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高分子专业英语课文翻译

高分子专业英语课文翻译
高分子专业英语课文翻译

高分子专业英语课文翻译

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A 高分子化学和高分子物理

UNIT 1 What are Polymer?

第一单元什么是高聚物,

What are polymers? For one thing, they are complex and giant molecules and

什么是高聚物, 首先,他们是合成物和大分子,而且不同于低分子化合物,譬are different from low molecular weight compounds like, say, common salt. To 如说普通的盐。

contrast the difference, the molecular weight of common salt is only 58.5, while 与低分子化合物不同的是,普通盐的分子量仅仅是58.5,

that of a polymer can be as high as several hundred thousand, even more than thousand 而高聚物的分子量高于105,甚至大于106。

thousands. These big molecules or ‘macro-molecules’ are made up of much smaller

这些大分子或“高分子”由许多小分子组成, 小分子相互结合形成大分子,molecules, can be of one or more chemical compounds. To illustrate, imagine that 大分子能够是一种或多种化合物。举例说明,

a set of rings has the same size and is made of the same material. When these things 想象一组大小相同并由相同的材料制成的环。当这些环相互连接are

interlinked, the chain formed can be considered as representing a polymer from 起来,可以把形成的链看成是具有同种分子量化合物组成的高聚物。

molecules of the same compound. Alternatively, individual rings could be of

另一方面,独特的环可以大小不同、材料不同,

different sizes and materials, and interlinked to represent a polymer from 相连接后形成具有不同分子量化合物组成的聚合物。

molecules of different compounds.

This interlinking of many units has given the polymer its name, poly meaning

许多单元相连接给予了聚合物一个名称,poly意味着“多、聚、重复”,

‘many’ and mer meaning ‘part’ (in Greek). As an example, a gaseous compound

mer意味着“链节、基体”(希腊语中)。例如:称为丁二烯的气态化合物,called butadiene, with a molecular weight of 54, combines nearly 4000 times and 分子量为54,化合将近4000次,

gives a polymer known as polybutadiene (a synthetic rubber) with about 200 得到分子量大约为200000被称作聚丁二烯(合成橡胶)的高聚物。

高分子专业英语选讲课文翻译资料

000molecular weight. The low molecular weight compounds from which the polymers

形成高聚物的低分子化合物称为单体。

form are known as monomers. The picture is simply as follows:

下面简单地描述一下形成过程:

butadiene + butadiene + ??? + butadiene--?polybutadiene

(4 000 time)

丁二烯,丁二烯,…,丁二烯——?聚丁二烯

4000次) (

One can thus see how a substance (monomer) with as small a molecule weight

因而能够看到分子量仅为54的小分子物质(单体)

as 54 grow to becom e a giant molecule (polymer) of (54×4 000?)200 000 molecular

如何逐渐形成分子量为200000的大分子(高聚物)。

weight. It is essentially the ‘giantness’ of the size of the polymer molecule

实质上,正是由于聚合物的巨大的分子尺寸才使其性能不同于象苯这样的一般化that makes

its behavior different from that of a commonly known chemical compound 合物。

such as benzene. Solid benzene, for instance, melts to become liquid benzene at

例如,固态苯,在5.5?熔融成液态苯,进一步加热,煮沸成气态苯。

5.5? and , on further heating, boils into gaseous benzene. As against this

与这类简单化合物

well-defined behavior of a simple chemical compound, a polymer like polyethylene 明确的行为相比,像聚乙烯这样的聚合物不能在某一特定的温度快速地熔融成纯净的液

does not melt sharply at one particular temperature into clean liquid. Instead, 体。

it becomes increasingly softer and, ultimately, turns into a very viscous, tacky 而聚合物变得越来越软,最终,变成十分粘稠的聚合物熔融体。

molten mass. Further heating of this hot, viscous, molten polymer does convert

将这种热而粘稠的聚合物熔融体进一步加热,会转变成各种气体,

it into various gases but it is no longer polyethylene. (Fig. 1.1) . 但它不再是聚乙烯(如图1.1)。

固态苯——?液态苯——?气态苯

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加热,5.5? 加热,80?

