Hidden Conditional Random Fields Research Articles

Hidden conditional random field-based equalizer for the 3D-CAP-64 transmission of OAM mode-division multiplexed ring-core fiber communication.

As a key technique for achieving ultra-high capacity optical fiber communications, orbital angular momentum (OAM) mode-division multiplexing (MDM) is affected by severe nonlinear impairments, including modulation related nonlinearities, square-law nonlinearity and mode-coupling-induced nonlinearity. In this paper, an equalizer based on a hidden conditional random field (HCRF) is proposed for the nonlinear mitigation of OAM-MDM optical fiber communication systems with 20 GBaud three-dimensional carrierless amplitude and phase modulation-64 (3D-CAP-64) signals. The HCRF equalizer extracts the stochastic nonlinear feature of the OAM-MDM 3D-CAP-64 signals by estimating the conditional probabilities of the hidden variables, thereby enabling the signals to be classified into subclasses of constellation points. The nonlinear impairment can then be mitigated based on the statistical probability distribution of the hidden variables of the OAM-MDM transmission channel in the HCRF equalizer. Our experimental results show that compared with a convolutional neural network (CNN)-based equalizer, the proposed HCRF equalizer improves the receiver sensitivity by 2 dB and 1 dB for the two OAM modes used here, with l = + 2 and l = + 3, respectively, at the 7% forward error correction (FEC) threshold. When compared with a Volterra nonlinear equalizer (VNE) and CNN-based equalizer, the computational complexity of the proposed HCRF equalizer was found to be reduced by 30% and 41%, respectively. The bit error ratio (BER) performance and reduction in computational complexity indicate that the proposed HCRF equalizer has great potential to mitigate nonlinear distortions in high-speed OAM-MDM fiber communication systems.

Spatiotemporal Analysis of Static and Dynamic Traffic Elements From Road Scenes

Spatiotemporal analysis of road scenes is a hot research topic in the communities of computer vision and intelligent transportation systems. In this paper, we propose a new framework for spatiotemporal analysis of static and dynamic traffic elements from road scenes. In the first stage, a bottom-up analysis method for static traffic elements is proposed based on a hierarchical spatiotemporal model using hidden conditional random fields (HCRF). The bottom-level features are extracted from sub-regions in the hierarchical model, and the local and global features of the image sequence are then fully combined for spatial and temporal layers. In the second stage, a lightweight multi-stream 3DCNN network is developed for the behavior classification of dynamic traffic elements, which is composed of three parts. Firstly, a SELayer-3DCNN is designed to extract the appearance, motion and edge information from the image sequences. Secondly, the channel attention fusion strategy (CAF) is introduced to enhance the feature fusion ability. Finally, the 3D-RFB module is incorporated to expand the receptive field of the convolution kernel. The experimental results well demonstrate the effectiveness of the proposed framework.

Analysis of instantaneous brain interactions contribution to a motor imagery classification task.

The purpose of this study is to analyze the contribution of the interactions between electrodes, measured either as correlation or as Jaccard distance, to the classification of two actions in a motor imagery paradigm, namely, left-hand movement and right-hand movement. The analysis is performed in two classifier models, namely, a static (linear discriminant analysis, LDA) model and a dynamic (hidden conditional random field, HCRF) model. The impact of using the sliding window technique (SWT) in the static and dynamic models is also analyzed. The study proved that their combination with temporal features provides significant information to improve the classification in a two-class motor imagery task for LDA (average accuracy: 0.7192 no additional features, 0.7617 by adding correlation, 0.7606 by adding Jaccard distance; p < 0.001) and HCRF (average accuracy: 0.7370 no additional features, 0.7764 by adding correlation, 0.7793 by adding Jaccard distance; p < 0.001). Also, we showed that adding interactions between electrodes improves significantly the performance of each classifier, regarding the nature of the interaction measure or the classifier itself.

