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BlockTree: a nonlinear structured, scalable and distributed ledger scheme for processing digital transactions

CLUSTER COMPUTING-THE JOURNAL OF NETWORKS SOFTWARE TOOLS AND APPLICATIONS 2021年第4期24卷 3751-3765页

作者： Vishwakarma, Lokendra Das, Debasis Indian Inst Technol Jodhpur Rajasthan India

The security of Bitcoin heavily relies on the distributed consensus algorithm. There are many consensus algorithms used in different cryptocurrencies to provide security for transactions in the blockchain. Along with the consensus algorithm, the blockchain structure is also an important aspect that affects the performance of the cryptocurrency. However, most of the state-of-the-art schemes have some serious concern for scalability issues such as less throughput, high consensus delay, and high block interval time. The consensus algorithm and structure of blockchain have direct implications on these performance parameters. Therefore, we proposed a scheme called BlockTree, a sharding-based secure, scalable, and decentralized ledger scheme. Unlike Bitcoin, BlockTree is a nonlinear data structure based scheme, which partitioned the miners with fixed group size whenever the number of miners becomes more than the set limit called "m", and the blockchain is forked from that instance. Due to this partitioning, the BlockTree supports the parallel execution of the transaction, which has improved the throughput and consensus delay while keeping the high level of security. The BlockTree used the leader selection algorithm to select a leader and the data block verification algorithm to reach consensus among miners on the next set of the transactions to append blocks in the blockchain. The BlockTree is analyzed based on real-world parameters such as throughput, consensus delay, different block sizes, block generation intervals, and network propagation compared to existing technologies.

关键词： consensus algorithms Blockchain structure Cryptocurrency Fork prevention Sharding transaction

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Blockchain for decentralization of internet: prospects, trends, and challenges

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CLUSTER COMPUTING-THE JOURNAL OF NETWORKS SOFTWARE TOOLS AND APPLICATIONS 2021年第4期24卷 2841-2866页

作者： Zarrin, Javad Phang, Hao Wen Saheer, Lakshmi Babu Zarrin, Bahram Anglia Ruskin Univ East Rd Cambridge CB1 1PT England Tech Univ Denmark Dept Appl Math & Comp Sci DTU Compute DK-2800 Lyngby Denmark Microsoft Kanalvej 7 DK-2800 Lyngby Denmark

Blockchain has made an impact on today's technology by revolutionizing the financial industry through utilization of cryptocurrencies using decentralized control. This has been followed by extending Blockchain to span several other industries and applications for its capabilities in verification. With the current trend of pursuing the decentralized Internet, many methods have been proposed to achieve decentralization considering different aspects of the current Internet model ranging from infrastructure and protocols to services and applications. This paper investigates Blockchain's capacities to provide a robust and secure decentralized model for Internet. The paper conducts a critical review on recent Blockchain-based methods capable for the decentralization of the future Internet. We identify and investigate two research aspects of Blockchain that provides high impact in realizing the decentralized Internet with respect to current Internet and Blockchain challenges while keeping various design in considerations. The first aspect is the consensus algorithms that are vital components for decentralization of the Blockchain. We identify three key consensus algorithms including PoP, Paxos, and PoAH that are more adequate for reaching consensus for such tremendous scale Blockchain-enabled architecture for Internet. The second aspect that we investigated is the compliance of Blockchain with various emerging Internet technologies and the impact of Blockchain on those technologies. Such emerging Internet technologies in combinations with Blockchain would help to overcome Blockchain's established flaws in a way to be more optimized, efficient and applicable for Internet decentralization.

关键词： Blockchain consensus algorithms Decentralization Decentralized cloud Future internet

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Cooperative Voltage Control in MV Distribution Networks With Electric Vehicle Charging Stations and Photovoltaic DGs

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IEEE SYSTEMS JOURNAL 2021年第2期15卷 2989-3000页

作者： Li, Hanlin Azzouz, Maher A. Hamad, Amr A. Univ Windsor Windsor ON N9B 3P4 Canada Univ Windsor Dept Elect & Comp Engn Windsor ON N9B 3P4 Canada Natl Res Council Canada Measurement Sci & Stand Ottawa ON K1A 0R6 Canada

