我国C2C电子商务的地理格局及其演化机制

从空间计量经济学的角度,从省域和市域两个空间层次对中国的C2C电子商务发展极其演化机制进行实证研究。研究结果表明,中国的C2C电子商务发展存在由东部沿海到内陆地区梯度降低的空间分布趋势,空间集聚程度非常高,且对当地物流行业发展起到推动作用。C2C电子商务水平与当地的经济发达程度高度相关,社会经济观念的转变、居民受教育程度的提高、互联网相关技术的普及、物流业的迅猛发展以及适当的地方产业集聚等都是促进C2C电子商务发展的重要因素。     

Exporting, linkages and productivity spillovers from foreign direct investment

Abstract.  In this paper we analyse productivity spillovers from foreign direct investment using firm-level panel data for U.K. manufacturing industries from 1992 to 1999. We investigate spillovers through horizontal, backward, and forward linkages; distinguish spillovers from export-oriented vs domestic-market-oriented FDI; and allow for differing effects, depending on domestic firms' export activities. The results suggest that the mechanisms through which spillovers affect domestic firms are very complex and that there are substantial differences in spillover benefits for domestic exporters and non-exporters, and from different types of inward investment.     

NiO/SiO2气凝胶合成多壁纳米碳管工艺参数的研究

以Ni(NO3)2.6H2O和正硅酸乙酯(TEOS)为制备原料,采用溶胶-凝胶和超临界干燥法制备成NiO/SiO2气凝胶,用NiO/SiO2气凝胶作催化剂,采用化学气相沉积法高温裂解CH4,通过不同的工艺参数合成多壁纳米碳管。研究结果表明:反应温度、甲烷与氢气流量以及反应时间影响碳产率,从而影响多壁纳米碳管的质量和产率。实验中NiO/SiO2气凝胶合成多壁纳米碳管适宜的反应温度为600℃;甲烷与氢气流量分别为180 mL/min,60 mL/min;反应时间为30 min。     

溶胶-凝胶法制备SiO2/TiO2多层膜的研究

通过对溶胶、热处理温度以及溶胶-凝胶过程中反应和存放的环境温度及湿度等参数的调整,研究了在实验室条件下制备SiO2/TiO2多层膜的方法.已制备出折射率可调的溶胶,所镀制的SiO2薄膜折射率在1.18～1.41之间可调,TiO2薄膜折射率在1.80～2.20之间可调.采用椭偏仪、红外分光光度计、紫外-可见分光光度计等对所制得的多层膜的性能进行了研究,结果表明,实验条件对SiO2/TiO2多层膜的制备非常重要.     

贸易视角下经济增长和环境质量的内在机理研究——基于中国30个省市环境库兹涅茨曲线的面板数据分析

经济增长与环境质量问题已引起众多学者的关注。本文利用中国30个省、市、自治区15年的面板数据检验中国是否存在倒U型的EKC曲线,并且在考虑贸易与投资的基础上,得出如下结论:东部地区存在倒U型的EKC,西部地区存在正U型的EKC,中部地区不存在EKC;外贸依存度与碳排放呈现出显著地正相关关系,FDI对碳排放虽有影响但很微弱;贸易和投资对拐点到达的时间并无影响,但却能够提高拐点到达时的人均GDP水平。     

Interplay between ethanol and electric vehicles as low carbon mobility options for passengers in the municipality of São Paulo

The Brazilian cities as well as many of the large urban centers in the world continue to expand, increasing the demand for mobility and transport, while, at the same time, the same cities are investing in greenhouse gas (GHG) mitigation to avoid climate change. Brazil's urbanization rate increased from 26% in 1940 to almost 70% in 1980. During this period, the Brazilian population tripled and the urban population multiplied by seven. In 2010, the transport sector in São Paulo accounted for 71% of the total emissions released by the energy sector. Ethanol has been considered a fuel with less greenhouse gas emissions, when compared with fossil fuels. However, ethanol production would have to double to meet the expected demand. Electric vehicles (EVs) market is expanding around the world, and is also an option to reduce the transport emissions, if powered by clean electricity. To assess whether the adoption of EVs might bring more benefits than the current ethanol, we develop prospective scenarios supported by the Long-range Energy Alternatives Planning (LEAP) simulation tool, taking a bottom-up tank-to-wheel approach to consider the CO₂ emissions of car in São Paulo. The scenario considering a substitution of 25% of gasoline-powered cars by EV in 2030 showed a reduction in energy consumption and CO₂ emissions, around 15% and 26% respectively in that year in comparison with 2015. We discuss the interplay between ethanol and EV, also considering emission coefficients from life cycle analysis conducted in Brazil, and concluded EV will have higher positive impact on climate change mitigation than ethanol.     

Accounting for Negative,Zero and Positive Willingness to Pay for Landscape Change in a National Park

In contingent valuation, despite the fact that many externalities manifest themselves as costs to some and benefits to others, most studies restrict willingness to pay to being non‐negative. In this paper, we investigate the impact of allowing for negative, zero and positive preferences for prospective changes in woodland cover in two UK national parks, the Lake District and the Trossachs. An extended spike model is used to accomplish this. The policy implications of not allowing for negative values in terms of aggregate benefits are also investigated, by comparing the extended spike model with a simple spike making use of only zero and positive bids, and a model which considers positive bids only. We find that ignoring negative values over‐states the aggregate benefits of a woodland planting project by up to 44%.     

3-氨基-1-（4-氯苯基）-1氢-苯并[f]色烯-2-碳酸乙酯的合成和晶体结构研究

以氰乙酸乙酯、2-萘酚和对氯苯甲醛为反应原料,得到了3-氨基-1-（4-氯苯基）-1氢-苯并[f]色烯-2-碳酸乙酯,通过X-射线单晶衍射对其结构进行表征。结果表明：晶体属于三斜晶体,空间群为P-1。晶胞参数为：Z=2,a=9.2916（7）A°,b=9.4505（8）A°,c=10.9761（7）A°;α=95.077（2）°,β=98.200（2）°,γ=102.892（2）°,V=922.65（12）A°3;R1=0.0466,wR2=0.1326。     

基于P2P的多媒体流过滤技术的研究与分析

现有过滤系统中绝大多数方案都采用了传统的过滤技术,这些过滤技术无法制止不良多媒体信息在网络上传播。基于此,提出了一种基于内容的分布式多媒体流过滤系统的模型,该系统采用内容识别与包过滤相结合的方式,让内容识别过程与包过滤规则匹配并行进行,实现过滤系统的实时性;同时该系统设计的补偿Agent在屏蔽非法信息的同时,保证了多媒体文件的完整性。     

基于P2P流媒体点播系统的研究

基于P2P的流媒体视频点播服务是现在影视服务的另一种模式。基于P2P流媒体点播系统由内容服务器、目录服务器和P2P节点构成。当前播放节点下载得到的媒体片段能为后续子节点提供相同的媒体点播服务,就能减轻了服务器的负载,达到低带宽下更多节点共同播放同一个媒体文件的目的。进行模拟实现证明服务器负载下降到原来30％左右。