Three layers of volcanic tephra, sampled from ODP 1143 Site in the South China Sea, were observed at the mcd depth of 5.55 m, 42.66 m, and 48.25 m, and named, in this paper, layers of A, B, and C, respectively. All of...Three layers of volcanic tephra, sampled from ODP 1143 Site in the South China Sea, were observed at the mcd depth of 5.55 m, 42.66 m, and 48.25 m, and named, in this paper, layers of A, B, and C, respectively. All of these tephra layers have an average thickness of ca. 2 cm. They were constrained in age of ca. 0.070 Ma, ca. 0.80 Ma, and ca. 1.00 Ma, respectively, by the microbiostratigraphy data. These tephra layers were predominated by volcanic glass shards with a median grain size of 70-75μm in diameter. Major chemical compositions analyzed by EMPA and comparison with the previous data from other scatter areas suggest that these three layers of tephra can correspond to the three layers of Toba tephra, YTT, OTT, and HDT, respectively, erupting during the Quaternary. The occurrence of these tephra layers in the South China Sea implies that the Toba eruptions often occurred in the summer monsoon seasons of the South China Sea during the Quaternary, and that the strength of eruptions was probably stronger than that previously estimated.展开更多
As the Internet of Medical Things (IoMT) continues to expand, smart health-monitoring devices generate vast amounts of valuable data while simultaneously raising critical security and privacy challenges. Blockchain te...As the Internet of Medical Things (IoMT) continues to expand, smart health-monitoring devices generate vast amounts of valuable data while simultaneously raising critical security and privacy challenges. Blockchain technology presents a promising avenue to address these concerns due to its inherent decentralization and security features. However, scalability remains a persistent hurdle, particularly for IoMT applications that involve large-scale networks and resource-constrained devices. This paper introduces a novel lightweight sharding method tailored to the unique demands of IoMT data sharing. Our approach enhances state bootstrapping efficiency and reduces operational overhead by utilizing a dual-chain structure comprising a main chain and a snapshot chain. The snapshot chain periodically records key blockchain states, allowing nodes to synchronize more efficiently. This mechanism is critical in reducing the time and resources needed for new nodes to join the network or existing nodes to recover from outages. Additionally, a block state pruning technique is implemented, significantly minimizing storage requirements and lowering transaction execution overhead during initialization and reconfiguration processes. This is crucial given the substantial data volumes inherent in IoMT ecosystems. By adopting an optimistic sharding strategy, our model allows nodes to swiftly join the snapshot shard, while full shards retain the complete ledger history to ensure comprehensive transaction verification. Extensive evaluations across diverse shard configurations demonstrate that this method significantly outperforms existing baseline models. It provides a comprehensive solution for IoMT blockchain applications, striking an optimal balance between security, scalability, and operational efficiency.展开更多
Blockchain-based user-centric access network(UCAN)fails in dynamic access point(AP)management,as it lacks an incentive mechanism to promote virtuous behavior.Furthermore,the low throughput of the blockchain has been a...Blockchain-based user-centric access network(UCAN)fails in dynamic access point(AP)management,as it lacks an incentive mechanism to promote virtuous behavior.Furthermore,the low throughput of the blockchain has been a bottleneck to the widespread adoption of UCAN in 6G.In this paper,we propose Overlap Shard,a blockchain framework based on a novel reputation voting(RV)scheme,to dynamically manage the APs in UCAN.AP nodes in UCAN are distributed across multiple shards based on the RV scheme.That is,nodes with good reputation(virtuous behavior)are likely to be selected in the overlap shard.The RV mechanism ensures the security of UCAN because most APs adopt virtuous behaviors.Furthermore,to improve the efficiency of the Overlap Shard,we reduce cross-shard transactions by introducing core nodes.Specifically,a few nodes are overlapped in different shards,which can directly process the transactions in two shards instead of crossshard transactions.This greatly increases the speed of transactions between shards and thus the throughput of the overlap shard.The experiments show that the throughput of the overlap shard is about 2.5 times that of the non-sharded blockchain.展开更多
Blockchain technologies have been used to facilitate Web 3.0 and FinTech applications.However,conventional blockchain technologies suffer from long transaction delays and low transaction success rates in some Web 3.0 ...Blockchain technologies have been used to facilitate Web 3.0 and FinTech applications.However,conventional blockchain technologies suffer from long transaction delays and low transaction success rates in some Web 3.0 and FinTech applications such as Supply Chain Finance(SCF).Blockchain sharding has been proposed to improve blockchain performance.However,the existing sharding methods either use a static sharding strategy,which lacks the adaptability for the dynamic SCF environment,or are designed for public chains,which are not applicable to consortium blockchain-based SCF.To address these issues,we propose an adaptive consortium blockchain sharding framework named ACSarF,which is based on the deep reinforcement learning algorithm.The proposed framework can improve consortium blockchain sharding to effectively reduce transaction delay and adaptively adjust the sharding and blockout strategies to increase the transaction success rate in a dynamic SCF environment.Furthermore,we propose to use a consistent hash algorithm in the ACSarF framework to ensure transaction load balancing in the adaptive sharding system to further improve the performance of blockchain sharding in dynamic SCF scenarios.To evaluate the proposed framework,we conducted extensive experiments in a typical SCF scenario.The obtained experimental results show that the ACSarF framework achieves a more than 60%improvement in user experience compared to other state-of-the-art blockchain systems.展开更多
