Добірка наукової літератури з теми "Mesh repairing"

In this paper, we propose a novel mesh repairing method for repairing voids from several meshes to ensure a desired topological correctness. The input to our method is several closed and manifold meshes without labels. The basic idea of the method is to search for and repair voids based on a multi-labeled mesh data structure and the idea of graph theory. We propose the judgment rules of voids between the input meshes and the method of void repairing based on the specified model priorities. It consists of three steps: (a) converting the input meshes into a multi-labeled mesh; (b) searching for quasi-voids using the breadth-first searching algorithm and determining true voids via the judgment rules of voids; (c) repairing voids by modifying mesh labels. The method can repair the voids accurately and only few invalid triangular facets are removed. In general, the method can repair meshes with one hundred thousand facets in approximately one second on very modest hardware. Moreover, it can be easily extended to process large-scale polygon models with millions of polygons. The experimental results of several data sets show the reliability and performance of the void repairing method based on the multi-labeled triangular mesh.

The application of mesh to reconstruct pelvic floors is considered a state-of-the-art method for the treatment of pelvic floor dysfunction. Polypropylene (PP) is the most frequently used synthetic graft material in gynecology departments due to its good mechanical property and non-degradability. Pelvic repairing meshes are required to have good biocompatibility, stability and low shrinkage with sufficient softness. Meshes should also adhere to surrounding tissues to support pelvic organs after implantation. This work designed two kinds of lightweight PP macroporous meshes with different structures. The meshes were designed based on analyzing properties of Gynemesh® PS, which is a common pelvic repairing mesh in clinical use. The requirements of mesh design were as follows: mesh weight <45 g/m2, pore size >75 µm, porosity >60%. Two kinds of meshes were fabricated according to design requirements and named the S1 mesh and S2 mesh. Several structural parameters, including thickness, weight, pore size, porosity and mechanical properties, including bursting strength, tensile strength, suture pulling off force and flexibility, were tested and analyzed. S1 mesh and S2 mesh were then implanted in the onlay position of rabbits for 90 days. The biocompatibility was evaluated through operation situation, postoperative recovery, mesh adhesion, shrinkage, histological evaluation of mesh and surrounding tissues. The results revealed that the two kinds of meshes were both beneficial to promote tissue growth; most animals recovered well. However, S1 mesh had greater shrinkage, while there existed one case of infection in the S2 mesh group because of mesh folding.

