• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.644-652
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• 2016

This paper presents an improved single-stage ac-dc LED-drive flyback converter using the transformer-coupled lossless (TCL) snubber. The proposed converter is derived from the integration of a full-bridge diode rectifier and a conventional flyback converter with a simple TCL snubber. The TCL snubber circuit is composed of only two diodes, a capacitor, and a transformer-coupled auxiliary winding. The TCL snubber limits the surge voltage of the switch and regenerates the energy stored in the leakage inductance of the transformer. Also, the switch of the proposed converter is turned on at a minimum voltage using a formed resonant circuit. Thus, the proposed converter achieves high efficiency. The proposed converter utilizes only one general power factor correction (PFC) control IC as its controller and performs both PFC and output power regulation, simultaneously. Therefore, the proposed converter provides a simple structure and an economic implementation and achieves a high power factor without the need for any separate PFC circuit. In this paper, the operational principle of the proposed converter is explained in detail and the design guideline of the proposed converter is briefly shown. Experimental results for a 40-W prototype are shown to validate the performance of the proposed converter.

• 전기학회논문지P
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• 제67권2호
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• pp.82-89
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• 2018

This paper presents a novel prototype of dual mode control based phase shift ZVS PWM high frequency load resonant inverter with lossless snubber capacitors in addition to a single active auxiliary resonant snubber for electromagnetic induction heating(IH) foam metal based consumer fluid dual packs(DPA) heater. The operating principle in steady state and unique features of this voltage source soft switching high frequency inverter circuit topology are described in this paper. The lossless snubber and auxiliary active resonant snubber assisted constant frequency phase shift ZVS PWM high frequency load resonant inverter employing IGBT power modules actually is capable of achieving zero voltage soft commutation over a widely specified power regulation range from full power to low power. The steady state operating performances of this dual mode phase shift PWM series load resonant high frequency inverter are evaluated and discussed on the basis of simulation and experimental results for induction heated foam metal heater which is designed for compact and high efficient moving fluid heating appliance in the consumer pipeline systems.

• 한국게임학회 논문지
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• 제9권6호
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• pp.171-178
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• 2009

다층 변위 매핑 기법은 여러 층으로 구성된 변위 맵들을 사용하여 단층의 변위 맵으로 표현할 수 없는 복잡한 형태를 재현할 수 있으며, 영화와 게임 등의 디지털 콘텐츠에서 보다 사실적인 표현을 저비용으로 제공할 수 있다. 하지만 다층 변위 맵 자료 구조의 특성상 표현을 자세히 할수록 여러 층의 변위 맵이 필요해지고 하단부의 변위 맵일수록 변위 정보를 저장하고 있지 않은 공간이 많이 생긴다. 본 논문에서는 저장 공간을 비효율적으로 사용하는 다층 변위맵을 비손실 압축하고 렌더링하는 방법을 제안한다. 제안하는 렌더링 방법은 비손실 압축 변위맵 정보를 사용하기 때문에 원본 변위 맵의 렌더링 결과와 동일한 화질을 보장한다.

• 한국게임학회 논문지
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• 제14권6호
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• pp.59-68
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• 2014

초고해상도 UHD($096{\times}2160$) 게임 영상의 메모리 대역폭 요구량은 기하급수적으로 늘어난다. 본 논문에서는 화질 저하 없이 메모리 대역폭 문제를 해결하기 위하여 CUDA 환경에서 비트 병렬 파이프라인을 지원하는 논문 [4]의 DDPCM-GR 압축 알고리즘을 변형한 DPCM-GR 방식을 적용한 무손실 압축을 구현하였다. CUDA 공유메모리 사용을 통한 효율성을 증대하였으며, paged-locked 호스트 메모리 비동기 전송을 통한 커널과 데이터 전송 중첩의 다양한 구성을 구현하였다. 실험을 통하여 CPU 방식에 비하여 최대 31.3배 속도 향상을 이루었으며, 비동기 전송 구성의 변화를 통하여 최대 30.3% 수행 시간이 감소하였다.

