bluuebunny/crossref_metadata_2025 huggingface dataset:
Efficiency of Time Segmentation Parallel Simulation of Finite Markovian Queueing Networks
Authors: Andradóttir Sigrún , Hosseini-Nasab Mehdi
Published: December 2003

We present an approach for using parallel processors to simulate long sample paths of Markovian queueing networks with finite buffers and both loss and blocking stations. Parallelism is achieved by distributing the available processors among segments of the time domain of the simulation. We conduct the simulation in such a way that all sample paths of the system will eventually couple (i.e., become identical), regardless of their starting states. This coupling property is exploited to generate valid sample paths of the system by combining the information collected on consecutive time segments of the simulation. The efficiency of our approach depends heavily on the magnitude of the coupling times of the sample paths. We study how the expected coupling times depend on the system parameters through a variety of theoretical and numerical results. Our main results give conditions under which the expected coupling times grow slowly (no faster than linearly) with respect to the number of stations and buffer capacities in the system. These results suggest that our time segmentation approach is likely to perform well on a substantial class of finite Markovian queueing networks.
Centralized and Competitive Inventory Models with Demand Substitution
Authors: Netessine Serguei , Rudi Nils
Published: December 2003

A standard problem in operations literature is optimal stocking of substitutable products. We consider a consumer-driven substitution problem with an arbitrary number of products under both centralized inventory management and competition. Substitution is modeled by letting the unsatisfied demand for a product flow to other products in deterministic proportions. We obtain analytically tractable solutions that facilitate comparisons between centralized and competitive inventory management under substitution. For the centralized problem we show that, when demand is multivariate normal, the total profit is decreasing in demand correlation.
Optimal EOQ for Announced Price Increases in Infinite Horizon
Authors: Huang Wei , Kulkarni Vidyadhar G. , Swaminathan Jayashankar M.
Published: December 2003

In this paper we consider an infinite horizon economic order quantity (EOQ) model with single announced price increase, with an option of placing a special order just before the price increase takes effect. We extend earlier work where it is assumed that the special order is an integral multiple of the new EOQ quantity. In the process, we show that when the assumption of integrality is not valid, the earlier approach of minimizing the cost difference over a finite horizon is no longer valid and establish the periodicity of cost difference function. Next, we show that the Cesaro limit of the function exists and utilize that to derive the optimal special-order quantity. We find that the optimal special-ordering policy is of (s,S) type.
Large Deviations-Based Asymptotics for Inventory Control in Supply Chains
Authors: Paschalidis Ioannis Ch. , Liu Yong
Published: December 2003

We consider a model of a capacitated single-class supply chain consisting of production facilities (stages) in tandem. External demand is met from the available finished goods inventory maintained in front of the most downstream facility; unsatisfied demand is backlogged. Every stage orders from its upstream facility, thus production is constrained by the local production capacity and the availability of upstream inventory. We propose production policies in two separate cases: (1) when each facility has information about its local inventory only, and (2) when each facility has knowledge of the total downstream inventory. In case (1) the proposed policy guarantees that stockout probabilities at each stage stay bounded below given constants (service level constraints). In case (2) the proposed policy minimizes total expected inventory cost subject to desirable service-level constraints. In both cases the parameters of the proposed policies are obtained analytically based on large deviations asymptotics, which leads to drastic computational savings compared to simulation. An important feature of our model is that it accommodates autocorrelated demand and service processes, both critical features of modern failure-prone manufacturing systems. We demonstrate that detailed distributional information on demand and service processes, which is incorporated into large deviations asymptotics, is critical in inventory control decisions. We discuss extensions to a multiclass setting and to a model where unsatisfied demand is lost instead of backordered.
A Note on “Inventory Models with Cost Changes”
Authors: Luo Jianwen , Huang Peiqing
Published: December 2003

This note is concerned with the inventory models with finite horizon and cost changes. We presented more specific results on the optimal inventory policy than those in previous papers and showed that some of the results in Lev and Weiss' (1990) paper are not necessarily optimal.
An Empirical Study of Service Differentiation for Weapon System Service Parts
Authors: Deshpande Vinayak , Cohen Morris A. , Donohue Karen
Published: December 2003

