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31.
We study the classical dynamics of the RbCs molecule in the presence of a static electric field. Under the Born–Oppenheimer approximation, we perform a rovibrational investigation which includes the interaction of the field with the molecular polarizability. The stability of the equilibrium points and the phase space structure of the system are explored in detail. We find that, for strong electric fields or for energies close to the dissociation threshold, the molecular polarizability causes relevant effects on the system dynamics. 相似文献
32.
The dynamics of a driven stadium-like billiard is considered using the formalism of discrete mappings. The model presents a resonant velocity that depends on the rotation number around fixed points and external boundary perturbation which plays an important separation rule in the model. We show that particles exhibiting Fermi acceleration (initial velocity is above the resonant one) are scaling invariant with respect to the initial velocity and external perturbation. However, initial velocities below the resonant one lead the particles to decelerate therefore unlimited energy growth is not observed. This phenomenon may be interpreted as a specific Maxwell’s Demon which may separate fast and slow billiard particles. 相似文献
33.
34.
Patrick Jenny Hamdi A. Tchelepi Seong H. Lee 《Journal of computational physics》2009,228(20):7497-7512
This paper addresses the convergence properties of implicit numerical solution algorithms for nonlinear hyperbolic transport problems. It is shown that the Newton–Raphson (NR) method converges for any time step size, if the flux function is convex, concave, or linear, which is, in general, the case for CFD problems. In some problems, e.g., multiphase flow in porous media, the nonlinear flux function is S-shaped (not uniformly convex or concave); as a result, a standard NR iteration can diverge for large time steps, even if an implicit discretization scheme is used to solve the nonlinear system of equations. In practice, when such convergence difficulties are encountered, the current time step is cut, previous iterations are discarded, a smaller time step size is tried, and the NR process is repeated. The criteria for time step cutting and selection are usually based on heuristics that limit the allowable change in the solution over a time step and/or NR iteration. Here, we propose a simple modification to the NR iteration scheme for conservation laws with S-shaped flux functions that converges for any time step size. The new scheme allows one to choose the time step size based on accuracy consideration only without worrying about the convergence behavior of the nonlinear solver. The proposed method can be implemented in an existing simulator, e.g., for CO2 sequestration or reservoir flow modeling, quite easily. The numerical analysis is confirmed with simulation studies using various test cases of nonlinear multiphase transport in porous media. The analysis and numerical experiments demonstrate that the modified scheme allows for the use of arbitrarily large time steps for this class of problems. 相似文献
35.
In this paper we analyze the equilibrium limit of the constitutive model for two-phase granular mixtures introduced in Papalexandris (2004) [13], and develop an algorithm for its numerical approximation. At, equilibrium, the constitutive model reduces to a strongly coupled, overdetermined system of quasilinear elliptic partial differential equations with respect to the pressure and the volume fraction of the solid granular phase. First we carry a perturbation analysis based on standard hydrostatic-type scaling arguments which reduces the complexity of the coupling of the equations. The perturbed system is then supplemented by an appropriate compatibility condition which arises from the properties of the gradient operator. Further, based on the Helmholtz decomposition and Ladyzhenskaya’s decomposition theorem, we develop a projection-type, Successive-Over-Relaxation numerical method. This method is general enough and can be applied to a variety of continuum models of complex mixtures and mixtures with micro-structure. We also prove that this method is both stable and consistent hence, under standard assumptions, convergent. The paper concludes with the presentation of representative numerical results. 相似文献
36.
Mircea Grigoriu 《Journal of computational physics》2010,229(22):8406-8429
Mathematical requirements that the random coefficients of stochastic elliptical partial differential equations must satisfy such that they have unique solutions have been studied extensively. Yet, additional constraints that these coefficients must satisfy to provide realistic representations for physical quantities, referred to as physical requirements, have not been examined systematically. 相似文献
37.
Single crystals of the organic nonlinear optical material γ-glycine have been grown in the presence of Zinc sulphate by slow evaporation technique at ambient temperature for the first time. Bulk growth of γ-glycine single crystals was grown by Top-seeded solution growth method. The γ-phase of glycine was confirmed by powder X-ray diffraction and the FTIR analysis. Elemental analysis CHN was performed to confirm the non-inclusion of zinc sulphate species into the solution. Inductively coupled plasma optical emission spectrometry study (ICP-OES) was employed to quantify the concentration of Zinc element in the grown γ-glycine single crystals. The optical transmission was ascertained from UV–Vis–NIR spectrum. The optical band gap was estimated for γ-glycine single crystal using UV–Vis–NIR study. Differential scanning calorimetry analysis was employed to explore information about thermal stability, phase transition and melting point of the grown crystal. The second harmonic generation relative efficiency was measured by Kurtz and Perry powder technique. 相似文献
38.
This paper studies the compressional dispersive Alfvén (CDA) waves where Noether symmetries will be calculated from which the corresponding conservation laws will be obtained via Noether's theorem. Furthermore, one case of double reduction is performed via the association of a conserved vector with a Noether symmetry (with zero gauge). The conserved quantities of optical solitons in the presence of intermodal dispersion that is governed by the perturbed nonlinear Schrödinger's equation with Kerr law nonlinearity. The invariance-multiplier method is adopted to carry out the analysis, from which the conserved densities are then retrieved. Finally, the conserved quantities are obtained using the 1-soliton solution of the governing equation. 相似文献
39.
The nonlinear theory of slow-wave electron cyclotron masers (ECM) with an initially straight electron beam is developed. The evolution equation of the nonlinear beam electron energy is derived. The numerical studies of the slow-wave ECM efficiency with inclusion of Gaussian beam velocity spread are presented. It is shown that the velocity spread reduces the interaction efficiency. 相似文献
40.
为了得到光折变晶体中非相干耦合空间孤子对统一理论的结果,基于单光子光折变空间光孤子的基本理论模型,建立了稳态条件下有分压电阻和e偏振非相干均匀背景光辐照的单光子光伏光折变晶体中非相干耦合空间孤子对理论. 研究表明:这种孤子对是由两束偏振方向和波长都相同的互不相干光束耦合形成的, 孤子对两光束都能在晶体中稳定传播;当分压电阻、e偏振背景光、外加电场和光伏场取不同值时, 可获得14种光折变非相干耦合空间孤子对. 本文的结果对完善和充实光折变空间孤子理论体系有重要意义. 相似文献