플륨 모니터링에 의한 SM45C 레이저 용접특성 평가

유영태,김재열,노경보,양동조,오용석,임기건,김지환 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.6

With the increased use of lasers in industrial welding applications, techniques for monitoring and controlling these processes become increasingly important. It is very important that we understand the dynamic behaviors of the laser induced plume in welding because the laser induced plume has considerable effects on welding efficiency and the quality of materials. As the plume fluctuation was associated with keyhole instability, unstable vapor plume indicated the process was unstable and would result in poor welds. An Infrared Themal-vision Camera can be utilized compensate for incurracies encountered in real-time monitoring during laser welding. We have results that instabilities of plume are closely dated with hot cracking and defect of laser welding.

오스테나이트계 스테인리스강과 SM45C의 연속파형 Nd:YAG 레이저 용접특성비교

유영태,오용석,노경보,임기건 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.3

Welding characteristics of austienite 304 stainless steel and SM45C using a continuous wave Nd:YAG laser are experimentally investigated. Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and deep penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional welding processes, leading to a rather small weld zone. Experiments are performed for 304 stainless steel plates changing several process parameter such as laser power, welding speed, shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar and plates, etc. The Nd:YAG laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration. This paper describes the weld ability of SM45C carbon steel for machine structural use by Nd:YAG laser. The follow conclusions can be drawn that laser power and welding speed have a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted in an increase in weld depth/aspect ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power.

Homocysteine-thiolactone 이 유발시키는 소 혈관내피세포의 손상효과

유동찬,김보은,전가영,권오형,지광환 금오공과대학교 2007 論文集 Vol.28 No.-

The homocysteine-thiolactone, a reactive metabolic compound of homocysteine has been implicated in human cardiovascular diseases. The increasing of total plasma homocysteine concentration lead to homocystinuria, which may cause to elevate the concentration of homocysteine-thiolactone in the blood serum. It might be one of the risk factor which is responsible for the development of several vascular diseases. The present study is to demonstrate the harmful effect of homocysteine-thiolactone induced on calf pulmonary artery endothelial (CPAE) cells. CPAE were cultured in RPMI1640 medium supplemented with 10% FBS. CPAE were grown in humidified atmosphere of 5% C₂ in air at 3TC. Cells cultured with homocysteine-thiolactone at concentrations ranging from 0.1mM, lmM, 5mM and l0mM (dissolved in dH₂O). After incubation, cells were stained with MTT. Cell viability was evaluated under the UV-visible absorbance at 540nm. Cells viability was significantly decreased by increasing the concentration of homocysteine-thiolactone, Our data provide the evidence to understand the effect of homocysteine-thiolactone on the cardiovascular system.

오스테나이트계 304 스테인레스강과 Nd-YAG 레이저빔과의 상호작용

유영태,오용석,노경보,임인호 조선대학교 에너지.자원신기술연구소 2002 에너지·자원신기술연구소 논문지 Vol.24 No.1

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. The experiments are performed for 304 stainless steel plate applying variation of : laser power(600~2000W), welding speed (3~10m/min), shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar and plates, etc. The variation of brightness temperature versus modification of operational parameters is found, certain typical welding defects can be detected.

한국 성인여성의 심미적 상악절치 위치에 관한 두부방사선 계측학적 연구

유보영,김종철 전남대학교 치과대학 1991 전남치대논문집 Vol.3 No.1

Esthetic is one of the prime goal of the orthodontic treatment. The upper incisor position is important because it is decisive in balanced smile. This study was attemped to obtain the standards and equations on the esthetic upper incisor position. Lateral cephalometric rediographs of 66 Korean young adult females who were candidates of Miss Korea Beauty Contest were traced, measured and statistically analyed. The results were as follows ; 1. The mean and standard deviation of the measurement for upper incisor position were obtained in the Korean Beauty. 2. Among the measurements for the axis of upper incisor,1_ to Sn and 1_ to FH were highly correlated with FH-MP, ANB, FH-NPog, NAPog, Y-axis, but 1_ to SN(Is-Pr) to present axial inclination of labial surface of upper incisor didn't have any correlation with the measurements for dentofacial pattern. 3. Among the measurements for the vertical position of upper incisor, 1_ to stom had low correlation with the measurements for dentofacial pattern and 1_ to PP(mm) was highly correlated with the measurements for facial growth direction. 4. Sixteen multiple regression equations were established to predict esthetic upper incisor position balancing with dentofacial pattern. 5. It doesn't have much power of persuation to predict esthetic upper incisor position from the measurements for dentofacial pattern.

