Academic literature on the topic 'Compression de modèle'
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Journal articles on the topic "Compression de modèle":
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Zodrow, Erwin L., and Jose A. D'Angelo. "Compression map: Improved means for studying Carboniferous foliage." Atlantic Geology 49 (August 14, 2013): 126. http://dx.doi.org/10.4138/atlgeol.2013.006.
Abstract:
A medullosalean-pteridosperm specimen, 22 cm long, from the Sydney Coalfield, Nova Scotia, Canada, illustrates the advantage of studying the fossilization history of compressed foliage freed from the rock matrix by hydrofluoric acid, as compared to the examination of compressions still in the rock matrix. The image of any freed frond segment of compression foliage that has been reprocessed digitally to represent its original structure is called a compression map. Interpretation of a compression map is reliant on a physicogeochemical model of preservation processes.RÉSUMÉUn spécimen fossile d’une ptéridospermée du genre Medulossa mesurant 22 cm de longueur et excavé dans le bassin houiller de Sydney, en Nouvelle-Écosse (Canada), illustre bien l’avantage d’étudier l’histoire géologique de fossiles de feuilles extraits de la matrice rocheuse au moyen de l’acide fluorhydrique plutôt que d’examiner des compressions qui sont encore dans la matrice. On désigne carte de compression l’image d’un segment de fronde compressé extrait de la matrice dont on a fait l’extrapolation numérique pour voir sa structure originale. L’interprétation d’une carte de compression repose sur un modèle physicogéochimique des processus de préservation.[Traduit par la redaction]
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Vignon, Jean-Marc, and Didier Mazon. "Modèle de transfert de chaleur périodique en compression-détente pure." International Journal of Thermal Sciences 38, no. 1 (January 1999): 89–97. http://dx.doi.org/10.1016/s0035-3159(99)80019-1.
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Andrieux, M., A. Vigouroux, and P. Sixou. "Étude par photoélasticité d'un composite modèle monofilamataire en traction et en compression." Journal de Physique III 6, no. 4 (April 1996): 449–73. http://dx.doi.org/10.1051/jp3:1996134.
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Vignon, J. "Modèle de transfert de chaleur périodique en compression-détente purePeriodic heat transfer model for pure compression-expansion modelling." Revue Générale de Thermique 38, no. 1 (January 1999): 89–97. http://dx.doi.org/10.1016/s0035-3159(99)88019-2.
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Sanchez, C., O. Gabay, C. Salvat, Y. Henrotin, and F. Berenbaum. "Etude des effets de la compression sur le métabolisme des ostéoblastes: un nouveau modèle 3D de compression in vitro." Revue du Rhumatisme 74, no. 10-11 (November 2007): 1068. http://dx.doi.org/10.1016/j.rhum.2007.10.075.
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Del Piero, Gianpietro, and Giampiero Pampolini. "Un modèle viscoélastique pour la réponse des mousses polymériques à la compression cyclique." Mécanique & Industries 10, no. 3-4 (May 2009): 261–66. http://dx.doi.org/10.1051/meca/2009054.
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Benderradji, Razik, Hamza Gouidmi, and Abdelhadi Beghidja. "Etude numérique de transition RR / MR dans l’interaction onde de choc / choc de compression." Journal of Renewable Energies 19, no. 4 (October 17, 2023): 595–604. http://dx.doi.org/10.54966/jreen.v19i4.597.
Abstract:
La présente étude s’intéresse à la fois au développement de la couche limite turbulente en écoulement supersonique sur une plaque plane, à la distance requise pour qu’elle envahisse toute la section de la plaque, ainsi qu’aux effets de la taille de la zone d'interaction sur le développement de la même couche limite. L'augmentation de la force de l'interaction est une augmentation de la taille des zones d'interactions conduisant à la formation d'une bulle de re-circulation qui est une zone des pertes de charge importantes. Pour cette raison, on peut diminuer, puis augmenter le nombre de Mach pour voir une réflexion de Mach qui explique l'impact de l'onde de choc incident forte avec la couche limite. L'augmentation et la diminution du nombre de Mach a causé l'apparition d’une transition dans les interactions réflexion régulière (RR), réflexion de Mach (MR), qui est représenté par les iso contours des champs de la masse volumique. Ces études sont bien en accord par rapport à l'essai qui a été présenté par Délery et al. (2009). On a donné une autre contribution et des investigations du phénomène de l'interaction onde de choc/couche limite turbulente. Le modèle utilisé dans cette étude est le modèle kwSST, il est considéré comme étant le plus approprié pour ce genre de problème, avec un traitement spécial de la zone proche de la paroi. Des simulations numériques ont été faites à l’aide de logiciel FLUENT.
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Dumont, Pierre, Steven Le COrre, Laurent Orgéas, and Denis Favier. "Un modèle biphasique pour simuler la mise en forme par compression des composites à fibres courtes." Revue des composites et des matériaux avancés 12, no. 3 (December 23, 2002): 477–97. http://dx.doi.org/10.3166/rcma.12.477-497.
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Jacquet, E., P. Garbuio, and J. N. Pernin. "Élaboration et validation d'un modèle numérique reflétant le comportement mécanique du fémur sous chargement statique de compression." Journal de Physique IV (Proceedings) 12, no. 11 (December 2002): 79–86. http://dx.doi.org/10.1051/jp4:20020478.
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Marigo, Jean-Jacques, and Kyrylo Kazymyrenko. "A micromechanical inspired model for the coupled to damage elasto-plastic behavior of geomaterials under compression." Mechanics & Industry 20, no. 1 (2019): 105. http://dx.doi.org/10.1051/meca/2018043.
Abstract:
We propose an elasto-plastic model coupled with damage for the behavior of geomaterials in compression. The model is based on the properties, shown in [S. Andrieux, et al., Un modèle de matériau microfissuré pour les bétons et les roches, J. Mécanique Théorique Appliquée 5 (1986) 471?513], of microcracked materials when the microcracks are closed with a friction between their lips. That leads to a macroscopic model coupling damage and plasticity where the plasticity yield criterion is of the Drucker–Prager type with kinematical hardening. Adopting an associative flow rule for the plasticity and a standard energetic criterion for damage, the properties of such a model are illustrated in a triaxial test with a fixed confining pressure.
Dissertations / Theses on the topic "Compression de modèle":
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Pedroso, Meloni Luis Geraldo. "Compression spectrale du signal vocal par modification du modèle autorégressif." Nancy 1, 1985. http://www.theses.fr/1985NAN10275.
Abstract:
Une technique pour améliorer la réception de la parole par les malentendants présentant des troubles auditifs neurosensoriels dans les hautes fréquences. Cette technique est basée sur la modélisation du conduit vocal par prédiction linéaire, suivie d'une modification convenable du filtre de synthèse. Les fréquences et les largeurs de bande des formants sont réduites de façon non-uniforme par le déplacement des pôles dans le plan complexe. La parole est synthétisée par le modèle modifié à partir du signal d'erreur. Le signal obtenu est soumis à un filtrage qui aligne les amplitudes des pics spectraux du modèle modifié, sur celles du modèle original. Il a été conçu et réalisé un système architecturé autour d'un processeur de traitement du signal, qui a permis l'étaude sur l'exécution de la méthode en temps réel. Des résultats obtenus sur quelques dizaines de mots traités montrent une bonne intelligibilité, ainsi qu'une bonne conservation des structures temporelles telles que les traits rythmiques, la durée des segments, le contour de la période fondamental
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Salazar, Betancourt Luis Fernando. "Modélisation de la compression de SMCs haute-performance." Thesis, Paris Sciences et Lettres (ComUE), 2017. http://www.theses.fr/2017PSLEM079.
