技术聚焦:北美市场的干式双离合器变速器

<正>双离合器变速器(DCT)是由两个离合器组合在一起的自动换档变速器,一个离合器控制奇数档,另一个控制偶数档,让驾驶员更加平顺地换档,没有扭矩迟滞。从一个离合器转换到另一个离合器只需几毫秒。双离合器变速器(DCT)的效率在于它不会像使用行星齿轮结构     

Experimental study of the characteristics of idle vibrations that result from axial forces and the spider positions of constant velocity joints

The vibrational characteristics of automotives during idling were studied experimentally by considering the axial forces of the drive shaft and the spider positions in a constant-velocity joint. The generated forces, such as PF (plunging force) and GAF (generated axial force) in the assembly of the drive-shaft module, were measured directly by an experimental apparatus. Measurements of the GAF and PF did not show the same trends as the joint angles. They depended instead on the types of CV joints. In addition, the relationship between the offset values of the shaft and the spider positions in the tulip of the constant-velocity joint were studied. As a result, the idle vibration characteristics were affected by the variation of the spider positions and the vibrational characteristics in the axial direction of the shaft, including the amplitude and the harmonic periods.     

Computer Aided Simulation on Precision Cold Forging of Universal Joint Cross

IntroductionThefiwtee1emenmethod(FEM)playsanextrmelyimPortantroleintheanalysesofengineeringproblems.ForalongtimethismethodhasmainlybeenaPPliedinthelinearfieldandshownitsgreatpower.HoweveealOtofnonlinearengineeringPrOblemsWhichcanneitherbesimPlyreducedtolinearonesnorrCPresentedbylinearlyanalogywhichshallchnsethePfacticalconditionsrelativelymuch,havechallengedfiniteelementmethod(FEM).RecentymuchProgresshasbeenmadebothinthemathematicalandmechanicaltheoryandthecomPulertechnologysothatevent…     

Benthic foraminifera in the surface sediments of the Beaufort Shelf and slope, Beaufort Sea, Canada: Applications and implications for past sea-ice conditions

This paper presents new data on distribution patterns of modern benthic foraminifera and other microfossils from the Canadian Arctic, specifically the Beaufort Shelf and slope. The material was collected in June to August of 2004 and is the first of its kind in this area to be collected since 1970. We examined the smaller sizes (45–63µm) as well as > 63µm and discovered that many species had been severely underrepresented in previous studies. Deep sea forms, that had been overlooked previously, were common on the shelf; two species (Elphidiella arctica and Ammotium cassis) appeared in preliminary results to be indicators of methane seepage; and it was possible to make determinations of sea-ice coverage using a combination of foraminifera and tintinnids (planktic ciliates). Our data indicated the presence of many of the same species as previous studies from this area, but improved techniques of sample processing greatly increased the number of specimens and species found (particularly the small deep sea arctic species Buliminella hensoni and Bolivina arctica) which provide much more reliable data for paleoceanographic determinations. One of the primary objectives for this work was to provide baseline data to help determine paleo-ice cover; these data cover a broad range of conditions on the Beaufort Shelf that make it possible to achieve this objective as well as improving what it is known about the assemblages on this shelf as compared to other arctic shelf areas, such as the Siberian Shelf).     

Stability and Riding Quality of Railway Vehicles

The so-called critical speed of a linearized railway vehicle is shown to be no useful measure for the stability of the system in practice. The important interaction between vehicle and track can be taken into account by the riding quality for a certain vehicle on every particular piece of track. The riding quality is determined by the accelerations transmitted to the payload, weighted according to comfort standards, and the relative displacements between wheel and rail. From the riding quality demands both for vehicle design and for maintenance of the track can be derived.     

