• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part2
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• pp.1179-1180
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• 2006

Y-type barium ferrite ($Ba_2Me_2Fe_{12}O_{22};$ Me=Zn, Co, Cu) expected as an electromagnetic wave absorber were prepared by the glass-ceramic method. The glasses with composition of $0.1ZnO{\cdot}0.9(xB_2O_3{\cdot}yBaO{\cdot}(1-x-y)Fe_2O_3)$ were prepared. Single-phase powders of Y type barium ferrite were obtained with the composition $0.1ZnO{\cdot}0.9(0.2B_2O_3{\cdot}0.5BaO{\cdot}0.3Fe_2O_3)$. The shape of Y-type crystals depended strongly on the heating temperature and changed from a plate-like hexagon to a complex polyhedron with increasing heating temperature. Correlation was recognized between saturation magnetization and crystal shape. Electromagnetic wave absorption characteristics was affected by the saturation magnetization and crystal shape.

• Nuclear Engineering and Technology
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• 제53권11호
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• pp.3784-3789
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• 2021

We report a simple technique for direct neutron spectroscopy using pure LaCl₃ crystals. Pure LaCl₃ crystals exhibit considerably better pulse shape discrimination (PSD) capabilities with relatively good energy resolution as compared with Ce-doped LaCl₃ crystals. Single crystals of pure and Ce-doped LaCl₃ were grown using an inhouse-developed Bridgman furnace. PSD capabilities of these crystals were investigated using ²⁴¹Am and ¹³⁷Cs sources. Fast neutron detection was tested using a²⁵²Cf source and three separate bands corresponding to electron, proton, and alpha were observed. The proton band induced by the ³⁵Cl(n,p)³⁵S reaction can be used for direct neutron spectroscopy because proton energy is proportional to incident neutron energy. Owing to good scintillation performance and excellent PSD capabilities, pure LaCl₃ is a promising candidate for space detectors and other applications that necessitate gamma/fast neutron discrimination capability.

• 한국결정성장학회지
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• 제13권5호
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• pp.247-253
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• 2003

본 연구에서는 반응기의 유입 확대부의 형상이 반응기 내의 유동 및 증착특성에 미치는 영향을 연구하기 위하여 수평형 MOCVD 반응기에서 TMGa와 $AsH_3$로부터의 GaAs 증착에 관한 수치적 연구를 수행하였다. 두 개의 기하학적인자(확대각, 확대부 형상)가 증착률, 증착률 균일도. 유속 균일도, 압력강하에 미치는 영향을 연구하였다 웨이퍼 위에서의 증착률 균일도, 평균증착률, 유속 균일도를 고려한 결과, 직선형 확대부의 최적 확대각은 $50^{\circ}$∼$55^{\circ}$이며 포물선형 확대부의경우, $40^{\circ}$∼$45^{\circ}$이다. 또한 확대부의 확대각의 변화는 평균증착률 보다 증착률의 균일도에 큰 영향을 미치고 있음을 알 수 있으며 직선확대부보다 포물선형의 확대부에서 더 민감하게 나타남을 알 수 있었다.

• 한국결정성장학회지
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• 제19권5호
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• pp.246-250
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• 2009

NiO 나노 결정을 수소 분위기에서 환원시켜 Ni 금속이 형성되는 거동에 대하여 고찰하였다. NiO 나노 결정은 $Ni(NO_3)_2\cdot6H_2O$를 열처리하여 얻었고, 200~500 nm의 입도와 정 팔면체의 형상을 나타내었다. 이 결정은 일반적인 합성조건에서는 잘 형성되지 않는 불안정 상태인 불안정상태인 (111)면이 발달한 결정체였다. 환원은 300과 $600^{\circ}C$에서 15분과 60분간 수행하였다. NiO 결정의 환원은 불안정한 (111)면에서 우선적으로 일어나기 시작하였으며, $300^{\circ}C$ 환원에서는 팔면체 형상을 유지하면서 Ni로 환원되었다. $600^{\circ}C$ 환원에서는 팔면체 결정의 facet 면이 사라지고, 인접한 결정립들 간의 neck가 형성되면서 Ni 상의 입자로 응집되어가는 것을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.1048-1052
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• 2008

