解卷积的多重信号分类算法方位谱低背景处理方法

针对信噪比较低时,多重信号分类(Multiple Signal Classification,MUSIC)算法方位谱背景级较高的问题,提出了一种解卷积的MUSIC方位估计算法(Deconvolvecd MUSIC,D-MUSIC)。该方法用一个类似冲激函数作为MUSIC算法输出方位谱的点散射函数(Point Scattering Function,PSF),然后基于解卷积图像复原理论,利用该点散射函数和RichardsonLucy(R-L)迭代算法对MUSIC算法的方位谱进行解卷积,获得D-MUSIC算法的方位谱,达到降低方位谱背景级的目的。仿真表明,该方法继承了MUSIC算法的高分辨性能,且可以明显降低方位谱的背景级,具有较好的方位估计性能。对南海海上试验的水平阵数据进行处理,分析比较了利用MUSIC算法和解卷积MUSIC算法获得的方位谱时间历程图,分析结果有效验证了D-MUSIC算法性能的优越性。     

Acoustic classification of multiple simultaneous bird species: a multi-instance multi-label approach

Although field-collected recordings typically contain multiple simultaneously vocalizing birds of different species, acoustic species classification in this setting has received little study so far. This work formulates the problem of classifying the set of species present in an audio recording using the multi-instance multi-label (MIML) framework for machine learning, and proposes a MIML bag generator for audio, i.e., an algorithm which transforms an input audio signal into a bag-of-instances representation suitable for use with MIML classifiers. The proposed representation uses a 2D time-frequency segmentation of the audio signal, which can separate bird sounds that overlap in time. Experiments using audio data containing 13 species collected with unattended omnidirectional microphones in the H. J. Andrews Experimental Forest demonstrate that the proposed methods achieve high accuracy (96.1% true positives/negatives). Automated detection of bird species occurrence using MIML has many potential applications, particularly in long-term monitoring of remote sites, species distribution modeling, and conservation planning.     

色噪声背景下微弱正弦信号的混沌检测

提出一种利用混沌在特定状态下对参数的敏感性来实现微弱正弦信号检测的新方案-该方案可以有效地将深陷在色噪声背景中的微弱正弦信号检测出来-给出了混沌检测的方法,分析了混沌检测中噪声对系统状态的影响-仿真实验表明该混沌检测系统对小信号非常敏感，对任何零均值色噪声均具有极强的抑制能力- 关键词： 微弱正弦信号 混沌检测 色噪声 信噪比     

Reduction of electronic delay in active noise control systems--a multirate signal processing approach

Electronic delay has been a critical problem in active noise control (ANC) systems. This is true whether a feedforward structure or a feedback structure is adopted. In particular, excessive delays would create a causality problem in a feedforward ANC system of a finite-length duct. This paper suggests a multirate signal-processing approach for minimizing the electronic delay in the control loop. In this approach, digital controllers are required in decimation and interpolation of discrete-time signals. The computation efficiency is further enhanced by a polyphase method, where the phases of low-pass finite impulse response (FIR) filters must be carefully designed to avoid unnecessary delays. Frequency domain optimization procedures based on H1, H2, and Hinfinity norms, respectively, are utilized in the FIR filter design. The proposed method was implemented by using a floating-point digital signal processor. Experimental results showed that the multirate approach remains effective for suppressing a broadband (200-600 Hz) noise in a duct with a minimum upstream measurement microphone placement of 20 cm.     

兵器辐射噪声信号的非线性特性及其在被动声信号分类中的应用

首先利用双谱分析检验了兵器辐射噪声信号的非高斯、非线性特性,结果表明准确的兵器辐射噪声信号模型应为非线性模型。然后,提出了利用一种双线性参数模型对信号进行预处理,并给出了参数估计算法。最后,利用提取的双线性参数模型的系数建立了一积隐含马尔可夫模型,对声信号进行分类。分类结果表明,基于双线性参数模型的积隐含马尔可夫模型分类器,在性能上优于传统的基于AR参数模型的隐含马尔可夫模型分类器,在被动声信号分类中具有良好的应用前景。     

Manifestations of phase-coherent transport in graphene

The electronic transport properties of graphene exhibit pronounced differences from those of conventional two dimensional electron systems investigated in the past. As a consequence, well established phenomena such as the integer quantum Hall effect and weak localization manifest themselves differently in graphene. Here we present an overview of recent experiments that we have performed to probe phase coherent transport. In particular, we have investigated in great detail Josephson supercurrent and superconducting proximity effect in junctions consisting of a graphene layer in between superconducting electrodes. We have also used the same devices to measure aperiodic conductance fluctuations and weak localization. The experimental results clearly indicate that low-temperature transport in graphene is phase coherent on a ∼ 1μm length scale, irrespective of the position of the Fermi level. We discuss the different behavior of Josephson supercurrent and weak localization in terms of the unusual properties of the electronic states in graphene upon time reversal symmetry.     

Interferometric method of quasi-stationary signal isolation in a noise background

Scientific Research Radiophysical Institute. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 32, No. 10, pp. 1250–1257, October, 1989.     

