• Journal of Digital Contents Society
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• v.1 no.1
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• pp.53-64
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• 2000

This paper is related to color image segmentation scheme which makes it possible to achieve the excellent segmented results by block-based segmentation using Y/C bit-plane summation image. First, normalized chrominance summation image is obtained by normalizing the image which is summed up the absolutes of color-differential values between R, G, B images. Secondly, upper 2 bits of the luminance image and upper 6bits of and the normalized chrominance summation image are bitwise operated by the pixel to generate the Y/C bit-plane summation image. Next, the Y/C bit-plane summation image divided into predetermined block size, is classified into monotone blocks, texture blocks and edge blocks, and then each classified block is merged to the regions including one more blocks in the individual block type, and each region is selectively allocated to unique marker according to predetermined marker allocation rules. Finally, fine segmented results are obtained by applying the watershed algorithm to each pixel in the unmarked blocks. As shown in computer simulation, the main advantage of the proposed method is that it suppresses the over-segmentation in the texture regions and reduces computational load. Furthermore, it is able to apply global parameters to various images with different pixel distribution properties because they are nonsensitive for pixel distribution. Especially, the proposed method offers reasonable segmentation results in edge areas with lower contrast owing to the regional characteristics of the color components reflected in the Y/C bit-plane summation image.

• Journal of the Korea Computer Industry Society
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• v.5 no.1
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• pp.147-156
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• 2004

In this paper, a new fast motion estimation algorithm which is based on the Block Sum Pyramid Algorithm(BSPA) is presented. The Spiral Diamond Mesh Search scheme and Partial Distortion Elimination scheme of Efficient Multi-level Successive Elimination Algorithm were improved and then the improved schemes were applied to the BSPA. The motion estimation accuracy of the proposed algorithm is nearly 100% and the cost of Block Sum Pyramid Algorithm was reduced in the proposed algorithm. The efficiency of the proposed algorithm was verified by experimental results.

• Journal of the Korea Computer Industry Society
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• v.5 no.2
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• pp.275-280
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• 2004

In this paper, a very fast block matching scheme was proposed to reduce the computations of Block Sum Pyramid Algorithm for motion estimation in video coding. The proposed algorithm is based on Block Sum Pyramid Algorithm and Efficient Multi-level Successive Elimination Algorithm. The proposed algorithm can reduce the computations of motion estimation greatly with 100% motion estimation accuracy. The efficiency of the proposed algorithm was verified by experimental results.

• Proceedings of the Korea Information Processing Society Conference
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• 2020.11a
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• pp.49-52
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• 2020

블록체인은 분산 시스템 환경에서 비가역적 정보를 탈중앙화된 방식으로 검증하는 기술로 다양한 산업에서 적용되어 새로운 가치를 만들어내고 있다. 본 연구에서는 허가형 블록체인 기술을 대표하는 오픈소스 프로젝트인 하이퍼레저 패브릭 환경에서 체인코드 및 레저 유형에 따른 합의 작업에 대한 성능을 분석하였으며, 결과에 대한 분석을 통해 블록체인 기반 분산 어플리케이션의 성능 요구사항 도출에 활용 가능한 정보를 제시하였다. 이를 통해 다양한 산업에서 블록체인 도입 시 활용할 수 있는 객관적 성능 지표의 역할을 수행하여 블록체인 기술 활성화에 기여할 것으로 기대된다.

• The Journal of Bigdata
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• v.7 no.1
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• pp.1-14
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• 2022

The proof-of-work consensus algorithm used by most blockchains is causing a massive waste of computing resources in the form of mining. A useful proof-of-work consensus algorithm has been studied to reduce the waste of computing resources in proof-of-work, but there are still resource waste and mining centralization problems when creating blocks. In this paper, the problem of resource waste in block generation was solved by replacing the relatively inefficient computation process for block generation with distributed artificial intelligence model learning. In addition, by providing fair rewards to nodes participating in the learning process, nodes with weak computing power were motivated to participate, and performance similar to the existing centralized AI learning method was maintained. To show the validity of the proposed methodology, we implemented a blockchain network capable of distributed AI learning and experimented with reward distribution through resource verification, and compared the results of the existing centralized learning method and the blockchain distributed AI learning method. In addition, as a future study, the thesis was concluded by suggesting problems and development directions that may occur when expanding the blockchain main network and artificial intelligence model.

