Experiments with adaptation strategies for a prototype-based recognition system for isolated handwritten characters

This paper describes an adaptive recognition system for isolated handwritten characters and the experiments carried out with it. The characters used in our experiments are alphanumeric characters, including both the upper- and lower-case versions of the Latin alphabets and three Scandinavian diacriticals. The writers are allowed to use their own natural style of writing. The recognition system is based on the k-nearest neighbor rule. The six character similarity measures applied by the system are all based on dynamic time warping. The aim of the first experiments is to choose the best combination of the simple preprocessing and normalization operations and the dissimilarity measure for a multi-writer system. However, the main focus of the work is on online adaptation. The purpose of the adaptations is to turn a writer-independent system into writer-dependent and increase recognition performance. The adaptation is carried out by modifying the prototype set of the classifier according to its recognition performance and the user's writing style. The ways of adaptation include: (1) adding new prototypes; (2) inactivating confusing prototypes; and (3) reshaping existing prototypes. The reshaping algorithm is based on the Learning Vector Quantization. Four different adaptation strategies, according to which the modifications of the prototype set are performed, have been studied both offline and online. Adaptation is carried out in a self-supervised fashion during normal use and thus remains unnoticed by the user. Received June 30, 1999 / Revised September 29, 2000     

Prototype learning for structured pattern representation applied to on-line recognition of handwritten Japanese characters

This paper describes prototype learning for structured pattern representation with common subpatterns shared among multiple character prototypes for on-line recognition of handwritten Japanese characters. Prototype learning algorithms have not yet been shown to be useful for structured or hierarchical pattern representation. In this paper, we incorporate cost-free parallel translation to negate the location distributions of subpatterns when they are embedded in character patterns. Moreover, we introduce normalization into a prototype learning algorithm to extract true feature distributions in raw patterns to aggregate distributions of feature points to subpattern prototypes. We show that our proposed method significantly improves structured pattern representation for Japanese on-line character patterns.     

A prototype classification method and its use in a hybrid solution for multiclass pattern recognition

In this paper, we propose a prototype classification method that employs a learning process to determine both the number and the location of prototypes. This learning process decides whether to stop adding prototypes according to a certain termination condition, and also adjusts the location of prototypes using either the K-means (KM) or the fuzzy c-means (FCM) clustering algorithms. When the prototype classification method is applied, the support vector machine (SVM) method can be used to post-process the top-rank candidates obtained during the prototype learning or matching process. We apply this hybrid solution to handwriting recognition and address the convergence behavior and runtime consumption of the prototype construction process, and discuss how to combine our prototype classifier with SVM classifiers to form an effective hybrid classifier.     

Semi-supervised learning for character recognition in historical archive documents

Training recognizers for handwritten characters is still a very time consuming task involving tremendous amounts of manual annotations by experts. In this paper we present semi-supervised labeling strategies that are able to considerably reduce the human effort. We propose two different methods to label and later recognize characters in collections of historical archive documents. The first one is based on clustering of different feature representations and the second one incorporates a simultaneous retrieval on different representations. Hence, both approaches are based on multi-view learning and later apply a voting procedure for reliably propagating annotations to unlabeled data. We evaluate our methods on the MNIST database of handwritten digits and introduce a realistic application in form of a database of handwritten historical weather reports. The experiments show that our method is able to significantly reduce the human effort that is required to build a character recognizer for the data collection considered while still achieving recognition rates that are close to a supervised classification experiment.     

基于自动弱标注数据的跨领域命名实体识别

近年来,在大规模标注语料上训练的神经网络模型大大提升了命名实体识别任务的性能.但是,新领域人工标注数据获取代价高昂,如何快速、低成本地进行领域迁移就显得非常重要.在目标领域仅给定无标注数据的情况下,该文尝试自动构建目标领域的弱标注语料并对其建模.首先,采用两种不同的方法对无标注数据进行自动标注;然后,采用留"同"去"异...     

