Scaling Membership of Byzantine Consensus

2020 ◽  
Vol 38 (3-4) ◽  
pp. 1-31
Author(s):  
Burcu Canakci ◽  
Robbert Van Renesse
Keyword(s):  
Fault Tolerant ◽  
Initial Conditions ◽  
Low Latency ◽  
Energy Costs ◽  
Prior Work ◽  
Improve Performance ◽  
Consensus Protocol ◽  
Normal Case ◽  
Network Topologies ◽  
And Performance

Scaling Byzantine Fault Tolerant (BFT) systems in terms of membership is important for secure applications with large participation such as blockchains. While traditional protocols have low latency, they cannot handle many processors. Conversely, blockchains often have hundreds to thousands of processors to increase robustness, but they typically have high latency or energy costs. We describe various sources of unscalability in BFT consensus protocols. To improve performance, many BFT protocols optimize the “normal case,” where there are no failures. This can be done in a modular fashion by wrapping existing BFT protocols with a building block that we call alliance . In normal case executions, alliance can scalably determine if the initial conditions of a BFT consensus protocol predetermine the outcome, obviating running the consensus protocol. We give examples of existing protocols that solve alliance. We show that a solution based on hypercubes and MAC s has desirable scalability and performance in normal case executions, with only a modest overhead otherwise. We provide important optimizations. Finally, we evaluate our solution using the ns3 simulator and show that it scales up to thousands of processors and compare with prior work in various network topologies.

Hashgraph the Future of Decentralized Technology and the End of Blockchain

2018 ◽  
Vol 2 (2) ◽  
pp. 86
Author(s):  
Ledina Hoxha
Keyword(s):  
Data Structure ◽  
Stock Market ◽  
High Throughput ◽  
Open Problem ◽  
Fault Tolerant ◽  
Consensus Algorithm ◽  
Consensus Protocol ◽  
Collaborative Applications ◽  
And Performance ◽  
Very High

Hashgraph is data structure and consensus algorithm that is fast, with a very high throughput and low consensus latency, secure because of the asynchronous byzantine fault tolerant and fair due to the fairness of access, ordering, and timestamps. These properties enable new decentralized applications such as a stock market, improved collaborative applications, games, and auctions. Hashgraph is a new consensus protocol that has garnered attention lately by being projected as a technology that will make blockchains obsolete. Hashgraph currently scales only in the number of transactions processed but does not scale with the number of nodes in the network. Hashgraph will face the same issues that other public blockchains are facing today and may not be able to maintain its security and performance. In fact, scalability is still an open problem for public blockchains.

A Scalable Diffusion Algorithm for Dynamic Mapping and Load Balancing on Networks of Arbitrary Topology

1997 ◽  
Vol 08 (03) ◽  
pp. 329-346 ◽  
Author(s):  
A. Heirich
Keyword(s):  
Load Balancing ◽  
Interconnection Networks ◽  
Fault Tolerant ◽  
Initial Conditions ◽  
Laplacian Matrix ◽  
Mapping Algorithms ◽  
Massively Parallel Computers ◽  
Dynamic Mapping ◽  
Network Topologies ◽  
Cluster Computers

The problems of mapping and load balancing applications on arbitrary networks are considered. A novel diffusion algorithm is presented to solve the mapping problem. It complements the well known diffusion algorithms for load balancing which have enjoyed success on massively parallel computers (MPPs). Mapping is more difficult on interconnection networks than on MPPs because of the variations which occur in network topology. Popular mapping algorithms for MPPs which depend on recursive topologies are not applicable to irregular networks. The most celebrated of these MPP algorithms use information from the Laplacian matrix of a graph of communicating processes. The diffusion algorithm presented in this paper is also derived from this Laplacian matrix. The diffusion algorithm works on arbitrary network topologies and is dramatically faster than the celebrated MPP algorithms. It is delay and fault tolerant. Time to convergence depends on initial conditions and is insensitive to problem scale. This excellent scalability, among other features, makes the diffusion algorithm a viable candidate for dynamically mapping and load balancing not only existing MPP systems but also large distributed systems like the Internet, small cluster computers, and networks of workstations.

Replication of the Superstition and Performance Study by

2014 ◽  
Vol 45 (3) ◽  
pp. 239-245 ◽  
Author(s):  
Robert J. Calin-Jageman ◽  
Tracy L. Caldwell
Keyword(s):  
Task Difficulty ◽  
Statistical Power ◽  
Meta Analysis ◽  
A Priori ◽  
Significant Heterogeneity ◽  
Performance Study ◽  
Improve Performance ◽  
Research Designs ◽  
Series Of Experiments ◽  
And Performance

A recent series of experiments suggests that fostering superstitions can substantially improve performance on a variety of motor and cognitive tasks ( Damisch, Stoberock, & Mussweiler, 2010 ). We conducted two high-powered and precise replications of one of these experiments, examining if telling participants they had a lucky golf ball could improve their performance on a 10-shot golf task relative to controls. We found that the effect of superstition on performance is elusive: Participants told they had a lucky ball performed almost identically to controls. Our failure to replicate the target study was not due to lack of impact, lack of statistical power, differences in task difficulty, nor differences in participant belief in luck. A meta-analysis indicates significant heterogeneity in the effect of superstition on performance. This could be due to an unknown moderator, but no effect was observed among the studies with the strongest research designs (e.g., high power, a priori sampling plan).