The proliferation of distributed generators (DGs) and electric vehicle charging stations (EVCSs) has brought voltage regulation challenges to distribution networks. This article proposes a distributed control algorithm to dispatch surplus reactive power from EVCSs and DGs for proper voltage regulation without violating their converters' capacities or stressing conventional voltage control devices, such as on-load tap changers (OLTCs). Further, an active power curtailment strategy is proposed for DGs to properly integrate OLTCs in voltage regulation when the reactive power support is deficient. The proposed control algorithms rely on the average consensus theory and sensitivity analysis to provide optimized voltage support while satisfying the agents' self-objectives. Simulation results of a typical distribution network confirm the effectiveness of the proposed distributed control algorithms in maintaining proper voltage regulation with minimum voltage support from EVCSs and DGs, and reduced daily tap operation for OLTC.

关键词： Voltage control Reactive power Distribution networks Electric vehicle charging Batteries Decentralized control Generators consensus algorithms distributed generators (DGs) electric vehicle charging stations (EVCSs) sensitivity analysis voltage regulation

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ASYMPTOTIC consensus OF DYNAMICAL POINTS IN A STRICT MAX-CONVEX SPACE AND ITS APPLICATIONS

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SIAM JOURNAL ON CONTROL AND OPTIMIZATION 2020年第4期58卷 1984-2005页

作者： Chen, Sheng Lim, Cheng-Chew Shi, Peng Lu, Zhenyu Nanjing Univ Informat Sci & Technol CICAEET B DAT Sch Automat Nanjing 210044 Peoples R China Univ Adelaide Sch Elect & Elect Engn Adelaide SA 5005 Australia Nanjing Univ Informat Sci & Technol Sch Artificial Intelligence Nanjing 210044 Peoples R China

This paper explores the design problem of consensus algorithms in a class of convex geometric metric spaces. Using the techniques of convex analysis and possibility analysis, a simple assumption for designing consensus algorithms in a strict max-convex space is proposed, under which all dynamical points in a system achieve consensus asymptotically if and only if their associated interaction graph uniformly contains at least one directed spanning tree. Three efficient consensus algorithms under the assumption are presented, and their applications are demonstrated together with efficiency studies.

关键词： consensus algorithms algorithm design geometric spaces convex analysis possibility analysis

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Expected Convergence Rate to consensus in Asymmetric Networks: Analysis and Distributed Estimation

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IEEE TRANSACTIONS ON SYSTEMS MAN CYBERNETICS-SYSTEMS 2020年第3期50卷 972-987页

作者： Asadi, Mohammad Mehdi Khosravi, Mohammad Aghdam, Amir G. Blouin, Stephane Concordia Univ Dept Elect & Comp Engn Montreal PQ H3G 1M8 Canada Swiss Fed Inst Technol Automat Control Lab CH-8092 Zurich Switzerland Def Res & Dev Canada Atlantic Res Ctr Dartmouth NS B2Y 3Z7 Canada

This paper investigates the expected rate of convergence to consensus in an asymmetric network represented by a weighted directed graph. The initial state of the network is represented by a random vector and the expectation is taken with respect to the random initial condition of the network. The proposed convergence rate is described in terms of the eigenvalues of the Laplacian matrix of the network graph. The generalized power iteration algorithm is then introduced based on the Krylov subspace method to compute the proposed expected convergence rate in a centralized fashion. To this end, the Laplacian matrix of the network is transformed to a new matrix such that existing techniques can be used to find the eigenvalue representing the expected convergence rate of the network. The convergence analysis of the centralized algorithm is performed with a prescribed upper bound on the approximation error of the algorithm. A distributed version of the centralized algorithm is then developed using the notion of consensus observer. The efficiency of the algorithms is subsequently demonstrated by simulations.

