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Journal of Materials Science & Technology 2020年第24期59卷 195-202页

作者： Kyungeun Jung Du Hyeon kim Jaemin kim Sunglim Ko Jae Won Choi ki Chul kim Sang-Geul Lee Man-Jong Lee Department of Advanced Technology Fusion Konkuk UniversitySeoul05029Republic of Korea a Department of Chemistry Konkuk UniversitySeoul05029Republic of Korea Department of Mechanical Design and Production Engineering Konkuk UniversitySeoul05029Republic of Korea Division of Chemical Engineering Konkuk UniversitySeoul05029Republic of Korea Daegu Center Korea Basic Science InstituteDaegu41566Republic of Korea

The effect of ultraviolet-ozone(UVO)irradiation on amorphous(am)SnO_(2) and its impact on the photoconversion efficiency of MAPbI3-based perovskite solar cells were investigated in *** treatment was found to increase the amount of chemisorbed oxygen on the am-SnO_(2) surface,reducing the surface energy and contact *** changes in the am-SnO_(2) surface lowered the Gibbs free energy for the densification of perovskite films and facilitated the formation of homogeneous perovskite *** addition,the Fermi energy of the UVO-treated am-SnO_(2) shifted upwards to achieve an ideal band offset for MAPbI3,which was verified by theoretical calculations based on the density functional *** achieved a champion efficiency of 19.01% with a statistical reproducibility of 17.01±1.34% owing to improved perovskite film densification and enhanced charge transport/extraction,which is considerably higher than the 13.78±2.15% of the ***,UVO-treated,am-SnO_(2)-based devices showed improved stability and less hysteresis,which is encouraging for the future application of up-scaled perovskite solar cells.

关键词： UV-ozone Amorphous SnO_(2) Electron selective layers Planar perovskite solar cells Hysteresis

Ruled Real Hypersurfaces of A Complex Space Form

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Acta Mathematica Sinica,English Series 1994年第4期10卷 401-409页

作者： ki, U-Hang kim, Nam-Gil Department of Mathematics Kyungpook University Taegu Korea Department of Mathematics Chosun University Kwangju Korea

The purpose of this paper is to define a ruled real hypersurface of a complex space form M_n(c),c≠0,and to give characterizations of this hypersurface by the infinitesimal affine transformation of the structure vecto... 详细信息

关键词： Math real Ruled Real Hypersurfaces of A Complex Space Form

Across and along-wind responses of tall building

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Journal of Central South University 2014年第11期21卷 4404-4408页

作者： kim Young-moon YOU ki-pyo YOU Jang-youl Department of Architecture Engineering Long-Span Steel Frame System Research CenterChonbuk National UniversityChonju 561-756 Korea KOCED Wind Tunnel Center Chonbuk National UniversityChonju 561-756 Korea

Most modern tall buildings using lighter construction materials are more flexible, which can lead to excessive wind-induced vibrations resulting in occupant discomfort and structural unsafety. It is necessary to predict and mitigate such wind-induced vibration at the preliminary design stage. Fluctuating across and along-wind loads acting on a tall building that could not be formulated theoretically were simulated numerically in the time domain using known across and along-wind load spectra. These simulated wind loads were used to estimate the across and along-wind responses of a tall building, which are less narrow-banded processes, based on the state space variable approach. The simulated across-wind response of root-mean-square value(0.0047) and that of KAREEM's(0.0040) and the simulated along-wind response of root-mean-square value(0.021) and that of SOLARI's(0.027) were compared. It is found that these are good approximations of closed form responses. Therefore, these numerically simulated across and along-wind loads can be used for across and along-wind responses estimation for the wind-resistant design of a tall building at the preliminary design stage.

关键词： across-wind load along-wind load across and along-wind responses tall building

Passive control of along-wind response of tall building

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Journal of Central South University 2014年第10期21卷 4002-4006页

作者： kim Young-moon YOU ki-pyo YOU Jang-youl Department of Architecture Engineering Chonbuk National University Long-Span Steel Frame System Research Center Chonbuk National University KOCED Wind Tunnel Center Chonbuk National University

Most of modern tall buildings using lighter construction materials with high strength and less stiffness are more flexible, which occurs excessive wind-induced vibration, resulting in occupant discomfort and structural unsafety. It is necessary to predict wind-induced vibration response and find out a method to mitigate such an excessive wind-induced vibration at the preliminary design stage. Recently, many studies have been conducted in using actuator control force based on the linear quadratic optimum control algorithm. It was accepted as a common knowledge that the performance of passive tuned mass damper(TMD) could increase by incorporating a feedback active control force in the design of TMD, which is called active tuned mass damper(ATMD). However, the fact that ATMD is superior to TMD to reduce wind-induced vibration of a tall building is still a question. The effectiveness of TMD for mitigating the along-wind vibration of a tall building was investigated. Optimum parameters of tuning frequency and damping ratio for TMD under a random load which has a white noise spectra were used. Fluctuating along-wind load acting on a tall building treated as a stationary Gaussian random process was simulated numerically using the along-wind load spectra. And using this simulated along-wind load, along-wind responses of a tall building with and without TMD were calculated and the effectiveness of TMD in mitigating the along-wind response of a tall building was found out.

