Commuting costs and the residential mobility of job changers

In traffic and transport research, attention is given to the relevance of location patterns of activities to moving behaviour, the inverse causality being mostly left out of account. This paper considers what influence (changes in) travel costs have on moving behaviour and residential choice. The analysis has been carried out for employed people who change jobs. The residential choice has been split into a marginal probability of moving and a conditional destination choice. Both choices appear to be influenced significantly by travel‐cost variables.     

A review of the impact of parking policy measures on travel demand

This paper reviews the empirical evidence relating to the impact of parking policy measures on the demand for parking and for travel. Disaggregate modal choice models, disaggregate parking location models and site‐specific studies of parking behaviour are examined. With regard to modal choice models, it is concluded that few studies deal adequately with parking factors, but that there is some support for the view that parking policy measures are a relatively important influence on modal choice. When parking location models are examined parking policy variables are shown to have a substantial impact on choice of parking location. With regard to site‐specific studies, the paper concludes that there is a great variation in the parking price elasticities quoted, which reflects partly the methodological problems associated with such studies. Suggestions to improve model specification are made.     

The wind-forced response on a buoyant coastal current: Observations of the western Gulf of Maine plume

The freshwater plume in the western Gulf of Maine is being studied as part of an interdisciplinary investigation of the physical transport of a toxic alga. A field program was conducted in the springs of 1993 and 1994 to map the spatial and temporal patterns of salinity, currents and algal toxicity. The observations suggest that the plume's cross-shore structure varies markedly as a function of fluctuations in alongshore wind forcing. Consistent with Ekman drift dynamics, upwelling favorable winds spread the plume offshore, at times widening it to over 50 km in offshore extent, while downwelling favorable winds narrow the plume width to as little as 10 km.Using a simple slab model, we find qualitative agreement between the observed variations of plume width and those predicted by Ekman theory for short time scales of integration. Near surface current meters show significant correlations between cross-shore currents and alongshore wind stress, consistent with Ekman theory. Estimates of the terms in the alongshore momentum equation calculated from moored current meter arrays also indicate a dominant Ekman balance within the plume. A significant correlation between alongshore currents and winds suggests that interfacial drag may be important, although inclusion of a Raleigh drag term does not significantly improve the alongshore momentum balance.     

基于手机传感器数据的交通出行调查实证评估

应用手机传感器与调查问卷, 同步采集了校园内高校学生2周的真实出行轨迹; 考虑了真实出行环境下的手机传感器数据特征, 结合高斯滤波预处理数据, 根据轨迹点的时空聚类特性, 用时空聚类算法识别了出行端点和出行时间, 结合轨迹点速度、加速度特征, 利用支持向量机识别了出行方式; 将手机传感器数据与调查问卷、查核线数据对比, 分析了手机传感器数据出行特征识别的准确程度, 验证了出行特征的提取效果。分析结果表明: 手机传感器与问卷调查识别出行链的成功匹配比例为81.66%, 说明手机传感器数据可有效记录出行轨迹; 时空聚类算法参数中核心点空间半径为26.92 m, 最小样本点为129, 时间约束为129 s时, 出行端点识别准确率为93.02%, 出行时间识别准确率为90.84%, 说明手机传感器识别出行端点和出行时间的效果较好; 当支持向量机设置类型为经典支持向量机, 核函数为径向基函数, 惩罚系数为0.797, 核参数为2.260时, 出行方式识别准确率为89.86%, 即利用手机传感器能够有效识别出行方式。可见, 手机传感器数据识别结果合理, 能为手机传感器数据应用于实际出行调查做支撑。     

印度应对城市机动化策略

为应对快速的城市机动化进程及其带来的负面影响,印度政府早期采取诸如修建立交桥和拓宽道路等办法,结果却导致了更多的机动车数量增加和更严重的交通拥堵。为此,印度政府实施了＂国家城市交通政策＂,重点投资公共交通和非机动交通方式;同时还制定了＂国家城市更新计划＂,以此建立鼓励地方政府执行国家政策的激励机制,提高对城市基础设施的投资水平。这些创新政策的实施,推动了一系列公共交通项目的发展,也促进了城市内部交通体制改革和城市综合交通发展规划的制定。     

