In recent years,Blockchain is gaining prominence as a hot topic in academic research.However,the consensus mechanism of blockchain has been criticized in terms of energy consumption and performance.Although Proof-of-A...In recent years,Blockchain is gaining prominence as a hot topic in academic research.However,the consensus mechanism of blockchain has been criticized in terms of energy consumption and performance.Although Proof-of-Authority(PoA)consensus mechanism,as a lightweight consensus mechanism,is more efficient than traditional Proof-of-Work(PoW)and Proof-of-Stake(PoS),it suffers from the problem of centralization.To this end,on account of analyzing the shortcomings of existing consensus mechanisms,this paper proposes a dynamic reputation-based consensus mechanism for blockchain.This scheme allows nodes with reputation value higher than a threshold apply to become a monitoring node,which can monitor the behavior of validators in case that validators with excessive power cause harm to the blockchain network.At the same time,the reputation evaluation algorithm is also introduced to select nodes with high reputation to become validators in the network,thus increasing the cost of malicious behavior.In each consensus cycle,validators and monitoring nodes are dynamically updated according to the reputation value.Through security analysis,it is demonstrated that the scheme can resist the attacks of malicious nodes in the blockchain network.By simulation experiments and analysis of the scheme,the result verifies that the mechanism can effectively improve the fault tolerance of the consensus mechanism,reduce the time of consensus to guarantee the security of the system.展开更多
Strained Hg Te thin films are typical three-dimensional topological insulator materials.Most works have focused on Hg Te(100)films due to the topological properties resulting from uniaxial strain.In this study,straine...Strained Hg Te thin films are typical three-dimensional topological insulator materials.Most works have focused on Hg Te(100)films due to the topological properties resulting from uniaxial strain.In this study,strained Hg Te(111)thin films are grown on Ga As(100)substrates with Cd Te(111)buffer layers using molecular beam epitaxy(MBE).The optimal growth conditions for Hg Te films are determined to be a growth temperature of 160℃and an Hg/Te flux ratio of 200.The strains of Hg Te films with different thicknesses are investigated by highresolution x-ray diffraction,including reciprocal space mapping measurements.The critical thickness of Hg Te(111)film on Cd Te/Ga As is estimated to be approximately 284 nm by Matthews'equations,consistent with the experimental results.Reflection high-energy electron diffraction and high-resolution transmission electron microscopy investigations indicate that high-quality Hg Te films are obtained.This exploration of the MBE growth of Hg Te(111)films provides valuable information for further studies of Hg Te-based topological insulators.展开更多
With the growing maturity of blockchain technology,its peer-topeer model and fully duplicated data storage pattern enable blockchain to act as a distributed ledger in untrustworthy environments.Blockchain storage has ...With the growing maturity of blockchain technology,its peer-topeer model and fully duplicated data storage pattern enable blockchain to act as a distributed ledger in untrustworthy environments.Blockchain storage has also become a research hotspot in industry,finance,and academia due to its security,and its unique data storage management model is gradually becoming a key technology to play its value in various fields’applications.However,with the increasing amount of data written into the blockchain,the blockchain system faces many problems in its actual implementation of the application,such as high storage space occupation,low data flexibility and availability,low retrieval efficiency,poor scalability,etc.To improve the above problems,this paper combines off-chain storage technology and deduplication technology to optimize the blockchain storage model.Firstly,this paper adopts the double-chain model to reduce the data storage of the major chain system,which stores a small amount of primary data and supervises the vice chain through an Application Programming Interface(API).The vice chain stores a large number of copies of data as well as non-transactional data.Our model divides the vice chain storage system into two layers,including a storage layer and a processing layer.In the processing layer,deduplication technology is applied to reduce the redundancy of vice chain data.Our doublechain storage model with high scalability enhances data flexibility,is more suitable as a distributed storage system,and performs well in data retrieval.展开更多
基金This work is supported by the Key Research and Development Project of Sichuan Province(No.2021YFSY0012,No.2020YFG0307,No.2021YFG0332)the Key Research and Development Project of Chengdu(No.2019-YF05-02028-GX)+1 种基金the Innovation Team of Quantum Security Communication of Sichuan Province(No.17TD0009)the Academic and Technical Leaders Training Funding Support Projects of Sichuan Province(No.2016120080102643).
