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Artykuły w czasopismach na temat "Modèle voxel":
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Zhao, Lin, Siyuan Xu, Liman Liu, Delie Ming i Wenbing Tao. "SVASeg: Sparse Voxel-Based Attention for 3D LiDAR Point Cloud Semantic Segmentation". Remote Sensing 14, nr 18 (7.09.2022): 4471. http://dx.doi.org/10.3390/rs14184471.
Streszczenie:
3D LiDAR has become an indispensable sensor in autonomous driving vehicles. In LiDAR-based 3D point cloud semantic segmentation, most voxel-based 3D segmentors cannot efficiently capture large amounts of context information, resulting in limited receptive fields and limiting their performance. To address this problem, a sparse voxel-based attention network is introduced for 3D LiDAR point cloud semantic segmentation, termed SVASeg, which captures large amounts of context information between voxels through sparse voxel-based multi-head attention (SMHA). The traditional multi-head attention cannot directly be applied to the non-empty sparse voxels. To this end, a hash table is built according to the incrementation of voxel coordinates to lookup the non-empty neighboring voxels of each sparse voxel. Then, the sparse voxels are grouped into different groups, and each group corresponds to a local region. Afterwards, position embedding, multi-head attention and feature fusion are performed for each group to capture and aggregate the context information. Based on the SMHA module, the SVASeg can directly operate on the non-empty voxels, maintaining a comparable computational overhead to the convolutional method. Extensive experimental results on the SemanticKITTI and nuScenes datasets show the superiority of SVASeg.
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Tang, Jiaxiang, Xiaokang Chen, Jingbo Wang i Gang Zeng. "Not All Voxels Are Equal: Semantic Scene Completion from the Point-Voxel Perspective". Proceedings of the AAAI Conference on Artificial Intelligence 36, nr 2 (28.06.2022): 2352–60. http://dx.doi.org/10.1609/aaai.v36i2.20134.
Streszczenie:
We revisit Semantic Scene Completion (SSC), a useful task to predict the semantic and occupancy representation of 3D scenes, in this paper. A number of methods for this task are always based on voxelized scene representations. Although voxel representations keep local structures of the scene, these methods suffer from heavy computation redundancy due to the existence of visible empty voxels when the network goes deeper. To address this dilemma, we propose our novel point-voxel aggregation network for this task. We first transfer the voxelized scenes to point clouds by removing these visible empty voxels and adopt a deep point stream to capture semantic information from the scene efficiently. Meanwhile, a light-weight voxel stream containing only two 3D convolution layers preserves local structures of the voxelized scenes. Furthermore, we design an anisotropic voxel aggregation operator to fuse the structure details from the voxel stream into the point stream, and a semantic-aware propagation module to enhance the up-sampling process in the point stream by semantic labels. We demonstrate that our model surpasses state-of-the-arts on two benchmarks by a large margin, with only the depth images as input.
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He, Qingdong, Zhengning Wang, Hao Zeng, Yi Zeng i Yijun Liu. "SVGA-Net: Sparse Voxel-Graph Attention Network for 3D Object Detection from Point Clouds". Proceedings of the AAAI Conference on Artificial Intelligence 36, nr 1 (28.06.2022): 870–78. http://dx.doi.org/10.1609/aaai.v36i1.19969.
Streszczenie:
Accurate 3D object detection from point clouds has become a crucial component in autonomous driving. However, the volumetric representations and the projection methods in previous works fail to establish the relationships between the local point sets. In this paper, we propose Sparse Voxel-Graph Attention Network (SVGA-Net), a novel end-to-end trainable network which mainly contains voxel-graph module and sparse-to-dense regression module to achieve comparable 3D detection tasks from raw LIDAR data. Specifically, SVGA-Net constructs the local complete graph within each divided 3D spherical voxel and global KNN graph through all voxels. The local and global graphs serve as the attention mechanism to enhance the extracted features. In addition, the novel sparse-to-dense regression module enhances the 3D box estimation accuracy through feature maps aggregation at different levels. Experiments on KITTI detection benchmark and Waymo Open dataset demonstrate the efficiency of extending the graph representation to 3D object detection and the proposed SVGA-Net can achieve decent detection accuracy.
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Chen, Yuhong, Weilong Peng, Keke Tang, Asad Khan, Guodong Wei i Meie Fang. "PyraPVConv: Efficient 3D Point Cloud Perception with Pyramid Voxel Convolution and Sharable Attention". Computational Intelligence and Neuroscience 2022 (13.05.2022): 1–9. http://dx.doi.org/10.1155/2022/2286818.
Streszczenie:
Designing efficient deep learning models for 3D point cloud perception is becoming a major research direction. Point-voxel convolution (PVConv) Liu et al. (2019) is a pioneering research work in this topic. However, since with quite a few layers of simple 3D convolutions and linear point-voxel feature fusion operations, it still has considerable room for improvement in performance. In this paper, we propose a novel pyramid point-voxel convolution (PyraPVConv) block with two key structural modifications to address the above issues. First, PyraPVConv uses a voxel pyramid module to fully extract voxel features in the manner of feature pyramid, such that sufficient voxel features can be obtained efficiently. Second, a sharable attention module is utilized to capture compatible features between multi-scale voxels in pyramid and point cloud for aggregation, as well as to reduce the complexity via structure sharing. Extensive results on three point cloud perception tasks, i.e., indoor scene segmentation, object part segmentation and 3D object detection, validate that the networks constructed by stacking PyraPVConv blocks are efficient in terms of both GPU memory consumption and computational complexity, and are superior to the state-of-the-art methods.
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Li, Guangping, Zuanfang Mo i Bingo Wing-Kuen Ling. "AMFF-Net: An Effective 3D Object Detector Based on Attention and Multi-Scale Feature Fusion". Sensors 23, nr 23 (22.11.2023): 9319. http://dx.doi.org/10.3390/s23239319.
Streszczenie:
With the advent of autonomous vehicle applications, the importance of LiDAR point cloud 3D object detection cannot be overstated. Recent studies have demonstrated that methods for aggregating features from voxels can accurately and efficiently detect objects in large, complex 3D detection scenes. Nevertheless, most of these methods do not filter background points well and have inferior detection performance for small objects. To ameliorate this issue, this paper proposes an Attention-based and Multiscale Feature Fusion Network (AMFF-Net), which utilizes a Dual-Attention Voxel Feature Extractor (DA-VFE) and a Multi-scale Feature Fusion (MFF) Module to improve the precision and efficiency of 3D object detection. The DA-VFE considers pointwise and channelwise attention and integrates them into the Voxel Feature Extractor (VFE) to enhance key point cloud information in voxels and refine more-representative voxel features. The MFF Module consists of self-calibrated convolutions, a residual structure, and a coordinate attention mechanism, which acts as a 2D Backbone to expand the receptive domain and capture more contextual information, thus better capturing small object locations, enhancing the feature-extraction capability of the network and reducing the computational overhead. We performed evaluations of the proposed model on the nuScenes dataset with a large number of driving scenarios. The experimental results showed that the AMFF-Net achieved 62.8% in the mAP, which significantly boosted the performance of small object detection compared to the baseline network and significantly reduced the computational overhead, while the inference speed remained essentially the same. AMFF-Net also achieved advanced performance on the KITTI dataset.
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Shuang, Feng, Hanzhang Huang, Yong Li, Rui Qu i Pei Li. "AFE-RCNN: Adaptive Feature Enhancement RCNN for 3D Object Detection". Remote Sensing 14, nr 5 (27.02.2022): 1176. http://dx.doi.org/10.3390/rs14051176.
