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Wyświetlanie 1-15 z 39
Tytuł:
2×2 MIMO VLC optical transmission system based on LEDs in a double role
Autorzy:
Kowalczyk, M.
Powiązania:
https://bibliotekanauki.pl/articles/1065670.pdf
Data publikacji:
2016-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
07.50.Qx
07.60.-j
42.72.Bj
42.79.-e
42.82
Opis:
The article presents the concept solution of two main issues of visible light communication systems, i.e. the lack of a cost-effective feedback channel and the handling of high throughput. The concept is based on merging of the multiple input multiple output approach, well-known from radio transmission domain, with using of LEDs in a double role, i.e. both as emitters and detectors of light. The feasibility of the proposal was confirmed by the results of the research, carried out for two-channel system of this type.
Źródło:
Acta Physica Polonica A; 2016, 130, 1; 41-44
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Entropy Change Calculations for Pure Gd and a Ni-Mn-Cu-Ga Heusler Alloy: Constant Field vs. Constant Temperature Experiment
Autorzy:
Ferenc, J.
Kowalczyk, M.
Wróblewski, R.
Cieślak, G.
Sielicki, K.
Leonowicz, M.
Kulik, T.
Powiązania:
https://bibliotekanauki.pl/articles/1402338.pdf
Data publikacji:
2015-07
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Sg
65.40.gd
Opis:
The magnetocaloric effect may be assessed indirectly by expressing it as the change in magnetic entropy in varying magnetic field, H, as the function of temperature, T. Magnetization, M=f(T,H), may be experimentally acquired from a series of isothermal measurements with variable field, or from a series of constant field measurements with variable temperature. The accuracy of magnetic entropy calculation depends on the number of series in these experiments. The aim of this work is to determine how little data is sufficient to obtain accurate results of magnetic entropy change calculations, on the basis of real, magnetocaloric materials. Pure gadolinium and a Ni-Mn-Cu-Ga Heusler alloy were studied. For both materials, the magnetic entropy change and relative cooling power were calculated from both experiments, with the decreasing number of experimental data. For both materials, the constant field experiment with only 6 field values provided only a 5% error of calculations, as compared to the experiment with 100 field values. The Arrott plots were also drawn for constant field mode with 6 field values, easily indicating the order of transition. Comparison of the calculation results suggests that the constant field mode magnetization measurement may be more accurate and faster than isothermal mode.
Źródło:
Acta Physica Polonica A; 2015, 128, 1; 111-115
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
X-Rays Response of Diamond Detectors Constructed Using Diamond Layers Produced by Low Power Microwave Chemical Vapor Deposition Reactor
Autorzy:
Kordyasz, A.
Bednarek, A.
Kowalczyk, M.
Tarasiuk, J.
Kulczycka, E.
Teodorczyk, M.
Gajewski, M.
Kordyasz, Ł.
Rowiński, O.
Lamparski, K.
Karwański, Ł.
Lipczewski, T.
Powiązania:
https://bibliotekanauki.pl/articles/1402641.pdf
Data publikacji:
2015-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
52.75.-d
81.15.Gh
29.40.Vj
07.85.Fv
Opis:
The low power reactor for microwave chemical vapor deposition process is described. The rotating Mo holder of 12 mm diameter and 6 mm height with the diamond substrate was heated by 2.45 GHz microwaves to temperature about 800°C in the range of (1.5-7)% $CH_{4}//H_{2}$ mixture to create plasma at pressure 70 Tr. Stabilization of the holder temperature was performed by optical observation of radiation from the holder followed by adjusting of the magnetron power. Diamond detectors are produced using microwave chemical vapor deposition process grown on single crystal diamond high pressure high temperature Sumimoto substrates, [100] oriented. The response of diamond detectors for X-rays has been measured in the current mode using medical X-rays tube. The linear response of the diamond detector current versus X-ray tube current (dose) is presented.
Źródło:
Acta Physica Polonica A; 2015, 127, 5; 1555-1559
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermoelectric Power and Thermal Conductivity of Heavy Fermion $CeCu_4Al$
Autorzy:
Falkowski, M.
Kowalczyk, A.
