自适应有限元分析的网格自动生成方法的选择

针对当前存在的、具有代表性的网格自动生成方法进行分析讨论，从网格控制机理的角度，分析这些方法是否适合于自适应有限元分析系统。结果表明，一般情况下，４／８叉树网格生成方法非常适合用于自适应有限元分析系统。     

From traces to trajectories: How well can we guess activity locations from mobile phone traces?

Passively generated mobile phone dataset is emerging as a new data source for research in human mobility patterns. Information on individuals’ trajectories is not directly available from such data; they must be inferred. Many questions remain in terms how well we can capture human mobility patterns from these datasets. Only one study has compared the results from a mobile phone dataset to those from the National Household Travel Survey (NHTS), though the comparison is on two different populations and samples. This study is a very first attempt that develops a procedure to generate a simulated mobile phone dataset containing the ground truth information. This procedure can be used by other researchers and practitioners who are interested in using mobile phone data and want to formally evaluate the effectiveness of an algorithm.To identify activity locations from mobile phone traces, we develop an ensemble of methods: a model-based clustering method to identify clusters, a logistic regression model to distinguish between activity and travel clusters, and a set of behavior-based algorithms to detect types of locations visited. We show that the distribution of the activity locations identified from the simulated mobile phone dataset resembles the ground truth better than the existing studies. For home locations, 70% and 97% of identified homes are within 100 and 1000 m from the truth, respectively. For work places, 65% and 86% of the identified work places are within 100 and 1000 m from the true ones, respectively. These results point to the possibility of using these passively generated mobile phone datasets to supplement or even replace household travel surveys in transportation planning in the future.     

基于弓网电弧动态模型的高速列车弓网电弧产生机理

分析了高速列车弓网电弧产生的机理,结合受电弓和接触网间的离线时间、材料缺陷、电腐蚀等问题,解析了弓网电弧与高速列车安全的关联机制。依据电弧理论的动态模型算法,推导了Cassie模型和Mayr模型的理论公式,并论述了这两种模型的适用条件和应用范围。提出了高速列车弓网电弧方面目前仍存在的问题及未来电弧研究的展望。     

SMS水动力学软件

简要介绍了水动力学软件SMS的基本功能,并用简单实例对其前后处理功能做了展示。     

电力电子与绿色能源

介绍了绿色能源的概念,以风力发电为重点介绍了电力电子技术在绿色能源发展中的应用以及分布式发电在绿色能源系统方面的应用.     

Multi-activity access: How activity choice affects opportunity

It is commonly seen that accessibility is measured considering only one opportunity or activity type or purpose of interest, e.g., jobs. The value of a location, and thus the overall access, however, depends on the ability to reach many different types of opportunities. This paper clarifies the concept of multi-activity accessibility, which combines multiple types of opportunities into a single aggregated access measure, and aims to find more comprehensive answers for the questions: what is being accessed, by what extent, and how it varies by employment status and by gender. The Minneapolis - St. Paul metropolitan region is selected for the measurement of multi-activity accessibility, using both primal and dual measures of cumulative access, for auto and transit. It is hypothesized that workers and non-workers, and males and females have different accessibility profiles. This research demonstrates its practicality at the scale of a metropolitan area, and highlights the differences in access for workers and non-workers, and men and women, because of differences in their activity participation.     

Planning transport for social inclusion: An accessibility-activity participation approach

Social equity is increasingly becoming an important objective in transport planning and project evaluation. This paper provides a framework and an empirical investigation in the Greater Toronto and Hamilton Area (GTHA) examining the links between public transit accessibility and the risks of social exclusion, simply understood as the suppressed ability to conduct daily activities at normal levels. Specifically, we use a large-sample travel survey to present a new transport-geography concept termed participation deserts, neighbourhood-level clusters of lower than expected activity participation. We then use multivariate models to estimate where, and for whom, improvements in transit accessibility will effectively increase activity participation and reduce risks of transport-related social exclusion. Our results show that neighbourhoods with high concentrations of low-income and zero-car households located outside of major transit corridors are the most sensitive to having improvements in accessibility increase daily activity participation rates. We contend that transit investments providing better connections to these neighbourhoods would have the greatest benefit in terms of alleviating existing inequalities and reducing the risks of social exclusion. The ability for transport investments to liberate suppressed activity participation is not currently being predicted or valued in existing transport evaluation methodologies, but there is great potential in doing so in order to capture the social equity benefits associated with increasing transit accessibility.     

Making time count: Traveler activity engagement on urban transit

In practice, travel time is assigned a cost and treated as a disutility to be minimized. There is a growing body of research supporting the hypothesis that travel time has some value of its own, and the proliferation of information and communication technology (ICT) may be contributing to that value. Travelers’ attitudes are confounded with their mode choice, and as telecommunications mediate travel behavior, analysts must recognize the interaction between time use and customer satisfaction for appropriate travel demand management. To that end, this paper presents results from jointly estimated models of travelers’ latent satisfaction and on-board activity engagement using Chicago transit rider data gathered in April 2010. The simple questionnaire and small sample corroborate the findings of past research indicating travel attitudes and activity engagement have potential to influence travelers’ value of time, and many transit riders consider transit a better use of time and/or money than driving. The findings affirm the need for a more holistic understanding of value of time for travel demand management and infrastructure valuation. As time use has an influence on users’ valuation of the transit mode, offering opportunities to conduct certain leisure activities could improve the perceived value of travel time.     

Should we all just stay home? Travel,out-of-home activities,and life satisfaction

How and why travel contributes to our life satisfaction is of considerable import for transportation policy and planning. This paper empirically examines this relationship using data from the American Time Use Survey. It finds that, controlling for relevant demographic, geographic, and temporal covariates, travel time per day is significantly and positively associated with life satisfaction. This relationship is attenuated, but still significant, when the amount of time spent participating in out-of-home activities is controlled for. Time spent bicycling is strongly associated with higher life satisfaction, though it attains significance only in some models; time spent walking is also quite positive, though it is not significant. However, both walking and bicycling are positively and significantly associated with life satisfaction when time spent on purely recreational walking and bicycling is included. Life satisfaction is positively and significantly associated with time spent traveling for the purposes of eating and drinking, religious activities, volunteering, and playing and watching sports. Travel time exhibits a strong positive relationship with life satisfaction in smaller towns and cities, but in large cities the association weakens, and for very large cities travel time may actually not be associated with life satisfaction at all. This may be due to the costs of traffic congestion, which disproportionately exists in large cities. In all, while the associations between travel and life satisfaction are clear, the causal story is complex, with the positive relationships potentially being explained by (1) travel allowing us to access destinations that make us happy, (2) the act of travel itself being fulfilling, and/or (3) intrinsically happier people being more likely to travel. In all likelihood, all three factors are at play.