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…     

广义相积分简正波理论在双轴海洋声道中的推广与应用

双轴声道常出现于大洋中。双轴声道传播是一检验海洋声学计算方法的\     

水平缓变声道中的WKBZ绝热简正波理论

本文利用具有海面相移修正的本征函数的ＷＫＢＺ近似，并同时考虑波导简正波和海底反射简正波的贡献，提出了适合于水平缓变水下声道的ＷＫＢＺ绝热简正波理论。数值结果表明，会聚区声场主要由波导简正波决定，而影区声场主要由海底反射简正波决定。在菲律宾海中，频率范围在１０９ＨＺ至８６０ＨＺ，距离至２５０ｋｍ范围时，用ＷＫＢＺ绝热简正波理论计算的结果与实验数据符合得很好。     

基于BDRM理论的深海声场快速预报研究

深海存在深海声道和双轴声道两种典型环境，WKBZ简正波方法已实现了深海声道中声场的快速准确预报，而对于双轴海洋声道则存在一定的误差。本文在WKBZ本征函数的基础上，推导出了参考界面相位修正的一致表达式，并将浅海声传播的波束位移射线简正波（BDRM）理论应用于计算双轴海洋声道中的声场，进行了数值模拟并与传统简正波方法进行比较，结果表明应用BDRM理论计算的传播损失具有很高的精度和速度。     

三维耦合简正波-抛物方程理论及算法研究

研究三维海洋环境下声传播的快速数值预报方法。在广义相积分(WKBZ)理论和波束位移射线简正波(BDRM)理论的基础上,将二维耦合简正波-抛物方程理论推广至三维。三维耦合简正波-抛物方程(CMPE3D))理论的级数解由垂直方向的本地简正波和水平与方位角方向的简正波幅度系数组成。为了实现该理论的快速算法,在垂直方向上采用WKBZ理论和BDRM理论进行简正波分析,在水平与方位角方向采用与抛物方程模型FOR3D[Lee D.et al., \     

Numerical simulations and experiment ofreverberation loss in shallow water

I.IntroductionUndcrwatersoundrevcrberationhasrccentlybecomeatopicofgreatinterestlI-3l.Sincethcrcverberationincludescombincdeffcctsofsoundpropagahonandscattering,andthesoundpropagationinshallowwaterismuchmorecomplicatedthanthatinthedeepsea,itisnecessarytOstudycarefullybothintheoryandexperimcnt.Fortheshortrangereverberationinshal1owwatcrtheray-basedmodelisavai1ab1e,whilefOr1ongrangethewave-basedmodelmustbeusedbecauscofcomp1icatcdmu1tipaths,refractioneffcctsandfrequencydependence.Thenorma1-mode…     

浅海中的混响衰减

本文定义混响衰减作为描述浅海混响的基本物理量。对不同的声速剖面和海底散射模型，分别用射线方法和ＷＫＢＺ简正波方法（考虑和不考虑复本征值的影响）计算了混响衰减随时间（距离）的变化。数值模拟结果表明复本征值的影响不能忽略，在中等距离上按射线方法计算的混响衰减与考虑了复本征值影响的ＷＫＢＺ方法计算结果相一致。负跃层浅海中的实验结果表明混响衰减与源和接收器的深度有关，但与带宽无关。理论预示的混响强度的几何平均规律也从实验得到了证实。     

Manipulating atomic coherence and interference in a coupled atom-cavity system

Collective coupling of multiple atoms with a cavity mode produces two normal modes that are separated in energy by Vacuum Rabi splitting. We show that quantum coherence and interference can be produced by a control laser that couples the atoms confined in the cavity mode from free space, which leads to suppression of the normal mode excitation, or polariton excitation of the cavity-atom system. The control laser splits the normal mode of the cavity-atoms system and opens two excitation channels. The destructive quantum interference between the two channels renders the cavity-atoms system opaque to the light coupled into the cavity mode. We demonstrate suppression of the normal mode (polariton) excitation by the destructive quantum interference in an experiment with cold Rb atoms confined in an optical cavity.     

