Slam events of high-speed catamarans in irregular waves

Slam events experienced by high-speed catamarans in irregular waves were characterised through experiments using a hydroelastic segmented model. The model was designed to represent the dynamic behaviour of the full-scale Incat 112 m vessel and to allow the measurement of the slam load on the centrebow and wet deck. It was tested in irregular head seas at two speeds relating to Froude numbers of 0.32 and 0.60. Nearly 300 slams were identified in the test data and analysed with respect to kinematic parameters. Slams were found to have a large range of magnitudes, with the largest equivalent to 1785 tonnes full scale (approximately 70% of vessel displacement); however, the majority of events were of relatively low severity. Differences in slam characteristics were found for the two model speeds tested; slams at the slower speed generally occurred further forward on the hull, prior to the wave crest and with a bow down pitch angle. Immersion of the centrebow to the two-dimensional filling height of the cross-section between the centrebow and demihulls is shown to be a better indicator of slam occurrence than immersion to the top of the archway.     

Modelling multiple yacht sailing interactions between upwind sailing yachts

An approach for enhancing the realism of yacht fleet race simulations based on a lifting line method is developed. The wake of an upwind sailing yacht is represented as a single heeled horseshoe vortex and image system. At each time step, changes in vortex strength are convected into the wake as a pair of vortex line elements. These subsequently move in accordance with the local wind, the self-induced velocity and the velocity induced by the presence of the wakes of other yachts. In addition, the lifting line model has a model for the viscous wake due to the drag associated with the yacht and its sails superimposed on it. A synthesis of sail yacht wake representations based on detailed 3D Reynolds-averaged Navier–Stokes computational fluid dynamics calculations with wind tunnel test results is used to capture the initial strength of the combined main-jib vortex system and its vertical height. The implementation of the lifting line algorithm within Robo-Race, a real-time yacht race strategy analysis tool, is described. Two upwind race interaction case studies are presented, and these show that the newly implemented wake model makes an important contribution to enhancing the realism of the sailing simulation.     

Coordinating buses and rapid rail in the San Francisco Bay Area: The case of Bay Area Rapid Transit

This paper examines attempts by planners and policy makers to analyze and bring about the coordination of rail and bus transit in the San Francisco Bay Area. Drawing on studies and plans before and after the creation of the rapid rail system BART (Bay Area Rapid Transit), the author points to technical, analytical and political problems in attempts to link BART and buses. Some options and cautions are presented for planners considering route coordination, feeder buses, transfers and institutional arrangements to manage bus and rail services.     

向顾客提供预防性检修服务

用户手册中的内容包括车辆的详情介绍和使用建议,介绍所涉及的是车辆的操作以及各设备的功能,建议则讲述车辆应当如何保养以得到其最佳性能。下面所说的就是这些建议所组成的一套预防性检修(PM)的规程。 通常我们对车辆的保养需求提出建议是按照平均情况下的行驶里程数和时间定的,因此这些建议也会存在问题,即许多车辆的驾驶状况是截然不同的,维修保养的建议也应该有所区别。例如,经常行驶于炎热的沙漠地带中的HondaCivic(本田 市民)在菲尼克斯的保养和在北达科他州迈诺特市的雪堆中穿行的     

A theoretical and empirical model of trip chaining behavior

This paper addresses the theoretical and empirical issues involved in modeling complex travel patterns. Existing models have the shortcoming of not representing the interdependencies among trip links in trip chains with multiple non-home stops. A theoretical model based on utility theory and explicitly accounting for the trade-offs involved in the choice of multiple-stop chains is developed. Using this theoretical model, utility maximizing conditions for a household's choice of a daily travel pattern are derived. The optimum travel pattern is described in terms of the number of chairs (tours) traveled on a given day and in terms of the number of stops (sojourns) made on each of those chains. For a given household, the form of the optimum pattern is a function of the transportation expenditures (time, cost) required to reach potential destinations. Constraints on the conditions of optimality due to the limited and discrete nature of travel pattern alternatives are also considered. Parameters of the general utility function were estimated empirically using actual travel data derived from a home interview survey taken in Washington, D.C. The multinomial logit model is used to relate utility scores for the alternative travel patterns to choice probabilities. The resulting parameter estimates agree with theoretical expectations and with empirical results obtained in other studies. In order to demonstrate the empirical and theoretical implications of the model, forecasts for various transportation policies (e.g., gasoline price increases, transit fare reductions), as made by this model and by other less complex models, are compared. The results of these comparisons indicate the need for expanding the scope of existing travel forecasting models to explicit considerations of trip chaining behavior.     

全轮驱动车辆传动系统的养护

多年的工作经验表明,熟悉全轮驱动车辆(AWD)传动系统的一些技术细节,将十分有助于增强在四轮驱动车辆(4WD)传动系统的保养与维修方面的业务竞争力。 当我们嘟嘟囔囔发着牢骚,一肚子怨气地看着运货卡车停在皮卡车的后面时,当然也会看到了红色的4x4平头驾驶室连同两个车轮悬在半空中。但悬置在     

故障一点通

福特公司密歇根卡车装配车间1997年至1999年12月9日期间生产的1997—2000年款Expedition和Navigator的拖车牵引挂接装置出现了问题。因此,福特公司向这些车型的车主发出了拖车牵引挂接装置召回通知。     

Flexible parking requirements for office developments: New support for public parking and ridesharing

The author examines new, flexible parking requirements in several U.S. cities and Canada. Flexible requirements provide relaxations in zoning code specifications for off-street parking in return for developer commitments to ridesharing measures, support of transit or in-lieu fees for public parking. Issues examined include whether developers take advantage of flexible requirements, whether agreements with developers lead to agreed-upon action, and whether actions lead to desired results. Based on experiences of several cities, implications and cautions are drawn for local planners. The first caution relates to cities using flexible requirements to collect in-lieu fees in support of public parking. Where cities delay providing parking, inflation may make it difficult to provide the desired parking supply. Or, developers may not choose to pay the fee, such as in the case where cities grant relaxations for other measures more attractive than paying the fees.Other implications relate to flexible requirements in support of ridesharing or transit. Developers will not necessarily take advantage of relaxations tied to support of these modes. Generally, developers will take the least-cost ways to gain relaxations. They may choose to provide the parking where transit or ridesharing measures are too costly or complex. Or, they may take relaxations easier to obtain than those for ridesharing and transit. Finally, even where developers do agree to ridesharing measures, the measures may not be effective. On the other hand, developer-sponsored actions have proven effective in some cities where tight or expensive parking prevails, or where neighborhood residents have organized against office commuters parking on neighborhood streets, or where other economic or community variables favor ridesharing and transit.     

Travelers’ compliance with social routing advice: evidence from SP and RP experiments

Transportation - This study examines to what extent travel information can be used to direct travelers to system-optimal routes that may be sub-optimal for them personally, but contribute to...