A survey on blockchain consensus mechanism: research overview, current advances and future directions

Purpose-As the core technology of blockchain,various consensus mechanisms have emerged to satisfy the demands of different application scenarios.Since determining the security,scalability and other related performance of the blockchain,how to reach consensus efficiently of consensus mechanism is a critical issue in the blockchain.Design/methodology/approach-The paper opted for a research overview on the blockchain consensus mechanism,including the consensus mechanisms’consensus progress,classification and comparison,which are complemented by documentary analysis.Findings-This survey analyzes solutions for the improvement of consensus mechanisms in blockchain that have been proposed during the last few years and suggests future research directions around consensus mechanisms.First,the authors outline the consensus processes,the advantages and disadvantages of the mainstream consensus mechanisms.Additionally,the consensus mechanisms are subdivided into four types according to their characteristics.Then,the consensus mechanisms are compared and analyzed based on four evaluation criteria.Finally,the authors summarize the representative progress of consensus mechanisms and provide some suggestions on the design of consensus mechanisms to make further advances in this field.Originality/value-This paper summarizes the future research development of the consensus mechanisms.

Self-catalytic pyrolysis thermodynamics of waste printed circuit boards with co-existing metals

Waste printed circuit boards(WPCBs)are generated increasingly recent years with the rapid replacement of electric and electronic products.Pyrolysis is considered to be a potential environmentally-friendly technology for recovering organic and metal resources from WPCBs.Thermogravimetric analysis and kinetic analysis of WPCBs were carried out in this study.It showed that the co-existing metals(Cu,Fe,Ni)in WPCBs have positive self-catalytic influence during the pyrolysis process.To illustrate their catalytic effects,the apparent activation energy was calculated by differential model.Contributions of different reactions during catalytic pyrolysis process was studied and the mechanism function was obtained byŠesták-Berggren model.The results showed that Cu,Fe,Ni can promote the reaction progress and reduce the apparent activation energy.Among the three metals,Ni plays better catalytic role than Cu,then Fe.This work provides theoretical base for understanding the three metals’catalytic influence during the pyrolysis of non-metal powders in WPCBs.