PKI技术与应用

PKI是基于公钥加密体制的提供公钥加密和数字签名服务的系统或平台,主要由认证中心(CA)、数字证书库、密钥备份及恢复系统、证书撤销处理系统和应用程序接口(API)组成。其中CA是PKI的核心环节,具有证书发放、更新、撤销和验证等功能。PKI技术已在很多领域得到了广泛的应用。     

实施层级和综合教学管理的思考

加强人文基础课的教学管理,是全面提高教学质量和提升大学文化品质的关键。实行目标层级管理和系统综合管理能更有效发挥人文基础课的文化承载功能。     

Partner Choice and the Differential Retreat From Marriage

The contemporary retreat from marriage in the United States has had a differential impact across socioeconomic and racial groups. Here, 1990 marriage rates and propensities for Virginia, North Carolina, and Wisconsin are analyzed regarding (a) the likelihood that persons in different groups ever marry and (b) patterns of partner choice with respect to race and educational level. Marriage remains strong in most race‐education groups but is substantially lower among Blacks and among those with less than 12 years of education. Patterns of partner choice have shifted to show greater symmetry between the educational levels of brides and grooms. Changes have been modest with regard to the level and pattern of interracial (Black‐White) marriage. Marriage is increasingly a union of equals, but a union chosen more by Whites than by Blacks and more by the well educated than by the poorly educated.     

隐含合约和专用资产投资:日本分包制研究

日本制造业中,制造商往往和其零部件供应商形成长期连续交易关系,彼此之间紧密协作,形成系列化的企业集团。在这种企业集团内部,零部件供应商有更大的激励进行专用资产的投资,进而降低生产成本,提高产品质量。甚至在适当的条件下,供应商直接参与零部件产品的设计。这种日本式的分包制采用一种隐含的承包合约形成长期连续交易关系,使企业之间能更好的合作,极大的提高了日本企业集团的竞争力。本文建立一个简单的模型,引入一种简单隐含合约的形式,即发包商给予承包商部分议价权利,在此基础上分析承包商专用资产投资行为,并对上述现象进行解释。     

20世纪40年代四川省新县制下地方自治的施行

本文探讨了 2 0世纪 4 0年代四川省新县制下的基层社会控制及民主的实际状况 ,指出四川省在当时所推行的基层地方自治仍未摆脱受行政控制的从属地位 ,行政工作先于、多于自治工作 ,“民意机构”非民众直接选举产生并且多反映地方有力者的意志 ,它在解决民众最感痛苦的诸如“摊筹派募”、“征丁”以及“吏治腐败”等问题上的作用十分有限。国民政府在基层所实行的“以官治求自治”的所谓地方自治政策 ,非但未能发展地方事业 ,反而从根本上动摇了其统治基础     

环境会计信息披露的有关问题

企业作为环境污染的主要肇事者, 理应承担起治理环境污染的责任, 由此就会产生相应的环境支出和环境收益, 并因而影响企业的财务状况和经营成果。将环境活动纳入企业会计核算体系, 反映企业对自然资源的消耗和对环境的污染及其治理情况, 披露环境会计信息, 成为传统会计面临的新课题, 本文主要对环境会计信息披露的内容和方式进行探讨     

经管类学科实践教学的特征

经管类实验室的运行规律取决于经管类学科的本身特点。经管类学科特征是边缘性 ,既具有工科类知识体系的技术性又具有文科类的人文性和社会性。因此 ,经管类实践教学体系应该包括实验室教学环节和社会直接实践教学环节。经管类学科体系知识是关于人际关系和基于这种关系而建立的各种社会机制架构的学科 ,应该包括社会直接的实践教学 ,因为基于人际关系而建立的社会机制是无法人为复制的。     

对任务型语言教学模式的探讨与体会

借助教学实验探讨在本科院校英语专业学生的精读教学课堂里实施基于任务的教学模式的必要性和可行性.实验结果和统计分析表明:两组学生对语言知识的掌握和语言能力方面没有显著意义上的差别,但实验组学生在语言行为方面要优于对照组.他们不仅获得了语言知识,同时还表现出较好的跨文化交际能力.     

Exposure Reconstruction for the TCDD-Exposed NIOSH Cohort Using a Concentration- and Age-Dependent Model of Elimination

Recent studies demonstrating a concentration dependence of elimination of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) suggest that previous estimates of exposure for occupationally exposed cohorts may have underestimated actual exposure, resulting in a potential overestimate of the carcinogenic potency of TCDD in humans based on the mortality data for these cohorts. Using a database on U.S. chemical manufacturing workers potentially exposed to TCDD compiled by the National Institute for Occupational Safety and Health (NIOSH), we evaluated the impact of using a concentration- and age-dependent elimination model (CADM) (Aylward et al., 2005) on estimates of serum lipid area under the curve (AUC) for the NIOSH cohort. These data were used previously by Steenland et al. (2001) in combination with a first-order elimination model with an 8.7-year half-life to estimate cumulative serum lipid concentration (equivalent to AUC) for these workers for use in cancer dose-response assessment. Serum lipid TCDD measurements taken in 1988 for a subset of the cohort were combined with the NIOSH job exposure matrix and work histories to estimate dose rates per unit of exposure score. We evaluated the effect of choices in regression model (regression on untransformed vs. ln-transformed data and inclusion of a nonzero regression intercept) as well as the impact of choices of elimination models and parameters on estimated AUCs for the cohort. Central estimates for dose rate parameters derived from the serum-sampled subcohort were applied with the elimination models to time-specific exposure scores for the entire cohort to generate AUC estimates for all cohort members. Use of the CADM resulted in improved model fits to the serum sampling data compared to the first-order models. Dose rates varied by a factor of 50 among different combinations of elimination model, parameter sets, and regression models. Use of a CADM results in increases of up to five-fold in AUC estimates for the more highly exposed members of the cohort compared to estimates obtained using the first-order model with 8.7-year half-life. This degree of variation in the AUC estimates for this cohort would affect substantially the cancer potency estimates derived from the mortality data from this cohort. Such variability and uncertainty in the reconstructed serum lipid AUC estimates for this cohort, depending on elimination model, parameter set, and regression model, have not been described previously and are critical components in evaluating the dose-response data from the occupationally exposed populations.