Optimal capacity in a coordinated supply chain

We consider a supply chain in which a retailer faces a stochastic demand, incurs backorder and inventory holding costs and uses a periodic review system to place orders from a manufacturer. The manufacturer must fill the entire order. The manufacturer incurs costs of overtime and undertime if the order deviates from the planned production capacity. We determine the optimal capacity for the manufacturer in case there is no coordination with the retailer as well as in case there is full coordination with the retailer. When there is no coordination the optimal capacity for the manufacturer is found by solving a newsvendor problem. When there is coordination, we present a dynamic programming formulation and establish that the optimal ordering policy for the retailer is characterized by two parameters. The optimal coordinated capacity for the manufacturer can then be obtained by solving a nonlinear programming problem. We present an efficient exact algorithm and a heuristic algorithm for computing the manufacturer's capacity. We discuss the impact of coordination on the supply chain cost as well as on the manufacturer's capacity. We also identify the situations in which coordination is most beneficial. © 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

Risk‐sensitive sizing of responsive facilities

We develop a risk‐sensitive strategic facility sizing model that makes use of readily obtainable data and addresses both capacity and responsiveness considerations. We focus on facilities whose original size cannot be adjusted over time and limits the total production equipment they can hold, which is added sequentially during a finite planning horizon. The model is parsimonious by design for compatibility with the nature of available data during early planning stages. We model demand via a univariate random variable with arbitrary forecast profiles for equipment expansion, and assume the supporting equipment additions are continuous and decided ex‐post. Under constant absolute risk aversion, operating profits are the closed‐form solution to a nontrivial linear program, thus characterizing the sizing decision via a single first‐order condition. This solution has several desired features, including the optimal facility size being eventually decreasing in forecast uncertainty and decreasing in risk aversion, as well as being generally robust to demand forecast uncertainty and cost errors. We provide structural results and show that ignoring risk considerations can lead to poor facility sizing decisions that deteriorate with increased forecast uncertainty. Existing models ignore risk considerations and assume the facility size can be adjusted over time, effectively shortening the planning horizon. Our main contribution is in addressing the problem that arises when that assumption is relaxed and, as a result, risk sensitivity and the challenges introduced by longer planning horizons and higher uncertainty must be considered. Finally, we derive accurate spreadsheet‐implementable approximations to the optimal solution, which make this model a practical capacity planning tool.© 2008 Wiley Periodicals, Inc. Naval Research Logistics, 2008     

Strategic capacity decision‐making in a stochastic manufacturing environment using real‐time approximate dynamic programming

In this study, we illustrate a real‐time approximate dynamic programming (RTADP) method for solving multistage capacity decision problems in a stochastic manufacturing environment, by using an exemplary three‐stage manufacturing system with recycle. The system is a moderate size queuing network, which experiences stochastic variations in demand and product yield. The dynamic capacity decision problem is formulated as a Markov decision process (MDP). The proposed RTADP method starts with a set of heuristics and learns a superior quality solution by interacting with the stochastic system via simulation. The curse‐of‐dimensionality associated with DP methods is alleviated by the adoption of several notions including “evolving set of relevant states,” for which the value function table is built and updated, “adaptive action set” for keeping track of attractive action candidates, and “nonparametric k nearest neighbor averager” for value function approximation. The performance of the learned solution is evaluated against (1) an “ideal” solution derived using a mixed integer programming (MIP) formulation, which assumes full knowledge of future realized values of the stochastic variables (2) a myopic heuristic solution, and (3) a sample path based rolling horizon MIP solution. The policy learned through the RTADP method turned out to be superior to polices of 2 and 3. © 2010 Wiley Periodicals, Inc. Naval Research Logistics 2010     

A general strategic capacity planning model under demand uncertainty

Capacity planning decisions affect a significant portion of future revenue. In equipment intensive industries, these decisions usually need to be made in the presence of both highly volatile demand and long capacity installation lead times. For a multiple product case, we present a continuous‐time capacity planning model that addresses problems of realistic size and complexity found in current practice. Each product requires specific operations that can be performed by one or more tool groups. We consider a number of capacity allocation policies. We allow tool retirements in addition to purchases because the stochastic demand forecast for each product can be decreasing. We present a cluster‐based heuristic algorithm that can incorporate both variance reduction techniques from the simulation literature and the principles of a generalized maximum flow algorithm from the network optimization literature. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2006     

海区变化对新型舰船海水淡化装置性能的影响

针对舰船远航时某新型海水淡化装置性能随海水盐度等因素变化而改变的问题,分析了该型海水淡化装置主要影响因素,并对其造水量进行了热力校核计算.实例计算结果表明,某航行海区较设计海区排污系数相对增大近25倍,造水量由原来的2 042 kg/h下降到1 847 kg/h,下降了9.55%.     

数字化坦克营作战能力灰色聚类评估

评估数字化坦克营的作战能力对推动数字化装甲部队建设、提高部队战斗力具有一定的现实意义。以灰色系统理论为基础,将层次分析法和灰色评估法相结合,建立了数字化坦克营的灰色聚类评估模型,论述了利用该模型进行评估的基本步骤,结合实例对数字化坦克营作战能力进行了聚类评估,提出了提高数字化坦克营作战能力的方法。评估结果比较符合实际情况,证明了该模型的正确性。     

弹药生产响应能力综合评价指标权重组合方法

针对战时弹药需求的不确定性而造成对生产能力冲击的特点,为科学地确定综合评价指标权重,评价军工企业弹药生产响应能力,运用基于偏差平方和最小的综合评价指标粗糙集与网络分析法的权重组合算法,将定性与定量评价方法相结合,为客观评价企业弹药生产响应能力提供了科学的依据,对提高弹药生产决策的军事经济效益具有重要的意义。     

有粘结预应力BFRP筋混凝土梁受弯性能理论研究

玄武岩纤维筋是一种新型复合材料,在国防和特殊建筑工程领域具有重要的应用价值.对不同预应力度的3根有粘结预应力BFRP筋混凝土试验梁进行理论研究,初步探讨和建立预应力BFRP筋混凝土梁的破坏模式判别、正截面受弯承载力、短期刚度、平均裂缝间距、平均裂缝宽度的计算方法,理论计算值与试验结果吻合较好,为建立新型预应力BFRP筋...     

武警部队重大改革必须向“能打胜仗”的战斗力聚焦

从关于国防和军队重大改革的重要论述入手,系统地阐述了武警部队重大改革必须向“能打胜仗”的战斗力聚焦。主要从三个层面进行分析：一是向提高部队整体素质及优化规模结构聚焦;二是向提高部队武器装备保障效能聚焦;三是向增强部队以执勤处突为中心的军事能力聚焦。     

带运力限制及单边时变约束下多出发机场航空战略投送兵力分配模型研究

利用民航力量由多个机场向一个目标机场实施航空战略投送时,由于各民航机场都具有运力限制约束,不可能无限制地快速投送兵力,因此,考虑了在多个出发机场存在运力限制约束的情况下,构建了"投送时间最短,动员机场最少"多目标决策模型,并给出了优化算法和算例.