• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.3
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• pp.36-44
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• 2006

In general, the generated harmonics and noise of the PWM inverter are affected by PWM switching method, switching frequency, dv/dt and di/dt. Since multilevel inverters are often applied to the high power system, and operates with low switching frequency, theyproduce large size of harmonic contents and noise. Thus it is necessary to install output filters in the multilevel inverter. In this paper a filter design approach for the harmonic and noise reduction the three phase induction motor driving system using H-bridge 7-level inverter system is presented. The passive filter that has low cost and simple structure and can effectively reduce harmonics and noise, is designed and applied to the three phase induction motor drive having multilevel inverter system. The designed system is implemented and verified by simulation and experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.2064-2071
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• 1998

A new digital clock level translator has been designed in order to produce a clock source of the internal logic circuits. The translator output has 50% duty ratio from small sinusoidal input such as TCXO which oscillates itself in poratable components. The circuit consists of positive and negative comparators, RS latch, charge pump, and reference vol- tage generator. It detects pulse width of the output waveform and feedbacks the control signal to the input com-parator. It detects pulse width of the output waveform and feedbacks the control signal to the input com-parator reference, producing output waveform with valid 50% duty ratio of the digital signal level. The designed level translator can be used as a sampling clock source of ADC, PLL and the colck source of the clock synthesizer. The circuit wasdesigned in a 0.8.mu.m analog CMOS technology with double metal, double poly, and BSIM3 circuit simulation model. From our experimental results, a stable operating characteristics of 50 +3% duty ratio was obtained from the sinusoidal input wave of 370 mV.

• Journal of the Institute of Convergence Signal Processing
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• v.11 no.4
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• pp.310-319
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• 2010

In this paper, digital watermarking method using wavelet transform and quad-tree algorithm is proposed. The proposed algorithm transforms the input image by DWT(Discrete Wavelet Transform) and AWPT(Adaptive Wavelet Packet Transform), inserts the watermark by quad-tree algorithm and the Cox's algorithm. The simulation for performance analysis of the proposed algorithm is implemented about the effect of embedding watermark in each subband coefficient (HH, LH, HL) of DWT, each DWT level, and each AWPT level. The simulation result by using DWT is compared with that using AWPT in the proposed algorithm. In addition, the effect of embedding watermark in the lowest frequency band (LL) is simulated. As a simulation result using DWT, the watermarking performance of simultaneously embedding in HH, LH, and HL band of DWT(6 level) is better than that of different cases. The result of AWPT(3 level) improves the correlation value compared to that of DWT(3 level). In addition, insertion the watermark to the LL band about 30~60% of all watermarks improves the correlation value while PSNR performance decreases 1~2dB.

• The Transactions of the Korea Information Processing Society
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• v.1 no.4
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• pp.490-501
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• 1994

In this study the problems of cell marking method used in the field of ATM network traffic control are presented. Also an extended cell marking method considering the user level priority is proposed. The conventional traffic monitoring schemes set the CLP bit of a cell to 1 only under the circumstance of the violation of traffic contract. It causes that the number of low level cells increases and the levels of cells are lowered regardless of the user level priority. The three level priority control method combining FCI bit with CLP bit has also been proposed. It divides CLP=0 cells into two levels. Consequently, the proposed method preserves more cells in high level than the conventional one and the real loss of high level cells can be reduced. The performance of the proposed scheme has also been analyzed by the PBS(partial buffer sharing) with two thresholds for the proposed three levels. The result shows that the PBS with two thresholds can give more efficient control than the scheme with no priority, or the PBS with one threshold.

• Korean Journal of Remote Sensing
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• v.35 no.3
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• pp.389-400
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• 2019

Level meters are non-invasively capable of measuring the level of the medium, and a growing variety of level meters are being used in the industry in connection with safety and maintenance. The level meter can be measured according to various kinds of medium such as solid medium such as coal, flour, rice and liquid medium such as water and petroleum. In order to reduce the error depending on the medium, the measurement using the Doppler Effect can compensate the measurement error, However, the number of signal processing steps is increased, the operation speed is further increased, the hardware complexity increases, and a high cost structure is required. In this paper, we propose a method to improve the signal processing operation structure of the remote measurement level meter to reduce the amount of computation and the resource usage of the required FPGA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38C no.10
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• pp.928-936
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• 2013

