A Sweepline Algorithm for Generalized Delaunay Triangulations
DEFF Research Database (Denmark)
Skyum, Sven
We give a deterministic O(n log n) sweepline algorithm to construct the generalized Voronoi diagram for n points in the plane or rather its dual the generalized Delaunay triangulation. The algorithm uses no transformations and it is developed solely from the sweepline paradigm together...
Advancing-Front Algorithm For Delaunay Triangulation
Merriam, Marshal L.
1993-01-01
Efficient algorithm performs Delaunay triangulation to generate unstructured grids for use in computing two-dimensional flows. Once grid generated, one can optionally call upon additional subalgorithm that removes diagonal lines from quadrilateral cells nearly rectangular. Resulting approximately rectangular grid reduces cost per iteration of flow-computing algorithm.
Advancing-Front Algorithm For Delaunay Triangulation
Merriam, Marshal L.
1993-01-01
Efficient algorithm performs Delaunay triangulation to generate unstructured grids for use in computing two-dimensional flows. Once grid generated, one can optionally call upon additional subalgorithm that removes diagonal lines from quadrilateral cells nearly rectangular. Resulting approximately rectangular grid reduces cost per iteration of flow-computing algorithm.
An efficient advancing front algorithm for Delaunay triangulation
Merriam, Marshal L.
1991-01-01
There has been some recent interest in fluid dynamics calculations on unstructured meshes. One method of unstructured mesh generation involves Delaunay triangulation. This method has certain advantages but it can be expensive to implement. Furthermore, there can be problems with crossing grid lines near boundaries. A method shown here avoids many of the robustness and efficiency problems previously associated with Delaunay triangulation. As an added feature, a simple algorithm is shown which allows removal of diagonal edges from cells that are nearly rectangular. This can result in significant savings in the cost per iteration of a flow solver using this grid.
An efficient advancing front algorithm for Delaunay triangulation
Merriam, Marshal L.
1991-01-01
There has been some recent interest in fluid dynamics calculations on unstructured meshes. One method of unstructured mesh generation involves Delaunay triangulation. This method has certain advantages but it can be expensive to implement. Furthermore, there can be problems with crossing grid lines near boundaries. A method shown here avoids many of the robustness and efficiency problems previously associated with Delaunay triangulation. As an added feature, a simple algorithm is shown which allows removal of diagonal edges from cells that are nearly rectangular. This can result in significant savings in the cost per iteration of a flow solver using this grid.
Parallel implementation of an algorithm for Delaunay triangulation
Merriam, Marshal L.
1992-01-01
The theory and practice of implementing Tanemura's algorithm for 3D Delaunay triangulation on Intel's Gamma prototype, a 128 processor MIMD computer, is described. Efficient implementation of Tanemura's algorithm on a conventional, vector processing supercomputer is problematic. It does not vectorize to any significant degree and requires indirect addressing. Efficient implementation on a parallel architecture is possible, however. Speeds in excess of 20 times a single processor Cray Y-MP are realized on 128 processors of the Intel Gamma prototype.
Automated Photogrammetric Image Matching with Sift Algorithm and Delaunay Triangulation
DEFF Research Database (Denmark)
Karagiannis, Georgios; Antón Castro, Francesc/François; Mioc, Darka
2016-01-01
An algorithm for image matching of multi-sensor and multi-temporal satellite images is developed. The method is based on the SIFT feature detector proposed by Lowe in (Lowe, 1999). First, SIFT feature points are detected independently in two images (reference and sensed image). The features...... of each feature set for each image are computed. The isomorphism of the Delaunay triangulations is determined to guarantee the quality of the image matching. The algorithm is implemented in Matlab and tested on World-View 2, SPOT6 and TerraSAR-X image patches....
Automated Photogrammetric Image Matching with Sift Algorithm and Delaunay Triangulation
Karagiannis, Georgios; Antón Castro, Francesc; Mioc, Darka
2016-06-01
An algorithm for image matching of multi-sensor and multi-temporal satellite images is developed. The method is based on the SIFT feature detector proposed by Lowe in (Lowe, 1999). First, SIFT feature points are detected independently in two images (reference and sensed image). The features detected are invariant to image rotations, translations, scaling and also to changes in illumination, brightness and 3-dimensional viewpoint. Afterwards, each feature of the reference image is matched with one in the sensed image if, and only if, the distance between them multiplied by a threshold is shorter than the distances between the point and all the other points in the sensed image. Then, the matched features are used to compute the parameters of the homography that transforms the coordinate system of the sensed image to the coordinate system of the reference image. The Delaunay triangulations of each feature set for each image are computed. The isomorphism of the Delaunay triangulations is determined to guarantee the quality of the image matching. The algorithm is implemented in Matlab and tested on World-View 2, SPOT6 and TerraSAR-X image patches.
Stereo Matching Algorithm Based on 2D Delaunay Triangulation
Directory of Open Access Journals (Sweden)
Xue-he Zhang
2015-01-01
Full Text Available To fulfill the applications on robot vision, the commonly used stereo matching method for depth estimation is supposed to be efficient in terms of running speed and disparity accuracy. Based on this requirement, Delaunay-based stereo matching method is proposed to achieve the aforementioned standards in this paper. First, a Canny edge operator is used to detect the edge points of an image as supporting points. Those points are then processed using a Delaunay triangulation algorithm to divide the whole image into a series of linked triangular facets. A proposed module composed of these facets performs a rude estimation of image disparity. According to the triangular property of shared vertices, the estimated disparity is then refined to generate the disparity map. The method is tested on Middlebury stereo pairs. The running time of the proposed method is about 1 s and the matching accuracy is 93%. Experimental results show that the proposed method improves both running speed and disparity accuracy, which forms a steady foundation and good application prospect for a robot’s path planning system with stereo camera devices.
OPTIMAL DELAUNAY TRIANGULATIONS
Institute of Scientific and Technical Information of China (English)
Long Chen; Jin-chao Xu
2004-01-01
The Delaunay triangulation, in both classic and more generalized sense, is studied in this paper for minimizing the linear interpolation error (measure in Lp-norm) for a given function. The classic Delaunay triangulation can then be characterized as an optimal triangulation that minimizes the interpolation error for the isotropic function ‖x‖2 among all the triangulations with a given set of vertices. For a more general function, a functiondependent Delaunay triangulation is then defined to be an optimal triangulation that minimizes the interpolation error for this .function and its construction can be obtained by a simple lifting and projection procedure.The optimal Delaunay triangulation is the one that minimizes the interpolation error among all triangulations with the same number of vertices, i.e. the distribution of vertices are optimized in order to minimize the interpolation error. Such a function-dependent optimal Delaunay triangulation is proved to exist for any given convex continuous function.On an optimal Delaunay triangulation associated with f, it is proved that ▽f at the interior vertices can be exactly recovered by the function values on its neighboring vertices.Since the optimal Delaunay triangulation is difficult to obtain in practice, the concept of nearly optimal triangulation is introduced and two sufficient conditions are presented for a triangulation to be nearly optimal.
Redesign of a conformal boundary recovery algorithm for 3D Delaunay triangulation
Institute of Scientific and Technical Information of China (English)
CHEN Jian-jun; ZHENG Yao
2006-01-01
Boundary recovery is one of the main obstacles in applying the Delaunay criterion to mesh generation. A standard resolution is to add Steiner points directly at the intersection positions between missing boundaries and triangulations. We redesign the algorithm with the aid of some new concepts, data structures and operations, which make its implementation routine.Furthermore, all possible intersection cases and their solutions are presented, some of which are seldom discussed in the literature. Finally, numerical results are presented to evaluate the performance of the new algorithm.
Formal study of plane Delaunay triangulation
Dufourd, Jean-François
2010-01-01
This article presents the formal proof of correctness for a plane Delaunay triangulation algorithm. It consists in repeating a sequence of edge flippings from an initial triangulation until the Delaunay property is achieved. To describe triangulations, we rely on a combinatorial hypermap specification framework we have been developing for years. We embed hypermaps in the plane by attaching coordinates to elements in a consistent way. We then describe what are legal and illegal Delaunay edges and a flipping operation which we show preserves hypermap, triangulation, and embedding invariants. To prove the termination of the algorithm, we use a generic approach expressing that any non-cyclic relation is well-founded when working on a finite set.
Chen, Jun; Luo, Chaomin; Krishnan, Mohan; Paulik, Mark; Tang, Yipeng
2010-01-01
An enhanced dynamic Delaunay Triangulation-based (DT) path planning approach is proposed for mobile robots to plan and navigate a path successfully in the context of the Autonomous Challenge of the Intelligent Ground Vehicle Competition (www.igvc.org). The Autonomous Challenge course requires the application of vision techniques since it involves path-based navigation in the presence of a tightly clustered obstacle field. Course artifacts such as switchbacks, ramps, dashed lane lines, trap etc. are present which could turn the robot around or cause it to exit the lane. The main contribution of this work is a navigation scheme based on dynamic Delaunay Triangulation (DDT) that is heuristically enhanced on the basis of a sense of general lane direction. The latter is computed through a "GPS (Global Positioning System) tail" vector obtained from the immediate path history of the robot. Using processed data from a LADAR, camera, compass and GPS unit, a composite local map containing both obstacles and lane line segments is built up and Delaunay Triangulation is continuously run to plan a path. This path is heuristically corrected, when necessary, by taking into account the "GPS tail" . With the enhancement of the Delaunay Triangulation by using the "GPS tail", goal selection is successfully achieved in a majority of situations. The robot appears to follow a very stable path while navigating through switchbacks and dashed lane line situations. The proposed enhanced path planning and GPS tail technique has been successfully demonstrated in a Player/Stage simulation environment. In addition, tests on an actual course are very promising and reveal the potential for stable forward navigation.
平面域中的Delaunay三角算法%Delaunay Triangulation Algorithm in Planar Domain
Institute of Scientific and Technical Information of China (English)
张洁; 陈世元
2007-01-01
对目前广泛使用的Delaunay三角网格生成方法的基本原理进行阐述,对目前流行的几类DT(Delaunay Triangulation)算法,逐点插入算法、分治算法、三角网生长算法的原理进行了分析,对它们的特点进行了介绍.
IMPROVED DELAUNAY TRIANGULATION FOR TRIMMED NURBS SURFACE
Institute of Scientific and Technical Information of China (English)
SUNKe-hao
2004-01-01
An improved algorithm of Delaunay triangulation is proposed by expanding the scope from a convex polygon to an arbitrary polygon area in which holes can be contained in the subdivision procedure. The data structure of generated triangles and the exuviationslike method play a key role, and a single connectivity domain (SCD) without holes is constructed as the initial part of the algorithm. Meanwhile, some examples show that the method can be applied to the triangulation of the trimmed NURBS surface. The result of surface tessellation can be used in many applications such as NC machining, finite element analysis, rendering and mechanism interference detection.
Löffler, Maarten
2012-01-01
We show that Delaunay triangulations and compressed quadtrees are equivalent structures. More precisely, we give two algorithms: the first computes a compressed quadtree for a planar point set, given the Delaunay triangulation; the second finds the Delaunay triangulation, given a compressed quadtree. Both algorithms run in deterministic linear time on a pointer machine. Our work builds on and extends previous results by Krznaric and Levcopolous and Buchin and Mulzer. Our main tool for the second algorithm is the well-separated pair decomposition(WSPD), a structure that has been used previously to find Euclidean minimum spanning trees in higher dimensions (Eppstein). We show that knowing the WSPD (and a quadtree) suffices to compute a planar Euclidean minimum spanning tree (EMST) in linear time. With the EMST at hand, we can find the Delaunay triangulation in linear time. As a corollary, we obtain deterministic versions of many previous algorithms related to Delaunay triangulations, such as splitting planar De...
Delaunay triangulation and computational fluid dynamics meshes
Posenau, Mary-Anne K.; Mount, David M.
1992-01-01
In aerospace computational fluid dynamics (CFD) calculations, the Delaunay triangulation of suitable quadrilateral meshes can lead to unsuitable triangulated meshes. Here, we present case studies which illustrate the limitations of using structured grid generation methods which produce points in a curvilinear coordinate system for subsequent triangulations for CFD applications. We discuss conditions under which meshes of quadrilateral elements may not produce a Delaunay triangulation suitable for CFD calculations, particularly with regard to high aspect ratio, skewed quadrilateral elements.
I/O-Efficient Construction of Constrained Delaunay Triangulations
DEFF Research Database (Denmark)
Agarwal, Pankaj Kumar; Arge, Lars; Yi, Ke
2005-01-01
In this paper, we designed and implemented an I/O-efficient algorithm for constructing constrained Delaunay triangulations. If the number of constraining segments is smaller than the memory size, our algorithm runs in expected O( N B logM/B NB ) I/Os for triangulating N points in the plane, where M...
Constrained Delaunay Triangulation for Ad Hoc Networks
Directory of Open Access Journals (Sweden)
D. Satyanarayana
2008-01-01
Full Text Available Geometric spanners can be used for efficient routing in wireless ad hoc networks. Computation of existing spanners for ad hoc networks primarily focused on geometric properties without considering network requirements. In this paper, we propose a new spanner called constrained Delaunay triangulation (CDT which considers both geometric properties and network requirements. The CDT is formed by introducing a small set of constraint edges into local Delaunay triangulation (LDel to reduce the number of hops between nodes in the network graph. We have simulated the CDT using network simulator (ns-2.28 and compared with Gabriel graph (GG, relative neighborhood graph (RNG, local Delaunay triangulation (LDel, and planarized local Delaunay triangulation (PLDel. The simulation results show that the minimum number of hops from source to destination is less than other spanners. We also observed the decrease in delay, jitter, and improvement in throughput.
Wu, Huayi; Guan, Xuefeng; Gong, Jianya
2011-09-01
This paper presents a robust parallel Delaunay triangulation algorithm called ParaStream for processing billions of points from nonoverlapped block LiDAR files. The algorithm targets ubiquitous multicore architectures. ParaStream integrates streaming computation with a traditional divide-and-conquer scheme, in which additional erase steps are implemented to reduce the runtime memory footprint. Furthermore, a kd-tree-based dynamic schedule strategy is also proposed to distribute triangulation and merging work onto the processor cores for improved load balance. ParaStream exploits most of the computing power of multicore platforms through parallel computing, demonstrating qualities of high data throughput as well as a low memory footprint. Experiments on a 2-Way-Quad-Core Intel Xeon platform show that ParaStream can triangulate approximately one billion LiDAR points (16.4 GB) in about 16 min with only 600 MB physical memory. The total speedup (including I/O time) is about 6.62 with 8 concurrent threads.
Institute of Scientific and Technical Information of China (English)
邵铁政; 李世森
2013-01-01
提出空间散乱点集Delaunay四面体剖分的一种新算法,定义了一个新的Delaunay四面体判定标准即最大球缺角,并在Fortran平台上实现了这种算法,验证算法的准确性和高效性,对于解决空间De-launay四面体剖分来说是一个新的计算思路.将Delaunay四面体的判定改进为量化的判定,这样的判定方法相对以前的方法更容易、更快捷.%A new algorithm of spatial scattered point set Delaunay Triangulation was put forward in this paper,and a new criteria for Delaunay Tetrahedron which was the maximum ball-lacking angle was defined.The new algorithm was carried out in the Fortran development environment to verify the correctness and effectiveness of the algorithm.It is a new calculated idea as for solving spatial Delaunay Triangulation.Improving the determination of Delaunay Tetrahedron to the quantitative determination is easier and faster than the previous methods.
Extending particle tracking capability with Delaunay triangulation.
Chen, Kejia; Anthony, Stephen M; Granick, Steve
2014-04-29
Particle tracking, the analysis of individual moving elements in time series of microscopic images, enables burgeoning new applications, but there is need to better resolve conformation and dynamics. Here we describe the advantages of Delaunay triangulation to extend the capabilities of particle tracking in three areas: (1) discriminating irregularly shaped objects, which allows one to track items other than point features; (2) combining time and space to better connect missing frames in trajectories; and (3) identifying shape backbone. To demonstrate the method, specific examples are given, involving analyzing the time-dependent molecular conformations of actin filaments and λ-DNA. The main limitation of this method, shared by all other clustering techniques, is the difficulty to separate objects when they are very close. This can be mitigated by inspecting locally to remove edges that are longer than their neighbors and also edges that link two objects, using methods described here, so that the combination of Delaunay triangulation with edge removal can be robustly applied to processing large data sets. As common software packages, both commercial and open source, can construct Delaunay triangulation on command, the methods described in this paper are both computationally efficient and easy to implement.
Quality Tetrahedral Mesh Smoothing via Boundary-Optimized Delaunay Triangulation.
Gao, Zhanheng; Yu, Zeyun; Holst, Michael
2012-12-01
Despite its great success in improving the quality of a tetrahedral mesh, the original optimal Delaunay triangulation (ODT) is designed to move only inner vertices and thus cannot handle input meshes containing "bad" triangles on boundaries. In the current work, we present an integrated approach called boundary-optimized Delaunay triangulation (B-ODT) to smooth (improve) a tetrahedral mesh. In our method, both inner and boundary vertices are repositioned by analytically minimizing the error between a paraboloid function and its piecewise linear interpolation over the neighborhood of each vertex. In addition to the guaranteed volume-preserving property, the proposed algorithm can be readily adapted to preserve sharp features in the original mesh. A number of experiments are included to demonstrate the performance of our method.
Strategies for nonobtuse boundary Delaunay triangulations
Energy Technology Data Exchange (ETDEWEB)
Murphy, M. [Univ. of Maryland, College Park, MD (United States). Dept. of Computer Science]|[Los Alamos National Lab., NM (United States); Gable, C.W. [Los Alamos National Lab., NM (United States). Earth and Environmental Science Div.
1998-12-31
Delaunay Triangulations with nonobtuse triangles at the boundaries satisfy a minimal requirement for Control Volume meshes. They motivate this quality requirement, discuss it in context with others that have been proposed, and give point placement strategies that generate the fewest or close to the fewest number of Steiner points needed to satisfy it for a particular problem instance. The advantage is that this strategy places a number of Steiner points proportional to the combinatorial size of the input rather than the local feature size, resulting in far fewer points in many cases.
Fast topological construction of delaunay triangulations and voronoi diagrams
Tsai, Victor J. D.
1993-11-01
This paper describes a Convex Hull Insertion algorithm for constructing the Delaunay triangulation and the Voronoi diagram of randomly distributed points in the Euclidean plane. The implemented program on IBM-compatible personal computers takes benefits from the partitioning of data points, topological data structures of spatial primitives, and features in C++ programming language such as dynamic memory allocation and class objects. The program can handle arbitrary collections of points, and delivers several output options to link with GIS and CAD systems. Empirical results of various sets of up to 50,000 points show that the proposed algorithm speeds up the construction of both tessellations of irregular points in expected linear time.
Onomatopoeia characters extraction from comic images using constrained Delaunay triangulation
Liu, Xiangping; Shoji, Kenji; Mori, Hiroshi; Toyama, Fubito
2014-02-01
A method for extracting onomatopoeia characters from comic images was developed based on stroke width feature of characters, since they nearly have a constant stroke width in a number of cases. An image was segmented with a constrained Delaunay triangulation. Connected component grouping was performed based on the triangles generated by the constrained Delaunay triangulation. Stroke width calculation of the connected components was conducted based on the altitude of the triangles generated with the constrained Delaunay triangulation. The experimental results proved the effectiveness of the proposed method.
A new insertion sequence for incremental Delaunay triangulation
Institute of Scientific and Technical Information of China (English)
Jian-Fei Liu; Jin-Hui Yan; S.H.Lo
2013-01-01
Incremental algorithm is one of the most popular procedures for constructing Delaunay triangulations (DTs).However,the point insertion sequence has a great impact on the amount of work needed for the construction of DTs.It affects the time for both point location and structure update,and hence the overall computational time of the triangulation algorithm.In this paper,a simple deterministic insertion sequence is proposed based on the breadth-first-search on a Kd-tree with some minor modifications for better performance.Using parent nodes as search-hints,the proposed insertion sequence proves to be faster and more stable than the Hilbert curve order and biased randomized insertion order (BRIO),especially for non-uniform point distributions over a wide range of benchmark examples.
Computing 2D constrained delaunay triangulation using the GPU.
Qi, Meng; Cao, Thanh-Tung; Tan, Tiow-Seng
2013-05-01
We propose the first graphics processing unit (GPU) solution to compute the 2D constrained Delaunay triangulation (CDT) of a planar straight line graph (PSLG) consisting of points and edges. There are many existing CPU algorithms to solve the CDT problem in computational geometry, yet there has been no prior approach to solve this problem efficiently using the parallel computing power of the GPU. For the special case of the CDT problem where the PSLG consists of just points, which is simply the normal Delaunay triangulation (DT) problem, a hybrid approach using the GPU together with the CPU to partially speed up the computation has already been presented in the literature. Our work, on the other hand, accelerates the entire computation on the GPU. Our implementation using the CUDA programming model on NVIDIA GPUs is numerically robust, and runs up to an order of magnitude faster than the best sequential implementations on the CPU. This result is reflected in our experiment with both randomly generated PSLGs and real-world GIS data having millions of points and edges.
Skin lesion image segmentation using Delaunay Triangulation for melanoma detection.
Pennisi, Andrea; Bloisi, Domenico D; Nardi, Daniele; Giampetruzzi, Anna Rita; Mondino, Chiara; Facchiano, Antonio
2016-09-01
Developing automatic diagnostic tools for the early detection of skin cancer lesions in dermoscopic images can help to reduce melanoma-induced mortality. Image segmentation is a key step in the automated skin lesion diagnosis pipeline. In this paper, a fast and fully-automatic algorithm for skin lesion segmentation in dermoscopic images is presented. Delaunay Triangulation is used to extract a binary mask of the lesion region, without the need of any training stage. A quantitative experimental evaluation has been conducted on a publicly available database, by taking into account six well-known state-of-the-art segmentation methods for comparison. The results of the experimental analysis demonstrate that the proposed approach is highly accurate when dealing with benign lesions, while the segmentation accuracy significantly decreases when melanoma images are processed. This behavior led us to consider geometrical and color features extracted from the binary masks generated by our algorithm for classification, achieving promising results for melanoma detection.
Institute of Scientific and Technical Information of China (English)
杨小运; 陈和平; 顾进广; 杨剑
2012-01-01
In the study of the existing algorithms of constrained Delaunay triangulation. To the disadvantages of low efficiency of locating points and complexity of searching influence area in the traditional synthesis algorithms, two improvements in the algorithms are presented: First, quickly locating the triangle which the insertion point in; Next, optimizing the process of searching of the influence domain. Effectively reduce the time of the searching process of the point and the influence domain of the constitute grid. And the simulation experiments are finished respectively using the traditional synthesis algorithm and the improved algorithm combined with the finite element algorithm in the "blast furnace lining erosion curve prediction" project The results show that this algorithm is more stable and more efficiency.%在研究现有约束Delaunay三角网生成算法后,针对传统合成算法中点定位过程效率低,搜索影响域算法复杂的缺点,对合成算法进行了两点改进:一是快速定位点所在的三角形；二是优化搜索影响域的算法.改进后的算法有效的缩短了构网过程中定位点和搜索影响域的时间,提高了构网效率.分别利用传统合成算法与改进后的算法结合有限元算法在高炉炉衬侵蚀曲线预测工程项目中进行了分组仿真实验.实验数据表明,改进后的算法更加稳定,剖分效率更高.
COMBINED DELAUNAY TRIANGULATION AND ADAPTIVE FINITE ELEMENT METHOD FOR CRACK GROWTH ANALYSIS
Institute of Scientific and Technical Information of China (English)
Pramote DECHAUMPHAI; Sutthisak PHONGTHANAPANICH; Thanawat SRICHAROENCHAI
2003-01-01
The paper presents the utilization of the adaptive Delaunay triangulation in the finite element modeling of two dimensional crack propagation problems, including detailed description of the proposed procedure which consists of the Delaunay triangulation algorithm and an adaptive remeshing technique. The adaptive remeshing technique generates small elements around crack tips and large elements in the other regions. The resulting stress intensity factors and simulated crack propagation behavior are used to evaluate the effectiveness of the procedure. Three sample problems of a center cracked plate, a single edge cracked plate and a compact tension specimen, are simulated and their results assessed.
Solving the horizontal conflation problem with a constrained Delaunay triangulation
Ledoux, Hugo; Ohori, Ken Arroyo
2017-01-01
Datasets produced by different countries or organisations are seldom properly aligned and contain several discrepancies (e.g., gaps and overlaps). This problem has been so far almost exclusively tackled by snapping vertices based on a user-defined threshold. However, as we argue in this paper, this leads to invalid geometries, is error-prone, and leaves several discrepancies along the boundaries. We propose a novel algorithm to align the boundaries of adjacent datasets. It is based on a constrained Delaunay triangulation to identify and eliminate the discrepancies, and the alignment is performed without moving vertices with a snapping operator. This allows us to guarantee that the datasets have been properly conflated and that the polygons are geometrically valid. We present our algorithm, our implementation (based on the stable and fast triangulator in CGAL), and we show how it can be used it practice with different experiments with real-world datasets. Our experiments demonstrate that our approach is highly efficient and that it yields better results than snapping-based methods.
一种改进的用于三维DT剖分的三角网生长算法%An improved triangulation growth algorithm for 3D delaunay triangulation
Institute of Scientific and Technical Information of China (English)
许克平
2014-01-01
三角网生长法具有独特的优势，但将其扩展到三维的研究远远少于逐点插入法、分治法以及二者的合成算法，研究扩展三角网生长法实现三维 DT 剖分的算法。引入k 近邻思想优化了原始算法，时间复杂度可达 O （ NlogN ），且改进对二维、三维算法都有效。通过 AE 二次开发完成了数据操作、算法实现和二维、三维显示等功能，后续能够较方便地添加和扩展 ArcGIS 相关功能以及其他数据挖掘算法模块。用两组6个点集数据进行实验分析，网格构建时间对比验证了算法性能。%Triangulation growth algorithm has its unique advantages, but researches about developing it into an 3d algorithm are much more less than the ones about developing incremental insertion algorithm, divide & conquer algorithm and their compound algorithm. This paper studies the algorithm for 3d delaunay triangulation by developing triangulation growth algorithm, optimizes the original algorithm with k-nearest neighbors thought so that algorithm time complexity becomes O ( NlogN ) , the optimization is valid both for 2d and 3d algorithm. Uses ArcGIS Engine secondary development program to achieve data manipulation, algorithm implementation, and display of two three-dimensional mesh graph, some ArcGIS related functions and other data mining algorithms modules can be easily added to the program. Taking six sets of point data as example for experimental analysis, grid construct time comparison verifies the ability of the algorithm.
Numerical Conformal Mapping Using Cross-Ratios and Delaunay Triangulation
Driscoll, Tobin A.; Vavasis, Stephen A.
1996-01-01
We propose a new algorithm for computing the Riemann mapping of the unit disk to a polygon, also known as the Schwarz-Christoffel transformation. The new algorithm, CRDT, is based on cross-ratios of the prevertices, and also on cross-ratios of quadrilaterals in a Delaunay triangulation of the polygon. The CRDT algorithm produces an accurate representation of the Riemann mapping even in the presence of arbitrary long, thin regions in the polygon, unlike any previous conformal mapping algorithm. We believe that CRDT can never fail to converge to the correct Riemann mapping, but the correctness and convergence proof depend on conjectures that we have so far not been able to prove. We demonstrate convergence with computational experiments. The Riemann mapping has applications to problems in two-dimensional potential theory and to finite-difference mesh generation. We use CRDT to produce a mapping and solve a boundary value problem on long, thin regions for which no other algorithm can solve these problems.
Adaptive mesh generation for viscous flows using Delaunay triangulation
Mavriplis, Dimitri J.
1990-01-01
A method for generating an unstructured triangular mesh in two dimensions, suitable for computing high Reynolds number flows over arbitrary configurations is presented. The method is based on a Delaunay triangulation, which is performed in a locally stretched space, in order to obtain very high aspect ratio triangles in the boundary layer and the wake regions. It is shown how the method can be coupled with an unstructured Navier-Stokes solver to produce a solution adaptive mesh generation procedure for viscous flows.
A Novel Model of Conforming Delaunay Triangulation for Sensor Network Configuration
Directory of Open Access Journals (Sweden)
Yan Ma
2015-01-01
Full Text Available Delaunay refinement is a technique for generating unstructured meshes of triangles for sensor network configuration engineering practice. A new method for solving Delaunay triangulation problem is proposed in this paper, which is called endpoint triangle’s circumcircle model (ETCM. As compared with the original fractional node refinement algorithms, the proposed algorithm can get well refinement stability with least time cost. Simulations are performed under five aspects including refinement stability, the number of additional nodes, time cost, mesh quality after intruding additional nodes, and the aspect ratio improved by single additional node. All experimental results show the advantages of the proposed algorithm as compared with the existing algorithms and confirm the algorithm analysis sufficiently.
Selecting the aspect ratio of a scatter plot based on its delaunay triangulation.
Fink, Martin; Haunert, Jan-Henrik; Spoerhase, Joachim; Wolff, Alexander
2013-12-01
Scatter plots are diagrams that visualize two-dimensional data as sets of points in the plane. They allow users to detect correlations and clusters in the data. Whether or not a user can accomplish these tasks highly depends on the aspect ratio selected for the plot, i.e., the ratio between the horizontal and the vertical extent of the diagram. We argue that an aspect ratio is good if the Delaunay triangulation of the scatter plot at this aspect ratio has some nice geometric property, e.g., a large minimum angle or a small total edge length. More precisely, we consider the following optimization problem. Given a set Q of points in the plane, find a scale factor s such that scaling the x-coordinates of the points in Q by s and the y-coordinates by 1=s yields a point set P(s) that optimizes a property of the Delaunay triangulation of P(s), over all choices of s. We present an algorithm that solves this problem efficiently and demonstrate its usefulness on real-world instances. Moreover, we discuss an empirical test in which we asked 64 participants to choose the aspect ratios of 18 scatter plots. We tested six different quality measures that our algorithm can optimize. In conclusion, minimizing the total edge length and minimizing what we call the 'uncompactness' of the triangles of the Delaunay triangulation yielded the aspect ratios that were most similar to those chosen by the participants in the test.
Institute of Scientific and Technical Information of China (English)
李振海; 罗志才; 钟波
2012-01-01
Gravity modeling of three-dimensional geological body is one of the key problems for interpreting and applying gravity data. Aiming at three-dimensional geological body with irregular structure and varying density, we presented the gravity modeling approach based on 3D Delaunay triangulation algorithm in the paper. With 3D Delaunay triangulation, the geological body was divided into various tetrahedral vexels in optimal way, and then the gravity forward calculation formula for a tetrahedral vexel was derived, as well as the linear equations between the residual densities and the gravity anomalies. Taking a cuboid with varying density and a hybrid geological body with inclined step and varying density as examples, we compared and analyzed the validity for the forward computation of gravity anomalies using traditional cuboid vexel and 3D Delaunay triangulation algorithm respectively. Moreover, the density distribution of the hybrid geological body with inclined step and varying density was recovered by inversion using conjugate gradient algorithm with constrained density, and the inversion results were very consistent with the real geological body. Simulation results verified the correctness and validity of the gravity modeling method given in the paper. The gravity modeling based on 3D Delaunay triangulation algorithm could be applied to the gravity forward and inversion computation for the complicated and heterogeneous geological body with folds, cracks, faults and etc.%地质体的重力建模是正确解释和应用重力资料的关键问题之一.针对非规则形状变密度的三度体,本文提出了基于3D Delaunay剖分算法的重力建模方法.采用3D Delaunay剖分算法将三维目标地质体分解为若干变密度四面体体元,推导了基于四面体体元的重力正演公式,建立了剩余密度值与重力异常值的线性方程组；以变密度的长方体和倾斜台阶组合体为例,比较分析了常规块体算法和3D Delaunay
Feature-preserving surface mesh smoothing via suboptimal Delaunay triangulation.
Gao, Zhanheng; Yu, Zeyun; Holst, Michael
2013-01-01
A method of triangular surface mesh smoothing is presented to improve angle quality by extending the original optimal Delaunay triangulation (ODT) to surface meshes. The mesh quality is improved by solving a quadratic optimization problem that minimizes the approximated interpolation error between a parabolic function and its piecewise linear interpolation defined on the mesh. A suboptimal problem is derived to guarantee a unique, analytic solution that is significantly faster with little loss in accuracy as compared to the optimal one. In addition to the quality-improving capability, the proposed method has been adapted to remove noise while faithfully preserving sharp features such as edges and corners of a mesh. Numerous experiments are included to demonstrate the performance of the method.
DELAUNAY TRIANGULATION METHOD OF CURVED SURFACES BASED ON RIEMANNIAN METRIC
Institute of Scientific and Technical Information of China (English)
无
2003-01-01
A method for quality mesh generation of parametric curved surfaces is proposed. It is shown that the main difference between the proposed method and previous ones is that our meshing process is done completely in the parametric domains with the guarantee of mesh quality. To obtain this aim, the Delaunay method is extended to anisotropic context of 2D domains, and a Riemannian metric map is introduced to remedy the mapping distortion from object space to parametric domain. Compared with previous algorithms, the approach is much simpler, more robust and speedy. The algorithm is implemented and examples for several geometries are presented to demonstrate the efficiency and validity of the method.
A Data Forwarding Scheme Based on Delaunay Triangulation for Cyber-Physical Systems
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Junhai Luo
2013-01-01
Full Text Available Cyber-physical system (CPS cooperates with physical processes, computing, communication, and control (3C into multiple levels of information processing and operation management to streamline and fortify the operation of physical systems. Due to the unique characteristics, such as unpredictable node mobility, low node density, lack of global information and network intermittent connectivity, an algorithm for data forwarding in CPS is a considerably difficult and challenging problem, and there is no good solution to it in existing works. In this paper, we propose a fully-fledged data forwarding algorithm tailored to the CPS environment. The proposed protocol, called data forwarding based on Delaunay triangulation (DFDT, takes into account the computational geometry based on Delaunay triangulation to form a few triangle communities according to nodes’ connectivity. Data in a community are forwarded to other nodes once a node comes into this community to increase the data delivery ratio. DFDT achieves a good performance by data gathering and sending data to other nodes with higher probability of meeting the link. An extensive simulation has been performed to validate the analytical results and to show the effectiveness of our approach compared with the three existing popular data forwarding algorithms.
The worst visibility walk in a random Delaunay triangulation is $O(\\sqrt{n}$
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Olivier Devillers
2016-07-01
Full Text Available We show that the memoryless routing algorithms Greedy Walk, Compass Walk, and all variants of visibility walk based on orientation predicates are asymptotically optimal in the average case on the Delaunay triangulation. More specifically, we consider the Delaunay triangulation of an unbounded Poisson point process of unit rate and demonstrate that, for any pair of vertices $(s,t$ inside $[0,n]^2$, the ratio between the longest and shortest visibility walks between $s$ and $t$ is bounded by a constant with probability converging to one (as long as the vertices are sufficiently far apart. As a corollary, it follows that the worst-case path has $O(\\sqrt{n}\\,$ steps in the limiting case, under the same conditions. Our results have applications in routing in mobile networks and also settle a long-standing conjecture in point location using walking algorithms. Our proofs use techniques from percolation theory and stochastic geometry.
Institute of Scientific and Technical Information of China (English)
王雯; 苏天赟; 王国宇
2015-01-01
为了更好地提高对二维点云数据的Delaunay构网效率, 并充分考虑点云数据规模庞大、分布多样的特点, 提出一种Hilbert曲线与多重网格划分相结合的算法. 首先通过多重网格划分解决规则网格对非均匀点集划分程度无法统一的问题; 其次通过添加控制点和采用 Hilbert 曲线顺序遍历网格的方式, 避免逐行遍历网格时产生大量需要重复创建和删除的狭长三角形的情况; 最后通过调整相邻网格间Hilbert曲线遍历顺序, 避免遍历过程的"跳跃"现象, 降低相邻网格插入点的点定位搜索步长. 实验结果表明, 与CGAL、规则网格和多重网格划分算法相比, 该算法的构网效率对于分布均匀和非均匀的点云数据都有明显提升.%Given the enormous scale and diverse distribution of 2D point cloud data, a multi-grid combined with Hilbert curve insertion algorithm is proposed for improving the efficiency of Delaunay Triangulation. First of all, the division problem caused by regular grid insertion scheme for non-uniform distributed point set can be resolved by the multi-grid one. Then, a large amount of conflicting elongated triangles, which have to be created and deleted many times, can be avoided by adding control points and adopting Hilbert curve traversing grids. Lastly, searching steps for positioning inserting point can be reduced by adjusting the Hilbert curve in adjacent grids for the avoided "jumping" phenomenon. The experimental results show that the efficiency of Delaunay triangulation by multi-grid combined with Hilbert curve insertion algorithm can be improved significantly for both uniform and non-uniform distributed point cloud data compared with CGAL, regular grid insertion and multi-grid insertion algorithm.
Energy Technology Data Exchange (ETDEWEB)
Muecke, E.P.; Saias, I.; Zhu, B.
1996-05-01
This paper studies the point location problem in Delaunay triangulations without preprocessing and additional storage. The proposed procedure finds the query point simply by walking through the triangulation, after selecting a good starting point by random sampling. The analysis generalizes and extends a recent result of d = 2 dimensions by proving this procedure to take expected time close to O(n{sup 1/(d+1)}) for point location in Delaunay triangulations of n random points in d = 3 dimensions. Empirical results in both two and three dimensions show that this procedure is efficient in practice.
Institute of Scientific and Technical Information of China (English)
无
2005-01-01
Adaptive Delaunay triangulation is combined with the cell-centered upwinding algorithm to analyze inviscid high-speed compressible flow problems. The multidimensional dissipation scheme was developed and included in the upwinding algorithm for unstructured triangular meshes to improve the computed shock wave resolution. The solution accuracy is further improved by coupling an error estimation procedure to a remeshing algorithm that generates small elements in regions with large change of solution gradients, and at the same time, larger elements in other regions. The proposed scheme is further extended to achieve higher-order spatial and temporal solution accuracy. Efficiency of the combined procedure is evaluated by analyzing supersonic shocks and shock propagation behaviors for both the steady and unsteady high-speed compressible flows.
Fine-grained Delaunay triangulation in a simulation of tumor spheroid growth
Fabbro, A D; Milotti, E; Chignola, Roberto; Fabbro, Alessio Del; Milotti, Edoardo
2006-01-01
The simulation of many-particle systems often requires the detailed knowledge of proximity relations to reduce computational complexity and to provide a basis for specific calculations. Here we describe the basic scheme of a simulator of tumor spheroid growth: the calculation of mechanical interactions between cells and of the concentrations of diffusing chemicals requires a backbone provided by the Delaunay triangulation and the volumes of the associated Voronoi regions. Thus the Delaunay triangulation provides both the proximity relations needed to reduce the computational complexity and the basic structures that are needed to carry out the calculation of the biochemical interactions between cells and with the enviroment. A 3D version of the simulator uses the CGAL library as an essential component for the efficient computation of the Delaunay triangulation and of the Voronoi regions.
Institute of Scientific and Technical Information of China (English)
鲍蕊娜; 李向新; 麻明; 孙晓丽; 贺瑞喜
2011-01-01
As an important expression of DEM, the generation algorithm of TIN drew people' s attention. the principle of traditional generation algorithms according are summarized and analyzed to there characteristics, described the principle and method to establish TIN with the convex hull. In accordance with the state that many of computational geometry books simplified the process of building the convex hull by limiting points, this paper shows an improvement in the process of forming a convex hull. The improved algorithm, which eliminates the repeat point when the points are sorting; it also eliminate co-line in the process of constructing new convex hull. When all the points are contained in the convex hull, the process of establishing the triangulation is completed. LOP optimization based on the triangle public edge which makes all the triangles satisfy the rule of the Delaunay triangulation.Through tests, its running speed faster than the traditional generation algorithms, at the sane time, the improved algorithm can deal with some particular cases, such as repeat points, three points are on a straight line.%TIN作为DEM的一种重要表达模型,其生成算法一直备受关注.首先对传统的生成算法原理进行总结,并针对其特点进行了分析,对利用凸壳建立TIN的原理和方法进行简单描述.由于许多计算几何学对点集进行限制以简化凸壳的建立过程,对凸壳的生成过程进行了改进.在点集的排序过程中剔除重复点,将点联入原凸壳过程中,排除共线这一特殊情况,建立新的凸壳,直至所有点都被包含在凸壳中.至此,三角网建立完毕.通过对三角形公共边进行LOP优化,使其满足Delaunay三角网的特性.当所有三角形满足特性时,Delaunay三角网构建完毕.该算法的优势在于构网速度较快,并能够对重复点进行处理,同时在生成网的过程中对共线这种特殊情况进行处理.
Alpha shape and Delaunay triangulation in studies of protein-related interactions.
Zhou, Weiqiang; Yan, Hong
2014-01-01
In recent years, more 3D protein structures have become available, which has made the analysis of large molecular structures much easier. There is a strong demand for geometric models for the study of protein-related interactions. Alpha shape and Delaunay triangulation are powerful tools to represent protein structures and have advantages in characterizing the surface curvature and atom contacts. This review presents state-of-the-art applications of alpha shape and Delaunay triangulation in the studies on protein-DNA, protein-protein, protein-ligand interactions and protein structure analysis.
Meyer-Hermann, Michael
2008-01-01
Mathematical methods in Biology are of increasing relevance for understanding the control and the dynamics of biological systems with medical relevance. In particular, agent-based methods turn more and more important because of fast increasing computational power which makes even large systems accessible. An overview of different mathematical methods used in Theoretical Biology is provided and a novel agent-based method for cell mechanics based on Delaunay-triangulations and Voronoi-tessellations is explained in more detail: The Delaunay-Object-Dynamics method. It is claimed that the model combines physically realistic cell mechanics with a reasonable computational load. The power of the approach is illustrated with two examples, avascular tumor growth and genesis of lymphoid tissue in a cell-flow equilibrium.
Kinetic convex hulls, Delaunay triangulations and connectivity structures in the black-box model
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Mark de Berg
2012-12-01
Full Text Available Over the past decade, the kinetic-data-structures framework has become thestandard in computational geometry for dealing with moving objects. A fundamental assumption underlying the framework is that the motions of the objects are known in advance. This assumption severely limits the applicability of KDSs. We study KDSs in the black-box model, which is a hybrid of the KDS model and the traditional time-slicing approach. In this more practical model we receive the position of each object at regular time steps and we have an upper bound on dmax, the maximum displacement of any point in one time step.We study the maintenance of the convex hull and the Delaunay triangulation of a planar point set P in the black-box model, under the following assumption on dmax: there is some constant k such that for any point p in P the disk of radius dmax contains at most k points. We analyze our algorithms in terms of Δk, the so-called k-spread of P. We show how to update the convex hull at each time step in O(min(n, kΔklog nlog n amortized time. For the Delaunay triangulation our main contribution is an analysis of the standard edge-flipping approach; we show that the number of flips is O(k2Δk2 at each time step.
Fast and automatic identification of particle tilt pairs based on Delaunay triangulation.
Vilas, J L; Navas, J; Gómez-Blanco, J; de la Rosa-Trevín, J M; Melero, R; Peschiera, I; Ferlenghi, I; Cuenca, J; Marabini, R; Carazo, J M; Vargas, J; Sorzano, C O S
2016-12-01
Random conical tilt (RCT) and orthogonal tilt reconstruction (OTR) are two remarkable methods for reconstructing the three-dimensional structure of macromolecules at low resolution. These techniques use two images at two different sample tilts. One of the most demanding steps in these methods at the image processing level is to identify corresponding particles on both micrographs, and manual or semiautomatic matching methods are usually used. Here we present an approach to solve this bottleneck with a fully automatic method for assigning particle tilt pairs. This new algorithm behaves correctly with a variety of samples, covering the range from small to large macromolecules and from sparse to densely populated fields of view. It is also more rapid than previous approaches. The roots of the method lie in a Delaunay triangulation of the set of independently picked coordinates on both the untilted and tilted micrographs. These triangulations are then used to search an affine transformation between the untilted and tilted triangles. The affine transformation that maximizes the number of correspondences between the two micrographs defines the coordinate matching. Copyright © 2016 Elsevier Inc. All rights reserved.
Cheng, Siu-Wing; Shewchuk, Jonathan
2013-01-01
Written by authors at the forefront of modern algorithms research, Delaunay Mesh Generation demonstrates the power and versatility of Delaunay meshers in tackling complex geometric domains ranging from polyhedra with internal boundaries to piecewise smooth surfaces. Covering both volume and surface meshes, the authors fully explain how and why these meshing algorithms work.The book is one of the first to integrate a vast amount of cutting-edge material on Delaunay triangulations. It begins with introducing the problem of mesh generation and describing algorithms for constructing Delaunay trian
Qin, Junping; Sun, Shiwen; Deng, Qingxu; Liu, Limin; Tian, Yonghong
2017-06-02
Object tracking and detection is one of the most significant research areas for wireless sensor networks. Existing indoor trajectory tracking schemes in wireless sensor networks are based on continuous localization and moving object data mining. Indoor trajectory tracking based on the received signal strength indicator (RSSI) has received increased attention because it has low cost and requires no special infrastructure. However, RSSI tracking introduces uncertainty because of the inaccuracies of measurement instruments and the irregularities (unstable, multipath, diffraction) of wireless signal transmissions in indoor environments. Heuristic information includes some key factors for trajectory tracking procedures. This paper proposes a novel trajectory tracking scheme based on Delaunay triangulation and heuristic information (TTDH). In this scheme, the entire field is divided into a series of triangular regions. The common side of adjacent triangular regions is regarded as a regional boundary. Our scheme detects heuristic information related to a moving object's trajectory, including boundaries and triangular regions. Then, the trajectory is formed by means of a dynamic time-warping position-fingerprint-matching algorithm with heuristic information constraints. Field experiments show that the average error distance of our scheme is less than 1.5 m, and that error does not accumulate among the regions.
带约束折线的平面散点集Delaunay三角剖分%Delaunay Triangulation of 2D Scattered Point Set with Constrained Polylines
Institute of Scientific and Technical Information of China (English)
王中辉; 闫浩文
2011-01-01
This paper first triangulates the original scattered points with all constrained points to form the initial Delaunay triangulation. Then each constrained segment is embedded in the existent triangulation in turn through local updating, eventually to form the Delannay triangulation with constrained polylines. The algorithm is concise and easy to program and the generated triangulation is in good shape.%首先将原始散点与约束点一起进行三角剖分,形成初始Delaunay三角网,然后再将各条约束线段通过局部更新,依次嵌入已存在的三角网中,从而生成带有约束折线的平面散点集的Delaunay三角剖分.该算法思路简捷,易于编程,生成的三角网形态优良.
Directory of Open Access Journals (Sweden)
GUO Peipei
2016-08-01
Full Text Available Building aggregation is an important part of research on large scale map generalization. A triangulation based approach is proposed from the perspective of shape features, six measure parameters of triangles in a constrained Delaunay triangulation are proposed. First of all, use the six measure parameters to determine which triangles are retained and which are erased. Then, the contours of retained triangles, as bridge areas between buildings, are automatically identified and right angle processed. And then, the buildings are aggregated with right angle feature retained by merging the bridge areas with connecting buildings. Finally, the approach is verified by being carried out on actual data. Experimental result shows that it is efficient and practical.
A General-division Grid Pattern Delaunay-TIN Parallel Algorithm
Directory of Open Access Journals (Sweden)
HAN Yuanli
2015-06-01
Full Text Available This paper achieves out a new Delaunay triangulation algorithm. Firstly, the self-adaptation grid space division was proposed to realize the balanced logical grid division for massive point cloud data. Secondly, from far to near order the sequence of points in each grid by distance to the grid center and find out the nearest point and mark it as the central point. Thirdly, the TIN was built with by a new general-division Delaunay triangulation algorithm, which uses traditional insertion method to build TIN and add only one point from each grid at one times to form new TIN. When building TIN we use find-insertion method firstly and hereafter use topology-insertion method to keep high efficiency. This algorithm has good efficiency because it successfully avoided the merge process of sub grid triangulation mesh. Finally, the topological closure detection mechanism was established, and the independent parallel multithreading was started to model the rest points by topology-insertion algorithm limit to every grid space, which made the triangulation modeling of the whole space efficient. The method of this paper improved the support capacity of space modeling for massive point cloud data obviously.
DIVE in the cosmic web: voids with Delaunay triangulation from discrete matter tracer distributions
Zhao, Cheng; Tao, Charling; Liang, Yu; Kitaura, Francisco-Shu; Chuang, Chia-Hsun
2016-07-01
We present a novel parameter-free cosmological void finder (DIVE, Delaunay TrIangulation Void findEr) based on Delaunay Triangulation (DT), which efficiently computes the empty spheres constrained by a discrete set of tracers. We define the spheres as DT voids, and describe their properties, including a universal density profile together with an intrinsic scatter. We apply this technique on 100 halo catalogues with volumes of 2.5 h-1Gpc side each, with a bias and number density similar to the Baryon Oscillation Spectroscopic Survey CMASS luminous red galaxies, performed with the PATCHY code. Our results show that there are two main species of DT voids, which can be characterized by the radius: they have different responses to halo redshift space distortions, to number density of tracers, and reside in different dark matter environments. Based on dynamical arguments using the tidal field tensor, we demonstrate that large DT voids are hosted in expanding regions, whereas the haloes used to construct them reside in collapsing ones. Our approach is therefore able to efficiently determine the troughs of the density field from galaxy surveys, and can be used to study their clustering. We further study the power spectra of DT voids, and find that the bias of the two populations are different, demonstrating that the small DT voids are essentially tracers of groups of haloes.
DIVE in the cosmic web: voids with Delaunay Triangulation from discrete matter tracer distributions
Zhao, Cheng; Liang, Yu; Kitaura, Francisco-Shu; Chuang, Chia-Hsun
2015-01-01
We present a novel parameter-free cosmological void finder (\\textsc{dive}, Delaunay TrIangulation Void findEr) based on Delaunay Triangulation (DT), which efficiently computes the empty spheres constrained by a discrete set of tracers. We define the spheres as DT voids, and describe their properties, including an universal density profile together with an intrinsic scatter. We apply this technique on 100 halo catalogues with volumes of 2.5\\,$h^{-1}$Gpc side each, with a bias and number density similar to the BOSS CMASS Luminous Red Galaxies, performed with the \\textsc{patchy} code. Our results show that there are two main species of DT voids, which can be characterised by the radius: they have different responses to halo redshift space distortions, to number density of tracers, and reside in different dark matter environments. Based on dynamical arguments using the tidal field tensor, we demonstrate that large DT voids are hosted in expanding regions, whereas the haloes used to construct them reside in collap...
Calculation of mean central dose in interstitial brachytherapy using Delaunay triangulation.
Astrahan, M A; Streeter, O E; Jozsef, G
2001-06-01
In 1997 the ICRU published Report 58 "Dose and Volume Specification for Reporting Interstitial Therapy" with the objective of addressing the problem of absorbed dose specification for reporting contemporary interstitial therapy. One of the concepts proposed in that report is "mean central dose." The fundamental goal of the mean central dose (MCD) calculation is to obtain a single, readily reportable and intercomparable value which is representative of dose in regions of the implant "where the dose gradient approximates a plateau." Delaunay triangulation (DT) is a method used in computational geometry to partition the space enclosed by the convex hull of a set of distinct points P into a set of nonoverlapping cells. In the three-dimensional case, each point of P becomes a vertex of a tetrahedron and the result of the DT is a set of tetrahedra. All treatment planning for interstitial brachytherapy inherently requires that the location of the radioactive sources, or dwell positions in the case of HDR, be known or digitized. These source locations may be regarded as a set of points representing the implanted volume. Delaunay triangulation of the source locations creates a set of tetrahedra without manual intervention. The geometric centers of these tetrahedra define a new set of points which lie "in between" the radioactive sources and which are distributed uniformly over the volume of the implant. The arithmetic mean of the dose at these centers is a three dimensional analog of the two-dimensional triangulation and inspection methods proposed for calculating MCD in ICRU 58. We demonstrate that DT can be successfully incorporated into a computerized treatment planning system and used to calculate the MCD.
