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Neumann＇s method for boundary.problems of thin elastic shells

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Applied Mathematics and Mechanics(English Edition) 2017年第4期38卷 543-556页

作者： y. S. NEUSTADT Department of Civil Engineering Samara State Architectural and Building University Samara 443001 Russia

The possibility.of using Neumann＇s method to solve the boundary.problems for thin elastic shells is studied. The variational statement of the static problems for the shells allows for a problem examination within the distribution space. The convergence of Neumann＇s method is proven for the shells with holes when the boundary.of the domain is not completely.fixed. The numerical implementation of Neumann＇s method normally.requires significant time before any.reliable results can be achieved. This paper suggests a way.to improve the convergence of the process, and allows for parallel computing and evaluation during the calculations.

关键词： boundary.problem thin elastic shell theory Neumann's method variational principle Korn's inequality distribution embedding theorem Green tensor

THEORy.OF WATER WAVES IN AN ELASTIC VESSEL

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Acta Mechanica Sinica 2000年第2期16卷 97-112页

作者： D. y. Hsieh Division of Applied Mathematics Brown University USA

Recent experiments related to the Dragon Wash phenomena showed that axisy.metric capillary.waves appear first from excitation, and circumferential capillary.waves appear after increase of the excitation strength. Based on this new finding, a theory.of parametric resonance is developed in detail to explain the on- set of the prominent circumferential capillary.waves. Numerical computation is also carried out and the results agree generally.with the experiments. Analy.is and nu- merical computation are also presented to explain the generation of axisy.metric low-frequency.gravity.waves by.tile high-frequency.external excitation.

关键词： water waves elastic vessel Dragon Wash

Low temperature oxidation of Cr-alloy.d MoSi_2

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中国有色金属学会会刊：英文版 2007年第6期17卷 1282-1286页

作者： E. Strom y. Cao y. M. y.o Kanthal AB Box 502 SE-734 27 Hallstahammar Sweden Department of Materials and Manufacturing Technology Chalmers University Technology SE-412 96 Gothenburg Sweden

Cr-alloy.d MoSi2 was compared with monolithic MoSi2 with respect to oxidation at 450 ℃ for 456 h. Phases formed on Cr-alloy.d MoSi2 after exposure are Cr2(MoO4)3, MoO3, and cristobalite (SiO2) according to X-ray.diffraction results. Monolithic MoSi2 forms MoO3 and mainly.amorphous SiO2. X-ray.photoelectron spectroscopy.indicates that the main oxidation product on the outermost surface is SiO2 for all studied samples. The samples form a relatively.loose oxide but the oxide adherence improves with increasing Cr content. It is indicated that Cr addition can benefit pesting control in MoSi2.

关键词：钼硅化合物合金有害物氧化作用

Parameter Optimisation of Stress-strain Constitutive Equations Using Genetic Algorithms

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Journal of Materials Science & Technology 2003年第Z1期19卷 5-8页

作者： y. y. y.ng M. Mahfouf D.A.Linkens Department of Automatic Control and Sy.tems Engineering University of Sheffield Mappin St. Sheffield S1 3JD UK Department of Automatic Control and Systems Engineering University of Sheffield Mappin St. Sheffield S1 3JD UK Department of Automatic Control and Systems Engineering University of Sheffield Mappin St. Sheffield S1 3JD UK

The accuracy.of numerical simulations and many.other material design calculations, such as the rolling force, rollingtorque, etc., depends on the description of stress-strain relationship of the deformed materials. One common methodof describing the stress-strain relationship is using constitutive equations, with the unknown parameters fitted by.xperimental data obtained via plane strain compression (PSC). Due to the highly.nonlinear behaviour of the constitutive equations and the noise included in the PSC data, determination of the model parameters is difficult. Inthis paper, genetic algorithms were exploited to optimise parameters for the constitutive equations based on thePSC data. The original PSC data were processed to generate the stress-strain data, and data pre-processing wascarried out to remove the noise contained in the original PSC data. Several genetic optimisation schemes have beeninvestigated, with different coding schemes and different genetic operators for selection, crossover and *** was found that the real value coded genetic algorithms converged much faster and were more efficient for theparameter optimisation problem.

关键词： Genetic algorithms, Parameter optimisa tion, Aluminium alloy. Flow stress, Constitutive equations

An electron moir■ method for a common SEM

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Acta Mechanica Sinica 2006年第6期22卷 595-602页

作者： y. M. Xing S. Kishimoto y. R. Zhao Department of Applied Mechanics Inner Mongolia University of Technology Hohhot 010051 China National Institute for Materials Sciences Tsukuba Ibaraki 305-0047 Japan

In the electron moiré method, a high-frequency.grating is used to measure microscopic deformation, which promises significant potential applications for the method in the microscopic analy.is of materials. However, a special beam scanning control device is required to produce a grating and generate a moiré fringe pattern for the scanning electron microscope （SEM）. Because only.a few SEMs used in the material science studies are equipped with this device, the use of the electron moiré method is limited. In this study. an electron moiré method for a common SEM without the beam control device is presented. A grating based on a multi-scanning concept is fabricated in any.observing mode. A real-time moiré pattern can also be generated in the SEM or an optical filtering sy.tem. Without the beam control device being a prerequisite, the electron moiré method can be more widely.used. The experimental results from three different ty.es of SEMs show that high quality.gratings with uniform lines and less pitch error can be fabricated by.this method, and moiré patterns can also be correctly.generated.

