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991.
The Ensemble Kalman filter (EnKF) has been applied to a 1-D complex ecosystem model coupled with a hydrodynamic model of the Ligurian Sea. In order to improve the performance of the EnKF, an ensemble subsampling strategy has been used to better represent the covariance matrices and a pre-analysis step for correcting the non-normality of the members distribution has been implemented. Twin experiments have been realized to assess the performance of the developed tool and a real data assimilation experiment has been conducted to hindcast the ecosystem at the Dyfamed site during the year 2000. Finally the performance of the EnKF has been compared with a Singular Evolutive Extended Kalman (SEEK) filter with a fixed basis. We conclude that, on one hand, there is a benefit in using the subsampling strategy and the lognormal transformation with the EnKF, and on the other hand, this filter presents better performance than the fixed basis version of the SEEK filter. However, it also incurs a large computational cost. 相似文献
992.
Data assimilation is used in numerical simulations of laboratory experiments in a stratified, rotating fluid. The experiments are performed on the large Coriolis turntable (Grenoble, France), which achieves a high degree of similarity with the ocean, and the simulations are performed with a two-layer shallow water model, using the SEEK method for data assimilation. Since the flow is measured with a high level of precision and resolution, a detailed analysis of a forecasting system is feasible. The procedure is tested for the baroclinic instability of a two-layer vortex. It is shown that the method of data assimilation properly captures the details of the initial flow perturbation. Then it is shown by sensitivity studies that an error of the model, attributed to small non-hydrostatic effects, can be distinguished from the error growth associated with the intrinsic instability of the system. Finally, it is experimentally demonstrated that the velocity field in the lower layer can be well controlled by data assimilation limited to the top layer. 相似文献
993.
B. Unver Y. Koyuncuoglu M. Gokasan S. Bogosyan 《International Journal of Automotive Technology》2016,17(1):13-34
The ultimate aim of this study is the development of an engine modeling approach that would facilitate the design of model-based control techniques for diesel engines. This will allow for the development of more generalized, modular control strategies for different engine types and sizes as opposed to the commonly practiced map-based engine control strategies that depend on maps and feedforward control and require lengthy modifications every time a change is made. Also, most engine modeling studies focus on either airpath or combustion systems, treating these models and their validation individually, and not as an integrated system as is actually the case. To address the need for more realistic models suitable for model-based control design, this study develops a combined airpath and combustion model for the engine, using analytical models wherever possible and derives a model with appropriate control inputs and outputs that could be used in a control scheme. The inclusion of the actuator dynamics of the Exhaust gas recirculation (EGR), variable geometry turbine (VGT), and Throttle (THR) valves in the airpath model and the consideration of nonlinearities in the combustion model allow for the development of a more thorough engine model, as well as the validation of subsystems and the whole integrated engine model using a complete World Harmonized Transient Cycle (WHTC). This test cycle finds limited use due to its challenging transients, and yet, is the demanded test cycle for emission regulations nowadays. These are unique aspects of this modeling study, the results of which indicate that the developed engine model could be used in control design and hardware-in-the-loop simulation (HILS) based engine control prototyping. 相似文献
994.
Internalisation of the external costs of transport is currently the subject of much debate. Estimation of costs such as those
of pollution and congestion is a primary element in any strategy involving policies for use in the internalisation of these
costs. The objective of the TRENEN II STRAN project, funded by the EU, was to develop a methodology for estimation of the
marginal external costs of transport. The model developed during the project was used in a series of case studies. One of
the case studies, that conducted for Dublin, is reported in this paper. A brief summary of the TRENEN approach is presented
followed by the results for Dublin produced from policies such as Do Nothing, Uniform pricing (internalising external costs
by means of fuel taxation), Congestion Pricing (cordon pricing) and a first-best policy, the Full Optimum where one assumes
that the policy maker has perfect pricing instruments available. As one would expect, the model shows that the greatest reduction
in traffic level and external costs would occur if it were possible to introduce a highly differentiated and sophisticated
pricing system. Increased taxation on fuel is not an efficient policy as it does not address the marginal external costs of
congestion in a way that time-differentiated road-use pricing would. The results from testing of the different measures are
interesting particularly those relating to parking and the way in which residents within the CBD and commuters to the CBD
are dealt with.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
995.
Mark T. Lusk Young-Kook Lee Herng-Jeng Jou William H. Elliott Gerard M Ludtka . Materials Science Program Division of Engineering Colorado School of Mines Golden CO. U.S. . Questek Innovations LCC Maple Avenue Evanston IL U.S. 《上海交通大学学报(英文版)》2000,(1)
QuanitativelyaccuratePredictionsofquenchinduceddistOnionandresidualstressrelyontheabilitytopredictthemicrosthectUralevolUtionthroughOutthequenchProcess.InlowaIloysteels,cUrrenresearchMshavefOcusedontheformationldneticsoffetrite,pearlite,bainiteandmartensite.However,temPeringcanhavealargeinfluenceondistOnionandresidualstrCss,andeffortstoaccountforthislagbehindthemodelingofthePrimnyphasetransihons.AsafirststeptowardsaccountingfortemPerillg,wehavedevelOpedanintemalstatevariablemodelthatuses… 相似文献
996.
In the globalization era, lean initiatives and environmental management systems are increasingly implemented in the automotive industry. The aim of this report is to investigate and perform structural analysis of Lean Six Sigma (LSS) and Organizational Performance (OP). Data were obtained from 252 top management leaders in the Malaysian automotive industry. This report presents the results of the Exploratory Factor Analyses (EFA), Confirmatory Factor Analysis (CFA), and reliability analysis, which are empirically verified and validated. A set of assessment measurements of LSS and OP is expected to be suitable for their characteristics and improve their competitiveness. Thus, the main objective of the analysis was to provide additional insight into the relationship between LSS and OP by examining the effects of ISO 14001 certification as a moderator. The results indicate that ISO 14001 certification does not significantly moderate the relationship between LSS and OP in the Malaysian automotive industry. However, the OP values for ISO 14001 certified companies are higher than those without ISO 14001 certification. 相似文献
997.