scholarly journals PSX-8 Effects of dietary concentrate level and limited feed access on feed intake and performance by lactating Alpine dairy goats

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 455-456
Author(s):  
Luana P Ribeiro ◽  
Ryszard Puchala ◽  
Terry A Gipson ◽  
Raquel V Lourencon ◽  
Arthur L Goetsch
Keyword(s):  
Feed Intake ◽  
Milk Fat ◽  
Protein Concentration ◽  
Free Choice ◽  
Energy Yield ◽  
Dairy Goats ◽  
Improve Performance ◽  
Entire Study ◽  
And Performance ◽  
Concentrate Level

Abstract The objective was to determine if effects of different limited feed access treatments on performance by lactating Alpine dairy goats vary with dietary concentrate level. Primiparous (29; 55.2±0.8 kg BW) and multiparous Alpine goats (29; 70.2±1.06 kg) were used in a 24-wk study of 3 8-wk phases beginning at 7.1±0.37 d after kidding. Diets of 40 or 60% concentrate (40C and 60C, respectively) were offered free choice in Calan gate feeders, with access continuously (CON), for 8 h between morning and afternoon milkings (DAY), or for 2 h after each milking (FRH). Although there were many interactions involving phase, ADG during the entire study was greater for CON vs. FRH (P < 0.05; -20, -41, and -61 g for CON, DAY, and FRH, respectively; SEM = 8.6). Intake of DM also was greater for CON than for FRH (P < 0.05; 2.17, 2.03, 2.01, 2.29, 2.07, and 1.80 kg/d for 40C-CON, 40C-DAY, 40C-FRH, 60C-CON, 60C-DAY, and 60C-FRH, respectively; SEM=0.093). There were interactions (P < 0.02) between concentrate level and access treatment in milk yield (2.55, 2.41, 2.61, 3.21, 2.66, and 2.27 kg/d; SEM=0.103) and protein concentration (2.65, 2.55, 2.60, 2.67, 2.70, and 2.49%; SEM = 0.042), and milk fat concentration was greatest among treatments (P < 0.05) for FRH (2.79, 2.77, 3.18, 2.86, 2.89, and 3.02% for 40C-CON, 40C-DAY, 40C-FRH, 60C-CON, 60C-DAY, and 60C-FRH, respectively; SEM=0.103). As a consequence, milk energy yield was 6.14, 5.70, 6.67, 7.83, 6.58, and 5.61 MJ/d (SEM=0.251) and the ratio of milk energy to DMI was 3.01, 2.87, 3.37, 3.47, 3.28, and 3.18 MJ/kg for 40C-CON, 40C-DAY, 40C-FRH, 60C-CON, 60C-DAY, and 60C-FRH, respectively; SEM=0.123). Overall, limited feeder access treatments did not improve performance and, in fact, the shortest access treatment increased BW loss; however, efficiency of feed DM usage for milk energy yield was not adversely impacted.

A fault-tolerant control scheme within adaptive disturbance observer for hypersonic vehicle

2017 ◽  
Vol 233 (3) ◽  
pp. 1071-1088 ◽  
Author(s):  
Jun Zhou ◽  
Jing Chang ◽  
Zongyi Guo
Keyword(s):  
Disturbance Observer ◽  
Fault Tolerant ◽  
Sliding Mode ◽  
Fault Tolerant Control ◽  
Lyapunov Theory ◽  
Sliding Mode Controller ◽  
Performance Guarantees ◽  
Uncertain Model ◽  
Control Scheme ◽  
And Performance

The paper describes the design of a fault-tolerant control scheme for an uncertain model of a hypersonic reentry vehicle subject to actuator faults. In order to improve superior transient performances for state tracking, the proposed method relies on a back-stepping sliding mode controller combined with an adaptive disturbance observer and a reference vector generator. This structure allows for a faster response and reduces the overshoots compared to linear conventional disturbance observers based sliding mode controller. Robust stability and performance guarantees of the overall closed-loop system are obtained using Lyapunov theory. Finally, numerical simulations results illustrate the effectiveness of the proposed technique.

A New Aluminium Silicon-Boron Nitride Abradable for Compressor Components

1998 ◽  
Author(s):  
K. Boddenberg ◽  
B. Kock ◽  
M. Dorfman ◽  
L. Russo ◽  
M. Nestler
Keyword(s):  
Boron Nitride ◽  
Raw Materials ◽  
Electrical Energy ◽  
Air Separation ◽  
Energy Costs ◽  
Performance Improvements ◽  
And Performance ◽  
Materials Used ◽  
Abradable Coatings ◽  
Optimization And Performance

Abstract Air separation plants use centrifugal compressors where air and electrical energy are the only raw materials used in the production process. So energy costs play a crucial role and the compressors are heavily penalized when guaranteed performance levels are not achieved. In order to better generate performance, abradable coatings, previously used in the gas turbine industry, have been designed into turbocompressors. This paper will show the optimization and performance improvements of a new aluminium silicon-boron nitride material.

