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    Location Accuracy of Commercial IP Address Geolocation Databases
    (Kaunas University of Technology, 2017-10-04) Komosný, Dan; Vozňák, Miroslav; Rehman, Saeed
    This paper deals with finding the geographical location of Internet nodes remotely with no need to communicate with the nodes located (client-independently). IP geolocation is used in a number of areas, such as content personalisation, on-line fraud prevention and detection, and digital media law enforcement. One of the main concerns when studying the accuracy of client-independent geolocation is the groundtruth dataset. As we show in the related work, the used groundtruth influences the results a lot. We construct an error-free groundtruth dataset consisting of nodes with GPS-precise locations. We also record the country, region, city, and ISP for each groundtruth node. Using the created groundtruth, we study the accuracy of eight IP location databases in a number of scenarios, such as effect of city area and population, effect of ISP assignment, and number of not-returned locations.
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    Universal Pseudo-Differential Filter Using DDCC and DVCCs
    (Kaunas University of Technology, 2017-12-18) Sládok, Ondřej; Koton, Jaroslav; Herencsár, Norbert
    In the paper, a universal preudo-differential second-order filter operating in voltage mode, where both input and output are differential, is presented. The circuit is formed by one differential difference current conveyor (DDCC), two differential voltage current conveyors (DVCCs), and five passive elements. The filter is characterized by high input impedance, minimum number of passive elements that are all grounded, and high common-mode rejection ratio (CMRR). The proposed filter structure is able to realize all five standard frequency filter responses. Non-ideal analysis has been performed by considering the real parasitic parameters of the active elements. The optimization of passive element values has been done in terms of minimal shift of the pole-frequency and to obtain the maximum stop-band attenuation of the high-pass filter response. Functionality is verified by simulations and experimental measurements using readily available integrated circuit UCC-N1B 0520.
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    Differential Second-Order Voltage-Mode All-Pass Filter Using Current Conveyors
    (Kaunas University of Technology, 2016-10-10) Koton, Jaroslav; Herencsár, Norbert; Horng, Jiun-Wei
    In this paper, a new circuit solution of analogue pseudo-differential second-order all-pass filter operating in the voltage mode is presented. Pseudo-differential, since both input and output terminals are differential, however, the circuit topology features single-ended structure. As active elements the differential difference current conveyors and second-generation current conveyors are advantageously used. The proposed filter features quality factor control without disturbing the polefrequency using single passive element. The designed circuit is less complex compared to fully-differential solutions by maintaining sufficient common-mode rejection ratio. The behaviour of the filter is described by means of symbolic analysis and also by simulations using the UCC-N1B integrated circuit. Furthermore, the performance of the proposed pseudo- differential filter has been validated by experimental measurements.
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    Gabor frames and deep scattering networks in audio processing
    (MDPI, 2019-09-26) Bammer, Roswitha; Dörfler, Monika; Harár, Pavol
    This paper introduces Gabor scattering, a feature extractor based on Gabor frames and Mallat's scattering transform. By using a simple signal model for audio signals specific properties of Gabor scattering are studied. It is shown that for each layer, specific invariances to certain signal characteristics occur. Furthermore, deformation stability of the coefficient vector generated by the feature extractor is derived by using a decoupling technique which exploits the contractivity of general scattering networks. Deformations are introduced as changes in spectral shape and frequency modulation. The theoretical results are illustrated by numerical examples and experiments. Numerical evidence is given by evaluation on a synthetic and a "real" data set, that the invariances encoded by the Gabor scattering transform lead to higher performance in comparison with just using Gabor transform, especially when few training samples are available.
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    Privacy-preserving security solution for cloud services
    (Universidad Nacional Autónoma de México, 2015-03-18) Malina, Lukáš; Hajný, Jan; Dzurenda, Petr; Zeman, Václav
    We propose a novel privacy-preserving security solution for cloud services. Our solution is based on an efficient non-bilinear group signature scheme providing the anonymous access to cloud services and shared storage servers. The novel solution offers anonymous authenticationfor registered users. Thus, users' personal attributes (age, valid registration, successful payment) can be proven without revealing users' identity, and users can use cloud services without any threat of profiling their behavior. However, if a user breaks provider's rules, his access right is revoked.