• 대한방사선치료학회:학술대회논문집
• /
• 대한방사선치료학회 2004년도 제1차 학술발표회
• /
• pp.6-6
• /
• 2004

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권7호
• /
• pp.3239-3267
• /
• 2018

Image and video dehazing is a popular topic in the field of computer vision and digital image processing. A fast, optimized dehazing algorithm was recently proposed that enhances contrast and reduces flickering artifacts in a dehazed video sequence by minimizing a cost function that makes transmission values spatially and temporally coherent. However, its fixed-size block partitioning leads to block effects. The temporal cost function also suffers from the temporal non-coherence of newly appearing objects in a scene. Further, the weak edges in a hazy image are not addressed. Hence, a video dehazing algorithm based on well designed spectral clustering is proposed. To avoid block artifacts, the spectral clustering is customized to segment static scenes to ensure the same target has the same transmission value. Assuming that edge images dehazed with optimized transmission values have richer detail than before restoration, an edge intensity function is added to the spatial consistency cost model. Atmospheric light is estimated using a modified quadtree search. Different temporal transmission models are established for newly appearing objects, static backgrounds, and moving objects. The experimental results demonstrate that the new method provides higher dehazing quality and lower time complexity than the previous technique.

• 한국통신학회논문지
• /
• 제39B권5호
• /
• pp.317-322
• /
• 2014

데이타 보안과 무결성은 유무선 통신 환경에서 데이터 전송 시에 중요한 요소이다. 대량의 데이터는 전송 전에, 통상 암호 연산 모드를 이용한 블록 암호 알고리즘에 의하여 암호화된다. ECB, CBC 등의 기존 연산 모드 외에 블록 암호 연산 모드로 RBF 모드가 제안된 바 있다. 본 논문에서는, 알려진 평문 공격 (known plaintext attack) 및 선택 평문 공격 (chosen plaintext attack)에 대한, RBF 모드의 안전성을 기존 모드들과 비교 분석한 내용을 소개한다. 분석 결과, 기존의 연산 모드들이 알려진/선택 평문 공격에 취약한데 반하여, RBF 모드는 이들 공격에 안전함을 알 수 있었다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2009년도 춘계학술대회 논문집
• /
• pp.61-62
• /
• 2009

This paper describes the characteristics of lightning impulse current of ZnO block for transmission line arrester with external gap. The ageing parameters of lightning arresters ate impulse current, moisture ingress, temperature ageing and so on. Especially it is important to estimate the change of electrical characteristics by impulse current. Total energy applied to the ZnO arrester each time is $4/10{\mu}s$, 30kA and $2/20{\mu}s$, 10kA impulse current. Before and After the test, the residual voltage variation of varistors passed was below 5%. According to the test, it is thought that the ZnO arrester shows good stability with impulse current test.

• Journal of Communications and Networks
• /
• 제9권4호
• /
• pp.466-472
• /
• 2007

Single carrier block transmission with frequency domain equalization(SC-FDE) has been shown to be a promising candidate in ultra-wideband(UWB) communications. In this paper, we analyze the performance of SC-FDE over UWB communications with channel estimation error. The probability density functions of the frequency domain minimum mean-squared error(MMSE) equalizer taps are derived in closed form. The error probabilities of single carrier block transmission with frequency domain MMSE equalization under imperfect channel estimation are presented and evaluated numerically. Compared with the simulation results, our semi-analytical analysis yields fairly accurate bit error rate performance, thus validating the use of the Gaussian approximation method in the performance analysis of the SC-FDE system with channel estimation error.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 하계학술대회 논문집 Vol.8
• /
• pp.458-459
• /
• 2007

This paper describes the characteristics of lightning impulse current of ZnO block for transmission line arrester with external gap. The ageing parameters of lightning arresters are impulse current, moisture ingress, temperature ageing and so on. Especially it is important to estimate the change of electrical characteristics by impulse current. Total energy applied to the ZnO arrester each time is $4/10{\mu}s$, 30kA and $2/20{\mu}s$, 10kA impulse current. Before and After the test, the residual voltage variation of varistors passed was below 5%. According to the test, it is thought that the ZnO arrester shows good stability with impulse current test.

