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991.
A. Gauchia V. Diaz M. J. L. Boada B. L. Boada 《International Journal of Automotive Technology》2010,11(1):41-47
In this paper, the structural optimization of a real bus structure is proposed. The proposed optimization has been accomplished
by means of genetic algorithms. The structural behavior of the bus structure when subjected to weight and torsion was also
analyzed using the finite element method (FEM). The results demonstrate that improved weight and torsional stiffness are achieved
with the optimized structure. 相似文献
992.
Until recently, passenger cars have primarily interested in pedestrian protection performance. Nowadays, however, it is important
for a sport-utility vehicle (SUV) to meet the bumper system standards for pedestrian safety. For a SUV bumper system, there
are some difficulties in attaining a high level of pedestrian performance for the lower legform. An SUV has a high bumper
position from the ground level, and the bumper approach angle must also be secured, which has an effect on car insurance fees.
Due to these reasons, it is difficult to meet the pedestrian performance of the lower legform for an SUV. In this paper, a
comparative study was performed on various SUV bumper systems, and a concept model for a SUV bumper system was developed,
which is expected to meet the pedestrian performance by using the Pugh method. The design control factors were defined to
affect the bumper pedestrian performance through the experiences of tests and analyses. For the noise factor to affect the
pedestrian performance, the deviation of the impactor position was selected at the moment of impact. The design control factors
were optimized by using the Taguchi optimization technique. For the Taguchi method, an L18 orthogonal array table of design
control factors was used in the optimization process. Particularly, for the optimization of the bumper corner region, an optimization
analysis was performed three times to meet pedestrian performance. Based on the results of the Taguchi optimization method,
the sensitivity of the bumper design parameters was studied, and a new SUV bumper system is proposed that satisfies the pedestrian
performance of the lower legform. The optimized bumper system should obtain a full Euro-NCAP score of 6 points for the bumper
test. The pedestrian performance of the optimized bumper system is validated by using a CAE (Computer Aided Engineering) analysis,
which has been proven to be in accurate. A comparison between the test and analysis results is shown for the validation of
accuracy. By using the optimized bumper system, the tests and development costs of a bumper can be reduced. 相似文献
993.
Recently, the demands for improved fuel economy have been continually rising because of environmental protection policies,
legislative pressures on emissions and increases in the price of oil. Reducing the friction power loss in a production engine
may be regarded as one of the most effective technologies for improving fuel economy because the technology is cost effective
and applicable to a great number of vehicles. This paper describes attempts to measure the torque needed to drive a camshaft
and to examine the sources of the torque fluctuations in order to analyze the friction in valvetrains. The measurements were
performed through a cam sprocket-type torquemeter, which was able to measure the torque of the valvetrain under actual engine
operating conditions. In the cam torque measured, the fluctuations were mainly dependent on the primary oscillations caused
by cam events and the secondary oscillations caused by the valvetrain natural frequency. The range of the fluctuations became
greater at high speed because of the inertial mass. The resulting FMEP (friction mean effective pressure) of the valvetrain
decreased, and the effective peak tension increased with an increase in the engine speed. 相似文献
994.
Subjective well-being related to satisfaction with daily travel 总被引:1,自引:0,他引:1
Cecilia Jakobsson Bergstad Amelie Gamble Tommy Gärling Olle Hagman Merritt Polk Dick Ettema Margareta Friman Lars E. Olsson 《Transportation》2011,38(1):1-15
Previous research demonstrates an impact on subjective well-being (SWB) of affect associated with routine performance of out-of-home
activities. A primary aim of the present study is to investigate whether satisfaction with daily travel has a positive impact
on SWB, either directly or indirectly through facilitating the performance of out-of-home activities. A secondary aim is to
determine whether emotional-symbolic or instrumental reasons for car use results in higher satisfaction with daily travel
than other travel modes. A survey of a population-based sample of 1,330 Swedish citizens included measures of car access and
use, satisfaction with daily travel, satisfaction with performance of out-of-home routine activities, and affective and cognitive
SWB. The results confirmed that the effect on affective and cognitive SWB of satisfaction with daily travel is both direct
and indirect via satisfaction with performance of activities. Percent weekly car use had a small effect on satisfaction with
daily travel and on affective SWB, although fully mediating the effect of satisfaction with performance of the activities.
This suggests that car use plays a minor role for satisfaction with daily travel and its effect on SWB. This role may be larger
if investigated after a forced reduced car use. 相似文献
995.
