Bibliographies thématiques / Reconstruction de la densité

Littérature scientifique sur le sujet « Reconstruction de la densité »

Auteur : Grafiati
Publié le 24 février 2024

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Articles de revues sur le sujet "Reconstruction de la densité"

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Rutherford, S., M. E. Mann, T. J. Osborn, K. R. Briffa, P D Jones, R. S. Bradley et M. K. Hughes. « Proxy-Based Northern Hemisphere Surface Temperature Reconstructions : Sensitivity to Method, Predictor Network, Target Season, and Target Domain ». Journal of Climate 18, no 13 (1 juillet 2005) : 2308–29. http://dx.doi.org/10.1175/jcli3351.1.

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Abstract Results are presented from a set of experiments designed to investigate factors that may influence proxy-based reconstructions of large-scale temperature patterns in past centuries. The factors investigated include 1) the method used to assimilate proxy data into a climate reconstruction, 2) the proxy data network used, 3) the target season, and 4) the spatial domain of the reconstruction. Estimates of hemispheric-mean temperature are formed through spatial averaging of reconstructed temperature patterns that are based on either the local calibration of proxy and instrumental data or a more elaborate multivariate climate field reconstruction approach. The experiments compare results based on the global multiproxy dataset used by Mann and coworkers, with results obtained using the extratropical Northern Hemisphere (NH) maximum latewood tree-ring density set used by Briffa and coworkers. Mean temperature reconstructions are compared for the full NH (Tropics and extratropics, land and ocean) and extratropical continents only, withvarying target seasons (cold-season half year, warm-season half year, and annual mean). The comparisons demonstrate dependence of reconstructions on seasonal, spatial, and methodological considerations, emphasizing the primary importance of the target region and seasonal window of the reconstruction. The comparisons support the generally robust nature of several previously published estimates of NH mean temperature changes in past centuries and suggest that further improvements in reconstructive skill are most likely to arise from an emphasis on the quality, rather than quantity, of available proxy data.
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Rus, Guillermo, et Juan Melchor. « Logical Inference Framework for Experimental Design of Mechanical Characterization Procedures ». Sensors 18, no 9 (7 septembre 2018) : 2984. http://dx.doi.org/10.3390/s18092984.

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Optimizing an experimental design is a complex task when a model is required for indirect reconstruction of physical parameters from the sensor readings. In this work, a formulation is proposed to unify the probabilistic reconstruction of mechanical parameters and an optimization problem. An information-theoretic framework combined with a new metric of information density is formulated providing several comparative advantages: (i) a straightforward way to extend the formulation to incorporate additional concurrent models, as well as new unknowns such as experimental design parameters in a probabilistic way; (ii) the model causality required by Bayes’ theorem is overridden, allowing generalization of contingent models; and (iii) a simpler formulation that avoids the characteristic complex denominator of Bayes’ theorem when reconstructing model parameters. The first step allows the solving of multiple-model reconstructions. Further extensions could be easily extracted, such as robust model reconstruction, or adding alternative dimensions to the problem to accommodate future needs.
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Ionita, Sabina, Serban Popescu et Ioan Lascar. « Polypropylene meshes and other alloplastic implants for soft tissue and cartilage nasal reconstructive surgery – a literature review ». Romanian Journal of Rhinology 5, no 18 (1 juin 2015) : 87–94. http://dx.doi.org/10.1515/rjr-2015-0010.

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Abstract BACKGROUND. The reconstructive surgery is a domain in continuous research for new techniques and alloplastic materials for replacement of complex defects. Different biomaterials are used in soft tissue reconstruction including polypropylene meshes covered with collagen, which have the best results in abdominal and pelvic surgery, but are not yet used in nasal surgery. MATERIAL AND METHODS. We analysed the studies from the literature regarding the different alloplastic implants used in nasal reconstruction surgery, their benefits and contraindications for nasal defects. RESULTS. The most used polymers are Silicone, Medpor®, Mersilene® and polypropylene. Silicone is no longer widely used in facial reconstructive surgery because of its many complications. Medpor® (high-density polyethylene) is used for reconstruction of the facial skeleton and for aesthetic contour enhancement, including nasal reconstruction. Mersilene® (polyethylene terephthalate) is used for dorsum nasal defect reconstruction. Gore-Tex® is used for soft-tissue augmentation in the nose and is not recommended as a structural graft. Polypropylene meshes (Marlex®) are widely used in abdominal and chest wall reconstructive surgeries, with few studies on using them in nasal cartilage reconstruction. CONCLUSION. Nasal reconstructive surgery is a difficult part of plastic surgery than can cause many problems to the surgeon, the need for soft tissue and cartilage reconstruction are difficult to solve in a repeatedly operated nose with few autogenous graft options and complex reconstructive surgeries, especially in posttraumatic defects and revision rhinoplasties. There are many alloplastic implants that can be used with excellent results.
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Durbec, M., N. Mayer, D. Vertu-Ciolino, F. Disant, F. Mallein-Gerin et E. Perrier-Groult. « Reconstruction du cartilage nasal par ingénierie tissulaire à base de polyéthylène de haute densité et d’un hydrogel ». Pathologie Biologie 62, no 3 (juin 2014) : 137–45. http://dx.doi.org/10.1016/j.patbio.2014.03.001.