Powiązania:
https://bibliotekanauki.pl/articles/1426875.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
72.10.Fk
72.15.Eb
72.15.Jf
72.15.Qm
Opis:
The thermal conductivity and thermopower are discussed for the heavy fermion $CeCu_4Al$ compound. $CeCu_4Al$ is paramagnetic and follows the modified Curie-Weiss law with $μ_{eff}$ = 2.53 $μ_{B}$/f.u. and $\Theta_{P}$ = - 10 K indicating on the presence of well localized magnetic moments of $Ce^{3+}$ ions. The determined electronic specific heat coefficient γ = 2.2 J $mol^{-1}K^{-2}$ confirms the heavy fermion character of this compound. Thermopower is positive over the whole temperature range and below $T_{max}$ = 25 K falls rapidly. Based on a simple band model the position and width of the 4f peak nearest to the Fermi level have been estimated. The measured total thermal conductivity of the $CeCu_4Al$ compound increases almost linearly with increasing temperature.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1056-1058
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermoelectric Properties of $CeCu_4Ag$ Compound
Autorzy:
Kowalczyk, A.
Toliński, T.
Falkowski, M.
Timko, M.
Powiązania:
https://bibliotekanauki.pl/articles/1534756.pdf
Data publikacji:
2010-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
65.80.-g
72.15.Cz
72.20.Pa
Opis:
The magnetic and electronic properties including electrical resistivity, thermal conductivity and thermopower are discussed for the heavy fermion $CeCu_4Ag$ compound. The electrical resistivity shows a Kondo-like logarithmic increase up to a maximum at T = 75 K. Thermopower is positive over the whole temperature range and below $T_\text{max}$ = 25 K falls rapidly. The measured thermal conductivity of the $CeCu_4Ag$ compound increases with increasing temperature.
Źródło:
Acta Physica Polonica A; 2010, 118, 5; 936-937
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetocaloric Effect in $NdNi_4Si$ Compound
Autorzy:
Falkowski, M.
Toliński, T.
Kowalczyk, A.
Powiązania:
https://bibliotekanauki.pl/articles/1429061.pdf
Data publikacji:
2012-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.Sg
75.30.Kz
75.47.Np
75.40.-s
Opis:
On the basis of the thermodynamic approach, we report the magnetocaloric properties of the ternary ferromagnetic $NdNi_4Si$ compound with magnetic phase transition temperature $T_{C}$ at 8 K. The saturated magnetic moment in H = 9 T is equal to 1.5 $μ_{B}$/f.u. at 4.2 K and the compound crystallizes in the hexagonal $CaCu_5$-type structure (space group P6/mmm). The magnetocaloric effect was calculated in terms of the isothermal magnetic entropy change Δ $S_{M}$ as well as the adiabatic temperature change Δ $T_{ad}$ using the specific heat data and magnetization measurements. Within the second order phase transition significant values of these parameters have been observed.
Źródło:
Acta Physica Polonica A; 2012, 121, 5-6; 1290-1292
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Specific Heat of $YbNi_4Si$ Compound
Autorzy:
Falkowski, M.
Kowalczyk, A.
Toliński, T.
Powiązania:
https://bibliotekanauki.pl/articles/1813487.pdf
Data publikacji:
2008-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
82.80.Pv
65.40.Ba
75.20.Hr
Opis:
The specific heat of $YbNi_4Si$ has been analyzed considering the electronic contribution and the lattice contributions in frames of the Debye model. Based on the specific heat measurements, the electronic specific heat coefficient γ = 25 mJ $mol^{-1} K^{-2}$ and the Debye temperature $θ_D$ = 320 K were derived. This small value shows that $YbNi_4Si$ cannot be classified as a heavy fermion system. These studies are completed by magnetic susceptibility, X-ray photoemission spectroscopy, and electrical resistivity.
Źródło:
Acta Physica Polonica A; 2008, 113, 2; 641-644
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Magnetic Susceptibility of Pb$\text{}_{1-x-y}$Sn$\text{}_{y}$Mn$\text{}_{x}$Se
Autorzy:
Górska, M.
Anderson, J.
Kowalczyk, L.
