学术论文中的引言(Introduction)是对全文内容和结构的总体勾画。引言尽管不像摘要那样有一定的篇幅限制和相对固定的格式，但在内容和结构模式上也有需要遵循的规律。本章首先介绍这些规律，然后探讨需要掌握的语言技巧。
8.1 引言的内容与结构布局
引言的主要任务是向读者勾勒出全文的基本内容和轮廓。它可以包括以下五项内容中的全部或其中几项：
介绍某研究领域的背景、意义、发展状况、目前的水平等;
对相关领域的文献进行回顾和综述，包括前人的研究成果，已经解决的问题，并适当加以评价或比较；
指出前人尚未解决的问题，留下的技术空白，也可以提出新问题、解决这些新问题的新方法、新思路，从而引出自己研究课题的动机与意义；
说明自己研究课题的目的；
概括论文的主要内容，或勾勒其大体轮廓。
如何合理安排以上这些内容，将它们有条有理地给读者描绘清楚，并非容易之事。经验告诉我们，引言其实是全文最难写的—部分。这是因为作者对有关学科领域的熟悉程度，作者的知识是渊博、还是贫乏，研究的意义何在、价值如何等问题，都在引言的字里行间得以充分体现。
我们可以将引言的内容分为三到四个层次来安排(如图8.1所示)。第一层由研究背景、意义、发展状况等内容组成，其中还包括某一研究领域的文献综述；第二层提出目前尚未解决的问题或急需解决的问题，从而引出自己的研究动机与意义；第三层说明自己研究的具体目的与内容；最后是引言的结尾，可以介绍一下论文的组成部分。
第一层：1) Introducing the general research area including its background, importance, and present level of development……………………………………………………………2) Reviewing previous research in this area……………………………………………………………………第二层： Indicating the problem that has not been solved by previous research, raising a relevant question ……………………………………………………………………………………………………………………………………………………………………………………………第三层：Specifying the purpose of your research………………………………………………………………………………………………………………第四层：1) Announcing your major findings ……………………………………………………………………………………………………………2) Outlining the contents of your paper …………………………………………………………………………………………………………………………………………………………………………………
图8.1 引言的结构布局之一
值得注意的是，引言中各个层次所占的篇幅可以有很大差别。这一点与摘要大不一样，摘要中的目的、方法、结果、结论四项内容各自所占的篇幅大体比例一样(见7.2节)。而在引言中，第一个层次往往占去大部分篇幅。对研究背景和目前的研究状况进行较为详细的介绍。研究目的可能会比较简短。
引言与摘要还有一点不同的是，摘要中必须把主要研究结果列出，而在引言中(如果摘要与正文一同登出)结果则可以省略不写，这是因为正文中专门有一节写结果(results)，不必在引言中重复。
下面这段引言的例子摘自一篇关于混合电动汽车的研究论文，大部分篇幅介绍研究背景。
例1
A Hybrid Internal Combustion Engine/Battery Electric Passenger Car for Petroleum Displacement I. Forster and J. R. Bumby INTRODUCTION [1] The finite nature of the world's oil resources and the general concern about automobile emissions have prompted the adoption of energy conservation policies and emphasized the need to transfer energy demand from oil to other sources of energy, such as natural gas, coal and nuclear. [2] A transfer of energy from oil to electricity can be achieved to a limited extent in the road trans- port sector by the increased use of electric vehicle. However, such vehicles are limited in range due to the amount Of energy that can he realistically stored on-board the vehicle without affecting payload. As a consequence of this, electric vehicles must he used in situations where daily usage is well defined, for example, in urban delivery duty. Indeed, it has been in such vehicles as the urban milk delivery vehicles that electric traction drives have been traditionally applied with a great deal of success. Currently the demand is for urban electric vehicles to he developed with greater traffic compatibility in terms of speed and range. 分析：第一层(第1—5段)：介绍混合电动汽车的研究背景、意义、目前的发展水平，需要解决的问题等。第1段：指出混合电动汽车的研究背景。世界石油资源的有限性及人们对汽车排放问题的广泛关注使得能源转换问题尤为重要。第2段：使用电动汽车能够从某种程度上实现能源转换。但问题是电动汽车的续驶里程比内燃机车短。所以目前要解决的问题是提高电动汽车的速度和续驶里程。
[3] Although urban delivery vehicle applications will help to reduce the dependence of the road transport sector on petroleum-based fuels, the major part of this market requires vehicles that are not limited in range and have a performance compatible with internal combustion, i.e. engine vehicles. The use of advanced traction battery technology to overcome the range limitation of electric vehicles is one possible solution. However, this would still result in a vehicle limited in range and may in itself create additional problems. For example, due to the much greater on- board stored energy, the