The question of how to effectively manage items with heterogeneous attributes and differing service requirements has become increasingly important to supply chains that support the delivery of after-sales service. However, there has been little investigation to date on how organizations actually manage inventory levels under such circumstances. This study provides such an investigation, focusing on the logistic system used to manage consumable service parts for weapon systems in the U.S. military. Our findings, based on interviews and rigorous analysis of part attribute and performance data, suggest that in practice a part's service level is negatively affected by an item's cost and is less affected by attributes such as its priority code. We introduce a simple inventory model to explain our empirical findings and explore how variations in item attributes can interact with an inventory policy to affect system performance. Based on this model, we recommend using explicit service-level targets for priority categories to achieve performance consistent with part priority. We show, using military data, that a service differentiation strategy can be an effective way of allocating inventory investment by providing higher service for critical parts at the expense of accepting lower service levels for parts with less importance.
Enhanced Model Formulations for Optimal Facility Layout
Authors: Sherali Hanif D. , Fraticelli Barbara M. P. , Meller Russell D.
Published: December 2003

This paper presents an improved mixed-integer programming (MIP) model and effective solution strategies for the facility layout problem and is motivated by the work of Meller et al. (1999). This class of problems seeks to determine a least-cost layout of departments having various size and area requirements within a rectangular building, and it is challenging even for small instances. The difficulty arises from the disjunctive constraints that prevent departmental overlaps and the nonlinear area constraints for each department, which existing models have failed to approximate with adequate accuracy. We develop several modeling and algorithmic enhancements that are demonstrated to produce more accurate solutions while also decreasing the solution effort required. We begin by deriving a novel polyhedral outer approximation scheme that can provide as accurate a representation of the area requirements as desired. We also design alternative methods for reducing problem symmetry, evaluate the performance of several classes of valid inequalities, explore the construction of partial convex hull representations for the disjunctive constraints, and investigate judicious branching variable selection priority schemes. The results indicate a substantial increase in the accuracy of the layout produced, while at the same time providing a dramatic reduction in computational effort. In particular, three previously unsolved test problems from the literature for which Meller et al.'s algorithm terminated prematurely after 24 cpu hours of computation (on a SUN Ultra 2 workstation with 390 MB RAM) with respective optimality gaps of 10.14%, 26.45%, and 40%, have been solved to exact optimality with reasonable effort using our proposed approach.
Admission Control with Incomplete Information of a Queueing System
Authors: Lin Kyle Y. , Ross Sheldon M.
Published: December 2003

We consider a multiple-server loss model where customers arrive at a gatekeeper according to a Poisson process. A costcis incurred if a new arrival is blocked from entering the system by the gatekeeper, while a larger cost K is incurred if an admitted customer finds all servers busy and therefore has to leave the system. The key assumption is that the gatekeeper is informed when an admitted customer finds all servers busy, but is not informed when served customers depart. Assuming an exponential service distribution, we show that, in the case of a single server, a threshold-type policy that blocks for a certain amount of time after a new arrival is admitted is optimal. When there are multiple servers, we propose two types of heuristic policies. We analytically compute the best policy of the first type, and use simulation to estimate that of the other.
Inventory Cost Effect of Consolidating Several One-Warehouse Multiretailer Systems
Authors: Lim Wei-Shi , Ou Jihong , Teo Chung-Piaw
Published: December 2003

Consolidation of warehouses is a new trend in global logistics management, and the reduction in order processing and inventory costs is often cited as one of the main motivations. In this note we show that when retailers face constant demand rates and their ordering costs are independent of the warehouse that services them, consolidated systems are rarely suboptimal and always lead to close-to-optimal inventory replenishment costs. In particular, we prove that using two (one) properly selected warehouses, the systemwide inventory replenishment cost is in the worst case at most 2% (14.75%) more than the optimal.
Necessary and Sufficient Conditions for Delay Moments in FIFO Multiserver Queues with an Application Comparing s Slow Servers with One Fast One
Authors: Scheller-Wolf Alan
Published: December 2003

In this paper we establish the weakest known sufficient conditions for the existence of stationary delay moments in FIFO GI/GI/s queues, for s≥2. These conditions involve not only the service time distribution, as in the classic Kiefer and Wolfowitz conditions, but also the interplay of the traffic intensity and the number of servers in the queue. We then prove the necessity of our conditions for a large class of service times having finite first, but infinite αth, moment for some finite α. Such service time distributions include many, but not all of, the class of heavy-tailed distributions: The Pareto and Cauchy are members; the Weibull is not.

