改进的传输层非对称加密方案设计

合作方协同设计的PDM项目中,采用Web Services模式下分布式数据系统,在进行数据传输时,既要符合系统安全性,又要满足系统易用性、效率等非功能需求,对数据传输层在传统的非对称加密方案上重新进行设计,加入了自定义的算法,设计了一种改进了的传输层非对称加密方案。     

高透明性超支化聚酰亚胺液晶取向膜

用4种二酐与1种四胺单体聚合制备了4种超支化聚酰胺酸,特性粘度在0.15-0.95dl/g之间,具有良好的成膜性.酰亚胺化后得到4种超支化聚酰亚胺（HBPI）,被用作液晶取向膜,具有良好的液晶取向性能,预倾角均在2.以上.紫外-可见光光谱表明HBPI薄膜具有良好的透光性,在400nm处透光率最低仍达90％以上.热重分析表明4种HBPI均具有良的热稳定性,T5最高可达362℃,T1o都在390℃以上.玻璃化转变温度（Tg）均在175℃以上.     

温度影响下的橡胶沥青应力吸收层的应力分析

高温开裂已经成为沥青路面的主要危害之一。橡胶沥青是良好的沥青改性剂,其具有吸收应力,改善沥青高温性能、延长路面使用寿命、延缓反射裂缝等优点。利用ABAQUS有限元软件,选取15℃、20％和60℃下沥青路面的热特性参数,分析在不同温度下橡胶沥青应力吸收层对半刚性基层路面结构和柔性基层路面结构的应力应变规律,推荐合理的沥青路面结构层设计参数,为工程实践提供理论依据。     

基于Matlab的有限元结构内力分析

介绍了Matlab语言的特点,详细介绍了用MATLAB语言编制结构内力分析的有限元方法,并通过实例对平面框架结构进行了内力和位移分析.     

测定2OCr钢渗碳层深度方法的比较

用金相法和有效硬化层深法测定20Cr钢渗碳后渗碳层深度，试验分析了与碳浓度梯度之间的关系。结果表明20Cr钢渗碳后用金相法测量渗碳层深与用硬化层法测量有效硬化层深其差别很小，因此在热处理检验时可采用金相法测量。金相法测量的渗碳层深度自表面开始测至珠光体含量约占50％左右处。     

有限群为π-幂零群的特征

本文给出了有限群G为π—幂零群的一个充要条件,并利用导群给出了群G为π—幂零群的一个充分条件.     

基于FDTD方法研究一维孔径菲涅耳衍射

应用时域有限差分FDTD方法研究一维孔径菲涅耳衍射花样的基本特征．首先简介了FDTD的基本原理和实现方法,接着从理论上分析了一维孔径菲涅耳衍射花样的规律,最后给出应用FDTD方法的数值仿真结果,该结果与理论分析相吻合．     

Optimal design of pressure vessel using an improved genetic algorithm

As the idea of simulated annealing （SA） is introduced into the fitness function, an improved genetic algorithm （GA） is proposed to perform the optimal design of a pressure vessel which aims to attain the minimum weight under burst pressure constraint. The actual burst pressure is calculated using the arc-length and restart analysis in finite element analysis （FEA）. A penalty function in the fitness function is proposed to deal with the constrained problem. The effects of the population size and the number of generations in the GA on the weight and burst pressure of the vessel are explored. The optimization results using the proposed GA are also compared with those using the simple GA and the conventional Monte Carlo method.     

Dynamic response analysis of a moored crane-ship with a flexible boom

The dynamic response of moored crane-ship is studied. Governing equations for the dynamic response of a crane-ship coupled with the pendulum motion of the payload are derived based on Lagrange＇s equations. The boom is modeled based on finite element method, while the payload is modeled as a planar pendulum of point mass. The dynamic response was studied using numerical method. The calculation results show that the large-amplitude responses occur at wave periods near the natural period of the payload. Load swing angle is smaller for crane-ship with flexible boom, in comparison with rigid boom. The ship surge motions have large vibrations for crane-ship with flexible boom, which were not observed for a rigid boom. The analysis identifies the significance of key parameters and reveals how the system design can be adjusted to avoid critical conditions.     

稻米的品质及其影响因素

自改革开放,尤其是中国加入世贸来,随着人民生活水平的提高以及稻米贸易对品质的要求,促使我国开始重视对稻米品质问题的研究.本文分别对近年来国内外关于稻米的品质及其影响因子研究进展情况作以简要论述.