Suchergebnisse

This study analyses two authoritative texts and a map from the Ming and Qing eras to examine the political relationship between China and Tibet in the Ming period. It finds that in these documents Tibet was not classified as being a part of the realm governed by the Ming Empire. This casts doubt on the claim advanced by the People's Republic of China that Tibet has been a part of China 'since antiquity'. An important conclusion of this study is that, when taking recourse to historical texts to justify or refute territorial claims, the structure and content of the text as a whole, and not just isolated phrases or formulations, should be taken into account.

It is obvious that an inventory item's lead time demand is affected by the length of the lead time as well as the actual demand on each day during the lead time. In a situation where the lead time and the daily demand are both stochastic, the probability distribution of an item's lead time demand is then determined by the probability distributions of the item's daily demand and lead time. This article presents a computationally simple method for determining the lead time demand's probability distribution from estimations of the item's daily demand and lead time probability distributions; no restriction is placed on the distribution forms of the daily demand, the lead time and the lead time demand. After obtaining the lead time demand distribution, this article illustrates the computation of "reorder points" and "protection levels" for an inventory item.

ABSTRACTThis paper presents a practical method for determining the waiting time distribution of a single‐stage queueing system for general distribution of inter‐arrival/service times. The method requires the matrix solution of Lindley's equation for waiting time distribution by treating time in discrete units. Some important characteristics of the method are: a) it is easily programmable; b) it has high accuracy; c) it has modest CPU time and storage requirements; and, d) it requires no mathematical functional form for inter‐arrival/service time distributions.

AbstractThe purpose of this paper is to comment on and give historical perspective to two methdologies for estimating parameters of beta distributions. Fielitz and Myers [3] [4] developed and advocated a methodology using the method of moments, while Romesburg [20] advocated a methodology usingthe method of maximum likelihood. However, what Fielitz and Myers presented as new research and suggested as an area needing further study is ground already trampled. The authors have prepared a graph to underline the superiority of the maximum likelihood method in fitting beta distributions.

AbstractWe state a balancing problem for mixed model assembly lines with a paced moving conveyor as: Given the daily assembling sequence of the models, the tasks of each model, the precedence relations among the tasks, and the operations parameters of the assembly line, assign the tasks of the models to the workstations so as to minimize the total overload time. Several characteristics of the problem are investigated. A line‐balancing heuristic is proposed based on a lower bound of the total overload time. A practical procedure is provided for estimating the deviation of any given line‐balance solution from the theoretical optimum. Numerical examples are given to illustrate the methodology. © 2004 Wiley Periodicals, Inc. Naval Research Logistics, 2004.

AbstractFor computing an optimal (Q, R) or kindred inventory policy, the current literature provides mixed signals on whether or when it is safe to approximate a nonnormal lead‐time‐demand ("LTD") distribution by a normal distribution. The first part of this paper examines this literature critically to justify why the issue warrants further investigations, while the second part presents reliable evidence showing that the system‐cost penalty for using the normal approximation can be quite serious even when the LTD‐distribution's coefficient of variation is quite low—contrary to the prevalent view of the literature. We also identify situations that will most likely lead to large system‐cost penalty. Our results indicate that, given today's technology, it is worthwhile to estimate an LTD‐distribution's shape more accurately and to compute optimal inventory policies using statistical distributions that more accurately reflect the LTD‐distributions' actual shapes. © 2003 Wiley Periodicals, Inc. Naval Research Logistics, 2003

ABSTRACTThis paper explores the two‐product newsboy problem. Solution procedures are developed to find the optimal production quantities of each product that will maximize the probability of achieving a profit target. The problem is shown to be surprisingly challenging, and numerical results obtained for only the more restrictive cases exhibit interesting behavior with important decision implications. For example, the results suggest that, if a firm has two single‐product divisions and each will receive a bonus for achieving a profit target, it is beneficial for the two divisions to cooperate if the targets are lax and the profit margins are high, but not if the targets are tight and the profit margins low. Also, between two products having different profit margins, one should produce more of the product with the lower profit margin if the target is sufficiently lax. This exploration motivates further efforts in solving the two‐product problem for the more general cases and also in extending the problem to three or more products.

ABSTRACTMany studies have claimed that the stable‐Paretian distribution should be used to model a wide variety of financial variables, ranging from stock and futures prices to exchange rates. Using a newly developed method, this study shows that the stable distribution is unsuitable for modeling most financial variables that are stable‐distributed. We found that the distributions of a few accounting ratios may be stable. Our conclusions support a change in the future directions of financial‐variable modeling.

ABSTRACTA recent Decision Sciences paper considered maximizing the probability of achieving a profit target in a two‐product newsboy problem. Numerical solutions to this problem revealed some intriguing properties, but the authors were unable to analytically explain many of their results. This paper presents an analytical solution procedure to this problem for the case of uniformly distributed demands. The analytical structure reveals more intriguing properties and these properties are proven and explained.

AbstractIn order‐quantity reorder‐point formulations for inventory items where backordering is allowed, some of the more common ways to prevent excessive stockouts in an optimal solution are to impose either a cost per unit short, a cost per stockout occasion, or a target fill rate. We show that these popular formulations, both exact and approximate, can become "degenerate" even with quite plausible parameters. By degeneracy we mean any situation in which the formulation either cannot be solved, leads to nonsensical "optimal" solutions, or becomes equivalent to something substantially simpler. We explain the reasons for the degeneracies, yielding new insight into these models, and we provide practical advice for inventory managers. © 2002 Wiley Periodicals, Inc. Naval Research Logistics 49: 686–705, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/nav.10037