• 대한치과보철학회지
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• 제38권4호
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• pp.461-471
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• 2000

This study evaluated the effect of degassing on the ceramic bond strength of two Ni-Cr alloys under varying holding time at the upper limit temperature and atmospheric conditions. Metal specimens were divided into 5 groups for each alloy according to degassing conditions prior to porcelain application no degassing, degassing under vacuum without hold, degassing under vacuum with hold for 5 min. and 10 min. respectively at the upper limit temperature and degassing in air. Total number of metal ceramic specimens was eighty and each group had eight specimens. The ceramic bond strength was measured by four-point flexural test using Instron and the fractured surface was examined under SEM. The results obtained were as follows. 1. Degassing in air improved the ceramic bond strength of Ni-Cr alloys. 2. In degassing under vacuum, hold at the upper limit temperature was advantageous to the ceramic bonding of Ni-Cr alloys. 3. After ceramic metal bond test, metal surfaces were partially covered with the thin porcelain layer, and the cohesive failures in porcelain were predominant in groups showing higher ceramic bond strength.

• 한국산업융합학회 논문집
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• 제25권5호
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• pp.835-842
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• 2022

In this study, the membrane degassing process of the sweep gas - vacuum combination type was proposed for ammonia wastewater treatment. The effect of pH, initial ammonia concentration and scale-up on ammonia degassing performance was investigated. As a result, as the pH and the initial ammonia concentration increased, the degassing permeate flux was improved. On the other hand, the ammonia mass transfer coefficient increased as the initial ammonia reduced, which seems to be due to the driving force of the sweep gas-vacuum combination type membrane degassing system proposed in this study. In addition, 80 mg NH₃/min of the ammonia degassing rate was achieved using a 6×28 inch size module. Better degassing performance is expected if consideration for maintaining vacuum pressure is involved in the scale-up design.

• 한국주조공학회지
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• 제20권6호
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• pp.407-418
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• 2000

The effect of various factors on the results of degassing of AC4C aluminum alloy melt by using rotary degasser were investigated. The difference between the effects of nitrogen gases of commercial pure and high purity grades on the degassing results was not significant. The optimum degassing condition was obtained. The effect of holding and degassing temperature was not significant, either. The result of degassing was deteriorated by the modification treatment of eutectic silicon, meanwhile improved by the grain refining. The effect of the latter was stronger than that of the former when the melt was treated simultaneously. The volume fractions of hydrogen porosity of the castings obtained from the molds with water moisture such as natural and green sand molds were much higher than those from the molds without that such as pep-set and $CO_2$ molds.

• Carbon letters
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• 제5권2호
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• pp.55-61
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• 2004

Adsorption isotherms of p-nitrophenol from its aqueous solutions on two samples of activated carbon fibres and two samples of granulated activated carbons have been determined in the concentration range 40~800 mg/L (ppm). The surface of these carbons was modified by oxidation with nitric acid and oxygen gas, and by degassing the carbon surface under vacuum at temperatures of $400^{\circ}C$, $650^{\circ}C$ and $950^{\circ}C$. The oxidation of carbon enhances the amount of carbon-oxygen surface groups, while degassing decreases the amount of these surface groups. The adsorption of p-nitrophenol does not depend upon the surface area alone but appears to be influenced by the presence of oxygen groups on the carbon surface. The adsorption decreases on oxidation while the degassing of the carbon surface enhances the adsorption. The decrease in adsorption depends upon the strength of the oxidative treatment being much larger in case of the oxidation with nitric acid, while the decrease in adsorption on degassing depends upon the temperature of degassing. The results show that while the presence of acidic surface groups which are evolved as $CO_2$ on degassing suppress the adsorption of p-nitrophenol, the presence of non acidic surface groups which are evolved as CO on degassing tend to enhance the adsorption. Suitable mechanisms compatible with the results have been presented.

