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강병욱(Byeong-Uk Kang),이상석(Sang-Suk Lee) 한국자기학회 2019 韓國磁氣學會誌 Vol.29 No.5
The characteristics of the measured 80 data during 7 months for the systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), and the systolic time (S.time) were investigated according to the conditions of the low frequency acupuncture electrical stimulator(AES). The S.time of the radial artery pulse wave was measured by a clip-type pulsimter equipped with a permanent magnet and a Hall effect sensor. The mean SBP, DBP, and HR decreased by 5.7 mmHg, 2.1 mmHg and 1.4 /min at 124.1 mmHg, 66.4 mmHg and 87 /min, respectively, after the low frequency treatment by AES. The S.time was 108.6 ms having an increase of 2.6 ms after electrical stimulation at 30 Hz rather than 8 Hz and 15 Hz. The low frequency electrical stimulation was found to effectively stabilize the blood pressure and increase the blood flow in the human body.
김기범(Gi-Beom Kim),강병욱(Byeong-UK Kang) 한국정보과학회 1993 한국정보과학회 학술발표논문집 Vol.20 No.2
C++언어는 기존 C언어의 간결성과 실행시 신속성을 잃지 않으면서 클래스, 자료추상화, 및 오브젝트 지향 패러다임을 지원하도록 만들어진 언어니다. C++언어는 C언어를 알면 누구나 쉽게 배울수 있다. 또한 C언어가 그러하듯이 상당히 효율적인 프로그램을 작성할 수 있다. C++언어는 현재에도 조금씩 변화하고 있으며 아직 완성된 것은 아니다. C++언어가 이와 같은 장점을 가지지만 반면에 문제점도 계속 지적되고 있다. 본 연구에서는 먼저 Booch와 Meyer의 오브젝트 지향 프로그래밍 모델과 C++언어를 비교 분석 하였다. 그 다음 실제로 프로그래밍하면서 발견한 여러 문제를 분석하였다. 그 결과, C++언어가 계승 메커니즘과 관련된 동적 형 검사, 계승 구조의 문제, 다형성의 문제, 인터페이스와 구현의 분리, 영구 저장, 소멸자 메커니즘 등에서 부족하다는 것을 발견하였다.
거대자기저항-스핀밸브와 고온초전도체 사이에 있는 틈 층에 의한 전류전달효과 특성연구
양우일(Woo-Il Yang),강병욱(Byeong-Uk Kang),최종구(Jong-Gu Choi),카지드마(Purevdorj Khajidmaa),이상석(Sang-Suk Lee) 한국자기학회 2018 韓國磁氣學會誌 Vol.28 No.5
A giant magnetoresistive - spin valve (GMR-SV) NiFe/CoFe/Cu/CoFe/IrMn/Ta multilayer film was fabricated by ion beam deposition on a commercial high - temperature superconductor Y₁Ba₂Cu₃O<SUB>7 - x</SUB> (YBCO) film. The thickness of the hybrid YBCO thin film was 300 nm and one of the antiferromagnetic IrMn-based GMR-SV thin film was 55 nm. The superconductor characteristics of the YBCO thin films were confirmed by the R-T curve measured with 4-terminal and the Q-T and I-V curves measured with a microwave cavity resonator. In particular, the phenomenon of negative magnetoresistance (MR) ratio in the reversed MR curve of -7.4% is explained by the current transfer effect from the MR and the I-V curves measured by the 2-, 3-, and 4-probe methods at 77 K below the critical temperature. It was also confirmed by SEM image that a gap layer of 9.3 nm was present between the YBCO film and the GMR-SV multilayer. The residual resistance of 0.456 Ω was measured due to the presence of the gap layer and the difference in current transfer was caused by the superconductor depending on the change of the spin magnetization array configuration of GMR-SV.
