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991.
K. N. Volkov 《Computational Mathematics and Mathematical Physics》2013,53(4):503-519
The features of a simplified approach to coupled thermal analysis problems as based on the integration of the energy equation for a viscous compressible gas are discussed. The gas velocity field is assumed to be frozen, and a single iteration is run to update it at each step of the coupling procedure. The equation describing the temperature distribution in a solid is discretized using the finite element method, while the Navier-Stokes equations describing the velocity and gas temperature distributions are discretized using the finite-volume method. The system of difference equations resulting from the finite-volume discretization is solved by applying a multigrid method and the generalized minimal residual method. The capabilities of the approaches developed are demonstrated by solving several model problems. The accelerations of the computational algorithm obtained with the use of the full and simplified approaches to the solution of the problem and various methods for solving the system of difference equations are compared. 相似文献
992.
E. A. Volkov 《Computational Mathematics and Mathematical Physics》2013,53(10):1494-1498
The existence and uniqueness of a classical solution to the nonlocal boundary value problem for Poisson’s operator on a two-dimensional rectangular domain is proved in detail by applying the contraction mapping principle. 相似文献
993.
Zh. A. Devizorova A. V. Shchepetilnikov Yu. A. Nefyodov V. A. Volkov I. V. Kukushkin 《JETP Letters》2014,100(2):102-109
One-body mechanisms of spin splitting of the energy spectrum of 2D electrons in a one-side doped (001) GaAs/Al x Ga1 ? x As quantum well have been studied theoretically and experimentally. The interfacial spin splitting has been shown to compensate (enhance) considerably the contribution of the bulk Dresselhaus (Bychkov-Rashba) mechanism. The theoretical approach is based on the solution of the effective mass equation in a quasi-triangular well supplemented by a new boundary condition at a high and atomically sharp hetero-barrier. The model takes into account the spin-orbit interaction of electrons with both bulk and interfacial crystal potential having C 2v symmetry, as well as the lack of inversion symmetry and nonparabolicity of the conduction band in GaAs. The effective 2D spin Hamiltonian including both bulk and interface contributions to the Dresselhaus (αBIA) and Rashba (αSIA) constants has been derived. The analytical relation between these constants and the components of the anisotropic nonlinear g-factor tensor in an oblique quantizing magnetic field has been found. The experimental approach is based, on one hand, on the detection of electron spin resonance in the microwave range and, on the other hand, on photoluminescence measurements of the nonparabolicity parameter. The interface contributions to αBIA and αSIA have been found from comparison with the theory. 相似文献
994.
The composite materials Cs(HSO4)1?x (H2PO4) x were investigated by X-ray phase analysis, differential scanning calorimetry, nuclear magnetic resonance (NMR) relaxation, pulsed field gradient NMR (PFG-NMR) and impedance spectroscopy. Three composite materials types x = 0.1 ÷ 0.3 mixture CsHSO4, α-Cs3(HSO4)2(H2PO4), β-Cs3(HSO4)2.5(H2PO4)0.5—compositions of area I; x = 0.4 ÷ 0.5 mixture α-Cs3(HSO4)2(H2PO4) and Cs2(HSO4)(H2PO4)—compositions of area II; x = 0.6 ÷ 0.9 mixture Cs2(HSO4)(H2PO4) and CsH2PO4—compositions of area III, were synthesized. The phase transition temperature from the low-to-high conductive phase for obtained composite materials is notably below (about 100 °C) than that for the individual components. The proton self-diffusion coefficients measured by PFG-NMR are lower than the diffusion coefficients calculated from proton conductivities data. The correlation times τ d controlling the 31P–1H magnetic dipole–dipole interaction were calculated according to data of the spin–lattice relaxation on 31P nuclei. The self-diffusion coefficients estimated from the Einstein equation are in good agreement with the experimental self-diffusion coefficients measured by PFG-NMR. It confirms the fact that the proton mobility is caused by the rotation of PO4 anion tetrahedra. 相似文献
995.
