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Assignment2

Reading Report ⅠSource of the reading material InternetTitle The Road to Success Author Andrew CarnegieSummary:In this article , the author tells us a prime condition and great secret for achieving success during our future career life . That is , concentrating our energy , thought , and capital exclusively upon the business in which we are engaged . It is well that young men should begin at the beginning and occupy the most subordinate positions . Once we have begun in one line , we should resolve to fight it out on that line , lead in it , adopt every improvement , have the best machinery , and know the most about it .Reflection or Response:During our future life , we should act as what the author told us , that is aiming for the highest , concentrating , expenditure always within revenue and being patient . If we keep the belief that ―My place is at the top‖ in mind , we will be successful someday . A s Emerson says,―no one can cheat you out of ultimate success but yourselves.‖Vocabulary explanation list：1.subordinate adj. 次要的,从属的2.threshold n. 开始,开端,极限3.janitor n. 守卫,门警,管理人4.extensive adj. 广阔的,广泛的5.exclusively adv. 排外地,专有地6.scatter v. 分散,散开,撒开7.tumble v. 翻倒,摔倒,倒塌8.speculate v. 推测,思索9.expenditure n. 支出,花费10.at the threshold of 在…的开始11.salutary adj. 有益的,有用的,有益健康的12.put all one's eggs in one basket 孤注一掷1.But if by chance the professional sweeper is absent any morning, the boy who has the genius of the future partner in him will not hesitate to try his hand at the broom.【结构解析】“by chance”的意思是“碰巧”，“who has the genius of the future partner in him”是定语从句修饰“the boy”。

Assignment 2,有车一族翻译

Assignment 225 years ago, what China’s consumer most wanted was a color TV set, besides, “buy wheels” means buy a bicycle. Today, China has made a great change. After more than 30 years’ economic reform, Chinese people becomes richer and richer. With the development of national car Industry, car price have been ratcheting down, which means ordinary people can afford a car.Zhangming, an employee in a foreign company, bought a car last year, when it comes to the reason why he bought the car, he said that buying a car is always his dream. When he was a child, he saw people driving freely for shopping and traveling in the foreign movies. He really admired this kind of life. Now, given that his income was pretty good and the car price was acceptable, he decided to buy one, which later led him to a more convenient and colorful life. He can drive to work comfortably while listening the music instead of taking the bus. Besides, he can drive the car to travel with friends to suburban areas on weekends. comparing to the days that having not yet bought this car, he had to stay at home or strolling within the downtown. The car owner like Zhangming, they have experienced both happiness and annoyance from their cars. The first is traffic jam. As the number of private cars increases, cities’ traffic problem has been increasingly severe. Therefore, Zhangming has to leave home at 7:00 a.m. everyday for work to make sure staying ahead of 8:00 a.m. working time, in spite of the close proximity to his company. Secondly, the oilprice is increasing everyday, which pushed up the running costs of the car. As for many car owners, they may be able to afford a car, but unable to run it.“If the traffic keeps worsening and gasoline price continues to rise,” he added, “I’m going to take subway to work, which only takes 20 minutes. The ticket price is quite lower than the cost of driving.”Zhang’s idea is typical for general car owners. With the development of public transportation in China becomes more and more convenient and comfortable, an increasing number of car owners would prefer public transportation. The Chinese people, like many in other foreign metropolises, would certainly undergo a circle in transportation that they begin with private cars but end up with public transportation service.。

Assignment2(1)

DS 310Assignment 2Please submit your solution to Canvas by 11:59pm,February 24th.Problem 1-Logistic Regression (10pts)Let g (z )=11+e −z be the logistic function.Please •(5pts)Show that d dz g (z )=g (z )(1−g (z ))•(5pts)Show that 1−g (z )=g (−z )•(Optional)Consider the cross entropy loss function for logistic regression simpliﬁed so there is only one training example:J (θ)=−y log h θ(x )−(1−y )log(1−h θ(x )),h θ(x )=g (θT x )=11+e −θT x (1)Show that the partial derivative with respect to θj is:∂∂θj J (θ)=(h θ(x )−y )x j (2)Problem 2-Multi-class Logistic Regression (10pts)For multi-class classiﬁcation using binary logistic regression,one way is to use the One-vs-All (One-vs-Rest)as we discussed in the class.Another way is to extend the binary logistic regression to multi-class logistic regression using softmax function.Assume there are K classes,for a data sample x ∈R n ×1,the predicted probability that x belongs to class k is given as (for simplicity,we don’t add intercept)P (y =k |x ;W )=exp(w T k x ) K i =1exp(w T i x )(3)where w k ∈R n ×1is the parameters to be learned.•(3pts)Please simplify Eq.(3)for K=2.Does the simpliﬁed one have the same formatas binary logistic regression?Hint:exp(w T 2x )exp(w T 1x )=exp((w 2−w 1)T x )•(5pts)Assume that K=3,x =[1,2,2],w 1=[1,0,1],w 2=[0,1,1]and w 3=[1,1,0],please calculate P (y =1|x ;W ),P (y =2|x ;W ),and P (y =3|x ;W ).•(2pts)For the above example,i.e.,x =[1,2,2].Based on the calculation,which class should we classify x =[1,2,2]and why?•(Optional)For simplicity of notation,let’s denote y k =P (y =k |x ;W ),with P (y =k |x ;W )=exp(w T k x ) K i =1exp(w T i x )as deﬁned in Eq.(3),please derive the partial derivative ∂y k ∂w j ,j =kProblem 3(5pts)You run gradient descent for 15iterations with α=0.3and compute J (θ)after each iteration.You ﬁnd that the value of J (θ)decreases quickly then levels oﬀ.Based on this,which of the following conclusions seems most plausible?A:Rather than use the current value of α,it would be more promising to try a larger value of α(say α=1.0).B:α=0.3is an eﬀective choice of learning rate.C:Rather than use the current value of α,it would be more promising to try a smaller value of α(say α=0.1).Problem 4(5pts)Suppose you have the following training set,and ﬁt a logistic regression classiﬁer h θ(x )=g (θ0+θ1x 1+θ2x 2).Which of the following are true?Check all that apply.A:J (θ)will be a convex function,so gradient descent should converge to the global minimum.B:Adding polynomial features (e.g.,instead using h θ(x )=g (θ0+θ1x 1+θ2x 2+θ3x 21+θ4x 1x 2+θ5x 22)could increase how well we can ﬁt the training data.C:The positive and negative examples cannot be separated using a straight line.So,gradient descent will fail to converge.D:Because the positive and negative examples cannot be separated using a straight line, linear regression will perform as well as logistic regression on this data.Problem5(5pts)Suppose you train a logistic classiﬁer hθ(x)=g(θ0+θ1x1+θ2x2).You obtainθ0=−6,θ1=1andθ2=0.Which of the followingﬁgures represents the decision boundary found by your classiﬁer?(a)A(b)B(c)C(d)DProblem6Feature Scaling(10pts)For the data samples shown below,please perform normalization and standardization.x1x2y1.52.00.3-1.0 2.0-0.2-2.0-1.00.12.0-2.50.4Problem7Use Sklearn Logistic Regression(10pts)We will use the implementation of Sklearn for Logistic Regression.Please download the notebookﬁle“Assignment2Q5”from Canvas.You can either upload the notebookﬁle to Google Colab toﬁnish this question or run locally.Following the instructions in the notebook andﬁll in the key code.After that, in the browser,click on“File”,Select“Print”,and choose“Save as PDF”.Submit the pdf along with your solution to other problems to Canvas.。

assignment-2

assignment-2 Questions of module01Read the chapter01-chapter03 of textbook, answer the following questions:1.Discuss the meaning of each of the following terms:(a) dataData is the physical symbols that represent different kinds of information.(b) databaseA Shared collection of logically related data (and a description of this data), designed to meet the information needs of an organization.(c) database management systemDatabase management system is a software system that enables users to define, create, and maintain the database and that provides controlled access to this database.(d) data independenceThis is essentially the separation of underlying file structures from the programs that operate on them,also called program-data independence.(e) views.A virtual table that does not necessarily exist in the database but is generated by the DBMS from the underlying base tables whenever it’s accessed.2.What is the difference between conceptual and logical data models? Giveexamples of each.Conceptual data models: Used to describe data independently of any system；Purpose is to represent the concepts of the real world；Used in early stages of database design；Example: entity-relationship (E-R) modelLogical data models:Used in DBMSs for the organization of data at a level that abstracts from physical structuresExample:the relational data modelthe network data modelthe hierarchical data model3.Define the terms relation, schema, instance and attribute. Give examples.Relations is a table with columns and rows.Example:Courses（course,tutor,room）The schema represents the structure of the data .Example:Schema of Courses is (Course, Tutor, Room)The instance represents the actual values.Example:The instances of Courses are the contents of the tables4.What is the purpose of the three levels (i.e. physical, logical and external) fora DBMS?Separate each user’s view of the database from the way the database is physically represented.5.What is the difference between the DML and DDL parts of SQL? What partwould you use to (i) create a table to hold information about employees, (ii) add information about a new employee to the table, and (iii) find out thesalary of one of the employees?The database administrator often interacts with the database via a “Data Definition Language” or DDL.Database users interact with the database via a “Data Manipulation Language” or DML.DDL DML DML6.Describe the five components of the DBMS environment and discuss howthey relate to each other.Hardware:The computer system(s) that the DBMS and the application programs run on. This can range from a single PC, to a single mainframe(主机), to anetwork of computers.Software:The DBMS software and the application programs, together with theoperating system, including network software if the DBMS is being used over a network.Data:Used by the organization.The data acts as a bridge between the hardware and software components and the human components.Procedures:Instructions and rules（操作说明和规则）that should be applied to the design and use of the database and DBMS.People:Includes DBMS designers and implementers(实现者), database designers, database administrators ( DBAs), application programmers, and end-users.7.What is logical data independence?Logical data independence refers to the immunity of the external schema to the changes in the conceptual schema.8.what is physical data independence?Physical data independence refers to the immunity of the conceptual schema to the changes in the internal schema.。

ASSIGNMENT 2 Solutions

E(x2 )

