Charles Darwin Essays (716 words) - Charles Darwin, Coleopterists

Charles Darwin annon Like many modern students, Charles Darwin exceeded only in subjects that intrigued him. Although his father was a physician, Darwin was uninterested in medicine and he was unable to stand the sight of surgery. He did eventually obtain a degree in theology from Cambridge University, although theology too was of minor interest to him. What Darwin really liked to do was to tramp over hills, observing plants and animals, collecting new specimens, scrutinizing their structures, and categorizing his findings. In 1831, when Darwin was only 22 years old, the British government sent Her Majesty^?s Ship Beagle on a 5 year expedition that would take them first along the coastline of South America and then onward around the world. As was common on such expeditions, the Beagle would carry along a naturalist to observe and collect geological and biological specimens encountered along the route. Thanks to the recommendation of one of Darwin^?s previous college professors, he was offered the position of naturalist aboard the Beagle. The Beagle sailed to South America, making many stops along the coast. Here Darwin observed the plants and animals of the tropics and was stunned by the diversity of species compared with Europe. Perhaps the most significant stopover of the voyage was the month spent in the Galapagos Islands off of the northwestern coast of South America. It was here that Darwin found huge populations of tortoises; and he found that different islands were home to distinctively different types of tortoises. He then found that on islands without tortoises, pricky pear cactus plants grew with their juicy pads and fruits spread out over the ground. And on islands that had hourdes of tortoises, the prickly pears grew substantially thick, tall trunks, bearing the fleshy pads and fruits high above the reach of the tough mouthed tortoises. He then wondered if the differences in these organisms could have arisen after they became isolated from one another on seperate islands. In 1836, Darwin returned to England after the 5 years with the expedition. He became established as one of the foremost naturalist of his time. But constantly gnawing at his mind was the problem of the origin of the species. Darwin sought to prove his ideal of evolution with simple examples. The various breeds of dogs provided a striking example of what Darwin sought to prove. Dogs descended from wolves, and even today the two will readily cross-breed. With rare exceptions, however, few modern dogs actually resemble wolves. Some breeds, such as the Chihuahua and the Great Dane, are so different from one another that they would be considered seperate species in the wild. If humans could cross-breed such radically different dogs in only a few hundred years, Darwin reasoned that nature could produce the same spectrum of living organisms given the hundreds of millions of years that she had been allowed. Darwin also maintained that seperate species evolve as a result of the principles of natural selection, or survival of the fittest. He knew that many more members of a species are born than can possibly survive. He also postulated that strong positive genes would be bred and rebred into each new generation of animals. Darwin, contrary to popular belief, never said that human beings evolved from apes. He said that all life began as a primordial soup, with molecules acting on each other. So from the first single celled organism all life came. One single organism, when acted on by several different molecules could give rise to many different species of animals. It is in this way that he stated that Ape and man were similar..each having a similar life^?s beginning. Darwin^?s theories caused the people of the time to begin to question where it was that they actually came from. His response was the book On the Origin of Species. In it he addressed the concerns of the people. He said It is interesting to contemplate an entangled bank, clothed with many plants of many kinds, with birds singing in the bushes, with various insects flitting about, and with worms crawling through the damp earth, and to reflect that these elaborately constructed forms....have all been produced by laws acting around us. These laws, taken in the highest sense, being Growth with Reproduction; Inheritance and Variability...; a Ratio of Increase so high as to lead to a struggle for life, and as a consequence to Natural Selection, entailing Divergence of Character and Extinction of less-improved forms....There is grandeur in this view of life, with its several powers, having been originally breathed into a few forms or into one, and that, whilst this planet has gone cycling on according to the fixded laws of gravity, from so simple a beginning endless forms most beautiful and most wonderful have been, and are being, evolved.

