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.     

Thermal and crystallization characteristics of poly(ethylene terephthalate) with poly(oxybenzoate‐p‐trimethylene terephthalate) copolymer

Poly(ethylene terephthalate) (PET) was blended with two different poly(oxybenzoate‐p‐trimethylene terephthalate) copolymers, designated T28 and T64, with the level of copolymer varying from 1 to 15 wt %. All samples were prepared by solution blending in a 60/40 (by weight) phenol/tetrachloroethane solvent at 50°C. The crystallization behavior of the samples was studied by DSC. The results indicate that both T28 and T64 accelerated the crystallization rate of PET in a manner similar to that of a nucleating agent. The acceleration of PET crystallization rate was most pronounced in the PET/T64 blends with a maximum level at 5 wt % of T64. The melting temperatures for the blends are comparable to that of pure PET. The observed changes in crystallization behavior are explained by the effect of the physical state of the copolyester during PET crystallization as well as the amount of copolymer in the blends. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1599–1606, 2002     

负载型Au催化剂的研究进展

金一直被认为是一种相对惰性的化学元素，但是近年来的研究发现，金催化剂对于CO及VOCs的低温氧化表现出很高的催化活性。本文综述了近年来金催化剂研究的进展情况，系统介绍了金催化剂的制备方法，以及金催化剂在不同反应中的催化活性和反应的机理。     

对叔丁基苄胺的合成研究

摘要选择Delepine反应法的路线合成对叔丁基苄胺，并对反应投料比、反应温度及酸化后的反应时间进行了优化试验，得到了较好的反应条件：反应温度为40℃，对叔丁基苄氯与乌洛托品投料比为1：1；加入酸和醇后的保温时间为2h，从而使反应收率稳定在90％以上，含量达到95％。     

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.     

江苏省泗洪县湿地公园雕塑创作浅析

江苏省泗洪县有着悠久的历史底蕴和深厚的文化背景,泗洪湿地公园是国家级湿地保护区.笔者受当地县政府委托在湿地公园入口处设计制作一幅大型浮雕壁画,前景是两尊立体的2.8米圆雕人物,照壁30米长,2.8米高,记载历史故事和民俗风情.以当地的泗洪湿地的特色飞禽白鹭贯穿始终,将不同时期的人物与景观自然地连贯穿插.并以文武两位名士的圆雕塑像为主要历史文脉,提升湿地公园的历史和人文内涵.湿地公园的雕塑寓意深刻、内涵丰富、品味高雅.雕塑紧扣泗洪县当地的自然环境和历史文化,为泗洪湿地公园增添了风采和神韵.     

Application of structural curvature of coalbed floor on CBM development in the Zaoyuan block of the southern Qinshui Basin

Based on controls of structural style and the position in coalbed methane(CBM)development,we used a method of curvatures to study its relations with CBM development parameters.We calculated structural curvatures of contours of the No.3coal seam floor of the Shanxi Formation in the Zaoyuan block of the Qinshui Basin and analyzed its relations with development parameters of coalbed methane wells.The results show that structural curvature is negatively related to coal reservoir pressure,while positively related to permeability.With an increase in structural curvature,the average production of coalbed methane wells increases at first and then decreases,reaching the highest production at 0.02 m-1 of structural curvature.Therefore,structural curvature can be an important index for potential evaluation of coalbed methane development and provide a basis for siting coalbed methane wells.     

基于模块化模型的自适应预失真技术

系统地比较和分析了OFDM传输系统里高功率放大器（HPA）预失真方法的优缺点,提出一种基于模块化模型的有记忆高功率放大器自适应数字预失真方法,该方法分别基于Wiener、Hammerstein和Wiener-Hammerstein模型各自构成一个有记忆HPA的自适应预失真器。从而避免了因分别估计Wiener-Hammerstein模型各个环节特性参数所带来的复杂性。使得有记忆高功率放大器的预失真设计变得简单了。     

深基坑工程安全评价的尖点突变模型

为评价深基坑工程失稳的突变特征,采用突变理论建立了深基坑工程尖点突变安全评价模型.根据工程安全监控理论,引入突变理论,以基坑水平变形为例,考虑深基坑土体的流变特性,建立了基于时效影响因子的深基坑工程尖点突变安全评价模型.实例分析表明,尖点突变安全评价模型克服了采用常规设置监控值评价时参数选择困难,并能反映基坑失稳突变性的特点,可以量化评价基坑安全程度,正确评价安全状态,具有适应性强、精度高的优点.     

开封引黄灌区灌溉条件下稻田土壤盐分阈值研究

结合各生育期水稻耐盐度、各处理实际种前初始土壤含盐量和对应生育期最高的土壤含盐量,分析了各灌溉处理条件下的稻田土壤含盐量在水稻各生育期的动态变化规律和允许初始土壤含盐量阈值.结果表明:控制灌溉及控制灌溉加淋洗条件下,各水稻生育期土壤含盐量均有不同程度降低,随着淋洗水量的增加土壤含盐量逐渐降低,并获得了不同灌溉方式下的允许稻田初始土壤含盐量阈值.此结论对实际应用有指导意义.