关键词： tuned mass damper(TMD) along-wind vibration tall building

Effects of casting speed on microstructure and segregation of electromagnetically stirred Aluminum alloy in continuous casting process

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Rare Metals 2006年第Z2期25卷 118-123页

作者： LEE Dock-Young KANG Suk-Won CHO Duck-Ho kim ki-Bae Division of Materials Korea Institute of Science and Technology P.O. Box 131 Cheongryang Seoul 130-650 Korea Department of Applied Materials Engineering Hanbat National University Daejeon 305-719 Korea

Recently, a semi-solid metal processing has been acknowledged as a cost-effective technique to be able to manufacture high quality product for the transportation industry. In this study a hypo-eutectic Al alloy was fabricated by means of an electromagnetic stirrer in continuous casting process and the microstructural change during solidification due to a fluid flow by electromagnetic stirring was examined. Due to the forced fluid flow during solidification a dendritic phase of primary α phase of Al alloy was turned into a globular phase, which can make the Al alloy get a thixotropic behavior in the semi-solid region. In order to establish the quantitative relationship between microstructure and the process parameters, the morphology shape, a silicon distribution and a size of primary α phase were observed according to casting speed in continuous casting machine. The primary α phase was turned into the degenerate dendrites approaching a spherical configuration with increasing casting speed. The fine-grained and equiaxed microstructure appeared at higher casting speed. A segregation behavior of Si element was declined with increasing casting speed and a very uniform distribution of Si element was observed on the billet at a casting speed of 600 mm·min-1. A thickness of the solidifying shell of the billet was shortened with increasing the casting speed.

关键词： semi-solid slurry electromagnetic stirring casting speed segregation Al alloy

Improving Method of Anomaly Detection Performance for Industrial IoT Environment

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Computers, Materials & Continua 2022年第9期72卷 5377-5394页

作者： Junwon kim Jiho Shin ki-Woong Park Jung Taek Seo Department of Information Security Engineering Gachon UniversitySeongnam13120Korea Police Science Institute Korea National Police UniversityAsan31539Korea SysCore Lab. Sejong UniversitySeoul05006Korea Department of Computer Engineering Gachon UniversitySeongnam13120Korea

Industrial Control System(ICS),which is based on Industrial IoT(IIoT),has an intelligent mobile environment that supports various mobility,but there is a limit to relying only on the physical security of the ICS *** to various threat factors that can disrupt the workflow of the IIoT,machine learning-based anomaly detection technologies are being presented;it is also essential to study for increasing detection performance to minimize model errors for promoting stable ICS *** this paper,we established the requirements for improving the anomaly detection performance in the IIoT-based ICS environment by analyzing the related *** that,we presented an improving method of the performance of a machine learning model specialized for IIoT-based ICS,which increases the detection rate by applying correlation coefficients and clustering;it provides a mechanism to predict thresholds on a ***,we adopted the HAI dataset environment that actively reflected the characteristics of IIoT-based ICS and demonstrated that performance could be improved through comparative experiments with the traditional method and our proposed *** presented method can further improve the performance of commonly applied error-based detection techniques and includes a primary method that can be enhanced over existing detection techniques by analyzing correlation coefficients between features to consider feedback between ICS *** can contribute to improving the performance of several detection models applied in ICS and other areas.

关键词： Industrial IoT industrial control system anomaly detection clustering algorithm correlation coefficient

A Case Study of Mesoscale Convective Band(MCB) Development and Evolution along a Quasi-stationary Front

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Advances in Atmospheric Sciences 2014年第4期31卷 901-915页

作者： Daeun JEONG ki-Hong MIN Gyuwon LEE Kyung-Eak kim Climate Research Department Asia-Pacific Economic Cooperation Climate Center Center for Atmospheric Remote Sensing Kyungpook National University Department of Astronomy and Atmospheric Sciences Kyungpook National University Department of Earth Atmospheric and Planetary Sciences Purdue University

