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排序方式: 共有258条查询结果,搜索用时 15 毫秒
1.
In recent years, calibration estimation has become an important field of research in survey sampling. This paper proposes a new calibration estimator for the population mean in the presence of two auxiliary variables in stratified sampling. The theory of new calibration estimator is given and optimum calibration weights are derived. A simulation study is carried out to performance of the proposed calibration estimator over other existing calibration estimators. The results reveal that the proposed calibration estimators are more efficient than other existing calibration estimators in stratified sampling.  相似文献   
2.
四川省三州地区地处中国一二级阶梯过渡地带,地质构造复杂,新构造运动强烈,属断裂构造发育,极易因强降水等极端天气诱发山洪、泥石流、崩塌、滑坡等灾害,导致该区域路网灾害发生频率高、强度大和多灾并发。这在高山峡(深)谷区尤为严重。通过分析四川省三州地区的路网灾害风险管理体制机制,发现主要问题在于:灾害科学研究相对薄弱、灾害应急与防治技术较为缺乏、灾害危害度和路网基础设施的易损性较大、路网系统的抗灾能力和恢复力较弱。为了在四川三州地区构建安全可靠、应急保障能力强的现代路网体系,需要通过构建时空、纵向、横向三位一体的综合灾害风险治理体系和健全灾害科学、应急技术、风险管理三者有机结合的防灾减灾机制等措施,不断提升四川三州地区的路网气候恢复力。  相似文献   
3.
Historically, the news media have engaged in high rates victim blaming in their reporting of sexual assaults. However, in recent years, gains in civil rights and renewed attention to Title IX may mean sexual assault victims are receiving less-biased news coverage. Using a content analysis, we examined the tone and message of all crime stories published in one United States university newspaper from academic year 2015–2016 (n = 99). Comparing attributions of responsibility made to both victims and offenders across several major crime categories (rape, murder, sexual assault, robbery, physical assault, sexual misconduct, and sexual abuse), and consistent with historical trends, we found higher levels of victim blaming in stories on rape and sexual assault than any other crime. We identify rhetorical devices commonly used to discredit the victim and/or absolve the perpetrator. Despite perceived gains achieved by Title IX, news coverage continues to buttress victim blaming culture.  相似文献   
4.
陶杰  高岩 《管理科学》2021,24(3):32-44
非线性优化模型中经常出现多重Lagrange乘子现象,导致决策者错误地计算资源的影子价格.本文针对该问题指出最小欧几里得范数的Lagrange乘子是影子价格.同时,还提出了一个无约束优化模型用以求解最小欧几里得范数 Lagrange乘子,该无约束优化模型可以通过经典的非光滑优化算法求解.最后,本文提出一个基于次梯度的算法求解影子价格,该算法是次线性收敛的,且计算时间与约束条件的个数及自变量的个数线性相关.  相似文献   
5.
We show that the Lagrange multiplier (LM) unit root test exhibits size distortions when a break in the innovation variance exists but is ignored. We develop a modified LM unit root test that is based on a generalized least-squares transformation of the original series. The asymptotic null distribution of the new modified LM unit root test is derived. Finite-sample simulation evidence shows that the modified LM unit root test maintains its size and has reasonable power against the trend stationary alternative.  相似文献   
6.
我国的刑罚体系经历了奴隶制刑罚、封建制刑罚、近代刑罚、当代刑罚,直至发展到现代刑罚。整个刑罚历史呈现出由残暴、落后朝着慎刑、文明的轻刑化方向发展。相较于其他先进国家和地区的刑罚体系而言,我国当前适用的刑罚体系在诸多方面仍表现出了重刑色彩。为实现刑罚的轻缓化,需要健全社区矫正制度,提升罚金刑的刑罚地位,并进一步完善资格刑的内容。除此之外,司法上的重视和重刑观念的转变则是刑罚轻缓化的最有效途径。实现刑罚轻缓化,应当做到司法先行,立法跟进。  相似文献   
7.
考虑单电网公司与双发电商所组成的渠道结构,构建了发电商投资减排、电网公司投资消纳的优势互补的异质型垂直合作减排的随机微分对策模型,先后考察并比较了分散决策和集成决策下的反馈均衡结果。在此基础上,讨论了利润共享契约下系统增量利润的分配问题。研究表明:对于分散决策,电网公司选择性承担发电商的减排费用;两种决策下的发电商减排和电网公司购电价格以及分散决策下的减排补贴与发电商之间的减排竞争强度相关;在一定条件和范围内,合作博弈有利于提高电网公司购电电价,同时为此所带来的风险增大。  相似文献   
8.
The access divide was once the basic form of the digital divide. The development of Internet infrastructure has narrowed the access divide and increased application coverage, but it has also touched off a connectivity dividend difference. Taking the online market as an example, we examine the sources of the dividend difference and the factors influencing it with in a connectivity framework. We found that the narrowing of the access divide has resulted in enhanced connectivity and platform development, giving people the chance to benefit from transforming the various assets in which they have previously invested into differentiated compound connectivity capital. In the course, the scale and rate of the conversion are affected by two multiplier effects and especially by online platforms. The process is ultimately expressed in the dividend difference.  相似文献   
9.
具有高功能密度的小卫星项目蓬勃发展,大大增强了私营实体和非航天大国参与空间活动的能力,引发了规则修订的需求。国家应建立空间活动的分级、分类许可条件,放宽小卫星行业的准入要求,并根据小卫星项目的目的、成本、收益和风险来设定第三者责任保险要求,规范小卫星的登记实践。空间碎片减缓应作为小卫星项目许可条件之一,以切实履行国家的外空环境保护责任。应简化国际电信联盟卫星频率和轨道位置协调程序,建立适应小卫星轨道特性、运行寿命和业务类型的管理规则。  相似文献   
10.
Computer simulation is an effective tool for assessing mitigation strategies, with recent trends concentrating on agent-based techniques. These methods require high computational efforts in order to simulate enough scenarios for statistical significance. The population individuals and their contacts determined by agent-based simulations form a social network. For some network structures it is possible to gain high accuracy estimates of contagion spread based on the connection structure of the network, an idea that is utilized in this work. A representative social network constructed from the 2006 census of the Greater Toronto Area (Ontario, Canada) of 5 million individuals in 1.8 million households is used to demonstrate the efficacy of our approach. We examine the effects of six mitigation strategies with respect to their ability to contain disease spread as indicated by pre- and post-vaccination reproduction numbers, mean local clustering coefficients and degree distributions. One outcome of the analysis provides evidence supporting the design of mitigation strategies that aim to fragment the population into similarly sized components. While our analysis is framed in the context of pandemic disease spread, the approach is applicable to any contagion such as computer viruses, rumours, social trends, and so on.  相似文献   
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