STATE-OF-THE-ART SURVEY: OPEN QUEUEING NETWORKS: OPTIMIZATION AND PERFORMANCE EVALUATION MODELS FOR DISCRETE MANUFACTURING SYSTEMS

In this survey we review methods to analyze open queueing network models for discrete manufacturing systems. We focus on design and planning models for job shops. The survey is divided in two parts: in the first we review exact and approximate decomposition methods for performance evaluation models for single and multiple product class networks. The second part reviews optimization models of three categories of problems: the first minimizes capital investment subject to attaining a performance measure (WIP or lead time), the second seeks to optimize the performance measure subject to resource constraints, and the third explores recent research developments in complexity reduction through shop redesign and products partitioning.     

AN OVERVIEW OF TRADEOFF CURVES IN MANUFACTURING SYSTEMS DESIGN

In this paper we review the use of tradeoff curves in the design of manufacturing systems that can be modeled as open queueing networks. We focus particularly on the tradeoff between expected work-in-process (or product leadtime) and capacity investment in job shops. We review the algorithms in the literature to derive tradeoff curves and illustrate their application in evaluating the efficiency of the system, in deciding how much capacity to have, how to allocate resources between the reduction of uncertainty and the introduction of new technologies, and how to assess the impact of changes in products throughput and product mix. The methodology is illustrated with an example derived from an actual application in the semiconductor industry.     

AN OPERATIONAL PLANNING CONCEPT FOR DEEP LANE STORAGE SYSTEMS

The main advantage of deep lane storage systems compared with conventional high bay warehouses is seen in a better space utilization, because products are stored in channels one pallet behind the other. However, for deep lane storage systems the last-in-first-out principle holds and direct access to pallets is lost apart from the last pallet entering a channel. To operate deep lane storage systems effectively, namely, providing high throughput rates even at times of high storage rack utilization requires a sophisticated operational planning system. We will describe a totally new concept consisting of five modules for storage and retrieval assignments, as well as for a reorganization of storage location occupations.     

SERVICE SYSTEM DESIGN FOR THE PROPERTY AND CASUALTY INSURANCE INDUSTRY

This paper describes the changes that are forcing property and casualty insurance firms to rethink their service system design and in particular their distribution strategies. A set of questions related to distribution that are uppermost in the minds of executives in this industry are presented along with a literature survey of models that can be used to answer some of these questions. Based on the survey, a normative framework for designing the distribution system is proposed. Qualitative and quantitative analysis based on the proposed framework is presented along with empirical data to demonstrate the usefulness of the framework. The paper concludes with an agenda for further research.     

CELLULAR PRODUCTION SYSTEMS: A CONCURRENT CLUSTER ANALYTIC FRAMEWORK

We propose an agglomerative heuristic cluster analysis framework for application to the part-family and machine-cell formation problems associated with group technology. This framework addresses the notion of concurrently forming clusters of parts (families) and machines (cells) based on natural between-part and between-machine relationships and the strength of association relating pairs of parts with pairs of machines. An illustrative model is presented and operational aspects demonstrated using a small problem.     

EFFECTS OF ENVIRONMENTAL MANAGEMENT SYSTEMS ON ENVIRONMENTAL MANAGEMENT PRACTICES AND OPERATIONS

To date, it is unclear as to how Environmental Management Systems (EMS) are implemented and what effects these systems have on other environmental and operational practices. This study reports empirical insights to EMS practices based on the largest EMS survey of manufacturing firms in the United States. The objective of the study is to test for a relationship between environmental management systems and perceived operations performance while considering direct and indirect effects of various environmental practices. The results of this study are supported by several field studies and provide a new source of information regarding EMS theory development. The results also indicate a positive relationship between an EMS, the environmental practices a firm engages, and operations performance measures.     

AN EVALUATION OF FORECAST ERROR IN MASTER PRODUCTION SCHEDULING FOR MATERIAL REQUIREMENTS PLANNING SYSTEMS.

Typical forecast-error measures such as mean squared error, mean absolute deviation and bias generally are accepted indicators of forecasting performance. However, the eventual cost impact of forecast errors on system performance and the degree to which cost consequences are explained by typical error measures have not been studied thoroughly. The present paper demonstrates that these typical error measures often are not good predictors of cost consequences in material requirements planning (MRP) settings. MRP systems rely directly on the master production schedule (MPS) to specify gross requirements. These MRP environments receive forecast errors indirectly when the errors create inaccuracies in the MPS. Our study results suggest that within MRP environments the predictive capabilities of forecast-error measures are contingent on the lot-sizing rule and the product components structure When forecast errors and MRP system costs are coanalyzed, bias emerges as having reasonable predictive ability. In further investigations of bias, loss functions are evaluated to explain the MRP cost consequences of forecast errors. Estimating the loss functions of forecast errors through regression analysis demonstrates the superiority of loss functions as measures over typical forecast error measures in the MPS.     

