YAG:RE3+(RE=Eu,Tb)的制备及发光特性研究

利用柠檬酸-凝胶方法,以Y2O3,Eu2O3,Tb4O7和Al(NO3)3·9H2O作为初始原料,柠檬酸作为配位剂,成功制备出了Y3Al5O12:Eu3+(Tb3+)发光材料,其烧结温度为1?000℃,时间4?h.通过X射线衍射测试,表征Y3Al5O12为单相;计算其晶胞参数,发现晶胞体积v随着pH值的增大而增大.对Y3Al5O12:Eu3+(Tb3+)系列样品在紫外光谱区域和真空紫外光谱区域的发光性能进行了研究,结果表明:在真空紫外光谱区域激发下,Eu3+(Tb3+)的猝灭浓度比在紫外光谱区域激发下的低.     

Order statistics from trivariate normal and -distributions in terms of generalized skew-normal and skew- distributions

We consider here a generalization of the skew-normal distribution, GSN(λ₁,λ₂,ρ), defined through a standard bivariate normal distribution with correlation ρ, which is a special case of the unified multivariate skew-normal distribution studied recently by Arellano-Valle and Azzalini [2006. On the unification of families of skew-normal distributions. Scand. J. Statist. 33, 561–574]. We then present some simple and useful properties of this distribution and also derive its moment generating function in an explicit form. Next, we show that distributions of order statistics from the trivariate normal distribution are mixtures of these generalized skew-normal distributions; thence, using the established properties of the generalized skew-normal distribution, we derive the moment generating functions of order statistics, and also present expressions for means and variances of these order statistics.Next, we introduce a generalized skew-t_ν distribution, which is a special case of the unified multivariate skew-elliptical distribution presented by Arellano-Valle and Azzalini [2006. On the unification of families of skew-normal distributions. Scand. J. Statist. 33, 561–574] and is in fact a three-parameter generalization of Azzalini and Capitanio's [2003. Distributions generated by perturbation of symmetry with emphasis on a multivariate skew t distribution. J. Roy. Statist. Soc. Ser. B 65, 367–389] univariate skew-t_ν form. We then use the relationship between the generalized skew-normal and skew-t_ν distributions to discuss some properties of generalized skew-t_ν as well as distributions of order statistics from bivariate and trivariate t_ν distributions. We show that these distributions of order statistics are indeed mixtures of generalized skew-t_ν distributions, and then use this property to derive explicit expressions for means and variances of these order statistics.     

基于“3R＆I”原则的循环经济模式研究

我国当前经济高速增长的要求与有限资源和环境支持能力之间存在严重矛盾。实施循环经济是贯彻落实我国节能减排政策的有效途径，如何发展循环经济是我们面临的重大课题。目前循环经济的实施主要是依据“3R”原则，而这些原则有明显的不足之处。针对“3R”原则的局限性，提出基于创新的循环经济“3R＆I”原则。创新是实现“减量化”、“再利用”、“资源化”的前提，也是实现经济持续循环的保证。循环经济本质上是一种创新经济。     

基于Solid works蜗轮蜗杆三维建模的研究

在Solid works环境下进行了蜗轮蜗杆三维设计研究,这对类似复杂曲面的零件设计具有实际意义。     

The social security number: A small device underpinning big systems

The possession and use of a personal social security number helps to structure people's daily lives. However, despite its fundamental normative importance, the social security number remains a little‐known entity. Increasingly universal and yet diverse in form, it is a legal and technical norm which is as much a mechanism for surveillance and monitoring as it is a necessary instrument for giving effect to social rights. Analysis of this constituent element of social security systems permits as assessment of some of the technical difficulties presented by the ever‐increasing movement of people and data. Overcoming these technical difficulties should permit to envisage a first technical step towards realizing a universal and global social security system.     

Do people think about absolute or relative price differences when choosing between substitute goods?

The article presents experimental evidence that shows that people often consider relative price differences in addition to absolute differences when choosing between substitute goods. Because the choice between substitute goods is a very common one, this is an important finding. The experiment uses scenarios in various consumption categories: hotel rooms, flights, and books. Subjects were either students or participants in an economics conference. The data allow to reject the hypothesis that people think only about relative price differences in favor of the hypothesis that people think about both relative and absolute price differences. Whether the price given to the subjects is that of the high-quality good or of the low-quality good makes a large difference, a result that is related to the endowment effect and the status quo bias. Implications of the results for business strategy and other areas are also discussed.     

Family farmers and major retail chains in the Brazilian organic sector: Assessing new development pathways. A case study in a peri-urban district of São Paulo

The expansion of the organic sector in Brazil is seen as a leverage for the social emancipation of the small family farmers. Next to the traditional alternatives circuits of organic food and farming, new powerful capitalistic actors, such as supermarket chains, are rapidly entering the Brazilian organic arena. Can family farming benefit from the development of these “conventional” commercialisation circuits in the organic sector? Research undertaken in 2007, in a green belt rural community of São Paulo, shows how family farmers may have benefited from the implication of large retail chains in the organic sector and how an economically and ecologically outstanding agriculture may arise from these circumstances. However, we highlight the crucial role played by social regulation: only strong solidarity between farmers and the implication of technicians, militants and researchers in the process made it possible to counter the negative effects of the liberal logic governing the development of organic farming via the major retailers. Still, as tougher competition is expected on the regional organic market, the development of short supply chains involving “committed” consumers and the broader integration of the local farmers in networks of organic militancy appear crucial. It would guarantee a continuous enhancement of the local human and social capital, reinforce an emerging process of internal conversion and allow for a stronger social regulation of the future local development pattern.     

儿童文学与上海出版业的渊源

上海为什么会成为中国儿童文学的摇篮?儿童文学在中国上海的出现是历史的必然选择还是一种意外收获?本文将着重从西法印刷、晚清传教士办报以及商务印书馆和中华书局的创建,考察早期著名儿童刊物的创刊、早期重要儿童文学论著的出版,解析上海近现代出版业的兴起与儿童文学的渊源,探寻儿童文学在中国发生、发展的坎坷之路。     

东西相遇：中德双校园学习差异性比较分析——基于Z大学中德合作2＋3项目学生的访谈

在对Z大学中德合作2＋3项目留德学生访谈的基础上，以差异性分析为视角，从教学组织、专业学习和校园生活三个纬度，分析了项目学生对两校园学习的差异性体验，并从文化价值、教育体制、教育投入方面探究其原因，提出了强化国际合作、提升师资能力水平、加大工程实训领域投入等对策。     

论3G时代高校图书馆的发展

3G时代图书馆工作面临新的考验。为了应对这一革命性的冲击，高校图书馆要做好数字化的核心准备工作，逐步建立并完善例如“手机图书馆”的建设。一方面可以提高数字化图书的普及与使用率，另一方面也可以在演进的过程中确实保护高校的既得利益。