共查询到20条相似文献，搜索用时 93 毫秒
1.
This paper investigates the consensus problem for third-order discrete-time multi-agent systems in directed networks. For the case when each agent can only receive the information of position and velocity from its neighbors, necessary and sufficient conditions for consensus have been proposed. In contrast to the preceding work, we not only present the exact consensus value, but also illustrate the influence of scaling parameters and nonzero eigenvalues of the involved Laplacian matrix on consensus. Two numerical examples are given to demonstrate the effectiveness of the obtained results. 相似文献
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根据社交网络信息传播多维度、多元化和基于人际关系的特点,构建一种基于用户相对传播能力的分层网络传播模型,对社交网络传播模型研究中缺少实例验证和用户层次分类的问题进行补充分析和证明。通过调查收集"平江火电厂重启事件"中公众对火电项目的态度变化数据,对政府相关宣传内容的传播过程、方式和效果进行归纳总结;采取K-Means方式对抽样的数据节点进行分类,构建以节点传播能力为划分标准的分层网络传播模型,分析模型中信息的传播路径、传播特征及权重关系。研究表明:(1)基于用户相对传播能力的分层网络传播模型更能真实地体现社交网络中信息传递的特点;(2)意见领袖层节点在信息传播过程中具有导向性作用,其网络影响程度约为普通群众的4倍(意见领袖节点的平均权重为2.6,普通群众节点的平均权重为0.6);(3)用户网络地位影响信息传递的效果,政府在提高公众支持度的问题上应该充分发挥意见领袖的作用,引导社会舆论。社会信息传播网络仍然是复杂网络研究中的难点,信息传递的方向、节点出度和入度都有待在未来的研究中进一步完善。 相似文献
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In this work, we analyze the performance degradation of stealthy attacks against sensor measurements in vector systems. Two types of attacks are considered. One is strictly stealthy attack and the other is ?-stealthy attack. For the strictly stealthy attack, we characterize the upper bound of the performance degradation and design an optimal strictly stealthy attack that can achieve the upper bound. For the ?-stealthy attack, we quantify the upper bound of the performance degradation and propose a sub-optimal ?-stealthy attack approximately achieving the upper bound. Numerical results are given to illustrate the trade off between performance degradation versus the stealthiness level of the attack. 相似文献
4.
M. Sami Fadali 《Journal of The Franklin Institute》2011,348(2):239-260
In this paper, we use input and output maps to develop simple procedures to obtain minimal realizations for linear continuous-time systems. The procedures developed are numerically efficient and yield explicit formulae for the state-space matrices of the realization in terms of the system parameters, notably the system eigenvalues. Both systems with distinct eigenvalues and repeated eigenvalues are treated. We also present a procedure for transforming a realization obtained through the input or output map to Jordan canonical form. The transformation matrices required to transform the realization to Jordan canonical form are specified entirely in terms of the system eigenvalues. We illustrate the results obtained with several examples. 相似文献
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Performance analysis of a spreading sequence estimator for spread spectrum transmissions 总被引：4，自引：0，他引：4
C. Bouder 《Journal of The Franklin Institute》2004,341(7):595-614
Direct sequence spread spectrum transmissions (DS-SS) are now widely used for secure communications, as well as for multiple access. They have many interesting properties, including low probability of interception. Indeed, DS-SS transmitters use a periodical pseudo-random sequence to modulate the baseband signal before transmission. A receiver which does not know the sequence cannot demodulate the signal.In this paper, we propose a new method which can estimate the spreading sequence in a noncooperative context. The method is based on eigenanalysis techniques. The received signal is divided into windows, from which a covariance matrix is computed. We show that the sequence can be reconstructed from the two first eigenvectors of this matrix, and that useful information, such as desynchronisation time, can be extracted from the eigenvalues.The main achievement of the present paper is a performance analysis of the proposed spreading sequence estimation procedure. An analytical approach is first considered owing to matrix perturbation theory and Wishart matrix properties. Then, complementary Monte Carlo simulations are performed to show the effectiveness of the proposed method. 相似文献
6.
公司创业投资者与创业企业家之间的信息困境及进化博弈分析 总被引：2，自引：0，他引：2
对公司投资者和创业企业家之间的信息困境进行了分析，在此基础上建立了二者的信息博弈模型，并运用进化博弈理论分析了公司创业投资市场主体的博弈过程和进化稳定策略，讨论了不同强度的知识产权保护环境对博弈的影响。最后，对如何规范市场主体行为提出了建议。 相似文献
7.
