bluuebunny/crossref_metadata_2025 huggingface dataset:
Evaluation of One-for-One Replenishment Policies for Multiechelon Inventory Systems
Authors: Svoronos Antony , Zipkin Paul
Published: November 2008

This paper is concerned with multiechelon inventory systems, where each demand triggers a separate order (one-for-one replenishment policies). The exogenous demands are independent Poisson processes. The transit times between locations may be stochastic. The way we model these transit times follows closely the standard treatment of stochastic leadtimes in single-location models. This is different, however, from the usual approach in the multiechelon setting (e.g., METRIC).

We describe simple methods for computing or approximating the steady-state behavior of the system. The results show that, in sharp contrast to prior multiechelon models, transit-time variances play an important role in system performance.
The Pointwise Stationary Approximation for Queues with Nonstationary Arrivals
Authors: Green Linda , Kolesar Peter
Published: November 2008

We empirically explore the accuracy of an easily computed approximation for long run, average performance measures such as expected delay and probability of delay in multiserver queueing systems with exponential service times and periodic (sinusoidal) Poisson arrival processes. The pointwise stationary approximation is computed by integrating over time (that is taking the expectation of) the formula for the stationary performance measure with the arrival rate that applies at each point in time. This approximation, which has been empirically confirmed as a tight upper bound of the true value, is shown to be very accurate for a range of parameter values corresponding to a reasonably broad spectrum of real systems.
Problem Restructuring in Negotiation
Authors: Sycara Katia P.
Published: November 2008

To achieve movement towards a negotiated settlement, it is often necessary to restructure the problem under negotiation. Problem restructuring can lead to changed perception of the issues by the parties, thus breaking deadlocks and increasing the parties' willingness to compromise. We present a framework and mechanisms for problem restructuring based on the goals and goal relationships of the negotiating parties as well as means of manipulating the parties' utility estimates. In addition, previous negotiations are a source of heuristic advice in the restructuring task. The restructuring approach has been implemented in the PERSUADER, a computer program that acts as a labor mediator in labor management disputes. To achieve its task, the PERSUADER negotiates separately with each party, company and union, to guide them in reaching agreement.
Airline Buyout: Evolutionary Systems Design and Problem Restructuring in Group Decision and Negotiation
Authors: Shakun Melvin F.
Published: November 2008

We discuss problem restructuring involving evolution of the problem representation in group decision and negotiation support systems. We develop the evolutionary systems design (ESD) approach to restructuring involving a heuristic controls/goals/values referral process and other domain-independent methodological knowledge, such as constraint relaxation, contingency planning, coalition formation and flexible goal target. These ideas are applied to multiple problem restructuring in a scenario motivated by labor-management negotiations and buyout in the airline industry, in particular, a composite of negotiations at Eastern Airlines, TWA and UAL.
The Judgment Policies of Negotiators and the Structure of Negotiation Problems
Authors: Mumpower Jeryl L.
Published: November 2008

The structure of negotiation problems refers to characteristics of their feasible settlement spaces and efficient frontiers. These characteristics are determined by the joint distribution of negotiators' utilities across possible settlements. Variations in negotiators' judgment policies (i.e., how they judge the utility of potential settlements) may result in distinctly different negotiation problem structures. Depending on the structure of the negotiation problem, settlements that are efficient, maximize joint utility, and minimize inequality are sometimes possible, sometimes not. When such settlements are possible, different strategies may be necessary, to reach them. They sometimes can be reached only by a “compromise” strategy in which the disputants split their differences on each issue, sometimes only by a “horsetrading” strategy involving trade-offs among extreme values on issues, sometimes by either, and sometimes by neither strategy. Settlements on the efficient frontier that yield equal utility to both negotiators will sometimes leave both relatively well satisfied, sometimes not. When equal-valued settlements yield low levels of utility, negotiators are likely to feel dissatisfied and may presume that the other negotiator must be comparatively better satisfied. Even seemingly simple negotiation problems often pose a high degree of cognitive complexity. In the face of uncertainty about the nature of the problem structure, negotiators may resort to simple bargaining tactics (e.g., incrementally offering concessions on the issue for which the marginal rate of loss of utility is least). For many commonly encountered problem structures, such tactics lead toward satisfactory settlements, but not always. Analyses of the judgment policies of negotiators and resultant negotiation problem structures will contribute to better understanding of negotiation processes and help to inform the design of negotiation support systems.
Integrating Distribution Strategy and Tactics: A Model and an Application
Authors: Rangan V. Kasturi , Jaikumar Ramchandran
Published: November 2008

