气控软体驱动器结构分析与优化设计

气控软体驱动器的结构特性对其运动和力学特性影响显著,目前气控软体驱动器支反力和倾角性能亟须提升.基于ABAQUS提供的脚本接口,采用Python语言开发脚本建立气控软体驱动器参数化仿真模型,将尺寸因子作为优化变量,联立Isight和ABAQUS,采用单因子试验方法确定倾角和支反力两个目标量的高敏感性影响因子.运用归一化...     

基于参数稳态判定的两阶段序贯仿真分析策略

两阶段序贯分析方法是仿真(模拟)实验研究中的一种常用方法,它虽然可以通过控制实验给出符合精度要求的结果数据,但以其现有形式有时却无法避免冗余计算的存在和实验过早终止的可能.在回顾了现有终态仿真解算终止策略特点的基础上,分析了所需样本总数的估计值与当前可用样本间的变化关系,提出了一种基于参数稳态判定的改进两阶段序贯方法....     

Periodic review inventory management with contingent use of two freight modes with fixed costs

We study a stochastic inventory model of a firm that periodically orders a product from a make‐to‐order manufacturer. Orders can be shipped by a combination of two freight modes that differ in lead‐times and costs, although orders are not allowed to cross. Placing an order as well as each use of each freight mode has a fixed and a quantity proportional cost. The decision of how to allocate units between the two freight modes utilizes information about demand during the completion of manufacturing. We derive the optimal freight mode allocation policy, and show that the optimal policy for placing orders is not an (s,S) policy in general. We provide tight bounds for the optimal policy that can be calculated by solving single period problems. Our analysis enables insights into the structure of the optimal policy specifying the conditions under which it simplifies to an (s,S) policy. We characterize the best (s,S) policy for our model, and through extensive numerical investigation show that its performance is comparable with the optimal policy in most cases. Our numerical study also sheds light on the benefits of the dual freight model over the single freight models. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

现行火灾事故调查制度应用分析及完善路径探讨

《火灾事故调查规定》是规范火灾事故调查,保障公安机关消防机构依法履行职责,保护火灾当事人合法权益的基本规章。结合《火灾事故调查规定》的应用实践,阐述了新修订的《火灾事故调查规定》一些制度设计对火灾事故调查工作的影响,分析了其适用中存在的问题,提出了解决这些问题的对策,有助于进一步完善火灾事故调查制度。     

基于聚类算法的多无人机系统任务分配

针对现有任务分配方法在任务点较多时不易解算,且计算量大的问题,提出了基于模糊C-均值聚类算法的多无人机系统任务分配方法.首先,利用模糊C-均值聚类算法得到的隶属度矩阵对任务点进行初始分配;其次,针对基于空间划分聚类可能造成各UAV任务不均衡的问题,设计任务的局部优化调整规则;最后,结合单旅行商问题,利用Tabu Sea...     

Optimal sample size allocation for tests with multiple levels of stress with extreme value regression

In this article, we discuss the optimal allocation problem in a multiple stress levels life‐testing experiment when an extreme value regression model is used for statistical analysis. We derive the maximum likelihood estimators, the Fisher information, and the asymptotic variance–covariance matrix of the maximum likelihood estimators. Three optimality criteria are defined and the optimal allocation of units for two‐ and k‐stress level situations are determined. We demonstrate the efficiency of the optimal allocation of units in a multiple stress levels life‐testing experiment by using real experimental situations discussed earlier by McCool and Nelson and Meeker. Monte Carlo simulations are used to show that the optimality results hold for small sample sizes as well. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

Quantifying the performance effects of idle time utilization in multiserver systems

In many practical multiserver queueing systems, servers not only serve randomly arriving customers but also work on the secondary jobs with infinite backlog during their idle time. In this paper, we propose a c‐server model with a two‐threshold policy, denoted by (e d), to evaluate the performance of this class of systems. With such a policy, when the number of idle servers has reached d (<c), then e (<d) idle agents will process secondary jobs. These e servers keep working on the secondary jobs until they find waiting customers exist in the system at a secondary job completion instant. Using the matrix analytic method, we obtain the stationary performance measures for evaluating different (e, d) policies. © 2006 Wiley Periodicals, Inc. Naval Research Logistics, 2007.     

存在自干扰码时的短周期伪码截获技术

针对伪码截获这一无线电侦察和导航战中的难题,从模式识别的角度研究存在自干扰码时的伪码截获问题。通过对干扰码的载波频率、相位等参数的估计和补偿,将自干扰码下的伪码截获问题转换为模式识别问题。结合伪码的周期性,采用二进制积累的方法大大降低了判决前所要求的信噪比,使得对扩频信号直接解调以截获伪码成为可能,改变了过去依靠大口径天线提高信噪比的方法。     

机电系统故障—时间应力的关联分析技术研究

时间应力测量装置技术是一种测量和存储各种应力数据以及对这些数据进行挖掘与分析的技术。简要介绍了时间应力的基本概念及其研究应用的发展历程。在此基础上,提出了基于故障模式、影响及应力分析(FMESA)的时间应力与机电系统故障的定性关联分析方法和基于多元logistic回归的定量关联分析方法。最后,以某型航空地平仪为对象进行了案例研究。案例分析结果表明,文中提出的时间应力与机电系统故障的关联分析方法能分析出影响系统性能的关键应力因素,为机电系统的故障诊断及故障预测提供基础。     

小波相关特征尺度熵在滚动轴承故障诊断中的应用

将小波相关滤波方法与Shannon信息熵相结合,提出了一种故障检测与诊断的方法——小波相关特征尺度熵故障法。首先利用小波相关滤波方法提取滚动轴承故障振动信号的微弱故障信息特征,以求得信噪比较高的尺度域小波系数;然后结合Shannon信息熵理论给出了沿尺度分布的小波相关特征尺度熵定义及其计算方法。小波相关特征尺度熵能够定量表征不同尺度的能量分布,各尺度能量分布的均匀性可以反映滚动轴承的运行状态的差别,选取最能反映故障特征的小波相关特征尺度熵作为特征参数,通过所选取的小波相关特征尺度熵大小判断滚动轴承的工作状态和故障类型。实验证明该方法能有效地判断滚动轴承故障特征,为滚动轴承故障诊断提供了新的思路。