Ignition Timing Advance Of The Petrol Engine Engineering Essay

Ignition Timing Advance Of The Petrol Engine Engineering Essay Ignition Timing: as applied to the spark ignition engines (petrol engines) is a process of setting the time at which the spark plug should fire in the combustion chamber during the compression with respect to the piston position and the crankshaft angular velocity. The spark plug should fire before TDC and the flame should terminate after TDC. Setting the appropriate ignition timing is very crucial as it decides the time available for combustion of the air-fuel mixture. Hence, the ignition timing affects many variables including fuel economy and engine power output. Earlier engines that use mechanical spark distributors rely on the inertia of rotating weights and springs and manifold vacuum in order to set the ignition timing throughout the RPM range of the engine; whereas the latest engines consists of an ECU (engine control unit) which uses a computer to control the ignition timing throughout the engines RPM range. Factors influencing ignition timing: Type of ignition system used. Engine speed. Load of the engine: with more load (larger throttle opening) requiring less advance (as the mixture burns faster). Components used in the ignition system. Settings of the ignition system components. Temperature of the engine; lower temperature allows for more advance. The ignition timing to some extent also depends on the octane number of the fuel, and the air-fuel ratio as this determines the speed with which the fuel burns. Usually, any major engine changes or upgrades will require a change to the ignition timing settings of the engine. Timing Advance: refers to the number of degrees before top dead centre (bTDC) that the spark will ignite the air-fuel mixture in the combustion chamber during the compression stroke. In contrast to that, timing retard refers to the changing in ignition timing, so that the fuel ignition takes place later than the manufacturers specified time. As an example, if the set ignition time was 12Â ° bTDC, then when the fuel ignition starts later than 12Â ° bTDC, it is known as ignition retard; similarly when the air-fuel mixture is ignited at an angle greater than 12Â ° bTDC, it would be known as ignition advance. Timing advance is necessary because it takes time for the combustion of the air-fuel mixture to complete. Igniting the mixture before the piston ends its compression stroke would maximize the limit to which the mixture burns completely, and hence help to build up maximum pressure soon after the piston reaches the TDC. This would ensure maximum power output by maximizing the force with which the piston is pushed down, by maximizing the pressure as soon as the piston starts going down when the power stroke is initiated. Ideally, the mixture should be completely burnt by 20Â ° aTDC (after TDC). If the ignition occurs at a position that is too advanced relative to the piston position, the rapidly expanding air-fuel mixture can actually push against the piston still moving up, causing detonation and lost power; whereas if the ignition is too retarded relative to the piston position, the maximum cylinder pressure will occur after the piston has already travelled too far down the cylinder. This would result in lost power accompanied by high emissions and unburnt fuel. Why is Ignition timing advance required? The ignition timing needs to be increasingly advanced (relative to the TDC) as the engine speed increases, so that the air-fuel mixture has the correct amount of time to burn completely. As the engine speed increases, the time available to burn the mixture decreases while the burning itself proceeds at the same speed; this requires the burning to start earlier to complete in time. The correct timing advance for a given engine speed will allow for maximum cylinder pressure to be achieved at the correct crankshaft angular position. Combustion in SI Engines: The combustion process in SI engines consists of three major parts: Ignition and flame development, Flame propagation, and Flame termination. Consumption of the first 5-10% of the air-fuel mixture is generally considered as the flame development. During the flame development period, the spark plug fires and the combustion process starts, but very little pressure rise is observed (graph-1). Almost all the useful work is produced in an engine cycle during the flame propagation period of the combustion process. During this period 80-90% of the air-fuel mass is burnt; the cylinder pressure is greatly increased which provides the force to produce work in the expansion stroke. The final 5-10% of the air-fuel mass which burns is classified as flame termination. During this time, pressure drops and combustion is finally terminated. The combustion process ideally consists of an exothermic sub-sonic flame progression through a premixes almost homogenous air-fuel mixture. The spread of the flame front is greatly enhanced by the induced turbulence and swirl within the cylinder. Ignition and Flame Development: The process of combustion is initiated