Analytical Solution of Weak-Coupling Periodically Driven Two-Level System

We present an approximate analytical solution to periodically driven two-level system in the weak-coupling regime. The analytical solution is in good agreement with the exact numerical solution in resonance and near resonance cases when Ω≤0.3ω_a with Ω and ω_a denoting the Rabi and transition frequencies respectively.     

周期性波纹通道内换热与流动的数值研究

采用曲线坐标系下压力与速度耦合的SIMPLER算法,数值研究了一种紧凑换热器中波纹通道内周期性充分发展的层流流动与换热情况,流动Re数的范围为100~1100,Pr数为0.7.计算考察了不同波纹高度、波纹间距对流动与换热的影响,并对模型参数进行了性能评价.计算结果表明,整体Nu数及fRe数随着流动Re数的增加而增加.随着波纹高度的增加或波纹间距的减小,换热增强,特别是在高Re数下波纹高度的增加更加强化换热.最佳波纹高度和间距分别为1.15 mm和13 mm.     

Two‐parameter anisotropic homogenization for a Dirichlet problem for the Poisson equation in an unbounded periodically perforated domain. A functional analytic approach

We consider a Dirichlet problem for the Poisson equation in an unbounded periodically perforated domain. The domain has a periodic structure, and the size of each cell is determined by a positive parameter δ, and the level of anisotropy of the cell is determined by a diagonal matrix γ with positive diagonal entries. The relative size of each periodic perforation is instead determined by a positive parameter ε. For a given value of γ, we analyze the behavior of the unique solution of the problem as tends to by an approach which is alternative to that of asymptotic expansions and of classical homogenization theory.     

Periodically Poled Titanium-Diffused Lithium Niobate Wavelength Filters Utilizing Šolc-Type TE↔TM Mode Converters

Abstract

?olc-type wavelength filters have been demonstrated in a 52-mm long periodically poled titanium-diffused lithium niobate channel waveguide with a domain period of 16.6 μm. At room temperature, the center wavelength and the full-width at half maximum of the filter were about 1,272.49 nm and 0.23 nm, respectively. The nearest side-lobe is about 7 dB. New structures of flat-top bandpass filters and an optical add/drop multiplexer utilizing ?olc-type TE?TM mode converters are proposed for the first time.     

Bifurcation and dynamics in double-delayed Chua circuits with periodic perturbation

Rank-1 attractors play a vital role in biological systems and the circuit systems.In this paper,we consider a periodically kicked Chua model with two delays in a circuit system.We first analyze the local stability of the equilibria of the Chua system and obtain the existence conditions of supercritical Hopf bifurcations.Then,we derive some explicit formulas about Hopf bifurcation,which could help us find the form of Hopf bifurcation and the stability of bifurcating period solutions through the Hassards method.Also,we show that rank-1 chaos occurs when the Chua model with two delays undergoes a supercritical Hopf bifurcation and encounters a periodic kick,which shows the effect of two delays on the circuit system.Finally,we illustrate the theoretical analysis by simulations and try to explain the mechanism of delay in our system.     

Electro‐optical interferometric microscopy of periodic and aperiodic ferroelectric structures

The ferroelectric domain structures of periodically poled KTiOPO₄ and two‐dimensional short range ordered poled LiNbO₃ crystals are determined non‐invasively by interferometric measurements of the electro‐optically induced phase retardation. Owing to the sign reversal of the electro‐optical coefficients upon domain inversion, a π phase shift is observed for the inverted domains. The microscopic setup provides diffraction‐limited spatial resolution allowing us to reveal the nonlinear and electro‐optical modulation patterns in ferroelectric crystals in a non‐destructive manner and to determine the poling period, duty cycle and short‐range order as well as detect local defects in the domain structure. Conversely, knowing the ferroelectric domain structure, one can use electro‐optical microscopy so as to infer the distribution of the electric field therein.

     

Homogenization of the variational inequality corresponding to a problem with rapidly varying boundary conditions

In the present paper, we investigate the asymptotic behavior of the solution of a variational inequality with one-sided constraints on ?-periodically located subsets G _ε belonging to the boundary ?Ω of the domain Ω ? ?³. We construct a limit (homogenized) problem and prove the strong (in H ₁(Ω)) convergence of the solutions of the original inequality to the solution the limit nonlinear boundary-value problem as ? → 0 in the so-called critical case.     

Surface Magnetoelastic Shear Waves in Periodic Ferrite-Dielectric Regularly Stratified Structures

Surface magnetoelastic Love waves in a regularly stratified medium with ferrite and dielectric layers are studied based on the Hamilton formalism and numerical procedures. The dispersion relations are analyzed for particular structures     

Propagation of Coupled Waves Interacting with an Electromagnetic Field in Periodically Inhomogeneous Media

The paper is concerned with coupled (electroelastic, electromagnetoelastic, and magnetoelastic) waves in inhomogeneous media     

周期性锯齿型通道内流动和换热研究

用非稳态层流模型对锯齿型通道内周期性充分发展流动与换热进行了数值模拟．Re=600时数值结果已发生明显振荡,而从入口段算起的第9、10个几何周期的平均Nu数与用周期性充分发展条件计算得到的平均Nu数吻合良好;在此基础上,计算通道周期长度L与通道垂直高度b的比值及通道倾角α等几何结构尺寸对周期性充分发展流动和换热的影响,计算结果表明,增大α和减小L／b都易促使流动产生涡旋,从而增强换热．