《Information processing & management》2023,60(2):103206
A news article’s online audience provides useful insights about the article’s identity. However, fake news classifiers using such information risk relying on profiling. In response to the rising demand for ethical AI, we present a profiling-avoiding algorithm that leverages Twitter users during model optimisation while excluding them when an article’s veracity is evaluated. For this, we take inspiration from the social sciences and introduce two objective functions that maximise correlation between the article and its spreaders, and among those spreaders. We applied our profiling-avoiding algorithm to three popular neural classifiers and obtained results on fake news data discussing a variety of news topics. The positive impact on prediction performance demonstrates the soundness of the proposed objective functions to integrate social context in text-based classifiers. Moreover, statistical visualisation and dimension reduction techniques show that the user-inspired classifiers better discriminate between unseen fake and true news in their latent spaces. Our study serves as a stepping stone to resolve the underexplored issue of profiling-dependent decision-making in user-informed fake news detection. 相似文献
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A two-step iterative method (1,2) for a reduction in the order of linear continuous-time systems, given in the state equation or the transfer function, is extended to reduce discrete-time systems. The method requires the optimization of the residues and eigenvalues (or poles) belonging to an objective function. The objective function to be minimized is chosen as the finite sum of the squares of the error between the step responses of the reduced model and the original system. This scheme is continued cyclically until the objective function is satisfactorily minimized. By investigating the initial selection of the eigenvalues in the reduced-order model, it is found that the dominant eigenvalues of the original system give a good approximation. Further, the resulting model is always stable, assuming the original system is stable. As shown in a numerical example, the proposed method is superior to the other methods of model reduction in both steady-state and transient responses, and in the value of the sum of the squares of the error. 相似文献
10.
《中国科学院院刊(英文版)》2009,23(1):62-63
While observing the world around us via an optical telescope withinformation carried by visible light, which constitutes only a small portion of the electromagnetic spectrum, astronomers use the remainder of the spectrum to reveal extensive data about celestial objects. For instance, they use telescopes operating in the radio spectrum to explore the universe. 相似文献
11.
T.K. Gaisser 《Journal of The Franklin Institute》1974,298(4):271-287
Cosmic ray extensive air shower observations can give clues about the properties of high-energy particle interactions above 1015eV, in addition to giving information about the primary cosmic ray spectrum at these energies. A brief review of recent high energy accelerator data and its theoretical interpretation is given to explain the necessity for obtaining information from cosmic rays about hadronic interactions beyond machine energies. In particular, it is shown that recent measurements of the energy dependence of total cross-sections and of production cross-sections suggest some sort of threshold behavior in the 1000 GeV region. Studies at higher energies are required to understand the nature of this behavior. The use of air shower data for this purpose is illustrated by comparing shower size us depth measurements with the expectations of various models of strong interactions. 相似文献
12.
随着移动互联网、物联网的快速发展,我们面对的海量信息正以几何级快速增长。数据挖掘技术建立在关系型数据库上,通过大量的数据访问、分析、统计找出隐藏在数据中的规律从而建立决策模型。介绍如何利用数据挖掘技术,导出对读者、用户有用的关键信息,帮助他们做出决策和战略规划,改善和提高图书馆的服务质量。为了更好的说明这种数据分析方法的概念与过程,文章通过一个专业图书馆的详细数据资源的实际案例分析,一步一步地获得了数据内在关联的互动信息与影响图书馆管理、战略规划的因素指标。描述了图书馆如何通过数据的分析,导出对决策者提升管理质量的有用信息的数据与知识挖掘过程。可以通过其它更大量的数据分析,进一步定义一些关于服务质量提升的新指标。在当今信息飞速发展时代,图书馆馆员与管理者应当利用新的技术充分分析图书馆数据,才能达到提升服务的目标。 相似文献
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Knut Holt 《Research Policy》1978,7(4):342-360
For more and more firms product innovation is becoming the key to survival and future growth. Successful product innovation cannot be based only upon inspiration, fantasy and random ideas; in most firms a purposeful and systematic approach also is required. Information is a key concept in this context. As product innovation activities are very different from day-to-day activities, a special information system is required.Based on an in-depth study of a large firm, it appears that systematic innovation requires: (a) a sound business concept with future oriented strategies and policies; (b) a competent staff who master the necessary tools; (c) an efficient organization with an appropriate information system; (d) relevant methods for diversification studies and product planning; and (e) development of individual products based on systematical provision of information about user needs and proper specification of requirements.In small firms innovations are based more on the entrepreneurial approach. Such firms often demonstrate a very innovative attitude, but many of them are hampered by lack of skills in marketing and management. They also lack supporting services which can provide information about the environment.Considering the importance of small firms in economic development and social progress, they should be given support in their innovative attempts. This can be done by organizing innovation centers which arrange studies, develop courses, and give practical assistance to firms engaged in innovative work. Governments should develop policies and provide information stimulating both small and large firms to innovations that are more desirable from a social point of view. 相似文献
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M.T. Martín-Valdivia M.C. Díaz-GalianoA. Montejo-Raez L.A. Ureña-López 《Information processing & management》2008
Nowadays, access to information requires managing multimedia databases effectively, and so, multi-modal retrieval techniques (particularly images retrieval) have become an active research direction. In the past few years, a lot of content-based image retrieval (CBIR) systems have been developed. However, despite the progress achieved in the CBIR, the retrieval accuracy of current systems is still limited and often worse than only textual information retrieval systems. In this paper, we propose to combine content-based and text-based approaches to multi-modal retrieval in order to achieve better results and overcome the lacks of these techniques when they are taken separately. For this purpose, we use a medical collection that includes both images and non-structured text. We retrieve images from a CBIR system and textual information through a traditional information retrieval system. Then, we combine the results obtained from both systems in order to improve the final performance. Furthermore, we use the information gain (IG) measure to reduce and improve the textual information included in multi-modal information retrieval systems. We have carried out several experiments that combine this reduction technique with a visual and textual information merger. The results obtained are highly promising and show the profit obtained when textual information is managed to improve conventional multi-modal systems. 相似文献
17.