by an electric discharge across the electrodes of a spark plug anywhere between 10Â ° to 30Â ° bTDC, depending on the geometry of the combustion chamber. The high-temperature plasma discharge between the electrodes ignites the air-fuel mixture in the immediate vicinity, and the flame spreads outwards from here. Graph . The increase in pressure rise is very slow after ignition during the flame development period. This results in a slow pressure force increase on the piston and a smooth engine cycle. Maximum pressure occurs 5Â ° to 10Â ° aTDC. The combustion starts very slowly due to the high heat losses to the relatively cold spark plug and the gas mixture. The flame can generally be detected at about 6Â ° of crank rotation after the spark plug firing. The applied potential across the spark plug is usually 25,000-40,000 V. overall spark discharge lasts about 0.001 second with an average temperature of about 6000 K. The discharge of the spark plug delivers about 30 to 50 mJ of energy, most of which is lost by heat transfer. Ignition Systems: The few commonly used methods used to produce the high voltage potential, which is required to cause the electrical discharge across the spark plug electrodes, are: Battery-coil combination: Most automobiles use a 12-volt electrical system, including a 12-volt battery. This voltage is multiplied many times by the coil that supplies the very high potential delivered to the spark plug. Capacitor Discharge: Some systems use a capacitor to discharge across the spark plug electrodes at the proper time. Magneto system: Most small engines and some larger ones use a magneto driven off the engine crankshaft to generate the needed spark plug voltage. Some engines have a separate high-voltage generation system for each spark plug, while the others have a single system with a distributor that shifts from one cylinder to the next. The Spark Plug: The gap between the electrodes on a modern spark plug is about 0.7 to 1.7 mm. smaller gaps are acceptable if there is a rich air-fuel mixture or if the pressure is high (i.e. high inlet pressure by turbocharging or a high compression ratio). Normal temperature of spark plug electrodes between firings should be about 650Â ° to 700Â ° C. A temperature above 950Â °C risks the possibility of surface ignition, and a temperature below 350Â °C tends to promote surface fouling over extended time. For older engines with worn piston rings that burn an excess of oil, hotter plugs are recommended to avoid fouling. Hotter plugs have a greater heat conduction resistance than colder plugs. Modern spark plugs have a greater life span than the old ones. Some of the high quality spark plugs with platinum-tipped electrodes are made to last 160,000 km or more. Harley Davidson uses gold-tipped spark plugs. One reason this is desirable is the difficulty in replacing spark plugs in some modern engines due to the complexity and compactness of engine and increased amount of engine equipment. Figure . An NGK spark plug Spark plug firing: When a spark plug fires, the plasma discharge ignites the air-fuel mixture between and near the electrodes. This creates a spherical flame front that propagates outward into the combustion chamber. At first, the flame front moves very slowly because of its original size; it does not generate enough energy to quickly heat the surrounding gases and thus propagates very slowly. As a result of this, the cylinder pressure is not raised quickly and very little compression heating is experienced. Once the first 5-10% of the air-fuel mass is burnt, the flame velocity reaches higher values with corresponding rise in pressure, the flame propagation region. It is desirable to have a rich air-fuel mixture around the electrodes of the spark plug at ignition, as it ignited easily and more readily, has a faster flame speed and initiates the combustion process well. Spark plugs are generally located near the intake valves to assure a richer mixture, especially when starting a cold engine. Latest developments in spark plug/ignition system technology: The efforts to develop better ignition system continue. Spark plugs with several electrodes and two or more simultaneous sparks are now available. They give a more consistent ignition and quicker flame development. One of the modern systems still under development gives a continuing arc after the initial discharge; this additional spark will speed up combustion and give a more complete combustion as the air-fuel mixture swirls through the combustion chamber. Development work has been done to create a spark plug with variable electrode gap size. This would allow flexibility in ignition for different operating conditions. At least one automobile manufacturer is experimenting with engines that use a point on top of the piston as one of the spark electrodes. Using this system, spark ignition can be initiated across the gaps of 1.5 to 8 mm with a reported lowering of fuel consumption and emissions. Flame Propagation: Induced turbulence and swirl causes the flame propagation speed to increase by 10 times than if there were a laminar