Technical note: Worst‐case performance of power‐of‐two policies for serial inventory systems with incremental quantity discounts

This study presents power‐of‐two policies for a serial inventory system with constant demand rate and incremental quantity discounts at the most upstream stage. It is shown that an optimal solution is nested and follows a zero‐inventory ordering policy. To prove the effectiveness of power‐of‐two policies, a lower bound on the optimal cost is obtained. A policy that has a cost within 6% of the lower bound is developed for a fixed base planning period. For a variable base planning period, a 98% effective policy is provided. An extension is included for a system with price dependent holding costs. © 2007 Wiley Periodicals, Inc. Naval Research Logistics, 2007     

What made American Civil War soldiers fight?

James M. McPherson, For Cause and Comrades: Why Men Fought in the Civil War. New York: Oxford University Press, 1997. Pp.xv + 237, appendix, notes, index. £20 (cloth); $13.95 (paper). ISBN 0–10–512499–5     

Algorithms for solving the conditional covering problem on paths

Consider the conditional covering problem on an undirected graph, where each node represents a site that must be covered by a facility, and facilities may only be established at these nodes. Each facility can cover all sites that lie within some common covering radius, except the site at which it is located. Although this problem is difficult to solve on general graphs, there exist special structures on which the problem is easily solvable. In this paper, we consider the special case in which the graph is a simple path. For the case in which facility location costs do not vary based on the site, we derive characteristics of the problem that lead to a linear‐time shortest path algorithm for solving the problem. When the facility location costs vary according to the site, we provide a more complex, but still polynomial‐time, dynamic programming algorithm to find the optimal solution. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005.     

Manpower allocation with time windows and job‐teaming constraints

In this work, we study manpower allocation with time windows and job‐teaming constraints. A set of jobs at dispersed locations requires teams of different types of workers where each job must be carried out in a preestablished time window and requires a specific length of time for completion. A job is satisfied if the required composite team can be brought together at the job's location for the required duration within the job's time window. The objective is to minimize a weighted sum of the total number of workers and the total traveling time. We show that construction heuristics used with simulated annealing is a good approach to solving this NP‐hard problem. In experiments, this approach is compared with solutions found using CPLEX and with lower bounds obtained from a network flow model. © 2005 Wiley Periodicals, Inc. Naval Research Logistics, 2005.     

Expected time delay in multi‐item inventory systems with correlated demands

This paper considers multi‐item inventory systems where a customer order may require several different items (i.e., demands are correlated across items) and customer satisfaction is measured by the time delays seen by the customers. Most inventory models on time delay in the literature assume each demand only requires one item (i.e., demands are not correlated across items or are independent). In this paper, we derive an exact expression for the expected total time delay. We show that when items are actually correlated, assuming items are independent leads to an overestimate of the total time delay. However, (1) it is extremely difficult in practice to obtain the demand information for all demand types (especially in a system with tens of thousands of part numbers), and (2) the problem becomes too complicated to be of practical interest when the correlation is considered. We then explore the possibility of including the demand information partially and develop bounds for the time delays. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 671–688, 1999     

Northwest corner and banded matrix approximations to a Markov chain

In this paper, we consider approximations to discrete time Markov chains with countably infinite state spaces. We provide a simple, direct proof for the convergence of certain probabilistic quantities when one uses a northwest corner or a banded matrix approximation to the original probability transition matrix. © 1999 John Wiley & Sons, Inc. Naval Research Logistics 46: 187–197, 1999     

Keeping Nothing Secret: United Kingdom Chemical Warfare Policy in the 1960s

After renouncing an offensive chemical warfare programme in 1956, the UK Cabinet Defence Committee decided in 1963 to re-acquire a chemical warfare retaliatory capability. This article describes how the re-acquisition decision was engendered by a combination of novel research findings, changes in strategic thinking, new intelligence and pressures from NATO. Despite the 1963 decision, no new chemical weapons capability was acquired by the UK and information that Britain lacked a stockpile of chemical weapons was eventually leaked to the public, initiating a fierce debate between ministries over the significance of this leak. This paper argues that non-existent technology is equally problematic for government secrecy, and equally consequential for government action, as what exists. Furthermore, actors' different interpretations of what constituted a secret, point towards a more subtle understanding of secrecy than simply construing it as the hiding or uncovering of items of information.     

抗战期间国民政府在黄泛区的资源整合与国家调度——以豫东地区为例

1938年6月花园口决堤后,国民政府从民族抗战大局出发,对豫东黄泛区进行了一系列的资源整合和国家调度活动,目的在于增进灾区民众的凝聚力和对敌斗争的信心.主要有:一、开展大规模的政治宣传,给灾区和难民以道德旌扬和精神抚慰;二、密切关注新黄河的水势水情,扩大以水代兵的军事价值;三、制定善后政策,规范善后活动,增进善后力度;四、采取具体措施,对难民实施直接救助和救济.这些活动未必都卓有成效,但是在当时极其艰难的斗争条件下,对于拯救灾民、聚拢人心、激发民族抗战意志、实行持久抗战所起的作用,还是应当给予应有的肯定的.