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Wyświetlanie 1-15 z 19
Tytuł:
The Influence of Lamellar Graphite Cast Iron Annealing on Hardness and Structure
Autorzy:
Roučka, J.
Prochazka, J.
Kana, V.
Krutis, V.
Nedelova, K.
Powiązania:
https://bibliotekanauki.pl/articles/380964.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
cast iron
welding
annealing
cast iron hardness
structure stability
żeliwo
spawanie
wyżarzanie
twardość żeliwa
struktura
stabilność
Opis:
An analysis has been carried out of the influence of annealing time at the preheating temperature of 650 °C on the change in hardness and alloy structure of lamellar graphite cast iron in the working as well as in the laboratory conditions. This preheat temperature is common during reclaiming welding of castings with complex shapes. The changes in unalloyed cast iron EN-GJL 200 to EN-GJL 300 according to ISO 1690 standard and cast iron with low amount of elements such as Sn, Cu, Cr, and Mo and their combinations were assessed. It was found that the cast iron of higher strength grades has better hardness and structural stability. Cast iron alloyed with chromium or its combinations has the highest stability. In unalloyed cast iron, a partial degradation of pearlite occurs; in alloyed cast iron the structural changes are not conclusive.
Źródło:
Archives of Foundry Engineering; 2019, 4; 105-112
1897-3310
2299-2944
Pojawia się w:
Archives of Foundry Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Analytical method for determining antropometric parameters in body mass reduction process in the aspect of health safety
Analityczna metoda określania parametrów antropometrycznych w procesie redukcji masy ciała w aspekcie bezpieczeństwa zdrowia
Autorzy:
Ślęzak, A.
Ślęzak-Prochazka, I.
Batko, K. M.
Zyska, A.
Gawrys, W.
Jóźwiak, J.
Powiązania:
https://bibliotekanauki.pl/articles/103598.pdf
Data publikacji:
2017
Wydawca:
Uniwersytet Humanistyczno-Przyrodniczy im. Jana Długosza w Częstochowie. Wydawnictwo Uczelniane
Tematy:
overweight reduction
mathematical model
bioelectric impendance method
overweight reduction coefficient
low-sugar diet
health security
redukcja nadwagi
model matematyczny
metoda impedancji bioelektrycznej
współczynniki redukcji nadwagi
dieta niskocukrowa
bezpieczeństwo zdrowotne
Opis:
In this study, for the first time we developed a mathematical model showing that the reduction in parameters such as total body mass, total fat mass, visceral fat mass, waist circumference, hip circumference and body mass index (BMI) can be described using exponential equations. Constants kt, kf, kfv, kBMI, kp, kb that occur in particular equations characterize individual features related to these anthropometric parameters. The presented model was verified using experimental data obtained by analysis of body composition. These individuals were overweight in the initial moment of the experiment and eliminated or limited easily digestible products containing sugar from their diet. We showed that there is a critical time, when each individual achieved normal values of body mass index, fat mass, visceral fat mass, waist circumference, hip circumference, and waist-hip ratio. This critical time ranged between 35 and 46 weeks.
W tym badaniu jako pierwsi opracowaliśmy model matematyczny pokazujący, że zmniejszenie parametrów, takich jak całkowita masa ciała, całkowita masa tłuszczu, trzewna masa tłuszczowa, obwód talii, obwód bioder i wskaźnik masy ciała (BMI), można opisać za pomocą równania wykładniczego. Stałe kt, kf, kfv, kBMI, kp, kb występujące w poszczególnych równaniach charakteryzują poszczególne cechy związane z tymi parametrami antropometrycznymi. Przedstawiony model zweryfikowano za pomocą danych eksperymentalnych uzyskanych poprzez analizę składu ciała. Osoby badane miały nadwagę w początkowym momencie eksperymentu i wyeliminowały lub ograniczyły z diety łatwo przyswajalne produkty zawierające cukier. Pokazaliśmy krytyczny czas, kiedy każdy człowiek osiąga normalne wartości wskaźnika masy ciała, masy tłuszczu, masy trzewnej, obwodu talii, obwodu bioder i stosunku talii do bioder. Ten krytyczny czas waha się od 35 do 46 tygodni.
