• 한국전산유체공학회지
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• 제3권1호
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• pp.100-107
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• 1998

A numerical analysis of thermal stress over temperature variations near the crystal-melt interface is carried out for a floating-zone growth of Cadmium Telluride (CdTe). Thermocapillary convection determines crystal-melt interfacial shape and signature of temperature in the crystal. Large temperature gradients near the crystal-melt interface yield excessive thermal stresses in a crystal, which affect the dislocations of the crystal. Based on the assumption that the crystal is elastic and isotropic, thermal stresses in a crystal are computed and the effects of operating conditions are investigated. The results show that the extreme thermal stresses are concentrated near the interface of a crystal and the radial and the tangential stresses are the dominant ones. Concentrated heating profile increases the stresses within the crystal, otherwise, the pulling rate decreases the stresses.

• 한국세라믹학회지
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• 제34권10호
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• pp.1045-1052
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• 1997

Barium ferrites (BaFe12O19) were synthesized at the various temperature by the coprecipitation-oxidation method. X-ray diffraction Rietveld analysis for barium ferrites were performed, their microstructures were observed and their magnetic properties were measured, in order to analyze the crystal structures and determine the optimal temperature of heat-treatment. The barium ferrite, its average particle size 80 nm, was formed at 600℃ through the hematite (α-Fe2O3), but the site occupations of the Fe's in tetrahedral and bipyramidal sites and of the Ba relatively low. Increasing the heating temperature, these occupations and the magnetization increased, and the crystal c-axis decreased. These changes were very small at the heat treatment of above 800℃, but the particles were rapidly grown. It is suggested that the optimal temperature of heat-treatment is 800℃, at which temperature crystal structure is relatively stable and the particles hardly ever grow.

• Bulletin of the Korean Chemical Society
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• 제30권11호
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• pp.2608-2612
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• 2009

The unequivocal solid-state structure and stereochemistry of the hetaryl leuco-TAM dye, 2,2’-(2-phenyl propane- 1,3-diylidene) bis(1,3,3- trimethylindoline) derivatives were established using X-ray single crystal analysis. The X-ray crystal analysis showed that the (Z, E)-isomers only formed stereoselectively, with a so-called “threebladed propeller” conformation, from the reaction of a Fischer base and benzaldehyde derivatives. These isomers were stacked in a juxtaposition to form a dimer or a double dimer, adopting either a triclinic, with P-1, or monoclinic crystal system with a space group P21/n in the unit cell of the crystal.

• 한국결정성장학회지
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• 제7권1호
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• pp.27-40
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• 1997

The heat in Czochralski method is transfered by all transport mechanisms such as convection, conduction and radiation and convection is caused by the temperature difference in the molden pool, the rotations of crystal or crucible and the difference of surface tension. This study delvelops the simulation model of Czochralski growth by using the finite difference method with fixed grids combined with new latent heat treatment model. The radiative heat transfer occured in the surfce of the system is treated by calculating the view factors among surface elements. The model shows that the flow is turbulent, therefore, turbulent modeling must be used to simulate the transport phenomena in the real system applied to 8" Si single crystal growth process. The effects of a cusp magnetic field imposed on the Czochralski silicon melt are studied by numerical analysis. The cusp magnetic field reduces the natural and forced convection due to the rotation of crystal and crucible very effectively. It is shown that the oxygen concentration distribution on the melt/crystal interface is sensitively controlled by the change of the magnetic field intensity. This provides an interesting way to tune the desired O concentration in the crystal during the crystal growing.

• 한국결정성장학회지
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• 제19권5호
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• pp.215-222
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• 2009

Many concepts of external magnetic field applications in crystal growth processes have been developed to control melt convection, impurity content and growing interface shape. Especially, travelling magnetic fields (TMF) are of certain advantages. However, strong shielding effects appear when the TMF coils are placed outside the growth vessel. To achieve a solution of industrial relevance within the framework of the $KRISTMAG^{(R)}$ project inner heater-magnet modules(HMM) for simultaneous generation of temperature and magnetic field have been developed. At the same time, as the temperature is controlled as usual, e.g. by DC, the characteristics of the magnetic field can be adjusted via frequency, phase shift of the alternating current (AC) and by changing the amplitude via the AC/DC ratio. Global modelling and dummy measurements were used to optimize and validate the HMM configuration and process parameters. GaAs and Ge single crystals with improved parameters were grown in HMM-equipped industrial liquid encapsulated Czochralski (LEC) puller and commercial vertical gradient freeze (VGF) furnace, respectively. The vapour pressure controlled Czochralski (VCz) variant without boric oxide encapsulation was used to study the movement of floating particles by the TMF-driven vortices.