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YANG Wei
2017-02-01
Full Text Available Extraction of road boundary accurately from crowdsourcing trajectory lines is still a hard work.Therefore,this study presented a new approach to use vehicle trajectory lines to extract road boundary.Firstly, constructing constrained Delaunay triangulation within interpolated track lines to calculate road boundary descriptors using triangle edge length and Voronoi cell.Road boundary recognition model was established by integrating the two boundary descriptors.Then,based on seed polygons,a regional growing method was proposed to extract road boundary. Finally, taxi GPS traces in Beijing were used to verify the validity of the novel method, and the results also showed that our method was suitable for GPS traces with disparity density,complex road structure and different time interval.
A Road Map Refinement Method Using Delaunay Triangulation for Big Trace Data
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Luliang Tang
2017-02-01
Full Text Available With the rapid development of urban transportation, people urgently need high-precision and up-to-date road maps. At the same time, people themselves are an important source of road information for detailed map construction, as they can detect real-world road surfaces with GPS devices in the course of their everyday life. Big trace data makes it possible and provides a great opportunity to extract and refine road maps at relatively low cost. In this paper, a new refinement method is proposed for incremental road map construction using big trace data, employing Delaunay triangulation for higher accuracy during the GPS trace stream fusion process. An experiment and evaluation were carried out on the GPS traces collected by taxis in Wuhan, China. The results show that the proposed method is practical and improves upon existing incremental methods in terms of accuracy.
Feature-preserving surface mesh smoothing via suboptimal Delaunay triangulation ☆
Gao, Zhanheng; Yu, Zeyun; Holst, Michael
2012-01-01
A method of triangular surface mesh smoothing is presented to improve angle quality by extending the original optimal Delaunay triangulation (ODT) to surface meshes. The mesh quality is improved by solving a quadratic optimization problem that minimizes the approximated interpolation error between a parabolic function and its piecewise linear interpolation defined on the mesh. A suboptimal problem is derived to guarantee a unique, analytic solution that is significantly faster with little loss in accuracy as compared to the optimal one. In addition to the quality-improving capability, the proposed method has been adapted to remove noise while faithfully preserving sharp features such as edges and corners of a mesh. Numerous experiments are included to demonstrate the performance of the method. PMID:23580890
Delaunay Triangulation as a New Coverage Measurement Method in Wireless Sensor Network
Chizari, Hassan; Hosseini, Majid; Poston, Timothy; Razak, Shukor Abd; Abdullah, Abdul Hanan
2011-01-01
Sensing and communication coverage are among the most important trade-offs in Wireless Sensor Network (WSN) design. A minimum bound of sensing coverage is vital in scheduling, target tracking and redeployment phases, as well as providing communication coverage. Some methods measure the coverage as a percentage value, but detailed information has been missing. Two scenarios with equal coverage percentage may not have the same Quality of Coverage (QoC). In this paper, we propose a new coverage measurement method using Delaunay Triangulation (DT). This can provide the value for all coverage measurement tools. Moreover, it categorizes sensors as ‘fat’, ‘healthy’ or ‘thin’ to show the dense, optimal and scattered areas. It can also yield the largest empty area of sensors in the field. Simulation results show that the proposed DT method can achieve accurate coverage information, and provides many tools to compare QoC between different scenarios. PMID:22163792
Institute of Scientific and Technical Information of China (English)
王中辉; 闫浩文
2011-01-01
算法首先将离散点与约束边界点一起进行Delaunay三角剖分，形成初始Delaunay三角网，然后将约束边界上的各条约束线段通过局部更新依次嵌入已有的三角网，最后再删除多余的三角形，从而得到带内外边界约束的平面点集Delaunay三角剖分.%The algorithm first triangulates the scattered points together with the constrained points to form the initial Delaunay triangulation, then each constrained segment in the constrained boundaries is interpolated to the existent triangulation in turn through local updating,finally the redundant triangles are removed, so Delaunay triangulation of a 2-dimension scattered point set with inner and outer boundary constrains is generated.
DELAUNAY-BASED SURFACE RECONSTRUCTION ALGORITHM IN REVERSE ENGINEERING
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
Triangulation of scattered points is the first important section during reverse engineering. New concepts of dynamic circle and closed point are put forward based on current basic method. These new concepts can narrow the extent which triangulation process should seek through and optimize the triangles during producing them. Updating the searching edges dynamically controls progress of triangulation. Intersection judgment between new triangle and produced triangles is changed into intersection judgment between new triangle and searching edges. Examples illustrate superiorities of this new algorithm.
Qu, Rui; Liu, Shu-Shen; Zheng, Qiao-Feng; Li, Tong
2017-03-13
Concentration addition (CA) was proposed as a reasonable default approach for the ecological risk assessment of chemical mixtures. However, CA cannot predict the toxicity of mixture at some effect zones if not all components have definite effective concentrations at the given effect, such as some compounds induce hormesis. In this paper, we developed a new method for the toxicity prediction of various types of binary mixtures, an interpolation method based on the Delaunay triangulation (DT) and Voronoi tessellation (VT) as well as the training set of direct equipartition ray design (EquRay) mixtures, simply IDVequ. At first, the EquRay was employed to design the basic concentration compositions of five binary mixture rays. The toxic effects of single components and mixture rays at different times and various concentrations were determined by the time-dependent microplate toxicity analysis. Secondly, the concentration-toxicity data of the pure components and various mixture rays were acted as a training set. The DT triangles and VT polygons were constructed by various vertices of concentrations in the training set. The toxicities of unknown mixtures were predicted by the linear interpolation and natural neighbor interpolation of vertices. The IDVequ successfully predicted the toxicities of various types of binary mixtures.
A new approach for categorizing pig lying behaviour based on a Delaunay triangulation method.
Nasirahmadi, A; Hensel, O; Edwards, S A; Sturm, B
2017-01-01
Machine vision-based monitoring of pig lying behaviour is a fast and non-intrusive approach that could be used to improve animal health and welfare. Four pens with 22 pigs in each were selected at a commercial pig farm and monitored for 15 days using top view cameras. Three thermal categories were selected relative to room setpoint temperature. An image processing technique based on Delaunay triangulation (DT) was utilized. Different lying patterns (close, normal and far) were defined regarding the perimeter of each DT triangle and the percentages of each lying pattern were obtained in each thermal category. A method using a multilayer perceptron (MLP) neural network, to automatically classify group lying behaviour of pigs into three thermal categories, was developed and tested for its feasibility. The DT features (mean value of perimeters, maximum and minimum length of sides of triangles) were calculated as inputs for the MLP classifier. The network was trained, validated and tested and the results revealed that MLP could classify lying features into the three thermal categories with high overall accuracy (95.6%). The technique indicates that a combination of image processing, MLP classification and mathematical modelling can be used as a precise method for quantifying pig lying behaviour in welfare investigations.
Zhang, K.; Sheng, Y. H.; Li, Y. Q.; Han, B.; Liang, Ch.; Sha, W.
2006-10-01
In the field of digital photogrammetry and computer vision, the determination of conjugate points in a stereo image pair, referred to as "image matching," is the critical step to realize automatic surveying and recognition. Traditional matching methods encounter some problems in the digital close-range stereo photogrammetry, because the change of gray-scale or texture is not obvious in the close-range stereo images. The main shortcoming of traditional matching methods is that geometric information of matching points is not fully used, which will lead to wrong matching results in regions with poor texture. To fully use the geometry and gray-scale information, a new stereo image matching algorithm is proposed in this paper considering the characteristics of digital close-range photogrammetry. Compared with the traditional matching method, the new algorithm has three improvements on image matching. Firstly, shape factor, fuzzy maths and gray-scale projection are introduced into the design of synthetical matching measure. Secondly, the topology connecting relations of matching points in Delaunay triangulated network and epipolar-line are used to decide matching order and narrow the searching scope of conjugate point of the matching point. Lastly, the theory of parameter adjustment with constraint is introduced into least square image matching to carry out subpixel level matching under epipolar-line constraint. The new algorithm is applied to actual stereo images of a building taken by digital close-range photogrammetric system. The experimental result shows that the algorithm has a higher matching speed and matching accuracy than pyramid image matching algorithm based on gray-scale correlation.
Wan, Min; Lim, Calvin; Zhang, Junmei; Su, Yi; Yeo, Si Yong; Wang, Desheng; Tan, Ru San; Zhong, Liang
2013-01-01
This study proposes a novel method to reconstruct the left cardiac structure from contours. Given the contours representing left ventricle (LV), left atrium (LA), and aorta (AO), re-orientation, contour matching, extrapolation, and interpolation are performed sequentially. The processed data are then reconstructed via a variational method. The weighted minimal surface model is revised to handle the multi-phase cases, which happens at the LV-LA-AO junction. A Delaunay-based tetrahedral mesh is generated to discretize the domain while the max-flow/min-cut algorithm is utilized as the minimization tool. The reconstructed model including LV, LA, and AO structure is extracted from the mesh and post-processed further. Numerical examples show the robustness and effectiveness of the proposed method.
Zou, Bin; Wang, Debby D.; Ma, Lichun; Chen, Lijiang; Yan, Hong
2016-05-01
Epidermal growth factor receptor (EGFR) mutation is a pathogenic factor of non-small cell lung cancer (NSCLC). Tyrosine kinase inhibitors (TKIs), such as gefitinib, are widely used in NSCLC treatment. In this work, we investigated the relationship between the number of EGFR residues connected with gefitinib and the response level for each EGFR mutation type. Three-dimensional trimmed Delaunay triangulation was applied to construct connections between EGFR residues and gefitinib atoms. Through molecular dynamics (MD) simulations, we discovered that when the number of EGFR residues connected with gefitinib increases, the response level of the corresponding EGFR mutation tends to descend.
Institute of Scientific and Technical Information of China (English)
熊敏诠
2012-01-01
Delaunay三角剖分方法在空间分析中具有重要地位,文中简要介绍了Delaunay三角网特性和常用的3类算法,并对随机增长法实现过程进行了详细阐述.根据三角分片线性插值原理,求得插值系数,实现对任意点的三角分片线性插值.利用2008年中国2200个观测站的08时24 h降水量资料,对全中国范围及划分的8个区域内相应的0.28125°×0.28125°降水量格点场,使用交叉检验方法,对比分析了三角分片线性插值和反距离权重法的估值准确率.结果表明:在各区域,三角分片线性插值法的均方根误差偏小；在站点较密集的区域,均方根误差、平均绝对误差比较中,三角分片线性插值都有一定的优势；在平均误差对比中,三角分片线性插值优势明显,在全中国范围交叉检验中,三角分片线性插值法对应的年平均误差是0.005 mm,而反距离权重法为-0.107 mm,对其可能的原因进行了分析,证明了Delaunay三角剖分法的合理性.同时,从图形上展示了降水量的Delaunay三角网的三维结构图和三角分片线性插值后的格点场,在直观上,Delaunay三角剖分后得到降水分布和实况保持一致,并有较好的视觉效果；通过三角分片线性插值得到的格点场降水量分布图,克服了反距离权重法的固有缺陷,使获得的降水量格点场趋于合理,提高了插值精度.最后,探讨了Delaunay三角网在气象领域的应用前景.%Delaunay triangulated method plays an important role in the spatial analysis. The characteristic of Delaunay triangu-lation and three kinds of generation algorithm are introduced in this article. The stochastic growth algorithm is also discussed in detail. Based on the principle of the triangulated slice linear interpolation the coefficient is attained and thus the value at an arbitrary point can be calculated through the triangulated slice linear interpolation algorithm. By using the daily precipitation
基于格网划分的Delaunay三角剖分算法研究%Study of Massive Data Delaunay Triangulation Based on Grid Partition Method
Institute of Scientific and Technical Information of China (English)
李小丽; 陈花竹
2011-01-01
为了提高海量数据的Delaunay三角网的构网速度,本文采用格网划分的三角剖分方法,首先将数据按照线性四叉树方式划分为若干格网块,构建块内子三角网,然后按照自下而上的合并方式对块进行合并,形成全局Delaunay三角网.在此基础上,为了避免出现过小锐角的情况,通过加入约束角来对三角格网进行优化.%To raise the speed of the construction of Delaunay triangulation oriented massive data, this thesis uses the grid partition method. At first, it divides the data into certain grid tiles by quadtree method, constructs sub Delaunay triangulation. Then, it merges two triangulations from bottom up to form the whole Delaunay triangulation. On the basis of that, to avoid producing too acute angles, we give a threshold angle to improve the angles of the triangulation.
The finite body triangulation: algorithms, subgraphs, homogeneity estimation and application.
Carson, Cantwell G; Levine, Jonathan S
2016-09-01
The concept of a finite body Dirichlet tessellation has been extended to that of a finite body Delaunay 'triangulation' to provide a more meaningful description of the spatial distribution of nonspherical secondary phase bodies in 2- and 3-dimensional images. A finite body triangulation (FBT) consists of a network of minimum edge-to-edge distances between adjacent objects in a microstructure. From this is also obtained the characteristic object chords formed by the intersection of the object boundary with the finite body tessellation. These two sets of distances form the basis of a parsimonious homogeneity estimation. The characteristics of the spatial distribution are then evaluated with respect to the distances between objects and the distances within them. Quantitative analysis shows that more physically representative distributions can be obtained by selecting subgraphs, such as the relative neighbourhood graph and the minimum spanning tree, from the finite body tessellation. To demonstrate their potential, we apply these methods to 3-dimensional X-ray computed tomographic images of foamed cement and their 2-dimensional cross sections. The Python computer code used to estimate the FBT is made available. Other applications for the algorithm - such as porous media transport and crack-tip propagation - are also discussed.
Triangulation Algorithm Based on Empty Convex Set Condition
Directory of Open Access Journals (Sweden)
Klyachin Vladimir Aleksandrovich
2015-11-01
Full Text Available The article is devoted to generalization of Delaunay triangulation. We suggest to consider empty condition for special convex sets. For given finite set P ⊂ Rn we shall say that empty condition for convex set B ⊂ Rn is fullfiled if P ∩ B = P ∩ ∂B. Let Φ = Φα, α ∈ A be a family of compact convex sets with non empty inner. Consider some nondegenerate simplex S ⊂ Rn with vertexes p0,...,pn. We define the girth set B(S ∈ Φ if qi ∈ ∂B(S, i = 0, 1, ..., n. We suppose that the family Φ has the property: for arbitrary nondegenerate simplex S there is only one the girth set B(S. We prove the following main result. Theorem 1. If the family Φ = Φα, α ∈ A of convex sets have the pointed above property then for the girth sets it is true: 1. The set B(S is uniquely determined by any simplex with vertexes on ∂B(S. 2. Let S1, S2 be two nondegenerate simplexes such that B(S1 ≠ B(S2. If the intersection B(S1 ∩ B(S2 is not empty, then the intersection of boundaries B(S1, B(S2 is (n − 2-dimensional convex surface, lying in some hyperplane. 3. If two simplexes S1 and S2 don’t intersect by inner points and have common (n − 1-dimensional face G and A, B are vertexes don’t belong to face G and vertex B of simplex B(S2 such that B ∉ B(S1 then B(S2 does not contain the vertex A of simplex S1. These statements allow us to define Φ-triangulation correctly by the following way. The given triangulation T of finite set P ⊂ Rn is called Φ-triangulation if for all simlex S ∈ T the girth set B(S ∈ Φ is empty. In the paper we give algorithm for construct Φ-triangulation arbitrary finite set P ⊂ Rn. Besides we describe examples of families Φ for which we prove the existence and uniqueness of girth set B(S for arbitrary nondegenerate simplex S.
Häfner, M; Liedlgruber, M; Uhl, A; Vécsei, A; Wrba, F
2012-09-01
In this work we propose a method to extract shape-based features from endoscopic images for an automated classification of colonic polyps. This method is based on the density of pits as used in the pit pattern classification scheme which is commonly used for the classification of colonic polyps. For the detection of pits we employ a noise-robust variant of the LBP operator. To be able to be robust against local texture variations we extend this operator by an adaptive thresholding. Based on the detected pit candidates we compute a Delaunay triangulation and use the edge lengths of the resulting triangles to construct histograms. These are then used in conjunction with the k-NN classifier to classify images. We show that, compared to a previously developed method, we are not only able to almost always get higher classification results in our application scenario, but that the proposed method is also able to significantly outperform the previously developed method in terms of the computational demand.
ConnectViz: Accelerated Approach for Brain Structural Connectivity Using Delaunay Triangulation.
Adeshina, A M; Hashim, R
2016-03-01
nodes and the edges. The framework is very efficient in providing greater interactivity as a way of representing the nodes and the edges intuitively, all achieved at a considerably interactive speed for instantaneous mapping of the datasets' features. Uniquely, the connectomic algorithm performed remarkably fast with normal hardware requirement specifications.
Directory of Open Access Journals (Sweden)
Mauro Massayoshi Sakamoto
2008-01-01
Full Text Available In this work, a software package based on the Delaunay´s algorithm is described. The main feature of this package is the capability in applying discretization in geometric domains of teeth taking into account their complex inner structures and the materials with different hardness. Usually, the mesh generators reported in literature treat molars and other teeth by using simplified geometric models, or even considering the teeth as homogeneous structures.
Kinetic Stable Delaunay Graphs
Agarwal, Pankaj K; Guibas, Leonidas J; Kaplan, Haim; Koltun, Vladlen; Rubin, Natan; Sharir, Micha
2011-01-01
We consider the problem of maintaining the Euclidean Delaunay triangulation $\\DT$ of a set $P$ of $n$ moving points in the plane, along algebraic trajectories of constant description complexity. Since the best known upper bound on the number of topological changes in the full $\\DT$ is nearly cubic, we seek to maintain a suitable portion of it that is less volatile yet retains many useful properties. We introduce the notion of a stable Delaunay graph, which is a dynamic subgraph of the Delaunay triangulation. The stable Delaunay graph (a) is easy to define, (b) experiences only a nearly quadratic number of discrete changes, (c) is robust under small changes of the norm, and (d) possesses certain useful properties. The stable Delaunay graph ($\\SDG$ in short) is defined in terms of a parameter $\\alpha>0$, and consists of Delaunay edges $pq$ for which the angles at which $p$ and $q$ see their Voronoi edge $e_{pq}$ are at least $\\alpha$. We show that (i) $\\SDG$ always contains at least roughly one third of the Del...
A Simple Quality Triangulation Algorithm for Complex Geometries
This paper presents a new and simple algorithm for quality triangulation in complex geometries. The proposed algorithm is based on an initial equilateral triangle mesh covering the whole domain. The mesh nodes close to the boundary edges satisfy the so-called non-encroaching criterion: the distance ...
约束数据域的Delaunay三角剖分与修改算法%Delaunay Triangulation of Constrained Data Set
Institute of Scientific and Technical Information of China (English)
刘学军; 龚健雅
2001-01-01
顾及地形特征线的散点域（约束数据域）三角剖分是建立高精度数字地面模型的基础，在GIS、地学分析、计算几何、多分辨率DTM等领域中有着广泛的应用。本文研究了约束数据域的Delaunay三角剖分问题，简要分析了现存的算法特点并提出了约束数据域的Delaunay三角剖分的迭代算法和删除算法。%The triangulation of constrained data set is widely used inGeographic Information System(GIS)，geo-science，computational geometry，multi-resolution and high precision DTM， et al. This paper researches the triangulation of constrained data set and briefly analyses some existing algorithms. A new iterative algorithm and deleting algorithm for triangulating constrained data is proposed.
Alán, Lukáš; Špaček, Tomáš; Ježek, Petr
2016-07-01
Data segmentation and object rendering is required for localization super-resolution microscopy, fluorescent photoactivation localization microscopy (FPALM), and direct stochastic optical reconstruction microscopy (dSTORM). We developed and validated methods for segmenting objects based on Delaunay triangulation in 3D space, followed by facet culling. We applied them to visualize mitochondrial nucleoids, which confine DNA in complexes with mitochondrial (mt) transcription factor A (TFAM) and gene expression machinery proteins, such as mt single-stranded-DNA-binding protein (mtSSB). Eos2-conjugated TFAM visualized nucleoids in HepG2 cells, which was compared with dSTORM 3D-immunocytochemistry of TFAM, mtSSB, or DNA. The localized fluorophores of FPALM/dSTORM data were segmented using Delaunay triangulation into polyhedron models and by principal component analysis (PCA) into general PCA ellipsoids. The PCA ellipsoids were normalized to the smoothed volume of polyhedrons or by the net unsmoothed Delaunay volume and remodeled into rotational ellipsoids to obtain models, termed DVRE. The most frequent size of ellipsoid nucleoid model imaged via TFAM was 35 × 45 × 95 nm; or 35 × 45 × 75 nm for mtDNA cores; and 25 × 45 × 100 nm for nucleoids imaged via mtSSB. Nucleoids encompassed different point density and wide size ranges, speculatively due to different activity stemming from different TFAM/mtDNA stoichiometry/density. Considering twofold lower axial vs. lateral resolution, only bulky DVRE models with an aspect ratio >3 and tilted toward the xy-plane were considered as two proximal nucleoids, suspicious occurring after division following mtDNA replication. The existence of proximal nucleoids in mtDNA-dSTORM 3D images of mtDNA "doubling"-supported possible direct observations of mt nucleoid division after mtDNA replication.
Yet another method for triangulation and contouring for automated cartography
De Floriani, L.; Falcidieno, B.; Nasy, G.; Pienovi, C.
1982-01-01
An algorithm is presented for hierarchical subdivision of a set of three-dimensional surface observations. The data structure used for obtaining the desired triangulation is also singularly appropriate for extracting contours. Some examples are presented, and the results obtained are compared with those given by Delaunay triangulation. The data points selected by the algorithm provide a better approximation to the desired surface than do randomly selected points.
Algorithm for Triangulating Visual Landmarks and Determining Their Covariance
2012-01-01
gyroscopes ........................................ 22 1 1. INTRODUCTION The work described in this report has to do with the problem of vision...IMUs. Because of the small magnitude of random Euler angle errors from even inexpensive gyroscopes , the presented algorithm for triangulation is...gyroscopes9. Silicon-Vibratory MEMs Tactical-grade IFOGs Aviation-Grade Spinning Mass Random gyro rate noise 1 hr/ 0.1 hr/ 0.002 hr/ Random
Morphological algorithms based on Voronoi and Delaunay graphs: microscopic and medical applications
Bertin, Etienne; Marcelpoil, Raphael; Chassery, Jean-Marc
1992-06-01
We illustrate a cooperation between Voronoi diagram and Mathematical Morphology in 2-D and 3-D. Domains of application are multiple: 2-D image segmentation, and 3-D image representation, cellular sociology in 2-D and 3-D. The principal tool that we use is the algorithm of research of connected components in a graph abiding by constraints. The originality takes place in the choice of the constraint parameters. Other tools are used: binary dilation, labeling, and influence zone on graphs. The graph support of our work is the Voronoi diagram, well known for its power of modelling for natural reality. The dual graph of this space partition is the Delaunay graph containing all the neighboring information. The first developed application concerns a method for 2-D and 3-D images segmentation. We have elaborated tools to measure intra-graph structures distance, search of connected component under constraints to extract a 3-d object included in a volume data. The second application we developed concerns the theory of cellular sociology where the set of points identified the location of cells. Our method makes it possible to determine for a given set of cells, a model including its nearest homogeneous set, and the intrinsic disorder to which it refers. In this paper, our methods will be discussed and illustrated in the biological domain.
Institute of Scientific and Technical Information of China (English)
刘洪华; 邓学飞; 杨大哲
2015-01-01
This paper introduces contour-based three-dimensional terrain reconstruction algorithm. The three-dimensional data of discrete points are obtained by digitized contour lines. Delaunay density of discrete points is determined by the density of three-dimensional of contour line points. Three-dimensional model is established by using Delaunay triangulation with the height of discrete points, and then the coordinates and height of each interior point are then calculated. The three-dimensional terrain reconstruction is carried out in PDMS (Plant Design Management System),through which the method described in this article has been proved to be efficient and precise.%提出了一种基于等高线的三维地形重建算法,通过等高线数字化获取离散点的三维数据,根据等高线点的三维密度确定离散点的Delaunay密度值,采用Delaunay三角网结合离散点的高程值进行三维建模,并计算出每一个内点的坐标及高程,然后在PDMS (工厂三维布置设计管理系统)中进行地形的三维重建,实验证明所述方法速度快,精度高.
Experimental study on subaperture testing with iterative triangulation algorithm.
Yan, Lisong; Wang, Xiaokun; Zheng, Ligong; Zeng, Xuefeng; Hu, Haixiang; Zhang, Xuejun
2013-09-23
Applying the iterative triangulation stitching algorithm, we provide an experimental demonstration by testing a Φ120 mm flat mirror, a Φ1450 mm off-axis parabolic mirror and a convex hyperboloid mirror. By comparing the stitching results with the self-examine subaperture, it shows that the reconstruction results are in consistent with that of the subaperture testing. As all the experiments are conducted with a 5-dof adjustment platform with big adjustment errors, it proves that using the above mentioned algorithm, the subaperture stitching can be easily performed without a precise positioning system. In addition, with the algorithm, we accomplish the coordinate unification between the testing and processing that makes it possible to guide the processing by the stitching result.
DEFF Research Database (Denmark)
Gold, Christopher M.; Mioc, Darka; Anton, François
2008-01-01
This chapter presents a methodology for automated cartographic data in- put, drawing and editing. This methodology is based on kinematic algorithms for point and line Delaunay triangulation and the Voronoi diagram. It allows one to automate some parts of the manual digitization process and the to......This chapter presents a methodology for automated cartographic data in- put, drawing and editing. This methodology is based on kinematic algorithms for point and line Delaunay triangulation and the Voronoi diagram. It allows one to automate some parts of the manual digitization process...... as part of the research has been presented. We also describe two reversible line-drawing methods for cartographic applications based on the kinetic (moving-point) Voronoi diagram. Our ob jectives were to optimize the user’s ability to draw and edit the map, rather than to produce the most eﬃcient batch...
Algorithms for Sampling 3-Orientations of Planar Triangulations
Miracle, Sarah; Streib, Amanda Pascoe; Tetali, Prasad
2012-01-01
Given a planar triangulation, a 3-orientation is an orientation of the internal edges so all internal vertices have out-degree three. Each 3-orientation gives rise to a unique edge coloring known as a Schnyder wood that has proven powerful for various computing and combinatorics applications. We consider natural Markov chains for sampling uniformly from the set of 3-orientations. First, we study a "triangle-reversing" chain on the space of 3-orientations of a fixed triangulation that reverses the orientation of the edges around a triangle in each move. It was shown previously that this chain connects the state space and we show that (i) when restricted to planar triangulations of maximum degree six, the Markov chain is rapidly mixing, and (ii) there exists a triangulation with high degree on which this Markov chain mixes slowly. Next, we consider an "edge-flipping" chain on the larger state space consisting of 3-orientations of all planar triangulations on a fixed number of vertices. It was also shown previou...
DEFF Research Database (Denmark)
Gold, Christopher M.; Mioc, Darka; Anton, François
2008-01-01
This chapter presents a methodology for automated cartographic data in- put, drawing and editing. This methodology is based on kinematic algorithms for point and line Delaunay triangulation and the Voronoi diagram. It allows one to automate some parts of the manual digitization process...... as part of the research has been presented. We also describe two reversible line-drawing methods for cartographic applications based on the kinetic (moving-point) Voronoi diagram. Our ob jectives were to optimize the user’s ability to draw and edit the map, rather than to produce the most eﬃcient batch...... and the topological editing of maps that preserve map updates. The manual digitization process is replaced by computer assisted skeletonization using scanned paper maps. We are using the Delaunay triangulation and the Voronoi diagram in order to extract the skeletons that are guaranteed to be topologically correct...
Dynamic Data Updating Algorithm for Image Superresolution Reconstruction
Institute of Scientific and Technical Information of China (English)
TAN Bing; XU Qing; ZHANG Yan; XING Shuai
2006-01-01
A dynamic data updating algorithm for image superesolution is proposed. On the basis of Delaunay triangulation and its local updating property, this algorithm can update the changed region directly under the circumstances that only a part of the source images has been changed. For its high efficiency and adaptability, this algorithm can serve as a fast algorithm for image superesolution reconstruction.
Manacher, G. K.; Zobrist, A. L.
1979-01-01
The paper addresses the problem of how to find the Greedy Triangulation (GT) efficiently in the average case. It is noted that the problem is open whether there exists an efficient approximation algorithm to the Optimum Triangulation. It is first shown how in the worst case, the GT may be obtained in time O(n to the 3) and space O(n). Attention is then given to how the algorithm may be slightly modified to produce a time O(n to the 2), space O(n) solution in the average case. Finally, it is mentioned that Gilbert has found a worst case solution using totally different techniques that require space O(n to the 2) and time O(n to the 2 log n).
Triangulation of cubic panorama for view synthesis.
Zhang, Chunxiao; Zhao, Yan; Wu, Falin
2011-08-01
An unstructured triangulation approach, new to our knowledge, is proposed to apply triangular meshes for representing and rendering a scene on a cubic panorama (CP). It sophisticatedly converts a complicated three-dimensional triangulation into a simple three-step triangulation. First, a two-dimensional Delaunay triangulation is individually carried out on each face. Second, an improved polygonal triangulation is implemented in the intermediate regions of each of two faces. Third, a cobweblike triangulation is designed for the remaining intermediate regions after unfolding four faces to the top/bottom face. Since the last two steps well solve the boundary problem arising from cube edges, the triangulation with irregular-distribution feature points is implemented in a CP as a whole. The triangular meshes can be warped from multiple reference CPs onto an arbitrary viewpoint by face-to-face homography transformations. The experiments indicate that the proposed triangulation approach provides a good modeling for the scene with photorealistic rendered CPs.
Incremental triangulation by way of edge swapping and local optimization
Wiltberger, N. Lyn
1994-01-01
This document is intended to serve as an installation, usage, and basic theory guide for the two dimensional triangulation software 'HARLEY' written for the Silicon Graphics IRIS workstation. This code consists of an incremental triangulation algorithm based on point insertion and local edge swapping. Using this basic strategy, several types of triangulations can be produced depending on user selected options. For example, local edge swapping criteria can be chosen which minimizes the maximum interior angle (a MinMax triangulation) or which maximizes the minimum interior angle (a MaxMin or Delaunay triangulation). It should be noted that the MinMax triangulation is generally only locally optical (not globally optimal) in this measure. The MaxMin triangulation, however, is both locally and globally optical. In addition, Steiner triangulations can be constructed by inserting new sites at triangle circumcenters followed by edge swapping based on the MaxMin criteria. Incremental insertion of sites also provides flexibility in choosing cell refinement criteria. A dynamic heap structure has been implemented in the code so that once a refinement measure is specified (i.e., maximum aspect ratio or some measure of a solution gradient for the solution adaptive grid generation) the cell with the largest value of this measure is continually removed from the top of the heap and refined. The heap refinement strategy allows the user to specify either the number of cells desired or refine the mesh until all cell refinement measures satisfy a user specified tolerance level. Since the dynamic heap structure is constantly updated, the algorithm always refines the particular cell in the mesh with the largest refinement criteria value. The code allows the user to: triangulate a cloud of prespecified points (sites), triangulate a set of prespecified interior points constrained by prespecified boundary curve(s), Steiner triangulate the interior/exterior of prespecified boundary curve
Duals of Orphan-Free Anisotropic Voronoi Diagrams are Triangulations
Canas, Guillermo D
2011-01-01
We show that, under mild conditions on the underlying metric, duals of appropriately defined anisotropic Voronoi diagrams are embedded triangulations. Furthermore, they always triangulate the convex hull of the vertices, and have other properties that parallel those of ordinary Delaunay triangulations. These results apply to the duals of anisotropic Voronoi diagrams of any set of vertices, so long as the diagram is orphan-free.
Generation of Delaunay meshes in implicit domains with edge sharpening
Belokrys-Fedotov, A. I.; Garanzha, V. A.; Kudryavtseva, L. N.
2016-11-01
A variational algorithm for the construction of 3D Delaunay meshes in implicit domains with a nonsmooth boundary is proposed. The algorithm is based on the self-organization of an elastic network in which each Delaunay edge is interpreted as an elastic strut. The elastic potential is constructed as a combination of the repulsion potential and the sharpening potential. The sharpening potential is applied only on the boundary and is used to minimize the deviation of the outward normals to the boundary faces from the direction of the gradient of the implicit function. Numerical experiments showed that in the case when the implicit function specifying the domain is considerably different from the signed distance function, the use of the sharpening potential proposed by Belyaev and Ohtake in 2002 leads to the mesh instability. A stable version of the sharpening potential is proposed. The numerical experiments showed that acceptable Delaunay meshes for complex shaped domains with sharp curved boundary edges can be constructed.
Institute of Scientific and Technical Information of China (English)
周雪梅; 黎应飞
2013-01-01
TIN(Triangulated Irregular Network) has better performance on shaping terrain. The generation algorithm has been great concerned. This paper has discussed the data structure design of triangulation, and designed and implemented the algorithm based on Bowyer-Watson idea that is an incremental insertion algorithm. This paper analyzes why the algorithms may arise the phenomenon of cross during the experiment, and gives the improved idea. The improved algorithm has been used to visualize the terrain modeling, to obtain good results, for the research triangulation has some value.%不规则三角网(Triangulated Irregular Network,TIN)在表示地形的形态方面具有较好的表现,其生成算法一直备受关注.讨论了三角网的数据结构的设计,采用逐点插入算法中的Bowyer-Watson算法思想为研究重点,设计并实现了该算法,对算法实验过程中可能出现的交叉现象进行分析,给出算法的改进.该改进算法已用于地形的可视化建模中,获得了较好的效果,对于三角剖分的相关研究具有一定的价值.
Fast Dynamic Meshing Method Based on Delaunay Graph and Inverse Distance Weighting Interpolation
Wang, Yibin; Qin, Ning; Zhao, Ning
2016-06-01
A novel mesh deformation technique is developed based on the Delaunay graph mapping method and the inverse distance weighting (IDW) interpolation. The algorithm maintains the advantages of the efficiency of Delaunay-graph-mapping mesh deformation while possess the ability for better controlling the near surface mesh quality. The Delaunay graph is used to divide the mesh domain into a number of sub-domains. On each of the sub-domains, the inverse distance weighting interpolation is applied to build a much smaller sized translation matrix between the original mesh and the deformed mesh, resulting a similar efficiency for the mesh deformation as compared to the fast Delaunay graph mapping method. The paper will show how the near-wall mesh quality is controlled and improved by the new method while the computational time is compared with the original Delaunay graph mapping method.
Efficient Delaunay Tessellation through K-D Tree Decomposition
Energy Technology Data Exchange (ETDEWEB)
Morozov, Dmitriy; Peterka, Tom
2017-08-21
Delaunay tessellations are fundamental data structures in computational geometry. They are important in data analysis, where they can represent the geometry of a point set or approximate its density. The algorithms for computing these tessellations at scale perform poorly when the input data is unbalanced. We investigate the use of k-d trees to evenly distribute points among processes and compare two strategies for picking split points between domain regions. Because resulting point distributions no longer satisfy the assumptions of existing parallel Delaunay algorithms, we develop a new parallel algorithm that adapts to its input and prove its correctness. We evaluate the new algorithm using two late-stage cosmology datasets. The new running times are up to 50 times faster using k-d tree compared with regular grid decomposition. Moreover, in the unbalanced data sets, decomposing the domain into a k-d tree is up to five times faster than decomposing it into a regular grid.
Delaunay Refinement Mesh Generation
1997-05-18
determinant evaluation that considers floating- point operands, except for one limited example: Ottmann , Thiemt, and Ullrich [74] advocate the use of an...Sandia National Labo- ratories, October 1996. [74] Thomas Ottmann , Gerald Thiemt, and Christian Ullrich. Numerical Stability of Geometric Algorithms
Energy Technology Data Exchange (ETDEWEB)
Golin, M.J. [Hong Kong Univ. of Science and Technology, Kowloon (Hong Kong)
1996-12-31
Let MWT(n) be the weight of a minimum-weight triangulation of n points chosen independently from the uniform distribution over [0, 1]{sup 2}. Previous work has shown that E(MWT(n)) = {Theta} ({radical}n). In this paper we develop techniques for proving that MWT(n)/{radical}n actually converges to a constant in both expectation and in probability. An immediate consequence is the development of an O(n{sup 2}) time algorithm that finds a triangulation whose competive ratio with the MWT is, in a probabilistic sense, exactly one. The techniques developed to prove the above results are quite general and can also prove the convergence of certain types of probabilistic recurrence equations and other Euclidean Functionals. This is illustrated by using them to prove the convergence of the weight of MWTs of random points in higher dimensions and a sketch of how to use them to prove the convergence of the degree probabilities for Delaunay triangulations in {Re}{sup 2}.
Sequential triangulation of orbital photography
Rajan, M.; Junkins, J. L.; Turner, J. D.
1979-01-01
The feasibility of structuring the satellite photogrammetric triangulation as an iterative Extended Kalman estimation algorithm is demonstrated. Comparative numerical results of the sequential against batch estimation algorithm are presented. Difficulty of accurately modeling of the attitude motion is overcome by utilizing the on-board angular rate measurements. Solutions of the differential equations and the evaluation of state transition matrix are carried out numerically.
Sequential triangulation of orbital photography
Rajan, M.; Junkins, J. L.; Turner, J. D.
1979-01-01
The feasibility of structuring the satellite photogrammetric triangulation as an iterative Extended Kalman estimation algorithm is demonstrated. Comparative numerical results of the sequential against batch estimation algorithm are presented. Difficulty of accurately modeling of the attitude motion is overcome by utilizing the on-board angular rate measurements. Solutions of the differential equations and the evaluation of state transition matrix are carried out numerically.
Quasi-greedy triangulations approximating the minimum weight triangulation
Energy Technology Data Exchange (ETDEWEB)
Levcopoulos, C.; Krznaric, D. [Lund Univ. (Sweden)
1996-12-31
This paper settles the following two open problems: (1) What is the worst-case approximation ratio between the greedy and the minimum weight triangulation? (2) Is there a polynomial time algorithm that always pro- duces a triangulation whose length is within a constant factor from the minimum? The answer to the first question is that the known {Omega}({radical}n) lower bound is tight. The second question is answered in the affirmative by using a slight modification of an O(n log n) algorithm for the greedy triangulation. We also derive some other interesting results. For example, we show that a constant-factor approximation of the minimum weight convex partition can be obtained within the same time bounds.
Pre-Processing Rules for Triangulation of Probabilistic Networks
Bodlaender, H.L.; Koster, A.M.C.A.; Eijkhof, F. van den
2003-01-01
The currently most efficient algorithm for inference with a probabilistic network builds upon a triangulation of a network’s graph. In this paper, we show that pre-processing can help in finding good triangulations for probabilistic networks, that is, triangulations with a minimal maximum clique siz
Pre-processing for Triangulation of Probabilistic Networks
Bodlaender, H.L.; Koster, A.M.C.A.; Eijkhof, F. van den; Gaag, L.C. van der
2001-01-01
The currently most efficient algorithm for inference with a probabilistic network builds upon a triangulation of a networks graph. In this paper, we show that pre-processing can help in finding good triangulations for probabilistic networks, that is, triangulations with a minimal maximum clique
Pre-processing for Triangulation of Probabilistic Networks
Bodlaender, H.L.; Koster, A.M.C.A.; Eijkhof, F. van den; Gaag, L.C. van der
2001-01-01
The currently most efficient algorithm for inference with a probabilistic network builds upon a triangulation of a networks graph. In this paper, we show that pre-processing can help in finding good triangulations for probabilistic networks, that is, triangulations with a minimal maximum clique
New Virtual Cutting Algorithms for 3D Surface Model Reconstructed from Medical Images
Institute of Scientific and Technical Information of China (English)
WANG Wei-hong; QIN Xu-Jia
2006-01-01
This paper proposes a practical algorithms of plane cutting, stereo clipping and arbitrary cutting for 3D surface model reconstructed from medical images. In plane cutting and stereo clipping algorithms, the 3D model is cut by plane or polyhedron. Lists of edge and vertex in every cut plane are established. From these lists the boundary contours are created and their relationship of embrace is ascertained. The region closed by the contours is triangulated using Delaunay triangulation algorithm. Arbitrary cutting operation creates cutting curve interactively.The cut model still maintains its correct topology structure. With these operations,tissues inside can be observed easily and it can aid doctors to diagnose. The methods can also be used in surgery planning of radiotherapy.
Three-Dimensional TIN Algorithm for Digital Terrain Modeling%数字地形建模的真三维TIN算法研究
Institute of Scientific and Technical Information of China (English)
朱庆; 张叶廷; 李逢春
2008-01-01
The problem of taking an unorganized point cloud in 3D space and fitting a polyhedral surface to those points is both important and difficult. Aiming at increasing applications of full three dimensional digital terrain surface modeling, a new algorithm for the automatic generation of three dimensional triangulated irregular network from a point cloud is proposed. Based on the local topological consistency test, a combined algorithm of constrained 3D Delaunay triangulation and region-growing is extended to ensure topologically correct reconstruction. This paper also introduced an efficient neighboring triangle location method by making full use of the surface normal information. Experimental results prove that this algorithm can efficiently obtain the most reasonable reconstructed mesh surface with arbitrary topology, wherein the automatically reconstructed surface has only small topological difference from the true surface. This algorithm has potential applications to virtual environments, computer vision, and so on.
GENERATE TRIANGULATED SURFACES FROM MASSIVE UNORGANIZED POINTS
Institute of Scientific and Technical Information of China (English)
无
2006-01-01
A region-growing method for reconstructing triangulated surfaces from massive unorganized points is presented. To save memory space, a ring data-structure is adopted to build connections between points and triangulated surfaces. The data-structure allows the efficient retrieval of all neighboring vertices and triangles of a given vertice. To narrow the search range of adjacent points and avoid triangle intersection, an influence area is defined for each active-edge. In the region-growing process of triangulated surfaces, a minimum-edge-angle-product algorithm is put forward to select an appropriate point to form a new triangle for an active edge. Results indicate that the presented method has high efficiency and needs less memory space, optimized triangulated surfaces with reliable topological quality can be obtained after triangulation.
Institute of Scientific and Technical Information of China (English)
王家桢; 马良; 张惠珍
2015-01-01
Euclidean Steiner minimum tree problem , a classical NP-hard problem in combination optimization , has been widely studied in many fields .Euclidean Steiner minimal tree problem in 3-space is the generalization of Euclidean Steiner minimum tree problem in 2-space .The research results on Euclidean Steiner minimal tree problem in 3-space have been rarely published because of their difficulties .In this paper , a hybrid intelligent method is designed by using Delaunay tetrahedron mesh generation technology to solve the Euclidean Steiner min -imal tree problem in 3-space , which can not only avoid falling into local optima , but also has good effects in solving large scale problems .Promising results are obtained by using this hybrid method coded in MATLAB to solve series of Euclidean Steiner minimum tree problem instances in 3-space .%Steiner最小树问题是组合优化中经典的NP难题，在许多实际问题中有着广泛的应用，而三维欧氏Stei-ner最小树问题是对二维欧氏Steiner最小树问题的推广。由于三维欧氏Steiner树问题的求解非常困难，至今为止的相关成果较为少见。本文针对该问题，利用Delaunay四面体网格剖分技术，提出了一种混合型智能求解方法，不仅可以尽量避免拓扑结构陷入局部最优，且对较大规模的问题求解亦有良好的效果。算法在Matlab环境下编程实现，经实例测试，获得了满意的效果。
High-Performance Computation of Distributed-Memory Parallel 3D Voronoi and Delaunay Tessellation
Energy Technology Data Exchange (ETDEWEB)
Peterka, Tom; Morozov, Dmitriy; Phillips, Carolyn
2014-11-14
Computing a Voronoi or Delaunay tessellation from a set of points is a core part of the analysis of many simulated and measured datasets: N-body simulations, molecular dynamics codes, and LIDAR point clouds are just a few examples. Such computational geometry methods are common in data analysis and visualization; but as the scale of simulations and observations surpasses billions of particles, the existing serial and shared-memory algorithms no longer suffice. A distributed-memory scalable parallel algorithm is the only feasible approach. The primary contribution of this paper is a new parallel Delaunay and Voronoi tessellation algorithm that automatically determines which neighbor points need to be exchanged among the subdomains of a spatial decomposition. Other contributions include periodic and wall boundary conditions, comparison of our method using two popular serial libraries, and application to numerous science datasets.
Energy Technology Data Exchange (ETDEWEB)
Lindstrom, P
2009-12-23
We describe a simple and efficient algorithm for two-view triangulation of 3D points from approximate 2D matches based on minimizing the L2 reprojection error. Our iterative algorithm improves on the one by Kanatani et al. by ensuring that in each iteration the epipolar constraint is satisfied. In the case where the two cameras are pointed in the same direction, the method provably converges to an optimal solution in exactly two iterations. For more general camera poses, two iterations are sufficient to achieve convergence to machine precision, which we exploit to devise a fast, non-iterative method. The resulting algorithm amounts to little more than solving a quadratic equation, and involves a fixed, small number of simple matrixvector operations and no conditional branches. We demonstrate that the method computes solutions that agree to very high precision with those of Hartley and Sturm's original polynomial method, though achieves higher numerical stability and 1-4 orders of magnitude greater speed.
Protein packing quality using Delaunay complexes
DEFF Research Database (Denmark)
Fonseca, Rasmus; Winter, Pawel; Karplus, Kevin
2011-01-01
A new method for estimating the packing quality of protein structures is presented. Atoms in high quality protein crystal structures are very uniformly distributed which is difficult to reproduce using structure prediction methods. Packing quality measures can therefore be used to assess structures...... of low quality and even to refine them. Previous methods mainly use the Voronoi cells of atoms to assess packing quality. The presented method uses only the lengths of edges in the Delaunay complex which is faster to compute since volumes of Voronoi cells are not evaluated explicitly. This is a novel...... application of the Delaunay complex that can improve the speed of packing quality computations. Doing so is an important step for, e.g., integrating packing measures into structure refinement methods. High- and low-resolution X-ray crystal structures were chosen to represent well- and poorly-packed structures...
Simulating triangulations. Graphs, manifolds and (quantum) spacetime
Energy Technology Data Exchange (ETDEWEB)
Krueger, Benedikt
2016-07-01
Triangulations, which can intuitively be described as a tessellation of space into simplicial building blocks, are structures that arise in various different branches of physics: They can be used for describing complicated and curved objects in a discretized way, e.g., in foams, gels or porous media, or for discretizing curved boundaries for fluid simulations or dissipative systems. Interpreting triangulations as (maximal planar) graphs makes it possible to use them in graph theory or statistical physics, e.g., as small-world networks, as networks of spins or in biological physics as actin networks. Since one can find an analogue of the Einstein-Hilbert action on triangulations, they can even be used for formulating theories of quantum gravity. Triangulations have also important applications in mathematics, especially in discrete topology. Despite their wide occurrence in different branches of physics and mathematics, there are still some fundamental open questions about triangulations in general. It is a prior unknown how many triangulations there are for a given set of points or a given manifold, or even whether there are exponentially many triangulations or more, a question that relates to a well-defined behavior of certain quantum geometry models. Another major unknown question is whether elementary steps transforming triangulations into each other, which are used in computer simulations, are ergodic. Using triangulations as model for spacetime, it is not clear whether there is a meaningful continuum limit that can be identified with the usual and well-tested theory of general relativity. Within this thesis some of these fundamental questions about triangulations are answered by the use of Markov chain Monte Carlo simulations, which are a probabilistic method for calculating statistical expectation values, or more generally a tool for calculating high-dimensional integrals. Additionally, some details about the Wang-Landau algorithm, which is the primary used
Minimal triangulations of simplotopes
Seacrest, Tyler
2009-01-01
We derive lower bounds for the size of simplicial covers of simplotopes, which are products of simplices. These also serve as lower bounds for triangulations of such polytopes, including triangulations with interior vertices. We establish that a minimal triangulation of a product of two simplices is given by a vertex triangulation, i.e., one without interior vertices. For products of more than two simplices, we produce bounds for products of segments and triangles. Our analysis yields linear programs that arise from considerations of covering exterior faces and exploiting the product structure of these polytopes. Aside from cubes, these are the first known lower bounds for triangulations of simplotopes with three or more factors. We also construct a minimal triangulation for the product of a triangle and a square, and compare it to our lower bound.
Denzin, Norman K.
2012-01-01
The author's thesis is simple and direct. Those in the mixed methods qualitative inquiry community need a new story line, one that does not confuse pragmatism for triangulation, and triangulation for mixed methods research (MMR). A different third way is required, one that inspires generative politics and dialogic democracy and helps shape…
Denzin, Norman K.
2012-01-01
The author's thesis is simple and direct. Those in the mixed methods qualitative inquiry community need a new story line, one that does not confuse pragmatism for triangulation, and triangulation for mixed methods research (MMR). A different third way is required, one that inspires generative politics and dialogic democracy and helps shape…
An overview of the stereo correlation and triangulation formulations used in DICe.
Energy Technology Data Exchange (ETDEWEB)
Turner, Daniel Z. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2017-02-01
This document provides a detailed overview of the stereo correlation algorithm and triangulation formulation used in the Digital Image Correlation Engine (DICe) to triangulate three dimensional motion in space given the image coordinates and camera calibration parameters.
Efficient triangulation of Poisson-disk sampled point sets
Guo, Jianwei
2014-05-06
In this paper, we present a simple yet efficient algorithm for triangulating a 2D input domain containing a Poisson-disk sampled point set. The proposed algorithm combines a regular grid and a discrete clustering approach to speedup the triangulation. Moreover, our triangulation algorithm is flexible and performs well on more general point sets such as adaptive, non-maximal Poisson-disk sets. The experimental results demonstrate that our algorithm is robust for a wide range of input domains and achieves significant performance improvement compared to the current state-of-the-art approaches. © 2014 Springer-Verlag Berlin Heidelberg.
Triangulated categories (AM-148)
Neeman, Amnon
2014-01-01
The first two chapters of this book offer a modern, self-contained exposition of the elementary theory of triangulated categories and their quotients. The simple, elegant presentation of these known results makes these chapters eminently suitable as a text for graduate students. The remainder of the book is devoted to new research, providing, among other material, some remarkable improvements on Brown''s classical representability theorem. In addition, the author introduces a class of triangulated categories""--the ""well generated triangulated categories""--and studies their properties. This
Triangulation of NURBS Surfaces
Samareh-Abolhassani, Jamshid
1994-01-01
A technique is presented for triangulation of NURBS surfaces. This technique is built upon an advancing front technique combined with grid point projection. This combined approach has been successfully implemented for structured and unstructured grids.
Triangulation of NURBS Surfaces
Samareh-Abolhassani, Jamshid
1994-01-01
A technique is presented for triangulation of NURBS surfaces. This technique is built upon an advancing front technique combined with grid point projection. This combined approach has been successfully implemented for structured and unstructured grids.
Flip to Regular Triangulation and Convex Hull.
Gao, Mingcen; Cao, Thanh-Tung; Tan, Tiow-Seng
2017-02-01
Flip is a simple and local operation to transform one triangulation to another. It makes changes only to some neighboring simplices, without considering any attribute or configuration global in nature to the triangulation. Thanks to this characteristic, several flips can be independently applied to different small, non-overlapping regions of one triangulation. Such operation is favored when designing algorithms for data-parallel, massively multithreaded hardware, such as the GPU. However, most existing flip algorithms are designed to be executed sequentially, and usually need some restrictions on the execution order of flips, making them hard to be adapted to parallel computation. In this paper, we present an in depth study of flip algorithms in low dimensions, with the emphasis on the flexibility of their execution order. In particular, we propose a series of provably correct flip algorithms for regular triangulation and convex hull in 2D and 3D, with implementations for both CPUs and GPUs. Our experiment shows that our GPU implementation for constructing these structures from a given point set achieves up to two orders of magnitude of speedup over other popular single-threaded CPU implementation of existing algorithms.
Data Reduction and Triangulation Approach to Scattered Points
Institute of Scientific and Technical Information of China (English)
JIANG Dan; WANG Lan-cheng
2004-01-01
For the generation of the model in reverse engineering, a laser scanner is currently used a lot due to the fast measuring speed and high precision. Direct triangulation of data points captured from a physical object has a great advantage in that it can reduce the time and error in modeling process. It is important to reduce the number of data points for triangulating points with maintaining precision. To triangulate data points within a tolerance ε a new approach is developed in this paper. Different level of triangulations can be generated directly from data points using the proposed strategy that reduces and triangulates data points based on triangulation of 3D parametric surfaces. An experimental example is presented to demonstrate the effectiveness and efficiency of the proposed algorithm.
