共查询到20条相似文献，搜索用时 31 毫秒
1.
In this paper, we propose a novel method for addressing the multi-equilibria consensus problem for a network of n agents with dynamics evolving in discrete-time. In this method, we introduce, for the first time in the literature, two concepts called primary and secondary layer subgraphs. Then, we present our main results on directed graphs such that multiple consensus equilibria states are achieved, thereby extending the existing single-state consensus convergence results in the literature. Furthermore, we propose an algorithm to determine the number of equilibria for any given directed graph automatically by a computer program. We also analyze the convergence properties of multi-equilibria consensus in directed networks with time-delays under the assumption that all delays are bounded. We show that introducing communication time-delays does not affect the number of equilibria of the given network. Finally, we verify our theoretical results via numerical examples. 相似文献
2.
Recent investigations have revealed that dynamics of complex networks and systems are crucially dependent on the temporal structures. Accurate detection of the time instant at which a system changes its internal structures has become a tremendously significant mission, beneficial to fully understanding the underlying mechanisms of evolving systems, and adequately modeling and predicting the dynamics of the systems as well. In real-world applications, due to a lack of prior knowledge on the explicit equations of evolving systems, an open challenge is how to develop a practical and model-free method to achieve the mission based merely on the time-series data recorded from real-world systems. Here, we develop such a model-free approach, named temporal change-point detection (TCD), and integrate both dynamical and statistical methods to address this important challenge in a novel way. The proposed TCD approach, basing on exploitation of spatial information of the observed time series of high dimensions, is able not only to detect the separate change points of the concerned systems without knowing, a priori, any information of the equations of the systems, but also to harvest all the change points emergent in a relatively high-frequency manner, which cannot be directly achieved by using the existing methods and techniques. Practical effectiveness is comprehensively demonstrated using the data from the representative complex dynamics and real-world systems from biology to geology and even to social science. 相似文献
3.
Webpages are mainly distinguished by their topic (e.g., politics, sports etc.) and genre (e.g., blogs, homepages, e-shops, etc.). Automatic detection of webpage genre could considerably enhance the ability of modern search engines to focus on the requirements of the user’s information need. In this paper, we present an approach to webpage genre detection based on a fully-automated extraction of the feature set that represents the style of webpages. The features we propose (character n-grams of variable length and HTML tags) are language-independent and easily-extracted while they can be adapted to the properties of the still evolving web genres and the noisy environment of the web. Experiments based on two publicly-available corpora show that the performance of the proposed approach is superior in comparison to previously reported results. It is also shown that character n-grams are better features than words when the dimensionality increases while the binary representation is more effective than the term-frequency representation for both feature types. Moreover, we perform a series of cross-check experiments (e.g., training using a genre palette and testing using a different genre palette as well as using the features extracted from one corpus to discriminate the genres of the other corpus) to illustrate the robustness of our approach and its ability to capture the general stylistic properties of genre categories even when the feature set is not optimized for the given corpus. 相似文献
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In this work a procedure for obtaining polytopic λ-contractive sets for Takagi–Sugeno fuzzy systems is presented, adapting well-known algorithms from literature on discrete-time linear difference inclusions (LDI) to multi-dimensional summations. As a complexity parameter increases, these sets tend to the maximal invariant set of the system when no information on the shape of the membership functions is available. λ-contractive sets are naturally associated to level sets of polyhedral Lyapunov functions proving a decay-rate of λ. The paper proves that the proposed algorithm obtains better results than a class of Lyapunov methods for the same complexity degree: if such a Lyapunov function exists, the proposed algorithm converges in a finite number of steps and proves a larger λ-contractive set. 相似文献
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《Information processing & management》2003,39(4):543-559
In this paper, we present a new method to improve the performance of query processing in a spatial database. The previous approach can process the retrieval of spatial objects by topological relations using R-tree structures based on minimum bounding rectangles. In our approach, we add internal rectangle to the leaf nodes of the R-tree as additional information for helping objects retrieval. As a result, the number of false hits can be reduced and part of the true hits can be identified at the early stage of searching. The experiments demonstrated that the performance of database systems can be improved because both the number of objects accessed and the number of objects requiring detailed inspection are much less than those in the previous approach. 相似文献
7.
