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Analytical solutions for the interfacial viscous capillary-gravity waves due to an oscillating Stokeslet

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Journal of Hydrodynamics 2019年第6期31卷 1139-1147页

作者： dong-qiang Lu Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai UniversityShanghai 200072China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai 200072China

The fundamental solutions of the Stokes/Oseen equations due to a point force in an unbounded viscous fluid are referred to as the Stokeslet/Oseenlet,for which a systematic derivation are analytically presented here in terms of a uniform *** means of integral transforms,the closed-form solutions are explicitly deduced in a formula which involves the Hamiltonian,Hessian,and Laplacian operators,and elementary ***,interfacial viscous capillary-gravity waves between two semi-infinite fluids due to oscillating singularities,including a simple source in the upper inviscid fluid and a Stokeslet in the low viscous fluid,were analytically studied by the Laplace-Fourier integral transform and asymptotic *** dynamics responses consist of the transient and steady-state components,which are dealt with by the method of stationary phase and the Cauchy residue theorem,*** transient response is made up of one short capillarity・dominated and one long gravity-dominated wave with the former riding on the *** steady-state wave has the same frequency as that of oscillating *** solutions for the wave profiles and the exact solution for the wave number are analytically derived,which show the combined effects of fluid viscosity,surface capillarity and an upper layer fluid.

关键词： Interfacial wave surface tension viscosity Stokeslet asymptotic solution singularity method

Effects of oceanic ice cover and density stratification on the propagation of hydroacoustic waves

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Journal of Hydrodynamics 2022年第6期34卷 1151-1155页

作者： Ya-dong Liu dong-qiang Lu Ming-song Zou Shanghai Institute of Applied Mathematics and Mechanics School of Mechanics and Engineering ScienceShanghai UniversityShanghai200072China China Ship Scientific Research Center Wuxi214082China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai200072China

The propagation characteristic of hydroacoustic waves is studied for an ideal compressible two-layer fluid with different densities covered by an elastic ice *** conditions are simplified by adopting linear assumption and then the dispersion relation is *** analysis and visualization of the dispersion relation present the introduction of compressibility leads to the appearance of hydroacoustic wave modes while the density stratification leads to the appearance of interfacial wave *** ice thickness and the density ratio of the two fluid layers increase the wave number and group speed of hydroacoustic waves at the same frequency while the phase speed decreases.

关键词： Ocean ice sheet density stratified fluid hydroacoustic propagation

Ceramic membrane separation technique for washing nano-sized ceramic powder precursors

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Particuology 2011年第5期9卷 492-496页

作者： qiang dong Xingqin Liu Tianshu Zhang Department of Chemistry ＆ Materials Engineering. Hefei University Hefei 230022 China USTC Lab for Solid State Chemistry and Inorganic Membranes Department of Materials Science ＆ Engineering University of Science ＆ Technology of China Hefei 230026 China School of Materials Science and Engineering The University of New South Wales Sydney NSW2052 Australia

Washing using ceramic micro-filtration membranes was studied in the preparation of nano-sized TiO2 and A1203 powder precursors obtained by wet chemical methods. The key parameters for the washing process, such as operation pressure, cross-flow velocity, and slurry concentration, were examined and optimized. The shape and size of particles influenced the structure of the filter cake, leading to different permeation flux for different systems. The results demonstrated that washing using ceramic membranes is superior to the traditional plate-and-frame filtration and could be considered an advanced technique for ultra-fine powder preparation by wet-chemical method.

关键词： Nano-sized ceramic powder Wet-chemical method Ceramic membrane Washing Filtration

Waves propagating over a two-layer porous barrier on a seabed

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Journal of Hydrodynamics 2018年第3期30卷 453-462页

作者： qiang Lin Qing-rui Meng dong-qiang Lu China Ship Scientific Research Center Wuxi 214082China Shanghai Oriental Maritime Engineering Technology Company Limited Shanghai 200011China Shanghai Institute of Applied Mathematics and Mechanics Shanghai UniversityShanghai 200072China Shanghai Key Laboratory of Mechanics in Energy Engineering Shanghai 200072China

