Route first—Cluster second methods for vehicle routing

In this paper we consider route first—cluster second methods for the vehicle routing problem. Extensions to the basic method both to improve its effectiveness and to enable it to cope with practical constraints are described. Computational results are given for the method applied to standard vehicle routing problems drawn from the literature.     

The competitive advantage potential of vertical integration

There is a widely held belief that backward vertical integration provides firms with the potential for a low-cost competitive advantage, and forward vertical integration provides them with the potential for a differentiation advantage. This study builds theory that underpins that belief, and then tests the theory using a sample of large firms. While our findings do not support the relationship between backward vertical integration and low cost, they do provide strong support for arguments linking forward vertical integration with differentiation-based competitive advantage.     

Examining the Effects of Feedback Accuracy and Timing on Skill Acquisition

ABSTRACT

Feedback involves providing information about past performance and indicating how to improve future performance. Although the literature contains numerous examples of feedback as an effective method for improving performance across a range of organizational settings, much remains unknown about the specifics of how feedback acts to change behavior. This study evaluated the combined effects of feedback accuracy (100%, 80%, 20%) and timing (feedback following each trial or after a block of 25 trials) on skill acquisition in undergraduate students when presented with a computerized match-to-sample task that required participants to learn the names of shapes. Results reveal that feedback accuracy had a significantly greater effect on performance than the timing of the feedback.     

An Ecological Risk Assessment of Nonnative Boas and Pythons as Potentially Invasive Species in the United States

The growing international trade in live wildlife has the potential to result in continuing establishment of nonnative animal populations in the United States. Snakes may pose particularly high risks as potentially invasive species, as exemplified by the decimation of Guam's vertebrate fauna by the accidentally introduced brown tree snake. Herein, ecological and commercial predictors of the likelihood of establishment of invasive populations were used to model risk associated with legal commercial imports of 23 species of boas, pythons, and relatives into the United States during the period 1989-2000. Data on ecological variables were collected from multiple sources, while data on commercial variables were collated from import records maintained by the U.S. Fish and Wildlife Service. Results of the risk-assessment models indicate that species including boa constrictors (Boa constrictor), ball pythons (Python regius), and reticulated pythons (P. reticulatus) may pose particularly high risks as potentially invasive species. Recommendations for reducing risk of establishment of invasive populations of snakes and/or pathogens include temporary quarantine of imports to increase detection rates of nonnative pathogens, increasing research attention to reptile pathogens, reducing the risk that nonnative snakes will reach certain areas with high numbers of federally listed species (such as the Florida Keys), and attempting to better educate individuals purchasing reptiles.     

Emotions in context: Revolutionary accelerators,hope, moral outrage,and other emotions in the making of Nicaragua's revolution

Building on the social movement/revolutions and recent social movement emotions literature and using interviews and oral history from revolutionary Nicaragua, I make a case for recognizing the significance of emotions when studying revolutions. The essay aims for a contextual understanding of the role of emotions in the making of revolution during the insurrectionary period in Nicaragua. These are examined from the vantage point of revolutionary accelerators the conflictual event-contexts from which revolutionary actors emerge. Through the historical analysis of testimonies associated with a number of politically significant events that changed the course of political dynamics in 1970s Nicaragua, the piece illustrates: (1) how events function as generators of revolutionary action and (2) how event-related emotions such as anger and fear, but primarily moral outrage and hope, contribute to a transformation in consciousness that leads potential participants to define their circumstances as needing their revolutionary involvement. It also attempts to demonstrate how the latter two emotions—moral outrage and hope—are dominant under different event-contexts. Lastly, the relationships between these emotions and how these are connected to revolutionary accelerators are similarly explored.     

Measuring college students' alcohol consumption in natural drinking environments: field methodologies for bars and parties

In recent years researchers have paid substantial attention to the issue of college students' alcohol use. One limitation to the current literature is an over reliance on retrospective, self-report survey data. This article presents field methodologies for measuring college students' alcohol consumption in natural drinking environments. Specifically, we present the methodology from a large field study of student drinking environments along with some illustrative data from the same study. Field surveys, observational methods, sampling issues, and breath alcohol concentration sample collection are detailed.     

Perceptions of environmental supports on the physical activity behaviors of university men and women: a preliminary investigation

OBJECTIVE: To examine perception differences between genders of university sidewalks and safety from crime on the physical activity (PA) behaviors of undergraduate students. PARTICIPANTS: Five hundred and sixty undergraduate students participated in this study. METHODS: The authors derived questions from the South Carolina Environmental Supports for Physical Activity Questionnaire (SCESPAQ) and National College Health Risk Behavior Survey (NCHRS) PA module. RESULTS: The authors found a significant mean difference between genders for the Moderate Intensity Item (eg, walking and biking) and the Flexibility Item, t(558)=3.602, p=.001, and t(558)=1.946, p=.050, respectively. Of participants surveyed, 30% of women perceived this campus to be extremely safe compared with 49% of men, t(558)=4.240, p=.001. Gender and the perceptions of sidewalk presence were significantly related (p<.05) to respondents' walking or bicycling patterns. CONCLUSIONS: Perceptions of sidewalks and safety from crime on this university campus were related to students' PA behaviors.     

Perceptions of the availability of recreational physical activity facilities on a university campus

OBJECTIVE: The author's purpose in this study was to assess perceptions of recreational physical activity (PA) facilities on a university campus. PARTICIPANTS: Four-hundred and sixty-seven undergraduate students participated in this study (women = 293; men = 174). RESULTS: The author found a significant percentage difference between women and men concerning the availability of racquetball courts on campus, 47% vs 63%, t (465) = -3.274. The author similarly found a significant percentage difference between women and men's perceptions concerning the availability of tennis courts. Twenty-seven percent of women were unaware or did not know tennis courts were available for PA, in comparison with 19% of men t (465) = -2.413. Awareness of recreational facilities revealed significant differences (Pillai's Trace = .189, p < .05) between freshmen and upperclassmen. Freshmen perceived themselves to have access to fewer recreational facilities on campus. CONCLUSION: More efforts to increase awareness of PA facilities are needed on university campuses.     

Erratum to: On the Social Validity of Behavior-Analytic Communication: a Call for Research and Description of One Method

The Analysis of Verbal Behavior -     

A flexible parametric survival model which allows a bathtub-shaped hazard rate function

A new parametric (three-parameter) survival distribution, the lognormal–power function distribution, with flexible behaviour is introduced. Its hazard rate function can be either unimodal, monotonically decreasing or can exhibit a bathtub shape. Special cases include the lognormal distribution and the power function distribution, with finite support. Regions of parameter space where the various forms of the hazard-rate function prevail are established analytically. The distribution lends itself readily to accelerated life regression modelling. Applications to five data sets taken from the literature are given. Also it is shown how the distribution can behave like a Weibull distribution (with negative aging) for certain parameter values.