The blockchain trilemma—balancing decentralization,security,and scalability—remains a critical challenge in distributed ledger technology.Despite significant advancements,achieving all three attributes simultaneousl...The blockchain trilemma—balancing decentralization,security,and scalability—remains a critical challenge in distributed ledger technology.Despite significant advancements,achieving all three attributes simultaneously continues to elude most blockchain systems,often forcing trade-offs that limit their real-world applicability.This review paper synthesizes current research efforts aimed at resolving the trilemma,focusing on innovative consensus mechanisms,sharding techniques,layer-2 protocols,and hybrid architectural models.We critically analyze recent breakthroughs,including Directed Acyclic Graph(DAG)-based structures,cross-chain interoperability frameworks,and zero-knowledge proof(ZKP)enhancements,which aimto reconcile scalability with robust security and decentralization.Furthermore,we evaluate the trade-offs inherent in these approaches,highlighting their practical implications for enterprise adoption,decentralized finance(DeFi),and Web3 ecosystems.By mapping the evolving landscape of solutions,this review identifies gaps in currentmethodologies and proposes future research directions,such as adaptive consensus algorithms and artificial intelligence-driven(AI-driven)governance models.Our analysis underscores that while no universal solution exists,interdisciplinary innovations are progressively narrowing the trilemma’s constraints,paving the way for next-generation blockchain infrastructures.展开更多
The long transaction latency and low throughput of blockchain are the key challenges affecting the large-scale adoption of blockchain technology. Sharding technology is a primary solution by divides the blockchain net...The long transaction latency and low throughput of blockchain are the key challenges affecting the large-scale adoption of blockchain technology. Sharding technology is a primary solution by divides the blockchain network into multiple independent shards for parallel transaction processing. However, most existing random or modular schemes fail to consider the transactional relationships between accounts, which leads to a high proportion of cross-shard transactions, thereby increasing the communication overhead and transaction confirmation latency between shards. To solve this problem, this paper proposes a blockchain sharding algorithm based on account degree and frequency (DFSA). The algorithm takes into account both account degree and weight relationships between accounts. The blockchain transaction network is modeled as an undirected weighted graph, and community detection algorithms are employed to analyze the correlations between accounts. Strong-correlated accounts are grouped into the same shard, and a multi-shard blockchain network is constructed. Additionally, to further reduce the number of cross-shard transactions, this paper designs a random redundancy strategy based on account correlation, which randomly selects strong-correlated accounts and stores them redundantly in another shard, thus original cross-shard transactions can be verified and confirmed within the same shard. Simulation experiments demonstrate that DFSA outperforms the random sharding algorithm (RSA), modular sharding algorithm (MSA), and label propagation algorithm (LPA) in terms of cross-shard transaction proportion, latency, and throughput. Therefore, DFSA can effectively reduce cross-shard transaction proportion and lower transaction confirmation latency.展开更多
Blockchain technology,with its attributes of decentralization,immutability,and traceability,has emerged as a powerful catalyst for enhancing traditional industries in terms of optimizing business processes.However,tra...Blockchain technology,with its attributes of decentralization,immutability,and traceability,has emerged as a powerful catalyst for enhancing traditional industries in terms of optimizing business processes.However,transaction performance and scalability has become the main challenges hindering the widespread adoption of blockchain.Due to its inability to meet the demands of high-frequency trading,blockchain cannot be adopted in many scenarios.To improve the transaction capacity,researchers have proposed some on-chain scaling technologies,including lightning networks,directed acyclic graph technology,state channels,and shardingmechanisms,inwhich sharding emerges as a potential scaling technology.Nevertheless,excessive cross-shard transactions and uneven shard workloads prevent the sharding mechanism from achieving the expected aim.This paper proposes a graphbased sharding scheme for public blockchain to efficiently balance the transaction distribution.Bymitigating crossshard transactions and evening-out workloads among shards,the scheme reduces transaction confirmation latency and enhances the transaction capacity of the blockchain.Therefore,the scheme can achieve a high-frequency transaction as well as a better blockchain scalability.Experiments results show that the scheme effectively reduces the cross-shard transaction ratio to a range of 35%-56%and significantly decreases the transaction confirmation latency to 6 s in a blockchain with no more than 25 shards.展开更多