Our results are then applied to provide one answer to the classic question: When are s slow servers (operating at rate 1/s) better than one fast server (operating at rate 1)? We consider this question with respect to the rate of decay of the tail of stationary customer delay. In a system characterized by service times that have finite mean but lack some higher moments, such as are often used to model telecommunications traffic, for s greater than a traffic-related constant, the answer is always. Our results help to quantify the benefits of extra servers, while also pointing the way towards the derivation of bounds and asymptotics for the stationary delay distribution of multiserver queues having these types of service times. Such queues are attracting a great deal of academic research, motivated by their practical use modeling telecommunications systems.
Efficient Algorithms for the Inverse Spanning-Tree Problem
Authors: Hochbaum Dorit S.
Published: December 2003

The inverse spanning-tree problem is to modify edge weights in a graph so that a given tree T is a minimum spanning tree. The objective is to minimize the cost of the deviation. The cost of deviation is typically a convex function. We propose algorithms here that are faster than all known algorithms for the problem. Our algorithm's run time for any convex inverse spanning-tree problem is O(nm log2 n) for a graph on n nodes and m edges plus the time required to find the minima of the n convex deviation functions. This not only improves on the complexity of previously known algorithms for the general problem, but also for algorithms devised for special cases. For the case when the objective is weighted absolute deviation, Sokkalingam et al. (1999) devised an algorithm with run time O(n 2 m log(nC)) for C the maximum edge weight. For the sum of absolute deviations our algorithm runs in time O(n 2 log n), matching the run time of a recent (Ahuja and Orlin 2000) improvement for this case. A new algorithm for bipartite matching in path graphs is reported here with complexity of O(n 1.5 log n). This leads to a second algorithm for the sum of absolute deviations running in O(n 1.5 log n log C) steps.
From Fluid Relaxations to Practical Algorithms for High-Multiplicity Job-Shop Scheduling: The Holding Cost Objective
Authors: Bertsimas Dimitris , Gamarnik David , Sethuraman Jay
Published: December 2003

We design an algorithm for the high-multiplicity job-shop scheduling problem with the objective of minimizing the total holding cost by appropriately rounding an optimal solution to a fluid relaxation in which we replace discrete jobs with the flow of a continuous fluid. The algorithm solves the fluid relaxation optimally and then aims to keep the schedule in the discrete network close to the schedule given by the fluid relaxation. If the number of jobs from each type grow linearly with N, then the algorithm is within an additive factor O(N) from the optimal (which scales as O(N2)); thus, it is asymptotically optimal. We report computational results on benchmark instances chosen from the OR library comparing the performance of the proposed algorithm and several commonly used heuristic methods. These results suggest that for problems of moderate to high multiplicity, the proposed algorithm outperforms these methods, and for very high multiplicity the overperformance is dramatic. For problems of low to moderate multiplicity, however, the relative errors of the heuristic methods are comparable to those of the proposed algorithm, and the best of these methods performs better overall than the proposed method.
Toward a Stakeholder Theory of the Firm: The Saturn Partnership
Authors: Kochan Thomas A. , Rubinstein Saul A.
Published: December 2003

This paper seeks to engage the organization theory community in contemporary debates over the role of the corporation in American society by using the case of the Saturn corporation to develop and illustrate a stakeholder theory of the firm. One normative and three positive questions are posed for a stakeholder theory: The normative question is: Why should stakeholder models be given serious consideration at this moment in history? The positive questions are: (1) Under what conditions is a stakeholder firm likely to emerge in the United States, (2) what are the critical determinants of performance in a stakeholder firm, and (3) what will determine the sustainability and diffusion of this organizational form in the American environment? The history, design features, and dynamics of the labormanagement partnership at Saturn are used to illustrate and interpret a specific case of employees as stakeholders. Saturn's original mission, governance structure, and internal processes fit the characteristics of a stakeholder firm. Employees establish themselves as influential, definitive stakeholders by using their knowledge to improve organizational performance. The local union likewise contributes to firm performance by organizing workers into a dense social network that contributes to problem solving, conflict resolution, and quality improvement. However, the legal and political environment in which the firm operates produces considerable uncertainty over the sustainability and diffusion of Saturn's features in particular, and the stakeholder organizational form in general. Additional hypotheses and research questions are proposed to continue theory building around the more general model of the stakeholder firm. Researchers are encouraged to take up the analysis of stakeholder models and thereby contribute to the contemporary and future debates over the role of the corporation in American society.
Stretching the Iron Cage: The Constitution and Implications of Routine Workplace Resistance
Authors: Prasad Pushkala , Prasad Anshuman
Published: December 2003

