• 전자공학회논문지
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• 제52권4호
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• pp.175-183
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• 2015

본 논문은 글자 영상을 효과적으로 확대 (up-scaling)하기 위한 학습 기반 초고해상도 (super-resolution; SR) 기법을 제안한다. 제안 기법은 크게 학습 단계와 합성 단계로 나뉜다. 학습 단계에서 다양한 HR (high-resolution) /LR (low-resolution) 글자 영상 쌍들을 수집한다. LR영상들은 양자화를 하고, 충분히 많은 수의 HR-LR 블록쌍들을 추출한다. 양자화된 LR블록을 기준으로 블록 쌍들을 소정의 개수의 클래스들로 구분한다. 클래스 별로 최적의 2D-FIR 필터 계수를 계산하고, 양자화한 후색인용 LR 블록과 함께 사전에 저장한다. 합성 단계에서 입력 LR 영상 내 각 블록을 양자화한 후 사전 내 양자화된 LR블록들과 정합하여 가장 근사한 블록에 대응하는 FIR 필터계수를 선정한다. 마지막으로 선택된 FIR필터로 HR 블록을 합성하여 최종적인 HR영상을 생성한다. 또한, 우리는 잡음이 있는 글자 영상에 대응하기 위해 학습과정에서 잡음 세기에 따른 복수개의 사전들을 제작한다. 입력 LR 영상의 잡음 레벨에 맞는 사전을 선택하여 HR영상을 합성한다. 실험 결과는 제안 기법이 종래 기법보다 잡음이 없는 환경에서는 물론 잡음이 있는 환경에서 우수한 주관적/객관적 화질을 가짐을 보인다.

• 한국소음진동공학회논문집
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• 제20권8호
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• pp.753-760
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• 2010

In this paper, the lifting analysis of a floating crane with a shipbuilding block is performed. Since floating cranes are operated in ocean waves, six degree-of-freedom motions are considered in the dynamic equations of motions of the floating crane and the block. The boom of the floating crane is considered as an elastic body in the analysis, and is modeled as three dimensional beam based on the finite element formulation. The hydrostatic and hydrodynamic forces by a regular wave are considered as external forces. By solving the equations of motions numerically, the dynamic responses of the floating crane and the block are simulated. The simulation results with different wave directions are compared and the conditions which cause maximum responses are discussed.

• 한국멀티미디어학회논문지
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• 제3권5호
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• pp.445-453
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• 2000

본 논문에 서 는 그룹화 블록 스네이크를 이용한 도로 영상 차선추출 알고리즘을 제안하였다. 제안한 알고리즘에서는 먼저 영상을 $8\times{8}$ 블록으로 나눈 후 전체 영상을 확률적 접근 방식에 의해 잡음을 포함한 블록들을 제거하였으며, 차선과 겹치는 배경 영상과의 분리를 위해 허프 변환을 사용하였다. 도로 영상에 포함된 차선추출을 위해 전영역 탐색 방법보다는 블록을 그룹화한 후 탐색하는 방법을 사용하였다. 제안한 방법은 기존의 화소 단위의 스네이크에 비해 계산량의 감소와 화소 단위의 잡음을 제거하는 장점을 가진다.

• 소음진동
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• 제9권3호
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• pp.587-592
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• 1999

Piston slap is one of the sources producing engine block surface vibration and mechanical noise. To analyze piston slap-induced vibration, a realistic but simple model is proposed and verified experimentally. A piston is modeled by 3 degree of freedom system and an impact point between piston skirt and cylinder wall by 2 degree of freedom system. Numerical simulation estimates impact forces of piston in cylinder, and the engine block surface vibration response is predicted by the convoluton of the impact forces with measured impulse responses. Experimental verification on the predicted response has been also performed by using a commercial 4-cylinder diesel engine. the predicted and experimental vibration responses confirm that the suggested model is practically useful.

• Journal of Communications and Networks
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• 제8권3호
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• pp.306-312
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• 2006

This paper studies theoretically the bit error rate (BER) performance of cooperative transmission using space-time block code (STBC) in a fully distributed manner. Specifically, we first propose a STBC-based cooperative signaling structure to make the cooperation of three single-antenna terminals possible. Then, we derive the closed-form BER expressions for both cooperation and noncooperation schemes under flat Rayleigh fading channel plus additive white Gaussian noise (AWGN). The validity of these expressions is verified by Monte-Carlo simulations. A variety of numerical and simulation results reveal that the cooperative transmission achieves higher diversity gain and better performance than the direct transmission for the same total transmit power.

