Design and implementation methodology based on Petri net formalism of flexible manufacturing systems control

This paper presents an aided design methodology of flexible manufacturing system control with a view to industrial implementation. The approach considered through a modelling phase, the a validation phase by simulation and finally a distributed implementation phase. In the modelling phase, based on the Petri net formalism, we demonstrate the hierarchical aspect which separates the part flow control and the product resource control. In addition, we emphasize generic aspects which allow us to use an object-oriented approach. These aspects and the set of modelled objects are directly used in the simulation and production phases after an automatic translation in an implementation language (ADA in our case). In consequence, the distributed location for those two phases is well facilitated from the viewpoint of the approach used.     

MOONLIGHTING OVER THE BUSINESS CYCLE

Using data from the 1979 National Longitudinal Survey of Youth, we examine the cyclicality of moonlighting by gender. We estimate a random-effects Tobit model of moonlighting among working men and women and find that while male moonlighting behavior does not fluctuate significantly with the business cycle, female moonlighting does. The cyclicality of female moonlighting has, nonetheless, varied over the course of the past 35 yr. Female moonlighting seemed to behave countercyclically during much of the 1980s and early 1990s, confirming the popular media belief that moonlighting is more likely to occur during periods of economic distress. Yet, this countercyclical behavior disappears during the 1993–1999 period to become procyclical by the early twentieth century. The recent procyclicality of female moonlighting supports the idea that female workers respond to a need for "just-in-time" employment following the economic upturn of the mid- to late 1990s. ( JEL J2, E32)     

Is More Truly Merrier?: Mentoring and the Practice of Law

Cet article examine deux questions sur le mentorat. D'abord, qui est le plus susceptible de bénéficier de services de mentorat au cours de sa carrière? Ensuite, comment le mentorat influence‐t‐il les carrières des professionnels? En utilisant une enquête longitudinale sur des avocats, les auteures évaluent l'incidence des postes et des aspirations en début de carrière sur les chances de bénéficier de services de mentorat. Elles mesurent les bénéfices du mentorat au moyen des récompenses de carrière intrinsèques et extrinsèques, pour découvrir que le contexte organisationnel et les attributs individuels constituent d'importants prédicteurs de qui bénéficiera de mentorat. Les professionnels ayant de multiples mentors se sont avérés les grands gagnants, en ce qu'ils obtiennent des récompenses de carrière plus importantes et plus diversifiées que ceux n'ayant pas de mentor. This paper addresses two questions regarding mentoring: First, who is most likely to receive mentorship during their career? And second, how does mentorship shape the careers of professionals? Using a longitudinal survey of lawyers, we evaluate the impact of early career positions and aspirations on the chances for mentorship. We assess the benefits of mentorship across extrinsic and intrinsic career rewards. We find organizational context and individual attributes are important predictors of who receives mentorship. Professionals with multiple mentors were the big winners in that they obtain greater and more diverse career rewards over those with one or no mentors.     

History and social theory: notes on the contribution of British Marxist historiography to our understanding of class

Conçu comme une contribution au dialogue actuel entre l'histoire et la sociologie, cet essai étudie le travail des historiens marxistes britanniques, Maurice Dobb, Rodney Hilton, Christopher Hill, E.J. Hobsbawm, et E.P. Thompson, des perspectives de leur emploi et développement du concept de classe. On prétend qu'ils ont contribuéà la compréhension de l'histoire et de la classe dans la mesure où ils ont essayé de corriger le caractère figé de la notion marxiste de base/superstructure et de celle de sociologie de la classe-comme-catégorie en interprétant la notion de classe comme un phénomène historique et en redéfinissant l'analyse de classe comme l'analyse de la lutte des classes.
Intended as a contribution to the current dialogue between history and sociology, this essay surveys the work of the British Marxist historians, Maurice Dobb, Rodney Hilton, Christopher Hill, E.J. Hobsbawm, and E.P. Thompson, in terms of their use and development of the concept of class. It is argued that through their historical studies and critical essays, in which they have sought to overcome the 'statics' of the base-superstructure model of Marxism and the class-as-category model of sociology by emphasizing class as an historical phenomenon and reformulating class analysis as 'class struggle' analysis, they have contributed to our understanding of the historical process and to our understanding of class.     