Three volcanic ash layers were identified in a deep-sea Core IR-GC1 from the north-eastern Indian Ocean, adjacent to western Indonesian arc. They were dominated by glass shards with minor mineral crystals, such as pla...Three volcanic ash layers were identified in a deep-sea Core IR-GC1 from the north-eastern Indian Ocean, adjacent to western Indonesian arc. They were dominated by glass shards with minor mineral crystals, such as plagioclase, biotite, and hornblende. According to the morphology and major element compositions of the representative glass shards, combined with theδ18O-based age, it is suggested that ash Layer A is cor-related to the youngest Toba tuff （YTT）, Layer B is supposed to be associated with a new eruption of Toba caldera in an age of 98 to 100 ka. Ash Layer C is different the geochemistry characteristics than those of Layer A and Layer B, suggesting that Layer C was not originated from Toba but registered another volcanic erup-tion event.展开更多
随着企业信息化进程的不断推进和业务复杂性的提升,企业信息系统主要面临业务连续性无法保障、硬件资源利用率低、运维复杂性高等问题。本文提出了基于VMware v Sphere的基础设施即服务层企业云平台构建方案,并在某企业部署实施应用于...随着企业信息化进程的不断推进和业务复杂性的提升,企业信息系统主要面临业务连续性无法保障、硬件资源利用率低、运维复杂性高等问题。本文提出了基于VMware v Sphere的基础设施即服务层企业云平台构建方案,并在某企业部署实施应用于生产系统中,通过Sharding技术实现了数据库的扁平化。运行结果表明,私有云平台保障了业务连续性,实现了服务器、存储及网络资源的整合及动态按需分配,提升了资源利用率和运维效率,更好地满足了企业信息化发展的需求。展开更多
Traditional Chinese Medicine(TCM)is one of the most promising programs for disease prevention and treatment.Meanwhile,the quality of TCM has garnered much attention.To ensure the quality of TCM,many works are based on...Traditional Chinese Medicine(TCM)is one of the most promising programs for disease prevention and treatment.Meanwhile,the quality of TCM has garnered much attention.To ensure the quality of TCM,many works are based on the blockchain scheme to design the traceability scheme of TCM to trace its origin.Although these schemes can ensure the integrity,sharability,credibility,and immutability of TCM more effectively,many problems are exposed with the rapid growth of TCM data in blockchains,such as expensive overhead,performance bottlenecks,and the traditional blockchain architecture is unsuitable for TCM data with dynamic growth.Motivated by the aforementioned problems,we propose a novel and lightweight TCM traceability architecture based on the blockchain using sharding(LBS-TCM).Compared to the existing blockchain-based TCM traceability system,our architecture utilizes sharding to develop a novel traceability mechanism that supports more convenient traceability operations for TCM requirements such as uploading,querying,and downloading.Specifically,our architecture consists of a leader shard blockchain layer as its main component,which employs a sharding mechanism to conveniently TCM tracing.Empirical evaluations demonstrated that our architecture showed better performance in many aspects compared to traditional blockchain architectures,such as TCM transaction processing,TCM transaction querying,TCM uploading,etc.In our architecture,tracing TCM has become a very efficient operation,which ensures the quality of TCM and provides great convenience for subsequent TCM analysis and retrospective research.展开更多
Recently,sharded-blockchain has attracted more and more attention.Its inherited immutabili-ty,decentralization,and promoted scalability effectively address the trust issue of the data sharing in the Internet of Things...Recently,sharded-blockchain has attracted more and more attention.Its inherited immutabili-ty,decentralization,and promoted scalability effectively address the trust issue of the data sharing in the Internet of Things(IoT).Nevertheless,the traditional random allocation between validator groups and transaction pools ignores the differences of shards,which reduces the overall system per-formance due to the unbalance between computing capacity and transaction load.To solve this prob-lem,a load balance optimization framework for sharded-blockchain enabled IoT is proposed,where the allocation between the validator groups and transaction pools is implemented reasonably by deep reinforcement learning(DRL).Specifically,based on the theoretical analysis of the intra-shard consensus and the final system consensus,the optimization of system performance is formed as a Markov decision process(MDP),and the allocation of the transaction pools,the block size,and the block interval are jointly trained in the DRL agent.The simulation results show that the proposed scheme improves the scalability of the sharded blockchain system for IoT.展开更多
In the 21st century,increasingly significant or entirely new global issues have continued to emerge and accumulate.In response to the spread of global crises such as terrorism,nuclear proliferation,the refugee crisis,...In the 21st century,increasingly significant or entirely new global issues have continued to emerge and accumulate.In response to the spread of global crises such as terrorism,nuclear proliferation,the refugee crisis,climate change,and the spread of disease,the existing global governance system“has lost the momentum for progress.”*1 Its effectiveness under the leadership of certain Western countries has begun to be questioned by many parties and has fallen into a dilemma marked by stagnation.The reform of the global governance system has become an inevitable requirement for international relations.With today?s unprecedented changes,not only are global financial,developmental,and ecological issues constantly erupting,but the sudden emergence of the new COVID-19 virus poses a serious threat to human health and safety.In this context,the world is obviously facing instability and uncertainty,and the reform o f the global governance system is at a historical turning point.The existing global governance mechanisms have been unable to adapt to the new complex and diverse situation,and the old global order is further disintegrating.China is actively promoting for the reform of the global governance system to build a community with a shared future for mankind that will lead the world into a new global governance structure.It is also an important practice of China's major-country diplomacy with Chinese characteristics in the new era.展开更多