3D crosstalk is one of the disturbing things to recognize 3D images. This is caused by the phenomenon that input image for left eye is transferred at the right eye and right eye is transferred at the left eye because of the imperfect isolation by the device characteristics. In this paper, we review the 3D PDP (Plasma Display Panel) operation using active shutter glasses and crosstalk measurement method and investigate the major cause of 3D crosstalk and extend conventional 3D crosstalk using full white and full black image input to Gray-to-Gray (GtoG) 3D crosstalk. We suggest a specific method to reduce Gray-to-Gray 3D crosstalk by using Look up Table (LUT) and sub-field mapping in PDP. And then, we verify the method by measuring GtoG 3D crosstalk rate through specific test images and numerical results.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.15-16
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• 2013

전기자동차용 급속 충전기에서 전력변환 효율은 절연형 DC-DC 컨버터에 의해 좌우된다. 이때 DC-DC 컨버터의 출력 전압 범위가 넓기 때문에 기존의 3레벨 컨버터를 사용할 경우 충전전압이 낮을 때 순환전류가 커지는 문제점이 있다. 본 논문에서는 넓은 충전전압범위를 갖는 전기자동차용 급속충전기를 위한 3레벨 DC-DC 컨버터의 하이브리드 스위칭 기법을 제안한다. 제안한 하이브리드 스위칭 기법은 충전전압이 낮을 때 순환전류를 줄일 수 있어 주로 낮은 배터리 전압에서 동작하는 CC충전 모드 시 도통 손실을 줄일 수 있다. 또한 커플인덕터를 사용하여 순환전류를 줄이고 Lagging Lag 스위치의 ZCS 턴오프를 성취시켜 손실을 줄일 수 있다. 기존의 스위칭 방법과 하이브리드 스위칭 기법에 따른 손실을 비교하여 제안한 스위칭 기법의 타당성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2013.11a
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• pp.19-20
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• 2013

3상 250레벨의 MMC형 HVDC시스템의 구현에서는 한 개의 상마다 500여개의 SM(sub module)이 필요하게 되고 MM(master module)에서 10Khz의 샘플링을 처리한다고 하면 100us동안에 500여개의 SM에서 각종 데이터를 받아서 처리한 후에 다시 SM에 처리된 정보를 전송해 줘야한다. 따라서 SM에서 데이터를 받고 전송하는데 따른 100us 동안의 필요한 처리양과 네트워크의 속도 및 오버헤드(overhead)등의 구성과 토포로지에 관해 알아보았고, 이를 적용하여 멀티레벨의 HVDC에 필요한 데이터 네트워크에의 전송량 계산에 대한 소프트웨어를 제작하여 손쉽게 설계할 수 있도록 하였다.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.356-357
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• 2011

3-레벨 중성점 다이오드 클램프 (NPC) 인버터는 우수한 토폴로지로 알려져 있지만 구조적으로 중성점 전위가 변동하는 문제가 내제하고 있다. 본 논문에서는 3-레벨 NPC 인버터 중 성점 전압의 변동을 제어하기 위해 중성점 전류의 예측을 활용한 간단한 제어 기술이 제안되었다. 제안된 방법은 한 샘플링 앞선 시점의 중성점 전류를 예측하고 중성점 평형 요소를 포함하는 오프셋 전압(Voffset)을 이용하여 중성점 전압을 제어 한다. 중성점 전위 변동은 간단히 제어할 수 있고 제안된 중성점 전압 제어의 유효함은 시뮬레이션 결과를 통해 입증하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.439-441
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• 2003

최근 3D 가상환경에서 아바타를 활용한 분야가 많은 관심을 받고 있으며, 아바타를 이용함으로써 사람들의 흥미를 효과적으로 이끌어 낼 수 있는 장점을 가진다. 현재 이러한 아바타의 행위를 생성하고 제어하기 위해 모션캡쳐 장비를 이용하거나 3D MAX와 같은 전문 그래픽 편집툴, 혹은 자체 개발된 특정 어플리케이션등을 사용하고 있다. 그러나 이와 같은 기존 환경은 비용이 많이 들거나 생성된 아바타 행위의 활용이 특정 어플리케이션 환경에 국한되어 재사용이 어려운 단점이 있다. 본 연구에서는 이러한 기존의 문제점을 해결하기 위해 다양한 도메인 환경에서 필요로 하는 작업레벨의 아바타 행위를 생성, 제어할 수 있는 3D 아바타 행위 편집기를 제안하고자 한다. 본 편집기를 통해서 사용자는 아바타 객체를 직접 조작하여 원하는 작업레벨 행위를 생성하고, 생성된 행위는 표준 아바타형식인 H-anim을 지원하는 XML 스크립트로 저장되어 모든 애플리케이션에서 제약 없이 사용할 수 있다. 또한 저장된 스크립트의 간단한 파라미터 조작만으로 새로운 행위를 생성할 수 있으므로 스크립트의 재사용이라는 측면에서 효과적이다.