
CSH crystals. On other hand, the structure of concrete with addition of HYPR produces
100
consistent bubble structure with a uniform small air voids system (80.41 µm) it seems to be more
compact. These findings may indicate that HYPR uniform the air void system which explain the
lowering of the compressive strength, these results are great confirm previous findings (Qaraman
,2016)
Figure (4): SEM of hardened concrete after 28 days hydration (X = 5000).
a) Without HYPR b) With 0.02% HYPR
5. Conclusion:
The following concluding remarks were obtained from the experimental observation:
a. The addition of HYPR enhanced the workability and reduced slump loss problem of concrete.
b. The addition of HYPR increasing the slump without any significant segregation.
c. The compressive strength affected adversely due to the air entraining in the concrete mix, these
air voids weaken the strength of concrete.
d. The entrained air increased as the HYPR concentration increased.
e. The optimum content of HYPR is 0.5% by cement weight; the using of higher dosage than 0.50
% does not show any significant improvement to concrete slump. At 0.50 %, content of HYPR
admixture the slump value of concrete was enhanced to reach 220 mm. However, the
compressive strength at this ratio is 23.4 MPa.
101
References:
1. Algurnon, S. R. ,"Structural lightweight aerated concrete", M.Sc. thesis, Stellenbosch
University, South Africa, pp. 9-10, 2013.
2. Andersen, P. J. (1986). The effect of superplasticizers and air-entraining agents on the zeta
potential of cement particles. Cement and Concrete Research,16(6), 931-940.
3. Baalbaki, M., & Aitcin, P. C. (1994). Cement/superplasticizer/air-entraining agent
compatibility. Special Publication, 148, 47-62.
4. Dodson, V.H., "Concrete Admixtures", New York, Van Nostrand Reinhold, pp129-211, 1990.
5. Felekoglu, B., and Sarıkahya H. 2008. Effect of chemical structure of polycarboxylate-based
superplasticizers on workability retention of selfcompacting concrete. Construction and
Building Materials, 22(9), 1972–1980.
6. Golaszewski, J., and Szwabowski, J. 2004. Influence of superplasticizers on rheological
behaviour of fresh cement mortars. Journal of Cement and Concrete Research, 34(2), 235–
248.
7. Hameed, A., H. 2012. Effect of superplasticizer dosage on workability of self-compact
concrete. Diyala journal of Engineering Sciences, 5(2), 66-81.
8. MacInnis, C., & Racic, D. (1986). The effect of superplasticizers on the entrained air-void
system in concrete. Cement and Concrete Research, 16(3), 345-352.
9. Qaraman A. F. A., & Zuhud, A. A. (2018). The ınfluence of usıng cocamıdopropyl betaıne as
chemıcal addıtıve on thermal and physıcal propertıes of foam mortar. Asian journal of natural
and applied sciences, 7(1), 12-21.
10. Qaraman A. F. A., Musalum, A and Alhassayna, I. M. (2017). The Behevior of Lauryl
glucoside as cement paste admixture. Israa university jornal of applied sciences, 2(1), 12-21.
11. Qaraman A., Hegazy, W., Mahmoud, F. and Mohamed, M., "Effect of Addition of HYPR and
CABP on the Physiochemical and Mechanical Properties of Cement Pastes ", International
Journal of Science and Research, 2006-2011 (2016).
12. Sahmaran, M., Christianto, H.A., and Yaman, I.O. (2006): The effect of chemical admixtures
and mineral additives on the properties of selfcompacting mortars. Cement and Concrete
Composites, 28(5), 432–40.
201
Rotavirus Gastroenteritis among Children Under five years of age
in Gaza, Palestine.
Abed El Kader Y. Elottol*1, Akram M. Altaher1, Basma F. Alnajjar1, Felastin H. AbSitta1,Asala
S. Abu Adwan1, Aya A. Dheer1
1Medical Science department, University College of Science and Technology, Khan Younis,
Gaza strip, Palestine.
Email : [email protected]
ABSTRACT
Background: Rotavirus belongs to the Reoviridae family, a group of segmented double stranded
Ribonucleic acid viruses. The virus is a major cause of gastroenteritis and diarrhea in infants
and young children worldwide. Rotaviral gastroenteritis may result in mortality for populations
at risk such as infants, the elderly and immune compromised patients.
Objective: This study aims to evaluate occurrence of rotavirus among under five years children
with acute gastroenteritis attending Nasser complex and European Gaza Governmental
Hospitals, Palestine during august 2018.
Methods: Cross sectional design used in this study, Fecal samples from 100 children with ages
ranging from less than 1 month to 5 years, living in the south Gaza, who presented with acute
gastroenteritis and diarrhea episodes, were analyzed. sufficient quantity of faces (1-2 grams or
milliliters for liquid sample one per each subject) is collected as soon as the children were
admitted to the hospital by the help of their parents in clean and dry containers (no preservatives
or transport media are used). The samples was been tested immediately using an immune
chromatography-based diagnostic kit. The study was conducted during the peak diarrheal season
August of the year 2018.
Results: Rotavirus was detected in 35% of the fecal specimens examined, and most of positive
tested patients (86%) were under 24 months old, the infection rates was increase with the
decreasing of the age. Children infected with rotavirus were more likely to be watery stool
65.7%, fever 60%, vomiting 82.8% and dehydration 68.6%.
201
Conclusions: The findings of this study demonstrated that Percentage of positive samples among
children younger than 5 years still nearly the same or slightly higher than that have been detected
in Gaza since 2006. Reflect that no effectiveness of vaccine in reducing morbidity or infection.
Keywords: Rotavirus, Gastroenteritis, Gaza, Palestine.
201
Introduction
Acute gastroenteritis is considered as one of the leading causes of illness and death in children
under the age of 5 years (Youssef et al.,2000). It’s characterized by acute onset of diarrhea, which
is not accompanied by nausea, vomiting, fever, abdominal pain, and dehydration. Acute
gastroenteritis is prevalent worldwide and associated with high rates of morbidity and mortality
in developing countries (Fruhwirth et al.,2001). Acute gastroenteritis and diarrhea are common
and costly problems that cause significant morbidity and mortality in children worldwide. In
Palestine, diarrhea is one of the major causes of outpatient visits and hospitalizations (Abu
Elamreen et al. ,2006& World Health Organization,2009). Viral infections cause about 70% of
diarrhea in children, where rotavirus remain the most commonly pathogen (Barnes etal.,1998).
Rotaviruses are an icosahedral 76.5 nanometer, double-shelled RNA virus of the family
Reoviridae, a family of double-stranded segmented RNA genome viruses (Pesavento et al.,
2006).
A appropriate and quick diagnosis of rotavirus infection in acute diarrheal cases will help to
choose the suitable treatment and stop the needless use of antibiotics (DhiMan et al., 2015).After
the introduction of the vaccines, there has been a marked reduction in the incidence of viral
diarrhea especially in Europe, Australia and the United States of America (Grimwood et al.,
2007). The effectiveness of the application of vaccine in the Gaza strip is not evaluated yet.
Worldwide epidemiology of rotaviruses ranged from 9.35% in Brazil with prevalence rates
11.12% in the pre-vaccine to 5.07% in the post-vaccine period, 25% in Africa, 25.6% in Tirupati
India, 40% among inpatients and 23% among outpatients in Eastern Mediterranean region, and
46.4% in the eastern India(Badur et al., 2015, Sarangi et al., 2015, Assis et al., 2013, Waggie et
al., 2010 & Malek et al., 2010), In Gaza strip, Palestine before the admission of rotavirus
vaccination the prevalence was 28% (Abu Elamreen et al., 2006).
To our knowledge, this is the first report on the occurrence of rotavirus infection among children
of Gaza after the application of vaccines.
201
2. Materials and Methods
2.1 Study population and period
During August 2018, one hundred stool samples were randomly collected from children under
the age of 5 years with acute gastroenteritis attending the two largest hospitals in the south of
Gaza ( Nasser complex hospital and Gaza European Hospital), A consent form about the study
has been obtained from the parents of the children.
2.2 Samples collection and biochemical test
Sufficient quantity of feces (1-2 grams or millimeters of liquid sample) were collected in clean
and dry containers as soon as the children were admitted to the hospital by the help of their
parents, no preservatives or transport media were used.
The fresh diarrheal fecal specimen was transferred immediately within one hour to the university
college of Science and Technology laboratories for macroscopically, microscopically and
serology testing. Rotavirus antigen was detected by rotaStick one-step test kit (Novamed Ltd,
Jerusalem), according to manufacturer’s instructions, in brief, a little sample (50mg) is picked up
from fecal specimen and put into the testing tube with buffer solution. The content of a test tube
was then mixed vigorously to suspend the specimen, the dipstick test strip was placed vertically
into the sample tube and removed after 10 seconds or when the fluid had reached the middle of
the test area of the dipstick, results were reported after 10 minutes, a red color band is an
indication for the presence of rotavirus.
For parasitological examination samples were microscopy and macroscopy tested for the
presence of parasites, worms, blood and mucus.
2.3 Questionnaire interview
A face-to-face questionnaire was filled for each child containing information such as age, gender,
residence, clinical data, fever, vomiting, and dehydration rate, type of diarrhea and previous
hospitalization, parent’s education level and employment. .
201
3. Data analysis
The data was collected and analyzed using the statistical package for social sciences (SPSS
Version 22.0) . Differences in proportions were assessed by chi-square test, p-value ≤ 0.05
4. Results
During August 2018, One hundred samples (55 male and 45 female) were collected from children
under the age of 5 years suffering from particularly diarrhea, Sixty five samples were collected
from Nasser Medical Complex and thirty-five samples from European Gaza Hospital.
The mean age of the patients was 14.28 month, standard deviation ±12.9 months, the minimum
age was less than 1 month where the maximum age was 60 months. The distribution of samples
according to age groups indicated that (86%) of diarrhea was observed in the age ≤ 24 months,
(57%) of the infected cases was Infants ≤ 12 months and (29%) of the infected cases was 12 to
24 months. Rotavirus antigen was detected in (35% of the tested samples, no statistically
significant difference was found between rotavirus results and age groups (p=0.11) (Table1).