Sharding is a promising technique to tackle the critical weakness of scalability in blockchain-based unmanned aerial vehicle(UAV)search and rescue(SAR)systems.By breaking up the blockchain network into smaller partiti...Sharding is a promising technique to tackle the critical weakness of scalability in blockchain-based unmanned aerial vehicle(UAV)search and rescue(SAR)systems.By breaking up the blockchain network into smaller partitions called shards that run independently and in parallel,shardingbased UAV systems can support a large number of search and rescue UAVs with improved scalability,thereby enhancing the rescue potential.However,the lack of adaptability and interoperability still hinder the application of sharded blockchain in UAV SAR systems.Adaptability refers to making adjustments to the blockchain towards real-time surrounding situations,while interoperability refers to making cross-shard interactions at the mission level.To address the above challenges,we propose a blockchain UAV system for SAR missions based on dynamic sharding mechanism.Apart from the benefits in scalability brought by sharding,our system improves adaptability by dynamically creating configurable and mission-exclusive shards,and improves interoperability by supporting calls between smart contracts that are deployed on different shards.We implement a prototype of our system based on Quorum,give an analysis of the improved adaptability and interoperability,and conduct experiments to evaluate the performance.The results show our system can achieve the above goals and overcome the weakness of blockchain-based UAV systems in SAR scenarios.展开更多
The mega-constellation is a major future development direction for space-based technologies in communications,navigation,remote sensing,and other fields.However,there are marked security threats to the mega-constellat...The mega-constellation is a major future development direction for space-based technologies in communications,navigation,remote sensing,and other fields.However,there are marked security threats to the mega-constellation.Traditional password-based security protection techniques are inefficient for vast node access authentication because they lack a unified management system and methodology.To address the aforementioned issues,this work presents a mega-constellation node security access authentication technique based on sharding blockchain via the“1+N+1”mega-constellation security and trustworthiness architecture.We build a distributed node security access authentication system based on functional domains and functional cross-domains,and we develop mathematical models for the complexity of messaging and space,the throughput of transactions,and the overall estimation of sharding blockchain systems.The results demonstrate that every indicator outperforms conventional blockchain techniques,which has major implications for mega-constellation by creating a complete link security and trustworthiness system.A universal solution for the number of consensus nodes I and the number of shards N is found,which can be used to guide parameter design in mega-constellation sharding blockchain systems.展开更多
Volatiles erupted from large-scale explosive volcanic activities have a significant impact on climate and environmental changes.As an important ecological factor,the occurrence of fire is affected by vegetation cover,...Volatiles erupted from large-scale explosive volcanic activities have a significant impact on climate and environmental changes.As an important ecological factor,the occurrence of fire is affected by vegetation cover,and fire can feed back into both vegetation and climatic change.The causes of fire events are diverse;and can include volcanic eruptions.The amount of charcoal in sediment sequences is related to the frequency and intensity of fire,and hence under good preservation conditions fire history can be reconstructed from fossil charcoal abundance.Until now,little research on the role of fire has been carried out in northeastern China.In this study,through research on charcoal and tephra shards from Gushantun and Hanlongwan,Holocene vegetation change in relation to fire and volcanic events in Jilin,Northeastern China,was investigated.Where tephra shards are present in Gushantun it is associated with low level of both conifers and broadleaved trees,and is also associated with a pronounced charcoal peak.This suggests forest cover was greatly reduced from a fire caused by an eruption of the Tianchi volcano.We also detected one tephra layer in Hanlongwan,which also has the almost same depth with low level forest pollen values and one charcoal peak.This was caused probably by an eruption of the Jinlongdingzi volcano.展开更多
A volcanic ash layer was observed in the 3 ice cores on the Nelson Ice Cap,Antarctica.A comparison of major elemental composition of glass shards from the 3 tephra layers with average whole-rock compositions of 1967-1...A volcanic ash layer was observed in the 3 ice cores on the Nelson Ice Cap,Antarctica.A comparison of major elemental composition of glass shards from the 3 tephra layers with average whole-rock compositions of 1967-1970 eruptions on the Deception Island and of glass shards from other suspected De- ception Island eruptions collected from Antarctic ice and firn indicate that the most reasonable source for the tephra in the Nelson Ice Cap cores is the 1970 eruption on the Deception Island.From the depth of the vol- canic ash layer and measured density profile of the cores,the net accumulation rate at the summit,Core GW,is 1200 g·cm^(-2)·a^(-1) during the past 20 years,and the net accumulation rates are 700 g·cm^(-2)·a^(-1) and 6 g·cm^(-2)·a^(-1) at sites N30 and N50,respectively.In the eastern part of the Nelson Ice Cap,the accu- mulation rate may be higher than that in the northern part,because no volcanic ash in ice cores was observed at similar depths collected from this region.展开更多
基金the NSFC, the National Natural Science Foundation of China (Grant No. 49999560).
