Conjugate gradients for symmetric positive semidefinite least-squares problems

The cgSLS (conjugate gradients for symmetric positive semidefinite least-squares) algorithm is presented. The algorithm exploits the cyclic property of invariant Krylov spaces to reduce the least-squares problem with a symmetric positive semidefinite matrix A to the minimization of the related energy function with the Hessian A on the range of A, so that a simple modification of the conjugate gradient (CG) method is applicable. At the same time, the algorithm generates approximations of the projection of the right-hand side to the range of A. The asymptotic rate of convergence of the new algorithm is proved to be the same as that of the CG method for the related consistent problem. An error bound in terms of the square root of the regular condition number of A is also given. The performance of the algorithm is demonstrated by numerical experiments.     

Effect of clay treatment on structure and mechanical behavior of elastomer-containing polyamide 6 nanocomposite

The effect of clay organophilization on mechanical behavior and structure of PA6/EPR blends was studied. It has been shown that the modification of clay affected simultaneously the degree of PA6 matrix reinforcement, size and structure of dispersed EPR. The localization of clay with less polar treatment in the interfacial area brought an important new effect consisting intensification of toughening effect of dispersed elastomer by formation of “core-shell” particles. Basic aspects governing formation of this advantageous structure are reported.The best balanced mechanical behavior was achieved when combining two differently modified clays, whereas the clay with less polar treatment is preblended with EPR. In this way, a high degree of matrix reinforcement (exfoliation of clay with more polar treatment) was combined with favorable size and structure of dispersed EPR phase. Additionally, at lower clay content, synergy between clay and elastomer phase, monitoring itself by enhancement of toughness, was found.     

TiO2-photocatalysis as a tertiary treatment of naturally treated wastewater

Solar TiO₂-photocatalysis was applied to waters from a natural wastewater treatment plant located in the Universidad de Las Palmas de Gran Canaria. Degussa P-25 TiO₂ and its mixture with activated carbon (AC–TiO₂) were used as catalysts. The presence of ozone and certain ions such as phosphates on the photocatalytic degradation of organic matter was also studied.

Disinfection experiments have provided interesting results, particularly when using the catalyst AC–TiO₂ and ozone, since total disinfection was achieved in less than 60 min. No bacterial reappearance at 24 or 48 h was observed. Additionally, this catalyst gave important TOC and some ions concentrations reductions.

Studies in catalyst reuse revealed that the catalyst AC–TiO₂ showed almost no deactivation.     

Musically meaningful fitness and mutation for autonomous evolution of rhythm accompaniment

Autonomous evaluation of computer generated musical pieces remains one of the most challenging open problems in evolutionary music composition. This paper introduces the design of novel mutation and fitness operators for autonomous evolution of human-competitive rhythm accompaniment using genetic algorithm. We propose several fitness operators that autonomously evaluate the quality of generated rhythm phrases according to patterns of another accompanying instrument, such as bass or rhythm piano, and according to user’s specified criteria such as a density of rhythm accompaniment. In the next, we introduce four musically meaningful mutation operators that alter rhythm consonance, dynamic phrasing, drum stroke types or perform syncopation of rhythm phrases. We also provide a complete example of mutation and fitness settings used for evolution of a rhythm accompaniment to Dizzy Gillespie’s “Night In Tunisia” jazz tune.     

Impact of the brewing process on the concentration of silicon in lager beer

Silicon is an important trace element that is believed to be essential, especially for the proper functioning of connective tissues. Beer is claimed to be an excellent source of bioavailable silicon. However, little is known about the impact of the brewing process on the concentration of silicon in beer. To clarify this relationship, the concentration of silicon in various lager beer samples was determined by instrumental neutron activation analysis, and the mass balance of silicon during the brewing process was calculated. The concentration of silicon ranged from 13.7 to 44.2 mg/L and was highly dependent on the type and quantity of the raw materials used, as well as on the brewing technology. The concentration of silicon in beers of the same brands brewed by distinct breweries did not differ significantly. The silicon mass balance showed that the main silicon source in beer is the barley malt and that the concentration of silicon in solution increases significantly after mashing, whereas it decreases after fermentation. The majority of silicon remains in the spent grains and the resulting beer contains only about 10% of the silicon present in the raw materials. The results confirmed that beer is a rich source of silicon in the human diet. In addition, the important factors that determine the silicon concentration in beer were identified. Copyright © 2014 The Institute of Brewing & Distilling     

