• 한국전기전자재료학회논문지
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• 제13권11호
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• pp.901-907
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• 2000

As the minimum feature size for making ULSI approaches the wavelength of light source in optical lithography, the aerial image is so hardly distorted because of the optical proximity effect that the accurate mask image reconstruction on wafer surface is almost impossible. We applied the Optical Proximity Correction(OPC) on isolated patterns assuming Attenuated Phase Shift Mask(APSM) as well as binary mask, to correct the widening of isolated patterns. In this study, we found that applying OPC to APSM shows much better improvement not only in enhancing the resolution and fidelity of t도 images but also in enhancing the process margin than applying OPC to the binary mask. Also, we propose the OPC method of APSM for isolated patterns, the size of which is less than the wavelength of the ArF excimer laser. Finally, we predicted the resolution limit of optical lithography through the aerial image simulation.

• Tribology and Lubricants
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• 제13권3호
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• pp.56-62
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• 1997

Sealing an oil-air mixture plays important roles to have an enhanced lubrication for high speed spindle. High speed spindles require non-contact type sealing mechanism. In this study, an optimum seal design to minimize leakage is concerned in the aspect of flow control. This paper categorizes geometries of mostly used non-contact type seals and analyzes each leakage characteristics to minimize a leakage on sealing area. Effect of minimum clearance and its position are considered according to variation of detail geometry. The estimation of non-leaking property is determined by amount of pressure drop in the leakage path assuming constant leakage flow. To simulate an oil jet or oil mist type high speed spindle lubrication, the working fluid is regarded as two phases that are mixed flow of oil phase and air phase. Both of the turbulence and the compressible flow model were introduced in CFD(Computational Fluid Dynamics) analysis. Design parameters has been induced to minimize leakage in limited space, and a methodological study on geometrical optimization has been conducted.

• Bulletin of the Korean Chemical Society
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• 제18권9호
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• pp.985-994
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• 1997

The reaction of gas-phase atomic hydrogen with hydrogen atoms chemisorbed on Fe(110) surface is studied by use of classical trajectory procedures. Flow of energy between the reaction zone and bulk solid phase has been treated in the generalized Langevin equation approach. A London-Eyring-Polanyi-Sato energy surface is used for the reaction zone interaction. Most reactive events are found to occur in strong single-impact collisions on a subpicosecond scale via the Eley-Rideal mechanism. The extent of reaction is large and a major fraction of the available energy goes into the vibrational excitation of H2, exhibiting a vibrational population inversion. Dissipation of reaction energy to the heat bath can be adequately described using a seven-atom chain with the chain end bound to the rest of solid. The extent of reaction is not sensitive to the variation of surface temperature in the range of Ts=0-300 K in the fixed gas temperature, but it shows a minimum near 1000 K over the Tg=300-2500 K.

• 공업화학
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• 제4권3호
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• pp.537-543
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• 1993

N-헥산과 증류수로 이루어진 비혼화성 액상계에서 교반에 의한 액-액분산을 해석하였다. 교반기는 blade형태가 flat, 60mesh와 40mesh의 금망, 그리고 60mesh금망의 외부에 금속띠를 두른 4가지의 6-bladed turbine 교반기를 사용하였다. 실험결과, 동일한 교반속도에서 유기상의 분산정도와 교반기의 소요동력은 blade형태가 flat>solid edged>60mesh>40mesh의 순서이었으며 유기상의 부피비가 증가할수록 완전분산에 필요한 최소교반속도가 증가되었다. 또한 분산상의 액적의 평균직경은 교반속도의 증가에 따라 감소하였으며 동일한 교반속도에서는 Solid edged$d_{32}$)은 다음과 같이 유기상의 부피비(${\phi}$)와 Weber number($N_{We}$)의 함수로 나타낼 수 있었다.$d_{32}/D=a(1+b{\phi})N_{We}{^{-0.6}}$.

• 한국산학기술학회논문지
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• 제15권11호
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• pp.6702-6709
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• 2014

본 연구는 3차원 자화강조영상 획득 시 재구성되는 위상영상의 겹쳐진 위상과 현격한 자화율 차이에 의한 영상의 불균일성을, 낮은 주파수 대역폭을 제한하는 High Pass Filter(HPF)를 적용함으로써 개선하고자 하였다. 연구방법은 2013년 11월부터 2014년 3월까지 3차원 자화강조영상 검사를 받은 환자를 대상으로 high pass filter의 적용 전후 영상 간 차이를 확인하기 위하여 기존의 위상영상과 HPF를 적용한 새로운 위상영상의 최대, 최소 신호강도 차이 및 불균일도를 비교 분석하였다. 연구결과, HPF 적용 전후에 따른 최대, 최소 신호강도의 차이는 274.16%(498.98), 불균일도는 439.55%(19.83) 감소하였다. 이는 HPF를 적용하여 낮은 주파수를 차단한 새로운 위상영상이 기존의 위상영상에 비해 겹쳐진 위상신호를 효과적으로 제거하여 영상의 균일도가 높아졌음을 의미한다. 결론적으로 3차원 자화강조영상 획득 시 재구성되는 위상영상에 HPF를 적용하면 겹쳐진 위상과 현격한 자화율 차이에 의한 영상의 불균일성을 효과적으로 개선할 수 있어 영상의 질을 크게 개선할 수 있다.

