Worcester Polytechnic Institute

About: Worcester Polytechnic Institute is a education organization based out in Worcester, Massachusetts, United States. It is known for research contribution in the topics: Computer science & Population. The organization has 6270 authors who have published 12704 publications receiving 332081 citations. The organization is also known as: WPI.

Infeasibility of super efficiency data envelopment analysis models

Abstract: The paper investigates the infeasibility of super-efficiency data envelopment analysis (DEA) models in which the unit under evaluation is excluded from the reference set. Necessary and sufficient conditions are provided for infeasibility of the super-efficiency DEA measures. By the returns to scale (RTS) classifications obtained from the standard DEA model, we can further locate the position of the unit under evaluation when infeasibility occurs. It is shown that the ranking of the total set of efficient DMUs is impossible because of the infeasibility of super-efficiency DEA models. Also we are able to identify the endpoint positions of the extreme efficient units. The results are useful for sensitivity analysis of efficiency classifications.

Verification and change-impact analysis of access-control policies

Abstract: Sensitive data are increasingly available on-line through the Web and other distributed protocols. This heightens the need to carefully control access to data. Control means not only preventing the leakage of data but also permitting access to necessary information. Indeed, the same datum is often treated differently depending on context. System designers create policies to express conditions on the access to data. To reduce source clutter and improve maintenance, developers increasingly use domain-specific, declarative languages to express these policies. In turn, administrators need to analyze policies relative to properties, and to understand the effect of policy changes even in the absence of properties. This paper presents Margrave, a software suite for analyzing role-based access-control policies. Margrave includes a verifier that analyzes policies written in the XACML language, translating them into a form of decision-diagram to answer queries. It also provides semantic differencing information between versions of policies. We have implemented these techniques and applied them to policies from a working software application.

Technological Embeddedness and Organizational Change

Abstract: While various theories have been proposed to explain how technology leads to organizational change, in general they have focused either on the technology and ignored the influence of human agency, or on social interaction and ignored the technology. In this paper, we propose a new theory of technology-mediated organizational change that bridges these two extremes. Using grounded theory methodology, we conducted a three-year study of an enterprise system implementation. From the data collected, we identified embeddedness as central to the process of change. When embedded in technology, organizational elements such as routines and roles acquire a material aspect, in addition to the ostensive and performative aspects identified by Feldman and Pentland (2003). Our new theory employs the lens of critical realism because in our view, common constructivist perspectives such as structuration theory or actor network theory have limited our understanding of technology as a mediator of organizational change. Using a critical realist perspective, our theory explains the process of change as a three-stage cycle in which the ostensive, performative, and material aspects of organizational elements interact differently in each stage.

The Economics of Director Heterogeneity

Abstract: We investigate the potential costs and benefits of firms constituting a heterogeneous pool of directors relative to more homogeneous boards. We measure director heterogeneity along six separate dimensions and divide board heterogeneity into occupational and social components. Our empirical analysis indicates that corporate complexity and managerial control exhibit significant influence on board heterogeneity. Using the heterogeneity of the county population of the firm’s headquarters as an instrument, we also find that investors place valuation premiums on heterogeneous boards in complex firms but discount heterogeneity in less complex firms. Overall, our analysis indicates greater heterogeneity may not necessarily improve board efficacy. Government agencies, shareholder groups, and social activists frequently advocate and call for greater heterogeneity among directors on corporate boards. Proponents of greater board heterogeneity argue that managers and firms benefit from directors bringing diverse social and occupational viewpoints to the boardroom. Large international firms such as PepsiCo and Aon Corp indicate social heterogeneity among directors proves helpful in developing new products and strategies. 1 A 1995 Catalyst (2004) survey found that Fortune 500 chief executive officers (CEOs) considered director heterogeneity an important “bottom-line” or profitability consideration. Activist investor groups such as Catalyst, ICCR, and TIAA-CREF argue that homogeneous boards composed of the CEO’s own peers may be less effective advisors and monitors. In early 2009, the California Public Employees Retirement System issued a report indicating that board diversity leads to greater shareholder returns and firm profitability. Yet, the push for less uniformity in the boardroom may be driven by social or ethical reasons rather than firm profitability (Agrawal and Knoeber, 2001). Farrell and Hersch (2005) examine gender heterogeneity and find women board members have no influence on firm performance. They argue that firms simply include members of minority groups to build a public image of inclusiveness or tokenism. In contrast, Adams and Ferreira (2009) state that gender diversity has a positive and significant impact on board effectiveness. In a general analysis using a large survey of 30,000 interviews from the United States, Putnam (2007) reports that heterogeneity among individuals decreases cooperation, impedes communication, and leads to social loafing. Board

Power System Observability: A Practical Algorithm Using Network Topology

Abstract: A power system is observable if the measurements made on it allow determination of bus voltage magnitude and angle at every bus of the network. This paper outlines the theoretical basis for an algorithm for determining observability. Based on this theory, an algorithm for networks containing both bus injection and line flow measurements is presented.