A multiple layer fusion approach on keystroke dynamics

In this paper, we present a novel keystroke dynamic recognition system by means of a novel two-layer fusion approach. First, we extract four types of keystroke latency as the feature from our dataset. The keystroke latency will be transformed into similarity scores via Gaussian Probability Density Function (GPD). We also propose a new technique, known as Direction Similarity Measure (DSM), which measures the absolute difference between two sets of latency. Last, four fusion approaches coupled with six fusion rules are applied to improve the final result by combining the scores that are produced by GPD and DSM. Best result with equal error rate of 1.401% is obtained with our two-layer fusion approach.     

人脸识别反欺诈研究进展

当前,人脸识别理论和技术取得了巨大的成功,被广泛应用于政府、金融和军事等关键领域.与其他信息系统类似,人脸识别系统也面临着各类安全问题,其中,人脸欺诈(facespoofing,FS)是最主要的安全问题之一.所谓的人脸欺诈,是指攻击者采用打印照片、视频回放和3D面具等攻击方式,诱骗人脸识别系统做出错误判断,因而是人脸识别系统所必须解决的关键问题.对人脸反欺诈(faceanti-spoofing,FAS)的最新进展进行研究:首先,概述了FAS的基本概念;其次,介绍了当前FAS所面临的主要科学问题以及主要的解决方法及其优缺点;在此基础上,将已有的FAS工作分为传统方法和深度学习方法两大类,并分别进行详细论述;接着,针对基于深度学习的FAS域泛化和可解释性问题,从理论和实践的角度进行说明;然后,介绍了FAS研究所使用的典型数据集及其特点,并给出了FAS算法的评估标准和实验对比结果;最后,总结了FAS未来的研究方向并对发展趋势进行展望.     

The geometry of time-varying cross-correlation random fields

The goal of this paper is to assess the P-value of local maxima of time-varying cross-correlation random fields. The motivation for this comes from an electroencephalography (EEG) experiment, where one seeks connectivity between all pairs of voxels inside the brain at each time point of the recording window. In this way, we extend the results of [Cao, J., Worsley, K.J., 1999b. The geometry of correlation fields with an application to functional connectivity of the brain. The Annals of Applied Probability 9 (4), 1021-1057] by searching for high correlations not only over all pairs of voxels, but over all time points as well. We apply our results to an EEG data set of a face recognition paradigm. Our analysis determines those time instants for which there are significantly correlated regions involved in face recognition.     

模糊支持向量机在人脸识别中的应用

本文首先介绍了人脸图像的代数特征抽取方法 ICA,再对模糊支持向量机(Fuzzy Support Vector Machine,FSVM)作了重点分析和研究。将抽取的人脸特征应用到基于FSVM和基于模糊系统的算法上,采用基于模糊分类系统和二叉决策树相结合的方法进行人脸识别,可以达到理想的识别效果。     

Audio-visual human recognition using semi-supervised spectral learning and hidden Markov models

This paper presents a multimodal system for reliable human identity recognition under variant conditions. Our system fuses the recognition of face and speech with a general probabilistic framework. For face recognition, we propose a new spectral learning algorithm, which considers not only the discriminative relations among the training data but also the generative models for each class. Due to the tedious cost of face labeling in practice, our spectral face learning utilizes a semi-supervised strategy. That is, only a small number of labeled faces are used in our training step, and the labels are optimally propagated to other unlabeled training faces. Besides requiring much less labeled data, our algorithm also enables a natural way to explicitly train an outlier model that approximately represents unauthorized faces. To boost the robustness of our system for human recognition under various environments, our face recognition is further complemented by a speaker identification agent. Specifically, this agent models the statistical variations of fixed-phrase speech using speaker-dependent word hidden Markov models. Experiments on benchmark databases validate the effectiveness of our face recognition and speaker identification agents, and demonstrate that the recognition accuracy can be apparently improved by integrating these two independent biometric sources together.     

Unsupervised representation learning with Minimax distance measures

Machine Learning - We investigate the use of Minimax distances to extract in a nonparametric way the features that capture the unknown underlying patterns and structures in the data. We develop a...     