2 2 x f ( x)dx x 2 xdx 0
1
1 41 1 x 0 2 2
ASSIGNMENT 2
1. Three balls are drawn in succession without replacement from an urn containing 2 red balls and 3 black balls. Let W be a random variable giving the number of black balls minus the number of red balls drawn. List the elements of the sample space S for the three draws and to each sample point assign a value w of W. Key: S ●●● ●●● ●●● ●●● ●●● ●●● ●●● W -1 -1 -1 1 1 1 3
3. Consider the density function
2x ke , x 0 f ( x) 0, elsewhere
(a) Find the value of k (b) Find F(x) and use it to calculate P(-0.5<x<-0.2 ). Key:
3 0.1 0.133 0.167
0 X 1 2
(a) (b) (c) (d)
0 0.033 0.067
0.033 0.067 0.1
0.067 0.1 0.133
P( X P( X P( X P( X
1, Y 2) 0.067 0.1 0.167 ; 1, Y 1) 0.033 0.067 0.1 0.067 0.1 0.133 0.5 ; Y ) 0 0.033 0.067 0.1 0.067 0.1 0.133 0.133 0.167 0.8 ; Y 3) 0.1 0.1 0.1 0.3 ;

高级写作 Assignment2 (2)

WangKang0901010303Class 3Review of “The Decline and Fall of the British University”IntroductionUniversities are probably the most common institutions in the modern society. Almost every young man gets the opportunity to be exposed to one university. However, in the past, the universities are places that not everybody has a chance to get into. The gate of the universities was open only to a few people who could read and write and wanted to learn. The universities are places that people in there can achieve and disseminate knowledge. So Dr. Mark Tarver who used to be a lecturer in a university thought that the British university is in a decline and fall in his article “The Decline and Fall of the British University”.SummaryIn the article, Dr. Mark Tarver said that the education in university had changed over these years. In his years as a lecturer, he experienced the expansion of the university system happened in the post-war Britain. The universities had to peg their incomes and reduce the funding for students. So the universities were forced to face the choice of less money and redundancies or reduce their demands. And because of this kind of expansion, the educational quality of the university had fallen. If the universities want more money, they have to keep the students as more as possible. So it is getting harder for the lecturers to fail their students, and the lecturers have to simplify their assignments. And so did the lecturers’ quality. Tarver said that today’slecturers believe that the more papers they write, the better a lecturer they will be. So the lecturers began to concentrate on working with paper after paper. Tarver believed that such a kind of life of a lecturer was a lie so he quitted and this new kind of educational system would bring the students less knowledge and more debts. Arguments and EvaluationIn his article, Dr. Mark Tarver pointed out three problems as his arguments to convince his thesis. In his opinion, the British universities were in a decline and fall. He believed that today’s educational system is getting worse and worse. However, there are some important points that Dr. Mark Tarver should have considered carefully when he makes his viewpoint. Tarver thought the expansion of the university system has bad influence for modern universities. Actually, the expansion can help to disseminate the modern knowledge to some degree. It would improve the level of education. It would be much easier for normal people to get higher education. And the educational quality is not really falling. Because there are more and more people get into the university, the lecturers’ assignments should adapt to the overall standard of students’knowledge. So the lecturers should not fail so many students. Dr. Mark Tarver pointed out some potential risks in today’s Britain universities. For example, the lecturers’ paper works may really have some disadvantages to the lecturers’ quality. Yet most of his evidence was based on his own experience as a lecturer in a computer school, which was too unbalanced to judge the whole situation of Britain universities. Actually in some other universities, the situation was not like what Tarver had said. So it was not right to believe what Dr. Mark Tarver said just because of his personalexperience.ConclusionAs a former lecturer of a university, Dr. Mark Tarver awakens people of the potential dangers of the modern educational system of the universities. He pointed out the shortage of the modern system of university education. However, his view of this current situation is somehow too rash and his understanding of it is obviously limited. So we should recognize the reality clearly and try to find out the advantage of today’s educational system.(611words)。

assignment 2

Marking Symbols and Grades∙Agr (Agreement)∙Amb (Ambiguity)∙Awk (Awkward)∙Colloq (Colloquial)∙Constr (Construction)∙CS (Comma Splice)∙Dgl (Dangling Modifier)∙Frag (Fragment)∙Id (Idiom)∙Para(Paragraph)∙ll (Parallelism)∙P (Pronoun Reference)∙Ref (Punctuation)∙Red (Redundant)∙Rep (Repitition)∙R-O (Run On)∙Sp (Spelling)∙T (Tense)∙Trans (Transition)∙Wdy (Wordiness)∙WW (Wrong Word)∙Grades Or Why Did I Get That B-Agreement (Agr)Subject and verb do not match, or pronoun and antecedent. The easiest way to make this error is simply to forget an "s":"The quick brown fox jump over the lazy dog."More complicated agreement problems arise with multiple subjects, intervening phrases and pronouns. See the section on agreement in the grammar section for further information.Ambiguous (Amb)Whether the error is one of grammar or diction, the comment ambiguous means that what you have written is confusing. An example of grammatical ambiguity is the following pair of sentences:Biff is presented to us as an All-American boy. As he grows up all Willy can do is criticize his son.This construction implies that it is Willy who is doing the growing-up, rather than Biff. (The sentences need to be reworked:"Biff is presented to us as an All-American boy. As he grows up, he receives nothing but criticism from Willy."Ambiguity can also be produced by a mistake in vocabulary (many examples are dealt with in the Dictionary of Usage (45Kb)--see, for example, the entries on allusion/illusion and continual/continuous or word order (is a "big boys' school" a big school for boys or a school for big boys?).Awkward (Awk)This term can cover a variety of errors, but in general applies to anything unwieldy in your essay.Sentences become awkward through a combination of structural flaws, wordiness and incorrect usage.For King Lear, because of the one fault he makes, he pays for it dearly.This sentence is awkward because it contains an extra phrase that does not fit grammatically ("For King Lear") and because the student uses "fault" unidiomatically (a better word would be "error").A subordinate clause or phrase placed incorrectly can cause confusion or awkwardness:Besides that of her parents, it is not until Jane arrives at Lowood that she experiences love.The opening clause should be at the end:It is not until Jane arrives at Lowood that she experiences love other than that of her parents.The construction of the sentence can also lead to awkwardness:Cocteau seems to almost ridicule, in the process, the Greek belief in nobility.The phrase "in the process" interrupts the flow of the sentence; it should come at the beginning or the end. In addition, the modifier "almost" is placed awkwardly: it splits an infinitive, and should be closer to the verb it modifies. A more effective way to structure the sentence would be this:In the process, Cocteau almost seems to ridicule the Greek belief in nobility.Awkward indicates that a variety of problems are making your sentences unreadable.Colloquial (Colloq)The word or phrase you have used is inappropriate in a formal essay, because it is too slangy:The very idea of Titania falling in love with Bottom seems a tad preposterous.Or the grammar may be too loose, too conversational:Another thing is, every sentence ends with a question mark.Construction (Const)The construction of your sentence has made it awkward or confusing. Often the problems are the result of starting the sentence with the wrong clause or phrase. When a sentence doesn't work, start it from a different part. Pick it up and shake it. See the pages on sentences for problems to avoid in construction.Comma splice (CS)You have joined two sentences together with a comma:Lear was a majestic ruler when he was young, however, as he became older, his temptations clouded his thought.See the full discussion on comma splices in the pages about sentences.Dangling or Misplaced Modifier (Dgl)A dangling modifier has been placed in a sentence where it has nothing to modify:Flying into Victoria, the trees looked lovely.This sentence suggests that the trees are flying. The sentence must be reworked so that the person doing the flying is mentioned.A misplaced modifier has been placed next to the wrong word:He attacked the dragon with a sword.The sentence suggests that it's the the dragon that has the sword. While the meaning is often clear in context, the sentence would benefit from rewritingHe drew his sword and attacked the dragon.For more, see the discussion on dangling modifiers in the section on sentences.Fragment (Frag)A sentence fragment is a sentence without a verb. Usually the student is appending a phrases to a sentence, but does not understand the function of semi-colons or parentheses:There are a few events in the play which are important both in themselves and symbolically. The first one being the plucking of Gloucester's eyes.Every sentence must have a subject and a verb (in this case, there is no verb, only a participle ).For more, see the page on sentence fragments in the section on sentences.Idiom (id)An idiom is an accepted combination of words whose meaning is greater than the sum of its grammatical parts. Some idioms, such as "such as" or "have lunch", are established components of written language; others, like "Let's do lunch" or "What's up?" are informal or slang. The comment "idiom" may mean that you have used an informal idiom inappropriately, or that you have deviated from standard idiomatic usage.For example, while it would be logical and grammatical to say "get into the bus," English idiom requires that we say "get onto the bus." See the page on awkwardness for another example.ParagraphIf this symbol occurs in the middle of a paragraph, it means that you should have started a new paragraph at that point. This line joining paragraphs indicates that the two paragraphs should have been one. This Guide includes extensive information on paragraphing.ParallelismFaulty parallel sentences occur endlessly in student essays. A parallel sentence must have the same grammatical structure in each of its clauses (hence the term "parallel"). See the section on sentences for fuller instructions on parallelism.Pronoun Reference (P)This comment may mean that you have used the wrong pronoun (e.g. "He which hesitates is lost") or that it is unclear what the pronoun refers to.Confusion is particularly prevelant when you are writing about two people of the same sex, in which case you often end up with sentences like this one:She told her that her face was dirty, and she told her to take a bath.Another pronoun problem is the indeterminate "this":Because of this, I can't go to the moon.The reader will ask, "This what?" When you use a pronoun, make sure that its meaning is absolutely clear.For more information, see the pages about subject/verb agreement,pronoun agreement, and the general discussion on agreement.Punctuation (Ref)You have used the wrong punctuation symbol (e.g. a period instead of a comma). Usually sheer carelessness is the reason, but students often misuse more complicated punctuation marks like the colon and the dash.For a general discussion, see the pages on punctuation and the comma splice.Redundant (Red)You have qualified a word that needs no qualification.For example, a student wrote of Lear and Cordelia that their bond is "mutual." A bond between two people can only be mutual. Another example is the description "He wore a hat on his head." There is no need to mention that the hat is on his head; one can assume that he would wear it there. Be aware of the implications of words to avoid redundant observations.Another common redundancy is the use of synonyms. Students feel that they need to produce lists instead of single words, and thus write sentences like "If you own or possess something of value." "Own" and "possess" are virtually the same word, so using both is redundant.Repetition (Rep)You have repeated a word or phrase unnecessarily.For example, in this sentence a pronoun should have been used:The desire people have to nurture their dogs arises from human tendency to identify with their dogs.The second half of the sentence should read: "...from the common tendency to identify with them."Repetition may also refer to ideas that you have used more than once or to sentences that are rewrites of previous ones. Make sure your essays move forward with each sentence and do not belabor your points.Run-On Sentence (R-O)Similar to a comma splice,but without the comma. A run-on sentence simply welds two sentences together with no break:I like to study I like to surf.Again, be certain that you understand what a main clause is.Spelling (Sp)You have made a spelling error. If it is a typo, be sure to proofread your next paper; if it is a genuine spelling error, learn and remember the correct spelling. See the spelling pages for more rules and advice.Tense (T)A common problem in literary essays is switching tense when discussing plot.It is standard practice to talk about events in a narrative in the present tense:When Kit and Port arrive in El Ga'a, Port becomes ill.Only use the past tense if you are discussing one event and wish to make reference to something that happens earlier in the book:Port discovers that his passport is missing, and realizes that Eric must have stolen it when they were togetherTransition (Trans)A faulty connection has been made between two ideas.One possibility is that you have not joined them effectively enough; for example, a linking word such as because might be needed. Another possibility is that you have used a transition incorrectly; perhaps you have linked two ideas that should not really be related. See the page on paragraph transitions for more details.Wordy (Wdy)Like awkward, a sign that your essay does not flow well. There are numerous suggestions on how to avoid wordiness throughout this Guide. Wrong WordYou have used one word where another would be more accurate (e.g. using "continual" instead of "continuous"). This mistake can be disastrous, as when Dan Quayle proudly stated that "Republicans understand the meaning of bondage between a mother and child." See the Usage dictionary (12 k) for a list of words commonly confused or misused.Grades—Or, Why Did I Get That B-?What A Grade MeansThe University of Victoria uses a nine point grading system divided into first class (A+, A, A-), second class (B+, B, B-), pass (C+, C, D) and fail (E, F). The Department of English offers these guidelines to its instructors on the meaning of the grades that are assigned:First Class ("A" range)Given for excellence in style and content, with evidence of perceptiveness and originality;ideas are formulated clearly and understood fully by the writer; the first class paper demonstrates a superior performance in most areas of expression and content.Second Class ("B" range)Given for good work, which may be flawed by omissions or by minor weaknesses of style or organization; often the paper tends toward vagueness or formlessness, as if the ideas are not quite clear in the writer's mind; often, too, it may contain a limited number or range of ideas, as if the writer has some general knowledge of the subject, but has not thought the material through; although papers in the upper range may suggest superior work, the second class essay remains a good, solid, but not spectacular performance. Pass ("C" range and "D")Given for satisfactory writing which contains errors in content, style, and organization;ideas are pedestrian and suggest no firm grasp of the material; sentences and ideas are dull and repetitive; "C" papers (C+ and C; there is no C- grade) are in no danger of failing, but have little hint of anything more than an average performance. "D" papers are on the borderline; they suggest incompetence in content and style; organization and substantiation are probably deficient, and the writing shows difficulty in dealing with written language; there may be some redeeming factors, but the result suggests failure rather than a passing grade.Fail ("E" and "F")Given for unsatisfactory performance; mechanical errors seriously inhibit understanding;any points made tend to be superficial; there is no sense of audience, of paragraphing, of making an argument, or of understanding the material. An "E" paper may suggest possibilities for improvement (and may qualify for a supplemental examination), but both failing papers clearly demonstrate incompetence.Here is another comment, specifically on the kind of paper that earns a respectable but unspectacular grade, a B-:The common B- paper will have nothing really bad, nothing really good. There will be a thesis, but it will probably be obvious, almost a truism; there will be paragraphs, but they will be short, and there will be only a few details of support for generalizations; there will be a conscious attempt at organization, but it will again be obvious (this is my introductory passage. . . here comes the conclusion. . .); sentences will be accurate but short, and will tend to be monotonous;there will be a few comma errors (one where there should be two) but probably no run-on sentences; vocabulary will be unadventurous.Then there is the less common, more frustrating B-. There will be ideas, and signs of an active intelligence, but there will be more serious problems of expression: syntax in particular will be unbalanced or contorted, with awkward parallel constructions, problems of agreement,and dangling modifiers; there may be more spelling errors, often of less common words (though this is the kind of paper where you get the its/it's confusion).Grading is more complicated than summaries such as this can show; if you do not understand why you were given a particular grade, you should first of all read over the essay carefully, deciphering the instructor's comments. Then, if the reason is still not clear, you should consult the instructor directly.There are many reasons why you may not be performing as well as you expect. Statistics show that students coming to university from high school will on the whole earn grades almost one grade point lower than they are used to; those transferring from colleges may expect to perform about half a grade lower. Essays at the university level inevitably require more intellectual effort, and the result of dealing with more complex ideas is that sometimes the sentences and paragraphs you are used to using are no longer adequate.< p> The purpose of this manual is to give you the tools to improve your performance, not only in English courses, but in all courses that require thinking, organizing, and writing. There are not many at the University that do not.。

