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带展向曲率的超音速混合层中扰动演化的研究
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作者 钱琳 罗纪生 《力学学报》 EI CSCD 北大核心 2007年第2期162-170,共9页
超音速混合层的流动不稳定性较之亚音速或不可压的混合层大大减弱,为了提高混合效率,通过数值模拟的方法分别研究了展向曲率、展向速度、来流马赫数等因素对混合效率所起的作用.计算结果表明:在给定展向速度的情况下,带有展向曲率的三... 超音速混合层的流动不稳定性较之亚音速或不可压的混合层大大减弱,为了提高混合效率,通过数值模拟的方法分别研究了展向曲率、展向速度、来流马赫数等因素对混合效率所起的作用.计算结果表明:在给定展向速度的情况下,带有展向曲率的三维混合层,曲率越大三维扰动增长率越大,而且法向的卷起范围也越大.当展向曲率不为零时,展向速度的增大也能有效地增强混合能力.由流场中的高频扰动波产生的涡,在向下游发展过程中会有破碎、拉伸,低频扰动波没有发现这一现象.对于有展向曲率和展向速度的混合层,提高来流马赫数时,流场中最不稳定扰动的增长率仍很大.因此,这是一种提高混合层混合效率的新途径. 展开更多
关键词 三维超音速混合层 增强混合 展向曲率 展向速度 扰动演化
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超音速混合层稳定性分析及增强混合的研究 被引量:6
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作者 罗纪生 吕祥翠 《力学学报》 EI CSCD 北大核心 2004年第2期202-207,共6页
利用流动稳定性提高超音速混合层的混合效率,对于提高超音速流的高效混合是一个有效途径。研究结果表明,有展向曲率的三维混合层中,三维扰动的增长率很大,且法向的掺混能力也较强,可以有效地增强混合。对于高马赫数来流的超音速混合层,... 利用流动稳定性提高超音速混合层的混合效率,对于提高超音速流的高效混合是一个有效途径。研究结果表明,有展向曲率的三维混合层中,三维扰动的增长率很大,且法向的掺混能力也较强,可以有效地增强混合。对于高马赫数来流的超音速混合层,这一特性依然存在,这将有利于提高高超音速混合层的混合能力。 展开更多
关键词 超音速混合层 三维混合层 增强混合 流动稳定性 展向曲率 马赫数 流体力学
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Comparative evaluation of geological disaster susceptibility using multi-regression methods and spatial accuracy validation 被引量:14
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作者 蒋卫国 饶品增 +2 位作者 曹冉 唐政洪 陈坤 《Journal of Geographical Sciences》 SCIE CSCD 2017年第4期439-462,共24页
Geological disasters not only cause economic losses and ecological destruction, but also seriously threaten human survival. Selecting an appropriate method to evaluate susceptibility to geological disasters is an impo... Geological disasters not only cause economic losses and ecological destruction, but also seriously threaten human survival. Selecting an appropriate method to evaluate susceptibility to geological disasters is an important part of geological disaster research. The aims of this study are to explore the accuracy and reliability of multi-regression methods for geological disaster susceptibility evaluation, including Logistic Regression(LR), Spatial Autoregression(SAR), Geographical Weighted Regression(GWR), and Support Vector Regression(SVR), all of which have been widely discussed in the literature. In this study, we selected Yunnan Province of China as the research site and collected data on typical geological disaster events and the associated hazards that occurred within the study area to construct a corresponding index system for geological disaster assessment. Four methods were used to model and evaluate geological disaster susceptibility. The predictive capabilities of the methods were verified using the receiver operating characteristic(ROC) curve and the success rate curve. Lastly, spatial accuracy validation was introduced to improve the results of the evaluation, which was demonstrated by the spatial receiver operating characteristic(SROC) curve and the spatial success rate(SSR) curve. The results suggest that: 1) these methods are all valid with respect to the SROC and SSR curves, and the spatial accuracy validation method improved their modelling results and accuracy, such that the area under the curve(AUC) values of the ROC curves increased by about 3%–13% and the AUC of the success rate curve values increased by 15%–20%; 2) the evaluation accuracies of LR, SAR, GWR, and SVR were 0.8325, 0.8393, 0.8370 and 0.8539, which proved the four statistical regression methods all have good evaluation capability for geological disaster susceptibility evaluation and the evaluation results of SVR are more reasonable than others; 3) according to the evaluation results of SVR, the central-southern Yunnan Province are the highest sus-ceptibility areas and the lowest susceptibility is mainly located in the central and northern parts of the study area. 展开更多
关键词 geological disaster susceptibility multi-regression methods geographical weighted regression sup-port vector regression spatial accuracy validation Yunnan Province
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