Lim K.,Pohang University of Science and Technology |
Lee K.,Rutgers Business School |
Chang S.Y.,Pohang University of Science and Technology
Theoretical Computer Science | Year: 2011
We consider the online parallel machine scheduling problem of minimizing the makespan under eligibility constraints that restrict each job to be processed only on one of its eligible machines. The greedy approach known as AW is known to be optimal for this problem when the number of machines, m, is a power of 2, i.e. m=2k. However, in other cases, the gap between the best known competitive ratio and its lower bound can be as large as 1. In this paper, we construct new competitive ratio and its lower bound whose gap is no more than an irrational number which is approximately 0.1967 and establish optimality for the cases when the number of machines can be written as a sum of two powers of 2, i.e. m=2k+2k′for k≠k′. We further analyze the case with seven machines showing that their gap is no more than 1180(≈0.00556). Moreover, we present new lower bounds of the competitive ratio for the cases with interval and nested eligibility as well as improved competitive ratios for several cases with GoS eligibility. © 2011 Elsevier B.V. All rights reserved.
Gao S.,City University of Hong Kong |
Chen W.,Rutgers Business School
Automatica | Year: 2015
Abstract A lot of problems in automatic control aim at seeking top designs for discrete-event systems. In many cases, these problems are most suitable to be modeled as simulation optimization problems, and a key question for solving these problems is how to efficiently and accurately select the top designs given a limited simulation budget. This paper considers the generalized problem of selecting the top m designs from a finite set of design alternatives based on simulated outputs, subject to a constraint on the total number of samples available. The quality of the selection is measured by the expected opportunity cost, which penalizes particularly bad choices more than the slightly incorrect selections and is preferred by risk-neutral practitioners and decision makers. An efficient simulation budget allocation procedure, called EOC-m, is developed for this problem. The efficiency of the proposed method is illustrated through numerical testing. © 2015 Elsevier Ltd.
Gibbs J.L.,Rutgers University |
Rozaidi N.A.,Rutgers University |
Eisenberg J.,Rutgers Business School
Journal of Computer-Mediated Communication | Year: 2013
This study explores the ways in which the affordances of social media not only increase open communication and knowledge sharing, but also promote covert behavior, creating dialectical tensions for distributed workers that must be communicatively managed. Drawing on a case study of the engineering division of a distributed high tech start-up, we find our participants navigate tensions in visibility-invisibility, engagement-disengagement, and sharing-control and strategically manage these tensions to preserve both openness and ambiguity. These findings highlight ways in which organizational members limit as well as share knowledge through social media, and the productive role of tensions in enabling them to attend to multiple goals. © 2013 International Communication Association.
Lee K.,Rutgers Business School |
Lim K.,BK21 Project
Journal of Scheduling | Year: 2013
We consider the semi-online parallel machine scheduling problem of minimizing the makespan given a priori information: the total processing time, the largest processing time, the combination of the previous two or the optimal makespan. We propose a new algorithm that can be applied to the problem with the known total or largest processing time and prove that it has improved competitive ratios for the cases with a small number of machines. Improved lower bounds of the competitive ratio are also provided by presenting adversary lower bound examples. © 2013 Springer Science+Business Media New York.
Dobrzykowski D.,Rutgers Business School |
Saboori Deilami V.,University of Toledo |
Hong P.,University of Toledo |
Kim S.-C.,Hanyang University
International Journal of Production Economics | Year: 2014
As the operations management (OM) and supply chain management (SCM) field has evolved, a greater emphasis on services has emerged. The healthcare industry represents an important sector within services, however, little is known about the current state of research into healthcare OM and SCM. The purpose of this research is to conduct a structured analysis of OM and SCM studies conducted in healthcare and inform three key questions: (1) what are the primary topics or themes in the extant healthcare OM and SCM literature, (2) what are the prevalent methodological approaches employed in healthcare OM and SCM, and (3) what does the future of OM and SCM research in healthcare hold? The questions are informed via a structured analysis of healthcare papers published between 1982 and 2011 in seven esteemed scholarly journal outlets in the OM and SCM field - Decision Sciences Journal, International Journal of Operations and Production Management, International Journal of Production Economics, Journal of Operations Management, Journal of Supply Chain Management, Production and Operations Management, and Supply Chain Management: An International Journal. Through screening 9979 papers, and carefully analyzing the literature, this study makes at least four important contributions by: (1) using quantitative methods to identify the current investigatory themes, (2) quantifying methodological trends, (3) providing a qualitative narrative description of the top research themes, and 4) qualitatively describing directions for future research. © 2013 Elsevier B.V.