摘要: The performance indexes of three kinds of base asphalts modified with different SBS contents were tested, grey correlation analysis method was used, SBS content was as reference sequence, the performance indexes of modified asphalt, such as penetration, softening point, ductility, elasticity recovery and kinematic viscosity at 135 ℃, were as comparison sequence, correlation grades between SBS content and main performance indexes were calculated and sequenced.The weight of each performance index was calculated by normalizing correlation grade coefficients, the relationship between conventional performance indexes and SBS content was set up, a test method of SBS content based on multiple indexes was put forward, and the method was validated by using sample groups with known SBS contents.Analaysis result indicates that the main performance indexes with significant correlation to SBS content are softening point, elasticity recovery and kinematic viscosity at 135 ℃.The absolute deviations of SBS contents for three kinds of modified asphalts are all within 0.15%, so the method is reliable.更多>
摘要: The working principles of two types of coupler systems were analysed.Based on considering the friction pairs of coupler tails and real-time aligning shoulders, coupler system models were set up by using control system simulation method.Nonlinear draft gear with hysteresis characteristic was modelled by using table lookup method.DFC-E100 system and 13A/QKX-100 system were simulated in a train model consisting of two 8-axle locomotives and one simplified wagon.The theoretical calculation of carbody-stabilizing-coupler ability was performed.Calculation result indicates that the models can rationally reflect the dynamic behaviour of freight locomotive's coupler systems.The distinct angling behaviour of DFC-E100 system is only observed when buff forces are larger than a certain value, but the aligning shoulder of DFC-E100 system can effectively prevent coupler from excessive angling.The error of carbody-stabilizing-coupler ability between simulation value and field test value is 4.23%, and the error between theoretical calculation value and field test value is 10.65%.The friction pair of 13A/QKX100 system is key element in the control of coupler dynamic behaviour, and can prevent coupler from distinct angling under buff condition.更多>
摘要: The control strategy of CVT transmission ratio, the power performance and fuel economy of vehicle on long uphill highway were analyzed. Multiple work points between the best dynamic and best economical rotational speeds of engine at equal interval were selected, and the influence of transmission ratio of every working point on the power performance and the fuel economy was studied. The optimal control strategy of CVT transmission ratio under considering the two properties was found by Simulink simulation. Simulation result indicates that the acceleration response time of the optimal control strategy decreases by 1.2 s compared with the best dynamic control strategy, the fuel consumption rate of the optimal control strategy decreases by 7.9% compared with the best economical control strategy, and the acceleration curve is smooth. Therefore, the two performances of vehicle on long uphill highway can be effectively improved by using the optimal control strategy of transmission ratio. 3 tabs, 12 figs, 14 refs.更多>
摘要: Based on random regret minimization(RRM) theory and random utility maximization(RUM) theory, RRM-MNL model and RUM-MNL model were set up to research the choice behaviors of travel modes respectively.Aiming at RRM-MNL model and RUM-MNL model, the parameters and the goodnesses of fit were compared, their difference on the evaluation of traffic management measures was analyzed through direct elasticity, and practical verification was carried out based on four travel data such as aircraft, train, coach and car during intercity travel.Analysis result shows that compared with RUM-MNL model, in RRM-MNL model, the partial compensatory decision-making behavior and compromise effect during the choice process of multi-attribute method are described better, and the choice process of travel behavior can be reflected more really.The choice probabilities of wait time, travel time and travel cost on three travel methods such as aircraft, train and coach have significant elaticities.In RRM-MNL model, the elasticities of wait time for aircraft, train and coach all are lower than those in RUM-MNL model, and reduce by 7.30%, 13.14% and 7.70% respectively.So, for the same attribute variable, while the traveler has different choice preferences, the different choice behaviors will be displayed.更多>
