结构设计对混响室场性能影响的仿真研究

通过仿真计算,分别研究了尺寸比例设计对混响室场均匀性的影响和体积变化对混响室电场强度大小的影响。数据结果表明：混响室内工作区域的场均匀性随着混响室长／宽比值增大而变差,且为获得场均匀性较优的测试环境,长宽比例应〈2。同时证明了混响室存在一临界体积上限,小于临界体积上限时,随着体积的增大,室内的电场强度逐渐减小,场均匀性逐渐提高;达到临界体积上限后,室内的场均匀性开始变差,混响室逐渐丧失对电磁波的混响作用。通过仿真计算得出混响室模型临界体积上限为10^4m^3。     

概率分布模型的飞机战备完好率评估与预测

飞机战备完好率是军用飞机战斗力的重要体现.在分析目前部队常用的飞机战备完好率算法缺陷的基础上,建立了基于概率分布的飞机战备完好率计算模型,该模型体现了飞机任务可靠性、维修性与战备完好性之间的关系.以某型飞机为例,通过分析飞机任务可靠度,利用飞机可靠性、维修性、保障性及作战训练任务的历史统计数据,依据概率分布模型对飞机的...     

考虑腐蚀因素的船体结构寿命预测方法

为建立考虑腐蚀因素的船体结构寿命预测方法,在分析现有常用的船体结构腐蚀损伤时变模型的基础上,根据舰船维修保障实际情况建立了考虑腐蚀防护系统作用时间和维修时间等因素的腐蚀时变模型。根据相关规范选择了船体结构腐蚀寿命标准,并建立了一种计算船体结构腐蚀寿命的方法。该方法建立了船体结构腐蚀寿命与腐蚀防护系统作用时间和修理时间等因素之间的量化关系,可以用于预测均匀腐蚀条件下船体结构寿命,也可以反过来指导腐蚀防护系统设计指标的选择和船体结构维修策略的确定。     

Effect of organo-modified montmorillonite nanoclay on mechanical,thermal and ablation behavior of carbon fiber/phenolic resin composites

The mechanical, thermal and ablation properties of carbon phenolic (C-Ph) composites (Type-I) rein-forced with different weight percentages of organo-modified montmorillonite (o-MMT) nanoclay have been studied experimentally. Ball milling was used to disperse different weight (wt) percentages (0, 1,2,4,6 wt.％) of nanoclay into phenolic resin. Viscosity changes to resin due to nanoclay was studied. On the other hand, nanoclay added phenolic matrix composites (Type-II) were prepared to study the dispersion of nanoclay in phenolic matrix by small angle X-ray scattering and thermal stability changes to the matrix by thermogravimetric analyser (TGA). This data was used to understand the mechanical, thermal and ablation properties of Type-I composites. Inter laminar shear strength (ILSS), flexural strength and flexural modulus of Type I composites increased by about 29％, 12％and 7％respectively at 2 wt.％ addition of nanoclay beyond which these properties decreased. This was attributed to reduced fiber volume fraction (％Vf) of Type-I composites due to nanoclay addition at such high loadings. Mass ablation rate of Type-I composites was evaluated using oxy acetylene torch test at low heat flux (125 W/cm2) and high heat flux levels (500 W/cm2). Mass ablation rates have increased at both flux levels marginally up to 2 wt.％ addition of nanoclay beyond which it has increased significantly. This is in contrast to increased thermal stability observed for Type-I and Type-Ⅱ composites up to 2 wt.％addition of nanoclay. Increased ablation rates due to nanoclay addition was attributed to higher insulation effi-ciency of nanolcay, which accumulates more heat energy in limited area behind the ablation front and self-propagating ablation mechanisms triggered by thermal decomposition of organic part of nanoclay.     

