bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Periodic Review, Production Planning Model with Uncertain Capacity and Uncertain Demand—Optimality of Extended Myopic Policies
Authors: Ciarallo Frank W. , Akella Ramakrishna , Morton Thomas E. 
Published: November 2008

Increasing product complexity, manufacturing environment complexity and an increased emphasis on product quality are all factors leading to uncertainties in production processes. These uncertainties are in the form of unplanned machine maintenance, varying production yields and rework, among others. In planning for production, an adequate model must incorporate these uncertainties into the representation of the production process. This paper treats the aggregate planning problem for a single product with random demand and random capacity. In the single-period problem, random capacity does not affect the optimal policy but results in a unimodal, nonconvex cost function. In the multiple-period and infinite-horizon settings order-up-to policies that are dependent on the distribution of capacity are shown to be optimal in spite of a nonconvex cost. In the infinite-horizon setting an intuitive description of the situation leads to the notion of a class of extended myopic policies, requiring the consideration of review periods of uncertain length.
“Sticky Information” and the Locus of Problem Solving: Implications for Innovation
Authors: von Hippel Eric 
Published: November 2008

To solve a problem, needed information and problem-solving capabilities must be brought together. Often the information used in technical problem solving is costly to acquire, transfer, and use in a new location—is, in our terms, “sticky.” In this paper we explore the impact of information stickiness on the locus of innovation-related problem solving. We find, first, that when sticky information needed by problem solvers is held at one site only, problem solving will be carried out at that locus, other things being equal. Second, when more than one locus of sticky information is called upon by problem solvers, the locus of problem solving may iterate among these sites as problem solving proceeds. When the costs of such iteration are high, then, third, problems that draw upon multiple sites of sticky information will sometimes be “task partitioned” into subproblems that each draw on only one such locus, and/or, fourth, investments will be made to reduce the stickiness of information at some locations. Information stickiness appears to affect a number of issues of importance to researchers and practitioners. Among these are patterns in the diffusion of information, the specialization of firms, the locus of innovation, and the nature of problems selected by problem solvers.
An Experiment Assessing Group Support System and Facilitator Effects on Meeting Outcomes
Authors: Anson Robert , Bostrom Robert , Wynne Bayard 
Published: November 2008

This paper is dedicated to the memory of Bye Wynne, who never held back from life, charging those he touched with his vigor, heart, and mind. Thanks. This article reports on an experiment investigating the effects of a human facilitator and a computerized Group Support System (GSS) on group meeting outcomes. These treatments were applied in the same way as they are in real organizational situations, with experimental conditions used to control confounding influences of other outside factors. Forty-eight groups were supported by one, both, or neither of the GSS and facilitator treatments. Groups designed a coordinated production strategy during the meeting and then implemented their strategy. Group performance, perceptions of group cohension, and group interaction processes were assessed as the primary dependent variables. Facilitated groups experienced improved group processes and greater cohesion, whereas the GSS-supported groups did not. Facilitator and GSS support together tended to enhance one another's effective influence on cohesion and processes. No significant treatment effects on Performance were found. Supplemental analyses revealed that the quality of facilitators and the restrictiveness of different GSS tools moderated their impacts on appropriation processes and group outcomes.
Sensitivity Analysis for Base-Stock Levels in Multiechelon Production-Inventory Systems
Authors: Glasserman Paul , Tayur Sridhar 
Published: November 2008

Effective management of inventories in large-scale production and distribution systems requires methods for bringing model solutions closer to the complexities of real systems. Motivated by this need, we develop simulation-based methods for estimating sensitivities of inventory costs with respect to policy parameters. These sensitivity estimates are useful in adjusting optimal parameters predicted by a simplified model to complexities that can be incorporated in a simulation. We consider capacitated, multiechelon systems operating under base-stock policies and develop estimators of derivatives with respect to base-stock levels. We show that these estimates converge to the correct value for finite-horizon and infinite-horizon discounted and average cost criteria. Our methods are easy to implement and experiments suggest that they converge quickly. We illustrate their use by optimizing base-stock levels for a subsystem of the PC assembly and distribution system of a major computer manufacturer.
Principles on the Benefits of Manufacturing Process Flexibility
Authors: Jordan William C. , Graves Stephen C. 
Published: November 2008

