• 한국정보과학회논문지:컴퓨팅의 실제 및 레터
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• 제14권8호
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• pp.793-797
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• 2008

멀티미디어 서비스의 다양한 재생장치와 네트워크 환경에 적용 가능한 멀티미디어 코덱을 위해 ISO/IEC MPEG와 ITU-T VCEG의 JVT팀에서는 계층구조를 가지는 H.264/AVC Scalable Video Coding(SVC)을 제안하였다. H.264/AVC SVC는 향상계층의 비트율과 왜곡에 관한 효율을 높이기 위해 계층 간 예측, 계층적 B 구조 등 다양한 기법이 적용하며 이로 인해 계산복잡도가 증가하여 부호화 시간이 길어지는 단점이 있다. 본 논문에서는 부호화 시간을 단축시키기 위해 예측모드를 분석하고 그 결과에 따라 기준 값을 선정하여 단계적으로 예측모드를 선택하는 기법을 제안한다. 실험결과 제안하는 기법이 계산복잡도를 감소시켜 평균 38%의 부호화 시간을 단축시키며 화질의 저하는 평균 0.01dB로 무시할 수 있을 정도로 작음을 확인하였다.

• 동력기계공학회지
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• 제5권2호
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• pp.13-21
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• 2001

Diesel emission control is being addressed worldwide to help preserve the global environment. This paper mainly deals with the effects of oxidation catalysts to reduce emissions from the automotive heavy-duty diesel engine. Two types of the oxidation catalyst with different kinds of precious material were used. An 11 litter displacement diesel engine with turbocharger was operated to evaluate DOC with various engine speed, load conditions under D-13 mode cycle. We could propose the detail emission data of an automotive heavy-duty diesel engine and the characteristics of the conversion efficiency of the DOC under the D-13 mode. It was found that the mean conversion efficiencies of CO and THC were 49.7% and 61% under the D-13 mode test, respectively.

• Smart Structures and Systems
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• 제20권5호
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• pp.525-537
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• 2017

This paper explores different vibration control strategies for the cancellation of human-induced vibration on a structure with time-varying modal parameters. The main motivation of this study is a lively urban stress-ribbon footbridge (Pedro $G\acute{o}mez$ Bosque, Valladolid, Spain) that, after a whole-year monitoring, several natural frequencies within the band of interest (normal paring frequency range) have been tracked. The most perceptible vibration mode of the structure at approximately 1.8 Hz changes up to 20%. In order to find a solution for this real case, this paper takes the annual modal parameter estimates (approx. 14000 estimations) of this mode and designs three control strategies: a) a tuned mass damper (TMD) tuned to the most-repeated modal properties of the aforementioned mode, b) two semi-active TMD strategies, one with an on-off control law for the TMD damping, and other with frequency and damping tuned by updating the damper force. All strategies have been carefully compared considering two structure models: a) only the aforementioned mode and b) all the other tracked modes. The results have been compared considering human-induced vibrations and have helped the authors on making a decision of the most advisable strategy to be practically implemented.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제48권9호
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• pp.467-475
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• 1999

This paper presents an analysis method of a forward converter, using both the finite element method considering the external circuit and a state variables equation. The converter operates at 50kHz and its one period is divided into two modes for the simplicity of the analysis. In the first mode, the switching transistor turns on and an input power is transferred into the load by the electromagnetic conversion action of a ferrite transformer. In the second mode, the switching transistor turns off and the stored energy in an inductor is delivered to the load, and the transformer core is demagnetized by the reset winding current. In this paper, time-stepping finite element method taking into account the on-state electrical circuit of the converter in used to analyze both the electrical circuit and electromagnetic field of the magnetic device during the first mode and the demagnetization period of the transformer core. Then a state variables equation for the circuit which the inductor current flows is constituted and solved during the second mode. As a result, the simulation results have been good agreement with the results obtained form experiment.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제54권12호
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• pp.601-608
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• 2005

This paper presents a novel single-stage high-power-factor electronic ballast for fluorescent lamps operating in critical conduction mode. The proposed topology is based on integration of boost converter as power factor corrector(PFC) and a half-bridge high frequency parallel resonant inverter into a single stage. The input stage of the boost converter is operating in critical conduction mode for positive and negative half cycle voltage respectively at line frequency(60Hz). So that a boost converter makes the line current follow naturally the sinusoidal line voltage waveform. The simulated and experimental results for 100W fluorescent lamps operating at 42kHz switching frequency and 220V line voltage have been obtained. This proposed inverter will be able to be practically used as a power supply in various fields as induction heating applications, fluorescent lamp and DC-DC converter etc.

