• 대한방사선기술학회지:방사선기술과학
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• 제44권1호
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• pp.25-30
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• 2021

The purpose was to reduce the distortion of the image that occurs in the temporal bone area due to the very strong differences in susceptibility. A new SS-TSE technique was applied when examining the diffusion-weighted image of the temporal bone, where the auditory and facial nerves to be imaged were very thin and were adjacent to the cranial base including bone and air. This study was conducted from March 2020 to August of the same year, targeting 32 subjects who underwent the diffusion-weighted imaging of the temporal bone. To compare the distortion, existing SS-EPI technique and the new SS-TSE technique were both applied on the temporal bone area. As a result of the study, applying the new SS-TSE technique appeared to lower the distortion of images by 87.44, 46.13 and 42.35 % on the b-value 0, 800 and the ADC images, respectively. In conclusion, when using the new SS-TSE technique on the temporal bone DWI, distortion can be reduced, and thus images with high diagnostic value can be obtained.

• 한국자기학회지
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• 제7권5호
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• pp.265-273
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• 1997

연자성 자유자성층과 피속박자성층을 각각 2중층 Ni$_{81}$fe$_{19}$/ $Co_{90}$ Fe$_{10}$와 $Co_{90}$ Fe$_{10}$로 하고, 반강자성 속박층을 NiO로 하는 NiFe/CoFe/Cu/CuFe/NiO 구조를 갖는 spin-valve 박막을 sputtering 방법으로 유리기판위에 제작하고, 자기저항비(MR), 자기장감응도(field sensitivity), 반강자성층과 피속박자성층사이의 교환결합 자기장(exchange coupling field), 자유자성층과 피속박자성층사이의 층간결합자기장(interlayer coupling field) 등의 비자성 사이층 Cu 두께, 자유자성층두께, 피속박자성층 두께 및 반강자성층 두께 의존성을 조사하였다. 2중층 자유자성층에 연자성 NiFe가 20 .angs. 이상 포함됨으로써 10 Oe의 보자력을 가져 연자성특성을 향상시키는 것을 확인할 수 있었다. Cu의 두께가 30 .angs. 일 때 극대 MR비를 가졌으며 두께증가에 따라 감소하는 경향을 보였다. 피속박자성층 CoFe의 두께가 35 .angs. 일 때 그대 MR비 6.3%를 나타내며 두께증가에 따라 감소하며 교환결합자기장도 CoFe 두께가 증가함에 따라 감소하였다. NiO 두께가 800 .angs. 일 때 극대 MR비를 보이며 교환결합자기장은 두께증가에 따라 50 Oe 정도로 포화되어 NiO가 반강자성 특성을 유지하기 위해서는 일정한 두께이상이 되어야 함을 알 수 있었다. 열처리온도 200 .deg. C 까지는 MR비 5.3%를 유지하다 이보다 높하지면 점점 감소하여 300 .deg. C에서도 약 3% 정도를 유지하여 열적 안정성이 향상되었다. 따라서 CoFe 합금을 사용하여 NiFe(40 .angs. )/CoFe(50 .angs. )/Cu(30 .angs. )/CoFe(35 .angs. )/NiO(800 .angs. ) 구조를 갖는 spin-valve 박막은 극대 MR비 6.3%, 유효자기장감응도 약 0.5(%/Oe)를 보여 spin-valve head 재료로 적합함을 알 수 있었다.다.다.다.

• Journal of Magnetics
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• 제11권1호
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• pp.8-11
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• 2006

Recently half-metallic full-Heusler alloy films have attracted significant interests for spintronics devices. As these alloys have been known to have a high spin polarization, very large TMR ratio is expected in magnetic tunnel junctions. Among these alloys, $Co_2MnSi$ full-Heusler alloy with a high spin polarization and a high Curie temperature is considered a good candidate as an electrode material for spintronic devices. In this study, the magnetic and structural properties of $Co_2MnSi$ Heusler alloy films were investigated. TMR characteristics of magnetic tunnel junctions with a $Co_2MnSi/SiO_2/CoFe$ structure were studied. A maximum MR ratio of 39% with $SiO_2$ substrates and 27% with MgO(100) substrates were obtained. The lower MR ratio than expectation is considered due to off-stoichiometry and atomic disorder of $Co_2MnSi$ electrode together with oxidation of the electrode layer.

