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SUBMARINES1

Brief History Any study should begin with an examination of what has occurred in the past, otherwise one can end up reinventing what is already known or even ignoring critical information. It is important to understand the reasons for the shape of submarines at different stages of their development and why changes were made. Important phases in development will now be outlined. Submarines have existed as early as 1776 with Bushnell and his Turtle followed by Fulton and his Nautilus in 1800. These American vessels, designed to beat the British blockade, suffered from lack of a suitable power plant, which was overcome later by the inventions of both the internal combustion engine and the battery.

1 Holland A major improvement was made in 1899 by an Irish American schoolmaster, John Holland, with his design “Holland”, which included many of the features of modern submarines. It was a vessel displacing 63 tons, a length overall of 53 feet (16.2m) and a submerged speed of 5 knots (2.6 m/s). Its range was 1500 nautical miles (2,778km). There was an aft propeller with control vanes for steering. Its general proportions were not that different from the later, more sophisticated “Albacore”. Its profile was streamlined, a small rounded nose increasing to the full cross-section followed by a tapering tail. Its length to breadth ratio of 5.05 was a little full but not far from the optimum. Because of its need of oxygen for combustion, the petrol engine could not be used when the submarine was submerged. However, when the craft was on the surface and the hatch open, the engine could operate a generator to recharge batteries and it could also then propel the ship. Then it suffered from water entering through the open hatch due to the low freeboard, which prompted the addition of a larger raised conning tower in later designs. A single propeller was arranged at the tail with control vanes, a rudder and elevators. A copy of a 1900 photograph shows the bow view and the steering position from which the boat was navigated while just awash. The bulbous protrusion spoils the otherwise ideal streamline shape.

1 Mahdis Osouli; Sadaf Haghi; Shafagh Keyvanian

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2 Protector A second American inventor, Simon Lake, independently arrived at the solution, combining the petrol engine and the battery. His vessel, Protector, was launched in 1902. His greatest contribution was to overcome the problem of sight because submarines when submerged were blind. With the aid of a professor of optics, from John Hopkins, they constructed the forerunner of the periscope. Lake’s submarines were sold to Russia and Austria. Later they were bought by the US Navy, as were those of Holland.

3 Diesel Engine Although the submarine could now see when submerged and could travel considerable distances, there remained one dangerous problem. Petrol fumes were ever present within the hull with all the chances of a catastrophic explosion. The problem was solved by the invention of the compression ignition engine by a German engineer, Rudolf Diesel, in the 1890s. With no electric spark and running on cheaper, much less volatile fuel oil, the diesel engine, as it was called, was more efficient and more economical giving greater range. Far more important, the fumes were less toxic and volatile. Henceforward it became the accepted main source of power until the advent of nuclear power.

4 U-boats World War I accelerated progress in the design of submarines. The German navy developed its long, heavy, long ranging, diesel powered Unterseeboote or U-boats, as they were known through two world wars. They were essentially surface running ships with fine bows and usually mounting a gun, a large bridge fin and superstructure, under slung twin propellers, many excrescences and innumerable flooding and venting holes for rapid surfacing and submerging. No attention was paid to underwater performance.

5 Snorkels Snorkels were introduced in about 1944, conceived by the Dutch and taken over by the conquering Germans, they helped U-boats to survive the Allied sub-hunters. But they were not without their problems. If the intake dipped below the surface a valve would shut and the diesels would gulp air from the hull creating a partial vacuum that could affect the crew. The trim of the boat was delicate. The problems remain, especially that of detection when snorkeling.

6 Type 21 In response to the mounting U-boat losses in 1943, a submarine research centre was created by the Germans at Blankenburg in the Harz Mountains, with the aim of producing an operational high-speed U-boat capable of prolonged submergence.

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The Type 21 that resulted represented a compromise since it was aimed at AIP using hydrogen peroxide and the Walter propulsion system, which had not then advanced beyond the experimental stage. Coupled with the scarcity of hydrogen peroxide, the designers adopted enhanced diesel-electric power. The hull was dramatically streamlined removing the exposed gun and any external feature that would heighten resistance as well as reducing the size and profile of the conning tower (Fig. 5). Range and battery time were improved and underwater speed was raised to 18 knots, over 10 knots faster than before. Their design diving depth was improved dramatically. They arrived too late for war service.

7 Albacore Following the end of World War II both the British and United States Navies acquired some Type 21s for evaluation. They were amazed at the advances in the German boat. The United States then played “catch-up” and the Bureau of Ships adapted the extremely successful American fleet submarine of World War II for greater underwater speed by streamlining the hull and conning tower, removing all appendages – including the guns –and dramatically increasing the battery power. The submerged speed increased from 8.75 knots to 18.2 knots. They went even further in copying the German approach. In 1948, the Committee on Undersea Warfare of the National Research Council initiated an effort to accumulate the collective wisdom of the naval and scientific communities on the hydrodynamics of submerged bodies. Out of this evolved the design of Albacore with a shape giving the minimum underwater resistance based on the best available hydrodynamic research. A larger single screw, slower revolving propeller provided the best propulsive efficiency. The control arrangements were varied in a number of modifications to give the shortest turning circle. Most importantly, the sonar was later placed in the streamlined nose for maximum effect [3]. Snap roll was reduced by trailing an adjustable trailing edge flap on the fin. The fin was made as small as possible in order to reduce drag (a streamlined fin represents about 25% of the total drag). The length-to-draft ratio of Albacore was 7.723, which compares to Collins at 9.96. Albacore on batteries reached a submerged speed of 33 knots and a surface speed of 25 knots. Its radical diesel engines with a vertical crankshaft produced more power per unit weight than before, but were unreliable. The vertical arrangement required less critical longitudinal space and they developed 15,000 SHP. The large single screw showed a remarkable propulsive efficiency of 0.9.

Biogas Plant2

First let us see what Biogas is. According to the definition, biogas is the gas produced by anaerobic digestion or fermentation of biodegradable materials (biomass) such as: Forestry and

2 Arsalan Pourdavar

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Agricultural crops and residues, Municipal sewage and wastes, Animal waste materials and certain types of industrial residues.

Biogas has almost 80% heat value of the pipeline fossil gas and is mainly composed of CH4 (Methane), CO2 (Carbon dioxide) and very little amounts of H2 (Hydrogen), N2 (Nitrogen), H2S (Hydrogen Sulfide) and CO (carbon monoxide).

The presence of Methane in Biogas is what that makes it important and valuable as a fuel. Methane is 20 times worse than CO2 in the greenhouse effect if it's ever leaked to the atmosphere. Methane is naturally made at landfills which may be exploded and cause harm at certain densities; so it is logical to collect biogas as much as possible and then burn it to produce energy and in the meantime decrease the speed of the greenhouse effect by turning methane into less dangerous carbon dioxide and water.

There are numerous companies that manufacture from small electric generators to power plant size gas turbines specially designed to work with biogas as their main fuel. Biogas can also replace CNG (concentrated natural gas) in automotive vehicles as it is now being used in some countries like Sweden to power city buses. It is also possible to turn most of the biogas into hydrogen by a process which includes injecting CO into it. Needless to say that hydrogen is the basic element required for the fuel cell technology and it is very hard to extract, so easier ways to produce it are always welcomed.

The important feature of biogas is that it has a cycle of recreation which is easily accessible, low time consuming, environmentally friendly and virtually infinite.

