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821.
K. -B. Kim K. -W. Choi K. -H. Lee 《International Journal of Automotive Technology》2012,13(3):401-407
A relatively new approach for improving fuel economy and automotive engine performance involves the use of automotive combined
cycle generation technologies. The combined cycle generation, a process widely used in existing power plants, has become a
viable option for automotive applications due to advances in materials science, nanotechnology, and MEMS (Mico-Electro Mechanical
Systems) devices. The waste heat generated from automotive engine exhaust and coolant is a feasible heat source for a combined
cycle generation system, which is basically a Rankine cycle in the context of this study. However, there are still numerous
technical issues that need to be solved before the technology can be implemented in automobiles. A simulation was performed
to examine the amount of waste energy that could be recovered through the use of a combined cycle system. A simulation model
of the Rankine cycle was developed using Cycle-Tempo software. The simulation model was ultimately used to evaluate the rate
of waste heat recovery and the consequential increase in the overall thermal efficiency of the engine with the combined cycle
generation system under typical engine operating conditions. The most effective automotive combined cycle system recovered
68% of the waste heat from the exhaust and coolant, resulting in a 6% improvement in engine efficiency. The results are expected
to be beneficial for evaluating the feasibility of combined cycle generation systems in automotive applications. 相似文献
822.
This paper develops a computational model that can analyze the kinematics and compliance characteristics of the front suspension
of a commercial vehicle. This computational model is called the flexible multi-body dynamic model because it is developed
by interfacing the finite element model of the multi-leaf spring with the dynamic model of the front suspension. In this paper,
the bump mode and roll mode tests are performed with a suspension parameter measuring device (SPMD). An excitation load for
creating the bump mode and roll mode motion is applied on the left and right tires slowly in in-phase and out-of-phase modes.
In the test, wheel rate, toe angle change, caster angle change, and camber angle change, which together represent the wheel
alignment, are measured along with the longitudinal and lateral wheel center loci which together represent the wheel center
trajectory change. The reliability of the developed computational model is verified by comparing the simulation results with
the SPMD test results. The developed flexible multi-body computational model will provide useful information on kinematics
and compliance characteristics in the earliest stages of the commercial vehicle design process. 相似文献
823.
J. -H. Choi S. -H. Choi D. Park C. -H. Park B. -O. Rhee D. -H. Choi 《International Journal of Automotive Technology》2012,13(2):273-277
The quality of an injection molded part is largely affected by the mold cooling. Consequently, this makes it necessary to
optimize the mold cooling circuit when designing the part but prior to designing the mold. Various approaches of optimizing
the mold cooling circuit have been proposed previously. In this work, optimization of the mold cooling circuit was automated
by a commercial process integration and design optimization tool called Process Integration, Automation and Optimization (PIAnO),
which is often used for large automotive parts such as bumpers and instrument panels. The cooling channels and baffle tubes
were located on the offset profile equidistant from the part surface. The locations of the cooling channels and the baffle
tubes were automatically generated and input into the mold cooling computer-aided engineering program, Autodesk Moldflow Insight
2010. The objective function was the deviation of the mold surface temperature from a given design temperature. Design variables
in the optimization were the depths, distances and diameters of the cooling channels and the baffle tubes. For a more practical
analysis, the pressure drop and temperature drop were considered the limited values. Optimization was performed using the
progressive quadratic response surface method. The optimization resulted in a more uniform temperature distribution when compared
to the initial design, and utilizing the proposed optimization method, a satisfactory solution could be made at a lower cost. 相似文献
824.
Z. J. Haritos 《Transportation》1987,14(3):193-207
Since the mid-1970s many western governments have felt that liberalization of market forces through deregulation and better control or privatization of public enterprises would raise productivity and reduce inflation and government deficits. This paper reviews the recent literature on public enterprise and draws on the Canadian experience. It discusses the rationale for and concept of public enterprise and focuses on two reform proposals, accountability and privatization. To increase the degree of accountability would require, on the one hand, that the government establish a formal mandate and role for the enterprise and periodically provide formal government directives, and on the other hand, provide an appropriate evaluation framework. Government compensation for imposed public duties is addressed. Full or partial privatization should be pursued when the rationale for a public enterprise has been significantly altered. This applies particularly to public transport enterprises which are in competition with the private sector.An earlier version of this paper was presented at the Fourth World Conference on Transport Research, Vancouver, Canada, 1986. The author wishes to acknowledge the financial support of the Research Branch of the Canadian Transport Commission, and the valuable input provided by Dr Gennady Orzornoy. 相似文献
825.
826.
