摘要:

AbstractAs database servers proliferate in modern information systems architectures in organizations, the issue of protecting and recovering the databases becomes of utmost importance. By developing an analytical model based on a closed network of queues, this paper analyses how different database recovery mechanisms impact on the normal transaction processing. Such a model enables one to capture intricate effects that are peculiar to complex, tightly coupled, multi-component systems, such as database recovery systems, and can be used to facilitate the design and the tuning of database recovery managers. The proposed model provides important performance measures in terms of average transaction processing time and overall systems throughput. Numerical experiments using actual recovery methods demonstrate the effectiveness of the modelling approach.

ISSN:0160-5682    

DOI:10.1057/jors.1996.11

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractIt is important to consider the decision making unit (DMU)'s or decision maker's preference over the potential adjustments of various inputs and outputs when data envelopment analysis (DEA) is employed. On the basis of the so-called Russell measure, this paper develops some weighted non-radial CCR models by specifying a proper set of‘preference weights’that reflect the relative degree of desirability of the potential adjustments of current input or output levels. These input or output adjustments can be either less or greater than one; that is, the approach enables certain inputs actually to be increased, or certain outputs actually to be decreased. It is shown that the preference structure prescribes fixed weights (virtual multiplier bounds) or regions that invalidate some virtual multipliers and hence it generates preferred (efficient) input and output targets for each DMU. In addition to providing the preferred target, the approach gives a scalar efficiency score for each DMU to secure comparability. It is also shown how specific cases of our approach handle non-controllable factors in DEA and measure allocative and technical efficiency. Finally, the methodology is applied with the industrial performance of 14 open coastal cities and four special economic zones in 1991 in China. As applied here, the DEA/preference structure model refines the original DEA model's result and eliminates apparently efficient DMUs.

ISSN:0160-5682    

DOI:10.1057/jors.1996.12

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractThe multi-item, single-level, capacitated, dynamic lot-sizing problem, commonly abbreviated as CLSP, is considered. The problem is cast in a tight mixed-integer programming model (MIP); tight in the sense that the gap between the optimal value of MIP and that of its linear programming relaxation (LP) is small. The LP relaxation of MIP is then solved by column generation. The resulting feasible solution is further improved by adopting the corresponding set-up schedule and re-optimizing variable costs by solving a minimum-cost network flow (trans-shipment) problem. Subsequently, the improved solution is used as a starting solution for a tabu search procedure, with the worth of moves assessed using the same trans-shipment problem. Results of computational testing of benchmark problem instances are presented. They show that the heuristic solutions obtained are effective, in that they are extremely close to the best known solutions. The computational efficiency makes it possible to solve realistically large problem instances routinely on a personal computer; in particular, the solution procedure is most effective, in terms of solution quality, for larger problem instances.

ISSN:0160-5682    

DOI:10.1057/jors.1996.13

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractA current problem in production scheduling is related to the multi-criteria nature of the task. No matter how effective a heuristic or algorithm is, there remains a need to use human judgement to find a balance between an organization's conflicting objectives, such as meeting due-dates and minimizing work-in-progress. The problem is that heuristics do not have convenient input parameters that relate to these organizational objectives. In this paper we introduce the concept of a‘control mechanism’that would allow the scheduler to direct the search for a schedule on the basis of preferences with respect to multiple performance criteria. The feasibility of such a system is dependent on there being a predictable relationship between the input parameters of the scheduling heuristic and the performance measures. We describe a prototype Visual Interactive implementation of the proposed system, present the results of some initial experimental work, which indicates that the method has some potential, and comment on potentially fruitful areas for further research.

ISSN:0160-5682    

DOI:10.1057/jors.1996.14

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractThis paper examines the problem of scheduling jobs on a single machine with set-up times. The jobs are divided into mutually exclusive classes and a set-up task is required when processing switches from a job of one class to a job of another class. The set-up times are assumed to be sequence independent. A number of necessary conditions for a schedule to minimize mean flow time have previously been stated, but do not uniquely define the optimal solution, and the problem is apparently NP-complete. We propose a new polynomial-time heuristic, based on these conditions, and compare its performance with some existing heuristics.

ISSN:0160-5682    

DOI:10.1057/jors.1996.15

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractIn this note we study the multidimensional maximin rectilinear location problem. A general framework is given, partial optimal solutions introduced—together with an algorithm and its properties—and an upper bound analysis is conducted.

ISSN:0160-5682    

DOI:10.1057/jors.1996.16

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

摘要:

AbstractIn this paper we present an exact solution for the inventory replenishment problem with shortages, in which items are deteriorating at a constant rate. The demand rates are increasing with time over a known and finite planning horizon. We also present a dynamic programming solution to the problem. Both these methods provide a net improvement over existing methods.

ISSN:0160-5682    

DOI:10.1057/jors.1996.17

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor

ISSN:0160-5682    

DOI:10.1057/jors.1996.18

出版商:Taylor&Francis    

年代:1996

数据来源: Taylor