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    Wyświetlanie 1-9 z 9
    Tytuł:
    The possible mechanism for a frequency shift by a time-varying of medium features
    Autorzy:
    Nerukh, A.G.
    Scherbatko, I.V.
    Marciniak, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/308740.pdf
    Data publikacji:
    2000
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    frequency shift
    moving plasma boundary
    Opis:
    The optical frequency shift of an electromagnetic wave reflecting from a boundary of a medium is studies for two cases: for temporal variations of medium permittivity, and for a moving plasma boundary. It has been shown that a simultaneous occurence of both cases leads to an enhanced frequency shift.
    Źródło:
    Journal of Telecommunications and Information Technology; 2000, 1-2; 46-51
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Numerical simulations of sound wave generation in a random medium
    Autorzy:
    Murawski, K.
    Selwa, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1955700.pdf
    Data publikacji:
    2004
    Wydawca:
    Politechnika Gdańska
    Tematy:
    sound waves
    random waves
    frequency shift
    amplitude alteration
    Opis:
    In turbulent media, both sound wave sources and the speed of sound can be stochastic variables. By means of numerical simulations of one-dimensional Euler equations with random source terms we have studied two cases in a homogeneous stochastic random medium for which the speed of sound and sound sources are: (1) correlated and (2) uncorrelated. The numerical simulations indicate that, if the source and the speed of sound fluctuations are uncorrelated, the acoustic field is incoherent, with a zero expectation value. The mean field is non-zero in the correlated case. The correlated and uncorrelated cases are clearly distinguishable by the mean field, but also - to some extent - in the power spectrum, which displays a modified Lorentzian profile with a shift in frequency.
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2004, 8, 1; 109-114
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Sound waves in a wave noise
    Autorzy:
    Murawski, K.
    Tarnowski, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1955702.pdf
    Data publikacji:
    2004
    Wydawca:
    Politechnika Gdańska
    Tematy:
    sound waves
    random waves
    frequency shift
    amplitude alteration
    Opis:
    We examine by analytical and numerical means sound waves which propagate in a space- and time-dependent random mass density field in the form of dispersionless wave noise of its spectrum E(kappa,omega) ~ E(kappa) delta (omega-crk), where cr is a random speed. Numerical simulations are in agreement with the analytical theory which shows that at cr=omega/k resonance occurs and the cyclic frequency omega tends to infinity. For values of cr which are close to the resonance point, the sound waves are slowed down and attenuated (accelerated and amplified) for cr < omega/k (cr > omega/k).
    Źródło:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk; 2004, 8, 1; 103-108
    1428-6394
    Pojawia się w:
    TASK Quarterly. Scientific Bulletin of Academic Computer Centre in Gdansk
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Determination of hazardous metal ions in the water with resonant MEMS biosensor frequency shift – concept and preliminary theoretical analysis
    Autorzy:
    Rahimi, Z.
    Yazdani, J.
    Hatami, H.
    Sumelka, W.
    Baleanu, D.
    Najafi, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/202229.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    micro-mechanical sensor
    hazardous metals
    resonant frequency shift
    micro mass-sensor
    drinking water
    Opis:
    Heavy metal ions (e.g. cadmium, chromium, copper, nickel, arsenic, lead, zinc) have significantly serious side effects on the human health. They can bind with proteins and enzymes, altering their activity, increasing neurotoxicity, generating reactive oxygen species (ROS), promote cellular stress and resulting in their damage. Furthermore, the size, shape and type of metal are important for considering nano- or microtoxicity. It then becomes clear that the levels of these metals in drinking water are an important issue. Herein, a new micro-mechanical sensor is proposed to detect and measure these hazardous metals. The sensor consists of a micro-beam inside a micro-container. The surface of the beam is coated with a specific protein that may bind heavy metals. The mass adsorbed is measured using the resonant frequency shift of the micro-beam. This frequency shift due to the admissible mass (which is considered acceptable for drinking water based on the World Health Organization (WHO) standard) of manganese (Mn), lead (Pb), copper (Cu) and cadmium (Cd) is investigated for the first, second and third mode, respectively. Additionally, the effects of micro-beam off-center positions inside the micro-container and the mass location and investigated.