연속파형 Nd:YAG SM45C 레이저 용접의 결함 감소연구

유영태,오용석,노경보,신호준 朝鮮大學校 機械技術硏究所 2003 機械技術硏究 Vol.6 No.1

본 연구에서는 Nd:YAG 연속파형 레이저를 이용하여 레이저 용접시 레이저빔의 출력에 대한 레이저범의 이송속도를 변화시켜 심입용접을 실시했다. 열처리를 하지 않고 용접을 실시했을 경우 매우 조대한 기공이 많이 발생하였지만 열처리 후 용접을 실시했을 때는 몇몇 미세한 기공만 발생하였다. Present investigation reports on the effect of incorporating pre-heating on the mechanical properties of laser weldi'ng joints. The Nd:YAG laser in combination with the optical fiber increase the automation and the flexibility of a whole industry. The Nd:YAG laser welding process is one of the most advenced menufacturing technologies owing to its high sped and penetration. This paper describes the weldability of Sh4456 carbon steel fox machine structural use by Nd:YAG laser. Optical microscopy SEM were performed to observe the micro structures and to determine the structures of welded zone. In addtion, mechanical propreties, were measured by tensile test to evaluate the formablity of the welded specimen. The results show that proper selection of the control parameters for per-heating technique can result the porosity and cracking of the welding significantly, and improve the welded joints mechanical properties, such as higher tensile strength and better durability.

오스테나이트계 304 스테인레스강의 Nd:YAG 레이저 초점크기와 용접특성

유영태,오용석,노경보 조선대학교 에너지.자원신기술연구소 2002 에너지·자원신기술연구소 논문지 Vol.24 No.2

Laser beam welding is increasingly being used in welding of structural steels. The laser welding process is one of the most advanced manufacturing technologies owing to its high speed and penetration. The thermal cycles associated with laser welding are generally much faster than those involved in conventional arc welding processes, leading to a rather small weld zone. The experiments are performed for 304 stainless steel plate applying variation of : laser power(1500~2000W), welding speed (3~5m/min), shielding gas flow rate, presence of surface pollution, with fixed or variable gap and misalignment between the similar and dissimilar and plates, etc. The follow conclusions can be drawen that unlikely laser power, welding speed has a pronounced effect on size and shape of the fusion zone. Increase in welding speed resulted inan increase in weld depth/ welding ratio and hence a decrease in the fusion zone size. The penetration depth increased with the increase in laser power.

