• Journal of information and communication convergence engineering
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• 제17권3호
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• pp.167-173
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• 2019

This study investigates the problem of leader-following consensus for multi-agent systems with output saturations. This study assumes that the agents are described as a neutrally stable system, and the leader agent generates the bounded trajectory within the saturation level. Then, the objective of the leader-following consensus is to track the trajectory of the leader by exchanging information with neighbors. To solve this problem, we propose an observer-based distributed consensus algorithm. Then, we provide a consensus analysis by applying the Lyapunov stability theorem and LaSalle's invariance principle. The result shows that the agents achieve the leader-following consensus in a global sense. Moreover, we can achieve the consensus by choosing any positive control gain. Finally, we perform a numerical simulation to demonstrate the validity of the proposed algorithm.

• 제어로봇시스템학회논문지
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• 제20권12호
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• pp.1225-1230
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• 2014

This paper investigates the group average-consensus and group formation-consensus problems for first-order multi-agent systems. The control protocol for group consensus is designed by considering the positive adjacency elements. Since each intra-group Laplacian matrix cannot be satisfied with the in-degree balance because of the positive adjacency elements between groups, we decompose the Laplacian matrix into an intra-group Laplacian matrix and an inter-group Laplacian matrix. Moreover, average matrices are used in the control protocol to analyze the stability of multi-agent systems with a fixed and undirected communication topology. Using the graph theory and the Lyapunov functional, stability analysis is performed for group average-consensus and group formation-consensus, respectively. Finally, some simulation results are presented to validate the effectiveness of the proposed control protocol for group consensus.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제15권4호
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• pp.1389-1408
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• 2021

Proof-of-Work (PoW) is the first and still most common consensus protocol in blockchain. But it is costly and energy intensive, aiming at addressing these problems, we propose a consensus algorithm named Proof-of-Work-and-Block-Compression (PoW-BC). PoW-BC is an improvement of PoW to compress blocks and adjust consensus parameters. The algorithm is designed to encourage the reduction of block size, which improves transmission efficiency and reduces disk space for storing blocks. The transaction optimization model and block compression model are proposed to compress block data with a smaller compression ratio and less compression/ decompression duration. Block compression ratio is used to adjust mining difficulty and transaction count of PoW-BC consensus protocol according to the consensus parameters adjustment model. Through experiment and analysis, it shows that PoW-BC improves transaction throughput, and reduces block interval and energy consumption.

• 전자통신동향분석
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• 제37권1호
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• pp.63-72
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• 2022

Recently, blockchain has been attracting attention as a high-reliability technology in various fields. However, the Proof-of-Work-based distributed consensus algorithm applied to representative blockchains, such as Bitcoin and Ethereum, has limitations in applications to various industries owing to its excessive resource consumption and performance limitations. To overcome these limitations, various distributed consensus algorithms have appeared, and recently, hybrid distributed consensus algorithms that use two or more consensus algorithms to achieve decentralization and scalability have emerged. This paper introduces the technological trends of the latest high-performance distributed consensus algorithms by analyzing representative hybrid distributed consensus algorithms.

• International Journal of Computer Science & Network Security
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• 제23권6호
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• pp.181-192
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• 2023

Blockchain system brought innovation in the area of accounting, credit monitoring and trade secrets. Consensus algorithm that considered the central component of blockchain, significantly influences performance and security of blockchain system. In this paper we presented four consensus protocols specifically as Proof of Work (PoW), Proof of Stake (PoS), Delegated Proof of Stake (DPoS) and Practical Byzantine Fault-Tolerance (PBFT), we also reviewed different security threats that affect the performance of Consensus Protocols and precisely enlist their counter measures. Further we evaluated the performance of these Consensus Protocols in tabular form based on different parameters. At the end we discussed a comprehensive comparison of Consensus protocols in terms of Throughput, Latency and Scalability. We presume that our results can be beneficial to blockchain system and token economists, practitioners and researchers.

