基于OpenMP的短波射线追踪并行计算

在基于分布共享存储结构的高性能计算机上,研究三维短波射线追踪的并行化计算。通过对三维射线追踪串行程序的分析,给出了程序在并行计算时需要考虑的因素,最后采用OpenMP的并行计算技术,对短波射线追踪算法进行了仿真计算。仿真结果表明运行速度得到了大幅度的提高,证明了该算法的有效性。     

电离层三维射线追踪的快速计算方法

基于三维射线追踪的Haselgrove方程,实现了快速电离层短波数字的三维射线追踪.根据射线传播的几何关系,给出在电离层以下部分的射线参数计算方法.根据电子浓度梯度的变化和自适应Runge-Kutta法,给出了三维射线追踪中自适应改变积分步长的快速计算方法,并以准抛物电离层模型为例,讨论了利用本文方法与解析解相比的精度,以及与各种不同步长相比的时间和精度.结果表明:采用本文方法在相同精度下速度至少可以提高一个数量级.     

GCC编译器生成代码中的C++对象模型分析

本文对GCC编译器编译C++程序时使用的对象模型进行了讨论,重点分析了GCC实现C++对象模型过程中采用的相关数据结构和算法。本文的分析可以帮助程序开发者及C++编译器的设计者理解GCC编译器中C++对象模型的实现机制,或在C++程序安全分析领域帮助开发者设计C++程序安全模型。     

电离层短波三维射线追踪及其应用研究

从三维射线追踪的Haselgrove方程出发,采用龙格-库塔法求解沿射线路径的电波传播参数,实现了电离层短波数字三维射线追踪,重点对数字三维射线追踪具体实现的一些关键问题处理进行了深入分析研究.本研究工作是结合传播工程技术问题开展的,以一类具体的电离层模型,给出了三维射线追踪在一些传播工程中的具体应用.     

基于高斯光束与射线追踪的短波波场计算算法

短波通信中几何光学理论难以计算焦散波场的传播问题,提出一种基于高斯光束的短波传播计算算法.首先,采用高斯光束法将产生高频波场的波源分解为若干个高斯光束;然后,通过射线追踪法与拉格朗日公式计算每个高斯光束,通过沿光束中心射线的ODE(常微分方程)计算曲率与光束宽度等定量;最终,采用泰勒展开式决定中心射线附近光束的贡献度,将接收点附近的高斯光束进行加权求和,获得接收端的波场.实验结果表明,本算法可有效地计算焦散的短波传播,并且与几何光学法的误差极为接近.     

基于ARM9体系架构的编译优化研究

在嵌入式系统软件开发过程中, GCC编译循环程序时的窥孔优化比较欠缺，编译代码在性能上较ARM商业编译器低。文中提出针对于ARM9处理器的循环计数值组合、循环处理数据合并和循环最优展开等3种窥孔优化方法优化汇编代码。选取矩阵乘法，图像合并和内存设置等经典程序运行在ARM9平台上，分别验证3种窥孔优化方法。实验数据表明，与GCC编译代码相比，经文中提出的方法优化后的代码在寄存器使用数量上，平均节省了50%,性能提升近2倍。     

基于数值射线追踪的短波电离层传播轨迹研究

从电波传播的射线方程出发,在不考虑地磁场和碰撞的条件下,推导出了球坐标系下描述短波在电离层传输的轨迹方程.以准抛物电子密度模型为例,给出了求解参数方程组的初始条件.采用改进Euler数值方法求解轨迹参数方程组,得到短波轨迹的参数,实现了短波在电离层中的轨迹计算及仿真.仿真结果结果表明,用数值射线追踪法研究短波在电离层中的传播可以为短波天波通信的轨迹模拟和参数优选提供参考.     