Streszczenie:
The point clouds scanned by lidar are generally sparse, which can result in fewer sampling points of objects. To perform precise and effective 3D object detection, it is necessary to improve the feature representation ability to extract more feature information of the object points. Therefore, we propose an adaptive feature enhanced 3D object detection network based on point clouds (AFE-RCNN). AFE-RCNN is a point-voxel integrated network. We first voxelize the raw point clouds and obtain the voxel features through the 3D voxel convolutional neural network. Then, the 3D feature vectors are projected to the 2D bird’s eye view (BEV), and the relationship between the features in both spatial dimension and channel dimension is learned by the proposed residual of dual attention proposal generation module. The high-quality 3D box proposals are generated based on the BEV features and anchor-based approach. Next, we sample key points from raw point clouds to summarize the information of the voxel features, and obtain the key point features by the multi-scale feature extraction module based on adaptive feature adjustment. The neighboring contextual information is integrated into each key point through this module, and the robustness of feature processing is also guaranteed. Lastly, we aggregate the features of the BEV, voxels, and point clouds as the key point features that are used for proposal refinement. In addition, to ensure the correlation among the vertices of the bounding box, we propose a refinement loss function module with vertex associativity. Our AFE-RCNN exhibits comparable performance on the KITTI dataset and Waymo open dataset to state-of-the-art methods. On the KITTI 3D detection benchmark, for the moderate difficulty level of the car and the cyclist classes, the 3D detection mean average precisions of AFE-RCNN can reach 81.53% and 67.50%, respectively.
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Bourbonne, V., V. Jaouen, M. Rehn, M. Hatt, O. Pradier, D. Visvikis, F. Lucia i U. Schick. "Développement et validation d’un modèle basé sur l’analyse par voxel pour la prédiction de la toxicité pulmonaire aiguë chez les patients pris en charge par arcthérapie volumétrique pour un cancer du poumon localement évolué". Cancer/Radiothérapie 25, nr 6-7 (październik 2021): 736. http://dx.doi.org/10.1016/j.canrad.2021.07.020.
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Wang, Yu, i Chao Tong. "H2GFormer: Horizontal-to-Global Voxel Transformer for 3D Semantic Scene Completion". Proceedings of the AAAI Conference on Artificial Intelligence 38, nr 6 (24.03.2024): 5722–30. http://dx.doi.org/10.1609/aaai.v38i6.28384.
Streszczenie:
3D Semantic Scene Completion (SSC) has emerged as a novel task in vision-based holistic 3D scene understanding. Its objective is to densely predict the occupancy and category of each voxel in a 3D scene based on input from either LiDAR or images. Currently, many transformer-based semantic scene completion frameworks employ simple yet popular Cross-Attention and Self-Attention mechanisms to integrate and infer dense geometric and semantic information of voxels. However, they overlook the distinctions among voxels in the scene, especially in outdoor scenarios where the horizontal direction contains more variations. And voxels located at object boundaries and within the interior of objects exhibit varying levels of positional significance. To address this issue, we propose a transformer-based SSC framework called H2GFormer that incorporates a horizontal-to-global approach. This framework takes into full consideration the variations of voxels in the horizontal direction and the characteristics of voxels on object boundaries. We introduce a horizontal window-to-global attention (W2G) module that effectively fuses semantic information by first diffusing it horizontally from reliably visible voxels and then propagating the semantic understanding to global voxels, ensuring a more reliable fusion of semantic-aware features. Moreover, an Internal-External Position Awareness Loss (IoE-PALoss) is utilized during network training to emphasize the critical positions within the transition regions between objects. The experiments conducted on the SemanticKITTI dataset demonstrate that H2GFormer exhibits superior performance in both geometric and semantic completion tasks. Our code is available on https://github.com/Ryanwy1/H2GFormer.
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Guo, Xindong, Yu Sun i Hua Yang. "FF-Net: Feature-Fusion-Based Network for Semantic Segmentation of 3D Plant Point Cloud". Plants 12, nr 9 (1.05.2023): 1867. http://dx.doi.org/10.3390/plants12091867.
Streszczenie:
Semantic segmentation of 3D point clouds has played an important role in the field of plant phenotyping in recent years. However, existing methods need to down-sample the point cloud to a relatively small size when processing large-scale plant point clouds, which contain more than hundreds of thousands of points, which fails to take full advantage of the high-resolution of advanced scanning devices. To address this issue, we propose a feature-fusion-based method called FF-Net, which consists of two branches, namely the voxel-branch and the point-branch. In particular, the voxel-branch partitions a point cloud into voxels and then employs sparse 3D convolution to learn the context features, and the point-branch learns the point features within a voxel to preserve the detailed point information. Finally, an attention-based module was designed to fuse the two branch features to produce the final segmentation. We conducted extensive experiments on two large plant point clouds (maize and tomato), and the results showed that our method outperformed three commonly used models on both datasets and achieved the best mIoU of 80.95% on the maize dataset and 86.65% on the tomato dataset. Extensive cross-validation experiments were performed to evaluate the generalization ability of the models, and our method achieved promising segmentation results. In addition, the drawbacks of the proposed method were analyzed, and the directions for future works are given.
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Peng, Hao, Guofeng Tong, Zheng Li, Yaqi Wang i Yuyuan Shao. "3D object detection combining semantic and geometric features from point clouds". Cobot 1 (12.01.2022): 2. http://dx.doi.org/10.12688/cobot.17433.1.
Streszczenie:
Background: 3D object detection based on point clouds in road scenes has attracted much attention recently. The voxel-based methods voxelize the scene to regular grids, which can be processed with the advanced feature learning frameworks based on convolutional layers for semantic feature learning. The point-based methods can extract the geometric feature of the point due to the coordinate reservations. The combination of the two is effective for 3D object detection. However, the current methods use a voxel-based detection head with anchors for classification and localization. Although the preset anchors cover the entire scene, it is not suitable for detection tasks with larger scenes and multiple categories of objects, due to the limitation of the voxel size. Additionally, the misalignment between the predicted confidence and proposals in the Regions of the Interest (ROI) selection bring obstacles to 3D object detection. Methods: We investigate the combination of voxel-based methods and point-based methods for 3D object detection. Additionally, a voxel-to-point module that captures semantic and geometric features is proposed in the paper. The voxel-to-point module is conducive to the detection of small-size objects and avoids the presets of anchors in the inference stage. Moreover, a confidence adjustment module with the center-boundary-aware confidence attention is proposed to solve the misalignment between the predicted confidence and proposals in the regions of the interest selection. Results: The proposed method has achieved state-of-the-art results for 3D object detection in the Karlsruhe Institute of Technology and Toyota Technological Institute (KITTI) object detection dataset. Actually, as of September 19, 2021, our method ranked 1st in the 3D and Bird Eyes View (BEV) detection of cyclists tagged with difficulty level ‘easy’, and ranked 2nd in the 3D detection of cyclists tagged with ‘moderate’. Conclusions: We propose an end-to-end two-stage 3D object detector with voxel-to-point module and confidence adjustment module.
Rozprawy doktorskie na temat "Modèle voxel":
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Parvathaneni, Keerthi Krishna. "Characterization and multiscale modeling of textile reinforced composite materials considering manufacturing defects". Electronic Thesis or Diss., Ecole nationale supérieure Mines-Télécom Lille Douai, 2020. http://www.theses.fr/2020MTLD0016.
