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1.
A panel method is described for calculating potential flow around near-surface submarines. The method uses Havelock sources which automatically satisfy the linearized free-surface boundary condition. Outputs from the method include pressure field, pressure drag, wave resistance, vertical force, trim moment and wave pattern. Comparisons are made with model tests for wave resistance of Series 58 and DARPA SUBOFF hulls, as well as with wave resistance, lift force and trim moment of three length-to-diameter variants of the DSTO Joubert submarine hull. It is found that the Havelock source panel method is capable of determining with reasonable accuracy wave resistance, vertical force and trim moment for submarine hulls. Further experimental data are required in order to assess the accuracy of the method for pressure field and wave pattern prediction. The method is implemented in the computer code “HullWave” and offers potential advantages over RANS-CFD codes in terms of speed, simplicity and robustness. 相似文献
2.
Edward Langlois 《Coastal management》2013,41(2):171-176
Abstract An estuarine sanctuary is a store of public values due to the ecological, cultural, recreational, aesthetic, historic, and economic services provided by the preserve. These values may be expected to increase over time because of (1) growth in the population demanding estuarine services, (2) growth in the willingness to pay for such services, and (3) growth in the actual quality and quantity of services which are provided by a protected natural system. Thus an estuarine sanctuary will be more valuable to future generations than to current generations. When weighing the cost and benefits of a preservation or development decision, a preservation decision which seems currently undesirable may in fact be socially beneficial when growth in the value of estuarine services is included. 相似文献
3.
R. G. Langlois R. J. Anderson 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》1995,24(1):65-97
The potential performance improvement using preview control for active vehicle suspension was first recognized in the late nineteen sixties. All work done since that time has been based on optimal control theory using simple vehicle models.
In this article, the performance of quarter vehicle preview controllers when applied to a real off-road vehicle is simulated using both two degree of freedom quarter and ten degree of freedom full vehicle models. The results, which are compared with non-preview active and conventional passive suspensions, confirm that preview control reduces vertical acceleration of the body centre of gravity, which results in improved ride quality. Further, reductions in pitch and roll motion result from smaller vertical displacements of the vehicle quarters. Coupling between quarters, through the vehicle body, appears to have a smoothing effect on the control.
As an alternative to optimal control theory based controllers, a simple ad hoc preview controller based on isolating the vehicle body from dynamic loads transmitted through the suspension is proposed. Simulation results show that such a controller outperforms the optimal control theory based controllers over small discrete disturbances but responds poorly to disturbances encountered from other than steady state. 相似文献
In this article, the performance of quarter vehicle preview controllers when applied to a real off-road vehicle is simulated using both two degree of freedom quarter and ten degree of freedom full vehicle models. The results, which are compared with non-preview active and conventional passive suspensions, confirm that preview control reduces vertical acceleration of the body centre of gravity, which results in improved ride quality. Further, reductions in pitch and roll motion result from smaller vertical displacements of the vehicle quarters. Coupling between quarters, through the vehicle body, appears to have a smoothing effect on the control.
As an alternative to optimal control theory based controllers, a simple ad hoc preview controller based on isolating the vehicle body from dynamic loads transmitted through the suspension is proposed. Simulation results show that such a controller outperforms the optimal control theory based controllers over small discrete disturbances but responds poorly to disturbances encountered from other than steady state. 相似文献
4.
Edward Weiner 《Transportation》1975,4(4):351-367
Taxicab transportation is a significant segment of urban transportation. Taxicabs, along with other “paratransit” type systems, provide service with characteristics between the automobile and mass transportation. Consequently, they are well suited to a number of special purposes. Taxicabs currently serve a wide range of trip purposes by travellers with varied socio-economic characteristics. Taxicab transportation is most attractive for serving lower density area and off-peak travel particularly where there is only minimal mass transit service. In this regard, taxicabs are a supplement to conventional mass transit. The use of taxicabs for collection and distribution functions for both passengers and freight is gradually being realized. The multiple use of taxicabs offers advantages of increasing taxicab productivity and reducing individual trip costs. Many of the problems related to taxicabs are regulatory and institutional in nature. Unless these constraints are eased or removed, wider application of taxicab transportation, including productivity gains, will be limited. 相似文献
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Edward Weiner 《先进运输杂志》1984,18(2):113-124
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Edward N. Skomal 《先进运输杂志》1984,18(3):259-277
Through an examination of the dependence of several key performance parameters of a public bus system upon Automatic Vehicle Location (AVL) estimation accuracy, it becomes possible to place in perspective the value of AVL technology to improved public conveyance performance. Important bus transportation system performance measures dependent upon AVL estimation accuracy are: (1) Headway Control Error; (2) Time-Of-Passage Error, and (3) Required Layover Reserve. An analytical model of the dependence of these bus system performance measures upon AVL estimation error has been constructed. In addition, error models of three basic types of AVL systems, i.e., dead reckoning, proximity, and radio location have been developed and validated by experimental comparisons. By employing both sets of models, i.e. for the bus transport and AVL systems it becomes possible to recommend appropriate AVL technologies that best meet the performance requirements of a public bus service. The accompanying text synopsizes the noted models and provides an example of their use. 相似文献