Abstract:
Ce travail porte sur la simulation numérique et la modélisation du comportement thermo-mécanique des matériaux composites renforcés par des fibres. Spécifiquement les matériaux SMC (Sheet Moulding Compound) sont utilisés dans le processus de moulage par compression pour construire des pièces automobiles de haute performance. Ce travail est divisé en quatre chapitres, décrivant tout d’abord un modèle thermo-mécanique entièrement couplé pour les matériaux SMC standards et innovants à haute concentration en fibres (> 25% en volume). Le SMC est traité comme un mélange incompressible de fibre et de résine complété éventuellement par une phase de porosité compressible. Son anisotropie est modélisée au moyen de tenseurs structurels. La cinétique de réaction et de consolidation de la pièce est également modélisée et étudiée. Les données expérimentales mécaniques et thermiques enregistrées sur des échantillons de matériaux SMC sont comparées au modèle et à la solution numérique fournie par ce travail. D’un point de vue numérique, nous utilisons la méthode des domaines immergées o`u chaque phase est distinguée par une fonction distance signée. Nous décrivons le procédé de moulage par compression en proposant une résolution compressible anisotrope unifiée capable de décrire la transition compressible / incompressible du matériau SMC sous déformation. Cela permet de décrire la réponse mécanique du SMC et de prédire localement la consolidation (durcissement) de la pièce le long du cycle thermiqueThis work deals with the numerical simulation and modeling of thermomechanical analysis of fiber reinforcedcomposites materials. Specifically for SMC (Sheet Molding Compound) materials that are used in compression molding processes to build automotive high performance parts. The work is divided into fourchapters, firstly describing a fully coupled thermo-mechanical model for standard SMC materials and for innovative SMC with high fiber concentration (> 25% in volume). The SMC is treated as an incompressible mixtureof fibers and paste complemented by a compressible porosity phase. Its anisotropy is modeled by means of structural tensors. Kinetic of reaction and consolidation of the part is also modeled and studied. Mechanicaland thermal experimental data recorded on samples of SMC materials are compared to the model and numerical solution provided in this work. A numerical framework, we use the immersed boundary method and the level set method. We describe the compression molding process by proposing an unified anisotropic compressible resolution able to describe the transition between compressible/ incompressible of SMC materials under deformation. We are able to describe the mechanical response of the SMC and to predict locally the consolidation (curing) of thepart throughout the thermal cycle
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Ngadi, Abderrazzaq. "Fluctuations de forces dans le processus de compression d'un milieu granulaire modèle." Paris 6, 1999. http://www.theses.fr/1999PA066670.
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Caillaud, Florian. "Compression progressive de maillages surfaciques texturés." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI004/document.
Abstract:
Depuis plusieurs années, les modèles 3D deviennent de plus en plus détaillés. Cela augmente considérablement le volume de données les décrivant. Cependant, dans un même temps, un nombre croissant d’applications sont contraintes en mémoire et/ou en vitesse (visualisation sur périphériques mobiles, jeux vidéos, etc.). Dans un contexte Web, ces difficultés sont encore plus présentes. Cette situation peut entraîner des incompatibilités, des latences de transmission ou d’affichage qui sont souvent problématiques. La compression progressive de ces modèles est une des solutions envisageables. Le but étant de compresser les informations (géométrie, connectivité et attributs associés) de façon à pouvoir reconstruire progressivement le maillage. À la différence d’une compression dite single-rate, la compression progressive propose très rapidement un aperçu fidèle du modèle 3D pour ensuite le raffiner jusqu’à retrouver le maillage complet. Ceci permet un meilleur confort pour l’utilisateur et une adaptation de la quantité d’éléments à visualiser ou à traiter en fonction des capacités du périphérique de réception. Généralement, les approches existantes pour la compression progressive se focalisent sur le traitement de maillages 2-variétés triangulaires. Très peu de méthodes sont capables de compresser progressivement des maillages surfaciques non-variétés et, à notre connaissance, aucune ne permet de compresser génériquement un maillage surfacique quel que soit son type (i.e. non-variété et polygonal). Pour supprimer ces limitations, nous présentons une méthode de compression progressive générique permettant de traiter l’ensemble des maillages surfaciques (non-variétés et polygonaux). De plus, notre approche tient compte de l’attribut de texture potentiellement associé à ces maillages, en gérant correctement les coutures éventuelles. Pour ce faire, nous décimons progressivement le maillage à l’aide d’un nouvel opérateur générique de simplification. Cette décimation est guidée par une métrique locale qui a pour but de préserver la géométrie et la paramétrisation de la texture. Durant cette simplification, nous encodons progressivement les informations nécessaires à la reconstruction. Afin d’améliorer le taux de compression, nous mettons en oeuvre certains procédés de réduction de l’entropie, ainsi que des dispositifs de prédiction basés sur la géométrie pour l’encodage de la connectivité et des coordonnées de texture. Pour finir, l’image de texture est compressée progressivement puis multiplexée avec les données relatives au maillage. Ce multiplexage est réalisé à l’aide d’une métrique perceptuelle afin d’obtenir le meilleur rapport débit-distorsion possible lors de la décompressionSince several years, 3D models become more and more detailed. This increases substantially the amount of data needed to describe them. However, in the same time, a rising number of applications are constrained in memory and/or in speed (mobile device visualization, video games, etc.). These difficulties are even more visible within a Web context. This situation can lead to incompatibilities, latency in transmission or rendering, which is generally an issue. The progressive compression of these models is a possible solution. The goal is to compress the information (geometry, connectivity and associated attributes) in order to allow a progressive reconstruction of the mesh. Contrary to a single-rate compression, progressive compression quickly proposes a faithful draft of the 3D model and, then, refines it until the complete mesh is recovered. This allows a better comfort for the user and a real adaptation of the rendered element number in adequacy with the terminal device properties. The existing approaches for progressive compression mainly focus on triangular 2- manifold meshes. Very few methods are able to compress progressively non-manifold surface meshes and, to our knowledge, none can deal with every surface meshes (i.e. nomanifold and polygonal), in a generic way. So as to suppress these limitations, we present a new generic progressive method allowing the compression of polygonal non-manifold surface meshes. Moreover, our approach takes care of the texture attribute, possibly associated to these meshes, by handling properly potential texture seams. For that purpose, we progressively decimate the mesh using a new generic simplification operator. This decimation is driven by a local metric which aims to preserve both the geometry and the texture parametrisation. During the simplification, we progressively encode the necessary information for the reconstruction. In order to improve the compression rate, we propose several entropy reduction mechanisms, as well as geometry based prediction strategies for the connectivity and UV coordinates encoding. Finally, the texture map is progressively compressed then multiplexed with mesh data. This multiplexing is achieved using a perceptual metric to provide the best rate-distortion ratio as possible during the decompression
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Mira, Anna. "Modèle biomécanique du sein pour l’évaluation de la compression et de la perception d’inconfort en mammographie." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAS009/document.
