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Wyświetlanie 1-11 z 11
Tytuł:
Formation and Annealing of Micropores in Hematite
Autorzy:
Dauwe, C.
Da Costa, G. M.
Van Hoecke, T.
Segers, D.
Powiązania:
https://bibliotekanauki.pl/articles/1933484.pdf
Data publikacji:
1995-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
In iron oxide powders positrons are trapped in the surface layers and the value of the S-parameter is an indicator of the total specific surface, including external surface and internal surfaces of micropores. The evolution of micropores is followed when α-FeOOH is thermally decomposed into α-Fe$\text{}_{2}$O$\text{}_{3}$. It is shown that the micropore formation is not linked to the decomposition process, but that they also form in hematite synthesized from a ferrihydrite precursor in aqueous solution.
Źródło:
Acta Physica Polonica A; 1995, 88, 1; 119-123
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Weak Localization of Short Pulses in Disordered Waveguides
Autorzy:
Skipetrov, S. E.
van Tiggelen, B. A.
Powiązania:
https://bibliotekanauki.pl/articles/2044615.pdf
Data publikacji:
2006-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.25.Dd
78.90.+t
Opis:
We consider the phenomenon of weak localization of a short wave pulse in a quasi-1D disordered waveguide. We show that the long-time decay of the average transmission coefficient is not purely exponential, in contradiction with predictions of the diffusion theory. The diffusion theory breaks down completely for times exceeding the Heisenberg time. We also study the survival probability of a quantum particle in a disordered waveguide and compare our results with previous calculations using the super-symmetric nonlinear sigma model.
Źródło:
Acta Physica Polonica A; 2006, 109, 1; 101-108
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spectroscopy and Thermoluminescence of LuAlO$\text{}_{3}$:Ce
Autorzy:
Wiśniewski, D.
Drozdowski, W.
Wojtowicz, A.
Lempicki, A.
Dorenbos, P.
de Haas, J. T. M.
van Eijk, C. W. E.
Bos, A. J. J.
Powiązania:
https://bibliotekanauki.pl/articles/1945649.pdf
Data publikacji:
1996-08
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.90.+t
78.55.-m
61.80.Ed
29.40.-n
Opis:
The present status of the LuAlO$\text{}_{3}$:Ce scintillator is reviewed. Scintillation mechanism of this material is based on capture by Ce$\text{}^{3+}$ of holes and then electrons from their respective bands. Results of spectroscopic and thermoluminescence experiments are presented to support this model.
Źródło:
Acta Physica Polonica A; 1996, 90, 2; 377-384
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Do Van Hove Singularities in Leads Influence Tunneling Current through Quantum Dot?
Autorzy:
Krawiec, M.
Domański, T.
Wysokiński, K. I.
Powiązania:
https://bibliotekanauki.pl/articles/1991636.pdf
Data publikacji:
1998-09
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.40.Gk
72.15.Qm
71.27.+a
Opis:
Using the Landauer type formula for the current through quantum dot we have studied the influence of the singularities in the density of states in leads on the differential conductance of the system and answered affirmatively the above question. The presence of Van Hove singularities in the leads may induce an additional structure on the conductance vs. voltage curve. The dot itself has been described by the single impurity Anderson model with a very strong "on-dot" Coulomb repulsion. We also simulate the effect of electron-phonon interaction in the dot by allowing for the fluctuations of the "impurity" energy level.
Źródło:
Acta Physica Polonica A; 1998, 94, 3; 411-414
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetization Steps in Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te Observed in Coherent Transport
Autorzy:
Jaroszyński, J.
Dietl, T.
Wróbel, J.
Karczewski, G.
Wojtowicz, T.
Kossut, J.
Maude, D. K.
van der Linden, P.
Portal, J. C.
Powiązania:
https://bibliotekanauki.pl/articles/1968114.pdf
Data publikacji:
1997-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.15.Rn
73.61.Ga
73.20.Fz
Opis:
Magnetoconductance measurements on submicron wires of n$\text{}^{+}$-Cd$\text{}_{1-x}$Mn$\text{}_{x}$Te were carried out up to 27 T and down to 100 mK. The inverse correlation field of the universal conductance fluctuations is found to increase abruptly in the vicinity of the magnetization steps due to Mn pairs in CdMnTe. No such effect is observed in similar wires of CdTe. These findings support a recent model, according to which the correlation field of the universal conductance fluctuations in magnetic systems is inversely proportional to the magnetic susceptibility of the localized spins.