Free Essays on Germany

As a young adult in 1989, I remember the joyous displays of people crossing the border from East Germany to West Germany. I was unknowledgeable about the significance of the â€Å"fall of the Berlin Wall†, but I understood through the media that it was an important historical event of the twentieth century and would surely become a significant part of world history. German reunification became a reality that many Germans had dreamed of for years. The Reunification of the two Germanys was met with great excitement and expectations. Could this merging of two worlds live up to the dream of those who stood by the wall as it came crashing down? After World War II, Germany divided into four sections or zones. While this was meant to be a temporary move, the Cold War interceded and eventually the three western zones combined to form the Federal Republic of Germany while the eastern zone formed the German Democratic Republic. (Sandford) Berlin, the capital was also divided. The two areas of Germany, East Germany and West Germany began to experience a deteriorating relationship and conflicts arose. On Sunday August 12, 1961 plans for the beginning of the Berlin Wall were instituted. Led by Erich Honecker, the plans were kept secret. In fact, only twenty or so top-level East German officials knew of the plans. With limited written plans, the wall was erected with little knowledge until its completion. For the next 28 years the Berlin wall would separate East and West Germany. The divided areas of Germany would lead very different lives, with West Germany, a democratic union where the people and economy prospered. Yet , on the other hand, East Germany, under communist rule suffered tremendous economic dismay, and it people were offered few liberties. During the 1980’s, political changes in Eastern Europe gave Germans the hope for a reunified country, but the dream was unattainable as long as the communists held East Germany. In ... Free Essays on Germany Free Essays on Germany Germany in transition 1815 – Congress of Vienna – the ordering of German speaking countries After the defeat of France the victorious powers, Britain, Russia, Austria and Prussia, concluded peacemaking recognising the 38 States of the German Confederation. Some of these states were newly created states while others were restorations of the Holy Roman Empire. Although losing eastern territory to Russia, Prussia was doubled in size after land in the Rhineland and Westphalia was granted to her, making her the dominant power in northern Germany. Monarchies and principalities were in still in operation using their own courts and applying their own oaths of allegiance. However there were problems with newly established monarchs where loyalties had to be constructed through manufacturing of an image ( Frederich William III ). The states organised themselves, especially Prussia, more authoritatively than before in areas such as, security of borders, taxes, the military and education. Many of the natural resources became state owned, especially the coal mines of Saarland and the many German forests. Universities were founded and very well funded with an emphasis based on uniformity of approach especially in the area of university degrees. In the period between 1814 –1819 eleven different states drew up constitutions. In the most liberal of these, Baden, a house of parliament containing both a house for the lords and commons was established. Burschenschaften (1815) drew up the modern three striped German flag of today, leaving liberal reformers optimistic. However this optimism was short lived with the reactionary decade of the 1820s, with formal politics replaced by societies and the mass circulation of political pamphlets. 1830 Revolts – Reasons 1) Limited freedom of the 1820s, especially where the right to vote was concerned. 2) Poor harvest in 1830, as well as a rise in the price of bread. 3) Cus... Free Essays on Germany Communications The German Basic Law guarantees the freedom of the press. Germany has high newspaper readership and a well-informed population. In 1998, the country had 398 daily papers, with a total daily circulation of 25.5 million copies. Major daily publications include the Frankfurter Allgemeine, Sà ¼ddeutsche Zeitung, Die Welt, and the Berlin Tagesspiegel. Der Spiegel and Die Zeit are weeklies with national circulation. Party-owned and government-run publications in the former East Germany were privatized after 1989. Fees tied to the ownership of television sets finance the three major German public television channels. The channels are organized into 12 broadcasting regions, each with several radio stations. The channels produce their own shows or purchase foreign films and programs. Additional private and foreign channels and cable television are available. Television ownership is nearly universal. The German telephone system is modern, automatic. The system relies on satellites, cable, and microwave radio relay (MRR) networks. Before unification, this state of development did not apply to East Germany, where only the government and the secret police had efficient communications at their disposal. Since 1990, however, massive Western transfer payments have given East Germany a highly advanced communications systems, although the distribution of private telephones has not yet caught up with West German standards. Transportation Germany has a highly developed transportation system including a limited-access superhighway known as the autobahn. There is no