本讲专门谈谈科技论文引言的写作，这也是青年人写论文的一个薄弱环节。我认为，先要认识引言对全文的重要作用，进而了解引言的内容和写法，改掉常见的缺点。

•引言的重要性• 在科技论文中，引言极其重要，是引领全文的“先锋”，人们可以从中了解作者的意图（motivation）、思路（idea）和成果（results），与问题、摘要一起，形成勾起读者“探究欲”的三要素，更是让读者理解所报告的工作的“引子”。因此，不可等闲视之。

•引言的内容• 简述工作的缘起、背景和意义；综述相关的研究动态和前人成果；指明亟待解决的关键问题；陈述本人的工作和主要成果，讲清对以往工作的发展；列出本文的架构（对于长文不可或缺）。

•引言的篇幅• 引言要有足够的长度，约占全文篇幅的1/6～1/5，也就是说，一篇五六页的论文，引言至少为一页；一篇一百页的学位论文，引言（概论、绪论）应有二十页左右的篇幅。

•引言写作的常见问题• 下面列举初学科技论文写作者的常见问题：

——过于简略。这是国内青年作者的论文中最常见的问题，由于思想上不重视引言的重要性，写得浮皮潦草，篇幅甚短，语焉不详，平淡乏味。

——侈谈意义。对于论文工作的意义需要有简短陈述，但不必长篇大论，因为读者是同行，对一项工作的重要性自有共识。

——忽略回顾。有些论文对前人工作很少提及或不屑一顾，没有把论文与相关的近期进展联系起来，使论文成为无源之水，无本之木，似乎此工作是作者天马行空第一份。

——平铺直叙。简单罗列前人工作，未做详尽分析，特别是不曾指出前人工作中的不足之处和亟待解决的关键问题。

——轻描淡写。只用一两句话点明本人工作，使读者难以了解取得成果的思路、方法，以及作者工作的继承性和创造性。

——重述摘要。不少作者写作论文时动用剪贴工具，简单地重复摘要的内容，这是万万使不得的。

•引言写作的五招•

——充分认识引言的“开宗明义，引领全文”的关键作用。化大力气写引言，通常，写作的最后阶段才写引言（绪论）；

——言简意赅地写明论文的背景。话不在多，点到即可；

——重点写好前人工作综述。在充分调研的基础上，全面、扼要地简述以往的相关工作（包括自己的），特别应指出急需解决的又是本文关注的关键问题；

——恰如其分地概述本文工作。尤其要点明创新点；

——简述本文的结构。通常放在引言的最后一段：“本文是这样组织的……”。

•引言写作的案例•

这里引用两位普通作者的论文引言，此文发表在Journal of Hydrodynamics的2006年第6期上。

【案例点评】

这一引言基本上达到了上文所述的要求，亦即，简明扼要地描述了论文的背景；恰当充分地综述了相关的成果（共引参考文献17篇，包括自己的工作）；点明了现有工作的不足；简述了本文工作要点。缺点是对本文的工作进展描述得不够充分，尤其是没有说清所得的数值解与解析解、实验数据比较的结果。

Numerical modeling of wave evolution and runup in shallow water

1 Introduction

In shallow waters of coastal zones, shoreward wave propagation generally leads to complex phenomena, such as wave breaking and runup, which are of fundamental importance in coastal and ocean engineering. For instance, wave breaking often induces energy dissipation, sediments transportation and momentum exchange between waves and nearshore currents, while wave runup has direct relevance to tsunami hazard mitigation.

Solitary waves and cnoidal waves are two typical forms of nonlinear shallow water waves, which have received much attention. Lin et al [1] and Guignard et al [2] investigated solitary wave breaking and runup on sloping beaches. Jensen et al [3] presented experiments on runup of strongly nonlinear waves on a beach of 10.54°inclination, and obtained free surface profiles and velocity fields. Liu & Tao [4] simulated the process of solitary wave runup and rundown on the seaward wall of different breakwaters. Chang et al [5] studied vortex generation and evolution due to flow separation around a submerged rectangular obstacle under incoming cnoidal waves. Guyenne & Grilli [6] performed simulations in a three-dimensional numerical wave tank to investigate the shoaling and breaking of solitary waves over a sloping ridge.

Early studies on shallow waves were mostly based on potential flow theory [6-8] and shallow water equations [9, 10]. With the potential flow equations, Grilli et al [7] simulated shoaling and breaking of solitary waves on different slopes systematically. Liu et al [8] reported simulations of propagation and endwall reflection of a fully nonlinear solitary wave with the boundary integral equation method. Li & Raichlen [9] presented a nonlinear solution to the classical shallow water equation for solitary wave runup on plane slope. Lynett et al [10] developed a moving boundary technique to investigate wave runup and rundown with Boussinesq equations. With the development of computer technique and numerical method in recent years, more and more attention have been attracted to models based on the Navier-Stokes (N-S) equations [1, 2, 4, 5, 11-15]. Lin & Liu [11] and Qi & Hou [15] developed a numerical model based on the RANS equations and model for studying the evolution of periodic wave train, respectively. Chen et al [12] investigated plunging breakers of Stokes waves with the classical two-dimensional N-S equations and VOF method. Christensen & Deigaard [13] and Lubin et al [14] presented and discussed the results obtained from simulating 3D plunging breaking waves by solving the N-S equations coupled with a Large Eddy Simulation (LES) model.

The commercial CFD software which is developing rapidly provides a powerful tool to investigate water wave problems. It releases investigators from the heavy work of programming and allow them to focus on the analysis of physical phenomena or the development of new mathematical models, e.g., Lu et al [16] and Dong & Zhan [17]. In the present work, utilizing the commercial platform FLUENT, a dynamic mesh model is developed to save computational resources for the simulation of solitary wave propagating on constant depth. Cnoidal waves are generated with the technique that linking FORTRAN IMSL library to C programming language. Cnoidal wave theories to different orders are then compared. Wave evolution and runup are simulated and analyzed systematically. The influence of grid size on accuracy is discussed in the 3D simulation of cnoidal wave runup around circular cylinder. All the results are compared with experimental data or analytical solutions.

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写于2011年2月14日