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이정한,김형식,허문창,김정회,Yi, Jeong-Han,Kim, Hyung-Sik,Hur, Moon-Chang,Kim, Jung-Hoe 대한의용생체공학회 2006 의공학회지 Vol.27 No.6
Medical magnetic stimulator generates strong magnetic field pulses. Clinical applications of the magnetic pulse are the stimulation of nervous system and the contraction of muscle. The unique source of the strong magnetic pulse is a capacitor-inductor resonator and this inductor generates a strong sinusoidal magnetic pulse by discharging the capacitor with high initial voltage. Continuous muscle contraction needs sequential generation of the magnetic pulses. However, to keep the magnitude of sequential pulses identical, an expensive high-voltage power supply have to support voltage drop of the capacitor between the pulses. A protection circuit between the supply and the resonator is necessary to protect the supply from reverse current caused by capacitor voltage reversal. In this paper, a new circuit structure of the magnetic stimulator adopting a low-frequency fly-back switching is proposed. The new circuit supports sequential pulse generation and allows the reverse current without damage. Performance of the new circuit is examined and a low-cost magnetic stimulator for urinary incontinence therapy is being developed using the presented method.
고농도 산소 공급량 변화에 따른 남/녀 혈중 산소 포화도의 차이
이정한(Jeong-Han Yi),최미현(Mi Hyun Choi),김지혜(Ji Hye Kim),이수정(Su-Jeong Lee),양재웅(Jae-Woong Yang),정순철(Soon-Cheol Chung),임대운(Dae-Woon Lim),이동형(Dong-Hyung Lee),민병찬(Byung-Chan Min) 한국산업경영시스템학회 2009 한국산업경영시스템학회지 Vol.32 No.4
The purpose of this study was to examine differences between male and female in blood oxygen saturation due to 93% oxygen administration of the three levels (1L/min, 3L/min, 5L/min) Ten healthy male (25 0±1 8 years) and ten female (23 7±1 9 years) college students were selected as the subjects for this study The experiment consisted of three runs, ie, the three levels of 93% oxygen administration, respectively The each run consisted of three phases, ie, Rest 1 (5 min), Hyperoxia (10 min), and Rest 2 (5 min) Blood oxygen saturation sere measured throughout the three phases By increasing the supply rate of highly concentrated oxygen, rising rate of blood oxygen saturation was increased Blood oxygen saturation of female was higher than male regardless of supply rate of highly concentrated oxygen and phases
표면 전극용 기능적 전기자극 시스템의 개발 및 하반신 마비환자의 보행
송동진,이정한,강곤,Song Tongjin,Yi Jeong Han,Khang Gon 대한의용생체공학회 2003 의공학회지 Vol.24 No.6
본 연구에서는 표면 전극을 사용하는 8채널 전기자극 시스템을 개발하였고. 이 시스템을 이용하여 하반신 마비한자의 근력강화를 위한 전기자극 엑서사이즈와 FES 보행을 하였다. 본 연구에서 개발한 전기자극 시스템은 컴퓨터 프로그램, 전기자극기, 그리고 컴퓨터 프로그램과 전기자극기를 연결하는 통신부분으로 구성되어 있다. 컴퓨터 프로그램에서는 마우스를 이용하여 임의의 자극 패턴을 손쉽게 구성하고 편집학 수 있으며 이렇게 구성/편집된 자극 패턴은 동원곡선(recruitment curve)을 통하여 자극 파라미터로 변환된다. 자극 파라미터는 직렬통신을 이용하여 전기자극기에 전달된다. 전기자극기는 주제어부에 1개, 각 채널에 1개씩 총 9개의 마이크로프로세서로 구성되어 있다. 주제어부의 마이크로프로세서가 컴퓨터 프로그램과 통신을 하고 각 채널의 마이크로프로세서를 제어한다. 본 연구에서 개발한 기능적 전기자극 시스템으로 하반신 마비환자에게 100주 동안 전기자극 엑서사이즈를 실시한 결과 근력, 다리둘레, 그리고 피로저항성의 증가를 볼 수 있었다. 전기자극 엑서사이즈로 무릎신근(knee extensor muscle)이 체중을 지지한 수 있을 정도로 증가한 후에 FES 보행을 시작하였고, 현재 2분 동안 50m 이상 보행할 수 있다. We developed a PC-based 8-channel electrical stimulation system for transcutaneous functional electrical stimulation (FES), and applied it to FES exercise and paraplegic walking. The PC program consists of four parts: a database, a stimulation pattern generator, a stimulus parameter converter, and an exercise program. The stimulation pattern can be arbitrarily generated and edited by using the mouse on the PC screen, and the resulting stimulus parameters arc extracted from the recruitment curves, and transmitted to the 8-channel stimulator through the serial port. The stimulator has nine microprocessors: one master and eight slaves, Each channel is controlled by the slave microprocessor, and is operated independently. Clinical application of the system to a paraplegic patient showed significant increase in the knee extensor torque, the fatigue resistance, and the leg circumference, The patient can now walk about 50 meters for more than 2 minutes.
개방형 자기공명영상시스템용 경사자계코일의 새로운 설계기법
이수열,박부식,이정한,이완,Lee, Soo-Yeol,Park, Bu-Sik,Yi, Jeong-Han,Yi, Wan 대한전자공학회 1997 電子工學會論文誌, S Vol.s34 No.1
Most open magnetic resonance imaging systems have used the planar gradient coils whose inductances were minimized through the magnetic energy minimization procedure in the spatial frequency domain. Though the planar gradient coils have smaller inductance than conventional gradient coils, the planar gradient coils often suffer from their poor magnetic field linearity. Scaling the spatial frequencies of the current density function designed by the magnetic energy minimization, magnetic field linearity of the planar gradient coils can be greatly improved with small sacrifice of gradient coil inductance. We have found that the figure of merit of the planar gradient coils, defined by the gradient strength divided by the linearity error and the inductance, can be improved by proposed technique.