speed limit on the autobahns, but frequent reconstruction projects and congestion keep the speed down. Since East German roads had not been upgraded and expanded much since the 1930s and the volume of motor vehicles on them rose greatly after unification, a large part of the funds transferred from the West have gone to expand the German highway system. The country's ex... Free Essays on Germany The Germany of the past had a low attendance at church. The German’s had placed a tax on all churches. The tax was collected by the state. Catholicism was the dominant religion for most of the 14th to 19th centuries. The Catholics stayed mostly to the south, as the Protestants and Lutherans lived in the north. During the era of World War II, the small population of German Jews was killed by the Nazis. More than 500,000 Jews were killed during this time. After the war, only 40,000 Jews remained in Germany. Today’s population of over 82 million Germans, is divided into several different religions. Still the dominant religion is Catholicism. The economy was developed in 1949 with Democratic Republic houses. Since the rise in the economy house hold income, cars, and hospitals increased. The eastern sides of Germany had the technological advances, and the western parts were more towards the manual labor. Of course Germany’s greatest low was during the end of World War II. Germany’s rebuild toward economic growth began in the late 50’s. As the economy have changed from it’s communist ways, it continues to grow today. The workers of Germany’s society out rank the homeless and those on welfare.... Free Essays on Germany Historically, Versailles’s reparations have taken the complete blame for the Weimar’s Eyears of hyperinflation; however, Versailles only tells half of the story and the Weimar’s economic break down desires a critical examination of the Reichstag’s macro–economic policies. As disproportionate as reparations demanded by Versailles were The underlying fact is that they could not have caused the hyperinflation unless they in concert with the irresponsible actions of Reichstag.  EIt is generally assumed that there was no alternative to inflationary policies in Germany immediately after the First World War, because of the costs of demobilization and reparations. However, this view fails to distinguish between political miscalculation and economic reality. EWrites in Niall Niall Ferguson in an article titled Constraints and Room for Maneuver in the German Inflation of the Early 1920s for the journal The Economic History Review. Economists lik e Ferguson speculate that Weimar structure and inability to deal with criticizes were to blame for the great inflation. Weimar political weakness is rooted in the polarization of the German population following the contentious and in German opinion controversial negotiation that led to the Versailles treaty. The public be fractured and radicalized and as a result the radical parties of nationalist and communist doubled in size leaving any political debate being highly divisive. Writing for the Arthur van Riel and Arthur Schram support this argument and contend that the Weimar contraversal orgins and subsqental need to appease the masses explain the government’s lack fiscal respocbiltuy The Weimar Republic is often seen as an unwished-for, improvised result of the chaos that followed World War I and of a fundamental controversy over socioeconomic conditions and matters of political representation. These conflicts had been inherited from the Wilhelm inian period, and, although economic... Free Essays on Germany As a young adult in 1989, I remember the joyous displays of people crossing the border from East Germany to West Germany. I was unknowledgeable about the significance of the â€Å"fall of the Berlin Wall†, but I understood through the media that it was an important historical event of the twentieth century and would surely become a significant part of world history. German reunification became a reality that many Germans had dreamed of for years. The Reunification of the two Germanys was met with great excitement and expectations. Could this merging of two worlds live up to the dream of those who stood by the wall as it came crashing down? After World War II, Germany divided into four sections or zones. While this was meant to be a temporary move, the Cold War interceded and eventually the three western zones combined to form the Federal Republic of Germany while the eastern zone formed the German Democratic Republic. (Sandford) Berlin, the capital was also divided. The two areas of Germany, East Germany and West Germany began to experience a deteriorating relationship and conflicts arose. On Sunday August 12, 1961 plans for the beginning of the Berlin Wall were instituted. Led by Erich Honecker, the plans were kept secret. In fact, only twenty or so top-level East German officials knew of the plans. With limited written plans, the wall was erected with little knowledge until its completion. For the next 28 years the Berlin wall would separate East and West Germany. The divided areas of Germany would lead very different lives, with West Germany, a democratic union where the people and economy prospered. Yet , on the other hand, East Germany, under communist rule suffered tremendous economic dismay, and it people were offered few liberties. During the 1980’s, political changes in Eastern Europe gave Germans the hope for a reunified country, but the dream was unattainable as long as the communists held East Germany. In ...

