Search results for "FAST"

Áreas Ecoculturales y espacios de comunicación : el espacio iberoamericano

1983

Residual Stresses Induced by Cold Expansion of Adjacent and Cut-Out Holes

2012

Fatigue life of fastener holes can be enhanced via a cold-expansion process to introduce a compressive residual stress field around the hole edge and to reduce crack growth propagation. Considering that aerospace components contain multiple rows of holes, the present investigation focuses on the evaluation of the three-dimensional residual stress distribution in adjacent cold-expanded (CE) holes. The redistribution of residual stresses caused by a cut introduced between two adjacent holes was also investigated. Finite element (FE) analysis and experimental technique were used to assess the residual stress distribution in a 6082-T6 aluminum plate with two adjacent holes expanded sequentially…

Contribución al conocimiento algológico del litoral levantino (España, Mediterráneo) III

1991

Se cita la presencia de 18 táxones de algas marinas interesantes procedentes del litoral levantino (España, Medinterráneo occidental). Veinticuatro constituyen nuevas citas para dicho tramo del litoral mediterráneo peninsular. Destaca la presencia de Peyssonnelia feldmannii, Ceramium fastigiatum var. flaccida, y Cystoseria sauvageauana va. polyoedematis. The records of 28 taxa of marine algae from the Central Mediterranean coast of Spain are given. 24 are new records for this sector of Spanish coast. Specilly interesting are Peyssonnelia codana, recorded for first time in the mediterranean coasts of Spain, Peyssonnelia feldmannii, Ceramium fastigiatum var. flaccida, y Cystoseria sauvageauan…

On the accuracy of the fast hierarchical DBEM for the analysis of static and dynamic crack problems

2010

In this paper the main features of a fast dual boundary element method based on the use of hierarchical matrices and iterative solvers are described and its effectiveness for fracture mechanics problems, both in the static and dynamic case, is demonstrated. The fast solver is built by representing the collocation matrix in hierarchical format and by using a preconditioned GMRES for the solution of the algebraic system. The preconditioner is computed in hierarchical format by LU decomposition of a coarse hierarchical representation of the collocation matrix. The method is applied to elastostatic problems and to elastodynamic cases represented in the Laplace transform domain. The application …

Quasi-Newton approach to nonnegative image restorations

2000

Abstract Image restoration, or deblurring, is the process of attempting to correct for degradation in a recorded image. Typically the blurring system is assumed to be linear and spatially invariant, and fast Fourier transform (FFT) based schemes result in efficient computational image restoration methods. However, real images have properties that cannot always be handled by linear methods. In particular, an image consists of positive light intensities, and thus a nonnegativity constraint should be enforced. This constraint and other ways of incorporating a priori information have been suggested in various applications, and can lead to substantial improvements in the reconstructions. Neverth…

Fast algorithms for free-space diffraction patterns calculation

1999

Here we present a fast algorithm for Fresnel integral calculation. Some fast algorithms using the fast Fourier transform are analysed and their performance has been checked. These methods are of easy implementation, but are only valid for a specific range of distances. Fast algorithms based on the Fractional Fourier transform allow accurate evaluation of the Fresnel integral from object to Fraunhofer domain in a single step.

Effect of anion substitution on the structural and transport properties of argyrodites Cu7PSe6−xSx

2019

Inspired by the good performance of argyrodites as ion conducting thermoelectrics and as solid electrolytes we investigated the effect of isovalent S2- substitution for Se2- in Cu7PSe6. At room temperature Cu7PSe6 crystallizes in the primitive cubic β-polymorph of the argyrodite structure and transforms to the face-centered high-temperature (HT) γ-modification above 320 K. The transition for the homologous Cu7PS6 occurs at 510 K. Promising thermoelectric and ion conducting properties are observed only in the HT modification, where the cations are mobile. Using Rietveld refinements against X-ray diffraction data the effect of isovalent S2- substitution for Se2- on the structural and transpor…

Optical control of vibrational coherence triggered by an ultrafast phase transition

2019

Femtosecond time-resolved x-ray diffraction is employed to study the dynamics of the periodic lattice distortion (PLD) associated with the charge-density-wave (CDW) in K0.3MoO3. Using a multi-pulse scheme we show the ability to extend the lifetime of coherent oscillations of the PLD about the undistorted structure through re-excitation of the electronic states. This suggests that it is possible to enter a regime where the symmetry of the potential energy landscape corresponds to the high symmetry phase but the scattering pathways that lead to the damping of coherent dynamics are still controllable by altering the electronic state population. The demonstrated control over the coherence time …

The computational complexity of the relative robust shortest path problem with interval data

2004

Abstract The paper deals with the relative robust shortest path problem in a directed arc weighted graph, where arc lengths are specified as intervals containing possible realizations of arc lengths. The complexity status of this problem has been unknown in the literature. We show that the problem is NP -hard.

A class of label-correcting methods for the K shortest paths problem

2001

In this paper we deal with the problem of finding the first K shortest paths from a single origin node to all other nodes of a directed graph. In particular, we define the necessary and sufficient conditions for a set of distance label vectors, on the basis of which we propose a class of methods which can be viewed as an extension of the generic label-correcting method for solving the classical single-origin all-destinations shortest path problem. The data structure used is characterized by a set of K lists of candidate nodes, and the proposed methods differ in the strategy used to select the node to be extracted at each iteration. The computational results show that: 1. some label-correct…