• Journal of Microbiology and Biotechnology
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• 제30권1호
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• pp.146-154
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• 2020

With the advantages of biocatalytic method, enzymes have been excavated for the synthesis of chiral amino acids by the reductive amination of ketones, offering a promising way of producing pharmaceutical intermediates. In this work, a robust phenylalanine dehydrogenase (PheDH) with wide substrate spectrum and high catalytic efficiency was constructed through rational design and active-site-targeted, site-specific mutagenesis by using the parent enzyme from Bacillus halodurans. Active sites with bonding substrate and amino acid residues surrounding the substrate binding pocket, 49L-50G-51G, 74M,77K, 122G-123T-124D-125M, 275N, 305L and 308V of the PheDH, were identified. Noticeably, the new mutant PheDH (E113D-N276L) showed approximately 6.06-fold increment of k_cat/Km in the oxidative deamination and more than 1.58-fold in the reductive amination compared to that of the wide type. Meanwhile, the PheDHs exhibit high capacity of accepting benzylic and aliphatic ketone substrates. The broad specificity, high catalytic efficiency and selectivity, along with excellent thermal stability, render these broad-spectrum enzymes ideal targets for further development with potential diagnostic reagent and pharmaceutical compounds applications.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(2)
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• pp.477-480
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• 2004

We studied the characteristics of impedance and electromechanical coupling coefficient in ZnO and AIN thin films by using resonance frequency spectrum method. The response peak of impedance decreased with the decrease of thickness of piezoelectrics, the number of mode of response peak increased with the increase of substrate thickness. An error of $k_{t}^{2}$ estimated from input $k_{t}^{2}$ increased as the thickness of piezoelectrics decreased and the thickness of substrate increased. Also, the error was increased in case of a large acoustic impedance of substrate. It was found that the composite resonator operating in optimized condition could be designed through the resonance frequency spectrum analysis of composited resonator consisted of piezoelectric thin film and substrate.

• 한국전기전자재료학회논문지
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• 제21권5호
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• pp.463-467
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• 2008

Aluminum nitride (AlN) thin films have been deposited on Au electrodes by using reactive RF magnetron sputtering method in a gas mixture of Ar and $N_2$ at different substrate temperature. It was found that substrate temperature was varied in the range up to $400^{\circ}C$, highly c-axis oriented film can be obtained at $300^{\circ}C$ with full width at half maximum (FWHM) $3.1^{\circ}$. Increase in surface roughness from 3.8 nm to 5.9 nm found to be associated with increase in grain size, with substrate temperature; however, the AlN film fabricated at $400^{\circ}C$ exhibited a granular type of structure with non-uniform grains. The Al 2p and N 1s peak in the X-ray photoelectron spectroscopy (XPS) spectrum confirmed the formation of Al-N bonds. The XPS spectrum also indicated the presence of oxynitrides and oxides, resulting from the presence of residual oxygen in the vacuum chamber. It is concluded that the AlN film deposited at substrate temperature of $300^{\circ}C$ exhibited the most desirable properties for the application of high-frequency surface acoustic devices.

• 한국진공학회지
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• 제7권4호
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• pp.410-414
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• 1998

본 연구에서는 플라즈마 중합 반응의 기판 재질과 전극 위치에 대한 의존성을 규명 하기 위해서 Ar방전의 발광 분석을 행하였으며 제작된 박막의 가교성을 확인하기 위해서 전자빔 노광을 시켜보았다. 기판의 재질이 도체 및 절연체인 양자의 경우를 비교해 보면 전 자는 후자에 비해서 전체적으로 발광 스펙트럼의 피이크 강도가 크게 나타났으며, 준안정상 태에 대한 피이크와 이온에 대한 피이크를 검토한 결과, 기판이 절연물일 때는 전극의 위치 를 멀게 할수록 이온의 피이크 강도가 극단까지 떨어짐을 알 수 있었다. 제작된 중합스티렌 박막을 통하여 발광 스펙트럼의 변화에 따라서 막의 가교성 변화가 생기는 것을 알 수 있었 으며 이 막을 전자빔에 노광하였을 때, 기판이 절연물인 경우에는 패턴을 제작하는 것이 가 능하였다.

• 한국정보통신학회논문지
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• 제16권10호
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• pp.2273-2279
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• 2012

동시진공증발법(co-evaporation)으로 Cu(In,Ga)$Se_2$ 박막을 제작하는 논문으로서 1단계($1^{st}$-stage)에서 기판온도(substrate temperature)가 $400^{\circ}C$에서 $In_2Se_3$상($In_2Se_3$ phase)이 존재하였으며 2,3단계($2^{nd}$-stage, $3^{rd}$-stage)에서 기판온도 변화에 따른 흡수 스펙트럼(absorbency spectrum)은 차이가 크지 않다. 이것은 박막의 두께가 전부 $1{\mu}m$ 이상이므로 흡수 스펙트럼(absorbency spectrum)은 거의 차이가 없다. 2,3단계에서 기판온도 변화에 따른 SEM과 XRD를 분석한 결과, 기판온도가 증가할수록 결정구조(crystal structure)의 밀도(density)가 증가하고 기공(vacancy)이 감소하며 $480^{\circ}C$, $500^{\circ}C$에서 Cu(In0.7Ga0.3)$Se_2$상(${\mu}m$)이 형성되었다.