One of the most efficient and economical ways of producing biogas is the anaerobic digestion of manure from farm animals. In fact one cow can produce enough manure each day to completely power a 100 watt lamp for 24 hours. Researches in US shows that by utilizing the whole manure produced in the country each year to make biogas and burn it, it will be possible to decrease 4% of the global warming growth speed.

The simplest type of a biogas plant is manure using rural one operating with slurry made from mixing of manure and water. This rural plant has many benefits to its owners and villagers:

This type of plant decreases health concerns related to leaving manure around the village provides reliable energy for villages and settlements far from gas pipelines and in some places it is the only possible solution. One of these places is south-eastern Iran which has sandy winds that cause harm to wind turbine blades and solar cells. The digested manure is a far richer bio fertilizer than normal manure and it is parasite and odor free since the parasites die in the digestion tank and the source of the odor (biogas) is extracted and used somewhere else.

This plant needs a mixer and an underground digestion tank to operate. These are very accessible and easy to provide requirements considering many third world and developing countries as well as developed ones like Germany has made extensive use of local biogas plants (like Nepal, India

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and Pakistan). It is also necessary to control and maintain the temperature, PH, density and the amount of toxic chemicals in the digestion chamber.

There is another type of local biogas plant that operates on kitchen waste instead of manure and it is capable of producing enough gas to cook every day meals of a house.

There are certain ways of improving and concentrating biogas to make it meet pipeline gas standards (95% methane) which include: Water washing (most common), pressure swing absorption, Selexol absorption and amine gas treating.

Biogas in Iran: modern biogas was first introduced by person named Davy in 1808, Germany; however it is believed that Sheikh Bahai's public bath in the 11th century hijri used biogas to provide heat.

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Robotics3

First of all, let’s answer the following question: What is a robot? Isn’t it obvious? According to Google, over 20 million people each month surf the Internet to find out what a robot is! The original notion of a robot was the manipulator arm used in factory automation.

Now let’s raise another question: What is a broader notion of a robot? Joseph Engelberger, a pioneer in industrial robotics, once remarked: “I can’t define a robot, but I know one when I see one. For example when you see Asimo, you say that Asimo is a robot! ”

The term robot derives from the Czech word robata, meaning forced to work. Robota in Czech is a word for worker or servant.

In fact, there is no definition of robot that satisfies every one…In what follows, you are provided with a definition of robot by the Robot Institute of America: “Any machine made by one of our members”!! It seems funny but it’s one of the primary definitions of a robot.

Now, we can say a robot is a mechanical or virtual artificial agent, usually an electro-mechanical machine that is guided by a computer program or an electronic circuitry. As you see, the notion of what qualifies as a robot has changed greatly over the years.

The next question that can be raised is “Why robotics?”

The answer is because robots can do jobs that are dangerous or impossible for humans, for example, cleaning the main circulating pump housed in nuclear power plants. The next reason is that they can do repetitive jobs that are boring, stressful, or labor-intensive for humans, for example, working in a packing line. They can work 24 hours a day and 7 days a week and they never get sick nor do they need some time off so they may be cheaper than human workers over a long period of time.

Robots can do high precision tasks or those requiring high quality, for example, welding robots or robots used for micro surgeries. And, finally, they do menial tasks that humans don’t want to do - cleaning a toilet, for example.

Now, it’s time to see some applications of robots. Of course, before that, we can divide robot bases into two main groups, namely fixed and mobile.

Robotic manipulators used in manufacturing are examples of fixed robots. They can’t move their base away from the work being done. Conversely, mobile bases are typically platforms with wheels or tracks attached to them. Of course, instead of wheels or tracks, some robots employ legs in order to move about. Based on this categorization, the applications of robots are enlisted as follows:

3 Ehsan Jafarzadeh; Mohammad Saleh Sedaghat

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First of all, automobiles and other manufactured products are the most common applications of robots nowadays. These common applications include welding, painting, cutting, dispensing, assembling, polishing and material handling which, in turn, includes packaging, palletizing and machine loading.

The second application of robots is in the area of health care which includes hospitals, patient care, and robotic surgery.

The third application of robots is in military operations in which robots are used for demining, surveillance, attack, espionage, etc.

The fourth application of robots refers to their usage in dangerous environments such as Trov which is a robot operating under water that is used in Antarctica and Hazbot which is a robot operating in atmospheres containing combustible gases.

Last but not least is the application of robots in the area of house chores and services! It contains robots that are capable of doing tasks related to cleaning, housekeeping, rehabilitation, agriculture, harvesting, mining, entertainment as well as acting as a friend for human beings. In fact, many universities around the world are working on human friend robots. Imagine, you have a robot with whom you can talk about your sorrows, for example, and then having listened to your problems, your new robot friend somehow tries to sympathize with you, for instance, it hugs you and it may even start crying and you shall see drops of tears running down from the corner of its eyes to its cheeks! Indeed, scientists working in this field actually expect improving models of robot friends to be the future of robotics.

The usage of robots in our life is increasing rapidly. They are going to have an influence on almost all aspects of our life. In the future, robots will be able to substitute humans in most manufacturing and service jobs. To further familiarize you with robotics in the future, some of the major projects in robotics that different countries are going to do in the future are enlisted as follows:

• From 2015 up to 2020, every South Korean and many European households will have a robot.

• In 2018, robots will routinely carry out different surgeries.

Furthermore, in the future, the technology of robotics will improve and one of these technologies is artificial intelligence. Artificial Intelligence has four types of meanings:

1. Building systems that think like humans 2. Building systems that act like humans 3. Building systems that act rationally 4. Building systems that think rationally.

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The future robots are capable of doing things like humans and will do them easily such as: running, washing the dishes, cooking, driving, playing chess, doing hard physical activities such as a soldier, etc. As a result, it can be concluded that the future robots will do everything like humans. Human beings are capable of dividing things into concepts. Then, a robot should also be able to do that. But let’s ask: what is a concept? For example, let us consider a chair. If you look around yourself, you can see different objects. Then, you can identify a chair and distinguish it from a table and a whiteboard or a waste basket. You can even identify different types of chairs that may be found in room. In other words, human beings know the concept of a chair and can compare the image of a chair with the concept of a chair. In fact, the concept of a chair refers to a place and an object on which anyone can sit.

Similarly, an advanced robot should also learn the concept of many things and choose be able to choose the best one. This is the real meaning of the artificial intelligence. To explain more about it, an example of real usage of artificial intelligence can be provided in what follows:

Stanley is a robot (robocar) that is able to drive 150 miles with natural and manmade hazards. No driver and no remote control were used in this project that was done in 2004. In fact, Stanley is capable of modeling its environment and finding the safest way on which it can move without being exposed to danger. Stanley is choosing the best way like a skilled soldier. Stanley knows the concept of the best way.

In short, future robots will be fast, intelligent and out of control so robotics is not only part of the future; In fact, robotics is the whole of future!

Failure has different methods that depend on the material, crystal lattice structure, size, position and the kind of defect (crack), the state of stress and so on.

It is important to know that failure is not just fracture but in most cases, the change in shape (deformation) is considered to be a kind of failure as we cannot use that part anymore and we have to substitute it.

The most important kinds of failure are:

• Ductile failure (yielding and plastic deformation)• Brittle failure • Fatigue • Corrosion • Creep • thermal fatigue • synthetic kind like creep fatigue

All of the above types of failure can be classified into two static failure, the part just bears a constant load until it fails, but in dynamic failure the part bears variable loads.

