• Title/Summary/Keyword: 자기적성질

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Research Trend and Prospect in Ferromagnetic Superconductor (강자성 초전도체의 연구동향과 전망)

  • Han, Sang-Wook
    • Journal of the Korean Magnetics Society
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    • v.22 no.2
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    • pp.66-72
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    • 2012
  • The findings of ferromagnetic superconductor have attracted much attention not only for fundamental research to investigate how the antagonistic properties of ferromagnetism and superconductivity coexist peacefully but also for potential technological applications. Firstly, in order to help for understanding the ferromagnetic superconductor, I have explained the orbital and paramagnetic pair-breaking effects of magnetic field, which breaks the superconducting Cooper pairs. In addition to such effects of magnetic field, the singlet Cooper pairs become unstable upon going through the ferromagnetic materials by the proximity effect. The proximity effect occurs at the interface of thin films composing of superconductor and ferromagnet and leads to have very short penetration depth of Cooper pairs. However, a type of odd-frequency triplet in comparison with the singlet could be very stable and has a longer effective depth. It needs to be explored for the innovative spintronic devices. Finally, various ferromagnetic superconductors coexist and the lower-dimensional materials under the Quantum confinement effect have been introduced.

Performance Evaluation of DiffServ Networks Considering Self-Similar Traffic Characteristics (자기유사 트래픽 특성을 고려한 차등서비스 망의 성능 평가)

  • Park, Jeong-Sook;Jeon, Yong-Hee
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.33 no.5B
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    • pp.344-355
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    • 2008
  • In this paper, we are dealing with the problems of performance evaluation of Differentiated Services(DiffServ) networks. For successful performance evaluation, the ability to accurately represent "real" traffic on the network by suitable traffic models is an essential ingredient. Many research results on the nature of real traffic measurements demonstrated LRD(long-range dependence) property for the Internet traffic including Web, TELNET, and P2P traffic. The LRD can be effectively represented by self-similarity. In this paper, we design and implement self-similar traffic generator using the aggregated On/Off source model, based on the analysis of the On-Off source model, FFT-FGN(Fast Fourier Transform-Fractional Gaussian Noise) model, and RMD(Random Midpoint Displacement) model. We confirmed the self-similarity of our generated traffic by checking the packet inter-arrival time of TCPdump data. Further we applied the implemented traffic generator to the performance evaluation of DiffServ networks and observed the effect of performance to the a value of the On/Off model, and performance of EF/BE class traffic by CBQ.

Structural and Magnetic Properties of Fe Doped CuO (Fe 첨가된 CuO의 구조적, 자기적 특성)

  • Park, Young-Ran;Kim, Kwang-Joo;Park, Jae-Yun;Ahn, Geun-Young;Kim, Chul-Sung
    • Journal of the Korean Magnetics Society
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    • v.16 no.1
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    • pp.34-39
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    • 2006
  • Pure and Fe-doped CuO thin-film and powder samples were prepared using a sol-gel method. Undoped CuO films exhibited monoclinic structure and p-type electrical conductivity $(\~10^{-2}\;{\Omega^{-1}\;cm^{-1}$ due to copper deficiency. On the other hand, CuO: Fe films were found to be insulating and Li doping on the films led to a restoration of p-type conductivity and a ferromagnetic hysteresis behaviour at room temperature. The observed properties far the CuO : Fe, Li films can be explained in terms of hole creation by substitution of $Li^+$ for $Cu^{2+}$ sites and mediation of long-range interactions between $Fe^{3+}$ ions by the $Li^+$-induced defect states. CuO: Fe powders exhibited a ferromagnetism at room temperature with its strength being dependent on post-annealing temperature. Mossbauer measurements on the CuO: Fe films and powders revealed that the octahedral $Cu^{2+}$ sites are mostly substituted by $Fe^{3+}$ ions.

