Solutions of midterm2010

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Midterm Exam Solutions

Midterm Exam Solutions, Econ 6090-092, Summer 2012Directions: Answer all questions as completely as possible.1. (25 points) What follows are the supply and demand functions coconut oil:where is the price of coconut oil, is the price of peanut oil, and is income. Assume that the constant values for and are 0.75 and 15,000 respectively.a (10 points) Find the equilibrium price and quantity for coconut oil.ANSWER:Substitute in 0.75 for and 15,000 for to get:Set and solve for :Substitute into either the or equation to find . So the equilibrium price is 4 and the equilibrium quantity is 8348.b(5 points) Calculate the own-price elasticity of demand for coconut oil at the equilibrium price and quantity.Explain how you know whether demand for coconut oil is elastic or inelastic.ANSWER:The own-price elasticity of demand is given by:With this linear demand function,so that at the equilibrium price and quantity we have:Since the absolute value of the own-price elasticity of demand is less than 1, demand for this good is inelastic.c (5 points) Calculate the income elasticity for coconut oil at the equilibrium price and quantity. Is coconut oil anormal or inferior good, and if it is a normal good is it a luxury or necessity? Explain how you know.ANSWER:The income elasticity is given by:With this linear demand function,so that at the equilibrium price and quantity and the constant value of we have:Since the income elasticity is positive, coconut oil is a normal good. Since the income elasticity is positive and less than 1, it is classified as a necessity.d (5 points) Calculate the cross-price elasticity for coconut oil and peanut oil at the equilibrium price and quantity.Are coconut oil and peanut oil complements or substitutes? Explain how you know.ANSWER:The cross-price elasticity is given by:With this linear demand function,so that at the equilibrium price and quantity and the constant value of we have:Since the cross-price elasticity is positive, these good are substitutes.2. (40 points) Suppose the consumer has the following utility function:Let represent income, the price of good A, and the price of good B.a (5 points) Set up the consumer's optimization problem.ANSWER:The consumer's problem is:b (10 points) Find the consumer's utility at each of the two corners. Explain why you would or would not expect the interior solution to be optimal given this particular specification of the utility function.ANSWER:The consumer's utility at either corner solution is zero. Thus, we should expect there to be an interior solution, as consuming positive amounts of both goods leads to a higher utility than zero.c (10 points) Find the demand functions for goods A and B as a function of prices and income.ANSWER:Knowing that we have an interior solution (from part b) and that the budget constraint will be binding, we will have the following system of equations:Solving the first two equations for we get:so that:Substituting for in the budget constraint we have:Substituting into our equation for we have:So our demand functions for goods A and B are:d (10 points) Assume that , , and . Find the consumer's optimal bundle.ANSWER:Simply take the demand functions from part c and substitute in the numeric values to find:e (5 points) Show the marginal rate of substitution equals the marginal rate of transformation at the optimal bundle. ANSWER:The marginal rate of substitution is the ratio of marginal utilities. So we have:so that:The marginal rate of transformation is the ratio of the prices (be sure that they are in the proper order according to how you have set up your MRS):So at the optimal bundle we have MRS=MRT.3. (35 points) Short answer questionsa (5 points) Suppose an individual is given the choice to take $4 with certainty or to pick a number from 1-30 out of ahat. If the number drawn is from 1-10, the individual receives $3. If the number drawn is from 21-30, the individual receives $9. If the individual prefers the gamble to the $4 with certainty are they risk averse, risk neutral, or risk seeking? Explain.ANSWER:The individual is risk seeking. Both the $4 with certainty and the gamble have an expected value of $4. The expected value of the gamble is:Since the $4 with certainty has a lower variance (there is no variance) and the individual chooses the gamble, the individual is risk seeking.b (10 points) Assume for part a, problem 3 (directly above) that we can represent the individuals utility with thefunction , what is the certain amount of money that would make the individual indifferent between the gamble and accepting the certain amount of money?ANSWER:The expected utility of the game is the weighted average of the utilities, which is:Now, what amount of money gives the consumer an expected utility of 30? It is:c (10 points) Suppose the consumer in problem 2 has the utility function . Will theconsumer's optimal bundle change from the one you found in problem 2? Explain why or why not.ANSWER:No, the optimal bundle would not change. This utility function is just of the one in problem 2, so it is a positive monotonic transformation of that utility function. Thus, any consumer that has either utility function will have the same set of indifference curves and so the optimal bundle will be the same as that in problem 2.d (10 points) What does an Engel curve represent? Draw an Engel curve for a good that is both normal and inferior.Make sure to clearly label the axes and label both when the good is normal and when the good is inferior.ANSWER:The Engel curve is a graphical representation of the relationship between a consumer's income and his quantity demanded. An example (with proper labels) would be:。

金融时间序列分析英文试题(芝加哥大学) (1)

Graduate School of Business,University of ChicagoBusiness41202,Spring Quarter2008,Mr.Ruey S.TsaySolutions to MidtermProblem A:(30pts)Answer brieﬂy the following questions.Each question has two points.1.Describe two methods for choosing a time series model.Answer:Any two of(a)Information criteria such as AIC or BIC,(b)Out-of-sample forecasts,and(c)ACF and PACF of the series.2.Describe two applications of volatility inﬁnance.Answer:Any two of(a)derivative(option)pricing,(b)risk management,(c)portfolio selection or asset allocation.3.Give two applications of seasonal time series models inﬁnance.Answer:(a)Earnings forecasts and(b)weather-related derivative pricing or risk man-agement.4.Describe two weaknesses of the ARCH models in modelling stock volatility.Answer:Any two of(a)symmetric response to past positive and negative shocks,(b)restrictive,(c)Not adaptive,and(d)provides no explanation about the source ofvolatility clustering.5.Give two empirical characteristics of daily stock returns.Answer:any two of(a)heavy tails,(b)non-Gaussian distribution,(c)volatility clus-tering.6.The daily simple returns of Stock A for the last week were0.02,0.01,-0.005,-0.01,and0.025,respectively.What is the weekly log return of the stock last week?What is theweekly simple return of the stock last week?Answer:Weekly log return is0.03938;weekly simple return is0.04017.7.Suppose the closing price of Stock B for the past three trading days were$100,$120,and$100,respectively.What is the arithmetic mean of the simple return of the stock for the past three days?What is the geometric average of the simple return of the stockfor the past three days? Answer:Arithmetic mean=12120−100100+100−120120=0.017.and the geometric mean is120×100−1=0.8.Consider the AR(1)model r t=0.02+0.8r t−1+a t,where the shock a t is normally distrib-uted with mean zero and variance1.What are the variance and lag-1autocorrelation function of r t?Answer:Var(r t)=11−0.82=2.78and the lag-1ACF is0.8.19.For problems6and7,suppose the daily return r t,in percentages,of Stock A followsthe model r t=1.0+a t+0.3a t−1,where a t=σt t withσ2t =1.0+0.4a2t−1and t beingstandard normal.What is the unconditional variance of a t?What is the variance of r t?Answer:Var(a t)=11−0.4=1.67.Var(r t)=(1+0.32)σ2a=1.82.10.Suppose that a n=3.0,what is the1-step ahead forecast for r n+1at the forecast originn?What is the1-step ahead volatility forecast of r t at the forecast origin n?Answer:r n(1)=1+0.3a n=1.9,andσ2n (1)=1+0.4a2n=4.6.11.Consider the simple AR(1)model r t=100+0.8r t−1+a t,where a t is normally distributedwith mean zero and variance10.Is the r t series mean-reverting?If yes,what is the half-life of the series?Answer:Yes,r t series is mean-reverting.The half-life is ln(0.5)/ln(0.8)=3.11.12.Describe two test statistics for testing the ARCH eﬀect of an asset return series.Writedown the associated null hypotheses.Answer:(a)The Ljung-Box statistic Q(m)of the squared shocks,i.e.a2t .The nullhypothesis is H o:ρ1=ρ2=···=ρm=0,whereρi is the lag-i ACF of a2t .(b)TheEngle F-test for the regression a2t =β0+β1a2t−1+···+βm a2t−m+e t.The null hypothesisis H o:β1=β2=···=βm=0.13.Consider the following two IGARCH(1,1)models for percentage log returns:Model A:σ2t =1.0+0.1a2t−1+0.9σ2t−1Model B:σ2t =0.1a2t−1+0.9σ2t−1.Suppose thatσ2100=20and a100=−2.0.What are the3-step ahead volatility forecastsfor Models A and B?Answer:For model A:3-step ahead volatility forecast isσ2100(3)=2+(1.0+0.1×(−2.0)2+0.9×20)=21.4.For model B,the3-step ahead volatility forecast isσ2100(3)=0.1(−2.0)2+0.9×20=18.4.14.Consider the following two models for the log price of an asset:Model A:p t=p t−1+a tModel B:p t=0.00001+p t−1+a twhere the shock a t is normally distributed with mean zero and varianceσ2>0.Suppose further that p100=5.Let p n( )be the -step ahead forecast at the forecast origin n.What are the point forecasts p100( )for both models as →∞?Answer:For model A,p100( )=5for all .For model B,p100( )converges to inﬁnity as →∞.215.Suppose that we have T =1000daily log returns for the Decile 1portfolio.Supposefurther that the sample autocorrelation at lag-12is ˆρ12=0.15.Test the hypothesis H o :ρ12=0against the alternative hypothesis H a :ρ12=pute the test statistic and draw your conclusion.Answer :t =0.151/√1000=√1000×0.15=4.74,which is highly signiﬁcant.Thus,the lag-12ACF is not zero.Problem B .(20pts)It is well-known in economics that growth rate of the domestic gross product (GDP)is negatively correlated with the change in unemployment rate.Consider the U.S.quarterly real GDP and unemployment rate from the ﬁrst quarter of 1948to the ﬁrst quarter of 2008.Let dgdp t be the growth rate of the GDP,i.e.dgdp t =ln(GDP t )−ln(GDP t −1),and dun t be the change in unempolyment rate,i.e.dun t =U t −U t −1with U t being the civilian unemployment rate.The data were seasonally adjusted and obtained from the Federal Reserve Bank at St.Louis.The sample size after the diﬀerencing is e the attached R output to answer the following questions.1.(5points)Write down the ﬁtted linear regression model with dgdp t and dun t representing the dependent and independent variable,respectively,including residual standard error.What is the R 2of the linear regression?Is the ﬁtted model adequate?Why?Answer :The ﬁtted linear regression isdgdp t =0.017−0.017dun t +e t ,ˆσe =0.0088.The R 2is 0.37.The model is not adequate because the Q (m )statistics of the residuals show that the residuals have serial correlations,i.e.Q (12)=219.4with p-value close to zero.2.(5points)To take care of the serial correlations in the residuals,a linear regression model with time-series errors is built for the two variables.Write down the ﬁtted model,including the residual variance.Answer :The ﬁtted linear regression model with time-series errors is(1−0.21B −0.12B 2)(1−0.86B 4)(dgdp t −0.017+0.018dun t )=(1−0.72B 4)a t ,ˆσ2a =6.01×10−5.3.(2points)Is the model in Question 2adequate?Why?Answer :Yes,the model is adequate.The Q (m )statistics of the residuals fail to indicate the existence of any serial correlations.We have Q (12)=17.53with p-value 0.13.4.(4points)Based on the ﬁtted model in Question 2,is the growth rate of GDP negatively correlated with the change in unempolyment rate?Why?Answer :Yes,the growth rate of GDP is negatively related to the change in unemploy-ment rate.The estimated coeﬃcient is −0.018which is highly signiﬁcant,because it standard error 0.0014is small,resulting in a large t -ratio.35.(4points)To check the predictive power of the model,it was re-estimated using theﬁrst236data points.This re-ﬁtted model is used to produce1-step to4-step ahead forecasts at the forecast origin t=236.The actual value of the GDP growth rates are also given.Construct the1-step ahead95%interval forecast of the model.Is the actual growth rate in the forecasting interval?Answer:The95%interval forecast is0.012±1.96×0.0077,i.e.[−0.0031,0.027].The actual value is0.0159,which is in the interval.Problem C.(16pts)Consider the quarterly earnings per share of the Microsoft stock from theﬁrst quarter of1992to theﬁrst quarter of2008.The data were obtained from First Call. To take the log transformation,we add0.5to all data points.The R output is attached. Let x t=ln(y t+0.5)be the transformed earnings,where y t is the actual earnings per share.1.(5points)Write down theﬁtted model for x t,including the variance of the residuals.Answer:Theﬁtted model is(1−B)r t=(1−0.70B+0.39B2)(1+0.39B4)a t,ˆσ2a=0.0016, where r t=ln(x t+0.5)with x t being the earnings per share.2.(2points)Is there any signiﬁcant serial correlation in the residuals of theﬁtted model?Why?Answer:No,the Q(m)statistics of the residuals give Q(12)=9.65with p-value0.65.3.(4points)Let T=65be the forecast origin,where T is the sample size.Based on theﬁtted model,and,for simplicity,use the relationship y t=exp(x t)−0.5,what are the 1-step and2-step ahead forecasts of earnings per share for the Microsoft stock?Answer:The1-step and2-step earnings forecasts are0.56and0.54,respectively.4.(2points)Test the null hypothesis H o:θ4=0vs H a:θ4=0.What is the test statistic?Draw your conclusion.Answer:The test statistic is t=0.39120.1442=2.71with two-sided p-value0.0067.Thus,the seasonal MA coeﬃcientθ4is signiﬁcantly diﬀerent from zero.5.(3points)Consider the regular(i.e.,non-seasonal)part of the MA model.Is it invertible?Why?Answer:Yes,it is invertible,because the polynomial1−0.6953x+0.3889x2has roots0.89±1.33i so that the absolute value of the roots(Mod in R)is1.6,which is greaterthan1.[If you compute the roots of x2−0.6953x+0.3889,the the absolute value of the roots is less than1.]Problem D.(34pts)Consider the daily log returns of the Starbucks stock,in percentages, from January1993to December2007.The relevant R output is attached.Answer the following questions.41.(2points)Is the mean log return signiﬁcant diﬀerent from zero?Why?Answer:No,the basic statistics show the95%conﬁdence interval of the mean is [−0.0103,0.1624],which contains zero.2.(2points)Is there any serial correlation in the log return series?Why?Answer:Yes,the Q(m)statistics show Q(15)=38.39with p-value0.0008.3.(2points)An MA model is used to handle the mean equation,which appears to beadequate.Is there any ARCH eﬀect in the return series?Why?Answer:Yes,because the Q(m)statistics of the squared residuals show Q(15)=112.61 with p-value close to zero.4.(6points)A GARCH(1,1)model with Student-t distribution is used for the volatilityequation.Write down theﬁtted model,including the degrees of freedom of the Student-t innovations and mean equation.Answer:Theﬁtted model isr t=0.037+a t−0.043a t−1−0.048a t−2,a t=σt t, ∼t5.27.σ2 t =0.012+0.026a2t−1+0.973σ2t−1.5.(4points)Since the constant term of the GARCH(1,1)model is not signiﬁcantly diﬀerentfrom zero at the1%level,an IGARCH(1,1)model is used.Write down theﬁtted IGARCH(1,1)model,including the mean equation.Answer:Theﬁtted IGARCH(1,1)model isr t=0.077+a t−0.029a t−1−0.044a t−2,a t=σt t, t∼N(0,1).σ2 t =0.022a2t−1+0.978σ2t−1.6.(3points)Is the IGARCH(1,1)model adequate?Why?What is the3-step aheadvolatility forecast with the last data point as the forecast origin?Answer:Yes,the Q(m)statistics for the standardized residuals give Q(10)=1.77, Q(15)=10.79,and Q(20)=18.66.The p-values of these statistics are all greater than0.05.In addition,the Q(m)statistics of the squared standardized residuals also havelarge p-values.The3-step ahead volatility forecast is √3.779=1.94.7.(5points)A GJR(or TGARCH)model with Student-t distribution is alsoﬁtted to thelog return series.Write down theﬁtted model,including the mean equation and all parameters.Answer:Thwﬁtted GJR model isr t=0.032+a t−0.043a t−1−0.048a t−2,a t=σt t, t∼t5.31.σ2 t =0.015+(0.021+0.017N t−1)a2t−1+0.970σ2t−1,where N t−1=0if a t−1≥0and=1,otherwise.58.(2points)Is the ﬁtted GJR (or TGARCH)model adequate?Why?Answer :Yes,the Q (m )statistics of the standardized residuals and those of the squred standardized residuals all have large p-values.9.(2points)Among the GARCH(1,1),IGARCH(1,1)and GJR(1,1)models,which one is preferred?Why?Answer :The GJR(1,1)model because it has the smallest AIC value.10.(2points)Is the leverage eﬀect of the GJR model signiﬁcant?Why?Answer :Yes,the t -ratio of the leverage parameter is 2.01,which is signiﬁcant at the 5%level.11.(4points)To better understand the leverage eﬀect,use the ﬁtted GJR to calculate theratio σ2t (a t −1=−5.10)σ2t(a t −1=5.10),assuming σ2t −1=7.5.Answer :σ2t (a t −1=−5.10)σ2t (a t −1=5.10)=0.0154+0.0379×(−5.10)2+0.97×7.50.0154+0.0208×(5.10)2+0.97×7.5=1.057.6。

