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저에너지 양전자 소멸 분광법을 이용한 MgB<sub>2</sub> 박막 구조 특성
Lee, C.Y.,Kang, W.N.,Nagai, Y.,Inoue, K.,Hasegawa, M. 한국진공학회 2008 Applied Science and Convergence Technology Vol.17 No.2
저속 에너지 도플러 넓어짐 양전자 소멸 분광법으로 $MgB_2$ 박막내의 원자 크기 정도 고체 구조 특성에 대하여 조사하였다. 양전자와 전자의 쌍소멸로 발생하는 511keV 감마선 스펙트럼의 수리적 해석 방법인 S-변수를 사용하여, 상전이 근처 온도에서 박막의 구조 변화를 측정하였다. 비등방성 구조로 된 $MgB_2$ 박막에서 초전도 특성을 갖는 상전이 온도 근처에서 S-변수를 측정하였다. 양전자의 입사 에너지 10keV에서 측정된 S-변수의 최고치는 박막의 온도가 30K에서 0.567이고, 50 K에서는 0.570로 큰 변화는 없었다. 이 결과로부터 양전자가 Boron 층의 초 전자와 소멸하기 보다는 Mg층 근처의 상 전자와 소멸하는 것으로 판단된다. $MgB_2$의 박막의 외층은 Mg층으로 이루어졌다고 할 수 있다. The Characterization of $MgB_2$ Thin Film by Slow Positron Annihilation Spectroscopy Enhance signal-to-noise ratio, slow positron coincidence Doppler Broadening method has been applied to study of characteristics of $MgB_2$ superconductor film, which were performed at 30 K and 50 K sample temperature near Tc of it. In this investigation the numerical analysis of the Doppler spectra was employed to the determination of the shape parameter, S, defined as the ratio between the amount of counts in a central portion of the spectrum and the total counts of whole spectrum. The S-parameter values were increased then decreased while the positron implantation energies were increasing, that indicated the diffusion into the samples. The S-parameters of the anisotropic 1 ${\mu}m$ $MgB_2$ thin film which were implanted by positrons at 10 keV are 0.567 at 30 K and 0.570 at 50 K. It is believed that the positrons annihilate with normal-electrons instead of super-electrons in the $MgB_2$ superconductor.
저에너지 양전자 소멸 분광법을 이용한 MgB₂ 박막 구조 특성
이종용(C. Y. Lee),강원남(W. N. Kang),M. Hasegawa,Y. Nagai,K. Inoue 한국진공학회(ASCT) 2008 Applied Science and Convergence Technology Vol.17 No.2
저속 에너지 도플러 넓어짐 양전자 소멸 분광법으로 MgB₂ 박막내의 원자 크기 정도 고체 구조 특성에 대하여 조사하였다. 양전자와 전자의 쌍소멸로 발생하는 511keV 감마선 스펙트럼의 수리적 해석 방법인 S-변수를 사용하여, 상전이 근처 온도에서 박막의 구조 변화를 측정하였다. 비등방성 구조로 된 MgB₂ 박막에서 초전도 특성을 갖는 상전이 온도 근처에서 S-변수를 측정하였다. 양전자의 입사 에너지 10keV에서 측정된 S-변수의 최고치는 박막의 온도가 30K에서 0.567이고, 50 K에서는 0.570로 큰 변화는 없었다. 이 결과로부터 양전자가 Boron 층의 초 전자와 소멸하기 보다는 Mg층 근처의 상 전자와 소멸하는 것으로 판단된다. MgB₂의 박막의 외층은 Mg층으로 이루어졌다고 할 수 있다. Enhance signal-to-noise ratio, slow positron coincidence Doppler Broadening method has been applied to study of characteristics of MgB₂ superconductor film, which were performed at 30 K and 50 K sample temperature near Tc of it. In this investigation the numerical analysis of the Doppler spectra was employed to the determination of the shape parameter, S, defined as the ratio between the amount of counts in a central portion of the spectrum and the total counts of whole spectrum. The S-parameter values were increased then decreased while the positron implantation energies were increasing, that indicated the diffusion into the samples. The S-parameters of the anisotropic 1 ㎛ MgB₂ thin film which were implanted by positrons at 10 keV are 0.567 at 30 K and 0.570 at 50 K. It is believed that the positrons annihilate with normal-electrons instead of super-electrons in the MgB₂ superconductor.
