最新《原油流变学》(复习资料)

第一章

1.流变学(Rheology)是研究物质变形与流动的科学。实际物质在外力作用下怎样变形与流动，这是物质本身固有的性质，可以称其为物质的流变性(即物质在外力作用下变形与流动的性质)。流变学就是研究物质流变性的科学。

2.流变学研究的是纯弹性固体和牛顿流体状态之间所有物质的变形与流动问题。

3.流变学更注重不同物质的力学性质与其内部结构之间的关系

4.流变学中物质所受到的力用应力或应力张量表示

5.流变学中用应变或应变速率表示物质的运动状态即变形或流动。

6.流体质点就是流体中宏观尺寸非常小而微观尺寸又足够大的任意一个物理实体。

7.物质状态的变化称为变形，而物质连续无限地变形就是流动。

8.流变学中有三种基本变形：简单拉伸、简单剪切和体积压缩与膨胀

9.反映材料宏观性质的数字模型称为本构方程，亦称为流变状态方程和流变方程

10.对一些简单的流变性制的描述也可以用曲线形式表示，如剪切应力与剪切速率关系曲线，粘度随剪切速率变化曲线等，并称之为流变曲线。

第二章

1.散体系是指将物质(固态、液态或气态)分裂成或大或小的粒子，并将其分布在某种介质(固态、液态或气态)之中所形成的体系。

2.分散体系可以是均匀的也可以是非均匀的系统。均匀分散体系是由一相所组成的单相体系，而非均匀分散体系是指由两相或两相以上所组成的多相体系。

3.非均匀分散体系必须具备2个条件：①在体系内各单位空间所含物质的性质不同；②存在着分界的物理界面。

4. 对非均匀分散体系，被分散的一相称为分散相或内相，把分散相分散于其中的一相称为分散介质，亦称外相或连续相。

5.尽管非牛顿流体在微观上往往是非均匀的多相分散体系，或非均匀的多相混合流体，但在用连续介质理论或宏观方法研究其流变性问题时，一般可以忽略这种微观的非均匀性，而认为体系为一种均匀或假均匀分散体系。

6.对非牛顿流体，没有恒定的粘度概念，不同的剪切速率下有不同的表观粘度，这是非牛顿流体的一大特点。

7、一受力就有流动，但剪切应力与剪切速率的不成比例，随着剪切速率的增大，剪切应力的增加速率越来越大，即随着剪切速率的增大，流体的表观粘度增大，这种特性被称为剪切增稠性（shear thickening）。因此，膨肿性流体具有剪切增稠性。随着剪切速率的增加，表观

粘度是减小的因此，常说假塑性流体具有剪切稀释性。

是使体系产生流动所需要的最小剪切应力，即使流体产生大于0的剪切速率所需的最8、τ

小剪切应力，称之为屈服值。屈服值的大小是体系所形成的空间网络结构的性质所决定的。塑性流体：凡是具有屈服值的流体

塑性流动：外力克服其屈服值而产生的流动。

9、在恒定的剪切应力或剪切速率作用下，表观粘度随时间连续下降，并在剪切应力或剪切速率消除后，表观粘度随之恢复的现象，称为触变性。

10、反触变性流体即在恒定的剪切应力或剪切速率作用下，流体表观粘度随时间而增加

二、触变性特征：(1)在静止条件下，流体结构发展增强；(2)在剪切作用下，这种结构能够被破坏；(3)结构的破坏和恢复是等温可逆的，但结构恢复往往要比构的破坏所需的时间长得多；(4)在恒剪切速率作用下，流体流变性有如下表现：

b)如果流体以前经受较高的剪切速率剪切，那么，剪切应力将随时间而增加

(6) 在剪切速率连续增加而后又连续减小的循环程序下，剪切应力与剪切速率的变化曲线将是顺时针方向的滞回曲线。

如果剪切变形最终不能恢复至零，则说物质产生了流动。即使在微小的应力作用下，如果物质产生了流动，则说这种物质为流体（流变学中一般不考虑气体），否则，物质为固体。

如果物质没有变形的恢复发生，则称物质为非弹性的。

对一种流体来说，如果其变形能部分地恢复，则称其为弹性液体。

考虑到时间因素，若固体的变形与恢复是瞬时发生的，则这种物质具有理想弹性；

否则，固体的变形与恢复比较慢，即有一个时间过程，则这种固体称为弹粘性固体。

弹性液体，也称为粘弹性流体，其变形和恢复也需一个时间过程。

粘弹性流体是一类既有粘性又有弹性的液体，其受外力作用时，由于弹性而要产生一定的变形（有一定的时间过程），外力消除后，这种变形要完全恢复（有一定时间过程）；又由于粘性，其在外力作用下要产生一定的流动，其对应的变形是不可恢复的。

