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Wyświetlanie 1-6 z 6
Tytuł:
Time-Frequency Analysis of Nonstationary Optical Signals Using Husimi Type Function
Autorzy:
Davidović, Miloš
Davidović, Milena
Vojisavljevic, Vuk
Powiązania:
https://bibliotekanauki.pl/articles/1795642.pdf
Data publikacji:
2009-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.60.Hj
Opis:
Time-frequency analysis is important to identify the localized information of a non-stationary signal in the time and frequency domains simultaneously. There are few different time-frequency analysis methods available with their own specialty and suitability. In quantum mechanics Husimi function of any quantum mechanical state arises naturally whenever the simultaneous measurement of both coordinate and momentum is performed on this state with maximal accuracy allowed by the Heisenberg uncertainty relations. The Husimi function is a probability distribution for the statistics of simultaneous unsharp measurement of both coordinate and momentum. In general, like the Wigner function, the Husimi function can be defined in the space of any pair of conjugate variables. In particular, in the studies of signal processing, this space is the time-frequency space. In the present work we consider the Husimi function in this space, and apply it to analyse the multicomponent signals. The time-frequency representations of the simulated signals by using the Husimi distribution clearly show the frequency features along the time axis. The results are encouraging and indicate that, like in corresponding analogous problems in quantum mechanics, the Husimi distribution approach in the time-frequency analysis for non-stationary optical signals may provide some insights which are not so easily obtained in other, more spread approaches.
Źródło:
Acta Physica Polonica A; 2009, 116, 4; 675-677
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Perceptual Evaluation of the Effect of Threshold in Selective Mixing of Sounds
Autorzy:
Kleczkowski, P.
Pluta, M.
Powiązania:
https://bibliotekanauki.pl/articles/1196825.pdf
Data publikacji:
2014-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.60.Hj
43.60.+d
43.75.Zz
43.66.Lj
Opis:
Signal processing methods make possible such a mixing of signals that their overlapping in the time-frequency plane is reduced. This can be achieved by reducing the number of overlapping signals by discarding contributions from weaker signals and leaving only contributions from stronger ones. When applied to acoustic signals, this is referred to by the authors as selective mixing of sounds. Previous research has shown, that this rule, when applied to signals of musical instruments can provide some perceptual advantages over simple adding up the sound sources. In this paper, an experiment was carried out to determine the threshold of the value of relative energy of sound sources to control the decision about discarding a contribution from a particular sound source.
Źródło:
Acta Physica Polonica A; 2014, 125, 4A; A-117-A-121
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Masking a Frequency Band in a Musical Fragment Played by a Single Instrument
Autorzy:
Kleczkowski, P.
Plewa, M.
Pluta, M.
Powiązania:
https://bibliotekanauki.pl/articles/1504380.pdf
Data publikacji:
2011-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.66.Dc
43.66.Lj
43.66.Ba
43.60.Hj
Opis:
The phenomenon of masking in the environment of musical sounds has not yet been deeply investigated. An experiment was conducted to find out whether masking of a band of frequencies in a musical instrument sound by the remaining spectral content of that instrument could be explained by "energetic" masking, i.e. masking resulting from overlapping patterns of excitation on the basilar membrane. An isolated, about one octave wide, band of frequencies of the saxophone sound playing a couple of notes legato was masked alternatively by two maskers: CBN - the band of noise occupying the same frequency range plus the remaining spectral content of the saxophone sound, and BN - the same band of noise acting alone. For both maskers, the level of noise was increased gradually to detect the respective thresholds of masking. Masker CBN was more efficient in masking by about 15 dB, indicating that the harmonics below and above the analysed band contributed substantially more to masking than noise inside the band. As energetic masking of those harmonics was weak, non-energetic or "informational" masking prevailed.
Źródło:
Acta Physica Polonica A; 2011, 119, 6A; 991-995
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrasound Frequency Analysis of a Magnetic Fluid in Low-Intensity External Magnetic Field
Autorzy:
Kurimský, J.
Rajňák, M.
