• 한국재료학회지
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• 제27권8호
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• pp.445-450
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• 2017

YSZ (Yttria-stabilized zirconia) is a ceramic material that is used for electronic and structural materials due to its excellent mechanical properties and specific electrical characteristics according to the Yttrium addition. Hydrothermal synthesis has several advantages such as fine particle size, uniform crystalline phase, fast reaction time, low process temperature and good dispersion condition. In order to synthesize YSZ nanoparticles with high crystallinity, hydrothermal synthesis was performed at various concentrations of NaOH. The hydrothermal process was held at a low temperature ($100^{\circ}C$), with a short process time (2,4,8 hours); the acidity or alkalinity of solution was controlled in a range of pH 2~12 by addition of NaOH. The optimum condition was found to be pH 12, at which high solubility levels of Y(OH) and Zr(OH) were reported. The synthesized nano powder showed high crystallinity and homogenous composition, and uniform particle size of about 10 nm.

• Applied Microscopy
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• 제45권4호
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• pp.195-198
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• 2015

Gas-assisted etching (GAE) with focused ion beam (FIB) was applied to prepare plan-view specimens of Cu thin-layer on a silicon substrate for transmission electron microscopy (TEM). GAE using $XeF_2$ gas selectively etched the silicon substrate without volume loss of the Cu thin-layer. The plan-view specimen of the Cu thin film prepared by FIB milling with GAE was observed by scanning electron microscopy and $C_S$-corrected high-resolution TEM to estimate the size and microstructure of the TEM specimen. The GAE with FIB technique overcame various artifacts of conventional FIB milling technique such as bending, shrinking and non-uniform thickness of the TEM specimens. The Cu thin film was uniform in thickness and relatively larger in size despite of the thickness of <200 nm.

• 소성∙가공
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• 제11권1호
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• pp.45-53
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• 2002

The forming process of metal matrix composites by die casting and squeeze casting process are limited in size and dimension In term of final parts. The melt strirring method have the problems that the homogeneous distribution of the reinforcements is difficult due to the low weldability and the density difference between the molten metal and the reinforcement. The thixoforming process for metal matrix composites has numerous advantages compacted to die casting, squeeze casting and compocasting. However, for the thixofoming process, the billet with the desired volume fraction must be heated to obtain a uniform temperature distribution over the entire cross-sectional areas. To obtain the reheating conditions of composites, the particulate reinforced metal matrix composites for thixoforming were fabricated by combined stirring process which is simultaneously performed with electro-magnetic stirring and mechanical stirring process. The matrix alloy and reinforcement are used to aluminum alloy(A357) and SiCp with diameter 14, $25{\mu}m$, respectively. The microstructure characteristics were investigated by changing the volume fraction and reinforcement size. The heating conditions to obtain the uniform temperature distribution in cross section area of fabricated metal matrix composites billet are proposed with heating time, the heating temperature and the holding time.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.489-496
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• 2001

Two perforated plates are used to investigate local heat/mass transfer characteristics in an impingement/effusion cooling system. A naphthalene sublimation method is conducted to determine the local heat/mass transfer coefficients on the upward facing surface of the effusion plate. The two plates are placed in parallel position with gap distances of 1, 2, 4 and 6 times of effusion hole diameter. The effects of hole arrangements of the plates are studied for staggered, square, and hexagonal arrays. The experiments are conducted at Reynolds number of 10,000 based on the effusion hole diameter. The results show that the smaller hole size in the staggered array has the higher transfer coefficients on the stagnation region due to the formation of higher momentum flows through the impingement holes. In the square array, heat/mass transfer on the target plate is more uniform as the number of impingement holes increases. High and uniform heat/mass transfer coefficients are obtained in the hexagonal array.

• 한국응용곤충학회지
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• 제32권1호
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• pp.61-67
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• 1993

점박이응애(Tetranychus urncae)의 알밀도(10~80), 공간분포〈집중 빛 균일분포) 및 서석면적크기 (3, 9, 16 $cm^2$)에 따른 긴털이리응애(Amblyseius longispinosus)의 가능반응을 연구하여 다음과 같은 결과를 얻었다. 긴털이리웅애의 점박이응애 발견효율은 밀도와 공간분포의 영향을 받았으나, 면적의 영향은 없었다. 포식량과 피식자간의 거리와는 매우 높은 역상관관계를 보였다(r=강.85; p=0.0001). 포식반응은 제2형의 기능반응을 보였다. 긴털이리응애의 기능반응은 random predator equation으로 잘 설명되었으며, 탐색률은 피식자의 집중분포하에서 반응면적에 따라 0.1030 - 0.1504였고 균일분포하에서는 0.0546~0.0276였다.

