基于随机冲击的相关竞争失效可靠性评估

针对电子产品在工程实践中受随机冲击应力的影响及多失效模式的问题,以累积冲击和极限冲击来描述产品的冲击过程,考虑失效模式相关性并建立了随机冲击下产品竞争失效模型。以具有自然耗损和突发耗损特点金属化膜脉冲电容器为对象,进行了可靠性对比分析,验证了模型的合理性和有效性,为遭受复合应力影响的电子产品的可靠性评估提供了一种新方法。     

燃烧室-喷管流场数值解

本文用时间相关法计算了固体火箭发动机燃烧室─喷管亚跨声速流场数值解,控制方程用ＭａｃＣｏｒｍａｃｋ二步显格式：边界点参数用物理边界条件和参考平面上的特征方程计算。计算表明,达到收敛的数值积分步数比纯喷管的跨声速计算要多得多。虽然喷管壁上和轴线上的马赫数分布与纯喷管计算类似,但喷管中的等马赫线分布与纯喷管计算的结果［３］相差较远。     

防空通信系统性能评价及抗毁性分析

分析了防空通信系统的组织结构和对抗特点,利用性能评价过程代数描述防空通信系统的状态演化,提出一种防空通信系统抗毁特性分析方法。通过具体案例,对通信系统的组织结构、抗击软硬杀伤的能力进行建模和仿真验证。实验结果表明,该方法适用于防空通信系统的建模与分析,能够实现对防空通信系统的结构进行对抗过程的建模;通信系统的不同要素对抗毁性能的影响不同,可以采取有效策略以提高防空通信系统的抗毁能力。     

新疆双语教师专业化发展问题研究——基于绩效技术视角

本文通过对新疆喀什地区中小学双语教师专业化发展现状调查,运用绩效技术手段,找出当前中小学双语教师专业化发展中存在的主要问题及引发问题的根源,构建中小学双语教师专业化发展的绩效改进过程模型,并提出中小学双语教师专业化绩效改进建议。     

Approximation algorithms for capacitated stochastic inventory systems with setup costs

We develop the first approximation algorithm with worst‐case performance guarantee for capacitated stochastic periodic‐review inventory systems with setup costs. The structure of the optimal control policy for such systems is extremely complicated, and indeed, only some partial characterization is available. Thus, finding provably near‐optimal control policies has been an open challenge. In this article, we construct computationally efficient approximate optimal policies for these systems whose demands can be nonstationary and/or correlated over time, and show that these policies have a worst‐case performance guarantee of 4. We demonstrate through extensive numerical studies that the policies empirically perform well, and they are significantly better than the theoretical worst‐case guarantees. We also extend the analyses and results to the case with batch ordering constraints, where the order size has to be an integer multiple of a base load. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 304–319, 2014     

Some aging properties of parallel and series systems with a random number of components

In this article, we study aging properties of parallel and series systems with a random number of components. We show that the decreasing likelihood ratio property is closed under the formation of random minima. We also show, by counterexamples, that other aging properties are not closed under the formation of random minima or maxima. Some mistakes in the literature are corrected. © 2014 Wiley Periodicals, Inc. Naval Research Logistics 61: 238–243, 2014     

用非概率理论分析混合不确定性结构的可靠性

针对不确定性结构可靠性分析中的输入变量分布参数具有不确定性和输入变量为区间模型的混合不确定性结构展开研究。考虑到可用信息最少的情况,将分布参数的不确定性描述为区间模型。通过等概率转换方法将随机变量与其分布参数进行分离,使问题转化为随机与区间变量混合的可靠性问题,建立了混合不确定性问题的可靠性分析模型。基于非概率可靠性理论,建立混合不确定结构分析模型的二级极限状态函数并结合Kriging代理模型建立了高效的求解方法。将所建立的混合不确定模型应用于飞行器结构的不确定性分析中,验证了所建模型的合理性和所提方法的高效性和准确性。     

临近空间大型柔性充气囊体结构特性分析

以临近空间平流层飞艇柔性充气囊体为研究对象,根据充气结构设计理论对充气囊体结构的最小压差和应力进行计算,建立平流层飞艇充气囊体结构有限元模型。在模型验证的基础上,采用非线性有限元方法对平流层飞艇充气囊体结构特性进行仿真分析,得到了囊体结构在不同压差和吊舱载荷作用下应力和变形分布及变化规律,并分析了结构加强配置对囊体应力和变形的影响,为平流层飞艇结构设计提供技术支撑和参考依据。     

GNSS多波束抗干扰接收机的反欺骗性能分析

为分析存在欺骗干扰的场景下GNSS多波束抗干扰接收机的反欺骗性能,提出欺骗抑制比这一性能指标。推导了在快拍数有限的情况下,多波束抗干扰接收机采用最小方差无失真响应(minimum variance distortionless response,MVDR)算法处理后输出真实信号和欺骗信号功率的理论公式。详细分析了欺骗信号到达天线阵口面的功率对真实信号和欺骗信号输出功率的影响。分析得出:即使欺骗信号功率在噪声水平之下,使用MVDR算法的多波束抗干扰接收机依然能对欺骗干扰进行抑制,且在欺骗信噪比高时,抑制效果更加显著。通过仿真和硬件平台实测验证了结论的正确性。     

Bivariate models from univariate life distributions: A characterization cum modeling approach

Bivariate life distribution models are of importance for studying interdependent components. We present a generic approach by introducing a new concept of characterized model in stead of a characterized distribution. It strikes a balance between characterization and modeling approaches to eliminate their individual limitations and incorporate their respective strengths. The proposed model, being a characterized one, admits many important properties irrespective of the choice of marginal distributions. The retention of univariate IFR, DFR, IFRA, DFRA, NBU, and NWU class properties in the bivariate setup has been ensured along with some results on series combinations and convolution. No other models, available in the literature, can ensure simultaneous retention of these fundamental and extremely important class properties. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004