Organizational scholars have shown considerable interest in the rise of complex systems of organizational control, sometimes referred to metaphorically as the process of tightening the iron cage, as well as patterns of workplace resistance to it. More recently, the scholarly spotlight seems to have shifted from formal modes of employee resistance to more informal or routine forms of workplace resistance. This paper presents a detailed ethnographic account of informal resistance and its ability to limit managerial control in a health maintenance organization undergoing the computerization of its administrative functions. Our study adopts a more problematic approach to understanding routine resistance, tracing its discursive constitution in the workplace. Using the findings of an ethnographic study involving observation and interviews, we show how routine resistance was discursively constituted and how it limited organizational control in interesting and unexpected ways. This discursive constitution was achieved through (a) owning resistance, (b) naming resistance, and (c) designating indirect resistance. The paper also analyzes how these different discursive constructions limited managerial control by affirming autonomous self-identities, renegotiating roles and relationships, and reinterpreting dominant managerial discourses. Finally, broader implications for understanding routine resistance in organizations are drawn.
Extending the Cyert-March Duopoly Model: Organizational and Economic Insights
Authors: Prietula Michael J. , Watson Harry S.
Published: December 2003

Two studies were conducted to further explore the organizational and economic insights provided by the Cyert-March duopoly model (C-M) described in A Behavioral Theory of the Firm (ABTOF, Cyert and March 1963). Study 1 examined the extent to which two firms that differed solely in the decision behavior of a routine would also differ in organizational (quasiresolution of conflict, uncertainty avoidance, problem-driven search, and organizational learning) and economic (profit, price, market share, cost) measures and impacts. Three such manipulations were separately examined, where each manipulation altered the relative propensity of the firm to be more or less reactive to three events: production growth pressure, price adjustment under organizational goal conflict, and initial price adjustment under profit goal failure. Analysis of the behaviors revealed how subtle changes in these key routines could generate complex organizational and economic effects that impact firm success. The dominant result demonstrated that organizations that did not perform well organizationally did not perform well economically. In addition, higher reactivity resulted in higher costs, in part because of quantified organizational constructs (e.g., slack, pressure). Study 2 examined the data from the first study to determine the extent to which the performance of the duopoly was consistent with a set of eight stylized economic facts drawn from the empirical literature on oligopoly. Study 2 demonstrated consistency with five of the eight stylized economic facts and provided partial support for two others. We conclude that behavioral constructs of ABTOF, as articulated in the Cyert-March duopoly model, provide behavior and performance capabilities that bridge the gap between game-theoretic models of duopoly and the computational and informational realities of organizations.
Organizational Incentives and Organizational Mortality
Authors: Shane Scott
Published: December 2003

Despite a long tradition of research on organizational mortality, organizational theorists have not examined the effect of incentive contracting on firm survival. This paper fills this gap by examining the effect of incentive contracting on the survival of U.S. business format franchise systems over the period 1984-1996. The paper finds empirical support for several hypotheses derived from efficient contracting theory. In general, large firms that adopt policies which screen agents, signal quality, and control agents' free-riding are more likely to survive than large firms which do not adopt these policies.
The Dynamics of Alignment: Insights from a Punctuated Equilibrium Model
Authors: Sabherwal Rajiv , Hirschheim Rudy , Goles Tim
Published: December 2003

Several prior articles have emphasized the importance of alignment between business and information system (IS) strategies, and between business and IS structures. Seeking to advance our understanding of alignment, we examine the dynamics of changes in alignment through strategy/structure interactions in the business and IS domains. More specifically, we address the following question: In what ways does alignment evolve over time?

Changes in the strategic IS management profile (which includes business strategy, IS strategy, business structure, and IS structure) over time are examined using a punctuated equilibrium model, involving long periods of relative stability, or evolutionary change, interrupted by short periods of quick and extensive, or revolutionary, change. Case studies of changes in business and IS strategies and structure over long time periods in three organizations suggest that the punctuated equilibrium model provides a valuable perspective for viewing these dynamics.

The cases suggest that a pattern of alignment may continue over a long period, because either the level of alignment is high or the managers do not recognize the low alignment as a problem. Revolutions, involving changes in most or all dimensions of the strategic IS management profile, interrupt the evolutionary changes. However, organizations hesitate to make such revolutionary changes in strategic IS management profiles. Complete revolutions apparently require a combination of strong triggers. Finally, post-revolution adjustments to one dimension of the strategic IS management profile seem to follow revolutionary changes.
Teamwork Quality and the Success of Innovative Projects: A Theoretical Concept and Empirical Evidence
Authors: Hoegl Martin , Gemuenden Hans Georg
Published: December 2003