基于模糊模型相似测量的字符无监督分类法

该文提出一种基于模糊模型相似测量的文本分析系统的字符预分类方法 ,用于对字符的无监督分类 ,以提高整个字符识别系统的速度、正确性和鲁棒性 .作者在字符印刷结构归类的基础上 ,采用模板匹配方法将各类字符分别转换成基于一非线性加权相似函数的模糊样板集合 .模糊字符的无监督分类是字符匹配的一种自然范例并发展了加权模糊相似测量的研究 .该文讨论了该模糊模型的特性、模糊样板匹配的规则 ,并用于加快字符分类处理 ,经过字符分类 ,在字符识别时由于只需针对较小的模糊样板集合而变得容易和快速     

Collective recall via the brain-state-in-a-box network

A number of approaches to pattern recognition employ variants of nearest neighbor recall. This procedure uses a number of prototypes of known class and identifies an unknown pattern vector according to the prototype it is nearest to. A recall criterion of this type that depends on the relation of the unknown to a single prototype is a non-smooth function and leads to a decision boundary that is a jagged, piecewise linear hypersurface. Collective recall, a pattern recognition method based on a smooth nearness measure of the unknown to all the prototypes, is developed. The prototypes are represented as cells in a brain-state-in-a-box (BSB) network. Cells that represent the same pattern class are linked by positive weights and cells representing different pattern classes are linked by negative weights. Computer simulations of collective recall used in conjunction with learning vector quantization (LVQ) show significant improvement in performance relative to nearest neighbor recall for pattern classes defined by nonspherically symmetric Gaussians.     

基于原型与正交投影学习的图像集分类算法

为了利用图像集中的集合信息来提高图像识别精度以及对图像变化的鲁棒性,从而大幅降低诸如姿态、光照、遮挡和未对齐等因素对识别精度的影响,提出了一种用于图像集分类的图像集原型与投影学习算法（LPSOP）。该算法针对每个图像集学习有代表性的点（原型）以及一个正交的全局投影矩阵,使得在目标子空间的每个图像集可以被最优地分类到同类的最近原型集中。用学习到的原型来代表该图像集,既能降低冗余图像干扰,又能减少存储和计算开销,学习到的投影矩阵则能够大幅提高分类精度与噪声鲁棒性。在UCSD/Honda、CMU MoBo和YouTube celebrities这三个数据集上的实验结果表明,LPSOP比目前流行的图像集分类算法具有更高的识别精度和更好的鲁棒性。     

Self-splitting competitive learning: a new on-line clusteringparadigm

Clustering in the neural-network literature is generally based on the competitive learning paradigm. The paper addresses two major issues associated with conventional competitive learning, namely, sensitivity to initialization and difficulty in determining the number of prototypes. In general, selecting the appropriate number of prototypes is a difficult task, as we do not usually know the number of clusters in the input data a priori. It is therefore desirable to develop an algorithm that has no dependency on the initial prototype locations and is able to adaptively generate prototypes to fit the input data patterns. We present a new, more powerful competitive learning algorithm, self-splitting competitive learning (SSCL), that is able to find the natural number of clusters based on the one-prototype-take-one-cluster (OPTOC) paradigm and a self-splitting validity measure. It starts with a single prototype randomly initialized in the feature space and splits adaptively during the learning process until all clusters are found; each cluster is associated with a prototype at its center. We have conducted extensive experiments to demonstrate the effectiveness of the SSCL algorithm. The results show that SSCL has the desired ability for a variety of applications, including unsupervised classification, curve detection, and image segmentation.     

弱监督与少样本学习场景下视频行为识别综述

近年来各类人体行为识别算法利用大量标记数据进行训练,取得了良好的识别精度。但在实际应用中,数据的获取以及标注过程都是非常耗时耗力的,这限制了算法的实际落地。针对弱监督及少样本场景下的视频行为识别深度学习方法进行综述。首先,在弱监督情况下,分类总结了半监督行为识别方法和无监督领域自适应下的视频行为识别方法;然后,对少样本场景下的视频行为识别算法进行详细综述;接着,总结了当前相关的人体行为识别数据集,并在该数据集上对各相关视频行为识别算法性能进行分析比较;最后,进行概括总结,并展望人体行为识别的未来发展方向。     

基于实时样本采集的个性化手写汉字输入系统设计

手写汉字识别是手写汉字输入的基础。目前智能设备中的手写汉字输入法无法根据用户的汉字书写习惯,动态调整识别模型以提升手写汉字的正确识别率。通过对最新深度学习算法及训练模型的研究,提出了一种基于用户手写汉字样本实时采集的个性化手写汉字输入系统的设计方法。该方法将采集用户的手写汉字作为增量样本,通过对服务器端训练生成的手写汉字识别模型的再次训练,使识别模型能够更好地适应该用户的书写习惯,提升手写汉字输入系统的识别率。最后,在该理论方法的基础上,结合新设计的深度残差网络,进行了手写汉字识别的对比实验。实验结果显示,通过引入实时采集样本的再次训练,手写汉字识别模型的识别率有较大幅度的提升,能够更有效的满足用户在智能设备端对手写汉字输入系统的使用需求。     

Automatic extraction of human-recognizable shape and execution prototypes of handwritten characters

The novel prototype extraction method presented in this paper aims to advancing in the comprehension of handwriting generation and improving on-line recognition systems. The extraction process is performed in two stages. First, using Fuzzy ARTMAP we group character instances according to classification criteria. Then, an algorithm refines these groups and computes the prototypes. Experimental results on the UNIPEN international database show that the proposed system is able to extract a low number of prototypes that are easily recognizable. In addition, the extraction method is able to condense knowledge that can be successfully used to initialize an LVQ-based recognizer, achieving an average recognition rate of 90.15%, comparable to that reached by human readers.     

