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황병철,이성학,김영민,김낙준,유장용 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.3
This study is concerned with the effects of microstructure on fracture properties of a high-toughness API X70 pipeline steel. Twelve kinds of steel specimens were fabricated by vacuum-induction melting and hot-rolling, and their microstructures were varied by the rolling conditions. Charpy V-notch (CVN) impact test and drop-weight tear test (DWTT) were conducted on the rolled steel specimens in order to analyze low-temperature properties. Charpy impact test results indicated that the energy transition temperature (ETT) was below -100℃ when the finish cooling temperature range was 350~500℃, implying excellent low-temperature toughness. The ETT increased because of the formation of bainitic ferrite and martensite at low finish cooling temperatures and because of the increase in effective grain size due to the formation of coarse ferrites at high finish cooling temperatures. Most of the specimens also showed excellent DWTT properties as the percent shear area well exceeded 85%, irrespective of finish rolling temperatures or finish cooling temperatures, although a large amount of inverse fracture area occurred at some finish cooling temperatures.
Novel Multiple Output Converter using Quasi Load
Kyusik Choi(최규식),Byeongchul Hyun(현병철),Seoungwoon Lee(이승운),Bohyung Cho(조보형) 전력전자학회 2010 전력전자학술대회 논문집 Vol.2010 No.7
In this paper, a novel multiple output converter using quasi load is proposed. Conventional multiple output converters using multiwinding transformer has poor output voltage regulations. To solve this problem, there are many proposals like post regulation method, weighted control method, and etc. However, the post regulation method regulates output voltage tightly but its conduction loss and cost are increased. And the weighted control can achieve high efficiency and low cost but its regulation is not enough. To solve these problems, this paper proposes a novel multiple output converter using quasi load. The proposed method uses a quasi load which acts like an active dummy load for tight regulation but there is rarely increase of loss and cost. The proposed method is verified by hardware test by two output(24V and 15V) flyback type converter.
이한상,황병철,이성학,안병두,신동혁,이창길 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.4
Dynamic deformation and fracture behavior of ultra-fine-grained low-carbon steels fabricated by equal channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests were conducted on four steel specimens, two of which were annealed after ECAP, using a torsional Kolsky bar, and then the test data were compared via microstructures, tensile properties, and fracture mode. The ECAP'ed specimen consisted of very he, elongated grains of -0.5 μm in size, which were slightly coarsened and had an equiaxed shape after annealing. The dynamic torsional test results indicated that maximum shear stress decreased, while fracture shear strain increased, with increasing annealing time. Some adiabatic shear bands were observed at the gage center of the dynamically deformed torsional specimen, and their width was smaller in the ECAP'ed specimen than in the 1-hr annealed specimen, although they were not found in the 24-hr annealed specimen. Ultra-he, equiaxed grains of 0.05-0.3 μm in size were formed inside the adiabatic shear band, and their boundaries had characteristics of high-angle grain boundaries. These phenomena were explained by dynamic recovery and recrystallization due to the highly localized plastic deformation and temperature rise inside the adiabatic shear band. (Received February 11, 2004)
식물병원균에 대해 항균능을 지닌 Bacillus sp. LH1의 특징 연구
한경림 ( Kyoung-rim Han ),홍병철 ( Byeongchul Hong ),안영희 ( Yeonghee Ahn ),이건 ( Geon Lee ) 한국환경기술학회 2018 한국환경기술학회지 Vol.19 No.5
식물병원균에 항균능이 있는 Bacillus sp. LH1을 분리·동정하여 Bacillus sp. LH1의 배양학적 특성과 식물의 생육에 미치는 영향을 조사하였다. Bacillus sp. LH1는 분자계통학적 분석으로 Bacillus subtilis subsp. subtilis로 동정되었다. Bacillus sp. LH1의 배양학적 특성은 pH 6, 배양온도 35 ℃, 탄소원 fructose 1 %, 질소원 yeast extract 0.5 %, 무기염 KH<sub>2</sub>PO<sub>4</sub> 0.5 %와 K<sub>2</sub>HPO<sub>4</sub> 0.5 %, 그리고 금속염 MnSO<sub>4</sub>·5H<sub>2</sub>O 0.001 %를 첨가 하였을 때 가장 높은 생육도를 보였다. 식물병원균에 대한 항균능 조사에서 Bacillus sp. LH1가 식물병원균인 Fusarium oxysporum f. sp. cucumerinum, Glomerella cingulata, Fusarium sp., Rhizoctonia solani, Phytophthora capsici, 그리고 Sclerotinia sclerotiorum 에 대해 가장 높은 항균능을 보였다. Bacillus sp. LH1를 이용한 액비의 식물 생육에 미치는 영향을 조사한 결과 고추, 토마토, 무, 배추, 상추의 5작물에 대한 비해는 없었으며, Bacillus sp. LH1를 이용한 액비를 처리하였을 때 상추의 엽장이 4.86 % ± 1.39 %, 엽폭이 3.35 % ± 0.10 % 증가하여 생육이 향상되었고 수확량은 7.01 %-9.97 % 향상되었다. 따라서 Bacillus sp. LH1를 이용한 액비가 생물학적 방제제로서 이용 가치가 있을 것으로 판단된다. Bacillus sp. LH1 with antifungal activity against plant pathogens was isolated and identified as Bacillus subtilis subsp. subtilis based on molecular phylogenetic analysis. Maximal growth was observed when Bacillus sp. LH1 was cultured in medium consistiong of 1 % fructose, 0.5 % yeast extract, 0.5 % KH<sub>2</sub>PO<sub>4</sub>, 0.5 % K<sub>2</sub>HPO<sub>4</sub>, and 0.001 % MnSO<sub>4</sub>·5H<sub>2</sub>O, at pH 6, and 35 ℃. In antigenicity study of plant pathogens, Bacillus sp. LH1 showed the highest antagonism for Fusarium oxysporum f. sp. cucumerinum, Glomerella cingulata, Fusarium sp., Rhizoctonia solani, Phytophthora capsici, and Sclerotinia sclerotiorum. There were no apparent injuries for five crops of pepper, tomato, radish, cabbage and lettuce by liquid fertilizer containg Bacillus sp. LH1. When liquid fertilizer containing Bacillus sp. LH1 was used as treatment, lettuce showed increases in leaf area (4.86 % ± 1.39 %), leaf width (3.35 % ± 0.10 %), and yield (7.01 %-9.97 %). Therefore, liquid fertilizer using Bacillus sp. LH1 is expected to be useful as a biological control agent.