A Stochastic Approach for Blind Estimation of Multiple Co-Channel Signals Received at an Antenna Array

A stochastic maximum likelihood approach for blind estimation of co-channel signals received at an antenna array is proposed in this letter. A hidden Markov model formulation of the problem is introduced and the Baum-Welch algorithm for the associated stochastic maximum likelihood estimation procedure is modified. The performance of the proposed algorithm based on the evaluation of approximate Cramer-Rao bounds is studied. Finally, some simulation results are presented.     

交替使用小波去噪和全变差正则化的盲图像恢复算法

盲图像恢复就是在点扩散函数未知情况下从降质观测图像恢复出原图像.该文提出了一种交替使用小波去噪和全变差正则化的盲图像恢复算法.观测模型首先被分解成两个相互关联的子模型,这种分解转化盲恢复问题成为图像去噪和图像恢复两个问题,可以交替采用图像去噪和图像恢复算法求解.模糊辨识阶段,使用全变差正则化算法估计点扩散函数;图像恢复阶段,使用小波去噪和全变差正则化相结合的算法恢复图像.实验结果和与其它方法的比较表明该文算法能够获得更好的恢复效果.     

A blind SNR estimator for digital bandpass signals

A subspace-based blind Signal-to-Noise Ratio （SNR） estimation algorithm for digital bandpass signals in Additive White Gaussian Noise （AWGN） channel is discussed. The lower bounds of the mean and variance of the estimation are derived, and simulations are performed for the commonly used digital bandpass signals, such as MPSK （M=2, 4, 8）, MFSK （M=2, 4） and MQAM （M=16, 64, 128, 256） signals. Theoretical analyses and simulation results indicate that the proposed algorithm is effective even when the SNR is below 0dB. Furthermore, the algorithm can provide a blind estimator in that it needs neither the parameters of the received signals, such as the carrier frequency, symbol rate and modulation scheme, nor the synchronization of the system.     

An EME blind source separation algorithm based on generalized exponential function

This letter investigates an improved blind source separation algorithm based on Maximum Entropy （ME） criteria. The original ME algorithm chooses the fixed exponential or sigmoid ftmction as the nonlinear mapping function which can not match the original signal very well. A parameter estimation method is employed in this letter to approach the probability of density function of any signal with parameter-steered generalized exponential function. An improved learning rule and a natural gradient update formula of unmixing matrix are also presented. The algorithm of this letter can separate the mixture of super-Gaussian signals and also the mixture of sub-Gaussian signals. The simulation experiment demonstrates the efficiency of the algorithm.     

Some blind FRESH equalization algorithms with anti-interference capabilities

Some novel blind FREquency-SHift （FRESH） equalizer algorithms are proposed for the equalization of Finite Impulse Response （FIR） single channel with anti-interference capabilities. These algorithms based on FRESH filter can work well without any training sequence. Simulation results show that the equalizer algorithms can effectively reject many types of interferences and the performances of these new equalizer algorithms are superior to the conventional equalizer algorithms.     

Blind identification of a class of nonlinear systems with cyclostationary input

This letter deals with blind identification of nonlinear discrete Hammerstein system under the input signal that is cyclostationary. The first-order moment of the specific input as well as the inverse nonlinear mapping of the Hammerstein model are combined to establish a relationship between the system output and the system parameters, which implies an approach to identifying the system blindly. Simulation results demonstrate the effectiveness of this approach to blind identification of a class of nonlinear systems.     

微波原位合成Ag NPs/MoS2复合材料及其电化学性能

二硫化钼纳米片(MoS₂)受到带电杂质、结构缺陷和易聚集等因素的影响,导致其电子转移性能下降,使其应用受限。将银纳米颗粒(Ag NPs)与少层MoS₂纳米片复合,可提升MoS₂纳米片的电化学性能。本研究创新性地采用微波还原法,使Ag NPs原位沉积于MoS₂,得到Ag NPs/MoS₂复合材料。结果表明,将Ag NPs/MoS₂复合材料修饰于丝网印刷电极(screen printed electrodes,SPE)后,测得的循环伏安(cyclic voltammetry,CV)曲线峰电流值为同浓度单一MoS₂修饰电极的1.8倍,方波伏安(square wave voltammetry,SWV)曲线峰电流值为单一MoS₂修饰电极的3.4倍,电化学阻抗谱(electrochemical impedance spectroscopy,EIS)的电子转移阻抗值(Ret)仅为167Ω,相比MoS₂/S...     

天顶附近三轴光电跟踪系统Z轴运动状态分析

针对三轴光电跟踪系统在地平式盲区内的跟踪策略所具有的多样性,对天顶附近三轴光电跟踪系统Z轴运动状态进行了分析.仿真结果表明：地平式盲区内Z轴做匀角速运动有利于     

基于独立向量分析的脑电信号中肌电伪迹的去除方法

脑电数据经常被各种电生理信号伪迹所污染。在常见伪迹中,肌电伪迹特别难以去除。文献中最常用的方法包括诸如独立分量分析(Independent Component Analysis, ICA)和典型相关分析(Canonical Correlation Analysis, CCA)等盲源分离技术。该文首次提出一种基于独立向量分析(Independent Vector Analysis, IVA)的新方法,用以去除脑电中的肌电伪迹。IVA同时使用高阶统计量和二阶统计量,因此该方法能够充分利用肌电伪迹的非高斯性和弱相关性,兼具ICA方法和CCA方法的优势。实验表明,使用IVA方法可以在保留脑电成份的同时极大抑制肌电伪迹,效果显著优于ICA法和CCA法。     

基于快速独立成分分析的RoQ攻击检测方法

降质服务(Reduction of Quality, RoQ)攻击比传统的拒绝服务攻击(Denial of Service, DoS)攻击更具有隐秘性和多变性,这使得检测该攻击十分困难。为提高检测准确率并及时定位攻击源,该文将攻击流量提取建模为一个盲源分离过程,提出了基于快速ICA (Independent Component Analysis)的攻击流特征提取算法,从若干观测网络和终端设备中分离出RoQ攻击流,然后提取表征攻击流的特征参数。接着设计了一种基于支持向量机的协同检测系统和检测算法,通过用已标记的有攻击和无攻击的样本训练SVM分类器,最终实现RoQ攻击的检测。仿真结果表明该方法能够有效检测并定位伪造IP地址的RoQ攻击,检测率达到90%以上,而选取合适的ICA参数会提高检测效果。