Abstract:
Contexte: La mammographie est une modalité d’imagerie médicale à faible dose permettant la détection du cancer mammaire à un stade précoce. Lors de l'examen, le sein est comprimé entre deux plaques afin d'uniformiser son épaisseur et d'étaler les tissus. Cette compression améliore la qualité clinique de l'examen mais elle est également source d'inconfort chez les patientes. Bien que la mammographie soit la méthode de dépistage la plus efficace du cancer du sein, l’inconfort ressenti peut dissuader les femmes de passer cet examen. Par conséquent, une technique alternative de compression du sein prenant en compte le confort de la patiente, en plus de l’amélioration de la qualité d'image, présente un grand intérêt.Méthodes: Dans ce travail, nous avons proposé un nouvel environnement de simulation permettant l'évaluation de différentes techniques de compression du sein. La qualité de la compression a été caractérisée en termes de confort de la patiente, de la qualité d'image et de la dose glandulaire moyenne délivrée. Afin d'évaluer la déformation du sein lors de la compression, un modèle biomécanique par éléments finis du sein a été développé. Ce dernier a été calibré et évalué en utilisant des volumes IRM d'une volontaire dans trois configurations différentes (sur le dos, le ventre et de côté). Par ailleurs, la qualité d'image a été évaluée en utilisant un environnement de simulation d'imagerie auparavant validé pour la simulation de l'acquisition d'images en mammographie.Résultats: La capacité de notre modèle biomécanique à reproduire les déformations réelles des tissus a été évaluée. Tout d'abord, la géométrie du sein dans les trois configurations a été estimée en utilisant des matériaux Néo-Hookeens pour la modélisation des tissus mous. Les propriétés mécaniques des différents constituants du sein ont été estimés afin que les géométries du sein dans les positions couchée sur le ventre et couchée soient le plus proches possibles des mesures. La distance de Hausdorff entre les données estimées et les données mesurées est égale à 2.17 mm en position couché sur le ventre et 1.72 mm en position couché sur le dos. Le modèle a ensuite été évalué dans une troisième configuration sur le côté, avec une distance de Hausdorff étant alors égale à 6.14 mm. Cependant, nous avons été montré que le modèle Néo-Hookeen ne peut pas décrire intégralement le comportement mécanique riche des tissus mous. Par conséquent, nous avons introduit d'autres modèles de matériaux basés sur la fonction d'énergie de Gent. Cette dernière hypothèse a permis de réduire l'erreur maximale dans la configuration couchée sur le ventre et dos incliné d’environ 10 mm.Le couplage entre la simulation de la mécanique du sein et la simulation d'aquisition d'image nous ont permis d'effectuer deux études préliminaires. Dans la première étude, les différences entre les pelotes de compression standard rigide et flex ont été évaluées. Selon les simulations effectuées, l'utilisation de la pelote flex pour la compression du sein a le potentiel d'améliorer le confort de la patiente sans affecter la qualité de l'image ou la dose glandulaire moyenne.Dans la seconde étude, l'impact du positionnement du sein sur la mécanique globale de la compression mammaire a été étudié. Nos simulations confirment que rapprocher la pelote de compression de la cage thoracique peut augmenter l'inconfort de la patiente. Selon les données estimées, pour une même épaisseur du sein sous compression, la force appliqée au sein peut être s'accroitre de 150%.Conclusion: L'estimation réaliste de la géométrie du sein pour différentes configurations sous l'effet de la gravité, ainsi que les résultats conformes aux descriptions cliniques sur la compression du sein, ont confirmé l'interêt d'un environnement de simulation dans le cadre de nos étudesBackground: Mammography is a specific type of breast imaging that uses low-dose X-rays to detect breast cancer at early stage. During the exam, the women breast is compressed between two plates in order to even out the breast thickness and to spread out the soft tissues. This compression improves the exam quality but can also be a source of discomfort. Though mammography is the most effective breast cancer screening method, the discomfort perceived during the exam might deter women from getting the test. Therefore, an alternative breast compression technique considering the patient comfort in addition to an improved clinical image quality is of large interest.Methods: In this work, a simulation environment allowing the evaluation of different breast compression techniques was put forward. The compression quality was characterized in terms of patient comfort, image quality and average glandular dose. To estimate the breast deformation under compression, a subject-specific finite element biomechanical model was developed. The model was calibrated and evaluated using MR images in three different breast configurations (supine, prone and supine tilted). On the other hand, image quality was assessed by using an already validated simulation framework. This framework was largely used to mimic image acquisitions in mammography.Findings: The capability of our breast biomechanical model to reproduce the real breast deformations was evaluated. To this end, the geometry estimates of the three breast configurations were computed using Neo-Hookean material models. The subject specific mechanical properties of each breast's structures were assessed, such as the best estimates of the supine and prone configurations were obtained. The Hausdorff distances between the estimated and the measured geometries were equal to 2.17 mm and 1.72 mm respectively. Then, the model was evaluated using a supine tilted configuration; with a Hausdorff distance of 6.14 mm was obtained in that case. However, we have showed that the Neo-Hookean strain energy function cannot totally describe the rich mechanical behavior of breast soft tissues. Therefore, alternative material models based on the Gent strain energy function were proposed. The latter assumption reduced the maximal error in supine tilted breast configuration by about 10 mm.The coupling between the simulations of the breast mechanics and the X-ray simulations allowed us to run two preliminary studies. In the first study, the differences between standard rigid and flex compression paddles were assessed. According to the performed simulations, using the flex paddle for breast compression may improve the patient comfort without affecting the image quality and the delivered average glandular dose.In the second study, the impact of breast positioning on the general compression mechanics was described. Our simulations confirm that positioning the paddle closer to the chest wall is suspected to increase the patient discomfort. Indeed, based on the estimated data, for the same breast thickness under compression, the force applied to the breast may increase by 150%.Conclusion: The good results we get for the estimation of breast deformation under gravity, as well as the conforming results on breast compression quality with the already published clinical statements, have shown the feasibility of such studies by the means of a simulation framework
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Deschênes, Jean-Daniel. "Modélisation interactive : amélioration du processus de reconstruction d'un modèle 3D par la compression temps réel." Thesis, Université Laval, 2008. http://www.theses.ulaval.ca/2008/25372/25372.pdf.
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Kouyoumdjian, Pascal. "Mise au point d’un modèle de compression médullaire chez la souris : étude comportementale et histopathologique." Montpellier 2, 2009. http://www.theses.fr/2009MON20017.
Abstract:
Malgré des efforts considérables effectués au cours des deux dernières décennies, il n'existe jusqu'à présent aucune approche thérapeutique efficace dans les lésions de la moelle épinière (SCI). Ceci est attribuable, du moins en partie, aux difficultés rencontrées pour l'élaboration de modèles animaux prédictifs pre��cis. Des études antérieures ont identifié deux conditions pertinentes à ces modèles. D'abord, on note l'intérêt de valider des modèles de SCI de souris à partir des données provenant de modèles chez le rat. Ceci permet d'avoir accès à un large répertoire de modèles transgéniques afin de valider les hypothèses physiopathologiques. L'autre élément est l'exploration des conséquences de chaque mécanisme de traumatisme de la moelle. Ceci requiert la modélisation des différents aspects étiologiques de la lésion (c'est-à-dire l'ischémie, la contusion et la compression). Ainsi, nous avons conçu un nouveau modèle de compression de la moelle épinière de souris en utilisant un dispositif olivaire que nous décrivons. Nous rapportons les premiers résultats fonctionnels moteurs et histologiques pour 3 différents calibres d'olive et différentes durées de compressions. Nous montrons que le modèle est calibré et reproductible, avec un retentissement fonctionnel et une extension lésionnelle, tous les deux corrélés à la gravité de la compression. Pour étayer la caractérisation de ce modèle, nous l'avons validé pharmacologiquement par un antagoniste du récepteur NMDA, la gacyclidine, et démontré l'implication de l'excitotoxicité dans mécanisme lésionnel. Nous avons donc la preuve que ce modèle de compression chez la souris est reproductible, bien caractérisé et prévisible. Son caractère non magnétique et contrôlable à distance permettra en outre l'analyse de la SCI en temps réel par IRM, donnant un aperçu de la caractérisation spatiale et temporelle de l'évolution de la lésion. En outre, il ouvre la voie à des études in vivo de SCI chez en animaux génétiquement modifiésDespite considerable efforts over the last two decades there is so far no efficient therapeutic approach in spinal cord injuries (SCI). This may be attributable, at least in part, to difficulties encountered for elaborating predictive and accurate experimental animal models of this pathology. Previous studies have identified two relevant conditions of such model. First, the comparison of data arising from rat models by developing mice models that permits to have access to a large repertory of transgenic models, thus allowing to probe precise pathophysiological hypotheses. Second, the exploration of the consequences of each mechanism of the spinal trauma requires modeling the different etiologic aspects of the injury (i. E. Ischemia, mechanic contusion and compression). In order to fulfill these two conditions we have devised a new model of compression injury of the mouse spinal cord using a thread-driven olive-shaped compressive device. We havecharacterized early motor, sensory and histological outcomes using three olive diameters anddifferent compression duration. We show a gradual and reproducible functional severity thatcorrelates with lesion extension. To further substantiate the characterization of this model, wedispensed a non-competitive NMDA antagonist and demonstrated the involvement ofexcitotoxicity in this model. We thus demonstrate that spinal olive-compression injury in the mouse is a reproducible, well-characterized and predictable model to analyse early event following SCI. The nonmagnetic and remote controlled design of this model will allow further real-time MRI studies that will give insights in the characterization of spatial and temporal evolution of SCI. Moreover it paves the way toward in vivo studies of functional and histological outcomes following SCI in genetically engineered animals
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Abou, Rached Ghady. "Experimental and numerical study of a cooled compression by oil injection in a screw compressor." Thesis, Université Paris sciences et lettres, 2020. http://www.theses.fr/2020UPSLM057.
