Learning Skill Essay Example for Free

Learning Skill Essay ?The attributes of the learners and how they can help the learners to be successful in an online learning environment Education of children is compulsory, formal and standardized. Adult learning is voluntary and intentional. The purpose of adult education is the independent self-directed learner. Adults tend to resist a learning process which is incongruent with their self-concept as autonomous individuals and does not correspond to their needs and interests. Adults focus on direct application. Given their daily duty in job, profession, family and community, they learn to cope with the pressures and problems of life they are facing. For that reason, the adult educator’s concern is primarily focused on the needs and interests of the learners. Andragogy (adult education) calls for program builders and teachers who are person-centered, who don’t teach subject matter but rather help persons learn (Knowles). Hence, the interests of adults are their real needs. Or the solutions learners have in mind do not solve their problems. The adult educator often has to register into a needs negotiation (Bhola) with learners when teaching new needs about boiled water or a balanced diet, about clean surroundings, preventive health practices or small families. In the dialectical process of needs negotiation the needs as felt by the learners and the needs as seen by the adult educators must be showed together to reach a consensus on the real needs. These real needs must agree to the experience of adult learners. If an adult gets the impression that his experience is not being valued he feels turned down as a person. New learnings take on meaning as adults are able to relate them to their life experience. Experienced adult educators, so, build into the design of their learning experiences provision for the learners to plan and rehearse how they are going to apply their learnings in their day-to-day lives or duties and combine training with transfer and application. A workshop then really can become a workplace where educational materials are produced or evaluation studies are designed. According to Knox’s proficiency theory the learning needs for an adult move upward from life situations and interpersonal communication. Social expectation motivates and empowers an adult to search for more knowledge, better expertness and more suitable performance. Adult learning is based on experience, on the learners’ own experience and on the experience of others. Learning settings of adults usually have a participatory and collaborative basic part. Adults prefer to meet as equals in small groups to explore outcome and concerns and then to take common action as a result of dialogue and inter-learning by discourse. The group becomes the learning co-operative. The group provides the opportunity for inter-learning. Within the group the teacher as well as the other group members plays the task of facilitators. All group members become co-agents (Bhola) in learning. The absence of formal accreditation or certification facilitates collaboration not only on a specific product or outcome but even in structuring and restructuring the learning process according to the needs and interests of the group. The learning process becomes as important as the learning outcome, and a balance between both is often not easy to maintain. How much freedom can actually be given to the adult learner in choice of content and way? Adult learning is life-centered. It is learning by doing, by application and experience, and if need be by trial and error. Adults do not simply to get knowledge created by outsiders, but should examine their own reality themselves and make a positive declaration about it. Praxis is the focus of effective adult learning and praxis means analysis and examination of reality in order to transform it. Adult learning is without interval process of investigation and exploration followed by proccess of doing something grounded in this exploration, followed by reflection on this action, leading to further investigation and so on. The principle is testing not banking (P. Freire) of knowledge. Exploration of new opinion, skills and knowledge take place in the context of the learners’ experience. In settings where skills are being learned, learners become acquainted with skills, apply these in real life settings, redefine hoe these skills may be altered by context, re-apply these in other settings and so on. Adults explained the meaning of ideas, skills and knowledge through the medium of their life-experience and test them in real life settings. To make the learner self-directed is the intention of adult education. But the self-directed learner is neither the one who can retrieve information or locate resources nor the one who appears in group dynamics. The inner-directed, self-operating learner (R. Kidd) is the one who reflects critically on his own assumptions and is keen to find alternative and better solutions. The learning process contributes largely to the success of learning. But learning is more than just the learning process. A participative learning process which fails to assist the learners in  acquiring knowledge and competence is a failure. A participative learning process may take more time because it means active involvement of everybody, discussing all the pro’s and con’s, despite that it must lead to concrete results combining commitment with competence. Education is, as Brookfield points out a â€Å"transactional encounters. That means that the sole responsibility for determining curricula or for selecting appropriate methods does not rest either with the educator or with the learner. If the first acquires, then we have an authoritarian style and a one-way transmission of knowledge and skills. If curricula, methods and evaluative criteria become predetermined solely by what learners say they want, then the cafeteria approach governs the educational process. Accepting the felt needs logical basis without any further inquiry and needs negotiation means that the facilitator has to give up responsibility for the learning process and the accomplishment of learning aims and objectives. Successful learning especially in workshop settings means to keep the balance between the learning process and the learning outcome so that the results justify the efforts and if they are not excellent they should be at least and always â€Å"good enough. Successful distance learners are self-motivated, self-reliant and self disciplined. Distance learning students are the architects of their own learning surrounding, have the ability to manage their study time and schedule. Students can often customize their learning projects to fit their personal interests and there is great chance for personal growth and individual academic success. This requires both internal personal motivation and discipline, and also requires the establishment of a supportive personal learning environment and may require elimination of certain activities to make room for online learning in daily life. Distance learners should be self sufficient, self-directed individuals. The online environment enables students to learn at their own pace, relieving some of the pressure of traditional seated learning and making learning more enjoyable but requires that the student is able to identify learning goals and objectives and focus their attention accordingly. Distance learners become independent problem solvers, doing their own research and expanding their lifelong learning skills. This process helps them to grow critical thinking skills and the ability to interpret and synthesize reading materials, articles and research papers with differing points of view and in the process develop their own positions and beliefs about the subject matter. Some computer and Information literacy is necessary for a distance learner. Distance learners should possess a working knowledge of email, the Internet, and basic keyboard skills. Instructional material within the learning management system will provide all the other skills needed to access and begin the online or distance lesson. Distance learners may be required to develop skills for researching and locating information from several sources and differentiate and assess them for inclusion in distance learning assignments and research projects. Distance learners should be energetic and disciplined managers of their own time. Students must be able to organize and plan their own best study schedule. While individual learners may prefer a different time of day or times in the week to give up to their distance learning study and projects, it is important to devote time each week to course work and it is vital that the distance learner understand that the same amount of time is involved in distance education courses, and traditional seated courses. The distance learner should assess his or her best time of day for study, either it is early morning or evening, every person has a best time of day for learning and thinking. A intentional effort must be made to carve out time in the student’s daily schedule for an optimal study time. Study time should not be the time that is left at the end of the day, unless that is the time when the student is most lively and attentive. All learners and especially distance learners need effective communication skills. The particular nature of distance education requires that communication be done in a written format, whether it is email, written assignments or discussion forums, the written word is vital in distance education. The ability to write clearly and communicate ideas becomes more important since it is the primary means of communication in distance learning. The successful distance learner has a strong sense of responsibility and personal commitment to academic success. Online learning, like many things in life, reaps rewards equal to the energy put into the changes. The independent nature of distance education to insist upon the presence of motivation, and discipline but commitment and follow-through are also vital.