• 대한전자공학회논문지TC
• /
• 제49권8호
• /
• pp.12-18
• /
• 2012

본 논문에서는 하향링크 다중사용자(multi-user, MU) 다중입출력(multi-input multi-ouput, MIMO) 시스템에 블록 Tomlinson-Harashima 전처리기(block Tomlinson-Harashima precoder, BTHP)를 적용했을 때, 시스템의 송신 전력에 대한 정확한 분석 결과를 제공하였다. 각 사용자별로 상위 사용자들로부터 전달되는 간섭신호를 BTHP를 통해 제거하는 과정에서 큰 간섭신호 가정을 이용한 기존의 분석과는 달리, 실제로 전달되는 간섭신호의 통계적 특성을 분석함으로써 향상된 정확도를 갖는 분석 방법을 제안하였고, 모의실험을 통해 제안한 분석 결과가 기존 결과보다 정확함을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제18권2호
• /
• pp.511-527
• /
• 2024

This paper proposes a block-based self-organizing time-division multiple access (BSO-TDMA) protocol for very high frequency (VHF) data exchange system (VDES) in shipborne ad-hoc networks (SANETs). The BSO-TDMA reduces the collisions caused by the simultaneous transmission of automatic identification system (AIS) messages by uniformly allocating channel resources using a block-wise frame. For this purpose, the BSO-TDMA includes two functional operations: (1) frame configuration and (2) slot allocation. The first operation consists of block division and block selection. A frame is divided into multiple blocks, each consisting of fixed-size subblocks, by using the reporting interval (RI) of the ship. Then, the ship selects one of the subblocks within a block by considering the number of occupied slots for each subblock. The second operation allocates the slots within the selected subblock for transmitting AIS messages. First, one of the unoccupied slots within the selected subblock is allocated for the periodic transmission of position reports. Next, to transmit various types of AIS messages, an unoccupied slot is randomly selected from candidate slots located around the previously allocated slot. Experimental simulations are conducted to evaluate the performance of BSO-TDMA. The results show that BSO-TDMA has better performance than that of the existing SOTDMA.

• 한국정보통신학회논문지
• /
• 제17권10호
• /
• pp.2259-2264
• /
• 2013

본 논문에서는 듀얼 홉 multiple-input multiple-output(MIMO) 중계 시스템에서 직교시공간블록코드 전송과 송신안테나 선택 전송을 선택적으로 이용하는 선택적 MIMO 전송 기술을 제안한다. 독립적인 레일레이 페이딩 채널을 가정하여 선택적 MIMO 전송 기술 기반의 디코딩 후 전달 중계 시스템에 대한 아웃티지 확률을 분석하고, 수치적 결과를 통해 직교시공간블록코드 전송 또는 송신안테나 선택 전송을 모든 홉에서 동일하게 이용하는 기존 시스템과 아웃티지 성능을 비교한다. 또한, 성능 비교를 통해 제안 기술이 아웃티지 성능의 저하 없이 시스템 오버헤드를 감소시킬 수 있음을 보인다.

• ETRI Journal
• /
• 제25권1호
• /
• pp.1-8
• /
• 2003

This paper introduces an efficient iterative decoding method for high-dimensional block turbo codes. To improve the decoding performance, we modified the soft decision Viterbi decoding algorithm, which is a trellis-based method. The iteration number can be significantly reduced in the soft output decoding process by applying multiple usage of extrinsic reliability information from all available axes and appropriately normalizing them. Our simulation results reveal that the proposed decoding process needs only about 30% of the iterations required to obtain the same performance with the conventional method at a bit error rate range of $10^{-5}\;to\;10^{-6}$.