A dielectric rod waveguide coupled with metal rectangular waveguide

Measurements have been done in the millimeter wave region on a composite waveguide which comprises a dielectric rod waveguide connecting two metal rectangular waveguides. Such a waveguide has been used by us in a Josephson harmonic mixer installed in a small metal cryostat, to prevent the thermal invasion from outside environment and to transmit both signal and LO waves with small losses. The measured transmission loss, that is caused mainly by the coupling loss between metal rectangular waveguides (TE₁₀ mode) and a dielectric rod waveguide (HE₁₁ mode), has been less than 2dB in the frequency range of 52–104 GHz.     

Propagation of longitudinal ultrasonic waves in RbH2PO4 near its ferroelectric phase transition temperature

Ferroelectric phase transition in RbH₂PO₄ has been investigated using propagation of longitudinal acoustic waves along the polar axis near the transition temperature. The velocity of this mode is continuous across the transition temperature. Velocity data in the ferroelectric phase are analyzed in terms of coupled soft modeacoustic mode model of Pytte to obtain the temperature dependence of the soft mode frequency. The attenuation data in the ferroelectric phase show power law dependence. It follows scaling behaviour of the type predicted by Kawasaki from the mode-mode coupling theory and the dynamical scaling.     

TE mode coupling between end separated buried waveguides: expressions and calculations

In this paper the power coupling expression between two identical axially aligned and spatially separated waveguides is presented. Calculations using the coupling expression for a Gaussian mode profile in the input waveguide produce results that are in excellent agreement with experimental observations.     

The WKBZ mode approach to sound propagation in range-independent ocean channels

I.IntroductionThenorma1-modeapproachcangiveanexactso1utiontotheacousticfie1dinastratifiedmedium,soitisoftenusedtocomparewithotherapproximatemethodssuchasraytheory,parabo1icequationl'](PE)methodandGaussianbeam[21approach,andtakenasacriteriontochecktheaccuracyofapproximatemeth0dsl3J.Themodeapproachmayalsobeextendedtorange-dcpendente..i,onmentsl4.5l.Thoughtherearemanynumerica1propagationcodesbasedonthemodeapproachI'],theconventionalmodeapproachisawkwardtoapplyt0'higherfrequencya-ndbroadbandprop…     

二次型复折射率介质中的光导现象

本文讨论了n(z,r)=n_0(z)+n_2(z)r~2/r_e~2型复折射率介质中的激光传输问题,给出了激光传输参数(光束半径和波阵面曲率)的演化公式。指出只要存在一定大小的n_(21),在传输过一段特征距离z_c之后,将出现完全光导(即自相似模的传播),而且自相似模是激光体系的特征模式。其传输参数只与n_2有关,而与激光初始参数无关。自相似模必定是高斯球面波,而不是高斯平面波。     

An approximate analysis of the interaction between two tearing modes of the same helicity

The interaction between tearing modes with the mode numbersm=1,n=1 andm=2,n=2 is investigated for different initial amplitudes of the modes, using a single helicity approximation, a step-current profile and a time-independent resistivity. Also included are the results on the temporal behaviour of the amplitude of the uncoupled modem=2,n=2 in the situation with identical equilibrium parameters as ours.     

An injection-locked single-mode tea CO2 laser for SMM laser pumping

A D₂O laser has been developed for collective Thomson scattering measurements of ion temperature in high temperature plasmas. A pulse duration and a spectral width of a high power D₂O laser has been successfully controlled for this purpose, by using a TEA CO₂ laser injection-locked by an etalon-tuned TEA CO₂ laser as a pump source.     

亚乙基硫脲分子键伸缩模式与全耦合模式键极化率的对比及其拉曼激发虚态的相关研究

从拉曼峰强着手,得到了键伸缩模式与全耦合模式两种不同计算条件下,亚乙基硫脲(ethylene thiourea,ETU)分子的键极化率,并比较分析了两种计算结果的异同.研究表明:在键伸缩模式的算法中,仅考虑势能分布中键对称伸缩比重相对较大的部分拉曼峰参与极化率计算,显然忽略了键伸缩与键弯曲间的相互耦合,造成了与弯曲振动耦合较强的部分键伸缩极化率值存在一定误差.因此,此方法虽能使问题简化,但却丢失了一些信息.而全耦合模式算法考虑了所有振动模式(键伸缩与键弯曲)相互影响的情况,能更全面的反映键电荷的分布情况,但却会使问题的求解过程变得复杂.同时,在拉曼激发虚态的相关研究中,两种计算方法却得到几乎一致的键极化率弛豫方式(呈单指数规律衰减)及相同的衰减特征时间.