임플란트의 collar design이 변연골과 연조직에 미치는 영향

유현상,강선녀,정창모,윤미정,허중보,전영찬 대한치과보철학회 2012 대한치과보철학회지 Vol.50 No.1

연구 목적: 임플란트 경부가 잘 설계된 경우 양호한 연조직 반응을 통해 변연골을 보존하는데 도움이 된다. 본 실험에서는 연, 경조직 경계부에 가장 가까이 위치하는 임플란트의 collar design이 변연골 변화와 연조직 반응에 미치는 영향을 동물실험을 통해 알아보고자 하였다. 연구 재료 및 방법: 2마리의 건강한 Beagle dog에 임플란트 collar design만 다른 두 종류의 임플란트(Neobiotech Co. Seoul, Korea)를 식립하였다. Collar에 bevel 을 부여한 군(Bevel 군)과 "S"자 형태를 부여한 군(Bioseal 군)으로 나누어 마리 당 7개, 군당 7개, 총 14개의 임플란트를 무작위로 식립한 후 Healing abutment를 즉시 체결하였다. 디지털 표준구내 방사선사진을 이용해 4주 간격으로 총 12주간 근원심 변연골 변화를 관찰하였고, 12주에 희생하여 조직학적 분석을 통해 협설 변연골 흡수 및 임플란트 주변 연조직 반응을 평가하였다. Mann-Whitney test를 통해 동일한 방사선 사진 촬영 시점에서 근원심 변연골 변화량 및 조직계측치를 군 간 비교하였고, Kruskal-Wallis test를 통해 방사선 사진상 근원심 변연골 변화량이 시간에 따른 차이가 있는지 군 내 분석 한 후 Duncan test를 통해 사후 검증하였다(α=.05). 결과: 방사선학적 분석 결과 각 촬영 시점에서 두 군간 근원심 변연골 변화량의 차이를 보이지 않았다(P>.05). 군 내에서 시간에 따른 근원심 변연골의 흡수량을 분석한 결과 Bevel 군에서는 시간에 따른 차이를 보이지 않았으나 (P>.05), Bioseal 군에서는 시간에 따른 차이를 보였으며, 4주및8주와 비교했을 때 12주에서 변연골의 증가를 보였다(P<.05). 조직학적 분석 결과 협설측 변연골 흡수량에서 두 군간 차이를 보이지 않았으나 (P>.05), Bevel 군에 비해 Bioseal 군에서 더 견고한 결합조직부착을 관찰할 수 있었으며, 생물학적 폭경의 값은 두 집단 간 차이를 보이지 않은 반면에 (P>.05), 접합상피부착은 Bevel 군에서 유의하게 길었고, 결합조직부착은 Bioseal 군에서 더 길게 나타났다(P<.05). 결론: Bevel 군에 비해 Bioseal 군에서 결합조직부착은 길게 형성된 반면에 접합상피부착은 더 짧게 나타났으며, 생물학적 폭경과 초기 변연골 흡수에는 차이가 없음을 알 수 있었다. 연조직 반응의 차이가 실제 기능하중 하에서 변연골 변화에 미치는 영향에 대해서 향후 연구가 필요할 것으로 생각된다. PURPOSE. The purpose of this study was to investigate the effects of implant collar design on marginal bone change and soft tissue response by an animal test. MATERIALS AND METHODS. Two types of Implant (Neobiotech Co. Seoul, Korea) that only differs in collar design were planted on two healthy Beagle dogs. The implants were divided into two groups, the first group with a beveled collar (Bevel Group) and the second group with "S" shaped collar (Bioseal group). Standardized intraoral radiographs were used to investigate the mesio-distal change of the marginal bone. Histological analysis was done to evaluate the bucco-lingual marginal bone resorption and the soft tissue response adjacent to the implant. Mann-Whitney test was done to compare the mesio-distal marginal bone change at equivalent time for taking the radiographs and the tissue measurements between the groups. RESULTS. Radiographic and histological analysis showed that there was no difference in marginal bone change between the two groups (P>.05). Histological analysis showed Bioseal group had more rigid connective tissue attachment than the Bevel group. There was no difference in biological width (P>.05). Bevel group showed significantly longer junctional epithelium attachment and Bioseal group showed longer connective tissue attachment (P<.05). CONCLUSION. For three months there were no differences in marginal bone change between the Bevel group and the Bioseal group. As for the soft tissue adjacent to the implant, Bioseal group showed longer connective tissue attachment while showing shorter junctional epithelium attachment. There were no differences in biologic width.

중증 정신지체 아동에 있어서 강화제 술래잡기 게임이 과제수행 향상에 미치는 영향

정보인,윤현숙,유은영 연세대학교 보건과학연구소 2001 보건과학논집 Vol.11 No.-

지역별 오존농도 조사자료의 비교 : 부산시를 중심으로 the city of Busan

전보경,유수영,최금찬 동아대학교 환경문제연구소 2002 硏究報告 Vol.25 No.1

This study was to charaterize the concentrations of the spring and summer seasons for ozone. Ozone measured using the O3 Analyzer(49C, TEI.). Samples were measured from April to May, 1937 and from July to August, 1998. Five areas were investigated in Busan of which measured sites were Seomyeon, Sasang, Geumjeong, Yeongdo, Guseodong. Ozone concentrations in industry area(Sasang) were higher than the other sites. The maximum concentration is 0.038 ppm and the minimum is 0.012 ppm in this site