Increasing manufacturing flexibility is a key strategy for efficiently improving market responsiveness in the face of uncertain future product demand. Process flexibility results from being able to build different types of products in the same plant or production facility at the same time. In Part I of this paper, we develop several principles on the benefits of process flexibility. These principles are that 1) limited flexibility (i.e., each plant builds only a few products), configured in the right way, yields most of the benefits of total flexibility (i.e., each plant builds all products) and 2) limited flexibility has the greatest benefits when configured to chain products and plants together to the greatest extent possible. In Part II, we provide analytic support and justification for these principles. Based on a planning model for assigning production to plants, we demonstrate that, for realistic assumptions on demand uncertainty, limited flexibility configurations (i.e., how products are assigned to plants) have sales benefits that are approximately equivalent to those for total flexibility. Furthermore, from this analysis we develop a simple measure for the flexibility in a given product-plant configuration. Such a measure is desirable because of the complexity of computing expected sales for a given configuration. The measure is ∏(M*), the maximal probability over all groupings or sets of products (M) that there will be unfilled demand for a set of products while simultaneously there is excess capacity at plants building other products. This measure is easily computed and can be used to guide the search for good limited flexibility configurations.
A Sequence of Servers with Arbitrary Input and Regular Service Times Revisited
Authors: Avi-Itzhak Benjamin , Levy Hanoch 
Published: November 2008

The March 1965 issue of Management Science saw a sequence of two papers by Avi-Itzhak and Yadin, the first presenting analysis of a two-server tandem system, with manufacturing blocking and no intermediate queue, leading to the second paper, which analyzes an arbitrary number of tandem servers with manufacturing blocking. In this work we present generalized results for the same systems under k-stage blocking. One-stage blocking is the so-called manufacturing blocking in which a job entering the jth service position in the sequence requires attendance by the jth server only. Upon completion of service the job will move to position (j + 1) if that position is not occupied. Otherwise, it will continue to stay in position j, blocking it, until the next position is vacated. Two-stage blocking is the so-called communication blocking in which a job entering the jth position needs simultaneous attendance by the jth and the (j + 1)-th servers. Thus, start of service may be delayed until the (j + 1)-th server is freed. In k-stage blocking, the job requires at each position in the sequence the joint attendance of the server of that position together with the servers of the next k − 1 positions. One interesting result is that for k > 1 the waiting times are not order-insensitive while the G/D/1 equivalence is maintained.
The Impact of Outliers and Leverage Points for Technical Efficiency Measurement Using High Breakdown Procedures
Authors: Seaver Bill L. , Triantis Konstantinos P. 
Published: November 2008

Given that most data used for production studies have not been accumulated for such purposes, it is important that the quantitative tools for messy data which can affect the accuracy of computed technical efficiency measures be found. In this study, high breakdown robust methods are used in conjunction with a robust distance measure defined relative to the minimum volume ellipsoid estimator. The standardized robust residuals from the high breakdown estimators and the robust distance measures are used to statistically and graphically depict both multivariate outliers and leverage points. Once these points are found, their relationship to those observations that exhibit strong technically efficient or inefficient behavior, scale inefficiency and/or unusual production characteristics is analyzed for three linerboard manufacturing facilities. Additionally, the impact of the outliers and leverage points on the estimated least squares coefficients which are used by the corrected ordinary least squares methodology to compute the full-frontier technical efficiency measures is explored. Finally, a sensitivity analysis of the impact of outliers and leverage points on the computed linear programming based technical efficiency measures is presented.
Effects of Setup and Processing Time Reductions on WIP in the JIT Production Systems
Authors: Samaddar Subhashish , Kaul Tej 
Published: November 2008

Sarkar and Zangwill (S-Z, [Sarkar, D., W. I. Zangwill. 1991. Variance effects in cyclic production systems. Management Sci. 37(4, April) 444–453.]) have shown that in the presence of variance, setup and processing time reductions can have “detrimental” effects on the work-in-process (WIP) inventory in both push and pull (JIT) systems. In this note, we point out that the merits of such a warning for JIT production systems are questionable. If we treat a setup as a PERT network, it is difficult to accept S-Z claim that waiting queues can grow without bound when setup time is reduced. Furthermore, we show that the amount of setup cut, in addition to the level of variance, can determine whether waiting time grows or not. This finding can help in planning a viable setup reduction project. Additionally, we use S-Z example to show that, even when the variances are not reduced proportionately, the expected waiting time does not necessarily increase.
Union-Firm Bargaining and the Influence of Product Market Power and Production Technology on Systematic Risk
Authors: Bughin Jacques 
Published: November 2008