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Hasenberger, Birgit, et João Alves. « AVIATOR : Morphological object reconstruction in 3D ». Astronomy & ; Astrophysics 633 (janvier 2020) : A132. http://dx.doi.org/10.1051/0004-6361/201936095.

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Reconstructing 3D distributions from their 2D projections is a ubiquitous problem in various scientific fields, particularly so in observational astronomy. In this work, we present a new approach to solving this problem: a Vienna inverse-Abel-transform based object reconstruction algorithm AVIATOR. The reconstruction that it performs is based on the assumption that the distribution along the line of sight is similar to the distribution in the plane of projection, which requires a morphological analysis of the structures in the projected image. The output of the AVIATOR algorithm is an estimate of the 3D distribution in the form of a reconstruction volume that is calculated without the problematic requirements that commonly occur in other reconstruction methods such as symmetry in the plane of projection or modelling of radial profiles. We demonstrate the robustness of the technique to different geometries, density profiles, and noise by applying the AVIATOR algorithm to several model objects. In addition, the algorithm is applied to real data: We reconstruct the density and temperature distributions of two dense molecular cloud cores and find that they are in excellent agreement with profiles reported in the literature. The AVIATOR algorithm is thus capable of reconstructing 3D distributions of physical quantities consistently using an intuitive set of assumptions.
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He, Yuhang, Zhiheng Ma, Xing Wei, Xiaopeng Hong, Wei Ke et Yihong Gong. « Error-Aware Density Isomorphism Reconstruction for Unsupervised Cross-Domain Crowd Counting ». Proceedings of the AAAI Conference on Artificial Intelligence 35, no 2 (18 mai 2021) : 1540–48. http://dx.doi.org/10.1609/aaai.v35i2.16245.

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This paper focuses on the unsupervised domain adaptation problem for video-based crowd counting, in which we use labeled data as source domain and unlabelled video data as target domain. It is challenging as there is a huge gap between the source and the target domain and no annotations of samples are available in the target domain. The key issue is how to utilize unlabelled videos in the target domain for knowledge learning and transferring from the source domain. To tackle this problem, we propose a novel Error-aware Density Isomorphism REConstruction Network (EDIREC-Net) for cross-domain crowd counting. EDIREC-Net jointly transfers a pre-trained counting model to target domains using a density isomorphism reconstruction objective and models the reconstruction erroneousness by error reasoning. Specifically, as crowd flows in videos are consecutive, the density maps in adjacent frames turn out to be isomorphic. On this basis, we regard the density isomorphism reconstruction error as a self-supervised signal to transfer the pre-trained counting models to different target domains. Moreover, we leverage an estimation-reconstruction consistency to monitor the density reconstruction erroneousness and suppress unreliable density reconstructions during training. Experimental results on four benchmark datasets demonstrate the superiority of the proposed method and ablation studies investigate the efficiency and robustness. The source code is available at https://github.com/GehenHe/EDIREC-Net.
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Jäger, M., P. Hübner, D. Haitz et B. Jutzi. « A COMPARATIVE NEURAL RADIANCE FIELD (NERF) 3D ANALYSIS OF CAMERA POSES FROM HOLOLENS TRAJECTORIES AND STRUCTURE FROM MOTION ». International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLVIII-1/W1-2023 (25 mai 2023) : 207–13. http://dx.doi.org/10.5194/isprs-archives-xlviii-1-w1-2023-207-2023.

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Abstract. Neural Radiance Fields (NeRFs) are trained using a set of camera poses and associated images as input to estimate density and color values for each position. The position-dependent density learning is of particular interest for photogrammetry, enabling 3D reconstruction by querying and filtering the NeRF coordinate system based on the object density. While traditional methods like Structure from Motion are commonly used for camera pose calculation in pre-processing for NeRFs, the HoloLens offers an interesting interface for extracting the required input data directly. We present a workflow for high-resolution 3D reconstructions almost directly from HoloLens data using NeRFs. Thereby, different investigations are considered: Internal camera poses from the HoloLens trajectory via a server application, and external camera poses from Structure from Motion, both with an enhanced variant applied through pose refinement. Results show that the internal camera poses lead to NeRF convergence with a PSNR of 25 dB with a simple rotation around the x-axis and enable a 3D reconstruction. Pose refinement enables comparable quality compared to external camera poses, resulting in improved training process with a PSNR of 27 dB and a better 3D reconstruction. Overall, NeRF reconstructions outperform the conventional photogrammetric dense reconstruction using Multi-View Stereo in terms of completeness and level of detail.
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Skamarock, William C., et Maximo Menchaca. « Conservative Transport Schemes for Spherical Geodesic Grids : High-Order Reconstructions for Forward-in-Time Schemes ». Monthly Weather Review 138, no 12 (1 décembre 2010) : 4497–508. http://dx.doi.org/10.1175/2010mwr3390.1.

