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Ivanov I.,Ecole Polytechnique Federale de Lausanne | Vajda P.,VU University Amsterdam | Vajda P.,Etvs Lornd University | Lee J.-S.,KAIST
IEEE Signal Processing Magazine | Year: 2012

Tagging in online social networks is very popular these days, as it facilitates search and retrieval of multimedia content. However, noisy and spam annotations often make it difficult to perform an efficient search. Users may make mistakes in tagging and irrelevant tags and content may be maliciously added for advertisement or self-promotion. This article surveys recent advances in techniques for combatting such noise and spam in social tagging. We classify the state-of-the-art approaches into a few categories and study representative examples in each. We also qualitatively compare and contrast them and outline open issues for future research. © 2012 IEEE.

Tatrai A.,Etvs Lornd University
Journal of Parallel and Distributed Computing | Year: 2011

In this paper the author make a comprehensive comparison of different parallelizations of a sequential number theoretic algorithm having large memory requirements. Brunotte's algorithm is one of the currently known best methods for the decision of the canonical number system (or more generally shift radix system) property. Still, it can be very space-consuming in some cases. Pushing the algorithm to its limits may hopefully shed light on mathematical patterns that would otherwise not be discernible. The algorithm contains many n-dimensional vector operations and set operations like insert, find, clear, etc. The parallel algorithms encounter two difference kinds of concurrency problems. First, they need computationally intensive arithmetic vector operations, second, the set implementations require a huge amount of memory and general purpose processors. The algorithms described in this article are basically designed for two platforms. The first platform is a generic symmetric multiprocessing (SMP) architecture without any vector processor extension, the second is the Cell Broadband Engine. The SMP platforms have several general purpose processors in contrast with the Cell Broadband Engine where the processors have Synergistic vector processors. © 2010 Elsevier Inc. All rights reserved.

Ladanyi A.,University of Bedfordshire | Lopez-Perez D.,Kings College London | Juttner A.,Etvs Lornd University | Chu X.,Kings College London | Zhang J.,University of Bedfordshire
2011 IEEE GLOBECOM Workshops, GC Wkshps 2011 | Year: 2011

This paper proposes a decentralized model for the allocation of modulation and coding schemes, subchannels and transmit power to users in OFDMA femtocell deployments. The proposed model does not rely on any exchanged information between cells, which is especially useful for femtocell networks. Coordination between femtocells is achieved through the intrinsic properties of minimising transmit power independently at each cell, which leads the network to self-organize into an efficient frequency reuse pattern. This paper also provides a two-level decomposition approach for solving this intricate resource assignment problem that is able to find optimal solutions at cell level in reduced periods of time. System-level simulations show a significant performance improvement in terms of user outages and network capacity when using the proposed distributed resource allocation in comparison with scheduling techniques based on uniform power distributions among subcarriers. © 2011 IEEE.

Kereszturi A.,Institute for Advanced Study | Kereszturi A.,C Laborc Street | Kereszturi A.,Etvs Lornd University
Planetary and Space Science | Year: 2010

Six tributaries of Shalbatana outflow channel were analyzed based on visible imagery by THEMIS, MOC, HRSC, and HiRISE, as well as on topographic data by MOLA. Two different sections could be identified on the tributaries: the upper and the lower reaches. The upper reaches are shallow, showing U-shaped cross-sectional profiles. Their bottom level is filled with sediments, forming a plain. They have nearly horizontal longitudinal profiles, suggesting either the formation under long term fluvial erosion, or their bottom level represents a strong subsurface layer, until which the valley could cut itself downward into the rocks. Lower reaches show wider and deeper cross-sectional V-shaped profiles, with a narrow, infilled central bottom level. They show steep and at some occasion convex longitudinal profiles, indicating other erosional processes than the upper reaches, and/or that the erosion did not have time to form an equilibrium-like profile. They were formed after the Shalbatana outflow channel, probably by a process different from the formation of the upper reaches that may not involve fluvial erosion, or under different environmental conditions. Two possible scenarios are proposed to explain the formation of these two classes of reaches: (1) They may have formed under different climatic conditions on Mars, and show examples for surface forming forces that changed during the planetary evolution. Such different valley sections may point to differences both in lithology and differences in the Martian surface conditions if they formed at different periods. (2) The other possibility is that they formed roughly during the same period, and the two different sections represent differences only in lithology and erodibility. The incut of the upper reach happened in a harder rock unit, forming a nearly horizontal longitudinal profile, and was not deep enough to reach the deeper, more erodible rock level. At the lower reach a different type of erosion took place because of different lithology, and formed the deeper, steeper lower reaches there. © 2010 Elsevier Ltd. All rights reserved.

Karsai I.,East Tennessee State University | Kampis G.,Etvs Lornd University
BioScience | Year: 2010

Biology is changing and becoming more quantitative. Research is creating new challenges that need to be addressed in education as well. New educational initiatives focus on combining laboratory procedures with mathematical skills, yet it seems that most curricula center on a single relationship between scientific knowledge and scientific method: that of the validity of knowledge claims, judged in terms of their consistency with data. Collecting data and obtaining results (however quantitative) are commonly part of science, but are not science itself. We envision that the operative use of the complete scientific method will play a critical role in providing the necessary underpinning for the integration of math and biology at various professional levels. © 2010 by American Institute of Biological Sciences. All rights reserved.

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