Abstract:
L’objectif de cette thèse est de concevoir un système d’injection d’huile pour réussir la compression refroidie pour les compresseurs à vis utilisant le R134a, un réfrigérant à basse pression. Les atomiseurs bi fluides ont été identifiés pour générer des gouttelettes d’huile assez fine et adaptées du régime de pression du R134a. Une étude expérimentale est conduite pour caractériser cette famille d’injecteurs en termes de taille de particules et débits massiques. Des corrélations sont proposées pour déterminer ces deux entités en fonction des pressions aux terminaux de l’injecteur. Un système d’injection complet est conçu et construit pour un refroidisseur d’eau commercial utilisant le R134a comme réfrigérant, où les conditions d’injection ont été variées systématiquement. Un modèle 1D est aussi développé qui considère l'ensemble du compresseur. Il est divisé en 3 parties : Zones de pré-compression, compression et post compression. Les paramètres du modèle ont été identifiés à partir des données expérimentales. Une étude paramétrique a déterminé un point de fonctionnement optimal, avec les meilleurs résultats et conditions opératoires. Le résultat de cette thèse est une conception innovante avec une haute performance énergétique et un coût modéré d’un système de compression refroidie dédié aux compresseurs à vis. L’étude expérimentale a validé une augmentation du COP de 3% et une réduction maximale de la température de refoulement de 7°C. Le modèle prédit jusqu’à 20% d’amélioration du COP si certaines conditions sont rempliesThis thesis’ objective is designing a dedicated oil injection system in order to achieve a cooled compression solution for compressors using R-134a, a relatively low pressure refrigerant. Bi fluid atomizers are identified as a technology capable of generating fine droplets of oil suitable with the pressure regime of R-134a. An experimental study was carried out to characterize this family of injectors in terms of particle sizes and mass flow rates. Correlations were suggested in order to determine these magnitudes as a function of pressure conditions at the outlet of the injector. A complete injection system is then designed and built for a commercial R134a screw compressor water chiller, where the injection conditions were varied systematically. A 1D model was also developed taking into consideration the whole compressor. It is divided into three main parts: Pre compression, compression and post compression zones. The model parameters were fitted using the experimental results. A parametric study was conducted to determine an optimal functioning point with best results and best operating conditions. The main result of this thesis is an innovative design with high energy performance and moderate cost of a compression cooling system dedicated for a screw compressor. The experimental study validated an increase of COP of 3% and a maximal temperature discharge reduction of 7°C. The model predicts up to 20% of COP improvement if certain operating conditions are met
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Cavaro-Ménard, Christine. "Compression d'images basée sur un modèle contour-texture : adaptation d'un système de codage aux images biomédicales." Tours, 1991. http://www.theses.fr/1991TOUR3308.
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Saidou, Adamou. "Étude du comportement en compression-cisaillement d'isolateurs sismiques en caoutchouc." Mémoire, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/6209.
Abstract:
L'isolation sismique à la base est une méthode de conception parasismique qui consiste à introduire de la flexibilité à la base d'une structure afin de réduire sa vulnérabilité aux séismes. La flexibilité introduite permet de séparer la fréquence propre de la structure de la plage de fréquences naturelles du séisme. Les grands déplacements qui surviennent à cause de la flexibilité peuvent être contrôlés par introduction d'amortissement dans le système. Les isolateurs sismiques permettent ainsi de réduire significativement la demande en force et en déformation sur les principaux éléments structuraux. Il en résulte une augmentation du niveau de performance de la structure en cas de séisme. Les isolateurs sismiques en élastomère (ISE) font partie des types d'isolateur les plus utilisés à cause de leur facilité de fabrication, d'installation et d'entretien. Toutefois, ces isolateurs présentent un comportement mécanique non linéaire dépendant de plusieurs facteurs qui varient durant la phase d'utilisation (température, déformation interne, fréquence de chargement...). Il s'ensuit que, pour assurer la sécurité de l'ouvrage isolé, il est important de connaître l'impact de la variation de chacun des facteurs sur les propriétés mécaniques des isolateurs en caoutchouc. Le présent projet de recherche étudie l'influence du niveau de compression axiale sur les propriétés mécaniques des isolateurs sismiques en caoutchouc naturel. Des essais expérimentaux ont été réalisés sur une série de douze isolateurs sismiques pour étudier l'effet de la charge axiale sur la rigidité latérale et le niveau de dissipation d'énergie. Les résultats ont montré une réduction de la rigidité et une augmentation du niveau d'amortissement avec l'augmentation de la contrainte axiale. Une analyse par éléments finis a aussi été menée pour étudier la stabilité des isolateurs à l'état déplacé. L'étude numérique a montré une concordance avec les prédictions théoriques à l'état non déplacé et une sous-estimation de la capacité de l'isolateur à l'état déplacé. L'étude a aussi fait ressortir une relation entre le facteur de forme, l'élancement et la capacité de l'isolateur à l'état déplacé. Le projet de recherche est réalisé sous la direction du professeur Patrick Paultre, dans le cadre des travaux du centre de recherche en génie parasismique (CRGP) sur la réduction de la vulnérabilité sismique des structures.
Books on the topic "Compression de modèle":
1
Rice, Robert F. Algorithms for a very high speed universal noiseless coding module. Pasadena, Calif: National Aeronautics and Space Administration, Jet Propulsion Laboratory, California Institute of Technology, 1991.
2
Mielikaïnen, Jarno. Lossless compression of hyperspectral images. Lappeenranta: Lappeenranta University of Technology, 2003.
3
C, Pauly Christopher, Pindera M. J. 1951-, and United States. National Aeronautics and Space Administration., eds. Experimental characterization and micromechanical modeling of woven carbon/copper composites. [Washington, D.C.]: National Aeronautics and Space Administration, 1997.
4
Porter, Nathan. Wage compression, employment restrictions, and unemployment: The case of Mauritius. [Washington, D.C]: International Monetary Fund, Finance Dept., 2004.
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W, Davison L., and Shahinpoor Mohsen, eds. High-pressure shock compression of solids III. New York: Springer, 1998.
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Ng, Y. K. Eddie. Compressor instability with integral methods. Berlin: Springer, 2007.