Face recognition under arbitrary illumination using illuminated exemplars

Recently, the importance of face recognition has been increasingly emphasized since popular CCD cameras are distributed to various applications. However, facial images are dramatically changed by lighting variations, so that facial appearance changes caused serious performance degradation in face recognition. Many researchers have tried to overcome these illumination problems using diverse approaches, which have required a multiple registered images per person or the prior knowledge of lighting conditions. In this paper, we propose a new method for face recognition under arbitrary lighting conditions, given only a single registered image and training data under unknown illuminations. Our proposed method is based on the illuminated exemplars which are synthesized from photometric stereo images of training data. The linear combination of illuminated exemplars can represent the new face and the weighted coefficients of those illuminated exemplars are used as identity signature. We make experiments for verifying our approach and compare it with two traditional approaches. As a result, higher recognition rates are reported in these experiments using the illumination subset of Max-Planck Institute face database and Korean face database.     

Learning representations from dendrograms

Machine Learning - We propose unsupervised representation learning and feature extraction from dendrograms. The commonly used Minimax distance measures correspond to building a dendrogram with...     

整合原始人脸图像和其虚拟样本的人脸分类算法

人脸识别作为最具吸引力的生物识别技术之一,由于会受到不同的照明条件、面部表情、姿态和环境的影响,仍然是一个具有挑战性的任务.众所周知,一幅人脸图像是对人脸的一次采样,它不应该被看作是脸部的绝对精确表示.然而在实际应用中很难获得足够多的人脸样本.随着稀疏表示方法在图像重建问题中的成功应用,研究人员提出了一种特殊的分类方法,即基于稀疏表示的分类方法.受此启发,提出了在稀疏表示框架下的整合原始人脸图像和虚拟样本的人脸分类算法.首先,通过合成虚拟训练样本来减少面部表示的不确定性.然后,在原始训练样本和虚拟样本组成的混合样本中通过计算来消除对分类影响较小的类别和单个样本,在系数分解的过程中采用最小误差正交匹配追踪(Error-Constrained Orthogonal Matching Pursuit,OMP)方法,进而选出贡献程度大的类别样本并进行分类.实验结果表明,提出的方法不仅能获得较高的人脸识别的精度,而且还具有更低的计算复杂性.     

Face recognition using adaptively weighted patch PZM array from a single exemplar image per person

Though numerous approaches have been proposed for face recognition, little attention is given to the moment-based face recognition techniques. In this paper we propose a novel face recognition approach based on adaptively weighted patch pseudo Zernike moment array (AWPPZMA) when only one exemplar image per person is available. In this approach, a face image is represented as an array of patch pseudo Zernike moments (PPZM) extracted from a partitioned face image containing moment information of local areas instead of global information of a face. An adaptively weighting scheme is used to assign proper weights to each PPZM to adjust the contribution of each local area of a face in terms of the quantity of identity information that a patch contains and the likelihood of a patch is occluded. An extensive experimental investigation is conducted using AR and Yale face databases covering face recognition under controlled/ideal conditions, different illumination conditions, different facial expressions and partial occlusion. The system performance is compared with the performance of four benchmark approaches. The encouraging experimental results demonstrate that moments can be used for face recognition and patch-based moment array provides a novel way for face representation and recognition in single model databases.     

基于SVM的人脸检测研究

支持向量机（SVM）是在统计学习理论基础上发展起来的一种新的机器学习算法。依据SVM良好识别和泛化能力,实现了一种基于支持向量机的图像人脸识别方法。利用Opencv提取样本类的低层特征,训练具有径向基核函数的SVM分类器,在VS2008和Qt平台下实现识别软件开发。运行结果表明,软件具有良好的图像人脸检测能力。     

Face Photo-Sketch Synthesis and Recognition

In this paper, we propose a novel face photo-sketch synthesis and recognition method using a multiscale Markov Random Fields (MRF) model. Our system has three components: 1) given a face photo, synthesizing a sketch drawing; 2) given a face sketch drawing, synthesizing a photo; and 3) searching for face photos in the database based on a query sketch drawn by an artist. It has useful applications for both digital entertainment and law enforcement. We assume that faces to be studied are in a frontal pose, with normal lighting and neutral expression, and have no occlusions. To synthesize sketch/photo images, the face region is divided into overlapping patches for learning. The size of the patches decides the scale of local face structures to be learned. From a training set which contains photo-sketch pairs, the joint photo-sketch model is learned at multiple scales using a multiscale MRF model. By transforming a face photo to a sketch (or transforming a sketch to a photo), the difference between photos and sketches is significantly reduced, thus allowing effective matching between the two in face sketch recognition. After the photo-sketch transformation, in principle, most of the proposed face photo recognition approaches can be applied to face sketch recognition in a straightforward way. Extensive experiments are conducted on a face sketch database including 606 faces, which can be downloaded from our Web site (http://mmlab.ie.cuhk.edu.hk/facesketch.html).     