Źródło:
Acta Physica Polonica A; 1997, 92, 4; 797-800
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Spin Chain in Magnetic Field: Limitations of the Large-N Mean-Field Theory
Autorzy:
Wohlfeld, K.
Chen, Cheng-Chien
van Veenendaal, M.
Devereaux, T.
Powiązania:
https://bibliotekanauki.pl/articles/1384813.pdf
Data publikacji:
2015-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.10.Fd
75.10.Jm
75.10.Pq
Opis:
Motivated by the recent success in describing the spin and orbital spectrum of a spin-orbital chain using a large-N mean-field approximation, we apply the same formalism to the case of a spin chain in the external magnetic field. It occurs that in this case, which corresponds to N=2 in the approximation, the large-N mean-field theory cannot qualitatively reproduce the spin excitation spectra at high magnetic fields, which polarize more than 50% of the spins in the magnetic ground state. This, rather counterintuitively, shows that the physics of a spin chain can under some circumstances be regarded as more complex than the physics of a spin-orbital chain.
Źródło:
Acta Physica Polonica A; 2015, 127, 2; 201-203
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Photovoltaic Effect on PbTe p-n Junction in the Presence of Magnetic Field
Autorzy:
Le Van, Khoi
Grodzicka, E.
Witkowska, B.
Story, T.
Gałązka, R. R.
Powiązania:
https://bibliotekanauki.pl/articles/1929738.pdf
Data publikacji:
1993-10
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.25.Tn
78.20.Ls
72.80.Ga
Opis:
Photovoltaic spectra of PbTe p-n junction have been measured in the infrared spectral region in the temperature range of 8-260 K. The p-n junctions have been formed by cadmium diffusion into the p-type PbTe crystals. From the positions of the photovoltaic maxima the energy gap of the diode material has been determined. In the presence of a magnetic field up to 7 T, a pronounced oscillatory behavior of the photovoltage was observed in the Faraday and Voigt configurations. Experiments were performed as a function of the magnetic field intensity at a constant wavelength of the incident light. The energy of the interband magnetooptical transitions between the Landau levels in PbTe was determined and compared with the theoretical model of Adler, describing the energy band structure for the IV-VI compounds.
Źródło:
Acta Physica Polonica A; 1993, 84, 4; 721-724
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Novel Modulator Topology for Corona Plasma Generation
Autorzy:
Ariaans, T.
Pemen, A.
Winands, G.
Liu, Z.
van Heesch, E.
Powiązania:
https://bibliotekanauki.pl/articles/1807899.pdf
Data publikacji:
2009-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
52.50.Dg
52.70.Ds
52.70.Kz
52.80.Hc
82.33.Xj
96.60.pf
Opis:
Gas cleaning using plasma technology is slowly introduced into industry nowadays. Several challenges still have to be overcome: increasing the scale, safety, life-time and reducing costs. In 2006 we demonstrated a 20 kW nanosecond pulsed corona system. The electrical efficiency was > 90%. O-radical yields were found to be very high (3-7 mole/kWh). However, to be competitive, high costs of the pulsed power technology are still a major hurdle. Here we present a novel modulator for efficient generation of large volume corona plasma. Only a small amount of expensive high-voltage components are required. Switching is done at an intermediate voltage level of 1 kV with standard thyristors. At the high-voltage side, only a diode and a pulse transformer are needed. The estimated costs are about 5 kEuro/kW, whereas for state-of-the-art pulsed power technology these costs usually are about 20-30 kEuro/kW. Detailed investigations on the modulator and a wire-plate corona reactor will be presented. Modulator parameters have been varied systematically as well as reactor parameters (number of electrodes, electrode-plate distance). The O-radical yield was determined from the measured ozone concentrations at the exhaust of the reactor. With a detailed kinetic model, ozone concentrations could be calculated back to the initial O*-yields. The following conclusions will be discussed: for all parameters, an electrical efficiency of > 90% could be obtained. With fast imaging, the average streamer width was found to be ∼ 737 μm and an estimate for the plasma volume was made. The obtained yields of O-radicals (1-4 mole/kWh) are excellent. The conditions to obtain high yields will be discussed.