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United States. National Aeronautics and Space Administration., ed. Compression strength of composite primary structural components: Semiannual status report, performance period, November 1, 1992 to April 30, 1993. Blacksburg, Va: Aerospace and Ocean Engineering Dept., Virginia Polytechnic Institute and State University, 1993.
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United States. National Aeronautics and Space Administration., ed. Compression strength of composite primary structural components: Semiannual status report, performance period, May 1, 1992 to October 31, 1992. Blacksburg, Va: Aerospace and Ocean Engineering Dept., Virginia Polytechnic Institute and State University, 1992.
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United States. National Aeronautics and Space Administration., ed. Compression strength of composite primary structural components: Semiannual status report, performance period, November 1, 1992 to April 30, 1993. Blacksburg, Va: Aerospace and Ocean Engineering Dept., Virginia Polytechnic Institute and State University, 1993.
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United States. National Aeronautics and Space Administration., ed. Compression strength of composite primary structural components: Semiannual status report, performance period, May 1, 1993 to October 31, 1993. Blacksburg, Va: Aerospace and Ocean Engineering Dept., Virginia Polytechnic Institute and State University, 1993.
Book chapters on the topic "Compression de modèle":
1
Ahlswede, Rudolf. "Data Compression." In Identification and Other Probabilistic Models, 191–97. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-65072-8_12.
2
Li, Zhihui. "Research of Helium Thermal Power System Based on Lead-Cooled Fast Reactor." In Springer Proceedings in Physics, 919–29. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-1023-6_78.
Abstract:
AbstractThe Helium Brayton cycle with re-compression has the advantages of compact layout, simple structure, thermal high efficiency, good heat transfer characteristics and small friction characteristics, its application in the power conversion system of the lead-cooled fast reactor and the high temperature gas-cooled reactor helps the miniaturization of the whole system. In this paper, the mathematical model was established for Helium Brayton cycle with re-compression and the 100 MWt lead-cooled fast reactor power system was calculated. The effects of several key factors such as the turbine inlet temperature, the turbine outlet pressure, the high pressure compressor outlet pressure, the low pressure compressor outlet pressure and the recuperator outlet temperature were analyzed. The results show that the turbine outlet pressure, the turbine inlet temperature and the high/low pressure compressor outlet pressure have remarkable effects on thermal efficiency of the system. Thermal efficiency of the system increases first and then decreases with the turbine outlet pressure increasing as well as increases with turbine inlet temperature. The research results of this paper could provide important theoretical reference both for thermal cycle parameters for 100 MWt lead-cooled fast reactor and system design of power cycle based on the lead-cooled fast reactor.
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Oneto, Luca. "Compression Bound." In Model Selection and Error Estimation in a Nutshell, 59–63. Cham: Springer International Publishing, 2019. http://dx.doi.org/10.1007/978-3-030-24359-3_6.
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Jiang, Di, Chen Zhang, and Yuanfeng Song. "Topic Deduplication and Model Compression." In Probabilistic Topic Models, 111–20. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-99-2431-8_9.
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Yu, Faxin, Hao Luo, Zheming Lu, and Pinghui Wang. "3D Mesh Compression." In Three-Dimensional Model Analysis and Processing, 91–160. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-12651-2_2.
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Leclerc, D., and S. Rebouillat. "Dewatering by Compression." In Mathematical Models and Design Methods in Solid-Liquid Separation, 356–91. Dordrecht: Springer Netherlands, 1985. http://dx.doi.org/10.1007/978-94-009-5091-7_15.
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Graham, Robert A. "Basic Concepts and Models." In Solids Under High-Pressure Shock Compression, 15–52. New York, NY: Springer New York, 1993. http://dx.doi.org/10.1007/978-1-4613-9278-1_2.
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Kurz, Bodo, Melanie L. Hart, and Bernd Rolauffs. "Mechanical Articular Cartilage Injury Models and Their Relevance in Advancing Therapeutic Strategies." In Advances in Experimental Medicine and Biology, 107–24. Cham: Springer International Publishing, 2023. http://dx.doi.org/10.1007/978-3-031-25588-5_8.
Abstract:
AbstractThis chapter details how Alan Grodzinsky and his team unraveled the complex electromechanobiological structure-function relationships of articular cartilage and used these insights to develop an impressively versatile shear and compression model. In this context, this chapter focuses (i) on the effects of mechanical compressive injury on multiple articular cartilage properties for (ii) better understanding the molecular concept of mechanical injury, by studying gene expression, signal transduction and the release of potential injury biomarkers. Furthermore, we detail how (iii) this was used to combine mechanical injury with cytokine exposure or co-culture systems for generating a more realistic trauma model to (iv) investigate the therapeutic modulation of the injurious response of articular cartilage. Impressively, Alan Grodzinsky’s research has been and will remain to be instrumental in understanding the proinflammatory response to injury and in developing effective therapies that are based on an in-depth understanding of complex structure-function relationships that underlay articular cartilage function and degeneration.
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Li, Jia, and Robert M. Gray. "Joint Compression and Classification." In Image Segmentation and Compression Using Hidden Markov Models, 103–19. Boston, MA: Springer US, 2000. http://dx.doi.org/10.1007/978-1-4615-4497-5_7.
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Li, Jia, and Robert M. Gray. "Testing Models." In Image Segmentation and Compression Using Hidden Markov Models, 91–102. Boston, MA: Springer US, 2000. http://dx.doi.org/10.1007/978-1-4615-4497-5_6.
Conference papers on the topic "Compression de modèle":
1
Khan, Jobaidur R. "Comparison Between Discrete Phase Model and Multiphase Model for Wet Compression." In ASME Turbo Expo 2013: Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-96022.
Abstract:
Gas turbine inlet fog / overspray cooling is considered as a simple and effective method to increase power output. To help understand the water mist transport in the compressor flow passage, this study conducts a computational simulation of wet compression in a single rotor-stator compressor stage using the commercial code, Fluent. A sliding mesh scheme is used to simulate the stator-rotor interaction in a rotating frame. Previous researchers have modeled wet compression using DPM (Discrete Phase Model), where spray amount is very small (1–2%). Compressor washing is also becoming a new interest in the wet compression technology, which involves much higher amount of water (10–15%), which is not easy to handle with DPM. It can be done by multiphase model. To start compressor washing it is important to validate wet compression (1–2% spray) using DPM and the same using multiphase. This study takes the initial step to compare these two models, however multiphase model needs further development to perform an apple to apple comparison with DPM.
2
Jahanian, Shahriar, and A. J. McPhate. "Approximate Residual Interface Compression in a Laminated Magnet." In ASME 1993 Design Technical Conferences. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/detc1993-0072.
Abstract:
Abstract Present design of large laminated magnets are based on effective modulus of elasticity for the plate stack that is invariant with interplate compression. Experimental results indicates this is not a valid assumption. This analysis considers the specific design used for compact electron storage ring dipole magnet at the Center for Advanced Micro Devices (CAMD) at Louisiana State University. An iterative technique, using FEM is developed to approximate the effective modulus throughout the magnet structure. This particular magnet is constructed from 1424 steel plates (1.5mm × 610mm × 780mm) by first compressing a 45° 2.93m raduis curvilinear stack to a specified preload and then welding straight and curved straps to the exterior of the stack. Release of the preload allowsexpansion of the stack and forces stretch of the straps, the resultant interplate compression is considerably different from the initial preload and varies throughout the magnet. The analysis technique introduced in this paper is a simplified approach to the interplate compression modeling and consists of the supeposition of two simple analysis; one with straps attached, one without straps attached. An iterative approach is used to incorporate the dependence of effective compressive modulus on the interplate compression. An estimate of the average modulus is assumed for the entire stack and residual compression is calculated. From this residual compression and from experimental data, a distribution of compressive modulus throughout the magnet is computed. From this computed distribution, a new estimate for the compressive modulus is made for each element of the model and the analysis iterated. The net results are the compressive modulus distribution throughout the magnet ia a form suitable in subsequent dynamic analysis.
