车灯光源优化问题的探讨

本文讨论了在一定的光源设计前提下，光照强度及其分布所满足的规律，并在此基础上，分析了车灯线光源的优化设计的途径。在分析的方法上，我们侧重于计算机数值模拟辅以理论推导，提出了一系列创新的技术，用以克服离散途径解决连续问题时所遇到的困难。在基本的方法上，我们将线光源用离散的点光源逼近，将抛物面离散为网格。这里我们从法向量变化率出发，提出按曲率划分而非单纯尺寸长度划分，大大提高了模拟精度.在处理离散条件下点线相交时，我们引入了连通集这一重要概念，以克服（屏上点，源）1－＞（抛面面上点）映射时的多值性，解决了因细分抛物面而产生的多重光路的问题。，在实现过程中，我们应用了广度优先的线性复杂度算法，使计算效率一跃提升了近500倍.在解决多点采样问题时，我们又开发了并行连通集算法，减少了串行算法的重复计算，使计算速度加快了近2000倍。在验证模型合理性和进行数据分析时，在第一题中我们郑重地于收敛的程度问题，并证明我们的模型是稳定的，能克服误差的影响；第二小题中，我们着重分析光强分布的合理性问题，并结合第三小题的要求，对图象进行分析，最终得出题目中的设计规范是符合实际应用需要的，并且光源消耗很优化，光强分布合理。     

车灯线光源的优化设计

本文研究了一车灯反射光在测试屏上的光强分布,并给出了在一定的设计规范下,使车灯线光源功率最小的设计 方案。我们采用计算机作数值模拟,把线光源分割为点光源,将反射面划分成小块,求出点光源发出的光线经过 小块反射到测试屏上的区域位置和强度,经叠加得到该点光源在测试屏上的光强分布,最后求出线光源在该屏上 的光强分布。利用以上方法,我们求得在同一设计规范下,线光源功率最小时的长度为3.98～4.02毫米。     

车灯线光源的优化设计

本文研究了一车灯反射光在测试屏上的光强分布，并给出了在一定的设计规范下，使车灯线光源功率最小的设计方案。我们采用计算机作数值模拟，把线光源分割为点光源，将反射面划分成小块，求出点光源发出的光线经过小块反射到测试屏上的区域位置和强度，经叠加得到该点光源在测试屏上的光强分布，最后求出线光源在该屏上的光强分布。利用以上方法，我们求得在同一设计规范下，线光源功率最小时的长度为3．98－4．02毫米。     

车灯线光源的优化设计方案

本问题是一个车灯线光源的优化设计问题。 首先,我们建立了一个连续的数学模型来描述这个优化问题,此模型研究了线光源上任意一点发出的光线 经过抛物面反射后到达光屏的情况,对于给定的考察点(B或C)得到一个联系该点与光的发射点,反射点这3 个点关系的方程组。由于光在传播过程中会有发散的现象,我们用Jacobi行列式做了一个变换来描述这种散射。 根据C点的光强度必须大于一个确定的值(文中设为1),B点的光强度必须大于该值的2倍的约束条件将这个 问题抽象成一个非线性规划问题。 由于解非线性规划问题是很复杂的过程,我们选择了将连续模型简化成一个离散模型。但是离散模型将光 离散成一条一条光线时,一般不能考虑光在传播过程中的散射问题。根据我们连续模型中用Jacobi行列式算出 的结果知可以考虑光在传播过程中的散射问题,但是Jacobi行列式是很难求出来的,为了解决这个困难我们将光 的散射用连续的方法做了一个简化。简化的方法是用向量投影的方法粗略作出了两个面积微元之间的关系,从 而得到了光线打在光屏上的散射效果与光线的起始单位方向向量和该光线经抛物面反射时的反射点的坐标的 关系。 运用以上的离散模型的算法,得到最优的线光源长度为3.39mm。     

车灯线光源的优化设计问题

本文依据反射定律讨论了从光源上一点发出的光线能反射到B点或C点的条件，比较准确地确定了反射点的个数。本文的另一个优点是简洁、明确地给出了问题中求解最优光源长度的数学模型（优化模型），并给出了相应的算法。本文的不足之处是没有考虑光线照度的余弦定律，并且没有考虑到反射面到接收屏之间光照面积的变化。本文针对车灯优化设计问题，在指定的测试方案下，给出了计算线光源长度2l的方法。首先我们利用光学知识和Mathematica计算得到B，C两点的光强EB，EC与线光源长度2l的关系，结合测试方案的要求，即EB≥2E0，EC≥E0，且使线光源功率最小，由于eB(x)和eC(x)的显式式无法给出，故我们用数值方法求得最优线光源长度2l=3.7mm。其次，我们使用计算机模拟技术作出了测试屏的亮区。最后，在对测试方案进行综合评价时发现，题设所给出测试方案有一定的优点，但仍有许多有待改进之处。     

