Optimal Structure from Motion: Local Ambiguities and Global Estimates

Structure From Motion (SFM) refers to the problem of estimating spatial properties of a three-dimensional scene from the motion of its projection onto a two-dimensional surface, such as the retina. We present an analysis of SFM which results in algorithms that are provably convergent and provably optimal with respect to a chosen norm.In particular, we cast SFM as the minimization of a high-dimensional quadratic cost function, and show how it is possible to reduce it to the minimization of a two-dimensional function whose stationary points are in one-to-one correspondence with those of the original cost function. As a consequence, we can plot the reduced cost function and characterize the configurations of structure and motion that result in local minima. As an example, we discuss two local minima that are associated with well-known visual illusions. Knowledge of the topology of the residual in the presence of such local minima allows us to formulate minimization algorithms that, in addition to provably converge to stationary points of the original cost function, can switch between different local extrema in order to converge to the global minimum, under suitable conditions. We also offer an experimental study of the distribution of the estimation error in the presence of noise in the measurements, and characterize the sensitivity of the algorithm using the structure of Fisher's Information matrix.     

球罐水喷雾冷却系统消防用水量的一种计算方法

提出了一种确定球罐水喷雾系统的喷头总数量、计算固定式消防冷却水用量和水雾喷淋强度的计算方法     

球内接三通接头的设计及其展开图的计算机绘制

根据“球面上圆构造椭圆锥面”的原理，设计了球内接三通接头。对这种接头的表面展开进行了解析分析。进而确定了展开方法，并提供了按这种方法用计算机绘制的展开图例。     

Numerical solution of viscous flow past a solid sphere with the control volume formulation

The control volume formulation with the QUICK finite difference scheme is used to solveincompressible liquid flow past a solid sphere in terms of stream function and vorticity.Several tech-nical points are addressed on improving the accuracy and efficiency of numerical simulation of similarproblems of fluid flow.In particular,the importance of suitable specification of the distortion func-tion to enforcing the far field boundarv conditions is emphasized.     

具有滚动齿的新型包络蜗杆分度凸轮机构

在总结弧面分度凸轮机构和一些包络蜗杆分度凸轮机构的基础上，提出具有滚动齿的球面及锥面包络蜗杆分度凸轮机构，并对机构的滚动齿进行设计。     

浅谈环氧丙烷罐区工艺设计

环氧丙烷为易燃易爆品,并有毒性,其储存方式的选择关系到安全、环保、人身安全等方面,文章结合工艺设计实例,从设备的选择、工艺设计及设备布置方面谈谈一些体会。     

Mass and heat transfer from or to a single sphere in simple extensional creeping flow

The first detailed numerical investigation on the mass and heat transfer both outside and inside a solid or liquid sphere immersed in a simple extensional flow for a larger range of Peclet numbers (1–100,000) is presented. By making use of the known Stokes velocity field at small Reynolds numbers, a finite difference method with the control volume formulation is adopted to solve the convection‐diffusion transport equation. Simulation results show that the transport rate, which is represented by Sherwood number, is significantly affected by Peclet number and viscosity ratio. The flow direction, no matter a uniaxial extensional flow or a biaxial extensional flow, has no effect on the total transport rate but affects the concentration distribution a lot. Some comparisons between present simulations and previous studies are made to validate each other and confirm the reliability and applicable scopes of reported correlations. A few new correlations are put forward to predict the transfer rate at finite Peclet numbers for various values of viscosity ratios. © 2011 American Institute of Chemical Engineers AIChE J, 58: 3214–3223, 2012     

锂离子电池球形正极材料的研究进展

球形化可以提高锂离子正极材料的压实密度、体积比容量并改善其加工性能和极片的质量。简要介绍了球形材料的特点,综述了球形LiCoO2、LiNixM1-xO2、LiMn2O4、LiFePO4等的制备及其性能,展望了球形正极材料的应用前景。     

球面上的K最近邻查询算法

针对球面上数据对象点集的特征和K最近邻查询的需求，提出2种处理球面上K最近邻查询的算法：基于查询轴的K最近邻查询算法(PAM方法)和基于查询圆面的K最近邻查询算法(PCM方法)。对2种算法进行实验比较，结果表明，PAM方法和PCM方法都适合处理球面上的最近邻查询问题，PAM方法在存储量和查询复杂度方面相对于PCM方法具有一定优势，但PAM方法的可扩展性远低于 PCM方法，尤其不适合处理受限查询和带方向的查询。     

基于Sphere-OBB的改进碰撞检测算法及其应用

静态或动态环境中两个或者多个几何模型之间的碰撞检测是计算机图形学基础问题之一,基于层次包围盒的碰撞检测算法是一种比较有效的碰撞检测算法。提出了OBB包围盒与球包围盒相结合的高效碰撞检测算法,该算法既具有OBB的包围紧密性,又具有球包围盒的测试简便性。用高效的球包围盒排除大量距离远的不相交物体,剩下距离近的物体用分离轴测试,其中一些分离轴效率更高应该优先被测试。将该算法用于虚拟针灸训练系统,实验结果表明算法减少了查询时间并增强了实时性。