Examining Hydrogen Fuel Cells Environmental Sciences Essay

Hydrogen fuel cells are potentially the energy beginning of the hereafter. Due to its efficiency and low pollution H fuel cells are far better than conventional gasoline engines. With increasing gasoline monetary values and pressing environmental issues, a new feasible energy beginning is required such as the H fuel cell, ( Swain, D. 2007 ) . ( 5 ) A fuel cell is an electrochemical device that produces current by the transition of H and O into H2O, ( Nice, K, Strickland, J. ) . ( 2 ) The first fuel cell was invented in 1839 by Sir William Grove. Fuel cells operate in a similar mode to a battery nevertheless they will continually bring forth heat and electricity if fuel is supplied, ( Anonymous ) . ( 1 ) Fuel cells run on H. Hydrogen is the most common and simplistic gas. It is exceptionally light and produces the highest sum of energy per unit of weight of 52000 Btu/lb, which is three times that of gasolene, ( Anonymous ) . ( 1 ) A H fuel cell is made up of two electrodes environing an electrolyte. Hydrogen passes over the anode of the cell and the free negatrons are conducted into the external circuit. ( 2 ) The O passes over the cathode. Electrons are conducted back from the external circuit to the accelerator where the H and O recombine to organize H2O. A proton exchange membrane is the electrolyte. If a polymer exchange mem brane is used this must be hydrated to stay stable functionality, ( Nice, K, Strickland, J. ) . ( 2 ) A Pt accelerator must be used to help the reaction, ( Nice, K, Strickland, J. ) . ( 2 ) The merchandises formed include H2O, heat and electricity. The two most promising fuel cells are the polymer exchange membrane fuel cell ( PEMFC ) and the solid oxide fuel cell ( SOFC ) , ( Nice, K, Strickland, J. ) . ( 2 ) The PEM fuel cell is used for transit such as in powering vehicles. This fuel cell has a low operating temperature signifier 60 & A ; deg ; C to 80 & A ; deg ; C and a high operating denseness, ( Nice, K, Strickland, J. ) . ( 2 ) The solid oxide fuel cells operate at really high temperatures of 700-1000 & A ; deg ; C. This cell will be used in big scale power coevals such as in mills, ( Nice, K, Strickland, J. ) . ( 2 ) One of the primary advantages of the H fuel cells is the low emanations, ( Swain, D. 2007 ) . ( 5 ) Gasoline powered autos emit pollutants such as SO2 and NO. Fuel cells rely on chemical science and non on burning which reduces emanations, ( Snyder, A. 2003 ) . ( 4 ) The lone gas released is H2O vapor. This reduces air pollution and combats planetary heating. ( 6 ) Hydrogen fuel cells are besides really effectual as they have the ability to covert fuel to energy from the minute of coevals. This eradicates multiple stairss and additions efficiency, ( Anonymous,2002 ) . ( 3 ) If pure H is used the H fuel cell can be 65 % efficient, ( Nice, K, Strickland, J. ) . If impure H utilized a reformist is required to alter the hydrocarbon into H which lowers the efficiency degree, nevertheless it is still far greater ( up to three times ) than a gasoline engine, ( Nice, K, Strickland, J. ) ( Anonymous,2002 ) . ( 2 ) ( 3 ) Due to the fact that much energy is lost turning pumps and fans in gasoli ne vehicles the overall efficiency is really low of 20 % , ( Nice, K, Strickland, J. ) . ( 2 ) In add-on to this H fuel cells achieve the letter writer of 65 stat mis to the gallon doing them a feasible energy beginning, ( Anonymous,2002 ) . ( 3 ) The dependability of a H fuel cell is a major advantage. Whereas burning engines, such as gasoline engines, have many traveling parts that require care, the fuel cell has really few. ( 3 ) This will cut down care costs and increase dependability. In add-on to this a fuel cell will non travel dead ( as batteries do ) if there is a changeless flow of chemicals into the cell, ( Nice, K, Strickland, J. ) . ( 2 ) Although ab initio production costs would