Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 27 for “"octree"”.
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NC verification using octree
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1998.
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Development of an AMR Octree DSMC approach for shock dominated flows
… program are described. The code employs an Octree based adaptive mesh refinement (AMR) that gives flexibility in capturing multi-scale physics. It is coupled with a robust cut-cell algorithm to incorporate complex triangulated geometries. With the use of distributed memory systems and …
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Adaptive Slicing in Additive Manufacturing Process using a Modified Boundary Octree Data Structure
… study. This method, termed as Modified Boundary Octree Data Structure (MBODS), is used to convert the STL file of an object to an octree data structure, by considering the part’s geometry, the AM machine parameters, and user defined tolerance values. This algorithm ensures that the fabricated …
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Automatic parallel octree grid generation software with an extensible solver framework and a focus on urban simulation
… dynamic, parallel, Cartesian, linear forest-of-octree grid generator and partial differential equation (PDE) solver framework is presented. This research is bundled into an application programmed with C++ which uses MPI for distributed parallelism. The application is named paros which stands for …
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A real-time robot collision avoidance safety system
… arms. The data structure is a variant of the octree, which serves as a spatial index. An octree recursively decomposes three dimensional space into eight equal cubic octants (nodes) until each octant meets some decomposition criteria. Our octree stores cylspheres (cylinders with spheres on …
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A Family of Hierarchical Encoding Techniques for Image and Video Communications
… encoding techniques based on the quadtree and octree representation methods.</p> <p>First we developed an image encoding technique using the quadtree representation of images and vector quantization. We use a mean-removal technique to separate the means image and the difference image. The …
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Incremental volume rendering using hierarchical compression
… data. This exploits the multiscale nature of the octree data structure. The algorithm reduces the memory footprint of the original Shear-Warp Factorisation algorithm by a factor of more than two, while maintaining good rendering performance. These factors make our octree algorithm more suitable …
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Use of molecular dynamics simulations to study the impact of weak to strong non-covalent chemical interactions
… As an efficient alternative, we developed a new octree-based Coulomb interaction model. For the octree-based method, Coulomb interactions were categorized as intra- and inter-leaf Coulomb interactions based on a criterion related to the Bjerrum length of the IL. The octree-based method was found …
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Dynamic multilevel graph layout and visualisation
… groups of vertices much like the Barnes Hut Octree. The method suggests better representation of the graphs underlying relationships. In experiments this algorithm, referred to as Multilevel Global Force (MGF), reduces running time by an average of 40% compared to the popular Barnes Hut …
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Parallelization of the Advancing Front Local Reconnection Mesh Generation Software Using a Pseudo-Constrained Parallel Data Refinement Method
… and consists of the following steps: (i) use an octree data-decomposition scheme to divide the original geometry into subdomains (octree leaves), (ii) refine each subdomain with the proper adjustments of its neighbors using the given refinement code, and (iii) combine all subdomain data into a …
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Precision Navigation for Indoor Mobile Robots
… generator and a simplistic path planner. A 3D octree costmap based on the OctoMap library was also developed for collision detection. Geometric parameterizations for path segments were developed for use by those components. The precision navigation system was evaluated using a physical robot, …
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Implementierung und Untersuchung paralleler Volumen-Rendering-Techniken für Graphikprozessoren
… innerhalb der Volumendaten, mit Hilfe eines Octrees beschleunigt werden. Hierbei ist es das Ziel den Raycaster mit dem Octree auf die spezifischen Gegebenheiten der GPU anzupassen. Insbesondere soll versucht werden die SIMD-Effizienz und damit die Performance durch eine geschickte Kombination …
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A z-ordering cartesian grid method and its application in flow simulation
… By deploying this ordering to quadtree/octree, a robust grid navigation algorithm is developed. The algorithm simplifies the grid's navigation procedure, which is usually the most time consuming part in both the grid generation and flow simulation. A binary coding system is developed to …
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Automated segmentation, detection and fitting of piping elements from terrestrial LIDAR data
… radius of each detected pipe element. ^ A robust octree-based split and merge segmentation algorithm is proposed in this dissertation that can efficiently process LIDAR data. Following octree decomposition of the point cloud, graph theory analysis is used during the splitting process to separate …
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Performance evaluation and enhancement of Dendro
… uses the Message Passing (MPI). Dendro uses an octree data-structure to solve image-registration problems using finite element techniques. For analyzing the behavior of the package in terms of speed-up and scalability, it is important to know which part of the package is consuming most of the …
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Guidance and Control System for VTOL UAVs operating in Contested Environments
… been explored. To perform this partitioning, the Octree algorithm is implemented. In this thesis, we test this algorithm to find a parameter set that optimizes this algorithm. Having selected goal points, we perform a comparison of the LPA* and A* path planning algorithms with a custom heuristic …
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MODEL-BASED 3-D VISION
… of the models is generated by first creating the octree representation of the 3-D objects based on three orthogonal views of the objects and employing the volume intersection method. Subsequently, by using the multi-level boundary search algorithm, the object of interest can be displayed quickly …
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CHAOS: A multi-GPU PIC-DSMC solver for modeling gas and plasma flows
… solver called Cuda-based Hybrid Approach for Octree Simulations (CHAOS) that is presented in this work. This computational tool has been applied to candidate PICA-like TPS materials that consist of an irregular porous network of fibers to allow high-temperature boundary layer gases as well as …
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A Homegrown DSMC-PIC Model for Electric Propulsion
… electric propulsion plumes. SINATRA uses an octree mesh, is written in C++, and is designed to be expanded by further research. SINATRA has been initially validated through several tests and comparisons to theoretical data and other DSMC models. This thesis examines expanding the …
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Digitizing a Three-Dimensional Brain Atlas: Image Sequence Alignment and Volumetric Encoding
… method and long range correlation. An octree variant, scalable hyperspace file (SHSF), was developed to encode the volumetric data set. SHSF can facilitate volume accessing so that efficient virtual brain slicer and surface viewer are possible to implement. Since a high-resolution brain …
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