如何撰写科技论文的引言部分精选PPT.ppt

关于如何撰写科技论文的引言部分第1页，讲稿共17张，创作于星期日引言的主要内容研究工作的主要目的、范围，即为什么写这篇论文以及要解决什么问题；前人在本课题相关领域内所做的工作和尚存的知识空白，作简要的历史回顾和现在国内外情况的横向比较；研究的理论基础、技术路线、实验方法和手段，以及选择特定研究方法的理由；预期研究结果及其意义。第2页，讲稿共17张，创作于星期日撰写引言时存在的问题(1)重点不突出。这类作者在引言中用大量篇幅讲述立题、选题的背景及研究过程,罗列一大堆与论文无关或关系不大的材料,忽视了引言的真正目的。(2)不交代与论文有关的国内外研究概况,看不出来龙去脉。(3)引言的内容与摘要有雷同之处,这类作者将摘要与引言混为一谈,不知其各自的概念与界限。第3页，讲稿共17张，创作于星期日(4)引言与结论混淆,互不照应。引言是引出本文的主题给读者以引导;而结论是整篇文章的最后总结,两者不可混淆。另外,有些作者不能兼顾文章的整体性,写作线索不清晰,在引言中提出的问题,在结论中没有解答,找不到对应的地方。(5)在引言中出现插图、列表、数学公式,这类作者不清楚引言的写作要求和规范。撰写引言时存在的问题第4页，讲稿共17张，创作于星期日科技论文引言的写作要点第一层由研究背景、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。根据论文题目的情况，可以有所侧重。第5页，讲稿共17张，创作于星期日直奔主题：读者多为同行，甚至是专家，阅读文章是想了解最新研究动态。因此，科技论文引言强调开门见山，落笔直奔主题，一语道破。言之有物：引言要简述研究背景能使读者了解研究的意义及可能解决的问题，如果引言写得过于简单，易使读者对此研究意义产生疑惑。富有新意：在引言中一般教科书中定论的知识，或人所共知、显而易见的功用或意义不必赘述，也不必罗列一些与本研究无关或关系不大的文献。主观评价：论述问题要客观、严谨，尊重前人的工作、成果，切莫轻易批评、否定或蓄意贬低。对自己工作的评价要实事求是，但也要注意避免不必要的套话引言与摘要的不同：引言中各个层次所占的篇幅可以有很大差别，摘要中各项比例大体一样，而引言对研究背景和研究状况介绍较为详细，研究目的可能会较简短；摘要中必须把主要研究结果列出，而在引言中结果则可以省略。科技论文引言的写作要点第6页，讲稿共17张，创作于星期日引言的写作要求引言内容不得繁琐，文字不可冗长，能吸引读者。引言根据论文篇幅和内容，一般为200600字，短的可少于100字，长则可达1000字左右。比较短的论文可不单列“引言”一节，在论文正文前只写一段文字即可起到引言的效用。不可与摘要雷同，不要写成摘要的注释。一般教科书中有的知识，在引言中不必赘述。有关于历史回顾和前人工作的综合评述，以及理论分析等，则可将引言单独写成一章，用足够的文字详细加以叙述。第7页，讲稿共17张，创作于星期日引言的目的是向读者提供足够的背景知识，不要给读者悬念。不必过于谦虚，也不能自吹自擂。引言中各个层次所占的篇幅可以有很大差别。比较简短的论文，引言也可以相对比较简短。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叙述结果，不必在引言中重复。在援引他人的研究成果时，必须标注出处；下一步便介绍作者自己的研究动机、目的与内容；研究目的完全可以作为引言的结尾。也可简单介绍文章结构及每一部分的主要内容。引言的写作要求第8页，讲稿共17张，创作于星期日科技论文引言实例分析一实例1：基于幅值和相位解调分析的齿轮箱起动过程故障诊断 旋转机械的升降速过程包含了丰富的状态信息,一些在平稳运行时不易反映的故障征兆可能会充分地表现出来1,2。但旋转机械的升降速过程信号比平稳过程信号要复杂得多,不适合用常规的频谱分析方法进行分析处理。目前,在故障诊断中处理非平稳信号通常有两种方法:时频分析和阶次分析。时频分析是处理非平稳信号的有效方法,已经得到了广泛的应用,但当被分析的振动信号具有复杂的频率成分或旋转机械的速度变化非常剧烈(如齿轮箱起动过程)时,时频分析就难以具有有效的处理结果3。但在旋转机械的振动信号分析中,其振动信号往往与机器的转速有密切的关系,因此阶次分析是目前齿轮箱升降速过程振动信号分析与处理的最有效方法之一,它可以有效地对齿轮箱升降速过程的非稳态振动信号进行分析2-7。而幅值和相位解调分析是非常有效的齿轮故障检测方法,在 齿 轮 故障诊断中得到了广泛的应用8,9,但传统幅值和相位解调分析只适用于处理平稳的振动信号。本文将阶次分析、角域平均和幅值、相位解调分析技术相结合,提出了基于幅值和相位解调分析的齿轮箱升降速过程故障诊断方法,并成功地应用到齿轮箱起动过程的齿轮故障诊断中。实验结果表明:该方法能有效地提取齿轮齿根裂纹的故障特征信息,为齿轮箱升降速过程故障诊断提供了一种新的方法。第9页，讲稿共17张，创作于星期日科技论文引言实例分析一这片引言开篇直奔主题，说明所研究的问题背景，然后用较大的比例介绍目前的研究成果与方法，并说明其存在的不足之处（如但当被分析的振动信号具有复杂的频率成分或旋转机械的速度变化非常剧烈(如齿轮箱起动过程)时），最后针对这些不足给出自己的研究方法,并点出研究成果。整段引言不赘述无用部分，由目前研究状况的不足突出所研究的重点，整体子路比较清晰，让读者一目了然。第10页，讲稿共17张，创作于星期日科技论文引言实例分析二实例2：NaCl胁迫对黄瓜种子萌发及幼苗生长的影响5 黄瓜在我国蔬菜设施栽培中占有重要地位。由于设施栽培采用特殊的覆盖结构,改变了黄瓜生长的内部生态环境及自然状态下的水热平衡,尤其是大大改变了土壤的理化性质,致使土壤次生盐化的程度越来越高,给黄瓜周年生产造成巨大损失(介绍研究对象基本特征)。目前,关于作物盐胁迫效应方面的研究多集中于粮食作物、造林植物以及蔬菜作物中的番茄、黄瓜、西瓜、佛手瓜等,而对黄瓜的这方面研究报道较少(目前研究对象存在的问题,本研究的理由和背景)。本研究采用人工控制盐分浓度的方法,研究了 NaCl 胁迫对黄瓜种子的萌发特性以及黄瓜幼苗的生长、根系活力、细胞保护酶活性及膜脂过氧化的影响,为黄瓜的栽培、耐抗盐性的筛选和育种工作提供理论和技术依据(本研究成果和意义)。该引言比较简短，简述了研究背景，使读者了解研究的意义及可能解决的问题，所研究主题是目前研究较少的黄瓜，说明文章具有新意，同时也说明了本文研究的依据与内容，从而引出主题，给出自己的研究方法，说明了研究意义。