Simulation of heat transfer of supercritical water in obstacle-bearing vertical tube

The heat transfer coefficient is very low at bulk temperatures higher than the pseudo-critical point,because the supercritical pressure leads to a vapor-like fluid.In this paper,the heat transfer downstream an obstacle-bearing vertical tube is simulated by the CFD code of Fluent 6.1,using an adaptive grid in the supercritical condition.The reliable results are obtained by the RNG k-ε model using the enhanced wall treatment.The blockage ratio and local temperature of obstacle affect greatly the heat transfer enhancement,and the resultant influence region and decay trend are compared with the existing equations.     

障碍物对火焰加速实验研究

针对水平管道式气体--粉尘爆炸装置,设计出了两种不同形状的障碍物:环形和半圆形.确定了其在管道中的最佳放置位置.并在此基础上研究障碍物对火焰传播的加速机理.     

Generalized finite difference method for solving two-dimensional non-linear obstacle problems

In this study, the obstacle problems, also known as the non-linear free boundary problems, are analyzed by the generalized finite difference method (GFDM) and the fictitious time integration method (FTIM). The GFDM, one of the newly-developed domain-type meshless methods, is adopted in this study for spatial discretization. Using GFDM can avoid the tasks of mesh generation and numerical integration and also retain the high accuracy of numerical results. The obstacle problem is extremely difficult to be solved by any numerical scheme, since two different types of governing equations are imposed on the computational domain and the interfaces between these two regions are unknown. The obstacle problem will be mathematically formulated as the non-linear complementarity problems (NCPs) and then a system of non-linear algebraic equations (NAEs) will be formed by using the GFDM and the Fischer–Burmeister NCP-function. Then, the FTIM, a simple and powerful solver for NAEs, is used solve the system of NAEs. The FTIM is free from calculating the inverse of Jacobian matrix. Three numerical examples are provided to validate the simplicity and accuracy of the proposed meshless numerical scheme for dealing with two-dimensional obstacle problems.     

一种移动机器人的路径规划算法

本文提出一种移动机器人路径规划最短切线路径算法。依据此算法，机器人能顺利地避开障碍物到达目标位置，其原理简单，计算快捷，容易实现。仿真结果验证了它的有效性和实用性。     

Multilevel projection algorithm for solving obstacle problems

Obstacle problems are nonlinear free boundary problems and the computation of approximate solutions can be difficult and expensive. Little work has been done on effective numerical methods of such problems. This paper addresses some aspects of this issue. Discretizing the problem in a continuous piecewise linear finite element space gives a quadratic programming problem with inequality constraints. A new method, called the multilevel projection (MP) method, is established in this paper. The MP algorithm extends the multigrid method for linear equations to nonlinear obstacle problems. The convergence theorems of this method are also proved. A numerical example presented shows our error estimate is sharp and the MP algorithm is robust.     

未知环境下机器人避障设计研究

随着信息技术的发展,各个领域越来越需要高性能的自动化系统。机器人技术飞速发展,研究重点已经转向在复杂、未知、不可预测环境中独立工作的自主式智能机器人。介绍了机器人Q学习避障算法的实现方法,并构建了仿真实验平台,模拟了移动机器人在未知环境下自主地、安全地从起始点到达目标点的过程。通过仿真实验验证了Q学习实现机器人在未知环境下的行为选择控制是可行的、有效的,并验证机器人在未知环境下具有良好的越障性能。     

智能天线及其提高移动通信系统容量的分析

采用智能天线,可以降低移动通信系统的同频干扰,增加移动通信系统容量。介绍了智能天线的基本原理及其在移动通信系统中的应用,建立了基于智能天线的同频干扰的统计模型,对智能天线提高移动通信系统容量进行了分析。     

基于多传感器融合的机器人障碍物检测和识别

该文研究了在移动机器人中基于神经网络的多种传感器信息融合技术。通过由CCD摄像机获得的彩色图像与超声波传感器组获得的距离作为辅助视觉系统实现整个视觉系统功能。移动机器人的障碍物检测和识别的可靠性与精度比在任何单一传感器所获得的信息都有很大的提高。     

机器人关节空间障碍的特性分析

以二维 RR臂为例 ,阐述了工作空间障碍向关节空间映射的几个重要性质 ,分析了点、直线 (线段 )及圆的关节空间障碍 ,为机器人关节空间内路径规划的环境建模提供了新途径     

光电负阻晶体管PNEGIT的电路模型和模拟

给出了光表面控制负阻晶体管 PNEGIT( Photo- Controlled Surface Negative ImpedanceTransistor)的电路模型 ,从栅控晶体管数学模型出发并结合光电池的电路模型 ,用电路模型描写带有表面复合和体复合的器件 ,模型为研究 PNEGIT和表面控制负阻晶体管 NEGIT( Surface- Controlled Negative Impedance Transistor)以及探讨该类器件的新用途提供了一种手段 ,把模拟结果与实验进行了对比