• 대한치과기공학회지
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• 제9권1호
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• pp.39-49
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• 1987

This study done to evaluate some surface treatment methods in metal coping which can increase the bond strength between porcelain and metal. Therefore this experiment was performed according to the Mc Lean's Theory of bond strength between porcelain and strength between porcelain and metal. In the experiment the author measured respective thermal expansion coefficents in three types of metal(Tallasium, Vera Bond and Rexillium) and Vita Porcelain to get the differences in the coefficents between porcelain and metals. And using insteron testing machine, the author also performed Planar interface shear bond tests on the 45 specimens(15 specimens in oxide surface, rough surface and fine surface treatment methods respectively) to measure bond strength between metal and porcelain. The results Were as follows, 1. The differences in thermal expansion coefficients between three types of metal and Vita procelain: Talladium - $1.2\;10^{-6/0}\;C$, Vera Bond - $1.6\;10^{-6/0}\;C$, Rexillium - $1.9\;10^{-6/0}\;C$. 2. The bond strength in oxide surface on the Shear bond test was the lowest among the treatment methods. 3. There was no significant differences in treatment methods of rough surface of fine surface. 4. In the oxide surface treatment method, there were significant differences(P<0.05)between Vera bond and Rexillium, and between Talladium and Rexillium. 5. In the fine surface treatment, there was a significant difference(P<0.05)between Talladium and Rexillium.

• 대한기계학회논문집A
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• 제26권8호
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• pp.1615-1622
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• 2002

The purpose of this study is comparing cold expansion method with interference fit. Cold expansion method and interference fit of fastener hole is using in the aerospace industry. These treatment lead to an improvement of fatigue life to the compressive residual stresses developed on the hole surface. But Research is nothing to about difference effect of between cold expansion method and interference fit. So, this paper, it is shown that Comparing cold expansion method with interference fit using the finite element method. It is further shown that residual stress distribution according to plate thickness and clamping force.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.419-424
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• 2001

The purpose of this study is comparing cold expansion method with interference fit. Cold expansion method and interference fit of fastener hole is using in the aerospace industry. These treatment lead to an improvement of fatigue life to the compressive residual stresses developed on the hole surface. But Research is nothing to about difference effect of between cold expansion method and interference fit. So In this paper, It is shown that Comparing cold expansion method with interference fit. and It is further shown that residual stress distribution according to plate thickness.

• 한국기계가공학회지
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• 제6권4호
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• pp.81-85
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• 2007

A safety valve is used for protecting the pressure vessel and facilities by discharging the operating fluid into the valve from the accident when the pressure is over the designated value. The fluid is sulfurous acid and nitric acid. etc. in the semi-conductor assembly line. Thus the valve elements material must be acid resistance. Teflon, which is used generally as inner parts of a valve, tends to easily sticks to sliding surface by thermal expansion under high temperature. Some studies are performed to change teflon to another material and shape to have a better fluidity under the condition. The analysis of the thermal expansion is conducted by commercial FEM software to improve the problems. Boundary conditions were temperature and load in this study. From the analysis, the thermal expansion of stainless steel is verified to be lower than that of teflon under high temperature. Thus coupled teflon/stainless steel-made valve is applied to assembly line without danger due to thermal expansion.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.470-474
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• 2000

Cold expansion of fastener holes is a mechanical process widely used in the aerospace industry. This treatment leads to an improvement of fatigue behavior due to the developed compressive residual stresses on the hole surface. The residual stress profile depends on the parameters of cold expansion, which are, expanding rate, inserting direction of mandrel, material properties etc. and the method to confirm this profile is only measurement by X-ray diffractometer. Despite its importance to aerospace industries, little attention has been devoted to the accurate modelling of the process. In this paper, Two-dimensional axisymmetric finite element simulations have been conducted for the cold expansion in an aluminium plate in order to predict the magnitude and distribution of the residual stress and plastic deformation. Maximum compressive residual stress could be increase about 7 percent using the 2-step cold expansion method.

• 대한공간정보학회지
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• 제13권4호
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• pp.59-65
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• 2005

효율적인 국토관리를 위해서 과거로부터의 토지피복/토지이용 변화를 탐지하고 미래의 도시계획에 반영하는 것은 매우 중요하다고 할 수 있다. 본 연구에서는 시계열 Landsat 영상을 이용하여 토지피복/토지이용 분류를 수행함으로써 도시변화를 분석하고 도시화에 따른 지표온도의 변화를 조사하였다. 해상도 30m의 Landsat 영상에서 도시변화 후보지역을 추출하고 자세한 변화 상황을 고찰하기 위해 고해상도 항공사진을 함께 사용하는 계층적 변화탐지기법을 사용하였다. 또한, 도시의 발달과 지표온도의 상관성을 평가하기 위하여 Landsat 영상의 열적외선 파장영역을 이용하여 온도를 계산하여 실제기온과 비교하고 토지피복별 지표온도를 계산하였다. 연구 결과 도심지의 팽창을 수치적으로 확인 할 수 있었고 도시화로 인한 온도 상승을 탐지할 수 있었다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.23-24
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• 2020

In this study, effect of surface modification of waste glass for fine aggregates on the mechanical properties and alkali silica reaction of mortar was analyzed. As a result, it was confirmed that the incorporation of waste glass fine aggregate decreases the mechanical properties of the mortar and increase the alkali silica reaction expansion. On the other hand, the surface modification of the waste glass fine aggregate is effective in improving this problem. However, unlike green and brown waste glass, it is judged that an additional experiment to determine the cause is necessary for white waste glass where alkali silica reactive expansion occurs extremely.

• 소음진동
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• 제8권4호
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• pp.654-662
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• 1998

To predict the radiating noise from the vibrating surface, it is required to know the velocity distribution of vibrating surface exactly as possible as it can. Although it can be obtained by finite element method, their accuracy is limited by theuncertainty of preparing input data such as material propoerties, damping, excitation, and the actual boundary conditions. Experimental values are accurate but are seldom available as many asthe data points compared to FEM mesh. Therefore, hybrid method of experiment and finite element method, called modal expansion technique, is investigated for the preparatin of accurate element method at specified frequencies and for the verification of this scheme, related experiment is performed. In high frequency range above 2000 Hz, piezo-electric material is used as an actuator.

• 한국표면공학회지
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• 제17권1호
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• pp.1-6
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• 1984

The fluidized bed electrode reactor(FBER) with conducting particles has been made use of the removal of metals from dilute electroplating rinse water. The electrolysis was carried out under the conditions of diaphragm current density with 2~28A/$dm^2$ and bed expansion with 20~50%. Recirculating batch operations have been shown that the metal concentration dropped exponentially and may be taken down to 10 ppm. And then, the current efficiency at a concentration of 10 ppm copper was 37% under the conditions of 30% bed expansion and 6 A/$dm^2$, and at concentrated electrolyte (2000ppm copper) was over 80% in the range of 8~28A/$dm^2$ and 20~50% bed expansion. One of the technical possibilities of fluidized bed electrolysis is the separation of copper and nickel from a mixed solution of copper and nickel.

• 대한치과기공학회지
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• 제9권1호
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• pp.79-88
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• 1987

According as the density of prosthetic by casting among the prosthetic restorations is increasing now, the definition and the bounds as to the casting, the method of making the right casting and the establishment of concepts about a minute report and so on, the establishment of the basic principles like those are unavoidable, and then the casting shrinkage must be compensated by setting expansion thermal expansion. Hygroscopic expansion in making the good casting types as we demonstrated that already asbestos lining. We confirmed the fact that the considerable concern about the surface tension and the gas inspiration? Is necessary in making better the casting.