The Use of Latent Semantic Analysis in Operations Management Research

In this article, we introduce the use of Latent Semantic Analysis (LSA) as a technique for uncovering the intellectual structure of a discipline. LSA is an emerging quantitative method for content analysis that combines rigorous statistical techniques and scholarly judgment as it proceeds to extract and decipher key latent factors. We provide a stepwise explanation and illustration for implementing LSA. To demonstrate LSA's ability to uncover the intellectual structure of a discipline, we present a study of the field of Operations Management. We also discuss a number of potential applications of LSA to show how it can be used in empirical Operations Management research, specifically in areas that can benefit from analyzing large volumes of unstructured textual data.     

Optimal Policy for a Stochastic Scheduling Problem with Applications to Surgical Scheduling

We consider the stochastic, single‐machine earliness/tardiness problem (SET), with the sequence of processing of the jobs and their due‐dates as decisions and the objective of minimizing the sum of the expected earliness and tardiness costs over all the jobs. In a recent paper, Baker ( 2014 ) shows the optimality of the Shortest‐Variance‐First (SVF) rule under the following two assumptions: (a) The processing duration of each job follows a normal distribution. (b) The earliness and tardiness cost parameters are the same for all the jobs. In this study, we consider problem SET under assumption (b). We generalize Baker's result by establishing the optimality of the SVF rule for more general distributions of the processing durations and a more general objective function. Specifically, we show that the SVF rule is optimal under the assumption of dilation ordering of the processing durations. Since convex ordering implies dilation ordering (under finite means), the SVF sequence is also optimal under convex ordering of the processing durations. We also study the effect of variability of the processing durations of the jobs on the optimal cost. An application of problem SET in surgical scheduling is discussed.     

Approximations to Optimal k‐Unit Cycles for Single‐Gripper and Dual‐Gripper Robotic Cells

We consider the problem of scheduling operations in bufferless robotic cells that produce identical parts using either single‐gripper or dual‐gripper robots. The objective is to find a cyclic sequence of robot moves that minimizes the long‐run average time to produce a part or, equivalently, maximizes the throughput. Obtaining an efficient algorithm for an optimum k‐unit cyclic solution (k ≥ 1) has been a longstanding open problem. For both single‐gripper and dual‐gripper cells, the approximation algorithms in this paper provide the best‐known performance guarantees (obtainable in polynomial time) for an optimal cyclic solution. We provide two algorithms that have a running time linear in the number of machines: for single‐gripper cells (respectively, dual‐gripper cells), the performance guarantee is 9/7 (respectively, 3/2). The domain considered is free‐pickup cells with constant intermachine travel time. Our structural analysis is an important step toward resolving the complexity status of finding an optimal cyclic solution in either a single‐gripper or a dual‐gripper cell. We also identify optimal cyclic solutions for a variety of special cases. Our analysis provides production managers valuable insights into the schedules that maximize productivity for both single‐gripper and dual‐gripper cells for any combination of processing requirements and physical parameters.     

Optimal Coordination in Distributed Software Development

The construction of a software system requires not only individual coding effort from team members to realize the various functionalities, but also adequate team coordination to integrate the developed code into a consistent, efficient, and bug‐free system. On the one hand, continuous coding without adequate coordination can cause serious system inconsistencies and faults that may subsequently require significant corrective effort. On the other hand, frequent integrations can be disruptive to the team and delay development progress. This tradeoff motivates the need for a good coordination policy. Both the complexity and the importance of coordination is accentuated in distributed software development (DSD), where a software project is developed by multiple, geographically‐distributed sub‐teams. The need for coordination in DSD exists both within one sub‐team and across different sub‐teams. The latter type of coordination involves communication across spatial boundaries (different locations) and possibly temporal boundaries (different time zones), and is a major challenge that DSD faces. In this study, we model both inter‐ and intra‐sub‐team coordination in DSD based on the characteristics of the systems being developed by the sub‐teams, the deadline for completion, and the nature of division adopted by the sub‐teams with respect to development and integration activities. Our analysis of optimal coordination policies in DSD shows that integration activities by one sub‐team not only benefit that sub‐team (as is the case in co‐located development) but can also help the other sub‐teams by providing greater visibility, thereby resulting in a higher integration frequency relative to co‐located development. Analytical results are presented to demonstrate how the characteristics of the projects and the sub‐teams, and the efficiency of communication across the sub‐teams, affect coordination and productivity. We also investigate the pros and cons of using specialized integration sub‐teams and find that their advantage decreases as the project schedule becomes tighter. Decentralized decisions and asymmetric subsystems are also discussed.     

A New Variant of the Bivariate Setting the Clock Back to Zero Property

Raja Rao et al. (1993 Raja Rao , B. , Damaraju , C. V. , Alhumoud , J. M. ( 1993 ). Setting the clock back to zero property of a class of bivariate life distributions . Commun. Statist. Theor. Meth. 22 ( 7 ): 2067 – 2080 .[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) introduced the bivariate setting the clock back to zero property. A new variant of this property is introduced that is appropriate for analysing a broader area of practical situations. Some distributions possessing the proposed property are presented. Applications of this property for simplifying the computation of the bivariate mean residual life function and the bivariate percentile residual life function are studied. The relation between the proposed property with the one studied by Raja Rao and Talwalker (1990 Raja Rao , B. , Talwalker , S. (1990). Setting the clock back to zero property of a family of life distributions. J. Statist. Plann. Infer. 24:347–352. [Google Scholar]) and the bivariate lack of memory property is studied.     

English Language Proficiency Among the Foreign Born in the United States, 1980–2007: Duration,Age, Cohort Effects

This study employs pooled data from the 1980 through 2000 censuses and 2001 through 2007 American Community Survey data to study English language proficiency among foreign‐born in a dynamic framework. Our findings show continuing significance of duration of stay and age at migration and declining English language proficiency across successive cohorts. Additionally, analysis enabled by availability of single‐year data from 2000 to 2007 indicates acquisition of language proficiency as steepest during first 9 years upon arrival and for migrating age group 6–17. Further, we find significant differences by education, regions of origin, racial groups, and by regions of residence.