Search results for "fibres"

A note on coverings with special fibres and monodromy group $ S_{d}$

2012

We consider branched coverings of degree over with monodromy group , points of simple branching, special points and fixed branching data at the special points, where is a smooth connected complex projective curve of genus , and , are integers with . We prove that the corresponding Hurwitz spaces are irreducible if .

Compression and injection molding of recycled polyethylene for greenhouses in presence of the natural fibres

2003

Time-resolved X-ray microtomographic measurement of water transport in wood-fibre reinforced composite material

2016

Natural fibre composites are prone to absorb moisture from the environment which may lead to dimensional changes, mold growth, degradation of mechanical properties or other adverse effects. In this work we develop a method for direct non-intrusive measurement of local moisture content inside a material sample. The method is based on X-ray microtomography, digital image correlation and image analysis. As a first application of the method we study axial transport of water in a cylindrical polylactic acid/birch pulp composite material sample with one end exposed to water. Based on the results, the method seems to give plausible estimates of water content profiles inside the cylindrical sample.…

A systematic literature review on less common natural fibres and their biocomposites

2018

Abstract Interest in utilization of renewable resources is increasing because of public's environmental awareness and economic considerations. Lignocellulosic fibres have already attracted growing attention as reinforcement of polymeric matrices instead of synthetic ones (mainly glass) from the academic and industrial fields. In addition to kenaf, hemp, sisal, flax and jute, which are the subject of extensive investigations for composite applications since the 1970s, in the last years several researchers suggested the use of less common natural fibres, due to their low cost and availability. This paper reviews the extraction methods, chemical, morphological, thermal and mechanical propertie…

Inclusion ratio based estimator for the mean length of the boolean line segment model with an application to nanocrystalline cellulose

2014

A novel estimator for estimating the mean length of fibres is proposed for censored data observed in square shaped windows. Instead of observing the fibre lengths, we observe the ratio between the intensity estimates of minus-sampling and plus-sampling. It is well-known that both intensity estimators are biased. In the current work, we derive the ratio of these biases as a function of the mean length assuming a Boolean line segment model with exponentially distributed lengths and uniformly distributed directions. Having the observed ratio of the intensity estimators, the inverse of the derived function is suggested as a new estimator for the mean length. For this estimator, an approximation…

Spontaneous emission of a sodium Rydberg atom close to an optical nanofibre

2019

International audience; We report on numerical calculations of the spontaneous emission rate of a Rydberg-excited sodium atom in the vicinity of an optical nanobre. In particular, we study how this rate varies with the distance of the atom to the bre, the bre's radius, the symmetry s or p of the Rydberg state as well as its principal quantum number. We nd that a fraction of the spontaneously emitted light can be captured and guided along the bre. This suggests that such a setup could be used for networking atomic ensembles, manipulated in a collective way due to the Rydberg blockade phenomenon.

Concrete columns confined with fibre reinforced cementitious mortars: Experimentation and modelling

2014

Abstract The structural behaviour of concrete columns strengthened with a system made up of fibre nets embedded in an inorganic stabilized cementitious matrix under an uniaxial load was investigated. Medium size specimens with circular and square cross-section were cast and subjected to monotonic uniaxial compression, to investigate the efficiency of a p-Phenylene BenzobisOxazole (PBO) Fibre Reinforced Cementitious Mortar (FRCM) system in increasing both strength and ductility. The experimental results show that the confinement system adopted produced a noticeable increment in strength and ductility, though the low mechanical ratios of fibre considered were not always able to ensure hardeni…

Génération de supercontinuum infrarouge et enjeux de vieillissement au sein de fibres optiques à coeur suspendu hautement non linéaires en verre de c…

2014

The work reported in this thesis deals with the fabrication of suspended core chalcogenide microstructured optical fibers (MOFs) for supercontinuum generation (SCG) beyond 6 μm. In this context, As2S3-based suspended-core MOFs were fabricated under vacuum, and loss threshold of 1-2 dB/m at 2.9µm were systematically registered. In addition, MOFs were designed with core diameter ranging from 1.5 to 3.5µm, allowing therefore to control the MOF's dispersive properties and to shift corresponding zero dispersion wavelength to 2.0-2.5 µm range. SCG experiments were performed by pumping the fabricated MOFs in their anomalous dispersion regime by means of tunable femtosecond laser source. Simultaneo…

Contribution to the development of 100% bio-based composites : synthesis of bio-based polyepoxides, supercritical CO2 treatment of hemp fibers and im…

2018

This thesis contributes to the development of 100% bio-based hemp/epoxy composites. Current environmental issues favor the emergence of materials derived from renewable resources such as plant fibres and a wide range of bio-based building-blocks, source of epoxy prepolymers in particular. An intensive investigation of the two constituents (hemp fibres and polyepoxidic matrix) is carried out before the composites manufacturing. Supercritical CO2 treatment is applied to hemp fibres used as reinforcement in composite materials. This treatment, not optimized, leads to better individualization as well as a decrease in the hygroscopic power of the fibres. These aspects, which are essential in ord…

Modulational instability and domain wall solitons in optical fibers

2000

The first part of this thesis presents some theoretical and experimental results about modulational instability and domain wall solitons in bimodal fibers.In the second part is devoted to the interaction of counter-propagating waves in an isotropic optical fiber