Invertis Journal of Science Technology Vol. 6 No. 1 January-March 2013

Dr. Anil KumarFormer DirectorLaser Science & Technology CentreNew DelhiINDIADr. Ashok KumarHead, Ultrasonics GroupNational Physical LaboratoryNew Delhi - 110012INDIAProf. Ashutosh SharmaPresident & Chief ExecutiveInstitute of Diagnostic Engg.MEI-Charlton, Inc.U.S.A.Prof. D. BahugunaIndian Institute of TechnologyKanpurINDIADr. Bhagwati PrasadAdvisorInvertis UniversityBareillyINDIAProf. George e GeorgiouResearch ProfessorDept. of Electrical EngineeringNJIT, Newark - NJU.S.A.Prof. Kehar SinghIndian Institute of TechnologyNew DelhiINDIAProf. N.U. KhanFormer Dean, Faculty of Engineering & TechnologyJamia Milia IslamiaNew DelhiINDIADr. Krishan LalFormer Director, CSIR-NPL, New DelhiPresidentINSA, New DelhiINDIADr. B.S. PatelFromer Additional DirectorLaser Science & Technology CentreNew DelhiINDIA

Prof. Syed B. QadriU.S. Naval Research LaboratoryWashingtonU.S.A.Dr. P.J. SebastianScientistCentro de Investigacian en Energia-UNAMMEXICOProf. J.N. SinhaBanaras Hindu UniversityVaranasiINDIAProf. R.S. SirohiFormer Vice-ChancellorInvertis UniversityBareillyUttar PradeshINDIAProf. M.S. SodhaFormer DirectorIndian Institute of TechnologyNew DelhINDIADr. Vikram KumarFormer Director,CSIR-NPL, New DelhiProf. EmeritusIIT, New DelhiINDIAProf. Wencai DuProf & DeanCollege of Information Science & TechnologyHainan UniversityCHINADr. Xavier MathewScientistCentro de Investigacion en Energia-UNAMMEXICOProf. M. Zafar IqbalQuaid-i-Azam UniversityIslamabadPAKISTAN

Prof. Kamal Nain ChopraMAIT, GGSIP UniversityNew DelhiINDIA

INTERNATIONAL ADVISORY BOARD

Invertis Journal of Science & Technology

Volume 6 January-March 2013 No. 1

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CONTENTS

Temperature Dependence of the Specific Heat ofPr1-xTbxCoO3(0 ≤ × ≤ 1) 1Renu Choithrani and N.K. Gaur

Energy of Core-Excited States of Sodium Atom 6Maqsood Alam and Anil Kumar

Three Dimensional Periodic Orbits Around the CollinearLiberation Points in the Restricted Problem when Boththe Primaries are Axis Symmetric Bodies 11Anurag and Sanjay Jain

Estimation of Breakdown Strength of Solid InsulatingMaterials in Ambient Medium 16A. Masood, M.U. Zuberi and M.M. Mohsin

Rainfall and Convective Instability 20Satish Prakash, R.K. Giri and Adesh

Optimized Private Searching in World of Web 32Mohammad Danish

The Relation between CMMI and Lean SoftwareDevelopment 39 Jyoti Yadav and Aman Jatain

Women Empowerment and Entrepreneurship 44S.M. Mustafa, N.U.K. Sherwani and Mini Walia

Evalution of Excimer Lasers : A Review 53N.R. Das

PatronUmesh Gautam

Chief EditorZ.H. Zaidi

Mushahid HusainJamia Millia Islamia,

Editors

New Delhi

H.C. RaiGuru Govind Singh -

Editorial AssistanceAnimesh Rai

Indraprastha University,New Delhi

Temperature Dependence of the Specific Heat of Pr1-xTbxCoO3(0≤ × ≤ 1)

1

Temperature Dependence of the Specific Heat ofPr1-xTbxCoO3(0 ≤≤≤≤≤ ××××× ≤≤≤≤≤ 1)

RENU CHOITHRANI* and N.K. GAURDepartment of Physics, Barkatullah University, Bhopal - 462 026 (MP)

*E-mail: [email protected]

AbstractIn the present work, the specific heat of the perovskite-type rare earth cobalt oxide Pr1-xTbxCoO3(0≤ × ≤ 1) hasbeen investigated for the first time using extended rigid ion model (ERIM) after improving modified rigid ionmodel developed by Renu Choithrani et al. Our computed specific heat values with temperature and thecorresponding experimental data by H. Hashimoto et al show same trend of variation for almost all thecompositions (x) of Pr1-xTbxCoO3 with minor deviations at higher temperatures. The system exhibits cubicphase for x = 0 and 0.25 while orthorhombic phase above 0.5, results in the distortion of CoO6 octahedron. Inaddition, we have used ERIM to compute the thermodynamical pproperties whose results are discussed indetail for the present system of cobalt oxides and found in good agreement with the available experimentalresults.

Key words : Specific heat, perovskites, thermodynamic properties, debye temperature, cohesive energy.

1. Introduction

Rare earth perovskite cobaltates have generalformula RCoO3 (where R is a trivalent rare earth)attracted much significance due to not only theinteresting physical properties [1,2] but also thescientific and technological applications [3-5] rangesover a wide variety of fields from sensor devices,gas separation membranes, chemical reactorscatalyst to components in solid oxide fuel cells. Allthe RCoO3 (where R is a trivalent rare earth)systems with a 3D network of corner-sharing CoO6

octahedra show an insulating ground state based onthe diamagnetic low-spin state of trivalent cobaltthat in the limit of fully localized electrons in strongcrystal field corresponds to filled t 2g levels andempty eg states (LS, t6

2ge0

g, S=0). With increasingtemperature they undergo two magnetic transitions

Invertis Journal of Science & Technology, Vol. 6, No. 1, 2013; pp. 1-5

connected with excitations either to the intermediatespin state (IS, t5

2ge1

g , S=1) or to the high spin state(HS, t4

2ge2

g, S=2). The second magnetic transitionis accompanied by an insulator-metal (I-M) transition.It has remained controversial whether this transitionis from a LS to a HS state or to an IS state. Originally,the LS-HS scenario was proposed [6]. In thisframework, the anomalies would be due to anincrease of the thermal population of the HS state.However, it was later claimed that this interpretationis inconsistent with photoemission data [7].

Perovskite-type rare earth cobalt oxide solidsolutions Pr1-xTbxCoO3 (x = 0, 0.25, 0.5, 0.75, and 1)have been prepared by Hashimoto et al. and theyinvestigated their metal-insulator transition behaviorfrom the temperature dependence of electricalconductivity and specific heat. The system exhibitscubic perovskite for x = 0 and 0.25 whileorthorhombic phase above 0.5, results in thedistortion of CoO6 octahedron [8]. The metal-insulator transition temperature of Pr1-xTbxCoO3

determined from both the electrical conductivity

Paper presented at National Conference on Materials forAdvanced Technology (2012), ABV-IIITM, Gwalior (M P).Proceedings published in Invertis Journal of RenewableEnergy; Vol. 2, No. 3 (2012).

Renu Choithrani and N.K. Gaur

2

and specific heat measurements increasedsystematically with increasing x values [8]. It is thusconsidered that the average ionic size of the R-siterare earth elements had an important role on themetal-insulator transition behavior and hence on theelectrical properties. These results suggested thatthe metal-insulator transition temperature could becontrolled by the chemical composition of the solidsolutions of two type rare earth elements containingcobalt oxides. In Section 2, we briefly describe thecomputational techniques used for the present study.The most relevant results obtained for the structural,elastic, cohesive and thermodynamic propertiessuch as the temperature dependence of cohesiveenergy (φ), Restrahalen frequency (ν0), Debyetemperature (θD), Gruneisen parameter (γ) andspecific heat (Cp) of Pr1-xTbxCoO3 compounds arepresented and discussed.

2. Formalism of Extended Rigid Ion Model(ERIM)

The extended rigid ion model (ERIM) has beenrecently developed by Renu Choithrani byincorporating the long-range (LR) Coulombattraction, the short-range (SR) Hafemeister-Flygare(HF) type overlap repulsion effective up to thesecond neighbour ions, the van der Waals (vdW)attraction due to the dipole-dipole (d-d) and dipole-quadrupole (d-q) interactions and zero point energy(ZPE) effects in the framework of modified rigidion model (MRIM) developed earlier by us [9, 10].

The framework of ERIM is derived from thefollowing interionic interaction potential:

φERIM = φMRIM + φZPE

where, φERIM potential is given by

3 4

0

9 1

⎛ ⎞= ⎜ ⎟ −⎝ ⎠

∫θ

θ

DT x

V xD

T e xC R dxe

(2)

(1)

′ ′ ′ ′ ′

−′ ′

′

′β + − ρ +

β − ρ +β − ρ

− −′ ′ ′ ′

′ ′

φ = +

⎡ ⎤⎢ ⎥⎢ ⎥⎣ ⎦

− θ

∑

∑ ∑

1 k k ' kk ' 1

2 kk k kk 2 k k k k k 2

21

ERIM k k kkkk

nb kk exp(r r r / n'

b [ exp(2r r ) / exp(2r r ) / 2

6 8kk kk kk kk D

kk kk

eZ Z r

2

- c r d r +(9/4)K

The symbols involved Eqs. (1) and (2) are thesame as those defined in our earlier papers [9, 10].Here, k(k’) denote the positive (negative) ions andthe sum is taken over all the ions (kk’). βkk' are thePauling coefficients expressed as:

φkk’=1+(zk/nk)+(zk’/nk’)

with zk (zk') and nk (nk') as the valence and numberof electrons in the outermost orbit of k(k’) ions andrkk' and rkk (= rk'k') are the first and second neighbourion separations, respectively. In Eq. (2), the firstterm represents the long-range Coulomb attraction,the second and third terms are the short-rangeHafemeister-Flygare type repulsion operating uptothe second neighbour ions. The fourth and fifthterms in it are the vdW attraction energies due tothe dipole-dipole (d-d) and dipole-quadrupole(d-q) interactions with ckk' and dkk' as thecorresponding vdW coefficients.

The specific heat of the doped manganites atconstant volume (Cv) is calculated using the followingexpression [9]:

at different temperature (T). Here, the notationsinvolved have the same meaning as defined by us[9].

The specific heat at constant pressure (Cp) iscalculated using [9]:

Cp = T V a2 BT + Cv

where a is the linear thermal expansion coefficient,BT is the isothermal bulk modulus, and V is the unitcell volume.

3. Results and Discussion

The input data for Pr1-xTbxCoO3(0≤ × ≤ 1) aretaken from the experimental data [8, 11-17] andthermodynamic relations [9, 10]. Using these inputdata and the vdW coefficients (ckk' and dkk') calculatedusing the expressions [9, 10], the model parameters

(4a)

(4b)


3

Model parameters of Pr1-xTbxCoO3(0≤ × ≤ 1)

Table 1

Compound Co-O Co-O Pr/Tb-O Pr/Tb-O

ρ1 (Å) b1(10-12 erg) r2(Å) b2(10-12 erg)

PrCoO3 0 .319 1.898 0.472 1.543

Pr0.75Tb0.25CoO3 0.314 2.008 0.467 1.660

Pr0.5Tb0.5CoO3 0.310 2.119 0.462 1.777

Pr0.25Tb0.75CoO3 0.305 2.230 0.457 1.894

TbCoO3 0.301 2.341 0.452 2.011

Fig. 1. The variations of specific heat with temperature for Pr1-xTbxCoO3(0≤ × ≤ 1)

400 400 600 700 800 900Temperature, T/K

0.4

0.5

0.6

0.7

Spec

ific

heat

, C/Jg

Kp

-1-1

PrCoO3Expt

Pr0.75Tb0.25CoO3

Pr0.5Tb0.5CoO3

Pr0.25Tb0.75CoO3

TbCoO3 Cal

(r1, b1 and r2, b2) have been evaluated using theirEqs. [9, 10] upto 873 K for Pr1-xTbxCoO3(0≤ × ≤ 1)and listed them in Table 1. Taking the values of modelparameters, the cohesive energy (φ) forPr1-xTbxCoO3(0≤ × ≤ 1) have been computed(Table 2) to test the validity of our model. It is foundfrom Table 2 that the values of the cohesive energy

(φ) are in good agreement with the availablemeasured data for the parent member SmCoO3 [15]of the cobaltate perovskites family. The negativevalues of the cohesive energy indicate the stabilityof the compound. The calculated values ofRestrahalen frequency by the ERIM showsconformity with the available experimental value of

Renu Choithrani and N.K. Gaur

4

Thermodynamic Properties of Pr1-xTbxCoO3(0≤≤≤≤≤x≤≤≤≤≤1)

Table 2

Compound φφφφφ(ev) ννννν0(THz) θθθθθD(K) g

PrCoO3 -142.16 12.18 589 2.19

Pr0.75Tb0.25CoO3 -142.13 12.12 586 2.17

Pr0.5Tb0.5CoO3 -142.10 12.08 584 2.13

Pr0.25Tb0.75CoO3 -142.05 12.04 582 2.11

TbCoO3 -142.01 12.00 580 2.01

(-144.54)15 (12.41)8 (600)8 (2-3)18

u0=12.41 THz [8]. It is also noticed from Table 2that calculated values of Debye temperatures ofPr1-xTbxCoO3(0≤ × ≤ 1) decreases with increasingdoping compositions (x) in Pr1-xTbxCoO3(0≤ × ≤ 1)and found closer to the available experimental valueof ≤D = 600 K [8]. The higher values of Debyetemperatures indicate the presence of higherphonon frequencies in these materials and alsocomparable to the range (300-650 K) [9, 10] oftenfound in perovskite compounds. The values ofGrüneisen parameter for Pr1-xTbxCoO3(0≤ × ≤ 1))lies in between 2 and 3 as reported by Dai et al [18](Table 2). The specific heat (Cp) curve of Pr1-

xTbxCoO3(0≤ × ≤ 1) obtained using ERIM is in goodagreement with the experimental curve as observedby Hashimoto et al [8] (Fig. 1). It is interesting tonote from Fig. 1 that both the present modelcalculated specific heat values and the experimentalspecific heat values [8] increase linearly withtemperature indicating the display of phononiccontributions (~T3) in Pr1-xTbxCoO3(0≤ × ≤ 1).Further, the existence of the peaks in specific heatresults suggested that these compounds undergometal-insulator transition [8]. The broad peaks ofCp curves for x = 0.0 to 1.0 found to shift to thehigh temperature side with increasing x values.These features are exhibited by both theexperimental and theoretical results.

4. Conclusion

Specific heat and thermodynamical propertiesof Pr1-xTbxCoO3(0≤ × ≤ 1) have been presented inthe present work. The computed results by ERIMare in closer agreement with the availableexperimental data. This reveals the suitability andappropriateness of ERIM for the Pr1-xTbxCoO3(0≤ × ≤ 1) materials. Some of the results are,probably, being reported for the first time and henceour comment on their reliability are restricted untilthe report of experimental data on them. Presently,these values are of academic interest and they canserve as guide to the experimental workers in future.

Acknowledgement

Renu Choithrani would like to thank the Scienceand Engineering Research Board, Department ofScience and Technology (DST), Government of India,New Delhi for providing the financial assistance andthe Fast Track Young Scientist Award.

References

[1] Z. Ropka and R. Radwanski, Phys. Rev., B67(2003) 172401.

[2] Y. Kobayashi, T. Nakajima and K. Asai, J. Magn.Magn. Mater., 83 (2004) 272.


5

[3] J.S. Park, K.K. Yu, H.K. Lee, H.R. Bae, Y.P. Leeand V.G. Prokhorv, J. Korean Phys. Soc., 46(2005) S201.

[4] H. Chang, C.L. Chen, T. Garrett, X.H. Chen,X.D. Xiang, C.W. Chu, Q.Y.Zhang and C.Dong, Appl. Phys. Lett., 80 (2002) 4333.

[5] V.G. Prohkorov, Y.P. Lee, K.W. Kim, V.M.Ishchuk and I.N. Chukanova, Appl. Phys. Lett.,80 (2002) 2352.

[6] J.B. Goodenough, J. Phys. Chem. Solids, 6(1958) 287.

[7] M. Abbate, J.C. Fuggle, A. Fujimori, L.H.Tjeng, C.T. Chen, R. Potze, G.A. Sawatzky,H. Eisaki and D. Uchida, Phys. Rev., B47(1993) 16124.

[8] H. Hashimoto, T. Kusunose and T. Sekino, J.Alloy Compd., 494 (2010) L3.

[9] Renu Choithrani, N.K. Gaur and R.K. Singh, J.Alloys Compd., 480 (2009) 427.

[10] Renu Choithrani and N.K. Gaur, J. Comput.Mater. Sci., 49 (2010) 107 and referencestherein.

[11] K. Knizek, J. Hejtmanek, Z. Jirak, P. Tomes, P.Henry and G. Andre, Phys. Rev., B79 (2009)134103.

[12] M. Itoh, M. Mori, S. Yamaguchi and Y. Tokura,Physica B902 (1999) 259.

[13] Y.Q. Jia, J. Solid State Chem., 95 (1991) 184.[14] Svein Stølen, Fredrik Grønvold, Hendrik

Brinks, Tooru Atake and Hideki Mori, J. Chem.Thermodynamics, 30 (1998) 365.

[15] M.A. Farhan and M.J. Akhtar, J. Phys.: Condens.Matter, 22 (2010) 075402.

[16] M.Tachibana, T. Yoshida, H. Kawaji, T. Atakeand E.T. Muromachi, Phys. Rev., B77 (2008)094402.

[17] T. Arima, Y. Tokura and J.B. Torrance, Phys.Rev., B48 (1993) 17006.

[18] P. Dai, J. Zhang, H.A. Mook, S.H. Lion, P.A.Dowben and E.W. lummer, Phys. Rev., B54(1996) R3694.

Maqsood Alam and Anil Kumar

6

Energy of Core-Excited States of Sodium Atom

MAQSOOD ALAM* and ANIL KUMARDeptt. of Applied Sciences, Al-Falah School of Engineering &Technology, Dhauj, Faridabad-21004 (Haryana)


AbstractThe electron impact excitation of Na atoms is important for modeling of low temperature Plasma and gases ofatom and molecules. There are many theoretical and experimental results for the first excited state but littleinformation is available for excitation of higher states. We are concerned with the ground state of the np levelof Sodium (Na) (n=3) to higher state. We present here the energy of many shells of Sodium (Na) atom alongwith other reliable published results. The data has been compared with available results. The excitation crosssection to the resonance level of Sodium has been shown. The scaled Born (PWBA) results are in very goodagreement with available results. It has been observed that a few high level results are satisfactory. Theexcitation to the further higher states results varies sharply.

Keywords: Excitation, Resonance, potassium, ionization potential, Genetic Programming, Collision, Scattering, Dipole Polarisation

1. Introduction

There is an increasing interest in the innershellexcitation of alkali and alkaline earth metals. TheFunction of distorted wave Born approximation nextto the Plane Wave Born Approximation (PWBA) isused. The Asymmertic Green FunctionApproximation (AGFA) integral with availableexperimental observation and other theoreticalresults are taken into consideration. The AGFAexhibits resonance behavior near threshold whereasPWBA is significantly different in nature qualitatively.The inner shell excitation plays very significant rolein explaining the structure observed in ionizationand total cross section by electron-impact .Therelation with automisation to the direct ionizationprocess is very significant in alkali like metal atomsWe have applied Asymptotic Green function usedfor lower and intermediate energy regions. PWBAis not valid in low and intermediate energy regionbut it is valid in high energy range. From the last

Invertis Journal of Science and Technology, Vol. 6, No. 1, 2013 ; pp. 6-10

four decades there has been much interest in theelectron atom collision process. The works remainconcentrated on the elastic collision; scattering andthe excitation of the lowest energy level. The totalcollision cross sections have been estimated bydifferent experimental groups. The classical modelof polarization was first used by Bierman et al [1]The origin of core polarization picture may be tracedeven to semi classical study of sodium atom byHeisenberg [2]. J Migdalek and W.E. Baylis [3]proposed to introduce cut off function directly intoexpression for the effective electric field E, producedby valance electron. The BE f scaled estimated resultof excitation of the resonance line of sodium hasbeen shown in Figs. 1 and 2. The convergent closecoupling (CCC) calculations of Bray [4] are in goodagreement with Phelps et al [5]. Their result showsthat optical excitation from higher level calculationtransition probability is in good agreement withexperimental results. Our results are in goodagreement with Enemark and Gallagher [6]. The


7

(2)

(3)

(4)

(5)

polarization of the core electron by the valanceelectron is important in sodium and other alkali metalatoms. The core polarization effect is not verynoticeable for sodium than potassium by Kim [7].The BE scaling alone or in combination with f scalingtransformed PWB cross section for dipole allowedand spin allowed excitation into reliable cross sectioncomparable to the convergent close coupling (CCC)it is also known as accurate experiment. We haveused the accurately calculated f value of Siegel elal[8] for the scaling of Na and value from silvercalculation Migdalek and Kim [9] for the f scale forthe potassium. These calculated values rather thanthe experimental values have been used because theyare available for the fine structure component. ForNa the experimental f value have been shown in thefigures. The measurement of Filippov and Prokofiev[10] for n = 3 to n = 8, normalize to 3p. The 3s -3p measurement of Volz el al [11] for n = 9 to n =24. The Na values are from recent measurement ofNawaz et al [12].

