FPGA在测试系统中的应用

介绍一种压力变化量测试系统的工作原理和设计方案，阐述了采用高密度、高速度的大规模可编程器件ＦＰＧＡ设计测试系统中控制器和数据处理器的方法和成效。

Wave Motion of Smoke in Subway Fire Environment

Wave motion in subway or tunnel fire is an intrinsic property of smoke.As the pressure of smoke changes with mass of certain power,a kind of linear wave equation for smoke can be derived from the conservation equations of its mass and momentum,under nearly homogeneous zone assumption.The smoke movement of 4 subway fires was simulated with Airpak.By fitting the pressure-mass functions to the simulated data,wave equations of the smoke were derived,and wave motions of smoke were thus validated.It can be seen that smoke wave is a kind of mass wave,whose velocity is inversely proportional to smoke mass,and wave of a bigger fire propagates slower.

Application of pressure relief and permeability increased by slotting a coal seam with a rotary type cutter working across rock layers

Pressure relief to increase permeability significantly improves gas extraction efficiency from coal seams. In this paper we report results from simulations using FLAC3D code to analyze changes in coal displace- ment and stress after special drill slots were formed. We investigated the mechanism of pressure relief and permeability increase in a high-gas and low-permeability coal seam through the modeling of gas flow. This allows the development of the technology. Slotting across rock layers in the coal seam with a rotary type cutter was then applied in the field. The results show that pressure relief and permeability increases from slotting the coal seam can increase the transport and the fracture of the coal. This expands the range of pressure relief from the drilling and increases the exposed area of the seam. The total quan- tity of gas extracted from slotted bore holes was three times that seen with ordinary drilling. The concen- tration of gas extracted from the slotted drills was from two to three times that seen using ordinary drills. The gas flow was stable at 80%. Improved permeability and more efficient gas extraction are the result of the slotting. The roadway development rate is increased by 30-50% after gas drainage. This technology diminishes the lag between longwall production and roadway development and effectively prevents coal and gas outburst, which offers the Drosnect of broad anDlication.

Analytical investigation for stress measurement with the rheological stress recovery method in deep soft rock

Due to the difficulty and weakness of current stress measurement methods in deep soft rock, a new rheological stress recovery method of the determination of the three-dimensional(3D) stress tensor is proposed. It is supposed that rock stresses will recovery gradually with time and can be measured by embedding transducers into the borehole. In order to explore the applicability and accuracy of this method, analytical solutions are developed for stress measurement with the rheological stress recovery method in a viscoelastic surrounding rock, the rheological properties of which are depicted as both the Burger's model and a 3-parameter solid model. In such conditions, explicit analytical expressions for predicting time-dependent pressures on the transducer are derived. A parametric analysis is then adopted to investigate the influences of the grout solidification time and the mechanical properties of the grout layer. The results indicate that this method is suitable for stress measurement in deep soft rock, the characteristics of which are soft, fractured and subjected to high geo-stress.

液体对容器底部与容器对支持面的压力、压强

液体对容器底部的压力、压强是由液体产生的,而容器对支持面的压力、压强则是由固体产生的.液体对容器底部的压力、压强与容器对支持面的压力、压强是考生学习中易混淆的知识,由于这类问题在考察时往往和浮力知识相结合,所以,此类问题综合性强、难度大,是学习中的难点和易错点.本文讨论几种常见的情况下这两类压力、压强的求解.

Preliminary analysis on the source properties and seismogenic structure of the 2017 M_s7.0 Jiuzhaigou earthquake

At GMT time 13：19, August 8, 2017, an M1.0 earthquake struck the Jiuzhaigou region in Sichuan Province, China, causing severe damages and casualties. To investigate the source properties, seismogenic structures, and seismic hazards, we systematically analyzed the tectonic environment, crustal velocity structure in the source region, source parameters and rupture process, Coulomb failure stress changes, and 3-D features of the rupture plane of the Jiuzhaigou earthquake. Our results indicate the following： （1） The Jiuzhaigou earthquake occurred on an unmarked fault belonging to the transition zone of the east Kunlun fault system and is located northwest of the Huya fault. （2） Both the mainshock and aftershock rupture zones are located in a region where crustal seismic velocity changes dramatically. Southeast to the source region, shear wave velocity at the middle to lower crust is significantly low, but it rapidly increases northeastward and lies close to the background velocity across the rupture fault. （3） The aftershock zone is narrow and distributes along the northwest-southeast trend, and most aftershocks occur within a depth range of 5-20 km. （4） The focal mechanism of the Jiuzhaigou earthquake indicates a left-lateral strike-slip fault, with strike, dip, and rake angles of 152~, 74~ and 8~, respectively. The hypocenter depth measures 20 km, whereas the centroid depth is about 6 kin. The co-seismic rupture mainly concentrates at depths of 3-13 km, with a moment magnitude （Mw） of 6.5. （5） The co-seismic rupture also strengthens the Coulomb failure stress at the two ends of the rupture fault and the east segment of the Tazang fault. Aftershocks relocation results together with geological surveys indicate that the causative fault is a near vertical fault with notable spatial variations： dip angle varies within 660-89~ from northwest to southeast and the average dip angle measures -84~. The results of this work are of fundamental importance for further studies on the source characteristics, tectonic environment, and seismic hazard evaluation of the Jiuzhaigou earthquake.

Mechanocaloric materials for solid-state cooling

This article reviews the up-to-date progress in mechanocaloric effect and materials near ambient temperature. For elastocaloric materials, we focus on directly measured temperature change and its entropy origin in nonmagnetic and magnetic shape memory alloys. In terms of barocaloric materials, change in magnetic state, volume and shift of transition temperature due to hydrostatic pressure are systematically compared. We propose advantages and challenges of elastocaloric materials for solidstate cooling. Strategies to enhance elastocaloric and mechanical stability under long-term mechanical cycles are presented. Finally, we conclude with an outlook on the prospect of elastocaloric cooling application.

压缩空气与天然气降压过程的火用对比分析

分析压缩空气降压过程与高压管道天然气降压过程比焓火用、比压力火用、比温度火用的变化,对两者进行对比分析。天然气降压过程与压缩空气降压过程比焓火用变化量变化趋势基本一致。终了压力相同时,随着初始压力的增大,天然气和空气的比焓火用变化量差值增大。在利用压缩空气模拟天然气降压过程中,对压缩空气比温度火用变化量和比压力火用变化量进行修正,给出了修正系数。