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본태성 진전 환자의 검지에서의 자세성 진전에 대한 감각자극 효과
이상기,김지원,권유리,이영재,이정환,엄광문,권도영,이찬녕,서유미,김미경,박건우,정호춘,Lee, S.K.,Kim, J.W.,Kwon, Y.R.,Lee, Y.J.,Lee, J.H.,Eom, G.M.,Kwon, D.Y.,Lee, C.N.,Seo, Y.M.,Kim, M.K.,Park, K.W.,Jeong, H.C.,Manto, M. 대한의용생체공학회 2013 의공학회지 Vol.34 No.3
The essential tremor is an involuntary oscillatory movement of body parts. Conventional treatments of essential tremor have little effects in some patients and also leads to significant side effects. Alternative to these treatments, sensory stimulation may have beneficial effects on the essential tremor. The purpose of this study was to analyze an effect of sensory stimulation on essential tremor. Ten patients with essential tremor ($67.4{\pm}8.82$ yrs, 5 men and 5 women) participated in this study. Three-axis gyro sensors were attached on index finger, hand and forearm of patients. Task of 'arms outstretched forward' was performed with and without sensory stimulation. Vectorsum of three dimensional angular velocities (pitch, roll, yaw) was calculated. Outcome measures included root-meansquare (RMS) mean of the vector-sum amplitude, total power, peak power and peak frequency. RMS amplitude, total power and peak power were reduced by sensory stimulation (p < 0.05). Peak frequency was not affected by sensory stimulation. The results indicate that the sensory stimulation is useful to suppress the essential tremor.
M/E<sub>n</sub>/1 대기모형에서 얼랑분포의 성질을 이용한 오버슛의 분포에 대한 근사
이상기,배종호,Lee, Sang-Gi,Bae, Jongho 한국통계학회 2015 응용통계연구 Vol.28 No.1
본 논문은 $M/E_n/1$ 대기모형에서 작업부하량과정의 오버슛의 분포함수에 대한 근사식을 제안한다. 오버슛이란 작업부하량과정이 미리 정해진 한계점을 처음으로 초과할 때 초과하는 양을 말하는데 정확한 분포함수는 수학적인 표현으로만 얻어졌을 뿐 분포함수를 실제로 계산하는 것은 거의 불가능하다. 그래서 기존 연구에서는 오버슛에 관한 몇가지 성질을 이용하여 오버슛의 분포함수에 대한 근사식이 구해졌다. 본 논문은 고객의 서비스시간의 분포가 얼랑분포라는 점을 활용하여 기존에 얻어진 근사식보다 더 정확한 근사식을 제안한다. 그리고 제안한 근사식이 얼마나 참값에 가까운지 판단하기 위하여 시뮬레이션을 통하여 얻어진 오버슛의 분포함수와 비교한다. We consider an $M/E_n/1$ queueing model where customers arrive at a facility with a single server according to a Poisson process with customer service times assumed to be independent and identically distributed with Erlang distribution. We concentrate on the overshoot of the workload process in the queue. The overshoot means the excess over a threshold at the moment where the workload process exceeds the threshold. The approximation of the distribution of the overshoot was proposed by Bae et al. (2011); however, but the accuracy of the approximation was unsatisfactory. We derive an advanced approximation using the property of the Erlang distribution. Finally the newly proposed approximation is compared with the results of the previous study.
위상차 전압 변환기를 이용한 Fractional-N 위상고정루프
이상기,최영식,Lee, Sang-Ki,Choi, Young-Shig 한국정보통신학회 2012 한국정보통신학회논문지 Vol.16 No.12
본 논문에서는 기존의 fractional-N 위상고정루프의 가장 큰 문제점인 fractional 스퍼를 억제하기 위해 위상차-전압 변환기(Phase Difference-to-Voltage Converter : PDVC)를 도입하였다. PDVC는 위상주파수 검출기 출력 신호의 위상차에 따라 전하펌프의 전류량을 조절한다. 제안한 구조는 위상 주파수 검출기(phase frequency detector) 신호들의 위상차가 커지면 전하펌프(charge pump) 전류를 감소시켜 fractional 스퍼를 줄일 수 있는 구조이다. 회로는 1.8V $0.18{\mu}m$ CMOS 공정의 파라미터를 이용하여 HSPICE로 시뮬레이션을 수행하고 회로의 동작을 검증하였다. In this paper, a Phase Difference-to-Voltage Converter (PDVC) has been introduced into a conventional fractional-N PLL to suppress fractional spurs. The PDVC controls charge pump current depending on the phase difference of two input signals to phase frequency detector. The charge pump current decreases as the phase difference of two input signals increase. It results in the reduction of fractional spurs in the proposed fractional-N PLL. The proposed fractional-N PLL with PDVC has been designed based on a 1.8V $0.18{\mu}m$ CMOS process and proved by HSPICE simulation.
