This paper analyzes the interaction between two kinds of internal length scales when the rate dependen plasticity is introduced to a multiphase material model to study the dynamic strain localization phenomenon of satu rated and partially saturated porous media. The stability analysis demonstrates that the enhanced porous media mode preserves the well-posedness of the initial value problem for both axial and shear waves because an internal length scale parameter is introduced in the visco-plasticity model. On the other hand, the interaction between the length scale intro duced by the rate dependent model and that naturally con tained in the governing equations of fully and partially satu rated model will take place. A basic method is presented to investigate the internal length scale of the multiphase porou media under the interaction of these two kinds of length scale parameters. Material stability analysis is carried out for a certain permeability from which the results of wave number domain with real wave speed are distinguished. A one dimen sional example is given to illustrate the theoretical findings.
In this paper, the authors present airflow field characteristics of human upper airway and soft palate movement attitude during breathing. On the basis of the data taken from the spiral computerized tomography images of a healthy person and a patient with Obstructive Sleep Apnea-Hypopnea Syndrome （OSAHS）, three-dimensional models of upper airway cavity and soft palate are reconstructed by the method of surface rendering. Numerical simulation is performed for airflow in the upper airway and displacement of soft palate by fluid-structure interaction analysis. The reconstructed threedimensional models precisely preserve the original configuration of upper airways and soft palate. The results of the pressure and velocity distributions in the airflow field are quantitatively determined, and the displacement of soft palate is presented. Pressure gradients of airway are lower for the healthy person and the airflow distribution is quite uniform in the case of free breathing. However, the OSAHS patient remarkably escalates both the pressure and velocity in the upper airway, and causes higher displacement of the soft palate. The present study is useful in revealing pathogenesis and quantitative mutual relationship between configuration and function of the upper airway as well as in diagnosingdiseases related to anatomical structure and function of the upper airway.
Xiuzhen Sun Chi Yu Yuefang Wang Yingxi Liu State Key Lab.of Struct.Anal.for Ind.Equip.,Dalian University of Technology,Dalian 116024,China The Second Affiliated Hospital,Dalian Medical University,Dalian 116027,China
In the present paper, a multi-linearity method is used to address the nonlinear slip control equation for the hydrodynamic analysis of a two-dimensional （2-D） slip gap flow. Numerical analysis of a finite length slider bearing with wall slip shows that the surface limiting shear stress exerts complicated influences on the hydrodynamic behavior of the gap flow. If the slip occurs at either the stationary surface or the moving surface （especially at the stationary surface）, there is a transition point in the initial limiting shear stress for the proportional coefficient to affect the hydrodynamic load support in two opposite ways： it increases the hydrodynamic load support at higher initial limiting shear stresses, but decreases the hydrodynamic load support at lower initial limiting shear stresses. If the slip occurs at the moving surface only, no fluid pressure is generated in the case of null initial limiting shear stress. If the slip occurs at both the surfaces with the same slip property, the hydrodynamic load support goes off after a critical sliding speed is reached. A small initial limiting shear stress and a small proportionality coefficient always give rise to a low friction drag.
