Search results for "matrix"
showing 10 items of 3205 documents
Stylolite interfaces and surrounding matrix material: Nature and role of heterogeneities in roughness and microstructural development
2010
Rough pressure solution interfaces, like stylolites, are one of the most evident features of localized slow deformation in rocks of the upper crust. There is a general consensus that the development of these rough structures is a result of localized, stress enhanced, dissolution of material along a fluid filled interface, but little is known on the initiation of this roughness. The aim of this article is to reveal the role of heterogeneities initially present in the host-rock on roughness initiation. This should give insights on whether stylolite roughness is generated by a stress-induced instability or by the presence of disorder in the material (i.e. quenched noise). We use a microstructu…
A deep semantic segmentation-based algorithm to segment crops and weeds in agronomic color images
2022
Abstract In precision agriculture, the accurate segmentation of crops and weeds in agronomic images has always been the center of attention. Many methods have been proposed but still the clean and sharp segmentation of crops and weeds is a challenging issue for the images with a high presence of weeds. This work proposes a segmentation method based on the combination of semantic segmentation and K-means algorithms for the segmentation of crops and weeds in color images. Agronomic images of two different databases were used for the segmentation algorithms. Using the thresholding technique, everything except plants was removed from the images. Afterward, semantic segmentation was applied usin…
MICELLAR CHROMATOGRAPHIC PROCEDURE WITH DIRECT INJECTION FOR THE DETERMINATION OF SULFONAMIDES IN MILK AND HONEY SAMPLES
2001
The capability of liquid chromatography with micellar mobile phases of sodium dodecyl sulfate (SDS), of allowing the direct injection of biological fluids into reversed-phase columns, was applied to the determination of sulfonamides in milk and honey samples. The chromatographic behavior of a group of 15 sulfonamides was studied at pH 3.0 where the drugs showed a greater separation space. Acetonitrile was added to the mobile phase to decrease the retention of the most hydrophobic drugs and increase the efficiencies, which yielded a higher resolution. The samples were diluted with 0.10 M SDS to facilitate the solubilization of the matrix compounds and release the protein-bound drugs. The pro…
Polymer-matrix route to (Bi, Pb)2Sr2Ca2Cu3O10+δ: The role of Ca2CuO3☆
1993
Abstract The use of polyethylenimine as active matrix agent has provided a fast synthesis method for (Bi, Pb)2Sr2Ca2Cu3O10+δ, starting from aqueous acetic solutions combined with careful control of the procedural variables. The 110 K phase is obtained as the only superconducting phase after sintering in air during 42 h at 860°C. This technique yields homogeneously sized, large (ca. 20 μm) platelets of the superconducting material. The presence of an excess of calcium and copper over the stoichiometric requirements accelerates the formation of the superconducting phase. This excess, which appears in the resulting material as Ca2CuO3, influences the superconducting properties, other than Tc, …
A sliding mode approach to robust stabilisation of Markovian jump linear time-delay systems with generally incomplete transition rates
2015
Abstract This paper is devoted to investigating the problem of robust sliding mode control for a class of uncertain Markovian jump linear time-delay systems with generally uncertain transition rates (GUTRs). In this GUTR model, each transition rate can be completely unknown or only its estimate value is known. By making use of linear matrix inequalities technique, sufficient conditions are presented to derive the linear switching surface and guarantee the stochastic stability of sliding mode dynamics. A sliding mode control law is developed to drive the state trajectory of the closed-loop system to the specified linear switching surface in a finite-time interval in spite of the existing unc…
Isolated roundings and flattenings of submanifolds in Euclidean spaces
2005
We introduce the concepts of rounding and flattening of a smooth map $g$ of an $m$-dimensional manifold $M$ to the euclidean space $\R^n$ with $m<n$, as those points in $M$ such that the image $g(M)$ has contact of type $\Sigma^{m,\dots,m}$ with a hypersphere or a hyperplane of $\R^n$, respectively. This includes several known special points such as vertices or flattenings of a curve in $\R^n$, umbilics of a surface in $\R^3$, or inflections of a surface in $\R^4$.
Currents reconstruction by means of a new 2D extrapolation matrix
2007
The equivalent currents reconstructed on the surface of an antenna from its far field measurements have a limited resolution. This is because just the visible part of the spectrum, i.e. the inner part of the circle of radius k (the wavenumber), can be obtained with this technique. The zero padding technique is used for improving the precision; however this technique does not improve the resolution and additional methods must be applied. One of the most used is the Gerchberg-Papoulis algorithm. This technique obtains the non visible spectrum from just the visible region and the maximum size of the antenna. The main disadvantage of this algorithm is that, since it is iterative, it takes a lon…
Packing meterials with surface barriers, controlled distribution and topography of ligands for sample clean-up and analysis of biologically active so…
1991
Various types of, so-called, restricted access packings have been developed for sample clean-up and analysis of biologically active solutes by means of HPLC. The unique feature of these packings is that they prevent the access of matrix components such as protein whilst selectively retaining the drug components and their metabolites. This results from the fact that the particles of the packings possess a surface barrier for large solutes at the external or internal surface area and exhibit a controlled gradient in the chemical surface composition. They are grouped, according to their particle structures, into internal-surface reversed phases (ISRP), shielded hydrophobic phases (SHP), semi-p…
Surface Reflectance: An Optical Method for Multiscale Curvature Characterization of Wear on Ceramic–Metal Composites
2020
Surface gradient characterization by light reflectance (SGCLR) is used for the first time for multiscale curvature calculations and discrimination of worn surfaces on six damaged ceramic&ndash
The effect of detergents on the basement membrane complex of a biologic scaffold material
2013
The basement membrane complex (BMC) is a critical component of the extracellular matrix (ECM) that supports and facilitates the growth of cells. This study investigates four detergents commonly used in the process of tissue decellularization and their effect upon the BMC. The BMC of porcine urinary bladder was subjected to 3% Triton-X 100, 8 mM 3-[(3-cholamidopropyl) dimethylammonio]-1-propanesulfonate (CHAPS), 4% sodium deoxycholate or 1% sodium dodecyl sulfate (SDS) for 24 h. The BMC structure for each treatment group was assessed by immunolabeling, scanning electron microscopy (SEM) and second harmonic generation (SHG) imaging of the fiber network. The composition was assessed by quantif…