• Journal of Welding and Joining
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• 제22권1호
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• pp.43-49
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• 2004

Contact tip is located so near to welding arc that it is heated to high temperature during long time welding. In such a situation, tip changes in its microstructure and in turn its mechanical properties. This study was intended to investigate those changes by using simulated heat treatment. As a result of this study, it was confirmed that tip of Cu-P alloy hardened with severe cold deformation lose its initial hardness to a large extent within 60 min due to the occurrence of rapid recrystallization while that of Cu-Cr composition hardened by proper aging treatment can preserve its intial hardness for about 1,000 min or longer. Based on these results, suggested was a guideline that can classify contact tips into two different grades: deformation-hardened type and precipitation-hardened type. Following a guideline, a tip with Cu-Cr composition can be classified into the deformation-hardened type if it is in the over-aged condition. Such a guideline is well described.

• 대한치과교정학회지
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• 제25권3호
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• pp.323-331
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• 1995

본 연구는 교정치료가 끝난 26명의 환자에서 T-scan을 이용하여 교정치료직후와 3개월후에 교합접촉의 변화를 구하여 시간의 경과에 따른 총접촉수의 변화와 전치부접촉수의 변화, 구치부 접촉수의 변화 및 총접촉되는 치아수와 전치부와 구치부의 접촉되는 치아수의 변화를 비교분석한 바 다음의 결론을 얻었다. 1. 평균적인 총접촉수의 변화는 교정치료 종료시 11.27개에서 3개월후 13.15개로 증가하였는데, 통계학적으로 유의한 차이를 보였다(P<0.05). 2. 전치부 접촉수에 있어서는 변화가 없었다. 3. 구치부 접촉수의 변화는 통계학적 유의성이 있었다(P<0.01).총접촉수의 변화는 구치부 접촉수의 변화에 기인하였다. 4. 총접촉치아수에 있어 변화는 통계학적 유의성이 있었다(P<0.05). 5. 전치부의 접촉치아수는 약간 증가하기는 하였으나, 유의한 차이를 보이지 않았다(P>0.05). 6. 구칙부 접촉치아수의 변화는 통계학적으로 유의성을 보였다(P<0.05). 7. 초기 치아접촉수와 시간의 경과에 따른 접촉수의 변화량은 약한 역상관관계를 보였는데, 이는 초기 접촉수가 적을 수록 보다 많은 접촉수의 증가가 있었다는 것을 보인다(r=-0.38, p<0.05).

• 대한치과기공학회지
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• 제35권2호
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• pp.137-142
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• 2013

Purpose: This study was to observe the surface and interfacial characteristic of Zirconia by surface treatment. And it was observed the roughness and contact angle according to processing, and the interfacial properties by surface treatment on zirconia. Methods: The oxide formation and ion diffusion between core and veneer ceramic were determined by the X-ray Dot Mapping of EPMA(Electron probe micro analyzer). The roughness was measured by 3D Digital microscope and the contact angle according to processing of zirconia was observed using distilled water on the surface. Results: The surface roughness of the specimens Z04, Z12, Z15 was measured $0.67({\pm}0.03){\mu}m$, $0.50({\pm}0.12){\mu}m$, $0.35({\pm}0.09){\mu}m$, respectively. As results of contact angle test, Z04, Z12, Z15 of specimen group without binder treatment was measured $46.79({\pm}3.17)^{\circ}$, $57.47({\pm}4.83)^{\circ}$, $56.19({\pm}2.66)^{\circ}$, respectively. but, L04, L12, L15 of specimen group without binder treatment was measured $63.84({\pm}2.20)^{\circ}$, $66.08({\pm}0.16)^{\circ}$, $65.10({\pm}1.01)^{\circ}$, respectively. Average contact angle of L15 was measured $65.10({\pm}1.01)^{\circ}$. In X-ray Dot Mapping results, thickness of binder including Al element was measured that each of L04, L12, L15 were $20{\mu}m$, $15{\mu}m$, $10{\mu}m$. Conclusion: The more rough surface increases the wettability, but the sintered exclusive binder decreases the wettability.

• 접착 및 계면
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• 제8권3호
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• pp.1-8
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• 2007

폴리우레탄 폼 소재에 평판형 플라즈마 전처리 방식을 적용시켜 접촉각 및 접착력을 향상시켰다. 플라즈마 반응기의 최적의 반응조건을 조사하기 위해서 반응가스(질소, 아르곤, 산소, 공기), 가스의 유량(30~150 mL/min), 그리고 반응시간(0~30초) 등을 변화시켜 전처리하여 진공식 플라즈마 방식과 비교 검토하였다. 처리 후 소재의 표면 변화는 SEM과 ATR-FTIR을 이용하여 측정하였다. 폴리우레탄 폼에서 질소의 유량이 100 mL/min이고 반응시간이 10초일 때 접촉각의 저하에 따른 가장 좋은 접착력의 결과를 보여 주었다. 결과적으로 평판형 플라즈마 조작 방식에 의한 처리로 폴리우레탄 폼의 접촉각과 접착박리강도가 개선되었음을 확인하였다.

• 한국의류학회지
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• 제29권3_4호
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• pp.561-568
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• 2005

The irradiation of Ultra-Violet (UV) is an efficient treatment for polymer to improve hydrophilic properties. 4-Channel PET knit fabrics were treated with UVA and UVC to develop functional and environment-friendly fabric. The fabric was treated with various treatment times and distances from UV lamps having different wavelength. FT-IR and XPS investigated the chemical changes. To confirm the change of surface properties, contact angle, surface energy and SEM were examined. The study of UV as a treatment for PET knit fabric shows significant changes in chemical and surface properties, which is proved by analyses. FT-IR and XPS analyses prove the augmentation of carboxylic, Hydrophilic groups on the surfaces treated by UV. The increase of water contact angle and surface energy means more water wettable and surface energy of PET film was substantially increased by UV irradiation time. The ageing after surface treatment had little influence on the surface energy of the irradiated PET film. SEM proves the surface modification of PET such as etching, bubble and crack. The negative effects are increased in accordance with increasing treatment time.