• 한국세라믹학회지
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• 제31권3호
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• pp.265-274
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• 1994

Intermetallic Ti-Si system ceramics were synthesized from stochiometric mixtures of titanium and silicone powders in vacuum by Self-propagating High-temperature Synthesis(SHS). In each cases of Ti5Si3, Ti5Si4 and TiSi, and TiSi2 synthesis, 20wt% product dilution, direct ignition and SHS chemical furnace method were employed. The combustion modes, which were observed during the synthesis process by using the high speed camera, of Ti5Si3, Ti5Si4, TiSi, and TiSi2 exhibit spin, osciallatory, steady-state, and spin combustion, respectively. With increasing Ti/Si molar ratio an decrease of combustion velocities was found. From the results on the measurement of the flexural strength, the specimen hot pressed at 135$0^{\circ}C$ for 30 min using synthesized Ti5Si4 powders showed the highest flexural strength at 215 MPa.

• 한국결정성장학회지
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• 제6권3호
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• pp.424-430
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• 1996

태양전지의 공정중 고온공정을 줄여줌으로서 최종 태양전지의 가격을 저가화할 수가 있다. 이 논문은 점액 상태의 인을 희석시켜서 접촉 홈에 확산공정을 마친 후, 그 기본 특성을 조사하였다. 점액상태점의 희석도와 스핀속도가 산화막의 두께에 영향을 미치는 것이 확인되었다. 희석도가 높을수록 산화막은 두꺼워지고 균일도는 낮아졌다. 희석도 60%의 인이 홈에서의 균일도와 깊이를 고려할 때 가장 적당한 것으로 사료된다.

• 천문학회지
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• 제44권3호
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• pp.89-96
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• 2011

We present results of two-color VR photometry of the intermediate polar RXS J1803. The data were aquired using the Korean 1-m telescope located at Mt. Lemmon, USA. Different "high" and "low" luminosity states, similar to other intermediate polars, were discovered. No statistically significant variability of the color index with varying luminosity was detected. The orbital variability was found to be not statistically significant. Spin maxima timings were determined, as well as the photometric ephemeris for the time interval of our observations. The spin period variations, caused by interaction of the accretion structure with the rotating magnetic white dwarf, were also detected. These variations are of complicated character, and their study requires further observations. We determine the color transformation coefficients for our photometric systems, and improve on the secondary photometric standards.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 14TH KACG TECHNICAL MEETING AND THE 5TH KOREA-JAPAN EMGS (ELECTRONIC MATERIALS GROWTH SYMPOSIUM)
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• pp.39-43
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• 1998

Single crystals of{{{{ { Zn}_{ 1-x} {Mn }_{x }{Te} }}}} with x=0.3-0.6 were prepared by the standard Bridgeman method. Diffuse neutron diffraction intensities due to the short range magnetic ordering is found in the vicinities of 1 1/2 0 reciprocal point and its equivalent point, indicating that the magnetic correlation of the clusters is the type III antiferromangetic one do the F-type Bravais class crystals, being identical with that of {{{{{ Cd}_{ 1-x} {Mn }_{x }Te }}}}. Neutron inelastic scattering measure-ment has been performed for {{{{{ Zn}_{ 0.6} { Mn}_{ 0.4}Te }}}} sample using the cold neutron spectrometer. AGNES. High resolution measurement with the energy resolution of {{{{ TRIANGLE E= +- .01meV}}}} was carried out in the temperature range from 10K to the ambient. Critical scattering, closely related with the spin glass transition, has been observed for the first time in this semimagnetic semi-conductor. The critical scattering is observed at temperatures in the vicinity of the spin glass transition temperature, 17K. The scattering is observed as a kind of quasielastic scattering in the reciprocal range where the elastic magnetic diffuse scattering has been observed, e.g., 11/20 reciprocal point, indicating the spin fluctuation has dynamic components in this material. Photoconductivity has been discovered below 150K in {{{{{ Zn}_{ 0.4} {Mn }_{0.6 } Te}}}}. The electric AC conductivity has been increased dramatically under the laser light with the wave lengths of {{{{ lambda =6328,5145 and4880 }}}}$\AA$ ,respectively. After the light was darkened, the conductivity was reduced to the original level after about 2000 seconds at 50K, being above the spin glass transition temperature. This phenomenon is the typical persistent photoconductivity; PPC which was similarly found in {{{{ { Zn}_{ 1-x} { Mn}_{x} Te}}}}.

