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파킨슨병 말초신경병증과 당뇨병성 말초신경병증에 대한 호모시스테인의 임상적 가치
최현아(Hyun-Ah Choi),김영도(Young-Do Kim),조현지(Hyun-Ji Cho),송인욱(In-Uk Song),정성우(Sung-Woo Chung) 대한임상노인의학회 2012 대한임상노인의학회지 Vol.13 No.4
연구배경: 말초신경병증이 파킨슨병 또는 당뇨병과 동반된 환자에서 발생이 높다고 알려져 있다. 하지만 말초신경병증의 발생 기전이 매우 다양하여 아직까지 명확히 확립되어 있지 않다. 최근에 고호모시스테인혈증이 산소성 스트레스를 증가시켜 혈관내피에 병변을 일으킬 수 있다고 주장하고 있어 말초신경병증 발생을 유발하는데 기여할 수 있으리라 생각되고 있다. 따라서 저자들은 파킨슨병 및 당뇨병이 동반된 말초신경병증에 혈중 호모시스테인 농도가 영향을 주는지를 평가하고 당뇨병이 동반된 말초신경병증과 파킨슨병에 동반된 말초신경병증사이에 호모시스테인의 차이에 대해 연구하고자 한다. 방법: 본 연구에 파킨슨병이 동반된 말초신경병증을 가진 환자 31명, 당뇨병에 동반된 말초신경병증 환자 36명, 그리고 정상군 43명이 선택되었다. 모든 대상군은 신경생리검사를 통해서 말초신경병증을 확인하였고, 양 질환군사이의 혈중 호모시스테인의 농도에 대한 분석을 하였다. 파킨슨병을 동반한 말초신경병증 환자에 대해서는 Hoehn and Yahr Stage를 사용하여 운동증상의 심한 정도와 호모시스테인의 관련성을 분석하였다. 결과: 혈중 호모시스테인 농도는 두 질환군에서 정상군보다 의미있는 증가를 보였고, 두 질환군의 비교에서도 파킨슨병을 동반한 말초신경병증에서 의미 있게 높은 혈중 호모시스테인 농도를 보였다. 하지만 파킨슨병 증상의 심한정도와 호모시스테인 농도와는 관련성을 보이지 않았다. 결론: 본 연구에서 저자들은 호모시스테인의 혈중농도는 파킨슨병과 당뇨병이 동반된 말초신경병증의 위험인자로써 작용할 수 있다는 것을 추정할 수 있었다. 뿐만 아니라 파킨슨병의 발생에도 호모시스테인의 혈중농도 증가가 위험 인자로써 영향을 줄 수 있다고 조심스럽게 추정하는 바이다. Background: Peripheral neuropathy (PN) has been described in significantly higher proportions in patients with Parkinson’s disease (PD) or diabetes mellitus (DM) than in healthy controls. However, pathophysiological mechanisms underlying the development of PN are not well understood. It is currently thought that hyperhomocysteinaemia may induce endothelial dysfunction through increasing oxidative stress. It is not known if hyperhomocysteinemia is associated with PN and may thus be a contributing factor in the pathogenesis of PN. In view of these considerations, we investigated to clarify relationship between hyperhomocysteinemia and PN with PD or DM and to assess difference between the role of homocysteine in PN with PD and DM. Methods: We recruited 31 PD with PN, 36 type 2 DM with PN and 43 healthy controls. All subjects underwent electrophysiological test to clarify presence of PN and subjects with PD were evaluated the motor severity by using modified Hoehn and Yahr Stage. We analyzed correlation between plasma homocysteine level and neuropathy with PD or DM. Results: Plasma homocysteine levels in patients with PN showed higher plasma concentration than those in healthy controls. Interestingly, this study also demonstratedsignificant higher plasma homocysteine concentration in PN with PD than those in PN with DM. Conclusion: The present study showed that hyperhomosyteinemia might play a role in risk factor of PN in patients with PD and DM. Moreover, we could also suggest that increased plasma homocysteine concentration may contribute to the pathogenesis of PD because PN patients with PD have higher plasma homocysteine concentration than those with DM.
각가속도 변화에 의해 탐지된 슬립에 기반한 주행로봇의 견인력 제어
최현도(Hyun Do Choi),우춘규(Chun Kyu Woo),강현석(Hyun Suk Kang),김수현(Soohyun Kim),곽윤근(Yoon Keun Kwak) 제어로봇시스템학회 2009 제어·로봇·시스템학회 논문지 Vol.15 No.2
The common requirements of rough terrain mobile robots are long-term operation and high mobility in rough terrain to perform difficult tasks. In rough terrain, excessive wheel slip could cause an increase in the amount of dissipated energy at the contact point between the wheel and ground or, even more seriously, the robot could lose all mobility and become trapped. This paper proposes a traction control algorithm that can be independently implemented to each wheel without requiring extra sensors and devices compared with standard velocity control methods. The proposed traction algorithm is analogous to the stick-slip friction mechanism. The algorithm estimates the slippage of wheels by angular acceleration change, and controls the increase or decrease state of torque applied to wheels Simulations are performed to validate the algorithm. The proposed traction control algorithm yielded a 65.4% reduction of total slip distance and 70.6% reduction of power consumption compared with the standard velocity control method.
