浅海信道宽带信号波形快速预报方法

随着信号处理技术的发展,对浅海信道传输特性的研究与利用日益受到重视。文章研究了浅海典型环境中水下宽带信号波形的快速数值预报方法。基于波束位移射线简正波（BDRM）理论,利用傅立叶方法求解宽带传播模型,在宽带模型计算过程中,通过宽带模型频域近似展开和模型并行化两种方式,实现快速准确的宽带信号波形预报。     

不完全信息下的CGF主体决策行为及模型研究

着重分析了决策的风险特性,建立了CGF主体的决策行为模型。分析加入感知行为后对决策行为复杂性的影响;提出了一种不确定型决策方法用于处理不完全感知信息对决策行为的影响;最后用示例说明了该方法的有效性。     

基于声基阵的目标被动探测建模与仿真

文章主要进行了舰船目标噪声和等距直线声基阵建模研究,采用波束形成、自适应限幅处理和极性相关等技术对目标进行被动声探测,并进行了仿真试验,验证了模型的准确性和探测方法的有效性。     

螺旋桨自动化几何建模和网格划分技术

为了快速实现船用螺旋桨有限元建模,为极限强度分析和疲劳校核做准备,针对船用螺旋桨的结构特点,利用MSC.Patran前后处理器的二次开发技术,开发了1套螺旋桨自动化建模软件,定义了螺旋桨建模的型值表标准格式,实现了螺旋桨几何建模和网格划分的自动化.对某冰区加强螺旋桨进行了建模和计算,结果表明,系统建立的螺旋桨模型能保持良好的光顺效果和网格质量,满足计算要求.本文提出了基于MSC.Patran的螺旋桨自动建模方法,避免了传统手工建模中复杂和重复的工作,大幅提高了螺旋桨设计分析效率,具有重要的参考价值.     

基于模块化方法的核动力汽轮机建模

汽轮机为核动力装置二回路系统重要部件,对整个系统的特性具有重要影响.根据模块化建模思想,将汽轮机划分为通用子模块,主要包括流动阻力型模块、流动存储型模块和转子模块.建立这些通用子模块的详细数学模型,利用不同模块的组合可以开发多种类型的汽轮机,提高汽轮机建模的效率.计算结果表明,建立的汽轮机模型可以满足大工况变动要求,为...     

对海上非法砂石船有效监管问题的思考

近年来,渤海湾海上交通安全形势严峻,海上非法采砂船、砂石运输船险情频发,船沉人亡事故时有发生。文中通过对渤海湾砂石船事故原因的分析,并结合海事监管工作实际,对非法采砂船、砂石运输船的长效监管问题提出了看法和相关建议。     

Carpooling and carpool clubs: Clarifying concepts and assessing value enhancement possibilities through a Stated Preference web survey in Lisbon, Portugal

The increase of urban traffic congestion calls for studying alternative measures for mobility management, and one of these measures is carpooling. In theory, these systems could lead to great reductions in the use of private vehicles; however, in practice they have obtained limited success for two main reasons: the psychological barriers associated with riding with strangers and poor schedule flexibility. To overcome some of the limitations of the traditional schemes, we proposed studying a carpooling club model with two main new features: establishing a base trust level for carpoolers to find compatible matches for traditional groups and at the same time allowing to search for a ride in an alternative group when the pool member has a trip schedule different from the usual one. A web-based survey was developed for the Lisbon Metropolitan Region (Portugal), including a Stated Preference experiment, to test the concept and confirm previous knowledge on these systems’ determinants. It was found through a binary logit Discrete Choice Model calibration that carpooling is still attached with lower income strata and that saving money is still an important reason for participating in it. The club itself does not show promise introducing more flexibility in these systems; however, it should provide a way for persons to interact and trust each other at least to the level of working colleagues.     

Assessing the cost of transfer inconvenience in public transport systems: A case study of the London Underground

Few studies have adequately assessed the cost of transfers² in public transport systems, or provided useful guidance on transfer improvements, such as where to invest (which facility), how to invest (which aspect), and how much to invest (quantitative justification of the investment). This paper proposes a new method based on path choice,³ taking into account both the operator’s service supply and the customers’ subjective perceptions to assess transfer cost and to identify ways to reduce it. This method evaluates different transfer components (e.g., transfer walking, waiting, and penalty) with distinct policy solutions and differentiates between transfer stations and movements.The method is applied to one of the largest and most complex public transport systems in the world, the London Underground (LUL), with a focus on 17 major transfer stations and 303 transfer movements. This study confirms that transfers pose a significant cost to LUL, and that cost is distributed unevenly across stations and across platforms at a station. Transfer stations are perceived very differently by passengers in terms of their overall cost and composition. The case study suggests that a better understanding of transfer behavior and improvements to the transfer experience could significantly benefit public transport systems.     

Bicycling renaissance in North America? An update and re-appraisal of cycling trends and policies

This paper reviews trends in cycling levels, safety, and policies in Canada and the USA over the past two decades. We analyze aggregate data for the two countries as well as city-specific case study data for nine large cities (Chicago, Minneapolis, Montréal, New York, Portland, San Francisco, Toronto, Vancouver, and Washington). Cycling levels have increased in both the USA and Canada, while cyclist fatalities have fallen. There is much spatial variation and socioeconomic inequality in cycling rates. The bike share of work commuters is more than twice as high in Canada as in the USA, and is higher in the western parts of both countries. Cycling is concentrated in central cities, especially near universities and in gentrified neighborhoods near the city center. Almost all the growth in cycling in the USA has been among men between 25-64 years old, while cycling rates have remained steady among women and fallen sharply for children. Cycling rates have risen much faster in the nine case study cities than in their countries as a whole, at least doubling in all the cities since 1990. They have implemented a wide range of infrastructure and programs to promote cycling and increase cycling safety: expanded and improved bike lanes and paths, traffic calming, parking, bike-transit integration, bike sharing, training programs, and promotional events. We describe the specific accomplishments of the nine case study cities, focusing on each city’s innovations and lessons for other cities trying to increase cycling. Portland’s comprehensive package of cycling policies has succeeded in raising cycling levels 6-fold and provides an example that other North American cities can follow.     

Much Ado about Nothing? - An analysis of economic impacts and ecologic effects of the EU-emission trading scheme in the aviation industry

From 2012 on, all CO₂ emissions from flights departing from or arriving at airports within the European Union have to be offset. We analyze the economic and ecological impacts that are caused by an inclusion of the aviation industry into the proposed emissions trading scheme (ETS). Building on the now fixed system design we employ a simulation model to estimate the impacts of the scheme. Our results indicate that financial impacts are highly dependant on external settings, such as allowance prices and demand growth. We show that the financial burden on the aviation industry will be rather modest in the first years after the introduction of the system and therefore induce only low competition distortions. Likewise, emission reductions within air transportation will be comparably low. While aviation will induce a decline of emissions in other sectors, significant absolute reductions within air transportation can only be reached by a more restrictive system design.