Papers by Keyword: Anisotropic

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Authors: Yu Zhou Sun, Dong Xia Li, Hui Wang
Abstract: This paper presents a boundary element-free computational method for the fracture analysis of 2-D anisotropic bodies. The study starts from a derived traction boundary integral equation (BIE) in which the boundary conditions of both upper and lower crack surfaces are incorporated into and only the Cauchy singular kernal is involved. The boundary element-free method is achieved by combining this new BIE and the moving least-squares (MLS) approximation. The new BIE introduces two new variables: the displace density and The dislocation density. For each crack, the dislocation density is first expressed as the product of the characteristic term and unknown weight function, and the unknown weight function is approximated with the MLS approximation. The stress intensity factors (SIFs) can be calculated from the the weight function. The examples of the straight and circular-arc cracks are computed, and the convergence and efficiency are discussed.
Authors: Huai Ning Ruan, Man Lu Luo, Di Wang, J. W. Ju
Abstract: A failure criterion is proposed for complex rocks and soils. Their anisotropic and nonlinear behavior is analyzed theoretically and experimentally. The influence of the intermediate principal stress is taken into account. The nonhomogeneous strength and the effect of geological temperature are also discussed. Many classical failure criteria are special cases of the proposed condition. The criterion is applied in the analysis of the bedrock of Ankang Dam in China. The case study illustrates the potential of the proposed general model in engineering application.
Authors: Xiang Li, Yue Shun He, Xuan Zhan, Feng Yu Liu
Abstract: Direction transform; image fusion; infrared images; fusion rule; anisotropic Abstract Based on analysing the feature of infrared and the visible, this paper proposed an improved algorithm using Directionlet transform.The feature is like this: firstly, separate the color visible images to get the component images, and then make anisotropic decomposition for component images and inrared images, after analysing these images, process them according to regional energy rules ,finally incorporate the intense color to get the fused image. The simulation results shows that,this algorithm can effectively fuse infrared and the visible image, moreover, not only the fused images can maintain the environment details, but also underline the edge features, which applies to fusion with strong edges, therefore,this algorithm is of robust and convenient.
Authors: Shun Yu Su, Jian Chen
Abstract: Heat conduction in anisotropic materials is quite different from that in isotropic materials. Heat flux vector is commonly not perpendicular to the isothermal surface in anisotropic materials. The advantage and disadvantage of anisotropic materials were analyzed in this paper. The thermal conductivities at one point are not equal in all directions for anisotropic materials. The technique of double skin facade has been successfully applied in many building designs. The application of combining building envelope of anisotropic materials and double skin facade was proposed to avoid its disadvantage. Basing on the combination of anisotropic materials and double skin facade in building envelope, the indoor cooling and heating load decrease in summer and winter respectively. Especially in summer, the effect of energy saving is obvious since the partial magnitude of conductive heat in the envelope made of anisotropic materials could be brought out from the cavity of double skin facade by natural or forced ventilation through it.
Authors: Jian Jun Song, Shuai Lei, He Ming Zhang, Hui Yong Hu
Abstract: Applying KP theory combined with deformation potential we obtained the valence band structure, and based on this result we calculated the orientation-dependent effective mass which is also called conductivity effective mass in strained Si1-xGex/(001)Si in this research, and furthermore ,we established the scattering rate model by using the density-of-states effective mass. On the basis of conductivity effective mass and scattering rate model, utilizing analytical method and relaxation time approximation we obtained the dependence of the value of hole mobility on stress and doping concentration in strained Si1-xGex/(001)Si along different crystal orientations. Compare to the unstrained Si, the anisotropy of hole mobility is more obvious in strained Si1-xGex/(001)Si, for example, It shows that under the same stress and doping concentration (Ni=1x1014cm-3, x=0.4), the value of hole mobility along [010] crystal orientation is visibly higher than other crystal orientations. This result can provide valuable references to the research of hole mobility of strained Si1-xGex materials and the design of devices.
Authors: Carlos Morón, Alfonso Garcia, Enrique Tremps, Jose Andrés Somolinos
Abstract: Related with the detection of weak magnetic fields, the anisotropic magnetoresistive (AMR) effect is widely utilized in sensor applications. Exchange coupling between an antiferromagnet (AF) and the ferromagnet (FM) has been known as a significant parameter in the field sensitivity of magnetoresistance because of pinning effects on magnetic domain in FM layer by the bias field in AF. In this work we have studied the thermal evolution of the magnetization reversal processes in nanocrystalline exchange biased Ni80Fe20/Ni-O bilayers with large training effects and we report the anisotropic magnetoresistance ratio arising from field orientation in the bilayer.
Authors: Xu Ping Qin, Fang Zhao, Sheng Yu Feng
Abstract: Anisotropic hydrogels based on acrylamide were prepared by frontal photopolymerization. First hydrophilic microgels (HM) were spreparaed by inverse emulsion photopolymerization, and secondly hydrophilic reactive microgels (HRM) with C=C double bonds were synthesis by chemical modification of the HM used N-methylolacrylamide, Last, HRM hydrogels were synthesis by frontal photopolymerization using HRM as crosslinkers. Only one direction of the HRM hydrogels show excellent fracture strength and tensile elongation but the other two directions show little fracture strength and tensile elongation. The reason of the high mechanical performance in the given direction is that the hydrogels are crosslinked by HRM as a new crosslinking agent instead of the conventional crosslinking agents and these nanoparticles can self-assemble into anisotropic structures and the structure can be stabilized by free radical polymerization. The anisotropic hydrogels could use potential materials such as artificial muscles tissue.
Authors: M. Kitayama
Abstract: A model for anisotropic Ostwald ripening was developed using a chemical potential (weighted mean curvature) difference as a driving force for mass-transport. Based on this model, grain growth simulations of silicon nitride during the phase transformation and Ostwald ripening were performed. Comparison with experimental results during the phase transformation suggests that grain growth be controlled by interfacial reaction. Simulations of Ostwald ripening predict that the growth exponent be 3 for the reaction-controlled case, and increases up to 5 as the growth kinetics shifts from reaction-controlled to diffusion-controlled. It was reported that the mean aspect ratio of silicon nitride crystals increased during the phase transformation, and decreased during Ostwald ripening. These behaviors were successfully simulated by this model. The concave depression at the tip of silicon nitride crystal that was experimentally observed. Simulations by the Ostwald ripening model demonstrated that it could be developed when the liquid phase was super-saturated, and further that the tip shape was a function of the liquid concentration.
Authors: M.G. Ardakani, H. Basoalto, B.A. Shollock, Malcolm McLean
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