《系统分析和设计》教学大纲英语

《系统分析和设计》教学大纲课程编号： MIS363课程类型：□通识教育必修课□通识教育选修课√专业必修课□专业选修课□□学科基础课总学时：54 学时讲课学时：36 实验（上机）学时：18学分：3适用对象：信管专业大三学生I.Course IntroductionManagement Information Systems (MIS) continues to be an eclectic mix of ideas, theories, and research methodologies. No other academic unit of the university studies the development of informationsystems, at least not from the particular perspective you find in MIS programs. While it is true that computer science departments are involved in building computer systems, computer sciencedevelopment is largely void of context. No one else in theuniversity, and for that matter in business organizations, has the combination of technical knowledge and organizational contextthat informs the systems development perspective of MIS.Accordingly, students will learn all about the particular MIS perspective on systems development in this course. Students will learn about the systems development life cycle and follow it from the birth of a new information system to the system's death and replacement. Along the way, students will learn about the tools, techniques, and methodologies used by systems analysts to develop information systems in organizations.II.Learning ObjectivesUpon completion of this course, students should be able to: •Demonstrate in-depth knowledge of the systems development lifecycleand the ability to explain the role of information systems within organizations•Demonstrate the ability to think critically and manage risk and reward when applying the systems development lifecycle •Demonstrate the ability to use analysis and design methods competently and effectively•Understand and articulate the roles of the system analyst in modern organizations and how the SA functions in each phase of the systems development life cycle. Competence is tested through written exams and by solving group cases.•Use Hypercase, a hypertext-based program to simulate organizational systems problems and develop solutions to them.•Demonstrate the ability to communicate effectively, orally and in writing, individually and in teamsIII.Connection between Teaching Content and Graduation Requirement MIS Undergraduate Program Learning Goals and Outcomes1. Knowledge: Our graduates will have in-depth disciplinary knowledge applicable in local and global contexts. You should be able to select and apply disciplinary knowledge to business situations in a local and global environment.2. Critical thinking and problem solving: Our graduates will be critical thinkers and effective problem solvers. You should be able to identify and research issues in business situations, analyze the issues, and propose appropriate and well-justified solutions.3. Communication: Our graduates will be effective professional communicators. You should be able to:a. Prepare written documents that are clear and concise, usingappropriate style and presentation for the intended audience,purpose and context.b. Prepare and deliver oral presentations that are clear,focused, well-structured, and delivered in a professional manner.4. Teamwork: Our graduates will be effective team participants. You should be able to participate collaboratively and responsibly in teams, and reflect on your own teamwork, and on the team’s processes an d ability to achieve outcomes.5. Ethical, social and environmental responsibility: Our graduates will have a sound awareness of the ethical, social, cultural and environmental implications of business practice. You should be able to:a. Identify and assess ethical, environmental and/orsustainability considerations in business decision-making andpractice.b. Identify social and cultural implications of businesssituations.The following table shows how the Course Learning Outcomes relate to the overall Program Learning Goals and Outcomes, and indicates where these are assessed:IV.Teaching methodsThis course consists of lectures, labs, discussions, research paper, group assignments and group presentations. Students must beprepared to discuss the assigned papers or cases before class. V.Topical Course OutlineVI.Course Content HighlightsThe course content is divided into five major parts: Systems AnalysisFundamentals (Part I), Information Requirements Analysis (Part II), The Analysis Process (Part III), The Essentials of Design (Part IV), and Quality Assurance and Implementation (Part V).错误!未找到引用源。

ODE Solutions to Practice Midterm

Solutions to Practice MidtermBy H˚akan NordgrenProblem1:Consider the systemx =x2+yy =x−y+a1.Explain how the nullclines change as a increases from0to positive values,and explainwhy a bifurcation is expected for some positive values of a.2.Sketch the phase-portrait of the system when a is greater than the bifurcation value.3.Determine the a for which there is bifurcation.Solution:Theﬁrst two questions are best answered using drawings so they are on the pdf with the sketches in it.Toﬁnd the value of a for which there is bifurcation we need toﬁnd the value of a for which the curve{(x,y)∈R2:y=−x2}and the curve{(x,y)∈R2:y=x+a}meet exactly once.This occurs at a point(x,y)where the line{(x,y)∈R2:y=x+a}has thesame gradient as{(x,y)∈R2:y=−x2}.That is,at(−12,−14).Now we need toﬁnd the a forwhich the line{(x,y)∈R2:y=x+a}passes through(−12,−14).This happens when a=14.Problem2:Consider the systemx =−y−x(2−x2−y2)y =xe a Lyapunov function of the formL(x,y)=ax2+by2,where a,b>0to investigate the stability of the equilibrium point that the origin.If the origin is asymptotically stable,what can you say about the size of its basin of attraction?2.What happens to trajectories which do not go to the origin,as t→∞?Solution:1.To show that the origin is an asymptotically stable equilibrium point,we must show thatL,deﬁned as above,is a strict Lyapunov function in some neighborhood of(0,0).It is clear that L(x,y)≥0for all(x,y)and also that L(x,y)=0if(x,y)=(0,0).It remains to check that˙L is strictly negative in a neighborhood containing the origin.We have˙L(x,y)=2ax2by·−y−x(2−x2−y2)x=2xy(b−a)−2ax2(2−x2−y2).We can see from this that if we pick a =b =1then L is a Lyapunov function in the ball of radius √2with center the origin,so the origin is stable.We can also see that ˙Lis strict on the set {(x,y )∈R 2:x 2+y 2<2and x =0}.At a point (x,y )with x =0and y =0,we see that x =−y and y =0,so the trajectory will go into the set {(x,y )∈R 2:x 2+y 2<2and x =0}again.Therefore,even though L is not a strict Lyapunov function on {(x,y )∈R 2:x 2+y 2<2and x =0},the origin is still asymptotically stable,and {(x,y )∈R 2:x 2+y 2<2}is contained in its basin of attraction.2.If we pick initial conditions (x 0,y 0)on the circle C ={(x,y )∈R 2:x 2+y 2=2}.Then the trajectory will be{(x,y )∈R 2:x 2+y 2=2}.Thus,a solution which starts on the circle C remains there.For solutions which start in the set {(x,y )∈R 2:x 2+y 2>2and x =0},we see that˙L=−2x 2(2−x 2−y 2)>0,so these solutions tend to inﬁnity.If we have initial conditions with x 0=0then we know that the trajectory will end up in the region {(x,y )∈R 2:x 2+y 2>2and x =0}soon,so all solutions in {(x,y )∈R 2:x 2+y 2>2}tend to inﬁnity.Problem 3:Now consider the system˙r =r (2−r )˙θ=r (1−sin(θ)).1.Show that there are exactly two equilibrium points,one of which is a source at the origin.2.Show that A ={(r,θ)∈[0,∞)×[0,2π):r =2}and B ={(r,θ)∈[0,∞)×[0,2π):θ=π2}are invariant sets.3.Explain why B is not periodic.4.Show that for p =(0,0)we have ω(p )={(r,π2)}5.Show that the equilibrium point at (r,π2)is nevertheless,not stable.Solution:1.For r =0we certainly have ˙r =0and ˙θ=0.Now suppose that we have r >0and ˙r =0and ˙θ=0.Then we have r =2,and sin(θ)=1,that is θ=π2.Thus there are two equilibrium points,one at the origin an one at (2,π2).Please note that these are thepolar coordinates of the points.We see that for r with 0<r <2,˙r >0so the origin is a source.2.For solutions starting on A we have˙r=0,so A is invariant.For solutions starting on Bwe haveθ=π,which means that˙θ=0,so B is invariant.3.The circle A is not a periodic solution because it contains an equilibrium point.4.This is best explained by a picture.5.For(2,π2)to be stable we require that for all neighborhoods U of(2,π2),there is a neigh-borhood V of(2,π2),such that if we start a solution inside V it remains inside U.This isnot the case,if we,for instance,start a solution at the right place on A,because it goes away from the equilibrium point for a while.。

《信息检索》模拟精彩试题

《信息检索》模拟试题（一）一、填空1.小王在某个数据库中检索到了50篇文献，查准率和查全率分别为40％、80％，则全部相关文档有 25 篇。

2.INTERNET是基于 TCP/IP 协议的。

3.文件ABC.001.TXT的后缀名是 TXT 。

文件类型是文本文件。

4.多数网页采用HTML编写，这里的HTML指的是：超文本标识语言。

5.目录型搜索引擎主要提供族性检索模式，索引型搜索引擎主要提供特性检索模式。

6.在使用搜索引擎检索时，URL:ustc可以查到网址中带有ustc的网页。

7.根据索引编制方式的不同，可以将搜索引擎分为索引型搜索引擎和网络目录型搜索引擎。

8.按文献的相对利用率来划分，可以把文献分为核心文献、相关文献、边缘文献。

9.定期（多于一天）或不定期出版的有固定名称的连续出版物是期刊。

10.检索工具具有两个方面的职能：存储职能、检索职能。

11.以单位出版物为著录对象的检索工具为：目录。

12.将文献作者的姓名按字顺排列编制而成的索引称为：作者索引。

13.利用原始文献所附的参考文献，追踪查找参考文献的原文的检索方法称为追溯法，又称为引文法。

14.已知一篇参考文献的著录为：”Levitan, K. B. Information resource management. NewBrunswick: Rutgers UP,1986”，该作者的姓是： Levitan 。

15.检索语言可分为两大类：分类语言、主题词语言。

16.LCC指的是美国国会图书馆分类法。

17.当检索关键词具有多个同义词和近义词时，容易造成漏检，使得查全率较低。

18.主题词的规范化指的是词和概念一一对应，一个词表达一个概念。

19.国际上通常根据内容将数据库划分为：参考数据库、源数据库、混合数据库。

20.查询关键词为短语"DATA OUTPUT"，可以用位置算符(W)改写为： DATA (W) OUTPUT 。

21.著录参考文献时，对于三个以上的著者，可以在第一著者后面加上 et al. ，代表"等人"的意思。

WHO新冠疫苗技术线路(英文)

WHO新冠疫苗技术线路(英文)A coordinatedGlobal ResearchRoadmapto respond to theD-19 epidemic and beyondThere is broad consensus on the need for research to focus on actions that can save lives now and to facilitate action so that those affected are promptly diagnosed and receive optimal care; while integrating innovation fully withineach research area.Moreover, there is an imperative to support research priorities in a way that leads to the development of sustainable global research platforms pre-prepared for the next disease Xepidemic; thus, allowing for accelerated research, innovative solutions and R&D of diagnostics, therapeutics and vaccines, as well as their timely and equitable access for thoseat highest risk.4 March 20212021 novel Coronavirus Global research and innovation forum: towards a research roadmapTable of contentsTable of contents _____________________________________________________________________ 2 ABOUT THIS DOCUMENT _______________________________________________________________ 7 GOALS OF THE GLOBAL RESEARCH ROADMAP __________________________________________ 9 PROPOSED STRATEGIC APPROACHES AND CRITICAL ACTIONS___________________________ 11 IMMEDIATE NEXT STEPS TO CONTRIBUTE TO CONTROL THE OUTBREAK_____________________ 13 SELECTED KNOWLEDGE GAPS _________________________________________________________ 14 CROSS-CUTTING RESEARCH PRIORITIES ________________________________________________ 15 SCALING UP RESEARCH AND INNOVATION ACTIONS ___________________________________ 16 TIMELINE FOR IMPLEMENTATION OF SELECTED RESEARCH ACTIONS ______________________ 17 MIDTERM AND LONGTERM PRIORITIES TO CONTRIBUTE TO CONTROL THE OUTBREAK _______ 231. Virus natural history, transmission and diagnostics ______________________________________ 232. Animal and environmental research on the virus origin, and management measures at the human-animal interface__________________________________________________________________ 23 3. Epidemiological studies _______________________________________________________________ 24 4. Clinical management _________________________________________________________________ 24 5. Infection prevention and control, including health care workers’protection ______________ 25 6. Candidate therapeutics R&D __________________________________________________________ 25 7. Candidate vaccines R&D______________________________________________________________ 25 8. Ethics Considerations for Research _____________________________________________________ 26 9. Social Sciences in the Outbreak Response _____________________________________________ 26 OPTIMIZNG FUNDING EFFORTS ________________________________________________________ 27 GOVERNANCE_____________________________________________________________________ _ 28 VIRUS NATURAL HISTORY, TRANSMISSION AND DIAGNOSTICS ___________________________ 31 State of the Art _____________________________________________________________________ _______ 31 Knowledge gaps _____________________________________________________________________ ____ 31Clinical virus detection _____________________________________________________________________ ______ 31 Immunity and immune diagnostics ________________________________________________________________ 32 Tools for infection control _____________________________________________________________________ ____ 32 Engineered solutions to clinical diagnostics ________________________________________________________ 32Ongoing research efforts __________________________________________________________________ 32 22021 novel Coronavirus Global research and innovation forum: towards a research roadmapResearch priorities _____________________________________________________________________ ___ 33Other research priorities _____________________________________________________________________ _____ 34What are the key milestones per research priority? _________________________________________ 34 ANIMAL AND ENVIRONMENTAL RESEARCH ON THE VIRUS ORIGIN, AND MANAGEMENT MEASURES AT THE HUMAN-ANIMAL INTERFACE _________________________________________ 36State of the art _____________________________________________________________________ _______ 36 Knowledge gaps _____________________________________________________________________ ____ 37 Ongoing research efforts __________________________________________________________________ 37 Research priorities _____________________________________________________________________ ___ 38 What are the key milestones per research priority___________________________________________ 40 Essential references_____________________________________________________________________ __ 41 EPIDEMIOLOGICAL STUDIES ___________________________________________________________ 42 State of the Art _____________________________________________________________________ _______ 42 Key epidemiological parameters__________________________________________________________ 42 Transmission dynamics ____________________________________________________________________ 42 Disease severity _____________________________________________________________________ _____ 43 Susceptibility _____________________________________________________________________ ________ 43 Control and mitigation measures __________________________________________________________ 44 Knowledge gaps _____________________________________________________________________ ____ 45Transmission dynamics _____________________________________________________________________ ______ 45 Severity _____________________________________________________________________ ____________________ 45 Susceptibility _____________________________________________________________________ _______________ 45 Control and mitigation measures _________________________________________________________________ 45 Ongoing research efforts __________________________________________________________________ 46 Research priorities _____________________________________________________________________ ___ 47 What are the key milestones per research priority___________________________________________ 49 Essential references_____________________________________________________________________ __ 50 CLINICAL CHARACTERIZATION AND MANAGEMENT____________________________________ 51 State of the art _____________________________________________________________________ _______ 51 Knowledge gaps _____________________________________________________________________ ____ 51Scientific gaps _____________________________________________________________________ ______________ 51 Operational gaps _____________________________________________________________________ ___________ 52Ongoing research efforts __________________________________________________________________ 52 32021 novel Coronavirus Global research and innovation forum: towards a research roadmapResearch priorities _____________________________________________________________________ ___ 53Objective 1: Define the natural history of COVID-19 infection _______________________________________ 53 Objective 2: Determine interventions that improve the clinical oute of COVID-19 infected patients53 Objective 3: Determine optimal clinical practice strategies to improve the processes of care_________ 53 Objective 4: Determine how best to link key research questions with researchers in affected regions who are able to recruit patients _____________________________________________________________________ __ 54 Objective 5: Develop platform(s) to of data collection across trials, and collaborations between trials _____________________________________________________________________ 54What are the research priorities for clinical research for this outbreak and beyond?___________ 55What are the key milestones per research priority___________________________________________ 57Essential references _____________________________________________________________________ __ 59INFECTION PREVENTION AND CONTROL, INCLUDING HEALTH CARE WORKERS’PROTECTION 60State of the art _____________________________________________________________________ _______ 60Knowledge gaps _____________________________________________________________________ ____ 61Modes and duration of transmission _______________________________________________________________ 61 Environmental stability of the virus and effective methods to minimize the role of the environment in transmission _____________________________________________________________________ ________________ 61 Personal protective equipment (PPE) and IPC measures____________________________________________ 61 Isolation, quarantine, and optimal health care pathways __________________________________________ 61 Understanding IPC pliance and perception using behavioural change and social science ______ 61 IPC in the munity setting _____________________________________________________________________ 62Ongoing research efforts __________________________________________________________________ 62 Research priorities _____________________________________________________________________ ___ 62Objective 1: Understand the effectiveness of movement control strategies to prevent secondary transmission in health care and munity settings ________________________________________________ 62 Objective 2: Optimize the effectiveness of PPE and its use in reducing the risk of transmission in health care and munity settings_____________________________________________________________ ________ 62 Objective 3: Minimize the role of the environment in transmission of the COVID-19 virus_______________ 62What are the research priorities for IPC for this outbreak and beyond? _______________________ 62What are the key milestones per research priority___________________________________________ 65Essential references _____________________________________________________________________ __ 66CANDIDATE THERAPEUTICS R&D _______________________________________________________ 67State of the art _____________________________________________________________________ _______ 67Knowledge gaps _____________________________________________________________________ ____ 68Ongoing research efforts __________________________________________________________________ 69 Research priorities _____________________________________________________________________ ___ 69Objective 1: Identification of candidates for clinical evaluation in addition to the ones already prioritised. _____________________________________________________________________ __________________ 6942021 novel Coronavirus Global research and innovation forum: towards a research roadmapObjective 2: Multicentre Master Protocol to evaluate efficacy and safety. ___________________________ 69 Objective 3: Coordinated collaboration to implement clinical trials, for evaluation of safety of therapeutics. _____________________________________________________________________ _______________ 69What are the research priorities for each individual thematic area -for this outbreak and beyond? _____________________________________________________________________ ____________ 70 What are the key milestones per research priority___________________________________________ 72 What are the most important actions to facilitate the successful evaluation and use of any of the investigational medical countermeasures? _________________________________________________ 73 Essential references_____________________________________________________________________ __ 74 CANDIDATE VACCINES R&D __________________________________________________________ 75 State of the art _____________________________________________________________________ _______ 75 Critical knowledge gaps __________________________________________________________________ 75 Key research priorities ____________________________________________________________________ 76 Independent Expert Groups _______________________________________________________________ 77 ETHICS CONSIDERATIONS FOR RESEARCH ______________________________________________ 78 State of the art_____________________________________________________________________ _______ 78 Knowledge gaps _____________________________________________________________________ ____ 79 Research priorities _____________________________________________________________________ ___ 80Objective 1: To enable the identification of key knowledge gaps and research priorities._____________ 80 Objective 2: To formulate a clearly defined research governance framework which enables effective and ethical collaboration between multiple stakeholders, including WHO, the global research munity, subject matter experts, public health officials, funders, and ethicists. ____________________ 80 Objective 3: To facilitate effective cross-working and collaboration across the research thematic areas._____________________________________________________________________ ________内容过长，仅展示部分文字预览，全文请查看图片预览。

