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21.
Given the fragmented structure of child‐care assistance in the United States, it has been difficult to obtain accurate estimates of which families are assisted, through which mechanisms, and at what level. Making use of survey data from New York City, we analyze the distribution of several forms of public child‐care assistance. Results suggest that about 40% of all families with young children receive some form of child‐care assistance. Considering all forms of assistance, the distribution of child‐care help is targeted in both expected and some unexpected ways. Implications of these results are discussed in the context of U.S. child‐care policies governing access and benefit levels.  相似文献   
22.
This article uses data from 50 qualitative interviews with female part‐time workers in low‐level jobs in Britain to illustrate their attitudes, orientations and aspirations towards paid work. The research reports two main findings. Firstly, even female part‐time workers at the bottom end of the occupational structure are not a homogeneous group of workers. Secondly, they are not all highly satisfied with their jobs. The article argues that many women (especially those in working‐class households) still do not have a genuine choice between ‘family work’ and ‘market work’. It concludes by presenting a theoretical model of orientations to work.  相似文献   
23.
The author characterizes the copula associated with the bivariate survival model of Clayton (1978) as the only absolutely continuous copula that is preserved under bivariate truncation.  相似文献   
24.
Evolution strategies (ESs) are a special class of probabilistic, direct, global optimization methods. They are similar to genetic algorithms but work in continuous spaces and have the additional capability of self-adapting their major strategy parameters. This paper presents the most important features of ESs, namely their self-adaptation, as well as their robustness and potential for parallelization which they share with other evolutionary algorithms.Besides the early (1 + 1)-ES and its underlying theoretical results, the modern ( + )-ES and (, )-ES are presented with special emphasis on the self-adaptation of strategy parameters, a mechanism which enables the algorithm to evolve not only the object variables but also the characteristics of the probability distributions of normally distributed mutations. The self-adaptation property of the algorithm is also illustrated by an experimental example.The robustness of ESs is demonstrated for noisy fitness evaluations and by its application to discrete optimization problems, namely the travelling salesman problem (TSP).Finally, the paper concludes by summarizing existing work and general possibilities regarding the parallelization of evolution strategies and evolutionary algorithms in general.  相似文献   
25.
Path analysis is used to examine the causal relationships among selected objective and subjective factors associated with a household's expectation of future financial condition. Results indicate that respondents who perceive the effect of changes in the external environment on their own household's financial condition as positive are younger, have higher net worth, perceive more internal control over their situation, and report that most of the changes in the external environment are positive. Respondents who are younger, have higher income, perceive more internal control over their situation, and believe the effect of changes in the external environment on their household's financial condition are positive are more likely to be optimistic about their financial future. It is important that educators and financial advisors recognize the significant role perception of being in control plays in determining expectations of future financial condition.Journal Paper No. J-15256 of the Iowa Agriculture and Home Economics Experiment Station, Project No. 2809. Data were collected in conjunction with the cooperative regional research project NC-182, Family Resource Utilization as a Factor in Determining Economic Well-Being of Rural Families. Cooperating states are Arizona, California, Illinois, Indiana, Iowa, Kansas, Michigan, and Minnesota.Her current research interests include family financial management and consumer bankruptcy; she received her Ph.D. from the University of Missouri.She received her Ph.D. from the University of Illinois; her current research interests include gender roles, family financial management, and economic well-being.She received her Ph.D. from the University of Illinois. Her research interests are economic well-being and quality of life.Her current research interests include the economic well-being of various family forms. She received her Ph.D. from the University of Illinois.  相似文献   
26.
从数字技术应用素养、数字内容社交素养、数字媒体创新素养和数字安全保护素养4个维度构建农村居民数字素养评价指标体系,探讨数字素养对农村居民数字生活参与的影响效应和作用机制。研究发现,农村居民数字素养总体偏低。数字素养显著正向影响农村居民数字消费、数字文娱、数字出行、数字教育、数字医疗和数字生活参与度。社会网络、社会学习和自我效能感在上述影响中发挥部分中介作用,并且对不同领域数字生活的影响有较显著差异。进一步研究发现,数字素养通过强弱社会关系网络对农村居民各领域数字生活影响存在差异,尤其是弱关系网络对参与复杂数字生活有显著影响。据此提出建立健全数字教育培育体系,提高农村居民自我效能感,统筹协调强、弱社会网络,提升社会学习能力等对策建议。  相似文献   
27.
