Microstructure, Tensile and Fatigue Properties of Al–5 wt.%Mg Alloy Manufactured by Twin Roll Strip Casting

Joon‑Young Heo,Min‑Seok Baek,Kwang‑Jun Euh,Kee‑Ahn Lee 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.5

This study investigated the microstructure, tensile and fatigue properties of Al–5 wt.%Mg alloy manufactured by twin rollstrip casting. Strips cast as a fabricated (F) specimen and a specimen heat treated (O) at 400 °C/5 h were produced andcompared. In the F specimen, microstructural observation discovered clustered precipitates in the center area, while in theO specimen precipitates were relatively more evenly distributed. Al, Al 6 (Mn, Fe), Mg 2 Al 3 and Mg 2 Si phases were observed. However, most of the Mg 2 Al 3 phase in the heat-treated O specimen was dissolved. A room temperature tensile test measuredyield strength of 177.7 MPa, ultimate tensile strength of 286.1 MPa and elongation of 11.1% in the F specimen and167.7 MPa (YS), 301.5 MPa (UTS) and 24.6% (EL) in the O specimen. A high cycle fatigue test measured a fatigue limit of145 MPa in the F specimen and 165 MPa in the O specimen, and the O specimen achieved greater fatigue properties in allfatigue stress conditions. The tensile and fatigue fracture surfaces of the above-mentioned specimens were observed, and thisstudy attempted to investigate the tensile and fatigue deformation behavior of strip cast Al–5 wt.%Mg based on the fi ndings.

다변량 분석법을 이용한 소양강댐 상류 유역의 하천 수질 평가

최한규,백효선,허준영 江原大學校 産業技術硏究所 2002 産業技術硏究 Vol.22 No.A

The object of this study is to evaluate the factors affecting the water quality and to propose the influence of dominant factor quantitatively. The correlation analysis was performed to know the correlationship among the water quality items. As a result of partial correlation analysis, it was shown that the water quality items are affected by the rainfall item directly. The factor analysis was performed to grasp some number of factors on each point for deducing the items of similar variable characteristics. The four points were divided into different factor groups. It was grasped that NH_3-N and NO_3-N items have different variable characteristics after comparing the items. The Multiple regression analysis can decrease the number of observation. In the deduced multiple regression formula, it was shown that the rate of T-N, NH_3-N and NO_3-N in the independent variable took about 60% among all the regression formulas.

산불진화정보 관리를 위한 Mobile GIS 공간 데이터 압축기법 개발

조명희,이명보,이시영,김준범,권봉겸,허영진 한국지리정보학회 2004 한국지리정보학회지 Vol.7 No.2

최근 무선 인터넷 및 통신기술의 눈부신 발달과 LBS(location based service)개념을 기반으로 한 mobile GIS 기술 개발은 대규모 산불 발생시 정확한 현장 파악과 신속한 상황보고 뿐만 아니라 사고 예방과 분석·평가에 이르기까지 의사결정지원시스템으로 자리를 잡고 있다. 본 연구에서는 지상진화대의 정확한 위치와 이동상황을 실시간으로 파악하여 안전한 진화작업 유도 및 산불진화 환경정보를 제공을 목적으로 mobile GIS 기술 기반의 산불진화정보 관리시스템을 설계하고 네트워크 부하감소를 위하여 '.gci'라는 공간 데이터 압축기법을 개발하여 면, 선, 주기 데이터에 대하여 51~62%의 높은 압축률을 구현하였다. 따라서 대규모 산불 발생시 일어날 수 있는 안전사고를 미연에 방지하고 사고 발생시 신속한 후속조치로 안전하고 과학적인 산불진화 업무를 수행할 수 있도록 하였다. Recently GPS and mobile GIS technologies based on LBS (location based service) have played an important role as DSS (decision supporting system) for domestic forest fire extinguishment policies. In this study forest fire extinguishments information management system based on mobile GIS technique was designed to seize the exact location on wireless network so that it helps to guide the safe and efficient extinguishments affairs and provide the extinguishments environment toward ground fighting teams and the central forest government in real time. Moreover, possibly to operate this system, the foundation technologies by the name of `. gci such as the spatial data compression method, the spatial data transmission method over wireless network and the spatial analysis interface on PDA should be mainly considered. Especially, in this study the spatial data compression method having high compression rate from 51% to 62% for each polygon, line, and point data, without the loss of data was developed.

제주 차귀도 연안해역 미생물 분포 및 이화학적 특성

문영건,김만철,이준백,송춘복,여인규,김종만,박근태,손홍주,최우봉,허문수 한국환경과학회 2006 한국환경과학회지 Vol.15 No.3

Fosfomycin의 항균효과 및 capillary electrophoresis에 의한 측정법에 관한 연구

윤효인,박승춘,이규승,권진욱,조준형,신광순,김무열,허강준,조명행 충남대학교 수의과대학 동물의과학연구소 1996 動物醫科學硏究誌 Vol.4 No.-

Fosfomycin, a low molecular antibiotic, is to be easily synthesized, therefore to be possibly used in veterinary sectors due to econimic reasons. In this study, we determined the antibacterial activities of fosfomycin against some domestic animal-origin pathogens, and its combined effects with some important antibacterials available. We also compared detection methods of fosfomycin from various measuring instruments. The results obtained through this experiment were as follows: 1. Antibacterial activities of fosfomycin against the pathogens used in this experiment were appeared fairly low. We found the antobacterial activities depanded on the kinds of media and the addition of some material thereins, which suggests the importance of appropriate medium so as to judge the antibacterial activity of fosfomycin. 2. Fosfomycin showed varying antibacterial effects in combination with other antibacterials, which should be taken into consideration when combining other antobacterials especially in the clinical settings. Of the combined antivacterials, fosfomycin had synergistic effects in combination with amoxicillin but antagonistic effects with oxytetracyline. 3. Conventional detection methods using HPLC, GC and spectrophotometer were not appropriate to measure fosfomycin. Capillary electrophoresis by the way of the indirect ultraviolet detection method was good enough to detect fosfomycin in the range of expected concentration in tissues, with the limit of quantitation (LOQ) of 1.25 ㎍/㎖. We recommend the eletrophoresis method could be used to detect fosfomycin, thereby being able to set the optimal dosage for animals and providing the measures in relation with the residual concentration in the meat.