Moment analysis of the Delaunay tessellation field estimator
Lieshout, M.N.M. van
2009-01-01
The Campbell-Mecke theorem is used to derive explicit expressions for the mean and variance of Schaap and Van de Weygaert's Delaunay tessellation field estimator. Special attention is paid to Poisson processes.
Abercromby, Andrew F. J.; Thaxton, Sherry S.; Onady, Elizabeth A.; Rajulu, Sudhakar L.
2006-01-01
The Science Crew Operations and Utility Testbed (SCOUT) project is focused on the development of a rover vehicle that can be utilized by two crewmembers during extra vehicular activities (EVAs) on the moon and Mars. The current SCOUT vehicle can transport two suited astronauts riding in open cockpit seats. Among the aspects currently being developed is the cockpit design and layout. This process includes the identification of possible locations for a socket to which a crewmember could connect a portable life support system (PLSS) for recharging power, air, and cooling while seated in the vehicle. The spaces in which controls and connectors may be situated within the vehicle are constrained by the reach and vision capabilities of the suited crewmembers. Accordingly, quantification of the volumes within which suited crewmembers can both see and reach relative to the vehicle represents important information during the design process.
Oostrom, V. van; Zantema, Hans
2012-01-01
We introduce a process, dubbed triangulation, turning any rewrite relation into a confluent one. It is more direct than usual completion, in the sense that objects connected by a peak are directly oriented rather than their normal forms. We investigate conditions under which this process preserves d
Triangulation in aetiological epidemiology.
Lawlor, Debbie A; Tilling, Kate; Davey Smith, George
2016-12-01
Triangulation is the practice of obtaining more reliable answers to research questions through integrating results from several different approaches, where each approach has different key sources of potential bias that are unrelated to each other. With respect to causal questions in aetiological epidemiology, if the results of different approaches all point to the same conclusion, this strengthens confidence in the finding. This is particularly the case when the key sources of bias of some of the approaches would predict that findings would point in opposite directions if they were due to such biases. Where there are inconsistencies, understanding the key sources of bias of each approach can help to identify what further research is required to address the causal question. The aim of this paper is to illustrate how triangulation might be used to improve causal inference in aetiological epidemiology. We propose a minimum set of criteria for use in triangulation in aetiological epidemiology, summarize the key sources of bias of several approaches and describe how these might be integrated within a triangulation framework. We emphasize the importance of being explicit about the expected direction of bias within each approach, whenever this is possible, and seeking to identify approaches that would be expected to bias the true causal effect in different directions. We also note the importance, when comparing results, of taking account of differences in the duration and timing of exposures. We provide three examples to illustrate these points. © The Author 2017. Published by Oxford University Press on behalf of the International Epidemiological Association.
Oostrom, V. van; Zantema, Hans
2012-01-01
We introduce a process, dubbed triangulation, turning any rewrite relation into a confluent one. It is more direct than usual completion, in the sense that objects connected by a peak are directly oriented rather than their normal forms. We investigate conditions under which this process preserves d
Potts model on directed small-world Voronoi-Delaunay lattices
Marques, R. M.; Lima, F. W. S.; Costa Filho, Raimundo N.
2016-06-01
The critical properties of the Potts model with q = 3 and 4 states in two-dimensions on directed small-world Voronoi-Delaunay random lattices with quenched connectivity disorder are investigated. This disordered system is simulated by applying the Monte Carlo update heat bath algorithm. The Potts model on these directed small-world random lattices presents in fact a second-order phase transition with new critical exponents for q = 3 and value of the rewiring probability p = 0.01, but for q = 4 the system exhibits only a first-order phase transition independent of p (0 < p < 1).
Position and orientation inference via on-board triangulation.
Advani, Madhu; Weile, Daniel S
2017-01-01
This work proposes a new approach to determine the spatial location and orientation of an object using measurements performed on the object itself. The on-board triangulation algorithm we outline could be implemented in lieu of, or in addition to, well-known alternatives such as Global Positioning System (GPS) or standard triangulation, since both of these correspond to significantly different geometric pictures and necessitate different hardware and algorithms. We motivate the theory by describing situations in which on-board triangulation would be useful and even preferable to standard methods. The on-board triangulation algorithm we outline involves utilizing dumb beacons which broadcast omnidirectional single frequency radio waves, and smart antenna arrays on the object itself to infer the direction of the beacon signals, which may be used for onboard calculation of the position and orientation of the object. Numerical examples demonstrate the utility of the method and its noise tolerance.
Institute of Scientific and Technical Information of China (English)
巩垠熙; 何诚; 冯仲科; 李文钊; 闫飞
2013-01-01
针对树冠结构复杂和点云数据量大的特点,为了提高测算单木因子中树冠表面积和体积的精度和效率,通过改进Delaunay三角网的算法机制,提出一种基于空间分割的分块优先级机制的三角网表面重建算法,用于重构树冠表面,形成一种高精度高效率的树冠表面积和体积因子提取方法.利用地面三维激光扫描系统获取树冠点云数据,分别通过传统人工方法、点云量测法、数字高程模型算法与提出的改进SD Delaunay算法,计算实验区域研究对象的树冠表面积与体积,并进行对比分析,结果表明提出的算法完全满足计算精度,同时该计算方法的耗时只有传统人工法的41％,数字高程模型法的62％,大大提高了运算效率.%Crown structure is complex and has huge amount of point cloud data. In order to achieve more accurate and more efficient measurement of crown surface area and volume, the characteristics of existing algorithms were analyzed and an improved triangular mesh surface reconstruction algorithm which is based on spatial division block priority mechanism was proposed for the reconfiguration of the crown surface. A precise and efficient factor extraction method for crown surface area and volume was formed. Crown point cloud data obtained through ground 3-D laser scanning system was used. Through the traditional artificial method, cloud point measurement method, the classics digital elevation model algorithm and the proposed algorithm, the crown surface and volume of the experimental subjects was calculated respectively. The inter comparison of the algorithm results fully meets the calculation accuracy. The time consumption of the proposed algorithm only accounts for 41% of the traditional way and 62% of digital elevation model method, which appears to greatly improve the operation efficiency.
Triangulating Trimmed NURBS Surfaces
2000-01-01
Curve and Surface Design: Saint-Malo 1999 381 Pierre-Jean Laurent, Paul Sablonnibre, and Larry L. Schumaker ( eds .), pp. 381-388. Copyright 0 2000 by...the boundary of its neighboring surface. References 1. Baehmann, P. L., S. L. Wittchen , M. S. Shephard, K. R. Grice and M. A. Yerry, Robust...and D. Eppstein, Mesh generation and optimal triangulation, in Computing in Euclidean Geometry, 2nd ed ., D.-Z. Du and F. K. Hwang, ( eds .), World
Advanced Triangulation Displacement Sensors
Poteet, Wade M.; Cauthen, Harold K.
1996-01-01
Advanced optoelectronic triangulation displacement sensors undergoing development. Highly miniaturized, more stable, more accurate, and relatively easy to use. Incorporate wideband electronic circuits suitable for real-time monitoring and control of displacements. Measurements expected to be accurate to within nanometers. In principle, sensors mass-produced at relatively low unit cost. Potential applications numerous. Possible industrial application in measuring runout of rotating shaft or other moving part during fabrication in "zero-defect" manufacturing system, in which measured runout automatically corrected.
Advanced Triangulation Displacement Sensors
Poteet, Wade M.; Cauthen, Harold K.
1996-01-01
Advanced optoelectronic triangulation displacement sensors undergoing development. Highly miniaturized, more stable, more accurate, and relatively easy to use. Incorporate wideband electronic circuits suitable for real-time monitoring and control of displacements. Measurements expected to be accurate to within nanometers. In principle, sensors mass-produced at relatively low unit cost. Potential applications numerous. Possible industrial application in measuring runout of rotating shaft or other moving part during fabrication in "zero-defect" manufacturing system, in which measured runout automatically corrected.
Institute of Scientific and Technical Information of China (English)
无
2002-01-01
This paper focuses on the methods and process of spatial aggregation based on semantic and geometric characteristics of spatial objects and relations among the objects with the help of spatial data structure (Formal Data Structure),the Local Constrained Delaunay Triangulations and semantic hierarchy.The adjacent relation among connected objects and unconnected objects has been studied through constrained triangle as elementary processing unit in aggregation operation.The hierarchical semantic analytical matrix is given for analyzing the similarity between objects types and between objects.Several different cases of aggregation have been presented in this paper.
Research on Image processing in laser triangulation system
Energy Technology Data Exchange (ETDEWEB)
Liu Kai; Wang Qianqian; Wang Yang; Liu Chenrui, E-mail: qqwang@bit.edu.cn [School of Optoelectronics, Beijing Institute of Technology, 100081 Beijing (China)
2011-02-01
Laser Triangulation Ranging is a kind of displacement distance measurement method which is based on the principle of optical triangulation using laser as the light source. It is superior in simple structure, high-speed, high-accuracy, anti-jamming capability and adaptability laser triangulation ranging. Therefore it is widely used in various fields such as industrial production, road test, three-dimensional face detection, and so on. In current study the features of the spot images achieved by CCD in laser triangulation system were analyzed, and the appropriate algorithms for spot images were discussed. Experimental results showed that the precision and stability of the spot location were enhanced significantly after applying these image processing algorithms.
Refining a triangulation of a planar straight-line graph to eliminate large angles
Energy Technology Data Exchange (ETDEWEB)
Mitchell, S.A.
1993-05-13
Triangulations without large angles have a number of applications in numerical analysis and computer graphics. In particular, the convergence of a finite element calculation depends on the largest angle of the triangulation. Also, the running time of a finite element calculation is dependent on the triangulation size, so having a triangulation with few Steiner points is also important. Bern, Dobkin and Eppstein pose as an open problem the existence of an algorithm to triangulate a planar straight-line graph (PSLG) without large angles using a polynomial number of Steiner points. We solve this problem by showing that any PSLG with {upsilon} vertices can be triangulated with no angle larger than 7{pi}/8 by adding O({upsilon}{sup 2}log {upsilon}) Steiner points in O({upsilon}{sup 2} log{sup 2} {upsilon}) time. We first triangulate the PSLG with an arbitrary constrained triangulation and then refine that triangulation by adding additional vertices and edges. Some PSLGs require {Omega}({upsilon}{sup 2}) Steiner points in any triangulation achieving any largest angle bound less than {pi}. Hence the number of Steiner points added by our algorithm is within a log {upsilon} factor of worst case optimal. We note that our refinement algorithm works on arbitrary triangulations: Given any triangulation, we show how to refine it so that no angle is larger than 7{pi}/8. Our construction adds O(nm+nplog m) vertices and runs in time O(nm+nplog m) log(m+ p)), where n is the number of edges, m is one plus the number of obtuse angles, and p is one plus the number of holes and interior vertices in the original triangulation. A previously considered problem is refining a constrained triangulation of a simple polygon, where p = 1. For this problem we add O({upsilon}{sup 2}) Steiner points, which is within a constant factor of worst case optimal.
Algebraic Error Based Triangulation and Metric of Lines.
Wu, Fuchao; Zhang, Ming; Wang, Guanghui; Hu, Zhanyi
2015-01-01
Line triangulation, a classical geometric problem in computer vision, is to determine the 3D coordinates of a line based on its 2D image projections from more than two views of cameras with known projection matrices. Compared to point features, line segments are more robust to matching errors, occlusions, and image uncertainties. In addition to line triangulation, a better metric is needed to evaluate 3D errors of line triangulation. In this paper, the line triangulation problem is investigated by using the Lagrange multipliers theory. The main contributions include: (i) Based on the Lagrange multipliers theory, a formula to compute the Plücker correction is provided, and from the formula, a new linear algorithm, LINa, is proposed for line triangulation; (ii) two optimal algorithms, OPTa-I and OPTa-II, are proposed by minimizing the algebraic error; and (iii) two metrics on 3D line space, the orthogonal metric and the quasi-Riemannian metric, are introduced for the evaluation of line triangulations. Extensive experiments on synthetic data and real images are carried out to validate and demonstrate the effectiveness of the proposed algorithms.
Observation, innovation and triangulation
DEFF Research Database (Denmark)
Hetmar, Vibeke
2007-01-01
In the article the focus is on classroom research which aims at offering some evidence-based description of the interplay between the logic of practice in school and schooling on the one hand and the teachers' efforts to realize notions of innovation and change on the other hand. Based...... on experiences from a pilot project in three different classrooms methodological possibilities and problems are presented and discussed: 1) educational criticism, including the concepts of positions, perspectives and connoisseurship, 2) classroom observations and 3) triangulation as a methodological tool....
The use of triangulation in qualitative research.
Carter, Nancy; Bryant-Lukosius, Denise; DiCenso, Alba; Blythe, Jennifer; Neville, Alan J
2014-09-01
Triangulation refers to the use of multiple methods or data sources in qualitative research to develop a comprehensive understanding of phenomena (Patton, 1999). Triangulation also has been viewed as a qualitative research strategy to test validity through the convergence of information from different sources. Denzin (1978) and Patton (1999) identified four types of triangulation: (a) method triangulation, (b) investigator triangulation, (c) theory triangulation, and (d) data source triangulation. The current article will present the four types of triangulation followed by a discussion of the use of focus groups (FGs) and in-depth individual (IDI) interviews as an example of data source triangulation in qualitative inquiry.
Genus dependence of the number of (non-)orientable surface triangulations
Krüger, Benedikt; Mecke, Klaus
2016-04-01
Topological triangulations of orientable and nonorientable surfaces with arbitrary genus have important applications in quantum geometry, graph theory and statistical physics. However, until now, only the asymptotics for 2-spheres have been known analytically, and exact counts of triangulations are only available for both small genera and triangulations. We apply the Wang-Landau algorithm to calculate the number N (m ,h ) of triangulations for several orders of magnitude in system size m and type h (equals genus in orientable triangulations). We verify that the limit of the entropy density of triangulations is independent of genus and orientability and are able to determine the next-to-leading-order and the next-to-next-to-leading-order terms. We conjecture for the number of surface triangulations the asymptotic behavior N (m ,h )→(170.4 ±15.1 )hm-2 (h -1 )/5(256/27) m /2, which might guide a mathematician's proof for the exact asymptotics.
一种基于SfM重建点云的三角网格化算法%Triangulation algorithm based on point clouds reconstructed by SfM
Institute of Scientific and Technical Information of China (English)
陈庭旺; 王庆
2011-01-01
This paper proposed an improved region growing based triangulation algorithm for surface modeling problem from point clouds reconstructed by SfM. Defined a k-nearest neighbor influence region to improve the topological stability. It organized candidate triangles efficiently by binary sort tree and accomplished holes detection by a searching strategy using undirected loop. Finally, achieved a complete triangular mesh. Experimental results show that, compared to Possion surface reconstruction, the algorithm can significantly improve the computational efficiency and acquire a high reconstructed accuracy,which helps to improve the performance of 3D surface reconstruction and model rendering.%针对SfM重建点云的曲面建模问题,提出一种改进的区域增长网格化算法.定义k近邻影响域提高拓扑稳定性,引入二叉排序树高效地组织候选三角片,采用无向环搜索策略完成孔洞的检测,最终获得完整的三角网格面.实验结果表明,该算法相比于Possion曲面重建,在获得高的重建精度的同时显著提高了计算效率,有助于提升3D曲面重建与模型表现的性能.
Mutating loops and 2-cycles in 2-CY triangulated categories
Bertani-Økland, Marco Angel
2010-01-01
We derive an algorithm for mutating quivers of 2-CY tilted algebras that have loops and 2-cycles, under certain specific conditions. Further, we give the classification of the 2-CY tilted algebras coming from standard algebraic 2-CY triangulated categories with a finite number of indecomposables. These form a class of algebras that satisfy the setup for our mutation algorithm.
Introduction to causal dynamical triangulations
DEFF Research Database (Denmark)
Görlich, Andrzej
2013-01-01
The method of causal dynamical triangulations is a non-perturbative and background-independent approach to quantum theory of gravity. In this review we present recent results obtained within the four dimensional model of causal dynamical triangulations. We describe the phase structure of the mode...
一种适合VRML应用的平面三角剖分快速算法%A Fast Planar Region Triangulation Algorithm Fit for VRML Application
Institute of Scientific and Technical Information of China (English)
孙宏伟; 王健; 杨百龙; 张树生
2001-01-01
产品数据向Web使能数据的格式转换是实现异地、异构环境下产品信息共享的一条有效途径.VRML作为三维场景的描述语言得到了广泛应用，成为产品数据Web使能的载体.为了满足VRML应用的需要，提出了一种改进的从平面多连通域到单连通域的快速切分归并方法，介绍了一种任意平面连通域的三角剖分算法，并对生成的三角面片进行合并.整个算法具有速度快、生成三角面片较少的优点.%Transforming product data into Web-enabled format is a feasible way to realize the product information sharing in a distributed heterogeneous environment. VRML is widely used as the Web-enabled description language to present 3D views of products. The authors introduced an improved fast algorithm for transforming multiple connected planar regions into simple connected ones, tessellate it into triangular meshes and combine small triangles into large ones. This algorithm has the merits of fast speed and few triangles， thus suitable to be applied to VRML presentation.
Fundamental triangulation networks in Denmark
Directory of Open Access Journals (Sweden)
Borre Kai
2014-04-01
Full Text Available The first triangulation activity on Danish ground was carried out by the astronomer Tycho Brahe who resided on the island Hven. He wanted to determine the longitude difference of his observatory Uraniborg to Copenhagen. A by-product was a map of his island made in 1579. In 1761 the Royal Danish Academy of Sciences and Letters initiated a mapping project which should be based on the principle of triangulation. Eventually 24 maps were printed in varying scales, predominantly in 1:120 000. The last map was engraved in 1842. The Danish GradeMeasurement initiated remeasurements and redesign of the fundamental triangulation network. This network served scientific as well as cartographic purposes in more than a century. Only in the 1960s all triangulation sides were measured electronically. A combined least-squares adjustment followed in the 1970s
Spanning quadrangulations of triangulated surfaces
DEFF Research Database (Denmark)
Kündgen, André; Thomassen, Carsten
2017-01-01
In this paper we study alternating cycles in graphs embedded in a surface. We observe that 4-vertex-colorability of a triangulation on a surface can be expressed in terms of spanninq quadrangulations, and we establish connections between spanning quadrangulations and cycles in the dual graph which...... are noncontractible and alternating with respect to a perfect matching. We show that the dual graph of an Eulerian triangulation of an orientable surface other than the sphere has a perfect matching M and an M-alternating noncontractible cycle. As a consequence, every Eulerian triangulation of the torus has...... a nonbipartite spanning quadrangulation. For an Eulerian triangulation G of the projective plane the situation is different: If the dual graph G∗ is nonbipartite, then G∗ has no noncontractible alternating cycle, and all spanning quadrangulations of G are bipartite. If the dual graph G∗ is bipartite, then it has...
`Optimal' triangulation of surfaces and bodies
Traas, C.R.
1999-01-01
A new criterion is given for constructing an optimal triangulation of surfaces and bodies. The triangulation, called the {\\em tight} triangulation, is convexity preserving and accepts long, thin triangles whenever they are useful. Both properties are not shared by the maxmin triangulation, which in
"Optimal" triangulation of surfaces and bodies
Traas, C.R.
1999-01-01
A new criterion is given for constructing an optimal triangulation of surfaces and bodies. The triangulation, called the {\\em tight} triangulation, is convexity preserving and accepts long, thin triangles whenever they are useful. Both properties are not shared by the maxmin triangulation, which in
DEFF Research Database (Denmark)
an overview of existing triangulation methods with emphasis on performance versus optimality, and will suggest a fast triangulation algorithm based on linear constraints. The structure and camera motion estimation in a SFM system is based on the minimization of some norm of the reprojection error between...
Issues in using methodological triangulation in research.
Casey, Dympna; Murphy, Kathy
2009-01-01
This paper describes how methodological triangulation was used in two nursing research studies. The literature identified a number of principles in reporting studies that used triangulation, including giving the rationale for using triangulation, detailing the process used to assist with triangulation and explaining how rigour was maintained. A brief review of triangulated studies revealed that few adhered fully to these principles. A 'within method' and an 'across method' study are used to illustrate how methodological triangulation was used, and the ways in which rigour was addressed are also described. In addition, the different contributions of triangulation to nursing research are highlighted.
Fat Triangulations and Differential Geometry
Saucan, Emil
2011-01-01
We study the differential geometric consequences of our previous result on the existence of fat triangulations, in conjunction with a result of Cheeger, M\\"{u}ller and Schrader, regarding the convergence of Lipschitz-Killing curvatures of piecewise-flat approximations of smooth Riemannian manifolds. A further application to the existence of quasiconformal mappings between manifolds, as well as an extension of the triangulation result to the case of almost Riemannian manifolds, are also given. In addition, the notion of fatness of triangulations and its relation to metric curvature and to excess is explored. Moreover, applications of the main results, and in particular a purely metric approach to Regge calculus, are also investigated.
The Construction of Sorkin Triangulations
Tuckey, P A
1993-01-01
Some time ago, Sorkin (1975) reported investigations of the time evolution and initial value problems in Regge calculus, for one triangulation each of the manifolds $R*S^3$ and $R^4$. Here we display the simple, local characteristic of those triangulations which underlies the structure found by Sorkin, and emphasise its general applicability, and therefore the general validity of Sorkin's conclusions. We also make some elementary observations on the resulting structure of the time evolution and initial value problems in Regge calculus, and add some comments and speculations.
Indian Academy of Sciences (India)
R Sharma; O P Sha
2006-10-01
Design of fair surfaces over irregular domains is a fundamental problem in computer-aided geometric design (CAGD), and has applications in engineering sciences (in aircraft, automobile, ship science etc.). In the design of fair surfaces over irregular domains deﬁned over scattered data, it was widely accepted till recently that the classical Delaunay triangulation be used because of its global optimum property. However, in recent times it has been shown that for continuous piecewise linear surfaces, improvements in the quality of ﬁt can be achieved if the triangulation pattern is made dependent upon some topological or geometric property of the data set or is simply data dependent. The fair surface is desired because it ensures smooth and continuous surface planar cuts, and these in turn ensure smooth and easy production of the surface in CAD/CAM, and favourable resistance properties. In this paper, we discuss a method for construction of $C^1$ piecewise polynomial parametric fair surfaces which interpolate prescribed $\\mathfrak{R}^3$ scattered data using spaces of parametric splines deﬁned on $\\mathfrak{R}^3$ triangulation. We show that our method is more speciﬁc to the cases when the projection on a 2-D plane may consist of triangles of zero area, numerically stable and robust, and computationally inexpensive and fast. Numerical examples dealing with surfaces approximated on plates, and on ships have been presented.
Obtaining the Andersen's chart, triangulation algorithm
DEFF Research Database (Denmark)
Sabaliauskas, Tomas; Ibsen, Lars Bo
Andersen’s chart (Andersen & Berre, 1999) is a graphical method of observing cyclic soil response. It allows observing soil response to various stress amplitudes that can lead to liquefaction, excess plastic deformation or stabilizing soil response. The process of obtaining the original chart has...
Directory of Open Access Journals (Sweden)
Rongxin Tang
2015-10-01
Full Text Available Mobile sensor networks are an important part of modern robotics systems and are widely used in robotics applications. Therefore, sensor deployment is a key issue in current robotics systems research. Since it is one of the most popular deployment methods, in recent years the virtual force algorithm has been studied in detail by many scientists. In this paper, we focus on the virtual force algorithm and present a corresponding parameter investigation for mobile sensor deployment. We introduce an optimized virtual force algorithm based on the exchange force, in which a new shielding rule grounded in Delaunay triangulation is adopted. The algorithm employs a new performance metric called ’pair-correlation diversion’, designed to evaluate the uniformity and topology of the sensor distribution. We also discuss the implementation of the algorithm’s computation and analyse the influence of experimental parameters on the algorithm. Our results indicate that the area ratio, φs, and the exchange force constant, G, influence the final performance of the sensor deployment in terms of the coverage rate, the convergence time and topology uniformity. Using simulations, we were able to verify the effectiveness of our algorithm and we obtained an optimal region for the (φs, G-parameter space which, in the future, could be utilized as an aid for experiments in robotic sensor deployment.
Fundamental triangulation networks in Denmark
DEFF Research Database (Denmark)
Borre, Kai
2014-01-01
Academy of Sciences and Letters initiated a mapping project which should be based on the principle of triangulation. Eventually 24 maps were printed in varying scales, predominantly in 1:120 000. The last map was engraved in 1842. The Danish GradeMeasurement initiated remeasurements and redesign...
Surface roughness measurement with laser triangulation
Bai, Fuzhong; Zhang, Xiaoyan; Tian, Chaoping
2016-09-01
A surface roughness measurement method is introduced in the paper, which is based on laser triangulation and digital image processing technique. In the measuring system, we use the line-structured light as light source, microscope lens and high-accuracy CCD sensor as displacement sensor as well. In addition, the working angle corresponding to the optimal sensitivity is considered in the optical structure design to improve the measuring accuracy. Through necessary image processing operation for the light strip image, such as center-line extraction with the barycenter algorithm, Gaussian filtering, the value of roughness is calculated. A standard planing surface is measured experimentally with the proposed method and the stylus method (Mitutoyo SJ-410) respectively. The profilograms of surface appearance are greatly similar in the shape and the amplitude to two methods. Also, the roughness statistics values are close. The results indicate that the laser triangulation with the line-structured light can be applied to measure the surface roughness with the advantages of rapid measurement and visualized display of surface roughness profile.
Phenomenology of Causal Dynamical Triangulations
Mielczarek, Jakub
2015-01-01
The four dimensional Causal Dynamical Triangulations (CDT) approach to quantum gravity is already more than ten years old theory with numerous unprecedented predictions such as non-trivial phase structure of gravitational field and dimensional running. Here, we discuss possible empirical consequences of CDT derived based on the two features of the approach mentioned above. A possibility of using both astrophysical and cosmological observations to test CDT is discussed. We show that scenarios which can be ruled out at the empirical level exist.
Volumes of Polytopes Without Triangulations
Enciso, Michael
2014-01-01
We introduce a new formalism for defining and computing the volumes of completely general polytopes in any dimension. The expressions that we obtain for these volumes are independent of any triangulation, and manifestly depend only on the vertices of the underlying polytope. As one application of this formalism, we obtain new expressions for tree-level, n-point NMHV amplitudes in N=4 Super Yang-Mills (SYM) theory.
Random discrete Morse theory and a new library of triangulations
DEFF Research Database (Denmark)
Benedetti, Bruno; Lutz, Frank Hagen
2014-01-01
We introduce random discrete Morse theory as a computational scheme to measure the complexity of a triangulation. The idea is to try to quantify the frequency of discrete Morse matchings with few critical cells. Our measure will depend on the topology of the space, but also on how nicely the space......” for testing algorithms based on discrete Morse theory. We propose a new library containing more complicated (and thus more meaningful) test examples....
On the isomorphism between the medial axis and a dual of the Delaunay graph
DEFF Research Database (Denmark)
Sharma, Ojaswa; Anton, François; Mioc, Darka
2009-01-01
In this paper, we show a graph isomorphism between a dual graph of the Delaunay graph of the sampled points and the medial axis of the sampled features. This dual graph captures the fact that two Delaunay triangles share two vertices or an edge. Then, we apply it to the computation of the medial ...... of (satellite) imagery and scanned maps. Applications include coastline extraction, extraction of fields, clear cuts, clouds, as well as heating or pollution monitoring and dense forest mapping among others....
Surface Triangulation for CSG in Mercury
Energy Technology Data Exchange (ETDEWEB)
Engel, Daniel [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Georgia Inst. of Technology, Atlanta, GA (United States); O' Brien, Matthew J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
2015-08-26
Visualization routines for rendering complicated geometries are very useful for engineers and scientists who are trying to build 3D prototypes of their designs. A common way to rapidly add interesting features to a 3D model is through the use of a concept called Constructive Solid Geometry. CSG uses compositions of the boolean set operations to manipulate basic geometric primitives to form more complicated objects. The most common boolean operations employed are union, intersection, and subtraction. Most computer-aided design software packages contain some sort of ability visualize CSG. The typical workflow for the user is as follows: The user specifies the individual primitive components, the user arbitrarily combines each of these primitives with boolean operations, the software generates a CSG tree structure which normally stores these solids implicitly with their defining equation, the tree is traversed and a general algorithm is applied to render the appropriate geometry onto the screen. Algorithms for visualizing CSG have been extensively developed for over a decade. Points sampled from the implicit solids are typically used as input by variations of algorithms like marching cubes and point-cloud surface reconstruction. Here, we explain a surface triangulation method from the graphics community that is being used for surface visualization in the framework of a Monte-Carlo neutron transport code called Mercury.
3D building reconstruction from lidar data based on Delaunay TIN approach
Zhang, Dongdong; Du, Peijun
2011-10-01
With a great progress in the research on digital city and related commercial applications, the construction of 3D city models has been matured gradually as a research topic in recent years. When constructing 3D city models on large scale, it is inevitable to have available reconstruction tools that offer a high level of automation and produce valid models reliably within the required accuracy. In this paper, a new method for the automatic generation of 3D building models from directly observed point cloud captured by airborne LiDAR system is presented. At first, Delaunay TIN model is constructed based on the building points. Then an edge length ratio based trace algorithm is used for refining the building's boundary. And the extracted outlines are regularized applying the regression analysis to obtain the better geometric quality. Then the same plane points set are clustered via those points in a triangle facet having the similar normal vector value, which determines the roof structures. Finally, with the regular outlines and roof structures information, the building models are constructed. The data in the study area provided by www.terrasolid.fi are used to test the approach. The experimental results show that this proposed approach is able to construct building models effectively.
The role of convexity for solving some shortest path problems in plane without triangulation
An, Phan Thanh; Hai, Nguyen Ngoc; Hoai, Tran Van
2013-09-01
Solving shortest path problems inside simple polygons is a very classical problem in motion planning. To date, it has usually relied on triangulation of the polygons. The question: "Can one devise a simple O(n) time algorithm for computing the shortest path between two points in a simple polygon (with n vertices), without resorting to a (complicated) linear-time triangulation algorithm?" raised by J. S. B. Mitchell in Handbook of Computational Geometry (J. Sack and J. Urrutia, eds., Elsevier Science B.V., 2000), is still open. The aim of this paper is to show that convexity contributes to the design of efficient algorithms for solving some versions of shortest path problems (namely, computing the convex hull of a finite set of points and convex rope on rays in 2D, computing approximate shortest path between two points inside a simple polygon) without triangulation on the entire polygons. New algorithms are implemented in C and numerical examples are presented.
Triangulation of Data Analysis Techniques
Directory of Open Access Journals (Sweden)
Lauri, M
2011-10-01
Full Text Available In psychology, as in other disciplines, the concepts of validity and reliability are considered essential to give an accurate interpretation of results. While in quantitative research the idea is well established, in qualitative research, validity and reliability take on a different dimension. Researchers like Miles and Huberman (1994 and Silverman (2000, 2001, have shown how these issues are addressed in qualitative research. In this paper I am proposing that the same corpus of data, in this case the transcripts of focus group discussions, can be analysed using more than one data analysis technique. I refer to this idea as ‘triangulation of data analysis techniques’ and argue that such triangulation increases the reliability of the results. If the results obtained through a particular data analysis technique, for example thematic analysis, are congruent with the results obtained by analysing the same transcripts using a different technique, for example correspondence analysis, it is reasonable to argue that the analysis and interpretation of the data is valid.
On a Linear Program for Minimum-Weight Triangulation
Yousefi, Arman
2011-01-01
Minimum-weight triangulation (MWT) is NP-hard. It has a polynomial-time constant-factor approximation algorithm, and a variety of effective polynomial- time heuristics that, for many instances, can find the exact MWT. Linear programs (LPs) for MWT are well-studied, but previously no connection was known between any LP and any approximation algorithm or heuristic for MWT. Here we show the first such connections: for an LP formulation due to Dantzig et al. (1985): (i) the integrality gap is bounded by a constant; (ii) given any instance, if the aforementioned heuristics find the MWT, then so does the LP.
Mixed Methods, Triangulation, and Causal Explanation
Howe, Kenneth R.
2012-01-01
This article distinguishes a disjunctive conception of mixed methods/triangulation, which brings different methods to bear on different questions, from a conjunctive conception, which brings different methods to bear on the same question. It then examines a more inclusive, holistic conception of mixed methods/triangulation that accommodates…
Mixed Methods, Triangulation, and Causal Explanation
Howe, Kenneth R.
2012-01-01
This article distinguishes a disjunctive conception of mixed methods/triangulation, which brings different methods to bear on different questions, from a conjunctive conception, which brings different methods to bear on the same question. It then examines a more inclusive, holistic conception of mixed methods/triangulation that accommodates…
The DEEP2 Galaxy Redshift Survey: The Voronoi-Delaunay Method Catalog of Galaxy Groups
Energy Technology Data Exchange (ETDEWEB)
Gerke, Brian F.; /UC, Berkeley; Newman, Jeffrey A.; /LBNL, NSD; Davis, Marc; /UC, Berkeley /UC, Berkeley, Astron.Dept.; Marinoni, Christian; /Brera Observ.; Yan, Renbin; Coil, Alison L.; Conroy, Charlie; Cooper, Michael C.; /UC, Berkeley, Astron.Dept.; Faber, S.M.; /Lick Observ.; Finkbeiner, Douglas P.; /Princeton U. Observ.; Guhathakurta, Puragra; /Lick Observ.; Kaiser, Nick; /Hawaii U.; Koo, David C.; Phillips, Andrew C.; /Lick Observ.; Weiner, Benjamin J.; /Maryland U.
2012-02-14
We use the first 25% of the DEEP2 Galaxy Redshift Survey spectroscopic data to identify groups and clusters of galaxies in redshift space. The data set contains 8370 galaxies with confirmed redshifts in the range 0.7 {<=} z {<=} 1.4, over one square degree on the sky. Groups are identified using an algorithm (the Voronoi-Delaunay Method) that has been shown to accurately reproduce the statistics of groups in simulated DEEP2-like samples. We optimize this algorithm for the DEEP2 survey by applying it to realistic mock galaxy catalogs and assessing the results using a stringent set of criteria for measuring group-finding success, which we develop and describe in detail here. We find in particular that the group-finder can successfully identify {approx}78% of real groups and that {approx}79% of the galaxies that are true members of groups can be identified as such. Conversely, we estimate that {approx}55% of the groups we find can be definitively identified with real groups and that {approx}46% of the galaxies we place into groups are interloper field galaxies. Most importantly, we find that it is possible to measure the distribution of groups in redshift and velocity dispersion, n({sigma}, z), to an accuracy limited by cosmic variance, for dispersions greater than 350 km s{sup -1}. We anticipate that such measurements will allow strong constraints to be placed on the equation of state of the dark energy in the future. Finally, we present the first DEEP2 group catalog, which assigns 32% of the galaxies to 899 distinct groups with two or more members, 153 of which have velocity dispersions above 350 km s{sup -1}. We provide locations, redshifts and properties for this high-dispersion subsample. This catalog represents the largest sample to date of spectroscopically detected groups at z {approx} 1.
The DEEP2 Galaxy Redshift Survey: The Voronoi-Delaunay Method Catalog of Galaxy Groups
Energy Technology Data Exchange (ETDEWEB)
Gerke, Brian F.; /UC, Berkeley; Newman, Jeffrey A.; /LBNL, NSD; Davis, Marc; /UC, Berkeley /UC, Berkeley, Astron.Dept.; Marinoni, Christian; /Brera Observ.; Yan, Renbin; Coil, Alison L.; Conroy, Charlie; Cooper, Michael C.; /UC, Berkeley, Astron.Dept.; Faber, S.M.; /Lick Observ.; Finkbeiner, Douglas P.; /Princeton U. Observ.; Guhathakurta, Puragra; /Lick Observ.; Kaiser, Nick; /Hawaii U.; Koo, David C.; Phillips, Andrew C.; /Lick Observ.; Weiner, Benjamin J.; /Maryland U.
2012-02-14
We use the first 25% of the DEEP2 Galaxy Redshift Survey spectroscopic data to identify groups and clusters of galaxies in redshift space. The data set contains 8370 galaxies with confirmed redshifts in the range 0.7 {<=} z {<=} 1.4, over one square degree on the sky. Groups are identified using an algorithm (the Voronoi-Delaunay Method) that has been shown to accurately reproduce the statistics of groups in simulated DEEP2-like samples. We optimize this algorithm for the DEEP2 survey by applying it to realistic mock galaxy catalogs and assessing the results using a stringent set of criteria for measuring group-finding success, which we develop and describe in detail here. We find in particular that the group-finder can successfully identify {approx}78% of real groups and that {approx}79% of the galaxies that are true members of groups can be identified as such. Conversely, we estimate that {approx}55% of the groups we find can be definitively identified with real groups and that {approx}46% of the galaxies we place into groups are interloper field galaxies. Most importantly, we find that it is possible to measure the distribution of groups in redshift and velocity dispersion, n({sigma}, z), to an accuracy limited by cosmic variance, for dispersions greater than 350 km s{sup -1}. We anticipate that such measurements will allow strong constraints to be placed on the equation of state of the dark energy in the future. Finally, we present the first DEEP2 group catalog, which assigns 32% of the galaxies to 899 distinct groups with two or more members, 153 of which have velocity dispersions above 350 km s{sup -1}. We provide locations, redshifts and properties for this high-dispersion subsample. This catalog represents the largest sample to date of spectroscopically detected groups at z {approx} 1.
Automatic Generation of CFD-Ready Surface Triangulations from CAD Geometry
Aftosmis, M. J.; Delanaye, M.; Haimes, R.; Nixon, David (Technical Monitor)
1998-01-01
This paper presents an approach for the generation of closed manifold surface triangulations from CAD geometry. CAD parts and assemblies are used in their native format, without translation, and a part's native geometry engine is accessed through a modeler-independent application programming interface (API). In seeking a robust and fully automated procedure, the algorithm is based on a new physical space manifold triangulation technique which was developed to avoid robustness issues associated with poorly conditioned mappings. In addition, this approach avoids the usual ambiguities associated with floating-point predicate evaluation on constructed coordinate geometry in a mapped space, The technique is incremental, so that each new site improves the triangulation by some well defined quality measure. Sites are inserted using a variety of priority queues to ensure that new insertions will address the worst triangles first, As a result of this strategy, the algorithm will return its 'best' mesh for a given (prespecified) number of sites. Alternatively, the algorithm may be allowed to terminate naturally after achieving a prespecified measure of mesh quality. The resulting triangulations are 'CFD-ready' in that: (1) Edges match the underlying part model to within a specified tolerance. (2) Triangles on disjoint surfaces in close proximity have matching length-scales. (3) The algorithm produces a triangulation such that no angle is less than a given angle bound, alpha, or greater than Pi - 2alpha This result also sets bounds on the maximum vertex degree, triangle aspect-ratio and maximum stretching rate for the triangulation. In addition to tile output triangulations for a variety of CAD parts, tile discussion presents related theoretical results which assert the existence of such all angle bound, and demonstrate that maximum bounds of between 25 deg and 30 deg may be achieved in practice.
Interferometer predictions with triangulated images
DEFF Research Database (Denmark)
Brinch, Christian; Dullemond, C. P.
2014-01-01
Interferometers play an increasingly important role for spatially resolved observations. If employed at full potential, interferometry can probe an enormous dynamic range in spatial scale. Interpretation of the observed visibilities requires the numerical computation of Fourier integrals over...... the synthetic model images. To get the correct values of these integrals, the model images must have the right size and resolution. Insufficient care in these choices can lead to wrong results. We present a new general-purpose scheme for the computation of visibilities of radiative transfer images. Our method...... requires a model image that is a list of intensities at arbitrarily placed positions on the image-plane. It creates a triangulated grid from these vertices, and assumes that the intensity inside each triangle of the grid is a linear function. The Fourier integral over each triangle is then evaluated...
On deformations of triangulated models
De Deken, Olivier
2012-01-01
This paper is the first part of a project aimed at understanding deformations of triangulated categories, and more precisely their dg and A infinity models, and applying the resulting theory to the models occurring in the Homological Mirror Symmetry setup. In this first paper, we focus on models of derived and related categories, based upon the classical construction of twisted objects over a dg or $A_{\\infty}$-algebra. For a Hochschild 2 cocycle on such a model, we describe a corresponding "curvature compensating" deformation which can be entirely understood within the framework of twisted objects. We unravel the construction in the specific cases of derived A infinity and abelian categories, homotopy categories, and categories of graded free qdg-modules. We identify a purity condition on our models which ensures that the structure of the model is preserved under deformation. This condition is typically fulfilled for homotopy categories, but not for unbounded derived categories.
Unaldi, Numan; Temel, Samil; Asari, Vijayan K.
2012-01-01
One of the most critical issues of Wireless Sensor Networks (WSNs) is the deployment of a limited number of sensors in order to achieve maximum coverage on a terrain. The optimal sensor deployment which enables one to minimize the consumed energy, communication time and manpower for the maintenance of the network has attracted interest with the increased number of studies conducted on the subject in the last decade. Most of the studies in the literature today are proposed for two dimensional (2D) surfaces; however, real world sensor deployments often arise on three dimensional (3D) environments. In this paper, a guided wavelet transform (WT) based deployment strategy (WTDS) for 3D terrains, in which the sensor movements are carried out within the mutation phase of the genetic algorithms (GAs) is proposed. The proposed algorithm aims to maximize the Quality of Coverage (QoC) of a WSN via deploying a limited number of sensors on a 3D surface by utilizing a probabilistic sensing model and the Bresenham's line of sight (LOS) algorithm. In addition, the method followed in this paper is novel to the literature and the performance of the proposed algorithm is compared with the Delaunay Triangulation (DT) method as well as a standard genetic algorithm based method and the results reveal that the proposed method is a more powerful and more successful method for sensor deployment on 3D terrains. PMID:22666078
Blind guidance system based on laser triangulation
Wu, Jih-Huah; Wang, Jinner-Der; Fang, Wei; Lee, Yun-Parn; Shan, Yi-Chia; Kao, Hai-Ko; Ma, Shih-Hsin; Jiang, Joe-Air
2012-05-01
We propose a new guidance system for the blind. An optical triangulation method is used in the system. The main components of the proposed system comprise of a notebook computer, a camera, and two laser modules. The track image of the light beam on the ground or on the object is captured by the camera and then the image is sent to the notebook computer for further processing and analysis. Using a developed signal-processing algorithm, our system can determine the object width and the distance between the object and the blind person through the calculation of the light line positions on the image. A series of feasibility tests of the developed blind guidance system were conducted. The experimental results show that the distance between the test object and the blind can be measured with a standard deviation of less than 8.5% within the range of 40 and 130 cm, while the test object width can be measured with a standard deviation of less than 4.5% within the range of 40 and 130 cm. The application potential of the designed system to the blind guidance can be expected.
Rail profile control using laser triangulation scanners
Boronahin, Ð. ńlexandr M.; Larionov, Daniil Yu.; Podgornaya, Liudmila N.; Shalymov, Roman V.; Filatov, Yuri V.; Bokhman, Evgueny D.
2016-11-01
Rail track geometric parameters measurement requires knowledge of left and right rail head location in each section. First of all displacement in transverse plane of rail head point located at a distance of 14 mm below the running surface, must be controlled [1]. It is carried out by detecting of each rail profile using triangulation laser scanners. Optical image recognition is carried out successfully in the laboratory, approaches used for this purpose are widely known. However, laser scanners operation has several features on railways leading to necessity of traditional approaches adaptation for solving these particular problems. The most significant problem is images noisiness due to the solar flashes and the effect of "Moon path" on the smooth rail surface. Using of optical filters gives inadequate result, because scanner laser diodes radiation frequency varies with temperature changes that forbid the use of narrow-band filters. Consideration of these features requires additional constructive and algorithmic solutions, including involvement of information from other sensors of the system. The specific usage of optical scanners for rail profiles control is the subject of the paper.
An, Xi-Zhong
2007-08-01
Micro structures of equal sphere packing (ranging from loose to dense packing) generated numerically by discrete element method under different vibration conditions are characterized using Voronoi/Delaunay tessellation, which is applied on a wide range of packing densities. The analysis on micro properties such as the total perimeter, surface area, and the face number distribution of each Voronoi polyhedron, and the pore size distribution in each Voronoi/Delaunay subunit is systematically carried out. The results show that with the increasing density of sphere packing, the Voronoi/Delaunay pore size distribution is narrowed. That indicates large pores to be gradually substituted by small uniformed ones during densification. Meanwhile, the distributions of face number, total perimeter, and surface area of Voronoi polyhedra at high packing densities tend to be narrower and higher, which is in good agreement with those in random loose packing.
Institute of Scientific and Technical Information of China (English)
AN Xi-Zhong
2007-01-01
@@ Micro structures of equal sphere packing (ranging from loose to dense packing) generated numerically by discrete element method under different vibration conditions are characterized using Voronoi/Delaunay tessellation, which is applied on a wide range of packing densities. The analysis on micro properties such as the total perimeter,surface area, and the face number distribution of each Voronoi polyhedron, and the pore size distribution in each Voronoi/Delaunay subunit is systematically carried out. The results show that with the increasing density of sphere packing, the Voronoi/Delaunay pore size distribution is narrowed. That indicates large pores to be gradually substituted by small uniformed ones during densification. Meanwhile, the distributions of face number,total perimeter, and surface area of Voronoi polyhedra at high packing densities tend to be narrower and higher,which is in good agreement with those in random loose packing.
Methodological triangulation: an approach to understanding data.
Bekhet, Abir K; Zauszniewski, Jaclene A
2012-01-01
To describe the use of methodological triangulation in a study of how people who had moved to retirement communities were adjusting. Methodological triangulation involves using more than one kind of method to study a phenomenon. It has been found to be beneficial in providing confirmation of findings, more comprehensive data, increased validity and enhanced understanding of studied phenomena. While many researchers have used this well-established technique, there are few published examples of its use. The authors used methodological triangulation in their study of people who had moved to retirement communities in Ohio, US. A blended qualitative and quantitative approach was used. The collected qualitative data complemented and clarified the quantitative findings by helping to identify common themes. Qualitative data also helped in understanding interventions for promoting 'pulling' factors and for overcoming 'pushing' factors of participants. The authors used focused research questions to reflect the research's purpose and four evaluative criteria--'truth value', 'applicability', 'consistency' and 'neutrality'--to ensure rigour. This paper provides an example of how methodological triangulation can be used in nursing research. It identifies challenges associated with methodological triangulation, recommends strategies for overcoming them, provides a rationale for using triangulation and explains how to maintain rigour. Methodological triangulation can be used to enhance the analysis and the interpretation of findings. As data are drawn from multiple sources, it broadens the researcher's insight into the different issues underlying the phenomena being studied.
Genus dependence of the number of (non-)orientable surface triangulations
Krüger, Benedikt
2016-01-01
Topological triangulations of orientable and non-orientable surfaces with arbitrary genus have important applications in quantum geometry, graph theory and statistical physics. However, until now only the asymptotics for 2-spheres are known analytically, and exact counts of triangulations are only available for both small genus and small triangulations. We apply the Wang-Landau algorithm to calculate the number $N(m,h)$ of triangulations for several order of magnitudes in system size $m$ and genus $h$. We verify that the limit of the entropy density of triangulations is independent of genus and orientability and are able to determine the next-to-leading and the next-to-next-to-leading order terms. We conjecture for the number of surface triangulations the asymptotic behavior \\begin{equation*} N(m,h) \\rightarrow (170.4 \\pm 15.1)^h m^{-2(h - 1)/5} \\left( \\frac{256}{27} \\right)^{m / 2}\\;, \\end{equation*} what might guide a mathematicians proof for the exact asymptotics.
Urban Road Detection in Airbone Laser Scanning Point Cloud Using Random Forest Algorithm
Kaczałek, B.; Borkowski, A.
2016-06-01
The objective of this research is to detect points that describe a road surface in an unclassified point cloud of the airborne laser scanning (ALS). For this purpose we use the Random Forest learning algorithm. The proposed methodology consists of two stages: preparation of features and supervised point cloud classification. In this approach we consider ALS points, representing only the last echo. For these points RGB, intensity, the normal vectors, their mean values and the standard deviations are provided. Moreover, local and global height variations are taken into account as components of a feature vector. The feature vectors are calculated on a basis of the 3D Delaunay triangulation. The proposed methodology was tested on point clouds with the average point density of 12 pts/m2 that represent large urban scene. The significance level of 15% was set up for a decision tree of the learning algorithm. As a result of the Random Forest classification we received two subsets of ALS points. One of those groups represents points belonging to the road network. After the classification evaluation we achieved from 90% of the overall classification accuracy. Finally, the ALS points representing roads were merged and simplified into road network polylines using morphological operations.
URBAN ROAD DETECTION IN AIRBONE LASER SCANNING POINT CLOUD USING RANDOM FOREST ALGORITHM
Directory of Open Access Journals (Sweden)
B. Kaczałek
2016-06-01
Full Text Available The objective of this research is to detect points that describe a road surface in an unclassified point cloud of the airborne laser scanning (ALS. For this purpose we use the Random Forest learning algorithm. The proposed methodology consists of two stages: preparation of features and supervised point cloud classification. In this approach we consider ALS points, representing only the last echo. For these points RGB, intensity, the normal vectors, their mean values and the standard deviations are provided. Moreover, local and global height variations are taken into account as components of a feature vector. The feature vectors are calculated on a basis of the 3D Delaunay triangulation. The proposed methodology was tested on point clouds with the average point density of 12 pts/m2 that represent large urban scene. The significance level of 15% was set up for a decision tree of the learning algorithm. As a result of the Random Forest classification we received two subsets of ALS points. One of those groups represents points belonging to the road network. After the classification evaluation we achieved from 90% of the overall classification accuracy. Finally, the ALS points representing roads were merged and simplified into road network polylines using morphological operations.
Reconstructing surface triangulations by their intersection matrices
2014-01-01
The intersection matrix of a finite simplicial complex has as each of its entries the rank of the intersection of its respective simplices. We prove that such matrix defines the triangulation of a closed connected surface up to isomorphism.
Hex-dominant mesh generation using 3D constrained triangulation
Energy Technology Data Exchange (ETDEWEB)
OWEN,STEVEN J.
2000-05-30
A method for decomposing a volume with a prescribed quadrilateral surface mesh, into a hexahedral-dominated mesh is proposed. With this method, known as Hex-Morphing (H-Morph), an initial tetrahedral mesh is provided. Tetrahedral are transformed and combined starting from the boundary and working towards the interior of the volume. The quadrilateral faces of the hexahedra are treated as internal surfaces, which can be recovered using constrained triangulation techniques. Implementation details of the edge and face recovery process are included. Examples and performance of the H-Morph algorithm are also presented.
Recent development of micro-triangulation for magnet fiducialisation
Vlachakis, Vasileios; Mainaud Durand, Helene; CERN. Geneva. ATS Department
2016-01-01
The micro-triangulation method is proposed as an alternative for magnet fiducialisation. The main objective is to measure horizontal and vertical angles to fiducial points and stretched wires, utilising theodolites equipped with cameras. This study aims to develop various methods, algorithms and software tools to enable the data acquisition and processing. In this paper, we present the first test measurement as an attempt to demonstrate the feasibility of the method and to evaluate the accuracy. The preliminary results are very promising, with accuracy always better than 20 μm for the wire position, and of about40 μm/m for the wire orientation, compared with a coordinate measuring machine.
Triangulation of 3D Surfaces Recovered from STL Grids
Directory of Open Access Journals (Sweden)
D. Rypl
2004-01-01
Full Text Available In the present paper, an algorithm for the discretization of parametric 3D surfaces has been extended to the family of discrete surfaces represented by stereolithography (STL grids. The STL file format, developed for the rapid prototyping industry, is an attractive alternative to surface representation in solid modeling. Initially, a boundary representation is constructed from the STL file using feature recognition. Then a smooth surface is recovered over the original STL grid using an interpolating subdivision procedure. Finally, the reconstructed surface is subjected to the triangulation accomplished using the advancing front technique operating directly on the surface. The capability of the proposed methodology is illustrated on an example.