基于Group Lasso的多重信号分类声源 定位优化算法*

多重信号分类算法因其抑制噪声能力强、计算速度快等优点,在声源定位领域得到广泛应用。但该算法在中低频段分辨率及聚焦性能较差。针对该问题,提出一种基于Group Lasso的多重信号分类优化算法。该算法将多重信号分类算法输出值作为初始值,并在Group Lasso算法组间计算时对目标信号进行稀疏、在组内计算时对该组信号进行平滑及阈值截断。仿真结果表明:该优化算法在中低频段可明显提高多重信号分类算法分辨率,同时改善因扫描位置与声源面位置不重合引起的聚焦性能下降问题。     

基于时间反转MUSIC的奥氏体不锈钢超声成像分析

奥氏体不锈钢管道广泛应用于核电及某些化工领域等,但奥氏体不锈钢焊缝缺陷的检测仍然比较困难。在时间反转的基础上,采用DORT算法和MUSIC算法对较低信噪比(-5 dB和-10 dB)的缺陷定位进行仿真分析,在定制的奥氏体不锈钢对接焊缝试块上(300 mm×90 mm×30 mm),采用16阵元超声相控阵探头对缺陷进行检测,引入TR-MUSIC算法对缺陷回波信号进行频域分析。结果表明,低信噪比时,TR-MUSIC算法较TR-DORT算法能更好的抑制旁瓣,使信号能量能更好的聚焦于缺陷;在奥氏体不锈钢焊缝相距25 mm的Φ2mm缺陷(深度为50 mm)检测实验数据基础上,TR-MUSIC算法能够更准确定位缺陷。     

A new approach to detecting weak signal in strong noise based on chaos system control

In this paper, a chaos system and proportional differential control are both used to detect the frequency of an unknown signal. In traditional methods the useful signal is obtained through the Duffing equation or other chaotic oscillators. But these methods are too complex because of using a lot of chaos oscillators. In this paper a new method is presented that uses the R?ssler equation and proportional differential control to detect a weak signal frequency. Substituting the detected signal frequency into the R?ssler equation leads the R?ssler phase state to be considerably changed. The chaos state can be controlled through the proportional differential method. Through its phase diagram and spectrum analysis, the unknown frequency is obtained. The simulation results verify that the presented method is feasible and that the detection accuracy is higher than those of other methods.     

Application of a noise signal in acoustic tomography of the arctic basin

The time correlation function of a noise signal propagating in an arctic-type waveguide is considered. For a coherent signal, the time cross-correlation function is formed with the use of either the total signal, or a single selected mode, or a reference signal at one of the correlator inputs. The use of narrow-band signals is shown to be preferable, because the waveguide dispersion affects the waveguide response. It is demonstrated that, for tomographic investigations in a waveguide irregular along the path, it is expedient to correlate the signals received at two different points that are selected on the path so as to enclose the waveguide part the variability of whose parameters is the object of interest.     

一种强噪声背景下微弱超声信号提取方法研究

为解决在强噪声背景下获取超声信号的难题,基于粒子群优化算法和稀疏分解理论提出一种强噪声背景下微弱超声信号提取方法.该方法将降噪问题转换为在无穷大参数集上对函数进行优化的问题,首先以稀疏分解理论和超声信号的结构特点为依据构建了粒子群优化算法运行所需要的目标函数及去噪后信号的重构函数,从而将粒子群优化算法和超声信号降噪联系在一起;然后根据粒子群优化算法可以在连续参数空间寻优的特点建立了用于匹配超声信号的连续超完备字典,并采用改进的自适应粒子群优化算法在该字典中对目标函数进行优化;最后根据对目标函数在字典上的优化结果确定最优原子,并利用最优原子按照重构函数重构出降噪后的超声信号.通过对仿真超声信号和实测超声信号的处理,结果表明本文提出的方法可以有效提取信噪比低至-4 dB的强噪声背景下的微弱超声信号,且和基于自适应阈值的小波方法相比本文方法表现出更好的降噪性能.     

Generation of a variable linear array of phase-coherent supercontinuum sources

We investigate the coherence properties of a linear array of white-light sources produced in bulk media by ultrashort laser pulses. The array is generated out of the spatial interference pattern between two laser pump pulses, so that the number of supercontinuum sources and their separations can be easily manipulated by varying the geometry of the laser beam interaction. We find that all the secondary white-light sources which arise from the generation of filaments in the optical medium are well phase-locked and are thus able to generate stable and high-visibility multiple-beam interference patterns in the far-field. Observations are compared to the results of a simple model which takes into account a clamping of the peak laser intensity inside the filaments and includes intensity-dependent phase shifts among the different sources. PACS 42.65.Jx; 42.65.Ky; 42.65.Re     

Time-reversal symmetry breaking of p-orbital bosons in a one-dimensional optical lattice

We study bosons loaded in a one-dimensional optical lattice of twofold p-orbital degeneracy at each site. Our numerical simulations find an anti-ferro-orbital p(x)+ip(y), a homogeneous p(x) Mott-insulator phase, and two kinds of superfluid phases distinguished by the orbital order (anti-ferro-orbital and paraorbital). The anti-ferro-orbital order breaks time-reversal symmetry. Experimentally observable evidence is predicted for the phase transition between the two different superfluid phases. We also discover that the quantum noise measurement is able to provide a concrete evidence of time-reversal symmetry breaking in the first Mott phase.     

Time-reversal invariance in the beta-decay of RaE

The question of the possible violation of time-reversal invariance in RaE beta decay has been reinvestigated. The ²-analysis of the available experimental data on spectrum shape together with the longitudinal polarization of beta electrons lead to an upper limit of 2° for the relative phase of the vector and axial vector coupling constants which is a lower value than that given in some previous papers.