A novel formulation of material nonlinear analysis in structural mechanics

This article demonstrates a novel approach for material nonlinear analysis. This analysis procedure eliminates tedious and lengthy step by step incremental and then iterative procedure adopted classically and gives direct results in the linear as well as in nonlinear range of the material behavior. Use of elastic moduli is eliminated. Instead, stress and strain functions are used as the material input in the analysis procedure. These stress and strain functions are directly derived from the stress-strain behavior of the material by the method of curve fitting. This way, the whole stress-strain diagram is utilized in the analysis which naturally exposes the response of structure when loading is in nonlinear range of the material behavior. It is found that it is an excellent computational procedure adopted so far for material nonlinear analysis which gives very accurate results, easy to adopt and simple in calculations. The method eliminates all types of linearity assumptions in basic derivations of equations and hence, eliminates all types of possibility of errors in the analysis procedure as well. As it is required to know stress distribution in the structural body by proper modelling and structural idealization, the proposed analysis approach can be regarded as stress-based analysis procedure. Basic problems such as uniaxial problem, beam bending, and torsion problems are solved. It is found that approach is very suitable for solving the problems of fracture mechanics. Energy release rate for plate with center crack and double cantilever beam specimen is also evaluated. The approach solves the fracture problem with relative ease in strength of material style calculations. For all problems, results are compared with the classical displacement-based liner theory.     

N、P源对微生物法处理石油烃效果的影响

在微生物法处理石油烃的过程中,微生物对N、P源的供给非常敏感,不同的微生物对不同的N、P源的生物利用度是不相同的,N、P源的选择对降解效果有较大影响,所以有必要对最佳的N、P源进行筛选。对N、P源的逸择和加入量对降解效果的影响进行了研究,确定了最佳的N、P源分别为(NH4)2SO4、KH2PO4。在(NH4)2SO4、KH2PO4的质量浓度分别为100mg／L和60mg／L时,废水中石油烃的去除率最高。     

多通道舰空导弹武器系统反导决策模型研究

当前水面舰艇面临着严重的反舰导弹威胁,特别是在饱和攻击的条件下,常规的单通道舰空导弹系统已经不能满足作战的需要。多通道舰空导弹武器系统具有同时引导多枚导弹拦截多批目标的能力,可以充分发挥系统的能力,相应的反导决策在防空作战中起到重要作用,反导决策的正确性和合理性直接影响防空作战效果。在对反导决策过程和制约因素进行分析的基础上,通过0-1决策模型,得到了舰空导弹武器反导的优化决策模型,较好地满足了使用多通道舰空导弹系统对多目标打击决策的合理性和有效性。     

机动作战地空导弹载波相位差分定位模型研究

地空导弹部队在防空作战中,导弹火力单元要按上级的命令适时机动,需要对所在位置进行精确定位并及时上报上级单位,以便尽快组成新的雷达网继续参加战斗。根据GPS测距和差分GPS定位原理,利用载波相位差分设备把采集的载波相位发送给用户站进行求差解算坐标,得到机动作战导弹火力单元的位置坐标。根据载波相位差分定位GPS载波相位差分接收机技术成熟,成本不高,适合机动作战导弹部队应用。通过编制相应的模型软件,以及加入通信接口,便可用于导弹火力单元雷达站址的快速定位。     

基于随机Petri网的维修质量管理组织结构建模与分析

简述了利用随机Petri网进行维修质量管理组织结构建模的方法。根据实际需求,建立了2种组织结构形式的仿真模型。以模型为基础,对维修质量管理组织结构的静态结构和动态行为进行了研究,解决了维修质量管理组织结构的优选问题,对组织结构设计具有一定的指导作用。     

基于矩阵的C4ISR系统结构设计评价

主要目的是提出两种矩阵方法对C4ISR系统结构进行评价.其中邻接矩阵法用于评价C4ISR系统之间的互连互通性,对于评价规模较大、结构复杂的系统结构较为适用;模糊矩阵法用于评价系统之间的相似性,通过科学的评价指标体系消除系统之间的冗余.这些方法是当前主流的经验评价方法(如ATAM方法)的有效补充,具有一定的科学性和合理性.最后分别给出了两种方法的一个应用实例,体现了其在工程实践上的价值.