• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2017년도 춘계학술대회
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• pp.691-693
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• 2017

본 논문에서는 시간 차 감지기와 LSI(Lock Status Indicator)를 사용하여 빠른 위상고정 시간을 갖는 위상고정루프를 제안하였다. 제안된 위상고정루프는 1.8V $0.18{\mu}m$ CMOS 공정을 사용하여 설계하였고, Hspice 시뮬레이션을 통해 회로의 동작을 검증하였다.다음은 요약문입니다.

• Membrane and Water Treatment
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• 제13권4호
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• pp.201-208
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• 2022

Emulsion Liquid Membrane (ELM) is a prominent technique for the separation of heavy metal ions from wastewater due to the fast extraction and is a single-stage operation of stripping-extraction. The selection of the components (Surfactant and Carrier) of ELM is a very significant step for its preparation. In the ELM technique, the primary water- in-oil (W/O) emulsion is emulsified in water to produce water-in-oil-in-water (W/O/W) emulsion. The water in oil emulsion was prepared by mixing the membrane phase and internal phase. To prepare the membrane phase, the extractant D2EHPA (di-2-ethylhexylphosphoric acid) was used as a mobile carrier, Span-80 as a surfactant, and Paraffin as a diluent. Moreover, the internal (receiving) phase was prepared by dissolving sulphuric acid in water. Di-(2- ethylhexyl) phosphoric acid such as surfactant concentration, carrier concentration, sulphuric acid concentration in the receiving (internal) phase, agitation time (emulsion phase and feed phase), the volume ratio of the membrane phase to the receiving phase, the volume ratio of the external feed phase to the primary water-in-oil emulsion and pH of feed were studied on the percentage extraction of metal ions at 20℃. The results show that it is possible to remove 78% for As(V), 98% for Cd(II), and 99% for Pb(II). Emulsion Liquid Membrane (ELM) is a well-known technique for separating heavy metal ions from wastewater due to the fast extraction and is a single-stage operation of stripping-extraction. The selection of ELM components (Surfactant and Carrier) is a very significant step in its preparation. In the ELM technique, the primary water-in-oil (W/O) emulsion is emulsified to produce water-in-oil-in-water (W/O/W) emulsion. The water in the oil emulsion was prepared by mixing the membrane and internal phases. The extractant D2EHPA (di-2-ethylhexylphosphoric acid) was used as a mobile carrier, Span-80 as a surfactant, and Paraffin as a diluent. Moreover, the internal (receiving) phase was prepared by dissolving sulphuric acid in water. Di-(2-ethylhexyl) phosphoric acid such as surfactant concentration, carrier concentration, sulphuric acid concentration in the receiving (internal) phase, agitation time (emulsion phase and feed phase), the volume ratio of the membrane phase to the receiving phase, the volume ratio of the external feed phase to the primary water-in-oil emulsion and pH of feed were studied on the percentage extraction of metal ions at 20℃. The results show that it is possible to remove 78% for As(V), 98% for Cd(II), and 99% for Pb(II).

• Journal of Electrical Engineering and Technology
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• 제9권6호
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• pp.1988-1994
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• 2014

In a single-phase grid-connected power system consisting of a DC/DC converter and a DC/AC converter, the current drawn from renewable energy sources has a tendency to be pulsated and contains second-order frequency ripple components, which results in several drawback such as a power harvesting loss and a shortening of the energy source's life. This paper presents a new second-order harmonic current reduction scheme with a fast dc-link voltage loop for two-stage dc-dc-ac grid connected systems. In the frequency domain, an adequate control design is performed based on the small signal transfer function of a two-stage dc-dc-ac converter. To verify the effectiveness of proposed control algorithm, a 1 kW hardware prototype has been built and experimental results are presented.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 하계학술대회 논문집 Vol.3 No.2
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• pp.1132-1135
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• 2002

In this paper, we propose a phase-locked loop (PLL) with dual loops in which advantages of both loops can be combined. Frequency-locked loop (FLL) which is composed of two frequency-to-voltage converters (FVC) and an amplifier makes the frequency synchronize very fast and output signal is synchronized in phase with the input reference signal by charge pump PLL. This structure can improve the trade-off between acquisition behavior and locked behavior.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1303-1310
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• 2000

GPS carrier phase is supposed to provide the tool for the most precise 3 dimensional positioning information. The FAST, an OTF technique, has been developed by the GPS System Laboratory of Konkuk University, and has been shown several millimeter level accuracy in root-mean-square sense. This OTF's high precision positioning capability provides an adequate tool of low frequency vibration monitoring of large structures. In this paper, the possibility of vibration measurement of a cantilever beam using FAST has been tested, which is supposed to be extended to more practical applications. The results of the experiment have been compared with those by a strain gage and laser sensor.

