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조병무,유익수,이성휘,이동주 한국공작기계학회 2008 한국공작기계학회 추계학술대회논문집 Vol.2008 No.-
In manufacturing process, the. free-formed surface machining using a ball end mill of CNC machining center is important and the geometric accuracy of a 3D workpiece is effected by the cutting characteristics. Machining error is defined the normal distance between designed surface and actual tool path with tool deflection. This is inevitably caused by the tool deflection, tool wear, thermal effect and machine tool errors and so forth. In this study, the geometric accuracies such as roundness in semi-cylinder, free-formed profile and surface roughness were measured using a Coordinate Measurement Machine(CMM) and a contact type surface roughness measuring device. The results will be useful as a guidance for cutting condition to improve the geometrical accuracy of free-formed surface in ball end milling.
복합레진의 exponential 중합법이 상아질접착제의 미세인장접착강도에 미치는 영향
성소래,서덕규,이인복,손호현,조병훈 大韓齒科保存學會 2010 Restorative Dentistry & Endodontics Vol.35 No.2
접착제를 통해 치아에 접착되는 상부의 복합레진의 빠른 중합은 접착제층에 높은 중합수축응력을 발생시킨다. 중합수축응력을 경감시키기 위해서, LED 광중합기의 하나인 Elipar FreeLight 2 (3M ESPE, USA)에서는 최초 5초 이내에 광강도를 증가시키는 exponential 중합법을 채택하고 있다. 본 연구에서는 짧은 시간내에 광강도를 증가시키는 exponential 중합법이 복합레진의 초기 중합수축속도를 효과적으로 조절할 수 있는지를 알아보기 위해 접착제 적용 후 상부의 복합레진을 exponential 중합법과 continuous 중합법으로 중합하여 상아질접착제의 미세인장접착강도를 비교하였다. 3M사의 Scotchbond Multipurpose Plus (MP), Single Bond 2 (SB), 및 Adper Prompt (AP)의 세 종류의 접착제를 발치한 대구치의 교합면 상아질에 제조사의 지시에 따라 적용하고, 혼합형 복합레진인 Denfil (Vericom, Korea)을 두 가지 광중합방법으로 중합하였다. 접착 후 48시간에 미세인장접착강도를 측정하고, 파절면은 FE-SEM.으로 관찰하였다. 그 결과, 각각의 접착제에서 중합방법에 따른 접착강도의 차이는 관찰할 수 없었다(Two-way ANOVA, p > 0.05). MP와 SB의 미세인장접착강도는 AP에 비해 유의하게 높았다(p < 0.05). 대부분의 파절시편에서는 혼합형 파절이 가장 많이 관찰되었으나, 중합방법에 따른 파절양상의 차이는 없었다. 결론적으로 5초 이내의 짧은 시간에 광강도를 증가시키는 exponential 중합법은 continuous 중합법과 비교하여 상아질접착제의 미세인장접착강도에 영향을 주지 않았다. Objectives: Rapid polymerization of overlying composite resin causes high polymerization shrinkage stress at the adhesive layer. In order to alleviate the shrinkage stress, increasing the light intensity over the first 5 seconds was suggested as an exponential curing mode by an LED light curing unit (Elipar FreeLight2, 3M ESPE). In this study, the effectiveness of the exponential curing mode on reducing stress was evaluated with measuring microtensile bond strength of three adhesives after the overlying composite resin was polymerized with either continuous or exponential curing mode. Methods: Scotchbond Multipurpose Plus (MP, 3M ESPE), Single Bond 2 (SB, 3M ESPE), and Adper Prompt (AP, 3M ESPE) were applied onto the flat occlusal dentin of extracted human molar. The overlying hybrid composite (Denfil, Vericom, Korea) was cured under one of two exposing modes of the curing unit. At 48h from bonding, microtensile bond strength was measured at a crosshead speed of 1.0 mm/min. The fractured surfaces were observed under FE-SEM. Results: There was no statistically significant difference in the microtensile bond strengths of each adhesive between curing methods (Two-way ANOVA, p > 0.05). The microtensile bond strengths of MP and SB were significantly higher than that of AP (p < 0.05). Mixed failures were observed in most of the fractured surfaces, and differences in the failure mode were not observed among groups. Conclusion: The exponential curing method had no beneficial effect on the microtensile dentin bond strengths of three adhesives compared to continuous curing method.