车灯线光源的优化设计方案

本问题是一个车灯线光源的优化设计问题。首先，我们建立了一个连续的数学模型来描述这个优化问题，此模型研究了线光源上任意一点发出的光线经过抛物面反射后到达光屏的情况,对于给定的考察点（B或C）得到一个联系该点与光的发射点，反射点这3个点关系的方程组。由于光在传播过程中会有发散的现象，我们用Jacobi行列式做了一个变换来描述这种散射.根据C点的光强度必须大于一个确定的值（文中设为1），B点的光强度必须大于该值的2倍的约束条件将这个问题抽象成一个非线性规划问题。由于解非线性规划问题是很复杂的过程，我们选择了将连续模型简化成一个离散模型。但是离散模型将光离散成一条一条光线时，一般不能考虑光在传播过程中的散射问题。根据我们连续模型中用Jacobi行列式算出的结果知可以考虑光在传播过程中的散射问题，但是Jacobi行列式是很难求出来的，为了解决这个困难我们将光的散射用连续的方法做了一个简化。简化的方法是用向量投影的方法粗略作出了两个面积微元之间的关系，从而得到了光线打在光屏上的散射效果与光线的起始单位方向向量和该光线经抛物面反射时的反射点的坐标的关系。     

车灯线光源的优化设计问题

本文针对车灯优化设计问题,在指定的测试方案下,给出了计算线光源长度2l的方法。首先我们利用光学知识 和Mathematica计算得到B,C两点的光强E_B,E_C与线光源长度2l的关系,结合测试方案的要求,即E_B≥2E_0,E_C ≥E_0,且使线光源功率最小,由于e_B(x)和e_C(x)的显式表达式无法给出,故我们用数值方法求得最优线光源长 度2l=3.7 mm。其次,我们使用计算机模拟技术作出了测试屏的亮区。最后,在对测试方案进行综合评价时发 现,题设所给出测试方案有一定的优点,但仍有许多有待改进之处。     

基于SMS法的大功率COB光源窄光束设计

针对集成光源难以实现小发光角的问题,提出了一种大功率COB光源实现窄光束的设计方法。根据COB光源的出射光分布以及预设的光分布范围选用折射-折射(RR)系统。以选定的COB光源的光谱分布及配光曲线为标准建立光源模型,由复合抛物面(CPC)实现朗伯光源60°的聚光之后,再利用光学扩展量守恒以及同步多曲面方法(SMS)求得透镜前后两个曲面轮廓上点的坐标,进行曲线拟合获得轮廓曲线,进而得到透镜的三维模型。采用光学仿真软件对系统进行光线追迹,结果表明:系统在出光口处的发散角控制在30°之内,半光强度角为11.336°,整体光效达到89.398%,效果良好。     

大靶面光幕靶中发光二极管阵列线光源的设计

采用发光二极管阵列构造线了一种大尺度线光源．文中分析了发光二极管阵列光源能量在空间上的分布,用光照度计实测能量分布数据．以二维坐标给出了能量平面分布图．设计的线光源满足大靶面弹丸测速光幕靶的要求,文中给出了在光幕靶接收器件处阵列线光源光能量的计算公式．实验验证了分析的正确性．     

积分球内壁漫射照度分布的近似矩阵计算法

本文推导了位于积分球中心处的光源在球内壁及挡屏表面的漫射照度分布的近似矩阵计算方法。此计算可归结为根据积分球的基本参数确定“光通量交换系数矩阵”的矩阵元问题。 对几种不同光强空间分布的光源在积分球内壁产生的漫射照度分布进行了计算,并将对两个光源的计算结果与用R.Brown的数值法的结果作了比较,符合较好。     

Service reliability and performance in grid system with star topology

The paper considers grid computing systems in which the resource management systems (RMS) can divide service tasks into subtasks and send the subtasks to different resources for parallel execution. In order to provide desired level of service reliability the RMS can assign the same subtasks to several independent resources for parallel execution.The service reliability and performance indices are introduced and a fast numerical algorithm for their evaluation for arbitrary subtask distribution in grid with star architecture is presented. This algorithm is based on the universal generating function technique.Illustrative examples are presented.     

Sampling 3-D seismic data

A 3-D seismic survey is usually achieved by recording a parallel profile network. The 3-D data thus obtained are sampled and processed in a cubic grid for which the sampling requirements are generally derived from the usual 1-D viewpoint. The spectrum of 3-D seismic data has a support (the region of the Fourier space in which the spectrum is not zero) that can be approximated by a domain bounded by two cones. Considering the particular shape of this support, we use a 3-D sampling theory to obtain results applicable to the recording and processing of 3-D seismic data. This naturally leads to weaker sampling requirements than the 1-D viewpoint does. We define the hexagonal non-cubic sampling grid and the triangular non-cubic sampling grid and show that fewer sample points are needed to represent 3-D seismic data with the same degree of accuracy. Thus, using the hexagonal non-cubic sampling grid we point out that the maximum value of the spatial sampling interval along the profiles is larger by 15.6% than the one of the cubic sampling grid. We also point out that the triangular non-cubic sampling grid requires a number of sample points equal to half the number required by a cubic sampling grid.     

