Constitutive theory of plasticity coupled with orthotropic damage for geomaterials was established in the framework of irreversible thermodynamics. Prime results include I evolution laws are presented for coupled evol...Constitutive theory of plasticity coupled with orthotropic damage for geomaterials was established in the framework of irreversible thermodynamics. Prime results include I evolution laws are presented for coupled evolution of plasticity and orthotropic damage 2) the orthotropic damage tensor is introduced into the Mohr-Coulomb criterion through homogenization. Both the degradation of shear strength and degradation of friction angle caused by damage are included in this model. The dilatancy is calculated with the so-called damage strain.展开更多
In this paper, an effective numerical method for physically nonlinear interaction analysis is studied, in which the elasto-plastic problem of coupled analysis between the structure and medium may be transformed into s...In this paper, an effective numerical method for physically nonlinear interaction analysis is studied, in which the elasto-plastic problem of coupled analysis between the structure and medium may be transformed into several linear problems by means of the perturbation technique, then, the finite strip method and finite layer method are used to analyze the underground structure and rock medium, respectively, for their corresponding linear problems, so the purpose of simplifying the calculation can be achieved. This kind of method has made use of the twice semi-analytical technique: the perturbation and semi-analytic solution function to simplify 3-D nonlinear coupled problem into 1-D linear numerical one. In addition, this method is a new advance of semi-analytical method in the application to nonlinear problems by means of combinating with the analytical perturbation method, and it is also a branch of the perturbational numerical method developed in last years.展开更多
A time-discontinuous Galerkin finite element method for dynamic analyses in saturated poro-elasto-plastic medium is proposed.As compared with the existing discontinuous Galerkin finite element methods,the distinct fea...A time-discontinuous Galerkin finite element method for dynamic analyses in saturated poro-elasto-plastic medium is proposed.As compared with the existing discontinuous Galerkin finite element methods,the distinct feature of the proposed method is that the continuity of the displacement vector at each discrete time instant is automatically ensured,whereas the discontinuity of the velocity vector at the discrete time levels still remains.The computational cost is then obviously reduced, particularly,for material non-linear problems.Both the implicit and explicit algorithms to solve the derived formulations for material non-linear problems are developed.Numerical results show a good performance of the present method in eliminating spurious numerical oscillations and providing with much more accurate solutions over the traditional Galerkin finite element method using the Newmark algorithm in the time domain.展开更多
在脑卒中幸存者中,卒中后认知障碍(Post-stroke cognitive impairment,PSCI)是导致残疾的主要原因之一,目前临床治疗多聚焦于药物治疗而其他干预手段有限。经颅直流电刺激(Transcranial direct current stimulation,tDCS)是一种无创的...在脑卒中幸存者中,卒中后认知障碍(Post-stroke cognitive impairment,PSCI)是导致残疾的主要原因之一,目前临床治疗多聚焦于药物治疗而其他干预手段有限。经颅直流电刺激(Transcranial direct current stimulation,tDCS)是一种无创的神经调控技术,广泛用于各种认知障碍的康复治疗,但其作用机制尚不明确。本文结合近年来国内外研究,概括了PSCI发病机制、tDCS治疗认知障碍的作用机制。文献复习结果表明,tDCS可能通过改善脑部神经-血管耦合、调节皮质兴奋性、促进突触可塑性、加强脑区间的功能连接等机制达到改善PSCI的效果。这些结果可以为PSCI及卒中后其他功能障碍的临床康复治疗提供理论依据。未来,还能基于“脑-肢协同治疗技术”理论,将tDCS与其他外周干预手段相结合,使其发挥最佳疗效。展开更多
文摘Constitutive theory of plasticity coupled with orthotropic damage for geomaterials was established in the framework of irreversible thermodynamics. Prime results include I evolution laws are presented for coupled evolution of plasticity and orthotropic damage 2) the orthotropic damage tensor is introduced into the Mohr-Coulomb criterion through homogenization. Both the degradation of shear strength and degradation of friction angle caused by damage are included in this model. The dilatancy is calculated with the so-called damage strain.
文摘In this paper, an effective numerical method for physically nonlinear interaction analysis is studied, in which the elasto-plastic problem of coupled analysis between the structure and medium may be transformed into several linear problems by means of the perturbation technique, then, the finite strip method and finite layer method are used to analyze the underground structure and rock medium, respectively, for their corresponding linear problems, so the purpose of simplifying the calculation can be achieved. This kind of method has made use of the twice semi-analytical technique: the perturbation and semi-analytic solution function to simplify 3-D nonlinear coupled problem into 1-D linear numerical one. In addition, this method is a new advance of semi-analytical method in the application to nonlinear problems by means of combinating with the analytical perturbation method, and it is also a branch of the perturbational numerical method developed in last years.
基金The project supported by the National Natural Science Foundation of China(19832010,50278012,10272027)the National Key Basic Research and Development Program(973 Program,2002CB412709)
文摘A time-discontinuous Galerkin finite element method for dynamic analyses in saturated poro-elasto-plastic medium is proposed.As compared with the existing discontinuous Galerkin finite element methods,the distinct feature of the proposed method is that the continuity of the displacement vector at each discrete time instant is automatically ensured,whereas the discontinuity of the velocity vector at the discrete time levels still remains.The computational cost is then obviously reduced, particularly,for material non-linear problems.Both the implicit and explicit algorithms to solve the derived formulations for material non-linear problems are developed.Numerical results show a good performance of the present method in eliminating spurious numerical oscillations and providing with much more accurate solutions over the traditional Galerkin finite element method using the Newmark algorithm in the time domain.
文摘在脑卒中幸存者中,卒中后认知障碍(Post-stroke cognitive impairment,PSCI)是导致残疾的主要原因之一,目前临床治疗多聚焦于药物治疗而其他干预手段有限。经颅直流电刺激(Transcranial direct current stimulation,tDCS)是一种无创的神经调控技术,广泛用于各种认知障碍的康复治疗,但其作用机制尚不明确。本文结合近年来国内外研究,概括了PSCI发病机制、tDCS治疗认知障碍的作用机制。文献复习结果表明,tDCS可能通过改善脑部神经-血管耦合、调节皮质兴奋性、促进突触可塑性、加强脑区间的功能连接等机制达到改善PSCI的效果。这些结果可以为PSCI及卒中后其他功能障碍的临床康复治疗提供理论依据。未来,还能基于“脑-肢协同治疗技术”理论,将tDCS与其他外周干预手段相结合,使其发挥最佳疗效。
