熔焊成型中截面填充算法及软件实现

本文针对熔焊成型的特点,提出了一套适合熔焊成型的截面填充算法。该算法对截面轮廓进行内、外轮廓以及复连通区域和单连通区域的判定,将复连通区域剖分并对单连通区域的单调划分,最后对单调区域进行填充扫描,生成用于熔焊快速成型的数控指令。该截面填充算法采用VC 、OpenGL编程实现,生成的数控代码在成型机床上得到验证。     

基于形状相似性的快速成型扫描算法检索实例

针对快速成型系统采用单一扫描算法带来的缺陷,提出了一种基于切片图形几何形状匹配的综合选取扫描路径的方法.根据pic文件格式,构造边角邻接矩阵(EAAM)和边属性向量(EAV)以表达切片图形的几何形状.并给出了基于上述模型的形式化定义;通过抽取表征EAAM和EAV特征参数建立了一个有效的实例索引机制,提出了形状相似性及实例相似性的度量和计算方法;最后给出了切片图形检索过程的关键算法实现,该方法具有较好的通用性和实用性,能够有效的提高快速成型系统效率.     

快速成型切片数据的优化算法研究

为了能够顺利地进行 STL模型切片轮廓数据的进一步处理 ,提出了对切片数据进行优化处理的算法 .对由于STL模型的缺陷造成切片之后的轮廓信息数据有大量的冗余数据 ,提出了一种冗余数据的滤除算法 ;针对切片轮廓的不封闭 ,给出了有效的修正算法 ;同时给出了对切片轮廓的内外边界进行自动识别的算法 .该算法高效简单 ,提高了后续的数据处理的效率和成型件的加工质量 ,改善了零件成型的加工性能     

快速成型制造中截面信息的计算方法研究

在快速成型制造中，截面信息的计算速度是影响分层处理效率的关键环节之一，文中分析了三角形面片与切平现的位置关系，提出了一种高效的截面信息计量方法，该算法还可用于有缺陷的STL模型的分层处理，采用该算法可以取消进行半径补偿时所需进行的内外轮廓识别这一环节，实际应用表明，该算法使分层处理速度大大提高。     

基于边界扫描的快速区域填充算法

提出一种基于边界扫描的区域填充新算法．该算法能对任意复杂的单连通区域进行快速填充,弥补了扫描线算法应用受限制的缺陷。并结合例子详细的讲解了算法原理,最后进一步分析出该算法找出所有正确匹配的区域左右边界点对的时间复杂度最优情况约为O（n）。     

激光快速成型中激光扫描路径的快速生成算法

在立体光固化（ＳＬ）快速成型中，零件是靠激光逐层扫描光敏树脂固化成型的，在由点到线、由线到面、由二维到三维的逐层累积过程中，扫描器要做大量的扫描，因而合理的扫描路径对提高成型效率无疑有重要意义；另外合理的扫描路径还能改善扫描器的工作状态，明显提高扫描器的使用寿命，本文提出了一种简捷有效的扫描路径生成算法，成功地于开发的快速成型机中。     

快速成型的医学应用现状与趋势

一、引言在20世纪80年代末期，现代RP技术一经出现很多制造行业即对其表现出浓厚的兴趣。最早采用RP技术的是航空、汽车和医学工业。10多年过去了，RP的概念已经深入人心，不但在这些行业深入下去了，而且扩散到其他的各行各业。虽然医学应用仍然只占10%的RP市场，但医学又对RP的应用提出了更高的要求。历史上，RP已经运用于种植体原型、监视系统和很多其他医疗设备原型的制作。运用生理数据的原型制作方法中采用了SLA、LOM、SLS和FDM等技术。这些模型向那些想不通过开刀就可观看病人骨结构的研究人员、种植体设计师和外科医生提…     

基于STL文件的快速成型分层算法与毗邻拓扑信息的快速提取

该文研究了实时的快速成型的分层算法,即从CAD模型转换成STL文件后,实时快速求出该模型与水平截面的轮廓线交线,为此,该文提出并建立了三角形网格的毗邻关系索引表,并构造相应的数据结构来表达STL文件的散乱三角形集合中的毗邻拓扑联系,而为了快速建立这种毗邻关系,该文进一步提出建立两套三角形网格的分组表,来缩小三角形网格的毗邻查找范围,为快速确定三角形网格的毗邻关系奠定基础。该文同时分析了该算法的时间与空间复杂度。计算实践表明,基于该文提出的毗邻关系索引表的分层算法能满足快速成型的实时要求。     

一种车牌字符快速分割算法

在深入研究了大部分常用的车牌字符分割算法的前提下,根据车牌区域图像的特征,文章提出了一种综合了连通区域法和先验知识相结合的车牌字符分割算法,该算法经过大量实验证明了其在准确率方面的优越性.     

