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991.
并行冲击/侵彻有限元数值模拟技术 总被引:4,自引:0,他引:4
探讨了冲击/侵彻问题涉及到的非线性材料模型、接触搜索算法、接触力计算公式、破坏模式等理论和算法,介绍了基于集群并行计算机的有限元法并行化基本思路和方法。应用实例表明本文中提出的有限元计算格式和并行化方法能够有效求解冲击/侵彻问题。 相似文献
992.
993.
空气和氧气气氛下p-GaN/Ni/Au合金性质 总被引:2,自引:1,他引:1
研究了p-CaN上的Au/Ni双金属层在空气气氛和氧气气氛下合金对其欧姆接触性质的影响。使用同步辐射高强度X射线衍射观察到明显的NiO衍射峰。随着合金时间的增加,NiO和Au的结晶性均明显变好,NiO的衍射峰强度随合金时间的增加而增强,同时发现Au(111)沿CaN的(0001)面择优形成单晶。测得Ni/Au-p-CaN-Ni/Au串联电阻在合金后明显降低,表明接触性质改善与结晶性的提高有关。同时发现氧气下合金比空气下合金形成NiO更快,相应的串联电阻也更快地下降。 相似文献
994.
Leticia Martínez-Lapuente Zenaida Guadalupe Paula Prez-Porras Ana Beln Bautista-Ortín Encarna Gmez-Plaza Beln Ayestarn 《Molecules (Basel, Switzerland)》2021,26(15)
The application of high-power ultrasounds (US) at 28 kHz to the crushed grapes and the use of different pomace contact times caused changes in the content and composition of monosaccharides and polysaccharides in the musts and wines. These differences were maintained from the moment of pressing (end of maceration) until the end of the alcoholic fermentation. The US increased the content of monosaccharides and polysaccharides in the musts by facilitating their extraction from the solid parts during maceration. The application of medium maceration time (3 days) to sonicated grapes led to an extraction of polysaccharides rich in arabinose and galactose, rhamnogalacturonan type II (RG-II) and mannoproteins (MP), similar to that observed in the control wines made with an extended maceration of 7 days (968.21 vs. 1029.45; 895.04 vs. 1700.50; 356.81 vs. 343.95, respectively). This fact was attributed to a higher extraction in the must during the sonication process and to an important release of pectic polysaccharides during the pressing of the sonicated pomace, which is reported here for the first time. Therefore, the US technology could be useful for increasing the polysaccharide content in the wines or for reducing the maceration time needed to achieve certain levels of wine polysaccharides. 相似文献
995.
YANG Chuang LI BangSheng REN MingXing & FU HengZhi School of Materials Science Engineering Harbin Institute of Technology Harbin China Micro-Nano Technology Research Center of Harbin Institute of Technology China State Key Laboratory of Solidification Processing Northwest Polytechnical University Xi’an 《中国科学B辑(英文版)》2009,52(7):868-873
To consider a sessile drop on an ideal solid surface in equilibrium with a vapor phase, the classic Young equation was given. The derivation of the Young equation was based on both the mechanics and the energy knowledge. According to the constant volume of the liquid in the wetting process of the liquid on a smooth and homogeneous solid surface and the low energy law, Young equation was ob-tained through the mathematic method in this paper. The previous work indicated that the contact angle θ was a function... 相似文献
996.
Theoretical modeling and experimental analysis of direct contact membrane distillation 总被引:1,自引:0,他引:1
A two-dimensional mathematical model was theoretically developed to predict the temperature polarization profile of direct contact membrane distillation (DCMD) processes. A concurrent flat-plate device was designed to verify the theoretical prediction of pure water productivity on saline water desalination. The numerical results from the temperature polarization profile were obtained using the finite difference technique to reduce the two-dimensional partial differential equations into an ordinary differential equations system. The resultant simultaneous linear equations system was solved with the fourth-order Runge-Kutta method. The results show theoretical prediction agreement with the measured values from the experimental runs. A combination of the Knudsen flow and Poiseuille flow models in the present mathematical formulation for membrane coefficient estimation was used to establish theoretical agreement. The influence of the inlet saline water temperature and volumetric flow rate on the pure water productivity as well as the hydraulic dissipated energy are also delineated. 相似文献
997.
Low metal-graphene contact resistance is important in making high-performance graphene devices.In this work,we demonstrate a lower specific contact resistivity of Au_(0.88)Ge_(0.12)/Ni/Au-graphene contact compared with Ti/Au and Ti/Pt/Au contacts.The rapid thermal annealing process was optimized to improve AuGe/Ni/Au contact resistance.Results reveal that both pre- and post-annealing processes are effective for reducing the contact resistance.The specific contact resistivity decreases from 2.5 × 10~(-4) to 7.8 × 10~(-5) Ω·cm~2 by pre-annealing at 300 ℃ for one hour,and continues to decrease to9.5 × 10~(-7) H·cm~2 after post-annealing at 490 ℃ for 60 seconds.These approaches provide reliable means of lowering contact resistance. 相似文献
998.
The observation motivating this contribution was a perceived lack of expeditious deformable terrain models that can match in mobility analysis studies the level of fidelity delivered by today’s vehicle models. Typically, the deformable terrain-tire interaction has been modeled using Finite Element Method (FEM), which continues to require prohibitively long analysis times owing to the complexity of soil behavior. Recent attempts to model deformable terrain have resorted to the use of the Discrete Element Method (DEM) to capture the soil’s complex interaction with a wheeled vehicle. We assess herein a DEM approach that employs a complementarity condition to enforce non-penetration between colliding rigid bodies that make up the deformable terrain. To this end, we consider three standard terramechanics experiments: direct shear, pressure-sinkage, and single-wheel tests. We report on the validation of the complementarity form of contact dynamics with friction, assess the potential of the DEM-based exploration of fundamental phenomena in terramechanics, and identify numerical solution challenges associated with solving large-scale, quadratic optimization problems with conic constraints. 相似文献
999.
We use previous theoretical results for the added mass, history and lubrication forces between two spheres colliding in a fluid with viscosity ν to investigate the effect of viscous dissipation on the coefficient of restitution during contact. We assume that the mechanical interaction is governed by Hertzian mechanical contact of small duration τ and that the minimum approach distance between particles is approximately equal to the height σ of surface micro-asperities. A non-dimensionalization of the equation of motion indicates that the contact dynamics is governed by two parameters – the ratio ϵ of the surface roughness σ and the sphere radius a, and a contact Stokes number defined as Stc = σ2/ντ. An asymptotic solution of the equation of motion in the limit of small ϵ/Stc is used to obtain an explicit expression for the coefficient of restitution during contact and the latter is compared with estimates based on numerical solutions of the non-linear equation of motion. 相似文献
1000.
In the present paper, a three-dimensional problem of elasticity of normal and tangential loading of surface of the functionally graded coated half-space is considered. In case when Poisson's ratio is constant and the Young's modulus is a power or exponential function of the distance from the surface of the half-space, analytical solution using Fourier transform is obtained. Stress field due to Hertz contact pressure in an elliptical region are studied as a function of the parameter b/a (where a and b are axes of the contact ellipse) and coating thickness. 相似文献