charging time required will be greater than at present. [4] The range limitations of the pure electric vehicle can be overcome by using a hybrid i.c. engine/electric drive which incorporates both an i.c. engine and an electric traction system. Al- though such a vehicle can be designed to meet a number of objectives, it has been argued that a vehicle which seeks to remove the range limitation of the electric vehicle while substituting a substantial amount of petroleum fuel by electrical energy is the vehicle most worth pursuing. With the emphasis of the vehicle design on the electric drive train, the intention may be to operate in an all-electric mode under urban conditions and to use the i.c. engine for long-distance motorway driving. The hybrid mode could then he used for extending urban range and/or improving vehicle accelerative performance on accelerator kick-down.[5] The concept of a hybrid electric vehicle capable of substituting petroleum fuel is' not new, 第3段：市场要求电动汽车的续驶里程及工作性能与内燃机汽车媲美，但是，即使先进电池可以提高电动汽车的续驶里程，但还会有一些问题不能解决。 第4段：续驶里程可以通过使用混合电动汽车来提高。混合电动汽车上既装有内燃机，又装有电动驱动系统，在必要时使用其中一种系统。第5段：回顾并评述前人关于混合电动汽车
Bosch and Volkswagen having built vehicles in the 1970s. More recently, the advent of the Electric and Hybrid Vehicle Research, Development and Demonstration Programme in the United States of America initiated the design and construction of a Near Term Hybrid Vehicle (NTHV) with the principal aim of substituting petroleum fuel by ' wall plug' electricity. [6] As part of the NTHV programme, a large number of conceptual studies were conducted but on vehicles aimed at the American passenger car market. In this paper optimization studies were conducted, but now on a vehicle suitable for the European medium-sized passenger car market. Such optimization studies are important as, with two sources of traction power available, the way in which they are controlled, and their relative sizing, is fundamental to the way the vehicle performs.[7] Before examining in detail the optimum control strategy for the drive train, Section 2 defines the hybrid arrangement under study. A description of the optimization process using an appropriate cost function is then presented in Section 3 followed by a method of translating the resulting control structure into a sub-optimum algorithm capable of being implemented in real time. Using the optimum control structure the effect of component ratings on the vehicle's performance is evaluated in Section 4, while Section 5 discusses the practical implementation of an overall vehicle control algorithm. Finally, in Section 6, an indication of the vehicle's potential for substituting petroleum fuel by electricity is given. 的研究成果。第二层(第6段第1句话)：指出前人研究的范围具有局限性。关于混合电动汽车的研究只针对美国市场。针对欧洲市场的研究还是空白。第三层(In this paper)本文的研究目的及意义：对欧洲中型客车市场进行优化研究。第四层为第7段：本文的组成部分及各部分的主要内容。
比较简短的论文，引言也可以相对比较简短。为了缩短篇幅，可以用一两句话简单介绍一下某研究领域的重要性、意义或需要解决的问题等。接着对文献进行回顾。然后介绍自己的研究动机、目的和主要内容。至于研究方法、研究结果及论文的组成部分则可以完全省略，如图8．2所示。
第一层: Introducing the importance of the research area and reviewing previous Research………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………第二层: Indicating the problem that has not been solved by previous research, raising a relevant question ………………………………………… ..................................................………………..............................................................................................................................第三层: Specifying the purpose of your research……………………….............................................