Prototyping of Land-SAF leaf area index algorithm with VEGETATION and MODIS data over Europe

The Satellite Application Facility on Land Surface Analysis (Land-SAF) aims to provide land surface variables for the meteorological and environmental science communities from EUMETSAT satellites. This study assesses the performance of a simplified (i.e. random distribution of vegetation is assumed) version of the Land-SAF algorithm for the estimation of Leaf Area Index (LAI) when prototyped with VEGETATION (processed in CYCLOPES program) and MODIS reflectances. The prototype estimates of LAI are evaluated both by comparison with validated CYCLOPES and MODIS LAI products derived from the same sensors and directly through comparison with ground-based estimates. Emphasis is given on evaluating the impact of the algorithm and input data on LAI retrieval discrepancies. Analysis is achieved over Europe for the 2000-2003 period. The results demonstrate the capacity of the Land-SAF algorithm to retrieve consistent LAI estimates from multiple optical sensors even when their reflectances present systematic differences. High spatial and temporal consistencies between Land-SAF prototype estimates and existing LAI products are found. The differences between Land-SAF and CYCLOPES LAI are lower than their uncertainties (RMSE (relative RMSE) within 0.4 (30%)). Land-SAF prototype estimates and MODIS LAI show larger discrepancies mainly due to differences in the vegetation structure representation and algorithm assumptions (RMSE ranging from 0.2 (30%) up to 0.8 (40%)). Land-SAF prototype provides higher LAI values than MODIS for herbaceous canopies (i.e. shrubs, grasses and crops) and lower values for woody biomes (i.e. savannas and forests). Direct validation indicates that LAI estimates from prototyping of the Land-SAF algorithm with CYCLOPES and MODIS reflectances achieve similar performances (differences with ground measurements are lower than 0.5 LAI units in 60% and 50% of the cases, respectively) as CYCLOPES and MODIS LAI products. Results from this prototyping exercise appear useful for improved retrieval of LAI and constitute a step forward for refinement, validation and consolidation of the Land-SAF algorithm.     

复杂背景下火灾疑似区域快速提取算法

针对火灾场景图像容易受到噪声干扰、光照变化等干扰因素的影响,难以实时有效地提取出火灾运动区域的问题,设计了一种适合于全天候高效工作的火灾火焰运动区域的快速提取算法,该算法根据像素点灰度信息分布和序列帧相关性,从时间域对背景模型和阈值进行自适应更新,并利用投影原理的二维统计原理,在基于运动目标区域空间相关性的基础上,实现了对火焰疑似区域的快速提取。实验结果表明,在1 920×1 080分辨率下,该算法总共消耗时间为0.232 ms。该算法解决了外界光线对目标区域提取的影响,同时火灾疑似区域检测的时间消耗以及算法复杂度也比区域聚类算法大大降低,较大地提高了算法的执行效率。     

MGSI-8CA标记算法

针对已有连通域标记算法不能适用于遥感数据等海量灰度图像八连通域快速标记的问题,设计并实现了一种MGSI-8CA标记算法。该算法对传统的八连通域标记算法进行八向变四向优化,采用列表机制解决连通域标记冲突问题,并引入了筛选机制和分块处理机制,实现了对海量灰度图像八连通域标记的快速处理,同时也得到了灰度图像连通域的正确划分及精确的连通域数目。实验结果证明,MGSI-8CA标记算法运行效率高,更能适应海量灰度图像处理的要求。     

基于快速成型技术的警用小型电子产品工业设计方法研究

本文介绍了一种基于快速成型技术的警用小型电子产品的工业设计方法。与传统设计方法相比较,该方法在创新设计理念、缩短产品研制周期、保证产品质量等方面都有了重大突破。同时,本文以电子护照读写机具设计为例,详细阐述了应用这种方法进行警用小型电子产品设计的方法和流程,并将该方法与传统设计方法进行了详细的分析和比较。     