开放集文字识别技术

开放环境下的模式识别与文字识别应用中,新数据、新模式和新类别不断涌现,要求算法具备应对新类别模式的能力。针对这一问题,研究者们开始聚焦开放集文字识别（open-set text recognition,OSTR）任务。该任务要求,算法在测试（推断）阶段,既能识别训练集见过的文字类别,还能够识别、拒识或发现训练集未见过的新文字。开放集文字识别逐步成为文字识别领域的研究热点之一。本文首先对开放集模式识别技术进行简要总结,然后重点介绍开放集文字识别的研究背景、任务定义、基本概念、研究重点和技术难点。同时,针对开放集文字识别三大问题（未知样本发现、新类别识别和上下文信息偏差）,从方法的模型结构、特点优势和应用场景的角度对相关工作进行了综述。最后,对开放集文字识别技术的发展趋势和研究方向进行了分析展望。     

An incremental learning vector quantization algorithm for pattern classification

Prototype classifiers have been studied for many years. However, few methods can realize incremental learning. On the other hand, most prototype classifiers need users to predetermine the number of prototypes; an improper prototype number might undermine the classification performance. To deal with these issues, in the paper we propose an online supervised algorithm named Incremental Learning Vector Quantization (ILVQ) for classification tasks. The proposed method has three contributions. (1) By designing an insertion policy, ILVQ incrementally learns new prototypes, including both between-class incremental learning and within-class incremental learning. (2) By employing an adaptive threshold scheme, ILVQ automatically learns the number of prototypes needed for each class dynamically according to the distribution of training data. Therefore, unlike most current prototype classifiers, ILVQ needs no prior knowledge of the number of prototypes or their initial value. (3) A technique for removing useless prototypes is used to eliminate noise interrupted into the input data. Results of experiments show that the proposed ILVQ can accommodate the incremental data environment and provide good recognition performance and storage efficiency.     

基于原型网络的小样本图像识别方法

当前的图像识别领域,大部分的分类或者识别方法都建立在已有大量数据的基础上,将大量数据投入训练,经过采样分析、特征提取后做判别分类。然而在现实世界中,大多数目标分类问题并没有大量的标注数据。为了解决基于小样本数据集的图像识别问题,本文首先使用数据增强方法扩充数据集,然后利用多层卷积神经网络将图像映射到高维嵌入空间中,再使用原型网络得到每个类的原型点,根据嵌入空间中测试图像与各个类原型点之间的距离将其分类。实验结果表明,该方法在小样本条件下具有较高的识别准确率和较强的鲁棒性。     

基于支持向量机的乐器识别方法

文章提出了一种基于支持向量机的乐器识别方法。与其它的模式识别方法不同,支持向量机是专门针对有限样本情况下的一种分类方法,在小样本的情况下,它的准确率一般优于传统的模式识别方法。它是建立在统计学习理论的VC维理论和结构风险最小原理基础上的,根据有限的样本信息在模型的复杂性(即对特定训练样本的学习精度)和学习能力(即无错误地识别任意样本的能力)之间寻求最佳折衷,以期获得最好的推广能力。实验以乐器的MFCC系数和它的一阶导数为声学特征,建立一个自底向上的二叉树的支持向量机模型。实验表明这种识别方法是一种有效的识别方法,它的准确率高于GMM方法。     

Learning handwriting by evolution: a conceptual framework for performance evaluation and tuning

In this paper we propose a method for evaluating the performance of an evolutionary learning system aimed at producing the optimal set of prototypes to be used by a handwriting recognition system. The trade-off between generalization and specialization embedded into any learning process is managed by iteratively estimating both consistency and completeness of the prototypes, and by using such an estimate for tuning the learning parameters in order to achieve the best performance with the smallest set of prototypes. Such estimation is based on a characterization of the behavior of the learning system, and is accomplished by means of three performance indices. Both the characterization and the indices do not depend on either the system implementation or the application, and therefore allow for a truly black-box approach to the performance evaluation of any evolutionary learning system.