A. Ductile Failure

The materials with FCC crystal lattice structure experience this kind of failuwith a large plastic deformation so we can recognize it before any bad incident happens. The steps of this kind are: necking, void nucleation, void coalescence, crack propagation and finally separation and fracture.

4 Hassan Khajvand

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Failure Mechanisms4

Failure has different methods that depend on the material, crystal lattice structure, size, position f defect (crack), the state of stress and so on.

It is important to know that failure is not just fracture but in most cases, the change in shape (deformation) is considered to be a kind of failure as we cannot use that part anymore and we

The most important kinds of failure are:

Ductile failure (yielding and plastic deformation)

synthetic kind like creep fatigue

All of the above types of failure can be classified into two kinds of static and dynamic failure. In static failure, the part just bears a constant load until it fails, but in dynamic failure the part bears

The materials with FCC crystal lattice structure experience this kind of failuwith a large plastic deformation so we can recognize it before any bad incident happens. The steps of this kind are: necking, void nucleation, void coalescence, crack propagation and finally

Failure has different methods that depend on the material, crystal lattice structure, size, position

It is important to know that failure is not just fracture but in most cases, the change in shape (deformation) is considered to be a kind of failure as we cannot use that part anymore and we

kinds of static and dynamic failure. In static failure, the part just bears a constant load until it fails, but in dynamic failure the part bears

The materials with FCC crystal lattice structure experience this kind of failure. It usually occurs with a large plastic deformation so we can recognize it before any bad incident happens. The steps of this kind are: necking, void nucleation, void coalescence, crack propagation and finally

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B. Brittle failure

If a material has BCC crystal lattice structure, this kind of failure can appear. It has a small plastic deformation and happens suddenly so it is very dangerous. Additionally, the fracture surface is smooth and glossy.

C. Creep

Creep is a slow and continuous deformation of a solid that happens in high temperature during a long time. When the temperature goes higher than 0.3T� (T� is the fusion temp), it is high. It means that for some materials like plastic, the ordinary temperature (room temp.) may be high. The effects of creep are mostly seen in materials working in high temperature, like ceramics. The time that is required for creep to happen is usually very long.

The steps of creep are:

• Primary creep: decreasing creep rate as dislocation microstructure develops to reduce

strain rate

• Secondary creep: equilibrium is established between deformation and recovery

mechanisms to maintain a steady state strain rate

• Tertiary creep: increasing creep rate and fracture

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D. Fatigue

When a part is under periodic (alternative) load (stress) fatigue can appear. This phenomenon was one of the most important kinds of failures in 1850 when it was observed that a part can be broken into a lower stress than its yielding stress so it is very important in the industry because about 90% of the failure is for fatigue damage. The defects (crack) appear on the surface of the material and grow toward its core.

Fatigue happens in three steps: initiation, crack growth, and failure.

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E. Thermal Fatigue

When a part is exposed to a change in temperature, this phenomenon can occur. It is an important kind of failure in thermal power plants and turbines. For example, if a fluid with variant temperature (hot and cold periodically) flows in a pipe, thermal fatigue can be developed in it. Thermal fatigue does not occur because of a load or stress; it is the effect of temperature changes only.

F. Creep Fatigue

As it is obvious from the name, in this kind of failure both fracture of fatigue and creep are effective. It means that the part is in periodic load in high temperature so its life significantly reduces. There are different methods to calculate the life of a part in this kind of failure and most of them consider that creep and fatigue have a linear effect. So the total life is calculated as the superposition of their effects.

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Nondestructive Testing5

Introduction to Nondestructive Testing

A general definition of nondestructive testing (NDT) is an examination, test, or evaluation performed on any type of test object without changing or altering that object in any way in order to determine the absence or presence of conditions or discontinuities that may have an effect on the usefulness or serviceability of that object. Nondestructive tests may also be conducted to measure other characteristics of the test object such as size, dimension, configuration, or structure including alloy content, hardness, grain size, etc. Nondestructive examination (NDE), nondestructive inspection (NDI), and nondestructive evaluation (NDE) are also expressions commonly used to describe this technology. Although this technology has been effectively in use for decades, it is still generally unknown by the average person who takes it for granted that buildings will not collapse, planes will not crash, and products will not fail. NDT, as a technology, has seen a significant growth and unique innovation over the past 25 years. Nondestructive testing, in fact, is a process that is performed on a daily basis by the average individual who is not even aware that it is taking place.

Nondestructive vs. Destructive Tests Destructive testing has been defined as a form of mechanical test (primarily destructive) of materials whereby certain specific characteristics of the material can be evaluated quantitatively. In some cases, the test specimens are subjected to controlled conditions that simulate service. The information that is obtained through destructive testing is quite precise but it only applies to the specimen being examined. Since the specimen is destroyed or mechanically changed, it is unlikely that it can be used for other purposes beyond the mechanical test. Such destructive tests can provide very useful information, especially relating to the material’s design considerations and useful life. Key benefits of destructive testing include:

• Reliable and accurate data from the test specimen

• Extremely useful data for design purposes

• Information useful for establishing standards and specifications

• Quantitative data obtained through destructive testing • Various measurable service conditions

• Prediction of useful life prediction

5 Sohrab Rezaei; Morteza Assadollahi; Mojtaba Dargahi

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Limitations of destructive testing include:

• Data applies only to the specimen being examined

• Most destructive test specimens cannot be used once the test is complete

• Many destructive tests require large, expensive equipment in a laboratory environment Benefits of nondestructive testing include:

• The part is not changed or altered and can be used after examination • Every item or a large portion of the material can be examined with no adverse

consequences • Materials can be examined for internal conditions and also those at the surface • Parts can be examined while they are still in service

• Many NDT methods are portable and can be taken to the object to be examined • Nondestructive testing is cost effective, overall

Limitations of nondestructive testing include:

• It is usually quite operator dependent

• Some methods do not provide permanent records of the examination • NDT methods do not generally provide quantitative data

• Orientation of discontinuities must be considered

• Evaluation of some test results are subjective and subject to dispute

• While most methods are cost effective, some, such as radiography, can be expensive • Defined procedures that have been qualified are essential

In conclusion, there are obvious benefits for requiring both nondestructive and destructive testing. Each is capable of providing extremely useful information, and when used jointly can be very valuable to the designer when considering useful life and application of the part.

History of Nondestructive Testing In ancient times, the audible ring of a Damascus sword blade would be an indication of how strong the metal would be in combat. This same “sonic” technique was used for decades by blacksmiths as they listened to the ring of different metals that were being shaped. This approach

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was also used by early bell-makers. By listening to the ring of the bell, the soundness of the metal could be established in a very general way. The roots of nondestructive testing began to take form prior to the 1920s, but the majority of the methods that are known today didn’t appear until late in the 1930s and into the early 1940s. Much of the latter developments came about as a result of the tremendous activity during the Second World War. In the 1920s, there was an awareness of some of the magnetic particle tests (MT) and, of course, the visual test (VT) methods, as well as X-radiography (RT), which at that time was primarily being used in the medical field. In the early days of railroading, the forerunner of the present day penetrant test (PT), a technique referred to as the “oil and whiting test,” had been widely used. And there were also some basic electrical tests using some of the basic principles of eddy current testing (ET). The sonic or “ringing” methods, as well as some archaic gamma radiographic techniques using radium as the source of radiation, were both used with limited success. From these roots, NDT technology has evolved to encompass the many sophisticated and unique methods that are in use today. (See Table 1-2 for a comprehensive overview of the major NDT methods.)

