一种基于混合概率模型的视频分割方法

该文提出一种新的基于混合概率模型视频分割方法。这个方法主要利用两个概率模型：隐马尔可夫模型和概率图模型建立一个混合的贝叶斯网概率模型,对视频输入中背景变化的时间和空间局部相关性（同现性）进行学习。在建立正确模型参数的基础上,贝叶斯信念传播算法根据图像输入预测当前背景状态的后验分布。并根据预测得到的背景状态对输入图像进行分割,实验结果显示方法的有效性和在复杂背景变化下的鲁棒性。     

光线变化下的视频图像分割

视频图像分割是视频目标定位和识别的基础,如果背景中光线变化,那么将会给分割带来很大的影响。文中利用贝叶斯学习方法进行视频图像分割,在每个象素点处对不断变化的背景建模,计算每个象素点处的颜色直方图,用这些直方图来表示该象素点处特征向量的概率分布,然后用贝叶斯学习方法来判断,在光线缓慢或者突然变化的时候,每个象素点是属于前景还是属于背景。     

基于贝叶斯学习的视频图像分割

如果背景中光线变化,那么视频图像分割将会变得比较困难。为了对光线变化的图像进行顺利侵害,提出了一种利用贝叶斯学习方法来进行视频图像分割的算法,即先在每个像素点处对不断变化的背景建模,同时计算每个像素点处的颜色直方图,再用这些直方图来表示该像素点处特征向量的概率分布,然后用贝叶斯学习方法来进行判断,以确定在光线缓慢或者突然变化的时候,每个像素点是属于前景还是属于背景。     

基于高斯混合模型的叶片检测分割算法

为解决光照变化、叶片自身表观变化和复杂背景对植物叶片图像准确分割所造成的困扰,提出一种组合式分割方法。该方法在多个尺度上采用滑动窗口扫描方式检测图像中的叶片;对检测到的叶片区域中心区域像素为初始前景,而叶片窗口之外的区域为初始背景,用高斯混合模型(GMM)分别对前景和背景建立初始概率模型;采用迭代法完成叶片分割,在每一轮迭代中,用标准的图割算法和上一轮GMM模型分割前景和背景,根据新的分割结果重新估计前景和背景的GMM;迭代过程在能量函数收敛时结束。叶片检测时,以能描述叶片的外观和形状的HOG特征为检测依据;为了应对实际叶片图像中叶片形态、角度变化较多的挑战,采用多子类分类器策略。以葡萄叶片为例,用该方法进行了分割实验。结果表明,该方法对上述复杂条件下叶片图像的分割具有较好的鲁棒性和较高的精度,能实现分割过程的完全自动化。     

基于同态滤波抑制光照变化的视频分割算法

针对光照变化较大时基于颜色差分直方图的视频分割算法不能有效更新背景,导致后续输入图像前景目标分割失效的问题,提出一种基于同态滤波抑制光照变化的视频分割算法。首先利用同态滤波算法对输入和背景图像(RGB)在HSV空间中亮度分量进行同参矫正,然后将矫正后图像转换到RGB空间,最后利用颜色差分直方图算法进行视频分割。文中算法有效解决颜色差分直方图算法无法将受光照变化影响较大区域更新到背景中的问题,实现背景的实时有效更新,保证稳健地从后续输入图像分割前景目标。3组视频仿真结果表明该算法与高斯混合和Codebook算法相比具有运算速度快,对光照变化鲁棒的优点。     

基于抽样的正交多项式混合模型图像分割

针对有限混合模型中参数估计方法对先验假设存在过分依赖和图像数据量大的问题,提出了一种基于抽样的非参数余弦正交序列的图像混合模型分割方法.首先,基于图像的直方图进行分层随机抽样得到样本数据,根据样本数据构建非参数正交多项式混合模型,对于模型的平滑参数采用最小均方差方法进行估计;其次,采用NEM(Nonparametric Expectation Maximum)算法求解混合模型中正交多项式系数和模型的混合比;最后,根据贝叶斯准则进行图像分割.此方法能够克服参数模型的基本假设与实际的物理模型之间存在的差异,实验表明该方法比GMM和Hermite混合模型分割方法分割质量高,而且分割速度快.     

基于t混合和SMEM算法的彩色图像分割

采用t混合模型建立图像的颜色,纹理及空间位置特征的联合分布,及改进的分裂—融合EM算法(SMEM)估计混合模型的参数,根据贝叶斯最小错误率准则对图像进行分割。由于t混合模型的稳健性和改进的SMEM算法对于数据的初始化不敏感,能收敛到全局最优,且能自适应的的选择分割的数目,因此该方法能取得更好的分割结果。     

彩色序列图像的人脸分割与识别技术研究

为了构造一个精度高、处理快速的人脸检测系统,本文结合颜色信息和人脸构造特征,提出了一种从序列图像中实现人脸分割与识别的新方法.该方法基于混合高斯模型与贝叶斯判别技术,分两步实现,即运动目标分割和人脸特征识别.首先,通过建立自适应的混合高斯模型,对背景图像建模,分割出前景运动人体区域;然后采用贝叶斯判别法对人脸区域进行识别.实验结果显示,该方法具有很高的检测精度和较低的漏警率,具有良好的实用价值和工程应用前景.     