Źródło:
Prace Naukowe Akademii im. Jana Długosza w Częstochowie. Technika, Informatyka, Inżynieria Bezpieczeństwa; 2017, T. 5; 191-208
2300-5343
Pojawia się w:
Prace Naukowe Akademii im. Jana Długosza w Częstochowie. Technika, Informatyka, Inżynieria Bezpieczeństwa
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positronium Probing of Pores in Zirconia Nanopowders
Autorzy:
Prochazka, I.
Cizek, J.
Lukac, F.
Melikhova, O.
Hruska, P.
Anwand, W.
Liedke, M.
Konstantinova, T.
Danilenko, I.
Powiązania:
https://bibliotekanauki.pl/articles/1033930.pdf
Data publikacji:
2017-11
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.Wx
61.46.Hk
78.70.Bj
Opis:
In the present paper, conventional positron lifetime measurements on selected zirconia-based nanopowders are reported. The nanopowders were doped with various metal cations (Y³⁺, Eu³⁺, Gd³⁺, Lu³⁺ and Mg²⁺). Lifetime experiments were conducted in air and supplemented with mass density measurements. In a range of lifetimes, from a few ns to ≈70 ns, up to two individual lifetime components could be identified. Such observations confirmed positronium (Ps) formation with subsequent ortho-Ps pick-off annihilation as well as the occurrence of pores of different size. Pore sizes were estimated using a shape-free model of the correlation between pore size and ortho-Ps lifetime. The origins of pores are discussed on the basis of the ortho-Ps data in combination with the results of mass density measurements.
Źródło:
Acta Physica Polonica A; 2017, 132, 5; 1564-1567
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Defects in Zirconia Nanomaterials Doped with Rare-Earth Oxides
Autorzy:
Prochazka, I.
Cizek, J.
Melikhova, O.
Konstantinova, T.
Danilenko, I.
Powiązania:
https://bibliotekanauki.pl/articles/1338541.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
81.07.Wx
61.46.Hk
78.70.Bj
Opis:
Positron lifetime and coincidence Doppler broadening measurements on $ZrO_2$+3 mol.% $RE_2O_3$ (RE = Eu, Gd, Lu) nanopowders and ceramics obtained by sintering these nanopowders are reported. The initial nanopowders were prepared by a co-precipitation technique and exhibited a mean particle size of ≈ 15 nm. The nanopowders were calcined and pressure-compacted. All compacted nanopowders exhibited the prevailing tetragonal phase with at most 15% of the monoclinic admixture. Positrons in compacted nanopowders were found to annihilate almost exclusively at grain boundaries: (i) vacancy-like misfit defects along grain boundaries and (ii) larger defects situated at intersections of grain boundaries (triple points). In nanopowders, a small portion of positrons formed positronium in pores between crystallites. Sintering of nanopowders at 1500C caused a substantial grain growth and formation of ceramics. Sintering-induced grain growth led to a disappearance of the triple points and pores. The ceramics containing Eu and Gd dopants consist of mixture of the monoclinic and the tetragonal phase, while the ceramics with Lu dopant exhibits almost exclusively the tetragonal phase.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 760-763
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Defects Studies of ZnO Single Crystals Prepared by Various Techniques
Autorzy:
Lukáč, F.
Čížek, J.
Procházka, I.
Melikhova, O.
Anwand, W.
Brauer, G.