    Źródło:
    Bulletin of the Polish Academy of Sciences. Technical Sciences; 2020, 68, 3; 529-537
    0239-7528
    Pojawia się w:
    Bulletin of the Polish Academy of Sciences. Technical Sciences
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Bidirectional DC–AC Converter-Based Communication Solution for Microgrid
    Autorzy:
    Zhang, Yixuan
    Ni, Kai
    Wang, Yangang
    Hu, Yihua
    Powiązania:
    https://bibliotekanauki.pl/articles/1193849.pdf
    Data publikacji:
    2020
    Wydawca:
    Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
    Tematy:
    bidirectional DC-AC converter
    frequency shift keying
    MATLAB simulation
    microgrid
    two-way communication
    Opis:
    The communication system of a microgrid can transfer the information of electricity price, power consumption and so on between users and the control centre. This capability is of great significance to improve the efficiency and sustainability of power facilities. In this paper, a bidirectional DC–AC converter topology is proposed to achieve the composite transmission of power and signals in microgrids. Since the transmitted signals are modulated by power switches of converters and integrated into the currents, the cost of signal couplers can be saved and the circuit structure can be simplified. In order to verify the feasibility of the proposed method, a simulation model of the proposed converter is implemented in MATLAB/Simulink. With the power supply frequency of 50 Hz, when the converter operates in the inverter mode and rectifier mode, the data transmission rate can reach 120 bit/s and 48 bit/s, respectively.
    Źródło:
    Power Electronics and Drives; 2020, 5, 40; 177-188
    2451-0262
    2543-4292
    Pojawia się w:
    Power Electronics and Drives
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Zastosowanie statystyk wyższego rzędu do pomiaru przesuwu częstotliwości sygnału FSK
    Frequency shift measurement in the FSK signal using higher-order statistic
    Autorzy:
    Kwiatosz, J.
    Jakubaszek, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/210577.pdf
    Data publikacji:
    2006
    Wydawca:
    Wojskowa Akademia Techniczna im. Jarosława Dąbrowskiego
    Tematy:
    teoria sygnałów
    analiza sygnałów
    sygnały
    pomiar przesuwu częstotliwości
    signal theory
    signals - analysis
    signals - frequency shift measurement
    Opis:
    Do przesyłania danych binarnych w systemach telekomunikacyjnych wykorzystywany jest sygnał z dwuwartościową manipulacją częstotliwości (FSK), którego podstawowym parametrem jest przesuw częstotliwości. W systemach rozpoznania radioelektronicznego często zachodzi potrzeba dokładnego pomiaru przesuwu częstotliwości w celu identyfikacji egzemplarza radiostacji. Stosowanie standardowych metod pomiaru tego parametru, opartych na analizie korelacyjnej lub widmowej nie daje zadowalających rezultatów, zwłaszcza przy małym stosunku sygnału i szumu. W referacie przedstawiono matematyczne podstawy oraz opis algorytmu i wyniki pomiaru przesuwu częstotliwości w oparciu o analizę wyższego rzędu, a ściślej kumulanty drugiego i czwartego rzędu. Wykorzystano algorytm MUSIC (ang. Multiple Signal Classification), który bazuje na analizie wektorów własnych macierzy korelacji sygnału z szumem. Badania symulacyjne przeprowadzono przy pomocy narzędzi MATLAB-SIMULINK dla różnych stosunków sygnału i szumu oraz różnej liczby próbek. Zastosowana metoda zapewnia dokładność pomiaru przesuwu częstotliwości rzędu dziesiątych części Hz przy stosunku sygnału i szumu 0 dB. Taki rezultat umożliwia wykorzystanie tej metody w procesie identyfikacji nadajnika radiowego.
    FSK signal is used for binary data transmission in telecommunication systems. Basic parameters for FSK signal is the frequency shift. Accurate measurement of the frequency shift is necessary in radio electronics reconnaissance for given radio station identification. Using standard measurement methods of this parameter, based on correlation or spectrum analysis is not efficient, especially in the presence of the small signal-to-noise ratio. In this paper mathematical rules as well as algorithm description and frequency shift measurements results based on higher order analysis are presented. Experiments carried out based on the second and the fourth cumulant analysis. Multiple Signal Classification method (MUSIC) based on eigenvector correlation matrix for signal with noise was used. Computer simulation experiments were carried on using Matlab-Simulink programmable science environment for various noise-to-signal ratios as well as various samples number. Method used in the presented experiments guarantees frequency shift accuracy measurement in the order ten parts per Hz in the presence signal-to-noise ratio OdB. This result enables this method to be used in the radio transmitter identification process.
    Źródło:
    Biuletyn Wojskowej Akademii Technicznej; 2006, 55, 2; 79-88
    1234-5865
    Pojawia się w:
    Biuletyn Wojskowej Akademii Technicznej
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of triple correlation and bispectrum for interference immunity improvement in telecommunications systems
    Autorzy:
    Molchanov, P.
