恒等逼近算子的收敛性

文章利用扩充伸缩的定义,结合函数分解的方法,在单位球面B'Rn上,证明了恒等逼近算子f*φA(x)的收敛性.     

Attenuation of weak shock waves along pseudo-perforated walls

In order to attenuate weak shock waves in ducts, effects of pseudo-perforated walls were investigated. Pseudo-perforated walls are defined as wall perforations having a closed cavity behind it. Shock wave diffraction and reflection created by these perforations were visualized in a shock tube by using holographic interferometer, and also by numerical simulation. Along the pseudo-perforated wall, an incident shock wave attenuates and eventually turns into a sound wave. Due to complex interactions of the incident shock wave with the perforations, the overpressure behind it becomes non-uniform and its peak value can locally exceed that behind the undisturbed incident shock wave. However, its pressure gradient monotonically decreases with the shock wave propagation. Effects of these pseudo-perforated walls on the attenuation of weak shock waves generated in high speed train tunnels were studied in a 1/250-scaled train tunnel simulator. It is concluded that in order to achieve a practically effective suppression of the tunnel sonic boom the length of the pseudo-perforation section should be sufficiently long. Received 23 June 1997 / Accepted 16 September 1997     

Attenuation of shock waves propagating in polyurethane foams

Shock wave attenuation in polyurethane foams is investigated experimentally and numerically. This study is a part of research project regarding shock propagation in polyurethane foams with high-porosities = 0.951 ~ 0.977 and low densities of ρc = 27.6 ~55.8 kg/m³. Sixty Millimeter long cylindrical foams with various cell numbers and foam insertion condition were installed in a horizontal shock tube of 50 mm i.d. and 5.4 mm in length. Results of pressure measurements in air/foam combination are compared with CFD simulation solving the one-dimensional Euler equations. In the case of a foam B fixed on shock tube wall, pressures at the shock tube end wall increases relatively slowly comparing to non-fixed foam, free to move and a foam A fixed on shock tube wall. This implies that elastic inertia hardly contributes to pressure build up. Pressures behind a foam C fixed on shock tube wall decrease indicating that shock wave is degenerated into compression wave. Dimensionless impulse and attenuation factor decrease as the initial cell number increases. The momentum loss varies depending on cell structure and cell number.     

基于DSP的中央空调风管清洁系统的设计

为了克服中央空调通风管道人工难以清洗的问题,设计了一个以C2000系列DSP-TMS320F2812芯片(简称F2812)作为核心控制器的智能清洁系统.该系统利用F2812丰富的功能外设构建了系统的硬件,并利用无线传输的通信方式实现了系统与外界的信息交换.结构上是以车轮式车体为基础,将清洁臂设计成可伸缩的清洁臂,增加了系统对空调风管的适应性.该系统能自动检测空调风管内的污染情况,具有良好的适应能力和较强的实用性.     

水上重大溢油事故围油栏协同调度方法研究

针对水上重大溢油事故,围控作业对围油栏调运数量和应急限制期的要求极高,为了尽可能提高待围控区域的应急调度效果,需要组织责任区间内各应急反应基地进行围油栏协同调度。文章将受溢油污染威胁区域划分为有限个待围控区域,分别计算各待围控区域的重要度权重、围油栏需求量和应急限制期。考虑各应急反应基地的围油栏可调运量及单次运载能力限制,针对不同重要度的待围控区域对围油栏调运数量和应急限制期的要求,构建多应急反应基地-多待围控区域的协同调度模型,确定各应急反应基地的围油栏调运去向和调运量。通过对比试验对本文模型的有效性进行验证,研究结果表明:组织多个应急反应基地进行围油栏协同调度,并差别化对待区域内不同敏感资源的应急调运要求,可以显著地提高受溢油污染威胁区域的整体应急调度效果。     

膛内弹上气室气流模型

在等熵流和准定常流假设条件下，采用集总参量法，建立了弹后高压火药气体通过小孔在弹体内气室与弹后空间之间流动的气体参数理论计算模型。理论模型与实验数据有良好一致性。理论研究表明，在发射过程中，膛内弹上气室压力能够达到弹后气体最大压力值，气室终止压力也存在最大值。气室工作压力可以在不大于弹后气体压力范围内改变。     

凿岩机器人钻臂的运动学研究

为实现凿岩机器人钻臂在凿岩过程中的自动定位,建立了多关节钻臂的运动学方程;根据钻臂的实际工作特点和工作范围提出了一种求逆解的方法．运算结果表明,该方法可以成功地实现快速、精确求解,具有较高的实用价值．     

围油栏辅助海面溢油的处理方法

海洋石油污染已经成为当今海洋环境破坏的主要因素之一。海面溢油事故发生时,可加强围油栏的使用,辅助海面溢油的回收。首先使用围油栏将溢油进行围控,局部增大油膜厚度,再放入堰式撇油器进行回收。最后进行实验室模拟海面溢油事故,试验分析得出,使用围油栏辅助溢油回收可以较大幅度提高堰式撇油器的工作效率。     

一种双作用多级液压缸的设计与应用

通过对一种双作用多级液压缸伸缩过程的分析,弄清了影响此种双作用多级液压缸动作顺序的几何要素和系统的力学要素,确定了此种双作用多级液压缸设计原则及液压缸正常工作的条件,为此种双作用多级液压缸的设计及应用提供了理论依据.     

超大伸缩比机械臂结构设计及其刚度优化方法

定期清理灰库内壁板结干灰已成为保障火电厂机组安全运营的重要措施。针对现有灰库清理机器人普遍存在的清理区间局限、整机刚度不足等突出问题,通过引入基于绳排的同步伸缩驱动机构,融合轻量化高刚度的多节箱式臂体及柔性周向回转关节,创新设计出一款基于超大伸缩比机械臂的灰库全域面清理机器人。在此基础上,通过深入力学分析建立伸缩臂力学模型并提出刚度条件。利用迭代法对伸缩臂截面参数进行优化,获得不同情况下最优截面参数。仿真实验表明经刚度优化后的伸缩臂整体刚度良好,满足灰库清理机器人长期作业要求。