自动交互图像分割中的贝叶斯网络模型构建

由于贝叶斯模型和各种图像测量结果,置信传播会更新每个节点的相关概率,提出了在自动交互图像分割过程中应用的新型贝叶斯网络模型。从过度分割模型中的超级像素点区域、边区域、顶点和测量结果之间的统计相关性来构造多层贝叶斯网络模型。除了自动图像分割,贝叶斯网络模型也可用于交互式图像分割中,现有交互分割往往被动地依靠用户提供的准确调整,提出新型主动输入选择方式作为准确调整。实验采用Weizmann数据集和VOC 2006图像集来评估,实验结果表明贝叶斯网络模型可以进行效果更好的自动分割,主动输入选择可以提高整体分割精度。     

自适应变步长高斯混合模型的工业烟尘目标分割方法

工业烟尘排放时的烟气黑度自动监测对提高环保质量和指导生产过程具有重要的应用价值, 针对传统的 高斯混合模型在进行背景建模时, 参数是在固定帧值的基础上进行参数更新, 导致烟尘检测不准确等问题, 提出一 种自适应变步长高斯混合模型的工业烟尘图像分割方法. 根据烟尘变化速度不均匀的特点, 通过分析检测出烟尘 与实际烟尘的检出率和检准率的和的最大值, 计算熵值差变化率对应的最佳步长, 得到熵值差变化率与最佳步长的 模型. 以熵值差变化率为依据, 确定最佳步长, 得到一个关于熵值差变化率与最佳步长的模型. 以熵值差变化率为 输入, 以最佳步长为输出, 在广义回归神经网络(GRNN)得到适用于本文工业烟尘图像分割的网络模型. 最后, 在多 个场景的烟尘视频中进行分割实验, 结果表明, 本文中方法能够有效的分割出视频中烟尘区域, 且具有一定的适用 性.     

基于视觉语义主题的图像自动标注

为减小图像检索中语义鸿沟的影响,提出了一种基于视觉语义主题的图像自动标注方法.首先,提取图像前景与背景区域,并分别进行预处理;然后,基于概率潜在语义分析与高斯混合模型建立图像底层特征、视觉语义主题与标注关键词间的联系,并基于该模型实现对图像的自动标注.采用corel 5数据库进行验证,实验结果证明了本文方法的有效性.     

基于混合概率模型的无监督离散化算法

现实应用中常常涉及许多连续的数值属性，而且前许多机器学习算法则要求所处理的属性取离散值，根据在对数值属性的离散化过程中，是否考虑相关类别属性的值，离散化算法可分为有监督算法和无监督算法两类。基于混合概率模型，该文提出了一种理论严格的无监督离散化算法，它能够在无先验知识，无类别是属性的前提下，将数值属性的值域划分为若干子区间，再通过贝叶斯信息准则自动地寻求最佳的子区间数目和区间划分方法。     

Speech Enhancement Using Gaussian Scale Mixture Models

This paper presents a novel probabilistic approach to speech enhancement. Instead of a deterministic logarithmic relationship, we assume a probabilistic relationship between the frequency coefficients and the log-spectra. The speech model in the log-spectral domain is a Gaussian mixture model (GMM). The frequency coefficients obey a zero-mean Gaussian whose covariance equals to the exponential of the log-spectra. This results in a Gaussian scale mixture model (GSMM) for the speech signal in the frequency domain, since the log-spectra can be regarded as scaling factors. The probabilistic relation between frequency coefficients and log-spectra allows these to be treated as two random variables, both to be estimated from the noisy signals. Expectation-maximization (EM) was used to train the GSMM and Bayesian inference was used to compute the posterior signal distribution. Because exact inference of this full probabilistic model is computationally intractable, we developed two approaches to enhance the efficiency: the Laplace method and a variational approximation. The proposed methods were applied to enhance speech corrupted by Gaussian noise and speech-shaped noise (SSN). For both approximations, signals reconstructed from the estimated frequency coefficients provided higher signal-to-noise ratio (SNR) and those reconstructed from the estimated log-spectra produced lower word recognition error rate because the log-spectra fit the inputs to the recognizer better. Our algorithms effectively reduced the SSN, which algorithms based on spectral analysis were not able to suppress.     

