Letteratura scientifica selezionata sul tema "Fibrés de Procesi"
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Articoli di riviste sul tema "Fibrés de Procesi"
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Harizi, T., S. Dhouib, S. Msahli e F. Sakli. "Bleaching Process Investigation of Tunisian Dromedary Hair". ISRN Textiles 2013 (4 giugno 2013): 1–5. http://dx.doi.org/10.1155/2013/532396.
Testo completoAbstract (sommario):
Successful bleaching of pigmented fibres was, generally, evaluated by a maximum whiteness, a minimum yellowness, and less damage to the bleached fibers. A review of the literature reveals that many studies on pigmented fibre bleaching are concerned with improving the whiteness and mechanical properties of bleached fibres. In this study, we investigate the effects of the hydrogen peroxide concentration, bleaching time, and clarification bath on the bleaching efficiency of Tunisian dromedary hair. It was showed that 30 min bleaching time gives better result in term of whiteness. However, an increased bleaching time gives an excessive damage to the bleached fibers. Further, the damage incurred by the dromedary hair was more important than that for wool, as is shown by the tenacity results. We found that oxalic acid, which is used for rinsing dromedary hair (after bleaching), provides improved results in term of whiteness obtained with bleaching. Certainly, oxalic acid made it possible to remove the maximum of iron remaining on fibre after bleaching. Bleaching methods demonstrate the excessive damage incurred by the fibre when using hydrogen peroxide particularly with raise concentration. This damage leads to adverse effects on the tenacity fibre.
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Swaroop, Dasagrandhi Veda. "Analysis of Mechanical Properties of Banana-Jute Hybrid Fiber-reinforced Epoxy composite by varying Stacking sequence". International Journal for Research in Applied Science and Engineering Technology 10, n. 3 (31 marzo 2022): 429–38. http://dx.doi.org/10.22214/ijraset.2022.40581.
Testo completoAbstract (sommario):
Abstract: Nowadays, the study on natural fibers has gradually increased because of the environmental concerns due to usage of synthetic fibers. The natural fibres properties such as biodegradability, availability, strength made them a potential replacement of synthetic fibers. Hybrid Fibre reinforced composites are the composites that comprises two or more different fibres. The banana and jute fibres are selected because of their strength, moisture absorption capacity , availability. The epoxy resin is selected as a matrix to bind the fibres and to transfer a uniform load. Banana-Jute Hybrid fibre reinforced epoxy composite with different stacking sequences (BJB, BBJ, JBJ,JJB where B=Banana Fibre, J=Jute Fibre) will be fabricated by Hand-layup process for analyzing Shore hardness of composite samples and the same composite samples will be modelled in ANSYS to analyse the Flexural properties, tensile properties and Impact strength of composite samples. Keywords: ANSYS, Hand-layup, Shore Hardness, Flexural properties, Tensile properties.
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Yatsenko, T. A., V. М. Rybachuk, O. I. Yusova, S. M. Kharchenko e T. V. Grinenko. "Effect of fibrin degradation products on fibrinolytic process". Ukrainian Biochemical Journal 88, n. 2 (25 aprile 2016): 16–24. http://dx.doi.org/10.15407/ubj88.02.016.
Testo completo
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Zhang, Wei, Xu Wang e Hong Wei Xing. "Numerical Simulation of the Cooling Process of the Blast Furnace Slag Fiber". Advanced Materials Research 934 (maggio 2014): 223–29. http://dx.doi.org/10.4028/www.scientific.net/amr.934.223.
Testo completoAbstract (sommario):
The cooling process of the blast furnace slag fibers was simulated and calculated by the numerical simulation software. The different length-diameter ratio fibers for 100:1 and 1000:1 were chosen and the temperature fields of the fibers cooling process under the different conditions were analyzed. The results showed that the single fiber’s solidification has begun at 0.1s, the fiber forms the whole shell on its surface at 0.9s, and the center of the fiber become solid at about 1.5s. Multi-fibers cooling process is different from the single fiber and the solidification time obviously become longer. 3-fibers’ solidification performs began at about 0.1s, and the whole solidification process needs about 5s.
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Wójcik, Grzegorz Michał. "Optimization of silica glass capillary and rods drawing process." Photonics Letters of Poland 11, n. 1 (3 aprile 2019): 19. http://dx.doi.org/10.4302/plp.v11i1.891.
Testo completoAbstract (sommario):
Diameter fluctuations of silica glass rods and capillaries, during drawing process have been studied. We investigated an influence of drawing conditions on the quality of capillaries and rods. We fabricated two preforms made from different quality material. Fabricated preforms were used to draw microstructured fibers. Full Text: PDF ReferencesS. Habib et al., "Broadband dispersion compensation of conventional single mode fibers using microstructure optical fibers", Int. J. Lig. Opt. 124, 3851-3855 (2013) CrossRef A. Ziolowicz et al. "Overcoming the capacity crunch: ITU-T G.657.B3 compatible 7-core and 19-core hole-assisted fibers", Proc SPIE 10130, 101300C (2017) CrossRef T.M. Monro et al. "Sensing with microstructured optical fibres", Meas. Sci. Technol. 12, 854-858 (2001) CrossRef G. Statkiewicz-Barabach et al.,"Hydrostatic Pressure and Temperature Measurements Using an In-Line Mach-Zehnder Interferometer Based on a Two-Mode Highly Birefringent Microstructured Fiber", Sensors 2017, 17, 1648 (2017) CrossRef T. Yoon, M. Bajcsy, "Laser-cooled cesium atoms confined with a magic-wavelength dipole trap inside a hollow-core photonic-bandgap fiber", Phys. Rev. A 99, 023415 (2019) CrossRef A.N. Ghosh et al., "Supercontinuum generation in heavy-metal oxide glass based suspended-core photonic crystal fibers", J. Opt. Soc. Am. B 35, 2311-2316 (2018) CrossRef G. Wójcik et al. "Microbending losses in optical fibers with different cross-sections", Proc. SPIE 10830, 108300H (2018) CrossRef F. Xu, Selected topics on optical fiber technology and applications (IntechOpen 2018) CrossRef
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Hernández, J. B., F. A. Aguirre, J. L. Martínez, C. E. Caballero, L. Pérez-Rea e V. M. Castaño. "Dielectric Dissipation of Fibre-modified Hydraulic Concretes". Advanced Composites Letters 7, n. 6 (novembre 1998): 096369359800700. http://dx.doi.org/10.1177/096369359800700603.
Testo completoAbstract (sommario):
Dielectric behavior of Portland cement-based concretes, modified with either polyester or polypropylene fibers was studied by measuring their dissipation factors at different frequencies. The results show that the fibers with non-polar surfaces (polyester) do not influence the hydration process of the cement matrix, whereas polypropylene fibres, with polar surfaces, have a definitive role on the curing properties of the composites.
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Davindrabrabu, Mathivanan, Parlaungan Siregar Januar, Bachtiar Dandi, Mat Rejab Mohd Ruzaimi e Tezara Cionita. "Effect of Fibre Loading on the Flexural Properties of Natural Fibre Reinforced Polymer Composites". Applied Mechanics and Materials 695 (novembre 2014): 85–88. http://dx.doi.org/10.4028/www.scientific.net/amm.695.85.
Testo completoAbstract (sommario):
The use of pineapple leaf fibres as reinforcement in plastics had increased rapidly in past few years. Thus this project was conducted to determine and compare the flexural strength of pure epoxy and pineapple leaf fibres reinforced epoxy. The natural fibres were mixed with epoxy and hardener by weight percentage fibre content. The process employed to fabricate the specimens was hand lay-up and the natural fibres was oriented randomly. The dimensions of the specimens for flexure test were based on ASTM D790 respectively. The results obtained shows that 15% PALF reinforced epoxy composite achieved the highest flexural strength among the natural fibers reinforced epoxy composites.
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Hery Sunarsono, Hazimah, Sari Rahmiati, Mohd Sapuan Salit, Ahmad Ilyas Rushdan e Fiqri Ardi Azhari. "Effect of Various Concentrations of Sodium Hydroxide/Hot Alkali Treatment on the Physical Properties of Ramie Fibres". Journal of Advanced Research in Fluid Mechanics and Thermal Sciences 115, n. 2 (1 aprile 2024): 96–102. http://dx.doi.org/10.37934/arfmts.115.2.96102.
Testo completoAbstract (sommario):
The preparation stages that precede the final treatment with a chemical treatment like alkali determine the physical characteristics of ramie fibres. It modified the hydroxyl group which is responsible for the hydrogen bonding of the fibres. This work examined the pre-treatment of ramie fibres with acetone followed by alkali or hot alkali with various concentrations. The immersion of ramie fibres in certain percentages of sodium hydroxide solution resulted in a good performance of their physical characteristics. The ramie fibres treated with 10% NaOH exhibit the best dispersion stability and low agglomeration or precipitation in water with an amount of 14%. When alkali is applied to ramie fibres, the hydrophilic group on their surface grows, potentially improving the fibre's capacity to absorb water. However, when the concentration is increased to 15%, the dispersion stability of sodium hydroxide performs less well. The fibres' ability to absorb water was diminished and they became brittle due to a high alkali content. In addition to the aforementioned characteristics, the properties of precipitation and water absorption were unaffected by the hot alkaline process for all samples. The hot alkali process (80°C) was not able to generate a further breakdown of hydrogen bonds of the fibres.
