RUV坐标系下再入段弹道目标跟踪研究

研究RUV坐标系下的再入段弹道目标跟踪算法,该算法利用RUV坐标系下量测线性的优点,可提高目标跟踪精度。针对再入弹道目标,以东北天坐标系下目标运动加速度为基础,通过坐标转换,推导雷达阵面坐标系下的运动加速度;在此基础上通过二次求导及坐标转换推导RUV坐标系下的运动加速度,给出RUV坐标系下独立的状态方程和量测方程,并对采用扩展卡尔曼滤波所需要的关键函数给出显式表达。蒙塔卡罗仿真不同情况下的RUV坐标系下的再入弹道目标跟踪,仿真结果表明,在RUV坐标系下的跟踪较混合坐标系下的跟踪,其精度有大幅提高。     

一类二阶差分算子的振动性

本文研究具有多时滞偏差变元的二阶中立型差分方程,由方程解的振动性,研究了差分算子的振动性,并得出了差分算子振动的一个充分条件.     

双喷嘴射流泵基本特性方程及其性能研究

以射流泵理论和能量守恒定律为基础,采用洛伦兹流体混合损失模型,推导出新型双喷嘴射流泵的基本特性方程。当流速比V=1时,射流泵的理想效率为100%;当0V1时,面积比R越大射流泵的理想效率越高。根据实验数据拟合出能量损失系数关系是:K_(td)K_cK_jK_s,得到了射流泵完整的特性方程和实际特性曲线,结果表明:随着面积比R的增大,压力比P增大,但射流泵的工作区间缩小,高效区的位置左移;射流泵最高效率随流量比M_1呈现先增大后减小的趋势,而压力比P则是一直减小,符合能量守恒规律;实验样机的最优面积比R_(opt)为0.30,最优流量比M_(opt)为1.04,新型射流泵的效率最大值为22.57%。     

基于数值模拟和Mindlin解的煤矿井塔纠偏研究

基于Mindlin应力解的桩筏基础、土钉墙、岩石锚杆等的理论计算及应用较多,但是对与煤矿井筒刚性连接的井塔进行纠偏处理在实际工程中比较少见。应力解除法在房屋纠偏中得到了良好的运用而在井塔纠偏中还无先例。应用有限元数值模拟和弹性力学Mindlin解2种方法对井塔应力解除纠偏进行验证。通过考虑土体开挖卸荷比对Mindlin解影响而对其进行修正,得到的结果与有限元数值模拟结果一致,可以验证:应力解除法能够有效运用于井塔纠偏;增大应力解除区宽度、减小应力解除孔到井筒的距离、适当增加应力解除孔深度和增大应力解除孔孔径可以有效提高纠偏效果。     

某核电厂内部结构支承反应堆冷却剂系统的结构刚度计算

使用有限元软件ANSYS建立某核电厂反应堆厂房内部结构三维模型,并根据工艺条件图所示的设备、管道支承位置施加单位荷载以计算相应柔度矩阵,为主设备、管道在反应堆冷却剂失水事故(LOCA)和地震工况下的计算提供基本参数。     

基于有限元分析方法对接地装置冲击特性研究

由于冲击电流的作用,接地体周围的土壤将会产生火花效应,使得土壤的电阻率会发生变化,进而对冲击电流的散流过程造成影响.因此本文采用有限元分析方法,利用COMSOL Multiphysics软件,构建了考虑火花效应的接地装置冲击散流模型,主要研究了垂直、水平接地体的冲击散流过程,通过模型的计算发现,接地装置在冲击散流的过程中电流主要从接地装置的末端散流到土壤中,这一情况也与实际情况相符合.     

Numerical analysis of coupled flows in porous and fluid domains by the Darcy-Brinkman equations

A numerical method to achieve the simultaneous computation of the seepage flows in porous media and the Navier-Stokes flows in the domain occupied purely by a fluid is presented in this paper. The method uses the Darcy-Brinkman equations with the continuous modelling of the interfacial flow velocity, and applies the finite volume method to the spatial discretization and the fractional step method to the numerical simulation of the incompressible fluid. The coupling of the two different flows is realized by the relevant interpolation of the pressure and the flow velocity onto the interface at which permeability and porosity are discontinuous. The interpolation schemes provide simple solutions to overcome the computational instability caused by the discontinuous change in permeability and to avoid having to resolve the considerably thin transition zone near the interface. Numerical analyses of the one-dimensional uniform flow, the lid-driven cavity flow, and the pipe-flow in a porous medium have been carried out. The results have shown that the proposed schemes enable a stable computation and fulfill the accurate and physically realistic numerical solutions.     

Collapse analysis of real RC spatial structures using known failure schemes of ferro‐cement shell models

Large‐span reinforced concrete (RC) shells collapses that occurred in the last decade caused many death toll as well as significant losses to national economies. The most famous cases were the collapse of the aqua park cover in Moscow on February 2004 and the 2E terminal roof destruction at Charles de Gaulle Airport near Paris on May 2004. Following the publications of the appropriate commissions that have studied the reasons of these events, the influence of concrete creep and changes in the shell geometry on buckling of RC thin‐walled shells was not properly considered in the design. This study is focused on buckling of such shells, taking into account geometrical and physical nonlinear behaviour of compressed concrete. Other important reasons of concrete shells collapse are also analysed. The study is based on available experimental and theoretical investigations of ferro‐cement shells' models previously performed by the first author. The results of these investigations, obtained for small‐scale ferro‐cement models of thin‐walled shallow RC shells, are discussed. Behaviour of the tested models is compared with that of the above‐mentioned real shells and similar structures, which also collapsed. The critical buckling loads for the shells are obtained. It is shown that these loads are lower than the actual ones; thus, the shells buckling was unavoidable. To prevent brittle shell failure, they should be designed using other dominant failure modes that appear before the buckling. Possible failure schemes of real RC shells can be predicted using dominant failure modes obtained by laboratory testing of scaled models. Copyright © 2012 John Wiley & Sons, Ltd.     

Model-based design of horizontal subsurface flow constructed treatment wetlands: a review

The increasing application of constructed wetlands for wastewater treatment coupled with increasingly strict water quality standards is an ever growing incentive for the development of better process design tools. This paper reviews design models for horizontal subsurface flow constructed treatment wetlands, ranging from simple rules of thumb and regression equations, to the well-known first-order k-C* models, Monod-type equations and more complex dynamic, compartmental models. Especially highlighted in this review are the model constraints and parameter uncertainty. A case study has been used to demonstrate the model output variability and to unravel whether or not more complex but also less manageable models offer a significant advantage to the designer.