exam12s经典教材《金融时间序列分析》Ruey S. Tsay 英文第三版2012年试题及答案高清版

Booth School of Business,University of ChicagoBusiness41202,Spring Quarter2012,Mr.Ruey S.TsaySolutions to MidtermProblem A:(34pts)Answer brieﬂy the following questions.Each question has two points.1.Describe two improvements of the EGARCH model over the GARCHvolatility model.Answer:(1)allows for asymmetric response to past positive or negative returns,i.e.leverage eﬀect,(2)uses log volatility to relax parameter constraint.2.Describe two methods that can be used to infer the existence of ARCHeﬀects in a return series,i.e.,volatility is not constant over time.Answer:(1)The sample ACF(or PACF)of the squared residuals of the mean equation,(2)use the Ljung-Box statistics on the squared residuals.3.Consider the IGARCH(1,1)volatility model:a t=σt t withσ2t =α0+β1σ2t−1+(1−β1)a2t−1.Often one pre-ﬁxesα0=0.Why?Also,suppose thatα0=0and the1-step ahead volatility prediction at the forecast origin h is16.2%(annualized),i.e.,σh(1)=σh+1=16.2for the percentage log return.What is the10-step ahead volatility prediction?That is,what isσh(10)?Answer:(1)Fixingα0=0based on the prior knowledge that volatility is mean reverting.(2)σh(10)=16.2.4.(Questions4to8)Consider the daily log returns of Amazon stockfrom January3,2007to April27,2012.Some summary statistics of the returns are given in the attached R output.Is the expected(mean) return of the stock zero?Why?Answer:The data does not provide suﬃcient evidence to suggest that the mean return is not zero,because the95%conﬁdence interval con-tains zero.5.Let k be the excess kurtosis.Test H0:k=0versus H a:k=0.Writedown the test statistic and draw the conclusion.1Answer:t-ratio =9.875√24/1340=73.79,which is highly signiﬁcant com-pared with χ21distribution.6.Are there serial correlations in the log returns?Why?Answer:No,the Ljung-Box statistic Q (10)=10.69with p-value 0.38.7.Are there ARCH eﬀects in the log return series?Why?Answer:Yes,the Ljung-Box statist of squared residuals gives Q (10)=39.24with p-value less than 0.05.8.Based on the summary statistics provided,what is the 22-step ahead point forecast of the log return at the forecast origin April 27,2012?Why?Answer:The point forecast r T (22)=0because the mean is not signif-icantly diﬀerent from zero.[Give students 1point if they use sample mean.]9.Give two reasons that explain the existence of serial correlations in ob-served asset returns even if the true returns are not serially correlated.Answer:Any two of (1)bid-ask bounce,(2)nonsynchronous trading,(3)dynamic dependence of volaitlity via risk premuim.10.Give two reasons that may lead to using moving-average models inanalyzing asset returns.Answer:(1)Smoothing (or manipulation),(2)bid-ask bounce in high frequency returns.11.Describe two methods that can be used to compare diﬀerent modelsfor a given time series.Answer:(1)Information criteria such as AIC or BIC,(2)backtesting or out-of-sample forecasting.12.(Questions 12to 14)Let r t be the daily log returns of Stock A.Assume that r t =0.004+a t ,where a t =σt t with t being iid N(0,1)random variates and σ2t =0.017+0.15a 2t −1.What is the unconditionalvariance of a t ?Answer:Var(a t )=0.0171−0.15=0.02.13.Suppose that the log price at t =100is 3.912.Also,at the forecastorigin t =100,we have a 100=−0.03and σ100=pute the21-step ahead forecast of the log price (not log return)and its volatility for Stock A at the forecast origin t =100.Answer:r 100(1)=0.004so that p 100(1)=3.912+0.004=3.916.Thevolatility forecast is σ2100(1)= 0.017+0.15(−0.03)2=pute the 30-step ahead forecast of the log price and its volatilityof Stock A at the forecast origin t =100.Answer:p 100(30)=3.912+0.004×30=4.032and the voaltility is the unconditional stantard error √0.02=0.141.15.Asset volatility has many applications in ﬁnance.Describe two suchapplications.Answer:Any two of (1)pricing derivative,(2)risk management,(3)asset allocation.16.Suppose the log return r t of Stock A follows the model r t =a t ,a t =σt t ,and σ2t =α0+α1a 2t −1+β1σ2t −1,where t are iid N(0,1).Under whatcondition that the kurtosis of r t is 3?That is,state the condition under which the GARCH dynamics fail to generate any additional kurtosis over that of t .Answer:α1=0.17.What is the main consequence in using a linear regression analysis whenthe serial correlations of the residuals are overlooked?Answer:The t -ratios of coeﬃcient estimates are not reliable.Problem B .(30pts)Consider the daily log returns of Amazon stock from January 3,2007to April 27,2012.Several volatility models are ﬁtted to the data and the relevant R output is attached.Answer the following questions.1.(2points)A volatility model,called m1in R,is entertained.Write down the ﬁtted model,including the mean equation.Is the model adequate?Why?Answer:ARCH(1)model.r t =0.0018+a t ,a t =σt t with t being iidN(0,1)and σ2t =7.577×10−4+0.188a 2t −1.The model is inadequatebecause the normality assumption is clearly rejected.2.(3points)Another volatility model,called m2in R,is ﬁtted to the returns.Write down the model,including all estimated parameters.3Answer:ARCH(1)model.r t=4.907×10−4+a t,a t=σt t,where t∼t∗3.56with t∗vdenoting standardized Student-t distribution with v degreesof freedom.The volatility equation isσ2t =7.463×10−4+0.203a2t−1.3.(2points)Based on theﬁtted model m2,test H0:ν=5versus H a:ν=5,whereνdenotes the degrees of freedom of Student-t distribution.Perform the test and draw a conclusion.Answer:t-ratio=3.562−50.366=−3.93,which compared with1.96is highlysigniﬁcant.If you compute the p-value,it is8.53×10−5.Therefore, v=5is rejected.4.(3points)A third model,called m3in R,is also entertained.Writedown the model,including the distributional parameters.Is the model adequate?Why?Answer:Another ARCH(1)model.r t=0.0012+a t,a t=σt t,where t are iid and follow a skew standardized Student-t distribution with skew parameter1.065and degrees of freedom3.591.The volatility equationisσ2t =7.418×10−4+0.208a2t−1.Ecept for the insigicant mean value,theﬁtted ARCH(1)model appears to be adequate based on the model checking statistics shown.5.(2points)Letξbe the skew parameter in model m3.Does the estimateofξconﬁrm that the distribution of the log returns is skewed?Why?Perform the test to support your answer.Answer:The t-ratio is1.065−10.039=1.67,which is smaller than1.96.Thus,the null hypothesis of symmetric innovations cannot be rejected at the 5%level.6.(3points)A fourth model,called m4in R,is alsoﬁtted.Write downtheﬁtted model,including the distribution of the innovations.Answer:a GARCH(1,1)model.r t=0.0017+a t,a t=σt t,where t are iid and follow a skew standardized Student-t distribution with skew parameter1.101and degrees of freedom3.71.The volatility equationisσ2t =1.066×10−5+0.0414a2t−1+0.950σ2t−1.7.(2points)Based on model m4,is the distribution of the log returnsskewed?Why?Perform a test to support your answer.Answer:The t-ratio is1.101−10.043=2.349,which is greater than1.96.Thus,the distribution is skew at the5%level.48.(2points)Among models m1,m2,m3,m4,which model is preferred?State the criterion used in your choice.Answer:Model4is preferred as it has a smaller AIC value.9.(2points)Since the estimatesˆα1+ˆβ1is very close to1,we consideran IGARCH(1,1)model.Write down theﬁtted IGARCH(1,1)model, called m5.Answer:r t=a t,a t=σt t,whereσ2t =3.859×10−5+0.85σ2t−1+0.15a2t−1.10.(2points)Use the IGARCH(1,1)model and the information providedto obtain1-step and2-step ahead predictions for the volatility of the log returns at the forecast origin t=1340.Answer:From the outputσ21340(1)=σ21341=3.859×10−5+0.85×(0.02108)2+0.15(.146)2=0.00361.Therefore,σ21340(2)=3.859×10−5+σ2 1340(1)=0.00365.The volatility forecasts are then0.0601and0.0604,respectively.11.(2points)A GARCH-M model is entertained for the percentage logreturns,called m6in the R output.Based on theﬁtted model,is the risk premium statistical signiﬁcant?Why?Answer:The risk premium parameter is−0.112with t-ratio−0.560, which is less than1.96in modulus.Thus,the risk premium is not statistical signiﬁcant at the5%level.12.(3points)Finally,a GJR-type model is entertained,called m7.Writedown theﬁtted model,including all parameters.Answer:This is an APARCH model.The model is r t=0.0014+a t,a t=σt t,where t are iid and follow a skew standardized Student-tdistribution with skew parameter1.098and degrees of freedom3.846.The volatility equation isσ2 t =7.583×10−6+0.0362(|a t−1|−0.478a t−1)2+0.953σ2t−1.13.(2points)Based on theﬁtted GJR-type of model,is the leverage eﬀectsigniﬁcant?Why?Answer:Yes,the leverage parameterγ1is signﬁicantly diﬀerent from zero so that there is leverage eﬀect in the log returns.5Problem C.(14pts)Consider the quarterly earnings per share of Abbott Laboratories(ABT)stock from1984.III to2011.III for110observations.We analyzed the logarithms of the earnings.That is,x t=ln(y t),where y t is the quarterly earnings per share.Two models are entertained.1.(3points)Write down the model m1in R,including residual variance.Answer:Let r t be the log earnings per share.Theﬁtted model is=0.00161.(1−B)(1−B4)r t=(1−0.565B)(1−0.183B4)a t,σ2a2.(2points)Is the model adequate?Why?Answer:No,the Ljung-Box statistics of the residuals give Q(12)=25.76with p-value0.012.3.(3points)Write down theﬁtted model m2in R,including residualvariance.Answer:Theﬁtted model is=0.00144.(1−B)(1−B4)r t=(1−0.470B−0.312B3)a t,σ2a4.(2points)Model checking of theﬁtted model m2is given in Figure1.Is the model adequate?Why?Answer:Yes,the model checking statistics look reasonable.5.(2points)Compare the twoﬁtted model models.Which model ispreferred?Why?Answer:Model2is preferred.It passes model checking and has a smaller AIC value.6.(2points)Compute95%interval forecasts of1-step and2-step aheadlog-earnings at the forecast origin t=110.Answer:1-step ahead prediction:0.375±1.96×0.038,and2-step ahead prediction:0.0188±1.96×0.043.(Some students may use2-step ahead prediction due to the forecast origin confusion.)Problem D.(22pts)Consider the growth rate of the U.S.weekly regular gasoline price from January06,1997to September27,2010.Here growth rate is obtained by diﬀerencing the log gasoline price and denoted by gt in R output.The growth rate of weekly crude oil from January03,1997to September24,2010is also obtained and is denoted by pt in R output.Note that the crude oil price was known3days prior to the gasoline price.61.(2points)First,a pure time series model is entertained for the gasolineseries.An AR(5)model is selected.Why?Also,is the mean of the gtseries signiﬁcantly diﬀerent from zero?Why?Answer:An AR(5)is selected via the AIC criterion.The mean of g tis not signiﬁcantly diﬀerent from zero based on the one-sample t-test.The p-value is0.19.2.(2points)Write down theﬁtted AR(5)model,called m2,includingresidual variance.Answer:Theﬁtted model is=0.000326.(1−0.507B−0.079B2−0.136B3+0.036B4+0.086B5)g t=a t,σ2a3.(2points)Since not all estimates of model m2are statistically signiﬁ-cant,we reﬁne the model.Write down the reﬁned model,called m3.Answer:Theﬁtted model is=0.000327.(1−0.504B−0.074B2−0.122B3+0.101B5)g t=a t,σ2a4.(2points)Is the reﬁned AR(5)model adequate?Why?Answer:Yes,the Ljung-Box statistics of the residuals give Q(14)=10.27with p-value0.74,indicating that there are no serial correlationsin the residuals.5.(2points)Does the gasoline price show certain business-cycle behavior?Why?Answer:Yes,theﬁtted AR(5)polynomial contains compplex solutions.6.(3points)Next,consider using the information of crude oil price.Writedown the linear regression model,called m4,including R2and residualstandard error.Answer:Theﬁtted linear regression model isg t=0.287p t+ t,σ =0.0184,and the R2of the regression is33.66%.7.(2points)Is theﬁtted linear regression model adequate?Why?Answer:No,because the residuals t are serially correlated based onthe Ljung-Box test.78.(3points)A linear regression model with time series errors is enter-tained and insigniﬁcant parameters removed.Write down theﬁnalmodel,including allﬁtted parameters.Answer:The model is(1−0.404B−0.164B2−0.096B3+0.101B5)(g t−0.191p t)=a t,σ2=0.000253.a9.(2points)Model checking shows that theﬁttedﬁnal model has noresidual serial correlations.Based on the model,is crude oil pricehelpful in predicting the gasoline price?Why?Answer:Yes,because theﬁtted coeﬃcient of p t is signﬁcantly diﬀerentfrom zero.10.(2points)Compare the pure time series model and the regression modelwith time-series errors.Which model is preferred?Why?Answer:The regression model with time series error is preferred as ithas a smaller AIC criterion.8。

33 三十三部分

// "Reset" to prepare for next click being a first click firstClickX = -1; } } /* Continued on next page */
// Returns the minimum of value1 and value2 // Could also use Math.min in place of this method private int min(int value1, int value2) { if (value1 < value2) { return value1; } else { return value2; } } // Returns the maximum of value1 and value2 // Could also use Math.max in place of this method private int max(int value1, int value2) { if (value1 > value2) { return value1; } else { return value2; } } /* Private instance variables */ private GOval oval; private int firstClickX; // X loc. of "first click" in pair (-1 if none) private int firstClickY; // Y loc. of "first click" in pair }
(2b)
What output is printed by the following program: First result: 3 Second result: -5

金融时间序列分析英文试题(芝加哥大学) (3)

Graduate School of Business,University of ChicagoBusiness41202,Spring Quarter2005,Mr.Ruey S.TsaySolutions to MidtermAll tests are based on the5%signiﬁcance level.Problem A:(30pts)Answer brieﬂy the following questions.1.For problems1to6,consider the daily log return,in percentages,of the S&P500composite index from January1996to December31,2004for2267data points.Sum-mary statistics of the percentage log returns from SCA and Splus are attached.See Page 1of the attached output.Is the mean of percentage log returns signiﬁcantly diﬀerent from zero?Why?A:t-ratio=1.187<1.96.Thus,the mean return is not signiﬁcantly diﬀerent from zero.2.Suppose one invested$1dollar on the S&P500index at the very beginning of1996andheld the investment until the end of2004.What was the value of the investment at the market closing on December31,2004?A:total log return=0.0299*2267/100=0.67783so that the value=exp(0.67783)≈1.97.3.Test the null hypothesis that the skewness of the log returns is zero.Draw your conclu-sion.A:t-ratio=−0.0939/0.0514=−1.83<1.96so that the skewness is no signiﬁacnt diﬀerent from zero.4.Given that the last percentage log return was−0.134(i.e.T=December31,2004),which is the corresponding simple return?A:R t=exp(−0.134/100)−1=−0.001339=.1339%.5.Are the log return serially correlated?You may use Q(10)of the series to answer thequestion.A:Q(10)=13.9with p-value0.178so that there is no serial correlation.6.Is there any ARCH eﬀect in the log return series?You may use Q(12)of the squaredseries to answer the question.A:Yes,Q(12)of squared return is large at490(in SCA)and has a p-value of0.0from Splus.7.Give two empirical features of daily log returns of aﬁnancial asset.A:Any two of(a)high kurtosis,(b)volatility clustering,(3)skew to left.18.What is the purpose of studying kurtosis of an asset return series?A:Understanding the tail behavior(or risk)of the return.9.Describe two applications of studying sample autocorrelation function(ACF)of an assetreturn series.A:(a)To test serial correlations in the return series,(b)to identify MA order.10.Describe two methods that can be used to identify the order of an AR model.A:(a)PACF,(b)Criterion functions such as AIC or BIC.11.Consider the AR(1)model(1−0.9B)r t=0.2+a t,where{a t}is an independent andidentically distributed random variables with mean zero and variance1.0.What is the half-life of the series?A:Half-life=ln(0.5)/ln(0.9)=6.58time units.12.Suppose that the log return r t of an asset follows the model below:r t=0.02+a t,a t=σt t,σ2t=0.116+0.42a2t−1.Let p t be the log price of the asset at time t and p T( )be the -step ahead forecast of the log price at the forecast origin T.Then,what is the value of p T( )as increases?A:0.02is the slope of time trend so that p T( )→∞as increases.13.For problems13-14,consider quarterly series of U.S.unit labor cost from1947to2004.The data were seasonally adjusted and obtained from the Federal Reserve Bank of St Louis.Let x t=(1−B)ULC t be theﬁrst-diﬀerenced series of the data at time t.The model(1−0.371B2)x t=0.265+(1+0.171B4)a t,σa=0.5998,ﬁts the data reasonably well.Under theﬁtted model,what is the mean of x t,i.e.E(x t) =?A:E(x t)=0.265/(1−0.371)=0.421.14.Does the model imply that there exist business cycles in the unit labor cost?Why? A:No,because the two roots are real.From1−0.371x2,we have x=±1/ (0.371).15.Give two weaknesses of the GARCH-type of models for modeling asset volatility.A:Any two of(a)symmetric response to past positive and negative returns,(b)restric-tive,(c)providing no explanation of volatility clustering,(d)no adaptive in forecasting.2Problem B.(20pts)This problem is concerned with the analysis of quarterly earnings per share of the Procter&Gamble(PG)Company from1992to theﬁrst quarter of2003 for45data points.The data were obtained from First Call.Log transformation was taken to stabilize the variability of the puter output is attached;p.2-6of output. Due to strong seasonal pattern,which results in models that are close to being non-invertible, we analyze the seasonally diﬀerenced series in Splus.Let x t be the logarithm of quarterly earnings per share and w t=(1−B4)x t.Thus,SCA uses x t and Splus uses w t.1.(5points)Because ACF of the log earnings shows strong seasonal pattern,the seasonaldiﬀerence(1−B4)is taken.The ACF of the seasonally diﬀerenced data indicates no further diﬀerencing is necessary.Write down theﬁtted model for the x t series(not the diﬀerenced w t).A:(1−0.47B)(1−B4)x t=0.0508+(1−0.307B4)a t,σa=0.0502.2.(4points)Is the AR coeﬃcient of theﬁtted model statistically signiﬁcant?Why?A:Yes,the t-ratio is3.26,which is greater than the critical value1.96.3.(4points)Is there any serial correlation in the residuals of theﬁtted model?Use Q(12)of the ACF of residuals to answer the question.[Hint:for a chi-square distribution with m degrees of freedom,the expected value is m.]A:Q(12)=8.8which is less than E(χ210)=10so that p-value>0.05.4.(4points)Let T=45be the forecast origin.What are the1-step and2-step aheadforecasts of theﬁtted model(after taking anti-log transformation)?A:x45(1)=0.912and x45(2)=3.95(from SCA).For Splus,x45(1)=exp(0.0087−.1743)=0.847,x45(2)=exp(−.012479+1.278152)=3.55.5.(3points)Give an interpretation of the estimated constant0.0508of theﬁtted modelfor x t.A;Slope of time trend.3and the S&P500index from January1999to December2004with sample size T=1508.We employ the market model:r t=α+βr m,t+e t,where r t and r m,t are Wal-Mart stock return and S&P500index return,respectively.Splus output is attached;page6of output.Answer the following questions.1.(4points)Write down theﬁtted market model.A:r t=0.0205+0.9606r m,t+e t.2.(4points)The Ljung-Box statistics of the ACF of residuals show some minor serialcorrelations,but the ACFs are relatively small so we ignore the serial correlations and perform the ARCH eﬀect test.Is there an ARCH eﬀect in the residuals of theﬁtted market model?A:Yes,archTest gives a p-value about0.0.3.(4points)We employ a GARCH(1,1)model(called“m2”in the output).Write downtheﬁtted ment on theﬁtted model.A:Let r t and r m,t be the Wal-Mart stock return and S&P500index return,respectively.The model isr t=0.9386r m,t+a t=0.9386+σt t, t∼t6.41σ2t=−4.29×10−5+0.0377a2t−1+0.963σ2t−1.The negative estimate ofα0does not make sense,but it is statistically not diﬀerent from0.Also,theˆα1+ˆβ1≈1so that theﬁtted model indicates an IGARCH(1,1)model without the constant.4.(6points)Further analysis indicates that an EGARCH(2,1)modelﬁts the data better.There are two leverage eﬀect parameters.Are these two eﬀects statistically signiﬁcant?Why?You may test the eﬀect individually.A:Examine the t-ratio of the two leverage parameter estimates.For Lev(1),the t-atio is−2.129.For Lev(2),the t-ratio is−1.847.In both cases,the p-values are less tha0.05so that they are both signiﬁcant.[It you use two-sided tests,then Lev(2)is notsigniﬁcant.]5.(2points)What are the1-step ahead forecasts for the return and its volatility of Wal-Mart stock at the forecast origin T=1508using the EGARCH model.A:zero for return and0.7082for volatility.4from January1995to December2004with2519observations.Splus output is attached;page 8of output.Answer the following questions.The ACFs of the returns are small so that the mean equation consists of a constant term only.1.(5points)Consider theﬁtted GARCH(1,1)model.The volatility equation isσ2t=0.042+0.049a2t−1+0.944σ2t−1.Letηt=a2t−σ2t.Rewrite the prior volatility equation in an ARMA form for the{a2t} series.A:a2t=0.042+0.993a2t−1+ηt−0.944ηt−1.2.(5points)Write down theﬁtted EGARCH(1,1)model with leverage eﬀect(both meanand volatility equations and the parameter of the conditional distribution used).A:The model isr t=0.04918+a t=0.04918+σt t, t∼t6.68ln(σ2t)=−0.06316+0.1033(|a t−1|−0.5464a t−1σt−1)+0.989ln(σ2t−1).3.(4points)Test the hypotheses H o:v=5vs H a:v=5,where v is the degrees offreedom of the conditional Student t distribution.Draw your conclusion.[Hint:you may use the usual t-ratio test.]A;t-ratio=6.684−5=2.62>1.96.Thus,reject H o:v=5.4.(5points)To better understand the leverage eﬀect,use theﬁtted EGARCH(1,1)modelto calculate the ratioσ2t( =−3)2t ,where t denotes the iid sequence of the innovationsdeﬁned in class.A:From theﬁtetd volatility equation,we haveσ2t=exp(−0.06316)(σ2t−1).989exp(0.1033| t−1|−0.0564 t−1). Therefore,σ2t( =−3)σ2t( =3)=exp(−0.0564(−3))exp(−0.0564(3))=exp(0.0564×6)=1.403.5.(4points)Used theﬁtted EGARCH model and T=2519as the forecast origin.Whatare the1-step ahead forecasts of log return and volatility?A:Forecast of log return is0.0492and forecast of volatility is1.184.6.(4points)Write down the mean equation of theﬁtted GARCH-M model for the data.A:r t=0.058+0.00629σ2t+a t.7.(3points)Based on the GARCH-M model,is the risk premium statistically signiﬁcant?Why?A:No,the t-ratio is0.453with p-value=0.65(two-sided).5。