数学建模Assignment-2

600*A1+300*A2+500*B1+200*B2<=1000S.t= A1+A2>=1;B1+B2<=1;-A1+B1<=0；-A2+B2<=0；A1,A2,B1,B2=0 or 1;TASK 4: 图可达性，如输入两个顶点，判断图中一个顶点到另一个顶点是否存在至少一条路径?（3 points)要求写出思路和伪代码即可。

思路：输入两个顶点，从第一个顶点开始遍历，如果在遍历过程中出现第二个顶点，则说明这两个顶点至少存在一条路径，否则不存在任何路径。

使用的语言：C++存储结构：邻接表伪代码：邻接表的存储结构：struct lindnode//邻接表中顶点的关系{ int vex;bool sh; // 0表明顶点还没被访问，1表明已被访问，防止重复访问linknode*next; }struct node //邻接表中的所有节点{ char data;linknode*head;node adj[ms];//创建一个数组，保存所有顶点输入图的数据函数的创建void createlink(){输入n; //n总顶点数量for(1 to n){adj[i].head=0;输入adj[i].data; //adj[i].data是图中顶点的名称输入m; //m是与当前输入点直接相连的点的数量}输入p->vex; //输入与此顶点直接相连的其他顶点}遍历（采用深度遍历）：viod DFS（int v,char tag）{p=new linknodep=adj[v].head;adj[v].sh=1；//标志此顶点已经被访问，防止重复访问if（adj[v].data等于tag）//如果遍历到的顶点与目标顶点相等{输出<<"在在至少一条路径";return；//结束这个函数}while(p!=0){ DFS(p->vex)p=p->next; }}main() //函数入口{createlink();cin>>A,B;for(i to n){ if( adj[i]=A)vv=i;break; }DFS（int vv，B）}BONUS（Optional):下载资源里的testcsv.zip文件，实际是代表一个大图的数据，要求用JAVA实现任意输入两个点，能返回是否有路径的结果及运算时间，所实现程序运行时间最短的同学有特殊奖品:）。

assignment 2 by 1-2高馨蕾+1-5王思予

Team Member： T1高馨蕾（1-2）T2王思予（1-5）- - - Period: 2 Score:1.Though Twitter, with 140m active users the world’s best-known microblogging service, isblocked in China, and Sina Weibo, a local variant, has over 250m users. Chinese is so succinct that most messages never reach that limit, says Shuo Tang, who studies social media at the University of Indiana.T1：虽然推特拥有1.4亿活跃用户，是世界上最著名的微博服务，但在中国无法使用。

而新浪微博作为一个当地变体，有2.5亿多用户。

印第安纳大学的社会媒体学者唐硕认为中国人崇尚简洁，大多数的信息没有达到这个限度。

T2：尽管推特作为世界上最著名的微博服务，并且拥有140百万活跃用户，被中国和有超过250百万用户的当地一个变体的新浪微博所阻止。

在印第安纳大学的社会媒体做研究的唐硕说：“中国是如此简洁，大多数消息从未达到这一限制。

”2.Yet the basic problems are the same everywhere. Mr. Lowenhaupt recalls an acquaintancefrom China teaching him a Chinese saying, “rice paddy to rice paddy in three generations”.The acquaintance was surprised to learn that other cultures have similar proverbs.T1：但基本问题都是一样的。

assignment-2(附答案)

====Word行业资料分享--可编辑版本--双击可删====Passage 1 (TAP, Translation Journal)Winners do not dedicate their lives to a concept of what they imagine they should be; rather, they are themselves and as such do not use their energy putting on a performance, maintaining pretence, and manipulating others. They are aware that there is a difference between being loving and acting loving, between being stupid and acting stupid, between being knowledgeable and acting knowledgeable. Winners do not need to hide behind a mask. Winners are not afraid to do their own thinking and to use their own knowledge. They can separate facts from opinions and don’t pretend to have all the answers. They listen to others, evaluate what they say, but come to their own conclusions. Although winners can adore and respect other people, they are not totally defined, demolished, bound, or awed by them.Winners do not play “helpless”, nor do they play the blaming game. Instead, they assume responsibility for their own lives.成功者不会穷其毕生之精力，执着于自我之臆想。

