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Tytuł:
Defects in Decomposing Copper Alloys Studied by Positrons
Autorzy:
Mikhalenkov, V. S.
de Lima, A. P.
Lopes Gil, C.
Powiązania:
https://bibliotekanauki.pl/articles/2008115.pdf
Data publikacji:
1999-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
81.30.Mh
Opis:
The evolution of defect structure during isochronal annealing of water-quenched Cu-4.83 at.% In and Cu-4.94 at.% Sn alloys was studied by measuring positron lifetime and Doppler broadening of annihilation line. The behaviour of annihilation parameters in both alloys is found to be analogous. In as-quenched alloys one component of about 180 ps is detected in the lifetime spectra. It remains intact up to the annealing temperature of 450 K and is attributed to positron annihilation at quenched-in vacancies associated with alloying atoms. When going above this temperature, the short component appears in the lifetime spectra, while intensity of the long component starts to drop giving evidence to the reduction of defect concentration. This process is observed to develop up to 550 K; thereafter all annihilation parameters level off. After crossing the phase separation temperature they begin to vary again since the defect structure comes into dependence on cooling conditions. The obtained results are discussed in terms of defect structure evolution in the course of precipitate formation.
Źródło:
Acta Physica Polonica A; 1999, 95, 4; 615-622
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Emission Spectra of Triple Activated SrS Phosphors
Autorzy:
Rao, A. P.
Sinha, O. P.
Machwe, V. G.
Mehta, A. S.
Powiązania:
https://bibliotekanauki.pl/articles/1945381.pdf
Data publikacji:
1996-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
33.50.-j
Opis:
Fluorescence spectra of strontium sulphide phosphors activated by three activators viz. Mn, Cu, and Gd individually and in different combinations have been discussed at length. X-ray is used as excitation source. Probable inferences are drawn regarding energy transfer phenomenon. The two channels for transfer of energy are concluded in present phosphor series. A model is also proposed.
Źródło:
Acta Physica Polonica A; 1996, 89, 4; 509-516
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The Nature of Potential Fluctuations in the MBE CdTe/CdMgTe Quantum Well in a Magnetic Field: Experiment and Theory
Autorzy:
Szot, M.
Karpierz, K.
Avetisyan, A. A.
Djotyan, A. P.
Kossut, J.
Grynberg, M.
Powiązania:
https://bibliotekanauki.pl/articles/2047014.pdf
Data publikacji:
2006-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.55.Gs
72.15.Rn
72.80.Ey
73.21.Fg
Opis:
Far infrared photoconductivity spectra of CdTe/Cd$\text{}_{0.8}$Mg$\text{}_{0.2}$Te quantum well uniformly n-type doped with iodine in barriers and in the well were investigated as a function of the magnetic field. The spectra were recorded for several fixed far infrared photon energies and peaks corresponding to intra donor transitions were observed. The magnetic field at which the peaks were observed was the same for all far infrared photon energies used. This is interpreted as an evidence of the presence of fluctuations of the electrostatic potential - quantum dots which reduce the dimensionality of the potential in which a shallow donor is placed. A characteristic size of the fluctuations was found to be of 23-25 nm and 30-40 nm. Theoretical calculations show a nonmonotonic dependence of the electron binding energy on the donor centre in such quantum dot, as a function of magnetic field. This explains why the position of experimentally observed peak is insensitive to far infrared photon energy used. Temperature evolution of spectra and the theoretical model proposed, indicate similarities between fluctuations in the two-dimensional structure investigated and fluctuations in bulk systems.
Źródło:
Acta Physica Polonica A; 2006, 110, 3; 379-387
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Optical Properties of InAs Quantum Dots
Autorzy:
Willander, M.
Zhao, Q. X.
Jacob, A. P.
Wang, S. M.
Wei, Y. Q.