一、元件模型

1.弹性元件用弹簧表示弹性元件。粘性元件用粘壶表示。

2.按照分散相颗粒的大小，可以把液体类的分散体系分为如下几类：①高粒度悬浮液，粒子直径大于10μm；②悬浮液，粒子直径为10～0.1μm；③溶胶，粒子直径为100～1nm；④真溶液，分子状态分散。

二、作用在分散相颗粒上的力

(1)胶体源力静电力：是极性分子的偶极子之间的引力；诱导力：是极性分子的偶极子

与其它分子的诱导偶极子之间的引力；色散力：是分子的诱导偶极子之间的引力。

(2) 静电排斥力

(3)大分子空间斥力

很显然，悬浮体系的宏观流变性质强烈依赖于因上述力所形成的微观结构

第三章

1.流动运动的描述有3个主要方向：流动方向、速度梯度方向、中性方向。

2.按形变历史，流动分为：稳定流动、瞬态流动、动态流动

3.稳态简单剪切流动的特点：1)在稳态简单剪切流动中，液层刚性的平移，其中任意2个液层微元之间的距离保持不变；2）每个微元在流动中保持体积不变，任意2个相邻剪切面之间的距离为常数；3）对稳态剪切流动，剪切线实际上是液态微元运动的轨迹。

4.流变测量的任务包括理论研究和实验技术2个方面。

5.端部效应：由于测量管段进出口流线的收缩与扩张造成额外压力损失的现象称为端部效应（管式流变仪）

第四章

1、蜡在原油中的状态与温度、原油的成分、溶解气的含量、压力等条件有关

2、晶体数目与尺寸有如下关系：在给定条件下形成结晶中心越多，形成的晶体也越多，但晶体的尺寸越小。在结晶过程中，溶解的石蜡浓度下降既可以是由于形成了新的晶核，也可以是既有晶体的长大。

3、蜡晶结构的规则性不仅与蜡的化学性质有关，而且还与烃链的长度以及是否有其它物质的杂质存在等有关。

4、胶质沥青质对蜡晶的生成与增长有如下影响：①抑制石蜡晶核的生成；②首先自身结晶形成晶核；③共晶与吸附；④增大内相颗粒与周围分散介质的表面张力。

5、胶质、沥青质对原油流变性的影响有2个显著特点：一是原油中的胶质、沥青质一般被认为是一种天然的表面活性物质，在核实的田间下，胶质、沥青质的活泼能够改善原油中蜡晶的结构形态，从而改善原油流变性；二是由于胶质、沥青质在原油中相对来说是大分子，高级性的物质，他们的大量存在会增大原油的粘稠程度。

6、改善高凝油流变性的最有前途的方法是改变石蜡的晶体结构，使结构强度大的大量细碎单晶变为结构强度小得多的少量树枝状或球粒状的粗大晶体，从而使原油的流变性得到改善（降低凝点、屈服值和粘度）

7、含蜡原油的流变性类型：牛顿流体类型，假塑性流体，屈服-假塑性流体

是原油有由流体特性到非牛顿流体特性的温度转变点，是原油呈现牛顿流体8、反常点：T

反

特性的最低温度。

9、含蜡原油表现出复杂的非牛顿流体特性，其根本是由含蜡原油的复杂胶体结构特性决定的。

10、原油中蜡晶的形状和尺寸受原油粘度、温度和冷却速度的影响，一般原油粘度越高、温度越低、冷却速度越大，所生成的蜡晶尺寸越小、蜡晶数目越多。

11、含蜡原油的蜡晶絮凝结构一般是一种强絮凝结构。在较大的蜡晶浓度下，会发展成蜡晶的整个空间网络结构。温度越低，蜡晶浓度越高，蜡晶絮凝作用越强。

12、悬浮液絮凝系统分为：1.强絮凝系统；2.弱絮凝系统

13、一般在反常点附近的非牛顿流体温度下，由于原油的内部结构较弱，其触变性在测量流变仪上显现不出来，因此可以认为原油没有触变性。随温度的进一步降低，原油开始明显显现出触变性，这一温度称之为原油的显触点。研究表明，原油的显触点取决于原油的组成、原油所经历的热历史、剪切历史，以及原油添加化学改性剂的条件等。