微观经济学曼昆课后答案2

ECONOMICS 2010 ASSIGNMENT 2 – CHAPTERS 4 & 5NAME____________________________________________1. What is a market?A MARKET IS A GROUP OF BUYERS AND SELLERS OF A PARTICULAR GOOD OR SERVICE--- BUYERS AS A GROUP DETERMINE DEMAND FOR THE PRODUCT OR SERVICE AND THE SELLERS AS A GROUP DETERMINE THE SUPPLY OF THE PRODUCT OR SERVICE2. What are the characteristics of a perfectly competitive market? Explain.A COMPETITIVE MARKET IS A MARKET IN WHICH THERE ARE MANY BUYERS AND MANY SELLERS. EACH BUYER AND SELLER HAS A NEGLIGIBLE IMPACT ON THE MARKET PRICE AND THERE IS FULL INFORMATION AMONGST BUYERS AND SELLERS.3. Explain what is meant by a) quantity demanded; b) a demand schedule;and c) the law of demand.THE QUANTITY DEMANDED IS THE AMOUNT OF A GOOD THAT BUYERS ARE WILLING AND ABLE TO PURCHASE.THE DEMAND SCHEDULE IS A TABLE OR LISTING THAT SHOWS THE RELATIONSHIP BETWEEN THE PRICE OF A GOOD OR SERVICE AND THE QUANTITY OF THE GOOD OR SERVICE DEMANDED.THE LAW OF DEMAND IS A CLAIM THAT ,OTHER THINGS EQUAL, THE QUANTITY DEMAND OF A GOOD OR SERVICE FALLS WHEN THE PRICE OF THE GOOD OR SERVICE RISES.4. Graph the demand curve given the data from the demand schedule for slices of cherry pie at different prices in the table below.$14 85. Define or identify the economic factors that shift the demand curve. CHANGES IN INCOME, CHANGES IN THE PRICES OF SUBSTITUTE AND COMPLEMENTARYGOODS, TASTES AND PREFERENCES, CHANGES IN EXPECTATIONS, AND CHANGES IN THE NUMBER OF BUYERS,.6. Define what is meant by the “Law of Supply”.THE LAW OF SUPPLY CLAIMS THAT, OTHER THINGS BEING EQUAL, THE QUANTITY SUPPLIED OF A GOOD OR SERVICE INCREASES WHEN THE PRICE OF THE GOOD OR SERVICE INCREASES.7. Look at the figure below and then indicate what factors, or variables, wouldcause the supply curve for Pizza to shift back from supply curve S1 tosupply curve S2.INCREASES IN THE COSTS (PRICES) OF INPUTS SUCH AS LABOR, CAPTITAL, MATERIALS, ENERGY WILL SHIFT THE SUPPLY CURVE FROM S1 TO S2. SIMILARLY CHANGES IN TECHNOLOGY THAT INCREASE THE COST OF PRODUCTION WILL SHIFT THE SUPPLY CURVE BACK IN ADDITION OF THE DAMPENING OF EXPECTATIONS ON HOW MUCH CAN BE SOLD. IFTHE NUMBER OF SELLERS (PRODUCERS) DECREASES AND THEIRPRODUCTION DECREASES, THEN SUPPLY WILL SHIFT BACK AS WELL.8. The supply of canvas covers from the Cheung Company to the canvasmarket is 300 canvases if the price per canvas is RNB2,000. The supply of canvases from the Liu Company is 314 canvases if the price per canvas is RNB2,000. What is the market supply of canvases at a price of RNB2,000?MARKET SUPPLY OF CANVASES AT ANY GIVEN PRICE IS THE ADDITION OF THE SUPPLY OF EACH PRODUCER AT THAT GIVEN PRICE, WHICH IN THIS CASE WOULD BE 614CANVASES IF THERE ARE ONLY THE TWO SUPPLIERS IN THE MARKET.9. The demand function for a good, Q, is given by Q D = 12 – P, while thesupply function for Q is given by Q S = 4 + 3P, where P = price. Solve for the equilibrium quantity, Q, and price, P, in the market.SET Q D = Q S, OR 12 – P = 4 + 3P, OR 4P = 8, OR P = 8/4 = 2, SO P = 2SUBSTITUTE P = 2 INTO Q D = 12 – P, OR Q = 12 – 2 = 10, SO Q = 1010. Now suppose that the demand for good Q shifts out (same as shiftingupwards on the supply curve) and the demand curve under theseconditions now becomes Q D = 14 – P. In addition, because of a shortage in inputs used to produce good Q, the supply of Q shifts back and the supply function becomes Q S = 2 + 3P. Now solve for the new equilibrium price, P, and quantity, Q, in the market.AGAIN SET Q D = Q S UNDER THE NEW SUPPLY AND DEMANDCONDITIONS: 14 –P = 2 + 3P, OR 4P = 12, AND P = 3SUBSTITUTE P = 3 INTO Q = 14 – P = 14 – 3 = 11, SO PRICE = 3 ANDQUANTITY = 11 BECAUSE OF THESE SHIFTS IN DEMAND AND SUPPLY.11. Define the economic meaning of the term, “Price Elasticity of Demand” inwords and also in terms of percentage changes.)THE PRICE ELASTICITY OF DEMAND IS A MEASURE OF HOW MUCHQUANTITY DEMANDED OF A GOOD OR SERVICE RESPONDS TO ACHANGE IN PRICE OF THE GOOD OR SERVICE, AND IS COMPUTED AS THE PERCENTAGE IN QUANTITY DEMANDED DIVIDED BY THEPERCENTAGE CHANGE IN THE PRICE OF THE GOOD OR SERVICE.12. Derive the price elasticity of demand using the midpoint method if thequantity purchased of a good is 60 units at price $HK8,000 and changes to70 units purchased at a price of $HK6,000.THE MIDPOINT METHOD OF COMPUTING THE PRICE ELASTICITY OFDEMAND = ((Q2– Q1)/ (Q2 + Q1)/2) / ((P2– P1)/(P2 + P1)/2)((70 – 60) / (70 + 60)/2 ) / ((6000 – 8000)/ (6000 + 8000)/2) = -0.5384613. a) The quantity of Women’s purses (in some locations women call thesehandbags) purchased decreases 67 % as price is increased by 22%. What is the price elasticity of demand for women’s purses?IN THIS CASE, PRICE ELASTICITY OF DEMAND =- 76 PERCENT / 22 PERCENT = - 3. 45455b) Do women’s purses have an elastic demand elasticity or an inelasticdemand elasticity from your answer derived in part a) above? Explain. THE ABSOLUTE VALUE OF THE ELASTIITY HERE IS 3.45455 > 1, SO THE ELASTICITY OF WOMENS PURSES IS ELASTIC MEANING THAT AS PRICE DECREASES, THE QUANTITY DEMANDED INCREASES MORE THAN THE PERCENTAGE DECREASE IN PRICE. OR, SAID ANOTHER WAY, AS PRICE INCREASES, THE QUANTITY DEMANDED DECREASES GREATER THANTHE PECENTAGE PRICE INCREASE.14. You are the manager of a clothing store and you have information that thepric e elasticity of demand on men’s shirts is -1.568. What would you do to increase shirt revenues? (Choose from the choices below and explain your choice)a) Increase price?b) Initiate a sale from time to time by decreasing prices of men’s shirts?c) Only sell men’s cotton pants?THE PRICE ELASTICITY OF DEMAND HERE SUGGESTS THAT MEN’SSHIRTS HAVE ELASTIC DEMAND. SO A 10 PERCENTAGE DECREASE IN THE PRICE OF MEN’S SHIRTS INDUCES A GREATER THAN 10PERCENT INCREASE IN QUANTITY DEMANDED. SO THE STRATEGYWOULD BE TO DECREASE PRICES BY HAVING A SALE FROM TIME TO TIME IN ORDER TO INCREASE REVENUES ON THE SALE OF MEN’SSHIRTS, SINCE QUANTITY DEMANDED INCREASES GREATER THANPRICE DECLINE, THIS INCREASING REVENUE.15. The income elasticity of demand for watches in Hong Kong is 0.785. Whathappens to the demand for watches as incomes in Hong Kong increase?Explain.ONE SUCH SCENARIO WOULD BE THAT AS INCOMES INCREASE SAY BY10 PERCENT, THEN THE QUANTITY OF WATCHES DEMANDEDINCREASES BY 7.85 PERCENT. SO AS INCOMES INCREASE, THEDEMAND FOR WATCHES INCREASES. SUCH AN INCREASE IN INCOME CREATES AN OUTWARD SHIFT IN THE DEMAND FOR WATCHES.16. The cross-price elasticity of demand for oranges relative to the price ofpineapple is 0.286. Are oranges and pineapples complements orsubstitutes in consumption? Explain your answer.SINCE THE CROSS-PRICE ELASTICITY OF DEMAND IS POSITIVE, ANINCREASE IN THE PRICE OF PINEAPPLE INCREASES THE DEMAND FOR ORANGES, THAT IS THE DEMAND FOR ORANGES EXPERIENCES APOSITIVE (OUTWARD) SHIFT IN DEMAND. ORANGES AND PINEAPPLE ARE SUBSTITUTE GOODS ACCORDING TO THE CROSS-PRICEELASTICITY.17. Suppose the price of milk in the United States increases from $2.85 pergallon to $3.15 per gallon and the quantity supplied increases from 9,000 to 11,000 gallons per month. Derive the price elasticity of milk supply in the United States.USING THE MID-POINT METHOD OF CALCULATING THE SUPPLYELASCTITY WE OBTAIN,((11000 -9000)/(11000+9000)/2)/ ((3.15 – 2.85)/(3.15 + 2.85)/2) = 1.997AS THE PRICE ELASTICITY OF SUPPLY OF MILK.18. Both the demand for and supply of rice in Thailand are inelastic, but a newhybrid rice is developed that increases the yield of rice per hectare inThailand.a) Is this good news for Thai agriculture? Explain.YES, THIS IS GOOD NEWS FOR THAI AGRICULTURE, SINCE NOW MORE RICE CAN BE PRODUCED AND PRODUCED MORE EFFICIENTLY. THE SUPPLY CURVE OR FUNCTION FOR RICE SHIFTS OUTWARD. MORE RICE CAN NOW BE PRODUCED PER UNIT OF LAND IN THAILAND.b) Is this good revenue news for individual Thai rice farmers? ExplainTHE SUPPLY CURVE FOR RICE SHIFTS OUTWARD AND MORE RICE IS PRODUCED FROM THAI AGRICULTURE. IF THE DEMAND FOR RICE DOES NOT CHANGE, THEN THE PRICE FOR RICE IN THAILAND WILL FALL AND DEPENDING ON THE ELASTICITY OF DEMAND FOR RICE IN THAILAND, REVENUE TO THAI RICE FARMERS COULD DECREASE SINCE THEY ARE PRODUCING MORE RICE. IF THE DEMAND FOR RICE IS INELASTIC, THEN PRICE DECLINES ARE GREATER THAN INCREASES IN RICECONSUMPTION AND REVENUES TO THE FARMERS DECLINE.19. Explain the difference in prices changes in the short run relative to the longrun as a result in changes in demand and supply in the short run relative to the same changes over the long run.In the long run, both the price elasticities of supply and demand become less inelastic or more elastic and therefore more responsive to pricechanges relative to short run conditions of demand and supply. For any given shift of supply on a given demand, quantity increases or decreases are greater than price increases or decreases in the long run setting. In the long run there are more substitutes for any given product or servicemaking demand less inelastic or more elastic. On the supply side, smaller increases in price bring about greater increases in quantity suppliedrelative to the short run conditions of supply.20. Explain the factors or influences upon which the price elasticity of supplydepends.THE ELASTICITY OF SUPPLY DEPENDS ON THE FLEXIBILITY OFSELLERS TO CHANGE THE AMOUNT OF THE GOOD OR SERVICE THEY PRODUCE OR OFFER, ANDTHE TIME PERIOD BEING CONSIDERED, SUCH AS BEING MORE ELASTIC IN THE LONG RUN RELATIVE TO THE SHORT RUN.。

[斯坦福大学公开课：编程方法学] [答案] ASSIGNMENT2

斯坦福大学公开课：编程方法学ASSIGNMENT2Assignment #2: Simple Java ProgramsDue: 1:15pm on Friday, April 19th ,2013Your Early Assignment Help (YEAH) hours: time: tbd , Tues ., Apr . 16th in location:tbd自己写的代码，没有做过优化，这次的作业中问题不是很大，做的挺顺的。

