Home About us Contact
|
Home About us Contact | ||
|
|
||
Nodal Points (nodal + point)
Selected AbstractsAnalysis of thick functionally graded plates by local integral equation methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 8 2007J. Sladek Abstract Analysis of functionally graded plates under static and dynamic loads is presented by the meshless local Petrov,Galerkin (MLPG) method. Plate bending problem is described by Reissner,Mindlin theory. Both isotropic and orthotropic material properties are considered in the analysis. A weak formulation for the set of governing equations in the Reissner,Mindlin theory with a unit test function is transformed into local integral equations considered on local subdomains in the mean surface of the plate. Nodal points are randomly spread on this surface and each node is surrounded by a circular subdomain, rendering integrals which can be simply evaluated. The meshless approximation based on the moving least-squares (MLS) method is employed in the numerical implementation. Numerical results for simply supported and clamped plates are presented. Copyright © 2006 John Wiley & Sons, Ltd. [source] An interpolation-based local differential quadrature method to solve partial differential equations using irregularly distributed nodesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 7 2008Hang Ma Abstract To circumvent the constraint in application of the conventional differential quadrature (DQ) method that the solution domain has to be a regular region, an interpolation-based local differential quadrature (LDQ) method is proposed in this paper. Instead of using regular nodes placed on mesh lines in the DQ method (DQM), irregularly distributed nodes are employed in the LDQ method. That is, any spatial derivative at a nodal point is approximated by a linear weighted sum of the functional values of irregularly distributed nodes in the local physical domain. The feature of the new approach lies in the fact that the weighting coefficients are determined by the quadrature rule over the irregularly distributed local supporting nodes with the aid of nodal interpolation techniques developed in the paper. Because of this distinctive feature, the LDQ method can be consistently applied to linear and nonlinear problems and is really a mesh-free method without the limitation in the solution domain of the conventional DQM. The effectiveness and efficiency of the method are validated by two simple numerical examples by solving boundary-value problems of a linear and a nonlinear partial differential equation. Copyright © 2007 John Wiley & Sons, Ltd. [source] Abu Ghraib, the security apparatus, and the performativity of powerAMERICAN ETHNOLOGIST, Issue 2 2010STEVEN C. CATON ABSTRACT The critical discourse on U.S. military detainee abuse at Abu Ghraib prison has been dominated by Weberian-style arguments (a bureaucracy gone wrong, insufficient or badly applied administrative rules, or individuals acting as cogs in a machine). We argue that Michel Foucault's "security apparatus" provides a more insightful model for understanding the Abu Ghraib phenomenon. According to this model, the prison becomes a nodal point in an information-gathering nexus confronting unforeseen, emergent, and unclear events, a place where power is less disciplinary than improvisational, exercised through practical judgments about uncertain situations. The performance of such power at Abu Ghraib included the use of photography and acts that, we claim, resemble M. M. Bahktin's negative carnivalesque. [Abu Ghraib, security apparatus, improvisational power, photography, carnivalesque] [source] Understanding heart development and congenital heart defects through developmental biology: A segmental approachCONGENITAL ANOMALIES, Issue 4 2005Masahide Sakabe ABSTRACT The heart is the first organ to form and function during development. In the pregastrula chick embryo, cells contributing to the heart are found in the postero-lateral epiblast. During the pregastrula stages, interaction between the posterior epiblast and hypoblast is required for the anterior lateral plate mesoderm (ALM) to form, from which the heart will later develop. This tissue interaction is replaced by an Activin-like signal in culture. During gastrulation, the ALM is committed to the heart lineage by endoderm-secreted BMP and subsequently differentiates into cardiomyocyte. The right and left precardiac mesoderms migrate toward the ventral midline to form the beating primitive heart tube. Then, the heart tube generates a right-side bend, and the d-loop and presumptive heart segments begin to appear segmentally: outflow tract (OT), right ventricle, left ventricle, atrioventricular (AV) canal, atrium and sinus venosus. T-box transcription factors are involved in the formation of the heart segments: Tbx5 identifies the left ventricle and Tbx20 the right ventricle. After the formation of the heart segments, endothelial cells in the OT and AV regions transform into mesenchyme and generate valvuloseptal endocardial cushion tissue. This phenomenon is called endocardial EMT (epithelial-mesenchymal transformation) and is regulated mainly by BMP and TGF,. Finally, heart septa that have developed in the OT, ventricle, AV canal and atrium come into alignment and fuse, resulting in the completion of the four-chambered heart. Altered development seen in the cardiogenetic process is involved in the pathogenesis of congenital heart defects. Therefore, understanding the molecular nature regulating the ,nodal point' during heart development is important in order to understand the etiology of congenital heart defects, as well as normal heart development. [source] Ritz finite elements for curvilinear particlesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 5 2006Paul R. Heyliger Abstract A general finite element is presented for the representation of fields in curvilinear particles in two and three dimensions. The formulation of this element shares many similarities with usual finite element approximations, but differs in that nodal points are defined in part by contact points with other particles. Power series in the geometric coordinates are used as the starting basis functions, but are recast in terms of the field variables within the particle interior and the points of contact with other elements. There is no discretization error and the elements of the finite element matrices can all be evaluated in closed form. This approach is applicable to shapes in two and three dimensions, including discs, ellipses, spheres, spheroids, and potatoes. Examples are included for two-dimensional applications