14、对经历一定历史条件，并在一定的低温静置条件下形成胶凝结构的含蜡原油，在恒定的剪切应力下进行初次剪切，会得到一条典型的剪切应力随时间的衰减曲线，称之为初次裂降曲线

15、大量研究表明：含蜡原油的非牛顿流变性还依赖于原油所经历的各种历史，如：热历史、冷却速度大小、剪切历史、老化等，因为这些外部因素能对含蜡原油的内部结构特别是蜡晶结构产生较大的影响，所以这一特点被称为非牛顿含蜡原油的历史效应。

16、在最优加热温度下，含蜡原油低温流变性得到改善的机理: 一般观点是：具有表面活性的极性胶质、沥青质的存在对蜡晶的析出长大有以下几个方面的作用：①对晶核生成的抑制作用，从而使生成的蜡晶数目少，但体积大；②胶质的非极性部分(相当长的侧链)与石蜡分子结构相似，因而在蜡晶生长过程中与之共晶；③极性部分则吸附在蜡晶表面，从而阻碍新析出的蜡在蜡晶表面按既定方式絮凝长大。

17、当加热温度低于最优热处理温度时，含蜡原油的低温流变性恶化的机理: 在加热温度较低时，相对分子质量小的低熔点石蜡在原油中溶解，而从溶解的蜡晶上脱离出来的胶质、沥青质则会吸附到高熔点的石蜡晶体表面上；当冷却时，已溶解的石蜡重新结晶，但在重新结晶过程中缺少具有活性的胶质、沥青质共晶和吸附作用，这部分蜡晶的结构则不能得到改善，因而造成原油的低温流变性恶化。另外，即使加热温度升高到使蜡晶完全溶解的温度，但可能还不足以使胶质、沥青质分子的活性充分激发，因此在冷却过程中，胶质、沥青质难以有效改善蜡晶结构，仍会造成原油低温流变性恶化。

18、加热温度对含蜡原油低温流变性的影响与原油中蜡的分子组成、含量，液态油对蜡的溶解能力，以及胶质、沥青质的含量、活性大小等有较大的关系。

19、剪切历史是指含蜡原油在特定流变性表现以前所经受的各种剪切经历。

补充：

1.测定屈服值的方法：直接法，间接法（曲线外延法，方程回归法）

2.国内外利用热处理原理进行含蜡原油管道输送的所谓热处理输送工艺可分为2类：一、完整热处理输送工艺；二、简易热处理输送工艺

3.反常点 abnormal point：原油呈现牛顿流体的最低温度

4.本构方程 constitutive equation ：同状态方程，流变方程，一种联系应力，应变，时间的方程，有时还包括其他的一些变量，例如温度。

5.库埃特流动 Couette flow 由于流体的几何边界相对运动而产生的剪切流动，有时也称为拖流动

6.末端效应 end effect 用毛细管粘度计测定液体粘度要求液体处于完全层流状态。但实际上在毛细管两端不满足此状态，对测得的粘度会有一定的影响，这一影响叫做末端效应

