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Yang, Eun-hyeok,Noh, Young Su,Hong, Gi Hoon,Moon, Dong Ju Elsevier 2018 CATALYSIS TODAY - Vol.299 No.-
<P><B>Abstract</B></P> <P>The effect of Sr addition to LaNiO<SUB>3</SUB> perovskite catalysts was studied for the steam-CO<SUB>2</SUB> reforming of methane. X-ray diffraction (XRD) patterns indicate that different ionic radii caused distortion of the perovskite lattice and produced alien phases such as La<SUB>2-x</SUB>Sr<SUB>x</SUB>NiO<SUB>3±δ</SUB> and Sr<SUB>0.5</SUB>La<SUB>1.5</SUB>NiO<SUB>4</SUB>. Moreover, these different phases affected reduction behavior. The influence of Sr mainly appeared in the steam-CO<SUB>2</SUB> reforming of methane reaction. SrO species adsorbed CO<SUB>2</SUB> during the reaction and produced SrCO<SUB>3</SUB>, which has a better ability of eliminating carbon sources by producing La<SUB>2</SUB>O<SUB>2</SUB>CO<SUB>3</SUB>, and by this means, carbon formation was significantly suppressed. However, the addition of Sr species covered the support sites leading to large-sized nickel particles by reducing the interaction between the support and active metals, thus the catalytic activity was decreased by an increase in Sr concentration on the catalysts. Therefore, we recommend using a small amount of Sr in the perovskite-based catalysts to obtain superior resistance to carbon deposition with moderate catalytic activity.</P> <P><B>Highlights</B></P> <P> <UL> <LI> La<SUB>1-x</SUB>Sr<SUB>x</SUB>NiO<SUB>3</SUB> was prepared by EDTA-cellulose method. </LI> <LI> Each catalyst showed different physicochemical properties. </LI> <LI> Sr played role as increase in basicity and suppression of carbon formation. </LI> <LI> La<SUB>0.9</SUB>Sr<SUB>0.1</SUB>NiO<SUB>3</SUB> showed moderate catalytic activity and good resistance to carbon formation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Tests on Cementless Alkali-Activated Slag Concrete Using Lightweight Aggregates
Yang, Keun-Hyeok,Mun, Ju-Hyun,Lee, Kang-Seok,Song, Jin-Kyu Korea Concrete Institute 2011 International Journal of Concrete Structures and M Vol.5 No.2
Five all-lightweight alkali-activated (AA) slag concrete mixes were tested according to the variation of water content to examine the significance and limitation on the development of cementless structural concrete using lightweight aggregates. The compressive strength development rate and shrinkage strain measured from the concrete specimens were compared with empirical models proposed by ACI 209 and EC 2 for portland cement normal weight concrete. Splitting tensile strength, and moduli of elasticity and rupture were recorded and compared with design equations specified in ACI 318-08 or EC 2, and a database compiled from the present study for ordinary portland cement (OPC) lightweight concrete, wherever possible. Test results showed that the slump loss of lightweight AA slag concrete decreased with the increase of water content. In addition, the compressive strength development and different mechanical properties of lightweight AA slag concrete were comparable with those of OPC lightweight concrete and conservative comparing with predictions obtained from code provisions. Therefore, it can be proposed that the lightweight AA slag concrete is practically applicable as an environmental-friendly structural concrete.
Yang, Keun-Hyeok,Cheon, Ju Hyun,Kwon, Seung-Jun TECHNO-PRESS 2017 COMPUTERS AND CONCRETE Vol.19 No.2
Crack on concrete surface allows more rapid penetration of chlorides. Crack width and depth are dominant parameters for chloride behavior, however their effects on chloride penetration are difficult to quantify. In the present work, the previous anisotropic (1-D) model on chloride diffusion in concrete with single crack is improved considering crack shape and roughness. In the previous model, parallel-piped shape was adopted for crack shape in steady-state condition. The previous model with single crack is improved considering wedge shape of crack profile and roughness. For verifying the proposed model, concrete samples for nuclear power plant are prepared and various crack widths are induced 0.0 to 1.2 mm. The chloride diffusion coefficients in steady-state condition are evaluated and compared with simulation results. The proposed model which can handle crack shape and roughness factor is evaluated to decrease chloride diffusion and can provide more reasonable results due to reduced area of crack profile. The roughness effect on diffusion is evaluated to be 10-20% of reduction in chloride diffusion.
A Stress-Strain Model for Brick Prism under Uniaxial Compression
Yang, Keun-Hyeok,Lee, Yongjei,Hwang, Yong-Ha Hindawi Limited 2019 Advances in civil engineering Vol.2019 No.-
<P>This study proposes a simple and rational stress-strain relationship model applicable to brick masonry under compression. The brick prism compression tests were conducted with different mortar strengths and with constant brick strength. From the observation of the test results, shape of the stress-strain curve is assumed to be parabola. In developing the stress-strain model, the modulus of elasticity, the strain at peak stress, and the strain at 50% of the peak stress on the descending branch were formulated from regression analysis using test data. Numerical and statistical analyses were then performed to derive equations for the key parameter to determine the slopes at the ascending and descending branches of the stress-strain curve shape. The reliability of the proposed model was examined by comparisons with actual stress-strain curves obtained from the tests and the existing model. The proposed model in this study turned out to be more accurate and easier to handle than previous models so that it is expected to contribute towards the mathematical simplicity of analytical modeling.</P>
Affinity Maturation of an Anti-Hepatitis B Virus PreS1 Humanized Antibody by Phage Display
Yang, Gi-Hyeok,Yoon, Sun-Ok,Jang, Myung-Hee,Hong, Hyo-Jeong The Microbiological Society of Korea 2007 The journal of microbiology Vol.45 No.6
In a previous study we generated an anti-Hepatitis B Virus (HBV) preS1 humanized antibody (HzKR127) that showed in vivo HBV-neutralizing activity in chimpanzees. However, the antigen-binding affinity of the humanized antibody may not be sufficient for clinical use and thus affinity maturation is required for better therapeutic efficacy. In this study, phage display technique was employed to increase the affinity of HzKR127. All six amino acid residues (Glu95-Tyr96-Asp97-Glu98-Ala99-Tyr100) in the heavy (H) chain complementary-determining region 3 (HCDR3) of HzKR127 were randomized and phage-displayed single chain Fv (scFv) library was constructed. After three rounds of panning, 12 different clones exhibiting higher antigen-binding activity than the wild type ScFv were selected and their antigen-binding specificity for the preS1 confirmed. Subsequently, five ScFv clones were converted to whole IgG and subjected to affinity determination. The results showed that two clones (B3 and A19) exhibited an approximately 6 fold higher affinities than that of HzKR127. The affinity-matured humanized antibodies may be useful in anti-HBV immunotherapy.