关键词： Convergence Eigenvalues and eigenfunctions Laplace equations Approximation algorithms Observers Network topology Asymmetric networks consensus algorithms consensus observer expected convergence rate (ECR) Krylov subspace method

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A Survey on Decentralized consensus Mechanisms for Cyber Physical Systems

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IEEE ACCESS 2020年 8卷 54371-54401页

作者： Bodkhe, Umesh Mehta, Dhyey Tanwar, Sudeep Bhattacharya, Pronaya Singh, Pradeep Kumar Hong, Wei-Chiang Nirma Univ Inst Technol Dept Comp Sci & Engn Ahmadabad 382481 Gujarat India Jaypee Univ Informat Technol Dept Comp Sci & Engn Waknaghat 173234 India Oriental Inst Technol Dept Informat Management New Taipei 220 Taiwan

Modern industry 4.0 applications are shifting towards decentralized automation of computing and cyber-physical systems (CPS), which necessitates building a robust, secure, and efficient system that performs complex interactions with other physical processes. To handle complex interactions in CPS, trust and consensus among various stakeholders is a prime concern. In a similar direction, consensus algorithms in blockchain have evolved over the years that focus on building smart, robust, and secure CPS. Thus, it is imperative to understand the key components, functional characteristics, and architecture of different consensus algorithms used in CPS. Many consensus algorithms exist in the literature with a specified set of functionalities, performance, and computing services. Motivated from these facts, in this survey, we present a comprehensive analysis of existing state-of-the-art consensus mechanisms and highlight their strength and weaknesses in decentralized CPS applications. In the first part, we present the scope of the proposed survey and identify gaps in the existing surveys. Secondly, we present the review method and objectives of the proposed survey based on research questions that address the gaps in existing studies. Then, we present a solution taxonomy of decentralized consensus mechanisms for various CPS applications. Then, open issues and challenges are also discussed in deploying various consensus mechanisms in the CPS with their merits and demerits. The proposed survey will act as a road-map for blockchain developers and researchers to evaluate and design future consensus mechanisms, which helps to build an efficient CPS for industry 4.0 stakeholders.

关键词： Blockchain consensus algorithms cyber-physical systems IoT smart grid supply chain management intelligent transportation

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A Unified Approach to consensus Control of Three-Link Manipulators

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JOURNAL OF INTELLIGENT & ROBOTIC SYSTEMS 2020年第1期97卷 3-15页

作者： Zhai, Guisheng Nakamura, Satoshi Mardlijah Shibaura Inst Technol Dept Math Sci Saitama Japan Institut Teknol Sepuluh Nopember Dept Math Surabaya Indonesia

We consider a consensus control problem for a set of three-link manipulators connected by digraphs. Assume that the control inputs of each manipulator are the torques on its links and they are generated by adjusting the weighted difference between the manipulator's states and those of its neighbor agents. Then, we propose a condition for adjusting the weighting coefficients in the control inputs, so that full consensus is achieved among the manipulators. By designing complex Hurwitz polynomials, we obtain a necessary and sufficient condition for achieving the consensus. Moreover, the discussion is extended to the case of designing convergence rate of consensus. Numerical examples are provided to illustrate the condition and the design conditions.

关键词： Three-link manipulators consensus algorithms Graph Laplacian Complex Hurwitz polynomials consensus rate

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Emergence of blockchain-technology application in peer-to-peer electrical-energy trading: a review

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Clean Energy 2021年第1期5卷 104-123页

作者： Manish Kumar Thukral Manipal University Jaipur Electrical Engineering DepartmentJaipurIndia

Renewable-energy resources require overwhelming adoption by the common masses for safeguarding the environment from *** this context,the prosumer is an important emerging concept.A prosumer in simple terms is the one who consumes as well as produces electricity and sells it either to the grid or to a *** the present scenario,peer-to-peer(P2P)energy trading is gaining momentum as a new vista of research that is viewed as a possible way for prosumers to sell energy to *** P2P energy trading is the only method of making renewable-energy sources popular among the common *** making P2P energy trading successful,blockchain technology is sparking considerable interest among *** with smart contracts,a blockchain provides secure tamper-proof records of transactions that are recorded in distributed ledgers that are *** paper explores,using a thorough review of recently published research work,how the existing power sector is reshaping in the direction of P2P energy trading with the application of blockchain *** challenges that are being faced by researchers in the implementation of blockchain technology in the energy sector are ***,this paper presents different start-ups that have emerged in the energy-sector domain that are using blockchain *** give insight into the application of blockchain technology in the energy sector,a case of the application of blockchain technology in P2P trading in electrical-vehicle charging is *** the end,some possible areas of research in the application of blockchain technology in the energy sector are discussed.