Creative Essay Example | Topics and Well Written Essays - 250 words

Creative - Essay Example The python represents the rich, the sheep represents the poor while the herder symbolizes the society in general. The artwork, which is widely symbolic, shows that the current society is dominated by the rich who use all means to oppress and control the poor. This is proven by the modern capitalism that supports the wealthy to become richer but fails to offer a solution to the poor whose standards of living keeps on deteriorating. The inaction by the society towards the ever increasing atrocities against the poor is represented by the herder who watches the python swallowing the sheep, but he fails to take any action although it is a his responsibility to save the sheep. For many years, the society has been silent about the increasing levels of poverty which has resulted in social, economic and political problems facing the modern world. The aim of this work, which is highly symbolic, is to stir critical thinking in the society about the need to have an equitable society. The audience is the general society who plays an active role in policy making by electing responsible representatives to articulate their interests and the policy makers who are responsible for making laws and developing policies that affect the lives of

Effective Assessment Practices Research Paper Example | Topics and Well Written Essays - 1000 words

Effective Assessment Practices - Research Paper Example This research will begin with the definition of assessment as the process that is employed to identify gather and interpreted information related to a student’s learning. The core purpose of learning is to provide true indicative information on the student’s progress and achievement and enable the setting of appropriate direction for the ongoing learning and teaching. Assessment and grading practices based on the classroom environment have a greater potential to measure, report and promote learning. Research on the effective assessment has documented the possible benefits that accrue to regular users of diagnostic and formative forms of assessment as a learning feedback The following examples are among the specific assessment practices that have been effectively used to enhance teaching and learning. Rubrics are the multipurpose scoring tool guide that describes the best criteria for performance to learners at various levels. It is employed mainly to assess a studentâ⠂¬â„¢s product and performance. For the effective development of a rubric to optimize workability, The Journal for Effective Teaching provides three main rubric designing steps. Identifying performance criteria requires that the instructor determine the quality of the work prior to giving an assignment. The performance criteria require that the assessed performance should be observable and measurable. Setting performance level -the assessor needs to decide on the number of appropriate performance levels of assessment.  

Markiting Essay Example | Topics and Well Written Essays - 250 words - 6

Markiting - Essay Example f the drink, the chemical content, the taste, colour, standard of quality, smell, availability of the drink, and the refreshing nature of the soft drink. Withstanding other external factors like weather that may affect my selection, I mostly buy soft drinks from Coca-Cola Company. Indeed, I get significant value proposition when I seek to buy the Coca-Cola soft drink. A part from the brand being available in almost all outlets, the drink is internationally recognized and approved. Its taste, smell, and colour are my favourite and its refreshing nature serves my core purpose of wanting to buy it. In addition, the energy levels of the Coca-Cola soft drink are more relevant to my age and health and thus the motivation to buy it. The drink is free from other harmful chemicals and contains no caffeine hence medically viable. More so, the mode of packaging the brand is very convenient for me as it is highly portable and the plastic bottle is recyclable. The fact that I can get either a cold or a warm brand is also a value proposition for me. In conclusion, the price of the brand is also convenient compared to other soft drinks and the satisfaction I get from it. As such, the Coca-Cola brand suits my selection criteria and thus my value

Fuel Metering System In Si Engines

