Blockchain is a viable solution to provide data integrity for the enormous volume of 5G IoT social data, while we need to break through the throughput bottleneck of blockchain. Sharding is a promising technology to so...Blockchain is a viable solution to provide data integrity for the enormous volume of 5G IoT social data, while we need to break through the throughput bottleneck of blockchain. Sharding is a promising technology to solve the problem of low throughput in blockchains. However, cross-shard communication hinders the effective improvement of blockchain throughput. Therefore, it is critical to reasonably allocate transactions to different shards to improve blockchain throughput. Existing research on blockchain sharding mainly focuses on shards formation, configuration, and consensus, while ignoring the negative impact of cross-shard communication on blockchain throughput. Aiming to maximize the throughput of transaction processing, we study how to allocate blockchain transactions to shards in this paper. We propose an Associated Transaction assignment algorithm based on Closest Fit (ATCF). ATCF classifies associated transactions into transaction groups which are then assigned to different shards in the non-ascending order of transaction group sizes periodically. Within each epoch, ATCF tries to select a shard that can handle all the transactions for each transaction group. If there are multiple such shards, ATCF selects the shard with the remaining processing capacity closest to the number of transactions in the transaction group. When no such shard exists, ATCF chooses the shard with the largest remaining processing capacity for the transaction group. The transaction groups that cannot be completely processed within the current epoch will be allocated in the subsequent epochs. We prove that ATCF is a 2-approximation algorithm for the associated transaction assignment problem. Simulation results show that ATCF can effectively improve the blockchain throughput and reduce the number of cross-shard transactions.展开更多
Covalent organic frameworks(COFs)based photocatalysts utilizing infrared light remains unexplored due to the limitation of electronic absorption.Herein,two novel two-dimensional(2D)polyimide-linked phthalocyanine COFs...Covalent organic frameworks(COFs)based photocatalysts utilizing infrared light remains unexplored due to the limitation of electronic absorption.Herein,two novel two-dimensional(2D)polyimide-linked phthalocyanine COFs,namely MPc-DPA-COFs(M=Zn/Cu),were prepared from the imidization reaction of metal tetraanhydrides of 2,3,9,10,16,17,23,24-octacarboxyphthalocyaninato(M(TAPc))with 9,10-diphenyl anthracene(DPA).Both COFs possess highly crystalline eclipsed AA stacking structure with neighboring layer distance of 0.33 nm on the basis of powder X-ray diffraction analysis and high-resolution transmission electron microscopy.Effective π–π interaction between phthalocyanine chromophores in neighboring layers of 2D COFs leads to significant bathochromic-shift of narrow Q band from 697 nm for M(TAPc)to the infrared light absorption range of 760–1000 nm for MPc-DPA-COFs according to solid UV-vis diffuse reflectance spectra.This endows them in particular ZnPc-DPA-COF with excellent reactive oxygen species of•O_(2)^(–)and 1O_(2) generation activity under infrared light radiation(λ>760 nm)based on the electron spin resonance spectroscopy measurement,in turn resulting in the excellent photocatalytic capacity towards oxidation of sulfides under infrared light radiation.Corresponding quenching experiments reveal the contribution of both•O_(2)^(–)and 1O_(2) to the oxidation of sulfides,but the former•O_(2)^(–)species plays a leading role in this photocatalytic process.The present result not only provides a new efficient infrared light photocatalyst but also unveils the good potentials of phthalocyanine-based COFs in photocatalysis.展开更多
基金supported by Anhui Provincial Key R&D Program of China(202004a05020040),the open project of State Key Laboratory of Complex Electromagnetic Environment Effects on Electronics and Information System in China(CEMEE2018Z0102B)the open fund of Intelligent Interconnected Systems Laboratory of Anhui Province(PA2021AKSK0114),Hefei University of Technology.
文摘Blockchain is a viable solution to provide data integrity for the enormous volume of 5G IoT social data, while we need to break through the throughput bottleneck of blockchain. Sharding is a promising technology to solve the problem of low throughput in blockchains. However, cross-shard communication hinders the effective improvement of blockchain throughput. Therefore, it is critical to reasonably allocate transactions to different shards to improve blockchain throughput. Existing research on blockchain sharding mainly focuses on shards formation, configuration, and consensus, while ignoring the negative impact of cross-shard communication on blockchain throughput. Aiming to maximize the throughput of transaction processing, we study how to allocate blockchain transactions to shards in this paper. We propose an Associated Transaction assignment algorithm based on Closest Fit (ATCF). ATCF classifies associated transactions into transaction groups which are then assigned to different shards in the non-ascending order of transaction group sizes periodically. Within each epoch, ATCF tries to select a shard that can handle all the transactions for each transaction group. If there are multiple such shards, ATCF selects the shard with the remaining processing capacity closest to the number of transactions in the transaction group. When no such shard exists, ATCF chooses the shard with the largest remaining processing capacity for the transaction group. The transaction groups that cannot be completely processed within the current epoch will be allocated in the subsequent epochs. We prove that ATCF is a 2-approximation algorithm for the associated transaction assignment problem. Simulation results show that ATCF can effectively improve the blockchain throughput and reduce the number of cross-shard transactions.
文摘Covalent organic frameworks(COFs)based photocatalysts utilizing infrared light remains unexplored due to the limitation of electronic absorption.Herein,two novel two-dimensional(2D)polyimide-linked phthalocyanine COFs,namely MPc-DPA-COFs(M=Zn/Cu),were prepared from the imidization reaction of metal tetraanhydrides of 2,3,9,10,16,17,23,24-octacarboxyphthalocyaninato(M(TAPc))with 9,10-diphenyl anthracene(DPA).Both COFs possess highly crystalline eclipsed AA stacking structure with neighboring layer distance of 0.33 nm on the basis of powder X-ray diffraction analysis and high-resolution transmission electron microscopy.Effective π–π interaction between phthalocyanine chromophores in neighboring layers of 2D COFs leads to significant bathochromic-shift of narrow Q band from 697 nm for M(TAPc)to the infrared light absorption range of 760–1000 nm for MPc-DPA-COFs according to solid UV-vis diffuse reflectance spectra.This endows them in particular ZnPc-DPA-COF with excellent reactive oxygen species of•O_(2)^(–)and 1O_(2) generation activity under infrared light radiation(λ>760 nm)based on the electron spin resonance spectroscopy measurement,in turn resulting in the excellent photocatalytic capacity towards oxidation of sulfides under infrared light radiation.Corresponding quenching experiments reveal the contribution of both•O_(2)^(–)and 1O_(2) to the oxidation of sulfides,but the former•O_(2)^(–)species plays a leading role in this photocatalytic process.The present result not only provides a new efficient infrared light photocatalyst but also unveils the good potentials of phthalocyanine-based COFs in photocatalysis.
