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排序方式: 共有495条查询结果,搜索用时 15 毫秒
31.
A. De-Juan R. Sancibrian F. Viadero 《International Journal of Automotive Technology》2012,13(7):1033-1046
This paper presents an approach to optimize planar mechanisms for function generation synthesis. It is applied to the design of different steering linkages used in road vehicles where the Ackermann condition is formulated as the objective function. Four different mechanisms are kinematically defined and synthesized in terms of the proposed method. Limitations of the size of the elements are also considered by means of inequality constraints. Solutions are presented as the difference between desired behaviour, established by Ackermann, and actual generated performance. The results show that the accuracy achieved by the proposed procedure is satisfactory for working conditions in this type of linkages. 相似文献
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33.
Abstract In southern Rhode Island, there is growing concern that housing and recreational demands will soon overwhelm the capacity of the coastal salt ponds to absorb wastes, produce seafood, and maintain scenic qualities. As a result, coastal towns have been studying the feasibility of using land controls such as downzoning to protect these coastal amenities. The paper presents an economic analysis of the downzoning program proposed in the town of South Kingstown. Hedonic price and contingent valuation methods are used to value coastal amenities. The estimated net present value of “swimmable” water is shown to be $3.1 million. 相似文献
34.
Numerous real-world problems related to ship design can be solved by various alternatives. However, the scantling design has conflicting objectives such as minimum production cost, minimum weight and maximum moment of inertia (stiffness). Therefore a multi-purpose solution had to be settled in order to meet all these requirements at once. Ship design is a complex endeavour requiring successful coordination of many different disciplines, both technical and non-technical. Basic design is the least defined stage of the ship design process and seeks to define the optimal amidships section structure. For that purpose, recent improvements have been made to a numerical tool in order to optimise the scantling of ship sections by considering production cost, weight and moment of inertia in the optimisation objective function. A multi-criteria optimisation of a LNG carrier is conducted in this paper to illustrate the analysis process. Pareto frontiers are obtained and results have been validated by the Bureau Veritas rules. The methodology presented in this paper has demonstrated its effectiveness in optimising scantling of ships at a very early design stage thanks to a management of critical problems usually studied at a later stage of the design. 相似文献
35.
E. Alcalá F. Badea Á. Martin F. Aparicio 《International Journal of Automotive Technology》2013,14(5):817-827
The analysis of structures with finite elements methods (FEM) represents a widely spread technique. For large tubular structures similar to the buses and coaches upper structures, beam type elements are utilized due to the fact that these elements provide satisfactory results at relatively reduced computational performances. However the beam type elements have a main disadvantage determined by the fact that the modeled joints have an infinite rigid behavior. This shortcoming determines a stiffer behavior of the modeled structures which translates into an error source for the structural simulations (up to 45%). To overcome this problem, a simple methodology was conceived and an alternative optimized equivalent beam model obtained. The methodology studies the behavioral characteristics of beam modeled T-junctions determining their limitations and comparing them to equivalent T-junctions modeled with shell and volume elements. This way an improved Tjunction has been obtained, in which the behavioral error was reduced to less than 5%. Furthermore the FEM obtained results were validated with real T-junctions. 相似文献
36.
Carlos F. Daganzo 《Transportation Research Part B: Methodological》1980,14(3):229-239
This paper complements the preceding one, which showed how one could modify equilibrium traffic assignment algorithms for networks with many centroids. In this one it is shown how one can substitute centroids by zones with continuous population densities. The technique, which is mathematically guaranteed to approximate a flow pattern in accordance with Wardrop's user equilibrium criterion, requires some geometrical calculations which can be handled off-line. With the suggested approach, it is possible to represent the spatial distribution of trip ends more realistically and this allows traffic assignment models to capture the effects of short and intrazonal trips in a way previously impossible. The method is shown to be computationally feasible. 相似文献
37.
38.
F. Payri A. J. Torregrosa A. Broatch L. Monelletta 《International Journal of Automotive Technology》2009,10(6):761-769
Combustion noise in passenger cars powered with direct injection (DI) diesel engines is frequently the main reason why end-users
are reluctant to drive this type of vehicle. Thus, the great potential of diesel engines for environment preservation — due
to their lower CO2 emissions — could be missed. This situation worsens with the current design trends (engine downsizing) and the emerging new
diesel combustion concepts (Homogeneous Charge Compression Ignition-HCCI, Premixed Charge Compression Ignition-PCCI, etc.),
which are intrinsically noisy. This negative feature can be even more critical in transient operation due to the contribution
of the temporal changes of both source and transmission path on engine noise. Therefore, combustion noise must be considered
as an additional essential factor in engine development, together with performance, emissions and driveability. Thus, suitable
evaluation procedures that can be integrated into the global engine development process in a timely and cost-effective manner
are imperative. Regarding the evaluation procedures, most of the work available in the literature addressed combustion noise
at steady operation. To surpass this limitation, two possible approaches — adapted from the classical and multiple regression
methods — for the overall level assessment of combustion noise in transient conditions are evaluated in this paper. 相似文献
39.
Traditional liner carriers, operating in the highly competitive commercial environment of the last few years, have attempted to lower the marginal cost of each box carried. Technological improvements in both construction and propulsion systems have led to a steady growth in carrying capacity. Ships of 600+ TEUs are now in service and, as a result of this trend, have displaced 'smaller' ships from the major east-west trades. The more competitive environment of these trades has in turn led to a redeployment of ships in the 2500+ TEU range to the north-south trades. The result has been a rapid increase in north-south capacity, including feeder services and falling freight rates. Despite the current excess supply in shipping and historically low freight rates, significant developments in technology have created opportunities for new fast containerships. The paper analyses the key economic factors in the differentiation of the new fast ship technology from the traditionally designed containerships and demonstrates the potential financial viability to owners of these new 'greyhounds'. 相似文献
40.
F. Soriano M. Moreno-Eguilaz J. Alvarez J. Riera 《International Journal of Automotive Technology》2016,17(5):873-882
In this two-part paper, a topological analysis of powertrains for refuse-collecting vehicles (RCVs) based on the simulation of different architectures (internal combustion engine, hybrid electric, and hybrid hydraulic) on real routes is proposed. In this first part, a characterization of a standard route is performed, analyzing the average power consumption and the most frequent working points of an internal combustion engine (ICE) in real routes. This information is used to define alternative powertrain architectures. A hybrid hydraulic powertrain architecture is proposed and modelled. The proposed powertrain model is executed using two different control algorithms, with and without predictive strategies, with data obtained from real routes. A calculation engine (an algorithm which runs the vehicle models on real routes), is presented and used for simulations. This calculation engine has been specifically designed to analyze if the different alternative powertrain delivers the same performance of the original ICE. Finally, the overall performance of the different architectures and control strategies are summarized into a fuel and energy consumption table, which will be used in the second part of this paper to compare with the different architectures based on hybrid electric powertrain. The overall performance of the different architectures indicates that the use of a hybrid hydraulic powertrain with simple control laws can reduce the fuel consumption up to a 14 %. 相似文献