Quasiperiodic Sturmian words and morphisms

We characterize all quasiperiodic Sturmian words: A Sturmian word is not quasiperiodic if and only if it is a Lyndon word. Moreover, we study links between Sturmian morphisms and quasiperiodicity.     

On the structure of bispecial Sturmian words

A balanced word is one in which any two factors of the same length contain the same number of each letter of the alphabet up to one. Finite binary balanced words are called Sturmian words. A Sturmian word is bispecial if it can be extended to the left and to the right with both letters remaining a Sturmian word. There is a deep relation between bispecial Sturmian words and Christoffel words, that are the digital approximations of Euclidean segments in the plane. In 1997, J. Berstel and A. de Luca proved that palindromic bispecial Sturmian words are precisely the maximal internal factors of primitive Christoffel words. We extend this result by showing that bispecial Sturmian words are precisely the maximal internal factors of all Christoffel words. Our characterization allows us to give an enumerative formula for bispecial Sturmian words. We also investigate the minimal forbidden words for the language of Sturmian words.     

Conjugacy of morphisms and Lyndon decomposition of standard Sturmian words

Using the notions of conjugacy of morphisms and of morphisms preserving Lyndon words, we answer a question of G. Melançon. We characterize cases where the sequence of Lyndon words in the Lyndon factorization of a standard Sturmian word is morphic. In each possible case, the corresponding morphism is given.     

On the arithmetical complexity of Sturmian words

Using the geometric dual technique by Berstel and Pocchiola, we give a uniform O(n³)$O\left(n^3\right)$ upper bound for the arithmetical complexity of a Sturmian word. We also give explicit expressions for the arithmetical complexity of Sturmian words of slope between 1/3 and 2/3 (in particular, of the Fibonacci word). In this case, the difference between the genuine arithmetical complexity function and our upper bound is bounded, and ultimately 2-periodic. In fact, our formula is valid not only for Sturmian words but for rotation words from a wider class.     

Special factors and the combinatorics of suffix and factor automata

The suffix automaton (resp. factor automaton) of a finite word w is the minimal deterministic automaton recognizing the set of suffixes (resp. factors) of w. We study the relationships between the structure of the suffix and factor automata and classical combinatorial parameters related to the special factors of w. We derive formulae for the number of states of these automata. We also characterize the languages L_SA and L_FA of words having respectively suffix automaton and factor automaton with the minimal possible number of states.     

On the equivalence between global recurrence and the existence of a smooth Lyapunov function for hybrid systems

We study a weak stability property called recurrence for a class of hybrid systems. An open set is recurrent if there are no finite escape times and every complete trajectory eventually reaches the set. Under sufficient regularity properties for the hybrid system we establish that the existence of a smooth, radially unbounded Lyapunov function that decreases along solutions outside an open, bounded set is a necessary and sufficient condition for recurrence of that set. Recurrence of open, bounded sets is robust to sufficiently small state dependent perturbations and this robustness property is crucial for establishing the existence of a Lyapunov function that is smooth. We also highlight some connections between recurrence and other well studied properties like asymptotic stability and ultimate boundedness.     

情感倾向判断中基准词的选择

针对已有研究工作中基准词选择的不足之处,提出了一种情感倾向判断中基准词选择的方法.依照基准词的定义,分别从情感度、情感倾向度、情感歧义性3个方面考虑,选择出数量尽可能少、最具有代表性的情感词作为基准词.首先从《知网》所发布的情感词语中,筛选出最初的候选基准词,计算出这些候选基准词的情感度.然后分别计算出情感度排名靠前的正面情感词和负面情感词的情感倾向度.最后选择情感倾向度较大的词语,作为最终的基准词.实验结果表明,按照文中所选择的基准词所得到的情感倾向判断的准确率较高.     

Estimation of the length of reset words for automata with simple idempotents

A quadratic upper bound on the length of a minimal reset word is obtained for finite automata with simple idempotents. Each input symbol of the automata considered induces a transformation that is an idempotent with the unit defect or a bijection on the set of states. This bound is only twice as large as the well-known lower bound of this length. Translated from Kibernetika i Sistemnyi Analiz, No. 3, pp. 32–39, May–June, 2000.     

超像素词包模型与SVM分类的图像标注

为了改善基于词包模型与支持向量机(SVM)分类一幅图对应一个标签的单标签分类问题,提出了一种基于超像素词包模型与SVM分类的图像标注算法.将超像素分割结果作为词包模型的基本单元,用词包模型生成的视觉词汇表示超像素区域特征,保留了图像中的同质区域,很好地利用了图像的区域特征.仿真结果表明,该方法能有效改善基于词包模型与SVM分类的单标签分类问题,且分类的准确性有所提高.     

Balancing and clustering of words in the Burrows-Wheeler transform

Compression algorithms based on Burrows-Wheeler transform (BWT) take advantage of the fact that the word output of BWT shows a local similarity and then turns out to be highly compressible. The aim of the present paper is to study such “clustering effect” by using notions and methods from Combinatorics on Words.The notion of balance of a word plays a central role in our investigation. Empirical observations suggest that balance is actually the combinatorial property of input word that ensure optimal BWT compression. Moreover, it is reasonable to assume that the more balanced the input word is, the more local similarity we have after BWT (and therefore the better the compression is). This hypothesis is here corroborated by experiments on “real” text, by using local entropy as a measure of the degree of balance of a word.In the setting of Combinatorics on Words, a sound confirmation of previous hypothesis is given by a result of Mantaci et al. (2003) [27], which states that, in the case of a binary alphabet, there is an equivalence between circularly balanced words, words having a clusterized BWT, and the conjugates of standard words. In the case of alphabets of size greater than two, there is no more equivalence. The last section of the present paper is devoted to investigate the relationships between these notions, and other related ones (as, for instance, palindromic richness) in the case of a general alphabet.     