All alkali metal atoms have been subject ofinterest in several theoretical and experimentalinvestigations and in electron atom collision processbecause of their various interesting properties. It issimple structure, low ionization potential varies from3.9 eV to 5.4 eV and larger polarisibility the mosteffective property is existence of resonance line inpresence of electromagnetic spectrum. Geneticprogramming has been used properly by El-Bakryand Radi [13]. The calculations have been performedin the frame work of Genetic Programming (GP)by researcher group of Riolo and Worzel [14].The total collision cross section measured orestimated by team group Surdutovich et al [15]for electron-impact of Na atom. The Geneticprogramming has been running based on the totalcollisional cross section used by Siegel et al [8] anddipole polarizability have been used by Koza et al[16] as input variable to fined the total collision crosssection of scattering of electron.

2. Theory

The first Scaling method, the BE replace theincident energy A in the denominator of PWB cross

(1)

section, therefore expression can be given by

The Entire cross section by ratio of an f value tothe less accurate f value calculated by unsealed PWBcross section

The function fsc represent Single configuration andfaccu give more accurate value obtained fromcorrelated Wave function with core polarization.The calculation of f value are closer to accurateexperiment, therefore BE and f scaling may beapplied

The complete quantum approach to the corepolarization effect was presented by Bottcher andDalgarno[17] and Magdalek and Baylis[3] proposedto introduce Electric field E produced by a valenceelectron at the core.

The represent core polarization potential. Wepresent the calculated cross section for Sodium Nain Table -1, which can be extended to higher incidentenergy by using well known bathe approximation.The Asymptotic expression can be given

where a, b & c are dimensionless quantities incidentelectron energy and R Redberg energy

3. Discussion and Conclusion

The excitation and cross section of sodium varies

BE PWBA

A B Cξ ξ = + +

παξ = + + + +

204

( ) ln accuAstmptotic

sC

R fA CRA a b

A B C R T f

accuf PWB

sc

ff

ξ ξ

=

ξ ξ

=

accuBEf BE

SC

ff

αν = +

2

32 22d

p

ν p

c

r

r r


8

The excitation cross section of Na lower state to higher state. The excitation energy E is in eVand the value of constant a,b and c are included. The Experimental ionization energy

B=5.139 eV has been used in scaling

Table 1

Table 2

The value of uncorrelated function (fsc) and accurate function f. The BEf-Scaled excitationcross section ξξξξξBEf in A2 as function of incident electron with energy T in ev

Final state 3p 4p 5p 6p 7p 8p 9p 10p 11p

E 2.104E+00 3.753E+00 4.345E+00 4.624E+00 4.778E+00 4.872E+00 4.934E+00 4.976E+00 5.007E+00

fsc 9.650E-01 1.180E-02 1.591E-03 4.480E-04 1.810E-04 9.100E-05 5.200E-05 3.300E-05 2.200E-05

faccu 9.720E-01 1.331E-02 1.980E-03 6.020E-04 2.580E-04 1.340E-04 7.900E-05 5.100E-05 3.500E-05

Const. a 6.241E+00 4.276E-02 4.981E-03 1.319E-03 5.160E-04 2.530E-04 1.430E-04 8.900E-05 5.900E-05Const. b 1.611E+01 5.477E-01 1.396E-01 5.822E-02 3.037E-02 1.802E-02 1.163E-02 7.972E-03 5.714E-03Const. c -2.062E-01 -4.093E-02 -8.539E-03 -3.035E-03 -1.417E-03 -7.780E-04 -4.750E-04 -3.130E-04 -2.180E-04

Final state σBEf σBEf σBEf σBEf σBEf σBEf σBEf σBEf σBEf

100 1.283E+01 3.114E-01 8.077E-02 3.541E-02 1.932E-02 1.188E-02 7.883E-03 5.518E-03 4.020E-03

110 1.198E+01 2.873E-01 7.431E-02 3.254E-02 1.775E-02 1.091E-02 7.239E-03 5.067E-03 3.691E-03

120 1.125E+01 2.667E-01 6.882E-02 3.011E-02 1.642E-02 1.009E-02 6.693E-02 4.684E-03 3.412E-03

130 1.060E+01 2.490E-01 6.409E-02 2.802E-02 1.527E-02 9.383E-03 6.224E-03 4.355E-03 3.173E-03

140 1.004E+01 2.336E-01 5.998E-02 2.620E-02 1.428E-02 8.769E-03 5.816E-03 4.070E-03 2.965E-03

150 9.531E+00 2.200E-01 5.637E-02 2.461E-02 1.340E-02 8.232E-03 5.459E-03 3.820E-03 2.782E-03

160 9.078E+100 2.079E-01 5.318E-02 2.320E-02 1.263E-02 7.757E-03 5.143E-03 3.599E-03 2.621E-03

170 8.669E+00 1.971E-01 5.033E-02 2.194E-02 1.194E-02 7.334E-03 4.863E-03 3.402E-03 2.478E-03

180 8.299E+00 1.971E-01 4.778E-02 2.082E-02 1.133E-02 6.955E-03 4.611E-03 3.226E-03 2.349E-03

190 7.961E+00 1.787E-01 4.547E-02 1.980E-02 1.077E-02 6.613E-03 4.384E-03 3.067E-03 2.234E-03

200 7.652E+00 1.708E-01 4.339E-02 1.888E-02 1.027E-02 6.304E-03 4.179E-03 2.923E-03 2.129E-03

225 6.981E+00 1.538E-01 3.893E-02 1.692E-02 9.199E-03 5.645E-03 3.741E-03 2.617E-03 1.905E-03

250 6.427E+00 1.399E-01 3.531E-02 1.533E-02 8.332E-03 5.111E-03 3.387E-03 2.369E-03 1.725E-03

275 5.960E+00 1.284E-01 3.232E-02 1.402E-02 7.615E-03 4.670E-03 3.094E-03 2.164E-03 1.575E-03

300 5.561E+00 1.187E-01 2.980E-02 1.292E-02 7.012E-03 4.299E-03 2.848E-03 1.992E-03 1.450E-03

350 4.913E+00 1.032E-01 2.580E-02 1.116E-02 6.056E-03 3.712E-03 2.458E-03 1.719E-03 1.251E-03

400 4.409E+00 9.140E-02 2.276E-02 9.833E-03 5.331E-03 3.266E-03 2.163E-03 1.512E-03 1.100E-03

450 4.005E+00 8.206E-02 2.036E-02 8.788E-03 4.762E-03 2.917E-03 1.931E-03 1.350E-03 9.820E-04

500 3.674E+100 7.450E-02 1.843E-02 7.946E-03 4.303E-03 2.635E-03 1.744E-03 1.219E-03 8.870E-04

600 3.160E+00 6.299E-02 1.550E-02 6.672E-03 3.610E-03 2.209E-03 1.462E-03 1.022E-03 7.430E-04

700 2.780E+00 5.464E-02 1.339E-02 5.753E-03 3.110E-03 1.903E-03 1.259E-03 8.800E-04 6.400E-04

800 2.486E+00 4.828E-02 1.179E-02 5.058E-03 2.733E-03 1.672E-03 1.106E-03 7.720E-04 5.620E-04

900 2.252E+00 4.329E-02 1.054E-02 4.515E-03 2.438E-03 1.491E-03 9.860E-04 6.890E-04 5.010E-04

1000 2.060E+00 3.925-02 9.527E-03 4.078E-03 2.201E-03 1.346E-03 8.900E-04 6.210E-04 4.520E-04


9

Fig. 1. The deep dark curve represent our Scaled plane Wave(PWB) result, where as spots aretheoretical from Close coupling method of Bray et al [4] (1994) has been shown in the Fig. 1. The

circle are experimental results of Phelps et al [5] (1979). All results are closely similar to each other.

Fig. 2. The excitation cross section of Sodium 3p-3d has been shown .the triangles are calculatedresults of Moores et al [19](1974) and cross points are results of Chen and Gallagher [10]. The deepdark curve is our Scaled Plane Wave Born (PWB) results for excitation where as dottes are results of

Unscaled (PWB)cross section

with energies. The lowest excitation state of Nahas very large cross section compare to higherexcitation state. This reflect fact that the f value forthe former excitation almost unity, and is little forhigher excitation.

We have compared the BE f Scaled calculationwith experimental data for excitation from the 3pexcited level of Na to the 3d level. These resultsare shown in the figures in result of Chen and

Gallagher[18] and lose coupling results of Moore etal [5] are in good agreement with experiment results.Our approach is to use the experimental data of thetotal cross section at certain value of incident energyof electron. Atomic number and the static dipolepolarizability of Sodium Na alkali target atoms havebeen discussed, which produce total cross sectionfor each target atoms. The alkali metal atoms arehighly liable to polarize target. Therefore, the reliableestimate of the effect of distortion of Na metal target


10

atom is rather essential to predict Scattering. Thevalue of the static dipole polarizability of Na is takenas 163a [16].The experimental calculated result oftotal cross section are relatively similar and shownin the figure share very good agreement withavailable data and facts by different researchers. Theresults are differ only by a negligible amount as shownin fingers due to resonance factor. The cross sectionfor more higher state np levels are converging tothe ratio n*value raised to the 3rd power which canbe scaled as (n*)3 for convenience and betterunderstanding.

The dotted curve is scaled plane wave Born(PWB) result for the excitation of Na. This curve isshowing 3p-3d electron excitation of sodium. Thecross are experiment result of Chen and Gallagher[18] and calculated result of Moores el al [19] arecompared. The solid curve shows BEF scaled crosssection, triangle and cross are results of Enemarkand Gallagher [6] results respectively.

Acknowledgement

Authors are grateful to Prof Krishana MohanSingh, P.G Deptt of Physics , Veer Kunwer SinghUniversity, Ara (Bihar) and Prof M.Y. Khan, Al-FalahSchool of Engg & Tech, Dhauj and former Head ofthe Department of Physics, Jamia Millia Islamia NewDelhi for their valuable suggestions and guidance.

References

[1] L. Biermann, Z. Astrophys. 22 (1943) 157.[2] W. Heisenberg, "Über die Spektra von

Atomsystemen mit zwei Elektronen," Z. Phys.39 (1926) 499.

[3] J. Migdalek and W.E. Baylis, J. Phys. B: At. Mol.Phys., 11 (1978) L497.

[4] I. Bray, Phys. Rev., A49 (1994) 1066.[5] J.O. Phelps, J.E Solomon, D.F Korff and C.C

Lin, Phys Rev, A20 (1979) 1418.[6] E.A. Enemark and A. Gallagher, Phys. Rev.,

A6 (1972) 192.[7] Y.K. Kim, Phys. Rev., A64 (2001) 032713.[8] W. Siegel, J. Migdalek and Y.K. Kim, Atomic

and nuclear physics data table, 68 (1998) 303.[9] J. Migdalek and Y.K. Kim (J. Phys. B, 31, 1947

[1998][10] A. Filippov and V.K. Prokofiev, Z. Phys. 56

(1929) 458.[11] U. Volz, M. Majerus, H. Liebel, A. Schmitt,

and H. Schmoranzer, Phys. Rev. Lett., 76(1996) 2862.

[12] M. Nawaz, W.A. Farooq and J.P. Connerade,J. Phys, B25 (1992) 5327.

[13] M.Y. El-Bakry and A. Radi, International Journalof Modern Physics C, 17 (2006).

[14] Rick Riolo and Bill Worzel, GeneticProgramming Theory and Practical, Springer,(2003).

[15] E. Surdutovich, W.E. Kauppila, C.K. Kwan,E.G. Miller, S.P. Prikh, K.A. Price and T.S. Stein,Nuclear Instruments and Methods, B221(2004) 97.

[16] J. Koza, M. Keane, M. Streeter, W. Mydlowec,J. Yu and G. Lanza, Genetic Programming IV:Routine Human, Competitive MachineIntelligence, Kluwer, (2003).

[17] C. Bottcher and A. Dalgarno, Proc. R. Soc.(London) Ser. A340 (1974) 187. C. Bottcherand A. Dalgarno, Proc. Soc., A340 (1974) 187.

[18] S.T. Chen and A.C. Gallagher. Phys. Rev. A17(1978) 551.

[19] D.L. Moores, D.W. Norcross and V.B.Sheorey, J. Phys., B7 (1974) 371.

Three Dimensional Periodic Orbits Around the Collinear ....... Axis Symmetric Bodies

11

Three Dimensional Periodic Orbits Around the CollinearLiberation Points in the Restricted Problem when Both the

Primaries are Axis Symmetric Bodies

ANURAG1* and SANJAY JAIN2

1Guru Prem Shukh Memorial College of Engineering, Delhi2Ratan Institute of Technology, Palwal*E-mail: [email protected].

Abstract

Three dimensional periodic orbits around the collinear liberation points Li(i=1,2,3) in the restricted three bodyproblem has been studied when both the primaries (earth -moon) are axis symmetric bodies with one of theiraxes as axis of symmetry and equatorial planes coinciding with the plane of motion by taking different values ofsemi-axes of the axis symmetric bodies(earth-moon). With the help of predictor corrector method, we havecomputed the initial conditions by taking different values of the semi-axes of the axis symmetric bodies. Withthese initial conditions, we have drawn three dimensional periodic orbits in the different cases.

Key words : Axis symmetric body, collinear points, restricted three body, periodic orbits.

1. Introduction

In our previous paper [1], we have studied thethree dimensional periodic orbits around thecollinear liberation points in the restricted threebody problem by assuming the bigger primary asan axis symmetric rigid body with its equatorialplane coinciding with the plane of motion. In thispaper, we wish to generalize the earlier by takingboth the primaries as axis symmetric bodies viz.the earth-moon system. We continue theinvestigation using the value for µ=0.01215 for themass parameter of the problem. The numericalstudy presented here is based on the same methodand techniques as the investigations mentioned inearlier paper.

2. Equations of Motion

By adopting the notations and terminology ofSzebehely and taking the distance between the


primaries unity and the sum of the masses of theprimaries as one, unit of time is so chosen so as tomake gravitational constant G=1. Equations ofmotion of m3 in dimensionless variables and Cartesianform can be written as

(1)

where

2 ,xx ny− = Ω

2 ,Yy nx+ = Ω

,zz = Ω

2 ,Yy nx+ = Ω

2 2 2 2

1 2 1 25 3

1 1

2

1 1 25 3

1 2 1 2

2 2

1 2 15 5

2 2

1 3(1 ) (1 )( ) ( ) (2 )

2 2 2

(1 ) 3(1 )(2 )

2 2

3 3( ) ,

2 2

n x y yr r

zr r r r

y zr r

µ µσ σ σ σ

µ µ µ µσ σ σ

µ µσ σ σ

− −Ω = + − − + −

− − ′ ′+ + − + −

′ ′ ′− − −

Anurag and Sanjay Jain

12

2 ,mµ =11 ,mµ− =

1 2 3 1 2 3, , , , ,a a a a a a′ ′ ′ are the lengths of the semi axes ofthe axis symmetric bodies of masses m1 and m2.The mean motion n of the primaries is given by

R=Dimensional distance between the primaries.

G=Gravitational Constant, (2)

(3)

(4)

1 2 1 2

55

6(1 )(2 ) 6 (2 ),

| | | 1|LLx xµ σ σ µ σ σ

µ µ′ ′− − −+

− − +

1 22 75

(1 )( ) 5(1 )(2 )( )3

| | | |[ LL

LL

xxA

x xµ µ µ σ σ µ

µ µ− − − − −= − +

− −

1 2

75

( 1 ) 5 (2 )( 1),

| 1 | | 1|]LL

LL

x xx x

µ µ µ σ σ µµ µ

′ ′+ − − − ++ ++ − − +

3 55

(1 )( ) ( 1 )32 | | | 1 |[ LL

LL

x xA

x xµ µ µ µ

µ µ− − + −= + +

− + −

2 12 1

77

5(1 )(2 )( ) 5(1 )( )( )2| | | |

LL

LL

x xx x

µ σ σ µ µ σ σ µµ µ

− − − − − −+ +− −

where

3. Collinear Libration Points

3.1 (L1, L2, L3)

The libration points are given by the solution of

Since in each of the open intervals

the function isstrictly increasing in each of them.

Therefore, there exists one and only one valueof x in each of the above intervals. Further

Therefore,there are only three real roots, one lying in each ofthe intervals and Thus there are three collinear libration points. Thefirst collinear point is located left of the primary ofmass m1, the second is between the primaries, andthe third collinear libration point is to the right ofthe primary of mass m2.

3.2 Motion around the Collinear Libration Points

Let L be any of the collinear libration pointsLj, j=1, 2, 3. If a new coordinate system is definedwith L as origin and x, y and z its axes, parallel to Ox,Oy and Oz respectively, the transformationbetween the two systems is given by the relations:

Then the Equations of motion are transformedthrough (2) in the Lxyz coordinate system as,

Putting values of various derivative in Eq. (3), weget

2 2 2 2

1 3 2 31 2 1 22 2

2 2 2 2

1 3 2 31 2 1 22 2

( ), , , 1,

5 5( )

, , , 1,5 5

a a a aR R

a a a aR R

σ σ σ σ

σ σ σ σ

− −= = <

′ ′ ′ ′− −′ ′ ′ ′= = <

2

1 2 1 2

3 31 (2 ) (2 ).

2 2n σ σ σ σ′ ′= + − + −

0, 0, 0.x y zΩ = Ω = Ω =

0XΩ >

( , 1),( 1, ),( , )µ µ µ µ−∞ − − ∞ Ω

,( 1) 0 0,

,( 1) 0 0.X

X

Also as x or

and as x or

µ µµ µ

Ω →−∞ →−∞ − + +Ω →∞ →∞ − − −

( 2) 0, (0) 0µΩ − < Ω ≤ ( 1) 0.and µΩ + >

( 2, 1),µ µ− − ( 1, )µ µ− ( , 1).µ µ +

,

,

.

Lx x x

y y

z z

→ +→→

2 ( , , ),

2 ( , , ),

( , , ).

x L

y L

z L

x ny x x y z

y nx x x y z

z x x y z

− = Ω ++ = Ω +

= Ω +

2 2 2

1 2 3 4

1 2

1 2

2 ,

2 ,

.

x ny A x A x A y A z

y nx B y B xy

z C z C xz

− = + + +− = += +

2

1 3 3

2(1 ) 2| | | 1 |L L

A nx x

µ µµ µ

−= + + +

− + −


13

4 55

(1 )( ) ( 1 )32 | | | 1 |[ LL

LL

x xA

x xµ µ µ µ

µ µ− − + −= + +

− + −

121

77

5(1 )(2 )( ) 5(1 ) ( )2| | | |

LL

LL

x xx x

µ σ σ µ µ σ µµ µ

− − − − −+ +− −

121

77

5 (2 )( 1) 5 ( 1),

2| 1| | 1|]LL

LL

x xx x

µ σ σ µ µσ µµ µ

′ ′ ′− − + − ++− + − +

2 1 21 533

3(1 )(2 )(1 )| | | 1 | 2| |LLL

B nx x x

µ σ σµ µµ µ µ

− −−= − − −− + − −

1 2 1 2 1 2

555

3(1 )( ) 3 (2 ) 3 ( )| | 2| 1 | | 1 |LLLx x x

µ σ σ µ σ σ µ σ σµ µ µ

′ ′ ′ ′− − − −− − −− + − + −

2 55

3(1 )( ) 3 ( 1 )| | | 1 |

LL

LL

x xB

x xµ µ µ µ

µ µ− − + −= + +

− + −

2121

77

15 (2 )( 1) 15 ( )( 1),

2| 1| | 1|LL

LL

x xx x


′ ′ ′ ′− − + − − ++− + − +

1 2 11 5533

3(1 )(2 ) 3(1 )(1 )| | | 1 | 2| | | |LLLL

Cx x x x

µ σ σ µ σµ µµ µ µ µ

− − −− −= − − −− + − − −

121

55

3 (2 ) 3,

2| |1| | 1|LLx xµ σ σ µσ

µ µ′ ′ ′−− −

− + − +

2 55

3(1 )( ) 3 ( 1 )| | | 1 |

LL

LL

x xC

x xµ µ µ µ

µ µ− − + −= + +

− + −

121

77

15(1 )(2 )( ) 15(1 ) ( )2| | | |

LL

LL

x xx x

µ σ σ µ µ σ µµ µ

− − − − −+ +− −

121

77

15 (2 )( 1) 15 ( 1)2| 1| | 1|

LL

LL

x xx x

µ σ σ µ µσ µµ µ

′ ′ ′− − + − ++− + − +

2

1 2

2

1 2

2

1 2

( ) ( ) ( ) ,

( ) ( ) ( ) ,

( ) ( ) ( ) .

x x x

y y y

z z z

τ τ ε τ ετ τ ε τ ετ τ ε τ ε

= += += + (5)

(6)

where

4

11

( ) ( ),i ii

y d Expτ λτ=

= ∑

(7a)

(7b)

4. Second Order Approximation of PeriodicSolution

We search for periodic solutions in the form ofsecond order expansions in powers of a parameterε : (0 to 0.009).