A research of wave propagation over a two-layer porous barrier, each layer of which is with different values of porosity and friction, is conducted with a theoretical model in the frame of linear potential flow theory. The model is more appropriate when the seabed consists of two different properties, such as rocks and breakwaters. It is assumed that the fluid is inviscid and incompressible and the motion is irrotational. The wave numbers in the porous region are complex ones, which are related to the decaying and propagating behaviors of wave modes. With the aid of the eigenfunction expansions, a new inner product of the eigenfunctions in the two-layer porous region is proposed to simplify the calculation. The eigenfunctions, under this new definition, possess the orthogonality from which the expansion coefficients can be easily deduced. Selecting the optimum truncation of the series, we derive a closed system of simultaneous linear equations for the same number of the unknown reflection and transmission coefficients. The effects of several physical parameters, including the porosity, friction, width, and depth of the porous barrier, on the dispersion relation, reflection and transmission coefficients are discussed in detail through the graphical representations of the solutions. It is concluded that these parameters have certain impacts on the reflection and transmission energy.

关键词： Two-layer porous barrier inner product matched eigenfunction expansions

Conductive Au nanowires regulated by silk fibroin nanofibers

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Frontiers of Materials Science 2014年第1期8卷 102-105页

作者： Bo-Ju dong qiang LU National Engineering Laboratory for Modern Silk College of Textile and Clothing Engineering Soochow University Suzhou 215123 China

Conductive Au-biopolymer composites have promising applications in tissue engineering such as nerve tissue regeneration. In this study, silk fibroin nanofibers were formed in aqueous solution by regulating silk self-assembly process and then used as template for Au nanowire fabrication. We performed the synthesis of Au seeds by repeating the seeding cycles for several times in order to increase the density of Au seeds on the nanofibers. After electroless plating, densely decorated Au seeds grew into irregularly shaped particles following silk nanofiber to fill the gaps between particles and finally form uniform continuous nanowires. The conductive property of the Au-silk fibroin nanowires was studied with current-voltage （I-V） measurement. A typical ohmic behavior was observed, which highlighted their potential applications in nerve tissue regeneration.

关键词： silk Au nanowire electrical conductivity biological device

Treadmill training improves neurological deficits and suppresses neuronal apoptosis in cerebral ischemic stroke rats

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Neural Regeneration Research 2019年第8期14卷 1387-1393页

作者： Li-Mei Cao Zhi-qiang dong qiang Li Xu Chen Department of Neurology Shanghai No.8 People’s Hospital

RehabilNation training is believed to be beneficial to patients with stroke, but its molecular mechanism is still unclear. Rat models of cerebral ischemic stroke were established by middle cerebral artery occlusion/reperfusion, and then received treadmill training of different intens让ies, twice a day for 30 minutes for 1 week. Low-intensity training was conducted at 5 m/min, with a 10-minute running, 10-minute rest, and 10-minute running cycle. In the moderate-intensity training, the intensity gradually increased from 5 m/min to 10 m/min in 5 minutes, with the same rest cycle as above. In high-intensity training, the intensity gradually increased from 5 m/min to 25 m/min in 5 minutes, with the same rest cycle as above. The Bederson scale was used to evaluate the improvement of motor function. Infarct volume was detected using 2,3,5-triphenyltetrazolium chloride staining. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining was applied to detect the apoptosis of nerve cells in brain tissue. Western blot assay was employed to analyze the activation of cyclic adenosine monophosphate (cAMP)/protein kinase A and Akt/glycogen synthase kinase-3卩 signaling pathways in rat brain tissue. All training intensities reduced the neurological deficit score, infarct volume, and apoptosis in nerve cells in brain tissue of stroke rats. Training intensities activated the cAMP/protein kinase A and Akt/glycogen synthase kinase-3 beta signaling pathways. This activation was more obvious with higher training intensities. These changes were reversed by intracerebroventricular injection of protein kinase A inhibitor Rp-cAMP. Our findings indicate that the neuroprotective effect of rehabilitation training is achieved via activation of the cAMP/ protein kinase A and Akt/glycogen synthase kinase-3 beta signaling pathways. This study was approved by the Ethics Committee of Animal Experimentation in Shanghai No. 8 Peoples Hospital, China.