固体聚乙烯——?熔化的聚乙烯——?各种分解产物-但不是聚乙烯

加热加热

图1.1 低分子量化合物(苯)和聚合物(聚乙烯)受热后的不同行为

Another striking difference with respect to the behavior of a polymer and that

发现另一种不同的聚合物行为和低分子量化合物行为是关于溶解过程。

of a low molecular weight compound concerns the dissolution process. Let us take,

for example, sodium chloride and add it slowly to s fixed quantity of water. The 例如,让我们研究一下,将氯化钠慢慢地添加到固定量的水中。

salt, which represents a low molecular weight compound, dissolves in water up to 盐,代表一种低分子量化合物,在水中达到点(叫饱和点)溶解,s point (called saturation point) but, thereafter, any further quantity added does

但,此后,进一步添加盐不进入溶液中却沉到底部而

not go into solution but settles at the bottom and just remains there as solid. 保持原有的固体状态。

The viscosity of the saturated salt solution is not very much different from that 饱和盐溶液的粘度与水的粘度不是十分不同。

of water. But if we take a polymer instead, say, polyvinyl alcohol, and add it

但是,如果我们用聚合物替代,譬如说,将聚乙烯醇添加到固定量的水中,聚to a fixed quantity of water, the polymer does not go into solution immediately. 合物不是马上进入到溶液中。

The globules of polyvinyl alcohol first absorb water, swell and get distorted in 聚乙烯醇颗粒首先吸水溶胀,发生形变,经过很长的时间以后进入到溶液中。

shape and after a long time go into solution. Also, we can add a very large quantity

同样地,我们可以将大量的聚合物加入到

of the polymer to the same quantity of water without the saturation point ever 同样量的水中,不存在饱和点。

being reached. As more and more quantity of polymer is added to water, the time

将越来越多的聚合物加入水中,认为聚合物溶解的时间明显地增加,最

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taken for the dissolution of the polymer obviously increases and the mix ultimately 终呈现柔软像面团一样粘稠的混合物。

assumes a soft, dough-like consistency. Another peculiarity is that, in water,

另一个特点是,在水中聚乙烯醇不会像过量

polyvinyl alcohol never retains its original powdery nature as the excess sodium 的氯化钠在饱和盐溶液中那样能保持其初始的粉末状态。

chloride does in a saturated salt solution. In conclusion, we can say that (1)

总之,我们可以讲(1)聚乙烯醇的溶

the long time taken by polyvinyl alcohol for dissolution, (2) the absence of a 解需要很长时间, (2)不存在饱和点,

saturation point, and (3) the increase in the viscosity are all characteristics

(3)粘度的增加是典型聚合物溶于溶液中的特性,这些特性主要

of a typical polymer being dissolved in a solvent and these characteristics are 归因于聚合物大分子的尺寸。

attributed mainly to the large molecular size of the polymer. The behavior of a

low molecular weight compound and that of a polymer on dissolution are illustrated 如图1.2说明了低分子量化合物和聚合物的溶解行为。

in Fig.1.2.

氯化钠晶体加入到水中——?晶体进入到溶液中.溶液的粘度不是十分不同于充分搅拌

水的粘度——?形成饱和溶液.剩余的晶体维持不溶解状态.

加入更多的晶体并搅拌

氯化钠的溶解

聚乙烯醇碎片加入到水中——?碎片开始溶胀——?碎片慢慢地进入到溶液中允许维持现状充分搅拌

——?形成粘稠的聚合物溶液.溶液粘度十分高于水的粘度

继续搅拌

聚合物的溶解

图1.2 低分子量化合物(氯化钠)和聚合物(聚乙烯醇)不同的溶解行为

——Gowariker VR, Viswanathan N V, Sreedhar J. Polymer Science. New York:

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John Wiley & Sons, 1986.6

UNIT 2 Chain Polymerization

第二单元链式聚合反应

Many olefinic and vinyl unsaturated compounds are able to form chain-0like

Staudinger第一个发现一例现象,许多烯烃和不饱和烯烃通过打开双键可

macromolecules through elimination of the double bond, a phenomenon first 以形成链式大分子。

recognized by Staudinger. Diolefins polymerize in the same manner, however, only

二烯烃以同样的方式聚合,然而,仅限于两个双键中

one of the two double bonds is eliminated. Such reactions occur through the initial 的一个。这类反应是通过单体分子首先加成到引addition of a monomer molecule to an initiator radical or an

initiator ion, by 发剂自由基或引发剂离子上而进行的,靠这些反应活性中心由引发剂转移到被

which the active state is transferred from the initiator to the added monomer. 加成的单体上。