Designing distribution systems requires two decisions, one strategic (i.e., the number of levels between the producer and the customer) and the other tactical (i.e., channel management policies such as trade discounts and rebates). While the modeling literature focuses on one or the other, evidence from the field indicates that the two decisions are in fact interactive. In this paper, we develop and then apply an integrated model that solves the strategic issue of channel levels and the tactical issue of price rebates simultaneously.
Informational Dynamics of Censored Observations
Authors: Braden David J. , Freimer Marshall
Published: November 2008

The analysis of stochastic models is often greatly complicated if there are censored observations of the random variables. This paper characterizes families of distributions which help keep tractable the analysis of such models. Our primary motivation is to provide guidance to practitioners in the selection of distributions: If a modeler feels that no member of the families we characterize is a reasonable approximation, then he will almost surely encounter serious analytic and computational problems if his data include censored observations.

We characterize a family of distributions for which there exist fixed-dimensional sufficient statistics of purely censored observations. We also characterize an important subset of this family, appropriate for situations where data include both censored and exact observations. We derive the corresponding predictive distributions using arbitrary priors and present some general results relating stochastic dominance among predictive distributions to the parameters of the prior. We also analyze the cases of discrete and mixed random variables.
Strong Consistency and Other Properties of the Spectral Variance Estimator
Authors: Damerdji Halim
Published: November 2008

Consistent estimation of the variance parameter of a stochastic process allows construction, under certain conditions, of a confidence interval for the mean of the process. If the variance estimator is strongly consistent, fixed-width confidence interval construction is valid for large samples. It has long been known that the spectral variance estimator of steady-state simulation output analysis is consistent in the mean-square sense. Here, we provide strong consistency of this estimator, thereby justifying fixed-width confidence interval construction for the spectral method. A characterization of spectral density function estimators is also introduced. This characterization provides insight into the relation between spectral methods and overlapping batch means-type variance estimators. Finally, some of the mathematical conditions provide qualitative insight into the relation between the process correlation and certain parameters of spectral methods.
Competitive Strategies for Two Firms with Asymmetric Production Cost Structures
Authors: Eliashberg Jehoshua , Steinberg Richard
Published: November 2008

We model joint production-marketing strategies for two firms with asymmetric production cost structures in competition. The first firm, called the “Production-smoother,” faces a convex production cost and a linear inventory holding cost. The second firm, called the “Order-taker,” faces a linear production cost and holds no inventory. Each firm is assumed to vary continuously over time both its production rate and its price in view of an unstable “surge” pattern of demand. The underlying theoretical motivation is to investigate the temporal nature of the equilibrium policies of two competing firms, one operating at or near capacity (the Production-smoother), and one operating significantly below capacity (the Order-taker).

We characterize and compare the equilibrium strategies of the two competing firms. Among our results, we show that if the duopolistic Production-smoother finds it optimal to hold inventory, then he will begin the season by building up inventory, continue by drawing down inventory until it reaches zero, and conclude by following a “zero inventory” policy until the end of the season. This result, which is robust with respect to the market structure, is compared with a monopolistic Production-smoother policy. We also show that due to the “coupling” effect between the two competing firms, the time at which the Production-smoother begins his zero inventory policy is also critical for the Order-taker who divides his production and pricing strategies into two parts determined by the Production-smoother's zero inventory point. Numerical examples that illustrate certain aspects of our analyses are provided as well.
Uncertain Search: A Model of Search Among Technologies of Uncertain Values
Authors: Lippman Steven A. , McCardle Kevin F.
Published: November 2008

In the standard search problem there is an infinite pool of items whose distribution of values is known. A decision maker draws an item from the pool, observes its value, and decides whether to keep it or to draw another item. He can keep only one item, and he seeks the item with the largest value. In the standard uncertainty resolution problem there is only one item, and the value of that item remains uncertain even after it is drawn. The decision maker sequentially collects observations on the value of the item and decides whether to keep the item, discard the item, or take another observation. Uncertain search marries the sequential drawing from a pool of items from the search literature with the unknown value of a drawn item from the uncertainty resolution literature. Presented in the context of technology adoption, it considers drawing from a pool of new technologies whose values remain unknown even after being drawn. The decision maker sequentially purchases information in order to Bayesianly update the prior distribution of the technology's value. After each observation, the decision maker either adopts the technology (and hence quits searching), takes another costly observation, rejects the technology and quits searching, or rejects the technology and draws the next technology from the pool for observation. The solution to this uncertain search problem is surprisingly simple: solve the version of the uncertainty resolution problem in which the return to rejecting the technology is replaced by an exit value. Then use successive approximation to find a fixed point: an exit value that equals the expected value of the uncertainty resolution problem.
Comments on “One-Warehouse Multiple Retailer Systems with Vehicle Routing Costs”
Authors: Hall Randolph W.
Published: November 2008