Streszczenie:
L’influence des porosités induites par les procédés de fabrication sur les propriétés mécaniques des composites textiles a été étudiée à la fois par caractérisation expérimentale et par modélisation multi-échelle. En particulier, les porosités ont été caractérisés en termes de fraction volumique, taille, forme et distribution, et les effets de chaque caractéristique sur les propriétés mécaniques des composites textiles ont été analysés. De nombreuses plaques de composites textiles ont été fabriquées par le procédé Resin Transfer Molding (RTM). Ainsi, un renfort textile en verre interlock 3D a été imprégné par une résine époxy injectée sous une pression constante pour générer différents types de porosités. Des essais mécaniques ont été réalisés pour examiner la dépendance du module et de la résistance en traction des composites par rapport au taux de porosité total, intra-toron et inter-toron et également par rapport aux caractéristiques géométriques des porosités. Des analyses au microscope électronique ont été effectuées pour obtenir des informations locales sur les fibres (diamètre et distribution) et les porosités intra-toron (rayon, rapport d’aspect et distribution). A partir de ces résultats, un nouvel algorithme a été développé pour générer le Volume Elémentaire Représentatif (VER) qui est statistiquement équivalent au composite contenant les porosités. De plus, l’effet de la morphologie, du diamètre et de la distribution spatiale des porosités (homogène, aléatoire et concentré) sur les propriétés homogénéisées des torons a également été étudié par la méthode des éléments finis. La tomographie par rayons X a été utilisée pour extraire la géométrie méso-échelle réelle en trois dimensions et les porosités intra-toron. Ensuite, ces données ont été utilisées pour créer un modèle numérique à l’échelle mésoscopique (VER) et prédire les propriétés élastiques des composites avec porosités. Une étude paramétrique utilisant une méthode numérique multi-échelle a été effectuée pour étudier l’effet de chaque caractéristique des porosités, c.-à-d. le taux volumique, la taille, la forme, la distribution et la localisation sur les propriétés élastiques de composites. Ainsi, la méthode multi-échelle proposée permet d’établir une corrélation entre les porosités à différentes échelles et les propriétés mécaniques des composites textilesThe influence of void-type manufacturing defects on the mechanical properties of textile composites was investigated both by experimental characterization and by multiscale modeling. In particular, voids characteristics such as not only void volume fraction but also its size, shape, and distribution have been characterized for textile composites and their effect on the mechanical properties have been analyzed. Several textile composite plates were fabricated by the resin transfer molding (RTM) process where 3D interlock glass textile reinforcement was impregnated by epoxy resin under a constant injection pressure to generate different types of voids. A series of mechanical tests were performed to examine the dependency of tensile modulus and strength of composites on the total void volume fraction, intra & inter-yarn void volume fraction, and their geometrical characteristics. Microscopy observations were performed to obtain the local information about fibers (diameter and distribution), and intra-yarn voids (radius, aspect ratio and distribution). Based on these results, a novel algorithm was proposed to generate the statistically equivalent representative volume element (RVE) containing voids. Moreover, the effect of void morphology, diameter and spatial distribution (homogeneous, random and clustering) on the homogenized properties of the yarns was also investigated by the finite element method. X-ray micro-computed tomography was employed to extract the real meso-scale geometry and inter-yarn voids. Subsequently, this data was utilized to create a numerical model at meso-scale RVE and used to predict the elastic properties of composites containing voids. A parametric study using a multiscale numerical method was proposed to investigate the effect of each void characteristic, i.e. volume fraction, size, shape, distribution, and location on the elastic properties of composites. Thus, the proposed multiscale method allows establishing a correlation between the void defects at different scales and the mechanical properties of textile composites
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Feron, Maryse. "Étude des mécanismes neurophysiologiques de l'instabilité posturale dans la sclérose latérale amyotrophique à partir d'un modèle biomécanique de l'initiation de la marche". Thesis, Paris 10, 2016. http://www.theses.fr/2016PA100187/document.
Streszczenie:
L'instabilité posturale est souvent observée chez les patients atteints de la sclérose latérale amyotrophique (SLA). Cependant, les mécanismes neuronaux impliqués dans cette instabilité posturale demeurent largement inconnus. Comparés aux patients SLA sans instabilité postural, les patients atteints de SLA avec instabilité posturale présentent des APA altérés avec un déplacement postérieur du centre de pression du pied diminué (CP) et une durée des APA augmentée, la longueur et la vitesse du premier pas sont réduites, enfin, le contrôle postural dynamique est déficitaire avec une diminution spectaculaire de l'indice de freinage. A l'inverse, nous n’observons aucune modification des phases d’anticipation et d’exécution du pas chez les patients SLA sans instabilité posturale comparés aux sujets témoins. Le faible recul du CP au cours de la phase d’anticipation est corrélé positivement de façon significative à l’atrophie de la substance grise du PCC, SPL, PPN et le CN ; et la durée augmentée de la phase d’anticipation est corrélée négativement de façon significative à l’atrophie de la matière grise du AMS et du cervelet. Les réductions de la vitesse et de la longueur du premier pas sont liées de façon significative à l’atrophie de la matière grise dans le PMC, le PPN et le vermis cérébelleux, enfin, l’absence de freinage actif est corrélée à une diminution du volume de la matière grise du CUN. Ces résultats suggèrent que l'instabilité posturale des patients atteints de SLA est causée, au moins en partie, par le dysfonctionnement des régions et des réseaux connus pour être impliqués dans l'initiation de la marche et dans le contrôle de l’équilibrePostural instability is frequently reported in Amyotrophic Lateral Sclerosis (SLA) patients. However, the neural mechanisms that contribute to postural instability in SLA patients remain largely unknown. In comparison to both SLA patients without postural instability and controls, SLA patients with postural instability presented an altered anticipatory postural adjustment (APA) phase with a decreased posterior displacement of the center of foot pressure (CP) and a increased APA duration, decreased length and velocity of the first step and deficit of the dynamic postural control with a dramatic decreased braking index. Conversely, the gait initiation was not significantly modified in SLA patients without postural instability in comparison to controls. The reduced posterior CP displacement during the APA was significantly related to reduced grey matter volume of the left PCC, left SPL, right PPN and caudate nucleus, and the increased APA duration to the reduced grey matter volume of the left AMS and right cerebellum. The reduced velocity of the first step was significantly related to a decreased grey matter volume within the left PMC, right PPN and cerebellar vermis and the reduced braking index to decreased grey matter volume of the right CUN. These results suggest that postural instability of SLA patients result, at least partly, from dysfunction of brain regions and networks known to be involved in gait initiation and balance controls in human
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Heide, Dr Bernd. "A Method For Modifying Segmented Human Voxel Models". Universitätsbibliothek Chemnitz, 2002. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200200823.
