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441.
针对船舶电力推进系统方案论证效率低、成本高等问题,开发了一款组态式船舶电力推进系统仿真软件。对船舶电力推进系统进行结构划分,并建立了系统的数学模型和仿真模型,并封装形成模型库。使用Matlab/GUI开发界面层,用M语言对Simulink模型进行调用与控制。使用SQL Server 2008创建数据库,实现数据的存取和管理功能。基于该软件对某船舶电力推进系统设计方案进行组态式的图形化建模,并设计了典型工况的仿真实验。结果表明,仿真模型较好预报了实船运行工况。由此可见,该软件可有效验证船舶电力推进系统设计方案。 相似文献
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为了研究装卸同步工艺下的集卡配置,建立了包括船舶,桥吊,集卡和龙门吊等现代码头作业设备的系统仿真模型,采用Flexsim-CT软件分别对作业面与作业线下的集卡运输作业进行了在装卸同步工艺下的模型仿真,并对两种运输策略在同步装卸工艺下的集卡作业效率和整体作业时间进行了比较。经过试验得到了在不同集卡资源条件下的最优集卡配置方案,并对方案的仿真指标进行了对比分析。研究为装卸同步工艺下的集卡配置方案提供了重要的参考。 相似文献
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Ancor Suárez-Alemán Tomás Serebrisky Oscar Ponce De León 《Maritime Policy and Management》2018,45(5):665-683
Appropriate port regulation and competitive forces tend to be related to higher levels of operational and economic performance of ports. From a policy-making perspective, pursuing efficiency and securing competition in ports to reach a level playing field is a two-step process requiring (1) ex-ante regulations to set the rules that maximize the competition for the market, especially when the policy objective is to attract private operations to ports on competitive concession processes and (2) ex-post competition policy to monitor and preserve competition in the market. This paper studies port regulation in Latin America and the Caribbean (LAC) from a competition perspective, analyzing both ex-ante and ex-post policies implemented in the region. The analysis reveals that the competitive environment in LAC is low, giving room for possible anticompetitive practices in the LAC port sector. Since the end of the 1990s, approximately 80% of container terminals in the region were granted to only five companies. Chile and Mexico have been found to be the best practices in the region, with better conditions assuring robust competition in the market. The main policy implication from this analysis is the need for a stronger involvement of antitrust agencies throughout the port concession processes. 相似文献
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In the short run, there can be substantial differences in spot freight earnings between geographical regions of the global freight market for bulk carriers. Such differences can be consistent with an efficient market if they are temporary and if they cannot be exploited financially by pursuing chartering strategies that are based on publicly available information. In this paper, we apply a simple optimal switching model to evaluate whether such chartering strategies exist. We model the spot freight rate differential between the Atlantic and Pacific basins as a mean-reverting Ornstein–Uhlenbeck process and the entry–exit decision using the discount factor approach, which results in optimal trigger values for the entry/exit from each basin. Our empirical results suggest that the market is spatially efficient during normal freight market conditions when there is a surplus of vessels. The tight market conditions during the 2003–2008 freight market boom caused a persistent upward bias in Atlantic freight rates, but also here we find little added value from pursuing an active switching strategy. 相似文献
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Car ownership is growing very rapidly in China; whilst this is a reflection of sustained economic growth, it presents a major challenge to Chinese transport policymakers. The consequences of China's motorization also extend beyond the national borders, however, via mechanisms such as increased demand for new automobiles produced in North America and Europe and the global atmospheric concentration of greenhouse gases. Chinese cities are also experimenting with innovative transport policies to manage increasing car ownership, which in a number of cases go beyond the menu of policy options that have traditionally been considered in the West. Despite policy interest for these reasons, China's motorization process is poorly understood, in part due to a scarcity of relevant data.This paper contributes to the body of literature regarding this phenomenon by drawing on a unique data resource: the 2011 wave of the China Household Finance Survey (n = 8438 households). This is a disaggregate national-scale survey dataset developed to monitor economic conditions in China, though to the authors' knowledge the CHFS has not previously been employed to study patterns of car ownership.We report a set of three analyses, to identify factors associated with: 1) whether a household owns at least one car, 2) multiple car ownership, and 3) whether a household owns a new car. Amongst other empirical results, we find that living in a rural area is negatively associated with car ownership, net of confounding effects, and that within towns/cities poor accessibility (i.e. long travel time) to the town/city centre is also negatively associated with car ownership. These findings regarding spatial effects are contrary to typical findings in the West, where car ownership is generally lowest in urban centres.An earlier version of this study was presented at the 2017 Transportation Research Board conference. 相似文献
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