Only one fitting for bironchigrams

We present an algorithm that uses a square grid in a Ronchi test. We assume that the point coordinates of this pattern (termed a bironchigram) are affected by Gaussian errors. To calculate the optical path difference, we apply only one nonlinear least-squares fit to the dot coordinates. The relevant equations are deduced, and experimental results are shown.     

Gridding-based direct Fourier inversion of the three-dimensional ray transform

We describe a fast and accurate direct Fourier method for reconstructing a function f of three variables from a number of its parallel beam projections. The main application of our method is in single particle analysis, where the goal is to reconstruct the mass density of a biological macromolecule. Typically, the number of projections is extremely large, and each projection is extremely noisy. The projection directions are random and initially unknown. However, it is possible to determine both the directions and f by an iterative procedure; during each stage of the iteration, one has to solve a reconstruction problem of the type considered here. Our reconstruction algorithm is distinguished from other direct Fourier methods by the use of gridding techniques that provide an efficient means to compute a uniformly sampled version of a function g from a nonuniformly sampled version of Fg, the Fourier transform of g, or vice versa. We apply the two-dimensional reverse gridding method to each available projection of f, the function to be reconstructed, in order to obtain Ff on a special spherical grid. Then we use the three-dimensional gridding method to reconstruct f from this sampled version of Ff. This stage requires a proper weighting of the samples of Ff to compensate for their nonuniform distribution. We use a fast method for computing appropriate weights that exploits the special properties of the spherical sampling grid for Ff and involves the computation of a Voronoi diagram on the unit sphere. We demonstrate the excellent speed and accuracy of our method by using simulated data.     

One machine,one minute,three billion tetrahedra

This paper presents a new scalable parallelization scheme to generate the 3D Delaunay triangulation of a given set of points. Our first contribution is an efficient serial implementation of the incremental Delaunay insertion algorithm. A simple dedicated data structure, an efficient sorting of the points, and the optimization of the insertion algorithm have permitted to accelerate reference implementations by a factor three. Our second contribution is a multithreaded version of the Delaunay kernel that is able to concurrently insert vertices. Moore curve coordinates are used to partition the point set, avoiding heavy synchronization overheads. Conflicts are managed by modifying the partitions with a simple rescaling of the space-filling curve. The performances of our implementation have been measured on three different processors: an Intel core-i7, an Intel Xeon Phi, and an AMD EPYC, on which we have been able to compute three billion tetrahedra in 53 seconds. This corresponds to a generation rate of over 55 million tetrahedra per second. We finally show how this very efficient parallel Delaunay triangulation can be integrated in a Delaunay refinement mesh generator, which takes as input the triangulated surface boundary of the volume to mesh.     

点云数据区域分割方法

为了便于逆向工程中模型的重建，针对散乱无组织的点云数据，提出了一种新的区域分割方法。首先对点云数据进行网格划分和稀化处理，对每个网格内的数据点用抛物面进行局部拟合，得到点云中每个点的法矢和曲率等微分信息，然后由“绝对标准”得到边界候选区域，再由“相对标准”得到最终边界点，连接这些边界点或对这些边界点进行曲线拟合，完成点云的区域分割。实践证明，通过该方法得到的边界点能满足工程应用的需要。     

Large-scale three-dimensional object measurement: a practical coordinate mapping and image data-patching method

In a practical three-dimensional (3-D) sensing system, the measurement of a large-scale object cannot be completed in only one operation. A relieflike object is generally divided into several subregions, an optical sensor positioned at each of these locations, and the shape of the whole object obtained by patching together all the 3-D data of the subregions. It is important to have accurate 3-D coordinates (x, y, z) for each subregion. We propose a new phase-to-height mapping algorithm and an accurate lateral coordinate calibration method with which to obtain the 3-D coordinates. After all the subregions are measured, it is necessary to transform the local coordinates into global world coordinates; here we present a new image data-patching method based on a flood algorithm. This method provides the optimal path along which to patch all the subregions into the shape of the entire object. We have measured and successfully patched a large sandy pool (9 m x 5 m), and the reliability and feasibility of our method have been demonstrated by experiment.     

基于局部估计的多光源图像颜色恒常性计算

目的解决多光源场景图像的颜色矫正问题。方法首先采用网格划分和关键点取样2种方法对多光源图像划分区域,然后对划分后的区域采用单光源颜色恒常性算法估计光源,把每一个区域对场景光源颜色的贡献整合为复合光源颜色作为多光源场景的近似估计,最后采用对角模型进行矫正,并将此方法与单独用单光源颜色恒常性算法估计做对比。结果通过对多光源图像划分区域,可以弱化多个光源对图像的影响,与单独用单光源颜色恒常性算法估计对比,对图像的矫正效果显著。结论通过局部估计多光源图像,所提出的方法可以有效解决多光源室外场景图像的颜色恒常性问题。