• Maxillofacial Plastic and Reconstructive Surgery
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• 제34권3호
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• pp.215-219
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• 2012

Cemento-ossifying fibroma (COF) is a benign fibro-osseous tumor with fibrous tissue, abnormal cement and bone, or a combination of such elements. These are slow-growing lesions and are more frequent in women. Here, we report the case of a 28-year-old Korean woman. The patient having no underlying disease complained about facial swelling and asymmetry. A firm mass with impacted molars and teeth deviation on the right maxilla was observed. A computed tomography scan was taken and an incisional biopsy was performed. Following this, COF was diagnosed. Complete surgical removal of the lesion was carried out. A post-operative follow-up was conducted and 3 months later the patient reported no discomfort or any sign of recurrence in regards to the lesion. Differential diagnosis with fibrous dysplasia and the COF is important because of the treatment choice. We report a case of COF and offer a review of the literature on this article.

• 대한치과교정학회지
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• 제45권1호
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• pp.29-37
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• 2015

Objective: The coefficients of friction (COFs) of aesthetic ceramic and stainless steel brackets used in conjunction with stainless steel archwires were investigated using a modified linear tribometer and special computer software, and the effects of the bracket slot size (0.018 inches [in] or 0.022 in) and materials (ceramic or metal) on the COF were determined. Methods: Four types of ceramic (one with a stainless steel slot) and one conventional stainless steel bracket were tested with two types of archwire sizes: a $0.017{\times}0.025$-in wire in the 0.018-in slots and a $0.019{\times}0.025$-in wire in the 0.022-in slot brackets. For pairwise comparisons between the 0.018-in and 0.022-in slot sizes in the same bracket, an independent sample t-test was used. One-way and two-way analysis of variance (ANOVA) and Tukey's post-hoc test at the 95% confidence level (${\alpha}$ = 0.05) were also used for statistical analyses. Results: There were significant differences between the 0.022-in and 0.018-in slot sizes for the same brand of bracket. ANOVA also showed that both slot size and bracket slot material had significant effects on COF values (p < 0.001). The ceramic bracket with a 0.022-in stainless steel slot showed the lowest mean COF (${\mu}$ = 0.18), followed by the conventional stainless steel bracket with a 0.022-in slot (${\mu}$ = 0.21). The monocrystalline alumina ceramic bracket with a 0.018-in slot had the highest COF (${\mu}$ = 0.85). Conclusions: Brackets with stainless steel slots exhibit lower COFs than ceramic slot brackets. All brackets show lower COFs as the slot size increases.

• 대한구강악안면병리학회지
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• 제42권6호
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• pp.189-198
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• 2018

A 31 years old female had been suffered from a bony swelling in right premolar region of the mandible for 12 years, recently grown rapidly. A fistula tract developed on the right anterior mandibular border, but the lesion was relatively asymptomatic. In the radiological examination, the tumor mass was irregularly mixed with radiolucent and radiopaque areas, forming multiple cystic spaces. Under the diagnosis of calcifying odontogenic cyst, the mandibular mass was resected and examined pathologically. After decalcification, the dissected tumor mass showed multiple small cystic spaces and calcifying fibrous tissue, mimicking calcifying odontogenic cyst or ameloblastoma. Histological observation showed many calcifying cementoid materials and ossifying trabeculae. The cystic spaces were turned out to be dilated vascular channels lined by endothelial cells, containing plasma fluid. However, the main lesion was diagnosed as cemento-ossifying fibroma (COF), and the atypical vascular channels were greatly dilated and gradually expanded the whole tumor mass. The present COF was examined through immunohistochemical (IHC) array, and investigated for tumor cell characteristics, exhibiting abnormal ossification and aneurysmal cystic changes. IHC array disclosed that the tumor cells grew progressively in the lack of apoptosis, and that they showed lower expression of RUNX2 than BMP-2, RANKL, and OPG, and increases of protein expression in $HIF-1{\alpha}$, VEGF-A, and CMG2. These data suggested that the reduced expression of RUNX2, osteoblast differentiation factor, be relevant to abnormal ossification of COF, and that the consistent expressions of angiogenesis factors be relevant to de novo angiogenesis in COF, subsequently resulted in aneurysmal cystic changes.

• 한국안전학회지
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• 제28권3호
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• pp.33-38
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• 2013

Many occupational workers or professionals have to walk on the various floors for a long period of time. The objective of this study was to develop the safety shoes with increased traction through the material selection. In order to fulfill our objective, first, two kinds of filler were selected to compare the wear mechanism at outsole surface. The developed rubber materials were tested with two kinds of portable slip meters. The sample safety shoes with developed rubber materials were also tested with subject in the laboratory. During walking, the safety shoes were naturally abraded with counter surface. The coefficient of friction(COF) was gradually decreased with number of steps to 30,000, while the COF was abruptly increased from 30,000 to 40,000. The experimental results showed that COF tested with silica rubber was at least 10% higher than that with carbon black rubber in wet or detergent condition. It has been well recognized that filler properties play a important role in wet traction in the tire industry. However it has been unclear that filler properties would be decisive factor in safety shoes. Our study shows that silica exhibits a higher slip resistance than carbon black without reference to wear states in wet or detergent condition. So, this results will provide guides for outsole compounders to develop new products and improve product performance.

