• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.461-461
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• 2011

최근의 나노기술의 발전과 함께 나노미터크기의 물질들의 물성과 미세구조 등을 분석하기 위한 노력들이 활발히 이루어지고 있다. 투과전자현미경(transmission electron microscope; TEM)은 나노물질의 미세구조 관찰, 화학성분 분석, 전자기적 특성평가가 가능한 초정밀 분석장비이다. TEM 관찰을 위한 시편의 제작방법중 TEM 그리드(grid)를 사용하는 방법은, 분석하고자 하는 물질을 망(mesh) 형태의 그리드에 도포하여 샘플을 준비하는 방법으로 다른 방법에 비해 아주 빠르고 간편한 장점이 있다. 그러나 TEM 그리드에 나노물질을 분산/도포하여 공중에 떠있는 형태로 샘플을 제작하려면, 나노물질이 mesh 사이로 빠져나오지 않도록 그리드 mesh의 간격이 아주 미세하여야 하는데, 일반적으로 mesh의 크기가 미세할수록 그리드의 가격은 높아진다. 또한 기존에 사용되고 있는 비정질 탄소박막으로 덮여진 그리드는 극미세 크기의 나노물질 및 탄소나노물질을 분석할 경우, 고해상도의 TEM상을 얻는데 한계가 있다. 한편 그래핀은 2차원의 육각판상의 구조로 탄소원자가 빼곡히 채워진 흑연 한 층의 나노재료이다. 이는 원자단위 두께로 가장 얇은 물질로서 기계적 강도가 우수하여 지지막으로의 응용이 가능하다고 알려져 있다. 따라서 TEM grid막으로 사용할 경우 기존의 고가의 미세한 mesh가 형성된 그리드를 사용하지 않아도 나노물질을 효과적으로 분석할 수 있을 것으로 예상 된다. 본 연구에서는 열화학증기증착법(thermal chemical vapor deposition; TCVD)을 이용하여 300 nm 두께의 니켈박막이 증착된 기판위에 대면적으로 합성한 그래핀을 TEM 관찰용 그리드 위에 전사(transfer)함으로써 나노물질이 그리드 mesh사이로 빠져나오지 않는 저가의 TEM 그리드 제작 방법 및 응용 가능성에 대하여 보고한다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.45 no.10
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• pp.1-9
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• 2008

In this paper, a simple and efficient three cell based clustered-cell coordination is proposed with well hewn zero-forcing beamforming (ZF-BF) with a semi-orthogonal user selection (SUS) as transmission and scheduling scheme. For a modified Wyner's channel model with two classes of user groups for a hexagonal cellular system, the upper bound of asymptotic sum rate scaling of ZF-BF in a proposed coordination is shown to be proportional to the number of transmit antennas and double logarithms of the number of users. The numerical results verify the efficiency of the proposed cell coordination. It is also numerically shown that ZF-BF with the SUS in CCCT actually achieves the upper bound of asymptotic sum rate sum rate scaling.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.1C
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• pp.23-33
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• 2007

Video compression is essential technique for fast and efficient transmission of a large amount of video data maintaining high quality. Also, motion estimation and motion compensation is most important technique for efficient video compression. A proposed method is improved diamond search method which uses split diamond pattern and rotated diamond pattern. In particular, the proposed method shows superb result when it is used for the sequence with a direction of camera moving. Moreover when it is used for the sequence with little motion, complexity is reduced considerably by using fewer search points. Also, by varying the number of initial search points, the propose method can provide several options in terms of duality or speed. Simulation results shows that the proposed method sustains better visual quality compared with diamond search method and HEXBS even by using fewer search points. Besides, compared with existing methods, it is able to conduct a motion estimation more efficiently by changing the number of search points adaptively according to motion of video data.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.11-16
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• 2010

Various researches have been performed on the topic of pedestrian traffic flow. At the beginning, the modeling and simulation method for the vehicular traffic flow was simply applied to pedestrian traffic flow. Recently, CA based simulation models are frequently applied to pedestrian flow analysis. Initially, the square Lattice Model is a base model for applying to pedestrians of counterflow and then Hexagonal Lattice Model improves its network as a hexagonal cell for more realistic movement of the avoidance of pedestrian conflicts. However these lattice models express only one directional movement because they express only one directional movement. In this paper, MLPM (the Multi-Layer Pedestrian Model) is suggested to give various origins and destinations for more realistic pedestrian motion in some place.