What is NDT? The field of Nondestructive Testing (NDT) is a very broad, interdisciplinary field that plays a critical role in assuring that structural components and systems perform their function in a reliable and cost effective fashion. NDT technicians and engineers define and implement tests that locate and characterize material conditions and flaws that might otherwise cause planes to crash, reactors to fail, trains to derail, pipelines to burst, and a variety of less visible, but equally troubling events. These tests are performed in a manner that does not affect the future usefulness of the object or material. In other words, NDT allows parts and material to be inspected and measured without damaging them. Because it allows inspection without interfering with a product's final use, NDT provides an excellent balance between quality control and cost-effectiveness. Generally speaking, NDT applies to industrial inspections. The technologies that are used in NDT are similar to those used in the medical industry, but nonliving objects are the subjects of the inspections. What is NDE? Nondestructive evaluation (NDE) is a term that is often used interchangeably with NDT. However, technically, NDE is used to describe measurements that are more quantitative in nature. For example, an NDE method would not only locate a defect, but it would also be used to measure something about that defect such as its size, shape, and orientation. NDE may be used to

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determine material properties, such as fracture toughness, formability, and other physical characteristics. Some NDT/NDE Technologies: Many people are already familiar with some of the technologies that are used in NDT and NDE from their uses in the medical industry. Most people have also had an X-ray taken and many mothers have had ultrasound used by doctors to give their baby a checkup while still in the womb. X-rays and ultrasound are only a few of the technologies used in the field of NDT/NDE. The number of inspection methods seems to grow daily, but a quick summary of the most commonly used methods is provided below.

• Visual and Optical Testing (VT)

The most basic NDT method is visual examination. Visual examiners follow procedures that range from simply looking at a part to see if surface imperfections are visible, to using computer controlled camera systems to automatically recognize and measure features of a component.

• Radiography (RT)

RT involves using penetrating gamma- or X-radiation on materials and products to look for defects or examine internal or hidden features. An X-ray generator or radioactive isotope is used as the source of radiation. Radiation is directed through a part and onto film or other detector. The resulting shadowgraph shows the internal features and soundness of the part. Material thickness and density changes are indicated as lighter or darker areas on the film or detector. The darker areas in the radiograph below represent internal voids in the component.

• Magnetic Particle Testing (MT) This NDT method is accomplished by inducing a magnetic field in a ferromagnetic material and then dusting the surface with iron particles (either dry or suspended in liquid). Surface and near-surface flaws disrupt the flow of the magnetic field within the part and force some of the field to leak out at the surface. Iron particles are attracted and concentrated at sites of the magnetic flux leakages. This produces a visible indication of defect on the surface of the material. The images above demonstrate a component before and after inspection using dry magnetic particles.

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• Ultrasonic Testing (UT)

In ultrasonic testing, high-frequency sound waves are transmitted into a material to detect imperfections or to locate changes in material properties. The most commonly used ultrasonic testing technique is pulse echo, whereby sound is introduced into a test object and reflections (echoes) from internal imperfections or the part's geometrical surfaces are returned to a receiver. Below is an example of shear wave weld inspection. Notice the indication extending to the upper limits of the screen. This indication is produced by sound reflected from a defect within the weld.

• Penetrant Testing (PT) With this testing method, the test object is coated with a solution that contains a visible or fluorescent dye. Excess solution is then removed from the surface of the object but is left in surface breaking defects. A developer is then applied to draw the penetrant out of the defects. With fluorescent dyes, ultraviolet light is used to make the bleedout fluoresce brightly, thus allowing imperfections to be readily seen. With visible dyes, a vivid color contrast between the penetrant and developer makes the bleedout easy to see. The red indications in the image represent a defect in this component.

• Electromagnetic Testing (ET) There are a number of electromagnetic testing methods but the focus here will be on eddy current testing. In eddy current testing, electrical currents (eddy currents) are generated in a conductive material by a changing magnetic field. The strength of these eddy currents can be measured. Material defects cause interruptions in the flow of the eddy currents which alert the inspector to the presence of a defect or other change in the material. Eddy currents are also affected by the electrical conductivity and magnetic permeability of a material, which makes it possible to sort some materials based on these properties. The technician in the image is inspecting an aircraft wing for defects.

• Leak Testing (LT) Several techniques are used to detect and locate leaks in pressure containment parts, pressure vessels, and structures. Leaks can be detected by using electronic listening devices, pressure gauge measurements, liquid and gas penetrant techniques, or simple soap-bubble tests.

• Acoustic Emission Testing (AE) When a solid material is stressed, imperfections within the material emit short bursts of acoustic energy called "emissions." As in ultrasonic testing, acoustic emissions can be

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detected by special receivers. Emission sources can be evaluated through the study of their intensity and arrival time to collect information (such as their location) about the sources of the energy.

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Renewable Energies

Greenhouse Effect There is little doubt that the large-scale utilization of fossil fuels is putting significant stress on the environment. The effects of combustion products on air quality and the climate are both local and global in nature. The local effects, primarily in the form of air pollution and smog formation in large urban areas, have been known for many decades, and in recent years government regulations to reduce the effects of air pollution have been significantly strengthened. These include both exhaust emission standards for vehicles as well as emissions regulations for large fixed installations, such as fossil-fueled power stations. These regulations have been pioneered in the USA … but similar measures have now been adopted in most of the developed world. On a global scale, there is increasing evidence and concern about the role of CO2 and other so-called greenhouse gases on global climate change. In what follows, we will examine both the localized and global effects of these air emissions, and describe current mitigation techniques. On a global scale, it is the greenhouse effect and the prospect of global warming which has drawn the most attention. … Solar radiation produced as a result of the very high temperature of the sun is composed primarily of short wavelengths visible or near visible radiation for which the atmosphere is largely transparent. In other words, although a small fraction of this radiation is reflected by the earth’s atmosphere back out into space, most of it passes straight through (as if the atmosphere is a window glass) and warms the earth’s surface. The warm earth then re-radiates some of this energy back out into space, but since it is produced at relatively low temperatures it is primarily long wavelength, or infrared radiation. Some of the gases in the earth’s atmosphere just like window glass, are particularly opaque (or have a low transmissivity) to this long wavelength radiation and are, therefore, referred to as greenhouse gases (GHGs). Much of the long wavelength radiation is, therefore, reflected back to the earth’s surface and there is then a net imbalance in the energy absorbed by the earth and that re-radiated back out, with the result being a warming of the earth’s surface and the surrounding atmosphere, just as in a greenhouse.

