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The destruction of shallow aquifers by water-conducting fractures of overlying strata caused by underground coal mining is the most representative form of mining-induced damage in the Yushenfu mining area. It has become an important factor restricting the green mining of coal in the Yushenfu mining area and even the ecological protection and high-quality development of the middle reaches of the Yellow River. As the key scientific problem of water-preserved coal mining, the scientific understanding of the development law and main influencing factors of water-conducting fractures in overlying strata has attracted great attention. Taking the geological occurrence characteristics of the main coal seam in Yushenfu mining area as the prototype, 24 different types of numerical models are constructed with the key characteristics of the overburden structure, such as the number of layers of sandstone in the overburden (sand layer coefficient) and the thickness ratio of sandstone and mudstone in the overburden (sand–mud ratio), as the main variables. By means of numerical simulation experiment and theoretical calculation, combined with field measurement and comparison, the influence of the key characteristics of overburden structure on the development height of water-conducting fracture is studied and revealed. It is proposed that the effective area for the study area to achieve water-preserved coal mining by using the height-limited mining method must conform to the coal seam overburden structure characteristics of "sand–mud ratio 6:4 and sand layer coefficient less than 70%" and "sand–mud ratio 8:2 and sand layer coefficient less than 80%". The results not only enrich and deepen the research on the influence of geological factors and the law of controlling the development of water-flowing fractures in overlying strata, but also provide theoretical support for the precise protection of groundwater resources in the Yushenfu mining area in the middle reaches of the Yellow River. [ABSTRACT FROM AUTHOR]

The flexible piezoresistive sensors based on polydimethylsiloxane (PDMS) as substrate have a rapid development in recent years, and has a broad application in fields such as human motion and health detection, electronic skin, and smart robots. The sensing mechanism and main performance indices of the flexible piezoresistive sensors were firstly introduced, and then the research progress of the PDMS-based flexible piezoresistive sensors was summarized in details, especially the combination of PDMS and various conductive fillers and the construction of microstructure. Finally, the problems were pointed out, and the development direction of PDMS was discussed. [ABSTRACT FROM AUTHOR]

Superhydrophobic materials with special functions of electrical conductivity, magnetism, photothermal conversion and others have been paid considerable attention in the emerging fields including wearable electronics, long-distance manipulation and seawater desalination. Herein, we report a facile approach to fabricate superhydrophobic and conductive cotton fabric (CF) for piezoresistive pressure sensor. It was based on the utilization of the reduced graphene oxide (rGO) layer on CF to form conductive pathways. Meanwhile, the in-situ generated hybrid of polydimethylsiloxane (PDMS)/titanium dioxide (TiO2) on rGO layer through the hydrolysis-condensation and cross-linking reactions between dihydroxyl-terminated PDMS and tetrabutyl titanate played the role of constructing rough structure and decreasing surface energy. The fabricated PDMS/TiO2@rGO coated CF exhibited a high water contact angle of 159.3° and possessed outstanding self-cleaning ability. Interestingly, owing to the existence of TiO2, the CF also had the capability to degrade organic contaminations and the degradation rate reached 96.4% after being exposed under UV light for 90 min. In addition, the PDMS/TiO2@rGO coated CF with a low electrical surface resistance of 0.76 kΩ cm−1 was utilized to design and prepare a multilayer piezoresistive pressure sensor by means of the large number of air gaps between the fibers and the increase of contact points under external pressure. The sensor showed high sensitivity, fast response and good repeatability, and was successfully applied for detecting different human behaviors including pulse, voice recognition, and body motion. Our findings conceivably stand out as a new methodology to fabricate functional superhydrophobic materials and surfaces for practical applications in the fields of electronic skin, human healthcare, interactive wearable device and smart robotics. [ABSTRACT FROM AUTHOR]