Powiązania:
https://bibliotekanauki.pl/articles/2035579.pdf
Data publikacji:
2002
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.67.Hc
78.55.Cr
Opis:
InAs quantum dots grown on GaAs substrate were investigated by optical spectroscopy. We particularly emphasized on the photoluminescence intensity, the stability of the photoluminescence intensity versus temperatures and wavelength of the InAs dot emission at various thermal treatments and different structures. We found that hydrogen can strongly passivate nonradiative centers without causing any structure degradation, and both n- and p-type modulation doping can reduce the decrease in the photoluminescence intensity when the sample temperature increases from the helium temperature to room temperature. The emission wavelength and the efficiency of the InAs quantum dots can also be manipulated by choosing proper materials of cap layer.
Źródło:
Acta Physica Polonica A; 2002, 102, 4-5; 567-576
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of the γ-Radiation on the Generation Characteristics of the YAlO_{3}:Nd Crystals
Autorzy:
Sugak, D. Yu
Matkovskii, A. O.
Grabovskii, V. V.
Prokhorenko, V. I.
Suchocki, A.
Durygin, A. M.
Solskii, I. M.
Shakhov, A. P.
Powiązania:
https://bibliotekanauki.pl/articles/1968884.pdf
Data publikacji:
1998-04
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.70.Hj
61.72.Ji
Opis:
The results of investigation of the influence of γ-radiation by $\text{}^{60}$Co-source on the YAlO$\text{}_{3}$:Nd laser generation characteristics are presented in this paper. The significant decrease in the output energy after γ-irradiation was obtained. The energetic characteristics are restored after illumination of the γ-irradiated laser rods by 1000-10000 pulses of the pumping lamp light. The additional absorption spectrum is induced by γ-irradiation in the crystals. The nature of the created in this way colour centres is discussed. The mechanism of influence of the colour centres on generation properties of the crystals is discussed.
Źródło:
Acta Physica Polonica A; 1998, 93, 4; 643-648
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Silver Surface Structure on Luminescence Characteristics of Europium Doped Polymer Films
Autorzy:
Denisenko, G. A.
Malashkevich, G. E.
Tziganova, T. V.
Galstyan, V. G.
Voitovich, A. P.
Pershukevich, P. P.
Kalosha, I. I.
Bazilev, A. G.
Mchedlishvili, B. V.
Stręk, W.
Oleinikov, V. A.
Powiązania:
https://bibliotekanauki.pl/articles/1945485.pdf
Data publikacji:
1996-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.55.Hx
Opis:
The luminescence characteristics of Eu$\text{}^{3+}$ ions in Eu(NO$\text{}_{3}$)$\text{}_{3}$·6H$\text{}_{2}$O salt contained in polymer films coating the silver metallic surfaces were studied. The surfaces were specially prepared to consist of silver tip arrays with the height of tips in micron and surface density in 10$\text{}^{-8}$ cm$\text{}^{-2}$ ranges. The evaluation of enhancement per one europium ion gave a value 3.5 10$\text{}^{2}$ for one polymer layer coating of tip array silver surface in comparison with the case of glass substrate coating.
Źródło:
Acta Physica Polonica A; 1996, 90, 1; 121-126
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positronium Trapping in Porous Solids: Means and Limitations for Structural Studies
Autorzy:
Kajcsos, Zs.
Liszkay, L.
Duplâtre, G.
Varga, L.
Lohonyai, L.
Pászti, F.
Szilágyi, E.
Lázár, K.
Kótai, E.
Pál-Borbély, G.
Beyer, H. K.
Caullet, P.
Patarin, J.
Azenha, M. E.
Gordo, P. M.
Lopes Gil, C.
de Lima, A. P.
Ferreira Marques, M.