Dynamic response of the train–track–bridge system subjected to derailment impacts

Derailments on bridges, although not frequent, when occurs due to a complex dynamic interaction of the train–track–bridge structural system, are very severe. Furthermore, the forced vibration induced by the post-derailment impacts can toss out the derailed wagons from the bridge deck with severe consequences to the traffic underneath and the safety of the occupants of the wagons. This paper presents a study of the train–track–bridge interaction during a heavy freight train crossing a concrete box girder bridge from a normal operation to a derailed state. A numerical model that considers the bridge vibration, train–track interaction and the train post-derailment behaviour is formulated based on a coupled finite-element – multi-body dynamics (FE-MBD) theory. The model is applied to predict the post-derailment behaviour of a freight train composed of one locomotive and several wagons, as well as the dynamic response of a straight single-span simply supported bridge containing ballast track subjected to derailment impacts. For this purpose, a typical derailment scenario of a heavy freight train passing over a severe track geometry defect is introduced. The dynamic derailment behaviour of the heavy freight train and the dynamic responses of the rail bridge are illustrated through numerical examples. The results exhibit the potential for tossing out of the derailed trains from the unstable increase in the yaw angle signature and a lower rate of increase of the bridge deck bending moment compared to the increase in the static axle load of the derailed wheelset.     

Effect of fuel injection strategies on the combustion process in a PFI boosted SI engine

A low-cost solution based on fuel injection strategies was investigated to optimize the combustion process in a boosted port fuel injection spark ignition (PFI SI) engine. The goal was to reduce the fuel consumption and pollutant emissions while maintaining performance. The effect of fuel injection was analyzed for the closed and open valve conditions, and the multiple injection strategies (MIS) based on double and triple fuel injection in the open-valve condition. The tests were performed on an optical accessible single-cylinder PFI SI engine equipped with an external boost device. The engine was operated at full load and with a stoichiometric ratio equivalent to that of commercial gasolines. Optical techniques based on 2D-digital imaging were used to follow the flame propagation from the flame kernel to late combustion phase. In particular, the diffusion-controlled flames near the valves and cylinder walls, due to fuel deposition, were studied. In these conditions, the presence of soot was measured by two-color pyrometry, and correlated with engine parameters and exhaust emissions measured by conventional methods. The open valve fuel injection strategies demonstrated better combustion process efficiency than the closed ones. They provided very low soot levels in the combustion chamber and engine exhaust, and a reduction in specific fuel consumption. The multiple injection strategies proved to be the best solution in terms of performance, soot concentration, and fuel consumption.     

Empirical approach for predicting the cetane number of biodiesel

The cetane number is an indicator of ignition quality and thus of fuel quality in the realm of diesel engines. It is conceptually similar to the octane number used for gasoline. Generally, a compound that has a high octane number tends to have a low cetane number and vice versa. The cetane number of a diesel fuel is related to the ignition delay time. In our work the first approach is a statistical one the accuracy of which depends upon the data obtained from various papers and literature sources, as all equations used were based on this data. During prediction using more than one equation is a good approach, as it provides the accuracy as well as the relative error. The second approach is also a statistical one, but its value depends upon the saponification number and iodine value. Therefore the accuracy of this equation may be higher, since we can collect the data for saponification numbers and iodine values from literature, without needing to calculate them. Using the saponification number and iodine value we can select an optimal biodiesel as generally a good biodiesel is selected using these three values. Thus the second approach allows us the freedom to select a biodiesel.     

空心板材固有频率的求解及优化设计

用扩展Ｄｉｒａｃ函数一表示空心板材在刚度以及质量密度上由空洞而引起的非连续变化,从而不连续函数的求解问题为连续函数的求解问题,继而用Ｇａｌｅｒｋｉｎ法对其固有频率进行了求解,得到了适应于任意大小、任意分布空调的空心板材的固有频率计算公式。计算结果显示：空心板材的固有频率不仅与板材的几何尺寸有关,而且还与各空调的位置即分布方式有关,除此之外还与混凝土的Ｐｏｉｓｓｏｎ比有关。     

Texture Development of a Cold-rolled CuZnAl Alloy

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