Factors associated with bicycle ownership and use: a study of six small U.S. cities

As a means of transportation and as a form of physical activity, bicycling generates benefits to the bicyclist as well as to the community as a whole. Bicycling now accounts for less than 1 percent of all trips for all purposes in the U.S., but evidence from other western countries suggests that under the right conditions, bicycling levels can be significantly higher. Indeed, the experiences of some U.S. cities suggest that it is possible to create conditions conducive to higher levels of bicycling even in the U.S. However, the extent to which bicycle investments have contributed to bicycling levels in these communities has not been rigorously assessed. The purpose of this study is to provide a better understanding of the determinants of bicycle ownership and use as a basis for identifying ways to promote bicycling. A cross-sectional study of six cities was designed to test the importance of bicycle infrastructure and other physical environment factors relative to individual factors and social environment factors, using a nested logit model to examine ownership and use decisions jointly. The results show strong effects of individual attitudes and physical and social environment factors on bicycle ownership and use.     

Mass transit systems of Beijing: governance evolution and analysis

Developing a more efficient mass transit system, in highly populated cities, improves the mobility, decreases the dependency of private cars, alleviates traffic congestion, and provides a more environmentally friendly means of travel. Recently, the city of Beijing decided to have a target of becoming as a ‘public-transport city’ with a fascinating mass transit system within a larger plan, of building humanistic, scientific and technological, and green public-transport systems. This work discusses the governance evolution of the mass transit system of Beijing between 1949–2008, comprised of two groups of transit systems, the road surface public-transport system (bus, tram, trolley, etc.), and the subway public-transport system. In addition, a time-series analysis is introduced in an attempt to examine the effect of governance evolution on the two transit systems, and of the impacts of the governance structural changes on the mass transit system. The time-series model is introduced using the annual statistics data of the period 1949–2008. The outcome of the analysis is viewed with precaution because of the incompleteness of the many endogenous and exogenous factors to affect the public-transport demand. Generally speaking it is concluded that the governance evolution provides beneficial effect of the Beijing mass transit activity; however, for satisfying the significant increase of the Beijing city’s travel demand and maintaining sustainable development, the governance-involvement pattern needs to be reformed.     

Exploring public transport usage trends in an ageing population

An ageing population remains one of the most significant challenges for Western society in the 21st century. Whilst public transport use has attractive sustainability features for older generations there is mixed evidence with regard to trends in travel and public transport use in ageing societies. This paper explores public transport trip rates amongst older age groups using travel survey evidence collected from a household travel survey in Melbourne, Australia for the period 1994 to 1999. A particular aim of the research was to establish trends in trip rates so as to explore the impact of the ageing Baby Boomer generation on travel by public transport. The results suggested that compared to those aged below 60, those aged over 60 years demonstrated 30% lower trip making overall and 16% lower public transport trip rates. Longitudinal trends in trip rates showed those aged over 60 had a very small decline in trip rates by public transport (−0.004 average daily trips per annum) but increasing rates for car trips. A further analysis showed a small but significant increase in longitudinal trip rates of public transport use amongst Baby Boomers (0.004 daily trips p.a., p < .05) while car usage for Baby Boomers was steady. The implication of these findings is that trends in the existing over 60s population are not necessarily going to flow through to behaviour patterns in the Baby Boomer generations. The Baby Boomer age group showed longitudinal trends in travel behaviour which contrasted with those of the existing over 60s generation notably with a trend towards increased public transport usage.     

Extending stated choice analysis to recognise agent-specific attribute endogeneity in bilateral group negotiation and choice: a think piece

This paper is a think piece on variations in the structure of stated preference studies when modelling the joint preferences of interacting agents who have the power to influence the attribute levels on offer. The approach proposed is an extension of standard stated choice methods, known as ‘stated endogenous attribute level’ (SEAL) analysis. It allows for interactive agents to adjust attribute levels off a base stated choice specification that are within their control, in an effort to reach agreement in an experimental setting. This accomplishes three goals: (1) the ability to place respondents in an environment that more closely matches interactive settings in which some attribute levels are endogenous to a specific agent, should the modeller wish to capture such behaviour; (2) the improved ability of the modeller to capture the behaviour in such settings, including a greater wealth of information on the related interaction processes, rather than simply outcomes; and (3) the expansion of the set of situations that the modeller can investigate using experimental data.