第11页，讲稿共17张，创作于星期日实例3：A Frequency-Shift Synchrosqueezing Method for Instantan-eous Speed Estimation of Rotating Machinery Nowadays,condition monitoring and fault diagnosis of rotating machinery are among the major scientific issues for improving machine availability 13.Under these industrial requirements,analysis and comprehensive expertise involve many research fields ranging from the dynamic modeling of machine behaviors to development of accurate signal processing tools and complex data analyses 47.IS of rotating machinery usually carries a lot of useful information about its operation conditions,which is of great significance for real-time control,condition monitoring,and fault diagnosis of rotating machinery 812.Accurate estimation of IS has been the focus of the research in recent years 1315.The direct measurement of the IS of rotating equipment is based on the pulse signals generated by the rotary encoders used in connection with an analog-to-digital(A/D)converter and a data acquisition system.Then,the IS can be estimated by processing the pulse signals with dedicated methods,for example,the well known elapse time method8,9,1619.However,the rotary encoder is not always accessible,科技论文引言实例分析三第12页，讲稿共17张，创作于星期日either due to prohibitive operating conditions or due to shaft accessibility problems,making the direct measurement of the IS of the rotating machinery impossible.Thus,methods for the indirect estimation of the IS based on vibration measurements have been an issue of intensive research in recent years due to its importance in a broad range of mechanical engineering applications such as condition monitoring and the real-time control 2022.Additionally,methods for indirect estimation of the instantaneous rotational speed are also of special importance and additional value in cases where vibration measurements exist without the synchronous measurement of the rotation speed,then the estimated instantaneous rotational speed will be used to resample the measured vibration signals(e.g.,the tacho-less order tracking)2328.In those cases,the IS can be recovered indirectly from vibration measurements.To achieve this goal,a number of methods have been proposed,including phase demodulation methods 25,29,signal modeling methods15,30,and TF representation methods 14,2022.A general framework of IF estimation from vibration measurements has been developed 15.