다이캐스팅한 SiC 입자강화 알루미늄 복합재료의 피로균열 전파특성

김송희,윤여범,이기호,오준도,주희위,이지환 대한금속재료학회(대한금속학회) 1998 대한금속·재료학회지 Vol.36 No.8

This study is to investigate the effect of load ratio on fatigue crack of die-cast SiC particulate aluminum composites. Fundamental fatigue crack propagation tests were performed with sub-sized C-T specimens at a load ratio of 0.1, 0.3 and 0.5 respectively. Crack closure measurements were conducted for explaning the effect of load ratio on fatigue crack growth. The experimental results showed that the fatigue crack growth rate increases with the load ratio, especially at near threshold. The composite reinforced with 20 vol.% SiC particles was better in fatigue crack growth resistance than that with 10 vol.% SiC particles. Through the measurement of Kop and ΔK at various R ratios the concept of effective stress intensity factor range ratio. U was reviewed to evaluate the stress ratio effect on fatigue crack growth. Relationships between U and variables such as ΔK and R were obtained empirically so that we could predict ΔK_(eff) that is of critical importance for the prediction of fatigue crack propagation rate.

TiNi 가 섬유가 TiNi (Co)/Al 형상기억복합재료의 피로균열전파에 미치는 영향

박영철,윤두표,김순국,이준희,이규창 대한금속재료학회(대한금속학회) 1999 대한금속·재료학회지 Vol.37 No.5

In this paper, TiNiCo/Al shape memory composites were fabricated by powder metallurgy method. TiNi and TiNiCo were used as fiber for reinforcement. To investigate the fatigue crack propagation behavior due to the compressive residual stress which exists in the composites, fatigue test was performed at room temperature and above the inverse transformation temperature A_f of TiNi and TiNiCo shape memory alloy. Results are as follows; At 363 K, both composites have lower fatigue crack propagation rate than pure matrix in the same ΔK area and the fatigue crack propagation of TiNi/Al composite is lower than that of TiNiCo/Al composite.

조사료의 종류가 홀스타인 송아지 유선의 발달 , 반추위 돌기 및 성장률에 미치는 영향

조광근,최윤재,박영우,윤연화,한영근,윤상기,권웅기 한국영양사료학회 1999 韓國營養飼料學會誌 Vol.23 No.6

본 연구는 홀스타인 송아지에 대한 세 종류의 조사료가 유선조직, 반추위 유두, 번식성적 및 성장률에 미치는 영향을 조사하기 위하여 실시하였다. 출생 후 4일된 송아지(42.9±0.9㎏) 24두를 무작위로 선발하여 출생 후 4∼44일까지 전유를 급여하다가 45일에 그룹 1은 볏짚, 그룹 2는 오차드 그래스, 그룹 3은 알괄파를 급여하였다. 또한 유선조직과 반추위의 발달을 측정하기 위하여 3, 9, 18개월령에 도달하였을 때 각 처리구의 송아지를 1마리씩 도살하였다. 알팔파를 급여한 그룹 3은 다른 처리구에 비하여 중체율이 높았으며, 그룹 2는 영양소 이용률과 번식성적이 높은 경향을 나타내었다. 반추위의 무게는 3개월령 도달시에는 그룹 3이 가장 무거웠으나, 9개월과 18개월령 도달시에는 그룹 2에서 가장 무거운 것으로 나타났다. 반추위의 유두 수는 유두의 성장과 함께 일반적으로 감소하는 경향을 나타내어 유두의 길이와 유두 수와는 서로 상대적인 관계를 나타내었다. 유선의 기능적 활성을 나타내는 RNA/DNA 함량은 3개월 시에는 그룹 3이 가장 낮은 경향을 보였으나 9, 18개월 시에는 반대로 가장 높은 경향으로 나타났으며, 유선세포의 크기를 나타내는 protein/DNA 함량은 18개월 시에 그룹 2가 가장 높은 경향을 보였다. 결론적으로 본 연구에서 볏짚은 반추위의 초기 발달을 촉진하고 알팔파와 오차드그래스는 성장과 번식성적을 증가시키며 또한 초기에 유선의 발달을 촉진시키는 것으로 나타났다. Twenty-four Holstein calves were used to evaluate the effects of three different forages on growth and reproductive performances, and ruminal papillary and mammary developments. Four-day-old Holstein calves weighing 42.9±0.9 ㎏ were randomly assigned to three forage groups of rice straw (group 1), orchard grass hay (group 2), and alfalfa (group 3). All calves received whole milk from day 4 through day 44. At 45 days of age, the animals were assigned at random to one of the three dietary treatments. When calves reached the ages of 3, 9, and 18 months, one calf in each group was sacrifced for evaluation of ruminal and mammary tissue developments. Calves of group 3 gained more body weight than those of other groups, while group 2 showed an effective nutrient utilization and reproduction performance. At 3 months, the stomach weight of group 3 was the highest, however, group 2 provided the highest stomach weight at 9 and 18 months. A remarkable reduction in papillae number was observed in the rumens of all 3- to 9-month-old heifers. A decrease in number of these papillae was observed in all groups exhibiting papillary growth. There was a reciprocal relationship between the number and the length of ruminal papillae. Among the 3-month-old calves, the functional activity (RNAI DNA contents) of the mammary glands of group 3 was lower than those of other groups, whereas the trend was opposite for 9- and 18-month-old heifers. The size of mammary cell (protein / DNA contents) was the greatest for group 2 at 18 months of age. The results suggest that rice straw stimulated earlier development of rumen. Alfalfa and orchard grass improved the growth, reproduction performance, and earlier development of mammary glands.