Bioenergy

Bioenergy is renewable energy produced by living things like plant matter or by the waste that living creatures produce, such as manure. These living things and their waste products are called biomass. Biomass is organic matter (which comes from living things), just like fossil fuels (coal, oil, or natural gas, which are formed in the earth from plant and/or animal remains), but it is much more recently created and is renewable on a time scale that is useful to humans. Fossil fuels take millions of years to form. During this time they accumulate large amounts of carbon, which is returned to the atmosphere during burning. Plants grow continuously, animals

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constantly produce manure, and people throw away waste material all the time. Using these items for fuel does not deplete them because they are always being made. For this reason, many experts believe that bioenergy will be a major source of power in the future. Besides being renewable, many kinds of bioenergy are considered less polluting than fossil fuels. They can be used as direct substitutes for fossil fuels, powering diesel or gasoline engines, heating buildings, and producing electricity. They can be made and used locally, which can make individual areas more self-sufficient and less reliant on foreign suppliers for energy. Bioenergy is created by using biofuels. Biofuels are made from sources of biomass including wood, plant matter, and other waste products. These sources can then be turned into biofuels. There are three types of biofuels: solid, liquid, and gas. Solar Energy

Solar energy is energy made from sunlight. Light from the sun may be used to make electricity, to provide heating and cooling for buildings, and to heat water. Solar energy has been used for thousands of years in other ways as well. Most life on Earth could not exist without the sun. Most plants produce their food via a chemical process called photosynthesis that begins with sunlight. Many animals include plants as part of their diet, making solar energy an indirect source of food for them. People can eat both plants and animals in a food chain providing one example of the importance of the suns energy. In direct or indirect fashion, the sun is responsible for nearly all the energy sources to be found on Earth. All the coal, oil, and natural gas were produced by decaying plants millions of years ago. In other words, the primary fossil fuels used today are really stored solar energy. The heat from the sun also drives the wind, which is another renewable source of energy. Wind arises because Earth’s atmosphere is heated unevenly by the sun. The only power sources that do not come from the suns heat are the heat produced by radioactive decay at Earth’s core; ocean tides, which are influenced by the moons gravitational force; and nuclear fusion and fission. Solar energy has been used for scientific purposes for several centuries. One scientist, Joseph Priestly, used sunlight to accomplish his discovery and isolation of oxygen in the 1770s. He heated and broke down mercuric oxide using heat created by concentrated sunlight. An early nineteenth-century development was the greenhouse. Greenhouses are essentially passive solar energy collectors that collect the suns energy to help grow plants. They capture light energy and retain heat while holding in humidity, which is used to water the plants. Greenhouses make it possible to grow plants even in winter. Significant discoveries that advanced the use and efficiency of solar technology occurred in the nineteenth and twentieth centuries: photovoltaic cells and solar collectors, dish systems and trough systems, and power towers.

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Wind Energy The use of wind energy dates back to ancient times when it was employed to propel sailboats. Extensive application of wind turbines seems to have originated in Persia where it was used for grinding wheat. The Arab conquest spread this technology throughout the Islamic world and China. In Europe, the wind turbine made its appearance in the eleventh century. Two centuries later it had become an important tool, especially in Holland. The development of the American West was aided by wind-driven pumps and sawmills. The first significant wind turbine designed specifically for the generation of electricity was built by Charles Brush in Cleveland, Ohio. It operated for 12 years, from 1888 to 1900 supplying the needs of his mansion. Charles Brush was a mining engineer who made a fortune with the installation of arc lights to illuminate cities throughout the United States. His wind turbine was of the then familiar multi-vane type (it supported 144 blades) and, owing to its large solidity, rotated rather slowly and required gears and transmission belts to speed up the rotation by a factor of 50 so as to match the specifications of the electric generator. The wind turbine itself had a diameter of 18.3 meters and its hub was mounted 16.8 meters above ground. The tower was mounted on a vertical metal pivot so that it could orient itself to face the wind. The whole contraption massed some 40 tons. Owing to the intermittent nature of the wind, electric energy had to be stored in this case in 400 storage cells. Although the wind is free, the investment and maintenance of the plant caused the cost of electricity to be much higher than that produced by steam plants. Consequently, the operation was discontinued in 1900 and from then on the Brush mansion was supplied by the Cleveland utility. In 1939, construction of a large wind generator was started in Vermont. This was the famous Smith-Putnam machine, erected on a hill called Grandpa's Knob. It was a propeller-type device with a rated power of 1.3 MW at a wind speed of 15 m/s. Rotor diameter was 53 m. The machine started operation in 1941, feeding energy synchronously directly into the power network. Owing to blade failure, in March 1945, the operation was discontinued. It ought to be mentioned that the blade failure had been predicted but during World War II there was no opportunity to redesign the propeller hub. After World War II, the low cost of oil discouraged much of the alternate energy research and wind turbines were no exception. The 1973 oil crises re-spurred interest in wind power as attested by the rapid growth in federal funding. This led to the establishment of wind farms that were more successful in generating tax incentives than electric energy. Early machines used in such farms proved disappointing in performance and expensive to maintain. Nevertheless, the experience accumulated led to an approximately 5-fold reduction in the cost of wind-generated electricity. In the beginning of 1980, the cost of 1 kWh was around 25 cents; in 1996 it was, in some installations, down to 5 cents. To be sure, the determination of energy costs is, at best, an unreliable art. Depending on the assumptions made and the accounting models used, the costs may vary considerably.

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Even though the real cost of wind generated energy may be uncertain, what is certain is that it has come down dramatically these last 15 years. In 1997, the selling of wind-generated electricity under a scheme called \green pricing" started becoming popular.

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Second-Law Aspects of Daily Life

Thermodynamics is a fundamental natural science that deals with various aspects of energy, and

even nontechnical people have a basic understanding of energy and the first law of thermodynamics since there is hardly

any aspect of life that does not involve the transfer or

transformation of energy in different forms. All the dieters, for example, base their lifestyle on

the conservation of energy principle. Although the first-law aspects of thermodynamics are readily

understood and easily accepted by most people there is not a public awareness about the

second law of thermodynamics, and the second-law aspects are not fully appreciated even by

people with technical backgrounds. This causes some students to view the second law as something that is of theoretical interest rather than an important and practical engineering tool. As a result, students show little interest in a detailed study of the second law of thermodynamics. This is unfortunate because the students end up with a one-sided view of thermodynamics and miss the balanced, complete picture. Many ordinary events that go unnoticed can serve as excellent vehicles to convey

important

concepts of thermodynamics. Below we will attempt to demonstrate the relevance of the second-

law concepts such as exergy, reversible work, irreversibility, and the second-law efficiency to various aspects of daily life using examples with which even nontechnical people can identify. Hopefully, this will enhance our understanding and appreciation of the second law of thermodynamics and encourage us to use it more often in technical and even nontechnical areas. The critical reader is reminded that the concepts presented below are soft and difficult to quantize, and that they are offered here to stimulate interest in the study of the second law of thermodynamics and to enhance our understanding and appreciation of it. The second-law concepts are implicitly

used in various aspects of daily life. Many successful

people seem to make extensive use of them without even realizing it. There is growing awareness

that quality plays as important a role as quantity in even ordinary daily activities. The following appeared in an article in the Reno Gazette-Journal on March 3, 1991: 51. Dr. Held considers

himself a survivor of the tick-tock conspiracy. About four years ago, right around his 40th

birthday, he was putting in 21-hour days - working late, working out, taking care of his three children and getting involved in sports. He got about four or five hours of sleep a night. “Now I’m in bed by 9:30 and I’m up by 6,” he says. “I get twice as much done as I used to. I don't have to do things twice or read things three times before I understand them.” The statement above has a strong relevance to the second-law discussions. It indicates that the problem is not how much time we have (the first law), but, rather, how effectively we use it (the second law). For a person to get more done in less time is no different than for a car to go more miles on less fuel. In thermodynamics, reversible work for a process is defined as the maximum useful work output (or minimum work input) for that process. It is the useful work that a system would deliver (or

24

consume) during a process between two specified states if that process is executed in a reversible