In order to erase any secular term in futureanalysis and retaining terms of powers in ε notgreater than two and denoting by dot(.) the τ-

derivatives and ignoring the terms 2 , 1,2i iσ ε = . Wehave to solve the system:

(7c)

The general solution of the Eq. (6) is given by;

where , 1,2,3,4i iλ = are the characteristic roots ofthe system given by the Eqs. (7a) and (7b) and

, 5,6j jλ = are given by Eq. (7c). Periodic orbits canbe obtained if at least one pair of Imaginary rootsexists. By a suitable choice of the coefficients of theexponential of (7), we may have a special periodic

1 2 1 2

7 7

5 (2 )( 1) 5 ( )( 1),

2| 1| | 1|]L L

L L

x xx x


′ ′ ′ ′− − + − − ++

− + − +

1 2 1 2

7 7

15(1 )(2 )( ) 15(1 )( )( )2| | | |

L L

L L

x xx x


− − − − − −+ +

− −

1

1

1

0

( ) 0

0

x

F D y

z

=

2

1

2

1

2

1

2 0

( ) 2 0

0 0

D A nD

F D nD D B

D C

− −

= − −

4

11

( ) ( ),i ii

x c Expτ λτ=

= ∑

6

15

( ) ( ).j jj

z e Expτ λτ=

=∑

Anurag and Sanjay Jain

14

'Bεω

=

(8)

where

g1 (τ) = K0 + K1cos 2ωτ,

g2 (τ) = Λ1 sin 2ωτ,

g2 (τ) =Λ2 sin 2ωτ.

and

12

2 1

2 2

( ) cos2 ,

( ) sin2 ,

( ) sin2 .

ox M M

y N

z N

τ ωττ ωττ ωτ

= +==

Periodic Solution of Eq. (9) is given by

where

1

2

1 1 1 1 1

2

1 1 1 1 1

22 2

1

4 2 2

1 1 1

,

1( 4 4 ),

1( 4 4 ),

,( 4 )

16 4(4 ) .

oo

KM

A

M K n B K

N k n A

NC

n A B AB

ω ωψ

ω ωψ

ωψ ω ω

−=

= − + Λ −

= − Λ + − Λ

Λ=− −

= − − − +

2

1

2*

1

2'

2

( , ) cos [ cos2 ] ,

( , ) sin sin2 ,

( , ) sin sin2 .

ox t A t M M t

y t B t N t

z t B t N t

ε ω ε ω εε ω ε ω εε ω ε ω ε

= + += += +

Period of this solution is, 2.T

πω

=

( 0.01215)µ =

2

1

2* .

( )nB

AB

ωω

=+

solution which contains only the frequency ω.Equation (7) admit the periodic solution,

where the coefficients A, B, A*, B*, A' and B' aregiven by

Without any loss of generality, we put 1(0) 0,y =

then and consequently,

B=0. This means that and

too. Finally, the above solution becomes,

The second order system is given by

(9)

(10)

Finally, a second order approximation of periodicsolutions around the collinear libration points, as afunction of parameter, ε is obtained as

5. Numerical Results

Using the formulae (4) we find, a firstapproximation, which are close to Lj, j = 1, 2, 3.Then, by a linear predictor-corrector algorithmbased on numerical integration of the equations of

1

* *

1

1

( ) cos sin ,

( ) cos sin ,

( ) cos sin ,

x A B

y A B

z A B

τ ωτ ωττ ωτ ωττ ωτ ωτ

= +

= +′ ′= +

2

1

2* .

nAB

Bω

ω−

=+

1(0) 0z = * 0,A = 0A′ =

1(0) 0,x = 1(0) 0y ≠

1(0) 0z ≠

1

*

1

1

( ) cos ,

( ) sin ,

( ) cos .

x A

y B

z B

τ ωττ ωττ ωτ

=

=′=

2 1

2 2

2 3

( )

( ) ( )

( )

x g

F D y g

z g

τττ

=

2 *2 2

2 3 4

2 *2 2

1 2 3 4

*

1 2

2 2

1[ ],

21

[ ],21

[ ],21

[ ].2

oK A A A B A B

K A A A B A B

B AB

C AB

′= + +

′= − −

Λ =

′Λ =


15

Table 1

Cases 1 2 3 4 5

a1 6400 6400 6400 6400 6400

a2 6400 6390 6380 6370 6360

a3 6400 6380 6360 6340 6320

1750 1750 1750 1750 1750

1750 1740 1730 1720 1710

1750 1730 1710 1690 1670

motion we can draw three dimensional periodicorbits for different values of σ1 and σ2. Table 1 givesthe parameter of earth and moon where as Table 2gives the collinear libration points for various valuesof σ1 and σ2.

are the semi-axes of the earthand the moon respectively.

Table 2

Collinear liberation points

Ca 1 2 3 4 5

σ1 0 9.42x10-8 1.873x10-7 2.794 x10-7 3.703 x10-7

σ2 0 4.697x10-8 9.312x10-8 1.385 x10-7 1.83x10-7

0 3.46x10-7 6..908x10-7 1.0345x10-6 1.377x10-6

0 1.728x10-7 3.449x10-7 5.161x10-7 6.865x10-7

L1 -1.15567991 -1.1556813 -1.1556828 -1.1556843 -1.1556857

L2 -.836918007 -.83691163 -.83691470 -.83691306 -.83691142

L3 1.005062401 1.00506213 1.00506186 1.00506161 1.00506136

6. Conclusion

With the help of predictor method, we havecomputed the initial conditions by taking differentvalues of the semi-axeses of the axes-symmetricbodies. With these initial conditions, we can drawactual three dimensional periodic orbits.

Acknowledgment

We are thankful to center for FundamentalResearch in Space Dynamics and Celestial Mechanics(CFRSC) for providing all facilities in the completionof this work.

References

[1] Anurag, T.P. Singh and Sanjay Jain, Accepted inGPM Journal of Technology.

[2] V. Szebehely, Theory of Orbits, (Academic,New York) (1967).

[3] C.L. Goudas, Icarus, 2 (1963) 1.[4] K.E. Papadakis, Astrophysics and Space Science,

191 (1992) 223.[5] V.V. Markellos., Celest. Mech and Dyn. Astron.,

9 (1993) 365.[6] Olle Merce and Pacha R. Joan, Astron. Astrophy.,

351 (1999) 1149.

[7] E.A. Perdios, Astrophysics and Space Science,278 (2001) 405.

[8] E.A. Perdios, S.S. Kanavos and V.V. Markellos,Astrophysic and Space Science, 262 (2004) 75-87.

[9] T. Kalvouridis, A. Mavraganis and C. Pangalos,Astrophysics and Space Science, (2004)255.

1 2 3 1 2 3, , ,a a a and a a a′ ′ ′

0.01215, 384400Earth Mooncase R kmµ− = =

A. Masood, M.U. Zuberi and M.M. Mohsin

16

Estimation of Breakdown Strength of Solid InsulatingMaterials in Ambient Medium

A. MASOOD, M.U. ZUBERI and M.M. MOHSINDepartment of Electrical Engineering, Z.H.College of Engineering and Technology

Aligarh Muslim University, Aligarh - 202 002 (Uttar Pradesh)

Abstract

The objective of this research was to determine if a relationship could be found between dielectric strength andother properties of electrical insulating materials in ambient medium on an empirical basis by using variablespredicted by basic theory. A simple equation of the form E=A+Blog (ρv / ξr tanδ ) to predict the dielectricstrength of a solid insulating material in the ambient medium has been proposed using ASTM electrode system.The constant 'B' has been obtained as a function of thickness 't' of solid insulating materials. The equationrequires the values of volume resistivity ( v), relative permittivity (ξr) and loss tangent (tanδ), which may beobtained easily by low voltage non-destructive measurements. The values of electric strength calculated usingthis equation for Polyethylene, Fibre-glass, Leatheroid, Mica, Empire cloth, Kraft paper and Polyethylenecoated Leatheroid are quite in agreement with the experimentally measured values. It is expected that theequations obtained will help the designers as a handy tool for quick estimation of breakdown strength of soliddielectrics.

Key words : Breakdown strength, loss tangent, volume resistivity, relative permittivity, solid dielectrics, polyethylene, mica, empire cloth, kraft paper.

1. Introduction

The theory behind dielectric breakdown hasalways been to a great extent equal part ofspeculation, art and science. The interaction of fields,particles and atoms on a microscopic level is socomplex that exact quantum mechanical solution toall but the simplest atomic structure has beenimpossible [1,2]. A myriad of factors, which mightinfluence dielectric strength, could be listed andevaluated [3-5]. These include intrinsic materialproperties, a host of external environmental factorsand assorted test conditions that may exist.However, if the environmental factors and testconditions are kept constant the list can beshortened considerably. If this were the case, thena list of intrinsic material properties which mightaffect the dielectric strength such as relativepermittivity (ξr), loss tangent (tanδ), ionizationenergy (Ei), sample thickness (t), mobility of charge


carriers (μ), number of charge carriers (n), free pathamong molecules (λ) and free volume of the material(Vf) would result [6,7].

Out of the above parameters ξr, tanδ, and t canbe measured in a relatively straight forward manner.However, the others cannot be measured readily.

Mobility of charge carriers is very difficult todefine [8]. However, the volume resistivity (ρv)measurement can be used to determine μ throughthe equation ρv=1/neμ, if the number of chargecarriers are known.

The mean free path of a free electron in a materialis dependent upon the free volume of a material andthe molecular agitation within the material. Both ofthese are temperature dependent. The increase infree volume with temperature leads to an increasein the mean free path. However, the increased

Estimation of Breakdown Strength of Solid Insulating Materials in Ambient Medium

17

molecular agitation at high temperatures tends todecrease this path. Thus, the measurement andcalculation of this parameter is most difficult.

Furthermore, from the energy considerations,the kinetic energy which an electron acquires whensubjected to an electric field is dependent upon themean free path between collisions. Also, the meanfree path should be equal to the cube root of thefree volume, Vf.

With these constraints in measuring the abovelisted intrinsic properties, Swanson et al [6]suggested a relationship given by Eq. (1) to correlatethe dielectric strength E with volume resistivity,relative permittivity and loss tangent.

Dielectric Strength, E=A+Blog (ρv/ξr tanδ ) (1)

This is based on the assumption of performingexperiments on the test samples of same thicknessin a group, which is again an approximation toeliminate t from the above equation.

Though Eq. (1) holds good for the evaluationof dielectric strength of a number of solid insulatingmaterials, it suffers from the disadvantage that it isvalid for a particular large thickness of 1.397 mmand cannot be used for dielectrics of smallerthickness. However it is well established that thethickness affects the dielectric strength of solidinsulating material.

Using the above approach the breakdownstrength (BDS), relative permittivity (ξξξξξr), losstangent (tan δ δ δ δ δ) and thickness (t) of different solidinsulating materials in the ambient medium have beenmeasured and correlated incorporating the thicknessof the samples to estimate the BDS of solid insulants.

2. Experimental Techniques

2.1 Measurement of Relative Permittivity, andLoss Tangent of Solid Dielectrics

Figure 1 shows the three-electrode system asdescribed in [9] to measure the relative permittivityand loss tangent of various dielectrics. Measurementswere made using a LCR data bridge (Forbes Tinsley

Co. Ltd) with an accuracy of ±0.1% at 100 Hz.

Measurement of ξr and tanδ were carried onPolyethylene, Fibre-glass, Leatheroid, Mica, Empirecloth, Kraft paper and Polyethylene coatedLeatheroid.

2.2 Breakdown Strength of Solid Dielectrics

The electrode assembly for obtaining the electricstrength is as per IS: 2584-1963[10]. Five samplesof equal thickness were tested with this arrangement.Taking the ratio of average breakdown voltage toaverage thickness of the sample, electric strengthwas determined.

2.3 Sample Preparation

No special efforts were made to clean or modifythe test samples i.e. Polyethylene, Fibre-glass,Leatheroid, Mica, Empire cloth, Kraft paper andPolyethylene coated Leatheroid in any way since itwas assumed that any contaminants such as ionicimpurities which would influence the dielectricstrength would also influence other properties beingmeasured. Thus the materials were tested asreceived in the laboratory.

The sample thickness was measured at somerandomly distributed 20 points, spread all over thesheet area with a micrometer having a least countof 0.01mm. The average of the 20 measurementswas taken as the average thickness of the sample.

3. Results

Volume resitivities of the materials were notmeasured practically but noted from the literatureavailable [11-13].

Collecting all relevant data for different insulatingmaterial samples, log (ρv)/ξrtanδ was calculated foreach of them. Samples were grouped togetheraccording to thickness and for each group measuredelectric strength was plotted against the quantitylog (ρv)/ξrtanδ.

The plot is as shown in Fig. 2. For thick samplesthe slope of straight line is lesser than the slope forthin samples and this decreases in a regular fashion.

A. Masood, M.U. Zuberi and M.M. Mohsin

18

Table 1

Material Dielectric Dissipation log( v)/ Thickness Measured Calculated E %Constant ξr Factor tan δ ξrtanδ 't' mm E(kV/mm) (kV/mm) Error

Polyethylene 2.312 0.0035 18.41 0.41 60.02 59.99 0.04

2.401 0.0045 18.28 0.59 50.00 52.32 4.64

2.012 0.0055 18.27 0.82 46.95 44.32 5.60

Fibre-glass 6.321 0.0045 14.20 0.16 46.25 43.56 5.80

6.732 0.0044 14.19 0.34 43.38 44.55 2.69

Leatheroid 4.007 0.0500 10.90 0.15 32.00 33.67 5.21

4.301 0.0610 10.78 0.32 30.46 29.54 3.02

Mica 7.120 0.0050 16.07 0.20 55.00 55.9 1.63

7.128 0.0060 15.99 0.45 50.00 47.96 4.08

7.894 0.0090 15.77 0.88 36.00 34.21 4.90

Empire cloth 2.563 0.0200 15.02 0.15 50.00 52.60 5.20

2.462 0.0250 14.94 0.33 46.06 47.13 2.32

Polyethylene 3.120 0.0050 13.32 0.27 40.00 41.76 4.40Coated 3.137 0.0060 13.25 0.52 34.57 35.17 1.73Leatheroid

Kraft paper 2.258 0.4000 8.74 0.41 18.53 19.45 4.90

Estimation of Electric Strength of solid insulating materials with percentage error

Fig. 1. Three-electrode system used to investigate therelative permittivity and loss tangent

E1 = 4.373x - 19.42 (0.1-0.4 mm)

E2 = 3.724x - 17.26 (0.5-0.7 mm)

E3= 3.357x - 17.15 (0.8-0.9 mm)

-10

0

10

20

30

40

50

60

70

0 5 10 15 2x=log(Volume Resistivity/loss index)

E=B

reak

dow

n st

reng

th (k

V/m

m)

Fig. 2. Estimation of electric strength

Equations (2) to (4) plotted in Fig. 2. are for threevarious thickness groups of samples (0.1-0.4mm,0.5-0.7mm,0.8-.9mm) while Eq. (5) is for aparticular thickness of 1.397 mm given by Swanson [6].

E1= -19.42+4.373 log (ρv)/ξrtanδ

E2= -17.26+3.724 log (ρv)/ξrtanδ

E3= -17.15+3.357 log (ρv)/ξrtanδ

E4 = -11.75+2.1875 log (ρv)/ξrtanδ

Thus all the measured data can be put in the(2)

(3)

(4)

(5)

Estimation of Breakdown Strength of Solid Insulating Materials in Ambient Medium

19

B = -1.896t + 4.878

00.5

11.5

22.5

33.5

44.5

5

0 0.5 1 1.5

B

Sample thickness (mm)

B-t curve

Fig. 3. Constant 'B' vs. thickness't' curve

form of an equation

E= -A+B log (ρv)/ξrtanδ

Considering the mean value of a particular rangeof thickness of samples, it was observed that thatconstant 'B' is inversely related to thickness't' of thesample. Figure 3 shows a plot between 'B' valuesversus thickness't' of sample which is again a straightline and mathematically expressed as;

B= 4.878-1.896t

Thus final Eq. (6) may be expressed as

E = -16.395+ (4.878-1.896t) log (ρv)/ξrtanδ

here 16.395 is the average of 'A' values of Eqs. (2)-(5).

The calculated values using eqs. (7) and measuredvalues of electric strength of various solid insulatingmaterials mentioned earlier are listed in Table 1.Theyare in quite in agreement with the earlier reported results[7] and error in most of the cases is within ± 5 %.

4. Conclusion

Empirical formula suggested as given by Eq. (7)for estimation of electric strength of solid insulatingmaterial is simple and gives accurate results and thusmay be useful provided thickness is small. It is

(5)

(6)

(7)

expected that the equation obtained will help thedesigners as a handy tool for quick estimation ofbreakdown strength of solid dielectrics.

References

[1] A.K. Joncher, "Dielectric relaxation in solids",Chelsea Dielectrics Press, London, (1996).

[2] R. Bartnikas and R.M. Eichhorn (eds.),Engineering Dielectrics, Vol. II A, ElectricalProperties of Solid Insulating Materials: MolecularStructure and Electrical Behavior, STP 783,Philadelphia: ASTM, (1983).

[3] Petru V. Notingher, Laurentiu Badicu,Laurentiu Marius Dumitran, Gabriel Tanasescuand Dorin Popa, "Dielectric Losses inCellulose-Based Insulations" 7th InternationalConference on Electromechanical and PowerSystems, Lasi, Romania, (2009).

[4] T.K. Saha, "Review of modern diagnostictechniques for assessing insulation conditionin aged transformers", IEEE Trans. Dielectr. andElectr. Insul., 10 (2003) 903.

[5] W.S. Zaengl, "Dielectric spectroscopy in timeand frequency domain for HV powerequipment, Part I: theoretical considerations",IEEE Electrical Insulation Magazine, 19 (2003) 5.

[6] J.W. Swanson and Fredric C. Dall, IEEE Trans.Electr. Insul, 12 (1977) 142.

[7] E. Husain, M.M. Mohsin and R.S. Nema, IEEEElectr. Insul. Dielectr. Phenomena (CEIDP),(1989) 453.

[8] J. Mort, 8th Symposium on Electr. Insul., Japan(1975).

[9] E.W. Golding, Electrical Measurement andMeasuring Instruments, Wheeler Publication,London, (1980).

[10] IS: 2584, "Method of Test for Electric strengthof solid insulating materials at powerfrequencies", (1963).

[11] Hippel, Dielectric Materials and Applications,The Technology Press of MIT, Wiley (1954).

[12] F.M. Clark, Insulating materials for design andEngineering Practice, Wiley, (1962).

[13] Bogoroditsky, Pasynkov and Tareev, ElectricalEngineering Materials, MIR Publications,(1979).

Satish Prakash, R.K. Giri and Adesh

20

Rainfall and Convective Instability

SATISH PRAKASH1, R.K. GIRI2* and ADESH1

1Meerut College,Meerut - 250 004 (Uttar Pradesh)2India Meteorological Department, Lodhi Road, New Delhi -110 003


AbstractConvection and rainfall association is very old and sounding of the atmosphere either remote sensing orconventional methods can help to know the possibility of it. In this article author describes the brief about thevarious thermodynamic indices by conventional methods and utility of other tools like T-Phi gram to measurethe convective instability in the atmosphere. The Convective Available Potential Energy (CAPE) and ConvectiveInhibition Energy (CINE) of the year 2002 and 2006 obtained from radiosonde data (0000 and 1200 UTC) forDelhi and Chennai. The contrasting behavior of the South West Monsoon season with the help of CAPE andCINE is also highlighted.

Key words : Convective available potential energy, convective inhibition energy, instability, indices and T-phi gram.

1. Introduction

Convective precipitation is a major source oflatent heat and major forcing for general circulationof atmosphere. Global circulation is closelyassociated with the large scale precipitationanomalies, Rasmusson and Carpenter, [31]; Horeland Wallace, [18] and it is very important indiagnosing the behavior of global climate. Knowledgeof actual precipitation averaged over large area is ofpotentially great importance for general circulationmodels of climate, Mintz, [28]. The forecasting ofdeep convection involves four steps, Convey et al[7]: (a) Early warning of convection (b) theforecasting of convection (3) the detecting andidentifying convection and (4) the forecasting ofconvective evolution. Hence forecaster assesses thepotential instability in the environment as well aspossibility of the forcing mechanisms. Thesemechanisms are important to trigger theconvection. The various stability parametersdiscussed in this paper are primarily derived fromupper air sounding data. Numerical weatherprediction (NWP) model output helps in providinga clue to forecasting in different time and spatialdomain. For synoptic or meso scale weathersystems various stability parameters like convective


available potential energy (CAPE), convectiveinhibition energy (CIN), total-total index, humidityindex, deep convective index, K-index, surface liftedindex, upper level trough and short wave troughneed to be assessed for diagnosis. In this connectionvarious sources of data like satellite derived cloudtop temperature (CTT), satellite imageries in variousspectral bands like Infrared, Visible and Water vapor,imagery as well as temperature and moisture profiledata from Polar orbiting satellites and radar basedreflectivity, velocity spectrum etc are available.Upper air sounding thermodynamic diagram like T-Phi diagram is also operationally utilized daily invarious weather centers /departments. This diagramis used to see the areas of positive and negative areasof instability in the atmosphere. If the positive areais more than negative area then the air will be morepositively buoyant and responsible for the convectiveinstability or weather over the area. Figure 9 showsthe isopleths lines in tephigram (temperatureentropy diagram) which are very useful in diagnosingthe processes in the atmosphere. Various processesare also graphically represented by this diagram andvery useful in the diagnosing the convective activity.The information of thunder activity or icingphenomena is very dangerous activity for aviation.Downdraughts, therefore, can result in fatal


21

accidents, particularly for small aircraft (Figs. 10 &11).