图8.2 引言的结构布局模式之二
例2
Forest Decline and Tree Mortality in a Southeastern Ohio Oak(橡树) -Hickory( 山核桃树) ForestGRETCHEN M. WALTERS AND BRIAN C. MCCARTRY INTRODUCTION[1] Forest decline results from a reduction in growth and vigor and may be accompanied by widespread mortality of trees over a relatively large geographic area. There has been a considerable increase in the reporting of forest decline throughout the hardwood forest of eastern North America and thus possible cause for concern. The source of decline is often much more difficult to pinpoint and is frequently the result of multiple stresses including ozone, atmospheric pollution, climatic extremes, and pests. 分析：第一层(第1—3段)：提出森林资源减少和树木死亡这一值得关注的问题，以及有关这一问题的研究状况。第1段：共三句话，提出问题并简单介绍造成这一问题的几种因素。
[2] The condition of eastern hardwood species and ecosystems of the United States has been summarized by Weiss and Rizzo (1987) and Millers et al. (1989). One of the more prominent examples of large scale species decline in northeastern North America is the sugar maple (糖槭树). Observed patterns of decline stimulated the creation of the North American Sugar Maple Decline Project, a joint endeavor between the United States and Canada, to monitor the changing conditions in sugar maples (Hertel and MeKinney- McNeal 1991 ). Concurrently, the Forest Response Program was created to examine the effects of and ozone on forest health and productivity. Since then, numerous studies have been completed and many regions are establishing long-term forest health surveys to better monitor changes occurring in the eastern forest (Loncks 1992). [3]Througout the eastern United States, large scale compositional changes have been observed in forests dominated by oak and hickory (Christensen 1977, Lorimer 1984, McCarthy et al. 1987, Pallardy et al. 1988). Many of these changes are believed to be successional in nature and appear to be linked to regeneration problems (Lorimer 1993). Failure of the oaks to regenerate has been tied to a variety of factors including competition (e. g., shade intolerance), altered disturbance regimes (e.g., fire), wildlife populations (e.g., insects, deer), and a variety of influences over the past century ( Lorimer 1993). Certainly, increased stress or decline in the oaks would adversely affect tree reproduction (Marion 1991). 第2段：回顾并评述该领域的研究与发展过程。以糖槭树作为例子，说明树种的减少所引起的关注以及对该问题的研究项目等。第3段：关于美国东部地区森林结构的观察研究状况。以橡树和山核桃树为主的森林在结构上发生了变化。原因是多种多样的。橡树与山核桃树的减少会对树木的再生长造成不良影响。
[4] In Ohio, there have been few specific reports in the literature of oak and hickory decline (Millers et al. 1989). Regionally, oak mortality has been linked to a variety of causes including drought, insects, and diseases. Hickory mortality has usually been associated with insect outbreaks (e.g., hickory bark beetle and gypsy moth) (Millers et al. 1989). Hanson et al. (1976) noted oak mortality and decline associated with drought and insects throughout a multi-state region of the midwest, including Ohio. McCarthy (1995) documented 50% hickory mortality, associated with insects, in a ten year study of forest dynamics in two hardwood areas in southeastern Ohio forest. The lack of decline reports for oak-hickory vegetation in Ohio may simply be because the forest is essentially healthy. Alternatively, decline symptoms may be present but not reported due to a shortage of studies explicitly designed to evaluate decline in certain forest types.[5] The purpose of this study was to conduct a preliminary forest health study of a representative oak-hickory forest of southeastern Ohio. A decline index was employed to categorize present symptoms and predict future dynamics while mortality was used as an indicator of past decline and its resultant effects on present forest dynamics. 第二层(第4段)：指出研究的空白。关于俄亥俄州橡树与山核桃树减少与死亡的研究报告却很少见。第三层(第5段)：说明本研究项目的目的。为了填补上述空白，本文对俄亥俄州东南部地区的橡树与山核桃树的健康状况进行初步研究。
可见，引言一般分为三到四个层次。每个层次都有各自的任务与目的。而在语言上也有各自的特点，掌握这些特点会使写作过程化难为易。下面将对引言各层次的写作特点和技巧分别加以介绍。
8.2 如何写引言的开头
引言开头(即第一层)最主要目的是告诉读者论文所涉及的研究领域及其意义是什么，研究要解决什么问题，目前状况或水平如何。也就是说，开头要回答如下问题：
l What is the subject of the research?
l What is the importance of this subject?
l How is the research going at present?
l In what way is it important, interesting, and worth studying?
l What problem does the research solve?
