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RISS 인기검색어
- 검색키워드
- 저자 : Hesham Rakha (검색결과 3 건)
- 무료
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Kiseok Sung,Hesham Rakha 한국경영과학회 2009 Management Science and Financial Engineering Vol.15 No.1
A network model and a Genetic Algorithm (GA) is proposed to solve the simultaneous estimation of the trip distribution and traffic assignment from traffic counts in the congested networks in a logitbased Stochastic User Equilibrium (SUE). The model is formulated as a problem of minimizing a non-linear objective function with the linear constraints. In the model, the flow-conservation constraints are utilized to restrict the solution space and to force the link flows become consistent to the traffic counts. The objective of the model is to minimize the discrepancies between two sets of link flows. One is the set of link flows satisfying the constraints of flow-conservation, trip production from origin, trip attraction to destination and traffic counts at observed links. The other is the set of link flows those are estimated through the trip distribution and traffic assignment using the path flow estimator in the logit-based SUE. In the proposed GA, a chromosome is defined as a real vector representing a set of Origin-Destination Matrix (ODM), link flows and route-choice dispersion coefficient. Each chromosome is evaluated by the corresponding discrepancies. The population of the chromosome is evolved by the concurrent simplex crossover and random mutation. To maintain the feasibility of solutions, a bounded vector shipment technique is used during the crossover and mutation.
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Salah A. M. Elmoselhy,Waleed F. Faris,Hesham A. Rakha 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.10
Supercharged diesel engines are a key element in diesel powertrains that have been extensively modelled yet often without explainable mathematical trends. The present paper demonstrates the analytical modelling of in-cylinder gas speed dynamics and engine brake power. These analytical models provide explainable mathematical trends. In addition, they provide gear-shifting-based modeling because the model parameters can be adjusted to reflect different driving conditions without the need for gathering field data. An unprecedented sensitivity analysis was conducted on these developed models for simplifying them. They were validated using experimental data and the relative error of the developed model of the in-cylinder gas speed dynamics was 9.8%. The study demonstrates with 73% coefficient of determination that the average percentage of deviation of the simulated results from the corresponding field data on the engine brake power is 6.9%. The relative error of the developed model of the engine brake power is 7%. These values of relative error are an order of magnitude of deviation that is less than that of widely recognized models in the field of vehicle powertrain modeling such as the CMEM and GT-Power. These analytically developed models serve as widely valid models. Having addressed and corrected flaws in the corresponding models, such as the model of the in-cylinder gas speed dynamics presented in a key reference in this research area, these developed models can help in better analyzing and assessing the performance of diesel engines.
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Experimentally validated analytical modeling of diesel exhaust HC emission rate
Salah A. M. Elmoselhy,Waleed F. Faris,Hesham A. Rakha 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.10
Supercharged diesel engines are a key source of hazardous regulated emissions that have been extensively modelled, yet without explainablemathematical trends. The present paper demonstrates the analytical modeling of the percentage of unburned Hydrocarbon andthe HC emission rate in four-stroke diesel engines for trucks. The study presents as well the analytical modeling of the supercharged airdensity. A sensitivity analysis has been conducted on these developed models. The study shows that the average percentage of deviationof the simulated results from the corresponding freeway cycles field data on the percentage of unburned Hydrocarbon and the HC emissionrate is 10.6% and 4%, respectively. The corresponding coefficient of determination is 70% and 83%, respectively. The relative errorof the developed models of the percentage of unburned Hydrocarbon and the HC emission rate is 10.6% and 2%, respectively. The studydemonstrates with 99% coefficient of determination that the average percentage of deviation of the simulated results from the correspondingfield data under the steady speed operating condition for all freeway cycles on the supercharged air density is 3.7%. The relativeerror of the developed model of the supercharged air density is 4%. These values of relative error are in an order of magnitude ofdeviation that is less than that of widely recognized models in the field of vehicle powertrain modeling, such as the CMEM. These developedanalytical models serve as widely valid models that follow entirely from the principles of physics and the results of these developedmodels have explainable mathematical trends. The fact that these developed models are dimensionally correct further supports the validityof these models. The present models can help in better analyzing the performance of diesel engines and in developing and assessingthe performance of these engines.
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