• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.263-266
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• 1999

In this work, a A/D converter is implemented to obtain 8bit resolution at a conversion rate of 10MS/s for video applications. This architecture is proposed using the Pipelined architecture for high speed conversion rate and the Successive - Approximation architecture for low power consumption, and consists of two identical stages that consist of sample/hold circuit, low power comparator, voltage reference circuit and MDAC of binary weighted capacitor array. Proposed A/D converter is designed using 0.25${\mu}{\textrm}{m}$ CMOS technology The SNR is 80㏈ at a sampling rate of 10MHz with 1.95MHz sine input signal. When an 8bit 10MS/s A/D converter is simulated, the Differential Nonlinearity / Integral Nonlinearity (DNL/ INL) error are $\pm$0.5 / $\pm$2 LSB, respectively. The power consumption is 13㎽ at 10MS/s.

• 한국환경과학회지
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• 제18권10호
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• pp.1071-1077
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• 2009

A novel pretreatment technique was applied to the conventional Pt/alumina catalyst to prepare for the highly efficient catalyst for the preferential oxidation of carbon monoxide in hydrogen-rich condition. Their performance was investigated by selective CO oxidation reaction. CO conversion with the oxygen-treated Pt/Alumina catalyst increased remarkably especially at the low temperature below $100^{\circ}C$. This result is promising for the normal operation of the proton exchange membrane fuel cell (PEMFC) without CO poisoning of the anode catalyst. XRD analysis results showed that metallic Pt peaks were not observed for the oxygen-treated catalyst. This implies that well dispersed small Pt particles exist on the catalyst. This result was continued by high resolution transmission electron microscopy (HRTEM) analysis. Consequently, it can be concluded that highly dispersed Pt nanoparticles could be prepared by the novel pretreatment technique and thus, CO conversion could be increased considerably especially at the low temperatures below $100^{\circ}C$.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1988년도 전기.전자공학 학술대회 논문집
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• pp.571-573
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• 1988

A new ripple analog-to-digital converter(ADC) has been developed. It consists of two parallel ADCs and a switching network. The circuit operates on the input signal in two serial steps. First a coarse conversion is made to determine the most significant bits by the first parallel ADC. The results control a switching network to connect the series resistor segment, the analog signal is contained within, to the second parallel ADC. At second step, a fine conversion is made to determine the least signification bits by the second parallel ADC. The circuit requires 2(2$\frac{N}{2}$) comparators, 2(2$\frac{N}{2}$) resistors, and 2(2$\frac{N}{2}$) switches for N-bit resolution.

• Current Optics and Photonics
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• 제1권2호
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• pp.150-156
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• 2017

A diffraction limited optical system for head mounted displays (HMDs) was designed. This optical system consists of four modules, including 1:5 mm and 5:30 mm beam expanders, polarization grating-polarization conversion system (PG-PCS) and refractive/diffractive projection optical module. The PG-PCS module transforms the unpolarized Gaussian beam to a linearly polarized beam and it simultaneously homogenizes the spatial intensity profile. The optical projector module has a $30^{\circ}$ field of view, a 22 mm eye relief, and a 10 mm exit pupil diameter with a compact structure. Common acrylic materials were utilized in the optical design process; therefore, the final optical system was lightweight. The whole optical system is suitable for a 0.7 inch liquid crystal on silicon microdisplay (LCOS) with HDTV resolution ($1920{\times}1080$) and $8.0{\mu}m$ pixel pitch.

• 한국전자통신학회논문지
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• 제4권1호
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• pp.33-36
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• 2009

Incremental converters provide a solution for such measurement applications, as they retain most of the advantages of conventional ${\Delta}{\Sigma}$ converters, and yet they are capable of offset-free and accurate conversion. Most of the previous research on incremental converters was for single-channel and dc signal applications, where they can perform extremely accurate data conversion with more than 20-bit resolution. In this paper, a design technique for implementing multi-channel incremental data converters to convert narrow bandwidth ac signals is discussed. It incorporates the operation principle, topology, and digital decimation filter design. The theoretical results are verified by simulation results.

• 한국컴퓨터정보학회:학술대회논문집
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• 한국컴퓨터정보학회 2015년도 제52차 하계학술대회논문집 23권2호
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• pp.268-271
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• 2015