下面列举几段例子，以说明引言开头如何开门见山点明研究主题，回答以上问题。
例3
Purple loosestrife (紫千曲菜) is a wetland plant which invaded North America in the early 1800s. It is well established in the United States and Canada with serious infestations in the Great Lakes and St. Lawrence regions.
研究主题是purple loosestrife。这种植物之所以值得研究，是因为它严重侵扰了五大湖区及圣劳伦斯地区。
例4
Forecast of the tracks of hurricanes (飓风)have improved steadily over the past three decades, owing to a combination of better observations and much improved numerical models. These improvements, along with advances in warning systems and preparedness for emergencies, have brought about a significant decline in loss of life.
研究主题是 forecast of the tracks of hurricanes(对飓风轨道的预测)。这一领域取得了进步，意义是大大减少人员伤亡损失。
例5
Environmental indicators(环境指数)attempt to accurately describe environmental conditions and make available scientifically valid information on environmental trends．
研究主题是environmental indicators。环境指数的意义是能够精确地描述环境状况，并能够提供关于环境倾向的科学、有效的信息。
例6
Acoustic problem occur extensively in long spaces. For example, in road or rail tunnels noise pollution is a serious problem, and in underground stations poor speech intelligibility of public address systems can cause misunderstanding of vital instructions during an emergency.
研究主题是acoustic problem of longs paces(长空间的声学问题)，例如，公路与铁路隧道上的噪声污染就是一个严重的问题。地铁站的广播系统语言清晰度差，造成在紧急状态下信息误解，因此，这个问题值得研究解决。
通过分析例3到例6，还可以发现如下特点。
首先，关键词往往出现在第一句话，回答What is the research area? 这个问题，迅速将主题告诉读者，避免转弯抹角，影响信息传递。然后简单介绍该研究领域的意义。
第二，引言开头句子的谓语动词或者是一般现在时态，或者是现在完成时态。这是因为这些动词所描述的是某研究领域的现状，而不是过去的情况。
引言的开头常用句型还有：
句型1：研究主题+谓语动词be… ．
例7
a．Fuel cell(燃料电池)is a technology for the clean and efficient conversion from chemical energy in fossil fuels to electricity．
b. Spot welding (点焊) is the most widely used joining method in the automobile manufacturing industry.
c. Accurate prediction of springback (回弹预测) for sheet metal forming process is vital to the design of tools used in automotive sheet stamping operations.
句型2: 研究主题+ has become …
a. Semiconductor based industry (基于半导体的工业)has be come the largest industry for the USA and it has influenced every other industry and every aspect of human life.
b. The battery technology has become increasingly popular in automotive industry.
c. Forest decline has become a favorite topic for environmental studies.
a. Synthetic polymers (聚合物) are widely used in contact with
biological systems in applications such as medicine, biotechnology, food processing and natural water environment.
b. Air pollution has been extensively studied in recent years.
c. The causes of glaucoma have been widely investigated recently.
d. The importance of safe driving is now well established.
句型4: Recently, there has been growing interest in / concern about + 研究主题
例10
a. Recently, there has been growing concern about waste-water
biosolid, the residual organic matter produced during waste water treatment.
b. In the 1990s there has been growing interest in the development of electric vehicles in response to the public demand for cleaner air.
句型5: Recently there have / has been extensive / increasing /numerous publications / literature / reporting on + 研究领域
例11
a. There have been numerous publications over the last ten years on the need for nursing education to keep pace with the increase in knowledge of biological science.
b. There has been increasing reporting about forest decline in North America.
句型6: Researchers have become increasingly interested in +研究领域
或:Researchers have recently focused their attention on +研究领域
Researchers are recently paying more attention to + 研究领域
例12
a. Researchers have become more interested in environmental indicators.
b. Researchers are paying more attention to high pressure injection (高压喷射).