Table 1: distribution of rotavirus results.
Rotavirus
Age by months
Total 1 - <12 12 - <24 24 - <36 36 - <48
48 - <
60
Positive 21 7 3 1 3 35
Negative 36 22 0 3 4 65
Total 57 29 3 4 7 100
P value = 0.111
Stool samples were tested for parasitic infection, and the results show that (74%) were negative
for parasitic infections, (19%) were positive for Entamoeba histolytica only and (1%) were
positive for Giardia lamblia, (6%) mixed infections was found between Entamoeba histolytica
and rotavirus (table2).
201
Table 2 : serological and Parasitological examination results
Test results Percent
Negative )45% )
Rotavirus positive (29%)
Entameba histolytica )19%)
Rotavirus and Entameba
histolytica
(6%)
Giardia lamblia )1%)
Total (100%)
Relationship between Rotavirus, patient’s age and sex
Although there was a slightly increased in males attending the hospitals due to acute diarrhea
(55%) Than females (45%) no statistically significant difference was found (P value = 0.3). on
the other hand Although most of the affected children were less than one year no statistically
significant difference was found among different ages (P = 0.111) ( table 3,1).
Table 3: Distribution tested cases according to sex
Rota result Patient sex Total
Male Female
Positive 21 14 35
Negative 34 31 65
Total 55 45 100
P value= 0.3
Relationship between rotavirus and parents education and mother employee:
No statistically significant difference was found between education level of both parents with
rotavirus infections, also no statistically significant difference was found between mother
employee with rotavirus infections (p =0.20 and 0.3 respectively)(table 4,5).
201
Tables 4 : Cross tabulation between rotavirus and fathers and Mothers education level
Father
Rota
Result
Education level of fathers Total
Primary
school
Preparatory
school
Secondary
school
University
Positive 4 7 17 7 35
Negative 5 9 27 24 65
Total 9 16 44 31 100
P value=0.33
Mother
Rota Result
Education level of mothers
Total Primary
school
Preparatory
school
Secondary
school
University
Positive 2 2 17 14 35
Negative 1 5 25 34 65
Total 3 7 42 48 100
P value=0.43
Tables 5 : cross tabulation between rotavirus and mothers Jobs
Rota result Mothers jobs Total
Housewife Working
Positive 34 1 35
Negative 64 1 65
Total 98 2 100
P value =0.580
Relationship between rotavirus and Vomiting , Fever , Dehydration and Types of
diarrhea :
there were no statistically significant difference with vomiting, fever and dehydration of
patients, on the other hands a statistically significant difference was found between rotavirus
infection and type of stool were most of positive rotavirus patients have watery diarrheal stool
201
(table 6, 7,,8,9). Tables 6 : Cross tabulation between rotavirus and vomiting
Rota result Vomiting
Total yes No
Positive 29 6 35
Negative 48 17 65
Total 77 23 100
P value = 0.222
Table 7 : Cross tabulation between rotavirus and Fever
Table 8: cross tabulation between rotavirus and dehydration
Rota result Dehydration
Total
yes No
Positive 24 11 35
Negative 36 29 65
Total 60 40 100
P value = 0.142
Rota result Fever present
Total yes No
Positive 21 14 35
Negative 43 22 65
Total 64 36 100
P value = 0.345
220
Table 9: Cross tabulation between rotavirus and types of diarrhea
Rota result types of diarrhea
Total mucoid Watery Others
Positive 12 23 0 35
Negative 40 22 3 65
Total 52 45 3 100
P value =0.004
5. Discusion
Rotavirus was detected in (35%) of the fecal specimens collected from children of < 5 years of
age with acute diarrhea, using an immune-chromatographic assay, this percentage was higher
than detected previously in Gaza in 2006 (28%) before application of vaccine, this explain by
that vaccine may decrease severity and mortality, but not morbidity. and that in Middle East and
North Africa (34%) and Less than in Eastern Mediterranean region (40%) for in patients (Zaraket
et al., 2017, Malek et al., 2010 & Abu Elamreen et al., 2006). The low or high rates of rotavirus
infections presented by different investigators can be explained by several factors including, the
study population, the incidence rate of the virus in different environments, the living conditions
and standards of the study group, and the season on which the study was conducted.
Out of the 100 diarrheal patients enrolled in the study, (86%) of patients were less than 24 months
of age, this finding is consistent with previous study in Gaza (84%)(Abu Elamreen et al., 2006).
The children enrolled in this study were divided into five age groups, (86%) of all cases of
rotavirus occurred in children <24months, which is in agreement with many other studies in Gaza
(90%), in Middle East and North Africa (MENA) Region (40%) , in Iraq (67.1%), and in India
(69%) (Zaraket et al., 2017, Sarangi et al., 2015, AL-Khafaji et al., 2013 & Abu Elamreen et al.,
2006 ).
222
Decreasing rates of rotavirus infection was observed with the increasing of age due to protective
immunity accepted by children during previous infection with rotavirus, this finding was
mentioned by other authors in Gaza, in Georgia, and in Thailand (Abu Elamreen et al., 2006,
Jiang et al., 2002& Maneekarn et al., 2000). Fifty-five percent of male and forty-five percent of
female cases of acute diarrhea were examined in this study. Slightly more males were admitted
to the hospital due to diarrhea, rotavirus prevalence was higher in male cases 38.2% than in
females 31.1%, this disagree with study in Gaza where female higher than male , and India were
males to females ratio was approximately equal(John et al., 2014 & Abu Elamreen et al., 2006
).
Although Children infected with rotavirus were more likely to have watery stool (65.7%), fever
(60%), vomiting (82.9%) and dehydration (86.6%) these clinical symptoms have no statistically
significant with rotavirus infections, on the other hands there was statistically significant relation
between rotavirus infection and type of stool where most of positive rotavirus patients have
watery stool, this was in agreement with a number of studies in Gaza, Italy, Argentina and
Vietnam (Abu Elamreen et al., 2006, Cuestas et al., 2005, Nguyen et al., 2004 & Cascio et al.,
2001) .
Our results showed no statistically significant relation between rotavirus infection and parents
education or mother jobs this disagree with other studies in Uganda, and Baghdad that show
significant association between rotavirus infection with education level of mothers (Hussein et
al., 2015 & Nakawesi et al., 2010) .
Also the current study showed that no effect of vaccine application on the percentage of positive
samples with rotavirus in children less than 5 years that attended to hospitals with acute
gastroenteritis this explain by that vaccine may decrease severity and mortality, but not
morbidity, this finding disagree with other studies in Brazil that indicated reduction in prevalence
rate from (11.12%) to (5.07%) after application of vaccine, in Latin America there was a reduce
risk of any severity with rotavirus related gastroenteritis by (65%) and in systemic review
Efficacy against severe rotavirus diarrhea ranged from (90.6%) in the developed region to
(88.4%) in Eastern/ South-eastern Asia, (79.6%) in Latin America and the Caribbean, (50.0%)
in Southern Asia and (46.1%) in sub-Saharan Africa (, Velázquez et al., 2017, Lamberti., 2015&
Assis et al., 2013).
221
6. Conclusions
Percentage of positive samples among children younger than 5 years still nearly the same or
slightly higher than that have been detected in Gaza since 2006. Reflect that no effectiveness of
vaccine in reducing morbidity or infection.
7. Recommondations
Other studies needed to evaluate the affectivity of it against mortality and severity factors like
degree of dehydration, fever, vomiting, duration and electrolytes values, and PH that may help
in determination of severity.
221
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116
Improvement of Steam Power Plants Performance Using a Heat
Exchanger
M. Alnahhal*1 , M. Elnaggar2 , and M. Ghazal1
1Department of Refrigeration, Air conditioning and Heating Engineering, Israa University, Gaza, Palestine.
2Laboratory of Refrigeration and Air conditioning, Department of Engineering Professions, Palestine Technical
College, Deir El-Balah, Palestine
.
E-mail: [email protected]
ABSTRACT
The present work focuses on the improvement of the ideal Rankine cycle performance
used in steam power plants. Improving the steam power plant efficiency, or its components
performance is desirable where the absence of renewable energy power conversion systems
and the shortage of conventional fuels sources take place. The present work studies the
possibility of using a counter flow heat exchanger along with the main components of the ideal
Rankine cycle. The proposed counter flow heat exchanger will include the flow of compressed
liquid exiting the pump and the flow of superheated steam exiting the steam turbine. The
advantages of the proposed system which is investigated here include extracting heat through
the heat exchanger which can be added to boiler for superheated steam production and thus
reduce the amount fuel needed. In addition, since the proposed system assumes a superheated
steam at the exit of the steam turbine, so no moisture is expected to form and thus increased
effeciency of the steam turbine will be expected. The presents results show that the amount of
heat extracted through the proposed heat exchanger for diffrent systematic four test cases of
differet exits' temperatures of steam turbines and heat exchanger is systematically increasing
when the those temperatures are decreasing suggesting the advantage of the proposed heat
exchanger. In addition, however the proposed system eliminated the presence of moisture at the
steam turbine which improve the performance of the steam turbine, a systematic reduction
reduction in the delivered work by the steam turbine.
117
Keywords: Ideal Rankine Cycle; Steam Power Plants; Heat Exchangers in Steam Power
Plants; Steam Turbine Performance Improvement.