7.流变曲线 flow curve 联系剪切应力和剪切速率的曲线

8.凝点 freezing point 在规定实验条件下，试管内油品开始失去流动性的最高温度，它是衡量油品流动性的条件性质保

9.胶凝点/失流点get point of crude oil原油由溶胶状态转变为凝胶状态而失去流动性个临界温度

10.宏观流变学macrorheology将材料作为连续介质处理的流变学，并不明确考虑微观结构，同时称为连续介质流变学和唯象流变学

11.麦克斯韦模型Maxwell model虎克固体模型与牛顿流体模型的串联

12.微观流变学microrheology考虑材料微观结构的流变学

13.泊肃叶流动Poiseuille flow在恒定压力梯度之下牛顿流体在圆形截面管道中的流层

14.假塑性流pseudoplastic flow一种非牛顿流动。在剪切速率增大时，表现粘度减小的流动称为假塑性流

15.流变学rheology研究物质形变与流动的科学

16.触变性thixotropy在切应力作用下，表现粘度下降，当应力除去后，粘度又逐渐恢复。这是一种时间依赖性效应

17.显触点thixotropy appearance point原油开始显现触变性的最高温度

18.屈服点yield point在应力-应力或应力-应力速率曲线上，对应与从弹性向塑性形变转变的那一点

19.用凝点、粘度、屈服值三个指标，来综合确定流变性质。

中考文言文阅读精选100题（附答案）

（一）阅读下列文言文语段，完成1－ 5题。（连云港）

［甲］先帝知臣谨慎，故临崩寄臣以大事也。受命以来，夙夜忧叹，恐托付不效，以伤先帝之明，故五月渡泸，深入不毛。今南方已定，兵甲已足，妆奖率三军，北定中原，庶竭驽钝，攘除奸凶，兴复汉室，还于旧都。此臣所以报先帝而忠陛下之职分也。（节选自诸葛亮《出师表》）

［乙］臣受命之日，寝不安席，食不甘味。思惟北征，宜先入南。故五月渡沪，深入不毛，并日而食。臣非不自惜也，顾王业不可偏安于蜀都，故冒危难，以奉先帝之遗愿，而议者谓为非计。今贼适疲于西，又务于东，兵法乘劳，此进趋之时也。（节选自诸葛亮《后出师表》）

1.解释下列句子中加点的词语。

①故临崩寄．臣以大事也②庶竭驽钝，攘除

．．奸凶

③思惟北征，宜．先入南④今贼适．疲于西

2.下列各组句子中加点词语的意义和用法相同的一项是：（）

A.先帝知臣谨慎

B.阡陌交通，鸡犬相闻

C.故冒危难，以奉先帝之遗愿

D.每有会意，便欣然忘食

3.下列各组句子中加点词语的意义和用法相同的一项是（）

A．兴复汉室，还于旧都 B. 以奉先帝之遗愿

顾王业不可偏安于蜀都辍耕之垄上

C．而议者谓为非计 D. 故临崩寄臣以大事也

水落而石出者以是人多以书假余

4.翻译下面句子。

①此臣所以报先帝而忠陛下之职分也

②故五月渡沪，深入不毛，并日而食

5.纵观甲乙两段内容，简要概括诸葛亮请求兴北伐的三个理由

①

②

③（连云港）答案： 1、①寄：托付②攘除：铲除③宜：应该④适：正好，正逢

2、D 3．A 4、①这就是用来报答先帝、尽忠陛下的职责。②

大学英语四级考试模拟试题

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大学英语四级考试模拟试卷及参考答案(第一套)

大学英语四级专项训练

大学英语四级专项训练——选词填空（一） Americans are proud of their variety and individualty, yet they love and respect few things more than a uniform. Why are uniforms so __1__ in the United States Among the arguments for uniforms, one of the first is that in the eyes of most people they look more __2__ than civilian（百姓的）clothes. People have become conditioned to __3__ superior quality from a man who wears a uniform. The television repairman who wears a uniform tends to __4__ more trust than one who appears in civilian clothes. Faith in the __5__ of a garage mechanic is increased by a uniform. What an easier way is there for a nurse, a policeman, a barber, or a waiter to __6__ professional identity（身份）than to step out of uniform Uniforms also have many __7__ benefits. They save on other clothes. They save on laundry bills. They are often more comfortable and more durable than civilian clothes. Primary among the arguments against uniforms is their lack of variety and the consequent loss of __8__ experienced by people who must wear them. Though there are many types of uniforms, the wearer of any particular type is generally stuck with it, without __9__, until retirement. When people look alike, they tend to think, speak, and act __10__, on the job at least. [A]skill [B]popular [C]get [D]change [E]similarly 、[F]professional [G]character [H]individuality [I] inspire [J] differently [K]expect [L]practical [M] recall [N] lose [O] ordinary （二）、 Psychologists take opposing views of how external rewards, from warm praise to cold cash, affect motivation and creativity. Behaviorists, who study the relation between actions and their consequences, argue that rewards can __1__ performance at work and school. Cognitive( 认识派的) researchers, who study various aspects of mental life, maintain that rewards often destroy creativity by encouraging dependence on __2__ and gifts from others. The latter view has gained many supporters, __3__ among educators. But the careful use of small __4__ rewards speaks creativity in grade school children, suggesting that properly presented inducements( 刺激) indeed __5__inventiveness, according to a study in the June Journal of Personality and Social Psychology. “If kids know they’re working f or a reward and can focus on a relatively __6__ task, they show the most creativity,” says Robert Eisenberger of the University of Delaware in Newark. “But it’s easy to __7__ creativity by giving rewards for poor performance or creating too much anticipation for rewards.