Difficulties in developing process of Liquid Crystal Display(LCD) products such as frequent design modifications, various design requirements, and short-term development period bring on the need of integrated design approach that is efficient and easy to handle. Back Light Unit(BLU) of the LCD, which drastically affects the optical performance of LCD products, is divided into in-coupling part and out-coupling part. Serration of the in-coupling part flattens the light received from point light sources and dot pattern of the out-coupling part regularizes the light sent to screen. Therefore, the optical performance of a LCD product is largely influenced by the shape of serration and the arrangement of dot pattern. In this research, a new design approach which enables to improve the optical performance of LCD products and overcome the prementioned difficulties in developing process of LCD products is proposed. The shape of serration is parameterized to 3 parameters and out-coupling part is partitioned into 10 partitions to apply the optimization technique to this problem. 3 parameters for the shape of serration and densities of 10 partitions are used as design variables in the design optimization. Optical simulation tool named SPEOS is used to evaluate the optical performance of the LCD product. Since the optical simulation uses the random ray tracing technique, numerical noise may possibly be included in the simulation process. To solve the problem caused by numerical noise, the PQRSM which can stably find the solution of the noise problem is used in this research.

• 한국산업보건학회지
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• 제26권2호
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• pp.119-138
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• 2016

Objectives: The purpose of this study is to review size, shape, and crystal structure-dependent toxicity of major metal oxide particles such as silicon dioxide, tungsten trioxide, aluminum oxide, and titanium dioxide as byproducts generated in semiconductor fabrication facility. Methods: To review the toxicity of major metal oxide particles, we used various reported research and review papers. The papers were searched by using websites such as Google Scholar and PubMed. Keyword search terms included '$SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$) toxicity', 'health effects $SiO_2$(or $WO_3$ or $Al_2O_3$ or $TiO_2$). Additional papers were identified in references cited in the searched papers. Results: In various cell lines and organs of human and animals, cytotoxicity, genotoxicity, hepatoxicity, fetotoxicity, neurotoxicity, and histopathological changes were induced by silicon dioxide, tungsten trioxide, aluminium oxide, and titanium dioxide particles. Differences in toxicity were dependent on the cell lines, organs, doses, as well as the chemical composition, size, surface area, shape, and crystal structure of the particles. However, the doses used in the reported papers were higher than the possible exposure level in general work environment. Oxidative stress induced by the metal oxide particles plays a significant role in the expression of toxicity. Conclusions: The results cannot guarantee human toxicity of the metal oxide particles, because there is still a lack of available information about health effects on humans. In addition, toxicological studies under the exposure conditions in the actual work environment are needed.

• 한국결정성장학회지
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• 제32권1호
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• pp.33-39
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• 2022

3D 프린터 관련 특허가 만료되고 주요 기술이 공개되면서 3D 프린터 가격이 하락하면서 원하는 제품을 쉽게 찾을 수 있는 환경이 조성되고 있다. 특히 가장 저렴한 FDM(Fused Deposition Modeling) 3D 프린터가 다양한 분야에서 사용되고 있다. FDM 방식은 형상을 출력할 때 특정 조건이상에서는 지지대(Support)를 붙여야만 형상의 무너짐 없이 제작이 가능하다. 지지대를 달지 않고 형상을 출력할 때 특정 각도에서 발생하는 불규칙한 표면은 제품에 있어서는 불량이지만 예술과 공예적 측면에서는 또 다른 재미를 느낄 수 있는 요소로 활용될 수 있다고 사료된다. 본 논문에서는 이러한 불규칙한 표면을 얻기 위해 출력에 영향을 줄 수 있는 요인들을 제어하고 출력 각도만 변위요소로 실험하였다. 실험 결과 수직에서 62°~70°의 각도로 프린팅 시 필라멘트가 흘러내리지 않고 불규칙한 표면을 얻을 수 있었다. 또한 인위적으로 불규칙한 표면을 공예적인 제품에 적용해 보았다.

