Vector-based arc segmentation in the machine drawing understandingsystem environment

Arcs are important primitives in engineering drawings. Extracting these primitives during the lexical analysis phase is a prerequisite to syntactic and semantic understanding of engineering drawings within the machine drawing understanding system. Bars are detected by the orthogonal zig-zag vectorization algorithm. Some of the detected bars are linear approximations of arcs. As such, they provide the basis for arc segmentation. An arc is detected by finding a chain of bars and a triplet of points along the chain. The arc center is first approximated as the center of mass of the triangle formed by the intersection of the perpendicular bisectors of the chords these points define. The location of the center is refined by recursively finding more such triplets and converging to within no more than a few pixels from the actual arc center after two or three iterations. The high performance of the algorithm, demonstrated on a set of real engineering drawings, is due to the fact that it avoids both raster-to-vector and massive pixel-level operations, as well as any space transformations     

基于函数依赖的结构匹配方法

模式匹配是模式集成、数据仓库、电子商务以及语义查询等领域中的一个基础问题,近来已经成为研究的热点,并取得了丰硕的成果.这些成果主要利用元素(典型的为关系模式中的属性)自身的信息来挖掘元素语义,目前,这方面的研究已经相当成熟.结构信息作为模式中一种重要的信息,能够为提高模式匹配的精确性提供有用的支持,但是目前关于如何利用结构信息提高模式匹配的精确性的研究还很少.将模式元素之间的相似度分为语义相似度(根据元素自身信息得到的相似度)和结构相似度(根据元素之间的关联关系得到的相似度),并采用新的统计方法计算元素间的结构相似度,然后再综合考虑语义相似度得到元素间的相似概率;最后根据相似概率得到模式元素间的映射关系(模式元素之间的对应关系).实验结果表明,该算法在查准率、查全率及全面性等方面都优于已有的其他算法.     

基于模糊逻辑的K-means算法研究

K-means算法的基本思想是通过迭代方法把所有的元素都唯一聚类到不同的簇中,使得同一簇中的质点具有最小相异度,不同簇间的元素具有最大相异度。但是,这种聚类方法使得那些属于不同簇的交叉区域中的质点也被简单地聚类到了某个簇中,因此无法表达某些元素的跨簇特性。本文提出了基于模糊逻辑的K-means算法,利用模糊逻辑来计算不同簇交叉区域中质点属于某个簇的权重,在获得聚类结果的同时可以有效描述质点的跨簇特性。实验结果表明该算法是有效的。     

多波束天线通道幅相误差的自校正算法

多波束天线利用多信号分类(MUSIC)算法对目标参数进行精确估计时,存在多波束天线的通道幅度和相位误差的失配现象,使MUSIC算法的性能严重下降;针对基于MUSIC的数字波束通道不一致问题,给出了一种新的基于MUSIC算法的最小化代价函数的波束无源自校正算法,利用阵列结构的先验知识对接收数据进行预处理,得到校正矩阵后自校正,并根据多波束阵列天线形成网络天线实测参数,加入随机幅度和相位误差进行计算机模拟仿真,验证仿真算法的正确性。     

脉冲MIG焊电弧双模模糊控制

针对脉冲M IG焊焊钢时的电弧稳定性控制,采用峰值弧压反馈的方式,设计了基于修正因子的电弧双模模糊控制器,当峰值弧压偏差较大时采用基于修正因子的粗调模糊控制规则,以送丝速度Vf为控制量,而当峰值弧压偏差较小时采用基于修正因子的细调模糊控制规则,以基值时间Tb为控制量,以查表方式实现模糊控制器.最后通过试验验证了在焊接过程中弧长变化时所设计的模糊控制器可保持电弧的稳定从而保证焊接过程的稳定.     

一种带物元的动态描述逻辑

针对动态描述逻辑框架中只有概念和关系,在表述由于动作作用而引起的概念或个体的属性及值的变化和变化后的影响方面能力不强的问题,本文引入物元的概念及其发散规则扩充动态描述逻辑,给出了一种新的带物元的动态描述逻辑(MDDL).文中按照传统描述逻辑的语义解释方法给出了物元的语义解释,然后引入物元及物元"一物多征"的发散推理规则,扩充动态描述逻辑的Tableau算法,生成二种新的Tableau-M算法.最后根据该算法深入研究了MDDL的基本推理问题,即实例断言集的一致性检测问题和概念与物元的可满足性检测问题.     