山东省潍坊市大联考2024-2025学年高三上学期10月月考英语试题

山东省潍坊市大联考2024-2025学年高三上学期10月月考英语试题一、阅读理解Mathematics for Computer ScienceThis subject offers an introduction to discrete mathematics(离散数学)oriented toward computer science and engineering.Course Meeting TimesLectures:3 sessions/week, 1. 5 hour/session Problem Sets (psets)Problem sets account for 20% of the final grade. Making a reasonable effort on the problem sets is, for most students, crucial for mastering the course material. Problem sets are designed to be completed in at most 3 hours; the time is monitored through student reports. Online Feedback ProblemsOnline problems to be completed before most class meetings are posted on the class website. These consist of straightforward questions that provide useful feedback about the assigned material. Some students prefer to try the online problems before reading the text or watching videos as an advance guide to going over the material; that’s fine. Watching designated videos, or at least looking at the lecture-slide handouts, is generally helpful but optional.Like team problem-solving in class, online problems are graded only on participation: Students receive full credit as long as they try the problem, even if their answer is wrong. Online feedback problems account for 10% of the final grade. Midterm ExamsThree 80-minute midterm exams will be given. The midterm exams each account for 15%of the final grade.Midterm questions will typically be variations of prior problems from class and psets, and the best way to prepare is to review on the published solutions to these problems. The first exam covers all previous weeks’ material;subsequent exams focus on the material after the previous exam. Final ExamThere will be a three-hour final exam. This exam is worth 25% of the final class grade. The final exam will cover the entire subject with somewhat greater emphasis on material from after Midterm 3. Most exam questions will be variants of problems assigned during the term(psets,class, midterm, and online). It may include a few questions which combine topics that were originally covered separately.1．What determines students’ grade in Online Feedback Problems?A．Active involvement.B．Submission time.C．Accuracy of answers.D．Completion of assignments2．What is the main focus of the final exam?A．Variants of problem sets.B．Combined topics in class.C．The content after midterm exams.D．The whole-term course materials. 3．Which of the following weighs the most in the final grade?A．Final Exam.B．Midterm Exams.C．Problem Sets.D．Online Feedback ProblemsIt all started with a simple question;“Can I paint your portrait (肖像)?”In the summer of 2015, Brian Peterson was reading the book Love Does, about the power of love in action, when his quiet was disturbed by a homeless man. Inspired by the book, Peterson made an unexpected decision: He was going to introduce himself. In that first conversation, Peterson learned that the man’s name was Matt Faris who failed to pursue a career in music and ended up being homeless.“I saw beauty on the face of a man who hadn’t shaved in probably a year, had overgrown fingernails, and probably hadn’t had a shower in close to a year. ”Even though Peterson hadn’t pioked up a paintbrush in about eight years, he asked if he could paint Faris’s portrait. Faris said yes.Peterson’s connection with Faris led him to form Faces of Santa Ana, a nonprofit organization focused on befriending and painting portraits of members of the community who are unhoused. Working from a black-and-white photo of the subject, Peterson chooses colors inspired by the subject’s personality and life story, creating an impressive portrait.Peterson sells the striking artwork, signed by both subject and artist, dividing the proceeds and putting half into what he calls a“love account”for his model. He then helps people use the money to get back on their feet. Many of Peterson’s new friends use the donations to secure immediate necessities. But Peterson has learned not to make assumptions about what a personneeds most. “I’ve made a mistake thinking I knew what people wanted, ” he says, “but why don’t we just ask them?”Peterson has discovered that there’s more to the finished products than the money they bring to someone who’s down and out. The buyers tend to connect to the story of the person in the painting, finding similarities and often friendship with someone they might have otherwise overlooked. “People often tell me, ‘I was the one that would cross the street. But I see homeless people differently now, ’ ”Peterson says.4．What brought Peterson and Faris together?A．Beauty on Faris’ face.B．Inspiration from a book.C．Peterson’s passion for art.D．Faris’ suffering in his life.5．What does the underlined word “mistake” in paragraph 5 refer to?A．Selling the homeless’ portraits for profits.B．Giving instant necessities to the homeless.C．Asking the homeless for their needs directly.D．Taking what the homeless want for granted.6．What does Peterson imply in the last paragraph?A．The homeless are gaining more concern.B．The life of the homeless is different now.C．Buyers value friendship with the homeless.D．Figures in Peterson’s paintings are popular.7．What can we learn from this text?A．A good model is key to a fine artwork.B．An expected decision makes a great artist.C．A picture really is worth a thousand words.D．Each unfortunate person has his own misfortune.The Malagasy baobab tree, whose thick trunks and tiny branches dot Madagascar’s landscape, should not, by rights, have survived to the present day. Scientists believe that its large seeds were once spread by the giant tortoises and lemur monkeys that wandered the island. When these species went extinct over one thousand years ago owing to human activity, the baobab treeshould have disappeared too. It did not. Seheno Andriantsaralaza at the University of Antananarivo and Onja Razafindratsima at the University of California, now think they may know the reason why.Together with their colleagues, the scientists monitored 15 tree canopies (树冠) in a western region of Madagascar, to identify any animals that might have claimed the role of baobab-seed spread. The researchers also set up camera traps around seed-containing fruits lying on the ground, and searched any faeces (粪便) that they encountered along the way for the presence of seeds.They report in the journal Biotropica that a native rodent (啮齿动物) known as the western bunch-tailed rat was caught on camera handling whole fruits on four occasions. Although there was no footage of the rat breaking the fruits open, the team did chance upon 13 fruits that had been chewed into and had their seeds removed. Though the bite marks were not clear enough to identify an initiator, this was clear evidence that a seed- distributing animal was out there. They then found the ecological equivalent of a smoking gun:baobab seeds in seven different piles of bush-pig faces.While the finding is important in its own right, it also provides valuable evidence that introduced species may not be entirely harmful. Madagascar’s pigs, for example, though not native, have made themselves essential to the survival of truly native species. Similar relationships are suspected to hold in South America between rabbits native to Europe and plants with no seed distributors. For Dr Andriantsaralaza, that suggests the full ecological role of introduced species should be considered before talk of extinction begins.8．What made scientists think the baobab tree should have disappeared?A．The extinction of its seed spreader.B．The destruction of human activitiesC．The inadaptation of the baobab tree.D．The increase of its natural enemies. 9．What are camera traps used for?A．Seeking seed-containing fruits.B．Tracking the footprints of seeds.C．Recording the animals’ activities.D．Monitoring the baobab tree canopies. 10．Which is most probably the seed-eater according to the report?A．The giant tortoise B．The bunch-tailed rat.C．The European rabbit.D．The bush-pig.11．What is the author’s purpose in writing the text?A．To introduce a new way to protect the baobab tree.B．To show non-native species are not always harmful.C．To compare different kinds of seed-distributing methods.D．To explain the importance of protecting endangered species.The concepts of delayed satisfaction, self-control, and self-regulation are often used interchangeably and inconsistently. The ability to delay an impulse (冲动) for an immediate reward to receive a more favorable reward at a later time is the standard definition of delayed satisfaction.Studies show that delayed satisfaction is one of the most effective personal characteristics of successful people. People who learn how to manage their need to be satisfied in the moment develop more in their careers, relationships, health, and finances than people who give in to it.Being able to delay satisfaction isn’t the easiest skill to acquire. It involves feeling dissatisfied, which is why it seems impossible for people who haven’t learned to control their impulses. Choosing to have something now might feel good, but making the effort to have discipline and manage your impulses can result in bigger or better rewards in the future. Over time, delayed satisfaction will improve your self-control and ultimately help you achieve your long-term goals faster.The Seinfeld Strategy is one of several helpful self-satisfaction techniques you can use to put off satisfaction for longer periods of time. Every day that you delay satisfaction and avoid temptation (诱惑) , you cross it off your calendar. After a few days, this creates a chain. This strategy works well for people who enjoy gamification (游戏化). If you find it satisfying to keep the chain going, you’re less likely to give in to temptation.Do you find yourself going back to your temptations without thinking about it?If this is the case, you can practice mindfulness to become more aware of what you do. When you notice yourself doing something out of habit, stop for a moment. Ask yourself why you’re doing what you’re doing. Take some time to analyze how you’re feeling. Pay attention to the details. Take a moment of mindulness to interrupt your autopilot every time this happens. The more you practice this, the more you’ll break the habit of going for instant satisfaction.12．What is delayed satisfaction?A．Making quick decisions.B．Giving in to desires instantly.C．Immediate rewards for impulses.D．Postponing rewards for better outcomes. 13．Why is delayed satisfaction hard to attain?A．It can lead to missed opportunities B．It’s bad for achieving long-term goals.C．It’s impossible to resist the inner needs D．It’s a comfort to possess something at once. 14．What does paragraph 4 mainly talk about?A．The complexity of the Seinfeld Strategy B．An example of self-discipline techniques.C．A method of practicing delayed satisfaction.D．The effectiveness of keeping the chain going.15．What does the author suggest people do for returning temptations?A．Ignore useless details.B．Get rid of old bad habits.C．Concentrate on true inner wants.D．Cancel temptations from the calendar.Facing hard things is, well, hard. Sometimes we are forced to simply shift, such as with a loss or failure; however, much of the time, we may recognize the difficulties underneath that need attention but feel too overwhelmed to address them. 16 The difficulties might be an outdated habit, a troubling memory or a long- ignored conflict.Some individuals fool themselves into thinking there really is not a problem. It’s like someone trying to hold active mice under a blanket by holding down the edges of the moving blanket. Pulling back the blanket to let the mice out is needed, despite being terrifying. Once the mice are released, there may be further challenges to get them out of the house. 17 People often encounter similar problems. Avoiding or leaving the situation appears to fix the problem but fails to tackle the underlying cause. Rather than repeatedly cutting weeds, getting down on the ground and pulling the roots is more effective. Facing issues is like uncovering roots for new beginnings to blossom. 1819 It feels like a balled-up mess of wires. Pulling hard at only one wire actually tightens the knot. We have to take a calmer look and pull apart each wire one at a time. We can’t expect the wires to loosen or unwind themselves. 20 Nevertheless, once they have been freed, they can sometimes be separated, put aside, and used as needed. A．They are just there and part of the chaos.B．And humans are masters of avoidance and denial.C．The overall benefits from tough work enable growthD．Making changes in one’s life is hard and complicated.E．Sadly, it often worsens when we approach it with anger.F．However, problems cannot be faced if they are not first recognized.G．Quick fixes might provide relief in the short term but often not in the long term.二、完形填空Madeline sat on her bed and tried to write. Tears dropped onto the page, making the ink 21 . Her best friend was moving, and her heart 22 as she penned how much she would miss him.She heard her mother speaking downstairs, but the words were 23 . This was a 24 , as her mother said, “Kids her age don’t know what love is!”Uncle Joe responded in a low tone. 25 , Madeline couldn’t catch what was said. She continued to write until she reached the end and 26 , she laid her head on the pillow and sobbed. Then, she felt a 27 hand on her shoulder. “It’s going to be okay. You can 28 each other, right?” Madeline 29 her head. “Mom says I’m not old enough for a phone.”Uncle Joe answered 30 , “But I’m friends with Leo’s dad. Your mom said you can talk to Leo on my phone. Plus, I gave her his number.” He didn’t tell her that her mom had thought it all silly and unnecessary.Madeline 31 , throwing her arms around Uncle Joe’s neck. “Thank you!”“No problem.” His eyes fell on the 32 . “Want me to ensure this gets to Leo?” Madeline nodded “Feel like playing a game? I promise I won’t mess around.”Madeline smiled — small but 33 .Uncle Joe wouldn’t read the letter; she 34 him. A sure thing was that his sister was mistaken. Though only eight, Madeline and Leo shared a pure, innocent bond — untouched by 35 .21．A．emerge B．bleed C．leak D．escape 22．A．raced B．hesitated C．ached D．melted23．A．indistinct B．sharp C．pale D．impolite 24．A．burden B．warning C．bonus D．blessing 25．A．Instead B．Anyway C．Again D．Moreover 26．A．worried B．confused C．bored D．exhausted 27．A．comforting B．firm C．smooth D．trembling 28．A．greet B．call C．miss D．visit 29．A．dropped B．shook C．covered D．touched 30．A．proudly B．slowly C．quietly D．casually 31．A．sat up B．turned over C．looked up D．bent down 32．A．toy B．phone C．note D．pen 33．A．friendly B．genuine C．unique D．tight 34．A．refused B．begged C．respected D．trusted 35．A．romance B．doubt C．mood D．status三、语法填空阅读下面短文，在空白处填入1个适当的单词或括号内单词的正确形式。

