Search results for "65"
showing 10 items of 1111 documents
Finite element approximation for a div-rot system with mixed boundary conditions in non-smooth plane domains
1984
The authors examine a finite element method for the numerical approximation of the solution to a div-rot system with mixed boundary conditions in bounded plane domains with piecewise smooth boundary. The solvability of the system both in an infinite and finite dimensional formulation is proved. Piecewise linear element fields with pointwise boundary conditions are used and their approximation properties are studied. Numerical examples indicating the accuracy of the method are given. peerReviewed
Inverse problems and invisibility cloaking for FEM models and resistor networks
2013
In this paper we consider inverse problems for resistor networks and for models obtained via the finite element method (FEM) for the conductivity equation. These correspond to discrete versions of the inverse conductivity problem of Calderón. We characterize FEM models corresponding to a given triangulation of the domain that are equivalent to certain resistor networks, and apply the results to study nonuniqueness of the discrete inverse problem. It turns out that the degree of nonuniqueness for the discrete problem is larger than the one for the partial differential equation. We also study invisibility cloaking for FEM models, and show how an arbitrary body can be surrounded with a layer …
On FE-grid relocation in solving unilateral boundary value problems by FEM
1992
We consider FE-grid optimization in elliptic unilateral boundary value problems. The criterion used in grid optimization is the total potential energy of the system. It is shown that minimization of this cost functional means a decrease of the discretization error or a better approximation of the unilateral boundary conditions, Design sensitivity analysis is given with respect to the movement of nodal points. Numerical results for the Dirichlet-Signorini problem for the Laplace equation and the plane elasticity problem with unilateral boundary conditions are given. In plane elasticity we consider problems with and without friction. peerReviewed
A fast Fourier transform based direct solver for the Helmholtz problem
2018
This article is devoted to the efficient numerical solution of the Helmholtz equation in a two‐ or three‐dimensional (2D or 3D) rectangular domain with an absorbing boundary condition (ABC). The Helmholtz problem is discretized by standard bilinear and trilinear finite elements on an orthogonal mesh yielding a separable system of linear equations. The main key to high performance is to employ the fast Fourier transform (FFT) within a fast direct solver to solve the large separable systems. The computational complexity of the proposed FFT‐based direct solver is O(N log N) operations. Numerical results for both 2D and 3D problems are presented confirming the efficiency of the method discussed…
Science and law in the time of cholera: the mystery of the biscuits in Torroja (1865)
2018
By focussing on a case of collective poisoning in 1865, four features of forensic cultures are analysed: technologies for detection, authorized voices, regulations in action and the predominant social anxieties. Local newspapers and archival documents kept in the medical academies of Barcelona and Madrid are analysed. The analysis shows the tensions between various types of proof employed in legal medicine and the ambiguities between epidemic diseases and poisoning accidents. In the first section, I review the fears caused by the cholera epidemic in 1865, which was the first explanation of the accident. The changes of popular perception are also discussed by analysing contemporary newspaper…
Dealing with a Trauma Burdened Past: between Remembering and Forgetting
2017
Recognition that societies will not be able to build a future as long as they do not face the ‘demons of the past’ has become a kind of universal truth over the last decades of the 20th Century (Gibney et al., 2008, p. 1). This view, though challenging and ambiguous, is reflected in the globally present attempts to improve or rebuild relations within and between different communities at the domestic and international level. The question concerning, on the one hand, the essence and most essential elements and, on the other hand, the instruments and the limitations of rebuilding relations, as well as the political implications of those processes have become the broad area of interest and the …
Il Fast Track nelle fratture di femore può davvero favorire risultati clinici migliori?
2016
Le attuali linee guida raccomandano di effettuare il trattamento chirurgico di stabilizzazione o sosti- tuzione protesica entro 24-48 ore dall’accesso ospedaliero, al ne di migliorare il risultato funziona- le, ridurre il rischio di mortalità, la degenza ospedaliera e le complicazioni post-operatorie. Tuttavia, la mancanza di studi randomizzati rappresenta un importantissimo limite scienti co dal momento che ad oggi la migliore evidenza scienti ca sul timing chirurgico nelle fratture di collo femore si basa esclusivamente su studi prospettici e retrospettivi. In questo articolo, viene descritto il percorso ospedaliero per il trattamento delle fratture del collo del femore nel paziente anzia…
Quasisymmetric extension on the real line
2015
We give a geometric characterization of the sets $E\subset \mathbb{R}$ that satisfy the following property: every quasisymmetric embedding $f: E \to \mathbb{R}^n$ extends to a quasisymmetric embedding $f:\mathbb{R}\to\mathbb{R}^N$ for some $N\geq n$.
Fuzzy Systems Based on Multispecies PSO Method in Spatial Analysis
2012
We present a method by using the hierarchical cluster-based Multispecies particle swarm optimization to generate a fuzzy system of Takagi-Sugeno-Kang type encapsulated in a geographical information system considered as environmental decision support for spatial analysis. We consider a spatial area partitioned in subzones: the data measured in each subzone are used to extract a fuzzy rule set of above mentioned type. We adopt a similarity index (greater than a specific threshold) for comparing fuzzy systems generated for adjacent subzones.
Gene expression in TGFbeta-induced epithelial cell differentiation in a three-dimensional intestinal epithelial cell differentiation model
2006
Abstract Background The TGFβ1-induced signal transduction processes involved in growth and differentiation are only partly known. The three-dimensional epithelial differentiation model, in which T84 epithelial cells are induced to differentiate either with TGFβ1 or IMR-90 mesenchymal cell-secreted soluble factors, is previously shown to model epithelial cell differentiation seen in intestine. That model has not been used for large scale gene expression studies, such as microarray method. Therefore the gene expression changes were studied in undifferentiated and differentiated three-dimensional T84 cultures with cDNA microarray method in order to study the molecular changes and find new play…