Fuel Metering System In Si Engines Carburetor: is a device which is used in automobiles, with spark ignition engines, for the purpose of fuel metering, i.e. to mix the appropriate amount of fuel with the incoming air which is to be supplied to the engine cylinders. The basic principle upon which the carburetor works is flow of air through the venturi. The fuel enters the carburetor through the air filter, which filters the air to remove any dust particles in the air; passing through the choke valve it enters the venturi (a converging-diverging nozzle), where due to decrease in cross-sectional area, the velocity of the air increases, decreasing the pressure in that area. A decrease in the pressure results in fuel flowing out of the float chamber and mixing with the air, hence forming an air-fuel mixture. Figure . Cross-sectional view of a basic carburetor Basic Requirements: In a spark ignition engine the torque and power output of the engine is controlled by controlling the amount of air-fuel mixture that enters the engine cylinder; and this is done by incorporating a butterfly valve (throttle valve) in the carburetor. In order to achieve complete combustion inside the engine cylinder and avoid the wastage of fuel into the exhaust, a stoichiometric mixture is required; which is a mixture that contains precise proportions of fuel and air required for the complete combustion of both the fuel and the air, which is equally important. In gasoline engines, this ratio is around 15:1. Even if this ratio is achieved, practically the mixture is still not combusted completely owing to the extremely short time available to the air-fuel mixture for combustion. The air-fuel mixture is unable to form a completely homogenous mixture resulting in exhaust gases containing traces of oxygen, carbon monoxide and some unburned and partially burnt fuel. The range of air-fuel ratio for ignitable mixture varies from 18:1 to around 7:1. The basic purpose of using a carburetor is to: Measure the airflow of the engine Deliver the correct amount of fuel to keep the air-fuel mixture in the proper range Mix the air and fuel finely and evenly The proper air-fuel mixture is required to be delivered to the engine cylinder at the various commonly faced conditions during the vehicle operation, namely: Cold start Hot start Idling or slow-running Acceleration High speed/high power at full throttle Cruising at part throttle The deficiencies of the elementary/early carburetor: At low loads the mixture becomes leaner; the engine requires the mixture to be enriched at low loads. At intermediate loads, the mixture equivalence ratio increases slightly as the air flow increases. The engine requires an almost constant equivalence ratio. As the air flow approaches the maximum wide-open throttle value, the equivalence ratio remains essentially constant. However, the mixture equivalence ratio should increase to 1.1 or greater to provide maximum engine power. The elementary carburetor cannot compensate for transient phenomena in the intake manifold. Nor can it enrich the mixture during engine starting and warm-up. The elementary carburetor cannot adjust to changes in ambient air density (due primarily to changes in altitude). Modern Carburetor Design: The changes required in the elementary carburetor for better and more efficient performance are: The main metering system must be compensated to provide essentially constant lean or stoichiometric mixtures over the 20 to 80 percent air flow range. An idle system must be added to meter the fuel flow at idle and light loads. An enrichment system must be added so the engine can provide its maximum power as wide-open throttle is approached. An accelerator pump which injects additional fuel when the throttle is opened rapidly is required to maintain constant the equivalence ratio delivered to the engine cylinder. A choke must be added to enrich the mixture during engine starting and warm-up to ensure a combustible mixture within each cylinder at the time of ignition. Altitude compensation is required to adjust the fuel flow to changes in air density. It is also necessary to increase the magnitude of the pressure drop available for controlling the fuel flow. Figure . Modern Carburetor design Basic Working and different parts of the Carburetor: Figure . Simple Carburetor with additional basic features 1) Float 2) Float needle 3) Float chamber 4) Main jet 5) Air tunnel(venture) 6) Throttle plate ( a. no-load operation) b. partial load; c. full load) 7) Air correction nozzle 8) Mixing tube 9) Mixing tube holes 10) Enrichment pipe 11) Jet (calibrated drilling) 12) No-load operation fuel nozzle 13) Idle run air duct 14) Idle mixture adjustment screw 15) Bypass drilling 16) Accelerator pump 17) Choke (for cold start) 18) Ventilation A carburetor basically consists of an open pipe, a throat/barrel through which the air passes into the inlet manifold of the engine. The pipe is in the form of a venturi; it narrows in section and then widens again, causing the airflow to increase in speed in the narrowest part. Below the venturi is a butterfly valve called the throttle valve (a rotating disc that can be turned end-on to the airflow), so as to hardly restrict the flow at all, or can be rotated so that it almost completely blocks the flow of air. This valve controls the flow of air through the carburetor throat and thus the quantity of air/fuel mixture