DYNAMIC INTERACTION OF PRICE AND DESIGN QUALITY FOR PRODUCTS WITH CONVEX PRODUCTION COSTS

Price and design quality define value for customers and are often used by firms to position products in the marketplace. Setting price and quality level on a new product for the first time and making appropriate changes over time to these variables to reflect changing conditions in the market requires careful coordination of design, manufacturing, and marketing variables. We present a control theoretic model to study the complex interaction among price, quality, and cost during the life cycle of a product. Our model considers the major design-manufacturing-marketing tradeoffs and helps determine optimal pricing, design quality, and production strategies in a dynamic environment with convex production costs.     

POLICE PATROL BEAT DESIGN: ALLOCATION OF EFFORT AND EVALUATION OF EXPECTED PERFORMANCE*

This paper describes an iterative process for deploying police patrol force manpower. An application of the process is described as a case study of the St. Louis County Police Department (Missouri). The application is based on the county geographic information system (COGIS) and uses the hypercube queuing model (HQM). The procedures presented illustrate the generation of performance characteristics associated with a specific beat deployment. The application results indicate that the iterative model presented is a reliable and valid instrument for allocating police patrols.     

APPLICATION OF A PRODUCTIVITY MODEL FOR COMPUTER SYSTEMS*

The performance evaluation of computer systems as they impact on final user requirements for services is a complex task. A management-oriented approach to the issue based on conventional economic theory was described in a previous report as an outgrowth of a joint university-industry research project. In this sequel we report our experience in estimating, testing, and applying this conceptual model.     

AN EVALUATION OF SEQUENCING RULES FOR AN ASSEMBLY SHOP

Research relating to sequencing rules in simple job shops has proliferated, but there has not been a corresponding proliferation of research evaluating similar sequencing rules in more complex assembly job shops. In a simple job shop, all operations are performed serially; but an assembly shop encompasses both serial and parallel operations. As a result of the increased complexity of assembly shops, the results associated with the performance of sequencing rules in simple job shops cannot be expected for an assembly shop. In this paper, 11 sequencing rules (some of which are common to simple job shops and some decigned specifically for assembly shops) are evaluated using a simulation analysis of a hypothetical assembly shop. The simulation results are analyzed using an ANOVA procedure that identifies significant differences in the results of several performance measures. Sensitivity analysis also is performed to determine the effect of job structure on the performance of the sequencing rules.     

AN EVALUATION OF ORDER PICKING POLICIES FOR MAIL ORDER COMPANIES

This paper is concerned with the problem of order picking in mail order companies. Order picking is the retrieval of items from their warehouse storage locations to satisfy customer orders. Five order picking policies, strict order, batch, sequential zone, batch zone, and wave, are evaluated using labor requirements, processing time, and customer service as performance measures. A simulation model was developed to investigate these picking policies in a mail order environment. Prior research has focused on the study of individual picking policies. This study extends the prior research by evaluating multiple picking policies under varying operating conditions. The results of the study seem to indicate that (1) wave picking and batch picking perform well across the range of operating conditions considered in this study, and (2) sequential zone and batch zone picking do not perform well, especially as the order volume increases. However, the benefits and drawbacks to each picking policy must be taken into account. The key to effective implementation of an order picking system is to match the firm's business strategy, capabilities, technology, and space requirements with an order picking policy that maximizes the benefits of order picking to the firm and its customers.     

AN ANALYSIS OF THE USEFULNESS OF DISAGGREGATED ACCOUNTING DATA FOR FORECASTS OF CORPORATE PERFORMANCE*

The purpose of this paper is to derive the conditions under which disaggregated accounting data contribute to more accurate forecasts of corporate performance. A comparison formula is derived and applied to actual data. The results obtained indicate that disaggregated data do not necessarily produce better forecasts of corporate performance than do aggregated data. The paper concludes with implications of the results to some reporting issues.     

AN EXPERIMENTAL MODEL FOR INVESTIGATING THE SENSITIVITY OF JOB SHOP PERFORMANCE TO JOB RELEASE TIME DISTRIBUTION PARAMETERS

Work flows in a job shop are influenced by the load per release and time interval between release factors. We focus on the latter factor, job release times. Building on Elvers' work, this study evaluates the impact of different job release time distributions on shop performance. Using a computer simulation of a random job shop and a full factorial experimental design, we demonstrate that the type of distribution does affect performance–a finding consistent with results from job shops characterized by good shop floor control practices. These findings are explained by examining the shape and variance traits of the underlying job release time distributions.     

A NOTE ON THE RELATIONSHIPS AMONG FINENESS,GARBLING, AND SUFFICIENCY FOR THE COMPARISON OF INFORMATION SYSTEMS*

Choice among competing information systems is an important problem for both the providers and users of information. When the attributes of the decision makers and decision problems for which information is produced are unknown or heterogeneous, it is difficult to choose among alternative information sources. Three criteria for such comparisons of information systems are available in the theory of information economics. These criteria may be distinguished by the differing restrictions that they impose on the generality of the studies in which they are used. This note explicates the relationships among these criteria and discusses the various limitations that they impose on generality.