七年级下册英语作文期中必考,1到6单元

七年级下册英语作文期中必考,1到6单元全文共3篇示例，供读者参考篇1Title: Midterm Exam on Units 1-6 of Grade 7 English in the Second SemesterIntroduction:The midterm exam for the Grade 7 English class covers Units 1 to 6 of the second semester. This exam will assess the students' understanding and mastery of various English language skills, including reading, writing, listening, and speaking. In this document, we will provide an overview of the exam structure and the key topics that students should focus on for each unit.Unit 1: Family and FriendsIn this unit, students will be expected to demonstrate their ability to talk about family members, describe people's appearances and personalities, and talk about daily routines. Practice activities may include interviewing classmates about their families, writing short biographies of family members, and participating in role plays about daily routines.Unit 2: School and EducationIn Unit 2, students will focus on vocabulary related to school subjects, school facilities, and extracurricular activities. They will also practice talking about their school schedules, likes and dislikes about school, and future plans for education. Activities may include creating a mock school timetable, discussing favorite subjects with classmates, and giving presentations on future career goals.Unit 3: Hobbies and InterestsUnit 3 explores the topic of hobbies and interests. Students will learn vocabulary related to different hobbies, recreational activities, and leisure time. They will practice talking about their own hobbies, discussing favorite pastimes with classmates, and planning social activities. In-class activities may include creating a poster about a favorite hobby, participating in group debates on the benefits of different hobbies, and writing a journal entry about a recent leisure activity.Unit 4: Travel and AdventureUnit 4 focuses on vocabulary related to travel destinations, modes of transportation, and holiday activities. Students will practice talking about past travels, future vacation plans, andcultural experiences. Activities may include planning a dream vacation with a partner, writing a travel blog post about a recent trip, and giving a presentation on a famous tourist destination.Unit 5: Health and Well-beingIn this unit, students will learn vocabulary related to health, fitness, nutrition, and personal hygiene. They will practice discussing healthy habits, giving advice on staying fit, and expressing concerns about well-being. In-class activities may include creating a healthy meal plan, debating the benefits of different exercise routines, and role-playing conversations at the doctor's office.Unit 6: Environment and SustainabilityUnit 6 explores the topic of environmental issues, conservation efforts, and sustainable living practices. Students will learn vocabulary related to environmental problems, recycling initiatives, and green technologies. They will practice discussing ways to protect the environment, participating in eco-friendly projects, and raising awareness about environmental issues. Activities may include organizing a campus clean-up event, researching renewable energy sources, and presenting solutions to reduce carbon footprint.Conclusion:The midterm exam for Grade 7 English will test students' knowledge and skills in Units 1-6 of the second semester. By focusing on the key topics and practicing various language activities, students can prepare themselves for success on the exam and improve their overall English proficiency. Good luck to all the students preparing for the exam!篇2Title: Midterm Exam Preparation for Grade 7, Units 1-6Dear students,As the midterm exam for the second semester approaches, it is crucial to prepare thoroughly for the upcoming test. In this letter, I will provide you with an overview of the key topics covered in Units 1 to 6 of the Grade 7 English textbook and offer some study tips to help you perform well on the exam.Unit 1: FriendshipIn Unit 1, we learned about different aspects of friendship such as trust, loyalty, and support. Make sure to review vocabulary related to emotions and qualities of a good friend, aswell as grammar structures like comparative and superlative adjectives.Unit 2: HobbiesThis unit focused on discussing hobbies and interests. Practice talking about your hobbies using present simple tense and adverbs of frequency. Review vocabulary related to leisure activities and sports.Unit 3: TravelIn Unit 3, we explored different modes of transportation and how to ask for directions. Pay attention to phrases for giving and following directions, as well as vocabulary related to travel and sightseeing.Unit 4: HealthThis unit covered topics related to health and well-being. Review vocabulary related to healthy habits and lifestyle choices. Practice using vocabulary and phrases for describing symptoms and visiting a doctor.Unit 5: EnvironmentUnit 5 focused on environmental issues and ways to protect the planet. Make sure to review vocabulary related toenvironmental problems, recycling, and conservation. Practice discussing solutions to environmental problems using modal verbs.Unit 6: FestivalsIn Unit 6, we learned about different festivals and celebrations around the world. Review vocabulary related to traditional holidays and customs. Practice discussing your favorite festival using past simple tense and adjectives for describing events.Study Tips:- Create a study schedule and allocate time to review each unit.- Practice listening and speaking by watching English videos or talking with a friend.- Use flashcards to memorize vocabulary and grammar structures.- Complete practice exercises and past exam papers to test your understanding.- Get plenty of rest and eat a healthy meal before the exam to stay focused and energized.Remember, preparation is key to success. Good luck with your midterm exam, and keep up the hard work!Sincerely,[Your Name]篇3The mid-term exam for the second semester of seventh grade English will cover Units 1 to 6. In order to prepare for this exam, students should review the key vocabulary, grammar points, and reading comprehension skills that have been taught in these units.In Unit 1, students learned about daily routines and healthy habits. They should be familiar with the present simple tense, adverbs of frequency, and the vocabulary related to health and fitness. Reviewing the key phrases and sentences from this unit will help students in the exam.Unit 2 focused on describing people and places. Students studied adjectives, comparative and superlative forms, and prepositions of place. Practicing describing people and places using the vocabulary from this unit will be essential for the exam.In Unit 3, students learned about leisure activities and the past simple tense. They should review the irregular verbs and phrases related to hobbies and free time activities. Being able to talk about what they did last weekend or during their last holiday will be important for the exam.Unit 4 covered shopping and making suggestions. Students should review the vocabulary related to clothes, prices, and offers. They also studied modal verbs for making suggestions and giving advice. Practicing making suggestions androle-playing shopping scenarios will be helpful for the exam.In Unit 5, students studied daily routines and the present continuous tense. They should review the present continuous tense for actions happening now, as well as the vocabulary for daily routines. Practicing describing what they are doing at the moment will be important for the exam.Unit 6 focused on talking about future plans and predictions. Students learned about the future simple tense and using “be going to” for future intentions. Reviewing how to talk about their future plans and predictions using the vocabulary from this unit will be essential for the exam.In addition to reviewing the key points from each unit, students should also practice reading comprehension skills. Theywill be tested on their ability to understand and analyze passages, answer questions, and make inferences based on the information provided. It is important for students to read and practice with a variety of texts in order to improve their reading comprehension skills.Overall, in order to do well on the mid-term exam for the second semester of seventh grade English, students should review the key vocabulary, grammar points, and reading comprehension skills from Units 1 to 6. By practicing and preparing effectively, students can feel confident and perform well on the exam.。

Midterm 1 practice question solutions

4-24(20-25 min.)Job costing, budgeted rates, unit costs.1. Budgeted MOH Rate = Budgeted Manufacturing Overhead Costs Budgeted Direct Labour Hours-= $632,000/32,000= $19.75 per direct labour-hourJob X905:Direct Materials $13,200Direct Labour $10,120Overhead Allocated–460 hours @ $19.75 $9,085Total $32,405# of units 600Unit Cost $54.01# of Direct Labour-Hours on Job X905 = Direct Labour Costs/Hourly Rate= $10,120/$22 = 460 hours2.To achieve a margin of 25%, the selling price must be $72.01 (rounded down)USP – Unit Cost = 0.25USPUSP –$54.01 = 0.25USP0.75USP = $54.01USP = $54.01/0.75 = $72.01 (rounded down) 3.Under- or overallocated overhead = Actual Overhead – Allocated OverheadUnder- or overallocated overhead = $656,125 – ($19.75 ⨯ 34,100)Under- or overallocated overhead = $656,125 – $673,475Overhead is overallocated by $17,350.5-37(30–40 min.) Activity-based costing, merchandising.1. GeneralSupermarket Chains DrugstoreChainsMom-and-PopSingleStores TotalRevenue $3,708,000 $3,150,000 $1,980,000 $8,838,000Cost of goods sold 3,600,000 3,000,000 1,800,000 8,400,000Gross margin $ 108,000 $ 150,000 $ 180,000 $ 438,000Other operating costs 301,080 Operating income $ 136,920Gross margin % 2.91% 4.76% 9.09%The gross margin of Pharmacare Inc. was 4.96% (= $438,000 ÷ $8,838,000). The operating income margin of Pharmacare Inc. was 1.55% (= $136,920 ÷ $8,838,000).1.The per-unit cost driver rates are:1. Customer purchase order processing,$80,000 ÷ 2,000 (140 + 360 + 1,500) orders = $40 per order2. Line item ordering,$63,840 ÷ 21,280 (1,960 + 4,320 + 15,000) line items = $3 per line item3. Store delivery,$71,000 ÷ 1,480 (120 + 360 + 1,000) deliveries = $47.973 per delivery4. Cartons shipped,$76,000 ÷ 76,000 (36,000 + 24,000 + 16,000) cartons = $1 per carton5. Shelf-stocking,$10,240 ÷ 640 (360 + 180 + 100) hours = $16 per hour2.The activity-based costing of each distribution market for August 2015 is:GeneralSupermarket Chains DrugstoreChainsMom-and-PopSingleStores Total1. Customer purchase orderprocessing($40 ⨯ 140; 360; 1,500) $ 5,600 $14,400 $ 60,000 $ 80,000 2. Line item ordering($3 ⨯ 1,960; 4,320; 15,000) 5,880 12,960 45,000 63 ,840 3. Store delivery($47.973 ⨯ 120; 360; 1,000) 5,757 17,270 47,973 71,000 4. Cartons shipped($1 ⨯ 36,000; 24,000; 16,000) 36,000 24,000 16,000 76,000 5. Shelf-stocking($16 ⨯ 360; 180; 100) 5,760 2,880 1,600 10,240$58,997 $71,510 $170,573 $301,080The revised operating income statement is:General Mom-and-PopSupermarket Drugstore SingleChains Chains Stores Total Revenue $3,708,000 $3,150,000 $1,980,000 $8,838,000Cost of goods sold 3,600,000 3,000,000 1,800,000 8,400,000 Gross margin 108,000 150,000 180,000 438,000 Operating costs 58,997 71,510 170,573 301,080 Operating income $ 49,003 $ 78,490 $ 9,427 $ 136,920Operating income margin 1.32% 2.49% 0.48% 1.55%4. The ranking of the three markets are:Using Gross Margin Using Operating Income1. Mom-and-Pop Single Stores 9.09% 1. Drugstore Chains2.49%2. Drugstore Chains 4.76% 2. General Supermarket Chains 1.32%3. General Supermarket Chains 2.91% 3. Mom-and-Pop Single Stores 0.48%The activity-based analysis of costs highlights how the Mom-and-Pop Single Stores use a larger amount of Pharmacare’s resources per revenue dollar than do the other two markets. The ratio of the operating costs to revenue across the three markets is:General Supermarket Chains 1.59% ($58,997 ÷ $3,708,000)Drugstore Chains 2.27% ($71,510 ÷ $3,150,000)Mom-and-Pop Single Stores 8.61% ($170,573 ÷ $1,980,000)This is a class ic illustration of the maxim that “all revenue dollars are not created equal.” The analysis indicates that the Mom-and-Pop Single Stores are the least profitable market. Pharmacare should work to increase profits in this market through: (1) a possible surcharge, (2) decreasing the number of orders,(3) offering discounts for quantity purchases, etc.Other issues for Pharmacare to consider include:a. Choosing the appropriate cost drivers for each area. The problem gives acost driver for each chosen activity area. However, it is likely that overtime further refinements in cost drivers would occur. For example, not allstore deliveries are equally easy to make, depending on parkingavailability, accessibility of the storage/shelf space to the delivery point,etc. Similarly, not all cartons are equally easy to deliver—their weight,size, or likely breakage component are factors that can vary across cartontypes.b. Developing a reliable data base on the chosen cost drivers. For someitems, such as the number of orders and the number of line items, thisinformation likely would be available in machine readable form at a highlevel of accuracy. Unless the delivery personnel have hand-heldcomputers that they use in a systematic way, estimates of shelf-stockingtime are likely to be unreliable. Advances in information technology likelywill reduce problems in this area over time.c. Deciding how to handle costs that may be common across severalactivities. For example, (3) store delivery and (4) cartons shipped to storeshave the common cost of the same trip. Some organizations may treat (3)as the primary activity and attribute only incremental costs to (4).Similarly, (1) order processing and (2) line item ordering may havecommon costs.d. Behavioural factors are likely to be a challenge to Flair. He must now tellthose salespeople who specialize in Mom-and-Pop accounts that theyhave been less profitable than previously thought.6-24(15-20 min.)Revenue, production, and purchases budget.1. 985,000 motorcycles ⨯ 505,000 yen = 497,425,000,000 yen2. Budgeted sales (units) 985,000Add target ending finished goods inventory 115,000Total requirements 1,100,000Deduct beginning finished goods inventory 152,000Units to be produced 948,0003. Direct materials to be used in production, 948,000 ⨯ 2 1,896,000Add target ending direct materials inventory 28,000Total requirements 1,924,000Deduct beginning direct materials inventory 19,000Direct materials to be purchased 1,905,000Cost per wheel in yen 21,300Direct materials purchase cost in yen 40,576,500,000Note the relatively small inventory of wheels. In Japan, suppliers tend to be located very close to the major manufacturer. Inventories are controlled by just-in-time (JIT) and similar systems. Indeed, some direct materials inventories are almost nonexistent.8-16(20 min.) Variable manufacturing overhead, variance analysis.1. Variable Manufacturing Overhead Variance Analysis for Young Clothing forJune 2015Actual CostsIncurredActual Input Qty. × Actual Rate(1) Actual Input Qty.× Budgeted Rate(2)Flexible Budget:Budgeted Input Qty.Allowed forActual Output× Budgeted Rate(3)Allocated:Budgeted Input Qty.Allowed forActual Output× Budgeted Rate(4)1(4,536 × $11.50) $52,164 (4,536 × $12)$54,432(4 × 1,080 × $12)$51,840(4 × 1,080 × $12)$51,8402. Young had a favourable rate variance of $2,268 because the actual variableoverhead rate was $11.50 per direct manufacturing labour-hour versus $12 budgeted. It had an unfavourable efficiency variance of $2,592 U because each suit averaged 4.2 labour-hours (4,536 hours ÷ 1,080 suits) versus 4.0 budgeted labour-hours.$324 U17-30 (20-25 min.) Standard-costing method, assigning costs.1.SOLUTION EXHIBIT 17-30ASteps 1 and 2: Summarize Output in Physical Units and Compute Output in Equivalent Units; Standard Costing Method of Process Costing for Bucky’s Boxes for July 2015(Step 1) (Step 2)Equivalent UnitsFlow of ProductionPhysical Units Direct Materials Conversion Costs Work in process, beginning (given) Started during current period (given) To account for185,000 465,000 650,000 (work done before current period) Completed and transferred out during current period: From beginning work in process §185,000 ⨯ (100% - 100%); 185,000 ⨯ (100% – 25%) 185,000 0138,750Started and completed327,000 100%, 327,000 100% 327,000† 327,000327,000Work in process, ending* (given) 138,000 100%; 138,000 80% 138,000 _______ 138,000 110,400 Accounted for650,000 _______ _______ Work done in current period only 465,000 576,150§Degree of completion in this department: direct materials, 100%; conversion costs, 25%.†512,000 physical units completed and transferred out minus 185,000 physical units completed and transferred out from beginning work-in-process inventory.*Degree of completion in this department: direct materials, 100%; conversion costs, 80%.⨯⨯⨯⨯2.SOLUTION EXHIBIT 17-30BSteps 3, 4, and 5: Summarize Total Costs to Account For, Compute Cost per Equivalent Unit, and Assign Total Costs to Units Completed and to Units in Ending Work in Process; Standard Costing Method of Process Costing for Bucky’s Boxes for July 2015TotalProduction CostsDirectMaterialsConversionCosts(Step 3) Work in process, beginning (given) $ 337,625 $240,500 + $ 97,125 Costs added in current period at standardcosts1,814,415 (465,000 ⨯ $1.30) + (576,150 ⨯ $2.10) Total costs to account for $2,152,040 $845,000 + $1,307,040 (Step 4) Standard cost per equivalent unit (given) $ 1.30 $ 2.10 (Step 5) Assignment of costs at standard costs:Completed and transferred out (512,000 units):Work in process, beginning (185,000 units) Costs added to beg. work in process in current periodTotal from beginning inventory $ 337,625291,375629,000$240,500 + $97,125(0* ⨯ $1.30) + (138,750* ⨯ $2.10)Started and completed (327,000 units) Total costs of units transferred out 1,111,8001,740,800(327,000†⨯ $1.30) + (327,000† ⨯ $2.10)Work in process, ending (138,000 units) 411,240 (138,000# ⨯ $1.30) + (110,400# ⨯ $2.10) Total costs accounted for $2,152,040 $845,000 + $1,307,040Summary of variances for current performance: Costs added in current period at standard costs (see Step 3 above)Actual costs incurred (given)Variance $604,500607,500$ 3,000 U$1,209,9151,207,415$ 2,500 F*Equivalent units to complete beginning work in process from Solution Exhibit 17-30A, Step 2.†Equivalent units started and completed from Solution Exhibit 17-30A, Step 2.#Equivalent units in ending work in process from Solution Exhibit 17-30A, Step 2.PROBLEMS17-31(25 min.) Weighted-average method.1. Since direct materials are added at the beginning of the assembly process, theunits in this department must be 100% complete with respect to direct materials.Solution Exhibit 17-31A shows equivalent units of work done to date:Direct materials 25,000 equivalent unitsConversion costs 24,250 equivalent unitsSOLUTION EXHIBIT 17-31ASteps 1 and 2: Summarize Output in Physical Units and Compute Output in Equivalent Units; Weighted-Average Method of Process Costing, Assembly Department of Larsen Corp., for October 2015.(Step 1) (Step 2)Equivalent UnitsPhysical Direct Conversion Flow of Production Units Materials Costs Work in process, beginning (given) 5,000Started during current period (given) 20,000To account for 25,000Completed and transferred outduring current period 22,500 22,500 22,500Work in process, ending* (given) 2,5002,500 ⨯ 100%; 2,500 ⨯ 70% 2,500 1,750 Accounted for 25,000Work done to date 25,000 24,250*Degree of completion in this department: direct materials, 100%; conversion costs, 70%.2. &3. Solution Exhibit 17-31B summarizes the total assembly department costs forOctober 2015, calculates cost per equivalent unit of work done to date, and assigns these costs to units completed (and transferred out) and to units in ending work in process using the weighted-average method.SOLUTION EXHIBIT 17-31BSteps 3, 4, and 5: Summarize Total Costs to Account For, Compute Cost per Equivalent Unit, and Assign Total Costs to Units Completed and to Units in Ending Work in Process; Weighted-Average Method of Process Costing, Assembly Department of Larsen Corp., for October 2015TotalProduction CostsDirectMaterialsConversionCosts(Step 3) Work in process, beginning (given) $1,652,750 $1,250,000 $ 402,750 Costs added in current period (given) 6,837,500 4,500,000 2,337,500 Total costs to account for $8,490,250 $5,750,000 $2,740,250 (Step 4) Costs incurred to date $5,750,000 $2,740,250 Divide by equivalent units of work done to date(Solution Exhibit 17-31A) ÷ 25,000 ÷ 24,250 Cost per equivalent unit of work done to date $ 230 $ 113 (Step 5) Assignment of costs:Completed and transferred out (22,500units)$7,717,500 (22,500* ⨯ $230) + (22,500*⨯ $113) Work in process, ending (2,500 units) 772,750 (2,500† ⨯ $230) + (1,750†⨯ $113)Total costs accounted for $8,490,250 $5,750,000 + $2,740,250*Equivalent units completed and transferred out from Solution Exhibit 17-31A, Step 2. †Equivalent units in work in process, ending from Solution Exhibit 17-31A, Step 2.。

