二氧化碳压力对甲烷水合物置换速率的影响

通过检测置换过程中气相组分的变化情况,研究了CO2注入压力对置换CH4水合物中CH4气体程度与速率的影响.在274.15 K时,研究了3.97,4.56,4.84,6.26M Pa 4个不同的CO2注入压力下置换反应的进行情况.实验表明,当置换反应结束时,分别有20.0%,26.4%,44.9%,9.1%的CH4被置换出来.在一定压力范围内(3.97~4.84 M Pa),CO2气体注入压力越高,被置换出来的CH4量越大,但当CO2气体注入压力接近液化压力时,CH4回收量反而明显下降.     

Commercial public bus transport services in Germany: How a market in motion struggles with its regulatory framework

After decades of stagnation, the competitive market for commercial public bus transport services in Germany is beginning to move. Nevertheless, compared to the total market volume, the number of cases where competition is observable remains small. An empirical analysis of competition in the commercial services market as compared to competition in the non-commercial services market confirms that entry barriers do exist. These barriers clearly impede competitive developments in this embryonic market, which relies on the market initiatives of operators to develop. The paper identifies a key entry barrier in the institutional framework: for potential market entrants, the overall uncertainty regarding competitive procedures for commercial services is significantly higher than usual in tendering procedures. This high uncertainty poses the main disadvantage for newcomers as compared to incumbents.     

Equilibrium properties of taxi markets with search frictions

The equilibrium properties of an aggregate taxi market are investigated using a general bilateral searching and meeting function which characterizes the search frictions between vacant taxis and unserved customers. Three specific issues are analyzed for meeting functions that exhibit increasing, constant and decreasing returns to scale. Firstly, service quality in terms of customer wait/search time and average profit per taxi are examined jointly in relation to taxi fleet size, and a Pareto-improving win-win situation is identified, where an increase in taxi fleet size leads to improvements in both service quality and market profitability. Such a Pareto-improving situation is found to emerge if and only if the meeting functions show increasing returns to scale. Secondly, the properties of the socially optimal solution are examined. It is found that the taxi fleet size should be chosen such that the total cost of operating vacant taxis equals the total cost of customer waiting time multiplied by an asymmetric factor of the meeting function, and that taxi services should be subsidized at social optimum only when the meeting functions show increasing returns to scale. Thirdly, the Pareto-efficient services are examined for trade-offs between social welfare and profits in the light of partially conflicting objectives of the public sector and the private taxi firms using a bi-objective maximization approach. The taxi utilization rate and the customer wait/search time or service quality are proved to be constant along the Pareto frontier and equal to those at social optimum if the meeting functions show constant returns to scale. Extensions are made to the cases with increasing and decreasing returns to scale.     

国内外城市地下空间资源开发利用的发展和问题

城市地下空间开发利用能够拓展城市发展空间、改善城市居住环境、实现城市可持续发展,对其研究具有重要现实意义。首先,总结国外城市地下空间开发利用概况、特点和功能特色,介绍我国城市轨道交通地铁和地下综合体发展概况,并以南京江北新区和重庆市江北区北城天街城市地下空间开发项目为例,对我国城市地下空间利用进行介绍。然后,阐述城市地下空间开发利用在交通治堵、节能减排、土地和资源开发利用、防汛排涝抗旱等方面的效益和功能,介绍我国城市地下空间开发利用的数字化技术、地下车库建设及基坑、改建、盾构、顶管、沉管等方面的新技术、新工艺。最后,总结我国城市地下空间开发利用的进展,认为我国城市地下空间的开发和利用现已呈现出空间上多层次化和功能上多样化的特征; 分析制约其发展的因素（初期投入大、效益空间不够理想、功能特色发挥不够、运营安全和防灾问题以及节能减排与环保问题）及存在的问题,希望我国地下空间开发在视觉美感和对舒适度的追求方面再上一个台阶; 并对进一步建设和发展城市地下空间进行思考,提出若干建议。     

