梁在拉伸力和弯曲力矩联合作用下的动态塑性断裂

本文采用刚塑性分析方法,研究了韧性材料带裂纹有限长梁在轴向拉伸力和弯曲力矩联合作用下的全塑性断裂过程,其外加轴向拉伸力和弯曲力矩为准静态加载,并在梁的断裂过程中保持不变,为定常载荷。在外力作用下,梁的断裂截面首先进入塑性变形,当裂纹尖端张开位移 CTOD 达到其材料临界值时,裂纹将启裂扩展。本文考虑了应变率对断裂过程的影响,给出了梁在断裂过程中其裂纹扩展长度,裂纹扩展速度以及断裂截面上的轴向抗力和弯曲抗力随时间的变化规律,并比较了在不同轴向拉伸力作用下梁的动态塑性断裂过程的变化,说明了轴向作用力对梁的断裂过程的影响。     

关系数据库自动生成器

本文论述了使用函数依赖(FD)的概念进行关系数据库的设计。对于给定一组函数依赖,确定全部最小覆盖的传统综合算法进行了改进,给出了一个改进的新算法。并且开发了称为“关系数据库自动生成器”的关系数据库自动设计工具,该工具使用编译dBASEⅢ语言编写,在长城0520机上运行,它支持需求分析阶段的信息收集,关系数据库设计阶段的概念性和逻辑性设计。     

面向对象计算机系统若干问题的研究

现有面向对象的软件环境大都建立在传统的Von Neumann 型计算机结构上,其执行效率很低。传统系统是无法支持面向对象风格高效实现的。很有必要开发新型的体系结构以支持这种良好的程序设计风格。本文从介绍面向对象程序设计的基本思想入手,建立面向对象思想与计算机系统的联系,阐述有关研究问题并给出初步的解决办法。     

后勤管理信息系统生成系统的设计与实现

本文论述了一个后勤管理信息系统生成系统(LMIS-GS)的设计与实现,本系统综合采用了数据库模式自动生成技术、软件可重用技术、操作对象、控制信息与程序相分离的模块编码技术,系统中通过引入部件的概念,把庞大复杂的LMIS系统划分为若干个可独立研制开发的部件实体。LMIS的生成就是部件的组装,部件的生成就是数据基的组装与填写。系统还提供了数据库生成的两种方式,即可自动生成3NF的关系数据库模式。     

评估C4ISR系统的目标分配质量

分析了影响防空C4ISR系统目标分配质量的主要因素,并以此定义了5个基本指标.利用线性加权法给出了一架歼击机对一架目标机的分配能力的计算方法,以此为基础提出了不同机场的多类歼击机对多批目标的分配能力的算法.最后通过实例计算验证了模型的正确性和实用性.     

Theoretical design of new bridge-ring insensitive high energy compounds by selected normal Diels-Alder reactions between NH2-substituted oxazoles and NO2/NF2/NHNO2-substituted ethylenes/acetylenes

In this work, NH₂-substituted oxazoles and NO₂/NF₂/NHNO₂-substituted ethylenes/acetylenes were designed and used as dienes and dienophiles, respectively, in order to develop new bridge-ring insensitive high energy compounds through the Diels-Alder reaction between them. The reaction type, reaction feasibility and performance of reaction products were investigated in detail theoretically. The results showed that dienes most possibly react with dienophiles through the HOMO-diene controlled normal Diels-Alder reaction at relatively low energy barrier. Tetranitroethylene could react with the designed dienes much more easily than other dienophiles, and was employed to further design 29 new bridge-ring energetic compounds. Due to high heat of formation, density and oxygen balance, all designed bridge-ring energetic compounds have outstanding detonation performance, 16 of them have higher energy than HMX (1,3,5,7-tetranitro-1,3,5,7-tetrazocine) and 2 others even possess comparative energy with the representative of high energy compounds CL-20 (2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane). The predicted average h₅₀ value of these bridge-ring energetic compounds is 83 cm, showing their low impact sensitivity. The NH₂ groups could obviously impel the proceeding of Diels-Alder reactions, but would slightly decrease the energy and sensitivity performance. In all, the new designed bridge-ring compounds have both high energy and low sensitivity, and may be produced through Diels-Alder reactions at relatively low energy barrier. This paper may be helpful for the theoretical design and experiment synthesis of new advanced insensitive high energy compounds.     

