A two‐echelon inventory‐location problem with service considerations

We study the problem of designing a two‐echelon spare parts inventory system consisting of a central plant and a number of service centers each serving a set of customers with stochastic demand. Processing and storage capacities at both levels of facilities are limited. The manufacturing process is modeled as a queuing system at the plant. The goal is to optimize the base‐stock levels at both echelons, the location of service centers, and the allocation of customers to centers simultaneously, subject to service constraints. A mixed integer nonlinear programming model (MINLP) is formulated to minimize the total expected cost of the system. The problem is NP‐hard and a Lagrangian heuristic is proposed. We present computational results and discuss the trade‐off between cost and service. © 2009 Wiley Periodicals, Inc. Naval Research Logistics 2009     

Free riding in a multi‐channel supply chain

Free riding in a multichannel supply chain occurs when one retail channel engages in the customer service activities necessary to sell a product, while another channel benefits from those activities by making the final sale. Although free riding is, in general, considered to have a negative impact on supply chain performance, certain recent industry practices suggest an opposite view: a manufacturer may purposely induce free riding by setting up a high‐cost, customer service‐oriented direct store to allow consumers to experience the product, anticipating their purchase at a retail store. This article examines how the free riding phenomenon affects a manufacturer's supply chain structure decision when there are fixed plus incremental variable costs for operating the direct store. We consider factors such as the effort required to find and buy the product at a retail store after visiting the direct store, the existence of competing products in the market, and the extent of consumer need to obtain direct‐store service. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009     

Two‐machine flow shop scheduling with common due window to minimize weighted number of early and tardy jobs

This article studies two due window scheduling problems to minimize the weighted number of early and tardy jobs in a two‐machine flow shop, where the window size is externally determined. These new scheduling models have many practical applications in real life. However, results on these problems have rarely appeared in the literature because of a lack of structural and optimality properties for solving them. In this article, we derive several dominance properties and theorems, including elimination rules and sequencing rules based on Johnsos order, lower bounds on the penalty, and upper bounds on the window location, which help to significantly trim the search space for the problems. We further show that the problems are NP‐hard in the ordinary sense only. We finally develop efficient pseudopolynomial dynamic programming algorithms for solving the problems. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009     

Approximation algorithms for general one‐warehouse multi‐retailer systems

Logistical planning problems are complicated in practice because planners have to deal with the challenges of demand planning and supply replenishment, while taking into account the issues of (i) inventory perishability and storage charges, (ii) management of backlog and/or lost sales, and (iii) cost saving opportunities due to economies of scale in order replenishment and transportation. It is therefore not surprising that many logistical planning problems are computationally difficult, and finding a good solution to these problems necessitates the development of many ad hoc algorithmic procedures to address various features of the planning problems. In this article, we identify simple conditions and structural properties associated with these logistical planning problems in which the warehouse is managed as a cross‐docking facility. Despite the nonlinear cost structures in the problems, we show that a solution that is within ε‐optimality can be obtained by solving a related piece‐wise linear concave cost multi‐commodity network flow problem. An immediate consequence of this result is that certain classes of logistical planning problems can be approximated by a factor of (1 + ε) in polynomial time. This significantly improves upon the results found in literature for these classes of problems. We also show that the piece‐wise linear concave cost network flow problem can be approximated to within a logarithmic factor via a large scale linear programming relaxation. We use polymatroidal constraints to capture the piece‐wise concavity feature of the cost functions. This gives rise to a unified and generic LP‐based approach for a large class of complicated logistical planning problems. © 2009 Wiley Periodicals, Inc. Naval Research Logistics, 2009     

某型飞机大气数据系统设计

大气数据系统是重要的机载电子设备,其性能、精度直接关系到飞机的飞行安全.在介绍某型号飞机大气数据系统的软硬件体系结构的基础上,从三个方面深入研究了提高大气数据系统精度的途径:大气数据计算模型;基于BP神经网络的压力测量温度误差补偿方法;一种计算型静压源误差补偿方法.其大气数据系统系统性能稳定,结构紧凑,速度快,精度高,软硬件升级简单.试验证明其大气数据系统能很好满足某型号飞机的使用要求.     

新课程实施中家长如何有效协同学校教育

家庭教育是学校教育的延伸和拓展,是学生素质教育体系中不可或缺的重要部分,家长是否有效地协同学校对孩子进行教育,直接决定着学校教育的效果。本文旨在探讨在新课程实施背景下,家长如何有效地协同学校教育。     

一种INSAS的干涉相位初值的估计方法

分析了干涉合成孔径声纳(InSAS)处理中初始相位误差对数字高程图的影响。提出了采用多点的配准时延信息估计干涉相位初值的方法,该方法可提高干涉相位初值估计的精度和可靠性。对几种配准时延信息计算方法估计的干涉相位初值进行了比较和分析。干涉仪合成孔径声纳湖试样机试验数据处理结果,验证了该方法的有效性。     

随动系统实时仿真模型实现及应用

提出了一种新型随动系统实时仿真模型的实现方法。该方法利用实时工具将基于Matlab／Simulink建立的随动系统模型转换成C语言代码,并进一步封装,使之能方便地应用于实时仿真系统。通过典型实例对实时性和准确性进行分析的结果表明,该方法是可行的。     

浅谈型号研制的几种质量管理方法

本文针对目前型号研制过程质量管理的现状,从科学组建质量师系统、实施量化的质量目标管理、坚持关键评审的的预审制度、开展质量督察与监理等方面详细介绍了型号研制中加强质量管理的方法及在设计、制造总装、试验等阶段过程中的质量管理。     

基于A~*算法的虚拟士兵城市作战路径规划

针对虚拟士兵在城市作战仿真领域的需求,重点研究了虚拟士兵在城市环境中路径规划问题。通过对三维城市虚拟环境空间进行分层信息处理,生成虚拟士兵能够感知的虚拟信息层。用A*算法求出虚拟士兵从初始位置到达目标位置的最佳路径,并给出算法的具体设计与实现。