A flexible spatially dependent discrete choice model: Formulation and application to teenagers’ weekday recreational activity participation

This study proposes a simple and practical Composite Marginal Likelihood (CML) inference approach to estimate ordered-response discrete choice models with flexible copula-based spatial dependence structures across observational units. The approach is applicable to data sets of any size, provides standard error estimates for all parameters, and does not require any simulation machinery. The combined copula–CML approach proposed here should be appealing for general multivariate modeling contexts because it is simple and flexible, and is easy to implementThe ability of the CML approach to recover the parameters of a spatially ordered process is evaluated using a simulation study, which clearly points to the effectiveness of the approach. In addition, the combined copula–CML approach is applied to study the daily episode frequency of teenagers’ physically active and physically inactive recreational activity participation, a subject of considerable interest in the transportation, sociology, and adolescence development fields. The data for the analysis are drawn from the 2000 San Francisco Bay Area Survey. The results highlight the value of the copula approach that separates the univariate marginal distribution form from the multivariate dependence structure, as well as underscore the need to consider spatial effects in recreational activity participation. The variable effects indicate that parents’ physical activity participation constitutes the most important factor influencing teenagers’ physical activity participation levels. Thus, an effective way to increase active recreation among teenagers may be to direct physical activity benefit-related information and education campaigns toward parents, perhaps at special physical education sessions at the schools of teenagers.     

Measuring unobserved prices using the structural time-series model: The case of cycling

This study presents a means of determining a historic (generalised cost based) price index for cycling in the UK for the period 1949–2006 using annual demand data. By specifying demand as a function of generalised price and income and then applying a structural time-series model to elucidate the unobserved component of prices (while controlling for observed income levels), it is illustrated that the role of prices in influencing demand is non-trivial. Over the sample period price responses generally influence demand for cycling to a greater extent than income effects.     

Nonlinear pricing of taxi services

This paper examines the effects of nonlinear fare structures in taxi markets using an extended taxi model with an explicit consideration of perceived profitability. The expected profit, defined as the profit per unit time (inclusive of both occupied and vacant taxi times), that a taxi driver expects to receive from picking up a customer in a particular zone or location, has great impact on the taxi driver’s choice of location in the search for customers. The fare structure directly governs the profitability of taxi rides of different distances originating from different locations. With these explicit considerations, the extended model is intended to look into the market effects of adopting a nonlinear fare structure with declining incremental charges. The proposed nonlinear fare structure could help restore a level-playing field for taxi operators whose businesses have been affected by some taxi drivers who resort to practices such as offering fare discounts or accepting requests for discounted fares from passengers for long-haul trips. Analysis of sensitivity of social welfare and profit gain as well as taxi/customer wait/search times is conducted with respect to the parameters in the nonlinear fare structure for the Hong Kong taxi market, and Pareto-improving nonlinear fare amendments are identified that neither disadvantage any customer nor reduce the taxi operators’ profits.     

Estimating spatial interdependence in automobile type choice with survey data

In this article, we show that vehicle type ownership is spatially dependent at both the regional and household-level even after controlling for income and population density. We discuss reasons for the existence of spatial effects in vehicle ownership, and note potential implications for policymakers. Our results point to the importance of spatial relationships in transportation research and highlight the hazards of ignoring their role in affecting transportation outcomes. For example, if vehicle type choice is affected by neighborhood spillovers, agencies that regulate traffic flow and road safety could tailor their choice projections and policy tools to account for such interdependence.     