    Totsky, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/907903.pdf
    Data publikacji:
    2008
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    telekomunikacja
    bispektrum
    przesuw częstotliwości
    kluczowanie częstotliwości
    kodowanie nadmiarowe
    korelacja potrójna
    telecommunications
    frequency shift keying
    redundant encoding
    triple correlation
    bispectrum
    Opis:
    This paper presents a new noise immunity encoding/decoding technique by using the features of triple correlation and bispectrum widely employed in digital signal processing systems operating in noise environments. The triple correlationand bispectrum-based encoding/decoding algorithm is tested for a digital radio telecommunications binary frequency shift keying system. The errorless decoding probability was analyzed by means of computer simulation for the transmission and reception of a test message in a radio channel disturbed by both additive white Gaussian noise (AWGN) and a mixture of an AWGN and an impulsive noise. Computer simulation results obtained for varying and less than unity signal-to-noise ratios at the demodulator input demonstrate a considerable improvement in the noise immunity of the technique suggested in comparison with the traditional redundant linear block encoding/decoding technique.
    Źródło:
    International Journal of Applied Mathematics and Computer Science; 2008, 18, 3; 361-367
    1641-876X
    2083-8492
    Pojawia się w:
    International Journal of Applied Mathematics and Computer Science
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Single parallel stubs as broadband microwave phase shifters
    Autorzy:
    Rutkowski, Adam
    Powiązania:
    https://bibliotekanauki.pl/articles/220484.pdf
    Data publikacji:
    2020
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    phase shift
    differential phase shift
    microwave phase shifter
    parallel stub
    instantaneous frequency measurement
    IFM
    Opis:
    Structures and characteristics of wideband small-size phase shifters made with the use of single parallel stubs are presented in this paper. The stubs can be short-circuited or open-circuited on termination. Such devices are well known, but are primarily used as components of filters or matching circuits. The novelty, then, comes from the establishment of simple, but helpful formulae, which enable to describe the insertion phase shift and differential phase shift of a line with short and open stubs connected in parallel. These equations can be very useful for designing complex microwave multi-ports. The results of simulations and measurements of the devices, which were designed and made, are shown herein. It was also proved that the presented device shave several usable operating frequency sub-bands, and that the differential phase shift values in the higher sub-bands are greater than those in the lower operating frequency ranges. Thanks to this, the described phase shifters can be used in more than one frequency sub-band. It was stated that in the conditions under analysis, larger phase shifts can be achieved using open-circuited stubs rather than short-circuited stubs. However, the phase shifters with shorted parallel stubs can operate in a wider frequency band.
    Źródło:
    Metrology and Measurement Systems; 2020, 27, 1; 91-102
    0860-8229
    Pojawia się w:
    Metrology and Measurement Systems
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Attribute analysis as a tool for determining the areas of the late diagenetic Main Dolomite deposits and assessing the stability of the seismic signal parameters
    Autorzy:
    Smalera, Norbert
    Powiązania:
    https://bibliotekanauki.pl/articles/2124699.pdf
    Data publikacji:
    2022
    Wydawca:
    Akademia Górniczo-Hutnicza im. Stanisława Staszica w Krakowie. Wydawnictwo AGH
    Tematy:
    seismic attributes
    Zechstein
    Main Dolomite
    fault shadow
    dominant frequency
    phase shift map
    attenuation
    Opis:
    The results of the lithofacial analysis of data from the Moracz 3D seismic survey were among the main premises leading to the positioning of the new petroleum exploration well in that area. Unfortunately, the reservoir properties of the drilled part of the Main Dolomite carbonates differed significantly from those anticipated by the analysis of the amplitudes of the seismic signal recorded. Such surprisingly negative results impelled the reinterpretation of 3D seismic data. Hence, a number of analyses of the amplitudes, the frequencies, and the variability of phase shift were carried out in order to determine the influence of these parameters on the lithofacial interpretation of seismic data. The results revealed a fundamental error of amplitude with the extraction maps. It appeared that the distribution of amplitudes is not essentially controlled by the reservoir properties of the Main Dolomite carbonates but by the fault shadow effect coming from Mesozoic graben in the overburden. In addition, a large diversity of frequency spectra was found, which, combined with the small thickness of the exploration level, could have contributed to incorrect identification of seismic reflections. There was also a change in seismic signatures from the same reflection in different parts of the survey, raising doubts about the distribution of the phase rotation. In order to recognize phase rotation diversity, a new seismic data analysis was based upon the selected Triassic sediments of high impedance. The obtained maps demonstrated significant variability within the data volume due to attenuation. The reinterpreted data from the Moracz 3D seismic survey proved the uneven and unstable distribution of amplitudes, frequencies, and phase which resulted in erroneous conclusions of petroleum exploration. After modeling with the use of different frequency ranges, an analysis of the amplitude extraction of the horizons related to the Main Dolomite was performed. Then the amplitude ratio attribute was selected which eliminated the influence of the regional amplitude and frequency distribution and showed the distribution. of dolomite properties more reliably than the amplitude extraction maps.
    Źródło:
    Geology, Geophysics and Environment; 2022, 48, 2; 111--132
    2299-8004
    2353-0790
    Pojawia się w:
    Geology, Geophysics and Environment
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
      Wyświetlanie 1-9 z 9

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