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이용호,권혁찬,김기웅,김진목,박용기 한국뇌학회 2002 한국뇌학회지 Vol.2 No.2
두뇌 신경세포의 전기생리학전인 활동에 의해 발생되는 자기장의 분포를 머리 밖에서 초전도양자간섭소자(Superconducting QUantum Interference Device; SQUID)로 측정한 것이 뇌자도(Magnetoencephalogram; MEG) 이다. MEG 기술은 뇌신경활동에 참여하는 세포내 전류가 만드는 자기장 신호를 측정하므로 뇌신경활동을 직접 알 수 있는 장점이 있고, 비접촉 . 비파괴적인 측정방법이며 우수한 시간 . 공간분해능을 가지므로 뇌기능 연구 및 기능적 질환진단에 중요하게 사용될 수 있다. 이미 선진연구기관 또는 병원에서는 정밀한 뇌기능 연구 및 진단에 MEG 기술을 본격적으로 활용하기 시작하였다. 뇌신경회로의 미약한 전류에 의해 발생되는 MEG 신호는 매우 미약하기 때문에 정밀측정기술이 요구되는 데 고감도 SQUID의 개발, 환경자기잡음 제거기술, 신호처리기술 등이 개발됨으로써 MEG 측정이 가능하게 되었다. MEG의 주된 목적은 두뇌 활동전류의 위치, 크기 및 방향을 동적으로 표시하는 것으로서, 측정된 다채널 MEG 신호로부터 활동전류의 정보를 구하기 위하여 역문제의 해법을 풀고, MRI 데이터에 시각적으로 표시함으로써 임상적으로 유용한 정보가 된다. MEG는 뇌신경세포에서의 전기적 활동을 직접 관찰할 수 있다는 점에서 다른 뇌기능 영상진단법과는 구분되는 특징을 가지며, MEG 기술의 주된 응용분야는 수술전 대뇌피질의 기능조사, 간질 발생부위의 국소화, 정신분열 등 임상진단과 인지기능 연구이다. 본 논문에서는 MEG 신호의 발생원, MEG 기술의 특징, 측정에 필요한 요소기술, MEG의 응용예에 대해 소개하고자 한다. Magnetoencephalogram (MEG) is the magnetic fields produced by the electrophysiological activity of the brain. By measuring the MEG signals using the magnetic sensors, superconducting quantum interference devices (SQUID_s), localization and diagnosis of the brain function are possible with superior temporal and spatial resolution. Since the human head is transparent to the magnetic field and MEG measures the magnetic field signals without any disturbance, we can get precise information on the neural currents directly. However, the magnetic field strength of the MEG signals is very weak, typically smaller than 1 pT. In order to measure and analyze MEG signals, very sensitive SQUID sensors, elimination of environmental magnetic noises, signal processing and localization of current dipoles are necessary. As a totally noninvasive metho, MEG is currently used routinly in many advanced clinics for the locaization of epileptic foci and presurgical localization of the important brain regions.
박용기,김인선,이용호,권혁찬,김진목,김기웅 한국비파괴검사학회 2003 학술대회 논문집 Vol.- No.1
SQUID is the most sensitive magnetic sensor known. It is able to detect the magnetic field as small as few femto Tesla (fT), which is equivalent to one of 10 billionth of earth magnetic field (about 50 ??T). SQUID can be applied in the various fields and its need will be increased greatly in the future. If SQUID is applied in the medical technology, there will be improvement in accurate diagnosis of brain and heart by supplying more information about the functions of such human organs. The nondestructive evaluation (NDE) of deep-lying flaws in the inner layer of lab jointed structures of aircraft, which is very difficult with the existing method became possible using high T_c SQUID. In this paper, the current status of SQUID applications in both medical and NDE fields will be reviewed.