Cubic Spline Interpolation on a Class of Triangulations%一类三角域上的三次样条插值
Institute of Scientific and Technical Information of China (English)
陈丽娟; 罗钟铉
2008-01-01
In this paper, we consider spaces of cubic C1-spline on a class of trian-gulations. By using the inductive algorithm, the posed Lagrange interpolation sets are constructed for cubic spline space. It is shown that the class of triangulations considered in this paper are nonsingular for S13 spaces. Moreover, the dimensions of those spaces exactly equal to L. L. Schumaker's low bounds of the dimensions. At the end of this paper, we present an approach to construct triangulations from any scattered planar points, which ensures that the obtained triangulations for S13 space are nonsingular.
Locally Causal Dynamical Triangulations in Two Dimensions
Loll, Renate
2015-01-01
We analyze the universal properties of a new two-dimensional quantum gravity model defined in terms of Locally Causal Dynamical Triangulations (LCDT). Measuring the Hausdorff and spectral dimensions of the dynamical geometrical ensemble, we find numerical evidence that the continuum limit of the model lies in a new universality class of two-dimensional quantum gravity theories, inequivalent to both Euclidean and Causal Dynamical Triangulations.
TRIANGULATION OF METHODS OF CAREER EDUCATION
Marija Turnsek Mikacic
2015-01-01
This paper is an overview of the current research in the field of career education and career planning. Presented results constitute a model based on the insight into different theories and empirical studies about career planning as a building block of personal excellence. We defined credibility, transferability and reliability of the research by means of triangulation. As sources of data of triangulation we included essays of participants of education and questionnaires. Qualitative analysi...
Generating triangulated macromolecular surfaces by Euclidean Distance Transform.
Directory of Open Access Journals (Sweden)
Dong Xu
Full Text Available Macromolecular surfaces are fundamental representations of their three-dimensional geometric shape. Accurate calculation of protein surfaces is of critical importance in the protein structural and functional studies including ligand-protein docking and virtual screening. In contrast to analytical or parametric representation of macromolecular surfaces, triangulated mesh surfaces have been proved to be easy to describe, visualize and manipulate by computer programs. Here, we develop a new algorithm of EDTSurf for generating three major macromolecular surfaces of van der Waals surface, solvent-accessible surface and molecular surface, using the technique of fast Euclidean Distance Transform (EDT. The triangulated surfaces are constructed directly from volumetric solids by a Vertex-Connected Marching Cube algorithm that forms triangles from grid points. Compared to the analytical result, the relative error of the surface calculations by EDTSurf is <2-4% depending on the grid resolution, which is 1.5-4 times lower than the methods in the literature; and yet, the algorithm is faster and costs less computer memory than the comparative methods. The improvements in both accuracy and speed of the macromolecular surface determination should make EDTSurf a useful tool for the detailed study of protein docking and structure predictions. Both source code and the executable program of EDTSurf are freely available at http://zhang.bioinformatics.ku.edu/EDTSurf.
COUNTING FAIR NEAR-TRIANGULATIONS ON THE DISC
Institute of Scientific and Technical Information of China (English)
无
2000-01-01
In this paper various kinds of fair near-triangulations are enumerated and several other types of near-triangulations are counted with the root-face valency,the number of edges and faces as the parameters.
Tradeoffs in Design Research: Development Oriented Triangulation
Turnhout, Koen van; Craenmehr, Sabine; Holwerda, Robert; Menijn, Mark; Zwart, Jan-Pieter; Bakker, René
2013-01-01
The Development Oriented Triangulation (DOT) framework in this paper can spark and focus the debate about mixed-method approaches in HCI. The framework can be used to classify HCI methods, create mixed-method designs, and to align research activities in multidisciplinary projects. The framework is g
Tradeoffs in Design Research: Development Oriented Triangulation
Jan-Pieter Zwart; René Bakker; Robert Holwerda; Mark Menijn; Koen van Turnhout; Sabine Craenmehr
2013-01-01
The Development Oriented Triangulation (DOT) framework in this paper can spark and focus the debate about mixed-method approaches in HCI. The framework can be used to classify HCI methods, create mixed-method designs, and to align research activities in multidisciplinary projects. The framework is
Methodological triangulation in work life research
DEFF Research Database (Denmark)
Warring, Niels
Based on examples from two research projects on preschool teachers' work, the paper will discuss potentials and challenges in methodological triangulation in work life research. Analysis of ethnographic and phenomenological inspired observations of everyday life in day care centers formed the basis...
Spectral Properties of Unimodular Lattice Triangulations
Krüger, Benedikt; Schmidt, Ella M.; Mecke, Klaus
2016-05-01
Random unimodular lattice triangulations have been recently used as an embedded random graph model, which exhibit a crossover behavior between an ordered, large-world and a disordered, small-world behavior. Using the ergodic Pachner flips that transform such triangulations into another and an energy functional that corresponds to the degree distribution variance, Markov chain Monte Carlo simulations can be applied to study these graphs. Here, we consider the spectra of the adjacency and the Laplacian matrix as well as the algebraic connectivity and the spectral radius. Power law dependencies on the system size can clearly be identified and compared to analytical solutions for periodic ground states. For random triangulations we find a qualitative agreement of the spectral properties with well-known random graph models. In the microcanonical ensemble analytical approximations agree with numerical simulations. In the canonical ensemble a crossover behavior can be found for the algebraic connectivity and the spectral radius, thus combining large-world and small-world behavior in one model. The considered spectral properties can be applied to transport problems on triangulation graphs and the crossover behavior allows a tuning of important transport quantities.
Altitude, Orthocenter of a Triangle and Triangulation
Directory of Open Access Journals (Sweden)
Coghetto Roland
2016-03-01
Full Text Available We introduce the altitudes of a triangle (the cevians perpendicular to the opposite sides. Using the generalized Ceva’s Theorem, we prove the existence and uniqueness of the orthocenter of a triangle [7]. Finally, we formalize in Mizar [1] some formulas [2] to calculate distance using triangulation.
Gaussian vector fields on triangulated surfaces
DEFF Research Database (Denmark)
Ipsen, John H
2016-01-01
proven to be very useful to resolve the complex interplay between in-plane ordering of membranes and membrane conformations. In the present work we have developed a procedure for realistic representations of Gaussian models with in-plane vector degrees of freedoms on a triangulated surface. The method...
Nonequilibrium phase transition in directed small-world-Voronoi-Delaunay random lattices
Lima, F. W. S.
2016-01-01
On directed small-world-Voronoi-Delaunay random lattices in two dimensions with quenched connectivity disorder we study the critical properties of the dynamics evolution of public opinion in social influence networks using a simple spin-like model. The system is treated by applying Monte Carlo simulations. We show that directed links on these random lattices may lead to phase diagram with first- and second-order social phase transitions out of equilibrium.
Triangulation using synthetic aperture radar images
Wu, Sherman S. C.; Howington-Kraus, Annie E.
1991-01-01
For the extraction of topographic information about Venus from stereoradar images obtained from the Magellan Mission, a Synthetic Aperture Radar (SAR) compilation system was developed on analytical stereoplotters. The system software was extensively tested by using stereoradar images from various spacecraft and airborne radar systems, including Seasat, SIR-B, ERIM XCL, and STAR-1. Stereomodeling from radar images was proven feasible, and development is on a correct approach. During testing, the software was enhanced and modified to obtain more flexibility and better precision. Triangulation software for establishing control points by using SAR images was also developed through a joint effort with the Defense Mapping Agency. The SAR triangulation system comprises four main programs, TRIDATA, MODDATA, TRISAR, and SHEAR. The first two programs are used to sort and update the data; the third program, the main one, performs iterative statistical adjustment; and the fourth program analyzes the results. Also, input are flight data and data from the Global Positioning System and Inertial System (navigation information). The SAR triangulation system was tested with six strips of STAR-1 radar images on a VAX-750 computer. Each strip contains images of 10 minutes flight time (equivalent to a ground distance of 73.5 km); the images cover a ground width of 22.5 km. All images were collected from the same side. With an input of 44 primary control points, 441 ground control points were produced. The adjustment process converged after eight iterations. With a 6-m/pixel resolution of the radar images, the triangulation adjustment has an average standard elevation error of 81 m. Development of Magellan radargrammetry will be continued to convert both SAR compilation and triangulation systems into digital form.
Alimohammadi, Shahrouz; Cavaglieri, Daniele; Beyhaghi, Pooriya; Bewley, Thomas R.
2016-11-01
This work applies a recently developed Derivative-free optimization algorithm to derive a new mixed implicit-explicit (IMEX) time integration scheme for Computational Fluid Dynamics (CFD) simulations. This algorithm allows imposing a specified order of accuracy for the time integration and other important stability properties in the form of nonlinear constraints within the optimization problem. In this procedure, the coefficients of the IMEX scheme should satisfy a set of constraints simultaneously. Therefore, the optimization process, at each iteration, estimates the location of the optimal coefficients using a set of global surrogates, for both the objective and constraint functions, as well as a model of the uncertainty function of these surrogates based on the concept of Delaunay triangulation. This procedure has been proven to converge to the global minimum of the constrained optimization problem provided the constraints and objective functions are twice differentiable. As a result, a new third-order, low-storage IMEX Runge-Kutta time integration scheme is obtained with remarkably fast convergence. Numerical tests are then performed leveraging the turbulent channel flow simulations to validate the theoretical order of accuracy and stability properties of the new scheme.
Constant-work-space algorithms for geometric problems
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Tetsuo Asano
2011-07-01
Full Text Available Constant-work-space algorithms may use only constantly many cells of storage in addition to their input, which is provided as a read-only array. We show how to construct several geometric structures efficiently in the constant-work-space model. Traditional algorithms process the input into a suitable data structure (like a doubly-connected edge list that allows efficient traversal of the structure at hand. In the constant-work-space setting, however, we cannot afford to do this. Instead, we provide operations that compute the desired features on the fly by accessing the input with no extra space. The whole geometric structure can be obtained by using these operations to enumerate all the features. Of course, we must pay for the space savings by slower running times. While the standard data structure allows us to implement traversal operations in constant time, our schemes typically take linear time to read the input data in each step.We begin with two simple problems: triangulating a planar point set and finding the trapezoidal decomposition of a simple polygon. In both cases adjacent features can be enumerated in linear time per step, resulting in total quadratic running time to output the whole structure. Actually, we show that the former result carries over to the Delaunay triangulation, and hence the Voronoi diagram. This also means that we can compute the largest empty circle of a planar point set in quadratic time and constant work-space. As another application, we demonstrate how to enumerate the features of an Euclidean minimum spanning tree (EMST in quadratic time per step, so that the whole EMST can be found in cubic time using constant work-space.Finally, we describe how to compute a shortest geodesic path between two points in a simple polygon. Although the shortest path problem in general graphs is NL-complete (Jakoby and Tantau 2003, this constrained problem can be solved in quadratic time using only constant work-space.
Jafari, Rahim; Sadeghi, Mehdi; Mirzaie, Mehdi
2016-05-01
The approaches taken to represent and describe structural features of the macromolecules are of major importance when developing computational methods for studying and predicting their structures and interactions. This study attempts to explore the significance of Delaunay tessellation for the definition of atomic interactions by evaluating its impact on the performance of scoring protein-protein docking prediction. Two sets of knowledge-based scoring potentials are extracted from a training dataset of native protein-protein complexes. The potential of the first set is derived using atomic interactions extracted from Delaunay tessellated structures. The potential of the second set is calculated conventionally, that is, using atom pairs whose interactions were determined by their separation distances. The scoring potentials were tested against two different docking decoy sets and their performances were compared. The results show that, if properly optimized, the Delaunay-based scoring potentials can achieve higher success rate than the usual scoring potentials. These results and the results of a previous study on the use of Delaunay-based potentials in protein fold recognition, all point to the fact that Delaunay tessellation of protein structure can provide a more realistic definition of atomic interaction, and therefore, if appropriately utilized, may be able to improve the accuracy of pair potentials.
Coefficient adaptive triangulation for strongly anisotropic problems
Energy Technology Data Exchange (ETDEWEB)
D`Azevedo, E.F.; Romine, C.H.; Donato, J.M.
1996-01-01
Second order elliptic partial differential equations arise in many important applications, including flow through porous media, heat conduction, the distribution of electrical or magnetic potential. The prototype is the Laplace problem, which in discrete form produces a coefficient matrix that is relatively easy to solve in a regular domain. However, the presence of anisotropy produces a matrix whose condition number is increased, making the resulting linear system more difficult to solve. In this work, we take the anisotropy into account in the discretization by mapping each anisotropic region into a ``stretched`` coordinate space in which the anisotropy is removed. The region is then uniformly triangulated, and the resulting triangulation mapped back to the original space. The effect is to generate long slender triangles that are oriented in the direction of ``preferred flow.`` Slender triangles are generally regarded as numerically undesirable since they tend to cause poor conditioning; however, our triangulation has the effect of producing effective isotropy, thus improving the condition number of the resulting coefficient matrix.
Abdoli, M.; de Long, J. R.; Pruim, J.; Dierckx, R. A. J. O.; Zaidi, H.
2011-01-01
Metallic implants, such as hip implants, are known to induce streaking artifacts in CT images which can cause over/underestimation of the activity uptake in CT-based attenuation corrected PET images. Hence, metal artifact reduction (MAR) of CT images is essential in order to obtain accurate quantifi
Liu, Yuangang; Guo, Qingsheng; Sun, Yageng; Ma, Xiaoya
2014-01-01
Scale reduction from source to target maps inevitably leads to conflicts of map symbols in cartography and geographic information systems (GIS). Displacement is one of the most important map generalization operators and it can be used to resolve the problems that arise from conflict among two or more map objects. In this paper, we propose a combined approach based on constraint Delaunay triangulation (CDT) skeleton and improved elastic beam algorithm for automated building displacement. In this approach, map data sets are first partitioned. Then the displacement operation is conducted in each partition as a cyclic and iterative process of conflict detection and resolution. In the iteration, the skeleton of the gap spaces is extracted using CDT. It then serves as an enhanced data model to detect conflicts and construct the proximity graph. Then, the proximity graph is adjusted using local grouping information. Under the action of forces derived from the detected conflicts, the proximity graph is deformed using the improved elastic beam algorithm. In this way, buildings are displaced to find an optimal compromise between related cartographic constraints. To validate this approach, two topographic map data sets (i.e., urban and suburban areas) were tested. The results were reasonable with respect to each constraint when the density of the map was not extremely high. In summary, the improvements include (1) an automated parameter-setting method for elastic beams, (2) explicit enforcement regarding the positional accuracy constraint, added by introducing drag forces, (3) preservation of local building groups through displacement over an adjusted proximity graph, and (4) an iterative strategy that is more likely to resolve the proximity conflicts than the one used in the existing elastic beam algorithm.
Numerical Validation of the Delaunay Normalization and the Krylov-Bogoliubov-Mitropolsky Method
Directory of Open Access Journals (Sweden)
David Ortigosa
2014-01-01
Full Text Available A scalable second-order analytical orbit propagator programme based on modern and classical perturbation methods is being developed. As a first step in the validation and verification of part of our orbit propagator programme, we only consider the perturbation produced by zonal harmonic coefficients in the Earth’s gravity potential, so that it is possible to analyze the behaviour of the mathematical expressions involved in Delaunay normalization and the Krylov-Bogoliubov-Mitropolsky method in depth and determine their limits.
Metodologisk triangulering i arbejdslivsforskning – potentialer og udfordringer
DEFF Research Database (Denmark)
Warring, Niels
2015-01-01
Metodologisk triangulering i arbejdslivsforskning – potentialer og udfordringer Med inddragelse af eksempler fra to forskningsprojekter om pædagogers arbejdsliv, vil der blive argumenteret for det frugtbare i metodologisk triangulering, når der forskes i moderne arbejdsliv – og ikke mindst, når...... ambitionen er at bidrage til at åbne for kritiske perspektiver og mulige forandringspotentialer. I de to projekter var etnografisk og fænomenologisk inspirerede observationer af hverdagen i daginstitutionerne første skridt i den metodologiske triangulering. Tolkning og analyse af scener fra hverdagen dannede...... udviklede sig i dialog med deltagernes såvel praktiske hverdagsviden som teoretisk baserede pædagogisk-faglige viden. Metodologisk triangulering er af Denzin (opr. 1970) foreslået som en blandt flere former for triangulering. Øvrige former er teoretisk triangulering (hvor flere teorier benyttes til at tolke...
Implementing a triangulation protocol in bereavement research: a methodological discussion.
Briller, Sherylyn H; Meert, Kathleen L; Schim, Stephanie Myers; Thurston, Celia S; Kabel, Allison
2008-01-01
Triangulation is a comparative strategy for examining data that strengthens qualitative and multi-method research. Despite the benefits of triangulation noted in the research methods literature, few concrete models for operationalization of protocols exist. Lack of documentation of explicit triangulation procedures is especially true in the area of bereavement research. This article describes how an interdisciplinary research team implemented a triangulation protocol in a study of the needs of bereaved parents. Triangulation enabled the integration of diverse data sources, methods, and disciplinary perspectives. These processes yielded a more meaningful typology of bereaved parents' needs than would have otherwise been possible. Extending the use of triangulation will enhance multi-faceted understandings of bereavement.
Wilson Fermions on a Randomly Triangulated Manifold
Burda, Z; Krzywicki, A
1999-01-01
A general method of constructing the Dirac operator for a randomly triangulated manifold is proposed. The fermion field and the spin connection live, respectively, on the nodes and on the links of the corresponding dual graph. The construction is carried out explicitly in 2-d, on an arbitrary orientable manifold without boundary. It can be easily converted into a computer code. The equivalence, on a sphere, of Majorana fermions and Ising spins in 2-d is rederived. The method can, in principle, be extended to higher dimensions.
Diffractive triangulation of radiative point sources
Vespucci, Stefano; Maneuski, Dzmitry; O'Shea, Val; Winkelmann, Aimo
2016-01-01
We describe a general method to determine the location of a point source of waves relative to a two-dimensional active pixel detector. Based on the inherent structural sensitivity of crystalline sensor materials, characteristic detector diffraction patterns can be used to triangulate the location of a wave emitter. As a practical application of the wide-ranging principle, a digital hybrid pixel detector is used to localize a source of electrons for Kikuchi diffraction pattern measurements in the scanning electron microscope. This provides a method to calibrate Kikuchi diffraction patterns for accurate measurements of microstructural crystal orientations, strains, and phase distributions.
Computational Hardness of Enumerating Satisfying Spin-Assignments in Triangulations
Jiménez, Andrea
2011-01-01
Satisfying spin-assignments in triangulations of a surface are states of minimum energy of the antiferromagnetic Ising model on triangulations which correspond (via geometric duality) to perfect matchings in cubic bridgeless graphs. In this work we show that it is NP-complete to decide whether or not a surface triangulation admits a satisfying spin-assignment, and that it is #P-complete to determine the number of such assignments. Both results are derived via an elaborate (and atypical) reduction that maps a Boolean formula in 3-conjunctive normal form into a triangulation of an orientable closed surface.
TRIANGULATION OF METHODS OF CAREER EDUCATION
Directory of Open Access Journals (Sweden)
Marija Turnsek Mikacic
2015-09-01
Full Text Available This paper is an overview of the current research in the field of career education and career planning. Presented results constitute a model based on the insight into different theories and empirical studies about career planning as a building block of personal excellence. We defined credibility, transferability and reliability of the research by means of triangulation. As sources of data of triangulation we included essays of participants of education and questionnaires. Qualitative analysis represented the framework for the construction of the paradigmatic model and the formulation of the final theory. We formulated a questionnaire on the basis of our own experiences in the area of the education of individuals. The quantitative analysis, based on the results of the interviews, confirms the following three hypotheses: The individuals who elaborated a personal career plan and acted accordingly, changed their attitudes towards their careers and took control over their lives; in addition, they achieved a high level of self-esteem and self-confidence, in tandem with the perception of personal excellence, in contrast to the individuals who did not participate in career education and did not elaborate a career plan. We used the tools of NLP (neurolinguistic programming as an additional technique at learning.
Good Random Multi-Triangulation of Surfaces.
de Medeiros Filho, Esdras; Siqueira, Marcelo
2017-05-12
We introduce the Hierarchical Poisson Disk Sampling Multi-Triangulation (HPDS-MT) of surfaces, a novel structure that combines the power of multi-triangulation (MT) with the benefits of Hierarchical Poisson Disk Sampling (HPDS). MT is a general framework for representing surfaces through variable resolution triangle meshes, while HPDS is a well-spaced random distribution with blue noise characteristics. The distinguishing feature of the HPDS-MT is its ability to extract adaptive meshes whose triangles are guaranteed to have good shape quality. The key idea behind the HPDS-MT is a preprocessed hierarchy of points, which is used in the construction of a MT via incremental simplification. In addition to proving theoretical properties on the shape quality of the triangle meshes extracted by the HPDS-MT, we provide an implementation that computes the HPDS-MT with high accuracy. Our results confirm the theoretical guarantees and outperform similar methods. We also prove that the Hausdorff distance between the original surface and any (extracted) adaptive mesh is bounded by the sampling distribution of the radii of Poisson-disks over the surface. Finally, we illustrate the advantages of the HPDS-MT in some typical problems of geometry processing.
Pleissner, K P; Hoffmann, F; Kriegel, K; Wenk, C; Wegner, S; Sahlström, A; Oswald, H; Alt, H; Fleck, E
1999-01-01
Protein spot identification in two-dimensional electrophoresis gels can be supported by the comparison of gel images accessible in different World Wide Web two-dimensional electrophoresis (2-DE) gel protein databases. The comparison may be performed either by visual cross-matching between gel images or by automatic recognition of similar protein spot patterns. A prerequisite for the automatic point pattern matching approach is the detection of protein spots yielding the x(s),y(s) coordinates and integrated spot intensities i(s). For this purpose an algorithm is developed based on a combination of hierarchical watershed transformation and feature extraction methods. This approach reduces the strong over-segmentation of spot regions normally produced by watershed transformation. Measures for the ellipticity and curvature are determined as features of spot regions. The resulting spot lists containing x(s),y(s),i(s)-triplets are calculated for a source as well as for a target gel image accessible in 2-DE gel protein databases. After spot detection a matching procedure is applied. Both the matching of a local pattern vs. a full 2-DE gel image and the global matching between full images are discussed. Preset slope and length tolerances of pattern edges serve as matching criteria. The local matching algorithm relies on a data structure derived from the incremental Delaunay triangulation of a point set and a two-step hashing technique. For the incremental construction of triangles the spot intensities are considered in decreasing order. The algorithm needs neither landmarks nor an a priori image alignment. A graphical user interface for spot detection and gel matching is written in the Java programming language for the Internet. The software package called CAROL (http://gelmatching.inf.fu-berlin.de) is realized in a client-server architecture.
Triangulation, Respondent Validation, and Democratic Participation in Mixed Methods Research
Torrance, Harry
2012-01-01
Over the past 10 years or so the "Field" of "Mixed Methods Research" (MMR) has increasingly been exerting itself as something separate, novel, and significant, with some advocates claiming paradigmatic status. Triangulation is an important component of mixed methods designs. Triangulation has its origins in attempts to validate research findings…
Triangulation, Respondent Validation, and Democratic Participation in Mixed Methods Research
Torrance, Harry
2012-01-01
Over the past 10 years or so the "Field" of "Mixed Methods Research" (MMR) has increasingly been exerting itself as something separate, novel, and significant, with some advocates claiming paradigmatic status. Triangulation is an important component of mixed methods designs. Triangulation has its origins in attempts to validate research findings…
Graph Triangulations and the Compatibility of Unrooted Phylogenetic Trees
Vakati, Sudheer
2010-01-01
We characterize the compatibility of a collection of unrooted phylogenetic trees as a question of determining whether a graph derived from these trees --- the display graph --- has a specific kind of triangulation, which we call legal. Our result is a counterpart to the well known triangulation-based characterization of the compatibility of undirected multi-state characters.
A TQFT of Turaev-Viro type on shaped triangulations
Kashaev, Rinat; Vartanov, Grigory
2012-01-01
A shaped triangulation is a finite triangulation of an oriented pseudo three manifold where each tetrahedron carries dihedral angles of an ideal hyberbolic tetrahedron. To each shaped triangulation, we associate a quantum partition function in the form of an absolutely convergent state integral which is invariant under shaped 3-2 Pachner moves and invariant with respect to shape gauge transformations generated by total dihedral angles around internal edges through the Neumann-Zagier Poisson bracket. Similarly to Turaev-Viro theory, the state variables live on edges of the triangulation but take their values on the whole real axis. The tetrahedral weight functions are composed of three hyperbolic gamma functions in a way that they enjoy a manifest tetrahedral symmetry. We conjecture that for shaped triangulations of closed 3-manifolds, our partition function is twice the absolute value squared of the partition function of Techm\\"uller TQFT defined by Andersen and Kashaev. This is similar to the known relations...
Measuring and Controlling Fairness of Triangulations
Jiang, Caigui
2016-09-30
The fairness of meshes that represent geometric shapes is a topic that has been studied extensively and thoroughly. However, the focus in such considerations often is not on the mesh itself, but rather on the smooth surface approximated by it, and fairness essentially expresses a mesh’s suitability for purposes such as visualization or simulation. This paper focusses on meshes in the architectural context, where vertices, edges, and faces of meshes are often highly visible, and any notion of fairness must take new aspects into account. We use concepts from discrete differential geometry (star-shaped Gauss images) to express fairness, and we also demonstrate how fairness can be incorporated into interactive geometric design of triangulated freeform skins.
New deghosting method based on generalized triangulation
Institute of Scientific and Technical Information of China (English)
Bai Jing; Wang Guohong; Xiu Jianjuan; Wang Xiaobo
2009-01-01
A new deghosting method baaed on the generalized triangulation is presented. First, two intersection points corresponding to the emitter position are obtained by utilizing two azimuth angles and two elevation angles from two jammed 3-D radars (or 2-D passive sensors). Then, hypothesis testing baaed deghosting method in the multiple target scenarios is proposed using the two intersection points. In order to analyze the performance of the proposed method, the correct association probability of the true targets and the incorrect association probability of the ghost targets are defined. Finally, the Monte Carlo simulations are given for the proposed method compared with the hinge angle method in the cases of both two and three radars. The simulation results show that the proposed method has better performance than the hinge angle method in three radars case.
Exploring Torus Universes in Causal Dynamical Triangulations
DEFF Research Database (Denmark)
Budd, Timothy George; Loll, R.
2013-01-01
Motivated by the search for new observables in nonperturbative quantum gravity, we consider Causal Dynamical Triangulations (CDT) in 2+1 dimensions with the spatial topology of a torus. This system is of particular interest, because one can study not only the global scale factor, but also global...... shape variables in the presence of arbitrary quantum fluctuations of the geometry. Our initial investigation focusses on the dynamics of the scale factor and uncovers a qualitatively new behaviour, which leads us to investigate a novel type of boundary conditions for the path integral. Comparing large......-scale features of the emergent quantum geometry in numerical simulations with a classical minisuperspace formulation, we find partial agreement. By measuring the correlation matrix of volume fluctuations we succeed in reconstructing the effective action for the scale factor directly from the simulation data...
Exploring Torus Universes in Causal Dynamical Triangulations
Budd, T G
2013-01-01
Motivated by the search for new observables in nonperturbative quantum gravity, we consider Causal Dynamical Triangulations (CDT) in 2+1 dimensions with the spatial topology of a torus. This system is of particular interest, because one can study not only the global scale factor, but also global shape variables in the presence of arbitrary quantum fluctuations of the geometry. Our initial investigation focusses on the dynamics of the scale factor and uncovers a qualitatively new behaviour, which leads us to investigate a novel type of boundary conditions for the path integral. Comparing large-scale features of the emergent quantum geometry in numerical simulations with a classical minisuperspace formulation, we find partial agreement. By measuring the correlation matrix of volume fluctuations we succeed in reconstructing the effective action for the scale factor directly from the simulation data. Apart from setting the stage for the analysis of shape dynamics on the torus, the new set-up highlights the role o...
Employee-satisfaction: A triangulation approach
Directory of Open Access Journals (Sweden)
P. J. Visser
1997-06-01
Full Text Available The research on employee-satisfaction was conducted in the manufacturing industry. The sample consisted of 543 employees. The methodology could be described as a "triangulation approach" where a combination of quantitative and qualitative measurements were utilised and the results of both types of measurement integrated in the study of the construct. The research confirms existing findings that although the measurement of dimensions such as equitable rewards, working conditions, supportive colleagues, job content, etc. yield results on the level of employee-satisfaction, a single question, namely, "How satisfied are you with your job?" compares favourably with the general index. The findings also suggest the advantage of complimenting the quantitative data with qualitative information. The conclusions confirm the value of a qualitative method in cross-cultural research in an African environment. Opsomming Die navorsing omtrent werknemerstevredenheid is uitgevoer in die vervaardigingsbedryf. Die steekproef het bestaan uit 543 werknemers. Die metode van ondersoek kan beskryf word as 'n "driekantige benadering" (triangulation approach waar daar van kwantitatiewe en kwalitatiewe meting gebruik gemaak is en die resultate geihtegreer is in die bestudering van die konstruk. Die navorsing bevestig bestaande bevindinge dat die meting van dimensies soos vergelykbare belonings, werkstoestande, ondersteunende kollegas, inhoud van werk, ens. resultate lewer rakende die vlak van werknemerstevredenheid, 'n enkel vraag, naamlik, "Hoe tevrede is jy met jou werk?" gunstig vergelyk met die algemene indeks. Die bevindinge dui ook op die voordele van 'n benadering waar die kwantitatiewe data gekomplimenteer word deur kwalitatiewe inligting soos verkry uit individuele onderhoude. Die gevolgtrekkings bevestig die waarde wat die kwalitatiewe navorsingsmetode inhou vir kruis-kulturele navorsing in 'n Afrika konteks.
Directory of Open Access Journals (Sweden)
Elena V. Zabelina
2012-08-01
Full Text Available The article deals with an avant-garde trend simultaneism, which primarily emerged in painting, then developed in textile painting, clothes design and cinematography. The article attempts to interpret simultaneism theoretically as a holistic phenomenon and determine its place in the art of the XX century. Certain displays of simultaneism trend in painting and textile design have been studied well. But special displays of simultaneism in cinematography and architecture have been studied insufficiently. This fact prevents interpreting simultaneism as a holistic phenomenon. To study the impact of simultaneism on landscape architecture, the article uses such scientific methods as stylistic-formal analysis and comparative analysis. The article discloses principles of simultaneism, the trend, which originates at the intersection of art and science, traces the impact of Robert and Sonia Delaunay research activities on Guevrekian’s creative concept. The author introduces for the scientific use some sources, unknown to the domestic study of art.
Measuring the Scalar Curvature with Clocks and Photons: Voronoi-Delaunay Lattices in Regge Calculus
McDonald, Jonathan R
2008-01-01
The Riemann scalar curvature plays a central role in Einstein's geometric theory of gravity. We describe a new geometric construction of this scalar curvature invariant at an event (vertex) in a discrete spacetime geometry. This allows one to constructively measure the scalar curvature using only clocks and photons. Given recent interest in discrete pre-geometric models of quantum gravity, we believe is it ever so important to reconstruct the curvature scalar with respect to a finite number of communicating observers. This derivation makes use of a new fundamental lattice cell built from elements inherited from both the original simplicial (Delaunay) spacetime and its circumcentric dual (Voronoi) lattice. The orthogonality properties between these two lattices yield an expression for the vertex-based scalar curvature which is strikingly similar to the corresponding hinge-based expression in Regge calculus (deficit angle per unit Voronoi dual area). In particular, we show that the scalar curvature is simply a ...
Los Triángulos de Delaunay como Procesamiento Previo para Extractores Difusos
Directory of Open Access Journals (Sweden)
Manuel Ramírez Flores
2014-01-01
Full Text Available La información biométrica que se extrae de las huellas dactilares tiende a ser diferente en cada adquisición, dada la incertidumbre existente en las mediciones y la presencia de ruido en las muestras, lo cual puede ocasionar que las palabras código generadas dentro de un extractor difuso posean un número de errores tal que rebase la capacidad de corrección de la codificación. Como consecuencia se tiene que lo anterior puede ocasionar que las huellas dactilares de una misma persona sean catalogadas como no coincidentes en su verificación o bien, que huellas de individuos diferentes parezcan demasiado similares. Para mitigar los efectos antes mencionados y sobrepasar las dificultades del pre-alineamiento de huellas dactilares, se propuso el uso de triángulos de Delaunay, lo cual permite proveer de estabilidad estructural local a la representación espacial de la información biométrica. En esa propuesta, las minucias de la huella son utilizadas como vértices de las triangulaciones y la red formada por éstas es tolerante a distorsiones, rotaciones y traslaciones. Sin embargo, en dicha propuesta se considera a la dispersión de minucias de huellas dactilares como no degenerativa y por tanto no se mencionan los umbrales o criterios necesarios para la formación de dichas triangulaciones, lo cual repercute en el desempeño de los extractores difusos. Con base en ello, este artículo presenta los resultados obtenidos al probar la formación de triangulaciones de Delaunay en imágenes de huella dactilar, en donde se aplican umbrales y criterios geométricos para luego contabilizar los triángulos coincidentes entre las estructuras formadas y definir los umbrales que maximicen dichas coincidencias.
From Causal Dynamical Triangulations To Astronomical Observations
Mielczarek, Jakub
2015-01-01
This essay discusses phenomenological aspects of the diffusion time dependence of the spectral dimension predicted by the Causal Dynamical Triangulations (CDT) approach to quantum gravity. The deformed form of the dispersion relation for the fields defined on the CDT space-time is reconstructed. Using the \\emph{Fermi} satellite observations of the GRB 090510 source we find that the energy scale of the dimensional reduction is $E_* > 6.7 \\cdot 10^{10}$ GeV at (95 $\\%$ CL). By applying the deformed dispersion relation to the cosmological perturbations it is shown that, for a scenario when the primordial perturbations are formed in the UV region, the scalar power spectrum $\\mathcal{P}_S \\propto k^{n_S-1}$ where $n_S-1\\approx \\frac{3r(d_{\\rm UV}-2)}{r+48(d_{\\rm UV}-3)}$. Here, $d_{\\rm UV} \\approx 2$ is obtained from the CDT value of the spectral dimension in the UV limit and $r$ is the tensor-to-scalar ratio. We find that, the predicted deviation from the scale-invariance ($n_S=1$) is in contradiction with the up...
Reconstructing Surface Triangulations by Their Intersection Matrices 26 September 2014
2015-01-01
The intersection matrix of a simplicial complex has entries equal to the rank of the intersecction of its facets. We prove that this matrix is enough to define up to isomorphism a triangulation of a surface.
Land Elevation TINs (Triangulated Irregular Networks) for Jefferson County, WI
Federal Emergency Management Agency, Department of Homeland Security — The Land Elevation TINs (Triangulated Irregular Networks) in this directory are generated from 2 foot contour lines from Jefferson County. Little is known about the...
Aerial Triangulation Close-range Images with Dual Quaternion
Directory of Open Access Journals (Sweden)
SHENG Qinghong
2015-05-01
Full Text Available A new method for the aerial triangulation of close-range images based on dual quaternion is presented. Using dual quaternion to represent the spiral screw motion of the beam in the space, the real part of dual quaternion represents the angular elements of all the beams in the close-range area networks, the real part and the dual part of dual quaternion represents the line elements corporately. Finally, an aerial triangulation adjustment model based on dual quaternion is established, and the elements of interior orientation and exterior orientation and the object coordinates of the ground points are calculated. Real images and large attitude angle simulated images are selected to run the experiments of aerial triangulation. The experimental results show that the new method for the aerial triangulation of close-range images based on dual quaternion can obtain higher accuracy.
From recollement of triangulated categories to recollement of abelian categories
Institute of Scientific and Technical Information of China (English)
无
2010-01-01
In this paper,we prove that if a triangulated category D admits a recollement relative to triangulated categories D’ and D″,then the abelian category D/T admits a recollement relative to abelian categories D’/i(T) and D″/j(T) where T is a cluster tilting subcategory of D and satisfies i i (T) T,j j (T) T.
A TQFT of Tuarev-Viro type on shaped triangulations
Energy Technology Data Exchange (ETDEWEB)
Kashaev, Rinat [Geneva Univ. (Switzerland); Luo, Feng [Rutgers Univ., Piscataway, NJ (United States). Dept. of Mathematics; Vartanov, Grigory [Deutsches Elektronen-Synchrotron (DESY), Hamburg (Germany)
2012-10-15
A shaped triangulation is a finite triangulation of an oriented pseudo three manifold where each tetrahedron carries dihedral angles of an ideal hyberbolic tetrahedron. To each shaped triangulation, we associate a quantum partition function in the form of an absolutely convergent state integral which is invariant under shaped 3-2 Pachner moves and invariant with respect to shape gauge transformations generated by total dihedral angles around internal edges through the Neumann-Zagier Poisson bracket. Similarly to Turaev-Viro theory, the state variables live on edges of the triangulation but take their values on the whole real axis. The tetrahedral weight functions are composed of three hyperbolic gamma functions in a way that they enjoy a manifest tetrahedral symmetry. We conjecture that for shaped triangulations of closed 3-manifolds, our partition function is twice the absolute value squared of the partition function of Techmueller TQFT defined by Andersen and Kashaev. This is similar to the known relationship between the Turaev-Viro and the Witten-Reshetikhin-Turaev invariants of three manifolds. We also discuss interpretations of our construction in terms of three-dimensional supersymmetric field theories related to triangulated three-dimensional manifolds.
TRIANGULATION OF THE INTERSTELLAR MAGNETIC FIELD
Energy Technology Data Exchange (ETDEWEB)
Schwadron, N. A.; Moebius, E. [University of New Hampshire, Durham, NH 03824 (United States); Richardson, J. D. [Massachusetts Institute of Technology, Cambridge, MA 02139 (United States); Burlaga, L. F. [Goddard Space Flight Center, Greenbelt, MD 20771 (United States); McComas, D. J. [Southwest Research Institute, San Antonio, TX 78228 (United States)
2015-11-01
Determining the direction of the local interstellar magnetic field (LISMF) is important for understanding the heliosphere’s global structure, the properties of the interstellar medium, and the propagation of cosmic rays in the local galactic medium. Measurements of interstellar neutral atoms by Ulysses for He and by SOHO/SWAN for H provided some of the first observational insights into the LISMF direction. Because secondary neutral H is partially deflected by the interstellar flow in the outer heliosheath and this deflection is influenced by the LISMF, the relative deflection of H versus He provides a plane—the so-called B–V plane in which the LISMF direction should lie. Interstellar Boundary Explorer (IBEX) subsequently discovered a ribbon, the center of which is conjectured to be the LISMF direction. The most recent He velocity measurements from IBEX and those from Ulysses yield a B–V plane with uncertainty limits that contain the centers of the IBEX ribbon at 0.7–2.7 keV. The possibility that Voyager 1 has moved into the outer heliosheath now suggests that Voyager 1's direct observations provide another independent determination of the LISMF. We show that LISMF direction measured by Voyager 1 is >40° off from the IBEX ribbon center and the B–V plane. Taking into account the temporal gradient of the field direction measured by Voyager 1, we extrapolate to a field direction that passes directly through the IBEX ribbon center (0.7–2.7 keV) and the B–V plane, allowing us to triangulate the LISMF direction and estimate the gradient scale size of the magnetic field.
Boat's hull modeling with low-cost triangulation scanners
Guidi, Gabriele; Micoli, Laura L.; Russo, Michele
2005-01-01
In a 3D acquisition project range maps collected around the object to be modeled, need to be integrated. With portable range cameras these range maps are taken from unknown positions and their coordinate systems are local to the sensor. The problem of unifying all the measurements in a single reference system is solved by taking contiguous range maps with a suitable overlap level; taking one map as reference and doing a rototranslation of the adjacent ones by using an "Iterative Closest Point" (ICP) method. Depending on the 3D features over the acquired surface and on the amount of overlapping, the ICP algorithm convergence can be more or less satisfactory. Anyway it always has a random component depending on measurement uncertainty. Therefore, although each individual scan has a very good accuracy, the error's propagation may produce deviations in the aligned set respect to real surface points. In this paper a systematic study of the different alignment modality and the consequent total metric distortions on the final model, is shown. In order to experiment these techniques a case-study of industrial interest was chosen: the 3D modeling of a boat's hull mold. The experiments involved a triangulation based laser scanner integrated with a digital photogrammetry system. In order to check different alignment procedures, a Laser Radar capable to scan all the object surface with a single highly accurate scan, was used to create a "gold-standard" data set. All the experiments were compared with this reference and from the comparison several interesting methodological conclusions have been obtained.
Measuring the Scalar Curvature with Clocks and Photons: Voronoi-Delaunay Lattices in Regge Calculus
Miller, Warner; McDonald, Jonathan
2008-04-01
The Riemann scalar curvature plays a central role in Einstein's geometric theory of gravity. We describe a new geometric construction of this scalar curvature invariant at an event (vertex) in a discrete spacetime geometry. This allows one to constructively measure the scalar curvature using only clocks and photons. Given recent interest in discrete pre-geometric models of quantum gravity, we believe it is ever so important to reconstruct the curvature scalar with respect to a finite number of communicating observers. This derivation makes use of a fundamental lattice cell built from elements inherited from both the original simplicial (Delaunay) spacetime and its circumcentric dual (Voronoi) lattice. The orthogonality properties between these two lattices yield an expression for the vertex-based scalar curvature which is strikingly similar to the corresponding hinge-based expression in Regge Calculus (deficit angle per unit Voronoi dual area). In particular, we show that the scalar curvature is simply a vertex-based weighted average of deficits per weighted average of dual areas.
Research on spot of CCD subdivided locating methods in laser triangulation displacement measurement
Wang, Hongjun; Hui, Lei; Zhang, Jiaying
2017-02-01
In order to improve the measurement accuracy of the laser displacement sensor, the laser triangulation displacement measuring system is established. The spot subdivision location algorithms of the system are studied, such as the Gaussian curve fitting, traditional gray weighted centroid and gray square weighted centroid. First, according to the principle of laser triangulation, the displacement measuring system is built. Then, objects are moved by the high-precision motorized stage, obtaining multiple sets of image data. Next, these data respectively are processed by the above several algorithms to obtain the corresponding coordinates of the laser spot, the system is calibrated respectively. Finally, comparing the displacement of calibration results calculating with the actual displacement. The results show that: those data that are processed by the gray square weighted centroid are used to calibrate , calculating the minimum error, and is 71.1 μm. It concludes that gray square weighted centroid is an ideal location segmentation method, which is not only simple and easy to implement, but also has a higher positioning accuracy.
Laser triangulation measurements of scoliotic spine curvatures.
Čelan, Dušan; Jesenšek Papež, Breda; Poredoš, Primož; Možina, Janez
2015-01-01
The main purpose of this research was to develop a new method for differentiating between scoliotic and healthy subjects by analysing the curvatures of their spines in the cranio-caudal view. The study included 247 subjects with physiological curvatures of the spine and 28 subjects with clinically confirmed scoliosis. The curvature of the spine was determined by a computer analysis of the surface of the back, measured with a non-invasive, 3D, laser-triangulation system. The determined spinal curve was represented in the transversal plane, which is perpendicular to the line segment that was defined by the initial point and the end point of the spinal curve. This was achieved using a rotation matrix. The distances between the extreme points in the antero-posterior (AP) and left-right (LR) views were calculated in relation to the length of the spine as well as the quotient of these two values LR/AP. All the measured parameters were compared between the scoliotic and control groups using the Student's t-Test in case of normal data and Kruskal-Wallis test in case of non-normal data. Besides, a comprehensive diagram representing the distances between the extreme points in the AP and LR views was introduced, which clearly demonstrated the direction and the size of the thoracic and lumbar spinal curvatures for each individual subject. While the distances between the extreme points of the spine in the AP view were found to differ only slightly between the groups (p = 0.1), the distances between the LR extreme points were found to be significantly greater in the scoliosis group, compared to the control group (p < 0.001). The quotient LR/AP was statistically significantly different in both groups (p < 0.001). The main innovation of the presented method is the ability to differentiate a scoliotic subject from a healthy subject by assessing the curvature of the spine in the cranio-caudal view. Therefore, the proposed method could be useful for human posture
Measurement Uncertainty of Microscopic Laser Triangulation on Technical Surfaces.
Mueller, Thomas; Poesch, Andreas; Reithmeier, Eduard
2015-12-01
Laser triangulation is widely used to measure three-dimensional structure of surfaces. The technique is suitable for macroscopic and microscopic surface measurements. In this paper, the measurement uncertainty of laser triangulation is investigated on technical surfaces for microscopic measurement applications. Properties of technical surfaces are, for example, reflectivity, surface roughness, and the presence of scratches and pores. These properties are more influential in the microscopic laser triangulation than in the macroscopic one. In the Introduction section of this paper, the measurement uncertainty of laser triangulation is experimentally investigated for 13 different specimens. The measurements were carried out with and without a laser speckle reducer. In the Materials and Methods section of this paper, the surfaces of the 13 specimens are characterized in order to be able to find correlations between the surface properties and the measurement uncertainty. The last section of this paper describes simulations of the measurement uncertainty, which allow for the calculation of the measurement uncertainty with only one source of uncertainty present. The considerations in this paper allow for the assessment of the measurement uncertainty of laser triangulation on any technical surface when some surface properties, such as roughness, are known.
Analysis of imaging for laser triangulation sensors under Scheimpflug rule.
Miks, Antonin; Novak, Jiri; Novak, Pavel
2013-07-29
In this work a detailed analysis of the problem of imaging of objects lying in the plane tilted with respect to the optical axis of the rotationally symmetrical optical system is performed by means of geometrical optics theory. It is shown that the fulfillment of the so called Scheimpflug condition (Scheimpflug rule) does not guarantee the sharp image of the object as it is usually declared because of the fact that due to the dependence of aberrations of real optical systems on the object distance the image becomes blurred. The f-number of a given optical system also varies with the object distance. It is shown the influence of above mentioned effects on the accuracy of the laser triangulation sensors measurements. A detailed analysis of laser triangulation sensors, based on geometrical optics theory, is performed and relations for the calculation of measurement errors and construction parameters of laser triangulation sensors are derived.
Moving sound source localization based on triangulation method
Miao, Feng; Yang, Diange; Wen, Junjie; Lian, Xiaomin
2016-12-01
This study develops a sound source localization method that extends traditional triangulation to moving sources. First, the possible sound source locating plane is scanned. Secondly, for each hypothetical source location in this possible plane, the Doppler effect is removed through the integration of sound pressure. Taking advantage of the de-Dopplerized signals, the moving time difference of arrival (MTDOA) is calculated, and the sound source is located based on triangulation. Thirdly, the estimated sound source location is compared to the original hypothetical location and the deviations are recorded. Because the real sound source location leads to zero deviation, the sound source can be finally located by minimizing the deviation matrix. Simulations have shown the superiority of MTDOA method over traditional triangulation in case of moving sound sources. The MTDOA method can be used to locate moving sound sources with as high resolution as DAMAS beamforming, as shown in the experiments, offering thus a new method for locating moving sound sources.
Degree-Regular Triangulations of Torus and Klein Bottle-Erratum
Indian Academy of Sciences (India)
Basudeb Datta; Ashish Kumar Upadhyay
2005-08-01
A triangulation of a connected closed surface is called weakly regular if the action of its automorphism group on its vertices is transitive. A triangulation of a connected closed surface is called degree-regular if each of its vertices have the same degree. Clearly, a weakly regular triangulation is degree-regular. In [8], Lutz has classified all the weakly regular triangulations on at most 15 vertices. In [5], Datta and Nilakantan have classified all the degree-regular triangulations of closed surfaces on at most 11 vertices. In this article, we have proved that any degree-regular triangulation of the torus is weakly regular. We have shown that there exists an -vertex degree-regular triangulation of the Klein bottle if and only if is a composite number ≥ 9. We have constructed two distinct -vertex weakly regular triangulations of the torus for each ≥ 12 and a (4+2)-vertex weakly regular triangulation of the Klein bottle for each ≥ 2. For 12 ≤ ≤ 15, we have classified all the -vertex degree-regular triangulations of the torus and the Klein bottle. There are exactly 19 such triangulations, 12 of which are triangulations of the torus and remaining 7 are triangulations of the Klein bottle. Among the last 7, only one is weakly regular.
The Use of Triangulation Methods in Qualitative Educational Research
Oliver-Hoyo, Maria; Allen, DeeDee
2006-01-01
Triangulation involves the careful reviewing of data collected through different methods in order to achieve a more accurate and valid estimate of qualitative results for a particular construct. This paper describes how we used three qualitative methods of data collection to study attitudes of students toward graphing, hands-on activities, and…
Methodological triangulation of the students' use of recorded lectures
Gorissen, Pierre; Bruggen, Jan van; Jochems, Wim
2013-01-01
A lot of research into the use of recorded lectures has been done by using surveys or interviews. We will show that triangulation of multiple data sources is needed. We will discuss how students use recorded lectures according to their self-report and what actual usage of the recorded lectures can b
Multi-Sensor Triangulation of Multi-Source Spatial Data
Habib, Ayman; Kim, Chang-Jae; Bang, Ki-In
2007-01-01
The introduced methodologies are successful in: a) Ising LIDAR features for photogrammetric geo-refererncing; b) Delivering a geo-referenced imagery of the same quality as point-based geo-referencing procedures; c) Taking advantage of the synergistic characteristics of spatial data acquisition systems. The triangulation output can be used for the generation of 3-D perspective views.
Analysing students' use of recorded lectures through methodological triangulation
Gorissen, Pierre; Van Bruggen, Jan; Jochems, Wim
2012-01-01
Gorissen, P., Van Bruggen, J., & Jochems, W. M. G. (2012). Analysing students' use of recorded lectures through methodological triangulation. In L. Uden, E. S. Corchado Rodríquez, J. F. De Paz Santana, & F. De la Prieta (Eds.), Workshop on Learning Technology in Cloud (LTEC’12) (pp. 145-156). Heidel
Ideal Triangulations of Pseudo-Anosov Mapping Tori
Agol, Ian
2010-01-01
We show how to construct an ideal triangulation of a mapping torus of a pseudo-Anosov map punctured along the singular fibers. This gives rise to a new conjugacy invariant of mapping classes, and a new proof of a theorem of Farb-Leininger-Margalit. The approach in this paper is based on ideas of Hamenstadt.
A Triangulation Method for Identifying Hydrostratigraphic Locations of Well Screens
Energy Technology Data Exchange (ETDEWEB)
Whiteside, T. S. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL). Radiological Performance Assessment
2015-01-31
A method to identify the hydrostratigraphic location of well screens was developed using triangulation with known locations. This method was applied to all of the monitor wells being used to develop the new GSA groundwater model. Results from this method are closely aligned with those from an alternate method which uses a mesh surface.
Internet information triangulation: Design theory and prototype evaluation
Wijnhoven, Alphonsus B.J.M.; Brinkhuis, Michel
2014-01-01
Many discussions exist regarding the credibility of information on the Internet. Similar discussions happen on the interpretation of social scientific research data, for which information triangulation has been proposed as a useful method. In this article, we explore a design theory—consisting of a
Internet information triangulation: Design theory and prototype evaluation
Wijnhoven, Fons; Brinkhuis, Michel
2014-01-01
Many discussions exist regarding the credibility of information on the Internet. Similar discussions happen on the interpretation of social scientific research data, for which information triangulation has been proposed as a useful method. In this article, we explore a design theory—consisting of a
The Use of Triangulation Methods in Qualitative Educational Research
Oliver-Hoyo, Maria; Allen, DeeDee
2006-01-01
Triangulation involves the careful reviewing of data collected through different methods in order to achieve a more accurate and valid estimate of qualitative results for a particular construct. This paper describes how we used three qualitative methods of data collection to study attitudes of students toward graphing, hands-on activities, and…
Chow groups and intersection products for tensor triangulated categories
Klein, S.A.
