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Resistance and Reactance of Monopole Fields Induced by a Test charge Drifting Off-Axis in a cold and collisional cylindrical Plasma

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chinese Physics Letters 2018年第8期35卷 49-53页

作者： M.s.Bawa'aneh A.M.Al-Khateeb y.-c.Ghim Department of Physics Yarmouk University Department of Nuclear and Quantum Engineering KAIST

We study the interaction of a uniform, cold and collisional plasma with a test charged particle moving off-axis at a constant speed down a cylindrical tube with a resistive thick metallic wall. Upon matching the electromagnetic field components at all interfaces, the induced monopole electromagnetic fields in the plasma are obtained in the frequency domain. An expression for the plasma electric resistance and reactance is derived and analyzed numerically for some representative parameters. Near the plasma resonant frequency, the plasma resistance evolves with frequency like a parallel RLc resonator with peak resistance at the plasma frequency pe, while the plasma reactance can be capacitive or inductive in nature depending on the frequency under consideration.

关键词： In Resistance and Reactance of Monopole Fields Induced by a Test charge Drifting Off-Axis in a cold and collisional cylindrical Plasma

Dislocation self-interaction in TiAl:Evolution of super-dislocation dipoles revealed by atomistic simulations

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Journal of Materials science & Technology 2021年第10期69卷 138-147页

作者： Z.Zhen H.Wang c.y.Teng c.G.Bai D.s.Xu R.yang Institute of Metal Research Chinese Academy of SciencesShenyang 110016China school of Materials science and Engineering University of Science and Technology of China.Shenyang 110016China school of Materials science and Engineering University of Shanghai for Science and TechnologyShanghai 200093China Laboratory of Fundamental Research AVIC China Aero-Polytechnology EstablishmentBeijing 100028.China

As one of the fundamental outcomes of dislocation self-interaction,dislocation dipoles have an important influence on the plastic deformation of materials,especially on fatigue and *** this work,superdislocation dipoles inγ-TiAl andα_(2)-Ti_(3)Al were systematically investigated by atomistic simulations,with a variety of dipole heights,orientations and annealing tempe *** results indicate that non-screw super-dipoles transform into locally stable dipolar or reconstructed cores at low temperature,while into isolated or interconnected point defect clusters and stacking fault tetrahedra at high temperature via short-range diffu ***-screw super-dipoles inγ-TiAl andα_(2)-Ti_(3)Al exhibit similar features as fcc and hcp metals,***,over long-term annealing where diffusion is significant,60°superdipoles inγ-TiAl are stable,whereas the stability of super-dipoles inα2-Ti3 Al increases with dipole height and orientation *** influence on mechanical properties can be well evaluated by integrating these results into mesoscale or constitutive models.

关键词： TiAl Dislocation Dipole Mechanical property Atomistic simulation

Effects of building aspect ratio,diurnal heating scenario,and wind speed on reactive pollutant dispersion in urban street canyons

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Journal of Environmental sciences 2012年第12期24卷 2091-2103页

作者： Nelson y.O.Tong Dennis y.c.Leung Department of Mechanical Engineering The University of Hong Kong

A photochemistry coupled computational fluid dynamics （cFD） based numerical model has been developed to model the reactive pollutant dispersion within urban street canyons, particularly integrating the interrelationship among diurnal heating scenario （solar radiation affections in nighttime, daytime, and sun-rise/set）, wind speed, building aspect ratio （building-height-to-street-width）, and dispersion of reactive gases, specifically nitric oxide （NO）, nitrogen dioxide （NO2） and ozone （O3） such that a higher standard of air quality in metropolitan cities can be achieved. Validation has been done with both experimental and numerical results on flow and temperature fields in a street canyon with bottom heating, which justifies the accuracy of the current model. The model was applied to idealized street canyons of different aspect ratios from 0.5 to 8 with two different ambient wind speeds under different diurnal heating scenarios to estimate the influences of different aforementioned parameters on the chemical evolution of NO, NO2 and 03. Detailed analyses of vertical profiles of pollutant concentrations showed that different diurnal heating scenarios could substantially affect the reactive gases exchange between the street canyon and air aloft, followed by respective dispersion and reaction. Higher building aspect ratio and stronger ambient wind speed were revealed to be, in general, responsible for enhanced entrainment of 03 concentrations into the street canyons along windward walls under all diurnal heating scenarios. comparatively, particular attention can be paid on the windward wall heating and nighttime uniform surface heating scenarios.