In this series a large number of studies havebeen done by various authors, some of them arelisted below.

Multidecadal trends in tropical convectivepotential energy (CAPE), Gettelman et al, [17] for15 tropical radiosonde stations mostly showspositive trends during the period 1958-1997. In amoist atmosphere CAPE can be calculatedtroposphere to a finite vertical displacementrepresents the conditional stability of theatmosphere, Emanuel et al, [13]. Many climatemodel convective schemes use CAPE as a variablefor calculating convective heating Arakawa andSchubert [2].

Murugavel et al [23] studied trends ofConvective Available Potential Energy over the Indianregion and its effect on rainfall using 32 stations overIndian region data from 1984 -2008. They foundthat the seasonal variations show that the CAPE ishigher during the monsoon compared to pre-monsoon or post-monsoon seasons and it suggeststhat thermodynamic conditions favourable for highCAPE together with large-scale dynamics arenecessary for organized monsoon convections overthis region. In comparison with a large increase inthe all-India average of CAPE during monsoon season,which is about 38 J Kg-1year-1, the all-India summermonsoon rainfall increases about 1.3 mm year-1. Thesystematic increasing trend in Cape May becompensating for weakening of monsoon circulationand, thus, maintaining the monsoon rainfall over theIndian region. Campe et al [8] made a globalclimatology of CAPE and CIN is presented in termsof seasonal means, variances, and trends based on44 years (1958-2001) of six-hourly ERA-40reanalysis (European Centre for Medium-RangeWeather Forecast ECMWF, T106 resolution). Theyhave found that CAPE shows large values and highvariability in the tropics with maxima over thecontinents; the seasonal changes are dominated byspecific humidity. CIN shows large means andvariability in the subtropics.

Campe et al [9] found that the memory ofconvective precipitation is estimated via the analysisof the convective parameters convective availablepotential energy (CAPE) and convective inhibition(CIN). Regional and global memory in CAPE and CIN

is compared between observations (ECMWF re-analysis, in 1979-2001) and simulated data(ECHAM5/MPIOM, 20C simulation, in 1900-2001).Both datasets agree on the memory pattern in CAPEand CIN with highest values of the Hurst exponentalong the equatorial Pacific which decrease towardshigher latitudes; however, longest memory up todecades is found in CAPE south-east of Greenland.CAPE denotes the potential energy available to formcumulus convection which leads to convectiveprecipitation. The energy is characterised by apositive virtual temperature difference between anidealised rising air parcel and its environment. Onthe other hand, CIN denotes the energy needed bythe parcel to overcome the boundary layer to reachthe CAPE above. Therefore, high values of CAPEdo not necessarily lead to convection, if the ascentof air is prevented by a stable boundary layerindicated by also high values of CIN.

CAPE and CIN have been used for severeweather analysis and forecasting, Colby, [10];Rasmussen and Blanchard, [32], Craven et al [11];Markowski et al [24], Mukhopadhyay [25] Brookset al [3, 4], Doswell and Evans [12]. CAPE is alsoused in cumulus parameterisation in generalcirculation models, Moncrieff and Miller, [26],Ye et al [40]; Washington and Parkinson, [41], Schulz, [35].

High values of CAPE do not necessarily lead tostrong convection, as the simulated air parcel needsto overcome a usually stable layer between thesurface (SFC) and LFC. The intensity of this stablelayer is defined by CIN. The temperature differencebetween the same rising air parcels as in CAPE iscalculated between SFC and LFC, Williams andRenno [42].

( ) ln( )LFC

d ve vpSFC

CIN R T T d p= −∫

CAPE is defined as the positive temperaturedifference between an idealized rising air parcel Tvpand its environment Tve within two specific heightlevels multiplied with the gas constant of dry air RdEmanuel [15].

( ) ln( )LNB

d vp veLFC

CAPE R T T d p= −∫

As moisture is taken into account the virtualtemperature TV is used. The air parcel rises dry


22

adiabatically from the surface to the liftingcondensation level (LCL). Above the LCL the parcelrises pseudo adiabatically which means thatcondensate moisture will immediately fall out of theparcel as rain. CAPE is calculated between the levelof free convection (LFC) and the level of neutralbuoyancy (LNB) referred to as bottom and top ofthe cloud. Surface based CAPE is calculated pseudoadiabatically from temperature (T) and relativehumidity (RH) fields on 13 vertical pressure levelsbetween 1000 hPa and 100 hPa. These parametersare derived globally from ERA-40 datasets Kållberget al., [20]. Salvati and Berlusconi [36] show thatthunderstorm occurrence is still a difficult task forboth NWP models and weather forecasters due tothe small spatial and temporal scales involved. Thelow predictability of convective phenomena stilljustifies the operational practice of using empiricallydeveloped stability indexes to evaluate theatmospheric potential for storm development. Tobe used effectively indexes and reference thresholdsshould be verified and tuned using local stormclimatology.

Over Indian scenario various authors, Srinivasanet al [37]; Ravi et al [33]; Patra et al [29]; Singh andGiri [38] studied the thermodynamic indices tostudy the convection over the area. The calculationof the indices of instability Total-Totals and Showalterindex is useful for convective analysis. Theassessment of profiles of potential temperature (θ),equivalent potential (θe) and saturation equivalentpotential (θes) provided the thermodynamicbehavior of the structure and dynamics of theatmosphere.

The weather has a direct influence on our dailylives, the more are the wild weather conditions, thegreater the impact in various activities that weundertake daily. The most impressive meteorologicalphenomena that are severe storms with gusts ofwind, hail, and prolonged droughts, heat waves overor extreme cold, flooding and/or flooding. Theeconomic and social damage caused by severestorms can reach large areas such as agriculture,livestock, and enrooting houses, break windows,cars, damage to power lines, traffic jams, falling treesand advertising board.

2. Aims and Objectives

Convection and its evaluation is verycomprehensive task and depends in-situ as well as

remote sensing measurements. These measure-ments access it based on the atmosphere under-standing and algorithms or formulas. As theconvective potential is the prime base of weatheractivity its assessment in a proper way can improvethe forecasting as well as understanding of thecomplex understanding of the land, ocean andatmosphere. In this present paper, author's tries toexplain the various thermodynamic parameters usedto access the stabilities or instabilities in theatmosphere through upper air sounding data. Theuse of CAPE and CINE for the contrasting monsoonyear 2002, 2006 is explained. This upper airsounding for the atmosphere is operationally doneat 0000 and 1200 UTC daily all over the globe. IndiaMeteorological Department (IMD) has a networkof 39 upper air observations over Indian region. Theinformation received from upper air soundings isvery useful in validating the remotely sensed data aswell as to know the vertical structure or convectionin the atmosphere surrounded by the station.

3. Database and Methodology

The upper air sounding data used for the studyis taken from the global web link: http://weather.uwyo.edu/upperair/sounding.html). TheIndian Summer Monsoon Rainfall (ISMR) data is takenfrom India Meteorological Department, Lodi Road,New Delhi. The methodology adopted here is basedon the assessment of convection using upper airsounding data. The CAPE shows the connectivepotential of the different layers of the atmosphereand CINE is the inhibition threshold. There shouldbe optimum balance for rainfall and persistentconvective activity. These energies (CAPE or CINE)are region specific and have different threshold fordifferent regions of the country or globe. This isbecause the tropical and extra tropical convectionhave different characteristics. The upper dataderived CAPE, CINE thermodynamic indices forcontrasting monsoons helps to understand theanomalous behavior of summer monsoon.Comparison of CAPE and CINE with ISMR (2002 &2006) is also brought out to signify the importanceof the above said indices.

4. Results and Discussion

The results or discussions of this article arebased on the role of different parameters orsubgroups used in assessing the convection.


23

4.1 CAPE and CINE

The CAPE and CINE values are closelyassociated with the convective activity or instabilityin the atmosphere. Instabilities in the atmospherecan be monitored or calculated by variousThermodynamic diagrams like one T-Phi gramwhich is widely used for assessing the instabilities inthe atmosphere by measuring the positive area overthe region around the station from quite old times.Similarly several indices derived from radiosondedata is another way of assessing the convection andthe range of these parameter will be different fromregion to region. As the availability of the moisturein tropics is inhomogeneous in both time and spacewhich in turn decides the variability of convection.In this paper an effort has been made to bring outthe CAPE and CINE values for two contrasting years(2002 and 2006) which are monsoon deficient andnormal rainfall years for the country as a whole. ForDelhi the departure for monsoon season for 2002and 2006 is -39% and -24% respectively which liesin monsoon deficient regime. Similarly for Chennai2002 seems to be drought year and 2006 is normalfor SW monsoon season. Figures (1-8) representthe CINE and CAPE values for Chennai and Delhi(2002 & 2006) respectively. In the Figures Morningvalues represents 0000 UTC and Evening 1200 UTCrespectively. It has been seen from the Figs. (2 & 4)that there is a 38% increase of CAPE in the year2006 as compared to the year 2002 for Chennai.Delhi Radiosonde data after June 2006 was notavailable so indices could not be derived. It is clear

Fig. 1. CINE of Chennai for the year 2002, 0000 UTC and1200 UTC observations

Fig. 2. CAPE of Chennai for the year 2002, 0000 UTC and1200 UTC observations

Fig. 3. CINE of Chennai for the year 2006, 0000 UTC and1200 UTC observations

Fig . 4. CAPE of Chennai for the year 2006, 0000 UTCand 1200 UTC observations


24

( )=

2

2

NRi

dUdz

from the Figs. (6-8) that the value of CAPE for thecontrasting year 2002 & 2006 is more than 42%which will be the indication of more convectiongenerated especially in 1200 UTC more prominent.In the same time the value of convective inhibitionalso plays an important role in obstructing thetriggering the convection energy. This capping typeof inversion obstructs the precipitation. It is broughtout from the study that for Delhi the morning timethe average value of CAPE at 0000 UTC was morethan 1200 UTC and on the same time the value ofthe CINE is also higher. It is seen that although CAPEvalue is supported the possibility of thunder butCINE inhibit its action and in some cases even lowvalue of CAPE and higher value of CINE resultsthunder and precipitation. So, the convectioninstability in the atmosphere also changes with thelocal environments and sources of moisturetransport, direction and persistency of meso as wellas synoptic scale weather systems. The day to dayvariability of the CAPE and CINE suggests the surgesor phases of the available moisture during monsoonseason. Some times continuous two to three dayswe have sufficient energy in the atmosphere forpersistent moisture availability or convectiveinstability. The degree of thunderstorm days aremore in the June month of the year 2006 ascompared to the year 2002 for Delhi. This may bedue to the less value of CINE and capping inversion.For Chennai the June and July month of the year2002 do not have the sufficient convection energywhich results very less amount of precipitation, Figs.(2 & 4) and Table 1. Chennai area normally comes inrain shadow region for South West monsoon season.The possibility of rainfall in the month of October isagain prominent as the Easterly wave brings themoisture during North East monsoon season. Thisis clearly seen the increase values of CAPE for boththe years (2002 & 2006). The average values ofCAPE and CINE are higher for the year 2006 ascompared to the year 2002. The values of CAPE inthe evening time are generally higher as comparedto the morning (0000 UTC). Year 2002, ChennaiJune and September month shows negative lineartrend of CAPE from the beginning to ending of themonth whereas the July and august months CAPEshows positive linear trend for both 0000 and 1200UTC. Similarly, for the year 2006 of Chennai theJune and July month for both 0000 and 1200 UTCshows positive linear trend in CAPE values whereasAugust and September months shows negative lineartrend of CAPE. June and August month of Delhi for

the year 2002 shows monotonically increasing lineartrend of CAPE whereas July and September showsalmost constant linear trend for both 0000 and 1200UTC. Almost the same trend for both Delhi andChennai CINE values shows for both the years 2002and 2006. The June month of Delhi for the year2006 shows positive linear trend of CAPE and CINEvalues.

4.2 Convective vertical Current and Turbulence

Table 2 shows the vertical currents due toconvection and associated turbulence based onWorld Meteorological Organization (WMO)convection. Table 3 shows the brief description ofcommonly used thermodynamic indices to measurethe convection in the atmosphere. The convectionpotential like weak, moderate or severe is based onthe local conditions, geography or topography overthe area. The convection and associated weather isreshaped or modified by the hilly or valley, plain orcoastal areas. In this way, the impact associated bythe mesoscale or synoptic scale weather is alsodifferent in different areas.

4.3 Richardson Number

Kelvin-Helmholtz instability can be evaluated viareference to the Richardson number Ri which itselfis the ratio of the turbulence production by staticinstability to the one by shear

where, N being the Brunt-Vaisala frequency.

In the above equations U is the wind speed, gthe gravitational acceleration (about 9.8 m/sec), θthe potential temperature, and z height. Note thateven in the stratosphere where static stability ishigh, turbulence and breaking waves can still begenerated if the wind shear is of sufficient magnitude.

θθ

=2

g

Nddz


25

Fig. 7. CINE of Delhi for the year 2006, 0000 UTC and1200 UTC observations

Fig.9. The isopleths on a tephigram (source: http://cirrus.unbc.ca/408/lab3/index.html)

Fig. 10. Winds hear. How a downdraught would affect theflight path of an aircraft if the pilot failed to correct for thegain and loss of lift (Source: WMO aviation hazard manual,

ETR 20, page 3)

Fig. 6. CAPE of Delhi for the year 2002, 0000 UTC and1200 UTC observations

Fig. 5. CINE of Delhi for the year 2002, 0000 UTC and1200 UTC observations

Fig. 8. CAPE of Delhi for the year 2006, 0000 UTC and1200 UTC observations


26

Values of Ri less than 0.25 will allow the productionof 'breaking waves'. Values of between 0.25 and 1.0

Fig. 11. Maritime Convective Cell patterns, and related surface wind speed. From Pearson and Stogaitis, 1998.

2002 (Chennai) SW Monsoon June July August September

% departure % departure % departure % departure % departure

-19 -59 - 37 -9 4

2006 (Chennai) SW Monsoon June July August September

% departure % departure % departure % departure % departure

-2 3 -10 -7 7

2002 (Delhi) SW Monsoon June July August September

Season (2002) % departure % departure % departure % departure % departure

-39 -9 -92 -42 51

2006 (Delhi) SW Monsoon June July August September

Season (2006) % departure % departure % departure % departure

-24 54 -16 -64 -1

Rainfall Departure of SW monsoon season (2002 & 2006) for Chennai and Delhi

Source: India Meteorological Department, New Delhi

Table 1

with day to day or seasons depending on the typeof weather system approaches or affected. In this

paper authors is not carried out any such study butonly brief description has been given for thecompleteness of the article on convective instability.

4.5 Verification Matrix

Table 4 shows the verification of convectiveactivity based on the skill scores of the eventcaptured well or not or its occurrence or absent.This verification is a also not done in the paper butfor completeness of the article this table is enclosed.

will allow the persistence of turbulence, whereasvalues greater that 1.0 will tend to cause any existingturbulence to subside (Source: WMO aviation hazardmanual, ETR 20, page 16).

4.4 Thermodynamic Indices and Convection

Table 3 shows the various thermodynamicindices and associated weather of possible mode ofintensity (weak, moderate or severe) of convection.These parameters are locally modified and variable


27

Table 3

Thermodynamic indices

Index Reference Formula used Comments

K George (1960) (T+Td)850-T500-(T700-Td700) T and Td are dry bulb and dew

point temperature

Total -Total Index (TTI) Miller (1967) 2( T850-T500)-(T850-Td850) Notations same as above

Surface lifted Index (SLI) Means (1952) T500-Tsfc500 T is the environmental

temperature (°C) at 500 hPa. Tsfc500

is the temperatureof the parcel at 500

hPa after it is lifted dry adiabatically

from surface (sfc) to its condensation

level.

Humidity Index Litynska et al (1976) (T-Td) 850+ (T-Td)700+ Notations as above

(T-Td) 500

Deep Convective Index Barlow (1993) (T+Td)850-SLI Notations as above

(DCI)

Showalter Index (SI) Showalter, 1953 T500-Tp500 Tp500 is the 500 hPa temperature if a

parcel will achieve if its lifted dry

adiabatically from 850 hPa to LCL and

then Moist adiabatically to 500 hPa

Table 2

Typical vertical currents due to convection

Regime Vertical velocity Turbulence

(m/s) ~kt ~ft/min

Small/medium Cumulus 1-3 2-6 200-600 Light

Towering cumulus 3-10 6-20 600-2000 Moderate

Cumulonimbus 10-25 20-50 2000-5000 Severe

Severe storms (eg in USA) 20-65 40-130 4000-13000 Extreme

Dry thermals 1-5 2-10 200-1000 Light/Moderate

Downdraughts 3-15 6-30 600-3000 Moderate/Severe

Downdraughts up to -25 up to 50 up to 5000 Extreme

Source: WMO aviation hazard manual, ETR 20, page 5


28

Showalter Index (SI) Activity

SI≤≤≤≤≤+3 Indicative of showers and possible thunderstorm activity

SI≤≤≤≤≤-3 Indicative of severe convective activity

Index K Index (K) Activity

K<15 Indicates very weak potential of thunder activity

15<K< 20 (20 %) Indicates weak potential of thunder activity

21<K<25 (20-40 %) Indicates some potential of thunder activity

26<K<30 (40 -60 %) Indicates good potential of thunder activity

31<K>35 (60 -80 %) Indicates very good potential of thunder activity

36<K<40 (80-90 %) Indicates strong potential of thunder activity

K>40 (~ 100 %) Indicates very strong potential of thunder activity

Total -Total Index(TT) Activity

44>TT<50 Indicates possibility of thunder at isolated places or few places

50<TT55 Indicates the possibility of moderate thunder activity at widespread places

TT>55 Indicates the possibility of severe thunder activity at fairly widespread places

Lifted Index (LI) Activity

LI~0 Indicates very weak possibility of thunderstorms

0<LI<-3 Indicates possibility of weak to moderate thunder activity

-3<LI<-6 Indicates the possibility of moderate to severe thunder events

-6<LI <-9 Indicates the possibility severe thunder events

LI<-9 Indicates the possibility of very severe thunder events

Deep Convective Index (DCI) Activity

DCI<30 Indicated very weak potential of thunder activity

30<DCI or higher Indicates strong thunder activity

Convective Available Potential Activity

Energy (CAPE) (J/kg)

CAPE < 0 Indicates stable atmosphere with no possibility of thunder events

0 <CAPE <1000 Indicates marginally stable atmosphere with the possibility of thunder at isolated or few

places

1000 < CAPE < 2500 Indicated moderately unstable atmosphere and possibility of thunder at few places

2500 < CAPE <3500 Indicates very unstable atmosphere and the possibility of thunder at few of fairly widespread

places

CAPE >3000-4000 Indicated extremely unstable atmosphere and the possibility of thunder at most places

Convective Inhibition Energy Activity

(CIN) (J/kg)

It will be zero to negative values. CIN represents the amount of negative buoyant energy available to inhibit or suppress

High CIN values in the presence upward vertical acceleration. It is basically is the opposite of CAPE and represents the

of little or no lift can cap or suppress negative area in sounding.

convective development, despite

possibly high CAPE values.

Surface based lifted index (SLI) Activity

More prominent during afternoon Parcel is lifted from the surface using surface-based moisture and temperature values,

hours where surface characteristics as well as assigned environmental temperatures at 500 mb. More instability resides above

are similar to those in the lowest the surface, and parcels may be lifted to form thunderstorms from the top of the inversion.


29

50 to 100 mb layer.

Bulk Richardson's Number (BRN) Activity

BRN <10 Strong vertical wind shear and weak CAPE. The thunder activity may develop.

10 <BRN <15 It indicates with the weak to moderate thunder events at isolated to few.

BRN >50 Relatively weak vertical wind shear and high CAPE and possibility of moderate to severe

thunder activity at fairly widespread places.

