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탄화물 입자 강화 7075 Al 합금 기지 복합재료의 미끄럼마멸 특성 연구
강석하,박형철,강신철,김용석 국민대학교 생산기술연구소 2002 공학기술논문집 Vol.25 No.-
Effects of the type and volume fraction of carbide-particle-reinforcements on dry sliding wear behavior of 7075 Al alloy matrix composites were investigated. SiC, TiC and B₄C reinforced 7075 Al alloy matrix composites were manufactured by a pressureless infiltration technique and wear tested. Wear tests were carried out using a pin-on-disk wear tester with varying loads of 3N-160N at a constant sliding velocity of 0.2m/s. AISI 52100 bearing steel ball was a counterpart of the composites. Wear resistance of the composites was always higher than that of the monolithic alloy except the TiC reinforced 7075 Al matrix composite. The resistance increased with the increase of volume fraction of the reinforcing particles. Among the composites, the TiC reinforced composite had the lowest wear resistance and the B4C reinforced composite showed the highest wear resistance.
탄화물 입자 강화 7075 Al 합금 기지 복합재료의 미끄럼마멸 특성에 미치는 기지 합금 변형의 영향
강석하,강신철,김용석 대한금속재료학회 2004 대한금속·재료학회지 Vol.42 No.4
Sliding wear behavior of 7075 Al alloy matrix composites was investigated. Reinforcements of the composite were SiC, TiC, and B_(4)C particles with various size and volume fractions. Sliding wear tests were carried out in an ambient atmosphere using a pin-on-disk wear tester with various loads of 5N-150N against a bearing steel ball counterpart. The composites showed higher wear resistance than the monolithic matrix alloy. Sliding wear of the composites proceeded by a grinding mechanism at low loads and by a delamination of a deformed layer at high loads. Wear resistance of the composites increased with the size and volume fraction of the reinforcements, and the increase was more significant at high applied loads. Deformation of the matrix was found to control the wear at high loads. The effect of heat treatment and reinforcement variation including size, volume fraction and species on the wear was discussed in connectin with the deformation of the matrix. (Received September 19, 2003)
지역별 중학생들의 체격, 체력 및 비만에 관한 비교조사 연구 : 서울 강동구와 충남 아산시를 중심으로
윤규태,강석하 순천향대학교 기초과학연구소 2008 순천향자연과학연구 논문집 Vol.14 No.2
This research is to comparative study on the physique and the physical fitness and the obesity of the Regions that S middle school which is located in Seoul, which are 172 students(90 boys, 82 girls) and that 84 boys from A middle school, 74 girls from F middle school also located in Chungnam. totally 330 students. Then after we got the result we compared the result with the average of examination of the physical fitness for whole students reported by the Ministry of Education and Human Resour Development. Obtain the result follow: First, in the structure of physique, The Seoul area students appeared the Chungnam area students compared to 4.2cm height and 2.7kg weight highly. The Seoul area girls students who was higher 1.4cm and lower weight 0.6kg, than Chungnam area girl students. In the physical fitness, the average figures of boys in Chungnam are higher than the average figures of boys in Seoul in a standing long jump, a push-up, sit-ups, sit and reach. the average figures of girls in Chungnam was higher than the average figures of girls in Seoul in a standing long jump, fixed-arm hanging and a long distance race. Second, in the structure of physique fitness the height and for boys and girls studnts Seoul and Chungnam girl students are higher than the national average. Weight was appeared highly seoul area man and two area girls students than the national average. In the physical fitness the students in Seoul have under average in all items except push-ups. And boys in Chungnam have higher result than the national average in sit-ups and sit and reach. In two area girls students, there was appeared more lowly the national average than from all items. Third, in the degree of obesity, A Seoul area boy students was under weight(0.5%) and hi degree of obesity(1.6%) than Chungnam area boys. A Seoul area girl studnts was low of over weight(5.6%) and hi degree of obesity(1.8%) than a Chungnam area girls
Risk Factors for Distant Metastasis in Follicular Thyroid Carcinoma in Korea
조신돌,이준협,강석하,김윤영,전용순,박형규,최상태,강진모,정유승 대한갑상선-내분비외과학회 2019 The Koreran journal of Endocrine Surgery Vol.19 No.1
Purpose: Follicular thyroid cancer (FTC) can frequently metastasize to distant organs, which worsens the prognosis. This study evaluated the risk factors of distant metastasis in FTC. Methods: We retrospectively reviewed 149 patients diagnosed with primary FTC and underwent operations between 2001 and 2017. Results: The mean age of all patients was 44.8±14.4 years and 82.6% were female. The mean tumor size was 3.44±1.77 cm and a total thyroidectomy was performed in 41.6% of cases. The follow-up duration was 65.4±43.5 months. Distant metastases occurred in 8 patients (5.4%): 5 patients had synchronous and 3 had metachronous distant metastasis. The most common metastatic site was the bone, with bone metastasis observed in 5 of 8 patients, followed by the lung (3 of 8). Bone metastases occurred in 4 of 5 patients with synchronous distant metastasis and in 1 of 3 with metachronous distant metastasis. Distant metastasis was associated with old age (≥45 years), the presence of vascular invasion, widely invasive FTC, and high thyroglobulin (Tg) levels in the first postoperative month. Multivariate analysis showed that old age and the presence of vascular invasion were predictive factors for distant metastasis (P=0.016 and P=0.013, respectively). Conclusion: Old age and vascular invasion were significant factors for distant metastasis. The possibility of bone and lung distant metastases should be assessed when a patient is old (≥45 years), FTC is widely invasive, and when Tg levels are high in the first postoperative month.