Powiązania:
https://bibliotekanauki.pl/articles/1196118.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
61.72.J-
Opis:
The aim of the present work was a comparison of defects in ZnO crystals grown by various techniques available nowadays, namely hydrothermal growth, pressurized melt, Bridgman method growth and vapor phase growth. Positron annihilation spectroscopy was employed as a principal tool for characterization of defects in ZnO crystals grown by above mentioned various techniques. ZnO crystals can be divided into two groups: (i) hydrothermal grown crystals, which exhibit positron lifetime of 179-182 ps and (ii) ZnO crystals grown by the other techniques (pressurized melt, Bridgman method, vapor phase growth) which are characterized by the lower lifetimes falling in the range of 160-173 ps. Comparison of experimental data with ab initio theoretical calculations revealed that HT grown ZnO crystals contains Zn vacancies associated with hydrogen atom in a bond-centered site. On the other hand, ZnO crystals prepared by other techniques contain most probably stacking faults created by stresses induced by temperature gradients in the melt.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 748-751
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hydrogen-Induced Defects in Palladium
Autorzy:
Melikhova, O.
Čížek, J.
Procházka, I.
Powiązania:
https://bibliotekanauki.pl/articles/1338026.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
61.72.-y
Opis:
In the present work positron annihilation spectroscopy was employed for investigation of hydrogen-induced defects in Pd. Well annealed Pd samples were electrochemically charged with hydrogen and development of defects with increasing hydrogen concentration $x_{H}$ was investigated. At low concentrations (α-phase, $x_{H}$ < 0.017 H/Pd) hydrogen loading introduced vacancies, since absorbed hydrogen segregating at vacancies lowers remarkably the vacancy formation energy. When hydrogen concentration exceeds 0.017 H/Pd, particles of palladium hydride (PdH) are formed. Stress induced by growing PdH particles leads to plastic deformation which generates dislocations and vacancies in the sample.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 752-755
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Investigation of Precipitation Effects in Mg-Tb and Mg-Tb-Nd Alloys
Autorzy:
Vlček, M.
Čížek, J.
Melikhova, O.
Hruška, P.
Procházka, I.
Powiązania:
https://bibliotekanauki.pl/articles/1196115.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
61.72.J-
Opis:
Investigation of precipitation effects in solution treated Mg-Tb and Mg-Tb-Nd alloy was performed. Solution treated alloys were compared with samples deformed by high pressure torsion to examine influence of deformation on precipitation effects. Dislocations present in samples processed by high pressure torsion can serve as diffusion channels for atoms and also as nucleation sites for precipitates. Therefore precipitation of some phases in high pressure torsion deformed samples was observed at lower temperatures than in solution treated ones.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 744-747
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Precipitation Effects in Mg-Zn Alloys Studied by Positron Annihilation and Hardness Testing
Autorzy:
Hruška, P.
Čížek, J.
Vlček, M.
Melikhova, O.
Procházka, I.
Powiązania:
https://bibliotekanauki.pl/articles/1196079.pdf
Data publikacji:
2014-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
61.72.J-
Opis:
In the present work positron annihilation spectroscopy combined with Vickers hardness testing were employed in order to investigate precipitation effects in Mg-Zn alloys. It was found that incoherent precipitates of a metastable Zn-rich phase formed in the samples isochronally annealed above 200C cause hardening of the alloy.
Źródło:
Acta Physica Polonica A; 2014, 125, 3; 718-721
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Hydrogen Interaction with Vacancies in Electron Irradiated Niobium
Autorzy:
Čižek, J.
Procházka, I.
Brauer, G.
Anwand, W.
Gemma, R.
Nikitin, E.
Kirchheim, R.
Pundt, A.
Powiązania:
https://bibliotekanauki.pl/articles/1812478.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
61.72.-y
Opis:
Defect studies of Nb irradiated with 10 MeV electrons were performed in the present work by means of positron annihilation spectroscopy. The lattice defects were characterized by positron lifetime spectroscopy. Moreover, defect depth profiles were studied by slow positron implantation spectroscopy. The experimental investigations were accompanied by first principles theoretical calculations of positron parameters. It was found that irradiation-induced vacancies in Nb specimens are surrounded by H, which causes a shortening of the lifetime of trapped positrons. The influence of a Pd and Cr over-layer on the H concentration in the Nb specimens was examined.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1293-1299
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Influence of Ceramic Nanoparticles on Thermal Stability of Ultra Fine Grained Copper
Autorzy:
Čížek, J.
