Integrated size and topology optimization of skeletal structures with exact frequency constraints

The present paper studies the integrated size and topology optimization of skeletal structures under natural frequency constraints. It is found that, unlike the conventional compliance-oriented topology optimization problems, the considered problem may be strongly singular in the sense that the corresponding feasible domain may be disconnected and the global optimal solutions are often located at the tips of some separated low dimensional sub-domains when the cross-sectional areas of the structural components are used as design variables. As in the case of stress-constrained topology optimization, this unpleasant behavior may prevent the gradient-based numerical optimization algorithms from finding the true optimal topologies. To overcome the difficulties posed by the strongly singular optima, some particular forms of area/moment of inertia-density interpolation schemes, which can restore the connectedness of the feasible domain, are proposed. Based on the proposed optimization model, the probability of finding the strongly singular optimum with gradient-based algorithms can be increased. Numerical examples demonstrate the effectiveness of the proposed approach.     

橡胶对HIPS树脂落锤指标的影响

通过对高抗冲聚苯乙烯树脂出现产品落锤指标偏低问题的分析，从橡胶配量及其粒径大小上进行了改进，同时改进了工艺操作，采取了提高反应釜搅拌速度、降低乙苯浓度等措施。结果产品合格率达到９９％以上，优级品率达到９８％以上。     

Effects of the reinforcement and toughening of acrylate resin/CaCO3 nanoparticles on rigid poly(vinyl chloride)

Novel composite particles based on nanoscale calcium carbonate (nano‐CaCO₃) as the core and polyacrylates as the shell were first synthesized by in situ encapsulating emulsion polymerization in the presence of the fresh slush pulp of calcium carbonate (CaCO₃) nanoparticles. Subsequently, these modified nanoparticles were compounded with rigid poly(vinyl chloride) (RPVC) to prepare RPVC/CaCO₃ nanocomposites. At the same time, the effects of the reinforcement and toughening of these modified nanoparticles on RPVC were investigated, and the synergistic effect of modified nanoparticles with chlorinated polyethylene (CPE) was also studied. The results showed that in the presence of nano‐CaCO₃ particles, the in situ emulsion polymerization of acrylates was carried out smoothly, and polyacrylates successfully encapsulated on the surface of nano‐CaCO₃ to prepare the modified nanoparticles, breaking down nano‐CaCO₃ particle agglomerates, improving their dispersion in the matrix, and also increasing the particle–matrix interfacial adhesion. Thus, the effects of the reinforcement and toughening of these modified nanoparticles on RPVC were very significant, and the cooperative effect of the nanoparticles with CPE occurred in the united modification system. Scanning electron microscopy analyses indicated that large‐fiber drawing and network morphologies coexisted in the system of joint modification of nanoparticles with CPE. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3940–3949, 2007     

十二烷基苯磺酸钠水溶液聚集性质的研究

用滴体积法测出十二烷基苯磺酸钠（ＳＤＢＳ）稀水溶液的表面张力；然后求出其临界胶束浓度（ＣＭＣ）。同时通过溶液的电导率、吸收光谱以及荧光光谱测定求出其ＣＭＣ。这样测出的ＣＭＣ值为１．２～１．６×１０－３ｍｏｌ／Ｌ，与文献值相符。也研究了部分水解的聚丙烯酰胺（ＰＨＰＡＭ）对ＳＤＢＳ聚集性质的影响；发现ＳＤＢＳ的ＣＭＣ值随ＰＨＰＡＭ的加人而减少并且ＰＨＰＡＭ水溶液的粘度随ＳＤＢＳ的存在而急剧降低（类似盐效应）。这些方法与性质对强化采油（ＥＯＲ）是重要的。     

Interbay物料自动搬运系统性能分析

Interbay物料自动搬运系统的运行效率对于晶圆制造系统影响较大,研究Interbay物料自动搬运系统的绩效具有较大的意义[1]。该文以带有捷径的单闭环背脊式布局的物料自动搬运系统为研究对象,通过问题描述,简化、假设将实际问题抽象为导引运输模型。然后,建立数学模型,采用Dijkstra算法确定工件搬运的最短路径。最后,利用Arena仿真软件建立含有导引运输设备的模型,采用控制变量法探究小车数量小车占用轨道的方式、调度规则等因素对于产出的影响,发现对于本文中的模型,其它条件相同时,搬运系统采用Release-at-end的控制方式,系统最大搬运量越大。     

PP/纳米级CaCO_3复合材料的研究

研究了纳米级CaCO3填充粒状、粉状PP复合材料的力学性能,并用SEM观察纳米级碳酸钙在PP中的分散状态及用SALS分析了其结晶行为。结果表明,粉状PP更有利于纳米级碳酸钙在PP中的分散,并具有更好的加工性能、力学性能。同时纳米级碳酸钙改性PP的SALS图像变得弥散、模糊,PP球晶变得不完善,晶粒更小。     

Effect of fretting amplitudes on fretting wear behavior of steel wires in coal mines

Given that fretting wear causes failure in steel wires, we carried out tangential fretting wear tests of steel wires on a self-made fretting wear test rig under contact loads of 9 and 29 N and fretting amplitudes ranging from 5 to 180 μm. We observed morphologies of fretted steel wire surfaces on an S-3000N scanning electron microscope in order to analyze fretting wear mecha-nisms. The results show that the fretting regime of steel wires transforms from partial slip regime into mixed fretting regime and gross slip regime with an increase in fretting amplitudes under a given contact load. In partial slip regime, the friction coefficient has a relatively low value. Four stages can be defined in mixed fretting and gross slip regimes. The fretting wear of steel wires in-creases obviously with increases in fretting amplitudes. Fretting scars present a typical morphology of annularity, showing slight damage in partial slip regime. However, wear clearly increases in mixed fretting regime where wear mechanism is a combination of plastic deformation, abrasive wear and oxidative wear. In gross slip regime, more severe degradation is present than in the other regimes. The main fretting wear mechanisms of steel wires are abrasive wear, surface fatigue and friction oxidation.     

生活质量视阈下的大学生“精神贫困”测量指标研究

高校大学生＂精神贫困＂现象已引起人们重视,成为多方关注话题。本文在梳理前人研究成果基础上,对＂精神贫困＂测量指标进行研究,以获得科学的测量指标体系,为获得真实科学的一手资料打进行理论论证。     

脂肪醇生物活性和理化性质的QSAR/QSPR研究

为了研究脂肪醇结构-性质(活性)的定量关系,用相对键长取代拓扑距离,结合距离矩阵,提出了距离调和拓扑指数Te,Te和醇的许多理化性质和生物活性具有良好的相关性.用Te及δ(醇中和羟基相连的碳原子的支化度)与脂肪醇的溶解度、辛醇/水分配系数、急性生物毒性、蒸发热、摩尔磁化率关联,复相关系数分别为0.9955,0.9951,0.9941,0.9964,0.9968,优于文献.同时与脂肪醇的气相色谱保留指数也相关得很好,相关系数为0.9956.结果表明,Te指数可用于醇多种理化性质和生物活性的预测.     

盈余质量与公司治理关系的实证研究

对公司治理系统中的主要特征变量与盈余质量关系的统计分析结果表明:独立董事的比例和盈余质量之间存在倒U型曲线关系;董事会会议次数和盈余质量正相关;而董事会规模和盈余质量的关系不显著;债务约束不构成中国上市公司盈余管理的动机;而提高净资产收益率的动机非常明显.政策结论在于:单纯的独立董事制度改革对提高盈余质量的作用有限,公司治理改革必须配合市场改革措施才能更有效地发挥提高盈余质量的作用.