the system will deliver, thereby regulating engine power and speed. The throttle is connected, usually through a cable or a mechanical linkage of rods and joints or rarely by pneumatic link to the accelerator pedal on a car or the equivalent control on other vehicles or equipment. Fuel is introduced into the air stream through small holes at the narrowest part of the venturi and at other places where pressure will be lowered when not running on full throttle. Fuel flow is adjusted by means of precisely-calibrated orifices, referred to as jets. Idle circuit: As the throttle plate is opened slightly from the fully closed position, the additional fuel delivery passages are uncovered behind the throttle plate. The low pressure area is created due to the throttle plate blocking the air flow; this allows more fuel to flow as well as compensating for the reduced vacuum that occurs when the throttle is opened. This smoothens the fuel flow through the jets when moving from closed throttle position to the open throttle circuit. This circuit plays its role when the engine is running on no load condition or is known as idling. The air enters from the idle run air duct, certain amount of fuel is mixed with this air depending on the no-load operation fuel nozzle and then goes into the intake manifold through the idle mixture screw path. This idle mixture screw is adjusted to regulate the amount of air-fuel mixture when idling. Main open-throttle circuit: When the throttle is opened, the vacuum inside the manifold decreases due to decreased restriction in the airflow. This reduces the flow through the idle and off-idle circuits. The airflow through the throat increases, and in accordance with the Bernoullis principle the pressure drops in the throat and the fuel flow through the jet, which is placed in the centre of the venturi, increases. Similarly, when the throttle is closed, the airflow through the venturi drops till the point when the lowered pressure is insufficient to maintain the fuel flow, and the idle circuit takes over. At times booster venturis are used to enhance the fuel flow out of the jet and into the air stream. Accelerator Pump: The inertia of the liquid gasoline is more than that of the air, which shows that when the throttle is opened suddenly during sudden acceleration, the amount of air that will flow would be far greater than the amount of fuel flow resulting in a temporary lean mixture, causing the engine to stumble under acceleration. This is not a desirable effect. In order to eliminate this unwanted effect, a small mechanical pump usually of diaphragm type is employed. It propels a small amount of gasoline through a jet, from where it is injected into the carburetor throat. This extra shot of fuel counteracts the transient lean condition during sudden acceleration. The accelerator pump is also used to prime the engine with fuel prior to a cold start. Excessive priming, like an improperly-adjusted choke, can cause flooding. This is when too much fuel and not enough air are present to support combustion. For this reason, some carburetors are equipped with an unloader mechanism: The accelerator is held at wide open throttle while the engine is cranked, the unloader holds the choke open and admits extra air, and eventually the excess fuel is cleared out and the engine starts. Choke: when the engine is cold, the fuel does not vaporize properly, instead it condenses on the walls of the intake manifold, and hence very little fuel is delivered to the cylinders. This makes it difficult for the engine to start. This calls for the need of a richer mixture to start and run the engine until it warms up, as the richer mixture is easier to ignite. Figure . Cross-sectional view of a choke To provide the extra fuel, a choke is typically used. It is a device that restricts the flow of air at the entrance to the carburetor, before the venturi. With this restriction in place, extra vacuum is developed in the carburetor barrel, which pulls extra fuel through the main metering system to supplement the fuel being pulled from the idle circuit. This provides the rich mixture required to sustain operation at low engine temperatures. Even in this era of advanced technology, cars like Suzuki Mehran still employ a choke which is connected to a pull-knob on the dashboard operated by the driver. In some carbureted cars it is automatically controlled by a thermostat employing a bimetallic spring, which is exposed to engine heat, or to an electric heating element. This heat may be transferred to the choke thermostat via simple convection, via engine coolant, or via air heated by the exhaust. More recent designs use the engine heat only indirectly: A sensor detects engine heat and varies electrical current to a small heating element, which acts upon the bimetallic spring to control its tension, thereby controlling the choke. A choke unloader is