文摘Three layers of volcanic tephra, sampled from ODP 1143 Site in the South China Sea, were observed at the mcd depth of 5.55 m, 42.66 m, and 48.25 m, and named, in this paper, layers of A, B, and C, respectively. All of these tephra layers have an average thickness of ca. 2 cm. They were constrained in age of ca. 0.070 Ma, ca. 0.80 Ma, and ca. 1.00 Ma, respectively, by the microbiostratigraphy data. These tephra layers were predominated by volcanic glass shards with a median grain size of 70-75μm in diameter. Major chemical compositions analyzed by EMPA and comparison with the previous data from other scatter areas suggest that these three layers of tephra can correspond to the three layers of Toba tephra, YTT, OTT, and HDT, respectively, erupting during the Quaternary. The occurrence of these tephra layers in the South China Sea implies that the Toba eruptions often occurred in the summer monsoon seasons of the South China Sea during the Quaternary, and that the strength of eruptions was probably stronger than that previously estimated.
基金supported by the National Natural Science Foundation of China(62272207)the Key Project of Natural Science Foundation of Jiangxi Province(20224ACB202009)+1 种基金the Science and Technology Project of theDepartment of Education of Jiangxi Province(GJJ2200925)the Jiangxi Provincial Health Commission Science and Technology Plan(202311147).
文摘As the Internet of Medical Things (IoMT) continues to expand, smart health-monitoring devices generate vast amounts of valuable data while simultaneously raising critical security and privacy challenges. Blockchain technology presents a promising avenue to address these concerns due to its inherent decentralization and security features. However, scalability remains a persistent hurdle, particularly for IoMT applications that involve large-scale networks and resource-constrained devices. This paper introduces a novel lightweight sharding method tailored to the unique demands of IoMT data sharing. Our approach enhances state bootstrapping efficiency and reduces operational overhead by utilizing a dual-chain structure comprising a main chain and a snapshot chain. The snapshot chain periodically records key blockchain states, allowing nodes to synchronize more efficiently. This mechanism is critical in reducing the time and resources needed for new nodes to join the network or existing nodes to recover from outages. Additionally, a block state pruning technique is implemented, significantly minimizing storage requirements and lowering transaction execution overhead during initialization and reconfiguration processes. This is crucial given the substantial data volumes inherent in IoMT ecosystems. By adopting an optimistic sharding strategy, our model allows nodes to swiftly join the snapshot shard, while full shards retain the complete ledger history to ensure comprehensive transaction verification. Extensive evaluations across diverse shard configurations demonstrate that this method significantly outperforms existing baseline models. It provides a comprehensive solution for IoMT blockchain applications, striking an optimal balance between security, scalability, and operational efficiency.
基金supported by the National Natural Science Foundation of China(NSFC)under Grant 61931005.
文摘Blockchain-based user-centric access network(UCAN)fails in dynamic access point(AP)management,as it lacks an incentive mechanism to promote virtuous behavior.Furthermore,the low throughput of the blockchain has been a bottleneck to the widespread adoption of UCAN in 6G.In this paper,we propose Overlap Shard,a blockchain framework based on a novel reputation voting(RV)scheme,to dynamically manage the APs in UCAN.AP nodes in UCAN are distributed across multiple shards based on the RV scheme.That is,nodes with good reputation(virtuous behavior)are likely to be selected in the overlap shard.The RV mechanism ensures the security of UCAN because most APs adopt virtuous behaviors.Furthermore,to improve the efficiency of the Overlap Shard,we reduce cross-shard transactions by introducing core nodes.Specifically,a few nodes are overlapped in different shards,which can directly process the transactions in two shards instead of crossshard transactions.This greatly increases the speed of transactions between shards and thus the throughput of the overlap shard.The experiments show that the throughput of the overlap shard is about 2.5 times that of the non-sharded blockchain.