关键词： nerve regeneration ischemic stroke treadmill training neuronal deficit apoptosis cyclic adenosine monophosphate protein kinase A glycogen synthase kinase-3^ neuroprotective effect neural regeneration

UNSTEADY INTERFACIAL WAVES DUE TO SINGULARITIES IN TWO SEMI-INFINITE INVISCID FLUIDS

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Journal of Hydrodynamics 2005年第6期17卷 730-736页

作者： LU dong-qiang WEI Gang YOU Yun-xiang The State Key Laboratory of Ocean Engineering Shanghai Jiaotong University Shanghai 200030 China Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China School of Naval Architecture Ocean and Civil Engineering Shanghai Jiaotong University Shanghai200030 China

The generation of unsteady interfacial gravity waves by a singularity immersed in two semi-infinite fluids was analytically investigated in detail by the methods of integral transform and of stationary-phase analysis. The fluids were assumed to be initially stationary, immiscible, inviscid and incompressible. The disturbed flows, generated by an impulsive and oscillatory source/dipole immersed above or be neath the interface, were governed by the *** equations. The kinematic and dynamic boundary conditions on the interface were linearized for the small-amplitude waves. By means of the stationary phase analysis on the exact integral form solutions, the asymptotic representations for the interracial waves were derived for large time with a fixed distance to time ratio. The relation between a submerged singularity and a sur face pressure point was discussed. It is found that the local wavelength and the local wave period of the interracial waves are elongated in comparison with those of free-surface waves for a single fluid.

关键词： interfacial waves singularity two-fluid system asymptotic representation

SURFACE AND INTERFACIAL GRAVITY WAVES INDUCED BY AN IMPULSIVE DISTURBANCE IN A TWO-LAYER INVISCID FLUID

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Journal of Hydrodynamics 2009年第1期21卷 26-33页

作者： LU dong-qiang CHEN Ting-ting Shanghai Institute of Applied Mathematics and Mechanics Shanghai University Shanghai 200072 China

The transient gravity waves due to an impulsive source in a two-layer fluid system are investigated analytically. The fluid is assumed to be inviscid and incompressible. The density of each of the two layers is constant. Five different boundary conditions are considered. The depth of each of the two layers is infinite or finite. The upper fluid of finite depth is covered by a rigid lid or a free surface. Based on the assumption of small-amplitude waves, a linear system is established. The integral solutions for the free-surface and interfacial waves are obtained by means of the Fourier-Laplace transform. The corresponding asymptotic representations are derived for large time with a fixed distance-to-time ratio by the Stokes and Scorer methods of stationary phase. The analytical solutions show that there are two different modes, namely the free-surface and interracial wave modes. The wave profiles observed depend on the relation between the distance-to-time ratio and the maximal group velocities and on the limiting values of the second derivatives of the frequencies as well.

关键词： impulsive disturbances imerfacial waves free surface waves stationary-phase methods

Comparison of two bedside evaluation methods of dysphagia in patients with acute stroke

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Stroke & Vascular Neurology 2018年第4期3卷 237-244页

作者： Ting Ye Shengyan Huang Yi dong qiang dong Neurology Unit Huashan HospitalFudan UniversityShanghaiChina State Key Laboratory of Medical Neurobiology Fudan UniversityShanghaiShanghaiChina

Background Dysphagia is a common complication after *** swallowing test(WST)is a recognised but limited tool in providing details about dysphagia,including severity and how to adjust the diet based on the test *** We performed a prospective observational study of comparing WST and volume-viscosity swallow test(V-VST)in patients with acute stroke within 14 *** patients had WST and if failed would have a *** primary outcome was to compare the dysphagia levels assessed by these two test *** secondary outcome was to explore the predictive capability in patients who were at high risk of pneumonia by these two swallowing *** Consecutively 276 patients with stroke were enrolled in our study,and 197 had normal *** 79 patients who had both WST and V-VST,20 showed swallowing safety and effectiveness by *** chance of being on tube feeding was strongly related to the positive results of failed WST(p<0.001).Both tests showed good predictive ability in patients with stroke for pneumonia even some of them were placed on tube feeding(p=0.001 in WST and p<0.001 in V-VST).Conclusions V-VST performed better as a clinical screening test for dysphagia in patients with acute stroke at the *** registration number ChiCTR1800016442.

关键词： patients details viscosity