An extensive body of literature indicates the importance of teamwork to the success of innovative projects. This growing awareness, that “good teamwork” increases the success of innovative projects, raises new questions: What is teamwork, and how can it be measured? Why and how is teamwork related to the success of innovative projects? How strong is the relationship between teamwork and various measures of project success such as performance or team member satisfaction? This article develops a comprehensive concept of the collaboration in teams, called Teamwork Quality (TWQ). The six facets of the TWQ construct, i.e., communication, coordination, balance of member contributions, mutual support, effort, and cohesion, are specified. Hypotheses regarding the relationship between TWQ and project success are tested using data from 575 team members, team leaders, and managers of 145 German software teams. The results of the structural equation models estimated show that TWQ (as rated by team members) is significantly associated with team performance as rated by team members, team leaders, and team-external managers. However, the magnitude of the relationship between TWQ and team performance varies by the perspective of the performance rater, i.e., manager vs. team leader vs. team members. Furthermore, TWQ shows a strong association with team members' personal success (i.e., work satisfaction and learning).
Controlling Decision-Making Practice in Organizations
Authors: Sutcliffe Kathleen M. , McNamara Gerry
Published: December 2003

How are decision practices fostered in organizations and how are they linked to decision outcomes? This study addresses these questions by examining one financial institution's efforts to standardize and control decision making across geographically separated organizational units. We argue that decision-maker behavior is situated and is not simply a function of individual choice. Rather, in organizational settings decision-makers are subject to a hierarchy of influences that affect the decision processes they use and their resulting decision choices. To test our ideas, we examined 900 borrower “risk rating” decisions and found general support for our hypotheses. Decision makers were more likely to use the prescribed practice when decisions were important, when the decision target was known, and when the decision maker was located in a larger subunit. Decision makers altered their decision practices in the short term, but in the long term they appeared to partially revert to their earlier practices. Reliance on prescribed practice fostered stability in decisions, but surprisingly appeared to negatively affect future judgments. The findings indicate that organizations can change the more microaspects of decision making, but these changes may be transitory. Moreover the results suggest that decision makers may become complacent when they rely on prescribed decision practices, a tendency that can have untoward consequences for the organizations in which they are embedded.
Networks, Diversity, and Productivity: The Social Capital of Corporate R&D Teams
Authors: Reagans Ray , Zuckerman Ezra W.
Published: December 2003

We argue that the debate regarding the performance implications of demographic diversity can be usefully reframed in terms of the network variables that reflect distinct forms of social capital. Scholars who are pessimistic about the performance of diverse teams base their view on the hypothesis that decreased network density—the average strength of the relationship among team members—lowers a team's capacity for coordination. The optimistic view is founded on the hypothesis that teams that are characterized by high network heterogeneity, whereby relationships on the team cut across salient demographic boundaries, enjoy an enhanced learning capability. We test each of these hypotheses directly and thereby avoid the problematic assumption that they contradict one another. Our analysis of data on the social networks, organizational tenure, and productivity of 224 corporate R…D teams indicates that both network variables help account for team productivity. These findings support a recasting of the diversity-performance debate in terms of the network processes that are more proximate to outcomes of interest.
Real Options Analysis and Strategic Decision Making
Authors: Bowman Edward H. , Moskowitz Gary T.
Published: December 2003

The real options approach is frequently advocated as an approach that offers a positive and radical reassessment of the value of risk and exploration. We examine a recent case where Merck used the real options approach to justify an investment in an R&D project. This case is used to highlight some of the problems associated with using real options. We note that the assumptions incorporated in most standard option valuation models can conflict with the conclusions reached by strategic analysis. As a result, users of real options models should understand the quantitative aspects of these models, and may often need to create a customized model for each situation. The difficulty of developing customized models may explain, in part, the limited use of the real options approach in strategic analysis.
Information Processing Moderators of the Effectiveness of Trust-Based Governance in Interfirm R&D Collaboration
Authors: Carson Stephen J. , Madhok Anoop , Varman Rohit , John George
Published: December 2003

It is generally assumed that improved outcomes accompany the use of trust as a governance mechanism in an interfirm relationship. Briefly, trust is a social lubricant that reduces the friction costs of existing trade and/or serves to increase the scope of trade. In contrast to this universalistic view, we posit that the performance of trust-based governance is contingent on the ability of trading partners to “read” each other and learn about counterpart behavior. These information-processing abilities allow firms to assess partner trustworthiness better, which reduces the risk of misplaced trust. The increased efficacy of communication and learning from one another also enables them to better capitalize from the adaptation and revision possibilities uncovered through trust-based governance during the task-execution phase. Given the central role of these cognitive requirements, we assess these contingent effects with data from a knowledge-intensive task setting. Using a sample of 129 firms that have engaged outside contractors on client-sponsored R&D projects, we find strong support for our thesis. Specifically, we find that trust-based governance has a larger positive impact on task performance when the client is more skilled at understanding the outsourced tasks at hand, the task itself requires skills that are relatively more readily taught (less tacit), and the task itself is organized in parallel with work being done at the contractor as well as the client. As a corollary, we also find that firms adopt trust-based governance to a greater extent as these information-processing abilities increase, as well as with the colocation of the contractor and client. Suggestions for engineering trust-based governance are offered.
Shifting Gears, Shifting Niches: Organizational Inertia and Change in the Evolution of the U.S. Automobile Industry, 1885–1981
Authors: Dobrev Stanislav D. , Kim Tai-Young , Carroll Glenn R.
Published: December 2003