Adaptive Control of 4WS System by Using Neural Network

An adaptive control system of the model following type is proposed for drive motion control of a four wheel steering (4WS) car with using neural network (NN) which has mastered nonlinear friction force between tire and road surface. A model of one rigid body is adopted which represents appropriately two kinds of car motion caused by steering action, namely the lateral displacement and the yawing rotation, and an equation of motion is described in a simplified form to make a system equation for motion control possible. Nonlinear relation between the cornering force of tire and the slip angle is obtained by numerical analysis with the tire model proposed by E. Fiala, taking friction coefficient and car speed as the parameters. The result is used as the teaching signal for NN. Three NN are used in the control system composed of both the feed-forward and the feedback circuits in order to realize adaptive control. Validity and usefulness of the proposed adaptive control system with NN are verified by three kinds of computer simulation.     

Influence of travel attributes on modal choice in an Indian city

Modal split models tried for Indian cities have not gone in depth in studying the impact of the attitude of users towards various travel attributes. The main difficulty with this has been non-availability of data. The study presented here tried two methodologies, attitude measurement and trade-off game approach, using data collected through household surveys conducted for the purpose on limited stratified samples in some locations in Madras. The results indicate how commuters value time and comfort factors more than the cost, given a choice. Due to prevailing economic conditions, cost plays a vital role, but analysis shows that users are prepared to incur additional cost, if they are assured of quicker and more comfortable services. Relative quantification between the influence of different attributes is also possible.     

The implications on willingness to pay of respondents ignoring specific attributes

Individuals processing the information in a stated choice experiment are typically assumed to evaluate each and every attribute offered within and between alternatives, and to choose their most preferred alternative. However, it has always been thought that some attributes are ignored in this process for many reasons, including a coping strategy to handle ones perception of the complexity of the choice task. Nonetheless, analysts typically proceed to estimate discrete choice models as if all attributes have influenced the outcome to some degree. The cognitive processes used to evaluate trade-offs are complex with boundaries often placed on the task to assist the respondent. These boundaries can include prioritising attributes and ignoring specific attributes. In this paper we investigate the implications of bounding the information processing task by attribute elimination through ignoring one or more attributes. Using a sample of car commuters in Sydney we estimate mixed logit models that assume all attributes are candidate contributors, and models that assume certain attributes are ignored, the latter based on supplementary information provided by respondents. We compare the value of travel time savings under the alternative attribute processing regimes. Assuming that all attributes are not ignored and duly processed, leads to estimates of parameters which produce significantly different willingness to pay (WTP) to that obtained when the exclusion rule is invoked.     

An evaluation of web site services in liner shipping in Taiwan

This paper empirically evaluates web site services in the liner shipping industry based on the service requirements of the user firms, i.e., shippers. The results suggest that shippers perceive tracing to be the most important service attribute of a web site, followed by customs response, vessel schedules, and electronic document service. Based on the concept of market segmentation, we employed cluster analysis to classify users (shippers) of web site services provided by liner shipping companies into four segments, namely support and performance services oriented firms, equipment information oriented firms, performance information oriented firms, and transaction services oriented firms. Theoretical and practical implications of the research findings are discussed.     

Refocusing the Modelling of Freight Distribution: Development of an Economic-Based Framework to Evaluate Supply Chain Behaviour in Response to Congestion Charging

The distribution of freight is a major contributor to the levels of traffic congestion in cities. However it is much neglected in the research and planning activities of government, where the focus is disproportionately on passenger vehicle movements. Despite the recent recognition of the contribution of freight transportation to the performance of urban areas under the rubric of city logistics, we see a void in the study of how the stakeholders in the supply chain might cooperate through participation in distribution networks, to reduce the costs associated with traffic congestion. Given that transport costs are typically over 45 of all distribution costs, with congestion a major contributor in the urban setting, the importance of establishing ways in which supply chain partnerships might cooperate to reduce levels of freight vehicle movements has much merit. This paper sets out a framework to investigate how agents in a retail supply chain might interact more effectively to reduce the costs of urban freight distribution. We propose an interactive agency choice method as a way of formalising a framework for studying the preferences of participants in the supply chain to support specific policy initiatives. Such a framework is a powerful way of investigating the behavioural response of each agent to many policies, including congestion pricing, as a way of improving the efficient flow of traffic in cities.