Powiązania:
https://bibliotekanauki.pl/articles/2042216.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
36.10.Dr
78.70.Bj
61.43.Gt
Opis:
Positron annihilation techniques are used for the structural investigation of solids but the interpretation of results in grainy and porous media is still unclear. A unique picture can be obtained assuming that the dominant process is Ps trapping in competing "extended free volume" sites. In samples with a large amount of free volumes near-saturation Ps trapping will rule the lifetime pattern, and very long lifetimes of over 100 ns might arise from o-Ps trapped in mesopores. It is shown that lifetime parameters must be corrected for the 3γ/2γ counting efficiency ratio. The results demonstrate the high sensitivity of Ps to mesopores in zeolites but also that Ps-trapping poses limitations on the applicability of lifetime to structural investigation in porous systems. The evolution of the lifetime spectra upon changes in the sample and measuring conditions should be considered in a complex way, observing not only changes in some selected components but in the whole lifetime pattern simultaneously.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 729-737
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On the Management of Direct and Reflected Sounds in the 5.0 Surround Sound Reproduction System
Autorzy:
Kleczkowski, P.
Król, A.
Małecki, P.
Powiązania:
https://bibliotekanauki.pl/articles/1402174.pdf
Data publikacji:
2015-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.38.Md
43.60.-c
43.55.Lb
43.66.Lj
Opis:
Direct and ambient sounds are usually reproduced through the same loudspeakers. In multichannel systems, with the use of anechoic recordings and auralization techniques it is possible to separate these sound components so that they are reproduced via different loudspeakers. Four basic options of management of direct and reflected sounds were investigated in a perceptual experiment. One sound source and the standard 5.0 surround sound system was used. It was found that listeners consistently preferred sound reproduction with direct sound radiated from only one loudspeaker.
Źródło:
Acta Physica Polonica A; 2015, 128, 1A; A-11-A-16
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Properties of Magnetic Nano-Particles
Autorzy:
Lindgård, P. A.
Powiązania:
https://bibliotekanauki.pl/articles/1953165.pdf
Data publikacji:
1997-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Ds
75.40.Gb
76.20.+q
Opis:
The intrinsic thermodynamic magnetic properties of clusters are discussed using spin wave theory for a Heisenberg model, with a fixed magnitude of the spins S$\text{}_{i}$=S and site independent nearest neighbor exchange interaction. The consequences of the more realistic Hubbard model is considered in which we allow for a magnetization profile at T=0 and a structural relaxation, which in turn will give rise to a site dependent exchange interaction. It is concluded that correlation effects among the electrons play a very important role in small clusters, albeit not modifying the thermodynamic properties drastically. The finite cluster size gives foremost rise to a discrete excitation spectrum with a large energy gap to the ground state. The relaxation of the magnetization during the reversal of the external magnetic field is discussed. A first step towards a quantitative understanding of the nonequilibrium statistical mechanics in single-domain ferromagnetic particles is a systematic study of the kinetic Ising model. Results from Monte Carlo simulation and droplet theory are reviewed with particular attention to the effects of various boundary conditions, including a decrease in the number of surface bonds and an addition of surface anisotropy. A new dynamic "outside-in" flip mode is proposed.
Źródło:
Acta Physica Polonica A; 1997, 91, 1; 121-133
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analysis of the quantum spin Hall and quantum anomalous Hall effects in a two-dimensional decorated lattice using entanglement spectrum
Autorzy:
Piekarska, A.
Potasz, P.
Wójs, A.
Powiązania:
https://bibliotekanauki.pl/articles/1160112.pdf
Data publikacji:
2016-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.At
73.43.Cd
Opis:
We study topological properties of a two-dimensional decorated lattice using entanglement spectrum and trace index. Using these measures, we distinguish various phases of the system predicted recently, including the quantum spin Hall effect and quantum anomalous Hall effect. The topologically trivial and non-trivial phases are identified, with assignment of a Chern number to each of the bands.
Źródło:
Acta Physica Polonica A; 2016, 129, 1a; A-87-A-89
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Precise Measurements of the Hyperfine Structure of the Levels Belonging to the Terms $3d^{5}4s$ $\text{}^{5}G$ and $\text{}^{5}P$ in $Cr(I)$
Autorzy:
Krzykowski, A.
Głowacki, P.
Jarosz, A.
