共查询到20条相似文献,搜索用时 218 毫秒
1.
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 相似文献
2.
Yinhua C Wei L Yu MY 《Physical review. E, Statistical physics, plasmas, fluids, and related interdisciplinary topics》1999,60(3):3249-3252
The modulational interaction of finite-amplitude high-frequency electrostatic waves propagating at an arbitrary angle to an external magnetic field with slow plasma motion is considered. A set of nonlinear evolution equations describing the interaction is obtained. New types of solitary waves propagating at near sonic speeds are found. 相似文献
3.
Kh. B. Tolipov 《Acoustical Physics》2013,59(4):447-452
Stagnant antisymmetric waves in an elastic wedge-shaped plate were studied theoretically and experimentally. The solution to the nonuniform problem was obtained in the approximation of a small and smooth field nonuniformity. The vibration amplitudes in a standing wave were calculated and measured for a small wedge angle. Experimental measurements were performed on an original setup. 相似文献
4.
We report on the first observation of mirrorless oscillation in BaTiO3 pumped by two nearly counterpropagating mutually incoherent light waves, both containing an ordinary and an extraordinary component. The oscillation waves appear at a certain angle defined by the phase matching condition for four-wave mixing of orthogonally polarized waves. 相似文献
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6.
通过使用推广的 Poincar-Lighthill-Kuo 摄动方法,研究了二维热离子等离子体中两个沿不同方向传播的离子声孤波的相互作用,得到了两个分别描述沿ξ和η方向传播的孤波的KdV方程以及两个孤波以任意夹角碰撞后的相移和轨道.同时还研究了离子温度比σ、热容比γ和碰撞夹角α对孤波相移的影响.研究表明,这些参量可以明显地改变孤波的相移,且在该系统中存在压缩型孤波.
关键词:
热离子等离子体
离子声孤波
Poincar-Lighthill-Kuo方法
相移 相似文献
7.
G. Jäkel J. Neumann S. Odoulov U. van Olfen E. Krätzig 《Applied physics. B, Lasers and optics》1995,61(5):415-419
We report on the observation of mirrorless oscillation in photorefractive BaTiO3 pumped by two pairs of two nearly counterpropagating light waves, each of them containing an ordinary and an extraordinary component of polarization. The oscillation waves are located on a cone with an apex angle defined by the phase-matching conditions of this process. 相似文献
8.
N. I. Pushkina 《Physics of Wave Phenomena》2012,20(3):204-207
Nonlinear interaction of three acoustic waves in a sandy sediment is studied in the frequency range where there is a considerable wave velocity dispersion. The possibility of an experimental observation of the generation of a sound wave by two pump waves propagating at an angle to each other is estimated. 相似文献
9.
Z. E. Eremenko Yu. F. Filipov 《International Journal of Infrared and Millimeter Waves》1996,17(3):579-593
I. Abstract The eigen electromagnetic waves in dielectric rod with arbitrary direction of anisotropy axis were studied analytically and numerically. The rigorous dispersion eguation has been obtained. New types of surface and volume waves in anisotropic rod were discovered. Essential dependence of spectral characteristics on tilt angle of anisotropy was shown. 相似文献
10.
This paper investigates the collision between two nonlinear waves with different propagation directions in two-dimensional dust crystals. Using the extended Poincaré--Lighthill-Kuo perturbation method, two Korteweg--de Vries equations for nonlinear waves in both the ξ and eta directions are obtained, respectively, and the analytical phase shifts and trajectories after the collision of two nonlinear waves are derived. Finally, the effects of parameters of the lattice constant a, the arbitrary constant u0η, the forces f(r), and the colliding angle θ on the phase shifts of both colliding nonlinear waves are examined. 相似文献
11.
Excitation of potential surface waves by a nonrelativistic electron beam traveling in a vacuum space near the boundary of
a layered superconductor is studied theoretically. Dispersion relations for surface waves at an arbitrary angle between superconductor
layers and interface are obtained. Allowance is made for an arbitrary direction of wave propagation in the interfacial plane.
Increments of kinetic and hydrodynamic instabilities are found. It is shown that absolute instability may occur. 相似文献
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Excitation and propagation of non-axisymmetric guided waves in a hollow cylinder is studied by using the normal mode expansion method (NME). Different sources such as angle beam, tube end excitation with normal beam, and comb transducer possibilities are discussed based on the derivations of the NME method. Numerical calculations are focused on the case of angle beam partial loading. Based on the NME method, the amplitude coefficients for all of the harmonic modes are obtained. Due to the difference of phase velocities for different modes, the superimposed total field varies with propagating distances and hence makes particle displacement distribution patterns (angular profile) change with distance. This varying non-axisymmetric angular profile of guided waves represents a nonuniform energy distribution around the hollow cylinder and thus has an impact on the inspection ability of guided waves. The angular profiles of an angle beam source are predicted by theory and then verified by experiments. The predicted angular profiles also provide information for determining the transducer location to find defects in a certain position on the hollow cylinder. 相似文献
14.
A. P. Bogatov 《Journal of Russian Laser Research》1994,15(5):417-453
The electromagnetic field inside a nonlinear active medium of a laser is considered as a system of counterpropagating waves.
