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Blockchain is an innovative application of distributed storage, consensus mechanism, cryptographic algorithm, and other computer technologies. As the underlying architecture of blockchain, consensus is the key to realizing service-oriented applications of blockchain in terms of its security, efficiency, and scalability optimization. In some high-complexity consensus, such as Practical Byzantine Fault Tolerance (PBFT), throughput is severely reduced as the number of nodes increases. Even in low-complexity algorithms such as Raft, the load on the leader is severely affected as the network size increases, negatively affecting consensus efficiency. To solve these problems, we propose a node reliable shard model based on guarantee tree that achieves high scalability while maintaining a certain degree of decentralization and security based on consortium blockchain. Firstly, we create a guarantee mechanism to represent the trust relationship between nodes, and then, we design a reliable node selection strategy based on the guarantee mechanism to evaluate the node guarantee results and consensus behavior, determine the node trust status, and identify malicious nodes and choose a list of trusted leaders. Secondly, we propose a Dual-Leaders supervision mechanism, in which the deputy senses the heartbeat of leader while the deputy activity is detected by consensus nodes. Finally, we use a guarantee mechanism and reliable node selection strategy to design a network partitioning method to achieve high concurrent consensus for multiple partitions and significantly improve consensus efficiency. Subsequent experiments show that the throughput of the proposed algorithm improves by 48% over Raft and is significantly greater than PBFT, which has better throughput but lower consensus latency. [ABSTRACT FROM AUTHOR]

Currently, blockchain is facing a serious storage explosion problem. While most storage scaling schemes are focused on permissionless blockchain, we propose the ring-overlap mechanism for consortium blockchain and use it to scale Hyperledger Fabric. In our scheme, all accounting nodes are divided into clusters, and each cluster contains several nodes; then, a portion of the entire block data is stored in a cluster. Block data is stored overlappingly on some cluster nodes, and each block is guaranteed to have some copies in a cluster. Theoretical analysis and simulation show that the storage occupied by nodes is significantly reduced in blockchain applications with frequent transactions, and the mechanism can still guarantee data integrity in the case of partial node failures in a single cluster. Furthermore, for transaction-frequent applications, storage space consumption can be significantly reduced without increasing excessive query time overhead. [ABSTRACT FROM AUTHOR]

Currently, blockchain is facing a serious storage explosion problem. While most storage scaling schemes are focused on permissionless blockchain, we propose the ring-overlap mechanism for consortium blockchain and use it to scale Hyperledger Fabric. In our scheme, all accounting nodes are divided into clusters, and each cluster contains several nodes; then, a portion of the entire block data is stored in a cluster. Block data is stored overlappingly on some cluster nodes, and each block is guaranteed to have some copies in a cluster. Theoretical analysis and simulation show that the storage occupied by nodes is significantly reduced in blockchain applications with frequent transactions, and the mechanism can still guarantee data integrity in the case of partial node failures in a single cluster. Furthermore, for transaction-frequent applications, storage space consumption can be significantly reduced without increasing excessive query time overhead.

Hazard analysis methods such as HAZOP and STPA have proven to be effective methods for assurance of system safety for years. However, the dimensionality and human factors uncertainty of many assistive robotic applications challenges the capability of these methods to provide comprehensive coverage of safety issues from interdisciplinary perspectives in a timely and cost-effective manner. Physically assistive tasks in which a range of dynamic contexts require continuous human–robot physical interaction such as e.g., robot-assisted dressing or sit-to-stand pose a new paradigm for safe design and safety analysis methodology. For these types of tasks, considerations have to be made for a range of dynamic contexts where the robot-assistance requires close and continuous physical contact with users. Current regulations mainly cover industrial collaborative robotics regarding physical human–robot interaction (pHRI) but largely neglects direct and continuous physical human contact. In this paper, we explore limitations of commonly used safety analysis techniques when applied to robot-assisted dressing scenarios. We provide a detailed analysis of the system requirements from the user perspective and consider user-bounded hazards that can compromise safety of this complex pHRI.

Software defined networking controller platforms support clustering architectures to provide scalability and availability to large-scale carrier-grade networks. OpenDaylight, a well-known open source project, provides a clustering and distributed datastore architecture. The datastore is distributed into shards such that a subset of the shards can be located in any cluster member. To guarantee strong consistency in the datastore so all shard replicas have the same value, only the shard leader is responsible for accepting data updates. Even though OpenDaylight supports a distributed shard leader election algorithm, elected leaders are not distributed over the cluster members due to a lack of centralized control. Since update requests for the datastore are inherently concentrated in the leader, this results in unbalanced CPU usage of the controller cluster, as well as degradation of throughput in the distributed datastore. In this paper, we propose a shard leader distribution algorithm that maximizes the throughput of the distributed datastore by distributing the shard leaders to cluster members as evenly as possible. The shard leader distribution algorithm restricts the maximum number of leaders that a cluster member may have by monitoring the status of the shards within the cluster members. In the performance evaluation, we prove that shard leader distribution significantly improves the throughput of the datastore by load balancing data update requests to the cluster. [ABSTRACT FROM AUTHOR]

