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In order to effectively prevent and control the rock burst in the asymmetric pressure-relief working face under protective layer, taking the 0291 working face of Tangshan Coal Mine as the engineering background, the theoretical analysis and numerical simulation methods were adopted, and the potential influence factors of rock burst in the working face and the occurrence area were analyzed. The results show that the mining depth, bursting tendency of coal seam and its roof, residual pillars in upper protective layer and goaf of the coal seam and thick and hard roof are the potential influence factors of rock burst. Before mining, under the influence of the residual pillars in the protective layer and goaf, the stress of the two tunnels in the 0291 working face shows an asymmetrical distribution. The high stress area of the return airway is mainly located below the cutting line and stop line of the 0250 goaf, while the high stress area of the transportation roadway is mainly located below the cutting line of the 0251 goaf. The working face had obvious zonal characteristics. In the early stage of mining, the advanced stress in surrounding rock of transportation roadway is higher than that of return airway. It is necessary to strengthen the monitoring of transportation roadway and take pressure-relief measures in time. When the working face enters the lower part of 0251 goaf, the surrounding rock stress of the transport roadway decreases rapidly, and the prevention focus should be transferred from the transport roadway to the return air roadway. According to the results of numerical simulation, the impact zones can be divided and the prevention and control measures of impact zones in the mining were put forward. Field monitoring results show that the measures taken can effectively reduce the occurrence of rock burst.

The paleovegetation and paleoclimate characteristics are studied in the Palaeogene strata of Hetao Basin, Subei Basin and Qaidam Basin in China, and the Cretaceous Guyang Formation (K1g) in the Hetao Basin. These three basins receive high attention, different distribution areas, representative. Pollen evidence shows that: (1) The sporopollen assemblage of Palaeogene Linhe Formation (E3l) in Hetao Basin is characterised by Pinaceae-Ephedripites-Ulmipollenites-Chenopodipollis. It reflects that the ancient vegetation types were mainly coniferous and evergreen woody plants, and the climate was cold temperature. The sporopollen assemblage characteristics of the upper member of the Palaeogene Xiaganchaigou Formation (E32) in the Qaidam Basin are similar to it. (2) The sporopollen characteristics of the K1g in the Hetao Basin reflect that its ancient vegetation was dominated by evergreen woody plants and belongs to a warm and humid subtropical climate. (3) The assemblage of Palaeocene Funing Formation (E1f) in Subei Basin was Pterisisporites undulatus-Ulmipollenites minor-Taxodiaceaepollenites hiatus. The climate type was humid north temperate climate, vegetation was mainly deciduous trees and evergreen woody plants. (4) Leiosphaeridia/Granodiscus, Pediastrum and Botryococcus were also detected in the E1f of Subei Basin. The appearance of these algae indicates the special saline water environment and good hydrocarbon potential. [ABSTRACT FROM AUTHOR]

This article addresses the backstepping control problem of the nonlinear strict-feedback system with an immeasurable state. To eliminate the effect coming from the immeasurable state variable, a new adaptive state observer method is developed for backstepping design by employing a neural network (NN) approximation strategy. As one of the highlighting contributions, the observer method can be performed with the relaxed condition because it does not require the design parameters to satisfy the Hurwitz equation, therefore it can be more easily applied and extended to serve for nonlinear system control than the existing observer methods. Finally, by integrating the observer dynamic into the backstepping design, the adaptive tracking control is achieved. Lastly, the feasibility of the method is proved by both stability theory and computer simulation. [ABSTRACT FROM AUTHOR]

In order to meet the increasing demands of wireless communication for ISM bands, a 433 MHz transmitter RF front-end is designed using a 55 nm low-power CMOS technology. The circuits consist of an active mixer, a driver amplifier and a class-E power amplifier (PA). A double-balanced Gilbert active mixer is designed to realize binary phase-shift keying (BPSK) modulation. The driver is used to preamplify the modulated RF signals. The class-E PA adopts a parallel four-branch cascode structure to control the output power level. The load network of the PA is implemented through an off-chip circuit, in which a finite DC-feed inductance load network is selected to reduce the power loss. The mixer and driver are designed with a 1.2 V supply voltage, while the PA is operated at a 1.8 V supply voltage. The area of the chip is 0.206 mm × 0.089 mm, and the measured results show that it achieves a maximum output power of 2.7 dBm, with a total power consumption of 6.72 mW. At a drain efficiency (DE) of 34.5%, an S 22 less than −10 dB over the frequency ranges from 393.79 MHz to 455.70 MHz can be measured for the PA. With 192 kbps BPSK data modulated at 433 MHz, the measured EVM is about 0.83% rms. [ABSTRACT FROM AUTHOR]