盘形钻头刮切实验数据分析处理

简要介绍了盘形钻头的结构特点及工作机理,着重对盘形牙轮钻头9种不同结构参数的盘形切削齿与目前镶齿牙轮钻头上使用的瓢形和楔形齿在重庆砂岩上进行了刮切对比实验的实验数据进行了分析处理。求出了刮切实验中测得的不同牙齿在刮切过程中的刮切力的最大值、最小值、平均值和刮切单位体积岩石所需的刮切力的大小,得到了不同结构牙齿在刮切重庆砂岩时的刮切效果,为进一步设计出实用于中硬及软地层并具有较高综合工作性能的盘形钻头提供了实验数据。     

中国的离婚率与社会结构变化分析

从中国的离婚率与社会结构变化的时间序列分析中可以看出 :离婚率随非农产业人口比重的提高而提高 ,并有三年的时滞 ;离婚率也和人口城市化的发展有密切的关系 ,两者的比重一并提高 ,但约有五年的时滞。因这两方面社会结构的变化 ,直接影响妇女就业率提高和妇女职业结构的变化 ,而由此引起的人口迁移流动的大变动 ,也必然影响婚姻家庭观念的变化     

浅谈建筑幕墙设计中的成本控制

建筑幕墙成本控制的重点在设计阶段 ,设计方案对成本的控制是决定性的。设计对项目成本的控制是战略性、全局性的 ,而施工过程的管理对项目成本的控制是战术性、局部性的。幕墙设计中如何达到控制成本的目的至关重要。把技术与经济融为一体 ,在设计中既保证幕墙安全、实用、美观 ,又做到控制和降低成本 ,是施工企业适应市场的关键     

The Human Capital Model of Selection and Immigrant Economic Outcomes

This article examines the trends in the economic advantage that highly educated immigrants hold over less educated immigrants in Canada, focusing on the differences between short‐run and longer‐run outcomes. Using data from the Longitudinal Immigration Database covering the period from the 1980s to the 2000s, this study finds that the relative entry earnings advantage that higher education provides to new immigrants has decreased dramatically over the last 30 years. However, university‐educated immigrants had a much steeper earnings trajectory than immigrants with trades or a high school education. The earnings advantage among highly educated immigrants increases significantly with time spent in Canada. This pattern is observed for virtually all immigrant classes and arrival cohorts. The results suggest that short‐run economic outcomes of immigrants are not good predictors of longer‐run results, at least by educational attainment. The implications of these findings for immigration selection policy are discussed in the conclusion.     

家庭背景如何影响儿童学业成就?——义务教育阶段家庭社会经济地位影响差异分析

对于家庭背景与儿童学业成就间的关系,既有研究大多着眼于家庭背景对最终教育获得的影响,但教育获得是一个连续过程,对受教育过程缺少分析,就难以理解家庭背景影响儿童受教育机会的过程性机制。本文通过分析中国家庭追踪调查基线数据(CFPS2010),探讨了家庭背景影响儿童学业成就的路径和机制。本文分析结果表明:(1)家庭通过其社会经济资源为儿童提供有差异的教育机会,进而影响儿童的学业表现;(2)家庭通过家长的教育参与和行为支持,培养儿童的学习态度和学习习惯,从而对其学业成就产生影响。进一步的探讨还发现,家庭背景对儿童学业成就的影响路径和机制具有显著的城乡差别,家庭社会经济地位对城市学生成绩的影响大于对农村学生的影响;相比城市学生而言,农村学生的学业成就更多地依赖于自身的学习行为。本文的研究发现对如何缩小儿童学业成就的阶层差异以及促进教育公平提供了依据。     

