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In order to improve the performance of unsupervised hash learning and achieve robust hashing image retrieval,this paper proposes a novel robust hash learning method based on dual-teacher self-supervised distillation.Specifically,the proposed method contains two stages:a self-supervised dual-teacher learning stage and a robust hash learning stage.In the first stage,a modified cluster algorithm is designed to effectively improve the accuracy of hard pseudo labels.Then,we fine-tune the teacher networks by hard pseudo labels to get the initial soft pseudo labels.In the second stage,we filter the initial soft pseudo labels by our soft pseudo label denoising method,which combines a hybrid denoising strategy and a dual-teacher denoising strategy.Then,we train the student network with the denoised soft pseudo labels by knowledge distillation,so that robust hash codes for label-free images are obtained.Extensive experiments on CIFAR-10,FLICKR25K and EuroSAT datasets show that the proposed robust hash learning method outperforms the state-of-the-art methods.In detail,the MAP of our method is 18.6% higher than that of the TBH method on CIFAR-10,2.4% higher than that of the DistillHash method on FLICKR25K,and 18.5% higher than that of the ETE-GAN method on EuroSAT.

The realization of high energy density and fast-charging capability is severely limited by the low intrinsic electronic conductivity and slow ion diffusion rates for the Na3V2(PO4)2O2F (NVPOF) cathode in sodium-ion batteries (SIBs). Inspired by the rapid transport of carriers in two-dimensional (2D) frames, we designed a carbonless fast-charging 2D-NVPOF cathode material using H2O molecules as the initial green exfoliant for the first time, which achieves the breakage of strong interlayer ionic bonds under mild and safe conditions. After exfoliation operation via mechanical expansion with the assistance of a thermal field, the H2O molecules can enter into interlayers of 2D-NVPOF and further coordinate with the defective V atoms, thus enhancing the electronic conductivity, structural robustness and Na+ diffusion kinetics, which can be verified from the enhanced (002) lattice plane exposure, reduced band gap and lower Na+ migration energy barrier of 2D-NVPOF. In concert, these merits contribute to achieving the excellent fast-charging properties (80% of total battery capacity in 120 s of charging), higher energy density (up to 465 W h kg−1), and long-term cycling stability of 2D-NVPOF, highlighting the great potential for practical application in SIBs. This strategy implies that the enhancement of electronic/ionic conductivity in the NASICON structure is achievable without introducing carbon and altering the active center, thus sparking new ideas for improving the fast-charging characteristics of cathodes for SIBs. [ABSTRACT FROM AUTHOR]

The NASICON cathode, Na3V2(PO4)3, has garnered significant attention due to its robust framework with fast Na+ migration. To expand its application scenarios by diversified electronic reaction, the substitution of vanadium with cost‐effective and abundant redox elements is a special research topic. Nevertheless, in terms of reducing toxicity, increasing Na content and widening voltage range, the V4+/5+ redox couple in Na4FeV(PO4)3 often accompanies asymmetric and irreversible electrochemical reactions that pose a dilemma for capacity and structural stability, especially at high currents. Herein, in this work, Na4FeV1/3Ti2/3(PO4)3 (NFVT) has achieved highly reactive of multiple electron transfer (Ti2+/3+, Fe2+/3+, and V3+/4+/5+) by utilizing the redox reaction with quasi‐monophase behavior, and it can reserve great capacity retention after 3,000 cycles. More competitively, its boosting kinetics makes the fast‐charging characteristic, just requiring only 3.63 min to reach 80% state of charge at 2 C. The rapid ion/electron transport dynamics can achieve the decay of only 0.043% per cycle by unlocking the quasi‐monophase behavior in the framework of NFVT full cells. The present study provides a fresh perspective on designing cathode materials with fast‐charging capabilities for sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

2D compounds exfoliated from weakly bonded bulk materials with van der Waals (vdW) interaction are easily accessible. However, the strong internal ionic/covalent bonding of most inorganic crystal frameworks greatly hinders 2D material exfoliation. Herein, we first proposed a radical/strain‐synergistic strategy to exfoliate non‐vdW interacting pseudo‐layered phosphate framework. Specifically, hydroxyl radicals (⋅OH) distort the covalent bond irreversibly, meanwhile, H2O molecules as solvents, further accelerating interlayered ionic bond breakage but mechanical expansion. The innovative 2D laminar NASICON‐type Na3V2(PO4)2O2F crystal, exfoliated by ⋅OH/H2O synergistic strategy, exhibits enhanced sodium‐ion storage capacity, high‐rate performance (85.7 mAh g−1 at 20 C), cyclic life (2300 cycles), and ion migration rates, compared with the bulk framework. Importantly, this chemical/physical dual driving technique realized the effective exfoliation for strongly coupled pseudo‐layered frameworks, which accelerates 2D functional material development. [ABSTRACT FROM AUTHOR]

Environmental, social, and governance (ESG) performance has increasingly become the most pressing concern for governments, social organizations, companies, and other stakeholders. Understanding macro ESG behavior can assist governments in achieving their sustainable development goals (SDGs). In this paper, we investigate whether the macro ESG index of OPEC and non‐OPEC oil‐producing countries over the period 1990–2020 exhibits mean‐reversion behavior and whether the external shocks are transient or permanent. By conducting a series of advanced panel stationarity tests, we find that the macro ESG indices of the sample countries do not exhibit mean‐reversion and that an external shock has a permanent effect. We also identifies the yearly structural breaks that occur in the sample countries and attempts to explain why. Our research suggests that governments should use policy interventions to counteract external shocks to macro ESG behavior so as to achieve sustainable development and long‐term performance stability. [ABSTRACT FROM AUTHOR]