一、PythagoreanTheorem/** File: PythagoreanTheorem.java* Name:* Section Leader:* -----------------------------* This file is the starter file for the PythagoreanTheorem problem.*/import acm.program.*;public class PythagoreanTheorem extends ConsoleProgram {public void run() {println("enter vlues to compute the pythagorean theorem.");double a=readDouble("a=");double b=readDouble("b=");println ("c =" + Math.sqrt(a*a+b*b));}}二、Hailstone/** File: Hailstone.java* Name:* Section Leader:* --------------------* This file is the starter file for the Hailstone problem. */import acm.program.*;public class Hailstone extends ConsoleProgram {public void run() {int a=readInt("Enter a number:");int n=0;while(a!=1){n++;if(a%2==0){println(a+" is even,so I take half : "+even(a));a=even(a);}else{println(a+" is odd,so I make 3n + 1 : "+odd(a));a=odd(a);}}println("The process took "+ n +" to reach 1.");}private int even(int x){int y=x/2;return y;}private int odd(int x){int y=3*x+1;return y;}}三、 FindRange/** File: FindRange.java* Name:* Section Leader:* --------------------* This file is the starter file for the FindRange problem.*/import acm.program.*;public class FindRange extends ConsoleProgram {public void run() {println("The program find the largest and smallest numbers."); int i=readInt("?");int max=i;int min=i;if(i==0){println("NO NUMBER");}while(i!=0){i=readInt("?");if(i>max){max=i;}if(i<min){min=i;}}println("largest："+max);println("smallest:"+min);}}四、Target/** File: Target.java* Name:* Section Leader:* -----------------* This file is the starter file for the Target problem.*/import acm.graphics.*;import acm.program.*;import java.awt.*;public class Target extends GraphicsProgram {public void run() {int x=getWidth()/2;int y=getHeight()/2;GOval outerCircle=new GOval(x-72,y-72,72*2,72*2);outerCircle.setFilled(true);outerCircle.setColor(Color.RED);add(outerCircle);GOval Circle=new GOval(x-46.5,y-46.5,46.5*2,46.5*2);Circle.setFilled(true);Circle.setColor(Color.WHITE);add(Circle);GOval innerCircle=new GOval(x-21,y-21,21*2,21*2);innerCircle.setFilled(true);innerCircle.setColor(Color.RED);add(innerCircle);}}五、ProgramHierarchy/** File: ProgramHierarchy.java* Name:* Section Leader:* ---------------------------* This file is the starter file for the ProgramHierarchy problem. */import acm.graphics.*;import acm.program.*;import java.awt.*;public class ProgramHierarchy extends GraphicsProgram {private static final int m=150;private static final int n=50;private static final double c=0.2;private static final double d=1.6;public void run() {double x=getWidth();double y=getHeight();double my=y/2+n*d/2;add(rect(x/2-m/2,y/2-n*(1+d/2)));add(rect(x/2-m/2,my));add(rect(x/2-m*(1.5+c),my));add(rect(x/2+m*(0.5+c),my));add(line(x/2,y/2-n*d/2,x/2,my));add(line(x/2,y/2-n*d/2,x/2-m*(1+c),my));add(line(x/2,y/2-n*d/2,x/2+m*(1+c),my));GLabel lab1=new GLabel("Program");GLabel lab2=new GLabel("GraphicsProgram");GLabel lab3=new GLabel("ConsoleProgram");GLabel lab4=new GLabel("DialogProgram");lab1.setLocation(lx(x/2-m/2,lab1.getWidth()),ly(y/2-n*(1+d/2),lab1.getAscent( )) );lab2.setLocation(lx(x/2-m*(1.5+c),lab2.getWidth()),ly(my,lab2.getAscent()) ); lab3.setLocation(lx(x/2-m/2,lab3.getWidth()),ly(my,lab3.getAscent()) );lab4.setLocation(lx(x/2+m*(0.5+c),lab4.getWidth()),ly(my,lab4.getAscent()) ); add(lab1);add(lab2);add(lab3);add(lab4);}private GRect rect(double x,double y){GRect e=new GRect(x,y,m,n);return e;}private GLine line(double x1,double y1,double x2,double y2){GLine e=new GLine(x1,y1,x2,y2);return e;}private double lx(double x,double lw){double lx= x+(m-lw)/2;return lx;}private double ly(double y,double lh){double ly= y+(n+lh)/2;return ly;}}六、Pyramid/** File: Pyramid.java* Name:* Section Leader:* ------------------* This file is the starter file for the Pyramid problem.* It includes definitions of the constants that match the* sample run in the assignment, but you should make sure* that changing these values causes the generated display* to change accordingly.*/import acm.graphics.*;import acm.program.*;import java.awt.*;public class Pyramid extends GraphicsProgram {/** Width of each brick in pixels */private static final int BRICK_WIDTH = 8;/** Width of each brick in pixels */private static final int BRICK_HEIGHT = 8;/** Number of bricks in the base of the pyramid */private static final int BRICKS_IN_BASE =50;public void run() {for(int i=1;i<=BRICKS_IN_BASE;i++){double x=getWidth()/2-(double)(BRICKS_IN_BASE-i+1)/2*BRICK_WIDTH; double y=getHeight()-i*BRICK_HEIGHT;for(int j=1;j<=(BRICKS_IN_BASE-i+1);j++){add(rect(x+(j-1)*BRICK_WIDTH,y));}}}private GRect rect(double x,double y){GRect e=new GRect(x,y,BRICK_WIDTH,BRICK_HEIGHT);return e;}}。

assignment2

Chap24/11P, 33,44P; Chap25/8P,9PProblem 1 (Chap 24/11P) A point charge q is placed at one corner of a cube of edge a . What is the flux through each of the cube faces? [Solution]Note that when a point charge is placed at one corner of a cube, the field lines from the charge is tangential to the three faces meeting at the point charge (See the above diagram). So the flux through the these faces must be zero.To find the flux through the other faces, we can build a large cube composed of 8 identical smaller cubes and place the charge at the center of the large one (See the above diagram). According to the Gauss ’ law, 0encE q εΦ=, the flux flowing out of the large cube is 0E qεΦ=.Note that the faces of the large cube is composed of 24 faces of the smaller cube, and the fluxes through each smaller face have the same value due to the symmetry, namely24each small face q εΦ=. This is just the flux through each of the other three faces of a cube when a point charge q is placed at its corner.[Problem 2] Chap24/25P. Charge is distributed uniformly throughout the volume of an infinitely long cylinder of radius R . (a) Show that, at a distance r from the cylinder axis (for r R <),2r E ρε=where ρis the volume charge density. (b)Write an expression for E when r R > .[Solution] Due to the cylindrical symmetry of the charge distribution, we choose a circular cylinder of radius r and height h , coaxial with the charged cylinder, as the Gaussian surface (asshown in the diagram). Two end caps are included to ensure the Gaussian surface is closed. Then the electric field lines will flow throught out of the cylindrical part of the Gaussian surface uniformly and perpendicularly no matter r R < or r R > if the charge is positive.:ρhAccordingly, the electric flux through the Gaussian surface is given by(2)E E rh πΦ=where E is the field magnitude at the cylindrical surface of radius r and 2rh π is the area of this side surface.On the other hand, the net charge enclosed by the Gaussian surface is given by22(), for (), for encr h r R q R h r R ρπρπ⎧<⎪=⎨>⎪⎩Applying the Gauss ’s law 0encE q εΦ=, we have the magnitude of the electric field at a distancer from the cylinder axis as20, for 2, for 2rr R E R r R rρερε⎧<⎪⎪=⎨⎪>⎪⎩The direction of the field is radially outward.[Problem 3] Chap24/33. A planar slab of thickness d and volume charge densityρ.[Solution](1) The magnitude of the electric field inside the slab, at a distance x from the central plane of theslab.The charge distribution has a planar symmetry, so we choose a closed cylinder perpendicular to the slab as the Gaussian surface. The end caps of area A are located at a distance x from the central plane of the slab, above and below respectively.From the symmetry, we know that the electric field Eat any point on the end caps must havethe same magnitude and be perpendicular to the caps in an either outward or inward direction.( In the above diagram, the electric field lines are assumed to flow out of the end caps. ) So the flux through the end caps is determined by12cap cap EA Φ=Φ=For the cylindrical part, the electric field is parallel to the surface at any point so that there is no flux through it, namely,0cyl Φ=The total flux through the Gauss surface is given by122cly cap cap EA Φ=Φ+Φ+Φ=And the charge enclosed by this Gauss surface is2enc xA ρρ=⋅According the the Gauss ’ law 0/enc ρεΦ= , we have022/EA xA ρε=So the magnitude of the electric field at a distance x<d/2 from the central plane is given by0/E x ρε=(2) The magnitude of the electric field outside the slab, at a distance x from the central plane ofthe slab.Similarly, we choose a closed cylinder as the Gaussian surface. The distance from the end caps to the central plane now satisfies x >d /2, as shown in the above diagram. The total flux through the Gaussian surface is still122cly cap cap EA Φ=Φ+Φ+Φ=,But the enclosed charge is given by enc Ad ρρ=. Then the Gauss ’ law 0/enc ρεΦ= reduces to02/EA Ad ρε=So that the magnitude of electric field outside the slab is always0/2E d ρε=,independent of the distance x from the central plane.[Problem 4] Chap.24/44P The figure shows a spherical shell of charge with uniform volme charge density ρ. Plot E due to the shell for distances r from the center of t he shell ranging from zero to 30cm. Assume that 631.010C/m ρ-=⨯, 10cm a = and 20cm b =.[Solution ] According to the spherical symmetry of the charge distribution, we choose a concentric sphere of radius r as the Gaussian surface. The net charge enclosed by this surface is133enc23330, for ( S in the diagam)4(), for ( S34(), for ( S in the diagam)3r a r a q a r b b a r b πρπρ⎧⎪<⎪-⎪=⋅≤<⎨⎪⎪-⋅≥⎪⎩Since the electric field Eat any point on the Gaussiansurface must have the same magnitude and be perpendicular to the surface in any case, the electric flux Φ through the Gaussian surface is always given by24E r πΦ=⋅.Then the Gauss ’ law 0/enc ρεΦ=reduces to 24encq E r πε⋅=, so the magnitude of the electricfield inside the sphere at a distance r from the centre is332033200, for(), for 3(), for 3r a r a E a r b r b a r b r ρερε⎧⎪<⎪⎪-⎪=⋅≤<⎨⎪⎪-⎪⋅≥⎪⎩. Substituting 10cm a =, 20cm b = and 31C/m ρμ= we have3220, for 10cm (0.001), for 10cm 20cm , for 20cm r A r E r r Br r ⎧<⎪⎪-⎪=≤<⎨⎪⎪≥⎪⎩ with -1-137664(N C m )A ≈⋅⋅ and -12263.65(N C m )B ≈⋅⋅.From these expressions we can get the value of the field magnitude at any positions. For example,3976(N/C)E ≈ at 10cm r =, 6591(N/C)E ≈ at 20cm r =, and 2929(N/C)E ≈ at30cm r =. Also we can find30.002(1)0dE A dr r=+> and2240.006(1)0d E A dr r =-< for 10cm 20cm r ≤<. The dependence of E on the distance r is given in the following figure.0.000.050.100.150.200.250.30-100001000200030004000500060007000E =3976N/CE =6591N/CE (N /C )r (m)E =2929N/CChap 25/ 8PA nonconducting sphere of radius R . The electric field inside the sphere 30()4qr E r Rπε=. TakeV =0 at the center. V (r )=? Potential difference between the surface and the center? Which point has a higher potential if q is positive?[Solution](a) Suppose point P located inside the sphere at a distance r from the center O . Set V=0 at the center, the potential at P is given by()P OV r E ds =-⋅⎰Since Eis directed radially, we choose a pathalong the field lines from O to P as shown in the diagram. The differential displacement dsof this path is parallel to the electric field(here we have assumed q is positive) and has length dr ’, so the integral is evaluated as22''333'0'0000'()(')''4428r rr rr r qr q r qr V r E r dr dr R R Rπεπεπε=====-=-=-=-⎰⎰If the charge q is negative, it is easy to find that this result still holds.(b) On the surface, the potential is0()8q V R Rπε=-This is also the difference in potential between the point on the surface and the center.(c) If q is positive, the potential on the surface is negative, which means the potential at the center is higher. We can also get this conclusion according to the positive work done by the electric field when a positive charge is moved from O to P .Chap 25/ 9PThe same sphere as that in 8P, but take V =0 at infinity. [Solution]Since the potential is set as zero at infinity, thepotential at point P is now given byinfinity()PV r E ds =-⋅⎰According the formula of the field due to auniformly-charged sphere, the electric field Eat adistance r ’ from the center is directed radially and has magnitude2300', for ' (inside the sphere)4('), for ' (outside the sphere)4'qr r R R E r q r R r πεπε⎧<⎪⎪=⎨⎪>⎪⎩We choose a path along the field lines from infinity to point P so that the differential displacement dslocated at r ’ is antiparallel to the field and has length -dr ’(Note here '0dr < since 'r decreases from ∞ to point P). The potential at P can be calculated as2''''3''''00''223300000''22233000'()(')'(')'''44''()4'84883(3)888r Rr rr Rr rr r Rr r R r R r rr r Rq qr V r E r dr E r dr dr dr R r qqr qqr qr R R R Rq qr q R r R R Rπεπεπεπεπεπεπεπεπεπε=====∞==∞====∞==-⋅-⋅=-⋅-=+-=--=-=-⎰⎰⎰⎰The difference between the center and the surface is given by0003()(0)488q q q V r R V r RRRπεπεπε=-==-=-The value of the potential at P is different from the result in 8P since different potential reference is chosen, while the potential difference is independent of the location of the zero-potential point.V =。

