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961.
962.
Michal Maniowski 《Vehicle System Dynamics: International Journal of Vehicle Mechanics and Mobility》2016,54(4):526-544
ABSTRACTThe paper presents an innovative method for a lap time minimisation by using genetic algorithms for a multi objective optimisation of a race driver–vehicle model. The decision variables consist of 16 parameters responsible for actions of a professional driver (e.g. time traces for brake, accelerator and steering wheel) on a race track part with RH corner. Purpose-built, high fidelity, multibody vehicle model (called ‘miMa’) is described by 30 generalised coordinates and 440 parameters, crucial in motorsport. Focus is put on modelling of the tyre tread thermodynamics and its influence on race vehicle dynamics. Numerical example considers a Rear Wheel Drive BMW E36 prepared for track day events. In order to improve the section lap time (by 5%) and corner exit velocity (by 4%) a few different driving strategies are found depending on thermal conditions of semi-slick tyres. The process of the race driver adaptation to initially cold or hot tyres is explained. 相似文献
963.
以港珠澳大桥珠海连接线拱北隧道为工程实例,研究管幕冷冻法工艺中地层的冻胀控制原理和技术。基于热力耦合原理,采用有限元预测人工冷冻过程中的土体温度变化及地表冻胀位移,比较和分析管幕周围土体预注浆和采用限位管模式对地表冻胀的控制效果。结果表明: 管幕周围土体的预注浆降低了土体的渗透系数及冻胀率,抑制了土中水分迁移,是冻胀控制技术的主体;限位管有效地降低了冻土的发展速率,加强了冻胀控制效果,是冻胀控制技术的有效补充。通过对现场地表冻胀实测数据与有限元模拟结果的比较分析,从地层温度和地表位移分布规律说明了冻胀控制技术的工作原理。研究结果为拱北隧道的顺利实施提供了技术保障,提高了我国复杂条件下超大断面隧道建造的总体技术,还可为类似人工冷冻法隧道施工提供技术参考。 相似文献
964.
Long Run;Ke Changguo(Naval Representative's Office in Xiangtan, Xiangtan 411100, Hunan, China;Wuhan Institute of Marine Electric Propulsion, Wuhan 430064, China) 相似文献
965.
966.
967.
The degradation of crosslinked polyethylene (XLPE) cable insulation during service, such as thermo-oxidation and water treeing may lead to a premature electrical breakdown of the XLPE insulation cables. Therefore, it is necessary to optimize the period of replacement to evenly distribute the replacement cost by ascertaining the deterioration degree. Estimation of the aging degree is at present the most important task for diagnosis of the residual lifetime of the power cable insulation. This paper presents a study on the changes in the dielectric properties of the thermally aged XLPE cables in the frequency range from 0.07~10 MHz. Based on electrical and physicochemical characterization, some new "dactylograms" for the thermally aged XLPE cable insulation have been proposed. 相似文献
968.
969.
为解决中厚板高强钢埋弧焊(Submerged Arc Welding, SAW)焊缝热影响区(Heat Affected Zone, HAZ)热循环参数准确测量难题,自主研制多通道热电偶测温软/硬件系统,测量并比较不同焊丝组合(单丝和冷热多丝复合)对应的焊缝HAZ热循环主要参数。试验结果表明:与单丝SAW工艺相比,冷热多丝复合SAW工艺可解决SAW较大热输入产生的焊缝HAZ脆化问题,提高焊缝组织性能和焊接质量;在中厚板高强钢焊接过程中,冷热多丝复合SAW工艺可为温度场数值模拟计算分析提供实测数据,为各种工艺参数的确定与优化、焊缝HAZ的组织性能改善提供必要的理论基础。 相似文献
970.
[Objective]To meet the efficient thermal management needs of electronic devices such as ships and underwater vehicles, this study focuses on the constructal design of a tree-shaped microchannel disc heat sink with wavy walls. [Method]A design prototype of the heat sink with wavy walls is first proposed. Based on constructal theory, the amplitude and wavelength of the wavy walls are designed under the constraints of fixed heat sink volume and fixed microchannel volume by maximizing the comprehensive performance evaluation criteria (PEC) while considering both heat transfer and flow pressure drop. [Results]The results show that the wavy walls increase the heat transfer surface areas and generate vortices in their cavities, effectively reducing the maximum temperature. When the inlet Reynolds number is fixed at 700, 900 or 1100 respectively, the maximum temperature is reduced by 13.5 K by increasing the amplitude of the wavy walls, while the pressure drop increases significantly; and the maximum temperature is reduced by 4.7 K by reducing the wavelength of the wavy walls, while the pressure drop increases slightly. There are optimal amplitudes that raise the comprehensive performance evaluation criteria to extreme values for given larger wavelengths, while the comprehensive performance evaluation criteria increase monotonously as the amplitude increases for given smaller wavelengths. [Conclusion]Wavy walls can significantly improve the thermal performance of tree-shaped microchannel disc heat sinks, and the use of constructal design can realize optimal geometric constructs with optimal comprehensive performance evaluation criteria. © 2023 Authors. All rights reserved. 相似文献