Numerical investigation of powder aerosolization in a mining rock dust dispersion chamber

We have conducted numerical simulations of dust dispersion within the NIOSH Rock Dust Dispersion Chamber. The apparatus consists of a low-speed background ventilation flow down a long box in which is placed a tray containing a rock dust powder. A nozzle upstream of the tray introduces a short pulse of a turbulent horizontal jet flow just above the powder surface. We have utilized an incompressible Reynolds-Averaged Navier-Stokes k-ω model for the turbulent flow; particles are incorporated within a one-way Euler-Lagrangian formalism. The Rock Dust Dispersion Chamber ventilation flow exhibits a recirculation zone just above the powder-containing tray. Aerosolization proceeds via the interplay of the jet pulse flow with the background recirculation flow. The air flow is not well-mixed. The aerosolized dust is convected as a concentration cloud downstream towards the detection zone. For larger particles, gravitational settling depletes the convected cloud, so the instrument behaves as a horizontal elutriator. The instrument is robust with respect to misalignment of the jet nozzle. However, reduced streamwise drift velocity allows mixing to disperse the optically detected dust cloud concentration pulse. Our large particle simulation results compare favorably with published experimental results for large, polydisperse calcium carbonate rock dust.     

Study on acceleration and suppression properties of coal gangue with different void fractions on gas explosion propagation

Gas explosion is one of the main disasters in coal mining. Plenty of coal gangue are generally distributed in the disaster areas in gob. Experiments were carried out to explore the propagation law of the gas explosion distributed by coal gangue. The variation characteristics of the overpressure, pressure rise rate, and flame shape with void fractions were analyzed. The results showed that the effect of the coal gangue on the explosion intensity changed from suppression to acceleration with the increase of void fraction, the flame front upstream blockage area changed from laminar state to turbulent divergent state, and a reverse flame was formed. When the void fraction of the coal gangue was 0.50–0.65, the maximum overpressure downstream of the blocked area were positively correlated with the void fraction and the critical suppression range was between 0.50 and 0.55. When the void fraction was lower than 0.50, the flame was quenched in the coal gangue, neither the flame nor the pressure could pass through the blocked area. It is helpful to guide the improvement of coal recovery process to avoid the expansion of the explosion impact in coalmine gob.     

基于新内点测试与Grid-SCAN的铀尾矿库监测定位算法

面向铀尾矿库放射性核素污染WSN监测中,由于监测环境制约,针对该条件下节点密度低、带状分布网络连通性差等问题,为保证一定定位精度,提出一种新的定位算法。新内点测试利用RSSI值与海伦公式判断是否在三角形内外,无需未知节点周围其他节点信息,并采用Grid-SCAN寻找概率模型选取点,使该算法满足低密度条件的定位并减少其计算量。约束范围内计算网格内各点RSSI值的概率,并以最大概率坐标为定位结果。经过仿真,新算法较APIT算法在定位精度上提高了55%~69%。     

爆炸灾害的预防和控制乃当务之急

我国爆炸事故近年来屡屡发生，灾害严重，损失巨大。爆炸灾害的预防与控制己是当务之急。当前的主要研究内容，有各种工业粉尘爆炸、气液贮罐爆炸、工业生产中的静电灾害、各种爆炸灾害的实验观测和监控技术、防护与控制技术、模拟与仿真技术、易燃易爆物的危险性评估和系统安全性分析、燃烧转爆炸机理和热爆炸（热自燃）机理等方面。简略介绍了爆炸灾害预防、控制国家重点实验室的筹建工作，希望得到同行专家的指导和帮助，并开展合作研究。     

Effect of initial temperature on the explosion pressure of various liquid fuels and their blends

In this work, the effect of initial temperature on the explosion pressure, P_ex, of various liquid fuels (isooctane, toluene and methanol) and their blends (isooctane-toluene and methanol-toluene, with three different fuel-fuel ratios) was investigated by performing experiments in a 20-l sphere at different concentrations of vaporized fuel in air. The initial temperature was varied from 333 K to 413 K.Results show that, as the fuel-air equivalence ratio, Φ, is increased, a transition occurs from a “thermodynamics-driven” explosion regime to a “radiant heat losses-driven” explosion regime. The maximum pressure, P_max, is found in the former regime (Φ < 3), which is characterized by a trend of decreasing P_ex with increasing initial temperature. This trend has been explained by thermodynamics. In the latter regime (Φ > 3), P_ex increases with increasing initial temperature. This trend has been addressed to the decrease in emissivity (and, thus, radiant heat losses) with the increase in temperature.     

混沌在种群动态中的应用

通过对种群数量变化模型和空间格局的分析，结合不稳定系统动力学的混沌现象，对种群动态中存在的混沌进行了粗略的探讨．认为CSR三角形中的S-对策者具有混沌的特点．由于生态场中因子具有混沌性质，及其相互作用过程中的不稳定系统动力学的影响，种群也具有混沌特点．     

基于三角网格的电磁数据的内插和可视化方法

研究了从采集的离散点场强生成整个平面区域的场强的插值方法,及生成的场强数据可视化的颜色映射方法.采用基于三角网格的内插技术,先对二维离散点构造三角网格;假定每个三角形的顶点场强、坐标构成一平面空间,三角形内部的未采集点场强可以由顶点决定的场强平面方程插值求得.给出了插值结果可视化的四段制颜色映射解决方案,与目前国际上主流电磁软件颜色映射方式一致.     

硅烷的危险特性及安全操作

硅烷作为一种提供硅组分的气体源 ,广泛应用于微电子、光电器件以及高纯度多晶硅生产 ,潜在应用前景更为广阔。随着硅烷应用领域的扩大 ,硅烷安全使用和处理已成为首要的问题。通过对硅烷着火的研究和事故分析表明 ,硅烷的危险特性在于它与氧反应的极强活性 :自燃 ,着火下限低 ,燃烧能量大。由于硅烷的自燃特性 ,对它的安全防范 ,与一般的易燃易爆物质相比 ,除一些共同点之外 ,还有显著的不同之处。在操作中必须预防高浓度硅烷与氧接触发生自燃着火。同时还必须防止硅烷泄漏在有限的空间内与氧混合 ,形成不稳定爆炸性气团。笔者综合分析和研讨了硅烷着火和爆炸的最新进展和成果 ,在实践经验和分析典型硅烷事故的基础上 ,提出了处理和使用硅烷的安全操作要点。     

新型复合粘弹阻尼器不同加载波下的性能研究

为了研究新型复合粘弹阻尼器在不同加载波下的力学性能,分别对其施加正弦波与三角波进行抗疲劳与变幅相关性试验,比较2种加载波下新型复合粘弹阻尼器的力学性能变化规律.结果表明:新型复合粘弹阻尼器,在抗疲劳试验中正弦波加载下的力学性能优于三角波加载;变幅试验中,随着应变幅值的增大,三角波加载下的最大剪应力、存储剪切模量和等效刚...     

垃圾填埋场爆炸灾害的发生与控制途径

论述了垃圾填埋场爆炸灾害的严重性，探讨了垃圾填埋场爆炸灾害发生的影响因素。并以此提出了垃圾填埋场爆炸灾害的控制技术途径。