Mitigating Backdoors in Federated Learning with FLD

Federated learning allows clients to collaboratively train a global model without uploading raw data for privacy preservation. This feature, i.e., the inability to review participants' datasets, has recently been found responsible for federated learning's vulnerability in the face of backdoor attacks. Existing defense methods fall short from two perspectives: 1) they consider only very specific and limited attacker models and unable to cope with advanced backdoor attacks, such as distributed backdoor attacks, which break down the global trigger into multiple distributed triggers. 2) they conduct detection based on model granularity thus the performance gets impacted by the model dimension. To address these challenges, we propose Federated Layer Detection (FLD), a novel model filtering approach for effectively defending against backdoor attacks. FLD examines the models based on layer granularity to capture the complete model details and effectively detect potential backdoor models regardless of model dimension. We provide theoretical analysis and proof for the convergence of FLD. Extensive experiments demonstrate that FLD effectively mitigates state-of-the-art backdoor attacks with negligible impact on the accuracy of the primary task

The impact of shared leadership on team performance in college student teams: The mediating role of team trust

With the improvement in the diversity of college students’ teams, the environment they face is becoming increasingly complex and dynamic. It is particularly important for team members to cooperate for mutual progress and growth. From the perspective of college student teams, this study explored the influence of shared leadership on team performance and analysed the mediating role of team trust. A questionnaire was administered to 185 college students. The results show that shared leadership positively impacts team performance; shared leadership has a positive impact on team trust; team trust mediates between shared leadership and team performance. Finally, based on the research results, this study proposes corresponding management suggestions and provides a feasible direction for improving the efficiency of teams of college students

Microstructure and mechanical properties of Ti6321 alloy welded joint by EBW

Titanium and its alloys have excellent combination of properties, such as low density, high specific strength and corrosion resistance, and they are extensively used in many industrial fields. This work is aiming at investigation on the microstructure and mechanical properties of Ti–6Al–3Nb–2Zr–1Mo (Ti6321) alloy joints by Electron beam welding (EBW). The results show that the microstructure of the weld metal (WM) is composed of a mixture of acicular α, acicular α′, and β. The heat affected zone (HAZ) near WM consists of acicular α, primary α, acicular β phase and lots of acicular martensite α′. The HAZ near base metal consists of primary α phase and transformed β containing acicular α. The micro-hardness of the weld metal and heat affected zone are higher than that of base metal, and there are the peak values for the HAZ near the weld metal. The tensile strength of joint is equal to that of base metal, and the fracture locations of all the tensile specimens are in base metal, and it is well in accordance with the relationship between microstructure and mechanical properties of welded joints. Keywords: Ti6321, Electron beam welding, Microstructure, Propertie

Two-dimensional spinel CuCo2S4 nanosheets as high efficiency cathode catalyst for lithium-oxygen batteries

In this work, a novel 2D CuCo2S4 (CCS)nanosheets with spinel type structure is fabricated and used as the cathode catalyst for rechargeable Li-O2 battery. The characteristic 2D nanosheets structure with exposure of special (113), (004), and (044)crystal faces provide sufficient active sites for ORR and OER, which promote the rate capability immensely as well as improve discharge capacity and cycle life of the battery. Specifically, Li-O2 batteries with CCS electrodes show excellent cycle stability of more than 176 cycles at limiting capacity 500 mA h g−1 and superior rate performance (2254 mA h g−1 at 2000 mA g−1). For comparison, nanostructures of CuS and Co3S4 have been synthesized employing the similar process used for CCS. When compared to conventional carbon material (Super P)and these two binary metal sulfides, CCS NSs provided the highest catalytic activities at the same mass loading. Which can be attributed to the introduction of copper in the Co3S4 lattice offers the oxygen evolution and kinetics by enhancing Cu2+ sites and also by providing a high-active high-spin stat of octahedral Co3+ for ORR and OER catalysis

The Synthesis of Cu-Coated Ti₂SnC Ceramic and Its Tribological Behaviors as a Lubricant Additive

Lubricant additive plays an important role in reducing the friction and wear for base oil. MAX phase ceramics may have superior advantages for additive application due to their unique nanolayered structure. In this paper, Ti2SnC ceramic is prepared by sintering the elemental mixtures at 1250 °C. In addition, Cu-coated Ti2SnC ceramic is successfully prepared using a chemical plating method for the first time. It is confirmed that the Ti2SnC ceramic has good self-catalytic activity, and a layer of stacking Cu nano-particles can be deposited on the Ti2SnC surface without pretreatment. When the Cu-coated Ti2SnC ceramic powder is doped into PAO10 base oil, the oil can exhibit excellent lubrication properties, where the friction coefficient is as low as 0.095. A layer of tribo-film can be formed during the sliding process when the Cu-coated Ti2SnC ceramic is incorporated into PAO10 base oil, which can reduce the friction coefficient. The superior lubrication properties can be attributed to the synergistic lubrication effect of Ti2SnC ceramic and Cu nano-particles

Morphology regulation of Li2O2 by flower-like ZnCo2S4 enabling high performance Li-O2 battery

The development of high-efficiency oxygen electrode with well structural and chemical stability is critical to boost the rapid development of lithium-oxygen (Li-O2) batteries. Which are reckoned as a potent contender for next-generation energy storage devices due to their ultra-high theoretical energy density. Here, a flower-like three-dimensional self-standing ZnCo2S4-based electrode without an addition of binders are fabricated and employing as positive electrode for Li-O2 batteries. The bifunctional catalytic activity of flower-like ZnCo2S4 is conducive to improving the hysteresis kinetics of oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Representative ultrathin petal edge exposes adequate active sites and provides a sufficient contact interface between Li2O2 and positive electrode, which are essential for reducing the charge overpotential during OER. Compared with the control electrodes, the flower-like ZnCo2S4@Ni-based Li-O2 battery shows decreased overpotential (0.78 V) and improved cycle stability (over 500 cycles)