Streszczenie:
A method for modifying segmented human voxel models is depicted. The method is a practical approach to set up voxel models for dose calculations in medical physics. It could also be applied in other fields requiring human voxel models. The basic strategy of the method is: 1. Generate triangulated surfaces from voxel representations of the objects (organs, bones, or tissues) of a segmented human voxel model. 2. Perform surface deformations and/or rearrangements. 3. Reconstruct voxel representations from the triangulated surfaces and put them back into the segmented human voxel model. The voxel volume of the modified organs can be adjusted up to the volume of half a voxel. The practicability of the method is demonstrated by means of the spleen of a leukaemia patientEs wird eine praktische Methode zum Verändern von segmentierten menschlichen Voxel-Modellen dargelegt. Die Methode kann in der Medizinphysik im Zusammenhang mit Strahlendosisberechnungen angewendet werden. Sie kann jedoch auch in anderen Gebieten benutzt werden, bei denen menschliche Voxel-Modelle zur Anwendung kommen. Die grundlegende Strategie der Methode besteht aus den folgenden Schritten: 1. Erzeugung triangulierter Oberflächen aus Objekten (Organen, Knochen, Geweben) eines segmentierten menschlichen Voxel-Modells. 2. Durchführung interaktiver Oberflächendeformationen und/oder Verschiebungen. 3. Re-Überführung der triangulierten Oberflächen in Voxel-Darstellungen der Organe und Rückschreibung in das segmentierte menschliche Voxel-Modell. Das Voxel-Volumen der modifizierten Organe kann mindestens bis auf ein halbes Voxel genau eingestellt werden. Die Anwendbarkeit der Methode wird anhand der Milz einer Leukämie-Patientin demonstriert
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Vogel, Helena [Verfasser]. "Modelle zur Leistungsverschlechterung von Turboluftstrahltriebwerken / Helena Vogel". München : Verlag Dr. Hut, 2019. http://d-nb.info/1178899020/34.
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Mazzolini, Ryan. "Procedurally generating surface detail for 3D models using voxel-based cellular automata". Master's thesis, University of Cape Town, 2016. http://hdl.handle.net/11427/20502.
Streszczenie:
Procedural generation is used extensively in the field of computer graphics to automate content generation and speed up development. One particular area often automated is the generation of additional colour and structural detail for existing 3D models. This empowers artists by providing a tool-set that enhances their existing work-ow and saves time. 3D surface structures are traditionally represented by polygon mesh-based models augmented by 2D mapping techniques. These methods can approximate features, such as caves and overhangs, however they are complex and difficult to modify. As an alternative, a grid of voxels can model 3D shapes and surfaces, similar to how 2D pixels form an image. The regular form of voxel-based models is easier to alter, at the cost of additional computational overhead. One technique for generating and altering voxel content is by using Cellular Automata (CA). CAs are able to produce complex structures from simple rules and also easily map to higher dimensions, such as voxel datasets. However, creating CA rule-sets can be difficult and tedious. This is especially true when creating multidimensional CA. In our work we use a grammar system to create surface detail CA. The grammar we develop is similar to formal grammars used in procedural generation, such as L-systems and shape grammars. Our system is composed of three main sections: a model converter, grammar and CA executor. The model converter changes polygon-mesh models to and from a voxel-based model. The grammar provides a simple language to create CA that can consider 3D neighbourhoods and query parameters, such as colour or structure. Finally, the CA executor interprets the produced grammars into surface-oriented CAs. The final output of this system is a polygon-mesh model, altered by the CA, which is usable for graphics applications. We test the system by replicating a number of CA use-cases with our grammar system. From the results, we conclude that our grammar system is capable of creating a wide range of 3D detail CA. However, the high resolution of resulting meshes and slow processing times make the process more suited to o_-line processing and pre-production.
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Dawa, Hazem. "Modélisation surfacique par voxels d'une structure osseuse. Application à la simulation d'ostéotomies faciales". Toulouse 3, 1997. http://www.theses.fr/1997TOU30080.
Streszczenie:
Cette etude consiste tout d'abord, en la definition d'une structure de donnees permettant la representation (visage de patient), connue sous la forme des donnees volumiques issues de couches scanner. Sont ensuite definies et presentees les procedures a appliquer a cette structure de donnees, afin d'assurer les traitements classiques sur une structure osseuse : visualisation, transformations geometriques, operations booleennes. La premiere partie est consacree a l'aspect modelisation et visualisation de l'etude. Il s'agit d'un expose des principales techniques de representation utilisees dans ce domaines, et regroupees dans les deux methodes : volumique et surfacique. Nous justifions ensuite le choix d'une representation surfacique par voxels exterieurs, sur les criteres de capacite de memoire et de temps de traitement. En effet, les structures osseuses considerees sont definies par un tres grande quantite de donnees, et nous nous placons dans le cas (le plus courant) ou les ressources disponibles -capacite de memoire et puissance de calcul- sont moyennes voire faibles. Les manipulations de la structure osseuse sont presentees dans la deuxieme partie. Guides par l'application simulation d'osteotomies faciales, nous presentons les procedures a appliquer a la structure de donnees permettant de realiser les differentes transformations souhaitees par le chirurgien sur le massif osseux. La troisieme partie est orientee vers la simulation des osteotomies faciales. On y considere la representation de la partie cutanee du visage, ainsi que l'estimation des deformation entrainees par les deplacements osseux.
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Falk, Thorsten [Verfasser], i Olaf [Akademischer Betreuer] Ronneberger. "From voxels to models : towards quantification in 3-D confocal microscopy". Freiburg : Universität, 2016. http://d-nb.info/1119898862/34.
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Côté, Jean-Francois. "Un modèle d'architecture 3D par voxels pour simuler les paramètres structuraux des couverts forestiers de conifères". Mémoire, Université de Sherbrooke, 2006. http://savoirs.usherbrooke.ca/handle/11143/2443.
Streszczenie:
La qualité des mesures indirectes de la structure du couvert végétal repose principalement sur la connaissance de l'architecture des couverts végétaux. Nous avons développé des modèles d'architecture du couvert forestier selon plusieurs niveaux de détails afin d'aider l'interprétation des images de télédétection. C'est le cas pour le modèle VoxTreK (Voxel Tree with 3D-Kites) qui utilise les données géométriques recueillies sur le terrain pour reproduire l'architecture du couvert au niveau de détail des branches. Ce modèle est conçu pour son utilisation par les modèles de réflectance en télédétection. Toutefois, la photographie hémisphérique est utilisée dans cette étude comme complément aux approches de télédétection satellitaire ou aéroportée pour sa capacité à déceler un plus grand détail de la structure du couvert. L'objectif principal est de déterminer les apports du modèle d'architecture par voxels VoxTreK dans l'estimation des paramètres structuraux à l'aide de la photographie hémisphérique."--résumé abrégé par UMI.
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LOPEZ, COELLO LIMBANO IVAN 784713, i COELLO LIMBANO IVAN LOPEZ. "Cálculo con GEANT4 de valores S en maniquí hembra/macho tipo voxel de modelo murino (MOBY) para el 67Ga". Tesis de maestría, Universidad Autónoma del Estado de México, 2018. http://hdl.handle.net/20.500.11799/98794.
Streszczenie:
La medicina nuclear y radioterapia, aunque ya están bien establecidas siguen evolucionando rápidamente gracias al uso de modelos animales que ayudan a de_nir una dosimetría más precisa en los procedimientos de imagen molecular y dosimetría interna. Modelos de animales pequeños como el ratón han sido ampliamente usados en protocolos experimentales que involucran el uso de radiaciones ionizantes. Los estudios de dosimetría en animales pequeños son usados principalmente en la terapia preclínica de radionúclidos para evaluar la toxicidad de los nuevos radiofármacos antes de comenzar a ser aplicados en humanos. Entendiendo la respuesta de dosis, los efectos de la radiación y la toxicidad del radiofármaco hacen que estos estudios sean muy importantes ya que pueden ser trasladados a estudios preclínicos en humanos. La evaluación de la e_cacia terapéutica es esencial y debe basarse en una dosimetría precisa la cual a su vez está basada en modelos geométricos realistas que describen adecuadamente el transporte de radiación. El propósito de este trabajo fue determinar el impacto que tienen las diferencias anatómicas de las hembras y machosde murinos de la cepa CD-1 en la dosimetría interna , esto se logró a través de la simulación Monte Carlo con el código de transporte Geant4, la plataforma de manejo de imágenes GATE y un maniquí especi_co por genero creado con el software MOBY. Dos modelos fueron creados con diferentes masas para calcular los valores S del radioisotopo 67Ga. La simulación fue validada calculando valores S para 18F y comparando estos valores con los reportados en otros trabajos.