James L. Dolby 《Information processing & management》1977,13(1):69-77
One of the fundamental problems in information science is to distinguish various objects (such as books or journal articles) on the basis of associated values (such as authors and titles). Where the values fail to distinguish two distinct objects we say that the objects are ambigious under the given value assignment. To obtain a measure of ambiguity, it is only necessary to count the number of ways that the objects can be arranged for each set of ambiguous objects, multiply these counts and take logarithms. It is shown that such an approach leads to a measure in the formal sense and that the measure depends only on the definition of equality of values so that it can be simply extended to sets of values and ordered sets of values. It is also shown that it is possible to construct a function of ambiguity that one can call “information” and that the information loss that occurs when distinct values are grouped into equivalence classes (as in the use of search and sort keys) is also a measure. Finally, it is shown that ambiguity and information as here defined are directly related to Shannon's definition of “information” thus tieing this approach to that portion of information theory associated with the derivation of optimal distributions frequently used in information science models. 相似文献
8.
Daqing He Peter Brusilovsky Jaewook Ahn Jonathan Grady Rosta Farzan Yefei Peng Yiming Yang Monica Rogati 《Information processing & management》2008
Exploratory search increasingly becomes an important research topic. Our interests focus on task-based information exploration, a specific type of exploratory search performed by a range of professional users, such as intelligence analysts. In this paper, we present an evaluation framework designed specifically for assessing and comparing performance of innovative information access tools created to support the work of intelligence analysts in the context of task-based information exploration. The motivation for the development of this framework came from our needs for testing systems in task-based information exploration, which cannot be satisfied by existing frameworks. The new framework is closely tied with the kind of tasks that intelligence analysts perform: complex, dynamic, and multiple facets and multiple stages. It views the user rather than the information system as the center of the evaluation, and examines how well users are served by the systems in their tasks. The evaluation framework examines the support of the systems at users’ major information access stages, such as information foraging and sense-making. The framework is accompanied by a reference test collection that has 18 tasks scenarios and corresponding passage-level ground truth annotations. To demonstrate the usage of the framework and the reference test collection, we present a specific evaluation study on CAFÉ, an adaptive filtering engine designed for supporting task-based information exploration. This study is a successful use case of the framework, and the study indeed revealed various aspects of the information systems and their roles in supporting task-based information exploration. 相似文献
9.
Ann Blandford Anne Adams Simon Attfield George Buchanan Jeremy Gow Stephann Makri Jon Rimmer Claire Warwick 《Information processing & management》2008
The strongest tradition of IR systems evaluation has focused on system effectiveness; more recently, there has been a growing interest in evaluation of Interactive IR systems, balancing system and user-oriented evaluation criteria. In this paper we shift the focus to considering how IR systems, and particularly digital libraries, can be evaluated to assess (and improve) their fit with users’ broader work activities. Taking this focus, we answer a different set of evaluation questions that reveal more about the design of interfaces, user–system interactions and how systems may be deployed in the information working context. The planning and conduct of such evaluation studies share some features with the established methods for conducting IR evaluation studies, but come with a shift in emphasis; for example, a greater range of ethical considerations may be pertinent. We present the PRET A Rapporter framework for structuring user-centred evaluation studies and illustrate its application to three evaluation studies of digital library systems. 相似文献
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Mouna Torjmen-Khemakhem Karen Pinel-Sauvagnat Mohand Boughanem 《Information processing & management》2013
Multimedia objects can be retrieved using their context that can be for instance the text surrounding them in documents. This text may be either near or far from the searched objects. Our goal in this paper is to study the impact, in term of effectiveness, of text position relatively to searched objects. The multimedia objects we consider are described in structured documents such as XML ones. The document structure is therefore exploited to provide this text position in documents. Although structural information has been shown to be an effective source of evidence in textual information retrieval, only a few works investigated its interest in multimedia retrieval. More precisely, the task we are interested in this paper is to retrieve multimedia fragments (i.e. XML elements having at least one multimedia object). Our general approach is built on two steps: we first retrieve XML elements containing multimedia objects, and we then explore the surrounding information to retrieve relevant multimedia fragments. In both cases, we study the impact of the surrounding information using the documents structure. 相似文献
11.
《Journal of The Franklin Institute》1986,321(5):289-298
This paper uses the Jacobi series to analyze linear optimal control systems incorporating observers. The method simplifies the system of equations into the successive solution of a set of linear algebraic equations. An illustrative example is included to demonstrate that only a small number (m = 6) of shifted-Jacobi series are needed to obtain an accurate solution. 相似文献
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提出了一种利用YCrCb颜色信息提高块匹配精确度的运动估计方法,在对背景、光照等环境条件不是十分理想的条件下,利用这个方法我们可以动态跟踪一个物体。 相似文献
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从复杂适应系统(CAS)视角,构建了网络信息生态系统的复杂适应系统分析框架。在深入剖析网络信息生态系统的复杂适应性特征基础上,全面分析了网络信息资源、网络信息主体、网络信息生态环境及其相互关系所构成的网络信息生态系统形态结构和演化结构,并对网络信息生态系统的动态演化行为及特征进行了探索研究。 相似文献
14.