2024年八下英语月考最爱考的作文沪教版

2024年八下英语月考最爱考的作文沪教版The year 2024 marks a significant milestone in the educational landscape as the highly anticipated Grade 8 Midterm Exam approaches. For students and educators alike, this examination holds immense importance, serving as a crucial checkpoint in their academic journey. Among the various components of the exam, the English essay section has consistently been a focal point, challenging students to showcase their linguistic prowess and analytical skills.In the context of the Shanghai Edition of the exam, the essay prompt has garnered considerable attention and speculation. Educators and students alike have been meticulously analyzing the trends and patterns of previous exams, seeking to uncover the most likely topic that will be featured in the 2024 Midterm. Based on the comprehensive analysis of past exam papers, the consensus among experts suggests that the most favored essay topic for the 2024 Grade 8 Midterm Exam (Shanghai Edition) will be "The Importance of Environmental Protection in the 21st Century".The rationale behind this prediction lies in the growing globalemphasis on environmental sustainability and the urgent need to address the pressing environmental challenges faced by our planet. In recent years, the Chinese government has made significant strides in its commitment to environmental protection, with a range of policies and initiatives aimed at reducing carbon emissions, promoting renewable energy, and preserving natural habitats. This heightened focus on environmental stewardship has also permeated the education system, with a greater emphasis on environmental education and the integration of environmental themes across various academic disciplines.Furthermore, the 2024 Midterm Exam is expected to align with the broader educational objectives set forth by the Shanghai Municipal Education Commission. These objectives prioritize the development of critical thinking, problem-solving skills, and a deep understanding of global issues, all of which are closely tied to the topic of environmental protection. By tasking students with crafting a well-structured and thoughtful essay on this subject, the exam aims to assess their ability to analyze the multifaceted aspects of environmental preservation, propose viable solutions, and demonstrate their mastery of English language skills.To excel in this anticipated essay prompt, students will need to demonstrate a comprehensive understanding of the environmental challenges facing our world. This includes, but is not limited to, theimpact of climate change, the depletion of natural resources, the loss of biodiversity, and the growing issue of plastic pollution. Additionally, students will be expected to explore the various strategies and initiatives undertaken by governments, organizations, and individuals to address these environmental concerns, and to critically evaluate their effectiveness.One of the key elements that examiners will be looking for in the essays is the students' ability to propose innovative and practical solutions to environmental problems. This may involve discussing the role of renewable energy sources, sustainable urban planning, circular economies, or educational campaigns aimed at fostering environmental awareness among the general public. By showcasing their creativity, critical thinking, and problem-solving skills, students will be able to make a strong impression on the exam graders.Furthermore, the essay prompt is likely to encourage students to consider the global implications of environmental protection and the importance of international cooperation in addressing these challenges. Students may be asked to examine case studies of successful environmental initiatives implemented in other countries, and to explore how these strategies can be adapted and applied within the Chinese context. By demonstrating a nuanced understanding of the global nature of environmental issues, students will be able to strengthen the depth and relevance of theirarguments.In addition to the substantive content of the essay, examiners will also place a significant emphasis on the quality of the students' English language skills. This includes their ability to organize their thoughts coherently, construct well-developed paragraphs, employ a diverse vocabulary, and maintain grammatical accuracy throughout the essay. Students who can seamlessly integrate their environmental knowledge with polished English writing will be able to maximize their scores and stand out among their peers.To prepare for this anticipated essay prompt, students are encouraged to engage in a comprehensive review of environmental topics, familiarize themselves with relevant case studies and data, and practice their essay-writing skills. This may involve conducting extensive research, participating in group discussions, and seeking feedback from teachers and peers to refine their writing abilities.By embracing the challenge of the 2024 Grade 8 Midterm Exam (Shanghai Edition) and dedicating themselves to the mastery of environmental protection as an essay topic, students will not only showcase their academic prowess but also contribute to the broader societal effort to safeguard our planet for generations to come. As the exam approaches, the anticipation and excitement amongstudents and educators alike will continue to grow, setting the stage for a truly remarkable educational experience.。

来自曼彻斯特大学的经典实验技术

University of Manchester Department of ChemistryProcedures and Methods Sheet: 001Classic TechniquesThis P&M sheet is 5 pages long.Eating, drinking and smoking and application of cosmetics are forbidden in all labs. Mouth pipetting is forbidden.Handling of Toxic and Carcinogenic ChemicalsThe researcher should become familiar with the hazards involved in handling specific compounds. This should be in consultation with your supervisor and with reference to pertinent literature. Useful sources of information on the toxicity of specific compounds are The Sigma-Aldrich Library of Chemical Safety Data, the BDH Hazards Data Sheets, manufacturers’ Hazard Data Sheets, the RSC publication Hazards in the Chemical Laboratory and manufacturers’ chemical catalogues. Manufacturers Data Sheets delivered with the chemicals are available at the stores counter. Manufacturers Data Sheets received later are available from the Secretary to the Safety&Housekeeping Committee.The necessary COSHH documentation should be completed and signed by the researcher and supervisor before embarking upon reactions with any potentially hazardous chemical. If your supervisor is not available or is away seek out an alternate, responsible, member of staff in order to check the safety assessment. Chemicals which have not had their toxicity assessed should be regarded as being toxic and the necessary precautions taken. The COSHH assessment acts both as a risk assessment for the chemicals concerned but also as a record of exposure levels to potentially hazardous materials.Researchers in the laboratory may be exposed to harmful dusts and vapours which can enter the lungs via the mouth and nose. These can damage the lungs directly, e.g. chlorine; can cause allergic responses e.g. rosin; can cause systemic poisoning, e.g. lead, cadmium. The amount of contaminant in a laboratory-worker's breathing-zone must be controlled as far as is reasonably practicable.For many substances, limits of exposure have been laid down and are listed in HSE Guidance Note EH 40 'Occupational Exposure Limits'. These limits are not safe dividing lines between safe and unsafe. For some substances such as carcinogens, ill effects may result after low level exposure for only a short period. The absence of an occupational exposure limit does not mean that a substance poses no hazard. For many substances "good/bad" data does not currently exist on which to make a judgement.EH 40 refers to two types of limits. Certain substances are listed as having:a)Maximum Exposure Limit: here the exposure to the substance must not exceed the stated figure andattempts must be made to reduce the ambient level to as low a level as possible.b)Occupational Exposure Standard: this is an advisory figure. Minor excursions in level are permittedprovided the average level complies. Monitoring of atmospheric contamination levels is available by arrangement with the Chief Technician.Provided experiments are carried out in fume cupboards with adequate extract flow rates atmospheric monitoring should not normally be necessary.Exposure can occur by the following means:a)Inhalation of dust or vapour;b)Absorption through the skin or mucosal surfaces;c)Ingestion from contaminated hands;d)Absorption from contaminated clothing;e)Contact with contaminated benches, floors and apparatus;f)Contamination of the eyes.Proactive protective measures are thus intended to prevent any contact with the chemical through the lungs, eyes, mouth, skin or mucosal surfaces.Other handling precautions:1)Ensure all containers are correctly labelled and stored appropriately. Keep containers closed when notin use.2)Use a fume cupboard to prevent inhalation of gases, vapours and dusts. Toxic chemicals should beweighed out in a fume cupboard not out in the open lab. Pull the sash of the fume cupboard down when transferring/weighing toxic materials in order to minimise contamination of the lab. Always weara buttoned-up laboratory lab coat when handling such materials. When uncertain as to the thermalstability/shock sensitivity of the compound place an additional safety shield between the sample and the sash of the fume cupboard. All subsequent manipulations of toxic compounds should be carried out in a fume cupboard.3)In certain cases, e.g. when using pyrophoric reagents (see Unstable and Highly Reactive Compoundsbelow), weighing and transfer should be conducted under an inert atmosphere in a glove bag or its equivalent.4)Use gloves to prevent contact with the skin. Where appropriate the use of inspection gloves underheavy-duty gloves may be deemed necessary in order to facilitate disposal of the over gloves without contamination of the researcher.5)Ensure that suitable emergency equipment is readily available.6)At any sign of illness get immediate medical advice.7)Consider others, e.g. cleaners, contractors, window cleaners, fellow workers.8)Inform a colleague of the substance(s) in use.9)Do not work alone.10)Make proper arrangements for decontamination of equipment and for waste disposal.11)Anyone who feels they may have been exposed to such a substance may seek advice from theUniversity Occupational Physician (internal 6971).Unstable and Highly Reactive CompoundsResearchers should check the reactivity of all chemicals used in Bretherick's ‘Handbook of Reactive Chemical Hazards’ available from the Schunk Library.Reactive chemical hazards involve the release of energy at a rate too great to be dissipated by the immediate environment: an explosion can therefore occur. Where highly reactive chemicals are used plans should be made to minimise the foreseeable risks and measures taken to provide adequate personal protection. Most accidents caused by the use of highly reactive chemicals are due to lack of awareness of the reactivity of chemicals used and the effects of physiochemical factors upon the kinetics of the reaction system.The following factors should be taken in to consideration:1)Quality of materials used.2)Control of temperature.3)Proportions and quantities of materials used.4)Control of rate of addition.5)Degree of agitation.6)Control of reaction pressure.Assessment of a reactive hazard should be based on the overall composition and structure of the materials involved and a knowledge of previous examples of similar reactions.Reactions involving the risk of violent deflagration, explosion or detonation should, where possible, be avoided, but if essential, be carried out in the Special Purposes Laboratory using appropriate protective measures.Syringes and cannulae1)When using syringes and cannulae to transfer reactive/unstable intermediates stored under inert gas insure seal storage containers be certain to re-pressurise the container with the same inert gas.2)Be careful when bending cannulae and syringe needles: cracks or pin holes may develop which canthen admit air into a reaction mixture.3)Care must be exercised when using syringes in the transfer of volatile liquids (e.g. methyl iodide) into areactive flask; prior cooling of the syringe barrel and needle may be required.4)When the transfer is complete wash out the syringe and needle carefully. If reactive species such asalkyl lithiums, aluminium hydrides etc. have been transferred, remove the barrel from the syringe before carefully placing the syringe into an excess of a suitable quenching agent (see P&M012).5)Disposable plastic syringes may react with some solvents or reagents. Whenever possible use glasssyringes.6)When disposing of old syringes and needles do so in the proper sharps bins which are obtainable fromthe Stores.7)In the event of a needlestick injury the best immediate response is usually to allow the injury to bleed.Seek advice as soon as possible from a qualified first-aider.Sample Preparation for Analytical TechniquesThere is a wide range of analytical techniques available within the Department. The main hazards occur:1. when purifying the compound prior to analysis;2. when handling the compound once pure;3. and on exposure to solvents or matrices used in preparing the compound for analysisThere may be additional hazards specific to the technique. Methods for preparing samples for analysis are covered in the departmental publication 'Analytical Techniques Handbook' available from Chemistry Stores. A generic COSHH form should be filled out covering the specific chemical hazards, such as solvents, for each technique a researcher uses. Specific training should be acquired before using any open access analytical equipment; this includes IR, UV/Vis, NMR and chromatography.If a sample is sent to one of the analytical services (i.e. NMR, Mass Spectrometry, X-ray Crystallography, Microanalysis, etc.) you must ensure that you appraise the analytical section of any hazard associated with that sample on the service submission sheets.CentrifugesWhen running, a centrifuge has considerable kinetic energy and can expel debris, or even move bodily for a considerable distance in the event of mechanical failure. Centrifuges should, if possible, be anchored or secured to a solid working surface to restrict vibrational movement, and should be fitted with a device which prevents access to the rotor whilst it is rotating.When using a centrifuge:1Familiarise yourself with the manufacturer's instructions.2Use only the accessories recommended by the manufacturer.3Check the centrifuge, and accessories, for signs of damage before using.4Do not overfill centrifuge tubes.5Distribute the load symmetrically around the rotor so that it is evenly balanced. Balancing must be achieved by using similar components and by weighing samples.6Clean up any spillages immediately, taking care to minimise the possibility of corrosion.7Dry all components after cleaning.8Do not attempt to open a centrifuge whilst the rotor is in motion.9Centrifuge rotors should be annually inspected for cracks or other damage.10The User should arrange annual inspection of rotors by the manufacturer.Special precautions should be taken when centrifuging toxic or flammable chemicals, radioisotopes or other hazardous materials. Obtain specialist advice if necessary.Working Under Reduced PressureRotary evaporators1.Ensure that the condenser of the rotary evaporator is shielded with plastic mesh, which can beobtained from the main stores. Dreschel bottles must not be used as vacuum traps.2.Do not use flasks which have star cracks.3.Before spinning the sample ensure that a good vacuum has developed in the apparatus, if not the flaskmay fall off.4.Do not hold onto the sample whilst it is revolving: failure of the flask could result in seriouslacerations to the hands.5.Slowly admit air back into the apparatus after evaporation of the solvent is complete.6.Clean the apparatus after use. Do not mix halogenated and non-halogenated solvents in the receiver. Filtration under vacuumBuchner flasks are made of thick glass to withstand external pressure, but are liable to crack if subjected to thermal shock. They should be uniformly preheated in an oven before being used to receive hot filtrates. Never heat them on a free flame or on a steam bath. They should be clamped before filtration is started.Vacuum DesiccatorsVacuum desiccators present an implosion hazard. During evacuation and when evacuated, they should be surrounded by the covers provided. Let air in slowly. Avoid thermal and mechanical shocks. Chipped, cracked or heavily scratched desiccators should be either repaired or disposedof immediately.GlassCareless manipulation of glass is the most common cause of laboratory injury. Glass rods and the ends of glass tubing must be rounded in a flame to remove sharp edges.To cut glass tubing or rod of up to 1 cm diameter: make a short cut with a glass knife, hold the glass in both hands with the cut away from the body. Apply gentle pressure with the thumbs behind the cut at the same time pulling the glass in the direction of its length away from the point at which to is to break. Different techniques are used for cutting tubing over 1 cm diameter. The glassblower should be consulted for advice on this and other problems.Use a batwing (fishtail) burner for bending tubes of up to 1 cm diameter; a Bunsen burner will often produce a weak and constricted bend and must not be used.When pushing glass tubing or rod through a hole in a bung or cork, lubricate with water, glycerine, or liquid paraffin; if the tube is to be left in place for several days use Vaseline. Never try to force the tube or rod through the bung - increase the diameter of the hole instead. For greater safety hold the items in a thick cloth. Never try to withdraw tubing which has become firmly stuck in corks or bungs, since it may shatter in your hand. Rest the cork or bung on a firm surface and cut it away.Cleaning contaminated glasswareDO NOT USE Nitric acid or mixtures of nitric acid and solvent. The following cleaning systems can be used and are listed in order of increasing strength and corresponding hazard.1)Decon or similar detergent.2)Base bath: which is a solution of potassium hydroxide in methanol to the following recipe. 50 g ofKOH should be dissolved in the minimum amount of water, with cooling. This should then be added to 500 ml of methanol. Multiply up to give the required final volume. This solution is HIGHLY CAUSTIC.3)Ultrasonic treatment in a concentrated detergent solution.4)Chromic acid in extreme cases only. Chromic acid is HIGHLY CORROSIVE and CARCINOGENICUniversity of Manchester Department of ChemistryProcedures and Methods Sheet: 002Distillation and SublimationThis P&M sheet is 1 page long.Distillation or Sublimation Under Reduced PressureYour supervisor or other responsible person should be consulted before first attempting to carry out operations under a reduced pressure. Each procedure should have a generic COSHH assessment. The operation should have the undivided attention of the operator.1.Ensure that all the glassware to be used in the set-up is free from star-cracks or fractures. Only useround bottomed flasks or pear-shaped flasks. ‘Quick-fit’ conical flasks are unsuitable.2. A safety screen (or screens) should be set up so that the operator and others are adequately shielded.A fume cupboard with the front pulled down provides a shielded area for distillations under reducedpressure.e a cold trap between the pump and the apparatus.For Distillation1.The vortex method, i.e. use of a magnetic stirrer bar, provides the safest way of effecting controlleddistillation.2.Nitrogen should be used instead of air if a bleed is deemed necessary. Decomposition and otherassociated hazards (see below) may occur if air is passed through the sample at elevated temperatures.Allow residues to cool and remove the cold trap before letting air into the system: hot residuesoccasionally explode on contact with air. Let air into all the system before disconnecting.3.When using a pig be sure to secure the collection flasks properly as they may fall off when air isadmitted back into the system after completion of the distillation.When air-sensitive compounds have been purified in this manner an inert gas, rather than air, should be introduced into the apparatus after completion of the distillation.Rotary evaporators - See P&M001Associated Hazards and Precautions1.Liquid nitrogen should be removed from traps before admitting air to the system, so that condensationof liquid oxygen is avoided.2.Vacuum lines mounted on metal frames should have the frame electrically earthed.3.Rotating shafts, belts and pulleys on vacuum pumps should be guarded.4.All glassware must be taped in order to minimise hazards of implosion. Dreschel bottles are notsuitable for vacuum traps.5.Rotary pumps should be exhausted to a fume cupboard or to a safe place if toxic or flammablevapours are emitted.6.Oil mist filters will prevent pollution of the atmosphere and in many cases can obviate the need forpiped exhaust.University of Manchester Department of ChemistryProcedures and Methods sheet: 003CryogenicsThis P&M sheet is 2 pages long.Cryogenic substances MUST NOT be carried in the Passenger lifts. The hazards associated with the handling and transportation of cryogenic fluids and solids fall into four sections.1) Asphyxiation in oxygen deficient atmospheresNitrogen, argon and helium may produce local oxygen deficient atmospheres which will produce asphyxia if breathed, this being especially true in confined spaces. Atmospheres which contain less than 20% oxygen are considered dangerous. If the cryogenic fluid is being used, transported or dispensed in a situation where this is possible, an oxygen monitor must be installed similar to that installed in the Stores loading bay where liquid nitrogen dewars are filled.Symptoms of the possible onset of asphyxia can include: Rapid and gasping breathing, Rapid fatigue, Nausea, Vomiting, Collapse or Unusual behaviour.2) Fire in oxygen enriched atmospheresMany materials not usually combustible in air will burn fiercely in an oxygen enriched atmosphere. Smoking must therefore be prohibited in the vicinity of liquid oxygen and suitable notices displayed. It should also be prohibited in the vicinity of liquid helium and when large quantities of liquid nitrogen are being used in view of the possibility of localised atmospheric enrichment with oxygen.3) Cold burns, frostbite and hypothermia from the intense coldBecause of the low temperatures of liquefied atmospheric gases, the liquid or even the cold vapour can produce damage to the skin similar to heat burns. Unprotected parts of the skin coming into contact with uninsulated items of cold equipment may stick fast to them and flesh may be torn on removal.Prolonged exposure to cold vapours may cause frostbite. There can be little or no initial pain. The frozen tissues are painless but may appear waxy or have a pale yellowish colour. Thawing of the tissue can cause intense pain and shock may occur.Protective clothing is only intended to protect the wearer from accidental contact with cold equipment, cold liquids or solids or cold gases. Non-absorbent leather gloves should always be worn and these should be a loose fit so that they can easily be removed if liquid should splash onto or into them. For this reason, gauntlet gloves are not recommended.Hospital attention must be sought for all but the most superficial injuries.4) Overpressurisation from the large volume expansion of the liquidOne volume of cryogenic liquid can release 683 times that volume of gas so care must be taken that all bursting discs are in good mechanical order (i.e. no corrosion) and are not obstructed in any way otherwise a severe explosion hazard may exist.In the Department, Liquid Nitrogen dewars are filled at a transfer point located in the Stores loading bay. When filling large dewars note must be taken of the above points. The outside doors must be open to ensure adequate ventilation; always use the correct gloves when handling the cold transfer tubes; take care to avoid splashing the liquid nitrogen onto yourself or any others that may be present. Before filling dewars for the first time instruction from your supervisor or other competent person must be sought.An insulated box containing Cardice (Dry-Ice or Solid CO2) is located next to the Stores window. Suitablegloves must be worn when dispensing the pellets (see Frostbite above) and the Cardice transported in an insulated container back to the place of use. Take no more than is needed. Unused Cardice should be left to evaporate in a fume hood and not put down the sinks where it can freeze the water in the under-sink traps and cause them to crack. When making Dry-Ice/Solvent baths always add the dry-ice piece by piece to the solvent to avoid the fast evolution of gas (see 4 above) sending large quantities of solvent over the bench (and you).Special precautions needed when handling Liquid Heliumtemperature. Vessels containing liquid helium must not be left open to the air for longer than is absolutely necessary (ca 15s). Liquid helium must be transferred between vessels only by means of special vacuum insulated tubes, and the use of helium gas as a pressurizing agent if needed. Liquid helium must always be stored and used in vessels designed for the purpose and so marked.University of Manchester Department of ChemistryProcedures and Methods Sheet: 004ChromatographyResearcher signed: date:Supervisor signed: date:This P&M Sheet is 1 page longRefer to Purification of Laboratory Chemicals, D. D. Perrin and W. L. F. Armarego, (Butterworth and Heineman, 1988) for a full description of chromatographic techniques. Each solvent system used and any specific chemical developer used should be given a generic COSHH assessment before it is used for the first time.1. Thin Layer Chromatography (TLC)TLC and preparative TLC plates should be developed in a closed container which should be placed in a fume cupboard to minimise exposure to eluent solvent. Visualisation with UV light should be carried out without looking directly at the UV light source. Development with iodine should be carried out in a sealed container placed in a fume cupboard or spray booth. Development with other chemical systems, especially if they involve spraying should be carried out in a fume cupboard or spay booth.2. Column ChromatographyUse of silica gel.Silica (and alumina) used for flash, gravity and preparative thin layer chromatography can present chronic exposure problems if this hazard is not realised. Inhalation of fine silica particles, in particular, “flash”silica gel, is known to be the cause of the serious lung disease silicosis. Silica gel should be weighed out and transferred in a fume cupboard.Care must be taken during the loading of chromatographic columns to minimise exposure to silica dust. Columns should be prepared and used in a fume cupboard and all spillage of silica dust must be cleaned up immediately. Cracked or broken columns must not be used and should be repaired by the glassblower. Note that silica gel can become warm on contact with solvent and this can cause a build-up of pressure if a volatile solvent is used as the eluent. Care should be taken to prevent this happening.On completion of the column, the silica gel should be transferred to a solid waste container and disposed of carefully. Columns should be cleaned and emptied in a fume cupboard. The waste silica should be stored prior to proper disposal (through the stores) in a designated storage area, in sealable containers. Any spillages should be tidied up immediately. Face-masks should be worn when handling silica.University of Manchester Department of ChemistryProcedures and Methods Sheet: 005High Pressure GasesThis P&M sheet is 3 pages long.Correct Treatment of CylindersHigh Pressure Gas cylinders are bombs waiting to go off. They should always be treated with the respect they deserve and not be taken for granted. Familiarity breeds not contempt but an ‘I’ve done this dozens of times and I’ve never had any problems’ attitude. Whether you’ve been handling cylinders all your life or this is the first time you’ve touched one the following rules MUST be followed. Where appropriate these points should be applied to other pieces of high pressure apparatus such as microwave digestors or bomb calorimeters. Any apparatus normally operated at pressures above one atmosphere and which has a blow-off device should be treated as a cylinder.1)Gas cylinders in use must always be fitted with the correct regulator and a key.2)use.3)When not in use the cylinder valve must be closed.4)Gas cylinders must always be transported in one of the trolleys provided for this purpose. The cylindermust be turned off at the cylinder head valve and preferably have the regulator removed whilst in transit.Cylinders should never be transported in the passenger lifts. Only the Goods lift should be used.5)The number of gas cylinders in laboratories should be kept to an absolute minimum and they should bereturned to the stores immediately when empty or unlikely to be used in the near future. Remember that the rental on a cylinder kept for a few months and not used can be more than the cost of the gas in the cylinder.6)Gas cylinders should never be dropped or banged against each other.7)Gas cylinders containing liquefied gases must be stored vertically.8)When using or storing flammable gases ensure that there are no sources of ignition in the area and donot use or store in the vicinity of an oxygen, or other oxidising gas, cylinder.9)In a system where a reactive gas is used, protection against suck-back, in the form of an empty reservoir,must be located between the regulator and the reaction vessel. If the gas is insoluble then a blow-off device is necessary. The correct arrangement is cylinder - suck-back trap - blow-off device.10)Acetylene must not be used at pressures above 9 psi except in approved circumstances. Copper pipes orvessels must never be used or allowed to come into contact with acetylene. Flash back arresters must be used in conjunction with B.S.hosepipe.11)Colour codes for gas cylinders are in the process of being changed to conform with EEC regulations.The new colour codings will, in most cases, indicate the hazard associated with the gas.(a) The new colours will only apply to the shoulder of the cylinder. The body or barrel colour is theresponsibility of the supplier and may vary from firm to firm. Where there is a significant colourchange, cylinders in the new colour will be identified by a large capital “N” on the shoulder in two places.(b) Four basic shoulder colours will be used to identify the property of the gas in the cylinder:Yellow Toxic or poisonous already usedRed Flammable already usedLight Blue Oxidising (fire intensifying)newLight Green Un-reactive/compressed newc) Three common gases will have specific shoulder colours:Oxygen White(new)Nitrous Oxide Gentian Blue(new)Acetylene Dusty Red(minor change)d) Four other gases will have optional shoulder colours beside light green :Nitrogen Black(as now)Helium Brown(as now)Argon Dark Green(new)Carbon dioxide Grey(new)For example:Gas Old colour New ColourAir Grey Light Blue Shoulder / Grey Body Argon Peacock Blue Dark GreenArgon Welding mixtures Pink Shoulder / Peacock BlueBodyBright Green Shoulder /Ocean Blue or Sapphire BlueBodyCarbon Dioxide Black GreyHelium Balloon Gas Manilla Shoulder / Brown Body Brown Shoulder / Grey BodyHelium Welding Mixtures Pink Shoulder / Brown Body Bright Green Shoulder / BrownBodyOxygen Black White Shoulder / Black BodyAcetylene Maroon Dusty RedHelium Brown BrownHydrogen Red RedNitrogen Black Shoulder / Grey Body Black Shoulder / Grey BodyPropane Red RedRegulatorsRegulators should be inspected frequently for signs of corrosion or mechanical damage. Oil or grease should never be used to obtain a gas seal especially between the regulator and the cylinder head.1.The recommended maximum lifetime for any regulator is 5 years from manufacture (even if unused) ifused in conjunction with a non-corrosive gas. Regulators for corrosive gases (e.g. chlorine, ammonia) should be changed every two years.2.Regulators should carry the BSI kitemark and BS5741. Older or non-compliant gauges may not havecaptive dials/needles and may fail catastrophically.3.Cylinder pressures have increased over the years. 230 bar is common and values of 300 bar are to beexpected in the near future. Many older regulators are only rated to 200 bar and should not be used in conjunction with these high pressure cylinders.4.Always ensure that the cylinder colour code, the cylinder contents and pressure label and the regulatormatch. Do not rely on the cylinder’s colour alone. If the label is missing illegible or differs from the colour code the cylinder should be returned to the manufacturer.5.Oils or lubricants should not be used when fitting regulators. The use of PTFE tape should also beminimised as it can contain low molecular weight residues which may present an explosion hazard with compressed oxygen. If leaks are apparent this probably indicates either defects, wear or that an incorrect regulator is being used.。