be high for H fuel cells this will diminish and mass production costs will go low because of the simple building of the cell. ( 3 ) Equally good as this the H fuel cell is safe. Unlike gasoline, H will non do environmental jeopardies such as spillages. Similar to petrol H will fire when lit nevertheless it merely becomes explosive when stored up in an enclosed country, which is improbable as H disperses easy, ( Anonymous,2002 ) 3. ( 3 ) This makes H fuel cells a safe option. Hydrogen can be produced from coal, natural gas and oil. Since these militias are being depleted it is a great adventage that H for the fuel cells can be produced from biomass, sunshine and H2O, ( Swain, D. 2007 ) . ( 5 ) There are many beginnings of H on Earth. Hydrogen is found combined with other elements, chiefly C and O, ( Anonymous ) . ( 1 ) However it can be easy extracted and used to do the ultimate clean and efficient energy beginning, ( Anonymous ) . ( 1 ) Like all fuels and signifiers of energy H fuel cells have their disadvantages. One of the largest disadvantages of H fuel cells is that presently they are really expensive, ( Nice, K, Strickland, J. ) ( Snyder, A. 2003 ) . ( 2 ) ( 4 ) Many of the constituents that make up a H fuel cell such as the Pt accelerator and proton exchange membrane are dearly-won, ( Nice, K, Strickland, J. ) . ( 2 ) This would hold to diminish mostly to be economically feasible. Once this has decreased, for illustration by utilizing an alternate accelerator, mass production costs will diminish, ( Snyder, A. 2003 ) . ( 4 ) The production costs of H besides pose a disadvantage. Most H comes from coal, natural gas and oil. The pollution caused by the production of H from these resources is similar to the sum of that of gasoline engines, ( Snyder, A. 2003 ) . ( 4 ) Hydrogen can be produced by sunshine and air current to power electrolysis which does non make any pollution nevertheless this is excessively expensi ve to use extensively, ( Snyder, A. 2003 ) . ( 4 ) Another job with H fuel cells arise with storage. Due to the fact that H is such a light gas and disperses easy it is really hard to hive away a big sum in a confined country, ( Anonymous ) . ( 1 ) The challenge posed is for applied scientists to fit the 300-mile vehicle scope. However this is non impossible as it has been done in some recent vehicles, ( Anonymous ) . ( 1 ) Research workers are besides coming up with new ways of hive awaying the H such the usage of H armored combat vehicles and metal loanblends, ( Anonymous ) . ( 1 ) For H fuel cells to go feasible a PEMFC membrane must be developed that can run in high temperatures ( 100 & A ; deg ; C ) every bit good as bomber zero temperatures, ( Nice, K, Strickland, J. ) . ( 2 ) PEMFC membranes are hydrated to reassign H protons nevertheless at temperatures greater than 80 & A ; deg ; C the hydration is lost. These high temperatures are of import as the fuel cell will hold an increased tolerance to drosss. ( 2 ) Fuel cells must stay stable where every bit presently when the vehicle is turned on or off or temperatures are high the membrane tends to degrade, ( Nice, K, Strickland, J. ) . ( 2 ) Further research is required to battle this. In add-on to this exchanging to hydrogen fuel would necessitate an accommodation of substructure where H fuel Stationss, grapevines and distribution channels are required, ( Snyder, A. 2003 ) . ( 4 ) This is possible nevertheless it will take many old ages and money to construct, ( Snyder, A. 2003 ) . ( 4 ) Like all fuels hydrogen fuel cells do hold disadvantages nevertheless many of these can be combated with farther research and over clip, ( Anonymous ) . ( 1 ) Presently hydrogen fuel cells are non a feasible beginning of energy nevertheless due to their low emanations, high efficiency and many other advantages they have the possible to in the hereafter go a feasible energy beginning that is more effectual than gasoline engines.

