강중비금속소재물의 자동측정에 관한 고찰

김기철,김재남,박세열,윤의박 대한금속재료학회(대한금속학회) 1984 대한금속·재료학회지 Vol.22 No.3

In determining non-metallic inclusion rating in steel, the efficiency and reliability of conventional manual method and computer aided automatic method using image analyzer have been investigated. To see the effect of shape change of the inclusions on the cleanliness value based on existing test standards, the test coupons examined were taken from continuously casted slab, hot rolled plate and from cold rolled sheet where some inclusions were extremely elongated. Results show that the cleanliness values determined by two methods agree fairly well for both samples with globular oxide inclusions and with properly elongated inclusions. For samples with extremely elongated inclusions, however, the cleanliness value processed by image analyzer tends to be smaller than that of manual count. It appears that the automatic method gives faster and more reliable cleanliness value since the image analyzer determines the value in area fraction instead of in point fraction.

중공슬래브 바닥판의 진동 및 충격음 특성에 관한 실험연구

김기철,김광만 대한건축학회 2007 大韓建築學會論文集 : 構造系 Vol.23 No.4

The efforts to solve the problem of floor impact noise and vibration of residential building have been realized. As a result, numerous products have been distributed. But, contrary to diversity of products, it also has been known that the sound insulation performance for heavy-weight impact did not show a remarkable improvement. Therefore new slab systems and products are required. The result of this study can be used to supply constructor and consumer basic data to estimate vibration and sound insulation performance of hollow slab. There is little difference between the hollow slab and general slab in vibration and sound insulation performance for impact. Moreover the hollow of slab filled with expanded polystyrene is expected to obtain the remarkable performance in vibration and sound insulation. And it was known that the amount of materials of concrete and reinforced bar could be cut down because the weights of slab was reduced by the hollow system. The study of sound insulation performance as the materials, depth and distance of hollow in slab system is required to verify vibration and sound insulation performance of hollow slab system.

공간구조물의 지진응답 저감을 위한 중간면진장치의 적용

김기철,강주원,김형만,Kim, Gee-Cheol,Kang, Joo-Won,Kim, Hyung-Man 한국공간구조학회 2009 한국공간구조학회지 Vol.9 No.4

면진장치는 기초와 구조물 사이 에 면진장치를 설치하여 상부로 전달되는 지진에너지를 감소시키는 장치로 면진장치의 설치위치에 따라서 기초면진과 중간(지붕)면진으로 구분할 수 있다. 본 연구에서는 면진장치 설치 위치에 따른 아치구조물의 지진응답을 비교 분석하여 면진장치의 효용성을 검증하였다. 지붕면진 시스템은 기초면진 시스템과 비교하여 상부 지붕구조의 지진응답 저감에 있어서 보다 효과적이다. 또한 하부구조와 상부구조의 강성 및 질량변화 그리고 시공성에 있어서 지붕면진이 기초면진 시스템 보다 우수한 것으로 사료된다. The seismic isolation system reduces the seismic vibration that is transmitted from foundation to upper structure. This seismic isolation system can be classified into base isolation and mid-story isolation by the installation location. In this study, the seismic behavior of arch structure with mid-story isolation is analyzed to verify the effect of seismic isolation. Mid-story isolation is more effective than base isolation to reduce the seismic responses of roof structure. Also, this isolation would be excellent in structural characteristics and construction.

MR 감쇠기에 대한 성능평가 실험

김기철,강주원,Kim, Gee-Cheol,Kang, Joo-Won 한국공간구조학회 2008 한국공간구조학회지 Vol.8 No.6

Mitochondrial haplogroup B is negatively associated with elite Korean endurance athlete status

김기철,진한준,김욱 한국유전학회 2012 Genes & Genomics Vol.34 No.5

Mitochondrial DNA (mtDNA) mutations could contribute to aerobic performance, since they provide information to generate aerobic ATP energy by oxidative phosphorylation (OXPHOS) in their respiratory chain. Owing to haploid and absence of recombination, specific mutations in the mtDNA genome associated with human exercise tolerance or intolerance arise and remain in particular genetic lineages referred to as haplogroups. Recent studies have suggested that certain mtDNA lineages were associated with individual differences in trainability and physical capacity, but their origins and replicate test remain to be elucidated. We have therefore analyzed mtDNA haplogroup B variants to assess the possible role of the lineages to differences in elite athletic performance in a population-based case-control study in Cheonan, Korea. We demonstrated a significant negative association between mtDNA haplogroup B and the status of elite endurance athlete [n=378, odds ratio = 0.37 (95% CI: 0.14 - 0.97, p = 0.016)]. Thus, our results imply that specific mtDNA lineages may provide a significant effect on elite Korean endurance status, although larger sample sizes functional studies are necessary to further substantiate these findings.

