50,277 research outputs found
The motion of a deformable drop in a second-order fluid
The cross-stream migration of a deformable drop in a unidirectional shear flow of a second-order fluid is considered. Expressions for the particle velocity due to the separate effects of deformation and viscoelastic rheology are obtained. The direction and magnitude of migration are calculated for the particular cases of Poiseuille flow and simple shear flow and compared with experimental data
Computation of topside ionograms from N/h/ profiles
Computation of topside ionograms from electron concentration profile
Spin-dependent tunneling through a symmetric semiconductor barrier: the Dresselhaus effect
Spin-dependent tunneling through a symmetric semiconductor barrier is studied
including the k^3 Dresselhaus effect. The spin-dependent transmission of
electron can be obtained analytically. By comparing with previous work(Phys.
Rev. B 67. R201304 (2003) and Phys. Rev. Lett. 93. 056601 (2004)), it is shown
that the spin polarization and interface current are changed significantly by
including the off-diagonal elements in the current operator, and can be
enhanced considerably by the Dresselhaus effect in the contact regions.Comment: 10 pages, 5 figures, to appear in PR
Monte Carlo simulations of bosonic reaction-diffusion systems
An efficient Monte Carlo simulation method for bosonic reaction-diffusion
systems which are mainly used in the renormalization group (RG) study is
proposed. Using this method, one dimensional bosonic single species
annihilation model is studied and, in turn, the results are compared with RG
calculations. The numerical data are consistent with RG predictions. As a
second application, a bosonic variant of the pair contact process with
diffusion (PCPD) is simulated and shown to share the critical behavior with the
PCPD. The invariance under the Galilean transformation of this boson model is
also checked and discussion about the invariance in conjunction with other
models are in order.Comment: Publishe
An Efficient Block Circulant Preconditioner For Simulating Fracture Using Large Fuse Networks
{\it Critical slowing down} associated with the iterative solvers close to
the critical point often hinders large-scale numerical simulation of fracture
using discrete lattice networks. This paper presents a block circlant
preconditioner for iterative solvers for the simulation of progressive fracture
in disordered, quasi-brittle materials using large discrete lattice networks.
The average computational cost of the present alorithm per iteration is , where the stiffness matrix is partioned into
-by- blocks such that each block is an -by- matrix, and
represents the operational count associated with solving a block-diagonal
matrix with -by- dense matrix blocks. This algorithm using the block
circulant preconditioner is faster than the Fourier accelerated preconditioned
conjugate gradient (PCG) algorithm, and alleviates the {\it critical slowing
down} that is especially severe close to the critical point. Numerical results
using random resistor networks substantiate the efficiency of the present
algorithm.Comment: 16 pages including 2 figure
Leaf segmentation and tracking using probabilistic parametric active contours
Active contours or snakes are widely used for segmentation and tracking. These techniques require the minimization of an energy function, which is generally a linear combination of a data fit term and a regularization term. This energy function can be adjusted to exploit the intrinsic object and image features. This can be done by changing the weighting parameters of the data fit and regularization term. There is, however, no rule to set these parameters optimally for a given application. This results in trial and error parameter estimation. In this paper, we propose a new active contour framework defined using probability theory. With this new technique there is no need for ad hoc parameter setting, since it uses probability distributions, which can be learned from a given training dataset
Phase transition in the Higgs model of scalar dyons
In the present paper we investigate the phase transition
"Coulomb--confinement" in the Higgs model of abelian scalar dyons -- particles
having both, electric and magnetic , charges. It is shown that by dual
symmetry this theory is equivalent to scalar fields with the effective squared
electric charge e^{*2}=e^2+g^2. But the Dirac relation distinguishes the
electric and magnetic charges of dyons. The following phase transition
couplings are obtained in the one--loop approximation:
\alpha_{crit}=e^2_{crit}/4\pi\approx 0.19,
\tilde\alpha_{crit}=g^2_{crit}/4\pi\approx 1.29 and \alpha^*_{crit}\approx
1.48.Comment: 16 pages, 2 figure
Calculation of composition distribution of ultrafine ion-H2O-H2SO4 clusters using a modified binary ion nucleation theory
Thomson's ion nucleation theory was modified to include the effects of curvature dependence of the microscopic surface tension of field dependent, nonlinear, dielectric properties of the liquid; and of sulfuric acid hydrate formation in binary mixtures of water and sulfuric acid vapors. The modified theory leads to a broadening of the ion cluster spectrum, and shifts it towards larger numbers of H2O and H2SO4 molecules. Whether there is more shifting towards larger numbers of H2O or H2SO4 molecules depends on the relative humidity and relative acidity of the mixture. Usually, a broadening of the spectrum is accompanied by a lowering of the mean cluster intensity. For fixed values of relative humidity and relative acidity, a similar broadening pattern is observed when the temperature is lowered. These features of the modified theory illustrate that a trace of sulfuric acid can facilitate the formation of ultrafine, stable, prenucleation ion clusters as well as the growth of the prenucleation ion clusters towards the critical saddle point conditions, even with low values of relative humidity and relative acidity
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