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961.
Study on sloshing in cargo tanks including hydroelastic effects 总被引:3,自引:0,他引:3
The sloshing problem in cargo tanks is studied through experiments and numerical analysis. The fluid motion is described
using a higher-order boundary element method and the structural response by a thin plate theory. It was found that hydraulic
jumps are formed when the excitation frequency is close to the resonance frequency in the case of low filling depth. In the
case of high filling depth, the flow resonates and hits the top of the tank, thus inducing a large impact pressure. The pressure
on the flexible plate shows amplified initial peaks followed by oscillatory components, the frequency of which coincides with
the natural frequencies of the plate in water as a result of hydroelastic effects.
Received for publication on Nov. 18, 1998; accepted on May 14, 1999 相似文献
962.
In the course of the last two decades Korean shipping has emerged as a major player in the liner market. In 1970 there was not a single container ship in the Korean fleet; yet, within the next two decades, shipping companies from Korea have become included among the top 10 liner operators in the world, in the context of a spectacular ascent of Asian companies in international container shipping. During the same period the organization of liner shipping itself underwent major changes. In the 1970s and 1980s, pools and powerful consortia prevailed, maximizing frequency and optimizing fleet deployment under pressure from the high investment entailed by containerization. The era of consortia, however, came to a close in the early 1990s; intermodalism and the expansion of the major liner companies into forward and backward segments of the transport chain rendered them inflexible for pursuing individual strategies of product diversification with a view to larger market shares. Global alliances were finally born as a result of a major reshuffling of co-operation agreements and of the globalization of the production process on the demand side. The aim of this paper is to follow and assess the options available to an aggressive low-cost national fleet in its journey to competitive maturity through a period of changing organization of liner shipping, focusing on the course of the leading Korean container company, and one of the largest in the world today, Hanjin. It highlights at the same time both the deep structural changes which liner shipping has undergone in the last two decades and the effects of current changes, such as the recent wave of mergers in this sector. 相似文献
963.
This article derives from a study concerned with the traffic implications of a proposed redevelopment of the Central Market in Ghana's second largest city, Kumasi, which is situated almost in the geographic centre of the country. The market adjoins a big roundabout which is located at the point of intersection not only of north-south national routes but also at a point on which most of the city's main roads carrying cross-town traffic converge. The problem of traffic in terms of accessibility and environment is described in relation to the functions of the market. This is compared with a similar situation in London's Piccadilly Circus. Based on the results of traffic surveys and an analysis of the urban structure, alternative solutions to the problem in Kumasi are examined and tested using traffic assignment techniques. Consequently, on the basis of accessibility and environmental requirements, proposals are made as to the best line of action to take. The article ends with some lessons of the study. 相似文献
964.
965.
Safety in density (SID) potentially explains the safety in numbers (SIN) phenomenon by positing that ‘the SIN effect can be reproduced simply through encouraging behaviour that leads to the formation of higher-density cyclist groups’. The study further explores this hypothesis using event-based exposure, queues and groups of road users. Using three different definitions of encounters between road users, these were manually counted at signalized intersections, and their relationship to traffic volume was assessed. Based only on the frontmost motor vehicle in a queue and one cyclist among the several passing in front of that vehicle, the results show a less than linear relationship between meetings and traffic volume. An increase in the number of cyclists entails a general increase in cyclists passing in front of each motor vehicle, and an increase in motor vehicles increases queue lengths. However, crash data from the Swedish accident database (STRADA) show that it is exceedingly rare for multiple cyclists to be injured in the same crash. Together with results from a crash-encounter model, this suggests that the SID hypothesis may help to explain SIN 相似文献
966.
R.C. Lin Graduate Student D. Cebon Lecturer D.J. Cole Royal Society University Research Fellow 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1996,26(1):17-43
This paper describes an investigation into active roll control of articulated vehicles. The objective is to minimise lateral load transfer using anti-roll bars incorporating low bandwidth hydraulic actuators. Results from handling tests performed on an articulated vehicle are used to validate a nonlinear yaw/roll model of the vehicle. The methodology used to design lateral acceleration controllers for vehicles equipped with active anti-roll bars is developed using a simplified linear articulated vehicle model. The hardware limitations and power consumption requirements of the active elements are studied. The controller is then implemented in the validated articulated vehicle model to evaluate the performance of an articulated lorry with active anti-roll bars. The simulation results demonstrate the possibility of a significant improvement in transient roll performance of the vehicle, using a relatively low power system (10 kW), with low bandwidth actuators (5 Hz). 相似文献
967.
Optimal Control of a Vehicle Suspension Incorporating the Time Delay between Front and Rear Wheel Inputs 总被引:2,自引:0,他引:2
N. Louam D. A. Wilson R. S. Sharp 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1988,17(6):317-336
An optimal control law for a vehicle suspension is developed using a discrete linear quadratic regulator framework. The time delay between the disturbance due to the road at the front and rear wheels is incorporated into the model, and it is shown that the optimal control law requires information gathered at the front wheels. A comparison is made between the optimal control law and a suboptimal one which does not incorporate front wheel road information. 相似文献
968.
R. C. Redfield D. C. Karnopp 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1988,17(5):267-280
With a simplified approach for creating road surface elevation information for simulation of vehicle vertical response to roadway unevenness, roadways for single and parallel track simulations and averaged roads for variable velocity simulation are developed. Sets of correctly chosen random roadway slopes are averaged appropriately for the variable velocity simulation. The procedure generates approximately “white” slope spectral density roadways in the frequency ranges of interest, and the elevation profiles are representative of average road profiles. The method is simple in practice yet suffices for many parameter studies of suspensions and vehicle dynamics. 相似文献
969.
I. G. Salisbury D. J. N. Limebeer 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2017,55(6):775-801
The majority of motion cueing algorithms have been developed for passenger car applications, with correspondingly less research dedicated to race-car and high-performance vehicle simulators. In the high-performance context, the focus is on cueing the vehicle's behavioural and handling characteristics, particularly when driving near the limits of performance. In race-car simulators the cueing requirements are therefore quite different, with the problem made all the more challenging by the presence of large accelerations. To understand the drivers' cueing needs, the vehicle's stability and handling response characteristics must be examined near the performance boundary. Frozen-time eigenvalue analyses are used to determine stability and response characteristics across all vehicle operating conditions, including accelerating and braking under cornering, with the results used to determine motion cueing algorithm requirements. Lateral acceleration and yaw cueing filters are designed in order to retain information critical to understanding the vehicle's behaviour on its performance boundary. Cueing filters are then tested, with the help of a professional race-car driver, and are found to provide the cues necessary for the driver to control the vehicle on the limit of performance. 相似文献
970.
Some vehicle components are developed by setting target weights to the gram level at their design stages to accomplish a lightweight design. Recently, there have been many studies that have focused on lightweight design through the use of ultra-high-strength steels. However, a lightweight design can face many challenges if the reliability of the analysis is not also secured at the design stage. Such challenges include difficulties in coupled analyses when the file formats are different among PAM-STAMP, ABAQUS, and NASTRAN. In this study, we developed a mapping interface that enables mapping between the file formats of various software programs. Buckling analysis was coupled to the forming analysis, in which pre-strain test data were applied in considering the material’s strain hardening, to evaluate the rigidity of the front lower control arm that controls the wheels and transfers loads. The influence of forming effects on endurance was evaluated, and residual stresses around the weld zone were calculated. A comparison of experimental and analytical results indicated that the proposed analysis was highly reliable. 相似文献