118
1. Introduction
Producing electrical energy through steam power plants is considered to be one the reliable
methods that are used to provide electrical energy to domestic, commercial, and industrial
sectors however this method faces some obstacles through generation. These obstacles varies
among plant and fuel initial cost, operating cost, and environmental effects. In addition, the
availability of plant operating fuel forms another challenge to energy authorities due to several
reasons such as cost, transportation, and sometimes-regional political condition (Badr et al.,
1990, Wu et al., 2015, Desai and Bandyopadhyay, 2016). Therefore, solar steam power plant
became a promising solution to overcome above obstacles (Aboelwafa et al., 2018) . Moreover,
steam power plants requires maintenance to their components not only to reduce the
replacement costs but also to maintain constant operating with high efficiency (Wu et al.,
2015). Steam power plant are mostly operated through ideal Rankine cycles. It is well-known
that the overall effeciency of Rankine cycle can be increased through the readjustment of
pressure and temperature of the working fluid i.e. increasing the boiler pressure, increasing the
superheated steam temperature, or lowering the condenser pressure. In addition, the
introduction of some devices such as reheater or regenerator can further increase the overall
thermal effeciency of the plant resulting in ideal reheat Rankine cycle and ideal regenerative
Rankine cycle, respectively (Çengel and Boles 2008, Moran et al., 2010).
Increasing the overall thermal effeciency of steam power plant is always a subject of interest
due to the reasons mentioned at the begining of this introduction and thus many researchers are
always looking to further increase its effeciency and improve its various components
performance (Çengel and Boles 2008).
The over thermal effeciency of steam power plant is the ratio of the difference between the
work delivered by the turbine and consumed by the pump to the heat added in the boiler, thus
higher thermal effeciencies are suspected mainly in the presence of larger amounts of
mechanical energy output or smaller amounts of thermal energy input having in mind that the
work consumed is relatively smaller amount in comparison to work delivered by steam turbine.
Therefore, several systems have been proposed theoretically and others are used in practice
such as ones that use multiple steam turbines, reheater, or regenratos, which attain larger
119
overall thermal effeciencies. But if we look to this issue in an other way, we see that increasing
the overall thermal effeciency we need to have larger heat to be added to boiler i.e., larger qin ,
which conradicts with the definition of the thermal effeciency. İn fact, at a specified boiler
pressure, highest temperature at the boiler exit (steam turbine inlet) indicates higher enthalpy
which we would like to convert to work through the steam turbine, and thus theortically
increasing that enthalpy may result in a larger work out put hence steam turbibe effeciency and
overall thermal effeciency of the plant.
Another practice problem that reduces the efficiency of the steam turbine and thus the overall
efficiency of the steam power plant is represented by the excessive presence of moisture at the
steam turbine exit. The excessive presence of moisture at the steam turbine exit erodes the
turbine blades and thus reducing the steam turbine and over all thermal efficiencies. Therefore,
several methods have been introduced to reduce the amount of moisture at the steam turbine
exit; these methods include superheating the steam to high temperatures, or expand the steam in
turbine in two stages and use reheaters (Çengel and Boles 2008). Therefore, in order to improve
the overall thermal effeciency of steam power plant we still may think to:
i) For a specified cycle, find any possible ways to compensate any reduction from the amount
of the heat added in the boiler.
ii) Find means to increase the work delivered by the steam turbibe.
The present work look further to increase the overall thermal effeciency of the ideal Rankine
cycle i.e., decrease heat added in the boiler and/or increase work delivered by steam turbine and
in addition, improve the performance of steam turbine i.e., eliminate the excessive presence of
moisture at the steam turbine exit. The present system in addition to main components of ideal
Rankine cycle (i.e., pump, boiler, steam turbine, and condenser) includes a counter flow heat
exchanger. The introduced heat exchanger will be located in a location where it includes the
flow of the superheated steam that leaves the steam turbine, and the flow of compressed liquid
that leaves the pump. The steam will leave the steam turbine as superheated despite ideal
Rankine cycle where it leaves as saturated mixture i.e. presence of moisture. The heat will be
removed from the superheated steam exiting the steam turbine and added to the leaving
compressed liquuid from the pump throough the proposed heat exchanger. The present system
120
will ensure a better performance of the steam turbine due to the absence of any moisture at the
steam turbine exit thus increase its effeciency, in addition the heat removed from the
superheated steam existing the steam turbine will be added reducing the required heat in the
boiler which is supposed to be produce the superheated heated at a specified temperature and
pressure. The present system is investigated to highlight any advantages that can be associated
with presence of the heat exchanger e.g. reducing amount of fuel needed in the boiler hence
reduce fuel cost, increase the steady state efficiency of the boiler.
It is may be of interest to note that the present system can accompany any of the modified ideal
Rankine cycles e.g. reheat or regenrative (not studied yet) hence higher efficiency with better
components performance may be maintained. The expected improvement of ideal Rankine
performance using this system will be demonstrated and explored through the evalulation of
heat that can be extracted in the heat exchanger, work delivered by steam turbine and over all
thermal effeciency systematically for four test cases that have different temperatures at the exits
of both steam turbine and heat exchanger.
2. Investigation methodology
In the present investigation the a counter heat exchanger is added to the simple Rankine cycle
main components i.e., pump, boiler, steam turbine, and condenser as shown in Fig. 1.
Figure 1: The ideal RC components with a heat exchanger
121
The introduced heat exchanger will include the flow of the working fluid (water) that exits the
steam turbine in superheating state and the subcooled water that leaves the pump and that exits
from the pump in compressed liquid state in such a way that the heat exchanger will grantee the
extraction of heat from the superheated steam that leaves the steam turbine and added it to the
compressed water from the pump. As consequences of that compressed water from the pump
will be heated in the same amount of the heat extracted from the superheated steam and thus
the amount of heat in put to the boiler will reduced of that amount extracted. It should be
mentioned that the heat extraction process in heat exchanger will be undertaken in a pressure
between the exit steam turbine pressure and the condensation pressure. In other hand, the state
of the working fluid that leaves the turbine will be superheated and thus ensure that no moisture
is present at the steam turbine exit where its presence can erodes the steam turbine blades and
thus reduce the steam turbine efficiency.
The modified simple Rankine cycle with the heat exchanger investigated in this paper is shown
represented on T-s diagram as shown in Fig. 2.
Figure 2: The modified ideal RC with a heat exchanger on T-s diagram
For clarity purpose and more insight to the present proposed system, the characterstics of all
states shown in Fig. 2 are included in table 1 describing the their locations and phases.
122
Table 1: The inlet and exit characteristics of proposed system's components
State Location and device Water Condition (or phase)
1 Pump inlet, Condenser exit Saturated liquid
2 Pump exit, Heat exchanger inlet Compressed liquid
3 Heat exchanger exit Compressed liquid
4 Steam turbine inlet Superheated steam
5 Steam turbine exit, Heat exchanger
inlet Superheated steam
6 Heat exchanger exit, Condenser inlet Superheated steam
Going back to Fig.2, we should note that the state 6 (i.e., heat exchanger exit) must be higher
and (thus its temperature) than the state 2 (i.e., pump exit) and thus its temperature. In fact, if
we consider opposite condition, the heat exchanger will subtract heat from the compressed
water adding it to the superheated steam that exit the steam turbine and that’s why T6 must be
higher than T2. In addition, state 5 (i.e., turbine exit) must be higher (thus its temperature) than
the state 3 (i.e., heat exchanger exit ) and thus its temperature to ensure that the heat exchanger
is working effectively i.e., that’s extracting the maximum possible heat from expanded
superheated steam i.e., T3 < T5. It should be noted that the other states 1, 2, and 4 are similar to
ones found in simple ideal Rankine cycle.
3. Mathematical relations and computations
The investigation is carried out by supposing that an ideal Rankine cycle is operating between
condensation pressure of 100 kPa and boiler pressure of 2.5 MPa and the temperature of
superheated steam that enters the steam turbine is 400 oC. The mathematical relations can be
found in reference 3.
The mathematical computations which performed here are first made baed on simple ideal
Rankine cycle (i.e., no heat exchanger) as presented on T-s diagram shown in Fig. 3 and thus
the mathematical computations have led to the following results:
123
State 1
P1=100 kPa (saturated liquid)
h1=hf @100kPa= 417.51 kJ/kg
v1=vf@100kPa =0.001043 m3/kg
s1=sf@100kPa =1.3028 kJ/kg.K
T1= 99.97oC
State 2
P1=100 kPa
P1=2.5 MPa
v1=vf =0.001043 m3/kg
s2=s1@100kPa = 1.3028 kJ/kg.K
wpump= v1(P2 – P1)
= 0.001043 (2.5 x103 – 100)
=2.5032 kJ/kg
Wpump = h2 –h1
h2 = wpump + h1
= 2.5032 kJ/kg + 417.51
= 420.01 kJ/kg
T2= 100oC
State 3
P3=2.5 MPa (superheated steam)
T3= 400oC
h3=3240.1kJ/kg
s3=7.0170 kJ/kg.K
T3sat= 223.95oC
Cycle characteristics
qboiler,in = h3 – h2 = 2820.09 kJ/kg
124
qcondenser,out= h4 - h1 = 2128.82 kJ/kg
wturbine=h3 – h4 = 693.77 kJ/kg
wnet = wturbine - wpump = 691.26 kJ/kg
ηth, ideal = wnet / qboiler = 24 %
Figure 3: The ideal Rankine cycle on T-s diagram
The previous calculations for states points 1, 2 and 3 in simple Rankine cycle will remain the
same while evaluating the use of the proposed heat exchanger holding notations 1, 2, and 4,
respectively. Based on this suituations, missing properties are that on points 3, 5, and 6 which
are computed accoriding to the following relations and assumptions.
