Evaluating the performance of BSBL methodology for EEG source localization on a realistic head model

In this paper, we evaluate the performance of block sparse Bayesian learning (BSBL) method for EEG source localization. By exploiting the internal block structure, the BSBL method solves the ill‐posed inverse problem more efficiently than other methods that do not consider block structure. Simulation experiments were conducted on a realistic head model obtained by segmentation of MRI images of the head. Two definitions of blocks were considered: Brodmann areas and automated anatomical labeling (AAL). The experiments were performed both with and without the presence of noise. Six different noise levels were considered having SNR values from 5 dB to 30 dB with 5dB increment. The evaluation reveals several potential findings—first, BSBL is more likely to produce better source localization than sparse Bayesian learning (SBL), however, this is true up until a limited number of simultaneously active areas only. Experimental results show that for 71‐channel electrodes setup BSBL outperforms SBL for up to three simultaneously active blocks. From four simultaneously active blocks SBL turns out to be marginally better and the difference between them is statistically insignificant. Second, different anatomical block structures such as Brodmann areas or AAL does not seem to produce any significant difference in EEG source localization relying on BSBL. Third, even when the block partitions are not known exactly BSBL ensures better localization than SBL as soon as block structure persists in the signal. © 2017 Wiley Periodicals, Inc. Int J Imaging Syst Technol, 27, 46–56, 2017     

混响环境中突发声源定向方法及性能

针对突发性声源在混响条件下的定向技术进行了研究。基于传统广义互相关时延估计的定向方法,通过对互相关函数计算结果进行判别与约束、对数据帧采用滑动方式、对时延估计结果进行能量加权选举等措施,有效提高了声源定向结果的稳定性。实验结果表明,改进的算法在混响条件下能有效地对突发性声源进行可靠定向,可用于对枪声、爆炸声等突发性信号进行精确定向和定位。     

Maximum a posteriori probability direction finding and the dynamic programming algorithm

Abstract

In this paper, a dynamic programming (DP) algorithm is proposed to compute the maximum a posteriori probability (MAP) estimate of the random location of multiple sources by passive sensor array. Based on the principle of optimality, the multivariate MAP decision problem can be transformed into a multistage one‐dimensional maximization problem. By a recursive computation and backward optimum searching technique, the MAP solution can be obtained. The computational complexity is much less than that of the direct MAP searching method, especially when the number of sensors and/or the number of sources is large. In addition, the DP computation technique is equally applicable both in the case of correlated sources and the case of uncorrelated sources.     

Performance analysis of the maximum a posteriori probability direction finding

Abstract

In this paper, the mean square error performance of the maximum a posteriori (MAP) probability direction finding by sensor array in terms of its Cramer‐Rao lower bound (CRLB) is analyzed. Based on the principle of Bayesian estimator, a log posteriori probability function is formed when the a priori knowledge of location is given. The Fisher information matrix (FIM) is found accordingly. It shows that the CRLB of the MAP estimator is much lower than that of maximum likelihood technique, especially when the element SNR is low and/or the number of snapshots is small. In addition, the CRLB remains at a relatively low level in terms of the variance of DOA of sources. It also shows that the location variance dominates the behavior of the MAP direction finder when locations of sources are Gaussian distributed.     

小区域高精度实时三维声源定位系统

设计了一个基于AT89S52单片机的适用于低频(20Hz～2000Hz)、小区域的高精度实时三维声源定位系统。该系统包括三个模块:声源采集和模数转换模块;时间延迟采集模块;串口通信和定位算法模块。在1000m3范围内,根据该系统可以实时快速地定位出三维空间声源的位置,且定位最大水平偏向角误差为±0.3°,最大俯仰角误差为±0.5°。     