Verbumculus and the discovery of unusual words

Measures relating word frequencies and expectations have been constantly of interest in Bioinfor-matics studies. With sequence data becoming massively available, exhaustive enumeration of such measures have become conceivable, and yet pose significant computational burden even when limited to words of bounded maximum length. In addition, the display of the huge tables possibly resulting from these counts poses practical problems of visualization and inference.VERBUMCULUS is a suite of software tools for the efficient and fast detection of over- or under-represented words in nucleotide sequences. The inner core of VERBUMCULUS rests on subtly interwoven properties of statistics, pattern matching and combinatorics on words, that enable one to limit drastically and a priori the set of over-or under-represented candidate words of all lengths in a given sequence, thereby rendering it more feasible both to detect and visualize such words in a fast and practically useful way. This paper is devoted to the descri     

基于全切分获取网络流行语方法研究*

利用统计和规则相结合的算法从互联网的动态信息流中提取网络流行语。在利用全切分算法获取候选词集的基础上,依次对候选词集进行三次过滤：首先基于向量空间模型的权重过滤,运用语言模型进行过滤;然后利用垃圾串过滤规则获取网络流行词语候选词集;最后利用提出的流行词语评分模型进行筛选得到网络流行词语。实验表明,在不影响流行词语准确率的前提下,利用该方法自动获取网络流行词语的速度明显提高。     

HEp-2 image classification using intensity order pooling based features and bag of words

Human Epithelial type 2 (HEp-2) cells play an important role in the diagnosis of autoimmune disorder. Traditional approach relies on specialists to observe HEp-2 slides via the fluorescence microscope, which suffers from a number of shortcomings like being subjective and labor intensive. Pattern recognition techniques have been recently introduced to this research issue to make the process automatic. However, performances of current systems available in literature are not satisfying. We propose in this paper a framework using intensity order pooling based gradient feature and bag of words for HEp-2 classification. By pooling the gradient features based on the intensity orders of local grid points, the pooled feature is rotationally invariant without requirement of orientation estimation. The proposed approach was fully tested using publicly available ICPR dataset and our own SZU dataset. Experimental results show that the propose method significantly outperformed widely used SIFT feature and the winner of ICPR contest 2012. Encouraging 100% image level accuracy was achieved on the SZU dataset.     

一种结合显著性检测与词袋模型的目标识别方法

针对词袋模型易受到无关的背景视觉噪音干扰的问题,提出了一种结合显著性检测与词袋模型的目标识别方法。首先,联合基于图论的视觉显著性算法与一种全分辨率视觉显著性算法,自适应地从原始图像中获取感兴趣区域。两种视觉显著性算法的联合可以提高获取的前景目标的完整性。然后,使用尺度不变特征变换描述子从感兴趣区域中提取特征向量,并通过密度峰值聚类算法对特征向量进行聚类,生成视觉字典直方图。最后,利用支持向量机对目标进行识别。在PASCAL VOC 2007和MSRC-21数据库上的实验结果表明,该方法相比同类方法可以有效地提高目标识别性能。     

基于关系对齐的汉语虚词抽象语义表示与分析

虚词具有丰富的语法意义,对句子理解起着不可或缺的作用。虚词的语言学研究成果丰富,但缺乏形式化表示,无法直接被计算机利用。为了表示虚词的句法语义信息,该文首先在抽象语义表示(abstract meaning representation,AMR)这种基于概念图的语义表示方法的基础上,增加了词语和概念关系的对齐信息,使得虚词对应于概念节点或节点之间的关系弧。其次,选取了语言规范的人教版小学语文课本8 587句作为语料,进行AMR的标注。然后,针对语料中24 801个虚词实例进行统计,发现介词、连词、结构助词对应概念间的关系,占虚词总数的58.80%;而语气词和体助词表示概念,占41.20%。这表明AMR可以动态地描写出虚词功能,为整句句法语义分析提供更好的理论与资源。     

Relation between spinal load factors and the high-risk probability of occupational low-back disorder

Spinal compression is traditionally assumed the principal biomechanical mechanism associated with occupationally related low-back disorders (LBD). However, there is little conclusive evidence demonstrating that compression is related to occupational LBD. The objective of this research was to examine whether axial compression in the lumbar spine can predict the probability that a lifting task should be classified as high risk for LBD. Furthermore, the improvement in predictive ability was examined when analyses include 3-D, dynamic biomechanical factors. Ten experienced warehouse workers transferred 12 pallet loads of boxes in a simulation of warehouse working conditions. Biomechanical estimates of 2-D static and 3-D dynamic spinal compression, shear loads and tissue strains were achieved from the subjects during each lifting exertion. Each lift was also assessed for probability of high LBD risk classification. Regression analyses were performed to examine the relationship between biomechanical and epidemiological factors. Results indicate 2-D static estimates of spinal compression describe ? 13% of the probability of high LBD risk variability. Dynamic estimates of spinal compression describe >44% of the variability. A multifactor regression model including 3-D spinal loads and tissue strains further improved the predictive ability, but the improvement was not statistically significant. This research demonstrates the biomechanical source of low-back pain is dynamic, multifaceted and multidimensional. Significant improvements in ergonomics assessments can be achieved by examining interactions of dynamic biomechanical factors. Unfortunately, this improved predictive ability is generated at the high cost of computational complexity. However, less realistic biomechanical representations may ignore the injury mechanisms associated with the greater number of workplace injuries. Thus, improved understanding of the dynamic biomechanical interactions influencing the tolerance and injury mechanisms of the spine may permit more accurate assessments of workplace injury factors associated with LBD and reduced incidence of occupationally related low-back pain.