Les modèles numériques 3D compacts et précis de bâtiments sont couramment utilisés par les praticiens pour la visualisation d'environnements existants ou imaginaires, les simulations physiques ou la fabrication d'objets urbains. La génération de tels modèles prêts à l'emploi est cependant un problème difficile. Lorsqu'ils sont créés par des designers, les modèles 3D contiennent généralement des erreurs géométriques dont la correction automatique est un défi scientifique. Lorsqu'ils sont créés à partir de mesures de données, généralement des balayages laser ou des images multivues, la précision et la complexité des modèles produits par les algorithmes de reconstruction existants n'atteignent souvent pas les exigences des praticiens. Dans cette thèse, j'aborde ce problème en proposant deux algorithmes : l'un pour réparer les erreurs géométriques contenues dans les formats spécifiques de modèles de bâtiments, et l'autre pour reconstruire des modèles compacts et précis à partir de nuages ​​de points générés à partir d'un balayage laser ou d'images stéréo multivues. Le composant clé de ces algorithmes repose sur une structure de données de partitionnement d'espace capable de décomposer l'espace en cellules polyédriques de manière naturelle et efficace. Cette structure de données permet à la fois de corriger les erreurs géométriques en réassemblant les facettes de modèles 3D chargés de défauts, et de reconstruire des modèles 3D à partir de nuages ​​de points avec une précision et complexité proche de celles générées par les outils interactifs de Conception Assistée par Ordinateur.Ma première contribution est un algorithme pour réparer différents types de modèles urbains. Les travaux antérieurs, qui reposent traditionnellement sur une analyse locale et des heuristiques géométriques sur des maillages, sont généralement conçus sur-mesure pour des formats 3D et des objets urbains spécifiques. Nous proposons une méthode plus générale pour traiter différents types de modèles urbains sans réglage fastidieux des paramètres. L'idée clé repose sur la construction d'une structure de données cinétiques qui décompose l'espace 3D en polyèdres en étendant les facettes du modèle d'entrée imparfait. Une telle structure de données permet de reconstruire toutes les relations entre les facettes de manière efficace et robuste. Une fois construites, les cellules de la partition polyédrique sont regroupées par classes sémantiques pour reconstruire le modèle de sortie corrigé. Je démontre la robustesse et l'efficacité de l'algorithme sur une variété de modèles réels chargés de défauts et montre sa compétitivité par rapport aux techniques traditionnelles de réparation de maillage à partir de données de modélisation des informations du bâtiment (BIM) et de systèmes d'information géographique (SIG). Ma deuxième contribution est un algorithme de reconstruction inspiré de la méthode Kinetic Shape Reconstruction, qui améliore cette dernière de différentes manières. En particulier, je propose une technique pour détecter des primitives planaires à partir de nuages ​​de points 3D non organisés. Partant d'une configuration initiale, la technique affine à la fois les paramètres du plan continu et l'affectation discrète de points d'entrée à ceux-ci en recherchant une haute fidélité, une grande simplicité et une grande complétude. La solution est trouvée par un mécanisme d'exploration guidé par une fonction énergétique à objectifs multiples. Les transitions dans le grand espace des solutions sont gérées par cinq opérateurs géométriques qui créent, suppriment et modifient les primitives. Je démontre son potentiel, non seulement sur des bâtiments, mais sur une variété de scènes, des formes organiques aux objets fabriqués par l'homme
Compact and accurate digital 3D models of buildings are commonly used by practitioners for the visualization of existing or imaginary environments, the physical simulations or the fabrication of urban objects. Generating such ready-to-use models is however a difficult problem. When created by designers, 3D models usually contain geometric errors whose automatic correction is a scientific challenge. When created from data measurements, typically laser scans or multiview images, the accuracy and complexity of the models produced by existing reconstruction algorithms often do not reach the requirements of the practitioners. In this thesis, I address this problem by proposing two algorithms: one for repairing the geometric errors contained in urban-specific formats of 3D models, and one for reconstructing compact and accurate models from input point clouds generated from laser scanning or multiview stereo imagery. The key component of these algorithms relies upon a space-partitioning data structure able to decompose the space into polyhedral cells in a natural and efficient manner. This data structure is used to both correct geometric errors by reassembling the facets of defect-laden 3D models, and reconstruct concise 3D models from point clouds with a quality that approaches those generated by Computer-Aided-Design interactive tools.My first contribution is an algorithm to repair different types of urban models. Prior work, which traditionally relies on local analysis and heuristic-based geometric operations on mesh data structures, is typically tailored-made for specific 3D formats and urban objects. We propose a more general method to process different types of urban models without tedious parameter tuning. The key idea lies on the construction of a kinetic data structure that decomposes the 3D space into polyhedra by extending the facets of the imperfect input model. Such a data structure allows us to re-build all the relations between the facets in an efficient and robust manner. Once built, the cells of the polyhedral partition are regrouped by semantic classes to reconstruct the corrected output model. I demonstrate the robustness and efficiency of the algorithm on a variety of real-world defect-laden models and show its competitiveness with respect to traditional mesh repairing techniques from both Building Information Modeling (BIM) and Geographic Information Systems (GIS) data.My second contribution is a reconstruction algorithm inspired by the Kinetic Shape Reconstruction method, that improves the later in different ways. In particular, I propose a data fitting technique for detecting planar primitives from unorganized 3D point clouds. Departing from an initial configuration, the technique refines both the continuous plane parameters and the discrete assignment of input points to them by seeking high fidelity, high simplicity and high completeness. The solution is found by an exploration mechanism guided by a multi-objective energy function. The transitions within the large solution space are handled by five geometric operators that create, remove and modify primitives. I demonstrate its potential, not on buildings only, but on a variety of scenes, from organic shapes to man-made objects

Computational fluid dynamics (CFD) is now widely used as an essential tool in the development of automotive aerodynamics. However, the time required for repairing non-watertight geometries has recently become a serious problem in current CFD processes. Therefore, we developed an efficient simulation method that allows the flow around a non-watertight geometry to be computed on a Cartesian grid. This method can substantially reduce the turnaround time and effort required for CFD processes, because the repair work can be eliminated. The proposed method adopts an embedded boundary condition technique to capture arbitrary shapes more accurately on the background Cartesian grid. In addition, a local mesh refinement technique enables higher computational efficiency to be realized, and large-eddy simulation (LES) is used to reproduce high-Reynolds-number turbulent flow. Preliminary tests were performed on an engine bay configuration that had non-watertight geometries and a 1/5-scale model of an automobile configuration. As a result, the proposed method was confirmed to enable rapid grid generation and flow simulation around non-watertight geometries. Moreover, the computed results showed good agreement with experimental data.