2014-01-01
This thesis deals with a generalization of an important family of invariants from algebraic geometry (the Chow groups of an algebraic variety) to the setting of tensor triangulated categories. It is shown that these tensor triangular Chow groups recover the usual notion of Chow groups of an
Quantum Computing in Decoherence-Free Subspace Constructed by Triangulation
Directory of Open Access Journals (Sweden)
Qiao Bi
2010-01-01
Full Text Available A formalism for quantum computing in decoherence-free subspaces is presented. The constructed subspaces are partial triangulated to an index related to environment. The quantum states in the subspaces are just projected states which are ruled by a subdynamic kinetic equation. These projected states can be used to perform ideal quantum logical operations without decoherence.
Satisfying states of triangulations of a convex n-gon
Jiménez, Andrea; Loebl, Martin
2009-01-01
In this work we count the number of satisfying states of triangulations of a convex n-gon using the transfer matrix method. We show an exponential (in n) lower bound. We also give the exact formula for the number of satisfying states of a strip of triangles.
Eckstein, Johannes; Lei, Wang; Becker, Jonathan; Jun, Gao; Ott, Peter
2006-04-01
In this paper a distance measurement sensor is introduced, equipped with two integrated optical systems, the first one for rotationally symmetric triangulation and the second one for imaging the object while using only one 2D detector for both purposes. Rotationally symmetric triangulation, introduced in [1], eliminates some disadvantages of classical triangulation sensors, especially at steps or strong curvatures of the object, wherefore the measurement result depends not any longer on the angular orientation of the sensor. This is achieved by imaging the scattered light from an illuminated object point to a centered and sharp ring on a low cost area detector. The diameter of the ring is proportional to the distance of the object. The optical system consists of two off axis aspheric reflecting surfaces. This system allows for integrating a second optical system in order to capture images of the object at the same 2D detector. A mock-up was realized for the first time which consists of the reflecting optics for triangulation manufactured by diamond turning. A commercially available appropriate small lens system for imaging was mechanically integrated in the reflecting optics. Alternatively, some designs of retrofocus lens system for larger field of views were investigated. The optical designs allow overlying the image of the object and the ring for distance measurement in the same plane. In this plane a CCD detector is mounted, centered to the optical axis for both channels. A fast algorithm for the evaluation of the ring is implemented. The characteristics, i.e. the ring diameter versus object distance shows very linear behavior. For illumination of the object point for distance measurement, the beam of a red laser diode system is reflected by a wavelength bandpath filter on the axis of the optical system in. Additionally, the surface of the object is illuminated by LED's in the green spectrum. The LED's are located on the outside rim of the reflecting optics. The
Fosco, Gregory M.; Grych, John H.
2010-01-01
Although triangulation into parental conflict is a risk factor for child and adolescent maladjustment, little is known about how triangulation affects adolescents' functioning or the factors that lead children to be drawn into parental disagreements. This prospective study examined the relations between triangulation, appraisals of conflict, and…
Fosco, Gregory M.; Grych, John H.
2010-01-01
Although triangulation into parental conflict is a risk factor for child and adolescent maladjustment, little is known about how triangulation affects adolescents' functioning or the factors that lead children to be drawn into parental disagreements. This prospective study examined the relations between triangulation, appraisals of conflict, and…
THE DEEP2 GALAXY REDSHIFT SURVEY: THE VORONOI-DELAUNAY METHOD CATALOG OF GALAXY GROUPS
Energy Technology Data Exchange (ETDEWEB)
Gerke, Brian F. [KIPAC, SLAC National Accelerator Laboratory, 2575 Sand Hill Road, MS 29, Menlo Park, CA 94725 (United States); Newman, Jeffrey A. [Department of Physics and Astronomy, 3941 O' Hara Street, Pittsburgh, PA 15260 (United States); Davis, Marc [Department of Physics and Department of Astronomy, Campbell Hall, University of California-Berkeley, Berkeley, CA 94720 (United States); Coil, Alison L. [Center for Astrophysics and Space Sciences, University of California, San Diego, 9500 Gilman Drive, MC 0424, La Jolla, CA 92093 (United States); Cooper, Michael C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California-Irvine, Irvine, CA 92697 (United States); Dutton, Aaron A. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 5C2 (Canada); Faber, S. M.; Guhathakurta, Puragra; Koo, David C.; Phillips, Andrew C. [UCO/Lick Observatory, University of California-Santa Cruz, Santa Cruz, CA 95064 (United States); Konidaris, Nicholas; Lin, Lihwai [Astronomy Department, Caltech 249-17, Pasadena, CA 91125 (United States); Noeske, Kai [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Rosario, David J. [Max Planck Institute for Extraterrestrial Physics, Giessenbachstr. 1, 85748 Garching bei Muenchen (Germany); Weiner, Benjamin J.; Willmer, Christopher N. A. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Yan, Renbin [Department of Astronomy and Astrophysics, University of Toronto, 50 St. George Street, Toronto, ON M5S 3H4 (Canada)
2012-05-20
We present a public catalog of galaxy groups constructed from the spectroscopic sample of galaxies in the fourth data release from the Deep Extragalactic Evolutionary Probe 2 (DEEP2) Galaxy Redshift Survey, including the Extended Groth Strip (EGS). The catalog contains 1165 groups with two or more members in the EGS over the redshift range 0 < z < 1.5 and 1295 groups at z > 0.6 in the rest of DEEP2. Twenty-five percent of EGS galaxies and fourteen percent of high-z DEEP2 galaxies are assigned to galaxy groups. The groups were detected using the Voronoi-Delaunay method (VDM) after it has been optimized on mock DEEP2 catalogs following similar methods to those employed in Gerke et al. In the optimization effort, we have taken particular care to ensure that the mock catalogs resemble the data as closely as possible, and we have fine-tuned our methods separately on mocks constructed for the EGS and the rest of DEEP2. We have also probed the effect of the assumed cosmology on our inferred group-finding efficiency by performing our optimization on three different mock catalogs with different background cosmologies, finding large differences in the group-finding success we can achieve for these different mocks. Using the mock catalog whose background cosmology is most consistent with current data, we estimate that the DEEP2 group catalog is 72% complete and 61% pure (74% and 67% for the EGS) and that the group finder correctly classifies 70% of galaxies that truly belong to groups, with an additional 46% of interloper galaxies contaminating the catalog (66% and 43% for the EGS). We also confirm that the VDM catalog reconstructs the abundance of galaxy groups with velocity dispersions above {approx}300 km s{sup -1} to an accuracy better than the sample variance, and this successful reconstruction is not strongly dependent on cosmology. This makes the DEEP2 group catalog a promising probe of the growth of cosmic structure that can potentially be used for cosmological tests.
Institute of Scientific and Technical Information of China (English)
FA WenZhe; XU Feng; JIN YaQiu
2009-01-01
Based on the statistics of the lunar cratered terrain, e.g., population, dimension and shape of craters, the terrain feature of cratered lunar surface is numerically generated. According to the Inhomogeneous distribution of the lunar surface slope, the triangulated irregular network (TIN) is employed to make the digital elevation of lunar surface model. The Kirchhoff approximation of surface scattering is then applied to simulation of lunar surface scattering. The synthetic aperture radar (SAR) image for compre-hensive cratered lunar surface is numerically generated using back projection (BP) algorithm of SAR Imaging. Making use of the digital elevation and Clementlne UVVIS data at Apollo 15 landing site as the ground truth, an SAR Image at Apollo 15 landing site Is simulated. The image simulation is verified using real SAR image and echoes statistics.
Experiences with systematic triangulation at the Global Environment Facility.
Carugi, Carlo
2016-04-01
Systematic triangulation may address common challenges in evaluation, such as the scarcity or unreliability of data, or the complexities of comparing and cross-checking evidence from diverse disciplines. Used to identify key evaluation findings, its application has proven to be effective in addressing the limitations encountered in country-level evaluation analysis conducted by the Independent Evaluation Office of the Global Environment Facility (GEF). These include the scarcity or unreliability of national statistics on environmental indicators and data series, especially in Least Developed Countries; challenges in evaluating the impacts of GEF projects; and inherent difficulties in defining the GEF portfolio of projects prior to the undertaking of the evaluation. In addition to responding to the need for further developing triangulation protocols, procedures and/or methodologies advocated by some authors, the approach offers a contribution to evaluation practice. This applies particularly to those evaluation units tasked with country-level evaluations in international organizations, facing similar constraints.
RESEARCH ON ADAPTIVE DATA COMPRESSION METHOD FOR TRIANGULATED SURFACES
Institute of Scientific and Technical Information of China (English)
Wang Wen; Wu Shixiong; Chen Zichen
2004-01-01
NC code or STL file can be generated directly from measuring data in a fast reverse-engineering mode.Compressing the massive data from laser scanner is the key of the new mode.An adaptive compression method based on triangulated-surfaces model is put forward.Normal-vector angles between triangles are computed to find prime vertices for removal.Ring data structure is adopted to save massive data effectively.It allows the efficient retrieval of all neighboring vertices and triangles of a given vertices.To avoid long and thin triangles,a new re-triangulation approach based on normalized minimum-vertex-distance is proposed,in which the vertex distance and interior angle of triangle are considered.Results indicate that the compression method has high efficiency and can get reliable precision.The method can be applied in fast reverse engineering to acquire an optimal subset of the original massive data.
Detectability of active triangulation range finder: a solar irradiance approach.
Liu, Huizhe; Gao, Jason; Bui, Viet Phuong; Liu, Zhengtong; Lee, Kenneth Eng Kian; Peh, Li-Shiuan; Png, Ching Eng
2016-06-27
Active triangulation range finders are widely used in a variety of applications such as robotics and assistive technologies. The power of the laser source should be carefully selected in order to satisfy detectability and still remain eye-safe. In this paper, we present a systematic approach to assess the detectability of an active triangulation range finder in an outdoor environment. For the first time, we accurately quantify the background noise of a laser system due to solar irradiance by coupling the Perez all-weather sky model and ray tracing techniques. The model is validated with measurements with a modeling error of less than 14.0%. Being highly generic and sufficiently flexible, the proposed model serves as a guide to define a laser system for any geographical location and microclimate.
Personal authentication using hand vein triangulation and knuckle shape.
Kumar, Ajay; Prathyusha, K Venkata
2009-09-01
This paper presents a new approach to authenticate individuals using triangulation of hand vein images and simultaneous extraction of knuckle shape information. The proposed method is fully automated and employs palm dorsal hand vein images acquired from the low-cost, near infrared, contactless imaging. The knuckle tips are used as key points for the image normalization and extraction of region of interest. The matching scores are generated in two parallel stages: (i) hierarchical matching score from the four topologies of triangulation in the binarized vein structures and (ii) from the geometrical features consisting of knuckle point perimeter distances in the acquired images. The weighted score level combination from these two matching scores are used to authenticate the individuals. The achieved experimental results from the proposed system using contactless palm dorsal-hand vein images are promising (equal error rate of 1.14%) and suggest more user friendly alternative for user identification.
Scale-dependent homogeneity measures for causal dynamical triangulations
Cooperman, Joshua H
2014-01-01
I propose two scale-dependent measures of the homogeneity of the quantum geometry determined by an ensemble of causal triangulations. The first measure is volumetric, probing the growth of volume with graph geodesic distance. The second measure is spectral, probing the return probability of a random walk with diffusion time. Both of these measures, particularly the first, are closely related to those used to assess the homogeneity of our own universe on the basis of galaxy redshift surveys. I employ these measures to quantify the quantum spacetime homogeneity as well as the temporal evolution of quantum spatial homogeneity of ensembles of causal triangulations in the well-known physical phase. According to these measures, the quantum spacetime geometry exhibits some degree of inhomogeneity on sufficiently small scales and a high degree of homogeneity on sufficiently large scales. This inhomogeneity appears unrelated to the phenomenon of dynamical dimensional reduction. I also uncover evidence for power-law sc...
Evaluating habitat selection with radio-telemetry triangulation error
Samuel, M.D.; Kenow, K.P.
1992-01-01
Radio-telemetry triangulation errors result in the mislocation of animals and misclassification of habitat use. We present analytical methods that provide improved estimates of habitat use when misclassification probabilities can be determined. When misclassification probabilities cannot be determined, we use random subsamples from the error distribution of an estimated animal location to improve habitat use estimates. We conducted Monte Carlo simulations to evaluate the effects of this subsampling method, triangulation error, number of animal locations, habitat availability, and habitat complexity on bias and variation in habitat use estimates. Results for the subsampling method are illustrated using habitat selection by redhead ducks (Aythya americana ). We recommend the subsampling method with a minimum of 50 random points to reduce problems associated with habitat misclassification.
Optimizing 3D Triangulations to Recapture Sharp Edges
DEFF Research Database (Denmark)
Bærentzen, Jakob Andreas
2006-01-01
sharp edges. The energy is minimized using edge swapping, and this can be done either in a greedy fashion or using simulated annealing. The latter is more costly, but effectively avoids local minima. The method has been used on a number of models. Particularly good results have been obtained on digital......In this report, a technique for optimizing 3D triangulations is proposed. The method seeks to minimize an energy defined as a sum of energy terms for each edge in a triangle mesh. The main contribution is a novel per edge energy which strikes a balance between penalizing dihedral angle yet allowing...... terrain models. It is demonstrated how the method has been able to recapture sharp edges which are clearly present in the data but not reflected by the original triangulation of the elevation points....
The Stabilization and Idempotent Completion of a Left Triangulated Category
Institute of Scientific and Technical Information of China (English)
Lin XIN; Yixin FU
2012-01-01
Let ((ψ),Ω,△) be a left triangulated category with a fully faithful endofunctor Ω.We show a triangle-equivalence (S((ψ)),(Ω),(△)) ≌ (S((ψ)),(Ω),(△)),where (S((ψ)),(Ω),(△)) denotes the stabilization of the idempotent completion of ((ψ),Ω,△) and (S((ψ)),(Ω),(△)) denotes the idempotent completion of the stabilization of ((ψ),Ω,△).
Grounded theory, feminist theory, critical theory: toward theoretical triangulation.
Kushner, Kaysi Eastlick; Morrow, Raymond
2003-01-01
Nursing and social science scholars have examined the compatibility between feminist and grounded theory traditions in scientific knowledge generation, concluding that they are complementary, yet not without certain tensions. This line of inquiry is extended to propose a critical feminist grounded theory methodology. The construction of symbolic interactionist, feminist, and critical feminist variants of grounded theory methodology is examined in terms of the presuppositions of each tradition and their interplay as a process of theoretical triangulation.
The transfer matrix in four-dimensional Causal Dynamical Triangulations
Görlich, Andrzej
2013-01-01
Causal Dynamical Triangulations is a background independent approach to quantum gravity. In this paper we introduce a phenomenological transfer matrix model, where at each time step a reduced set of quantum states is used. The states are solely characterized by the discretized spatial volume. Using Monte Carlo simulations we determine the effective transfer matrix elements and extract the effective action for the scale factor. In this framework no degrees of freedom are frozen, however, the obtained action agrees with the minisuperspace model.
Optical triangulation-based microtopographic inspection of surfaces.
Costa, Manuel F M
2012-01-01
The non-invasive inspection of surfaces is a major issue in a wide variety of industries and research laboratories. The vast and increasing range of surface types, tolerance requirements and measurement constraints demanded during the last decades represents a major research effort in the development of new methods, systems and metrological strategies. The discreet dimensional evaluation the rugometric characterization and the profilometric inspection seem to be insufficient in many instances. The full microtopographic inspection has became a common requirement. Among the different systems developed, optical methods have the most important role and among those triangulation-based ones have gained a major status thanks to their flexibility, reliability and robustness. In this communication we will provide a brief historical review on the development of optical triangulation application to the dimensional inspection of objects and surfaces and on the work done at the Microtopography Laboratory of the Physics Department of the University of Minho, Portugal, in the development of methods and systems of optical triangulation-based microtopographic inspection of surfaces.
Excerpt from Triangulations: Narrative Strategies for Navigating Latino Identity
Directory of Open Access Journals (Sweden)
David J. Vázquez
2011-12-01
Full Text Available Just as mariners use triangulation, mapping an imaginary triangle between two known positions and an unknown location, so, David J. Vázquez contends, Latino authors in late twentieth-century America employ the coordinates of familiar ideas of self to find their way to new, complex identities. Through this metaphor, Vázquez reveals how Latino autobiographical texts, written after the rise of cultural nationalism in the 1960s, challenge mainstream notions of individual identity and national belonging in the United States.In a traditional autobiographical work, the protagonist frequently opts out of his or her community. In the works that Vázquez analyzes in Triangulations, protagonists instead opt in to collective groups—often for the express political purpose of redefining that collective. Reading texts by authors such as Ernesto Galarza, Jesús Colón, Piri Thomas, Oscar “Zeta” Acosta, Judith Ortiz Cofer, John Rechy, Julia Alvarez, and Sandra Cisneros, Vázquez engages debates about the relationship between literature and social movements, the role of cultural nationalism in projects for social justice, the gender and sexual problematics of 1960s cultural nationalist groups, the possibilities for interethnic coalitions, and the interpretation of autobiography. In the process, Triangulations considers the potential for cultural nationalism as a productive force for aggrieved communities of color in their struggles for equality.
A Monte Carlo study of size and angular properties of a three-dimensional Poisson-Delaunay cell
Kumar, Susmit; Kurtz, Stewart K.
1994-05-01
On the basis of simulation of 1.2×106 three-dimensional Poisson-Delaunay cells, the statistical properties of their size and angular parameters have been studied. The moments of the volume, face area, and edge length distributions are found to be equal to those obtained from the exact expressions of Miles and of Moller. The volume, surface area, and face area distributions can be described by the two-parameter gamma distribution. The normal distribution can be used to describe the distributions of the total edge length of a cell and the perimeter of a face. The edge length distribution has also been studied. The distribution of the angle in a face is found to be in accordance with its theoretical distribution.
A displacement measurement system based on optical triangulation method
Institute of Scientific and Technical Information of China (English)
FU Xian-bin; LIU Bin; ZHANG Yu-cun
2011-01-01
A new displacement measurement system is described in this paper according to the basic principles of traditional laser triangulation method.The range of the traditional measuring method is enlarged by measuring in sections.Three independent CCDs,which are distributed uniformly along the optical axis,are used to achieve subsection measurement.The plane mirror is regarded as a virtual detector.When imaging beam is reflected by the plane mirror,the beam is imaged on the CCD.The designed system is equivalent to add a CCD.The feasibility of the displacement measurement system is verified by the experiment.
Nested cycles in large triangulations and crossing-critical graphs
Hernandez-Velez, Cesar; Thomas, Robin
2009-01-01
We show that every sufficiently large plane triangulation has a large collection of nested cycles that either are pairwise disjoint, or pairwise intersect in exactly one vertex, or pairwise intersect in exactly two vertices. We apply this result to show that for each fixed positive integer $k$, there are only finitely many $k$-crossing-critical simple graphs of average degree at least six. Combined with the recent constructions of crossing-critical graphs given by Bokal, this settles the question of for which numbers $q>0$ there is an infinite family of $k$-crossing-critical simple graphs of average degree $q$.
3D vesicle dynamics simulations with a linearly triangulated surface
Boedec, G.; Leonetti, M.; Jaeger, M.
2011-02-01
Simulations of biomembranes have gained an increasing interest in the past years. Specificities of these membranes propose new challenges for the numerics. In particular, vesicle dynamics are governed by bending forces as well as a surface incompressibility constraint. A method to compute the bending force density resultant onto piecewise linearly triangulated surface meshes is described. This method is coupled with a boundary element method solver for inner and outer fluids, to compute vesicle dynamics under external flows. The surface incompressibility constraint is satisfied by the construction of a projection operator.
Comparative Study of Triangulation based and Feature based Image Morphing
Directory of Open Access Journals (Sweden)
Ms. Bhumika G. Bhatt
2012-01-01
Full Text Available Image Morphing is one of the most powerful Digital Image processing technique, which is used to enhancemany multimedia projects, presentations, education and computer based training. It is also used inmedical imaging field to recover features not visible in images by establishing correspondence of featuresamong successive pair of scanned images. This paper discuss what morphing is and implementation ofTriangulation based morphing Technique and Feature based Image Morphing. IT analyze both morphingtechniques in terms of different attributes such as computational complexity, Visual quality of morphobtained and complexity involved in selection of features.
Combining Block and Corner Features for Content-Based Trademark Retrieval
Institute of Scientific and Technical Information of China (English)
HONG Zhiling; JIANG Qingshan; WU Meihong
2007-01-01
In order to retrieve a similarly look trademark from a large trademark database, an automatic content based trademark retrieval method using block hit statistic and comer Delaunay Triangulation features was proposed. The block features are derived from the hit statistic on a series of concentric ellipse. The comers are detected based on an enhanced SUSAN (Smallest Univalue Segment Assimilating Nucleus) algorithm and the Delaunay Triangulation of corner points are used as the corner features. Experiments have been conducted on the MPEG-7 Core Experiment CE-Shape-1 database of 1 400 images and a trademark database of 2 000 images. The retrieval results are very encouraging.
Dynamic ray tracing and its application in triangulated media
Energy Technology Data Exchange (ETDEWEB)
Rueger, A.
1993-07-01
Hale and Cohen (1991) developed software to generate two-dimensional computer models of complex geology. Their method uses a triangulation technique designed to support efficient and accurate computation of seismic wavefields for models of the earth`s interior. Subsequently, Hale (1991) used this triangulation approach to perform dynamic ray tracing and create synthetic seismograms based on the method of Gaussian beams. Here, I extend this methodology to allow an increased variety of ray-theoretical experiments. Specifically, the developed program GBmod (Gaussian Beam MODeling) can produce arbitrary multiple sequences and incorporate attenuation and density variations. In addition, I have added an option to perform Fresnel-volume ray tracing (Cerveny and Soares, 1992). Corrections for reflection and transmission losses at interfaces, and for two-and-one-half-dimensional (2.5-D) spreading are included. However, despite these enhancements, difficulties remain in attempts to compute accurate synthetic seismograms if strong lateral velocity inhomogeneities are present. Here, these problems are discussed and, to a certain extent, reduced. I provide example computations of high-frequency seismograms based on the method of Gaussian beams to exhibit the advantages and disadvantages of the proposed modeling method and illustrate new features for both surface and vertical seismic profiling (VSP) acquisition geometries.
Triangulation of the Gigantic Jets in 20 August 2014
Kang-Ming, P.; Hsu, R. R.; Su, H. T.; Chen, A. B. C.; Chou, J. K.; Chang, S. C.; Wu, Y. J.; Chien-Lun, H.; Yang, I. C.; Tsai, S. H.
2015-12-01
Coordinate optical observation campaigns on TLEs near Taiwan are held since 2011 with the aim to triangulate TLEs. Currently, there are four stations with baseline varying from 100 to 400 km between them. Our optical observation systems recorded 48 various types of TLEs on the night of 20 August 2014, with eight of them being gigantic jets that were recorded by at least two stations. Due to the length of baselines and the TLE occurring locations, the earth curvature needed to be taken into account by means of spherical trigonometry method. The preliminary results shows the gigantic jets occurred over the northern Taiwan and the accuracy of geolocation is less than 1 km and the accuracy of the retrieval height on the key structures is less than 0.5 km. The triangulation results of the eight events indicate most of these gigantic jets terminated at 80-90km, but one of the gigantic jets is likely extend to 100 km. Three of the eight gigantic jets occurred consequently after previous one with time interval of 500ms to more than 100s. The previous gigantic jet is likely to influence the consequent gigantic jet for usually the consequent gigantic jet has more beads structures in high altitude and one of the streamer column of a consequent gigantic jets at 55 -60 km is identified to re-bright, which is more than 100s after the previous gigantic jet.
Eccentric error and compensation in rotationally symmetric laser triangulation
Institute of Scientific and Technical Information of China (English)
Wang Lei; Gao Jun; Wang Xiaojia; Johannes Eckstein; Peter Ott
2007-01-01
Rotationally symmetric triangulation (RST) sensor has more flexibility and less uncertainty limits becauseof the abaxial rotationally symmetric optical system.But if the incident laser is eccentric,the symmetry of the imagewill descend,and it will result in the eccentric error especially when some part of the imaged ring is blocked.Themodel of rotationally symmetric triangulation that meets the Schimpflug condition is presented in this paper.The errorfrom eccentric incident 1aser is analysed.It iS pointed out that the eccentric error is composed of two parts.one is acosine in circumference and proportional to the eccentric departure factor,and the other is a much smaller quadricfactor of the departure.When the ring is complete,the first error factor is zero because it is integrated in whole ring,but if some part of the ring iS blocked,the first factor will be the main error.Simulation verifies the result of the a-nalysis.At last,a compensation method to the error when some part of the ring is lost is presented based on neuralnetwork.The results of experiment show that the compensation will make the absolute maximum error descend tohalf,and the standard deviation of error descends to 1/3.
Identification of novel autoantigens by a triangulation approach.
Cottrell, Tricia R; Hall, John C; Rosen, Antony; Casciola-Rosen, Livia
2012-11-30
High titer autoantibodies, which are often associated with specific clinical phenotypes, are useful diagnostically and prognostically in systemic autoimmune diseases. In several autoimmune rheumatic diseases (e.g. myositis and Sjogren's syndrome), 20-40% of patients are autoantibody negative as assessed by conventional assays. The recent discovery of new specificities (e.g., anti-MDA5) in a subset of these autoantibody-negative subjects demonstrates that additional specificities await identification. In this manuscript, we describe a rapid multidimensional method to identify new autoantigens. A central foundation of this rapid approach is the use of an antigen source in which a pathogenic pathway active in the disease is recapitulated. Additionally, the method involves a modified serological proteome analysis strategy which allows confirmation that the correct gel plug has been removed prior to sending for sequencing. Lastly, the approach uses multiple sources of information to enable rapid triangulation and identification of protein candidates. Possible permutations and underlying principles of this triangulation strategy are elaborated to demonstrate the broad utility of this approach for antigen discovery.
A MODIFIED METHOD FOR IMAGE TRIANGULATION USING INCLINED ANGLES
Directory of Open Access Journals (Sweden)
B. Alsadik
2016-06-01
Full Text Available The ongoing technical improvements in photogrammetry, Geomatics, computer vision (CV, and robotics offer new possibilities for many applications requiring efficient acquisition of three-dimensional data. Image orientation is one of these important techniques in many applications like mapping, precise measurements, 3D modeling and navigation. Image orientation comprises three main techniques of resection, intersection (triangulation and relative orientation, which are conventionally solved by collinearity equations or by using projection and fundamental matrices. However, different problems still exist in the state – of –the –art of image orientation because of the nonlinearity and the sensitivity to proper initialization and spatial distribution of the points. In this research, a modified method is presented to solve the triangulation problem using inclined angles derived from the measured image coordinates and based on spherical trigonometry rules and vector geometry. The developed procedure shows promising results compared to collinearity approach and to converge to the global minimum even when starting from far approximations. This is based on the strong geometric constraint offered by the inclined angles that are enclosed between the object points and the camera stations. Numerical evaluations with perspective and panoramic images are presented and compared with the conventional solution of collinearity equations. The results show the efficiency of the developed model and the convergence of the solution to global minimum even with improper starting values.
a Modified Method for Image Triangulation Using Inclined Angles
Alsadik, Bashar
2016-06-01
The ongoing technical improvements in photogrammetry, Geomatics, computer vision (CV), and robotics offer new possibilities for many applications requiring efficient acquisition of three-dimensional data. Image orientation is one of these important techniques in many applications like mapping, precise measurements, 3D modeling and navigation. Image orientation comprises three main techniques of resection, intersection (triangulation) and relative orientation, which are conventionally solved by collinearity equations or by using projection and fundamental matrices. However, different problems still exist in the state - of -the -art of image orientation because of the nonlinearity and the sensitivity to proper initialization and spatial distribution of the points. In this research, a modified method is presented to solve the triangulation problem using inclined angles derived from the measured image coordinates and based on spherical trigonometry rules and vector geometry. The developed procedure shows promising results compared to collinearity approach and to converge to the global minimum even when starting from far approximations. This is based on the strong geometric constraint offered by the inclined angles that are enclosed between the object points and the camera stations. Numerical evaluations with perspective and panoramic images are presented and compared with the conventional solution of collinearity equations. The results show the efficiency of the developed model and the convergence of the solution to global minimum even with improper starting values.
4-D XRD for strain in many grains using triangulation
Energy Technology Data Exchange (ETDEWEB)
Bale, Hrishikesh A.; Hanan, Jay C.; Tamura, Nobumichi
2006-12-31
Determination of the strains in a polycrystalline materialusing 4-D XRD reveals sub-grain and grain-to-grain behavior as a functionof stress. Here 4-D XRD involves an experimental procedure usingpolychromatic micro-beam X-radiation (micro-Laue) to characterizepolycrystalline materials in spatial location as well as with increasingstress. The in-situ tensile loading experiment measured strain in a modelaluminum-sapphire metal matrix composite using the Advanced Light Source,Beam-line 7.3.3. Micro-Laue resolves individual grains in thepolycrystalline matrix. Results obtained from a list of grains sorted bycrystallographic orientation depict the strain states within and amongindividual grains. Locating the grain positions in the planeperpendicular to the incident beam is trivial. However, determining theexact location of grains within a 3-D space is challenging. Determiningthe depth of the grains within the matrix (along the beam direction)involved a triangulation method tracing individual rays that producespots on the CCD back to the point of origin. Triangulation wasexperimentally implemented by simulating a 3-D detector capturingmultiple diffraction images while increasing the camera to sampledistance. Hence by observing the intersection of rays from multiple spotsbelonging to the corresponding grain, depth is calculated. Depthresolution is a function of the number of images collected, grain to beamsize ratio, and the pixel resolution of the CCD. The 4DXRD methodprovides grain morphologies, strain behavior of each grain, andinteractions of the matrix grains with each other and the centrallylocated single crystal fiber.
A Detailed Evaluation of a Laser Triangulation Ranging System for Mobile Robots
1983-08-01
A RPI TECHNICAL REPORT MP-82 A DETAILED EVALUATION OF A LASER - TRIANGULATION RANGING SYSTEM FOR MOBILE ROBOTS by Thomas J. Clement Contract MDA-903...Polytechnic Institute Technical Report MP-79, Troy, N.Y., May 1982. 9. McNellis, T., "Evaluation of a Laser Triangulation Ranging System for Mobile Robots ." Rensselaer
Schwartz, Terry Ann; Kaplan, Michael H.
The benefits accrued through the use of triangulation as both a design strategy and an analytic tool cannot be overstated. Triangulation allows for the clustering and organizing of disparate yet related data. Finding out what the data have in common and how the data are different allow the researcher to eliminate (or reduce) the number of…
A REST Service for Triangulation of Point Sets Using Oriented Matroids
Directory of Open Access Journals (Sweden)
José Antonio Valero Medina
2014-05-01
Full Text Available This paper describes the implementation of a prototype REST service for triangulation of point sets collected by mobile GPS receivers. The first objective of this paper is to test functionalities of an application, which exploits mobile devices’ capabilities to get data associated with their spatial location. A triangulation of a set of points provides a mechanism through which it is possible to produce an accurate representation of spatial data. Such triangulation may be used for representing surfaces by Triangulated Irregular Networks (TINs, and for decomposing complex two-dimensional spatial objects into simpler geometries. The second objective of this paper is to promote the use of oriented matroids for finding alternative solutions to spatial data processing and analysis tasks. This study focused on the particular case of the calculation of triangulations based on oriented matroids. The prototype described in this paper used a wrapper to integrate and expose several tools previously implemented in C++.
Directory of Open Access Journals (Sweden)
Gabriela ȘTEFURA
2014-04-01
Full Text Available The research in tax compliance has approached various methods of data collection, but almost never methodological triangulation has been used. Triangulation helps the researcher in obtaining more reliable results, if they prove to be similar after each method used and also it increases the validity of the entire study. The purpose of the paper is to highlight the importance of triangulation and especially methodological triangulation, by presenting the use of it in researching the compliance behaviour of three categories of individual Romanian taxpayers (doctors, lawyers/notaries and self-employed accountants towards income reporting. Two studies have been conducted: a survey on actual taxpayers and a quasi-experiment on potential taxpayers. The studies had similar results, so the usefulness of triangulation is once again confirmed. The results may be useful to both theorists and practitioners.
Extrinsic curvature in 2-dimensional Causal Dynamical Triangulation
Glaser, Lisa; Weinfurtner, Silke
2016-01-01
Causal Dynamical Triangulations (CDT) is a non-perturbative quantisation of general relativity. Ho\\v{r}ava-Lifshitz gravity on the other hand modifies general relativity to allow for perturbative quan- tisation. Past work has given rise to the speculation that Ho\\v{r}ava-Lifshitz gravity might correspond to the continuum limit of CDT. In this paper we add another piece to this puzzle by applying the CDT quantisation prescription directly to Ho\\v{r}ava-Lifshitz gravity in 2 dimensions. We derive the continuum Hamiltonian and we show that it matches exactly the Hamiltonian one derives from canonically quantising the Ho\\v{r}ava-Lifshitz action. Unlike the standard CDT case, here the intro- duction of a foliated lattice does not impose further restriction on the configuration space and, as a result, lattice quantisation does not leave any imprint on continuum physics as expected.
Quantum Gravity and Matter: Counting Graphs on Causal Dynamical Triangulations
Benedetti, D
2006-01-01
An outstanding challenge for models of non-perturbative quantum gravity is the consistent formulation and quantitative evaluation of physical phenomena in a regime where geometry and matter are strongly coupled. After developing appropriate technical tools, one is interested in measuring and classifying how the quantum fluctuations of geometry alter the behaviour of matter, compared with that on a fixed background geometry. In the simplified context of two dimensions, we show how a method invented to analyze the critical behaviour of spin systems on flat lattices can be adapted to the fluctuating ensemble of curved spacetimes underlying the Causal Dynamical Triangulations (CDT) approach to quantum gravity. We develop a systematic counting of embedded graphs to evaluate the thermodynamic functions of the gravity-matter models in a high- and low-temperature expansion. For the case of the Ising model, we compute the series expansions for the magnetic susceptibility on CDT lattices and their duals up to orders 6 ...
Calibration procedure for a laser triangulation scanner with uncertainty evaluation
Genta, Gianfranco; Minetola, Paolo; Barbato, Giulio
2016-11-01
Most of low cost 3D scanning devices that are nowadays available on the market are sold without a user calibration procedure to correct measurement errors related to changes in environmental conditions. In addition, there is no specific international standard defining a procedure to check the performance of a 3D scanner along time. This paper aims at detailing a thorough methodology to calibrate a 3D scanner and assess its measurement uncertainty. The proposed procedure is based on the use of a reference ball plate and applied to a triangulation laser scanner. Experimental results show that the metrological performance of the instrument can be greatly improved by the application of the calibration procedure that corrects systematic errors and reduces the device's measurement uncertainty.
Spatial analysis of the Chania prefecture: Crete triangulation network quality
Achilleos, Georgios
2016-08-01
The network of trigonometric points of a region is the basis upon which any form of cartographic work is attached to the national geodetic coordinate system (data collection, processing, output presentations) and not only. The products of the cartographic work (cartographic representations), provide the background which is used in cases of spatial planning and development strategy. This trigonometric network, except that, provides to a single cartographic work, the ability to exist within a unified official state geodetic reference system, simultaneously determines the quality of the result, since the trigonometric network data that are used, have their own quality. In this paper, we present the research of spatial quality of the trigonometric network of Chania Prefecture in Crete. This analysis examines the triangulation network points, both with respect to their spatial position (distribution in space), and in their accuracy (horizontally and vertically).
Public Health Triangulation to inform decision-making in Belgium.
Bossuyt, N; Van Casteren, V; Goderis, G; Wens, J; Moreels, S; Vanthomme, K; De Clercq, E
2015-01-01
We assessed the impact of a nation-wide ambulatory care complex intervention (the "care trajectory program") on quality of care in Belgium. We used the three-step public health triangulation method described in this paper and data from four different data sources: a national reimbursement database, an electronic patient record-based general practitioner network, the Belgian general practitioner sentinel network, and a new national registry for care trajectory patients. By applying our method and using the available evidence, we identified key findings that have been accepted by experts and stakeholders. We also produced timely recommendations for the decision-making process, four years after the start of the care trajectory program.
Magnetic Properties and Thermal Entanglement on a Triangulated Kagome Lattice
Ananikian, N S; Chakhmakhchyan, L A; Kocharian, A N
2011-01-01
The magnetic and entanglement thermal (equilibrium) properties in spin-1/2 Ising-Heisenberg model on a triangulated Kagome lattice are analyzed by means of variational mean-field like treatment based on Gibbs-Bogoliubov inequality. Because of the separable character of Ising-type exchange interactions between the Heisenberg trimers the calculation of quantum entanglement in a self-consistent field can be performed for each of the trimers individually. The concurrence in terms of three qubit isotropic Heisenberg model in effective Ising field is non-zero even in the absence of a magnetic field. The magnetic and entanglement properties exhibit common (plateau and peak) features observable via (antferromagnetic) coupling constant and external magnetic field. The critical temperature for the phase transition and threshold temperature for concurrence coincide in the case of antiferromagnetic coupling between qubits. The existence of entangled and disentangled phases in saturated and frustrated phases is establishe...
Extrinsic curvature in two-dimensional causal dynamical triangulation
Glaser, Lisa; Sotiriou, Thomas P.; Weinfurtner, Silke
2016-09-01
Causal dynamical triangulation (CDT) is a nonperturbative quantization of general relativity. Hořava-Lifshitz gravity, on the other hand, modifies general relativity to allow for perturbative quantization. Past work has given rise to the speculation that Hořava-Lifshitz gravity might correspond to the continuum limit of CDT. In this paper we add another piece to this puzzle by applying the CDT quantization prescription directly to Hořava-Lifshitz gravity in two dimensions. We derive the continuum Hamiltonian, and we show that it matches exactly the Hamiltonian derived from canonically quantizing the Hořava-Lifshitz action. Unlike the standard CDT case, here the introduction of a foliated lattice does not impose further restriction on the configuration space and, as a result, lattice quantization does not leave any imprint on continuum physics as expected.
Causal Dynamical Triangulations in the Spincube Model of Quantum Gravity
Vojinovic, Marko
2015-01-01
We study the implications of the simplicity constraint in the spincube model of quantum gravity. Relating the edge-lengths to integer triangle areas, the simplicity constraint imposes a very strong restrictions between them, ultimately leading to a requirement that all 4-simplices in the triangulation must be almost mutually identical. As a surprising and unexpected consequence of this property, one can obtain the CDT state sum as a special case of the spincube state sum. This relationship brings new insight into the long-standing problem of the relationship between the spinfoam approach and the CDT approach to quantum gravity. In particular, it turns out that the spincube model contains properties of both approaches, providing a single unifying framework for their analysis and comparison. In addition, the spincube state sum also contains some other special cases, very similar but not equivalent to the CDT state sum.
The Subjectivity Problem: Improving Triangulation Approaches in Metaphor Analysis Studies
Directory of Open Access Journals (Sweden)
Sonya L. Armstrong
2011-06-01
Full Text Available Metaphor analysis procedures for uncovering participant conceptualizations have been well-established in qualitative research settings since the early 1980s; however, one common criticism of metaphor analysis is the trustworthiness of the findings. Namely, accurate determination of the conceptual metaphors held by participants based on the investigation of linguistic metaphors has been identified as a methodological issue because of the subjectivity involved in the interpretation; that is, because they are necessarily situated in specific social and cultural milieus, meanings of particular metaphors are not universally constructed nor understood. In light of these critiques, this article provides examples of two different triangulation methods that can be employed to supplement the trustworthiness of the findings when metaphor analysis methodologies are used.
On-Line Metrology with Conoscopic Holography: Beyond Triangulation
Álvarez, Ignacio; Enguita, Jose M.; Frade, María; Marina, Jorge; Ojea, Guillermo
2009-01-01
On-line non-contact surface inspection with high precision is still an open problem. Laser triangulation techniques are the most common solution for this kind of systems, but there exist fundamental limitations to their applicability when high precisions, long standoffs or large apertures are needed, and when there are difficult operating conditions. Other methods are, in general, not applicable in hostile environments or inadequate for on-line measurement. In this paper we review the latest research in Conoscopic Holography, an interferometric technique that has been applied successfully in this kind of applications, ranging from submicrometric roughness measurements, to long standoff sensors for surface defect detection in steel at high temperatures. PMID:22399984
Technique Triangulation for Validation in Directed Content Analysis
Directory of Open Access Journals (Sweden)
Áine M. Humble PhD
2009-09-01
Full Text Available Division of labor in wedding planning varies for first-time marriages, with three types of couples—traditional, transitional, and egalitarian—identified, but nothing is known about wedding planning for remarrying individuals. Using semistructured interviews, the author interviewed 14 couples in which at least one person had remarried and used directed content analysis to investigate the extent to which the aforementioned typology could be transferred to this different context. In this paper she describes how a triangulation of analytic techniques provided validation for couple classifications and also helped with moving beyond “blind spots” in data analysis. Analytic approaches were the constant comparative technique, rank order comparison, and visual representation of coding, using MAXQDA 2007's tool called TextPortraits.
Can causal dynamical triangulations probe factor-ordering issues?
Maitra, R L
2009-01-01
The causal dynamical triangulations (CDT) program has for the first time allowed for path-integral computation of correlation functions in full general relativity without symmetry reductions and taking into account Lorentzian signature. One of the most exciting recent results in CDT is the strong agreement of these computations with (minisuperspace) path integral calculations in quantum cosmology. Herein I will describe my current project to compute minisuperspace (Friedman-Robertson-Walker) path integrals with a range of different measures corresponding to various factor orderings of the Friedman-Robertson-Walker Hamiltonian. The aim is to compare with CDT results and ask whether CDT can shed light on factor-ordering ambiguities in quantum cosmology models.
Causal Dynamical Triangulation of 3D Tensor Model
Kawabe, Hiroshi
2016-01-01
We extend the string field theory of the two dimensional (2D) generalized causal dynamical triangulation (GCDT) with the Ishibashi-Kawai (IK-) type interaction formulated by the matrix model, to the three dimensional (3D) model of the surface field theory. Based on the loop gas model, we construct a tensor model for the discretized surface field and then apply it the stochastic quantization method. In the double scaling limit, the model is characterized by two scaling dimensions $D$ and $D_N$, the power indices of the minimal length as the scaling parameter. The continuum GCDT model with the IK-type interaction is realized with the similar restriction in the $D_N$-$D$ space, to the 2D model. The distinct property in the 3D model is that the quantum effect contains the IK-type interaction only, while the ordinary splitting interaction is excluded.
DEFF Research Database (Denmark)
Bhuiyan, Tanveer Ahmed; Graff, Claus; Kanters, J.K.;
2013-01-01
Drug-induced triangulation of the cardiac action potential is associated with increased risk of arrhythmic events. It has been suggested that triangulation causes a flattening of the electrocardiographic T-wave but the relationship between triangulation, T-wave flattening and onset of arrhythmia...
Exact computation of the Voronoi Diagram of spheres in 3D, its topology and its geometric invariants
DEFF Research Database (Denmark)
Anton, François; Mioc, Darka; Santos, Marcelo
2011-01-01
In this paper, we are addressing the exact computation of the Delaunay graph (or quasi-triangulation) and the Voronoi diagram of spheres using Wu’s algorithm. Our main contribution is first a methodology for automated derivation of invariants of the Delaunay empty circumcircle predicate for spheres...... and the Voronoi vertex of four spheres, then the application of this methodology to get all geometrical invariants that intervene in this problem and the exact computation of the Delaunay graph and the Voronoi diagram of spheres. To the best of our knowledge, there does not exist a comprehensive treatment...... of the exact computation with geometrical invariants of the Delaunay graph and the Voronoi diagram of spheres. Starting from the system of equations defining the zero-dimensional algebraic set of the problem, we are following Wu’s algorithm to transform the initial system into an equivalent Wu characteristic...
Rindlisbacher, Tobias
2015-01-01
The transition between the two phases of 4D Euclidean Dynamical Triangulation [1] was long believed to be of second order until in 1996 first order behavior was found for sufficiently large systems [5,9]. However, one may wonder if this finding was affected by the numerical methods used: to control volume fluctuations, in both studies [5,9] an artificial harmonic potential was added to the action; in [9] measurements were taken after a fixed number of accepted instead of attempted moves which introduces an additional error. Finally the simulations suffer from strong critical slowing down which may have been underestimated. In the present work, we address the above weaknesses: we allow the volume to fluctuate freely within a fixed interval; we take measurements after a fixed number of attempted moves; and we overcome critical slowing down by using an optimized parallel tempering algorithm [12]. With these improved methods, on systems of size up to 64k 4-simplices, we confirm that the phase transition is first ...
Euclidean Dynamical Triangulation revisited: is the phase transition really first order?
Rindlisbacher, Tobias
2014-01-01
The transition between the two phases of 4D Euclidean Dynamical Triangulation [1] was long believed to be of second order until in 1996 first order behavior was found for sufficiently large systems [3,4]. However, one may wonder if this finding was affected by the numerical methods used: to control volume fluctuations, in both studies [3,4] an artificial harmonic potential was added to the action; in [4] measurements were taken after a fixed number of accepted instead of attempted moves which introduces an additional error. Finally the simulations suffer from strong critical slowing down which may have been underestimated. In the present work, we address the above weaknesses: we allow the volume to fluctuate freely within a fixed interval; we take measurements after a fixed number of attempted moves; and we overcome critical slowing down by using an optimized parallel tempering algorithm [6]. With these improved methods, on systems of size up to 64k 4-simplices, we confirm that the phase transition is first o...
Energy Technology Data Exchange (ETDEWEB)
Grazzini, Jacopo [Los Alamos National Laboratory; Prasad, Lakshman [Los Alamos National Laboratory; Dillard, Scott [PNNL
2010-10-21
The automatic detection, recognition , and segmentation of object classes in remote sensed images is of crucial importance for scene interpretation and understanding. However, it is a difficult task because of the high variability of satellite data. Indeed, the observed scenes usually exhibit a high degree of complexity, where complexity refers to the large variety of pictorial representations of objects with the same semantic meaning and also to the extensive amount of available det.ails. Therefore, there is still a strong demand for robust techniques for automatic information extraction and interpretation of satellite images. In parallel, there is a growing interest in techniques that can extract vector features directly from such imagery. In this paper, we investigate the problem of automatic hierarchical segmentation and vectorization of multispectral satellite images. We propose a new algorithm composed of the following steps: (i) a non-uniform sampling scheme extracting most salient pixels in the image, (ii) an anisotropic triangulation constrained by the sampled pixels taking into account both strength and directionality of local structures present in the image, (iii) a polygonal grouping scheme merging, through techniques based on perceptual information , the obtained segments to a smaller quantity of superior vectorial objects. Besides its computational efficiency, this approach provides a meaningful polygonal representation for subsequent image analysis and/or interpretation.
The Cayley-Bacharach Theorem for Continuous Piecewise Algebraic Curves over Cross-cut Triangulations
Institute of Scientific and Technical Information of China (English)
Renhong WANG; Shaofan WANG
2011-01-01
A piecewise algebraic curve is a curve determined by the zero set of a bivariate spline function.In this paper,we propose the Cayley-Bacharach theorem for continuous piecewise algebraic curves over cross-cut triangulations.We show that,if two continuous piecewise algebraic curves of degrees m and n respectively meet at mnT distinct points over a cross-cut triangulation,where T denotes the number of cells of the triangulation,then any continuous piecewise algebraic curve of degree m + n - 2 containing all but one point of them also contains the last point.
Žbontar, Klemen; Mihelj, Matjaž; Podobnik, Boštjan; Povše, Franc; Munih, Marko
2013-04-20
This paper describes a custom, material-type-independent laser-triangulation-based measurement system that utilizes a high-quality ultraviolet laser beam. Laser structuring applications demand material surface alignment regarding the laser focus position, where fabrication conditions are optimal. Robust alignment of various material types was solved by introducing dynamic symmetrical pattern projection, and a "double curve fitting" centroid detection algorithm with subsurface scattering compensation. Experimental results have shown that the measurement system proves robust to laser intensity variation, with measurement bias lower than 50 μm and standard deviation lower than ±6.3 μm for all materials. The developed probe has been integrated into a PCB prototyping system for material referencing purposes.
A FAST ITERATIVE METHOD FOR SOLVING THE EIKONAL EQUATION ON TRIANGULATED SURFACES.
Fu, Zhisong; Jeong, Won-Ki; Pan, Yongsheng; Kirby, Robert M; Whitaker, Ross T
2011-01-01
This paper presents an efficient, fine-grained parallel algorithm for solving the Eikonal equation on triangular meshes. The Eikonal equation, and the broader class of Hamilton-Jacobi equations to which it belongs, have a wide range of applications from geometric optics and seismology to biological modeling and analysis of geometry and images. The ability to solve such equations accurately and efficiently provides new capabilities for exploring and visualizing parameter spaces and for solving inverse problems that rely on such equations in the forward model. Efficient solvers on state-of-the-art, parallel architectures require new algorithms that are not, in many cases, optimal, but are better suited to synchronous updates of the solution. In previous work [W. K. Jeong and R. T. Whitaker, SIAM J. Sci. Comput., 30 (2008), pp. 2512-2534], the authors proposed the fast iterative method (FIM) to efficiently solve the Eikonal equation on regular grids. In this paper we extend the fast iterative method to solve Eikonal equations efficiently on triangulated domains on the CPU and on parallel architectures, including graphics processors. We propose a new local update scheme that provides solutions of first-order accuracy for both architectures. We also propose a novel triangle-based update scheme and its corresponding data structure for efficient irregular data mapping to parallel single-instruction multiple-data (SIMD) processors. We provide detailed descriptions of the implementations on a single CPU, a multicore CPU with shared memory, and SIMD architectures with comparative results against state-of-the-art Eikonal solvers.
Geometry-Experiment Algorithm for Steiner Minimal Tree Problem
Directory of Open Access Journals (Sweden)
Zong-Xiao Yang
2013-01-01
Full Text Available It is well known that the Steiner minimal tree problem is one of the classical nonlinear combinatorial optimization problems. A visualization experiment approach succeeds in generating Steiner points automatically and showing the system shortest path, named Steiner minimum tree, physically and intuitively. However, it is difficult to form stabilized system shortest path when the number of given points is increased and irregularly distributed. Two algorithms, geometry algorithm and geometry-experiment algorithm (GEA, are constructed to solve system shortest path using the property of Delaunay diagram and basic philosophy of Geo-Steiner algorithm and matching up with the visualization experiment approach (VEA when the given points increase. The approximate optimizing results are received by GEA and VEA for two examples. The validity of GEA was proved by solving practical problems in engineering, experiment, and comparative analysis. And the global shortest path can be obtained by GEA successfully with several actual calculations.
3D Laser Triangulation for Plant Phenotyping in Challenging Environments.
Kjaer, Katrine Heinsvig; Ottosen, Carl-Otto
2015-06-09
To increase the understanding of how the plant phenotype is formed by genotype and environmental interactions, simple and robust high-throughput plant phenotyping methods should be developed and considered. This would not only broaden the application range of phenotyping in the plant research community, but also increase the ability for researchers to study plants in their natural environments. By studying plants in their natural environment in high temporal resolution, more knowledge on how multiple stresses interact in defining the plant phenotype could lead to a better understanding of the interaction between plant responses and epigenetic regulation. In the present paper, we evaluate a commercial 3D NIR-laser scanner (PlantEye, Phenospex B.V., Herleen, The Netherlands) to track daily changes in plant growth with high precision in challenging environments. Firstly, we demonstrate that the NIR laser beam of the scanner does not affect plant photosynthetic performance. Secondly, we demonstrate that it is possible to estimate phenotypic variation amongst the growth pattern of ten genotypes of Brassica napus L. (rapeseed), using a simple linear correlation between scanned parameters and destructive growth measurements. Our results demonstrate the high potential of 3D laser triangulation for simple measurements of phenotypic variation in challenging environments and in a high temporal resolution.
Laser triangulation measurement of the level in a coal silo
Institute of Scientific and Technical Information of China (English)
Sun Jiping; Jiang Jing
2011-01-01
Laser triangulation theory was used to develop a novel contact-free method for measuring the coal level in a silo under harsh environmental conditions found in coal mines,such as the presence of dense dust,high humidity,and low illumination.A laser source and a camera were mounted at the top of the silo.The laser spot projected into the silo was imaged by the camera.The pinhole imaging principle allows the level to be found from the lateral shift of the spot image on the sensor.A pre-calibrated look-up table of the coal depth versus spot position was used to obtain the depth.The measurement accuracy depends on the step size used during pre-calibration.The actual application of a device designed according to these principles shows that it is easy to implement.The detection of the coal level in a silo at the low illumination level found in coal mines is demonstrated.
