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최영수,이윤동,Choi, Youngsoo,Lee, Yoon-Dong 한국통계학회 2013 응용통계연구 Vol.26 No.5
일반화적률추정법(GMM)은 금융자료에 대한 모형모수의 추정에 자주 이용되는 방법이다. 특히 GMM은 현대금융 공학 이론의 기본을 이루는 확산모형의 추정에도 매우 자주 사용된다. 그러나 최근의 연구에서 GMM은 확산모형의 모수, 특히 확산계수에 관계되는 모수의 추정에 있어서 그 성능이 좋지 못함이 지적되었다. 본 연구에서는 GMM의 이러한 단점을 개선하기 위한 대안적 방법들을 제시하고 그 통계적 성능을 시뮬레이션 연구를 통해서 비교하게 된다. 이런 과정을 통하여 제안되고 검토된 추정방법들 중, Shoji와 Ozaki (1998)가 제안한 국소선형근사법의 결과를 적용하여 GMM의 성능을 개선한 NGMM-Y 추정량이 매우 우수한 성질을 가지고 있음을 확인하게 된다. 특히 NGMM-Y 추정량은 확산계수에 관계된 모수의 추정에 있어서 비교대상이 된 다른 대안적 GMM 방법들에 비하여 우수한 성질을 가지고 있음을 확인하게 된다. Generalized Method of Moment(GMM) is a popular estimation method to estimate model parameters in empirical financial studies. GMM is frequently applied to estimate diffusion models that are basic techniques of modern financial engineering. However, recent research showed that GMM had poor properties to estimate the parameters that pertain to the diffusion coefficient in diffusion models. This research corrects the weakness of GMM and suggests alternatives to improve the statistical properties of GMM estimators. In this study, a simulation method is adopted to compare estimation methods. Out of compared alternatives, NGMM-Y, a version of improved GMM that adopts the NLL idea of Shoji and Ozaki (1998), showed the best properties. Especially NGMM-Y estimator is superior to other versions of GMM estimators for the estimation of diffusion coefficient parameters.
UPnP 환경에서 협력작업을 이용한 자율적인 복구 방법
최영수 ( Youngsoo Choi ),노상욱 ( Sanguk Noh ),최경희 ( Kyunghee Choi ),정기현 ( Gihyun Jung ) 한국정보처리학회 2005 한국정보처리학회 학술대회논문집 Vol.12 No.1
네트워크에 연결된 장치나 자원은 심각한 네트워크 단절로 인해 사용이 불가능할 수도 있다. 견고한 네트워크 연결성을 제공하기 위해 본 논문에서는 협력작업(teamwork)을 이용한 UPnP 환경에서의 자동화된 복구 방법을 제안한다. 제안한 복구 방법에서는 복구 가능한 제어 포인트(control point)들과 이와 연관된 복구 장치들이 팀을 이루어 제어 포인트에 장애(failure)가 발생하여도 다른 팀 구성원이 장치들을 자동으로 연결하여 공통의 목표를 달성한다. 제안한 복구 방법이 효과적임을 실험을 통해 검증하였는데, 이 실험에서 복구 가능한 제어 포인트는 팀 내의 다른 제어 포인트에 장애가 발생하였을 경우에도 장치로부터의 이벤트를 성공적으로 처리하였다.
망고 잎 열수 추출물의 모유두 세포에서 탈모 관련 유전자 발현에 미치는 영향 연구
최영수 ( Youngsoo Choi ),김은미 ( Eunmi Kim ),이성희 ( Seong Hee Lee ),한효상 ( Hyosang Han ),김기광 ( Keekwang Kim ) 대한본초학회 2021 大韓本草學會誌 Vol.36 No.3
Objectives : Mangifera indica leaves are well known for having a variety of benefits, including anti-inflammatory, anti-tumor, diabetic retinopathy and diabetic vasculosis. However, the effects of Mangifera indica leaves on hair loss inhibition have not been studied. In this study, we investigated to find out the activity of Mangifera indica leaves on hair loss. Methods : 2,2'-azino-bis-3-ethylbenzothiazoline-6-sulphonic acid(ABTS) analysis was performed to confirm the antioxidant efficacy of the water extract of Mangifera indica leaves (WEML). To examine the effect of WEML on cell viability in dermal papillar (DP) cells, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl) -2H-tetra Zolium (MTS) analysis was performed. The changes in the mRNA expression level of the hair loss and hair growth-related genes in dermal papilla cells by WEML treatment were confirmed by quantitative RT-PCR. Results : In dermal papilla (DP) cells, ABTS analysis and MTS analysis of WEML showed antioxidant efficacy and low cytotoxicity. As a result of gene expression analysis through Quantitative RT-PCR, no changes in hair growth-related genes BMP6 and CTNNB1 was confirmed. but inhibitory activity of WEML on hair loss-related genes EGR1, SGK, DKK1, SRD5A1 and SRD5A2 was confirmed. Conclusion : We confirmed that WEML has excellent antioxidant efficacy and a inhibitory activity of hair loss-related genes including 5α-reductase genes. These results suggest that Mangifera indica leaves have a potential activity as a hair loss treatment for hair loss and hair growth. Biochemical or molecular biological research on hair loss is needed.
CO₂ 아크 용접에서 퍼지 제어기를 이용한 회전 아크센서에 관한 연구
최영수(Youngsoo Choi),박현성(Hyunsung Park) 한국생산제조학회 2004 한국생산제조학회지 Vol.13 No.5
In automatic welding process using a robot, seam tracking is one of the important parts. Sensor for seam tracking is divided broadly into two categories as non contact sensor and contact sensor. The arc sensor is one of the non contact sensors, and it can be applied in weaving arc and rotating arc welding process. In such the arc sensors, rotating arc sensor can be applied to high speed welding over tens of ㎐. The decrease of self regulation by high rotating speed causes to improve accuracy and response of sensor. In this study, fuzzy controller was used to track the seam for the CO₂ arc welding which had unstable arc. It could be shown that the rotating arc sensor was better than the weaving arc sensor.
최영수(Youngsoo Choi),김종혁(Jonghyuk Kim),윤용문(Yongmun Yun),최지훈(Jihun Choi),박종찬(Jongchan Park) 한국자동차공학회 2019 한국 자동차공학회논문집 Vol.27 No.9
Vehicle speed estimation is the most important task in car accident reconstruction and intelligent transportation system design. Recent studies have been conducted in order to evaluate the speed of a vehicle by using the images of various surveillance cameras. However, the limitation is that it is necessary to know whether the calibration coefficient of the camera or only the average speed analysis of a specific interval is possible. In this study, we propose a novel technique for estimating vehicle speed by using a vehicle or structure already recognized as geometric information from the uncalibrated surveillance camera. The digital image processing technique tracks the specific coordinates information in all video frames and calculates the velocity change according to the video frame rate by using a cross ratio, which is the perspective invariant. The results of this method are verified through simulation and actual car evaluation. As a result, it is confirmed that it is possible to accurately analyze the change in the moving speed of a vehicle in different conditions.