• 한국융합학회논문지
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• 제10권11호
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• pp.41-46
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• 2019

최근에 작업 증명(PoW) 블록체인 합의 알고리즘들이 에너지 낭비, 확장성 부족 등의 문제점들이 나타나면서 비잔틴 장애 허용(BFT) 계열 합의 알고리즘들이 주목을 받고 있다. BFT 계열 합의 알고리즘들의 큰 특징 중 하나는 검증자 집합을 형성하여 그 안에서 합의를 이루는 것이다. 본 논문에서는 BFT 계열 합의 알고리즘들 중에서도 알고랜드, 스텔라, 이오스의 검증자 집합 형성 방법들의 확장성, 목표가 설정된 공격 가능 여부, 시빌 공격 가능 여부에 대해서 비교, 분석하였다. 또한 데이터 분석을 통한 각 검증자 형성 방법들의 문제점들을 발견하였고, 해당 합의 알고리즘들은 공통적으로 소수의 권력 있는 노드들이 전체 시스템을 지배하는 중앙화 현상이 나타남을 밝혔다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제13권8호
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• pp.4093-4107
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• 2019

Proof of Work (PoW) based blockchains have limitations in throughput, time consumption, and energy efficiency. In these systems, a miner will consume significant time and resources to obtain a reward for contributing to the blockchain. To overcome these limitations, recent research on blockchains are focused on accelerating the speed, scalability, and enhancing the security level. By enhancing specific procedures of blockchain system, the level of data integrity supported by the blockchain can become more robust, and efficient. In this paper, a new blockchain consensus model based on the Bryllite Consensus Protocol (BCP) is proposed to support a hyper-connected massively multiplayer online game (MMOG) ecosystem. The BCP scheme enables users to participate directly in new consensus processes through a Proof of Participation (PoP) algorithm. In this model, the consensus algorithm has a simpler form while maintaining high security level. In addition, because the BCP scheme gives users an equal chance to make a contribution to the blockchain, rewards are distributed in an equal fashion, which motivates user participation. The analysis of the proposed scheme is applied to the Bryllite consortium blockchain system (homed in Hong Kong), which is a new blockchain network developed for international game industries, gamers, and game events.

• 한국동물위생학회지
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• 제35권4호
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• pp.289-294
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• 2012

Mycoplasmas are highly fastidious bacteria, difficult to culture and slow growing. Infections with Mycoplasma species can cause a variety of problems in living organisms and in vitro cell cultures. In this study, we investigated the usefulness of a genus-specific consensus PCR analysis method to detect Mycoplasma species. The developed consensus primer pairs MycoF and MycoR were designed specifically to amplify the 16S ribosomal RNA gene (rRNA) of Mycoplasma species by the optimized PCR system. The developed consensus PCR system effectively amplified 215 bp of Mycoplasma genus-specific region of 16S rRNA. In conclusion, we recommend this consensus PCR for monitoring Mycoplasma species in animals, human and cell culture system.

• 한국과학교육학회지
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• 제39권5호
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• pp.681-694
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• 2019

This study intends to delineate the characteristics of various perspectives on the nature of science (NOS) through the textbook analysis. Thus, centering on a science textbook called Science Laboratory Experiments, this study analyzes the elements of the NOS from three different perspectives: the consensus view, features of science (FOS), and family resemblance approach (FRA). While the consensus view highlights the similar elements of the NOS across the topics, the FOS is concerned about empirical ways for doing science. The FRA rather focuses on socio-cultural aspects of science activities. While the consensus view is useful to reify the features of the NOS, the FRA helps to understand science from various viewpoints. Regarding the philosophical account for three perspectives, all of them are ambiguous to some extent. The consensus view holds contradictory dispositions e.g., relativism vs. (post-)positivism, and critical realism and instrumentalism. The FOS supports empirical tradition but cannot effectively cope with the anomalous situation. The FRA is useful to show up the ways of science in both microscopic (personal) and macroscopic (social) viewpoints. However, the broader concept about science may mislead understanding of the NOS. Consequently, this study provides some implication for improving the framework of the NOS and teaching the NOS in the classroom.

• 산업경영시스템학회지
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• 제45권1호
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• pp.1-9
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• 2022

The PoN (Proof of Nonce) distributed consensus algorithm basically uses a non-competitive consensus method that can guarantee an equal opportunity for all nodes to participate in the block generation process, and this method was expected to resolve the first trilemma of the blockchain, called the decentralization problem. However, the decentralization performance of the PoN distributed consensus algorithm can be greatly affected by the network transaction transmission delay characteristics of the nodes composing the block chain system. In particular, in the consensus process, differences in network node performance may significantly affect the composition of the congress and committee on a first-come, first-served basis. Therefore, in this paper, we presented a problem by analyzing the decentralization performance of the PoN distributed consensus algorithm, and suggested a fairness control algorithm using a learning-based probabilistic acceptance rule to improve it. In addition, we verified the superiority of the proposed algorithm by conducting a numerical experiment, while considering the block chain systems composed of various heterogeneous characteristic systems with different network transmission delay.