Such an approach changes radically an earlier studied behavior of the lateral field instability due to self-deformaion (or
self-focusing). In our calculations we used an expression for a laser field in the form of two “strong” counterpropagating
waves whose complex amplitudes have weak perturbations. Amplitude perturbations of each of the “strong” waves can be presented
by two spatial harmonics corresponding to two weak perturbation waves with wave vectors making some tilted angle ±φ with the
cavity axis. Thus six waves would participate in the interaction: two counterpropagating strong waves and two pairs of weak
waves. Using this approach, we have developed a theory for the propagation of four “weak” perturbation waves in a nonlinear
amplifying medium in the presence of two counterpropagating “strong” waves. It is shown that perturbation waves with tilted
angle φ⋍0.5–1.2° inside the active region, and respecively, with the side lobes of the far-field pattern at ∼1.7–4°, have
the greatest growth increment. These perturbation waves produce lateral intensity modulation with period 10–30 μm for the
0.85 μm lasing wavelength. The appearance of such waves corresponds to the instability threshold of a homogeneous lateral
distribution of optical power in a diode laser.
The present theory makes it possible to investigate the stability of the homogeneous lateral optical intensity distribution
in a diode laser of any design. This allows one to choose a suitable design of a laser with a homogeneous lateral distribution
at high radiation power.
Translated from Preprint No. 43 (1992) of the Lebedev Physics Institute, Russian Academy of Sciences. 相似文献
15.
基于传输线原理,构建了均匀分布在单位球表面的入射波用于模拟混响室内"全向辐照"的电磁辐照模型,并利用Agrawal散射电压公式计算双导线传输线模型的终端负载响应电流。研究了均匀分布在球面入射波的入射方向、极化方向以及入射波数量对传输线终端响应的影响,并将数值计算结果与蒙特卡罗方法的计算结果进行对比。结果表明:分布在球面上的电磁波入射角为0~π、极化角度为0~π时,即可满足响应信号的数值完整性;入射电磁波数量达到100时,能够满足混响室内"全向辐照"的要求;理论模型计算结果与蒙特卡罗方法的计算结果吻合较好,该模型可以用于混响室内散射场场线耦合规律计算。 相似文献
16.
Tal Ellenbogen 《Optics Communications》2007,277(2):423-426
Whereas the commonly used collinear quasi-phase-matched interaction is usually suitable for phase matching only a single nonlinear process, non-collinear interactions offer rich variety of phase matching possibilities, employing different elements of the nonlinear tensor, and various orders of quasi phase matching. By studying the dependence of the second harmonic process on the angle and the phase matching order in a periodically poled LiNbO3 crystal, we can non-destructively derive the duty cycle of the structure. The obtained duty cycle agrees well with surface scan measurements using an atomic force microscope. Furthermore, by proper selection of the non-collinear angle, we demonstrate simultaneous second harmonic generation of two cross polarized waves. 相似文献
17.
This paper reports experimental and analytical results on optical second harmonic generation when a noncollinear arrangement is employed. The dependence of second harmonic power on crystal length, absorption, beam radius and the angle between the two fundamental waves is obtained. Double refraction of the crystal is taken into account, but the divergence and depletion of the fundamental waves are neglected. The results of the calculations are confirmed by experiments carried out with a KDP crystal in the near field of two intersecting TEM00 ruby laser beams.An extension of the theory to nonlinear interactions other than second harmonic generation - e.g. four-wave interaction - is possible. 相似文献
18.
By the coupled waves method, the process of spatial energy transfer between ordinary and extraordinary waves in an anisotropic media with the twisting is investigated. Without applying any approximate methods, exact analytical expressions describing the spatial dynamics of such an energy transfer are obtained. It is shown that a twist oriented cell of a nematic liquid crystal operates as an achromatic λ/2 plate at sufficiently large thicknesses and at any value of an azimuthal angle of the input linearly polarized wave despite the absence of the phenomenon of adiabatic following. 相似文献
19.
The problem of one-dimensional propagation of low-frequency electromagnetic waves in homogeneous ionospheric plasma at an angle to the external magnetic field is examined. An oscillating pulse function is obtained for such waves. The shape of the envelope is determined by the Pedersen conductivity. The oscillation period increases with distance and the angle between the propagation direction and the external magnetic field. The period is determined by the Hall and Pedersen conductivities and varies from tenths of a second to seconds.All-Union Scientific-Research Institute of Optical-Physical Measurements. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 35, No. 5, pp. 375–380, May, 1992. 相似文献
20.
提出了一种基于有限宽超声束反射的固-固界面退化特性评价方法,从理论和数值仿真角度进行了分析和计算。将两固体界面间的薄层简化为界面弹簧模型,以界面法向和切向劲度系数表征界面的退化程度。通过数值计算求得有限宽超声纵波束在不同入射角和界面不同退化程度下的反射横波、反射纵波的镜面反射系数。进一步地,通过建立二维有限元模型,仿真研究了有限宽超声纵波束在给定入射角及界面不同退化程度下镜面反射系数的变化规律。结果表明,反射纵波和反射横波的镜面反射系数随有限宽超声纵波束的入射角及界面劲度系数的改变而变化,且存在镜面反射系数随界面劲度系数单调且敏感变化的入射角,据此可准确评价界面的退化程度。 相似文献