• 한국재료학회지
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• 제22권12호
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• pp.706-710
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• 2012

The growing conditions of barium nitrate $Ba(NO_3)_2$ single crystals using the aqueous solution method have been studied. Supersaturation can be calculated by measuring the temperature of the solution and its equilibrium temperature. Supersaturation of $Ba(NO_3)_2$ was 0.7% at $32.0^{\circ}C$ and about 3% at $34.0^{\circ}C$. The obtained single crystals have three kind of morphology: tetrahedral, cubic, and, rarely, dodecahedral. The normal growth rate is proportional to the supersaturation; it is necessary to make the solution below 5% supersaturation in order to obtain transparent $Ba(NO_3)_2$ single crystals. The normal growth rate for {1$\bar{1}$1} faces was $2.51{\times}10^{-6}$ mm/s for the 0.7% supersaturation condition ($32.0^{\circ}C$), $6.43{\times}10^{-6}$ mm/s for the the condition of 3.0% supersaturation, and $7.01{\times}10^{-6}$ mm/s for the condition of 5.0% supersaturation. The quality of the grown crystals depends on the nature of the seed, the cooling rate employed, and the agitation of the solution. The faces of the obtained crystals have been identified uising an X-ray diffractometer. The surface diffusion is responsible for the low growth rates of the {1$\bar{1}$1} faces.

• 한국세라믹학회지
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• 제56권6호
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• pp.589-595
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• 2019

The top-seeded solution growth (TSSG) method is an effective approach for the growth of high-quality SiC single crystals. In this method, the temperature gradient in the melt is the key factor determining the crystal growth rate and crystal quality. In this study, the effects of the aperture at the top of the hot-zone on the growth of the SiC single crystal obtained using the TSSG method were evaluated using multiphysics simulations. The temperature distribution and C concentration profile in the Si melt were taken into consideration. The simulation results showed that the adjustment of the aperture at the top of the hot-zone and the temperature gradient in the melt could be finely controlled. The surface morphology, crystal quality, and polytype stability of the grown SiC crystals were investigated using optical microscopy, high-resolution X-ray diffraction, and micro-Raman spectroscopy, respectively. The simulation and experimental results suggested that a small temperature gradient at the crystal-melt interface is suitable for growing high-quality SiC single crystals via the TSSG method.

• 생물환경조절학회지
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• 제12권2호
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• pp.89-94
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• 2003

본 실험은 토마토의 순환식 시스템 양액재배에서 배액의 재순환 시 안정된 pH와 균형적인 양분 공급 방법을 구명하고자 수행되었다. 배액의 pH나 무기성분을 교정하지 않는 구(대조구), EC측정 및 양분 분석 교정구를 처리내용으로 두었다. 초기생육인 초장은 처리간에 차이가 없었으나 생체중 및 건물중은 양분분석구가 대조구에 비해 무거웠다. 후기생육에서는 양분분석구가 대조구에 비해 과중이 무겁고, 착과수가 많아 수량이 증가하였다 배액 EC는 대조구에 비해 EC측정구와 양분분석구가 전반적으로 낮았다. 배액의 pH는 전 생육기간에서 양분 분석구 및 EC측정구는 6.2∼6.5를 유지하였으나 대조구는 지속적으로 높아져 후기에는 7.2정도 되었다. 배액의 무기성분에서 N, P 및 K의 함량은 모든 처리구에서 셍육이 경과함에 따라 적어졌으며, 대조구에 비해 양분분석구가 적었다 Ca 및 Mg의 함량은 모든 처리구에서 생육초기에는 급격히 감소하였으며 생육후기에는 앙분 분석구와 EC측정구는 적은 상태로 유지되었으나 대조구는 급격히 증가하는 경향이었다. 이상의 결과에서 순환식 시스템을 이용한 토마토의 양액재배시 배액의 양분을 분석한 후 교정하는 것이 생육에 효과적이었다.

• Korean Journal of Mathematics
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• 제23권3호
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• pp.379-391
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• 2015

We investigate the existence of solutions of the nonlinear biharmonic equation with variable coefficient polynomial growth nonlinear term and Dirichlet boundary condition. We get a theorem which shows that there exists a bounded solution and a large norm solution depending on the variable coefficient. We obtain this result by variational method, generalized mountain pass geometry and critical point theory.

