An electron tomography algorithm for reconstructing 3D morphology using surface tangents of projected scattering interfaces

Upon discerning the mere shape of an imaged object, as portrayed by projected perimeters, the full three-dimensional scattering density may not be of particular interest. In this situation considerable simplifications to the reconstruction problem are possible, allowing calculations based upon geometric principles. Here we describe and provide an algorithm which reconstructs the three-dimensional morphology of specimens from tilt series of images for application to electron tomography. Our algorithm uses a differential approach to infer the intersection of projected tangent lines with surfaces which define boundaries between regions of different scattering densities within and around the perimeters of specimens. Details of the algorithm implementation are given and explained using reconstruction calculations from simulations, which are built into the code. An experimental application of the algorithm to a nano-sized Aluminium tip is also presented to demonstrate practical analysis for a real specimen.

Program summary

Program title: STOMO version 1.0Catalogue identifier: AEFS_v1_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEFS_v1_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 2988No. of bytes in distributed program, including test data, etc.: 191 605Distribution format: tar.gzProgramming language: C/C++Computer: PCOperating system: Windows XPRAM: Depends upon the size of experimental data as input, ranging from 200 Mb to 1.5 GbSupplementary material: Sample output files, for the test run provided, are available.Classification: 7.4, 14External routines: Dev-C++ (http://www.bloodshed.net/devcpp.html)Nature of problem: Electron tomography of specimens for which conventional back projection may fail and/or data for which there is a limited angular range. The algorithm does not solve the tomographic back-projection problem but rather reconstructs the local 3D morphology of surfaces defined by varied scattering densities.Solution method: Reconstruction using differential geometry applied to image analysis computations.Restrictions: The code has only been tested with square images and has been developed for only single-axis tilting.Running time: For high quality reconstruction, 5-15 min     

设计素描观察能力的培养

观察能力的培养是设计素描训练的基本任务之一。设计素描应以传统素描的观察方法为基础,并更加强调用理性的、逻辑的、创造性的思维方法来观察、认识、分析物象。设计素描的观察方法必须经过由感性到理性的循序渐进的过程。文章通过:1、整体对比的观察。2、宏观与微观的观察。3、不同视点与角度的观察,三个依次渐进的过程来分析设计素描的观察方法。通过分析,希望在设计素描教学中把观察能力的培养提升到一个相当重要的位置。只有这样才能为日后设计专业学习打下良好的设计创意思维基础。     

三维几何信号经验模式分解及其应用

针对三维几何信号非线性、非平稳的特点,提出基于经验模式分解的三维几何信号处理方法。将信号球面参数化,映射到平面,进行均匀规则采样。对平面信号进行限领域的经验模式分解,得到各个内蕴模式图层。从图层信号得到不规则的原始映射信号,逆映射回三维几何模型信号。将该方法用于几何模型的光顺及增强处理,实验结果表明,该方法能够有效处理三维几何信号。     

基于GPU粒子系统的大规模场景高效雨雪实时模拟

粒子系统实现的雨雪效果能有效增强三维场景的真实感,传统基于中央处理器（CPU）运算模拟的粒子系统占用了大量CPU运算时间,难以达到实时模拟的要求。为此提出了一种基于图形处理器的（GPU）运算的粒子系统来模拟的雨雪场景。该方法通过在GPU中重复使用消亡粒子在视点坐标系内生成新粒子,并在几何着色器中将粒子的点坐标转换为矩形坐标,将CPU从复杂庞大的几何运算中解放出来,从而大幅增加了场景绘制的微粒数,使雨雪场景模拟的实时性和逼真度得到增强。     

