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Curvatures are important geometric attributes of surfaces. There are many applications that require as a first step the accurate estimation of curvatures at arbitrary vertices on a triangulated surface. Chen and Schmitt (1992) and Taubin (1995)presented two simple methods to estimate principal curvatures. They used circular arcs to approximate the normal curvature. We find this may cause large error in some cases. In this paper, we describe a more accurate method to estimate the normal curvature,and present a novel algorithm to estimate principal curvatures by simplifying the Chen and Schmitt's method. Some comparison results are also shown in this paper. 相似文献
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Vicky Vandenbossche Joris Van de Velde Stind Avet Wouter Willaert Stian Soltvedt Noeska Smit Emmanuel Audenaert 《Anatomical sciences education》2022,15(4):731-744
High-fidelity anatomical models can be produced with three-dimensional (3D) scanning techniques and as such be digitally preserved, archived, and subsequently rendered through various media. Here, a novel methodology—digital body preservation—is presented for combining and matching scan geometry with radiographic imaging. The technique encompasses joining layers of 3D surface scans in an anatomical correct spatial relationship. To do so, a computed tomography (CT) volume is used as template to join and merge different surface scan geometries by means of nonrigid registration into a single environment. In addition, the use and applicability of the generated 3D models in digital learning modalities is presented. Finally, as computational expense is usually the main bottleneck in extended 3D applications, the influence of mesh simplification in combination with texture mapping on the quality of 3D models was investigated. The physical fidelity of the simplified meshes was evaluated in relation to their resolution and with respect to key anatomical features. Large- and medium-scale features were well preserved despite extensive 3D mesh simplification. Subtle fine-scale features, particular in curved areas demonstrated the major limitation to extensive mesh size reduction. Depending on the local topography, workable mesh sizes ranging from 10% to 3% of the original size could be obtained, making them usable in various learning applications and environments. 相似文献
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由于无线网路中链路质量的不稳定、信号的广播传输模式和节点之间存在的相互干扰，针对提高无线网状网络性能的信道分配和路由选择将更加复杂。采用多信道成为一种可选的提高网络容量的方法。本文提出了一种基于2.4GHz 802.11无线网状网络的一种固定信道分配方法，采用了多输入多输出技术使得网络中的数据流以流水线的方式进行传输。在这个场景下多条并行的流可以同时被激活，以此来提升UDP和TCP的传输性能。通过对802.11b网络中1、6和11三个相互不重叠的信道的分配，该信道分配算法在空间上实现邻居节点之间的干扰最小化，其中信道1和11被分配给网状网络的主干传输部分，信道6被分配给用户接入网络。文章最后通过NS2仿真实验，并对本文提出的算法进行了分析。实验结果证明网络的平均吞吐率有大幅度提升，且多跳传输的延迟也被降低。 相似文献
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对盆底脏器脱垂疾病（简称POP）的临床诊断和症状学进行调查研究,评估该疾病对日常生活的影响及治疗后,临床疗效的观察;能够客观反映POP程度的国际量化分期系统,在临床研究中应用较为广泛;引起POP的相关危险因素,制定相应的预防措施;POP的治疗方式,包括非手术治疗和手术治疗的适应症及适用人群,比较了传统手术方式的利与弊,论述了现较为流行的网片修补技术的不足,展望了新兴的盆底重建外科学的发展前景及临床应用价值。 相似文献
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真实感人脸动画一直是计算机图形学一个重要而富有挑战性的课题．改变传统的计算机动画系统只实现对一个人脸模型模拟动画．实现了对任意特定人脸表情动画进行逼真模拟,采用了基于改进的散乱数据插值算法构建线性弹性模型,基于多视角照片从一般人脸模型到特定人脸模型修改,自适应人脸肌肉模型特定化技术以及基于肌肉模型的皱纹模拟技术．实验证明,这一系列技术所得到的人脸动画效果优于传统的动画效果． 相似文献
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傅祖清 《湖南城市学院学报》1994,(5)
方框图法是全面定量计算负反馈放大器性能参数的主要方法。本文结合四种典型反馈电路，运用人们所熟悉的网孔法推导反馈放大器的基本放大电路，是学习反馈电路的另一途径。 相似文献
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ALSHOAIBI Abdulnaser M. ARIFFIN Ahmad Kamal 《浙江大学学报(A卷英文版)》2006,7(8):1336-1342
INTRODUCTION The finite element method (FEM) has been widely employed for solving linear elastic and elas-tic-plastic fracture problems. The evaluation of stress intensity factors in 2D geometries by FEM is a tech-nique widely used for non-standard crack configura-tions. Basically, there are two groups of estimation methods, those based on field extrapolation near the crack tip (Chan et al., 1970; Shih et al., 1976) and those using the energy release when the crack propagates. However… 相似文献
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宣兆成 《天津工程师范学院学报》2005,15(4):1-7,13
给出了偏微分方程的h型有限元分析的双层网格最优精化设计方法。第一层是细化后验误差相对大的单元？后验误差是通过简化计算由单元平均流量为连接的单元Neumann型子问题而得到的误差界。简化计算就是只把由1／2单元尺寸所构成的网格上的泛函作为单元残余误差方程的试探函数，这样计算成本将非常小。某些精化后的网格的几何性质将变得很差，所以第二层又用Laplace光顺算法对网格的质量进行改进，并用两个例题验证了该方法。结果表明，算法达到最优收敛率，并提高了精度。 相似文献
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马驰 《武汉工程职业技术学院学报》2009,21(1):34-38
3DS MAX是美国AutoDesk公司开发的三维设计、动画制作软件。利用3DS MAX软件,制作建筑装饰效果图,其制作思路和绘图技巧尤为重要。文章通过图片和实例归纳总结了创建建筑装修三维立体模型的具体分类、特点及应用。 相似文献