This paper presents a case study of mesoscale convective band （MCB） development along a quasi-stationary front over the Seout metropolitan *** MCB,which initiated on 1500 UTC 20 September 2010 and ended on 1400 UTC 21 September 2010,produced a total precipitation amount of 259.5 *** MCB development occurred during a period of tropopause folding in the upper level and moisture advection with a low-level *** analyses show that the evolution of the MCB can be classified into five periods：（1） the cell-forming period,when convection initiated; （2） the frontogenetic period,when the stationary front formed over the Korean peninsula; （3） the quasi-stationary period,when the convective band remained over Seoul for 3 h; （4） the mature period,when the cloud cover was largest and the precipitation rate was greater than 90 mm h-1; and （5） the dissipating period,when the MCB diminished and *** synoptic,thermodynamic,and dynamic analyses show that the MCB maintained its longevity by a tilted updraft,which headed towards a positive PV *** was concentrated under this area,where a tilted ascending southwesterly converged with a tilted ascending northeasterly,at the axis of cyclonic *** formation of the convective cell was attributed in part by tropopause folding,which enhanced the cyclonic vorticity at the surface,and by the low-level convergence of warm moist air and upperlevel *** southwesterly flow ascended in a region with high moisture content and strong relative vorticity that maintained the development of an MCB along the quasi-stationary front.

关键词： convective band quasi-stationary front potential vorticity tropopause folding heavy precipitation

Remarkably slow corrosion rate of high-purity Mg microalloyed with 0.05wt% Sc

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Journal of Magnesium and Alloys 2023年第3期11卷 991-997页

作者： Soo-Min Baek Jeong-ki kim Du-Won Min Sung Soo Park Department of Materials Science and Engineering Ulsan National Institute of Science and TechnologyUlsan 44919Republic of Korea

We report that the corrosion resistance of Mg is significantly improved by adding 0.05wt%*** rates evaluated from weight loss values after room-temperature immersion in 0.6 M NaCl solution for two weeks were 0.27 and 4.0 mm y^(-1)for the high-purity Mg samples with and without microalloyed 0.05wt%Sc,*** beneficial effect of Sc microalloying on the corrosion resistance of Mg is discussed in connection with Sc-induced microstructural modifications.

关键词： Magnesium Microalloying Intermetallic phase Microgalvanic corrosion

Deformation prediction of porcelain-enameled steels with strain history by press forming and high-temperature behavior of coating layer

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中国有色金属学会会刊：英文版 2012年第S3期22卷 838-844页

作者： Young-ki SON Chan-Joo LEE Jung-Min LEE Byung-Min kim School of Mechanical Engineering Pusan National University Dongnam Regional Division Korea Institute of Industrial Technology

Porcelain enamel coatings were widely applied for the protection of steel products because they offered high corrosion protection,resistance to heat and abrasion,high hardness,hygiene and ease of *** typical process to produce enameled steels is roughly divided into two stages:the first stage consists of a forming process to give the desired shape to a steel substrate,and the second stage consists of a firing process to bond enamel frits on the *** firing process requires a high temperature above 800 °C,which may lead to austenitic transformation and severe thermal deformation of the steel *** aim of this study is to develop a finite element analysis (FE analysis) technique to predict the mechanical and thermal deformations of the enameled steels during forming and any further enameling process,including *** FE analysis involves analyzing the strain history of the steel substrate,which comprises the stress and thickness distributions of the substrate and its deformed shape,and the high-temperature behavior of the enamel coating *** validity of the FE analysis is verified through the U-bending test and firing test with various numbers and positions of enamel coating layers on the *** results reveal that the FE analysis results agree well with the experimental results with 8% error.

关键词： porcelain enamel firing process finite element analysis enameled steel thermal deformation

Fault area estimation using traveling wave for wide area protection

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Journal of Modern Power Systems and Clean Energy 2016年第3期4卷 478-486页

作者： Jae-Won LEE Won-ki kim Joon HAN Won-Hyeok JANG Chul-Hwan kim Department of Electrical and Computer Engineering Sungkyunkwan UniversitySuwonRepublic of Korea Daewoo Shipbuilding&Marine Engineering Co. Ltd.GeojeRepublic of Korea Electrical and Computer Engineering Department University of Illinois at Urbana-ChampaignChampaignILUSA

As the increasing number of Phasor Measurement Units(PMUs) are deployed, wide area protection in power systems has been gaining interest. In particular, fault detection, fault classification and fault area estimation are essential to reduce the damage of faults, and even prevent catastrophic cascades of failures. In this paper, we present a scheme for fault area estimation using PMUs and traveling wave theory. The purpose of this paper is to formulate a scheme for fault area estimation by calculating the approximate fault location based on traveling wave *** research has targeted at reliable operation of wide transmission system through the estimation of fault *** verify the suggested scheme, the various simulations are performed in practical Korean power transmission *** simulation results show that the proposed scheme has a good performance with high accuracy for estimating fault area.

关键词： Fault area estimation Phasor measurement unit(PMU) Transmission line system Traveling wave Wide area protection