OpenCL：多核ARM处理器编译器

意法半导体全资子公司PortlandGroup（PGI）推出基于ARM内核的ST-EricssonNovaThor移动平台专用PGIOpenCL开发框架。该开发框架包括一个把多核ARMCPU视为一个计算设备的PGIOpenCL编译器,并增强了OpenCLGPU（图形处理器）编译器功能。NovaThor是一个高集成度的完整的移动平台,     

MATLAB中M-文件的编译和优化

MATLAB 是美国MathWorks 公司推出的一个非常优秀的数学软件，它具有很强的数值计算能力和卓越的数据可视化能力。但在MATLAB5 及以前的版本中，并没有提供对其M -文件进行编译和创建外部应用程序的工具，从而大大限制了它与其他应用程序的结合和应用。在MATLAB 最新的5 .2 版本中，增加了MATLAB 编译器以及C/C++Math 库，它们与C/C++编译器一起对M-文件进行编译，生成相应的C或C++源代码及二进制的MEX-文件。通过MATLAB编译器和C 或C++的编译器来完成链接，可以得到独立于M A T L AB 之外的应用程序。1 、编译M-文件…     

程序分析中的设计模式应用

基于反射原理和开放编译技术的软件植入方法是程序的动态分析,准确获取理解面向对象软件系统运行时信息的有效手段,文章提出的软件触发器植入算法是在应用设计模式扩展开放编译器功能的基础上实现的,以提高可复用性和可扩展性,并通过实验验证了该算法实现的有效性.     

A 3‐D Propagation Model Considering Building Transmission Loss for Indoor Wireless Communications

In the development of a new wireless communications system, a versatile and accurate radio channel for indoor communications is needed. In particular, the investigation of radio transmission into buildings is very important. In this letter, we present an improved three‐dimensional electromagnetic wave propagation prediction model for indoor wireless communications that takes into consideration building penetration loss. A ray tracing technique based on an image method is also employed in this study. Three‐dimensional models can predict any complex indoor environment composed of arbitrarily shaped walls. A speed‐up algorithm, which is a modified deterministic ray tube method, is also introduced for efficient prediction and computation.     

一种高效的自适应射线束追踪方法

提出了一种高效的射线追踪方法.该扩展传统射线追踪法的射线管成射线束.射线束可以根据求解空间自适应裁剪,解决了传统射线追踪法对空间的离散采样问题;摒弃了接收球技术,还解决了接收球技术带来的双计误差.该方法采用了基于Pluecker坐标系的射线束-三角形碰撞检测算法,使得提出的射线束追踪法具有很高的计算效率.该方法成功地应用于复杂场景下室内信道的预测,并与已公开发表的论文的测量值进行对比,一致性良好.     

提高射线跟踪法运算效率的一种方法

分析了影响射线跟踪法运算效率主要因素，提出了一种提高室内二维射线跟踪运算效率的方法。该方法将室内电波传播区域内物体进行适当的分区和分组从而减少射线与物体示谘运算的次数。模拟计算结果证明了该方法的有效性。     

An FDTD/ray-tracing analysis method for wave penetration through inhomogeneous walls

A novel method of studying wave penetration through inhomogeneous walls using the hybrid technique based on combining finite-difference time-domain (FDTD) and ray tracing methods is presented . The FDTD method is used to analyze the transmission characteristics of inhomogeneous walls. Using the knowledge of the tangential electric and magnetic field distributions along the borders of the FDTD computation domain, rays are sent out to cover the rest of the environment so that prediction of signal coverage can be made more efficiently without compromising the accuracy. Numerical results of the method have been compared and shown to agree very well with those of measurement and those of full wave analysis. Examples have shown the inadequacy of the traditional ray tracing method in the presence of walls made of concrete blocks. However, the proposed method can accurately predict signal coverage by taking into account the scattered fields by the inhomogeneity inside the walls. The method does not add much to computational complexity. Reduction in computation time is even more significant when the incident waves can be approximated to be plane waves and the wall structure is periodic.     

光束会聚对光学偏振探测影响的分析

为了得到由于偏振成像系统自身的光束会聚现象导致仪器偏振测量产生误差的规律,采用空间偏振光束追击矩阵理论,对平行于光轴方向振动的透射光强对偏振测量精度的影响进行了理论分析.结果表明,偏振光束会聚导致实际测量的偏振度小于光束真实的偏振度;光束会聚程度越高,测量的偏振度与光束真实偏振度的误差越大;在光束会聚状态和偏振测量条件...     