• 정보처리학회논문지B
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• 제13B권3호
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• pp.231-238
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• 2006

본 논문에서는 모바일 게임의 전체 용량 중 상당 부분을 차지하는 이미지를 무손실로 압축하기 위한 방법을 제안하였다. 이미지의 압축률을 높이기 위해 실제로 압축을 수행하기 전에 전처리 과정에서 이미지를 재구성 한 후 RFC-1951에 정의된 Deflate 알고리즘으로 압축하였다. 전처리 과정에서는 이미지의 정보를 바탕으로 사전 기반 부호화의 특징인 사전의 크기를 얻고, 픽셀 패킹과 DPCM 예측 기법을 사용하여 이미지를 재구성하는 방법을 사용하여 일반적인 방법으로 압축할 때 보다 압축률을 향상시켰다. 제안된 압축 방법을 다양한 모바일 게임 이미지에 적용하여 압축률을 실험한 결과 기존 모바일 이미지 포맷에 비해 약 9.7%의 압축률이 향상됨을 보였다.

• 디지털산업정보학회논문지
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• 제12권2호
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• pp.41-49
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• 2016

Lossless encryption methods are more applicable than lossy encryption methods when marginal distortion is not tolerable. In this research, the author propose a novel lossless symmetric key encryption/decryption technique. In the proposed algorithm, the image is transformed into the frequency domain using the lifting wavelet transform, then the image sub-bands are encrypted in a such way that guarantees a secure, reliable, and an unbreakable form. The encryption involves scattering the distinguishable frequency data in the image using a reversible weighting factor amongst the rest of the frequencies. The algorithm is designed to shuffle and reverse the sign of each frequency in the transformed image before the image frequencies are transformed back to the pixel domain. The results show a total deviation in pixel values between the original and encrypted image. The decryption algorithm reverses the encryption process and restores the image to its original form. The proposed algorithm is evaluated using standard security and statistical methods; results show that the proposed work is resistant to most known attacks and more secure than other algorithms in the cryptography domain.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 1999년도 KOBA 방송기술 워크샵 KOBA Broadcasting Technology Workshop
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• pp.83-88
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• 1999

In this paper, a novel gray-scale lossless image coder combining context-based minimum mean squared error (MMSE) prediction and entropy coding is proposed. To obtain context of prediction, this paper first defines directional difference according to sharpness of edge and gradients of localities of image data. Classification of 4 directional differences forms“geometry context”model which characterizes two-dimensional general image behaviors such as directional edge region, smooth region or texture. Based on this context model, adaptive DPCM prediction coefficients are calculated in MMSE sense and the prediction is performed. The MMSE method on context-by-context basis is more in accord with minimum entropy condition, which is one of the major objectives of the predictive coding. In entropy coding stage, context modeling method also gives useful performance. To reduce the statistical redundancy of the residual image, many contexts are preset to take full advantage of conditional probability in entropy coding and merged into small number of context in efficient way for complexity reduction. The proposed lossless coding scheme slightly outperforms the CALIC, which is the state-of-the-art, in compression ratio.

• Journal of Information Processing Systems
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• 제13권1호
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• pp.40-56
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• 2017

Since the progress of digital medical imaging techniques, it has been needed to compress the variety of medical images. In medical imaging, reversible compression of image's region of interest (ROI) which is diagnostically relevant is considered essential. Then, improving the global compression rate of the image can also be obtained by separately coding the ROI part and the remaining image (called background). For this purpose, the present work proposes an efficient reversible discrete cosine transform (RDCT) based embedded image coder designed for lossless ROI coding in very high compression ratio. Motivated by the wavelet structure of DCT, the proposed rearranged structure is well coupled with a lossless embedded zerotree wavelet coder (LEZW), while the background is highly compressed using the set partitioning in hierarchical trees (SPIHT) technique. Results coding shows that the performance of the proposed new coder is much superior to that of various state-of-art still image compression methods.

• 전자공학회지
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• 제28권6호
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• pp.92-92
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• 2001

• ETRI Journal
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• 제32권2호
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• pp.319-326
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• 2010

Photonics offers a solution to data communication between logic devices in computing systems; however, the integration of photonic components into electronic chips is rather limited due to their size incompatibility. Dimensions of photonic components are therefore being forced to be scaled down dramatically to achieve a much higher system performance. To integrate these nano-photonic components, surface plasmon-polaritons and/or energy transfer mechanisms are used to form plasmonic chips. In this paper, the operating principle of plasmonic waveguide devices is reviewed within the mid-infrared spectral region at the 2 ${\mu}m$ to 5 ${\mu}m$ range, including lossless signal propagation by introducing gain. Experimental results demonstrate that these plasmonic devices, of sizes approximately half of the operating free-space wavelengths, require less gain to achieve lossless propagation. Through optimization of device performance by means of methods such as the use of new plasmonic waveguide materials that exhibit a much lower minimal loss value, these plasmonic devices can significantly impact electronic systems used in data communications, signal processing, and sensors industries.