2.9% 과산화수소를 함유한 부착형 미백제의 임상적 효능과 안정성에 관한 연구
박은숙,성소래,홍성태,김지은,이소영,황수연,이신재,진보형,손호현,조병훈 大韓齒科保存學會 2006 Restorative Dentistry & Endodontics Vol.31 No.4
2.9%의 과산화수소를 함유한 시험용 부착형 미백제(Medison dental whitening strip, Samsung medical Co.,Anyang,Korea)를 실험군 피험자 23명, 시험용 미백제에서 과산화수소를 제외한 동일한 제재를 대조약으로 대조군 피험자 24명에게 매일 1시간 30분씩, 2주간 적용하여 임상적 효능과 안전성을 평가하였다. 미백 효과는 Shade Vision, Chroma Mete 및 Vitapan classical shade guide를 이용하여 색변화를 측정하여 다음과 같은 결론을 얻었다. 1. 실험군에서의 전체 치아의 색변화량(ΔE^(*))은 세 가지 측정법에서 모두 대조군에 비해 통계적으로 유의한 차이를 보였고 (p < 0.05). 쉽게 인지할 수 있는 정도였다. 2. 색변화는 색좌표 상에서 명도의 증가와 녹색조 및 청색조로의 변화에 의해 얻어졌다. 3. 치아별로는 어두운 견치의 색변화량이 가장 컸고, 측절치, 중절치 순으로 감소하였다. 4. 47명의 피험자 중 5명이 경도의 과민증을 경험하였으나 곧 완화되었다, 치은염증지수와 전기치수검사 결과 시험 전후에 차이가 없어 안전성을 확인하였다. This study evaluated the effectiveness and safety of an experimental bleaching strip (Medison dental whitening strip, Samsung medical Co., Anyang, Korea) containing 2.9% hydrogen peroxide. Twenty-three volunteers used the bleaching strips for one and a half hour daily for 2 weeks. As control group, the same strips in which hydrogen peroxide was not included were used by 24 volunteers with the same protocol. The shade chang (ΔE^(*), color differnce) of twelve anterior teeth was measured using Shade Vision (X-Rite Inc., S. W. Grandville, MI, USA), Chroma Meter (Minota Co., Ltd. Osaka, Japan) and Vitapan classical shade guide (Vita Zahnfabrik, Germany). The shade change of overall teeth in the experimental group was significantly greater than that in the control group (p < 0.05) and was easily perceivable. The change resulted from the increase of lightness (CIE L^(*) value) and the decrease of redness (CIE a^(*) value) and yellowness (CIE b^(*) value). The shade change of individual tooth was greatest in canine, can smallest in central incisor. The safety of the bleaching strip was also confirmed. 〔J Kor Acad Cons Dent 31(4):269-281, 2006〕
SNU mini-pig convergence research center (SNU MPCRC)
Seong Yong Cho,Jeong Su Kwon,Byeong Hwan Won,Hee Joong Sim,Jong Min Kim,Jeong Hwan Che,Jeong Hun Kim,Chung Gyu Park,Byeong Cheol Kang 한국실험동물학회 2021 한국실험동물학회 학술발표대회 논문집 Vol.2021 No.7
Mini-pigs are widely used in research on xenotransplantation, the development of new drugs/medical devices, tissue engineering, and regenerative medicine because of their similar size and physiology to human. The Seoul National University Mini- Pig Convergence Research Center (SNU MPCRC) has been established and has been operated to build infrastructures for domestic mini pig research through the production, maintenance, breeding, and experimental support of SNU mini-pigs for biomedical science research and xenotransplantation research. SNU mini-pigs, which are being bred at the SNU MPCRC, have been maintained at the world"s highest level of cleanliness and have been keeping designated pathogen free status for 17 years. In addition, a lot of background data have been secured and provided to researchers, and it has been well reported both domestically and internationally through the acquisition of 20 patents and the publication of 196 papers. Based on the excellence of SNU mini-pigs, we intend to establish a foundation for mass production of SNU mini-pigs and efficient supply to domestic and foreign researchers. We utilize SNU mini-pigs as future bio-strategic resources through SNU MPCRC.
Cho, Byeong Seong,Oh, Hyun Joo,Uhm, Han S.,Kang, Seung Oun,Kim, Changjo,Choi, Yoon,Choi, Eun Ha Elsevier 2011 CURRENT APPLIED PHYSICS Vol.11 No.5
<P><B>Abstract</B></P><P>The liquid metal ion sources (LMIS) in focused ion beam (FIB) system have many advantages of high current density, high brightness and low ion energy spread. There are two electrodes being emitter and extractor for field ion emission in LMIS. But several LMIS have a new electrode called the suppressor. Characteristics of LMIS with a suppressor are investigated in terms of the electric field change due to the suppressor. The threshold and extinguishing voltages are investigated under the varying a suppressor voltage for a specified source voltage, and also current–voltage (<I>I</I>–<I>V</I>) characteristics have been observed in terms of the voltage difference between the source and extractor for the various suppressor voltages. It is found that the emission current decreases as the suppressor voltage increases since the increase in the suppressor voltage reduces the electric field. It is also noted that the threshold and extinguishing voltages are increased as the suppressor voltage increases.</P>