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    Wyświetlanie 1-8 z 8
    Tytuł:
    Chaotic-based Orthogonal Frequency Division Multiplexing with Index Modulation
    Autorzy:
    Hussien, Sura H.
    Abdullah, Hamsa A.
    Powiązania:
    https://bibliotekanauki.pl/articles/2174449.pdf
    Data publikacji:
    2022
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    AWGN
    chaos communications
    DCSK
    index modulation
    Opis:
    Orthogonal frequency division multiplexing with index modulation (OFDM-IM), stands out among conventional communication technologies, as it uses the indices of the available transmit entities. Thanks to such an approach, it offers a novel method for the transmission of extra data bits. Recent years have seen a great interest in chaos-based communications. The spectrum-spreading signals used in chaotic signal modulation technologies are orthogonal to the existing mixed signals. This paper presents how well a non-coherent differential chaos shift keying communication system performs across an AWGN. Different types of detection methods are simulated, bit error rate and power spectral density are calculated and then compared with standard OFDM with index modulation. The results of simulations concerning the performance of a DCSK system, adding to the security of the proposed solution and offering a comparable bit error rate performance, are presented in the paper as well.
    Źródło:
    Journal of Telecommunications and Information Technology; 2022, 4; 33--38
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Localization of Copy-Move Forgery in Speech Signals Through Watermarking Using DCT-QIM
    Autorzy:
    Lalitha, N.V.
    Rao, Ch. Srinivasa
    Jaya-Sree, P.V.Y.
    Powiązania:
    https://bibliotekanauki.pl/articles/227242.pdf
    Data publikacji:
    2019
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    watermarking
    copy-move forgery
    discrete Cosine
    transform
    quantization index modulation
    hash bits
    Opis:
    Digital speech copyright protection and forgery identification are the prevalent issues in our advancing digital world. In speech forgery, voiced part of the speech signal is copied and pasted to a specific location which alters the meaning of the speech signal. Watermarking can be used to safe guard the copyrights of the owner. To detect copy-move forgeries a transform domain watermarking method is proposed. In the proposed method, watermarking is achieved through Discrete Cosine Transform (DCT) and Quantization Index Modulation (QIM) rule. Hash bits are also inserted in watermarked voice segments to detect Copy-Move Forgery (CMF) in speech signals. Proposed method is evaluated on two databases and achieved good imperceptibility. It exhibits robustness in detecting the watermark and forgeries against signal processing attacks such as resample, low-pass filtering, jittering, compression and cropping. The proposed work contributes for forensics analysis in speech signals. This proposed work also compared with the some of the state-of-art methods.
    Źródło:
    International Journal of Electronics and Telecommunications; 2019, 65, 3; 527-532
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Estimation of acoustically induced refractive index perturbation in silicon and germanium slab for optical applications
    Autorzy:
    Sharma, G.
    Kumar, S.
    Kumar, D.
    Singh, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/173371.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    dispersion relation
    Lamb wave mode in silicon and germanium
    displacement field
    refractive index modulation
    Opis:
    In-plane displacement field and refractive index variation for silicon and germanium in the presence of Lamb wave is estimated for optical applications. The required dispersion equation in a thin silicon and germanium plates is obtained using the method of potentials with boundary conditions involving the bulk and surface stress of the materials considered. The eigen-values thus obtained are used to compute the Lamb wave modes for the slab of silicon and germanium at same thickness. The fundamental anti-symmetric and symmetric plate modes and their overtones are observed due to confinement of acoustic energy within the slab thickness. In addition, the excited symmetric modes in silicon have longer wavelengths than those of germanium at a fixed frequency. Therefore, the refractive index modulation through the Lamb wave in silicon is always larger as compared to that of germanium. This refractive index modulation can be treated as periodic sinusoidal refractive index variation and may be considered as a tunable one-dimensional photonics crystal.
    Źródło:
    Optica Applicata; 2015, 45, 4; 491-500
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modeling and simulation of novel stepped DC coupled quasi Z-Multilevel Inverter for single phase systems
    Autorzy:
    Meenakshi, T.