이상기,김영원,신동윤,임미경,이자형,송정모,김락형,Lee, Sang-Gi,Kim, Young-Won,Shin, Dong-Yun,Lim, Mi-Kyoung,Yi, Ja-Hyeong,Song, Jung-Mo,Kim, Lak-Hyung 사상체질의학회 2007 사상체질의학회지 Vol.19 No.2
1. Objectives The objective of this study was to measure the differences of EEG changes accoring to emotional stimulus in Sasangin. 2. Methods 44 healthy volunteers(Soyangin 10, Soeumin 14, Taeumin 20) were participated. Sasang Constitution was diagnosed by Sasang specialist. Volunteers watched horror movie as the emotional stimulus. We recorded EEG data during pre-stimulus rest(120sec), during-stimulus(197sec), rest-stimulus(120sec). Power spectral analysis was done and relitive power and ${\alpha}/{\beta}$ ratio were compared among each groups. 3. Results (1) The mean of relative ${\alpha}$ of Taeumin was significantly decreased according to stimulus compared with Soyagnin. (2) Relative ${\alpha}$ of Soeumin was significantly decreased in T3 area according to stimulus compared with Taeumin. (3) Relative ${\beta}$ of Taeumin group was significantly increased in Fp2 area according to stimulus compared with Soeumin. 4) Relative $high-{\beta}$ of Soyangin group was significantly decreased in F3 by the post-stimulus rest compared with Soeumin. (5) ${\alpha}/{\beta}$ ratio of Soeumin was significantly increased according to stimulus compared with other groups. 4. Conclusions Soyangin showed sensitive changes according to the emotional simulus compared with Soeumin and Taeumin. Above results suggest that the emotional characteristics of Sasangin can be measured by objective methods as by EEG.
OAI 기반 Open Digital Library 연구
이상기,Lee, Sang-Gi 한국과학기술정보연구원 과학기술정보센터 2004 Journal of Information Science Theory and Practice Vol.35 No.3
Digital library technology is facing issues such as interoperability, content extension, and the need for a more efficient management environment. A system that is based on standardization and interoperability is required to resolve these issues. Open Digital Library is the system for the next generation that resolves the above problems. We have conducted some research on issues such as OAI and OAI-PMH, which are the basic knowledge behind the Open Digital Library technology and also investigated the Open Digital Library framework, cases of study and implementation of this technology. Finally, we have made some suggestions on the extendability of Open Digital Library technology using the standardized technologies. 현재 디지털라이브러리는 상호운용성의 문제, 콘텐트 확장의 한계, 편리한 관리 환경의 필요성에 직면해 있다. 이를 해결하기 위해선 표준화와 상호운용성이 전제된 시스템이 필요하다. 이런 문제를 근원적으로 해결해 줄 수 있는 차세대 디지털라이브러리 시스템으로 주목 받고 있는 것이 Open Digital Library이다. 여기서는 Open Digital Library의 사상적 기반이 된 OAI 및 OAI-PMH에 대해 조사하였으며, Open Digital Library 프레임워크, 설계 주안점, 적용사례를 연구하였다. 끝으로 표준화된 요소기술을 활용한 Open Digital Library의 발전방향과 확장성을 제시하였다.
나이브베이즈 분류모델과 협업필터링 기반 지능형 학술논문 추천시스템 연구
이상기,이병섭,박병용,황혜경,Lee, Sang-Gi,Lee, Byeong-Seop,Bak, Byeong-Yong,Hwang, Hye-Kyong 한국과학기술정보연구원 과학기술정보센터 2010 Journal of Information Science Theory and Practice Vol.41 No.4
정보기술과 인터넷의 발달로 학술정보가 폭발적으로 증가하고 있다. 정보 과잉으로 인해 연구자들은 필요한 정보를 찾거나 필터링하는데 더 많은 시간과 노력을 투입하고 있다. 이용자들이 원하는 정보를 예측하여 관심 가질만한 정보를 선별하여 추천하는 시스템을 전문가시스템, 데이터마이닝, 정보검색 등 다양한 분야에서 오래 전부터 연구하여 왔다. 최근에는 콘텐츠기반추천시스템과 협업필터링을 결합하거나 다른 분야 모델을 접목한 하이브리드 추천시스템으로 발전하고 있다. 본 연구에서는 기존 추천시스템 문제를 해결하고 대규모 정보센터나 도서관에서 학술논문을 효율적이고 지능적으로 추천하기 위해 협업필터링과 나이브베이즈모델을 결합한 새로운 방식의 추천시스템을 제시하였다. 즉, 협업필터링 방식으로 과도한 특성화(Over-specialization) 문제를 해결하고, 나이브베이즈모델을 통해 평가정보나 이용정보가 부족한 신규콘텐츠 추천문제를 해소하였다. 본 모델을 검증하기 위해 한국과학기술정보연구원 NDSL에서 제공하는 식품과 전기 분야 학술논문에 적용하여 실험하였다. 현재 NDSL 이용자 4명에게 피드백을 받은 결과 추천논문에 상당히 만족하는 것으로 나타났다. Scholarly information has increased tremendously according to the development of IT, especially the Internet. However, simultaneously, people have to spend more time and exert more effort because of information overload. There have been many research efforts in the field of expert systems, data mining, and information retrieval, concerning a system that recommends user-expected information items through presumption. Recently, the hybrid system combining a content-based recommendation system and collaborative filtering or combining recommendation systems in other domains has been developed. In this paper we resolved the problem of the current recommendation system and suggested a new system combining collaborative filtering and Naive Bayes Classification. In this way, we resolved the over-specialization problem through collaborative filtering and lack of assessment information or recommendation of new contents through Naive Bayes Classification. For verification, we applied the new model in NDSL's paper service of KISTI, especially papers from journals about Sitology and Electronics, and witnessed high satisfaction from 4 experimental participants.