Research on Evolution Characteristics of Shale Crack Based on Simultaneous Monitoring of Multi-Parameters

Meso-crack evolution mechanism of shale is a key factor affecting the mechanical properties of shale. In order to explore evolution laws of cracks in shale during loading, a meso-crack monitoring system, loading test equipment and an automatic ultrasonic data acquisition system were set up. On this basis, a set of experimental apparatus simultaneous monitoring multi-parameters of shale micro-crack was designed, and destruction experiments of shale samples with different bedding angles were carried out to find out evolution characteristics of cracks. The results show the following: (1) The designed apparatus can monitor ultrasonic, mechanical and video information simultaneously of crack evolution in the entire process of shale destruction under load to provide information for analyzing acoustic and mechanical characteristic responses of crack propagation at key time nodes. (2) With an increase in load, shale will undergo four stages of destruction: crack initiation, propagation, penetration and overall failure. In the course of these stages, acoustic characteristics and mechanical characteristics are in good agreement, which proves the validity of predicting rock mechanical parameters with acoustic data. (3) During the loading process of shale, the main amplitude of acoustic wave is more sensitive than mechanical parameters to the change of rock cracks. Research results have important theoretical reference value for evaluating wall stability of shale gas horizontal well with ultrasonic data.

Controllable preparation and electrocatalytic hydrogen evolution characteristics of Fe3S4 nanocrystals

In order to obtain better electrocatalytic hydrogen evolution performance, Fe3S4 with different morphologies was synthesized by controlling the reaction conditions. During that progress, the ferric oleate as an iron source, and the sulfur powder dissolved in oleylamine as a sulfur source. Fe3S4 with particle morphology proved to have the best electrochemical catalytic activity after adding 40% carbon black. In dehydrogenation, the overpotential was 234 mV and the Tafel slope was 213 mV/dec at a current density of 10 mA/cm2. Meanwhile, Fe3S4 with a particle morphology exhibited superior electrochemical stability. Therefore, the controllably fabricated Fe3S4 with a particle morphology is a promising electrocatalyst for dehydrogenation.

Analysis of the Spatial Structure of Regional Enterprises and Its Impact on Regional Economic Development Based on the Data Envelopment Analysis Model (DEA)

This paper adopts the data envelopment analysis (DEA) model to conduct an in-depth study and analysis of the spatial structure of regional enterprises and their impact on regional economic development and to apply the analysis of the impact between the two. Firstly, the concepts of urban agglomeration, regional spatial pattern evolution, and coordinated regional development and their connotations are explained to define the research topic of this paper. Then, we systematically analyze the theory of regional economic growth, development stage theory, spatial polarization theory, and regional spatial association theory and review the existing studies on regional economic growth, regional development stage, regional spatial association, and pattern evolution, as well as the efficiency and quality of regional economic growth, which further clarify the research focus and research ideas of this paper. The time evolution, spatial divergence, and spatial association characteristics of the economic growth rate of the central urban agglomerations are measured, then the DEA model and entropy value method are used to calculate the economic growth efficiency and economic growth quality of the urban agglomerations, respectively, the time evolution characteristics and spatial pattern evolution characteristics of the economic growth efficiency and economic growth quality are analyzed, and finally, the coupled model of regional economic growth rate, efficiency, and quality is constructed. Finally, a coordination model of the coupling of regional economic growth rate, efficiency, and quality is constructed and the time-series evolution characteristics and spatial-temporal divergence characteristics of the coupling coordination degree of the three are comprehensively analyzed, and the spatial classification of the coupling coordination type of each county unit is made. The direction and path of regulation for the optimization of spatial structure and coordinated spatial development of urban agglomerations are proposed, and finally, the leading factors for the reorganization of the regional economic spatial structure are analyzed, and the regulatory countermeasures for the optimization of the economic spatial structure of urban agglomerations are proposed according to the spatial structure of urban agglomerations and their evolutionary characteristics.

Simulation Analysis of Arc Interruption Characteristics in Disconnector

Wind and solar energy are examples of clean energy that are widely developed and utilized in order to achieve the goal of carbon neutrality. Higher requirements for the safety and reliability of the power grid are put forward after they are connected to it. In the case of disconnectors, as the power system’s protection equipment, their arc interruption characteristics are closely tied to the safety and reliability of the power system. In addition, a disconnector is required to be able to break the DC arc in the photovoltaic power generation system. Therefore, this paper focuses on the arc evolution characteristics in disconnectors. A magnetohydrodynamics (MHD) model of disconnectors was built. In this model, not only are the coupling of the electromagnetic field and the airflow field considered, but also the characteristics of the external circuit. Therefore, not only can arc evolution characteristics be obtained through this simulation model, but the breaking performance will also be directly obtained. The temperature, pressure and velocity distribution are obtained to analyze the evolution process. The curve of current versus time is calculated to analyze the breaking performance. The evolution characteristics of AC and DC arcs in the disconnector are analyzed by calculation and comparison. This provides theoretical guidance for the optimal design of DC disconnectors through simulation analysis.