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콘크리트 수축에 의한 급속경화궤도 균열 발생 가능성 검토
이성철 ( Lee Seong-cheol ),이동민 ( Lee Dongmin ),이경찬 ( Lee Kyoung Chan ),이일화 ( Lee Il-wha ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.1
In this paper, possibility of cracks in fast hardening track has been analyzed with consideration of shrinkage of fast hardening concrete. To evaluate tensile stress on fast hardening track, the analysis considers restrain effects by frictions due to subgrade and rail fastener. The analysis results indicated that the maximum tensile stress in fast hardening track increased as the continuous casting length of fast hardening concrete increased. To prevent cracks due to shrinkage, it was investigated that the continuous casting length be less than 66.9 m.
Exact Holography of Massive M2-brane Theories and Entanglement Entropy
Jang, Dongmin,Kim, Yoonbai,Kwon, O-Kab,Tolla, D. D.,Gwak, B.,Kang, G.,Kim, C.,Kim, H.-C.,Lee, C.-H.,Lee, J.,Lee, S.,Lee, W. EDP Sciences 2018 The European Physical Journal Conferences Vol.168 No.-
<P>We test the gauge/gravity duality between the <I>N</I> = 6 mass-deformed ABJM theory with U<I>k</I>(<I>N</I>) × U<I>-k</I>(<I>N</I>) gauge symmetry and the 11-dimensional supergravity on LLM geometries with <I>SO</I>(4)=ℤ<I>k</I> × <I>SO</I>(4)=ℤ<I>k</I> isometry. Our analysis is based on the evaluation of vacuum expectation values of chiral primary operators from the supersymmetric vacua of mass-deformed ABJM theory and from the implementation of Kaluza-Klein (KK) holography to the LLM geometries. We focus on the chiral primary operator (CPO) with conformal dimension Δ = 1. The non-vanishing vacuum expectation value (vev) implies the breaking of conformal symmetry. In that case, we show that the variation of the holographic entanglement entropy (HEE) from it’s value in the CFT, is related to the non-vanishing one-point function due to the relevant deformation as well as the source field. Applying Ryu Takayanagi’s HEE conjecture to the 4-dimensional gravity solutions, which are obtained from the KK reduction of the 11-dimensional LLM solutions, we calculate the variation of the HEE. We show how the vev and the value of the source field determine the HEE.</P>
이동민 ( Lee Dongmin ),이성철 ( Lee Seong-cheol ),이경찬 ( Lee Kyoung Chan ),이일화 ( Lee Il-wha ) 한국구조물진단유지관리공학회 2019 한국구조물진단유지관리공학회 학술발표대회 논문집 Vol.23 No.1
In this paper, an experimental program has been conducted to investigate shrinkage of fast hardening concrete (FHC) which is used to replace the existing ballasted track with concrete track. In the test, curing method was considered as a test variable. The test results indicated that autogenous shrinkage was dominant on FHC while drying shrinkage was negligible. To represent shrinkage of FHC, a new model has been proposed through regression of the test results.
Uncoordinated tetrazole ligands in metal–organic frameworks for proton‐conductivity studies
Lee Daeyeon,Lee Sangho,Son Younghu,Kim Jun Yeong,Cha Seungheon,Kwak Dongmin,Lee Jooyeon,Kwak Jaesung,Yoon Minyoung,Kim Min 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.7
Zr-based metal–organic frameworks (MOFs) were modified with pendant tetrazole ligands for proton conductivity studies. Although tetrazolate ligands coordinated to metal cations have been widely utilized to construct MOFs or porous coordination polymers, to date, the use of uncoordinated tetrazole groups in MOFs has been limited. In this study, a benzene-1,4-dicarboxylic acid with pendant tetrazole groups (BDC-N4) was synthesized and used to prepare a Zr-based UiO-66 MOF using a mixed-ligand strategy. The tetrazolefunctionalized UiO-66-N4 was compared to MOFs containing other acidic functional groups (hydroxyl, carboxylic acid, and sulfonic acid) with respect to their proton conductivities and acidities (calculated pKa). Interestingly, UiO-66-N4 showed a significant decrease in the activation energy with increase in the amount of added tetrazole groups, suggesting the Grotthuss proton conduction mechanism for uncoordinated tetrazole-containing MOFs.
Lee, Jaegi,Lee, Jimin,Ryu, Dongmin,Lee, Hochan,Ye, Sung-Joon Institute of Physics in association with the Ameri 2018 Physics in medicine & biology Vol.63 No.19
<P>A Fano cavity test was performed for four general-purpose Monte Carlo codes, EGSnrc, PENELOPE, MCNP6 and Geant4 to evaluate the accuracy of their electron transport algorithms in magnetic fields. In the simulations, a plane-parallel ionization chamber was modelled as a circular gas disk sandwiched between two circular solid wall disks. It was assumed that an isotropic and uniform line source per unit mass along the central axis of the gas and solid emits mono-energetic electrons with energies 0.01, 0.1, 1.0 and 3.0 MeV at different magnetic field strengths 0, 0.35, 1.0, 1.5 and 3.0 T in the electron transport mode (no Bremsstrahlung). The relative difference between the calculated dose to the gas region and the initial total energy of emitted electrons per unit mass was defined as the accuracy of Monte Carlo codes. In all results, EGSnrc with the enhanced electric and magnetic field (EEMF) macros was not considerably sensitive to the step size parameters and showed accuracy less than 0.18% ± 0.06% with a coverage factor <I>k</I> = 2. The other codes could not achieve competent accuracy with their default settings of step size parameters, compared to EGSnrc with the EEMF macros. With the step size parameters carefully selected, the accuracy of PENELOPE and MCNP6 was within 1.0% and 0.4%, respectively. However, Geant4 showed accuracy within 1.7% except in 3.0 T. EGSnrc with the EEMF macros achieved the best accuracy for the Fano test at the electron energies and the magnetic field strengths investigated in this study and thus, would be recommended to simulate dose responses of ionization chambers in the presence of magnetic fields.</P>