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Kenned, Florêncio da Costa Roberto. "Radiografias digitais sintéticas utilizando modelos computacionais de exposição do tipo Fantomas de Voxels EGS4". Universidade Federal de Pernambuco, 2008. https://repositorio.ufpe.br/handle/123456789/9725.
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Previous issue date: 2008As imagens radiográficas quando digitalizadas podem ser agrupadas em arquivos para gerar um modelo antropomórfico de elementos de volume, chamados fantomas tal como o MAX (Male Adult voXel) e o FAX (Female Adult voXel). Estes fantomas acoplados a um código Monte Carlo, que simula o transporte de radiação na matéria como o EGS4 (Elétron Gama Shower-versão 4), e um algoritmo de uma fonte radioativa constituem um Modelo Computacional de Exposição (MCE). Este modelo além de possuir o código e a fonte radioativa, possui sub-pastas com os fantomas MAX/FAX e um código do usuário (USERCODE). Nas pastas dos fantomas MAX/FAX encontram-se arquivos importantes para execução do MCE, tais como: mspectra.dat, o pegs4.dat,o max/fax.data,o max/fax.bone.data e o expo.input que contém dados operacionais do usuário e construído com a utilização do software FANTOMAS. Na pasta USERCODE foi declarada no arquivo max/fax.code.mor uma matriz, específica para este trabalho, chamada de RADDIGITAL que é preenchida pela transferência, feita pelo software DIP (Digital Image Processing), de valores de energia (em keV) dos arquivos EnergiaPorVoxel.dat oriundos da execução do MCE. A compilação de toda massa de dados (código EGS4, fantomas MAX/FAX com seus arquivos e os arquivos da pasta USERCODE gerou os arquivos Max.for e Fax.for que recompilados e vinculados geraram os arquivos Max.exe e Fax.exe que executam os MCE. A execução dos MCE geraram arquivos externos com informações de energia depositada nos voxels. Com estes arquivos, com o fantoma segmentado e utilizando o software DIP pode-se construir fantomas de saída com base em energia depositada por voxel e com base em valores de dose efetiva. Para se obter nos fantomas baseados na dose efetiva foi criado internamente no software DIP um vetor contendo os fatores de ponderação tecidual à radiação, aqui chamados de wDIP, calculado neste trabalho com base nos dados de radiosenssibilidade da ICRP 60. Desta forma, foram obtidos os fantomas contendo informações das frações de dose efetiva dos órgãos e tecidos radiosenssíveis. Assim foi possível ajustar, por exemplo, a energia máxima para 255 no fantoma de saída, chamados de fantomas sintéticos, para se ter uma distribuição de energia resultando numa distribuição de tons de cinza similar à observada nas radiografias convencionais e nas imagens de 8 bits. Os fantomas sintéticos são uma pilha cujas vistas radiográficas sagitais, coronais e transversais, em qualquer profundidade, foram chamadas de radiografias digitais sintéticas, onde utilizou-se técnicas de realce de imagens digitais no domínio espacial com a utilização do software DIP. A utilidade clínica destes fantomas pode diminuir os erros relacionados com a excessiva repetição de exames radiográficos convencionais e reduzir assim a dose recebida pelos pacientes
Książki na temat "Modèle voxel":
1
Graham, Dennis. Vowel Sounds and Easy Words (Reading Safari Learning Module). Educational Insights, Inc, 1996.
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Module 10-Vowel Digraphs and Diphthongs: (1-3) with Book(s). Dale Seymour Publications, 2001.
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Module 10-Vowel Digraphs and Diphthongs Lab Pack: (1-3) with Book(s). Dale Seymour Publications, 2001.
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van der Hulst, Harry. Other cases of vowel harmony. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198813576.003.0010.
Streszczenie:
This Chapter discusses a number of cases of vowel harmony ‘on various continents’ and in various language families which have been reported as being either ‘unique’ (sometimes just because of their language family affiliation) or controversial in terms of their properties. Although the data on these languages is too limited to allow very specific analysis, the chapter will discuss them on the basis of the available data, and suggest ways of fitting them into the model that has been tested in the preceding six chapters. Among others, the following languages will be discussed: Middle Korean, Chukchi, Nez Perce, Karajá, Djingili, Kimaragang, Maltese, Assamese, Telugu, Pasiego Spanish, and Chamorro.
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Alban Berg und der Blaue Vogel: Eine Auto-Biographie. Wien: Alban Berg Stiftung, 2017.
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van der Hulst, Harry. Palatal harmony. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198813576.003.0004.
Streszczenie:
This chapter applies the model that was developed in Chapters 2 and 3 to some well-known and well-studied cases of palatal vowel harmony. Palatal harmony is common in, and almost confined to, Finno-Ugric and Altaic languages. In the latter, palatal harmony often co-occurs with labial harmony. The chapter first discusses variation in the behavior of neutral vowels in Balto-Finnic languages and some special cases in this family. It then analyzes palatal harmony systems in Hungarian and considers the systems of several other languages. The focus is on asymmetries in vowel harmony involving disharmonic suffixes, anti-harmonic roots, disharmonic roots, and non-alternating suffixes.
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van Rooy, Bertus. English in South Africa. Redaktorzy Markku Filppula, Juhani Klemola i Devyani Sharma. Oxford University Press, 2014. http://dx.doi.org/10.1093/oxfordhb/9780199777716.013.017.
Streszczenie:
South African English (SAfE) traces its roots to the 1820 British settlers. From here, it spread to the descendants of Indian indentured labourers, who later shifted to English as home language. English diffused as second language to the indigenous African population and speakers of Afrikaans, and today occupies an important position as language of government, education, business, and the media. SAfE has borrowed vocabulary from Afrikaans, ancestral Indian languages, and in recent years also from other South African languages. Phonetically, SAfE has raised front vowels, the short front /i/ has allophones that range from high front in KIN to centralized in PIN, and a back vowel realization of START. Non-native varieties display various degrees of vowel contrast reduction. The modal must is used more extensively than in other varieties of English, while Black SAfE also uses the progressive aspect for a wider timespan than just temporariness.
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van der Hulst, Harry. The RcvP Model. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198813576.003.0002.
Streszczenie:
The theory of phonological structure (called ‘Radical CV Phonology’) is first outlined in Chapter 2. This theory is a development of Dependency Phonology. The chapter introduces a theory of elements and minimal vowel representations based on the Successive Division Algorithm. Other topics of relevance are underspecification, markednes, and enhancement. The model of Radical CV Phonology functions as the theoretical background of the set of elements that are active in the harmony systems that will be analyzed in Chapters 4–10 and is, as such, of interest to readers who want to know why we have these particular elements.
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Beck, Joachim, Jürgen Stember i Andreas Lasar, red. Gleichwertigkeit der Lebensverhältnisse. Nomos Verlagsgesellschaft mbH & Co. KG, 2020. http://dx.doi.org/10.5771/9783748923411.
