Automatically extracting sheet-metal features from solid model

INTRODUCTION With the development of modern industry,mass produced sheet-metal parts have been widelyapplied in mechanical, communication, electronics,and light industries in recent decades. Statisticsshowed that in the US, some 100 000 metal stamp-ings could be found in the average American homein the 1980s (Cheok and Nee, 1998). In Singapore,the manufacturing sector contributes more than25% to the GDP or a Total Gross Value of morethan US$24 billion (Tan, 1993). In China, th…     

Automatic recognition of intersecting features of freeform sheet metal parts

This paper presents an approach for recognizing both isolated and intersecting geometric features of freeform surface models of parts, for the purpose of automating the process planning of sheet metal forming. The developed methodology has three major steps： subdivision of B-spline surfaces, detection of protrusions and depressions, and recognition of geometric features for sheet metal forming domain. The input geometry data format of the part is based on an IGES CAD surface model represented in the form of trimmed B-spline surfaces. Each surface is classified or subdivided into different curvature regions with the aid of curvature property surfaces obtained by using symbolic computation of B-spline surfaces. Those regions satisfying a particular geometry and topology relation are recognized as protrusion and depression （DP） shapes. The DP shapes are then classified into different geometric features using a rule-based approach. A verified feasibility study of the developed method is also presented.     

Product information platform based on STEP

The intemational standard ISO 10303.called STEP.has been used to deal with problems in the ex change of product models and the associated data between difierent computer-aided systems.A platform based on STEP for managing product information is presented.This platform includes three components:a product geometry information model,a product feature model and a product visualization model.An information extracting pattern,in which information is extracted from low level elements to high level ones,is adopted in establishing the product geometry information model.Relative elements lists are created based on the extracted product information.With the traversing of these lists,feature extraction methods are proposed,which take advantage of boundary information in product model and avoid the determination of concavity and convexity of curves.Information correlating to features iS stored in a structure named as feature block and the product visualization model iS founded from it.The feature block is used in the platform for information communication and synchronous update among the three components.     

毕节方言特色地名词的新价值--以毕节特色旅游为视角

毕节方言特色地名词具有词源多样性特色、风俗语义特色,既有方言研究的意义,也有文化研究的价值,对打造毕节旅游特色,形成特色旅游,具有不可替代的作用。毕节生态人文旅游的发展战略,需要高于旅游业的视野。毕节方言地名特色词反映独特的自然地理风貌和历史人文内容,是特色旅游的有机组成部分。     

Feature-based multiresolution techniques for product design

INTRODUCTION 3D CAD systems for the feature-based B-rep solid models (Choi et al., 2002; Kim et al., 2003; 2005; Koo and Lee, 2002; Lee et al., 2004; Lee, 2005a) are becoming more suitable for CAD when compared with the conventional polygon-based mul- tiresolution modelling in computer graphics (Cignoni et al., 1998; Schr?der et al., 1992). As illustrated in Fig.1b, the object of the feature-based multiresolution modelling is a solid model where the suppressed ob- jects are form feat…     

Single gate optimization for plastic injection mold

This paper deals with a methodology for single gate location optimization for plastic injection mold. The objective of the gate optimization is to minimize the warpage of injection molded parts, because warpage is a crucial quality issue for most injection molded parts while it is influenced greatly by the gate location. Feature warpage is defined as the ratio of maximum displacement on the feature surface to the projected length of the feature surface to describe part warpage. The optimization is combined with the numerical simulation technology to find the optimal gate location, in which the simulated annealing algorithm is used to search for the optimum. Finally, an example is discussed in the paper and it can be concluded that the proposed method is effective.     

网络教学环境下的形成性评价模式研究

大学英语教学改革的最终目的是培养学生的自主学习能力,体现学生学习过程、突出学生主体地位的形成性评价成为培养学生自主学习能力的最重要教学评价模式,重视形成性评价是现代大学英语教学发展的必然要求。本文从网络教学环境下师生的角色定位,形成性评价的意义、原则、内容和方式等方面展开探讨,旨在探索提高大学生自主学习能力的教学评价模式。     

汉语词性标注特征模板设定定量分析

在利用条件随机场（CRFs）进行汉语词性标注时,特征模板的选取是非常重要的一个环节,本文设计了两组特征模板,选取Bakeofl2007的CTB、NCC、PKU三种语料,使用CRF＋ ＋0.53工具包进行了对比实验,定量分析了影响词性标注的模板参数.通过实验得出以下结论：（1）词性标注的准确率与特征窗口大小不成正比,上文对当前词的词性的影响比下文要大,当前词的词性与其紧邻的前后两个词关系紧密;（2）产生的特征数多的模板训练较难进行;（3）词性转移特征对准确率有一定的影响.     

