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941.
Z. C. Kan D. M. Lou Z. Z. Cao Z. Y. Hu S. Liu Z. H. Yang 《International Journal of Automotive Technology》2017,18(2):209-217
Altitude has a significant effect on combustion of heavy-duty diesel engines, especially during cold start. An experimental study on a heavy-duty diesel engine operating at different altitudes was conducted. Tests were based on a direct injection (DI) turbocharged diesel engine with intake and exhaust pressure controlled by the plateau simulation test system to stimulate altitude conditions including 0 m, 1000 m, 2000 m, 3000 m and 4000 m. Results indicated that the compression and expansion resistance moment reduced and the speed increased during the cranking period. The peak pressure of several cycles was increased during the start-up period; however, the expansion pressure dropped more and the indicated mean effective pressure (IMEP) reduced as the altitude rose. While at an altitude of over 2000 m, the peak pressure fluctuated obviously during the start-up period. The higher the altitude was, the more the fluctuation amplitude and cycle number increased and combustion instability enhanced, which resulted the start-up period time increasing at high altitude. When the altitude rose, the cycle-to-cycle variation of the peak pressure and speed fluctuation increased during the idle, the ignition and CA50 were delayed and the combustion duration was shortened. The effect of altitude on combustion characteristics of the diesel engine was more significant during the start-up period than during its idle period. 相似文献
942.
Elsayed M. Elbeheiry Ph. D. Student Dean C. Karnopp Professor Mohamed E. Elaraby Professor Chairman Ahmed M. Abdelraaouf Professor Chairman 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1995,24(3):231-258
This bibliographical list classifies the extensive literature related to the dynamic analysis and control design aspects of advanced ground vehicle suspension systems. It is restricted to the design of advanced suspensions for ride quality and safety. Brief generalized notices and definitions are presented. 相似文献
943.
The purpose of this study is to examine the effect of the steady airflow field of a rear spoiler on the coefficients of drag (CD) and downforce (CDF). The type of spoiler is suggested as a two-jointed arm model that mimics the flapping flight mechanism of the Canada goose. Computational fluid dynamics (CFD) technique was used for the steady airflow analysis of a vehicle implemented with various spoiler topologies. We evaluated CD and CDF due to the three types of airfoils and the five phases of each airfoil. We obtained the following conclusions from the results: (1) We found that the best cases for CD and CDF were the case of Phase 5 and symmetry airfoil, and the case of Phase 1 and reverse airfoil, respectively. (2) It is clear that CD becomes the largest at Phase 1 of the reverse airfoil, since the eddy magnitude at the rear of the vehicle is the largest, and CDF also becomes the largest during that phase, since the pressure distribution on the upper surface of the spoiler is very large. (3) As Phase 1 moves to Phase 5 in the same type of airfoil, it is advantageous for CD and disadvantageous for CDF, respectively. 相似文献
944.
This paper presents a method that estimates the vehicle sideslip angle and a tire-road friction coefficient by combining measurements of a magnetometer, a global positioning system (GPS), and an inertial measurement unit (IMU). The estimation algorithm is based on a cascade structure consisting of a sensor fusing framework based on Kalman filters. Several signal conditioning techniques are used to mitigate issues related to different signal characteristics, such as latency and disturbances. The estimated sideslip angle information and a brush tire model are fused in a Kalman filter framework to estimate the tire-road friction coefficient. The performance and practical feasibility of the proposed approach were evaluated through several tests. 相似文献
945.
A cooperative control algorithm for an in-wheel motor and an electric booster brake is proposed to improve the stability of an in-wheel electric vehicle. The in-wheel system was modeled by dividing it into motor and mechanical parts, and the electric booster brake was modeled through tests. In addition, the response characteristics of the in-wheel system and the electric booster brake were compared through a frequency response analysis. In the cooperative control, the road friction coefficient was estimated using the wheel speed, motor torque, and braking torque of each wheel, and the torque limit of the wheel to the road was determined using the estimated road friction coefficient. Based on the estimated road friction coefficient and torque limit, a cooperative algorithm to control the motor and the electric booster brake was proposed to improve the stability of the in-wheel electric vehicle. The performance of the proposed cooperative control algorithm was evaluated through a hardware-in-the-loop simulation (HILS). Furthermore, to verify the performance of the proposed cooperative control algorithm, a test environment was constructed for the anti-lock braking system (ABS) hydraulic module hardware, and the performance of the cooperative control algorithm was compared with that of the ABS by means of a HILS test. 相似文献
946.
