三苯基硫膦的合成与表征

以三苯基膦和二甲基二硫醚为反应原料,得到了三苯基硫膦,通过X-射线单晶衍射对其结构进行表征。结果表明:晶体属于单斜晶系,空间群为P2(1)/c。晶胞参数为:Z=4,a=18.342(2),b=9.6269(10),c=18.044(2),α=90.00°,β=106.102(6)°,γ=90.00°,V=3 061.2(6)3;R1=0.1336,wR=0.1420。     

“三维”外语写作教学范式的构建与应用——以英语电子邮件为例

外语写作教学承载着培养学生外语书面表达技能的重任,随着社会文化的发展和科学技术的进步,外语写作教学范式也经历了相应的变迁.本文在辩证分析各范式的基础上提出了由结果(语篇)维度、过程(能力)维度和交际策略维度构成的“三维”范式框架及其内容体系,并以英语电子邮件为例进行了新范式的应用实践,以期解决教学实践中单个范式应用效果不理想的问题.     

基于C51单片机的MP3解码器的设计与实现

MP3编码标准压缩率高,压缩质量好,是广为应用的音频压缩格式。文章介绍了一种基于C51内核的单片机MP3解码原理,对系统的软、硬件部件进行了设计,实现了实时解码过程。     

城市商圈布局的三维动态模型构建与述评

商贸产业是维系一个城市经济运转的原动力之一,城市商圈是这个经济发展动力的重要载体.本文在吸收西方经典商圈理论模型的基础上,结合我国城市商圈发展现状,从外部环境、内部成长和时间三个维度分析其影响因素,构建了城市商圈布局的三维动态模型,以期对城市商圈布局和城市经营提供一定的现实参考价值.     

基于SWOT分析的中国联通3G发展战略探讨

SWOT分析是进行公司战略分析的重要工具。依据对中国联通发展3G战略的SWOT分析,中国联通3G发展战略应定位于专注C网,综合发展,差异服务,规模领先,赶超移动,做强做大。     

2,3-环氧丙基三甲基氯化铵壳聚糖接枝共聚物的制备研究

通过2,3-环氧丙基三甲基氯化铵(ETA)对壳聚糖进行接枝改性,探讨了影响其接枝改性的主要因素。结果表明,壳聚糖与ETA接枝的较合适反应条件是:壳聚糖与ETA摩尔比为1∶3、pH值为7、温度80℃、时间10小时、引发剂浓度0.5mmol/L;最后,通过红外光谱图进一步表征了壳聚糖接枝物的生成。     

基于三维技术的《机械制图》教学改革探讨

《机械制图》是各层次工科类大学机械类专业和近机械类专业必修的、高度实践性的一门技术基础课。目前流行的几种三维CAD软件,可以满足包括三维造型与三维设计、计算机辅助工程分析、机构运动分析与仿真、装配干涉检验、三维转二维、图样档案管理等各种应用需要。随着先进的三维设计、制造手段和技术应用的不断发展,相应的《机械制图》课程的各个知识结构部分的教学方法、教学手段等方面的改革势在必行。     

A new economics approach to modelling policies to achieve global 2020 targets for climate stabilisation

This paper explores a Post Keynesian, ‘new economics’ approach to climate policy, assessing the opportunities for investment in accelerated decarbonisation of the global economy to 2020 following the Great Recession of 2008–2009. The risks associated with business-as-usual growth in greenhouse gas (GHG) concentrations in the atmosphere suggest that avoiding dangerous climate change will require that the world’s energy-economy system is transformed through switching to low-carbon technologies and lifestyles. Governments have agreed a target to hold the increase in temperatures above pre-industrial levels to at most 2°C and have offered reductions by 2020 in GHG emissions or the carbon-intensity of GDP. The effects of policies proposed to achieve pathways to 2020 towards this target are assessed using E3MG, an Energy-Environment-Economy (E3) Model at the Global level. E3MG is an annual simulation econometric model, estimated for 20 world regions over 1972–2006 adopting a new economics approach. Additional low-GHG investment of some 0.7% of GDP, with carbon pricing and other policies, is sufficient to achieve a pathway consistent with a medium chance of achieving the long-term target. GDP is above reference levels because decarbonisation reduces world oil prices and increases investment. Employment is some 0.9% above reference levels by 2020 and public finances are almost unaffected.     

A STATE‐LEVEL ANALYSIS OF BUSINESS CYCLE ASYMMETRY

This paper provides a comprehensive examination of asymmetry in US state‐level business cycles. We consider two different types of asymmetry in the adjustment process of a stationary time series: deepness and steepness. The data used in the study are a comparable set of state‐level coincident indexes (SCIs) developed by the Federal Reserve Bank of Philadelphia. Specifically, results from using the momentum‐threshold autoregressive model provide evidence of asymmetry in the growth rate of 23 SCIs as well as the equivalent national coincident index.     

Incentives and the Sorting of Altruistic Agents into Street‐Level Bureaucracies*

Many street‐level bureaucrats have the dual task of helping some clients, while sanctioning others. We develop a model of a street‐level bureaucracy, and we study the implications of its personnel policy on the self‐selection and allocation decisions of agents who differ in altruism towards clients. When bureaucrats are paid flat wages, they do not sanction, and the most altruistic types sort into bureaucracy. Pay‐for‐performance induces some bureaucrats to sanction, but it necessitates an increase in compensation, which can result in sorting from the top and bottom of the altruism distribution. We also explain why street‐level bureaucrats often experience an overload of clients.