본 논문에서는 고해상도 비디오를 위한 프레임 레이트 변환 방법을 제시한다. 서로 다른 방식이나 포맷을 가진 영상 신호를 변환할 때에는 시각적으로 거슬리는 움직임 지터(motion jitter)나 영상의 모서리에서의 블러링(blurring) 현상이 일어날 수 있다. 제시하는 방법에서는 이러한 문제점을 해결하기 위해 양방향 움직임 추정/보상을 이용하여 프레임 레이트를 증가 변환한다. 또한 보다 정확한 움직임 벡터를 찾기 위해 다중 프레임을 통한 양방향 탐색 방법을 제안한다. 먼저, 픽셀 값을 알고 있는 현재 프레임과 이전 프레임간의 움직임 벡터를 이용하여 양방향 움직임 벡터를 얻는다. 얻은 움직임 벡터는 벡터 스무딩 블록을 거친다. 그 후 OBMC(Overlapped Block Motion Compensation)를 이용하여 보간 프레임을 구성한다. 실험 결과는 기존 방법들보다 제안 방법이 주관적 화질 면에서 우수함을 나타낸다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1993년도 하계학술대회 논문집 A
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• pp.450-452
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• 1993

In this study, a method is suggested to design the A/D conversion system which has high resolution to convert load cell signal. First, hardware was designed to reduce the offset voltage of integrator and comparator. And then, a calibration software technique was performed to obtain the stable data from A/D converter. The optimal parameters of each elements in the circuits was selected using the SPICE simulation. The main advantage of our method is high precision A/D converter can be constructed with low cost and high confidence. Therefore proposed method is expected to be used in the industrial field where a high precision measurement is required.

• 한국광학회지
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• 제14권6호
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• pp.573-577
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• 2003

Hong-Ou-Handel 간섭계를 이용한 광자쌍의 4차 간섭실험에서 두 광자의 뭉침이 단일계수에 미치는 영향을 조사하였다. 검출기의 단일광자 시간 분해능보다 짧은 시간간격으로 두 광자가 검출기에 입사할 때 하나의 검출기에서 측정되는 단일계수가 현저하게 줄어드는 변화를 확인하였다.

• KSBB Journal
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• 제23권3호
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• pp.257-262
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• 2008

본 연구에서는 lipase를 이용한 라세믹-naproxen 2,2,2-trifluoroethyl thioester의 광학분할 반응을 향상시키기 위하여 반응 용매, 반응 온도, 기질 및 lipase 농도 그리고 교반속도의 변수들을 최적화 하였고, isooctane과 물의 계변을 증가시키기 위한 계면 활성제의 영향을 조사하였다. 조사된 유기용매 중 isooctane이 가장 높은 전환율 (92.19%), $V_s\;(2.340{\times}10^{-2}mM/h)$, E값 (36.12) 그리고 $V_s/(E_t)$ ($7.80{\times}10^{-4}mmol/h{\cdot}g$)를 나타내어 lipase 를 이용한 라세믹-naproxen2,2,2-trifluoroethyl thioester의 광학 분할 반응을 위한 가장 효과적인 유기용매로 판단하였다. 반응 표면 분석법을 이용한 반응조건 최적화에서는 반응 온도 $48.2^{\circ}C$, 기질 농도 3.51 mM, lipase 농도 30.11 mg/ml 그리고 교반속도 180 rpm을 최적 반응 조건으로 도출하였고, 이 최적화된 반응 조건으로 광학분할 반응을 수행한 결과, $V_s$, $V_s/(E_t)$ 그리고 전환 율이 각각 19.54%, 19.12%, 4.05% 증가하였다. 계면활성제로써 첨가된 NP-10은 (S)-naproxen 2,2,2-trifluoroethyl thioester의 가장 높은 전환율 (89.43%)을 나타내었고, 반응속도의 감소를 둔화시켰으며, lipase의 광학선택성 (E=59.24)을 향상시켰다.

• 한국환경과학회지
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• 제29권1호
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• pp.95-108
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• 2020

Silver nanoparticles were loaded onto g-C₃N₄ (CN) with a nanoroll-type morphology (Ag/CN) synthesized using a co-polymerization method for highly selective conversion of toxic nitrobenzene to industrially-valuable aminobenzene. Scanning electron microscopy and high-resolution transmission electron microscopy (HRTEM) images of Ag/CN revealed the generation of the nanoroll-type morphology of CN. Additionally, HRTEM analysis provided direct evidence of the generation of a Schottky barrier between Ag and CN in the Ag/CN nanohybrid. Photoluminescence analysis and photocurrent measurements suggested that the introduction of Ag into CN could minimize charge recombination rates, enhancing the mobility of electrons and holes to the surface of the photocatalyst. Compared to pristine CN, Ag/CN displayed much higher ability in the photocatalytic reduction of nitrobenzene to aminobenzene, underscoring the importance of Ag deposition on CN. The enhanced photocatalytic performance and photocurrent generation were primarily ascribed to the Schottky junction formed at the Ag/CN interface, greater visible-light absorption efficiency, and improved charge separation associated with the nanoroll morphology of CN. Ag would act as an electron sink/trapping center, enhancing the charge separation, and also serve as a good co-catalyst. Overall, the synergistic effects of these features of Ag/CN improved the photocatalytic conversion of nitrobenzene to aminobenzene.