EEG source localization using a sparsity prior based on Brodmann areas

Localizing the sources of electrical activity in the brain from electroencephalographic (EEG) data is an important tool for noninvasive study of brain dynamics. Generally, the source localization process involves a high‐dimensional inverse problem that has an infinite number of solutions and thus requires additional constraints to be considered to have a unique solution. In this article, we propose a novel method for EEG source localization. The proposed method is based on dividing the cerebral cortex of the brain into a finite number of “functional zones” which correspond to unitary functional areas in the brain. To specify the sparsity profile of human brain activity more concisely, the proposed approach considers grouping of the electrical current dipoles inside each of the functional zones. In this article, we investigate the use of Brodmann's areas as the functional zones while sparse Bayesian learning is used to perform sparse approximation. Numerical experiments are conducted on a realistic head model obtained from segmentation of MRI images of the head and includes four major compartments namely scalp, skull, cerebrospinal fluid (CSF), and brain with relative conductivity values. Three different electrode setups are tested in the numerical experiments. The results demonstrate that the proposed approach is quite promising in solving the EEG source localization problem. In a noiseless environment with 71 electrodes, the proposed method was found to accurately locate up to 6 simultaneously active sources with accuracy >70%.     

声源定位系统动态校准方法研究

基于空间移动的标准点声源设计,建立声源定位系统动态校准装置。提出空气声声源定位系统动态校准方法,获得声源定位系统动态定位实验测量结果,分析影响动态定位结果的主要因素,并进行测量结果不确定度的评定。为车辆通过噪声源定位、飞行器飞行中噪声源定位的实验室动态校准提供了计量技术支撑。     

Method of determining the coordinates and magnetic moment of a dipole field source

Translated from Izmeritel'naya Tekhnika, No. 6, pp. 41–43, June, 1990.     

Method of determining the coordinates of a source of magnetic dipole moment

A method of determining the coordinates of a source of dipole magnetic moment is considered. The initial data are the measured values of the magnetic flux from the source passing through the loops of the primary measuring transducer of the magnetic-measuring system. The requirements imposed on the measuring system are analyzed and recommendations are made on the arrangement of the measuring windings. A definition of the equivalent dipole moment for practical objects is proposed. Translated from Izmeritel'naya Tekhnika, No. 5, pp. 50–54, May, 1998.     

A method of determining the direction to a high-energy charged-particle source

Translated from Izmeritel'naya Tekhnika, No. 8, pp. 51–52, August, 1991.     

Implementation of physical optics analysis of spiral antenna radiations in the presence of Bor radome structure for the application of direction finding

Abstract

A practical physical optics (PO) implementation procedure is employed to study the radiations of multi‐arm spiral antennas in the presence of a body of revolution (BOR) radome structure in direction finding applications. This procedure potentially simplifies the geometrical optics ray tracing procedure based on characteristics of spiral antennas, which is required to define the equivalent currents of PO, and provides efficient formulations to compute the radiation fields due to PO currents that are equivalent to the radiation of spiral antennas in the presence of the same type radome structure.     

基于声压幅度比的多声源分离定位决策研究

利用声压幅度比模型,提出了一种基于声压幅度比的多声源分离定位方法,该方法利用盲信号分离算法实现混合声源信号的分离,根据谱估计的相似度确定接收信号中各声源的分配情况,结合幅度差异因子获得传感器的声源信号分布,再通过单声源的声压幅度比模型确定声源位置,实现多声源定位。由于盲信号分离算法比较成熟,且实际中的声源信号大多为非高斯,因而满足盲信号分离条件。该方法具有实用强、应用性广等特点,对其它分离、定位问题也有借鉴作用。     

一种可作为声源定位与声场空间特性分析的测量系统

提出了一种由重复发射的声源配合缓慢转动的传声器组成的、等效于圆形传声器阵列的室内声学测量系统。阐述了这种测量系统的特点及其理论基础,介绍了它在室内声场中若干涉及声源定位及声场空间特性测量等方面的应用,并结合实例作了讨论。系统具有较强的适应性及实用性,在室内声学测量中具有广泛的应用前景。     