A Comprehensive Review on Reconfigurable Drones: Classification, Characteristics, Design and Control Technologies

2021 ◽  
pp. 1-27
Author(s):  
Saddam Hocine Derrouaoui ◽  
Yasser Bouzid ◽  
Mohamed Guiatni ◽  
Islam Dib
Keyword(s):  
Fault Tolerant ◽  
Control Strategies ◽  
Cluttered Environments ◽  
Viable Solution ◽  
Promising Solution ◽  
Design Characteristics ◽  
And Performance ◽  
Control Technologies ◽  
And Control ◽  
Near Future

Recently, reconfigurable drones have gained particular attention in the field of automation and flying robots. Unlike the conventional drones, they are characterized by a variable mechanical structure in flight, geometric adaptability, aerial reconfiguration, high number of actuators and control inputs, and variable mathematical model. In addition, they are exploited to flight in more cluttered environments, avoid collisions with obstacles, transport and grab objects, cross narrow and small spaces, decrease different aerial damages, optimize the consumed energy, and improve agility and maneuverability in flight. Moreover, these new drones are considered as a viable solution to provide them with specific and additional functionalities. They are a promising solution in the near future, since they allow increasing considerably the capabilities and performance of classical drones in terms of multi-functionalities, geometric adaptation, design characteristics, consumed energy, control, maneuverability, agility, efficiency, obstacles avoidance, and fault tolerant control. This paper explores very interesting and recent research works, which include the classification, the main characteristics, the various applications, and the existing designs of this particular class of drones. Besides, an in-depth review of the applied control strategies will be presented. The links of the videos displaying the results of these researches will be also shown. A comparative study between the different types of flying vehicles will be established. Finally, several new challenges and future directions for reconfigurable drones will be discussed.

HR analytics and performance appraisal system

2017 ◽  
Vol 40 (6) ◽  
pp. 684-697 ◽  
Author(s):  
Anshu Sharma ◽  
Tanuja Sharma
Keyword(s):  
Conceptual Framework ◽  
Performance Management ◽  
Performance Appraisal ◽  
Appraisal System ◽  
Improve Performance ◽  
Content Type ◽  
Organizational Settings ◽  
Employees Satisfaction ◽  
Management Area ◽  
And Performance

PurposeThis paper aims to explore the role of human resource (HR) analytics on employees’ willingness to improve performance. In doing so, the paper examines issues related to the performance appraisal (PA) system which affect employees’ willingness to improve performance and how HR analytics can be a potential solution to deal with such issues. Design/methodology/approachThe paper develops a conceptual framework along with propositions by integrating both academic and practitioner literatures, in the field of HR analytics and performance management. FindingsThe paper proposes that the use of HR analytics will be negatively related to subjectivity bias in the PA system, thereby positively affecting employees’ perceived accuracy and fairness. This further positively affects employees’ satisfaction with the PA system, which subsequently increases employees’ willingness to improve performance. Research limitations/implicationsThe paper provides implications for both researchers and practitioners in the performance management area for improving employees’ performance by applying HR analytics as a strategic tool in the PA system. It also provides implications for future researchers to empirically test the conceptual framework in different organizational settings. Originality/valueThe paper offers insights into how the use of HR analytics can deal with issues of subjectivity bias in the PA system and positively affects employees’ willingness to improve performance.

scholarly journals ECLB: Edge-Computing-Based Lightweight Blockchain Framework for Mobile Systems

2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Qingqing Xie ◽  
Fan Dong ◽  
Xia Feng
Keyword(s):  
Mobile Devices ◽  
Security Analysis ◽  
Edge Computing ◽  
Mobile Systems ◽  
Superior Performance ◽  
Consensus Protocol ◽  
Open Problems ◽  
Blockchain Technology ◽  
Natural Solution ◽  
And Performance

The blockchain technology achieves security by sacrificing prohibitive storage and computation resources. However, in mobile systems, the mobile devices usually offer weak computation and storage resources. It prohibits the wide application of the blockchain technology. Edge computing appears with strong resources and inherent decentralization, which can provide a natural solution to overcoming the resource-insufficiency problem. However, applying edge computing directly can only relieve some storage and computation pressure. There are some other open problems, such as improving confirmation latency, throughput, and regulation. To this end, we propose an edge-computing-based lightweight blockchain framework (ECLB) for mobile systems. This paper introduces a novel set of ledger structures and designs a transaction consensus protocol to achieve superior performance. Moreover, considering the permissioned blockchain setting, we specifically utilize some cryptographic methods to design a pluggable transaction regulation module. Finally, our security analysis and performance evaluation show that ECLB can retain the security of Bitcoin-like blockchain and better performance of ledger storage cost in mobile devices, block mining computation cost, throughput, transaction confirmation latency, and transaction regulation cost.

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