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Wyświetlanie 1-15 z 270
Tytuł:
Light Propagation in a Magnetic Field: Random Green Matrix Approach
Autorzy:
Pinheiro, F. A.
Rusek, M.
Orłowski, A.
van Tiggelen, B. A.
Powiązania:
https://bibliotekanauki.pl/articles/2037256.pdf
Data publikacji:
2004-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.25.Dd
78.20.Ls
Opis:
We studied the spectral properties of the matrices describing multiple scattering of electromagnetic waves from randomly distributed point-like magneto-optically active scatterers under an external magnetic field B. We showed that the complex eigenvalues of these matrices exhibit some universal properties such as the self-averaging behavior of their real parts, as in the case of scatterers without magneto-optical activity. However, the presence of magneto-optically active scatterers is responsible for a striking particularity in the spectra of these matrices: the splitting of the values of the imaginary part of their eigenvalues. This splitting is proportional to the strength of the magnetic field and can be interpreted as a consequence of the Zeeman splitting of the energy levels of a single scatterer.
Źródło:
Acta Physica Polonica A; 2004, 105, 4; 339-347
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Nonlinear Effects of Magnetoacoustic Perturbations in Optically Thin Quasi-Isentropic Plasmas
Autorzy:
Perelomova, A.
Ratkowski, F.
Powiązania:
https://bibliotekanauki.pl/articles/1030551.pdf
Data publikacji:
2018-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.25.-x
43.25.Nm
Opis:
Nonlinear effects of planar magnetosound perturbations in a plasma are discussed. Plasma is non-adiabatic due to optically thin radiation and external heating. For these reasons, thermal instability of a plasma may appear which makes it acoustically active. The plasma is assumed to be initially homogeneous ideal gas with infinite electrical conductivity permeated by a straight magnetic field which is orthogonal to the trajectories of gas particles. The instantaneous dynamic equations which describe nonlinear effects of intense sound in quasi-isentropic plasma, are derived. Nonlinear interaction of periodic and aperiodic magnetoacoustic perturbations with the non-wave modes, are discussed. The conclusions concern dissipative or active behavior of magnetoacoustic perturbations which is determined by the kind of the heating-cooling function.
Źródło:
Acta Physica Polonica A; 2018, 133, 1; 194-200
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Location of Partial Discharge Sources and Analysis of Signals in Chosen Power Oil Transformers by Means of Acoustic Emission Method
Autorzy:
Olszewska, A.
Witos, F.
Powiązania:
https://bibliotekanauki.pl/articles/1418066.pdf
Data publikacji:
2012-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
52.80.-s
77.22.Jp
84.70.+p
43.40.Le
43.60.Lq
Opis:
The original system useful for analysis of signals recorded during investigations of partial discharges within power oil transformers by means of acoustic method is presented. This method includes the basic and advanced analysis of recorded data. In the frame of basic analysis of data recorded signals undergo filtration in chosen frequency bands and next the analysis is made - in domain of time, frequency, time-frequency and discrimination threshold. In the frame of advanced analysis of data the amplitude distributions of acoustic emission signals and the acoustic emission descriptors (defined by the authors) are calculated in order to outline maps of acoustic emission descriptors on lateral walls of a transformer; it is a base for location of sources of partial discharges by means of the original method consisted in determination of advance degree of a signal. Results of this analysis, for signals recorded in two chosen transformers with identical construction (partial discharge occurred only within one of them), are presented in the paper. The source of partial discharge, situated within oil near transformer tank, was localized; the revision confirmed this result. Properties of recorded emission acoustic signals at chosen measuring points situated on the tank, in function of distance between the partial discharge source and measuring points, are presented.
Źródło:
Acta Physica Polonica A; 2012, 122, 5; 921-926
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Many-Channel Landauer-Like Conductance Formula in a Uniform Magnetic Field
Autorzy:
Benamira, F.
Abdellaoui, A.
Powiązania:
https://bibliotekanauki.pl/articles/1418271.pdf
Data publikacji:
2012-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.23.-b
Opis:
Linear-response theory is combined with the Landauer viewpoint to describe quantitatively transport in a four-lead mesoscopic structure within the presence of a uniform magnetic field. A new multichannel magnetoconductance formula is derived in the case where the magnetic field is perpendicular to the current-flow. The invariance under magnetic reversal test is confirmed.