论现代大学的三重属性

现代大学具有学术、行政、产业三重属性。学术属性是大学的本质属性,行政、产业属性是大学发展到现代逐渐衍生的属性。充分认识现代大学的三重属性及其相互关系,对于大学管理者正确选择大学办学行为具有重要的现实意义。当前我国大学在办学过程中应强化学术行为,淡化行政行为,规范产业行为。     

关于中国医药城建设人力资源服务产业园的研究

人力资源服务业是现代服务业的重要组成部分,具有高度知识密集、产业辐射强大的绿色产业特征。随着产业的不断成长和壮大,人力资源服务业或将成为推动现代服务业发展的战略性增长极。当前,中国医药城已经进入产业化和城市化进程加速的重要时期,大力培育和发展人力资源服务业,加快筹建人力资源服务产业园,为产业园建设注入创新动力,打造国际化的医药产业人力资源平台。     

An XML-based information model for archaeological pottery

INTRODUCTION There is growing consensus among computa-tional scientists that observational data, result of computation and other forms of information produced by an individual or a research group need to be shared and used by other authorized groups across the world through the entire life cycle of the information (Wil-liams, 1998; Rowe et al., 2001). The Web has revo-lutionized the electronic publication of data. It has relied primarily on HTML that emphasizes a hypertext document app…     

安徽省村庄特征区域划分与优化策略研究

我国已进入工业化中期阶段,在一定程度上具备了以工促农,以城带乡的经济基础。由于安徽省地区经济发展区域差异显著,各地区的经济发展水平、地形地貌不同。其村庄建设的内容、重点、模式和方式上也都不同。基于此,以村庄分布特征、地形地貌特征、村庄发展阶段为视角,以县（市）域为单位,将安徽省的村庄分布划分为五个特征区域;结合安徽省的分区城乡统筹模式,提出各特征地区村庄发展的优化策略。     

An image retrieval system based on fractal dimension

INTRODUCTIONWiththerapiddevelopmentofthetechnologyofimagecollection ,storage,processionanddis play,digitalimagesarewidelyused (Zhangetal.,2 0 0 1 ) .However,itisdifficulttomanageahugeimagedatabase ,sothestudyoftheimagedatabasemanagementsystemandtheimagein…     

An image retrieval system based on fractal dimension

This paper presents a new kind of image retrieval system which obtains the feature vectors of images by estimating their fractal dimension; and at the same time establishes a tree-structure image database. After preprocessing and feature extracting, a given image is matched with the standard images in the image database using a hierarchical method of image indexing.     

从《平妖传》时间副词使用情况看近代汉语时间副词发展的特点及原因

《平妖传》是一部近代汉语文献,一直以来,关于该书的研究成果不多见。笔者经过初步考察,发现其中一些语言现象是有深入研究的必要的。近代汉语时期,时间副词得到了长足发展,主要呈现出五个方面的特点:1、数量的增加;2、新旧的更替;3、表时分工的细致化;4、文言词语使用的定型化;5、“三时”发展的不平衡。究其原因主要与汉语自身的特点有密切关系。     

汉语属性词的共性与个性

汉语属性词全体成员的共性是作定语修饰名词、粘着,这个共性也是它与其他词类相区别的个性。属性词内部成员的个性则表现为构造特色、兼类特色、带的特色、加最特色以及功能游移特色等等。     

基于特征的大尺寸零件序列局部视觉测量方法

为了实现常规尺寸和大尺寸机械零件的视觉测量,提出一种新的基于序列局部图像尺寸特征的测量方法.不进行图像拼接,而是提取序列局部图像的尺寸特征,并以图像序列之间的关联关系为依据求解零件尺寸.针对影响测量精度的相面旋转问题,充分利用工件表面纹理信息,提出了基于纹理特征的序列局部图像校准方法,获得序列图像之间的相对旋转角度,解决了测量过程中相机抖动或零件旋转引起的尺寸特征方向变动问题.通过实例说明了所提方法的实现过程及其有效性.实验表明,对大尺寸零件采用序列图像测量法,相对测量误差在0.012%以内,满足板类零件的精密测量要求.     

绿色产品制造工艺的评价与选择

制造绿色产品是目前制造业研究的热点,制造工艺的合理选择是提高制造绿色产品的重要途径之一。根据绿色产品制造工艺的特点,可建立由资源、产品、能耗、环境和费用等五大决策目标及22个评价指标组成的绿色产品制造工艺数学选择模型与评价体系,并运用AHM与模糊综合评价法相结合对决策模型进行了求解。结果表明,该方法可为企业在制造绿色产品过程中正确选择制造工艺提供依据。     

Prediction of shelled shrimp weight by machine vision

The weight of shelled shrimp is an important parameter for grading process. The weight prediction of shelled shrimp by contour area is not accurate enough because of the ignorance of the shrimp thickness. In this paper, a multivariate prediction model containing area, perimeter, length, and width was established. A new calibration algorithm for extracting length of shelled shrimp was proposed, which contains binary image thinning, branch recognition and elimination, and length reconstruction, while its width was calculated during the process of length extracting. The model was further validated with another set of images from 30 shelled shrimps. For a comparison purpose, artificial neural network (ANN) was used for the shrimp weight predication. The ANN model resulted in a better prediction accuracy (with the average relative error at 2.67%), but took a tenfold increase in calculation time compared with the weight-area-perimeter (WAP) model (with the average relative error at 3.02%). We thus conclude that the WAP model is a better method for the prediction of the weight of shelled red shrimp.      

几何非可展异型盒形件拉深毛坯近似展开计算

提出了一种映射变换方法:在分析传统拉深件毛坯尺寸计算方法的基础上.建立异型盒形件的毛坯近似展开的计算模型.利用微分几何中的诱导映射理论求得非可展曲面到平面城内的变换关系.分析该变换关系的简化算法,以一换挡板拉深件为实例验证了该算法的有效性.结果表明,该算法与传统毛坯计算方法相结合,可以获得符合生产的毛坯尺寸和形状,对异型盒形件的毛坯展开计算具有普适意义.