개발도상국 해외자회사의 역진적 지식이전 유형에 관한탐색적 연구: 중국 해외자회사 사례를 중심으로
최현도 ( Hyun Do Choi ) 한국국제경영학회 2015 國際經營硏究 Vol.26 No.1
It is no surprise that firms in developed countries have heavily invested on developing countries. We have paid little attention on these subsidiaries due to low technological capabilities in developing countries so far. However, they have the potential as a source of technological innovations from a different perspective. This study aims to suggest four propositions on reverse knowledge flow of subsidiaries in developing countries. We developed a research frame synthesized from economics of technological innovations and development studies and applied it to the three cases based on secondary sources and patent data. Four propositions in this study could contribute to restructuring the global value chain consisting of the new partnerships between firms in developing and developed countries.
최현도(Hyun Do Choi),김준형(Jun Hyung Kim),김수현(Soohyun Kim),곽윤근(Yun Kun Kwak) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4
In many applications, piezoelectric motor has been used in the areas where excellent controllability, fine position resolution are required or magnetic field noise should be eliminated. However the piezoelectric motor has two major demerits. One is difficulty in maintaining vibration amplitude constantly with temperature rise and wear, and the other is heat generation induced by dielectric and mechanical loss. In this thesis, piezoelectric motor to overcome these problems is proposed. And proposed piezoelectric motor is operated using momentum exchange between bimorph and rotor. To maximize steady state velocity and static torque of proposed motor, the guideline is established using two bimorph models. Then the guideline is partially proved by comparison between simulation and experiment. There was no heat generation in the few hours of experiments.
강현석(Hyun-Suk Kang),곽윤근(Yoon Keun Kwak),최현도(Hyun-Do Choi),정해관(Hae-Kwan Jeong),김수현(Soo-Hyun Kim) 제어로봇시스템학회 2008 제어·로봇·시스템학회 논문지 Vol.14 No.10
When mobile robots perform the mission in the rough terrain, the traversability depended on the terrain characteristic is useful information. In the travers abilities, wheel-terrain maximum friction coefficient can indicate the index to control wheel-terrain traction force or whether mobile robots to go or not. This paper proposes estimating wheel-terrain maximum friction coefficient. The existing method to estimate the maximum friction coefficient is limited in flat terrain or relatively easy driving knowing wheel absolute velocity. But this algorithm is applicable in rough terrain where a lot of slip occurred not knowing wheel absolute velocity. This algorithm applies the tire-friction model to each wheel to express the behavior of wheel friction and classifies slip-friction characteristic into 3 major cases. In each case, the specific algorithm to estimate the maximum friction coefficient is applied. To test the proposed algorithm’s feasibility, test bed(ROBHAZ-6WHEEL) simulations are performed, And then the experiment to estimate the maximum friction coefficient of the test bed is performed. To compare the estimated value with the real, we measure the real maximum friction coefficient. As a result of the experiment, the proposed algorithm has high accuracy in estimating the maximum friction coefficient.
청소년의 시스템 사고 교육을 통한 창의성의 기반이 되는 사고의 확장 효과 분석
김도훈 ( Do Hoon Kim ),이미숙 ( Mi Sook Yi ),홍영교 ( Young Kyo Hong ),최현아 ( Hyun Ah Choi ) 한국시스템다이내믹스학회 2006 한국시스템다이내믹스 연구 Vol.7 No.1
This research assumes that expanding the depth and range of thinking can be achieved through systems thinking education to the youth. To verify this assumption, degree of expansion of thinking was evaluated after the systems thinking education was done to middle school students in Kyeongi province. As a result, significant statistical difference was found. More variables were presented after systems thinking education. This means education program enhances student`s thinking ability. Possibility of systems thinking application can be verified through systems thinking education to the various ranges of students in the future.
최지혁(Choi Jee-Hyuck),최현도(Choi Hyun-Do),김수현,곽윤근(Kwak Yoon-Keun) 대한기계학회 2006 대한기계학회 춘추학술대회 Vol.2006 No.11
The market of mobile robot is increasingly expanding and the function of robot diversifies. Robot cleans room, educates children, guards home and so on. As a result, the power which robot needs is increasing. So many mobile robots need the recharging for its working. During recharging, robot can’t work and this is a serious defect especially in security. To solve this problem, this study suggests a docking station for battery change. At docking station, robot changes its discharged battery to charged battery autonomously. We design a docking mechanism and battery changing system by using axiomatic design. Docking mechanism compensates for offset error and orientation error without actuator. Battery change system change discharged battery to charged battery by using simple mechanism and two motors. We make a 3D model and simulate the model. The model changes battery successfully.