W.M. Zhai C.B. Cai S.Z. Guo 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1996,26(1):61-79
A new dynamic model of vehicle/track interaction is presented. The model considers the vehicle and the track as a whole system and couples the vertical interaction with the lateral interaction. The vehicle subsystem is modeled as a multi-body system with 37 degrees of freedom, which runs on the track with a constant velocity. The track substructure is modeled as a discretely supported system of elastic beams representing the rails, sleepers and ballasts. The normal contact forces between wheels and rails are described by Hertzian nonlinear elastic contact theory and the tangential wheel/ rail forces are decided by the creep theory. Numerical results are compared with those of conventional dynamic models of railway vehicles. Applications of the coupling model to the investigation of safety limits against derailment due to the track twist and the combined alignment and cross-level irregularities are reported at the end of the paper. 相似文献
827.
Y. M. Asri E. A. Azrulhisham A. W. Dzuraidah A. Shahrir A. Shahrum Z. Azami 《International Journal of Automotive Technology》2011,12(5):713-719
A stub axle is a part of a vehicle constant-velocity system that transfers engine power from the transaxle to the wheels.
The stub axle is subjected to fatigue failures due to cyclic loads arising from various driving conditions. The aim of this
paper was to introduce a probabilistic framework for fatigue life reliability analysis that addresses uncertainties that appear
in the mechanical properties. Service loads in terms of response-time history signal of a Belgian pave were replicated on
a multi-axial spindle-coupled road simulator. The stress-life method was used to estimate the fatigue life of the component.
A fatigue life probabilistic model of a stub axle was developed using Monte Carlo simulation where the stress range intercept
and slope of the fatigue life curve were selected as random variables. Applying the goodness-of-fit analysis, lognormal was
found to be the most suitable distribution for the fatigue life estimates. The fatigue life of the stub axle was found to
have the highest reliability between 8000–9000 cycles. Because of uncertainties associated with the size effect and machining
and manufacturing conditions, the method described in this paper can be effectively applied to determine the probability of
failure for mass-produced parts. 相似文献
828.
S.-J. Lee M.-S. Jang Y.-G. Kim G.-T. Park 《International Journal of Automotive Technology》2011,12(3):425-432
Occupant classification in a passenger seat is one of the critical components for any advanced airbag system. Many automotive
electronic suppliers and engineers predict that the camera will be the next generation sensor for active and passive safety
systems because it has several advantages compared to other sensors. The present paper describes a stereovision-based occupant
classification system (OCS) and intelligent algorithm with embedded system by which triggering of the airbag deployment can
be controlled. The system consists of a pair of stereo cameras and dual Digital Signal Processor (DSP): the first DSP is for
the stereo matching processing, and the second is for occupant classification. The results show that the reaches 97%, and
the processing time is 960 ms. Such performance indicates that the feasibility of the system as an embedded OCS is high. 相似文献
829.
Attitudes towards public transport (PT) in New Zealand’s three largest cities (Auckland, Wellington, and Christchurch) were
examined in a cross-sectional survey of drivers. A measure of prejudice to PT was developed to assess the strength and nature
of attitudinal differences. Auckland residents had the highest levels of PT prejudice while Wellington residents had the lowest,
and these differences were not related to demographic differences between the samples. Direct contact with PT was associated
with reduced levels of PT prejudice, but measures of indirect contact, beliefs about using PT, and environmental attitudes
were stronger predictors of PT prejudice scores. Controlling for these variables resulted in the difference in PT prejudice
levels between Wellington and Christchurch becoming non-significant, while the differences between Auckland and the other
two cities remained. This suggests that the difference between Wellington and Christchurch was primarily based on social norms
regarding PT prejudice, while quality of service was a factor in the difference between Auckland and the other two cities.
It is suggested that campaigns promoting PT ridership should focus both on the quality of service and on presenting PT usage
as socially normal. 相似文献
830.
Bonnet weight reduction and VRU protection: Design proposals implementing non-conventional materials
G. Belingardi G. Chiandussi E. Gobetto A. Scattina 《International Journal of Automotive Technology》2010,11(6):831-842
The use of non-conventional and innovative materials is increasingly important in automotive design. They allow reductions
in the weights of structures with consequent reductions in fuel consumption and carbon dioxide emissions. At the same time,
they ensure excellent safety levels. Once excellent results in terms of active and passive safety have been obtained, the
attention of car manufacturers, and of the public opinion, is focused on the safety of vulnerable road users (VRU), pedestrians
and cyclists. Some examples concerning the redesign of a bonnet with the double targets of weight reduction and pedestrian
safety are illustrated. Hybrid metal/plastic and more conventional metal sheet solutions are compared. The static performance
(stiffness and denting resistance), as well as the impact against a pedestrian head, are evaluated by means of FEM models
along with actual regulations. 相似文献