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ZHU, Sufeng, Zenghui ZHAO, Yinping YUE, Xufeng DONG e Min QI. "Influence of the Chemical Modification of Carbon Nanotube Fibers on Electrical properties and Electromechanical Response". Progress in Chinese Materials Sciences 3, n. 2 (28 giugno 2024): 20–28. http://dx.doi.org/10.48014/pcms.20240218001.
Testo completoAbstract (sommario):
The electromechanical response (EMR) of carbon nanotube (CNT) fibers is related to the densification process of the CNT network driven by electromagnetic force. The study of the interaction between the electrical properties and the electromechanical response of carbon nanotubes is of great theoretical significance for exploring the microstructure of carbon nanotube fibers and developing the related flexible electronic devices. This study investigated the relationship between the conductive pathway network and EMR, by analyzing the internal structural characteristics of the CNT fibers after undergoing hydrogen peroxide oxidation and iodine modification. The results show that impurities such as amorphous carbon impeded electron transport and deformation of CNT networks. After hydrogen peroxide oxidation treatment, he carbon nanotube surface impurities inside the fibres were reduced, the van der Waals forces between carbon nanotubes were increased, the deformation of the carbon nanotube network was enhanced, and the negative effect of the decrease in the elastic modulus of the fibres caused by the increase in temperature was weakened. In the case of iodine-decorated CNT fibers, carbon-iodine bonds effectively strengthened the interaction between CNTs, but hinders the contraction of the carbon nanotube network, resulting in a weaker electromechanical response. Hydrogen peroxide oxidation treatment is more beneficial than iodine modification to improve the shrinkage and deformation ability of carbon nanotube fibres in the electromechanical response.
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Perelles, D. H., M. F. Medeiros e M. R. Garcez. "Aplicação da análise hierárquica como ferramenta de tomada de decisão para escolha do compósito de reforço com polímeros reforçados com fibras". Revista ALCONPAT 3, n. 3 (30 settembre 2013): 161–76. http://dx.doi.org/10.21041/ra.v3i3.52.
Testo completoAbstract (sommario):
RESUMOO reforço de estruturas com Polímeros Reforçados com Fibras (PRF) é uma alternativa que tem sido muito utilizada em intervenções executadas em elementos de concreto armado. A fibra de carbono é a mais empregada na formação dos compósitos de reforço utilizados em obras civis. Existe, no entanto, a possibilidade de se ampliar as opções de fibras formadoras do compósito utilizando as fibras de aramida e de vidro. Como uma ferramenta alternativa de tomada de decisão, o Método de Análise Hierárquica, baseado em critérios analisados de forma qualitativa e quantitativa, será utilizado neste trabalho para a avaliação das fibras de carbono, aramida e vidro, de forma a se obter qual material seria o mais apropriado para a execução de um reforço estrutural considerando como principais parâmetros de análise os custos dos materiais e as tensões e as deformações que os elementos poderão apresentar. A aplicação desta técnica de interpretação de resultados se mostrou muito útil, podendo ser considerada adequada para estudos que exijam uma tomada de decisão entre diferentes sistemas de reforço com PRF.Palabras clave: Reforço estrutural; polímeros reforçados com fibras; carbono; aramida; vidro; método da análise hierárquica.ABSTRACTStrengthening structures with Fiber Reinforced Polymers (FRP) is an alternative that has been used in interventions performed on reinforced concrete elements. Carbon fibers are the most used in the formation of composite reinforcement used in civil works. There is, however, possible to expand the options of forming fibers using the composite fibers of aramid and glass. As an alternative decision-making tool, the Analytic Hierarchy Process, based on criteria analyzed qualitatively and quantitatively, will be used in this work for the evaluation of carbon, aramid and glass fibers in order to obtain what material would be more suitable for the implementation of a structural reinforcement considering how key parameters of analysis material costs and the tensions and strains that may exhibit elements. This decision-making tool showed useful and can be considered suitable to select different FRP systems.Keywords: Structural strengthening; fiber-reinforced polymers; carbon; aramid; glass; hierarchical analysis method.
Tesi sul tema "Fibrés de Procesi"
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Paegelow, Raphaël. "Action des sous-groupes finis de SL2(C) sur la variété de carquois de Nakajima du carquois de Jordan et fibrés de Procesi". Electronic Thesis or Diss., Université de Montpellier (2022-....), 2024. http://www.theses.fr/2024UMONS005.
Testo completoAbstract (sommario):
Dans cette thèse de doctorat, nous avons, dans un premier temps, étudié la décomposition en composantes irréductibles du lieu des points fixes sous l’action d’un sous-groupe fini Γ de SL2(C) de la variété de carquois de Nakajima du carquois de Jordan. La variété de carquois associé au carquois de Jordan est isomorphe soit au schéma ponctuel de Hilbert dans C2 soit à l’espace de Calogero-Moser. Nous avons décrit ces composantes irréductibles à l’aide de variétés de carquois du carquois de McKay associé au sous-groupe fini Γ. Nous nous sommes ensuite intéressés à la combinatoire découlant de l’ensemble d’indexation de ces composantes irréductibles en utilisant une action du groupe de Weyl affine introduite par Nakajima. De plus, nous avons construit un modèle combinatoire lorsque Γ est de type D, qui est le seul cas original et remarquable. En effet, si Γ est de type A, un tel travail a déjà été fait par Iain Gordon et si Γ est de type E, nous avons montré que les points fixes qui sont aussi des points fixes du tore diagonal maximal de SL2(C) sont les idéaux monomiaux du schéma ponctuel de Hilbert dans C2 indexés par les partitions en escaliers. De manière plus précise, si Γ est de type D, nous avons obtenu un modèle de l’ensemble indexant les composantes irréductibles contenant un point fixe du tore maximal diagonal de SL2(C) en termes de partitions symétriques. Enfin, si n est un entier plus grand que 1, en utilisant la classification des résolutions projectives et symplectiques de la singularité (C2)n/Γn où Γn est le produit en couronne du groupe symétrique Sn des n premiers entiers et de Γ, nous avons obtenu une description de toutes ces résolutions projectives et symplectiques en termes de composantes irréductibles du lieu des Γ-points fixes du schéma ponctuel de Hilbert dans C2.Dans un second temps, nous nous sommes intéressés à la restriction de deux fibrés vectoriels au-dessus d’une composante irréductible du lieu des Γ-points fixes du schéma de Hilbert dans C2 fixée. Le premier fibré est le fibré tautologique dont nous avons exprimé la restriction en termes de fibrés tautologiques de Nakajima sur la variété de carquois du carquois de McKay associée à la composante irréductible fixée. Le second fibré vectoriel est le fibré de Procesi. Ce fibré a été introduit par Marc Haiman dans ces travaux démontrant la conjecture n!. Nous avons étudié les fibres de ce fibré en tant que (Sn × Γ)-module. Dans la première partie du chapitre de cette thèse consacré au fibré de Procesi, nous avons démontré un théorème de réduction qui exprime le (Sn × Γ)-module associé à la fibre de la restriction du fibré de Procesi au-desus d’une composante irréductible C du lieu des Γ-points fixes du schéma de Hilbert de n points dans C2 comme l’induit de la fibre de la restriction du fibré de Procesi au-dessus d’une composante irréductible du lieu des Γ-points fixes du schéma de Hilbert de k points dans C2 où l’entier k ≤ n est explicite et dépend de la composante irréductible C et de Γ. Ce théorème est ensuite démontré avec d’autres outils dans deux cas particuliers pour Γ de type A. Enfin, lorsque Γ est de type D, certaines formules explicites de réduction des fibres de la restriction du fibré de Procesi au lieu des Γ-point fixes ont étéobtenues.Pour finir, si l est un entier plus grand que 1, alors dans le cas où Γ est le sous-groupe cyclique d’ordre l contenu dans le tore maximal diagonal de SL2(C) noté µl, le théorème de réduction restreint l’étude des fibres du fibré de Procesi au-dessus du lieu des µl-points fixes du schéma ponctuel de Hilbert dans C2 à l’étude des fibres au-dessus des points du schéma de Hilbert associés aux idéaux monomiaux paramétrés par les l-cœurs. Les (Sn × µl)-modules que l’on obtient semble être reliés à l’espace de Fock de l’algèbre de Kac-Moody ˆsll(C). Une conjecture dans ce sens est énoncée dans le dernier chapitreIn this doctoral thesis, first of all, we have studied the decomposition into irreducible components of the fixed point locus under the action of Γ a finite subgroup of SL2(C) of the Nakajima quiver variety of Jordan’s quiver. The quiver variety associated with Jordan’s quiver is either isomorphic to the punctual Hilbert scheme in C2 or to the Calogero-Moser space. We have described the irreducible components using quiver varieties of McKay’s quiver associated with the finite subgroup Γ. We were then interested in the combinatorics coming out of the indexing set of these irreducible components using an action of the affine Weyl group introduced by Nakajima. Moreover, we have constructed a combinatorial model when Γ is of type D, which is the only original and remarkable case. Indeed, when Γ is of type A, such work has already been done by Iain Gordon and if Γ is of type E, we have shown that the fixed points that are also fixed under the maximal diagonal torus of SL2(C) are the monomial ideals of the punctual Hilbert scheme in C2 indexed by staircase partitions. To be more precise, when Γ is of type D, we have obtained a model of the indexing set of the irreducible components containing a fixed point of the maximal diagonal torus of SL2(C) in terms of symmetric partitions. Finally, if n is an integer greater than 1, using the classification of the projective, symplectic resolutions of the singularity (C2)n/Γn where Γn is the wreath product of the symmetric group on n letters Sn with Γ, we have obtained a description of all such resolutions in terms of irreducible components of the Γ-fixedpoint locus of the Hilbert scheme of points in C2.Secondly, we were interested in the restriction of two vector bundles over a fixed irreducible component of the Γ-fixed point locus of the punctual Hilbert scheme in C2. The first vector bundle is the tautological vector bundle that we have expressed the restriction in terms of Nakajima’s tautological vector bundle on the quiver variety of McKay’s quiver associated with the fixed irreducible component. The second vector bundle is the Procesi bundle. This vector bundle was introduced by Marc Haiman in his work proving the n! conjecture. We have studied the fibers of this bundle as (Sn × Γ)-module. In the first part of the chapter of this thesis dedicated to the Procesi bundle, we have shown a reduction theorem that expresses the (Sn × Γ)-module associated with the fiber of the restriction of the Procesi bundle over an irreducible component C of the Γ-fixed point locus of Hilbert scheme of n points in C2 as the induced of the fiber of the restriction of the Procesi bundle over an irreducible component of the Γ-fixed point locus of the Hilbert scheme of k points in C2 where k ≤ n is explicit and depends on the irreducible component C and Γ. This theorem is then proven with other tools in two edge cases when Γ is of type A. Finally, when Γ is of type D, some explicit reduction formulas of the restriction of the Procesi bundle to the Γ-fixed point locus have been obtained.To finish, if l is an integer greater than 1, then in the case where Γ is the cyclic group of order l contained in the maximal diagonal torus of SL2(C) denoted by µl, the reduction theorem restricts the study of the fibers of the Procesi bundle over the µl-fixed points of the punctual Hilbert scheme in C2 to the study of the fibers over points in the Hilbert scheme associated with monomial ideals parametrized by the l-cores. The (Sn × Γ)-module that one obtains seems to be related to the Fock space of the Kac-Moody algebra ˆsll(C). A conjecture in this direction has been stated in the last chapter
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Araújo, Maico Dutra de. "Efeito do processamento e da inclusão de fibras nas propriedades mecânicas e ópticas de uma porcelana odontológica". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/23/23140/tde-07112011-105946/.
Testo completoAbstract (sommario):
O objetivo dessa tese foi avaliar o efeito da adição de fibras e tipo de processamento (sinterização versus injeção) na microestrutura, propriedades mecânicas (resistência à flexão f e parâmetros de Weibull m, 0 e 5%), parâmetros de crescimento subcrítico (n e f0) e propriedades ópticas de razão de contraste (RC), parâmetro de translucidez (PT) e índice de opalescência (IO) de uma porcelana odontológica à base de leucita. Fibras de hexatitanato de potássio foram misturadas a uma porcelana à base de leucita que foi processada por sinterização e por injeção (com e sem fibras). Por meio de um estudo piloto realizado, variando-se temperaturas de sinterização e de injeção com 5% ou 10% de fibras, em massa, foram escolhidos o grupo controle (CS) sinterizado conforme recomendações do fabricante; o grupo sinterizado com fibras (SF), o grupo injetado sem fibras (ISF) e o grupo injetado com fibras (IF). A adição de fibras à porcelana processada por sinterização resultou em um material com fração volumétrica de poros mais do que duas vezes maior do que aquela encontrada para o grupo controle e a área média desses poros também foi mais do que o dobro da área média dos poros do controle. Outro problema apresentado pelo grupo sinterizado com fibras foi o aumento significativo da sua opacidade, representada pela razão de contraste que aumentou de 0,7 no controle para 1,0 no grupo sinterizado com fibras. Além disso, adição de fibras ao material processado por sinterização, apesar de ter causado aumento significativo da densidade e coeficiente de Poisson, não causou alterações significativas no módulo de elasticidade, dureza e tenacidade à fratura. Com relação à resistência à flexão biaxial, a adição de fibras na porcelana sinterizada causou aumento significativo da resistência média (f), porém os parâmetros da análise de Weibull (módulo de Weibull, m, resistência característica, 0, e resistência correspondente à probabilidade de falha de 5%, 5%) não foram alterados significativamente em relação ao grupo controle. Os parâmetros de crescimento subcrítico (coeficiente de susceptibilidade ao crescimento subcrítico, n, e resistência inicial, f0) também não foram alterados significativamente após a adição de fibras no material sinterizado. Embora o processamento por injeção sem adição de fibras não tenha afetado significativamente (em relação ao grupo controle) algumas propriedades como tenacidade à fratura, dureza, módulo de elasticidade, módulo de Weibull e 5%, houve um aumento significativo de parte das propriedades avaliadas como a resistência média, resistência característica e parâmetros de crescimento subcrítico. Com relação às propriedades ópticas, o processamento por injeção resultou em aumento da translucidez da porcelana, o que foi comprovado pela queda significativa no valor de razão de contraste e no aumento significativo no valor do parâmetro de translucidez em comparação com o grupo controle. Uma característica importante observada para o grupo injetado sem fibras foi seu baixo grau de porosidade em relação ao controle e também em relação aos outros dois grupos experimentais (SF e IF). Com relação ao grupo IF, o mesmo problema de alto grau de porosidade observado para o grupo sinterizado com fibras (SF) foi notado. Entretanto, os poros do grupo IF apresentaram área média significativamente menor e tamanho de poro aproximadamente 3 vezes menor do que os dos poros do grupo SF. Dentre as propriedades que não se alteraram comparando-se os grupos controle e injetado com fibras estão o módulo de elasticidade, coeficiente de Poisson, tenacidade à fratura, 5%, e as propriedades ópticas de razão de contraste e parâmetro de translucidez. Entretanto, é importante ressaltar que o grupo injetado com fibras obteve maiores valores médios em relação ao grupo controle para os seguintes parâmetros: densidade, dureza, resistência média, resistência característica, coeficiente de susceptibilidade ao crescimento subcrítico (foi o maior de todo o experimento) e resistência inicial (f0).The objective was to evaluate the processing methods (conventional sintering and heat pressing) and fibers incorporation on the microstructure, mechanical properties (flexural strength f, and Weibull parameters m, 0 e 5%), slow crack growth parameters (n e f0) and contrast ratio (CR), translucency parameter (TP), opalescence parameter (OP) optical properties. Potassium Titanate fibers were mixed with a feldspathic porcelain, and then processed with conventional sintering and heat pressing (with or without fibers). A pilot study was carried out varying the sintering and heat pressing temperature with 5 or 10 wt% of fibers. The selected groups were the control group (CG), conventionally sintered processes following manufactures recommendations; conventionally sintered with fibers (SF); heat pressed without fibers (HP) and heat pressed with fibers (HPF). The hypothesis were: 1) The incorporation of fibers to the conventionally processed porcelain would improve the mechanical properties and slow crack growth parameters and would not affect the optical properties; 2) heat pressing the porcelain without fibers would improve the mechanical properties and slow crack growth parameters and would not affect the optical properties. 3) heat pressing the porcelain with fibers would improve the mechanical properties and slow crack growth parameters and would not affect the optical properties. Specimens were tested for biaxial flexural strength in water. Weibull analysis was used to determine m, 0 and 5% and the dynamic fatigue test was used to determine n e f0 values. The SF group showed percentage of porosity two times higher than the CG, higher values of f, but had no improvement on the Weibull parameters m, 0 and 5% values and slow crack growth parameters n and f0. It presented significant optical changes reaching 100% of opacity. The first hypothesis was partially accepted because there was increase only in f. The HP group presented 10 times lower porosity than CG. It showed higher values of f, and 0 but had no improvement on m and 5%. The HP group also showed higher values of n and f0 and significantly higher TP, and lower CR and OP. The second hypothesis was partially accepted as well because there were mechanical properties increases and changes in optical properties. The HPF group showed porosity two times higher than the CG, higher values of f, and showed an improvement on the Weibull parameters 0 and 5% and slow crack growth parameters n and f0. It presented significant changes OP.
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Romakkaniemi, I. (Idamaria). "Biodegradation of synthetic textile fibres". Bachelor's thesis, University of Oulu, 2018. http://urn.fi/URN:NBN:fi:oulu-201808232664.
Testo completoAbstract (sommario):
Synthetic fibres are a raw-materials, that have rapidly become more commonly used in the textile industry. They are used in many everyday products as such or as blends with other fibres like cotton. Synthetic fibres are utilized to achieve the wanted special abilities in textiles. Synthetic textile fibres are composed of polymers and mainly do not decompose in nature as such. Accumulation of these fibres is a growing environmental problem across the globe. If digested, synthetic fibres can be dangerous to organisms. To solve this problem, research has been done to find biological ways of degrading synthetic fibres. Different kinds of micro-organisms have been examined to find organisms that can utilize synthetic fibres in their metabolism. In this bachelor’s thesis the aim was to gather as much information as possible on researches done on synthetic fibre biodegradation to date. Different kinds of fibres and their components were identified and the production processes were examined. Biodegradation of each fibre and their components by microbes and enzymes was investigated. The majority of results were found on polyurethane fibres while less results related to aromatic polyamide fibres. As a result of this data collection it could be stated, that the topic needs more scientific research to find effective ways to biodegrade synthetic fibres. The goal of this literary research is to give an extensive overview on the pollution problem caused by synthetic textile fibres and the biological methods of degrading them as well as to emphasize that the gathered information should be utilized to solve the problemSynteettiset kuidut ovat nopeasti yleistynyt materiaali tekstiiliteollisuudessa. Niitä käytetään monissa arkipäiväisissäkin tuotteissa sellaisenaan tai sekoitettuna muiden kuitujen kuten puuvillan kanssa. Niillä pyritään saavuttamaan tekstiilille halutut erityisominaisuudet. Synteettiset tekstiilikuidut koostuvat polymeereistä ja eivät pääsääntöisesti hajoa luonnossa sellaisenaan. Niiden kerääntyminen luontoon ja meriin on kasvava ympäristöongelma ympäri maailmaa. Synteettiset polymeerit voivat olla vaarallisia eliöille joutuessaan niiden ruuansulatukseen. Tämän ongelman ratkaisemiseksi on pyritty löytämään biologisia menetelmiä hajottaa synteettisiä kuituja. Erilaisia mikro-organismeja on tutkittu, jotta löydettäisiin organismeja, jotka pystyisivät hyödyntämään synteettisiä kuituja metaboliassaan. Tässä kandidaatin työssä pyrittiin keräämään mahdollisimman kattavasti tietoa tähän päivään mennessä tehdyistä tutkimuksista synteettisten kuitujen biohajoamisesta. Erilaiset kuitulajit ja niiden komponentit määriteltiin ja selvitettiin, millaisella prosessilla niitä valmistetaan. Jokaisen kuidun ja niiden komponenttien biohajoamista selvitettiin mikrobien ja entsyymien avulla. Eniten tutkimustuloksia löytyi polyuretaanikuiduista ja vähiten aromaattisista polyamidikuiduista. Tiedonhankinnan tuloksena voisi todeta, että aihe vaatii yhä tieteellistä lisätutkimusta, jotta löydetään tehokas biologinen keino hajottaa synteettisiä kuituja. Tämä kirjallisuustutkielman tavoite on antaa laaja yleiskuva synteettisten tekstiilikuitujen aiheuttamasta saasteongelmasta ja niiden biologisesta hajottamisesta sekä pyrkiä korostamaan, että kerättyjä taustatietoja tulisi hyödyntää ongelman ratkaisemisessa
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López, Sánchez Ángel. "Influencia del proceso de reciclado sobre las propiedades de los materiales compuestos obtenidos por inyección de poliestireno reforzado con fibras lignocelulósicas". Doctoral thesis, Universitat de Girona, 2004. http://hdl.handle.net/10803/7759.
Testo completoAbstract (sommario):
The objective of this research is to study the influence of several recycling cycles on the mechanical properties of four different materials made by the injection of polystyrene. The four materials studied have different characteristics. The first one is polystyrene (PS), the second one is polystyrene reinforced with hemp fibers (PSf), the third one is polystyrene reinforced with hemp fibers modified with AKD (PSft) and the last one is polystyrene reinforced with fiberglass (PSfv). With all these materials tensile strength, bending, hardness and impact is measured. After the measurement of these physical properties, materials are recycled to obtain new injection samples, and its physical properties are measured again. This process is repeated during 24 cycles.
After each recycling cycle material physical properties are related with polystyrene molecular weight, melt flow, FTIR spectra and DSC.
From reinforced materials, fibers are recovered and through microscopy and image analysis they are characterized to study the influence that recycling has on its structure.
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Poumadère, Thomas. "Etude du couplage procédé/propriétés d’un matériau à fibres discontinues de carbone et à matrice époxy mis en oeuvre par un procédé innovant d’injection/transfert". Thesis, Toulouse, ISAE, 2013. http://www.theses.fr/2013ESAE0003.
Testo completoAbstract (sommario):
Les matériaux composites sont largement utilisés dans l'aéronautique où leurs hautes performances mécaniques combinées à leur légèreté leur permettent de concurrencer les matériaux métalliques. Cependant il est aujourd'hui difficile de fabriquer en série des pièces structurales ayant des formes tridimensionnelles complexes,Si les procédés d'injection de thermoplastiques chargés de fibres courtes (100 à 1 mm) sont bien connus, les études sur l'injection des thermodurcissables à fibres longues sont rares en raison de la difficulté à les faire s'écouler sur plusieurs dizaines de millimètres pour remplir complètement les moules.La société Equip'Aéro Technique a initié des travaux portant sur le développement d'un nouveau procédé de fabrication par injection-transfert (PIMOC) de composites thermodurcissables à fibres longues (> 1 mm) discontinues. Il permet de réaliser en une seule étape des pièces aux formes tridimensionnelles sans usinage.Dans ce travail de thèse le procédé d'injection-transfert a été mis au point et fiabilisé. Ses paramètres principaux ont été identifiés. L'influence des paramètres de fabrication sur les propriétés du matériau a été établie. Les propriétés mécaniques ont ainsi pu être optimisées. Enfin, un modèle de comportement élastique endommageable avec rupture et basé sur une approche multi-critères a été développé dans le but d'initier une méthodologie de dimensionnement de pièces composites à fibres discontinues. Ces critères d'endommagement et de rupture ont été développés en accord avec les observations du comportement mécanique du matériau. L'ensemble des résultats expérimentaux et numériques a été appliqué à la fabrication et au dimensionnement d'un démonstrateur technologiqueComposite materials are widely used in aeronautics. Their high mechanical properties combined to their lightness make it possible for thern to compete With metallic materials. However mass production of complex 3D shape composite structural parts is not usual.Injection process of short fibers (100um à 1 mm) filted thermoplastics is well known. Nevertheless there are few studies about long fibers (>1 mm) filled thermosets. It is very difficult to make the material flow into a closed mold.Equip iAéro Technique carried out research on the deve(opment of a new injection-transfer process (called PIMOC) to manufacture long discontinuous fibers filled thermoset composites. This process makes it possible to produce one shot complex 3D shape parts without machining.ln this work, the injection-transfer process has been developed and is now reliable. Its main parameters have been identified. The influence of manufacuring parameters on material properties have been determined, Thus mechanical properties have been optimizecl. Finally an elastic damage model has been devetoped in order to introduce a methodology or sizing discontinuous fibers composite parts. The model includes failure and is based on a multi-criteria approach. Theses damage and failure criteria have been deveioped according to observations of material mechanical behavior. Experimental and numerical results have been applied for sizing and manufacturing a technical demonstrator
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Riul, Cassius. "Desenvolvimento de compósitos estruturais de politetrafluoretileno (PTFE) com fibras contínuas". Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18146/tde-14082011-104816/.
Testo completoAbstract (sommario):
Este trabalho apresenta o desenvolvimento de compósitos estruturais de politetrafluoretileno (PTFE) com fibras de vidro contínuas e tem como objetivo a obtenção de um compósito com propriedades mecânicas que possibilite o uso em aplicações estruturais e que mantenham as características inerentes do PTFE sem reforços, tais como: baixo coeficiente de atrito, baixa interação química e elevada temperatura de trabalho. O PTFE é um polímero termoplástico, mas sua elevada viscosidade no estado fundido impede a utilização de moldagem por injeção. Componentes fabricados com PTFE são geralmente obtidos por compactação a frio do material granulado seguido de tratamento térmico. Neste estudo foi desenvolvida uma metodologia de fabricação de um laminado de PTFE e fibras contínuas, a partir do empilhamento, prensagem e tratamento térmico, de tecidos de fibra de vidro impregnados com PTFE. Foram estudadas as influências dos parâmetros de fabricação (prensagem e tratamento térmico) e de mecanismos que levam à degradação do laminado durante a fabricação, nas propriedades mecânicas finais dos compósitos. Foi também estudada a adição de uma quantidade complementar de PTFE ao laminado, com o intuito de se averiguar a possibilidade de se obter compósitos com revestimentos mais espessos de PTFE. O laminado foi avaliado por meio de ensaios de flexão 3-pontos e tração, para verificação dos ganhos na rigidez e resistência mecânica frente ao PTFE puro e por um ensaio de adesão fibra-matriz, baseado na norma ASTM D3167-03a. Como resultados, foram encontrados valores expressivos de resistência máxima aproximadamente 165 MPa e rigidez módulo de elasticidade de aproximadamente 14 GPa para valores adequados de processo de fabricação que minimizam efeitos de degradação dos laminados durante a fabricação. O trabalho mostrou a viabilidade de fabricação dos compósitos propostos e indicou uma rota a ser seguida para esta fabricação.This work presents a study of the manufacturing of Polytetrafluoretylene (PTFE) composite with continuous fibres, which has the purpose of obtaining a composite with mechanical properties equivalent or better than that of engineering polymers, but that preserve the characteristics of PTFE products with no reinforcement (as low friction coefficient, low chemical interaction and high work temperature amplitude). The PTFE is a thermoplastic material, however its high molten viscosity prevents the use of melt injection techniques, and its components are obtained through cold compaction process followed by sintering. In this study it is proposed a methodology of PTFE laminate with continuous fibre manufacturing. The laminate was obtained by the pilling of PTFE-coated glass-fibre fabric in a metallic mold for the pressing and that were sinterised afterwards. The mechanisms that lead to degradation of the laminate and process parameters which influence the final mechanical properties of the product were speciafied. It was also studied the possibility of addition of a larger quantity of PTFE to the laminate in order to verify the possibility of making continuous laminate coating. The material was analysed through three-point bending test and tensile test applied to the manufactured test specimen to verify the gains of mechanical stiffness and strength in comparison to the pure PTFE and an adhesion test based on ASTM D3167-03a. The experimental results showed significant values of mechanical stiffness and strength for appropriate values of process parameters that minimize the effects of degradation of the laminate.
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Cadu, Thomas. "Contribution au développement de l'utilisation des fibres naturelles dans les composites structuraux. Étude du comportement d'un composite Lin/Epoxy lors d'un vieillissement hygrothermique". Thesis, Bourgogne Franche-Comté, 2018. http://www.theses.fr/2018UBFCK055/document.
Testo completoAbstract (sommario):
Les composites bio-sourcés et notamment à base de fibres de lin connaissent depuis quelques années un regain d’intérêt, particulièrement dans les domaines des transports, de la mobilité et des loisirs. En effet, le faible coût énergétique et environnemental de la fibre de lin lui confère un avantage face à la fibre de verre, tout en la concurrençant en termes de propriétés mécaniques spécifiques. Cependant le comportement à long terme en environnement humide des composites à base de fibres de lin reste méconnu et constitue un frein à leur utilisation à plus grande échelle. Les objectifs de ces travaux sont de donner des clés pour produire un composite lin/époxy de haute qualité et de contribuer à l’amélioration de la connaissance de la durabilité de ces matériaux. Tout d’abord, l’influence de nombreux paramètres de mise en œuvre [(i) le pré conditionnement des renforts, (ii) la température de cuisson, (iii) la pression appliquée lors de la cuisson, (iv) la vitesse de refroidissement, (v) la température de sortie de la plaque, (vi) la température de post-cuisson et (vii) la durée de post-cuisson] sur les propriétés mécaniques des composites a été étudiée afin d’obtenir des matériaux de haute qualité. Une méthode de vieillissement « réaliste » a ensuite été développée afin d’étudier la durabilité de ce type de composites en présence d’eau. Des cycles de vieillissements hygrothermiques ont ainsi été menés en laboratoire sur des éprouvettes de composite, de résine et des faisceaux de fibres. Puis des analyses multi-échelles basées sur des caractérisations physico-chimiques, microstructurales et morphologiques du composite lin/époxy au cours de ce vieillissement ont permis de mieux comprendre les mécanismes responsables de leurs évolutions de propriétés mécaniques longitudinales et transverses au cours du tempsIn recent years there is renewed interest for bio-sourced composites, including those based on flax fibers, and especially in the field of transport, mobility and leisure. In fact, the lower energy cost and environmental impact of flax fiber give it an advantage over glass fiber, while competing with its specific mechanical properties. However, flax fibers based composites long-term behavior remains poorly known in damp environments and constitutes an obstacle to a wider use. This work aims to provide adapted parameters to produce a high-grade flax/epoxy composite and to contribute to improve the durability knowledge of these materials. First, the influence of many processing parameters [(i) conditioning of the reinforcements, (ii) curing temperature, (iii) curing pressure, (iv) cooling speed, (v) exit temperature, (vi) post curing temperature and (vii) post curing duration] on the composites’ mechanical properties have been studied in order to manufacture high-grade materials. Then a “realistic” ageing method has been developed to study the durability of this kind of composites when exposed to water. Thus cyclic hygrothermal ageing has been applied to composite, resin and fiber bundles in the laboratory. Then multi-scale analyzes based on physicochemical, microstructural and morphological characterizations of the flax/epoxy composites helped to better understand the mechanisms responsible for the longitudinal and transverse mechanical properties’ evolutions over time
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Sandhu, Suki. "Process-microstructure studies in TiAl/SiCâ†f composites". Thesis, University of Surrey, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267847.
Testo completo
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Kennerley, Jonathan. "Recycling fibres recovered from composite materials using a fluidised bed process". Thesis, University of Nottingham, 1998. http://eprints.nottingham.ac.uk/12849/.
Testo completoAbstract (sommario):
This work is concerned with the characterisation and reuse of fibres recovered from end of life thermoset composites by fluidised bed thermal processing. Emphasis is placed on the properties of recovered glass fibres and their reuse in a dough moulding compound and a tissue product. The need for a recycling process is demonstrated by a survey of the market for thermoset composites with particular consideration given to the potential growth in automotive applications. A study of processes developed to recycle such materials and the effect on the structural properties of composites containing such recyclate shows that a process capable of generating recyclate of greater value is required, particularly for the case of contaminated materials. A review of investigations into the effect of prior heat treatment on the mechanical properties of glass fibres shows that their strength will be reduced by a deterioration of the fibre surface during fluidised bed thermal recovery but that their stiffness is likely to be unaffected. The implications of these effects on possible applications for the recovered fibres are described. Tests are reported on the structural properties of laminates containing heat treated glass cloth which show that there is a strength reduction which is both time and temperature dependent but that modulus is not significantly affected. Strength loss increases with up to 20 minutes heating but then remains constant. In some cases the strength loss can be reduced by resizing the cloth. Measurement of the properties of fibres recovered using the fluidised bed process shows that the recovered fibre strength decreases with increasing processing temperature. Glass and carbon fibres recovered at 450°C retain approximately 50% and 80% of their virgin strengths respectively. The Young's modulus of the recovered fibres is shown to be largely unaffected by the process for both glass and carbon fibres. Investigation of the lengths of the recovered glass fibres by image analysis techniques suggests that their distribution depends on the structure of the composite and the method of size reduction. A weighted mean fibre length of 3.5 mm to 5.5 mm is possible with the apparatus described in this thesis. The reduced reinforcement potential of the recovered fibres is confirmed by experiment. Recovered glass fibres are used to displace virgin fibres in a dough moulding compound. At replacement levels of up to 50% there is no significant effect on the mechanical properties of a compression moulded plate. Above this level, tensile, flexural and impact strengths are reduced and with complete replacement the reduction is by approximately 40%, 50% and 70% respectively. These results are confirmed on a pilot plant scale. Recovered glass fibres can be successfully incorporated with virgin fibres into a veil. Replacement of virgin fibres reduces both wet and dry strength because the recovered fibres are both shorter and weaker. The permeability of the veil is found to depend on its porosity and not its recovered fibre content. The experimental veils can be used to protect and improve the surfaces of mouldings.
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Sinden, Jane. "The electrokinetic aspect of cellulose fibres used in the papermaking process". Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244904.
Testo completoLibri sul tema "Fibrés de Procesi"
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Knott, Jean. Fine animal fibres and their depigmentation process. Guimaraes: Universidade do Minho, 1990.
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Ltd, Courtaulds Fibres, e Great Britain. Energy Efficiency Office., a cura di. Cost reductions on a man-made fibre plant identified by a process integration study at Courtaulds Fibres Ltd. London: [Energy Efficiency Office], 1987.
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Haghi, A. K., e G. E. Zaikov. Electrospinning process and nanofiber research. Hauppauge, N.Y: Nova Science Publishers, 2011.
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Printing Industries Research Association. paper and board division. De-inked fibre: The product and the process. Leatherhead: P.I.R.A, 1985.
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Reza, Zinolabedini, e United States. National Aeronautics and Space Administration., a cura di. Graphite fiber intercalation: Dynamics of the bromine intercalation process. [Washington, DC]: National Aeronautics and Space Administration, 1985.
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Dalton, Robert. Lunar fiberglass: Properties and process design, 1987 report. [Washington, D.C.?: National Aeronautics and Space Administration, 1987.
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Eftekhari, Abe. A capacitive technique for real-time monitoring polymer coating thickness on carbon filaments during prepregging process. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1990.
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J, Chapman John, e Langley Research Center, a cura di. A capacitive technique for real-time monitoring polymer coating thickness on carbon filaments during prepregging process. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1990.
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Betts, Diane. Wool fibers: Ways to produce, select, process, and spin them by hand. Auburn, Calif: D.F. Betts Enterprises, 1995.
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Yāñʻ, Soʻʺ. Mranʻ māʹ rui ̋rā sabhāva chui ̋che ̋nhaṅʻʹ Panʻʹ puṃ ruikʻ lupʻ ṅanʻ ̋ʼa tatʻ paññā. Tā Suvaṇṇa, Ranʻ kunʻ: Mui ̋Kyoʻ Cā pe, 2005.
Cerca il testo completoCapitoli di libri sul tema "Fibrés de Procesi"
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Veit, Dieter. "Process for the Production of Monofilaments". In Fibers, 527–29. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-15309-9_21.
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Veit, Dieter. "Process for the Production of Carpet Yarns". In Fibers, 531–35. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-15309-9_22.
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Veit, Dieter. "Process for the Production of Film Yarns". In Fibers, 537–41. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-15309-9_23.
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Nawab, Yasir, Khubab Shaker e Abdelghani Saouab. "Process Induced Residual Stresses". In Natural Fibers to Composites, 95–107. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-20597-2_5.
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van Zee, G., J. de Graauw e J. A. Wesselingh. "Compact Separation Equipment Using Sorption by Fibers". In Precision Process Technology, 315–26. Dordrecht: Springer Netherlands, 1993. http://dx.doi.org/10.1007/978-94-011-1759-3_24.
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Mohamed, H., D. W. Bao e R. Snooks. "Super Composite: Carbon Fibre Infused 3D Printed Tectonics". In Proceedings of the 2020 DigitalFUTURES, 297–308. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-33-4400-6_28.
Testo completoAbstract (sommario):
AbstractThis research posits an innovative process of embedding carbon fibre as the primary structure within large-scale polymer 3D printed intricate architectural forms. The design and technical implications of this research are explored and demonstrated through two proto-architectural projects, Cloud Affects and Unclear Cloud, developed by the RMIT Architecture Snooks Research Lab. These projects are designed through a tectonic approach that we describe as a super composite – an approach that creates a compression of tectonics through algorithmic self-organisation and advanced manufacturing. Framed within a critical view of the lineage of polymer 3D printing and high tech fibres in the field of architectural design, the research outlines the limitations of existing robotic processes employed in contemporary carbon fibre fabrication. In response, the paper proposes an approach we describe as Infused Fibre Reinforced Plastic (IFRP) as a novel fabrication method for intricate geometries. This method involves 3D printing of sacrificial formwork conduits within the skin of complex architectural forms that are infused with continuous carbon fibre structural elements. Through detailed observation and critical review of Cloud Affects and Unclear Cloud (Fig. 2), the paper assesses innovations and challenges of this research in areas including printing, detailing, structural analysis and FEA modelling. The paper notes how these techniques have been refined through the iterative design of the two projects, including the development of fibre distribution mapping to optimise the structural performance.
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Tseng, Huan-Chang, Jim Hsu, Anthony Yang, Sebastian Goris, Yu-Yang Song, Umesh N. Gandhi e Tim A. Osswald. "Process Simulation for Discontinuous Fibers". In Discontinuous Fiber-Reinforced Composites, 261–310. München: Carl Hanser Verlag GmbH & Co. KG, 2020. http://dx.doi.org/10.3139/9781569906958.007.
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Tseng, Huan-Chang, Jim Hsu, Anthony Yang, Sebastian Goris, Yu-Yang Song, Umesh N. Gandhi e Tim A. Osswald. "Process Simulation for Discontinuous Fibers". In Discontinuous Fiber-Reinforced Composites, 261–310. München, Germany: Carl Hanser Verlag GmbH & Co. KG, 2020. http://dx.doi.org/10.1007/978-1-56990-695-8_7.
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Mitchell, T. A. "Methods Used in Monitoring and Controlling the Quality of Bread with Particular Reference to the Mechanical Dough Development Process". In Plant Fibers, 313–31. Berlin, Heidelberg: Springer Berlin Heidelberg, 1989. http://dx.doi.org/10.1007/978-3-642-83349-6_17.
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Fischer, K., H. Sendner, R. Büchner e A. Schlesinger. "On the wet spinning process of viscose fibres". In Progress and Trends in Rheology II, 388–91. Heidelberg: Steinkopff, 1988. http://dx.doi.org/10.1007/978-3-642-49337-9_134.
Testo completoAtti di convegni sul tema "Fibrés de Procesi"
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Diduk, Iryna, Yurii Chuvashov, Olga Yashchenko, Nataliya Koshelenko e Ganna Grytsak. "Modification of basalt fibers to improve operational efficiency in aggressive environments". In IXth INTERNATIONAL SAMSONOV CONFERENCE “MATERIALS SCIENCE OF REFRACTORY COMPOUNDS”. Frantsevich Ukrainian Materials Research Society, 2024. http://dx.doi.org/10.62564/m4-id9285.
Testo completoAbstract (sommario):
The use of basalt fibre as a reinforcing element, including in cement-concrete compositions, is increasing. However, the surface layer of fibers is dissolved during long-term use in the cement matrix, which is associated with cement hydration. Increasing the corrosion resistance of basalt fibers can be achieved by modifying the fibers by heat treatment. The influence of the temperature and processing time of basalt fibers on the chemical stability of fibers in alkaline and acidic environments is studied. For the experiment, fibers with a surface area of 5000 cm2 were taken and kept in solutions of 2N NaOH and 2N HCl at boiling for 3 hours. Chemical resistance was evaluated by the loss of fibre weight. The fibres were preliminarily subjected to thermal treatment in a muffle furnace in the temperature range from 300 to 800 C every 100 C, and the time of treatment was 10, 20, and 30 min at each temperature. The average diameter of the studied fibres was 10-14 µm. The fibres were produced under the same forming parameters on a single-filament laboratory stand. The raw material used was basalt with an acidity modulus of Mk = 4.7 and an initial fibre stability in 2N NaOH of 83.8 % and in 2N HCl of 78.7 %. It has been determined that the maximum increase in alkali resistance is observed at holding temperatures of 400 C and 800 C. The maximum increase in acid resistance is observed during heat treatment at higher temperatures of 600, 700, 800 C and is an increase of 20-25 % from the initial one. With an increase in treatment time, the values in both cases decrease, so the optimal isothermal treatment time does not exceed 10 minutes. In the process of heat treatment of fibres, structural changes occur due to phase transitions of iron oxides Fe2+ to Fe3+, with a change in colour, basalt fibres acquire a browner (reddish) shade of colour. The phase transition is accompanied by the appearance of crystalline phase, which causes an increase in fibre density by 10-20 %
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Wágberg, Lars, e Göran Annergren. "Physicochemical Characterization of Papermaking Fibres". In The Fundamentals of Papermaking Materials, a cura di C. F. Baker. Fundamental Research Committee (FRC), Manchester, 1997. http://dx.doi.org/10.15376/frc.1997.1.1.
Testo completoAbstract (sommario):
The purpose of this paper is to present as complete as possible, a picture of our present knowledge about papermaking fibres and their physico-chemical characteristics. The properties of the papermaking fibres are, in most cases, significantly influenced by the morphology of the wood fibres, but, from one and the same kind of wood fibres, paper can be produced with widely different properties as a result of different pulping and papermaking processes. Dissolution of material from the fibre wall and the middle lamella, structural changes of the polymeric material, and mechanical work on the fibrous material (defibration, refining, and to a certain extent undesired mechanical damage to the fibres in the pulp mill machinery) combine to produce the fibre properties required in the papermaking process. Starting from the structure of the wood, a survey is given of the pattern of dissolution of different important pulping processes and the resulting bulk composition of the pulps. Characterisation of papermaking properties should include effects of both bulk and surface of the fibres and for that reason they are both discussed. The bulk composition has been studied for many years and we have a fairly good knowledge of the main features, although there is still a need for more detailed knowledge. The properties of the fibre surface are less known, but they have been the subject of several recent studies. They are therefore dealt with in more detail, particularly the problem of making reliable and relevant measurements. Dissolution of lignin and other components in the pulping process is also important for the chemical composition of the surface. Mechanical removal of the remaining middle lamella and the outer layers of the fibre wall (the primary wall and SI of the secondary wall) substantially change the surface composition and create fines with a large surface area, which may interact with the wet-end chemicals in the paper mill and decrease the over-all effects of these chemicals. Removal of the outer layers will also change the fibre properties as a whole since, for instance, the SI layer restricts outward swelling of the main part of the secondary wall, S2, and preserves fibre rigidity. Swelling of the fibres influences there fining behaviour of a pulp. For lignin-containing pulps, swelling facilitates refining. For bleached pulps with a very low content of residual lignin, the effect of swelling on refining is rather difficult to as will be briefly discussed.
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Steffens, H. D., M. Brune, E. Müller e R. Dittrich. "The Manufacture of SiC Fiber Reinforced ΑI2O3 Coatings by Plasma Spraying". In ITSC 1996, a cura di C. C. Berndt. ASM International, 1996. http://dx.doi.org/10.31399/asm.cp.itsc1996p0311.
Testo completoAbstract (sommario):
Abstract Oftentimes, the application of bulk ceramics and ceramic coatings is limited by their poor fracture toughness and low strength. The mechanical properties of ceramics can be significantly improved by the incorporation of fibres, whiskers or particles of high strength, like SiC. Due to the high oxygen content of commercially available SiC fibers in combination with the elevated process temperatures, the SiC decomposes during plasma spraying. Therefore commercial SiC fibres were coated for temporary oxidation protection with C, TiN or Al2O3. By different agglomeration techniques using an organic binder SiC/Al2O3 composite powders were produced. Powder mixtures consisting of coated fibres and pure alumina as well as agglomerated powders have been successfully sprayed to form deposits. Recent results of the manufacture of SiC fibre-reinforced ceramic composites by plasma spray technology are presented. The properties of the composite coatings are compared to plasma sprayed pure alumina.
4
Seth, R. S., H. F. Jang, B. K. Chan e C. B. Wu. "Transverse Dimensions of Wood Pulp Fibres and Their Implications for End Use". In The Fundamentals of Papermaking Materials, a cura di C. F. Baker. Fundamental Research Committee (FRC), Manchester, 1997. http://dx.doi.org/10.15376/frc.1997.1.473.
Testo completoAbstract (sommario):
The transverse dimensions of pulp fibres influence strongly their response to the papermaking process, and most end-use properties of products. However, fibre transverse dimensions are difficult to measure. Confocal microscopy combined with image analysis has been used for rapid and accurate measurement of fibre wall cross-sectional area,perimeter, and thickness. Results on kraft pulp fibres obtained from a variety of wood species are presented. They demonstrate how fibre transverse dimensions are distributed within a species, and can be described analytically. Comparison between different species shows that species with coarse or thick-walled fibres are likely to be more heterogeneous. Implications for pulp quality and fibre selection for end-use requirements are discussed.
5
Guo, Zheying, e Raffaella De Vita. "Microstructural Constitutive Equation for Sprain Analysis". In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67709.
Testo completoAbstract (sommario):
A new constitutive equation is presented to describe the damage evolution process in parallel fibered collagenous tissues such as ligaments and tendons. The model is formulated by accounting for the fibrous structure of the tissues. The tissue’s stress is defined as the average of the collagen fiber’s stresses. The fibers are assumed to be undulated and straighten out at different stretches that are defined by a Weibull probability density function. After becoming straight each fiber is assumed to be linear elastic. Its waviness is defined by a Weibull distribution. Tissue’s damage is assumed to occur at the fiber level and is defined as a reduction in the fiber’s stiffness. The proposed model is validated by using experimental data published in the biomechanics literature by Provenzano et al. [1].
6
"PMMA OPTICAL FIBRE IRRADIATED WITH CO-60 FOR OPTICAL FIBRE SENSORS". In RAD Conference. RAD Centre, Niš, Serbia, 2023. http://dx.doi.org/10.21175/radproc.2023.07.
Testo completoAbstract (sommario):
Plastic optical fibres (POF) made of polymethyl methacrylate (PMMA) have several advantages over traditional optical fibres, including lower cost, the possibility of larger diameters and better mechanical resistance. These properties make them an attractive option for sensor technologies, including radiation dosimetry. This paper compares PMMA optical fibre with pure silica core optical fibre. Both fibres are useful for ionising radiation measurements. To evaluate the effect of ionising radiation, we have developed and designed a measurement system that allows continuous measurement of attenuation during the ionising radiation irradiation process. We used a technique that measured changes in laser power transmitted through an optical fibre at a constant gamma radiation dose rate.
7
LILLI, MATTEO, MILAN ZVONEK, VLADIMIR CECH, CHRISTINA SCHEFFLER, JACOPO TIRILLÒ e FABRIZIO SARASINI. "PLASMA POLYMERIZATION ON UNSIZED BASALT FIBRES FOR IMPROVING THE INTERFACIAL STRENGTH WITH POLYMER MATRICES". In Thirty-sixth Technical Conference. Destech Publications, Inc., 2021. http://dx.doi.org/10.12783/asc36/35903.
Testo completoAbstract (sommario):
Basalt fibres are becoming a promising alternative to synthetic fibres as a green reinforcement phase in polymeric matrix composites, showing excellent mechanical, chemical and thermal properties. In this work we synthetized tetravinylsilane (TVS) or a mixture formed by tetravinylsilane and different percentages of oxygen on the surface of unsized basalt fibres through the Plasma-Enhanced Chemical Vapor Deposition (PECVD) technique for improving the fibre/matrix adhesion. Single fibre tensile test proved the effectiveness of the process, without any degradation of the mechanical properties of modified basalt fibres. Finally, through pull out tests, the interfacial properties of basalt fibres were studied, measuring increases up to 80% of the IFSS for modified fibres compared to neat fibres. This result is the consequence of a greater chemical compatibility between the fibres and the matrix, thanks to the presence of a higher number of Si-O-C groups, and of a mechanical interlocking effect promoted by the increased surface roughness of the plasma-modified fibres.
8
Nilsson, Boel, Lars Wågberg e Derek Gray. "Conformability of Wet Pulp Fibres at Small Length Scales". In The Science of Papermaking, a cura di C. F. Baker. Fundamental Research Committee (FRC), Manchester, 2001. http://dx.doi.org/10.15376/frc.2001.1.211.
Testo completoAbstract (sommario):
The conformability of wet pulp fibres has long been recognized as a key factor in the papermaking process. In order for fibres to bond in the sheet, their surfaces must be brought into contact. The conformability of wet pulp fibre surfaces at extremely low forces (nN) and displacements (nm) was investigated by micro-indentation measurements with a standard AFM tip and cantilever. Force-distance curves were measured as the tip impacted wet sulphate softwood fibre surfaces. The surface stiffness showed a large variability, even at different locations on the same fibre surface. Rough estimates of the local apparent elastic modulus of the wet fibres gave low values in the 0.01 GPa range.
9
Trask, Richard S. "Ultrasonic Assembly of Biologically Inspired Anisotropic Short Fibre Reinforced Composites". In ASME 2014 Conference on Smart Materials, Adaptive Structures and Intelligent Systems. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/smasis2014-7558.
Testo completoAbstract (sommario):
In nature, both material and structure are formed according to the principles of biologically controlled self-assembly, a process defined as the spontaneous and reversible ordering of small molecular building blocks under the influence of non-covalent, static interactions. The orientation and distribution of reinforcing entities in engineering composites is key to enabling structural efficiency, yet the architecture remains simplistic when compared to the distinctive and unique hierarchies found in Nature. These biological ‘composite’ materials achieve such configurations by accurately controlling the orientation of anisotropic nano- and micro-sized ‘building blocks’, thereby reinforcing the material in specific directions to carry the multidirectional external loads at different length scales. Capturing the design principles underlying the exquisite architecture of such biological materials will overcome many of the mechanical limitations of current engineering composites. The scientific vision for this study is the development of a novel and highly ordered complex architecture fibrous material for additive layer manufacturing. Using novel chemistry and controlled field-effect assembly, functionally graded, stiffness modulated architectures, analogous to those found in nature, are synthesised to realise enhanced mechanical performance, multi-dimensional composite structures. To achieve this, both hierarchical discontinuous fibres (glass fibres with ZnO nanrods) and a new type of ultrasonic device has been developed. The two studies reported here have been successfully employed to manufacture and mechanically characterise the fibres and aligned discontinuous fibres. A 43 % improvement in strength was observed for samples tested parallel to the direction of the fibre reinforcement over those strained normal to the fibre direction, despite the relatively low volume percentage of the reinforcement phase. This technique shows great potential for the low cost instantaneous alignment of structural reinforcement to generate the light-weight high performance structures required for the future.
10
Görres, J., R. Amiri, M. Grondin e J. R. Wood. "Fibre Collapse and Sheet Structure". In Products of Papermaking, a cura di C. F. Baker. Fundamental Research Committee (FRC), Manchester, 1993. http://dx.doi.org/10.15376/frc.1993.1.285.
Testo completoAbstract (sommario):
A stylus profilometer has been used to evaluate the effect of wet pressing on the collapse of individual fibres from mechanical, chemimechanical and chemical pulps. The chemimechanical and chemical pulp fibres begin to collapse at low pressures and approach complete collapse at high pressures, while the mechanical pulp fibres do not exceed 80% collapse to 5000 kPa. The degree of collapse of southern pine TMP at a given pressure is about the same as that of northeastern spruce/balsam TMP. Since the thick-walled Southern pine fibres are less flexible, it is concluded that transverse collapsibility and flexibility are two independent fibre properties. On the basis of modelling results and the difference between fibre thickness-measurement from networks pressed in contact with smooth and with rough surfaces, it is suggested that wet pressure transferred locally at fibre contacts within a sheet leads to local collapse forces higher- than expected from nominal wet pressure values. Fibre contacts are initially present in the unpressed sheet.On pressing, free fibre segments will be deflected into contact with other segments above or below them, producing additional fibre crossings as pressing progresses . The effective pressing pressure will be highest at the initial fibre contacts, decreasing to zero at contacts just formed at the end of pressing. Because of the demonstrated effect of wet pressure on fibre collapse, it is the thickness at the initial fibre contacts or those formed early in the pressing process that is important in determining sheet density. Use of the more appropriate fibre thicknesses, substantially improves the prediction of sheet density by the Interactive Multiplanar Model of sheet structure for a range of pulp types.
Rapporti di organizzazioni sul tema "Fibrés de Procesi"
1
Pullammanappallil, Pratap, Haim Kalman e Jennifer Curtis. Investigation of particulate flow behavior in a continuous, high solids, leach-bed biogasification system. United States Department of Agriculture, gennaio 2015. http://dx.doi.org/10.32747/2015.7600038.bard.
Testo completoAbstract (sommario):
Recent concerns regarding global warming and energy security have accelerated research and developmental efforts to produce biofuels from agricultural and forestry residues, and energy crops. Anaerobic digestion is a promising process for producing biogas-biofuel from biomass feedstocks. However, there is a need for new reactor designs and operating considerations to process fibrous biomass feedstocks. In this research project, the multiphase flow behavior of biomass particles was investigated. The objective was accomplished through both simulation and experimentation. The simulations included both particle-level and bulk flow simulations. Successful computational fluid dynamics (CFD) simulation of multiphase flow in the digester is dependent on the accuracy of constitutive models which describe (1) the particle phase stress due to particle interactions, (2) the particle phase dissipation due to inelastic interactions between particles and (3) the drag force between the fibres and the digester fluid. Discrete Element Method (DEM) simulations of Homogeneous Cooling Systems (HCS) were used to develop a particle phase dissipation rate model for non-spherical particle systems that was incorporated in a two-fluid CFDmultiphase flow model framework. Two types of frictionless, elongated particle models were compared in the HCS simulations: glued-sphere and true cylinder. A new model for drag for elongated fibres was developed which depends on Reynolds number, solids fraction, and fibre aspect ratio. Schulze shear test results could be used to calibrate particle-particle friction for DEM simulations. Several experimental measurements were taken for biomass particles like olive pulp, orange peels, wheat straw, semolina, and wheat grains. Using a compression tester, the breakage force, breakage energy, yield force, elastic stiffness and Young’s modulus were measured. Measurements were made in a shear tester to determine unconfined yield stress, major principal stress, effective angle of internal friction and internal friction angle. A liquid fludized bed system was used to determine critical velocity of fluidization for these materials. Transport measurements for pneumatic conveying were also assessed. Anaerobic digestion experiments were conducted using orange peel waste, olive pulp and wheat straw. Orange peel waste and olive pulp could be anaerobically digested to produce high methane yields. Wheat straw was not digestible. In a packed bed reactor, anaerobic digestion was not initiated above bulk densities of 100 kg/m³ for peel waste and 75 kg/m³ for olive pulp. Interestingly, after the digestion has been initiated and balanced methanogenesis established, the decomposing biomass could be packed to higher densities and successfully digested. These observations provided useful insights for high throughput reactor designs. Another outcome from this project was the development of low cost devices to measure methane content of biogas for off-line (US$37), field (US$50), and online (US$107) applications.
2
López Tejeda, Evaristo. Evaluación de impacto ambiental: Fibra de vicuña en la Reserva Nacional Salinas y Aguada Blanca. Inter-American Development Bank, gennaio 2009. http://dx.doi.org/10.18235/0010300.
Testo completoAbstract (sommario):
El siguiente estudio ambiental contribuye al "Proyecto de Encadenamientos Productivos Sostenibles en Áreas Naturales Protegidas" del Perú. Dado que una de las principales actividades económicas de las comunidades campesinas peruanas es la obtención de fibra de vicuña, se realiza el presente Estudio de Impacto Ambiental sobre los efectos en el medio ambiente con el fin de levantar información sobre los recursos en la Reserva Nacional Salinas y Aguada Blanca y sus principales amenazas, con especial interés en la vicuña, determinar los impactos producidos en el proceso de extracción de la fibra de la vicuña, caracterizar los impactos determinados en el proceso de obtención de fibra de esta recurso, proponer los programas que sean pertinentes a objeto de minimizar y/o mitigar los impactos negativos en el proceso de obtención de fibra vicuña, y proponer los programas que refuercen el conocimiento de los recursos biológicos de la Reserva Nacional Salinas y Aguada Blanca y su utilización racional y sustentable.
3
Chong Chen, Elliot B. Kennel, Liviu Magean, Pete G. Stansberry, Alfred H. Stiller e John W. Zondlo. PRODUCTION OF FOAMS, FIBERS AND PITCHES USING A COAL EXTRACTION PROCESS. Office of Scientific and Technical Information (OSTI), giugno 2004. http://dx.doi.org/10.2172/827482.
Testo completo
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Nixdorf, R. D. Development of a Commercial Process for the Production of Silicon Carbide Fibrils. Office of Scientific and Technical Information (OSTI), aprile 1999. http://dx.doi.org/10.2172/7914.
Testo completo
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Nixdorf, RD. Development of a Commercial Process for the Production of Silicon Carbide Fibrils - Draft Phase II Final Report. Office of Scientific and Technical Information (OSTI), ottobre 2002. http://dx.doi.org/10.2172/814172.
Testo completo
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Hollar, W. E. Jr, e W. H. Mills. Engineering scale development of the Vapor-Liquid-Solid (VLS) process for the production of silicon carbide fibrils. Office of Scientific and Technical Information (OSTI), settembre 1993. http://dx.doi.org/10.2172/10125692.
Testo completo
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Tanaka, Eri, Regina Schwerd, Wolfgang Hofbauer e Daniel Zirkelbach. Laboratory tests on decay of natural fibre insulation materials suggest a more differentiated evaluation and higher RH thresholds. Department of the Built Environment, 2023. http://dx.doi.org/10.54337/aau541651346.
Testo completoAbstract (sommario):
To reduce CO2 emissions and save grey energy, natural materials like wood and wooden materials are becoming more and more important. However, these products are particularly sensitive to moisture, as they can be attacked by mould or decay fungi. In contrast to mould growth, which typically is associated with visual impairment and health problems, the growth of decay fungi may result in structural defects which clearly must be excluded. Up to now it is mostly assumed that wooden materials are more sensitive to such attack than solid wood. Therefore, different wood fibre insulation materials were inoculated with decay fungi and exposed to different climates to determine the requirements for the decay process and to compare them with the requirements of decay by the same fungi of solid wood. The results prove that some natural fibre materials are equally or even more resistant to decay fungi than solid wood, while others are less. The resistant products can therefore be assessed like solid wood – for which already temperature dependent thresholds and in part also transient decay prediction models are available. Maybe even specific higher moisture levels can be acceptable. However, the results also suggest a differentiated view on natural fibre insulations, as they have a very different susceptibility to wood decay. Uniform and significantly lower limits than for solid wood are not justified.
8
Delmer, Deborah P., Douglas Johnson e Alex Levine. The Role of Small Signal Transducing Gtpases in the Regulation of Cell Wall Deposition Patterns in Plants. United States Department of Agriculture, agosto 1995. http://dx.doi.org/10.32747/1995.7570571.bard.
Testo completoAbstract (sommario):
The combined research of the groups of Delmer, Levine and Johnson has led to a number of interesting findings with respect to the function of the small GTPase Rac in plants and also opened up new leads for future research. The results have shown: 1) The Rac13 protein undergoes geranylgeranlyation and is also translocated to the plasma membrane as found for Rac in mammals; 2) When cotton Rac13 is highly- expressed in yeast, it leads to an aberrant phenotype reminiscent of mutants impaired in actin function, supporting a role for Rac13 in cytoskeletal organization; 3) From our searches, there is no strong evidence that plants contain homologs of the related CDC42 genes found in yeast and mammals; 4) We have identified a rather unique Rac gene in Arabidopsis that has unusual extensions at both the N- and C-terminal portions of the protein; 5) New evidence was obtained that an oxidative burst characterized by substantial and sustained production of H202 occurs coincident with the onset of secondary wall synthesis in cotton fibers. Further work indicates that the H202 produced may be a signal for the onset of this phase of development and also strongly suggests that Rac plays an important role in signaling for event. Since the secondary walls of plants that contain high levels of lignin and cellulose are the major source of biomass on earth, understanding what signals control this process may well in the future have important implications for manipulating the timing and extent of secondary wall deposition. 6) When the cotton Rac13 promoter is fused to the reporter gene GUS, expression patterns in Arabidopsis indicate very strong and specific expression in developing trichomes and in developing xyelm. Since both of these cell types are engaged in secondary wall synthesis, this further supports a role for Rac in signaling for onset of this process. Since cotton fibers are anatomically defined as trichomes, these data may also be quite useful for future studies in which the trichomes of Arabidopsis may serve as a model for cotton fiber development; the Rac promoter can therefore be useful to drive expression of other genes proposed to affect fiber development and study the effects on the process; 7) The Rac promoter has also been shown to be the best so far tested for use in development of a system for transient transformation of developing cotton fibers, a technique that should have many applications in the field of cotton biotechnology; 8) One candidate protein that may interact with Rac13 to be characterized further in the future is a protein kinase that may be analogous to the PAK kinase that is known to interact with Rac in mammals.
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Ohnsorg, R. W., W. E. Jr Hollar, S. K. Lau, F. K. Ko e K. Schatz. Engineering scale development of the vapor-liquid-solid (VLS) process for the production of silicon carbide fibrils. Phase 2. Office of Scientific and Technical Information (OSTI), aprile 1995. http://dx.doi.org/10.2172/200670.
Testo completo
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Feigelson, R. S., R. K. Route e R. C. DeMattei. Growth of high {Tc} superconducting fibers using a miniaturized laser-heated float zone process. Progress report, November 6, 1990--December 31, 1991. Office of Scientific and Technical Information (OSTI), dicembre 1991. http://dx.doi.org/10.2172/266723.
Testo completo