We examine how experiential learning affects organizational change and its consequences on firm mortality. We develop hypotheses about the interactions of experiences with a specific type of organizational change on the one hand, and environmental stability, organizational size, and organizational niche width on the other hand. Our findings draw from analysis of the U.S. automobile industry between 1885 and 1981 and support the general prediction that “process” effects of change in the organizational core elevate the hazard of failure. We also find that a dynamic interpretation of organizational environments as comprised of other organizations helps to explicate the interplay between organization and environmental forces that shape the occurrence and outcome of transformation.
Sharing Meaning Across Occupational Communities: The Transformation of Understanding on a Production Floor
Authors: Bechky Beth A.
Published: December 2003

This paper suggests that knowledge is shared in organizations through the transformation of occupational communities' situated understandings of their work. In this paper, I link the misunderstandings between engineers, technicians, and assemblers on a production floor to their work contexts, and demonstrate how members of these communities overcome such problems by cocreating common ground that transforms their understanding of the product and the production process. In particular, I find that the communities' knowledge-sharing difficulties are rooted in differences in their language, the locus of their practice, and their conceptualization of the product. When communication problems arise, if members of these communities provide solutions which invoke the differences in the work contexts and create common ground between the communities, they can transform the understandings of others and generate a richer understanding of the product and the problems they face.
Cascading Organizational Change
Authors: Hannan Michael T. , Pólos László , Carroll Glenn R.
Published: December 2003

This article develops a formal theory of the structural aspects of organizational change. It concentrates on changes in an organization's architecture, depicted as a code system. It models the common process whereby an initial architectural change prompts other changes in the organization, generating a cascade of changes that represents the full reorganization. The main argument ties centrality of the organizational unit initiating a change to the total time that the organization spends reorganizing and to the associated opportunity costs. The central theorem holds that the expected deleterious effect of a change in architecture on the mortality hazard increases with viscosity and the intricacy of the organizational design.
Sequential Variety in Work Processes
Authors: Pentland Brian T.
Published: December 2003

This paper introduces the concept of sequential variety as a way to measure variability in the sequence of steps used to perform a work process. There is reason to expect that such variability may influence a range of outcomes, such as flexibility and quality. Two alternative ways to operationalize sequential variety are demonstrated and compared to traditional measures of task variety in four task units. The findings provide empirical support for treating sequential variety as a distinct construct. In particular, sequential variety appears to provide an index of tacit, procedural knowledge, while task variety may relate more closely to explicit, declarative knowledge.
Interaction Value Analysis: When Structured Communication Benefits Organizations
Authors: Nasrallah Walid , Levitt Raymond , Glynn Peter
Published: December 2003

We present a mathematical model that predicts and explains the circumstances under which a management-defined communication structure can add value to an organization. This model provides a game-theoretical basis for contingent organizational design by relating empirical observations of real organizations to the solution of a rational choice model based on game theory. We constructed a multiple-player, noncooperative game in which players have full knowledge of, and universal communication access to, each other. These players allocate the scarce resource of their attention among potential interaction partners. It struck us that this game sometimes did and sometimes did not have a “core,” i.e., a confluence of individual optima (Nash equilibrium) that was also optimal for the whole group. Some circumstances allow the best structure to emerge from many individual decisions, whereas other circumstances require the imposition of structured communication channels by a central decision maker. Strong management control of communication structure adds no value in business environments where the game has a “core” i.e., where a centrally imposed optimum would dictate the same communications patterns as those defined by the Nash equilibrium that emerges spontaneously when each participant optimizes locally. Trade in an ideal market is the iconic example of such environments. In our model, other combinations of conditions fail to yield a core, even though a single stable Nash equilibrium always exists. The difference between aggregate effectiveness at the Nash equilibrium and the maximal feasible aggregate effectiveness that could be centrally dictated is the value that management can provide through enforcing the globally optimum communication regime. The predictions of this simple model about the conditions that favor more- or less-structured communications agree surprisingly well with accepted organizational contingency theory. Our simple model thus provides a sound theoretical foundation for many aspects of contingent organizational design.
Developing the Professional Self-Concept: Role Model Construals in Early, Middle, and Late Career Stages
Authors: Gibson Donald E.
Published: December 2003