(perfect) manner. The difference between the reversible work and the actual useful work is due to imperfections and is called irreversibility (the wasted work potential). For the special case of the final state being the dead state or the state of the surroundings, the reversible work becomes a maximum and is called the exergy of the system at the initial state. The irreversibility for a reversible or perfect process is zero. The exergy of a person in daily life can be viewed as the best job that person can do under the most favourable conditions. The reversible work in daily life, on the other hand, can be viewed as the best job a person can do under some specified conditions. Then the difference between the reversible work and the actual work done under those conditions can be viewed as the irreversibility or the exergy destroyed. In engineering systems, we try to identify the major sources of irreversibilities and minimize them in order to maximize performance. In daily life, a person should do just that to maximize his or her performance. The exergy of a person at a given time and place can be viewed as the maximum amount of work he or she can do at that time and place. Exergy is certainly difficult to quantify because of the interdependence

of physical and intellectual capabilities of a person. The ability to perform

physical and intellectual tasks simultaneously complicates things even further. Schooling and training obviously increase the exergy of a person. Aging decreases the physical exergy. Unlike most mechanical things, the exergy of human beings is a function of time, and the physical and/or intellectual exergy of a person goes to waste if it is not utilized at the time. A barrel of oil loses nothing from its exergy if left unattended for 40 years. However, a person will lose much of his entire exergy during that time period if he or she just sits back. A hard-working farmer, for example, may make full use of his physical exergy but very little use of his intellectual exergy. That farmer, for example, could learn a foreign language or a science by listening to some educational tapes at the same time he is doing his physical work: This is also true for people who spend considerable time in the car commuting

to work. It is hoped that

some day we will be able to do exergy analysis for people and their activities. Such an analysis will point out the way for people to minimize their exergy destruction, and get more done in less time. Mainframe computers can perform several tasks at once. Why, shouldn't human beings be able to do the same?

Children are born with different levels of exergies (talents) in different areas. Giving aptitude tests to children at an early age is simply an attempt to uncover the extent of their “hidden” exergies, or talents. The children are then directed to areas in which they have the greatest exergy. As adults, they are more likely to perform at high levels without stretching the limits if they are naturally fit to be in that area.

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We can view the level of alertness of a person as his or her exergy for intellectual affairs. When a

person is well-rested, the degree of alertness and thus intellectual exergy, is at a maximum and this exergy decreases with time as the person gets tired. Different tasks in daily life require different levels of intellectual exergy, and the difference between available and required alertness can be viewed as the wasted alertness or exergy destruction. To minimize exergy destruction, there should be a close match between available

alertness and required alertness.

Consider a well-rested student who is planning to spend her next 4 h studying and watching a 2-h-long movie. From the first-law point of view, it makes no difference in what order these tasks are performed. But from the second-law point of view, it makes a lot of difference. Of these two tasks, studying requires more intellectual alertness than watching a movie does, and thus it makes thermodynamic sense to study first when the alertness is high and to watch the movie later when the alertness is lower. A student who does it backwards will waste a lot of alertness while watching the movie and she will have to keep going back and forth while studying because of insufficient alertness, thus getting less done in the same time period.

In thermodynamics, the first-law efficiency (or thermal efficiency) of a heat engine is defined as the ratio of net work output to total heat input. That is, it is the fraction

of heat that is converted

to net work. In general, the first-law efficiency can be viewed as the ratio of the desired output to the required input. The first-law efficiency makes no reference to the best possible performance, and thus the first-law efficiency alone is not a realistic measure of performance. To overcome this deficiency, we defined the second-law efficiency, which is a measure of actual performance relative to the best possible performance, under the same conditions.

In daily life, the first-law efficiency or performance of a person can be viewed as the accomplishment

of that person relative to the effort he or she puts in. The second-law efficiency

of a person, on the other hand, can be viewed as the performance of that person relative to the best possible performance under the circumstances. Happiness is closely related to the second-law efficiency. Small children are probably the happiest human beings because there is so little they can do, but they do it so well, considering their limited capabilities. That is, children have very high second-law efficiencies in their daily lives. The term “full life” also refers to second-law efficiency. A person is considered to have a full life, and thus very high second-law efficiency, if he or she has utilized all of his or her abilities to the limit during a lifetime.

Even a person with some disabilities will have to put in considerably more effort to accomplish what a physically fit person accomplishes. Yet, despite accomplishing less with more effort, the person with disabilities who gives an impressive

performance will probably get more praise.

Thus we can say that this person with disabilities had a low first-law efficiency (accomplishing little with a lot of effort) but a very high second-law efficiency (accomplishing as much as possible under the circumstances).

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In daily life, exergy can also be viewed as the opportunities that we have and the exergy destruction as the opportunities wasted. Time is the biggest asset that we have, and the time wasted is the wasted opportunity to do something useful.

The examples above show that several parallels can be drawn between the supposedly

abstract

concepts of thermodynamics related to the second law and daily life, and that the second-law concepts can be used in daily life as frequently

and authoritatively

as the first-law concepts.

Relating the abstract concepts of thermodynamics to ordinary events of life benefits both engineers and social scientists: it helps engineers to have a clearer picture of those concepts and to understand them better, and it enables social scientists to use these concepts to describe and formulate

some social or psychological phenomena better and with more precision. This is like

mathematics and sciences being used in support of each other: abstract mathematical concepts are best understood using examples from sciences, and scientific phenomena are best described and formulated with the help of mathematics. I have only just a minute, Only 60 seconds in it, Forced upon me - can't refuse it Didn't seek it, didn't choose it. But it is up to me to use it. I must suffer if I lose it. Give account if I abuse it, Just a tiny little minute-But eternity

is in it.

(anonymous)

I have only just a minute,

Only 60 seconds in it,

Forced upon me - can't refuse it

Didn't seek it, didn't choose it.

But it is up to me to use it.

I must suffer if I lose it.

Give account if I abuse it,

Just a tiny little minute-

But eternity is in it.

(anonymous)

A poetic expression of exergy and exergy destruction

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Saving Fuel and Money by Driving Sensibly

Two-thirds of the oil used in the United States is used for transportation. Half of this oil is consumed by passenger cars and light trucks that are used to commute

to and from work (38

percent), run a family business (35 percent), and for recreational, social, and religious activities (27 percent). The overall fuel efficiency of the vehicles has increased considerably over the years due to improvements primarily in aerodynamics, materials, and electronic controls. However, the average fuel consumption of new vehicles has not changed much from about 20 miles per gallon (mpg) because of the increasing consumer trend

towards purchasing

larger and less fuel-efficient

cars, trucks, and sport utility vehicles. Motorists also continue to drive more each year: 11,725 miles in 1999 compared to 10,277 miles in 1990. Consequently, the annual gasoline use per vehicle in the United States has increased to 603 gallons in 1999 (worth $905 at $1.50/gal) from506 gallons in 1990.

Saving fuel is not limited to good driving habits. It also involves purchasing the right car, using it responsibly, and maintaining

it properly. A car does not burn any fuel when it is not running, and

thus a sure way to save fuel is not to drive the car at all - but this is not the reason we buy a car. We can reduce driving and thus fuel consumption by considering viable

alternatives

such as

living close to work and shopping areas, working at home, working longer hours in fewer days, joining a car pool

or starting one, using public transportation, combining errands

into a single

trip and planning ahead, avoiding rush hours and roads with heavy traffic and many traffic lights and simply walking or bicycling instead of driving to nearby places, with the added benefit of good health and physical fitness. Driving only when necessary is the best way to save fuel, money, and the environment too.

