基于DSDV的无线Mesh网络跨层路由设计

在DSDV协议的基础上,提出一种跨层路由设计的方法,选择一条具有合理长度和最小重传概率的路由进行测试。该链路质量机制可应用到基于IEEE802.11x的无线Mesh网络中,无须对现有的MAC层进行修改,即可作为一个单独模块加入到现有协议。在多跳网络中使用该跨层方案进行路由选择,能节省系统开销,优化系统的整体性能。     

多路径DSR和AODV路由协议性能研究

在支持移动节点和自组织网络的路由协议中,最典型的单径路由协议是DSR和AODV协议,对它们进行扩展分别得到相应的多径路由协议。通过仿真比较分析这2种多径路由协议在混合无线Mesh网络和移动AdHoc网络中的性能。结果显示,混合无线Mesh网络中的这2种多径路由协议具有分组传输率高、端到端的平均延时和路由开销小等优点。以DSR协议为基础扩展得到的多径路由协议,在高度动态的网络环境中,性能得到了改善,能广泛应用于移动性强的环境中。     

Mesh网络中两跳邻居地址借用策略

IEEE 802.15.5标准提供了mesh联网功能,它为节点绑定逻辑地址,因而具有不需要路由表进行路由的优点。在一个动态性很强的mesh网络中,节点加入或离开网络会造成孤儿节点问题,即新来节点因其父节点无剩余地址可分配导致其无法加入网络。提出了适用于mesh网络的两跳邻居节点地址借用策略以克服孤儿节点问题,提高节点加入成功率和地址利用率。理论分析和仿真表明,所提出的地址借用策略在节点加入成功率、地址利用率和能耗方面均优于已有地址分配方案。     

无线传感mesh网络的分段地址分配策略及其路由

无线传感器网络中的设备具有能量、缓存空间、通信和计算能力受限的特点。因此,无线传感器网络路由算法需要具备低存储开销、低计算复杂度、无路由发现等特征。HiLow是一种分层路由协议,它完全符合上述特点,且比IEEE 802.15.5具有更好的路由特性。但HiLow存在一些不足,如地址利用率低、仅适用于小规模网络等,无法应用于如环境监测、动物保护等具有较多节点数量和较大网络规模的应用场景。提出了一种两段地址分配策略TFA,它将16位地址分成两段,前段地址用于全功能设备的地址分配,后段地址用于精简功能设备的地址分配。理论分析和数值仿真显示, 相比于HiLow,TFA具有更大的地址利用率和路由树最大深度,能够适用于更大规模的无线传感网络。分析了TFA的mesh路由优化特性,提出了基于TFA的mesh路由算法。仿真结果表明,基于TFA的mesh路由在存储空间使用和能耗等方面都优于IEEE 802.15.5。     

Optimized P2P streaming for wireless distributed networks

The future Internet will support pervasive applications and communications models that require end-nodes cooperation, such as fog computing and machine-to-machine communications. Among the many applications, also video streaming can be provided with a cooperative and peer-to-peer approach. Cooperative distribution requires building a distribution overlay on top of the physical topology (the underlay). This work proposes an optimized, cross-layer approach to build this overlay minimizing the impact on the underlay. We design an optimal strategy, which is proven to be NP-complete, and thus not solvable with a distributed, lightweight protocol. The optimal strategy is relaxed exploiting the knowledge on the betweenness centrality of the nodes in the underlay topology, obtaining two easily implementable solutions applicable to any link-state protocol for distributed wireless mesh networks. The additional introduction of heuristic improvements further optimizes the performance in real network scenarios. Extensive simulation results support the theoretical findings using three different network topologies. They show that the relaxed implementations are reasonably close to the optimal solution, and provide vast gains compared to the traditional overlay topologies that peer-to-peer applications build.     

基于改进Marching Cubes算法的乳腺MRI肿块三维重建

核磁共振成像MRI(Magnetic Resonance Imaging)是目前乳腺癌肿块诊断的常用辅助手段,对图像的正确解析是关键,针对传统MC(Marching Cubes)面绘制算法应用于乳腺MRI图像的不足,提出了改进方法。首先利用乳腺MRI序列图相邻帧间图像灰度分布的相似,肿块组织形状相近等相关性,在RSF(Region-Scalable Fitting)模型的基础上利用初始轮廓迭代的方法提取肿块区域。接着将多组参数下获得的结果,依据每一帧与其前后帧的重叠面积越大越好作为条件进行筛选,使提取的等值面最优化。最后采用基于加权二次误差度量的三角形折叠方法,对面绘制产生的大量三角网格进行了简化。将所提出的改进方法应用于30例乳腺MRI序列图,实验结果表明,对于乳腺MRI肿块的三维重建在精度和绘制速度上都比使用传统MC算法有很大提高。     

Multiple levels of cell by cell Adaptive Mesh Refinement in the Lagrangian step of the ALE code CORVUS

A multi-level cell by cell Adaptive Mesh Refinement (AMR) hydrodynamics capability has been developed for the Lagrangian step of the 2D Arbitrary Lagrangian Eulerian (ALE) code CORVUS. Connectivity arrays are used rather than a hierarchical data structure. We solve only on the dynamic unstructured mesh rather than on every level of a refinement hierarchy. The strength, artificial viscosity, slide and programmed burn methods have been generalised to work with AMR. Results are presented for a range of Lagrangian test problems.     

Paint Mesh Cutting

We present a novel progressive painting‐based mesh cut out tool, called Paint Mesh Cutting, for interactive mesh segmentation. Different from the previous user interfaces, the user only needs to draw a single stroke on the foreground region and then obtains the desired cutting part at an interactive rate. Moreover, the user progressively paints the region of interest using a brush and has the instant feedback on cutting results as he/she drags the mouse. This is achieved by efficient local graph‐cut based optimizations based on the Gaussian mixture models (GMM) on the shape diameter function (SDF) metric of the shape. We demonstrate a number of various examples to illustrate the flexibility and applicability of our system and present a user study that supports the advantages of our user interface.     

行星式搅拌釜内高黏固液两相流的数值研究

行星式搅拌装置适用于固体颗粒与高黏度聚合物熔体的混合,搅拌釜内高黏度流体的流动状况非常复杂,实验方法很难获得搅拌釜内流场细节.利用FLUENT软件数值模拟了新型行星式搅拌釜内高黏固液两相流的流场,分析了不同转速条件下搅拌釜不同截面的速度场和浓度场.计算中采用欧拉模型,使用动网格技术,利用FLUENT的用户自定义函数确定...