Combining data-driven systems for improving Named Entity Recognition

The increasing flow of digital information requires the extraction, filtering and classification of pertinent information from large volumes of texts. All these tasks greatly benefit from involving a Named Entity Recognizer (NER) in the preprocessing stage. This paper proposes a completely automatic NER system. The NER task involves not only the identification of proper names (Named Entities) in natural language text, but also their classification into a set of predefined categories, such as names of persons, organizations (companies, government organizations, committees, etc.), locations (cities, countries, rivers, etc.) and miscellaneous (movie titles, sport events, etc.). Throughout the paper, we examine the differences between language models learned by different data-driven classifiers confronted with the same NLP task, as well as ways to exploit these differences to yield a higher accuracy than the best individual classifier. Three machine learning classifiers (Hidden Markov Model, Maximum Entropy and Memory Based Learning) are trained on the same corpus in order to resolve the NE task. After comparison, their output is combined using voting strategies. A comprehensive study and experimental work on the evaluation of our system, as well as a comparison with other systems has been carried out within the framework of two specialized scientific competitions for NER, CoNLL-2002 and HAREM-2005. Finally, this paper describes the integration of our NER system in different NLP applications, in concrete Geographic Information Retrieval and Conceptual Modelling.     

基于主动学习的分类器融合算法

本文提出了基于主动学习的分类融合算法,将度量层输出的分类器融合问题看作二级分类器的设计问题,将SVM主动学习引入二级分类器设计。该算法在有效减少标注代价的同时获得了较高的分类性能。实验证明该算法在分类性能和标注代价两方面都优于传统分类器融合方法。     

A 3D face and hand biometric system for robust user-friendly authentication

A complete authentication system based on fusion of 3D face and hand biometrics is presented and evaluated in this paper. The system relies on a low cost real-time sensor, which can simultaneously acquire a pair of depth and color images of the scene. By combining 2D and 3D facial and hand geometry features, we are able to provide highly reliable user authentication robust to appearance and environmental variations. The design of the proposed system addresses two basic requirements of biometric technologies: dependable performance under real-world conditions along with user convenience. Experimental evaluation on an extensive database recorded in a real working environment demonstrates the superiority of the proposed multimodal scheme against unimodal classifiers in the presence of numerous appearance and environmental variations, thus making the proposed system an ideal solution for a wide range of real-world applications, from high-security to personalization of services and attendance control.     

On the independence requirement in Dempster-Shafer theory for combining classifiers providing statistical evidence

In classifier combination, the relative values of beliefs assigned to different hypotheses are more important than accurate estimation of the combined belief function representing the joint observation space. Because of this, the independence requirement in Dempster’s rule should be examined from classifier combination point of view. In this study, it is investigated whether there is a set of dependent classifiers which provides a better combined accuracy than independent classifiers when Dempster’s rule of combination is used. The analysis carried out for three different representations of statistical evidence has shown that the combination of dependent classifiers using Dempster’s rule may provide much better combined accuracies compared to independent classifiers.     

Classification by evolutionary ensembles

This paper is about building an ensemble of classifiers each of which is trained based on a particular weighting over the training examples (a weighting is a set of weights associated with the examples). The task concerns search in a tremendous weighting space. In this view we propose to incorporate a genetic algorithm (GA). It performs a wide yet efficient search for appropriate weightings (chromosomes). The difference from a traditional GA is that all the weightings throughout evolution will be exploited to form the final ensemble, not just the best weighting. Our algorithm is tested on the UCI benchmark data sets and used to design a face detection system. Robust and consistently accurate classification is experienced. Comparative results with two other algorithms, i.e. AdaBoost and Bagging, are also given.     

Feature representation and discrimination based on Gaussian mixture model probability densities—Practices and algorithms

This study promotes the use of statistical methods in specific classification tasks since statistical methods have certain advantages which advocate their use in pattern recognition. One central problem in statistical methods is estimation of class conditional probability density functions based on examples in a training set. In this study maximum likelihood estimation methods for Gaussian mixture models are reviewed and discussed from a practical point of view. In addition, good practices for utilizing probability densities in feature classification and selection are discussed for Bayesian and, more importantly, for non-Bayesian tasks. As a result, the use of confidence information in the classification is proposed and a method for confidence estimation is presented. The propositions are tested experimentally.     

A Feature-Based Serial Approach to Classifier Combination

: A new approach to the serial multi-stage combination of classifiers is proposed. Each classifier in the sequence uses a smaller subset of features than the subsequent classifier. The classification provided by a classifier is rejected only if its decision is below a predefined confidence level. The approach is tested on a two-stage combination of k-Nearest Neighbour classifiers. The features to be used by the first classifier in the combination are selected by two stand-alone algorithms (Relief and Info-Fuzzy Network, or IFN) and a hybrid method, called ‘IFN + Relief’. The feature-based approach is shown empirically to provide a substantial decrease in the computational complexity, while maintaining the accuracy level of a single-stage classifier or even improving it. Received: 24 November 2000, Received in revised form: 30 November 2001, Accepted: 05 June 2002 ID="A1" Correspondence and offprint requests to: M. Last, Department of Information Systems Engineering, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel. Email: mlast@bgumail.bgu.ac.il     

RADAR HRRP RECOGNITION BASED ON THE MINIMUM KULLBACK-LEIBLER DISTANCE CRITERION

To relax the target aspect sensitivity and use more statistical information of the High Range Resolution Profiles （HRRPs）, in this paper, the average range profile and the variance range profile are extracted together as the feature vectors for both training data and test data representation. And a decision rule is established for Automatic Target Recognition （ATR） based on the minimum Kullback-Leibler Distance （KLD） criterion. The recognition performance of the proposed method is comparable with that of Adaptive Gaussian Classifier （AGC） with multiple test HRRPs, but the proposed method is much more computational efficient. Experimental results based on the measured data show that the minimum KLD classifier is effective.     

一种高效的挖掘SJEP的算法

SJEP（即最有效的跳跃显露模式）是近年来提出的一种特殊的JEP（即跳跃显露模式），实验表明，仅使用SJEP足以用来建立精确的分类法。因为将现有挖掘JEP的算法直接应用于SJEP无法取得满意的效果，所以该文先压缩存储数据到一棵扩展树结构中，然后通过引入后缀子树的方法，给出了一个高效的SJEP挖掘算法，实验证明，该算法可以在很短的时间内（通常为若干秒）完成学习阶段。     

转子型气力超细分级机分级性能的研究

本文对新型转子型超细分级机的分级性能进行了研究，找出了该分级机的最佳转速、粉尘浓度风机风量、二次风量范围。对该机所得的粗细产品进行粒度分析并与原料粒度分析结果对比，表明该分级机的效果良好，达到了工业生产的需求。