468 research outputs found
Coarsening Dynamics of a Nonconserved Field Advected by a Uniform Shear Flow
We consider the ordering kinetics of a nonconserved scalar field advected by
a uniform shear flow. Using the Ohta-Jasnow-Kawasaki approximation, modified to
allow for shear-induced anisotropy, we calculate the asymptotic time dependence
of the characteristic length scales, L_parallel and L_perp, that describe the
growth of order parallel and perpendicular to the mean domain orientation. In
space dimension d=3 we find, up to constants, L_parallel = gamma t^{3/2},
L_perp = t^{1/2}, where gamma is the shear rate, while for d = 2 we find
L_parallel = gamma^{1/2} t (ln t)^{1/4}, L_perp = gamma^{-1/2}(ln t)^{-1/4} .
Our predictions for d=2 can be tested by experiments on twisted nematic liquid
crystals.Comment: RevTex, 4 page
Dynamics and delocalisation transition for an interface driven by a uniform shear flow
We study the effect of a uniform shear flow on an interface separating the
two broken-symmetry ordered phases of a two-dimensional system with
nonconserved scalar order parameter. The interface, initially flat and
perpendicular to the flow, is distorted by the shear flow. We show that there
is a critical shear rate, \gamma_c, proportional to 1/L^2, (where L is the
system width perpendicular to the flow) below which the interface can sustain
the shear. In this regime the countermotion of the interface under its
curvature balances the shear flow, and the stretched interface stabilizes into
a time-independent shape whose form we determine analytically. For \gamma >
\gamma_c, the interface acquires a non-zero velocity, whose profile is shown to
reach a time-independent limit which we determine exactly. The analytical
results are checked by numerical integration of the equations of motion.Comment: 5 page
Influence of off-cut angle of (0001) 4H-SiC on the crystal quality of InN grown by RF-MBE
AbstractThe effect of the off-cut angle of a 4H-SiC (0001) substrate on the growth of InN thick layer by RF-plasma assisted molecular beam epitaxy (RF-MBE) has been investigated. The off-cut angle used in this study was inclined from 0° (just surface) toward the [11–20] direction of 4° and 8°. Crystalline quality and surface morphology were remarkably sensitive to the value of off-angle. Higher off-cut angles result in a reduction of the full-widths at half-maximum of HRXRD (0002) ω-scans, compared to that of the layer on the (0001)-just surface. In addition, the full-widths at halfmaximum of μ-Raman scattering spectra at 490cm-1, which is attributed to E2 (high) phonon mode, was decreased with increase in off-cut angle. Furthermore, In-droplets, which are commonly observed on the (0001) InN grown surface under In rich-growth condition, were found to be suppressed owing to an improvement of a nucleation on the off-cut angle surface. In our case, the use of 8°-off substrate increased film density and growth rate, while a surface roughness was reduced. These results clearly demonstrate that the larger off-cut angles improve the crystalline quality of InN film with reducing the In-droplets due to a higher step surface density on the off-cut angle surface
High Resolution T-O-F Positron Emission Tomograph
開始ページ、終了ページ: 冊子体のページ付
A Program for Computation of Magnetic Field of an Electromagnet
開始ページ、終了ページ: 冊子体のページ付
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