A Lightweight Human Action Classification Method for Green IoT Sport Applications

This paper proposes a lightweight human action classification method for Green Internet of Things (IoT) sport applications. This method classifies the human motion data collected by wearables or other IoT devices with energy-efficient techniques, by enabling a small number of sample training and incremental classification to achieve the purpose of energy-efficient. To lessen the complexity of the model and reduce the number of samples required for parameter estimation, we propose a shared Hidden Conditional Random Field (sHCRF) model. The sHCRF model adds a shared-classification layer structure to reduce the parameter computation. In the experiments, the classification accuracy of the sHCRF model is above 95%. This paper introduces an incremental learning method based on knowledge distillation. The new model suppresses the forgetting of existing classification knowledge while fitting new data to learn new classification knowledge. In the incremental scenarios, the classification accuracy of the sHCRF model is above 70%. The experimental results show that this method can lightly implement convenient and fast automatic classification of action acquisition.

Two-stage time-varying hidden conditional random fields with variable selection for process operating mode diagnosis

In industrial processes, the availability of a large amount of process variables provides flexibility for process monitoring; however, too many process variables with possible redundant information can also contribute to high false positives. In order to make good use of the relevant information included in the process variables, a novel two-stage hidden conditional random field (HCRF) algorithm is developed in this paper to perform real-time process operating mode diagnosis. In the first-stage HCRF, the max-margin training strategy is employed to discriminate multiple operating modes, and by recursively eliminating the fault-irrelevant variables, the most relevant variables can be selected during the first-stage training process. On the basis of the first-stage HCRF outputs, the second-stage HCRF is proposed to adapt the dynamic changes of the process with time-varying model structure. Therefore, switchings among process operating modes can be captured to make timely diagnosis. To demonstrate the performance of the proposed algorithm, two case studies are conducted with comparisons to the conventional algorithms. Superior performance is observed through the examples.

Human activity recognition using robust adaptive privileged probabilistic learning

In this work, a supervised probabilistic approach is proposed that integrates the learning using privileged information (LUPI) paradigm into a hidden conditional random field (HCRF) model, called HCRF+, for human action recognition. The proposed model employs a self-training technique for automatic estimation of the regularization parameters of the objective function. Moreover, the method provides robustness to outliers by modeling the conditional distribution of the privileged information by a Student’s t-density function, which is naturally integrated into the HCRF+ framework. The proposed method was evaluated using different forms of privileged information on four publicly available datasets. The experimental results demonstrate its effectiveness concerning the state of the art in the LUPI framework using both hand-crafted and deep learning-based features extracted from a convolutional neural network.

An improved gaussian mixture hidden conditional random fields model for audio-based emotions classification

The analysis of human emotions plays a significant role in providing sufficient information about patients in monitoring their feelings for better management of their diseases. Audio-based emotions recognition has become a fascinating research interest for such domains during the last decade. Mostly, audio-based emotions systems depend on the recognition stage. The existing model has a common issue called objectivity suppositions problem, which might decrease the recognition rate. Therefore, this study investigates the improved version of a classifier that is based on hidden conditional random fields (HCRFs) model to classify emotional speech. In this model, we introduced a novel methodology that will incorporate multifaceted dissemination with the help of employing a combination of complete covariance Gaussian concreteness function. Due to this incorporation, the proposed model tackle most of the limitations of existing classifiers. Some of the well-known features like Mel-frequency cepstral coefficients (MFCC) are extracted in our experiments. The proposed model has been validated and evaluated on two publicly available datasets likes Berlin Database of Emotional Speech (Emo-DB) and the eNTER FACE’05 Audio-Visual Emotion dataset. For validation and comparison against the existing techniques, we utilized 10-fold cross validation scheme. The proposed method achieved significant improvement under the p-value <0.03 for classification. Moreover, we also prove that computational wise, our computation technique is less expensive against state of the art works.