In the same way by means of a chain reaction, one monomer molecule after the other 以同样的方式,借助于链式反应,单体分子一个接一个地被加成(每秒2000,

is added (2000~20000 monomers per second) until the active state is terminated 20000个单体)直到活性中心通过不同的反应类型而终止。

through a different type of reaction. The polymerization is a chain reaction in

聚合反应是链式反应的原因有两种:

two ways: because of the reaction kinetic and because as a reaction product one

因为反应动力学和因为作为反应产物它是一种链式分子。链分子的长度与动力

obtains a chain molecule. The length of the chain molecule is proportional to the 学链长成正比。

kinetic chain length.

One can summarize the process as follow (R. is equal to the

initiator radical):

链式反应可以概括为以下过程(R?相当与引发剂自由基):略

One thus obtains polyvinylchloride from vinylchloride, or polystyrene from 因而通过上述过程由氯乙烯得到聚氯乙烯,或由苯乙烯获得聚苯乙烯,或乙烯

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styrene, or polyethylene from ethylene, etc.

获得聚乙烯,等等。

The length of the chain molecules, measured by means of the degree of

借助于聚合度估算的分子链长,在一个大范围内可以通过选择适宜的反应

polymerization, can be varied over a large range through selection of suitable 条件被改变。

reaction conditions. Usually, with commercially prepared and utilized polymers,

通常,通过大量地制备和利用聚合物,聚合度在1000,

the degree of polymerization lies in the range of 1000 to 5000, but in many cases 5000范围内,但在许多情况下可低于500、高于10000。

it can be below 500 and over 10000. This should not be interpreted to mean that

这不应该把所有聚合物材料的分子量理解

all molecules of a certain polymeric material consist of 500, or 1000, or 5000 为由500,或1000,或5000个单体单元组成。

monomer units. In almost all cases, the polymeric material consists of a mixture

在几乎所有的事例中,聚合物材料由不同聚合度的聚合物分子的混合物组成。

of polymer molecules of different degrees of polymerization.

Polymerization, a chain reaction, occurs according to the same mechanism as

聚合反应,链式反应,依照与众所周知的氯(气)-氢(气)反应和光气的分解机理进行。

the well-known chlorine-hydrogen reaction and the decomposition of phosegene.

The initiation reaction, which is the activation process of the double bond,

双键活化过程的引发剂反应,可以通过热、辐射、超声波或引发剂产生。

can be brought about by heating, irradiation, ultrasonics, or initiators. The

initiation of the chain reaction can be observed most clearly with radical or ionic 用自由基型或离子型引发剂引发链式反应可以很清楚地进行观察。

initiators. These are energy-rich compounds which can add suitable unsaturated

这些是高能态的化合物,它们能够加成不饱和化合物(单体)并保持自由基

compounds (monomers) and maintain the activated radical, or ionic, state so that 或离子活性中心以致单体可以以同样的方式进一步加成。

further monomer molecules can be added in the same manner. For the individual steps

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of the growth reaction one needs only a relatively small activation energy and 对于增长反应的各个步骤,每一步仅需要相当少的活化能,therefore through a single activation step (the actual initiation reaction) a large 因此通过一步简单的活化反应(即引发反应)即可将许多烯类单体分子转化成聚合物,

number of olefin molecules are converted, as is implied by the term “chain

这正如连锁反应这个术语的内涵那样。

reaction”. Because very small amounts of the initiator bring about the formation

因为少量的引发剂引发形成大量的聚合物原料(1:1000,1:10000),

of a large amount of polymeric material (1:1000 to 1:1000), it is possible to regard

从表面上看聚合反应很

polymerization from a superficial point of view as a catalytic reaction. For this 可能是催化反应。

reason, the initiators used in polymerization reactions are often designated as 由于这个原因,通常把聚合反应的引发剂看作是聚合反应的引发剂,

polymerization catalysts, even though, in the strictest sense, they are not true

但是,严格地讲它们不是真正意义上的催化剂,

catalysts because the polymerization initiator enters into the reaction as a real

因为聚合反应的催化剂进入到反应内部而成为一部分,同时可

partner and can be found chemically bound in the reaction

product ,i.e. ,the 以在反应产物,既聚合物的末端发现。

polymer, In addition to the ionic and radical initiators there are now metal complex

此外离子引发剂和自由基引发剂有的是金属络合物引发剂

initiators (which can be obtained, for example, by the reaction of titanium

(例如,通过四氯化钛或三氯化钛与烷基铝的反应可以得到),

tetrachloride or titanium trichloride with aluminum alkyls), which play an Z引发剂在聚合反应中起到了重要作用,

important role in polymerization reactions (Ziegler catalysts) ,The mechanism of their catalytic action is not yet completely clear.

