AN OPTIMIZATION-BASED METHODOLOGY FOR RELEASE SCHEDULING

Operational-level scheduling decisions on the factory floor include the release policy and the dispatching rule. Recent work by researchers suggests that factory performance depends heavily on the release policy. Several heuristic factory release rules have been developed that generate release decisions based on the status of the bottleneck machine. The heuristic rules perform very well in reducing the work-in-process inventory. However, factory output schedules generated by these rules generally fail to match the demand pattern, creating excessive finished goods inventory and/or excessive backorders. To overcome these difficulties, a computationally efficient integer programming model is proposed for release scheduling.     

ANALYSIS OF THE LEAD TIME AND LEARNING FOR CAPACITY EXPANSIONS

Firms capable of reducing the time required to bring new products to the marketplace realize significant competitive gains. In this context, the existing literature on capacity expansion is limited because it does not consider the lead time required to construct and operationalize new capacity. Models are introduced here that capture the capacity expansion lead time as well as two types of learning. Specifically, learning may reduce the lead time or cost required to complete an expansion. Analytic and numerical results show that the optimal solution can be significantly affected by the explicit treatment of the lead time and learning.     

THE HUMAN SIDE OF MISTAKE‐PROOFING

Poka‐yoke (mistake‐proofing) is a powerful quality improvement approach, which usually employs relatively simple devices to achieve marked improvements. Inexpensive jigs, fixtures, switches, and gauges act as obvious environmental cues to signal mistake detection. Poka‐yoke has been largely ignored as an avenue for serious academic research. This paper provides scientific underpinning to the largely anecdotal mistake‐proofing literature, by drawing upon research from psychology and cognitive science concerning human error. We delineate areas where additional research would be worthwhile, and guide practitioners in understanding what they are trying to accomplish and how poka‐yoke devices attain this end.     

Models for Dependent Extremes Using Stable Mixtures

Abstract.  This paper unifies and extends results on a class of multivariate extreme value (EV) models studied by Hougaard, Crowder and Tawn. In these models, both unconditional and conditional distributions are themselves EV distributions, and all lower-dimensional marginals and maxima belong to the class. One interpretation of the models is as size mixtures of EV distributions, where the mixing is by positive stable distributions. A second interpretation is as exponential-stable location mixtures (for Gumbel) or as power-stable scale mixtures (for non-Gumbel EV distributions). A third interpretation is through a peaks over thresholds model with a positive stable intensity. The mixing variables are used as a modelling tool and for better understanding and model checking. We study EV analogues of components of variance models, and new time series, spatial and continuous parameter models for extreme values. The results are applied to data from a pitting corrosion investigation.     

Variance Reduction in Smoothing Splines

Abstract.  We develop a variance reduction method for smoothing splines. For a given point of estimation, we define a variance-reduced spline estimate as a linear combination of classical spline estimates at three nearby points. We first develop a variance reduction method for spline estimators in univariate regression models. We then develop an analogous variance reduction method for spline estimators in clustered/longitudinal models. Simulation studies are performed which demonstrate the efficacy of our variance reduction methods in finite sample settings. Finally, a real data analysis with the motorcycle data set is performed. Here we consider variance estimation and generate 95% pointwise confidence intervals for the unknown regression function.     

Rewiring global networks at local events: congresses in the stock photo trade

Digital technologies have enabled the geographical expansion of production and the distribution of creative goods and communication. Simultaneously, the number of trade fairs and congresses has increased. This rise of temporary encounters has led to theorizations of events as marketplaces, learning sites and field‐configuring practices. This article elaborates on the metaphor of rewiring to propose and empirically demonstrate a further role of industry events for global business. Drawing on the case of the global stock photo trade, we use a unique survey to map the global network of sales partnerships as well as interviews conducted at international lead congresses to demonstrate how these events are enacted as social relays. Our findings demonstrate how temporary face‐to‐face contact facilitates long distance relationships between organizations and how it dynamically shapes the global industry network. Thus, we contribute to closing the gap between social action at the micro level, organizational linkages at the meso level and the structure of global industry networks at the macro level.     

