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21.
In this work we extend the method of the constrained large-eddy simulation(CLES) to simulate the turbulent flow over inhomogeneous rough walls. In the original concept of CLES, the subgrid-scale(SGS) stress is constrained so that the mean part and the fluctuation part of the SGS stress can be modelled separately to improve the accuracy of the simulation result. Here in the simulation of the rough-wall flows, we propose to interpret the extra stress terms in the CLES formulation as the roughness-induced stress so that the roughness inhomogeneity can be incorporated by modifying the formulation of the constrained SGS stress. This is examined with the simulations of the channel flow with the spanwise alternating high/low roughness strips. Then the CLES method is employed to investigate the temporal response of the turbulence to the change of the wall condition from rough to smooth. We demonstrate that the temporal development of the internal boundary layer is just similar to that in a spatial rough-tosmooth transition process, and the spanwise roughness inhomogeneity has little impact on the transition process. 相似文献
22.
本文报道了经过对我国四株常用的酒精发酵菌株,K氏酵母(Saccharomyces cere-visiae Haasen var. ellipsoideus(Hansea)Dekk)、1038(Saccharomyces cerevi-siae Haasen)、Rasse j(Saccharomyces cerevisiae Hsanen)、Rasse皿(Sac-charomyces cerevisiae Hansen)的发酵效率和耐热性能等生理特性的分析比较,发现虽然1038的耐热性能比其它三个菌株强(42℃时发酵效率为77.16劣),但鉴于它发酵效率下降幅度远大于K氏酵母(在40℃发酵效率下降13,53劣,而K氏酵母下降9.21男一,据此,从既具一定的耐热性,又具较高的产酒率这点出发,拟尽 K氏酵母菌株作为选育耐高温产酒酵母的出发菌株. 相似文献
23.
本文在文[1],[2]的基础上,进一步讨论了算子超等距膨胀的性质,证明了T∈L(H)可超等距膨胀的充分必要条件是T≌P_H M|_H,或者T≌∑■ P_H M|_H这里M是Bergman位移,H∈LatM~*。 相似文献
24.
Hydrogen is the most abundant chemical element in the Universe and is tightly related to human life. This article personifies hydrogen, bringing a close interaction between the hydrogen on the moon and the hydrogen on the Earth. Through lively and interesting dialogues, the history of hydrogen discovery and the properties are introduced, and the application of hydrogen in different aspects of the future is prospected. 相似文献
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Minghui Qi Shiyi Zhao Bin Zhou Min Zhang Hongyang Zhang Yuerong Wang Ping Hu 《Journal of separation science》2019,42(23):3503-3511
Forsythiaside A is the major component of Forsythia suspensa. This study investigated the degradation mechanism of forsythiaside A. Eight degraded components including forsythiaside I, forsythiaside H, forsythiaside E, caffeic acid, suspensaside A, β‐hydroxy forsythiaside I, β‐hydroxy forsythiaside H, and β‐hydroxy forsythiaside A were identified by using ultra‐high performance liquid chromatography quadrupole time‐of‐flight mass spectrometry. Then, the quantitative analysis of multi‐components by a single‐marker was performed with ultra‐high performance liquid chromatography to simultaneously determine forsythiaside A, forsythiaside H, and forsythiaside I in Forsythia suspensa preparations. The result showed good linear relationships within 2.871–287.1, 0.231–23.1, and 0.983–98.3 μg/mL (r > 0.9998), with average recoveries of 97.7, 95.7, and 95.8% and relative standard deviations of 1.4, 2.4, and 1.8%, respectively. Using forsythiaside A as an internal reference, the relative retention values of forsythiaside H and forsythiaside I to forsythiaside A were calculated to be 0.89 and 0.61, respectively, and the relative correction factors were 0.816 and 0.799, respectively. The method for quantitative analysis of multi‐components by a single‐marker was applied to evaluate the overall quality of forsythia preparations. There was no significant difference in the measurement results of the method developed and the method of external standard. 相似文献
27.
An acid-mediated multicomponent reaction has been developed for the direct synthesis of multifused 1,3-benzoxazine derivatives from simple and readily available arylglyoxal monohydrates and 2-aminobenzyl alcohols under mild conditions. This novel protocol is proposed to proceed through intramolecular poly-heterocyclizations, thus leading to the formation of three new rings and six new chemical bonds, including four CN and two CO bonds. 相似文献
28.
Shiyi Wei Prof. Fei Wu Dr. Jing Liu Dr. Wenliang Ji Dr. Xiulan He Ran Liu Prof. Ping Yu Prof. Lanqun Mao 《Angewandte Chemie (International ed. in English)》2023,62(52):e202315681
Nanoplastics are recently recognized as neurotoxic factors for the nervous systems. However, whether and how they affect vesicle chemistry (i.e., vesicular catecholamine content and exocytosis) remains unclear. This study offers the first direct evidence for the nanoplastics-induced neurotoxicity by single-vesicle electrochemistry. We observe the cellular uptake of polystyrene (PS) nanoplastics into model neuronal cells and mouse primary neurons, leading to cell viability loss depending on nanoplastics exposure time and concentration. By using single-vesicle electrochemistry, we find the reductions in the vesicular catecholamine content, the frequency of stimulated exocytotic spikes, the neurotransmitter release amount of single exocytotic event, and the membrane-vesicle fusion pore opening-closing speed. Mechanistic investigations suggest that PS nanoplastics can cause disruption of filamentous actin (F-actin) assemblies at cytomembrane zones and change the kinetic patterns of vesicle exocytosis. Our finding shapes the first quantitative picture of neurotoxicity induced by high-concentration nanoplastics exposure at a single-cell level. 相似文献
29.
This paper deals with a novel visualized attributive analysis approach for characterization and quantification of rice taste flavor attributes (softness, stickiness, sweetness and aroma) employing a multifrequency large-amplitude pulse voltammetric electronic tongue. Data preprocessing methods including Principal Component Analysis (PCA) and Fast Fourier Transform (FFT) were provided. An attribute characterization graph was represented for visualization of the interactive response in which each attribute responded by specific electrodes and frequencies. The model was trained using signal data from electronic tongue and attribute scores from artificial evaluation. The correlation coefficients for all attributes were over 0.9, resulting in good predictive ability of attributive analysis model preprocessed by FFT. This approach extracted more effective information about linear relationship between electronic tongue and taste flavor attribute. Results indicated that this approach can accurately quantify taste flavor attributes, and can be an efficient tool for data processing in a voltammetric electronic tongue system. 相似文献
30.