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Spintronic terahertz (THz) emission via spin-to-charge conversion (SCC) has been widely studied in ferromagnets (FM)/nonmagnets (NM) structures, in which various mechanisms of SCC have been confirmed in different NM materials. However, it is rare to find a material having multiple SCC mechanisms at the same time. Here, we report a ferromagnetic metal Ni film with diverse functions in the SCC process, by performing THz emission experiments in single Ni layer, FM/Ni, Ni/NM bilayers and FM/Ni/NM trilayers. It is demonstrated that in Ni monolayer, THz emission is radiated by the anomalous Hall effect and ultrafast demagnetization of Ni film. In FM/Ni, the Ni film acts as an SCC implementer and THz emission is mainly generated by the inverse spin Hall effect (ISHE) of Ni. In Ni/NM, the Ni film acts as a spin injector and provides spin currents to be converted to charge current via ISHE of heavy metal NM, inducing THz emission. In FM/Ni/NM, THz emission mainly comes from ISHE of FM/Ni, Ni/NM, and FM/NM, and their domination is relative to Ni thickness. Our findings show a ferromagnetic film not only acts as a spin injector but also as an SCC implementer, providing a new concept to design spintronic THz emitters.

To solve the problems of low efficiency and high risk of crack detection in high-rise buildings, the author proposes a building crack image acquisition and processing system based on unmanned aerial vehicle (UAV), expounds the working principle of the system, and analyzes the selection of hardware in the system. The experiment is carried out by combining the acquisition system with the image processing system of the ground station. Based on the characteristics of building surface crack image, an adaptive filtering method is introduced to improve the classic system file checker combination method. The experimental results show that the accuracy of Canny’s method was 96.88%. Canny-based crack target detection method is trained and tested on the crack data set to obtain the classification results and the best detection effect. It is proved that the Canny algorithm based on UAV images can effectively detect cracks on building surface.

Sustainable production of 1,4-pentanediol (1,4-PDO) from biomass is of great importance because 1,4-PDO is a monomer of degradable polyesters and plastics. This paper reviews the conversion of biomass-derived levulinic acid (LA) and furfural as well as their derivatives alkyl levulinate, γ-valerolactone (GVL) and furfuryl alcohol (FAL) into 1,4-PDO. MoOx or ReOx modified noble metal catalysts and non-noble metal catalysts with core–shell and alloy structures show a high 1,4-PDO yield and stability in LA hydrogenation under severe hydrothermal conditions. The conversion of furfural to 1,4-PDO involves the initial C＝O bond hydrogenation to form FAL, the consecutive acid-catalyzed ring-opening and the final hydrogenation. Therefore, it needs a bifunctional catalyst composed of metallic species and acid sites to improve the 1,4-PDO yield. Efforts are made here to highlight the employed catalysts, structure–performance relationship, reaction pathway and reaction mechanism in detail. The current challenges for large-scale applications of conversion of LA and furfural to 1,4-PDO have been proposed, including process development, catalyst cost, solvent and active site distribution. We believe that this review will provide new opportunities and expand the options for the production of 1,4-PDO via biorefining processes. [ABSTRACT FROM AUTHOR]

The studies of the nonlinear dynamics of the protective bearing-rotor system in the past 30 years were reviewed. Firstly, The development history of the local collision model was sorted out. the development of the system structure model from the two aspects of the rotor and the back-up bearing was summarized, and the characteristics of each model were given . Secondly, the main reason for back-up bearing-rotor system damage-backward whirl was analyzed. Then the relationship between the drop response results and the system structure and parameters was expoualded from three aspects of rotor structure, bearing structure and bearing parameters. Finally, some general guidelines for the design and selection of back-up bearings' structure and parameters were summarized, and some issues which was worth further study were pointed out. [ABSTRACT FROM AUTHOR]

Summary: Microalgae is an excellent type of biomass for bio‐energy production due to its high calorific value and fast growth. However, a large amount of ash would be generated during microalgae utilization. In this work, MCM41 was prepared from microalgae ash. The materials were calcined at different temperatures (450°C, 500°C, 550°C, and 600°C), and the effect of calcination temperature was investigated. Polyethyleneimine (PEI) was loaded in MCM41 by the impregnation method at different loading amounts (30%, 40%, 50%, and 60%). The CO2 capturing capacity was measured. The results showed that the MCM41 calcined at 450°C was the optimal material, which performed the most developed pore structure. Amine loading enhanced the CO2 capturing capacity of MCM41. The CO2 capturing capacity increased as PEI loading amount increased. The highest CO2 adsorption amount was 2.275 mmol/g with 60% amine loading at 25°C and 1 bar. Adsorption temperature had a mild impact on CO2 capture, and its CO2 adsorption amount decreased slightly with an increase in the adsorption temperature. It was considered that the CO2 uptake of amine‐impregnated MCM41 kept stable at different temperatures below 100°C. Also, it showed good cyclic stability. After 10 cycles, the CO2 capturing capacity of 1.6 mmol/g was exhibited. [ABSTRACT FROM AUTHOR]