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Understanding the hydrogen (H) capacity, which represents the tritium capacity in Li2TiO3 crystal has become an important aspect of the tritium release process of nuclear fusion. In this work, a systematic density-functional-theory (DFT) study is performed to investigate the trapping and accumulation of H in Li2TiO3 crystal. In perfect crystal, the H adsorption properties are investigated and the maximum number of trapped H atoms are obtained. In the defect models, by calculating the trapping energy and Bader charge, we find that a Li vacancy can capture four H atoms while the capacity of a Ti vacancy is seven and then other H atoms tend to be trapped by interstitial sites outside the vacancy. Then the H capacity both inside and outside the vacancy in the defect models is studied and analyzed. According to our calculations, crystals containing a vacancy present stronger H trapping abilities than perfect crystals, especially for the crystal with a Ti vacancy. In addition, the increase of H atoms in the vacancy facilitates the formation of the neighboring vacancy so that more H atoms can be accommodated in the crystal with vacancy. Our results reveal the H capacity of different Li2TiO3 models, which provide theoretical support for related tritium release experiments. [ABSTRACT FROM AUTHOR]

Modulation of electrolyte to tailor the activity and selectivity for photoelectrochemical (PEC) water splitting has been long neglected. Herein, we boosted H2O2 accumulation on a BiVO4 photoanode via PEC water oxidation in a series of carbon quantum dots (CQDs) aqueous solutions with aliphatic amino acids as precursors. Mott–Schottky measurements demonstrated CQDs solution can tune catalytic voltage location of the BiVO4 substrate. Open circuit voltage decay (OCVD) demonstrated that the system can achieve efficient charge separation owing to the fabricated dynamic heterojunction between CQDs particles and BiVO4 substrate. Owing to the energy gradient, water oxidation may occur on the more hydrophilic CQDs surface, which regulated H2O2 generation mediated by the formation of hydroxyl radicals (OH˙) from water, as evidenced by electron paramagnetic resonance (EPR). Assisted by a Clark electrode and linear sweep voltammetry, we evidenced that CQDs can efficiently retard H2O2 decomposition. Overall, H2O2 production was performed with a rate averaging 0.33 μmol min−1 cm−2 at 1.23 V with a Faraday efficiency (FE) of 93.5%, in which O2 evolution was nearly completely suppressed. By contrast, the commonly used HCO3− electrolyte only afforded an H2O2 evolution rate of 0.032 μmol min−1 cm−2, corresponding to FE of 18.2%. Here, we executed PEC water oxidative H2O2 accumulation in CQDs solution directly, and the innovation can hopefully draw more attention to catalytic media for improving PEC performance. [ABSTRACT FROM AUTHOR]

In this paper, we are concerned with the problem of finding fixed points of nonexpansive mappings on Hadamard manifolds. To solving this kind of problem, a modified Riemannian Halpern algorithm, which is a natural generalization of a modified Halpern algorithm in Euclidean space is proposed. By giving some mild assumptions and necessary lemmas, the global convergence of the proposed algorithm is established. Finally, when the problem is solved in the framework of Hadamard manifolds, the numerical experiments show the effectiveness of the proposed algorithm, especially in computational time and number of iterations. [ABSTRACT FROM AUTHOR]

A method is proposed to optimize gear modification for a spur planetary gear train with equal spaced planets at high power. In order to simplify the finite element model, a sub-system model with one-planet gear in the planetary system is set up, in which the displacement compatibility of the two boundaries on the part sun gear is determined by applying displacement constraint equations to the corresponding nodes at each side. Local refined elements coupling with the adjacent elements near the contact zone are modeled in order to improve the approximation precision of a profile, reduce the size of the finite element model and improve the solution efficiency and precision of the nonlinear contact analysis. A rapid and precise modeling approach of FEA for spur gear modification is presented. The reconstruction o:" the modified tooth surface is achieved by changing the nodes coordinates on the tooth surface according to the modification function. The parameters of the modified gear are optimized by iteratively solving stress distribution taking uniform stress as the main objective. [ABSTRACT FROM AUTHOR]