工程装备仿真实体在行军过程中的聚合和解聚

在工程兵作战仿真中多分辨率模型的聚合与解聚问题一直是困扰不同层次仿真系统集成的瓶颈问题。该文以工程兵工程装备行军过程为例,对工程装备行军过程仿真中不同层次仿真模型的聚合与解聚问题进行了研究,分析了该仿真过程中所需模型的分辨率,分别就工程装备仿真实体位置、速度、状态及毁伤的聚合与解聚进行分析,同时给出了仿真实体位置、速度、状态及毁伤的聚合与解聚解决方法,这些方法简单实用,节省资源,效率高,对解决工程兵作战仿真中的模型聚合与解聚问题具有一定的参考价值。     

一种双向元数据管理系统

作为企业级数据仓库的路径图,元数据在企业级数据仓库的建设中起着重要的作用。设计一个描述能力强、内容完善的元数据,是有效实现企业级数据仓库功能的重要环节。该文通过对双向体系元数据管理系统的研究,给出了一个企业级数据仓库的元数据管理的解决方案。该方案能够支持从企业级数据仓库子系统抽取元数据存储到元数据管理系统,同时也支持向数据仓库子系统提供其所需的元数据信息,解决诸多企业级数据仓库的运行管理问题,大大减少了企业级数据仓库的管理难度、保证了元数据的准确性、使得各子系统能高效地通信和稳定运行。     

基于Pro/E的雷达电子设备机箱的参数化设计

针对雷达电子设备机箱结构设计的设计特点及设计过程,应用Pro/E的参数化技术,实现雷达雷达电子设备机箱结构设计的参数化设计。     

浅析次世代单机游戏

近些年来游戏产业空前发展,现已成为网络经济及文化娱乐业的重要组成部分。次时代游戏有其独特的形式与审美视觉价值被大家所认知。随着国外信息技术不断冲击国内游戏产业促使国内网游业集成了新技术,譬如次时代网游,国内知名的游戏公司久游首先利用了法线技术,运用到中国式的网游业中。其二是电脑硬件的提升有利于新技术的空前发展。文章粗浅总结一下次世代游戏单机的三维制作基本流程。     

基于ADSP-BF561的英文字符库设计

针对以ADSP-BF561芯片为核心的目标跟踪系统中显示目标运动及提示信息的需要,提出了基于ADSP-BF561的英文字符库的设计方案.该字符库中包括26个小写英文字符(a～z)、10个数字(0～9),以及“:”和空格共计38个符号.该字符库通过使用存储在ADSP-BF561的L2存储器上的数据类型为布尔型、大小为16...     

LiveROMS: A virtual environment for ocean numerical simulations

LiveROMS is a bootable DVD that contains an Linux-based computer operating system which has a complete, functioning version of the ROMS ocean circulation model and an Octave version of ROMSTOOLS. It allows students and scientists to experiment with this ocean numerical model, with just a basic knowledge of Linux.     

Two new control signal approaches for obtaining the MRAS-CDM and a real-time application

The coefficient diagram method (CDM) is one of the most effective control design methods. It creates control systems that are very stable and robust with responses without the overshoot and small settling time. Furthermore, all control parameters of the control systems are changed by varying some adjustment parameters in CDM depending on the demands. The model reference adaptive systems (MRAS) are the systems that follow and change the control parameters according to a given model reference system. There are several methods to combine the CDM with MRAS. One of these is to use the MRAS parameters as a gain of the CDM parameters. Another is to directly use the CDM parameters as the MRAS parameters. In the industrial applications, the system parameters can be changed frequently, but if the controller, by self-tuning, recalculates and develops its own parameters continuously, the system becomes more robust. Also, if the poles of the controlled systems approach the jw axis, the response of the closed-loop MRAS becomes more and more insufficient. In order to obtain better results, CDM is combined with a self-tuning model reference adaptive system. Systems controlled by a model reference adaptive controller give responses with small or without overshoot, have small settling times, and are more robust. Thus, in this paper, a hybrid combination of MRAS and CDM is developed and two different control structures of the control signal are investigated. The two methods are compared with MRAS and applied to real-time process control systems.     

Numerical investigations on dynamic stall of low Reynolds number flow around oscillating airfoils

This paper presents a 2D computational investigation on the dynamic stall phenomenon associated with unsteady flow around the NACA0012 airfoil at low Reynolds number (Re_c ≈ 10⁵). Two sets of oscillating patterns with different frequencies, mean oscillating angles and amplitudes are numerically simulated using Computational Fluid Dynamics (CFD), and the results obtained are validated against the corresponding published experimental data. It is concluded that the CFD prediction captures well the vortex-shedding predominated flow structure which is experimentally obtained and the results quantitatively agree well with the experimental data, except when the blade is at a very high angle of attack.     

Hybrid LES/RANS modelling of free surface flow through vegetation

Vegetated channels are environmentally friendly and frequently used to convey water for drainage and recreational purposes. The design and assessment of these channels often requires the use of numerical models which are based on the Reynolds Averaged Navier-Stokes (RANS) approach or Large Eddy Simulations (LES). It is well accepted that both approaches have their advantages and disadvantages. To overcome these disadvantages a hybrid model combining the RANS and LES methodologies is proposed in this work. The major task for the model development is to couple the RANS and the LES models effectively. Various methods have been investigated and the results are as follows. At the inflow boundary of the computational domain, a semi-analytical velocity profile for submerged vegetation is used as the RANS inflow condition to shorten the unrealistic flow transition region. At the interface of the upstream RANS region and the downstream LES region, turbulence fluctuations are artificially generated using a spectral line processor, with the mean velocity determined by using the frozen cloud assumption. At the interface of the upstream LES region and the downstream RANS region, a virtual momentum sink is imposed to dissipate the sub-grid scale fluctuations and to shorten the transition region. The final model has been verified against experiments of flow through submerged and emergent vegetation, as well as a partly vegetated channel.     

基于矩形NAM和偏微分方程的灰度图像压缩方法

借助矩形NAM图像表示方法和偏微分方程技术,提出一种新的灰度图像压缩方法.该方法在编码端把原始图像逆布局为若干矩形子块,并采用坐标压缩方法存储每个子块的位置、大小.在解码端,采用偏微分方程进行图像修复,有效消除解码图像中的方块效应.该方法的时间复杂度为 ,其中n为灰度图像像素数.实验表明:在保持图像质量的前提下,该方法具有更高的压缩比和更少的块数,具有较高实用价值.