flame front moving through a stationary gas mixture. These motions also cause the flame front to expand spherically from the spark plug in stationary air and is greatly distorted and spread. As the gas mixture burns, the temperature and pressure rise to high values. Figure . A typical flame propagation pattern. The burnt gases behind the flame front are hotter than the unburnt gases before the flame front, with all the gases at about the same pressure. This decreases the density of the burnt gases and expands them to occupy a greater percentage of the total combustion chamber volume. Compression of the unburnt gases raises their temperature by compressive heating. In addition, radiation heating emitted from the flame reaction zone, which is at a temperature on the order of 3000 K, further heats the gases in the combustion chamber, unburnt and burnt, raising the pressure further. Heat transfer by conduction and convection are minor as compared to radiation, due to very short real time involved in each cycle. The environment inside the combustion chamber is such that the progressive increase in temperature and pressure in taking place, causing the reaction time to decrease and flame front speed to increase. The temperature of the burnt gases is not uniform. It is higher near the spark plug where the combustion had initiated. Ideally, the air-fuel mixture should be around two-thirds burnt at TDC and almost completely burnt at about 15Â ° aTDC. This causes the maximum pressure and temperature of the cycle to occur somewhere between 5Â ° and 10Â ° aTDC. A lesser pressure rise rate gives lower thermal efficiency and danger of knock. The combustion process is therefore a compromise between the highest thermal efficiency possible and a smooth engine cycle with some loss of efficiency. Burn angle, Ignition and Ignition advance: The typical burn angle, the angle through which the crankshaft turns during combustion, is about 25Â ° for most engines. If combustion is to be completed at 15Â ° aTDC then ignition should occur at about 20Â ° bTDC. If ignition is too early, the cylinder pressure will increase to undesirable levels before TDC, and useful work would be wasted in compression stroke. If ignition is late, peak pressure will not occur early enough, and work will be lost at the start of power stroke due to lower pressure. Graph . Average flame speed in the combustion chamber. Lean air-fuel mixtures have slower flame speeds, with maximum speed occurring when slightly rich mixture at an equivalence ratio near 1.2 Actual ignition timing is typically anywhere from 10Â ° to 30Â ° bTDC, depending on the fuel used, engine geometry, and engine speed. For any given engine, the combustion occurs faster at higher engine speed. Real time for combustion is therefore less, but real time for engine cycle is also less, and the burn angle is only slightly changed. This slight change is corrected by advancing the spark as the engine speed in increased. This initiates combustion slightly earlier in the cycle, peak temperature and pressure remaining at about 5Â ° to 10Â ° aTDC. At part throttle, ignition timing is advanced to compensate for the resulting slower flame speed. Graph . Burn angle as a function of engine speed. Timing adjustment in Modern engines: Modern engines automatically adjust ignition timing with electronic controls. These not only use engine speed to set the timing but also sense and make fine adjustment for knock and incorrect exhaust emissions. Earlier engines used a mechanical timing adjustment that consisted of a spring-loaded ignition distributor that changed with engine speed due to centrifugal forces. Ignition timing on many small engines is set at an average position with no adjustment possible. Graph . Average combustion chamber flame speed as a function of engine speed for a typical SI engine. Flame Termination: 90 95% of the air-fuel mass has been combusted by 15Â ° to 20Â ° aTDC and the flame front has reached the extreme corners of the combustion chamber. The last 5 10% of the mass has been compressed into a few percent of the combustion chamber volume by the expanding burning gases behind the flame front. Although at this point the piston has already moved away from TDC, the combustion chamber volume has only increased on the order of 10 20% from the very small clearance volume. This means that the last mass of air and fuel will react in a very small volume in the corner of the combustion chamber and along the chamber walls, at a reduced rate. Near the walls, turbulence and mass motion of the gas mixture have dampened out and there is a stagnant boundary layer. The large mass of metal cylinder walls also act as a heat sink and conduct away much of the energy being released in the reaction flame. Both these mechanisms reduce the rate of reaction and flame speed, and the flame is finally terminated as it slowly dies out. Although very little additional work is delivered by the piston during the flame termination, it still is a desirable occurrence. Because the rise in cylinder pressure tapers off slowly towards zero during this