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The debate on the equality of living conditions is on the agenda not only in Germany but throughout Europe. Thematic and/or functional aspects such as centre-periphery models, demographic change, consequences of digitisation, financing aspects, innovation aspects, regional funding - Europe of the Regions, regional funds, always also raise to the structural question of how to maintain the efficiency of public administration in all regions of Europe and Germany. What challenges for the design and performance of public administration and services of general interest arise in the context of increasing social, economic and spatial segregation, and what practical answers are possible, was the topic of the 3rd conference of the Practice and Research Network of German Universities for the Public Sector, which took place on 6 and 7 February 2020 at the University of Applied Sciences in Osnabrück. The anthology presents contributions by 35 authors on the topics "European Dimension", "Territorial, technical and social innovations" and "People and work". With contributions by Hans Adam, Barbara Bartels-Leipold, Kay Bonde, Cathrin Chevalier, Saskia Ehlers, Svenja Gödecke, Arnim Goldbach, Patricia Gozalbez Cantó, Prof. Dr. Johanna Groß, Dr. Norbert Jochens, Dr. Wolfram Karg, Frank Kupferschmidt, Joachim Lippott, Rainer Lisowski, Dr. Anne Melzer, Robert Müller-Török, Martina Röhrich, Prof. Dr. iur. Christoph Schewe, M.E.S. (Salamanca), Henning Schimpf, Andreas Schmid, Katrin Stegemann, Lisa Stegemann, Christiane Trüe, Dirk Villányi and Dr. Frank Vogel.
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Ballestero, Andrea, i Brit Ross Winthereik, red. Experimenting with Ethnography. Duke University Press, 2021. http://dx.doi.org/10.1215/9781478013211.
Streszczenie:
Experimenting with Ethnography collects twenty-one essays that open new paths for doing ethnographic analysis. The contributors—who come from a variety of intellectual and methodological traditions—enliven analysis by refusing to take it as an abstract, disembodied exercise. Rather, they frame it as a concrete mode of action and a creative practice. Encompassing topics ranging from language and the body to technology and modes of collaboration, the essays invite readers to focus on the imaginative work that needs to be performed prior to completing an argument. Whether exchanging objects, showing how to use drawn images as a way to analyze data, or working with smartphones, sound recordings, and social media as analytic devices, the contributors explore the deliberate processes for pursuing experimental thinking through ethnography. Practical and broad in theoretical scope, Experimenting with Ethnography is an indispensable companion for all ethnographers. Contributors. Patricia Alvarez Astacio, Andrea Ballestero, Ivan da Costa Marques, Steffen Dalsgaard, Endre Dányi, Marisol de la Cadena, Marianne de Laet, Carolina Domínguez Guzmán, Rachel Douglas-Jones, Clément Dréano, Joseph Dumit, Melanie Ford Lemus, Elaine Gan, Oliver Human, Alberto Corsín Jiménez, Graham M. Jones, Trine Mygind Korsby, Justine Laurent, James Maguire, George E. Marcus, Annemarie Mol, Sarah Pink, Els Roding, Markus Rudolfi, Ulrike Scholtes, Anthony Stavrianakis, Lucy Suchman, Katie Ulrich, Helen Verran, Else Vogel, Antonia Walford, Karen Waltorp, Laura Watts, Brit Ross Winthereik
Części książek na temat "Modèle voxel":
1
Vago, Robert M. "Vowel harmony in Finnish word games". W Linguistic Models, redaktorzy Harry van der Hulst i Norval Smith, 185–208. Berlin, Boston: De Gruyter, 1988. http://dx.doi.org/10.1515/9783110250497-010.
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Anderson, John, i Jacques Durand. "Vowel harmony and non-specification in Nez Perce". W Linguistic Models, redaktorzy Harry van der Hulst i Norval Smith, 1–18. Berlin, Boston: De Gruyter, 1988. http://dx.doi.org/10.1515/9783110250497-003.
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Jense, G. J., i D. P. Huijsmans. "Spatial Editing for Interactive Inspection of Voxel Models". W Visualization in Scientific Computing, 163–77. Berlin, Heidelberg: Springer Berlin Heidelberg, 1994. http://dx.doi.org/10.1007/978-3-642-77902-2_16.
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Sluyters, Willebrord. "Vowel harmony, rule formats and underspeciflcation: the dialect of Francavilla-Fontana". W Linguistic Models, redaktorzy Harry van der Hulst i Norval Smith, 161–84. Berlin, Boston: De Gruyter, 1988. http://dx.doi.org/10.1515/9783110250497-009.
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Zaugg, Brian, i Parris K. Egbert. "Voxel Column Culling: Occlusion Culling for Large Terrain Models". W Eurographics, 85–93. Vienna: Springer Vienna, 2001. http://dx.doi.org/10.1007/978-3-7091-6215-6_10.
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Schlattl, H., M. Zankl i C. Hoeschen. "Implementation of Tube Current Modulation in CT Dose Computations with Voxel Models". W IFMBE Proceedings, 329–32. Berlin, Heidelberg: Springer Berlin Heidelberg, 2009. http://dx.doi.org/10.1007/978-3-642-03902-7_93.
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Bäumler, Linda, i Frederik Hartmann. "Sociogeographical differences in the pronunciation of Anglicisms in Spanish". W Studies in Corpus Linguistics, 106–32. Amsterdam: John Benjamins Publishing Company, 2023. http://dx.doi.org/10.1075/scl.110.05bau.
Streszczenie:
In this paper we propose a possible statistical analysis of sociogeographical differences in two Spanish varieties in the context of loanword phonology. For this purpose, we extracted formant frequencies of Anglicisms from corpus data from Mexico and Spain, with a particular focus on the realisation of the English vowel /ʌ/ (e.g., [bɾʌnt͡ʃ]). We used a Multilevel Bayesian regression model to infer various fixed effects on the phonic realisation. The analysis shows that geographical proximity to the U.S. does not impact the realisation in our data. Speakers’ exposure and affinity towards the English language, on the other hand, favour imitation of the English vowel. This seems to be especially relevant in our globalised world, where English media are ubiquitously available.
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Peuchen, J., W. van Kesteren, V. Vandeweijer, S. Carpentier i F. van Erp. "Upscaling 1 500 000 synthetic CPTs to voxel CPT models of offshore sites". W Cone Penetration Testing 2022, 641–45. London: CRC Press, 2022. http://dx.doi.org/10.1201/9781003329091-93.
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Peuchen, J., W. van Kesteren, V. Vandeweijer, S. Carpentier i F. van Erp. "Upscaling 1 500 000 synthetic CPTs to voxel CPT models of offshore sites". W Cone Penetration Testing 2022, 641–45. London: CRC Press, 2022. http://dx.doi.org/10.1201/9781003308829-93.
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Hemmat, Hani Javan, Egor Bondarev i Peter H. N. de With. "Exploring Distance-Aware Weighting Strategies for Accurate Reconstruction of Voxel-Based 3D Synthetic Models". W MultiMedia Modeling, 412–23. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-04114-8_35.
Streszczenia konferencji na temat "Modèle voxel":
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Kniaz, Vladimir Vladimirovich, Petr V. Moshkantsev, Artem N. Bordodymov, Vladimir A. Mizginov i Daniil I. Novikov. "Semantic 3D Reconstruction of a Scene and Its Effective Visualisation". W 32nd International Conference on Computer Graphics and Vision. Keldysh Institute of Applied Mathematics, 2022. http://dx.doi.org/10.20948/graphicon-2022-179-193.
