综放工作面过断层期间微震规律分析

为有效预防深部矿井综放工作面过断层期间冲击矿压事故的发生,采用SOS微震监测系统对断层区域煤岩体内微震活动进行全时连续监测,并分析统计在过断层期间微震活动发生的次数和能量释放的变化规律。结合数值模拟的手段,对综放工作面过断层期间微震活动规律在机理上进行理论分析。研究表明：断层等弱面地质构造具有较高的不稳定性,随着回采工作面的逐渐临近,区域内每日震动释放总能量值和震动次数的起伏波动逐渐增大;强烈微震活动发生前有一段弱震活动时期,为强震的发生积蓄了更多的能量。     

基于弹性壳体模型的波箔型气体动压径向轴承静特性分析

采用有限单元法,对波箔型气体动压径向轴承的箔片建立了弹性壳体单元模型。该模型综合考虑了箔片膜效应与弯曲效应之间的耦合,更能真实地反映出波箔和平箔的变形。运用有限差分法及Newton-Raphson迭代法耦合求解Reynolds方程和气膜厚度方程,分析了轴承气膜厚度分布、压力分布、箔片变形量分布以及承载能力,并与实验结果进行了比较,证明了该方法的可行性和精确性。分析了转速、箔片厚度对轴承特性的影响,结果表明:转速上升,承载能力增大;箔片厚度小于0.2mm时,厚度的改变对轴承的影响较大。     

冗余系统切换输出扰动问题的研究——ControlLogix冗余系统应用解决方案

冗余系统切换时发生输出扰动,对控制现场危害很大,引起的原因可能是网络硬件组态,也可能是程序运行结果,文章主要列举了冗余切换输出扰动的引起原因及解决方案。     

铸链炉卡伤轴承套圈的解决方法

针对热处理铸链炉加工轴承套圈产生卡伤现象,对其产生原因进行分析,提出解决的方法。     

SnPb钎料熔滴与Au/Ni/Cu焊盘的反应过程

研究了熔融的SnPb钎料由固定高度滴落到Au/Ni/Cu焊盘上的温度变化过程和界面反应情况.结果表明:对钎料熔滴到达焊盘瞬时的接触温度,熔滴初始温度是其主要影响因素,而高度变化对其影响不大.钎料与焊盘界面产生的金属间化合物形态受钎料熔滴初始温度影响很大.随着滴落钎料初始温度的提高,界面层由Au层基本不反应,变为形成了连续层状AuSn2及针状AuSn4.当初始温度升高到450℃时,AuSn2完全转化为AuSn4,棒状AuSn4生长极为明显,在离界面不远的钎料里发现细小的AuSn4.由计算推出界面反应的时间约为6～7 ms,在如此短的时间内,发生Au的溶解和Au-Sn化合物的形成,其原因在于Au在熔融钎料中溶解速度随温度变化的特殊性.     

Flip-chip process using heat transfer from an induction-heating film

A new flip-chip technology to attach an IC chip directly to a substrate was studied using the heat transfer from an induction-heating film in an AC magnetic field. When applying a magnetic field of 230 Oe at 14 kHz, the temperature of a 600 μm-thick 5 mm × 5 mm Cu induction-heating film reached 250 °C within 60 s. The temperature of the glass substrate used in this process was kept below 118 °C at a distance of 1,350 μm from the Cu induction-heating film, which was maintained at 250 °C, implying that damage to a substrate can be minimized with the flip-chip process using heat transfer from an induction-heating film. Flip-chip bonding was successfully accomplished with the reflow of Sn-3.5Ag solder bumps by applying a magnetic field of 230 Oe at 14 kHz for 120 s to a Cu induction-heating film.     

Mechanism of Geogrid Reinforced Soil at Bridge Approach

Using Geogrid-Reinforced Soil （GRS） we studied the working mechanism and design method of GRS at bridge approach with high backfill by field experiment. In a highway section where the height of backfill is 13.5 meters, geogrids were used at two bridge approaches to address the bumping problems. Some soil pressure cells were used to measure the normal and lateral soil pressure at different locations in the roadbed. The experimental results indicate that geogrids in geogrid-reinforced soil （GRS） could produce an uplift force, the closer the location to the abutment, the larger the uplift force, and the reduction of measured soil pressures compared with theoretical values was the largest at the bottom of roadbed, less at the top than at the bottom, and the least in the mid-height of roadbed than at the bottom. These findings are different from those of the traditional greogrid-reinforced subgrade design method,     

快速凹凸贴图算法的改进与实现

凹凸贴图是一种使得物体光滑的表面看起来凹凸不平的计算机绘图技术.为了克服传统的快速凹凸贴图算法中光源位置不易控制等缺点,使用了不同的方法计算当前像素的值来模拟不同的光源位置,并根据像素距光源的距离来模拟光线的衰减效果,同时介绍了一种亮度查找表的产生算法.使用该改进算法产生出的凹凸贴图图像具有较真实的三维形态,而且速度快,开销小,可以应用在开发各种计算机虚拟现实、计算机绘图、动画程序中.     

Numerical analysis of bump foil bearings without nominal radial clearance

Bump foil bearings without nominal radial clearance were analyzed. An air film thickness model and a bearing theoretical analytical model were developed accounting for air compressibility and foil deformation. To analyze hydrodynamic characteristics of bump foil bearings with different operating eccentricities, the air film thickness equation and Reynolds equation were coupled through pressure and solved by Newton-Raphson Method （NRM） and Finite Difference Method （FDM）. The characteristics of an bump foil bearing model were discussed including load carrying capacity, film thickness and pressure distributions. The results of simulation show that bump foil bearing without nominal radial clearance can provide better stability and greater load capaci- ty. This numerical analytical method also reveals a good convergence in numerical calculation.     

Occurrence,predication,and control of coal burst events in the U.S.

Coal burst represented a major hazard for some U.S. mining operations. This paper provides an historical review of the coal burst hazards,identifies the fundamental geological factors associated with these events,and discusses mechanisms that can be used to avoid their occurrences. Coal burst are not common in most underground mines. Their occurrence almost always has such dramatic consequences to a mining operation that changes in practice are required. Fundamental factors influencing coal burst events include strong strata,abnormal strata caving,elevated stresses,critical size pillars and the lack of sufficiently sized barrier pillars during extraction. These factors interact to produce excessive stress,seismic shock and loss of confinement mechanisms. Over the 90 years of dealing with these hazards,many novel prevention controls have been developed including novel mine designs and extraction sequences,most of which are site specific in their application. Without an accurate assessment of the fundamental factors that influence coal burst and knowledge of their mechanisms of occurrence,control techniques may be misapplied and risk inadequately mitigated.