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171.
In this paper, vibration characteristics of the structure in the finite fluid domain are analyzed using a coupled finite element method. The added mass matrix is calculated with finite element method (FEM) by 8-node acoustic fluid elements. Vibration characteristics of the structure in finite fluid domain are calculated combining structure FEM mass matrix. By writing the relevant programs, numerical analysis on vibration characteristics of a submerged cantilever rectangular plate in finite fluid domain and loaded ship model is performed. A modal identification experiment for the loaded ship model in air and in water is conducted and the experiment results verify the reliability of the numerical analysis. The numerical method can be used for further research on vibration characteristics and acoustic radiation problems of the structure in the finite fluid domain. 相似文献
172.
To deal with the effect of compressible fluids on the supercavitating flow over the subsonic disk cavitator of a projectile, a finite volume method is formulated based on the ideal compressible potential theory. By using the continuity equation and Tait state equation as well as Riabouchinsky closure model, an “inverse problem” solution is presented for the supercavitating flow. According to the impenetrable condition on the surface of supercavity, a new iterative method for the supercavity shape is designed to deal with the effect of compressibility on the supercavity shape, pressure drag coefficient and density field. By this method, the very low cavitation number can be computed. The calculated results agree well with the experimental data and empirical formula. At the subsonic condition, the fluid compressibility will make supercavity length and radius increase. The supercavity expands, but remains spheroid. The effect on the first 1/3 part of supercavity is not obvious. The drag coefficient of projectile increases as the cavitation number or Mach number increases. With Mach number increasing, the compressibility is more and more significant. The compressibility must be considered as far as the accurate calculation of supercavitating flow is concerned. 相似文献
173.
北美铁路降低轮轨接触应力新进展 总被引:2,自引:0,他引:2
介绍了北美铁路在降低轮轨接触应力和轮轨作用力方面的研究成果. 相似文献
174.
175.
Wayne K. Talley 《Maritime Policy and Management》2001,28(2):175-186
This study investigates determinants of the vessel, cargo, and other-property damage costs of bulk barge accidents in US inland waterways. Tobit estimation of a three-equation recursive model suggests that, in bulk barge accidents: (1) vessel damage cost is greater for collision, fire/explosion, and material/equipment failure accidents than for groundings; (2) cargo damage cost is greater at night and when the weather is foggy and increases with barge age; and (3) otherproperty damage cost is greater for multi-vessel accidents, but decreases with barge size. A dollar of vessel damage cost increases other-property damage cost by $1.38, while a dollar of cargo damage cost increases this cost by $6.90. An important result for formulating bulk barge accident cost-reduction policies is that a given determinant might have a negative effect on one type of damage cost but a positive effect on another. 相似文献
176.
Upon the expiry of the concession contract signed between Lebanon and a private company for the Port of Beirut operation (in December 1990), the Government appointed a temporary commission to operate the port under the rules of the expiring concession. The legality of this measure has since always been questioned, while the temporary commission underwent three major personnel changes which clearly prevented any long-term thinking or planning. In 1998, the temporary commission entered into a 20-year joint venture for the establishment of a container terminal. Meanwhile, Lebanon's two main ports were facing major regional competition, while competing against each other to some degree. Thus, the need became urgent to end the temporary status and propose reforms to the entire sector. To that end, the Ministry of Public Works and Transport was commissed by the Government to propose a permanent institutional framework for the port of Beirut while assessing the need for a national maritime sector regulator. This paper presents the recommendations for the institutional reform of the Lebanese maritime transport sector. 相似文献
177.
Newell Garfield Mathew E. Maltrud Curtis A. Collins Thomas A. Rago Robert G. Paquette 《Journal of Marine Systems》2001,29(1-4)
During the period 1992–1998, 38 isobaric RAFOS floats were deployed to sample the subsurface flow of the California Undercurrent. The deployments, released over the California continental slope west of San Francisco, have sampled robust year-round poleward subsurface flow associated with the Undercurrent most seasons and the combined inshore current and Undercurrent in winter. Two other types of flow have been seen: a region of weak flow with little net displacement just west of the California Undercurrent, and an active westward propagating eddy field. This eddy field appears to be the primary mechanism for moving floats from the Undercurrent into the ocean interior. The observations and statistics from the RAFOS floats are compared with Lagrangian estimates of particles tracked in a global high resolution ocean simulation in order to evaluate the fidelity of the model along an eastern boundary. The results show that the model reproduces the general character of the flow reasonably well, but underestimates both the mean and eddy energies by a substantial amount. 相似文献
178.
A time-domain technique for estimating wave-induced ship hull bending moment from ship motion measurements is presented. This technique is developed to improve hull response monitoring systems. Artificial neural networks are used to model the time-domain relationship between the wave-induced vertical bending moment and the coupled heave and pitch motions. The application of the proposed technique is validated using experimental data. 相似文献
179.
A new approach for improving the performance of freight train timetabling for single-track railways is proposed. Using the idea of a fixed-block signaling system, we develop a matrix representation to express the occupation of inter- and intra-station tracks by trains illustrating the train blocking time diagram in its entirety. Train departure times, dwell times, and unnecessary stopping are adjusted to reduce average train travel time and single train travel time. Conflicts between successive stations and within stations are identified and solved. A fuzzy logic system is further used to adjust the range of train departure times and checks are made to determine whether dwell times and time intervals can be adjusted for passenger and freight trains at congested stations to minimize train waiting times. By combining manual scheduling expertise with the fuzzy inference method, timetable efficiency is significantly improved and becomes more flexible. 相似文献
180.
In this paper, three innovative car-sharing systems for urban areas are proposed, based on fleets of individual intelligent vehicles with three service characteristics: instant access, open-ended reservations and one-way trips. These features provide high flexibility but create an uneven distribution of vehicles among stations. Therefore, relocation of vehicles must be performed. Three different system procedures are proposed: in the first system, relocations are performed by users; in the other two, vehicles relocate automatically, thanks to their automation. In the first two systems, vehicles are accessible only at stations, whereas in the third they are also accessible along roads. In order to provide transport managers with a tool to test systems in different realities, an object-oriented simulator is developed. The simulation provides outputs of system performance, in terms of user waiting times and system efficiency. The proposed systems are simulated for the city of Genoa, in Italy, and a comparative analysis is presented. 相似文献