基于草绘的网格曲面拉伸变形算法

为提高产品概念设计中三维模型重构的效率,设计了一种基于草绘技术的网格曲面拉伸变形方法。以多模式交互方式选择拉伸区域,系统自适应调整拉伸区域网格模型拓扑结构;利用投影方法将自由形式或非自由形式二维拉伸轨迹曲线转化为空间三维曲线;将拉伸区域边界曲线进行扫掠处理,进而对已形成的相邻扫掠曲线进行连接,最终形成拉伸网格曲面模型。通过在自主开发的软件平台上进行多种工业模型拉伸变形测试,验证了该算法的有效性和工程可行性。     

利用CAXA实体设计快速绘制电风扇叶片

针对三维设计中复杂曲面建模的难点,介绍了一种利用CAXA实体设计快速生成电风扇叶片曲面的方法,该方法首先构造出叶根和叶缘的3D曲线,然后利用放样来生成叶片曲面,最后进行曲面加厚、倒角、三维球链接等。     

基于曲线约束的鞋楦曲面变形技术

在基于曲线长度约束的曲面变形设计方面,提出基于局部变换的约束变形算法,并与鞋楦曲面的编辑设计相结合,解决个性化鞋楦设计中的变形问题。其主要思想方法是对曲面的每一个曲线约束构造局部变换,以满足约束曲线的变形要求,再通过曲面的重新全局参数化,将约束曲线处的局部变换扩散到整个曲面。此约束变形方法与曲面的表示无关,没有采用能量优化方法来解,可以精确满足约束曲线的长度要求,算法简单高效,适用于实时编辑。     

基于Pro／E的螺旋桨曲面建模方法

结合螺旋桨结构特点及Pro／E功能特点,提出了一种螺旋桨桨叶建模的新方法。该方法采用Pro／E软件的曲线创建、缠绕及曲面创建合并等工具,实现直观的建模,摒弃了传统繁琐的三维坐标变换,并在建模过程中对原始设计数据进行检查,及时修正数据错误,可快速得到螺旋桨桨叶的三维实体模型。最后,实例验证了新方法的有效性和可行性。     

基于Hermite曲线的水泵叶片曲面动态调控方法

采用Hermite参数曲线构造水泵叶型的流线展开线,借助自由曲面造型技术,提出了在屏幕上动态调控叶片曲面的方法。此方法直观而灵活,非常适合于CAD系统,不仅能如实地在计算机上再现手工设计中广泛使用的方格网保角变换法叶片绘型过程,而且可直接得到叶片的三维曲面造型结果。     

一种离心叶轮三维叶片的快速成型方法

为了缩短离心叶轮叶片的三维设计周期，实现闭式离心叶轮自由曲面叶片的三维快速成型，本文提出了一种基于叶片中间面的自由曲面叶片快速成型方法。首先，采用三次均匀B样条理论对叶片中间面曲线坐标进行双向加密重构；然后，结合空间曲线参数方程及空间矢量相加法，则以重构后的中间网格面为基准建立初始叶片三维网格模型；最后，采用叶片中间面曲线坐标点绕轴旋转形成的空间曲线和初始叶片三维微元网格求交，求解获得单个自由曲面叶片曲面离散坐标。整个叶片三维建模过程可实现不同前、尾缘及厚度形状组合的离心叶轮三维叶片快速成型；该方法和传统的CAD建模方法相比，其调整叶片形状更加快捷便利，不仅能够提高离心叶片三维建模精度和效率，而且为叶片三维模型设计及优化提供了帮助。     

叶轮参数建模系统

针对离心叶轮建模的难点,探讨了基于SolidWorks环境下离心叶轮的三维设计方法与参数化设计的原理,给出了SolidWorks构造曲线曲面的数学模型。通过VB、MicrosoftAccess对Solid-Works进行二次开发实现了离心叶轮自动建模。对离心泵叶片的空间扭曲问题提出了有效的解决方法,提高了建模效率和设计精度。     

基于逆向工程的汽车覆盖件CAD建模技术研究

为了得到复杂曲面的三维模型,分析了利用逆向工程进行三维模型重建的关键技术,提出了一种实现汽车覆盖件快速CAD建模的方案.采用数字近景摄影测量技术和三维光学测量系统相结合的方法实现点云数据精确采集,利用Imageware和catia软件相结合的方法,经过点云处理、曲线曲面重构、精度分析,最终得到产品三维模型.结果表明,方案可以快速、精确的实现复杂曲面的三维建模.     

基于Geomagic和UG的快速参数化逆向建模方法

提出了一种基于逆向设计软件Geomagic和三维建模软件UG的产品快速参数化逆向建模新思路。首先,利用逆向设计软件Geomagic Studio对扫描获得的物体点云数据进行处理,主要包括三角化阶段和多边形阶段处理,获得网格包络曲线;其次,将构建的网格包络曲线导入三维建模软件UG中进行参数化曲面构建;最后,对新方法的建模精度进行了评价。实验结果表明,该方法不仅能获得高精度的曲面模型,还可以大幅度的缩短产品设计和开发周期。     

基于任意拓扑曲线网的曲面造型技术研究

插值由特征曲线组成的曲线网是最常用的曲面建模思路,而从简单矩形拓扑曲线网到任意拓扑曲线网的扩展不仅增强了曲面设计自由度,而且提高了曲面设计效率。以曲线网建模过程为序,介绍了任意拓扑曲线网的创建和编辑、插值曲面的构造以及曲线网建模系统研究等技术的研究现状,分析了Bezier和NURBS曲面、Gregory曲面片和细分曲面在曲线网插值中的应用特点,指出了今后研究的重点。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

