橡胶硫化促进剂二硫化四苄基秋兰姆制备及光谱分析

以双氧水为氧化剂,采用二步法合成出了二硫化四苄基秋兰姆(TBzDT),通过FTIR,XRD,TG-DTA对其进行检测,揭示了TBzDT的微观结构。FTIR从化学键角度解析了TBzDT元素之间键型,XRD从晶胞参数、晶面指数等晶体学数据,揭示出TBzDT晶体微观结构,完成了TBzDT物相组成和结构的定性鉴定。TG-DTA检测出了TBzDT的质量变化与热效应两种信息,TBzDT的相变和分解温度分别为142.5,200.9 ℃,TBzDT的分解温度偏高,为采用硫化仪研究TBzDT的橡胶硫化性能提供参考。FTIR和TG-DTA从不同侧面揭示出样品TBzDT 中蕴含少量的SC₂。     

Free-standing,curled and partially reduced graphene oxide network as sulfur host for high-performance lithium–sulfur batteries

Lithium–sulfur(Li–S) batteries have received more and more attention because of higher specific capacity and energy density of sulfur than current lithium–ion batteries. However, the low electrical conductivity of sulfur and its discharge product, and also the high dissolution of polysulfides restrict the Li–S battery practical applications. To improve their performances, in this work, we fabricate a novel free-standing, curled and partially reduced graphene oxide(CPrGO for short) network and combine it with sulfur to form a CPrGO–S composite as a cathode for Li–S battery. With sulfur content of 60 wt%, the free-standing CPrGO–S composite network delievers an initial capacity of 988.9 m Ah·g~(-1). After 200 cycles,it shows a stable capacity of 841.4 m Ah·g~(-1) at 0.2 C, retaining about 85% of the initial value. The high electrochemical performance demonstrates that the CPrGO–S network has great potential applications in energy storage system. Such improved properties can be ascribed to the unique free-standing and continous CPrGO–S network which has high specific surface area and good electrical conductivity. In addition, oxygen-containing groups on the partially reduced graphene oxide are beneficial to preventing the polysulfides from dissolving into electrolyte and can mitigate the "shuttle effect".     

三维显微图像复原及点扩散函数的研究

三维显微图像去卷积计算量巨大,运算时间长。评价和分析了三维点扩散函数、散焦像、光学切片以及不同三维点扩散函数去卷积的复原图像,进一步证明了散焦光信息对焦面像的干扰,主要来自于焦面像两侧附近的散焦像。提出了折中选择三维PSF的空间大小,可以获得良好的复原效果,并且减少运行时间。提出了频谱图均值的新概念,作为评价图像清晰及模糊程度的标准,并运用于散焦像、光学切片以及复原结果图的评价。     

体散射液晶导光板的光线追迹模拟

体散射集成导光板是一种新型的液晶背光照明系统设计。基于多重米氏(Mie)散射理论和蒙特卡罗(Monte Carlo)顺序抽样方法,对该类型导光板进行了光线追迹模拟计算与仿真设计。研究了填充粒子材料、粒径、浓度及导光板几何结构等光学参量对输出光强面分布均匀性、照明角度等背光性能的影响,并进行了初步的实验验证及设计评估。研究表明,各光学参量十分敏感,且相互制约,必须进行大量的优化计算才能获得符合实际需要导光板设计方案。导光板输出光面分布的均匀度主要由填充粒子浓度决定,视角特性主要由导光板尺寸,特别是底面倾角决定,色散程度则主要和填充粒子的直径和折射率有关。     

面发射分布反馈半导体激光器及光栅耦合半导体激光器

阐述了以曲线光栅面发射分布反馈半导体激光器（SEDFB）为代表的SE—DFB器件的原理和结构,讨论了它们的性能和特点并与其他类型的半导体激光器进行了比较。指出依靠曲线光栅特殊的衍射特性,可实现对模式的控制和二维漏模耦合阵列化出光,得到窄线宽（典型值0．08nm）、小发散角（典型值0．5mrad）、高亮度（单管近衍射极限3W（CW））和大功率（单管最高73w,列阵为kW级）的激光。综述了SE—DFB的发展历程、现状及未来的发展趋势,强调由于曲线光栅耦合SE—DFB激光器兼具边发射和面发射器件的优势和诸多其他优秀性能,将其应用于不同材料体系,不同结构的半导体激光器及其阵列,制作不同波段的高功率、高光束质量的SEDFB器件会有很好的研究意义和应用前景。     

Numerical simulation of quasi-streamwise hairpin-like vortex generation in turbulent boundary layer

A mechanism for generation of near wall quasi-streamwise hairpin-like vortex （QHV） and secondary quasi-streamwise vortices （SQV） is presented. The conceptual model of resonant triad in the theory of hydrodynamic instability and direct numerical simulation of a turbulent boundary layer were applied to reveal the formation of QHV and SQV. The generation procedures and the characteristics of the vortex structures are obtained, which share some similarities with previous numerical simulations. The research using resonant triad conceptual model and numerical simulation provides a possibility for investigating and controling the vortex structures, which play a dominant role in the evolution of coherent structures in the near-wall region.     

课本中一道习题的妙解

在学习列分式方程解应用题时,老师给出这样一道题: 甲、乙两杯各装10升A、B溶液,从甲杯取出若干升A液注入乙杯搅匀;再从乙杯取同量混合液注入甲杯搅匀,这时测得甲杯中A液与B液之比为5:1.求第一次从甲杯中取出多少升A溶液?     

Determination of the temporal structure of femtosecond laser pulses by means of laser-induced air plasma

A new approach is presented to reveal the temporal structure of femtosecond laser pulses by recording the corresponding time-resolved shadowgraphs of the laser-induced air plasma. It is shown that the temporal structures of femtosecond laser pulses, normally not observable by the ordinary intensity autocorrelator, can be detected through intuitively analyzing the ultrafast evolution process of the air plasma induced by the femtosecond laser pulses under examination. With this method, existence of pre- and post-pulses has been clearly unveiled within the time window of ±150 fs in reference with the main 50-fs laser pulses output from a commercial 1-kHz femtosecond laser amplifier. The unique advantage of the proposed method is that it can directly provide valuable information about the pulse temporal structures' effect on the laser-induced ionization or material ablation.     

LA-ICP-MS锆石U-Pb同位素定年存在的基体效应研究进展北大核心CSCD

激光剥蚀电感耦合等离子体质谱法(LA-ICP-MS)是开展锆石微区原位U-Pb同位素定年研究的重要技术方法。LA-ICP-MS锆石U-Pb同位素定年存在的基体效应是影响其分析结果准确度和精密度的主要因素。依据前人有关基体效应的研究成果,总结了基体效应的类型主要有元素基体效应、高铀或高D_(dpa)基体效应以及α通量基体效应,详细阐述了各种基体效应的性质和产生机理,探讨了已建立的基体效应应对策略存在的问题和不足(引用文献46篇)。     

LiNO3/N,N-二甲基甲酰胺溶液光谱性质的研究和模拟

利用红外光谱和量子化学计算方法研究了LiNO3/N,N-二甲基甲酰胺(DMF)溶液中离子溶剂化和离子缔合现象,得出了阳离子和阴离子在溶液中的存在形式以及DMF分子间自身的内部结构,并对(DMF)n结构进行了优化及热力学性质计算.在此基础上,提出阳离子进入溶剂化层的机理是,DMF分子之间相互作用形成不同形式的(DMF)n...