距离保持投影非线性降维技术的可视化与分类

 本文对高维数据距离保持投影方法进行了改进和扩展,采用测地线距离代替欧氏距离,能够正确地展开数据所在的流形,同时又准确地保留了每个数据点到其最近邻点和部分近邻点之间的距离.为了减少邻域大小难以选取问题,采取了对邻域大小不甚敏感的P-ISOMAP算法.与原方法和ISOMAP等高维数据降维方法相比,本文方法能更好地对数据进行降维和可视化.并且,为了进行分类,本文扩展了新的分类技术.实验表明本文方法在可视化、降维和分类方面效果不错.     

基于Autoencoder网络的数据降维和重构

在机器学习,模式识别以及数据挖掘等诸多研究领域中,往往会面临着维数灾难问题。因此,特征数据的降维方法,即将高维的特征数据如何进行简化投射到低维空间中再进行处理,成为当前数据驱动的计算方法研究热点之一。该文引入一种特殊的非线性降维方法,称为自编码(Autoencoder)神经网络,该方法采用CRBM(Continuous Restricted Boltzmann Machine)的网络结构,通过训练具有多个中间层的双向深层神经网络将高维数据转换成低维嵌套并继而重构高维数据。特别地,自编码网络提供了高维数据空间和低维嵌套结构的双向映射,有效解决了大多数非线性降维方法所不具备的逆向映射问题。将Autoencoder用于人工数据和真实图像数据的实验表明,Autoencoder不仅能发现嵌入在高维数据中的非线性低维结构,也能有效地从低维结构中恢复原始高维数据。     

高维数据降维技术及研究进展

降维技术旨在将高维数据映射到更低维的数据空间上以寻求数据紧凑表示,该技术有利于对数据做进一步处理。随着多媒体技术和计算机技术的高速发展,数据维度呈爆炸性增长,使得机器学习、图像处理等研究领域的数据分析变得为越来越困难。为消除上述问题造成的维度灾难,研究学者提出了一系列的解决方法。文中为探索这些降维技术的实用性,介绍了传统的降维技术以及近年推出的降维技术,分析了典型降维技术的性能,指出降维技术仍存在的问题并分析了未来值得关注的研究方向。     

文本数据的非线性降维方法研究

采用了空间解析几何中的球极映射方法,形成高维向量到低维向量的拓扑变换模型,实现了矩阵形武的高维空间文本集合到低维空间文本集合的一一映射,编制了相应的算法,从而有效地解决了文本挖掘中的非线性降维问题,克服了以往研究中的缺陷.     

基于正则化的半监督等距映射数据降维方法

针对等距映射(ISOMAP)算法无监督,不能生成显式映射函数等局限性,该文提出一种正则化的半监督等距映射(Reg-SS-ISOMAP)算法。该算法首先利用训练样本的标签样本构建K联通图(K-CG),得到近似样本间测地线距离,并作为矢量特征代替原始数据点;然后通过测地线距离计算核矩阵,用半监督正则化方法代替多维尺度分析(MDS)算法处理矢量特征;最后利用正则化回归模型构建目标函数,得到低维表示的显式映射。算法在多个数据集上进行了比较实验,结果表明,文中提出的算法降维效果稳定,识别率高,显示了算法的有效性。     

Analysis and Classification of Frequency-Domain Terahertz Reflection Spectra Using Supervised and Unsupervised Dimensionality Reduction Methods

Journal of Infrared, Millimeter, and Terahertz Waves - The unique properties of terahertz (THz) spectroscopy show a great potential for security and defense applications such as safe screening of...     

A Modified Minimum Classification Error (MCE) Training Algorithm for Dimensionality Reduction

Dimensionality reduction is an important problem in pattern recognition. There is a tendency of using more and more features to improve the performance of classifiers. However, not all the newly added features are helpful to classification. Therefore it is necessary to reduce the dimensionality of feature space for effective and efficient pattern recognition. Two popular methods for dimensionality reduction are Linear Discriminant Analysis (LDA) and Principal Component Analysis (PCA). While these methods are effective, there exists an inconsistency between feature extraction and the classification objective. In this paper we use Minimum Classification Error (MCE) training algorithm for feature dimensionality reduction and classification on Daterding and GLASS databases. The results of MCE training algorithms are compared with those of LDA and PCA.     

Dimensionality Reduction for Hyperspectral Data Based on Sample-Dependent Repulsion Graph Regularized Auto-encoder

To achieve high classification accuracy of hyperspectral data, a dimensionality reduction algorithm called Sample-dependent repulsion graph regularized auto-encoder (SRGAE) is proposed. Based on the sample-dependent graph, by applying the repulsion force to the samples from different classes but nearby, a sampledependent repulsion graph is built to make the samples from the same class will be projected to samples that are close-by and the samples from different classes will be projected to samples that are far away. The sampledependent repulsion graph can avoid the neighborhood parameter selection problem existing in the nearest neighborhood graph. By integrating advantages of deep learning and graph regularization technique, the SRGAE can maintain the learned deep features are consistent with the inherent manifold structure of the original hyperspectral data. Experimental results on two real hyperspectral data show that, when compared with some popular dimensionality reduction algorithms, the proposed SRGAE can yield higher classification accuracy.     