History and overview: Catalytic converter

History and overview: Catalytic converter A catalytic converter (colloquially, cat or catcon) is a device used to decrease the toxicity of emissions from an internal combustion engine. A catalytic converter works by using a catalyst to stimulate a chemical reaction in which toxic by-products of combustion are converted to less-toxic substances.First widely introduced on series-production automobiles in the U.S. market for the 1975 model year to comply with tightening EPA regulations on auto exhaust, catalytic converters are still most commonly used in motor vehicle exhaust systems. Catalytic converters are also used on generator sets, forklifts, mining equipment, trucks, buses, trains, airplanes and other engine-equipped machines. History The catalytic converter was invented by Eugene Houdry, a French mechanical engineer and expert in catalytic oil refining[1] who lived in the United States. Around 1950, when the results of early studies of smog in Los Angeles were published, Houdry became concerned about the role of automobile exhaust in air pollution and founded a special company, Oxy-Catalyst, to develop catalytic converters for gasoline engines an idea ahead of its time for which he was awarded a patent (US2742437). Widespread adoption had to wait until the extremely effective anti-knock agent tetraHYPERLINK http://en.wikipedia.org/wiki/Tetra-ethyl_lead-HYPERLINK http://en.wikipedia.org/wiki/Tetra-ethyl_leadethylHYPERLINK http://en.wikipedia.org/wiki/Tetra-ethyl_lead HYPERLINK http://en.wikipedia.org/wiki/Tetra-ethyl_leadlead was eliminated from most gasoline over environmental concerns, as the agent would foul the converter by forming a coating on the catalysts surface, effectively disabling it.[2] The catalytic converter was further developed by JohnHYPERLINK http://en.wikipedia.org/wiki/John_J._Mooney J. HYPERLINK http://en.wikipedia.org/wiki/John_J._MooneyMooney and CarlHYPERLINK http://en.wikipedia.org/wiki/Carl_D._Keith D. HYPERLINK http://en.wikipedia.org/wiki/Carl_D._KeithKeith at the EngelhardHYPERLINK http://en.wikipedia.org/wiki/Engelhard_Corporation HYPERLINK http://en.wikipedia.org/wiki/Engelhard_CorporationCorporation,[3] creating the first production catalytic converter . Metal-core converter Ceramic-core converter The catalytic converter consists of several components: The core, or substrate. The core is often a ceramic honeycomb in modern catalytic converters, but stainlessHYPERLINK http://en.wikipedia.org/wiki/Stainless_steel HYPERLINK http://en.wikipedia.org/wiki/Stainless_steelsteel foil honeycombs are also used. The honey-comb surface increases the amount of surface area available to support the catalyst, and therefore is often called a catalystHYPERLINK http://en.wikipedia.org/wiki/Catalyst_support HYPERLINK http://en.wikipedia.org/wiki/Catalyst_supportsupport. The ceramic substrate was invented by RodneyHYPERLINK http://en.wikipedia.org/wiki/Rodney_Bagley HYPERLINK http://en.wikipedia.org/wiki/Rodney_BagleyBagley, IrwinHYPERLINK http://en.wikipedia.org/wiki/Irwin_Lachman HYPERLINK http://en.wikipedia.org/wiki/Irwin_LachmanLachman and RonaldHYPERLINK http://en.wikipedia.org/w/index.php?title=Ronald_Lewis_(scientist)action=editredlink=1 HYPERLINK http://en.wikipedia.org/w/index.php?title=Ronald_Lewis_(scientist)action=editredlink=1Lewis at Cor ningHYPERLINK http://en.wikipedia.org/wiki/Corning_Glass HYPERLINK http://en.wikipedia.org/wiki/Corning_GlassGlass, for which they were inducted into the NationalHYPERLINK http://en.wikipedia.org/wiki/National_Inventors_Hall_of_Fame HYPERLINK http://en.wikipedia.org/wiki/National_Inventors_Hall_of_FameInventorsHYPERLINK http://en.wikipedia.org/wiki/National_Inventors_Hall_of_Fame HYPERLINK http://en.wikipedia.org/wiki/National_Inventors_Hall_of_FameHallHYPERLINK http://en.wikipedia.org/wiki/National_Inventors_Hall_of_Fame of HYPERLINK http://en.wikipedia.org/wiki/National_Inventors_Hall_of_FameFame in 2002. The washcoat. A washcoat is used to make converters more efficient, often as a mixture of silica and alumina. The washcoat, when added to the core, forms a rough, irregular surface, which has a far greater surface area than the flat core surfaces do, which then gives the converter core a larger surface area, and therefore more places for active precious metal sites. The catalyst is added to the washcoat (in suspension) before being applied to the core. The catalyst itself is most often a precious metal. Platinum is the most active catalyst and is widely used. It is not suitable for all applications, however, because of unwanted additional reactions and/or cost. Palladium and rhodium are two other precious metals used. Platinum and rhodium are used as a reduction catalyst, while platinum and palladium are used as an oxidization catalyst. Cerium, iron, manganese and nickel are also used, although each has its own limitations. Nickel is not legal for use in the European Union (due to reaction with carbon monoxide). Copper can be used everywhere except North America, where its use is illegal due to the formation of dioxin. How Catalytic Converters Work James L. Amos/National Geographic/Getty Images A large pile of platinum lined catalytic converters. See more green living pictures. There are millions of cars on the road in the United States, and each one is a source of air pollution. Especially in large cities, the amount of pollution that all the cars produce together can create big problems. To solve those problems, cities, states and the federal government create clean-air laws that restrict the amount of pollution that cars can produce. Over the years, automakers have made many refinements to car engines and fuel systems to keep up with these laws. One of these changes came about in 1975 with an interesting device called a catalytic converter. The job of the catalytic converter is to convert harmful pollutants into less harmful emissions before they ever leave the