大学英语四级试卷)

大学英语四级期末试卷 Part I: Multiple choice 20% Directions:For each of the following blanks, four choices are given. Choose the best word or phrase for each blank and mark A, B, C, or D on Answer Sheet. 1. Now that we’ve got a loan from the bank, our project is financially _____. A. constructive B. feasible C. favorable D. stiff 2. Due to his recent failure to meet the deadline, Jason is ____ from the list for promotion. . A. eliminated B. retreated C. pried D. wrenched 3. We need someone really ____ who can organize the office and make it run smoothly.. A. crucial B. realistic C. essential D. efficient 4. I am pleased to hear of your job offer-all that hard work at school has obviously __. A. paid off B. taken its toll C. made a difference D. shown up 5. As a reporter, I was paid to __ into other people’s lives. A. pry B. convert C. blurt D. carve 6. The mayor promised to trim the city budget without cutting ___ services. . A. essential B. appropriate C. equivalent D. lucrative 7. The doctor ___ Billy’s operation with x-rays and special exercises to make him stronger. A. went after B. followed up C. started up D. took on 8. A firm might sometimes sell at a loss to drive a competitor out of business, and__ increase its market power. A. therefore B. thereby C. hence D. further 9. You can ___ the video camera on a tripod (三脚架)，so that you don’t have to worry about holding it steady while you ask questions. A. withstand B. mount C. implement D. dwell 10. AIDS activists permanently changed and shortened America’s ___process for testing and approving new drugs of all kinds, for all diseases. A. efficient B. stagnant C. intricate D. appropriate 11.___ students should be motivated by a keen interest in theatre and should have some familiarity with plays in production.. A. prospective B. responsible C. ethnic D. realistic 12.However, the new law, once passed, will ___ the Bridlintong agreement illegal by giving workers the right to join unions of their choice.. A. convert B. render C. cancel D. eliminate 13.This course focuses on the ____ of economic analysis to the problems of inflation, unemployment, the balance of payments and enterprise behaviour. A. conception B. combination C. application D. introduction 14.The aircraft base is protected with specially designed shelters which are built to ___ ground and air attacks. A. launch B. withstand C. contest D. contend

大学英语四级考试模拟试卷及参考答案(第一套)

大学英语四级考试模拟试卷及参考答案(第一套） Part II Reading Comprehension (35 minutes) Directions: There are 4 reading passages in this part. Each passage is foll owed by some questions or unfinished statements. For each of them there are fou r choices marked A), B), C) and D). You should decide on the best choice and ma rk the corresponding letter on the Answer Sheet with a single line through the center. Passage One Questions 21 to 25 are based on the following passage. There is a difference between science and technology. Science is a method o f answering theoretical questions; technology is a method of solving practical problems. Science has to do with discovering the facts and relationships betwee n observable phenomena in nature and with establishing theories that serve to o rganize these facts and relationships; technology has to do with tools, techniq ues, and procedures for implementing the finding of science. Another distinction between science and technology has to do with the progr ess in each. Progress in science excludes the human factor. Scientists, who seek to comp rehend the universe and know the truth within the highest degree of accuracy an d certainty, cannot pay attention to their own or other people's likes or disli kes or to popular ideas about the fitness of things. What scientists discover m ay shock or anger people-as did Darwin's theory of evolution. But even an unple asant truth is more than likely to be useful; besides, we have the choice of re fusing to believe it! But hardly so with technology; we do not have the choice

大学英语四级模拟试题四(附含答案解析)