Streszczenie:
Single-image 3D scene reconstruction is required in multiple challenging tasks including mobile robotics, industrial monitoring and reconstruction of lost cultural heritage. While modern models demonstrate robust resolution of scene in real time with resolution up to 128 x 128 x 128 voxels, visualization of such detailed of a such detailed voxel model is challenging. A model with 128<sup>3</sup> voxels contains 2097152 simple cubes 16M vertices. It is unfeasible for modern hardware to perform visualization of such voxel models in real-time. Hence a voxel model simplification technique is required to demonstrate reconstruction results in real-time. In this paper, we propose a new algorithm for voxel model simplification using predefined camera views. The algorithm reduces a rigid-body voxel model to a shell voxel model. It keeps only the voxels that are visible from the required view. We demonstrate the effectiveness of the proposed algorithm using a case study with a mobile robot and a state-of-the-art SSZ single-photo 3D reconstruction neural network. We generated a real and a virtual scene with various objects including a statue. We use a mobile robot equipped with a single camera to collect real and synthetic data. We train the SSZ model using the collected data. We developed a dedicated visualization software that implements our algorithm. The comparison of the visualization performance for the full model and its reduced version demonstrates that our algorithm allows to increase the performance by 420 times.
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Wu, Jun, Ge Yu, Dangxiao Wang, Yuru Zhang i Charlie C. L. Wang. "Voxel-Based Interactive Haptic Simulation of Dental Drilling". W ASME 2009 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/detc2009-86661.
Streszczenie:
Haptics is one of the most important sensations for dentists to prepare cavity in dental surgery, which is however not easy to simulate in a computer system because of the large drilling force and the small speed of movement and material removal. In this paper, we present a fully voxel-based approach to interactively simulate dental drilling. Different from those voxel/mesh hybrid models, the drilling forces are computed directly from the voxel-representation while considering the factors of teeth’s material properties, the posture and forward speed of dentist’s drill and the contact surface area. To overcome force discontinuity caused by removal of tooth material, we define two layers of voxels on drill, where the boundary voxels are only employed to compute force feedback and the interior voxels are adopted to remove materials from teeth. The experimental result shows that our force model can produce smooth and large force feedback at a slow movement on haptic devices. Other than haptic rendering, a real-time filtering method directly using voxel representation has also been developed to improve visual rendering in dental simulation.
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Nishida, Isamu, Ryuma Okumura, Ryuta Sato i Keiichi Shirase. "Cutting Force Prediction of Ball End Milling Based on Fully Voxel Representation of Cutting Edge and Instantaneous Workpiece Shape". W ASME 2017 12th International Manufacturing Science and Engineering Conference collocated with the JSME/ASME 2017 6th International Conference on Materials and Processing. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/msec2017-2777.
Streszczenie:
A new cutting force simulator has been developed to predict cutting force in ball end milling. This new simulator discretely calculates uncut chip thickness based on a fully voxel representation of the cutting edge and instantaneous workpiece shape. Previously, a workpiece voxel model was used to calculate uncut chip thickness under a complex change of workpiece shape. Using a workpiece voxel model, uncut chip thickness is detected by extracting the voxels removed per cutting edge tooth for the amount of material fed into the cutting edge. However, it is difficult to define the complicated shape of a cutting edge using the workpiece voxel model; the shape of the cutting edge must be defined by a mathematical expression. It is also difficult to model the voxels removed by the cutting edge when the tool posture is non-uniformly changed. We therefore propose a new method to detect uncut chip thickness, one in which both the cutting edge and the instantaneous workpiece shape are fully represented by a voxel model. Our proposed method precisely detects uncut chip thickness at minute tool rotational angles, making it possible to detect the uncut chip thickness between the complex surface shape of the workpiece and the particular shape of the cutting edge. To validate the effectiveness of our proposed method, experimental 5-axis milling tests using a ball end mill were conducted. Estimated milling forces for several tool postures were found to be in good agreement with the measured milling forces. Results from the experimental 5-axis milling validate the effectiveness of our proposed method.
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Zhou, Bin, Ji Wang, Arnav Sanyal, Aaron J. Fields, Hong Wang, Tony M. Keaveny, Baohua Ji, X. Sherry Liu i X. Edward Guo. "Individual Trabecula Segmentation (ITS)-Based Plate-Rod Microstructural Finite Element Model Predicts Nonlinear Mechanical Properties of Human Trabecular Bone". W ASME 2012 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/sbc2012-80652.
Streszczenie:
Osteoporosis is a major bone disease characterized by low bone mass and microarchitecture deterioration, which affects primarily trabecular sites and leads to increased bone fragility. Trabecular bone mechanical properties have direct relations with bone fragility. High-resolution image based-finite element (FE) models with the detailed 3D microstructure have been widely utilized to assess the mechanical properties of trabecular bone. Voxel-based FE model can be generated by converting individual voxels of high resolution bone images into 8-node brick elements. A number of studies have compared mechanical properties predicted by the voxel model with those by mechanical testing and have demonstrated that the voxel FE model can accurately predict the Young’s modulus and yield strength of human trabecular bone (1). However, the computational expense of the voxel-based technique, in general, limits its clinical applications, especially the nonlinear analysis for whole bone strength. Thus, it is not applicable to apply this technique to clinical use with the respect of current computer capability. There is apparent need for an alternative modeling approach that is more computationally efficient while preserving the accuracy of the predictions.
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Chan, Rothanak, Karl R. Haapala i Matthew I. Campbell. "Assessing Component Machinability Using Voxelized Solid Models". W ASME 2018 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/detc2018-86022.
Streszczenie:
New automated approaches in design often generate nonmanufacturable component geometries. Improved machinability of topology optimized parts, for example, has been under exploration for over a decade with limited success. Recent work is pursuing novel design approaches enabled by developments in voxel-based representation and advanced process technologies. Research reported here suggests a featureless approach for analyzing the machinability of a given geometry using voxels. The input is a tessellated shape, which is converted into a voxel representation. The voxelized shape is then filled in the orthogonal toolpath directions defined by the minimum bounding box to approximate the reach of the cutting tool in each part orientation. The filled shapes are intersected with each other to achieve a solid representation that can be readily accessed by a cutting tool. Overlaying this solid shape against the original tessellated shape will highlight the non-machinable regions of the part when visualized. The volume of non-machinable material can be estimated and used to inform a larger search process for separating and adding part features together to improve component manufacturability.
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Eichler, Mark J., Chi Hyun Kim, Ralph Müller i X. Edward Guo. "Impact of Thresholding Techniques on Micro-CT Image Based Computational Models of Trabecular Bone". W ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-2588.
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Abstract Age-related bone fractures are mostly influenced by trabecular bone sites. Trabecular bone constantly adapts its bone volume fraction (BV/TV) and orientation, and thus its mechanical properties, to mechanical usage. Therefore, understanding the trabecular bone adaptation process and its consequences will contribute to the better understanding of the etiology of age-related fractures. Micro-computed tomography (micro-CT) is a relatively new method to quantify the complex three-dimensional (3D) trabecular bone architecture [1,2]. Finite element computational studies can be performed on these 3D microstructural images by converting each image voxel into an element [3,4,5]. Image thresholding techniques to segment bone voxels from bone marrow voxels have a major impact on the results of these models. However, the influence of different types of thresholding techniques on the mechanical properties of bone has not been examined carefully.
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Tonshal, Basavaraj, Yifan Chen i Pietro Buttolo. "Determine Mesh Orientation by Voxel-Based Principal Component Analysis". W ASME 2006 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/detc2006-99380.
