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Kim, Soonho,Kim, Min-Jae,Yoon, Hyunjo,Yoo, Doo-Yeol Elsevier 2018 Cryogenics Vol.93 No.-
<P><B>Abstract</B></P> <P>This study investigates the flexural and cracking behaviors of ultra-high-performance fiber-reinforced concrete (UHPFRC) before and after exposure to cryogenic temperatures for liquefied natural gas (LNG) storage tank applications. Normal concrete (NC), which has been used to make LNG storage tanks in Korea, was also considered for comparison. In order to evaluate the cracking resistance of NC and UHPFRC, several edge-type slabs were fabricated and tested by restraining their thermal deformation. Four-point bending tests were also performed to estimate the flexural performance before and after cryogenic cooling. Test results indicate that UHPFRC exhibited higher resistance to microcrack formation under these conditions. UHPFRC also showed substantially better flexural performance, both before and after exposure to cryogenic cooling, compared to NC. In addition, the microcracks in UHPFRC that were induced by the pre-cracking load were suddenly and effectively filled with calcium carbonate (CaCO<SUB>3</SUB>), which was formed by a chemical reaction between melting water and calcium ions. This was verified by energy dispersive X-ray spectroscopy analysis. CaCO<SUB>3</SUB> formation resulted in enhanced flexural performance, including higher strength, deflection capacity, and energy absorption capacity, as compared to the virgin UHPFRC specimens without any cracks.</P> <P><B>Highlights</B></P> <P> <UL> <LI> UHPFRC shows higher crack resistance than normal concrete under cryogenic temperature. </LI> <LI> UHPFRC provides substantially higher flexural performance than normal concrete. </LI> <LI> Microcracks in UHPFRC are suddenly and effectively filled with CaCO<SUB>3</SUB>. </LI> <LI> Self-healing capability of pre-cracked UHPFRC is achieved under cryogenic temperature. </LI> </UL> </P>
Kim, Soonho,Yoo, Doo-Yeol,Kim, Min-Jae,Banthia, Nemkumar Elsevier 2019 Cement & concrete composites Vol.104 No.-
<P><B>Abstract</B></P> <P>This study aims to examine flexural performance and self-healing capability of ultra-high-performance fiber-reinforced concrete (UHPFRC) after exposure to cryogenic temperature. To evaluate the effects of fiber type and curing condition on the flexural and self-healing properties, straight steel fibers with three different aspect ratios of 65, 97.5, and 100 and twisted steel fiber with an aspect ratio of 100 were incorporated into ultra-high-performance concrete (UHPC) mixture at identical volume fraction of 2% and two different curing processes (i.e., 3-day air curing and 28-day water curing) were applied. Test results indicate that incorporating the straight steel fibers with higher aspect ratios was more effective in enhancing the flexural performance of UHPC as compared to the short straight and twisted steel fibers. The UHPCs with straight steel fibers also exhibited better self-healing capacities than that with twisted steel fibers after exposure to cryogenic temperature. Just the 3-day air curing was enough for the UHPCs including straight steel fibers with aspect ratios of 65 and 97.5 to completely recover their flexural performance to the original level, while the 28-day water curing was even insufficient for that with twisted steel fibers to be fully recovered after cryogenic cooling. From a scanning electron microscopy with energy dispersive X-ray spectroscopy analysis, the cracks were filled with calcium carbonate (CaCO<SUB>3</SUB>), and the smaller cracks were more efficiently filled with the CaCO<SUB>3</SUB>, compared to the larger cracks.</P>
Trading costs, fat-tailed liquidity risk, and expected returns
Soonho Kim(Soonho Kim) 한국자료분석학회 2022 Journal of the Korean Data Analysis Society Vol.24 No.5
This paper examines the effect of liquidity cokurtosis(or fat-tailed liquidity) risk on asset prices using a utility function with investor wealth and trading costs considered simultaneously. This study develops a model that includes liquidity cokurtosis risk, or fat-tailed liquidity risk, which is captured by the covariance between stock i’s liquidity and the cubed market liquidity, or {(Cᵢ, C³m)} Conceptually, this refers to an individual stock’s contribution to a diversified portfolio’s liquidity kurtosis. Investors would regard a portfolio as less desirable when a stock is added to a portfolio that changes the portfolio’s liquidity distribution to a more fat-tailed shape. In the presence of a leptokurtic distribution in liquidity, the expected return is related to the systematic liquidity kurtosis, and investors require a higher premium for bearing the systematic liquidity kurtosis risks. Using factor model analysis, I find the systematic liquidity kurtosis is priced, and, according to the Hansen-Jagannathan(HJ) distance, systematic liquidity kurtosis reduces the pricing error.
Performance Analysis of 3D Localization for a Launch Vehicle Using TOA, AOA, and TDOA
Kwon, Soonho,Kim, Daeoh,Lee, Jihye,Moon, Sangmi,Chu, Myeonghun,Bae, Sara,You, Cheolwoo,Liu, Huaping,Kim, Jeong-Ho,Kim, Dae Jin,Park, Hosung,Kim, Jin Young,Kim, Cheol-Sung,Hwang, Intae Springer-Verlag 2018 Wireless personal communications Vol.103 No.2