In a recent paper, Anily and Federgruen developed a methodology for assigning retailers to vehicle tours, with the objective of minimizing long-run average transportation and inventory costs. This comment demonstrates that coordinating deliveries among tours can reduce cost over their solution.
The Effects of Information Sources and Communication Channels on the Diffusion of an Innovation
Authors: Nilakanta Sree , Scamell Richard W.
Published: November 2008

Swanson et al.'s comment, “Illusive Effects on the Diffusion of an Innovation: A Comment,” (Swanson et al. 1991, this issue) contains two major criticisms of our paper (Nilakanta and Scamell 1990), “Effects of Information Sources and Communication Channels on Diffusion of Innovation in a Data Base Development Environment:” (1) the significance and interpretations of the results and (2) the legitimacy of certain measures that appear in the questionnaire contained in the appendix (pp. 34–38). The purpose of this comment is to address these criticisms.
FW/SM: A Prototype Structured Modeling Environment
Authors: Geoffrion Arthur M.
Published: November 2008

A research prototype implementation has been evolving for several years in parallel with the vision, theory, language, and applicative aspects of structured modeling. The objective of this article is to describe the capabilities of this implementation as it now stands, and to comment on how it contributes toward fulfilling a previously published agenda for the development of a new generation of modeling environments. The intended audience is all modeling system designers and evaluators, including those who do not happen to take a structured modeling approach.
Scheduling of Project Networks by Job Assignment
Authors: Drexl Andreas
Published: November 2008

A recurring problem in project management involves the allocation of scarce resources to the individual jobs comprising the project. In many situations such as audit scheduling, the resources correspond to individuals (skilled labour). This naturally leads to an assignment type project scheduling problem, i.e. a project has to be processed by assigning one of several individuals (resources) to each job. In this paper we consider the nonpreemptive variant of a resource-constrained project job-assignment problem, where job durations as well as costs depend upon the assigned resource. Regarding precedence relations as well as release dates and deadlines, the question arises, to which jobs resources should be assigned in order to minimize overall costs. For solving this time-resource-cost-tradeoff problem we present a hybrid brand and bound/dynamic programming algorithm with a (rather efficient Monte Carlo type) heuristic upper bounding technique as well as various relaxation procedures for determining lower bounds. Computational results are presented as well.
Comparison of Weighting Judgments in Multiattribute Utility Measurement
Authors: Borcherding Katrin , Eppel Thomas , von Winterfeldt Detlof
Published: November 2008

This paper compares four weighting methods in multiattribute utility measurement: the ratio method, the swing weighting method, the tradeoff method and the pricing out method. 200 subjects used these methods to weight attributes for evaluating nuclear waste repository sites in the United States. The weighting methods were compared with respect to their internal consistency, convergent validity, and external validity. Internal consistency was measured by the degree to which ordinal and cardinal or ratio responses agreed within the same weighting method. Convergent validity was measured by the degree of agreement between the weights elicited with different methods. External validity was determined by the degree to which weights elicited in this experiment agreed with weights that were elicited with managers of the Department of Energy. In terms of internal consistency, the tradeoff method fared worst. In terms of convergent validity, the pricing out method turned out to be an outlier. In terms of external validity, the pricing out method showed the best results. While the ratio and swing methods are quite consistent and show a fair amount of convergent validity, their external validity problems cast doubt on their usefulness. The main recommendation for applications is to improve the internal consistency of the tradeoff method by careful interactive elicitation and to use it in conjunction with the pricing out method to enhance its external validity.
The Minimum Common-Cycle Algorithm for Cyclic Scheduling of Two Material Handling Hoists with Time Window Constraints
Authors: Lei Lei , Wang Tzyh-Jong
Published: November 2008

The problem of cyclic scheduling of two hoists is defined as follows. There are N + 1 workstations, S0, S1, …, SN, and two identical hoists that move jobs between stations. Jobs are identical and each job has to visit all stations in the order that stations are numbered. It is assumed that the hoist traveling times between stations are given constants. Each station can hold one job at a time, and each job must remain at station Si, for a period of at least ai and at most bi time units. Both ai and bi, i = 2, …, N, are given constants. Define mi, 0 ≤ i ≤ N, to be a move of a job from Si to Si+1. A cyclic schedule determines the order of N + 1 moves, mi, i = 0, 1, …, N, an assignment of these moves to hoists, and the start time of the moves in a cycle. The problem is to find a cyclic schedule that minimizes the total time (the cycle time) to complete all the N + 1 moves.

