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The data hierarchical Ciphertext-Policy Attribute-Based Encryption (CP-ABE) scheme implements multiple hierarchical data encryption of a single access policy, which reduces the computation and storage overhead. However, existing data hierarchical CP-ABE schemes have some problems, such as the leakage of personal privacy information through access policies or user attributes in plaintext form, and these schemes grant enough privileges to a single authorization center. If the authorization center is untrusted or attacked, keys can be used to illegally access data, which is the key escrow problem. To solve these problems, we propose an Attribute Hiding and Multiple Authorization Centers-based Data Hierarchical Encryption Scheme (AH-MAC-DHE). Firstly, we propose an Attribute Convergence Hiding Mechanism (ACHM). This mechanism solves the problem of personal privacy information leakage by hiding access policies and user attributes. Secondly, we design Privilege-Dispersed Multiple Authorization Centers (PD-MAC). PD-MAC solves the problem of key escrow by dispersing the privileges of the single authorization center to the user authorization center and attribute authorization center. Finally, we prove that AH-MAC-DHE is secure under the decisional q-parallel Bilinear Diffie-Hellman Exponent (BDHE) assumption, which also satisfies anti-collusion and privacy security. The experimental results indicate that compared with existing schemes, AH-MAC-DHE performs well. [ABSTRACT FROM AUTHOR]

The sluggish kinetics of complicated multiphase conversions and the severe shuttling effect of lithium polysulfides (LiPSs) significantly hinder the applications of Li‐S battery, which is one of the most promising candidates for the next‐generation energy storage system. Herein, a bifunctional electrocatalyst, indium phthalocyanine self‐assembled with carbon nanotubes (InPc@CNT) composite material, is proposed to promote the conversion kinetics of both reduction and oxidation processes, demonstrating a bidirectional catalytic effect on both nucleation and dissolution of Li2S species. The theoretical calculation shows that the unique electronic configuration of InPc@CNT is conducive to trapping soluble polysulfides in the reduction process, as well as the modulation of electron transfer dynamics also endows the dissolution of Li2S in the oxidation reaction, which will accelerate the effectiveness of catalytic conversion and facilitate sulfur utilization. Moreover, the InPc@CNT modified separator displays lower overpotential for polysulfide transformation, alleviating polarization of electrode during cycling. The integrated spectroscopy analysis, HRTEM, and electrochemical study reveal that the InPc@CNT acts as an efficient multifunctional catalytic center to satisfy the requirements of accelerating charging and discharging processes. Therefore, the Li–S battery with InPc@CNT‐modified separator obtains a discharge‐specific capacity of 1415 mAh g−1 at a high rate of 0.5 C. Additionally, the 2 Ah Li–S pouch cells deliver 315 Wh kg−1 and achieved 80% capacity retention after 50 cycles at 0.1 C with a high sulfur loading of 10 mg cm−2. Our study provides a practical method to introduce bifunctional electrocatalysts for boosting the electrochemical properties of Li–S batteries. [ABSTRACT FROM AUTHOR]

Volume changes, polysulfide shuttle effects, and low Li-ion/electronic conductivity of sulfide electrodes limit their application in Li-ion batteries with high-energy density. Here, micron FeS2 particles with bifunctional carbon nanotubes (FeS2@B–CNTs) including CNT internal conductive networks and external protective cages were prepared by a one-step solvothermal method. The internal CNTs anchor FeS2via chemical binding, which much more effectively inhibited the shuttle effect than physical confinement alone. Meanwhile, reticular CNT cages were generated on the surface of the composite FeS2 micron particles, buffering volumetric changes during cycling and further restraining the shuttle of polysulfides. Additionally, a three-dimensional CNT framework offered a primarily continuous charge transfer pathway. The FeS2@B–CNTs electrode had a high initial coulombic efficiency of 91.3% and delivered a capacity of 698 mA h g−1 over 500 cycles at 1000 mA g−1. The Li-ion diffusion coefficient is two orders of magnitude higher than those of previous reports, which improved the rate performance of the FeS2@B–CNTs electrode. These studies on micron FeS2 spheres shed light on the design strategies for the application of sulfide electrodes. [ABSTRACT FROM AUTHOR]

A low complexity scheme is proposed for direct detection orthogonal frequency division multiple access passive optical network, based on optical single sideband modulation and polarisation multiplexing. By utilising Hermitian symmetry mapping and Hilbert transformation, the hardware requirement is reduced. Theoretical expressions are presented to explain the cross-polarisation interference, and a channel estimation algorithm is proposed for polarisation crosstalk. In addition, system parameters are discussed to optimise the performance of the proposed scheme. [ABSTRACT FROM AUTHOR]