Failure probability evaluation for normally distributed load-strength model with unknown parameters

The failure probability evaluation methods for load-strength interference model are established when both load, L, and strength, S, follow normal distributions, assuming none of the normal distribution parameters are known. Based on Fisher's fiducial analysis, a failure probability evaluation method is obtained for single load application. A numerical integration method is developed to evaluate the failure probability for multiple load applications.     

生物降解型聚碳酸顺丁烯二酸亚乙酯 1、合成和表征

用CO_2、环氧乙烷、顺丁烯二酸酐进行三元共聚首次得到聚碳酸顺丁烯二酸亚乙酯(PECM),并用IR、~1H NMR、DSC等进行了表征,共聚物链中CO_2和MA单元随机分布,不饱和单元可在0～0.5mol分数之间调节。共聚过程不发生双键交联和构型转化。环氧乙烷的转化率可高达到93％。控制PECM链上的双键含量并使之发生自由基加成反应,得到对热较稳定的可溶性产物。     

Synthesis of ultrafine LiCoO2 powders by the sol-gel method

Ultrafine high-temperature (HT) LiCoO₂ powders were synthesized by the sol-gel method using polyacrylic acid (PAA) as a chelating agent. The decomposition process of the gel precursor was examined to determine the crystallization temperature and the dependence of the physicochemical properties of HT-LiCoO₂ powders on the PAA quantity was extensively investigated. Polycrystalline HT-LiCoO₂ powders, composed of very uniformly sized ultrafine particulates with an average particle size of 30–50 nm and a specific surface area of 2.3–17 m²g^–1, could be obtained at the lower calcination temperature of 550 °C and the shorter calcination time of 1 h compared to the solid-state reaction.     

DF_4内燃机车柴油机润滑油的热重分析

通过对DF_4内燃机车柴油机润滑油的热重曲线TG和微商热重曲线DTG的分析,探讨了这种润滑油的衰变规律。     

Interface microstructure and reaction in Gr/Al metal matrix composites

The interface structure in Gr/Al composites fabricated with liquid metal infiltration has been studied using transmission electron microscopy (TEM). Morphologies of interfacial reaction product, aluminium carbide Al₄C₃, formed at different manufacturing parameters were compared and, the growth mechanism of the carbide was studied by means of high resolution electron microscopy (HREM). It has been shown that the morphology of the carbide is intimately related to the processing parameters with which the composites were produced. There are two kinds of interfaces between the carbide and the aluminium matrix. They have different growth mechanisms and relative growth rates under different growth driving forces. Several crystal orientation relationships between the carbide and the aluminium matrix have been observed.     

Characteristics of aperture coupled microstrip antennas withvarious radiating patches and coupling apertures

A full wave moment method is applied to the analysis of aperture coupled microstrip antennas, in which all components of the electric and equivalent magnetic surface currents are considered. The electric current distributions on the rectangular patch for different coupling aperture positions are presented with their radiation patterns. The effects of the coupling aperture shape and size on the input impedance and radiation performance are also discussed. As an example of new radiators, slotted patches are studied, and it is shown that they can be used to achieve dual-frequency operation     

混沌光学系统的前向神经网络系统辨识研究

为解决混沌光学系统自适应控制所需之控制参考动力学模型问题，以布拉格声光混沌系统的系统辨识为例．研究了利用前向神经网络对混沌光学系统进行系统辩识的可行性。计算机仿真实验发现．在静态ＢＰ算法支持下一结构十分简单的三层ＢＰ前向神经网络（１：４：１）即可在一定的精度范围内完成对布拉格声光混沌系统的系统辨识．此结果表明．三层前向ＢＰ神经网络在静态ＢＰ算法的支持下确是一良好的混沌光学系统辨识器，因而可用来处理混沌光学时间序列以进行混沌光学系统的动力学重构。