我的成功秘诀英语作文有具体事例

我的成功秘诀英语作文有具体事例全文共3篇示例，供读者参考篇1Here's an essay on "My Success Secrets" written from a student's perspective, with concrete examples and in English (around 2000 words):My Success Secrets: A Student's Guide to Achieving Your GoalsAs a student, the path to success can often feel like an uphill battle. With countless assignments, exams, and extracurricular activities vying for our attention, it's easy to become overwhelmed and lose sight of our goals. However, through my personal experience, I've discovered a set of guiding principles that have helped me navigate the challenges of student life and unlock my full potential. In this essay, I'll share my success secrets, accompanied by real-life examples that have shaped my journey.Cultivate a Growth MindsetOne of the most profound lessons I've learned is the power of a growth mindset. Instead of viewing intelligence as a fixedtrait, I've embraced the belief that my abilities can be developed through dedication and hard work. This mindset shift has been a game-changer, allowing me to embrace challenges as opportunities for growth rather than obstacles to avoid.During my freshman year, I struggled immensely with calculus. Initially, I felt defeated and questioned my aptitude for mathematics. However, by adopting a growth mindset, I began viewing each failed attempt as a stepping stone towards mastery.I sought extra help from my professor, formed study groups with classmates, and consistently practiced problem sets. Over time, my efforts paid off, and calculus became one of my strongest subjects.Prioritize Time ManagementAs a student, time is our most precious resource, and effective time management is crucial for success. I've learned to prioritize my tasks, allocate dedicated study blocks, and avoid procrastination at all costs. By doing so, I've been able to stay on top of my academic responsibilities while still finding time for personal growth and self-care.One powerful tool I've employed is the Pomodoro Technique, which involves breaking work into focused 25-minute intervals separated by short breaks. This method has beeninstrumental in helping me maintain concentration and avoid burnout during marathon study sessions. Additionally, I've adopted the habit of creating weekly schedules, ensuring that I allocate sufficient time for each class, assignment, and extracurricular activity.Embrace CollaborationWhile individual effort is essential, I've found that collaborating with peers can be an invaluable asset in the pursuit of success. Engaging in study groups, participating in class discussions, and seeking feedback from classmates and professors have all contributed to my academic growth and personal development.During my sophomore year, I joined a research team focused on exploring sustainable energy solutions. Working alongside like-minded individuals from diverse backgrounds, we challenged each other's perspectives, shared knowledge, and collectively tackled complex problems. This experience taught me the value of teamwork, effective communication, and the power of diverse perspectives in driving innovation.Cultivate ResilienceSetbacks and failures are inevitable on the path to success, and cultivating resilience is crucial for bouncing back from adversity. I've learned to embrace failures as opportunities for self-reflection and growth, rather than allowing them to define my worth or derail my progress.One particularly challenging experience was when I failed a midterm exam in my core subject area. Initially, I felt devastated and doubted my abilities. However, after taking some time to process the setback, I reached out to my professor for guidance, identified my areas of weakness, and developed a comprehensive study plan. Through perseverance and a renewed sense of determination, I not only improved my performance in the subsequent exams but also gained a deeper understanding of the subject matter.Nurture a Balanced LifestyleWhile academic pursuits are undoubtedly important, I've come to realize that maintaining a balanced lifestyle is essential for sustained success. By prioritizing self-care, engaging in physical activity, and pursuing hobbies and interests outside of academics, I've been able to recharge my mental and emotional batteries, preventing burnout and maintaining a positive mindset.One of my favorite ways to unwind is through recreational sports. Throughout my college years, I've played intramural volleyball, which has not only provided me with a physical outlet but also fostered valuable friendships and a sense of camaraderie. Additionally, I've made it a habit to engage in mindfulness practices, such as meditation and yoga, which have helped me manage stress and cultivate a more focused and resilient mindset.In conclusion, success as a student is not solely determined by innate intelligence or academic prowess; it's a multifaceted journey that requires cultivating a growth mindset, effective time management, collaboration, resilience, and a balanced lifestyle. By embracing these principles and persevering through challenges, I've been able to unlock my full potential and achieve academic and personal growth. I hope that by sharing my success secrets and real-life examples, I can inspire and empower fellow students to embark on their own transformative journeys towards success.篇2My Secret to SuccessSuccess means different things to different people. For some, it's about accumulating wealth and status. For others, it's about achieving personal growth and leaving a positive impact on the world. Regardless of how you define it, success rarely comes without hard work, dedication, and a well-devised strategy. As a student, I've learned that cultivating the right habits and mindset is crucial for accomplishing my goals and paving the way for a fulfilling future. In this essay, I'll share my personal recipe for success, complete with real-life examples that have shaped my journey.Developing a Growth MindsetOne of the most transformative lessons I've learned is the power of a growth mindset. In my first year of high school, I struggled with math, and my fixed mindset led me to believe that I simply wasn't "good at numbers." However, after reading Carol Dweck's book "Mindset," I realized that intelligence isn't fixed; it can be developed through effort and perseverance. I decided to adopt a growth mindset, seeking help from my teachers, practicing consistently, and embracing challenges as opportunities to learn.This shift in perspective paid off tremendously. By the end of the year, my math grades had improved significantly, and I hadgained the confidence to tackle more advanced courses. The growth mindset taught me that failures and setbacks are temporary and that with the right mindset and effort, I could overcome any obstacle.Cultivating Self-DisciplineSuccess rarely comes without self-discipline, a trait that has served me well in my academic pursuits. In my sophomore year, I joined the school's debate team, which required extensive research, critical thinking, and public speaking skills. Juggling debate practices, homework, and extracurricular activities was a challenge, but I quickly learned the value of time management and prioritization.I developed a weekly schedule, allocating dedicated time slots for each task and activity. I also learned to eliminate distractions and stay focused during my study sessions. By consistently adhering to this routine, I was able to excel in my debate tournaments while maintaining excellent grades. The self-discipline I cultivated through this experience has become a invaluable asset, enabling me to tackle demanding projects and meet tight deadlines with ease.Building ResilienceSetbacks and failures are inevitable on the path to success, and learning to bounce back from these challenges is essential. During my junior year, I auditioned for the lead role in the school play, a part I had been preparing for months. Despite my best efforts, I didn't get the role, and I was devastated. However, instead of wallowing in self-pity, I decided to use this experience as a catalyst for growth.I sought feedback from the directors, and they pointed out areas where I could improve, such as projecting my voice and conveying emotions more authentically. I threw myself into acting classes, practicing diligently and stepping out of my comfort zone. The following year, I landed a supporting role in the play, and the experience taught me the value of resilience and perseverance. I learned that failure is not the opposite of success; it's an opportunity to learn, grow, and come back stronger.Seeking MentorshipNo one achieves success entirely on their own. Surrounding ourselves with mentors and role models who can guide us and share their wisdom is invaluable. In my senior year, I had the privilege of being mentored by a successful entrepreneur who visited our school as part of a career mentorship program.Through our regular meetings, my mentor shared insights into the entrepreneurial mindset, taught me valuable business skills, and challenged me to think critically about my future goals. Her guidance and support were instrumental in helping me navigate the college application process and identify potential career paths that aligned with my passions and strengths.Building a NetworkSuccess is often a collaborative effort, and building a robust network of peers, professionals, and mentors can open doors to new opportunities and invaluable support. Throughout my high school years, I made a conscious effort to attend networking events, join student organizations, and connect with professionals in fields that interested me.One particular experience that stands out was attending a local tech conference during my junior year. I had the opportunity to meet industry experts, learn about cutting-edge technologies, and even participate in a coding workshop. The connections I made at this event not only fueled my passion for technology but also led to an internship opportunity the following summer, where I gained valuable real-world experience and expanded my professional network further.Giving BackWhile personal success is gratifying, true fulfillment comes from using our talents and resources to positively impact the lives of others. Throughout my high school journey, I've made it a priority to engage in community service and volunteer work, believing that giving back is not only the right thing to do but also a key component of a well-rounded and meaningful life.One of my most rewarding experiences was volunteering at a local youth center, where I tutored underprivileged children in various subjects. Witnessing their progress and the joy on their faces as they grasped new concepts was incredibly fulfilling. This experience taught me the value of empathy, patience, and using my knowledge and skills to uplift others.In conclusion, the path to success is rarely a straight line. It's a journey filled with challenges, setbacks, and opportunities for growth. By cultivating a growth mindset, practicingself-discipline, building resilience, seeking mentorship, building a network, and giving back, I've equipped myself with the tools and mindset necessary to overcome obstacles and achieve my goals. While the specific strategies may vary, the underlying principles of hard work, perseverance, and a commitment to personal growth are universal keys to success. As I embark on the next chapter of my life, I carry these lessons with me,confident in my ability to continue growing, learning, and making a positive impact on the world around me.篇3My Secrets to SuccessSuccess means different things to different people, but to me, it's about achieving your goals and finding fulfillment in life. Over the years, I've developed several key habits and mindsets that have helped me stay motivated, focused, and driven to succeed. Here are my personal secrets to success.Have a Clear Vision and Set Specific GoalsOne of the biggest keys to my success has been having a clear vision of what I want to achieve and then setting specific, measurable goals to get there. It all started when I was in 10th grade and really struggled with math. I knew I wanted to go to a good university and study engineering, but my poor math grades were holding me back. That's when I got laser-focused - I set the goal of getting an A in math by the end of the year.I broke that big goal down into smaller, achievable steps. I met with my math teacher weekly for extra help. I joined a study group with some of the top students. I practiced math problems for at least an hour every night. Little by little, things startedclicking, and by the end of the year, I had raised my grade from a D to an A-. Setting that clear goal and breaking it down into actionable steps gave me the motivation to work hard and persevere.Develop a Growth MindsetOne of my biggest secrets has been developing a growth mindset - the belief that abilities can be developed through dedication and hard work. It's so easy to get discouraged when you struggle at something, but I've learned to embrace challenges as opportunities to grow.This mindset was really put to the test my first year of university when I took a brutal computer science course. At first, I felt completely lost and wanted to give up. But I forced myself to seek out help, spent long hours in the lab, and refused to get discouraged by mistakes. Little by little, I improved. While many classmates dropped the course, I stuck with it and ended up getting an A. That experience taught me that with enough grit and perseverance, I could overcome any obstacle.Build Good Habits and Be ConsistentWe've all heard it – success is the result of hard work and consistency over time. For me, establishing good daily habits androutines has been incredibly important for sustaining my momentum. During exam periods, I follow a strict schedule where I wake up early, exercise, and then study for a few hours before classes. I limit distractions by turning off notifications on my phone. I try to get assignments done well in advance rather than procrastinating.Building these habits of hard work, focus, and consistency doesn't happen overnight – it takes discipline. But the key is to start small and build the habits one by one. Looking back, it was developing simple habits like setting aside 30 minutes every night to review my class notes that laid the foundation for bigger achievements down the road.Learn from Failures and SetbacksDespite all the preparation and hard work, failures and setbacks are inevitable on the road to success. What separates those who succeed from those who don't is the ability to learn from mistakes, adapt, and persevere.One of my biggest setbacks was failing my driving test three times before finally passing. Each failed attempt was so demoralizing, and I remember feeling like giving up and resigning myself to being un-drivable. But instead of quitting, I analyzed where I was going wrong, got additional lessons, andworked relentlessly on parallel parking and other weaknesses. When I finally did pass, the feeling of accomplishment was like none other – and I knew the skills of perseverance and resilience would serve me well in the future.Find Balance and Take Care of YourselfWhile drive and determination are crucial, I've learned that it's just as important to find balance and take care of your overall wellbeing. It's easy to get consumed by the pursuit of success, but that level of intensity is unsustainable and can ultimately backfire.That's why I make sure to schedule breaks and fun activities to re-energize myself. I try to get enough sleep, eat nutritious foods, and exercise regularly. Having hobbies and interests outside of academics, like hiking and playing guitar, provides an outlet and balance. When I'm feeling overwhelmed, I don't hesitate。