Source: http://www.teachingboxes.org/avc/content/Severe_Weather_Indices.htm

Table 4

Thermodynamic indices

A (Hits) B (Misses)

C (False alarms) D (Non -event hits)

POD (Donaldson et al. 1975) A/(A+B) 0≤≤≤≤≤POD≤≤≤≤≤1

FAR (Donaldson et al. 1975) C/(A+C) 0≤≤≤≤≤FAR≤≤≤≤≤1

CSI ((Donaldson et al. 1975) A/(A+B+C) 0≤≤≤≤≤CSI≤≤≤≤≤1

TSS (Hansen and Kuippers 1965) (A/ (A+B) -(C/(C+D) -1≤≤≤≤≤TSS≤≤≤≤≤1

HSS (Brier and Allen 1952) 2(AD-BC)/(A+B)(C+D)+(A+C)(C+D) -1≤≤≤≤≤HSS≤≤≤≤≤1

Source: Brier, G.W. and R.A. Allen, 1952

5. Conclusion

The rainfall and convection are associatedmutually and upper air sounding and derivedparameters play an important role in assessing theconvective instability in the atmosphere. Thepresent article focuses on various thermodynamicindices by conventional methods and utility of othertools like T-Phi gram to measure the convectiveinstability in the atmosphere. The ConvectiveAvailable Potential Energy (CAPE) and ConvectiveInhibition Energy (CINE) of the year 2002 and 2006obtained from radiosonde data (0000 and 1200UTC) for Delhi and Chennai have been analyzed andfound in close association with the rainfall as seenthe graphs given for Delhi and Chennai. The localfactors like Chennai come in rain shadow region forISMR but Delhi is in plain area. The triggeringmechanisms will also be different and the type ofapproaching or affecting system duration andintensity, persistency and movement will be different.This viewpoint is clearly seen in the graphs likeCINE, because even higher value of CINE and lowvalue of CAPE can produce good rain. This indicatedthat the mutual association of these parameters isvery complex and can not be understood fully byCAPE, CINE or few thermodynamic parameters.The other sources like satellite radiance or DopplerWeather Radar or Automatic weather observations

and numerical model outputs products will beessential to understand the weather activitydynamics or structure.

Acknowledgement

The authors are grateful to the Director Generalof India Meteorological Department, Lodi Road,New Delhi and University of Wyoming [39] for thedata used in the study. Some of the terminologyand figures used from WMO documents in the studyare duly acknowledge.

References

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[3] H.E. Brooks, J.W. Lee and J.P. Craven. Thespatial distribution of severe thunderstorm andtornado environments from global reanalysisdata. Atmospheric Research 67-68: 73-94,DOI 10.1016/S0169-8095(03)00045-0,(2003).


30

[4] H.E. Brooks, A.R. Anderson, K. Riemann, I.Ebbers and H. Flachs. Climatological aspectsof convective parameters from the NCAR/NCEP reanalysis. Atmospheric Research 83(2007) 294.

[5] G.W. Brier and R.A. Allen, Verification ofweather forecasts. Compendium ofMeteorology, Boston, Amer. Meteor. Soc.,(1952) 841.

[6] W. Barlow, A new index for the prediction ofdeep convection. Preprints of the 17th

Conference on Severe Local Storms, St. Louis,4-8 October: 129 (1993).

[7] B. Conway, L. Gérard, J. Labrousse, E. LiljasSénési S Sunde, J. and Zwatz-Meise V.,Nowcasting: A Survey of Current Knowledge,Techniques and Practice. COST 78 Action.European Commission, ISBN 92 827 62041, EUR 16861. V Ducrocq, D Tzanos and SSénési 348, (1996).

[8] K.R. Campe, K. Fraedrich and F. Lunkeit.Global climatology of Convective AvailablePotential Energy CAPE) and ConvectiveInhibition (CIN) in ERA-40 reanalysis,Atmospheric Research, 93 (2009) 534.

[9] K.R. Campe, R. Blender and K. Fraedrich.Global memory analysis in observed andsimulated CAPE and CIN, International Journalof Climatology, 31 (2011) 3199.

[10] Colby JRFP. Convective inhibition as apredictor of convection during AVE-SESAMEII, Monthly Weather Review 112: 2239-2252,DOI: 10.1175/1520-0492(1984)112<2239:CIAAPO>2.0.CO;2,(1984).

[11] J.P. Craven, H.E. Brooks and J.A. Hart (2002).Baseline climatology of sounding derivedparameters associated with deep moistconvection. National Weather Digest, 28 (1)13.

[12] Doswell CA III and J.S. Evans, Proximitysounding analysis for derechos and supercells:an assessment of similarities and differences.Atmospheric Research, (2003) 67.

[13] K.A. Emanuel, J.D. Neelin and C.S. Bretherton,On large-scale circulations in convectingatmospheres, Qurterly Journal of Royal.Meteorological Society, 120 (1994) 1111.

[14] R. Donaldson, R. Dyer and M. Krauss, Anobjective evaluator of techniques for

predicting severe weather events. Preprints,Ninth Conf. on Severe Local Storms,American Meteorological Society, Norman,OK, (1975) 321.

[15] K.A. Emanuel, Atmospheric Convection.Oxford University Press.

[16] J.J. George. Weather forecasting forAeronautics, Academic Press, New York,(1960) 409.

[17] A. Gettelman, D.J. Seidel, M.C. Wheeler andR.J. Ross, Multi-decadal trends in tropicalconvective available potential energy, Journalof Geophysical Research, 107 (2002) 17-1-17-8.

[18] J.D. Horel and J.M. Wallace. Planetary scaleatmospheric phenomenon associated with theSouthern Oscillation, Monthly Weather Review,109 (1981) 813.

[19] A.W. Hanssen and W.J.A. Kuipers, On therelationship between the frequency of rain andvarious meteorological parameters. KoninklijkNederlands Meteorologish Institut, Meded.Verhand., 81 (1965) 2.

[20] P. Kållberg, A. Simmons, S. Uppala and M.Fuentes.The ERA-40 Archive.TechnicalReport, 17. ECMWF, (2004).

[21] Z. Litynska, J. Parfiniewicz and H. Pinkowski.The prediction of air mass thunderstorms andhails, W.M.O. No 450, (1976) 128.

[22] R.C. Miller, Notes on analysis and severe stormforecasting procedures of the MilitaryWeather Warning Center. AWS Tech. Rep. 200(revised), [Available from Headquarters, AirForce Weather Agency, Scott AFB, IL62225.], (1967) 170.

[23] P. Murugavel, S. Pawar and V. DandGopalakrishnan, Trends of ConvectiveAvailable Potential Energy over the Indianregion and its effect on rainfall, InternationalJournal of Climatology, doi: 10.1002/joc.2359.

[24] P.M. Markowski, J.M. Straka and E.N.Rasmussen, Direct surface thermodynamicobservations within rearflank downdrafts ofnontornadic and tornadic supercells. MonthlyWeather Review, 130 (2002) 1692.

[25] P. Mukhopadhyay, J. Sanjay and S.S. Singh.Objective forecast of thundery/non thunderydays using conventional indices over threeNortheast Indian stations. Mausam, 54 (2003)867.


31

[26] M.W. Moncrieff and M. Miller. The dynamicsand simulation of tropical cumulonimbus andsquall lines. The Quarterly Journal of the RoyalMeteorological Society, 102 (1976) 373.

[27] L.L. Means. On thunderstorm forecasting inthe central United States. Montly WeatherReview, 80 (1952) 165.

[28] Y. Mintz. A brief review of the present statusof global precipitation measurements fromspace. Precipitation measurements from-Workshop Report, NASA, Goddard SpaceFlight Centre, Geenbelt, MD, D1-D4.

[29] A.K. Patra, U.K. De and D. Lohar. Existenceof low level jet during pre-monsoon periodover eastern India and its role in the initiationof nocturnal thunderstorms. Atmosphera, 12(1998) 15.

[30] G.M. Pearson and G. Stogaitis. Satelliteimagery interpretation in synoptic andmesoscale meteorology. Environment Canada,(1988).

[31] E.M. Rasmusson and P.A. Arkin. Precipitationdata for climate diagnostic. PrecipitationMeasurement from space -Workshop Report,NASA, Goddard Space Flight Centre,Greenbelt, MD, D10-D18, (1981).

[32] E.N. Rasmussen and D.O. Blanchard. Baselineclimatology of sounding-derived supercell andtornado forecast parameters. Weather andForecasting 13 (1998) 1148.

[33] N. Ravi, U.C. Mohanty, O.P. Madan, R.K.Paliwal. Forecasting of thunderstorms in thepre-monsoon season at Delhi meteorologicalapplications 6 (1999) 29.

[34] A.K. Showalter, A stability index forthunderstorm forecasting, Bulletin of AmericanMeteorological Society, 34 (1953) 250.

[35] P. Schulz. Relationship of several stabilityindices to convective weather events innortheast Colorado, Weather Forecast 4(1989) 73.

[36] M.R. Salvati and D. Berlusconi. A statisticalstudy of stability indexes as convective weatherpredictors in Lombardia, 5th EuropeanConference on Severe Storms 12-16 October2009 - Landshut - GERMANY, (2009).

[37] V. Srinivasan, K. Ramamurthy and Y.R. Nene.Summer-Nor'westers, Andhis and large scaleconvective activity over Peninsula and centralparts of the country. India MeteorologicalDepartment, Forecasting Mannual: Part III,(1973).

[38] S. Singh and R.K. Giri. Variation of convectiveparameters over Srinagar. Vayumandal2006\Final September, (2008) 48.

[39] University of Wyoming. Atmosphericsoundings web site, University of Wyoming,Department of Atmospheric Science, Laramie,USA, (URL: http://weather.uwyo.edu/upperair/sounding.html), (2003).

[40] B. Ye, Del Genio AD and Lo KK-W. CAPEvariations in the current climate and in aclimate change. Journal of Climate 11 (1998)1997.

[41] W.M. Washington and C.L. Parkinson. AnIntroduction to Three-Dimensional ClimateModeling. University Science Books: UnitedStates of America, (2005).

[42] E. Williams and N. Renno. An analysis of theconditional instability of the tropicalatmosphere Monthly Weather Review, 121(1993) 21.

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32

Optimized Private Searching in World of Web

MOHAMMAD DANISHAl-Falah School of Engineering & Technology, Dhauj, Faridabad (Haryana)

E-mail: [email protected]

Abstract

Encrypted search - performing queries on protected data - has been explored in the past; however, its inherentinefficiency has raised questions of practicality. Here, we focus on improving the performance and extendingits functionality enough to make it practical. We do this by optimizing the system, and by stepping back from thegoal of achieving maximal privacy guarantees in an encrypted search scenario and consider efficiency andfunctionality as priorities.

We design and analyze the privacy implications of two practical extensions applicable to any keyword-basedprivate search system. We evaluate their efficiency by building them on top of a private search system, calledSADS [1, 2]. Additionally, we improve SADS performance, privacy guaranties and functionality. The extendedSADS system offers improved efficiency parameters that meet practical usability requirements in a relaxedadversarial model. We present the experimental results and evaluate the performance of the system. We alsodemonstrate analytically that our scheme can meet the basic needs of a major hospital complex's admission'srecords. Overall, we achieve performance comparable to a simply configured MySQL database system.

Key words: SADS , query router, search.

1. Introduction

Encrypted search - querying of protected datahas come into the foreground with growing concernsabout security and privacy. There are many variantsof the problem that protect different things: thesearchable data, queries, participant identities, etc.Existing schemes also differ in their expectedoperational environment. The majority of encryptedsearch mechanisms are concerned with dataoutsourcing and to a lesser degree in data sharing.Data outsourcing [4] concerns the case where oneparty wants to store its encrypted data on anuntrusted server and be able to search it later. Datasharing involves one party who provides limitedsearch access to its database to another. Thesetwo settings require different privacy guarantees ofan encrypted search system; data outsourcing isnot concerned with protecting the data from thequeried, since he is the owner. Furthermore, specific


implementations may return different things (e.g.,number of matches, document identifiers, relatedcontent, etc.) or may differ in numbers ofparticipants, trust assumptions, anonymityrequirements [7], revocation of search capability andother areas. All of these factors affect performance.Choosing a different definition of "sufficient" privacycan greatly affect inherent cost. Making the rightchoice, in accordance with the actual, rather thantheoretical, threat model can lead to a veryfunctional system, rather than one that istheoretically perfect but unusably costly in practice.

In this paper we step back from absolute privacyguarantees in favor of efficiency and real-worldrequirements. These requirements include not justwhat may leak, but to whom; depending on theparticular practical setting there may be parties whoare at least partially trusted. Our goal is to describeand build systems that meet the privacy guarantees


33

matching the actual goals for a given scenario, sothat we may improve efficiency. Towards this end,we present a set of generic extensions, applicableto any keyword- based private search system [5,6]. We discuss the importance of each of these, thechallenges for their secure implementation andanalyze their privacy implications in terms of leakage.To evaluate their efficiency, we developed them ontop of SADS, an efficient private search system thatuses Bloom filters. In addition, we describe andimplement a number of new features in SADS thatimprove its performance, privacy guarantees andfunctionality. Finally, we describe and analyze theperformance of the extended SADS system in a real-world scenario, using health records [9].

2. Secure Anonymous Database Search

The secure anonymous database search (SADS)scheme [27] provides the following searchcapability: it allows a search client (C) with akeyword to identify the documents of a databaseowner/server (S) containing the keyword withoutlearning anything more or revealing his query. Forthis purpose the architecture of the system involvestwo semi-trusted parties: index server (IS) and queryrouter (QR), which facilitate the search. In summarythe scheme works as follows: the database ownercomputes search structures for his database - aBloom filter (BF) per document built from theencryptions of all words of the document. Eachauthorized client receives keys that he uses tosubmit queries and decrypt the results; the QRreceives corresponding transformation keys for thequeries of that client. To submit a query, Ccomputes an encryption of his query and sends it toQR. QR verifies that the client is authorized,re-encrypts the query with the correspondingtransformation key, computes and sends the BFindices obtained from the encryption to IS. ISperforms search across the BFs it stores, encryptsthe identifiers of the matching documents and sendsthem to the QR; QR transforms the encryptionsand de- livers them to the client, who decrypts themto obtain his search results.

The original implementation of SADS alsoincludes a couple of optimizations/features enabled

by the use of BFs. First, storing the BFs intransposed order - called slicing optimizationminimizes the number of bits that need to be readduring search. That is because only bit slicescorresponding to specific indices are read during aquery and not all the BFs. This approach has twomain benefits. First, it has better cache behavior[9-11] because it fetches each slice once and uses itfor all the result vectors; second, in some cases itavoids reading several slice portions if thecorresponding bits of all the result vectors have beenzeroed out. In addition, SADS also supports Booleanqueries. One naive way to do this is to search foreach term separately and union or intersect theresults. However, BFs can more efficiently handleANDs by combining indices into a superset, andORs are handled in parallel by the slicingoptimization.

Fig. 1. Optimization methodology

3. Document Retrieval

There exist many systems for searchingdatabases to privately identify items of interest. Anextension of obvious use is a system to then retrievethose items privately. One way to do this is withprivate information retrieval techniques; howeverthese are very ex-pensive and can be even moreexpensive when fetching large numbers of records,or records of individually great size. We present asystem that is much more efficient, at the cost ofrequiring a trusted third party, and can be modularlyimplemented to extend any private search systemthat returns handles representing matches.

Systems both with and without documentretrieval have practical use. For example, a user may

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simply wish to establish that a server does havedocuments of interest to him, or may wish todetermine how many are of interest, or learn aboutcertain qualities concerning the data held there(subject to the search permissions granted by theserver). Furthermore, even in systems that includedocument retrieval, separating this functionality fromquery is worthwhile. For example, the server maybe running a paid service, and allow the user tooperate in an initial stage wherein he determineswhat he wants, and a bargaining stage wherein theynegotiate pricing, before purchasing the actualcontent.

Document retrieval [12-14] poses its ownchallenge, especially when the data is not owned bythe party retrieving it. In this scenario, returningadditional data is a privacy leak for the data owner;at the same time, revealing the matching documentsto the owner is a privacy leak for the retriever.Thus, the strongest security we would want to aimfor would require us to touch the contents of theentire database [9]. This is a prohibitively expensivecost for applications that aim to work in "real time"over a large data set. One way to avoid this cost isto relax our security definition and allow leak-age ofthe retrieval pattern (i.e. whether separate retrievalattempts touched the same documents). In the caseof data outsourcing, this amount of privacy leakageeasily suffices, since the untrusted server justsearches for and returns the encrypted files that hestores to the owner who has the correspondingdecryption keys [4, 8, and 13]. This approach,however, is not applicable to the case of data sharing,where leaking the matching documents to the ownerreveals more than the result pattern: he also knowsthe content of the documents, from which he caninfer information about the query.

4. Database Updates

So far we have assumed that the server'sdatabase does not change. It is preprocessed oncein the beginning and from that point on the samedata is used to answer all queries from the clients.However, in many practical situations the data ofthe server changes dynamically, which should bereflected correspondingly in the query results

returned. The naive solution [18] to run the pre-processing preparation of the database each time itchanges brings prohibitive efficiency cost. We wouldlike to avoid processing each record in the databasefor updates that affect a small fraction of it. From adifferent point of view, though, the updates of thedatabase can be considered private information ofthe server and thus the information about whatrecords have been changed is a privacy leakage[19, 24 and 25] to any other party (in our case tothe IS who holds the Bloom filter search structures).This type of leakage comes inherent with theefficiency requirement we posed above-if the updateprocessing does not touch a record, clearly it hasnot been modified. Therefore, we accept the updatepattern leakage as a necessary privacy trade-off forusable cost of the updates.

Now we look at the specific information thatchanges at the IS in the SADS scheme, and considerwhether it has leakage beyond the update patternof the documents:

Bloom filters: As we discussed before, if we use thesame hash function for the Bloom filters of alldocuments, then the search structures reveal thesimilarities between documents. In the case of anupdate this would be indicative to what fraction ofthe content of the document has been changed. If,however, each BF has a different set if hash functions,the update of a document would also include aselection of a new set of hash functions for its BF aswell. The only information that the IS could derivefrom the update will be the change of the length ofthe document based on the number of 1's in the BF.However, this information can be obtained also fromthe length of the encrypted document that the IS isstoring. In both cases, we can eliminate this leakageby padding the documents.

5. Optimizations

During the preprocessing stage, for eachdatabase document a Bloom filter containing itskeywords is generated. In the SADS scheme, addinga keyword to the BF of a document involvesencrypting the keyword under the server's key.Thus, preprocessing documents containing the same


35

keyword incurs repeated effort. In order to avoidthis unnecessary preprocessing cost, we can cachethe BF indices for keywords. This avoids somere-computation, but requires additional storagespace. Whether to do this, and how much to cache,depends on the nature of the documents andrepeat frequency. This is also applicable in the casewhen multiple hash functions are used where thepreprocessing of a keyword is not identical but sharesa common and expensive intermediary result thatcan be reused. The caching capability we implementuses LRU removal policy [14, 17].

In addition, SADS preprocesses each item ofthe dataset independently (i.e., computes the BFsearch structure for it), and furthermore, it handlesthe elements of each item separately (each word/value is inserted into the Bloom filer after acryptographic transformation). This computationalindependence makes for simple and robustparallelization. The search phase, especially whenusing multiple hash functions, also permitsparallelization of the computation of the searchindices for a query. We used the open sourceThreading Building Blocks library [21] to implementthe parallelization optimization. It is easy to use andwell-integrated with C++. After analyzing thesource code we found out that there is just oneinteger counter that we need to synchronize amongthe different threads: the Bloom filters counter.It took roughly 10 lines of code to parallelize theentire preprocessing phase - similar for the searchphase too.

6. Evaluation

To evaluate the practicality of our proposedextensions we implemented them in SADS (roughly4 Klocs of C++ code in total) and we performed anumber of measurements using realistic datasets:(i) the email dataset that was made public after theEnron scan- dal [31] and (ii) a synthetic dataset withpersonal information for 100K persons. The Enrondataset consists of about half a million emails withan average size of 900 bytes after stemming. Duringthe preprocessing phase of SADS, a distinct Bloomfilter for each email was created. Then, each of theemail files was tokenized and the tokens where

stored in the corresponding Bloom filter, after theywere properly encrypted. The format of the seconddataset is more close to a database than a collectionof documents. Its schema consists of a single tablewith 51 attributes of three types: strings (first name,last name, etc.), numbers (height, SSN, etc.) andfile links (fingerprint, private key, security image, etc.)and it is stored in a flat CSV (Comma SeparatedValue) file. The total size of that dataset, along withthe files pointed in the records, is 51GB and theaverage size for a record is 512KB. During thepreprocessing phase we created a distinct Bloomfilter for each record and each of the attribute valueswhere inserted after it was prefixed with theattribute name ("name_value") and properlyencrypted. In both cases, we configured the BFparameters so as the false positive rate would beless than 10-6.

7. Search Performance

The introduction of the multiple hash functionsfeature in SADS poses a trade-off between efficiencyand privacy. Not only because of the highercomputation overhead has it added but also becauseit is in- compatible with the slicing optimization. Inthis section we explore in detail the effects of themultiple hash function scheme and also how parallelsearch could help amortize some of theperformance penalty.

The search time reported in this figure is thetotal time elapsed from the point when the clientissues the query to the QR until it receives the setof matching document IDs if any no documentretrieval. As expected, the average query time growslinearly using the original SADS configuration, as theactual search is done linearly over all the Bloom filters.Next, we can see that the slicing optimization greatlyreduces search time to a point that it seems almostconstant across different dataset sizes.

8. Document Retrieval

We implemented document retrieval using PH-SAEP and standard RSA signatures to sign queryresults. Using PH-SAEP puts a (likely over-restrictive) limit on the length of plaintext values.

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36

To handle this, we encrypt larger files using AESprivate key encryption, and store the key encryptedwith PH-SAEP as a header in the encrypted file. Thefiles can thus be read by decrypting the header withthe appropriate PH-SAEP key and using the resultto decrypt the content of the file.