Probability Model Based on Cluster Analysis to Classify Sequences of Observations for Small Training Sets

The problem of recognizing patterns, when there are few training data available, is particularly relevant and arises in cases when collection of training data is expensive or essentially impossible. The work proposes a new probability model MC&amp;CL (Markov Chain and Clusters) based on a combination of markov chain and algorithm of clustering (self-organizing map of Kohonen, k-means method), to solve a problem of classifying sequences of observations, when the amount of training dataset is low. An original experimental comparison is made between the developed model (MC&amp;CL) and a number of the other popular models to classify sequences: HMM (Hidden Markov Model), HCRF (Hidden Conditional Random Fields),LSTM (Long Short-Term Memory), kNN+DTW (k-Nearest Neighbors algorithm + Dynamic Time Warping algorithm). A comparison is made using synthetic random sequences, generated from the hidden markov model, with noise added to training specimens. The best accuracy of classifying the suggested model is shown, as compared to those under review, when the amount of training data is low.

Unsupervised Extraction of Common Product Attributes From E-Commerce Websites by Considering Client Suggestion

Develop an unsupervised learning framework for extracting popular product attributes from product description pages originated from different E-commerce Web sites. Unlike existing information extraction methods that do not consider the popularity of product attributes, in this proposed framework is able to not only detect popular product features from a collection of customer reviews but also map these popular features to the related product attributes. Building an intelligent E-commerce systems typically involves a component that can automatically extract product attribute information from a variety of product description pages in different E-commerce Web sites. Web information extraction methods such as wrappers are able to automatically extract product attributes from the Web content One novelty in this framework is that it can bridge the vocabulary gap between the text in product description pages and the text in customer reviews. Technically,in this framework developed a discriminative graphical model based on hidden Conditional Random Fields. As an unsupervised model, this framework can be easily applied to a variety of new domains and Web sites without the need of labelling training samples. E-commerce is proposed for enhancing the capability. Covered by electronic commerce surroundings, facing therefore voluminous new recent business model, it's obligatory to conduct the analysis to the electronic commerce pattern analysis method and like this is often useful in North American nation uncover the new electronic commerce pattern as provide the approach for electronic commerce pattern modernization to be conjointly helpful within the enterprise outline the particular electronic commerce strategy and therefore the implementation step. Initiated from this encouragement, during this paper proposes the innovative construct of the E-commerce recent agricultural product selling supported the massive web knowledge platform later the rapid development of rebuilding and opening up, China's agriculture has entered a new historical stage of development. Evaluate the growth mechanism of agricultural production enterprises from the angle of resource dynamic provide. In the e-commerce environment, the enterprise data and economic information are relatively concentrated, so the economical accounting system can instantly grasp the current activities of the economical data, and quickly generate economical information.

Human Activity Recognition Using Gaussian Mixture Hidden Conditional Random Fields.

In healthcare, the analysis of patients' activities is one of the important factors that offer adequate information to provide better services for managing their illnesses well. Most of the human activity recognition (HAR) systems are completely reliant on recognition module/stage. The inspiration behind the recognition stage is the lack of enhancement in the learning method. In this study, we have proposed the usage of the hidden conditional random fields (HCRFs) for the human activity recognition problem. Moreover, we contend that the existing HCRF model is inadequate by independence assumptions, which may reduce classification accuracy. Therefore, we utilized a new algorithm to relax the assumption, allowing our model to use full-covariance distribution. Also, in this work, we proved that computation wise our method has very much lower complexity against the existing methods. For the experiments, we used four publicly available standard datasets to show the performance. We utilized a 10-fold cross-validation scheme to train, assess, and compare the proposed model with the conditional learning method, hidden Markov model (HMM), and existing HCRF model which can only use diagonal-covariance Gaussian distributions. From the experiments, it is obvious that the proposed model showed a substantial improvement with p value ≤0.2 regarding the classification accuracy.

