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中国科学技术大学国家同步辐射实验室核科学与技术在读博士生,主要从事高分子结晶与流变行为的分子动力学模拟研究。
Introduction作为论文的重要组成部分,对于文章的接受与影响力有着至关重要的作用。一个杂乱无章或有错误的Introduction会给人留下负面印象,而一个节奏清晰、有吸引力的Introduction不仅能提升审稿人的好感度。也能让读者对作者的分析能力、写作风格和研究方法产生高度评价,对于文章的传播具有积极的影响。Introduction在整篇文章中的作用包括了:使读者理解此项研究的价值,为什么这项研究值得进行,并使读者对于该研究怎样进行有一个初步认识,并且获得该研究的主要结论。
基于在科技论文写作课程中老师的讲解,结合自己对本领域的文章阅读与写作经验,我认为Introduction主要包括以下几个部分:
1.研究背景:引出本工作研究的科学问题,介绍研究的背景,研究范围与意义;
2.对该问题的相关工作进行总结回顾;
3. 说明研究目的,分析以往工作的局限,引出本工作的创新点;
4.总结介绍本工作内容:简明介绍研究方法,重要结果与讨论结论。
对于研究背景的写作,需要先给出研究的科学问题,以及对该问题进行研究的重要性。这里可以先介绍日常生活或工业生产中面临的问题,从本研究的相关应用中入手介绍。
也可以直接抛出对本领域的介绍。其中根据本论文讨论的科学问题是否涉及本领域内的通用名词,可选择是否添加对该科学问题的概念性介绍。
对前人的工作总结回顾是Introduction中的关键部分。一方面要把对本科学问题的主要研究进展列举出来。同时还要避免干巴巴的陈列。这里要注意列举的工作要与自己研究的问题相关,对于奠基性的研究、有重要进展的经典论文、相关最新的研究一定要介绍。另外添加的参考文献一定要准确。在阐述前人工作的局限性,需要遵循实事求是的原则,避免夸大,抓住自己工作针对的关键问题即可。
最后总结描述自己的工作内容。根据以上前人工作中对科学问题的研究缺陷,阐述自己工作的创新点,此时需要清晰表述自己针对以上表面的局限性的解决方案。介绍自己使用的研究方法,对自己得到的结果和讨论结论进行总结。
首先确定Introduction的架构,想好每段写什么。之后总结前人研究,总结自己工作。然后写研究背景。最后插参考文献。
首先介绍聚合物的缠结,引出科学问题:缠结对高分子结晶的影响。与小分子相比,聚合物晶体的均匀成核通常需要较大的过冷度,这意味着纠缠会抑制成核。目前尚不清楚这种成核抑制主要是源于纠缠增强的成核势垒还是受约束的链动力学。因此,理解纠缠在成核中的作用对于发展聚合物结晶理论至关重要,这是聚合物物理学中的一个长期挑战
前人研究:Yamazaki et al. proposed an empirical relation between the nucleation rate J and the entanglement density ve as J ~ exp(-k ve).Computer simulations demonstrated that the distribution of thickness of lamellar crystal statistically follows the local entanglement length.[22,23] Yet, no quantitatively thermodynamic analysis of the entanglement on nucleation has been reported.Classic nucleation theory (CNT) regards the nucleation of polymers as the behavior of independent monomers, and subsequent modifications only consider the chain connectivity in amorphous structure on the fold surface of nucleus.[24] Although the concept of reptation has been introduced into polymer crystallization model,[1,25] we still lack a nucleation theory incorporating the unique connectivity of polymer chain explicitly.In this work, we performed large-scale molecular dynamics (MD) simulations to study the role of entanglement in nucleation. Two methods are employed to obtain the nucleation barriers of systems with different entanglement densities, i.e., sampling nucleation events from the MD simulations directly, and theoretical calculation according to the CNT.本工作使用分子动力学模拟研究高分子成核过程,并用采样成核和经典理论计算了成核势垒。Regrettably, the nucleation barriers obtained by these two methods show opposite trends with increasing the entanglement density. We ascribed this contradiction to the absence of the entanglement effect in the CNT. To amend this defect of the CNT, we introduce the entanglement free energy:Gz = Uz − TSz , where and are the entanglement energy and entropy, respectively. By incorporating the effect of into the CNT, we propose a new theoretical approach for the nucleation of polymers, which is in a good agreement with the nucleation barriers obtained through sampling events in MD simulations.Polymers crystallize in nanometer thin lamellar structures which coexist with amorphous regions in nonequilibrium states [1–3]. The thickness of crystalline lamellae depends on their thermal history, in particular on the crystallization temperature. Since the properties of many polymer materials depend on their crystalline structures, understanding of polymer crystallization is of great technological importance and is still one of the major unresolved problems of polymer science, even after several decades of intense research.引出论文主题以及为什么研究:由于许多聚合物材料的财产取决于其结晶结构,因此了解聚合物结晶具有重要的技术意义,即使经过几十年的深入研究,它仍然是聚合物科学中尚未解决的主要问题之一In so-called self-seeding experiments, cooling a polymer melt just after melting of the semicrystalline state can result in significant memory effects where the subsequently formed crystals remember some positional and orientational information of the previous crystalline regions and the nucleation rate is muchenhanced [12,13].Hikosaka and Yamazaki showed that the nucleation rate decreases with the increase of apparent entanglement density and argued that the origin of memory effects basically arise from the change of the state of entanglement during annealing and not from the seeding of primary nuclei [14,15].前人工作解释了记忆效应的起源:Hikosaka和Yamazaki表明,成核速率随着表观纠缠密度的增加而降低,并认为记忆效应的起源基本上是由退火过程中纠缠状态的变化引起的,而不是由初级核的晶种引起的However, direct evidence of the entanglement related positional and orientational memory effects is still absent, also of the relation between lamellar thickness and entanglement density目前研究的缺点:然而,与纠缠相关的位置和方向记忆效应的直接证据,以及片层厚度和纠缠密度之间的关系,仍然缺乏One of the major experimental obstacles is the difficulty to determine or even to adjust the in situ entanglement density in a crystallization experiment since entanglement is a self-organized and self-adjusting property of the polymer system.介绍实验手段的缺陷,引出后文使用计算机模拟手段研究结晶