噻吩与小分子间弱相互作用的理论研究

在B3LPY/6-311+G**水平上计算了噻吩与NH3、H2O和HF形成的复合物的结构、能量及氢键关键点处电荷密度拓扑性质。结果表明,噻吩与NH3形成两种弱C-H…N氢键;N被O取代后,除C-H…O氢键外,形成更稳定的O-H…π结构;F取代O时形成强度更大的F-H…S和F-H…π氢键,这表明典型的氢键在电负性较小的分子复合物中较为普遍;在电负性较大的分子复合物中,小分子更倾向于从噻吩平面上方接近噻吩,形成其他类型的氢键和X-H…π氢键。氢键关键点处的电荷密度拓扑性质结果表明,这些氢键强度较弱,为闭壳层相互作用。本文结论为噻吩类超分子功能材料体系的设计和合成提供一定的指导。     

TSL:predicting popularity of Facebook content based on tie strength

The rapid development of online social networks leads to an explosion of information,however,there are great differences in the popularity of different messages,and accurate prediction is always a great difficulty is the current study.Popularity prediction of online content aims to predict the popularity in the future based on its early diffusion status.Existing models for popularity prediction were mostly based on discovering network features or fitting the equation into a varying time function that the accuracy of current popularity prediction model was not high enough.Therefore,with the help of the weak ties theory in sociology,the concept of tie strength was introduced and a multilinear regression equation was constructed combined with the early popularity.A TSL model to predict the popularity of Facebook’s well-known pages was proposed.The main contribution of this article was to solve the problem and few or no work based on sociology.A high linear correlation between the proportion of faithful fans was existed in Facebook homepage with frequent shares in the early and the future popularity.Compared with other baseline models,an experimental study of Facebook (including 1.54 million shares) illustrates the effectiveness of the proposed TSL model,and the performance is better than the existing similar methods.     

改进ILoG算子的故障检测方法

针对强背景噪声干扰下轮对轴承故障特征微弱、难以准确检测的问题,提出了一种自适应改进高斯拉普拉斯(improved Laplacian of Gaussian,简称ILoG)算子的微弱故障检测方法。ILoG算子滤波器具有优良的信号突变特征检测能力,将其用于轮对轴承故障信号的冲击特征检测,同时利用水循环算法(water cycle algorithm,简称WCA)的寻优特性,并行搜寻筛选最佳的ILoG算子影响参数,通过对参数优化后ILoG算子滤波后信号做进一步包络解调分析,提取出轮对轴承微弱的故障特征信息。对实际轮对轴承外圈和内圈故障信号分析的结果表明,该方法可以有效检测出轴承微弱故障特征频率,故障检测效果优于小波阈值和多尺度形态学差值滤波方法。     

Weak Delocalization in Graphene on a Ferromagnetic Insulating Film

Graphene has been predicted to develop a magnetic moment by proximity effect when placed on a ferromagnetic film, a promise that could open exciting possibilities in the fields of spintronics and magnetic data recording. In this work, the interplay between the magnetoresistance of graphene and the magnetization of an underlying ferromagnetic insulating film is studied in detail. A clear correlation between both magnitudes is observed but through a careful modeling of the magnetization and the weak localization measurements, that such correspondence can be explained by the effects of the magnetic stray fields arising from the ferromagnetic insulator is found. The results emphasize the complexity arising at the interface between magnetic and 2D materials.     

火灾条件下拱顶油罐弱连接结构的失效分析

拱顶油罐受外部火焰烘烤发生失效爆炸，易造成严重人员伤亡和巨大经济损失。为对火灾条件下拱顶油罐的失效爆炸进行预警，通过高温材料力学性能实验平台对拱顶油罐弱连接结构进行破坏测试，得出不同火灾温度条件下弱连接结构失效的拉断力和应力值。实验结果表明，当温度高于300℃时，拉断力和失效应力值变化显著，其中450℃为变化峰值温度。在此基础上，构建了拱顶油罐失效压力计算模型，推导出了不同容积拱顶油罐在不同火灾温度下的失效压力。所得结果可作为拱顶油罐失效的判定依据，为油罐的爆炸预警提供数据支撑。     

低压力下环保型络合剂和氧化剂对铝合金化学机械抛光的影响

在低平坦化压力下用壳寡糖(COS)环保型络合剂及H₂O₂氧化剂化学机械抛光铝合金，用原子力显微镜观测抛光后的表面质量，并用X射线光电子能谱仪分析其表面的钝化膜元素，用纳米压痕仪分析钝化膜的力学性能，研究COS及H₂O₂对铝合金CMP的作用机理。结果表明:H₂O₂质量分数为2%时，材料去除率随COS含量的增加而增大，当COS质量分数为0.32%时，材料的去除速率达861 nm/min，表面粗糙度最低为2.50 nm；COS质量分数为0.50%时，材料去除率随H₂O₂含量的增加先增大后减小，当H₂O₂质量分数为1.2%时，材料的抛光去除速率达840 nm/min，同时其表面粗糙度为3.52 nm。加入COS络合剂会在铝合金表面形成主要成分为Al-COS、Al₂O₃和Al(OH)₃的弱钝化膜。      

化学链燃烧中燃料气体在CaSO4(010)表面吸附扩散特性的分子动力学模拟

以CaSO4为载氧体，采用分子动力学研究了化学链燃烧中不同温度时CO在CaSO4(010)表面的吸附扩散特性，并在反应温度为1173 K时与CH4、H2在CaSO4(010)表面的吸附扩散特性对比。结果表明：CO在CaSO4(010)表面的吸附为物理吸附，吸附强度随温度升高而减弱，吸附层与体相层的分层点为距离CaSO4(010)表面0.66 nm处；CO在xy平面方向的扩散能力随温度升高而上升，符合分子碰撞理论； CO吸附于CaSO4(010)表面的原因主要为静电作用所造成的弱相互作用。与CH4、H2相比，CO在CaSO4(010)表面的吸附能力最强，吸附层中含量最多；H2在xy平面方向扩散能力最强，体相层中体积占比最大；而CH4较弱的静电作用与H2较强的位阻作用导致了二者在CaSO4(010)表面吸附能力弱于CO。研究结果可为钙基载氧体的改进与优化提供理论基础。     

双馈风机经VSC-HVDC接入弱受端系统运行特性分析

基于电压源换流器的高压直流输电(VSC-HVDC)是远距离风电并网的理想方案,同时可用于联接弱受端系统,但双馈风机经VSC-HVDC能够馈入多弱的受端系统仍待深入研究,有必要提出基于短路比的指标来衡量所能接入的受端系统。对此,基于定功率控制下VSC的稳定运行约束,分析系统稳态的临界运行点,总结出临界短路比的求解步骤。在此基础上,结合双馈风机的控制方程,详细讨论了风电场出力、弱交流系统等效阻抗和临界短路比的关系。仿真分析发现,受双馈风机无功特性的影响,接入受端系统的临界短路比未能达到理论值,引入基于无功补偿的有效短路比作为受端系统的强弱判断指标,使得所提临界短路比求解方法在此工况下依然成立。