Non-monotonic material contrast in scanning ion and scanning electron images

30 keV Ga⁺ focused ion beam induced secondary electron (iSE) imaging was used to determine the relative contrast between several materials. The iSE signal compared from C, Si, Al, Ti, Cr, Ni, Cu, Mo, Ag, and W metal layers does not decrease with an increase in target atomic number Z₂, and shows a non-monotonic relationship between contrast and Z₂. The non-monotonic relationship is attributed to periodic fluctuations of the stopping power and sputter yield inherent to the ion–solid interactions. In addition, material contrast from electron-induced secondary electron (eSE) and backscattered electron (BSE) images using scanning electron microscopy (SEM) also shows non-monotonic contrast as a function of Z₂, following the periodic behavior of the stopping power for electron–solid interactions. A comparison of the iSE and eSE results shows similar relative contrast between the metal layers, and not complementary contrast as conventionally understood. These similarities in the contrast behavior can be attributed to similarities in the periodic and non-monotonic function defined by incident particle–solid interaction theory.     

Application of Feature Extraction through Convolution Neural Networks and SVM Classifier for Robust Grading of Apples

This paper proposes a novel grading method of apples,in an automated grading device that uses convolutional neural networks to extract the size,color,texture,an...     

分布动态载荷识别的抗噪处理

针对正交多项式频域法在用多种响应对矩形薄板进行载荷识别中抗噪性较差的问题,综合运用平均法、矩阵预处理和奇异值截断法等方法对之进行改善,并引入空间映射的思想,将该方法的应用范围拓展为复杂的模型.利用仿真算例,证实了该方法具有较好的抗噪性.     

基于MELTAC-N平台的核电厂安全级DCS环网研究与测试

针对工程实践中环网通讯相关问题的处理缺乏理论基础及国产化安全级DCS平台的开发缺乏成熟经验借鉴问题,对基于MELTAC-N平台核电厂安全级DCS环网的软硬件实现进行了研究。提出了安全级DCS环网双环网冗余设计、光切换开关设计等硬件设计方法,以及以RPR协议为基础,采用全数据收发策略的软件设计方法。在CPR1000安全级DCS平台上对安全级DCS环网的可靠性及实时性进行了评价,并进行了容错能力、响应时间及响应时间稳定性测试验证实验。结果表明,基于MELTAC-N平台安全级DCS环网软硬件设计具有较好的容错能力及响应时间稳定性。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...     

End-to-End Multiview Gesture Recognition for Autonomous Car Parking System

The use of hand gestures can be the most intuitive human-machine interaction medium.The early approaches for hand gesture recognition used device-based methods....     

The laboratory simulation of abrasive wear

Abrasive wear has long been recognised as one of the most potentially serious tribological problems facing the operators of many types of plant and machinery; several industrial surveys have indicated that wear by abrasion can be responsible for more than 50% of unscheduled machine and plant stoppages. Locating the operating point of a tribological contact in an appropriate operational ‚map’︁ can provide a useful guide to the likely nature and origins of the surface degradation experienced in use, though care must be exercised in choosing the most suitable parameters for the axes of the plot. Laboratory testing of materials and simulations of machine contacts are carried out for a number of purposes; at one level for the very practical aims of ranking candidate materials or surface hardening treatments in order of their wear resistance, or in an attempt to predict wear lives under field conditions. More fundamentally, tests may be aimed at elucidating the essential physical mechanisms of surface damage and loss, with the longer term aim of building an analytical and predictive model of the wear process itself. In many cases, component surface damage is brought about by the ingress of hard, particulate matter into machine bearing or sealing clearances. These may be running dry although, more usually, a lubricant or service fluid is present at the interface. A number of standardised wear test geometries and procedures have been established for both two- and three-body wear situations, and these are briefly described. Although abrasive wear is often modelled as following an ‚Archard’︁ equation (i.e. a linear increase in material loss with both load and time, and an inverse dependence on specimen hardness) both industrial experience and laboratory tests of particularly lubricated contacts show that this is not always the case: increasing the hardness differential in an abrasively contaminated lubricated pair may not always reduce the rate of damage to the harder surface.     

ANGULAR DISTORTION ALLOWABLE VALUE AND ASSESS METHOD OF WELD ON COKE TOWER

A graph as the new engineering method for estimate the safety of bulging deformation of coke tower is proposed. Through stresses analysis of circumferential weld of coke tower and comparing the stresses produced by pressure with heat stress of steady state, residual stress, bending stress produced by both itself weight and wind loads, it showed that the stresses produced by pressure on the angle distortion are the main factor of equivalent stress of the combined stress. After comparing four kinds of stress controlling conditions, the relation to stress with depth of angular distortion, grade of curvature of angular distortion and half of region of angular distortion has been inferred. Graph of deformation allowable value of coke tower for different condition by angular distortion and half of region of angular distortion has been plotted. The five steps for its engineering use have been explained. The lighter the grade of curvature is, the larger of bulge allowance, may be, and the bigger of depth of angular distortion may pose too. For the coke tower with a popular structure of Dg 5 400 mm×28 mm, the result by graph is nearly more than the result of two formulas formed by other research, the error is less than 7.0%. But, the graph can be easily applied to different size of angular distortion.