穿越深海会聚区的声源定位方法研究

基于WKBZ近似深海会聚区预报模型和方位滤波方法建立了穿越会聚区声源运动参数的估计模型，模拟结果表明，方位误差较小时，在前三个会聚区内，目标运动参数估计结果与模拟设定参数符合较好。     

Comparison of simultaneous signals obtained from a dual-field-of-view lidar and its application to noise reduction based on empirical mode decomposition

Although the empirical mode decomposition (EMD) method is an effective tool for noise reduction in lidar signals, evaluating the effectiveness of the denoising method is difficult. A dual-field-of-view lidar for observing atmospheric aerosols is described. The backscattering signals obtained from two channels have different signal-to-noise ratios (SNRs). The performance of noise reduction can be investigated by comparing the high SNR signal and the denoised low SNR signal without a simulation experiment. With this approach, the signal and noise are extracted to one intrinsic mode function (IMF) by the EMD- based denoising; thus, the threshold method is applied to the IMFs. Experimental results show that the improved threshold method can effectively perform noise reduction while preserving useful sudden-change information.     

基于相关光子多模式相关性的InSb模拟探测器定标方法

利用基于参量下转换产生的相关光子可以实现“无溯源”的绝对定标. 将该方法推广应用于模拟探测器定标的过程中, 获取两路模拟光电流信号的有效相关信息是主要难点. 在相关光子的多模式相关性理论模型的基础上, 提出了一种新的光电流处理方案. 通过将某一时刻采集到的光电流所包含的电荷量转换为等效光子计数, 采用双光路平衡探测和双通道数据波动校正的技术思路, 开展了红外模拟探测器量子效率定标验证实验研究. 利用532 nm单波长激光器为抽运源、PPLN晶体为非线性晶体, 在25 ℃工作温度下获取了631和3390 nm的相关光子对, 定标了InSb红外模拟探测器在3390 nm处的绝对功率响应度. 结果表明, 对InSb模拟探测器的合成不确定度为7.785%. 根据量子效率与绝对功率响应度之间的函数关系, 定标结果与国内计量单位的校准结果的相对偏差为3.6%. 利用多模式相关性在模拟信号下实现红外模拟探测器的绝对功率响应度定标在国际上暂无此方面的报道, 该方法验证了应用多模式相关性理论开展模拟探测器定标方法的可行性, 对于探索基于相关光子的定标技术和拓宽辐射定标应用领域具有重要意义.     

COHERENT INFORMATION ON THERMAL RADIATION NOISE CHANNEL: AN APPROACH OF INTEGRAL WITHIN ORDERED PRODUCT OF OPERATORS

An analytical expression is given to the coherent information of the thermal radiation signal transmitted over the thermal radiation noise channel, one of the most essential quantum Gaussian channels. Focusing on the single normal mode of the thermal radiation signal and noise, we resolve the entangled state density operator, which characterizes quantum information transmission, into a direct product of two parts, with each part being a thermal radiation density operator. The calculation is aided by the technique known as "integral within ordered product of operators".     

New approach to the normal mode method in underwater acoustics

A new approach to the numerical solution of normal model problems in underwater acoustics is presented,in which the corresponding normal mode problem is transformed to the problem of solving a dynamic system.Three applications are considered:(1)the broad band normal mode problem;(2) the range-dependent problem with perturbation proportional to the range parameter;and (3) the evolution of the normal mode with environmental parameters.A numerical simulation for a broad band problem is performed,and the calculated eigenvalues have good agreement with those obtained by the standard normal mode code KRAKAN.     