基于DRNN神经网络的PD混合控制技术在船舶动力定位系统中的应用

船舶在海上运动是一种复杂的非线性运动，其水动力系数很难精确确定，而海洋环境的随机干扰因素也在不断地发生变化，因此需要研究具有鲁棒性和自适应能力的船舶动力定位控制技术。PID控制在优化参数的条件下，对于能够建立精确数学模型的确定性系统具有鲁棒性好和可靠性高的特点，但对于船舶运动这样复杂的非线性系统其控制效果不理想，而神经网络具有自学习和自适应能力，因此需要结合两者的特点，设计自适应能力强、鲁棒性好的控制技术。本文研究了基于DRNN神经网络的PD混合控制技术，并将其应用到船舶动力定位系统。仿真结果表明该方法有效，且具有较好的鲁棒性和自适应能力，提高了动力定位系统的精度和性能。     

An analysis of gravity model distance exponents

This study examines variations in the basic parameter of the gravity model: the distance or travel time exponent. In a conceptual examination of the exponent under ideal conditions, it is noted that the exponent will be low if either production or consumption of the phenomena is geographically concentrated. It is further noted that if all regions produce and consume the phenomena, this generally implies a large number of substitute regions, and therefore a large exponent. These three variables are made operational and related to a set of eighty exponents for 1967 commodity flows in the United States. A multiple regression model is derived and utilized to estimate the exponents. The latter are then used to reestimate the flows. The root mean squared errors are quite similar for the fitted and estimated exponents. Implications of the research appear to be consistent with variations of the exponent in the urban context.     

交通方式可达性差距——衡量交通可持续发展的指数

交通因其消耗大量能源而在可持续发展中扮演着重要角色,为了规划交通可持续发展,有必要提出能够评估和衡量交通可持续发展的指数。利用可达性概念和地理信息系统提出交通方式可达性差距指数。该指数由人口数量、就业岗位数、商店数以及学校数等决定,根据公共交通方式和私人交通方式间可达性指数差异计算。就能源效率而言,公共交通方式比私人交通方式更能实现可持续。可达性差距指数越高意味着可持续能力越强。通过比较香港1991年和1996年的可达性差距指数,来检验交通发展的可持续性是否有所提升。最后,讨论了如何运用可达性差距指数来检验土地利用以及交通发展政策和方案,以便确定更可持续的政策和方案。     

闽南早期历史研究的现代新趋势——《刺桐梦华录》书评

苏基朗的<刺桐梦华录>一书,通过三个交织在一起的主题:繁荣、区域和制度,来分析闽南泉州的经济演变,是史学界研究方法的一种突破.该书探讨了不少在前辈的研究中难以深入的问题,但终因缺少确凿的实证基础而只能采用逻辑推理的方法.这种研究方法使其得出的结论缺少客观性,但却为闽南史学研究提出了新的思考.     

Mathematical Models and Computer Simulation of Nitrogen Concentration Profiles in Pulse Ion Nitrided Layers

IntroductionThedireCtcrt(DC)ionndriding,whichhasbeenopliedfOrmanyyears,didn'tthoroughlysolvetheionnitridingproblemofsomecomPlexwOrkPlacesinshapeandstrUctUreunhlthepulse-iondridingPrOcessingaroseIl].Recentresultsshowthatthearc-CUttin-offsystemsincircuitcanbecancelled,thishasmadethecOntrOlsystemsofionnitridingequiPmentandhaacestwbessimPlnygreatiyMorehaPOrtantiy,theexcellentschcequalityofthewOrkPiecetreatedhasa1sobeenObtainedemPlovingPulseionchdingcomParedwithDCionnitriding.InOrdertOr…     

Biologie, transport, complexité

As a result of some of the analogies between biology and transport, including the concepts of evolution and selection, we are wondering whether some ideas and methods used in biology may not be used to provide research avenues within the field of transportation. We are interested in the idea of complexity, which is common to the two scientific fields, but not treated in the same way by either of the two disciplines. By observing the way in which systemic biology has developed, from a largely “data-driven” approach to research guided by data, we are questioning whether such a direction would be possible in the field of transportation. This investigation also leads us to ask questions about “modules”, or the boundaries of the subsystems studied in the field of transportation, through the observation that molecular biology defines these boundaries in terms of the function of the subsystems. In conclusion, we are expressing the notion that these comparisons will lead to new research avenues in the field of transportation.