On-road emissions from urban buses with SCR + Urea and EGR + DPF systems using diesel and biodiesel

Due to growing concerns about NO_x and particulate matter (PM) emissions from diesel engines, stricter regulations are being introduced requiring advanced emission control technology. In response the diesel industry has begun testing various emission control technologies and applying them. To assess vehicle renewal policies of bus companies, two exhaust after-treatment technologies are compared: the combination of a diesel particulate filter and an exhaust gas re-circulation system and the combination of a selective catalytic reduction and urea. On-board emission measurements were conducted under real-world driving conditions on a specific bus route in the city of Madrid.     

印度孟买采用双电流制电动车组

介绍了印度盂买双电流制电动车组的结构特点及主要的技术参数。     

Structure,conduct and performance on the major liner shipping routes 1

Market concentration on the major container shipping routes has the potential to reduce contestability, impede effective competition and, as a consequence, inhibit the positive relationship between trade and economic growth. This development could also hamper the ability of economic regions to realize their respective competitive and comparative advantages. Within this context, the structure-conduct-performance (SCP) framework is used to analyse liner shipping dynamics in the transpacific, Europe–Far East and transatlantic trade routes. The analysis finds no conclusive evidence that either the increased concentration of slot capacity or the attempts by shipping lines to boost potential slot capacity (mainly through collaborative arrangements) lead to improved financial performance. The paper concludes that, despite high and increasing concentration among carriers on each of the trade routes analysed, these markets remain contestable.     

Fuel conservation as a regulator of vessel routeing

The high cost of fuel for marine purposes, coupled with the trend towards longer sea routes indicates the substantial savings in fuel costs that might accrue from more efficient trading patterns. The author discusses fuel conservation with special reference to the combined carrier.     

Capacity Building for Integrated Coastal Management in Asia-Pacific: The Case for Case Studies

Development of awareness and capacity is a central component to the delivery of ICM and spans from local communities to national-level politicians. Education and training activities associated with ICM must be extremely varied to match both the existing capacity and role that the stakeholders play within the process of ICM. Consequently, there cannot be considered any effective “generic” ICM training; training must be tailored to match the requirements of target groups. The transfer and uptake of good-practice thus becomes an important aspect of quality enhancement in ICM capacity development. Six case studies from the Asia-Pacific region are presented that show diverse and innovative examples of good practice. A comparative analysis of these case studies is carried out in terms of institutional level of impact. In addition a generic systems-based evaluation framework is used to determine the extent to which the training impacts upon ICM implementation indicators. It is concluded that the exchange, transfer, and translation to local conditions of appropriate good practice in ICM capacity development can be an important element in enhancing the impact of ICM programs on the coastal environments and societies. Furthermore, there appears to be a positive link between the involvement of national/state/regional stakeholders in capacity-building initiatives and impacting a wider variety of indicators of ICM delivery.     

Power plant siting on Wisconsin's coasts: A case study of a displaceable use

Abstract

The issue of whether power plants should be located on Wisconsin's Lake Michigan shore or inland is addressed in this article. It is quite likely that sites for several large power plants will be needed before the year 2000. Available evidence on the comparative costs of condenser cooling indicates that there may or may not be substantial economies from locating these plants at lakeshore sites depending on site characteristics, fuel costs, and other variables. Environmental impacts of coastal and inland siting are surveyed and also appear to be highly site‐specific. Important issues arise with respect to the intense competition for coastal land and the aquatic impacts at both coastal and inland sites. A third alternative, that of utilizing sites that are in the coastal zone but set back from the water's edge, has some promising aspects, but data on costs are scarce and inconclusive. Conclusions center on the importance of not ruling out either coastal or inland locations in future efforts to identify suitable power plant sites, the need to review current water‐quality measures, and the need for further research on institutions to facilitate sound siting decisions.     

Vibration characteristics analysis of ring-stiffened conical shells based on power series method北大核心CSCD

[目的]旨在利用解析法求解环肋圆锥壳的振动方程,对环肋圆锥壳的振动特性进行理论研究。[方法]首先,对圆锥壳分段处理,将圆锥壳沿母线方向、环向和法向的位移分别写成幂级数解的形式,并推导出幂级数项前系数的递推关系式;然后,采用梁模型模拟不同环肋数对圆锥壳振动响应特性的影响;接着,将圆锥壳分段及其环肋边界条件、位移和内力矩阵进行组装求解,得到在外部简谐力激励下圆锥壳的振动响应特性,并将所得结果与ANSYS有限元数值方法的计算结果进行对比,验证所提计算方法的有效性。最后,运用所提理论方法进行环肋圆锥壳的振动特性分析。[结果]结果显示,圆锥壳安装的环肋可明显抑制圆锥壳的振动,具体表现为响应幅值降低、固有频率升高,且在相同频段内共振峰数量减小;增大壳体厚度会引起壳体振动响应幅值降低以及固有频率升高;此外,增大半锥角、轴线长度和环肋数均可降低环肋圆锥壳的振动响应幅值。[结论]研究表明,所用方法对环肋圆锥壳振动的理论研究具有一定意义。     

A strategic model of public–private partnerships in transportation: Effect of taxes and cost structure on investment viability

We formulate a game-theoretic model of a concession agreement between a government and a private party, a concessionaire, who has to engage a set of service providers as part of the operating responsibilities. We use the model to examine the importance of a government's tax policy to induce private investments in transportation infrastructure. Our analysis brings to fore insights that are useful in the design of partnership agreements, such as the importance of early and binding government commitments to ensure stable partnerships, and thus, successful projects. Our analysis shows that these strong commitments are even more critical in situations where the success of the partnership requires participation of additional, self-interested parties, such as specialized service providers. Finally, we consider variations of the model where government preferences are explicitly captured, and where the returns from the fixed cost portion of the concessionaire's investment are exempt from taxes. We show that both variations can lead to outcomes where the concessionaire's tax burden is shifted to the service providers. This flexibility can be critical in the design of partnership agreements for (high-risk or highly specialized transportation) projects where additional incentives may be needed to induce private party participation.     

Meroplankton abundance in the Northeast Water Polynya: Insights from oceanographic parameters and benthic abundance patterns

We investigated meroplankton (planktonic larvae of benthic organisms) abundance and distribution in the Northeast Water (NEW) Polynya, located on the northeast coast of Greenland, from July 15 to August 15, 1992. Meroplankton was present at all sites visited (0.03–84.83 individuals per m³); at one station meroplankton comprised 8.28% of total zooplankton. Total meroplankton abundance was correlated with total zooplankton abundance and total benthic infaunal abundance but was not correlated with either microscopic carbon concentration or primary productivity. Examination of distribution data for barnacle nauplii and adults indicated that both adults and larvae were concentrated at the same locations. Patterns of distribution were also examined for stelleroid plutei, polychaete larvae and trochophores. There were distinct geographic patterns in total and class-specific meroplankton distributions, with maximal abundances occurring over the Belgica Bank and in the eastern regions of the Westwind Trough and minimal abundances in the Belgica Trough. The apparent control of meroplankton distribution by the hydrography of the region, coupled with the correlation between meroplankton, zooplankton and adult infaunal abundance, reinforces the hypothesis that hydrography plays a major role in controlling the distribution of biota in the NEW polynya (Ambrose and Renaud, 1995; Ashjian et al., 1995, 1997-this volume; Smith et al., 1995; Piepenburg et al., 1997-this volume).