Search results for "Compres"

Image Compression by 2D Motif Basis

2011

Approaches to image compression and indexing based on extensions to 2D of some of the Lempel-Ziv incremental parsing techniques have been proposed in the recent past. In these approaches, an image is decomposed into a number of patches, consisting each of a square or rectangular solid block. This paper proposes image compression techniques based on patches that are not necessarily solid blocks, but are affected instead by a controlled number of undetermined or don't care pixels. Such patches are chosen from a set of candidate motifs that are extracted in turn from the image 2D motif basis, the latter consisting of a compact set of patterns that result from the autocorrelation of the image w…

Effect of air pressure on the electro-Fenton process at carbon felt electrodes

2018

Abstract The effect of air pressure on electro-Fenton (PrEF process) was evaluated using two organic substances (maleic acid and Acid Orange 7) as model organic pollutants. First experiments were performed using a conventional carbon felt (CF) cathode. At room pressure, a slow removal of maleic acid was obtained, together with the generation of formic acid. Conversely, using pressurized air, the removal of maleic acid was dramatically accelerated and the formation of formic acid was not detected. The utilization of a carbon felt modified by the deposition of carbon black + PTFE mixture (MCF) and of pressurized air allowed to achieve even faster and almost total (>95%) removal of total organ…

1980

Compression creep and stress-relaxation tests have been performed on PMMA at several deformations after the sample yielding. At large loading rates, the behaviour observed was found significantly affected by the temperature rise due to the plastic deformation. Creep and stress-relaxation data taken holding the samples at constant temperature after the material loading could be collected into single curves by means of a time shift factor proportional to the loading rate. Retardations- und Relaxationsuntersuchungen bei Druckbeanspruchung von PMMA wurden bei verschiedenen Deformationen oberhalb des Fliespunktes durchgefuhrt. Bei hohen Beanspruchungsgeschwindigkeiten wurde festgestellt, das das…

Dynamic Density Functional Theories for Inhomogeneous Polymer Systems Compared to Brownian Dynamics Simulations

2017

Dynamic density functionals (DDFs) are popular tools for studying the dynamical evolution of inhomogeneous polymer systems. Here, we present a systematic evaluation of a set of diffusive DDF theories by comparing their predictions with data from particle-based Brownian dynamics (BD) simulations for two selected problems: Interface broadening in compressible A/B homopolymer blends after a sudden change of the incompatibility parameter, and microphase separation in compressible A:B diblock copolymer melts. Specifically, we examine (i) a local dynamics model, where monomers are taken to move independently from each other, (ii) a nonlocal "chain dynamics" model, where monomers move jointly with…

Non-separable local polynomial regression cell-average multiresolution operators. Application to compression of images

2016

Abstract Cell-average multiresolution Harten׳s algorithms have been satisfactorily used to compress data. These schemes are based on two operators: decimation and prediction. The accuracy of the method depends on the prediction operator. In order to design a precise function, local polynomial regression has been used in the last years. This paper is devoted to construct a family of non-separable two-dimensional linear prediction operators approximating the real values with this procedure. Some properties are proved as the order of the scheme and the stability. Some numerical experiments are performed comparing the new methods with the classical linear method.

Non-linear Local Polynomial Regression Multiresolution Methods Using $$\ell ^1$$-norm Minimization with Application to Signal Processing

2015

Harten’s Multiresolution has been developed and used for different applications such as fast algorithms for solving linear equations or compression, denoising and inpainting signals. These schemes are based on two principal operators: decimation and prediction. The goal of this paper is to construct an accurate prediction operator that approximates the real values of the signal by a polynomial and estimates the error using \(\ell ^1\)-norm in each point. The result is a non-linear multiresolution method. The order of the operator is calculated. The stability of the schemes is ensured by using a special error control technique. Some numerical tests are performed comparing the new method with…

Non-consistent cell-average multiresolution operators with application to image processing

2016

In recent years different techniques to process signal and image have been designed and developed. In particular, multiresolution representations of data have been studied and used successfully for several applications such as compression, denoising or inpainting. A general framework about multiresolution representation has been presented by Harten (1996) 20. Harten's schemes are based on two operators: decimation, D , and prediction, P , that satisfy the consistency property D P = I , where I is the identity operator. Recently, some new classes of multiresolution operators have been designed using learning statistical tools and weighted local polynomial regression methods obtaining filters…

Accelerated weathering of polypropylene/wood flour composites

2008

Abstract Wood–plastic composites (WPCs) have received increasing attention during the last decades, because of many advantages related to their use. Some of their main applications are represented by outdoor furnishing and decking; therefore, it is important to assess their behaviour under UV exposure. In this work, polypropylene/wood flour composites were prepared and their resistance to photooxidation investigated. The composites were prepared by extrusion and compression moulding, and were subjected to mechanical tests, FTIR analysis and molecular weight measurements. The results showed that the composites retained a higher fraction of the original mechanical properties after accelerated…

Improved experimental characterization of crystallization kinetics

2005

Polymer solidification occurring in many processes, like for instance injection molding, compression molding and extrusion, is a complex phenomenon, strongly influenced by the thermo-mechanical history experienced by the material during processing. From this point of view, characterization of polymer crystallization in the range of processing con- ditions, i.e. including high cooling rate, is of great technological and academic interest. Quiescent, non-isothermal crys- tallization kinetics of two polypropylene resins were investigated using a new method, based on fast cooling of thin samples with air/water sprays and optical detection of the crystallization phenomenon. The range of cooling …

Quasi-brittle porous material: Simulated effect of stochastic air void structure on compressive strength

2021

Abstract The effect of porosity comprised of spherical air voids on the compressive strength of quasi-brittle material was studied via simulations. The simulated porous structures were based on pore size distributions of two mortar samples measured by X-ray microtomography. While the simulation method set practical limits on the size of sample, the base of the statistics was established by simulating 128 small structures generated by sampling from pore structures of two mortars. By studying the application of the classical strength-porosity formulas to the simulated data, a new simple model was formed. A linear relationship was achieved between the cubic root of air void fraction (porosity)…