Nonparametric estimation of renewal processes from count data

Abstract: The authors address the problem of estimating an inter‐event distribution on the basis of count data. They derive a nonparametric maximum likelihood estimate of the inter‐event distribution utilizing the EM algorithm both in the case of an ordinary renewal process and in the case of an equilibrium renewal process. In the latter case, the iterative estimation procedure follows the basic scheme proposed by Vardi for estimating an inter‐event distribution on the basis of time‐interval data; it combines the outputs of the E‐step corresponding to the inter‐event distribution and to the length‐biased distribution. The authors also investigate a penalized likelihood approach to provide the proposed estimation procedure with regularization capabilities. They evaluate the practical estimation procedure using simulated count data and apply it to real count data representing the elongation of coffee‐tree leafy axes.     

The Influence of Spanish‐Language Media on Latino Public Opinion and Group Consciousness*

Objective. This article determines if the use of Spanish‐language media among Latinos influences public opinion on various policy issues and group consciousness. Methods. Using a 2004 national public opinion survey of U.S. Latinos, a multivariate analysis is run to determine the effect of language media preference on immigration policy, abortion, same‐sex marriage, and three measures of group consciousness. Results. I find more frequent use of Spanish‐language media leads to more liberal attitudes toward immigration, but has no effect on opinions toward abortion and same‐sex marriage. I also find increased use of Spanish‐language media leads to increased levels of group consciousness. Conclusions. The differences in attitudes are due to the diverging goals of Spanish‐language and English‐language media. The effect of using Spanish‐language media serves to promote a sense of group consciousness among Latinos by reinforcing roots in Latin America and the commonalities among Latinos of varying national origin.     

Generalized Random Sign and Alert Delay models for imperfect maintenance

This paper considers the modelling of the process of Corrective and condition-based Preventive Maintenance, for complex repairable systems. In order to take into account the dependency between both types of maintenance and the possibility of imperfect maintenance, Generalized Competing Risks models have been introduced in “Doyen and Gaudoin (J Appl Probab 43:825–839, 2006)”. In this paper, we study two classes of these models, the Generalized Random Sign and Generalized Alert Delay models. A Generalized Competing Risks model can be built as a generalization of a particular Usual Competing Risks model, either by using a virtual age framework or not. The models properties are studied and their parameterizations are discussed. Finally, simulation results and an application to real data are presented.     

FAMILY VALUES AND THE REGULATION OF LABOR

To be efficient, flexible labor markets require geographically mobile workers. Otherwise firms can take advantage of workers' immobility and extract rents at their expense. In cultures with strong family ties, moving away from home is costly. Thus, to limit the rents of firms and to avoid moving, individuals with strong family ties rationally choose regulated labor markets, even though regulation generates higher unemployment and lower incomes. Empirically, we find that individuals who inherit stronger family ties are less mobile, have lower wages and higher unemployment, and support more stringent labor market regulations. We find a positive association between labor market rigidities at the beginning of the 21st century and family values prevailing before World War II, and between family structures in the Middle Ages and current desire for labor market regulation. Both results suggest that labor market regulations have deep cultural roots.     

基于批判性思维的大学英语课堂教学过程控制研究

基于传统的大学英语教学存在重知识传授,轻思维能力培养的倾向,学生课堂参与度低,英语教学费时低效.在此利用批判性思维设计课堂教学,将课堂教学过程看作一个系统,分析教师、学生和教学过程在本系统中的关系和地位.作为主体的教师需要通过有效的教学过程设计,借助教学过程中的新手段、方法和评价机制,促进作为客体的学生实现主动反馈,实现主客体间的有效信息交互和主体驱动下的客体主动反馈,最终实现提高课堂教学质量的目的.     

Degree-constrained orientations of embedded graphs

We investigate the problem of orienting the edges of an embedded graph in such a way that the resulting digraph fulfills given in-degree specifications both for the vertices and for the faces of the embedding. This primal-dual orientation problem was first proposed by Frank for the case of planar graphs, in conjunction with the question for a good characterization of the existence of such orientations. We answer this question by showing that a feasible orientation of a planar embedding, if it exists, can be constructed by combining certain parts of a primally feasible orientation and a dually feasible orientation. For the general case of arbitrary embeddings, we show that the number of feasible orientations is bounded by \(2^{2g}\), where \(g\) is the genus of the embedding. Our proof also yields a fixed-parameter algorithm for determining all feasible orientations parameterized by the genus. In contrast to these positive results, however, we also show that the problem becomes \(N\!P\)-complete even for a fixed genus if only upper and lower bounds on the in-degrees are specified instead of exact values.