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Abstract The finite-volume transport scheme of Miura, for icosahedral–hexagonal meshes on the sphere, is extended by using higher-order reconstructions of the transported scalar within the formulation. The use of second- and fourth-order reconstructions, in contrast to the first-order reconstruction used in the original scheme, results in significantly more accurate solutions at a given mesh density, and better phase and amplitude error characteristics in standard transport tests. The schemes using the higher-order reconstructions also exhibit much less dependence of the solution error on the time step compared to the original formulation. The original scheme of Miura was only tested using a nondeformational time-independent flow. The deformational time-dependent flow test used to examine 2D planar transport in Blossey and Durran is adapted to the sphere, and the schemes are subjected to this test. The results largely confirm those generated using the simpler tests. The results also indicate that the scheme using the second-order reconstruction is most efficient and its use is recommended over the scheme using the first-order reconstruction. The second-order reconstruction uses the same computational stencil as the first-order reconstruction and thus does not create any additional parallelization issues.
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Kunz, Torben, Andrew M. Dolman et Thomas Laepple. « A spectral approach to estimating the timescale-dependent uncertainty of paleoclimate records – Part 1 : Theoretical concept ». Climate of the Past 16, no 4 (11 août 2020) : 1469–92. http://dx.doi.org/10.5194/cp-16-1469-2020.

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Abstract. Proxy records represent an invaluable source of information for reconstructing past climatic variations, but they are associated with considerable uncertainties. For a systematic quantification of these reconstruction errors, however, knowledge is required not only of their individual sources but also of their auto-correlation structure as this determines the timescale dependence of their magnitude, an issue that has been often ignored until now. Here a spectral approach to uncertainty analysis is provided for paleoclimate reconstructions obtained from single sediment proxy records. The formulation in the spectral domain rather than the time domain allows for an explicit demonstration and quantification of the timescale dependence that is inherent in any proxy-based reconstruction uncertainty. This study is published in two parts. In this first part, the theoretical concept is presented, and analytic expressions are derived for the power spectral density of the reconstruction error of sediment proxy records. The underlying model takes into account the spectral structure of the climate signal, seasonal and orbital variations, bioturbation, sampling of a finite number of signal carriers, and uncorrelated measurement noise, and it includes the effects of spectral aliasing and leakage. The uncertainty estimation method, based upon this model, is illustrated by simple examples. In the second part of this study, published separately, the method is implemented in an application-oriented context, and more detailed examples are presented.
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Soufan, Alexandre T., Jan M. Ruijter, Maurice JB Van Den Hoff et Antoon FM Moorman. « QUANTITATIVE 3D RECONSTRUCTIONS AS IDENTIFICATION TOOL IN HEART DEVELOPMENT ». Image Analysis & ; Stereology 20, no 3 (3 mai 2011) : 193. http://dx.doi.org/10.5566/ias.v20.p193-198.

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A method for displaying quantitative information in 3D reconstructions of the embryonic heart was developed to investigate spatial distributions of cell division and cell density. The method utilizes serial sections to extract morphological as well as quantitative data. The morphological data are used to reconstruct the embryonic heart and the quantitative data are classified and superimposed on the resulting reconstruction. The bias, which would result from size differences between cell populations, was investigated. If present, it would influence the absolute number of particles (nuclei) per volume, although the classification applied on the reconstruction displaying the mitotic fraction remains unchanged. Although the reconstruction displaying the local densities is influenced by the bias, less than 2.5% of the regions is misclassified.
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Thèses sur le sujet "Reconstruction de la densité"

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Yan, Zeyin. « Reconstruction de densité d'impulsion et détermination de la matrice densité réduite à un électron ». Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC001/document.