State 6
P6=100 kPa (saturared liquid), and T3 = 100 oC
T6a= (T3 + na) where na = 50 oC [assumption]
= 100 +50 = 150 oC
h6a = 2776.6 kJ/kg (superheated steam)
T6b= (T3 + nb) where nb =100oC [assumption]
= 100 +100 = 200 oC
h6b = 2875.5 kJ/kg (superheated steam)
T6c= (T3 + nc) where nc = 150 oC [assumption]
= 100 +150 = 250 oC
h6c = 2974.5 kJ/kg (superheated steam)
125
T6d= (T3 + nd) where nd = 200 oC [assumption]
= 100 +200 = 300 oC
h6d = 3074.5 kJ/kg (superheated steam)
State 5
S5=7.0170 kJ/Kg.K &
T5 = (T6+n), where n=50 oC [assumption]
T5a= (T6a + n)
= 150 +50 = 200 oC
h5a = 2855.8 kJ/kg (superheated steam)
T5b= (T6b + n)
= 200 +50 = 250 oC
h5b = 2950.4 kJ/kg (superheated steam)
T5c= (T6c + n)
= 250 +50 = 300 oC
h5c = 3046.3 kJ/kg (superheated steam)
T5d= (T6d + n)
= 300 +50 = 350 oC
h5d = 3141.9 kJ/kg (superheated steam)
State 3
Thermodynamic balance in the heat exchanger is undertaken to find
h3,Mathematically, we have h5 + h2 = h3 + h6, then: h3 =(h5+h2) - h6
h3a= (h5a+h2) - h6a = 499.21 kJ/kg
h3b= (h5b+h2) - h6b = 494.91 kJ/kg
h3c= (h5c+h2) - h6c = 491.81 kJ/kg
h3d= (h5d+h2) - h6d = 487.41 kJ/kg
The heat extracted through the heat exchanger from the suprheated steam that exits the steam
turbine is equal to the heat added to the compressed liquid that leaves the pump i.e., qheat exchanger
= h3-h2 = h5 – h6. The amount of heat that extracted from superheated steam for various cases
are given below:
126
qheat exchanger,a = h3a – h2 = 79.2 kJ/kg
qheat exchanger,b = h3b – h2 = 74.9 kJ/kg
qheat exchanger,c = h3c – h2 = 71.8 kJ/kg
qheat exchanger,d = h3d – h2 = 67.4 kJ/kg
Then the amount of heat added to the bioler based on the presence of the heat exhchanger will
be the difference between the enthalpies of boiler exit and heat exchanger exit i.e., qboiler in, new =
h4 – h3. The heat added for different cases investigated here are given below:
qboiler in, new,a= h4 - h3a = 2740.89 kJ/kg
qboiler in, new,b= h4 - h3b = 2745.19 kJ/kg
qboiler in, new,c = h4 - h3c = 2748.29 kJ/kg
qboiler in, new,d = h4 - h3d = 2752.69 kJ/kg
The workdone per kg by the steam turbine based on the various condition studied will be
difference between the heats at the inlet and exit of the turbine i.e., wturbine,new = h5 – h6.
wturbine,new,a = h4 – h5a = 384.3 kJ/kg
wturbine,new,b = h4 – h5b = 289.7 kJ/kg
wturbine,new,c = h4 – h5c = 193.8 kJ/kg
wturbine,new,d = h4 – h5d = 98.2 kJ/kg
Therefore, the over all thermal effeciency of the proposed system at different investigated cases
are:
ηth,new,a = (wturbine,new,a –wpump) / qboiler in, new,a = 13.9 %
ηth,new,,b = (wturbine,new,b –wpump) / qboiler in, new,b = 10.4 %
ηth,new,c = (wturbine,new,c –wpump) / qboiler in, new,c = 6.9 %
ηth,new,d = (wturbine,new,d –wpump) / qboiler in, new,d = 3.5 %
127
4. Results and discussion
Figure 4 shows the amount of heat extracted by the heat exchanger from the superheating steam
that exits the steam turbine. As we can see the highest heat extracted is associated with lower
exit temperatures at the steam turbine and heat exchanger; the amount of heat extracted through
the heat exchanger is 79.2, 74.9, 71.8 and 67.4 kJ/kg, which represent a reduction of 2.8, 2.6,
2.5, and 2.4 % of the total heat added to the boiler of the ideal Rankine cycle (i.e., 2820.09
kJ/kg) corresponding to steam turbine exit temperatures and pressures of 200, 250, 300, and
350 oC, and 0.5, 0.8, 1.2, and 1.8 MPa and heat exchanger exit temperatures of 150, 200, 250,
and 300 oC, respectively.
Figure 4: Heat extracted by the heat exchanger for various test cases
It is may be noted that the highest heat extracted through the heat exchanger is obtained at the
lowest temperatures at the exits assumed temperatures at steam turbine and heat exchanger. To
find reasons of such trends first let see table 2 which shows the pressures at the steam turbines
exit with its saturation temperatures and the heat exchanger exit pressure which constant.
Table 2: The various cases investigated with their characteristics
C
a
s
e
Amount of
heat
extracted (%)
Steam
turbine
exit
pressure
(MPa)
Saturation
temperature at
steam turbine
exit pressure
(oC)
Heat exchanger
exit pressure
(MPa)
A 2.8 0.5 151 0.1
B 2.6 0.8 170 0.1
66
68
70
72
74
76
78
80
dba
Hea
t ext
ract
ed
by h
eat e
xcha
nger
, kJ/
kg
Investigated cases
Heat extracted by heat exchanger
c
128
C 2.5 1.2 188 0.1
D 2.4 1.8 206 0.1
In fact examining table 2 doesn’t give acceptable reasons for such trends since the status of
steam is superheated at both steam turbine and heat exchanger exits and thus having lowest
saturation temperature for case "a" doesn’t explain why have the highest heat extracted there
because the steam will leave both steam turbine and heat exchanger as superheated where no
flashing is to occur at that lowest saturation temperature. The only possible which may be used
to explain such increase in heat extracted i.e., case a at the heat exchanger is lowest exit
temperature at the heat exchanger exit which is associated with case "a" i.e., 150 oC in
comparison to other cases of higher temperature which suggest that at the lowest temperature a
larger of thermal energy is extracted when the exit heat exchanger temperature is maintained.
Based on the present results as shown Fig. 4, the amount of heat extracted by the heat
exchanger can reduce the the amount of heat supplied to the boiler. Figure Fig. 5 higlighs show
the amount of heat that needed to be added in the boiler for ideal case with no heat exchanger
and at various cases with heat exchanger where an obvious effect of the presence of the heat
exchanger which can reduce the amount of heat added in the boiler more significantly at lower
exit steam turbine Based on the present results as shown Fig. 4, the amount of heat extracted by
the heat exchanger can reduce the the amount of heat supplied to the boiler.
Fig. 5 higlighs show the amount of heat that needed to be added in the boiler for ideal case with
no heat exchanger and at various cases with heat exchanger where an obvious effect of the
presence of the heat exchanger which can reduce the amount of heat added in the boiler more
significantly at lower exit steam turbine and heat exchanger exits temperatures as was
discussed early.
129
Figure 5: Heat input to the boiler for the ideal case compared to various test cases with heat exchanger
It is may be of intest to note that since the condition of the steam at the steam turbine is
superheated steam at all cases hence no moisture is suspected there and thus better
performances of such systems are expected having in mind the amount of work delivered by
the steam turbine that are associated with such system which can affect the over all thermal
effeciency as it will be investigated in the following figure and sections.
Figure 6: work output by the steam turbine for the ideal case compared to various test cases with heat
exchanger
Work delivered by the steam trubine for the ideal case and for cases with heat exchanger are
graphically represented in Fig. 6. As we can see the steam turbine for the ideal case gives the
highest work output followed by cases a, b, c, and finally d. This is may be expected because in
the ideal cycle with no heat exchanger, the steam exits the steam turbine as saturated mixture
and in this suituation larger range of thermal energy can be converted to mechanical energy.
2700
2720
2740
2760
2780
2800
2820
2840
2860
2880
2900
Ideal dba
He
at
ad
de
d t
o t
he
bo
iler,
kJ/k
g
Investigated cases
Heat added to the boiler
c
100
200
300
400
500
600
700
Ideal dba
Wo
rk o
up
ut
by s
tea
m t
urb
ine
, kJ/k
g
Investigated cases
work output
c
130
But on contrary when the heat exchanger is used, the working fluid exits the steam turbine as
superheated steam where larger thermal energy can be missed and thus converted to work
energy as compared to ideal one. Again the increased amount of work delivered by steam
turbibe in case "a" can be attributed to increased of amount of heat extracted at the heat
exchanger in comparison to other cases as was discussed early (see Fig. 4)
Figure 7 shows the over all thermal effeciencies for the ideal Rankine cycle compared to the
other cases with heat exchanger. As expected the highest is found in the ideal case as it has the
highest work out put followed by cases a, b, c, and d. Improved overall thermal effeciency in
the ideal case can be attributed to higher work delivered by the steam turbine which is
decreasing in other cases investigated with heat exchanger.
0
5
10
15
20
25
30
Ideal dba
Th
erm
al e
ffe
cie
ncy
Investigated cases
Thermal effeciency
c
Figure 7: Thermal effeciency for the ideal case compared to various test cases with heat exchanger
5. Conclusions
The present study investigated the possibility of using a counter flow heat exchanger along the
ideal Rankine cycle main components (i.e., pump, boiler, steam turbine and condenser). Four
cases were investigated at different exit steam turbine and heat exchanger temperatures. The
present thermal analysis revealed that the presence of heat exchanger heat can be extracted and
added in the boiler as was observed by the four cases investigated cases, however, significant
amount of heat can be extracted at lower exit steam turbine and heat exchanger exit
temperature. But on the contrary however the moisture at the exit of steam turbine at all cases
131
was eliminated as steam will be superheat at the steam turbine exit, the amount of work
delivered by steam turbines in the presence of the heat exchanger reduced significantly when
the steam turbine and heat exchanger exit temperatures. Consequently, the overall thermal
effeciency of the proposed system with heat exchanger is less than the ideal case however,
reducing the exit temperatures at the exit steam turbine and heat exchanger can increase it.
132
References
1. Aboelwafa O., Fateen S., Soliman A., and Ismail I. M., A review on solar Rankine cycles:
Working fluids, applications, and cycle modifications, Renewable and Sustainable Energy
Reviews, Vol. 82 (1), pp. 868-885, 2018.