광학 필터를 이용한 광섬유 방사선 센서의 체렌코프 빛 제거
장경원,이봉수,조동현,김형식,이정한,이정환,김신,조효성,Jang, Kyoung-Won,Lee, Bong-Soo,Cho, Dong-Hyun,Kim, Hyung-Shik,Yi, Jeong-Han,Lee, Jeong-Whan,Kim, Sin,Cho, Hyo-Sung 한국광학회 2006 한국광학회지 Vol.17 No.4
본 연구에서는 유기 섬광체와 플라스틱 광섬유를 이용하여 치료용 전자선의 계측을 위한 광섬유 방사선 센서를 제작하였다. 또한, 선형가속기에서 발생되는 고 에너지 전자선에 의해 광섬유 방사선 센서를 이용한 전자선 계측에 있어 방해요소로 존재하는 체렌코프 빛을 감법 및 광학 필터링을 이용하여 제거하였고 두 가지방법들을 비교, 분석하였다. In this study, a miniature fiber-optic radiation sensor has been developed using a water-equivalent organic scintillator for electron beam therapy dosimetry. The intensity of Cerenkov light is measured and characterized as a function of the incident angle of the electron beam from a LINAC. Also, a subtraction method using a background optical fiber without a scintillator and an optical discrimination method using optical filters are investigated to remove Cerenkov light, which could cause problems or limit the accuracy for detecting a fluorescent light signal in a fiber-optic radiation sensor.
고 에너지 광자선 계측용 2차원 광섬유 방사선 센서의 제작 및 특성분석
장경원,조동현,신상훈,김형식,이정한,이봉수,김신,조효성,Jang, Kyoung-Won,Cho, Dong-Hyun,Shin, Sang-Hun,Kim, Hyung-Shik,Yi, Jeong-Han,Lee, Bong-Soo,Kim, Sin,Cho, Hyo-Sung 한국광학회 2007 한국광학회지 Vol.18 No.4
본 연구에서는 유기 섬광체와 플라스틱 광섬유를 이용하여 치료용 광자선의 계측을 위한 2차원 광섬유 방사선 센서를 제작하였다. 제작된 센서를 사용하여 광자선 조사야(Field size)와 에너지에 따른 선형가속기의 빔 분포도를 2차원적으로 측정하였으며 polymethylmethacrylate(PMMA)팬텀 내에서 깊이에 따른 섬광체의 광량을 측정하여 깊이선량 분포(Percent Depth Dose, PDD) 또한 2차원으로 측정하였다. 본 연구를 통하여 개발된 2차원 광섬유 방사선 센서는 고 분해능, 실시간 측정, 쉬운 보정 등 많은 장점을 가지고 있다. In this study, a two-dimensional fiber-optic radiation sensor has been developed using water-equivalent organic scintillators for photon beam therapy dosimetry. Two-dimensional photon beam distributions and percent depth doses(PDD) are measured according to the energies and field sizes of the photon beam. This sensor has many advantages such as high resolution, real-time measurement and ease of calibration over conventional radiation measurement devices.
치료용 고에너지 전자선 계측을 위한 광섬유 방사선 센서의 제작 및 특성 분석
장경원,조동현,유욱재,이봉수,이정한,탁계래,조효성,김신,Jang, Kyoung-Won,Cho, Dong-Hyun,Yoo, Wook-Jae,Lee, Bong-Soo,Yi, Jeong-Han,Tack, Gye-Rae,Cho, Hyo-Sung,Kim, Sin 대한의용생체공학회 2006 의공학회지 Vol.27 No.6
In this study, we have fabricated a fiber-optic radiation sensor using an organic scintillator for high energy electron beam therapy. The intensities of scintillating light from a fiber-optic radiation sensor are measured with different field size, electron beam energy and monitor unit of a clinical linear accelerator. To obtain percent depth dose(PDD), the amount of scintillating light is measured at different depth of polymethylmethacrylate(PMMA) phantom. Also the intensity of Cerenkov light is measured and characterized as a function of incident angle of electron beam and a subtraction method is investigated using a background optical fiber to remove a Cerenkov light.
보행속도변화에 따른 인지 과제 수행이 보행수 변동성에 미치는 영향
최진승,유지혜,김형식,정순철,이정한,이봉수,탁계래,Choi, Jin-Seung,Yoo, Ji-Hye,Kim, Hyung-Shik,Chung, Soon-Cheol,Yi, Jeong-Han,Lee, Bong-Soo,Tack, Gye-Rae 대한의용생체공학회 2006 의공학회지 Vol.27 No.6
The purpose of this study was to investigate the effect of performing a cognitive task during treadmill walking on the stride rate variability. Ten university students(age $24.0{\pm}0.25$, height $172{\pm}3.1cm$, weight $66{\pm}5.3kg$) were participated in dual task experiments which consist of both walking alone and walking with a cognitive task. Two-back task was selected for the cognitive task since it did not have learning effect during the experimental procedure.3D motion analysis system was used to measure subject's position data by changing walking speed with 4.8, 5.6, 6.4, 6.8, and 7.2 km/hr. Stride rate was calculated by the time between heel contact and heel contact. Accuracy rate of a cognitive task during walking, coefficient of variance, allometric scaling methods and Fano factor were used to estimated the stride rate variability. As the walking speed increased, accuracy rate decreased and the logarithmic value of Fano factor increased which showed the statistical difference. Thus it can be concluded that the gait control mechanism is distracted by the secondary attention focus which is the cognitive task ie. two-back task. Further study is needed to clarify this by increasing the number of subject and experiment time.