Focus on software

At least 15 percent of the growth in U.S. productivity during the last decade is attributable to computers, according to COMPCON Fall 77 keynoter Mark Shepherd, Jr.,* of Texas Instruments. Addressing an audience of 850 computer system designers at the Mayflower Hotel on Sept. 7 in Washington, the TI board chairman and chief executive officer stressed that the industry will make an even more significant impact on the ecoecoic problems besetting the country if the price/performance ratio of future computer equipment can be improved.     

基于模式的XML文档关系数据库存储研究

在XML文档中可以自定义元素标签,不同XML的应用名称同名的几率非常大.命名空间的使用可以区分来自不同XML文档应用的具有相同名称的元素和属性,避免元素和属性的同名冲突.命名空间在XML文档中是一类非常重要的信息,详细介绍XML文档在映射到关系数据库时对命名空间信息的提取映射.     

提高乙醇气体传感器性能的方法

提高乙醇气体传感器性能的途径有改变材料、结构以及工作原理。其中改变材料包括 :(1)添加催化剂 ,提高材料的活性 ;(2 )选择敏感特性更好的材料 ;(3)在表面涂敷一层特定材料 ,减小其它气体的干扰。改变结构包括 :(1)改变材料的微观结构———超微粒化 ;(2 )改变材料的宏观结构 :烧结型→厚膜型→薄膜型 ;(3)改变敏感元件的结构 :由一个敏感电阻器变为两个敏感电阻器     

Artificial Bee Colony (ABC) algorithm in the design optimization of RC continuous beams

The objective of this study is to obtain the optimum design for reinforced concrete continuous beams in terms of cross section dimensions and reinforcement details using a fine tuned Artificial Bee Colony (ABC) Algorithm while still satisfying the constraints of the ACI Code (2008). The ABC algorithm used in this paper has been slightly modified to include a Variable Changing Percentage (VCP) that further improves its performance when dealing with members consisted of multiple variables. The objective function is the total cost of the continuous beam which includes the cost of concrete, formwork and reinforcing steel bars. The design variables used are beam width, beam height, number and diameter of: bottom continuous reinforcing bars, bottom cutoff reinforcing bars, top continuous reinforcing bars and top cutoff reinforcing bars as well as the diameter of stirrups. Four RC beams of varying complexity are presented and optimized. The first three beams are used to fine tune the control parameters of the ABC algorithm, whereas the fourth beam was previously optimized by Arafa et al. (J Artif Intell 76–88, 2011) and is presented here to prove the superiority of this relatively new optimization algorithm.     

电路计算机辅助设计系统中电路图的处理

介绍如何使用数据库技术来处理电路图问题。即将电路图中的每一个元器件的名称、位置、大小和使用图片等属性保存在数据库表的一条记录里,对每个元器件的修改其实就是修改数据库里对应记录的内容,这样电路图中的元器件都能以分离元件的形式分别进行移动、删除和保存。程序结果表明,使用数据库技术来处理电路图,可以很方便地对各个元器件进行调整,而且保存后,以后还可以任意调整。     

Increasing deposition height stability in robotic GTA additive manufacturing based on arc voltage sensing and control

Robotic gas tungsten arc (GTA)-based additive manufacturing (AM) is a promising technique to produce high-quality and large-scale metal parts with low cost. Despite this fact, the key issue of ensuring deposition height stability has not been fully solved. In this study, an arc voltage sensing and control approach with little delay is proposed to increase the forming height stability in GTA-based AM. The deposition height stability is indirectly characterized by arc voltage signals sampled using a designed arc voltage detection system. A novel de-noising method, combining the anti-impulse interference moving average with the wavelet packet transform, is proposed to filter out interferences in the original arc voltage. A Fuzzy-PID controller is developed to control the arc voltage by adjusting the wire feed speed on next deposition layer. Constant parameter and closed-loop control experiments are compared via fabricating thin-walled parts. The more stable arc voltage and more excellent forming appearance in the closed-loop control test indicate that applying the arc voltage sensing and control system can greatly improve the forming height stability in robotic GTA-based AM.     