• 한국전기전자재료학회논문지
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• 제18권2호
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• pp.148-152
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• 2005

Atmospheric low-temperature plasma was produced using dielectric barrier discharge (DBD) plate-type plasma reactor and high frequency of 13.56 Hz. The surfaces of polyimide films for insulating and packaging materials were treated by the atmospheric low-temperature plasma. The contact angle of 67$^{\circ}$ was observed before the plasma treatment. The contact angle was decreased with deceasing the velocity of plasma treatment. In case of oxygen content of 0.2 %, electrode gap of 2 mm, the velocity of plasma treatment of 20 mm/sec, and input power of 400 W, the minimum contact angle of 13$^{\circ}$ was observed. The chemical characteristics of polyimide film after the plama treatment were investigated using X-ray photoelectron spectroscopy (XPS), and new carboxyl group bond was observed. The surfaces of polyimide films were changed into hydrophilic by the atmospheric low-temperature plasma. The polyimide films having hydrophilic surface will be very useful as a packaging and insulating materials in electronic devices.

• 한방안이비인후피부과학회지
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• 제10권1호
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• pp.263-283
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• 1997

The study has been carried out to investigate of the Contact dermatitis by referring to 37 literature. The results were as follows; 1. In oriental medical science, Contact dermatitis is belong to the cartegory of the 'Chilchang(漆瘡)', 'Honyoja(狐尿刺)', 'Bunhwachang(粉花瘡)', 'Goyakpoong(膏藥風)', 'Matongsun(馬桶癬)'. 2. The cause of a disease is combination of internal factor-the weak of skin or the constitutional factor and external factor-the toxic substance. When the toxic substance contacts skin, pathologial change-stagnation of vital energy and blood(氣血鬱滯)-appears, and after the stagnation of vital energy and blood change heat(化火熱). 3. The symptom of a disease is topical itching, burning pain, erythematous papule, vesicle etc in skin in the acute state and itching, pachyderma, lichenification etc in skin in the chronic state. The symptom is differentiated to wind-heat(風熱) syndrom, damp-heat(濕熱) syndrom, toxic heat(熱毒) syndrom in the acute state and blood dryness(血燥) sydrom in the chronic state. 4. The treatment-methodes is as follow ; Until chung dynasty(淸代) the greater part of treatment is externl treatment The present age in china use together internal treatment and external treatment, in the acute state use method of remove heat(淸熱), remove wind(祛風), remove damp(利濕), detoxicating(解毒), remove heat from blood(凉血), in the chronic state use method of remove wind(祛風) and nourishing the blood(養血).

• 한국재료학회:학술대회논문집
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• 한국재료학회 1999년도 추계학술발표강연 및 논문개요집
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• pp.80-80
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• 1999

• 대한전자공학회논문지TE
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• 제39권3호
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• pp.8-14
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• 2002

본 연구는 고분자 재료의 표면열화 발생 및 진행경로를 해석하기 위한 일환으로 열, 자외선 및 방전에 의한 열화를 각각 임의로 모의하여 접촉각 특성을 측정하여 열화 발생메커니즘을 해석하였으며, 특히 기존의 열화 연구와 달리 화학적 측면과 정전적 측면을 연계시킨 상관적 특성분석을 수행하였다. 표면활성화 상태를 측정한 접촉각 변화에 있어서, 일반적인 고분자의 표면은 73$^{\circ}$~91$^{\circ}$의 약소수성을 나타낸다. 그러나, 방전처리 및 350 nm 이하의 자외선 파장에 노출된 표면은 13.8$^{\circ}$ 및 20$^{\circ}$로 급격한 친수화를 나타내었고, 열처리 및 430~500nm 파장의 가시광 파장에 노출된 표면은 90$^{\circ}$와 80.1$^{\circ}$의 최대 접촉각 상승을 보이며 소수화를 나타냈다.

• 상하수도학회지
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• 제21권3호
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• pp.359-366
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• 2007

Slow sand filtrations have been widely used for water treatment in small communities, however their capacity is often limited by high turbidity in the raw water. For this reason, several pre-treatment facilities were required for a slow sand filter. Turbidity removal from the highly turbid raw water was investigated in roughing filters as a pre-treatment process. The roughing filters followed by rapid mixing tank were operated in the form of a contact filtration. In several jar tests, the predetermined optimum aluminium sulfate (alum) doses for turbid water of 30 and 120NTU were 30 and 50mg/L, respectively. At the optimum alum dose, physically optimum parameters including G value of $220sec^{-1}$ and rapid mixing time of 3 minutes were applied to the contact filtration system. Without addition of alum, the filtrate turbidity from the roughing filters, packed respectively with different media such as sand, porous diatomite ball and gravel, was in the range of 5~30NTU at filtration velocities of 30 and 50m/day. However, the application of a contact filtration to roughing filters showed stably lower filtrate turbidity below 1.0NTU at filtration velocity of 30 m/day. Although the filtration velocity increased to 50m/day, filtrate turbidity was still below 1.0NTU in both single and double layer roughing filters. At influent turbidity of 120NTU, the filtrate turbidity was over 5 NTU in the triple layer roughing filter, which shortened the filter run time. The flocs larger than $10{\mu}m$, formed in the rapid mixing tank, were almost captured through the roughing filter bed, while the almost flocs smaller than $10{\mu}m$ remained in filtrate.