• 전기학회논문지
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• 제63권7호
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• pp.1008-1012
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• 2014

Tunnel bracket is used in railway tunnel area in order to maintain insulation. Insulator performance evaluation test is proceeded refer to IEC 61109 but it is impossible to reflect all the field condition where insulator installed. Korea has clear four season in climatic condition and peninsula with lots of mountain in geomorphology condition. Tunnel bracket material which used in korea are butyl rubber, polymer and silicone. Most of them were installed without any internal climatic and geomorphology condition. According to the KORAIL operation data most of the insulator break down occurs in tunnel. So interval of inspection period is shorter then any other insulator and lots of maintenance cost incurs. Most major railway advanced country such as germany and japan maintain tunnel bracket with their own experience. For example visual inspection carried out with in one or two years and detailed inspection carried out between three to five years. This paper analyzed materials and shapes of tunnel bracket to in order to find optimized one in korea peninsula. Proposed bracket were tested under regulation and experience field data. Finally it was installed at the field and evaluated until now.

• 한국표면공학회지
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• 제41권4호
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• pp.163-168
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• 2008

The dental orthodontic bracket requires good mechanical properties, such as elastic strength and frictional resistance, combined with a high resistance to corrosion. The objective of this study was to investigate the effects of TiN and ZrN coating on corrosion resistance of orthodontic brackets using various electrochemical methods. Brackets manufactured by Ormco Co. were used, respectively, for experiment. Ion plating was carried out for coatings of bracket using Ti and Zr coating materials with nitrogen gas. Ion plated surface of each specimen was observed with field emission scanning electron microscopy(FE-SEM), energy dispersive Xray spectroscopy(EDS) and electrochemical tester. The corrosion potential of the TiN and ZrN coated bracket was comparatively high. The current density of TiN and ZrN coated bracket was smaller than that of non-coated bracket in 0.9% NaCl solution. Pit nucleated at angle of bracket slot.

• 대한치과교정학회지
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• 제35권2호
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• pp.116-126
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• 2005

본 연구는 고정성 장치를 이용한 교정 치료에서 브라켓과 교정용 호선 사이의 활주 이동 동안 발생하는 마찰력에 디자인과 재질이 다른 각각의 브라켓과 여러 종류의 호선 다양한 브라켓-호선 각도 등이 어떤 영향을 미치는가를 알아보기 위하여 4종의 브라켓 (stainless steel twin 브라켓인 Gemini, 좁은 근원심 폭경과 single bracket의 디자인이 포함된 Mini Uni-Twin. metal-reinforced 세라믹 브라켓인 Clarity. 세라믹 브라켓인 Transcend)을 사용하고, 3종의 교정용 호선(0.015"$0.010\times0.022"$ stainless steel 호선, 0.010" Nitinol)을 이용하여 브라켓-호선 각도를 각각 $0^{\circ},\; 3^{\circ}8^{\circ},\; 9^{\circ}$로 조절하면서 실험한 결과, Gemini는 유의하게 가장 낮은 정지, 운동 마찰력을 보였으며 (P<0.001). Clarity는 $0^{\circ}$의 브라켓-호선 각도에서 Transcend는 $5^{\circ}와\;9^{\circ}$의 각도에서 유의하게 가장 높은 정지, 운동 마찰력을 보였고 (P<0.001) $0.016{\times}0.022"$ stainless steel 각형 호선은 유의하게 가장 높은 정지, 운동 마찰력을 보였으며 (P<0.01). 0.016" stainless steel 원형 호선은 $0^{\circ}와\;3^{\circ}$의 브라켓-호선 각도에서 (P<0.01), 0.016" Nitinol은 $8^{\circ}와\;9^{\circ}$의 각도에서 (P<0.001) 유의하게 가장 낮은 정지. 운동 마찰력을 보였고 브라켓-호선 각도가 증가함에 따라 유의하게 정지, 운동 마찰력도 증가하였다 (P<0.001)

• 대한수학회지
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• 제44권6호
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• pp.1197-1211
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• 2007

In this article, we characterize the quasi-isomorphism classes of bracket groups in terms of vertices using vertex-switches. In particular, if two bracket groups are quasi-isomorphic, then there is a sequence of vertex-switches transforming a collection of vertices of a group to a collection of vertices of the other group.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제28권2호
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• pp.91-102
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• 2021

In this paper, we introduce Lie bracket Jordan derivations in Banach Jordan algebras. Using the direct method and the fixed point method, we prove the Hyers-Ulam stability of Lie bracket Jordan derivations in complex Banach Jordan algebras.

• 대한치과교정학회지
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• 제22권2호
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• pp.327-343
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• 1992

Metal brackets and ceramic brackets were bonded to natural teeth, porcelain crowns and gold crowns After stored in artificial saliva solution for 72 hours at $37^{\circ}C$, the shear bond strengths were measured by Instron and compared with them, the bonding sites and bracket bases were examined by scanning electron microscope and light optical stereomicroscope. The results were as follows: 1. The shear bond strengths of the group which metal brackets were bonded to natural teeth and the groups which ceramic brackets were bonded to natural teeth and porcelain crowns were comparable to each other, the shear bond strength of the group which metal brackets were bonded to gold crowns was significantly low. 2. The bond failed predominantly at the bracket base/adhesive interface with the bulk of adhesive remaining on enamel in the group which metal brackets were bonded to natural teeth. 3. The bond failed consistently at the crown/adhesive interface with all of adhesive remaining on the bracket babes in the group which metal brackets were bonded to gold crowns. 4. The bond failed at the enamel or crown/adhesive interface with the bulk of adhesive remaining on the bracket bases in the groups which cramic brackets were bonded to natural teeth and porcelain crowns. 5. The shear bond strengths of the groups which ceramic brackets were bonded to porcelain crowns were not affected by etching time.