a linkage arrangement that forces the choke open against its spring when the vehicles accelerator is moved to the end of its travel. This provision allows a flooded engine to be cleared out so that it will start. Some carburetors do not have a choke but instead use a mixture enrichment circuit, or enrichener. Typically used on small engines, notably motorcycles, enricheners work by opening a secondary fuel circuit below the throttle valves. This circuit works exactly like the idle circuit, and when engaged it simply supplies extra fuel when the throttle is closed. Float chamber: To ensure a ready mixture, the carburetor has a float chamber or bowl that contains a quantity of fuel at near-atmospheric pressure, ready for use. This reservoir is constantly replenished with fuel supplied by a fuel pump. Float: The correct fuel level in the bowl is maintained by means of a float controlling an inlet valve. The fuel arriving from the tank is held inside a constant level float chamber. The liquid pressure head on the various jets is relatively constant. The float chamber level is kept constant by means of a fuel inlet valve, actuated by a float that follows free surface of the liquid in the float chamber. As fuel is used up, the float drops, opening the inlet valve and admitting fuel. As the fuel level rises, the float rises and closes the inlet valve. By having a high float level, a greater fuel quantity is delivered compared to the case with a low float level, under all operating conditions and for all of the carburetors circuits. Vent Tubes: Usually, special vent tubes allow air to escape from the chamber as it fills or enter as it empties, maintaining atmospheric pressure within the float chamber; these usually extend into the carburetor throat. Placement of these vent tubes can be somewhat critical to prevent fuel from sloshing out of them into the carburetor, and sometimes they are modified with longer tubing. Notch Pin: With this type of carburetor, the maximum depression zone is beneath the throttle valve (slide) which is raised and lowered by the throttle cable, controlling the speed of the engine. As shown in the drawing, the bottom of the slide features a tapered needle which fits into the fuel pick-up tube (needle jet) to meter the fuel delivery of the tube from about 1/4 throttle to 3/4 throttle. From 3/4 throttle to full throttle, the needle will not affect the fuel flow. At this point, fuel flow is metered by the main jet (position at the bottom of the tube). The setting of the notch determines the amount of fuel being allowed to mix with the incoming air; notch 1 providing a lean mixture and richer mixture as we proceed to notch 4. Figure 11. Notch Pin Types of Carburetors: Carburetors can be classified into three types: Float Feed Suction Feed/Diaphragm Constant Vacuum/Constant Depression/Zenith-Stromberg The difference between these is the way the fuel is supplied to the Air Stream. Float Feed: Float feed carburetors are so named because they maintain a fuel staging area at approximately ambient pressure with a float valve. Fuel level is maintained to tight tolerances because fuel metering is a function of float level. Higher levels make it richer. Figure 12. Operation of needle valve As the fuel is drawn for the bowl area the float drops, opening the float valve. Then the fuel pump pressure causes the bowl to refill, floating the valve closed. Under normal operations the float valve remains slightly open to very open, keeping the level constant. Floats can be concentric or eccentric. Concentric are levers, first or second class, whereas eccentrics are a slide float. Floats can be adjusted by shims under the valve or by adjusting a valve contact tab. Floats need to be carefully inspected for leaks and possible deterioration. The main source of fuel metering force comes from the pressure differential between the low pressure area within the venture and the ambient pressure in the float chamber, or bowl. This is called air metering force. Figure 13. Air-metring force being applied Idle circuits will exist that feed fuel through separate ports. These are located just downstream of the throttle plate; there may also be transition ports to assist throttle transition from idle to midrange. Idle and transition ports will only be active when throttle plate is closed or transitioning (they function only when the throttle plate is causing high velocity air or flow close to the port and once the throttle plate opens enough, the port stops delivering fuel flow); these ports usually form a completely separate fuel circuit from the main fuel metering. They may also have air bleed systems. Figure 14. Demonstration of relation between Idle circuit and main throat operation Most of these carburetors are up draft or side draft, and the systems are identical with the position of the fuel discharge venturis and idle circuits upstream