2. Badr O., Probert S. D., and O'Callaghan P., Rankine Cycles for Steam Power-plants, Applied
Energy 36, pp. 191-231, 1990.
3. Çengel Y., and Boles M., Thermodynamics: An Engineering Approach 5th Edition, Mcgraw-
Hill College, 2008.
4. Desai N. B., Bandyopadhyay S., Thermo-economic comparisons between solar steam Rankine
and organic Rankine cycles, Applied Thermal Engineering, Volume 105 (25), pp. 862-875,
2016.
5. Moran M. J. , Shapiro H. N., Boettner D. D., Fundamentals of Engineering Thermodynamics,
7th Edition, Wiley, 2010.
6. Wu X., Shen J., Li Y., and Lee K. Y., Steam power plant configuration, design, and control,
WIREs Energy Environ 2015. doi: 10.1002/wene.161.
133
Synthesis of pure Zinc Oxid (Semiconductor) and ZnO:Ga Nanostructure
for Different Sensing Applications
كمتحسس في تطبيقات النانوي (ZnO:Ga)الزنك )شبه الموصل( النقي والمشوب تحضير أوكسيد
مختلفة
مروة عبد المحسن حسن .*1
افراح كاظم ,1, وهب باسم مهدي1, نزار خلف محان1, اماني عبد الله كميل1, ايمان محي علوان 1, اسماء هادي محمد
2شنشل
الجامعة المستنصرية, كلية العلوم, قسم الفيزياء, بغداد, العراق.1
2وزارة التربية, الرصافة الثانية, ثانوية المتميزيين, حي االدريسي, بغداد, العراق.
Abstract
The research involved the preparation of ZnO and ZnO:Ga by a simple chemical
process and inexpensive materials, namly a hydrothermal method by adding 0.05M of zinc
nitrate and 0.05M of hexamethylenetetramine (C6H12N4) to the cell manufactured for this
purpose. The cell is in a laboratory oven for eight hours at a constant temperature up to 150 oC.
For preparing of zinc oxide impregnated with Ga, 4% gallium nitride Ga (NO3)3.xH2O is added
to the previous prepared solution under continuous stirring effect using a magnetic mixer.
Several effects have been studied in the development of this hydrothermal method, which are
precipitated on the zinc oxide layer as a pre-prepared seed layer by fast thermal oxidation of
zinc metal 250 nm to achieve optimal conditions leading to the best results for applications. The
work also included a study and analysis of the optical and synthetic properties of the prepared
zinc oxide nanostructure. These prepared membranes have been used in the best conditions as
a multi-application sensors: gas sensors where the ZnO:Ga deposited on the basis of quartz
coated with antimony tin oxide as a gas sensor for very dangerous hydrogen gas. The effect of
different concentration of gas on resistance of ZnO:Ga over time has been studied. We also
studied and manufactured sensors that work as solar cells with high efficiency using Iraqi
materials equipped with Al-Mansour State Company and simple conventional devices available
in the local market. In this paper, a mechanical sensor is designed to monitor the salt content
and improve the water quality. Receptors (where the cell is placed between two ends: the first
end represents a piezo segment and the second end represents the ZnO:Ga precipitated on the
134
bases of quartz coated with antimony tin oxide). The range of operating frequencies used in this
research ranges from 1500-20000 KHz. Tests in this research included recording the resonant
frequency at the first rank of all prepared samples and calculating the damping factor as a
function of time.
Keywords: Nanoparticle Oxide, Mechanical Sensor, Zinc Oxide: Gallium, Hydrogen Gas
Sensor, Porous Silicon
الخالصة
بواسطة عملية كيميائية بسيطة (Ga) الخارصين النانوي النقي والمطعم بالغاليوم أغشية أوكسيدتحضير تضمن البحث
0.05Mمن نترات الزنك المائية و 0.05M إضافة( وذلك بhydrothermalدروثيرمل )أيومواد غير مكلفة هي عميلة اله
الخلية المصنعة لهذا الغرض ومن ثم وضع الخلية في فرن مختبري إلى 4N12H6hexamethylenetetramine (C(من
إضافةيتم Gaالمشوب بمادة الخارصين أوكسيد. ولتحضير Co150 إلىلمدة ثمان ساعات عند درجة حرارة ثابتة تصل
O2.xH3)34% gallium nitride Ga(NO التحريك المستمر باستخدام الخالط تأثيرالمحلول المحضر السابق تحت إلى
ذات التركيب السداسي النانوي المحضر بطريقة ألغشيةالعديد من المؤثرات على أنماء هذه ا تم دراسةلقد المغناطيسي.
األكسدةالمحضر سلفا بطريقة (seed layer) كطبقة بذور النمو الخارصين أوكسيددروثيرمل والمرسبة على طبقة أياله
النتائج أفضل إلىلغرض الحصول على الظروف المثلى المؤدية nm 250بسمك الخارصين الحرارية السريعة لمعدن
وكسيدأ ألغشيةية لتطبيقات المتحسسات المختلفة. كما تضمن البحث دراسة وتحليل للخصائص البصرية، والتركيب
الظروف كمتحسسات متعددة التطبيقات: أفضلالمحضرة في ألغشيةوقد استخدمت هذه ا النانوية المحضرة،الخارصين
المطعم بالغاليوم والمرسبة على قواعد الكوارتز المطلية الخارصين أوكسيد أغشيةحيث تم استخدام ؛متحسسات غازية
تالف اخ تأثيرحيث تم دراسة ا؛نتيمون كمتحسس غازي لغاز الهيدروجين الخطير جد أوكسيد القصدير المشوب باألبمادة
الغشاء المحضر ذو التركيب أظهراليوم مع مرور الزمن وقد غالمطعم بالالخارصين أوكسيدتركيز الغاز على مقاومة لغشاء
مسية ا شيمتحسسات تعمل كخأل أيضادراسة وتصنيع مث عالية للغاز وبدرجة حرارة الغرفة،السداسي النانوي تحسسية
تقليدية بسيطة متوفره في السوق ، وأجهزةذات كفاءة عالية باستخدام مواد عراقية مجهزة من شركة المنصور العامة
المحلية.
المطعم بالغاليوم على قواعد السيلكون المسامي. الخارصين وكسيدعملية ترسيب أل إجراءتمت عملية التصنيع من خالل
لى حيث يمكن الحصول عاألمالح وتحسين جودة المياه، تم تصميم متحسس ميكانيكي لغرض مراقبة نسبة هذا البحث وفي
( من خالل استخدام محول يقوم بنقل الموجات الميكانيكية في خلية تحتوي على الكهروضغطيةالكهرواجهادية ) اإلشارة
لطرف ا بالت )حيث توضع الخلية بين طرفين؛الناتجة عبر مستق إلشارةاالتقاط و، وبالتالي: استالم أ)ماء+ملح بنسبة معينة(
النانوي المطعم بالغاليوم والمرسب على قواعد الكوارتز الخارصين أوكسيديمثل :والطرف الثاني ،يمثل قطعة بيزو األول:
.القصدير المطعم باالنتيمون( أوكسيدالمطلية بمادة
135
وقد شملت الفحوصات في هذا (،(KHz 20000-1500ي هذا البحث فتتراوح بين أما مدى ترددات التشغيل المستخدمة ف
وحساب عامل التخميد كدالة للزمن. ،ى لجميع العينات المحضرةاألولتسجيل التردد الرنيني عند المرتبة :البحث
متحسس غاز الخارصين: الغاليوم،أوكسيد ميكانيكي،متحسس النانوي،الكلمات المفتاحية: أوكسيد الخارصين
السيلكون المسامي. الهيدروجين،
المقدمة
،الموجودة في الهواء الجويأشباه الموصالت للكشف عن تراكيز قليلة للغازات الخطيرة أكاسيداستخدمت المتحسسات الغازية:
وب والمعتمدة على وجود العي النانوي شبه الموصل أوكسيدصاص الغازات على سطح مد ميكانيكية الكشف على عملية امتحيث تعت
على سطح الغشاء التي تعمل على O-2 أيوناتوعلى التركيب البلوري للغشاء حيث تظهر ذرات األوكسجين على شكل ،الحجمية
مصدر لقنص جزيئات الغاز الممتزة على سطح أيضاوتمثل ،تكوين طبقة استنزاف ونمو حاجز الجهد عند الحدود الحبيبية
.[7-1] المتحسس
لسطح عند الحدود الحبيبية سوف الموجودة على ا O-2األوكسجين أيوناتن ( فإtype-nشبه موصل من نوع ) إلىبالنسبة
سوف يقل تركيز حامالت الشحن وينمو حاجز الجهد ليعرقل مرور حامالت الشحنة فعند تعريض الغشاء تمتص من قبل الغاز، أي:
األوكسجين الموجودة على السطح عند الحدود الحبيبية وبذلك سوف يقل يوناتأل ( يحصل امتصاص2NO) :غاز مؤكسد مثل إلى
2Hغاز مختزل مثل ) إلىما في حالة تعريض الغشاء أ ،ن التوصيلية تقلأي: إ ،تزداد مقاومة الغشاء ت الشحنة، أي:تركيز حامال
،S2H يقل حاجز الجهد أي: ،سوف يزداد تركيز حامالت الشحنة أي: ،صة على السطح سوف تقلأيونات األوكسجين الممت( فأن
.[10-7] تزداد التوصيلية :أي ،مقاومةالفبذلك تقل
إذ تتكون هذه ،(p-nالشمسية هي في الحقيقة عبارة عن مساحة كبيرة من ثنائيات اتصال ) الخالياالشمسية: إن أغلب الخاليا
التي nوفي لحظة اتصال هاتين المادتين تندفع اإللكترونات من المادة نوع من وصل مناطق نوع سالب ونوع موجب،الثنائيات
،nالتي تحيط بها الفجوات باتجاه المادة نوع pما الفجوات فإنها سوف تندفع من المادة نوع ، أpتفيض باإللكترونات نحو المادة
.[15-11] وذلك بسبب االنتشار لكي تمأل الفراغات المتكونة
ولكن بعض معها،( مع الفجوات المندفعة وتتحد head-on) كترونات المتحركة سوف تتصادم تصادما رأسيان بعض اإللإ
وذلك ألن محاوالت اإللكترونات سوف تحبط بوجود المجال ،pاإللكترونات تكون قادرة على أن تنفذ بمسافة قليلة داخل المادة نوع
.[19-16]الكهربائي
( ألن كثافة الناقالت المتحركة تتناقص في منطقة depletion regionبمنطقة االستنزاف أو النضوب )تسمى منطقة االنتقال
. [22-20] االنتقال إذ يمكن القول بأن منطقة االنتقال تستنزف الناقالت المتحركة
136
ت وهذه الشحنا ونا سالبايأ pفي حين تترك الفجوات في جانب نوع ونا موجباأيتترك خلفها nن اإللكترونات في جانب نوع إ
وتتكون بذلك حالة التوازن ،يعارض اتجاه حركة االنتشار الطبيعي لإللكترونات والفجوات المتخلفة تحدث مجاال كهربائيا
الحراري وفي هذه الحالة سوف يتطابق مستوى فيرمي للمادتين.