• 센서학회지
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• 제7권2호
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• pp.117-123
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• 1998

알루미나 기판위에 스핀코팅에 의해 $In_{2}O_{3}$ 박막을 형성하고 그 박막의 미세구조와 가스감지특성을 조사하였다. 코팅용액은 $In(OH)_{3}$ 수용액에 초산을 첨가하여 합성되었다. 이 용액에 바인더로써 암모니아 카르복실 셀루로오스를 섞어서 코팅용액으로 사용하였다. 이 용액을 $1{\sim}7$회 스핀코팅하고 $110^{\circ}C$에서의 건조와 $600^{\circ}C$에서의 열처리에 의해 두께 $71{\sim}210nm$의 $In_{2}O_{3}$ 박막을 얻을 수 있었다. 제조된 박막은 미세한 $In_{2}O_{3}$ 결정입자($23{\sim}27nm$)가 적층된 형태의 구조를 가지고 알루미나 기판의 결정입위에 균일하게 코팅되었다. 박막의 두께는 스핀코팅의 횟수에 선형적으로 증가하였다. 제조된 박막은 CO, $H_{2}$ 가스에 대해 높은 감도와 빠른 응답특성을 나타내었다.

• 한국해양바이오학회지
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• 제1권4호
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• pp.252-259
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• 2006

본 실험은 electron spin/paramagnetic resonance(ESR/EPR)를 이용하여 기존의 DPPH free radical 소거 활성을 측정하였고, 이를 해조류 유래 천연자원으로부터 새로운 항산화물질을 탐색하는데 적용해 보았다. 연구 결과, 녹조류 추출물에서는 참홑파래, 납작파래 및 청각의 고온 메탄올 추출물에서만 약간의 라디칼 소거활성을 나타내었고, 이 외의 추출물에서는 소거활성이 거의 보이지 않았다. 갈조류는 총 71개의 추출물 중 37개의 추출물에서 80% 이상의 소거율을 보여 아주 우수한 항산화 물질을 가진 family로 여겨지며, 특히 모자반류 (Sargassum spp.)는 수용성과 메탄올, 고온과 상온의 모든 추출물에서 높은 라디칼 소거 활성을 보여 앞으로의 신소재 물질 후보로 선별되었다. 홍조류에서는 수용성보다는 메탄올 추출물에서 대체적으로 높은 소거활성이 검색되어, 나중에는 유기용매 분획물을 제조하여 라디칼 소거능을 측정 할 수 있을 것이다. 이처럼 해조류는 라키칼 소거 능력을 가지는 성분을 여러 형태로 다량으로 함유 하고 있는 것으로 사료 되며 앞으로의 연구에 기대가치를 더해 줄 것으로 사료된다.

• 천문학논총
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• 제30권2호
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• pp.595-597
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• 2015

LMC X-4 is an eclipsing high-mass X-ray binary exhibiting a superorbital modulation with a period of ~ 30:5 days. We present a detailed study of the variations of the superorbital modulation period with a time baseline of ~ 18 years. The period determined in the light curve collected by the Monitor of All-sky X-ray Image (MAXI) significantly deviates from that observed by the All Sky Monitor (ASM) onboard the Rossi X-ray Timing Explorer (RXTE). Using the data collected by RXTE/ASM, MAXI, and the Burst Alert Telescope (BAT) onboard Swift, we found a significant period derivative, $\dot{P}=(2.08{\pm}0.12){\times}10^{-5}$. Furthermore, the O{C residual shows complex short-term variations indicating that the superorbital modulation of LMC X-4 exhibits complicated unstable behaviors. In addition, we used archive data collected by the Proportional Counter Array (PCA) on RXTE to estimate the orbital and spin parameters. The detected pulse frequencies obtained in small time segments were fitted with a circular orbital Doppler shift model. In addition to orbital parameters and spin frequency for each observation, we found a spin frequency derivative of $\dot{v}=(6.482{\pm}0.011){\times}10^{-13}Hz{\cdot}s^{-1}$. More precise orbital and spin parameters will be evaluated by the pulse arrival time delay technique in the future.