摘要:

This article considers a tool loading problem whose objective is to minimize the number of tool switches over time in order to process several parts on a flexible machine. New heuristics are presented and compared. Some of these are shown to be superior to existing methods.

ISSN:0740-817X    

DOI:10.1080/07408179808966514

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Commercial projects are undertaken with the expectation of maximizing financial returns. There are a variety of cash flow models in the literature in which payments, whose amounts depend on the type of contract quoted between the contractor and the client, are tied to the project events or to the completion times of activities. These models are of deterministic nature with respect to cash inflows, that is, the amount and timing of the payments, once determined, are fixed. However, there are situations specifically in the housing industry where the contractor is the owner of the project. In this case, the contractor starts with an initial capital to cover the activity expenditures and then, capital is augmented by the sale of flats which take place randomly over the progress of the project. In this risky environment, the contractor has to decide on the rate of expenditure at each decision time in order to maintain a positive cash balance. Hence, activities are represented by multiple performing modes with different activity durations and the same total cost. A heuristic to construct and re-construct schedules during the progress of the project is proposed here with the aim of maximizing the project Net Present Value while completing the project on time. The heuristic incorporates dynamic mode selection criteria which change adaptively according to the current status of the project. Computational experiments with the heuristic demonstrates that it provides satisfactory results regarding the feasibility of the schedules with respect to the project due date and the nonrenewable resource constraints.

ISSN:0740-817X    

DOI:10.1080/07408179808966515

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We study the optimality of make-to-order (MTO) versus make-to-stock (MTS) policies for a company producing multiple heterogeneous products at a shared manufacturing facility. Manufacturing times are general i.i.d. random variables, and different products may have different manufacturing-time distributions. Demands for the products are independent Poisson processes with different arrival rates. The costs of managing the production-inventory system are stationary and include inventory holding and backordering costs. Backordering costs may be $ per unit or $ per unit per unit time. We derive optimality conditions for MTO and MTS policies. We also study the impact of several managerial considerations on the MTO versus MTS decision.

ISSN:0740-817X    

DOI:10.1080/07408179808966516

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We study a strategy to manage demands that occur when an inventory system is temporarily out of stock: offer the customer facing the unsatisfied demand an economic incentive to backorder. We explore the benefits of this inventory management strategy by analyzing a model of an inventory system with stochastic demand and random supply disruptions, where the probability that a customer facing an unfilled demand will backorder (as opposed to becoming a lost sale) can be influenced by an economic incentive. Our results provide several insights regarding this inventory management strategy and suggest that the benefits of offering backorder incentives can be significant.

ISSN:0740-817X    

DOI:10.1080/07408179808966517

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

In this paper we analyze contracts for multiple products when the supplier offers business volume discounts. The contract takes the form of price discounts for total minimum dollar volume commitments over the horizon with flexibility to adjust the total purchases upwards by a fixed percentage about this minimum commitment. The optimal policy could be complex since it involves the solution of a constrained multi-period multi-product dynamic program. We suggest approximations that give us an upper bound. To develop this upper bound, we present the optimal policy for a similar contract for a single product problem. We then develop a lower bound for the multiproduct problem and show, numerically, that the gap is small. Given the approximations standard single period resource allocation algorithms can be used to solve the problem. The resulting solution methodology is fast and permits evaluation of various what-if scenarios.

ISSN:0740-817X    

DOI:10.1080/07408179808966518

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper addresses a scheduling problem for a two stage hybrid flowshop (HFS) environment with significant processing flexibility across stages. A job can be either completely processed at one of the stages or its processing is split in a prespecified fashion between stages. For the latter case, the routing is only in one direction, from the ‘upstream’ stage to the ‘downstream’ stage. A stage may consist of one or more parallel identical machines. We first study the special case of a single machine per stage and present a pseudopolynomial dynamic programming algorithm to minimize makespan. Then, we provide a heuristic for theHFSm1,m2problem withmkmachines at stagek= 1,2, and prove its worst case and average performance. Also, we extend our algorithms to the case of stage dependent processing times. Finally, we report computational results on the average performance ofHFSm1,m2with comparable flowshop and parallel machine environments, and provide managerial guidelines for process choice decisions.

ISSN:0740-817X    

DOI:10.1080/07408179808966519

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

This paper presents a continuous review inventory model with a lost sales assumption. The model is unique due to the inclusion of a time discount. Whenever the supplier faces the likelihood of being out of stock, he may issue a discount to motivate customers to accept delayed deliveries and thus avoid the occurrence of lost sales. We propose a control policy with four parametersR1,Q,R2andTwhereR1andQare the normal reorder point and quantity, respectively andR2andTare the triggers for this time discount. During each replenishment cycle, if the on-hand inventory drops toR2 at or before T after the reorder time epoch, the time discount will be granted. A derivation as well as a solution approach for the total cost function are provided. Based on computational results, such a system with a time discount is superior to that without a time discount in terms of minimizing the total system cost. Finally, we compare the performance of the time discount and the emergency ordering approaches.

ISSN:0740-817X    

DOI:10.1080/07408179808966520

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Contributed by the Book and Software Renew Department

ISSN:0740-817X    

DOI:10.1080/07408179808966521

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

ISSN:0740-817X    

DOI:10.1080/07408179808966522

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor