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Статті в журналах з теми "Flax fibre bundle"
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Rayyaan, Rishad, William Richard Kennon, Prasad Potluri, and Mahmudul Akonda. "Fibre architecture modification to improve the tensile properties of flax-reinforced composites." Journal of Composite Materials 54, no. 3 (July 17, 2019): 379–95. http://dx.doi.org/10.1177/0021998319863156.
Повний текст джерелаАнотація:
As far as the tensile properties of natural fibres as reinforcements for composites are concerned, flax fibres will stay at the top-end. However, an efficient conversion of fibre properties into their corresponding composite properties has been a challenge, due to the fibre damages through the conventional textile methods utilised to process flax. These techniques impart disadvantageous features onto fibres at both micro- and meso-scale level, which in turn degrade the mechanical performances of flax fibre-reinforced composites (FFRC). Undulation of fibre is one of those detrimental features, which occurs during traditional fibre extraction from plant and fabric manufacturing routes. The undulation or waviness causes micro-compressive defects or ‘kink-bands’ in elementary flax fibres, which significantly undermines the performances of FFRC. Manufacturing flax fabric with minimal undulation could diminish the micro-compressive defects up to a substantial extent. In this research, nonwoven flax tapes of highly aligned flax fibres, blended with a small proportion of polylactic acid have been manufactured deploying a novel technique. Composites reinforced from those nonwoven tapes have been compared with composites reinforced with woven Hopsack fabrics and warp knitted unidirectional fabrics from flax, comprising undulating fibres. The composites reinforced with the highly aligned tapes have shown 33% higher fibre-bundle strength, and 57% higher fibre-bundle stiffness in comparison with the composites reinforced with Hopsack fabric. The results have been discussed in the light of fibre undulation, elementary fibre individualisation, homogeneity of fibre distribution, extent of resin rich areas and impregnation of the fibre lumens.
2
Al-Hajaj, Zainab, Ahmed Sarwar, Radovan Zdero, and Habiba Bougherara. "In-situ damage assessment of a novel carbon/flax/epoxy hybrid composite under tensile and compressive loading." Journal of Composite Materials 53, no. 19 (March 29, 2019): 2701–14. http://dx.doi.org/10.1177/0021998319839129.
Повний текст джерелаАнотація:
Damage under progressive load–unload until failure was assessed for a new woven carbon fibre/flax fibre/epoxy hybrid composite via stiffness degradation D, permanent strain [Formula: see text], and crack density [Formula: see text]. Type A configuration had woven carbon fibres and unidirectional flax fibres (i.e. [0–90C2/0F12/0–90C2]), while Type B configuration had woven carbon fibres and ±45 ° obliquely angled flax fibres (i.e. [0–90C2/(±45)F6S/0–90C2]. Results were obtained for D in tension (Type A, 0.080; Type B, 0.089) and compression (Type A, 0.178; Type B, 0.207), [Formula: see text] in tension (Type A, 0.085%; Type B, 0.075%) and compression (Type A, 0.086%; Type B, 0.086%), and [Formula: see text] in tension (Type A, range = 0.12–1.06%; Type B, range = 0.6–1.43%) and compression (Type A, range = 0.65–1.20%; Type B, range = 1.05–2.20%). Failure involved flax fibre bundle cracks and interfacial cracks in the flax fibre/epoxy region.
3
Titok, V., V. Leontiev, L. Shostak, and L. Khotyleva. "Thermogravimetric Analysis of the Flax Bast Fibre Bundle." Journal of Natural Fibers 3, no. 1 (June 19, 2006): 35–41. http://dx.doi.org/10.1300/j395v03n01_04.
Повний текст джерела
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Charlet, Karine, and Alexis Beakou. "Interfaces within flax fibre bundle: Experimental characterization and numerical modelling." Journal of Composite Materials 48, no. 26 (November 18, 2013): 3263–69. http://dx.doi.org/10.1177/0021998313508871.
Повний текст джерела
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Arbelaiz, A., B. Fernández, J. A. Ramos, A. Retegi, R. Llano-Ponte, and I. Mondragon. "Mechanical properties of short flax fibre bundle/polypropylene composites: Influence of matrix/fibre modification, fibre content, water uptake and recycling." Composites Science and Technology 65, no. 10 (August 2005): 1582–92. http://dx.doi.org/10.1016/j.compscitech.2005.01.008.
Повний текст джерела
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Arbelaiz, A., B. Fernández, A. Valea та I. Mondragon. "Mechanical properties of short flax fibre bundle/poly(ε-caprolactone) composites: Influence of matrix modification and fibre content". Carbohydrate Polymers 64, № 2 (травень 2006): 224–32. http://dx.doi.org/10.1016/j.carbpol.2005.11.030.
Повний текст джерела
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Straumit, Ilya, Dirk Vandepitte, Martine Wevers, and Stepan V. Lomov. "Identification of the flax fibre modulus based on an impregnated quasi-unidirectional fibre bundle test and X-ray computed tomography." Composites Science and Technology 151 (October 2017): 124–30. http://dx.doi.org/10.1016/j.compscitech.2017.07.029.
Повний текст джерела
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Bismut, Jean-Michel, Xiaonan Ma, and Weiping Zhang. "ASYMPTOTIC TORSION AND TOEPLITZ OPERATORS." Journal of the Institute of Mathematics of Jussieu 16, no. 2 (June 11, 2015): 223–349. http://dx.doi.org/10.1017/s1474748015000171.
Повний текст джерелаАнотація:
We use Toeplitz operators to evaluate the leading term in the asymptotics of the analytic torsion forms associated with a family of flat vector bundles $F_{p}$. For $p\in \mathbf{N}$, the flat vector bundle $F_{p}$ is the direct image of $L^{p}$, where $L$ is a holomorphic positive line bundle on the fibres of a flat fibration by compact Kähler manifolds. The leading term of the analytic torsion forms is the integral along the fibre of a locally defined differential form.
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Ho, Man-Ho. "Local index theory and the Riemann–Roch–Grothendieck theorem for complex flat vector bundles." Journal of Topology and Analysis 12, no. 04 (December 7, 2018): 941–87. http://dx.doi.org/10.1142/s1793525319500699.
Повний текст джерелаАнотація:
The purpose of this paper is to give a proof of the real part of the Riemann–Roch–Grothendieck theorem for complex flat vector bundles at the differential form level in the even dimensional fiber case. The proof is, roughly speaking, an application of the local family index theorem for a perturbed twisted spin Dirac operator, a variational formula of the Bismut–Cheeger eta form without the kernel bundle assumption in the even dimensional fiber case, and some properties of the Cheeger–Chern–Simons class of complex flat vector bundle.
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CRASMAREANU, MIRCEA. "DIRAC STRUCTURES FROM LIE INTEGRABILITY." International Journal of Geometric Methods in Modern Physics 09, no. 04 (May 6, 2012): 1220005. http://dx.doi.org/10.1142/s0219887812200058.
Повний текст джерелаАнотація:
We prove that a pair (F = vector sub-bundle of TM, its annihilator) yields an almost Dirac structure which is Dirac if and only if F is Lie integrable. Then a flat Ehresmann connection on a fiber bundle ξ yields two complementary, but not orthogonally, Dirac structures on the total space M of ξ. These Dirac structures are also Lagrangian sub-bundles with respect to the natural almost symplectic structure of the big tangent bundle of M. The tangent bundle in Riemannian geometry is discussed as particular case and the 3-dimensional Heisenberg space is illustrated as example. More generally, we study the Bianchi–Cartan–Vranceanu metrics and their Hopf bundles.
Дисертації з теми "Flax fibre bundle"
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Nguyen, Minh Tuan. "Contribution à l'optimisation des processus de filature des fibres libériennes." Mulhouse, 1996. http://www.theses.fr/1996MULH0440.
Повний текст джерелаАнотація:
La régularité de masse linéique (titre) des structures textiles linéaires produites en filature constitue le critère de qualité le plus important. En se basant sur les théories stochastiques classiques de l'étirage en grappes des fibres textiles individualisées, l'auteur a proposé une modélisation originale et très générale applicable à toutes les fibres, individualisées ou agglomérées sous forme de faisceaux fibreux ; cette théorie concerne tout particulièrement les fibres libériennes telles que le jute et le lin qui se présentent toujours sous forme de «faisceaux techniques» dissociables au cours du processus de filature. Les développements théoriques ont été totalement validés par une expérimentation industrielle approfondie réalisée dans le centre d'essais N. Schlumberger, premier constructeur français de matériel de filature. Enfin, la limite de filabilité a été discutée
2
Gogoli, Komlavi. "Contribution à l'étude des faisceaux de fibres de lin : analyse des relations morphologie-comportement mécanique-ultrastructure." Thesis, Normandie, 2022. https://tel.archives-ouvertes.fr/tel-03789637.
Повний текст джерелаАнотація:
Afin de réduire l’impact écologique des processus industriels, on assiste à un intérêt croissant dans l’industrie pour les fibres végétales. En effet, en plus d’être biodégradables, ces fibres possèdent des propriétés mécaniques capables de concurrencer celles des fibres synthétiques. Cependant, leur usage est limité notamment par la variabilité de leurs propriétés mécaniques. De plus, ces fibres présentent un comportement mécanique non-linéaire qu’il convient d’élucider. Dans ce contexte, cette thèse se propose dans une première partie d’étudier l’influence de la morphologie des faisceaux de fibres de lin sur leur comportement mécanique. Les résultats révèlent une forte hétérogénéité de la morphologie et une dépendance du comportement mécanique par rapport aux paramètres morphologiques comme le vrillage des échantillons, l’état des lamelles mitoyennes ou la section transversale. Dans une deuxième partie, il est proposé une caractérisation par diffraction des rayons X de l’ultrastructure du lin afin d’améliorer la compréhension du comportement mécanique non-linéaire des fibres de lin. Le traitement des mesures de diffraction par la technique d’analyse combinée << structure/microstructure/texture >> a rendu possible, entre autres, la détermination de la distribution de l’Angle Micro-Fibrillaire et la forme des cristallites de cellulose. Cette méthode a ensuite permis de suivre l’évolution sous traction de l’ultrastructure de la fibre de lin. Nous avons pu ainsi proposer un scénario susceptible d’expliquer le comportement mécanique non-linéaire des fibres de linIn order to reduce the ecological impact of industrial processes, there is a growing interest in the industry for plant fibres. Indeed, in addition to being biodegradable, these fibres have remarkable mechanical properties, making them very competitive with synthetic fibres. However, the use of plant fibres is currently limited, in particular by the variability observed in their mechanical properties. In addition, these fibres have a non-linear mechanical behaviour that needs to be elucidated. In this context, this work proposes in a first part to study the influence of the morphology of flax fibre bundles on their mechanical behaviour. The results reveal a strong heterogeneity in the morphology and a dependence of the tensile mechanical behaviour on morphological parameters such as the twisting of the samples, the state of the middle lamellae or the cross-section. In a second part, an X-ray diffraction characterisation of the flax ultrastructure is proposed to improve the understanding of the non-linear mechanical behaviour of flax fibres. The use of the so-called combined analysis << structure/microstructure/texture >> approach for the X-ray diffraction data fit allows the determination of the Micro-Fibrillar Angle distribution and the shape of the cellulose crystallites. This method then made it possible to follow the evolution of the ultrastructure of flax fibres under tensile loading. Finally, this allowed us to propose a scenario that could explain the non-linear mechanical behaviour of flax fibres
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Ferreira, Lucas Conque Seco. "Expoentes de Morse vetoriais e semifluxos em fibrados flag." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/305812.
Повний текст джерелаАнотація:
Orientador: Luiz Antonio Barrera San MartinTese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica
Made available in DSpace on 2018-08-08T09:09:07Z (GMT). No. of bitstreams: 1 Ferreira_LucasConqueSeco_D.pdf: 1131500 bytes, checksum: 66cc2aa6d04a5d822ddfaf164072cebd (MD5) Previous issue date: 2007
Resumo: Essa tese estabelece um procedimento intrínseco que generaliza a decomposição esférica/radial clássica de semifluxos lineares para uma classe mais ampla de semifluxos de endomorfismos de fibrados G-principais, cujo grupo estrutural G é um grupo de Lie mais geral que o grupo linear geral G1(n,R). Nesse contexto mais geral essa tese estabelece uma relação estreita entre os comportamentos assintóticos esférico e radial generalizados do semifluxo de endomorfismos com respeito µa recorrência por cadeias por meio do conceito de expoentes de Morse vetoriais.
Abstract: This thesis establishes an intrinsic procedure which generalizes the classical spherical/radial decomposition of linear semiflows to a broader class of semiflows of endomorphisms of G- principal fiber bundles, whose structural group G is a Lie group that is more general than the general linear group G1 (n,R). In this more general context this thesis establishes an intimate relationship between the generalized spherical and radial asymptotic behavior of the semiflow of endomorphisms with respect to chain recurrence through the concept of vector valued Morse exponents.
Doutorado
Doutor em Matemática
4
Alves, Luciana Aparecida. "Expoentes de Lyapunov e de Morse em fibrados flag." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/305810.
Повний текст джерелаАнотація:
Orientador: Luiz Antonio Barrera San MartinTese (doutorado) - Universidade Estadual de Campinas, Instituto de Matemática, Estatística e Computação Científica
Made available in DSpace on 2018-08-16T23:30:55Z (GMT). No. of bitstreams: 1 Alves_LucianaAparecida_D.pdf: 1178366 bytes, checksum: 5ebc7f21a1a3cb0e5f3a743c8cc377a7 (MD5) Previous issue date: 2010
Resumo: Nesta tese, estuda-se o crescimento exponencial de cociclos contínuos, a valores vetoriais, sobre o fibrado flag maximal. Tais cociclos estão intimamente ligados com os expoentes de Lyapunov clássicos e, assim, o teorema ergódigo multiplicativo de Oseledets é provado em um contexto de teoria de Lie semi-simples. Com isto, estabelece-se uma conexão entre a decomposição de Oseledets e a decomposição de Morse em fibrados flag. Alem disso, para uma classe de transformações de calibre no fibrado, compara-se a decomposição de Morse obtida em cada fibra com a mais fina, obtida anteriormente por Braga e San Martin
Abstract: In this thesis, we study the exponential growth of continuous cocycles wich take vector values on the maximal ag bundle. Such cocycles are intimately connected with the classic Lyapunov exponents, and thus the Oseledets's multiplicative ergodic theorem is proved in the context of semi-simple Lie theory. With this, it is established a connection between the Oseledets decomposition and Morse decomposition in ag bundles. In addition, considering a class of gauge transformations in the bundle, we compare the Morse decomposition obtained in each fiber with the finest Morse decomposition, obtained by Braga and San Martin
Doutorado
Teoria de Sistemas Dinâmicos
Doutor em Matemática
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Patrão, Mauro Moraes Alves. "Semifluxos em fibrados flag e seus semigrupos de sombreamento." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/305830.
Повний текст джерелаАнотація:
Orientador: Luiz Antonio Barreira San Martin, Marco Antonio TeixeiraTese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Científica
Made available in DSpace on 2018-08-05T23:39:22Z (GMT). No. of bitstreams: 1 Patrao_MauroMoraesAlves_D.pdf: 1206233 bytes, checksum: 5ea367b133840cc39b04e05a28c59d28 (MD5) Previous issue date: 2006
Resumo: A presente tese fornece uma abordagem que estabelece conexões entre dinâmica e teoria de semigrupos. Esta abordagem, denominada de teoria de semigrupos de sombreamento, é aplicada com sucesso no estudo de semifluxos de endomorfismos de uma classe bastante ampla de fibrados, que inclui a classe dos fibrados projetivos. Os semifluxos de endomorfismos de um fibrado generalizam, por meio da linguagem geométrica de fibrados, os semifluxos de produto cruzado associados a um cociclo, definidos em fibrados triviais
Abstract: The present thesis provides an approach which establishes connections between dynamics and the theory of semigroup. This approach, named theory of shadowing semigroups, is successfully applied to study semiflows of endomorphisms of a wide class of fiber bundles, which includes the class of the projective bundles. The semiflows of endomorphisms of a fiber bundle generalize, by using the geometric concept of fiber bundle, the skew-product semiflows associated to a cocycle, which are defined in trivial bundles
Doutorado
Geometria e Topologia/Sistemas Dinamicos
Doutor em Matemática
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Manivel, Laurent. "Théorèmes d'annulation pour la cohomologie des fibrés vectoriels amples." Grenoble 1, 1992. http://www.theses.fr/1992GRE10079.
Повний текст джерелаАнотація:
Nous etablissons differentes generalisations des theoremes d'annulation connus pour la cohomologie de dolbeault des fibres vectoriels holomorphes amples sur les varietes complexes projectives. Nous suivons pour cela la demarche classique, qui consiste, via des arguments de suite spectrale, a se ramener a des fibres en droites sur des varietes de drapeaux du fibre vectoriel considere. La cohomologie des fibres homogenes sur les varietes de drapeaux intervient ainsi de maniere essentielle. La premiere partie de cette these mene donc une etude approfondie du cas de la grassmannienne, pour lequel le theoreme de bott et la formule de cauchy permettent des calculs explicites. Nous deduisons de nos resultats des theoremes d'annulation pour les puissances exterieures et symetriques d'un fibre ample, le premier prolongeant deux enonces de le potier, le second etendant le theoreme de griffiths en bidegre quelconque. Nous montrons au passage que la suite spectrale de borel-le potier ne degenere uniformement en aucun degre. Pour ce qui concerne la cohomologie des images d'un fibre ample par des representations plus generales du groupe lineaire, nous donnons un theoreme d'annulation, en degre maximal, pour une representation dont le poids dominant admet des composantes negatives. La suite spectrale de borel-le-potier nous permet d'en deduire une reponse partielle a une conjecture de jean-pierre demailly. Dans la derniere partie de cette these, nous appliquons les estimations l#2 de hormander a l'etude d'un probleme de prolongement, sous des hypotheses de positivite, des sections d'un fibre en droites definies sur une sous-variete d'une variete de stein ou projective, lorsque cette sous-variete est le lieu des zeros d'une section holomorphe d'un fibre hermitien
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Ferraiol, Thiago Fanelli 1984. "Diferenciabilidade dos expoentes de Lyapunov." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/305804.
Повний текст джерелаАнотація:
Orientador: Luiz Antonio Barrera San MartinTese (doutorado) - Universidade Estadual de Campinas, Instituto de Matematica, Estatistica e Computação Cientifica
Made available in DSpace on 2018-08-21T17:52:11Z (GMT). No. of bitstreams: 1 Ferraiol_ThiagoFanelli_D.pdf: 1248936 bytes, checksum: b0a3aefba1736bb7ff7be29e982d7aa0 (MD5) Previous issue date: 2012
Resumo: Nesta tese apresentamos resultados que fornecem a regularidade dos expoentes de Lyapunov com uma abordagem via teoria de Lie. A generalização dos expoentes de Lyapunov para fluxos em fibrados flag associados a um fibrado principal é utilizada para obter a diferenciabilidade de certas combinações lineares do espectro de Lyapunov. Essas combinações que são diferenciáveis são determinadas a partir da caracterização da decomposição de Morse mais fina do fluxo nos fibrados flag. A diferenciabilidade é tomada com repeito à perturbação do fluxo por elementos do grupo de calibre do fibrado principal
Abstract: In this thesis we present results about regularity of Lyapunov Exponents via a Lie Theory approach. The generalization of Lyapunov Exponents for flows in flag bundles is used to obtain the differenciability of certain linear combinations of the Lyapunov spectra. This specific combinations that are differentiable are determined by the caracterization of the finest Morse decomposition of the flows on flag bundles. The differenciability is taken with respect to the perturbation of the flow by elements in the gauge group of the principal bundle
Doutorado
Matematica
Doutor em Matemática
8
Connery-Grigg, Dustin. "Fibrés symplectiques et la géométrie des difféomorphismes hamiltoniens." Thèse, 2016. http://hdl.handle.net/1866/18774.
Повний текст джерелаАнотація:
Ce mémoire porte sur quelques éléments de la théorie des fibrés symplectiques et leurs usages en étudiant la géométrie hoferienne sur le groupe de difféomorphismes hamiltoniens. En particulier en assumant un certain confort avec les notions de base de la géométrie différentielle et de la topologie algébrique on développe dans le premier chapitre les rudiments nécessaires de la théorie des G-fibrés et, dans la deuxième, tous les faits nécessaires de la topologie symplectique et les difféomorphismes hamiltoniens pour comprendre la théorie de base des fibrés symplectiques, à voir le morphisme de flux et ses liens aux isotopies hamiltoniennes. Le troisième chapitre présente les fondements des fibrés symplectiques se conclu en construisant la forme de couplage dans un langage invariant et en présentant la caractérisation des fibrés symplectiques, dont le groupe de structure réduit au groupe hamiltonien. Le mémoire se termine en présentant quelques applications des fibrés hamiltoniens à la géométrie de Hofer, en particulier une caractérisation de la partie positive de la norme de Hofer d'un lacet hamiltonien en termes du K-aire du fibré au-dessus de la sphère associé et une démonstration de la non-dégénérescence de la norme de Hofer pour des variétés symplectiques fermées.This thesis presents a reasonably complete account of the elements theory of symplectic and Hamiltonian fibrations. We assume a familiarity and comfort with the basic notions of differential geometry and algebraic topology but little else. Proceeding from this, the first chapter develops the necessary notions from the theory of fiber bundles and G-fiber bundles, while the second chapter develops all the notions and theorems required to understand the later theory of symplectic fibrations. Most notably the second chapter includes a detailed account of the classical relationship between the flux homomorphism and Hamiltonian isotopies. The third chapter is where we develop the theory of symplectic and locally Hamiltonian fiber bundles, and in particular give an invariant construction of the coupling form on a symplectic fibration admitting an extension class. the third chapter ends with a proof of a structure theorem characterizing those symplectic fibrations for which the structure group reduces to the Hamiltonian group. In the final chapter, we present some applications of the theory of Hamiltonian fibrations by the way of characterizing the positive part of the Hofer norm of a Hamiltonian loop as the K-area of its associated Hamiltonian bundle over the sphere, and we finish by giving a proof of the non-degeneracy of the Hofer norm for closed symplectic manifolds.
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Jauffret, Colin. "Modules réflexifs de rang 1 sur les variétés nilpotentes." Thèse, 2016. http://hdl.handle.net/1866/19543.
Повний текст джерелаАнотація:
Soit G un groupe algébrique linéaire complexe, simple, connexe et simplement connexe.
Étant donné un sous-groupe parabolique P G et un idéal nilpotent n p, il existe un
morphisme propre d’effondrement G x P n = Gn. Il se factorise en une variété affine et
normale N := SpecC [G P n] que nous appelons variété nilpotente.
Sous l’hypothèse que l’effondrement soit génériquement fini, nous décrivons le groupe
des classes de diviseurs équivariants de N à l’aide de C[N]-modules réflexifs équivariants
de rang 1. Un représentant de chaque classe peut être choisi comme les sections globales
d’un fibré en droite sur G x P' n' où G x P' n' = Gn' est un effondrement possiblement
distinct qui se factorise à travers la même variété nilpotente.
