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171.
Doubly nonlinear parabolic-type equations as dynamical systems 总被引:1,自引:0,他引:1
In this paper, we study a class of doubly nonlinear parabolic PDEs, where, in addition to some weak nonlinearities, also some mild nonlinearities of porous media type are allowed inside the time derivative. In order to formulate the equations as dynamical systems, some existence and uniqueness results are proved. Then the existence of a compact attractor is shown for a class of nonlinear PDEs that include doubly nonlinear porous medium-type equations. Under stronger smoothness assumptions on the nonlinearities, the finiteness of the fractal dimension of the attractor is also obtained. 相似文献
172.
A new mathematical model is proposed for time-independent laminar flow through a rigid isotropic and consolidated porous medium of spatially varying porosity. The model is based upon volumetric averaging concepts. Explicit assumptions regarding the mean geometric properties of the porous microstructure lead to a relationship between tortuosity and porosity. Microscopic inertial effects are introduced through consideration of flow development within the pores. A momentum transport equation is derived in terms of the fluid properties, the porous medium porosity and a characteristic length of the microstructure. In the limiting cases of porosity unity and zero, the model yields the required Navier-Stokes equation for free flow and no flow in a solid, respectively. 相似文献
173.
横观各向同性三维热弹性力学通解及其势理论法 总被引:3,自引:0,他引:3
通过引入两个位移函数,对用位移表达的运动平衡方程作了简化.利用算子理论,严格地导出了横观各向同性非耦合热弹性动力学问题的通解.对于静力学问题,通解的形式可进一步简化成用4个准调和函数来表示.具体考察了横观各向同性体内平面裂纹上下表面有对称分布温度作用的问题,推广了势理论方法,导出了一个积分方程和一个微分-积分方程.针对币状裂纹表面受均布温度作用情形,给出了具体的解。 相似文献
174.
将水溶性手性二胺 (S,S)-1,2-二苯基乙二胺二磺酸钠 ((S,S)-DPENDS) 与钌膦配合物 ([RuCl2(TPPTS)2]2) 原位生成的催化剂用于催化水相中苄叉丙酮的不对称加氢反应. 在优化条件下, 羰基加氢产物 4-苯基-3-丁烯-2-醇的选择性可达 96.0%, 对映选择性可达 71.2%. 经正己烷简单萃取后即可实现催化剂与加氢产物的分离, 循环使用 5 次后, 目标产物 4-苯基-3-丁烯-2-醇选择性和对映选择性没有明显下降. 相似文献
175.
Yong Huang Ke-Yong Zhu Jun Wang 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(14):2363-2371
The curved ray-tracing method is extended to radiative transfer in the graded index medium with diffuse gray boundary conditions instead of black boundary conditions and the pseudo-source adding method is extended to the case of the linear-anisotropic scattering medium with graded index from non-scattering medium. Furthermore, the equivalence of the two methods is verified by formulation derivation. As exact analytical solutions, both the methods have high accuracy and fast computational speed. The predicted temperature distributions and dimensionless radiative heat flux at radiative equilibrium are determined by the proposed methods, and the numerical results are compared with the data in references. The results show that the present methods have a good accuracy. Influences of various combinations of refractive index and boundary emissivities on the temperature distributions and dimensionless radiative heat flux are also investigated. 相似文献
176.
The curved ray tracing method (CRT) is extended to radiative transfer in the linear-anisotropic scattering medium with graded index from non-scattering medium. In this paper, the CRT is presented to solve one-dimensional radiative transfer in the linear-anisotropic scattering gray medium with a linear refractive index and two black boundaries. The predicted temperature distributions and radiative heat flux at radiative equilibrium are determined by the proposed method, and numerical results are compared with the data in references. The results show that the CRT has a good accuracy for radiative transfer in the linear-anisotropic scattering medium with graded index and the dimensionless emissive power and dimensionless radiative heat flux depend on the dimensionless refractive index gradient. It can also be seen that the dimensionless refractive index gradient has important effects on the temperature discontinuity at the boundaries. 相似文献
177.
Time evolution characteristic of few-cycle pulse propagating in a ladder-type atomic medium is investigated. It is shown that, time evolution of few-cycle pulse has significant difference in the both cases on- and non-resonance. In the non-resonant case, if the pulse central frequency is twice as large as medium atomic transition frequency, the pulse form (including carry-envelope phase, pulse duration, oscillation amplitude and frequency) remains unchanging or remains unchanging basically (only carry-envelope phase has some variation) in the propagation process, which means that self-induced transparency (SIT) or approximate transparency phenomenon appears. However, in the resonant case, the pulse form changes obviously in the propagation process. In addition, there is evident difference in the propagating velocity for on- and non-resonance when the pulse area is smaller. 相似文献
178.
一阶速度-应力Biot双相各向同性介质弹性波 总被引:1,自引:0,他引:1
提出一种等价的一阶双曲型速度一应力Biot双相各向同性介质弹性波波动方程,以实现双相介质混合波场中纯快慢纵波和纯横波波场分离的问题.应用散度和旋度理论证明双相介质等价方程波场分离的可行性,采用高阶交错网格有限差分法构建高精度正演算子,推导其PML吸收边界条件和稳定性条件,并对均匀双相介质和层状非均匀双相介质模型进行数值... 相似文献
179.
180.