cars ­ exhaust system. Catalytic converters are amazingly simple devices, so it is incredible to see how big an impact they have. In this article, you will learn which pollutants are produced by an engine and how a catalytic converter deals with each of these pollutants to help reduce [edit] Types [edit] Two-way A two-way catalytic converter has two simultaneous tasks: Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ 2CO2 Oxidation of unburnt hydrocarbons (unburnt and partially-burnt fuel) to carbon dioxide and water: CxH2x+2 + [(3x+1)/2] O2 à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ xCO2 + (x+1) H2O (a combustion reaction) This type of catalytic converter is widely used on diesel engines to reduce hydrocarbon and carbon monoxide emissions. They were also used on gasoline engines in USA market automobiles until 1981. Due to their inability to control nitrous oxide NOHYPERLINK http://en.wikipedia.org/wiki/NOxx, they were superseded by three-way converters. [edit] Three-way Since 1981, three-way catalytic converters have been used in vehicle emission control systems in North America and many other countries on roadgoing vehicles. A three-way catalytic converter has three simultaneous tasks: Reduction of nitrogen oxides to nitrogen and oxygen: 2NOx à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ xO2 + N2 Oxidation of carbon monoxide to carbon dioxide: 2CO + O2 à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ 2CO2 Oxidation of unburnt hydrocarbons (HC) to carbon dioxide and water: CxH2x+2 + [(3x+1)/2]O2 à ¢Ã¢â‚¬  Ã¢â‚¬â„¢ xCO2 + (x+1)H2O These three reactions occur most efficiently when the catalytic converter receives exhaust from an engine running slightly above the stoichiometric point. This point is between 14.6 and 14.8 parts air to 1 part fuel, by weight, for gasoline. The ratio for LPG, natural gas and ethanol fuels is slightly different, requiring modified fuel system settings when using those fuels. Generally, engines fitted with 3-way catalytic converters are equipped with a computerized closed-loop feedback fuel injection system using one or more oxygen sensors, though early in the deployment of 3-way converters, carburetors equipped for feedback mixture control were used. While a 3-way catalyst can be used in an open-loop system, NOx reduction efficiency is low. Within a narrow fuel/air ratio band surrounding stoichiometry, conversion of all three pollutants is nearly complete. However, outside that band, conversion efficiency falls very rapidly. When there is more oxygen than required, the system is said to be running lean, and the system is in oxidizing condition. In that case, the converters two oxidizing reactions (oxidation of CO and hydrocarbons) are favoured, at the expense of the reduction of NOx. When there is excessive fuel, the engine is running rich; the reduction of NOx is favoured, at the expense of CO and HC oxidation. [edit] Oxygen storage Three-way catalytic converters can store oxygen from the exhaust gas stream, usually when the air fuel ratio goes lean.[5] When insufficient oxygen is available from the exhaust stream, the stored oxygen is released and consumed (see cerium(IV) oxide). This lean-ness occurs either when oxygen derived from NOx reduction is unavailable or certain maneuvers such as hard acceleration enrich the mixture beyond the ability of the converter to supply oxygen. [edit] Unwanted reactions Unwanted reactions can occur in the three-way catalyst, such as the formation of odiferous hydrogen sulfide and ammonia. Formation of each can be limited by modifications to the washcoat and precious metals used. It is difficult to eliminate these byproducts entirely. Sulfur-free or low-sulfur fuels eliminate or reduce hydrogen sulfide. For example, when control of hydrogen sulfide emissions is desired, nickel or manganese is added to the washcoat. Both substances act to block the adsorption of sulfur by the washcoat. Hydrogen sulfide is formed when the washcoat has adsorbed sulfur during a low temperature part of the operating cycle, which is then released during the high temperature part of the cycle and the sulfur combines with HC. [edit] For diesel engines For compression-ignition (i.e., diesel) engines, the most commonly used catalytic converter is the diesel oxidation catalyst. This catalyst uses O2 (oxygen) in the exhaust gas stream to convert CO (carbon monoxide) to CO2 (carbon dioxide) and HC (hydrocarbons) to H2O (water) and CO2. These converters often operate at 90% efficiency, virtually eliminating diesel odor and helping to reduce visible particulates (soot). But they cannot reduce NOx because chemical reactions always occur in the simplest possible way, and the existing O2 in the exhaust gas stream would react first. To reduce NOx on a compression ignition engine, the chemical composition of the exhaust must first be changed. Two main techniques are used: exhaust gas recirculation (EGR) and selective catalytic reduction (SCR). NOx trapping (with NOx absorbers) is a third method, but as of yet (2010), is not widely used. Diesel engine exhaust contains relatively high levels of particulate matter (soot), consisting in large part of elemental carbon. Catalytic converters cannot clean up elemental carbon, though they do remove up to 90% of the soluble organic fraction[citation needed], so particulates are cleaned up by a soot trap or diesel particulate filter (DPF). In the United States, all on-road heavy-duty vehicles powered by diesel and built after 1 January 2007 must be equipped with a catalytic converter and a diesel particulate filter.