한국 ETF 시장에서의 ETF 추적오차와 유동성에 관한 실증 연구

학위논문(석사) - 한국과학기술원 : 경영공학부, 2024.2,[iii, 44 p. :]This paper investigates the effect of exchange-traded fund(ETF) liquidity on ETF tracking errors , returns and volatility in the Korea. Illiquidity ETF tends to have significant tracking errors. The impact of ETF liquidity on tracking errors is different, and ETFs with optimized replications fewer tracking errors than ETFs with derivatives-used replication. In the Korean ETF market, the low trading frequency of ETFs does not necessarily affect the difference between ETF return variance and Net Asset Value (NAV) return variance. These findings suggest that illiquidity ETFs are more likely to deviate from NAV and the index, potentially implying different risks from the underlying portfolio.한국과학기술원 :경영공학부

Full-arch accuracy of five intraoral scanners: In vivo analysis of trueness and precision

Objective: To evaluate the trueness and precision of full-arch scans acquired using five intraoral scanners and investigate the factors associated with the dimensional accuracy of the intraoral scan data. Methods: Nine adult participants (mean age, 34.3 +/- 8.3 years) were recruited. Four zirconium spheres ((sic) 6 mm) were bonded to the canines and the molars. Following acquisition of reference scans using an industrial-grade scanner, five intraoral scanners, namely i500, CS3600, Trios 3, iTero, and CEREC Omnicam, were used to scan the arches. Linear distances between the four reference spheres were automatically calculated, and linear mixed model analysis was performed to compare the trueness and precision of the intraoral scan data among the different scanners. Results: The absolute mean trueness and precision values for all intraoral scanners were 76.6 +/- 79.3 and 56.6 +/- 52.4 mu m, respectively. The type of scanner and the measured linear distances had significant effects on the accuracy of the intraoral scan data. With regard to trueness, errors in the intermolar dimension and the distance from the canine to the contralateral molar were greater with Omnicam than with the other scanners. With regard to precision, the error in the linear distance from the canine to the molar in the same quadrant was greater with Omnicam and CS3600 than with the other scanners. Conclusions: The dimensional accuracy of intraoral scan data may differ significantly according to the type of scanner, with the amount of error in terms of trueness being clinically significant