Powiązania:
https://bibliotekanauki.pl/articles/1419711.pdf
Data publikacji:
2012-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
32.10.Fn
Opis:
The hyperfine structure intervals for the electronic levels belonging to the terms $3 d^5 (\text{}^4G) 4s a^5G$ and $a^5P$ of a chromium 53 atom were precisely measured with the use of the method of atomic beam magnetic resonance detected by laser induced resonance fluorescence. Magnetic-dipole and electric-quadrupole hyperfine interaction constants (A and B, respectively) for the electronic levels of interest were determined with the accuracy of a few kHz. The high precision of measurements also enabled an estimation of the octupole-coupling constants (C).
Źródło:
Acta Physica Polonica A; 2012, 122, 1; 78-81
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
In the Search of Electron Correlation Effects in DNA
Autorzy:
Wróbel, A.
Wróbel, P.
Powiązania:
https://bibliotekanauki.pl/articles/1537235.pdf
Data publikacji:
2010-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
87.14.gk
75.20.-g
71.10.Fd
Opis:
We discuss the energy scale separation induced in DNA by gaps between molecular orbital states of individual bases and by electron correlations. We also demonstrate how this separation gives rise to effective low energy models of electron transport in DNA.
Źródło:
Acta Physica Polonica A; 2010, 118, 2; 409-412
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Piezoceramic Transducers Selection Method for High Power Ultrasonic Devices
Autorzy:
Kluk, P.
Milewski, A.
Powiązania:
https://bibliotekanauki.pl/articles/1398757.pdf
Data publikacji:
2015-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
43.35.+d
43.35.-c
43.35.Zc
43.38.Fx
43.38.+n
43.38.-p
Opis:
A universal method for selecting piezoceramic transducers used in high power ultrasonic devices such as ultrasonic welding and cutting systems has been presented. The key element of such systems is a high power ultrasonic sandwich transducer consisting of a stack of piezoceramic transducers mounted between two masses. Because of relatively large dispersion of piezoceramic transducer parameters between production lots, they must be selected in order to obtain a high quality and long-life sandwich transducer. Presented selection method consists of three stages. First, the parametric identification of the Butterworth-Van Dyke equivalent circuit model is performed based on piezoceramic transducer electrical impedance measurements. Next, the electrical impedance frequency samples are estimated using the identified Butterworth-Van Dyke model. Finally, the k-means clustering algorithm is used to select the best fitted piezoceramic transducer sets.
Źródło:
Acta Physica Polonica A; 2015, 127, 3; 719-722
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Enhancement of Nematic Order of Liquid Crystals in Thin Cells
Autorzy:
Aswini, P.
Govind, A.
Powiązania:
https://bibliotekanauki.pl/articles/1489838.pdf
Data publikacji:
2012-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
61.30.Gd
61.30.-v
64.70.mf
Opis:
Experimental observations show that the nematic order parameter is significantly enhanced as the thickness of the cell is reduced. Calculations of earlier theories do not agree well with the experimental data. We propose a simple extension of Maier-Saupe theory to account for the enhancement. A molecule near the surface is assumed to feel the mean field potential (the Maier-Saupe type) and also the surface induced potential. This is included in the Maier-Saupe theory. Our calculations are in better agreement with the experimental data.
Źródło:
Acta Physica Polonica A; 2012, 121, 3; 625-627
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Recurrence Quantification Analysis of Lorenz Model Periodically Modulated at the Onset of Chaos
Autorzy:
Babinec, P.
Krafčík, A.
Powiązania:
https://bibliotekanauki.pl/articles/1493371.pdf
Data publikacji:
2011-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
05.40.-a
87.10.Mn
43.60.+d
43.71.+m
Opis:
Plots and quantitative measures obtained from recurrence quantification analysis - recurrence rate, determinism, entropy, and trapping time, were used for the sensitive detection of transitions from laminar (regular) to turbulent (chaotic) phases in the Lorenz model periodically modulated at the onset of chaos.
Źródło:
Acta Physica Polonica A; 2011, 120, 3; 368-370
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł

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