基金supported by the National Key Research and Development Program of China (2022YFC3302300)National Natural Science Foundation of China under Grant (No.61873309,No.92046024,No.92146002)Shanghai Science and Technology Project under Grant (No.22510761000)。
文摘Blockchain technologies have been used to facilitate Web 3.0 and FinTech applications.However,conventional blockchain technologies suffer from long transaction delays and low transaction success rates in some Web 3.0 and FinTech applications such as Supply Chain Finance(SCF).Blockchain sharding has been proposed to improve blockchain performance.However,the existing sharding methods either use a static sharding strategy,which lacks the adaptability for the dynamic SCF environment,or are designed for public chains,which are not applicable to consortium blockchain-based SCF.To address these issues,we propose an adaptive consortium blockchain sharding framework named ACSarF,which is based on the deep reinforcement learning algorithm.The proposed framework can improve consortium blockchain sharding to effectively reduce transaction delay and adaptively adjust the sharding and blockout strategies to increase the transaction success rate in a dynamic SCF environment.Furthermore,we propose to use a consistent hash algorithm in the ACSarF framework to ensure transaction load balancing in the adaptive sharding system to further improve the performance of blockchain sharding in dynamic SCF scenarios.To evaluate the proposed framework,we conducted extensive experiments in a typical SCF scenario.The obtained experimental results show that the ACSarF framework achieves a more than 60%improvement in user experience compared to other state-of-the-art blockchain systems.
文摘The blockchain trilemma—balancing decentralization,security,and scalability—remains a critical challenge in distributed ledger technology.Despite significant advancements,achieving all three attributes simultaneously continues to elude most blockchain systems,often forcing trade-offs that limit their real-world applicability.This review paper synthesizes current research efforts aimed at resolving the trilemma,focusing on innovative consensus mechanisms,sharding techniques,layer-2 protocols,and hybrid architectural models.We critically analyze recent breakthroughs,including Directed Acyclic Graph(DAG)-based structures,cross-chain interoperability frameworks,and zero-knowledge proof(ZKP)enhancements,which aimto reconcile scalability with robust security and decentralization.Furthermore,we evaluate the trade-offs inherent in these approaches,highlighting their practical implications for enterprise adoption,decentralized finance(DeFi),and Web3 ecosystems.By mapping the evolving landscape of solutions,this review identifies gaps in currentmethodologies and proposes future research directions,such as adaptive consensus algorithms and artificial intelligence-driven(AI-driven)governance models.Our analysis underscores that while no universal solution exists,interdisciplinary innovations are progressively narrowing the trilemma’s constraints,paving the way for next-generation blockchain infrastructures.
基金supported by the National Natural Science Foundation of China(Grant No.61802301)awarded to J.Lithe Postgraduate Innovation Fund Project of Xi’an Shiyou University(Grant No.YCX2513159).
文摘The long transaction latency and low throughput of blockchain are the key challenges affecting the large-scale adoption of blockchain technology. Sharding technology is a primary solution by divides the blockchain network into multiple independent shards for parallel transaction processing. However, most existing random or modular schemes fail to consider the transactional relationships between accounts, which leads to a high proportion of cross-shard transactions, thereby increasing the communication overhead and transaction confirmation latency between shards. To solve this problem, this paper proposes a blockchain sharding algorithm based on account degree and frequency (DFSA). The algorithm takes into account both account degree and weight relationships between accounts. The blockchain transaction network is modeled as an undirected weighted graph, and community detection algorithms are employed to analyze the correlations between accounts. Strong-correlated accounts are grouped into the same shard, and a multi-shard blockchain network is constructed. Additionally, to further reduce the number of cross-shard transactions, this paper designs a random redundancy strategy based on account correlation, which randomly selects strong-correlated accounts and stores them redundantly in another shard, thus original cross-shard transactions can be verified and confirmed within the same shard. Simulation experiments demonstrate that DFSA outperforms the random sharding algorithm (RSA), modular sharding algorithm (MSA), and label propagation algorithm (LPA) in terms of cross-shard transaction proportion, latency, and throughput. Therefore, DFSA can effectively reduce cross-shard transaction proportion and lower transaction confirmation latency.
基金supported by Shandong Provincial Key Research and Development Program of China(2021CXGC010107,2020CXGC010107)the Shandong Provincial Natural Science Foundation of China(ZR2020KF035)the New 20 Project of Higher Education of Jinan,China(202228017).
文摘Blockchain technology,with its attributes of decentralization,immutability,and traceability,has emerged as a powerful catalyst for enhancing traditional industries in terms of optimizing business processes.However,transaction performance and scalability has become the main challenges hindering the widespread adoption of blockchain.Due to its inability to meet the demands of high-frequency trading,blockchain cannot be adopted in many scenarios.To improve the transaction capacity,researchers have proposed some on-chain scaling technologies,including lightning networks,directed acyclic graph technology,state channels,and shardingmechanisms,inwhich sharding emerges as a potential scaling technology.Nevertheless,excessive cross-shard transactions and uneven shard workloads prevent the sharding mechanism from achieving the expected aim.This paper proposes a graphbased sharding scheme for public blockchain to efficiently balance the transaction distribution.Bymitigating crossshard transactions and evening-out workloads among shards,the scheme reduces transaction confirmation latency and enhances the transaction capacity of the blockchain.Therefore,the scheme can achieve a high-frequency transaction as well as a better blockchain scalability.Experiments results show that the scheme effectively reduces the cross-shard transaction ratio to a range of 35%-56%and significantly decreases the transaction confirmation latency to 6 s in a blockchain with no more than 25 shards.