Źródło:
Acta Physica Polonica A; 2012, 122, 4; 721-724
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Location and Identification of Acoustic Signals Recorded in Power Oil Transformers within the Band of 20-180~kHz
Autorzy:
Olszewska, A.
Witos, F.
Powiązania:
https://bibliotekanauki.pl/articles/1493254.pdf
Data publikacji:
2011-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
52.80.-s
77.22.Jp
84.70.+p
43.40.Le
43.60.Lq
Opis:
Emission acoustic signals, recorded in investigated power oil transformers, have been analyzed in the time, frequency and time-frequency domain. Analysis of each signal has been started by filtration within selected frequency band and subsequently the following quantities have been calculated: spectral power density, phase-time characteristic, averaging phase-time characteristic, short-time Fourier transform spectrograms, signal amplitude distributions, descriptors with acronyms ADC and ADP and thereafter maps of descriptors on lateral walls of transformers can be carried out. Frequency bands applied in order to filtration have been chosen in such a way so that signals coming from different sources (among other things from partial discharges, Barkhausen's effect, oil circulation and outer acoustic disturbances) can be differentiated. The sources have been localized using maps of descriptors calculated for selected frequency bands. The fundamental properties of obtained signals have been determined. Such properties describe: partial discharges, Barkhausen's acoustic effect and other acoustic interferences.
Źródło:
Acta Physica Polonica A; 2011, 120, 4; 709-712
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Discharge Currents Discrimination Technique Based on Multi-Linear Regression Line and Artificial Neural Networks for Power Transformers Diagnosis
Autorzy:
Benyahia, F.
Nacer, A.
Moulai, H.
Aberkane, F.
Beroual, A.
Powiązania:
https://bibliotekanauki.pl/articles/1399715.pdf
Data publikacji:
2013-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
77.22.Jp
52.80.Wq
Opis:
The proposed work will be consecrated to the study of positive pre-breakdown currents triggered in mineral transformer oil under 50 Hz alternating overvoltage. Since negative currents are recorded in low rates and for higher voltage levels than positive ones, only the latter will be prior taken into consideration. Both streamer propagation and arc discharge current types are identified and are used in the training process of an artificial neural network and the multi-linear regression line of these currents in order to develop a complementary diagnosis tool that can serve as an on-line transformer protection. More successful results than those obtained by other developed techniques are expected.
Źródło:
Acta Physica Polonica A; 2013, 123, 2; 250-253
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A Photoacoustic Study of Xenon Implantation in $CuInSe_2$
Autorzy:
Satour, F.
Zegadi, A.
Merabet, A.
Powiązania:
https://bibliotekanauki.pl/articles/1492557.pdf
Data publikacji:
2011-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.70.Cv
78.20.Ci
78.40.Fy
61.82.Fk
71.55.-i
Opis:
In this paper, we report a study on the optical properties of xenon ion implanted $CuInSe_2$ single crystals using a high resolution near-infrared photoacoustic spectrometer of the gas-microphone type. Samples of high quality of $CuInSe_2$, p-type conducting, have been implanted with $Xe^{+}$ at 40 keV with doses of $5 \times 10^{15},$ $10^{16}$ and $5 \times 10^{16}$ ions/$cm^2$. Photoacoustic spectra have been measured before and after implantation. A newly developed theoretical model based on a two-layer sample configuration has been used to single out the spectral dependence of the absorption coefficient of the implanted layer from that of the substrate. The absorption spectra were used to evaluate the gap energy and to establish ionization energies for several shallow and deep defect states. The resulting effects following the introduction of xenon into $CuInSe_2$ at different doses are discussed in the light of published literature.
Źródło:
Acta Physica Polonica A; 2011, 120, 6A; A-031-A-033
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Validity of Diffusional Model in Determination of Electric Transport Parameters of Semiconductor Compound
Autorzy:
Dussan, A.
Mesa, F.
