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Here, an approach to produce a hierarchical porous Fe‐N‐C@TABOH catalyst with densely accessible high intrinsic active FeNx sites is proposed. The method involves a single‐step pyrolysis of Zn/Fe‐zeolitic imidazolate framework (Zn/Fe‐ZIF‐H) with tetrabutylammonium hydroxide (TABOH) micelles, which is obtained by utilizing TABOH as a structural template and electronic mediator at room temperature for a brief duration of 16 min. Notably, the yield of Zn/Fe‐ZIF‐H is 3.5 times that of Zn/Fe‐ZIF‐N prepared by conventional method. Results indicate that in addition to expediting synthesis and increasing yield of the Zn/Fe‐ZIF‐H, the TABOH induces a hierarchical porous structure and fosters the formation of more and higher intrinsic active FeNx moieties in Fex‐N‐C@TABOH, showing that TABOH is a multifunctional template. Crucially, the increased mesoporosity/external surface area and optimized microenvironment of Fe‐N‐C@TABOH significantly enhance ORR activity by facilitating the formation of high intrinsic active FeNx sites, increasing accessible FeNx sites, and reducing mass transfer resistance. Through structure tailoring and microenvironment optimization, the resulting Fe‐N‐C@TABOH exhibits superior ORR performance. DFT calculation further validates that the synergistic effect of these two factors leads to low ORR barrier and optimized *OH adsorption energy. This study underscores the importance of structure and electronic engineering in the development of highly active ORR catalysts. [ABSTRACT FROM AUTHOR]

This paper presents a nonlinear model for analyzing the behavior of functionally graded material Euler‐Bernoulli thin‐walled beams with varying cross‐sections, while considering periodic perturbations in the rotating speed. The study focuses on an analytical exploration of the natural frequency and amplitude frequency response associated with the nonlinear parametric vibrations within this system. Initially, the governing differential equations for the transverse vibrations of the beams are derived through Hamiltonian principle. Subsequently, the perturbation method is employed to solve the established equations, and Galerkin method is adopted to determine the mode shapes and frequencies. Furthermore, this research extensively examines the influence of significant parameters on the vibration characteristics of the system. [ABSTRACT FROM AUTHOR]

The construction of highly active and stable transition phosphide-based materials is widely regarded as an alternative approach to the use of Pt-based catalysts in the field of electrocatalytic hydrogen evolution. Herein, self-supported heterostructure Co–Ni phosphides (denoted as CoxNi1−x-P) were synthesized with different metal ratios by a low temperature electrodeposition strategy. Impressively, the optimized heterogeneous Co0.5Ni0.5-P nanocomposites displayed outstanding hydrogen evolution performance, with low overpotentials of 67 mV and 181 mV to deliver current densities of 10 mA cm−2 and 100 mA cm−2 in alkaline electrolyte. X-ray photoelectron spectroscopy revealed the optimized electronic structure of Co0.5Ni0.5-P, which led to an improvement in the conductivity. Density functional theory calculations demonstrated that the Co0.5Ni0.5-P heterostructure could provide a more optimal water-dissociation-related Volmer process for hydrogen evolution reaction (HER), in which water molecules could be easily activated on Co0.5Ni0.5-P with a low energy barrier. Moreover, the downshift of the d-band center confirmed the optimized H adsorption, further accelerating the HER kinetics. [ABSTRACT FROM AUTHOR]

In recent years, with the development of urban rail transit, more and more attention has been paid to the vibration problems caused by its operation. As the main form of urban rail transit's underground construction, the shield tunnel is the first to bear the brunt. However, the existing researches on the vibration of shield tunnel usually take it as a homogeneous barrel and do not consider the impact of its assembly joints on the vibration propagation. In this paper, to study the influence of the joints caused by the shield tunnel's assembly forms on the propagation of vibration, two finite element models of shield tunnels with different assembly forms are established. The analysis and comparing results of these models show that the joints caused by segment assembly of shield tunnel have obvious hysteresis and reduction effect on the vibration waves and this ability is obviously related to its location. In addition, the ability to weaken the vibration wave is also related to the frequency of the vibration wave. [ABSTRACT FROM AUTHOR]

In order to study the vibration control effects of floating rail fasteners on the metro depot and its over-track buildings, a metro depot and its over-track buildings are selected for field test and the track-stratum-operation depot-platform coupling finite element calculation model is established and verified by the measured vibration response data. The track-stratum-operation depot-platform-buildings coupling large-scale dynamic finite element analysis model is established based on the extension of the former, and the reaction forces of ordinary fasteners and floating rail fasteners are input into the model respectively to solve the vibration responses of the over-track buildings and analyze the insertion loss of vibration level varying with frequency and maximum Z vibration level in order that the effects of floating rail fasteners on the vibration control of the over-track buildings are evaluated. The research shows that for the building forms studied in this paper, the significant vibration frequency of building floor is 31. 5 Hz when the vibration propagates to the over-track buildings through the depot and the over-track platform. The floating rail fastener has few obvious effects on vibration control at the vibration significant frequency 31. 5 Hz of this over-track buildings, mainly because its stable vibration reduction frequency band occurs above 31.5 Hz. The control effects are optimal near 63 Hz, and the maximum vibration reduction of 15 dB can be achieved. With the floating rail fasteners, the maximum Z vibration level of the over-track building floor generally decreases by 2-5 dB. The research results of this paper can provide reference and basis for the selection and design of damping track for the vibration control of the depot and over-track buildings. [ABSTRACT FROM AUTHOR]

The hydrogen evolution reaction (HER) plays a vital role for the production of pure hydrogen with zero carbon release. Developing high efficiency non-noble metal electrocatalysts could reduce its cost. Here, vanadium doped cobalt phosphide grown on carbon cloth (CC) was synthesized by the low temperature electrodeposition–phosphorization method. The influence of V dopants on the structural, morphological, and electrocatalytic performance of Vx–Co1−x–P composites was also investigated in-depth. Impressively, the optimized amorphous V0.1–Co0.9–P nano-electrocatalyst exhibits outstanding catalytic activity with a low overpotential of 50 mV at a current density of 10 mA cm−2 and a small Tafel value of 48.5 mV dec−1 in alkaline media. The results showed that V dopants in the composite change its crystal structure from the crystalline phase to the amorphous phase, resulting in the introduction of V–O sites, which regulate the electron density of the active sites and the exposure of surface active sites and thus promote the electrocatalytic HER process. This work provides a novel idea for the fabrication of high-efficiency metal phosphide based electrocatalysts. [ABSTRACT FROM AUTHOR]