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Shenzhen, China

Liang X.,Shenzhen AE Design Co. | Wang Z.,Hefei University of Technology
Guti Lixue Xuebao/Acta Mechanica Solida Sinica | Year: 2013

This paper aims at investigating the surface nonlinear evolution behavior of strained heteroepitaxial films on wavy substrates. In this work, the phase field microelasticity model is used, which is based on the Eshelby's equivalency approach, to simulate the morphological instability of the two-dimensional strained Si1-x Gex/Si film/substrate system. The free energy functional with respect to the equivalent eigenstrain and the long-range order parameter is established and the two time-dependent Ginzburg-Landau kinetic equations are solved simultaneously. The system free energy comprises chemical energy, elastic strain energy and interfacial energy between film, substrate and vacuum phase. The morphological evolution process is tracked and the profile of the quantum dots is given at some specific time. The results indicate that the quantum dots are inclined to form at the trough of the wavy substrate which is an energy preferable site and thus a more stable site than the crest. The profile, size and site of the quantum dots can be predicted by the phase field modeling in this paper, which can provide a guideline for controlling and producing periodic self-assembly surface nanostructures. Source

Niu C.,Harbin Institute of Technology | Tan Y.,Harbin Institute of Technology | Fu J.,Shenzhen AE Design Co.
ICPTT 2013: Trenchless Technology - The Best Choice for Underground Pipeline Construction and Renewal, Proceedings of the International Conference on Pipelines and Trenchless Technology | Year: 2013

The major safety problem of in-service welding municipal gas pipelines is burn-through and hydrogen induced cracking. In this paper, a numerical model to analyze the thermodynamic characteristics (temperature field and allowable stress)during the welding process at different working conditions is established.. This model is then applied to a testing case: the leakage section of the Harbin-Yilan long distance transmission pipelines. In this case, the impact of working parameters during the welding process (pipe-wall casing thickness, welding energy input and velocity of the flow medium) on the temperature field and allowable stress is analyzed. The optimal working parameters to avoid burn through and hydrogen induced cracking are also derived. The testing case shows that the model developed in this paper is useful in providing technical support for online welding process, and therefore can be applied widely in practice. © ASCE 2013. Source

Yi W.,Hunan University | Wang W.,Shenzhen AE Design Co.
Tumu Gongcheng Xuebao/China Civil Engineering Journal | Year: 2012

Statistical analysis is applied to the vertical earthquake, and a comparison with the horizontal earthquake ground motion is made to indirectly reflect the characteristics of vertical earthquake. Based on the classification of fault distance, earthquake magnitude, site condition and focal mechanism of earthquakes, their effects on the ratio of peak ground acceleration are investigated. By analyzing the influence of fault distance on the ratio of acceleration response spectrum, it is found that the pseudo acceleration response spectrum value of vertical ground motion is greater than that of the horizontal ground motion in the near-fault zone and short-period segment, and moreover the spectrum value is much greater than the coefficient of 0.65 specified in seismic design code. To verify the feasibility of the analyzing method, the OpenSees program is used for the earthquake response analysis of a RC frame on the earthquake shake table. Based on the analysis of nonlinear dynamic responses of an eight-story RC frame structure, it is observed that under the combined action of vertical and horizontal earthquake, the ultimate bearing capacity of columns for the frame in near-fault region may be controlled by the tension-bending and tension-shear forces. Source

Wang Z.-M.,Hefei University of Technology | Liang X.-D.,Shenzhen AE Design Co. | Shen X.,Anhui Agricultural University
Gongcheng Lixue/Engineering Mechanics | Year: 2013

This paper studied the effect of electro-mechanical coupling on the surface instability of a three-dimensional elastic conductive body. By adopting the linear perturbation theory, the diffusion-mediated surface instability of the elastic solid subjected to a uniaxial uniform far-field stress in an electric field has been analyzed. The curve of the perburbation growth rate versus the disturbance wave number is plotted. The elastic strain energy, the surface energy and the electrostatic energy are considered in the analysis. The results indicate that the surface energy always stabilizes the solid surface, the elastic strain energy always promotes the instability and the electrostatic energy destabilizes the surface. The conditions for the onset of instability depend on the Poisson's ratio, the relative value of the electric field intensity and the pre-stress. The periodic nanostructures can be formed by the mechanical stress and the electric stress-controlled surface self-assembly which is desirable for making the template for nanoelectronic devices. Source

Wang W.L.,Shenzhen University | He Z.C.,Shenzhen AE Design Co. | Wang X.F.,Shenzhen University | Xing F.,Shenzhen University
Life-Cycle of Structural Systems: Design, Assessment, Maintenance and Management - Proceedings of the 4th International Symposium on Life-Cycle Civil Engineering, IALCCE 2014 | Year: 2015

This paper examined the impacts of environmental humidity, concrete properties, chloride ion concentration, cover thickness and other factors on half-cell potential measurement results. The paper then proposes a quantitative determination standard on the critical corrosion potential of concrete reinforcement in practical engineering inspection through electrochemical acceleration corrosion experiments on reinforced concrete specimens. Research results indicated that (1) the slope change of a low frequency curve in electrochemical impedance spectroscopy (EIS) reflected the development of steel bar corrosion in concrete. As the slope decreased to 0, the steel bar gradually reached critical corrosion, and the corresponding critical corrosion time followed the Gumbel distribution. (2) Under practical humidity conditions, the variation of concrete reinforcement corrosion potential correlated with concrete internal Cl- concentration using an e exponential function relationship. While the Cl- concentration was greater than 0.2%, the potential variation would not increase any more after reaching 55mV. (3) With changes of cover thickness, the critical corrosion potential of concrete reinforcement exhibited a linear variation at a gradient of -1.64mV/mm. © 2015 Taylor & Francis Group, London. Source

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