[6] Instead of catalysis, a reagent such as ammonia pyrolyzed in situ from urea, is sometimes used to reduce the NOx into nitrogen. One trademark product to do this is AdBlue. [edit] For lean-burn engines For lean burn spark ignition engines, an oxidation catalyst is used in the same manner as in a diesel engine. [edit] Installation Many vehicles have a pre-catalyst located close to the engines exhaust manifold. This unit heats up quickly due to its proximity to the engine, and reduces cold-engine emissions by burning off hydrocarbons from the extra-rich mixture used in a cold engine. Many three-way catalytic converters utilize an air injection tube between the first (NOx reduction) and second (HC and CO oxidation) stages of the converter. This tube is fed by a secondary air injection system. The injected air provides oxygen for the catalysts oxidizing reaction. These systems also sometimes include an upstream air injector to admit oxygen to the exhaust system before it reaches the catalytic converter. This precleans the extra-rich exhaust from a cold engine, and helps bring the catalytic converter quickly up to operating temperature. Some newer systems do not employ air injection. Instead, they provide a constantly varying mixture that quickly and continually cycles between lean and rich to keep the first catalyst (NOx reduction) from becoming oxygen loaded, and to keep the second catalyst (CO oxidization) sufficiently oxygen-saturated. They also utilize several oxygen sensors to monitor the exhaust, at least one before the catalytic converter for each bank of cylinders, and one after the converter. Some systems contain the reduction and oxidation functions separately rather than in a common housing. [edit] Damage [edit] Poisoning Catalyst poisoning occurs when the catalytic converter is exposed to exhaust containing substances that coat the working surfaces, encapsulating the catalyst so that it cannot contact and treat the exhaust. The most notable contaminant is lead, so vehicles equipped with catalytic converters can only be run on unleaded gasoline. Other common catalyst poisons include manganese primarily from the gasoline additive MMT, and silicone which can enter the exhaust stream if the engine has a leak allowing coolant into the combustion chamber. Phosphorus is another catalyst contaminant. Although phosphorus is no longer used in gasoline, it (and zinc, another low-level catalyst contaminant) was until recently widely used in engine oil antiwear additives such as ZDDP. Beginning in 2006, a rapid phaseout of ZDDP in engine oils began.[citation needed] Depending on the contaminant, catalyst poisoning can sometimes be reversed by running the engine under a very heavy load for an extended period of time. The increased exhaust temperature can sometimes liquefy or sublimate the contaminant, removing it from the catalytic surface. However, removal of lead deposits in this manner is usually not possible due to leads high boiling point. [edit] Meltdown Any condition that causes abnormally high levels of unburned hydrocarbons raw or partially-burnt fuel to reach the converter will tend to significantly elevate its temperature, bringing the risk of a meltdown of the substrate and resultant catalytic deactivation and severe exhaust restriction. Vehicles equipped with OBD-II diagnostic systems are designed to alert the driver of a misfire condition, along with other malfunctions, by means of the Check Engine light on the dashboard. [edit] Regulations This section does not citeany references or sources. Please help improve this articleby adding citations to reliable sources. Unsourced material may be challengedand removed. (March 2009) Emissions regulations vary considerably from jurisdiction to jurisdiction. In North America, most spark ignition engines of over 25 brake horsepower (19 kW) output built after January 1, 2004 are equipped with three-way catalytic converters. In Japan, a similar set of regulations came into effect January 1, 2007, while the European Union has not yet enacted analogous regulations. Most automobile spark ignition engines in North America have been fitted with catalytic converters since the mid-1970s, and the technology used in non-automotive applications is generally based on automotive technology. Regulations for diesel engines are similarly varied, with some jurisdictions focusing on NOx (nitric oxide and nitrogen dioxide) emissions and others focusing on particulate (soot) emissions. The regulatory diversity is challenging for manufacturers of the engine as it may not be economical to design an engine to meet two sets of regulations. Regulations of fuel quality vary across jurisdictions. In North America, Europe, Japan, and Hong Kong, gasoline and diesel fuel are highly regulated, and CNG and LPG are being reviewed for regulation. In most of Asia and Africa, the regulations are often lax in some places sulfur content of the fuel can reach 20,000 parts per million (2%). Any sulfur in the fuel can be oxidized to SO2 (sulfur dioxide) or even SO3 (sulfur trioxide) in the combustion chamber. If sulfur passes over a catalyst, it may be further oxidized in the catalyst, i.e. (SO2 may be further oxidized to SO3). Sulfur oxides are precursors to sulfuric acid, a major component of acid rain. While it is possible to add substances like vanadium to the catalyst wash coat to combat sulfur oxide formation, such addition will reduce the effectiveness of the catalyst. The most effective solution is to further refine fuel at the refinery to produce ultra-low sulfur diesel. Regulations in Japan, Europe, and North America tightly restrict the amount of sulfur permitted in motor fuels. However, the expense of producing such clean fuel make it impractical for use in many developing countries. As a result, cities in these countries with high levels of vehicular traffic suffer from acid rain, which damages stone and woodwork of buildings and damages local ecosystems. [edit] Negative aspects Some early converter designs greatly restricted the flow of exhaust, which negatively affected vehicle performance, driveability, and fuel economy.[7] Because they were used with carburetors incapable of precise fuel/air mixture control, they could overheat and set fire to flammable materials under the car.