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排序方式: 共有10000条查询结果,搜索用时 453 毫秒
991.
Yolanda Blanco-Fernndez Jos J. Pazos-Arias Alberto Gil-Solla Manuel Ramos-Cabrer Martín Lpez-Nores Jorge García-Duque Ana Fernndez-Vilas Rebeca P. Díaz-Redondo Jesús Bermejo-Muoz 《Knowledge》2008,21(4):305-320
Recommender systems arose with the goal of helping users search in overloaded information domains (like e-commerce, e-learning or Digital TV). These tools automatically select items (commercial products, educational courses, TV programs, etc.) that may be appealing to each user taking into account his/her personal preferences. The personalization strategies used to compare these preferences with the available items suffer from well-known deficiencies that reduce the quality of the recommendations. Most of the limitations arise from using syntactic matching techniques because they miss a lot of useful knowledge during the recommendation process. In this paper, we propose a personalization strategy that overcomes these drawbacks by applying inference techniques borrowed from the Semantic Web. Our approach reasons about the semantics of items and user preferences to discover complex associations between them. These semantic associations provide additional knowledge about the user preferences, and permit the recommender system to compare them with the available items in a more effective way. The proposed strategy is flexible enough to be applied in many recommender systems, regardless of their application domain. Here, we illustrate its use in AVATAR, a tool that selects appealing audiovisual programs from among the myriad available in Digital TV. 相似文献
992.
班达 《数字社区&智能家居》2009,(14)
使用WiFi(Wireless Fidelity)IEEE 802.11b/g协议的无线局域网(WLAN)技术已经成为PC和笔记本电脑的标准而正在快速扩散到PDA(Personal Digital Assistant)和其它便携式设备。与此同时,蓝牙作为耳机,麦克风连到各种个样的无线设备的串口线的替代品已经越来越普遍。这两种无线协议都工作于2.40至2.48GHzISM(工业,科学和医疗)射频带。WiFi使用12个带宽为22MHz重叠的频道其中一个,而蓝在带宽为79MHz范围跳频[3]。因此,无论WiFi正在使用哪个频道两个系统间会存在互相干扰和共存的问题导致数据吞吐量的降低。实现IEEE802.11 WLAN协议的设使用FEC(Foward Error Correction)纠错技术来减轻于其它无线网的干扰。在该文中,我们将对RS(Reed Solomon)编码与BS(Binary Convolutional)编码使用于解决WLAN于BT共存问题的相对有效性进行一个调查并作出结论。 相似文献
993.
Geographic Routing(GR)algorithms require nodes to periodically transmit HELLO messages to allow neigh- bors to know their positions(beaconing mechanism).Beacon-less routing algorithms have recently been proposed to reduce the control overheads due to these messages.However,existing beacon-less algorithms have not considered realistic physical layers.Therefore,those algorithms cannot work properly in realistic scenarios.In this paper we present a new beacon- less routing protocol called BOSS.Its design is based on the conclusions of our open-field experiments using Tmote-sky sensors.BOSS is adapted to error-prone networks and incorporates a new mechanism to reduce collisions and duplicate messages produced during the selection of the next forwarder node.We compare BOSS with Beacon-Less Routing(BLR) and Contention-Based Forwarding(CBF)algorithms through extensive simulations.The results show that our scheme is able to achieve almost perfect packet delivery ratio(like BLR)while having a low bandwidth consumption(even lower than CBF).Additionally,we carried out an empirical evaluation in a real testbed that shows the correctness of our simulation results. 相似文献
994.
995.
Nowadays, the use of Radio Frequency Identification (RFID) systems in industry and stores has increased. Nevertheless, some
of these systems present privacy problems that may discourage potential users. Hence, high confidence and effient privacy
protocols are urgently needed. Previous studies in the literature proposed schemes that are proven to be secure, but they
have scalability problems. A feasible and scalable protocol to guarantee privacy is presented in this paper. The proposed
protocol uses elliptic curve cryptography combined with a zero knowledge-based authentication scheme. An analysis to prove
the system secure, and even forward secure is also provided.
This work is supported by the Generalitat de Catalunya under Grant No. FIC 2007FIC 00880, and the projects of the Spanish
MCyT MTM2007-66842-C02-02 and TIN2006-15662-C02-02. 相似文献
996.