用局域模型研究分子局域模振动态的振转光谱

利用描述伸缩振动泛频态的两种模型———NMDD简正模型和HCAO局域模型的波函数的等价关系，发展了用局域模型波函数求振转参数有效值的方法，并用这个方法推出XH_n型（n=2，3，4）分子局域模振动态的有效振转参数在局域模极限下满足改进的“α-关系”． 关键词：     

Potential energy surfaces in algebraic molecular models using coherent states

The potential energy surfaces provided by the coherent states formalism for the case of interacting one-dimensional oscillators is investigated. The case of two interacting oscillators modelled with Morse potentials are considered in detail. First the traditional treatment is presented in order to identify the need to establish a new transformation between the parameters and the classical variables that allow the full Hamiltonian to be recovered. To this end the connection between the su(2) algebraic model and the usual treatment in configuration space was taken into account. It is shown that the coherent state approach when applied to recover the potential energy surface (PES) from a polyad preserving Hamiltonian is viable only in systems with a local mode behaviour. For molecules with a normal mode behaviour the approach is still valid, but the polyad must be broken in order to recover the PES. Our approach is evaluated through the calculation of the force constants for H₂O and CO₂, representative examples of local and normal behaviours.     

Low-frequency broadband sound source localization using an adaptive normal mode back-propagation approach in a shallow-water ocean

A variety of localization methods with normal mode theory have been established for localizing low frequency (below a few hundred Hz), broadband signals in a shallow water environment. Gauss-Markov inverse theory is employed in this paper to derive an adaptive normal mode back-propagation approach. Joining with the maximum a posteriori mode filter, this approach is capable of separating signals from noisy data so that the back-propagation will not have significant influence from the noise. Numerical simulations are presented to demonstrate the robustness and accuracy of the approach, along with comparisons to other methods. Applications to real data collected at the edge of the continental shelf off New Jersey, USA are presented, and the effects of water column fluctuations caused by nonlinear internal waves and shelfbreak front variability are discussed.     

Coupled reverberation chambers for emulating MIMO channels

This article describes a new experimental set up for emulating MIMO channels, based on two mode stirred reverberation chambers (MSRC), coupled together with a waveguide. This guide allows one to control the order of the channel diversity, the chambers generating a Rayleigh environment. This set up could thus be used to perform tests of MIMO communication systems in perfectly defined environments and thus under reproducible conditions. After a brief recall of the advantages and drawbacks of using a single reverberation chamber, we describe the theoretical approach and the experimental results for the analysis of two coupled chambers.     

Transmission of two mode coded channels in one fibre using optical directional couplers as mode selective elements

Mode multiplexing, a method for transmitting two signals along one fibre without time-or wavelength-multiplexing is presented with theoretical and experimental results. It is shown that two mode coded channels can be separated using optical directional couplers with enhanced mode selectivity combined with a simple signal processing unit.     

Electronic instabilities in 3D arrays of small-diameter (3, 3) carbon nanotubes

We investigate the electronic instabilities of the small-diameter (3, 3) carbon nanotubes by studying the low-energy perturbations of the normal Luttinger liquid regime. The bosonization approach is adopted to deal exactly with the interactions in the forward-scattering channels, while renormalization group methods are used to analyze the low-energy instabilities. In this respect, we take into account the competition between the effective e–e interaction mediated by phonons and the Coulomb interaction in backscattering and Umklapp channels. Moreover, we apply our analysis to relevant experimental conditions where the nanotubes are assembled into large three-dimensional arrays, which leads to an efficient screening of the Coulomb potential at small momentum-transfer. We find that the destabilization of the normal metallic behavior takes place through the onset of critical behavior in some of the two charge stiffnesses that characterize the Luttinger liquid state. From a physical point of view, this results in either a divergent compressibility or a vanishing renormalized velocity for current excitations at the point of the transition. We observe anyhow that this kind of critical behavior occurs without the development of any appreciable sign of superconducting correlations.     

Simultaneous dual mode add/drop multiplexers for optical interconnects buses

For the potential realization of optical interconnect scheme based on modal diversity, we propose and analyze efficient mode add drop multiplexers (MADM). Each of the two types of MADM proposed here enables a simultaneous two channels (modes) add/drop to/from a multimode bus. The simultaneous operation is of importance in reducing the device footprint within the expected ultra-dense interconnects schemes. We developed analytical design rules for the adiabatic devices and verified by simulation that an implementation based on Silicon over Insulator waveguides, is exhibiting low loss and low channels crosstalk (below −22 dB).