[8] Removing a modern catalytic converter in new condition will only slightly increase vehicle performance without retuning,[9] but their removal or gutting continues.[7]HYPERLINK http://en.wikipedia.org/wiki/Catalytic_converter#cite_note-9[10] The exhaust section where the converter was may be replaced with a welded-in section of straight pipe, or a flanged section of test pipe legal for off-road use that can then be replaced with a similarly fitted converter-choked section for legal on-road use, or emissions testing.[9] In the US and many other jurisdictions, it is illegal to remove or disable a catalytic converter for any reason other than its immediate replacement[citation need ed]; vehicles without functioning catalytic converters generally fail emission inspections. The aftermarket supplies high-flow converters for vehicles with upgraded engines, or whose owners prefer an exhaust system with larger-than-stock capacity.[11] [edit] Warm-up period Most of the pollution put out by a car occurs during the first five minutes before the catalytic converter has warmed up sufficiently.[12] [edit] Environmental impact Catalytic converters have proven to be reliable and effective in reducing noxious tailpipe emissions. However, they may have some adverse environmental impacts in use: The requirement for a rich burn engine to run at the stoichiometric point means it uses more fuel than a lean burn engine running at a mixture of 20:1 or less. This increases the amount of fossil fuel consumed and the carbon dioxide emissions of the vehicle. However, NOx control on lean burn engines is problematic. Although catalytic converters are effective at removing hydrocarbons and other harmful emissions, they do not solve the fundamental problem created by burning a fossil fuel. In addition to water, the main combustion product in exhaust gas leaving the engine through a catalytic converter or not is carbon dioxide (CO2).[13] Carbon dioxide produced from fossil fuels is one of the greenhouse gases indicated by the Intergovernmental Panel on Climate Change (IPCC) to be a most likely cause of global warming.[14] Additionally, the U.S. Environmental Protection Agency (EPA) has stated catalytic converters are a significant and growing cause of global warming, due to their release of nitrous oxide (N2O), a greenhouse gas over 300 times more potent than carbon dioxide.[15] Catalytic converter production requires palladium or platinum; part of the world supply of these precious metals is produced near the Russian city of Norilsk, where the industry (among others) has caused Norilsk to be added to Time Magazines list of most polluted places.[16] [edit] Theft Due to the external location and the use of valuable precious metals including platinum, palladium, and rhodium, converters are a target for thieves. The problem is especially common among late-model Toyota trucks and SUVs, due to their high ground clearance and easily-removed bolt-on catalytic converters. Welded-in converters are also at risk of theft from SUVs and trucks, as they can be easily removed.[17]HYPERLINK http://en.wikipedia.org/wiki/Catalytic_converter#cite_note-17[18] Theft removal of the converter can often inadvertently damage the cars wiring or fuel line resulting in dangerous consequences. Rises in metal costs in the United States during recent years have led to a large increase in theft incidents of the converter,[19] which can then cost as much as $1000 to replace.[20] [edit] Diagnostics Various jurisdictions now legislate on-board diagnostics to monitor the function and condition of the emissions control system, including the catalytic converter. On-board diagnostic systems take several forms. [edit] Temperature sensors Temperature sensors are used for two purposes. The first is as a warning system, typically on 2-Way catalytic converters such as are still sometimes used on LPG forklifts. The function of the sensor is to warn of catalytic converter temperature above the safe limit of 750  °C (1,380  °F). More recent catalytic converter designs are not as susceptible to temperature damage and can withstand sustained temperatures of 900  °C (1,650  °F).[citation needed] Temperature sensors are also used to monitor catalyst functioning usually two sensors will be fitted, with one before the catalyst and one after to monitor the temperature rise over the catalytic converter core. For every 1% of CO in the exhaust gas stream the exhaust gas temperature will rise by 100 °C.[citation needed] [edit] Oxygen sensors The Oxygen sensor is the basis of the closed loop control system on a spark ignited rich burn engine, however it is also used for diagnostics. In vehicles with OBD II, a second oxygen sensor is fitted after the catalytic converter to monitor the O2 levels. The on-board computer makes comparisons between the readings of the two sensors. If both sensors give the same output, the computer recognizes the catalytic converter is not functioning or removed, and will operate a check engine light and retard engine performance. Simple oxygen sensor simulators have been developed to circumvent this problem by simulating the change across the catalytic converter with plans and pre-assembled devices available on the internet, though these are not legal for on-road use.[21] Similar devices apply an offset to the sensor signals, allowing the engine to run a more fuel economical lean burn that may however damage the engine or the catalytic converter.[22] [edit] NOx sensors NOx sensors are extremely expensive and are generally only used when a compression ignition engine is fitted with a selective catalytic reduction (SCR) converter, or a NOx absorber catalyst in a feedback system. When fitted to an SCR system, there may be one or two sensors. When one sensor is fitted it will be pre-catalyst, when two are fitted the second one will be post catalyst. They are utilized for the same reasons and in the same manner as an oxygen sensor the only difference is the substance being monitored.

