船舶结构强度直接计算中板单元应力的取法

以某油船外底加筋板为例,分析有限元计算中,板单元中面应力和表面应力的差别,说明衡准其强度时应该采用单元形心处的中面应力。     

造船市场2003年回顾与未来展望

20 0 3年世界经济复苏步伐加快 ,带动航运市场的迅速发展。航运市场的大好形势极大刺激了船东的订船热情 ,2 0 0 3年世界各国的船台基本都已订满直到 2 0 0 7年。中国国内造船业开始空前规模的大扩张 ,未来既充满着机遇又面临激烈竞争的风险     

管道完整性维护费用的效用函数优化方法

通过对管道完整性维修费用和收益的分析,提出了用效用函数来优化管道的完整性维修费用,给出了详细的求解方法。此方法建立在管道失效概率基础上,通过建立统一的损失度量标准来衡量直接经济损失、人身伤亡和环境破坏的影响,从而决定最优的维护费用。     

大众直接换档变速器的原理和展望

DSG(Direct Shift Gearbox)全称为直接换档变速器,是德国大众公司于2003年推出的用于改善动力性、降低油耗的一种基于全新原理的车用变速器,本文详细介绍DSG的结构、控制原理、换档过程及实际应用情况,阐述其发展趋势。     

The economic speed of an oceangoing vessel in a dynamic setting

The optimal (economic) speed of oceangoing vessels has become of increased importance due to the combined effect of low freight rates and volatile bunker prices. We examine the problem for vessels operating in the spot market in a tramp mode. In the case of known freight rates between origin destination combinations, a dynamic programming formulation can be applied to determine both the optimal speed and the optimal voyage sequence. Analogous results are derived for random freight rates of known distributions. In the case of independent rates the economic speed depends on fuel price and the expected freight rate, but is independent of the revenue of the particular voyage. For freight rates that depend on a state of the market Markovian random variable, economic speed depends on the market state as well, with increased speed corresponding to good states of the market. The dynamic programming equations in our models differ from those of Markovian decision processes so we develop modifications of standard solution methods, and apply them to small examples.     

Port investments on coastal and marine disasters prevention: Economic modeling and implications

Located along shorelines, seaports are highly vulnerable to coastal and marine natural disasters largely due to climate change. Damage caused by disasters can be prevented or alleviated if sufficient investments are made in a timely manner. However, despite a wide range of investment options and well-developed engineering expertise, port investment on disaster prevention remains a challenging task involving great complexities. This paper develops an integrated economic model for the analysis of disaster-prevention investments at a “landlord” port. It simultaneously considers the uncertainty of disaster occurrence and associated return of prevention investments, the information accumulation and related investment timing, and the benefit spillovers of investment among stakeholders. Our analysis shows that the timing of port investments depends on the probability of disasters. Immediate investment is optimal for disasters with very high probability, while investment should be postponed if such a probability is very low. Optimal timing for cases of intermediate probability cannot be determined analytically, as it is influenced by other factors such as discount rate, information accumulation and efficiency of investments. Positive spillovers between a port and its tenants lead to under-investment, which can be corrected by coordination between stakeholders. However, since there are risks of “overinvestment” (the marginal benefits of investments are zero ex post if there is no disaster), regulatory intervention is not always optimal when the regulator does not have a good understanding of disaster probability distribution. Therefore, scientific research would bring significant economic and strategic value to policy, planning and investment decisions.     

基于热管理的甲醇燃料电池增程器布置分析

由于纯电动汽车动力蓄电池储能有限,所以,燃料电池以高效率、无污染、高可靠性的特点成为电动汽车增程器的研究热点。文章以市场上某款纯电动汽车为研究对象,将甲醇燃料电池增程器布置在车辆前舱内,对不同车速下燃料电池增程器三维模型的温度场分布进行仿真。仿真结果表明:车辆静止时,甲醇燃料电池以额定功率工作会影响前舱部件正常工作,当车辆以超过30 km/h的速度行驶,可以忽略燃料电池增程器对前舱部件的影响。试验结果验证了仿真结果的准确性,对于实车燃料电池增程器的布置和控制策略的制定具有一定的参考价值。     

分段式尾压浪板对高速船阻力性能的影响

基于CFD技术,以排水型高速船Model 5b为模型,寻求改善高速船阻力性能的尾压浪板新形式。首先尾压浪板新形式的确定在静水条件下进行,然后在波浪条件下验证该压浪板的阻力性能。基于CFD软件建立三维数值波浪水池,静水条件下采用切割体网格技术预报船模的阻力性能。波浪条件下数值水池入口采用直接造波方法,尾部采用人工阻尼消波方法,自由面采用VOF方法处理,采用重叠网格技术预报船模的阻力性能以及运动响应。确定一种比常规压浪板阻力性能优良的分段式压浪板,为船舶节能附体的研究提供参考。     

Effects of regulation-driven green innovations on short sea shipping's environmental and economic performance

Despite its pivotal role in European trade, today’s short sea shipping (SSS) industry faces the dual challenge of lessening its environmental footprint while improving its economic performance. To reduce the pollution caused by their operations, SSS companies are required to comply with increasingly stringent environmental regulations enacted by global and regional authorities such as the European Union and the International Maritime Organization. However, the companies tend to regard those regulations as imposing an additional burden of cost that compromises their capacity to enhance their economic performance. This paper examines the impact of external institutional driver namely regulatory pressure on the adoption of green innovations in SSS and in turn, the impact of those innovations on the environmental and economic performance of SSS companies. To investigate the hypothesised relationships of those constructs, a structural equation model was developed and tested with data from a survey conducted amongst 101 short sea shipping companies headquartered in Europe. As detailed in the paper, the analysis revealed that regulatory pressure has generated green innovations that have enhanced the environmental and economic performance of European SSS companies and, as a result, led to a win–win situation for all parties involved. The paper discusses what those findings imply for SSS firm managers and policymakers who seek to improve the environmental or economic performance of Europe’s SSS industry.     

Parking Benefit Districts – The transferability of a measure to reduce car dependency to a European context

Parking Benefit Districts (PBDs) are a parking measure where revenues from on-street parking charges are returned to the area where they are charged, and stakeholders in the area participate in prioritizing how the revenues are to be spent. The purpose of this article is to analyse whether and how a PBD programme can be transferred to a European context, and whether it can contribute to reduced car dependency. The first part of the article provides an overview of some salient features of PBD programmes in the USA through a literature survey. This is followed by results from interviews and from a focus group with civil servants and a deputy mayor in Stockholm. The results are used to analyse the conditions for implementing a PBD programme in Stockholm, as well as for analysing how such a programme can be designed to reduce car dependency. A main conclusion is that there are no legal barriers that render a PBD programme impossible in Stockholm, even though there are some legal restrictions. We also conclude that a PBD programme might contribute to reduced car dependency in two different ways, either by increasing acceptance for parking charges or by improving the alternatives to private cars. There seem to be several aspects in a PBD programme that can contribute to increased acceptance for parking charges. However, there is no tradition of working with these principles in Sweden and the programme’s redistributional effects need to be taken into account when designing the programme.