3
Li, Xiangwei, Xuguang Lan, Meng Yang, Jianru Xue, and Nanning Zheng. "Efficient compressive sensing video compression method based on Gaussian mixture models." In 2016 Visual Communications and Image Processing (VCIP). IEEE, 2016. http://dx.doi.org/10.1109/vcip.2016.7805535.
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Montalvo-Catano, German, and Walter F. O’Brien. "Performance Modeling of a Power Generation Gas Turbine With Wet Compression." In ASME 2011 Turbo Expo: Turbine Technical Conference and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/gt2011-46584.
Abstract:
In the last 15 years more than 1000 power generation gas turbines have been modified with an OEM or aftermarket module to generate the wet compression phenomenon where “Hot Day” conditions are present on the site. This modification to the gas turbine increases power, but can produce performance problems including reduced compressor surge margin and possibly a shorter maintenance cycle because of resulting problems present in the compressor such as blade vibration and erosion with impingement of water droplets on the surface of the compressor blades[1]. In the last few years researchers in academia and the private sector have worked to understand the principles behind the wet compression process in order to know in depth how to use the application to best advantage with gas turbines. The main areas of the research on wet compression are thermodynamic analyses, computer fluid dynamic analysis, and the use of operational data. Because present technology is unable to obtain detailed operational data on the evaporation process within the compressor, researchers rely on computer simulations based upon aerothermodynamics and physical measurements of the gas turbines, and assumptions based upon available information. These computer simulations are typically aimed toward explaining the performance data from a specific gas turbine model. Most of these computer simulations are cycle analyses of the gas turbine [2–7], although a few are CFD analyses for a specific compressor using either in-house computer programs or commercial CFD software [8–10]. CFD analysis takes into account the fact that an evaporation model should be used in order to predict how the evaporation of the water droplets occurs through the stages of the compressor. Many of the CFD simulations that have been performed for wet compression assume that the mixture of air, liquid water, and water vapor is at equilibrium throughout the compressor. Also, a single water droplet size is sometimes used for the simulation instead of a size distribution for the droplets. These assumptions simplify the calculations for the software. The results of these simulations may over-forecast the effect of the wet compression and the power output of the gas turbine because of incorrect predictions of evaporation models, or because of the lack of a proper droplet size distribution affecting the calculation. An analysis that properly forecasts the power output of a gas turbine with wet compression is important for design, performance prediction, and operation. The intention of this paper is to show how performance predictions for a power generation gas turbine is affected by applying several evaporation models [2, 4, 5, 7] in a gas turbine model with a detailed, stage-by-stage compressor model. Model predictions are compared with available operational performance data. Conclusions are provided regarding the best evaporation model assumptions for accurate predictions of gas turbine performance with wet compression.
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Gopinath, Arathi K., Giridhar Jothiprasad, Trevor Wood, and Le Tran. "Wet Compression Effects on Axial Compressor Performance Using Pitch-Line Models." In ASME Turbo Expo 2010: Power for Land, Sea, and Air. ASMEDC, 2010. http://dx.doi.org/10.1115/gt2010-22214.
Abstract:
The impact of wet compression technology on compressor performance is studied using a coupled water-evaporation-pitch-line numerical model. The model uses an iterative approach to compute the modified flow conditions at blade-row stations due to inter-stage evaporation of water droplets introduced at the compressor inlet. The evaporation rate predicted by the model is compared with experimental data for stationary droplets in a duct. Performance predictions are compared with data for a GE-proprietary compressor. Study of various water droplet sizes and various water-to-air mass ratios is discussed.
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Saadat, Mohsen, Farzad A. Shirazi, and Perry Y. Li. "Modeling and Trajectory Optimization of Water Spray Cooling in a Liquid Piston Air Compressor." In ASME 2013 Heat Transfer Summer Conference collocated with the ASME 2013 7th International Conference on Energy Sustainability and the ASME 2013 11th International Conference on Fuel Cell Science, Engineering and Technology. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/ht2013-17611.
Abstract:
An efficient and sufficiently power dense air compressor/expander is the key element in a Compressed Air Energy Storage (CAES) approach. Efficiency can be increased by improving the heat transfer between air and its surrounding materials. One effective and practical method to achieve this goal is to use water droplets spray inside the chamber when air is compressing or expanding. In this paper, the air compression cycle is modeled by considering one-dimensional droplet properties in a lumped air model. While it is possible to inject water droplets into the compressing air at any time, optimal spray profile can result in maximum efficiency improvement for a given water to air mass ratio. The corresponding optimization problem is then defined based on the stored energy in the compressed air and the required input works. Finally, optimal spray profile has been determined for various water to air mass ratio using a general numerical approach to solve the optimization problem. Results show the potential improvement by acquiring the optimal spray profile instead of conventional constant spray flow rate. For the specific compression chamber geometry and desired pressure ratio and final time used in this work, the efficiency can be improved up to 4%.
7
XUE, JING, and KEDAR KIRANE. "STRENGTH SIZE EFFECT IN FIBER COMPOSITES FAILING UNDER LONGITUDINAL AND TRANSVERSE COMPRESSION." In Thirty-sixth Technical Conference. Destech Publications, Inc., 2021. http://dx.doi.org/10.12783/asc36/35873.
Abstract:
The size effect in the structural strength of fiber reinforced composites has been typically analyzed for tensile failures. However, this is not true for the equally important compressive failures, primarily due to the difficulties in conducting compression tests on specimens of multiple sizes. These size effects are analyzed here numerically for two important compressive failure mechanisms in composites, viz. (i) fiber kink bands forming under longitudinal compression (typically accompanied by axial splitting matrix cracks) and (ii) inclined shear cracks forming under transverse compression. The former mechanism is modeled by a semi-multiscale microplane model, while the latter by the fixed crack model. Both models are calibrated and verified using available test data on carbon fiber composites and then used to predict the failure and load bearing capacities of geometrically scaled pre-cracked specimens of different sizes. In all cases, the predicted failure is found to be of a propagating nature, accompanied by release of strain energy from the specimen causing a distinct size effect in the nominal strength. For the composite considered here, under longitudinal compression, the fracture process zone (FPZ) is found to be fairly small (<1 mm) and the strength size effect is seen to follow linear elastic fracture mechanics (LEFM). The size effect deviates from LEFM for smaller specimen sizes due to increased flaw size insensitivity but cannot be fitted by Bažant's size effect law since the geometric similarity of the failure mode is lost. On the other hand, under transverse compression the FPZ is found to be much larger (34 to 42 mm) and the size effect is found to obey Bažant's size effect law, deviating from LEFM. The failure is geometrically similar despite being inclined to the pre-crack. These findings provide evidence of the general applicability of fracture mechanics-based size effect laws to compressive failure in fiber composites, and prompt suitable experimental investigations.
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Park, Seonghun, Ramaswamy Krishnan, Steven B. Nicoll, and Gerard A. Ateshian. "Cartilage Interstitial Fluid Load Support in Unconfined Compression." In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32620.
Abstract:
Under physiological conditions of loading, articular cartilage is subjected to both compressive strains, normal to the articular surface, and tensile strains, tangential to the articular surface. Previous studies have shown that articular cartilage exhibits a much higher modulus in tension than compression. Theoretical analyses have suggested that this tension-compression nonlinearity enhances the magnitude of interstitial fluid pressurization during loading in unconfined compression, above a theoretical threshold of 33% of the average applied stress. The first hypothesis of this experimental study is that the peak fluid load support in unconfined compression is significantly greater than the 33% theoretical limit predicted for porous permeable tissues modeled with equal moduli in tension and compression [1]. The second hypothesis is that the peak fluid load support is higher at the articular surface side of the tissue samples than near the deep zone, because the disparity between the tensile and compressive moduli is greater at the surface zone.
