Suchergebnisse

Jointly determines the optimal level to which the mean of a critical variable should be set up, and the optimal number of repetitions until recalibration, for the case where the variable is distributed normally, the mean changes linearly with the number of repetitions, and the revenue per oversized and undersized item is unequal. Proves that the optimal set‐up level should be below the mid‐point between the specification limits by a distance which depends on the slope of change of the mean, on the recalibration cycle, and on a function of the per unit revenues, in such a manner that just prior to the recalibration the mean reaches a different distance above the mid‐point. Outlines a method for the numerical evaluation of the optimal number of cycle repetitions, and derives a general approximation formula which allows its closed loop determination. Provides a numerical example and sensitivity analysis.

ABSTRACTWhen customers call a motel or a hotel to reserve a particular room (large, small, suites, single‐bed, double‐bed, etc.) decisions have to be made concerning the allocation of the available rooms. This paper presents a model for determining the maximum number of specific bookings that should be made for each type of room. The objective is to maximize the expected contribution to profit per rental day. The model considers the distribution of requests for reservations over time as well as cancellations. Also included are the effects of late (unbooked) arrivals and overbookings.

In many countries there is no free foreign exchange market. There exists an official exchange rate, and besides it — due to liberal law enforcement policies — a black market flourishes. One such country is Israel, where the black market exchange rate is commonly known, and the daily rate is published in newspapers. Since the establishment of the State several devaluations have taken place which raised the official exchange rate from IL0.333 per dollar in 1949 to IL6.00 in the middle of 1975. Except for the immediate periods after the devaluations the black market rate of exchange was significantly higher than the official one. However, while till 1962 the average difference between the two was about 45%, with a high variance of 36.3, it went down to less than 10% with much smaller variance of 11.2 since then. This reduction in the free market premium and its variability over time could partially be explained by more frequent changes in the official exchange rate, but part of it is probably a result of government intervention in the free foreign currency exchange market.

AbstractA model is developed taking into consideration all the costs (namely cost of sampling, cost of not detecting a change in the process, cost of a false indication of change, and the cost of readjusting detected changes) incurred when a production process, using an unscheduled setup policy, utilizes fraction‐defective control charts to control current production. The model is based on the concept of the expected time between detection of changes calling for setups. It is shown that the combination of unscheduled setups and control charts can be utilized in an optimal way if those combinations of sample size, sampling interval, and extent of control limits from process average are used that provide the minimum expected total cost per unit of time.The costs of a production process that uses unscheduled setups in conjunction with the appropriate optimal control charts are compared to the costs of a production process that uses scheduled setups at optimum intervals in conjunction with its appropriate control charts.This comparison indicates the criteria for selecting production processes with scheduled setups using optimal setup intervals over unscheduled setups. Suggestions are made to evaluate the optimal process setup strategy and the accompanying optimal decision parameters, for any specific cost data, by use of computer enumeration. A numerical example for assumed cost and process data is provided.