Juan José Martín‐Romero Montserrat Gil‐Martínez Mario García‐Sanz 《国际强度与非线性控制杂志
》2009,19(17):1959-1971
》2009,19(17):1959-1971
This paper describes an analytical formulation to compute quantitative feedback theory (QFT) bounds in one‐degree‐of‐freedom feedback control problems. The new approach is based on envelope curves and shows that a QFT control specification can be expressed as a family of circumferences. Then, the controller bound is defined by the envelope curve of this family and can be obtained as an analytical function. This offers the possibility of studying the QFT bounds in an analytical way with several useful properties. Gridding methods are avoided, resulting in a lower computational effort procedure. The new formulation improves the accuracy of previous methods and allows the designer to calculate multivalued bounds. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
997.
Sanchez-Sanz M. Fernandez B. Velazquez A. 《Journal of microelectromechanical systems》2009,18(2):449-457
This paper explores the feasibility of using the unsteady forces generated by the Karman street around a microprism in the laminar flow regime as a means to generate mechanical work. In particular, the study has the objective of assessing whether this physical effect could be used for practical energy-harvesting purposes. The confined flow, either of a liquid or a gas, around a rectangular microprism, of which different aspect ratios have been studied, is considered at Reynolds 200 so as to make sure that the Karman street is developed and that the flow remains 2-D. The microprism is allowed to move freely in the direction perpendicular to the flow. The equation of motion of the prism includes a term that simulates its coupling with a vibration-driven micropower generator. Two different couplings have been considered: a velocity-damped resonant generator and a Coulomb-damped resonant generator. Different configurations have been studied, and comparisons have been carried out between them so as to draw a first set of design guidelines. Finally, it is shown that this type of energy-harvesting microdevice, which is basically 2-D, would yield a reasonable compromise between power output, manufacturing simplicity, and cost. 相似文献
998.
Sylvain Tourancheau Kjell Brunnström Börje Andrén Patrick Le Callet 《Journal of the Society for Information Display》2009,17(3):239-249
Abstract— The primary goal of this study was to find a measurement method for motion blur which is easy to carry out and gives results that can be reproduced from one lab to another. This method should be able to also take into account methods for reduction of motion blur such as backlight flashing. Two methods have been compared. The first method uses a high‐speed camera that permits us to directly picture the blurred‐edge profile. The second one exploits the mathematical analysis of the motion‐blur formation to construct the blurred‐edge profile from the temporal step response. Measurement results and method proposals are given and discussed. 相似文献
999.
Leopoldina Fortunati Mauro Sarrica John O'Sullivan Aukse Balcytiene Halliki Harro-Loit Phil Macgregor Nayia Roussou Ramón Salaverría Federico de Luca 《Journal of Computer-Mediated Communication》2009,14(4):928-963
This study investigates how European journalists evaluate the changes that have occurred in their profession since the Internet has been integrated in newsrooms. How do journalists perceive the features and innovations associated with the Internet? What are the principal changes in the profession? Do practitioners believe that the quality of journalism has been raised or lowered? To answer to these research questions, we carried out a survey across 11 European countries–Cyprus, Estonia, Finland, Greece, Ireland, Italy, Lithuania, United Kingdom, Slovenia, Spain, Sweden–of 239 journalists, working for 40 of the most‐read print/online news outlets in these countries. The survey shows that the opportunity to use the Internet to reinforce the social functions of journalism has not been fully recognised. 相似文献
1000.
M. Lozano P. Morillo J.M. Orduña V. Cavero G. Vigueras 《Journal of Network and Computer Applications》2009,32(2):474-482
Crowd simulation requires both rendering visually plausible images and managing the behavior of autonomous agents. Therefore, these applications need an efficient design that allows them to simultaneously handle these two requirements. Although several proposals have focused on the software architectures for these systems, no proposals have focused on the computer systems supporting them.In this paper, we analyze the computer architectures used in the literature to support distributed virtual environments. Also, we propose a distributed computer architecture which is efficient enough to support simulations of thousand of autonomous agents. This proposal consists of a cluster of interconnected computers in order to improve flexibility and robustness, as well as a hierarchical software architecture that efficiently provides consistency. Performance evaluation results show that the trade-off between flexibility and consistency allows to efficiently manage thousands of autonomous agents. Therefore, this network-based system architecture can provide the required scalability for large-scale crowd simulations. 相似文献