学术论文写作解析(1)—引言写作宏观逻辑

学术论文写作解析（1）—引言写作1

（转自微信公众号：土木sci工坊Pro）你身边最贴心的论文写作老师。

逻辑清晰的引言对于一篇学术论文来说至关重要，为什么这么说呢？首先，论文最重要的是它的创新，也就是我们常说的original contribution，那读者和审稿人怎么快速地知道一篇文章是否有original contribution呢？答案就是从引言中读到。引言需要对前人的研究做简单的回顾，然后指出前人研究的不足或者没研究到的地方，这也就是本研究的下手点，是original contribution的来源。从笔者作为审稿人的经验来看，一般在读完引言后就可以大概知道这篇文章是否值得发表。但是引言的重要性又时常被许多作者忽略，许多作者认为只要将把方法和结果写好即可，殊不知在审稿人读到方法和结果之前，必须先说服他们这个研究是值得做的。如果研究没有意义，那方法和结果写得再好，论文的价值也会大打折扣。这篇解析的目的就在于明确引言写作的结构和逻辑，为引言的写作提供理论的指导。

首先让我们看一个引言的例子，请仔细体会不同颜色标注文字的意义（读者不必细读具体内容，只需把握主干，体会加粗语句的作用）：

The vibration of bridges caused by the passing of vehicles or trains has been a subject of research since the nineteenth century [1–7]. Owing to the construction of high-speed railways and the upgrading of existing railways world-wide, the problem of train–bridge interactions has received increasing attention [8–14].Previously, vehicles were often approximated as moving loads, which in many cases allows the problem to be solved analytically. Aimed at consideration of the inertia effect of the moving vehicles, the moving mass model has been adopted instead [15–18]. However, for the case where the riding comfort or vehicle response is of concern, it is necessary to consider the effect of the suspension systems of the vehicles.The simplest model in this regard is a lumped mass supported by a spring–dashpot unit, often referred to as the sprung mass model [19– 21].Although still more sophisticated models can be devised for the vehicles, the efficiency of solution of the vehicle–bridge interaction (VBI) system becomes an issue of great concern, especially when there exists a number of vehicles. The VBI problem in this regard is complicated in that it is time-dependent and there are multiple contact points.

In analyzing the vehicle–bridge interaction systems, two sets of equations of motion of the second order must be written each for the vehicles and for the bridge. It is the interaction forces existing at the contact points that make the two subsystems coupled. As the contact points move from time to time, the system matrices are time-dependent and must be updated and factorized at each time step. To solve these two sets of equations, procedures of an iterative nature are often adopted [22–24]. One drawback with methods of iteration is that the convergence rate is likely to be low when dealing with the more realistic case of a bridge carrying a large number of vehicles in motion.In the literature, Lagr ange’s equation with multipliers and constraint equations has also been used [21].However, the use of Lagrange multipliers increases the number of unknowns and the effort of computation, especially when dealing with problems involving a large number of moving vehicles.

Still another category of methods exists for solving the VBI problems, e.g., those based on the condensation method. Garg and Dukkipati used the Guyan reduction technique to condense the vehicle degrees of freedom (DOFs) to the associated bridge DOFs [25]. These methods have been demonstrated to be efficient for computing the bridge response.However,because of the approximations made in relating the vehicle (slave) DOFs to the bridge (master) DOFs, they are not adequate for computing the vehicle response, which serves as an indicator of the riding

comfort generally required in the design of high-speed rail bridges.By using the Newmark finite difference scheme to discretize the vehicle equations, rather accurate master–slave relations have been established and used in eliminating the vehicle DOFs from the bridge equations. The result is an accurate VBI element that can be used efficiently in computing both the vehicle and bridge responses [27].

The objective of this paper is to develop suitable numerical models for handling both the vehicle and bridge responses that are of particular interest in high speed railways, but not to study solely the bridge impact response. In this study, the vehicle equations will be discretized by using the same Newmark finite difference scheme as in Ref. [27]. However, instead of establishing the master–slave relations, the contact forces will be solved from the discretized vehicle equations. With the contact forces made available, the VBI element can be directly derived from the bridge equations. The advantage of the present procedure is its versatility. It can be used to deal with vehicles of various complexities, ranging from moving loads, moving masses, sprung masses, to rigid car bodies supported by spring–dashpot units, and so on. The capability and reliability of the present procedure will be demonstrated in the study of several examples.