Powiązania:
https://bibliotekanauki.pl/articles/1887157.pdf
Data publikacji:
1991-02
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.20.Ck
75.30.Et
Opis:
Magnetic susceptibility has been measured in Pb$\text{}_{1-x-y}$Sn$\text{}_{y}$Mn$\text{}_{x}$Se with x values up to 0.02 and y values up to 0.05. The measurements were carried out using a SQUID system over a temperature range from 5 to 250 K. The susceptibility followed the Curie-Weiss relation with a small paramagnetic Curie temperature that indicated a weak antiferromagnetic exchange interaction between Mn ions. We analyzed the results together with our previously published data on high-field magnetization in this material. A reasonable agreement of the exchange parameters obtained from the low-field susceptibility and high-field magnetization data was obtained.
Źródło:
Acta Physica Polonica A; 1991, 79, 2-3; 385-387
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Structure and X-Ray Photoelectron Spectra of YNi$\text{}_{4}$B Compound
Autorzy:
Pugaczowa-Michalska, M.
Chełkowska, G.
Kowalczyk, A.
Powiązania:
https://bibliotekanauki.pl/articles/2036993.pdf
Data publikacji:
2003-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Eh
82.80.Pv
71.20.-b
63.70.+h
Opis:
The electronic structure of the ternary YNi$\text{}_{4}$B compound, crystallizing in the hexagonal CeCo$\text{}_{4}$B structure (P6/ mmm space group), was studied by X-ray photoelectron spectroscopy and ab initio calculations. Core levels and the valence band were investigated. The X-ray photoelectron spectroscopy valence band is compared with that obtained from ab initio calculations. The valence band spectrum at the Fermi level exhibits the domination of the Ni(3d) states, which are hybridized with 4d states of Y and 2p states of B. The theoretical electronic specific heat coefficientγ derived from N(E$\text{}_{F}$) is about 11.33 mJ/(mol K$\text{}^{2}$) for experimental lattice parameters. The calculated bulk modulus is B$\text{}_{0}$=1.61632 Mbar.
Źródło:
Acta Physica Polonica A; 2003, 104, 5; 487-494
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Valence Band and Core Levels of $Ce_5Ni_2Si_3$ Crystal Studied by X-ray Photoemission Spectroscopy
Autorzy:
Toliński, T.
Kowalczyk, A.
Chełkowska, G.
Mihalik, M.
Timko, M.
Powiązania:
https://bibliotekanauki.pl/articles/1813673.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.Eh
82.80.Pv
Opis:
The crystal of $Ce_5Ni_2Si_3$ was prepared by the Czochralski method. The X-ray photoemission spectroscopy was measured for the valence band and the core levels. Based on the Ce(3d) doublet and its satellites a small value of the hybridization parameter of the f-states with the conduction electrons Δ=4 meV and the f-occupancy $n_f$ close to 1 were found. X-ray photoemission spectroscopy shows that the region between 0 and 3 eV is predominated by the Ni(3d) and Ce(4f) peaks. Some features of the multiplet structure of the Ce(4f) states are also visible close to the Fermi level.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 327-330
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heat Capacity of Heavy Fermion Compound $CeCu_4Ga$ in High Magnetic Fields
Autorzy:
Kowalczyk, A.
Toliński, T.
Reiffers, M.
Zapotoková, M.
Falkowski, M.
Gažo, E.
Powiązania:
https://bibliotekanauki.pl/articles/1810399.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
65.40.Ba
71.20.Eh
71.27.+a
Opis:
The heat capacity in the applied magnetic field up to 9 T, susceptibility and magnetization of polycrystalline $CeCu_{4}Ga$ are presented. Magnetic ordering was not observed down to 2 K. For temperature T < 200 K a Curie-Weiss behavior is observable giving an effective magnetic moment $μ_\text{eff}$ =2.53 $μ_{B}$/f.u. The experimental value of $μ_\text{eff}$ is close to the calculated one for a free $Ce^{3+}$ ion ($μ_\text{eff}$ = 2.54 $μ_{B}$/f.u.), thus indicating the presence of well localized magnetic moments carried by the stable $Ce^{3+}$ ions. At low temperatures the electronic heat capacity coefficient value depends strongly on the temperature range used for the extrapolation and applied magnetic field. We observe a typical heavy fermion behavior with γ value of about 380 mJ $\text{mol}^{-1} K^{-2}$ obtained from extrapolation to T = 0 K of the temperature range above 7 K. However, extrapolation of the lowest temperatures range yields the γ value of 3.3 J $\text{mol}^{-1} K^{-2}$.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 123-125
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Heat Capacity Studies of $NdNi_4Si$ Compound
Autorzy:
Falkowski, M.
