The Internet of Things(IoT)access controlmechanism may encounter security issues such as single point of failure and data tampering.To address these issues,a blockchain-based IoT reputation value attribute access cont...The Internet of Things(IoT)access controlmechanism may encounter security issues such as single point of failure and data tampering.To address these issues,a blockchain-based IoT reputation value attribute access control scheme is proposed.Firstly,writing the reputation value as an attribute into the access control policy,and then deploying the access control policy in the smart contract of the blockchain system can enable the system to provide more fine-grained access control;Secondly,storing a large amount of resources fromthe Internet of Things in Inter Planetary File System(IPFS)to improve system throughput;Finally,map resource access operations to qualification tokens to improve the performance of the access control system.Complete simulation experiments based on the Hyperledger Fabric platform.Fromthe simulation experimental results,it can be seen that the access control system can achieve more fine-grained and dynamic access control while maintaining high throughput and low time delay,providing sufficient reliability and security for access control of IoT devices.展开更多
In this work,we successfully prepared vertically aligned NaNbO_(3)nanotube(NN-NT)with trapezoidal shapes,in which the orthorhombic and monoclinic phases coexisted.According to the structure analysis,the NN-NT/epoxy co...In this work,we successfully prepared vertically aligned NaNbO_(3)nanotube(NN-NT)with trapezoidal shapes,in which the orthorhombic and monoclinic phases coexisted.According to the structure analysis,the NN-NT/epoxy composite film had excellent flexoelectric properties due to the lattice distortion caused by defects and irregular shape.The flexoelectric effect is the greatest in the vertical direction in the flexible NN-NT/epoxy composite film,and the flexoelectric coefficient()is 2.77×10^(−8)C·m^(−1),which is approximately 5-fold higher than that of the pure epoxy film.The photovoltaic current of the NN-NT/epoxy composite film increased from 39.9 to 71.8 nA·cm^(−2)in the direction of spontaneous polarization when the sample was bent upward due to the flexoelectricity-enhanced photovoltaic(FPV)effect.The flexoelectric effect of the NN-NT/epoxy composite film could modulate the photovoltaic response by increasing it by 80%or reducing it to 65%of the original value.This work provides a new idea for further exploration in efficient and lossless ferroelectric memory devices.展开更多
文摘The Internet of Things(IoT)access controlmechanism may encounter security issues such as single point of failure and data tampering.To address these issues,a blockchain-based IoT reputation value attribute access control scheme is proposed.Firstly,writing the reputation value as an attribute into the access control policy,and then deploying the access control policy in the smart contract of the blockchain system can enable the system to provide more fine-grained access control;Secondly,storing a large amount of resources fromthe Internet of Things in Inter Planetary File System(IPFS)to improve system throughput;Finally,map resource access operations to qualification tokens to improve the performance of the access control system.Complete simulation experiments based on the Hyperledger Fabric platform.Fromthe simulation experimental results,it can be seen that the access control system can achieve more fine-grained and dynamic access control while maintaining high throughput and low time delay,providing sufficient reliability and security for access control of IoT devices.
基金supported by the National Key Research&Development project from the Ministry of Science and Technology in China(No.2021YFB3200303)It was also partially supported by the National Natural Science Foundation of China(No.52172082).
文摘In this work,we successfully prepared vertically aligned NaNbO_(3)nanotube(NN-NT)with trapezoidal shapes,in which the orthorhombic and monoclinic phases coexisted.According to the structure analysis,the NN-NT/epoxy composite film had excellent flexoelectric properties due to the lattice distortion caused by defects and irregular shape.The flexoelectric effect is the greatest in the vertical direction in the flexible NN-NT/epoxy composite film,and the flexoelectric coefficient()is 2.77×10^(−8)C·m^(−1),which is approximately 5-fold higher than that of the pure epoxy film.The photovoltaic current of the NN-NT/epoxy composite film increased from 39.9 to 71.8 nA·cm^(−2)in the direction of spontaneous polarization when the sample was bent upward due to the flexoelectricity-enhanced photovoltaic(FPV)effect.The flexoelectric effect of the NN-NT/epoxy composite film could modulate the photovoltaic response by increasing it by 80%or reducing it to 65%of the original value.This work provides a new idea for further exploration in efficient and lossless ferroelectric memory devices.
