Search results for "interpolation."
showing 10 items of 253 documents
Plantar flexor activation capacity and H reflex in older adults: adaptations to strength training.
2002
The purpose of this study was to investigate whether the voluntary neural drive and the excitability of the reflex arc could be modulated by training, even in old age. To this aim, the effects of a 16-wk strengthening program on plantar flexor voluntary activation (VA) and on the maximum Hoffman reflex (Hmax)-to-maximum M wave (Mmax) ratio were investigated in 14 elderly men (65–80 yr). After training, isometric maximum voluntary contraction (MVC) increased by 18% ( P < 0.05) and weight-lifting ability by 24% ( P < 0.001). Twitch contraction time decreased by 8% ( P < 0.01), but no changes in half relaxation time and in peak twitch torque were observed. The VA, assessed by twitch …
Three dimensional reconstruction to visualize atrial fibrillation activation patterns on curved atrial geometry
2021
BackgroundThe rotational activation created by spiral waves may be a mechanism for atrial fibrillation (AF), yet it is unclear how activation patterns obtained from endocardial baskets are influenced by the 3D geometric curvature of the atrium or ‘unfolding’ into 2D maps. We develop algorithms that can visualize spiral waves and their tip locations on curved atrial geometries. We use these algorithms to quantify differences in AF maps and spiral tip locations between 3D basket reconstructions, projection onto 3D anatomical shells and unfolded 2D surfaces.MethodsWe tested our algorithms in N = 20 patients in whom AF was recorded from 64-pole baskets (Abbott, CA). Phase maps were generated by…
Constructing a Pareto front approximation for decision making
2011
An approach to constructing a Pareto front approximation to computationally expensive multiobjective optimization problems is developed. The approximation is constructed as a sub-complex of a Delaunay triangulation of a finite set of Pareto optimal outcomes to the problem. The approach is based on the concept of inherent nondominance. Rules for checking the inherent nondominance of complexes are developed and applying the rules is demonstrated with examples. The quality of the approximation is quantified with error estimates. Due to its properties, the Pareto front approximation works as a surrogate to the original problem for decision making with interactive methods. Qc 20120127
Investigation of the crack tip stress field in a stainless steel SENT specimen by means of Thermoelastic Stress Analysis
2019
Abstract In this work a Thermoelastic Stress Analysis (TSA) setup is implemented to investigates the Thermoelastic and Second Harmonic signals on a fatigue loaded Single Edge Notched Tension (SENT) specimen made of stainless steel AISI 304L. Three load ratios are in particular applied, R=-1, 0, 0.1. The thermoelastic signal is used to evaluate the Stress Intensity Factor via two approaches, the Stanley-Chan linear interpolation method and the over-deterministic least-square fitting (LSF) method using the Williams’ series expansion. Regarding least-square fitting, an iterative procedure is proposed to identify the optimal crack tip position in the thermoelastic maps. The SIF and T-Stress are…
Analytical Prediction of the Flexural Response of External RC Joints with Smooth Rebars
2018
Nel presente lavoro viene presentato un modello analitico in forma chiusa in grado di riprodurre la risposta flessionale monotonica di nodi esterni trave-colonna in c.a. con armature lisce. La colonna viene sottoposta a carico verti-cale costante e la trave ad una forza laterale crescente monotonicamente applicata all’estremità. Il modello si basa sul comportamen-to flessionale di trave e colonna adottando un modello di cerniera plasticità concentrata che include lo scorrimento delle armature della trave. Si assume un dominio sforzo normale-momento bilineare semplificato da cui viene derivato il momento ultimo associato alla forza assiale di progetto. Per il nodo viene adottato un modello c…
Field estimation in wireless sensor networks using distributed kriging
2012
In this paper, we tackle the problem of spatial interpolation for distributed estimation in Wireless Sensor Networks by using a geostatistical technique called kriging. We present a novel Distributed Iterative Kriging Algorithm (DIKA) which is composed of two main phases. First, the spatial dependence of the field is exploited by calculating semivariograms in an iterative way. Second, the kriging system of equations is solved by an initial set of nodes in a distributed manner, providing some initial interpolation weights to each node. In our algorithm, the estimation accuracy can be improved by iteratively adding new nodes and updating appropriately the weights, which leads to a reduction i…
G1 rational blend interpolatory schemes: a comparative study
2012
Interpolation of triangular meshes is a subject of great interest in many computer graphics related applications, as, for example, gaming and realtime rendering. One of the main approaches to interpolate the positions and normals of the mesh vertices is the use of parametric triangular Bezier patches. As it is well known, any method aiming at constructing a parametric, tangent plane (G^1) continuous surface has to deal with the vertex consistency problem. In this article, we propose a comparison of three methods appeared in the nineties that use a particular technique called rational blend to avoid this problem. Together with these three methods we present a new scheme, a cubic Gregory patc…
Numerical Approximation of Elliptic Variational Problems
2003
This chapter is dedicated to the study of Elliptic Variational Inequalities (EVI). Different forms of such an EVI are considered. The Ritz—Galerkin discretization method is introduced, and methods to approximate the solution of an EVI are presented. The finite dimensional subspaces are built by use of the Finite Element Method. The discretized problems are solved using variants of the Successive OverRelaxation (SOR) method. The algorithms are tested on a typical example. The way to develop computer programs is carefully analysed.
Approximate survival probability determination of hysteretic systems with fractional derivative elements
2018
Abstract A Galerkin scheme-based approach is developed for determining the survival probability and first-passage probability of a randomly excited hysteretic systems endowed with fractional derivative elements. Specifically, by employing a combination of statistical linearization and of stochastic averaging, the amplitude of the system response is modeled as one-dimensional Markovian Process. In this manner the corresponding backward Kolmogorov equation which governs the evolution of the survival probability of the system is determined. An approximate solution of this equation is sought by employing a Galerkin scheme in which a convenient set of confluent hypergeometric functions is used a…
Error bounds for a convexity-preserving interpolation and its limit function
2008
AbstractError bounds between a nonlinear interpolation and the limit function of its associated subdivision scheme are estimated. The bounds can be evaluated without recursive subdivision. We show that this interpolation is convexity preserving, as its associated subdivision scheme. Finally, some numerical experiments are presented.