• 한국결정성장학회:학술대회논문집
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• 한국결정성장학회 1998년도 PROCEEDINGS OF THE 15TH KACG TECHNICAL MEETING-PACIFIC RIM 3 SATELLITE SYMPOSIUM SESSION 4, HOTEL HYUNDAI, KYONGJU, SEPTEMBER 20-23, 1998
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• pp.55-63
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• 1998

The growing conditions of barium nitrate Ba(NO3)2 single crystals by aqueous solution method have been studied. Supersaturation of Ba(NO3)2 was 0.7% at 32.0$^{\circ}C$ and about 3% 34.0$^{\circ}C$. The obtained single crystals have three kind of morphology; the tertrahedron, the cube and rarely dodecahedron face. The faces of obtained crystals have been identified by X-ray diffractometer.

• 한국세라믹학회지
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• 제22권4호
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• pp.26-32
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• 1985

The subcritical crack growth of sintered SiC is investigated under various corrosive atmospheres such as distilled water Murakami solution and saturated KOH solution. The KI-V diagrams are obtained by the load relaxation method and incremental displacement rate method using the double torsion technique. The obtained fracture mechanics parameters (n) of sintered SiC are 79 in Murakami solution and 39 in saturated KOH solution. These data indicate that the subcritical crack growth of sintered SiC is taking place in these two conditions and the stress-corrosion cracking is suggested to be the mechanism. With these KI-V diagrams the life of sintered SiC in these conditions is predicted.

• The Korean Journal of Ceramics
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• 제3권1호
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• pp.57-61
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• 1997

The effects of pH of solution on structural, electrical, and optical properties of CdS thin films prepared by solution growth method were investigated. With increasing pH of the solution, both crystallinity and transmittance of CdS thin film were deteriorated due to impurities and CdS particles, which were produced by homogeneous nucleation and adsorbed on the surface of CdS thin films. The films were strongly adherent to substrates and has low resistivity of 10~$10^2{\omega}cm$ regrardless of deposition conditions. After annealing at 30$0^{\circ}C$ in Ar atmosphere, the resistivity decreased due to desorption of impurity ions as well as the formation of S vacancies, but after annealing above 35$0^{\circ}C$ it increased by an agglomeration of S vacancies. After annealing in air atmosphere, the film resistivity increased because of the formation of oxide particle in grain boundaries.

• 한국결정성장학회지
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• 제13권4호
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• pp.153-156
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• 2003

Pure and Ethylenediaminetetraacetic acid (EDTA) doped L-arginine phosphate (LAP) single crystals were grown from the aqueous solution by temperature lowering method. The effect of EDTA additive on the solubility and metastable zone width of LAP solution has been investigated. Addition of EDTA has enhanced the metastable zone width of LAP and hence bulk crystals could be grown. The growth rate along the [100] direction increases with EDTA additive. Powder X-ray diffraction and FTIR studies reveal the absence of EDTA in the lattice of LAP, This reveals that the addition of EDTA to LAP doesn't influence the crystallinity. However, the transmittance and NLO properties significantly increase with EDTA additive and hence bulk LAP crystals are useful for laser fusion experiments.

• Korean Journal of Mathematics
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• 제13권2호
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• pp.161-176
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• 2005

We consider a model of population dynamics whose mortality function is unbounded. We note that the regularity of the solution depends on the growth rate of the mortality near the maximum age. We propose Gauss-Legendre methods along the characteristics to approximate the solution when the solution is smooth enough. It is proven that the scheme is convergent at fourth-order rate in the maximum norm. We also propose discontinuous Galerkin finite element methods to approximate the solution which is not smooth enough. The stability of the method is discussed. Several numerical examples are presented.

• 한국결정성장학회지
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• 제1권1호
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• pp.60-65
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• 1991

The hydrothermal growth of $GaPO_{4}$ Single Crystals was carried out by the horizontal temperature gradient method. The most promising solvents for the crystal growth of $GaPO_{4}$ are $H_{3}PO_{4}$ and HCl solutions. Single crystals have been hydothermally grown at temperatures over the range $210-290^{\circ}C$ in these solutions with seed crystals. The glowth rates in HCl solution were higher than that for comparable conditions in $H_{3}PO_{4}$ solution. Morphologies of crystals grown at temperatures below $200^{\circ}C$ tended to be bounded by small major rhombohedral(10$\bar{1}$1) faces. In the temperature range from 200 to $430^{\circ}C$, the single crystals have morphologies bounded by prism (10$\bar{1}$0), small major rhombohedral(10$\bar{1}$1) and minor rhombohedral(01$\bar{1}$1) faces at the early stage, and grew with well developed basal(0001) faces by increasing the growth temperature.