Efficient 3D reconstruction for face recognition

Face recognition with variant pose, illumination and expression (PIE) is a challenging problem. In this paper, we propose an analysis-by-synthesis framework for face recognition with variant PIE. First, an efficient two-dimensional (2D)-to-three-dimensional (3D) integrated face reconstruction approach is introduced to reconstruct a personalized 3D face model from a single frontal face image with neutral expression and normal illumination. Then, realistic virtual faces with different PIE are synthesized based on the personalized 3D face to characterize the face subspace. Finally, face recognition is conducted based on these representative virtual faces. Compared with other related work, this framework has following advantages: (1) only one single frontal face is required for face recognition, which avoids the burdensome enrollment work; (2) the synthesized face samples provide the capability to conduct recognition under difficult conditions like complex PIE; and (3) compared with other 3D reconstruction approaches, our proposed 2D-to-3D integrated face reconstruction approach is fully automatic and more efficient. The extensive experimental results show that the synthesized virtual faces significantly improve the accuracy of face recognition with changing PIE.     

Recognizing Human Emotional State From Audiovisual Signals

Machine recognition of human emotional state is an important component for efficient human-computer interaction. The majority of existing works address this problem by utilizing audio signals alone, or visual information only. In this paper, we explore a systematic approach for recognition of human emotional state from audiovisual signals. The audio characteristics of emotional speech are represented by the extracted prosodic, Mel-frequency Cepstral Coefficient (MFCC), and formant frequency features. A face detection scheme based on HSV color model is used to detect the face from the background. The visual information is represented by Gabor wavelet features. We perform feature selection by using a stepwise method based on Mahalanobis distance. The selected audiovisual features are used to classify the data into their corresponding emotions. Based on a comparative study of different classification algorithms and specific characteristics of individual emotion, a novel multiclassifier scheme is proposed to boost the recognition performance. The feasibility of the proposed system is tested over a database that incorporates human subjects from different languages and cultural backgrounds. Experimental results demonstrate the effectiveness of the proposed system. The multiclassifier scheme achieves the best overall recognition rate of 82.14%.     

Mobile JikesRVM: A framework to support transparent Java thread migration

Today’s complex applications must face the distribution of data and code among different network nodes. Computation in distributed contexts is demanding increasingly powerful languages and execution environments, able to provide programmers with appropriate abstractions and tools. Java is a wide-spread language that allows developers to build complex software, even distributed, but it cannot handle the migration of computations (i.e. threads), due to intrinsic limitations of many traditional JVMs. After analyzing the approaches in the literature, this paper presents our thread migration framework (called Mobile JikesRVM), implemented on top of the IBM Jikes Research Virtual Machine (RVM): exploiting some of the innovative techniques in the JikesRVM, we implemented an extension of its scheduler that allows applications to easily capture the state of a running thread and makes it possible to restore it elsewhere (i.e. on a different hardware architecture or operating system), but still with a version of the framework installed). Our thread serialization mechanism provides support for both proactive and reactive migration, available also for multi-threaded Java applications, and tools to deal with the problems of resource relocation management. With respect to previous approaches, we implemented Mobile JikesRVM without recompiling its JVM (Java Virtual Machine) source code, but simply extending JikesRVM functionalities with a full Java package to be imported when thread migration is needed.     

选择性多本征空间的多级人脸识别方法

针对人脸识别过程中仅靠人脸整体特征识别容易出现误识的问题,以及人脸局部特征的重要性。本着由粗到精的学习原则,设计了选择性多本征空间的多级人脸识别方法（SMEM）。首先对人脸划分为整体、上半部、鼻、眼四个本征区域;然后对各本征建立特征空间并构造BP神经网络人脸识别器;最后,以后验概率为依据,选择性调用各级识别器,直到类内阈值和类间阈值均满足设定值的分类为止。经实验证明,此方法有较高的识别精度。     

基于OLPP和信息向量机的人脸识别

结合正交局部保持投影(OLPP)和信息向量机(IVM),提出用于人脸识别的OLPP-IVM算法。应用OLPP对原始人脸图像数据进行特征提取,利用IVM在降维后的数据上实现人脸分类。与主成分分析、线性判别分析等算法的比较实验证明,用该算法进行人脸识别误差更小,性能更优越。     

基于支持向量机和纹理特征的人脸识别

提出了一种基于支持向量机和纹理特征的识别方法及框架模型。即在研究支持向量机理论的基础上,采用支持向量机的分类算法实现人脸识别系统的训练和测试,并将图像的纹理特征技术应用于人脸识别的预处理中。实验表明支持向量机和纹理特征相结合可以获得较好的识别率。