Kim, Jin-Mok,Lee, Yong-Ho,Kwon, Hyukchan,Kim, Kiwoong,Sasada, Ichiro IEEE 2007 IEEE transactions on applied superconductivity Vol.17 No.1
<P>A double relaxation oscillation SQUID with a reference junction (RJ-DROS) already has a fixed reference current, so that it holds a fixed flux-to-voltage characteristics when fabricated. When an additional current flows through the reference junction but not through the signal junction in the RJ-DROS, we have obtained the variation of its characteristics. The additional reference current has an effect on reducing the fixed reference current, which results in changing averaged relaxation voltage and transfer coefficient. In particular, while the critical current of the signal SQUID exceeds the reference current, the averaged relaxation voltage at the reference junction is enlarged by the added bias current combined with an additional current and an initial bias current. Therefore the additional reference current can provide the RJ-DROS with variable modulation depth and width within the operating range. Although the characteristics of RJ-DROSs are fixed differently each to each when they are fabricated, the additional current can adjust their characteristics to the same one, which is useful for controlling DROSs in a multichannel DROS system. However, an input-bias current in the preamplifier detecting the outputs at the reference junction, acts as an additional current, and then makes the reference current shift from the optimum current or deviate from the operating range, the input-bias current needs to be regulated within the operating range</P>
Acoustic stimulation on the round window for active middle ear implants
Seong, Kiwoong,Lee, Kyuyup,Puria, Sunil,Cho, Jin-Ho Elsevier 2018 Computers in biology and medicine Vol.97 No.-
<P><B>Abstract</B></P> <P>Many clinical reports have discussed the effectiveness of stimulating the ear's round window (RW) with a tool to mitigate conductive and mixed hearing loss. The RW is one of the two openings from the middle ear into the inner ear. Various methods have been proposed to construct a highly efficient, easily implanted, and reliable RW transducer. Devices, however, such as floating mass transducers, have difficulty establishing proper contact without some degree of bone incision around the RW. Additionally, vibration energy may not be fully transmitted to the cochlea, but instead will be spread through the soft tissue around the transducer. We propose a more direct RW stimulation with very high acoustical impedance using a receiver that is a volume velocity source. We expect this source to overcome large acoustic impedance by maximizing sound pressure in a confined space, the RW niche. To verify the effectiveness of the proposed method, ear canal pressure, RW pressure, and stapes velocity are measured by acoustic RW stimulation of human temporal bones.</P>
초소형 비행체용 하이브리드 엔진 냉각을 위한 3D 프린팅 카울 형상 및 재질 연구
이기웅(Kiwoong Lee),김우비(Woo Bee Kim),권혁록(Hyuk Rok Gwon),김대원(Dae Won Kim),정윤식(Yunsik Jung),이현석(Hyeon Seok Lee),조성진(Sung Jin Jo),이선형(Seon Hyeong Lee) 한국추진공학회 2019 한국추진공학회 학술대회논문집 Vol.2019 No.5
본 논문에서는 하이브리드 추진시스템에 사용하는 공랭식 엔진에 3D 프린터로 제작된 카울을 적용하기 위하여 고려되어야 할 형상과 재질 특성에 대해 살펴보았다. 열/유동 해석을 통해 냉각 성능 확인 및 카울에 영향을 줄 수 있는 요소들에 대하여 연구하였으며, 실물 모사 형상의 지상 시험을 통하여 최종적으로 냉각 카울로 적용할 형상 및 재질을 선정하였다. In this paper, we studied shape and material feature which must be considered for appling 3D printing cowls for air cooling hybrid propulsion system engine. Using Heat/Flow analysis, figured the cooling efficiency and factor that can influence to cowl, then confirmed final model by ground test with actual mock-up.
Bi-level optimizing control of a simulated moving bed process with nonlinear adsorption isotherms
Kim, Kiwoong,Kim, Jin-Il,Park, Hyukmin,Koo, Yoon-Mo,Lee, Kwang Soon Elsevier 2011 Journal of chromatography A Vol.1218 No.38
<P><B>Abstract</B></P><P>A bi-level optimizing control scheme originally proposed for a simulated moving bed (SMB) with linear isotherms has been extended to an SMB with nonlinear isotherms. Cyclic steady state optimization is performed in the upper level to determine the optimum switching period and time-varying feed/desorbent flow rates, and repetitive model predictive control is run in the lower level for purity regulation, taking the decision variables from the upper level as feed-forward information. Experimental as well as numerical study for an SMB process separating a high-concentration mixture of aqueous <SMALL>L</SMALL>-ribose and <SMALL>L</SMALL>-arabinose solutions showed that the proposed scheme performs satisfactorily against various disturbances. In contrast, an alternative scheme based on an SMB model with linear isotherms showed a limitation in the control performance; this scheme was apt to fail in purity regulation.</P>