يستخدم فيه مواد معينة لها خاصية توليد (device) ، وهو جهازأيضا بالمجس الكهروضغطيالمتحسسات الميكانيكية: ويعرف
:وهي ،، وهذه المواد مصدرها )تحمل صفات( مجموعتين أساسيتينئي عند تعرضها للضغط أو اإلهتزازالجهد الكهربا
وتعتمد هذه المواد في عملها على مبدأ الكهروضغطي، ) الكريستال )مادة الكوارتزو (PZT ceramic) السيراميك
Piezoelectricطاقة كهربائية والعكس صحيح، هذه الظاهرة عرفت إلىحيث تقوم بتحويل الطاقة الميكانيكية ؛
عندما السيليكون( للضغط أو لالهتزاز أو أوكسيدفعند تعرض بلورة الكوارتز ) ثاني piezoelectricity بالبيزوكهربائية
عرض بلورة الكوارتز لضغط كهربائي، فإنها وبالعكس ففي حال ت تصطدم بها موجات صوتية فيتولد عنها جهد كهربائي ،
وقيمة الجهد الكهربائي الناتج من البلورة تظام والدقة العالي، ، هذا االهتزاز والتذبذب يتسم باالنتتذبذب وتهتز بتردد معين
د الضغطات أو االهتزازات الحاصلةيتوقف على مقدار هذا الضغط ، بينما يتوقف تردد وشكل الموجة الكهربائية الناتجة على عد
إذا ما تم الضغط على سطح المادة بقوة فسوف يحدث انفصال للشحنات ، وعلى مقدار هذا الضغط وطبيعته أيضاو ،في زمن معين
-23] نتيجة لهذا االنفصال فسوف ينتج فرق جهد كهربائي بين طرفي المادةا عبر الشبكة البلورية للمادة، والكهربائية عنه
28].
137
العملي الجانب
التبلور أحاديةنتيمون ورقائق السليكون القصدير المطعم باأل أوكسيدفي هذا البحث تم تقطيع قواعد الكوارتز المطلية بمادة
حيث تم ؛سم (1.5×1.5)قطع متساوية ال تتجاوز إلى( 20.02Ω/cm-0.01( من نوع المانح ذات مقاومية )100وباتجاهية )
دقيقة لغرض 15وني مع جهاز الذبذبات الفوق الصوتية ولفترة زمنية مقدارها أياستخدام كحول الميثانول والماء المقطر الال
المواد العالقة بسطح العينات. إزالة
حيث يوضع السليكون ؛(1)مبين في الشكل رقم هو خلية خاصة كما المسامي بواسطةتتم عملية تحضير رقائق السليكون و
مل من حامض 1ثانول مع يمل من مادة كحول األ4 مل من محلول متكون من 5نود ويغمر ب يعمل كقطب أ الخلية،أسفل في
2mA/cm )50(يتم تمرير تيار ؛دروفلوريك ثم يتم يوضع قطب الكاثود الذي يصنع في الغالب من مادة البالتين النقي حيثياه
مخلفات التفاعل ثم تجفف زالةإل 3المخفف بنسبة % KOH بعد ذلك يتم غسل العينة بمحلول من مادة دقيقة (3:30) بزمن و
الخارصين كطبقة بذور النمو على قواعد الكوارتز أوكسيدشفافة موصلة من أغشيةتحضير . N)2بواسطة غاز النيتروجين )
ة الحرارية السريع األكسدةوقواعد السليكون المسامي باستخدام عملية نتيمونالقصدير المطعم باأل أوكسيدالمطلية بمادة
((RTO ةلغرض المقارن باستخدام تقنية التبخير الحراري في الفراغ المرسبة سلفاالخارصين أغشية أكسدةعن طريق.
من نترات الزنك المائية 0.05M إضافةدروثيرمل بياالخارصين النانوي بشكل قضيب من خالل عملية اله أوكسيدتم تحضير
ومن ثم وضع الخلية في فرن مختبري لمدة ثمان ،الخلية إلى 4N12H6hexamethylenetetramine (C(من M 0.05و
.oC 150ساعات عند درجة حرارة
المحلول المحضر إلى O2.xH3)34% gallium nitride Ga(NO إضافةيتم Gaالزنك المشوب بمادة ال أوكسيدولتحضير
يقية بنقاوة الرق األلمونيوم أغشيةالذهب و أغشيةاستخدمت التحريك المستمر باستخدام الخالط المغناطيسي. تأثيرسابق تحت ال
ومية.األالحصول على االتصاالت ألجل (% 99.999)عالية
كون المسامي المستخدمة في البحث.يا: خلية الس(1)شكل رقم
138
التالية:تضمنت القياسات الجوانب
ير وثم استخدامها في تحض ،الظروف في تحضير الغشاء أفضل: قياسات تتعلق بالغشاء المحضر للوقوف على األولالجانب
المتحسسات ذات التطبيقات المختلفة.
ازية،غقياسات متحسسات :وتشمل ،للمتحسس األداءالجانب الثاني: قياسات تتعلق بالمتحسس المصنع للوقوف على طبيعة
شمسية.متحسسات تعمل كخلية ، ومتحسسات كهرواجهاديةو
المناقشة
سح الما اإللكترونيباستخدام المجهر الخارصين المطعم بالغاليوم أوكسيد ألغشيةتم دراسة التركيب الكيميائي للسطح
(FESEM) المرسبة ذات توزيع منتظم نانوي بشكل نانو رود ) ألغشيةبأن التركيب السطحي ل أظهرحيث ؛(Nano rod
.(2)رقم األشكالمبين في هو كما (Hexagonal wurtzite) ذات التركيب السداسي المتراص ZnO ألغشية
139
)(SEMاإللكتروني.الخارصين المطعم بالغاليوم من خالل قياس الماسح وكسيديوضح التركيب السداسي النانوي أل :(a) (2)شكل رقم
(SEM). اإللكترونيالخارصين المطعم بالغاليوم من خالل قياس الماسح أوكسيديوضح التحليل الكيميائي لعناصر :(2) (b) شكل رقم ش
ة الغرفة لمدى طول موجي يتراوح الخصائص البصرية تمت دراستها بوساطة قياس طيف االمتصاصية عند درجة حرار
ن االمتصاصية النتائج بأت أظهر. حيث (4)، (3)مبين في الشكل رقم هو كما كدالة للعدد الموجي (4000nm – 400)من
ت ظهرأكما ،مما جعلها مالئمة لتطبيقات المتحسسات المختلفة ،الخارصين المطعم بالغاليوم عالية أوكسيدالبصرية لغشاء
.(n-type)المشوبة والنقية من النوع السالب ألغشيةا القياسات الكهربائية، بأن
والعدد الموجي لمعدن الخارصين المرسب بتقنية التبخير الحراري في الفراغ. ،يوضح العالقة بين االمتصاصية :(3)شكل رقم
140
دروثيرمل. يابطريقة اله بالغاليوم المحضرالخارصين المطعم وكسيدوالعدد الموجي أل ،يوضح العالقة بين االمتصاصية :(4)شكل رقم
141
وبكثافة تيار type-(pتم تحضير طبقة السليكون المسامي بطريقة التنميش الكهروكيميائية على شرائح السليكون من نوع )
250 mA/cm الخارصين المطعم بالغاليوم المحضر بطريقة أوكسيدبعد ذلك تم ترسيب غشاء دقيقة، 3:30وزمن
حيث كانت قيمة الكفاءة الكمية للخلية الشمسية المصنعة بحدود متحسس يعمل كخلية شمسية؛رض تصنيع دروثيرمل لغيااله
. (5)مبين في الشكل رقم هو كما جنبيةالشمسية المستوردة األ الخالياا لكفاءة وهي قيمة قريبة جد 8%
دروثيرمل والمرسب على قواعد يابالغاليوم المحضر بطريقة الهالخارصين المطعم وكسيديوضح العالقة بين التيار والفولتية أل :(5)شكل رقم ش
السليكون المسامي من النوع المانح.