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La diffraction des rayons X à haute résolution (XRD) et celle des neutrons polarisés (PND) sont couramment utilisées pour modéliser les densités de charge et de spin dans l'espace des positions. Par ailleurs, la diffusion Compton et diffusion Compton magnétiques sont utilisées pour observer les plus diffus des électrons appariés et non appariés, en fournissant les profils Compton directionnels de charge (DCPs) et les profils Compton magnétique directionnels (DMCPs). Il est possible d'utiliser plusieurs DCPs et DMCPs non équivalents pour reconstituer la densité d'impulsion à deux ou trois dimensions. Puisque toutes ces techniques décrivent les mêmes électrons dans différentes représentations, nous nous concentrons sur l'association de la densité d'impulsion, reconstituée par DCPs (DMCPs) avec la densité de charge et spin, telle que déterminée à parties données XRD (PND).La confrontation théorie-experience, ou --plus rarement-- entre différentes techniques expérimentales, requièrent généralement les representations des densités reconstruites dans les espaces des positions et des impulsions. Le défi que pose la comparaison des résultats obtenus par calculs ab-initio et par des approches expérimentales (dans le cas de Nit(SMe)Ph) montre la nécessité de combiner plusieurs expériences et celle d'améliorer les modèles sur lesquels reposent les approches théoriques. Nous montrons que, dans le cas d'une densité de probabilité de présence d'électrons résolue en spin, une approche simple de type Hartree-Fock ou DFT ne suffit pas. Dans le cas de YTiO3, une analyse conjointe des espaces position et impulsion (PND & MCS) met en évidence un possible couplage ferromagnétique selon Ti--O1-Ti. Pour cela, une densité magnétique de "super-position" est proposée et s'avère permettre une vérification aisée de la cohérence entre densité de charge (spin) et densité de 'impulsion déterminées expérimentalement, sans la nécessité d'une étape ab-initio. Pour aller plus loin, un modèle "de Ti isolé", basé sur des coefficients orbitaux affinés par PND, souligne l'importance du couplage cohérent métal-oxygène nécessaire à rendre compte des observations dans l'espace des impulsions.La matrice densité réduite à un électron (1-RDM) est proposée comme socle de base permettant de systématiquement combiner les espaces des positions et des impulsions. Pour reconstruire cette 1-RDM à partir d'un calcul ab-initio périodique, une approche "cluster" est proposée. Il devient alors possible d'obtenir la 1-RDM théorique résolue en spin sur des chemins de liaison chimique particuliers. Ceci nous permet notamment de clarifier la différence entre les couplages Ti--O1--Ti et Ti-O2--Ti. Il est montré que l'importance des contributions du terme d'interaction entre les atomes (de métal et d'oxygène) est différente selon que l'on considère une représentation des propriétés dans l'espace des positions ou des impulsions. Ceci est clairement observé dans les liaisons chimiques métal-oxygène et peut être illustré par une analyse séparant les contributions par orbitales. Les grandeurs decrivant les électrons dans l'espace des phases comme la fonction de Moyal peuvent également être déterminées par cette construction en "cluster". Ceci peut revêtir un intérêt particulier si la technique de diffusion Compton aux positions de Bragg pouvait être généralisée. Les premiers résultats d'un affinement de modèle simple de 1-RDM résolu en spin sont exposés. Le modèle respecte la N-représentabilité et est adapté pour plusieurs données expérimentales (telles que XRD, PND, CS, MCS ou XMD). Le potentiel de ce modèle n'est pas limité à une analyse en spin mais son usage est ici circonscrit à la description des électrons non appariés, ses limites sont identifiées et des voies d'amélioration future sont proposées
High resolution X-ray diffraction (XRD) and polarized neutron diffraction (PND) are commonly used to model charge and spin densities in position space. Additionally, Compton scattering (CS) and magnetic Compton scattering (MCS) are the main techniques to observe the most diffuse electrons and unpaired electrons by providing the “Directional Compton Profiles" (DCPs) and ”Directional magnetic Compton Profiles" (DMCPs), respectively. A set of such DCPs (DMCPs) can be used to reconstruct two-dimensional or three-dimensional electron momentum density. Since all these techniques describe the same electrons in different space representations, we concentrate on associating the electron momentum density reconstructed from DCPs (resp. DMCPs) with electron density refined using XRD (resp. PND) data.The confrontation between theory and experiment, or between different experiments, providing several sets of experimental data, is generally obtained from the reconstructed electron densities and compared with theoretical results in position and momentum spaces. The challenge of comparing the results obtained by ab-initio computations and experimental approaches (in the Nit(SMe)Ph case) shows the necessity of a multiple experiments joint refinement and also the improvement of theoretical computation models. It proves that, in the case of a spin resolved electron density, a mere Hartree-Fock or DFT approach is not sufficient. In the YTiO3 case, a joint analysis of position and momentum spaces (PND & MCS) highlights the possible ferromagnetic pathway along Ti--O1--Ti. Therefore, a “super-position" spin density is proposed and proves to allow cross-checking the coherence between experimental electron densities in posittion and momentum spaces, without having recourse to ab initio results. Furthermore, an ”isolated Ti model" based on PND refined orbital coefficients emphasizes the importance of metal-oxygen coherent coupling to properly account for observations in momentum space.A one-electron reduced density matrix (1-RDM) approach is proposed as a fundamental basis for systematically combining position and momentum spaces. To reconstruct 1-RDM from a periodic ab initio computation, an "iterative cluster" approach is proposed. On this basis, it becomes possible to obtain a theoretical spin resolved 1-RDM along specific chemical bonding paths. It allows a clarification of the difference between Ti--O1--Ti and Ti--O2--Ti spin couplings in YTiO3. It shows that interaction contributions between atoms (metal and oxygen atoms) are different depending on whether the property is represented in position or momentum spaces. This is clearly observed in metal-oxygen chemical bonds and can be illustrated by an orbital resolved contribution analysis. Quantities for electron descriptions in phase space, such as the Moyal function, can also be determinerd by this "cluster model", which might be of particular interest if Compton scattering in Bragg positions could be generalized. The preliminary results of a simple spin resolved 1-RDM refinement model are exposed. The model respects the N-representability and is adapted for various experimental data (e.g.: XRD, PND, CS, MCS, XMD etc.). The potential of this model is not limited to a spin analysis but its use is limited here to the unpaired electrons description. The limitations of this model are analysed and possible improvements in the future are also proposed
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Klose, Gerd. « Density matrix reconstruction of a large angular momentum ». Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/290012.

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A complete description of the quantum state of a physical system is the fundamental knowledge necessary to statistically predict the outcome of measurements. In turning this statement around, Wolfgang Pauli raised already in 1933 the question, whether an unknown quantum state could be uniquely determined by appropriate measurements--a problem that has gained new relevance in recent years. In order to harness the prospects of quantum computing, secure communication, teleportation, and the like, the development of techniques to accurately control and measure quantum states has now become a matter of practical as well as fundamental interest. However, there is no general answer to Pauli's very basic question, and quantum state reconstruction algorithms have been developed and experimentally demonstrated only for a few systems so far. This thesis presents a novel experimental method to measure the unknown and generally mixed quantum state for an angular momentum of arbitrary magnitude. The (2F + 1) x (2F + 1) density matrix describing the quantum state is hereby completely determined from a set of Stern-Gerlach measurements with (4F + 1) different orientations of the quantization axis. This protocol is implemented for laser cooled Cesium atoms in the 6S₁/₂(F = 4) hyperfine ground state manifold, and is applied to a number of test states prepared by optical pumping and Larmor precession. A comparison of the input and the measured states shows successful reconstructions with fidelities of about 0.95.
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Bianchetti, Morales Rennan. « Density profile reconstruction methods for extraordinary mode reflectometry ». Thesis, Université de Lorraine, 2018. http://www.theses.fr/2018LORR0031/document.

