479 research outputs found

    The Absolute Parameters of The Detached Eclipsing Binary V482 Per

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    We present the results of the spectroscopic, photometric and orbital period variation analyses of the detached eclipsing binary \astrobj{V482~Per}. We derived the absolute parameters of the system (M1_{1} = 1.51 M_{\odot}, M2_{2} = 1.29 M_{\odot}, R1_{1} = 2.39 R_{\odot}, R2_{2} = 1.45 R_{\odot}, L1_{1} = 10.15 L_{\odot}, L2_{2} = 3.01 L_{\odot}) for the first time in literature, based on an analysis of our own photometric and spectroscopic observations. We confirm the nature of the variations observed in the system's orbital period, suggested to be periodic by earlier works. A light time effect due to a physically bound, star-sized companion (M3_{3} = 2.14 M_{\odot}) on a highly eccentric (e = 0.83) orbit, seems to be the most likely cause. We argue that the companion can not be a single star but another binary instead. We calculated the evolutionary states of the system's components, and we found that the primary is slightly evolving after the Main Sequence, while the less massive secondary lies well inside it.Comment: Published in New Astronomy, Vol. 41, p. 42-4

    On Security and reliability using cooperative transmissions in sensor networks

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    Cooperative transmissions have received recent attention and research papers have demonstrated their benefits for wireless networks. Such benefits include improving the reliability of links through diversity and/or increasing the reach of a link compared to a single transmitter transmitting to a single receiver (single-input single-output or SISO). In one form of cooperative transmissions, multiple nodes can act as virtual antenna elements and provide diversity gain or range improvement using space-time coding. In a multi-hop ad hoc or sensor network, a source node can make use of its neighbors as relays with itself to reach an intermediate node with greater reliability or at a larger distance than otherwise possible. The intermediate node will use its neighbors in a similar manner and this process continues till the destination is reached. Thus, for the same reliability of a link as SISO, the number of hops between a source and destination may be reduced using cooperative transmissions as each hop spans a larger distance. However, the presence of ma-licious or compromised nodes in the network impacts the benefits obtained with cooperative transmissions. Using more relays can increase the reach of a link, but if one or more relays are malicious, the transmission may fail. However, the relationships between the number of relays, the number of hops, and success probabilities are not trivial to determine. In this paper, we analyze this problem to understand the conditions under which cooperative transmissions fare better or worse than SISO transmissions. We take into consideration additional parameters such as the path-loss exponent and provide a framework that allows us to evaluate the conditions when cooperative transmissions are better than SISO transmissions. This analysis provides insights that can be employed before resorting to simulations or experimentation. © Springer Science+Business Media, LLC 2012

    Preparation of Ion Imprinted SPR Sensor for Real-Time Detection of Silver(I) Ion from Aqueous Solution

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    The aim of the submitted study is to develop molecular imprinting based surface plasmon resonance (SPR) sensor for real-time silver ion detection. For this purpose polymeric nanofilm layer on the gold SPR chip surface was prepared via UV polymerization of acrylic acid at 395 nm for 30 minutes. N-methacryloyl- L cysteine used as the functional monomer to recognize the silver(I) ions from the aqueous solutions and methylene bisacrylamide used as the crosslinker for obtaining structural rigidity of the formed cavities. Silver(I) solutions with different concentrations were applied to SPR system to investigate the efficiency of the imprinted SPR sensor in real time. For the control experiments, non-imprinted SPR sensor was also prepared as described above without addition of template “silver(I) ions”. Prepared SPR sensors were characterized with atomic force microscopy (AFM). In order to show the selectivity of the silver(I) imprinted SPR sensor, competitive adsorption of Cu(II), Pb(II), Ni(II) ions was investigated. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3489