Źródło:
Acta Physica Polonica A; 2009, 115, 6; 1034-1036
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of van Hove Singularity on T$\text{}_{c}$ in Rb doped C$\text{}_{60}$
Autorzy:
Agrawal, B. K.
Agrawal, S.
Yadav, P. S.
Srivastava, P.
Srivastava, R.
Singh, S.
Powiązania:
https://bibliotekanauki.pl/articles/2035748.pdf
Data publikacji:
2003-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
74.25.Jb
74.62.Fj
74.70.Wz
Opis:
In the present study we investigate the role of van Hove singularity on the optimization of T$\text{}_{c}$ in Rb doped fullerenes C$\text{}_{60}$ Rb$\text{}_{3}$. A first principles self-consistent full potential linear muffin-tin orbital method using density functional theory in local density approximation was employed. The doped Rb atoms are of two types occupying the tetrahedral and interstitial positions in the fcc lattice. The added Rb atoms fill the t$\text{}_{1u}$ band of the undoped fullerenes C$\text{}_{60}$ up to half which makes C$\text{}_{60}$Rb$\text{}_{3}$ conducting. Saddle points leading to van Hove singularities are observed in the neighbourhood of the symmetry point L. The shifting of the van Hove singularity with the volume of the lattice is investigated. We observe a saddle point just at the Fermi level for a lattice constant of 14.435Å. The highest value of T$\text{}_{c}$ should thus be observed at the above lattice constant. This result is in excellent agreement with the observed high value of T$\text{}_{c}$ measured in C$\text{}_{60}$Rb$\text{}_{3}$ for a lattice constant of 14.435Å.
Źródło:
Acta Physica Polonica A; 2003, 103, 5; 477-482
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Effect of Molecular Orientation on Photovoltaic Efficiency and Carrier Transport in a New Semiconducting Polymer
Autorzy:
Kažukauskas, V.
Pranaitis, M.
Sentein, C.
Rocha, L.
Raimond, P.
Duyssens, I.
Van Severen, I.
Lutsen, L.
Cleij, T.
Vanderzande, D.
Powiązania:
https://bibliotekanauki.pl/articles/1813394.pdf
Data publikacji:
2008-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.50.-h
81.40.Rs
81.40.Tv
73.61.Ph
Opis:
New functionalized soluble poly(p-phenylene vinylene) derivative bearing polar molecules was designed and synthesized in order to investigate effects of molecular orientation in polymer photovoltaic devices. The active polar molecule is the 4-(N-butyl-N-2-hydroxyethyl)-1- nitro-benzene group. The grafting of the push-pull molecule with a donor/transmitter/acceptor structure, possessing a large ground state dipole moment, enables the molecular orientation by a dc electric field. An internal electric field stored in such system facilitates exciton dissociation and improves charge transport in single-layer devices. In our systems an increase in the external quantum efficiency by a factor of about 1.5 to 2 is estimated. The associated effects of orientation on the carrier injection and transport properties were evidenced.
Źródło:
Acta Physica Polonica A; 2008, 113, 3; 1009-1012
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Scanning Tunneling Spectroscopy Study of Surface States of 3d Metals: Chemical Identification, Magnetic Contrast and Orbital Kondo Resonance States
Autorzy:
Bischoff, M. M. J.
Fang, C. M.
de Groot, R. A.
Heijnen, G. M. M.
Katsnelson, M. I.
Kolesnychenko, O. Yu.
de Kort, R.
Lichtenstein, A. I.
Quinn, A. J.
Vasquez de Parma, A. L.
Yamada, T. K.
van Kempen, H.
Powiązania:
https://bibliotekanauki.pl/articles/2036891.pdf
Data publikacji:
2003
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
73.20.-r
68.37.-d
75.70.-i
Opis:
The surface states of 3d transition metals are studied by scanning tunneling microscopy and scanning tunneling spectroscopy. The results show that surface states can be used for chemical identification with high spatial resolution. The spin polarized nature of the surface states allows us to obtain magnetic contrast in scanning tunneling miroscopy imaging with near atomic resolution. For Cr(100) we found that the surface state close to the Fermi level can be explained by an orbital Kondo resonance surface state.
Źródło:
Acta Physica Polonica A; 2003, 104, 3-4; 231-243
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
    Wyświetlanie 1-11 z 11

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