울산공단지역의 대기중 휘발성 유기화합물에 대한 위해도 평가

이진홍,남병현,윤미정 한국산업안전학회 1999 한국안전학회지 Vol.14 No.2

This study focused on risk assessment for inhalation of airborne volatile organic compounds (VOCs) in Ulsan industrial complex area. For non-carcinogenic risk, even the highest hazard index of toluene was estimated to be 4.8 × 10^(-2), which was much lower than 1. The total hazard index of VOCs was estimated to be 5.8 × 10^(-2). However, lifetime average cancer risk from the inhalation of airborne VOCs was estimated to be about 1.1 × 10^(-3), which was much higher than a risk standard of 10^(-5). The risk of 4.4 × 10^(-5) came from benzene, the only human carcinogen among VOCs, while that of 1.05 × 10^(-3) from probable human carcinogens including 1,3-butadiene and 1,2-dichloroethane. About 70% and 20% of total VOC cancer risk was due to the inhalation of 1,3-butadiene and 1,2-dichloroethane, respectively. Therefore, proper risk management of these 3 VOCs was required for the protection of health from cancer burden in Ulsan industrial complex area.

허혈성 대장염의 임상 양상과 예후 인자

이미숙,손희정,강태욱,최규완,박동일,백승운,이준행,고광철,이종철,임윤정,이풍렬,김갑철,김재준 대한소화기내시경학회 2001 Clinical Endoscopy Vol.22 No.2

Background/Aims: Colonic ischemia is recognized as the most common vascular disorder of the intestines in the elderly. The severity of the disease may vary considerably with the prevalent benign transient forms, being amenable to conservative treatments and the severe gangrenous forms, requiring surgery. Correct diagnosis is usually made after the ischemic episode is over and colonic ischemia is frequently misdiagnosed. The aim of this study is to identify the clinical patterns and prognostic factors of ischemic colitis. Methods: We found 60 patients with nonoccusive ischemia of the large intestine, We analyzed age, sex, symptoms, signs, associated disease, location, endoscopy, hematologic, histologic, radiologic finding and treatment, retrospectively. Results: The mean age was 60.2±6.3 years. The most common symtoms were abdominal pain or bloody diarrhea. The most common sign was diffuse abdominal tenderness. The most common hematologic findings were anemia and leukocytosis. Associated medical illnesses wer diabetes, rhematoid arthritis and cerebrovascular accident, et al. Both computed tomography (CT) and endoscopy were useful diagnostic tools. The most common involved site was sigmoid colon. 46 patients were treated conservatively and 14 patients were managed surgically. Conclusions: Male gender, those with rebound tenderness, severe anemia, right or total colon involvement as well as rheumatoid arthritis had a poor prognosis. Both CT and endoscopy were useful in predicting prognosis.

역류성 식도염 환자에서 Helicobacter pylori 치료 1 년 후 증상과 내시경적 변화

김영호,손희정,최규완,박동일,백승운,이준행,고광철,이풍렬,이종철,임윤정,김재준 대한소화기내시경학회 2001 Clinical Endoscopy Vol.24 No.1

위장관 간질종양의 임상 및 병리학적 고찰

김영호,장우영,이순진,손희정,최규완,도재혁,백승운,이준행,이풍렬,이종철,박철근,임윤정,김갑철,김재준,임효근 대한소화기학회 2001 대한소화기학회지 Vol.37 No.3

Background & Aims: Gastrointestinal stromal tumor (GIST) constitutes primary nonepithelial neoplasms of the gastrointestinal tract and includes most tumors previously designated as leiomyomas/leiomyosarcomas. GIST is pathologically divided into benign, borderline and malignanct tumor. This study was carried out to delineate the clinical and pathologic features of GIST and to establish the features predicting malignancy. Methods: Clinicopathologic data of 84 patients who had GIST from 1995 to 1999 were reviewed. Results: The subjects were 42 men and 42 women, and their mean age was 59.3±13.2 years. We located fifty-two tumors in the stomach, 28 tumors in the small intestine and 4 tumors in the colorectum years. Histopathology revealed benign tumors in 23 of the 84 patients, borderline tumors in 22, malignant tumors in 39. The average size of tumors was 6.23 cm in diameter (range, 0.6-26 cm). Metastasis was noted in 15.5% of the patients at diagnosis. On endoscopy, ulceration was more common in malignancy. Endsonographic findings except size were not significant statistically. On contrast enhanced computed tomography, malignancy showed more irregular shape and variable attenuation than benign lesions, which seemed to be valuable factor. Conclusions: The variables predicting malignancy were large tumor size (≥5 cm), location of the colorectum, palpable abdominal mass, ulceration on endoscopy, and less uniformity in shape and variable attenuation on computed tomography.