    Screening Λ\Lambda in a new modified gravity model

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    We study a new model of Energy-Momentum Squared Gravity (EMSG), called Energy-Momentum Log Gravity (EMLG), constructed by the addition of the term f(TμνTμν)=αln(λTμνTμν)f(T_{\mu\nu}T^{\mu\nu})=\alpha \ln(\lambda\,T_{\mu\nu}T^{\mu\nu}), envisaged as a correction, to the Einstein-Hilbert action with cosmological constant Λ\Lambda. The choice of this modification is made as a specific way of including new terms in the right-hand side of the Einstein field equations, resulting in constant effective inertial mass density and, importantly, leading to an explicit exact solution of the matter energy density in terms of redshift. We look for viable cosmologies, in particular, an extension of the standard Λ\LambdaCDM model. EMLG provides an effective dynamical dark energy passing below zero at large redshifts, accommodating a mechanism for screening Λ\Lambda in this region, in line with suggestions for alleviating some of the tensions that arise between observational data sets within the standard Λ\LambdaCDM model. We present a detailed theoretical investigation of the model and then constrain the free parameter α\alpha', a normalisation of α\alpha, using the latest observational data. The data does not rule out the Λ\LambdaCDM limit of our model (α=0\alpha'= 0), but prefers slightly negative values of the EMLG model parameter (α=0.032±0.043\alpha'= -0.032\pm 0.043), which leads to the screening of Λ\Lambda. We also discuss how EMLG relaxes the persistent tension that appears in the measurements of H0H_0 within the standard Λ\LambdaCDM model.Comment: 17 pages, 11 figures, 1 table; matches the version published in EPJ

    Is Split Manufacturing Secure?

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    Abstract-Split manufacturing of integrated circuits (IC) is being investigated as a way to simultaneously alleviate the cost of owning a trusted foundry and eliminate the security risks associated with outsourcing IC fabrication. In split manufacturing, a design house (with a low-end, in-house, trusted foundry) fabricates the Front End Of Line (FEOL) layers (transistors and lower metal layers) in advanced technology nodes at an untrusted high-end foundry. The Back End Of Line (BEOL) layers (higher metal layers) are then fabricated at the design house's trusted low-end foundry. Split manufacturing is considered secure (prevents reverse engineering and IC piracy) as it hides the BEOL connections from an attacker in the FEOL foundry. We show that an attacker in the FEOL foundry can exploit the heuristics used in typical floorplanning, placement, and routing tools to bypass the security afforded by straightforward split manufacturing. We developed an attack where an attacker in the FEOL foundry can connect 96% of the missing BEOL connections correctly. To overcome this security vulnerability in split manufacturing, we developed a fault analysis-based defense. This defense improves the security of split manufacturing by deceiving the FEOL attacker into making wrong connections

    Network 'small-world-ness': a quantitative method for determining canonical network equivalence

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    Background: Many technological, biological, social, and information networks fall into the broad class of 'small-world' networks: they have tightly interconnected clusters of nodes, and a shortest mean path length that is similar to a matched random graph (same number of nodes and edges). This semi-quantitative definition leads to a categorical distinction ('small/not-small') rather than a quantitative, continuous grading of networks, and can lead to uncertainty about a network's small-world status. Moreover, systems described by small-world networks are often studied using an equivalent canonical network model-the Watts-Strogatz (WS) model. However, the process of establishing an equivalent WS model is imprecise and there is a pressing need to discover ways in which this equivalence may be quantified. Methodology/Principal Findings: We defined a precise measure of 'small-world-ness' S based on the trade off between high local clustering and short path length. A network is now deemed a 'small-world' if S. 1-an assertion which may be tested statistically. We then examined the behavior of S on a large data-set of real-world systems. We found that all these systems were linked by a linear relationship between their S values and the network size n. Moreover, we show a method for assigning a unique Watts-Strogatz (WS) model to any real-world network, and show analytically that the WS models associated with our sample of networks also show linearity between S and n. Linearity between S and n is not, however, inevitable, and neither is S maximal for an arbitrary network of given size. Linearity may, however, be explained by a common limiting growth process. Conclusions/Significance: We have shown how the notion of a small-world network may be quantified. Several key properties of the metric are described and the use of WS canonical models is placed on a more secure footing
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