NiFe/Cu/NiFe 박막과 YBa₂Cu₃O<SUB>7−x </SUB>박막 사이 NiO 층의 두께에 따른 전류전달효과에 의한 음의 자기저항비 특성 연구
카지드마(Purevdorj Khajidmaa),강병욱(Byeong-Uk Kang),최종구(Jong-Gu Choi),이상석(Sang-Suk Lee),양우일(Woo-Il Yang) 한국자기학회 2019 韓國磁氣學會誌 Vol.29 No.2
The magnetoresistance (MR) curves of giant magnetoresistive-spin valve (GMR-SV) multilayer on Corning glass and sapphire/high-temperature superconductor (HTS) YBa₂Cu₃O<SUB>7−x</SUB> (YBCO) film fabricated by magnetron sputtering were compared and analyzed. Hybrid type HTS and GMR-SV multilayer film with antiferromagnetic NiO thickness of 10 nm has a negative MR ratio of−7.7 %, an exchange coupling field (H<SUB>ex</SUB>) of 120 Oe, a coercive force (H<SUB>c</SUB>) of 125 Oe, respectively. However, there is exist a positive MR ratio of +7.3 % in case of NiO thickness of 60 nm. The glass/NiO/NiFe/Cu/NiFe/Ta multilayer showed linear current-voltage (IV) curve, but the Al₂O₃/YBCO/NiO(10 nm, 60 nm)/NiFe/Cu/NiFe/Ta multilayer showed a nonlinear I-V curve in which the resistance value of 1.15 Ω and 59.4 Ω decreased to 1.02 Ω and 50.2 Ω when the current of 15.7 mA increased to 1.67 mA, respectively. This results are explained by the current transfer effect in the 4-probe electrode measurement method occurred when the resistance of the YBCO film is 0.
반강자성체 NiO 층 기반 단일 구조 및 이중 구조형 거대자기저항-스핀밸브 다층박막의 자기저항 특성 비교
최종구(Jong-Gu Choi),강병욱(Byeong-Uk Kang),이상석(Sang-Suk Lee),카지드마(Purevdorj Khajidmaa) 한국자기학회 2019 韓國磁氣學會誌 Vol.29 No.2
GMR-SV (giant magnetoresistance-spin valve) multilayer films were fabricated on rf- and dc-magnetron sputtering systems in four different forms, in which NiO thin films were inserted into the bottom, top and middle layers. The magnetic properties of all thin film samples were investigated from the major and minor magnetoresistance curves measured at room temperature and at 77 K. The exchange coupling field (Hex) and coercivity (Hc) of the pinned NiFe layer, the Hc and interlayer coupling field (Hint), magnetoresistance ratio (MR (%)), and magnetic sensitivity (MS) of the free NiFe layer in the single-type GMR-SV multilayer with the inserted NiO layer thickness of 10 nm were 110 Oe, 115 Oe, 4.5 Oe, 6.0 Oe, 7.1%, and 1.0%/Oe, respectively. The hysteresis curves of the two free layers with the NiO thin film inserted into the middle layer formed a stable squareness ratio, which was 9.5% for the MRs of 3.5% and 6.0%, and 2.2%/Oe for the MS due to the specular and spin dependent scattering effects. On the other hand, the Hc and MS of the single structure of the bottom NiO film inserted and the dual-type GMR-SV multilayer of the bottom and top layers were greatly increased and decreased, respectively. The MRs of the GMR-SV multilayers with the magnetization of spin array configuration of the pinned layer, which is a ferromagnetic material, and the free layer are antiparallel to each other. The MR of dual-type GMR-SV multilayer showed the maximum value when the spin arrays of magnetization configuration of the pinned and free layers, is antiparallel to each other.
증류수 내 자성비드 용액의 자기장에 의존하는 자기저항 특성 연구
최종구(Jong-Gu Choi),강병욱(Byeong-Uk Kang),이상석(Sang-Suk Lee) 한국자기학회 2019 韓國磁氣學會誌 Vol.29 No.4
Two-electrode resistance of magnetic bead solution in deionized distilled water(ddH₂O) depending on the magnetic field was analyzed. The average diameter of magnetic bead composed of Silanol(Si-OH) group is about 1 μm. The distribution of the magnetic beads in solution is drawn according to the magnitude of the external magnetic field between the two-terminal Cu electrodes. As the magnitude of the external magnetic field increases and decreases, magnetic beads are split on both sides and evenly mixed, respectively. The maximum magnetoresistance ratio from magnetoresistance curve sweeping at 0.7 mHz was about -40 % at around ±10 Oe. Magnetoresistance ratios caused by hysteresis characteristics for the motion of magnetic beads were changed to -36% and -21 % as increasing of the sweeping frequency 3.7 mHz and 10.7 mHz, respectively. These results show the possibility of using magnetic beads as the material of sensitive magnetoresistance sensor.