Human Action Recognition Using Improved Sparse Gaussian Process Latent Variable Model and Hidden Conditional Random Filed

Owing to the fragile to external environment, current human activity recognition is still challenging in the area of computer vision. In particular, the recognition of subtle actions is a difficult task to distinguish from each other. In this paper, we proposed the methods for human action recognition based on improved sparse Gaussian process latent variable model (GPLVM) and hidden conditional random field (HCRF). We first fused the skeletal information and the motion characteristics of human body to extract human action features from a set of action sequences. And then, we proposed an improved sparse GPLVM algorithm for feature dimensionality reduction to satisfy the visualization and computation complexity for human actions recognition. Through sparse approximation with information vector machine and the dynamic process of human actions, the improved sparse GPLVM allows the action features to be represented by the low dimensional trajectory in manifold space. Furthermore, HCRF was applied to recognize the characteristics of human actions derived from manifold spaces and finally to classify human actions. The proposed methods are tested and evaluated on public action database. The experimental results show that our methods can achieve better performance of feature dimensionality reduction and visualization and obtain the average recognition accuracy of 93.68%.

Virtual Rehabilitation Using Sequential Learning Algorithms

Rehabilitation systems are becoming more impor-tant now because patients can access motor skills recovery treatment from home, reducing the limitations of time, space and cost of treatment in a medical facility. Traditional rehabilitation systems served as movement guides, later as movement mirrors, and in recent years research has sought to generate feedback messages to the patient based on the evaluation of his or her movements. Currently the most commonly used algorithms for exercise evaluation are Dynamic time warping (DTW), Hidden Markov model (HMM), Support vector machine (SVM). However, the larger the set of exercises to be evaluated, the less accurate the recognition becomes, generating confusion between exercises that have similar posture descriptors. This research paper compares two HMM classifiers and Hidden Conditional Random Fields (HCRF) plus two types of posture descriptors, based on points and based on angles. Point representation proves to be superior to angle representation, although the latter is still acceptable. Similar results are found in HCRF and HMM.

Event Detection based on Hidden Conditional Random Field Model in Sport Videos

Event Detection based on Hidden Conditional Random Field Model in Sport Videos

EMF- MHCRF: Enhanced Median Filter (EMF) Based Noise Removal and Multilayer Hidden Conditional Random Field (MHCRF) Model for Dense Depth Map Reconstruction

EMF- MHCRF: Enhanced Median Filter (EMF) Based Noise Removal and Multilayer Hidden Conditional Random Field (MHCRF) Model for Dense Depth Map Reconstruction

A Hierarchical Spatio-Temporal Model for Human Activity Recognition

There are two key issues in human activity recognition: spatial dependencies and temporal dependencies. Most recent methods focus on only one of them, and thus do not have sufficient descriptive power to recognize complex activity. In this paper, we propose a hierarchical spatio-temporal model (HSTM) to solve the problem by modeling spatial and temporal constraints simultaneously. The new HSTM is a two-layer hidden conditional random field (HCRF), where the bottom-layer HCRF aims at describing spatial relations in each frame and learning more discriminative representations, and the top-layer HCRF utilizes these high-level features to characterize temporal relations in the whole video sequence. The new HSTM takes advantage of the bottom layer as the building blocks for the top layer and it aggregates evidence from local to global level. A novel learning algorithm is derived to train all model parameters efficiently and its effectiveness is validated theoretically. Experimental results show that the HSTM can successfully classify human activities with higher accuracies on single-person actions (UCF) than other existing methods. More importantly, the HSTM also achieves superior performance on more practical interactions, including human–human interactional activities (UT-Interaction, BIT-Interaction, and CASIA) and human–object interactional activities (Gupta video dataset).

Recognizing Human Actions with Outlier Frames by Observation Filtering and Completion

This article addresses the problem of recognizing partially observed human actions. Videos of actions acquired in the real world often contain corrupt frames caused by various factors. These frames may appear irregularly, and make the actions only partially observed. They change the appearance of actions and degrade the performance of pretrained recognition systems. In this article, we propose an approach to address the corrupt-frame problem without knowing their locations and durations in advance. The proposed approach includes two key components: outlier filtering and observation completion . The former identifies and filters out unobserved frames, and the latter fills up the filtered parts by retrieving coherent alternatives from training data. Hidden Conditional Random Fields (HCRFs) are then used to recognize the filtered and completed actions. Our approach has been evaluated on three datasets, which contain both fully observed actions and partially observed actions with either real or synthetic corrupt frames. The experimental results show that our approach performs favorably against the other state-of-the-art methods, especially when corrupt frames are present.