Synchronous collaborative information retrieval (SCIR) is concerned with supporting two or more users who search together at the same time in order to satisfy a shared information need. SCIR systems represent a paradigmatic shift in the way we view information retrieval, moving from an individual to a group process and as such the development of novel IR techniques is needed to support this. In this article we present what we believe are two key concepts for the development of effective SCIR namely division of labour (DoL) and sharing of knowledge (SoK). Together these concepts enable coordinated SCIR such that redundancy across group members is reduced whilst enabling each group member to benefit from the discoveries of their collaborators. In this article we outline techniques from state-of-the-art SCIR systems which support these two concepts, primarily through the provision of awareness widgets. We then outline some of our own work into system-mediated techniques for division of labour and sharing of knowledge in SCIR. Finally we conclude with a discussion on some possible future trends for these two coordination techniques. 相似文献
15.
In 2019, the International Journal of Information Management (IJIM) celebrated its 40th year of publication. This study commemorates this event by presenting a retrospect of the journal. Using a range of bibliometric tools, we find that the journal has grown impressively in terms of publication and citation. The contributions come from all over the world, but the majority are from Europe and the United States. The journal has mostly published empirical articles, with its authors dominantly using quantitative methodology. Further, the culture of collaboration has increased among authors over the years. The journal publishes on a number of including managing information systems, information technologies and their application in business, technology acceptance among consumers, using information systems for decision making, social perspectives on knowledge management, and information research from the social science perspective. Regression analysis reveals that article attributes such as article order, methodology, presence of authors from Europe, number of references, number of keywords, and abstract length have a significant association with the citations. Finally, we find that conceptual and review articles have a positive association with citations. 相似文献
16.
专利质量指标评价探索 总被引：3，自引：0，他引：3
目前,对于专利我国存在着相应的描述性指标,如专利申请数量、专利授权以及相应的类型分类等,但这些都是对专利情况的简单描述.大量研究表明,不同专利的质量有很大差别.本文对专利质量指标体系进行了探索,筛选了29个专利质量指标,并将其分为引用指标、科学指标、内容指标等六类指标. 相似文献
17.
Output reversibility involves dynamical systems where for every initial condition and the corresponding output there exists another initial condition such that the output generated by this initial condition is a time-reversed image of the original output with the time running forward. Through a series of necessary and sufficient conditions, we characterize output reversibility in linear discrete-time dynamical systems in terms of the geometric symmetry of its eigenvalue set with respect to the unit circle in the complex plane. Furthermore, we establish that output reversibility of a linear continuous-time system implies output reversibility of its discretization. In addition, we present a control framework that allows to alter the system dynamics in such a way that a discrete-time system, otherwise not output reversible, can be made output reversible. Finally, we present numerical examples involving a discretization of a Hamiltonian system that exhibits output reversibility and an example of a controlled system that is rendered output reversible. 相似文献
18.
Howard D. White 《Information processing & management》1977,13(3):177-187
In the context of a general critique of the present system for providing information about public services, librarians are proposed as producers and deliverers of a file of “administrative publicity” for such services—particularly those affording opportunities, as opposed to relief from distress. Political rapport between libraries and other public agencies is seen as essential if maldistribution of information is to be overcome. Fourteen characteristics of an ideal file of administrative publicity are set forth, in an attempt to set standards by which maldistribution and shortcomings of present files may be judged. Practical models for an ideal file include the Catalog of Federal Domestic Assistance; the structure and indexing of these models are discussed. The essay as a whole is related to recent writings on libraries as community information centers, on cable television and libraries, and on the politics of information in the United States. 相似文献
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In this paper, we provide a new insight into clustering with a spring–mass dynamics, and propose a resulting hierarchical clustering algorithm. To realize the spectral graph partitioning as clustering, we model a weighted graph of a data set as a mass–spring dynamical system, where we regard a cluster as an oscillating single entity of a data set with similar properties. And then, we describe how oscillation modes are related with eigenvectors of a graph Laplacian matrix of the data set. In each step of the clustering, we select a group of clusters, which has the biggest number of constituent clusters. This group is divided into sub-clusters by examining an eigenvector minimizing a cost function, which is formed in such a way that subdivided clusters will be balanced with large size. To find k clusters out of non-spherical or complex data, we first transform the data into spherical clusters located on the unit sphere positioned in the (k−1)-dimensional space. In the sequel, we use the previous procedure to these transformed data. The computational experiments demonstrate that the proposed method works quite well on a variety of data sets, although its performance degrades with the degree of overlapping of data sets. 相似文献