Streszczenie:
In this paper we propose a new method to determine the part orientation of a 3D mesh based on Principal Component Analysis (PCA). Although the idea and practice of using PCA to determine part orientation is not new, it is not without practical issues. A major drawback of PCA, when it comes to dealing with meshes comprised of nodes and elements, is that the results are tessellation-dependent because of its sensitivity to variability. Two CAE meshes derived from the same CAD model but with different mesh node distribution characteristics, for instance, can yield different principal components. This is an undesirable outcome because the primary concern in model reorientation is shape, not the representational details of the shape. In order to reduce the influence of node characteristics, weight factors were proposed in the past, but the improvement is limited. To overcome this limitation, we must eliminate the influence of mesh node distribution. We achieve this by introducing an intermediate workspace, which is subsequently voxelized. We then find the intersection of the mesh model with the voxelized workspace. We collect the intersecting voxels to form an intermediate, tessellation-independent representation of the mesh. Applying PCA to this “neutralized” representation allows us to achieve mesh-property-independent results. The voxel representation also provides an opportunity of computational efficiency. We implemented an octree data structure to store the voxels and implemented a fast intersection (between a mesh element and a voxel) check procedure utilizing the interval overlap check derived from the separating axis theorem. Practical issues concerning determination of the voxel space resolution is addressed. A two-step trial and correction approach is proposed to enhance the consistency of results. Our voxel-based PCA is robust, fast, and straightforward to implement. Application examples are shown demonstrating the effectiveness and efficiency of this approach.
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Young, Jonathan M., Eric M. Beecher, Benjamen A. Filas, Larry A. Taber i Renato Perucchio. "FEM Voxel Modeling of the Tubular Embryonic Chick Heart for Finite Strain Analysis". W ASME 2008 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2008. http://dx.doi.org/10.1115/sbc2008-192756.
Streszczenie:
Significant progress has been made in the study of the developmental biomechanics of the embryonic chick heart through the use of the finite element method (FEM) [1, 2, 3]. Our work focuses on the geometry of the Hamburger-Hamilton stages 9–12 embryonic chick heart, approximately the time when the heart begins to function and undergoes drastic morphological changes, such as c-looping. Our objective is to devise a method for building an accurate 3D solid FEM mesh used for nonlinear analysis of the myocardium (MY) and cardiac jelly (CJ). The models are based on the extraction of voxels from optical coherence tomography (OCT) images of an arrested developing heart. To alleviate the problem of jagged edges introduced by the hexahedral voxel structure, we present a method for geometric smoothing and mesh coarsening. The performance of the voxel and smoothed models are tested given physiological loading conditions (pressure, biological growth, muscle contraction), to ascertain which model should be used for modeling the c-looping process.
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Pigazzi, Riccardo, Michele Bertolini, Marco Rossoni i Giorgio Colombo. "Voxel Printing of a Multi-Material 3D Printed Prosthetic Socket Based on FEM Simulations". W ASME 2023 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2023. http://dx.doi.org/10.1115/imece2023-113297.
Streszczenie:
Abstract Prosthetic socket for lower limb amputation needs to be customized based on the residual limb characteristics to satisfy functional and comfort requirements. One of the main causes for ill-fitting socket is the lack of appropriate application of material properties that match the characteristics of the amputee’s biological tissue. Additive manufacturing has the ability to confer inhomogeneous properties to the printed object. This paper presents a digital workflow for the design and fabrication of a prosthetic socket based on the results of numerical simulations and the use of multi-material voxel printing. A voxel model of the socket is generated and the contact pressure between the residual limb and the socket derived from FEA is mapped to the voxels, which were correspondingly assigned a material. This allow to define a material distribution at the voxel level and to generate printing instructions as a stack of bitmap images for voxel printing. The goal is to obtain a socket characterized by a spatial variation of material stiffness, according to the pressure map extracted from simulation, in order to adapt the socket to the patient’s anatomy and, consequently, to reduce contact pressure and discomfort.
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Mell, Maggie Mae, i Thomas Naselaris. "Voxel to voxel encoding models reveal unexpected structure in unexplained variance". W 2018 Conference on Cognitive Computational Neuroscience. Brentwood, Tennessee, USA: Cognitive Computational Neuroscience, 2018. http://dx.doi.org/10.32470/ccn.2018.1255-0.
Raporty organizacyjne na temat "Modèle voxel":
1
Nieto-Castanon, Alfonso. CONN functional connectivity toolbox (RRID:SCR_009550), Version 18. Hilbert Press, 2018. http://dx.doi.org/10.56441/hilbertpress.1818.9585.
Streszczenie:
CONN is a Matlab-based cross-platform software for the computation, display, and analysis of functional connectivity in fMRI (fcMRI). Connectivity measures include seed-to-voxel connectivity maps, ROI-to- ROI connectivity matrices, graph properties of connectivity networks, generalized psychophysiological interaction models (gPPI), intrinsic connectivity, local correlation and other voxel-to-voxel measures, independent component analyses (ICA), and dynamic component analyses (dyn-ICA). CONN is available for resting state data (rsfMRI) as well as task-related designs. It covers the entire pipeline from raw fMRI data to hypothesis testing, including spatial coregistration, ART-based scrubbing, aCompCor strategy for control of physiological and movement confounds, first-level connectivity estimation, and second-level random-effect analyses and hypothesis testing.
2
Nieto-Castanon, Alfonso. CONN functional connectivity toolbox (RRID:SCR_009550), Version 20. Hilbert Press, 2020. http://dx.doi.org/10.56441/hilbertpress.2048.3738.
Streszczenie:
CONN is a Matlab-based cross-platform software for the computation, display, and analysis of functional connectivity in fMRI (fcMRI). Connectivity measures include seed-to-voxel connectivity maps, ROI-to- ROI connectivity matrices, graph properties of connectivity networks, generalized psychophysiological interaction models (gPPI), intrinsic connectivity, local correlation and other voxel-to-voxel measures, independent component analyses (ICA), and dynamic component analyses (dyn-ICA). CONN is available for resting state data (rsfMRI) as well as task-related designs. It covers the entire pipeline from raw fMRI data to hypothesis testing, including spatial coregistration, ART-based scrubbing, aCompCor strategy for control of physiological and movement confounds, first-level connectivity estimation, and second-level random-effect analyses and hypothesis testing.
3
Nieto-Castanon, Alfonso. CONN functional connectivity toolbox (RRID:SCR_009550), Version 19. Hilbert Press, 2019. http://dx.doi.org/10.56441/hilbertpress.1927.9364.
Streszczenie:
CONN is a Matlab-based cross-platform software for the computation, display, and analysis of functional connectivity in fMRI (fcMRI). Connectivity measures include seed-to-voxel connectivity maps, ROI-to- ROI connectivity matrices, graph properties of connectivity networks, generalized psychophysiological interaction models (gPPI), intrinsic connectivity, local correlation and other voxel-to-voxel measures, independent component analyses (ICA), and dynamic component analyses (dyn-ICA). CONN is available for resting state data (rsfMRI) as well as task-related designs. It covers the entire pipeline from raw fMRI data to hypothesis testing, including spatial coregistration, ART-based scrubbing, aCompCor strategy for control of physiological and movement confounds, first-level connectivity estimation, and second-level random-effect analyses and hypothesis testing.
4
Bolch, Wesley. MicroCT-Based Skeletal Models for Use in Tomographic Voxel Phantoms for Radiological Protection. Office of Scientific and Technical Information (OSTI), marzec 2010. http://dx.doi.org/10.2172/978474.
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Gold, Bernard. Hopfield Model Applied to Vowel and Consonant Discrimination. Fort Belvoir, VA: Defense Technical Information Center, czerwiec 1986. http://dx.doi.org/10.21236/ada169742.