In this work, the cruise control problem of high-speed trains’ movements is investigated. Both cases of a single high-speed train and multiple high-speed trains are under consideration. Different with most existing studies where the centralized control or the decentralized control methods are adopted based on a single point mass model of the train, in this paper, a distributed control mechanism is proposed by virtue of the graph theory, and the high-speed train’s model is built as a cascade of point masses connected by flexible couplers. For a single high-speed train, the neighboring cars interact through the coupling force with each other, which can be described by a connected topological graph by regarding each car as a node. Besides, the speed information communication among the cars is considered to be described by another directed topological graph. A distributed control strategy is then developed, with which all the cars of a train track a desired speed asymptotically and the neighboring cars keep a safety distance from each other. For the multiple high-speed trains running on a railway line, the in-train force interaction topology and the speed information communication topology of all the trains are more complex than those of a single train. A new cluster consensus technique is developed, by which a distributed control law is designed. Under the control law, the trains can track the desired speeds asymptotically, the headway distance between adjacent trains and the distance between the neighboring cars of a train can be kept in appropriate ranges. Finally, simulations are provided to illustrate the effectiveness of the obtained theoretical results. 相似文献
18.
The conventional modal control theory is concerned with the problem of determining a state feedback matrix-valued gain which drives the system eigenvalues to prescribed positions. When the parameters of the open-loop system involve certain variations, the closed-loop eigenvalues, obtained by using a feedback gain determined as above, also contain variations. In the present paper the problem of choosing an additional state feedback gain such as to reduce the closed-loop eigenvalue variations as much as desired is solved. Specifically, upon the assumption that a nominal set of parameter values is given, and that a feedback modal control law which drives the eigenvalues of the nominal closed-loop system to the desired positions is known, two alternative expressions for the required additional reduced eigenvalue sensitivity feedback controller are derived. Both cases of known and unknown system state vector are considered. The theory is illustrated by several examples. 相似文献
19.
Jessica Litman 《Ethics and Information Technology》1999,1(3):213-225
For commercial purveyors of digital speech, information and entertainment, the biggest threat posed by the Internet isn't the threat of piracy, but the threat posed by free speech -- speech that doesn't cost any money. Free speech has the potential to squeeze out expensive speech. A glut of high quality free stuff has the potential to run companies in the business of selling speech out of business. We haven't had to worry about this before, because speaking in a meaningful way to a large audience was expensive, and people couldn't afford to do serious mass speaking for free for very long. The Internet has made it much cheaper. It doesn't take much to give out information to the whole world, every day, for free, for years. And people do. If we are trying to increase the abundant dissemination of information, free speech is good. If we are trying to increase commerce in information, free speech is arguably bad, in that it competes with pay speech. Information merchants would obviously prefer that the only speech in the marketplace be pay speech. In the past two years, commercial content owners have scored significant progress in herding free speakers off the Net. There's an important synergy between persuading the government to give your industry some friendly new laws or regulations, and using new and old legal tools to make life more difficult or expensive for inconvenient competitors who aren't necessarily doing anything illegal. Recently, businesses have been able to combine the two strategies to make the Internet a much safer place to sell speech, by making the Internet a less friendly, more dangerous place to give away speech for free. 相似文献
20.
Tércia Zavaglia TorresAuthor VitaeIvo Pierozzi Jr.Author Vitae Nadir Rodrigues PereiraAuthor VitaeAlexandre de CastroAuthor Vitae 《International Journal of Information Management》2011,31(2):121-127
The great contemporary organizational challenge for enterprises is to create a conceptual and methodological framework allows the management of knowledge by means of networks designed for social interaction. This statement is based on the premise that the competitive drive and sustainable success of the company depend on the introduction of new forms of production innovative processes, which can only be ensured through integrated approaches to knowledge management and the incorporation information technologies (IT). This is a reality that has already been accepted by the Brazilian Agricultural Research Corporation (Embrapa, its acronym in Portuguese), a Brazilian research, development, and innovation (RD&I) institution supporting agricultural sector. For some years now, Embrapa has been incorporating what it has learned about knowledge management into its strategic planning process. In this paper, we present a new approach to managing knowledge and information, and we analyze the need for research institutions to administer the knowledge they produce through an RD&I management model based multi- and inter-disciplinary teams, and multi-institutional research networks. 相似文献