• 방송공학회논문지
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• 제10권3호
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• pp.348-356
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• 2005

본 논문에서는 H.264로 부호화 된 비트스트림을 이전보다 낮은 비트율을 갖는 비트스트림으로 변환시키기 위한 고속 비트율 감축 트랜스코딩을 제안한다. 제안된 트랜스코딩 기법은, 복호기에서 나온 블록 모드 정보와 움직임 벡터를 이용하여, 확률 기반의 블록 모드 결정 기법과 움직임 벡터 재사용 및 정제 기법을 사용하였다. 그 결과, 직렬 화소 영역 트랜스코딩과 비교하였을 때 약 0.1$\∼$0.3 dB 정도의 화질 저하가 있지만, 부호화 시간을 비교하였을 때 약 40배 빠른 결과를 얻었다.

• Journal of the Optical Society of Korea
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• 제9권4호
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• pp.135-139
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• 2005

We demonstrate a simple and effective wavelength-tunable add/drop filter suitable for coarse wavelength division multiplexing (CWDM) systems. The filter consists of two fibers in contact side by side, with identical long-period fiber gratings (LPG) in each fiber. The LPG couples the power in the fundamental core mode to one of the cladding modes, which is then coupled to the same order cladding mode in the other fiber through evanescent-field coupling between two fibers. Finally, the cladding mode in the second fiber is coupled to its core mode with the help of the other LPG. With an optimal longitudinal offset distance of 10 em, coupling efficiency as high as -1.68 dB and side lobes smaller than -24 dB were experimentally obtained. The experimental results agreed well with the theoretical ones. The operating wavelength of the proposed add/drop filter was tunable by varying the temperature. The temperature sensitivity was measured to be -0.43 nm/$^{\circ}C$.

• 한국전자거래학회지
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• 제23권3호
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• pp.1-12
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• 2018

혼합 중요도 시스템은 중요도가 다른 컴포넌트의 조합으로 이루어져 있다. 최근 자동차 시스템과 항공기 시스템에서 사용되는 ISO 26262와 DO-178B 표준에서는 컴포넌트를 중요도에 따라 분류하고 있다. 기존 혼합 중요도 시스템 연구에서는 시스템 모드를 통해서, 효율적이면서 안전한 스케줄링을 추구했다. 이러한 연구의 단점은 고중요도 모드에서 저중요도 작업의 성능저하이다. 이러한 문제를 개선하고자 작업별 중요도 모드를 도입하여 저중요도 작업의 성능을 개선하고 확률적 성능 지표를 설계했다. 시뮬레이션을 통해서 기존 연구 대비 성능 향상 효과를 보였다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2021년도 추계학술대회
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• pp.640-642
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• 2021

많은 데이터들을 명확하고 효율적으로 수집하려면, 현재 설비들의 위치들을 파악하고 이동 데이터를 분석하는 것이 필수적이다. 현재 위치 수집을 위한 기술은 GPS (Global Positioning System) 센서를 이용하여 데이터 수집을 진행할 수 있으나, GPS의 경우 직진성이 강하며, 회절과 반사율이 낮아 실내 측위가 힘드며, 블루투스를 활용한 시리얼 통신은 신호 감도를 받을 수 없어서 서버와 클라이언트 간의 거리 측정이 불가능하다. 본 논문은 라즈베리파이3 B+에 비콘과 스캐너를 활용한 실내측위 시스템을 구현하고 있다. 스캐너 알고리즘을 이용하여 Advertise Mode와 Connection Mode를 동시에 제어한다.

• 미생물학회지
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• 제28권4호
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• pp.351-363
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• 1990

A mutant was selected by NTG treatment of Mycobacterium sp. NRRL B-3805, which was capable of degrading plant sterol to androsta-4-ene-3, 17-dione and yields was higher than NRRL B-3805. Also this mutant produced androst-4-ene-3, 17-dione faster than NRRL B-3805. It described the mode of sitosteroidal degradation, and the interrelation between cell membrane and its attachment to substrate during the sterol degradation process by this mutant and it was compared with Mvcobacterium sp. NRRL B-3805.