它们催化活动的机理还不是十分清楚。

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UNIT 3 Step-Growth Polymerization

第三单元逐步聚合

Many different chemical reactions may be used to synthesize polymeric 许多不同的化学反应通过逐步聚合可用于合成聚合材料。

materials by step-growth polymerization. These include esterification, amidation,

这些反应包括酯化、酰胺化、氨基甲酸

the formation of urethanes, aromatic substitution, etc. Polymerization proceeds 酯、芳香族取代物的形成等。

by the reactions between two different functional groups, e.g., hydroxyl and 通过反应聚合反应在两种不同的官能团,如,羟基和羧基,或异氰酸酯和羟基之间。

carboxyl groups, or isocyanate and hydroxyl groups.

All step-growth polymerization fall into two groups depending on the type of

所有的逐步聚合反应根据所使用单体的类型可分为两类。

monomer(s) employed. The first involves two different polyfunctional monomers in

第一类涉及两种不同的官能团单体,每一种单体仅具有一种官能团。

which each monomer possesses only one type of functional group. A polyfunctional monomer is one with two or more functional groups per

molecule. The second involves 一种多官能团单体每个分子有两个或多个官能团。

a single monomer containing both types of functional groups. The synthesis of 第二类涉及含有两类官能团的单种单体。

polyamides illustrates both groups of polymerization reactions. Thus, polyamides 聚酰胺的合成说明了聚合反应的两个官能团。因此聚酰胺可以由二can be obtained from the reaction of diamines with diacids

酸的反应或氨基酸之间的反应得到。元胺和二元

nH2N-R-NH2+nHO2C-R’-CO2H?

H-(-NH-R-NHCO-R’-CO-)n-OH+(2n-1)H2O (3.1)

or from the reaction of amino acids with themselves

nH2R-CO2H? H-(-NH-R-CO-)n-OH+(n-1)H20 (3.2)

The two groups of reactions can be represented in a general manner

by the equations 两种官能团之间的反应一般来说可以通过下列反应式表示as follows

A+B-B ?–[-A-A-B-B-]-A-B?–[-A-B-]-

反应式略

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Reaction (3.1) illustrates the former, while (3.2) is of the latter type. 反应(3.1)说明前一种形式,而反应(3.2)具有后一种形式。

图3.1 逐步聚合的示意图

(a) 未反应单体;(b)50%已反应;(c)83.3%已反应;(d) 100%已反应(虚线表示反

应种类)

Polyesterification, whether between diol and dibasic acid or intermolecularly

聚酯化,是否在二元酸和二元醇或羟基酸分子间进行,是逐步聚合反应过程的一个例子。

between hydroxy acid molecules, is an example of a step-growth polymerization

process. The esterification reaction occurs anywhere in the monomer matrix where

酯化反应出现在单体本体中两个单体分子相碰撞的位置,

two monomer molecules collide, and once the ester has formed, it, too, can react

且酯一旦形成,

further by virtue of its still-reactive hydroxyl or carboxyl groups. The net effect 依靠酯上仍有活性的羟基或羧基还可以进一步进行反应。

of this is that monomer molecules are consumed rapidly without any large increase 酯化的结果是单体分子很快地被消耗掉,而分子量却没有多少增加。

in molecular weight. Fig. 3.1 illustrates this phenomenon. Assume, for example,

图3.1说明了这个现象。

that each square in Fig. 3.a represents a molecule of hydroxy acid. After the 例如,假定图3.1中的每一个方格代表一个羟基酸分子。

initial dimmer molecules from (b), half the monomer molecules have been consumed (b)中的二聚体分子,消耗二分之一的单体分子聚合物种类的聚合度(DP)是2。

and the average degree of polymerization (DP) of polymeric species is 2. As trimer and more dimer molecules form (c), more than 80% of the monomer molecules have (c)中当三聚体和更多的二聚体形成,大于80%的单体分子已反应,但DP仅仅还是2.5。

reacted (d), DP is 4. But each polymer molecule that forms still has reactive end (d)中当所有的单体反应完,DP是4。但形成的每一种聚合物分子还有反应活性的端基;

groups; hence the polymerization reaction will continue in a stepwise fashion, 因此,聚合反应将以逐步的方式继续进行,其每一步酯化反应的反应速率和反应机理均与

with each esterification of monomers. Thus, molecular weight increases slowly even