基于独立成分分析的高光谱图像数据降维及压缩

该文提出了一种以高光谱图像分析为目标的基于独立成分分析的高光谱图像降维和压缩方法。该方法首先通过独立成分分析提取高光谱数据的光谱特征实现高光谱图像降维,再对降维后的图像采用预测和自适应算术编码的方法进行压缩。对220波段和64波段高光谱数据的实验结果表明,该方法与基于主成分分析的降维相比,压缩比有所提高,特别是更有利于后续的分析处理,但峰值信噪比有所降低。     

Dimensionality Reduction in Control and Coordination of the Human Hand

The concept of kinematic synergies is proposed to address the dimensionality reduction problem in control and coordination of the human hand. This paper develops a method for extracting kinematic synergies from joint-angular-velocity profiles of hand movements. Decomposition of a limited set of synergies from numerous movements is a complex optimization problem. This paper splits the decomposition process into two stages. The first stage is to extract synergies from rapid movement tasks using singular value decomposition (SVD). A bank of template functions is then created from shifted versions of the extracted synergies. The second stage is to find weights and onset times of the synergies based on $l_1$ -minimization, whose solutions provide sparse representations of hand movements using synergies.      

一种基于Gabor小波及互协方差降维运算的人脸识别方法

针对传统的人脸识别方法对人脸图像的曝光量、表情比较敏感,并且具有较大类内离散度的缺点,该文提出一种基于Gabor小波以及加权互协方差运算的人脸识别算法。该算法首先对人脸图像提取Gabor特征,然后使用加权的互协方差矩阵对经过处理的特征图像进行降维及特征提取;最后使用最近邻分类器进行分类。在ORL数据库和AR数据库上的实验表明,该方法的降维和识别性能优于传统2DPCA及其改进算法,能兼顾维度简约性和准确性,有效地提高了识别性能。     

EEG Data Classification for Mental State Analysis Using Wavelet Packet Transform and Gaussian Process Classifier

Stress is one of the most common problems that is faced by a majority of the students. Long-term stress can lead to serious health problems, for example, depression, heart disease, anxiety, and sleep disorder. This paper proposes an efficient stress level detection framework to detect the stress in students using Electroencephalogram (EEG) signals. The framework classifies stress into three levels; low stress, medium stress and high stress. In this experiment, EEG data is collected from six subjects by placing two electrodes in the prefrontal region. During each trial, the subject solves arithmetic questions under some time pressure. The EEG data is collected while the subject solves the question. The collected data is pre-processed using a band-pass filter to remove artefacts and appropriate features are extracted through the wavelet packet transform and PyEEG module. ReliefF feature selection method is used to select the best features for classification. The selected feature set is classified into three categories using Gaussian Classification. The proposed framework effectively classifies the level of stress with an accuracy of 94%.

     

基于FPGA的高光谱图像奇异值分解降维技术

为了解决高光谱图像维数高、数据量巨大、实时处理技术实现难的问题,提出了高光谱图像实时处理降维技术.采用奇异值分解(SVD)算法对高光谱图像进行降维,又在可编程门阵列(FPGA)芯片中针对这一算法划为自相关模块、特征求解模块、特征提取模块和降维实现模块4个模块进行编程实现、仿真和验证.仿真结果表明,高光谱图像降维后数据量为降维前的1/3,而降维后的分类像素点误差为0.2109%,证明了奇异值分解算法进行高光谱图像降维算法的有效性.     

基于全局背景与特征降维的视觉跟踪算法

相关滤波算法容易受到形变、运动模糊、相似背景等因素的干扰,导致跟踪任务失败。为了克服以上问题,该文提出一种基于全局背景与特征降维的视觉跟踪算法。该算法首先提取紧邻目标的图像区域作为负样本供分类器学习,以抑制相似背景的干扰;然后提出一种基于主成分分析的更新策略,构建降维矩阵压缩HOG特征的维度,在更新分类器的同时减少其冗余度;最后加入颜色特征表征运动目标,并根据特征对系统状态的响应强度进行自适应融合。在标准数据集上将该文提出的算法与Staple, KCF等其他算法进行了仿真对比,结果表明该文算法具有更强的鲁棒性,在形变因素的影响下,所提出的算法与Staple和KCF算法相比距离精度分别提升8.3%和13.1%。     

Unsupervised,Supervised and Semi-supervised Dimensionality Reduction by Low-Rank Regression Analysis

Techniques for dimensionality reduction have attracted much attention in computer vision and pattern recognition.However,for the supervised or unsupervised case,the methods combining regression analysis and spectral graph analysis do not consider the global structure of the subspace;For semi-supervised case,how to use the unlabeled samples more effectively is still an open problem.In this paper,we propose the methods by Low-rank regression analysis (LRRA) to deal with these problems.For supervised or unsupervised dimensionality reduction,combining spectral graph analysis and LRRA can make a global constraint on the subspace.For semi-supervised dimensionality reduction,the proposed method incorporating LRRA can exploit the unlabeled samples more effectively.The experimental results show the effectiveness of our methods.     