Investigation of Tensile Strength

Investigation of Tensile Strength Direct tension is another method to categorize fatigue cracking. In this test procedure, tensile strength is measured in terms of tensile stress and tensile strain. Tensile stress is basically the resistance to fracture damage and tensile strain at maximum load is the ductility potential. In this testing procedure uniaxial tension is applied on the specimen. A cylindrical specimen is required having a 4 inch (100 mm) diameter and 6 inch (150 mm) or 4 inch (100 mm) height.(Walubita et al., 2011). The load is usually monotonically increasing at loading rate is 0.05 in./min (1.3 mm/min) at 77 °F . (Walubita et al., 2005). For direct tension test specimen were compacted in the Superpave Gyratory Compactor having the mold height of 6.9 in (175 mm) in and a diameter of 5.9 in (150 mm) diameter. Sample is then put for curing for 24 hours and after that, it needs to be glued to the testing device carefully before running the test. Load, vertical displacement, and time, these are the t hree data that is obtained from the test.    For the DT test the tensile stress can be computed as à Ã†â€™t= P/(à Ã¢â€š ¬r2)=P/à Ã¢â€š ¬D2/4 Where à Ã†â€™t=Minimum tensile stress; p=load; r=specimen radius D= specimen diameter (Dissertation Walubita, 2006) And the tensile strain at maximum axial load can be computed as ÃŽÂ µt=10^6v/h ; ÃŽÂ µt=average axial tensile strain, V= average axial specimen deformation h= specimen height. This way, HMA stiffness can be obtained as St= à Ã†â€™t/ÃŽÂ µt, where St=Youngs Modulus (Stiffness); à Ã†â€™t= Tensile stress (Maximum) ÃŽÂ µt= Tensile strain at maximum axial load. (Walubita et al., 2005), suggested à Ã†â€™t>=65 psi ÃŽÂ µt= (Lytton, 2012) discussed about the procedure of testing field cores for direct tension. After getting the rectangular sample form the cylindrical field core, having length of 4 inch (102mm) and width of 3 inch (76 mm) and thickness of 1.5-3 inch (38-76 mm). As a steel cap is needed to be glued to the each specimen end, the authors used a special gluing jig to keep the specimen centrally aligned with the cap. In total six LVDTs were attached to measure the vertical and horizontal displacement at top, bottom and center layers. The authors run the test in different temperatures (10 °C 20  °C) in electro hydraulic servo machine (MTS) with a feedback frequency of 2Hz (done in an old machine) 20Hz (done in a new machine). Figure 2: Test setup with LVDT arrangement ((Lytton, 2012) References: Dissertation, A., Walubita, L. F. (2006). Comparison of Fatigue Analysis Approaches for Predicting Fatigue Lives of Hot-Mix Asphalt Concrete ( Hmac ) Mixtures Comparison of Fatigue Analysis Approaches for Predicting Fatigue Lives of Hot-Mix Asphalt Concrete ( Hmac ) Mixtures. Analysis, (May). Lytton, R. (2012). Analytical-Numerical Methodology To Measure Undamaged , Fracture and Healing Properties of Asphalt Mixtures, (December). Walubita, L. F., Jamison, B. P., Das, G., Scullion, T., Martin, A. E., Rand, D., Mikhail, M. (2011). Search for a Laboratory Test to Evaluate Crack Resistance of Hot-Mix Asphalt. Transportation Research Record: Journal of the Transportation Research Board, 2210(1), 73-80. https://doi.org/10.3141/2210-08 Walubita, L. F., Martin, A. E., Jung, S. H., Glover, C. J., Chowdhury, A., Park, E. S., Lytton, R. L. (2005). Project Title: Evaluate the Fatigue Resistance of Rut Resistance Mixes . URLà ¢Ã¢â€š ¬Ã‚ ¯: http://tti.tamu.edu/documents/0-4468-1.pdf. Security, 7(2). Wen, H., Investigation of Effects of Testing Methods on Characterization of Asphalt Concrete, Journal of Testing and Evaluation, Vol. 31, No. 6, pp. 1-7, 2003.