Driving efficiently starts before buying a car, just like raising good children starts before getting

married. The buying decision made now will affect the fuel consumption for many years. Under average driving conditions, the owner of a 30-mpg vehicle will spend $300 less each year on fuel than the owner of a 20-mpg vehicle (assuming a fuel cost of $1.50 per gallon and 12,000 miles of driving per year). If the vehicle is owned for 5 years, the 30-mpg vehicle will save $1500 during this period. The fuel consumption of a car depends on many factors such as the type of the vehicle, the weight, the transmission type, the size and efficiency of the engine, and the accessories

and the options installed. The most fuel-efficient cars are aerodynamically designed

compact cars with a small engine, manual transmission, low frontal area (the height times the width of the car), and bare essentials.

At highway speeds, most fuel is used to overcome aerodynamic drag or air resistance to motion, which is the force needed to move the vehicle through the air. This resistance force is proportional to the drag coefficient and the frontal area. Therefore, for a given frontal area, a sleek looking aerodynamically designed vehicle with contoured

lines that coincide with the

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streamlines of air flow will have a smaller drag coefficient and thus better fuel economy than a boxlike vehicle with sharp corners. For the same overall

shape, a compact car has a smaller

frontal area and thus better fuel economy compared to a large car.

Moving around the extra weight takes more fuel, and thus it hurts fuel economy. Therefore, the lighter the vehicle, the more fuel-efficient it will be. Also as a general rule, the larger the engine is, the greater its rate of fuel consumption will be. So you can expect a car with a 1.8 L engine to be more fuel efficient than one with a 3.0 L engine. For a given engine size, diesel engines operate on much higher compression ratios than the gasoline engines, and thus they are inherently more fuel-efficient. Manual transmissions are usually more efficient than the automatic ones, but this is not always the case. A car with automatic transmission generally uses 10 percent more fuel than a car with manual transmission because of the losses associated with the hydraulic connection between the engine and the transmission and the added weight. Transmissions with an overdrive

gear (found in four-speed automatic transmissions and five-

speed manual transmissions) save fuel and reduce noise and engine wear during highway driving by decreasing the engine rpm while maintaining the same vehicle speed.

Front wheel drive offers better traction (because of the engine weight on top of the front wheels), reduced vehicle weight and thus better fuel economy, with an added benefit of increased space in the passenger compartment. Four-wheel drive mechanisms provide better traction

and braking

thus safer driving on slippery loose 60 by transmitting torque to all four wheels. However, the

added safety comes with increased weight, noise, and cost, and decreased fuel economy. Radial

tires usually reduce the fuel consumption by 5 to 10 percent by reducing the rolling resistance, but their pressure should be checked regularly since they can look normal and still be underinflated. Cruise control saves fuel during long trips on open roads by maintaining steady speed. Tinted windows and light interior and exterior colors reduce solar heat gain, and thus the need for air-conditioning.

Before Driving

Certain things done before driving can make a significant difference on the fuel cost of the vehicle while driving. Below we discuss some measures such as using the right kind of fuel, minimizing idling, removing extra weight, and keeping the tires properly inflated.

Use Fuel with the Minimum Octane Number Recommended by the Vehicle Manufacturer

Many motorists buy higher-priced premium fuel, thinking that it is better for the engine. Most of

today's cars are designed to operate on regular unleaded fuel. If the owner's manual does not call for premium fuel, using anything other than regular gas is simply a waste of money. Octane number is not a measure of the “power’, or “quality” of the fuel, it is simply a measure of fuel's resistance to engine knock

caused by premature

ignition. Despite the implications of flashy

names like “premium,” “super,” or “power plus,” a fuel with a higher octane number is not a better fuel; it is simply more expensive because of the extra processing involved to raise the

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octane number. Older cars may need to go up one grade level from the recommended new car octane number if they start knocking.

Do Not Overfill the Gas Tank

Topping off the gas tank may cause the fuel to backflow during pumping. In hot weather, an overfilled tank may also cause the fuel to overflow due to thermal expansion. This wastes fuel, pollutes the environment, and may damage the car's paint. Also, fuel tank caps that do not close tightly will allow some gasoline to be lost by evaporation. Buying fuel in cool weather such as early in the mornings will minimize evaporative losses. Each gallon of spilled or evaporated fuel emits as much hydrocarbon to the air as 7500 miles of driving.

Park in the Garage

The engine of a car parked in a garage overnight will be warmer the next morning. This will reduce the problems associated with the warming-up period such as starting, excessive fuel consumption, and environmental pollution. In hot weather, a garage will block the direct sunlight and reduce the need for air-conditioning.

Start the Car Properly and Avoid Extended Idling

With today's cars, it is not necessary to prime the engine first by pumping

the accelerator pedal

repeatedly before starting. This only wastes fuel. Warming up the engine isn't necessary either. Keep in mind that an idling engine wastes fuel and pollutes the environment. Don't race a cold engine to warm it up. An engine will warm up faster on the road under a light load, and the catalytic converter will begin to function sooner. Start driving as soon as the engine is started, but avoid rapid acceleration and highway driving before the engine and thus the oil fully warms up to prevent engine wear. 2 In cold weather, the warm-up period is much longer, the fuel consumption during warm-up is much higher, and the exhaust emissions are much larger. At -20.C, for example, a car needs to be driven at least 3 miles to warm up fully. A gasoline engine will use up to 50 percent more fuel during warm-up than it does after it is warmed up. Exhaust emissions from a cold engine during warm-up are much higher since the catalytic converters do not function properly before reaching their normal operating temperature of about 390˚C.

Don't Carry Unnecessary Weight in or on the Vehicle

Remove any snow or ice from the vehicle, and avoid carrying unneeded items, especially heavy ones (such as snow chains, old tires, books) in the passenger compartment, trunk, or the cargo area of the vehicle. This wastes fuel since it requires extra fuel to carry around the extra weight. An extra 100 1bm decreases fuel economy of a car by about 1-2 percent.

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Some people find it convenient to use a roof rack or carrier for additional cargo space. However, if you must carry some extra items, place them inside the vehicle rather than on roof racks to

reduce drag. Any snow that accumulates1 on a vehicle and distorts

2 its shape must be removed for

the same reason. A loaded roof rack can increase fuel consumption by up to 5 percent in highway driving. Even the most streamlined empty rack will increase aerodynamic drag and thus fuel consumption. Therefore, the roof rack should be removed when it is no longer needed.

Keep Tires Inflated to the Recommended Maximum Pressure

Keeping the tires inflated properly is one of the easiest and most important things one can do to improve fuel economy. If a range is recommended by the manufacturer, the higher pressure should be used to maximize fuel efficiency. Tire pressure should be checked when the tire is cold since tire pressure changes with temperature (it increases by 1 psi for every 10° F rise in temperature due to a rise in ambient

temperature or just road friction). Underinflated tires run

hot and jeopardize safety, cause the tires to wear prematurely, affect the vehicle's handling

adversely, and hurt the fuel economy by increasing the rolling resistance. Overinflated tires cause unpleasant bumpy

rides, and cause the tires to wear unevenly. Tires lose about 1 psi

pressure per month due to air loss caused by the tire hitting holes, bumps, and curbs. Therefore, the tire pressure should be checked at least once a month. Just one tire underinflated by 2 psi will result in a 1 percent increase in fuel consumption. Under-inflated tires often cause fuel consumption of vehicles to increase by 5 or 6 percent.

It is also important to keep the wheels aligned. Driving a vehicle with the front wheels out of alignment increases rolling resistance and thus fuel consumption while causing handling problems, on the one hand and uneven tire wear, on the other. Therefore, the wheels should be aligned properly whenever necessary.