微时代微电影微文化

微时代的到来与微电影的勃兴互为表里。微时代的崭新媒介技术和手段,把我们认识的世界和对世界的认识过程变得和从前很不一样,为我们提供一种身体甚至心智之外的"精神"现实。媒介技术不仅成为我们了解和再现社会及其文化的一种工具,也成为一个切入点。在这个时代中应运而生的微电影在表达方面有着自身的特征,那就是:短(碎片叙事)、平(浅表达)、快(敏锐的即兴创作)。这既是微电影的艺术特征,亦是这个时代的文化特征。微电影以浓缩的"精微"突破了传统电影的线性叙事和固定观看模式,以一种新的步态走入我们生活的各种时间形态中,这使电影艺术走下原先高高在上的纯粹的审美神坛,走出影院,以平常的姿态走进了赛博空间,走进大众之间,带来了一种新的艺术样式,也使社会文化的转型在这里写下了重彩的一笔。     

绿色GDP与干部政绩考核

过去,用GDP衡量政绩,导致部分领导干部只顾经济的增长,忽视环境的保护;只抓表面的“政绩”工程,忽视群众的切身利益,在政绩观上出现了一些问题和偏差。而以“社会福利”为目标的广义绿色GDP,在强调经济增长的同时,坚持发展的可持续性,关注百姓的幸福或福利。因此,将绿色GDP与干部政绩考核挂钩符合“以人为本”,全面、协调、可持续的科学发展观,也有助于干部形成求真务实的工作作风,树立正确的政绩观。     

A quadratic time exact algorithm for continuous connected 2-facility location problem in trees

This paper studies the continuous connected 2-facility location problem (CC2FLP) in trees. Let \(T = (V, E, c, d, \ell , \mu )\) be an undirected rooted tree, where each node \(v \in V\) has a weight \(d(v) \ge 0\) denoting the demand amount of v as well as a weight \(\ell (v) \ge 0\) denoting the cost of opening a facility at v, and each edge \(e \in E\) has a weight \(c(e) \ge 0\) denoting the cost on e and is associated with a function \(\mu (e,t) \ge 0\) denoting the cost of opening a facility at a point x(e, t) on e where t is a continuous variable on e. Given a subset \(\mathcal {D} \subseteq V\) of clients, and a subset \(\mathcal {F} \subseteq \mathcal {P}(T)\) of continuum points admitting facilities where \(\mathcal {P}(T)\) is the set of all the points on edges of T, when two facilities are installed at a pair of continuum points \(x_1\) and \(x_2\) in \(\mathcal {F}\), the total cost involved in CC2FLP includes three parts: the cost of opening two facilities at \(x_1\) and \(x_2\), K times the cost of connecting \(x_1\) and \(x_2\), and the cost of all the clients in \(\mathcal {D}\) connecting to some facility. The objective is to open two facilities at a pair of continuum points in \(\mathcal {F}\) to minimize the total cost, for a given input parameter \(K \ge 1\). This paper focuses on the case of \(\mathcal {D} = V\) and \(\mathcal {F} = \mathcal {P}(T)\). We first study the discrete version of CC2FLP, named the discrete connected 2-facility location problem (DC2FLP), where two facilities are restricted to the nodes of T, and devise a quadratic time edge-splitting algorithm for DC2FLP. Furthermore, we prove that CC2FLP is almost equivalent to DC2FLP in trees, and develop a quadratic time exact algorithm based on the edge-splitting algorithm. Finally, we adapt our algorithms to the general case of \(\mathcal {D} \subseteq V\) and \(\mathcal {F} \subseteq \mathcal {P}(T)\).     

青少年公民教育的发展脉络、现实问题与未来方向

青少年公民教育是新时期促进国家发展,增加国家实力的基本保障。由于相关概念内涵的模糊不清、推行机制的不完善等原因,导致了我国青少年公民教育的理论体系和实施体系建设的相对滞后。直至20世纪90年代以后在国际和国内环境的双重推动下。青少年公民教育才开始有了实质性的发展和推进:同时也存在着理论体系建构滞缓、教学理念混淆、课程衔接乏力、教育内容知行脱节等现实问题。构建一个适应时代发展需求,符合青少年身心发展特征。校内外有机结合的积极有效的青少年公民教育体系成为了新时期发展青少年公民教育的重要任务。