关键词： photochemistry reactive pollutant dispersion building aspect ratio diurnal heating scenario wind speed urban streetcanyon

The effect of downstream resistance on flow diverter treatment of a cerebral aneurysm at a bifurcation: A joint computational-experimental study

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Journal of Hydrodynamics 2018年第5期30卷 803-814页

作者： ANDerson c.O.Tsang Billy y.s.yiu Abraham y.s.Tang W.c.chung Gilberto K.K.Leung AlexANDer K.K.Poon Alfred c.H.yu simon s.M.Lai K.W.chow Department of surgery Li Ka Shing Faculty of Medicine University of Hong Kong Department of Electrical and computer Engineering University of Waterloo Department of Mechanical Engineering University of Hong Kong Department of Electrical and Electronic Engineering University of Hong Kong

Intracranial aneurysm can lead to hemorrhagic stroke upon rupture. Deployment of flow diverters can restrict the blood flow into aneurysm and mitigate the rupture risk. computational fluid dynamics（cFD） and ultrasonography with pulse-wave and color Doppler ultrasound measurements were employed jointly to investigate the complex flow pattern in cerebral aneurysms, both before and after the deployment of flow diverters. Patient-specific configurations of both bifurcation and side-wall aneurysms were selected. The effect of downstream flow resistance was investigated by adjusting the volume flow rate and pressure at the outlet vessels computationally and experimentally. Velocity profiles in the aneurysm measured from ultrasonography showed good agreement with those from computer simulations. The discrepancy in velocity between the computational and experimental sets of data is less than 10%. The downstream resistance can alter the volume flux into a bifurcation aneurysm with a flow diverter deployed by 236%, while the corresponding value of a side-wall aneurysm is negligible. The vorticity of the aneurysmal flow was reduced by more than 80% in both cases after stenting. This study demonstrated that careful investigation of downstream flow resistance of a bifurcation aneurysm is essential to provide an accurate assessment of the aneurysmal flow dynamics after flow diverter deployment.

关键词： Intracranial aneurysms computational fluid dynamics (cFD) doppler ultrasound

A NEURAL NETWORK FOR WELD PENETRATION cONTROL IN GAs TUNGsTEN ARc WELDING

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Acta Metallurgica sinica(English Letters) 2006年第1期19卷 27-33页

作者： c.s. Wu J. Q. Gao y.H. Zhao Institute of Materials Joining Shandong University Jinan 250061 China

Realizing of weld penetration control in gas tungsten arc welding requires establishment of a model describing the relationship between the front-side geometrical parameters of weld pool and the back-side weld width with sufficient accuracy. A neural network model is developed to attain this aim. Welding experiments are conducted to obtain the training data set （including 973 groups of geometrical parameters of the weld pool and back-side weld width） and the verifying data set （108 groups）. Two data sets are used for training and verifying the neural network, respectively. The testing results show that the model has sufficient accuracy and can meet the requirements of weld penetration control.

关键词： neural network weld penetration control back-side weld width,gas tungsten arc welding

Effect of radiative loss mechanisms on FIR thermometric parameters of Nd^(3+)-doped lithium tellurite glasses

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Journal of Rare Earths 2024年第7期42卷 1250-1257,I0002页

作者： c.y.Morassuti A.P.L silva L.A.O.Nunes s.M.Lima L.H.c.Andrade Optical and Photothermal spectroscopy Group(GEOF) Center for Studies in Natural Resources(CERNA)State University of Mato Grosso do Sul(UEMS)C.P.351DouradosMSBrazil Renato Archer Information Technology center Dom Pedro I Highway(SP-65)Km 1436-Chácaras Campos dos AmaraisCampinasSPBrazil Institute of Physics of são carlos University of São PauloSão CarlosSPBrazil