• 한국실내디자인학회논문집
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• 제19권6호
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• pp.47-58
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• 2010

Frank Lloyd Wright(1867-1959) was regarded as the pioneer of the modern architecture in the beginning and transition period of 20th century. His works have the pure shape form which have the deep relationship with the organic architecture. Wright told himself that the Froebel System had an influence on his works a lot. This study have researched about the three dimensional application of the Froebel System in his works with assembling and disassembling. Also the two dimensional application in the diagonal and circular plans are the one of the subjects here. The following conclusions are reached. First, The similar of the Wright's works and the Froebel System was the application of the similar principles rather than the copy of the method, which are the accent of the center, the composition of the part and whole, the understanding of the composition principle through the unit system and the unfolding of the crystal by rotation. Even thought the Wright's works have the triangle, square, hexagonal shape, the way of the expansion from the centered space was same. Also the space formed by the division of the center space, unfolds making the part and whole by overlap and continuation. The 2nd Froebel make space decided by the Net and Crystal Lattices which have the crystal characteristics by the rotation. The new geometric architecture, pinwheel, was created by this method. The application of the Froebel in the Wright's works have the several sets which are the 3th, 4th, 5th, 6th Froebels, 2nd, 7th Froebels and the 3th, 5th, 9th Froebels. The geometrical analysis of the square shape and the diagonal shape of the Wright's works was possible. The unfolding of the centered space can be found in the Guggenheim Museum using the analysis of the circular geometric of the 9th Froebel. The above study proves that the Froebel was not a mere tool for the basic shape training but also the main body of Wright's works which consists of the organic idea and philosophy of the space.

• 한국전기전자재료학회논문지
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• 제19권7호
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• pp.673-679
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• 2006

A sublimation method using the SiC seed crystal and SiC powder as the source material is commonly adopted to grow SiC bulk single crystal. However, it has proved to be difficult to achieve the high quality crystal and the process reliability because SiC single crystal should be grown at very high temperature in closed system. In this study, SiC crystal boules were prepared with different angles in trapezoid-shaped graphite seed holders using sublimation physical vapor transport technique (PVT) and then their crystal quality was systematically investigated. The temperature distribution in the growth system and the crystal shape were varied with angles in trapezoid-shaped graphite seed holders, which was successfully simulated using 'Virtual Reactor'. The SiC polytype proved to be the n-type 6H-SiC from the typical absorption spectrum of SiC crystal. The micropipe densities of SiC wafers in this study were measured to be < $100/cm^2$. Consequently, SiC single crystal with large diameter was successfully achieved with changing angle in trapezoid-shaped graphite seed holders.

• 한국결정성장학회지
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• 제32권5호
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• pp.169-174
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• 2022

본 연구는 재생된 SiC 분말을 이용하여 단결정 성장 가능성을 검증하는 것을 목적으로 한다. 재활용 분말의 입도, 형상, 조성, 불순물 등의 기초적인 물성을 분석하고, 이를 활용하여 반응기 내부에서 일어날 수 있는 승화 거동을 예측하였다. 종합적인 판단 결과, 재생 분말의 물성은 단결정 성장에 적합 하였고, 이를 이용하여 단결정 성장 실험을 진행하였다. 높이 25 mm, 직경 100 mm 4H-SiC 단결정 잉곳을 다른 다형혼입 없이 성장 시켰다. 동공 결함 밀도는 0.02 ea/cm², 비저항은 0.015~0.020 ohm·cm² 측정되어 상용 수준의 품질을 얻었으나, 실제 소자 적용을 위해서는 전위 결함, 적층 결함과 관련된 추가 분석이 필요하다고 판단된다.