9. Related Work

Most of the existing constructions providingencrypted search capabilities aim to solve the caseof database outsourcing [4-6, 8, 13]. In this settinga party outsources the storage of his database to anuntrusted server and wants to enable the server toexecute searches on his behalf without learninginformation about either the data or the query.Unlike the data sharing scenario that we consider,this setting does not impose privacy requirementsfor the data with respect to the querier. A commontechnique in encrypted search schemes [4, 13] isto use trapdoors derived from query terms thatenable the server to determine if a cipher textmatches the specific term. This implies the searchcomplexity will be at best linear in the number ofsearchable tokens. A different approach in theset- ting of database outsourcing is to use invertedindices, where the search structures directly mapall possible search terms to matches [8, 13]. Searchthen consists of finding the appropriate entry in thesearch structure for a given query's trapdoor. Suchsolutions leak the search pattern across a sequenceof queries and are not easily extendable to allowmore complicated queries beyond exact matchwhen we need to preserve the privacy of thedatabase from the querier.

Protecting the search pattern imposes efficiencycosts. Bellare et al. [22] showed that in order toachieve sublinearity of the search complexity overencrypted ciphertexts, deterministic encryption isrequired, which leaks the search pattern. The worksof [24] and [17] combine the idea of usingdeterministic encryption with Bloom filters [3] assearch structures. However, the Bloom filter searchstructures constructed in these works leak thesimilarity of the underlying documents to the partywho uses them for search. The work of [12] offers

a scheme that exchanges search pattern leakage forefficiency improvement. While the suggestedapproach achieves sub linearity of the searchcomplexity in terms of the number of searchablerecords, using preprocessing that transformssearchable tokens occurring in multiple recordswith unique tokens per record, it still requires timelinear in the number of all searchable tokenscontained in the matching records. Thus this solutionis appropriate for scenarios with small numbers ofsearchable tokens per record; its efficiencyimprovements do not suffice in the case of longdocuments that contain many searchable keywords.

10. Conclusion

When we consider the question of securesearch in practical settings, the privacy guaranteesof a scheme are no longer the only relevant issue: aperfectly secure scheme that no one can useprovides no actual privacy. The efficiency of anapproach becomes a major factor in determiningits usability given the available resources.

We adopted the relaxed security model of theSADS scheme; we extended its functionality byconstructing a document retrieval protocol that runsin time proportional to the size of the returned setof documents and by providing range queries overinteger data at a cost comparable to simple keywordqueries in the average case. Both extensions takeno advantage of any specific feature of SADS, makingthem applicable to any keyword-based privatesearch sys-tem. Additionally, we improved SADSby: (i) providing a protocol that facilitates databaseupdates without requiring processing of the wholedatabase, (ii) using different hash functions fordifferent BFs which provide better privacyguarantees and (iii) developing two implementationlevel optimizations, parallelization and caching.

The experimental results for the extended SADSsystem demonstrate its practicality: we achievesearch and document retrieval time which is on theorder of the time of ssh transfer and much betterthan the results from the most recent PIRimplementation presented in [28] (note that the PIRprotocol actually has weaker privacy guarantees than


37

what we need since it does not provide databaseprivacy), while we provide better privacy guaranteesthan the original SADS. In other words, we haveprovided strong- enough security and privacy, andat an acceptable cost.

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[25] A. Boldyareva, M. Bellare and A. O'Neill,Deterministic and efficiently searchableencryption. In: Proceedings of Crypto'07, (2007).

[26] Michael Mitzenmacher and Salil Vadhan, Whysimple hash functions work: Exploiting theentropy in a data stream. In: Proceedings ofthe ACM-SIAM Symposium on DiscreteAlgorithms, (2008) 746.

[27] Moni Naor and Benny Pinkas, Efficientoblivious transfer protocols. In Proceedingsof the ACM-SIAM Symposium on DiscreteAlgorithms, Philadelphia, PA, USA, 448(2001).

[28] Femi Olumofin and Ian Goldberg, Privacy-preserving queries over relational databases.In: Proceedings of PETS, 100.

The Relation between CMMI and Lean Software Development

39

The Relation between CMMI and Lean SoftwareDevelopment

JYOTI YADAV* and AMAN JATAINIT Department, ITM University, Gurgaon


AbstractAgile software development is a method of improving the effectiveness and performance of work processes.Everyone is practicing agile methodologies. Along with these, most of the organizations rely on process maturitymodels to assess and improve their own processes, since it has been getting clear that most project failures aredue to undisciplined processes. Many organizations demand cmmi compliance of projects where agile methodsare employed. This paper analyzes the interrelations and mutual restrictions between lean software developmentand approaches for software process analysis and improvement.

Key words : Agile, CMMI, lean, lean software development, process areas, maturity levels.

1. Introduction

In large organizations there are policies whichenforce that all parts of organization have to achievecertain maturity levels ( like those of CMMI). At thesame time, Lean software development is makingits way from manufacturing to software community.New approaches are offered by Lean softwaredevelopment to the existing challenges in softwaredevelopment. In this paper we would investigatethe relation between CMMI model and Leansoftware development.

2. Lean and Agile

Agile Work has borrowed heavily from Leanthinking and practices [2]. The best definition isgiven by National Institute of Standards andTechnology in the United States which defines leanas "a systematic approach to identifying andeliminating wastes (non-value added activities)through continuous improvement by flowing theproduct only when the customer needs it(called"pull") in pursuit of perfection."

The term, "lean", was first coined by John Krafcik.


3. Lean Software Development [1]

Bob Charette, the originator, writes that themeasurable goal of Lean development is to buildsoftware with one-third the human effort, one-thirdthe development hour and one-third the investmentas compared to what SEI CMM Level 3 organization

Fig. I. Steps of lean software development

Jyoti Yadav and Aman Jatain

40

would achieve. Figure I shows the generalmethodology to be followed in developing a projectusing lean thinking.

3.1 Value

The only thing that adds value in SoftwareDevelopment is transformation of information andcode into what customer wants. It is very importantfor software team to know how does it create valuefor customers. Or simply, decrypt the formula:Customer (needs) → 'Cash (delivered software)

3.2 Software Development Value Stream

Problems, needs and ideas are translated intounits of development - functionality, user experience(interface, interactions, usability) and system qualities(performance, reliability, security, etc). A SoftwareDevelopment team transforms these pieces ofrequirements into a computer system using value-added and many not-so-value-added actions.

3.3 Creating Flow

3.3.1One-piece flow

The most effective flow is one-piece flow-customer need is immediately converted into adelivered software solution.

3.4 Establish Pull

3.4.1Pull system (Kanban)

Kanban is a signaling system to trigger action. Itadds to flow small buffers pulled by customerdemand. Kanban allows optimal use of people andnatural breaks in processes.

What Kanbans Are:

Kanban is Japanese term for sign or designatedplace. It is used in manufacturing to mean a visualsignal that tells when it is time to get or make moreof something.

What Kanbans Do:

Controls the amounts of raw material amounts

and of material in Work In Process

Smooths out flow, if sized properly

Tells when and where there is a problem in theprocess.

Assures there is always just enough material onhand to make what is needed.

4. Roots of Lean Software Development

Lean operating system or lean principles hasbeen implemented in countless manufacturingcompanies and also adapted for industries as diverseas insurance and healthcare. Lean principles weredeveloped as Toyota production system by Toyotamotor company earlier known as Toyoda. Theconcept behind lean principles is to produce goodsusing less of everything compared to massproduction: less human effort, less manufacturingspace, less investment in tools, and less engineeringtime to develop a new product. Wipro an Indiansoftware company introduced lean principles insoftware development in Indian IT industry.

Wipro designed their LEAN initiative with 4 rulesin mind [3]

Rule 1: All work shall be highly specified as tocontent, sequence, timing, and outcome.

Rule 2: Every customer-supplier connection mustbe direct, and there must be an unambiguous yesor no way to send requests and receive responses.

Rule 3: The pathway for every product and servicemust be simple and direct.

Rule 4: Any improvement must be made inaccordance with the scientific method, under theguidance of a teacher, at the lowest possible level inthe organization.

Wipro first launched its lean initiative in 2004with a core team of managers. By the end of 2006,Wipro had 603 lean projects completed.

5. Principles of Lean Thinking


41

Principle 1. Eliminate Waste

Principle 2. Increase Learning/ Feedback

Principle 3. Make Decisions as Late as Possible/ Delay commitment

Principle 4. Deliver as Quickly as Possible/ Deliver fast

Principle 5. Empower the Team

Principle 6. Building Integrity In

Principle 7. See the "Big Picture"/ See the Whole

6. CMMI

According to the Software Engineering Institute(SEI, 2008), CMMI helps "integrate traditionallyseparate organizational functions, set processimprovement goals and priorities, provide guidancefor quality processes, and provide a point ofreference for appraising current processes" [4].

7. Roots of CMMI

CMMI was developed by the CMMI project,which aimed to improve the usability of maturitymodels by integrating many different models intoone framework. It consisted of a group of expertsfrom industry, government, and the SoftwareEngineering Institute (SEI) and the Carnegie MellonSoftware Engineering Institute (SEI). The mainsponsors included the Office of the Secretary ofDefense (OSD) and the National Defense IndustrialAssociation.

CMMI is the successor of the capability maturitymodel (CMM) or Software CMM. The CMM wasdeveloped from 1987 until 1997. Table I shows thevarious versions of CMMI released so far along withthe year of their release:

Table IVersions of CMMI

Version 1.1 2002Version 1.2 August 2006Version 1.3 November 2010

8. CMMI: Continuous and Staged [4]

CMMI exists in two representations: continuousand staged. The continuous representation isdesigned to allow the user to focus on the specificprocesses that are considered important for theorganization's immediate business objectives, orthose to which the organization assigns a high degreeof risks. The staged representation is designed toprovide a standard sequence of improvements, andcan serve as a basis for comparing the maturity ofdifferent projects and organizations.

9. CMMI Process Areas

Process areas are the areas that will be coveredby the organization's processes. The process areashave been listed below:

i. Project Planningii. Project Monitoring and Controliii. Supplier Agreement Managementiv. Integrated Project Managementv. Risk Managementvi. Quantitative Project Managementvii. Requirements Managementviii. Requirements Developmentix. Technical Solutionx. Product Integrationxi. Verificationxii. Validationxiii. Measurement and Analysisxiv. Process and Product Quality Assurancexv. Configuration Managementxvi. Decision Analysis and Resolutionxvii. Causal Analysis and Resolutionxviii. Organizational Process Focusxix. Organizational Process Definitionxx. Organizational Trainingxxi. Organizational Process Performancexxii. Organizational Innovation and Deployment

10. Maturity Levels in CMMI

There are five maturity levels. However,

Jyoti Yadav and Aman Jatain

42

maturity level ratings are awarded for levels 2through 5. The following Table 2 depicts the fivematurity levels and their characteristics:

Table 2

CMMI maturity levels and theircharacteristics [4]

Maturity level Characteristics

5 (Optimizing) Focus on process improvement

4 (Quantitatively Process Measured and controlled

managed)

3 (Defined) Process characterized for the organization

and is proactive

2 (Managed) Process characterized for projects and is

often reactive

1 (Initial) Process unpredictable, poorly controlled and

reactive.

Table 3Process areas and maturity levels

11. The Mapping of Process Areas and MaturityLevels

The process areas can be divided into four maincategories, i.e., Process management, Projectmanagement, Engineering and Engineering support.Table III shows the mapping between these maincategories of process areas, the process areasmentioned in section 9 and the maturity levels [5]:

12. Generic Goals and Practices of CMMI

Generic goals and practices are a part of everyprocess area [7].

GG 1 Achieve Specific Goals

GP 1.1 Perform Specific Practices

GG 2 Institutionalize a Managed Process

GP 2.1 Establish an Organizational Policy

GP 2.2 Plan the Process

GP 2.3 Provide Resources

GP 2.4 Assign Responsibility

GP 2.5 Train People

GP 2.6 Control Work Products

GP 2.7 Identify and Involve Relevant Stakeholders

GP 2.8 Monitor and Control the Process

GP 2.9 Objectively Evaluate Adherence

GP 2.10 Review Status with Higher LevelManagement

GG 3 Institutionalize a Defined Process

GP 3.1 Establish a Defined Process

GP 3.2 Collect Process Related Experiences

13. Specific Goals and Practices of CMMI [7]

Each process area is defined by a set of goalsand practices. These goals and practices appear onlyin that process area.

For example consider Causal Analysis andResolution (CAR) which is a support process areaat Maturity Level 5. The purpose of Causal Analysisand Resolution (CAR) is to identify causes of selectedoutcomes and take action to improve processperformance.

Process areas Process management Project management Engineering Engineering support

Maturity levels

Maturity Level 5 OID CAR

Maturity Level 4 OPP QPM

Maturity Level 3 OPF, OPD, OT IPM, RSKM RD, TS, PI, DAR

Ver, Val

Maturity Level 2 PP, PMC, SAM REQM M&A, PPQA, CM


43

CMMI implies Lean implies

Procedural IterativeExtensive planning Quick decisionsHierarchical governance Flat hierarchy/team governanceCareful changes Rapid changesBudget grows to meet Scope shrinks to meet deadlinesscopeHeavy documentation Light documentationRework is avoided Low level of Rework is expectedthrough planning andmonitoringRequirements are not Flexibility in changing

requirementsProcess controlled Equal participation of teamsManagement, Team and individual drivencommittees drivenRules are monitored Teams are trusted to follow rules

Table 4

Differences between CMMI and Lean

Specific Practices by Goal

SG 1 Determine Causes of Selected Outcomes

sSP 1.1 Select Outcomes for Analysis

SP 1.2 Analyze Causes

SG 2 Address Causes of Selected Outcomes

SP 2.1 Implement Action Proposals

SP 2.2 Evaluate the Effect of Implemented Actions

SP 2.3 Record Causal Analysis Data

14. CMMI and Lean: Commonalities

After discussing what CMMI and Lean are about,it would be easy to compare both of these. Thefollowing Table 4 are the commonalities:

i. Focus on eliminating defects and rework

ii. Reliance on measurement and statistical methods

iii. Emphasis on understanding and reducingvariability

iv. Adaptation necessary to transition approachesbeyond manufacturing

v. Trend towards over-simplification and "windowdressing" with popularization

15. CMMI and Lean: Differences [6]

16. Conclusion

CMMI and lean software development areapproaches to continuous improvement. This paperconcludes that CMMI tends to reduce risk in leansoftware development. These practices make goodsense, and you could argue that it has alwaysinherently been expected as part of your agilemethod. In general the CMMI model provides agood understanding what practices to consider -but you will have to adopt it to your context, andfind lean implementations for the practices.

References

[1] M. Poppendieck and T. Poppendieck, LeanSoftware Development: An ImplementationGuide: Addison-Wesley, (2006).

[2] Mishkin Berteig, Agile Work Uses LeanThinking.

[3] Julia Hanna, Bringing 'Lean' Principles to ServiceIndustries, (2007).

[4] h t t p : / / e n . w i k i p e d i a . o r g / w i k i /File:Characteristics_of_Capability_Maturity_Model.svg

[5] Jeffery L. Dutton and Richard S. McCabe,Agile/ Lean Development and CMMI® (2006).

[6] Jeff Dalton, President and Broadsword, AgileCMMI, Process Innovation at the Speed ofLife.

[7] h t t p : / / e n . w i k i p e d i a . o r g / w i k i /Capability_Maturity_Model_Integration.

S.M. Mustafa , N.U.K. Sherwani and Mini Walia

44

Women Empowerment and Entrepreneurship

S.M. MUSTAFA*, N.U.K. SHERWANI and MINI WALIADepartment of Commerce and Business Studies

Jamia Millia Islamia, New Delhi - 110 025*E-mail: [email protected]

AbstractEntrepreneurship has been indispensable factor contributing for development of many countries. It is dearth ofentrepreneurship, which has been foremost factor for backwardness of developing countries. Entrepreneurshiphas potential not only to increase the rate of growth but also solve many social, political problems and improvestandard of living. India also suffers from many such problems: like low growth rate, unemployment regionalimbalances, illiteracy, worsening social economic condition of women. Women constitutes almost 50% of totalpopulation of India. They suffer on various accounts socially, economically and politically. Entrepreneurship canbecome a powerful instrument to improve the condition of women. The paper attempts to analyzeEntrepreneurship as an instrument of economic empowerment of women. The main objective is to understandconcept of Entrepreneurship relevant to the issue, economic empowerment through Entrepreneurship, problemsand impediments in women Entrepreneurship and measures to remove them, role of government inempowerment of women, policy suggestions for the development of women entrepreneurship.

Key words: Women empowerment, entrepreneurship, income generation.

1. Introduction

It is noticeable that Entrepreneurshipdevelopment and empowerment arecomplementary to each other. Womenempowerment depends on taking part in variousdevelopment activities. In other words, theinvolvement of women in various entrepreneurialactivities has empowered them in social, economicand cultural fields.

When we speak about the term "WomenEntrepreneurship" we mean, an act of businessownership and business creation that empowerswomen economically, increases their economicstrength as well as position in the society.

2. Entrepreneurship and Entrepreneur

The term entrepreneurship concept has evolvedover a period of time. There are competiting


theories for it. Table 1 condenses all such importantapproaches.

For our purposes we define entrepreneurship:as a process of creating something different withvalue by devoting necessary time effort; assumingthe accompanying financial psychological and socialrisk and receiving the resulting rewards andmonetary satisfaction.

2.1 Characteristics of Entrepreneurship

This definition stresses four basic aspects ofentrepreneurship regardless of the field.

2.1.1 Entrepreneurship involves the creation process (creating something new of value)

The creation has to have value to theentrepreneur and value to the audience for which itis developed. This audience can be: (a) the marketof a buyers in the case of a business innovation; (b)the hospital's administration in the case of a newadmitting procedure and software; (c) prospectivestudents in the case of a new course or even college

Presently HOD, Department of Commerce and BusinessStudies, Al-Falah School of Engineering & Technology, Dhauj,Faridabad (Haryana).


45

of Entrepreneurship; or (d) the constituency for anew service provided by a non-profit agency.

2.1.2 Entrepreneurship requires the devotionof the necessary time and effort

Only those going through the Entrepreneurialprocess appreciate the significant amount of timeand effort it takes to create something new and makeit operational.

2.13 Assuming the necessary risks

This is the third aspect of Entrepreneurship.These risks take a variety of forms, depending onthe field of effort of the Entrepreneur, but usuallycenter around financial, psychological and social areas.

2.1.4 Reward of being entrepreneur

The Rewards of being Entrepreneur includemonetary independence and personal satisfaction,

for some of these entrepreneur money becomesindicator of the success for some independence andpersonal satisfaction are the most important.

According to Schumpeter "Entrepreneur is ainnovator who introduces new things in economy"Alferd Marshall defines Entrepreneur as indispensablefactor of production and assembler of resources.The exact definition of entrepreneur depends upondegree of development In underdeveloped anddeveloping counties the "innovators" in Schumpetersense are rare, what is primarily needed in thesecountries is not innovators perse but adaptors andimitators who forsee the business opportunities andcapable of organizing and exploiting businessopportunities by establishing the business venture.

Thus in Indian context entrepreneur is moreadaptor, imitator and exploiter of business throughorganizing various factor of production andassumption of risk associated with the venture. Thus,he is more marshall's organizer of productive factorrather than a true innovator.

Source: Robert D. Hisrich, Entrepreneurship and Intrapereneurship: Methods for Creating New Companies That have an impacton the Economic Renaissance of an Area, IN Entrepreneurship Intrapreneurship and Venture Capital ed. Robert D. Hisrich(Lexington MA: Lexington Books, 1986) P.96.

Period and Personality Their Opinion on Entrepreneur

17th Century-Gen. Concept Person bearing risks of profits (loss) in a fixed price contract with government.1725: Richard Cantillon Person bearing risks is different from one supplying capital.1797: Beaudeau Person bearing risks, planning, supervising, organizing and owning.1803: Jean Baptiste Say Separated profits of entrepreneur from profits of capital.1876: Francis Walker Distinguished between those who supplied funds and received interest and those who received

profit from managerial capabilities.1934: Joseph Schumpeter An entrepreneur is an innovator and develops untried technology.1958: Haggen An entrepreneur is an economic man who tries to maximize his profits by innovations.1961: David McClelland Entrepreneur is an energetic moderate risk taker.1964: Peter Drucker Entrepreneur maximizes opportunities through systematic innovations.1975: Albert Shapero Entrepreneur takes initiative, organizes some socio-economic mechanisms, and accepts risk

of failure.

1980: Karl Vesper Entrepreneur seen differently by economists, psychologists, business persons, and politicians.1983: Gifford Pinchot Intrapreneur is an entrepreneur within an already established organization.1985: Robert Hisrich Entrepreneur is the process of creating something different with value by devoting the necessary

time and effort, assuming the accompanying financial, psychological, and social risks and receivingthe results rewards of monetary and personal satisfaction.

Development of Competing theories of Entrepreneurship.

Stems from French: means "between-taker" or "go-between".

Table 1


46

3. Empowerment

The World Bank defines empowerment as

"The process of increasing the capacity ofindividuals or groups to make choices and totransform those choices into desired actions andoutcomes. Central to this process are actions whichboth build individual and collective assets andimprove the efficiency and fairness of theorganizational and institutional context which governthe use of these assets."

