3.3V-65MHz 12비트 CMOS 전류구동 D / A 변환기 설계 ( A 3.3V-65MHz 12-bit CMOS Current-mode DIGITAL TO ANALOG CONVERTER )

류기홍,윤광섭 대한전자공학회 1998 대한전자공학회 학술대회 Vol.1998 No.7

12비트 CMOS 전류 셀 매트릭스 D/A 변환기 설계

류기홍,윤광섭,Ryu, Ki-Hong,Yoon, Kwang-Sub 대한전자공학회 1999 電子工學會論文誌, C Vol.c36 No.8

This paper describes a 12bit CMOS current cell matrix D/A converter which shows a conversion rate of 65MHz and a power supply of 3.3V. Designed D/A converter utilizes current cell matrix structure with good monotonicity characteristic and fast settling time, and it is implemented by using the tree structure bias circuit, the symmetrical routing method with ground line and the cascode current switch to reduce the errors of the conventional D/A converter caused by a threshold voltage mismatch of current cells and a voltage drop of the ground line. The designed D/A converter was implemented with a $0.6{\mu}m$ CMOS n-well technology. The measured data shows a settling time of 20ns, a conversion rate of 50 MHz and a power dissipation of 35.6mW with a single power supply of 3.3V. The experimental SNR, DNL, and INL of the D/A converter is measured to be 55dB, ${\pm}0.5LSB$, and ${\pm}2LSB$, respectively. 본 논문에서는 12비트의 해상도와 65MHz의 변환속도를 가지면서 단일 3.3V의 공급전압으로 동작하는 전류 셀 매트릭스 구조의 CMOS D/A 변환기를 제안하였다. 설계된 CMOS D/A 변환기는 우수한 단조증가성과 빠른 정착시간을 가지는 전류 셀 매트릭스 구조의 장점을 이용하면서 기존의 D/A 변환기의 전류셀 간의 문턱전압의 부정합과 접지선의 전압 강하에 의한 오차를 감소시키기 위해 트리 구조 바이어스 회로, 대칭적 접지선 연결, 캐스코드 전류 스위치를 사용하여 구현되었다. 설계된 전류 셀 매트릭스 12비트 D/A 변환기를 $0.6{\mu}m$ CMOS n-well 공정을 이용하여 제작하였다. 제작된 DAC칩을 +3.3V 단일 공급전원을 이용하여 측정한 결과, 정착시간이 20nsec로써 50MHz의 변환속도와 35.6mW의 전력소모를 나타내었다. 또한 측정된 SNR, DNL은 각각 55 dB, ${\pm}0.5LSB$,${\pm}2LSB$를 나타내었다.

3.3V-65㎒ 12비트 CMOS 전류구동 D/A 변환기 설계

류기홍(Ki Hong Ryu),윤광섭(Kwang Sub Yoon) 대한전자공학회 1998 대한전자공학회 학술대회 Vol.1998 No.6

Kinematics, kinetics and muscle activities of the lower extremity during the first four steps from gait initiation to the steady-state walking

박선우,최희석,류기홍,김사엽,김영호 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.1

In this study, biomechanical characteristics during the whole process of gait initiation for twenty normal healthy volunteers were determined by the motion analysis with six near-infrared cameras, four forceplates, and an EMG system. Gait initiation, a transitional movement phenomenon from quiet stance to steady-state walking, involves a series of muscular activities, GRFs, movements of COP and COM, and joint motions. Results showed that the location of the net COP to be most lateral during double limb stance at the beginning of gait initiation. During gait initiation, changes in anteroposterior components of GRFs were first found and then changes in vertical components followed. Hip and knee motions were found before the ankle joint motion. Walking speed, step length, and stride length gradually increased until the second step. The interaction between the COM and COP is tightly regulated to control the trajectory of the COM and thereby control total body balance.

Quick Phase Search Method on an Adsorbed System

유대황,김형국,류기홍,이호섭,백현종,황윤회 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.50 No.I

The desorption rate of adsorbed nitrogen on planar graphite was measured as the change in the adsorbed amount with increasing temperature. There exist regions in which the desorption rate changes with increasing temperature, and the regions coincide with the phase boundaries of nitrogen on graphite. These regions are caused by changes in the binding energy and the heat of adsorption under a phase transition in the adsorbed system, which affects the interaction between an adsorbed particle and either neighboring particles or the substrate. Those results show that this temperature scanning adsorption method is useful for a rough search of phases and phase boundaries in an adsorbed system without the help of other auxiliary measurements such as heat capacity measurements. This method is different from the traditional isothermal adsorption process in which much effort is needed to follow measurements repeated at different temperatures and in which other experimental methods are needed to obtain information for phases and phase changes related to the phase diagram for the adsorbed system. Through this experimental method, we can easily find the phases and the phase boundaries needed to complete the phase diagram of the adsorbed system, so the method saves much time for traditional isothermal adsorption experiments.