Optimization of buckling load for laminated composite plates using adaptive Kriging-improved PSO: A novel hybrid intelligent method

An effective hybrid optimization method is proposed by integrating an adaptive Kriging (A-Kriging) into an improved partial swarm optimization algorithm (IPSO) to give a so-called A-Kriging-IPSO for maxi-mizing the buckling load of laminated composite plates (LCPs) under uniaxial and biaxial compressions. In this method, a novel iterative adaptive Kriging model, which is structured using two training sample sets as active and adaptive points, is utilized to directly predict the buckling load of the LCPs and to improve the efficiency of the optimization process. The active points are selected from the initial data set while the adaptive points are generated using the radial random-based convex samples. The cell-based smoothed discrete shear gap method (CS-DSG3) is employed to analyze the buckling behavior of the LCPs to provide the response of adaptive and input data sets. The buckling load of the LCPs is maximized by utilizing the IPSO algorithm. To demonstrate the efficiency and accuracy of the proposed methodology, the LCPs with different layers (2, 3, 4, and 10 layers), boundary conditions, aspect ratios and load patterns (biaxial and uniaxial loads) are investigated. The results obtained by proposed method are in good agreement with the literature results, but with less computational burden. By applying adaptive radial Kriging model, the accurate optimal results-based predictions of the buckling load are obtained for the studied LCPs.     

Combustion of B4C/KNO3 binary pyrotechnic system

Presented herein is an experimental study on the combustion of B4C/KNO3 binary pyrotechnic system.Combustion products were tested using X-ray diffraction(XRD),scanning electron microscopy(SEM),and energy dispersive spectrometer(EDS).According to the results of tests and CEA calculation,the combustion reaction equation was established.The flames and burning rates were recorded by a high speed camera and a spectrophotometer.The effect of B4C particle size on the thermal sensitivity of B4C/KNO3 was investigated by differential scanning calorimetry(DSC)techniques.In addition,a reliable method for calculating the flame temperature was proposed.Based on the results of experiments,the combustion reaction mechanism was briefly analyzed.The burning rate,flame temperature and thermal sensitivity of B4C/KNC3 increase with the decrease of B4C particle size.The mass ratio of B4C/KNO3 has a great effect on combustion properties.Oxidizer-rich compositions have low flame temperatures,low burning rates,and provide green light emission.The combustion reactions of fuel-rich compositions are vigorous,and the B4C/KNO3 with mass ratio of 25:75 has the highest burning rate and the highest flame temperature.     

Damage to aircraft composite structures caused by directed energy system: A literature review

This paper presents a comprehensive review of the research studies on direct energy system effect on aircraft composite structures to develop a good understanding of state-of-the-art research and devel-opment in this area. The review begins with the application of composite materials in the aircraft structures and highlights their particular areas of application and limitations. An overview of directed energy system is given. Some of the commonly used systems in this category are discussed and the working principles of laser energy systems are described. The experimental and numerical studies re-ported regarding the aircraft composite structures subject to the effect of directed energy systems, especially the laser systems are reviewed in detail. In particularly, the general effects of laser systems and the relevant damage mechanisms against the composite structures are reported. The review draws attention to the recent research and findings in this field and is expected to guide engineers/researchers in future theoretical, numerical, and experimental studies.     

考虑交流侧特征谐波的电网换相换流器小信号建模

电网换相换流器(Line Commutated Converter,LCC)作为技术性能优越的电力电子装置,可广泛应用于车辆、飞机、船舶、雷达站供电等军用电力系统领域.以可为军用雷达站、军事基地供电的基于电网换相换流器型高压直流输电(Line Commutated Converter Based High Voltage Direct Current,LCC-HVDC)系统为例,基于开关函数模型,推导建立了包含LCC整流站、LCC逆变站和直流线路的双端LCC-HVDC系统小信号模型,并与PSCAD/EMTDC详细电磁暂态模型进行对比,验证了所建立小信号模型的准确性;对比分析了考虑交流侧特征谐波分量与仅考虑交流侧基频分量的LCC-HVDC小信号模型的差异.所得研究成果可为向军用电力系统供电的LCC-HVDC系统的控制参数选取及小干扰稳定性分析提供模型基础.