Simulation of deuterium reflection from plasma-sprayed tungsten

A method of computer simulation of the formation of plasma-sprayed tungsten surface is proposed. The dependencies of the reflection coefficients of hydrogen isotopes on the energy of incident particles in the range from 5 to 10⁴ eV were obtained for this surface. It is shown that, at energies about 10 eV, the reflection coefficient for the surface of plasma-sprayed tungsten is smaller than that for a smooth surface by a factor of 1.5; this decrease corresponds to the increase in the deuterium incorporation coefficient by a factor of 2.     

Structure and electrical properties of thin films of copper selenide

Electron-diffraction and electron-microscope methods were used to investigate the structure of Cu₂Se films of close to stoichiometric composition. It is shown that in polycrystalline and single-crystal films of thickness >400Å at room temperature, the tetragonal modification is stable, which at temperatures above 400°K is transformed into the cubical modification. In thinner films d<400 Å the cubical modification of copper selenide is stable at room temperature. A sharp peak is observed at 400°K on the temperature dependence of the resistance; this is connected with the phase transition. At room temperature, copper selenide is a degenerate p-type semiconductor with carrier concentration 5 · 10²²–8 · 10²⁰ cm^–3, depending on the thickness of the film.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 90–94, August, 1973.     

Lattice gauge theory calculations using an improved strong-coupling expansion and matrix Padé approximants

Matrix methods are used to obtain better convergence of low-order lattice calculations. Strong-coupling expansions for the Hamiltonian matrix in a non-degenerate subspace of states are extrapolated to zero lattice spacing using matrix Padé approximants. The method is applied first to the massive Schwinger model and the continuum estimates from different fourth-order calculations compared. Then it is used to calculate the ratios of the π, ? and ω meson masses to the nucleon mass in a Hamiltonian lattice formulation of QCD.     

Mean field and Monte Carlo studies of SU(N) chiral models in three dimensions

SU(N) chiral models defined on three-dimensional cubic lattices arestudied using mean field and Monte Carlo techniques. Mean field theory predicts first-order transitions for all finite N greater than two. The mean field estimates of the transition temperature and discontinuity of the order parameter are in good agreement with computer simulations for N = 3 and 4. The N → ∞ limit of mean field theory has a first-order phase transition.     

Anisotropy of the Refractive Indices and Thermal Expansion Coefficients of Rb2ZnCl4 Crystals

Crystallography Reports - The temperature dependences of the optical path difference ∆і(Т) and relative changes δlі/lі in the thickness of Rb2ZnCl4 crystals have...     

Optimal <Emphasis Type="Italic">L</Emphasis><Superscript>1</Superscript>-Control in Coefficients for Dirichlet Elliptic Problems: <Emphasis Type="Italic">W</Emphasis>-Optimal Solutions

In this paper, we study a Dirichlet optimal control problem associated with a linear elliptic equation the coefficients of which we take as controls in the class of integrable functions. The coefficients may degenerate and, therefore, the problems may exhibit the so-called Lavrentieff phenomenon and non-uniqueness of weak solutions. We consider the solvability of this problem in the class of W-variational solutions. Using a concept of variational convergence of constrained minimization problems in variable spaces, we prove the existence of W-solutions to the optimal control problem and provide the way for their approximation. We emphasize that control problems of this type are important in material and topology optimization as well as in damage or life-cycle optimization.     

Birefringence properties of mechanically clamped K2ZnCl4 crystals

The effect of uniaxial pressure applied along the principal crystallographic directions on the dispersion and temperature dependences of the birefringence Δn _i of K₂ZnCl₄ crystals has been studied. It has been established that the birefringence Δn _i is sensitive to uniaxial pressures and that the uniaxial stresses do not change the character of the dispersion and temperature dependences of Δn _i . A new “pseudoisotropic” state of this crystal has been revealed. It has been found that the points of the paraphase-incommensurate phase-commensurate phase transitions can be significantly shifted under pressure toward different temperature ranges depending on the direction of the applied pressure due to the effect of uniaxial stresses on the structure of the K₂ZnCl₄ crystal.     

Electrokinetic Removal of Hydrophobic Organic Compounds from Soil

Electrokinetic technique for soil decontamination to remove hydrophobic organic compounds, based on application of direct electric field to soil sample preliminarily treated with solutions of chelating agent and a nonionic surfactant, was developed. The influence of various factors on electroosmotic flow in soddy podzolic soil sample was studied.     

Simulation of dynamic changes in the surface composition of tungsten under ion irradiation with regard to carbon impurity deposition

Argon ion cleaning of a tungsten surface covered by a carbon film was simulated taking into account the redeposition of graphite. An increase in the argon ion energy from 200 to 1000 eV greatly enhances cleaning. The cleaning rate is lowered when the carbon flux to the surface increases.     

Self-assembled growth of nanostructural Ge islands on bromine-passivated Si(111) surfaces at room temperature

We have deposited relatively thick (∼60 nm) Ge layers on Br-passivated Si(111) substrates by thermal evaporation under high vacuum conditions at room temperature. Ge has grown in a layer-plus-island mode although it is different from the Stranski-Krastanov growth mode observed in epitaxial growth. Both the islands and the layer are nanocrystalline. This appears to be a consequence of reduction of surface free energy of the Si(111) substrate by Br-passivation. The size distribution of the Ge nanoislands has been determined. The Br-Si(111) substrates were prepared by a liquid treatment, which may not produce exactly reproducible surfaces. Nevertheless, some basic features of the nanostructural island growth are reasonably reproducible, while there are variations in the details of the island size distribution.