While previous literature tends to focus on role models as significant other people, particularly in one's early life, this study finds that individuals tend to construe their role models as a selection process of attributes from others throughout their career. I discovered that individuals primarily construe their role models along positive/negative, global/specific, close/distant, and hierarchically superior/peer-subordinate dimensions, and that across the career span, the tendency to observe role models did not change. Rather, the emphasis placed on different dimensions of role models changes. Early-stage respondents who are working on creating a viable self-concept were more likely to construe their role models as positive, close, and sources of a range of attributes. Middle- and late-stage respondents were more likely to see their role models as sources of specific, and often negative, attributes. The study suggests that these observed patterns are related to individuals' increasing confidence in their professional self-concept. In early stages, individuals pay attention to role models to create a viable self-concept; in middle stages, they seek to refine their self-concept, and in late stages, they seek to enhance and affirm their self-concept.
A Mean-Variance Model for Route Guidance in Advanced Traveler Information Systems
Authors: Sen Suvrajeet , Pillai Rekha , Joshi Shirish , Rathi Ajay K.
Published: December 2003

Traditional models of route generation are based on choosing routes that minimize expected travel-time between origin and destination. Such approaches do not account for the fact that travelers often incorporate travel-time variability within their decision making. Thus, a route with lower travel-time variability is preferred by some travelers, even if such a route is not one with the lowest mean travel-time. Such traveler behavior is best captured by a multiobjective model in which the choice of a route is based on the mean as well as the variance of the path travel-time. Our route-planning model is intended to help travelers make choices that reflect their decision-making process better. We formulate a network flow multiobjective model in which one of the objectives (expectation) is linear, whereas, the other (variance) is quadratic. In order to present the user with a series of options, we solve a series of parametric 0-1 quadratic integer programs. By utilizing the network structure of the problem, we devise an effective algorithm in which the 0-1 quadratic program is solved by using a continuous relaxation together with an enumeration of some selected paths. Finally, we note that the data requirements for the model can be easily satisfied in practice.
A Network Based Model for Traffic Sensor Location with Implications on O/D Matrix Estimates
Authors: Bianco Lucio , Confessore Giuseppe , Reverberi Pierfrancesco
Published: December 2003

In this paper, we define and solve the sensor location problem (SLP), that is, we look for the minimum number and location of counting points in order to infer all traffic flows in a transport network. We set up a couple of greedy heuristics that find lower and upper bounds on the number of sensors for a set of randomly generated networks. We prove that solving the SLP implies that the Origin/Destination (O/D) matrix estimation error be always bounded. With respect to alternative sensor location strategies, simulation experiments show that: (i) measurement costs being equal, the O/D estimation error is lower, and (ii) conversely, O/D estimation error being equal, the number of sensors is smaller.
Modeling the Commute Activity-Travel Pattern of Workers: Formulation and Empirical Analysis
Authors: Bhat Chandra
Published: December 2003

This paper proposes a methodological framework to analyze the activity and travel pattern of workers during the evening commute. The framework uses a discrete-continuous econometric system to model jointly the decision to participate in an activity during the evening commute and the following attributes of the participation: activity type, activity duration, and travel time deviation to the activity location relative to the direct travel time from work to home. The model parameters are estimated using a sample of workers from the 1991 Boston Household Activity Survey. The paper also presents mathematical expressions to evaluate the effect of changes in sociodemographic variables and policy-relevant exogenous variables on the temporal pattern of trips and cold starts attributable to commute stops. The application of the model indicates that failure to accommodate the joint nature of the activity decisions during the evening commute can lead to misdirected policy actions for traffic congestion alleviation and for mobile-source emissions reduction.
Simultaneous Estimation of the Origin-Destination Matrices and Travel-Cost Coefficient for Congested Networks in a Stochastic User Equilibrium
Authors: Yang Hai , Meng Qiang , Bell Michael G. H.
Published: December 2003

This article proposes an optimization model for simultaneous estimation of an origin-destination (O-D) matrix and a travel-cost coefficient for congested networks in a logit-based stochastic user equilibrium (SUE). The model is formulated in the form of a standard differentiable, nonlinear optimization problem with analytical stochastic user equilibrium constraints. Explicit expressions of the derivatives of the stochastic user equilibrium constraints with respect to origin-destination demand, link flow, and travel-cost coefficient are derived and computed efficiently through a stochastic network-loading approach. A successive quadratic-programming algorithm using the derivative information is applied to solve the simultaneous estimation model. This algorithm converges to a Karusch-Kuhn-Tucker point of the problem under certain conditions. The proposed model and algorithm are illustrated with a numerical example.
Fixed Point Approaches to the Estimation of O/D Matrices Using Traffic Counts on Congested Networks
Authors: Cascetta Ennio , Postorino Maria Nadia
Published: December 2003