In the traditional consortium blockchain system, all nodes jointly participate in the process of transaction consensus, so that the confidentiality of transaction data within and between organizations in the consortium cannot be protected; and the throughput of the existing consortium blockchain system is still low. In response to the above problems, we propose a two-layer consortium blockchain with transaction privacy protection based on sharding technology. The blockchain consists of a sharding layer and a root consensus layer, which supports internal transactions of distributed interactive organizations, confidential transactions across shards, and public transactions across shards. At the sharding layer, we shard the nodes and their corresponding UTXOs, and ensure the confidentiality of transaction data by authorizing nodes in different shards to access different transaction data. And through the root consensus layer, the processing reliability, tamper-proof and traceability of confidential transactions across shards and internal transactions are guaranteed. The system throughput is improved by parallel processing of transactions using sharding technology, and the blockchain system with an improved Byteball architecture inside the shard, which further improves the transaction throughput of the system. And through analysis, it shows that the consortium blockchain proposed in this scheme is reasonable and feasible. [ABSTRACT FROM AUTHOR]

We define a new lattice structure (W,\preceq ) on the elements of a finite Coxeter group W. This lattice, called the \emphshard intersection order, is weaker than the weak order and has the noncrossing partition lattice \NC (W) as a sublattice. The new construction of \NC (W) yields a new proof that \NC (W) is a lattice. The shard intersection order is graded and its rank generating function is the W-Eulerian polynomial. Many order-theoretic properties of (W,\preceq ), like Möbius number, number of maximal chains, etc., are exactly analogous to the corresponding properties of \NC (W). There is a natural dimension-preserving bijection between simplices in the order complex of (W,\preceq ) (i.e. chains in (W,\preceq )) and simplices in a certain pulling triangulation of the W-permutohedron. Restricting the bijection to the order complex of \NC (W) yields a bijection to simplices in a pulling triangulation of the W-associahedron. The lattice (W,\preceq ) is defined indirectly via the polyhedral geometry of the reflecting hyperplanes of W\!. Indeed, most of the results of the paper are proven in the more general setting of simplicial hyperplane arrangements.

The article investigates scientific techniques as they are applied to ancient Chinese shards' research in terms of the case study of Southern Song (AD 1127-1279) Guan (Imperial) shards in an early stage in the West, to review how the science aided art history study, how it enriched knowledge related to ancient Chinese porcelain and art works. It is apparent that in addition to considerable effort spent on aiding authentication of museum collections, some understandable information coming from scientific analytical results had been combined into the knowledge system of art history or cultural history in post-war publication related to ancient Chinese ceramics. [ABSTRACT FROM AUTHOR]

We define a new lattice structure $(W,\preceq)$ on the elements of a finite Coxeter group W. This lattice, called the shard intersection order, is weaker than the weak order and has the noncrossing partition lattice NC ( W) as a sublattice. The new construction of NC ( W) yields a new proof that NC ( W) is a lattice. The shard intersection order is graded and its rank generating function is the W-Eulerian polynomial. Many order-theoretic properties of $(W,\preceq)$, like Möbius number, number of maximal chains, etc., are exactly analogous to the corresponding properties of NC ( W). There is a natural dimension-preserving bijection between simplices in the order complex of $(W,\preceq)$ (i.e. chains in $(W,\preceq)$) and simplices in a certain pulling triangulation of the W-permutohedron. Restricting the bijection to the order complex of NC ( W) yields a bijection to simplices in a pulling triangulation of the W-associahedron. The lattice $(W,\preceq)$ is defined indirectly via the polyhedral geometry of the reflecting hyperplanes of W. Indeed, most of the results of the paper are proven in the more general setting of simplicial hyperplane arrangements. [ABSTRACT FROM AUTHOR]

Hazard analysis methods such as HAZOP and STPA have proven to be effective methods for assurance of system safety for years. However, the dimensionality and human factors uncertainty of many assistive robotic applications challenges the capability of these methods to provide comprehensive coverage of safety issues from interdisciplinary perspectives in a timely and cost-effective manner. Physically assistive tasks in which a range of dynamic contexts require continuous human-robot physical interaction such as e.g., robot-assisted dressing or sit-to-stand pose a new paradigm for safe design and safety analysis methodology. For these types of tasks, considerations have to be made for a range of dynamic contexts where the robot-assistance requires close and continuous physical contact with users. Current regulations mainly cover industrial collaborative robotics regarding physical human-robot interaction (pHRI) but largely neglects direct and continuous physical human contact. In this paper, we explore limitations of commonly used safety analysis techniques when applied to robot-assisted dressing scenarios. We provide a detailed analysis of the system requirements from the user perspective and consider user-bounded hazards that can compromise safety of this complex pHRI., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Delgado Bellamy, Chance, Caleb-Solly and Dogramadzi.)