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Advances in Atmospheric Sciences 2013年第5期30卷 1461-1478页

作者： Hyo-Eun JI soon-Hwan lee Hwa-Woon lee Division of Earth Environmental System Pusan National University Department of Earth Science Education Pusan National University

To examine the correlation between the sizes of sea breeze fronts and pollutants under the influence of synoptic fields, a numerical simulation was conducted in the southeast coastal area of the Korean Peninsula, where relatively high concentrations of pollutants occur because of the presence of various kinds of industrial developments. Sea breeze and sea breeze front days during the period 2005 09 were identified using wind profiler data and, according to the results, the number of days were 72 and 53, respectively. When synoptic forcing was weak, sea breeze fronts moved fast both in horizontal fields and in terms of wind velocity, while in the case of strong synoptic forcing, sea breeze fronts remained at the coast or moved slowly due to strong opposing flows. In this case, the sea breeze front development function and horizontal potential temperature difference were larger than with weak synoptic forcing. The ozone concentration that moves together with sea breeze fronts was also formed along the frontal surfaces. Ozone advection and diffusion in the case of strong synoptic forcing was suppressed at the frontal surface and the concentration gradient was large. The vertical distribution of ozone was very low due to the Thermal Internal Boundary Layer （TIBL） being low.

关键词： sea breeze front synoptic opposing flow wind profiler ozone numerical simulation

Nature Experience, Recreation Activity and Health Benefits of Visitors in Mountain and Urban Forests in Vienna, Zurich and Freiburg

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Journal of Mountain Science 2015年第6期12卷 1551-1561页

作者： Ju-hyoung lee Duk-jae lee Department of Forest Resources Faculty of Natural Resources Yeungnam University Department of Forest Resources College of Life & Environmental Science Daegu University

Mountain forests are managed for various purposes. Of these, recreation, leisure, and ecotourism are increasingly gaining prominence. Yet, with the development of new techniques for creating and managing urban forests, the perception of the public with regard to mountain forests and such urban forests is narrowing. For the purpose of this study, eight mountain forests and urban forests located in Zurich(Switzerland), Vienna(Austria) and Freiburg(Germany) were shortlisted. These places are renowned for their well-functioning management of mountain forests and creation of urban forests. As the study was to focus on the comparison of the perceptions of visitors in terms of their satisfaction in urban and mountain forests, the interview covered the following questions:(i) how satisfactory was the nature experience;(ii) how satisfactory were the outdoor recreational activities;(iii) whether the nature experiences influenced the mental and physical health of visitors. Responses thus received for each of the mountain forests and urban forests were assessed, with the total number of respondents being 247. Tourists visiting the selected areas were randomly chosen for a one-on-one interview survey. Results of the survey show that there is a clear perceptions of visitors differed between urban and mountain forests. However, the gap is insignificant or almost nonexistent with respect to satisfaction level of outdoor recreational activities and health benefits. These results are contrary to the findings of previous studies, which argued that the natural landscape of mountain areas is superior to other artificially built green spaces. Visitors did not perceive significant differences in outdoor recreational activities and health effects between the two spaces.

关键词： Europe Satisfaction Outdoor recreation Interview survey Preference

Prediction of Nitrogen Diffusivity in α-ferrite Based on Thermodynamics

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Journal of Iron and Steel Research International 2015年第8期22卷 743-745页

作者： jae-gil JUNG Seok-jae lee Light Metal Division Korea Institute of Materials Science Division of Advanced Materials Engineering Research Center for Advanced Materials Development Chonbuk National University

A thermodynamic based equation to predict the diffusivity of nitrogen in α-ferrite was investigated in consideration of the equilibrium nitrogen concentration. The temperature-dependent jump distance calculated from the lattice parameter of ferrite was used to derive the frequency factor as a function of temperature. The calculation accuracy for nitrogen diffusivity using the proposed thermodynamic based equation was improved by comparing the calculation results using previous empirical equations based on Arrhenius type relationship with measured diffusivity of nitrogen for α-ferrite at different temperatures.

关键词： nitrogen diffusivity ct-ferrite thermodynamics prediction

Development of analysis model for geometric error in turning processes

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Journal of Central South University 2011年第3期18卷 711-717页

作者： lee Mun-jae lee Choon-man Department of Mechanical Design and Manufacturing Engineering Changwon National University

A finite element model was established for analyzing the geometric errors in turning operations and a two-step analyzing process was proposed. In the first analyzing step, the cutting force and the cutting heat for the cutting conditions were obtained using the AdvantEdge. Also, the deformation of a workpiece was estimated in the second step using the ANSYS. The deformation was analyzed for a 150 mm-long workpiece at three different measuring points, such as 10, 70 and 130 mm from a reference point, and the amounts of the deformation were compared through experiments. /n the results of the comparison and analysis, the values obtained from these comparison and analysis represent similar tendencies. Also, it is verified that their geometric errors increase with the increase in temperature. In addition, regarding the factors that affect the deformation of a workpiecc, it can be seen that the geometric error in the lathe is about 15%, the error caused by the cutting force is about 10%, and the deformation caused by the heat is about 75%.