Previous approaches toward solving cyclic hoist scheduling problems have been limited to single-hoist cases. In this paper, we propose a heuristic algorithm that finds schedules for systems with two hoists, and discuss an extension to the problem with more than two hoists. The algorithm uses a partitioning approach by which a system is partitioned into two sets of contiguous workstations and each hoist is assigned to a set. A sequence of alternative partitions is evaluated. For each partition, two single-hoist subproblems are formed and the optimal (minimal) cycle time for each subproblem is independently computed. The two optimal single-hoist schedules are then coupled and refined into a feasible two-hoist schedule with a common-cycle time for both hoists. The best of the generated schedules, that results in the minimum common-cycle time among the different partitions, is given as the final solution. Computational experience with both randomly generated problems and a benchmark problem arising from a real system is discussed.
Software Piracy: An Analysis of Protection Strategies
Authors: Reavis Conner Kathleen , Rumelt Richard P.
Published: November 2008

Software piracy by users is generally believed to harm both software firms (through lower profits) and buying customers (through higher prices). Thus, it is thought that perfect and costless technological protection would benefit both firms and consumers. The model developed here suggests that in some circumstances, even with significant piracy, not protecting can be the best policy, both raising firm profits and lowering selling prices. Key to the analysis is joining the presence of a positive network externality with the fact that piracy increases the total number of program users. The network externality exists because consumers have an incentive to economize on post-purchase learning and customization costs.
An Information Processing Model of a Police Organization
Authors: Simms B. W. , Petersen E. R.
Published: November 2008

A model has been developed to study economic decision making in police organizations. The conceptual viewpoint taken is that police organizations are information processing systems, with activities connected in a communication network. The resulting model is process-oriented, and organizational decisions are analyzed by studying how the police force senses, learns about, and solves a stream of criminal events. Search theory is used to model the information processing activities and to study the value of unit memory, communication between units and the coordination of two or more units. A computer model links the units and activities in a simulation of the police force organization. Examples based on a municipal police force are used to highlight the concepts of the model building approach. The implementation of the computer model using police force data is reported.
The Maximal Covering Location Problem with Capacities on Total Workload
Authors: Pirkul Hasan , Schilling David A.
Published: November 2008

The Maximal Covering Location Problem (MCLP) has been the focus of considerable attention both in research and practice for some time, and numerous extensions have been proposed to broaden its appeal and enhance its applicability. In this paper, we are concerned with the addition of workload limits on the facilities. While not generally difficult to formulate, these capacity constraints make the model substantially more difficult to solve, as well as create certain pathological results, particularly in the assignment of uncovered demand to facilities. First we discuss these pathologies and extend the capacitated MCLP to address them. Then, we present an efficient solution procedure that is applicable to both simple and extended problem formulations. Finally, results of extensive tests on the solution procedure are presented and a “real-world” scale example is solved to explore the implications of the model.
SSB and Weighted Linear Utility As Expected Utility with Suspicion
Authors: Bordley Robert , Hazen Gordon B.
Published: November 2008

We show that a “suspicious” subjective expected utility (SEU) maximizer, i.e., one who treats potential consequences of states as information useful in assessing the probability of those states, may under reasonable circumstances act as though he were maximizing either weighted linear utility, or skew-symmetric bilinear (SSB) utility. SEU with suspicion, therefore, explains at least as many empirical violations of SEU theory as do these and similar models. We give examples to illustrate how several important types of SEU violations may seem to arise when suspicion is present.
Cyclical Schedules for Capacitated Lot Sizing with Dynamic Demands
Authors: Campbell Gerard M. , Mabert Vincent A.
Published: November 2008

Cyclical scheduling, where the time between production periods for each item is constant, offers simplicity and ease of control compared with noncyclical scheduling, where production periods are irregularly spaced. However, when demands are dynamic, flexibility in the spacing of production periods permits noncyclical scheduling to result in lower total costs. This study investigates the additional cost of cyclical scheduling.

We focus upon the capacitated lot sizing problem (CLSP), which deals with planning production on a single, capacitated machine serving multiple items with dynamic demands. To establish cyclical schedules, a mathematical programming model is developed along with a heuristic solution technique and a Lagrangian-based lower bounding procedure. For problems solved in this study, differences between solution costs and lower bounds average less than 1%.