Fourier-Based Feature Extraction for Classification of EEG Signals Using EEG Rhythms

In this paper, we propose a method for the analysis and classification of electroencephalogram (EEG) signals using EEG rhythms. The EEG rhythms capture the nonlinear complex dynamic behavior of the brain system and the nonstationary nature of the EEG signals. This method analyzes common frequency components in multichannel EEG recordings, using the filter bank signal processing. The mean frequency (MF) and RMS bandwidth of the signal are estimated by applying Fourier-transform-based filter bank processing on the EEG rhythms, which we refer intrinsic band functions, inherently present in the EEG signals. The MF and RMS bandwidth estimates, for the different classes (e.g., ictal and seizure-free, open eyes and closed eyes, inter-ictal and ictal, healthy volunteers and epileptic patients, inter-ictal epileptogenic and opposite to epileptogenic zone) of EEG recordings, are statistically different and hence used to distinguish and classify the two classes of signals using a least-squares support vector machine classifier. Experimental results, with 100 % classification accuracy, on a real-world EEG signals database analysis illustrate the effectiveness of the proposed method for EEG signal classification.     

遥感影像的半监督判别局部排列降维简

 针对遥感影像数据具有的高维数和少量已标记样本的特性,提出一种基于图的半监督判别局部排列降维方法.首先,针对全部已标记和未标记样本数据构造相似图和惩罚图.然后,基于同类近邻点的分散度最小且不同类近邻点的分散度最大的原则,分别确立相似图和惩罚图上的优化目标.最后,通过同时优化这两种图上的目标函数,得到从高维到低维的最优映射关系,从而达到对高维遥感影像数据维数约简的目的.ROSIS高光谱数据上的实验结果表明,所提算法能够有效提高高维遥感影像的总体精度和Kappa系数.     

压缩深层神经网络隐藏层维度对其分类性能的影响

为了使深层神经网络具有更好的泛化能力、少量训练时间的性能。文中汲取压缩神经网络的思想,通过将深层神经网络的输入层与隐藏层按照不同的比例将隐藏层的维度进行压缩,并在传统压缩深层神经网络的基础上,在其顶层添加一个分类层,使深层神经网络拥有分类的能力。实验将构建的深层神经网络应用于MNIST手写数据集的分类测试,结果表明,经过适当压缩的深层神经网络比未被压缩的深层神经网络具有更好的分类效果,而且节省了大量的训练时间。     

大型阵列降维-和差多波束形成的联合优化算法

 大型、超大型相控阵列由于具有高增益、指向性强等优点得到越来越广泛的应用,数字波束形成具有抗干扰、波束切换灵活等优点,而基于大型全阵列数字波束形成需要庞大馈电网络与接收/发射通道而面临高成本、低实时性等缺点.针对此,本文提出了一种用于大型阵列的阵列降维-和差数字多波束形成的联合优化算法,该算法对大型阵列采用模拟和数字联合和差多波束形成,通过基于模拟退火、遗传算法和粒子群智能优化算法的子阵划分优化和子阵级与阵元级的和差联合加权逼近优化,保证在模拟子阵方向图内无栅瓣的同时,获得尽可能好的和差波束主副比及差波束零陷深度,且增益损失较小.最后仿真实验和性能分析验证了所提算法的有效性和可行性.     

基于黎曼流形监督降维的矩阵CFAR增强检测

矩阵CFAR检测是从几何流形角度处理雷达目标检测问题的新技术。为进一步提升其在复杂杂波背景下的检测性能,本文提出一种黎曼流形监督降维的矩阵CFAR增强检测方法。首先,将检测问题视为目标与杂波的分类问题,分别构建黎曼流形上目标单元与杂波单元的类内和类间权重矩阵;其次,为增强目标与杂波的可分性,采用保持类内几何距离最小,类间几何距离最大的准则建立降维目标函数,并基于Grassmann流形求解降维优化问题获得映射矩阵;最后,提出一种矩阵CFAR增强检测方法,实现目标增强检测。采用蒙特卡罗方法对仿真数据和实测海杂波数据进行实验分析,结果表明,所提出的方法能够进一步提升检测性能。