flame termination, the forces transmitted to the piston also taper off slowly resulting in smooth engine operation. Self Ignition: During the flame termination period, self-ignition will sometimes occur in the end gas and engine knock will occur. The temperature of the unburnt gases in front of the flame front continues to rise during the combustion process, reaching a maximum in the last end gas. The maximum temperature is often above self-ignition temperature. Because the flame front moves slowly at this time, the gases are often not consumed during ignition delay time, and self-ignition occurs. The resulting knock is usually not objectionable or even noticeable. This is because there is so little unburnt air-fuel left at this time that self-ignition can only cause very slight pressure pulses. Maximum power is obtained from an engine when it operates with very slight self-ignition and knock at the end of the combustion process. This occurs when maximum pressure and temperature exist in the combustion chamber and knock gives a small pressure boost at the end of combustion. Abnormal Combustion: Abnormal combustion is referred to a combustion process in which a flame front may be started by hot combustion chamber surfaces either prior to or after spark ignition, or a process in which some part or all of the charge may be consumed at extremely high rates. Figure . Phenomenon of abnormal combustion The two important abnormal combustion phenomena of major concern are: Knock, and Surface Ignition They are of major concern, because: When severe, they can cause major engine damage; and Even if not severe, they are regarded as an objectionable source of noise by the engine or vehicle operator. Knock: is the name given to the noise which is transmitted through the engine structure when essentially spontaneous ignition of a portion of the end gas. This is when the fuel, air, residual gas, mixture ahead of the propagating flame occurs. When this process takes place, there is an extremely rapid release of much of the chemical energy in the end gas, causing very high local pressures and the propagation of pressure waves of substantial amplitude across the combustion chamber. Surface Ignition: is ignition of the fuel-air mixture by a hot spot on the combustion chamber walls such as an overheated valve or spark plug, or glowing combustion chamber deposit: i.e. by any other means other than the normal spark discharge. It can occur before the occurrence of the spark (pre-ignition) or after (post-ignition). Following the surface ignition, a turbulent flame develops at each surface-ignition location and starts to propagate across the chamber in an analogous manner to what occurs with normal spark ignition. Types of Abnormal Combustion in SI Engines: Spark Knock: A knock which is recurrent and repeatable in terms of audibility. It is controllable by the spark advance; advancing the spark increases the knock intensity and retarding the spark reduces the intensity. Surface Ignition: hot spots combustion chamber deposits: Surface ignition is ignition of the fuel-air mixture charge by any hot surface other than the spark discharge prior to the arrival of the normal flame front. It may occur before the spark ignites the charge (pre-ignition) or after normal ignition (post-ignition). Surface ignition can be of two types: Knocking surface ignition: Knock which has been preceded by surface ignition. It is not controllable by spark advance. Non-Knocking surface ignition: Surface ignition which does not result in knock. Run-on: It is the continuation of engine firing after the electrical ignition is shut off. Runaway surface ignition: Surface ignition which occurs earlier and earlier in the cycle. It can lead to serious overheating and structural damage to the engine. Wild Ping: Knocking surface ignition characterized by one or more erratic sharp cracks. It is probably the result of early surface ignition from deposit particles. Rumble: A low-pitched thudding noise accompanied by engine roughness. It is probably caused by high rates of pressure rise associated with early ignition or multiple surface ignitions. Knock primarily occurs under wide-open-throttle operating condition. It is thus a direct constraint on engine performance. It also constraints engine efficiency, since by effectively limiting the temperature and pressure of the end-gas, it limits the engine compression ratio. The occurrence and severity of the knock depend on the knock resistance of the fuel and on the anti-knock characteristics of the engine. Measures to avoid knocking: The ability of the fuel to resist knock is measures by its octane number; higher octane numbers indicate greater resistance to knock. Gasoline octane ratings can be improved by refining processes, such as catalytic cracking and reforming, which convert low-octane hydrocarbons to high-octane hydrocarbons. Also, antiknock additives such as alcohols, lead alkyls, or an organomanganese compound can be used. The octane number requirement of an engine depends on how its design and conditions under which it is operated affect the