Twenty-five years of natural coordinates

In the early eighties, the author and co-workers created and further developed the natural coordinates to describe the motion of 2-D and 3-D multibody systems. Natural coordinates do not need angles or angular parameters to define orientation, leading to constant inertia matrices and to the simplest form of the constraint equations. Natural coordinates are composed by the Cartesian coordinates of some points and the Cartesian components of some unit vectors distributed on the different bodies of the system. The points and vectors can be located in the joints, being shared by contiguous bodies, decreasing or even eliminating the need to set joint constraints and reducing the total number of variables. However, other authors prefer not to share variables in order to get even simpler equations and to keep a bigger decoupling of equations, which is preferable in some cases. In this paper the history of natural coordinates is reviewed, as well as the main contributions coming from other research groups. In the second part of the paper some application areas in which natural coordinates can be particularly advantageous are examined. Commemorative Contribution.     

X，Y定标方法在触摸屏中的应用

文章从屏前Ｘ，Ｙ位置如何定标的共同问题出发，讨论了常用的几种触摸屏光学的、电阻式、电容式和超声式的原理性结构和性能，最后还阐述了它们的应用场合     

基于超声导引的药品自动搬移系统的研制

阐述基于超声导引的药品智能搬移系统的研制方案,并给出主要设计电路。该系统用主从结构的两块TIMSP430F149单片机作为控制核心。从单片机控制搬移设备上的超声发送模块发送超声,坐标系上的三个超声接收器采集超声信号并做放大、滤波、单稳处理,处理后的信号发送给主单片机进行分析并发送控制命令给从单片机,从而实现对搬移设备的控制与定位。     

一种改进的人脸纹理映射方法

识别人脸图像优化问题,由于人脸纹理映射时容易出现的纹理扭曲和畸变现象,影响图像的真实性,提出一种改进的纹理图像映射方法。根据人脸特征点信息,利用特征块匹配法配准正侧面人脸图像,并使用加权平滑算法和金字塔方法对图像进行双重融合实现图像的平滑过渡;然后利用一种特殊的定位方法来计算三维人脸模型上顶点对应的纹理坐标;最后根据纹理坐标将纹理图像映射到三维特定人脸模型表面上,可得到具有真实感的三维人脸模型。实验结果表明,纹理合成方法简捷有效,纹理映射结果生动逼真,有效的避免了纹理图像的扭曲和畸变现象,具有较高的鲁棒性。     

Curvilinear grids for WENO methods in astrophysical simulations

We investigate the applicability of curvilinear grids in the context of astrophysical simulations and WENO schemes. With the non-smooth mapping functions from Calhoun et al. (2008), we can tackle many astrophysical problems which were out of scope with the standard grids in numerical astrophysics. We describe the difficulties occurring when implementing curvilinear coordinates into our WENO code, and how we overcome them. We illustrate the theoretical results with numerical data. The WENO finite difference scheme works only for high Mach number flows and smooth mapping functions, whereas the finite volume scheme gives accurate results even for low Mach number flows and on non-smooth grids.     

基于组播的LFMCW雷达显示系统设计与实现

基于组播传输机制设计并实现了雷达系统网络结构,定义了各种显控协议报文的数据结构以及与之相关的组播地址。针对数据报文中的极坐标数据,提出了一种基于三维优化查找表算法的坐标转换方法。对转换过程中的漏点和重点等问题进行了有效解决,并分析了组播在实现多屏显示和在综合船桥系统中的扩展优势。最终系统通过QT绘制界面,在以XC6SLX100T和DAVINCI DM3730为基础的硬件平台上完成了实际测试,验证了系统的可行性。     

优化变形能的平面多边形同构剖分

平面多边形间的同构三角剖分是平面形状渐进过渡与插值的基础,降低对应三角形的变形程度是获得高质量应用的关键.文中提出一种基于变形能优化的2个平面多边形的同构剖分算法,其中包含同构剖分生成和变形能最小化2个模块.首先根据用户指定的对应特征点对多边形进行顶点重采样,得到顶点一一对应的2个多边形;然后利用带约束的Delaunay剖分对其中的一个多边形进行三角化,得到源网格;再用重心坐标将源网格的内部顶点嵌入到另一个多边形得到同构剖分(目标网格);最后逐一检查三角形的变形能,对源网格中变形能超过阈值的三角形进行细分,用同构剖分模块生成新的目标网格.实验及数据统计分析表明,该算法可以得到较好的同构三角剖分,提升网格质量,并能很好地避免纹理细节失真.     

An efficient method for a numerical description of virgin olive oil color with only two absorbance measurements

Four polynomial expressions are obtained that provide a good approximation and an easy, rapid calculation of the chromatic coordinates and the chroma—L ^*, a ^*, b ^*, and C—for the illuminant C and the standard observer, for a virgin or extra virgin olive oil; absorbance is measured at only 480 and 670 nm. These are as follows: L ^*=0.556458(A₄₈₀)²−2.51145A₄₈₀+0.55504(A₆₇₀)²−8.53016A₆₇₀+98.4089; a ^*=0.177372(A₄₈₀)²+2.1363A₄₈₀+1.43254(A₆₇₀)²−0.789231A₆₇₀−13.9246; b ^*=−16.0277(A₄₈₀)²+79.8932A₄₈₀−5.06558(A₆₇₀)²+3.36169A₆₇₀+31.9405; C=−15.8439(A₄₈₀)²+78.9312A₄₈₀−5.26784(A₆₇₀)²+3.56917A₆₇₀+33.3927. These give acceptable results, making the method a practical alternative to the extremely laborious Commission Internationale d’Eclairage (CIE) L ^* a ^* b ^* system, by which 391 absorbance values must be measured individually, nanometer by nanometer, before applying more complex equations. The validity of the proposed method has been confirmed by comparison, using a set of 20 sample oils different from the set of 25 oils used to generate the order of the equations. The variations between the values provided by the proposed and standard methods, respectively, had a mean of 0.00 for each of the chromatic variables—L ^* , a ^* , b ^* , and C; SD were moderate (0.71, 0.52, 1.22, and 1.22, respectively); the root mean square and the R ²-terms also confirmed the validity of the method.     

免棱镜全站仪在已有建筑测绘中的应用方法

结合实际测绘情况,介绍了利用免棱镜全站仪的数据采集功能进行外业接坐标、现场人工绘草图、内业数据处理后在AutoCAD中展点成图,在此基础上结合钢尺测量数据,绘制平、立面图的方法,并对该测量方法的实施步骤和关键技术作了较为详细的介绍。