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构造两个曲面的拼接曲面 总被引:1,自引:1,他引:1
给出了当两个待拼接曲面的拼接线具有参数化形式或者可以参数化时,它们之间 G1光滑拼接曲面的构造方法。所得的拼接曲面是由一个空间曲线集定义的,每一条空间曲线由拼接线上的点对确定。并且拼接曲面都是参数曲面,它们的形状可以通过预设的参数很好地调整和控制。作为实例,讨论了两个截口是平面的或非平面的(由两个二次曲面定义)的二次曲面之间的拼接曲面的构造和一般的参数曲面的拼接曲面的构造。 相似文献
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本文在分析张量积有理B样条蒙皮面曲面方法不足的基础上,给出了用截面外形设计原理构造有理蒙皮曲面、回转曲面及扫掠曲面的方法,并提出了对G~1连续的有理曲线进行重新参数化使其达到C~1连续的方法。文中的实例表明用该方法能够产生满足设计要求的参数曲面。 相似文献
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参数Bezier三角曲面G1光滑拼接的相容性 总被引:1,自引:0,他引:1
本文对参数Bezier三角曲面拼接的相容性问题进行了研究。给出拼接的相容性条件。实现了任意多片参数三角曲面片的一阶几何连续拼接,可对任意复杂形状进行造型。 相似文献
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本文提出了一种新的参数曲面线投影求交计算方法,基于参数域摄动原理,将求交问题转化为一系列简单的参数摄动,映射,判断,比较等运算,能有效地解决参数曲面的线投影求交计算,大量的应用的实例表明这一算法的可靠性好,计算精度高,摄动速度快,已在复杂曲面测量造型和数控加工质量分析中取得了良好的应用效果。 相似文献
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通过在曲面细分过程中引入两个参数,给出一种新的细分曲面构造的算法,使得所得的细分曲面可调.通过调节一个参数值,可以得到一族细分曲面.另一个参数是细分过程的改变参数,改变它的初值,也可得细分结果.最后给出了曲面设计的实例,表明这种算法简单、有效. 相似文献
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自由曲面的CNC直接插补加工技术 总被引:5,自引:0,他引:5
在CNC系统上直接根据曲面几何定义与加工工艺参数对多轴贡面加工的连续运动轨迹进行实时插补控制,在CNC上直接在APT高级语言编程,极大地科化了零件程序,并可在线修改与补偿机床运动结构、刀具形状尺寸及加工作量等工艺参数,使曲在线曲面精加工经济而高效。在单CPU硬件环境下实现了从一般二次曲线到复杂的参数组合曲面,从两轴加工到复杂的五轴联动功能,可采用多种加工刀具与加工方式,可实时检测与处理刀具干涉,并 相似文献
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本文探索NURBS曲面求交及构造过渡曲面的方法。基于交线跟踪算法求出NURBS曲面间的交线,算法比较稳定、可靠;采用参数化平面与等距面求交找出两曲面空间等距点,具有自然与变半径过渡曲面的定义相呼应、找点快、准确、稳定的特点;过渡曲面表示为2×3次NURBS曲面,自然、充分地利用了NURBS曲线可精确表示圆弧段的特性,过渡曲面具有表达简单、比较准确、便于采用统一的NURBS曲面处理算法对其进行各种几何处理的优点;实验证明这些方法可行,效果令人满意。 相似文献
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自由曲面建模是三维建模软件教学的难点,也是许多三维建模工作者的薄弱点。该文从建模软件应用而非软件开发人员的视角,通过对自由曲面构成规律的总结,介绍了以型面分析法为核心的自由曲面三维建模方法的基本内容和分析方法,指出了三维自由曲面数字建模教学中的关键知识与内容。 相似文献
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以NURBS为数学模型,对曲面造型及加工系统进行了研究。在对各种算法分析、研究和改进的基础上,完成了一个集CAD/CAM于一体具有多种功能的曲面造型及加工系统,合理地将NURBS的主要核心配套技术和各种算法运用于NURBS造型系统中,通过交互方式成功实现了对多种曲线曲面(直线、圆弧、二次曲线、自由曲线、平面、二次曲面、旋转面、直纹面、雕塑曲面、截线面曲面、自由曲面、复杂组合曲面等)的造型生成。 相似文献
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Sukant Mittal Ian Y. Wong Ahmet Ali Yanik William M. Deen Mehmet Toner 《Small (Weinheim an der Bergstrasse, Germany)》2013,9(24):4207-4214
The microfluidic isolation of target cells using adhesion‐based surface capture has been widely explored for biology and medicine. However, high‐throughput processing can be challenging due to interfacial limitations such as transport, reaction, and non‐specific fouling. Here, it is shown that antibody‐functionalized capture surfaces with discontinuous permeability enable efficient target cell capture at high flow rates by decreasing fouling. Experimental characterization and theoretical modeling reveal that “wall effects” affect cell–surface interactions and promote excess surface accumulation. These issues are partially circumvented by reducing the transport and deposition of cells near the channel walls. Optimized microfluidic devices can be operated at higher cell concentrations with significant improvements in throughput. 相似文献
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V. V. Kharchenko A. Yu. Chirkov S. V. Kobel’skii V. I. Kravchenko V. A. Piminov I. F. Akbashev 《Strength of Materials》2010,42(1):17-24
We present the results of calculations of the kinetics of stress-strain state and stress intensity factors for surface and
under-the-cladding circumferential cracks in modeling the emergency core cooldown conditions for the WWER-1000 reactor. The
calculation procedure is based on a mixed finite-element method statement which provides stability of numerical solution and
a high accuracy of results for both the displacements as well as stresses and strains. The authors analyze the influence of
the density of the finite-element discretization of the crack-tip area for the surface and under-the-cladding circumferential
cracks on the accuracy and convergence of computation of fracture-mechanics parameters in the modeling of thermal shock conditions.
The results of calculation of kinetics of stress intensity factors allowing for the thermomechanical loading history and residual
process-induced stress fields are reported. It is demonstrated that if the elastoplastic deformation history and residual
process-induced stress fields are disregarded in the calculations of stress intensity factors for under-the-cladding cracks
the reactor pressure vessel strength and lifetime may turn out to be overestimated. 相似文献
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《Engineering Analysis with Boundary Elements》2002,26(5):435-445
Computational modeling often involves making assumptions; assumptions about geometric features, material characterizations or loading conditions. The validity of these assumptions will directly impact accuracy. It is an accepted practice in computational modeling of impressed current cathodic protection (ICCP) systems to define painted surfaces as perfectly insulated (‘perfect paint’). While many paint systems have a high resistance, the resistance is finite rather than infinite. In this work, painted surfaces are defined with varying material properties ranging from relatively high resistance (0.0001 of the polarization response of steel) to relatively low (steel). These different material properties are assigned to the painted surfaces of a previously validated shipboard ICCP system model. All other boundary conditions are held constant. A comparison of results quantifies the effects of large but finite paint resistance on computational results and validates use of the perfectly insulated surface assumption for painted surfaces. 相似文献
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A physical model of the metallic-type conductivity at the interface between an organic semiconductor or dielectric and a metals
or another organic material is proposed. The conductivity arises due to the formation of geminal pairs with a rather high
surface density at the interface. Conditions under which the transitions between molecules require neither thermal activation
nor tunneling for a significant fraction of charge carriers are determined. The values of electric conductivity and carrier
mobility are estimated using numerical modeling. 相似文献