• Journal of Industrial Convergence
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• v.20 no.6
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• pp.37-45
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• 2022

With the development of the Internet of Things (IoT), related network infrastructures require new technologies to protect against threats such as external hacking. This study proposes an L-PBFT consensus algorithm that can protect IoT networks based on a blockchain consensus algorithm. We designed a blockchain (private) model suitable for small networks, tested processing performance for ultra-small/low-power IoT devices, and verified stability. As a result of performance analysis, L-PBFT proved that at least the number of nodes complies with the operation of the consensus algorithm(minimum 14%, maximum 29%) and establishes a trust network(separation of secure channels) different from existing security protocols. This study is a 4th industry convergence research and will be a foundation technology that will help develop IoT device security products in the future.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.19 no.3
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• pp.25-32
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• 2019

The core of the block chain technology is solving the problem of agreement on double payment, and the PoW, PoS and DPoS algorithms used for this have been studied. PoW in-process proofs are consensus systems that require feasible efforts to prevent minor or malicious use of computing capabilities, such as sending spam e-mail or initiating denial of service (DoS) attacks. The proof of the PoS is made to solve the Nothing at stake problem as well as the energy waste of the proof of work (PoW) algorithm, and the decision of the sum of each node is decided according to the amount of money, not the calculation ability. DPoS is that a small number of authorized users maintain a trade consensus through a distributed network, whereas DPS provides consent authority to a small number of representatives, whereas PoS has consent authority to all users. If PoS is direct democracy, DPoS is indirect democracy. This study aims to contribute to the continuous development of the related field through the study of the algorithm of the block chain agreement.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.26 no.2
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• pp.271-277
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• 2022

PBFT (Practical Byzantine Fault Tolerant) is a consensus algorithm that can achieve consensus by resolving unintentional and intentional faults in a distributed network environment and can guarantee high performance and absolute finality. However, as the size of the network increases, the network load also increases due to message broadcasting that repeatedly occurs during the consensus process. Due to the characteristics of the PBFT algorithm, it is suitable for small/private blockchain, but there is a limit to its application to large/public blockchain. Because PBFT affects the performance of blockchain networks, the industry should test whether PBFT is suitable for products and services, and academia needs a unified evaluation metric and technology for PBFT performance improvement research. In this paper, quantitative evaluation metrics and evaluation frameworks that can evaluate PBFT family consensus algorithms are studied. In addition, the throughput, latency, and fault tolerance of PBFT are evaluated using the proposed PBFT evaluation framework.

• Journal of the Institute of Convergence Signal Processing
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• v.20 no.4
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• pp.218-225
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• 2019

Since the publication of Satoshi Nakamoto's white paper on Bitcoin in 2008, blockchain is in the spotlight as one of the core technologies of the Fouth Industrial Revolution, which can be used in various industries beyond simple cryptocurrency. various researches and developments are being conducted worldwide to utilize blockchain technology, and a global blockchain consortium is formed. In addition, attempts are being made to apply to various industries such as logistics, distribution, and medical care as well as the financial sector. However, blockchain tecnology developments still do not reach the level that meets these concerns and expectations. In this paper, we presents a comprehensive overview of blockchain technology by giving its brief concepts, consensus algorithms, standardization, and security threats.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.10a
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• pp.133-136
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• 2019

차량에서 생성되는 데이터의 가치가 상승함에 따라 데이터 소스와 데이터 내용에 대한 보안 위협 또한 증가하고 있다. 데이터 소스인 차량의 경우에는 운행의 안정성을 보장하고자 블록체인을 결합하려는 시도가 있어왔지만, 무결한 차량 운행 데이터 관리 시스템에 대한 이해 부족으로 데이터 위·변조 등 차량 데이터에 대한 사이버 공격에 적절히 대응하지 못하고 있다. 이에 본 논문은 수집된 차량 데이터의 무결성을 보장하고 수집된 데이터에 대한 질의가 가능한 블록체인 기반 데이터 베이스 시스템을 제안한다. 본 시스템을 통하여 분산 합의 기반 데이터 무결성 검증, 블록을 구성하는 해시트리의 복제 저장 없이 위·변조된 차량 데이터 검출, 일정 수준의 장애를 허용한 상태 하에서의 질의문 처리 등이 가능해진다. 본 시스템은 높은 공간 효율성과 확장성을 가지며, 수소전기차 공유 업체의 차량 운행 정보를 바탕으로 한 성능 평가 결과 평균적으로 데이터 블록 저장에 4.0 초, 각 블록 검증에 2.4 초, 질의 처리를 위한 합의 과정에 1.3 초가 소요됨을 확인하였다.