9
Li, Longbiao. "Micromechanical Modeling Tension-Compression Fatigue Hysteresis Loops Model of Fiber-Reinforced Ceramic-Matrix Composites Considering Fibers Failure." In ASME Turbo Expo 2021: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/gt2021-58485.
Abstract:
Abstract In this paper, a micromechanical tension-compression fatigue hysteresis loops model of fiber-reinforced ceramic-matrix composite (CMC) was developed considering fibers failure. Multiple fatigue damage mechanisms of fibers failure, interface debonding, slip and wear, and matrix fragmentation were considered and incorporated in the micromechanical fatigue hysteresis loops model. Upon unloading, the unloading stress-strain relationship was divided into three stages, including, (1) Unloading Stage I: the unloading interface counter slip stage and the unloading stress is between the tensile peak stress and the matrix crack closure stress; (2) Unloading Stage II: the unloading partial compressive stage and the unloading stress is between the matrix crack closure stress and the unloading complete compressive stress; and (3) Unloading Stage III: the unloading complete compressive stage and the unloading stress is between the unloading complete compressive stress and the compressive valley stress. Multiple micromechanical damage parameters of fibers failure probability, unloading/reloading transition stress, closure stress of the matrix cracking, compressive transition stress, complete compressive stress, unloading/reloading inverse tangent modulus (ITM), and interface counter slip/new slip ratio (ICSR/INSR) were adopted to characterize the tension-compression stress-strain hysteresis loops. Experimental tension-compression fatigue stress-strain hysteresis loops of unidirectional CMCs were predicted using the developed micromechanical models. The characteristics of the tension-compression fatigue hysteresis loops of unidirectional CMC are analyzed for different material properties, damage state, and tensile fatigue peak stress.
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Kang, Young Seok, Dong Ho Rhee, Byeung Jun Lim, Sangook Jun, Tae Choon Park, Yang Ji Lee, and Yong Min Jun. "Design of Turbo-Compression System for HALE UAV Propulsion System." In ASME 2018 5th Joint US-European Fluids Engineering Division Summer Meeting. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/fedsm2018-83354.
Abstract:
A turbo-compression system design and its performance analysis procedure for a high altitude long endurance UAV (HALE UAV), of which cruising altitude is within the stratosphere, is presented. To fly at a relatively low speed for a long time and to make engine performance less sensitive to flight altitude, a hydrogen fueled internal combustion engine was chosen for a propulsion system. To utilize an internal combustion engine as a propulsion system at a high altitude, a proper inlet pressure boost system such as a series of turbochargers is required. Hydrogen is highly reactive gas and sometimes backfiring or preignition may occur due to its low ignition energy at stoichiometric ratio. Therefore, fuel to air ratio should be reduced as low as 0.6 to avoid such phenomena. Then rarefied ambient intake air pressure should be boosted up to 1.7 bar to produce required power from the lean burn engine. To gain high pressure ratio from the turbo compression system, at least three stage serial turbocharger with proper intercooler system at each compressor exhaust is required. To analyze multi-stage turbocharger performance at the cruising altitude, an explicit one-dimensional analysis method has been established mainly by matching required power between compressors and turbines. Each compressor performances were corrected according to Reynolds number at a given flight altitude. Compressor efficiency and surge margin deteriorate as the operating altitude increases. Then compressor efficiencies were reflected as functions of flight altitude and corresponding Reynolds number. Once operating points of each turbocharger was determined, then adequate turbochargers were searched for from commercially available models based on performance analysis results. Also, adequate water to air intercoolers were chosen for the turbo-compression system to secure flexibility of placing main components inside the engine bay as well as to obtain high heat exchange efficiency of the heat exchangers. Based on the designed turbo-compression system, technical demonstration test of the turbo-compression system inside altitude environment test chamber in Korea Aerospace Research Institute is planned. Altitude condition in stratosphere is simulated mainly with two stage centrifugal compressor and additional fan will be used to fine control the flight altitude. The turbo compression system will be controlled with a single waste gate located just downstream of the engine to secure simple controllability of the turbo compression system. The test results will validate main components as well as system layout design methods and give more reliable control schedule of the turbo compressions system according to the flight altitude.
Reports on the topic "Compression de modèle":
1
Vankirk, George, Andreas Frank, Michael Roth, Brett Williams, and William Heard. Residual strength of a high-strength concrete subjected to triaxial prestress. Engineer Research and Development Center (U.S.), January 2024. http://dx.doi.org/10.21079/11681/48055.
Abstract:
This study investigates simplified mechanical loading paths that represent more complex loading paths observed during penetration using a triaxial chamber and a high-strength concrete. The objective was to determine the effects that stress-strain (load) paths have on the material’s unconfined compressive (UC) residual strength. The loading paths included hydrostatic compression (HC), uniaxial strain in compression (UX), and uniaxial strain load biaxial strain unload (UXBX). The experiments indicated that the load paths associated with nonvisible microstructural damage were HC and UX—which produced minimal impact on the residual UC strength (less than 30%)—while the load path associated with visible macro-structural damage was UXBX, which significantly reduced the UC strength (greater than 90%). The simplified loading paths were also investigated using a material model driver code that was fitted to a widely used Department of Defense material model. Virtual experiment data revealed that the investigated material model overestimated material damage and produced poor results when compared to experimental data.
2
Panek, Jeffrey, Adrian Huth, Alan Krol, and James McCarthy. PR-312-18208-R03 AERMOD Performance Assessments, Implementation Issues and Recommended Improvements. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), August 2022. http://dx.doi.org/10.55274/r0012232.
Abstract:
In 2010, the U.S. Environmental Protection Agency (EPA) adopted a 1-hour nitrogen dioxide (NO2) National Ambient Air Quality Standard (NAAQS) of 100 parts per billion (ppb) or approximately 188 micrograms per cubic meter (�g/m3) that is considerably more stringent than the longstanding annual standard of 53 ppb (100 �g/m3). New or modified compressor units may be encumbered by federal or state regulatory requirements to demonstrate compliance with the NO2 NAAQS using AERMOD, EPA's dispersion model, because the new NAAQS greatly reduces the compliance margin. Compressor stations have been increasingly requested to model source contribution to other nearby permitting actions through no new action on their part. Model conservatism and performance concerns has limited NO2 NAAQS compliance options necessitating the need to improve model estimates for reciprocating engine drivers at pipeline compressor stations. AERMOD was developed and validated with a primary focus on larger sources with taller stacks, such as electric utility boilers, which results in model conservatism for sources such as compressor stations with shorter stacks that result in near-field modeled impacts. This report summarizes additional analyses conducted and reviewed with EPA that were completed to assess and reduce model conservatism and improve overall model performance. This report presents a more detailed analysis of modeled versus observed results, model performance, and recommendations for model improvements. These analyses also evaluated other ongoing efforts (e.g., PRIME2 downwash improvements and integration of the ADMS chemistry module an alternative in AERMOD) using the data collected from this program may be used to assess these revisions. This final report summarizes the deeper dive into the NOx chemistry, dispersion, and downwash performance assessments within AERMOD based on the Balko dataset. Specific recommendations are made throughout this report to improve overall model performance.
3
Trim, M., Matthew Murray, and C. Crane. Modernization and structural evaluation of the improved Overhead Cable System. Engineer Research and Development Center (U.S.), March 2021. http://dx.doi.org/10.21079/11681/40025.
