Search results for " Fourier"

Complete isochromatic fringe order analysis in digital photoelasticity by Fourier Transform and load Stepping

2005

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…

Microstructure and characteristic properties of dogfish skin gelatin gels prepared by freeze/spray-drying methods

2020

International audience; The effects of two pretreatments (microwaves or oven-drying) on the dogfish (Squalus acanthias) skin as well as two drying processes (freeze-drying or spray-drying) on the extracted gelatins were studied. Thus six types of gelatins were obtained, three of which were freeze-dried (FG) and the others were spray-dried (SG), from the untreated skin (US), microwaves-pretreated skin (MS) and oven-pretreated skin (OS). The highest yield (8.67%) was obtained for the OSFG, while the lowest one (3.06%) was measured for the OSSG. Interestingly, all gelatins exhibited relatively high protein (84.02-89.53%), and low lipid (0.50-1.71%) and ash (3.05-7.17%) contents. In addition, g…

Physicochemical investigation of acrylamide solubilization in sodium bis(2-ethylhexyl)sulfosuccinate and lecithin reversed micelles.

2003

The state of acrylamide confined within dry sodium bis(2-ethylhexyl)sulfosuccinate (AOT) and lecithin reversed micelles dispersed in CCl4 has been investigated by FTIR and H-1 NMR spectroscopy. Measurements have been performed at 25 degreesC as a function of the acrylamide-to-surfactant molar ratio (R) at a fixed surfactant concentration (0.1 mol kg(-1)). The analysis of experimental data, corroborated by the results of SAXS measurements, is consistent with the hypothesis that acrylamide is quite uniformly distributed among reversed micelles mainly located in proximity to the surfactant head-group region and that its presence induces significant unidimensional growth of micellar aggregates.…

Structure of calcium and zinc pectinate films investigated by FTIR spectroscopy

2010

International audience; Calcium and zinc pectinate gels were prepared using a method which allowed calcium or zinc to diffuse from the cross-linking solution through a dialysis membrane to form a gel with amidated low-methoxyl pectin. The gel thus obtained was then dried, and the film structure was studied using FTIR spectroscopy as a function of the cation content (0%, 5%, 10%, and 15% w/v). Important consideration was given to the three functional groups (amide, carboxyl ester, and carboxylate groups) present in the pectin. When the zinc content was increased, the three wavenumber values corresponding to these three functional groups did not change significantly, while for calcium pectina…

Gastrosophie, gastroscience, gastropoésie. Les estomacs de Charles Fourier

2016

International audience

Bearing fault detection based on time-frequency representations of vibration signals

2015

To prevent failures of a rolling bearing in the gearbox drive system, acceleration sensors are used to detect fault-related signals of the bearing. It is a big challenge to observe and identify signals caused by bearing defects in the time domain or the frequency spectrum by a conventional Fourier analysis. The time-frequency representation of the fault-related signals implemented by the windowed Fourier transform is studied in this work. It is shown that the fault characteristic frequencies can be clearly identified in the time-frequency spectrum if a fault occurs in the bearing of the gearbox at different speeds. Otherwise, the shaft frequency and its multiples are the main harmonics in t…

The shell matrix of the freshwater mussel Unio pictorum (Paleoheterodonta, Unionoida). Involvement of acidic polysaccharides from glycoproteins in na…

2007

13 pages; International audience; Among molluscs, the shell biomineralization process is controlled by a set of extracellular macromolecular components secreted by the calcifying mantle. In spite of several studies, these components are mainly known in bivalves from only few members of pteriomorph groups. In the present case, we investigated the biochemical properties of the aragonitic shell of the freshwater bivalve Unio pictorum (Paleoheterodonta, Unionoida). Analysis of the amino acid composition reveals a high amount of glycine, aspartate and alanine in the acid-soluble extract, whereas the acid-insoluble one is rich in alanine and glycine. Monosaccharidic analysis indicates that the in…

Complexes of Glycolic Acid with Nitrogen Isolated in Argon Matrices. I. Structures and Thermal Effects.

2019

Molecular complexes between glycolic acid and nitrogen were studied in a low-temperature argon matrix with FTIR spectroscopy, and supported by MP2 and BLYPD3 calculations. The calculations indicate 11 and 10 stable complex structures at the MP2 and BLYPD3 levels of theories, respectively. However, only one hydrogen-bonded complex structure involving the most stable SSC conformer of glycolic acid was found experimentally, where the nitrogen molecule is bound with the carboxylic OH group of the SSC conformer. The complex shows a rich site structure variation upon deposition of the matrix in different temperatures and upon annealing experiments, which provide interesting prospects for site-sel…

Metal ions modulate thermal aggregation of betalactoglobulin: a join chemical and physical characterization

2014

Abstract Molecular basis of the role played by Cu 2 + and Zn 2 + ions during the thermal aggregation processes of beta-lactoglobulin (BLG) was studied by using a joint application of different techniques. In particular, Raman spectroscopy was very useful in identifying the different effects caused by the two metals at molecular level (i.e. changes in His protonation state, disulfides bridge conformation, and micro-environment of aromatic residues), evidencing the primary importance of the protein charge distribution during the aggregation process. Both metal ions are able to act on this factor and favor the protein aggregation, but Zn 2 + is able to alter the natural conformational state of…