Modeling cost-delivery trade-offs for distribution logistics by a generalized PVRP model

This article provides a mathematical model to support management in making decisions about cost-delivery trade-offs in the case of cost-delivery flexibilities in distribution logistics. The optimization problem can be modeled as a bi-objective periodic vehicle routing problem, which is known as NP-hard. In the periodic vehicle routing problem considered in this study, no delivery patterns are pre-defined, instead the patterns are the result of the optimization process of the model. In addition, delivery time flexibilities are incorporated in the model. A heuristic solution method for realistic problem sizes is based on the tabu search procedure, and a real case study illustrates the applicability of the solution concept.     

Beyond demand–control: Emotional labour and symptoms of burnout in teachers

Abstract

Teaching is a profession that involves a high level of emotional labour. This includes such behaviours as surface acting (displaying an emotion that is not actually felt), deep acting (the activity undertaken to actually feel a required emotion), and suppression of emotion. In many professions, this emotional labour is thought to be related to high levels of burnout. The aim of our study was to show that emotional labour has a unique relationship with burnout that is separate from its relationship with the variables of the Demand Control Support (DCS) model. Emotional labour was studied, together with the variables of the Karasek Job Demand Control Support model, in a random sample of 365 mathematics teachers in the Netherlands. We used the Dutch Questionnaire on Emotional Labor (D-QEL) that measures: (1) surface acting, (2) deep acting, (3) suppression, and (4) emotional consonance. In line with other studies, job characteristics were found to be specifically related to emotional exhaustion. Surface acting was significantly related to depersonalization, and emotional consonance (the absence of emotional labour) was related to personal accomplishment. We conclude that whereas the DCS model has been valuable for understanding emotional exhaustion, emotional labour provides an additional perspective for understanding work stress.     

Book reviews

Statistical Papers -     

Tagungen

Ohne Zusammenfassung     

An exact test for trend among binomial proportions based on a modified Baumgartner-Weiß-Schindler statistic

The Cochran-Armitage test is the most frequently used test for trend among binomial proportions. This test can be performed based on the asymptotic normality of its test statistic or based on an exact null distribution. As an alternative, a recently introduced modification of the Baumgartner-Weiß-Schindler statistic, a novel nonparametric statistic, can be used. Simulation results indicate that the exact test based on this modification is preferable to the Cochran-Armitage test. This exact test is less conservative and more powerful than the exact Cochran-Armitage test. The power comparison to the asymptotic Cochran-Armitage test does not show a clear winner, but the difference in power is usually small. The exact test based on the modification is recommended here because, in contrast to the asymptotic Cochran-Armitage test, it guarantees a type I error rate less than or equal to the significance level. Moreover, an exact test is often more appropriate than an asymptotic test because randomization rather than random sampling is the norm, for example in biomedical research. The methods are illustrated with an example data set.     

Zur Gestaltung des Verhältnisses von Erwerbsarbeit und Privatleben in den ‚Creative Industries‘

The “creative industries” are considered to be a model of the future world of work and “pioneers” of new forms of earning and new forms of “work and life”. On the basis of an empirical study of the creative industries sub-sector (architecture, advertising, design, film, IT services and multimedia etc.), the contribution is concerned with the effects of changed demands of employment on the relationship between work and life. The focus is on the temporal de-limitation of employment conditions in the form of flexibilisation of the place and length of working hours as well as on the spatial de-limitation in the form of changing places of work and increasing demands for mobility. We raise the question of whether workers in this field are just coping with the changes in work or whether they are developing their own, active strategies to redefine the boundaries of work and to find a new work-life balance.