• Journal of Microbiology and Biotechnology
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• 제9권4호
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• pp.498-503
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• 1999

Protease produced from Bacillus sp. FSE-68 was isolated from Meju, a Korean fermented soybean starter, and was purified by a two-consecutive aqueous two-phase system. The change of partition coefficient (K) in the polyethylene glycol (PEG)/potassium phosphate buffer (PPB) aqueous two-phase system was measured at different pHs (6.0- 9.2), PPB concentrations (8-12%), and temperatures (4 and $20^{\circ}C$). As the PPB concentration in the aqueous two-phase system increased, the protease concentration in the top phase (PEG-rich phase) increased, thereby enhancing the partition coefficient. The minimum partition coefficient of the protease was achieved at pH 7.0, whereas that of the total protein was at pH 6.0. The biggest difference in partition coefficients of total protein and protease occurred at pH 6.0. It was interesting to note that the partition coefficient of protease decreased as the temperature increased. The optimum condition of the primary aqueous two-phase extraction of Bacillus sp. FSE-68 was pH 6.0, 14% (w/w) PPB, and 16% (w/w) PEG at $4^{\circ}C$, and the crude enzyme concentration in this system was 50% (w/w). The protease, which was concentrated in the top phase, was further mixed with 15% (w/w) PPB (pH 7.0) in the ratio of 1:1 at $20^{\circ}C$ to elute the bottom phase (PPB-rich phase). Using these steps, the purification fold achieved was 9.2 with a 44.7% yield.

• International Journal of Aeronautical and Space Sciences
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• 제18권4호
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• pp.709-718
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• 2017

This paper proposes the guidance laws for an agile turn of air-to-air missiles during the initial boost phase. Optimal solution for the agile turn is obtained based on the optimal control theory with a simplified missile dynamic model. Angle-of-attack command generating methods for completion of agile turn are then proposed from the optimal solution. Collision triangle condition for non-maneuvering target is reviewed and implemented for update of terminal condition for the agile turn. The performance of the proposed method is compared with an existing homing guidance law and the minimum-time optimal solution through simulations under various initial engagement scenarios. Simulation results verify that transition to homing phase after boost phase with the proposed method is more effective than direct usage of the homing guidance law.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제26회 춘계학술대회논문집
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• pp.11-16
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• 2006

본 연구는 이종 접착 재질의 접착계면에서 미접착 결함을 검출하기 위한 새로운 시험 기법을 개발하기 위함이다. 접착계면과 미접착계면에서의 초음파 전달 현상을 이론적으로 해석하여 초음파 신호를 모델링하였고, 이론적 분석에 기초하여 미접착계면에서의 위상 반전 현상을 애용한 검사 방법을 FRP/고무 시편에 적용하였다. 정량적으로 결함의 최소 검출 능력을 평가하기 위하여 알루미늄/고무 시편에 평저공을 가공하여 제작하였고 일반적으로 사용하고 있는 펄스에코반사법과 새로운 시험 기법인 위상반전법을 상호 비교하였으며 이론적으로 예측한 초음파 신호와 실험에서 얻은 초음파 신호를 근거로 위상반전법으로 미접착 결함을 검출할 수 있다고 판단하였다.

• 한국세라믹학회지
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• 제18권1호
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• pp.27-34
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• 1981

The phase separation of low-alkali borosilicate glass with the composition of $6.25Na_2O$.$18.75B_2O_3$.$75.00SiO_2$(mole%) substituting $Li_2O$ for $Na_2O$ was studied. The phase separation in the temperature range of transformation was examined with various heating temperatures and soaking times. Durability to water, thermal expansion and specific density of the specimen were investigated and the microstructure of the separated phase was also observed by transmission electron micrograph techniques. The maximum alkali extraction result with the best phase separation effect was obtained when $Na_2O$ of the base glass was replaced with $1.88Li_2O$ (mole %) and electron micrograph of carbon film replica of $1.88Li_2O$$4.37Na_2O$.$18.75B_2O_3$.$75.00SiO_2$ (mole %) glass showed that the glass consisted of homogeneous two phases. The minimum specific density was shown with the specimen treated at 57$0^{\circ}C$ and it was also shown that the longer the treating time the lower the specific density. The apparent activation energies of approximately 45 kcal/mole by the alkali extraction and 43kcal/mole by the thermal expansion method were derived from the Arrhenius plots, respectively.

• ETRI Journal
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• 제42권3호
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• pp.324-332
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• 2020

In this paper, a blind symbol timing offset (STO) estimation method is proposed for offset quadrature phase-shift keying (OQPSK) modulated signals, which also works for other linearly modulated signals (LMS) such as binary-PSK, QPSK, 𝜋/4-QPSK, and minimum-shift keying. There are various methods available for blind STO estimation of LMS; however, none work in the case of OQPSK modulated signals. The popular cyclic correlation method fails to estimate STO for OQPSK signals, as the offset present between the in-phase (I) and quadrature (Q) components causes the cyclic peak to disappear at the symbol rate frequency. In the proposed method, a set of close and approximate offsets is used to compensate the offset between the I and Q components of the received OQPSK signal. The STO in the time domain is represented as a phase in the cyclic frequency domain. The STO is therefore calculated by obtaining the phase of the cyclic peak at the symbol rate frequency. The method is validated through extensive theoretical study, simulation, and testbed implementation. The proposed estimation method exhibits robust performance in the presence of unknown carrier phase offset and frequency offset.