Using imperfect advance demand information in ordering and rationing decisions

Cataloged from PDF version of article.In this paper, we consider an inventory problem with two demand classes having different priorities. The appropriate policy of rationing the available stock, i.e. reserving some stock for meeting prospective future demand of preferred customers at the expense of deliberately losing some of the currently materialized demand of lower demand class(es), relies on the estimation of the future demand. Utilizing current signals on future demand, which we refer to as imperfect advance demand information (ADI), decreases uncertainty on future demand and may help to make better decisions on when to start rejecting lower class demand. We develop a model that incorporates imperfect ADI with inventory ordering (replenishment) decision and rationing available stock. In a two-period setting, we show some structural properties, solve the rationing problem, and propose solution methods based on Monte Carlo simulation for the ordering problem. We conduct numerical tests to measure the impact of system parameters on the expected value of imperfect ADI, and provide useful managerial insights. (C) 2009 Elsevier B.V. All rights reserved

Centrifuge scaling considerations for fluid-particle systems

Two simulations are involved when a centrifuge is used to test models. First, the behaviour of the model in a uniform ng field is assumed to be similar to that of the prototype. Then the centrifuge is assumed to produce an equivalent ng gravitational field. For most static problems, the centrifuge does produce an equivalent ng gravitational field, but for some dynamic problems involving saturated soil these assumptions can break down. When the soil particles and fluid are moving relative to one another, the behaviour in the ng field is not similar to that in the 1g field unless the Reynolds number in both conditions is less than unity. Since this is a special circumstance, the centrifugal behaviour is not similar to that of the prototype in most cases. To illustrate this, the similarity requirements are examined for a single particle moving in a fluid. If different fluids are used in the model and prototype, then the difference in densities must also be accounted for

The Morphotropic Phase Boundary in the (1-x)PbZrO3–x[0.3Bi(Zn1/2Ti1/2)O3–0.7PbTiO3] Perovskite Solid Solution

Ceramics in the (1-x)PbZrO3–x[0.3Bi(Zn1/2Ti1/2)O3–0.7PbTiO3] solid solution system with 0.48 x 0.56 were investigated. A morphotropic phase boundary separating rhombohedral and tetragonal perovskite phases was identified at x = 0.52. This composition displays the maximum remanent polarization Pr of 40.7 μC/cm2 and the best piezoelectric coefficient d33 of 311 pC/N in the pseudo-binary system. However, the Curie temperature Tc for this MPB composition is 291 °C, much lower than initially expected