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811.
Peter J.H. Shewey 《Transportation Research Part B: Methodological》1983,17(5):391-397
In order to identify route choice, registration number surveys were carried out and the numbers were then matched. Because of the nature of the routes being investigated, it was found that the level of spurious matches was large relative to the number of tripmakers. This cast considerable doubt on the estimated number of tripmakers and their mean journey times. Accordingly, it was necessary to devise an algorithm which minimised the effect of such errors. This algorithm and a method of estimating the number of residual spurious matches is discussed in this paper and is compared with the original algorithm for an actual example. 相似文献
812.
M. G. H. Bell 《Transportation Research Part B: Methodological》1985,19(6):497-507
An expression is derived for the variances and covariances of the logarithms of origin- destination flows when estimated by one of a family of log-linear models. Among this family is the Furness growth factor model, the gravity model, the Willumsen model and the Van Zuylen-Bell model. Variances and covariances for the logarithms of the parameters incorporating prior information and for the values of the constraints with which the fitted values must conform are transformed linearly into approximate variances and covariances for the logarithms of the fitted values. Additional error due to misspecification of either the model or the constraints is not taken into account. Depending on the model, the prior information parameters may correspond to values of a deterrence function or to a base year trip matrix, while the constraints may represent design year trip end totals or traffic counts. As an illustration, the expression is applied to an example involving Willumsen's model. 相似文献
813.
Denis H.?NomiyamaEmail author Tsugukiyo?Hirayama 《Journal of Marine Science and Technology》2003,8(2):88-98
The importance of ocean waves parameters (propagation direction, mean period, significant wave height, etc.) is related to several aspects of a ships safety, efficiency in operation, routing, design, and maintenance. However, some available methods for obtaining those parameters have data limitations and inconvenient aspects. In severe weather conditions, an ocean-wave-field detector is necessary. This can provide two-dimensional ocean-wave-field information directly. Among other conventional methods, ship-borne wave radar has the ability to function as such a detector, and some researchers have tried to develop practical systems. A numerical approach using plan position indicator (PPI) images from conventional marine radars is proposed to retrieve valuable information from the ocean waves. A three-dimensional Fourier transform is applied to a set of consecutive radar PPI images to perform spectrum analysis. The removal of undesired elements in the spectrum is achieved by applying a hi-pass filter to remove static components, and by comparing the data with the expected dispersion shell to correct for nonocean-wave power. Numerical experiments under controlled conditions using simulated PPI images were performed through numerical simulations based on theoretical ocean-wave equations. The results include a comparison between the original wave parameters used in the simulation and the values retrieved from the spectrum analysis. 相似文献
814.
815.
L. F. P. Etman R. C. N. Vermeulen J. G. A. M. Van Heck A. J. G. Schoofs D. H. Van Campen 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2003,38(2):85-101
Summary A stroke dependent damper is designed for the front axle suspension of a truck. The damper supplies extra damping for inward deflections rising above 4 cm. In this way the damper should reduce extreme suspension deflections without deteriorating the comfort of the truck. But the question is which stroke dependent damping curve yields the best compromise between suspension deflection working space and comfort. Therefore an optimization problem is defined to minimize the maximum inward suspension deflection subject to constraints on the chassis acceleration for three typical road undulations. The optimization problem is solved using sequential linear programming (SLP) and multibody dynamics simulation software. Several optimization runs have been carried out for a small two degree of freedom vehicle model and a large full-scale model of the truck semi-trailer combination. The results show that the stroke dependent damping can reduce large deflections at incidental road disturbances, but that the optimum stroke dependent damping curve is related to the acceleration bound. By means of vehicle model simulation and numerical optimization we have been able to quantify this trade-off between suspension deflection working space and truck comfort. 相似文献
816.
An inverse railway wagon model and its applications 总被引:1,自引:0,他引:1
Fujie Xia Colin Cole Peter Wolfs 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2007,45(6):583-605
An inverse wagon model was developed to estimate wheel-rail contact forces using only measurements of wagon body responses as inputs. The purpose of this work was to provide mathematical modelling to embed in low-cost devices that can be mounted on each freight wagon in a large wagon fleet. To minimize cost, complication, and the maintenance inconvenience of these devices, the constraint is imposed that transducers and connections are limited to locations on the wagon body. Inputs to the inverse model developed include only vertical and lateral translational accelerations and angular accelerations of roll, pitch, and yaw of the wagon body. The model combines the integration and partial modal matrix (PMM) techniques together to form an IPMM method. Besides wheel-rail contact forces some motion quantities such as the lateral and yaw displacements of wheelset are also predicted. Results from the inverse model were compared with data from full scale laboratory suspension tests for vertical suspension excitations. The inverse model was also compared with results from simulations completed in VAMPIRE® for more complicated track input profiles. The model results and the applications of the model are discussed. 相似文献
817.
Gerhard Schandl Peter Lugner Christian Benatzky Martin Kozek Anton Stribersky 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2007,45(9):835-847
In order to improve the ride comfort of lightweight railway vehicles, an active vibration reduction system using piezo-stack actuators is proposed and studied in simulations. The system consists of actuators and sensors mounted on the vehicle car body. Via a feedback control loop, the output signals of the sensors which are measuring the flexible deformation of the car body generate a bending moment, which is directly applied to the car body by the actuators. This bending moment reduces the structural vibration of the vehicle car body. Simulations have shown that a significant reduction in the vibration level is achieved. 相似文献
818.
台湾近年来新兴轨道运输系统方兴未艾,都市轨道运输系统,因其路线多经过都市闹区,故常采用地下型式兴建,当发生意外事故或灾变时,乘客能否安全逃生必须倚赖系统对隧道内与地下车站之乘客安全疏散所设计的逃生设备及事前完备规划的操作程序;目前台北捷运系统在隧道段及地下车站之灾害处理对策部份,已属成熟,由于台北捷运系统为台湾都会区轨道运输系统最先施作者,其规划设计除参考国外捷运系统之相关规划设计准则外,并融合台北都会区域活动特性而订定了台北捷运系统地下隧道乘客逃生操作程序,本文将台北捷运系统规划隧道安全疏散程序及地下车站乘客疏散原则,作一全面性说明及分析,希望能提供国内其它轨道运输隧道系统安全规划之案例参考. 相似文献
819.
在巴黎车展上大众展示了一款最新的高尔夫衍生车型CrossGolf,它是一款目前非常流行的混合车型,结合了SUV多种路面通过能力和MPV多功能实用性的特点。 相似文献
820.
With the increasing trend of charging for externalities and the aim of encouraging the sustainable development of the air
transport industry, there is a need to evaluate the social costs of these undesirable side effects, mainly aircraft noise
and engine emissions, for different airports. The aircraft noise and engine emissions social costs are calculated in monetary
terms for five different sized airports, ranging from hub airports to small regional airports. The number of residences within
different levels of airport noise contours and the aircraft noise classifications are the main determinants for accessing
aircraft noise social costs. The environmental impacts of aircraft engine emissions include both aircraft landing and take-off
and 30-minute cruise. The social costs of aircraft emissions vary by engine type and aircraft category, depending on the damage
caused by different engine pollutants on the human health, vegetation, materials, aquatic ecosystem and climate. The results
indicate that the relationship appears to be curvilinear between environmental costs and the traffic volume of an airport.
The results and methodology of environmental cost calculation could be applied to the proposed European wide harmonised noise
charges as well as the social cost benefit analysis of airports. 相似文献