While Driving

The driving habits can make a significant difference in the amount of fuel used. Driving sensibly and practicing some fuel-efficient driving techniques such as those discussed below can improve fuel economy easily by more than 10 percent.

Avoid Quick Starts and Sudden Stops

Despite the attention they may get, the abrupt, aggressive “jackrabbit” starts waste fuel, wear the

tires, jeopardize safety, and are harder on vehicle components and connectors. The squealing

stops wear the brake pads prematurely, and may cause the driver to lose control of the vehicle. Easy starts and stops save fuel, reduce wear and tear, reduce pollution, and are safer and more courteous to other drivers.

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Drive at Moderate Speeds

Avoiding high speeds on open roads results in safer driving and better fuel economy. In highway driving, over 50 percent of the power produced by the engine is used to overcome aerodynamic drag (i.e., to push air out of the way). Aerodynamic drag and thus fuel consumption increase rapidly at speeds above 55 mph. On average, a car uses about 15 percent more fuel at 65 mph and 25 percent more fuel at 70 mph than it does at 55 mph. (A car uses about 10 percent more fuel at 100 km/h and 20 percent more fuel at 110 km/h than it does at 90 km/h.)

The discussion above should not lead one to conclude that the lower the speed [is], the better the fuel economy [will be] - because it is not. The number of miles that can be driven per gallon of fuel drops sharply at speeds below 30 mph (or 50 km/h). Besides, speeds slower than the flow of traffic can create a traffic hazard. Therefore, a car should be driven at moderate

speeds for best

fuel economy.

Maintain a Constant Speed

The fuel consumption remains at a minimum during steady driving at a moderate speed. Keep in mind that every time the accelerator is hard pressed, more fuel is pumped into the engine. The vehicle should be accelerated gradually and smoothly since extra fuel is squirted into the engine during quick acceleration. Using cruise control on highway trips can help maintain a constant speed and reduce fuel consumption: Steady driving is also safer, easier on the nerves, and better for the heart.

Anticipate Traffic Ahead and Avoid Tailgating

A driver can reduce fuel consumption by up to 10 percent by anticipating traffic conditions ahead and adjusting

the speed accordingly, and avoiding tailgating and thus unnecessary braking

and acceleration. Accelerations and decelerations waste fuel. Braking and abrupt stops can be minimized, for example, by not following too closely, and slowing down gradually by releasing the gas pedal when approaching a red light, a stop sign, or slow traffic. This relaxed driving style is safer, saves fuel and money, reduces pollution, reduces wear on the tires and brakes, and is appreciated by other drivers. Allowing sufficient time to reach the destination will make it easier to resist the urge to tailgate.

Avoid Sudden Acceleration and Sudden Braking (except in emergencies)

Accelerate gradually and smoothly when passing other vehicles or merging with faster traffic. Pumping or hard pressing the accelerator pedal while driving causes the engine to switch to a “fuel enrichment mode” of operation that wastes fuel. In city driving, nearly half of the engine power is used for acceleration. When accelerating with stick-shifts, the RPM of the engine

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should be kept to a minimum. Braking wastes the mechanical energy produced by the engine and wears the brake pads.

Avoid Resting Feet on the Clutch or Brake Pedal while Driving

Resting the left foot on the brake pedal increases the temperature of the brake components, and thus reduces their effectiveness and service life while wasting fuel. Similarly, resting the left foot on the clutch pedal lessens the pressure on the clutch pads, causing them to slip and wear prematurely, wasting fuel.

Use Highest Gear (Overdrive) During Highway Driving Overdrive improves fuel economy during highway driving by decreasing the vehicle’s engine speed (or RPM). The lower engine speed reduces fuel consumption per unit time as well as engine wear. Therefore, overdrive (the fifth gear in cars with overdrive manual transmission) should be used as soon as the vehicle's speed is high enough.

Turn the Engine Off Rather than Letting It Idle

Unnecessary idling during lengthy waits (such as waiting for someone or for service at a drive-up window being stuck in traffic, etc.) wastes fuel, pollutes the air, and causes engine wear (more wear than driving). Therefore, the engine should be turned off rather than letting it idle. Idling for more than a minute consumes much more fuel than restarting the engine. Fuel consumption in the lines of drive-up windows and the pollution emitted can be avoided altogether by simply parking the car and going inside.

Use the Air Conditioner Sparingly

Air-conditioning consumes considerable power and thus increases fuel consumption by 3 to 4 percent during highway driving, and by as much as 10 percent during city driving. The best alternative to air-conditioning is to supply fresh outdoor air to the car through the vents by turning on the flow - through ventilation

system (usually by running the air-conditioner in the

“economy” mode.) while keeping the windows and the sunroof closed. This measure will be adequate to achieve comfort in pleasant weather, and it will save the most fuel since the compressor of the air conditioner will be off. In warmer weather, however, ventilation cannot provide adequate cooling effect. In that case we can attempt to achieve comfort by rolling down the windows or opening the sunroof. This is, certainly a viable alternative for city driving, but not so on high-ways since the aerodynamic drag caused by wide-open windows or sun-roof at

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high speeds consumes more fuel than does the air conditioner. Therefore, at highway speeds, the windows or the sunroof should be closed and the air conditioner should be turned on instead to save fuel. This is especially the case for the newer, aerodynamically designed cars. Most air conditioners have a “maximum” or “recirculation” setting that reduces the amount of hot outside air that must be cooled, and thus the fuel consumption for air-conditioning. A passive measure to reduce the need for air conditioning is to park the vehicle in the shade, and to leave the windows slightly open to allow for air circulation.

After Driving

You cannot be an efficient person and accomplish much unless you take good care of yourself (eating right, maintaining physical fitness, having checkups, etc.), and the cars are no exception. Regular maintenance improves performance, increases gas mileage, reduces pollution, lowers repair costs, and extends engine life. A little time and money saved now may cost a lot later in increased fuel, repair, and replacement costs.

Proper maintenance such as checking the levels of fluids (engine oil, coolant, transmission, brake, power steering, windshield washer, etc.), the tightness of all belts, and formation of cracks or frays

on hoses, belts, and wires, keeping tires properly inflated, lubricating

the moving

components, and replacing clogged air, fuel, or oil filters will maximize fuel efficiency. Clogged

air filters increase fuel consumption (by up to 10 percent) and pollution by restricting airflow to

the engine, and thus they should be replaced. The car should be tuned up regularly unless it has electronic controls and a fuel-injection system. High temperatures (which may be due to a malfunction

of the cooling fan) should be avoided as they may cause the break down of the

engine oil and thus excessive wear of the engine, and low temperatures which may be due to a

malfunction of the cooling fan) may extend the engine’s warm-up period and may prevent the engine from reaching the optimum operating conditions. Both effects will reduce fuel economy.

Clean oil extends engine life by reducing engine wear caused by friction, removes acids, sludge, and other harmful substances from the engine, improves performance, reduces fuel consumption, and decreases air pollution. Oil also helps to cool the engine, provides a seal

between the

cylinder walls and the pistons, and prevents the engine from rusting. Therefore, oil and oil filter should be changed as recommended by the vehicle manufacturer. Fuel-efficient oils (indicated by “Energy Efficient API” label) contain certain additives that reduce friction and increase a vehicle’s fuel economy by 3 percent or more. In summary, a person can save fuel, money, and the environment by purchasing an energy-efficient vehicle, minimizing the amount of driving, being fuel-conscious while driving, and maintaining the car properly. These measures have the added benefits of enhanced safety, reduced maintenance costs, and extended vehicle life.