The relationship between the CAPM firm beta and the firm's microeconomic decisions is studied by a model under uncertainty, which combines the feature of an ex ante “inputs substituable” production technology and the existence of a union which bargains over various economic dimensions of the firm. It is shown that the earlier findings of a relationship between the firm beta, the firm product market power, and the labor-capital ratio may be reinforced through the indirect channel of labor market bargaining, but the relationship becomes more complex, and heavily depends on the scope of the union-firm bargaining process. This yields the empirical prediction, confirmed for a panel of Belgian firms, that any proper estimation of the determinants of firm beta, must control for firms in the sample being unionized.
On the Accuracy of the Simple Peak Hour Approximation for Markovian Queues
Authors: Green Linda V. , Kolesar Peter J. 
Published: November 2008

We empirically explore the accuracy of the simple stationary peak hour approximation (SPHA) for estimating peak hour performance in multiserver queuing systems with exponential service times and periodic (sinusoidal) Poisson arrival processes. We show that the SPHA is very good for a range of parameter values corresponding to a reasonably broad spectrum of real systems. However, we do find and document that there are many situations in which this approximation will be very inaccurate. We postulate and then support empirically a set of hypotheses that link the accuracy of the SPHA and the related point-wise stationary approximation (PSA) to key parameter values and model characteristics. We also present results on the time-dependent behavior of these systems as a function of key parameters. Finally we present results which indicate that our findings, developed for models with sinusoidal input streams, may apply to a much broader range of Markovian models with more general cyclic inputs.
Heuristics for Multimachine Scheduling Problems with Earliness and Tardiness Costs
Authors: Federgruen A. , Mosheiov G. 
Published: November 2008

We consider multimachine scheduling problems with earliness and tardiness costs. We first, analyze problems in which the cost of a job is given by a general nondecreasing, convex function F of the absolute deviation of its completion time from a (common) unrestrictive due-date, and the objective is to minimize the sum of the costs incurred for all N jobs. (A special case to which considerable attention is given is the completion time variance problem.) We derive an easily computable lower bound for the minimum cost value and a simple “Alternating Schedule” heuristic, both of which are computable in O(N log N) time. Under mild technical conditions with respect to F, we show that the worst case optimality (accuracy) gap of the heuristic (lower bound) is bounded by a constant as well as by a simple function of a single measure of the dispersion among the processing times. We also show that the heuristic (bound) is asymptotically optimal (accurate) and characterize the convergence rate as O(N−2) under very general conditions with respect to the function F. In addition, we report on a numerical study showing that the average gap is less than 1% even for problems with 30 jobs, and that it falls below 0.1% for problems with 90 or more jobs. This study also establishes that the empirical gap is almost perfectly proportional with N−2, as verified by a regression analysis. Finally, we generalize the heuristic to settings with a possibly restrictive due date and general asymmetric, and possibly nonconvex, earliness and tardiness cost functions and demonstrate its excellent performance via a second numerical study.
The Value of Marketing Expertise
Authors: Paşa Mehmet , Shugan Steven M. 
Published: November 2008

This paper has three objectives: (1) to construct a theoretical model that aids in evaluating marketing expertise, (2) to use that theoretical model to identify factors influencing the value of marketing expertise, and (3) to empirically test the model by observing how different market conditions influence whether companies emphasize marketing expertise. We accomplish these objectives as follows. First, we use decision theory to find an expression for the expected value of marketing expertise. We do not use decision-analysis in the normative tradition. Nor do we assume that firms actually use formal decision-analysis. Rather, we assume that firms are rational and that decision theory describes their actions. Given that assumption, we predict how firms should evaluate marketing. Here, marketing expertise helps a firm make better marketing decisions (at least on average). Hence, the value of marketing expertise increases as marketing decisions become more important. Second, consistent with decision theory, we predict that marketing decisions become more important with increases in the instability of the marketing environment (i.e., predictability), the profit impact of marketing decisions (i.e., opportunity profit), and the loss from marketing mistakes (i.e., potential loss). Third, we construct empirical measures of our theoretical constructs with data from 592 firms. Our empirical results are consistent with our predictions and reveal factors influencing the value of marketing expertise. For example, greater market instability and market presence increase the value of marketing expertise, while larger organization size, organization instability, and competition decrease its value.
When Should a Roving Server Be Patient?
Authors: Srinivasan Mandyam M. , Gupta Diwakar 
Published: November 2008

When polling systems are used to model real-world systems, it is typically assumed that the server switches continuously (“roves”) even when there are no waiting jobs in the system. However, requiring the server to be patient, instead of having it rove, might be more realistic. Furthermore, operational control of these systems can be improved by knowing answers to questions like “under what circumstances should be roving server be patient?” and “at which stations?”. This paper analyzes the patient server model and provides explicit expressions for the waiting time distributions, the mean waiting times and the pseudo-conservation law. Several variants of the patient server model are considered. We show that while the patient server mechanism is generally better than the roving server mechanism in the work-in-process (WIP) reduction sense, there do exist cases where roving is better. Counter-intuitive examples where reducing switchover time can increase WIP are also reported.
Paradox Lost? Firm-Level Evidence on the Returns to Information Systems Spending
Authors: Brynjolfsson Erik , Hitt Lorin 
Published: November 2008

