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후방산란법(RBS) / 양성자 여기 X-선 방출법(PIXE)을 이용한 다층자성박막의 두께 및 조성 정량분석
김태곤(T. G. Kim),전기영(G. Y. Jeon),황정남(C. N. Whang),신유하(Y. H. Shin),김영만(Y. M. Kim),송종한(J. H. Song),장성호(S. H. Jang),김광윤(K. Y. Kim) 한국자기학회 2001 韓國磁氣學會誌 Vol.11 No.6
A spin valve structure of Ta/NiFe/CoFe/Cu/CoFe/Ru/CoFe/FeMn/Ta which has a synthetic antiferromagnet (CoFe/Ru/CoFe), was fabricated by using a magnetron sputtering system. The thickness and composition of magnetic free and pinned layers affect the magnetic properties such as exchange interaction strength of each layer and so on. Even though Rutherford Backscattering Spectrometry (RBS) has advantages of quantitative and non-destructive analysis, it is almost impossible to determine the thickness and composition of magnetic thin films using RBS because of its poor mass resolution for a higher atom number (Z>20). In this study, quantitative analysis of the element composition and thickness for the spin valve sample was performed by combining both Proton Induced X-ray Emission Spectrometry (PIXE), which is one of element specific analysis techniques, and grazing-exit RES with a highly improved depth resolution and absolute quantitative analysis. For the quantitative analysis, standardization of PIXE was carried out with NiFe, CoFe, and FeMn layers, which are one of constituent layers of spin valve films. Through PIXE standardization and the aid of PIXE experimental results of the spin valve sample, the overlapped signal in a grazing-exit RBS spectrum were successfully resolved and the thickness of the Ru layer was determined with a resolution of ~1 Å.
유요한,전기영,정동택,Yoo, Y.H.,Jeon, G.Y.,Chung, D.T. 대한기계학회 1993 대한기계학회논문집 Vol.17 No.7
The stepped specimen which is subjected to step loading is modeled to study the initiation and growth of adiabatic shear band using explicit time integration finite element method. Three different clearance sizes are tested. The material model for the stepped specimen includes effects of strain hardening, strain rate hardening and thermal softening. It is found that the material inside the fully grown adiabatic shear band experiences three phase of deformation, (1) homogeneous deformation phase, (2) initiation/incubation phase, and (3) fast growth phase. The second phase of deformation is initiated after sudden shear stress drop which occurs at the same time regardless of the clearance size. The incubation time prior to fast growth phase increases, as the clearance size of the stepped specimen increases. Whereas, after incubation period, the growth rate of the adiabatic shear band decreases, as the clearance size decreases. It is also found that two adiabatic shear band may develop instead of one for the smaller clearance size.
모델기준적응시스템(MRAS) 기반의 부하토크관측기를 이용한 유도전동기 속도제어
김은기(E. G. Kim),이훈구(H. G. Lee),이승환(S. H. Lee),오봉환(B. H. Oh),정춘병(C. B. Chung),함년근(N. G. Hahm),전기영(K. Y. Jeon),이상현(S. H. Lee),한경희(K. H. Han) 대한전기학회 2006 대한전기학회 학술대회 논문집 Vol.2006 No.7
This paper investigates a speed sensorless control of induction motor. The control strategy is based on MRAS (Model Reference Adaptive System) using load-torque observer as a reference model for flux estimation. The speed response of conventional MRAS controller characteristics is affected by variations of load torque disturbance. In the proposed system, the speed control characteristics using a load-torque observer control isn't affected by a load torque disturbance. Simulation results are presented to prove the effectiveness of the adaptive sliding mode controller for the drive variable toad of induction motor.
김은기(E. G. Kim),이재훈(J. H. Lee),전기영(K. Y. Jeon),이승환(S. H. Lee),오봉환(B. H. Oh),이훈구(H. G. Lee),김용주(Y. J. Kim),한경희(K. H. Han) 전력전자학회 2007 전력전자학술대회 논문집 Vol.- No.-
The rotor speed and flux information is most important in the vector control. The accuracy of flux observers for induction machine inherently depends on parameter sensitivity. The control strategy is using online flux observer for flux estimation. In the proposed system, the speed control characteristics using a online flux observer control isn't affected by a load torque parameter disturbance. Simulation results are presented to prove the effectiveness of the adaptive sliding mode controller for the drive variable load of induction motor.
이온 조사된 Cu / Ni / Cu(001) / Si 자성박막에 있어서 X-ray reflectivity를 이용한 계면 연구
김태곤(T. G. Kim),송종한(J. H. Song),이택휘(T. H. Lee),채근화(K. H. Chae),황현미(H. M. Hwang),전기영(G. Y. Jeon),이재용(J. Lee),정광호(K. Jeong),황정남(C. N. Whang),이준식(J. S. Lee),이기봉(K. B. Lee) 한국자기학회 2002 韓國磁氣學會誌 Vol.12 No.5
The Cu/Ni/Cu(002)/Si(100) films which have perpendicular magnetic anisotropy were deposited by e-beam evaporation methods. From the reflection high energy electron diffraction pattern, the films were confirmed to be grown epitaxially on silicon. After 2×10^(16) ions/㎠ C+ irradiation, magnetic easy-axis was changed from surface normal to in-plane as shown in the hysteresis loop of magneto-optical Kerr effects. It became manifest from analysis of X-ray reflectivity and grazing incident X-ray diffraction that even though interface between top Cu layer and Ni layer became rougher, the contrast of Cu and Ni's electron density became manifest after ion irradiation. In addition, the strain after deposition of the films was relaxed after ion irradiation. Strain relaxation related with change of magnetic properties and mechanism of intermixed layer's formation was explained by thermo-chemical driving force due to elastic and inelastic collision of ions.
신철준(C. J Sin),전기영(K. Y. Jeon),이승환(S. H. Lee),강승욱(S. U. Kang),오봉환(B. H. Oh),정춘병(C. B. Chung),이훈구(H. G. Lee),한경희(K. H. Han) 전력전자학회 2007 전력전자학술대회 논문집 Vol.- No.-
In this paper, The authors study the boost Regulator as a DC-DC Converter like a power supply and describe the investigation result about the two phase with combined boost regulator which has the same effect that the switching frequency of the solid-state-switch is two times. As a result, the ripple of the input current and output current is better improved.
이재훈(J. H Lee),김은기(E. G Kim),전기영(K. Y Jeon),전지용(J. Y Chun),이승환(S. H Lee),오봉환(B. H Oh),이훈구(H. G Lee),한경희(K. H Han) 전력전자학회 2007 전력전자학술대회 논문집 Vol.- No.-
In this paper, The authors design the current controller which independently control the d, q axis current transformed by the synchronously rotating d, q axis and a Space Vector Pulse Width Modulation(SVPWM) to steadily control the output DC-Link voltage against the variable load of the three phase PWM converter. Also, This study improves the high power factor, stability, and rapid response by the phase angle control using the digital Phase Locked Loop(PLL).