Reflective Models

Model No. 01

Model No. 02

Model No. 03

Model No. 04Inherited Legacy

Women Entrepreneur

↓↓↓↓↓

Small Enterprise

↓↓↓↓↓

Middle Enterprise

↓↓↓↓↓

Large Enterprise

↓↓↓↓↓

Giant Enterprise(MNCs / TNCs etc.)

3.1 Characteristics of Empowerment

(i) Empowerment is multidimensional and refers tothe expansion of freedom of choice and actionin all spheres (social, economic and political) toshape one's life.

(ii) It also implies control over resources anddecisions. For women such freedom is oftenseverally curtailed due to gender inequality inthe household as well as in the society. Thus,for empowerment women require a set of assetsand capabilities at the individual level (such ashealth, education, and employment) and at thecollective level for (instance the ability toorganize and mobilize to take action to solvetheir problems).

3.2 Need for Empowerment of Women

(i) Our constitution in its Fundamental Rights, hasprovision for equality, social justice andprotection of women. These goals are yet tobe realized. Women continue to bediscriminated, exploited and exposed toinequalities at various levels.

(ii) By empowerment women would be able todevelop self-esteem and confidence, realize their

Factor leading to Women's growth

Women's growth

Women's Role (in the society)


47

potential and enhance their collective bargainingpower.

(iii) Women empowerment can be viewed as acontribution of several inter-related and mutuallyreinforcing components.

(iv) Awareness building about women's situations,discrimination, rights and opportunities will actas a step towards gender equality.

(v) Capacity building and skill development,especially the ability to plan, make decisions,organize, manage and execute will enable to dealwith people and institutions in the course ofbusiness.

(vi) Participation and greater control and decision-making power in the home, community andsociety will develop leadership qualities.

(vii)Action is needed at all levels to bring aboutgreater quality between men and women.

Thus empowerment is a process of awarenessand capacity building, leading to greater participation,greater decision-making power and control of thetransformative action. The empowerment of womencovers both individual and collective transformation.It strengthens their initiative ability through acquiringknowledge, power and experience.

3.3 Factors Affecting Empowerment of Women

Low status of women in society indicated byunfavourable sex ratio and low literacy level.

Strong preference for male child.

Gender discrimination

Low level of education.

Food nutritional status.

Violence against women

Poor health and lack of access to health care.

The most important factor that effects theempowerment is the poverty.

3.3.1 Kinds of empowerment

There are three kinds of empowerments.

(i) Social: It is a long different process and requiresa change in mind set of the people. This callsfor attitudinal change.

(ii) Political Empowerment: This calls for increasingthe participation of women in political decisionmaking.

(iii) Economic Empowerment: That calls for increasingincome of women to their disposal andownership over asset.

Economic Empowerment is a key to social andpolitical empowerment. As the income of womenand their participation in income generating activitiesincrease it not only increase their family income butalso brings economic independence among womenin household. This helps them to participate moreeffectively in intra-household decision-making andbetter access to information. The female workparticipation to ensure alone cannot ensure economicempowerment as ownership still be in hands of malemembers. Therefore, there is need to ensureautonomy and over resources. If this happens, thiswill elevate their status in family and society. Elevationof social and political status will elevate theirparticipation in political decision making also.

Economic Empowerment t hrough Entre-preneurship: Entrepreneurship women areeconomically more powerful than mere worker asownership of entrepreneur confers control overassets but also give her freedom to take decisions.

3.4 Benefits of Women Entrepreneurship

(i) It makes women more powerful than merelyworking. Entrepreneur women are economicallymore powerful than mere worker as ownershipof entrepreneur confers control over assets butalso give her freedom to take decisions.

(ii) Upliftment of social status significantly: Ownershipof resources and participation as controller ofenterprise not only generates income but alsobrings economic independence. This helps themto participate more effective in householddecision making this elevates their position infamily and society.


48

(iii) Reduction in poverty: The generation of incomethrough multiplier effect will result in povertyalleviation.

(iv) Entrepreneurship is likely to emerge as only viablealternative of income generation in changedcircumstances. Various changes like shrinkage ofgovernment sector jobs, population growth islikely to push more women intoentrepreneurship.

(v) Entrepreneurship helps to overcome constraintsrelated to female employment. Self-employmentof entrepreneurship will help women tocircumvent various institutional and culturalconstraints with respect to female employment.

(vi) Entrepreneurship can ultilize skills and practicesof women which are unsuitable to big organizedsector.

(vii)It turns to job seekers into job creators: Throughentrepreneurship a women will not only generateincome for herself, but also employment forother women in locality. Thus helping to solvetheir problem of unemployment.

Thus, it is evident that entrepreneurship is aninstrument for empowerment for women.

4. Women Entrepreneurs

Women Entrepreneurs may be defended aswomen or group of women, who initiate, organizeand operate a business enterprise.

According to the Government of India, "awomen entrepreneur is defined as 'an enterpriseowned and controlled by women having a minimumfinancial interest of 51% of capital and giving at least50% of employment generated in enterprise towomen'. This definition was revised in August 1991,by dispensing with the employment criterion forwomen workers.

4.1 Trends in Women Entrepreneurship in India

(i) Small percentage of women Entrepreneurshipas compare to men; women entrepreneurship

constitute a negligible proportion of the totalentrepreneurs attitudinal constraints socialtraditions, kenship system inhibit theentrepreneur.

(ii) Different kinds of women entrepreneurs; TheWomen Entrepreneurs can be classified intofollowing categories:

(a) women who take to entrepreneurshipbecause they have dire economic needs.

(b) women who take to entrepreneurshipbecause they had the family backgroundtradition or skill or trade, hence they wouldlike to have extra money for themselves andtheir families.

(c) women who take it up because they havecertain personality characteristics such asneed for achievement, need for power andinfluence etc.

(d) women who take it up as a leisure timeactivity, and

(e) on official advice and guidance.

(iii) Less Diversified Area of WomenEntrepreneurship:

The typical women enterprise all the extensionof kitchen activities. The 3 Ps Viz pickles, powder(masala) pappad, or the traditional cottage industriesof basket making handicarfts etc. But as theeducation is spreading and growing awarenessamong women, women entrepreneurs are enteringinto engineering electronics energy, and many otherindustries. Although the number of such units is smallwomen all putting up units to manufacture solarcookers T.V. capacitors, electronic ancillaries andsmall foundries.

In recent survey business women in Delhi andsurrounding areas it was estimated that 40% ofthese entrepreneurs have ventured into non-traditional areas such as electronics, engineeringconsultancy etc.

(iv) In India very few women entrepreneurs are inbig enterprise. They all mainly concentrated insmall scale.


49

4.2 Problem Faced by Women Entrepreneurs

It is important to know that impediments to thegrowth of women entrepreneurship. The mainimpediments are:

Shortage of Finance.

Inefficient arrangement for marketing and sale.

Change of role.

Time management

Lack of required education and skills.

Lack of exposure to business environment.

Less mobility of women.

Low risk taking capability.

Lack of access to credit due lack of informationabout schemes, collateral security.

Lack of inefficient arrangement market and sale.

Family responsibilities.

Social attitudes discriminating against women.

To overcome these impediments steps have tobe taken on the following fronts.

5. Remedies to Solve the Problems of WomenEntrepreneurs

The following measure may be adopted to solvethe problems faced by women entrepreneurs inIndia.

Finance Cells: In various public financial institutionsand banks special cells may be opened for providingeasy finance to women an entrepreneurs. These cellsshould be manned by women officers and clerks.Efforts should be make to provide finance at thelocal level. Finance to women entrepreneurs maybe provided at concessional rates of interest and oneasy repayment basis.

Marketing Cooperatives: Encouragement andassistance should be provided to womenentrepreneurs for setting up cooperatives. Thesecooperatives will pool the inputs of womenenterprises and sell them on remunerative prices.Such cooperative will help to eliminate themiddlemen. Central and State Government shouldgive priority to women entrepreneurs while

purchasing for their requirement.

Supply of Raw Materials: Scarce and imported rawmaterials may be made available to womenentrepreneurs on priority basis. A subsidy may alsobe given to make the products manufactured bywomen entrepreneurs cost competitive.

Education and Awareness: It is necessary to changenegative social attitudes towards women. Elders,particularly, mother - in- law, need to be made awareof the potential of girls and their due role in society.Unless the social attitudes are made positive notmuch progress can be made by womenentrepreneurs.

Training Facilities: Training all skills are essential forthe development of entrepreneurship. Trainingschemes should be so designed that women cantake full advantage. Family members do not likewomen to go away to far off places for training.Therefore, mobile training centers should bearranged. Similarly, part time training facilities,especially during afternoons will attract more womento acquire skills. Additional facilities like stipend, goodhygienic crèches, transport facilities etc should beoffered to attract more and more women to thetraining centers.

In solving these problems NGO's (like SEWA)and associations of women (like NAYE Indian Counselof Women Entrepreneurs IICCI, NationalCommission on Self-Employed in informationsector) are played an important role.

Role of Government in Empowerment of Women(with emphasis on 10th five year plan)

Women received attention of the governmentright from the beginning of Indian Planning. However,the shift from "Welfare" to "development" of womentook place in Sixth Five Year Plan (1980-85). TheEighth plan (1992-97) promised to ensure thatbenefits of development from different sectors donot bypass women. The Rashtriya Mahila Kosh wasset up in 1993 to meet the credit needs of poorand assetless women. The Ninth Plan (1997-2002)made two significant changes in the strategy of


50

planning for women. Firstly, "empowerment ofwomen" became a primary objective and secondlythe Plan attempted "convergence of existing services"available in both women-specific and women relatedsectors.

The Tenth Plan (2002-2007) has made a majorcommitment towards "empowering women as theagent of socio-economic change and development".Based on the recommendation of National Policyfor Empowerment of Women, the Tenth Plansuggests a three-fold strategy for empoweringwomen, though social empowerment economic,empowerment and gender justice.

(i) Social Empowerment: To create an enablingenvironment through various affirmativedevelopmental policies and programmes frodevelopment of women besides providing themeasy and equal access to all the basic minimumservices so as to enable them to realize theirfull potentials.

(ii) Economic Empowerment: to ensure provisionof training employment and income generationactivities with both forward and backwardlinkages with the ultimate objective of makingall potential women economically independentand self-reliant. And

Gender Justice: To eliminate all forms of genderdiscrimination and thus, allow women to enjoy notonly the de jure but also de facto rights andfundamental freedom at par in all the sphere, Viz.political, economic social, civil, cultural etc.

The Government is taking the following measuresfor empowering women.

(i) To adopt a special strategy of "women'sComponent Plan" to ensure that less than 30%of funds / benefits flow to women from otherdevelopment sectors.

(ii) To organize women into Self-Help Group andequip them with services of awarenessgeneration and income generation throughtraining, employment, credit and marketinglinkages to small entrepreneurs etc. progra-mmes like Indira Mahila Yojana (IMY) now recast

as Integrated Women's Empowerment Project,(IWEP), and Rural Women's Empowerment andDevelopment (RWEDEP) have been launched.Of the total Ninth Plan target of 50000 morethan 37000 groups wee set up benefiting abouta lakhs women.

(iii) To equip women with necessary skills in themodern upcoming trade which would keepthem gainfully engaged besides making themeconomically independent and self-reliant and

(iv) To increase access to credit through setting upof a development "Bank for WomenEntrepreneurs" in small and tiny sectors. Thecorpus of Rashtriya Mahila Kosh is beingenhanced for this purpose.

5.1 Income Generation

The Support of Training and EmploymentProgramme (STEP) provides a comprehensivepackage of up gradation of skills through training,extension inputs, market linkages, etc. in thetraditional sectors like agriculture, handicrafts etc.

Setting up of an Employment and IncomeGeneration Training -cum-Production Centre forWomen (NORAD) extends training for the poorand needy women in the age group of 18-45years in the upcoming non-traditional trades.

The Socio Economic Programme (SEP) provideswork and wages to the needy women and

The Condensed Courses of Education andVocational Training (CCEVT) provide new vistasof employment through continuing educationand vocational training for school dropouts.

5.2 Other Activities

In India, a large number of training andpromotional activities are being organized todevelop entrepreneurial skill among women. Someof these programmes are exclusively for the women,while others take women alongwith the maleparticipants. The institutions undertaking suchactivities can be divided into three broad categoriesviz (i) specialized institutions, which are responsiblefor training and entrepreneurship developmentmainly among small and medium enterprises (SMEs)


51

(ii) banks/ financial institutions (iii) governmentdepartments / agencies. The first category includesinstitutions like the Indian Institute ofEntrepreneurship (IIE) Guwahati, National Instituteof Small Industry Extension Training (NISIET)Hyderabad and the National Institute ofEntrepreneurship and Small Business (NISBUD),Ministry of MSME, Govt. of India, N. Delhi. WomenEntrepreneurs wing of NAYE Indian Council ofWomen Entrepreneurs, FICCI Ladies Organisation(FLO). Almost all public sector banks and the leadingfinancial institutions e.g. Small IndustriesDevelopment Bank of India (SIDBI) NABARD etc.conduct a number of training courses for womenentrepreneurs. Besides, various Ministries /Departments in the Union and State Governmentsalso organize from time to time various trainingprogrammes for skill upgradation and incomegeneration of the women.

In this era of post-economic reformsempowerment of women is vital for eliminatingpoverty and overall development of the economy.Since social empowerment is a long-termphenomenon, emphasis needs to be given economicempowerment of women. Once women areeconomically independent they will be able toovercome their dependency on the household aswell as the society. Entrepreneurship developmentor income generating business activities is a feasiblesolution for empowering women.

5.3 Suggestions for Women EntrepreneurshipDevelopment

Keeping in few the constraints faced by womenentrepreneurs following point are suggested forwomen entrepreneurship development.

Women entrepreneurship need to "start smallbut think big". Once the initial hurdles are crossedthey will be more confident to face challenges andtake risk. Later it is possible to expand the horizonof their business.

Should have some prior knowledge or skillbefore starting the enterprises.Undertaking feasibility study and risk assessmentbefore starting.

Better to have some start up capital.Use easily available resources (both physical andhuman)

Initially it is always better to work as a frachisee/supplier to a reputed company.Marketing of the products can be given tospecialized agencies. Collaboration with analready existing company is always better for astart up.

Women can also form, self-help groups(SHG'sGHs) or cooperatives if starting anindividual enterprise is not viable.

References

[1] S.K. Damaje, Women Entrepreneurs.Opportunities performance and Problems;Deep & Deep Publishers New Dehli, (2002).

[2] Deegam S. Rasia and Sargnadharam, WomenEntrepreneurship: Institutional support andProblems; New Publishing House, Edition,(1995).

[3] S. Ganeshan, Status of Women Entrepreneur-ship in India; New Delhi, Tanishakar Publishers.New Delhi.

[4] Vadhera Randeep, editor Sasi Kumar Writeview of Enterprise and Empowerment ofWomen Review, Vikas Publishing House, NewDelhi.

[5] Natha Bhola and Kumar Uppal, Issues onEmpowerment of Women; An IndianExperience, Mohil Publishers, (2004).

[6] Robert D. Hisrich "Entrepreneurship andIntrapreneurship: Methods for Creating NewCompanies that have an impact on theeconomic Renaissance of an Area, Lexington:Lexington Books (1986) 86.

[7] Peters P. Michael and Hisrich D. Roberts,Entrepreneurship Tata MC. Graw Hill Edition,Edition (2002).

[8] C.B. Gupta and Srinivasan, Entrepreneurshipdevelopment in India (Text and Cases) SultanChand & Sons, New Delhi.

[9] Drucker Peter, Innovation andEntrepreneurship Practice and Principles;William Heinemann Ltd. Great Britain, (1985).


52

[10] S.C. Poornima, Kumar Anil and K. Jayshree.[11] Entrepreneurship Development; New Age

International Pvt. Ltd., Publishers, New Delhi.[12] Mishra Dutt Bhaskar, Journals: Small

Enterprise: An Introduction to the Study ofpopulation; South Asian Publishers Pvt. Ltd.,New Delhi.

Journals1. Journals: SEDME (Small Enterprise

Development Mgt. and Extension Journal).2. Journal Small Business and Entrepreneurship.3. Census Report.4. Yojna.

Evalution of Excimer Lasers : A Review

53


N.R. DAS

Laser Science & Technology Centre, Metcalfe House, Delhi-110 054E-mail: [email protected]

AbstractThis paper reveals the latest emerging applications and trends of Excimer laser in industry. The widely knownareas of applications viz. material processing, engineering, metrology, scientific research, medical diagnosticstool, communications, holography and of course military applications are emphasized here. The most recentadvances in the application scenario like nano science and engineering are described elaborately. Among allindustrial lasers, Excimer lasers are becoming the most important and widely accepted tool to carry out variousapplications in the industry, specially in micromachining and marking applications. The paper describes adetailed theoretical case study of a small Excimer laser and its comparison with conventional Excimer laser.The various latest applications of small Excimer laser are also described here.

Key words : Nanoscience, carbon nanotubes, excimer laser, industrial applications.

1. Introduction

In 1965 the first industrial-laser processingsystem was installed by Raytheon Company at theBuffalo, N.Y plant of Western Electric Co. (now AT& T). The beam energy from a ruby laser was usedto drill holes in industrial diamonds to produce diesfor fine-wire drawing. From this modest start a vitaldynamic industry, currently producing multi billiondollars of industrial systems, evolved. The word'laser' is an acronym for 'Light Amplification byStimulated Emission of Radiation'. Laser radiation hasa number of unique properties - high intensity(power) of electromagnetic energy flux, highmonochromaticity and high spatial and temporalcoherence. Hence, laser radiation differs from othertypes of EM radiation in that it travels as a verynarrow focused high intensity beam. It is thisinherent property that is made use in almost all laserapplications.

The applications of lasers [1-6] have multipliedto such an extent that almost all aspects of our daily


lives are touched upon, albeit indirectly, by lasers.The widely known areas of applications are materialprocessing, engineering, metrology, scientificresearch, medical diagnostics tool, communications,holography and of course military applications. It isclearly impossible to give an exhaustive survey of allof these applications attempted worldwide. Theemphasis here has been to identify the importantemerging laser applications in novel areas of scienceand technology. Attempt has been made to highlightonly the most recent advances in the applicationscenario. There are plenty of commercial lasersavailable in the market viz. CO2 laser, Nd: YAG etc.Excimer lasers are becoming the most importantand widely accepted tool to carry out variousapplications in the industry, specially inmicromachining and marking applications.

It is for this reason, a typical case study of smallExcimer Laser application has been brought out.These are now the state of the art lasers because ofrelative ease of design, development, compactness,ease of operation and most of all efficient today for

N.R. Das

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all purpose industrial applications. Most of all thesenow require reasonably cheaper investments.

2. Latest Trends

2.1 Laser Ablation Technique in NanoscienceEngineering & Technology

Carbon nanotubes (CNT) discovered in theearly 1990s have high tensile strength, Young'smodulus and other mechanical properties holdpromise for high strength composites for structuralapplications. Some of the potential applications ofCNTs are nanoelectronics, sensors, field emission,displays, hydrogen storage, batteries, polymermatrix composites, body armour, reinforcementmaterial, nanoscale reactors, and electrodes. Thenanotube growth technique involves the arc processand the recent laser ablation process. It is thisprocess of laser ablation that is fast emerging as themost reliable and efficient growth techniquemechanism of CNTs. One of the most recent reportsays, NASA is now developing materials usingnanotubes for space applications, where weightdriven cost is the primary concern [7-12].Companies such as Samsung and NEC have investedtremendously and demonstrated product qualitydevices using CNTs for field - emission displays.

Another important aspect i.e Quantum Dotsmay not have attracted nearly as much mediaattention as carbon nanotubes, but are the stuff offuture flat-panel displays, lasers and lighting.A quantum dot is a cluster of atoms that measuresonly a few nanometers, which is microscopic.A human hair is about 80,000 nanometers wide.A quantum dot has the unique ability to absorb lightand then re-emit it in a different color. Different-sized quantum dots can emit colors that span thespectrum, from ultraviolet to infrared. Quantumdots are used for biological detection in drugdiscovery, life science research and medicaldiagnostics.

2.2 Nanostructured Materials

A surprising number of industries, fromceramics to cosmetics, metals to paints and coatings,

electronics and cutting tools rely on powderedmaterials to produce their products and theproduction of these powders is by no means amature technology. New, improved laser processingtechniques particularly the laser ablation processesare being developed for this. Indeed, it is advancingrapidly and creating new possibilities formanufacturers.

The goal of nearly all powder-based processinghas always been smaller size and improving theuniformity of particles. And new methods of powderproduction and synthesis are rapidly pushing the limitlower and lower. Particles of submicron sizes arenow critical to advancements in numerousapplications. Ultrafine powders are essential materialsin the production of catalysts, coatings and films,conductive pastes, cosmetics, electromagneticcomponents, electronic devices, fire retardantmaterials, magnetic fluids, sintered and injectionmolded metals, ceramic composites, magneticstorage media, phosphors, pigments, polishingmedia, and toners.

