大同矿区石炭系煤巷均压耦合支护原理及技术应用

针对大同矿区石炭系巷道具有煤层厚度大、断面大、火成岩侵入等,在开采过程中普遍存在采场压力大,矿压显现剧烈;区段煤柱宽,煤炭损失严重;煤巷支护困难等突出问题,本文基于多尺度全方位均压耦合支护理论,采用物理相似模拟实验和数值模拟的方法,对无支护、棚架支护和锚网支护情况下呈现出支护效果进行了对比分析,结果表明以锚网为主体的支护形式能较好地实现均压耦合支护,可有效阻止围岩松动圈的扩展,并在塔山矿5105巷得到了应用。     

Correlation between growth behavior,internal stress distribution and properties of ZnO:Zn crystals grown by carbon-assisted chemical vapor transport

Internal stress and stress-related defects are considered as the major obstacles that significantly hinder the growth of high-quality ZnO-based crystals. In this work, high-crystalline-quality ZnO:Zn bulk crystals were successfully grown by carbon-assisted chemical vapor transport (CVT). Internal stress in the crystal was directly measured by a neutron beam from a reactor, and stress distributions along the radial direction at different depths were obtained. The stress, temperature, and flow fields in the growth system were simulated by the finite element (FE) method, and the results agreed with the neutron stress analysis. The etch pit density (EPD), Hall properties, and optical transmittances of different crystal regions were studied in detail, and the distribution trend of the crystal properties was consistent with that of internal stress and stress-related defects in the crystal. It is found that the unique temperature filed in the growth system causes the crystal to bend to a slightly convex toward the growth direction and gives rise to a driving force for structural defect formation. The + c and –c faces of the crystal are subjected to tensile and compressive stress, respectively. The maximum stress values are about 280 MPa and -291 MPa near the central regions of ±c faces, while the crystal periphery is basically free of internal stress. The region near the center of +c face has an EPD of 7.5 × 10³ cm^-2 and a transmittance of 79.2% at 800 nm wavelength, while the corresponding carrier concentration and mobility are 2.27 × 10¹⁷ cm^?3 and 159 cm²/V·s, respectively. By comparison, the crystal periphery has an EPD of 10² cm^-2 with an 80.5% transmittance at 800 nm, while the carrier concentration and mobility are 1.85 × 10¹⁷ cm^?3 and 184 cm²/V·s, respectively.     

Demand aware transmission power cost optimization based on game theory and distributed learning algorithm for wireless body area network

Wireless Networks - This paper studied the issue of communication transmission power cost optimization for the personal body base station in wireless body area network (WBAN). With the limited...