미생물 Inulase 에 의한 돼지감자 중의 Inulin 분해에 관한 연구

김기철 한국농화학회 1975 Applied Biological Chemistry (Appl Biol Chem) Vol.18 No.3

The analysis of Jerusalem artichoke showed that it contains 12.09% of Inulin. The results obtained from the examination of the conditions for fructose production by cultivating Pencillum sp 1 in the Jerusalem articoke medium were as follows: 1. The optimum amount of water added to Jerusalem artichoke was 2.5 L of distilled water per ㎏ of fresh Jerusalem artichoke. It this case, the concentration of Inulin was 4% (w/v). 2. The optimum temperature was 30℃, the initial optimum pH was 5.0 and the optimum cultural period was 72 hours. 3. Shaking culture with 50 ㎖ of the medium and 120 oscills/min in 500 ㎖ shaking flask was most effective as the culture method. 4. 0.1% of NH₄H₂PO₄ as a nitrogen source, 0.001 of FeSO₄7H₂O and 0.001 of MgSO₄7H₂ as metal salts were most effective. 5. Fructose production continued to increase for 72 hours under the optimum conditions for cultivation and the highest production rate to the Inulin was 95.25%.

Shuffle Memory의 구조와 DFT에의 응용

金起撤 서울시립대학교 산업기술연구소 1997 산업기술연구소논문집 Vol.5 No.-

This paper proposes a new memory system called shuffle memory. The shuffle memory is an extension of transposition memory which has been widely used in 2-dimensional Discrete Cosine Transform and Discrete Fourier Transform. The shuffle memory receives MxN 2-D input array in row major order and provides MxN output array in column major order. The shuffle memory provides "read-then-write at the same address operation". In other words, an input array element is written at the same address an output element has been read. The shuffle memory is the first memory system that receives MxN inputs in row major order and provides MxN outputs in column order with the minimum amount of memory space.

강의실 밖에서 만난 미국

김기철 관훈클럽 2014 관훈저널 Vol.- No.132

박판 점용접부의 기계적 성질에 미치는 용접조건의 영향

김기철,이기호,윤의박 대한금속재료학회(대한금속학회) 1990 대한금속·재료학회지 Vol.28 No.8

Spot, weldability of the galvanized steel, galvanneld steel and cold rolled steel is compared exclusively in this study. In order to investigate the effects of welding parameters on the weld strength of each steel, welding current and welding time were systematically varied under a constant pressure. Spot weldability of surface coated steels was strongly dependent upon types of coating although the compositions of coating (Zn-Fe) and base plate were almost identical. As the welding heat input (current and time) increased, nugget size and strength increased. However, when heat input (especially current) was greater than a critical value, effects of energy input became minor. Results also demonstrate that the tensile shear strength can be expressed by a second order equation of welding current and welding time. Experimental data fall within 5% error limit of the calculated values.

구조용탄소강 레이저 용접부의 금속조직 특성

김기철,윤의박 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.3

With high power carbon dioxide laser system, C-Mn structural steel for automobile application was welded. Bead-on-plated welding process was applied with 6㎜ thick hot rolled steel plates, and the welding conditions such as travel speed, position of focus and laser output power were 1.2m/min, l.0㎜ under the sample surface and 2.1㎾, respectively. Microstructural examinations and calculation indicated that the microstructrue of the laser weld, which experienced very high heating and cooling cycle during welding process, may not be predicted from the founds in the conventional arc process. Test results also demonstrated tha the austenite nucleation takes place at the pearlite-ferrite boundaries instead of the interface between ferrite and cementite in the pearlite. In the laser welding, the initiation and completion temperature of austenite transformation are much higher than that in the arc welding. Hardness of martensite in the HAZ varies from 635 Hv to 350 Hv because the homogenization of austenite is not complete even at the temperatures far above the A₃.