확산모형에 대한 일반화적률추정법의 개선

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.

우선주와 보통주 간의 가격비율과 거래유동성: 유통 대비 유동 주식수

최영수 ( Youngsoo Choi ),박서영 ( Seo-young Park ),안우혁 ( Woo-hyuk An ) 한국재무관리학회 2022 財務管理硏究 Vol.39 No.3

보통주 대비 우선주 가격비율에 대한 기존 연구에서는 1) 유통주식수를 이용한 독립변수로 가격비율을 분석하고, 2) 가격비율과 거래유동성 간의 관계를 규명하고, 3) 분석 자료의 주기를 회계자료와 연동하여 분기 혹은 연간으로 분석 기간을 수년간으로 분석하고 있다. 본 연구에서는 2003년부터 2021년 7월까지의 유통/유동주식수 및 거래주식수 일별 자료를 사용하여 개별 기업의 특성을 반영한 패널분석(panel analysis)을 하였다. 실증 분석한 결과, 우선주 가격비율은 1) 의결권 가치 지표인 우선주 발행비율 및 시가총액에 부(-)의 영향을, 2) 유동성 관련 지표인 유통 대비 유동주식수비율과 거래량회전율에 우선주[보통주] 경우에는 정(+)[부(-)]의 영향을, 3) 보통주 대비 우선주 거래량비율에는 부(-)의 영향을 매우 유의적으로 받는다. 즉 일별 가격비율의 고변동성(high volatility)을 설명하려면 기업 지배구조에 관련된 유통주식수 대신에 주식 거래 유동성 특성을 고려할 수 있는 유동주식수 및 거래주식수 사용이 필요하다. 아울러 의결권 가치 혹은 유동성 지표 수준에 따라 주주친화정책 도입에 따른 우선주 가격상승을 보여주는 주식 그룹과 수급 쏠림에 기반한 머니게임 현상을 보이는 주식 그룹이 공존한다는 연구 결과를 정책 도입에 반영할 필요가 있다. Previous studies on the preferred-to-common stock price ratio were conducted as follows: (1) The price ratio is analyzed using the outstanding number of shares as an independent variable; (2) The relationship between the price ratio and liquidity is investigated; (3) Quarterly, or annual data ― in tandem with that of accounting data - is used over several sample years. We analyze a panel data from January 2003 until July 2021, at a daily frequency, with individual company characteristics including the floating and outstanding number of shares. We empirically find that the price ratio is (1) negatively affected by the issue ratio of preferred-to-common stocks and the market capitalization―which represent the value of voting rights; (2) positively (negatively) affected by the ratio of floating-to-outstanding shares and the turnover ratio of trading―which proxy for liquidity―for preferred (common) stocks; (3) negatively affected by the trading volume ratio of preferred-to-common stocks. Furthermore, to account for the high volatility of the daily price ratio, it is necessary to use the floating shares and the number of traded shares that can consider the characteristics of stock trading liquidity instead of the outstanding shares related to corporate governance. Lastly, according to the level of voting rights or liquidity indicators, it is necessary to reflect our finding in the regulatory policy that a bullish preferred stock-holding group upon a shareholder-friendly policy and a money-game group with excess demand and supply biases coexist.

차량용 초음파 센서의 간섭 예측

최영수(Youngsoo Choi),서영수(Youngsoo Seo),김영훈(Younghoon Kim) 한국자동차공학회 2018 한국자동차공학회 부문종합 학술대회 Vol.2018 No.6

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.

기계번역에 나타난 한일번역 양상

최영수(Choi Youngsoo) 한국번역학회 2012 번역학연구 Vol.13 No.4

블랙박스 영상의 비조화비를 이용한 교통사고 분석

최영수(Youngsoo Choi),박정만(Jungman Park),윤용문(Yongmoon Yun),박종찬(Jongchan Park),박하선(Hasun Park) 한국자동차공학회 2020 한국자동차공학회 학술대회 및 전시회 Vol.2020 No.11

프로젝터 회로 소음 및 진동 저감의 실험적 연구

최영수(Choi, Youngsoo),송근영(Song, Keunyoung),이종권(Yi, Jongkwon),오홍렬(Oh, Honglyeol),이승규(Lee, Seunggyu) 한국소음진동공학회 2013 한국소음진동공학회 논문집 Vol.23 No.6

This paper deals with noise reduction on a light source driving board in a projector. We analyze causes of noise/vibration in the circuit with the present increasing use of LD and LED driving boards. The main source of noise is the MLCC in the driving board. Our aim is to investigate how the mechanical arrangement of the circuit elements affects noise reduction. The result of our experiment shows that noise can be reduced by symmetrical arrangement and slots in PCB. This result is expected to facilitate a variety of applications for manufactures without a need to change circuit elements.

교통사고 조사의 핵심 도구: 사고기록 장치 데이터와 교차 검증 연구

최영수(Youngsoo Choi) 한국자동차공학회 2023 오토저널 Vol.45 No.12

감시 카메라 영상의 비조화비를 이용한 차량 사고 분석

최영수(Youngsoo Choi),김종혁(Jonghyuk Kim),윤용문(Yongmun Yun),최지훈(Jihun Choi),박종찬(Jongchan Park) 한국자동차공학회 2019 한국 자동차공학회논문집 Vol.27 No.10

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.

주행 차량의 엔진음을 이용한 속력 분석

최영수(Youngsoo Choi),박종찬(Jongchan Park),공승현(Seung-Hyun Kong) 한국자동차공학회 2022 한국 자동차공학회논문집 Vol.30 No.2

Vehicle speed at the time of an accident has a significant impact on the reliability of the reconstruction of the traffic accident. Recently, vehicle speed analysis methods, based on acoustic data from cameras, have been studied to overcome the limitation of image data due to blind spots and environmental conditions. In this paper, we proposed a speed analysis technique based on external noise and the Doppler effect generated by a moving vehicle. In particular, the frequency of vehicle engine sound was analyzed by using STFT, and the speed of the vehicle with respect to time was estimated by correcting the two-dimensional Doppler effect. Finally, the reliability of the proposed method was verified through acoustic simulation by using Matlab and actual vehicle evaluation by using acoustic data from dashboard cameras. Therefore, the proposed technique that utilizes acoustic data from cameras under limited conditions could estimate the speed of the vehicle in an accident.