Assignment 2答案

1.1选择题1. 在下列运算符中，（ d ）优先级最高。

(a) <= （b ）*= （c ）+ （d ）*2. 在下列运算符中，（ d ）优先级最低。

(a) ！（b ）&& （c ）！= （d ）？：3．设i=1，j=2，则表达式i+++j 的值为（ c ）。

(a) 1 （b ）2 （c ）3 （d ）44．设i=1，j=2，则表达式 ++i+j 的值为（ d ）。

(a)1 （b ）2 （c ）3 （d ）45．在下列表达式选项中，（ c ）是正确。

（a ）++（a++）（b ）a++b （c ）a+++b （d ）a++++b6．已知i=0，j=1，k=2，则逻辑表达式 ++i||--j&&++k 的值为（ b ）。

(a) 0 （b ）1 （c ）2 （d ）37. 执行下列语句后，x 的值是( d )，y 的值是( c )。

int x , y ;x = y = 1; ++ x || ++ y ;(a) 不确定 (b) 0 (c) 1 (d) 28.设X 为整型变量，能正确表达数学关系1< X < 5的C++逻辑表达式是( bcd )。

(a) 1<X<5 (b) X==2||X==3||X==4(c) 1<X&&X<5 (d) !(X<=1)&&!(X>=5)9. 已知x=5，则执行语句x += x -= x*x ；后，x 的值为（ c ）。

(a)25 （b ）40 （c ）-40 （d ）2010. 设a=1，b=2，c=3，d=4，则条件表达式a<b ？a ：c<d ？c ：d 的值为( a )。

(a) 1 （b ）2 （c ）3 （d ）411. 逗号表达式“(x=4*5，x*5)，x+25的值为（ d ）。

(a) 25 （b ）20 （c ）100 （d ）451.2把下列数学表达式写成c++算术表达式1．y x +++11111 答案：1/(1+1/(1+1/(x+y)))2.48cos 21π+ 答案:sqrt(1+3.14159/2*cos(48*3.14159/180))1.3 阅读下列程序，写出执行结果1.#include <iostream.h>void main(){int a = 1, b = 2, x, y;cout << a++ + ++b << endl;cout << a % b << endl;x = !a>b; y = x-- && b;cout << x << endl;cout << y << endl;}答案：42-12．#include <iostream.h>void main(){int x,y,z,f;x = y = z = 1;f = --x || y-- && z++;cout << "x =" << x << endl;cout << "y =" << y << endl;cout << "z =" << z << endl;cout << "f =" << f << endl;}答案：x = 0y = 0z = 2f = 11.4编程题1.输入一个三位整数，将它反向输出。

assignment 2 by 1-3李梅+1-5刘莹+3-1张瑜莹

1. Though Twitter, with 140m active users the world’s best-knownmicroblogging service, is blocked in China, and Sina Weibo, a localvariant, has over 250m users. Chinese is so succinct that mostmessages never reach that limit, says Shuo Tang, who studies socialmedia at the University of Indiana.T1：尽管推特有1.4亿活跃用户，并且是世界上广为人知的的微博平台，但是在中国还是被封锁了，而新浪微博，推特在中国的一个变体却有超过2.5亿的用户，中国人都是很简洁的，大多数的信息都达不到极限，唐硕说，他是在印第安纳大学社会传媒专业的学者。

T2: 尽管推特网有着1.4亿的活跃用户,是世界上最著名的微博客服务商,却在中国被禁,而且,新浪微博,作为一种地方变体,也有超过2.5亿的用户。

在印第安纳大学研究社会媒介的唐朔先生说,中文非常简洁,大多数的讯息是达不到所限制的字数的。

T3：尽管拥有1.4亿活跃用户和闻名全球的微博服务的推特在中国被封锁了，还有一个当地的新浪微博拥有超过2.5亿的用户。

在印第安纳大学学习社会媒体的Shuo Tang说，中国人都太严谨了以至于大部分的信息从来没有越过限制。

TT:尽管推特网有着1.4亿的活跃用户,是世界上最著名的微博客服务商,却在中国被屏蔽，而新浪微博，作为推特网在中国的一种变体，有超过2.5亿的用户。

在印第安纳大学研究社会媒体的唐朔先生说，中文非常简洁,大多数讯息的字数是不会超过上限的。

2. Yet the basic problems are the same everywhere. Mr. Lowenhauptrecalls an acquaintance from China teaching him a Chinese saying,“rice paddy to rice paddy in three generations”. The acquaintancewas surprised to learn that other cultures have similar proverbs.T1：最基本的问题在哪都一样。

