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Numerical Analysis of the Rapid Solidification Process of NiTi Binary Alloy

100%
Ternik P., Zadravec M., Svetec M., Rudolf R.
Acta Physica Polonica A
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2015
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vol. 128
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issue 1
43-47
EN
The objective of the present work is to analyse the solidification process of NiTi binary alloy. The physical medium is taken as an incompressible fluid where the heat is transferred by conduction and convection, including the thermal phase change phenomenon. The last one is modelled by the improvement procedure called enthalpy-porosity formulation, where the liquid-solid mushy zone is treated as a porous zone with porosity equal to the liquid fraction. The numerical model is based on the finite volume method in body fitted coordinates with a SIMPLER scheme to couple the pressure and velocity fields. The results are presented for the velocity and temperature field, as well as for the NiTi mass fraction during the solidification process.
2
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Ellipsometric Measurements of Plastically Deformed Copper

76%
Mirić M., Rudolf R., Anžel I., Hadžić B., Romčević M., Trajić J., Romčević N.
Acta Physica Polonica A
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2009
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vol. 116
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issue 4
715-717
EN
Chemically pure copper (99.99) prepared in the sample of square cross-section (10×10 mm^{2}) and length about 50 mm was extremely plastically deformed with the repeated application of equal channel angular pressing. Equal channel angular pressing was applied as an effective technique for producing bulk nanoscaled structures. It is well known that severe plastic deformation of metallic materials often leads to microstructure with ultrafine grains and cross-sections which remain about equal before and after deformation. Optical properties of the sample were studied using spectroscopic ellipsometry in UV-VIS range. The parameters of the sample like copper oxide and surface roughness overlayer were calculated using two-film model together with the Bruggeman effective medium approximation.
3
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Raman Spectroscopy of Multiphonon Emission Process in Ni-Doped PbTe

64%
Romčević N., Trajić J., Hadžić B., Romčević M., Stojanović D., Lazarević Z., Kuznetsova T., Khokhlov D., Rudolf R., Anžel I.
Acta Physica Polonica A
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2009
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vol. 116
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issue 1
91-92
EN
In this paper, we present room temperature unpolarized Raman scattering spectra of Ni doped PbTe single crystal sample. Crystal of PbTe(Ni) was grown by the Bridgman method. The Ni concentration in the sample used here was 1× 10^{19} at./cm^{3}. Well resolved peaks appear at about 126, 143, 181, 362 and 724 cm^{-1}. The modes at 126 and 143 cm^{-1}, which are also observed in other telluride compounds, originate from vibrations in TeO_2. We assume that the mode at about 181 cm^{-1} is connected to excitations of a local phonon mode in the vicinity of an impurity atom (donor Ni^{3+} state). Modes at about 362 cm^{-1} and 724 cm^{-1} are the second and fourth harmonic of a local phonon mode, registered here due to multiphonon emission.
4
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Determination of Stresses and Forces on the Orthodontic System by Using Numerical Simulation of the Finite Elements Method

64%
Ferčec J., Glišić B., Šćepan I., Marković E., Stamenković D., Anžel I., Flašker J., Rudolf R.
Acta Physica Polonica A
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2012
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vol. 122
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issue 4
659-665
EN
This study was addressed to use knowledge about the orthodontic system with numerical simulation of the finite elements method. For the first time we simulated the stresses on the orthodontic system and, in this manner, calculated the orthodontic force on the tooth. A 3D orthodontic model or orthodontic system was designed resembling moderate crowding in the dental arch with all supporting structures. CATIA V5 computer software was used to set up a model for the orthodontic system and ABAQUS was used for simulation of the stresses on the orthodontic system. Our attention was focused on the stresses on the tooth lateral incisor and its periodontal ligament. The results of the numerical simulation showed complex stresses on the tooth lateral incisor and its periodontal ligament. In this paper there is presented a calculation of the orthodontic force acting on the tooth lateral incisor due to the orthodontic wire. This orthodontic force was calculated from the stresses on the bracket. The calculated orthodontic force was in the area which is considered as the optimal orthodontic force for movement of the tooth.
5
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Optical Properties of Plastically Deformed Copper

64%
Trajić J., Rudolf R., Anžel I., Romčević M., Lazarević N., Mirić M., Lazarević Z., Hadžić B., Romčević N.
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issue 5
791-793
EN
Pure copper (99.99), prepared in the sample of square cross-section (10 × 10 mm^{2}) and length about 50 mm, was extremely plastically deformed with the repeated application of Equal Channel Angular Pressing (ECAP). ECAP was applied as an effective technique for producing bulk nano-scaled structures. Optical properties of the sample were investigated using Raman spectroscopy. Two types of lines: narrow (with width of ≈ 7 cm^{-1}) and wide ( ≈ 40 cm^{-1}) are registered. Existence of two types of lines indicates that in the specimen exists nano-sized crystal structures of both Cu and CuO related with three dimensional amorphous boundary spaces, which indicates that plastic deformation of the sample did not lead to total amorphisation of the specimen.
6
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Low-Frequency Raman Scattering from ZnO(Fe) Nanoparticles

64%
Kostić R., Romčević N., Romčević M., Hadžić B., Rudolf R., Kuryliszyn-Kudelska I., Dobrowolski W., Narkiewicz U., Sibera D.
Acta Physica Polonica A
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2009
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vol. 116
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issue 1
65-67
EN
Nanocrystalline samples of ZnO(Fe) were synthesized by wet chemical method. Samples were characterized by X-ray diffraction to determine the sample composition and the mean crystalline size. Low-frequency Raman modes were measured and assigned according to confined acoustic vibrations of spherical nanoparticles. Frequencies of these vibrational modes were analyzed in elastic continuum aproximation, which considers nanoparticle as homogeneous elastic sphere.
7
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Optical and Magnetic Properties of PbTe(Ni)

64%
Romčević N., Trajić J., Romčević M., Stojanović D., Kuznetsova T., Khokhlov D., Dobrowolski W., Rudolf R., Anžel I.
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EN
Far-infrared and magnetic properties of Ni doped PbTe (Z_Ni = 1× 10^{19} at./cm^{3}) single crystal are investigated in a broad range of temperature and magnetic fields. Far-infrared reflection spectra were analyzed using a fitting procedure based on the modified plasmon-two phonon interaction model. Together with the strong plasmon-two longitudinal optical phonon coupling we obtained a local mode of Ni at about 180 cm^{-1}. This mode intensity depends on temperature. Magnetic measurements shows that PbTe alloys doped with Ni reveals weak ferromagnetic interaction between magnetic ions.
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