振荡介质中平面波的反射

在复金慈堡-朗道方程描述的振荡介质中研究了平面波的反射.从理论上给出了产生反射的条件,导出了反射波和入射波这两个区域的分界线与两种介质分界线的夹角.发现两类反射,一类为回折射产生的反射,对于这类反射,理论上给出了反射角;另一类为纯反射,它与折射无关.理论分析与数值模拟结果均表明：只有当入射角大于临界入射角才会发生反射,而且反射角等于临界入射角;对于纯反射,反射角随波频率增大而增大. 关键词： 复金慈堡-朗道方程 平面波 反射     

Reflection and refraction of elastic wave at VTI-TTI media interface

We explore the physical phenomenon of acoustic waves induced at the interface between two different anisotropic rock media.Specifically,one medium is a transversely isotropic medium with a vertical axis of symmetry(VTI medium)and the other one is a transversely isotropic medium with a tilt axis of symmetry(TTI medium).By solving the Kelvin-Christoffel equation,an eighth-order polynomial is established for reflection and refraction angles,which is confirmed from SnelFs law.Three types of analytical expressions of the polarization coefficients of the induced waves are obtained corresponding to different incident angle regions.An effective algorithm has been developed for numerical analysis of the polarization coefficients.Applying characteristic anisotropic parameters reported in the literature,the influencing factors on reflection and refraction coefficients are analyzed,e.g.,the anisotropy,the tilt-angle of rock-layer,and the incident-angle.The calculated reflection and refraction coefficients have been rechecked for energy conservation.     

Reflection and refraction by interfaces of uniaxial crystals

We present a simple and complete approach to determining the directions and amplitudes of rays propagating through arbitrary systems of homogeneous and/or uniaxial materials. In the process we extend the work of Gu and Yen to full generality.     

电磁波在左右手介质界面折射与反射特性的研究

研究了电磁波在左右手介质界面折射与反射的特性,给出了折射系数和反射系数,从另外一个方面探讨了最小作用量原理在左手材料中的适用性;从电动力学和最小作用量原理证明了Snell定律,验证了Snell定律在左手材料中的适用性,并且得到Fresnell公式在左右手材料中的一致性.     

凹面相控阵聚焦声场在液固界面上的反射和折射

开展了凹面线性相控阵列辐射声场在液固界面上的反射和折射特性研究,利用射线近似方法,得到了凹面相控阵聚焦声场在液固界面上反射和折射后的声场渐近解析表达式,对声波在液固曲面上的反射和折射声场进行了分析和讨论. 利用这个解析表达式,对凹面线性聚焦声场在液固平界面和液固圆柱界面情况下固体中折射纵波和折射横波的相控阵声场进行了分析和讨论,发现凹面线阵声场在液固圆柱界面下比液固平界面具有更好的聚焦效果. 关键词： 凹面阵列 超声相控阵 反射与折射     

光的反射、折射和全反射演示器

利用自制教具演示了光的反射、折射和全反射现象 ,克服了传统实验仪器的不足 .本文介绍了教具的制作和使用方法     

The coefficients of reflection and refraction on interface of the crystals in the Savart polariscope

According to the boundary conditions of the electromagnetic field, the coefficients of reflection and refraction on the interface of crystal in the Savart polariscope are obtained for ordinary ray (o-ray) and extraordinary ray (e-ray).The coefficients of reflection and refraction are different from an isotropic medium and have more complicated forms than isotropic medium.     

Experimental study of traveling waves and target patterns in oscillatory reacting media

Recent experimental work on is presented traveling waves and target patterns developing in oscillatory Belousov-Zhabotinsky reagents. It only deals with trigger waves and relaxation oscillations. Measurements have been made on (1) the dispersion relation of waves, (2) the statistical properties of centers and targets, (3) the wavefront and speed near the core of the pattern. Several unanticipated results are reported.     

Reflection and transmission of acoustic waves on multilayered porous media

Based on the Boit theory of acoustic wave propagation in fluid-satu-rated porous medium we have studied in this paper the acoustic reflection andtransmission on multilayered porous media,in which the adequate boundaryconditions across the interfaces are taken into account.Numerical calculationsof the reflection and transmission coefficients at different incident angles andfrequencies of the fast compressional wave incident on porous media with threeor four layers are presented.The results indicate that the maximum or mini-mum reflection and transmission coefficients appear at certain ratios of thewavelength to the thickness.The acoustic incident angle and porous mediumproperties are shown to affect significantly these coefficients.As an example,the measured transmission coefficients in a water-saturated fused glass beadsample are in good agreement with theoretical prediction.     

折射定律与反射定律的推导

利用费马原理推导折射定律与反射定律,推导时不需做一些假定(如假定实际光线的光学长度是最小值或折射光线位于入射光线和界面法线所在的平面上),可加深学生对费马原理的理解.     