[Illness Concepts of Patients with Schizophrenia: A Triangulation Study].
Wigand, Moritz E; Reichhardt, Lea; Lang, Fabian U; Krumm, Silvia; Jäger, Markus
2017-04-03
Objective Therapists' and patients' concepts of illness often show severe discrepancies. This study explores the illness concepts of patients with schizophrenic disorders (n = 40). Methods Two German scales were used, the "Causal Belief Questionnaire" and the "Illness Concept Scale for Schizophrenic Patients". We compared our data with data published previously. A semi structured interview was performed in a convenience sample (n = 7). Results The domains "trust in medication" and "trust in the treating physician" yielded high scores, yet in comparison with data published 30 years ago, trust in medication is unaltered, while trust in psychiatrists is even slightly lower. Recent psychosocial factors scored high as a possible cause of mental illness. Several patients felt responsible for being mentally ill. No patient in the interview mentioned the neurotransmitter hypothesis of schizophrenia. Conclusion Illness concepts of patients with schizophrenic disorders are a complex phenomenon. Triangulation of quantitative and qualitative methods proves to be a promising approach for future studies. © Georg Thieme Verlag KG Stuttgart · New York.
Triangulating Nucleic Acid Conformations Using Multicolor Surface Energy Transfer.
Riskowski, Ryan A; Armstrong, Rachel E; Greenbaum, Nancy L; Strouse, Geoffrey F
2016-02-23
Optical ruler methods employing multiple fluorescent labels offer great potential for correlating distances among several sites, but are generally limited to interlabel distances under 10 nm and suffer from complications due to spectral overlap. Here we demonstrate a multicolor surface energy transfer (McSET) technique able to triangulate multiple points on a biopolymer, allowing for analysis of global structure in complex biomolecules. McSET couples the competitive energy transfer pathways of Förster Resonance Energy Transfer (FRET) with gold-nanoparticle mediated Surface Energy Transfer (SET) in order to correlate systematically labeled points on the structure at distances greater than 10 nm and with reduced spectral overlap. To demonstrate the McSET method, the structures of a linear B-DNA and a more complex folded RNA ribozyme were analyzed within the McSET mathematical framework. The improved multicolor optical ruler method takes advantage of the broad spectral range and distances achievable when using a gold nanoparticle as the lowest energy acceptor. The ability to report distance information simultaneously across multiple length scales, short-range (10-50 Å), mid-range (50-150 Å), and long-range (150-350 Å), distinguishes this approach from other multicolor energy transfer methods.
A study on the effect of different image centres on stereo triangulation accuracy
CSIR Research Space (South Africa)
De Villiers, J
2015-11-01
Full Text Available This paper evaluates the effect of mixing the distortion centre, principal point and arithmetic image centre on the distortion correction, focal length determination and resulting real-world stereo vision triangulation. A robotic arm is used...
Schaap, Harmen; De Bruijn, Elly; Van der Schaaf, Marieke; Baartman, Liesbeth; Kirschner, Paul A.
2011-01-01
Schaap, H., De Bruijn, E., Van der Schaaf, M. F., Baartman, L. K. J., & Kirschner, P. A. (2011). Explicating students’ personal professional theories in vocational education through multi-method triangulation. Scandinavian Journal of Educational Research, 55, 567-586.
Schaap, Harmen; De Bruijn, Elly; Van der Schaaf, Marieke; Baartman, Liesbeth; Kirschner, Paul A.
2011-01-01
Schaap, H., De Bruijn, E., Van der Schaaf, M. F., Baartman, L. K. J., & Kirschner, P. A. (2011). Explicating students’ personal professional theories in vocational education through multi-method triangulation. Scandinavian Journal of Educational Research, 55, 567-586.
Buehler, Cheryl; Welsh, Deborah P
2009-04-01
This study examined adolescents' emotional reactivity to parents' marital conflict as a mediator of the association between triangulation and adolescents' internalizing problems in a sample of 2-parent families (N = 416)[corrected]. Four waves of annual, multiple-informant data were analyzed (youth ages 11-15 years). The authors used structural equation modeling and found that triangulation was associated with increases in adolescents' internalizing problems, controlling for marital hostility and adolescent externalizing problems. There also was an indirect pathway from triangulation to internalizing problems across time through youths' emotional reactivity. Moderating analyses indicated that the 2nd half of the pathway, the association between emotional reactivity and increased internalizing problems, characterized youth with lower levels of hopefulness and attachment to parents. The findings help detail why triangulation is a risk factor for adolescents' development and which youth will profit most from interventions focused on emotional regulation.
National Research Council Canada - National Science Library
Kim, Katherine K; Browe, Dennis K; Logan, Holly C; Holm, Roberta; Hack, Lori; Ohno-Machado, Lucila
2014-01-01
.... This paper reports on a triangulated approach to developing DRN data governance requirements based on a combination of policy analysis with experts, interviews with institutional leaders, and patient focus groups...
Elbow arthroscopy: a new setup to avoid visual paradox and improve triangulation.
Sinha, Apurv; Pydah, Satya Kanth V; Webb, Mark
2013-05-01
Elbow arthroscopy is a useful diagnostic and therapeutic tool for various conditions. Conventional arthroscopy with the patient in the prone or lateral position where the screen is placed on the opposite side makes it difficult to interpret the image, results in visual paradox, and is associated with difficult triangulation. We present a modified setup for the operating room to help eliminate these problems and improve triangulation.
Thickness and topographic inspection of RPG contact lenses by optical triangulation
Costa, Manuel F. M.
2001-06-01
Optical triangulation as a non-destructive test method extensively proved its usefulness on the dimensional and topographic inspection of a large range of objects and surfaces. In this communication the issue of microtopographic and thickness inspection of hard contact lenses (RPG) is addressed. The use of optical triangulation is discussed based on the results of the application of our MICROTOP.03.MFC microtopographer to this kind of tasks will be presented.
Willsch, Michael; Villnow, Michael; Bosselmann, Thomas
2015-09-01
Commercial distance sensors basing on the triangulation principle are highly accurate and reliable. However due to their contained electronics and optoelectronics they cannot be used in harsh environments such as high temperatures and strong electromagnetic fields. An all fiber optical triangulation sensor principle is presented here which can be used for tip clearance measurements of rotors of large engines such as power generators and turbines.
Institute of Scientific and Technical Information of China (English)
黄江涛; 高正红; 白俊强; 周铸; 赵轲
2014-01-01
The vetex deformation pattern of multi-block grids is developed based on RBF technique cou-pling with Delaunay graphic mapping to establishe grid deformation platform.The Delaunay cell is generated using the grid sparse points and block vetexs.When aerodynamic configuration deforms,the block vetex will be moved by RBF technique and the Delaunay cells will be deformed,consequently,the mapping relation could be obtained to realize grid deformation.A certain lateral aerobus is taken as an typical example,jig shape is proposed firstly,static aeroelastic analysis is processed then to get the cruise shape of jig configura-tion,and the comparison with cruise design shape is investigated.The results show that the correction of jig shape design method established in this paper is validated.On the other hand,the “mapping surface”can be used to realized CFD/CSD data transformation effectively.%基于 RBF 径向基函数建立了多块对接网格块顶点运动模式，进一步耦合 Delaunay 图映射建立网格变形技术；利用基准网格的稀疏序列节点以及区域顶点建立 Delaunay 四面体映射单元，利用 RBF 技术操作区域顶点运动，使映射单元进行变形，从而应用映射关系实现网格变形；针对某型支线客机进行了型架外形设计，并进一步进行对型架外形进行静气动弹性计算与设计巡航外形对比，验证了所建立的型架外形设计方法的正确性；静气动弹性计算中，通过建立共用的“映射曲面”，实现 CFD/CSD 数据高效交换。
Becoming invisible: The effect of triangulation on children's well-being.
Dallos, Rudi; Lakus, Katarzyna; Cahart, Marie-Stephanie; McKenzie, Rebecca
2016-07-01
The study explored children's experience of triangulation in their families. In all, 15 children aged 11-16 years, who were attending an early intervention family therapy service, participated in the study. The children's understandings and emotional experience of triangulation were explored by comparing their responses to pictures from the Separation Anxiety Test (SAT) and a set of pictures designed for the study depicting a variety of triangulation conflicts in families. An interview regarding the children's personal family experiences of triangulation was also undertaken and clinical information about the children's family contexts was also utilised. Statistical analysis was conducted based on eight of children for whom a full data set was available. This indicated that children showed greater levels of anxiety in response to the triangulation as opposed to the separation scenarios. Qualitative analysis supported this finding and revealed that many of the children felt 'invisible' due to parents' pre-occupation with marital conflict, felt caught in the middle of conflicts and coerced to take sides. Although able to describe their reactions and showing greater negative emotional responses to the triadic pictures, they were not consciously aware of the negative impacts of triangulation on their sense of well-being. Clinical implications are discussed with a focus on encouraging child-centred approaches to family therapy.
a Line-Based 3d Roof Model Reconstruction Algorithm: Tin-Merging and Reshaping (tmr)
Rau, J.-Y.
2012-07-01
Three-dimensional building model is one of the major components of a cyber-city and is vital for the realization of 3D GIS applications. In the last decade, the airborne laser scanning (ALS) data is widely used for 3D building model reconstruction and object extraction. Instead, based on 3D roof structural lines, this paper presents a novel algorithm for automatic roof models reconstruction. A line-based roof model reconstruction algorithm, called TIN-Merging and Reshaping (TMR), is proposed. The roof structural line, such as edges, eaves and ridges, can be measured manually from aerial stereo-pair, derived by feature line matching or inferred from ALS data. The originality of the TMR algorithm for 3D roof modelling is to perform geometric analysis and topology reconstruction among those unstructured lines and then reshapes the roof-type using elevation information from the 3D structural lines. For topology reconstruction, a line constrained Delaunay Triangulation algorithm is adopted where the input structural lines act as constraint and their vertex act as input points. Thus, the constructed TINs will not across the structural lines. Later at the stage of Merging, the shared edge between two TINs will be check if the original structural line exists. If not, those two TINs will be merged into a polygon. Iterative checking and merging of any two neighboured TINs/Polygons will result in roof polygons on the horizontal plane. Finally, at the Reshaping stage any two structural lines with fixed height will be used to adjust a planar function for the whole roof polygon. In case ALS data exist, the Reshaping stage can be simplified by adjusting the point cloud within the roof polygon. The proposed scheme reduces the complexity of 3D roof modelling and makes the modelling process easier. Five test datasets provided by ISPRS WG III/4 located at downtown Toronto, Canada and Vaihingen, Germany are used for experiment. The test sites cover high rise buildings and residential
Exact and approximate computations of watersheds on triangulated terrains
DEFF Research Database (Denmark)
Tsirogiannis, Konstantinos; de Berg, Mark
2011-01-01
computations and the computation of an intermediate structure called the strip map. • Using our exact algorithm as a point of reference, we evaluate the quality of several existing heuristics for computing watersheds. We also investigate hybrid methods, which use heuristics in a first phase of the algorithm...
Locally-orthogonal, unstructured grid-generation for general circulation modelling on the sphere
Engwirda, Darren
2016-01-01
An algorithm for the generation of non-uniform, locally-orthogonal staggered unstructured grids on spheroidal geometries is described. This technique is designed to generate high-quality staggered Voronoi/Delaunay dual meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric simulation, ocean-modelling and numerical weather predication. Using a recently developed Frontal-Delaunay refinement technique, a method for the construction of guaranteed-quality, unstructured spheroidal Delaunay triangulations is introduced. A locally-orthogonal polygonal grid, derived from the associated Voronoi diagram, is computed as the staggered dual. The initial staggered Voronoi/Delaunay tessellation is iteratively improved through hill-climbing optimisation techniques. It is shown that this approach typically produces grids with very high element quality and smooth grading characteristics, while imposing relatively low computational expense. Initial results are presented for a se...
Evolutionary triangulation: informing genetic association studies with evolutionary evidence.
Huang, Minjun; Graham, Britney E; Zhang, Ge; Harder, Reed; Kodaman, Nuri; Moore, Jason H; Muglia, Louis; Williams, Scott M
2016-01-01
Genetic studies of human diseases have identified many variants associated with pathogenesis and severity. However, most studies have used only statistical association to assess putative relationships to disease, and ignored other factors for evaluation. For example, evolution is a factor that has shaped disease risk, changing allele frequencies as human populations migrated into and inhabited new environments. Since many common variants differ among populations in frequency, as does disease prevalence, we hypothesized that patterns of disease and population structure, taken together, will inform association studies. Thus, the population distributions of allelic risk variants should reflect the distributions of their associated diseases. Evolutionary Triangulation (ET) exploits this evolutionary differentiation by comparing population structure among three populations with variable patterns of disease prevalence. By selecting populations based on patterns where two have similar rates of disease that differ substantially from a third, we performed a proof of principle analysis for this method. We examined three disease phenotypes, lactase persistence, melanoma, and Type 2 diabetes mellitus. We show that for lactase persistence, a phenotype with a simple genetic architecture, ET identifies the key gene, lactase. For melanoma, ET identifies several genes associated with this disease and/or phenotypes related to it, such as skin color genes. ET was less obviously successful for Type 2 diabetes mellitus, perhaps because of the small effect sizes in known risk loci and recent environmental changes that have altered disease risk. Alternatively, ET may have revealed new genes involved in conferring disease risk for diabetes that did not meet nominal GWAS significance thresholds. We also compared ET to another method used to filter for phenotype associated genes, population branch statistic (PBS), and show that ET performs better in identifying genes known to associate with
Mesh Generation via Local Bisection Refinement of Triangulated Grids
2015-06-01
tb [Maubach 1995, Theorem 5.1]. This is exploited in the recursive algorithm RefineTriangle (Algorithm 2) to com- patibly refine a given triangle; the... recursion depth of RefineTriangle is bounded by the maximum level of refinement in T [Maubach 1995]. RefineTriangle calls itself repeatedly on a... sequence of triangles until a compatibly divisible triangle is found. This sequence of triangles is then bisected in reverse order to preserve
Bonzom, Valentin
2016-01-01
We review an approach which aims at studying discrete (pseudo--)manifolds in dimension $d\\geq 2$ and called random tensor models. More specifically, we insist on generalizing the two-dimensional notion of $p$-angulations to higher dimensions. To do so, we consider families of triangulations built out of simplices with colored faces. Those simplices can be glued to form new building blocks, called bubbles which are pseudo--manifolds with boundaries. Bubbles can in turn be glued together to form triangulations. The main challenge is to classify the triangulations built from a given set of bubbles with respect to their numbers of bubbles and simplices of codimension two. While the colored triangulations which maximize the number of simplices of codimension two at fixed number of simplices are series-parallel objects called melonic triangulations, this is not always true anymore when restricting attention to colored triangulations built from specific bubbles. This opens up the possibility of new universality clas...
Determination of the human spine curve based on laser triangulation.
Poredoš, Primož; Čelan, Dušan; Možina, Janez; Jezeršek, Matija
2015-02-05
The main objective of the present method was to automatically obtain a spatial curve of the thoracic and lumbar spine based on a 3D shape measurement of a human torso with developed scoliosis. Manual determination of the spine curve, which was based on palpation of the thoracic and lumbar spinous processes, was found to be an appropriate way to validate the method. Therefore a new, noninvasive, optical 3D method for human torso evaluation in medical practice is introduced. Twenty-four patients with confirmed clinical diagnosis of scoliosis were scanned using a specially developed 3D laser profilometer. The measuring principle of the system is based on laser triangulation with one-laser-plane illumination. The measurement took approximately 10 seconds at 700 mm of the longitudinal translation along the back. The single point measurement accuracy was 0.1 mm. Computer analysis of the measured surface returned two 3D curves. The first curve was determined by manual marking (manual curve), and the second was determined by detecting surface curvature extremes (automatic curve). The manual and automatic curve comparison was given as the root mean square deviation (RMSD) for each patient. The intra-operator study involved assessing 20 successive measurements of the same person, and the inter-operator study involved assessing measurements from 8 operators. The results obtained for the 24 patients showed that the typical RMSD between the manual and automatic curve was 5.0 mm in the frontal plane and 1.0 mm in the sagittal plane, which is a good result compared with palpatory accuracy (9.8 mm). The intra-operator repeatability of the presented method in the frontal and sagittal planes was 0.45 mm and 0.06 mm, respectively. The inter-operator repeatability assessment shows that that the presented method is invariant to the operator of the computer program with the presented method. The main novelty of the presented paper is the development of a new, non-contact method
Strongly minimal triangulations of $(S^{3}× S^{1})^{\\# 3}$ and $(S^{3}× S^{1})^{\\# 3}$
Indian Academy of Sciences (India)
Nitin Singh
2015-02-01
A triangulated -manifold , satisfies the inequality $\\binom{f_{0}(K)-d-1}{2}≥ \\binom{d+2}{2}_{1}(K;\\mathbb{Z}_{2})$ for $d≥ 3$. The triangulated -manifolds that meet the bound with equality are called tight neighbourly. In this paper, we present tight neighbourly triangulations of 4-manifolds on 15 vertices with $\\mathbb{Z}_{3}$ as an automorphism group. One such example was constructed by Bagchi and Datta (Discrete Math. 311 (2011) 986-995). We show that there are exactly 12 such triangulations up to isomorphism, 10 of which are orientable.
Fosco, Gregory M; Bray, Bethany C
2016-08-01
Youth appraisals and triangulation into conflicts are key mechanisms by which interparental conflict places youth at risk for psychological maladjustment. Although evidence suggests that there are multiple mechanisms at work (e.g., Fosco & Feinberg, 2015; Grych, Harold, & Miles, 2003), this body of work has relied on variable-centered analyses that are limited to the unique contributions of each process to the variance in outcomes. In reality, it is possible that different combinations of these risk mechanisms may account for multifinality in risk outcomes. Using latent profile analysis (LPA) we examined profiles of threat appraisals, self-blaming attributions, and triangulation in relation to internalizing and externalizing problems in a sample of 285, ethnically diverse high school students. The current analyses revealed 5 distinct profiles of appraisals and triangulation, including an overall low-risk group and a global high-risk group, in which all 3 processes were below average or above average, respectively. Additional profiles included combinations of threat and blame, threat and triangulation, and blame and triangulation. Links between these profiles and emotional distress, problem behavior, and academic outcomes are discussed. (PsycINFO Database Record
Assessment of teaching effectiveness in U.S. Dental schools and the value of triangulation.
Jahangiri, Leila; Mucciolo, Thomas W; Choi, Mijin; Spielman, Andrew I
2008-06-01
The routine evaluation of teaching effectiveness is important in improving faculty, departmental, and institutional efforts. There are three main categories of assessments: those performed by students, peers, and self. Although each category is independently valid, a collection of data from all three categories leads to a more comprehensive outcome and a creation of a triangulation model. The purpose of this study was to identify commonly used methods of assessing teaching effectiveness and to suggest the use of a triangulation model, which has been advocated in the literature on performance assessment as an optimal approach for evaluating teaching effectiveness. A twelve-question survey was sent to all U.S. dental schools to identify evaluation methods as well as to find evidence of triangulation. Thirty-nine out of fifty-seven schools responded. The majority of the schools used student evaluations (81 percent) and peer reviews (78 percent). A minority of schools reported using self-evaluations (31 percent). Less than one in five dental schools reported using all three strategies to achieve triangulation (19 percent). The three most commonly used evaluation methods ("performed routinely") were all in the student evaluation category. Less than half of the schools routinely evaluated clinical teaching effectiveness by any means (42 percent). In conclusion, dental schools should implement a triangulation process, in which evaluation data are obtained from students, peers, and self to provide a comprehensive and composite assessment of teaching effectiveness.
Fotheringham, Diane
2010-03-01
To review the use and usefulness of the methodological strategy of triangulation in the assessment of skill in nursing curricula. Systematic search of the literature relevant to the definition and assessment of skill, reliability and validity of assessment methods and triangulation of assessment strategies. One hundred and twenty papers from nursing, medical, educational and social scientific databases, relevant websites and relevant books were reviewed. Forty papers were included based on their relevance to the theory and methodology of clinical skills assessment of health care professionals, particularly nurses. Papers concerning vocational skills assessment and the assessment of skill in school children were excluded. There is a current imperative within the field of health care professional education to assess clinical skills and to quantify this assessment. However, clinical skill, as it relates to cognition, is poorly defined concept and may be viewed as a quality of the practitioner and, as such, is difficult to quantify. Very many methods of assessing clinical skill have been documented and there are inherent issues in ensuring both reliability and validity of these assessment strategies for clinical skill. This has led commentators to suggest that the process of triangulation should be employed. The paper fundamentally questions whether the concept of triangulation can be applied to skills assessment without dependable measures of reliability and validity of the tools of assessment and concludes that the process of applying multiple modes of assessment should not be confused with the process of triangulation. Copyright 2009 Elsevier Ltd. All rights reserved.
Exploring Euclidean Dynamical Triangulations with a Non-trivial Measure Term
Coumbe, Daniel
2014-01-01
We investigate a nonperturbative formulation of quantum gravity defined via Euclidean dynamical triangulations (EDT) with a non-trivial measure term in the path integral. We are motivated to revisit this older formulation of dynamical triangulations by hints from renormalization group approaches that gravity may be asymptotically safe and by the emergence of a semiclassical phase in causal dynamical triangulations (CDT). We study the phase diagram of this model and identify the two phases that are well known from previous work: the branched polymer phase and the collapsed phase. We verify that the order of the phase transition dividing the branched polymer phase from the collapsed phase is almost certainly first-order. The nontrivial measure term enlarges the phase diagram, allowing us to explore a region of the phase diagram that has been dubbed the crinkled region. Although the collapsed and branched polymer phases have been studied extensively in the literature, the crinkled region has not received the sam...
PACMAN study of FSI and micro-triangulation for the pre-alignment of CLIC
Kamugasa, William Solomon
2015-01-01
The alignment precision of linear colliders is extremely demanding owing to the very narrow beam size at the interaction point. Unlike circular colliders, particles in linear colliders have only one chance to collide and are hence tightly focused to maximise the number of interactions per collision. The PACMAN* project is dedicated to study the integration of both fiducialization and alignment of the components on a common support. FSI (Frequency Scanning Interferometry) and Micro-triangulation will contribute to this goal. FSI realized by Etalon AG’s Absolute Multiline system and Micro-triangulation implemented by QDaedalus system developed at ETH Zurich offer precision of 0.5 μm/m and 2.4 μm/m respectively. However, these systems need to be improved in order to provide the necessary geometric information via distance measurements (multilateration) and angle measurements (triangulation), respectively. The paper describes the current status and the future developments of Absolute Multiline and QDaedalus, ...
Geometric asymptotics for spin foam lattice gauge gravity on arbitrary triangulations
Hellmann, Frank
2012-01-01
We study the behavior of holonomy spin foam partition functions, a form of lattice gauge gravity, on generic 4d-triangulations using micro local analysis. To do so we adapt tools from the renormalization theory of quantum field theory on curved space times. This allows us, for the first time, to study the partition function without taking any limits on the interior of the triangulation. We establish that for many of the most widely used models the geometricity constraints, which reduce the gauge theory to a geometric one, introduce strong accidental curvature constraints. These limit the curvature around each triangle of the triangulation to a finite set of values. We demonstrate how to modify the partition function to avoid this problem. Finally the new methods introduced provide a starting point for studying the regularization ambiguities and renormalization of the partition function.
Triangulation and the importance of establishing valid methods for food safety culture evaluation.
Jespersen, Lone; Wallace, Carol A
2017-10-01
The research evaluates maturity of food safety culture in five multi-national food companies using method triangulation, specifically self-assessment scale, performance documents, and semi-structured interviews. Weaknesses associated with each individual method are known but there are few studies in food safety where a method triangulation approach is used for both data collection and data analysis. Significantly, this research shows that individual results taken in isolation can lead to wrong conclusions, resulting in potentially failing tactics and wasted investments. However, by applying method triangulation and reviewing results from a range of culture measurement tools it is possible to better direct investments and interventions. The findings add to the food safety culture paradigm beyond a single evaluation of food safety culture using generic culture surveys. Copyright © 2017. Published by Elsevier Ltd.
A second look at transition amplitudes in (2+1)-dimensional causal dynamical triangulations
Cooperman, Joshua H; Miller, Jonah M
2016-01-01
Studying transition amplitudes in (2+1)-dimensional causal dynamical triangulations, Cooperman and Miller discovered speculative evidence for Lorentzian quantum geometries emerging from its Euclidean path integral. On the basis of this evidence, Cooperman and Miller conjectured that Lorentzian de Sitter spacetime, not Euclidean de Sitter space, dominates the ground state of the quantum geometry of causal dynamical triangulations on large scales, a scenario akin to that of the Hartle-Hawking no-boundary proposal in which Lorentzian spacetimes dominate a Euclidean path integral. We argue against this conjecture: we propose a more straightforward explanation of their findings, and we proffer evidence for the Euclidean nature of these seemingly Lorentzian quantum geometries. This explanation reveals another manner in which the Euclidean path integral of causal dynamical triangulations behaves correctly in its semiclassical limit--the implementation and interaction of multiple constraints.
Institute of Scientific and Technical Information of China (English)
李文阁
2013-01-01
研究了无线Mesh骨干网部署优化问题，结合网络的拓扑结构及定向天线技术的传输特点对无线Mesh骨干网进行优化部署，提出一种基于Delaunay图形的无线Mesh骨干网部署优化算法，较好地解决了WMN骨干网信号干扰问题。%The author researched optimization of wireless Mesh network. Combining transfer features of topology structure of network and directional antenna technology, the author put forward optimization method based on Delaunay graphics, which solved signal interference of WMN backbone network.
Directory of Open Access Journals (Sweden)
Ashatu Hussein
2015-03-01
Full Text Available This article refers to a study in Tanzania on fringe benefits or welfare via the work contract1 where we will work both quantitatively and qualitatively. My focus is on the vital issue of combining methods or methodologies. There has been mixed views on the uses of triangulation in researches. Some authors argue that triangulation is just for increasing the wider and deep understanding of the study phenomenon, while others have argued that triangulation is actually used to increase the study accuracy, in this case triangulation is one of the validity measures. Triangulation is defined as the use of multiple methods mainly qualitative and quantitative methods in studying the same phenomenon for the purpose of increasing study credibility. This implies that triangulation is the combination of two or more methodological approaches, theoretical perspectives, data sources, investigators and analysis methods to study the same phenomenon.However, using both qualitative and quantitative paradigms in the same study has resulted into debate from some researchers arguing that the two paradigms differ epistemologically and ontologically. Nevertheless, both paradigms are designed towards understanding about a particular subject area of interest and both of them have strengths and weaknesses. Thus, when combined there is a great possibility of neutralizing the flaws of one method and strengthening the benefits of the other for the better research results. Thus, to reap the benefits of two paradigms and minimizing the drawbacks of each, the combination of the two approaches have been advocated in this article. The quality of our studies on welfare to combat poverty is crucial, and especially when we want our conclusions to matter in practice.
An improved Marching Cube algorithm for 3D data segmentation
Masala, G. L.; Golosio, B.; Oliva, P.
2013-03-01
The marching cube algorithm is one of the most popular algorithms for isosurface triangulation. It is based on a division of the data volume into elementary cubes, followed by a standard triangulation inside each cube. In the original formulation, the marching cube algorithm is based on 15 basic triangulations and a total of 256 elementary triangulations are obtained from the basic ones by rotation, reflection, conjugation, and combinations of these operations. The original formulation of the algorithm suffers from well-known problems of connectivity among triangles of adjacent cubes, which has been solved in various ways. We developed a variant of the marching cube algorithm that makes use of 21 basic triangulations. Triangles of adjacent cubes are always well connected in this approach. The output of the code is a triangulated model of the isosurface in raw format or in VRML (Virtual Reality Modelling Language) format. Catalogue identifier: AENS_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AENS_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 147558 No. of bytes in distributed program, including test data, etc.: 26084066 Distribution format: tar.gz Programming language: C. Computer: Pentium 4, CPU 3.2 GHz and 3.24 GB of RAM (2.77 GHz). Operating system: Tested on several Linux distribution, but generally works in all Linux-like platforms. RAM: Approximately 2 MB Classification: 6.5. Nature of problem: Given a scalar field μ(x,y,z) sampled on a 3D regular grid, build a discrete model of the isosurface associated to the isovalue μIso, which is defined as the set of points that satisfy the equation μ(x,y,z)=μIso. Solution method: The proposed solution is an improvement of the Marching Cube algorithm, which approximates the isosurface using a set of
Great Deluge Algorithm for the Linear Ordering Problem: The Case of Tanzanian Input-Output Table
Directory of Open Access Journals (Sweden)
Amos Mathias
2015-06-01
Full Text Available Given a weighted complete digraph, the Linear Ordering Problem (LOP consists of finding and acyclic tournament with maximum weight. It is sometimes referred to as triangulation problem or permutation problem depending on the context of its application. This study introduces an algorithm for LOP and applied for triangulation of Tanzanian Input-Output tables. The algorithm development process uses Great Deluge heuristic method. It is implemented using C++ programming language and tested on a personal computer with 2.40GHZ speed processor. The algorithm has been able to triangulate the Tanzanian input-output tables of size 79×79 within a reasonable time (1.17 seconds. It has been able to order the corresponding economic sectors in the linear order, with upper triangle weight increased from 585,481 to 839,842 giving the degree of linearity of 94.3%.
Upper bound theorem for odd-dimensional flag triangulations of manifolds
DEFF Research Database (Denmark)
Adamaszek, Michal Jan; Hladký, Jan
2016-01-01
We prove that among all flag triangulations of manifolds of odd dimension 2r-1, with a sufficient number of vertices, the unique maximizer of the entries of the f-, h-, g- and γ-vector is the balanced join of cycles. Our proof uses methods from extremal graph theory.......We prove that among all flag triangulations of manifolds of odd dimension 2r-1, with a sufficient number of vertices, the unique maximizer of the entries of the f-, h-, g- and γ-vector is the balanced join of cycles. Our proof uses methods from extremal graph theory....
A restricted dimer model on a 2-dimensional random causal triangulation
Ambjorn, J; Wheater, J F
2014-01-01
We introduce a restricted hard dimer model on a random causal triangulation that is exactly solvable and generalizes a model recently proposed by Atkin and Zohren. We show that the latter model exhibits unusual behaviour at its multicritical point; in particular, its Hausdorff dimension equals 3 and not 3/2 as would be expected from general scaling arguments. When viewed as a special case of the generalized model introduced here we show that this behaviour is not generic and therefore is not likely to represent the true behaviour of the full dimer model on a random causal triangulation.
Tchebyshev Approximation by S01(Δ)over Some Special Triangulations
Institute of Scientific and Technical Information of China (English)
Ren Hong WANG; Wei DAN
2012-01-01
The critical point set plays a central role in the theory of Tchebyshev approximation.Generally,in multivariate Tchebyshev approximation,it is not a trivial task to determine whether a set is critical or not.In this paper,we study the characterization of the critical point set of S01(△) in geometry,where △ is restricted to some special triangulations (bitriangular,single road and star triangulations). Such geometrical characterization is convenient to use in the determination of a critical point set.
Institute of Scientific and Technical Information of China (English)
李涛; 江玮
2015-01-01
在GIS应用领域中，Delaunay三角网通常被用于生成不规则三角网(TIN)模型，并用于描述地表形态。详细叙述了的现有的Delaunay三角网三种生成算法———逐点插入法、逐步生长法和分割-归并算法，并进行了比较。最后分析了Delaunay三角网构建中存在的问题及未来研究方向。%In GIS applications, Delaunay triangulation is commonly used to generate triangulated irregular network (TIN) model, and used for the description of the surface morphology. This paper describes and compares the existing Delaunay triangulation generation al-gorithm ——— Incremental insertion algorithm, Growth algorithm and Divide-conquer algorithm. Finally, this paper analyzes the problems existing in the construction of Delaunay triangulation , to indicate the future research direction.
Youngs, Howard; Piggot-Irvine, Eileen
2012-01-01
Mixed methods research has emerged as a credible alternative to unitary research approaches. The authors show how a combination of a triangulation convergence model with a triangulation multilevel model was used to research an aspiring school principal development pilot program. The multilevel model is used to show the national and regional levels…
Tonkin-Crine, Sarah; Anthierens, Sibyl; Hood, Kerenza; Yardley, Lucy; Cals, Jochen W L; Francis, Nick A; Coenen, Samuel; van der Velden, Alike W; Godycki-Cwirko, Maciek; Llor, Carl; Butler, Chris C; Verheij, Theo J M; Goossens, Herman; Little, Paul
2016-01-01
BACKGROUND: Mixed methods are commonly used in health services research; however, data are not often integrated to explore complementarity of findings. A triangulation protocol is one approach to integrating such data. A retrospective triangulation protocol was carried out on mixed methods data coll
Youngs, Howard; Piggot-Irvine, Eileen
2012-01-01
Mixed methods research has emerged as a credible alternative to unitary research approaches. The authors show how a combination of a triangulation convergence model with a triangulation multilevel model was used to research an aspiring school principal development pilot program. The multilevel model is used to show the national and regional levels…
Tonkin-Crine, Sarah; Anthierens, Sibyl; Hood, Kerenza; Yardley, Lucy; Cals, Jochen W L; Francis, Nick A; Coenen, Samuel; van der Velden, Alike W; Godycki-Cwirko, Maciek; Llor, Carl; Butler, Chris C; Verheij, Theo J M; Goossens, Herman; Little, Paul
2016-01-01
BACKGROUND: Mixed methods are commonly used in health services research; however, data are not often integrated to explore complementarity of findings. A triangulation protocol is one approach to integrating such data. A retrospective triangulation protocol was carried out on mixed methods data
Majasalmi, Titta; Korhonen, Lauri; Korpela, Ilkka; Vauhkonen, Jari
2017-07-01
We propose 3D triangulations of airborne Laser Scanning (ALS) point clouds as a new approach to derive 3D canopy structures and to estimate forest canopy effective LAI (LAIe). Computational geometry and topological connectivity were employed to filter the triangulations to yield a quasi-optimal relationship with the field measured LAIe. The optimal filtering parameters were predicted based on ALS height metrics, emulating the production of maps of LAIe and canopy volume for large areas. The LAIe from triangulations was validated with field measured LAIe and compared with a reference LAIe calculated from ALS data using logarithmic model based on Beer's law. Canopy transmittance was estimated using All Echo Cover Index (ACI), and the mean projection of unit foliage area (β) was obtained using no-intercept regression with field measured LAIe. We investigated the influence species and season on the triangulated LAIe and demonstrated the relationship between triangulated LAIe and canopy volume. Our data is from 115 forest plots located at the southern boreal forest area in Finland and for each plot three different ALS datasets were available to apply the triangulations. The triangulation approach was found applicable for both leaf-on and leaf-off datasets after initial calibration. Results showed the Root Mean Square Errors (RMSEs) between LAIe from triangulations and field measured values agreed the most using the highest pulse density data (RMSE = 0.63, the coefficient of determination (R2) = 0.53). Yet, the LAIe calculated using ACI-index agreed better with the field measured LAIe (RMSE = 0.53 and R2 = 0.70). The best models to predict the optimal alpha value contained the ACI-index, which indicates that within-crown transmittance is accounted by the triangulation approach. The cover indices may be recommended for retrieving LAIe only, but for applications which require more sophisticated information on canopy shape and volume, such as radiative transfer models, the
Surface meshing with curvature convergence
Li, Huibin
2014-06-01
Surface meshing plays a fundamental role in graphics and visualization. Many geometric processing tasks involve solving geometric PDEs on meshes. The numerical stability, convergence rates and approximation errors are largely determined by the mesh qualities. In practice, Delaunay refinement algorithms offer satisfactory solutions to high quality mesh generations. The theoretical proofs for volume based and surface based Delaunay refinement algorithms have been established, but those for conformal parameterization based ones remain wide open. This work focuses on the curvature measure convergence for the conformal parameterization based Delaunay refinement algorithms. Given a metric surface, the proposed approach triangulates its conformal uniformization domain by the planar Delaunay refinement algorithms, and produces a high quality mesh. We give explicit estimates for the Hausdorff distance, the normal deviation, and the differences in curvature measures between the surface and the mesh. In contrast to the conventional results based on volumetric Delaunay refinement, our stronger estimates are independent of the mesh structure and directly guarantee the convergence of curvature measures. Meanwhile, our result on Gaussian curvature measure is intrinsic to the Riemannian metric and independent of the embedding. In practice, our meshing algorithm is much easier to implement and much more efficient. The experimental results verified our theoretical results and demonstrated the efficiency of the meshing algorithm. © 2014 IEEE.
Triangulation and Mixed Methods Designs: Data Integration with New Research Technologies
Fielding, Nigel G.
2012-01-01
Data integration is a crucial element in mixed methods analysis and conceptualization. It has three principal purposes: illustration, convergent validation (triangulation), and the development of analytic density or "richness." This article discusses such applications in relation to new technologies for social research, looking at three…
Evaluating Team Project-Work Using Triangulation: Lessons from Communities in Northern Ghana
Clark, Gordon; Jasaw, Godfred Seidu
2014-01-01
This paper uses triangulation to assess key aspects of a team-based, participatory action research programme for undergraduates in rural communities across northern Ghana. The perceptions of the programme and its effects on the students, staff and host communities are compared, showing areas of agreement and disagreement. The successes of the…
Triangulation and Mixed Methods Designs: Data Integration with New Research Technologies
Fielding, Nigel G.
2012-01-01
Data integration is a crucial element in mixed methods analysis and conceptualization. It has three principal purposes: illustration, convergent validation (triangulation), and the development of analytic density or "richness." This article discusses such applications in relation to new technologies for social research, looking at three…
Hesse-Biber, Sharlene
2012-01-01
This article explores the deployment of triangulation in the service of uncovering subjugated knowledge and promoting social change for women and other oppressed groups. Feminist approaches to mixed methods praxis create a tight link between the research problem and the research design. An analysis of selected case studies of feminist praxis…
Modelling and calibration of the laser beam-scanning triangulation measurement system
Wang, Guoyu; Zheng, Bing; Li, Xin; Houkes, Z.; Regtien, P.P.L.
2002-01-01
We present an approach of modelling and calibration of an active laser beam-scanning triangulation measurement system. The system works with the pattern of two-dimensional beam-scanning illumination and one-dimensional slit-scanning detection with a photo-multiplier tube instead of a CCD camera. By
Xu, Jun; Lee, Jennifer C.
2013-01-01
In this article, we propose a shift in race research from a one-dimensional hierarchical approach to a multidimensional system of racial stratification. Building upon Claire Kim's (1999) racial triangulation theory, we examine how the American public rates Asians relative to blacks and whites along two dimensions of racial stratification: racial…
Zhang, Hanlin; Ren, Yongjie; Liu, Changjie; Zhu, Jigui
2014-07-10
High-speed surface profile measurement with high precision is crucial for target inspection and quality control. In this study, a laser scanner based on a single point laser triangulation displacement sensor and a high-speed rotating polygon mirror is proposed. The autosynchronized scanning scheme is introduced to alleviate the trade-off between the field of view and the range precision, which is the inherent deficiency of the conventional triangulation. The lateral synchronized flying spot technology has excellent characteristics, such as programmable and larger field of view, high immunity to ambient light or secondary reflections, high optical signal-to-noise ratio, and minimum shadow effect. Owing to automatic point-to-point laser power control, high accuracy and superior data quality are possible when measuring objects featuring varying surface characteristics even in demanding applications. The proposed laser triangulation scanner is validated using a laboratory-built prototype and practical considerations for design and implementation of the system are described, including speckle noise reduction method and real-time signal processing. A method for rapid and accurate calibration of the laser triangulation scanner using lookup tables is also devised, and the system calibration accuracy is generally smaller than ±0.025 mm. Experimental results are presented and show a broad application prospect for fast surface profile precision measurement.
Triangulation and Mixed Methods Designs: Data Integration with New Research Technologies
Fielding, Nigel G.
2012-01-01
Data integration is a crucial element in mixed methods analysis and conceptualization. It has three principal purposes: illustration, convergent validation (triangulation), and the development of analytic density or "richness." This article discusses such applications in relation to new technologies for social research, looking at three innovative…
Theoretical Triangulation as an Approach for Revealing the Complexity of a Classroom Discussion
van Drie, Jannet; Dekker, Rijkje
2013-01-01
In this paper we explore the value of theoretical triangulation as a methodological approach for the analysis of classroom interaction. We analyze an excerpt of a whole-class discussion in history from three theoretical perspectives: interactivity of the discourse, conceptual level raising and historical reasoning. We conclude that using…
DEFF Research Database (Denmark)
Zhang, Guojie; Pei, Zhang; Krawczak, Michael;
2010-01-01
Triangulation of the human, chimpanzee, and Neanderthal genome sequences with respect to 44,348 disease-causing or disease-associated missense mutations and 1,712 putative regulatory mutations listed in the Human Gene Mutation Database was employed to identify genetic variants that are apparently...
Some specific triangulated categories%几个具体的三角范畴
Institute of Scientific and Technical Information of China (English)
赵小娟
2012-01-01
Peng proposed two methods to construct triangulated categories from generalized chain complex categories and functors between them. In this paper, the author uses these methods to consider some specific triangulated categories, determines all the indecomposable objects of the triangulated categories and their concrete forms. Then, the author draws their Auslander-Reiten quivers. From these Auslander-Reiten quivers one can see that they also provide a new kind of realization for the orbit categories of some triangulated categories.%本文利用彭提出的用广义复形范畴以及广义复形范畴之间的锥扩张来构造三角范畴的方法,考虑了几类特殊的三角范畴,确定了这几类三角范畴的所有不可分解对象和它们的具体形式,并给出了它们的Auslander-Reiten箭图的结构.这些三角范畴提供了一些轨道范畴的一种新的实现.
A restricted dimer model on a two-dimensional random causal triangulation
DEFF Research Database (Denmark)
Ambjørn, Jan; Durhuus, Bergfinnur; Wheater, J. F.
2014-01-01
We introduce a restricted hard dimer model on a random causal triangulation that is exactly solvable and generalizes a model recently proposed by Atkin and Zohren (2012 Phys. Lett. B 712 445–50). We show that the latter model exhibits unusual behaviour at its multicritical point; in particular, its...
Modelling and calibration of the laser beam-scanning triangulation measurement system
Wang, G.Y.; Zheng, Bing; Li, Xin; Houkes, Z.; Regtien, Paulus P.L.
2002-01-01
We present an approach of modelling and calibration of an active laser beam-scanning triangulation measurement system. The system works with the pattern of two-dimensional beam-scanning illumination and one-dimensional slit-scanning detection with a photo-multiplier tube instead of a CCD camera. By
Xu, Jun; Lee, Jennifer C.
2013-01-01
In this article, we propose a shift in race research from a one-dimensional hierarchical approach to a multidimensional system of racial stratification. Building upon Claire Kim's (1999) racial triangulation theory, we examine how the American public rates Asians relative to blacks and whites along two dimensions of racial stratification: racial…
Evaluating Team Project-Work Using Triangulation: Lessons from Communities in Northern Ghana
Clark, Gordon; Jasaw, Godfred Seidu
2014-01-01
This paper uses triangulation to assess key aspects of a team-based, participatory action research programme for undergraduates in rural communities across northern Ghana. The perceptions of the programme and its effects on the students, staff and host communities are compared, showing areas of agreement and disagreement. The successes of the…
Theoretical Triangulation as an Approach for Revealing the Complexity of a Classroom Discussion
van Drie, Jannet; Dekker, Rijkje
2013-01-01
In this paper we explore the value of theoretical triangulation as a methodological approach for the analysis of classroom interaction. We analyze an excerpt of a whole-class discussion in history from three theoretical perspectives: interactivity of the discourse, conceptual level raising and historical reasoning. We conclude that using…
Oliver, Kathryn; Aicken, Catherine; Arai, Lisa
2013-01-01
Drawing lessons from research can help policy makers make better decisions. If a large and methodologically varied body of research exists, as with childhood obesity, this is challenging. We present new research and policy objectives for child obesity developed by triangulating user involvement data with a mapping study of interventions aimed at…
Symmetry and Transitive Properties of Monohedral f-triangulations of the Riemannian Sphere
Institute of Scientific and Technical Information of China (English)
Ana M. BREDA; J. M. SIGARRETA
2009-01-01
Here we give the complete description of the symmetry group and transitive properties of the set of all of monohedral triangulations of the Riemannian sphere by f-tilings. We shall also show that each monohedral f-tiling of the Riemannian sphere can be seen, up to a spherical isometry, as the singular set of a spherical isometric folding.
Hesse-Biber, Sharlene
2012-01-01
This article explores the deployment of triangulation in the service of uncovering subjugated knowledge and promoting social change for women and other oppressed groups. Feminist approaches to mixed methods praxis create a tight link between the research problem and the research design. An analysis of selected case studies of feminist praxis…
Four-dimensional Causal Dynamical Triangulations and an effective transfer matrix
Görlich, Andrzej
2013-01-01
Causal Dynamical Triangulations is a background independent approach to quantum gravity. We show that there exists an effective transfer matrix labeled by the scale factor which properly describes the evolution of the quantum universe. In this framework no degrees of freedom are frozen, but, the obtained effective action agrees with the minisuperspace model.
A Crust-based Method of Reconstructing Human Bone
Institute of Scientific and Technical Information of China (English)
MA Shu-chao; LIU Yi
2014-01-01
We present a crust-based procedure for modeling human being’s bone, which is based on voronoi diagram and its dual, Delaunay triangulation. In three-dimensional space, the crust algorithm can generate a 3D-model using a set of sample points. The purposes of this paper is to extract precise contour from CT series, then refer to these contours as sample points, and then apply the crust algorithm to these sample points to get three dimensional mesh.
Accuracy analysis for triangulation and tracking based on time-multiplexed structured light.
Wagner, Benjamin; Stüber, Patrick; Wissel, Tobias; Bruder, Ralf; Schweikard, Achim; Ernst, Floris
2014-08-01
The authors' research group is currently developing a new optical head tracking system for intracranial radiosurgery. This tracking system utilizes infrared laser light to measure features of the soft tissue on the patient's forehead. These features are intended to offer highly accurate registration with respect to the rigid skull structure by means of compensating for the soft tissue. In this context, the system also has to be able to quickly generate accurate reconstructions of the skin surface. For this purpose, the authors have developed a laser scanning device which uses time-multiplexed structured light to triangulate surface points. The accuracy of the authors' laser scanning device is analyzed and compared for different triangulation methods. These methods are given by the Linear-Eigen method and a nonlinear least squares method. Since Microsoft's Kinect camera represents an alternative for fast surface reconstruction, the authors' results are also compared to the triangulation accuracy of the Kinect device. Moreover, the authors' laser scanning device was used for tracking of a rigid object to determine how this process is influenced by the remaining triangulation errors. For this experiment, the scanning device was mounted to the end-effector of a robot to be able to calculate a ground truth for the tracking. The analysis of the triangulation accuracy of the authors' laser scanning device revealed a root mean square (RMS) error of 0.16 mm. In comparison, the analysis of the triangulation accuracy of the Kinect device revealed a RMS error of 0.89 mm. It turned out that the remaining triangulation errors only cause small inaccuracies for the tracking of a rigid object. Here, the tracking accuracy was given by a RMS translational error of 0.33 mm and a RMS rotational error of 0.12°. This paper shows that time-multiplexed structured light can be used to generate highly accurate reconstructions of surfaces. Furthermore, the reconstructed point sets can be
Core requirements for successful data linkage: an example of a triangulation method.
Hopf, Y M; Francis, J; Helms, P J; Haughney, J; Bond, C
2016-10-21
The aim was to explore the views of professional stakeholders and healthcare professionals (HCPs) on the linkage of UK National Health Service (NHS) data for paediatric pharmacovigilance purposes and to make recommendations for such a system. A mixed methods approach including a literature review, interviews, focus groups and a three-round Delphi survey with HCPs in Scotland was followed by a triangulation process using a systematic protocol. The survey was structured using the Theoretical Domains Framework of behaviour change. Items retained after applying the matrix-based triangulation process were thematically coded. Ethical approval was granted by the North of Scotland Research Ethics Service. Results from 18 papers, 23 interviewees, 23 participants of focus groups and 61 completed questionnaires in the Delphi survey contributed to the triangulation process. A total of 25 key findings from all four studies were identified during triangulation. There was good convergence; 21 key findings were agreed and remained to inform recommendations. The items were coded as practical/technical (eg, decision about the unique patient identifier to use), mandatory (eg, governed by statute), essential (consistently mentioned in all studies and therefore needed to ensure professional support) or preferable. The development of a paediatric linked database has support from professional stakeholders and HCPs in Scotland. The triangulation identified three sets of core requirements for a new system of data linkage. An additional fourth set of 'preferable' requirements might increase engagement of HCPs and their support for the new system. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.
The geometry of inner spanning trees for planar polygons
Energy Technology Data Exchange (ETDEWEB)
Ivanov, Alexandr O; Tuzhilin, Alexey A [P.G. Demidov Yaroslavl State University, Yaroslavl (Russian Federation)
2012-04-30
We study the geometry of minimal inner spanning trees for planar polygons (that is, spanning trees whose edge-intervals lie in these polygons). We construct analogues of Voronoi diagrams and Delaunay triangulations, prove that every minimal inner spanning tree is a subgraph of an appropriate Delaunay triangulation, and describe the possible structure of the cells of such triangulations.
Directory of Open Access Journals (Sweden)
jean yves fourniols
2013-02-01
Full Text Available This work focus on the structural health monitoring of aircrafts parts specimen structures made of 2024 Aluminum alloys using a reliable Joint Time Frequency Analysis calculation (Joint Temporal Frequency Analysis. In this paper we demonstrate the feasibility of a new non destructive control method capable to probe very large structures within a short time. The method we developed is based through a wide piezoelectric sensors network on a smart comparison between two acoustic signatures: the healthy structure response captured before the commissioning of the plane and “an after flight” response. The sensors network exploits the capability of piezoelectric patches to generate/measure specific Lamb wave’s modes. The system is therefore dynamically configured to localize mechanicals flaws using a triangulation algorithm that operates using different techniques like pitch-catch and pulse-echo. The aim of this paper is to highlight a methodology that is currently being integrated into reconfigurable qualified and certified hardware architecture. The idea behind is to interface the airplane's structure to an integrated modular avionics calculator (IMA.An analytic study is performed and tests to prove the proposed method feasibility on corroded and damaged structures specimens are provided at the end of this paper.
An Improved D-TEN Generate Algorithm and its Application in Mine Modeling%一种改进的D-TEN生成算法及其应用
Institute of Scientific and Technical Information of China (English)
邱佳; 李雯静; 林志勇
2012-01-01
First of all, the incremental insertion algorithm for Delaunay TEN generate was introduced in detailed. Then the position of the point for insertion which is the key step that affect the generate efficiency was improved by leveraging octree index and direction searching technology. And at last,the points were inserted into the tetrahedron network from both internal and external of the convex hull to handle the point insertion process. The experiment showed that the point position method not only can accelerate the Delaunay TEN generate process,but also independent of the size of the point cluster; and the approach that insertion from external of the convex hull made the insertion process more flexibility. Finally, combined with the spatial interpolation techniques, the Delaunay TEN generate method is used to the real 3D modeling of mine.%详细介绍了Delaunay TEN的生成算法——逐点插入法.利用空间八叉树索引及方向查找技术优化影响算法时间效率的关键步骤——插入点定位；结合壳内插入及壳外插入方法改进初始网格生成及加点过程.实验分析表明,点定位算法不仅能够快速对点进行定位,并且其效率与离散点规模无关；壳外插入法将插入点的位置扩展到网格外部,使初始网格的生成更加灵活.最后,结合空间插值技术,将D - TEN应用于矿床真3D建模技术中.
Stereo matching and view interpolation based on image domain triangulation.