Sentence alignment using P-NNT and GMM

Parallel corpora have become an essential resource for work in multilingual natural language processing. However, sentence aligned parallel corpora are more efficient than non-aligned parallel corpora for cross-language information retrieval and machine translation applications. In this paper, we present two new approaches to align English–Arabic sentences in bilingual parallel corpora based on probabilistic neural network (P-NNT) and Gaussian mixture model (GMM) classifiers. A feature vector is extracted from the text pair under consideration. This vector contains text features such as length, punctuation score, and cognate score values. A set of manually prepared training data was assigned to train the probabilistic neural network and Gaussian mixture model. Another set of data was used for testing. Using the probabilistic neural network and Gaussian mixture model approaches, we could achieve error reduction of 27% and 50%, respectively, over the length based approach when applied on a set of parallel English–Arabic documents. In addition, the results of (P-NNT) and (GMM) outperform the results of the combined model which exploits length, punctuation and cognates in a dynamic framework. The GMM approach outperforms Melamed and Moore’s approaches too. Moreover these new approaches are valid for any languages pair and are quite flexible since the feature vector may contain more, less or different features, such as a lexical matching feature and Hanzi characters in Japanese–Chinese texts, than the ones used in the current research.     

A Probabilistic Framework for the Hierarchic Organisation and Classification of Document Collections

This paper presents a probabilistic mixture modeling framework for the hierarchic organisation of document collections. It is demonstrated that the probabilistic corpus model which emerges from the automatic or unsupervised hierarchical organisation of a document collection can be further exploited to create a kernel which boosts the performance of state-of-the-art support vector machine document classifiers. It is shown that the performance of such a classifier is further enhanced when employing the kernel derived from an appropriate hierarchic mixture model used for partitioning a document corpus rather than the kernel associated with a flat non-hierarchic mixture model. This has important implications for document classification when a hierarchic ordering of topics exists. This can be considered as the effective combination of documents with no topic or class labels (unlabeled data), labeled documents, and prior domain knowledge (in the form of the known hierarchic structure), in providing enhanced document classification performance.     

改进混合高斯模型的运动目标检测算法

针对传统的混合高斯模型存在无法完整检测运动目标、易将背景显露区检测为前景等问题,提出了一种基于混合高斯模型的运动目标检测的改进算法。通过将混合高斯模型与改进帧差法进行融合,快速区分出背景显露区和运动目标区,从而提取出完整的运动目标。在运动目标由静止缓慢转为运动的情况下,为背景显露区给予较大背景更新速率,消除了背景显露区对运动目标检测的影响。在兼顾混合高斯模型在复杂场景中对噪声处理效果差的基础上,利用背景模型替换的方法来提高算法的稳定性。经过反复实验,结果表明改进后的算法在自适应性、正确率、实时性、实用性等方面有了很大的改进,能够在各种复杂因素存在的情况下正确有效地对运动目标进行检测。     

MLiT: mixtures of Gaussians under linear transformations

The curse of dimensionality hinders the effectiveness of density estimation in high dimensional spaces. Many techniques have been proposed in the past to discover embedded, locally linear manifolds of lower dimensionality, including the mixture of principal component analyzers, the mixture of probabilistic principal component analyzers and the mixture of factor analyzers. In this paper, we propose a novel mixture model for reducing dimensionality based on a linear transformation which is not restricted to be orthogonal nor aligned along the principal directions. For experimental validation, we have used the proposed model for classification of five “hard” data sets and compared its accuracy with that of other popular classifiers. The performance of the proposed method has outperformed that of the mixture of probabilistic principal component analyzers on four out of the five compared data sets with improvements ranging from 0.5 to 3.2%. Moreover, on all data sets, the accuracy achieved by the proposed method outperformed that of the Gaussian mixture model with improvements ranging from 0.2 to 3.4%.     

自然语言中时间信息的模型化

在自然语言理解中，时间一个重要的语境因素，本文提出一种独立于句子表层形式的多层次时间语义结构，浅层语义结构是时间描述的最化语义表示，深层语义结构描述事件的动态属性和存在特征，该时间语义模型表示时刻和时段，将时间基点明确区分为物理时间基点和说话者时间基点，并提供通用的时间语义计算方法，将各语言的时间描述映射到时间轴上，在该模型基础上，从语义观点出发，建立时，体的可计算模型及各事件时间相关性计算模型。     

On estimating simple probabilistic discriminative models with subclasses

Discriminative subclass models can provide good estimates of complex ‘continuous to discrete’ conditional probabilities for hybrid Bayesian network models. However, the conventional approach of specifying deterministic ‘hard’ subclasses via unsupervised clustering can lead to inaccurate models. The multimodal softmax (MMS) model is presented as a new probabilistic discriminative subclass model that overcomes this unreliability. By invoking fully probabilistic latent ‘soft’ subclasses, MMS permits learning via standard statistical methods without requiring explicit clustering/relabeling of data. MMS is also shown to be closely related to the mixture of experts model and the generative Gaussian mixture classifier. Synthetic and benchmark classification results demonstrate the MMS model’s correctness and usefulness for hybrid probabilistic modeling.