大学英语四级模拟题四 Part One Reading Comprehension (2’×10 = 20’) Directions: There are 2 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A), B), C) and D). You should decide on the best choice and mark the corresponding letter on the Answer Sheet with a single line through the centre. Passage One Air pollution can spread from city to city. It even spreads from one country to another. Some northern European countries have had “black snow”from pollutants that have traveled through the air from other countries and have fallen with the snow. So air pollution is really a global problem. Air pollution can kill babies, older people, and those who have respiratory（呼吸的）diseases. As found in cities, air pollution increases the risks of certain lung diseases. Air pollution can cause both airplane and car accidents because it cuts down visibility （能见度）. There are other possible health dangers from air pollution that we don’t know much about. For example, scientists are trying to find out whether chemicals that reach us from the air may cause changes in our cells. These changes might cause babies to be born with serious birth defects. Scientists are trying to learn how all the many chemicals are apt（易于的）to take into our bodies from air, water, food, and even medicines act together to affect our health and the way our bodies work. That is another reason why it is so important to begin to control pollution now instead of waiting until we learn all the answers. Air pollution costs us a lot of money. It corrodes（腐蚀）our buildings. It damages farm crops and forests. It has a destructive effect on our works of art. The cost of all this damage to our government is great. It would be much more worthwhile, both for us and for the government, to spend our tax dollars on air pollution control. 1. Air pollution may lead to airplane accidents because . A. it may cause pilots to be ill B. engines may fail from the air-borne dirt C. visibility is reduced D. it brings a lot of black snow 2. Scientists are trying to find a link between pollution and . A. intelligence levels B. birth problems C. man’s behavior D. the nervous system 3. Scientists have not yet determined . A. all of the effects of pollution on the human body B. how pollution can be controlled successfully C. when the atmosphere first became polluted D. how some snow becomes black 4. The author suggests that before air pollution becomes more serious, . A. factories will be forced to stop operating B. buildings should be protected C. the earth will begin to grow colder D. more money should be spent to solve the problem 5. We can conclude that . A. civilization may be ruined if pollution is not controlled B. pollution is more serious in Europe than it is in America C. most people do not know that pollution is a serious problem D. we should learn all the answers before we begin to control pollution Passage Two Stiletto heels could be banned from the workplace because of health and safety reasons, according to British Trade Union bosses. The Trade Union Congress, predominantly male, has proposed a motion arguing that high heels are disrespectful to women while they also contribute to long term injuries. They propose instead that women wear “sensible shoes”with an inch heel limit in an attempt to avoid future foot and back pain as well as injuries. The motion is due to be debated at next month’s conference. The motion states: “Congress believes high heels may look glamorous on the Hollywood catwalks but are completely in appropriate for the day-to-day working environment. Feet bear the burden of daily life, and for many workers prolonged standing, badly fitted footwear, and in particular high heels can be a hazard. Around two million days a year are lost through sickness as a result of lower limb disorders. Wearing high heels can cause long-term foot problems and also serious foot, knee and back pain and damaged joints. Many employers in the retail sector force women workers to wear high heels as part of their dress code. More must be done to raise awareness of this problem so that women workers and their feet are protected.” Nadline Dorries, the Tory Member of Parliament, however criticized the motion and said the extra height heels give women can help them when in the workplace. “I’m 5ft 3in and need every inch of my Christian Louboutin heels to look my male colleagues in the eye,”she said. “If high heels were banned in Westminster, no one would be able to find me. The Trade Union leaders need to get real, stop using obvious sexist tactics by discussing women’s

大学英语四级考试专项练习题：完形填空(一)

最牛英语口语培训模式：躺在家里练口语，全程外教一对一，三个月畅谈无阻！洛基英语，免费体验全部在线一对一课程：https://www.360docs.net/doc/138182518.html,/ielts/xd.html（报名网址） In a telephone survey of more than 2，000 adults，21% said they believed the sun revolved (旋转)around the earth. An 71 7% did not know which revolved around 72. I have no doubt that 73 all of these people were 74 in school that the earth revolves around the sun; 75 may even have written it 76 at test. But they never 77 their incorrect mental models of planetary (行星的) 78 because their every day observations didn’t support 79 their teachers told them: People see the sun moving 80 the sky as morning turns to night，and the earth seems stationary (静止的) 81 that is happening. Students can learn the right answers 82 heart in class，and yet never combined them 83 their working models of the world. The objectively correct answer the professor accepts and the 84 personal understanding of the world can 85 side by side，each unaffected by the other. Outside of class，the student continues to use the 86 model because it has always worked well 87 that circumstance. Unless professors address 88 errors in students’personal models of the world，students are not 89 to replace them with the 90 one. 71.A.excessive B. extraC. additionalD. added 72.A.what B. whichC. thatD. other 73.A.virtually B. remarkablyC. ideallyD. preferably 74.A.learned B. suggestedC. taughtD. advised 75.A.those B. theseC. whoD. they 76.A.on B. withC. underD. for 77.A.formed B. alteredC. believedD. thought 78.A.operation B. positionC. motionD. location 79.A.how B. whichC. thatD. what 80.A.around B. acrossC. onD. above 81.A.since B. soC. whileD. for 82.A.to B. byC. inD. with 83.A.with B. intoC. toD. along 84.A.adult’s B. teacher’sC. scientist’sD. student’s 85.A.exist B. occurC. surviveD. maintain 86.A.private B. individualC. personalD. own 87.A.in B. withC. onD. for 88.A.general B. naturalC. similarD. specific 89.A.obliged B. likelyC. probableD. partial 90.A.perfectB. betterC. reasonableD. correct 【答案】： 71.C72.B73.A74.C75.D76.A77.B78.C79.D80.B 81.C82.B 83.A84.D85.A86.C87.A88.D89.B90.D 【答案解析】： 71.C四个答案都有“额外”的意思，但各有偏重。A重在表达“过量、超过正常的部分”;B是“在一类事物之外的额外部分”;D是“外加的”。因此只有C答案符合本题要求：“另外有7%的人不知道是谁绕着谁转。”

