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41.
In the Brazilian Amazon during the 1980s,urban population growth outstripped rural growth, andby 1991, most of the region's population resided inurban areas. Much of this urban growth involvedestablishment of unplanned housing with inadequateinfrastructure, which resulted in rising pollution. This paper compares indicators of environmentalquality in urban populations of the Amazon in 1980 and1991, and among different kinds of urban populationsin 1991. The results show that environmental qualityin the region deteriorated during the 1980s as theproduction of and exposure to environmental hazardsrose while resources to ward off hazards eroded. Thefindings also show that environmental quality wasparticularly poor in more rapidly growing urbancenters. The urban Amazon may not afford an adequatestandard of living and this may generate out-migrationfrom the region.  相似文献   
42.
母亲的素质对孩子的优生优育有直接的重大影响 ,因此 ,提高妇女素质是全民族刻不容缓的任务  相似文献   
43.
Natural hybridization among wingless carabid beetles of the subgenusOhomopterus (Carabidae, genusCarabus) is reviewed, and its significance in the evolution of this subgenus discussed. Natural hybridization occurs between parapatric species of similar size. Two case studies of natural hybridization suggest that natural hybridization could have affected the evolution of this subgenus in different ways. When there is a large difference in genital morphology between hybridizing species, interspecific copulation often results in genital injuries that causes mortality of copulating individuals, and hence reduces the fitness of hybridizing individuals greatly. In such a case, hybridization may be effective in maintaining the parapatric distribution of the two species, and in the long term, may promote reinforcement selection for traits which are effective in prezygotic reproductive isolation. When the morphological difference in genitalia is not so large as to cause genital injury, a hybrid population may be established at the intermediate zone between two parental species, provided that the immigration rates of the two species into the intermediate zone are small. Thus, natural hybridization may have contributed to both divergence and reticulate evolution in this subgenus.  相似文献   
44.
随着高等教育改革的进一步发展,大学教育自身也呈现出新的发展动态。如何构建一个符合社会发展和高等教育发展,尤其是符合学生的主体发展需要的教育平台,充分体现大学教育在整个高等教育中的关键地位和重要作用,是当前教育改革的当务之急。  相似文献   
45.
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   
46.
目的/意义随着再制造经济效益和环境效益凸显,越来越多的企业进入再制造领域,与原制造商进行竞争或合作。考虑到碳排放约束,企业面临的生产决策更加复杂。设计/方法基于消费者对新产品和再制造产品的异质需求,构建了制造商和再制造商之间的竞争与合作博弈模型,探讨碳税对制造/再制造决策的影响;结合数值仿真,分析了竞争与合作模式下碳税对企业利润及碳排放的影响。结论/发现不同模式下,企业可根据再制造产品碳排放强度选择不同的生产策略;碳税总是会抑制新产品的生产,当再制造产品碳排放强度低于一定数值时,碳税会促进再制造产品的生产;再制造商竞争会挤兑新产品,使制造商利润减少,再制造门槛提高;当碳税不超过一定限度时,合作模式能够实现经济效益和环境效益双赢。  相似文献   
47.
目的/意义 平台经营者掌握着优势的规制权力,且可能对平台内经营者实施排他、歧视和剥削等不合理限制交易的行为,直接损害平台内经营者的合法权益,阻碍平台市场的自由和公平竞争,迫切需要法律规制。 设计/方法 通过对《电子商务法》实施前的法律规制体系梳理,可知平台经营者不合理限制交易的格式条款规制和竞争法规制兼存在漏洞。一方面,提示说明义务弱化、公平原则适用困难、平台规则备案审查作用有限,使格式条款规制体系无力应对;另一方面,不合理限制交易行为难以被《反垄断法》和《反不正当竞争法》规制体系完全覆盖。 结论/发现 《电子商务法》第35条通过设置不合理限制交易的“禁止+合理抗辩”条款,专门规定行政法律责任,是对平台经营者不合理限制交易法律规制的发展。《电子商务法》第35条所蕴含的“相对优势地位”“不合理限制”“明显不合理限制”等关键实施要点,有待进一步丰富、充实。  相似文献   
48.
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   
49.
This article examines the involvement of ministries of health in making health service coverage decisions in Denmark, England, France and Germany. The study aims to inform debate in England about the feasibility of reducing perceived ministerial and bureaucratic ‘interference’ in decisions affecting the National Health Service, based on interviews with senior government officials and other health system stakeholders. Ministries of health differ in their involvement in health system governance and coverage decisions (‘the benefits package’), reflecting differences in institutional arrangements. In all four countries, organizations at arm's length or independent from government are either involved in providing technical advice to the ministry of health or have been mandated to take these decisions themselves. However, ministries of health occasionally intervene in the decision‐making process or ignore the advice of these organizations. The Department of Health in England is not an aberrant case, at least in relation to coverage decisions. Indeed, ministries of health in Denmark and France play a larger role in making these decisions. Public pressure, often amplified by the media, is a shared reason for ministerial and ministry involvement in all four countries. This dynamic may thus limit the feasibility of attempts to further separate the NHS from both the Department of Health and wider political pressures.  相似文献   
50.
This study examined bidirectional, longitudinal associations between peer victimisation and self‐esteem in adolescents, and tested for moderator effects of undercontrolling, overcontrolling, and ego‐resilient personality types in these associations. Data were used from 774 adolescents ages 11–16 years who participated in a three‐wave (i.e., 2005, 2006, and 2007) longitudinal study. Structural equation modelling analyses in Mplus demonstrated that, controlling for earlier levels of self‐esteem, self‐reported peer victimization was associated with lower self‐esteem across one‐year time intervals. Vice versa, however, low self‐esteem was not predictive of subsequent self‐reported victimization. Evidence was also found for a moderator effect of personality type on the longitudinal associations between self‐esteem and victimization. Only in the subgroup of overcontrolling adolescents was lower self‐esteem related to subsequently higher levels of peer victimization; their undercontrolling and ego‐resilient peers were unaffected.  相似文献   
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