An M/G/1 clearing queueing system with setup time and multiple vacations for an unreliable server

This paper studies an M/G/1 clearing queueing system with setup time and multiple vacations, in which all present customers in the system are served simultaneously and breakdowns may occur in busy or setup period. We investigate the stationary distribution of system size and the Laplace–Stieltjes transform of sojourn time. In addition, various performance measures are discussed, such as the mean system size at arbitrary time and the mean length of a vacation circle. Moreover, a cost analysis is carried out for this queueing system. Numerical results are presented to study the sensitivity of the system parameters on the expected cost function and system performances.     

How Moroccan‐Dutch parents learn in communities of practice: Evaluating a bottom‐up parenting programme

Research shows that top‐down‐designed parenting programmes do not always meet the needs of postmigration parents. Bottom‐up programmes by migrant organizations hold a promise to fill this gap; however, research about these programmes and appropriate evaluation methodologies is scarce. Drawing upon Wenger's ( 2010 ) “communities of practice,” this paper explores an alternative perspective on parenting programme evaluation. Findings are presented from a study looking into social learning processes of postmigration parents who participated in a bottom‐up programme about raising teenagers in urban areas. Using an ethnographically inspired method combined with a preprogramme and postprogramme design, 115 Moroccan‐Dutch mothers and fathers from 15 programme groups participated. Results show that the programme provided a social learning space in which parents used themselves as resources to learn collectively about parenting. Moreover, parents consciously engaged in learning interactions across learning spaces stretched into their social networks. These analyses showed how parents' development of “learning citizenship” (Wenger, 2009 ) provides us with insight in collective learning dimensions present in a bottom‐up parenting programme, which is often not included in evaluation studies. Implications for practitioners as facilitators of parents' collective learning are presented.     

Measuring conflict management,emotional self-efficacy,and problem solving confidence in an evaluation of outdoor programs for inner-city youth in Baltimore,Maryland

Substantial evidence supports the value of outdoor education programs for promoting healthy adolescent development, yet measurement of program outcomes often lacks rigor. Accurately assessing the impacts of programs that seek to promote positive youth development is critical for determining whether youth are benefitting as intended, identifying best practices and areas for improvement, and informing decisions about which programs to invest in.We generated brief, customized instruments for measuring three outcomes among youth participants in Baltimore City Outward Bound programs: conflict management, emotional self-efficacy, and problem solving confidence. Measures were validated through exploratory and confirmatory factor analyses of pilot-testing data from two groups of program participants. We describe our process of identifying outcomes for measurement, developing and adapting measurement instruments, and validating these instruments.The finalized measures support evaluations of outdoor education programs serving urban adolescent youth. Such evaluations enhance accountability by determining if youth are benefiting from programs as intended, and strengthen the case for investment in programs with demonstrated success.     

社会资本与身心健康--概念辨析基础上的关系再检验

社会资本与健康研究领域存在核心概念界定不清与理论解释欠缺两大不足。文章在社会网络的视角下对社会资本、社会凝聚和社会支持三个相互杂糅的概念进行辨析区分，并在此基础上以调查数据实证检验了社会资本对身心健康的作用效果与影响机制。结果显示，在控制社会凝聚和社会支持作用的条件下，社会资本依然对自评健康和心理健康存在显著的独立影响，但其对两种健康在影响因素和影响方向上呈现一些差异。其中，网络规模和网络顶端对自评健康和心理健康都具有显著的正向作用，而心理健康同时还受到网络差异的负向影响。从这个角度而言，社会资本对个体身心健康的影响并不必然是积极正向的。     

The shifting landscape of LGBT organizational research

Over the past generation, sexual minorities—particularly lesbian, gay, bisexual, and transgender (LGBT) persons—have gained increased visibility in the public arena. Yet organizational research has lagged behind in recognizing and studying this category of organizational members. This article offers a critical review of this growing body of research. More specifically, we identify and discuss four dominant scholarly frames that have informed LGBT organizational research from the late nineteenth century to date. The frames include a “medical abnormality,” “deviant social role,” “collective identity,” and “social distinctiveness” view of sexual minorities. We argue that these frames have profoundly shaped the scope and range of organizational scholarship devoted to sexual minorities by showing that scholars using such contrasted frames have been drawn to very different research questions with respect to sexual minorities. We document and discuss the main and contrasted questions asked within each of these frames and show how they have both enabled and constrained LGBT organizational research. We conclude by calling for more attention to the frames organizational scholars adopt when studying sexual minorities, but also for more research on both minority and majority sexual orientations in organizations.     