基金The National Natural Science Foundation of China under contract Nos 41106052 91228101 and 41306056the Fundamental Research Funds for National Nonprofit Institute Grant under contract No.JG0910
文摘Three volcanic ash layers were identified in a deep-sea Core IR-GC1 from the north-eastern Indian Ocean, adjacent to western Indonesian arc. They were dominated by glass shards with minor mineral crystals, such as plagioclase, biotite, and hornblende. According to the morphology and major element compositions of the representative glass shards, combined with theδ18O-based age, it is suggested that ash Layer A is cor-related to the youngest Toba tuff （YTT）, Layer B is supposed to be associated with a new eruption of Toba caldera in an age of 98 to 100 ka. Ash Layer C is different the geochemistry characteristics than those of Layer A and Layer B, suggesting that Layer C was not originated from Toba but registered another volcanic erup-tion event.
文摘随着企业信息化进程的不断推进和业务复杂性的提升,企业信息系统主要面临业务连续性无法保障、硬件资源利用率低、运维复杂性高等问题。本文提出了基于VMware v Sphere的基础设施即服务层企业云平台构建方案,并在某企业部署实施应用于生产系统中,通过Sharding技术实现了数据库的扁平化。运行结果表明,私有云平台保障了业务连续性,实现了服务器、存储及网络资源的整合及动态按需分配,提升了资源利用率和运维效率,更好地满足了企业信息化发展的需求。
基金supported by the research and innovation program for graduate students of the Guangzhou University of Traditional Chinese MedicineThis work is also partially supported by the National Key Research and Development Program of China(2019YFC1710402)the research on tracing TCM Electronic Medical Records Based on the Lightweight Blockchain of Guangdong Provincial Bureau of Traditional Chinese Medicine(20222045).
文摘Traditional Chinese Medicine(TCM)is one of the most promising programs for disease prevention and treatment.Meanwhile,the quality of TCM has garnered much attention.To ensure the quality of TCM,many works are based on the blockchain scheme to design the traceability scheme of TCM to trace its origin.Although these schemes can ensure the integrity,sharability,credibility,and immutability of TCM more effectively,many problems are exposed with the rapid growth of TCM data in blockchains,such as expensive overhead,performance bottlenecks,and the traditional blockchain architecture is unsuitable for TCM data with dynamic growth.Motivated by the aforementioned problems,we propose a novel and lightweight TCM traceability architecture based on the blockchain using sharding(LBS-TCM).Compared to the existing blockchain-based TCM traceability system,our architecture utilizes sharding to develop a novel traceability mechanism that supports more convenient traceability operations for TCM requirements such as uploading,querying,and downloading.Specifically,our architecture consists of a leader shard blockchain layer as its main component,which employs a sharding mechanism to conveniently TCM tracing.Empirical evaluations demonstrated that our architecture showed better performance in many aspects compared to traditional blockchain architectures,such as TCM transaction processing,TCM transaction querying,TCM uploading,etc.In our architecture,tracing TCM has become a very efficient operation,which ensures the quality of TCM and provides great convenience for subsequent TCM analysis and retrospective research.
基金Supported by the National Natural Science Foundation of China(No.61901011)the Foundation of Beijing Municipal Commission of Edu-cation(No.KM202010005017,KM202110005021).
文摘Recently,sharded-blockchain has attracted more and more attention.Its inherited immutabili-ty,decentralization,and promoted scalability effectively address the trust issue of the data sharing in the Internet of Things(IoT).Nevertheless,the traditional random allocation between validator groups and transaction pools ignores the differences of shards,which reduces the overall system per-formance due to the unbalance between computing capacity and transaction load.To solve this prob-lem,a load balance optimization framework for sharded-blockchain enabled IoT is proposed,where the allocation between the validator groups and transaction pools is implemented reasonably by deep reinforcement learning(DRL).Specifically,based on the theoretical analysis of the intra-shard consensus and the final system consensus,the optimization of system performance is formed as a Markov decision process(MDP),and the allocation of the transaction pools,the block size,and the block interval are jointly trained in the DRL agent.The simulation results show that the proposed scheme improves the scalability of the sharded blockchain system for IoT.
文摘In the 21st century,increasingly significant or entirely new global issues have continued to emerge and accumulate.In response to the spread of global crises such as terrorism,nuclear proliferation,the refugee crisis,climate change,and the spread of disease,the existing global governance system“has lost the momentum for progress.”*1 Its effectiveness under the leadership of certain Western countries has begun to be questioned by many parties and has fallen into a dilemma marked by stagnation.The reform of the global governance system has become an inevitable requirement for international relations.With today?s unprecedented changes,not only are global financial,developmental,and ecological issues constantly erupting,but the sudden emergence of the new COVID-19 virus poses a serious threat to human health and safety.In this context,the world is obviously facing instability and uncertainty,and the reform o f the global governance system is at a historical turning point.The existing global governance mechanisms have been unable to adapt to the new complex and diverse situation,and the old global order is further disintegrating.China is actively promoting for the reform of the global governance system to build a community with a shared future for mankind that will lead the world into a new global governance structure.It is also an important practice of China's major-country diplomacy with Chinese characteristics in the new era.