8.3 如何写文献综述
文献综述是学术论文的重要组成部分，是作者对他人在某研究领域所做的工作和研究成果的总结与评述，包括他人有代表性的观点或理论、发明发现、解决问题的方法等。在援引他人的研究成果时，必须标注出处，即这一研究成果由何人在何时何地公开发表。
8.3.1文献出处的标注
引用文献时，不同的学科或领域可能采用各自约定俗成的体系或格式。在写论文时，应该了解自己学科采用的固定格式。目前最常见的体系有两种，一种是作者+出版年体系，另一种是顺序编码体系。下面对这两种体系分别加以介绍。
第一种体系的主要框架模式如下：
模式1：作者(年代)十谓语动词主动语态+研究内容／成果例13
a. Hanson et al. (1976) noted that oak mortality and decline were associated with drought and insects throughout a multi-state region of the mid-west.
b. McCarthy (1995) documented 50% hickory mortality, associated with insects, in a ten year study of forest dynamics in two hardwood areas in a southeastern Ohio forest.
c. Also, Fay (1991) found cooperative group projects integrated into science class to be successful experiences for students.
模式2：研究内容／成果+谓语动词被动语态+(作者年代)
例14
a. Success at this Science Day was found to be linked to parental support (Czemiak 1996).
b. Throughout the eastern United States, large scale compositional changes have been observed in forests dominated by oak and hickory (Christensen 1997, Lorimer 1984, McCarthy et al. 1987, Pallardy et al. 1988).
模式3：It has been十谓语动词被动语态+by作者(年代)+that从句
或：It has been+谓语动词被动语态+that从句(作者年代)
研究内容／成果+谓语动词被动语态+by作者(年代)
例15
a. It was found by Czemiak (1996) that success at this Science Day was linked to parental support.
或:It was found that success at this Science Day was linked to parental support (Czemiak 1996).
b. The condition of eastern hardwood species and ecosystems of the United States has been summarized by Weiss and Rizzo (1987) and Millers et al. (1989).
如果引用的文献有两个以上的作者，只标明第一作者，后面用拉丁文et al‘表示，意思是“等人”、“其他人”。如例13a中的“Hanson et al．”就是如此。
如果在综述中涉及几个项目或文献时，则将这些文献并列标注，必要时用逗号隔开。如例14b中的“…Christensen 1997， Lorimerl984，McCarthy et al．1987，Pallardy et al．1988)” 以及例15b中的“…Weiss and Rizzo(1987)and Millers et al．(1989)”。
标注参考文献另一种常见体系是按文献出现的先后顺序编号，置于方括号中，标在指引部分的右上角。被引用的作者、文献名、出版时间、地点等列入论文后面的参考文献中。其顺序要与正文中标注的顺序一致。
例16
Forecasts of the tracks of hurricanes have improved steadily over the past three decades [1], owing to a combination of better observations and much-improved numerical models. In contrast to the improvements in track forecasts, there has been comparatively little advance in predictions of intensity [1], in spite of the sophisticated numerical models. The best intensity forecasts today are statistically based[2]. Most of the research literature on hurricane intensity focuses on the pre-storm sea surface temperature and certain properties of the atmospheric environment[3] But it is well known that hurricanes alter the surface temperature of the ocean over which they pass[4] and that a mere 2.5 K decrease in ocean surface temperature near the core of the storm would be enough to shut down energy production entirely[51. Simulations with coupled atmosphere-ocean models[5-7] confirm that interaction with the ocean is a strong negative feedback on storm intensity…
文中标注的编号代表参考文献出现的顺序。"[l]"在文中出现两次，代表这两处所陈述的内容或观点出自同一篇文献，即正文后面参考文献中的第1条。“[5—7]”代表此处陈述的内容或观点涉及到三篇文献，即参考文献中第5—7条。
行文中的编号也可以不放在方括号里。如：例17
The sound attenuation along the length, a significant index in long spaces, has been intensively studied. Based on various assumptions and using various methods, a number of formulae have been given1-5. Another important index, reverberation time, has been seen to be different from that of the diffuse field6.