自适应空域矩阵滤波在匹配场定位中的应用

匹配场定位问题中,为了不影响观测结果,需要抑制观测区域存在的干扰。广义空域滤波在抑制拖曳舰船噪声及类似已知干扰的问题上起到了很好的效果,但对于强干扰或未知干扰声源信息的情况,需要寻找一种新的方法。波束形成目标方位估计问题中的自适应空域矩阵滤波器设计方法可以用来解决这一问题。对自适应空域矩阵滤波器增加稳健性约束处理后,针对匹配定位问题做了大量仿真实验,比较了广义空域矩阵滤波器和自适应空域矩阵滤波器对干扰的抑制效果。实验结果表明,如果选取正确的通带范围,自适应空域矩阵滤波在匹配场定位应用中可以非常有效地抑制未知强干扰。     

Chan算法在海上声源定位测量中的应用

针对到达时间差（Time Difference of Arrival,TDOA）体制下海上声源定位测量问题,研究了Chan算法在定位测量中的应用。建立了基于TDOA体制的海上声源被动定位模型,推导了Chan算法求解TDOA定位方程的步骤,采用了蒙特卡洛数值方法对Chan算法与初始值选择真值的泰勒（Taylor）级数展开法在不同阵元数条件下的定位精度进行了比较,得出了Chan算法在海上声源定位测量中应用条件及基阵布设原则。仿真结果表明,在一定条件下,Chan算法可应用于海上声源定位测量且定位精度较高,研究结果可为海上声源测量系统定位算法设计及基站布设提供参考依据。     

基于麦克风阵列的三维声源定位算法及其实现

从系统的角度对真实声场环境下基于到达时间差的的声源定位算法进行了研究,提出了一种改进的互功率谱相位（CSP）时延估计算法,在此基础上,提出了一种用于定位估计的基于球形差值（SI）的随机梯度下降（LMS）算法。为了验证算法的有效性,实际构建了三维空间中的点声源定位系统。实验结果表明所提出的算法具有较高的定位精度。     

基于鸡群算法的近场声源三维定位MUSIC算法

针对三维多重信号分类（Multiple Signal Classification,MUSIC）算法估计声源位置时计算速度慢,计算量大等缺点,提出了一种基于鸡群优化（Chicken Swarm Optimization,CSO）算法的近场声源三维定位算法。首先建立近场声源信号接收的数学模型,并选取三维MUSIC算法中的空间谱函数为文章算法中的适应度函数。通过不断迭代和局部搜索,以适应度值为指标对鸡群个体进行排序,最终得到最优鸡群个体的位置,即近场待测声源的坐标。仿真和实验结果表明：文中算法具有定位精度高、计算效率高、实时性好等优点,文中算法的平均用时仿真时为三维MUSIC算法平均用时的1.9%,实验时为三维MUSIC算法用时的3.2%。     

利用声压有效值信息进行白噪声声源识别

研究提出利用声信号有效值进行内积运算识别白噪声声源的方法,用传声器阵列测得声压信号有效值组成声压有效值向量,与虚拟点声源声压有效值向量做内积,搜索内积模的最大值,根据柯西施瓦兹不等式确定声源位置.建立相应的识别步骤,对白噪声声源进行仿真识别,分析测量误差与测量距离对识别效果的影响,通过增大传声器布置间距改善测量距离较远...     

基于深海会聚区声强匹配处理的声源定位方法

匹配场处理技术(Matched Field Processing MFP)近年来在声源被动定位、海洋环境声学参数反演等方面得到广泛的应用。根据深海声道中声场的会聚现象,提出了一种基于深海会聚区声强匹配处理(Matched Convergence Intensity Processing,MCIP)的深海声源定位方法。当声源和接收水听器处在会聚区深度范围内时,MCIP方法利用单个水听器即可实现声源距离和声源深度估计。对单个水听器的实测信号进行相位补偿到会聚区距离上,得到实测场声强,与拷贝场会聚区声强进行相关计算并搜索峰值来确定声源位置。数值仿真实验验证了MCIP方法,并分析了环境失配情况下MCIP的估计性能。