Operating characteristics of a two-echelon inventory system for repairable and consumable items under batch ordering and shipment policy

In this article we have generalized previous models on multiechelon recoverable inventory systems to cover the cases of batch ordering and shipment policy, and when items can either be repaired or condemned. The batch ordering and shipment policy is appropriate when the setup cost for shipment and order and/or the demand rates of the items are relatively high. The operating characteristics of such a system have been studied. Specifically, the probability distribution of backorder levels at the bases are analyzed for different repair-time distributions. An approximation scheme is proposed for this distribution, and is evaluated using extensive simulation results. The results indicate that the scheme is very effective in providing near-optimal stocking levels in such a system.     

Forecast horizons for the discounted dynamic lot-size problem allowing speculative motive

This article considers the dynamic lot-size problem under discounting, allowing speculative motive for holding inventory. A variable rolling-horizon procedure is presented, which, under certain regularity conditions, is guaranteed to generate an infinite-horizon optimal-production plan. We also discuss a fixed rolling-horizon procedure which provides a production plan that achieves an infinite-horizon cost within a user-specified tolerance ϵ of optimality. The fixed-horizon length T* needed in this procedure is given in terms of a closed-form formula that is independent of specific forecasted demands. We also present computational results for problems with a range of cost parameters and demand characteristics.     

Heuristic scheduling of resource-constrained projects with cash flows

Resource-constrained project scheduling with cash flows occurs in many settings, ranging from research and development to commercial and residential construction. Although efforts have been made to develop efficient optimal procedures to maximize the net present value of cash flows for resource-constrained projects, the inherent intractability of the problem has led to the development of a variety of heuristic methods to aid in the development of near-optimal schedules for large projects. This research focuses on the use of insights gained from the solution of a relaxed optimization model in developing heuristic procedures to schedule projects with multiple constrained resources. It is shown that a heuristic procedure with embedded priority rules that uses information from the revised solution of a relaxed optimization model increases project net present value. The heuristic procedure and nine different embedded priority rules are tested in a variety of project environments that account for different network structures, levels of resource constrainedness, and cash-flow parameters. Extensive testing with problems ranging in size from 21 to 1000 activities shows that the new heuristic procedures dominate heuristics using information from the critical path method (CPM), and in most cases outperform heuristics from previous research. The best performing heuristic rules classify activities into priority and secondary queues according to whether they lead to immediate progress payments, thus front loading the project schedule. © 1997 John Wiley & Sons, Inc. Naval Research Logistics 44: 365–381, 1997     

地空导弹反导作战拦截次数计算模型及仿真

在分析地空导弹武器系统拦截来袭目标过程的基础上,通过分析地空导弹发射区纵深建立了地空导弹武器系统可拦截次数模型.利用该模型可计算地空导弹武器系统对单个来袭目标在杀伤区内的拦截次数.仿真结果揭示了地空导弹武器系统在不同目标特性(速度、高度、航路捷径)下对目标的可拦截次数的影响.     

一种航空武器数据链MAC协议设计与研究

MAC协议是航空武器数据链组网通信的重要技术,网络的性能依赖于所采用的多址接入协议,也是航空武器数据链研究的难点之一。固定分配、竞争和预约三大类MAC协议各有优缺点以及适应场景,需要根据应用需求设计对应的多址接入协议,以满足通信网络的战术和技术性能指标。在分析数字化战场通信网络——战术数据链组网通信应用的主要MAC协议的基础上,结合航空武器数据链的通信特点和体系结构,提出一种基于固定分配TDMA的航空武器数据链MAC协议——ODTCFMA协议,并对协议的时延性能进行了仿真和分析。分析结果表明,该协议能够同时满足编队战术协同和武器制导的低时延要求,对航空武器数据链的研究具有一定的借鉴意义。     

Exact algorithms for integrated facility location and production planning problems

We consider a class of facility location problems with a time dimension, which requires assigning every customer to a supply facility in each of a finite number of periods. Each facility must meet all assigned customer demand in every period at a minimum cost via its production and inventory decisions. We provide exact branch‐and‐price algorithms for this class of problems and several important variants. The corresponding pricing problem takes the form of an interesting class of production planning and order selection problems. This problem class requires selecting a set of orders that maximizes profit, defined as the revenue from selected orders minus production‐planning‐related costs incurred in fulfilling the selected orders. We provide polynomial‐time dynamic programming algorithms for this class of pricing problems, as well as for generalizations thereof. Computational testing indicates the advantage of our branch‐and‐price algorithm over various approaches that use commercial software packages. These tests also highlight the significant cost savings possible from integrating location with production and inventory decisions and demonstrate that the problem is rather insensitive to forecast errors associated with the demand streams. © 2011 Wiley Periodicals, Inc. Naval Research Logistics, 2011     

一类微分方程组极限环的不存在性

在系统奇点唯一的条件下,研究了一类微分方程组不存在极限环的的充分条件,运用和发展了以往的结果。     

基于动力学与运动学的四轮全向移动机器人轨迹跟踪控制

建立了四轮全向移动机器人的运动学模型和动力学模型,并分析了四轮全向移动机器人执行器的机械特性。在此基础上,利用反馈控制设计了四轮全向移动机器人的运动学控制器,利用逆动力学补偿控制设计了四轮全向移动机器人的动力学控制器,实现了基于动力学与运动学的四轮全向移动机器人轨迹跟踪控制系统设计。最后,利用Matlab/Simulink完成了基于动力学与运动学的四轮全向移动机器人轨迹跟踪控制仿真实验,实验结果验证了该轨迹跟踪控制方法的有效性。     

飞机的红外隐身技术

目前采取的红外隐身措施主要是冷却、屏蔽、遮挡和红外隐身涂料等手段,降低或改变目标的红外辐射特征,实现对目标的低可探测性。概述了红外隐身技术的基本原理,通过对飞机红外隐身发展现状的分析,研究了飞机红外隐身技术所采取的措施。