• 전자공학회논문지B
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• 제28B권5호
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• pp.318-326
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• 1991

A Quantizer reconstruction level control method for block artifact reduction in DCT image coding is described. In our scheme, quantizer reconstruction level control is obtained by adding quantization level step size to the optimum quantization level in the direction of reducing the block artifact by minimizing the mean square error(MSE) and error difference(EDF) distribution in boundary without the other additional bits. In simulation results, although the performance in terms of signal to noise ratio is degraded by a little amount, mean square of error difference at block boundary and mean square error having relation block artifact is greatly reduced. Subjective image qualities are improved compared with other block artifact reduction method such as postprocessing by filtering and trasform coding by block overlapping. But the addition calculations of 1-dimensional DCT become to be more necessary to coding process for determining the reconstruction level.

• 한국전자파학회논문지
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• 제16권10호
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• pp.1043-1049
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• 2005

대용량 고속 광대역 전송에 적합한 OFDM(Orthogonal Frequency-Division Multiplexing) 통신 시스템에서 위상 잡음에 의해 발생하는 ICI(Inter-Sub-Carrier-Interference)는 부반송파 사이의 직교성을 깨뜨려 시스템 성능을 현저히 저하시킨다. 본 논문에서는 ICI 제거 기 법과 안테나, 시간, 주파수 다이버시티를 혼합한 새로운 STFBC(Space Time Frequency Block Coding) 방법을 이용하여 ICI를 효과적으로 제거한다. 먼저 위상잡음 선형 근사화 기법을 이용하여 제안한 STFBC OFDM 시스템에서 발생하는 CPE(Common Phase Error) 성분과 ICI 성분을 분석하고 PLL(Phase Locked Loop) 위상잡음에 의해 발생하는 시스템 성능 저하를 비교 분석하기 위하여 CIR(Carrier to Interference Ratio), PICR(Peak Interference to Carrier power Ratio) 그리고 BER(Bit Error Rate)을 토론한다. 분석 결과 제안한 STFBC 방법에서는 ICI를 뚜렷이 제거할 뿐만 아니라 기존의 STBC(Space Time Block Coding), SFBC(Space Frequency Block Coding) 등 다이버시티 코딩 기법에서 나타나는 SCI(Self Channel Interference)를 효과적으로 피면할 수 있다.

• IEIE Transactions on Smart Processing and Computing
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• 제2권1호
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• pp.20-26
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• 2013

Image noise reduction in the frequency domain by thresholding is simple, but quite effective. Wavelet domain thresholding has been an active area of research but relatively little work has been published on DCT domain denoising. A novel method for determining the hard threshold for the DCT domain denoising is proposed. The low amplitude DCT coefficients are discarded until the cumulative sum of the discarded signal energy is comparable to that of noise in each DCT block. Cycle spinning is also applied to reduce block artifacts. The proposed method is quite effective and simple enough to be used in portable devices.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 하계종합학술대회 논문집
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• pp.605-608
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• 1999

A conventional image coder, such as JPEG, requires not only DCT and quantization but also additional pre-filtering under noisy environment. Since the pre-filtering removes camera noise and improves coding efficiency dramatically, its efficient implementation has been an important issue. Based on well-known noise removal techniques in image processing fields, this paper introduces an efficient scheme by adapting a noise removal procedure to block-based image coders. By using two-dimensional DCT factorization, the proposed image coder has only a modified DCT and a VLC, and performs pre-filtering and quantization simultaneously in the modified DCT operation.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제55권2호
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• pp.100-105
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• 2006

In this paper, a low noise amplifier(LNA) in a receiver of a low noise block down converter (LNB) for direct broadcasting service(DBS) is implemented using GaAs HEMT. The LNA is designed for the bandwidth of 11.7 GHz-12.2 GHz. The two-stage LNA consists of a input matching circuit, a output matching circuit, DC-blocks and RF-chokes. Experimental results of the LNA show the noise figure less than 1.4 dB, the gain greater than 23 dB and the flatness of 1 dB in the bandwidth of 11.7 to 12.2 GHz.