The Characteristics and Main Controlling Factors for the Formation of Micropores in Shale from the Niutitang Formation, Wenshuicun Section, Southwest China

The characteristics of shale micro-pore development and its main influencing factors have important theoretical guiding significance for shale gas exploration and resource evaluation. In order to clarify the micro-pore development characteristics of lower Cambrian shale and the main controlling factors of micro-pore development, we used the lower Cambrian Niutitang formation shale, in the Wenshuicun section of the Guizhou Province in southwest China. The micro-pore development characteristics of the shale in the region were studied by argon ion profile field emission scanning electron microscopy and a low-temperature liquid nitrogen adsorption and desorption experimental system. The relationship between micro-pore and kerogen maceral composition, total organic carbon (TOC) content and different mineral content was analyzed in combination with mineral and geochemical characteristics. Inorganic pores (clay mineral pores, dissolution pores and pyrite intergranular pores) and micro-fractures (clay mineral shrinkage crack, tectonic fractures and overpressure fractures) were the main type of pore developed in the shale of the Niutitang formation in the Wenshuicun section, and no organic pores had developed. The pore size of shale is usually 2–50 nm, accounting for 58.33% of shale pores, e.g. mesopores. Clay mineral content has an obvious positive correlation with macropore volume and average pore diameter, and an obvious negative correlation with micropore volume. In addition, the content of feldspar in brittle minerals has a strong negative correlation with macropore volume and average pore diameter, and a strong positive correlation with micropore volume and BET-specific surface area. TOC content and the content of different kerogen macerals have no obvious correlation with the development of shale micropores in this region. It is concluded that inorganic mineral composition is the main controlling factor of micro-pore development within lower Cambrian shale, and organic matter abundance and maceral content have little influence on the micro-pore development. This study provides a case study for the characteristics of micropores in lower Cambrian shale in China

Floor Failure Evolution Mechanism for a Fully Mechanized Longwall Mining Face above a Confined Aquifer

In longwall mining, the risk of water inrushes from the floors of deeply buried coal seams is closely related to the degree and depth of the destruction for the mining floor. To analyze the main factors affecting floor failure and the evolution of such failures, this study considered the LW2703 working face of the Chengjiao Coal Mine in China, which is characterized by a large buried depth, complex fault structure, and high pressure from a confined aquifer. The characteristics affecting floor crack development depth were analyzed by considering friction angle, cohesion force, floor pressure, stress increase coefficient, and peak position. A FLAC3D simulation was performed to compare the degrees of floor damage that occurred for caving and backfilling methods during the mining process. High-density electrical detection was performed on-site and used to (1) determine the maximum depth range of the floor damage, (2) reveal the laws governing the evolution of damage in a mining floor, and (3) provide a reasonable basis for evaluating and preventing floor water inrush accidents

Written exposure therapy and app-delivered mindfulness-based meditation for PTSD and subthreshold PTSD in China: Design of a randomized controlled trial

Background: Posttraumatic stress disorder (PTSD) and subthreshold PTSD are still major global concerns, especially in developing areas short of mental health resources. Written exposure therapy (WET), a brief 5-session treatment, has been found to be effective in reducing PTSD symptoms, but no studies have examined it in an Eastern context. Mindfulness-based meditation mobile application may be a promising approach to reduce insomnia comorbid with PTSD. The current study aims to: 1) examine the effectiveness of WET for Chinese PTSD and subthreshold PTSD patients, and 2) examine the effectiveness of adding a mindfulness-based application (MBA) to WET for reducing comorbid insomnia. Methods: The randomized controlled trial will enroll 150 adults with subthreshold/full PTSD and comorbid insomnia. Participants will be randomly assigned to written exposure therapy plus mindfulness-based application condition (WET + MBA, n = 50), written exposure therapy alone (WET, n = 50), or minimal contact control (MMC, n = 50). Clinical interview of the primary outcome (PTSD symptoms) will be administrated at baseline, posttreatment, 3- and 6- month follow-up, while self-reported PTSD symptoms and secondary outcomes (insomnia severity) will be administrated at baseline, every week and all follow-ups. Discussion: This is the first study applying WET in Chinese PTSD patients, as well as examining a mindfulness-based mobile application as a treatment add-on for comorbid insomnia. Study findings will contribute to the knowledge of the effectiveness of WET and a mindfulness-based mobile application, and the development of a culture-adapted treatment protocol. Trial registration: ChiCTR, ChiCTR2000034119. Registered 24 June 2020, http://www.chictr.org.cn/showproj.aspx?proj=55,467

Design of embedded metamaterial solar absorber based on genetic algorithm

To effectively collect the solar energy, a metamaterial solar absorber operating in the UV to NIR wavelength range is designed, which consists of an embedded structure stacked with Ti and SiO2. The embedded structure can enhance the magnetic and electric fields to improve the absorption rate. However, the parameter space of the embedded structure is very huge to increase the optimization search time. Therefore, the absorption rate is calculated by the finite difference time domain method and the parameters of the absorber are optimized by genetic algorithm. The results show that the absorption rates of the optimized absorber are all over 95% in the 300–2500 nm and the average absorption rate is 98.7%, and the absorber is of polarization independence and the average absorption rate remains above 95% at an oblique incidence angle of 60°. By analyzing the electromagnetic field distribution of the absorber at the resonance wavelength, it can be concluded that the high absorption characteristics in the wideband are mainly achieved by the combined effects of local surface plasmon resonance, electric dipole resonance, propagating surface plasmon resonance and Fabry-Perot cavity resonance. Perfect absorber in the solar spectral range have significant value in fields such as solar energy harvesting and information detection