• 한국주조공학회지
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• 제43권6호
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• pp.271-278
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• 2023

본 연구에서는 임펠러 회전속도와 불활성 가스 유량을 바꾸어가며 A356 용탕 탈가스 실험을 수행하여 탈가스 시간에 따른 용탕 온도, 성분 및 밀도 변화를 측정하였다. 용탕 온도의 경우 탈가스 처리가 진행됨에 따라 서서히 감소하였으나 임펠러 회전속도 혹은 불활성 가스 유량과 용탕 열손실 간의 뚜렷한 상관관계는 확인할 수 없었다. 임펠러 회전속도와 불활성 가수 유량에 상관없이, A356 용탕 내 Mg 및 Ti 함량은 600초 이상 탈가스 처리 후에도 그 함량이 거의 변하지 않았으며, Sr의 경우 최대 70 ppm정도 그 함량이 낮아지는 것을 확인하였다. 측정된 용탕 밀도로부터 도출한 용탕 내 수소 농도와 탈가스 모델 식을 활용하여 실험 조건 별 탈가스 속도를 정량적으로 비교 분석해본 결과, 본 연구에서 다룬 탈가스 조업 환경에서는 임펠러 회전속도 보다는 불활성 가스 유량이 탈가스 속도에 영향을 미치는 것을 확인할 수 있었다.

• 한국포장학회지
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• 제22권2호
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• pp.33-37
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• 2016

주로 커피포장에 사용되던 포장용 One-way 가스배출밸브(아로마 밸브)가 최근 발효건강기능식품이나 전자렌지 조리용 즉석식품 포장 등 다양한 영역으로 적용이 확대되고 있다. 포장 식품의 효과적인 신선도 유지와 보존성 향상을 위해서는 대상 식품에 따른 최적의 가스배출 압력을 유지하는 것이 중요하며, 이를 위해 다양한 개방압력(Open Pressure)을 가진 밸브를 개발할 필요가 있다. 본 연구에서는 국내에서 개발된 링타입 고무막을 이용한 식품 포장용 가스배출 밸브(Degassing Valve)에 대하여 오일의 표면장력, 고무막의 재질특성 및 구조 역학적 특성을 분석하여 개방압력 예측이 가능하도록 수학적 분석 모델을 개발하였다. 직관적으로 보면 오일의 점도가 밸브의 개방압력에 영향을 미칠 것으로 예상되지만, 이론상으로 점도는 유체 내부의 요인에 의한 특성이고, 표면장력은 서로 다른 상태의 계면에서 발생되는 특성이므로 점도와 표면장력은 서로 무관하다. 이에 대해 본 연구의 실험을 통해 오일의 점도가 표면장력과는 무관하고 결과적으로 밸브의 개방압력과도 무관함을 확인할 수 있었으며, 수학적 모델에 의한 이론값이 재료의 실험값과 유사한 경향의 결과를 확인함으로써 제안한 수학적 모델의 유효성을 확인할 수 있었다. 따라서, 이 모델을 통해 포장용 가스 배출 밸브의 압력 설계 및 품질 신뢰성 확보를 위한 유용한 자료로 활용될 수 있을 것으로 기대된다.

• 한국포장학회지
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• 제20권2호
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• pp.35-39
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• 2014

