43 resultados para Posicionamento. IEEE 802.11. LVWNet. Free-space Path Loss. Wireless.Linux. Testbed. Prototipa
em Reposit
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Pós-graduação em Engenharia Elétrica - FEIS
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Internet access by wireless networks has grown considerably in recent years. However, these networks are vulnerable to security problems, especially those related to denial of service attacks. Intrusion Detection Systems(IDS)are widely used to improve network security, but comparison among the several existing approaches is not a trivial task. This paper proposes building a datasetfor evaluating IDS in wireless environments. The data were captured in a real, operating network. We conducted tests using traditional IDS and achieved great results, which showed the effectiveness of our proposed approach.
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Wireless networks are widely deployed and have many uses, for example in critical embedded systems. The applications of this kind of network meets the common needs of most embedded systems and addressing the particularities of each scenario, such as limitations of computing resources and energy supply. Problems such as denial of service attacks are common place and cause great inconvenience. Thus, this study presents simulations of denial of service attacks on 802.11 wireless networks using the network simulator OMNeT++. Furthermore, we present an approach to mitigate such attack, obtaining significant results for improving wireless networks.
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Pós-graduação em Engenharia Elétrica - FEIS
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Pós-graduação em Engenharia Elétrica - FEIS
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Faced with an imminent restructuring of the electric power system, over the past few years many countries have invested in a new paradigm known as Smart Grid. This paradigm targets optimization and automation of electric power network, using advanced information and communication technologies. Among the main communication protocols for Smart Grids we have the DNP3 protocol, which provides secure data transmission with moderate rates. The IEEE 802.15.4 is another communication protocol also widely used in Smart Grid, especially in the so-called Home Area Network (HAN). Thus, many applications of Smart Grid depends on the interaction of these two protocols. This paper proposes modeling, in the traditional network simulator NS-2, the integration of DNP3 protocol and the IEEE 802.15.4 wireless standard for low cost simulations of Smart Grid applications.
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Pós-graduação em Engenharia Elétrica - FEIS
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Pós-graduação em Engenharia Elétrica - FEIS
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Pós-graduação em Física - IFT
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An alternative formulation for guided electromagnetic fields in grounded chiral slabs is presented. This formulation is formally equivalent to the double Fourier transform method used by the authors to calculate the spectral fields in open chirostrip structures. In this paper, we have addressed the behavior of the electromagnetic fields in the vicinity of the ground plane and at the interface between the chiral substrate and the free space region. It was found that the boundary conditions for the magnetic field, valid for achiral media, are not completely satisfied when we deal with chiral material. Effects of chirality on electromagnetic field distributions and on surface wave dispersion curves were also analyzed.
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Pós-graduação em Engenharia Elétrica - FEIS
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Pós-graduação em Ciência da Computação - IBILCE
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The Internet of Things is a new paradigm where smart embedded devices and systems are connected to the Internet. In this context, Wireless Sensor Networks (WSN) are becoming an important alternative for sensing and actuating critical applications like industrial automation, remote patient monitoring and domotics. The IEEE 802.15.4 protocol has been adopted as a standard for WSN and the 6LoWPAN protocol has been proposed to overcome the challenges of integrating WSN and Internet protocols. In this paper, the mechanisms of header compression and fragmentation of IPv6 datagrams proposed in the 6LoWPAN standard were evaluated through field experiments using a gateway prototype and IEEE 802.15.4 nodes.
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We examine two-component Gross-Pitaevskii equations with nonlinear and linear couplings, assuming self-attraction in one species and self-repulsion in the other, while the nonlinear inter-species coupling is also repulsive. For initial states with the condensate placed in the self-attractive component, a sufficiently strong linear coupling switches the collapse into decay (in the free space). Setting the linear-coupling coefficient to be time-periodic (alternating between positive and negative values, with zero mean value) can make localized states quasi-stable for the parameter ranges considered herein, but they slowly decay. The 2D states can then be completely stabilized by a weak trapping potential. In the case of the high-frequency modulation of the coupling constant, averaged equations are derived, which demonstrate good agreement with numerical solutions of the full equations. (C) 2007 Elsevier B.V. All rights reserved.
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The present work had evaluated the efficiency of the pasteurization and the use of preservatives in mangos pulps (Mangifera indica L.) refrigerated. Before carrying out the treatments, the fruits had been cleaned in solution of sodium hypochlorite (NaOCl) at 100 mg. L(-1), for 10 minutes. After the processing, it was carried out through the adjustment of pH of pulps for 3.0 and the adjustment of the water activity (W(a)) at 0.95. The used variable had been the branching (hot water at 95 +/- 5 degrees C, for 0 and I minute), the addition of sodium benzoate in the concentrations of 0; 200 and 500 mL.L(-1) and, sulfite dioxide (SO(2)) in 0, 100 and 200 mL.L(-1). Then the pulps had been packed in low density polyethylene (LDPE) bags of 0,060 mm (0.10 x 0.12 m - without free space and content of 500g of pulp) and, conditioned in at 20 +/- 1 degrees C e 80 +/- 3% of R.H, for 28 days. At the end of the experiment, the treatments not submitted to the branching had shown the biggest ascorbic acid levels. However, in these same treatments had been noticed intense microbiological activity and raised levels of pH. There aren't significant differences between the tested treatments in the titratable acidity (TA) and soluble solids (SS) analyses. Due to the absence of black spot in the pulps used during all the experimental period, it couldn't be detected the differences between the application of the SO(2) and the use of the branching. The lower index of microbiological contamination and the preference of the judges in the sensorial panel had been attributed to the submitted treatments to the branching, addition of 500mL.L(-1) of sodium benzoate and addition of 200mL.L(-1) of sulfite dioxide.