• 대한치과교정학회지
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• 제25권2호
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• pp.165-174
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• 1995

이 연구의 목적은 교정용 bracket부착에 의한 교정치료시 법랑질 표면에 나타나는 탈회 형태 및 손상정도를 평가하고 이를 개선시킬수 있는 방법에 대하여 알아보기 위함이다. 건전한 법랑질 표면을 갖는 40개의 소구치를 산부식과 다양한 불소도포에 의해 처리한 뒤 환자의 구강에서 3개월동안 유지시켰다. 모든 견본 소구치를 발거하여 주사 전자현미경으로 법랑질 표면을 평가하였다. 이 연구로부터 얻어진 결과는 다음과 같다. 1. Bracket 부착에 의한 법랑질 표면에 어느 정도 탈회와 손상이 나타났다. 2. $2\%$ NaF을 전기이온 도포한 Group 6이 건전한 법랑질 표면에 가장 유사한 형태로 개선되었다. 3. 산 부식 후 아무런 처리도 하지 않은 Group 2에서 불소 도포한 다른 Group들 보다 더 큰 법랑질 탈회와 손상이 나타났다. 4. Bracket 부착에 의한 법랑질 표면의 탈회와 손상 정도는 불소 도포방법에 의하여 개선이 이루어 졌다.

• 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.

• 대한치과교정학회지
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• 제51권6호
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• pp.375-386
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• 2021

Objective: To evaluate the accuracy of a one-piece bracket jig system fabricated using computer-aided design and manufacturing (CAD/CAM) by employing three-dimensional (3D) digital superimposition. Methods: This in vitro study included 226 anterior teeth selected from 20 patients undergoing orthodontic treatment. Bracket position errors from each of the 40 arches were analyzed quantitatively via 3D digital superimposition (best-fit algorithm) of the virtual bracket and actual bracket after indirect bonding, after accounting for possible variables that may affect accuracy, such as crowding and presence of the resin base. Results: The device could transfer the bracket accurately to the desired position of the patient's dentition within a clinically acceptable range of ± 0.05 mm and 2.0° for linear and angular measurements, respectively. The average linear measurements ranged from 0.029 to 0.101 mm. Among the angular measurements, rotation values showed the least deviation and ranged from 0.396° to 0.623°. Directional bias was pronounced in the vertical direction, and many brackets were bonded toward the occlusal surface. However, no statistical difference was found for the three angular measurement values (torque, angulation, and rotation) in any of the groups classified according to crowding. When the teeth were moderately crowded, the mesio-distal, bucco-lingual, and rotation measurement values were affected by the presence of the resin base. Conclusions: The characteristics of the CAD/CAM one-piece jig system were demonstrated according to the influencing factors, and the transfer accuracy was verified to be within a clinically acceptable level for the indirect bracket bonding of anterior teeth.

• 대한치과교정학회지
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• 제30권5호
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• pp.625-642
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• 2000

본 연구는 열적 및 기계적 피로응력이 교정용 브라켓의 전단결합강도, 인장결합강도, 전단-인장 복합 결합강도에 미치는 영향과 결합상태에 미치는 영향, 그리고 접착파절 양상을 비교하는데 목적이 있다. 이를 위하여 기저부 형태가 다른 5종의 금속 브라켓을 교정치료를 목적으로 발거한 상$\cdot$하악 소구치에 부착하여, 계면에 200g의 전단-인장 복합 하중을 4주간 가한 기계적 피로시험과, 5,000회의 thermocycling을 시행한 열적 피로시험 후, 전단결합강도, 인장결합강도, 및 전단-인장 복합 결합강도를 측정하고, 파절양상을 분석하여 다음과 같은 결과를 얻었다. 1. 정적시험에서 얻은 브라켓 접착부의 결합강도는 Photoetched base가 가장 크고, Integral base가 가장 작았다(p<0.05). 모든 종류의 브라켓에서 전단결합강도가 가장 컸으며, 전단-인장 복합 결합강도는 전단결합강도의 1/3 수준으로 가장 작았다. 2. 4주간 200g의 전단-인장 복합 하중을 가한 후의 결합강도는 Photoetched base가 가장 크고, Integral base가 가장 작았으며 (p<0.05), 기계적 피로시험 후 Photoetched base와 Micro-Etched Foil Mesh base의 전단, 인장, 전단-인장 복합 결합강도가 감소하였고, Chessboard base의 전단결합강도가 감소하였다(p<0.05). 3. 5,000회의 thermocycling 후의 결합강도는 Photoetched base가 가장 컸고, integral base가 가장 작았으며(p<0.05), 열적 피로시험 후 Photoetched base와 Chessboard base, Micro-Etched Foil Mesh base의 결합강도가 모두 감소하였다(p<0.05). 4. 정적시험의 결합강도 측정 후 접착파절은 브라켓/레진 계면에서 일어났으며, thermocycling 후에는 브라켓/레진 계면과, 법랑질/레진 계면, 레진내 파절이 혼합되어 나타나 ARI 점수가 높아졌다. 기계적 피로시험 후에는 정적시험 때와 비슷한 ARI 점수를 보였다. 5. 모든 브라켓에서 thermocycling 후 브라켓/레진 계면과 법랑질/레진 계면에서 미세 균열이 관찰되었다.