Abstract Flexible Circuit Boards (FCB) are ubiquitous in most electronic devices used today. These are utilized in mobile phones, display cables in laptops, cameras, smart watches, robotic arms and more. They are mainly used in applications where space, flexibility and construction constraints limit the usage of conventional Printed Circuit Board (PCB). While FCBs offer numerous advantages over traditional PCBs, like enhanced reliability, capabilities, reduced weight, and lesser space utilization, on the other hand, they present different set of challenges like assembly, installation, and difficulty in repairing and reworking after installation. The flexes are generally bent at several points before conforming to the installed state which induces stresses before the actual operation or the working phase. These stresses are further magnified during the cyclic loading which can lead to breakage of these flexes. Due to intricacies involved in FCBs, numerical modeling of these components is challenging. In this work, a methodology is developed in Ansys Mechanical™ to model the installation and operating phase of the FCB. Stresses generated in both the phases are calculated and fatigue life is computed after the operational phase. Two different models are analyzed. The first model is a Rigid Flex PCB, where a FCB connects with the rigid PCBs. The second model is a standalone FCB cable. For both the models, shell elements are used to mesh the FCBs, which are typically thin structures and experience a large amount of rotation and bending loads. Trace mapping feature is used to accurately model the large number of intricate features such as copper traces, vias and other Electronic-CAD data. The trace mapping feature simplifies the model by modeling the geometry as dielectric layers and includes the effect of traces by mapping the metal fraction onto the dielectric layers. The loop forming capability of both the models is analyzed where they are subjected to a 180° bend. The fatigue induced due to this bending load is calculated for both the models. For the FCB cable case, the work is extended to study the stresses developed in the installation phase as it impacts the overall fatigue life of the FCB. Here the rigid surface bodies are used to push/deform the FCB cable to its final installation stage. Lastly, a detailed High-Performance Computing (HPC) scalability study is performed in-order to find the best balance between the number of cores and solution time.

High Performance Low-Invasion Fluids Technology Enhances, Optimizes Drilling Efficiency in the Gulf of Suez – Egypt Objectives / Scope: The main objective of this paper is to characterize the drilled shale formation in order to select and propose a "tailored" High Performance Low Invasion Fluids (HPLIF) system aided by Bridging Particles Optimization Tool (BPOT)(5),(6)(9)(11), capable of maximize hole stability in pressure depleted sands, allowing optimized well design through reactive and dispersible shale formations(7)(8) that eliminated one casing section, and to replace Oil Base Mud (OBM) and avoid its HSE issues related to use it, consequently, reduce formation damage, eliminate waste management cost, minimizing Non Productive Time (NPT) and finally enhances Drilling performance. Methods, Procedures, Process: This paper explain the reactivity information about Shale Samples recovered from different wells drilled in the-GOS-Egypt followed by extensive laboratory testing done(1) in order to characterize the main clay minerals presented in the samples using X-Ray Diffraction-(XRD) technology and their meso-and micro-structure by Scanning-Electron-Microscope-(SEM) and their reactivity to compare the inhibition efficiency of the proposed-(HPLIF)-System with Blank and Conventional Water-Base-Fluid-System. The reactivity of the cuttings was assessed by Dispersion, Swelling and Hardness tests. Field application experienced (HPLIF) System combined with Well-Bore Strengthening Materials (WSM) gives the required protection against induced losses and reducing the risk of differential sticking problems when mud overbalance is above 2500 psi(5), (6)(9)(11). Results, Observations, Conclusions: Compared with the use of conventional fluid systems, Field data demonstrated the successful application of (HPLIF) System combined with (WSM) and shows a great success during drilling through reactive clays, dispersive shale, naturally micro fractured(8), and depleted sand formations in many wells drilled in the GOS(2), (3), (4). Drilling operations reported no differential sticking, or wellbore instability issues even at highly mud overbalance or at highly deviated wells. The first challenged well R1-63 was drilled about 2391 ft, through 8.5" hole using 9.8-10.01 ppg using (HPLIF) system, penetrating through Thebes, Esna Shale, Sudr, Brown Lime Stone, Matulla, Nubia"A" Sand and Nubia "B" without any down-hole losses. Additionally, there was no sticking tendency experienced during drilling or while recording pressure points. The Non Productive Time NPT showed a reduction by about 19.2%. Finally, it ran and was cemented the "7" Liner in open hole successfully without problem. For the second challenged case well # 2, the Open hole was exposed to (HPLIF) water based mud system for a long period of time while rig repairing, rig switching, and during drilling operation. The well had 6" hole from 12,752 To/14,945 (2193.0ft) through Red bed, Thebes Esna, Sudr, Matulla and Nubia Sand formations with max inclination 68.6° and bottom hole temperature 325°F using 10.0-10.5 ppg (HPLIF) system, the 4.5"liner successfully was ran, cemented without any problems. The-HPLIF-System has also been shown to give excellent wellbore stability in brittle shales Fm where bedding planes or micro-fractures can become pressurized with mud, leading to wellbore instability. This innovation avoids induced lost circulation and differential sticking when the mud overbalance is expected to be greater than ±2500 psi. Additionally, the proposed solution enhances the drilling operation, reduces the waste management costs, eliminates a possible additional casing string, and finally minimizes the (NPT) which reflects on the overall cost of drilling these challenged wells.