Magnetoresistance of $[FeNi/Cu/CoFe(Co)/Cu]_N$ Spin-Valve Multilayers ($[FeNi/Cu/CoFe(Co)/Cu]_N$ Spin-Valve 다층박막의 자기저항 특성)

  • 김미양;이정미;최규리;오미영;이장로
    • Journal of the Korean Magnetics Society
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    • v.9 no.1
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    • pp.41-47
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    • 1999
  • $Buffer/[NiFe/Cu/CoFe(Co)/Cu]_N$ spin valve multilayers prepared by dc magnetron sputtering on a corning glass substrate using NiFe and CoFe(Co) posses different coercivities. Dependence of magnetoresistance on the type and thickness of buffer layer, thickness of Cu, NiFe, stacking number of multilayer, substrate temperature and annealing temperature in the form $[NiFe/Cu/CoFe(Co)/Cu]_N$ spin-valve multilayers were investigated. To evaluate effect of magnetoresistance for this samples, X-ray diffraction analysis, vibrating sample magnetometer analysis, and magnetoresistance measurement (4-probe method) were performed the maximum magnetoresistance ratio and coercivity were 7.5 % and 140 Oe, respectively for $Cr-50{\AA}/[NiFe-20{\AA}/Cu-{\AA}/Co-20{\AA}/Cu-50{\AA}]_10$ at substrate temperature of 9$0^{\circ}C$. Magnetoresistance slope maintained 0.25%/Oe until 15$0^{\circ}C$ of annealing temperature, and then decreased to 0.03%/Oe at 20$0^{\circ}C$. It was confirmed that the main factor of thermal stability was deteriorating of soft magnetic properties in the NiFe layer.

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WAVE MODEL DEVELOPMENT IN MULTI-ION PLASMAS (다중 이온 플라즈마 파동모델 개발)

  • 송성희;이동훈;표유선
    • Journal of Astronomy and Space Sciences
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    • v.16 no.1
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    • pp.41-52
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    • 1999
  • Near-earth space is composed of plasmas which embed a number of plasma waves. Space plasmas consist of electrons and multi-ion that determine local wave propagation characteristics. In multi-ion plasmas, it is difficult to find out analytic solutions from the dispersion relation in general. In this work, we have developed a model with an arbitrary magnetic field and density as well as multi-ion plasmas. This model allows us to investigate how plasma waves behave when they propagate along realistic magnetic field lines, which are assumed by IGRF(International Geomagnetic Reference Field). The results are found to be useful for the analysis of the in situ observational data in space. For instance, if waves are assumed to propagate into the polar region, from the equatorial region, our model quantitatively show how polarization is altered along earth travel path.

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A Study on Mossbauer Spectrum of the $NiAl_0.8Fe_1.2O_4$ ($NiAl_0.8Fe_1.2O_4$의 Mossbauer' Spectrum연구)

  • Lee, Cheol-Sae
    • The Journal of Natural Sciences
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    • v.7
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    • pp.19-25
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    • 1995
  • In this study, the Mossbauer effect of the $NiAl_0.8Fe_1.2O_4$ was investigated in the temperature range of 77K-1000K. The spectra were composed of two component, one is sixtet and the other doublet, at low temperature. From the temperature dependence of Mossbauer spectum, it is appeared that the magnetic properties of $NiAl_0.8Fe_1.2O_4$ varies from ferrimagnetism to paramagnetism as the increasing tempereture. And the magnetic relaxation patterns of the $NiAl_0.8Fe_1.2O_4$ were shown superparamagnetic effect.