Experiments are performed to evaluate the heuristic technique and to compare cyclical schedules with noncyclical ones. For comparison purposes, a noncyclical heuristic and problem sets from the literature are used. New problems based upon operating data from Ford Motor Company are also generated and solved. In this study, cyclical schedules average 4.4% higher in cost than noncyclical ones. Coefficient of demand variation most seriously influences differences in costs. Other significant factors include capacity utilization, setup time, time between orders, and number of items.
Sole Versus Dual Sourcing in Stochastic Lead-Time (s, Q) Inventory Models
Authors: Ramasesh Ranga V. , Ord J. Keith , Hayya Jack C. , Pan Andrew
Published: November 2008

When supply lead times are uncertain, the simultaneous procurement from two sources offers savings in inventory holding and shortage costs. Economies are achieved if these savings outweigh the increase in ordering costs. In this paper we analyze dual sourcing in the context of the “reorder point, order quantity” inventory model with constant demand and stochastic lead times and compare it with single sourcing. Two cases are studied, using the uniform and the exponential distributions, which may be thought of as two extreme ways of representing stochastic lead times. In our two-vendor model, the order quantity is split equally between the two vendors and the split orders are placed simultaneously when the inventory position reaches the reorder level. A comparison of the total expected costs suggests that when the uncertainty in the lead times is high and the ordering costs are low, dual sourcing could be cost effective.
Modelling Effectiveness-Equity Trade-Offs in Public Service Delivery Systems
Authors: Mandell Marvin B.
Published: November 2008

Distributional equity is a particularly salient objective in public sector decision making, in general, and decision making concerning the delivery of public services such as education, libraries, sanitation, and public safety, in particular. In this paper two related bicriteria mathematical programming models are developed for identifying the trade-offs between overall output (effectiveness) and equity that result from alternative allocations of service resources among different service delivery sites (branches). The models developed here incorporate equity in a more satisfactory manner than have previous efforts. An illustrative application of the models to the allocation of new books among the branches of a public library system is presented.
Interaction of Judgemental and Statistical Forecasting Methods: Issues & Analysis
Authors: Bunn Derek , Wright George
Published: November 2008

This paper reviews several of the current controversies in the relative value of judgemental and statistical forecasting methods. Where expert, informed judgemental forecasts are being used, a critical analysis of the evidence suggests that their quality is higher than many researchers have previously asserted, and circumstances favourable to this are identified. The issue of the interaction of judgemental and statistical methods is, however, identified as a more worthwhile line of inquiry, and research in this area is reviewed, differentiating approaches aimed at synthesising both of these inputs.
Optimal Linear Opinion Pools
Authors: DeGroot Morris H. , Mortera Julia
Published: November 2008

Consider a decision problem involving a group of m Bayesians in which each member reports his/her posterior distribution for some random variable θ. The individuals all share a common prior distribution for θ and a common loss function, but form their posterior distributions based on different data sets. A single distribution of θ must be chosen by combining the individual posterior distributions in some type of opinion pool. In this paper, the optimal pool is presented when the data observed by the different members of the group are conditionally independent given θ. When the data are not conditionally independent, the optimal weights to be used in a linear opinion pool are determined for problems involving quadratic loss functions and arbitrary distributions for θ and the data. Properties of the optimal procedure are developed and some examples are discussed.
Deriving and Analysing Optimal Strategies in Bayesian Models of Games
Authors: Young S. C. , Smith J. Q.
Published: November 2008

Wilson (1986) gives a backwards induction algorithm for sequentially obtaining the optimal next move in a repeated Bayesian game. In this paper we show how to identify the form of an optimal solution of such a game by a graphical procedure. By means of the Prisoner's Dilemma game, we illustrate how Wilson's algorithm can be enhanced using the derived analytic form of the solution to produce an explicit optimal strategy. We can then determine not only how P1 should play on all subsequent moves of the game, but also use ideas of Bayes rationality to discuss whether a given model of P2's reactions is realistic.
A Crane Scheduling Problem in a Computer-Integrated Manufacturing Environment
Authors: Matsuo Hirofumi , Shang Jen S. , Sullivan Robert S.
Published: November 2008

This paper addresses a crane scheduling and machine layout problem in a Computer Integrated Manufacturing (CIM) Environment. A single crame is used to move all the Work-in-Process (WIP) in the system. The overall system objective is to maximize the yield rate subject to the flow time limit of the WIP. We formalize the problem, and analytically and empirically show that cyclic scheduling provides a near optimal solution, which is superior to dispatching rules. First, we illustrate the optimality and benefits of cyclic scheduling in a simple environment. Then, for multiple-product problems, we show that for a given sequence, finding the minimum cycle time becomes the maximum cost circular network flow problem in a graph. Based on the insights developed, a heuristic for sequencing product types in a cycle is derived that approximately minimizes the cycle time over all sequences. Finally, computational experiments are reported and various assertions made in the paper are empirically verified.
Information and Profitability Estimates: Modelling the Firm's Decision to Adopt a New Technology
Authors: Oliva Terence A.
Published: November 2008