In contemporary times, Public–Private Partnership (PPP) in transport infrastructure has gained considerable attention in developing regions following its success in the developed countries. However, Sub-Saharan Africa (SSA) is among the developing regions with few transport PPP projects and among the regions with high number of failed projects. Meanwhile the region's transport infrastructure need far exceeds it current provision. This paper therefore aims to examine the project experiences (success and failure factors) of three highly profiled transport PPP projects, namely the Lekki toll road concession project (Nigeria), N4 toll road (South Africa/Mozambique) and Port of Maputo (Mozambique) in order to develop policy measures for effective future implementation. The experiences of the three projects show that transport PPP policy is indeed feasible in SSA. However, to realise its full applicability, proper policy actions and measures must be carefully observed and these include effective and efficient stakeholder management, transparent and competitive tendering process, high participation of local investors, stable macro-economic conditions and strong government commitment and regulatory framework. The projects experiences and policy actions developed are impactful in accelerating transport infrastructure development through PPP approach in SSA. Hence it is hoped that policy-makers and practitioners would be informed on the key strategies to employ in implementing future projects. 相似文献
947.
Effects of intersection field of view on emergent collision avoidance performance at unsignalized intersections: analysis based on driving simulator experiments 下载免费PDF全文
Proper intersection sight distance can effectively lower the possibility of intersection accidents. American Association of State Highway and Transportation Officials (2011) provide a series of recommended dimensions of intersection sight triangles for uncontrolled and stop/yield‐controlled intersections. However, in reality, although the actual intersection design for unsignalized intersections satisfies the requirements of sight distance and clear sight triangle in American Association of State Highway and Transportation Officials' guideline, there are still a large number of crashes occurring at unsignalized intersections for drivers running stop/yield signs or failing to slow down. This paper presents a driving simulator study on pre‐crash at intersections under three intersection field of view (IFOV) conditions. The aim was to explore whether better IFOVs at unsignalized intersections improve their emergent collision avoidance performance under an assumption of valid intersection sight distance design. The experimental results show drivers' ability to identify potential hazards to be significantly affected by their IFOVs. As drivers' IFOV improved, drivers were more likely to choose braking actions to avoid collisions. Better IFOVs were also associated with significant increases in brake time to intersection and significant reductions in deceleration rate and crash rate, thus leading to a lower risk of traffic crash involvement. The results indicate that providing a better IFOV for drivers at intersections should be encouraged in practical applications in order to improve drivers' crash avoidance capabilities. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
948.
Users’ perceptions are identified as key elements to understand bicycle use, whose election cannot be explained with usual mobility variables and socio-economic characteristics. A hybrid model is proposed to model the intention of bicycle use; it combines a structural equations model that captures intentions and a choice model. The framework is applied to a case of a university campus in Madrid that is studying a new internal bike system. Results show that four latent variables (convenience, pro-bike, physical determinants and external restrictions) help explaining intention to use bike, representing a number of factors that are linked to individual perceptions. 相似文献
949.
S. J. Lee S. J. Jeong W. S. Kim C. B. Lee 《International Journal of Automotive Technology》2008,9(6):659-670
The use of a diesel particulate filter (DPF) in a diesel aftertreatment system has proven to be an effective and efficient
method for removing particulate matter (PM) in order to meet more stringent emission regulations without hurting engine performance.
One of the favorable PM regeneration technologies is the NO2-assisted regeneration method due to the capability of continuous regeneration of PM under a much lower temperature than that
of thermal regeneration. In the present study, the thermal behavior of the monolith during regeneration and the conversion
efficiency of NO2 from NO with an integrated exhaust system of a diesel oxidation catalyst (DOC) and DPF have been predicted by one-channel
numerical simulation. The simulation results of the DOC, DPF, and integrated DOC-DPF models are compared with experimental
data to verify the accuracy of the present model for the integrated DOC and DPF modeling. The effects of catalyst loading
inside the DOC and the volume ratio between the DOC and DPF on the pressure drop, the conversion efficiency, and the oxidation
rate of PM, have been numerically investigated. The results indicate that the case of the volume ratio of ‘DOC/DPF=1.5’ within
the same diameter of both monoliths produced close to the maximum conversion efficiency and oxidation rate of PM. Under the
engine operating condition of 175 kW at 2200 rpm, 100% load with a displacement of 8.1, approximately 55 g/ft3 of catalyst (Pt) loading inside the DOC with the active Pt surface of 5.3 m2/gpt was enough to maximize the conversion efficiency and oxidation rate of PM. 相似文献
950.
C. Oh Y. S. Kang Y. Youn A. Konosu 《International Journal of Automotive Technology》2008,9(2):191-196
Pedestrian-related accidents are considered to be the most serious of traffic accidents due to the associated high fatality
rates. In Korea, pedestrian fatalities accounted for approximately 40% of all traffic-related fatalities in 2004. Significant
efforts have been made to develop effective countermeasures for pedestrian-vehicle collisions. A basis for devising such countermeasures
is to understand the characteristics of pedestrian-vehicle collisions. This study develops a pedestrian fatality model capable
of predicting the probability of fatality in pedestrian-vehicle collisions. Binary logistic regression and a probabilistic
neural network (PNN) are employed to estimate the probability of pedestrian fatality. Pedestrian age, vehicle type and collision
speed are used as independent variables of the fatality model. The models developed herein are valuable tools that can be
used to direct safety policies and technologies associated with pedestrian safety. 相似文献