Cimbala, R.
Dolník, B.
Tóthová, J.
Paulovičová, K.
Timko, M.
Kopčanský, P.
Kolcunová, I.
Petráš, J.
Džmura, J.
Balogh, J.
Powiązania:
https://bibliotekanauki.pl/articles/1032764.pdf
Data publikacji:
2017-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.58.+z
43.60.+d
47.65.Cb
82.70.Dd
83.80.Hj
Opis:
This work deals with an interaction of a magnetic fluid of a dielectric nature with a magnetic field by means of ultrasound waves measurements and analysis. Ultrasound analysis is known as a non-destructive inspection tool often used in technical diagnostics, moreover, it has numerous applications in medicine and biology, too. We report the low-frequency ultrasound analysis of a dielectric magnetic fluid in a low-intensity external static magnetic field. The studied magnetic fluid was composed of a transformer oil and dispersed magnetite nanoparticles coated with oleic acid. Experiments were carried out by using an ultrasonic testing cell. The cell was exposed to a magnetic field of 50 mT in both parallel and perpendicular direction to the waves propagation. A through-transmission mode measurement was applied, where two fixed narrow-band transducers with completely shielded crystal for maximum RFI/EMI immunity (Physical Acoustic R15I-AST, the resonant frequency 150 kHz) served as a transmitter and a receiver. In this way we carried out the measurement of the frequency-dependent ultrasonic response to a rectangle calibrating signal of 5 μs pulse width. Digitized signals were recorded for further analysis. We present the frequency domain analysis of the low-frequency ultrasound in magnetic fluid. The frequency spectrum in magnetic fluid colloidal system was calculated by the Fourier transformation method. Results show that there is a frequency shift in the amplitude-frequency spectrum caused by the step-up magnetic field. The higher the magnetic field, the higher the frequency of the peaks. The effect of particle aggregation in magnetic field on the ultrasound wave propagation is discussed in the paper.
Źródło:
Acta Physica Polonica A; 2017, 131, 4; 910-912
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acousto-Optic Devices Based on Potassium Rare-Earth Tungstates Laser Crystals
Autorzy:
Velikovskii, D.
Pozhar, V.
Mazur, M.
Powiązania:
https://bibliotekanauki.pl/articles/1383396.pdf
Data publikacji:
2015-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.70.Hj
42.79.Jq
42.60.Fc
43.35.Sx
Opis:
We present a family of original acousto-optical devices. They are based on new acousto-optical materials $KRE(WO_4)_2$, where RE = Y, Gd, Yb, Lu. A combination of features such as radiation resistance, optical biaxiality and appreciable acousto-optical figure of merit, makes possible creation of polarization-insensitive modulator with almost 100% of diffraction efficiency. The deflector with wide angular aperture and broad range of deflection, and collinear tunable filter are also suggested.
Źródło:
Acta Physica Polonica A; 2015, 127, 1; 75-77
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Ultrasonic Methods of the Cells Separation in Human Blood
Autorzy:
Włoch, A.
Czyż, H.
Jasiński, T.
Powiązania:
https://bibliotekanauki.pl/articles/1402588.pdf
Data publikacji:
2015-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.35.+d
47.35.Rs
62.60.+v
83.80.Hj
87.50.Y-
Opis:
This work deals with the problem of ultrasound in the context of biomedical and clinical applications. Ultrasonic waves can be used for the separation of cells in human blood. Under the influence of ultrasonic waves cells included in the liquid experience a certain characteristic displacement was referred to as drift. Presented work suggests that only radiation pressure should be taken into account as a mechanism of drifting in this situation. It has been demonstrated that the growth of cells concentration around the points of stable equilibrium is exponential. The time constant of this growth was estimated and the formulae which determine the time needed to obtain the assumed concentration increase have been derived. The theoretical studies of acoustic agglomeration of particles in the liquid have become a new focus in the ultrasonic research.
Źródło:
Acta Physica Polonica A; 2015, 128, 2; 234-236
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-6 z 6

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