德国最新可再生能源技术前瞻

德国大力推广可再生能源新技术 化石能源将越来越短缺,并且价格不断上涨.全球1/4的温室气体排放来自能源消费.     

Modeling attendance at Spanish professional football league

Prediction of demand for professional sports is increasingly drawing the attention of economists. We apply linear mixed models for modeling attendance figures at Spanish professional football. We investigate economic variables, such as the price of the tickets or the size of the market, and sporting variables, such as the quality of a team or the level of competition within the league, as potential predictors of attendance. It turns out that a model with temporally correlated random team effects provides good forecasts of attendance at a time horizon of two seasons. Results from this model agree with economic theory.     

Measuring Segregation When Units are Small: A Parametric Approach

This article considers the issue of measuring segregation in a population of units that contain few individuals (e.g., establishments, classrooms). When units are small, the usual segregation indices, which are based on sample proportions, are biased. We propose a parametric solution: the probability that an individual within a given unit belongs to the minority is assumed to be distributed as a mixture of Beta distributions. The model can be estimated and indices deduced. Simulations show that this new method performs well compared to existing ones, even in the case of misspecification. An application to residential segregation in France according to parents’ nationalities is then undertaken. This article has online supplementary materials.     

Parabolic acceleration of the EM algorithm

A new acceleration scheme for optimization procedures is defined through geometric considerations and applied to the EM algorithm. In many cases it is able to circumvent the problem of stagnation. No modification of the original algorithm is required. It is simply used as a software component. Thus the new scheme can be easily implemented to accelerate a fixed point algorithm maximizing some objective function. Some practical examples and simulations are presented to show its ability to accelerate EM-type algorithms converging slowly.     

Why Is Infant Mortality Higher in Boys Than in Girls? A New Hypothesis Based on Preconception Environment and Evidence From a Large Sample of Twins

Infant mortality is higher in boys than girls in most parts of the world. This has been explained by sex differences in genetic and biological makeup, with boys being biologically weaker and more susceptible to diseases and premature death. At the same time, recent studies have found that numerous preconception or prenatal environmental factors affect the probability of a baby being conceived male or female. I propose that these environmental factors also explain sex differences in mortality. I contribute a new methodology of distinguishing between child biology and preconception environment by comparing male-female differences in mortality across opposite-sex twins, same-sex twins, and all twins. Using a large sample of twins from sub-Saharan Africa, I find that both preconception environment and child biology increase the mortality of male infants, but the effect of biology is substantially smaller than the literature suggests. I also estimate the interacting effects of biology with some intrauterine and external environmental factors, including birth order within a twin pair, social status, and climate. I find that a twin is more likely to be male if he is the firstborn, born to an educated mother, or born in certain climatic conditions. Male firstborns are more likely to survive than female firstborns, but only during the neonatal period. Finally, mortality is not affected by the interactions between biology and climate or between biology and social status.     

A Matter of Reputation and Pride: Associations between Perceived External Reputation,Pride in Membership,Job Satisfaction and Turnover Intentions

This study investigates how job satisfaction and turnover intentions are related to external reputation as perceived by employees and their pride in membership. Based on a cross‐sectional survey including 439 employees, it also provides insights into external reputation as a possible source of collective pride. Study results indicate that, in agreement with social identity theory, outsiders' views of the organization are closely associated with employees' pride in organizational membership as well as job satisfaction. Both pride and job satisfaction mediate the relationship between perceived external reputation and turnover intentions. Hence, a favourable reputation matters in managing turnover intentions and is closely related to employee pride and satisfaction. Tenure of employees is positively associated with pride while intensive customer contact is negatively related to perceived external reputation and pride. Implications pinpoint the need for alignment of reputation management and human resources management. Furthermore, managers need to focus on new staff and employees with frequent customer contact and should implement pride‐building strategies according to the tenure of employees and intensity of customer contact.