Yazar "Demirci, M." seçeneğine göre listele

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    An analysis on the relation between the seed distance and vertical levitation force for the multi-seeded YBCO using the modified advanced frozen image (MAFI) and experimental methods
    (Elsevier Science Sa, 2019) Ozturk, K.; Guner, S. B.; Abdioglu, M.; Demirci, M.; Celik, S.; Cansiz, A.
    The higher magnetic levitation force and related stiffness values are very important for Maglev and magnetic bearing applications. Also, larger superconducting surface area is needed for continuous and larger magnetic mediums with different geometries and dimensions in real scale industrial applications of superconducting systems. In this study, the cylindrical YBCO superconductors were fabricated by top-seeded melt growth (TSMG) method in single and two-seeded forms with different seed distances and then the magnetic force and stiffness measurements were carried out by three axes magnetic force measurement system in different cooling heights (CH) of 20mm and 75 mm. Additionally, a new analytical method, based on the magnetic dipole approximation, is proposed to calculate the levitation force in this study, named as Modified Advanced Frozen Image Method (MAFI), since although the Advanced Frozen Image Method in literature can calculate the levitation force with hysteresis, this method does not include the size effect of the superconductor. In the experimental studies, it is seen that the maximum levitation force values obtained by PMG with three PMs (named PMG-1) are more than two times higher than that of obtained with single PM for all samples with different distance of seeds, because of the higher magnetic flux distribution of related PMG arrangement than the single PM. In addition, the maximum magnetic levitation force value firstly increased and then decreased due to current coupling effect weakness by increasing distance of seeds. The calculated analytical levitation force results are not compatible with the experimental results without current coupling effect, but a well agreement is observed when the current coupling effect is taken into account in calculations. Also the MAFI method was tested with different dimensions of superconductors and the obtained results indicated the success of the proposed method. The maximum levitation force values obtained with MAFI method increased with increasing dimensions of HTS and PMs. Thus, one can say that the MAFI method is useful for the levitation force calculations between multi-seeded superconductors and PMGs with different dimensions and for different CHs. As a result, the analytical levitation force values obtained with the MAFI method are agree with the experimental levitation force sufficiently and this method can give fast calculation results without any divergence problem. This method can be thought as an alternative to the numerical calculation methods, having serious divergence problems for much amount and bigger size superconducting samples, therefore it will be useful to clarify bulk superconducting properties as supporter to the experimental studies. (C) 2019 Elsevier B.V. All rights reserved.
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    Calculation of Fission Barrier of 230-234Pa Isotopes
    (Azerbaijan Journal of Physics - Fizika, 2010) Yılmaz, Ahmet Hakan; Engin, B.; Bayram, Tuncay; Demirci, M.
    The fission barriers of 230-234Pa have been carried out by using the BARRIER code developed by Garcia. The nuclear shape has been parameterized in terms of Cassini ovaloids proposed by Pashkevich. The single- particle energies have been calculated as function of the deformation parameters of an axially deformed Woods-Saxon potential, as input to the shell correction calculations. To obtain the total nuclear energy, it is also necessary to add a pairing energy in order to take into consideration the short range nuclear interactions.
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    Ground State Nuclear Properties of Some Rare Earth Nuclei in Relativistic Mean Field Theory
    (Azerbaijan Journal of Physics - Fizika, 2010) Yılmaz, Ahmet Hakan; Bayram, Tuncay; Demirci, M.; Engin, B.
    In this study, rare earth nuclei, 160Gd, 168Er , 170Er and isotopic chain of Dy were investigated using relativistic mean field theory with non-linear NL3 and NLSH parameters sets. Binding energies per nucleon, neutron radii, proton radii, charge radii, neutron and proton quadrupole moments of these nuclei were calculated. Also, these ground state properties were calculated using non-relativistic Hartree-Fock-Bogoliubov method with parameters set SKP. Predictions of this work were compared with available experimental data and some predictions calculated with different parameters set in relativistic mean field theory.
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    Ground State Nuclear Propertıes Of Mo And Ru Isotopes In Skyrme-Hartree-Fock-Bogolıubov Method
    (Balkan Physics Letters, 2011) Bayram, Tuncay; Yılmaz, Ahmet Hakan; Engin, B.; Demirci, M.
    Ground-state nuclear properties of Mo and Ru isotopes were studied within the Hartree-Fock-Bogoliubov method with SL y4 and SL y5 Skyrme forces. Nuclei which have neutron numbers close to magic number 50 have received much attention because the nuclei are known well deformed and exhibit anomalous behaviour in the isotope shifts. Therefore, a systematic study of even-even Mo and Ru isotopes was carried out. Almost all ground-state properties which include binding energy per nucleon, quadrupole deformation, nuclear radii, two -neutron separation energyand shape-coexistence for axially deformed Mo and Ru isotopes were analyzed. The results were compared with available experimental data and predictions of some nuclear models (Finite Range Liquid-Drop Model (FRDM), Extended Thomas Fermi Model with Strutinski Integral (ETF-SI) and Relativistic Mean Field (RMF) Theory) and discussed in detail. The results show that the HFB method with SLy4 and SL y5 Skyrme forces is capable of describing of isotopic chain of even-even Mo and Ru nuclei.
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    Ground-State Properties of Axially Deformed Sr Isotopes in Skyrme-Hartree-Fock-Bogoliubov Method
    (Azerbaijan Journal of Physics - Fizika, 2010) Yılmaz, Ahmet Hakan; Bayram, Tuncay; Demirci, M.; Engin, B.
    Binding energies, the mean-square nuclear radii, neutron radii, quadrupole moments and deformation parameters to axially deformed Strontium isotopes were evaluated using Hartree-Fock-Bogoliubov method. Shape coexistence was also discussed. The results were compared with experimental data and some estimates obtained within some nuclear models. The calculations were performed for Sly4 set of Skyrme forces and for a wide range of the neutron numbers of Sr isotopes.
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    Investigation Of Some Even-Even Mo Nuclei In Relativistic Mean Field Theory
    (Balkan Physics Letters, 2010) Bayram, Tuncay; Zengin, Z.; Demirci, M.; Yılmaz, Ahmet Hakan
    The structures of the nuclei on isotope chain of even-even Mo are investigated in the axially deformed relativistic mean-field theory with the NL-SH forces. We put an emphasis on the ground state properties of molybdenum nuclei. With high neutron number is correctly reproduced in the relativistic mean-field theory (RMF). In general, the RMF theory can give a good description of the isotope chain of Mo nuclei.