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Backplate의 유무에 따른 맞대기 용접 시험편의 피로강도 평가
한주호,김성민,이우일,강성원,김명현,Han, Ju-Ho,Kim, Seong-Min,Lee, Woo-Il,Kang, Sung-Won,Kim, Myung-Hyun 대한용접접합학회 2009 대한용접·접합학회지 Vol.27 No.1
In this study, a series of fatigue test was performed to evaluate the fatigue strength of butt welded specimens. Effective notch stress through finite element analysis was conducted to analyze the fatigue results. As a results, no significant decrease in fatigue strength was observed when backplates were present. The S-N curve that based on effective notch stress appeared a similar fatigue lift to FAT 225 curve without reference to existence of backplates.
한주호(Ju-Ho Han),이정수(Jeong-Soo Lee),김명현(Myung-Hyun Kim) 대한용접·접합학회 2017 대한용접·접합학회지 Vol.35 No.6
This study improves the durability of nozzle (CO₂ torch component) by changing the shape of a gas diffuser. In order to identify factors affecting the service life of nozzle, discarded nozzle was collected at random. As a result, it was confirmed that a main factor determining the service life of nozzle is the temperature of the nozzle during welding. In this study, we analyzed the factors that determine the temperature of CO₂ torch components (electrical resistance heat, arc radiant heat, protective gas convection, ambient air convection, thermal conduction) and improved the durability of nozzle by changing the shape of a gas diffuser. Inner diameter of a gas diffuser, size of a gas outlet, number of a gas outlet, etc. were selected as parameters and welding experiments was conducted. It was confirmed that the temperature of a nozzle changes according to the shape of a gas diffuser. A gas diffuser capable of lowering the maximum temperature during welding (capable of improving the durability) was developed. When the developed gas diffuser is used, it is expected that the durability of a nozzle improves.
Magnaporthiopsis poae에 의한 한지형 잔디의 여름잎마름병 보고
한주호 ( Ju Ho Han ),안창현 ( Chang Hyun Ahn ),이승열 ( Seung-yeol Lee ),백창기 ( Chang-gi Back ),강인규 ( In-kyu Kang ),정희영 ( Hee-young Jung ) 한국균학회 2016 韓國菌學會誌 Vol.44 No.3
2015년 6월 초순, 한지형 잔디인 Kentucky bluegrass“Midnight II” 품종이 식재된 서울시 소재 잔디밭에서 잎마름 증상, 뿌리썩음 증상 및 개구리 눈 모양의 전형적인 summerpatch 병징이 관찰되었다. 병원균의 정확한 동정을 위해 이병 잎과 뿌리에서 병원균을 분리하고, 배양학적 및 균학적 특징과 분자마커를 이용한 계통학적 유연관계 분석을 실시하였다. 그 결과, 분리된 병원균은 배양 10일 후 약 50~60 mm 가량 생장하였고, 균사는 회백색을 띄며 중앙부터 황록색 혹은 갈색으로 변색되었다. 경자(phialides)의 경우, 그 유사조직이 주로 균사의 말단에서 관찰되었으나, 분생포자는 관찰되지 않았다. 분리된 병원균의 정확한 동정과 계통학적 유연관계 분석을 위하여, large subunit (LSU)와 RNA polymerase II large subunit (RPB1) 유전자를 증폭시킨 후 염기서열 분석을 진행하고 계통학적 유연관계를 분석하였다. 그 결과, 분리된 병원균은 Magnaporthiopsis poaeM47 균주와 가장 근연한 관계에 있는 것으로 확인되었다. 또한 potato dextrose agar (PDA) 배지에서 배양된 병원균을 멸균된 메스로 잘라 동일한 품종의 잔디에 접종한 결과, 약 20일 후 잎마름 증상을 확인할 수 있었다. 따라서 본 연구에서는 국내 Kentucky bluegrass에 summer patch병을 일으키는 원인균을 Magnaporthiopsis poae로 보고하고, 위 병원균에 의한 한지형 잔디의 병징을 여름잎마름병으로 제안하고자 한다. Symptoms of summer patch were observed on Kentucky bluegrass (Poa pratensis L.) cv. “Midnight II” from mid-June in 2015 in Seoul, Korea. The symptoms appeared as leaf blight, root rot, and frog-eye patch, which are typical of summer patch. To identify the causal agent of these symptoms, a pathogen was isolated from diseased leaves and roots, and the cultural, morphological, and phylogenetic characteristics were analyzed. The isolate reached 50.60 mm on potato dextrose agar (PDA) after 10 days as a white-grey mycelium with septa, and became olive-green or brown from the center. Phialide-like structures were observed at the ends of hyphae, and conidia were rarely observed. A phylogenetic analysis was conducted based on large subunit (LSU) and RNA polymerase II large subunit (RPB1) sequences. According to this analysis, the isolated pathogen was confirmed to be Magnaporthiopsis poae. In a pathogenicity test, summer patch symptoms were observed at 20 days after inoculation using the same grass cultivar. This is the first report of summer patch disease caused by M. poae on cool season grass in Korea.