• 정보처리학회논문지B
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• 제13B권4호
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• pp.377-382
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• 2006

본 논문에서는 자동결함검출 방법으로 도광판의 다양한 패턴에 나타나는 돌출, 함몰, 점 등과 같은 작은 결함들을 검출하기 위해 모폴로지의 닫힘, 열림 방법을 이용하는 템플레이트 검사 방법을 사용하였고, 얼룩, 스크래치와 같은 큰 결함을 검출하기 위해 영상에서 격자와 같은 일정한 블록을 형성하여 각 블록을 비교하여 결함을 찾는 블록매칭 방법을 사용하였다. 또한 일정한 패턴이 없는 도광판의 결함에 대해 결함을 검출할 수 있는 개선된 오쯔 방법을 이용하였다. 이 알고리즘을 적용한 결과 결함 검출에 좋은 성능이 있음을 보여준다. 제안된 알고리즘은 자체 개발한 장비에서 실제 도광판의 영상을 얻어 테스트 하였다.

• Nuclear Engineering and Technology
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• 제52권4호
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• pp.811-818
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• 2020

Y-containing CLAM steels were melted via vacuum induction melting and electroslag remelting. In this study, the evolution, microstructure, and mechanical properties of the alloy inclusions (ESR-1 (0 wt.% Y), ESR-2 (0.016 wt.% Y) and ESR-3 (0.042 wt.% Y)) were investigated. Further, the number of inclusions in ESRed steel was observed to obviously decrease, and the distributions were more uniform. The fine Y-Al-O inclusions (1-2 ㎛) were the main inclusions in ESR-2. The addition of Y affected the prior austenite grain size (PAGZ), increasing the tensile strength at test temperature. Low ductile-brittle transition temperature (DBTT) was obtained because of the fine PAGZ and dispersive inclusions. For the ESRed CLAM steel with 0.016 wt.% Y, the yield strengths were 621 MPa at 20 ℃ and 354 MPa at 600 ℃ in air. Further, the uniform elongation and elongation of the ESR-2 alloy were 5.5% and 20.1% at 20 ℃, respectively. Meanwhile, the DBTT tested using full-size Charpy impact specimen (55 cm × 10 cm × 10 cm) was reduced to -83 ℃.

• 한국전기전자재료학회논문지
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• 제17권8호
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• pp.871-874
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• 2004

In recent, it is said that the trend of LCD is direction to pursue high qualities like as high transmittance, high contrast ratio, wide viewing angle, fast response time, and so on. Especially, it is known that these qualities are essential to large size LCD like as LCD TV and we can realize them through to uniform cell gap and deep black state. Until now, the ball spacer has been used to control of uniform cell gap. However, the existence of ball spacer inside the cell causes the deformation of the liquid crystal molecules and damage to alignment layer. Such a deformation of the liquid crystal causes light-leakage in the dark state, which lowers contrast ratio of the display. Nowadays, this problem has been solved by using Patterned Spacer on Color Filter. but Side Effect just as gravity mura has been induced. In this paper, we studied the mechanism on gravity mura in case of using patterned spacer on color filter.

• 한국화재소방학회:학술대회논문집
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• 한국화재소방학회 2008년도 춘계학술논문발표회 논문집
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• pp.144-147
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• 2008

유리밸브는 스프링클러 헤드용으로서 가장 간단하면서도 신뢰성이 높은 기구라 할 수 있다. 본 개발에서 우리는 정밀하게 동작하는 유리밸브를 개발하였다. 유리밸브는 유리앰플과 충진액 그리고 액 내부에 형성된 기포로 구성된다. 개발의 첫 단계는 균일한 유리 앰플의 양산기술 및 설비의 개발이었다. 두 번째 단계는 유리앰플에 충진될 액체의 종류와 형성시킬 기포의 크기에 대한 최적화였다. 액을 충진할 때 균일한 기포크기를 형성시킬 수 있는 양산공정의 개발 역시 어려운 문제 중 하나였다. 개발의 최종 단계는 유리밸브의 표면에 대한 처리를 통해 유리밸브의 파괴역학 제어기술개발이라 할 수 있다.

• Journal of Biosystems Engineering
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• 제28권1호
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• pp.35-44
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• 2003

This study was conducted to develop proper model for cold storage facility that could of for uniform heat movement and air movement f3r green grocery and improve improper design of the existing container-type cold storage facility. For that reason, new model(dome-type) cold storage facility was developed using 3-D CFD(computational fluid dynamics) simulation. The size was 6m${\times}$6m${\times}$5m. Its size and configuration were same to simulation model. Unit cooler was designed to send cold air in 4 side ways. A dome-type cold storage facility showed uniform distributions of air temperature and velocity because cold air was forced to move down along the ceiling and the wall and then circulated to the unit cooler from the central part of the floor. Dome-type cold storage facility also showed by low wind velocity, below 1 m/s that could minimized cold damage and quality deterioration.