الخارصين المطعم بالغاليوم والمرسب على قواعد من الكوارتز المطلية وكسيدة التحسس للمتحسس الغازي ألكفاءوضحت لقد أ
، ومقاومة الزنك المرسب الحبيبي ألوكسيدأنها تعتمد بشكل كبير على الحجم والشكل ؛نتيمونالقصدير المطعم باأل أوكسيدبغشاء
(عند 150-350)ppm مدى التراكيز من الهيدروجين ضمنن المقاومة تقل بزيادة تركيز غاز القاعدة المرسب عليها؛ حيث وجد أ
.(6)كما مبين في الشكل رقم درجة حرارة الغرفة
142
الخارصين المطعم بالغاليوم المحضر بطريقة وكسيدوالزمن عند تراكيز غاز هيدروجين مختلفة أل ،يوضح العالقة بين المقاومية: (6)شكل رقم ش
نتيمون.القصدير المطعم باأل أوكسيدوالمرسب على قواعد من الكوارتز المطلي ب ،دروثيرمليااله
التي shift)زاحة )فان اإل O) 2.7H4(MgSOماء مع الملحمن خالل قياس التردد الرنيني كدالة لسعة الموجة لنموذج ال
kHz 20000-1500قعة بين االمستلمة من النفط الخام تكون ضمن مدى الترددات الو اإلشارةو ،شارة المرسلةتحدث لإل
. Amplitude (Ao) (mVolt)كدالة لسعة الموجة
وفقا الموجودة في الماء األمالحرة للمتحسس تمكننا من الكشف عن نسبة يان هذا السلوك يمكن فهمه من خالل عمل معإ
المستلمة من قبل خلية الكوارتز )الوسط الذي يحتوي على الماء+الملح بنسبة اإلشارةو ،شارة المرسلةلإلزاحة الحاصلة لإل
.(7)مبين في الشكل رقم هو كما معينة(
الكهرواجهادية عن طريق استخدام محول يقوم بنقل الموجات الميكانيكية في خلية تحتوي اإلشارة حيث يمكن الحصول على
الناتجة من قبل مستقبالت. اإلشارةو التقاط تالم أعلى )ماء+ملح بنسب معينة( ومن ثم اس
للعالقة التالية: تم حساب قيم عامل التخميد وفقا
h(t) = Ao exp(−t/τ) sin (ω tˊ)
ن حيث أ
(𝐀𝐨) سعة الموجة عند التردد الرنيني
(𝐭ˊ =1/ f), (f) التردد المسلط
(ω = 2πf),
(τ) الزمن الرنيني.
143
الخارصين وكسيدأل kHz 20000-1500ضمن مدى الترددات الواقعة بين يوضح عامل التخميد كدالة للزمن : (7)شكل رقم
المطعم بالغاليوم.
االستنتاجات
النانوية المستخدمة في صناعة المتحسسات المختلفة التطبيقات )متحسس غازي، ZnO:Ga و ZnOأغشيةتحضير -1
الظروف في تحضيرها. أفضلواختيار ،متحسس كهرواجهادي ومتحسس يعمل كخلية شمسية(
ا باعتبارها ذات كلفة زهيدة مقارنة مع المواد واألجهزة المستوردة.جهزة المتوفرة محلي استخدام المواد واأل -2
ا والبخار الناتج من الغاز عند درجة حرارة الغرفة عند متحسنننسنننات سنننريعة االسنننتجابة لغاز الهيدروجين الخطر جد تصننننيع -3
تراكيز مختلفة للغاز.
الكهرواجهادية يمكن الحصول اإلشارةن حيث إ وتحسين جودة الماء، األمالحتصنميم متحسس ميكانيكي لغرض مراقبة نسب -4
م ومن ث ،قوم بنقل الموجات الميكانيكية خالل خلية تحتوي على )ماء+ملح بنسنننننبة معينة(عليها عن طريق اسننننتخدام محول ي
الناتجة. اإلشارةاستخدام مستقبالت تلتقط
ا يخاللا لكفاءة اوهذه نتيجة قريبة جد %8 ما يقارب إلىتصننيع متحسنس عالي الكفاءة الشعة الشمس بحيث وصلت الكفاءة -5
جنبية.الشمسية المستوردة األ
الخارصنننين ذات تركيب سنننداسننني نانوي بشنننكل نانو رود محضنننر أوكسنننيدثاني أغشنننيةن أ اإللكترونيت نتائج الماسنننح أظهر -6
دروثيرمل.يااله :وهي ،ا وغير مكلفةباستخدام طريقة كيميائية بسيطة جد
144
المصادر
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661-683.
2. González, G. B. (2012). Investigating the defect structures in transparent conducting oxides
using X-ray and neutron scattering techniques. Materials, 5(5), 818-850.
3. Krishna, R. M., Hayes, T. C., Krementz, D., Weeks, G., Torres, A. M., Brinkman, K., &
Mandal, K. C. (2012). Characterization of transparent conducting oxide thin films deposited on
ceramic substrates. Materials Letters, 66(1), 233-235.
4. Lewis, B. G., & Paine, D. C. (2000). Applications and processing of transparent conducting
oxides. MRS bulletin, 25(8), 22-27.
5. Suchea, M., Christoulakis, S., Moschovis, K., Katsarakis, N., & Kiriakidis, G. (2006). ZnO
transparent thin films for gas sensor applications. Thin solid films, 515(2), 551-554.
6. Saleem, M., Fang, L., Ruan, H. B., Wu, F., Huang, Q. L., Xu, C. L., & Kong, C. Y. (2012).
Effect of zinc acetate concentration on the structural and optical properties of ZnO thin films
deposited by Sol-Gel method. International Journal of Physical Sciences, 7(23), 2971-2979.
7. Min, Y. (2003). Properties and sensor performance of zinc oxide thin films (Doctoral
dissertation, Massachusetts Institute of Technology).
8. Perednis, D. (2003). Thin film deposition by spray pyrolysis and the application in solid oxide
fuel cells (Doctoral dissertation, ETH Zurich).
9. Chopra K.L., IndrajeetKaur (1983),"Thin Film Device Applications", Plenum Press,
Newyork.
10. PM, R. K. (2007). Spray pyrolysed zinc oxide thin films effects of doping and ion beam
irradiation.
11. Liu, C. Y., Chen, C. F., & Leu, J. P. (2009). Fabrication and CO sensing properties of
mesostructured ZnO gas sensors. Journal of The Electrochemical Society, 156(1), J16-J19.
12. Mahmoud, F. A., & Kiriakidis, G. (2009). Nanocrystalline ZnO thin film for gas sensor
application. Journal of Ovonic Research, 5(1), 15-20.
13. Canham, L. T. (Ed.). (1997). Properties of porous silicon. Institution of Electrical Engineers.
14. Lee, M. K. (2000). U.S. Patent No. 6,103,546. Washington, DC: U.S. Patent and Trademark
Office.
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15. Allaa A. J. H., (2011). "Effect of The Rapid Thermal Treatments on Photodiode Preparation
of Porous Silicon Prepared by Laser Assisted Etching" , MSc. (University of Technology).
16. Lee, M. K., Wang, Y. H., & Chu, C. H. (1997). High-sensitivity porous silicon
photodetectors fabricated through rapid thermal oxidation and rapid thermal annealing. IEEE
journal of quantum electronics, 33(12), 2199-2202.
17. Petrova‐Koch, V., Muschik, T., Kux, A., Meyer, B. K., Koch, F., & Lehmann, V. (1992).
Rapid‐thermal‐oxidized porous Si− The superior photoluminescent Si. Applied physics letters,
61(8), 943-945.
18. Yan, J., Shih, S., Jung, K. H., Kwong, D. L., Kovar, M., White, J. M., ... & Magel, L.
(1994). Study of thermal oxidation and nitrogen annealing of luminescent porous silicon. Applied
physics letters, 64(11), 1374-1376.
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F.G.Al- Huyanie, H.A.Ahmed, Al-Mosel University.
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wood Cliffs, N.J.
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Physicals", Translated by R.R. Basili, M.M.Frjo and R.Y.Yousif, (1st Ed.), Al-Basrah University.
23. Uhlir Jr, A. (1956). Electrolytic shaping of germanium and silicon. Bell System Technical
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Telecommunication Applications" , Msc. University of Rochester, New York.
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Semiconductor", prentice Hall, New York.
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66(5), 2027-2031.
146
Metal Oxide (Quantum Dots) for Gas Sensor Application
المعدن النقطي الكمي في تطبيق المتحسس الغازي أوكسيد
مروة عبد المحسن حسن*1, اسماء هادي محمد1, وهب باسم مهدي1, احسان صالح حسن1, اماني عبد الله كميل1, ايمان محي
علوان*, نزار خلف محان1
الجامعة المستنصرية, كلية العلوم, قسم الفيزياء, بغداد, العراق.1
Abstract
The research included the preparation of zinc oxide (Quantum Dots) with a diameter of 4.33-
6.37 nm as indicated in the results of transmissionelectron (HRTEM) microscopy at different
points of the colloidal (ZnO Q.Ds) produced using Iraqi materials and simple conventional
devices available in the local market. . The manufacturing process was carried out by a simple
chemical process by adding 0.4 g of crystallized zinc acetate to 100 ml of isopropyl alcohol
C3H 9O with constant stirring for a period of 30 minutes under the influence of 70 oC
temperature. The effect of adding sodium sulphide (Na2S) has been studied where the weight
(0.15 grams) was added to the previous solution prepared within the above paragraph and
then added 10 ml of TEA under the effect of constant stirring using a magnetic mixer for five
hours . Then a white colloidal ZnO was obtained and separated using a 6000 rpm centrifuge
for only one hour. The product was washed with distilled water and methanol and dried in a
vacuum oven for 7 hours at a drying temperature of 50 oC. The results of the synthesis
properties of zinc oxidized colloidal quantum dots by X-ray diffraction study showed that zinc
oxide granules were centered towards (102), (110), (103), (200), (112), (201), (101), (100)
and (002). The sensitivity results showed high efficiency of gas sensing under lighting effect.