of steady-state heat transfer and elastostatics. Copyright © 2005 John Wiley & Sons, Ltd. [source] Transient heat conduction analysis in a piecewise homogeneous domain by a coupled boundary and finite element methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2003I. Guven Abstract A coupled finite element,boundary element analysis method for the solution of transient two-dimensional heat conduction equations involving dissimilar materials and geometric discontinuities is developed. Along the interfaces between different material regions of the domain, temperature continuity and energy balance are enforced directly. Also, a special algorithm is implemented in the boundary element method (BEM) to treat the existence of corners of arbitrary angles along the boundary of the domain. Unknown interface fluxes are expressed in terms of unknown interface temperatures by using the boundary element method for each material region of the domain. Energy balance and temperature continuity are used for the solution of unknown interface temperatures leading to a complete set of boundary conditions in each region, thus allowing the solution of the remaining unknown boundary quantities. The concepts developed for the BEM formulation of a domain with dissimilar regions is employed in the finite element,boundary element coupling procedure. Along the common boundaries of FEM,BEM regions, fluxes from specific BEM regions are expressed in terms of common boundary (interface) temperatures, then integrated and lumped at the nodal points of the common FEM,BEM boundary so that they are treated as boundary conditions in the analysis of finite element method (FEM) regions along the common FEM,BEM boundary. Copyright © 2002 John Wiley & Sons, Ltd. [source] Thermoelastic stress field in a piecewise homogeneous domain under non-uniform temperature using a coupled boundary and finite element methodINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 3 2003I. Guven Abstract This study concerns the development of a coupled finite element,boundary element analysis method for the solution of thermoelastic stresses in a domain composed of dissimilar materials with geometric discontinuities. The continuity of displacement and traction components is enforced directly along the interfaces between different material regions of the domain. The presence of material and geometric discontinuities are included in the formulation explicitly. The unknown interface traction components are expressed in terms of unknown interface displacement components by using the boundary element method for each material region of the domain. Enforcing the continuity conditions leads to a final system of equations containing unknown interface displacement components only. With the solution of interface displacement components, each region has a complete set of boundary conditions, thus leading to the solution of the remaining unknown boundary quantities. The concepts developed for the BEM formulation of a domain with dissimilar regions is employed in the finite element,boundary element coupling procedure. Along the common boundaries of FEM,BEM regions, stresses from specific BEM regions are first expressed in terms of interface displacements, then integrated and lumped at the nodal points of the common FEM,BEM boundary so that they are treated as boundary conditions in the analysis of FEM regions along the common FEM,BEM boundary. Copyright © 2002 John Wiley & Sons, Ltd. [source] Latest view on the mechanism of action of deep brain stimulation,MOVEMENT DISORDERS, Issue 15 2008Constance Hammond PhD Abstract How does deep brain stimulation (DBS) applied at high frequency (100 Hz and above, HFS) in diverse points of cortico-basal ganglia thalamo-cortical loops alleviate symptoms of neurological disorders such as Parkinson's disease, dystonia, and obsessive compulsive disorders? Do the effects of HFS stem solely or even largely from local effects on the stimulated brain structure or are they also mediated by actions of HFS on distal structures? Indeed, HFS as an extracellular stimulation is expected to activate subsets of both afferent and efferent axons, leading to antidromic spikes that collide with ongoing spontaneous ones and orthodromic spikes that evoke synaptic responses in target neurons. The present review suggests that HFS interfere with spontaneous pathological patterns by introducing a regular activity in several nodal points of the network. Therefore, the best site of implantation of the HFS electrode may be in a region where the HFS-driven activity spreads to most of the identified, dysrhythmic, neuronal populations without causing additional side effects. This should help tackling the most difficult issue namely, how does the regular HFS-driven activity that dampens the spontaneous pathological one, restore neuronal processing along cortico-basal ganglia-thalamo-cortical loops? © 2008 Movement Disorder Society [source] The ,-reliable minimax and maximin location problems on a network with probabilistic weightsNETWORKS: AN INTERNATIONAL JOURNAL, Issue 2 2010Jiamin Wang Abstract We study the ,-reliable minimax and maximin location problems on a network when the weights associated with the nodal points are random variables. In the ,-reliable minimax (maximin) problem, we locate a single facility so as to minimize (maximize) the upper (lower) bound on the maximum (minimum) weighted distance from the nodes to the facility with a probability greater than or equal to a pre-specified level ,. It is shown that under some conditions the two probabilistic models are equivalent to their deterministic counterparts. Solution procedures are developed to solve the problems with weights of continuous and discrete probability distributions. © 2009 Wiley Periodicals, Inc. NETWORKS, 2010 [source] Visual axes in eyes that may be astigmatic and have decentred elementsOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 2 2010W. F. Harris Abstract The visual axis of the eye has been defined in terms of nodal points. However, astigmatic systems usually do not have nodal points. The purpose of this note is to offer a modified definition of visual axes that is in terms of nodal rays instead of nodal points and to show how to locate them from knowledge of the structure of the eye. A pair of visual axes (internal and external) is defined for each eye. The visual axes then become well defined in linear optics for eyes whether or not they are astigmatic or have decentred elements. The vectorial angle between the visual axes and the optical axis defines the visuo-optical angle of the eye. [source] | |||||||||||||