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861.
A reliability‐based traffic assignment model for multi‐modal transport network under demand uncertainty 下载免费PDF全文
In densely populated and congested urban areas, the travel times in congested multi‐modal transport networks are generally varied and stochastic in practice. These stochastic travel times may be raised from day‐to‐day demand fluctuations and would affect travelers' route and mode choice behaviors according to their different expectations of on‐time arrival. In view of these, this paper presents a reliability‐based user equilibrium traffic assignment model for congested multi‐modal transport networks under demand uncertainty. The stochastic bus frequency due to the unstable travel time of bus route is explicitly considered. By the proposed model, travelers' route and mode choice behaviors are intensively explored. In addition, a stochastic state‐augmented multi‐modal transport network is adopted in this paper to effectively model probable transfers and non‐linear fare structures. A numerical example is given to illustrate the merits of the proposed model. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
862.
Satu K. Hänninen Tommi Mikkola Jerzy Matusiak 《Journal of Marine Science and Technology》2014,19(1):103-115
Currently, little information exists on the validity of interface-capturing methods in predicting local ship wave loads in short and steep waves. This study compares computational and experimental results in such a case (kA = 0.24, L wave /L ship = 0.16). The results allow the variation of wave loading between ten locations in the bow area of the ship to be observed. The computations were performed with an unstructured RANS solver that models free-surface flows with a volume-of-fluid method. In the model tests, the wave loads were measured with pressure sensors. The analysis of the results focuses on the wave conditions and on the pressure histories of the local wave loads. The computational and experimental results are in good qualitative agreement and encourage the further use of the computational results. 相似文献
863.
Quality assessment process is based on a standard procedure. These standards are developed as a combined effort. It requires deep knowledge about structural material in addition to component`s behavior under external loads. Remanufactured components pose another difficulty to assess their quality in the form of unknown usage rate. This paper represents optimization of quality assessment criteria for remanufactured CV-joints. Working surface hardness of the CV-joint elements is measured at certain depth interval. A minimum acceptable surface hardness value for the BJ-outer joint elements is suggested based on existing research. Remanufactured CV-joint Housing, Inner race and Cage surface machining steps are studied and machining parameter optimization is performed through laboratory based durability test results. The test results of optimized machining parameters are compared with the test results of unmachined test samples. Mean-time-to-failure is calculated along with Weibull distribution parameters. Also, Birfield joint inner race bending and rotating torque are measured and standard parameters for remanufactured CV-joint are determined. Those quality assessment criteria for remanufactured CV-joints are developed. 相似文献
864.
This study investigates the time-dependent reliable shortest path problem (TD-RSPP), which is commonly encountered in congested urban road networks. Two variants of TD-RSPP are considered in this study. The first variant is to determine the earliest arrival time and associated reliable shortest path for a given departure time, referred to as the “forward” TD-RSPP. The second problem is to determine the latest departure time and associated reliable shortest path for a given preferred arrival time, referred as the “backward” TD-RSPP. It is shown in this article that TD-RSPP is not reversible. The backward TD-RSPP cannot be solved by the algorithms designed for the forward problem using the reverse search from destination to origin. In this study, two efficient solution algorithms are proposed to solve the forward and backward TD-RSPP exactly and the optimality of proposed algorithms is rigorously proved. The proposed solution algorithms have potential applications in both advanced traveler information systems and stochastic dynamic traffic assignment models. 相似文献
865.
From MY2010 US-NCAP, the 5th percentile female Hybrid III dummy has been used for the safety evaluation of the right front passenger position in the frontal impact test. In Korea, the Ministry of Land, Infrastructure and Transport (MLIT) decided to evaluate the safety of the 5th percentile female dummy in the frontal impact test from 2013 KNCAP. In this paper, using the frontal NCAP data for the 5 vehicles available from the NHTSA test database, the safety of the 5th percentile female dummy were examined. Using the evaluation and rating method by the KNCAP, 5 vehicles received 5 stars. Using the evaluation and rating method by the US-NCAP, only one vehicle received 5 stars and the remaining 4 vehicles received 4 stars. In the US-NCAP, the Nij was the most influential factor for the star rating. In the KNCAP, the evaluation and rating method for the 5th percentile female Hybrid III dummy is less stringent than the method of the US-NCAP. The evaluation and rating method is proposed to increase the stringency of the star rating for the female dummy in the KNCAP. 相似文献
866.