竞品分析在汽车整车开发中的应用

文章针对竞品分析在汽车整车开发过程中的应用进行了阐述,全面覆盖了整车开发的持续性市场研究阶段、战略输入及项目可行性分析阶段、产品概念设计阶段、工程设计阶段与设计验证阶段这五个阶段。每个阶段都详细地描述了整车开发项目亟须解决的问题以及竞品分析的实施内容,通过对每个阶段开展竞品的研究和对比分析,以此确保开发出的新车型具有市场竞争力,符合消费者的需求与技术发展趋势。此外,整车开发过程中的竞品分析还能够极大地减少研发投入、缩短研发周期并提高研发水平,这将是各大车企快速提升整车研发水平的重要途径。     

2009年乘用车市场分析与预测

2008年全球出现金融危机,世界各国的实体经济已经受到金融危机的严重影响,但我国的宏观经济形势要好于其他受金融危机影响的国家。文章从市场发展规律、经济增长和特殊因素分析和预测了2009年乘用车市场,指出我国2009年汽车市场仍有快速增长的基础,经济增长动力更大程度地依靠扩大内需,同时燃油税改革和汽车鼓励政策也刺激了乘用车需求的增长。     

新能源汽车真正走向市场要解决4大问题

面对全球范围日益严峻的能源形势和环保压力,世界主要汽车生产国都把发展新能源汽车作为主打产业,文章阐述了新能源汽车在我国前景广阔,可真正要走向市场,当务之急需要解决消费政策和完善服务网络等4大问题。指出发展新能源汽车,我国具有一定的有利条件,也符合我国的国情,只有共同努力,才能加快新能源汽车的发展。唯有如此,汽车业才能实现历史性的跨越。     

Post-entry container port capacity expansion

Port capacity development is a critical strategy for the growth of a new port, as well as for the development of existing ones, when both new and existing ports serve the same hinterland but have different competitive conditions. To study this strategy, we develop a two-stage duopoly model that comprises the pricing and capacity decisions of two heterogeneous players serving an increasing market. We identify the necessary condition for a port to increase its profit through capacity expansion, and characterize the condition when preemptive pricing by the dominant player is neither credible nor effective in preventing the smaller player from gaining market share. We also find the pure-strategy Nash equilibrium in the capacity expansion game for two ports that have different price sensitivities, as well as different operation and capacity investment costs. We apply the model results to the container port competition between Hong Kong and Shenzhen after Shenzhen port started its container operation in 1991. Our analysis explains the transition of market power from monopoly to duopoly, the fast development of Shenzhen Port, and the possible market structure changes with the continuing increase in demand.     

Grouping travelers on the basis of their different car and transit levels of use

Market segmentation studies in travel behavior research are ordinarily based on socioeconomic characteristics and personality traits. This study explores the usefulness of a different approach, where the actual overall mobility levels across different ground transportation modes, along with desired changes in the use of cars and transit, are used as clustering variables. Using a given mode can in fact influence the personal representation of that mode, which in turn has been proven to be a key element in transport behaviours. We form such multimodality-based clusters from two field studies, one involving employees of the French transportation research institute INRETS and the other a representative sample of residents of the US San Francisco Bay Area. We find that strong users of a given mode would like to bring more balance to their “modal consumptions” by decreasing the use of this mode more than the average, and increasing the use of the alternative mode. However, concerning ground transport travel budgets, the desire to travel more (or less) overall seems less strongly related to the composition of the modal balance. The US dataset shows also a greater latent demand for travel than the French one. Socioeconomic characteristics of the clusters could not explain the patterns that were found, confirming the importance of taking into account multimodality issues in travel behavior research. Some policy implications from these findings are finally reported.

"共有地悲剧"与绿色交通形成机制

交通具有共有资源的特性,没有排他性而有竞争性。交通竞争的失范和交通的外部性是造成交通“共有地悲剧”的内部和外部原因。发挥政府立法作用规范交通的竞争性,通过市场交易降低交通的负外部性,形成外部压力与内在诱导的双向激励机制,是利益共赢的绿色交通的形成机制。