关键词： geometric error machining accuracy finite element analysis turning cutting force, cutting temperature

Effect of light scattering on the performance of a direct absorption solar collector

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Frontiers in Energy 2018年第1期12卷 169-177页

作者： Kwang Hyun WON Bong jae lee Department of Mechanical Engineering Korea Advanced Institute ofScience and Technology Daejeon 34141 South Korea

Recently, a solar thermal collector often employs nanoparticle suspension to absorb the solar radiation directly by a working fluid as well as to enhance its thermal performance. The collector efficiency of a direct absorption solar collector （DASC） is very sensitive to optical properties of the working fluid, such as absorption and scattering coefficients. Most of the existing studies have neglected particle scattering by assuming that the size of nanoparticle suspension is much smaller than the wavelength of solar radiation （i.e., Rayleigh scattering is applicable）. If the nanoparticle suspension is made of metal, however, the scattering cross-section of metallic nanoparticles could be comparable to their absorption cross-section depending on the particle size, especially when the localized surface plasmon （LSP） is excited. Therefore, for the DASC utilizing a plasmonic nanofluid supporting the LSP, light scattering from metallic particle suspension must be taken into account in the thermal analysis. The present study investigates the scattering effect on the thermal performance of the DASC employing plasmonic nanofluid as a working fluid. In the analysis, the Monte Carlo method is employed to numerically solve the radiative transfer equation considering the volume scatter- ing inside the nanofluid. It is found that the light scattering can improve the collector performance if the scattering coefficient of nanofluid is carefully engineered depending on its value of the absorption coefficient.

关键词： direct absorption solar collector plasmonicnanofluid light scattering

FEA technique of hot plate forming process using cell-typed die with cooling device

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中国有色金属学会会刊：英文版 2012年第S3期22卷 831-837页

作者： Jung-Min lee In-Kyu lee Kyung-Hun lee Dae-soon KIM Byung-Min KIM Dongnam Regional Division Korea Institute of Industrial Technology School of Mechanical Engineering Pusan National University Industrial Technology Division Hyundai Heavy Industries

Hot plate forming using a cell-typed die is a process for forming a large thick plate with a spherical shape for the manufacture of a large spherical LNG ***-typed upper and lower dies made of a framework of steel plates fitted to make a grid pattern are used in this process,and an air-cooling device is separately installed inside the lower die.A finite element analysis (FEA) technique was developed,which included hot forming,air flow,cooling and thermal deformation analysis for the hot plate forming process using the cell-typed ***,the convective and interface heat transfer coefficients were used to reproduce analytically the effects of the cooling device in the hot plate forming analysis.A small-scale model test of the process was conducted to verify the FEA *** analysis results show that the curvature of the final plate agrees well with that of the designed experiment within a maximum relative error of 0.03% at the corner of the plate.

关键词： cell-typed die hot plate forming spherical LNG tank heat transfer coefficient

Effects of structure and electronic properties of D-π-A organic dyes on photovoltaic performance of dye-sensitized solar cells

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Journal of Energy Chemistry 2021年第3期30卷 208-216页

作者： Min-Woo lee jae-Yup Kim Hyung-Geun lee Hyun Gil Cha Duck-Hyung lee Min jae Ko Bio-Based Chemistry Research Center Advanced Convergent Chemistry DivisionKorea Research Institute of Chemical Technology(KRICT)Ulsan 44429Republic of Korea Department of Chemical Engineering Dankook UniversityYongin 16890Republic of Korea Department of Chemistry Sogang UniversitySeoul 04107Republic of Korea Department of Chemical Engineering Hanyang UniversitySeoul 04763Republic of Korea Institute of Nano Science and Technology Hanyang UniversitySeoul 04763Republic of Korea

Herein,we examine the performance of dye-sensitized solar cells containing five D-π-A organic dyes designed by systematic modification of π-bridge size and geometric *** dye has a simple push-pull structure with a triarylamino group as an electron donor,bithiophene-4,4-dimethyl-4 H-cyclopenta 1,2-b:5,4-b’]dithiophene(M11),4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophenethiophene(M12),thiophene-4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophene(M13),4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophene-benzene(M14),and 4,4-dimethyl-4 H-cyclopenta[1,2-b:5,4-b’]dithiophene(M15)units asπ-bridges,and cyanoacrylic acid as an electron acceptor/*** extension of theπ-bridge linkage favors wide-range absorption but,because of the concomitant molecular volume increase,hinders the efficient adsorption of dyes on the TiO_(2) film ***,higher loadings are achieved for smaller dye molecules,resulting in(i)a shift of the TiO_(2) conduction band edge to more negative values,(ii)a greater photocurrent,and(iii)suppressed charge recombination between the photoanode and the redox couple in the ***,under one-sun equivalent illumination(AM 1.5 G,100 mW/cm^(2)),the highest photovoltage,photocurrent,and conversion efficiency(η=7.19%)are observed for M15,which has the smallest molecular volume among M series dyes.

