排序方式: 共有21条查询结果,搜索用时 17 毫秒
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Large eddy simulation of hot and cold fluids mixing in a T-junction for predicting thermal fluctuations 总被引:1,自引:0,他引:1
Temperature fluctuations in a mixing T-junction have been simulated on the FLUENT platform using the large eddy simulation (LES) turbulent flow model and a sub-grid scale Smagorinsky-Lilly model. The normalized mean and root mean square temperatures for describing time-averaged temperature and temperature fluctuation intensity, and the velocity are obtained. The power spectrum densities of temperature fluctuations, which are key parameters for thermal fatigue analysis and lifetime evaluation, are analyzed. Simulation results are consistent with experimental data published in the literature, showing that the LES is reliable. Several mixing processes under different conditions are simulated in order to analyze the effects of varying Reynolds number and Richardson number on the mixing course and thermal fluctuations. 相似文献
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我国封闭式投资基金业绩评价实证研究 总被引:2,自引:1,他引:1
随着我国基金行业超常发展,恰当的分析和评价基金业绩已越来越重要。本文根据CAPM的基本原理,利用国外先进的基金业绩评价方法对我国封闭式基金的综合业绩进行实证研究。研究结果表明:总体来看,基金获得的市场超额收益显著为负。基金经理不具有证券选择能力,但具有一定的市场择时能力,但这两种能力均不显著。同时,我们还发现不同投资风格的基金经理具有不同的证券选择能力和市场择时能力。 相似文献
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利用曲面的局部微分性质给出二元函数极值存在的必要条件和充分条件,并将之运用于具有明显几何特征的曲面对应的二元函数极值的判别问题中. 相似文献
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基于维纳滤波反卷积的光声成像 总被引:2,自引:0,他引:2
为了提高光声成像(PAT)的对比度和分辨率,需对组织样品的光声(PA)信号进行基于探头脉冲响应的滤波反卷积以恢复其频谱特性.对宽带光声信号而言,由于带通滤波的截止频率由人为确定,噪声不能得到有效抑制,很难获得稳定的反卷积结果.针对此问题,提出了基于维纳滤波反卷积的光声成像方法,利用点光声源获得超声探头的脉冲响应.利用维纳滤波抑制反卷积过程中噪声的影响,滤波器参数由离散小波变换(DWT)动态估计,样品光声图像由时域后向投影算法重建.数值模拟与成像实验均表明该方法有效地抑制了噪声对反卷积的影响,提高了光声成像的对比度和分辨率. 相似文献
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本文在完备剩余格上引入了L-偏序集,给出了L-偏序集上L_k-素闭包算子和L_k-素内部算子的概念及其等价刻画,在此基础上推广得出了n重L_k-素闭包算子和n重L_k-素内部算子的概念及其等价刻画。 相似文献
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Mixing processes of hot and cold fluids in a tee with and without sintered copper spheres are simulated by FLUENT using the large-eddy simulation (LES) turbulent flow model and the sub-grid scale (SGS) Smagorinsky-Lilly (SL) model with buoyancy. Comparisons of numerical results of the two cases with and without sintered copper spheres show that the porous medium significantly reduces velocity and temperature fluctuations because the porous medium can effectively restrict the fluid flow and enhance heat transfer. The porous medium obviously increases the pressure drop in the main duct. The porous medium reduces the power spectrum density (PSD) of temperature fluctuations in the frequency range from 1 Hz to 10 Hz. 相似文献
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In this paper, we investigate the Galois connections between two partially ordered objects in an arbitrary elementary topos. Some characterizations of Galois adjunctions which is similar to the classical case are obtained by means of the diagram proof. This shows that the diagram method can be used to reconstruct the classical order theory in an arbitrary elementary topos. 相似文献