ZigBee Security

Heo Joon 한국통신학회 2004 한국통신학회 학술대회논문집 Vol.2004 No.7

Robust plasmonic sensors based on hybrid nanostructures with facile tunability

Heo, Chul-Joon,Jeon, Hwan Chul,Lee, Su Yeon,Jang, Se Gyu,Cho, Soojeong,Choi, Yeonho,Yang, Seung-Man The Royal Society of Chemistry 2012 Journal of materials chemistry Vol.22 No.28

<P>Here, we demonstrate the preparation of a hybrid nanoplasmonic probe array, a nanoforest, which consists of gold nanostructures coated on top of silica nanospheres and evaporated gold film structure onto bottom through masks. Optically tunable plasmonic surfaces could be achieved by varying the nanoforest fabrication conditions, which acted as a selective nanoantenna. Plasmon coupling effects were effectively controlled by adjusting the vertical distance (nanogap) between the gold nanostructures on the silica bead and the bottom. Such control is critical to highly sensitive molecular detection applications. As a proof of concept, nanoforests were used as colorimetric sensors of refractive index changes. The sensors were highly sensitive and displayed distinct colors for small refractive index (RI) changes. The flexible and sensitive near/far-field optical properties render these nanoforests excellent plasmonic substrates for quantitative, sensitive and label-free sensing with nanoscale spatial resolution.</P> <P>Graphic Abstract</P><P>Nanoforests of Au-capped pillars were fabricated by colloidal lithography for robust plasmonic sensors with facile tunability. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2jm31958f'> </P>

The Experiment of the Robust Multi-Variable Controller and the LQG/LTR Controller for the Stewart Platform

Heo. Seong-joon,Ko. Dong-Woo,Han. Myung-Chul 제어로봇시스템학회 2001 제어로봇시스템학회 국제학술대회 논문집 Vol.2001 No.10

A Study on Ground Acceleration Amplification Characteristics of Sea Dike according to the Seismic Wave Characteristics

( Joon Heo ),( Tae Ho Bong ) 대한지질공학회 2019 대한지질공학회 학술발표회논문집 Vol.2019 No.2

Earthquakes have become more frequent in South Korea of late, and the earthquake damage is clearly different depending on how to prepare for it, so there is a strong need to construct seismic infrastructures. As the seismic behavior of sea dike is very complicated, there is a dearth of actual cases of seismic behavior analysis and ground liquefaction evaluation. Damages like seismic ground displacement and liquefaction differ according to the seismic acceleration amplification characteristics. Thus, the ground acceleration amplification characteristics in the sea dike were analyzed according to the seismic waver characteristics (short cycle, long cycle, artificial seismic wave). To define the ground acceleration amplification characteristics according to the seismic wave characteristics, ground response analysis of the areas surrounding the sea dike was conducted, and 3D numerical analysis of the sea dike was conducted. Based on the ground investigation data, the representative ground cross-section and the ground parameters were set. Ground response analysis was conducted according to the input seismic waves, so as to analyze the ground acceleration amplification characteristics. 3D modeling was performed to analyze the earth-behaving sea dike. Dynamic analysis was conducted using the linear time history analysis method, and the displacement and ground acceleration were analyzed at the top of the sea dike. The findings of this study are expected to be used to evaluate the ground acceleration amplification characteristics and the possible liquefaction during earthquakes above the design earthquake level in sea dike, and to reduce the subsequent danger.

Effects of Heat Treatment on the Microstructures and High Temperature Mechanical Properties of Hypereutectic Al–14Si–Cu–Mg Alloy Manufactured by Liquid Phase Sintering Process

Joon-Young Heo,Jin-Han Gwon,Jong-Kwan Park,Kee-Ahn Lee 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.3

Hypereutectic Al–Si alloy is an aluminum alloy containing at least 12.6 wt.% Si. It is necessary to evenly control the primarySi particle size and distribution in hypereutectic Al–Si alloy. In order to achieve this, there have been attempts to manufacturehypereutectic Al–Si alloy through a liquid phase sintering. This study investigated the microstructures and high temperaturemechanical properties of hypereutectic Al–14Si–Cu–Mg alloy manufactured by liquid phase sintering process and changesin them after T6 heat treatment. Microstructural observation identifi ed large amounts of small primary Si particles evenlydistributed in the matrix, and small amounts of various precipitation phases were found in grain interiors and grain boundaries. After T6 heat treatment, the primary Si particle size and shape did not change signifi cantly, but the size and distributionof CuAl 2 ( θ ) and AlCuMgSi ( Q ) changed. Hardness tests measured 97.36 HV after sintering and 142.5 HV after heat treatment. Compression tests were performed from room temperature to 300 °C. The results represented that yield strength wasgreater after heat treatment (RT ~ 300 °C: 351 ~ 93 MPa) than after sintering (RT ~ 300 °C: 210 ~ 89 MPa). Fracture surfaceanalysis identifi ed cracks developing mostly along the interface between the primary Si particles and the matrix with somediff erences among temperature conditions. In addition, brittle fracture mode was found after T6 heat treatment.