基于快速原型的联想与类比法在产品概念开发中的作用

联想、类比是激发创造性思维的创新方法。文章从联想、类比产生的条件入手,分析了它们在新产品概念开发中的作用以及基于联想、类比法的新产品开发模式并指出了该模式的不足。在此基础上提出了基于快速原型的联想、类比法在新产品概念开发中的模式,分析了快速原型在激发与完善新产品创意中为联想、类比提供依据的作用以及加速完成新产品概念的功效。最后,结合RH治疗仪的概念开发过程进一步分析了基于快速原型的联想与类比法在产品概念开发中的作用。     

校园局域网防ARP病毒的研究和解决

该文针对目前校园局域网中地址解析协议(ARP)病毒的频繁发作,分析了ARP病毒攻击原理,并且给出了采取相关的防护措施和应对策略。最后给出了以后在防范过程中应该注意的几点建议。     

A MODIS direct broadcast algorithm for mapping wildfire burned area in the western United States

Improved wildland fire emission inventory methods are needed to support air quality forecasting and guide the development of air shed management strategies. Air quality forecasting requires dynamic fire emission estimates that are generated in a timely manner to support real-time operations. In the regulatory and planning realm, emission inventories are essential for quantitatively assessing the contribution of wildfire to air pollution. The development of wildland fire emission inventories depends on burned area as a critical input. This study presents a Moderate Resolution Imaging Spectroradiometer (MODIS) - direct broadcast (DB) burned area mapping algorithm designed to support air quality forecasting and emission inventory development. The algorithm combines active fire locations and single satellite scene burn scar detections to provide a rapid yet robust mapping of burned area. Using the U.S. Forest Service Fire Sciences Laboratory (FiSL) MODIS-DB receiving station in Missoula, Montana, the algorithm provided daily measurements of burned area for wildfire events in the western U.S. in 2006 and 2007. We evaluated the algorithm's fire detection rate and burned area mapping using fire perimeter data and burn scar information derived from high resolution satellite imagery. The FiSL MODIS-DB system detected 87% of all reference fires > 4 km², and 93% of all reference fires > 10 km². The burned area was highly correlated (R² = 0.93) with a high resolution imagery reference burn scar dataset, but exhibited a large over estimation of burned area (56%). The reference burn scar dataset was used to calibrate the algorithm response and quantify the uncertainty in the burned area measurement at the fire incident level. An objective, empirical error based approach was employed to quantify the uncertainty of our burned area measurement and provide a metric that is meaningful in context of remotely sensed burned area and emission inventories. The algorithm uncertainty is ± 36% for fires 50 km² in size, improving to ± 31% at a fire size of 100 km². Fires in this size range account for a substantial portion of burned area in the western U.S. (77% of burned area is due to fires > 50 km², and 66% results from fires > 100 km²). The dominance of these large wildfires in burned area, duration, and emissions makes these events a significant concern of air quality forecasters and regulators. With daily coverage at 1-km² spatial resolution, and a quantified measurement uncertainty, the burned area mapping algorithm presented in this paper is well suited for the development of wildfire emission inventories. Furthermore, the algorithm's DB implementation enables time sensitive burned area mapping to support operational air quality forecasting.     

A counterexample to an algorithm for computing monotone hulls of simple polygons

A two-stage algorithm was recently proposed by Sklansky (1982) for computing the convex hull of a simple polygon P. The first step is intended to compute a simple polygon $\text{P}{}^1$ which is monotonic in both the x and y directions and which contains the convex hull vertices of P. The second step applies a very simple convex hull algorithm on $\text{P}{}^1$. In this note we show that the first step does not always work correctly and can even yield non-simple polygons, invalidating the use of the second step. It is also shown that the first step can discard convex hull vertices thus invalidating the use of any convex hull algorithm in the second step.     

基于区域面积比的几何不变量构造算法*

几何不变量是物体几何结构信息的抽象与概括,在识别中可解决由目标移动产生的旋转或变形等问题。针对现有的算法在提取几何不变量特征时,易造成误差增大和效率不高的问题,提出了一个基于区域面积比的几何不变量构造算法。该算法利用质心和伪质心构成的直线,对灰度图像的面积区域应用划分策略,构建几何不变量的矢量表示形式。在哥伦比亚大学的fish及coil-100数据集上的实验表明,算法得到的不变量特征满足仿射不变性,在物体图像受到一定范围内干扰(被擦除、涂抹及遮挡)下,提取出的不变量特征具有良好的区分辨别能力。