榆次2024九年级一模英语作文

榆次2024九年级一模英语作文The year 2024 marked a significant milestone for the students of Yuci, as they embarked on their first midterm English composition challenge. This examination, designed to assess their proficiency in the English language, was a crucial step in their academic journey. As the students prepared to showcase their skills, they were filled with a mix of excitement and trepidation, knowing that this was their chance to demonstrate their hard work and dedication.The composition prompt challenged the students to delve into a topic that was both thought-provoking and relevant to their lives. They were asked to reflect on the role of technology in shaping their daily routines and its impact on their personal and social development. The students were eager to share their perspectives, drawing from their own experiences and observations.One student, Emma, began her essay by highlighting the ubiquitous presence of technology in her life. She described how her smartphone had become an extension of her hand, allowing her to access a wealth of information, communicate with friends, and stayconnected with the world around her. However, she also acknowledged the potential drawbacks of this reliance, noting how it had sometimes led to a sense of disconnection from the physical world and a distraction from more meaningful pursuits.Another student, Liam, took a different approach, focusing on the educational benefits of technology. He discussed how the integration of digital tools and resources into the classroom had transformed the learning experience, making it more engaging, interactive, and personalized. Liam highlighted the ways in which he could access online tutorials, collaborate with classmates on group projects, and receive instant feedback from his teachers, all of which had contributed to his academic growth and success.The essays also touched on the social implications of technology, with students exploring both the positive and negative aspects. One student, Sophia, wrote about how social media had enabled her to connect with a global community, sharing ideas, experiences, and perspectives with people from diverse backgrounds. However, she also expressed concern about the pressure to curate a perfect online persona and the potential for cyberbullying and social comparison.In contrast, another student, Ethan, delved into the ways in which technology had impacted his physical and mental well-being. He described how the constant need to be available and responsive hadled to feelings of anxiety and burnout, and how he had learned to set boundaries and prioritize self-care activities to maintain a healthy balance.As the students delved deeper into the topic, they demonstrated a nuanced understanding of the complex relationship between technology and their lives. They acknowledged the undeniable benefits of technological advancements, such as increased efficiency, access to information, and opportunities for collaboration and creativity. However, they also recognized the potential pitfalls, including the risk of addiction, social isolation, and the erosion of face-to-face interactions.The essays also highlighted the students' critical thinking skills, as they grappled with the ethical implications of technological progress. They explored the role of policymakers, educators, and individuals in shaping the responsible use of technology, and they proposed solutions to address the challenges they had identified.One student, Olivia, advocated for the implementation of digital literacy programs in schools, equipping students with the skills to navigate the online world safely and effectively. Another student, Jacob, suggested the creation of technology-free spaces and designated "unplugged" periods to encourage mindfulness and personal reflection.Throughout the compositions, the students demonstrated a remarkable depth of understanding and a willingness to engage with complex issues. Their essays were not mere recitations of facts but rather thoughtful explorations of the interplay between technology and the human experience.As the first midterm English composition came to a close, the students in Yuci felt a sense of accomplishment and pride. They had not only showcased their language proficiency but also their ability to think critically, express their ideas coherently, and contribute to the ongoing dialogue about the role of technology in their lives.The teachers who had the privilege of reading these essays were impressed by the students' level of engagement and the maturity of their perspectives. They recognized that these young individuals were not merely passive consumers of technology but active participants in shaping its impact on their personal and societal development.The Yuci 2024 Grade 9 First Midterm English Composition marked a pivotal moment in the academic and personal growth of these students. As they continued their educational journey, they would undoubtedly carry the lessons and insights they had gained from this experience, empowered to navigate the ever-evolving landscape oftechnology with wisdom, discernment, and a commitment to making a positive difference in the world.。

九年级下册英语中考指南答案人教版八年级

九年级下册英语中考指南答案人教版八年级全文共3篇示例，供读者参考篇1Grade 9 English Final Exam Guide - Answer KeyWelcome to the Grade 9 English Final Exam Guide! Below you will find the answer key to the Grade 9 English Final Exam, based on the People's Education Press 8th Grade English Textbook. This guide will help you review and prepare for your exam, ensuring that you are fully prepared and confident on exam day.Section A: Reading Comprehension1. C2. B3. A4. D5. CSection B: Vocabulary and Grammar1. B2. A3. C4. D5. B6. B7. D8. C9. A 10. D11. B 12. A 13. C 14. D 15. ASection C: Writing1. Sample answer (may vary):Dear Mr. Smith,I am writing to express my interest in the volunteer opportunity at your organization. The importance of community service has always been clear to me, and I believe that this opportunity will not only enhance my skills but also allow me to give back to my community. I am a dedicated and hardworking individual, and I am confident that I can contribute positively to your organization.I look forward to the opportunity to discuss my candidacy further. Thank you for considering my application.Sincerely,[Your Name]2. Sample answer (may vary):The benefits of learning a second language are numerous. Not only does it improve cognitive abilities such asproblem-solving and multitasking skills, but it also enhances communication skills and cultural understanding. In today's globalized world, being bilingual is a valuable asset that can open up many opportunities in both personal and professional life.In conclusion, learning a second language is not only a rewarding experience but also a practical skill that can benefit individuals in various aspects of their lives.Section D: Listening Comprehension1. C2. B3. A4. D5. CWe hope this Grade 9 English Final Exam Guide has been helpful in your preparation. Good luck on your exam, and remember to review the material thoroughly before the big day. If you have any questions or need further assistance, please don't hesitate to reach out to your teacher or school counselor. Best of luck!篇2Guide to the Junior High School Entrance Exam Answer Key for New Standard English Eighth GradeIntroduction:The Junior High School Entrance Exam is an important milestone for students in China. It is a comprehensive test that assesses students' knowledge and understanding of various subjects, including English. In this guide, we will provide theanswer key for the New Standard English Eighth Grade textbook, which is commonly used by schools across the country.Unit 1: My New Teacher1. A2. C3. A4. B5. C6. B7. A8. A9. B10. CUnit 2: Wear It Cool!1. B2. C3. A5. B6. A7. B8. C9. A10. BUnit 3: The Place We Live In1. A2. B3. C4. A5. B6. C7. A8. B9. BUnit 4: Food and Health1. C2. B3. A4. C5. A6. B7. B8. A9. C10. CUnit 5: The Last Frontier1. B2. C3. A4. B6. C7. A8. B9. A10. CUnit 6: How Do You Get to School?1. C2. A3. B4. C5. A6. B7. A8. C9. B10. AUnit 7: A Busy Day1. B2. C3. A4. B5. A6. C7. C8. A9. B10. CUnit 8: What Do You Think of Game Shows?1. A2. B3. C4. A5. B7. C8. B9. A10. CUnit 9: How Was Your Weekend?1. C2. A3. B4. A5. B6. C7. A8. B9. C10. AUnit 10: Our Water Resources2. C3. A4. B5. A6. C7. A8. B9. C10. AConclusion:With this answer key, students can review their answers and prepare for the Junior High School Entrance Exam. It is important to practice regularly and seek help from teachers or tutors if needed. Good luck to all the students taking the exam!篇3《九年级下册英语中考指南答案人教版八年级》Introduction:As students prepare for their upcoming final examinations, having access to the answers and solutions to their review materials can be incredibly beneficial. This document aims to provide the answer key to the 9th-grade English midterm exam, following the syllabus of the People's Education Press for 8th grade.Section 1: Reading ComprehensionDirections: Read the following passage and answer the questions below.1. True2. False3. Not Given4. B5. C6. ASection 2: VocabularyDirections: Choose the best option to complete the sentences.1. D3. A4. C5. D6. A7. C8. BSection 3: GrammarDirections: Choose the correct option to complete the sentences.1. C2. A3. B4. D5. C6. A7. DSection 4: WritingDirections: Write a composition on the topic given.(Answers may vary)Conclusion:Having access to the answer key for the 9th-grade English midterm exam can provide valuable guidance and assistance for students as they review for their final assessments. By using this document as a reference, students can check their answers, understand the correct solutions, and improve their overall performance in the examination. Good luck to all the students preparing for their exams!。

HowtoDoYourHomework

WINNING AT MATHHOW TO DO YOUR HOMEWORKDoing your homework can be frustrating or rewarding. Most students jump right into their homework, become frustrated and stop studying. These students usually go directly to the math problems and start working them without any preparation. When they get stuck on one problem, they flip to the back of the text for the answer. Then, they either try to work the problem backward, to understand the problem steps, or they just copy down the answer.Other students go to the solution guide and just copy the steps. After getting stuck several times, these students will inevitably quit doing their homework assignment. Their homework becomes a frustrating experience, and they may even quit doing their work altogether.To improve your homework success and learning, refer to the following 10 steps:10 Steps to Doing Your HomeworkStep 1 - Review the textbook material that relates to the homework. A proper review will increase the chances of successfully completing your homework. If you get stuck on a problem, you will have a better chance of remembering the location of similar problems. If you do not review prior to doing your homework, you could get stuck and not know where to find help in the textbook.Remember: To be successful in learning the material and in completing homework assignments, you must first review your textbook.Step 2 - Review your lecture notes that relate to the homework. If you could not understand the explanation of the textbook on how to complete the homework assignment, then review your notes.Remember: Reviewing your notes will give you a better idea about how to complete your homework assignment.Step 3 - Do your homework as neatly as possible. Doing your homework neatly has several benefits. When approaching your instructor about problems with your homework, he or she will be able to understand your previous attempts to solve the problem. The instructor will easily locate the mistakes and show you how to correct the steps without having to decipher your handwriting. Another benefit is that, when you review for midterm or final exams, you can quickly relearn the homework material without having to decipher your own writing. Remember: Neatly prepared homework can help you now and in the future.Step 4 - When doing your homework, write down every step of the problem. Even if you can do the step in your head, write it down anyway. This will increase the amount of homework time, but you are overlearning how to solve problems, which improves your memory. Doing everystep is an easy way to memorize and understand the material. Another advantage is that when you rework the problems you did wrong, it is easy to review each step to find the mistake.Remember: In the long run, doing every step of the homework will save you time and frustration.Step 5 - Understand the reasons for each problem step and check your answers. Do not get into the bad habit of memorizing how to do problems without knowing the reasons for each step. Many students are smart enough to memorize procedures required to complete a set of homework problems. However, when similar homework problems are presented on a test, the student cannot solve the problems. To avoid this dilemma, keep reminding yourself about the rules, laws, or properties used to solve problems.Example: Problem 2(a+5) = 0. What property allows you to change the equation to 2a + 10 = 0? Answer: The distributive property.Once you know the correct reason for going from one step to another in solving a math problem, you can answer any problem requiring that property. Students who simply memorize how to do problems instead of understanding the reasons for correctly working steps will eventually fail their math course.How to Check Your AnswersChecking your homework answers should be part of your homework duties. Checking your answers can improve your learning and help you prepare for tests.Check the answers of the problems for which you do not have the solutions. This may be the even-numbered or odd-numbered problems or the problems not answered in the solutions manual.First, check your answer by estimating the correct answer.Example: If you are multiplying 2.234 by 5.102 the answer should be a little over 10. Remember that 2 times 5 is 10.You can also check your answers by substituting the answer back into the equation or doing the opposite function required to the question. The more answers you check, the faster you will become. This is very important because increasing your answer checking speed can help you catch more careless errors on future tests.Step 6 - If you do not understand how to do a problem refer to the following points:•Point 1 - Review the textbook material that relates to the problem.•Point 2 - Review the lecture notes that relate to the problem.•Point 3 - Review any similar problems, diagrams, examples or rules that explain the misunderstood material.•Point 4 - Refer to another math textbook, solutions guide, math computer program software or video tape to obtain a better understanding of the material.•Point 5 - Call your study buddy.•Point 6 - Skip the problem and contact your tutor or math instructor as soon as possible for help.Step 7 - Always finish your homework by successfully completing problems. Even if you get stuck, go back and successfully complete previous problems before quitting. You want to end your homework assignment with feelings of success.Step 8 - After finishing your homework assignment, recall to yourself or write down the most important learned concepts. Recalling this information will increase your ability to learn these new concepts. Additional information about Step 8 will be discussed later in this chapter.Step 9 - Make up note cards containing hard-to-remember problems or concepts. Note cards are an excellent way to review material for a test. More information on the use of note cards as learning tools is presented later in this chapter.Step 10 - Getting behind in math homework is academic suicide. Math is a sequential learning process. If you get behind, it is difficult to catch up because each topic builds on the next. It would be like going to Spanish class without learning the last set of vocabulary words. The teacher would be talking to you using the new vocabulary, but you would not understand what was being said.Do Not Fall BehindTo keep up with your homework, it is necessary to complete the homework every school day and even on weekends. Doing your homework one-half hour each day for two days in a row is better than one hour every other day.If you have to get behind in one of your courses, make sure it is not math. Fall behind in a course that does not have a sequential learning process, such as psychology or history. After using the 10 Steps to Doing Your Homework, you may be able to combine two steps into one. Find your best combination of homework steps and use them.Remember: Getting behind in math homework is the fastest way to fail the course.。

临近期中考试作文

临近期中考试作文英文回答：Title: Prepare for the challengeTime flies, in a blink of an eye, the footsteps of the midterm exam has been close at hand. For us students, this is not only a test of the learning results of the past semester, but also an inspection of our self-management ability and improvisation ability. Facing the upcoming exam, I have a set plan and coping strategy.First of all, review is the key. I will make a detailed review plan before the exam, and break the key points and difficulties of each subject one by one. For me, mathematics has always been a hard bone, those complicated formulas and long process of solving problems always give me a headache. But I know running away is not the answer. Therefore, I plan to devote more time to math and improve my problem-solving ability by repeating exercises and reviewing error sets.Next, paying attention in class is also very important. Teachers always emphasize the key points and error-prone points in the period before the test. Therefore, I will pay more attention to every sentence of the teacher's explanation, and try to understand and digest the new knowledge in class, so that the review after class will get twice the result with half the effort.In addition, reasonable arrangement of work and rest time is also a part that can not be ignored. Enough sleep can ensure that I have enough energy to deal with the heavy study task. In addition to ensuring the sleep time at night, I will also use the 10 minutes between classes to carry out appropriate activities, so that my brain can rest and recover, so as to maintain the best learning state.Of course, a healthy diet is also essential. Whether it is mental or physical work, it needs the support of energy. Therefore, I pay attention to the balance of nutrition, avoid eating too much junk food and sugary drinks, and instead choose fresh fruits, vegetables and whole grains to ensure that I am in the best physical and mental condition.Finally, I believe that a positive attitude is also one of the keys to success. In the face of pressure, I will tell myself: "As long as you work hard, there is no difficulty that can not be overcome." This kind of optimistic attitude can help me keep a calm mind during the exam preparation, and when I encounter problems, I can think calmly and find solutions.Examination is not only a review of knowledge, but also a process of self-challenge. Through the unremitting pursuit of learning and the reasonable arrangement of life, I have the confidence to meet the challenge of this midterm exam. In this process, I will continue to improve myself, no matter what the outcome, I will regard it as a valuable experience on the road to growth.Now, I am ready, ready, and waiting for the midterm exam. No matter what the result of the exam is, I will take it seriously and learn from it to pave the way for the rest of my learning journey. During the preparation period, I am ready to go all out and meet every challenge.中文回答：标题：备战期中，迎接挑战时光匆匆，转眼间期中考试的脚步声已经近在咫尺。

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Solutions of the midterm exam 2010 spring
Accounting
Question 1: b d d d
Question 2:
（一）
（1）收到所有者投资
借：现金 6 600
贷：实收资本 6 600
（2）以现金购买设备
借：设备 3 200
贷：现金 3 200
（3）以现金购买存货
借：存货 2 000
贷：现金 2 000
（4）赊购设备
借：设备 2 000
贷：应付账款 2 000
（5）实现销售收入
借：现金 2 500
贷：销售收入 2 500
（6）支付工资
借：工资费用 1 100
贷：现金 1 100
（7）偿还应付账款
借：应付帐款500
贷：现金500
（8）盘结销售成本
借：销售成本 1 000
贷：存货 1 000
(1)The stockholders contributed 6600 in cash
Cash 6600
Contributed capital 6600
(2)Purchased equipment in cash
Equipment 3200
Cash 3200 (3)Purchased inventory in cash
Inventory 2000
Cash 2000 (4)Purchased equipment on account
Equipment 2000
Accounts payable 2000 (5)Recognized revenues
Cash 2500
Revenue 2500 (6)Employee wages were paid
Wages expense 1100
Cash 1100 (7)Accounts payable was paid
Accounts payable 500
Cash 500 (8)Recognized cost of good sold
Cost of good sold 1000
Inventory 1000
Queation3
Question 4
•B. (8 points)Use the Balance sheet
equation to record the write-off and the
recognition of bad debts expense for the
fiscal year ending 12/31/2005.
A/R ADA(-)RE
•BDE151-151
•Write-off-97-97
13
Or: 2111+17718-97-CC=2551
CC=17181
Or: CC=2111+17718-97-2551+(711-645) CC=17247
Question5:
(a)What would have been the ending inventory balance been under FIFO
accounting in 2004, 2005? (10 points)
2004 Ending Inventories under FIFO = 4738.00+736.40=5474.40
2005 Ending Inventories under FIFO = 5592.00+804.20=6396.20
(b)What would have Walgreens cost of sales been under FIFO accounting in 2004,
2005? (16 points)
2004: Under LIFO 4202.70+P-27310.40=4738
→P=27845.70
Under FIFO 4202.70+729.70+P-COGS=5474.40
→CO GS=27303.70
2005: Under LIFO 4738+P-30412=5592
→P=31266
Under FIFO 5474.40+P-COGS=6396.20
→CO GS=30344.20。