Analytic strategies for longitudinal networks with missing data

Missing data are often problematic when analyzing complete longitudinal social network data. We review approaches for accommodating missing data when analyzing longitudinal network data with stochastic actor-based models. One common practice is to restrict analyses to participants observed at most or all time points, to achieve model convergence. We propose and evaluate an alternative, more inclusive approach to sub-setting and analyzing longitudinal network data, using data from a school friendship network observed at four waves (N = 694). Compared to standard practices, our approach retained more information from partially observed participants, generated a more representative analytic sample, and led to less biased model estimates for this case study. The implications and potential applications for longitudinal network analysis are discussed.     

Why Frequency is Not Well Defined for Engineering Systems with Nonexponential Failure Times

Dr. Yellman proposes to define frequency as “a time‐rate of events of a specified type over a particular time interval.” We review why no definition of frequency, including this one, can satisfy both of two conditions: (1) the definition should agree with the ordinary meaning of frequency, such as that less frequent events are less likely to occur than more frequent events, over any particular time interval for which the frequencies of both are defined; and (2) the definition should be applicable not only to exponentially distributed times between (or until) events, but also to some nonexponential (e.g., uniformly distributed) times. We make the simple point that no definition can satisfy (1) and (2) by showing that any definition that determines which of any two uniformly distributed times has the higher “frequency” (or that determines that they have the same “frequency,” if neither is higher) must assign a higher frequency number to the distribution with the lower probability of occurrence over some time intervals. Dr. Yellman's proposed phrase, “time‐rate of events … over a particular time interval” is profoundly ambiguous in such cases, as the instantaneous failure rates vary over an infinitely wide range (e.g., from one to infinity), making it unclear which value is denoted by the phrase “time‐rate of events.”     

新时期贪污贿赂犯罪防控问题研究——基于法经济学视角的实证分析

贪污贿赂犯罪人员利用职权谋取私利具有经济学理性特征，因此，其行为必然遵从经济学的基本法则。用经济分析的方法研究了贪污贿赂犯罪的产生机理，探讨了贪污贿赂犯罪的预防措施。基于犯罪经济成本收益理论，通过实证分析，认为应增大犯罪成本，控制犯罪收益，以有效预防和减少贪污贿赂犯罪。     

‘We fight for all living things’: countering misconceptions about the radical animal liberation movement

This qualitative content analysis of online documents compiled from the North American Animal Liberation Front (ALF), Earth Liberation Kollective (ELK) and Grassroots Ontario Animal Liberation (GOAL) network websites and Facebook pages explores how activism within the Radical Animal Liberation Movement (RALM) intersects with other social movements. While most literature to date traces the RALM’s (dis)junctures with other forms of social justice activism through analyses of their broad ideological assumptions, or the views of renowned RALM scholars, this research provides authentic insights into the voices of Canadian, American and Mexican activists as they are represented in documents they author themselves. Like activists in anarchistic, anti-capitalist, immigrant rights, Indigenous, prison abolition, prisoner support and radical feminist movements, those in the RALM critique capitalism, colonialism, hierarchy, racism, sexism, state power and the prison industrial complex. Our research calls into question the existing narratives that depict the RALM as an extremist, single-issue movement oblivious to all other forms of social inequality, injustice, marginalization and oppression. Rather, RALM activists are building alliances with other radical social movements to achieve the common goal of ending both human and animal suffering and exploitation.     

Diffusion Indexes With Sparse Loadings

The use of large-dimensional factor models in forecasting has received much attention in the literature with the consensus being that improvements on forecasts can be achieved when comparing with standard models. However, recent contributions in the literature have demonstrated that care needs to be taken when choosing which variables to include in the model. A number of different approaches to determining these variables have been put forward. These are, however, often based on ad hoc procedures or abandon the underlying theoretical factor model. In this article, we will take a different approach to the problem by using the least absolute shrinkage and selection operator (LASSO) as a variable selection method to choose between the possible variables and thus obtain sparse loadings from which factors or diffusion indexes can be formed. This allows us to build a more parsimonious factor model that is better suited for forecasting compared to the traditional principal components (PC) approach. We provide an asymptotic analysis of the estimator and illustrate its merits empirically in a forecasting experiment based on U.S. macroeconomic data. Overall we find that compared to PC we obtain improvements in forecasting accuracy and thus find it to be an important alternative to PC. Supplementary materials for this article are available online.