下面让我们来看不同颜色文字在引言中发挥的作用：

1.蓝色：背景介绍

由于高铁桥的建设，列车与桥相互作用问题受到了更多的关注。

2.绿色：之前研究的回顾

（a）车辆的模拟方法：moving loads, moving masses, sprung masses；

（b）车桥耦合问题的求解方法1：iteration method；

（c）车桥耦合问题的求解方法2：condensation method。

3.红色：之前研究的不足

（a）将车辆模拟为moving loads不能考虑其惯性,将其模拟为moving masses不能考虑悬挂系统的作用, sprung masses解决以上问题，但当车辆较多时，车桥耦合问题求解计算量较大；（b）车桥耦合问题的求解方法1：iteration method收敛较慢，计算效率不够高；

（c）车桥耦合问题的求解方法2：condensation method虽提高了求解效率，但不能获取车辆的响应。

4.紫色：本研究的目标和解决的问题

本研究采用Newmark finite difference分离车辆方程，从而解得车辆响应，既能保证求解速度，又能获得车辆响应，克服了之前采用方法的弊端，故值得研究和推广。

从以上的范例，我们可以总结出引言的大体格式：

研究背景---之前研究的回顾---之前研究的不足---本研究的目标和解决的问题

任何一篇文章的引言都可以采用这个格式，但对于创新点不同的文章，例如，有的论文提出新方法，有的论文展示case study，有的论文对于规范条文提出建议，因其侧重不同，在具体的写法上也有明显差别，这一点将会在后期的解析中详细介绍。另外，关于怎么样找科研创新点，我们通过自己的实践经验做了总结，将在后期的专题中以理论加实例的形式进行解析。

在读范例的过程中，我们不难发现，引言中最重要的逻辑就是转折。转折前是对前人研究的回顾，而转折后则是对前人研究的批判，指出其不足或者空缺。转折的形式一般包括两种，第一种为强转折，强转折使用具体的转折词来实现转折，例如however，nevertheless，

转折词后接着就是对于之前研究批判的内容。第二种转折形式为弱转折，它与前者的区别在于没有具体的转折词出现，而是通过限定词（例如only，merely）或者数量词（例如most，few）来表达出转折的意思。例如，我们可以说most studies only considered the effect of… 或者说few studies account for…。在之前的例子中，我们注意到，作者提到：One drawback with methods of iteration is …, 。这也是弱转折的一种，虽然没有明显的“转折”，但drawback一词带有很强的批判性，可以理解为转折。既然有两种转折方式，那么什么时候用哪一种呢？答案是并没有所谓。两种方式没有本质的区别，但是笔者提倡不要一味使用某一种，交替使用会增加文章的多样性，也是良好的写作习惯。

同时，引言中还应存在因果的逻辑关系。之前的转折是为了说明前人的研究有不足或者没考虑到的问题，那么正是因为这个缺陷，所以我们的研究才有意义，有什么意义呢？我们研究的意义在于提出了某方法或做了某实验解决了之前研究的不足或存在的问题。在之前的例子中，我们看到作者提到之前的研究存在求解方法效率低或者不能获取车辆响应的问题，这就是因果的因；我们读到The objective of this paper is to develop… 这就是因果的果。大多学术论文的引言将果放在引言的最后一段，一般通过类似The objective of this paper is to，it is the intend of this research to的表达方式引出，告诉读者和审稿人本研究的目标，而这个目标之所以有研究意义正是因为之前对前人研究的评判。在说完果后，作者一般应对文章的内容做一个概括，让读者和审稿人对文章的结构有大概了解。但与摘要不同的是，这里不需要提到研究的结果。

以上的两种逻辑，是引言部分的整体逻辑，这里我们将其称为宏观逻辑，与其相对的是微观逻辑，它包括段与段之间和句与句之间的具体逻辑。

另外，与本解析配套的是笔者总结出的引言写作模板，以引言的大体格式为框架，笔者总结了每个部分常用的表达句式，读者在写作可以直接运用以提高效率。

下一期解析，我们将继续关注引言写作，介绍引言写作中的微观逻辑，同时通过正确和错误例子，更好地说明怎样把引言部分的逻辑写清楚，让审稿人和读者一目了然的领会到论文的价值。请大家关注我们的公众号来获取及时更新。