Chemical markers’ fishing and knockout for holistic activity and interaction evaluation of the components in herbal medicines

A strategy based on chemical markers’ fishing and knockout has been proposed for holistic activity and interaction evaluation of the bioactive components in herbal medicines (HMs). It was devised to screen bioactive-compound group that represents the efficacy of HM, estimate the bioactivity contribution of each component and elucidate the interactions of multi-components. This strategy was accomplished through the following steps: (1) screen out the chemical markers (target peaks) in a HM fingerprint using online two-dimensional turbulent flow chromatography/liquid chromatography–mass spectrometry technique, (2) fish target peaks and knockout any interested peak, and (3) evaluate the bioactivities of fishing and knockout portions. After comparison of the bioactivities of samples containing different target peaks, the efficacy of target-peak group, bioactivity contribution of each compound, and the interactions of multi-components are elucidated. Using Acetylcholinesterase (AChE) and Bulbs of Lycoris radiata (L. Herit.) Herb. (BLR) as the experimental materials, four target peaks were screened out as the AChE binders. By target peaks’ fishing and knockout, combined with activity evaluation, we observed that the bioactivity of the four-peak mixture is similar with the global bioactivity of BLR extract, and there are significant suppressive actions among these four target peaks. These results indicate that this proposed strategy is a useful approach for holistic screening of bioactive-compound group and elucidation of the multi-component interactions in HM.     

H_2/N_2湍射流抬升火焰的直接数值模拟

使用上海超算中心的并行计算机模拟了一个实验参数下的湍流射流抬升火焰。该实验的喷口直径为4.57 mm,实验雷诺数达到了23600。为了完成这个高雷诺数射流燃烧的直接数值模拟,共采用了1024个CPU,共计2.85亿网格。主要介绍了采用的直接数值模拟方法,实验的具体参数以及选取该实验作为模拟对象的原因。最后用直接数值模拟的结果具体分析该实验的着火机理。     

气膜冷却计算中湍流黏性系数的修正

燃气轮机高温叶片气膜冷却中的复杂涡系结构使得流动传热很难被准确预测.本文基于平板气膜冷却数值和实验研究结果,指出雷诺平均算法中常用的湍流模型在射流侧向输运和二次涡的捕捉上具有相当的局限性.文中对湍流黏性系数提出了各向异性对数率涡黏模型(ALEV模型)修正,基于ALEV模型修正后的湍流模型增强了射流的侧向输运,减弱了二次...     

Multigrid convergence acceleration for implicit and explicit solution of Euler equations on unstructured grids

The multigrid method is one of the most efficient techniques for convergence acceleration of iterative methods. In this method, a grid coarsening algorithm is required. Here, an agglomeration scheme is introduced, which is applicable in both cell‐center and cell‐vertex 2 and 3D discretizations. A new implicit formulation is presented, which results in better computation efficiency, when added to the multigrid scheme. A few simple procedures are also proposed and applied to provide even higher convergence acceleration. The Euler equations are solved on an unstructured grid around standard transonic configurations to validate the algorithm and to assess its superiority to conventional explicit agglomeration schemes. The scheme is applied to 2 and 3D test cases using both cell‐center and cell‐vertex discretizations. Copyright © 2009 John Wiley & Sons, Ltd.     

The Use of DNS to Define Stress Producing Events for Turbulent Flow over a Smooth Wall

Over the past 15 years direct numerical simulations (DNS) of turbulent flow and particle image velocimetry (PIV) have provided the opportunity to obtain information about a turbulent velocity field simultaneously at a large number of locations. This paper gives a personal viewpoint of how these techniques are providing new insights about the Reynolds stress producing structures in turbulence generated by flow over a smooth boundary. This revised version was published online in August 2006 with corrections to the Cover Date.     