基于数字图像处理的棒线材计数方法

棒线材自动计数是一个一直没有得到很好解决的问题,为解决此问题,提出了一种基于距离变换技术的图像识别方案。该方法先利用CCD摄像机采集棒线材的端面图像;然后采用中值滤波法、二值化分割、腐蚀及膨胀运算实现棒线材图像的预处理;最后根据距离变换的思想,采用距离变换图中搜索种子点的方法实现棒线材的计数。通过对现场采集到的图像进行的试验结果表明,该方法不仅不受棒线材种类及端面形态影响,而且对端头不齐、捆扎散乱的棒线材也有较好识别效果,具有一定的推广和应用价值。     

小型化柔性触觉再现装置

提出了一种小型化的具有实时触觉反馈作用的人机接口装置的设计方法,以控制弹性梁的有效变形长度为核心,保证了触觉再现的实时性和准确性,从而可以在操作者指端大范围再现虚拟对象或远程对象的刚度。介绍了该小型化人机触觉再现接口装置的硬件设计和软件设计。该实时触觉再现接口具有尺寸小、刚度再现范围大,可方便与鼠标相结合等特点,可广泛应用于遥操作机器人和虚拟现实领域。     

CAPP系统的开放式数据集成模型

本文提出计算机辅助工艺规划CAPP（computeraidedprocessplanning）系统的开放式数据集成模型．对工艺数据进行抽象概括，形成类层次结构，提高重用．用继承机制，改善标准协议作为用户环境中资源一般的拓展协议，模式演进为补充，完成开放性描述．效率反馈和资源引用构成工艺方法、形状特征、设备资源间的联系和驱动．在工艺规划过程中瞬间返回操作产生的结果，实现相关驱动，改善系统运行效率．模型在CAPP系统中得到实践：构造数据库和知识库耦合系统；数据库面向形状特征层的工艺规划，知识库辅助完成整个工艺     

基于相对Hamming距离的Web聚类算法

针对Web使用挖掘中聚类结果准确性不高的问题,提出了一种改进的基于相对Hamming距离和类不一致度的聚类算法。该算法首先以Web站点的URL为行、以UserID为列建立关联矩阵,元素值为用户的访问次数;然后,对所建立关联矩阵的列向量或行向量进行相似性度量,获得相似客户群体或相关页面。实验表明,该算法具有较高的准确性。     

Elastoplastic torsion by quadratic programming

A finite element scheme (together with a conjugate gradient algorithm) is demonstrated to be a very effective method for analyzing general elastoplastic torsion of prismatic bars posed as quadratic programming problems. Solutions for bars with elliptical and Sokolovsky's oval cross-sections are presented. The solutions for the elliptical bars agree with the existing elastic and limit plastic solutions at the two extremes of the elastic-plastic range. The algorithm also reproduces accurately the Sokolovsky solution and extends it beyond its limitations.     

基于Double Marching Cubes的表面重建算法

为克服基于Marching Cubes的表面重建算法在绘制三维表面时因二义性面的存在而使生成的表面网格易出现错误连接而形成层间空洞的不足,提出了基于Double Marching Cubes的表面重建算法.该算法采用双立方体体素作为生成表面网格的基本单元,以双立方体的12个特征点的标记情况为依据,建立一个双立方体体素索引表,通过查找索引表的方法绘制三维表面.该算法在建立双立方体索引表时就排除掉了二义性面的所有错误连接方式,因而生成的表面网格不会出现层间空洞,避免了为消除二义性面所进行的复杂计算,加快了表面重建的速度.     

Principal Component Analysis of the start-up transient and Hidden Markov Modeling for broken rotor bar fault diagnosis in asynchronous machines

This article presents a novel computational method for the diagnosis of broken rotor bars in three phase asynchronous machines. The proposed method is based on Principal Component Analysis (PCA) and is applied to the stator’s three phase start-up current. The fault detection is easier in the start-up transient because of the increased current in the rotor circuit, which amplifies the effects of the fault in the stator’s current independently of the motor’s load. In the proposed fault detection methodology, PCA is initially utilized to extract a characteristic component, which reflects the rotor asymmetry caused by the broken bars. This component can be subsequently processed using Hidden Markov Models (HMMs). Two schemes, a multiclass and a one-class approach are proposed. The efficiency of the novel proposed schemes is evaluated by multiple experimental test cases. The results obtained indicate that the suggested approaches based on the combination of PCA and HMMs, can be successfully utilized not only for identifying the presence of a broken bar but also for estimating the severity (number of broken bars) of the fault.