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861.
This paper presents an application of shallow water theory to describe the motion of floodwater inside a rolling ship in damage
condition. The time domain theoretical approach to the coupled problems of ship and water inside compartment motions is briefly
described, including the method used to solve for the water motion characteristics and forces exerted on the ship. This approach
is applied to the study of the behaviour of a passenger Ro–Ro ship in regular beam seas and numerical results are given for
the intact and damaged conditions. Comparison is made with experimental results. For the damaged condition, the characteristics
of the floodwater motion are studied in the time domain for a number of different wave frequencies. The shape of the free-surface
and phase of water motion in relation to the ship roll motion are shown for several wave frequencies. The dynamic floodwater
roll moment is also shown and compared with the static roll moment (flat horizontal free surface), allowing the conclusion
that the dynamic roll moment is much larger than the static roll moment, for high wave frequencies, and is in phase opposition
in relation to the roll motion. 相似文献
862.
Z. Shi I. Legate F. Gu J. Fieldhouse A. Ball 《International Journal of Automotive Technology》2010,11(3):363-373
An Antilock Braking System (ABS) is one of the most important safety facilities equipped in modern vehicles. A self-test is
therefore embedded into its ECU to identify any electronic malfunction. However there is no effective method to predict or
check its mechanical conditions routinely to ensure its functionality. Because the ABS system is merely actuated above a particular
speed in emergency stops, the current brake test facilities are not adequate for ABS test. Because of the dangers involved
it would not be acceptable to use a public road to implement such a practice for fault detection so an alternative means must
be sought. To provide a safe and convenient solution this paper proposes a novel method to predict ABS faults whilst the vehicle
is stationary. In this situation a model-based approach is applied to predict various faults from the ABS, especially from
its hydraulic subsystem. As such, a mathematic model is developed to describe the operating processes of ABS including possible
faulty conditions. An autonomous control strategy is also designed to actuate the control module independently without the
knowledge of the control algorithms embedded in an ABS control module. This approach is evaluated through a Simulink simulation. 相似文献
863.
864.
After 1975, the appearance of finite element numerical limit method and the application and development of computer technology have brought the elastic-plastic analytical calculation of engineering materials into a new era of numerical limit calculation. The new methods, namely, strength reduction method and load increment method, as well as the recently proposed ultimate strain method, are adopted in the rock tunnels studied in this paper. To solve the uncertainty of mechanical parameters of surrounding rock in rock tunnels and provide more scientific and reasonable mechanical parameters of surrounding rock, the surrounding rock classification must be made combining theory, investigation and experience. Taking the surrounding rock classification in rail transit tunnels as an example, the improvement of the classification level includes improving the strength index, mainly adopting the quantitative classification method, reasonably determining the basic index BQ value of rock mass quality, increasing the number of surrounding rock classifications, formulating the surrounding rock classification tables for the running tunnel and the station tunnel, and achieving the coordination and unification of qualitative and quantitative classification methods. Finally, the quantitative indexes of surrounding rock self-stability are determined, and the more scientific and reasonable physical and mechanical parameters of surrounding rocks are put forward through back calculation. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献
865.
Jodie Y.S. Lee William H.K. Lam 《Transportation Research Part A: Policy and Practice》2008,42(10):1314-1325
This paper presents a new pedestrian simulation (PS) model for signalized crosswalks in Hong Kong. This PS model is capable of estimating the variations of walking speed particularly on the effects of bi-directional pedestrian flows so as to determine the minimum required duration of pedestrian crossing time. Video records taken from the observational surveys at the selected crosswalk in urban area were used to extract the required data for model calibration. It was found that the design walking speed for signalized crosswalks should be varied by the effects of the bi-directional pedestrian flows. It was also interesting to note that the negative impact of the bi-directional flow effects (ranging from uni-directional to bi-directional pedestrian flows) on the chance of pedestrian crossing the crosswalk is increasing from free-flow to at-capacity flow conditions. The new PS model is also validated using an independent data set so as to examine the reliability of the simulation results. The validation results show that the new PS model can provide an accurate evaluation on the changes of walking speed and its standard deviation under different scenarios with particular emphasis on the effects of the bi-directional pedestrian flows. The advancement of this PS model can be applied to assess the effects of each improvement measure and to evaluate the benefits of each scenario in practice. 相似文献
866.