Keywords: zinc oxide, quantum dot metal, gas sensor
147
الخالصة
كما مبين في نتائج فحص nm 6.37-4.33بقطر يتراوح بين (Quantum Dots)تضمن البحث تحضير أوكسيد الخارصين
Transmissionelectron (HRTEM)microscopy عند نقاط مختلفة من الناتج المحضر colloidal(ZnO Q.Ds)
باستخدام مواد عراقية و اجهزه تقليدية بسيطة متوفره في السوق المحلية. تمت عملية التصنيع من خالل اجراء عملية كيميائية
مع التحريك المستمر O9 H3isopropyl alcohol Cمن ml 100غرام من خالت الخارصين المتبلورة الى 0.4بسيطة باضافة
Sodium sulphide. تم دراسة تاثير اضافة كبريتيد الصوديومCo 70دقيقة تحت تأثير درجة حرارة 30ولفترة زمنية مقدارها
S)2(Na 10غرام للمحلول السابق المحضر ضمن الفقرة اعاله ومن ثم تم اضافة (0.15)حيث تمت اضافة وزن ml منTEA
ابيض colloidal ZnOك المستمر باستخدام الخالط المغناطيسي لمدة خمس ساعات. بعد ذلك تم الحصول على تحت تاثير التحري
لمدة ساعة واحدة فقط. يغسل الناتج بالماء المقطر والميثانول rpm 6000اللون يتم فصلة باستخدام جهاز الطرد المركزي بسرعة
Colloidal. اظهرت نتائج الخصائص التركيبية ألوكسيد الخارصين Co50ساعات بدرجة تجفيف 7ويجفف بالفرن المفرغ لمدة
Quantum Dots (102) ,المنماة من خالل دراسة حيود االشعة السينية بان حبيبات أوكسيد الخارصين قد تمحورت باتجاه,
عالية لتحسس الغاز تحت تاثير . اظهرت نتائج التحسسية كفاءة ,(002) ,(100)(101) (201),(112), ,(200) ,(103) ,(110)
االضاءة.
الكلمات المفتاحية: أوكسيد الخارصين, المعدن النقطي الكمي, متحسس غازي.
148
المقدمة
:Quantum Dots هي نقاط كمية عبارة عن أشباه موصالت تتسم خصائصها اإللكترونية بأنها شديدة القرب واالرتباط بحجم
، وكلما تزايد فرق الطاقة فيما بين أعلى فجوة النطاق وبصورة عامة، كلما تناقص حجم البلورة، كلما كبرتوشكل البلورة المفردة
)حزمة التوصيل(، ومن ثم تكون هناك حاجة إلى المزيد من الطاقة إلثارة النقطة نطاق توصيلوأقل ، مة تكافؤحز (نطاق تكافؤ
Quantum ة فهناك ميزة رئيس. [3-1] ن الطاقة عند عودة البلورة لحالتها المستقرةالكمية، وفي الوقت ذاته، تنبعث المزيد م
Dots في أنه بسبب القدرة العالية على الضبط المسموح بها لحجم :تتمثلcrystal المنتجة، فمن الممكن أن يكون هناك ضبط
غشاء نانوي متدرج متنوعة األحجام ضمن Quantum Dots كما أنه يمكن تجميع ،وتحكم دقيق للخصائص اإلنتاجية للمادة
لموصالت المحددة والمقيدة ، فإن أشباه ا Quantum Dots باإلضافة إلى التقييد في الثالثة أبعاد كلها، ومثال ذلك متعدد الطبقات
:تشتمل على كموميا
: Quantum Wires لثوتسمح باالنتشار الحر في البعد الثا ،تقيد اإللكترونات أو الثقوب في بعدين مكانيينوالتي.
: Quantum Wells والتي تقيد اإللكترونات أو الثقوب في بعد واحد فقط وتسمح باالنتشار الحر في بعدين آخرين.
دي إلى وجود العديد من الطرق إلنتاج وتصنيعفي أشباه الموصالت، مما يؤ excitons هناك العديد من الطرق لتقييد وتحديد
Quantum Dots .وبصورة عامة، تنمو Quantum wires , Quantum wells وQuantum Dots، من خالل
األجهزة النانويةالتي أنتجتها الطرق الكيميائية أو عملية زراعة األيونات، أو في البلورات النانويةاألساليب الفوقية المتقدمة في
.[5-3] القائمة على الفن الطباعة الحجريةالتي أنتجتها أساليب
الجانب العملي
:ينيساستضمن الجانب العملي جزئين أي
اعالي الشفافية باستخدام طريقة كيميائية بسيطة جد Colloidal Quantum Dots)) الخارصين أوكسيد: تحضير ولالجانب األ
غير مكلفة.
الخصائص :وتشمل وكسيدفي تحضير األ الظروف أفضلالمحضر للوقوف على الخارصين أوكسيدالجانب الثاني: قياسات تتعلق ب
ومن ثم تحضير نبيطة مفرق هجين كمتحسس غازي عالي الكفاءة. ،والتركيبية ،البصرية
Colloidal Quantum Dots)) الزنك أوكسيدتحضير
100ضافتها الى المتبلورة وإ الخارصينغرام من خالت 0.4استعمال ml O9H3isopropyl alcohol C مع التحريك المستمر
.درجة 70دقيقة تحت تاثير حرارة 30ولفترة زمنية مقدارها
149
كبريتيد الصوديوم ضافةتم دراسة تأثير إ S)2sodium sulphide (Na0.15 ,0.1) مختلفة أوزانضافة حيث تمت إ ؛ and
تحت تاثير التحريك المستمر باستخدام TEAمن ml 10 ثم تم اضافة ومن لمحلول السابق المحضر ضمن الفقرة اعالهغرام ل (0.2
الخالط المغناطيسي لمدة خمس ساعات.
بعد ذلك تم الحصول على colloidal ZnO 6000 بيض اللون يتم فصلة باستخدام جهاز الطرد المركزي بسرعةأ rpm لمدة
واحدة فقط.ساعة
تجفيفساعات بدرجة 7يغسل الناتج بالماء المقطر والميثانول ويجفف بالفرن المفرغ لمدة Co 50.
تم ترسيب الناتج المتكون على شرائح من السليكون نوع n-type لتحضير مفرق هجين كمتحسس غازي عالي الكفاءة.
النتائج والمناقشة
، وذلك من خالل دراسة حيود المنماة Colloidal Quantum Dotsالخارصين وكسيدالخصائص التركيبية أل أظهرت نتائج
(201),(112) ,(200) ,(103) ,(110) ,(102), قد تمحورت باتجاه الخارصين أوكسيدحبيبات األشعة السينية بأن
الخارصين النقطي الكمي بحدود تتراوح أوكسيدوتم حساب قطر . (1)شكل التحضير شروط أفضلعند ,(002) ,(100)(101)
.nm 6.37-4.33بين
. Colloidal Quantum Dotsالخارصين وكسيد: يوضح حيود االشعة السينية أل(1)شكل رقم
؛ المحضر الخارصين وكسيدشعة السينية ألعلى حيود األ S2Sodium Sulphide (Na) ضافة كبريتيد الصوديومتم دراسة تأثير إ
0.15وزن هو أفضلن ريتيد الصوديوم المضاف للمحلول وأتزداد مع زيادة الوزن لكب (intensity)شدة التبلور نحيث وجد أ
غرام.
150
(Quantum Dots) الخارصين أوكسيدن بأ Transmission electron microscopy (HRTEM)أظهرت نتائج فحص
. (2)مبين في الشكل رقم هو كما غرام 0.15ضافة كبريتيد الصوديوم بوزن عند إnm 6.37-4.33 المحضر بقطر يتراوح بين
مما يجعله يمتلك خصائص كهربائية nm 6.37-4.33المحضر بقطر يتراوح بين (Quantum Dots) الخارصين أوكسيدن إ
الفجوة بين :، أيالطاقةاتساع فجوة )excitons and phonons وذلك بسبب ظاهرة حدوث الحبس الكمي ،وبصرية جديدة
.داخل التركيب النانوي حزمة التوصيل وحزمة التكافؤ(
. Colloidal Quantum Dotsالخارصين وكسيدأل Transmission electron microscopy (HRTEM)نتيجة : يوضح (2)شكل رقم
؛ حيث Photoluminescenceاالضاءة الضوئية وذلك من خالل قياس ،ة الغرفةرالخصائص البصرية عند درجة حراتضمنت
تابعة لالنبعاثات : تكون عرضيةوالثانية، nm 360تابعة لالنبعاثات فوق البنفسجية عند طول موجي :ولى، األمتينيظهرت قأ
.(3)مبين في الشكل رقم هو كما nm 475كما الخضراء عند الطول الموجي
151
. Colloidal Quantum Dotsالخارصين وكسيدالبصرية أل: يوضح الخصائص (3)شكل رقم
بين مهو عند درجة حرارة الغرفة كما ضاءةتحت تاثير اإلالهيدروجين السام غاز ئج التحسسية كفاءة عالية لتحسس ظهرت نتاأ
، مما يجعله متحسس الساممن الغاز سريع مع وجود نسبة قليلة جداللمتحسس ن زمن االستجابة ؛ حيث نالحظ أ(4)في الشكل رقم
ومعتمد في الكشف عن كميات ضئيلة للغازات القاتلة. ،ة عاليةيعمل بكفاء
. التحسسية العالية للكشف عن غاز الهيدروجين القاتل: يوضح (4)شكل رقم
0
100
200
300
400
500
600
700
350 400 450 500 550 600
ph
oto
lum
ine
sce
nce
Wavelength, λ (nm)
0.15 gm (sodium sulphide )
152
االستنتاجات
.6.37nm-4.33بقطر يتراوح بين (Quantum Dots)الخارصين أوكسيدتحضير -1
وذلك بسبب ظاهرة حدوث ،يجعله يمتلك خصائص كهربائية وبصرية جديدة ،(Quantum Dots) الخارصين أوكسيدنتاج إ -2
داخل التركيب النانوي. excitons and phononsالحبس الكمي
.اءة لكميات ضئيلة من الغازات القاتلةالنانوي كمتحسس عالي الكف الخارصين أوكسيداستخدام -3
153
المصادر
1. D. Haranath, SonalSahai, V. Shanker, M. Husain. (2011). "Synthesis of Optically
Transparent and Highly Luminescent ZnO Quantum Dots", Search & Research, Vol-II No.
2 (1-3).
2. Gillian Kiliani,1 Reinhard Schneider, Dimitri Litvinov, Dagmar Gerthsen, Mikhail Fonin,
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