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     

正反向量子斯特林循环有限时间热力学性能界限和优化准则

研究了正反向量子斯特林循环的最优性能.在经典极限下,导出了循环的有限时间热力学性能界限和优化准则.得到了斯特林热机、制冷机和热泵特性参数之间的优化关系.     

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     

An adaptive forecasting algorithm and inventory policy for products with short life cycles

Products with short life cycles are becoming increasingly common in many industries, such as the personal computer (PC) and mobile phone industries. Traditional forecasting methods and inventory policies can be inappropriate for forecasting demand and managing inventory for a product with a short life cycle because they usually do not take into account the characteristics of the product life cycle. This can result in inaccurate forecasts, high inventory cost, and low service levels. Besides, many forecasting methods require a significant demand history, which is available only after the product has been sold for some time. In this paper, we present an adaptive forecasting algorithm with two characteristics. First, it uses structural knowledge on the product life cycle to model the demand. Second, it combines knowledge on the demand that is available prior to the launch of the product with actual demand data that become available after the introduction of the product to generate and update demand forecasts. Based on the forecasting algorithm, we develop an optimal inventory policy. Since the optimal inventory policy is computationally expensive, we propose three heuristics and show in a numerical study that one of the heuristics generates near‐optimal solutions. The evaluation of our approach is based on demand data from a leading PC manufacturer in the United States, where the forecasting algorithm has been implemented. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004.     

Exact likelihood inference for the exponential distribution under generalized Type‐I and Type‐II hybrid censoring

Chen and Bhattacharyya [Exact confidence bounds for an exponential parameter under hybrid censoring, Commun Statist Theory Methods 17 (1988), 1857–1870] considered a hybrid censoring scheme and obtained the exact distribution of the maximum likelihood estimator of the mean of an exponential distribution along with an exact lower confidence bound. Childs et al. [Exact likelihood inference based on Type‐I and Type‐II hybrid censored samples from the exponential distribution, Ann Inst Statist Math 55 (2003), 319–330] recently derived an alternative simpler expression for the distribution of the MLE. These authors also proposed a new hybrid censoring scheme and derived similar results for the exponential model. In this paper, we propose two generalized hybrid censoring schemes which have some advantages over the hybrid censoring schemes already discussed in the literature. We then derive the exact distribution of the maximum likelihood estimator as well as exact confidence intervals for the mean of the exponential distribution under these generalized hybrid censoring schemes. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004     

A general approach to the shape of failure rate and MRL functions

Failure rate and mean residual life are two important characteristics for studying reliability of products. In literature, some work studied the shape of failure rate function based on the knowledge of the associated probability density function; some other work investigated the shape of mean residual life function based on the shape of the associated failure rate function separately for continuous case and discrete case. In this article, a general approach is developed which can be applied to the aforementioned studies. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004     

Optimal pricing for a short life‐cycle product when customer price‐sensitivity varies over time

Technology products often experience a life‐cycle demand pattern that resembles a diffusion process, with weak demand in the beginning and the end of the life cycle and high demand intensity in between. The customer price‐sensitivity also changes over the life cycle of the product. We study the prespecified pricing decision for a product that exhibits such demand characteristics. In particular, we determine the optimal set of discrete prices and the times to switch from one price to another, when a limited number of price changes are allowed. Our study shows that the optimal prices and switching times show interesting patterns that depend on the product's demand pattern and the change in the customers' price sensitivity over the life cycle of the product. © 2012 Wiley Periodicals, Inc. Naval Research Logistics, 2012     

对高重频PD雷达的舍脉冲干扰

高重频PD雷达是为解决测速模糊而在机载雷达中广泛采用的一种PD雷达工作模式,从PD雷达的特性来讲,由于带宽比较窄使得噪声干扰能量利用效率不是很高。采用DRFM精确获取雷达信号实施干扰是当前干扰的发展方向,但是对占空比接近50%的高重频PD雷达,采用对低重频PD及中重频PD可行的距离拖引,速度拖引等一系列在雷达信号脉冲串间隔内产生复杂调制的干扰方法是不合适的。主要针对高重频PD雷达重频高、占空比大的特点,提出了一种舍脉冲干扰方法,对DRFM截获的雷达信号进行快速部分转发,间隔一定脉冲数舍弃一个脉冲,改变原雷达信号的脉冲重复周期,使得在频域上产生多个速度欺骗性干扰信号,并通过仿真验证了干扰的有效性。     

基于复杂网络的空间信息支援力量体系结构同步能力研究

运用复杂网络理论的基本原理对空间信息支援力量体系结构的同步能力进行了研究,构建了空间信息支援力量体系结构的网络拓扑模型,给出了网络同步判定依据,分析了初始连接机制、通信节点数以及总节点数的变化对空间信息支援力量体系结构整体同步能力的影响,为空间信息支援力量体系论证和作用发挥等问题的深入研究提供了借鉴和参考．     

一类二次微分系统在三次多项式扰动下的极限环估计

计算了一类二次Hamilton微分系统的一阶Mel’nikov函数,通过此方法对该系统在三次多项式扰动下分岔的极限环个数进行了估计。