关键词： blockchain consensus algorithms microgrid peer-to-peer energy trading distributed energy resources electric-vehicle charging

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Beyond Bitcoin: Evaluating Energy Consumption and Environmental Impact across Cryptocurrency Projects

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ENERGIES 2023年第18期16卷 6610页

作者： Khosravi, Ali Saamaki, Fanni Univ Southern Denmark Ctr Ind Mech CIM Dept Mech & Elect Engn DK-6400 Sonderborg Denmark Aalto Univ Sch Engn Dept Mech Engn Espoo 02150 Finland

Since their inception with Bitcoin in the late 2000s, cryptocurrencies have grown exponentially, reshaping traditional financial paradigms. This transformative journey, while innovative, brings forth pressing concerns about their energy consumption and carbon footprint. While many studies tend to zoom in on Bitcoin, this paper broadens the perspective by evaluating energy consumption across various cryptocurrencies. We analyze nine cryptocurrency projects, chosen for their market value, technology, and data availability. These span a spectrum from pioneering to emerging digital coins, offering a holistic view of the crypto realm. To contextualize, we juxtapose the energy usage of these digital currencies with traditional payment means like Visa and Mastercard. Our analysis shows vast differences in energy use among cryptocurrencies, largely tied to their consensus algorithms. Notably, while Bitcoin stands out as highly energy-intensive, several newer digital currencies have energy footprints mirroring those of conventional payment methods. Additionally, CO2 emissions estimation presents challenges due to variances in miner locations and regional energy sources, with potential higher emissions if concentrated in carbon-intensive regions like China. Nonetheless, the silver lining emerges as many cryptocurrencies, especially those beyond Bitcoin, register considerably lower CO2 emissions. By moving the lens beyond Bitcoin, this paper paints a more nuanced picture of the environmental ramifications of the crypto world.

关键词： energy consumption bitcoin cryptocurrency CO2 emissions consensus algorithms

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Blockchain for healthcare systems: Architecture, security challenges, trends and future directions

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JOURNAL OF NETWORK AND COMPUTER APPLICATIONS 2023年第1期215卷

作者： Andrew, J. Isravel, Deva Priya Sagayam, K. Martin Bhushan, Bharat Sei, Yuichi Eunice, Jennifer Manipal Acad Higher Educ Manipal Inst Technol Dept Comp Sci & Engn Manipal 576104 Karnataka India Karunya Inst Technol & Sci Dept Comp Sci & Engn Coimbatore 641114 Tamil Nadu India Karunya Inst Technol & Sci Dept Elect & Commun Engn Coimbatore 641114 Tamil Nadu India Sharda Univ Sch Engn & Technol Dept Comp Sci & Engn Greater Noida 201310 Uttar Pradesh India Univ Electrocommun Dept Informat Chofu 1828585 Japan

Blockchain has become popular in recent times through its data integrity and wide scope of applications. It has laid the foundation for cryptocurrencies such as Ripple, Bitcoin, Ethereum, and so on. Blockchain provides a platform for decentralization and trust in various applications such as finance, commerce, IoT, reputation sys-tems, and healthcare. However, prevailing challenges like scalability, resilience, security and privacy are yet to be overcome. Due to rigorous regulatory constraints such as HIPAA, blockchain applications in the healthcare industry usually require more stringent authentication, interoperability, and record sharing requirements. This article presents an extensive study to showcase the significance of blockchain technology from both application and technical perspectives for healthcare domain. The article discusses the features and use-cases of blockchain in different applications along with the healthcare domain interoperability. The detailed working operation of the blockchain and the consensus algorithms are presented in the context of healthcare. An outline of the blockchain architecture, platforms, and classifications are discussed to choose the right platform for healthcare applications. The current state-of-the-art research in healthcare blockchain and available blockchain based healthcare applications are summarized. Furthermore, the challenges and future research opportunities along with the performance evaluation metrics in realizing the blockchain technology for healthcare are presented to provide insight for future research. We also layout the various security attacks on the blockchain protocol with the classifications of threat models and presented a comparative analysis of the detection and protection tech-niques. Techniques to enhance the security and privacy of the blockchain network is also discussed.

关键词： Blockchain consensus algorithms Cryptocurrency Distributed ledger Healthcare data Security & privacy

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