Procházka, I.
Cieslar, M.
Islamgaliev, R.
Kulyasova, O.
Powiązania:
https://bibliotekanauki.pl/articles/1812477.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
79.60.Jv
Opis:
A detailed study of the bulk ultra fine grained pure copper and copper with $Al_2O_3$ particles was carried out in the present work. The specimens were prepared by the high-pressure torsion and their microstructure was investigated by positron lifetime spectroscopy combined with transmission electron microscopy and microhardness tests. Defects in the as-deformed materials were characterized and the thermal stability of the ultra fine grained microstructure was subsequently examined in annealing experiments. An addition of $Al_2O_3$ nanoparticles was found to improve significantly the thermal stability of the ultra fine grained structure, the optimum content of $Al_2O_3$ being ≈0.5 wt.%.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1285-1292
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Performance of a High-Resolution Digital Positron-Lifetime Spectrometer
Autorzy:
Bečvář, F.
Čížek, J.
Procházka, I.
Powiązania:
https://bibliotekanauki.pl/articles/1812465.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
Opis:
This work describes a digital positron-lifetime spectrometer based on two ultrafast digitizers. Performance of the digital spectrometer in conditions of a routine measurement is compared with an analogue setup connected to the same detectors. It was found that engagement of the digital setup leads to an improvement of timing resolution (FWHM for $\text{}^{22}Na$) from 169 ps for the traditional analogue setup to 146 ps for the digital setup. The coincidence count rate for 1.2 MBq $\text{}^{22}Na$ source is 75-80 coinc./s for both configurations. These results clearly demonstrate the advantages of the digital timing over the traditional analogue setup.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1279-1284
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Positron Lifetimes in Zirconia-Based Nanomaterials
Autorzy:
Procházka, I.
Čížek, J.
Kuriplach, J.
Melikhova, O.
Konstantinova, T.
Danilenko, I.
Powiązania:
https://bibliotekanauki.pl/articles/1812546.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
61.46.Hk
81.05.Je
81.07.Wx
Opis:
Positron lifetime spectroscopy is employed in a comparative study of several zirconia-based materials: (i) the pressure-compacted nanopowders of the three zirconia polymorphs - pure $ZrO_2$ (monoclinic), yttria-stabilized $ZrO_2$+3 mol.% $Y_2O_3$ (tetragonal) and yttria-stabilized $ZrO_2$+8 mol.% $Y_2O_3$ (cubic), (ii) ceramic materials obtained by sintering of the above two yttria-stabilized zirconia nanopowders and (iii) the tetragonal and cubic yttria-stabilized zirconia monocrystals. Positron lifetime data observed on the nanopowders suggest that the two shortest components, exhibiting lifetimes of ≈180 and ≈370 ps, arise from the annihilation of positrons trapped in defects associated with grain boundaries, presumably the vacancy-like defects and tripple points, respectively. Positron lifetime spectra observed on the ceramic materials resemble those found for the corresponding monocrystals, giving thus an additional support to the above interpretation of the nanopowders results.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1495-1499
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simulation of Positron Annihilation Response to Mechanical Deformation of Nanostructured AgCo
Autorzy:
Melikhova, O.
Kuriplach, J.
Čížek, J.
Procházka, I.
Hou, M.
Pisov, S.
Zhurkin, E.
Powiązania:
https://bibliotekanauki.pl/articles/1812541.pdf
Data publikacji:
2008-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
71.15.Pd
61.46.Hk
Opis:
Nanostructured materials attract nowadays a broad attention due to their specific properties. Defects play an essential role in material properties so their characterisation is very important. The evolution of the various open volume defects in AgCo nanowire modelled samples obtained using molecular dynamics was studied. Isothermal and isoenergetic deformation mechanisms are considered. General analyses of open volume defects concerning their size and their chemical environment were performed. Positron lifetimes, binding energies, and high momentum parts of the momentum distribution of annihilationγ-quanta were calculated for selected defects.