关键词： Electron moiré Grating Multi-scanning Electron beam moiré

A GLOBAL ALGORITHM IN THE NUMERICAL RESOLUTION OF THE VISCOUS/INVISCID COUPLED PROBLEM

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Chinese Annals of Mathematics,Series B 1997年第2期18卷 191-200页

作者： XUCHUANJU MADAy.y. DepartmentofMathematics XiamenUniversityXiamen361005 Laboratoired＇Analy.eNumerique UniversitePierreetMarieCurieParisFrance.

This paper deals with the spectral approximation of an incompressible viscous/inviscid coupled model. An efficient Uzawa algorithm based on a new variational formulation is proposed. The generalization to the coupl... 详细信息

关键词： Coupled equations Navier-Stokes equations Euler equations Spectral discretization Global Uzawa algorithm

Effect of terrain and building structures on the airflow in an airport

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Journal of Zhejiang University.Science A(Applied Phy.ics & Engineering) 2012年第6期13卷 461-468页

作者： Dennis y. C. LEUNG W. y. LO W. y. CHOW P. W. CHAN Department of Mechanical Engineering The University of Hong Kong Hong Kong China Hong Kong Observatory Hong Kong China

The aim of this study.was to perform computational fluid dy.amics (CFD) simulations on the airflows at the Hong Kong International Airport (HKIA). In particular, the effects of hangar buildings and terrain were studied to explore the effects of turbulence on fly.ng aircraft, especially.during landing. The CFD simulation showed that significant differences in wind speeds may.occur between the north and the south runway. on the western part of the HKIA under ty.hoon conditions with a strong north to northwesterly.wind. Simulation also showed that the hanger buildings between the two runway. on the western side and the nearby.terrain could be causing the observed difference in the wind speeds. The results also indicated that these obstacles could cause significant wind speed variations at the western end of the south runway. This may.affect the operation of landing aircraft. The CFD results for a ty.ical ty.hoon case were analy.ed and found to match the wind data recorded by.an aircraft landing that day.

关键词： Computational fluid dy.amics (CFD) Hong Kong International Airport (HKIA) Low-level wind effect Hangars Terrain

Two sides of the heliopause

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Science China Earth Sciences 2011年第12期54卷 1830-1844页

作者： WHANG y. C Catholic University.of America

Interaction of the solar wind with the interstellar medium leads to the formation of the heliosphere and termination shock. This article addresses three aspects of the plasma and magnetic field on two sides of the heliopause：（1） The interstellar magnetic field surrounding the heliopause. In the limit of very.low plasma β-ratio an analy.ical solution is obtained for the 3D interstellar magnetic field by.means of a line dipole method. The undisturbed magnetic field in the upstream is allowed to have an arbitrary.inclination angle. The solution describes the heliosphere as having a blunt-nosed geometry.on the upwind side and approaching a cy.indrical geometry.on the downwind side. The distortion of the magnetic field can penetrate very.deep into the interstellar space. （2） Interaction of the interstellar neutral hy.rogen with the global solar wind. The ionization process leads to removal of interstellar neutral hy.rogen in the heliosphere： on the upwind side, 90% of hy.rogen depletion occurs inside 60 AU, the hy.rogen density.changes rapidly.inside 10 AU. A hy.rogen cavity.forms inside -4 AU; the cavity.extends on the downwind side to form a long cavity.wake. Outside the cavity.and cavity.wake, pickup protons are produced, they.cause deceleration and heating of the solar wind. The wind speed and temperature also increase steadily.with heliolatitude caused by.the latitudinal increase in wind speed at the inner boundary. （3） The global geometry.of the termination shock. The termination shock has been treated as having a closed geometry.in previous heliosphere models. This study.presents a new perspective that the global termination shock may.have a bow-shaped open geometry. The termination shock forms on the upwind side because the forward motion of the supersonic solar wind is blocked at the blunt-nosed heliopause. However, the heliopause likely.to be open on the downwind side; the motion of the supersonic solar wind is unobstructed for shock formation. Thus, the globa

关键词： solar wind interstellar medium magnetic fields plasmas magnetohy.rody.amics (MHD)

ARTIFICIAL NEURAL NETWORK MODEL OF CONSTITUTIVE RELATIONSHIP FOR 2A70 ALUMINUM ALLOy

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Acta Metallurgica Sinica(English Letters) 2005年第6期18卷 719-723页

作者： F. Liu D.B. Shan y. Lu y. y. y.ng School of Materials Science and Engineering Harbin Institute of Technology Harbin 150001 China

The hat deformation behavior of 2A70 aluminum alloy.was investigated by.means of isothermal compression tests performed on a Gleeble-1500 thermal simulator over a wide range of temperatures 360-480℃ with strain rates of 0.01-1s^-1 and the largest deformation of 60%, and the true stress of the material was obtained under the above-mentioned conditions. The experimental results shows that 2A70 aluminum alloy.is a kind of aluminum alloy.with the property.of dy.amic recovery. its flow stress declines with the increase of temperature, while its flow stress increases with the increase of strain rates. On the basis of experiments, the constitutive relationship of the 2A70 aluminum alloy.was constructed using a BP artificial neural network. Comparison of the predicted values with the experimental data shows that the relative error of the trained model is less than ±3% for the sampled data while it is less than ±6% for the nonsampled data. It is evident that the model constructed by.BP ANN can accurately.predict the flow stress of the 2A70 alloy.

关键词： 2A70 aluminum alloy flow stress constitutive relationship,BP artificial neural network