(完整word版)北航研究生算法设计与分析Assignment_2

用分支定界算法求以下问题：某公司于乙城市的销售点急需一批成品，该公司成品生产基地在甲城市。

甲城市与乙城市之间共有n 座城市，互相以公路连通。

甲城市、乙城市以及其它各城市之间的公路连通情况及每段公路的长度由矩阵M1 给出。

每段公路均由地方政府收取不同额度的养路费等费用，具体数额由矩阵M2 给出。

请给出在需付养路费总额不超过1500 的情况下，该公司货车运送其产品从甲城市到乙城市的最短运送路线。

具体数据参见文件：m1.txt: 各城市之间的公路连通情况及每段公路的长度矩阵(有向图); 甲城市为城市Num.1，乙城市为城市Num.50。

m2.txt: 每段公路收取的费用矩阵（非对称）。

思想：利用Floyd算法的基本方法求解。

程序实现流程说明：1.将m1.txt和m2.txt的数据读入两个50×50的数组。

2.用Floyd算法求出所有点对之间的最短路径长度和最小费用。

3.建立一个堆栈，初始化该堆栈。

4.取出栈顶的结点，检查它的相邻的所有结点，确定下一个当前最优路径上的结点，被扩展的结点依次加入堆栈中。

在检查的过程中，如果发现超出最短路径长度或者最小费用，则进行”剪枝”，然后回溯。

5.找到一个解后，保存改解，然后重复步骤4。

6.重复步骤4、5，直到堆栈为空，当前保存的解即为最优解。

时间复杂度分析：Floyd算法的时间复杂度为3O N，N为所有城市的个数。

()该算法的时间复杂度等于DFS的时间复杂度，即O(N+E)。

其中，E为所有城市构成的有向连通图的边的总数。

但是因为采用了剪枝，会使实际运行情况的比较次数远小于E。

求解结果：算法所得结果:甲乙之间最短路线长度是:464最短路线收取的费用是:1448最短路径是:1 3 8 11 15 21 23 26 32 37 39 45 47 50C源代码（注意把m1.txt与m2.txt放到与源代码相同的目录下，下面代码可直接复制运行）：#include<stdlib.h>#include<stdio.h>#include<time.h>#include<string.h>#define N 50#define MAX 52void input(int a[N][N],int b[N][N]);void Floyd(int d[N][N]);void fenzhi(int m1[N][N],int m2[N][N],int mindist[N][N],int mincost[N][N]);int visited[N],bestPath[N];void main(){clock_t start,finish;double duration;int i,j,mindist[N][N],mincost[N][N],m1[N][N],m2[N][N]; /* m1[N][N]和m2[N][N]分别代表题目所给的距离矩阵和代价矩阵*/// int visited[N],bestPath[N];FILE *fp,*fw;// system("cls");time_t ttime;time(&ttime);printf("%s",ctime(&ttime));start=clock();for(i=0;i<N;i++){visited[i]=0;bestPath[i]=0;}fp=fopen("m1.txt","r"); /* 把文件中的距离矩阵m1读入数组mindist[N][N] */if(fp==NULL){printf("can not open file\n");return;}for(i=0;i<N;i++)for(j=0;j<N;j++)fscanf(fp,"%d",&mindist[i][j]);fclose(fp); /* 距离矩阵m1读入完毕*/fp=fopen("m2.txt","r"); /* 把文件中的代价矩阵m2读入数组mincost[N][N] */if(fp==NULL){printf("can not open file\n");return;}for(i=0;i<N;i++)for(j=0;j<N;j++)fscanf(fp,"%d",&mincost[i][j]);fclose(fp); /* 代价矩阵m2读入完毕*/input(m1,mindist); /* mindist[N][N]赋值给m1[N][N]，m1[N][N]代表题目中的距离矩阵*/input(m2,mincost); /* mincost[N][N]赋值给m2[N][N]，m2[N][N]代表题目中的代价矩阵*/for(i=0;i<N;i++) /* 把矩阵mindist[i][i]和mincost[i][i]的对角元素分别初始化，表明城市到自身不连通，代价为0 */{mindist[i][i]=9999;mincost[i][i]=0;}Floyd(mindist); /* 用弗洛伊德算法求任意两城市之间的最短距离，结果存储在数组mindist[N][N]中*//*fw=fopen("1.txt","w");for(i=0;i<N;i++){for(j=0;j<N;j++)fprintf(fw,"%4d ",mindist[i][j]);fprintf(fw,"\n");}fclose(fw);// getchar();//*/Floyd(mincost); /* 用弗洛伊德算法求任意两城市之间的最小代价，结果存储在数组mincost[N][N]中*//*fw=fopen("2.txt","w");for(i=0;i<N;i++){for(j=0;j<N;j++)fprintf(fw,"%4d ",mincost[i][j]);fprintf(fw,"\n");}fclose(fw);// getchar();//*/fenzhi(m1,m2,mindist,mincost); /* 调用分支定界的实现函数，寻找出所有的可行路径并依次输出*/finish=clock();duration = (double)(finish - start) / CLOCKS_PER_SEC;printf( "%f seconds\n", duration );//*/}void Floyd(int d[N][N]) /* 弗洛伊德算法的实现函数*/{int v,w,u,i;for(u=0;u<N;u++){for(v=0;v<N;v++){for(w=0;w<N;w++)if(d[v][u]+d[u][w]<d[v][w]){//printf("v,w,u,d[v][u],d[u][w],d[v][w] %d %d %d %d %d %d",v+1,w+1,u+1,d[v][u],d[u][w],d[v][ w]);getchar();d[v][w]=d[v][u]+d[u][w];}}}}void input(int a[N][N],int b[N][N]) /* 把矩阵b赋值给矩阵a */{int i,j;for(i=0;i<N;i++)for(j=0;j<N;j++)a[i][j]=b[i][j];}void fenzhi(int m1[N][N],int m2[N][N],int mindist[N][N],int mincost[N][N]){int stack[MAX],depth=0,next,i,j; /* 定义栈，depth表示栈顶指针；next指向每次遍历时当前所处城市的上一个已经遍历的城市*/int bestLength,shortestDist,minimumCost,distBound=9999,costBound=9999;int cur,currentDist=0,currentCost=0; /* cur指向当前所处城市，currentDist和currentCost分别表示从甲城市到当前所处城市的最短距离和最小代价，currentDist和currentCost初值为0表示从甲城市出发开始深度优先搜索*/stack[depth]=0; /* 对栈进行初始化*/stack[depth+1]=0;visited[0]=1; /* visited[0]=1用来标识从甲城市开始出发进行遍历，甲城市已被访问*/while(depth>=0) /* 表示遍历开始和结束条件，开始时从甲城市出发，栈空，depth=0；结束时遍历完毕，所有节点均被出栈，故栈也为空，depth=0 *//* 整个while（）循环体用来实现从当前的城市中寻找一个邻近的城市*/{cur=stack[depth]; /* 取栈顶节点赋值给cur，表示当前访问到第cur号城市*/ next=stack[depth+1]; /* next指向当前所处城市的上一个已经遍历的城市*/for(i=next+1;i<N;i++) /* 试探当前所处城市的每一个相邻城市*/{if((currentCost+mincost[cur][N-1]>costBound)||(currentDist+mindist[cur][N-1]>=distBound)){ /* 所试探的城市满足剪枝条件，进行剪枝*///printf("here1 %d %d %d %d %d %d %d\n",cur,currentCost,mincost[cur][49],costBound,curre ntDist,mindist[cur][49],distBound); getchar();//printf("%d %d %d %d %d %d",cur,i,m1[cur][i],currentCost,mincost[cur][49],costBound); getchar();continue;}if(m1[cur][i]==9999) continue; /* 所试探的城市不连通*/if(visited[i]==1) continue; /* 所试探的城市已被访问*/if(i<N) break; /* 所试探的城市满足访问条件，找到新的可行城市，终止for循环*/ }if(i==N) /* 判断for循环是否是由于搜索完所有城市而终止的，如果是（i==N），进行回溯*/{// printf("here");getchar();depth--;currentDist-=m1[stack[depth]][stack[depth+1]];currentCost-=m2[stack[depth]][stack[depth+1]];visited[stack[depth+1]]=0;}else /* i!=N,表示for循环的终止是由于寻找到了当前城市的一个可行的邻近城市*/{//printf("%d %d %d %d %d %d\n",cur,i,m1[stack[depth]][i],m2[stack[depth]][i],currentCost,curre ntDist);//getchar();currentDist+=m1[stack[depth]][i]; /* 把从当前所处城市到所找到的可行城市的距离加入currentDist */currentCost+=m2[stack[depth]][i]; /* 把从当前所处城市到所找到的可行城市的代价加入currentCost */depth++; /* 所找到的可行城市进栈*/stack[depth]=i; /* 更新栈顶指针，指向所找到的可行城市*/stack[depth+1]=0;visited[i]=1; /* 修改所找到的城市的访问标志*/if(i==N-1) /* i==N-1表示访问到了乙城市，完成了所有城市的一次搜索，找到一条通路*/{// printf("here\n");for(j=0;j<=depth;j++) /* 保存当前找到的通路所经过的所有节点*/ bestPath[j]=stack[j];bestLength=depth; /* 保存当前找到的通路所经过的所有节点的节点数*/shortestDist=currentDist; /* 保存当前找到的通路的距离之和*/minimumCost=currentCost; /* 保存当前找到的通路的代价之和*///costBound=currentCost;distBound=currentDist; /* 更新剪枝的路径边界，如果以后所找到的通路路径之和大于目前通路的路径之和，就剪枝*/if(minimumCost>1500) continue; /* 如果当前找到的通路的代价之和大于1500，则放弃这条通路*/printf("最短路径:%3d,路径代价:%3d,所经历的节点数目:%3d,所经历的节点如下:\n",shortestDist,minimumCost,bestLength+1); /* 输出找到的通路的结果*/bestPath[bestLength]=49;for(i=0;i<=bestLength;i++) /* 输出所找到的通路所经过的具体的节点*/ printf("%3d ",bestPath[i]+1);(完整word版)北航研究生算法设计与分析Assignment_2 printf("\n");depth--; /* 连续弹出栈顶的两个值，进行回溯，开始寻找新的可行的通路*/currentDist-=m1[stack[depth]][stack[depth+1]];currentCost-=m2[stack[depth]][stack[depth+1]];visited[stack[depth+1]]=0;depth--;currentDist-=m1[stack[depth]][stack[depth+1]];currentCost-=m2[stack[depth]][stack[depth+1]];visited[stack[depth+1]]=0;// getchar();}}}}。

CETP1_Assignment2_Solution

CETP Solution for Assignment 2Notes: This is a solution for your reference, not provided by the professor. I hope Isolved the problems all correctly.Pre-solving:There is a key point to remember:Capital k t is a stock variable rather than a flow variable. It is determined by the past history, t herefore whenever there’s a change k t cannot change immediately, in other words it cannot suddenly jump to another level.However, consumption c t is not a stock variable so that we can change it at any time. Thus when a change comes, only consumption can jump to another level. Solving problems:I skip the process to figure out the partial derivative equation (PDE) for capital and consumption here.dc t c t∙dt =αk tα−1−ρ−δ−θgθdk tdt=k tα−c t−(n+g+δ)k tThe path is defined by αk tα−1−ρ−δ−θg=0and c t=k tα−(n+g+δ)k t.Question 1:If θchanges, only the PDE for consumption will change. Therefore the condition for steady k∗will also change,α(k t∗)α−1=ρ+δ+θgSince α−1<0, then θdecreases will lead to the increase for k∗. Thus,The initial balanced point is A. When θdecreases, capital does not change while consumption jumps to B immediately which is on the saddle path. Then economy moves from B to C. Clearly, the capital will gradually increase while consumption will decrease first and then increase to a higher level compared with A.Also there are two more cases we can talk about. In both of extension cases the economy moves in the same way as the above one. The only difference between these three cases is the magnitude of consumption in the balanced growth state.The capital will gradually increase while consumption will decrease first and then increase to an equal level compared with A in the left figure, while to a lower level in the right figure.(It’s encouraged to consider all these cases, however we only solve the first case in the following questions. We can think that the exogenous variable such as θ,g and δonly changes a little, therefore the new balanced state also changes a little compared with the old state which excludes the case 2 and case 3.)Question 2:If g changes, both of the two PDE will change. Firstly we consider the PDE for capital,α(k t∗)α−1=ρ+δ+θgSince α−1<0, then g decreases will lead to the increase for k∗.Now let’s t alk about the curve of c t=k tα−(n+g+δ)k t.Two endpoints on X-axisLet c t=0, thenk tα−(n+g+δ)k t=0Clearly one of the solution is 0 and another is k tα−1=n+g+δ. Therefore another solution is increasing as g decreases which means the gap on X-axis will be larger. Peak point horizontally=0,At the peak point which is the maximum point, we have dc tdk tαk tα−1−(n+g+δ)=0Therefore,k t#=(n+g+δα)1α−1=(∆α)1α−1Since α−1<0, then g decreases will lead to the increase for k t#. Therefore the peak point will move to the right horizontally.Peak point verticallySubstitute k t#into the equation, we can obtain the height for peak point c t#,c t#=(k t#)α−(n+g+δ)k t#Then we can check the relation between c t#and g,dc t# dg =−k t#=−(∆α)1α−1<0Then g decreases will lead to the increase for c t#. Therefore the peak point will move to the up vertically.Now combine the above three properties for the curve, we can obtainAbove all, we have figured out the change in both PDE,There may be two possible saddle path, one of which is in blue and another is in red: ●In first case, the consumption level immediately jumps from initial point A to alower level B1and then gradually increases to a higher level at C compared withA. And capital k gradually increases to a higher level.●In second case, the consumption level immediately jumps from initial point A to ahigher level B2and then gradually increases to a much higher level at C compared with A. And capital k gradually increases to a higher level.Question 3:According to αk tα−1−ρ−δ−θg=0and c t=k tα−(n+g+δ)k t and α=0.5, solve this equation set, we can easily get:k t∗=1()2c t∗=12(θg+ρ+δ)−n+g+δ4(θg+ρ+δ)2Question 4:When government is added into the model, the PDE is as follow:dc t t =αk tα−1−ρ−δ−θgdk tdt=k tα−G t−c t−(n+g+δ)k tClearly, only the PDE for capital is changed. Consider the government spending is permanent, then we will get the following figure,The consumption level jumps from initial point A to a lower level B and this point is namely the balanced growth state under permanent situation. The jump-gap here equals to the government spending raising ∆G.However if people know this government spending raising is just temporal, they will reduce their consumption less than∆G. If they directly jump to point B, then the economy is now on the balanced growth path in the new system, and therefore this economy will not move any more before the exit of government extra spending. However, people know that they will go back to point A and it’s their optimal choice to reach some point C on the original saddle path immediately after the exit of government extra spending. Thus, only if they jump to some point B1between A and B, the new system can force the economy to move gradually in advance.Therefore, people will reduce their consumption to B1which is between A and B immediately. Then move from B1to C during which capital is changing gradually, thus this process is not a jump. The economy reaches the saddle path at C at the moment government spending returns to its initial level. Finally, the economy goes back to A following the saddle path.Suppose government raises the spending at t1and ends it at t2, and according to the class notes we know rate of returns is defined by r t=α∙k tα−1−δ, therefore r t is decreasing as k t.2014/12/28End。