Environmental and human health issues associated with outdoor air pollution, such as ozone, sulfur dioxide, and other pollutants in metropolitan regions, are an area of growing concern for both policy officials and the general public. Increasing attention from the news media, new health data, and public debate over the effectiveness of clean air regulations have raised the importance of air quality in the public consciousness. While public perceptions of air quality have been studied thoroughly dating back to the 1960s, little empirical research has been conducted to explain the spatial aspects of these perceptions, particularly at the local level. Although recent studies suggest characteristics of local setting are important in shaping perceptions of air quality, the roles of proximity, neighborhood characteristics, and location have not been clarified. This study seeks to improve understanding of the major factors shaping public perceptions of air quality by examining the spatial pattern of local risk perception, the role of socioeconomic characteristics in forming these perceptions, and the relationship between perceived and scientifically measured air pollution. First, we map the spatial pattern of local air quality perceptions using Geographic Information Systems (GIS) across the Dallas and Houston metropolitan areas. Next, we explain these perceptions through local contextual factors using both bivariate correlations and multivariate regression analysis. Results indicate that perceptions of air quality in the study areas are not significantly correlated with air quality based on readings of air monitoring stations. Instead, perceptions appear to be influenced by setting (urban vs. rural), state identification, access to information, and socioeconomic characteristics such as age, race, and political identification. We discuss the implications of the findings and provide direction on how further research can provide a deeper understanding of the local contextual factors influencing public perceptions.  相似文献   
28.
《彼拉维德》以艺术的方式记录了处在边缘的美国黑人女性在白人和男人双重压迫下的痛苦挣扎和艰难的自我迫寻历程为了拥有一间属于自己的屋子,她们付出了惨重的代价为了摆脱“第二性”的地位,她们用自己的身体写作,以改变她们在历史上作为“隐形人”和“失声集团”的存在;她们打开自己的房间,让男人进来,共同书写那原来只是属于他的故事——历史,而所有这些又都被小说家编织进她那精巧的元小说叙述中去了。  相似文献   
29.
In this paper, we consider the problem of estimating the Laplace transform of volatility within a fixed time interval [0,T] using high‐frequency sampling, where we assume that the discretized observations of the latent process are contaminated by microstructure noise. We use the pre‐averaging approach to deal with the effect of microstructure noise. Under the high‐frequency scenario, we obtain a consistent estimator whose convergence rate is , which is known as the optimal convergence rate of the estimation of integrated volatility functionals under the presence of microstructure noise. The related central limit theorem is established. The simulation studies justify the finite‐sample performance of the proposed estimator.  相似文献   
30.
The objective of this article is to evaluate the performance of the COM‐Poisson GLM for analyzing crash data exhibiting underdispersion (when conditional on the mean). The COM‐Poisson distribution, originally developed in 1962, has recently been reintroduced by statisticians for analyzing count data subjected to either over‐ or underdispersion. Over the last year, the COM‐Poisson GLM has been evaluated in the context of crash data analysis and it has been shown that the model performs as well as the Poisson‐gamma model for crash data exhibiting overdispersion. To accomplish the objective of this study, several COM‐Poisson models were estimated using crash data collected at 162 railway‐highway crossings in South Korea between 1998 and 2002. This data set has been shown to exhibit underdispersion when models linking crash data to various explanatory variables are estimated. The modeling results were compared to those produced from the Poisson and gamma probability models documented in a previous published study. The results of this research show that the COM‐Poisson GLM can handle crash data when the modeling output shows signs of underdispersion. Finally, they also show that the model proposed in this study provides better statistical performance than the gamma probability and the traditional Poisson models, at least for this data set.  相似文献   
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