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Le but de cette thèse est d'améliorer les techniques d'analyse de données de la réflectométrie à balayage de fréquence pour la détermination du profil de densité des plasmas de fusion. Au cours des deux dernières décennies, des améliorations significatives ont été apportées sur la partie matérielle et sur d'extraction des signaux, mais l'analyse des données est en retard et nécessite d'autres améliorations pour répondre aux spécifications exigées pour un fonctionnement en continu des futurs réacteurs. Les améliorations obtenues lors de ce travail de thèse sur la reconstruction des profils de densité fournissent une meilleure précision en un temps plus court ceci même en présence de trou de densité conduisant à une mesure des propriétés de la turbulence suffisamment précise pour valider des modèles numériques et permettant la surveillance en temps réel de la forme et de la position du plasma
The goal of this PhD is to improve the data analysis techniques of frequency swept reflectometry for determination of the density profile of fusion plasmas. There has been significant improvements in the last two decades on the hardware design and signal extraction techniques, but the data analysis is lagging behind and require further improvements to meet the required standards for continuous operation in future reactors. The improvements obtained in this thesis on the reconstruction of density profiles provide a better accuracy in a shorter time, even in the presence of a density hole, also enabling sufficiently precise measurements of the properties of turbulence used to validate numerical models, and allowing real-time monitoring of the shape and position of the plasma
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Khalaf, Reem. « Image reconstruction for optical tomography using photon density waves ». Thesis, University of Hertfordshire, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302304.

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Lehovich, Andre. « List-mode SPECT reconstruction using empirical likelihood ». Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1098%5F1%5Fm.pdf&type=application/pdf.

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Zhang, Yu. « Further application of hydroxyapatite reinforced high density polyethylene composite - skull reconstruction implants ». Thesis, Queen Mary, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414001.

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Tafas, Jihad. « An algorithm for two-dimensional density reconstruction in proton computed tomography (PCT) ». CSUSB ScholarWorks, 2007. https://scholarworks.lib.csusb.edu/etd-project/3281.

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The purpose of this thesis is to develop an optimized and effective iterative reconstruction algorithm and hardware acceleration methods that work synonymously together through reconstruction in proton computed tomography, which accurately maps the electron density.
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Meredith, Kelly Robyn. « The Influence of Soil Reconstruction Methods on Mineral Sands Mine Soil Properties ». Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/31006.

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Significant deposits of heavy mineral sands (primarily ilmenite and zircon) are located in Virginia in Dinwiddie, Sussex and Greensville counties. Most deposits are located under prime farmland, and thus require intensive reclamation when mined. The objective of this study was to determine the effect of four different mine soil reconstruction methods on soil properties and associated rowcrop productivity. Treatments compared were 1) Biosolids-No Tillage, 2) Biosolids-Conventional Tillage, 3) Lime+NPK fertilized tailings (Control), and 4) 15-cm Topsoil over lime+P treated tailings. Treated plots were cropped to corn (Zea Mays L.) in 2005 and wheat (Triticum aestivum L.) in 2006. Yields were compared to nearby unmined prime farmland yields. Over both growing seasons, the two biosolids treatments produced the highest overall crop yields. The Topsoil treatment produced the lowest corn yields due to relatively poor physical and chemical conditions, but the effect was less obvious for the following wheat crop. Reclaimed land corn and wheat yields were higher than long-term county averages, but they were consistently lower than unmined plots under identical management. Detailed morphological study of 20 mine soil pedons revealed significant root-limiting subsoil compaction and textural stratification. The mine soils classified as Typic Udorthents (11), Typic Udifluvents (4) and Typic Dystrudepts (5). Overall, mined lands can be successfully returned to intensive agricultural production with comparable yields to long-term county averages provided extensive soil amendment and remedial tillage protocols are implemented. However, a significant decrease (~25 to 35%) in initial productivity should be expected relative to unmined prime farmland.
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Martin, Lorca Dario. « Implementation And Comparison Of Reconstruction Algorithms For Magnetic Resonance ». Master's thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/12608250/index.pdf.

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In magnetic resonance electrical impedance tomography (MR-EIT), crosssectional images of a conductivity distribution are reconstructed. When current is injected to a conductor, it generates a magnetic field, which can be measured by a magnetic resonance imaging (MRI) scanner. MR-EIT reconstruction algorithms can be grouped into two: current density based reconstruction algorithms (Type-I) and magnetic flux density based reconstruction algorithms (Type-II). The aim of this study is to implement a series of reconstruction algorithms for MR-EIT, proposed by several research groups, and compare their performance under the same circumstances. Five direct and one iterative Type-I algorithms, and an iterative Type-II algorithm are investigated. Reconstruction errors and spatial resolution are quantified and compared. Noise levels corresponding to system SNR 60, 30 and 20 are considered. Iterative algorithms provide the lowest errors for the noise- free case. For the noisy cases, the iterative Type-I algorithm yields a lower error than the Type-II, although it can diverge for SNR lower than 20. Both of them suffer significant blurring effects, especially at SNR 20. Another two algorithms make use of integration in the reconstruction, producing intermediate errors, but with high blurring effects. Equipotential lines are calculated for two reconstruction algorithms. These lines may not be found accurately when SNR is lower than 20. Another disadvantage is that some pixels may not be covered and, therefore, cannot be reconstructed. Finally, the algorithm involving the solution of a linear system provides the less blurred images with intermediate error values. It is also very robust against noise.
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Sun, Hongyan. « An investigation into the use of scattered photons to improve 2D Position Emission Tomography (PET) functional imaging quality ». Hindawi Publishing Corporation, 2012. http://hdl.handle.net/1993/31031.