美国大学英语写作课后答案PART2

Answer KeyPART TWO: PATTERNS OF ESSAY DEVELOPMENT8 DescriptionQuestions on the Student Essays, 170–1721. c2. I’d been visiting my cousins . . .3. c4. bsight hearing5. b. He was staring off into space, idly tapping his spoon against the table, while shesightsightdrew aimless parallel lines on her paper napkin with a bent dinner fork.touch sight sightc. The blouse is made of heavy eggshell-colored satin and reflects the light in itssightfolds and hollows.touch sight sightd. Her brows are plucked into thin lines, which are like two pencil strokes added tosighthighlight those fine, luminous eyes.6. dull hum, silently waiting, deserted cooking area7. b8. The most haunting feature in the photo . . .9. a10. aQuestions on the Professional Essay, 180–1811. Lou’s coffee shop is like “a fond but dysfunctional family.”(Wording may vary.)2. d3. Lou is concerned that she is smoking rather than eating.4. b5. sight, hearing, smell6. d7. After a moment . . .8. c9. a10. bPrewriting (Writing Assignment 2), 184–185A. Plucked eyebrowsOval faceWavy brown hairB. Silver earringsBraceletRingC. Ring from another manSignature (“Sincerely . . .”)9 NarrationQuestions on the Student Essays, 190–1921. “Adopting a Handicap”2. Thanks to a new building program . . .3. Pine Streethad a lot of antique stores . . .4. I hope my parents and I . . .sight touch sight touch sight5. a. My palms reddened and my wrist and forearm muscles started to ache as I tugged at thetouchheavy metal wheels.sightb. I could not see the minister, the choir, or the altar.hearinghearingc. The club thudded against the side of Victor’s head, making him yelp with pain.sightsightd. As we ran, I kept seeing him sprawled on the ground, blood from our beatingtrickling into his eyes.6. Victor, the biggest of us . . .7. three8. a. Coping with the wheelchair (or Learning how to use the wheelchair)b. Dealing with additional problems in the wheelchair9. After, When, As10. aQuestions on the Professional Essay, 197–1981. Answers will vary. One possibility: Vingo returned from prison to find that his wife stillloved him and wanted him back.2. b3. a4. b5. Answers may vary. Two examples:Vingo tells his story “slowly and painfully and with great hesitation.”Vingo asks his wife to leave a signal (the handkerchief) rather than confront her directly.6. Examples of Vingo’s being honorable: He doesn’t express any self-pity about being in jail.He owns up to his crime. He offers his wife her freedom.7. Fort Lauderdale, New Jersey, Washington, Jacksonville, the 34th StreetTerminal in New Y ork, Philadelphia, Brunswick8. But if she didn’t . . .9. d10. d10 ExamplesQuestions on the Student Essays, 207–2081. Some kids can be . . .2. Paragraph 2 in “Everyday Cruelty”3. To pass time as I walk . . .4. Then they did even more cruel things . . .5. A young woman chimed in . . .6. Explore the rise of Nazi Germany; play a trivia game; hear the life story of a stranger7. At lunchtime on Wednesday, Then, As people stared, Finally8. But no part of everyday life . . .9. “Altered States”: Confronted with inventions . . .10. bQuestions on the Professional Essay, 215–2161. b 7.102. c 8.a. When, The next year3. db. too4. cc. although5. But, I said, he kept . . . 9. a6. b 10.c11 ProcessQuestions on the Student Essays, 226–2281. First supporting paragraph; one example of a topic sentence: First, arrange time forexercise.2. b3. One of the problems . . .4. Then get out the simple materials . . .5. Paragraph 4 describes an incident with a plumber who left a bathtub dirty.6. Paragraph 3 describes an incident with a “lemon”bicycle and an incident concerning anovercharge by a department store.7. Next; To begin with; Then; Then8. first . . . next9. a10. dQuestions on the Professional Essay, 234–2361. The job-interview “game” may not be 5. dmuch fun, but . . . or Here are guidelines 6. First of all, Then, Finallyto help you play . . . 7. a2. d 8.On the other hand3. b 9.b4. c 10.bPrewriting (Writing Assignment 2), 238Step 1:Items 1 through 9 Step 3:Items 13 through 17Step 2:Items 10 through 1212Cause and EffectQuestions on the Student Essays, 243–2441. b2. The single time . . .3. In fact, my “antique” has opened my eyes to the advantages of owning an old car: economy,reliability, and familiarity. (Wording of answer may vary slightly.)4. b, d5. Because they are constantly observed . . .6. c7. In addition to the loss of privacy . . .8. In addition; also9. One; Last of all10. aQuestions on the Professional Essay, 249–2511. The thesis is implied in sentences 1 and2. It could be stated thus: There are variouspossible reasons why mothers tend to hold their babies in their left arms.2. d3. b4. a5. Fathers show less left-side bias than mothers.6. The effect:left-side biasTwo possible causes:Answers may vary. Any two of the following: Mother’s heart is on the left side; “left brain” is more “emotional”; baby usually turns head to right.7. therefore8. Recently a possible additional value . . .9. d10. b13Comparison and ContrastQuestions on the Student Essays, 261–2621. Paragraph 3: Eating at the Chalet is . . .2. Once, I forgot . . .3. 24. (Wording of answers may vary)a. Chalet is dimly lit; McDonald’s is bright.b. Waiters at the Chalet are formal; employees at McDonald’s are friendly.c. Food is unfamiliar at the Chalet; food is familiar at McDonald’s.5. Even the other diners . . .6. Now, I use several techniques . . .7. on the other hand8. most important9. c10. bQuestions on the Professional Essay, 268–2701. Stated in paragraph 6: “. . . the families that operate like Beaver Cleaver’s are . . .disappearing because three parts of our lives have changed . . .”2. c3. c4. Fast food, takeout, and heat-and-serve dishes make up much of the modern American diet.5. Television and computers6. 107. After, then8. Today the words . . .9. a10. dPrewriting (Writing Assignment 1), 270–273First point: Different playing requirementsSecond point: Different traits and skills involvedThird point: Different images14DefinitionQuestions on the Student Essays, 278–2791. Paragraph 2: Football fans just plain . . .2. Baseball fans go . . .3. Should their beloved team . . .4. c5. 46. dQuestions on the Professional Essay, 285–2871. Answers will vary. Example: Addiction to TV resembles addiction to alcohol or drugs inseveral ways.2. d3. b4. b5. The heroin addict’s damaged life; the alcoholic’s narrowed and dehumanized life6. a7. 68. Finally9. c10. b15Division and ClassificationQuestions on the Student Essays, 294–2951. Paragraph 42. Mall managers have obviously . . .3. These frogs are an example . . .4. Then, they wander . . .5. Paragraph 46. hearinga. Hearing the music of the antique carousel housed there, Jenny begs to ride herfavoritesightpony with its shining golden mane.hearing sightb. Shouting “I’m starving!” Fred, Jr., drags the family toward the food court, wheresmellhe detects the seductive odor of pizza.sighttouchc. Mom walks through a fabric store, running her hand over the soft velvets andtouchslippery silks.7. first, Then, Finally8. A second kind of ad . . .9. d10. aQuestions on the Professional Essay, 300–3021. Answers will vary. One example: V arious kinds of waiting interrupt everyone’s life.2. Answers will vary. One possibility: This is intentional; it is done for a humorous effect.3. Watched-Pot Wait; Forced Wait4. “Y ou have a choice” in the Forced Wait.5. He gives examples: protecting your car by not running it cold; preparing soup properly.6. Introduction: paragraphs 1–2Topic 1: paragraphs 3–5Topic 2: paragraphs 6–8Topic 3: paragraph 9Topic 4: paragraphs 10–11Conclusion: paragraphs 12–137. A cousin to the Watched-Pot Wait is . . .8. b9. d10. He uses an image in which all the waits are involved. (Wording may vary.)16ArgumentationQuestions on the Student Essays, 314–3151. Paragraph 4. Topic sentences will vary; one example: Local news is often lacking in depth.2. Is raising taxes . . .3. Stress is probably greater . . .4. “Teenagers and Jobs”: Also, teens who have money . . .“Once Over Lightly”: They too dilute the news . . .5. Paragraph 3 . . . However6. Weatherpersons, reporters, anchorpersons7. Paragraph 3: AnotherParagraph 4: Finally8. Change-of-direction: ButIllustration:For example9. b, c10. bQuestions on the Professional Essay, 320–3221. c2. d3. a4. c5. a6. Knives promote physical fitness, don’t ricochet, don’t kill people cleaning them.No, she is not really pro-knife; her point is that guns are even more dangerous than knives. (Answers may vary.)7. In the first place, plus, and8. We do, however, license . . .9. c10. a。