Over recent years, increasing attention has been devoted to the problem of estimating Origin/Destination (O/D) matrices by using traffic counts, named in the following O/D Count Based Estimation (ODCBE) problem. These methods combine traffic flow measures with other available information to “correct” and improve an initial estimate of the O/D trip matrix. Virtually all models and procedures proposed in the literature are formulated as mathematical programming problems. Most ODCBE models use a relationship relating traffic counts to the unknown O/D matrix; this relationship is often in the form of an explicit estimate of the assignment matrix, i.e., of the fractions of O/D flows using each link of the network for which traffic counts are available. The computation of the assignment matrix is not trivial for congested networks, where travel costs and path choice fractions depend on flows. This problem has been dealt with in relatively few papers in the literature, usually formulated as a bilevel optimisation model under the assumption of a Deterministic User Equilibrium (DUE) assignment model. In this paper, the general within-day static ODCBE problem for congested networks is formulated as a fixed-point problem of an implicit function which results from the solution of a mathematical programming problem. In other words, the solution of the ODCBE problem is an O/D matrix that, once assigned to the network, reproduces flows and costs consistent with the values used to compute the assignment matrix. Fixed-point theorems and algorithms have been extended to the problem at hand. Different fixed-point algorithms, namely, Functional Iteration, Method of Successive Averages, and Method of Successive Averages with Decreasing Reinitialisation are proposed, and their performances are compared on a small test network. It has been verified that all algorithms converge to the same solution, though with different speeds. Furthermore, the fixed-point solution outperforms the initial solution, both in terms of bias and capability to reproduce both counted and noncounted flows.
Models and Algorithms for Single-Depot Vehicle Scheduling
Authors: Freling Richard , Wagelmans Albert P. M. , Paixão José M. Pinto
Published: December 2003

Vehicle scheduling is the process of assigning vehicles to a set of predetermined trips with fixed starting and ending times, while minimizing capital and operating costs. This paper considers modeling, algorithmic, and computational aspects of the polynomially solvable case in which there is a single depot and vehicles are identical. A quasiassignment formulation is reviewed and an alternative asymmetric assignment formulation is given. The main contributions of the paper are a new two-phase approach which is valid in the case of a special cost structure, an auction algorithm for the quasiassignment problem, a core-oriented approach, and an extensive computational study. New algorithms are compared with the most successful algorithms for the vehicle-scheduling problem, using both randomly generated and real-life data. The new algorithms show a significant performance improvement with respect to computation time. Such improvement can, for example, be very important when this particular vehicle-scheduling problem appears as a subproblem in more complex vehicle- and crew-scheduling problems.
Scheduling Trains and Containers with Due Dates and Dynamic Arrivals
Authors: Yano Candace A. , Newman Alexandra M.
Published: December 2003

We consider the problem of scheduling trains and containers (or trucks and pallets) between a depot and a destination. Goods arrive at the depot dynamically over time and have distinct due dates at the destination. There is a fixed-charge transportation cost for each vehicle, and each vehicle has the same capacity. The cost of holding goods may differ between the depot and the destination. The goal is to minimize the sum of transportation and holding costs.

For the case in which all goods have the same holding costs, we consider two variations: one in which the holding cost at the destination is less than that at the origin, and one in which the relationship is reversed. For the first variation, we derive properties of the optimal solution which provide the basis for an O(T 2) solution procedure. For the second variation, we introduce a new definition of a regeneration state, derive strong characterizations of the shipment schedule within a regeneration interval, and develop an O(T 4) procedure.

We also analyze two multi-item scenarios. In the first, for each item, the holding cost at the origin is less than that at the destination; in the second, the relationship is reversed for all items. We generalize several of the structural results for the single-item problem to the corresponding multi-item case. We also show that the optimal vehicle schedule can be obtained by solving a related single-item problem in which the item demands are aggregated in a particular way. The optimal assignment of customer orders to vehicles can then be found by solving a linear program.
A Modeling Framework for Passenger Assignment on a Transport Network with Timetables
Authors: Nguyen Sang , Pallottino Stefano , Malucelli Federico
Published: December 2003

This paper presents a new graph theoretic framework for the passenger assignment problem that encompasses simultaneously the departure time and the route choice. The implicit FIFO access to transit lines is taken into account by the concept of available capacity. This notion of flow priority has not been considered explicitly in previous models. A traffic equilibrium model is described and a computational procedure based on asymmetric boarding penalty functions is suggested.