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The sedimentary characteristics of the special interlayer contained in the section of the Sparkling Lake dam revealed by the 8 August Jiuzhaigou earthquake in 2017 are obviously different from the tufa in the dam body, and they are considered to be historic flood relics. Based on the study of the particulate matter from the 8 August Jiuzhaigou earthquake, this study combined comparative petrographic, mineralogical, geochemical, and chronological studies of the special interbedded sediments of the Sparkling Lake dam with other genetic samples to obtain homology information and genetic links and to explore the tufa depositional dynamics and earthquake disaster subsidence. The paleoseismic benefit in the discontinuity layer was explored, and the paleoseismic information embedded in the profiles was extracted, providing a new idea for reconstructing the paleoseismic events in the tufa deposition sequence. According to X-ray diffraction, laser particle size analysis, and scanning electron microscope experiments, the particulate matter in the Jiuzhaigou mountains has its own specific mineralogical characteristics. The mineral composition of the particulate matter is basically calcite. The particle size is large, and single particles are mostly angular and subangular. The fracture morphology observed under the single-particle microscope was uneven, showing the characteristics of the dust caused by earthquake disasters. The geochemical analysis data show that the distribution patterns of rare earth elements in different types of particulate matter in the same area have similar characteristics. Moreover, an analysis of the elements Rb, Sr, and Ba shows that the particulate matter in Jiuzhaigou has a strong correlation (R2 = 0.9941), indicating the stability and uniformity of the material source. The source of the particulate matter was limestone of the carbonate strata from the Devonian to the Triassic. Combined with mineralogy and grain size morphology, the interbedded particles in the tufa depositional profile have the potential application of paleoseismic archives to record extreme seismic events. According to the chronological data of the special interlayer sediments in the tufa dam body, the paleoseismic age is inferred to be 1220 ± 30 BP. Therefore, the tufa bedding can be related to the paleoearthquake, and the special interlayer of the tufa section can be used to reconstruct paleoearthquakes. [ABSTRACT FROM AUTHOR]

With the rapid development of computational fluid dynamics (CFD) technology, it has been widely used to study the wind field characteristics of downbursts in mountainous areas. However, there is little guidance on the selection of different turbulence models for simulating downburst wind fields over hills using CFD, and few comparative studies have been conducted. This paper used nine turbulence models to simulate the wind field of a downburst over a 3D quadratic ideal hill. The simulated values of average and transient winds were compared with wind tunnel test data, and the flow characteristics at different moments under a downburst were analyzed. The flow characteristics in the wake region of the downburst over the hill are also quantitatively analyzed using the proper orthogonal decomposition (POD) method. The results show that approximately 85% of the results from the LES and REA models fall within a 30% error range, so the large eddy simulation (LES) model and the realizable k-ε model (REA) are more accurate in simulating the mean wind field, and the transient wind field simulated by the LES model is also in good agreement with the experimental data. In addition, this paper reveals the evolution mechanism of the transient wind field structure over a hill model under a downburst and finds that the first-order mode obtained by POD may be related to the acceleration effect on the hilltop. [ABSTRACT FROM AUTHOR]

The design of high-performance and low-cost oxygen evolution reaction (OER) electrocatalysts is crucial for environment friendly hydrogen production. Some transition metals have been proven to be good substitutes for noble metals due to their unique electronic structural characteristics and good electrocatalytic performances, with examples including nickel and cobalt, which are usually used to prepare OER electrocatalysts. In this work, we synthesized three-dimensional Ni-Co-Fe ternary layered double hydroxide nanosheet array electrocatalysts via hydrothermal process. Iron element was introduced into the Ni-Co based hydroxide. The ternary layered double hydroxide has a nanoarrays microstructure. Theoretical analysis confirms that by adjusting the ratio of Ni/Co/Fe, the microstructure of the catalyst changes significantly. Attributed to the special nanostructure, the catalysts show superior catalytic activities in oxygen evolution reaction (OER). The results show that a small overpotential of 222 mV at the current density of 20 mA·cm−2 for the OER in 1.0 M KOH is acquired. A small Tafel slope of 61.22 mVdec−1 and a maximum specific capacitance of 239 Fg−1 are also obtained. [ABSTRACT FROM AUTHOR]

Methanol‐to‐olefin (MTO) conversion on zeolites has encountered severe coke deposition and rapid deactivation. Creating different levels of porosity is essential to mitigate such issues. Herein, we demonstrate a facile and green strategy to synthesize uniform and hierarchically macro/mesoporous ZSM‐5 microspheres by combining spray‐freeze drying and steaming‐assisted crystallization (SAC). The structure, crystallinity, and porosity of the zeolite microspheres are controlled by adjusting the water/gel mass ratio and time in the SAC process. The structure evolution during the SAC process is revealed. In the catalytic MTO reaction, the representative hierarchically porous ZSM‐5 catalyst exhibits superior catalytic performance. At a very high weight hourly space velocity of 18 h−1, it shows a dramatically prolonged lifetime (47 h at >99% conversion) and much‐improved selectivity to ethylene and propylene compared with the conventional microporous ZSM‐5 and nano‐sized ZSM‐5. The enhanced performance is originated from the hierarchical structure and suitable acidity of the ZSM‐5 microspheres. [ABSTRACT FROM AUTHOR]