Does Concentrated Acid or Diluted Acid React Faster? :: Science Experiments Reaction Rates Essays

Does Concentrated Acid or Diluted Acid React Faster? Plan I am going to carry out a reaction between Magnesium ribbon and Hydrochloric acid. The aim of this investigation is to work out which reacts faster, concentrated acid or diluted acid. I will judge if the reaction is fast or slow by observing the bubbles which occur during the reaction and also observe if the Magnesium has disappeared. Only the concentration of the acid will be changed - the Magnesium is a solid. Magnesium + Hydrochloric Acid Magnesium Chloride + Hydrogen Mg(s) + 2HCl(aq) MgCl(aq) + H2 (g) There are four main factors which may affect rate of reaction. These are: - 1. Concentration 2. Temperature 3. Catalyst 4. Surface area CONCENTRATION- if the concentration of the acid is increased, the rate goes faster. In a concentrated acid there are more particles in it this means that there is a more chance of successful collisions occurring. If the acid was diluted, there are not many acid particles, which means that there is not much chance of an acid particle hitting a magnesium atom. At the start, there are plenty of Magnesium atoms and acid particles but they get used up during successful collisions. After, a time there a fewer Magnesium atoms and the acid is less concentrated so the reaction slows down. This graph shows this: - volume of hydrogen Time Diluted Acid Concentrated Acid = Acid particle = water molecule = Magnesiumatom TEMPERATURE - at low temperatures the particles of reacting substances don't have enough energy. So if the substances were heated this would mean the particles take in energy. This causes them to move faster and collide vigorously very often. Also making more successful collisions. Therefore the rate of reaction increases. CATALYST - using a catalyst can speed up reactions. If there is a catalyst in the reaction then the collision needs less energy in order to be successful. This results into more collisions becoming successful, so the reaction goes faster, catalysts are very important in industry. Reactions are speeded up at low temperatures, which means less fuel is needed so money is saved. SURFACE AREA - if the Magnesium had a large surface area the atoms in the outer layer will only collide with the acid particles but if the metal was powdered, many more atoms are exposed, so there is a greater chance of successful collisions. Concentrated Acid = Acid particle = water molecule = Magnesium atom COLLISION THEORY The Collision Theory is used to predict the rate of reaction. The Theory is based on the fact that for a reaction to take place, it is

Symbols and Symbolism Essay - The Symbolic Stage in The Glass Menagerie :: Glass Menagerie essays

The Symbolic Stage in The Glass Menagerie The symbolic stage properties in The Glass Menagerie reinforces the theme of escaping reality. Lack of a Father leaves Tom the responsibility of caring for the family. The responsibility acquired by Tom causes him to lack a normal life full of decisions and adventure. Instead, Tom is bound to his family by guilt and emotion. The only way Tom can feel that he is living the life he deserves is by escaping reality. The fire escape, the only chance for survival in a burning building of crisis situation. In Tom's mind, there is always an emergency exit, a chance to escape. The fire escape in Tom's mind is going to the movies for the adventure that he does not get at home or work. The silk scarf that Tom placed over Lara's face is the same silk scarf that the magician used. The magician made things appear and disappear. Therefore, covering Lara's face with the scarf shows that Tom's wants Lara and her memory to disappear so he will not feel guilty about leaving the family behind. Lara realizes that she can not sit around while she should be in college. Her mother shows her that she needs to take the initiative and go to school or get married. "School careers usually wind up getting married to some nice man"(1557). Amanda is telling Lara that she can not wait for the future to come to her, she needs to build her own future. Lara can not face reality and go so instead she visits penguins and plays with a glass menagerie. Lara's glass collection represents a world apart from others. She dreams of other lives and her imagination runs wild. Symbols and Symbolism Essay - The Symbolic Stage in The Glass Menagerie :: Glass Menagerie essays The Symbolic Stage in The Glass Menagerie The symbolic stage properties in The Glass Menagerie reinforces the theme of escaping reality. Lack of a Father leaves Tom the responsibility of caring for the family. The responsibility acquired by Tom causes him to lack a normal life full of decisions and adventure. Instead, Tom is bound to his family by guilt and emotion. The only way Tom can feel that he is living the life he deserves is by escaping reality. The fire escape, the only chance for survival in a burning building of crisis situation. In Tom's mind, there is always an emergency exit, a chance to escape. The fire escape in Tom's mind is going to the movies for the adventure that he does not get at home or work. The silk scarf that Tom placed over Lara's face is the same silk scarf that the magician used. The magician made things appear and disappear. Therefore, covering Lara's face with the scarf shows that Tom's wants Lara and her memory to disappear so he will not feel guilty about leaving the family behind. Lara realizes that she can not sit around while she should be in college. Her mother shows her that she needs to take the initiative and go to school or get married. "School careers usually wind up getting married to some nice man"(1557). Amanda is telling Lara that she can not wait for the future to come to her, she needs to build her own future. Lara can not face reality and go so instead she visits penguins and plays with a glass menagerie. Lara's glass collection represents a world apart from others. She dreams of other lives and her imagination runs wild.