Fickel, Guilherme Pinto; Jung, Claudio R; Malzbender, Tom; Samadani, Ramin; Culbertson, Bruce
2013-09-01
This paper presents a new approach for stereo matching and view interpolation problems based on triangular tessellations suitable for a linear array of rectified cameras. The domain of the reference image is initially partitioned into triangular regions using edge and scale information, aiming to place vertices along image edges and increase the number of triangles in textured regions. A region-based matching algorithm is then used to find an initial disparity for each triangle, and a refinement stage is applied to change the disparity at the vertices of the triangles, generating a piecewise linear disparity map. A simple post-processing procedure is applied to connect triangles with similar disparities generating a full 3D mesh related to each camera (view), which are used to generate new synthesized views along the linear camera array. With the proposed framework, view interpolation reduces to the trivial task of rendering polygonal meshes, which can be done very fast, particularly when GPUs are employed. Furthermore, the generated views are hole-free, unlike most point-based view interpolation schemes that require some kind of post-processing procedures to fill holes.
Mutation of torsion pairs in triangulated categories and its geometric realization
Zhou, Yu
2011-01-01
By generalizing mutation of rigid subcategories, maximal rigid subcategories and cluster tilting subcategories, the notion of mutation of torsion pairs in triangulated categories is introduced. It is proved that the mutation of torsion pairs in triangulated categories are torsion pairs. It is also proved that there is no non-trivial mutation of t-structures, but shift. A geometric realization of mutation of torsion pairs in the cluster categories of type $A_n$ or in the cluster categories of type $A_{\\infty}$ is given via the mutations (generalized flips) of Ptolemy diagrams of a regular $(n+3)-$gon $P_{n+3}$ or of a $\\infty-$gon $P_{\\infty}$ respectively.
Understanding how data triangulation identifies acute toxicity of novel psychoactive drugs.
Wood, D M; Dargan, P I
2012-09-01
Over the last decade, there has been an increase in the availability and use of novel psychoactive substances (also known as "legal highs"). There is limited information available on the potential acute toxicity (harms) associated with the use of these novel psychoactive substances. Gold standard evidence, such as animal studies or human clinical trials, is rarely available to users or healthcare professionals. However, it is possible to use triangulation of data on the acute toxicity from multiple sources to describe the overall pattern of toxicity associated with a novel psychoactive substance. In this review, we will describe these potential data sources, which include self-reported toxicity on internet discussion fora, data from sub-population user surveys, data from regional and national poisons information services and published case reports and case series. We will then describe how pattern of acute toxicity associated with the use of the cathinone mephedrone (4-methylmethcathinone) was established using triangulation of these different data sources.
Detection method of inclination angle in image measurement based on improved triangulation.
Zhang, Jinfeng; Zhang, Jiye
2015-02-01
Image distortion seriously affects the accuracy in microscope image measurement. One source of such distortion is related to the tilting of the microscope stage during laser scanning, thereby resulting in various degrees of inclination angles. This paper describes a novel technique that improves the traditional laser triangulation method by using multiple parallel laser beams that can solve the inclination problem. Moreover, a multi-light-spot measurement device, based on the improved laser triangulation technique, is proposed that can accurately detect the degree and directions of the inclination angles in real time. Furthermore, experimental results generated from a prototype of this device show that the new measurement system can effectively detect small inclination angles at a precision up to ±0.5 μrad.
Drug repurposing by integrated literature mining and drug-gene-disease triangulation.
Sun, Peng; Guo, Jiong; Winnenburg, Rainer; Baumbach, Jan
2017-04-01
Drug design is expensive, time-consuming and becoming increasingly complicated. Computational approaches for inferring potentially new purposes of existing drugs, referred to as drug repositioning, play an increasingly important part in current pharmaceutical studies. Here, we first summarize recent developments in computational drug repositioning and introduce the utilized data sources. Afterwards, we introduce a new data fusion model based on n-cluster editing as a novel multi-source triangulation strategy, which was further combined with semantic literature mining. Our evaluation suggests that utilizing drug-gene-disease triangulation coupled to sophisticated text analysis is a robust approach for identifying new drug candidates for repurposing. Copyright © 2016 Elsevier Ltd. All rights reserved.
Nther-type theorem of piecewise algebraic curves on triangulation
Institute of Scientific and Technical Information of China (English)
2007-01-01
The piecewise algebraic curve is a kind generalization of the classical algebraic curve. Nther-type theorem of piecewise algebraic curves on the cross-cut partition is very important to construct the Lagrange interpolation sets for a bivariate spline space.In this paper,using the properties of bivariate splines,the Nther-type theorem of piecewise algebraic curves on the arbitrary triangulation is presented.
Meedy Nugraha
2002-01-01
This paper proposes the importance of multiple instrumentation and data source (triangulation) in a needs analysis. Various data gathering methods developed in assessing learners' English language needs are reviewed. The justification of employing more than a single data gathering method and data source in a needs analysis is also presented by examining the strengths and weaknesses of each method and evaluating previous needs analyses carried out in some Asian countries. Highlights are then g...
Coarse error analysis and correction of a two-dimensional triangulation range finder
Institute of Scientific and Technical Information of China (English)
Huaqiao Gui; Liang Lü; Wei Huang; Jun Xu; Deyong He; Huanqin Wang; Jianping Xie; Tianpeng Zhao; Hai Ming
2006-01-01
@@ A real-time two-dimensional (2D) triangulation range finder is presented, which is composed of two linear complementary metal oxidation semiconductor (CMOS) chips, two camera lenses, and four light emitting diodes (LEDs). The high order distortion in image aberrations is the main factor responsible for the coarse errors. The theoretical prediction is in good agreement with experiments and the correction equation is used to obtain more reliable results with the unique distortion coefficient in the whole working region.
Zhang, Guojie; Zhang,Pei; Krawczak, Michael; Ball, Edward V.; Mort, Matthew; Kehrer-Sawatzki, Hildegard; Cooper, David N.
2010-01-01
Abstract Triangulation of the human, chimpanzee and Neanderthal genome sequences with respect to 44,348 disease-causing or disease-associated missense mutations and 1,712 putative regulatory mutations listed in the Human Gene Mutation Database was employed to identify genetic variants that are apparently pathogenic in humans but which may represent a `compensated? wild-type state in at least one of the other two species. Of 122 such `potentially compensated mutations? (PCMs) identi...
Chromatic Sums of Biloopless Nonseparable Near-Triangulations on the Projective Plane
Institute of Scientific and Technical Information of China (English)
Zhao-xiang Li; Yan-pei Liu; Bing-feng Si
2013-01-01
In this paper,the chromatic sum functions of rooted biloopless nonseparable near-triangulations on the sphere and the projective plane are studied.The chromatic sum function equations of such maps are obtained.From the chromatic sum equations of such maps,the enumerating function equations of such maps are derived.An asymptotic evaluation and some explicit expression of enumerating functions are also derived.
N(o)ther-type theorem of piecewise algebraic curves on triangulation
Institute of Scientific and Technical Information of China (English)
Chun-gang ZHU; Ren-hong WANG
2007-01-01
The piecewise algebraic curve is a kind generalization of the classical algebraic curve.N(o)ther-type theorem of piecewise algebraic curves on the cross-cut partition is very important to construct the Lagrange interpolation sets for a bivariate spline space. In this paper, using the properties of bivariate splines, the N(o)ther-type theorem of piecewise algebraic curves on the arbitrary triangulation is presented.
A triangulation of a homotopy-Deligne-Mumford compactification of the Moduli of curves
Gadgil, Siddhartha
2010-01-01
We construct a triangulation of a compactification of the Moduli space of a surface with at least one puncture that is closely related to the Deligne-Mumford compactification. Specifically, there is a surjective map from the compactification we construct to the Deligne-Mumford compactification so that the inverse image of each point is contractible. In particular our compactification is homotopy equivalent to the Deligne-Mumford compactification.
Rutherford, George W; McFarland, William; Spindler, Hilary; White, Karen; Patel, Sadhna V; Aberle-Grasse, John; Sabin, Keith; Smith, Nathan; Taché, Stephanie; Calleja-Garcia, Jesus M; Stoneburner, Rand L
2010-07-29
Public health triangulation is a process for reviewing, synthesising and interpreting secondary data from multiple sources that bear on the same question to make public health decisions. It can be used to understand the dynamics of HIV transmission and to measure the impact of public health programs. While traditional intervention research and meta-analysis would be ideal sources of information for public health decision making, they are infrequently available, and often decisions can be based only on surveillance and survey data. The process involves examination of a wide variety of data sources and both biological, behavioral and program data and seeks input from stakeholders to formulate meaningful public health questions. Finally and most importantly, it uses the results to inform public health decision-making. There are 12 discrete steps in the triangulation process, which included identification and assessment of key questions, identification of data sources, refining questions, gathering data and reports, assessing the quality of those data and reports, formulating hypotheses to explain trends in the data, corroborating or refining working hypotheses, drawing conclusions, communicating results and recommendations and taking public health action. Triangulation can be limited by the quality of the original data, the potentials for ecological fallacy and "data dredging" and reproducibility of results. Nonetheless, we believe that public health triangulation allows for the interpretation of data sets that cannot be analyzed using meta-analysis and can be a helpful adjunct to surveillance, to formal public health intervention research and to monitoring and evaluation, which in turn lead to improved national strategic planning and resource allocation.
Directory of Open Access Journals (Sweden)
Aberle-Grasse John
2010-07-01
Full Text Available Abstract Background Public health triangulation is a process for reviewing, synthesising and interpreting secondary data from multiple sources that bear on the same question to make public health decisions. It can be used to understand the dynamics of HIV transmission and to measure the impact of public health programs. While traditional intervention research and metaanalysis would be ideal sources of information for public health decision making, they are infrequently available, and often decisions can be based only on surveillance and survey data. Methods The process involves examination of a wide variety of data sources and both biological, behavioral and program data and seeks input from stakeholders to formulate meaningful public health questions. Finally and most importantly, it uses the results to inform public health decision-making. There are 12 discrete steps in the triangulation process, which included identification and assessment of key questions, identification of data sources, refining questions, gathering data and reports, assessing the quality of those data and reports, formulating hypotheses to explain trends in the data, corroborating or refining working hypotheses, drawing conclusions, communicating results and recommendations and taking public health action. Results Triangulation can be limited by the quality of the original data, the potentials for ecological fallacy and "data dredging" and reproducibility of results. Conclusions Nonetheless, we believe that public health triangulation allows for the interpretation of data sets that cannot be analyzed using meta-analysis and can be a helpful adjunct to surveillance, to formal public health intervention research and to monitoring and evaluation, which in turn lead to improved national strategic planning and resource allocation.
SUPERCONVERGENCE OF LEAST-SQUARES MIXED FINITE ELEMENTS FOR ELLIPTIC PROBLEMS ON TRIANGULATION
Institute of Scientific and Technical Information of China (English)
陈艳萍; 杨菊娥
2003-01-01
In this paper,we present the least-squares mixed finite element method and investigate superconvergence phenomena for the second order elliptic boundary-value problems over triangulations.On the basis of the L2-projection and some mixed finite element projections,we obtain the superconvergence result of least-squares mixed finite element solutions.This error estimate indicates an accuracy of O(h3/2)if the lowest order Raviart-Thomas elements are employed.
Kammerer, Yvonne; Jarodzka, Halszka
2011-01-01
Kammerer, Y., & Jarodzka, H. (2010, September). Das Auge als Datenquelle: Triangulation von Blickbewegungsdaten zur Analyse perzeptueller und kognitiver Prozesse in der angewandten Psychologie. Arbeitsgruppe auf dem 47. Kongress der Deutschen Gesellschaft für Psychologie (DGPs). Bremen.
Triangulated Irregular Networks (TIN), Published in 2005, 1:600 (1in=50ft) scale, Oconto County.
NSGIC GIS Inventory (aka Ramona) — This Triangulated Irregular Networks (TIN) dataset, published at 1:600 (1in=50ft) scale, was produced all or in part from LIDAR information as of 2005. Data by this...
NSGIC GIS Inventory (aka Ramona) — This Triangulated Irregular Networks (TIN) dataset, published at 1:24000 (1in=2000ft) scale, was produced all or in part from Orthoimagery information as of 2008....
NSGIC GIS Inventory (aka Ramona) — This Triangulated Irregular Networks (TIN) dataset, published at 1:1200 (1in=100ft) scale, was produced all or in part from Orthoimagery information as of 2000....
The triangulation of the gigantic jets observed by the optical observation network in Taiwan
Chen, Alfred B.; Huang, Chien-Fong; Peng, Kang-Ming; Su, Han-Tzong; Hsu, Rue-Ron
2015-04-01
The optical triangulation of sprites and elves by the multiple sites has been done in the past decades, but the similar observation on gigantic jets has never been reported yet. A ground optical observation network consisting of four stations at Kimen, Penghu, Tainan, and Taitung (from west to east) has been established in Taiwan since 2012. Each station equipped with two sets of Watec low-light sensitivity cameras, and the elevation and azimuth of the observation can be fully remote controlled to point toward the on-going convection system in the vicinity of Taiwan. In summer 2014, more than 6 gigantic jets were captured by at least two stations successfully. The triangulation and ULF sferics of these interesting events provides an excellent chance to explore the spatial and temporal evolution of the jets in different phases. In this presentation, this ground observation network will be introduced, the detail evolution of the recorded gigantic jets is presented. The preliminary result implies that the jets may not pop from the cloudtop straightforwardly, and some twists occur during the propagation of the jets. A more complicated analysis of the tomography for the advanced triangulation will be mentioned, too.
Durif-Bruckert, C; Roux, P; Morelle, M; Mignotte, H; Faure, C; Moumjid-Ferdjaoui, N
2015-07-01
The aim of this study on shared decision-making in the doctor-patient encounter about surgical treatment for early-stage breast cancer, conducted in a regional cancer centre in France, was to further the understanding of patient perceptions on shared decision-making. The study used methodological triangulation to collect data (both quantitative and qualitative) about patient preferences in the context of a clinical consultation in which surgeons followed a shared decision-making protocol. Data were analysed from a multi-disciplinary research perspective (social psychology and health economics). The triangulated data collection methods were questionnaires (n = 132), longitudinal interviews (n = 47) and observations of consultations (n = 26). Methodological triangulation revealed levels of divergence and complementarity between qualitative and quantitative results that suggest new perspectives on the three inter-related notions of decision-making, participation and information. Patients' responses revealed important differences between shared decision-making and participation per se. The authors note that subjecting patients to a normative behavioural model of shared decision-making in an era when paradigms of medical authority are shifting may undermine the patient's quest for what he or she believes is a more important right: a guarantee of the best care available.
Using GPS/INS data to enhance image matching for real-time aerial triangulation
Tanathong, Supannee; Lee, Impyeong
2014-11-01
Direct georeferencing is a promising technique for determining the exterior orientation parameters (EO) of a camera in real-time through the integration of GPS/INS sensors. Instead of using expensive devices, we improve the accuracy of the directly measured EOs through aerial triangulation (AT) and rely on tie-points. In this work, using GPS/INS data, we enhance the KLT tracker to achieve accuracy and speed that is compatible with real-time aerial triangulation. Given GPS/INS data from medium-grade sensors, the proposed system is 48% faster than the original work and tie-points extracted by our system are 6.33% more accurate and more evenly distributed than tie-points extracted by the original work. The AT processing results show that tie-points from the proposed work can reduce the RMSE of the directly measured EOs by 17.87% for position and 23.37% for attitude. Thus, we conclude that our proposed system can be integrated with real-time aerial triangulation.
Chromatic polynomials of planar triangulations, the Tutte upper bound and chromatic zeros
Shrock, Robert; Xu, Yan
2012-02-01
Tutte proved that if Gpt is a planar triangulation and P(Gpt, q) is its chromatic polynomial, then |P(Gpt, τ + 1)| ⩽ (τ - 1)n - 5, where \\tau =(1+\\sqrt{5} \\, )/2 and n is the number of vertices in Gpt. Here we study the ratio r(Gpt) = |P(Gpt, τ + 1)|/(τ - 1)n - 5 for a variety of planar triangulations. We construct infinite recursive families of planar triangulations Gpt, m depending on a parameter m linearly related to n and show that if P(Gpt, m, q) only involves a single power of a polynomial, then r(Gpt, m) approaches zero exponentially fast as n → ∞. We also construct infinite recursive families for which P(Gpt, m, q) is a sum of powers of certain functions and show that for these, r(Gpt, m) may approach a finite nonzero constant as n → ∞. The connection between the Tutte upper bound and the observed chromatic zero(s) near to τ + 1 is investigated. We report the first known graph for which the zero(s) closest to τ + 1 is not real, but instead is a complex-conjugate pair. Finally, we discuss connections with the nonzero ground-state entropy of the Potts antiferromagnet on these families of graphs.
Computational Modeling for What-Is, What-Might-Be,and What-Should-Be Studies—And Triangulation
DEFF Research Database (Denmark)
Burton, Richard M.; Obel, Børge
2011-01-01
In this essay, we examine what-is, what-might-be, and what-should-be computational models where the purpose is to explore new concepts, ideas, boundaries, and limitations going beyond what we know at the moment. Computational models complement well with other approaches: ethnographies, field stud...... studies, human subject lab studies, and surveys in novel triangulations. Triangulation of two or more complementary approaches permits us to broaden and deepen our understanding and insights....
Peleg, Ora
2014-12-01
This study examined the relationships between stressful life events in childhood and differentiation of self and intergenerational triangulation in adulthood. The sample included 217 students (173 females and 44 males) from a college in northern Israel. Participants completed the Hebrew versions of Life Events Checklist (LEC), Differentiation of Self Inventory-Revised (DSI-R) and intergenerational triangulation (INTRI). The main findings were that levels of stressful life events during childhood and adolescence among both genders were positively correlated with the levels of fusion with others and intergenerational triangulation. The levels of positive life events were negatively related to levels of emotional reactivity, emotional cut-off and intergenerational triangulation. Levels of stressful life events in females were positively correlated with emotional reactivity. Intergenerational triangulation was correlated with emotional reactivity, emotional cut-off, fusion with others and I-position. Findings suggest that families that experience higher levels of stressful life events may be at risk for higher levels of intergenerational triangulation and lower levels of differentiation of self.
A simplicial algorithm for testing the integral properties of polytopes : A revision
Yang, Z.F.
1994-01-01
Given an arbitrary polytope P in the n-dimensional Euclidean space R n , the question is to determine whether P contains an integral point or not. We propose a simplicial algorithm to answer this question based on a specifc integer labeling rule and a specific triangulation of R n . Starting from an
Multi-resolution unstructured grid-generation for geophysical applications on the sphere
Engwirda, Darren
2015-01-01
An algorithm for the generation of non-uniform unstructured grids on ellipsoidal geometries is described. This technique is designed to generate high quality triangular and polygonal meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric and ocean simulation, and numerical weather predication. Using a recently developed Frontal-Delaunay-refinement technique, a method for the construction of high-quality unstructured ellipsoidal Delaunay triangulations is introduced. A dual polygonal grid, derived from the associated Voronoi diagram, is also optionally generated as a by-product. Compared to existing techniques, it is shown that the Frontal-Delaunay approach typically produces grids with near-optimal element quality and smooth grading characteristics, while imposing relatively low computational expense. Initial results are presented for a selection of uniform and non-uniform ellipsoidal grids appropriate for large-scale geophysical applications. The use of user...
Engwirda, Darren
2017-01-01
An algorithm for the generation of non-uniform, locally orthogonal staggered unstructured spheroidal grids is described. This technique is designed to generate very high-quality staggered VoronoiDelaunay meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric simulation, ocean-modelling and numerical weather prediction. Using a recently developed Frontal-Delaunay refinement technique, a method for the construction of high-quality unstructured spheroidal Delaunay triangulations is introduced. A locally orthogonal polygonal grid, derived from the associated Voronoi diagram, is computed as the staggered dual. It is shown that use of the Frontal-Delaunay refinement technique allows for the generation of very high-quality unstructured triangulations, satisfying a priori bounds on element size and shape. Grid quality is further improved through the application of hill-climbing-type optimisation techniques. Overall, the algorithm is shown to produce grids with very high element quality and smooth grading characteristics, while imposing relatively low computational expense. A selection of uniform and non-uniform spheroidal grids appropriate for high-resolution, multi-scale general circulation modelling are presented. These grids are shown to satisfy the geometric constraints associated with contemporary unstructured C-grid-type finite-volume models, including the Model for Prediction Across Scales (MPAS-O). The use of user-defined mesh-spacing functions to generate smoothly graded, non-uniform grids for multi-resolution-type studies is discussed in detail.
Measuring teamwork in primary care: Triangulation of qualitative and quantitative data.
Brown, Judith Belle; Ryan, Bridget L; Thorpe, Cathy; Markle, Emma K R; Hutchison, Brian; Glazier, Richard H
2015-09-01
This article describes the triangulation of qualitative dimensions, reflecting high functioning teams, with the results of standardized teamwork measures. The study used a mixed methods design using qualitative and quantitative approaches to assess teamwork in 19 Family Health Teams in Ontario, Canada. This article describes dimensions from the qualitative phase using grounded theory to explore the issues and challenges to teamwork. Two quantitative measures were used in the study, the Team Climate Inventory (TCI) and the Providing Effective Resources and Knowledge (PERK) scale. For the triangulation analysis, the mean scores of these measures were compared with the qualitatively derived ratings for the dimensions. The final sample for the qualitative component was 107 participants. The qualitative analysis identified 9 dimensions related to high team functioning such as common philosophy, scope of practice, conflict resolution, change management, leadership, and team evolution. From these dimensions, teams were categorized numerically as high, moderate, or low functioning. Three hundred seventeen team members completed the survey measures. Mean site scores for the TCI and PERK were 3.87 and 3.88, respectively (of 5). The TCI was associated will all dimensions except for team location, space allocation, and executive director leadership. The PERK was associated with all dimensions except team location. Data triangulation provided qualitative and quantitative evidence of what constitutes teamwork. Leadership was pivotal in forging a common philosophy and encouraging team collaboration. Teams used conflict resolution strategies and adapted to the changes they encountered. These dimensions advanced the team's evolution toward a high functioning team. (c) 2015 APA, all rights reserved).
Stochastic triangulation for prostate positioning during radiotherapy using short CBCT arcs.
Hoegele, Wolfgang; Loeschel, Rainer; Dobler, Barbara; Koelbl, Oliver; Beard, Clair; Zygmanski, Piotr
2013-02-01
Fast and reliable tumor localization is an important part of today's radiotherapy utilizing new delivery techniques. This proof-of-principle study demonstrates the use of a method called herein 'stochastic triangulation' for this purpose. Stochastic triangulation uses very short imaging arcs and a few projections. A stochastic Maximum A Posteriori (MAP) estimator is proposed based on an uncertainty-driven model of the acquisition geometry and inter-/intra-fractional deformable anatomy. The application of this method was designed to use the available linac-mounted cone-beam computed tomography (CBCT) and/or electronic portal imaging devices (EPID) for the patient setup based on short imaging arcs. For the proof-of-principle clinical demonstration, the MAP estimator was applied to 5 CBCT scans of a prostate cancer patient with 2 implanted gold markers. Estimation was performed for several (18) very short imaging arcs of 5° with 10 projections resulting in 90 estimations. Short-arc stochastic triangulation led to residual radial errors compared to manual inspection with a mean value of 1.4mm and a standard deviation of 0.9 mm (median 1.2mm, maximum 3.8mm) averaged over imaging directions all around the patient. Furthermore, abrupt intra-fractional motion of up to 10mm resulted in radial errors with a mean value of 1.8mm and a standard deviation of 1.1mm (median 1.5mm, maximum 5.6mm). Slow periodic intra-fractional motions in the range of 12 mm resulted in radial errors with a mean value of 1.8mm and a standard deviation of 1.1mm (median 1.6mm, maximum 4.7 mm). Based on this study, the proposed stochastic method is fast, robust and can be used for inter- as well as intra-fractional target localization using current CBCT units. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.
1:500 Scale Aerial Triangulation Test with Unmanned Airship in Hubei Province
Feifei, Xie; Zongjian, Lin; Dezhu, Gui
2014-03-01
A new UAVS (Unmanned Aerial Vehicle System) for low altitude aerial photogrammetry is introduced for fine surveying and mapping, including the platform airship, sensor system four-combined wide-angle camera and photogrammetry software MAP-AT. It is demonstrated that this low-altitude aerial photogrammetric system meets the precision requirements of 1:500 scale aerial triangulation based on the test of this system in Hubei province, including the working condition of the airship, the quality of image data and the data processing report. This work provides a possibility for fine surveying and mapping.
Triangulation in Youth Sport: Healthy Partnerships among Parents, Coaches, and Practitioners.
Blom, Lindsey C; Visek, Amanda J; Harris, Brandonn S
2013-01-01
Youth sport is unique because it involves communication, coordination, and maintenance of relationships among multiple adults, all of whom are vested stakeholders in a child-athlete's sport experience. This dynamic becomes even more complex when a sport psychology practitioner is added; therefore, the purpose of this paper is to provide guidelines and considerations to assist sport psychology practitioners in managing the triangulation of adults who are involved in the consultation process with youth athletes. We first discuss specific dyads and considerations for the practitioner and then highlight recommendations for practitioners regarding transparency and confidentiality issues specific to youth athletes.
Triangulation of multistation camera data to locate a curved line in space
Fricke, C. L.
1974-01-01
A method is described for finding the location of a curved line in space from local azimuth as a function of elevation data obtained at several observation sites. A least-squares criterion is used to insure the best fit to the data. The method is applicable to the triangulation of an object having no identifiable structural features, provided its width is very small compared with its length so as to approximate a line in space. The method was implemented with a digital computer program and was successfully applied to data obtained from photographs of a barium ion cloud which traced out the earth's magnetic field line at very high altitudes.
Triangulations, Subdivisions, and Covers for Control of Affine Hypersurface Systems on Polytopes
Lin, Zhiyun
2009-01-01
This paper studies the problem for an affine hypersurface system to reach a polytopic target set starting from inside a polytope in the state space. We present an exhaustive solution which begins with a characterization of states which can reach the target by open-loop control and concludes with a systematic procedure to synthesize a feedback control. Our emphasis is on methods of subdivision, triangulation, and covers which explicitly account for the capabilities of the control system. In contrast with previous literature, the partition methods are guaranteed to yield a correct feedback synthesis, assuming the problem is solvable by open-loop control.
Satellite triangulation in Europe from WEST and ISAGEX data. [computer programs
Leick, A.; Arur, M.
1975-01-01
Observational data that was acquired during the West European Satellite Triangulation (WEST) program and the International Satellite Geodesy Experiment (ISAGEX) campaign was obtained for the purpose of performing a geometric solution to improve the present values of coordinates of the European stations in the OSU WN14 solutions, adding some new stations and assessing the quality of the WN14 solution with the help of the additional data available. The status of the data as received, the preprocessing required and the preliminary tests carried out for the initial screening of the data are described. The adjustment computations carried out and the results of the adjustments are discussed.
Quantum gravity on a laptop: 1 + 1 Dimensional Causal Dynamical Triangulation simulation
Israel, Norman S.; Lindner, John F.
2012-01-01
The quest for quantum gravity has been long and difficult. Causal Dynamical Triangulation is a new and straightforward approach to quantum gravity that recovers classical spacetime at large scales by enforcing causality at small scales. CDT combines quantum physics with general relativity in a Feynman sum-over-geometries and converts the sum into a discrete statistical physics problem. We solve this problem using a new Monte Carlo simulation to compute the spatial fluctuations of an empty universe with one space and one time dimensions. Our results compare favorably with theory and provide an accessible but detailed introduction to quantum gravity via a simulation that runs on a laptop computer.
Lutzke, Peter; Schaffer, Martin; Kühmstedt, Peter; Kowarschik, Richard; Notni, Gunther
2013-04-01
Active triangulation systems are widely used for precise and fast measurements. Many different coding strategies have been invented to solve the correspondence problem. The quality of the measurement results depends on the accuracy of the pixel assignments. The most established method uses phase shifted-patterns projected on the scene. This is compared to a method using statistical patterns. In both coding strategies, the number and the spatial frequency of the projected patterns is varied. The measurements and calculations for all presented results were done with exactly the same measurement setup in a narrow time window to avoid any changes and to guarantee identical technical preconditions as well as comparability.
Critical slowing down of cluster algorithms for Ising models coupled to 2-d gravity
Bowick, Mark; Falcioni, Marco; Harris, Geoffrey; Marinari, Enzo
1994-02-01
We simulate single and multiple Ising models coupled to 2-d gravity using both the Swendsen-Wang and Wolff algorithms to update the spins. We study the integrated autocorrelation time and find that there is considerable critical slowing down, particularly in the magnetization. We argue that this is primarily due to the local nature of the dynamical triangulation algorithm and to the generation of a distribution of baby universes which inhibits cluster growth.
Critical Slowing Down of Cluster Algorithms for Ising Models Coupled to 2-d Gravity
Bowick, M; Harris, G; Marinari, E
1994-01-01
We simulate single and multiple Ising models coupled to 2-d gravity using both the Swendsen-Wang and Wolff algorithms to update the spins. We study the integrated autocorrelation time and find that there is considerable critical slowing down, particularly in the magnetization. We argue that this is primarily due to the local nature of the dynamical triangulation algorithm and to the generation of a distribution of baby universes which inhibits cluster growth.
Höing, Andrea; Quinten, Marcel C; Indrawati, Yohana Maria; Cheyne, Susan M; Waltert, Matthias
2013-02-01
Estimating population densities of key species is crucial for many conservation programs. Density estimates provide baseline data and enable monitoring of population size. Several different survey methods are available, and the choice of method depends on the species and study aims. Few studies have compared the accuracy and efficiency of different survey methods for large mammals, particularly for primates. Here we compare estimates of density and abundance of Kloss' gibbons (Hylobates klossii) using two of the most common survey methods: line transect distance sampling and triangulation. Line transect surveys (survey effort: 155.5 km) produced a total of 101 auditory and visual encounters and a density estimate of 5.5 gibbon clusters (groups or subgroups of primate social units)/km(2). Triangulation conducted from 12 listening posts during the same period revealed a similar density estimate of 5.0 clusters/km(2). Coefficients of variation of cluster density estimates were slightly higher from triangulation (0.24) than from line transects (0.17), resulting in a lack of precision in detecting changes in cluster densities of triangulation and triangulation method also may be appropriate.
Multi-region unstructured volume segmentation using tetrahedron filling
Energy Technology Data Exchange (ETDEWEB)
Willliams, Sean Jamerson [Los Alamos National Laboratory; Dillard, Scott E [Los Alamos National Laboratory; Thoma, Dan J [MDI, INSTITUTES; Hlawitschka, Mario [UC DAVIS; Hamann, Bernd [UC DAVIS
2010-01-01
Segmentation is one of the most common operations in image processing, and while there are several solutions already present in the literature, they each have their own benefits and drawbacks that make them well-suited for some types of data and not for others. We focus on the problem of breaking an image into multiple regions in a single segmentation pass, while supporting both voxel and scattered point data. To solve this problem, we begin with a set of potential boundary points and use a Delaunay triangulation to complete the boundaries. We use heuristic- and interaction-driven Voronoi clustering to find reasonable groupings of tetrahedra. Apart from the computation of the Delaunay triangulation, our algorithm has linear time complexity with respect to the number of tetrahedra.
Hierarchical data visualization using a fast rectangle-packing algorithm.
Itoh, Takayuki; Yamaguchi, Yumi; Ikehata, Yuko; Kajinaga, Yasumasa
2004-01-01
This paper presents a technique for the representation of large-scale hierarchical data which aims to provide good overviews of complete structures and the content of the data in one display space. The technique represents the data by using nested rectangles. It first packs icons or thumbnails of the lowest-level data and then generates rectangular borders that enclose the packed data. It repeats the process of generating rectangles that enclose the lower-level rectangles until the highest-level rectangles are packed. This paper presents two rectangle-packing algorithms for placing items of hierarchical data onto display spaces. The algorithms refer to Delaunay triangular meshes connecting the centers of rectangles to find gaps where rectangles can be placed. The first algorithm places rectangles where they do not overlap each other and where the extension of the layout area is minimal. The second algorithm places rectangles by referring to templates describing the ideal positions for nodes of input data. It places rectangles where they do not overlap each other and where the combination of the layout area and the distances between the positions described in the template and the actual positions is minimal. It can smoothly represent time-varying data by referring to templates that describe previous layout results. It is also suitable for semantics-based or design-based data layout by generating templates according to the semantics or design.
Representations sociales et triangulation: une application en psychologie sociale de la sante
Directory of Open Access Journals (Sweden)
Thémis Apostolidis
Full Text Available La relation du contexte social et de la santé représente un enjeu de recherche important pour les développements actuels en psychologie sociale de la santé. L'approche des représentations sociales offre un cadre d'analyse de la pensée sociale profane concernant la maladie, en rupture avec la tradition cognitiviste et individualiste dominante dans les analyses psychosociales des risques sanitaires. Sur le plan théorico-méthodologique, cette approche permet une étude contextualisée des processus sociocognitifs qui interviennent dans la construction des risques, en opérationnalisant la double nature, produit/processus, de la représentation. Dans cette perspective, la triangulation en tant que stratégie de recherche inductive constitue une démarche privilégiée. Nous présentons une application de cette stratégie à travers une recherche sur les représentations des relations sexuelles et des risques liés au sida chez de jeunes adultes en France et en Grèce. Nous discutons la pertinence de la triangulation pour les approches "multi-niveaux" de la construction des risquesl.
Enhancing non-melonic triangulations: A tensor model mixing melonic and planar maps
Bonzom, Valentin; Rivasseau, Vincent
2015-01-01
Ordinary tensor models of rank $D\\geq 3$ are dominated at large $N$ by tree-like graphs, known as melonic triangulations. We here show that non-melonic contributions can be enhanced consistently, leading to different types of large $N$ limits. We first study the most generic quartic model at $D=4$, with maximally enhanced non-melonic interactions. The existence of the $1/N$ expansion is proved and we further characterize the dominant triangulations. This combinatorial analysis is then used to define a non-quartic, non-melonic class of models for which the large $N$ free energy and the relevant expectations can be calculated explicitly. They are matched with random matrix models which contain multi-trace invariants in their potentials: they possess a branched polymer phase and a 2D quantum gravity phase, and a transition between them whose entropy exponent is positive. Finally, a non-perturbative analysis of the generic quartic model is performed, which proves analyticity in the coupling constants in cardioid ...
Enhancing non-melonic triangulations: A tensor model mixing melonic and planar maps
Directory of Open Access Journals (Sweden)
Valentin Bonzom
2015-06-01
Full Text Available Ordinary tensor models of rank D≥3 are dominated at large N by tree-like graphs, known as melonic triangulations. We here show that non-melonic contributions can be enhanced consistently, leading to different types of large N limits. We first study the most generic quartic model at D=4, with maximally enhanced non-melonic interactions. The existence of the 1/N expansion is proved and we further characterize the dominant triangulations. This combinatorial analysis is then used to define a non-quartic, non-melonic class of models for which the large N free energy and the relevant expectations can be calculated explicitly. They are matched with random matrix models which contain multi-trace invariants in their potentials: they possess a branched polymer phase and a 2D quantum gravity phase, and a transition between them whose entropy exponent is positive. Finally, a non-perturbative analysis of the generic quartic model is performed, which proves analyticity in the coupling constants in cardioid domains.
Curvature Matrix Models for Dynamical Triangulations and the Itzykson-Di Francesco Formula
Szabó, R J; Szabo, Richard J.; Wheater, John F.
1996-01-01
We study the large-$N$ limit of a class of matrix models for dually weighted triangulated random surfaces using character expansion techniques. We show that for various choices of the weights of vertices of the dynamical triangulation the model can be solved by resumming the Itzykson-Di Francesco formula over congruence classes of Young tableau weights modulo three. From this we show that the large-$N$ limit implies a non-trivial correspondence with models of random surfaces weighted with only even coordination number vertices. We examine the critical behaviour and evaluation of observables and discuss their interrelationships in all models. We obtain explicit solutions of the model for simple choices of vertex weightings and use them to show how the matrix model reproduces features of the random surface sum. We show that a class of matrix models admits complex saddle-point solutions of the Itzykson-Di Francesco formula, and we present the general technique of dealing with such solutions. We find that the set...
Yang, Hongwei; Tao, Wei; Zhang, Zhengqi; Zhao, Siwei; Yin, Xiaoqia; Zhao, Hui
2017-05-15
Directional dithering of a laser beam potentially limits the detection accuracy of a laser triangulation displacement probe. A theoretical analysis indicates that the measurement accuracy will linearly decrease as the laser dithering angle increases. To suppress laser dithering, a scheme for reduction of the influence of laser beam directional dithering in a laser triangulation displacement probe, which consists of a collimated red laser, a laser beam pointing control setup, a receiver lens, and a charge-coupled device, is proposed in this paper. The laser beam pointing control setup is inserted into the source laser beam and the measured object and can separate the source laser beam into two symmetrical laser beams. Hence, at the angle at which the source laser beam dithers, the positional averages of the two laser spots are equal and opposite. Moreover, a virtual linear function method is used to maintain a stable average of the positions of the two spots on the imaging side. Experimental results indicate that with laser beam pointing control, the estimated standard deviation of the fitting error decreases from 0.3531 mm to 0.0100 mm , the repeatability accuracy can be lowered from ±7 mm to ±5 μ m , and the nonlinear error can be reduced from ±6 % FS (full scale) to ±0.16 % FS.
Indirect measurement of molten steel level in tundish based on laser triangulation
Energy Technology Data Exchange (ETDEWEB)
Su, Zhiqi; He, Qing, E-mail: heqing@ise.neu.edu.cn; Xie, Zhi [State Key Laboratory of Synthetical Automation for Process Industries, School of Information Science and Engineering, Northeastern University, Shenyang 110819 (China)
2016-03-15
For real-time and precise measurement of molten steel level in tundish during continuous casting, slag level and slag thickness are needed. Among which, the problem of slag thickness measurement has been solved in our previous work. In this paper, a systematic solution for slag level measurement based on laser triangulation is proposed. Being different from traditional laser triangulation, several aspects for measuring precision and robustness have been done. First, laser line is adopted for multi-position measurement to overcome the deficiency of single point laser range finder caused by the uneven surface of the slag. Second, the key parameters, such as installing angle and minimum requirement of the laser power, are analyzed and determined based on the gray-body radiation theory to fulfill the rigorous requirement of measurement accuracy. Third, two kinds of severe noises in the acquired images, which are, respectively, caused by heat radiation and Electro-Magnetic Interference (EMI), are cleaned via morphological characteristic of the liquid slag and color difference between EMI and the laser signals, respectively. Fourth, as false target created by stationary slag usually disorders the measurement, valid signals of the slag are distinguished from the false ones to calculate the slag level. Then, molten steel level is obtained by the slag level minus the slag thickness. The measuring error of this solution is verified by the applications in steel plants, which is ±2.5 mm during steady casting and ±3.2 mm at the end of casting.
Namasivayam, Mayooran; Adji, Audrey; O'Rourke, Michael F
2016-02-01
Pulsatile blood pressure rises with age, especially in the aorta. The comparative role of forward and reflected pressure waves (FW and RW, respectively), determined by aortic flow triangulation has not previously been explored in a large clinical cohort. This study aimed to identify the role of FW and RW in the rise in aortic pulse pressure with age. For 879 outpatients, aortic pressure waveforms were generated using a validated generalized transfer function applied to radial pressure waves recorded using applanation tonometry. FW and RW were subsequently determined using aortic flow triangulation. Contributions of FW and RW to rise in aortic pulse pressure with age were determined using multivariate linear regression and product of coefficient mediation analysis, with adjustment for height, weight, heart rate, and mean arterial pressure. Comparisons were made by gender and before and after age 60. In subjects aged 60 and below, RW was an important contributor to pulsatile pressure elevation with age, but FW was non-contributory in either gender after multivariate correction. In subjects aged above 60, both FW and RW were significant and equal contributors in both genders. In a clinical setting, both FW and RW are important to pulsatile aortic blood pressure across the lifespan, but RW appears to have a more pronounced effect across all ages, whereas FW has less effect in younger persons. © American Journal of Hypertension, Ltd 2015. All rights reserved. For Permissions, please email: journals.permissions@oup.com.
Arain, Nabeel A; Cadeddu, Jeffrey A; Hogg, Deborah C; Bergs, Richard; Fernandez, Raul; Scott, Daniel J
2012-09-01
This study evaluated operative outcomes and workload during single-site laparoscopy (SSL) using a magnetically anchored cautery dissector (MAGS) compared with a conventional laparoscopic hook cautery (LAP). Each cautery was used to perform six SSL porcine cholecystectomies. For MAGS, the cautery device was inserted through the umbilical incision, magnetically coupled, and deployed; two graspers and a laparoscope were used. For LAP, two percutaneous retraction sutures, one grasper, a hook cautery dissector, and a laparoscope were used. Operative outcomes, surgeon ratings (scale, 1-5; 1 = superior), and workload (scale, 1-10; 1 = superior) were evaluated. No significant differences were detected for operative outcomes and surgeon ratings, however, trends were detected favoring MAGS. Surgeon workload ratings were significantly better for MAGS (2.6 ± 0.2) vs. LAP (5.6 ± 1.1; p triangulation were excellent and the safe handling protocol was followed with no complications. For LAP, the parallelism of instruments and lack of triangulation hindered depth perception, caused instrument conflicts, and resulted in two minor complications (one superficial liver laceration and one inadvertent burn to the diaphragm). These data suggest that using the MAGS device for SSL cholecystectomy results in equivalent (or better) operative outcomes and less workload compared with LAP.
Indirect measurement of molten steel level in tundish based on laser triangulation.
Su, Zhiqi; He, Qing; Xie, Zhi
2016-03-01
For real-time and precise measurement of molten steel level in tundish during continuous casting, slag level and slag thickness are needed. Among which, the problem of slag thickness measurement has been solved in our previous work. In this paper, a systematic solution for slag level measurement based on laser triangulation is proposed. Being different from traditional laser triangulation, several aspects for measuring precision and robustness have been done. First, laser line is adopted for multi-position measurement to overcome the deficiency of single point laser range finder caused by the uneven surface of the slag. Second, the key parameters, such as installing angle and minimum requirement of the laser power, are analyzed and determined based on the gray-body radiation theory to fulfill the rigorous requirement of measurement accuracy. Third, two kinds of severe noises in the acquired images, which are, respectively, caused by heat radiation and Electro-Magnetic Interference (EMI), are cleaned via morphological characteristic of the liquid slag and color difference between EMI and the laser signals, respectively. Fourth, as false target created by stationary slag usually disorders the measurement, valid signals of the slag are distinguished from the false ones to calculate the slag level. Then, molten steel level is obtained by the slag level minus the slag thickness. The measuring error of this solution is verified by the applications in steel plants, which is ±2.5 mm during steady casting and ±3.2 mm at the end of casting.
Long, S. A. T.
1973-01-01
The triangulation method developed specifically for the Barium Ion Cloud Project is discussed. Expression for the four displacement errors, the three slope errors, and the curvature error in the triangulation solution due to a probable error in the lines-of-sight from the observation stations to points on the cloud are derived. The triangulation method is then used to determine the effect of the following on these different errors in the solution: the number and location of the stations, the observation duration, east-west cloud drift, the number of input data points, and the addition of extra cameras to one of the stations. The pointing displacement errors, and the pointing slope errors are compared. The displacement errors in the solution due to a probable error in the position of a moving station plus the weighting factors for the data from the moving station are also determined.
Ponappa, Sujata; Bartle-Haring, Suzanne; Holowacz, Eugene; Ferriby, Megan
2017-01-01
Guided by Bowen theory, we investigated the relationships between parent-child triangulation, parental differential treatment (PDT), sibling warmth, and individual depressive symptoms in a sample of 77 sibling dyads, aged 18-25 years, recruited through undergraduate classes at a U.S. public University. Results of the actor-partner interdependence models suggested that being triangulated into parental conflict was positively related to both siblings' perception of PDT; however, as one sibling felt triangulated, the other perceived reduced levels of PDT. For both siblings, the perception of higher levels of PDT was related to decreased sibling warmth and higher sibling warmth was associated with fewer depressive symptoms. The implications of these findings for research and the treatment of depression in the college-aged population are discussed. © 2016 American Association for Marriage and Family Therapy.
Proximity graph analysis for linear networks extraction from high-resolution satellite imagery
Skourikhine, Alexei N.
2006-05-01
Reliable and accurate methods for detection and extraction of linear network, such as road networks, in satellite imagery are essential to many applications. We present an approach to the road network extraction from high-resolution satellite imagery that is based on proximity graph analysis. We are jumping off from the classification provided by existing spectral and textural classification tools, which produce a set of candidate road patches. Then, constrained Delaunay triangulation and Chordal Axis transform are used to extract centerline characterization of the delineated candidate road patches. We refine produced center lines to reduce noise influence on patch boundaries, resulting in a smaller set of robust center lines authentically representing their road patches. Refined center lines are triangulated using constrained Delaunay triangulation (CDT) algorithm to generate a sub-optimal mesh of interconnections among them. The generated triangle edges connecting different center lines are used for spatial analysis of the center lines relations. A subset of the Delaunay tessellation grid contains the Euclidian Minimum Spanning Tree (EMST) that provides an approximation of road network. The approach can be generalized to the multi-criteria MST and multi-criteria shortest path algorithms to integrate other factors important for road network extraction, in addition to proximity relations considered by standard EMST.
A stereo triangulation system for structural identification: Analytical and experimental results
Junkins, J. L.; James, G. H., III; Pollock, T. C.; Rahman, Z. H.
1988-01-01
Identification of large space structures' distributed mass, stiffness, and energy dissipation characteristics poses formidable analytical, numerical, and implementation difficulties. Development of reliable on-orbit structural identification methods is important for implementing active vibration suppression concepts which are under widespread study in the large space structures community. Near the heart of the identification problem lies the necessity of making a large number of spatially distributed measurements of the structure's vibratory response and the associated force/moment inputs with sufficient spatial and frequency resolution. In the present paper, we discuss a method whereby tens of active or passive (retro-reflecting) targets on the structure are tracked simultaneously by the focal planes of two or more video cameras mounted on an adjacent platform. Triangulation (optical ray intersection) of the conjugate image centroids yield inertial trajectories of each target on the structure. Given the triangulated motion of the targets, we apply and extend methodology developed by Creamer, Junkins, and Juang to identify the frequencies, mode shapes, and updated estimates for the mass/stiffness/damping parameterization of the structure. The methodology is semi-automated, for example, the post experiment analysis of the video imagery to determine the inertial trajectories of the targets typically requires less than thirty minutes of real time. Using methodology discussed herein, the frequency response of a large number of points on the structure (where reflective targets are mounted) on the structure can be determined from optical measurements alone. For comparison purposes, we also utilize measurements from accelerometers and a calibrated impulse hammer. While our experimental work remains in a research stage of development, we have successfully tracked and stereo triangulated 20 targets (on a vibrating cantilevered grid structure) at a sample frequency of 200 HZ
Heraud, J. A.; Centa, V. A.; Bleier, T.
2015-12-01
During several sessions in past AGU meetings, reports on the progress of analysis of magnetometer data have been given, as our research moved from a one dimensional geometry, to two and finally to a three dimensional image. In the first case, we learned how to extract one coordinate, azimuth information, on the occurrence of an earthquake based on the processing of mono-polar pulses received at a single station. A two dimensional geometry was implemented through triangulation and we showed the use of this technique to find out where a future epicenter would occur. Recently, we have obtained compelling evidence that the pressure points leading to the determination of future epicenters originate at a plane, inclined with the same angle as the subduction zone, a three-dimensional position of the future hypocenter. Hence, an image of the subduction zone or interface between the Nazca plate and the continental plate in the northern area of Lima, Peru, has been obtained, corresponding to the subduction zone obtained by traditional seismic methods. Our work with magnetometers deployed along part of the Peruvian coast since 2009, has shown that it is possible to measure, with significant precision, the azimuth of electromagnetic pulses propagating from stress points in the earth's crust due to the subduction of tectonic plates, as to be able to determine precisely the origin of the pulses. The occurrence of earthquakes approximately 11 to 18 days after the appearance of the first pulses and the recognition of grouping of such pulses, has allowed us to determine accurately the direction and the timing of future seismic events. Magnetometers, donated by Quakefinder and Telefonica del Peru were then strategically installed in different locations in Peru with the purpose of achieving triangulation. During two years since 2013, about a dozen earthquakes have been associated with future seismic activity in a pre or post occurrence way. Our presentation will be based on animated
ANALYSIS OF TWO TRIANGLE-BASED MULTI-SURFACE REGISTRATION ALGORITHMS OF IRREGULAR POINT CLOUDS
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M. Al-Durgham
2012-09-01
Full Text Available The registration of multiple surface point clouds into a common reference frame is a well addressed topic, and the Iterative Closest Point (ICP is – perhaps – the most used method when registering laser scans due to their irregular nature. In this paper, we examine the proposed Iterative Closest Projected Point (ICPP algorithm for the simultaneous registration of multiple point clouds. First, a point to triangular patch (i.e. closest three points match is established by checking if the point falls within the triangular dipyramid, which has the three triangular patch points as a base and a user-chosen normal distance as the height to establish the two peaks. Then, the point is projected onto the patch surface, and its projection is then used as a match for the original point. It is also shown through empirical experimentation that the Delaunay triangles are not a requirement for establishing matches. In fact, Delaunay triangles in some scenarios may force blunders into the final solution, while using the closest three points leads to avoiding some undesired erroneous points. In addition, we review the algorithm by which the ICPP is inspired, namely, the Iterative Closest Patch (ICPatch; where conjugate point-patch pairs are extracted in the overlapping surface areas, and the transformation parameters between all neighbouring surfaces are estimated in a pairwise manner. Then, using the conjugate point-patch pairs, and applying the transformation parameters from the pairwise registration as initial approximations, the final surface transformation parameters are solved for simultaneously. Finally, we evaluate the assumptions made and examine the performance of the new algorithm against the ICPatch.
Optimal tetrahedral mesh generation for three-dimensional point set
Institute of Scientific and Technical Information of China (English)
秦开怀; 吴边; 关右江; 葛振州
1997-01-01
Three-dimensional (3D) tnangulation is a basic topic in computer graphics. It is considered very difficult to obtain the global optimal 3D triangulatlon, such as the triangulation which satisfies the max-min solid angle criterion A new method called genetic tetrahedral mesh generation algorithm (GTMGA for short) is presented. GT-MGA is based on the principle of genetic algorithm and aims at the global optimal triangulation. With a multi-objective fitness function, GTMGA is able to perform optimizations for different requirements. New crossover operator and mutation operator, polyhedron crossover and polyhedron mutation, are used in GTMGA. It is shown by the experimental results that GTMGA works better than both the 3D Delaunay triangulation and the algorithm based on local transformations.
Kleinberg, Jon
2006-01-01
Algorithm Design introduces algorithms by looking at the real-world problems that motivate them. The book teaches students a range of design and analysis techniques for problems that arise in computing applications. The text encourages an understanding of the algorithm design process and an appreciation of the role of algorithms in the broader field of computer science.
Wang, Lui; Bayer, Steven E.
1991-01-01
Genetic algorithms are mathematical, highly parallel, adaptive search procedures (i.e., problem solving methods) based loosely on the processes of natural genetics and Darwinian survival of the fittest. Basic genetic algorithms concepts are introduced, genetic algorithm applications are introduced, and results are presented from a project to develop a software tool that will enable the widespread use of genetic algorithm technology.
Triangulation and Gender Perspectives in ‘Falling Man’ by Don DeLillo
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Noemi Abe
2011-09-01
Susannah Radstone argues that the rhetorical response to 9/11 by the Bush administration is based on the opposition of two father figures: “the 'chastened' but powerful 'good' patriarchal father” Vs. “the 'bad' archaic father”. She explains: “In this Manichean fantasy can be glimpsed the continuing battle between competing versions of masculinity” (2002:459 that leaves women on the margins. The battle of the fathers of Bush’s rhetoric is counterposed in Falling Man by a battle between two men that stands for an unaccomplished fatherhood. Furthermore, the dualistic vision engendered by post-9/11 rhetoric and reflected in the novel should be evaluated in a trilateral dimension, given that at its core lies a triangulation built upon three stereotypical representations: the white middle-class man; the Arab terrorist; and a composite character in the middle, the woman, who shifts from ally, to victim, to a plausible supporter of the enemy.