of the throttle valve, regardless of the airflow direction. Figure 15. An up-draft carburetor Disadvantages: The three major disadvantages of float carburetors are: Various flight attitudes may cause the float system to malfunction. Carburetor icing is most prevalent with this type. Fuel metering and throttle transition is less accurate. Suction Feed: Suction Feed Carburetor is very similar to the float type. The one exception is there is no float to meter and control the level of fuel in the fuel chamber. The difference in pressure between the tank and the carburetor throat lifts the fuel up the fuel pipe past the main needle valve and through the discharge holes. Figure 16. Suction Feed Carburetor Figure 17. Cold Start Figure 18. Idling Constant Vacuum: The constant vacuum carburetor has a rubber diaphragm exposed to the cylinder intake stroke vacuum on one side and to atmospheric pressure on the other. The diaphragm moves against the inlet needle (cylindrical slide valve) allowing it to move from its seat. A spring returns the needle (cylindrical slide valve) to its seat when the vacuum stops. Figure . A typical Constant Vacuum type carburetor A few advantages of Carburetors: Carburetors are much easier to adjust/less technical skills required Cheaper to repair rebuild Less special equipment required. Problems with Carburetors: Have mechanical parts due to wear and tear needs periodic adjustments and maintenance. Flexibility limitations. Intake manifold length problems in the case of multi cylinder engines Carburetors arent very efficient as they cant make changes on the fly like fuel injection can. Conclusions: Keeping in mind the advantages and disadvantages of carburetor, regardless of the constant n continuous effort to improve the basic design into the most efficient one, the carburetors have finally been replaced by the latest technology referred to as fuel injectors. These fuel injectors are of various types, GDI being a personal favourite and the best technology available in the market. The fuel injectors efficiently meter the appropriate amount of fuel hence reducing the exhaust emissions, fuel wastage, the harmful pollutants and giving the best fuel economy possible.

Divorce Laws in the United States Essay examples -- Family Law

â€Å"Divorce is a decree by a court that a valid marriage no longer exists. It leaves both parties free to remarry. The court will award custody, divide property, and order spousal and child support† (The American Bar Association 71). â€Å"†¦till death do us part† is almost always heard at wedding ceremonies. But all too often does this phrase not hold up to its true meaning. Between 1960 and 1999 the divorce rate in the United States tripled (Porterfield vii). Out of all first time marriages, 41% end in divorce (Divorce Rate). According to the Centers for Disease control and Prevention, for every 1,000 people, 6.8 get married and 3.4 of those marriages will end in divorce (Marriage and Divorce). The Family Legal Guide from The American Bar Association confirms that of the couples who marry before the age of forty-five, one-half of them will get divorced (71). These numbers do not seem to be decreasing. They only seem to be increasing as time goes on. It is agreed by many that if two people can no longer find it in themselves to be passionate towards one another and they no longer desire the others company that they should end their marriage. However, the growing number of divorces is proving that, pe rhaps getting a divorce in the United States is too easy. The evidence proves that divorce laws should be made stricter throughout the United States. Every divorce is different; no two divorces are the same. Some involve children. Some are just a couple. Some have step children or half children. Some include hostile situations. Some are peaceful. Some are for a valid reason. Some are simply because the couple doesn’t feel like being together anymore. Some are mutual. Some are not. So why is every divorce so quickly done and so easily ob... ...2. â€Å"Marriage and Divorce.† Centers for Disease Control and Prevention. 5 Oct. 2010. Web. 26 Feb. 2012. Porterfield, Kay Marie. Straight Talk about Divorce. New York: Facts on File, 1999. Print. Portnoy, Ph.D. Sanford. â€Å"A Lawyer’s Primer Part 1- The Effects of Divorce on Adults.† Ed. Ron Brown. The Psychology of Divorce. 1(2006): 1-7. Print. Russo, Francine. â€Å"Can The Government Prevent Divorce?† The Atlantic. Oct. 1997. Web. 1 Apr. 2012. Shapiro v. Thompson. 2 Library of Congress Cataloging-in- Publication Data. U.S. Supreme Court. 21 Apr. 1969. Print. Tavernise, Sabrina, and Robert Gebeloff. â€Å"Once Rare in Rural American, Divorce is Changaing the Face of Its Families.† www.Nytimes.com. The New York Times. 23 Mar. 2011. Web. 27 Feb. 2012. The American Bar Association. Family Legal Guide. 3rd ed. New York: Random House, 2004. 71-88. Print.