Simultaneous untangling and smoothing of quadrilateral and hexahedral meshes using an object-oriented framework

In this work, we present a simultaneous untangling and smoothing technique for quadrilateral and hexahedral meshes. The algorithm iteratively improves a quadrilateral or hexahedral mesh by minimizing an objective function defined in terms of a regularized algebraic distortion measure of the elements. We propose several techniques to improve the robustness and the computational efficiency of the optimization algorithm. In addition, we have adopted an object-oriented paradigm to create a common framework to smooth meshes composed by any type of elements, and using different minimization techniques. Finally, we present several examples to show that the proposed technique obtains valid meshes composed by high-quality quadrilaterals and hexahedra, even when the initial meshes contain a large number of tangled elements.     

面向对象的液压系统CAD数据库的建立

在液压系统的设计过程中,一些液压元件和液压回路的选择非常重要.为了让设计者高效率地选用液压元件和回路,对其进行了统一规划,建立了一个面向对象的液压系统CAD数据库,通过调用该数据库可以很方便地达到设计目的.     

基于面向对象的高分辨率遥感影像建筑物提取研究

遥感影像上的建筑物是一种非常重要的地物.利用高分辨率遥感影像上建筑物的光谱、空间特征及上下文特征等,并通过贝叶斯理论计算对象的归属概率属性,提出了一种面向对象的高分辨率影像建筑物提取方法.实验证明该方法有较好的提取效果.     

基于面向对象和数据库技术的机床选择专家系统

机床选择是机械加工工艺设计中的一个重要环节。专家系统是人工智能的一个主要研究方向,非常适合处理需要大量经验知识的设计问题。提出将面向对象方法和数据库技术相结合,进行了机床选择专家系统总体结构设计,并介绍了各模块对应的功能,研究了基于产生式规则的知识表示方法、基于关系型数据库的知识库的管理和基于正向推理方式的推理机的设计和推理过程等关键技术,以Visual C++和Access为开发工具,实现了机床选择专家系统。     

Hierarchical model-based predictive control of a power plant portfolio

One of the main difficulties in large-scale implementation of renewable energy in existing power systems is that the production from renewable sources is difficult to predict and control. For this reason, fast and efficient control of controllable power producing units – so-called “portfolio control” – becomes increasingly important as the ratio of renewable energy in a power system grows. As a consequence, tomorrow's “smart grids” require highly flexible and scalable control systems compared to conventional power systems. This paper proposes a hierarchical model-based predictive control design for power system portfolio control, which aims specifically at meeting these demands.The design involves a two-layer hierarchical structure with clearly defined interfaces that facilitate an object-oriented implementation approach. The same hierarchical structure is reflected in the underlying optimisation problem, which is solved using Dantzig–Wolfe decomposition. This decomposition yields improved computational efficiency and better scalability compared to centralised methods.The proposed control scheme is compared to an existing, state-of-the-art portfolio control system (operated by DONG Energy in Western Denmark) via simulations on a real-world scenario. Despite limited tuning, the new controller shows improvements in terms of ability to track reference production as well as economic performance.     

An open source, parallel DSMC code for rarefied gas flows in arbitrary geometries

This paper presents the results of validation of an open source Direct Simulation Monte Carlo (DSMC) code for general application to rarefied gas flows. The new DSMC code, called dsmcFoam, has been written within the framework of the open source C++ CFD toolbox OpenFOAM. The main features of dsmcFoam code include the capability to perform both steady and transient solutions, to model arbitrary 2D/3D geometries, and unlimited parallel processing. Test cases have been selected to cover a wide range of benchmark examples from 1D to 3D. These include relaxation to equilibrium, 2D flow over a flat plate and a cylinder, and 3D supersonic flows over complex geometries. In all cases, dsmcFoam shows very good agreement with data provided by both analytical solutions and other contemporary DSMC codes.     

A FRAMEWORK FOR PARTITIONING STRUCTURED GRIDS WITH INHOMOGENEOUS WORKLOAD

A framework is presented for partitioning arrays with irregular workload. Within the framework structured and unstructured methods are combined in a new approach to partition data, based on blocks and block operations. A new variant of the recursive spectral bisection method suitable in this context is suggested. The use of the framework is demonstrated for a real life application, ocean modeling of the Baltic Sea. In this case study, the new approach gives very good results while standard partitioning methods cannot fulfill all the listed requirements. The operations have been implemented in a Fortran 90 software package with an object-oriented design.     

基于面向对象遗传算法的柔性车间调度研究

针对柔性车间作业调度问题,基于面向对象思想设计了一种遗传算法。该算法将实际操作封装成基因类,工件封装成工件类,机床封装成机床类,调度方案封装成染色体类,基于堆栈思想设计了染色体的创建方式,提出了全新的染色体解码方式及变异方式。通过仿真实例证明了该算法的有效性和实用性。     

基于多层分割的面向对象遥感影像分类方法研究

利用ALOS数据,在Definiens Developer 7软件中用分形网络演化法(FNEA)进行多级分割,获取影像对象。综合运用对象的光谱、空间特征和不同层对象之间的关系,提取了湖北省洪湖市试验区土地覆盖与土地利用信息。最后,用一种基于单层分割的面向对象分类方法和基于像素的最大似然法与这种基于多级分割的面向对象分类方法进行了对比分析。结果表明,基于多级分割的面向对象分类方法,不仅克服了基于像素的最大似然法出现的“椒盐”现象,在分类精度上较这两种分类方法也有大幅度的提高。     

基于分水岭变换与空间聚类的高分辨率遥感影像面向对象分类

面向对象方法已广泛应用于高分辨率遥感影像分类,提出一种结合改进分水岭变换与空间聚类的遥感影像面向对象分类新方法。首先,基于相位一致思想分析图像特征,由Gabor小波多尺度、多方向提取QuickBird全色影像的梯度信息;利用扩展最小变换与强制最小技术分别获取图像前景标识、重建相位一致梯度图像,利用改进后的分水岭变换获得分割对象。然后,提取各对象的多波段光谱特征,利用Gabor小波获取对象纹理矢量,并用独立成分分析方法进行特征选择,依次进行对象的光谱与纹理聚类。最后,通过分析对象间空间拓扑关系判断聚类后不确定对象的类别属性。实验结果表明该方法能取得较好结果,在一定程度上提高了影像分类的自动化水平。