• 한국정밀공학회지
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• 제12권11호
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• pp.52-62
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• 1995

In the laser surface hardening process the geometrical parameters, especially the depth, of the hardened layer are utilized to assess the integrity of the hardening layer quality. Monitoring of this geometrical parameter ofr on-line process control as well as for on-line quality evaluation, however, is an extremely difficult problem because the hardening layer is formed beneath a material surface. Moreover, the uncertainties in monitoring the depth can be raised by the inevitable use of a surface coating to enhance the processing efficiency and the insufficient knowledge on the effects of coating materials and its thicknesses. The paper describes the extimation results using neural network to estimate the hardening layer depth from measured surface temperanture and process variables (laser beam power and feeding velocity) under various situations. To evaluate the effec- tiveness of the measured temperature in estimating the harding layer depth, estimation was performed with or without temperature informations. Also to investigate the effects of coating thickness variations in the real industry situations, in which the coating thickness cannot be controlled uniform with good precision, estimation was done over only uniformly coated specimen or various thickness-coated specimens. A series of hardening experiments were performed to find the relationships between the hardening layer depth, temperature and process variables. The estimation results show the temperature informations greatly improve the estimation accuracy over various thickness-coated specimens.

• 한국안광학회지
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• 제7권2호
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• pp.175-180
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• 2002

렌즈의 thin film 균일성을 평가하기 위하여 spctrophotometer를 이용한다. 렌즈의 중심 중간, edge 등의 지점에서 파장의존상의 반사율을 측정하여 반사율 spectrum의 두 peak를 선택하여 비교하여, 박막 균일성 여부를 분석한다. 반사율의 두 peak의 파장 영역(${\lambda}_1,{\lambda}_2$)으로부터 thin film의 thickness(t)를 구한다. $$t=\frac{1}{2(n^2-\sin^2{\theta})^{1/2}}{\times}\frac{{\lambda}_1{\lambda}_2}{{\lambda}_2-{\lambda}_1}$$ 렌즈의 중심 중간, edge 등의 지점에서 반사율 pattern이 동일 값이면 coating 렌즈의 박막은 균일성 갖는다. coating 렌즈의 박막 균일성 평가 방법을 단층막 $MgF_2$(n=1.38) coating 렌즈에 적용하였다. 박막의 thickness 차이는 360nm 정도였다. 파장의존성에 대한 광반사율의 측정으로부터 coating 렌즈의 박막 균일성을 쉽게 분석할 수 있다.

• 한국전기전자재료학회논문지
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• 제26권6호
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• pp.425-428
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• 2013

In this paper, we present a novel hydrophilic coating material (Wellture Finetech, Korea) which can be utilized as a coating layer for anti-contamination for electrical and electronic system. The coating material was deposited on 4 inch silicon wafer with several different film thickness. The film thickness was controlled by spin coating speed. After curing of the film, we have scratched by permanent marker to check self-cleaning property of the film. Also we have executed several mechanical tests of the films. As the spin coating speed is increased, the film thickness was thinned from 230 nm to 125 nm. Contact angle of the film was lowered from $30^{\circ}$ to $12^{\circ}$ as the spin coating speed is increased from 700 to 2,500 rpm. On permanent marker scratched film surface coated at 1,000 rpm, we have poured regular city water to investigate self cleaning property of the film. The scratches were gradually separated from the film surface due to super-hydrophilicity of the film. Hardness of spin coated film was 9H measured by ASTM D3363 method. and adhesion of all film was 5B tested by ASTM D3359 method. Also, to get exact hardness value of the film, we have utilized a nano-indenter. As spin speed is increased, the hardness of film was increased from 3 GPa to 5 GPa.

• 대한의용생체공학회:의공학회지
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• 제18권3호
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• pp.217-222
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• 1997

Hydroxyapatite(HA)-coated metal composites were made by the dipping method. The specimen substrates were Ti plates with a thickness of 2 mm. The HA coating was carried out in HA-sol for 1 min by the dipping method. The concentration of HA-sol for the coating ranged from 3.28 to 9.99 wt%. Excellent coating was observed on Ti substrate dipped once in 9.99 wt% sol. Preparation of Ti plates by sandblasting provided the better environment for coating HA on Ti surface than non-treated surface. As the concentration of sol increased, the weight change and the coating thickness increased. Above 7 wt% sol, they increased sharply.