用于相位突变界面的广义的反射定律和折射定律

考虑到位于两物质界面上的Metasurface对光线传播行为的影响, 从费马原理和边界条件连续两种角度出发, 推导了可用于相位突变界面的广义反射与折射定律. 该定律在界面对光波的相位改变量为零的情况下, 回归为通常的反射定律和折射定律. 利用广义的折射定律和反射定律讨论了介质折射率、界面上的相位梯度等因素对光传播行为的影响, 发现利用广义的折射定律和反射定律很容易实现反常反射和反常折射行为, 并给出了出现反常反射和反常折射的条件, 以此为基础可以实现对光波的随意控制. 依据广义的折射定律和反射定律分析了一维相位掩模板对光场传播行为的影响. 关键词： 超材料 相位突变界面 反射定律 折射定律     

Reflection of spin waves from a ferromagnetic multilayer with interfacial coupling of finite strength (reflection of spin waves from multilayer)

The reflection coefficient of bulk spin waves from a ferromagnetic multilayer with periodically modulated parameters of the exchange interaction, the uniaxial magnetic anisotropy and the saturation magnetization (a magnonic crystal) is calculated. The dependence of the reflection coefficient upon the spin wave frequency and the values of the bias magnetic field, the parameter of interfacial coupling, and the internal structure of the unit cell are investigated.      

Discovering the generalized vectorial laws of multiple reflection and refraction

This paper reports on the discovery of the generalized vectorial laws of multiple reflection and refraction as an extension of the earlier discovery of the generalized vectorial laws of reflection and refraction reported in 2005. The present discovery is novel and original and interesting from academic point of view. It will enrich the field of optics.     

Optical bulk and surface waves with negative refraction

In materials with negative refraction, the direction of wave propagation is opposite to the direction of the wave vector. Using an approach that characterizes the optical response of a medium totally by a generalized dielectric permittivity, , we discuss the possibility of seeing negative refraction for optical waves in a number of nonmagnetic media. These include bulk waves in organic materials and in gyrotropic materials where additional exciton–polariton waves can have a negative group velocity. It is known that dispersion of surface waves can be engineered by tailoring a surface transition layer. We show how this effect can be used to obtain surface waves with negative refraction.     

左手材料的反射特性与负折射率行为

利用平板波导法研究了不同入射角度下周期排列开口谐振环负磁导率材料、周期排列金属杆负介电常数材料以及左手材料微波反射特性，并利用劈尖法研究了左手材料的负折射特性.实验结果表明：负磁导率材料反射率曲线形成反射峰，其对应的反射峰频率与材料的谐振频率一致；负介电常数材料反射率接近0dB；左手材料出现单个反射较小的反射峰，其峰值反射率随入射角度的增大而变大，即反射能力增强，且反射峰与透射峰有相对频移.劈尖法测量还表明，左手材料在9800MHz频率附近出现负折射现象，其折射率n为-0.796. 关键词： 左手材料 反射 负折射率     

Doppler effect of nonlinear waves and superspirals in oscillatory media

Nonlinear waves emitted from a moving source are studied. A meandering spiral in a reaction-diffusion medium provides an example in which waves originate from a source exhibiting a back-and-forth movement in a radial direction. The periodic motion of the source induces a Doppler effect that causes a modulation in wavelength and amplitude of the waves ("superspiral"). Using direct simulations as well as numerical nonlinear analysis within the complex Ginzburg-Landau equation, we show that waves subject to a convective Eckhaus instability can exhibit monotonic growth or decay as well as saturation of these modulations depending on the perturbation frequency. Our findings elucidate recent experimental observations concerning superspirals and their decay to spatiotemporal chaos.     

Numerical simulations of negative-index refraction in a lamellar composite with alternating single negative layers

Negative-index refraction is demonstrated in a lamellar composite with epsilon-negative (ENG) and mu-negative (MNG) materials stacked alternatively. Based on the effective medium approximation, simultaneously negative effective permittivity and permeability of such a lamellar composite are obtained theoretically and further proven by full-wave simulations. Consequently, the renowned left-handed metamaterial comprising split ring resonators and wires is interpreted as an analogy of such ENG--MNG layers. In addition, beyond the effective medium approximation, the propagating field squeezed near the ENG/MNG interface is demonstrated to be left-handed surface waves with backward phase velocity.     

Doppler instability of antispiral waves in discrete oscillatory reaction-diffusion media

This paper investigates antispiral wave breakup phenomena in coupled two-dimensional FitzHugh-Nagumo cells with self-sustained oscillation via Hopf bifurcation.When the coupling strength of the active variable decreases to a critical value,wave breakup phenomenon first occurs in the antispiral core region where waves collide with each other and spontaneously break into spatiotemporal turbulence.Measurements reveal for the first time that this breakup phenomenon is due to the mechanism of antispiral Doppler instability.     

Reflection and refraction of bulk acoustic waves in piezoelectrics under uniaxial stress

Basic equations that describe the conditions of reflection and refraction of bulk acoustic waves at the boundary between acentric crystalline media under uniaxial stress are presented. The effect of uniaxial stress on the anisotropy of reflection and refraction of bulk acoustic waves is numerically analyzed for boundaries of the crystal-vacuum, piezoelectric crystal-piezoelectric crystal, and piezoelectric crystal-elastic isotropic medium types.