科技论文引言实例分析三第13页，讲稿共17张，创作于星期日Among all these mentioned methods of IF estimation,TF representation methods have attracted much more attention,as they can provide a powerful tool for the analysis of time series signals and produce more reliable and more robust to noise results 15.There exist many types of TF algorithms;the overwhelming majority belongs to either“linear”or“quadratic”method 31.Typical methods used in IF estimation,such as the short-time Fourier transform(STFT)20,21,32 and wavelet transform(WT),belong to the linear method,while the methods including the WignerVille distribution 3335 and its variants,such as the Chirplet transform 36,the short scale transform 22,and the adaptive STFT 37,belong to the quadratic method.In these linear methods,due to the limitation of the Heisenberg uncertainty principle,the resolution attained in the TF plane is not always ideal.While in quadratic methods,a more focused TF representation with better TF resolution can be obtained.However,because the synchrosqueezing WT is based on the WT,the frequency interval of the synchrosqueezed TF representation is nonuniform.The 科技论文引言实例分析三第14页，讲稿共17张，创作于星期日frequency interval increases with the increase of the central frequency,resulting in the reduction of frequency resolution as the central frequency increases along the frequency coordinates in the TF plane.The frequency resolution in the high-frequency zone is usually too low to satisfy the requirements for the accurate IF estimation of high-frequency components,which limits the application of the synchrosqueezing transform.In this paper,a frequency-shift synchrosqueezing method is proposed to improve the IF estimation accuracy of high-frequency components.As the synchrosqueezed TF representation has nonuniform frequency resolution with higher frequency resolution in the low frequency zone,the proposed method is to shift the high-frequency component to the low frequency zone,without changing the fluctuation characteristic of the IF.Then the highfrequency resolution of the high-frequency component is obtained.In addition,the Viterbi algorithm,which is proved to be more reasonable and accurate than the method based on the peak detection 34,43,is used to extract the IF from the T科技论文引言实例分析三第15页，讲稿共17张，创作于星期日F representation.This paper is organized as follows.A brief introduction of the synchrosqueezing WT is given in Sec.2.The proposed method is presented in Sec.3.Some numerical studies and discussions are available in Sec.4.Two experimental validations are given in Sec.5.Finally,the conclusions are presented in Sec.6.这篇引言开篇指出现阶段的研究背景和研究状况，引出本文的研究主题，即Accurate estimation of IS has been the focus of the research in recent years 1315。然后由广到窄，由浅到深介绍本领域的相关技术，研究方法、策略，A general framework of IF estimation from vibration measurements has been developed。并说明其中TF representation methods have attracted much more attention,主要介绍“linear”or“quadratic”method，并指出其中的不足（However），进而说明The frequency resolution in the high-frequency zone limits the application of the synchrosqueezing transform。科技论文引言实例分析三第16页，讲稿共17张，创作于星期日感谢大家观看第17页，讲稿共17张，创作于星期日