Direct repair of self-intersecting meshes

A fast and exact algorithm to eliminate intersections from arbitrary triangle meshes is presented, without any strict requirement on the input. Differently from most recent approaches, our method does not rely on any intermediate representation of the solid. Conversely, we directly cut and stitch mesh parts along the intersections, which allows to easily inherit possible surface attributes such as colors and textures. We rely on standard floating point arithmetics whenever possible, while switching to exact arithmetics only when the available fixed precision is insufficient to guarantee the topological correctness of the result. Our experiments show that the number of these switches is extremely low in practice, and this makes our algorithm outperform all the state-of-the-art methods that provide a guarantee of success. We show how our method can be exploited to quickly extract the so-called outer hull even if the resulting model is non manifold by design and the single parts have boundaries, as long as the outer hull itself is unambiguously definable.     

A novel mesh subdivision algorithm for dense reconstruction from multi-image based on preliminary model

To solve the disadvantages of the recent three-dimensional (3D) reconstruction methods, this paper presents a dense reconstruction algorithm which incorporates image features into the mesh subdivision. A preliminary model is deformed from statistical deformation model (SDM) to catch the roughest features, and later densified under a multi-resolution frame to achieve a dense model until all image features are used. In every round of this framework, the image features are detected, and then cut into planar points. At the same time, the transitional model is re-projected into views, and all images are segmented to triangles. So the planar points are constrained by these triangles, and the corresponding relations among these triangles are certain. Then some new spatial points are generated from these planar points and subdivide the transitional model. Later, the transitional model is re-arranged to get a right topology, and becomes denser. This method contributes three novelties: (1) there is an inherited relationship between the later points and the early points; (2) if the hierarchy of multi-resolution frame and the number of new spatial points at every round are set appropriately, the transitional model evolves with a correct topology; (3) the density of the final model is proportional to the information account of views. The experiment validates these virtues.     

三维面模型的几何压缩技术综述

随着应用需求的增长,三维模型的规模和复杂度急剧增长,给模型的存储和在有限带宽的网络上传输带来了很大的困难.因此,研究空间需求小、适合于计算机网络传输的三维模型的表示方法具有十分重要的意义.三维模型的压缩主要包括拓扑压缩和几何压缩.由于压缩数据中的大部分是几何压缩数据,因此已发展了许多几何压缩方法,以提高模型的压缩效率.为使相关的学者和工程技术人员较好地了解几何压缩技术,本文对这方面的工作进行了较全面的介绍.本文首先介绍了几何压缩的基本流程及几种几何压缩方法的分类原则,然后将几何压缩技术分为基础压缩方法和经过模型变换的压缩方法两大类并分别进行详细的介绍,讨论了各个方法的特点,最后结合我们自身的工作认识对几何压缩技术进行小结和展望.     

四-(4-三甲铵苯基)卟啉测定食品中的超痕量锌

以水溶性α,β,γ,δ-四-(4-三甲铵苯基)卟啉[T-4-TAP)P]作显色剂,测定食品中的痕量锌。对实验条件及共存离子的干扰进行了探讨。室温下,在弱酸性介质中,经7-碘-8羟基卟啉-5-磺酸催化,反应生成1:1络合物。最大吸收波长为422nm摩尔吸收系数为4.0×10~5 1·mo1~(-1)·cm~(-1),桑德尔指数为0.16ng·cm~(2-1),变异系数为1.6—3.7%,回收率为90.8%。本方法适用于分析食品中的痕量锌。     

液压缸结构分析的网格自动生成

针对典型液压缸截面特征，给出一种简明的三角形单元网格生成算法。它作为液压缸CAD系统有限元分析前置处理的数学模型之一，可有效提高分析效率。     

散乱模型的四边形网格剖分方法

针对基于CAD几何信息的网格剖分方法无法避免繁琐模型修补,导致网格剖分效率低下的现状,提出一种基于散乱模型的全四边形网格剖分方法.使用散乱点或者STL格式文件作为网格剖分的输入模型,使用改进的基于散乱模型进行网格剖分的铺路算法,在很大程度上减少甚至避免了模型修补问题.提出以散乱模型作为背景网格,作为控制网格单元尺寸调整的依据:使用网格细分和网格粗化的手段实现网格疏密变化的光滑过渡;自动识别几何模型中的特征并在网格模型中保留.提出了一种高效的铺路面相交搜索方法,综合考虑影响相交处理的多种因素,有效地处理了铺路面相交问题.多个复杂的汽车覆盖件网格剖分的算例结果表明,运用所提出方法完成的网格模型质量很高,算法具有较强的工程实用性.     

基于Mesh网络的井下救援语音通信系统的设计与测试

为了在矿难发生时仍能进行可靠的通信,将无线Mesh网络技术和基于IP语音技术(VoIP)结合起来设计了煤矿井下语音通信系统。整个系统主要基于C#进行软件开发,并且选择基于Asterisk的IP02构建了系统语音服务器IPPBX,结合该服务器设计并实现了终端管理、群体呼叫、电话会议、语音菜单,以及语音邮箱等多种语音通信功能。在实验室环境下来模拟煤矿井下巷道,并对无线语音通信系统进行了实际测试。测试和分析表明所开发的无线语音通信系统的通信质量良好,实现了所设计的语音通信功能。     

不规则边界曲面的四边形-三角形混合网格展开法

提出了用四边形-三角形混合网格等面积展开的几何模拟法确定不规则边界曲面零件毛坯外形，并给出了四边形-三角形混合网格算法。     

Dynamic behavior of a two-stage gear train used in a fixed-speed wind turbine

The dynamic behavior of a two stage spur gear system used in a typical wind turbine is investigated in this paper. With the purpose of having an accurate simulation, for a given excitations, of the dynamic response of bearings, shafts and teeth in contact.In this study, we developed a lamped mass dynamic model with 12 DOFs. This model is excited by external and internal issues sources. The main factors of these excitations are the variability in the wind resource and the time varying mesh stiffness fluctuation.The aerodynamic torque is calculated from an empirical approach of the power coefficient. The incoming flow is modeled by an analytic equation test varies with time. The differential equations governing the system motion are solved by an implicit Newmark algorithm.     

WiMAX MMR网络的军事应用

为进一步提高战术通信网的性能,满足通信保障对网络传输带宽的需求,许多国家的军队使用了3G标准之一的WiMAX技术。WiMAX MMR网络基于IEEE802.16j标准,运用移动多跳接力技术,能有效解决现有WiMAX系统覆盖半径不足、信号传输不佳的问题。介绍WiMAX在军事通信领域的应用情况,结合IEEE802.16j MMR的特点,并就网络安全方面所面临的威胁提出了应对策略。分析表明:WiMAX MMR网络作为一种无线解决方案,具有良好的军事应用前景。