• Proceedings of the Korea Contents Association Conference
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• 2010.05a
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• pp.319-321
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• 2010

수리학에서 다루는 유체 현상은 물과 공기의 경계면인 자유수면을 포함할 때가 많다. 수표면의 곡률이 작은 경우에는 정수압 가정이 적절하지만, 그렇지 않은 경우에는 비정수압 분포를 고려하여야 한다. 이와 같은 문제에서는 수심적분된 천수방정식이 아닌, 네비어-스토크스 방정식(Navier-Stokes equations)에 의존해야 할 때가 많다. 특성이 다른 두 유체, 예를 들면, 물과 공기, 물과 기름과 같이 섞이지 않는 두 유체의 모의를 위하여 본 연구에서는 레블? 기법을 적용하였다. 고전적인 문제인 댐파괴 문제에 적용하여 이를 실험결과, 기존 수치모델링 결과와 비교하여 이의 효율성을 확인하였다.

• Electrical & Electronic Materials
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• v.2 no.2
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• pp.137-142
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• 1989

Piston and anvil법으로 제작한 (P $b_{0.75S}$ $b_{0.25}$)$_{45}$A $u_{55}$ 비정질의 결정화 과정을 시차열분석(DTA), X-선 회절, 전기저항의 온도 및 시간변화를 측정하여 결정화과정을 조사하였다. 두단계의 상변태를 거쳐 결정화가 되는데 첫번째 변태온도는 52.deg.C이며 A $u_{2}$Pb의 결정상이 나타난다. 두번째 변태온도는 253.deg.C이며 AuS $b_{2}$의 결정상이 나타난다. 일차변태는 핵생성 및 성장 반응에 의하여 이루어졌으며 이때의 활성화 에너지는 1.38Kcal/mol이다.다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2012.05a
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• pp.174-175
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• 2012

음극 아크법으로 증착한 $ZrO_2/Al_2O_3$ 박막의 고온특성을 대기중 $600-900^{\circ}C$에서 50시간동안 노출시킨후 XRD, XPS, AES. SEM, TEM을 이용하여 분석하였다. 증착된 박막은 비정질이었고, 고온에서 가열함에 따라 점차 결정질로 바뀌었다.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.14 no.4
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• pp.129-134
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• 2004

In this study, we investigated the effect of a nitrogen atom on the amorphization of V-Fe alloy through solid-gas reaction during mechanical alloying (MA). MA by planetary ball mill of $V_{70}Fe_{30}$ elemental powders was carried out under the nitrogen gas atmosphere. Amorphization has been observed after 160 hours of ball milling in this case. The DSC spectrum for the mechanically alloyed ($V_{70}Fe$_{30}$)_{0.89}N_{0.11}$ powders exhibits a sharp exothermic peak due to crystallization at about $600^{\circ}C$. Structural transformation from the bcc crystalline to amorphous states was also observed through X-ray and neutron diffractions. We take a full advantage of a negligibly small scattering length of the V atom in the neutron diffraction measurement. During amorphization process the octahedral unit, which is typical of a polyhedron formed in any crystal structures, was preferentially destroyed and transformed into the tetrahedral unit. Futhermore, neutron diffraction measurements revealed that a nitrogen atom is selectively situated at a center of the polyhedron formed by V atoms.

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.277-282
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• 1997

The complex refractive index of Diamond-like Carbon (DLC) thin films, which can be applied to optical devices or electrical devices, have been determined using optical methods. DLC thin films are grown on Si(100) substrates and vitreous silica substrates respectively, using the technique of plasma enhanced chemical vapor deposition (PECVD). The spectroscopic ellipsometry data($\psi$, $\Delta$) and the transmission spectra of these DLC films are obtained. These optical spectra are analyzed with the help of the Sellmeier dipersion relation and a quantum mechanically derived dispersion relation. Using spectroscopic ellipsometry data at their transparent region, the refractive index and the effective thickness of DLC films on vitreous silica are model calculated, Then the transmission spectra are inverted to yield the extinction coefficient spectra k(λ) at absorbing region. These spectra are fit to the quantum mechanical dispersion relation and the best fit dispersion constants are determined. The complex refractive indices are easily calculated with these constants. The spectroscopic ellipsometry data at the absorbing region in model calculated to give the packing densities and the degrees of surface microroughness of DLC films. Discussions are made in correlation with the growth condition of DLC films.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.655-659
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• 1998