• 공업화학
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• 제22권2호
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• pp.196-202
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• 2011

폴리올 에스테르 등의 에스테르 윤활제는 생분해성 및 윤활성능이 우수하여 금속가공유 및 유압작동유등의 윤활기유로 많이 사용되고 있다. 본 연구에서는 윤활성 향상제로 사용하기 위하여 알킬 무수 숙신산과 여러 가지 지방 알콜과의 축합반응을 행하여 알킬 숙시네이트 유도체를 합성하였다. 합성된 알킬 숙시네이트 유도체의 구조는 $^1H-NMR$ 및 FT-IR 스펙트럼으로 분석하였으며 GC 크로마토그램을 통하여 화합물의 순도를 확인하였다. 또한, 합성 유도체의 기본물성으로 점도특성, 굴절률, 전산가, 유동점 등을 측정하였으며 응용물성으로 윤활특성을 SRV 시험기와 4-ball 마모 시험기로 마찰계수(COF) 및 마모흔 직경(SRV WSD 및 4-ball WSD)을 측정하여 평가하였다. 기본물성 평가결과, 점도 특성, 굴절률 및 유동점은 알킬 숙시네이트 유도체에 함유된 알킬기의 탄소수가 증가할수록 높아졌으며 전산가는 0.2~4 mgKOH/g를 나타내어 금속가공유 및 유압작동유의 윤활제로 사용가능함을 알 수 있었다. 윤활성능 평가 결과, SRV WSD 0.391~0.689 mm, SRV COF 값은 0.110~0.138, 4-ball WSD 값은 0.49~0.55 mm를 나타내어 에스테르의 구조에 따라 차이를 나타내었다. 특히, SRV 시험에서 비교물질로 사용된 폴리올 에스테르인 TMPTO와 윤활성능을 비교하였을 때 SRV WSD 결과, 알킬기에 따라 다른 차이를 나타냈지만 비교물질에 비해 비교적 우수한 값으로, SRV COF 결과, 알킬기에 대한 영향을 받지 않고 비교물질에 비해 약간 떨어지는 값을 나타내었다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2007년도 제33회 하계학술대회 초록집
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• pp.229-229
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• 2007

• Imaging Science in Dentistry
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• 제45권2호
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• pp.109-115
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• 2015

Central odontogenic fibroma (COF) is a rare benign tumor that accounts for 0.1% of all odontogenic tumors. A case of COF (simple type) of the mandible in a four-year-old boy is described in this report. The patient showed asymptomatic swelling in the right inferior border of the lower jaw for one week. A panoramic radiograph showed a poorly-defined destructive unilocular radiolucent area. Cone-beam computed tomography showed expansion and perforation of the adjacent cortical bone plates. A periosteal reaction with the Codman triangle pattern was clearly visible in the buccal cortex. Since the tumor had destroyed a considerable amount of bone, surgical resection was performed. No recurrence was noted.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2003년도 춘계학술발표강연 및 논문개요집
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• pp.151-151
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• 2003

최근 휴대폰용 LCD, 컴퓨터용 TFT LCD, 가정용 PDP 등 평판 디스플레이 산업의 발달에 힘입어 평판 디스플레이 장치의 구동 칩 실장 부품인 TCP(tape carrier package), COF(chip on film) 제조 산업 또한 발전하고 있다. 이들 TCP, COF는 디스플레이 장치의 경박화에 따라 보다 가는 선폭의 회로가 요구되어지는데 이를 위해 회로를 구성하는 기본소재로 얇은 두께의 동박이 사용된다. 회로기판용 동박으로는 압연동박과 전해동박이 함께 사용되어 왔으나 박막의 제조가 어려운 압연동박의 단점과 면에 수직한 주상정 조직이 발달해 있어 일반 압연 동박에 비해 접착력이 뛰어나며 전류밀도 또는 티타늄 음극 드럼 회전 속도를 조절하여 두게 조절이 용이한 전해동박의 장점으로 인해 현재 압연동박의 전해동박으로의 대체가 증가하고 있다. 전해동박의 제조공정은 크게 제박 공정과 후처리 공정으로 나눌 수 있다. 전해동박은 먼저 드럼형태의 티타늄 음극과 불용성 납 양극으로 이루어진 제박기에 고 전류를 가하여 황산구리 용액 중 구리를 티타늄 음극에 석출시킴으로서 구리 원박을 제조한 후 접착력 향상을 위한 노듈 형성, 방식, 방청, 내열성 향상 등을 위한 여러 개의 단위 셀 조합으로 이루어진 후처리 공정을 거쳐 제조된다.

• Transactions on Electrical and Electronic Materials
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• 제8권1호
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• pp.15-20
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• 2007

Conditioner wear, copper polish rates, pad temperature and coefficient of friction (COF) are measured for two novel Mitsubishi Materials Corporation designs during an extended wear and polishing test. Both designs are coated with a $Teflon^{TM}$ film to reduce substrate wear and chemical attack. Using optical interferometry, changes in the coating that result in gradual changes in diamond exposure are measured. Theories of the COF, conditioning, and polishing are applied to explain the observed performance differences between the designs.

• 한국산업융합학회 논문집
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• 제11권4호
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• pp.171-175
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• 2008

The bigger size of the wafer to the meet the need of higher productivity and the smaller digital products for convene are examples of the main trends of the market among others. The higher integrity of chips is also an important task in semiconductor industry. In this thesis the COF(chop on film) technology has reviewed to investigate the best combinations of required functions and to develop a new system to save the installation area and to adapt to the variation of layout with flexibility. The new system shows the better and provides the improved safety with smaller size.