EDUCATIONAL BENEFITS AND MILITARY SERVICE: AN ANALYSIS OF ENLISTMENT,REENLISTMENT, AND VETERANS' BENEFIT USAGE 1991–2005*

Montgomery GI Bill (MGIB) educational benefits are a prime recruiting tool in today's all‐volunteer military. This paper studies the effects of changes in education benefits using data of the period 1990–2005. Higher benefits lead to higher separation due to both pure incentive effects and by attracting more college‐oriented youth into military service. We deal with potential selection issues by distinguishing between anticipated and unanticipated benefit changes. Higher education benefits are associated with higher separation from the Army and Air Force, but not the other services. A $10,000 increase in MGIB benefits is estimated to increase usage by about 5 percentage points, but the duration of usage is estimated to be insensitive to benefit levels. (JEL H52, I21, J24)     

The Dynamics of Occupational Prestige: 1975–2000*

Les données sur l'espace urbain recueillies à Kitchener-Waterloo, en Ontario, jumelées avec celles d'une première étude réalisée en 1975, sont utilisées comme point d'observation pour analyser à nouveau la stabilité historique du prestige professionnel. L'article suggère que la structure de la courbe de distribution du prestige a été négligée en faveur de statistiques décrivant la stabilité du classement par ordre de grandeur et que le changement historique depuis environ 1975 est, du point de vue qualitatif, différent de celui des périodes antérieures. Notre hypothèse est que la courbe de distribution du prestige professionnel est devenue plus constante et que le classement par ordre de grandeur s'est nettement déplacé.
Urban-area data collected in Kitchener-Waterloo, Ontario, twinned with an earlier study from 1975, are used as a vantage point for re-examining the historical stability of occupational prestige. The paper proposes that the shape of the prestige distribution has been neglected in favour of statistics describing stability in rank order and that historical change since around 1975 is qualitatively different than for earlier periods. Our hypothesis is that the distribution of occupational prestige has become more equal and that the rank order has shifted noticeably.     

STOCK OWNERSHIP AND CONGRESSIONAL ELECTIONS: THE POLITICAL ECONOMY OF THE MUTUAL FUND REVOLUTION

We find that higher stock ownership rates are linked to an upward shift in the Republican share of the House popular vote since the late 1980s, consistent with theories that property interests affect voting. To proxy for discontinuous stock ownership rates, we use equity mutual fund costs, which have fallen, are negatively correlated with stock ownership rates and the Republican vote share in the long run, and help explain short‐run changes along with midterm elections, economic conditions, and presidential popularity. Findings suggest that the major parties’ shares of the House popular vote will fluctuate around 50% until other factors trigger a political realignment. (JEL D72, G11)     

Students' Views on the Relationship between Religion and Science: Analyses of Results from a Comparative Survey*

Deux enquêtes ont été effectuées auprès d'étudiants de deux universitiés canadiennes sur leurs perceptions des relations entre la religion, la science et le sens de la vie. Les données démontrent que, tandis que les étudiants pensent régulièrement à la signification de la vie, leurs opinions sur la religion par rapport à la science ne laissent voir que de bas niveaux de corrélation. Les étudiants ont indiqué que leur plus grande préoccupation par rapport au sens de la vie était due à leur famille et à leurs amis. Dans l'ensemble, les données suggèrent que les étudiants considèrent la religion et la science comme des entités indépendantes, mais seulement en ce qui concerne la part qu'elles occupent dans la vie des individus et dans les affaires mondiales.
Students at two distinctly different Canadian universities were surveyed about their perceptions of the relationship between religion, science, and thinking about the meaning of life. The data show that while students regularly think about the latter, their views on religion and science show only low levels of correlation with each other. Students indicated that their greatest insights into the meaning of life came from family and friends. Overall, the data suggest that students view religion and science as independent entities, both with respect to the part that these play in the life of individuals and in world affairs.