8.3.2 文献综述中的动词运用技巧
(1)两类动词
从例13到例17中，我们可以发现，文献综述中常用state， note，observe，discuss，establish，find，present等动词。这些动词有两种特性，一种是描述性动词，客观地向读者介绍他人的工作；另一种是评价性动词，在一定程度上代表了作者对他人的工作的理解、解释或态度。文献综述中常用的描述性动词有：describe，discuss，explain，examine，present，state等。常见的评价性动词有：affirm，allege，argue，assume，claim，imply，maintain，presume，reveal，suggest等。
(2)动词时态
文献综述中最常见的时态是一般现在时、一般过去时和现在完成时三种时态。使用不同的动词时态会给句子的意义带来变化，基本原则如下：
原则1：当作者引用某人过去某个时间所做过的某一项具体的研究时，用一般过去时。如：例18
a. Hanson et al. (1976) noted that oak mortality and decline were associated with drought and insects throughout a multi-state region of the mid-west. …McCarthy (1995) documented 50% hickory mortality, associated with insects, in a ten year study of forest dynamics in two hardwood areas in a southeastern Ohio forest.
b. It was found by Czerniak (1996) that success at this Science Day was linked to parental support.
或:It was found that success at this Science Day was linked to
parental support (Czemiak 1996)...
原则2：在概括或总结某一研究领域里所做过的一些研究时，用现在完成时，如：
例19
a. The condition of eastern hardwood species and ecosystems of the United States has been summarized by Weiss and Rizzo (1987) and Millers et al. (1989). … Since then, numerous studies have been completed and many regions have established long-term forest surveys to better monitor changes occurring in the eastern forest (Loucks 1992).
b. The sound attenuation along the length, a significant index in long spaces, has been intensively studied. Based on various assumptions and using various methods, a number of formulae have been given [1-5]. Another important index, reverberation time, has been seen to be different from that of the diffuse field [6].
原则3：在谈及目前的知识水平、技术水平或存在的问题时，用一般现在时态。
例20
Acoustic problems occur extensively in long spaces. For example, in road or rail tunnels noise pollution is a serious problem, and in underground stations poor speech intelligibility of public address systems can cause loss of important travel information and misunderstanding of vital instructions during an emergency. An outstanding feature of long spaces is that classical room acoustic theory is not applicable since the assumption of a diffuse field does not hold with the extreme dimension condition. Consequently, works required for an understanding of the behavior of sound in long spaces and for an acoustic prediction which takes into account the relevant characteristics.
(3)衔接手段
如果综述中多处需要引用同一个作者或同一篇文章，那么，需要用一些连接手段使上下文衔接，让意思流畅、连贯，并起到提醒读者的作用。
例2l
a. The author goes on to say that…
b. The article further states that…
c. The author also states / argues / believes that …
d. The author concludes that …
8.4 如何写研究动机与目的
在介绍了他人在某领域的工作和成果之后，下一步便介绍作者自己的研究动机、目的与内容。介绍研究动机可以从两个角度人手，一是指出前人尚未解决的问题或知识的空白，二是说明解决这一问题，或填补知识空白的重要意义。
主要句型有：
句型1：用表示否定意义的词例little，few，no或none of+名词作主语。如：
例22
a．Little information／attention／work／research…
b．Few studies／investigations／researchers／attempts…
C．No studies／data／calculations…
d．None of these studies／findings／calculations…
注意：
(1)little后面的名词是不可数名词，而few后面是可数名词，而且是复数形式。
(2)no后面直接用名词(可数或不可数名词)，表示泛指，“到目前为止还没有……”的意思，而none of后用指示代词these，those(或定冠词the)+名词，表示“在特定的范围中还没有……”的意思。也就是说，在上文所提到过的那些研究中，还没有解决某一问题，由此来暗示知识的空白部分。
下面举几个表示否定意义的例子。
例23
a. Unfortunately, few educational opportunities exit to teach farmers and rural homeowners effective water supply management.
b. There have been few specific reports in the literature of oak and hickory decline.
c. There is, however, little qualitative information regarding purple loosestrife vegetative reproduction.
d. However, there exists little research on science fair projects.
句型2:里表示对照的句型。如:
例24
a. The research has tended to focus on…, rather than on…
b. These studies have emphasized…, as opposed to…
c. Although considerable research has been devoted to…, rather less attention has been paid to…
d. Although there is much hope that three-dimensional coupled models will lead to better understanding of the factors that control hurricane intensity and to increased reliability of hurricane intensity forecasts, the present generation of models may not have enough horizontal resolution to capture the full intensity of extreme storms.