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Positron emission tomography (PET) is a powerful metabolic imaging modality, which is designed to detect two anti-parallel 511 keV photons origniating from a positron-electron annihilation. However, it is possible that one or both of the annihilation photons undergo a Compton scattering in the object. This is more serious for a scanner operated in 3D mode or with large patients, where the scatter fraction can be as high as 40-60%. When one or both photons are scattered, the line of response (LOR) defined by connecting the two relevant detectors no longer passes through the annihilation position. Thus, scattered coincidences degrade image contrast and compromise quantitative accuracy. Various scatter correction methods have been proposed but most of them are based on estimating and subtracting the scatter from the measured data or incorporating it into an iterative reconstruction algorithm. By accurately measuring the scattered photon energy and taking advantage of the kinematics of Compton scattering, two circular arcs (TCA) in 2D can be identified, which describe the locus of all the possible scattering positions and encompass the point of annihilation. In the limiting case where the scattering angle approaches zero, the TCA approach the LOR for true coincidences. Based on this knowledge, a Generalized Scatter (GS) reconstruction algorithm has been developed in this thesis, which can use both true and scattered coincidences to extract the activity distribution in a consistent way. The annihilation position within the TCA can be further confined by adding a patient outline as a constraint into the GS algorithm. An attenuation correction method for the scattered coincidences was also developed in order to remove the imaging artifacts. A geometrical model that characterizes the different probabilities of the annihilation positions within the TCA was also proposed. This can speed up image convergence and improve reconstructed image quality. Finally, the GS algorithm has been adapted to deal with non-ideal energy resolutions. In summary, an algorithm that implicitly incorporates scattered coincidences into the image reconstruction has been developed. Our results demonstrate that this eliminates the need for scatter correction and can improve system sensitivity and image quality.
February 2016
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Livres sur le sujet "Reconstruction de la densité"

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Kim, Sukkoo. The reconstruction of the American urban landscape in the twentieth century. Cambridge, MA : National Bureau of Economic Research, 2002.

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(France), École nationale supérieure des beaux-arts. Densité +,- O. Paris : Ecole nationale supérieure des beaux-arts, 2004.

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McBride, R. A. Soil degradation risk indicator : Soil compaction component. Ottawa : Agriculture and Agri-Food Canada, 1997.

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North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development. Techniques expérimentales liées à l'aérodynamique à basse densité. Neuilly-sur-Seine : AGARD, 1990.

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1944-, Sarrazin Pierre, dir. L' espace et la densité : Entretiens avec Michel-Pierre Sarrazin. Montréal : Hexagone, 1993.

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Mies van der Rohe, Ludwig, 1886-1969. et Ramos Fernando, dir. Mies van der Rohe, espace et densité : Mur, colonne, interférences. Gollion : InFolio, 2006.

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Campoli, Julie. Visualizing density. Cambridge, Mass : Lincoln Institute of Land Policy, 2007.

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Ruggiero, Adriane. Reconstruction. New York : Marshall Cavendish Benchmark, 2006.

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Reconstruction. Edina, Minn : Abdo Pub., 2005.

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Howse, Jennifer. Reconstruction. New York : AV2 by Weigl, 2014.

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Chapitres de livres sur le sujet "Reconstruction de la densité"

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Korostelev, A. P., et A. B. Tsybakov. « Estimation of Support of a Density ». Dans Minimax Theory of Image Reconstruction, 182–97. New York, NY : Springer New York, 1993. http://dx.doi.org/10.1007/978-1-4612-2712-0_7.

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Liu, Tang-Kue, Rong-Sen Yang et Ying-Feng Hwang. « Distal Femoral Bone Density Following Total Knee Arthroplasty ». Dans Reconstruction of the Knee Joint, 318–23. Tokyo : Springer Japan, 1997. http://dx.doi.org/10.1007/978-4-431-68464-0_41.

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Schweingruber, Fritz H., et Keith R. Briffa. « Tree-Ring Density Networks for Climate Reconstruction ». Dans Climatic Variations and Forcing Mechanisms of the Last 2000 Years, 43–66. Berlin, Heidelberg : Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-61113-1_3.

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Jonsson, Erik, et Michael Felsberg. « Reconstruction of Probability Density Functions from Channel Representations ». Dans Image Analysis, 491–500. Berlin, Heidelberg : Springer Berlin Heidelberg, 2005. http://dx.doi.org/10.1007/11499145_50.

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Myszkowski, Karol. « Lighting Reconstruction Using Fast and Adaptive Density Estimation Techniques ». Dans Eurographics, 251–62. Vienna : Springer Vienna, 1997. http://dx.doi.org/10.1007/978-3-7091-6858-5_23.

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Reimer, Manfred. « Approximation of Density Functions and Reconstruction of the Approximant ». Dans International Series of Numerical Mathematics, 253–61. Basel : Birkhäuser Basel, 2003. http://dx.doi.org/10.1007/978-3-0348-8067-1_14.