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A Study on Iron Compounds of Scoria in Mid Mountain Area of Jeju (제주 중산간지역 스코리아의 철 화합물에 관한 연구)

  • Choi, Won-Jun;Ko, Jeong-Dae
    • Journal of the Korean Magnetics Society
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    • v.17 no.5
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    • pp.205-209
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    • 2007
  • It have been investigated the measured results of the XRF, the X-ray diffractometry and $^{57}Fe\;M{\ddot{o}}ssbauer$ spectrum for scoria samples which are distributed throughout different areas in Mid-mountain Area of Jeju island. We consider that the scoria samples are chiefly made of silicate minerals, like $SiO_2$, others silicate minerals and iron oxides minerals. We study that it's materiel is consisted of olivine, pyroxene, ilmenite, hematite and magnetite. Iron compounds in that are $Fe^{2+}$ of olivine, pyroxene, ilmenite and $Fe^{3+}$ of hematite, magnetite et al. The major Fe fractions of the scoria samples are 51.77 wt%, so Fe fractions of the scoria samples are almost 3+ charge state with a little of the 2+ charge state.

Magnetic Properties and Production of Fe-N Phases by Plasma Source Ion Implantation (플라즈마 이온주입 방법에 의한 질화철 제조 및 자기적 성질)

  • 김정기;김곤호;김용현;한승희;김철성
    • Journal of the Korean Magnetics Society
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    • v.8 no.1
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    • pp.6-12
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    • 1998
  • Fe-N(iron-nitrogen) crystal phases were prepared by nitrogen ion implantation into $\alpha$-Fe foil with Plasma Source Ion Implantation (PSII). Ion implantation time of sample is treated 15 minutes(FeN15) and 30 minutes (FeN30). The nitrogen depth profiles measured by Auger electron spectroscopy (AES) were determined to be about 12000 $\AA$ and 4000 $\AA$ for the samples of FeN15 and FeN30, respectively. The results of vibrating sample magnetometer (VSM) show that the saturation magnetization of the samples of as-implanted FeN15 and FeN30 was higher than that of pure $\alpha$-Fe foil, which may be owing to $\alpha$'-$Fe_8N$ or $\alpha$"-$Fe_{16}N_2$ phases. Accordingly this study shows the possibility of the partial formation of $\alpha$' or $\alpha$" phase in iron nitrogen produced by PSII method.II method.

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A High-Performance Fault-Tolerant Switching Network and Its Fault Diagnosis (고성능 결함감내 스위칭 망과 결함 진단법)

  • 박재현
    • Journal of KIISE:Information Networking
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    • v.31 no.3
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    • pp.335-346
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    • 2004
  • In this paper, we present a high-performance fault-tolerant switching networks using a deflection self-routing scheme, and present fault-diagnosis method for the network. We use the facts: 1) Each stage of the Banyan network is arrayed as the sequences of a Cyclic group of SEs. 2) There is the homomorphism between adjacent stages from a view of self-routing, so that all of each Cyclic group is the subgroup of the Cyclic group in the next stage, and there are factor groups due to such subgroup and homomorphism. We provide high-performance fault-tolerant switching networks of which the all links including augmented links are used as the alternate links detouring faulty links. We also present the fault diagnosis scheme for the proposed switching network that provide multiple paths for each input-output pair.

A Study on Iron Compounds of Scoria in The Western Seaside Area of Jeju (제주 서부 해안지역 스코리아의 철 화합물에 관한 연구)

  • Choi, Won-Jun;Ko, Jeong-Dae
    • Journal of the Korean Magnetics Society
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    • v.19 no.6
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    • pp.227-232
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    • 2009
  • Fe compounds of scoria samples distributed in the western seaside area of Jeju island were investigated by means of X-ray fluorescence spectroscopy (XRD), X-ray diffractometry (XRF) and $^{57}Fe$ Mossbauer spectroscopy. The samples were prepared from five parasite volcanos. We found that the samples were a typical basalt from the contents ratio of $SiO_2,\;Al_2O_3$ and Fe, and that they were silicate minerals. Underwater volcanoes scoria samples are shown only doublets in Mossbauer spectra and others scoria samples are shown sextets due to hematite and magnetite. And the balence state of Fe in the underwater volcanoes scoria samples are chiefly 2+ charge state with a little of the 2+ charge state. But the balence state of Fe in the others scoria samples are chiefly 3+ charge state.