句型3：提出问题或假设。如：
例25
a. However, it remains unclear whether…
b. It would thus be of interest to learn how…
c. If these results could be confirmed, they would provide strong evidence for …
d. These findings suggest that this treatment might not be so effective when applied to…
e. It would seem, therefore, that further investigations are needed in order to…
指出或暗示了知识领域里的空白，或提出了问题或假设之后，下一步理所当然应该告诉读者本研究的目的和内容，要解决哪些问题，以填补上述空白，或者证明所提出的假设。
此部分常见的句型请参见7.3.1节，如何写摘要中的目的部分。这里只略举几例。
例26
a. The aim of the present paper is to give …
b. This paper reports on the results obtained…
c. In this paper we give preliminary results for…
d. The main purpose of the experiment reported here was to…
e. This study was designed to evaluate…
f. The present work extends the use of the last model by…
g. We now report the interaction between…
h. The primary focus of this paper is on…
i．The aim of this investigation was to test…
j．It is the purpose of the present paper to provide…
从暗示知识的空白到本研究的目的与内容一般需要用一些过度词，以提示一下读者。如上面这些例句中，用了this paper，here，the present work，now，this investigation，the present paper等词或词组。
为了引起读者的注意，这些词或词组一般放在句首。
例27
…The fate of these sections is not clear. In this study we asked the questions: Do shoot sections remain viable and, if so, are they capable of further growth? We also examined the effect of habitat history and section length on survivorship.
如果一项研究、一篇论文不止一个目的，应该按目的的主次排列顺序，并用连接词或词组。
例28
The present work extends the use of the last model to asymmetric, body-vortex cases, thus increasing the range of flow patterns that can be investigated. In addition, an effort is made to improve the numerical procedure to accelerate the convergence of the iterative solution and to get a better rollup of the vortex lines representing the wake.
常见的连接词还有additionally, in addition to this, besides this, also, not only…but also…, further, furthermore, moreover 等
8.5 如何写引言的结尾
研究目的完全可以作为引言的结尾。也可以简单介绍一下文章的结构及每一部分的主要内容，从而起到画龙点睛的作用，使读者了解文章的轮廓和脉络。
至于研究结果，在引言中完全可以不写。研究结果是结论部分最主要的组成部分。例29是引言的结尾，介绍文章的结构。
例29
…Before examining in detail the optimum control strategy for the drivetrain, Section 2 defines the hybrid arrangement under study. A description of the optimization process using an appropriate cost function is then presented in Section 3 followed by a method of translating the resulting control structure into a sub-optimum algorithm capable of being implemented in real time. Using the optimum control structure the effect of component ratings on the vehicle's performance is evaluated in Section 4, while Section 5 discusses the practical implementation of an overall vehicle control algorithm. Finally, in Section 6, an indication of the vehicle's potential for substituting petroleum fuel by electricity is given.
在介绍全文的结构时，要避免使用同一个句型结构，如，Sections l describes…Section2 analyses…Section3 discusses…Section 4 summarizes…这样，每句话用同样的词开头，句型结构显得单调、枯燥乏味。
思考题
一、根据引言的结构规律排列次序。
1. A national assessment of water quality training needs for extension staff identified drinking water as a nation-wide concern (Bergsrud et al. 1990). According to the study, many county agents were concerned with the health risks of drinking water contaminants and the effectiveness of water treatment devices. But, as the assessment showed, most county agents felt ill-equipped to conduct proactive educational programs in drinking water quality.
2. The objectives of this project were to use a distance education training program to teach county extension agents (1)water quality and supply management principles and (2)how to use educational materials to teach water supply management to others. The expectation was that, once trained, extension agents would begin to reach out to the hundreds of thousands of Ohioans who might benefit from education in water supply management.
3. For decades, the Cooperative Extension System has conducted outreach educational programs for US citizens as a part of the land grant university system. Rural residents often perceive the county extension agent as the most familiar member of the Extension System. With offices in nearly every county in the country, extension agents have traditionally conducted educational programs for adults and youth in topics related to agriculture, home, and family. In the 1980s Cooperative Extension began a new national water quality initiative (Bergsrud et al. 1990). More than 95% of the nation's rural residents depend on groundwater as the major source of water supply. Teaching rural Americans about water quality issues presents both challenge and an opportunity for extension.