Answer Key

Professor Mumford [email  protected] edu Econ 360 – Fall 2012 Problem Set 1 Answers True/False (30 points) 1. FALSE If (ai , bi ) : i = 1, 2, . . . , n and (xi , yi ) : i = 1, 2,  ·  ·  · , n are sets of n pairs of numbers, then: n n n (ai xi + bi yi ) = i=1 i=1 ai x i + i=1 bi yi 2. FALSE If xi : i = 1, 2, . . . , n is a set of n numbers, then: n n n n n (xi ? x) = ? i=1 n i=1 2 x2 i ? 2? x i=1 xi + i=1 x = ? i=1 2 x2 ? n? 2 x i where x = ? 1 n i=1 xi 3. TRUE If xi : i = 1, 2, . . . , n is a set of n numbers and a is a constant, then: n n a xi = a i=1 n i=1 xi = a n x ? here x = ? 1 n i=1 xi 4. FALSE If X and Y are independent random variables then: E (Y |X) = E (Y ) 1 5. TRUE If {a1 , a2 , . . . , an } are constants and {X1 , X2 , . . . , Xn } are random variables then: n n E i=1 ai X i = i=1 ai E (Xi ) 6. FALSE For a random variable X, let  µ = E (X). The variance of X can be expressed as: V ar(X) = E X 2 ?  µ2 7. TRUE For random variables Y and X, the variance of Y conditional on X = x is given by: V ar(Y |X = x) = E Y 2 |x ? [E (Y |x)]2 8. TRUE An estimator, W , of ? is an unbiased estimator if E (W ) = ? for all possible values of ?. 9.FALSE The central limit theorem states that the average from a random sample for any population (with ? nite variance) when it is standardized, by subtracting the mean and then dividing by the standard deviation, has an asymptotic standard normal distribution. 10. TRUE The law of large numbers states that if X1 , X2 , . . . , Xn are independent, identically distributed random variables with mean  µ, then ? plim Xn =  µ 2 Multiple Choice Questions (a) ceteris paribus (b) correlation (c) causal e? ect (d) independence (20 points) 11. The idea of holding â€Å"all else equal† is known as 12.If our dataset has one observation for every state for the year 2000, then our dataset is (a) cross-sectional data (b) pooled cross-sectional data (c) time series data (d) panel data 13. If our dataset has one observation for every state for the year 2000 and another observation for each state in 2005, then our dataset is (a) cross-sectional data (b) pooled cross-sectional data (c) time series data (d) panel data 14. If our dataset has one observation for the state of Indiana each year from 1950-2005 then our dataset is (a) cross-sectional data (b) pooled cross-sectional data (c) time series data (d) panel data 15.Consider the function f (X, Y ) = (aX + bY )2 . What is (a) 2aX (b) a(aX + bY ) (c) 2a(aX + bY ) (d) a2 X ? f (X,Y ) ? X 3 Long Answer Questions (50 points) 16. The sum of squared deviations (subtracting the average value of x from each observation on x) is the sum of the squared xi minus n times the square of x. There are ? several ways to show this, here is one: n n xi (xi ? x) ? i=1 = i=1 n (xi ? x + x) (xi ? x) ? ? ? n = i=1 n (xi ? x) (xi ? x) + ? ? i=1 n x (xi ? x) ? ? = i=1 (xi ? x)2 + x ? ? i=1 n (xi ? x) ? (xi ? x) = 0, so ? and we know that i=1 n i=1 (xi ? x)2 ? 17. Th ere are several ways to show that this expression equals the sample covariance between x and y, here is one: n n xi (yi ? y ) ? i=1 = i=1 n (xi ? x + x) (yi ? y ) ? ? ? n = i=1 n (xi ? x) (yi ? y ) + x ? ? ? i=1 (yi ? y ) ? = i=1 (xi ? x) (yi ? y ) ? ? 18. Correlation and causation are not always the same thing. (a) A negative correlation means that larger class size is associated with lower test performance. This could be because the relationship is causal meaning that having a larger class size actually hurts student performance.However, there are other reasons we might ? nd a negative relationship. For example, children from more a? uent families might be more likely to attend schools with smaller class sizes, and a? uent children generally score better on standardized tests. Another possibility is that within a school, a principal might assign the better students to smaller classes. Or, some parents might insist that their children are in the smaller classes, and these same pare nts tend to be more involved in their children’s education. Given the potential for confounding factors such as these, ? ding a negative correlation between class size and test scores is not strong evidence that smaller 4 class sizes actually lead to better performance. Thus, without other information, we cannot draw a meaningful economic conclusions. A correct answer should explain that we should be careful about drawing economic conclusions from simple correlations. (b) The sample correlation between N and T is de? ned as: s rN T = N T sN sT where the sample covariance, sN T , is given by: sN T = 1 999 1000 ? Ni ? N i=1 ? Ti ? T and the sample standard deviations are given by: sN = 1 999 1000 Ni ? N i=1 2 sT = 1 999 1000 ? Ti ? T i=1 2 Note that there are several alternative ways to write this and statistical programs generally use other algorithms to calculate the correlation that are less prone to loss of precision due to roundo? error or storage over? ow. 19. Wage data ( a) There are 526 observations. (b) There are 274 men in the sample. This means that the sample is 52. 09 percent male. (c) The average level of education in the sample is 12. 6 years. The median level of education is 12 years. (d) The highest education level in the sample is 18 years of school. 9 people in the sample report having 18 years of education. (e) The average hourly wage in the sample is $5. 90. The median hourly wage in the sample is $4. 65. 20. Fertility data (a) There are 363 women in the sample. (b) The average number of children ever born to a woman in the sample is 2. 3. The median number is 2. (c) The largest number of children ever born to a woman in the sample 7. Six women report having seven children. (d) 25 percent of the sample lived in the eastern United States at age 16. (e) The average level of eduction in the sample is 13. 2 years. 5