PhLeGrA: Graph Analytics in Pharmacology over the Web of Life Sciences Linked Open Data.

Integrated approaches for pharmacology are required for the mechanism-based predictions of adverse drug reactions that manifest due to concomitant intake of multiple drugs. These approaches require the integration and analysis of biomedical data and knowledge from multiple, heterogeneous sources with varying schemas, entity notations, and formats. To tackle these integrative challenges, the Semantic Web community has published and linked several datasets in the Life Sciences Linked Open Data (LSLOD) cloud using established W3C standards. We present the PhLeGrA platform for Linked Graph Analytics in Pharmacology in this paper. Through query federation, we integrate four sources from the LSLOD cloud and extract a drug–reaction network, composed of distinct entities. We represent this graph as a hidden conditional random field (HCRF), a discriminative latent variable model that is used for structured output predictions. We calculate the underlying probability distributions in the drug–reaction HCRF using the datasets from the U.S. Food and Drug Administration’s Adverse Event Reporting System. We predict the occurrence of 146 adverse reactions due to multiple drug intake with an AUROC statistic greater than 0.75. The PhLeGrA platform can be extended to incorporate other sources published using Semantic Web technologies, as well as to discover other types of pharmacological associations.

Gesture-Based Adaptive Haptic Guidance: A Comparison of Discriminative and Generative Modeling Approaches

This paper investigates the incorporation of hidden conditional random fields (HCRF) as a discriminative statistical modeling technique into adaptive haptic guidance (HG) for physical human-robot interaction (pHRI). In this gesture-based HG approach, the knowledge and experience of experts are modeled to improve the unpredictable motions of novice trainees in a virtual minimally invasive surgery (MIS) training task. The HCRF models are developed for automatic gesture recognition and segmentation as well as generating guidance forces. The forces are adaptively calculated in real time with respect to gestural similarities among user motions and the gesture models. The HCRF-based approach is compared with a hidden Markov model-based (HMM-based) method for capturing the gestures of the user and providing adaptive HG. The experimental results show that the HCRF, as a discriminative method, can outperform HMM, as a generative method, in terms of user performance.

Extraction of texture and geometrical features from informative facial regions for sign language recognition

In general, the most common form of gestures is made up of movements of the hand and/or arm associated with facial expressions. In this, the hand is used to make different message signs, while facial movements are used to reflect the mood and emotion of the person. In this paper, some sign language gestures are recognized only with the help of associated facial expressions. Existing facial expression based sign language recognition (SLR) methods only used facial geometric features to recognize sign language gestures. However, the performance of geometric feature-based SLR methods depends on the accuracy of tracking algorithms and the number of facial landmark points. Additionally, facial textures are more informative as compared to the geometric features of a face. Inspiring from these facts, we propose to recognize sign language gestures with the help of spatio-temporal characteristics of facial texture patterns. For this, a new face model is proposed by extracting texture features only from the informative regions of a face. The proposed face model can also be employed to extract the geometrical features of a face. The features extracted from the informative regions of a face are significantly discriminative, and so the proposed face model can track/encode the facial dynamics of the associated facial expressions of a sign. Finally, a 3-state hidden conditional random field is employed to model the texture variations of facial gestures. Experimental results on RWTH-BOSTON data-set show that proposed method can achieve upto 80.06% recognition rate.

Multivariate Time-Series Classification Using the Hidden-Unit Logistic Model.

We present a new model for multivariate time-series classification, called the hidden-unit logistic model (HULM), that uses binary stochastic hidden units to model latent structure in the data. The hidden units are connected in a chain structure that models temporal dependencies in the data. Compared with the prior models for time-series classification such as the hidden conditional random field, our model can model very complex decision boundaries, because the number of latent states grows exponentially with the number of hidden units. We demonstrate the strong performance of our model in experiments on a variety of (computer vision) tasks, including handwritten character recognition, speech recognition, facial expression, and action recognition. We also present a state-of-the-art system for facial action unit detection based on the HULM.