This paper uses a response surface based on catastrophe theory to examine the interaction of information and profitability estimates on the firm's adoption of a new technology or innovation. As such, the paper builds on the conceptual ideas behind McCardle's (1985) work. An illustrative example using simulated data is presented to indicate how one might operationalize the key constructs for the purpose of estimating the model.
Measuring the Long-Term Effects of Public Policy: The Case of Narcotics Use and Property Crime
Authors: Powers Keiko , Hanssens Dominique M. , Hser Yih-Ing , Anglin M. Douglas
Published: November 2008

The effects of treatment and legal supervision on narcotics use and criminal activities were assessed by applying newly developed time-series methods that disentangle the long-term (permanent) and the short-term (temporary) effects of intervention. A multivariate systems approach was used to characterize the dynamic interplay of several related behaviors at a group level over a long period of time. Five variables—abstinence from narcotics use, daily narcotics use (or addiction), property crime, methadone maintenance treatment, and legal supervision—were derived by aggregating information from over 600 narcotic addiction histories averaging 12 years in length. Because of the long assessment period, age was also included as a control variable.

Overall, the system dynamics among the variables were characterized by long-term rather than short-term relationships. Neither methadone maintenance nor legal supervision had short-term effects on narcotics use or property crime. Methadone maintenance treatment demonstrated long-term benefits by reducing narcotics use and criminal activities. Legal supervision, on the other hand, did not reduce either narcotics use or property crime in the long run. Instead, there was a positive long-term relationship in which a higher level of legal supervision was related to higher levels of narcotics use and criminal activity. This latter finding is consistent with the observation that either narcotics use or criminal activity is likely to bring addicts to the attention of the legal system. However, these addicts, as a group, did not directly respond to legal supervision by changing their narcotics use or crime involvement except perhaps through coerced treatment. The paper explores the policy implications of these findings.
The Efficiency of One Long Run Versus Independent Replications in Steady-State Simulation
Authors: Whitt Ward
Published: November 2008

We evaluate the efficiency of one long run versus independent replications in steady-state discrete-event simulation, assuming that an initial portion of each replication will be deleted to allow the process to approach steady state. We provide supporting evidence in favor of one long run, but we also show that multiple replications can be more efficient. The advantage of one long run increases if the amount deleted increases or if the covariance function decreases more quickly (assuming it is nonnegative and decreasing). Thus, assuming that the amount deleted depends on the way the process approaches steady state, one long run tends to be efficient when the covariance function decays rapidly compared to the rate the process approaches steady state. We also discuss ways to determine the initial portion to delete. We consider the case of an exponential covariance function in detail, and use it as a basis for approximations. We also consider the M/G/∞ queueing model and reflected Brownian motion, the latter as an approximation for the G/G/1 queueing model. For these models starting at the origin, one long run is efficient, but a moderate number of independent replications is essentially equally efficient. In agreement with Kelton and Law (1984), for such examples our analysis only rules out many replications of very short runs.
An Extensible Visual Environment for Construction and Analysis of Hierarchically-Structured Models of Resource Contention Systems
Authors: Gordon Kurtiss J. , Gordon Robert F. , Kurose James F. , MacNair Edward A.
Published: November 2008

The development of models for evaluating the performance of resource contention systems, such as manufacturing systems, computer systems, and communication networks, is often a difficult and complex task. This modeling effort can be dramatically reduced by the use of appropriate software tools. The Research Queueing Package Modeling Environment (RESQME) provides a graphical environment for constructing, solving, and analyzing the results of extended queueing network models of resource contention systems. It supports a rich underlying modeling paradigm previously developed in the Research Queueing Package (RESQ) and provides a single integrated graphical interface throughout all tasks of the modeling lifecycle. In this paper we present a brief overview of RESQME and then focus on two of its most important features: the construction and analysis of hierarchically-structured models and the ability to extend and customize the RESQME environment for domain-specific modeling via the use of user-defined modeling elements. A manufacturing model is developed in order to illustrate these capabilities.
Some Extensions of the Discrete Lotsizing and Scheduling Problem
Authors: Salomon Marc , Kroon Leo G. , Kuik Roelof , Van Wassenhove Luk N.
Published: November 2008

In this paper the Discrete Lotsizing and Scheduling Problem (DLSP) is considered. DLSP relates to capacitated lotsizing as well as to job scheduling problems and is concerned with determining a feasible production schedule with minimal total costs in a single-stage manufacturing process. This involves the sequencing and sizing of production lots for a number of different items over a discrete and finite planning horizon. Feasibility of production schedules is subject to production quantities being within bounds set by capacity.

