受限于碳纳米管中水结构及其扩散的分子动力学模拟研究

运用分子动力学方法模拟了受限在单壁碳纳米管中水的结构与动力学行为.分别考察了水分子模型、温度、孔径对水的结构及其聚集特性的影响,探究了电偶极矩和电四极矩对水的扩散系数及其结构的影响.结果表明,三种水分子模型对体相水的聚集特性影响不大,但对碳纳米管中水的结构影响较大;电偶极矩对扩散系数起主要的作用,而电四极矩对水分子结构起主要的作用.同一管径不同温度下,温度越高,水的有序化程度越低.     

翘嘴红鲌群体遗传多样性分析

基于RAPD方法对江西(鄱阳湖)、湖北(梁子湖)和江苏(太湖)3个群体的翘嘴红鲌遗传多样性进行分析,以评价它们的群体遗传结构和良种选育的可行性。结果显示从30个随机引物中筛选出了20个多态性较高的引物,既可扩增出3个群体共同的DNA条带,也可扩增出单个群体特有的特征条带。从3个群体实验鱼中共检测到119个扩增片段,长度在0.2~1.7kb之间。鄱阳湖群体多态位点数61个,多态位点比为51.26%,梁子湖群体多态位点数50个,多态位点比为42.02%,太湖群体多态位点数67个,多态位点比为56.30%。3个群体的Shannon多样性指数分别为0.429 2,0.382 8和0.443 1。群体间遗传相似系数依次为:最高是鄱阳湖与梁子湖,为0.8055,其次是鄱阳湖与太湖,为0.801 6,最低是梁子湖与太湖,为0.785 2。结果提示,鄱阳湖与梁子湖亲源关系较近,与太湖稍远;所筛选出的引物应用RAPD技术可以方便地分析不同群体翘嘴红鲌的遗传多样性,并可为良种选育的亲本选择提供依据。     

Synthesis and Characterization of Two [2]Catenanes Based on Phenylene-diacetylene Crown Ethers

Two charged donor-acceptor [2]catenanes were synthesized by the cyclization of the π-acceptor 1,1 ＇-[1, 4-phenylenebis-（methylene）]bis（4,4＇-bipyridinium）bis（hexafluorophosphate）（2） and bis（bromomethyl）benzene with the templates of the π-donor phenylene-diacetylene crown ethers la and lb in the yields of 31%, 35%, respectively. The mass spectra, 1H and 13C NMR spectra confirm that the phenylene-diacetylene crown ethers, with a nonaromatic ~r-system, successfully template the cyclization of CBPQT4＋. The X-ray crystallography analysis shows that the CBPQT4＋ ring encircles around the phenylene motif of the crown ethers, leaving the 1,3-butadiyne fragment out of the cavity of CBPQT4＋ ring. The mechanically interlocked structure of [2]catenanes was stabilized by the cooperative effects of π-stacking and hydrogen bonding interactions.     

TiO2/SiO2双层减反射膜的制备及其性能研究

采用真空电子束蒸发法制备TiO2/SiO2双层减反射膜,实现宽波段范围内的低反射率,以满足砷化镓三结太阳电池对入射光的需求.主要研究了基片温度、电子束流和充氧量对TiO2、SiO2单层膜性能(膜层厚度、折射率)的影响.研究过程中,按照三因素两水平的正交实验进行,用分光光度计对TiO2、SiO2薄膜样品的折射率进行测试.实验结果显示,两种氧化物介质膜的折射率均随基片温度和束流的升高而增加,随氧压的升高而降低,工艺参数对TiO2膜性能影响较大.     

层数对梯度自润滑陶瓷刀具材料Al2O3/TiC/CaF2残余应力的影响

针对陶瓷减摩性能与耐磨性能不能在自润滑刀具中合理兼顾的难题,本研究将梯度功能材料设计思想引入Al2O3/TiC/CaF2自润滑陶瓷刀具材料的设计和制造中,并建立了该梯度自润滑陶瓷刀具材料的物理模型、组成分布模型和物性参数模型.采用有限元方法计算分析了层数对对称型梯度自润滑陶瓷刀具残余应力的影响,确定了最佳层数为7层.以本设计模型和有限元分析结果为基础,制备了分布指数为1.8的7层梯度自润滑陶瓷刀具材料Al2O3/TiC/CaF2.试验结果表明:所制备的梯度自润滑陶瓷刀具材料具有良好的力学性能.     