The effect of quenching speed of melt-spinning on intrinsic coercivity ($_iH_c$$) of annealed ribbons and the crystallization behavior from amorphous $Nd_{14.73}Fe_{78.67}B_{6.60}$ alloy have been studied. We have found that the intrinsic coecivity for annealed melt-spun ribbon is reduced with increasing of quenching rate. $\alpha$-Fe and $Fe_3B$ were formed as intermediate phases prior to the formation of $Nd_2Fe_{14}B$ phase during crystallization. The $Fe_3B$ is disappeared with crystallization of $Nd_2Fe_{14}B$ phase. But the $\alpha$-Fe phase is retained in fully crystallized ribbon by annealing. The intrinsic coercivity loss of annealed ribbon with increasing of quenching speed is believed to be due to existence of soft magnetic phase $\alpha$-Fe in annealed ribbons.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.7 no.1
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• pp.143-150
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• 1997

The electrical properties of polysilicon thin films implanted with $B_2H_6$ diluted in $H_2$ as dopant source using ion mass doping technique and the effect of radiation damage on the dopant activation behavior were investigated. Comparing the SIMS profiles of boron in polysilicon films with that obtained from computer simulation using TRIM92 the most probable ion species were $B_2H_x\;^+$(x＝1, 2, 3‥‥) type molecular ions. As a result of the Implantation of energetic massive ions, a continuous amorphized layer was created in polysilicon films where the fraction of amorphized layer varied with doping time. This amorphization comes from the fact that mass separation of implanting species is not employed in this ion mass doping technique. In the dopant activation behavior, reverse annealing phenomenon appeared in the intermediate annealing temperature range for a severely damaged specimen. The experimental result showed that the off-state current of the p-channel polysilicon thin film transistor is dependent on the degree of radiation damage.

• Journal of the Korean Ceramic Society
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• v.34 no.2
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• pp.195-201
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• 1997

The present paper describes the effect of dry mixed grinding on kaolinite-aluminum trihydroxide mixture with a planetary ball mill before sintering and its influence on mullite formation during sintering. The size reduction of the mixture is market in the early stage of grinding and the obtained fine particles agglomerate subsequently with an increase of grinding time. The crystal structure of the mixture is collapsed easily into an amorphous one by planetary ball milling, of which amount increases with an increase of grinding time. Only mullite phase except for anatase as an inherent impurity in kaolinite appeared in the sintered body of the mixtures with mixed grinding as relatively lower temperature 1523K, while corundum, cristobalite, and Al-Si spinel phases, besides mullite were formed in the sintered body of the mixture without mixed grinding. Therefore, the mixed grinding treatment is very effective to improve the homogeneous mixing and disp-ersion of the mixture of raw materials on a micro scale and to decrease the thermal decomposition tem-perature by crystal structure change of them so as to obatin direct preparation of mullite with high purity at relatively low temperature.

• Journal of the Mineralogical Society of Korea
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• v.25 no.2
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• pp.77-84
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• 2012

Anatase, one of the $TiO_2$ polymorphs, is known to show different phase transition paths depending on its crystalline and shape. Particle size of 15~25 nm anatase has been subjected to high-pressure Raman spectroscopy and X-ray diffraction studies using a diamond anvil cell. We observe that the starting sample transforms to an amorphous phase above approx. 20 GPa, which is retained upon pressure release to ambient condition. This is in contrast to previously established transition to baddeleyite phase and we suspect difference in the particle distribution state trigger phase instability of nanoparticles and hence amorphization.

• Journal of Convergence Society for SMB
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• v.6 no.1
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• pp.25-32
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• 2016

With the change and development of modem architecture, architectural configurations are increasingly diversified and irregular. However, the building configurations without proper seismic considerations may cause severe damages under earthquake loads. Therefore, it is necessary to establish and implement more properly classified, specific and advanced conceptual seismic design strategies. This study explores the relationship between building configurations and seismic performance by adopting several horizontal building configurations with various re-entrant corners. For the clear comparison of five different horizontal configuration models, almost aspects of structural properties are equalized. The equivalent static analyses are conducted with the aim of understanding the characteristics of various re-entrant comers under standard earthquake loads. The seismic advantages of regular configuration model are clearly approved and the structural weak points at the re-entrant comers are investigated numerically and graphically.