temperature and pressure of the end-gas ahead of the flame and the time required to burn the cylinder charge. An engines tendency to knock, as defined by its octane number is increased by factors that produce higher temperatures and pressures or lengthen the burning time. Octane Requirement: can be defined as the octane rating of the fuel required to avoid knock. Thus knock is a constraint that depends on both the quality of the available fuels and on the ability of the engine designer to achieve the desired normal combustion behavior while holding the engines tendency to knock at a minimum. Some major steps: The use of a fuel with higher octane number. The addition of octane-increasing additives in the fuel Ignition Timing Retardation . Use of a spark plug of colder heat range, in cases, where the spark plug insulator has become a source of pre-ignition leading to knock. Reduction of charge temperature e.g. through fuel evaporation inside the cylinder (GDI) Anti knock combustion chamber design. Consequences of engine knock: The engine can be damaged by knock in different ways: -piston ring sticking breakage of the piston rings failure of the cylinder head gasket -cylinder head erosion piston crown and top erosion -piston melting and holing Examples of component damage due to pre ignition and knock are shown below: Stroboscope: A stroboscope in an instrument used to make cyclically moving object appear to be moving slow or stationary. The principle is used for the study of rotating, reciprocating, oscillating or vibrating objects. Machine parts and vibrating strings are common examples. In its simplest form, a rotating disc with evenly-spaced holes is placed in the line of sight between the observer and the moving object. The rotational speed of the disc is adjusted so that it becomes synchronised with the movement of the observed system, which seems to slow and stop. The illusion is caused by temporal aliasing, commonly known as the stroboscopic effect. In electronic versions, the perforated disc is replaced by a lamp capable of emitting brief and rapid flashes of light. The frequency of the flash is adjusted so that it is an equal to, or a unit fraction below or above the objects cyclic speed, at which point the object is seen to be either stationary or moving backward or forward, depending on the flash frequency. Observations: Engine Speed Throttle Position Degree Advance 475 5% 10Â ° 580 8% 17Â ° 657 22% 22Â °

Digital Divide Essay example -- Access to Technology, Gender Roles

The following comment was written by an anonymous author in response to the digital divide that is so evident in our society today. â€Å"Power is necessarily unequal when one group knows what’s going on and the other group does not. And the powerless, lacking information as they do, almost necessarily function at the bottom of the economic and political pyramid of almost any society† (Racial divide,2010). Whether it is gender, racial, economic or disability related, our nation is segregated by the haves and the have-nots. Digital Divide defined What is meant by Digital Divide? The Digital Divide is the lack of ability for certain groups, usually socio-economic and cultural, to access necessary information and communication technology (ICT) (Gorski, 2001). The lack of access usually includes the unavailability to computer and internet services. As describe by Gorski (2001), the digital divide is further subdivided by gender, race, income and disabilities. Gender With the increase of availability of access to technology in society today, women are still lagging behind their male counterparts (Conversations for a Better World, 2010). Why is this still happening in the Twenty-first Century? Globally, the root cause is the cultural treatment of women. In many cultures worldwide, women are denied access to education let alone technology. Even if they are given the opportunity to use a computer, most often they lack the computer skills to effectively navigate most websites (Digital Gender Divide, n.d.). In America and other developed countries, the digital divide that separates gender is much narrower, and often equal to that of males, depending on the survey. If a digital divide does separate the genders in developed n... .... In summary, the Digital Divide is real and has placed a severe gap between certain groups of people in the American culture. The Land of Opportunity is not necessarily made available to all. In her CNet article, Sonia Arrison (2002), provides a unique perspective as to the reason behind the gap. â€Å"The digital divide is not a crisis, and it is certainly not the civil liberties issue of the 21st century. The real issues are the sorry state of education and the push to raise the taxes that affect lower income families most† (Arrison, 2002). Arrison states that if the Government could improve the education in the American schools and stop luxury taxes on so many services, the Digital Divide could easily be narrowed. By narrowing the divide, more families could afford Internet if so desired, and students could have access to a better education.