    Suthanthira Vanitha, N.
    Powiązania:
    https://bibliotekanauki.pl/articles/140968.pdf
    Data publikacji:
    2016
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    multilevel inverter
    shoot through
    quasi Z-Source
    modulation index
    Opis:
    This paper presents the modeling and simulation of a novel topology of quasi Z-Multilevel Inverter with stepped DC input. The proposed inverter incorporates a simple switching technique with reduced component count and is aimed at producing boosted multilevel output AC voltage. The inverter consists of two stages and the buck /boost operation is obtained by varying the shoot through period of the pulses obtained by maximum constant boost control with third harmonic injection. With all the advantages of the quasi Z-network, the proposed inverter eliminates the fly back diodes and capacitors present in a conventional Z-Multilevel Inverter. Further the stress on the devices is less which leads to reduction in component value and hence the cost. The novel stepped DC coupled Single Phase quasi Z-Multilevel Inverter is modeled and simulated in the MATLAB – SIMULINK environment and its performance is analyzed for varying input and switching conditions. The voltage and current waveforms across each stage of the inverter is analyzed and the results are presented for different levels of input.
    Źródło:
    Archives of Electrical Engineering; 2016, 65, 3; 437-448
    1427-4221
    2300-2506
    Pojawia się w:
    Archives of Electrical Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effect of viscosity on the far-field diffraction pattern of spatial self-phase modulation
    Autorzy:
    Nibu, A. G.
    Silpa, S. S.
    Ardra, S. N.
    Anisha, M. M.
    Ambika, D.
    Powiązania:
    https://bibliotekanauki.pl/articles/174699.pdf
    Data publikacji:
    2017
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    self-phase modulation
    nonlinear refractive index
    chlorophyll
    engine oil
    Opis:
    Effect of viscosity of a liquid on the far-field diffraction pattern due to spatial self-phase modulation is investigated. Chlorophyll extract in acetone at different concentrations is used as the low viscous nonlinear samples and commercial engine oils, synthetic and natural. It is also used as high viscous media. In the case of chlorophyll solution, the self-induced diffraction ring pattern in the far-field is a series of circular rings at the beginning; but later it is transformed to half circular symmetry. But for the high viscous engine oils we have observed circular fringes and there is no time dependent structural variation in the pattern. The coefficient of the intensity dependent nonlinear refractive index for all the liquid samples is evaluated.
    Źródło:
    Optica Applicata; 2017, 47, 4; 591-599
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Absorption coefficient along a propagated ultra-short laser pulse in the air based on Kramers–Kronig relations
    Autorzy:
    Malekshahi, M
    Naghavi, K
    Powiązania:
    https://bibliotekanauki.pl/articles/173894.pdf
    Data publikacji:
    2015
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    ultra-short laser pulse
    refractive index
    self-phase modulation
    absorption coefficient
    Kramers–Kronig relations
    Opis:
    In this manuscript, some effects such as nonlinear Kerr, stimulated Raman, and plasma generation effects lead to obtaining the nonlinear refraction index of the air along an intense ultra-short laser pulse based on one-dimensional propagation analysis. The variations in the pulse frequency by the self-phase modulation effect are investigated for achieving the functionality of the refractive index to the frequency. The mentioned functionality allows implementing Kramers–Kronig relations to measure the absorption coefficient. Results indicate that the front of the laser pulse faces a high rate of the energy loss whereas the back of the pulse experiences a gain. The implementation of Kramers–Kronig relations for a theoretical calculation of absorption coefficient variation along a laser pulse propagating in the air in which we have simultaneously taken into account the three above-mentioned effects distinguishes our work from other studies.
    Źródło:
    Optica Applicata; 2015, 45, 4; 501-512
    0078-5466
    1899-7015
    Pojawia się w:
    Optica Applicata
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Diagnostyka sinusoidalnych wahań napięcia w sieci elektroenergetycznej z wykorzystaniem wskaźnika ΔV10
    Diagnostics of sinusoidal voltage fluctuations in a power grid using the ΔV10 index
    Autorzy:
    Wiczyński, G.