Dans le cas où le groupe G est de type A ou dans le cas d’un effondrement provenant de
certains diagrammes de Dynkin pondérés spécifiques, nous démontrons que les représentants
proviennent de poids qui peuvent être choisis comme dominants. Dans ce cas, nous
démontrons que si le module représente un élément torsion du groupe des classes, alors il
est Cohen–Macaulay. Nous en déduisons un théorème d’annulation en cohomologie.Let G be a simple, connected, simply connected complex linear algebraic group with parabolic subgroup P G and nilpotent ideal n p. The proper collapsing map G x P n = Gn factors through the normal affine variety N := SpecC [G x P n] which is called a nilpotent variety. Assuming the collapsing is generically finite, we describe the equivariant divisor class group of N using rank 1 reflexive equivariant C[N]-modules. A representative of each class may be chosen as global sections of a line bundle over G x P' n' where G x P' n' = Gn' is a possibly distinct collapsing that factors through the same nilpotent variety. Assuming either G is of type A or the collapsing comes from specific weighted Dynkin diagrams,we showthat each representative arise from a weight that may be chosen dominant. Moreover, if the module represents a torsion element within the class group, then it is Cohen– Macaulay and we deduce a cohomological vanishing theorem.
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Jauffret, Colin. "Variétés de drapeaux et opérateurs différentiels." Thèse, 2009. http://hdl.handle.net/1866/3467.
Повний текст джерелаАнотація:
Soit G un groupe algébrique semi-simple sur un corps de caractéristique 0. Ce mémoire discute d'un théorème d'annulation de la cohomologie supérieure du faisceau D des opérateurs différentiels sur une variété de drapeaux de G. On démontre que si P est un sous-groupe parabolique de G, alors H^i(G/P,D)=0 pour tout i>0.
On donne en fait trois preuves indépendantes de ce théorème. La première preuve est de Hesselink et n'est valide que dans le cas où le sous-groupe parabolique est un sous-groupe de Borel. Elle utilise un argument de suites spectrales et le théorème de Borel-Weil-Bott. La seconde preuve est de Kempf et n'est valide que dans le cas où le radical unipotent de P agit trivialement sur son algèbre de Lie. Elle n'utilise que le théorème de Borel-Weil-Bott. Enfin, la troisième preuve est attribuée à Elkik. Elle est valide pour tout sous-groupe parabolique mais utilise le théorème de Grauert-Riemenschneider.
On présente aussi une construction détaillée du faisceau des opérateurs différentiels sur une variété.Let G be a semisimple algebraic group on a field of characteristic 0. This thesis discusses a vanishing theorem for the higher cohomology of the sheaf D of differential operators on a flag variety of G. We show that if P is a parabolic subgroup of G, then H^i(G/P,D)=0 for all i>0. In fact, we give three independent proofs of this theorem. The first proof, due to Hesselink, only works if the parabolic subgroup P is a Borel subgroup. It uses a spectral sequence argument as well as the Borel-Weil-Bott theorem. The second proof, due to Kempf, only works if the unipotent radical of P acts trivially on its Lie algebra. It only uses the Borel-Weil-Bott theorem. Finally, the third proof, due to Elkik, is valid for any parabolic subgroup. However, it uses the Grauert-Riemenschneider theorem. We also present a detailled construction of the sheaf of differential operators on a variety.
Книги з теми "Flax fibre bundle"
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Benedetti, R. Lectures on hyperbolic geometry. Berlin: Springer-Verlag, 1992.
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Kamber, Franz, and Philippe Tondeur. Flat Manifolds. Springer London, Limited, 2006.
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Benedetti, Riccardo, and Carlo Petronio. Lectures on Hyperbolic Geometry (Universitext). Springer, 2003.
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4
Benedetti, Riccardo, and Carlo Petronio. Lectures on Hyperbolic Geometry. Springer London, Limited, 2012.
Знайти повний текст джерелаЧастини книг з теми "Flax fibre bundle"
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Arbelaiz, A., J. Trifol, C. Pe˜a-Rodriguez, J. Labidi, and A. Eceiza. "Modification of Poly(lactic acid) Matrix by Chemically Modified Flax Fiber Bundles and Poly(ethylene glycol) Plasticizer." In Polyethylene-Based Biocomposites and Bionanocomposites, 429–45. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2016. http://dx.doi.org/10.1002/9781119038467.ch12.
Повний текст джерелаТези доповідей конференцій з теми "Flax fibre bundle"
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Shahinpoor, Mohsen, Martin W. J. Burmeister, and Wesley Hoffman. "Design, Modeling and Fabrication of Micro-Robotic Actuators With Ionic Polymeric Gel and SMA Micro-Muscles." In ASME 1995 Design Engineering Technical Conferences collocated with the ASME 1995 15th International Computers in Engineering Conference and the ASME 1995 9th Annual Engineering Database Symposium. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/detc1995-0626.
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Abstract Presented are the details for design and fabrication of a novel micro-robotic actuator in a few micron-size range. The model is in the form of contractile fiber bundles embedded in or around micron size helical compression springs. The fiber bundle is assumed to consist of a parallel array of contractile fibers made form either electrically or chemically (pH muscles) contractile ionic polymeric muscles such as polyacrylic acid plus sodium acrylate cross-linked with bisacrylamide (PAAM) or polyacrylonitrile (PAN) fibers or electrically contractile shape-memory alloy (SMA) fiber bundles. The proposed model considers the electrically or pH-induced contraction of the ionic polymeric fibers as well as resistive heating of the SMA fiber bundles in case of shape-memory alloys. A theoretical model is also presented for the dynamic modeling of such micron size robotic actuators. These robotic micro-actuators will open a new frontier to the micro-universes of biological, scientific, medical and engineering systems. On the fabrication side, helical compression springs and bellows in a few microns size range have been manufactured in our laboratories to serve as the main resilient structure for the micro-robotic actuator. In principle, any size micro-robotic linear actuator can be fabricated and tested in our laboratory. For the case of ionic polymeric gel fibers the model consists of an encapsulated hermetically sealed, helical compression spring-loaded cylindrical linear actuators containing a counterionic solution or electrolyte such as water+acetone, a cylindrical helical compression micro-spring and a collection of polymeric gel fibers (polyelectrolytes) such as polyvinyl alcohol (PVA) polyacrylic acid (PAA) or polyacrylamide. Furthermore, the helical micro-spring not only acts as a compression spring between the two hermetically sealed circular end-caps but contains snugly the polymeric gel fiber bundle and also acts as the cathode (anode) electrode -while the two actuator end-caps act as the other cathode (anode) electrodes. In this fashion, a DC electric field of a few volts per centimeter per gram of polymer gel can cause the polymer gel fiber bundle to contract (expand). This causes the compression spring to contract and pull the two end-caps closer to each other against the elastic resistance of the helical spring. By reversing the action by means of reversing the electric field polarities the gel is allowed to expand while the compression spring is also expanding and helping the linear expansion of the actuator since the polymeric gel muscle expands due to the induced alkalinity along the helical spring body. Thus, electrical control of the expansion and the contraction of the micro-robotic linear actuator is possible. A mathematical model is presented based on the proposed composite structure that takes into account all pertinent variables such as the pH of the gel fiber bundle, the pH of the surrounding medium, the hyperelastic parameters of the fiber bundle, the electrical variables of the gel, the electric field strength, the pH field strength and all pertinent dimensions followed by some numerical and experimental simulations and data. For the second model, we consider the fiber bundle of SMA to be either circumscribed inside a micron size helical compression spring with flat heads or in parallel with a number helical compression springs, end-capped by two parallel circular plates with embedded electrodes to which the ends of the SMA fibers are secured. Thus, the fibers can be electrically heated and subsequently contracted to compress the helical compression spring back and forth. Design details are first described. In essence the dynamic behavior of the actuator depends on the interaction between the current supplied to the wires and the heat transfer from the wires. Further, a mathematical model is presented to simulate the electro-thermo-mechanics of motion of such actuators. The proposed model takes into account all pertinent variables such as the strain ϵ, the temperature of the fibers T(t) as a function of time t, the ambient temperature T0, the martensite fraction ξ, the helical compression spring constant k and the overall heat transfer coefficient h. Numerical simulations are then carried out and the results are compared with experimental observations of a number of fabricated systems in a size range of a few mcrons.
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Aly-Hassan, Mohamed S., Yuka Takai, Asami Nakai, Hiroyuki Hamada, Yohei Shinyama, Yoshimi Hatsukade, and Saburo Tanaka. "Assessment of Fracture Behavior of Flat Braided CFRP Composites Under Tensile Loading With Assistance of SQUID Technique." In ASME 2011 International Mechanical Engineering Congress and Exposition. ASMEDC, 2011. http://dx.doi.org/10.1115/imece2011-62421.
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The goal of this research is to provide a sufficient understanding for the damage mechanism of ±45° flat braided CFRP composites under tensile loading based on in-situ macroscopic observations of surface cracking and off-line measurements for the state-of-fibers by Superconducting Quantum Interference Device (SQUID) technique to analyze the effect of the continuously oriented of all braided fiber bundles on the tensile and in-plane shear properties. SQUID technique displays an effective capability in inspection the state-of-fiber failure, whereas the in-situ surface macroscopic observation technique is very useful in observing the surface matrix cracking at different stages of damage. The damage mechanism of uncut-edges and cut-edges of ±45° flat braided CFRP composites are identified adequately by the above-mentioned experimental procedure. The cut-edges ±45° flat braided CFRP composites exhibit a pure shear damage mechanism associated with large shear deformation and no significant fiber failure, while the uncut-edges ±45° flat braided CFRP composites exhibit a slight fiber scissoring mechanism followed by a partially fiber failure. The enhancement of the tensile and in-plane strengths of the uncut-edges ±45° flat braided CFRP composites by about 60% higher than those of the cut-edges ±45° flat braided CFRP composites achieves not only by the effect of the continuously oriented carbon fibers at the edges but also by the effect of re-orientation of braiding fiber bundles with smaller angle than the original ±45° braiding angle of the fabricated composites, or so called fiber scissoring mechanism in composites.
