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    Analysis of Closing-To-Opening Phase Ratio in Top-To-Bottom Glottal Pulse Segmentation for Psychological Stress Detection
    (Kaunas University of Technology, 2016-10-10) Staněk, Miroslav; Sigmund, Milan
    This paper is focused on investigating the differences in glottal pulses estimated by two algorithms; Direct Inverse Filtering (DIF) and Iterative and Adaptive Inverse Filtering (IAIF) for normal and stressed speech. Individual glottal pulses are mined from recorded speech signal and then normalized in two dimensions. Each normalized pulse is divided into a closing and opening phase and further segmented into npercentage sectors in Top-To-Bottom (TTB) amplitude domain. Three parameters, the kurtosis, skewness and pulse area, as well as their Closing-To-Opening phase ratios, are analysed. Designed GMM classifier is trained on speakers from Czech ExamStress database a further applied on other part of ExamStress database and also for English database SUSAS to investigate the independency of presented approach on spoken language and speech signal quality. The results achieved by DIF indicate independency on language and records quality (contrary to methods using IAIF). The best npercentage sectors in the TTB segments can be seen between 5 % and 40 %. In this case, methods based on DIF reached a psychological stress recognition efficiency of 88.5 % in average. The average stress detection efficiency of methods based on IAIF approached 73.3 %.
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    New class of chaotic systems with circular equilibrium
    (2015-04-10) Götthans, Tomáš; Petržela, Jiří
    This paper brings a new mathematical model of the third-order autonomous deterministic dynamical system with associated chaotic motion. Its unique property lies in the existence of circular equilibrium which was not, by referring to the best knowledge of the authors, so far reported. Both mathematical analysis and circuitry implementation of the corresponding differential equations are presented. It is shown that discovered system provides a structurally stable strange attractor which fulfills fractal dimensionality and geometrical density and is bounded into a finite state space volume.
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    Series-, Parallel-, and Inter-Connection of Solid-State Arbitrary Fractional-Order Capacitors: Theoretical Study and Experimental Verification
    (IEEE, 2018-02-27) Kartci, Aslihan; Agambayev, Agamyrat; Herencsár, Norbert; Salama, Khaled Nabil
    In the paper, general analytical formulas are introduced for the determination of equivalent impedance, magnitude, and phase, i.e. order, for n arbitrary fractional-order capacitors (FoCs) connected in series, parallel, and their interconnection. The approach presented helps to evaluate these relevant quantities in the fractional domain since the order of each element has a significant effect on the impedance of each FoC and their equivalent capacitance cannot be considered. Three types of solid-state fractional-order passive capacitors of different orders, using ferroelectric polymer and reduced Graphene Oxide-percolated P(VDF-TrFE-CFE) composite structures, are fabricated and characterized. Using an impedance analyzer, the behavior of the devices was found to be stable in the frequency range 0.2MHz–20MHz, with a phase angle deviation of ±4 degrees. Multiple numerical and experimental case studies are given, in particular for two and three connected FoCs. The fundamental issues of the measurement units of the FoCs connected in series and parallel are derived. A MATLAB open access source code is given in Appendix for easy calculation of the equivalent FoC magnitude and phase. The experimental results are in good agreement with the theoretical assumptions.
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    Fractional-Order Oscillator Design Using Unity-Gain Voltage Buffers and OTAs
    (IEEE, 2017-08-06) Kartci, Aslihan; Herencsár, Norbert; Koton, Jaroslav; Brančík, Lubomír; Vrba, Kamil; Tsirimokou, Georgia; Psychalinos, Costas
    In this study, a new voltage-mode fractional-order oscillator using two unity-gain voltage buffers, two operational transconductance amplifiers, one resistor, and two capacitors is presented. The design procedure of integer-order as well as fractional-order oscillator employing in total 20 MOS transistors is discussed. Effects of fractional-order capacitors on amplitude, phase, condition of oscillation, and frequency of oscillation are shown. Various case examples are given while SPICE simulations using TSMC 0.35 µm level-3 CMOS process parameters with ±1.65 V supply voltages verify their operation and compare with theoretical ones.