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Louis, Alfred K., Uwe Schmitt, Felix Darvas, Helmut Büchner et Manfred Fuchs. « Spatio-Temporal Current Density Reconstruction from EEG-/MEG-Data ». Dans Mathematics — Key Technology for the Future, 472–82. Berlin, Heidelberg : Springer Berlin Heidelberg, 2003. http://dx.doi.org/10.1007/978-3-642-55753-8_38.

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Marchevsky, Ilia K., et Georgy A. Shcheglov. « Double Layer Potential Density Reconstruction Procedure for 3D Vortex Methods ». Dans Lecture Notes in Computational Science and Engineering, 287–95. Cham : Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-30705-9_25.

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Brida, G., M. Genovese, M. Gramegna, P. Traina, L. Ciavarella, S. Olivares et M. G. A. Paris. « Interferometric Technique for Density Matrix Reconstruction by On/Off Detectors ». Dans Lecture Notes of the Institute for Computer Sciences, Social Informatics and Telecommunications Engineering, 233–41. Berlin, Heidelberg : Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-11731-2_28.

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Bremer, M., et M. Grewing. « An Iterative Method for the Reconstruction of Two-Dimensional Density Distributions ». Dans Planetary Nebulae, 218. Dordrecht : Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-2088-3_90.

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Actes de conférences sur le sujet "Reconstruction de la densité"

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Gellee, T., et B. Philippe. « Utilisation combinée des biomatériaux xénogéniques et d’os autologue en chirurgie reconstructrice préimplantaire : Réflexions à propos de quatre indications méconnues ». Dans 66ème Congrès de la SFCO. Les Ulis, France : EDP Sciences, 2020. http://dx.doi.org/10.1051/sfco/20206602008.

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Introduction : Les comblements sous-sinusiens et les ROG représentent les indications principales des biomatériaux de substitution xénogénique en Chirurgie Reconstructrice Pré-Implantaire. D’autres indications moins répandues nous paraissent devoir être présentées, en particulier la prévention de la résorption centripète et l’harmonisation des contours squelettiques des greffes d’apposition d’os autologue, les coffrages et les comblements étendus ainsi que la gestion des résorptions tardives de certaines greffes d’appositions. L’objectif de cette communication consiste à présenter ces situations cliniques rarement décrites mais dont la prise en charge raisonnée mérite d’être connue afin de mieux répondre aux besoins des patients. Matériel et méthode : Cinq dossiers représentatifs de ces indications sont exposés. Les problématiques rencontrées, les moyens mis en œuvre comme les résultats cliniques et radiographiques sont abordés. Discussion : Les cas étudiés illustrent les raisons pour lesquelles l’utilisation conjointe des biomatériaux xénogènes et de l’os autogène trouve son indication. L’Os xénogénique ostéo-conducteur participe au maintien des volumes et à lobtention d’une densité é levée au sein des reconstructions. L’Os autogène ostéo-conducteur, ostéo- inducteur et ostéogénique permet dans sa forme massive la réalisation de reconstructions bi ou tridimensionnelles étendues. Les membranes xénogéniques permettent de maintenir l’équilibre dans la compétition de l’intégration entre les tissus durs et les tissus mous. L’adjonction de concentrés plaquettaires prélevés en phase liquide et mélangés à la thrombine activée assure si nécessaire l’aggrégation des granules calcifiés d’os xénogénique. Conclusion : L’utilisation combinée des biomatériaux de substitution xénogéniques avec l’os autogène constitue une aide significative dans la prise en charge de certaines reconstructions pré-implantaires complexes. La stabilité des reconstructions dans leur forme et dans le temps comme l’augmentation de la densité offerte aux implants constituent les principaux avantages attendus. Liens dintérêt : Aucun
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Yang, Hui, Hao Zhou, Bing Dong, Wentao Zhou, Weiguo Gu, Xinyu Zhang, Qingxin Lei, Chenyu Shan et Dezhong Wang. « A Novel Transmission Reconstruction Algorithm for Radioactive Drum Characterization ». Dans 2022 29th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icone29-90126.

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Abstract The accuracy of tomographic gamma scanning transmission reconstruction is a critical factor in reconstructing the activity of a radioactive drum. Traditional reconstruction algorithms produce severe grid artifacts and a high level of noise, thereby increasing the reconstruction error for both the density map and the activity. This paper proposes a novel algorithm for transmission reconstruction by combining maximum-likelihood expectation maximization and a convolutional neural network (CNN). Our experimental results indicate that the proposed reconstruction algorithm is capable of significantly reducing measurement errors, increasing spatial resolution while also eliminating grid artifacts, and being sufficiently robust when dealing with a noisy input image. The mean squared error of the output image decreased by 52.70% compared with the conventional reconstruction method, and the peak signal-to-noise ratio and structural similarity index improved by 21.89% and 17.33%, respectively. The spatial resolution was improved by 28 times, which demonstrates that CNN is a potentially useful new method for radioactive waste drum transmission image reconstruction.
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Spencer, Mark F., Jeffrey R. Beck, Jeremy P. Bos et Terry J. Brennan. « Investigation of branch-point density using traditional wave-optics techniques ». Dans Unconventional and Indirect Imaging, Image Reconstruction, and Wavefront Sensing 2018, sous la direction de Jean J. Dolne et Philip J. Bones. SPIE, 2018. http://dx.doi.org/10.1117/12.2319871.

