炸药近地爆炸的数值模拟及影响参数的分析

应用ANSYS/LS-DYNA有限元程序建模,在验证模型及参数选取正确可靠的基础上,研究了地面材料、炸药高度、空气域形状以及炸药当量等参数对马赫波超压的影响.结果表明:对于非近距离的爆炸,不同地面上的马赫波超压峰值相差不大,可简化为刚性地面;建模宜选择刚性壳体地面以及长方体空气域;与经验公式相比,数值模拟的马赫波超压峰值误差随着炸药当量的增大而减小,随着炸药高度的减小而增大.     

地面定向钻技术在综采面突水治理中的应用

朱庄煤矿是一座生产能力2.2百万吨/年的大型矿井,水文地质类型为极复杂型。发生突水的Ⅲ631综采工作面位于Ⅲ63采区上部,为该采区右翼首采面。开采煤层为山西组6煤层,含煤地层之下为太原群灰岩。工作面走向长412.5m,倾斜宽180m。煤层倾角16~18°,煤层厚度平均2.8m。     

涡桨五型发动机转速摆动的故障分析与预防

<正>涡桨五型发动机在转速摆动的同时,也会伴随着燃油压力和切油电压等参数的摆动,这些参数都是发动机各系统测量的指示参数,直接反映出发动机的工作状况。由于发动机转速往复波动而使发动机工作不稳定,需对其产生的原因进行分析和排除。1转速摆动的原因转速摆动说明了发动机转速调节系统稳定性不好。涡桨五型发动机在加速过程中的稳定性主要是由转速调节系统和转速调节校正系统两部分共同完成的,转速调节系统由调速器和螺旋桨组成,其功能是使发动机的转速保持在预定的平衡转速上,转速调节系统性能不     

First scanning Fabry-Perot interferometer developed in China

A scanning Fabry-Perot interferometer （SFPI） was first developed and deployed at the Langfang near Space Environment Field Scientific Observation Station （39.38°N, 116.65°E） of the National Space Science Center, CAS. The instrument is designed to measure the mesospheric and ther- mospheric wind velocities using the atomic oxygen 557.7-nm and 630.0-nm emissions. Data from February 28 to March 3 and February 28 to March 15 in 2011 were chosen for case study and mean value study, respectively. The errors of the meridional and zonal winds are 6.5 and 7.5 m/s at 557.7-nm and at 630.0-nm, they are 7.1 and 6.6 m/s, respectively. During the whole experiment, the instrument has performed in good condition and provided high-quality data. The mean neutral wind data were consistent with that predicted by HWM07. Good agreement has been found in between the SFPI and a neighbor Meridian Project Fabry-Perot interferometer （MP FPI）, with a corresponding coefficient （re） larger than 80 %. In general, the scanning FPI meets the design goal, and it is a useful ground-based instrument for measuring mesospheric and thermospheric winds at middle latitudes and is able to provide high-quality data for future scientific studies.     

应用于地面无人车辆的窗口约束马尔可夫定位

为解决地面无人车辆在GPS易受干扰区域的定位问题,提出一种窗口约束马尔可夫定位方法,通过在窗口范围内进行马尔可夫定位减少更新的状态空间范围. 窗口的位置在初始时刻参考地图中建立的路标估计,并随车辆运动信息在地图中移动. 该方法能够减少定位过程中的计算量,除初始时刻外不依赖于GPS进行短期外推定位,且实验证明具有较好的实时性和准确性.      

新太空望远镜GLAST升入太空

美国东部时间6月11日,美国将“伽马射线大区域太空望远镜（GLAST）”送入太空。美国的“大型观测台”计划包括“四大天王”．即“哈勃”太空望远镜、“钱德拉”X射线太空望远镜、“康普顿”伽马射线太空望远镜和“斯必泽”红外太空望远镜。其中．“康普顿”因为出现陀螺仪故障,被迫在地面控制下于2000年脱离轨道坠入大海。     

Ground effects on magnetooptic Bragg cells

Propagation equation of magnetostatic waves in an arbitrarily magnetized yttrium-iron-garnet/gadolinium-gallium-garnet waveguide coated with perfect metal planes is obtained using the method of the surface magnetic permeability. And ground effects on magnetooptic Bragg cells are investigated with the magnetooptic coupled-mode theory. Theoretical analysis indicates that, diffraction efficiency of guided optical waves can be improved by adjusting the spacing of the metal plane from the ferrite film, and ground effects on the diffraction efficiency will be enhanced using an appropriately tilted bias magnetic field. In the metal clad waveguide system, the magnetostatic wave frequency at which the diffraction efficiency peak is obtained corresponds to the “zero-dispersion” point, Performance of RF spectrum analyzers in this system can also be improved by comparing with the case of the sandwich waveguide. Therefore, magnetooptic Bragg cells with the metal clad waveguide are potential applications to the microwave communication and optical signal processing.     

孔压力嵌岩桩注浆漏失问题探析——以岩溶地区某工程为例

本文通过对岩溶地区一个工程实例,探讨了大直径冲孔嵌岩桩桩孔漏浆及预防的相关问题,指出通过对漏失地层压力注浆和调节泥浆的流变特性等方法可基本上达到预防漏浆目的,利用勘察孔压力注浆防止泥浆漏失是岩溶地区施工嵌岩桩的一种新的尝试。     

谈排屋地基纠偏与加固的施工

开发商未按地质报告地基处理要求采用沉管灌注桩。在厚为7.6m至8.2m淤泥层上进行回填宕渣、强夯处理地基,在此以条基作为排屋的基础。工程主体结束后产生不均匀沉降、房屋倾斜。采取沉井冲孔排土和高压喷射注浆法进行纠偏加固后,沉降均匀、稳定,倾斜率满足要求。     

混凝土裂缝的预防及处理

介绍了混凝土裂缝产生的原因,主要是由于温度、收缩、不均匀沉降等造成。提出了预防措施,阐述了处理混凝土裂缝的常用方法,介绍了注浆法。