4,249 research outputs found
Sintering behavior of ultrafine silicon carbide powders obtained by vapor phase reaction
The sintering behavior of ultrafine SiC powder with average particle size of about 0.01-0.06 microns produced by a vapor phase reaction of the Me4Si-H2 system was studied at the temperature range of 1400-2050 deg. It was found that the homogeneous dispersion of C on SiC particles is important to remove the surface oxide layer effectively. B and C and inhibitive effect on SiC grain growth
Microscopic description of light unstable nuclei with the stochastic variational method
The structure of the light proton and neutron rich nuclei is studied in a
microscopic multicluster model using the stochastic variational method. This
approach enables us to describe the weakly bound nature of these nuclei in a
consistent way. Applications for various nuclei Li, Be, B,
C, Be, B presented. The paper discusses the relation of
this model to other models as well as the possible extension for p and sd shell
nuclei.Comment: 11 pages, latex, no figures
Absence of surface mode in a visco-elastic material with surface tension
The surface waves in the visco-elastic media with the surface tension are
studied using the Voigt-Kelvin model of the visco-elasticity. It is shown that
the surface mode of oscillation does not exist in the parameter region where
the effect of surface tension is larger than that of the elastic stress at the
surface unless the viscous stress masks the elastic stress in the bulk. In the
region, the surface oscillation is suppressed and the oscillation beneath the
surface diffuses after the pulse goes into the bulk. The experimental relevance
of the present results is also discussed.Comment: 5 pages, 3 figure
Finite-size scaling for the Ising model on the Moebius strip and the Klein bottle
We study the finite-size scaling properties of the Ising model on the Moebius
strip and the Klein bottle. The results are compared with those of the Ising
model under different boundary conditions, that is, the free, cylindrical, and
toroidal boundary conditions. The difference in the magnetization distribution
function for various boundary conditions is discussed in terms of the
number of the percolating clusters and the cluster size. We also find
interesting aspect-ratio dependence of the value of the Binder parameter at
for various boundary conditions. We discuss the relation to the
finite-size correction calculations for the dimer statistics.Comment: 4 pages including 5 eps figures, RevTex, to appear in Phys. Rev. Let
Computer simulation of cold sprayed deposition using smoothed particle hydrodynamics
AbstractThe smoothed particle hydrodynamics (SPH) method is applied to simulate the cold spray (CS) process by modeling the impact of a spherical powder particle on substrate.In this work, the adhesive interaction between the contacting surfaces is described by intersurface forces using the cohesive zone model. The application of the SPH method permits simulation of the impact process without the use of mesh and thus avoids the disadvantages of traditional numerical method in handling large deformations and tracing moving interfaces in the highly transient non-linear dynamic CS process. The simulated deformed particle shape evolution and estimated critical velocity from other sources were compared and good agreement was obtained. The analyses demonstrate the feasibility of the presented SPH methodology and the adhesive interaction model for simulating the deformation behavior of CS particles
Shape Effects of Finite-Size Scaling Functions for Anisotropic Three-Dimensional Ising Models
The finite-size scaling functions for anisotropic three-dimensional Ising
models of size (: anisotropy parameter) are
studied by Monte Carlo simulations. We study the dependence of finite-size
scaling functions of the Binder parameter and the magnetization
distribution function . We have shown that the finite-size scaling
functions for at the critical temperature change from a two-peak
structure to a single-peak one by increasing or decreasing from 1. We also
study the finite-size scaling near the critical temperature of the layered
square-lattice Ising model, when the systems have a large two-dimensional
anisotropy. We have found the three-dimensional and two-dimensional finite-size
scaling behavior depending on the parameter which is fixed; a unified view of
3D and 2D finite-size scaling behavior has been obtained for the anisotropic 3D
Ising models.Comment: 6 pages including 11 eps figures, RevTeX, to appear in J. Phys.
Spin Wave Instability of Itinerant Ferromagnet
We show variationally that instability of the ferromagnetic state in the
Hubbard model is largely controlled by softening of a long-wavelength spin-wave
excitation, except in the over-doped strong-coupling region where the
individual-particle excitation becomes unstable first. A similar conclusion is
drawn also for the double exchange ferromagnet. Generally the spin-wave
instability may be regarded as a precursor of the metal-insulator transition.Comment: 11 pages, 8 figure
Important role of the spin-orbit interaction in forming the 1/2^+ orbital structure in Be isotopes
The structure of the second 0^+ state of ^{10}Be is investigated using a
microscopic model based on the molecular-orbit (MO) model.
The second 0^+ state, which has dominantly the (1/2^+)^2 configuration, is
shown to have a particularly enlarged structure. The kinetic
energy of the two valence neutrons occupying along the axis is
reduced remarkably due to the strong clustering and, simultaneously,
the spin-orbit interaction unexpectedly plays important role to make the energy
of this state much lower. The mixing of states with different spin structure is
shown to be important in negative-parity states. The experimentally observed
small-level spacing between 1^- and 2^- (~ 300 keV) is found to be an evidence
of this spin-mixing effect. ^{12}{Be} is also investigated using
model, in which four valence neutrons are considered to
occupy the (3/2^-)^2(1/2^+)^2 configuration. The energy surface of ^{12}Be is
shown to exhibit similar characteristics, that the remarkable
clustering and the contribution of the spin-orbit interaction make the binding
of the state with (3/2^-)^2(1/2^+)^2 configuration properly stronger in
comparison with the closed p-shell (3/2^-)^2(1/2^-)^2 configuration.Comment: 14 pages, 4 figure
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