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初始单体的酯化作用相同。因此,分子量缓慢增加直至高水平的单体转化率,at high levels of monomer conversion, and it will continue to increase until the 而且分子量将继续增加直到粘度的增加使其难以除去酯化反应的水或难以找到相互反应

viscosity build-up makes it mechanically too difficult to remove water of 的端基。

esterification or for reactive end groups to find each other.

It can also be shown that in the A-A+B-B type of polymerization, an exact

-A+B-B的聚合反应中也可以看到,在A

stoichiometric balance is necessary to achieve high molecular weights. If some 精确的当量平衡是获得高分子量所必需的。

monofunctional impurity is present, its reaction will limit the molecular weight 假如存在一些但官能团杂质,由于链的端基失活,反应将使分子量减少。

by rendering a chain end inactive. Similarly, high-purity monomers are necessary

同样,在A-B类的缩聚反应中高纯度的单体是必要的,

in the A-B type of polycondensation and it follows that high-yield reactions are 而且可以归结高收率的反应仅是形成聚合物的实际反应,the only practical ones for polymer formation, since side reactions will upset

因为副反应会破坏当量平衡。

the stoichiometric balance.

-------Stevens M P. Polymer Chemistry. London: Addison-Wesley Publishing Company, 1975. 13

UNIT 4 Ionic Polymerization

第四单元离子聚合反应

Ionic polymerization, similar to radial polymerization, also has the mechanism

离子聚合反应,与自由基聚合反应相似,也有链反应的机理。

of a chain reaction. The kinetics of ionic polymerization are, however,

但是,离子聚合的动力学明显地不同于自由基聚合反应。

considerably different from that of radical polymerization.

(1) The initiation reaction of ionic polymerization needs only a small

(1)离子聚合的引发反应仅需要很小的活化能。

activation energy. Therefore, the rate of polymerization depends only slightly

因此,聚合反应的速率仅对温度有较少的依赖性。

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on the temperature. Ionic polymerizations occur in many cases with explosive

在许多情况下离子聚合猛烈地发生甚至低于50?

violence even at temperature below 50?(for example, the anionic polymerization

(例如,苯乙烯的阴离子聚合反应在-70?在四氢呋喃中,

of styrene at –70? in tetrahydrofuran, or the cationic polymerization of 或异丁烯的阳离子聚合在-100?在液态乙烯中)。

isobutylene at –100? in liquid ethylene ).

(2) With ionic polymerization there is no compulsory chain termination

(2)对于离子聚合来说,不存在通过再结合反应而进行的强迫链终止,

through recombination, because the growing chains can not react with each other.

因为生长链之间不能发生链终止。

Chain termination takes place only through impurities, or through the addition 链终止反应仅仅通过杂质而发生,或者说通过和某些像水、醇、of certain compounds such as water, alcohols, acids, amines, or oxygen, and in 酸、胺或氧这样的化合物进行加成而发生,

general through compounds which can react with polymerization ions under the 且一般来说(链终止反应)可通过这样的化合物来进行,这种化合物在中性聚合物或没有聚合活性的离

formation of neutral compounds or inactive ionic species. If the initiators are 子型聚合物生成的过程中可以和活性聚合物离子进行反应。如果引发剂仅仅部分地离解,

only partly dissociated, the initiation reaction is an equilibrium reaction, where 引发反应即为一个平衡反应,在出现平衡反应的场合,reaction in one direction gives rise to chain initiation and in the other direction 在一个方向上进行链引发反应,而在另一个方向上则发生链终止反应。

to chain termination.

