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1.
Muge Sayit Sercan Demirci Yagiz Kaymak E. Turhan Tunali 《Peer-to-Peer Networking and Applications》2016,9(6):1074-1088
In this paper, we propose a new multicast tree framework to be used in peer-to-peer (P2P) live video streaming systems. The proposed system, adapts the tree links under high peer churn and runs in a totally distributed manner. In order to provide this dynamism and seamless streaming at the same time, we propose a cross layer design involving scalable video codec, backup parents and hierarchical clusters. The performance of the system is measured in real world environment PlanetLab that has nodes distributed all over the world. The experiments show that the proposed system provides high quality of experience (QoE) in terms of Peak Signal to Noise Ratio (PSNR), playback delay and duration of pauses. The proposed system also provides incentive mechanism to its users. 相似文献
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M. Fatih Demirci 《Machine Vision and Applications》2012,23(3):541-555
Graphs have become growingly important in representing shapes in computer vision. Given a query graph, it is essential to
retrieve similar database graphs efficiently from a large database. In this paper, we present a graph-based indexing technique
which overcomes significant drawbacks of the previous work (Demirci et al. in Comput Vis Image Underst 110(3):312–325, 2008)
using a recently developed theorem from the domain of matrix analysis. Our technique starts by representing the topological
structure of a graph in a vector space. As done in the previous work, the topological structure of a graph is constructed
using its Laplacian spectra. However, unlike the previous approach, which represents all sugraphs of a database graph in the
vector space to account for local similarity, a database graph in the proposed framework is represented as a single vector.
By performing a range search around the query, the proposed indexing technique returns a set with both partial and global
similarity. Empirical evaluation of the algorithm on an extensive set of retrieval trials including a comparison with the
previous approach in both 2D and 3D demonstrates the effectiveness, efficiency, and robustness of the overall approach. 相似文献
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In the present work, we studied the effect of metal chlorides, MCl2, on the thermal decomposition of ammonia borane NH3BH3 (AB). Some metals from row n = 4 of the periodic table were chosen and used as MCl2: namely, FeCl2, CoCl2, NiCl2, CuCl2, and ZnCl2. In addition, three metals from column VIII of the periodic table were considered: NiCl2, PdCl2 and PtCl2. The AB decomposition was followed by TGA and DSC; the decomposition gases analyzed by μGC/MSD coupling, and the solid by-products identified by XRD, IR and XPS. We observed that the presence of CuCl2 in AB is beneficial, making the decomposition occur in much milder conditions than for pristine AB; for example, the dehydrogenation of CuCl2-doped AB started at 25 °C, with the sample losing about 14 wt% at 85 °C. However, MCl2 does not hinder the evolution of the undesired borazine; it only contributes to a decrease in its content compared to pristine AB. To rationalize the better performance of CuCl2, we propose that Cu offers an optimal doping activity with intermediate binding energies for the intermediates: i.e. with H not too strongly bonded but optimally bonded to the N of AB. The germ Cu?NH2–BH2, then formed, acts as a Lewis acid through B and has an optimized reactivity towards a new AB molecule (head-to-tail dehydrocoupling). This is discussed herein. 相似文献
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Very fast H2 production from the methanolysis of NaBH4 by metal‐free poly(ethylene imine) microgel catalysts
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The polyethyleneimine (PEI) microgels prepared via microemulsion polymerization are protonated by hydrochloric acid treatment (p‐PEI) and quaternized (q‐PEI) via modification reaction with methyl iodide and with bromo alkanes of different alkyl chain lengths such as 1‐bromoethane, 1‐bromobutane, 1‐bromohexane, and 1‐bromooctane. The bare p‐PEI and q‐PEI microgels are used as catalysts directly without any metal nanoparticles for the methanolysis reaction of sodium borohydride (NaBH4). Various parameters such as the protonation/quaternization reaction on PEI microgels, the amount of catalyst, the amount of NaBH4, and temperature are investigated for their effects on the hydrogen (H2) production rate. The reaction of self‐methanolysis of NaBH4 finishes in about 32.5 min, whereas the bare PEI microgel as catalyst finishes the methanolysis of NaBH4 in 22 min. Surprisingly, it is found that when the protonated PEI microgels are used as catalyst, the same methanolysis of NaBH4 is finished in 1.5 min. The highest H2 generation rate value is observed for protonated PEI microgels (10 mg) with 8013 mL of H2/(g of catalyst.min) for the methanolysis of NaBH4. Moreover, activation parameters are also calculated with activation energy value of 23.7 kJ/mol, enthalpy 20.9 kJ/mol, and entropy ?158 J/K.mol. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
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Süleyman Karda Serkan elik Muhammed Ali Bingl Mehmet Sabir Kiraz Hüseyin Demirci Albert Levi 《Wireless Communications and Mobile Computing》2015,15(18):2150-2166
This paper examines Vaudenay's privacy model, which is one of the first and most complete privacy models that featured the notion of different privacy classes. We enhance this model by introducing two new generic adversary classes, k‐strong and k‐forward adversaries where the adversary is allowed to corrupt a tag at most k times. Moreover, we introduce an extended privacy definition that also covers all privacy classes of Vaudenay's model. In order to achieve highest privacy level, we study low cost primitives such as physically unclonable functions (PUFs). The common assumption of PUFs is that their physical structure is destroyed once tampered. This is an ideal assumption because the tamper resistance depends on the ability of the attacker and the quality of the PUF circuits. In this paper, we have weakened this assumption by introducing a new definition k‐resistant PUFs. k‐PUFs are tamper resistant against at most k attacks; that is, their physical structure remains still functional and correct until at most kth physical attack. Furthermore, we prove that strong privacy can be achieved without public‐key cryptography using k PUF‐based authentication. We finally prove that our extended proposal achieves both reader authentication and k‐strong privacy. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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