• 전력전자학회논문지
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• 제23권2호
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• pp.147-151
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• 2018

Phase-shift fullbridge (PSFB) converter detects the current in the primary side for operation of the peak current mode controller (PCMC). The PCMC must used the slope compensation to solve the problem when the effective duty is over 0.5. The voltage response of PSFB converters has slower than that of buck converter because of slew interval even if the voltage controllers of two converters have same bandwidth. To overcome these problems, this work proposes a compensating method of current reference considering slew interval and fast response in the PSFB converter. The effectiveness of the proposed method is proven using the PSIM simulation and experiment.

• ETRI Journal
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• 제36권4호
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• pp.537-544
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• 2014

In this paper, we present a new inter-carrier interference (ICI) self-cancellation scheme - namely, ISC scheme - for orthogonal frequency-division multiplexing systems to reduce the ICI generated from phase noise (PHN) and residual frequency offset (RFO). The proposed scheme comprises a new ICI cancellation mapping (ICM) scheme at the transmitter and an appropriate method of combining the received signals at the receiver. In the proposed scheme, the transmitted signal is transformed into a real signal through the new ICM using the real property of the transmitted signal; the fast-varying PHN and RFO are estimated and compensated. Therefore, the ICI caused by fast-varying PHN and RFO is significantly suppressed. We also derive the carrier-to-interference power ratio (CIR) of the proposed scheme by using the symmetric conjugate property of the ICI weighting function and then compare it with those of conventional schemes. Through simulation results, we show that the proposed ISC scheme has a higher CIR and better bit error rate performance than the conventional schemes.

• 한국자동차공학회논문집
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• 제10권5호
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• pp.90-97
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• 2002

The interaction between airflow and liquid phase LfG (Liquefied Petroleum Gas) sprays was investigated in a steady flow system embodied in a wind tunnel to simulate the variety of flow inside intake port of LPG engines with liquid injection system. The spray developments in flowing fields with the mean velocities of 5.4, 21.5 and 42.4m/s were identified by spray visualization techniques such as Mie scattering and shadowgraph. The microscopic visualization using a telescopic lens system was performed to investigate the shape and size of liquid droplets in the spray. PDA measurement was used to get 1-dimensional velocity and diameter of liquid droplets. The fast co-flows make the spray field be compact and be lead upward to the injection direction. SMD of the spray was smaller at the fast flowing field. Spray width got bigger and SMD of the spray was smaller with higher injection pressure.

• 한국안광학회지
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• 제10권4호
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• pp.305-312
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• 2005

분 논문에서는 Lohmann 방법과 FFT (fast Fourier transform)를 사용하여 홀로그램을 제작하였다. 먼저 수학적으로 정의되는 물체의 $128{\times}128$로 표본화된 점들에 대한 복소 파면을 FFT 연산으로 구하였다. 그리고 Lohmann의 방법을 사용하여 각각의 표본점에 대한 복소 파면의 진폭과 위상을 홀로그램 정보로 바꾸었다. PC와 레이저 프린터를 용하여 홀로그램 도면을 그렸으며, 그 도면을 사진 축소하여 CGH(computer generated holograms) 필름을 제작하였다. 헬륨-네온 레이저와 역퓨리에 변환 광학계를 사용하여 수학적으로 정의되는 물체의 홀로그램 상을 재생하였다. $32{\times}32$, $64{\times}64$, $128{\times}128$의 표본수, random 위상의 적용 여부, 진폭 절단 및 CGH 필름의 표백 정도에 따라 변화하는 홀로그램 상의 특성을 조사하였다. 이 실험을 통하여 우수한 홀로그램 상을 재생할 수 있는 최적 조건과 홀로그램 상에서 스페클 잡음을 줄일 수 있는 최적 조건을 얻을 수 있었다. 2진 위상 홀로그램을 프로그램하기 위하여 Lohmann의 알고리즘을 MS Visual BASIC 6.0으로 구현하였다.

• 한국전자파학회논문지
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• 제16권11호
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• pp.1123-1130
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• 2005

본 논문에서는 PAPR 저감 기법인 SPW(Sub-block Phase Weighting) 기법에서 PAPR(Peak-to-Average Power Ratio)이 저감되도록 조절한 부가 정보를 처리하는 방법을 제안한다. SPW기법은 입력 데이터를 여러 개의 서브블록으로 나누고 위상 회전 벡터를 곱해주는 것으로 피크 전력을 줄여준다. SPW 기법은 부반송파 수와 변조방식, 서브 블록의 수가 PTS 기법과 같을 때 서로 유사한 점을 지니고 있지만, 오직 한 개의 IFFT(Inverse Fast Fourier Transform)를 사용한다는 점에서 기존의 PTS(Partial Transmit Sequence)나 SLM(Selected Mapping) 기법과는 다르다. SPW기법은 비록 PAPR을 효율적으로 줄일 수 있지만 계산 복잡도 문제는 여전히 존재한다. 본 논문에서는 위상 조절을 위 한 방법으로서 flipping 알고리즘과 full iteration 알고리즘을 사용하였다. 컴퓨터 시뮬레이션을 통하여 제안 방식의 특성을 분석하고 성능을 검토하였다.