V. Ström,K.S. Kim,B.J. Jönsson,S.C. Yu,A. Inoue,K.V. Rao 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
We have studied the magnetization in fields up to IT at 5K, the saturation magnetization dependence on temperature and the temperature dependence of AC-susceptibility at very low fields (5mOe to 50mOe) of glassy Fe_(91-x)Zr_7B₂Ni_x (x = 0, 5, 10, 15) alloys. The temperature dependence of the magnetization follows the predictions of spin wave excitations with long wavelengths. At zero Ni concentration there is a clear competition between ferromagnetic and antiferromagnetic interactions giving rise to spin-glass behaviour. The addition of Ni drastically modifies the magnetic properties: the antiferromagnetic exchange coupling is reduced and finally disappears, the spin wave stiffness increases from 39.5 to 87.3 meVŲ and Tc increases from 230 K to 478 K. We develop a simple model to quantify the competing interactions and to relate the antiferromagnelically coupled Fe moments to the Ni concentration. We find that the initial susceptibility increases with increasing Ni content along with a decrease of the temperature dependence.
Park, S.H.,Lee, J.H.,Nam, T.H.,Lee, Y.J.,Inoue, K.,Lee, S.W.,Kim, J.I. Elsevier Sequoia 2013 Journal of alloys and compounds Vol.577 No.suppl1
In this study, the shape memory behavior of Ti-50.9at.% Ni alloys with time gradient annealing (TGA) was investigated via differential scanning calorimetry (DSC) and thermal cycling tests under constant load. The ingot was prepared using a high-frequency induction vacuum furnace. The as-cast ingot was hot forged and extruded, followed by cold-drawing and intermediate annealing to produce wires of 1.0mm in diameter, with a final cold-drawing of 30% reduction in cross-section. For the TGA treatment, a new type of radiant furnace was designed to maintain a constant temperature and create a time gradient along the length of the specimen. According to DSC measurements, a 34K variation in the R-phase transformation interval (i.e., R<SUB>s</SUB>-R<SUB>f</SUB>) was obtained along the length of the specimen (80mm) that was time-gradient annealed from 3min to 20min at 773K. The results of thermal cycling tests under constant load revealed that the temperature dependence of transformation elongation (d@?/dT) of the TGA specimen is smaller than that of the isochronously annealed specimen at every heat-treatment temperature (673-773K). The lowest d@?/dT of R-phase transformation (0.0031%/K) was obtained for the specimen that was TGA-treated at 673K. The difference in d@?/dT of R-phase and the martensitic transformation of the TGA-treated and isochronously annealed specimen was largest at 773K and increased with increasing stress. Such behavior provides superior controllability for actuation applications.
COSMIC RAYS AND GAMMA-RAYS IN LARGE-SCALE STRUCTURE
INOUE SUSUMU,NAGASHIMA MASAHIRO,SUZUKI TAKERU K.,AOKI WAKO The Korean Astronomical Society 2004 Journal of The Korean Astronomical Society Vol.37 No.5
During the hierarchical formation of large scale structure in the universe, the progressive collapse and merging of dark matter should inevitably drive shocks into the gas, with nonthermal particle acceleration as a natural consequence. Two topics in this regard are discussed, emphasizing what important things nonthermal phenomena may tell us about the structure formation (SF) process itself. 1. Inverse Compton gamma-rays from large scale SF shocks and non-gravitational effects, and the implications for probing the warm-hot intergalactic medium. We utilize a semi-analytic approach based on Monte Carlo merger trees that treats both merger and accretion shocks self-consistently. 2. Production of $^6Li$ by cosmic rays from SF shocks in the early Galaxy, and the implications for probing Galaxy formation and uncertain physics on sub-Galactic scales. Our new observations of metal-poor halo stars with the Subaru High Dispersion Spectrograph are highlighted.
TWIST AND CONNECTIVITY OF MAGNETIC FIELD LINES IN THE SOLAR ACTIVE REGION NOAA 10930
Inoue, S.,Kusano, K.,Magara, T.,Shiota, D.,Yamamoto, T. T. IOP Publishing 2011 The Astrophysical journal Vol.738 No.2
<P>Twist and connectivity of magnetic field lines in the flare-productive active region NOAA 10930 are investigated in terms of the vector magnetograms observed by the Solar Optical Telescope on board the Hinode satellite and the nonlinear force-free field (NLFFF) extrapolation. First, we show that the footpoints of magnetic field lines reconstructed by the NLFFF correspond well to the conjugate pair of highly sheared flare ribbons on the Ca II images, which were observed by Hinode as an X3.4 class flare on 2006 December 13. This demonstrates that the NLFFF extrapolation may be used to analyze the magnetic field connectivity. Second, we find that the twist of magnetic field lines anchored on the flare ribbons increased as the ribbons moved away from the magnetic polarity inversion line in the early phase of the flare. This suggests that magnetic reconnection might commence from a region located below the most strongly twisted field. Third, we reveal that the magnetic flux twisted more than a half turn and gradually increased during the last one day prior to the onset of the flare, and that it quickly decreased for two hours after the flare. This is consistent with the store-and-release scenario of magnetic helicity. However, within this active region, only a small fraction of the flux was twisted by more than one full turn and the field lines that reconnected first were twisted less than one turn. These results imply that the kink mode instability could hardly occur, at least before the onset of flare. Based on our results, we discuss the trigger process of solar flares.</P>