Źródło:
Acta Physica Polonica A; 2008, 113, 5; 1455-1464
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Local Magnetic and Electronic Properties of the A$\text{}_{2}$FeM'O$\text{}_{6}$ (A = Ba, Sr, Ca, M' = Mo, Re) Double Perovskites
Autorzy:
Zając, D.
Sikora, M.
Prochazka, V.
Borowiec, M.
Stępień, J.
Kapusta, Cz.
Riedi, P. C.
Marquina, C.
De Teresa, J. M.
Ibarra, M. R.
Powiązania:
https://bibliotekanauki.pl/articles/2047344.pdf
Data publikacji:
2007-06
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
75.30.-m
76.60.-k
76.60.Jx
78.80.En
Opis:
The results of a combined NMR, X-ray absorption spectroscopy and X-ray magnetic cirrcular dichroism study of the AA'FeMoO$\text{}_{6}$ and AA'FeReO$\text{}_{6}$ double perovskites are presented. They revealed a dependence of electronic and magnetic properties, including a d-electron transfer between Fe and Mo sites, on the structural tolerance factor. The maximum value of the 4d Mo electron occupation and the corresponding Mo moment is obtained for the tolerance factor of unity. This corresponds to the maximum strength of the magnetic interaction and, respectively, to the Curie temperature. The dominant T$\text{}^{5}\text{}^{/}\text{}^{2}$ type temperature dependence of the Mo hyperfine field reveals the half-metallicity of the AA'FeMoO$\text{}_{6}$ compounds. Antisite defects and antiphase boundaries have been identified in NMR measurements and the strength of their magnetic coupling have been determined. A considerable orbital contribution to the Re and Fe magnetic moments were found in the NMR and X-MCD measurements on the AA'FeReO$\text{}_{6}$ compounds. Its magnitude decreases with increasing structural tolerance factor and is correlated with their magnetic anisotropy.
Źródło:
Acta Physica Polonica A; 2007, 111, 6; 797-820
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Defects in Ultra-Fine Grained Mg and Mg-Based Alloys Prepared by High Pressure Torsion Studied by Positron Annihilation
Autorzy:
Čížek, J.
Procházka, I.
Smola, B.
Stulíková, I.
Kužel, R.
Matěj, Z.
Cherkaska, V.
Islamgaliev, R.
Kulyasova, O.
Powiązania:
https://bibliotekanauki.pl/articles/2043304.pdf
Data publikacji:
2005-05
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
78.70.Bj
79.60.Jv
61.72.-y
Opis:
Despite the favourable strength and thermal stability, a disadvantage of the Mg-based alloys consists in a low ductility. Recently it has been demonstrated that ultra fine grained metals with grain size around 100 nm can be produced by high pressure torsion. A number of ultra fine grained metals exhibit favourable mechanical properties consisting in a combination of a very high strength and a significant ductility. For this reason, it is highly interesting to examine microstructure and physical properties of ultra fine grained Mg-based light alloys. Following this purpose, microstructure investigations and defect studies of ultra fine grained pure Mg and ultra fine grained Mg-10%Gd alloy prepared by high pressure torsion were performed in the present work using positron annihilation spectroscopy combined with X-ray diffraction, TEM observations, and microhardness measurements. Positrons are trapped at dislocations in Mg and Mg-10%Gd alloy deformed by high pressure torsion. A number of dislocations increases with the radial distance r from the centre to the margin of the sample. No microvoids (small vacancy clusters) were detected. Mg-10%Gd alloy deformed by high pressure torsion exhibits a homogeneous ultra fine grained structure with a grain size around 100 nm and high dislocations density. On the other hand, pure Mg deformed by high pressure torsion exhibits a binomial type of structure which consists of "deformed regions" with ultra fine grained structure and a high dislocation density and dislocation-free "recovered regions" with large grains. It indicates a dynamic recovery of microstructure during high pressure torsion processing.
Źródło:
Acta Physica Polonica A; 2005, 107, 5; 738-744
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
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