A problem classification for DLSP is introduced and results on computational complexity are derived for a number of single and parallel machine problems. Furthermore, efficient algorithms are discussed for solving special single and parallel machine variants of DLSP.
Random Review Production/Inventory Systems with Compound Poisson Demands and Arbitrary Processing Times
Authors: Srinivasan Mandyam M. , Lee Hyo-Seong
Published: November 2008

A production/inventory system is considered in which a single production facility produces items of a given type. The demand for the item is assumed to arrive according to a compound Poisson process. The time required to produce an item is assumed to follow an arbitrary distribution. An (s, S) policy is considered in which production stops at the instant that the inventory level is raised to S and production resumes at an inspection point when the inventory level is observed to have dropped to or below s for the first time. The time interval between two successive inspection points during a nonproduction period is a random variable which follows an arbitrary distribution.

Under a cost structure which includes a set-up cost, a linear holding cost and a linear backorder cost, an expression for the expected cost per unit time is obtained for given control values. The operating cost during a cycle is shown to be convex in S for a given value of S-s. For the continuous review simple Poisson demand system, as well as some other special cases of the system considered here, it is shown that the expected cost per unit time is unimodal. Based on these properties, a procedure to find the optimal (s, S) policy is presented.
Due-Date Setting and Priority Sequencing in a Multiclass M/G/1 Queue
Authors: Wein Lawrence M.
Published: November 2008

The problem of simultaneous due-date setting and priority sequencing is analyzed in the setting of a multiclass M/G/1 queueing system. The objective is to minimize the weighted average due-date lead time (due-date minus arrival date) of jobs subject to a constraint on either the fraction of tardy jobs or the average job tardiness. Several parametric and nonparametric due-date setting policies are proposed that depend on the class of arriving job, the state of the queueing system at the time of the job's arrival, and the sequencing policy (the weighted shortest expected processing time rule) that is used. In a simulation experiment performed on a two-class M/M/1 system, these policies outperformed traditional due-date setting policies, and due-date setting had a larger impact on performance than priority sequencing.
A Methodology for Collective Evaluation and Selection of Industrial R&D Projects
Authors: Oral Muhittin , Kettani Ossama , Lang Pascal
Published: November 2008

This paper proposes a methodology for evaluating and selecting R&D projects in a collective decision setting, especially useful at sectorial and national levels. It consists of two major phases: Evaluation and Selection. The evaluation process repeatedly uses mathematical programming models to determine the “relative values” of a given R&D project from the viewpoint of the other R&D projects. The selection process of R&D projects is based on these “relative values” and is done through a model-based outranking method.

The salient features of the methodology developed are its ability to (1) permit the evaluation of an R&D project from the viewpoint of the other R&D projects without at first imposing a uniform evaluation scheme, and (2) maximize the level of consensus as to which projects should not be retained in the R&D Program being funded, thus minimizing the level of possible resentment in those organizations or departments whose projects are not included in the R&D Program.

Also discussed in this paper is an application of the methodology to evaluate and select major R&D projects in the iron and steel industry of Turkey.
Nonparametric Estimation of the Cumulative Intensity Function for a Nonhomogeneous Poisson Process
Authors: Leemis Lawrence M.
Published: November 2008

A nonparametric technique for estimating the cumulative intensity function of a nonhomogeneous Poisson process from one or more realizations is developed. This technique does not require any arbitrary parameters from the modeler, and the estimated cumulative intensity function can be used to generate a point process for Monte Carlo simulation by inversion. Three examples are given.
An Analytic Congestion Model for Closed Production Systems with IFR Processing Times
Authors: Spearman Mark L.
Published: November 2008

We present an analytic model relating the mean cycle time or throughput as a function of the number of jobs in a closed production system composed of a tandem network of queues having exponential and/or IFR processing times. This model exhibits macroscopic behavior that is predicted by results from queueing theory and involves three meaningful parameters: the bottleneck rate and the “raw process” time that can be determined from first moment data; and a dimensionless congestion coefficient that is typically obtained from a single WIP/average cycle time observation (e.g., simulation).

The derivation of the model is based on observations of the behavior of the relation between mean cycle time and WIP. This “engineering” approach is different from a purely “probabilistic” one in that we do not consider the distribution of processing times at individual station. We compare the accuracy of the model in predicting mean cycle times to other techniques such as mean value analysis and simulation.
Simultaneous Determination of Lot Sizes and Routing Mix in Job Shops
Authors: Calabrese Joel M. , Hausman Warren H.
Published: November 2008