文摘In recent years,Blockchain is gaining prominence as a hot topic in academic research.However,the consensus mechanism of blockchain has been criticized in terms of energy consumption and performance.Although Proof-of-Authority(PoA)consensus mechanism,as a lightweight consensus mechanism,is more efficient than traditional Proof-of-Work(PoW)and Proof-of-Stake(PoS),it suffers from the problem of centralization.To this end,on account of analyzing the shortcomings of existing consensus mechanisms,this paper proposes a dynamic reputation-based consensus mechanism for blockchain.This scheme allows nodes with reputation value higher than a threshold apply to become a monitoring node,which can monitor the behavior of validators in case that validators with excessive power cause harm to the blockchain network.At the same time,the reputation evaluation algorithm is also introduced to select nodes with high reputation to become validators in the network,thus increasing the cost of malicious behavior.In each consensus cycle,validators and monitoring nodes are dynamically updated according to the reputation value.Through security analysis,it is demonstrated that the scheme can resist the attacks of malicious nodes in the blockchain network.By simulation experiments and analysis of the scheme,the result verifies that the mechanism can effectively improve the fault tolerance of the consensus mechanism,reduce the time of consensus to guarantee the security of the system.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11634009,61874069,1177041280 and 11574336)Shanghai Science and Technology Foundation(Grant No.18JC1420401)。
文摘Strained Hg Te thin films are typical three-dimensional topological insulator materials.Most works have focused on Hg Te(100)films due to the topological properties resulting from uniaxial strain.In this study,strained Hg Te(111)thin films are grown on Ga As(100)substrates with Cd Te(111)buffer layers using molecular beam epitaxy(MBE).The optimal growth conditions for Hg Te films are determined to be a growth temperature of 160℃and an Hg/Te flux ratio of 200.The strains of Hg Te films with different thicknesses are investigated by highresolution x-ray diffraction,including reciprocal space mapping measurements.The critical thickness of Hg Te(111)film on Cd Te/Ga As is estimated to be approximately 284 nm by Matthews'equations,consistent with the experimental results.Reflection high-energy electron diffraction and high-resolution transmission electron microscopy investigations indicate that high-quality Hg Te films are obtained.This exploration of the MBE growth of Hg Te(111)films provides valuable information for further studies of Hg Te-based topological insulators.
基金This work is supported by the Key Research and Development Project of Sichuan Province(No.2021YFSY0012,No.2020YFG0307,No.2021YFG0332)the Key Research and Development Project of Chengdu(No.2019-YF05-02028-GX)+1 种基金the Innovation Team of Quantum Security Communication of Sichuan Province(No.17TD0009)the Academic and Technical Leaders Training Funding Support Projects of Sichuan Province(No.2016120080102643).
文摘With the growing maturity of blockchain technology,its peer-topeer model and fully duplicated data storage pattern enable blockchain to act as a distributed ledger in untrustworthy environments.Blockchain storage has also become a research hotspot in industry,finance,and academia due to its security,and its unique data storage management model is gradually becoming a key technology to play its value in various fields’applications.However,with the increasing amount of data written into the blockchain,the blockchain system faces many problems in its actual implementation of the application,such as high storage space occupation,low data flexibility and availability,low retrieval efficiency,poor scalability,etc.To improve the above problems,this paper combines off-chain storage technology and deduplication technology to optimize the blockchain storage model.Firstly,this paper adopts the double-chain model to reduce the data storage of the major chain system,which stores a small amount of primary data and supervises the vice chain through an Application Programming Interface(API).The vice chain stores a large number of copies of data as well as non-transactional data.Our model divides the vice chain storage system into two layers,including a storage layer and a processing layer.In the processing layer,deduplication technology is applied to reduce the redundancy of vice chain data.Our doublechain storage model with high scalability enhances data flexibility,is more suitable as a distributed storage system,and performs well in data retrieval.