Connecting the 3D DGS Calques3D with the CAS Maple

Many (2D) Dynamic Geometry Systems (DGSs) are able to export numeric coordinates and equations with numeric coefficients to Computer Algebra Systems (CASs). Moreover, different approaches and systems that link (2D) DGSs with CASs, so that symbolic coordinates and equations with symbolic coefficients can be exported from the DGS to the CAS, already exist. Although the 3D DGS Calques3D can export numeric coordinates and equations with numeric coefficients to Maple and Mathematica, it cannot export symbolic coordinates and equations with symbolic coefficients. A connection between the 3D DGS Calques3D and the CAS Maple, that can handle symbolic coordinates and equations with symbolic coefficients, is presented here. Its main interest is to provide a convenient time-saving way to explore problems and directly obtain both algebraic and numeric data when dealing with a 3D extension of “ruler and compass geometry”. This link has not only educational purposes but mathematical ones, like mechanical theorem proving in geometry, geometric discovery (hypotheses completion), geometric loci finding… As far as we know, there is no comparable “symbolic” link in the 3D case, except the prototype 3D-LD (restricted to determining algebraic surfaces as geometric loci).     

基于柱镜光栅的自由立体显示图像融合算法

针对现有的图像融合算法存在频域混叠现象及通用性差的问题,提出一种基于柱镜光栅的自由立体图像融合算法。在低通抗混叠滤波前对视点图像进行非等比例上采样,调整视点图像亚像素映射公式,强化公式的通用性。实验结果表明,该算法在定性的视觉效果及定量的图像质量评估方面都具有一定的优势。     

Toric forms of elliptic curves and their arithmetic

We scan a large class of one-parameter families of elliptic curves for efficient arithmetic. The construction of the class is inspired by toric geometry, which provides a natural framework for the study of various forms of elliptic curves. The class both encompasses many prominent known forms and includes thousands of new forms. A powerful algorithm is described that automatically computes the most compact group operation formulas for any parameterized family of elliptic curves. The generality of this algorithm is further illustrated by computing uniform addition formulas and formulas for generalized Montgomery arithmetic.     

Estimating the fundamental matrix based on least absolute deviation

The epipolar geometry is the intrinsic projective geometry between two views, and the algebraic representation of it is the fundamental matrix. Estimating the fundamental matrix requires solving an over-determined equation. Many classical approaches assume that the error values of the over-determined equation obey a Gaussian distribution. However, the performances of these approaches may decrease significantly when the noise is large and heterogeneous. This paper proposes a novel technique for estimating the fundamental matrix based on least absolute deviation (LAD), which is also known as the L₁ method. Then a linear iterative algorithm is presented. The experimental results on some indoor and outdoor scenes show that the proposed algorithm yields the accurate and robust estimates of the fundamental matrix when the noise is non-Gaussian.     

Effect of micro-electrode geometry on NO2 gas-sensing characteristics of one-dimensional tin dioxide nanostructure microsensors

Electrodes with micro-gaps are fabricated by using dc-sputtering and FIB techniques. SnO₂ nanowires are deposited on the micro-gap (1-30 μm) by suspension dropping method to fabricate a micro-gas sensor. The sensing ability of various SnO₂ micro-gap sensors is measured. A comparison between sensors reveals that the short-gap electrode has numerous advantages in terms of reliability, high sensitivity and detection of low concentrations of NO₂, while the large-gap electrode is relatively sensitive for high concentrations. Conductance measurements are carried out at different surface temperatures and NO₂ concentrations in order to investigate the effects that the gap size has on the overall sensor conductance. The results suggest that the interface between the electrode and sensitive layer has a very important role for the sensing mechanism of tin dioxide gas sensors.     

基于PCI总线的多功能可定制数据采集系统

为满足航空电子总线数据采集系统的通用性和多功能性,设计了基于PCI总线的多功能可定制数据采集系统;研究了相关总线板卡的驱动函数;采用自顶向下和模块化的方法设计了数据采集系统的系统运行管理模块、数据采集显示模块、数据分析处理模块和记录数据管理模块;使用了多线程、多视图、双缓存和Teechart控件等关键技术.设计实现的数...