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Variation Method (variation + method)
Selected AbstractsX, -DVM modelling of oxygen transport in YBa2Cu3O7-, and SrFeO3INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 10 2006Elmira I. YuryevaArticle first published online: 4 APR 200 Abstract The reasons for oxygen transport in YBa2Cu3O7-, and SrFeO3 were investigated, using the X, -discrete variation method. Reduced binding energy and other parameters of the electronic energy structure were calculated for a number of crystal fragments within the T and O phases of YBa2Cu3O7-, and the cubic phase of SrFeO3. The following results were obtained: (i) test calculations of reduced binding energy confirmed that high temperature should be a condition of existence of the T phase, as compared with the O phase of YBa2Cu3O7-,; (ii) an increase in temperature up to ,400°C points to the beginning of the Jahn,Teller dynamic effect in SrFeO3; and (iii) transport of neutral and charged oxygen atoms results in distributions of stable and unstable oxygen vacancies, respectively. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] The application of distance distribution functions to structural analysis of core,shell particlesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2007Oleksandr O. Mykhaylyk The structure of core,shell latex particles of polymethylmethacrylate (the core) and polyurethane (the shell) have been investigated by methods of small-angle X-ray scattering (SAXS) and atom-force microscopy. A set of SAXS patterns has been obtained using contrast variation method. Indirect methods have been used to follow the evolution of distance distribution functions from SAXS for lattices in various sucrose solutions over a range of solution density, yielding structural parameters of the particles such as core size, shell thickness and density of the polymers including density deviations within the particle's core and shell. A model for an ensemble of core,shell particles with a normal distribution of average electron density of both the core and the shell has been developed to fit the distance distribution functions using a random search algorithm. The effects of nanophase separation in the polyurethane is estimated using Monte Carlo simulations of the distance distribution functions where the phase-separated polyurethane is represented by spherical truncated cones in a shell simulating the location of hard and soft polyurethane blocks, respectively. [source] Anisotropic diffraction peak broadening and dislocation substructure in hydrogen-cycled LaNi5 and substitutional derivativesJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 4 2000Anisotropic peak broadening in hydrogen-cycled hexagonal LaNi5 and substitutional derivatives has been studied by means of synchrotron powder diffraction. The data have been analysed by a local lattice parameter variation method implemented in a Rietveld code and by an individual profile fitting using a dislocation peak broadening model. Two main dislocation systems, both with Burgers vector 1/3,110,, are activated by misfit of the lattice parameters between the intermetallic compounds and their hydrides. Two types of diffraction peak broadening effect were observed as a function of the substitution in LaNi5: (i) a decrease or disappearance of the broadening related to the decrease of the total dislocation density and (ii) a change in the anisotropy of the broadening related to the change of the nature of the dislocation system involved. The latter effect was attributed to a change in shape of the hydride precipitates. [source] Rheology behavior of high-density polyethylene/diluent blends and fabrication of hollow-fiber membranes via thermally induced phase separationJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2010Jianli Wang Abstract The phase-separation behavior of high-density polyethylene (HDPE)/diluent blends was monitored with a torque variation method (TVM). The torque variation of the molten blends was recorded with a rheometer. It was verified that TVM is an efficient way to detect the thermal phase behavior of a polymer,diluent system. Subsequently, polyethylene hollow-fiber membranes were fabricated from HDPE/dodecanol/soybean oil blends via thermally induced phase separation. Hollow-fiber membranes with a dense outer surface of spherulites were observed. Furthermore, the effects of the spinning temperature, air-gap distance, cold drawing, and HDPE content on the morphology and gas permeability of the resultant membranes were examined. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] | ||||||||||