S. Abdullah W. H. Kurniawan M. Khamas Y. Ali 《International Journal of Automotive Technology》2011,12(1):29-38
In an era in which environmental pollution and depletion of world oil reserves are of major concern, emissions produced by
automotive vehicles need to be controlled and reduced. An ideal solution is to switch to a cleaner fuel such as natural gas,
which generates cleaner emissions. In addition, control over the in-cylinder air-fuel mixture can be best achieved through
a direct-injection mechanism, which can further improve combustion efficiency. This need for cleaner automobiles provides
the motivation for this paper’s examination of the use of computational fluid dynamic (CFD) simulations to analyze the concentrations
of the exhaust gases produced by a compressed natural gas engine with a direct-fuel-injection system. In this work, a compressed
natural gas direct-injection engine has been designed and developed through a numerical simulation using computational fluid
dynamics (CFD) to provide an insight into complex in-cylinder behavior. The emissions analyzed in this study were carbon monoxide
(CO), nitric oxide (NO) and carbon dioxide (CO2), i.e. the main pollutants produced by natural gas combustion. Based on a stoichiometric mixture, the concentrations of CO
and NO were computed using the dissociation of carbon dioxide and the extended Zeldovich mechanism. CO2 was calculated using a mass balance of the species involved in the combustion process. The simulation results were then compared
with the experimental data generated by a single-cylinder research engine test rig. A good agreement was obtained with the
experimental data for the engine speeds considered for all emissions concentrations. 相似文献
998.
Road haulage is nowadays the main transport mode in France, demonstrating its ability to fulfil shippers’ demands. Among other success factors, the possibility for large companies to subcontract to very small ones, with very low fixed costs and greater flexibility, is often quoted as a major advantage. The ECHO survey, conducted in France in 2004, gives information about 10000 shipments made by 3000 shippers. This survey allows the analysis of subcontracting, by following at every stage how each shipment is given to another carrier by contract. The analysis shows that some subcontracts are mainly cost driven, but others aim at using the specialised skills of a particular haulier. For every transport segment (single parcel delivery service, parcel delivery service, less than truck load, full truck load), subcontracting is described in terms of sizes of the companies involved, services provided and the reasons for subcontracting. These results describe the main features of several different types of subcontracts. 相似文献
999.
Evaluation of natural and tracer fluorescent emission methods for droplet size measurements in a diesel spray 总被引:2,自引:0,他引:2
J. V. Pastor R. Payri J. M. Salavert J. Manin 《International Journal of Automotive Technology》2012,13(5):713-724
Spray sizing that records fluorescent emission and scattered light has been widely applied to spray diagnostics over the last two decades. Different experimental strategies have been developed, but comparing the different solutions offered has remained of interest to experimentalists. In this work, a comparison of two fluorescence strategies for measuring droplet size in the liquid phase of a last-generation DI diesel spray is conducted. The natural fluorescent emission of a commercial diesel fuel and the fluorescence emitted by a tracer (Rhodamine B) are compared using theoretical and experimental approaches. The LIF/Mie ratio commonly called Planar Droplet Sizing (PDS) technique is applied in two different ways to elucidate the possible advantages of using a fluorescent dopant. The sprays were injected under non-evaporative conditions into a constant pressure vessel that simulates densities present at the moment of injection in currently used passenger car diesel engines. Characterization of the signal properties was performed by measuring the absorption coefficient, fluorescence emission spectrum, quantum yield and lifetime of both configurations. The scattered light and fluorescence intensities were calculated to verify the dependencies of the droplet surface and volume. When applying the two techniques to quantify droplet size in dense diesel sprays, the results show that signal weakness and lack of control over the properties of natural fluorescence produce distortion in the shape of the spray and cause measurements to be unreliable. 相似文献
1000.
In recent years, railway tunnels in karst areas have frequently suffered flooding after high-intensity rainfall, which seriously affects the safety of tunnel operation and the order of transportation, and even interrupts the traffic. Based on the water hazard case in the Yuanbaoshan Tunnel on the Zhijin-Bijie Railway Line, this paper explores the causes of lining damage in terms of geology, rainfall, and the design and construction of water hazard sections, and puts forward the treatment technology for tunnel water hazards with the core concept of "making full use of existing structures and employing open drainage methods in key sections". Besides, this paper simulates and analyzes the formation of hazards and the treatment effect through numerical simulation. The results show that the subjective causes for the damage in tunnel linings include an insufficient understanding of the water-bearing formations at the geological investigation stage, the underestimation of water hazard risks posed by high-intensity rainfall during construction, and the unimproved waterproof and drainage system in the design alteration, while the objective reasons include the development of karst near the tunnel section that passes through the stratum, the strong connectivity of water conduits, and the high-intensity rainfall in a certain period of time on the tunnel site. As for the simulation results, they show that the increase of external water pressure caused by the sudden rise in groundwater level after rainstorm significantly increases the internal force of linings, and eventually leads to a much lower safety factor of sidewall linings and large scale damage, which is in consistency with the characteristics of the actual on-site damage. After on-site emergency treatment, the tunnel structure has become stable and even encountering unprecedentedly heavy rainfall twice, the tunnel has still remained in a good condition. Since then, no water hazards and other disasters have occurred, which proves that the treatment plan is valid. © 2022, Editorial Office of "Modern Tunnelling Technology". All right reserved. 相似文献