심장보조를 위한 흉부대동맥 근성형술 개발(예비 동물실험)

오중환,박승일,김은기,김영호,류기홍,이상헌,원주호,서재정 대한흉부심장혈관외과학회 2000 Journal of Chest Surgery (J Chest Surg) Vol.33 No.6

Background: Thoracic aortomyoplasty is one of the surgical treatment for heart failure and has advantages over artificial heart or intraaortic balloon pumps. It uses autogenous skeletal muscles and solves problems such as energy source. However its use in clinical settings has been limited. This preliminary study was designed to develop surgical technique and to determine the effect of acute descending thoracic aortomyoplsty. Material and Method: Thirteen adult Mongrel dogs were used. The left latissimus dorsi muscle was wrapped around the descending aorta under general anesthesis. Swan-Ganz and microtipped Millar catheter were used for the hemodynamics and endocaridial viability ratio. Data were collected with myostimulator on and off in normal hearts and the ischemic hearts. Result: In normal hearts, the mean aortic diastolic pressure increased from 72$\pm$15mmHg at baseline to 78$\pm$13mmHg with stimulator on. Coronary perfusion pressure increased from 61$\pm$11mmHg to 65$\pm$9mmHg. Diastolic time increased from 0.288$\pm$0.003 msec to 0.290$\pm$0.003msec. Systolic time decreased from 0.164$\pm$0.002msec to 0.160$\pm$0.002 msec. Endocardial viability ratio increased from 1.21$\pm$0.22 to 1.40$\pm$0.18. In ischemic hearts, mean aortic diastolic pressure incrased from 56$\pm$21mmHg at baseline to 61$\pm$15mmHg with stimulator on. Coronary perfusion pressure increased from 48$\pm$17mmHg to 52$\pm$15mmHg. Diastolic time increased from 0.290$\pm$0.003 msec to 0.313$\pm$0.004msec. Systolic time decreased from 0.180$\pm$0.002 msec to 0.177$\pm$0.003 msec. Endovascular viability ratio increased from 0.9$\pm$0.31 to 1.1$\pm$0.31. The limited number of cases ruled out the statistic significance. Conclusion: Descending thoracic aortomyoplasty is a simple operation designed to use patient's own skeletal muscles. It trends to increase diastolic augmentation and coronary perfusion pressure. Modification of surgical technique and stimulator protocol would maximize the effect to assist the heart.

헛디딤 보행특성 분석

황선홍(Sun Hong Hwang),류기홍(Ki Hong Ryu),금영광(Young Kwang Keum),김영호(Young Ho Kim) Korean Society for Precision Engineering 2007 한국정밀공학회지 Vol.24 No.1

In the present study, three-dimensional motion analyses were performed to determine biomechanics of the lower extremity in unexpected missing foot steps for ten healthy young volunteers. In unexpected missing foot steps, the whole plantar surface of the foot or the heel contacted to the ground. A rapid ankle dorsiflexion was found right after missing foot steps and an increased plantarflexion moment was noted during loading response. After the unexpected situation, the breaking force increased rapidly. At this time, both tibialis anterior and soleus were simultaneously activated. Moreover, the range of motion at ankle, knee and hip significantly decreased during stance. In pre-swing, rectus femoris and biceps femoris prevented the collapse of the lower limbs. During late stance, propulsive forces decreased and thus, both plantarflexion moment and power generation were significantly reduced. On the opposite side, hip extension and pelvic upward motion during terminal swing were significant. Due to the shortened pre-swing, the energy generation at the ankle to push sufficiently off the ground was greatly reduced. This preliminary study would be helpful to understand the biomechanics of unexpected dynamic perturbations and valuable to prevent frequent falling of the elderly and patients with gait disorders.

양끝이 열린 단층 탄소 나노튜브에 흡착된 질소에 대한 연구

유대황,김청식,황윤희,김형국,류기홍 한국물리학회 2002 새물리 Vol.45 No.1

The adsorption of N$_2$ on the open-ended single-walled carbon nanotube bundles was studied. The amount corresponding to the first coverage adsorbed on open-ended carbon nanotube bundles was three times larger than the amount adsorbed on close-ended nanotube bundles. The isosteric heat of adsorption was obtained from adsorption isotherm measurements performed at different temperatures ranging from 117 K to 130 K. The estimated heat of adsorption of nitrogen on the open-ended nanotube bundles was about twice that on the close-ended nanotube bundles. This directly leads to the conclusion that the binding energy of nitrogen on open-ended nanotubes is greater than that of nitrogen on close-ended nanotube bundles. 열린 단층 나노튜브에 흡착된 질소의 흡착에 대한 연구를 하였다. 열린 나노튜브에서 흡착된 첫 번째 층에 대응하는 질소 양의 크기는 닫힌 튜브에 흡착한 경우에 비하여 약 3배정도 증가하였다. 그리고 117 K에서 130 K 의 영역에서 등온 흡착 실험을 하여 얻은 등적 흡착열은 닫힌 나노튜브의 경우에 비해 약 두 배 더 큼을 알 수 있었다. 이것은 탄소 나노튜브의 내부에서 결합 에너지가 더 클 것이라는 이론적 예상과 일치한다.

열산화된 알루미늄이 첨가된 Tin black filter를 가지는 메탄센서

권오식,황숙이,심창현,임채근,방영일,김봉철,허증수,류기홍,이덕동 경북대학교 센서기술연구소 2002 센서技術學術大會論文集 Vol.13 No.1

뉴로모픽 시스템을 위한 간단한 SPICE 멤리스터 모델

최규민 ( Gyumin Choi ),박병준 ( Byeong-Jun Park ),류기홍 ( Gi-Hong Rue ),함성호 ( Sung-Ho Hahm ) 한국센서학회 2021 센서학회지 Vol.30 No.4

A simple memristor model is proposed for the neuromorphic system in the Simulation Program for Integrated Circuits Emphasis (SPICE). The memristive I-V characteristics with different voltage and frequencies were analyzed. And with the model, we configured a learning and inference system with 4 by 4 memristor array to show the practical use of the model. We examined the applicability by configuring the simplest neuromorphic circuit. The total simulation time for the proposed model was 18% lesser than that for the onememristor model. When compared with more memristor models in a circuit, the time became even shorter.