Coupled-channel optical calculation for positron-lithium scattering

Positron scattering with atomic lithium is investigated by using a coupled-channel optical method.The ionization continuum and positronium formation channels are taken into account via a complex equivalent-local optical potential.The positronium formation cross sections and the ionization cross sections,as well as the total scattering cross sections,are reported at energies above 3 eV and compared with available experimental and theoretical data.

POSITIVE SOLUTIONS TO THE p-LAPLACIAN WITH SINGULAR WEIGHTS

By the Mountain Pass Theorem, we study existence and multiplicity of posi- tive solutions of p-laplacian equation of the form - △pu =λf （x, u）, the nonlinearity f （x, u） grows as u^δ at infinity with a singular coefficient, where a ∈ （p - 1,p＊ - 1）. To manage the asymptotic behavior of its positive solutions with respect to λ, we establish a new Liouville-type theorem for the p-Laplacian operator.

STABILITY OF TIME-PERIODIC TRAVELING FRONTS IN BISTABLE REACTION-ADVECTION-DIFFUSION EQUATIONS

This paper is concerned with the global exponential stability of time periodic traveling fronts of reaction-advection-diffusion equations with time periodic bistable nonlinearity in infinite cylinders. It is well known that such traveling fronts exist and are asymptotically stable. In this paper, we further show that such fronts are globally exponentially stable. The main difficulty is to construct appropriate supersolutions and subsolutions.

Modulation of Void Motion Behavior in a Magnetized Dusty Plasma

Based on fluid equations, we show a time-dependent self-consistent nonlinear model for void formation in magnetized dusty plasmas. The cylindrical configuration is applied to better illustrate the effects of the static magnetic field, considering the azimuthal motion of the dusts. Tile nonlinear evolution of the dust void and the rotation of the dust particles are then investigated numerically. The results show that, similar to the unmagnetized one-dimensional model, the radial ion dragplays a crucial role in the evolution of the void. Moreover, the dust rotation is driven by the azimuthal ion drag force exerting on the dust. As the azimuthal component of ion velocity increases linearly with the strength of the magnetic field, tile azimuthal component of dust velocity increases synchronously. Moreover, the angular velocity gradients of the dust rotation show a sheared dust flow around the void.

Elastic and inelastic positron-helium scattering

Elastic and inelastic positron-helium scatterings have been investigated with the coupled-channel optical method （CCO）. Ionization continuum and positronium formation channels are included via a complex equivalent-local optical potential. Calculations are reported of cross sections of elastic scattering, total excitation and n=2, 3, and 4 excitations of ground-state helium for incident energies from 30 eV to 400 eV. The present calculation shows that the ionization and Ps-formation channels significantly affect the cross sections of elastic and inelastic positron-helium scatterings.

BOUNDARY BLOW-UP RATE OF THE LARGE SOLUTION FOR AN ELLIPTIC COOPERATIVE SYSTEM

In this article we consider positive large solution of cooperative systems of the form -△u1=λ1u1 + a1u1u2^q1 -b1(x)u1^p1+1,-△u2=λ2u2 + a2u1^q2u2 -b2(x)u2^p2+1 in a bounded smooth domainΩ■ R^N(λi ∈ R, ai, bi>0, 0 < qi < pj, i, j ∈{1, 2}, i ≠ j), Based on the construction of certain sup and sub-solution, we show existence, uniqueness and blow-up rate of the large solution.

SOLUTIONS TO NONLINEAR ELLIPTIC EQUATIONS WITH A GRADIENT

In this article, we consider existence and nonexistence of solutions to problem {-△pu＋g（x,u）｜↓△｜^p=f in -Ω,u=0 on Ω with 1〈p〈∞ where f is a positive measurable function which is bounded away from 0 in Ω, and the domain Ω is a smooth bounded open set in R^N（N≥2）. Especially, under the condition that g（x, s） = 1/｜s｜^α （α〉0） is singular at s = 0, we obtain that α 〈 p is necessary and sufficient for the existence of solutions in W0^1,p（Ω） to problem （0.1） when f is sufficiently regular.

Positron Impact Transitions of Atomic Sodium

We present a new investigation of elastic and inelastic positron-sodium scattering by using the coupled-channel optical method(CCO)at an incident energy region of 2–100 eV.The ionization continuum and positronium formation channels have been included via a complex equivalent-local optical potential.The present calculations are compared with available theoretical data and our investigation indicates that the inclusion of ionization and Ps-formation channels in the present calculations has a significant effect on the cross sections of elastic and inelastic positron-sodium scattering at lower energies.

Positronium Formation in Positron-Lithium Scattering

The positronium formation process in positron scattering with atomic lithium is investigated using the coupled-channel optical method.The cross sections of positronium formation into the n=1 and n=2 levels from 2 to 60 eV are reported.The present results show reasonable agreement with the available experimental measurements and theoretical calculations.

Theoretical investigation of structural and optical properties of semi-fluorinated bilayer graphene

We have studied the structural and optical properties of semi-fluorinated bilayer graphene using density functional theory. When the interlayer distance is 1.62A, the two graphene layers in AA stacking can form strong chemical bonds. Under an in-plane stress of 6.8 GPa, this semi-fluorinated bilayer graphene becomes the energy minimum. Our calculations indicate that the semi-fluorinated bilayer graphene with the AA stacking sequence and rectangular fluorinated configuration is a nonmagnetic semiconductor （direct gap of 3.46 eV）. The electronic behavior at the vicinity of the Fermi level is mainly contributed by the p electrons of carbon atoms forming C=C double bonds. We compare the optical properties of the semi- fluorinated bilayer graphene with those of bilayer graphene stacked in the AA sequence and find that the semi-fluorinated bilayer graphene is anisotropic for the polarization vector on the basal plane of graphene and a red shift occurs in the [010] polarization, which makes the peak at the low-frequency region located within visible light. This investigation is useful to design polarization-dependence optoelectronic devices.

Multidimensional stability of V-shaped traveling fronts in the Allen-Cahn equation

This paper is concerned with the multidimensional asymptotic stability of V-shaped traveling fronts in the Allen-Cahn equation under spatial decaying initial values.We frst show that V-shaped traveling fronts are asymptotically stable under the perturbations that decay at infnity.Then we further show that there exists a solution that oscillates permanently between two V-shaped traveling fronts,which indicates that V-shaped traveling fronts are not always asymptotically stable under general bounded perturbations.Our main technique is the supersolutions and subsolutions method coupled with the comparison principle.

Stability of planar waves in reaction-diffusion system

This paper is concerned with the asymptotic stability of planar waves in reaction-diffusion system on Rn, where n 2. Under initial perturbation that decays at space infinity, the perturbed solution converges to planar waves as t →∞. The convergence is uniform in Rn. Moreover, the stability of planar waves in reaction-diffusion equations with nonlocal delays is also established by transforming the delayed equations into a non-delayed reaction-diffusion system.