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Physical Boundaries (physical + boundary)

Distribution by Scientific Domains

Engineering	80%

Selected Abstracts

Simulation technique for wave generation

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2003
S. Aliabadi
Abstract In this paper, we present a new finite element technique for simulation of water waves impacting on floating structures. The emphasis will be on the numerical methods for water wave generation and propagation. In our approach, the governing equations are the Navier,Stokes equations written for two incompressible fluids. An interface function with two distinct values serves as a marker identifying the location of the free-surface. This function is transported throughout the computational domain with a time-dependent advection equation. The stabilized finite element formulations are written and integrated in an arbitrary Lagrangian,Eulerian domain. This allows us to handle the motion of the physical boundaries, such as the wave generator surface by moving the computational nodes. In the mesh-moving scheme, we assume that the computational domain is made of elastic materials. The linear elasticity equations are solved to obtain the displacements for each computational node. The numerical examples include 3D wave generation and wave breaking as they approach the coast, and the waves impacting on near-shore support columns. Copyright © 2003 John Wiley & Sons, Ltd. [source]

An integrated procedure for three-dimensional structural analysis with the finite cover method

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 15 2005
Kenjiro Terada
Abstract In this paper an integrated procedure for three-dimensional (3D) structural analyses with the finite cover method (FCM) is introduced. In the pre-process of this procedure, the geometry of a structure is modelled by 3D-CAD, followed by digitization to have the corresponding voxel model, and then the structure is covered by a union of mathematical covers, namely a mathematical mesh independently generated for approximation purposes. Since the mesh topology in the FCM does not need to conform to the physical boundaries of the structure, the mesh can be regular and structured. Thus, the numerical analysis procedure is free from the difficulties mesh generation typically poses and, in this sense, enables us to realize the mesh-free analysis. After formulating the FCM with interface elements for the static equilibrium state of a structure, we detail the procedure of the finite cover modelling, including the geometry modelling with 3D-CAD and the identification of the geometry covered by a regular mesh for numerical integration. Prior to full 3D modelling and analysis, we present a simple numerical example to confirm the equivalence of the performance of the FCM and that of the standard finite element method (FEM). Finally, representative numerical examples are presented to demonstrate the capabilities of the proposed analysis procedure. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Non-local damage model based on displacement averaging

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 1 2005
M. Jirásek
Abstract Continuum damage models describe the changes of material stiffness and strength, caused by the evolution of defects, in the framework of continuum mechanics. In many materials, a fast evolution of defects leads to stress,strain laws with softening, which creates serious mathematical and numerical problems. To regularize the model behaviour, various generalized continuum theories have been proposed. Integral-type non-local damage models are often based on weighted spatial averaging of a strain-like quantity. This paper explores an alternative formulation with averaging of the displacement field. Damage is assumed to be driven by the symmetric gradient of the non-local displacements. It is demonstrated that an exact equivalence between strain and displacement averaging can be achieved only in an unbounded medium. Around physical boundaries of the analysed body, both formulations differ and the non-local displacement model generates spurious damage in the boundary layers. The paper shows that this undesirable effect can be suppressed by an appropriate adjustment of the non-local weight function. Alternatively, an implicit gradient formulation could be used. Issues of algorithmic implementation, computational efficiency and smoothness of the resolved stress fields are discussed. Copyright © 2005 John Wiley & Sons, Ltd. [source]

Finite cover method for linear and non-linear analyses of heterogeneous solids

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 9 2003
Kenjiro Terada
Abstract We introduce the finite cover method (FCM) as a generalization of the finite element method (FEM) and extend it to analyse the linear and non-linear mechanical behaviour of heterogeneous solids and structures. The name ,FCM' is actually an alias for the manifold method (MM) and the basic idea of the method has already been established for linear analyses of structures with homogeneous materials. After reviewing the concept of physical and mathematical covers for approximating functions in the FCM, we present the formulation for the static equilibrium state of a structure with arbitrary physical boundaries including material interfaces. The problem essentially involves the discontinuities in strains, and possibly has the discontinuities in displacement caused by interfacial debonding or rupture of material interfaces. We simulate such non-linear mechanical behaviour after presenting simple numerical examples that demonstrate the equivalence between the approximation capabilities of the FCM and those of the FEM. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Symptomatology of Late-onset Schizophrenia and Paranoid Disorders

PSYCHOGERIATRICS, Issue 1 2002
Hidemichi Hamada
Abstract: There is controversy concerning the classification of late-onset paranoid disorders, but many interpret it as schizophrenia that is first manifested in old age. As a result of the revival of the concept of late-onset catatonia in recent years, the classification of late schizophrenia has been reorganized. Late-onset paranoid disorders have two characteristics in terms of their symptomatology: a transition from the boundaries of the self to material boundaries, and delusions of injury. In late-onset paranoid disorders there is adherence of the boundaries of the self to physical boundaries in an external form that can be seen with the eyes. Delusions of injury, in which living space within physical boundaries is infringed, become manifestations, such as delusions of robbery, jealousy, and delusions of infestation. [source]