등가응력구배 시편에 대한 J-Q 해석

윤정한(J. H. Yun),석창성(C. S. Seok),구재민(J. M. Koo),이정민(J. M. Lee),박건태(K. T. Park) 한국정밀공학회 2014 한국정밀공학회 학술발표대회 논문집 Vol.2014 No.5월

Induction of bone formation by <i>Escherichia coli</i>‐expressed recombinant human bone morphogenetic protein‐2 using block‐type macroporous biphasic calcium phosphate in orthotopic and ectopic rat models

Park, J‐,C.,So, S‐,S.,Jung, I‐,H.,Yun, J‐,H.,Choi, S‐,H.,Cho, K‐,S.,Kim, C‐,S. Blackwell Publishing Ltd 2011 Journal of periodontal research Vol.46 No.6

<P><I>Park J‐C, So S‐S, Jung I‐H, Yun J‐H, Choi S‐H, Cho K‐S, Kim C‐S. Induction of bone formation by</I> Escherichia coli<I>‐expressed recombinant human bone morphogenetic protein‐2 using block‐type macroporous biphasic calcium phosphate in orthotopic and ectopic rat models. J Periodont Res 2011; 46: 682–690. © 2011 John Wiley & Sons A/S</I></P><P><B>Background and Objective: </B> The potential of the <I>Escherichia coli</I>‐expressed recombinant human bone morphogenetic protein‐2 (ErhBMP‐2) to support new bone formation/maturation using a block‐type of macroporous biphasic calcium phosphate (bMBCP) carrier was evaluated in an orthotopic and ectopic rat model.</P><P><B>Material and Methods: </B> Critical‐size (Φ 8 mm) calvarial defects and subcutaneous pockets in 32 Sprague–Dawley rats received implants of rhBMP‐2 (2.5 μg) in a bMBCP carrier or bMBCP alone (control). Implant sites were evaluated using histological and histometric analysis following 2‐ and 8‐wk healing intervals (eight animals/group/interval).</P><P><B>Results: </B> ErhBMP‐2/bMBCP supported significantly greater bone formation at 2 and 8 wk (10.8% and 25.4%, respectively) than the control at 2 and 8 wk (5.3% and 14.0%, respectively) in calvarial defects (<I>p</I> < 0.01). Bone formation was only observed for the ErhBMP‐2/bMBCP ectopic sites and was significantly greater at 8 wk (7.5%) than at 2 wk (4.5%) (<I>p</I> < 0.01). Appositional and endochondral bone formation was usually associated with a significant increase in fatty marrow at 8 wk. The bMBCP carrier showed no evidence of bioresorption.</P><P><B>Conclusion: </B> ErhBMP‐2/bMBCP induced significant bone formation in both calvarial and ectopic sites. Further study appears to be required to evaluate the relevance of the bMBCP carrier.</P>

Synthesis and photovoltaic characterization of D/A structure compound based on N-substituted phenothiazine and benzothiadiazole

Yun, D.H.,Yoo, H.S.,Heo, S.W.,Song, H.J.,Moon, D.K.,Woo, J.W.,Park, Y.S. Korean Society of Industrial and Engineering Chemi 2013 Journal of industrial and engineering chemistry Vol.19 No.2

In this study, poly [(N-10'-dodecyl-phenothizin-3,7-ylene)-alt-(2,2'-bithiophen-5-yl)] (P1) and poly [(N-10'-dodecyl-phenothiazin-3,7-ylene)-alt-(5',6'-dioctyloxy-benzothiadiazole-bithiophene)] (P2) were synthesized by Suzuki coupling reaction. Optical and electrochemical characteristics of the synthesized polymers, P1 and P2, were then analyzed, indicating that their wavelength of maximum absorption was 453nm and 533nm, respectively, and their band-gap was 1.93eV and 1.74eV, respectively. The maximum power conversion efficiency (PCE) of organic photovoltaic cells created by using P1 and P2 were 0.74% (P1:PC<SUB>71</SUB>BM=1:4,w/w) and 1.00% (P2:PC<SUB>71</SUB>BM=1:3,w/w), respectively, and the short circuit current density (J<SUB>SC</SUB>), fill factor (FF), and open circuit voltage (V<SUB>OC</SUB>) of the device were 3.5mA/cm<SUP>2</SUP>, 31.8%, and 0.68V, respectively, for P1 and 3.9mA/cm<SUP>2</SUP>, 32.7%, and 0.78V, respectively, for P2.