The measure of all things: reflections on changing conceptions of the individual in travel demand modeling

Transportation demand modeling has evolved in scope, theory, and practice in the many decades since the US Bureau of Public Roads pioneered home interview transportation studies in metropolitan households in the early 1940s. The major currents of these developments are discussed in the present paper through consideration of the changing role of the individual—as a source of data, as a unit of analysis, and as the intended beneficiary. In addition to reviewing this history we raise, but are unable to resolve, a growing current concern, namely how the public interest can be best served when the transportation data of greatest value is collected by private entities.     

Behavior of taxi customers in hailing vacant taxis: a nested logit model for policy analysis

This study models and examines the taxi customers' preferences for hailing vacant taxis on streets. A stated preference survey was conducted to randomly select and interview 1242 taxi customers at taxi stands and pedestrians on streets, who had experiences of taking taxis recently, about their choices under different given hypothetical scenarios. In total, 4968 observations were collected and used for developing the discrete choice models for the analysis. To account for the potential correlations among alternatives, two nested logit models are developed, calibrated, and compared with a standard multinomial logit model in the investigation. The results of likelihood ratio test demonstrate that one of the developed nested logit models is better than the standard multinomial logit model to describe the search behavior of taxi customers. The model results also show that the walking time to and the waiting time at the location for hailing taxis, the extra travel time to the destination because of local circulation for finding a way from the pickup location heading to a passenger's destination, as well as the taxi customers' perceptions for walking to and waiting at taxi stands were found as significant factors to influence their decisions. In addition, the results of market segmentation analysis illustrate the variations in taxi‐search strategies of taxi customers in different districts and regions. Some policy implications on introducing more taxi stands and improving the utilization rates of taxi stands are also discussed. We believe that the proposed models, findings, and discussion are useful for developing micro‐simulation models to evaluate the performance of road traffic networks with taxi services and developing simulation‐based optimization models to answer policy questions related to taxi services. Copyright © 2015 John Wiley & Sons, Ltd.     

Discharge headway at signalized intersections in Hong Kong

This paper reports the analysis and comparisons of discharge headways at 26 sites in Hong Kong. Previous studies here established good understanding of the average discharge headway under various conditions but very few studies dealt with discharge headway of individual vehicles which is a vital component in the traffic simulation at signalized intersections. This study that looked into the discharge headway of individual vehicles found that the discharge headway at different queue position follows the Type I Extreme Value Distribution. A method of estimating site‐specific parameters for this distribution has also been proposed.     

Analysis of Clogging Mechanism and Filter-cake Structure of Slurry Containing Coarse-particle Materials in Sandy Strata北大核心CSCD

The problem of filter-cake formation in highly permeable strata is urgently to be solved for slurry shield tunnelling. Adding coarse-particle materials in slurry is an effective method to solve the problem. A selfdesigned test device of slurry invasion and filter-cake formation in strata was adopted, and one kind of lightweight sand was selected as coarse particle materials. By changing the particle sizes of light-weight sand particles, the filtrate mass and the time of filter-cake formation under the condition of different additive contents and pressures were measured. And the influence of particle size of coarse-particle materials on filter-cake formation characteristics was analyzed. A triangular constriction calculation method was proposed, which can be used to quickly determine the influence range of coarse-particle materials on the pore size variation of the strata. The test results show that: (1) the addition of coarse-particle materials can significantly reduce the inter-particle pore size and effectively improve the clogging effectiveness under the condition of this tested strata. (2) The particle size of coarse-particle materials has a great influence on filter-cake formation characteristics. The coarse-particle material with smaller particle size has a better clogging effect, and its filter-cake formation characteristics are more stable. The coarse-particle material with larger particle size has a higher volatility in its filter-cake formation characteristics. (3) Coarse-particle materials with different particle sizes result in different final filter-cake structures. When the coarse-particle materials possess a larger particle size, a mixed filtercake structure is formed, and when the particle size is small, a double-layer filter-cake structure is formed. © 2018, Editorial Office of "Modern Tunnelling Technology". All right reserved.     

