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A Lagrangian Stochastic Model for Turbulent Dispersion
Lee, Changhoon,Kim, Byunggu,Kim, Namhyun The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.12
A Lagrangian stochastic model is adopted for the calculations of turbulent dispersion in turbulent channel flows. Dispersion of a fluid particle and relative dispersion between two particles released at the sane location are investigated and compared with the classical seating relations for homogeneous turbulence. The viscous effect is realized by adding a Browinian random walk to the calculation of the position of a particle. The near-wall accumulation of particles is examined.
이창훈,김병구 서울시립대학교 산업기술연구소 1999 산업기술연구소논문집 Vol.7 No.-
Probability density function model is used to simulate a turbulent boundary layer, specially aiming at simulation of turbulent dispersion in near-wall flows. According to the Kolmogorov's scaling, the 2nd order Lagrangian velocity structure function in an is tropic turbulent flow behaves linearly in time. This leads to the Brownian walk model of the Lagrangian velocity increment. The Lagrangian motions of a number of particles are investigated by numerically solving the modeled equations for location and velocity of particles. The near-wall viscous effect is also considered through Brownian walk model along with an appropriate boundary collision modeling. The results for turbulent quantities are compared against the direct numerical simulation for a turbulent channel flow at Re= 100.
경계층 유동에서 입자확산의 예측을 위한 라그랑지안 확률모델
김병구(Byunggu Kim),이창훈(Changhoon Lee) 대한기계학회 2003 대한기계학회 춘추학술대회 Vol.2003 No.4
A new Lagrangian stochastic dispersion model is developed by combining the GLM(generalized Langevin<br/> model) and the elliptic relaxation method. Under the physically plausible assumptions a simple analytical<br/> solution of elliptic relaxation is obtained. To compare the performance of our model with other model, the<br/> statistics of particle velocity as well as concentration are investigated. Numerical simulation results show good<br/> agreement with available experimental data.
Large Scale Bending Properties of CR and TMCP Steel Plates for Wind Tower Safety
Kihyuk Kim(김기혁),Seung Hwan Lee(이승환),Donghyun Van(반동현),Hyunsoo, Park(박현수),Kwangsuk Lee(이광석),Byunggue Park(박병규),Jitack Kim(김지탁) 대한용접·접합학회 2021 대한용접학회 특별강연 및 학술발표대회 개요집 Vol.2021 No.11
In this study, the large scale weld bead bending test properties of five different alloying constituent EN10025 S355 grade high-strength low-alloy weldable structural steel plates were examined via control rolling and thermo-mechanically controlled processes. The contribution of chemical compositions in terms of carbon equivalent value on impending crack propagation during weld bead bend tests was studied through metallurgical consideration. The results revealed that TMCP steel plates with CEV of 0.33 exhibited higher toughness and better crack arrestability than that of CR steel plates with CEV of over 0.40. Also, the CR, and TMCP steel plates exhibited different microstructures in the base metal as well as, their maximum hardness and microstructures in the CGHAZ (by DIN EN 499-RR MMAW consumables approximately 20kJ/cm Heat input). The WBBT showed that crack initiation at the weld metal, easily propagated through the coarse-grain heataffected zone, and finally were arrested within the heat-affected zone (TMCP) or base metal (CR). An apparent decrease in the average crack length, which consequently indicated improvement in crack arrestability, was found with decreasing CEV. In addition, the relatively fine microstructure in the HAZ of low-CEV steel plates helped in preventing the crack from further propagation. Special emphasis was placed on the empirical expectation [Prediction equation for crack length=0.025exp(1,497CEV)] of critical CEV above which WBBT might fail.
Nam, Giwoong,Park, Youngbin,Ji, Iksoo,Kim, Byunggu,Lee, Sang-heon,Kim, Do Yeob,Kim, Soaram,Kim, Sung-O,Leem, Jae-Young American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.1
<P>In this study, we report a novel regrowth method of sol–gel-prepared ZnO films using a vapor-confined face-to-face annealing (VC-FTFA) technique in which mica was inserted between two films, followed by annealing with the FTFA method. The ZnO nanorods are regrown when zinc acetate dihydrate and zinc chloride (ZnCl<SUB>2</SUB>) are used as the solvent, because these generate ZnCl<SUB>2</SUB> vapor. The near-band-edge emission intensity of the ZnO nanorods was enhanced through the VC-FTFA method, increasing significantly by a factor of 56 compared to that of ZnO films annealed in open air at 700 °C. Our method may provide a route toward the facile fabrication of ZnO nanorods.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-1/am507439e/production/images/medium/am-2014-07439e_0010.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am507439e'>ACS Electronic Supporting Info</A></P>
Yoon, Hyunsik,Kim, Soaram,Park, Hyunggil,Nam, Giwoong,Kim, Yangsoo,Leem, Jae-Young,Kim, Min Su,Kim, Byunggu,Kim, Younggyu,Ji, Iksoo,Park, Youngbin,Kim, Ikhyun,Lee, Sang-heon,Jung, Jae Hak,Kim, Jin Soo Korean Physical Society 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.64 No.1
Undoped ZnO and Ga-doped ZnO (GZO) thin films with different Ga concentrations were prepared by using the sol-gel spin-coating method. The surface morphologies and the growth orientations of the films were measured by using scanning electron microscopy and X-ray diffraction, respectively. The electrical properties were measured by using the Hall effect. The optical transmittances and reflectances of the films were measured as functions of the wavelength by UV-vis spectroscopy. The undoped ZnO thin films exhibited rough surfaces with particle-like structures. When Ga was incorporated, the particle sizes dramatically decreased without changes in the surface morphologies, and the c-axis growth orientations of the GZO thin films were significantly decreased. The optical transmittances clearly exhibited shifts in the band edge, and those in the visible range gradually increased with increasing Ga concentration. The absorption coefficients, refractive indices, extinction constants, dielectric constants, and optical conductivities of the films gradually decreased with increasing Ga concentration.