关键词： Dye-sensitized solar cells Donor-acceptor dyes Electron-rich unit Wide-range absorption Impedance spectroscopy

Experimental and Computational Studies on Coanda Nozzle Flow for the Air Knife Application

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Journal of Thermal Science 2007年第2期16卷 164-169页

作者： soon-Bum KWON Dong-Won lee Young-Doo KWON School of Mechanical Engineering Kyungpook National University1370Sankyuk-dongDaegu 702-701Korea

To control the film thickness of zinc in the process of continuous hot-dip galvanizing, it is known from the early days that the gas wiping through an air knife is the most effective one. The gas wiping using in galvanizing process brings about a problem of splashing from the strip edge for a certain high speed of coating. So, in the present study, the effects of the deflection angle of Coanda nozzle on jet structure and the distribution of impinging pres- sure at the plate surface are investigated numerically and experimentally. In numerical analysis, the governing equations consisted of three-dimensional time dependent full Navier-Stokes equations, standard k-ε turbulence model to solve turbulent stTess and so on are employed. In experiment, 16 channel pressure scanning valve and 3-axis auto traversing unit are used to measure the impinging pressure at the strip surface. As a result, it is found that the smaller the deflection angle for the same nozzle slit of air knife is, the larger the impinging pressure is. To reduce the size of separation bubble and to enhance the cutting ability, it is recommendable to use an air knife with the Coanda nozzle.

关键词： Air knife Coanda effect edge splashing gas wiping hot-dip galvanizing impinging jet

Microstructure and Tensile Behavior of a Nano-Structured Al-Fe Based Alloy

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Journal of Rare Earths 2004年第z2期22卷 65-68页

作者： Won-Yong Kim jae-Sung Park Mok-soon Kim Tae-Yeub Ra Advanced Materials R&D Center Korea Institute of Industrial Technology # 472Kajwa-dongSuh-guIncheon 404-254Korea School of Materials Science and EngineeringInha University # 253Yonghyun-dongNam-guIncheon 402-751Korea School of Materials Science and EngineeringInha University # 253Yonghyun-dongNam-guIncheon 402-751Korea Advanced Materials R&D CenterKorea Institute of Industrial Technology # 472Kajwa-dongSuh-guIncheon 404-254Korea

Room temperature deformation behavior of A1-8Fe-2Mo-2V-1Zr alloy produced by spray forming and subsequent warm-extrusion at 693 K and/or rolling at 423 K was investigated in terms of tensile test and microstructural *** the specimen processed by spray forming and warm extrusion, the microstructure consisting of equiaxed grains with the average grain size of 500 nm in the matrix phase and uniformly dispersed fine intermetallic A13(Fe, Mo, V, Zr) and A16(Fe, Mo, V, Zr) phases less than 100 nm was characterized. It was revealed that subsequent warm rolling after warm extrusion promotes precipitation of a fine dispersoid from the supersaturated matrix phase. Warm rolling was found to be effective to increase the yield and tensile strength in the high strain rate regime. Elongation of the warm rolled specimen showed highe r value than extruded specimen over the whole strain rate region studied.

关键词： microstructure tensile deformation A1-Fe based alloy spray forming extrusion warm rolling precipitation strain rate sensitivity

Characteristics of bifurcation and buckling load of space truss in consideration of initial imperfection and load mode

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2013年第3期14卷 206-218页

作者： Su-deok SHON Seung-jae lee Kang-guk lee School of Architectural Engineering Korea University of Technology and Education1800 ChungjeolroCheonan ChungnamRepublic of Korea Research Center for Urban Affair Kyungil UniversityGyeongsan-city GyeongbukRepublic of Korea

This study investigated characteristics of bifurcation and critical buckling load by shape imperfection of space truss,which were sensitive to initial *** critical point and buckling load were computed by the analysis of the eigenvalues and determinants of the tangential stiffness *** two-free-nodes example and star dome were selected for the case study in order to examine the nodal buckling and global buckling by the sensitivity to the eigen buckling mode and the analyses of the influence,and characteristics of the parameters as defined by the load ratio of the center node and surrounding node,as well as rise-span ratio were *** sensitivity to the imperfection of the initial shape of the two-free-nodes example,which occurs due to snapping at the critical point,resulted in bifurcation before the limit point due to the buckling mode,and the buckling load was reduced by the increase in the amount of *** two sensitive buckling patterns of the numerical model are established by investigating the displaced position of the free nodes,and the asymmetric eigenmode greatly influenced the behavior of the imperfection shape whether it was at limit point or ***,the sensitive mode of the two-free-nodes example was similar to the in-extensional basis mechanism of a simplified *** star dome,which was used to examine the influence among several nodes,indicated that the influence of nodal buckling was greater than that of global buckling as the rise-span ratio was ***,global buckling is occurred with reaching bifurcation point as the value of load ratio was higher,and the buckling load level was about 50%-70% of load level at limit point.

关键词： Space truss Geometric nonlinearity Initial imperfection Snap-through Bifurcation Global buckling