In general ionic polymerization polymerization can be initiated through acidic

通常离子聚合反应能通过酸性或碱性化合物被引发。

or basic compounds. For cationic polymerization, complexes of BF3, AlCl, TiCl, 34

对于阳离子聚合反应来说,BF,AlCl,TiCl和SnCl 3344

and SnCl with water, or alcohols, or tertiary oxonium salts have shown themselves 4

与水、或乙醇,或叔烊盐的络合物提供了部分活性。正离子是产生链引发的化合物。

to be particularly active. The positive ions are the ones that cause chain

10

高分子专业英语选讲课文翻译资料

initiation. For example:

例如:(反应略)

三乙基硼氟酸烊

However, also with HCl, HSO, and KHSO, one can initiate cationic polymerization. 244

然而,BF也可以与HCl、HSO和KHSO引发阳离子聚合反应。 3244

Initiators for anionic polymerization are alkali metals and their organic 阴离子聚合反应的引发剂是碱金属和它们的有机金属化合物,compounds, such as phenyllithium, butyllithium, phenyl sodium, and 例如苯基锂、丁基锂和三苯甲基锂,

triphenylmethyl potassium, which are more or less strongly dissociated in

它们在不同的溶剂中或多或少地强烈分解。

different solvents. To this group belong also the so called Alfin catalysts, which

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翻译 Unit11 1、他暗示John是肇事者的企图是徒劳的。(insinuate,futile)暗示,无用的;无效的 His attempt at insinuating that John was the culprit turned out to be futile. 2、当他未能完成期望他做的事时,他很善于临时找个借口来为自己开脱。(improvise)临时做 He is very clever at improvising excuses when he fails to do what is expected of him. 3、他此行去西藏可以满足他想参观布达拉宫的愿望了。(gratify)使满足;使满意,使高兴 His trip to Tibet will gratify his desire to see Potala. (the Potala Palace) 4、这个公司拥有雄厚的人力资源。(command)命令,指挥;控制 This corporation commands excellent/rich/abundant human resources. 5、另外想个办法去款待你的客人。不要老是请他们看影视光碟。(alternative)二中择一;供替代的选择Think of an alternative way of entertaining your guests. Don’t always show them VCDs. 6、沉溺于胡思乱想和心血来潮是有害的。(caprice)任性,反复无常;随想曲 It is harmful to indulge in whims and caprices. 7、不属于你的东西不要作非分之想。(lay one’s hands on,be entitled to)2有权;有…的资格 Try not to lay your hands on anything that you are not entitled to. 8、他没有来参加竞赛。很可能他把这件事全部忘记了。(it may well be that)可能会是 He did not come to the competition. It may well be that he had forgotten all about it. Unit10 1、他奇特的行为与对良好举止的一般观念背道而驰。(run counter to)违反;与…背道而驰 His peculiar behavior runs counter to the popular concept of good conduct. 2、相对论对现代科学产生了巨大影响。(impact)对…造成影响; 产生影响 The theory of relativity made a great impact on modern science. 3、任何人都没有权利嘲笑残疾人的不利条件。(deride)vt. 嘲笑;嘲弄 No one has the right to deride the disadvantages of handicapped people. 4、在她毕业典礼哪天,Judy的叔叔婶婶以丰盛的晚餐来款待她。(sumptuous)华丽的,豪华的;奢侈的 On her graduation day, Judy was treated to a sumptuous dinner by her uncle and aunt. 5、关于他过去在公司的经历,没有什么人有不满。(with respect to)关于,至于;就…而言 With respect to his past record in the firm, no one has anything to complain about. 6、她深深地陷入反对校董会的密谋之中。(inextricably)adv. 逃不掉地;解不开地;解决不了地He is inextricably involved in the plot against the school board. 7、我年迈的叔祖母很不习惯那些充斥市场的一次性物品。(disposable)用完即可丢弃的 My aged great-aunt is not used to the disposable goods which flood the market today. 8、他在考试作弊被发现后,他的名字马上从应试者的名单上删去了。(eliminate)vt. 消除;排除His name was immediately eliminated from the list of candidates after he was caught cheating in the exam. Unit 9 1、如果对这器械有什么不清楚的地方,你可以写信到我们总公司去询问。(address) If there is anything you are not clear about the device, address your inquiry to your head office. 2、在执行计划之前,我们最好把它的每一个方面仔细考虑,看看是否切实可行。(scrutinize)vt. 详细检查;细看 Before we put the new plan into practice, we had bitter scrutinize every aspect of it to make sure that it is practicable.

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