April Morning by Howard Fast Essay

â€Å"April Morning† by Howard Fast is a novel that takes place during the Battle of Lexington on April 19, 1775. The entire book takes place during a 24 hour time period. Adam Cooper is the antagonist in this novel. When Adam goes to bed on the eve of April 18, 1775 he is a boy. When he awakens the next morning he is forced to become a man. In the early hours of the morning he, along with the rest of the town, is awakened by a lone rider racing to Lexington to warn them that a British army, of maybe a thousand men, is marching their way. Immediately the town is in a frenzy to prepare for the British arrival. The book is about Adam’s journey during the Battle of Lexington. Adam Cooper is just 15 years old when he chooses to fight alongside his father in the Battle of Lexington. He is a brave and courageous character. He admits, at least to himself, that he is scared to fight but it does not prevent him from fulfilling his duty to his people. During the battle Adam reveals that he does not enjoy killing and shooting people. His character is full of sarcasm and curiosity. He is constantly questioning everything including God which was practically unheard of in his time. Moses Cooper is Adam’s father. He is a strong man who loves to argue and debate with anyone. He is tough on Adam, so much so that Adam is convinced that his father hates him. There is only one point in this novel where Moses shows any kind of affection towards Adam, and it is right before the battle where Moses is killed. Solomon Chandler is an older man whom Adam runs into while running away from two redcoat soldiers. Solomon takes Adam under his wing so to say for the rest of the battle. He comforts Adam and provides Adam a shoulder to cry on after Adams father is shot and killed. Later we find out that Solomon has a darker side to him when he is shooting the Redcoat soldiers and laughing like it is a game. Granny also known as Goody Cooper is Adams grandmother. She and Adam seem very close. You can tell she is a tough woman but she is much more sensitive than her son Moses. Constantly you read about her reprimanding Moses even though he is full grown and has a family of his own. She is not afraid to voice her opinion to anyone. When the Redcoats are ransacking her home, she does not sit and cower, she follows them into every room and yells and screams at them calling them thieves and murderers. Ruth Simmons is Adams second cousin once removed. She is also his love interest in the story. Ruth has known Adam her whole life and decided when she was 13 years old that he was the man she wanted to marry. One of the many conflicts in this novel includes the physical size of the British Army verses the townspeople’s army. The British have an army of well over 1000 men, whereas Lexington was only able to acquire less than 100 men. When the British arrive at Lexington all of the men are faced with the option to both stand and fight, which was considered suicide, or they could run away. They had to make up their mind quick. Every single man ran and fled the town. Had they not there is no doubt that they would all have been slaughtered. Once the committees get together all the remaining men from nearby towns they plan to ambush the British. Adam describes how tiered and weak his body is. He is so tiered that he actually stops shooting and finds a spot under a tree where he falls asleep! He cannot physically stay awake any longer. At the end of the battle when Adam returns home he finds Ruth and they talk about the future. He confirms to Ruth that he does in fact love her, and to himself he confirms that he doesn’t want to marry any other girl but her. However, there is still the matter of Adam going to fight again and when Ruth asks Adam if he will sign the muster book he is torn between staying with his family and Ruth or going to war and fighting. As I read â€Å"April Morning† I found it very hard to stop reading. It is a fast moving book that goes through, in detail, each battle that Adam had to face in just 24 hours. I loved Adams character mostly because of his sarcasm in the beginning of the novel. I liked the fact that he did not really want to shoot and kill the Redcoats he just wanted them to leave. The book was cleverly written, and I admired Howard Fast for being able to write a book just about one day and still keeps it interesting the whole way through. I never found myself getting bored or tiered of reading it. I think it gives a great perspective on what the Battle of Lexington was like. It had everything a book, in my opinion, should have: love, hate, sorrow, terror, adventure, and action. A great read for anyone interested in learning more about our American history and how the American Revolution began.

