传热对水边界层流动的影响

本文评述了壁面传热对水边界层流体流动及其阻力的影响,同时分析了加热减阻的应用及其影响因素。传热不仅对层流流动、层流向湍流的转捩以及湍流流动有明显的影响,而且对流动分离以及由分离引起的空化也有显著影响。以热脉冲加热的主动式加热方式既可用来产生和消除边界层的T-S波,也能用来控制边界层的分离。因此,热控制技术可望在控制边界层转捩和分离,减小流动阻力等方面得到应用。     

气动剥离液滴的附面层分析方法

本文根据附面层理论,对高速气流中的液滴,因气流和液滴表面相互作用而产生的气动剥离现象进行了分析,建立了气液两相附面层耦合问题的理论分析模型,得到了发生气动剥离时的最小气流速度的计算公式,为液体燃料在高速气流申雾化机理研究提供参考。     

关于广义KKM定理的几点注记

本文在 H-空间中引入伪紧闭集的概念,得到一个广义 KKM 定理,从而获得了 KyFan 匹配定理以及极大极小不等式的一些新结果.     

某舰炮驻退复进机的液压阻力公式

某舰炮驻退复进机为液体气压式复进机,结构较复杂。特别是在复进运动过程中,由于某单向阀打开,使液体流动构成一差动连接回路。本文推导了该舰炮后座和复进过程的液压阻力公式,为对该炮进行反面设计提供了必要的技术储备。     

武器系统的故障诊断方式及其模糊决策

文中提出了多种用于单级或多级的实时诊断方式,并采用模糊决策法对其进行优化选择。为新型武器系统故障诊断装置的总体方案设计,提供了一定的依据。     

舰船武备系统故障诊断算法的探讨

本文以舰炮系统为主,论述了舰船武备系统在诊断中常用算法的基本原理及其特点,并指出今后进行理论研究的一些可行的途径。     

基于 AR 模型和SPRT 检验法的过程状态监测

本文利用自适应卡尔曼滤波器原理建立机械系统过程监测模型—AR模型,并根据AR模型系数的变化可以表征系统过程状态这一特点,通过序贯概率比(SPRT)这一假设检验法,对机械系统的运行状况进行判别。实验表明,该方法行之有效,最后,本文给出了实验结果。     

A Markovian model for process setup and improvement

We examine the setup and improvement policies for a production process with multiple performance states. Assume that the production process deteriorates randomly over time, following a Markovian process with known transition probabilities. In order to reduce the production cost incurred because of process deterioration, the process is inspected at the end of each period. Then one of three actions may be taken: do nothing, perform routine process setup, or perform routine setup and process improvement. The routine setup operation returns the process to its best performance state, whereas the process improvement action may reduce future production and setup costs and improve the process-state transition probabilities. A discounted Markovian model is formulated to find the strategy that minimizes the total cost of operating the production process. © 1997 John Wiley & Sons, Inc. Naval Research Logistics 44: 383–400, 1997     

Exact bayesian estimation of system reliability from component test data

System reliability is often estimated by the use of components' reliability test results when system test data are not available, or are very scarce. A method is proposed for computing the exact posterior probability density function, cumulative distribution function, and credible intervals for system reliability in a Bayesian setting, with the use of components' prior probability distributions and current test results. The method can be applied to series, parallel, and many mixed systems. Although in theory the method involves evaluating infinite series, numerical results show that a small number of terms from the infinite series are sufficient in practice to provide accurate estimates of system reliability. Furthermore, because the coefficients in the series follow some recurrence relations, our results allow us to calculate the reliability distribution of a large system from that of its subsystems. Error bounds associated with the proposed method are also given. Numerical comparisons with other existing approaches show that the proposed method is efficient and accurate. © 1997 John Wiley & Sons, Inc.     

Planning accelerated life tests for censored two‐parameter exponential distributions

We consider optimal test plans involving life distributions with failure‐free life, i.e., where there is an unknown threshold parameter below which no failure will occur. These distributions do not satisfy the regularity conditions and thus the usual approach of using the Fisher information matrix to obtain an optimal accelerated life testing (ALT) plan cannot be applied. In this paper, we assume that lifetime follows a two‐parameter exponential distribution and the stress‐life relationship is given by the inverse power law model. Near‐optimal test plans for constant‐stress ALT under both failure‐censoring and time‐censoring are obtained. We first obtain unbiased estimates for the parameters and give the approximate variance of these estimates for both failure‐censored and time‐censored data. Using these results, the variance for the approximate unbiased estimate of a percentile at a design stress is computed and then minimized to produce the near‐optimal plan. Finally, a numerical example is presented together with simulation results to study the accuracy of the approximate variance given by the proposed plan and show that it outperforms the equal‐allocation plan. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 169–186, 1999