An aspect ratio agglomeration multigrid for unstructured grids

A robust aspect ratio‐based agglomeration algorithm to generate high quality of coarse grids for unstructured and hybrid grids is proposed in this paper. The algorithm focuses on multigrid techniques for the numerical solution of Euler and Navier–Stokes equations, which conform to cell‐centered finite volume special discretization scheme, combines vertex‐based isotropic agglomeration and cell‐based directional agglomeration to yield large increases in convergence rates. Aspect ratio is used as fusing weight to capture the degree of cell convexity and give an indication of cell stretching. Agglomeration front queue is established to propagate inward from the boundaries, which stores isotropic vertex and also high‐stretched cell marked with different flag according to aspect ratio. We conduct the present method to solve Euler and Navier–Stokes equations on unstructured and hybrid grids and compare the results with single grid as well as MGridGen, which shows that the present method is efficient in reducing computational time for large‐scale system equations. Copyright © 2013 John Wiley & Sons, Ltd.     

A theory of plasticity for carbon nanotube reinforced composites

Carbon nanotubes (CNTs) possess exceptional mechanical properties, and when introduced into a metal matrix, it could significantly improve the elastic stiffness and plastic strength of the nanocomposite. But current processing techniques often lead to an agglomerated state for the CNTs, and the pristine CNT surface may not be able to fully transfer the load at the interface. These two conditions could have a significant impact on its strengthening capability. In this article we develop a two-scale micromechanical model to analyze the effect of CNT agglomeration and interface condition on the plastic strength of CNT/metal composites. The large scale involves the CNT-free matrix and the clustered CNT/matrix inclusions, and the small scale addresses the property of these clustered inclusions, each containing the randomly oriented, transversely isotropic CNTs and the matrix. In this development the concept of secant moduli and a field fluctuation technique have been adopted. The outcome is an explicit set of formulae that allows one to calculate the overall stress-strain relations of the CNT nanocomposite. It is shown that CNTs are indeed a very effective strengthening agent, but CNT agglomeration and imperfect interface condition can seriously reduce the effective stiffness and elastoplastic strength. The developed theory has also been applied to examine the size (diameter) effect of CNTs on the elastic and elastoplastic response of the composites, and it was found that, with a perfect interface contact, decreasing the CNT radius would enhance the overall stiffness and plastic strength, but with an imperfect interface the size effect is reversed. A comparison of the theory with some experiments on the CNT/Cu nanocomposite serves to verify the applicability of the theory, and it also points to the urgent need of eliminating all CNT agglomeration and improving the interface condition if the full potential of CNT reinforcement is to be realized.     

In situ AFM,XRD and Resistivity Studies of the Agglomeration of Sputtered Silver Nanolayers

In situ atomic force microscopy (AFM), X-ray diffraction (XRD) and resistivity studies have been made for RF cathode-sputtered silver nanolayers on different oxide surfaces during heating between room temperature and 400°C. Our earlier AFM and resistivity measurements revealed the agglomeration of layers during heating. The present in situ AFM, XRD and resistivity measurements show a sudden rapid agglomeration of the sputtered ultra-thin silver nanolayers during heating at specific temperatures, which depend on the layer thickness. When the AFM picturing was initiated from a layer surface at a temperature slightly below the specific agglomeration temperature of the layer, the AFM tip excited the surface starting the agglomeration in the area under picturing. This tip-assisted agglomeration phenomenon made it possible to restrict the area of agglomeration and to produce sub-micron structures in the silver nanolayer by AFM.     

小孔周期性泄流的实验与分析

通过对小孔泄流的周期性研究．发现泄流周期随着时间进程变化趋于增大，小孔的直径越大泄流周期越小,不相容的液体间不能形成小孔周期性泄流，并分析了有关现象．     

Numerical simulation of pollution and oil spill spreading by the stochastic discrete particle method

The features of the stochastic discrete particle method are discussed as applied to the simulation of pollutant advection and diffusion in a turbulent flow and to the spread of a thin film of a viscous substance (oil) on the surface of water. The diffusion tensor in the former problem depends on the scale of the pollution cloud, and the diffusivity in the latter problem depends nonlinearly on the desired function. For pollution dispersion by a turbulent flow, a stochastic discrete particle algorithm is constructed in the case when the diffusion tensor corresponds to the Richardson 4/3 law. The numerical and analytical results are shown to agree well. The problem of oil film spreading is described by a quasilinear advection-diffusion equation. For this problem, a random walking algorithm is constructed in which the variance of the walking particle step depends on the desired function. For both instantaneous and time-continuous sources of pollutants, the solution produced by the stochastic discrete particle method agrees well with the analytical and/or numerical solutions to the test problems under consideration.