In this paper, the combined power management/design optimization problem is investigated for a fuel cell/Liion battery PHEV. Formulated as a constrained multi-objective optimization problem (MOP), the combined optimization problem simultaneously minimizes the vehicle cost and fuel consumption subject to the vehicle performance requirements. With an emphasis on developing a generic optimization algorithm to find the Pareto front for the synthesized MOP, the Pareto based multi-objective particle swarm optimization (PMOPSO) algorithm is developed, which solely depends on the concept of Pareto dominance. Three approaches are introduced to the PMOPSO method to address the constrained MOP. They are: (i) by incorporating system constraints in the original objective functions, the constrained MOP is transformed to an unconstrained MOP; (ii) to avoid being trapped in local minima, a disturbance operator with a decaying mutation possibility is introduced; (iii) to generate a sparsely distributed Pareto front, the concept of crowding distance is utilized to determine the global guidance for the particles. Finally, under the Matlab/Simulink software environment, simulation results are presented to demonstrate the effectiveness of the PMOPSO in the derivation of the true Pareto front. 相似文献
867.
S. G. Zuo T. X. Ni X. D. Wu K. Wu X. W. Yang 《International Journal of Automotive Technology》2014,15(3):505-515
As a research method, finite element analysis (FEA) with ABAQUS can help researchers to study throughout the whole process of abnormal tire wear. For precise tread wear simulation, this paper introduces a tire finite element model building method. Then, the model is verified by comparing its simulation results with experiment data. Based on the verified model, tire high-speed rolling procedure is presented by combining steady-state transport analysis and dynamic analysis. To predict the wear distribution, micro tread wear calculation method is described. Finally, the wear prediction procedure of tread mesh evolving is introduced and tire polygonal wear pattern is simulated by this procedure. 相似文献
868.
Y. Liu S. I. Hwang J. K. Yeom S. S. Chung 《International Journal of Automotive Technology》2014,15(3):353-359
Compressed natural gas (CNG) is regarded as one of the most promising alternative fuels. In the spark-ignition (SI) engine, direct injection (DI) technology can significantly increase the engine volumetric efficiency and reduce “pumping losses” in engines without a throttle valve. DI allows engine operation with the stratified charge which enables relatively higher combustion efficiency. In this study, a combustion chamber with a visualization system is designed. The spray development and combustion propagation process of spark-ignition direct injection (SIDI) CNG were digital recorded and analyzed. The ignition probability was also examined. The results of this study can contribute important data for the design and optimization of the SIDI CNG engine. 相似文献
869.
S. C. Ko K. C. Oh C. K. Seo C. B. Lee 《International Journal of Automotive Technology》2014,15(3):347-352
Several NOx reduction technologies under development in recent years have now been commercialized, including selective catalytic reduction (SCR) with NH3 or hydrocarbons, and Lean NOx Trap. The aim of the present study is to investigate characteristics on NOx adsorption according to the oxygen concentration, de-NOx performance according to lean/rich injection cycle and toxic intermediates at LNT downstram for lean-burn gasoline engine. Under oxygen of 6%, NOx storage capacity was the highest, showed the highest NOx conversion of 98%. The reason for this phenomena is because the excited oxygen atoms at high oxygen concentration increased oxidizing power of NO. Under low temperature of 205°C, LNT catalyst showed the least NOx conversion of 14% because its activity became lower, while the generation rate of toxic HNCO was highest as CO which is generated during the rich condition, reacts with NOx stored on Ba site. 相似文献
870.
Large-Eddy Simulation (LES) was used to perform computations of air entrainment and mixing during diesel spray combustion.
The results of this simulation were compared with those of Reynolds Averaged Navier Stokes (RANS) simulations and an experiment.
The effect of LES on non-vaporizing and vaporizing sprays was evaluated. The validity of the grid size used for the LES analysis
was confirmed by determining the subgrid-scale (SGS) filter threshold on the turbulent energy spectrum plot, which separates
a resolved range from a modeled one. The results showed that more air was entrained into the jet with decreasing ambient gas
temperatures. The mass of the evaporated fuel increased with increasing ambient gas temperatures, as did the mixture fraction
variance, showing a greater spread in the profile at an ambient gas temperature of 920 K than at 820 K. Flame lift-off length
sensitivity was analyzed based on the location of the flame temperature iso-line. The results showed that for the flame temperature
iso-line of 2000oC, the computed lift-off length values in RANS matched the experimental values well, whereas in LES, the
computed lift-off length was slightly underpredicted. The apparent heat release rate (AHRR) computed by the LES approach showed
good agreement with the experiment, and it provided an accurate prediction of the ignition delay; however, the ignition delay
computed by the RANS was underpredicted. Finally, the relationships between the entrained air quantity and mixture fraction
distribution as well as soot formation in the jet were observed. As more air was entrained into the jet, the amount of air-fuel
premixing that occurred prior to the initial combustion zone increased, upstream of the lift-off length, and therefore, the
soot formation downstream of the flame decreased. 相似文献