Powiązania:
https://bibliotekanauki.pl/articles/1207470.pdf
Data publikacji:
2014-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.80.Ey
73.50.-h
73.61.Ga
73.50.Gr
Opis:
In this work we have studied the variable range hopping as a predominant electronic transport mechanism for semiconductor materials used as absorbent layer in photovoltaic devices. Dark conductivity measurements were carried out from 120 to 420 K in Si, $Cu_3BiS_3$, SnS, $Cu_2ZnSnSe_4$, and $CuInGaSe_2$ thin films. In the low-temperature range, variational range hopping was established for all samples. Using classical equations from the percolation theory and the diffusional model, the density of states near the Fermi level $(N_{F})$, as well as the hopping parameters (W - activation energy and R - hopping range) were calculated. A correlation between both models allowed us to evaluate the validity of the diffusional model in semiconductor compounds.
Źródło:
Acta Physica Polonica A; 2014, 125, 2; 171-173
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of Properties of Chosen Acoustic Emission Descriptors Describing Acoustic Signals Measured by Means of Acoustic Emission Method within Oil Transformers
Autorzy:
Witos, F.
Olszewska, A.
Powiązania:
https://bibliotekanauki.pl/articles/1506870.pdf
Data publikacji:
2010-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
52.80.-s
77.22.Jp
84.70.+p
Opis:
Authors of the paper present investigation results concerning properties of ADP, ADC and ADNC descriptors which have been obtained during measurements made within three oil transformers and then tested also by other methods (electric and dissolved gas analysis ones). Methodology which makes easier an analysis and identification of acoustic emission signals generated by partial discharges is presented. Results obtained by acoustic emission method have been referred to results coming from other measuring methods.
Źródło:
Acta Physica Polonica A; 2010, 118, 6; 1267-1271
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Anomalous Self-Energy Features in the 2D Hubbard Model
Autorzy:
Avella, A.
Mancini, F.
Powiązania:
https://bibliotekanauki.pl/articles/1813757.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
71.27.+a
71.10.-w
Opis:
The electronic self-energy of the two-dimensional Hubbard model, computed in the non-crossing approximation within the composite operator method, is studied as a function of frequency as well as temperature at the Fermi surface, for a value of doping at which the pseudogap is already well developed. For values of momentum belonging to the phantom arc of the Fermi surface, both dependences show anomalous power law behavior in contrast to that expected from the Fermi liquid theory.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 395-398
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
An Optical Hydrophone for the Single-Shot Field Measurements of High Power Pressure Pulse Fields
Autorzy:
Jamshidi-Rad, A.
Ueberle, F.
Powiązania:
https://bibliotekanauki.pl/articles/1383349.pdf
Data publikacji:
2015-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
06.20.-f
42.25.Fx
43.35.Sx
43.35.Yb
Opis:
The measurements of ultrasonic fields are often performed using polyvinylidene fluoride (PVDF) membrane hydrophones. Recently, optical hydrophones have gained popularity. Refractive type optical hydrophones are based on the change of refractive index at a glass-water interface when the shockwave passes the sensitive area. A major disadvantage of the optical and the PVDF hydrophones is the fact that they provide a single spot sensitive area, with the result that field measurements need a repositioning of the probe. In this work we introduce a multi-spot optical hydrophone with six measurement spots, for the single shot field measurement of shockwave fields. We measure a highly stable shockwave source with a calibrated hydrophone and the multi-spot optical hydrophone and we find good agreement for the calculated energy values of the shockwave field (depending on the energy settings 4% ± 1%).
Źródło:
Acta Physica Polonica A; 2015, 127, 1; 69-71
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electrodynamic Instability of a Self-Gravitating Fluid Cylinder under General Varying Electric Field
Autorzy:
Radwan, A. E.
Elhefnawy, A. R. F.
Powiązania:
https://bibliotekanauki.pl/articles/1920937.pdf
Data publikacji:
1992-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
47.55.Cy
Opis:
The electrodynamic instability of a self-gravitating dielectric fluid penetrated by a uniform axial electric field surrounded by a self-gravitating vacuum pervaded by general varying electric field is investigated. A general eigenvalue relation valid to all possible (symmetric and asymmetric) modes of perturbation for all (short and long) wavelengths is derived and discussed in detail. The model is gravitationally stable to the pure asymmetric disturbances modes while to symmetric modes it is so if the longitudinal wave number normalized with respect to the jet radius is equal to or greater than 1.0668 and vice versa. The axial electric fields pervaded interior and exterior to the cylinder are stabilizing or destabilizing for all disturbance modes according to some restrictions. The transverse varying electric field is purely stabilizing in the symmetric disturbances for all wavelengths, while it is stabilizing in the asymmetric disturbance under some restrictions. The electrodynamic force has a strong stabilizing influence in the symmetric mode and can suppress the gravitational instability above a certain value of the basic electric field.