J. Benajes S. Molina R. Novella R. Amorim H. Ben Hadj Hamouda J. P. Hardy 《International Journal of Automotive Technology》2010,11(2):139-146
The demand for reduced pollutant emissions has motivated various technological advances in passenger car diesel engines. This
paper presents a study comparing two fuel injection systems and analyzing their combustion noise and pollutant emissions.
The abilities of different injection strategies to meet strict regulations were evaluated. The difficult task of maintaining
a constant specific fuel consumption while trying to reduce pollutant emissions was the aim of this study. The engine being
tested was a 0.287-liter single-cylinder engine equipped with a common-rail injection system. A solenoid and a piezoelectric
injector were tested in the engine. The engine was operated under low load conditions using two injection events, high EGR
rates, no swirl, three injection pressures and eight different dwell times. Four injector nozzles with approximately the same
fuel injection rate were tested using the solenoid injection system (10 and 12 orifice configuration) and piezoelectric system
(6 and 12 orifice design). The injection system had a significant influence on pollutant emissions and combustion noise. The
piezoelectric injector presented the best characteristics for future studies since it allows for shorter injection durations
and greater precision, which means smaller fuel mass deliveries with faster responses. 相似文献
867.
Among disaggregate vehicle ownership models, which model the number and/or type of vehicles owned at the household level,
one can distinguish holdings models, which deal with the (optimal) household fleet at a single point in time, and transactions
models. The latter type of model explains changes to the household fleet, such as replacement and disposal. The paper describes
previous attempts at such dynamic models and sketches how a vehicle transactions model could look (as an example we discuss
an application to The Netherlands). This includes discussions of transaction probabilities, two-stage budgeting, introducing
vehicle quality in the utility functions, and the envisaged model structure and data it could use. 相似文献
868.
869.
Among the general problematic of the HEV power trains, the most critical point is the determination of the power-split ratio
between the mechanical and the electrical paths, known as the energy management strategy (EMS). Many EMS are proposed in the
literature, and can be grouped in two categories: the local optimization EMS and the global optimization EMS. The local optimization
category corresponds to the EMS based on human expertise and the knowledge of the power train components efficiency maps.
Thus, the local optimization EMS manages the power train operations by referring to predefined rules. The drawback of such
strategies is that it brings an instantaneous fuel consumption optimization, and does not fully optimize the fuel consumption
over the whole trip. Therefore, additional fuel savings are still possible. This paper presents an overall optimized predictive
EMS for the Toyota Hybrid System (THS-II) power train of the Prius. The proposed EMS is based on Dynamic Programming (DP),
where the prior knowledge of the route is required in order to predetermine the power-split ratio and optimize the fuel consumption
for the whole predicted route. The DP EMS proposed for the THS-II power train is designed with a very short computation time,
intended to be implemented in real-time applications. The potential of this DP-controller in reducing fuel consumption on
regulatory cycles are computed and compared to a rule-based controller and to the Prius published fuel consumption results.
Finally, the fuel reduction enhancements of the DP-controller are computed for real road tests achieved on a MY06 Prius in
Ile-de-France, by comparing to the associated observed consumption measurements. 相似文献
870.
The present study aims to make a thermodynamic analysis of an ethylene cascade re-liquefaction system that consists of the following two subsystems: a liquefaction cycle using ethylene as the working fluid and a refrigeration cycle operating with a hydrocarbon refrigerant. The hydrocarbon refrigerants considered are propane (R290), butane (R600), isobutane (R600a), and propylene (R1270). A computer program written in FORTRAN is developed to compute parameters for characteristic points of the cycles and the system’s performance, which is determined and analyzed using numerical solutions for the refrigerant condensation temperature, temperature in tank, and temperature difference in the cascade condenser. Results show that R600a gives the best performance, followed by (in order) R600, R290, and R1270. Furthermore, it is found that an increase in tank temperature improves system performance but that an increase in refrigerant condensation temperature causes deterioration. In addition, it is found that running the system at a low temperature difference in the cascade condenser is advantageous. 相似文献