荷坳隧道四洞小净距段支护结构设计研究北大核心CSCD

多洞空间小净距隧道支护结构参数量化设计与安全性分析是当前设计中的一大难题。文章针对深圳机荷高速公路荷坳隧道四洞小净距段的设计,采用总安全系数法对四洞的开挖与支护模式、各洞的开挖顺序及支护参数进行了研究比较,并采用隧规荷载-结构法、增量法、地层-结构法对支护结构的安全系数进行了对比计算,得出以下结论:(1)提出了基于总安全系数法原理的多洞空间小净距隧道设计方法;(2)根据总安全系数法得出了荷坳隧道四洞小净距段应采用“先行洞二次衬砌完成后再开挖下一孔隧道”的开挖与支护模式,且应按洞1→洞2→洞3→洞4的开挖顺序施工;(3)隧规荷载-结构法、增量法、地层-结构法虽无法得出结构的总承载安全系数,但在一定程度上可以反应部分支护结构的安全性。     

框架四叉树的自主水下航行器追踪动态目标研究(英文)

An autonomous underwater vehicle (AUV) must use an algorithm to plan its path to distant, mobile offshore objects. Because of the uneven distribution of obstacles in the real world, the efficiency of the algorithm decreases if the global environment is represented by regular grids with all of them at the highest resolution. The framed quadtree data structure is able to more efficiently represent the environment. When planning the path, the dynamic object is expressed instead as several static objects which are used by the path planner to update the path. By taking account of the characteristics of the framed quadtree, objects can be projected on the frame nodes to increase the precision of the path. Analysis and simulations showed the proposed planner could increase efficiency while improving the ability of the AUV to follow an object.     

溃坝模拟的光滑粒子流体动力学方法及其粘性特性(英文)

Smoothed particle hydrodynamics (SPH) is a Lagrangian meshless particle method. It is one of the best method for simulating violent free surface flows in fluids and solving large fluid deformations. Dam breaking is a typical example of these problems. The basis of SPH was reviewed, including some techniques for governing equation resolution, such as the stepping method and the boundary handling method. Then numerical results of a dam breaking simulation were discussed, and the benefits of concepts like artificial viscosity and position correction were analyzed in detail. When compared with dam breaking simulated by the volume of fluid (VOF) method, the wave profile generated by SPH had good agreement, but the pressure had only reasonable agreement. Improving pressure results is clearly an important next step for research.     

二维水翼型空化流的数值计算(英文)

In order to predict the effects of cavitation on a hydrofoil, the state equations of the cavitation model were combined with a linear viscous turbulent method for mixed fluids in the computational fluid dynamics (CFD) software FLUENT to simulate steady cavitating flow. At a fixed attack angle, pressure distributions and volume fractions of vapor at different cavitation numbers were simulated, and the results on foil sections agreed well with experimental data. In addition, at the various cavitation numbers, the vapor fractions at different attack angles were also predicted. The vapor region moved towards the front of the airfoil and the length of the cavity grew with increased attack angle. The results show that this method of applying FLUENT to simulate cavitation is reliable.     

经验模式能量在脉动信号分析中的应用(英文)

After an aerial object enters the water, physical changes to sounds in the water caused by the accompanying bubbles are quite complex. As a result, traditional signal analyzing methods cannot identify the real physical object. In view of this situation, a novel method for analyzing the sounds caused by an aerial object’s entry into water was proposed. This method analyzes the vibrational mode of the bubbles by using empitical mode decomposition. Experimental results showed that this method can efficiently remove noise and extract the broadband pulse signal and low-frequency fluctuating signal, producing an accurate resolution of entry time and frequency. This shows the improved performance of the proposed method.