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71.
应用有限元法对加筋复合材料层合板结构进行固有振动特性和导纳特性分析。基于一阶剪切理论的复合材料层合板理论,采用4节点Mindlin壳单元进行结构离散,通过动力学原理建立结构动力学有限元方程,并编制出相应的计算机程序。针对双向加筋复合材料结构进行分析,讨论不同结构模态阻尼系数、不同激励位置、不同边界条件和加筋的疏密程度对结构原点导纳及跨点导纳的影响。依据计算结果,可以进一步研究舰船复杂结构振动能量的传递和隔振效果,为追求最佳振动和声学设计提供分析方法。 相似文献
72.
This paper moves beyond traditional models of car ownership in that we propose a framework for modeling household-level decisions
to acquire specific types and numbers of mobility tools to fulfill the mobility needs of household members. The framework
is applied to a data set collected during the winter and spring of 2000/2001 in the German city Karlsruhe via an interactive
web-based stated response survey in which respondents could optimize their household mobility tool sets through on-line feedback
concerning the estimated costs of the sets. In our analysis, bivariate ordered probit models are estimated for three combinations
of mobility tools: season tickets (i.e., transit passes) and cars, season tickets and small cars and season tickets and large
cars. In all instances, strong substitution effects are found – that is, as the number of season tickets increases, the number
of cars decreases. This finding underscores the need to move beyond simple models of car ownership to comprehensive models
of mobility tool ownership. As demonstrated by our research, failure to do so is likely to lead to biased results. 相似文献
73.
为遏制疾病传播,错峰交通的政策被提出.本文旨在验证错峰通勤能否以及多大程度上能够发挥作用.以上海为例,基于手机数据反映人口实际通勤现状,用多代理人模拟方法模拟疾病的传播,考察不同错峰通勤策略的影响.研究发现:错峰通勤增强了人员流动性,反而会加快疾病的传播,错峰率越大,传播越快;早上班人群被感染的比例略低于晚上班人群;个人的通勤距离越长,家和工作地离市中心越近,越可能成为易感者和易播者. 相似文献
74.
Previous research has shown integrated planning to be important for achieving aims concerning more environmentally friendly transport operations, but less good at explaining prerequisites of implementation. This paper analyses how management and working practises in local authorities, here understood as steering cultures, affect implementation of integrated land-use and public transport planning approaches. The analysis builds on case studies of planning in two Swedish municipalities. These have developed two antithetical steering cultures, namely one that can be described as deliberative and one that can be described as sectorised. The paper describes the advantages and disadvantages of these steering cultures. The findings show the deliberative model to facilitate integration through advanced mechanisms of consensus and co-ordination between policy-makers and officials. The sectorised model has no such mechanisms, but this need not result in poor prospects of integrated planning. It is important for integrated planning approaches, whatever the steering culture, to be in line with the institutionalised norms and objectives by which planning practices are governed. Integration therefore needs a normative component, so as to ensure implementation. The important normative component in this context can be construed as discourses and rationales concerning transport and the urban development of which public transport forms part. 相似文献
75.
Emerging autonomous vehicles (AVs) and shared mobility systems per se will transform urban passenger transportation. Coupled together, shared AVs (SAVs) can facilitate widespread use of shared mobility services by providing flexible public travel modes comparable to private AV. Hence, it may be conjectured that future urban mobility is likely an on-demand service and AV private ownership is unappealing. Nonetheless, it is still unclear what observable and latent factors will drive public interest in (S)AVs, the answer to which will have important implications on transportation system performance. This paper aims to jointly model public interest in private AVs and multiple SAV configurations (carsharing, ridesourcing, ridesharing, and access/egress mode) in daily and commute travels with explicit treatment of the correlations across the (S)AV types. To this end, multivariate ordered outcome models with latent variables are employed, whereby latent attitudes and preferences describing traveler safety concern about AV, green travel pattern, and mobility-on-demand savviness are accounted for using structural and measurement equations. Drawing from a stated preference survey in the State of Washington, important insights are gained into the potential user groups based on the socio-economic, built environment, and daily/commute travel behavior attributes. Key policies are also offered to promote public interest in (S)AVs by scrutinizing the marginal effects of the latent variables. 相似文献
76.
77.
A well-functioning public bicycle system relates not only to its mode of operation, vehicle allocation, rental station layout and vehicle leasing configuration, but also the bicycle network structure and its formation. However, the latter aspects have been widely overlooked in China. Here, we help to further attract more researchers to conduct relevant studies and make suggestions for the development of public bicycle transport in many small and medium-sized cities across the world. We demonstrate how to explore the public bicycle network structure of a county-level Chinese city – Yixing – known for its clay ware and tourism. We show that complex network theory and shortest path analysis technology are useful in characterizing the public bicycle network structure, in aspects such as network topology, the spatial distribution of sub-networks and traffic flows. Finally, the paper proposes relevant urban planning strategies. 相似文献
78.
This research evaluated the potential for wireless dynamic charging (charging while moving) to address range and recharge issues of modern electric vehicles by considering travel to regional destinations in California. A 200-mile electric vehicle with a real range of 160 miles plus 40 miles reserve was assumed to be used by consumers in concert with static and dynamic charging as a strict substitute for gasoline vehicle travel. Different combinations of wireless charging power (20–120 kW) and vehicle range (100–300 miles) were evaluated. One of the results highlighted in the research indicated that travel between popular destinations could be accomplished with a 200-mile EV and a 40 kW dynamic wireless charging system at a cost of about $2.5 billion. System cost for a 200-mile EV could be reduced to less than $1 billion if wireless vehicle charging power levels were increased to 100 kW or greater. For vehicles consuming 138 kWh of dynamic energy per year on a 40 kW dynamic system, the capital cost of $2.5 billion plus yearly energy costs could be recouped over a 20-year period at an average cost to each vehicle owner of $512 per year at a volume of 300,000 vehicles or $168 per year at a volume of 1,000,000 vehicles. Cost comparisons of dynamic charging, increased battery capacity, and gasoline refueling were presented. Dynamic charging, coupled with strategic wayside static charging, was shown to be more cost effective to the consumer over a 10-year period than gasoline refueling at $2.50 or $4.00 per gallon. Notably, even at very low battery prices of $100 per kWh, the research showed that dynamic charging can be a more cost effective approach to extending range than increasing battery capacity. 相似文献
79.
Community severance occurs when transport infrastructure or motorised traffic divides space and people. Despite the growing awareness of its effects on the wellbeing of local communities, the problem is not usually assessed quantitatively or assigned a monetary value. This paper reviews existing practice and research on quantitative methods dealing with community severance. The problem is first decomposed into a series of questions, which are then used as a base to review the methods found in governmental guidance documents, technical reports, and academic studies. The paper ends with recommendations for the integration of severance issues into transport planning. 相似文献
80.