• Tribology and Lubricants
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• 제26권2호
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• pp.142-148
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• 2010

The purpose of this study is to find how to be formed the wet film thickness during the low friction coating process for a piston skirt with application to the theory of screen printing. In other words, in this research, it is to derive the general expressions predicting the pressure under a blade and the volume of coating fluid passing through the blade edge. Using these expressions, it is to be approved that the current operation characteristics of a screen printing system to a sample blade coating process for low friction coating on a piston skirt can be quantitatively assessed.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.892-894
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• 1995

This paper deals with developmeant and application of coating thickness control system in hot dip galvanizing process. According to the line conditions, such as line speed, strip size and target coating weight, a predictive preset model sets the initial oprating conditions. Referring the zine coating informations from the gauge, mean coating value controller adjusts the chamber pressure and horizontal distance between strip and air knife, while coating deviation controller adjusts the lip gap profile of the air knife. All adaptive gains are interactively calculated by numeric models based on the theoretical analysis. The operating result with this system effectively reduces the coating deviation in transverse direction as well as in longitudinal direction.

• 한국구조물진단유지관리공학회 논문집
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• 제23권5호
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• pp.23-29
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• 2019

본 연구는 굵은골재의 완전 리사이클 기술개발을 위해서 시멘트계 재료를 이용한 개질 페이스트를 이용하여 원골재의 표면을 코팅하는 표면개질 기술을 적용하고 있다. 이 때에 원골재와 개질 페이스트의 계면은 개질 페이스트의 점착력과 점도에 의존되어 개질골재의 피막두께가 결정된다고 생각할 수 있다. 본 연구에서는 굳지 않은 상태에서의 개질 페이스트의 유동특성을 파악하고 표면 개질골재의 피막 두께에 대해 검토한 결과, 개질 페이스트를 빙엄유체로서 가정하여, 잉여 페이스트 이론과 유동학 정수 (항복치)를 고려하는 것으로 개질 페이스트의 정량적인 피막 두께의 설계가 가능하여, 표면개질 골재를 이용한 콘크리트의 정량적인 배합설계가 가능할 것으로 판단된다.

• 반도체디스플레이기술학회지
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• 제22권4호
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• pp.19-25
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• 2023

With an attempt to investigate the correlation between the internal pressure distribution of slit nozzle and the thickness uniformity of slot-coated thin films, we have performed computational fluid dynamics (CFD) simulations of slit nozzles and slot coating of high-viscosity (4,800 cPs) polydimethylsiloxane (PDMS) using a gantry slot-die coater. We have calculated the coefficient of variation (CV) to quantify the pressure and velocity distributions inside the slit nozzle and the thickness non-uniformity of slot-coated PDMS films. The pressure distribution inside the cavity and the velocity distribution at the outlet are analyzed by varying the shim thickness and flow rate. We have shown that the cavity pressure uniformity and film thickness uniformity are enhanced by reducing the shim thickness. It is addressed that the CV value of the cavity pressure that can ensure the thickness non-uniformity of less than 5% is equal to and less than 1%, which is achievable with the shim thickness of 150 ㎛. It is also found that as the flow rate increases, the average cavity pressure is increased with the CV value of the pressure unchanged and the maximum coating speed is increased. As the shim thickness is reduced, however, the maximum coating speed and flow rate decrease. The highly uniform PDMS films shows the tensile strain as high as 180%, which can be used as a stretchable substrate.

• 한국식품영양과학회지
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• 제33권2호
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• pp.447-450
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• 2004

목재에 코팅재로 사용되는 에폭시 수지로부터의 총괄이행량에 대한 모델을 정립하고, 이를 이용하여 안전성확보에 필요한 두께의 정도를 계산하였다. 에폭시 수지를 통한 총괄이행은 위생적 관심영역에서 확산모델에 의하여 해석이 가능하였고, 투과성 겉보기 투과성 지표에 미치는 온도의 영향은 Arrhenius 방정식으로 설명이 가능하였다. 그리고 일반적인 식품공전의 6$0^{\circ}C$, 30분의 용출조건에서 위생적 한도를 만족시키기 위한 최소의 코팅두께는 0.004 mm였다.

• Korea-Australia Rheology Journal
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• 제16권4호
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• pp.227-233
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• 2004

Simplified model of slide-fed curtain coating flow has been developed and tested in this study. It rests on the sheet profile equations for curtain thickness in curtain flow and its trajectory derived by the integral momentum balance approach of Higgins and Scriven (1979) and Kistler (1983). It also draws on the film profile equation of film thickness variation in flow down a slide. The equations have been solved in finite difference approximation by Newton iteration with continuation. The results show that how inertia (Rey­nolds number), surface tension (capillary number), inclination angle of the slide, and air pressure difference across the curtain affect sheet trajectory and thickness profile. It has been revealed that approximate models can be useful to easily analyze coating flow dynamics without complex computations, giving qualitative agreement with full theory and with experiment.