Nd^(3+)-doped tellurite glasses are promising materials for thermometers based on the fluorescence intensity ratio(FIR)***,at high Nd^(3+)concentrations,energy transfer(ET)processes such as optical reabsorption and cross-relaxation can affect the Nd^(3+)emission,which has been little explored in the ***,the present work investigated the use of Nd^(3+)-doped tellurite glass(samples doped with Nd^(3+)at 0.2 mol%,0.5 mol%,2.0 mol%,and 4.0 mol%)in fluorescence thermometers,in the temperature range from 299 to 371 *** results indicate a strong dependence of the FIR parameters on the Nd^(3+)concentration,due to changes in the emission band profiles caused by optical reabsorption of the Nd^(3+)emissions and cross-relaxation processes.A decrease of the relative sensitivity of the ratio^(4)F_(5/2)→^(4)I_(9/2)/^(4)F_(3/2)→^(4)I_(9/2)is observed for samples doped with higher amounts of Nd^(3+).The maximum relative sensitivity at 299 K is 3.00%/K,which is the highest value among the reported Nd^(3+)ions.

关键词： Nd^(3+)-doped tellurite glass Fluorescence intensity ratio Optical thermometry Judd-Ofelt Rare earths

INVEsTIGATION ON THE DENsITy UNIFORMITy OF PREssED PARTs By LOW-VOLTAGE ELEcTROMAGNETIc cOMPAcTION

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Acta Metallurgica sinica(English Letters) 2004年第6期17卷 805-811页

作者： s.y.Huang Z.H.Meng y.c.Li B.Zhang W.Ouyang HarbinInstituteofTechnology Harbin150001China／／WuhanUniversityofTechnologyWuhan430070China WuhanUniversityofTechnology Wuhan430070China

Powder metallurgy is an efficient approach to fabricate varieties of high performance structure materials, function materials and special materials working under limited conditions. Research and development of new efficient technology to form high-density, high-performance and net shape parts is a key to widen application and development of powder materials. Recently, the low-voltage electromagnetic compaction (EMc) has been used by present authors to compacted copper, tin, aluminum powders and the products with 99% relative density have been acquired. In this work, the research has been extended to investigation on the density uniformity of pressed parts. The analysis results show that the density of the part compacted by low-voltage EMc decreases gradually in press direction as static compaction. But it is higher and more homogeneous. The density of the top part increases gradually from the center to the outer, which is just reversal of the bottom part. In some extent, the higher the discharging voltage is, the higher the density is and the more homogeneous the distribution is. In addition, repetitive compaction can improve the density of powder parts and the distribution uniformity.

关键词： powder low-voltage electromagnetic compaction density uniformity density distribution

sIMULATION OF TEMPERATURE AND THERMAL sTREss FIELD IN LAsER MILLING PROcEssING

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Acta Metallurgica sinica(English Letters) 2004年第1期17卷 43-46页

作者： G.F.yuan c.s.Ge X.y.Zeng state Key Laboratory of Laser Technology.Huazhong University of science and Technology Wuhan 430074China Anhui Institute of Architecture and IndustryHefei 230022 ChinaAnhui Institute of Architecture and IndustryHefei 230022 ChinaState Key Laboratory of Laser Technology Huazhong University of Science and Technology Wuhan 430074 China

The physical model of temperature field and thermal stress field are established in this paper, on which the numerical simulation with the assuming physical and laser milling parameters have been finished. The laser m... 详细信息

关键词： laser milling temperature field thermal stress field simulation

The Recursive Formulation of Particular solutions for some Elliptic PDEs with Polynomial source Functions

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communications in computational Physics 2009年第5期5卷 942-958页

作者： J.Ding H.y.Tian c.s.chen Department of Mathematics University of Southern MississippiHattiesburgMS 39406USA

In this paper we develop an efficient meshless method for solving inhomogeneous elliptic partial differential *** first approximate the source function by chebyshev *** then focus on how to find a polynomial particular solution when the source function is a *** the principle of the method of undetermined coefficients and a proper arrangement of the terms for the polynomial particular solution to be determined,the coefficients of the particular solution satisfy a triangular system of linear algebraic *** recursive formulas for the coefficients of the particular solutions are derived for different types of elliptic *** method is further incorporated into the method of fundamental solutions for solving inhomogeneous elliptic *** results show that our approach is efficient and accurate.

关键词： The method of fundamental solutions particular solution Helmholtz equation chebyshev polynomial Laplace-Helmholtz equation convection-reaction equation