Religion in Public Schools Essay -- Prayer In Public Schools

Religious Rights in Public Schools "JESUS in the classroom!" Are you feeling uncomfortable yet? Religion in the public school systems is among the top of the list of controversial topics in American society, We've long been advised to avoid this and other religiously politically intertwined subjects in polite conversation. If you're like most Americans, this topic makes you frustrated, high strung, or at least a little queasy. From the day the 1st amendment right appeared in the U.S. Constitution, to this present day, and surely into our nation's tomorrows, the proper role of religion in public schools has been, is, and will continue to be a subject of great debate. It is important for school officials, parents, and students to have a clear understanding of the 1st amendment and how it affects their religious rights and the religious rights of others in a public school setting. Unfortunately, most people are confused or misguided when it comes to this issue. The purpose of this paper is to guide the reader throu gh a clear understanding of the 1st amendment; the impact it has had in education, the religious freedoms it grants to students, and the religious freedoms it grants (or doesn't grant) to teachers. The Constitution exists precisely so that opinions and judgments, including can be formed, tested, and expressed. These judgments are for the individual to make, not for the Government to decree even with the mandate or approval of a majority (Supreme Court Justice Anthony M. Kennedy, 1999). In knowing that, the 1st amendment states, "Congress shall make no law respecting an establishment of religion or prohibiting free exercise thereof…" As you can see there are two clauses in this part of the amendment. ... ... First Amendment Court Cases. Schenck v. United States (1919). Riley, R. (1998). Secretary's statement on religious expression. Retrieved November 15, 2001, from, the World Wide Web: http://www.ed.gov/Speeches/08-1995/religion.html Staver, Mathew. Teachers' Rights on Public School Campuses. Retrieved November 16, 2001, from the World Wide Web: http://www.lc.org/OldResources/teachers_rights_0900.html United States Supreme Court. (1993). Lamb's Chapel v. Center. Washington DC. Government Printing Office. United States Supreme Court. (1994). Mozert v. Hawkins County Board of Education, 827 F.2d 1058 (6th Cir. 1987). Washington DC; US Government Printing Office. United States Supreme Court. (1969). Tinker v. Des Moines School Districk, 393 U.S. 503, 89 S. Ct. 733, 21 L. Ed. 2d. 731. Washington DC; US Government Printing Office.

English is Broken Here Essay

English is Broken Here: Notes on Cultural Fusion is a series of essays where Coco Fusco examines the work of Latino performance artists born in the United States of America and the themes of â€Å"otherness† and culture clash. Fusco’s work depicts cultural fusion thru live performances. She meant to educate people thru her work of art and being the â€Å"other,† even posed herself with Gomez-Pena, a performance artist, under public scrutiny. They created a live exhibit of various complex societies having multi-faceted traditions, rituals and lots of different languages. This might only appeal superficially to mainly white audience but they made a difference in this kind of performance. They stirred the audience’s imagination and sense of cultural awareness. Comments gathered from the audience regarding Housekeeper’s Diary varied to some extent. There were those who talked about their own discomfort of not understanding their housemaids or on how to treat them humanely. Some might have even lauded their maids to feel important and cheerful despite their indifference. Fusco and Gomez-Pena performed live in museums and municipal buildings to know the public reactions. They exhibited themselves as indigenous tribal members. They were in a cage on display as â€Å"two undiscovered Amerindians† from the island of Guatinau. Coco Fusco describes the performance in â€Å"The Other History of Intercultural Performance,† as: â€Å"Our plan was to live †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦ authentic Guatinaui male genitals for $5 (p. 9). † People watching them did not know what to believe in. Some of the audience thought that the performance was real. However, such presentation, no matter how believable or not, could only mean taking a second look on what is really going on in the daily lives of people. The curiosity of people paying just to have a peek on the male genitalia of Gomez-Pena acting as Guatinaui is somewhat a spectacular thing to some, as if the genitalia of the fictional Guatinaui is different from the existing humans. Among artists and scientists during the Renaissance, it was a prevailing belief that the artwork or study of the male form was in itself an artwork or study of God, thus they placed value on sculpture of the male form as one of the highest works of art. In the case of Fusco’s and Gomez-Pena’s live performance, it was their priceless work of art as it was tangible. In the course of their live exhibits, others would feed Fusco and Gomez-Pena with bananas and posing with them for some souvenir photos. A realization regarding the performance might have hit into some audience such as acting out their own fantasies in life. Another part of the essay is what Fusco wrote as: â€Å"Gomez-Pena found the experience of being continually †¦Ã¢â‚¬ ¦Ã¢â‚¬ ¦ of public objectification (p. 57). † In her perspective as a woman with varied experiences in life, the performance would make her deflect the scrutiny and objectifications of the audience. The possibility of having undergone more serious and debilitating experiences in life might have made her stronger and more open as accepting people’s objections and criticisms as well. While to Gomez-Pena, the experience of being exposed to people being someone else has depressed him to some extent. Psychologically, their performance also made an impact to themselves, which actually opened their minds as well and not only the audience that they wanted to observe them. What they did was something not all can do. It would take a lot of courage, determination and imagination for them to execute such a unique performance, a unique work of art, just to educate people on the existence of various cultures and expose them to the consequences of cultural fusion.