大学英语四级试卷-英语四级考试模拟题及答7

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Calculate for a moment what could be done with even a part of those hours. Five thousand hours, I am told, are what a typical college undergraduate spends working on a bachelor's degree. In 10,000 hours you could have learned enough to become an astronomer or engineer. You could have learned several languages fluently. If it appealed to you, you could be reading Homer in the original Greek or Dostoyevsky in Russian. If it didn't, you could have walked around the world and written a book about it. The trouble with television is that it discourages concentration. Almost anything interesting and rewarding in life requires some constructive, consistently applied effort. The dullest, the least gifted of us can achieve things that seem miraculous to those who never concentrate on anything. But Television encourages us to apply no effort. It sells us instant gratification(满意). It diverts us only to divert, to make the time pass without pain. Television's variety becomes a narcotic(麻醉的), nor a stimulus. Its serial, kaleidoscopic (万花筒般的)exposures force us to follow its lead. The viewer is on a perpetual guided tour: 30 minutes at the museum, 30 at the cathedral, 30 for a drink, then back on the bus to the next attraction—except on television., typically, the spans allotted arc on the order of minutes or seconds, and the chosen delights are more often car crashes and people killing one another. In short, a lot of television usurps(篡夺;侵占) one of the most precious of all human gifts, the ability to focus your attention yourself, rather than just passively surrender it. Capturing your attention—and holding it—is the prime motive of most television programming and enhances its role as a profitable advertising vehicle. Programmers live in constant fear of losing anyone's attention—anyone's. The surest way to avoid doing so is to keep everything brief, not to strain the attention of anyone but instead to provide constant stimulation through variety, novelty, action and movement. Quite

大学英语四级考试真题及答案(完整版)

大学英语四级考试真题及答案(绝对完整） Part I Writing (30 minutes) Directions: For this part, you are allowed 30 minute to write a short essay on the topic of students selecting their lectures. You should write at least 120 words following the outline given bellow: 1. 越来越多的博物馆免费对外开放的目的是什么？ 2. 也会带来一些问题 3. 你的看法？ Part II Reading Comprehension (Skimming and Scanning) (15 minutes)Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions on Answer Sheet 1. For questions 1-7, choose the best answer from the four choices marked A),B),C) and D). For questions 8-10, complete the sentences with the information given in the passage. How Do You See Diversity? As a manager, Tiffany is responsible for interviewing applicants for some of the positions with her company .During one interview, she noticed that the candidate never made direct eye contact. She was puzzled and somewhat disappointed because she liked the individual otherwise. He had a perfect resume and gave good responses to her questions, but the fact that he never looked her in the eye said “untrustworthy,” so she decided to offer the job to her second choice. “It wasn’t until I attended a diversity workshop that I realized the person we passed over was the perfect person,” Tiffany confesses. What she hadn’t known at the time of the interview was that the candidate’s “different” behavior was simply a cultural misunderstanding . He was an Asian-American raised in a household where respect for those in authority was shown by averting(避开) your eyes. “I was just thrown off by the lack of ye contact; not realizing it was cultural,” Tiffany says. “I missed out ,but will not miss that opportunity again.” Many of us have had similar encounters with behaviors we perceive as different. As the world becomes smaller and our workplaces more diverse, it is becoming essential to expand our under-standing of others and to reexamine some of our false assumptions . Hire Advantage At a time when hiring qualified people is becoming more difficult ,employers who can eliminate invalid biases(偏爱) from the process have a distinct advantage .My company, Mindsets LLC ,helps organizations and individuals see their own blind spots . A real estate recruiter we worked with illustrates the positive difference such training can make .