최근 커피시장의 고속 성장과 더불어 커피 포장용 가스배출 밸브(Degassing valve)의 수요도 급격히 증가하고 있다. 가스배출 밸브 주요 제조사(Big maker)로 Goglio사(이탈리아), Bosch사(독일) 및 Wipf사(스위스)가 있는데, 이들이 전세계 가스배출 밸브 포장재 소비량의 80%이상을 공급하고 있다. 국내시장 역시 대부분 수입에 의존하고 있어 수입 대체와 국내 포장산업 활성화를 위해 기술적 차별화와 동시에 선진기업 수준의 품질 성능을 갖춘 가스배출 밸브의 개발이 필요하였다. 따라서, 본 연구에서는 링타입 고무막을 적용하여 중앙 개폐형 가스배출 밸브(SP 밸브)를 개발하였으며, 실험을 통해 열림압력 820~1200 Pa, 닫힘압력 10~50 Pa, 가스 유동율 1.2~1.6 L/min로 Goglio 밸브와 대등한 수준의 품질 성능을 확인할 수 있었다. 또한, 식품용 기구 및 용기 포장 공전에 따른 밸브의 식품용기 품질 적합성을 확인하였으며, 향후 커피 포장용 밸브의 국내외 시장 점유율 확대와 함께 국내 발효식품 포장에 적용함으로써 한식 세계화에 기여할 것으로 기대된다.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1039-1040
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• 2006

Vacuum degassing is essential in the preparation of RS P/M aluminum alloys to remove adsorbates and for the decomposition of hydrated-$Al_{2}O_3$ on the powder surface. Changes in the surface characteristics during vacuum degassing were investigated by X-ray photoelectron spectroscopy and temperature-programmed desorption measurement. Hydrated-$Al_{2}O_3$ decomposition to crystalline-$Al_{2}O_3$ and hydrogen desorption on the surface of argon gas-atomized aluminum powder occurred at 623 K and 725 K, respectively. This temperature difference suggests that the reaction converting hydrated-$Al_{2}O_3$ to crystalline-$Al_{2}O_3$ during vacuum degassing should be divided into the two reactions $"2Al+Al_{2}O_3{\cdot}3H_2O\;2Al_{2}O_3+6H_{surf}"and"6H_{surf}3H_2"$.

• 대한치과보철학회지
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• 제29권3호
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• pp.181-196
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• 1991

The Purpose of this study was to evaluate the marginal fit of ceramo-metal crown according to the different ceramo-metal alloy types and the curvature of labio-cervical margin. Degudent $G^{(R)}$ as precious and $Verabond^{(R)}$ as non-precious ceramo-metal alloy were used. The abutment was preparaed with two different curvature types : a normal curvature type and a pronounced curvature type. 20 crowns were farbricated using four different combinations and their marginal fits were measured at 3 consecutive stages (before degassing, after degassing, after glazing) using microscope under 200 magnification. The results were as follows: 1 . Marginal fitness before degassing. The groups of precious ceramo-metal exhibited better marginal fit than the groups of non-precious ceramo-metal with significant difference(P<0.05) . In the same ceramo-metal groups, the normal curvature group exhibited better marginal fit than the pronounced curvature group but without significant difference(P>0.05). 2. Marginal fitness after degassing. By degassing, the group of pronounced curvature and non-precious ceramo-metal was deformed the most, and the degree of margin fitness of each group was the same as before degassing. 3. Marginal fitness after glazing The group of normal curvature and precious ceramo-metal exhibited better marginal fit than the group of pronounced curvature and non-precious ceramo-metal with significant difference(P>0.05), and the degree of margin fitness of each group was the same as before degassing.

• 한국산업융합학회 논문집
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• 제26권6_2호
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• pp.1171-1181
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• 2023

In this study, a sweep gas - vacuum hybrid type membrane degassing process was proposed for ammonia wastewater treatment. In addition, the ammonia selective recovery of the hybrid type membrane degassing process was also investigated. As a result, the hybrid type membrane degassing process showed better degassing performance (54.9 mg NH₃/m²min for 360 min) than the sweep gas type (32.3 mg NH₃/m²min) or vacuum type (22 mg NH₃/m²min). Additionally, the hybrid type membrane degassing process showed an excellent ammonia selectivity (103 times compared to Na+ Na⁺, 133 times compared to Ca²⁺). The ammonia selectivity was appeared to be due to the conversion characteristics of ammonium ion / dissolved ammonia depending on pH. The results in this study are expected to be used in the development of ammonia wastewater treatment and ammonia recovery in the future.