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유가 충격에 따른 국내주식시장의 비대칭적 변동성과 요인분석
정세미,제상영 한국자료분석학회 2011 Journal of the Korean Data Analysis Society Vol.13 No.6
This study exams the relationship among time-varying asymmetric volatility derived from EGARCH model (Nelson, 1991), macroeconomic activities such as CPI, IP, and IR and its determinants. The results of VECM and impulse response function are i) shocks of CPI, IP, and IR in durable goods markets are bigger than that in non-durable goods markets, and ii) impact of interest rate on the time-varying asymmetric volatility is the most sensitive. This finding is generally the same as interest rate is the key factor affecting on return in financial markets. 본 연구는 Nelson(1991)의 EGARCH 모형으로부터 시가변 비대칭적 변동성(time-varying asymmetric volatility)을 도출하여 거시경제활동변수인 소비자물가지수(CPI), 산업생산지수(IP), 이자율(IR)간의 관계를 검증하고, 벡터오차수정모형(VECM)을 통해 이에 대한 주요 원인변수(principle factor)를 찾고자 하였다. 분석 결과 변수들 간의 장기적이고 동태적인 상호관계, 즉 장기적인 균형관계를 확인하였고, 벡터오차수정모형(VECM)의 충격반응함수(impulse response function) 분석 결과, 먼저 원인변수 CPI, IP, IR에 대한 충격은 비내구재(non-durable goods)에 비해 내구재(durable goods)에 크게 미침을 알 수 있었다. 또 모든 주가지수의 시가변 비대칭적 변동성에 영향을 미치는 세 가지 거시경제활동 변수 중 IR(interest Rate)의 영향이 가장 큰 것으로 나타났다. 이는 일반적인 금융시장(financial markets)에서 수익률 결정에 이자율이 민감한 반응을 주는 것과 일치한다.
정세미,박석호,박종오,최현철,이정,고광준,심두선,임경섭,정명호,고성영 제어·로봇·시스템학회 2015 International Journal of Control, Automation, and Vol.13 No.6
This paper proposes a locomotive, therapeutic microrobot based on an electromagnetic actuation (EMA) system for intravascular treatment. The proposed EMA system consists of the two pairs of stationary Helmholtz and Maxwell coils along the x-axis and two pairs of rotational uniform saddle coil (USC) and gradient saddle coil (GSC) about the x-axis. A microrobot actuated by this type of EMA system can be used as a locomotive, therapeutic microrobot in medical applications. Especially, when we apply sinusoidal currents to the Maxwell coil and GSC pairs, the microrobot shows oscillatory forward and backward motion (which is called as hammering motion); however, when sinusoidal voltages are applied to the Maxwell coil and GSC pairs, the microrobot does not show the desired hammering motion. W proposes a compensation algorithm for the resistance and inductance variations and demonstrates the desired hammering motion for the effective therapeutic function of the microrobot. Through various experiments, we validate that the proposed microrobot using the EMA system can show precise locomotion and provide enhanced treatment. Through various experiments, we validate that the proposed microrobot using the EMA system can show precise locomotion and provide enhanced treatment.
Feasibility Study on Magnetically Steerable Guidewire Device for Percutaneous Coronary Intervention
정세미,최현철,고광준,이정,고성영,박종오,박석호 제어·로봇·시스템학회 2017 International Journal of Control, Automation, and Vol.15 No.1
In this paper, we proposed a magnetically steerable guidewire device composed of two parts: steeringpart and feeding part. The steering part consists of a magnet attached to the end of a commercial guidewire and2-pair Helmholtz coils, and the feeding part consists of a motorized stage and a device for holding the guidewire. In detail, the 2-pair Helmholtz coils generate a uniform magnetic field that can align the guidewire magnet inthe region of interest (ROI) along a desired direction. In addition, the feeding part remotely controls guidewireinsertion and the length of the flexible part of the guidewire extruded from a catheter. For accurate alignment at theend of the guidewire, we controlled the flexible length of the guidewire extruded from a catheter and the intensityand direction of the uniform magnetic field using the feed-forward method. In addition, to reduce alignment errordue to unpredicted disturbances and friction effects between the test-bed and the guidewire, proportional-integralderivativecontrol is introduced as a feedback control algorithm. Using the control algorithms, we demonstratedaccurate actuation of the steerable guidewire device with a steering angle error of less than 0:5◦. We expect that theproposed steerable guidewire device can be applied to the development of a 3-D locomotive guidewire with positionrecognition for percutaneous coronary intervention (PCI).