Suchergebnisse

AbstractProblems of inventory control for items with extremely low demand (say less than one unit per month average demand) have received relatively little attention in the literature. However, for military supply systems it is well known that an extremely large proportion of the total number of items fall into this category. The problem of designing a control system for these low demand items is therefore one of the most critical inventory management problems faced by the National Military Establishment.In the following, a single echelon, multidepot supply system is studied for low demand items having a stationary Poisson probability distribution for demand. Instantaneous information concerning inventory levels is assumed to be available. Procurement lead time is assumed to be constant as well as the time required for either of two available modes of redistribution. Items are ordered one at a time and decision rules are developed for allocation of new procurement, redistribution of stocks among the depots, and for determining system and depot stockage objectives in order to minimize the expected costs resulting from system and depot stockouts, cost of redistributing stocks among the depots, and costs of transportation from the source. The model is an extension of previous models in that redistribution costs and depot stockout costs are considered in the determination of the stockage objective for the system as a whole. When more than a single unit is on order, the allocation of a unit ready to be delivered is determined by the solution of a dynamic programming problem. When only a single unit is on order (and this is the one ready to be delivered), the optimal allocation procedure is reduced to allocating the unit to the depot which has the greatest probability of using it in a time period T + (1/λ) where T is the procurement lead time and λ the system demand rate for the item.

AbstractIn application of operations research models in the area of logistics, important constraints are typically encountered in the form of limitations on the funds appropriated. A supply system must be operated within whatever budgeted funds are appropriated by Congress. In the present article, various possible types of budget constraints are discussed as well as their impact on certain types of operations research models. The possible misallocations that can result from the setting of specific budgets designated for particular purposes are discussed. The confusion existing in the literature concerning the type of constraints that are actually encountered versus those that are imposed upon the mathematical models is pointed out as well as the typical inconsistency of budget constraints and steady‐state models. The difference between a steady‐state budget and a transition‐phase budget is clarified.

AbstractIt is shown that there are precisely nm‐1mn−1 bases in a transportation problem having m destinations and n origins. This number gives an upper limit to the number of iterations in solving the problem and is much smaller than that given by the combinatorial formula (mn)!/(m+n−1)1 (mn+1−m−n)1.

In the background of those physicians who have problems in medical practice serious enough to attract attention by the licensing body, there are factors that apparently can help predict such behavior. As a candidate for medical school the applicant more likely to have future problems has the following profile: (1) older than the average applicant with a lower grade point average; (2) more likely to have used tobacco; (3) did not receive a baccalaureate degree; (4) no military service; (5) turned in a sloppy handwritten application form, and (6) received a less than ideal character reference by the college from which applying. Furthermore, after admission to medical school the person more prone to future problems tends to be a poorer student than his peers and to receive a poorer rating in his first postgraduate year. The Loma Linda University graduate who has had such problems is also more likely to have settled in Southern California and to be in general practice.