论当前电子商务的发展

近年来,电子商务在世界各地得到蓬勃发展,在商贸活动中发挥着越来越重要的作用,电子商务的迅猛发展正在引起商贸环境的深刻变革,这种变革对社会经济生活和企业竞争力的影响正在逐步显现出来,电子商务将成为21世纪重要的商贸方式和推动全球经济增长的一个重要动力,其作用甚至可以与200年前工业革命对经济发展的促进作用相提并论。本文从多个不同的角度对当前电子商务的发展进行了详细的阐述。     

雪铁龙轿车ADC2防盗系统的工作过程和电路分析

介绍东风雪铁龙轿车第2代数码防盗（防起动）系统ADC2的工作过程,详细分析其工作电路电流流向,阐述探测防盗点火钥匙的过程。     

Can we reduce car use and, if so, how? A review of available evidence

Transport accounts for nearly a quarter of current energy-related carbon dioxide emissions with car travel constituting more than three quarters of all vehicle kilometres travelled. Interventions to change transport behaviour, and especially to reduce car use, could reduce CO₂ emissions from road transport more quickly than technological measures. It is unclear, however, which interventions are effective in reducing car use and what the likely impact of these interventions would be on CO₂ emissions. A two-stage systematic search was conducted focusing on reviews published since 2000 and primary intervention evaluations referenced therein. Sixty-nine reviews were considered and 47 primary evaluations found. These reported 77 intervention evaluations, including measures of car-use reduction. Evaluations of interventions varied widely in the methods they employed and the outcomes measures they reported. It was not possible to synthesise the findings using meta-analysis. Overall, the evidence base was found to be weak. Only 12 of the 77 evaluations were judged to be methodologically strong, and only half of these found that the intervention being evaluated reduced car use. A number of intervention approaches were identified as potentially effective but, given the small number of methodologically strong studies, it is difficult to draw robust conclusions from current evidence. More methodologically sound research is needed in this area.     

Impacts of an emission based private car taxation policy - First year ex-post analysis

This paper assesses the impacts of a targeted policy designed to influence car purchasing trends towards lower CO₂ emitting vehicles. Vehicle registration tax and annual motor tax rates in Ireland changed in July 2008 from being based on engine size to emissions performance of cars. This paper provides a one year ex-post analysis of the first year of the tax change, tracking the change in purchasing trends arising from the measure related to specific CO₂ emissions, engine size and fuel, and the implications for car prices, CO₂ emissions abatement, and revenue gathered. While engine efficiency improvements had been offset by purchasing trends towards larger and generally less efficient cars in the past, with the average MJ/km remaining constant from 2000 to 2007, this analysis shows that in the first year of the new taxation system the average specific emissions of new cars fell by 13% to 145 g/km. This was brought about, not by a reduction in engine size, but rather through a significant shift to diesel cars. Despite an unexpected reduction in car sales due to a recession in 2008, the policy measure has had a larger than anticipated impact on CO₂ emissions, calculated to be 5.9 ktCO₂ in the first year of the measure. The strong price signal did however result in a 33% reduction in tax revenue from VRT, in financial terms amounting to a drop of €166 million compared to a baseline situation.     

Well-to-wheel analysis for electric, diesel and hydrogen traction for railways

This paper derives the energy efficiencies and CO₂ emissions for electric, diesel and hydrogen traction for railway vehicles on a well-to-wheel basis, using the low heating value and high heating value of the enthalpy of oxidation of the fuel. The tank-to-wheel and well-to-tank efficiency are determined. Gaseous hydrogen has a WTW efficiency of 25% low heating value, if produced from methane and used in a fuel cell. This efficiency is similar to diesel and electric traction in the UK, US, and California. A reduction of about 19% in CO₂ is achieved when hydrogen gas is used in a fuel cell compared to diesel traction, and a 3% reduction compared to US electricity.     

海上钻井管线腐蚀原因分析和防治对策

调查和分析了南海某油田钻井管线典型腐蚀案例,得出结论为:流速导致磨损腐蚀、CO2腐蚀和高腐蚀性井下流体共同造成了钻井管线的严重损伤,其中流速是最主要的因素,它们在内部空间几何形状变化剧烈的管子内形成剧烈紊流并造成严重磨损腐蚀.关键控制方法是保持井下实际流速低于临界流速.讨论了流体含沙量对临界流速的影响,并提出其他可以采用的降低腐蚀/磨损的防护方法.     

连通液位计在桥梁竖向挠度测量上的应用

文章介绍了桥梁挠度测量的几种常用方法,分析了连通液位计测试桥梁挠度的优点,并对连通液位计在乌江二桥挠度测量中的应用进行了监测分析。实测数据表明连通液位计测量系统稳定可靠,能有效用于桥梁挠度的长期监测。     

A system dynamics model of CO2 mitigation in China’s inter-city passenger transport

Mitigation of greenhouse gas emissions from transportation has become increasingly important and challenging especially for developing countries. This paper takes the inter-city passenger transport in China as a case, and develops a system dynamics model for policy assessment and CO₂ mitigation potential analysis. It is found that the future demand for China’s inter-city passenger transport is expected to be large, with the turnover volume growing at a rate of 9% per annum and amounting to 6600 billion p-km in 2020. Major emissions reduction potential exists in inter-city passenger transport. In 2020, comparing to the case without any specific policies stressing mitigation, the reduction of CO₂ emissions ranges from 26% to 32% under those scenarios with policy controls. Sensitivity analysis reveals that the CO₂ mitigation will be best achieved by accelerating the development of railway network, together with slowing down the extension of highway network and imposing fuel taxes.     

开级配大粒径沥青碎石混合料劈裂试验的离散元数值分析

为了弥补现有沥青路面结构设计理论中将沥青混合料当作完全弹性体进行计算分析的不足,以AC-16,AC-20,开级配大粒径沥青碎石混合料OLSM-25的劈裂强度为研究对象,采用离散元方法,运用二维颗粒流程序(PFC2D),从细观角度入手,对AC-16,AC-20,OLSM-25的劈裂(间接拉伸)试验进行数值模拟,对比分析AC-16,AC-20,OLSM-25圆柱体试件内部集料颗粒之间的接触力、位移矢量、微裂缝数量及其分布规律.结果表明:在峰值轴向力作用下,当沥青混合料圆柱体试件开裂破坏时,随着沥青混合料公称最大粒径、空隙率的增大以及油石比的减小,试件内部集料颗粒之间的接触力由基本均匀趋于相对离散分布,位移矢量存在显著差异,微裂缝数量逐渐减少.与AC-16,AC-20相比,OLSM-25的间接拉伸抗裂效果显著.     

Implications of globalization for co 2 emissions from transport

Transport accounts for about 25% of global CO 2 emissions. Transport activities are on the rise in the coming decades. Would associated CO 2 emissions move upwards as well, and at what rate? The present paper explores the future of these CO 2 emissions, starting from four scenarios for global transport. Considering fuel consumption, energy efficiencies in transport, occupancy rates of transport means, size of cars on the market, and possible environmental policies we find CO 2 emissions are persistently increasing, especially in the less wealthy areas of the world. In Europe, policies that attempt to control mobility and also limit CO 2 emissions may succeed in reducing emissions growth by about 30%. Efforts to increase energy efficiency of transport, in particular road transport, would contribute most to such reduction.