顶湖—仙渡345 kV地下输电线路工程设计与施工

因都会区用电量增加,且为减低输电线路对市区景观及环境冲击,台电公司于台北市北投区大度路旁兴建地下电缆洞道,由顶湖超高压变电所引入345 kV二回线至仙渡超高压变电所。采用潜盾工法以降低交通及环境冲击的问题,因施工遭遇软硬不同土层及高水压影响,且穿越捷运淡水线关渡隧道下方,紧邻大度陆桥,因此在设计上采用大洞道方案、2道止水条、发进井调整位置及角度等方案,以降低施工对于附近结构物之冲击。     

Development of the performance simulator for electric scooters with an in-wheel motor

Due to the increasing use of fossil fuel, carbon dioxide emission also increased and environmental problems have emerged as social issues. Accordingly, the research about electric vehicles as personal transportation has been actively performed. An electric scooter is not as complex as an automobile, but it takes a lot of time and costs to design and develop a new vehicle due to trial and error in selecting the specifications of core components according to consumer’s requirements. In this paper, a performance simulator for an electric scooter with an in-wheel motor at the rear wheel was developed and the simulation results were verified through experiments. For a longer travelling distance with the same energy source, the regenerative braking algorithm that converts kinetic energy into electric energy during braking was applied. The usefulness of the regenerative braking control algorithm was verified through various simulation results.     

Simplified fatigue durability assessment for rear suspension structure

The eight-channel test rig is widely used in durability assessment of vehicle components while for some cases of rear suspension, this costly instrument is unnecessary. Based on the analysis of structure and forces, a simpler one-channel testing approach is presented for the durability calculation of a dependent rear suspension. Taking a punched rear shock tower as the study object, a FEA strain-stress analysis was first performed to determine the risk area. Then, the entire vehicle test system was created, and the proving ground tests were carried out so that the real strain on the part could be measured. Based on the road test data and the P-S-N curve of the component, the cumulative fatigue damage of a 15,000-kilometer proving ground test road was calculated, and the computational result indicates that the modified structure was safe for durability analysis. Moreover, a standard 50% S-N survival fraction curve was plotted using Corten and Dolan’s method, which can be utilized in the durability analysis for other similar components. Finally, the road test for this modified suspension structure was carried out, and the test result certified that the punched shock tower can be subjected to a 15,000-kilometer proving ground test road without the appearance of fatigue failure.     

基于模型预测的波能转换装置阵列的控制策略（英文）

To facilitate the commercialization of wave energy in an array or farm environment, effective control strategies for improving energy extraction efficiency of the system are important. In this paper, we develop and apply model-predictive control(MPC) to a heaving point-absorber array, where the optimization problem is cast into a convex quadratic programming(QP)formulation,which can be efficiently solved by a standard QP solver. We introduced a term for penalizing large slew rates in the cost function to ensure the convexity of this function. Constraints on both range of the states and the input capacity can be accommodated. The convex formulation reduces the computational hurdles imposed on conventional nonlinear MPC. For illustration of the control principles,a point-absorber approximation is adopted to simplify the representation of the hydrodynamic coefficients among the array by exploiting the small devices to wavelength assumption. The energycapturing capabilities of a two-cylinder array in regular and irregular waves are investigated. The performance of the MPC for this two-WEC array is compared to that for a single WEC, and the behavior of the individual devices in head or beam wave configuration is explained. Also shown is the reactive power required by the power takeoff system to achieve the performance.     

Development of a Remotely Controlled Testing Platform with Low-drag Air-ventilated Hull

This paper addresses the development and testing of a remotely controlled boat platform with an innovative air-ventilated hull. The application of air cavities on the underside of ship hulls is a promi...     

Activity‐based approaches to travel analysis: conceptual frameworks,models, and research problems

Recent policy discussions about information technology in transport and traffic demand management have increased interest in activity‐based approaches to the analysis of travel behaviour, in particular in the modelling of household activity scheduling which is at the core of many of the required changes in travel behaviour. This paper is a state‐of‐the‐art review of conceptualizations and models of activity scheduling with special regard to issues raised by the new policy instruments. In the course of the review, the validity of behavioural assumptions is examined critically and several needs for future research identified.