• 한국재료학회지
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• 제19권1호
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• pp.50-53
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• 2009

Multi-walled carbon nanotubes (MWNTs) were synthesized on different substrates (bare Si and $SiO_2$/Si substrate) to investigate dye-sensitized solar cell (DSSC) applications as counter electrode materials. The synthesis of MWNTs samples used identical conditions of a Fe catalyst created by thermal chemical vapor deposition at $900^{\circ}C$. It was found that the diameter of the MWNTs on the Si substrate sample is approximately $5{\sim}10nm$ larger than that of a $SiO_2$/Si substrate sample. Moreover, MWNTs on a Si substrate sample were well-crystallized in terms of their Raman spectrum. In addition, the MWNTs on Si substrate sample show an enhanced redox reaction, as observed through a smaller interface resistance and faster reaction rates in the EIS spectrum. The results show that DSSCs with a MWNT counter electrode on a bare Si substrate sample demonstrate energy conversion efficiency in excess of 1.4 %.

• 대한전자공학회논문지SD
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• 제42권1호
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• pp.9-17
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• 2005

공진주파수 스펙트럼법을 이용하여 ZnO 와 AIN 압전박막의 임피던스 특성 및 전기기계결합계수 특성에 대해 조사하였다. 압전박막의 두께가 얇을수록 전체적인 임피던스 응답 피크의 크기가 감소하였으며, 기판의 두께가 얇을수록 응답 피크의 모드 수가 감소하는 것이 관찰되었다. 입력 Kt² 값으로부터 평가된 Kt² 값을 통해 압전박막의 두께보다 기판의 두께 변화에 대한 영향이 더 큼을 알 수 있었고, 기판의 acoustic 임피던스에 의해서도 Kt² 값이 감소함을 알 수 있었다. 전극 효과가 첨가되면 임피던스 응답 피크의 크기가 감소하였으며, 전극의 acoustic 임피던스가 커짐에 따라 응답피크는 더 작아졌다. 공진주파수 스펙트럼법에서 전극은 질량부하로 고려되기 때문에 전극 효과가 첨가된 경우 Keff² 값은 증가하며, 전극의 acoustic 임피던스가 크면 그 효과는 더 커졌다. 공진주파수 스펙트럼법을 이용한 시뮬레이션을 통해 기판, 압전체, 전극으로 이루어진 composite 공진기의 특성 분석과 설계까지도 가능함을 알 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 춘계학술대회 논문집 센서 박막재료
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• pp.57-60
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• 2001

The characterization of organic Metal/Insulator/Metal(MIM) devices were investigated from LB films. The physicochemical properties of the LB films were by UV absorption spectrum and AFM. We give pressure stimulation into organic thin films and then manufacture a device under the accumulation condition that the state surface pressure is 2, 10, 30[mN/ml The stable images are probably due to a strong interaction between the monolayer film and glass substrate. We are unable to obtain molecule resolution in images of the films but did see a marked contrast between images of the bare substrate and those with the network structure film deposited onto it.

• 한국전기전자재료학회논문지
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• 제13권9호
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• pp.776-780
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• 2000

ZnGa$_2$O$_4$thin films were prepared on Si(100) wafer in terms of RF power, substrate temperatures and Ar/O$_2$flow rate by RF Magnetron Sputtering. Photoluminescence(PL) measurement was employed to observe the emission spectra of ZnGa$_2$O$_4$films. The influences of various deposition parameters on the properties of grown films were studied. The optimum substrate deposition temperature for luminous characteristics was about 50$0^{\circ}C$ in this investigation. PL spectrum of ZnGa$_2$O$_4$ thin films showed broad band luminescence spectrum.

• Current Photovoltaic Research
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• 제8권1호
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• pp.1-5
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• 2020

The most important factor in enhancing the performance of an optical device is to minimize reflection and increasing transmittance of light for a broad wavelength range. The choice of appropriate coating material is crucial in decreasing reflection losses at the substrate. The purpose of this review is to highlight anti-reflection coating (ARC) materials that can be applied to silicon solar cell and glass substrate for minimizing reflection losses. The optical and electrical behavior of ARC on a substrate is highly dependent on thickness and refractive index (RI) of ARC films that are being deposited on it. The coating techniques and performance of single and multi-layered ARC films after coated on a substrate in a wide range of wavelength spectrum will be studied in the paper.