• 한국결정성장학회지
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• 제8권3호
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• pp.419-423
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• 1998

형석$(CaF_2)$ 단결정 내부에 형성되는 다양한 결함에 대하여 현미경관찰, 성분분석 및 투과율분석을 하고 광투과에 미치는 영향을 고찰하였다. 내부 cavity의 종류로는 bubble과 결정면을 포함하는 공공형태의 negative crystals이 있으며, 특히 negative crystals이 결정에 고루 퍼져있는 경우, UV-Visible 파장영역에서 약 3%의 투과율 저하현상이 나타났다. 또한, 결정내부의 석출물은 주로 내부 cavite에 형성됨을 WDX 분석을 통하여 확인할 수 있었다. Violet colored 결정은 non-colored 결정에 비하여 전위밀도가 3배 정도 높았고, 성분분석 F이온이 적은 Ca와 F의 원자비가 나타내었다. 이러한 결과로 F이온의 부족으로 인하여 형성된 violet 색상이 발생되었음을 간접적으로 알 수 있었다.

• 한국결정성장학회지
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• 제31권3호
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• pp.116-126
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• 2021

코디어라이트(Mg₂Al₄Si₅O₁₈) 하니컴 세라믹스의 대표적 응용분야는 자동차 배기가스 정화용 필터(diesel particulate filter(DPF))이다. 천연광물, 조공제, 유기바인더를 혼합한 슬러리를 압출하여 DPF용 하니컴 코디어라이트를 성형한 후 980~1450℃ 범위에서 소결하였다. 소결온도에 따른 결정상(indialite, cordierite, cristobalite, alumina, spinel, mullite, pro-enstatite)의 형성과정을 XRD Rietveld 정밀화법을 이용하여 정량분석 하였다. 동시에, 세라믹 에칭(etching) 방법으로 소결 시료 표면의 비정질상을 제거한 후 SEM/EDS법을 사용하여 결정상들의 형상과 조성을 확인하였다. 이들 결과로부터 DPF 하니컴에서 결정상 형성 과정을 명확히 밝힐 수 있었다. 또한, DPF 하니컴의 소결온도에 따른 열팽창계수(linear coefficient of thermal expansion, CTE) 변화를 분석하였고, 결정상의 정량분석결과를 바탕으로 계산된 CTE와 비교하였다. 소결된 DPF 하니컴 내의 결정상들이 CTE 특성에 미치는 영향을 고찰하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.326-331
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• 2007

This paper conducts a vibratory loads reduction analysis of an Advanced Active Trailing-edge Flap (AATF) blade utilizing single crystal piezoelectric actuators. For an AATF blade, a new L-L piezostack actuator using single crystal PMN-PT materials is designed. The AATF blade is designed to have similar characteristics to the Advanced Active Twist Rotor (AATR) blade. The active trailingedge flap is assumed to be 20% of the blade span and 15% of the chord, located at 75% of the blade radius. In order to conduct the vibratory loads reduction analysis of the AATF blade in forward flight, DYMORE, a multi-body dynamics analysis code, is used. The simulation result shows that the hub vibratory loads may be reduced by approximately 89% even with a much lower input-voltage when comparing with the other active rotor systems.

• 화훼연구
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• 제26권4호
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• pp.195-201
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• 2018

농촌진흥청 국립원예특작과학원에서 육성된 formolongi-Asiatic (FA)종간잡종 나리 'Bonanza', 'Coral Candy', 'Purple Crystal'의 특성검정 및 FISH 분석을 통한 염색체 검경을 수행하였다. 'Bonanza', 'Coral Candy', 'Purple Crystal'의 개화시기는 6월 중하순, 중순, 상순으로 각각 중만생종, 중생종, 조생종에 해당한다. 개화방향은 3품종 모두 상향이며 약간의 향기를 가지고 있다. 절화장은 101.0cm('Purple Crystal')에서부터 142.3cm('Bonanza')로 초장 신장성이 우수하여 절화로서의 개발이 가능하다. 화폭은 'Bonanza'와 'Coral Candy'가 17,1cm, 16.9cm로 관찰되어 대형화로 분류되며 'Purple Crystal'은 12.3cm으로 좁으나 화폭이 4cm 이상으로 화폭이 안정적이다. 잎의 길이는 'Bonanza'는 15.7cm, 'Coral Candy'는 19.7cm, 'Purple Crystal'은 11.1cm로 관찰되었다. 염색체 분석 결과, 3품종 모두 3배체(2n=3x=36)로 관찰되었다. FISH 분석 결과, 'Bonanza', 'Coral Candy', 'Purple Crystal'의 5S/45S rDNA가 각각 4/11 loci, 4/12 loci, 4/11 loci로 관찰되었다. 3번 염색체를 제외하고 나머지 염색체에서 관찰되는 rDNA의 패턴이 달라 FISH 분석에 대한 결과는 품종을 구별하는 마커로 유용하게 이용 될 수 있을 것으로 기대할 수 있다.

• 한국결정성장학회지
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• 제15권4호
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• pp.129-134
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• 2005

초크랄스키 단결정장치내 실리콘 유동의 자기장효과에 대한 수치해석을 하였다. 8" 단결정 성장과정에서 난류 모형을 사용하여 수송현상을 계산하였다. 도가니 회전수가 작으면 자연대류가 지배적이었다. 도가니 회전수가 증가할수록 강제대류가 증가되며 온도 분포는 더 넓어진다. cusp 자기장을 인가하면 도가니근처의 유동이 크게 감소하며 온도분포는 전도의 경우와 비슷해진다.