The “productivity paradox” of information systems (IS) is that, despite enormous improvements in the underlying technology, the benefits of IS spending have not been found in aggregate output statistics. One explanation is that IS spending may lead to increases in product quality or variety which tend to be overlooked in the aggregate statistics, even if they increase output at the firm-level. Furthermore, the restructuring and cost-cutting that are often necessary to realize the potential benefits of IS have only recently been undertaken in many firms. Our study uses new firm-level data on several components of IS spending for 1987–1991. The dataset includes 367 large firms which generated approximately 1.8 trillion dollars in output in 1991. We supplemented the IS data with data on other inputs, output, and price deflators from other sources. As a result, we could assess several econometric models of the contribution of IS to firm-level productivity. Our results indicate that IS spending has made a substantial and statistically significant contribution to firm output. We find that the gross marginal product (MP) for computer capital averaged 81% for the firms in our sample. We find that the MP for computer capital is at least as large as the marginal product of other types of capital investment and that, dollar for dollar, IS labor spending generates at least as much output as spending on non-IS labor and expenses. Because the models we applied were similar to those that have been previously used to assess the contribution of IS and other factors of production, we attribute the different results to the fact that our data set is more current and larger than others explored. We conclude that the productivity paradox disappeared by 1991, at least in our sample of firms.
Self-Buffering, Self-Balancing, Self-Flushing Production Lines
Authors: Zavadlav Emil , McClain John O. , Thomas L. Joseph 
Published: November 2008

This research addresses a system of flexible worker assignments in a setting where there are more workers than machines. When organized using this system, a production line balances itself by shifting the workloads continuously and automatically in response to changes in the state of the system. The system is, in effect, buffering itself against variation by altering the work assignments on the fly. This allows the system to operate with very low levels of work-in-process inventory (WIP). In this paper, the workers (rather than machines) are the factor that limits the rate of output. We also assume that the line has a “U” shape, but many of the results do not depend on this topology. An industrial example is described. The system has some interesting and counter-intuitive properties which we demonstrate under a variety of circumstances through an exploratory approach that uses both Markovian and simulation models. Several different policies are compared under conditions of processing time uncertainty. We demonstrate that a flexible assignment system can outperform fixed assignments in a variety of circumstances. Of particular interest is the near absence of balance delay, even when the tasks cannot be divided equally among the workers.
Overlapping Start-Time Bands in Implicit Tour Scheduling
Authors: Jacobs Larry W. , Brusco Michael J. 
Published: November 2008

Many organizations face personnel scheduling decisions under conditions of variable demand for service across a seven-day planning horizon. These organizations must assign employees to daily shifts that efficiently satisfy the demand for labor, yet allow adequate time for rest between subsequent shifts of an employee's weekly tour schedule. To meet these diverse objectives, managers may permit shifts to begin (and end) in any planning period of the day, but place bands on shift-start times to which individuals may be assigned on each day of their tour schedule. We present a compact integer programming model that implicitly represents start-time band scheduling flexibility. We demonstrate the new model by applying it to requirements for toll collectors on the Illinois Tollway. Problems requiring up to two million variables using a general set covering formulation were represented using the new implicit programming model and often solved to optimality in just a few minutes on a Pentium-based microcomputer. The results indicate that start-time bands can provide an important improvement in scheduling efficiency when compared to the exclusive use of schedules that require workers to begin work on the same hour of the day on each day of their tour.
Fairness and Social Risk II: Aggregated Analyses
Authors: Fishburn Peter C. , Sarin Rakesh K. 
Published: November 2008

This paper is the second of a two-paper study of fairness issues for decisions that affect the benefits received and the risks encountered by a population. The study examines fairness for individuals and for homogeneous groups within the population. It considers fairness both for population benefit-risk profiles and for probability distributions over profiles. Our study bases fairness on notions of envy among individuals and groups. The first paper focused on fairness in profiles and profile distributions when benefits and risks are not aggregated. The present paper uses individual preferences to assess fairness when benefits and risks are aggregated within groups or over the population. It concentrates on intergroup envy measures and fairness indices that account for ways that aggregated benefits and risks might be allocated to members of groups or to groups within the population.