Źródło:
Acta Physica Polonica A; 1992, 82, 3; 451-459
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical and Structural Studies of Sol-Gel Deposited Nanostructured CdO Thin Films: Annealing Effect
Autorzy:
Abdolahzadeh Ziabari, A.
Ghodsi, F.
Powiązania:
https://bibliotekanauki.pl/articles/1493680.pdf
Data publikacji:
2011-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.20.Ci
78.66.Li
78.67.-n
81.20.Fw
Opis:
Nanocrystalline CdO thin films were prepared by sol-gel dip-coating method using a different solution. The as-deposited films were subjected to drying temperature of 120° in air. The prepared films were annealed in different temperatures of 200, 300 and 400°C. The characterization of samples was carried out by X-ray diffraction, scanning electron microscopy and UV-VIS spectroscopy. Results show that the samples are polycrystalline in nature and the crystallinity of the films improves with temperature. The average grain size is in the range of 19-34 nm. It was observed that the optical parameters of the films were affected by annealing temperature.
Źródło:
Acta Physica Polonica A; 2011, 120, 3; 536-540
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
All-Optical Diode Action in Quasiperiodic Fibonacci Nanostructures
Autorzy:
Namdar, A.
Ebadi-Garjan, F.
Powiązania:
https://bibliotekanauki.pl/articles/1400282.pdf
Data publikacji:
2013-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.65.-k
42.70.-a
78.20.-e
Opis:
We theoretically investigate the feasibility of nonreciprocal light propagation by using the unique features of quasiperiodic one-dimensional photonic crystals. The intrinsic spatial asymmetry of the Fibonacci sequence leads to strong non-reciprocal electric field distribution, so the nonlinear transmission becomes sensitive to the propagation direction. In this work we emphasise on bistability and all optical switching where the switching threshold for one propagation direction is lower than that for the other. In addition we demonstrate that this structure exhibits high transmission due to the existence of high transmission resonances in its linear transmission spectrum, and these features allow creating an all-optical diode.
Źródło:
Acta Physica Polonica A; 2013, 123, 1; 45-47
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Unfocused/Weakly Focused Pressure Pulse Sources for Pain Therapy: Measurements in Water and in a Dry Test Bench
Autorzy:
Ueberle, F.
Jamshidi-Rad, A.
Powiązania:
https://bibliotekanauki.pl/articles/1383801.pdf
Data publikacji:
2015-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.80.Gx
43.20.Px
87.50.yt
87.50.yk
Opis:
Unfocused/weakly focused pressure pulses (UPP) are generated by an "air-gun" like mechanism, with a projectile accelerated by pressurized air and impinging on a metal applicator. They were introduced in 1998 for the treatment of orthopedic soft tissue pain. The patient side of the applicator (a circular piston of 6-30 mm diameter) releases single pressure pulses of 2-10 MPa and 4-5 μs duration. Up today, there is no standard for the measurement of UPP sources (UPPS), so data are often reported on the basis of the focused lithotripter standard IEC61846. The purpose of this research is to establish methods to reliably measure UPPS acoustic parameters and establish a parameter set based on definitions from focused lithotripsy sources as applicable. Therefore, acoustic characteristics and wave fields of the pressure pulses of UPPS from different manufacturers were measured in a water bath and in a dry test bench. It was demonstrated by comparison with optical hydrophones that piezoelectric hydrophones are appropriate for the measurements of UPP. For on-axis measurements at a fixed distance, measurements in the dry test bench can replace water-bath measurements. Additionally, the dry test bench allows for reliable results at pulse rates >1 Hz.
Źródło:
Acta Physica Polonica A; 2015, 127, 1; 135-137
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 270

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