4. In Ohio, over 750,000 households (19%) rely on private individual water supplies (US Department of Commerce 1983). In these private water supplies the homeowner or farmer is responsible for providing high quality water for their family and livestock. Unfortunately, few educational opportunities exit to teach farmers and rural homeowners effective water supply management.
Correct order:
二、选句填空。将方格中的各个句子填入引言中合适的空格中。
a. However, they were unable to obtain stable solutions for sand transport and the quantitative predictions of concentration were far from satisfactory.
b. Most existing mathematical models for predicting sediment transport in sheet flow regime are based on the governing equations for single-phase flow[1-3].
c. The detailed computations are then carried out and the numerical predictions are compared with the experimental measurements.
d. It has been recognized that among all the transport modes the sheet flow condition is the most important due to the large transport rate involved.
e. None of these models were capable of predicting the peak values of the particle velocity profiles and providing as much insight into the fluid-particle interactions as would a complete two-phase modeling two-phase modeling approach.
f. The forcing terms such as the interaction force, the intergranular stresses and the turbulent stress were carefully formulated.
(1)______ Over the last two decades, considerable research efforts have been directed to the understanding and prediction of these flows. (2)_______ However, since the models of this-kind do not address the interaction between fluid and sediment in a fundamental way, the moving mechanism of the sediment in this high concentration region cannot be properly accounted for. Considering the fact that the intergranular stress and the interaction between fluid and sediment are dominant in the sheet flow regime, a natural and accurate approach is to treat the fluid and sediment as two-phase flow. Asano [4] and Ono et al. [5] are among those who proposed partial two-phased models in which the vertical velocity of particles was approximated by an empirical expression rather than solved in the same way as the horizontal velocity. (3)______ One of such models was developed by Li and Sawamoto[6]. They extended Asano's work and based their formulation on the complete set of linearized two-phase equations. (4)_______
In this paper a complete two-phase flow model is presented for the simulation of the sediment motions on a flat bed under unsteady flow conditions. (5) ______ In order to ensure the numerical stability, a mixed implicit and explicit finite difference scheme was developed to solve the nonlinear equations. (6)________
Answer:
(1) ________ (2)________ (3)________
(4) ________ (5)________ (6) ________
三、下面是一篇学术文章的引言，将括号中的动词变成合适的形式。
Introduction
The feeding habit of leopard frog (豹蛙) are poorly understood (Rittschof 1975 ). Past investigations (1)________ (indicate) that species feeds on a wide variety of prey (Knowlton 1944, Linzey 1967, Rittschof 1975 ). Rittschof (1975) (2)_______ (note) that the prey most commonly consumed (3)_________(be) slow moving individuals of the orders Coleoptera, Lepidoptera and Orthoptera, but he (4)_________ ( not determine ) if adult and young leopard frogs fed on significantly different types of prey. In Michigan populations, recently trans- formed juveniles ingested ants. These ants (5)__________ (never find ) in the stomachs of adult frogs (Rittschof 1975). Whether this (6)_________( reflect ) a true feeding preference by young frogs, or (7)__________ (be) simply a result of local prey availability, (8) __________ (be) unknown. Stomach content analyses (9)_________ (reveal) the presence of both diurnal and nocturnal prey suggesting that leopard frogs (10)_____________(feed) during both day and night (Hine et al. 1981, Rittschof 1975). The primary purpose of our investigation ( 11 )____________( be ) to document the prey consumption of adult and young leopard frogs from a restored wetland in northeastern Ohio. We note differences in the prey consumed by adult and juvenile frogs and (12)__________ (compare) the relative activity level of the prey types to determine if adult and young frogs specialize on active or inactive prey.
参考答案
一、根据引言的结构规律排列次序。
Correct order：3—l—4—2
二、选句填空。将方格中的各个句子填入引言中合适的空格中。
(1)d (2)b (3)e (4)a (5)f (6)c
三、下面是一篇学术文章的引言，将括号中的动词变成合适的形式。
(1) indicate (2) noted
(3) were (4) did not determine
(5) were never found (6) reflects
(7) is (8) is
(9) revealed (10) feed
( 11 ) is (12) compare
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