Abstract:
A modernized Overhead Cable System prototype for a 689 ft (210 m) Improved Ribbon Bridge crossing was designed, assembled, and structurally tested. Two independent structural tests were executed, i.e., a component-level compression test of the BSS tower was performed to determine its load capacity and failure mode; and a system-level ‘dry’ test of the improved OCS prototype was conducted to determine the limit state and failure mode of the entire OCS. In the component-level compression test of the BSS tower, the compressive capacity was determined to be 102 kips, and the failure mode was localized buckling in the legs of the tower section. During system-level testing, the prototype performed well up to 40.5 kips of simulated drag load, which corresponds to a uniformly distributed current velocity of 10.7 ft/s. If a more realistic, less conservative parabolic velocity distribution is assumed instead, the drag load for an 11 ft/s current is 21.1 kips. Under this assumption, the improved OCS prototype has a factor of safety of 1.9, based on a 689-ft crossing and 11-ft/s current. The OCS failed when one of the tower guy wires pulled out of the ground, causing the tower to overturn.
4
Lamancusa. L51542 Noise Research and Projection Models for Natural Gas Facilities. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), March 1988. http://dx.doi.org/10.55274/r0010520.
Abstract:
Covers research involving noise model requirements and evaluation of a number of existing models for applicability to pipeline compressor station conditions. Leads to development of improvements to existing AGASUM model. Resulting model, AGASOUND, is described and additional improvements still required are identified.
5
Daume, III, Marcu Hal, and Daniel. A Noisy-Channel Model for Document Compression. Fort Belvoir, VA: Defense Technical Information Center, January 2002. http://dx.doi.org/10.21236/ada459360.
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Sentcоv, Valentin, Andrei Reutov, and Vyacheslav Kuzmin. Electronic training manual "Acute poisoning with psychotropic substances". SIB-Expertise, January 2024. http://dx.doi.org/10.12731/er0777.29012024.
Abstract:
The significant variety of properties and wide distribution of opiates and opioids in the modern pharmaceutical industry entail not only positive, but also negative consequences in people's lives. The constant search for new drugs entails the emergence of new substances with psychotropic effects. The widespread use of vinegar essence in the food industry, nitrogen oxides in agriculture, and the frequent appearance of carbon disulfide in everyday life create an increased risk to public health. Positional compression syndrome very often accompanies poisoning with psychotropic substances, which leads to a high risk of disability for victims or even death. This electronic educational resourse consists of seven theoretical educational modules: opioid poisoning, acute psychostimulant poisoning, vinegar essence poisoning, acute carbon monoxide poisoning, acute nitrogen oxide poisoning, acute hydrogen sulfide and carbon disulfide poisoning, positional compression syndrome. The theoretical block of modules is presented by presentations, the text of lectures with illustrations. Control classes in the form of test control accompany each theoretical module. After studying all modules, the student passes the final test control. Mastering the electronic educational resourse will ensure a high level of readiness to provide specialized toxicological care by doctors of various specialties.
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Olsen and Willson. L51916 Pressure Based Parametric Emission Monitoring Systems (PEMS). Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), April 2002. http://dx.doi.org/10.55274/r0010181.
Abstract:
The natural gas industry operates over 8000 stationary large bore (bore greater than 14 in) natural gas engines for natural gas compression on pipelines and power generation. As emissions regulations become increasingly more stringent, the need for low cost methods for compliance demonstration arises. A PEMS model is one such approach. Research in this area has increased significantly during the last decade. PEMS models for this application utilize parameters commonly measured on industrial engines in the field to predict engine-out emissions. Monitoring emissions in this manner represents a significant cost savings over the periodic use of chemiluminescence NOX analyzers, which are not standard equipment in natural gas compressor stations. PEMS model accuracy is dependent on the quality of the input data, both the training NOX measurements and the selection of input parameters. Hence, it is important to have both reliable data measurement methods and an understanding of engine operating parameters relation to NOX. This work is part of the body of work referred to as the Integrated Test Plan (ITP), performed at the Engines and Energy Conversion Laboratory (EECL). This report details an investigation into Parametric Emissions Monitoring System (PEMS) models. It is the final document to be delivered under the ITP program. Much of the work performed under the ITP program focused on Hazardous Air Pollutants (HAPs) research. However, the emphasis of the PEMS work is on the prediction of oxides of nitrogen (NOX) emissions from large bore natural gas engines. In this work two different PEMS models are developed, a semi-empirical model and a neural network model. The semi-empirical model is based on general relationships between NOX emissions and engine parameters, but contains empirical constants that are determined based on the best fit to engine experimental data. The neural network model utilizes a similar set of input parameters, but relies on the neural network code to determine the relationships between input parameters and measured NOX emissions. The neural network model also contains empirical constants. The mathematics involved in both models is described. A single term semi-empirical model, which has been utilized in the literature as a PEMS model, is applied for comparative purposes.
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Blake, H. W., H. J. Grimsby, J. M. Starbuck, and D. E. Welch. Development of performance models for thick composites in compression. Office of Scientific and Technical Information (OSTI), November 1991. http://dx.doi.org/10.2172/10106720.
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Blake, H. W., H. J. Grimsby, J. M. Starbuck, and D. E. Welch. Development of performance models for thick composites in compression. Office of Scientific and Technical Information (OSTI), November 1991. http://dx.doi.org/10.2172/6110846.
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Kinikles, Dellena, and John McCartney. Hyperbolic Hydro-mechanical Model for Seismic Compression Prediction of Unsaturated Soils in the Funicular Regime. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, December 2022. http://dx.doi.org/10.55461/yunw7668.
Abstract:
A semi-empirical elasto-plastic constitutive model with a hyperbolic stress-strain curve was developed with the goal of predicting the seismic compression of unsaturated sands in the funicular regime of the soil-water retention curve (SWRC) during undrained cyclic shearing. Using a flow rule derived from energy considerations, the evolution in plastic volumetric strain (seismic compression) was predicted from the plastic shear strains of the hysteretic hyperbolic stress-strain curve. The plastic volumetric strains are used to predict the changes in degree of saturation from phase relationships and changes in pore air pressure from Boyle’s and Henry’s laws. The degree of saturation was used to estimate changes in matric suction from the transient scanning paths of the SWRC. Changes in small-strain shear modulus estimated from changes in mean effective stress computed from the constant total stress and changes in pore air pressure, degree of saturation and matric suction, in turn affect the hyperbolic stress-strain curve’s shape and the evolution in plastic volumetric strain. The model was calibrated using experimental shear stress-strain backbone curves from drained cyclic simple shear tests and transient SWRC scanning path measurements from undrained cyclic simple shear tests. Then the model predictions were validated using experimental data from undrained cyclic simple shear tests on unsaturated sand specimens with different initial degrees of saturation in the funicular regime. While the model captured the coupled evolution in hydro-mechanical variables (pore air pressure, pore water pressure, matric suction, degree of saturation, volumetric strain, effective stress, shear modulus) well over the first 15 cycles of shearing, the predictions were less accurate after continued cyclic shearing up to 200 cycles. After large numbers of cycles of undrained shearing, a linear decreasing trend between seismic compression and initial degree of saturation was predicted from the model while a nonlinear increasing-decreasing trend was observed in the cyclic simple shear experiments. This discrepancy may be due to not considering post shearing reconsolidation in the model, calibration of model parameters, or experimental issues including a drift in the position of the hysteretic shear-stress strain curve. Nonetheless, the trend from the model is consistent with predictions from previously- developed empirical models in the funicular regime of the SWRC. The developments of the new mechanistic model developed in this study will play a key role in the future development of a holistic model for predicting the seismic compression across all regimes of the SWRC.