Assessment Of Frontal Lobe Dysfunction

Assessment Of Frontal Lobe Dysfunction It has been established that the frontal lobes play a major part in an individual’s decision making, planning, problem solving, social, emotional and behavioural skills. Consequently dysfunction of the frontal lobe can cause a wide range of symptoms (Kolb and Wishaw 1996) leading to relatively specific clinical dysfunction therefore a neuropsychological assessment is necessary to be carried out on the patient. The present study looks at the case of patient Mr. A who is reported to experience attention difficulties and problems with planning and organising after sustaining a head injury. Three neuropsychological tests have been used; WCST, TMT and TEA in order to identify the extent of the deficit. In line with previous research Mr. A’s performed poorly on tests and scored low in comparison to the normative scores. Other tests have also been suggested as well as strategies of rehabilitation for the patient. Frontal lobe located at the front of the cerebral hemisphere is the largest lobe in the brain associated with an individual’s personality and emotional control. The frontal lobes are responsible for planning, organising, selective attention, personality, behaviour and emotions. As well as this the frontal lobes are also involved in motor function (Passingham 1995), Spontaneity of behaviour (Kolb and Milner 1981), initiation, judgement, impulse control (Milner 1964, Miller 1985), social and sexual behaviour (Damasio 1985). More specifically the right frontal lobe is associated with an individual’s sense of humour, self awareness, self face recognition and episodic memory (Stuss 1991, Fink et al 1996, Wheeler et al 1997, Levine et al 1998, Craik et al 1999, Keenan et al 1999, Shammi and Stuss 1999). It is the orbitofrontal cortex that arbitrates empathic, civil and socially appropriate behaviour (Mega and Cummings 1994). Furthermore it is also reported that executive processes of the prefrontal lobe are responsible for planning, mon itoring, energizing, switching and inhibition (Stuss 2007). In the recent years cognitive neuroscience studies have shown that damage to the frontal lobe can affect high level of cognitive functions as well as an individual’s personality, their social behaviour, personal memories and their self awareness (Alexander et al 1979, Brazzelli et al 1994, Damasio 1994, Adolphs et al 1995, Channon and Crawford 1999, Rogers et al 1999, Stuss et al 2001). Studies have also shown that damage to the prefrontal lobe particularly damage to the ventromedial frontal is associated with poor decision making (Eslinger and Damasio 1985, Harlow 1999, Ackerly 2000). In addition to this damage to the left or right orbitofrontal results in personality changes including indifference or impaired social judgement, impaired pragmatics, deficient effective responsiveness, poor self-regulation and lack of ability to relate social situations with personal experience (Nauta 1973, Stuss and Benson 1983, Kacz marek 1984). Damage to the orbitofrontal cortex also results in the patient’s change of personality whereby they might become more irritable, labile, display lack of self restraint and fail to respond to the conventions of socially acceptable behaviour. In some case studies patients have reported descriptions of behavioural changes that are related to social difficulties such as egocentrism, insensitivity to social cues, unresponsiveness to another’s opinion, lack of self restraint, diminished foresight, impaired self monitoring, a propensity to show signs of inappropriate affect and social withdrawal (Eslinger and Damasio 1985, Eslinger et al 1992, Price et al 1990). The famous case of Phineas Gage was the first case study to highlight the impact of frontal lobe damage on an individual’s personality, decision making and social behaviour (Damasio 1994). Phineas Gage suffered an extreme injury to the frontal lobe when a 13 pound, 3-foot-long tamping rod when thro ugh his head; entering through his left cheek and exiting through the midline of his skull. Astonishingly after the event Gage still had the ability to walk, communicate and remain lucid and was examined by Dr Harlow (1848) who noticed the changes in his behaviour. In his report Harlow identified that from previously being identified as a smart, efficient, dependable and capable foreman by his employers and diligent, honest and well liked by friends, after his accident Gage became fitful, irreverent, foulmouthed liar, impatient, extravagant, anti social and profane especially when advice was given to him that he didn’t like (Harlow 1868).

Public Policy Research Paper Example | Topics and Well Written Essays - 1000 words

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Understanding Sense of Belongingness Essay Example | Topics and Well Written Essays - 750 words - 3

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