• Korean Journal of Materials Research
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• v.11 no.8
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• pp.679-684
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• 2001

The surface of natural graphite has not only good electrical conductivities and lubrication properties but also has strong hydrophobicity. There are no functional groups and chemical properties on it. It is difficult to join with any other ions and to disperse in aqueous system. In order to increase dispersion ability throughout modification of surface property, it is necessary to let graphite have some function on its surface by the adsorption of surfactant molecules. In this study, using zeta potential adsorbed surfactant molecules(ABDM) on graphite surface and its surface Properties turn hydrophobic into hydrophilic. The dispersing mechanism of graphite particles in aqueous system has been explained using the DLVO theory, It is concluded that the high dispersable graphite suspension of which dispersing stability$(T_{1/2})$ is 44.5 hours at pH 10 and 22.5mV zeta potential can be produced.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.11 no.4
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• pp.154-159
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• 2001

(Li,Al)$MnO_2(OH)_2$:Co compound was synthesized by hydrothermal method. $MnO_2$, LiOH.$H_2$O, $Co_3O_4$ and $Al(OH)_3$ were used as starting materials and the optimum conditions for synthesis of monolithic (Li,Al)$MnO_2(OH)_2$:Co compound were as follows : reaction temperature; $200^{\circ}C$, reaction time; 3 days, hydrothermal solvent; 3M-KOH solution, reaction apparatus; seesaw type, atomic ratio of Li:Al:Mn;Co = 1:2.1:2.5~2:0.5~1. Monolithic(Li,Al)$MnO_2(HO)_2$:Co compound synthesized in this work had a god crystallinity and excellent color forming effect as a blue pigment compatible with natural mineral. The particles of the synthesized (Li,Al)$MnO_2(OH)_2$:Co compound have hexagonal plate shape with the size of 0.5~1 $\mu\textrm{m}$.

• Journal of the Mineralogical Society of Korea
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• v.13 no.3
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• pp.115-120
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• 2000

Oxidation of pyrite has caused a serious environmental problem such as the acidification of soil and surface water. The mineralogical change of acid sulfate weathering of hydrothermally altered andesite which contained 11.8% of pyrite and was exposed in atmosphere by lay out works for a residential area and a golf course was studied using X-ray diffraction (XRD) and electronmicroscopes. Ferrihydrite, jarosite, and an unidentified water soluble phase were observed as weathering products of the andesite. Under electronmicroscopes, showed aggregate of platy microcrystals; jarosite was platy morphology: water soluble Phase was columnar. Morphology of fresh Pyrite in the andesite changed from pyritrohedron to cubic in its frequency with increasing its particle size. The drainage water was acidic (pH 3.5) and in an equilibrium state with both ferrihydrite and jarosite.

• Composites Research
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• v.33 no.1
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• pp.30-37
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• 2020

Stress distributions dependent on fiber arrangements are studied using the two-dimensional representative volume element (RVE) model for uni-directionally continuous fiber-reinforced composites subjected to transverse tensile loading. It is easily expected that the stresses around the fibers are concentrated mainly due to the stiffness mismatch between the fiber and matrix materials. In this presentation, it is shown that the stresses are not always increased although the distance between two fibers is shortened. The 2D RVE models, originally having a regular hexagonal fiber array, is utilized to study the effect of the fiber locations on the stress distributions. As the central fiber is relocated, the stress distributions around the fiber are obtained through finite element analysis. It is found that the stresses around the fiber are strongly dependent on the fiber distance as well as the angle between the loading direction and the line connecting two fibers.

• Journal of the Korean Chemical Society
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• v.37 no.10
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• pp.867-873
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• 1993

Influences of crystallization time and $H_2O/Al_2O_3$ ratio of the reaction mixtures on the synthesis of AlPO$_4$-5 molecular sieve have been studied by X-ray powder diffraction, nitrogen adsorption, scanning electron microscope (SEM), and solid state $^{27}$Al magic angle spinning nuclear magnetic resonance (MAS NMR) techniques. The degree of crystallinity of AlPO$_4$-5 follows a sigmoid pattem as crystallization time increases. The induction period is shorter than 1 h when the crystallization process is carried out at 150$^{\circ}$C. The conversion of reactants to product, AlPO$_4$-5, can be clearly observed, and all of the determined physical properties change abruptly after about 2 h. It is found that increase in $H_2O/Al_2O_3$ ratio of the reaction mixtures not only changes the crystal morphology from aggregates to hexagonal single crystals, but also results in the formation of longer AlPO$_4$-5 crystals.

• Korean Journal of Food Science and Technology
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• v.4 no.2
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• pp.90-94
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• 1972

Protein and carbohydrate contents in polished barley were investigated for two leading varieties in Korea. The contents of crude protein $(total\;nitrogen{\times}5.83)$ were 8.60% for mean. 15.39% for maximum and 6.06% for minimum, and only one third of 22 varieties showed values above mean. the contents of crude protein was significantly correlated with dye binding capacity $(r=0.82^{**})$but insignificantly carbohydrate content. Kyong No.1 (15.39%), Kwan-Chui-Gi (12.42) and Yong-Weul-Yuk-Kak (11.95) can be classified as high protein varieties having appear to be unpopular to farmers. About 50% of barley field was occupied by varieties having protein content above mean, and Kyongnam-Daimaik no.89 (6.76%) a low protein variety, occupied about 8% of barley field, during last decade with little change.