2.3 Microelectronics & Opto-ElectronicsManufacturing

Global competitive pressures and the ever-increasing demand for faster, smaller, less expensiveelectronic systems have produced fundamentalchanges in processing technologies. Laserprocessing of materials, once largely curiosity driven,is now an established technology formicromachining, thin-film synthesis, deviceprototyping and even nanoscale synthesis [13-17]and processing of materials. The main driving forcebehind these developments is the seemingly limitlessadaptability of lasers in providing unique materialprocessing solutions, manufacturing of otherwiseunattainable devices, and the implementation of cost-effective solutions to complex manufacturingprocesses. The use of lasers for manufacturingmicroelectronic, optoelectronic and MEMS devicesis now becoming an established enabling technology.

2.4 Electrochemical Microfabrication

A variety of microelectronic components are


55

manufactured with high-yield, cost-effectiveelectrochemical processing. Electrochemical micro-fabrication uses electrochemical methods to createthin & thick-film-patterned microstructures.Electrochemical deposition (plating) is the oldestindustrial application of an electrochemical reaction.Both electroplating and electroless plating processesdeposit pure metals or alloys from metallic ions insolution.

Electrochemical processing through polymericphotoresist masks is a primary technique formicrofabrication of high-density patternedstructures. Photolithography is the exposure ofphotosensitive resist to ultraviolet light to transferan original image. Advances in optical lithographyhave continued to meet increasing demands for high-resolution patterning. Using X-ray lithography, it ispossible to pattern advanced three-dimensionalstructures in which high-aspect-ratio profiles withminimal distortion are required. Storage, packaging,device fabrication, and several other aspects ofmicroelectronics have been affected byelectrochemical processing.

Some of the practical applications of lasers inthe manufacturing process of micro and nanoscaleelectronic, photonic and hybrid devices beingattempted are

• laser modification of materials (annealing, doping,intermixing, photosensitivity). The processoffers a method of selecting area band-gapshifting (QW/QD intermixing) for writing ofmonolithically integrated (nano) photonicdevice. Figure 1 represents IR and UV laserbased rapid thermal annealing. Figure 2represents Excimer/UV laser controlledquantum well intermixing. The UV laser QWItechnique offers the ability to control amplitudeof the band-gap shift by monitoring surfaceproperties of the excimer laser irradiatedmaterial with photoluminescence, Ramanspectroscopy or other non-contact opticaltechniques.

• laser microwelding, drilling, cutting and etching

• laser cleaning, texturing, bending and repair

• laser micromachining and rapid prototyping• laser processing across wavelength scales from

VUV to IR• laser manufacture of MEMS and other devices• laser microprocessing of electronic and

optoelectronic materials for advanced devices• laser nano-engineering including nanostructures

and nanomaterials fabrication• diagnostics for laser produced plasmas, including

real-time monitoring techniques• generation and dynamics of laser ablation plumes,

including gas-dynamic effects, charge generationand charge transfer

• modeling of laser-materials and laser-plumeinteractions for quantitative prediction ofprocess parameters

It is widely recognized that further progress inthe photonics and telecommunication industry willbe related to novel concepts of using photons forincreased data transfer, manipulation and storage.On the device level, the task of increasing thenumber of different operations performed by aphotonic device in an ever-shrinking volume willrequire nanoscale manufacturing precision. This alsoapplies to even more technologically challengingquantum semiconductors, such as quantum dots(QDs), quantum wires, nanoclusters, and variousnano-composites. In spite of the spectacularprogress in this field, present-day technologies ofsemiconductor materials and devices are far fromadequate to meet the challenge of nanoscalemanufacturing precision of photonic devices. Thus,new enabling technologies and processing schemeshave to be developed to address this issue.

The fundamental technologies in our focus are:

a) Laser-induced quantum well intermixing (QWI),which is based either on IR/UV laser RapidThermal Annealing, or on UV laser (excimer)irradiation. In addition to GaAs and InP basedQW microstructures, we also investigatequantum dot intermixing (InAs-based and other).

b) Excimer laser surface modification andnanocrystal formation. Both II-VI and III-V

N.R. Das

56

materials are of primarily interest. However, wehave also been involved in crystallization of high-temperature oxides, such as SrFeyCo1-yO2.5-x.

Fig. 1. IR and UV laser based rapid thermal annealing

Fig. 2. Excimer/UV laser controlled quantum wellintermixing

2.5 Micro Electro-Mechanical Systems

Micro electro-mechanical systems (MEMS) areminiaturized machines that include sensors andactuators. Micro-fabrication of these componentswith silicon employs basic integrated circuitprocesses that incorporate special laser etching andbonding techniques to create three-dimensionalstructures with micrometer resolution.Electrochemical technology, which entered theelectronics industry as a manufacturing process forlow-end printed-circuit boards, is now employedfor advanced processing to fabricate complexcomponents, such as MEMS, high-end packages andstorage systems, and high-performance chipinterconnections. This has required an understandingof electrochemical transport, current distribution,

process monitoring and control, as well as the abilityto develop environmentally friendly processes. Thedevelopment of nano-processing for further MEMSminiaturization and fabrication of giantmagnetoresistance materials by lamination of asandwich of nanometer-thick electroplated layersare among the emerging applications ofelectrochemical microfabrication that may have animpact on the performance of future microelectronicdevices. All these are now becoming increasinglypossible because of new laser sources possible todo fine etching, scribing etc.

2.6 Manufacturing Opportunities

Free-electron lasers (FELs) offer substantial costand capability advantages -- including advantages forhigh-volume materials processing -- over othermanufacturing tools. FELs based on Jefferson Lab'ssuperconducting electron-accelerating technologyare being developed to process plastics, syntheticfibers, advanced materials, and metals as well ascomponents for electronics, microtechnology &nanotechnology. Prospective products includedurable yet attractive polymer fabrics for clothingand carpeting; cheap, easily recyclable beverage andfood packaging; corrosion-resistant metals withincreased toughness; mechanical and opticalcomponents with precisely micro-machinedfeatures; micro-circuitry; and electronics for use inharsh conditions. Consortium members expectadditional applications to evolve along with thetechnology itself. It may also be known that theselasers form one of the most important defencerelated applications for US Navy.

2.7 Chemical, Oil and Gas Industry

2.7.1Deadly gas leak detection by lasers

A revolutionary new laser device capable ofinstantly detecting potentially deadly gas leaks hasbeen developed by Scottish scientists. Thepioneering machine can create a detailed image ofescaping gas on a video screen within seconds ofsafety inspectors arriving at the scene. Gas-detectingdevices currently used by investigators can detectthe presence of gas which is invisible to the naked


57

eye but not the source of the leak. Valuable hours, ifnot days, can be lost in the search, with potentiallydisastrous results resulting in loss of money andhuman lives.

In recent laboratory trials of the prototype thescientists used it to obtain a picture of a cloud ofmethane gas escaping from a hose. It also meansthat gas suppliers will be able to more easily andquickly monitor their many miles of pipelines forfaults and take pre-emptive action before a life-threatening situation arises. The operator of the newdevice, which will also be portable, will be able toshine a laser beam around a room in which a leak issuspected. Any gas present will absorb the laser lightand the operator will see a darkened image appearon a video screen. If gas is present, very little lightwill go back to the detector and the operator willimmediately see a dark plume coming from the areawhere the leak is located. The new detector canalso be used to locate leaks from main pipes instreets and in industrial complexes which may havemany miles of piping.

2.8 Aerospace Industry

Due to its strict safety requirements, theaerospace industry has so far made little use ofthermal joining methods. Yet lasers offer immensepotential for reducing costs in this industry, too.Furthermore, lasers can significantly reduceproduction time, and aircraft manufacturers arebeginning to exploit the savings potential byincorporating lasers in their production processes.These factors will strongly promote the use of solid-state lasers in the aerospace industry, which meansthat significant growth potential exists in this marketsegment, as well. Lasers are finding their firstconcrete application in various projects, which isusing them to weld the outer skin of an aircraft tail.

3. Small Excimer Lasers Opening Up NewIndustrial Applications

The development of small excimer lasers [3]with relatively small pulse energies but with thecapability of reaching high repetition rates, coupledto acceptable gas lifetimes and good beam quality,

has opened up new opportunities for laserapplications in manufacturing. In some nicheapplications, such as ophthalmology andmicromachining, these lasers provide comparableenergy density to their much larger counterparts.With proper overall laser system design, sufficienttarget areas can be covered. Such small lasers allowproduction engineers to seriously consider using suchlasers systems due to the reduced capital investmentand small footprint.

Significant technical advances in laser design havecontributed to the acceptance of the excimer laseras one of the three principle laser sources formanufacturing. This advancement continues in theescalation of average power (200W) in order tomeet the through put demands of some key micro-electronic markets. At the other end of thespectrum, small excimer lasers (<2.0W) arebecoming more popular and are poised to join theindustrial establishment. Below are some criticalissues explored, some of the new applications andbenefits of this technology.

3.1 Whats a Small Excimer Laser?

Small excimer pulsed gas lasers operate in thedeep ultra-violet spectrum (193nm, 248nm) withan output pulse energy between 5mJ to 10mJ andwith repetition rates up to several hundred Hz.Typical beam sizes are in the order of 10 mm2 witha classic "top hat" profile in one direction and a nearGaussian distribution in the other direction. Full anglebeam divergences are less than 1mrad in somemodels. Pulse to pulse energy variations less than± 5%.

3.2 Beam Delivery

Unlike RF-excited excimer lasers whose pulseenergies are measured in terms of micro joules andutilize a focal point technique to machine materials,small excimers adopt the similar mask projectiontechniques used by conventional excimer lasersources.

The excimer laser beam illuminates a maskcontaining a motif or pattern which is then "imaged"

N.R. Das

58

on to the workpiece. With such a technique, smallcomplex patterns with relatively high resolution andsharpness can be etched on to a workpiece. Forrepeatable patterns, a positioning table is used in a"step & repeat" process to make multiple patterns.Rotary masks can be inserted into the beam path toallow for a series of different features to be machinedon to the workpiece. By carefully adjusting theposition of the mask and image lens, one can controlthe demagnification or "reduction" value whichaffects the final image size and energy density.

3.3 Energy Density

For the purposes of discussion, we can define aconventional 248nm excimer laser working in aproduction environment as having a pulse energy of250mJ with a beam size of approximately 25mm x10mm. This translates into a raw laser beam fluenceof approximately 100J/cm2. Taking into accounttransmission losses, the resultant target energydensity with a demagnification of 15 will exceed 20J/cm2. At such levels, the majority of materialsassociated with the medical device, micro-electronicand semiconductor industries can be machined,including plastics, polymers, ceramics, thin metalsand glass. In fact, most plastics and polymers willmachine very well below 5J/cm2.

Using the small excimer laser definition, the rawlaser beam fluence is comparable to a conventionalexcimer laser even though the conventional laserhas 25 times more pulse energy. This means thatpractical demagnification values can be used to obtainsuitable on target energy density when using a smallexcimer laser.

3.4 Target Area of Influence

One of the tradeoffs between using aConventional Excimer laser or a Small Excimer isthe illumination area at the target. Although bothlasers are capable of delivering the same energydensity to the target, the illumination area isproportional to the pulse energies of the laser types.For example, taking into account transmission losses,a 250mJ Conventional excimer laser can illuminate a8mm2 target with a fluence of 1.5J/cm2. At the same

energy density, a small laser can only illuminate0.25mm2 area. To put this number into perspective,0.25mm2 is equivalent to a 500 micron diameterhole. Therefore, a small excimer laser has sufficientphotons to drill or etch in many plastics andpolymers with features sizes below 500 microns.

As one increases the target energy density, theavailable illumination area will decrease linearly.Therefore etching ceramics and hard dielectrics willrequire typically 10J/cm2, equivalent to drilling a 200micron diameter hole. For thin metal foils such asstainless steel or nickel with a threshold of 20J/cm2,a hole measuring 150 microns can be drilled with asmall excimer laser.

3.5 Degree of Usage

Due to recent technical advances of conventionalexcimer lasers, the gas lifetime can be severalhundreds of millions of shots per gas fill. On theother hand, small excimer tend to have gas lifetimeson the order of 1 to 2 million shots. If an industrialapplication requires several million shots per day, itmay be impractical to use a small excimer due tothe number of refills required. Also conventionalexcimers have been used for medium to heavyindustrial applications for some time withcorresponding effort by manufacturers to improvecomponent lifetimes while small excimers have beenused predominantly in scientific and ophthalmologicapplications.

3.6 Size and Cost

One clear advantage of small excimers lies intheir initial capital costs, a factor two to four timesless expensive than conventional excimer lasers. Asa result, industrial turnkey systems incorporatingsmall excimers will also be less expensive. Also thelaser systems will have a smaller footprint which isparticularly important in applications requiring CleanRooms.

4. Emerging Applications of Small ExcimerLasers

4.1 Ophthalmology


59

Small excimer lasers, operating at 193nm, havebeen incorporated into corneal refractive surgeryequipment. The laser ablates the corneal tissue tocorrect myopic, hyperopic and astigmaticproblems. Using special beam delivery systems tosculpt the corneas (6 to 8mm in diameter), typicalmyoptic corrections of 6 diopter have beenperformed in less than 30 seconds. The resultingsurface profile seem to be quite smooth after theoperation.

4.2 X-Ray Camera Apertures

For x-ray generation systems, small aperturesare needed in front of a camera to monitor x-rays.Small pinholes in thin metal foils must be drilled withhigh precision accuracy. Many of these pinholes willbe less than 10 microns in diameter and will belocated on disks less than 1mm in diameter. Smallexcimer laser drilling is a viable solution.

4.3 Wire Stripping

Although wire stripping of hard disk drive sliderassemblies has been a favorite conventional excimerlaser application, there exists other market nichesin the medical device and coil actuator marketswhere a single wire of a very small length needs tobe stripped. In such cases, small excimers are foundto be more suitable candidate.

4.4 Smart Cards

Smart card technology has flourished in Europewhere microchips are imbedded in credit cards toallow on board intelligence for phone cards, banking,shopping etc. Small excimer lasers are used to dicepolycarbonate material by a combination of maskimaging long lines for fast linear cutting as well asfocal point drilling for complex contours.

5. Conclusion

As discussed in the introduction, the industrialapplications of lasers are numerous, undoubtedlybeyond the scope of this article. In the Indianindustrial environment, the reality is howeverdifferent. User here is more comfortable to use sucha sophisticated tool as a brought out item preferably

bearing a foreign label. The reasons are quite genuine.Big and small time manufacturers do understand thatthe quantity vis-à-vis quality is the key factor. Today,the high technology areas are being pursued withthe highest level of R&D to cater to high endproducts. And some of the products desire highestlevel of precision machining with no compromise.

Laser is one of the automatic choice for suchnature of jobs. Many of the Indian industries are intomass production of high precision products. Investingin laser as a tool would be worth exploring. In a longrun, it also favours a cost benefit analysis.

Some of the big Govt. of India Institutions andPSUs are now into the high technology areas ofR&D. With so much of privatization happening,many avenues are now opening up for possiblecollaborations for the product development stage.This is an opportunity for private industries toestablish the required facility for such work. Thiskind of infrastructure development requires bothcost, time and manpower. Big sectors, both Govt& Pvt. would probably be more willing to share thecost content, if a smaller partner is able to supportthe cause. It saves a lot of hassles for the biggerpartners both in terms of time and procedural delays.

At the end, one of the most important andcritical issue that should be highlighted is the 'poolingof resources'. Cost would be a major concern tomost of the small scale industry to set up such afacility. Since these constitute almost 50% of ourindustrial output. It would be appropriate if someof these small industries could join hands and set upa common central facility in select industrial areasthereby pooling the financial and manpowerresources.

6. Acknowledgement

The author is grateful to Dr A.K. Maini, DirectorLASTEC for his costant encouragement and support.It is a great pleasure to acknowledge to Sh R.K. Jain,Divisional Head, GDL Division, Sh A.K. Srivastavaand all resonator group members of GDL divisionfor all assistance to carry out this work.

N.R. Das

60

References

[1] Laser Industry markets, Laser Photonics, USA,(2010).

[2] Kevin Bullis, Nano Laser Probe Cell,Technology Review, US, (2010).

[3] David Belforte and Morris Levitt, TheIndustrial Laser Annual Handbook, edition,Pennwell publishing company, USA, (2010).

[4] James H. Rannon, 'Micropatterning ofsurfaces by excimer laser projection'. J. Vac.Sci. Technol., (1989) 1064.

[5] M. Rothschild and D.J. Ehrlich, 'A reviewof excimer laser projection lithography'. J.Vac. Sci. Technol., (1988) 1.

[6] S. Pissadakis, S. Mailis, L. Reekie, J.S.Wilkinson, R.W. Eason, N.A. Vainos, K.Moschovis and G. Kiriakidis, 'Permanentholographic recording in indium oxide thinfilms using 193 nm excimer laser'. Appl.Physics, (1999) 33.

[7] P.E. Dyer, R.J. Farley, R. Gied1 and D.M.Karnakis, 'Excimer laser ablation of polymersand glasses for grating fabrication'. Appl. SurfaceScience, (1996) 537.

[8] F. Beinhorn, J. Ihlemann, P. Simon, G.Marowsky, B. Maisenhoelde, J. Edlinger, D.Neuschaefer and D. Anselmetti, ' Sub-microngrating formation in Ta20 waveguides byfemtosecond uv-laser ablation'. Appl. SurfaceScience, (1999) 107.

[9] P. Simon, J. Ihlemann, 'Machining of submicronstructures on metals and semiconductorsby ultrashort uv laser pulses'. Appl. Physics,505.

[10] O. Kittelman, J. Ringling, F. Noack, U. Stamm,J. Kleinschmidt and F. Voss, 'High repetitionrate amplification of femtosecond pulses at248nm and 193nm excimer amplifier module'.Lambda Highlights No. 44.

[11] A.A.D.T. Adikaari, N.K. Mudugamuwa, S.R.P.Silva, N.K. Mudugamuwa and S.R.P. Silva,Nanocrystalline silicon solar cells from excimerlaser crystallization of amorphous silicon. SolarEnergy Materials & Solar Cells, 92 (2008) 634.

[12] R.A. Street (Ed.), Technology and Applicationsof Amorphous Silicon, Springer, eidelberg,(2000).

[13] H. Azuma, A. Takeuchi, T. Ito, H. Fukushima,T. Motohiro and M. Yamaguchi, Pulsed KrFexcimer laser annealing of silicon solar cell. Sol.Energy Mater. Sol. Cells, 74 (2002) 289.

[14] A.A.D.T. Adikaari and S.R.P. Silva, Thicknessdependence of properties of excimer lasercrystallized nano-polycrystalline silicon. J. Appl.Phys., 97 (2005) 114305.

[15] J.S. Im, H.J. Kim and M.O. Thompson, Phasetransformation mechanisms involved inexcimer laser crystallization of amorphoussilicon films. Appl. Phys. Lett., 63 (1993) 1969.

[16] A.A.D.T. Adikaari, J.D. Carey, V. Stolojan, J.L.Keddie and S.R.P. Silva, Bandgap enhancementof layered nanocrystalline silicon from excimerlaser crystallization. Nanotechnology, 17(2006) 5412.

[17] A.A.D.T. Adikaari, N.K. Mudugamuwa andS.R.P. Silva, Use of an asymmetric pulse profilefor higher crystalline volumes from excimerlaser crystallization of amorphous silicon, Appl.Phys. Lett., 90 (2007) 171912.

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Mathematical Expressions - Wherever possible, mathematical expressions should be typewritten, with subscriptsand superscripts clearly shown. It is helpful to identify unusual or ambiguous symbols in the margin when they firstoccur. To simplify typesetting, please use the "exp' form of complex exponential function and use fractional exponentsinstead of root signs. Equations must be displayed exactly as they should appear in print and numbered inparentheses placed at the right margin. Reference to equations in the text should use the form "Eq. (5)".

Tables - Tables should be typed on separate sheets, numbered consecutively with Arabic numerals, and have a shortdescriptive caption at the top. Extensive and/or complex tables must be typed carefully in the exact format desired.Computer printouts will normally be reproduced as illustrations. Tables should be placed together at the end ofthe manuscript.

References - Number references in the order in which they are cited in the text. Use Arabic numberswith square parentheses. Cite works in the reference list at the end according to the examples below. Abbreviationsfor the titles of journals should follow the system used by Chemical Abstract.

1. W. F. Bruce and L.F. Fieser, J. Am. Chem. Soc., 60 (1938) 1017.

2. J.B. Birks, Photophysics of Aromatic Molecules, Wiley Interscience, New York (1970) 225.

3. C.R. Tilford, New Developments in Barometric Range Pressure Standards, Proceedings ofNCSL Symp.,Washington D C, (1988) 35.1-35.15.

4. G. Klingenberg and H. Bauer, Final Report-CCM.V-K1 Metrologia, 41 (Techn. Suppl) 2004.

The editors and publisher of Invertis Journal of Science & Technology are not in anyway responsible for the viewsexpressed by the authors. The material published in IJST should not be reproduced or reprinted in any form, withoutthe prior written permission from the Editor/Publisher. A copyright transfer form has to be furnished by the authorsalongwith the corrected proof of their paper.

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Invertis Journal of Science Technology Vol. 6 No. 1 January-March 2013