射线跟踪中三维矢量数据库建立方法

射线跟踪信道建模方法需要场景的三维矢量数据库,包括场景数据库和可见元(面、劈)数据库。本文提出了一种适用于城市微蜂窝和室内场景的三维矢量数据库建立方法。首先通过简化的三维CAD建模方法建立三维场景模型和数据库,然后使用修正的透视投影法建立视点关于场景的三维可见元数据库,并进一步分析了基于三维可见元数据库的射线跟踪模型计算复杂度。仿真结果表明,该方法能有效地降低射线跟踪信道建模方法的计算复杂度。     

An efficient parallel architecture for ray-tracing

Real time rendering of three-dimensional scenes in high photorealistic details is a hard task, such as in the ray tracing rendering algorithm. In general, the performance achieved by a sequential software-based implementation of ray tracing is far from satisfactory. However, parallel implementations of ray tracing have been enabling reasonable real time performance, as the algorithm is embarrassingly parallel. Thus, a custom parallel design in hardware is likely to achieve an even higher performance. In this paper, we propose a hardware parallel architecture capable of dealing with the main desirable features of ray tracing, such as shadows and reflection effects, imposing low area cost and a promising rendering performance. Such architecture, called GridRT, is based on the Uniform Grid acceleration structure and is intended to deliver massive parallelism through parallel ray-triangle intersection tests as well as parallel processing of many rays. A hardware implementation of the proposed architecture is presented, together with some performance results and resources requirements. The rendering is reduced by 80% using a grid configuration of eight processing elements.     

A sensitivity study for an indoor channel

The context of this paper is the 3D wave propagation simulation with a software based on a ray tracing technique in typical indoor environments. The presented works are complementary to these of the literature which propose the validation of a propagation model in comparison with measurements. Indeed, the presented study consists of a sensitivity analysis of an already validated propagation model. The considered parameters are electromagnetic, geometric and electric; they directly intervene in the two parts of a simulation: the modelling of the wave propagation and of the environment. The aim of this study is to contribute to the setting up of parameterisation rules of a simulation software according to two criteria: the accuracy and the compromise between accuracy and computation time.     

Co-Synthesis to a Hybrid RISC/FPGA Architecture

Hybrid architectures combining conventional processors with configurable logic resources enable efficient coordination of control with datapath computation. With integration of the two components on a single device, housekeeping tasks and, optionally, loop control and data-dependent branching, can be handled by the conventional processor, while regular datapath computation occurs on the configurable hardware. This paper describes a novel approach to programming such hybrid devices that gives the programmer control over mapping of data and computation between conventional processor and configurable logic. With a simple set of pragma and intrinsic function directives, the NAPA C language provides for manual control over perhaps the most important aspect of programming such hybrid devices. Alternatively, as experience is gained about tradeoffs between the two computational resources, mapping directives may eventually be generated by an external tool. The paper further describes a research prototype compiler that targets the hybrid processor model, with a concrete implementation for the National Semiconductor NAPA1000 chip. The NAPA C compiler parses the mapping directives, performs semantic analysis, and co-synthesizes a conventional processor executable combined with a configuration bit stream for the configurable logic. Two major compiler phases, the synthesis of pipelined loops and the datapath synthesis, are described in detail.     

用蒙特卡罗方法和MATLAB计算冷屏效率

在制冷型红外成像系统中,冷屏具有定义视场角大小、限制杂散光辐射的作用．冷屏有各种孔径形状,但是冷屏效率的计算无解析公式,一般需要用数值方法求解．介绍了用蒙特卡罗方法和MATLAB计算简化的圆形冷屏结构、冷屏效率的一种途径．基于三维空间中的方向数概念,首先利用MATLAB命令生成冷屏区域内的随机点,再赋予该点一组随机方向数,获得一条随机直线方程;根据镜面反射的性质及解析几何公式,追踪该直线在冷屏上的反射光线并判断它是否落人探测器芯片区域,由此可以确定冷屏效率．方法具有编程简单、方便实用等特点．