A. V. Kanaki S. P. Buyakova S. A. Volkov S. N. Kulkov 《Russian Physics Journal》2011,53(12):1271-1274
Results obtained from differential scanning calorimetry and a thermogravimetric analysis of zirconia-based nanocrystalline
powder systems are presented. Heating is found to cause intense mass loss that increases with increase in the MgO content.
Differential scanning calorimetry has revealed that the total energy expended for reactions involved in the powder heating
process increases with increase in the MgO content. The heated powders are characterized by desorption of water. For 10 wt.
% MgO, residual nitrates are seen to decompose into NO2, N2O, or NO. 相似文献
996.
Because of a large (m = 1.8%) lattice mismatch between La0.67Ca0.33MnO3 and LaAlO3, manganite films grown on a lanthanum aluminate substrate experience biaxial mechanical compression stresses. Strong adhesion
to the substrate causes a substantial tetragonal distortion (γ ≈ 1.04) of the unit cell in a 20-nm-thick layer of the manganite
film coherently grown on (001)LaAlO3, while in the remaining part (≈75%) of the manganite film, stresses partially relax. The stress relaxation decreases γ and
increases the effective volume of the unit cell of the La0.67Ca0.33MnO3 film. The relaxed part of the La0.67Ca0.33MnO3 film consists of crystallites 50–200 nm across azimuthally misoriented by approximately 0.3°. The temperature dependences
of the resistivity and negative magnetoresistance of the manganite films exhibit maxima at 240 and 215 K, respectively. At
temperatures below 50 K, the dependence of the resistivity on the magnetic induction taken with the induction varying from
0 to 14 T and vice versa becomes hysteresis. 相似文献
997.
The uniaxial compaction of nanopowders is simulated using the granular dynamics in the 2D geometry. The initial arrangement
of particles is represented by (i) a layer of particles executing Brownian motion (isotropic structures) and (ii) particles
falling in the gravity field (anisotropic structures). The influence of size effects and the size of a model cell on the properties
of the structures are studied. The compaction of the model cell is simulated with regard to Hertz elastic forces between particles,
Cattaneo-Mindlin-Deresiewicz shear friction forces, and van der Waals-Hamaker dispersion forces of attraction. Computation
is performed for monodisperse powders with particle sizes ranging from 10 to 400 nm and for “cohesionless” powder, in which
attractive forces are absent. It is shown that taking into account dispersion forces makes it possible to simulate the size
effect in the nanopowder compaction: the compressibility of the nanopowder drops as the particles get finer. The mean coordination
number and the axial and lateral pressures in the powder systems are found, and the effect of the density and isotropy of
the initial structure on the compressibility is analyzed. The applicability of well-known Rumpf’s formula for the size effect
is discussed. 相似文献
998.
999.
N. V. Volkov I. V. Oleinikov E. A. Anan’eva 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2011,5(2):236-239
The results of study of ion-cleaned and -implanted surfaces of polycrystalline Be, Al, Ti, Fe, Cu, Mo, Zr, and W using optical
and infrared (IR) spectroscopy are presented. It is shown that major changes in the optical reflectance spectra are observed
in the range of 190–250 nm and are associated with both the formation of scattering centers and features of the chemical state
of near-surface layers of materials. It is established using IR spectroscopy that treatment by Ar+ ion beam with a broad energy spectrum increases the reflection coefficient of the modified surface and additional resonance
lines related to the formation of oxides themselves and hydroxyl groups are revealed in the reflectance spectrum in the case
of formation of oxide film on the surface. 相似文献
1000.
Sukhanova T. E. Vylegzhanina M. E. Volkov A. Ya. Gasilova E. R. Kutin A. A. Samy Moshera Abdallah Heba M. Ayoub Magdy M. H. 《Technical Physics》2019,64(12):1729-1737
Technical Physics - The morphology, structure, and optical properties of composites with biodegradable polymeric particles, which are based on poly-ε-caprolactone–polyvinyl alcohol... 相似文献