    Powiązania:
    https://bibliotekanauki.pl/articles/152302.pdf
    Data publikacji:
    2013
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    jakość energii elektrycznej
    modulacja amplitudy
    modelowanie
    wskaźnik ΔV10
    amplitude modulation
    modelling
    power quality
    ΔV10 index
    Opis:
    W artykule omówiono definicję wskaźnika ΔV10. Zaproponowano schemat blokowy miernika ΔV10 i wyznaczono jego równanie przetwarzania dla sinusoidalnej zmienności napięcia. Porównano wartości wskaźników ΔV10 i Pst. Prezentując wyniki porównań obu miar przybliżono możliwości diagnostyczne wskaźnika ΔV10. Odwołując się do zamieszczonych zależności ΔV10, Pst i ƒm wykazano, że dla zmienności napięć występujących w sieciach elektroenergetycznych niemożliwe jest przeliczanie jednej miary do drugiej.
    The ΔV10 index is a measure of voltage fluctuations in power grids proposed by the Japanese CRIEPI Institute [1] and used all over the Far East countries. European standards prefer Pst and Plt indicators in voltage fluctuation measurements [11]. The ΔV10 and Pst/Plt are different in terms of the characteristics of measurement signal chains [6]. Therefore the measures may be characterized by different diagnostic capabilities. This may lead to the situation where some receivers may be described as faultless while voltage fluctuations are acceptable for one measure and may be described as faulty with the voltage fluctuations being unacceptable for the other measure. On the other hand, some level of uncertainty may appear as the influence of a receiver may be classified as obnoxious with the use of one measure and not-obnoxious with the use of the other. The paper includes analytical determination of the ΔV10 index value dependency on the voltage fluctuation reproduced with a sinusoidal amplitude modulation (Eq. (2)). The calculations have been made for the assumed signal chain model of a ΔV10 index measuring instrument (Fig. 3). The values of ΔV10 and Pst indexes at a given sinusoidal voltage fluctuation have been compared (Figs. 4-6). On the basis of the obtained ΔV10 and Pst dependencies on ƒm it has been assumed that for the voltage fluctuations present in power grids of unknown type and frequency it is impossible to convert one measure into the other.
    Źródło:
    Pomiary Automatyka Kontrola; 2013, R. 59, nr 5, 5; 425-428
    0032-4140
    Pojawia się w:
    Pomiary Automatyka Kontrola
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analiza porównawcza własności akustycznych sali konferencyjnej na podstawie pomiarów rzeczywistych i symulacji komputerowej w programie EASE 3.0. cześć pierwsza . "Pomiary"
    Autorzy:
    Kowal, R.
    Powiązania:
    https://bibliotekanauki.pl/articles/373292.pdf
    Data publikacji:
    2006
    Wydawca:
    Centrum Naukowo-Badawcze Ochrony Przeciwpożarowej im. Józefa Tuliszkowskiego
    Tematy:
    akustyka
    funkcja przeniesienia modulacji
    pomiar
    pomieszczenie audytoryjne
    sala konferencyjna
    współczynnik zrozumiałości mowy
    acoustics
    auditorium space
    boardroom
    measurement
    modulation transfer function
    speech transmission index
    Opis:
    W pierwszej części artykułu omówiono na przykładzie "Sali Konferencyjnej" podstawy postępowania przy wykonywaniu pomiarów akustycznych wnętrz, celem porównania rzeczywistych wyników badań z symulacją komputerową.
    In order to compare the gathered results with computational simulation, it has been discussed in this article the fundamentals of acoustic measurements procedure within building premises basing on the Conference Hall as an example.
    Źródło:
    Bezpieczeństwo i Technika Pożarnicza; 2006, 1; 55-60
    1895-8443
    Pojawia się w:
    Bezpieczeństwo i Technika Pożarnicza
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-8 z 8

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