Flexibility and versatility of batch production job shops has increased in the last 25 years through the use of multi-purpose numerically controlled (NC) machine tools; these computer controlled machines can perform a wide variety of different operations. In recent years, even greater flexibility has been achieved by flexible manufacturing systems, where groups of NC machines are linked by automated material handling devices and controlled by computer. In such shops, a batch of product may have several possible alternative routes that it may follow through the shop. A number of researchers have shown that determining the proper mix of routes for each product can have a significant effect on shop throughput and work-in-process inventory. Other researchers have found that the lot sizing decision also affects these performance measures. The primary thrust of this paper is to develop a model to explore the interaction between routing and lot sizing decisions in a multi-machine, multi-work center job shop. A heuristic is developed for simultaneously determining lot sizes and routing mix in problems of practical size, and numerical examples are provided in order to illustrate the solution method. The examples show that there can be considerable potential for performance improvement by simultaneous consideration of routing and lot sizing.
The Queue Inference Engine: Addendum
Authors: Larson Richard C.
Published: November 2008

A simple modification of one equation in Larson (1990) reduces the computational complexity of the algorithm for the Queue Inference Engine (QIE) from O(N5) to O(N3), where N is the number of customers queued during a congestion period.
Locating Tax Facilities: A Graphics-Based Microcomputer Optimization Model
Authors: Domich Paul D. , Hoffman Karla L. , Jackson Richard H. F. , McClain Marjorie A.
Published: November 2008

This paper presents a mathematical model that selects locations for Internal Revenue Service Posts-of-Duty. The system is microcomputer-based and uses menus and graphically displayed zip code maps of IRS districts for interactive inputs and solution outputs. The mathematical model used for this problem is the uncapacitated, fixed charge, location-allocation model which minimizes travel and facility costs, given a specified level of activity. A greedy-interchange heuristic is used to obtain “good” solutions to the problem and is coupled with a lagrangian-relaxation technique providing a measure of how far from optimality the current solution can be. An example with Florida data illustrates the use of the model.
The Effects of Organizational Context on Quality Management: An Empirical Investigation
Authors: Benson P. George , Saraph Jayant V. , Schroeder Roger G.
Published: November 2008

While the quality literature abounds with prescriptions for how quality should be managed, no one has proposed an organization-theory explanation for how quality is managed in organizations. This paper proposes a system-structural model of quality management that relates organizational quality context, actual quality management, ideal quality management, and quality performance. The relationships between organizational quality context and actual and ideal quality management are investigated using data collected from 152 managers from 77 business units of 20 manufacturing and service companies. A previously reported instrument is used to measure managers' perceptions of ideal and actual quality management in terms of eight critical factors including product/service design, training, employee relations, and top management leadership. Several measures are used to characterize organizational quality context including company type, company size, degree of competition, and corporate support for quality. The results indicate that organizational quality context influences managers' perceptions of both ideal and actual quality management. This suggests that knowledge of organizational quality context is useful for explaining and predicting quality management practice. Important contextual variables are corporate support for quality, past quality performance, managerial knowledge, and the extent of external quality demands.
Production Lot Sizing with Machine Breakdowns
Authors: Groenevelt Harry , Pintelon Liliane , Seidmann Abraham
Published: November 2008

Economic lot sizing and batching models often assume reliable manufacturing facilities. In this research, we focus on the effects of machine breakdowns and corrective maintenance on the economic lot sizing decisions. Two production control policies are proposed for coping with these stochastic interferences. The first policy assumes that production of the interrupted lots is not resumed after a breakdown. Instead, the on-hand inventory is depleted before a new cycle is initiated. Under the second policy studied here, production is immediately resumed after a breakdown, if the current on-hand inventory is below a certain threshold level. It is shown that this control structure is optimal among all stationary policies. We show that under both policies the optimal lot sizes will always be bigger than the ones in a corresponding deterministic case, and that the optimal lot size increases with the failure rate. We also provide exact optimal and closed form approximate lot sizing formulas and derive tight bounds on the average cost per unit time for the approximations. In addition, we present various structural properties for these policies and operational insights relevant to such management decisions as machine replacement or maintenance schedules.
On Optimal Arrangement of Stations in a Tandem Queueing System with Blocking
Authors: Yamazaki Genji , Sakasegawa Hirotaka , Shanthikumar J. George
Published: November 2008

We consider tandem queueing networks with no waiting spaces and address the issue of ordering the stations so that the throughput (i.e., the departure rate) is maximized. Based on some theoretical and extensive empirical results, we propose two rules for ordering the stations. The first rule recommends arranging the two worst stations (according to our ordering) to the first and last stages. Numerical results show that this rule almost always agrees with the optimal ordering of stations. In cases where this rule does not agree with the optimal ordering, numerical results show that this rule leads to station arrangements that are near optimal. In addition, numerical results also indicate that the first rule is the most important one to achieve a near optimal throughput. The second rule arranges the remaining stations according to the so-called “bowl phenomenon.” Numerical results illustrate that an optimal arrangement of stations need not exhibit the “bowl phenomenon,” but the differences in the throughput between the optimal and the one obtained by the second rule are always very small (less than 0.5%).