Reiffers, M.
Zapotoková, M.
Kowalczyk, A.
Toliński, T.
Gažo, E.
Powiązania:
https://bibliotekanauki.pl/articles/1810401.pdf
Data publikacji:
2009-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
65.40.De
65.40.gd
71.20.Eh
71.70.-d
Opis:
The study of the heat capacity of the intermetallic compound $NdNi_{4}Si$ including the effect of the magnetic field is reported. This compound crystallizes in the hexagonal $CaCu_5$-type structure, space group P6/mmm. $NdNi_{4}Si$ is ferromagnetic with $T_C$ = 8 K and the saturation magnetic moment of 1.5 $μ_{B}$/f.u. at 4.2 K (in H = 9 T). The heat capacity was analyzed considering the electronic contribution, the Schottky anomaly, and the lattice contributions in the frames of the Debye model. The scheme of the energy levels created by the crystal electric field split is determined from the Schottky contribution to the specific heat. $NdNi_{4}Si$ was characterized by the electronic heat capacity coefficient γ = 85 mJ/(mol $K^2$) and the Debye temperature $Θp_D$ = 325 K.
Źródło:
Acta Physica Polonica A; 2009, 115, 1; 126-128
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Frequency Domain Optical Coherence Tomography Techniques in Eye Imaging
Autorzy:
Wojtkowski, M.
Kowalczyk, A.
Targowski, P.
Gorczyńska, I.
Powiązania:
https://bibliotekanauki.pl/articles/2035626.pdf
Data publikacji:
2002-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
42.30.Wb
42.66.Ew
42.66.-p
07.60.-j
07.60.Ly
Opis:
This contribution presents an application of frequency-domain optical tomography to ophthalmology. Essential theoretical foundations of time-domain and frequency-domain optical tomography are presented. Images of sections through the anterior chamber, the corneo-scleral angle and fundus of the eye are reconstructed from the spectral fringes. The morphological information gained by tomograms is important for diagnosing and planning of a treatment of glaucoma.
Źródło:
Acta Physica Polonica A; 2002, 102, 6; 739-746
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Electronic Properties of CeNiAl₄ Based on ab initio Calculations and XPS Measurements
Autorzy:
Werwiński, M.
Chełkowska, G.
Szajek, A.
Kowalczyk, A.
Powiązania:
https://bibliotekanauki.pl/articles/1030430.pdf
Data publikacji:
2018-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.b
74.25.Jb
Opis:
The CeNiAl₄ compound crystallizes in an orthorhombic YNiAl₄-type structure with a Cmcm space group. The earlier susceptibility data and X-ray photoelectron spectroscopy (XPS) suggested a localized character of the 4f states in CeNiAl₄ with a valence state close to a Ce⁺³ ion. In this work we present a combined theoretical and experimental study of the electronic structure for the Kondo dense system CeNiAl₄ based on the XPS data and ab initio calculations. Using the band structure calculations the theoretical XPS valence band spectra are evaluated. Below the Fermi energy the total density of states contains mainly 3d states of Ni hybridized with Ce 4f states.
Źródło:
Acta Physica Polonica A; 2018, 133, 3; 517-519
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Thermoelectric Power of $CeNi_4Si$ and $YbNi_4Si$ Compounds
Autorzy:
Falkowski, M.
Kowalczyk, A.
Tran, V.
Miiller, W.
Powiązania:
https://bibliotekanauki.pl/articles/1813661.pdf
Data publikacji:
2008-01
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.20.-b
72.20.Pa
71.28.+d
Opis:
The thermoelectric power was measured from 4.2 to 300 K for $CeNi_4Si$ and $YbNi_4Si$. The thermoelectric power was analysed in the framework of the phenomenological resonance model. According to the model the dominant contribution to thermopower is caused by scattering between electrons of a broad s-band and a narrow f-band with the Lorentzian shape. The electron-hole analogy is reflected in the thermoelectric power behaviour of the investigated compounds.
Źródło:
Acta Physica Polonica A; 2008, 113, 1; 303-306
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 39

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