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171.
从剖析实战面临的复杂电磁环境的特点以及对炮兵作战的影响入手,提出运用BP算法的收敛性,对不同的侦察工具的信息可信度确立合适的权值,消除由于复杂电磁环境对炮兵侦察和传递信息时所产生的误差甚至是错误的影响。 相似文献
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Competition and disruption in a dynamic urban supply chain 总被引:1,自引:0,他引:1
Terry L. Friesz Ilsoo Lee Cheng-Chang Lin 《Transportation Research Part B: Methodological》2011,45(8):1212-1231
Rapid changes and complexities in business environments have stressed the importance of interactions between partners and competitors, leading supply chains to become the most important element of contemporary business environments. There is a concomitant need for foresight in describing supply chain performance in all operating environments, including those involving punctuated disruptions. Furthermore, the urban metropolis is now widely recognized to be an environment which is especially vulnerable to supply chain disruptions and for which integrated supply chain decisions can produce very substantial net benefits. Accordingly, this paper presents a dynamic supply chain network model formulated as a differential variational inequality; the model is fashioned to allow consideration of supply chain disruption threats to producers, freight carriers, and retail enterprises. The DVI is solved using a fixed-point algorithm, and a simple numerical example, introduced to illustrate how the impacts of supply chain disruptions may be quantified, is presented. 相似文献
175.
Vikash V. Gayah Carlos F. Daganzo 《Transportation Research Part B: Methodological》2011,45(4):643-655
A recent study reported that the Macroscopic Fundamental Diagram of a medium size city exhibited a clockwise hysteresis loop on a day in which a major disturbance caused many drivers to use unfamiliar routes. It is shown below that, even in a perfectly symmetric network with uniform demand, clockwise loops are to be expected when there are disturbances, especially if the disturbances cause a significant fraction of the drivers to not change routes adaptively. It is also shown that when drivers are not adaptive networks are inherently more unstable as they recover from congestion than as they are loaded. In other words, during recovery congestion tends more strongly toward unevenness because very congested areas clear more slowly than less congested areas. Since it is known that uneven congestion distributions reduce network flows, it follows that lower network flows should arise during recovery, resulting in clockwise loops. Fortunately, the presence of a sufficient number of drivers that choose routes adaptively to avoid congested areas helps to even out congestion during recovery, increasing flow. Thus, clockwise loops are less likely to occur when driver adaptivity is high. 相似文献
176.
Gonçalo Correia José Manuel Viegas 《Transportation Research Part A: Policy and Practice》2011,45(2):81-90
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. 相似文献
177.
Bicycling renaissance in North America? An update and re-appraisal of cycling trends and policies 总被引:1,自引:0,他引:1
John Pucher Ralph Buehler Mark Seinen 《Transportation Research Part A: Policy and Practice》2011,45(6):451-475
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. 相似文献
178.
Much Ado about Nothing? - An analysis of economic impacts and ecologic effects of the EU-emission trading scheme in the aviation industry 总被引:1,自引:0,他引:1
Jan Vespermann Andreas Wald 《Transportation Research Part A: Policy and Practice》2011,45(10):1066-1076
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. 相似文献
179.
R. Smith M. Morison D. Capelle C. Christie D. Blair 《Transportation Research Part D: Transport and Environment》2011,16(8):614-618
Using the WPG03 duty cycle developed from global positioning data collected in Winnipeg, Canada, real world energy demands and costs are modeled. Three types of plug-in hybrid electric vehicles, four temperatures and two charging scenarios are compared to a vehicle with an internal combustion engine. Cold temperatures are shown to greatly affect vehicle operation energy costs, which is an important consideration for cold weather cities such as Winnipeg. The largest energy cost savings are obtained for smaller-battery plug-in hybrids that had the opportunity to charge during the day. 相似文献
180.
随着城市规模的扩展,各大城市都将城市轨道交通提上了建设日程。土地的集约利用,使得临线两侧的住宅开发增多,住宅区与线路的亲密接触,又使得轨道交通对城市的影响日益凸显。考虑房地产价格、轨道交通沿线其它经济因素、建设期对环境影响、运营期对环境影响、社会效益5个影响因素,建立因素集。备择集主要包含轻微影响、较小影响、较大影响和严重影响4个评判等级,通过德尔菲法确定各影响因素的权重,建立权重集。确定单个评判对象对备择集的隶属程度,得到单因素评价集,建立评价矩阵。最后,建立模糊综合评价集,对轨道交通城市影响进行评价。 相似文献