Ged 210 Unit 1 Examination Answers - 960 Words

GED 210 Unit 1 Examination Answers Follow Below Link to Download Tutorial https://homeworklance.com/downloads/ged-210-unit-1-examination-answers/ For More Information Visit Our Website ( https://homeworklance.com/ ) Email us At: Support@homeworklance.com or lancehomework@gmail.com 1. Which of the following would not be considered a specialization within the discipline of physical anthropology? †¢ human anatomy †¢ paleopathology †¢ primatology †¢ phonology 1. The material products of former societies are known as: †¢ artifacts †¢ fossils †¢ legacies †¢ antiquaries 1. Anthropologist, Spencer Wells, is the director of the geographic project which is: †¢ making significant contributions to the philosophy of archaeology.†¦show more content†¦Ã¢â‚¬ ¢ Navajo sand paintings. †¢ the Big Bang theory. 1. __________ may occur when one dominant group in a complex society imposes its cultural beliefs on subordinate ethnic groups. For example, the dominant ethnic group in the U.S. during the eighteenth and nineteenth centuries (the white, Anglo-Saxon Protestants) was able to impose its language, cultural beliefs, and practices on other minority groups in U.S. society. †¢ Cultural hegemony †¢ Cultural chaos †¢ Multiculturalism †¢ Ethnic superiority 1. Norms are: †¢ prohibitions against a particular kind of behavior. †¢ values that are accepted by every human society. †¢ a given society’s rules for right and wrong behavior. †¢ individuals who look like the majority of people. 1. In her classic work Patterns of Culture (1934), Ruth Benedict used the terms â€Å"apollonian† and â€Å"dionysian† to describe: †¢ cultural â€Å"personalities† of pueblo and plains Indians. †¢ religious cults of northern and southern Greece. †¢ rituals of warfare and celebration in the South Pacifi †¢ contrasting models of cultural diffusion. 1. Margaret Mead got most of her information on the behavior of adolescents in Samoa from: †¢ accounts of travelers and missionaries. †¢ newspaper accounts and government reports. †¢ watching ethnographic films. †¢ interviewing young women. 1. The central object of Mead’s study, Coming of Age in Samoa (1928), was to determine whether or not: †¢ kinship patterns inShow MoreRelatedHsc General Math Textbook with Answers153542 Words   |  615 Pageson the Student CD-ROM that is packed with this book. . Introduction vii Ackno ledgements Acknowledgements Chapter 1 1.1 1.2 1.3 1.4 1.5 viii iii 1 Credit and borrowing Flat-rate loans 1 Home loan repayments 8 Comparing loans Comparing loans 13 Credit cards 17 Reducing balance loans 22 Chapter summary t 29 Multiple choice questions ultiple-choice questions 30 Short-answer questions 31 Further applications of area and volume Area of circles, annuluses and sectors Area of ellipses 39 AreaRead MoreEffects of the Youth Unemployment in Kenya16576 Words   |  67 Pagestraining increased over time, while the number in school decreased steadily. These statistics all show that human capital increased steadily over the sample period for the average male of that age. The core subject of the research, however, is an examination of the effects of a period of unemployment on future employment. Lost Jobs Lead to Decreased Wages Early unemployment delays gains in experience and training that usually lead to increased earnings. Prior work experience has been found to have aRead MoreStephen P. Robbins Timothy A. Judge (2011) Organizational Behaviour 15th Edition New Jersey: Prentice Hall393164 Words   |  1573 PagesOrganizational behavior / Stephen P. Robbins, Timothy A. Judge. — 15th ed. p. cm. Includes indexes. ISBN-13: 978-0-13-283487-2 ISBN-10: 0-13-283487-1 1. Organizational behavior. I. Judge, Tim. II. Title. HD58.7.R62 2012 658.3—dc23 2011038674 10 9 8 7 6 5 4 3 2 1 ISBN 10: 0-13-283487-1 ISBN 13: 978-0-13-283487-2 Brief Contents Preface xxii 1 2 Introduction 1 What Is Organizational Behavior? 3 The Individual 2 3 4 5 6 7 8 Diversity in Organizations 39 Attitudes and Job Satisfaction 69 EmotionsRead MoreMedicare Policy Analysis447966 Words   |  1792 Pagespurposes. 1 Be it enacted by the Senate and House of Representa- 2 tives of the United States of America in Congress assembled, 3 SECTION 1. SHORT TITLE; TABLE OF DIVISIONS, TITLES, rmajette on DSK29S0YB1PROD with BILLS 4 5 AND SUBTITLES. (a) SHORT TITLE.—This Act may be cited as the 6 ‘‘Affordable Health Care for America Act’’. VerDate Nov 24 2008 12:56 Oct 30, 2009 Jkt 089200 PO 00000 Frm 00001 Fmt 6652 Sfmt 6201 E:\BILLS\H3962.IH H3962 2 1 2