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HASHIMOTO, Hideya, Misa OHASHI, and Kazuhiro SUZUKI. "NON-FLAT TOTALLY GEODESIC SURFACES OF SU(4)/SO(4) AND FIBRE BUNDLE STRUCTURES RELATED TO SU(4)." In 6th International Colloquium on Differential Geometry and its Related Fields. WORLD SCIENTIFIC, 2019. http://dx.doi.org/10.1142/9789811206696_0010.
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Pastore, Christopher, Benny Ong, Hoa Lam, Tommy Chen, Dean Nguyen, Tiffany Liao, Maury Grudza, Dave Jann, Robert Ciccarelli, and Stanley Ng. "Development of a 3D Braided Preform for Rotorcraft Flex-beam." In Vertical Flight Society 78th Annual Forum & Technology Display. The Vertical Flight Society, 2022. http://dx.doi.org/10.4050/f-0078-2022-17616.
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A novel 3-dimensional braiding concept, 4StepPlus, suitable for rotorcraft components where high damage tolerance and fatigue cycles are critical is explored in this paper. 3D textiles such as woven and braided fabrics provide through the thickness reinforcement and thus improved interlaminar strength properties over laminated composites. However, there are challenges in creating shapes with varying cross-sectional shapes and areas. A 4StepPlus 3D braiding approach is used to fabricate a subscale flexbeam with substantial changes in cross-section throughout the length of the part. The mechanical properties of 3D braided composites employing IM7 carbon and S2-glass with RTM epoxy are investigated. The effects of fiber bundle sizes is also assessed as it plays an important role in the performance as well as manufacturing of the component. The results indicate no significant effects of yarn size on the performance of the composites.
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Zhang, C., M. J. Pettigrew, and N. W. Mureithi. "Correlation Between Vibration Excitation Forces and the Dynamic Characteristics of Two-Phase Flow in a Rotated Triangular Tube Bundle." In ASME 2006 Pressure Vessels and Piping/ICPVT-11 Conference. ASMEDC, 2006. http://dx.doi.org/10.1115/pvp2006-icpvt-11-93797.
Повний текст джерелаАнотація:
Two-phase cross flow exists in many shell-and-tube heat exchangers. Flow-induced vibration excitation forces can cause tube motion that will result in long-term fretting-wear or fatigue. Detailed flow and vibration excitation force measurements in tube bundles subjected to two-phase cross flow are required to understand the underlying vibration excitation mechanisms. Some of this work has already been done. The distributions of both void fraction and bubble velocity in rotated-triangular tube bundles were obtained. Somewhat unexpected but significant quasi-periodic forces in both the drag and lift directions were measured. The present work aims at understanding the nature of such unexpected drag and lift quasi-periodic forces. An experimental program was undertaken with a rotated-triangular array of cylinders subjected to air/water flow to simulate two-phase mixtures. Fiber-optic probes were developed to measure local void fraction. Both the dynamic lift and drag forces were measured with a strain gage instrumented cylinder. The investigation showed that the quasi-periodic drag and lift forces are generated by different mechanisms that have not been observed so far. The quasi-periodic drag forces appear related to the momentum flux fluctuations in the main flow path between the cylinders. The quasi-periodic lift forces, on the other hand, are mostly correlated to oscillations in the wake of the cylinders. The relationships between the lift or drag forces and the dynamic characteristics of two-phase flow are established through fluid mechanics momentum equations. The quasi-periodic lift forces are related to local void fraction measurements in the unsteady wake area between upstream and downstream cylinders. The quasi-periodic drag forces correlate well with similar measurements in the main flow stream between cylinders.
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Skulborstad, Alyssa J., and N. C. Goulbourne. "A Structurally Motivated Constitutive Model for Bat Wing Skin." In ASME 2014 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/imece2014-39525.
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Unique among animal flyers, bats have highly flexible and stretchable thin wing membranes. The connection between the structural constituents of bat wing skin, its material behavior, and flight abilities is not yet known. In this work we propose a structurally motivated constitutive model for the wing skin. Within a continuum mechanics framework, the proposed strain energy function for the wing skin is the sum of contributions due to the matrix and two mesoscopic fiber families, one oriented primarily spanwise consisting of elastin fiber bundles and the other family oriented chordwise consisting of muscle fibers. While the fibers are flat and straight when the wing is somewhat open, the matrix exhibits corrugations due to compressive loading from the pre-stretched spanwise fibers. This mismatch in the natural configurations of components is accounted for in the model by a decomposition of the deformation gradient of the spanwise fibers. The material parameters are fit with a procedure motivated by the underlying deformation mechanisms of the tissue corresponding to the regions of the j-shaped constitutive curves. The proposed model is fit to the first set of biaxial experimental stress-strain data for bat wing skin and captures the general features of the tissue response well.