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RISS 인기검색어
- 검색키워드
- 저자 : A. Cheikhrouhou (검색결과 3 건)
- 무료
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Simple Code for the Growth Rates of Free-Electron Lasers
R.El-Bahi,M.N.Rhimi,A.W.Cheikhrouhou 한국물리학회 2002 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.40 No.2
A model for a free-electron laser (FEL) with helical and axial magnetic elds has been investigated theoretically. The dispersion relations for the transverse and the longitudinal modes for the onedimensional linear case are derived using a uid model for the electron beam. The modes with positive and negative helicities are clearly selected. An analytically solvable expression for the growth rates of the modes, exactly in resonance with the beam, is obtained. We present a simple computer code GRFEL, based on analytical formulae and obtained within the context of the theory of FEL, which requires negligible CPU time and runs on small computers. Fixing three of the ve parameters of the FELs (the wiggler field, the axial magnetic eld, the wiggler wavevector, the electron relativistic factor, and the plasma frequency), GRFEL sweeps the spectrum of the remaining parameters, giving three-dimensional curves of the growth rate. This enables us to select the best operating zones and exclude the forbidden regions for the FEL being investigated. An output sample of GRFEL describing the dependence of the growth rate on the parameters of the system is given.
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A. Mehri,W. Cheikhrouhou Koubaa,M. Koubaa,A. Cheikhrouhou 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.63 No.3
The influence of 20% of Na doping upon the magnetic and magnetocaloric properties ofLa0.5Ca0.5MnO3, Pr0.5Sr0.5MnO3, and Nd0.5Sr0.5MnO3 perovskite manganites has been investigated. Our samples have been elaborated using the conventional solid state reaction method athigh temperature. X-Ray diffraction analysis showed that our synthesized samples are single phaseand crystallize in the orthorhombic system with Pbnm space group. Magnetic measurements versusmagnetic applied field indicated that the substituted compounds are ferromagnetic at low temperatures. The Curie temperatures are found to be 279, 299 and 292 K for La0.5Ca0.3Na0.2MnO3(LCNM), Pr0.5Sr0.3Na0.2MnO3 (PSNM), and Nd0.5Sr0.3Na0.2MnO3 (NSNM) respectively. Oursamples exhibit an important magnetic entropy change with a maximum |ΔSMaxM | found to be 1.83,6.6 and 3.1 J/kgK for LCNM, PSNM and NSNM respectively under a magnetic applied field of 4T.
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Magnetocaloric Properties in Ordered Double-perovskite Ba2Fe1−xCrxMoO6 (0 ≤x ≤1)
R. M’nassri,A. Cheikhrouhou 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.6
The magnetocaloric proprieties of Ba2Fe1−xCrxMoO6 (cubic, Fm3m) have been investigated. With the help of the phenomenological model, the temperature dependences of the magnetizationfor Ba2Fe1−xCrxMoO6 (0 ≤ x ≤ 1) in a 1 T magnetic field were simulated. The behavior of thetemperature-dependent magnetocaloric effect was investigated in the vicinity of magnetic phasetransitions. The magnetic entropy change and the specific heat were obtained. The values of themaximum magnetic entropy change, the full width at half maximum, and the relative cooling powerfor a change in the magnetic field of 1 T were calculated. The values and the shapes of −SMand −Cp strongly depended on the Cr concentration. As x was increased, the maximum valuesof −SM and −Cp decreased and the peaks of −SM and −Cp became broader. Themagnetocaloric effect of this material is large and tunable, suggesting a possible technical applicationof the material at moderate magnetic fields at temperatures near room temperature. ForBa2Fe1−xCrxMoO6, the magnetic entropy change was shown to follow a master curve behavior.
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