基金supported by the National Key R&D Program of China(2022YFB2703200)the National Natural Science Foundation of China(Grant Nos.62202011,62172010).
文摘Sharding is a promising technique to tackle the critical weakness of scalability in blockchain-based unmanned aerial vehicle(UAV)search and rescue(SAR)systems.By breaking up the blockchain network into smaller partitions called shards that run independently and in parallel,shardingbased UAV systems can support a large number of search and rescue UAVs with improved scalability,thereby enhancing the rescue potential.However,the lack of adaptability and interoperability still hinder the application of sharded blockchain in UAV SAR systems.Adaptability refers to making adjustments to the blockchain towards real-time surrounding situations,while interoperability refers to making cross-shard interactions at the mission level.To address the above challenges,we propose a blockchain UAV system for SAR missions based on dynamic sharding mechanism.Apart from the benefits in scalability brought by sharding,our system improves adaptability by dynamically creating configurable and mission-exclusive shards,and improves interoperability by supporting calls between smart contracts that are deployed on different shards.We implement a prototype of our system based on Quorum,give an analysis of the improved adaptability and interoperability,and conduct experiments to evaluate the performance.The results show our system can achieve the above goals and overcome the weakness of blockchain-based UAV systems in SAR scenarios.
基金the specific grant from China’s National Social Science Foundation (U23B2025 and U22B2014).
文摘The mega-constellation is a major future development direction for space-based technologies in communications,navigation,remote sensing,and other fields.However,there are marked security threats to the mega-constellation.Traditional password-based security protection techniques are inefficient for vast node access authentication because they lack a unified management system and methodology.To address the aforementioned issues,this work presents a mega-constellation node security access authentication technique based on sharding blockchain via the“1+N+1”mega-constellation security and trustworthiness architecture.We build a distributed node security access authentication system based on functional domains and functional cross-domains,and we develop mathematical models for the complexity of messaging and space,the throughput of transactions,and the overall estimation of sharding blockchain systems.The results demonstrate that every indicator outperforms conventional blockchain techniques,which has major implications for mega-constellation by creating a complete link security and trustworthiness system.A universal solution for the number of consensus nodes I and the number of shards N is found,which can be used to guide parameter design in mega-constellation sharding blockchain systems.
基金supported by the National Natural Science Foundation of China (Grant No. 41202260)the Chinese Academy of Sciences Strategic Priority Research Program (Grant No. XDA01020304)Overseas Research Scholarship (UK, 2007–2010)
文摘Volatiles erupted from large-scale explosive volcanic activities have a significant impact on climate and environmental changes.As an important ecological factor,the occurrence of fire is affected by vegetation cover,and fire can feed back into both vegetation and climatic change.The causes of fire events are diverse;and can include volcanic eruptions.The amount of charcoal in sediment sequences is related to the frequency and intensity of fire,and hence under good preservation conditions fire history can be reconstructed from fossil charcoal abundance.Until now,little research on the role of fire has been carried out in northeastern China.In this study,through research on charcoal and tephra shards from Gushantun and Hanlongwan,Holocene vegetation change in relation to fire and volcanic events in Jilin,Northeastern China,was investigated.Where tephra shards are present in Gushantun it is associated with low level of both conifers and broadleaved trees,and is also associated with a pronounced charcoal peak.This suggests forest cover was greatly reduced from a fire caused by an eruption of the Tianchi volcano.We also detected one tephra layer in Hanlongwan,which also has the almost same depth with low level forest pollen values and one charcoal peak.This was caused probably by an eruption of the Jinlongdingzi volcano.
基金the National Natural Science Foundation of China the State Committee for Antarctic Research of China
文摘A volcanic ash layer was observed in the 3 ice cores on the Nelson Ice Cap,Antarctica.A comparison of major elemental composition of glass shards from the 3 tephra layers with average whole-rock compositions of 1967-1970 eruptions on the Deception Island and of glass shards from other suspected De- ception Island eruptions collected from Antarctic ice and firn indicate that the most reasonable source for the tephra in the Nelson Ice Cap cores is the 1970 eruption on the Deception Island.From the depth of the vol- canic ash layer and measured density profile of the cores,the net accumulation rate at the summit,Core GW,is 1200 g·cm^(-2)·a^(-1) during the past 20 years,and the net accumulation rates are 700 g·cm^(-2)·a^(-1) and 6 g·cm^(-2)·a^(-1) at sites N30 and N50,respectively.In the eastern part of the Nelson Ice Cap,the accu- mulation rate may be higher than that in the northern part,because no volcanic ash in ice cores was observed at similar depths collected from this region.