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George, Jacob, Thomas P. Jenkins, James D. Trolinger, Benjamin Buckner et Cecil F. Hess. « Simultaneous measurements of density field and wavefront distortions in high speed flows ». Dans Unconventional and Indirect Imaging, Image Reconstruction, and Wavefront Sensing 2017, sous la direction de Jean J. Dolne et Rick P. Millane. SPIE, 2017. http://dx.doi.org/10.1117/12.2275883.

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Rangel, Esteban, Nan Li, Salman Habib, Tom Peterka, Ankit Agrawal, Wei-Keng Liao et Alok Choudhary. « Parallel DTFE Surface Density Field Reconstruction ». Dans 2016 IEEE International Conference on Cluster Computing (CLUSTER). IEEE, 2016. http://dx.doi.org/10.1109/cluster.2016.40.

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Eckman, Peter M., et Gregory W. Faris. « Convolution Backprojection Reconstruction from Photon Density Waves ». Dans Advances in Optical Imaging and Photon Migration. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/aoipm.1996.ria305.

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Pearcy, J. A., G. D. Sutcliffe, T. M. Johnson, B. L. Reichelt, S. G. Dannhoff, D. Barnak, J. Frenje, M. Gatu-Johnson, R. D. Petrasso et C. K. Li. « Investigation of Electromagnetic Fields in HEDP Experiments Using Proton Radiography ». Dans 3D Image Acquisition and Display : Technology, Perception and Applications. Washington, D.C. : Optica Publishing Group, 2023. http://dx.doi.org/10.1364/3d.2023.jtu4a.11.

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Proton radiography is a critical diagnostic in high energy density physics (HEDP) experiments, and recent developments to radiography analysis enable detailed reconstruction of proton deflections from images. We discuss here methods for using such reconstructions to discriminate between electric and magnetic field deflections of probing particles.
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Wiedeman, Christopher, Wenxiang Cong et Ge Wang. « Simultaneous electron density and attenuation coefficient reconstruction ». Dans Developments in X-Ray Tomography XIII, sous la direction de Bert Müller et Ge Wang. SPIE, 2021. http://dx.doi.org/10.1117/12.2596280.

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Dupe, F. X., M. J. Fadili et J. L. Starch. « Data augmentation for galaxy density map reconstruction ». Dans 2011 18th IEEE International Conference on Image Processing (ICIP 2011). IEEE, 2011. http://dx.doi.org/10.1109/icip.2011.6115674.

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Anastasio, Mark A., Daxin Shi et Thomas Deffieux. « Image reconstruction in variable density acoustic tomography ». Dans Medical Imaging, sous la direction de William F. Walker et Stanislav Y. Emelianov. SPIE, 2005. http://dx.doi.org/10.1117/12.596131.

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Rapports d'organisations sur le sujet "Reconstruction de la densité"

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Sjue, Sky K. (TOWARD) DENSITY RECONSTRUCTION FROM PROTON FLASH RADIOGRAPHS USING THE BAYES INFERENCE ENGINE. Office of Scientific and Technical Information (OSTI), septembre 2013. http://dx.doi.org/10.2172/1093344.

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Klasky, Marc, Michelle Espy, Jennifer Disterhaupt et Michael McCann. High Fidelity Tomographic Density Reconstructions. Office of Scientific and Technical Information (OSTI), octobre 2021. http://dx.doi.org/10.2172/1827564.

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Klasky, Marc, Balasubramanya Nadiga, Jennifer Disterhaupt, Trevor Wilcox, Luke Hovey, Theodore Mockler, Christopher Fryer et al. Uncertainties in Density and Simulation Parameters for Radiographic Reconstructions Using Machine Learning. Office of Scientific and Technical Information (OSTI), juin 2020. http://dx.doi.org/10.2172/1632660.

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Brochardt, Gary C. Causal Reconstruction. Fort Belvoir, VA : Defense Technical Information Center, février 1993. http://dx.doi.org/10.21236/ada271692.

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Nicault, A., L. Cournoyer, T. Labarre et Y. Bégin. Analyse des relations entre le climat et les séries temporelles de densité de cerne. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328074.

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Shearer, Allan W., et Neive Tierney. Bagby Street Reconstruction. Landscape Architecture Foundation, 2015. http://dx.doi.org/10.31353/cs1000.

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Al-Chaar, Ghassan, Carey Baxter, Ammar Elmajdoub, Kevin Cupka-Head et George Calfas. Pre-reconstruction planning. Engineer Research and Development Center (U.S.), mars 2019. http://dx.doi.org/10.21079/11681/32321.

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Kazman, Rick, Liam O'Brien et Chris Verhoef. Architecture Reconstruction Guidelines. Fort Belvoir, VA : Defense Technical Information Center, août 2001. http://dx.doi.org/10.21236/ada388707.

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Buchbinder, Daniel, et Renata Khelemsky. Orbital Floor Reconstruction. Touch Surgery Simulations, juin 2015. http://dx.doi.org/10.18556/touchsurgery/2015.s0050.

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Strittmatter, P. A., et E. K. Hege. Speckle Image Reconstruction. Fort Belvoir, VA : Defense Technical Information Center, avril 1985. http://dx.doi.org/10.21236/ada158653.

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