An Analytical Model for Moisture Diffusion in Solid Objects During Drying

ABSTRACT

An analytical model is proposed to determine the moisture diffusivities in geometrical solid objects (namely, infinite slab, infinite cylinder, sphere) subjected to drying applications. The analysis for moisture diffusion is carried out on the basis of two imponant criteria: 0.l?Bi?100 and Bi>100. New correlations for the mots of the characteristic equations corresponding these objects are developed. For a drying application, using the similarity between cooling and drying profiles, drying coefficient and lag factor are obtained. The model is then verified using available data from literature.Results show that the presented model can be used to determine the moisture diffusion coefficients in such solid objects in a simple and accurate manner in a variety of drying applications.     

Growth and properties of few-layer graphene prepared by chemical vapor deposition

The structure and the electrical, mechanical and optical properties of few-layer graphene (FLG) synthesized by chemical vapor deposition (CVD) on a Ni-coated substrate were studied. Atomic resolution transmission electron microscope (TEM) images show highly crystalline single-layer parts of the sample changing to multi-layer domains where crystal boundaries are connected by chemical bonds. This suggests two different growth mechanisms. CVD and carbon segregation participate in the growth process and are responsible for the different structural formations found. Measurements of the electrical and mechanical properties on the centimeter scale provide evidence of a large scale structural continuity: (1) in the temperature dependence of the electrical conductivity, a non-zero value near 0 K indicates the metallic character of electronic transport; (2) Young’s modulus of a pristine polycarbonate film (1.37 GPa) improves significantly when covered with FLG (1.85 GPa). The latter indicates an extraordinary Young modulus value of the FLG-coating of TPa orders of magnitude. Raman and optical spectroscopy support the previous conclusions. The sample can be used as a flexible and transparent electrode and is suitable for use as special membranes to detect and study individual molecules in high-resolution TEM.     

Inactivation kinetics of food enzymes during ohmic heating

Ohmic heating of milk and fruit and vegetable juices was carried out at several incubation temperatures to investigate inactivation of alkaline phosphatase, pectin methylesterase and peroxidase. Mechanisms of inactivation of these enzymes and corresponding kinetic models were verified for each food material, using the multitemperature evaluation of inactivation data. Compared to inactivation by conventional indirect heating, kinetic parameters were changed but inactivation mechanisms remained the same. The kinetic parameter changes were relatively minor for pectin methylesterase and alkaline phosphatase. A significant destabilization of the labile isozyme fraction of peroxidase occurred by the effect of ohmic heating when the greatest decrease of stability was obtained for carrot juice.     

Effect of vanadium on grain boundary segregation of phosphorus in low alloy steels

The phosphorus grain boundary segregation at 853 K was investigated in three low alloy steels with different vanadium content. Kinetic dependence of the phosphorus grain boundary concentration was determined experimentally by means of AES and described theoretically, as well. To assess the influence of the individual alloying elements on the phosphorus segregation, the metal composition of carbide phases at 853 K was predicted by means of thermodynamic calculations and confirmed by experimental measurements (TEM + EDX). The vanadium was found to enhance the phosphorus grain boundary segregation by reducing the amount of dissolved and segregated carbon. Thereby, the equilibrium of mutual displacement C (segregated) ? P (segregated) was shifted to more phosphorus segregation. The results achieved indicate that vanadium indirectly increases sensitivity of low alloy steels to intergranular embrittlement.