A unique set of activity scheduling data is utilized in this paper to provide much needed empirical analysis of the sequence
in which activities are planned in everyday life. This is used to assess the validity of the assumption that activities are
planned in accordance to a fixed hierarchy of activity types: mandatory activities first (work/school), followed by joint maintenance, joint discretionary, allocated maintenance, and
individual discretionary activities. Such an assumption is typical of current generation activity and tour-based travel demand
models. However, the empirical results clearly do not support such assumptions. For instance, fewer than 50% of mandatory
activities were actually planned first in related out-of-home tours; remaining activity types also did not take any particular
precedence in the planning sequence. Given this, a search was made for the more salient attributes of activities (beyond activity
type) that would better predict how they are planned within tours. Several ordered response choice models for different tour
sizes were developed for this purpose, predicting the choice order of the 1st, 2nd, 3rd, etc. planned activity in the tour
as a function of activity type, activity characteristics (duration, frequency, travel time, and involved persons), and individual
characteristics. Activity duration played the most significant role in the models compared to any other single variable, wherein
longer duration activities tended to be planned much earlier in tours. This strongly suggests that the amount of time-use,
rather than the nature of the event as indicated by activity type, is a primary driver of within-tour planning order and offers
potential for a much improved and valid fit. 相似文献
996.
We develop a short turning model using demand information from station to station within a single bus line-single period setting,
aimed at increasing the service frequency on the more loaded sections to deal with spatial concentration of demand considering
both operators’ and users’ costs. We find analytical expressions for optimal values of the design variables, namely frequencies
(inside and outside the short cycle), capacity of vehicles and the position of the short turn limit stations. These expressions
are used to analyze the influence of different parameters in the final solution. The design variables and the corresponding
cost components for operators and users (waiting and in-vehicle times) are compared against an optimized normal operation
scheme (single frequency). Applications on actual transit corridors exhibiting different demand profiles are conducted, calculating
the optimal values for the design variables and the resulting benefits for each case. Results show the typical demand configurations
that are better served using a short turn strategy. 相似文献
997.
N. Louam D.A. Wilson R.S. Sharp 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1992,21(1):39-63
The problem of deriving control laws which minimize specified performance indices for a vehicle moving on a rough surface with preview of the surface elevation is considered. The approach is based on linear optimal tracking theory and consequently the system elements are taken to be linear and the performance index is constrained to be of quadratic form.
The ideas of overtaking optimality are applied to the problem in order to achieve a closed form solution for the control. Then, using the control laws derived, computer simulations of performance are conducted and time histories are shown. In the absence of limitations on either processing or actuator speeds, and for cases in which the preview is sufficient to give good control laws, the value of the preview in enhancing vehicle suspension performance is assessed. Comparisons are made with results in the literature. 相似文献
The ideas of overtaking optimality are applied to the problem in order to achieve a closed form solution for the control. Then, using the control laws derived, computer simulations of performance are conducted and time histories are shown. In the absence of limitations on either processing or actuator speeds, and for cases in which the preview is sufficient to give good control laws, the value of the preview in enhancing vehicle suspension performance is assessed. Comparisons are made with results in the literature. 相似文献
998.
J. S. Dodgson 《Transportation》1994,21(4):355-370
The European aviation industry is undergoing a process of liberalisation. One of the important lessons of American deregulation was that the industry is not perfectly contestable. One implication of this is that actual competition on a route is important in order to be able to secure the benefits of deregulation or liberalisation. Another is that effective competition policy is important in order to prevent anti-competitive mergers or predatory behaviour. This paper reviews the merger investigations in European aviation which have accompanied the search by carriers to secure the benefits of market power, and considers the extent of route competition within the European Community and its relationship to the different route licensing policies of different national governments. The paper considers the extent of present competition on the busiest routes, and stresses the importance of cabotage rights in opening up the European market to effective competition. 相似文献
999.
Brian S. Hoyle 《Maritime Policy and Management》1992,19(4):279-295
This paper reports on a component of a research project on Canadian Dimensions of Waterfront Revitalization wherein forty-five interviews were held in Canadian port cities with port authority representatives, urban planners and developers. Respondents were asked to fill in a questionnaire, and the findings from this questionnaire survey are discussed in this paper. Anticipated contrasts between planning philosophies in different professions were largely but not invariably confirmed. 相似文献
1000.