Occupational status attainments of university graduates: individual attributes and labour market effects compared

Ce document analyse le processus de realisation d'un statut professionnel pour cinq cohortes de diplômés d'université, hommes et femmes, durant la période s'étendant de 1960 à 1976. Après avoir reçu leurs diplômés, les hommes, comparés à leurs homologues féminins, sont parvenus, en general, à un statut professionnel plus élevé, réparti sur une échelle plus large. Les conséquences des differences socio-économiques sur la réalisation d'un statut professionnel se sont avèrées minimes ou insignifiantes pour les deux sexes. Les effets des différences de l'enseignement reçu sur le statut professionnel sont plus grands. Les rendements pour l'étudiant avec une moyenne académique élevée sont les mêmes pour les hommes que pour les femmes. Les hommes qui ont poursuivi de hautes études supérieures ont éprouvé un meilleur rendement de méme que les femmes qui se sont spécialisées en sciences. La condition du marché du travail au moment ou ces étudiants ont obtenu leurs diplômes s'est avérée le facteur le plus déterminant dans la réalisation d'un statut professionnel. L'on maintient que la recherche sur la réalisation d'un statut professionnel a largement négligé les facteurs structurels tels que les conséquences du marché du travail, et sa concentration sur le prestige professionnel a entretenu le déguisement des differences entre les sexes dans la réalisation d'un statut professionnel. This paper analyzes the occupational status attainment process for five cohorts of male and female university graduates spanning the time period 1960 to 1976. When compared to their female counterparts, males on the whole achieve higher occupational status after graduation and experience a wider distribution of status. The effect of socioeconomic variables on occupational attainment are found to be either small or insignificant for both sexes. The effects of educational variables on occupational attainment are greater. The returns to a high undergraduate academic average are similar for males and females; males experience a higher return to graduate study while females experience a larger return to majoring in science. The state of the labour market at time of graduation is found to have the largest effect on occupational status attainment. It is argued that occupational status attainment research has largely neglected such structural factors as labour market effects, and its focus on occupational prestige has tended to mask sex differences in occupational status attainment.     

Work Hard,Play Hard?: A Comparison of Male and Female Lawyers' Time in Paid and Unpaid Work and Participation in Leisure Activities

Les auteures tentent de déterminer le temps que les professionnels, hommes et femmes, passent à effectuer du travail rémunéré ou non, et la façon dont cela influe sur leur participation à différentes activités de loisirs. Elles se fondent sur des données provenant d'avocats professant dans différents milieux juridiques. Elles constatent que les hommes rapportent consacrer plus de temps au travail rémunéré et aux loisirs, alors que les femmes accordent plus de temps aux travaux ménagers ainsi qu'aux soins des enfants. Les résultats semblent démontrer que les occasions dans l'ensemble plus importantes de loisirs chez les hommes comparées à celles des femmes seraient attribuables à des relations inattendues entre la participation des hommes aux travaux domestiques et aux soins des enfants, et leurs activités de loisirs. Les auteures présentent différentes explications à ces résultats. There has been a considerable amount of research that documents how women and men spend their time in different work and home tasks. We examine how much time professional women and men spend in paid and unpaid work and how this relates to their participation in different leisure activities. We also explore whether time in paid and unpaid work has gender‐specific effects on leisure participation. In examining these issues, we rely on data from lawyers working in different legal settings. Our results show that, as hypothesized, men report more time in paid work and leisure whereas women devote more time to housework and childcare. An unexpected finding is that the time men spend in housework or childcare is either unrelated or positively related to their leisure participation. These results suggest that men's greater overall opportunities for leisure compared with women's appear to stem from the unanticipated relationships between men's involvement in housework and childcare and their leisure activities. We raise several possible explanations for these findings.     

A Non‐Parametric Estimator of the Spectral Density of a Continuous‐Time Gaussian Process Observed at Random Times

Abstract. In numerous applications data are observed at random times and an estimated graph of the spectral density may be relevant for characterizing and explaining phenomena. By using a wavelet analysis, one derives a non‐parametric estimator of the spectral density of a Gaussian process with stationary increments (or a stationary Gaussian process) from the observation of one path at random discrete times. For every positive frequency, this estimator is proved to satisfy a central limit theorem with a convergence rate depending on the roughness of the process and the moment of random durations between successive observations. In the case of stationary Gaussian processes, one can compare this estimator with estimators based on the empirical periodogram. Both estimators reach the same optimal rate of convergence, but the estimator based on wavelet analysis converges for a different class of random times. Simulation examples and an application to biological data are also provided.