完全烧结氧化锆牙科陶瓷材料的旋转超声加工实验研究

针对口腔修复领域中大量应用的预烧结氧化锆陶瓷存在二次烧结加工工艺复杂、收缩率难以控制、断裂率高等问题,提出了采用旋转超声加工完全烧结氧化锆陶瓷的方法.开展了完全烧结氧化锆陶瓷的旋转超声加工和普通金刚石磨削加工实验,重点研究了主轴转速对磨削力、最大边缘碎裂尺寸及亚表面损伤特性的影响规律.通过对比分析得到,旋转超声加工不仅能降低磨削力,有效抑制完全烧结氧化锆陶瓷材料的边缘碎裂,同时明显减少了其亚表面微裂纹,是实现完全烧结氧化锆陶瓷口腔修复体低损伤加工的新途径.     

Analysis and simulation of a coupled-cavity pulse compressor

An equivalent circuit model is built for a coupled-resonator pulse compressor. Based on the circuit, the general second order differential equation is derived and converted into the first order equation to save computing time. In order to analyze the transient response and optimize parameters for the pulse compressor, we have developed a simulation code. In addition, we have also designed a three-cavity pulse compressor to get the maximum energy multiplication factor. The size of the cavities and coupling apertures is determined by HFSS.     

社会化媒体对品牌偏好的影响研究:基于顾客感知价值的视角

本文结合社会化媒体购物新模式的特征,依据消费者需求和行为影响理论,重构了顾客感知价值维度。在上述基础上,提出社会化媒体对品牌偏好的影响理论模型,并利用层级回归方法,对新网络购物环境下的顾客感知价值和品牌偏好间的关系进行了实证研究。研究结果表明,顾客感知社交价值、质量价值、服务价值、形象价值和利他价值正向影响品牌偏好的形成,而经济价值对品牌偏好的影响并不显著;社会化媒体信息质量在不同的感知价值与品牌偏好之间起着不同程度的调节作用。最后,结合相关结论提出了相应的营销管理建议。     

O、Se和Te掺杂对单层MoS2电子能带结构和光学性质的影响

利用密度泛函理论第一性原理,计算了本征单层MoS2以及O、Se和Te掺杂单层MoS2的结构参数、能带结构、氧化还原电势、态密度、光吸收特性和光催化潜力.结果表明,本征和掺杂单层MoS2的晶胞参数、键长随原子半径的增大而增大,键角随原子半径的增大而减小.掺杂后禁带宽度变小,导电性增强.本征和掺杂的单层MoS2的导带底电位负于水解制氢反应的还原势,其价带顶电位正于水解制氢反应的氧化势,均具有光催化水解制氢的潜力.但是,本征和O掺杂,由于价带顶与导带底电位相应于水的氧化还原势和电子空穴需求量均存在不平衡,使其光解水性能不理想.然而,Se和Te掺杂可以平衡其还原与氧化能力,改善单层MoS2的光催化的性能,其中Se掺杂改善效果最为明显.同时,掺杂后的单层MoS2对可见光吸收效率增强.此研究有助于筛选合适的单层MoS2掺杂元素,提高单层MoS2材料的光催化水解制氢性能.     

Investigation of the Evolution Behavior of Light Tar During Bituminous Coal Pyrolysis in a Fluidized Bed Reactor

The evolution behavior of the light tar fraction of tar during large bituminous coal particle pyrolysis in a fluidized bed reactor at 500-900℃ was investigated to optimize the industrial process. The coal residence time was varied from 30 s to 150 s. The crude tar obtained was distilled and separated into the light fraction and the heavy fraction through an evaporator under conditions of 280℃ and 10⁴ Pa. The light tar was subjected to GC-MS analysis, and the 300 main species in each spectrum were determined and analyzed. The experimental results showed that the evolution behavior of the light tar fraction and the heavy tar fraction presented spectacularly different variation trends with pyrolysis temperature and coal residence time. The molecular weight and number of rings per aromatic compound molecule contained in the light tar fraction increased with increasing pyrolysis temperature because of polymerization. It was also observed that the amount of methyl substituents decreased with an increasing number of rings per molecule of poly-aromatic ring compounds. The chain aliphatic compound evolution was suppressed and underwent heterocyclization with increasing temperature.