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Tarja Tiainen
2006-10-01
Full Text Available This article contains critical reflections of a multidisciplinary research group studying the human and technological dynamics around some newly offered electronic services in a specific rural area of Finland. For their research, the group adopted ethnography. On facing the challenges of doing ethnographic research in a multidisciplinary setting, the group evolved its own breed of research practice based on multiple forms of triangulation. This implied the use of multiple data sources, methods, theories, and researchers, in different combinations. One of the outcomes of the work is a model for collaborative research. It highlights, among others, the importance of creating a climate for collaboration within the research group and following a process of individual and collaborative writing to achieve the potential benefits of such research. The article also identifies a set of remaining challenges relevant to collaborative research.
A tuned mesh-generation strategy for image representation based on data-dependent triangulation.
Li, Ping; Adams, Michael D
2013-05-01
A mesh-generation framework for image representation based on data-dependent triangulation is proposed. The proposed framework is a modified version of the frameworks of Rippa and Garland and Heckbert that facilitates the development of more effective mesh-generation methods. As the proposed framework has several free parameters, the effects of different choices of these parameters on mesh quality are studied, leading to the recommendation of a particular set of choices for these parameters. A mesh-generation method is then introduced that employs the proposed framework with these best parameter choices. This method is demonstrated to produce meshes of higher quality (both in terms of squared error and subjectively) than those generated by several competing approaches, at a relatively modest computational and memory cost.
Bristowe, Katherine; Siassakos, Dimitrios; Hambly, Helen; Angouri, Jo; Yelland, Andrew; Draycott, Timothy J; Fox, Robert
2012-10-01
Our purpose was to investigate health care professionals' beliefs about effective teamwork in medical emergencies based on their experiences. We used framework analysis of interprofessional focus groups in four secondary and tertiary maternity units. The participants were randomly selected senior and junior doctors, senior and junior midwives, and health care assistants, in five groups of 5 to 7 participants each. We found that optimal teamwork was perceived to be dependent on good leadership and availability of experienced staff. The participants described a good leader as one who verbally declares being the leader, communicates clear objectives, and allocates critical tasks, including communication with patients or their family, to suitable individual members. We triangulated the results with evidence from simulation to identify convergent findings and issues requiring further research. The findings will inform the development of teaching programs for medical teams who manage emergencies to improve patient safety and experience.
Measurements of indoor/outdoor atmospheric turbulence through optical triangulation method
de Oliveira, Gúbio; Silva, Vinicius N. H.; Barbero, Andrés P. L.; Ribeiro, Ricardo M.; Coelho, Thiago V. N.; Bessa dos Santos, A.
2017-05-01
Atmospheric turbulence degrades the performance of wireless optical communication links. This phenomenon distorts the light wave-front, and changes the spatial optical power distribution, spread and wander of the beam on the receiver plane. In this paper we present measurements of indoor and outdoor atmospheric turbulence taken using a simple and low-cost device based on an optical triangulation method. The device tracks a Gaussian beam due to the beam wander effect and measures the effective Gaussian width due to beam spread in order to calculate the refractive index structure constant in real time. Thus, the device operation principle, the outdoor/indoor turbulence profile during the day, the hotspot dispersion and the beam width variation are shown.
Thermal Entanglement and Critical Behavior of Magnetic Properties on a Triangulated Kagomé Lattice
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N. Ananikian
2011-01-01
Full Text Available The equilibrium magnetic and entanglement properties in a spin-1/2 Ising-Heisenberg model on a triangulated Kagomé lattice are analyzed by means of the effective field for the Gibbs-Bogoliubov inequality. The calculation is reduced to decoupled individual (clusters trimers due to the separable character of the Ising-type exchange interactions between the Heisenberg trimers. The concurrence in terms of the three qubit isotropic Heisenberg model in the effective Ising field in the absence of a magnetic field is non-zero. The magnetic and entanglement properties exhibit common (plateau, peak features driven by a magnetic field and (antiferromagnetic exchange interaction. The (quantum entangled and non-entangled phases can be exploited as a useful tool for signalling the quantum phase transitions and crossovers at finite temperatures. The critical temperature of order-disorder coincides with the threshold temperature of thermal entanglement.
Generalized Mom-structures and ideal triangulations of 3-manifolds with non-spherical boundary
Pervova, Ekaterina
2010-01-01
The so-called Mom-structures on hyperbolic cusped 3-manifolds without boundary were introduced by Gabai, Meyerhoff, and Milley, and used by them to identify the smallest closed hyperbolic manifold. In this work we extend the notion of a Mom-structure to include the case of 3-manifolds with non-empty boundary that does not have spherical components. We then describe a certain relation between such generalized Mom-structures, called protoMom-structures, internal on a fixed 3-manifold N, and ideal triangulations of N; in addition, in the case of non-closed hyperbolic manifolds without annular cusps, we describe how an internal geometric protoMom-structure can be constructed starting from Epstein-Penner or Kojima decomposition. Finally, we exhibit a set of combinatorial moves that relate any two internal protoMom-structures on a fixed N to each other.
Continuum interpretation of the dynamical-triangulation formulation of quantum Einstein gravity
Smit, Jan
2013-01-01
In the time-space symmetric version of dynamical triangulation, a non-perturbative version of quantum Einstein gravity, numerical simulations without matter have shown two phases, with spacetimes that are either crumpled or elongated like branched polymers, with strong evidence of a first-order transition between them. These properties have generally been considered unphysical. Using previously unpublished numerical results, we give an interpretation in terms of continuum spacetimes that have constant positive an negative curvature, respectively in the 'elongated' and 'crumpled' phase. The magnitude of the positive curvature leads naturally to average spacetimes consisting solely of baby-universes in a branched-polymer structure, whereas the negative curvature accommodates easily a large mother universe, albeit with a crumpling singularity. Nevertheless, there is evidence for scaling in the crumpled phase, which we compare with the well-known scaling in the elongated phase. Using constraint effective-action m...
Application of Blue Laser Triangulation Sensors for Displacement Measurement Through Fire.
Hoehler, Matthew S; Smith, Christopher M
2016-11-01
This paper explores the use of blue laser triangulation sensors to measure displacement of a target located behind or in the close proximity of natural gas diffusion flames. This measurement is critical for providing high-quality data in structural fire tests. The position of the laser relative to the flame envelope can significantly affect the measurement scatter, but has little influence on the mean values. We observe that the measurement scatter is normally distributed and increases linearly with the distance of the target from the flame along the beam path. Based on these observations, we demonstrate how time-averaging can be used to achieve a standard uncertainty associated with the displacement error of less than 0.1 mm, which is typically sufficient for structural fire testing applications. Measurements with the investigated blue laser sensors were not impeded by the thermal radiation emitted from the flame or the soot generated from the relatively clean-burning natural gas.
Zur Rekonstruktion einer Typologie jugendlichen Medienhandelns gemäß dem Leitbild der Triangulation
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Klaus Peter Treumann
2017-09-01
Full Text Available Die im Folgenden dargestellten Ergebnisse sind im Rahmen des von der DFG geförderten Forschungsprojekts „Eine Untersuchung zum Mediennutzungsverhalten 12- bis 20-Jähriger und zur Entwicklung von Medienkompetenz im Jugendalter“ entstanden, das gemeinsam von Klaus Peter Treumann, Uwe Sander und Dorothee Meister geleitet wird. Das Forschungsprojekt untersucht das Medienhandeln Jugendlicher sowohl hinsichtlich Neuer als auch alter Medien. Zum einen fragen wir dabei nach den Ausprägungen von Medienkompetenz in verschiedenen Dimensionen und zum anderen konzentrieren wir uns auf die Entwicklung einer empirisch fundierten Typologie jugendlichen Medienhandelns. Methodologisch ist die Untersuchung an dem Leitbild der Triangulation orientiert und kombiniert qualitative und quantitative Zugänge zum Forschungsfeld in Form von Gruppendiskussionen, leitfadengestützten Einzelinterviews und einer Repräsentativerhebung.
Fosco, Gregory M; Xia, Mengya; Lynn, Mark G; Grych, John H
2016-09-01
This study focuses on family predictors of conflict behavior in adolescent dating relationships, drawing on family systems and socialization perspectives. Mother-adolescent, father-adolescent, and triadic relationships each was examined as predictors of adolescent dating outcomes that hold importance for developmental and prevention science (positive conflict resolution, verbal abuse, and physical abuse). We conducted a longitudinal analysis using a 6-month longitudinal design with 236 ethnically diverse high school students. Findings indicate that triangulation into parental conflicts was related to increases in positive conflict resolution and with increases in verbally abusive behavior with dating partners over time. Parent-adolescent closeness and conflict each was related to positive conflict resolution and verbal abuse, but these associations were only found for boys. © 2015 The Authors. Journal of Research on Adolescence © 2015 Society for Research on Adolescence.
Shen, Zheng-Kang; Jackson, David D.
1993-06-01
We study tectonic deformation in the Southern Coast Range, California. We use triangulation and astronomic azimuth data collected since 1875, trilateration since 1970, and global positioning system data collected from 1986 to 1987. Two modeling techniques have been used. An elastic block-fault model is applied to study the tectonic motion of the San Andreas Fault and the San Gregorio-Hosgri Fault. Station velocities are modeled to study regional deformations. Results show that the regional deformation is predominantly controlled by deep strike-slip motion along the San Andreas Fault, at a rate of 33 +/- 2 mm/yr. Deep slip along the San Gregorio-Hosgri Fault is about 0-4 mm/yr, assuming a locked suit to a depth of 20 km. Convergence normal to the San Andreas Fault in the Southern Coast Ranges is not greater than 0.02 microrad/yr.
Application of blue laser triangulation sensors for displacement measurement through fire
Hoehler, Matthew S.; Smith, Christopher M.
2016-11-01
This paper explores the use of blue laser triangulation sensors to measure displacement of a target located behind or in the close proximity of natural gas diffusion flames. This measurement is critical for providing high-quality data in structural fire tests. The position of the laser relative to the flame envelope can significantly affect the measurement scatter, but has little influence on the mean values. We observe that the measurement scatter is normally distributed and increases linearly with the distance of the target from the flame along the beam path. Based on these observations, we demonstrate how time-averaging can be used to achieve a standard uncertainty associated with the displacement error of less than 0.1 mm, which is typically sufficient for structural fire testing applications. Measurements with the investigated blue laser sensors were not impeded by the thermal radiation emitted from the flame or the soot generated from the relatively clean-burning natural gas.
The transfer matrix method in four-dimensional causal dynamical triangulations
Ambjorn, J; Goerlich, A T; Jurkiewicz, J; Loll, R
2013-01-01
The Causal Dynamical Triangulation model of quantum gravity (CDT) is a proposition to evaluate the path integral over space-time geometries using a lattice regularization with a discrete proper time and geometries realized as simplicial manifolds. The model admits a Wick rotation to imaginary time for each space-time configuration. Using computer simulations we determined the phase structure of the model and discovered that it predicts a de Sitter phase with a four-dimensional spherical semi-classical background geometry. The model has a transfer matrix, relating spatial geometries at adjacent (discrete lattice) times. The transfer matrix uniquely determines the theory. We show that the measurements of the scale factor of the (CDT) universe are well described by an effective transfer matrix where the matrix elements are labelled only by the scale factor. Using computer simulations we determine the effective transfer matrix elements and show how they relate to an effective minisuperspace action at all scales.
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X.-Z. Zhou
2006-07-01
Full Text Available Another approach (Multiple Triangulation Analysis, MTA is presented to determine the orientation of magnetic flux rope, based on 4-point measurements. A 2-D flux rope model is used to examine the accuracy of the MTA technique in a theoretical way. It is found that the precision of the estimated orientation is dependent on both the spacecraft separation and the constellation path relative to the flux rope structure. However, the MTA error range can be shown to be smaller than that of the traditional MVA technique. As an application to real Cluster data, several flux rope events on 26 January 2001 are analyzed using MTA, to obtain their orientations. The results are compared with the ones obtained by several other methods which also yield flux rope orientation. The estimated axis orientations are shown to be fairly close, suggesting the reliability of the MTA method.
Jasso-Aguilar, Rebeca
1999-01-01
This study used qualitative methods, including observation, unstructured interviews, and questionnaires, for analyzing the vocational English-language-instruction needs of hotel maids. Methods and sources (maids, supervisor, executive housekeeper, human resources staff) were triangulated to determine reliability. An unbalanced distribution of…
Strijbos, Jan-Willem; Martens, Rob L.; Jochems, Wim M. G.; Broers, Nick J.
2007-01-01
In this article, the effect of functional roles on group performance and collaboration during computer-supported collaborative learning (CSCL) is investigated. Especially the need for triangulating multiple methods is emphasised: Likert-scale evaluation questions, quantitative content analysis of e-
Strijbos, Jan-Willem; Martens, Rob L.; Jochems, Wim M. G.; Broers, Nick J.
2007-01-01
In this article, the effect of functional roles on group performance and collaboration during computer-supported collaborative learning (CSCL) is investigated. Especially the need for triangulating multiple methods is emphasised: Likert-scale evaluation questions, quantitative content analysis of e-
Ott, Peter
2003-05-01
Classical triangulation sensors exhibit an orientation depend signal if the scattering properties of the work-piece are not symmetrical like at curved surface locations. This problem is avoided by rotational symmetric triangulation sensors. Due to this attractive property in a lot of applications such a sensor was introduced very recently on the market. This sensor is based on refractive optics and a special PSD detector, both custom made resulting in high costs. Additionally, the existing optical design approach does not offer an optical layout to start with, thus a good amount of trial and error is required and non-optimal solutions are probable. Therefore, there is great interest for a clear optical design strategy that results in layouts that are suitable also to use low cost commercial available detectors, such as CCD or CMOS image detectors. In this paper such a design procedure is presented for optical designs that use reflecting optical surfaces. Several solutions are depicted and discussed. The designs are not only attractive from the optical point of view and from detector considerations, but also from opto-mechanical design issues. For example designs with only one opto-mechanical part are possible. The resulting optical designs consist of aspherical surfaces which are obtained directly by using only some new relations of first order optics for off-axis objects. The designs are validated by exact ray tracing. These ray tracing results show already very good performance. Nevertheless, it was possible to further optimize the optical designs very efficiently using ray tracing software, thus yielding improved optical properties.
Donnellan, Andrea; Hager, Bradford H.; Larsen, Shawn
1988-01-01
Comparison of angles from historical triangulation observations dating as far back as 1932 with Global Positions System (GPS) measurements taken in 1987 indicates that rapid convergence may be taking place on decade timescales in the central and eastern part of the Ventura basin, an east-west trending trough bounded by thrust faults. Changes in angles over this time were analyzed using Prescott's modified Frank's method and in terms of a model which assumes that the regions to the north and south of the basin are rigid blocks undergoing relative motion. For the two block model, inversion of the observed angle changes over the last 28 years for the relative motion vector leads to north-south convergence across the basin of 30 + or - 5 mm/yr, with a left lateral component of 10 + or - 1 mm/yr in the Fillmore-Santa Paula area in the central part of the basin. The modified Frank's method yields strain rates of approximately 2 microrad/yr in both the east and central parts of the basin for measurements spanning the 1971 San Fernando earthquake. Assuming no east-west strain yeilds north-south compression of approximately 3.5 + or - .2 cm/yr. Comparison of triangulation data prior to the earthquake shows no strain outside the margin of error. The convergence rates determined by geodetic techniques are consistent with geologic observations in the area. Such large geodetic deformation rates, with no apparent near-surface creep on the major thrust, can be understood if these faults become subhorizontal at relatively shallow depths and if the subhorizontal portions of the faults are creeping. An alternative explanation of the large displacement rates might be that the pumping of oil in the vicinity of the benchmarks caused large horizontal motions, although it is unlikely that meter scale horizontal motions are due to oil withdrawal. These and other hypotheses are evaluated to better constrain the tectonics of this active region.
Detection of active emitters using triangulation and trilateration techniques: Theory and practice
Dean, A. M.
1992-11-01
Recent conflicts have highlighted the benefits of 'soft-kill' electronic warfare (stand off, escort, and self screening jamming), during intrusion into areas protected by Air Defence (AD) radar networks. These conflicts have highlighted the need to protect and supplement the Recognized Air Picture (RAP) with the ability to locate and track the intruding jammers. A Passive Jammer Location (PJL) system, and some of the theory behind it, currently under development at the Marconi Research Center are described. The two basic geometrical techniques for locating unknown emitters, usually termed triangulation and trilateration, are identified. The main problems associated with triangulation techniques, those of target ghosts and ghost resolution in denser scenarios, are discussed and trilateration processing using correlation offered as a solution. The main feature of an operational PJL system is noted as being the need to positively resolve jammer positions, to sub-beam accuracy, in dense jamming scenarios. This includes the 'pop-up' target appearing over the radar horizon and the agile sophisticated jammer. In addition a number of other features are identified which would be desirable in any future NATO PJL system. Over a number of years the UK MoD and GEC-Marconi have undertaken a number of studies relating to PJL architectures and data processing techniques. In 1991 these studies led to the Air Defence Emitter Location Equipment (ADELE) Technology Demonstrator. The objectives of the ADELE program are to demonstrate that the requirements of a PJL system can be met at a price affordable by AD system procurers. Additionally to confirm that the new PJL data processing techniques, developed during these previous studies, perform as predicted during live trials. The main hardware and software modules making up the ADELE demonstrator are discussed including: the multi beam antenna, the resistive matrix beam former, the PJL multi-channel signal sampling hardware, radar
Guérard, N C; Traebert, M; Suter, W; Dumotier, B M
2008-01-01
The role of IKr (rapidly-activating delayed rectifier K(+) current) block in triangulation of monophasic action potentials (MAP) and in development of torsade de pointes (TdP) arrhythmia is known. Combined IKr and IKs (slowly-activating delayed rectifier K(+) current) block has been demonstrated to promote TdP. The aim of this study was to describe a possible implication of IKs block in MAP triangulation. Four contact electrodes were placed on the epicardium of the left ventricle of Langendorff-perfused rabbit hearts to record monophasic action potentials (MAP), with an IKr blocker d,l-sotalol (3 to 100 microM, n=6) or a non-selective IKr blocker, quinidine (1 to 30 microM, n=6). Their effects were assessed with or without a specific IKs blocker chromanol 293B (20 microM, n=6), on MAP duration at 30, 60 and 90% of repolarization (APD30, 60 and 90, respectively) and MAP triangulation (APD90-APD30) at 1 and 0.2 Hz. D,L-sotalol increased significantly APD90 and triangulation with reverse use-dependency for concentrations > or =10 microM. Quinidine markedly prolonged APD90 and triangulation with reverse use-dependency at concentrations > or =3 microM. Chromanol 293B alone had no effects on APD, but when combined with D,L-sotalol or quinidine (i) increased APD prolonging effects, (ii) lowered values of pro-arrhythmic concentrations, (iii) increased incidence and length of D,L-sotalol- or quinidine-induced Early Afterdepolarizations (EADs) and TdP. All these events were primarily due to an important slowing of final repolarization, i.e. a marked increased triangulation. IKs, even of low amplitude in rabbits, plays a key role in ventricular repolarization. IKs is involved in prolonged MAP duration mainly by triangulation and subsequent increased drug arrhythmogenicity. Therefore drug affinity for IKs must be evaluated with IKr studies as part of preclinical drug cardiac safety assessment.
Joux, Antoine
2009-01-01
Illustrating the power of algorithms, Algorithmic Cryptanalysis describes algorithmic methods with cryptographically relevant examples. Focusing on both private- and public-key cryptographic algorithms, it presents each algorithm either as a textual description, in pseudo-code, or in a C code program.Divided into three parts, the book begins with a short introduction to cryptography and a background chapter on elementary number theory and algebra. It then moves on to algorithms, with each chapter in this section dedicated to a single topic and often illustrated with simple cryptographic applic
Hougardy, Stefan
2016-01-01
Algorithms play an increasingly important role in nearly all fields of mathematics. This book allows readers to develop basic mathematical abilities, in particular those concerning the design and analysis of algorithms as well as their implementation. It presents not only fundamental algorithms like the sieve of Eratosthenes, the Euclidean algorithm, sorting algorithms, algorithms on graphs, and Gaussian elimination, but also discusses elementary data structures, basic graph theory, and numerical questions. In addition, it provides an introduction to programming and demonstrates in detail how to implement algorithms in C++. This textbook is suitable for students who are new to the subject and covers a basic mathematical lecture course, complementing traditional courses on analysis and linear algebra. Both authors have given this "Algorithmic Mathematics" course at the University of Bonn several times in recent years.
Spectral triangulation: a 3D method for locating single-walled carbon nanotubes in vivo
Lin, Ching-Wei; Bachilo, Sergei M.; Vu, Michael; Beckingham, Kathleen M.; Bruce Weisman, R.
2016-05-01
Nanomaterials with luminescence in the short-wave infrared (SWIR) region are of special interest for biological research and medical diagnostics because of favorable tissue transparency and low autofluorescence backgrounds in that region. Single-walled carbon nanotubes (SWCNTs) show well-known sharp SWIR spectral signatures and therefore have potential for noninvasive detection and imaging of cancer tumours, when linked to selective targeting agents such as antibodies. However, such applications face the challenge of sensitively detecting and localizing the source of SWIR emission from inside tissues. A new method, called spectral triangulation, is presented for three dimensional (3D) localization using sparse optical measurements made at the specimen surface. Structurally unsorted SWCNT samples emitting over a range of wavelengths are excited inside tissue phantoms by an LED matrix. The resulting SWIR emission is sampled at points on the surface by a scanning fibre optic probe leading to an InGaAs spectrometer or a spectrally filtered InGaAs avalanche photodiode detector. Because of water absorption, attenuation of the SWCNT fluorescence in tissues is strongly wavelength-dependent. We therefore gauge the SWCNT-probe distance by analysing differential changes in the measured SWCNT emission spectra. SWCNT fluorescence can be clearly detected through at least 20 mm of tissue phantom, and the 3D locations of embedded SWCNT test samples are found with sub-millimeter accuracy at depths up to 10 mm. Our method can also distinguish and locate two embedded SWCNT sources at distinct positions.Nanomaterials with luminescence in the short-wave infrared (SWIR) region are of special interest for biological research and medical diagnostics because of favorable tissue transparency and low autofluorescence backgrounds in that region. Single-walled carbon nanotubes (SWCNTs) show well-known sharp SWIR spectral signatures and therefore have potential for noninvasive detection and
Abrams, D.; Williams, C.
1999-01-01
This thesis describes several new quantum algorithms. These include a polynomial time algorithm that uses a quantum fast Fourier transform to find eigenvalues and eigenvectors of a Hamiltonian operator, and that can be applied in cases for which all know classical algorithms require exponential time.
Tel, G.
1993-01-01
We define the notion of total algorithms for networks of processes. A total algorithm enforces that a "decision" is taken by a subset of the processes, and that participation of all processes is required to reach this decision. Total algorithms are an important building block in the design of distri
Teaching Resident Self-Assessment Through Triangulation of Faculty and Patient Feedback.
Keister, Drew M; Hansen, Susan E; Dostal, Julie
2017-01-01
To accurately determine one's ability in any clinical competency, an individual must be able to self-assess performance and identify personal limitations. Existing research demonstrates that physicians of all levels are unreliable self-assessors. This poses a concern in medical practice, which requires continuous updates to clinical competencies and awareness of personal limitations. Few published studies examine graduate medical education curricula designed to develop self-assessment skills. Conceptual models, such as self-determination theory, suggest that self-assessment is most effectively learned through reflective processes. The Family Medicine Residency Program at Lehigh Valley Health Network developed a learner-centered competency assessment process that integrates advising and performance review. The multisource, observable behavior-based process encourages conversation between resident and advisor. Utilizing feedback from clinical preceptors and patient surveys, advisors guide residents in determining individual learning needs in core competency areas, including relationship-centered care. Development of medical learners' capacity to form relationships is one means to improving the patient experience. This retrospective case study evaluates the accuracy of senior residents' self-assessment in relationship-centered care compared with that of junior residents. The study population includes the 34 residents enrolled from AY 2009-2012. Data sets represent specific 6-month periods and have 3 component scores-Self, Faculty, and Patient-which were triangulated to determine concordance rates by postgraduate year level. The concordance rate among first-years was 26.7%, whereas third-years saw 60.0% concordance. A discordance analysis found the Patient score most often deviated from the other 2 scores, whereas the Faculty score was never the sole dissenter. When all 3 scores differed, the Self score frequently fell between the other 2 scores. The principles of self
An algorithm to solve any tropical linear system $A\\odot x=B\\odot x$
Lorenzo, E
2010-01-01
An algorithm to solve any tropical linear system $A\\odot x=B\\odot x$ is presented. The given system is converted into two classical linear systems: a system of equations and a system of inequalities, each item (equation or inequality) involving exactly two variables, one with coefficient $1$, and another with coefficient $-1$. The two classical linear systems are solved, essentially, by triangulation and backward substitution.
Directory of Open Access Journals (Sweden)
Fernando Alberca-de-las-Parras
2015-04-01
Full Text Available Direct percutaneous endoscopic jejunostomy (DPEJ is an infrequent procedure as it is not always easy to obtain transillumination, being this the main reason for failure of this technique. In patients with previous surgery, this procedure is more complex and there are only 6 reported cases in pediatric population. In our case, we provide the use of an endoscopic triangulation system with "T" pexies not used before in these cases. With this technique, we guarantee not to replace the introduction system afterwards, obtaining the placement of a balloon fixation system initially. We also provide several improvements that helped us developing the procedure: Placement of the jejunostomy through a gastrostomy; use of water column to avoid penetration in hollow viscus; use of a guide wire, and a triangulation pexy system.
Alberca-de-Las-Parras, Fernando; Navalón-Rubio, María; Egea-Valenzuela, Juan; Álvarez-Higueras, Francisco-Javier; Antón-Ródenas, Gonzalo; Alajarín-Cervera, Miriam; Serrano-Giménez, Andrés; Gil-Ortega, David; Muñoz-Tornero, María; Ono-Ono, Akiko; Carballo-Álvarez, Luis Fernando
2015-04-01
Direct percutaneous endoscopic jejunostomy (DPEJ) is an infrequent procedure as it is not always easy to obtain transillumination, being this the main reason for failure of this technique. In patients with previous surgery, this procedure is more complex and there are only 6 reported cases in pediatric population. In our case, we provide the use of an endoscopic triangulation system with "T" pexies not used before in these cases. With this technique, we guarantee not to replace the introduction system afterwards, obtaining the placement of a balloon fixation system initially. We also provide several improvements that helped us developing the procedure: Placement of the jejunostomy through a gastrostomy; use of water column to avoid penetration in hollow viscus; use of a guide wire, and a triangulation pexy system.
Coupling a point-like mass to quantum gravity with causal dynamical triangulations
Energy Technology Data Exchange (ETDEWEB)
Khavkine, I; Loll, R; Reska, P, E-mail: i.khavkine@uu.n, E-mail: r.loll@uu.n, E-mail: p.m.reska@uu.n [Spinoza Institute and Institute for Theoretical Physics, Utrecht University, Leuvenlaan 4, NL-3584 CE Utrecht (Netherlands)
2010-09-21
We present a possibility of coupling a point-like, non-singular, mass distribution to four-dimensional quantum gravity in the nonperturbative setting of causal dynamical triangulations (CDT). In order to provide a point of comparison for the classical limit of the matter-coupled CDT model, we derive the spatial volume profile of the Euclidean Schwarzschild-de Sitter space glued to an interior matter solution. The volume profile is calculated with respect to a specific proper-time foliation matching the global time slicing present in CDT. It deviates in a characteristic manner from that of the pure-gravity model. The appearance of coordinate caustics and the compactness of the mass distribution in lattice units put an upper bound on the total mass for which these calculations are expected to be valid. We also discuss some of the implementation details for numerically measuring the expectation value of the volume profiles in the framework of CDT when coupled appropriately to the matter source.
3D digitization methods based on laser excitation and active triangulation: a comparison
Aubreton, Olivier; Mériaudeau, Fabrice; Truchetet, Frédéric
2016-04-01
3D reconstruction of surfaces is an important topic in computer vision and corresponds to a large field of applications: industrial inspection, reverse engineering, object recognition, biometry, archeology… Because of the large varieties of applications, one can find in the literature a lot of approaches which can be classified into two families: passive and active [1]. Certainly because of their reliability, active approaches, using imaging system with an additional controlled light source, seem to be the most commonly used in the industrial field. In this domain, the 3D digitization approach based on active 3D triangulation has had important developments during the last ten years [2] and seems to be mature today if considering the important number of systems proposed by manufacturers. Unfortunately, the performances of active 3D scanners depend on the optical properties of the surface to digitize. As an example, on Fig 1.a, a 3D shape with a diffuse surface has been digitized with Comet V scanner (Steinbichler). The 3D reconstruction is presented on Fig 1.b. The same experiment was carried out on a similar object (same shape) but presenting a specular surface (Fig 1.c and Fig 1.d) ; it can clearly be observed, that the specularity influences of the performance of the digitization.
Contingent dissociation between recognition and fragment completion: the method of triangulation.
Hayman, C A; Tulving, E
1989-03-01
Two experiments conforming to the logic of the method of triangulation were conducted. Following the study of a list of words, the first of two successive tests (recognition) was identical for two groups of subjects, but the second one, in which the same word-fragment cues were presented to both groups, differed with respect to retrieval instructions. Subjects in one group engaged in cued recall of study-list words, whereas those in the second group completed the fragments with the first word that came to mind. Both experiments yielded the same result: The dependency between the first and second tests, indexed by Yule's Q statistic, was greater for recognition and cued recall than it was for recognition and fragment completion. These results speak to the controversial issue of the usefulness of contingency analyses of data from successive memory tests. The results are interpreted in a theoretical framework consisting of an integration of the idea of a hypothetical quasi-memory system with the transfer-appropriate procedural approach.
Liu, Ying; Luhmann, Janet G; Vourlidas, Angelos; Bale, Stuart D; Lin, Robert P
2010-01-01
We describe a geometric triangulation technique, based on time-elongation maps constructed from imaging observations, to track coronal mass ejections (CMEs) continuously in the heliosphere and predict their impact on the Earth. Taking advantage of stereoscopic imaging observations from STEREO, this technique can determine the propagation direction and radial distance of CMEs from their birth in the corona all the way to 1 AU. The efficacy of the method is demonstrated by its application to the 2008 December 12 CME, which manifests as a magnetic cloud (MC) from in situ measurements at the Earth. The predicted arrival time and radial velocity at the Earth are well confirmed by the in situ observations around the MC. Our method reveals non-radial motions and velocity changes of the CME over large distances in the heliosphere. It also associates the flux-rope structure measured in situ with the dark cavity of the CME in imaging observations. Implementation of the technique, which is expected to be a routine possi...
Triangulation of Qualitative Methods for the Exploration of Activity Systems in Ergonomics
Directory of Open Access Journals (Sweden)
Monika Hackel
2008-08-01
Full Text Available Research concerning ergonomic issues in interdisciplinary projects often raises several very specific questions depending on project objectives. To answer these questions the application of research methods should be thoroughly considered, regarding both the expenditure and the options within the scope of the given resources. The project AQUIMO develops an adaptable modelling tool for mechatronical engineering and creates a related qualification program. The task of social scientific research within this project is to identify requirements viewed from the perspective of the subsequent users. This formative evaluation is based on the approach of "developmental work research" as set forth by ENGESTRÖM and, thus, is a form of "action research". This paper discusses the triangulation of several qualitative methods addressing the examination of difficulties in interdisciplinary collaboration in mechatronical engineering. After a description of both background and analytic approach within the project AQUIMO, the methods are briefly described concerning their advantages and critical points. Their application within the research project AQUIMO is explained from an activity theoretical perspective. URN: urn:nbn:de:0114-fqs0803158
Limits of active laser triangulation as an instrument for high precision plant imaging.
Paulus, Stefan; Eichert, Thomas; Goldbach, Heiner E; Kuhlmann, Heiner
2014-02-05
Laser scanning is a non-invasive method for collecting and parameterizing 3D data of well reflecting objects. These systems have been used for 3D imaging of plant growth and structure analysis. A prerequisite is that the recorded signals originate from the true plant surface. In this paper we studied the effects of species, leaf chlorophyll content and sensor settings on the suitability and accuracy of a commercial 660 nm active laser triangulation scanning device. We found that surface images of Ficus benjamina leaves were inaccurate at low chlorophyll concentrations and a long sensor exposure time. Imaging of the rough waxy leaf surface of leek (Allium porrum) was possible using very low exposure times, whereas at higher exposure times penetration and multiple refraction prevented the correct imaging of the surface. A comparison of scans with varying exposure time enabled the target-oriented analysis to identify chlorotic, necrotic and healthy leaf areas or mildew infestations. We found plant properties and sensor settings to have a strong influence on the accuracy of measurements. These interactions have to be further elucidated before laser imaging of plants is possible with the high accuracy required for e.g., the observation of plant growth or reactions to water stress.
Prostate cancer and quality of life: analysis of response shift using triangulation between methods.
Serdà I Ferrer, Bernat-Carles; Valle, Arantza Del; Marcos-Gragera, Rafael
2014-06-01
Quality of life (QoL) after prostate cancer treatment is uncertain. Patient responses to QoL questions shift for a number of reasons: measurement intervals no longer have the same psychological anchors (recalibration), the importance attributed to different QoL domains changes over time (reprioritization), and the definition of QoL differs throughout the disease continuum (reconceptualization). Therefore, the aim of this study was to describe QoL response shift in a cohort of 66 men with prostate cancer. The method involved carrying out a sequential triangulation between quantitative and qualitative methods. Patients were assessed at baseline (P1), followed by a posttest (P2) and a then-test measurement (P3). The difference between P3 and P1 was used to determine the response shift effect (recalibration). From baseline to posttest, QoL significantly decreased. The recalibration then-test confirmed a low QoL in all periods evaluated. Coping mechanisms were found to differ by age group, with older men less concerned about side effects than younger men. Health professionals should be alert to QoL changes over time and possible side effects, should coping skills fail.
A triangulation-invariant method for anisotropic geodesic map computation on surface meshes.
Yoo, Sang Wook; Seong, Joon-Kyung; Sung, Min-Hyuk; Shin, Sung Yo; Cohen, Elaine
2012-10-01
This paper addresses the problem of computing the geodesic distance map from a given set of source vertices to all other vertices on a surface mesh using an anisotropic distance metric. Formulating this problem as an equivalent control theoretic problem with Hamilton-Jacobi-Bellman partial differential equations, we present a framework for computing an anisotropic geodesic map using a curvature-based speed function. An ordered upwind method (OUM)-based solver for these equations is available for unstructured planar meshes. We adopt this OUM-based solver for surface meshes and present a triangulation-invariant method for the solver. Our basic idea is to explore proximity among the vertices on a surface while locally following the characteristic direction at each vertex. We also propose two speed functions based on classical curvature tensors and show that the resulting anisotropic geodesic maps reflect surface geometry well through several experiments, including isocontour generation, offset curve computation, medial axis extraction, and ridge/valley curve extraction. Our approach facilitates surface analysis and processing by defining speed functions in an application-dependent manner.
Two dimensional triangulation of breakdown in a high voltage coaxial gap.
Cordaro, S W; Bott-Suzuki, S C; Bendixsen, L S Caballero; Atoyan, Levon; Byvank, Tom; Potter, William; Kusse, B R; Greenly, J B
2015-07-01
We describe a technique by which magnetic field probes are used to triangulate the exact position of breakdown in a high voltage coaxial vacuum gap. An array of three probes is placed near the plane of the gap with each probe at 90° intervals around the outer (anode) electrode. These probes measure the azimuthal component of the magnetic field and are all at the same radial distance from the cylindrical axis. Using the peak magnetic field values measured by each probe, the current carried by the breakdown channel, and Ampères law we can calculate the distance away from each probe that the breakdown occurred. These calculated distances are then used to draw three circles each centered at the centers of the corresponding magnetic probes. The common intersection of these three circles then gives the predicted azimuthal location of the center of the breakdown channel. Test results first gathered on the coaxial gap breakdown device (240 A, 25 kV, 150 ns) at the University of California San Diego and then on COBRA (1 MA, 1 MV, 100 ns) at Cornell University indicate that this technique is relatively accurate and scales between these two devices.
Spectral triangulation: a 3D method for locating single-walled carbon nanotubes in vivo.
Lin, Ching-Wei; Bachilo, Sergei M; Vu, Michael; Beckingham, Kathleen M; Bruce Weisman, R
2016-05-21
Nanomaterials with luminescence in the short-wave infrared (SWIR) region are of special interest for biological research and medical diagnostics because of favorable tissue transparency and low autofluorescence backgrounds in that region. Single-walled carbon nanotubes (SWCNTs) show well-known sharp SWIR spectral signatures and therefore have potential for noninvasive detection and imaging of cancer tumours, when linked to selective targeting agents such as antibodies. However, such applications face the challenge of sensitively detecting and localizing the source of SWIR emission from inside tissues. A new method, called spectral triangulation, is presented for three dimensional (3D) localization using sparse optical measurements made at the specimen surface. Structurally unsorted SWCNT samples emitting over a range of wavelengths are excited inside tissue phantoms by an LED matrix. The resulting SWIR emission is sampled at points on the surface by a scanning fibre optic probe leading to an InGaAs spectrometer or a spectrally filtered InGaAs avalanche photodiode detector. Because of water absorption, attenuation of the SWCNT fluorescence in tissues is strongly wavelength-dependent. We therefore gauge the SWCNT-probe distance by analysing differential changes in the measured SWCNT emission spectra. SWCNT fluorescence can be clearly detected through at least 20 mm of tissue phantom, and the 3D locations of embedded SWCNT test samples are found with sub-millimeter accuracy at depths up to 10 mm. Our method can also distinguish and locate two embedded SWCNT sources at distinct positions.
Limits of Active Laser Triangulation as an Instrument for High Precision Plant Imaging
Directory of Open Access Journals (Sweden)
Stefan Paulus
2014-02-01
Full Text Available Laser scanning is a non-invasive method for collecting and parameterizing 3D data of well reflecting objects. These systems have been used for 3D imaging of plant growth and structure analysis. A prerequisite is that the recorded signals originate from the true plant surface. In this paper we studied the effects of species, leaf chlorophyll content and sensor settings on the suitability and accuracy of a commercial 660 nm active laser triangulation scanning device. We found that surface images of Ficus benjamina leaves were inaccurate at low chlorophyll concentrations and a long sensor exposure time. Imaging of the rough waxy leaf surface of leek (Allium porrum was possible using very low exposure times, whereas at higher exposure times penetration and multiple refraction prevented the correct imaging of the surface. A comparison of scans with varying exposure time enabled the target-oriented analysis to identify chlorotic, necrotic and healthy leaf areas or mildew infestations. We found plant properties and sensor settings to have a strong influence on the accuracy of measurements. These interactions have to be further elucidated before laser imaging of plants is possible with the high accuracy required for e.g., the observation of plant growth or reactions to water stress.
Triangulation theory applied to conflict over hormone herbicide drift in Natal, South Africa
Preston-Whyte, Robert A.; Laing, Mark D.
1994-05-01
Policies that arise out of conflict or collaboration between specific interest groups and government agencies are often explained by theoretical constructs that fall under the umbrella of group theory. Triangulation theory is one of these constructs and serves to explain the mutuality of interests that exist between government agencies and interest groups expressed as points linking geometric forms. Conflict tends to occur when competing interest groups are excluded from the linkage, in this case between the opponents and proponents of hormone herbicides in the Tala area in Natal, South Africa. In opposition to the use of hormone herbicides were vegetable farmers and their supporters: in linked support were agricultural interest groups who used hormone herbicides, the manufacturers of the herbicides, and the government agency responsible for agriculture. Because of the influence exerted through mutual support by the proponents of hormone herbicides, the formulation of policy decisions directed towards the resolution of the conflict was delayed. When the minister of agriculture finally intervened, the policy decisions were designed to secure the support of those opposing the use of hormone herbicides by introducing issues that cut across those maintaining the discord.
Challenges in the Area of Training and Prevention at the HIV Triangulation Clinic, Kerman, Iran.
Zolala, Farzaneh; Haghdoost, Ali Akbar; Zahmatkesh, Roohollah; Shafiei, Mehdi
2014-01-01
Since 2000, Iran has been delivering training and treatment services, including methadone therapy, to human immunodeficiency virus (HIV) positive patients through triangular clinics. This study aims to evaluate the effectiveness of these activities at the HIV Triangulation Centre in the city of Kerman, Iran, through clients' views. Participants were recruited using a convenience sample and assessed through in-depth interviews, and observations. Data were analyzed using a thematic analysis, matrix based method. The results found problems in training and counseling which was described by the staff to be due to the effects of the economic difficulties of the clients, not being of the same sex as the consultant, and lack of utilization of a variety of training methods by the clients. Furthermore, the absorption of clients was perceived as being affected by the appearance of the center, gossip around the center, limited working hours, and interpersonal relations between clients and staff. The clients also criticized the building of the center as it failed to maintain anonymity of the patients. The need for supplementary services, such as dentistry, was perceived by many clients. The application of appropriate strategies such as providing adequate training and removing the obstacles of absorption should be taken into account to increase the utility and coverage of the triangular clinic. These interventions could be a range of activities, such as relocating the center to a more decent place and encouraging the staff to appear in a professional white coat to help gain the trust of clients.
Manganelli, Joe; Threatt, Anthony; Brooks, Johnell O; Healy, Stan; Merino, Jessica; Yanik, Paul; Walker, Ian; Green, Keith
2014-01-01
This article presents the results of a qualitative study that confirmed, classified, and prioritized user needs for the design of a more useful, usable, and actively assistive over-the-bed table. Manganelli et al. (2014) generated a list of 74 needs for use in developing an actively assistive over-the-bed table. This present study assesses the value and importance of those needs. Fourteen healthcare subject matter experts and eight research and design subject matter experts engaged in a participatory and iterative research and design process. A mixed methods qualitative approach used methodological triangulation to confirm the value of the findings and ratings to establish importance. Open and closed card sorts and a Delphi study were used. Data analysis methods included frequency analysis, content analysis, and a modified Kano analysis. A table demonstrating the needs that are of high importance to both groups of subject matter experts and classification of the design challenges each represents was produced. Through this process, the list of 74 needs was refined to the 37 most important need statements for both groups. Designing a more useful, usable, and actively assistive over-the-bed table is primarily about the ability to position it optimally with respect to the user for any task, as well as improving ease of use and usability. It is also important to make explicit and discuss the differences in priorities and perspectives demonstrated between research and design teams and their clients. © 2014 Vendome Group, LLC.
Varpio, Lara; Ajjawi, Rola; Monrouxe, Lynn V; O'Brien, Bridget C; Rees, Charlotte E
2017-01-01
Qualitative research is widely accepted as a legitimate approach to inquiry in health professions education (HPE). To secure this status, qualitative researchers have developed a variety of strategies (e.g. reliance on post-positivist qualitative methodologies, use of different rhetorical techniques, etc.) to facilitate the acceptance of their research methodologies and methods by the HPE community. Although these strategies have supported the acceptance of qualitative research in HPE, they have also brought about some unintended consequences. One of these consequences is that some HPE scholars have begun to use terms in qualitative publications without critically reflecting on: (i) their ontological and epistemological roots; (ii) their definitions, or (iii) their implications. In this paper, we share our critical reflections on four qualitative terms popularly used in the HPE literature: thematic emergence; triangulation; saturation, and member checking. We discuss the methodological origins of these terms and the applications supported by these origins. We reflect critically on how these four terms became expected of qualitative research in HPE, and we reconsider their meanings and use by drawing on the broader qualitative methodology literature. Through this examination, we hope to encourage qualitative scholars in HPE to avoid using qualitative terms uncritically and non-reflexively. © 2016 John Wiley & Sons Ltd and The Association for the Study of Medical Education.
Kim, Katherine K; Browe, Dennis K; Logan, Holly C; Holm, Roberta; Hack, Lori; Ohno-Machado, Lucila
2014-01-01
There is currently limited information on best practices for the development of governance requirements for distributed research networks (DRNs), an emerging model that promotes clinical data reuse and improves timeliness of comparative effectiveness research. Much of the existing information is based on a single type of stakeholder such as researchers or administrators. This paper reports on a triangulated approach to developing DRN data governance requirements based on a combination of policy analysis with experts, interviews with institutional leaders, and patient focus groups. This approach is illustrated with an example from the Scalable National Network for Effectiveness Research, which resulted in 91 requirements. These requirements were analyzed against the Fair Information Practice Principles (FIPPs) and Health Insurance Portability and Accountability Act (HIPAA) protected versus non-protected health information. The requirements addressed all FIPPs, showing how a DRN's technical infrastructure is able to fulfill HIPAA regulations, protect privacy, and provide a trustworthy platform for research. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.
Dimensional metrology of bipolar fuel cell plates using laser spot triangulation probes
Muralikrishnan, Bala; Ren, Wei; Everett, Dennis; Stanfield, Eric; Doiron, Ted
2011-07-01
As in any engineering component, manufacturing a bipolar fuel cell plate for a polymer electrolyte membrane (PEM) hydrogen fuel cell power stack to within its stated design tolerances is critical in achieving the intended function. In a bipolar fuel cell plate, the dimensional features of interest include channel width, channel height, channel parallelism, side wall taper, straightness of the bottom or side walls, plate parallelism, etc. Such measurements can be performed on coordinate measuring machines (CMMs) with micro-probes that can access the narrow channels. While CMM measurements provide high accuracy (less than 1 µm), they are often very slow (taking several hours to measure a single plate) and unsuitable for the manufacturing environment. In this context, we describe a system for rapid dimensional measurement of bipolar fuel cell plates using two laser spot triangulation probes that can achieve comparable accuracies to those of a touch probe CMM, while offering manufacturers the possibility for 100% part inspection. We discuss the design of the system, present our approach to calibrating system parameters, present validation data, compare bipolar fuel cell plate measurement results with those obtained using a Mitutoyo UMAP (see footnote 1) fiber probe CMM, and finally describe the uncertainty in channel height and width measurements.
Aguilar, Juan J.; Albajez, José A.; Carlos Cajal; David Guillomía; Jorge Santolaria
2009-01-01
A technique for intrinsic and extrinsic calibration of a laser triangulation sensor (LTS) integrated in an articulated arm coordinate measuring machine (AACMM) is presented in this paper. After applying a novel approach to the AACMM kinematic parameter identification problem, by means of a single calibration gauge object, a one-step calibration method to obtain both intrinsic―laser plane, CCD sensor and camera geometry―and extrinsic parameters related to the AACMM main frame has been develope...
Bailey, Ajay; Hutter, Inge
2008-10-01
With 3.1 million people estimated to be living with HIV/AIDS in India and 39.5 million people globally, the epidemic has posed academics the challenge of identifying behaviours and their underlying beliefs in the effort to reduce the risk of HIV transmission. The Health Belief Model (HBM) is frequently used to identify risk behaviours and adherence behaviour in the field of HIV/AIDS. Risk behaviour studies that apply HBM have been largely quantitative and use of qualitative methodology is rare. The marriage of qualitative and quantitative methods has never been easy. The challenge is in triangulating the methods. Method triangulation has been largely used to combine insights from the qualitative and quantitative methods but not to link both the methods. In this paper we suggest a linked trajectory of method triangulation (LTMT). The linked trajectory aims to first gather individual level information through in-depth interviews and then to present the information as vignettes in focus group discussions. We thus validate information obtained from in-depth interviews and gather emic concepts that arise from the interaction. We thus capture both the interpretation and the interaction angles of the qualitative method. Further, using the qualitative information gained, a survey is designed. In doing so, the survey questions are grounded and contextualized. We employed this linked trajectory of method triangulation in a study on the risk assessment of HIV/AIDS among migrant and mobile men. Fieldwork was carried out in Goa, India. Data come from two waves of studies, first an explorative qualitative study (2003), second a larger study (2004-2005), including in-depth interviews (25), focus group discussions (21) and a survey (n=1259). By employing the qualitative to quantitative LTMT we can not only contextualize the existing concepts of the HBM, but also validate new concepts and identify new risk groups.
Directory of Open Access Journals (Sweden)
J. Vauhkonen
2015-03-01
Full Text Available Reconstruction of three-dimensional (3D forest canopy is described and quantified using airborne laser scanning (ALS data with densities of 0.6–0.8 points m-2 and field measurements aggregated at resolutions of 400–900 m2. The reconstruction was based on computational geometry, topological connectivity, and numerical optimization. More precisely, triangulations and their filtrations, i.e. ordered sets of simplices belonging to the triangulations, based on the point data were analyzed. Triangulating the ALS point data corresponds to subdividing the underlying space of the points into weighted simplicial complexes with weights quantifying the (empty space delimited by the points. Reconstructing the canopy volume populated by biomass will thus likely require filtering to exclude that volume from canopy voids. The approaches applied for this purpose were (i to optimize the degree of filtration with respect to the field measurements, and (ii to predict this degree by means of analyzing the persistent homology of the obtained triangulations, which is applied for the first time for vegetation point clouds. When derived from optimized filtrations, the total tetrahedral volume had a high degree of determination (R2 with the stem volume considered, both alone (R2=0.65 and together with other predictors (R2=0.78. When derived by analyzing the topological persistence of the point data and without any field input, the R2 were lower, but the predictions still showed a correlation with the field-measured stem volumes. Finally, producing realistic visualizations of a forested landscape using the persistent homology approach is demonstrated.
凹多边形三角剖分方法数上界的讨论%Research on Number of Triangulation of Concave Polygon
Institute of Scientific and Technical Information of China (English)
陈平; 汪国昭
2009-01-01
Discussed the relation between the number of triangulation and diagonal basing on "Euler triangulation problem". The article gives the caleulation formula of limit of triangulation of concave polygon by analyzing the number of triangulation of a polygon such as pentagon and hexagon which reduced some diagonals.%在"欧拉三角剖分"问题的基础上进一步考虑三角剖分方法数与对角线的关系.通过分析五边形和六边形在减少一些对角线后可能的三角剖分方法数,给出了凹多边形三角剖分方法数上界的计算公式.
NSGIC GIS Inventory (aka Ramona) — This Triangulated Irregular Networks (TIN) dataset, published at 1:2400 (1in=200ft) scale, was produced all or in part from Orthoimagery information as of 2000. It...
NSGIC GIS Inventory (aka Ramona) — This Triangulated Irregular Networks (TIN) dataset, published at 1:24000 (1in=2000ft) scale as of unknown. It is described as 'TIN raster file obtained from DASC'....
NSGIC GIS Inventory (aka Ramona) — This Triangulated Irregular Networks (TIN) dataset, published at 1:2400 (1in=200ft) scale, was produced all or in part from Orthoimagery information as of 2005. It...
NSGIC GIS Inventory (aka Ramona) — This Triangulated Irregular Networks (TIN) dataset, published at 1:4800 (1in=400ft) scale, was produced all or in part from Orthoimagery information as of 2007. It...
NSGIC GIS Inventory (aka Ramona) — This Triangulated Irregular Networks (TIN) dataset, published at 1:2400 (1in=200ft) scale, was produced all or in part from Orthoimagery information as of 2002....
NSGIC GIS Inventory (aka Ramona) — This Triangulated Irregular Networks (TIN) dataset, was produced all or in part from LIDAR information as of unknown. It is described as 'Compiled a TIN baed our...
Schaarup, Clara; Hartvigsen, Gunnar; Larsen, Lars Bo; Tan, Zheng-Hua; Årsand, Eirik; Hejlesen, Ole Kristian
2015-01-01
The Online Diabetes Exercise System was developed to motivate people with Type 2 diabetes to do a 25 minutes low-volume high-intensity interval training program. In a previous multi-method evaluation of the system, several usability issues were identified and corrected. Despite the thorough testing, it was unclear whether all usability problems had been identified using the multi-method evaluation. Our hypothesis was that adding the eye-tracking triangulation to the multi-method evaluation would increase the accuracy and completeness when testing the usability of the system. The study design was an Eye-tracking Triangulation; conventional eye-tracking with predefined tasks followed by The Post-Experience Eye-Tracked Protocol (PEEP). Six Areas of Interests were the basis for the PEEP-session. The eye-tracking triangulation gave objective and subjective results, which are believed to be highly relevant for designing, implementing, evaluating and optimizing systems in the field of health informatics. Future work should include testing the method on a larger and more representative group of users and apply the method on different system types.