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The object of this work is to investigate the effect of loop length on the geometrical and more particularly on the physical and mechanical properties of the plain weft knitted fabrics. Two sets of fabrics were produced from 2/26s worsted yarn using knitting machines different in type and gauge. The first set was knitted from single yarn and the second from two-ends with a wide range of loop length. Both sets were given three different relaxation treatments, dry, wet- and full-relaxation. Dimensional measurements and geometrical parameters were determined and examined and the results show that for some fabrics there is some deviation from the results of other workers in this field. The study also involved measurements and tests of certain yarn properties which provided useful background information about this yarn and which might help to explain certain properties of the knitted fabrics. The yarn properties measured and tested were, twist, friction, flexural rigidity, tensile and elastic properties. Experimental results indicate that an increase in loop length leads to an increase in air permeability and percentage weight loss when the fabric subjected to abrasion. It is found that for two-end fabrics the percentage weight loss is non-linearly related to the loop length and this reflects the yarn arrangement within the structural unit cell. While there is not always a direct relation between the loop length and the fabric thickness, there is however, a proportional relationship between the parameter t/L and the cover factor K. In this investigation, the predicted tensile strength and extension at the point of break worked out on the geometrical basis when the fabric is extended in walewise and coursewise direction. Once more the fabric made from two-ends behaved differently when it was subjected to tensile and to repeated cycles of extension. Fabrics made from two-ends are stronger at break but have lower recovery than the fabrics made from single yarn. While there is a relationship between the total elastic recovery and the loop length for the fabric made from one-end, it appeared that it is difficult to find a systematic relationship between the total elastic recovery and the loop length for fabrics made from two-ends in both the dry- and fully-relaxed state due to the involvement of the yarn arrangement within the structural unit cell of the fabric. In addition to the pattern of yarn arrangement within the structural unit cell in the two-end fabric, there is relative yarn movement which may affect the dimensions of the cell.

This thesis describes the investigation of time-division multiplexing for use in mUlticomponent laser Doppler anemometry (LDA). To make two- or three- dimensional velocity measurements of a flow, two or three separate velocity measurements in different, non-collinear or non-coplanar directions respectively must be taken from which the flow vector can be calculated. It is necessary to separate each velocity channel. Conventionally, the separation is carried out by optical techniques, such as separating the signal from each channel by wavelength or polarisation, with one detector per channel. In time division multiplexing, each channel is switched On and off in turn. A single detector records a stream of interleaved pulses, and each channel is extracted by taking every other or every third pulse. The envelope of the amplitudes of the pulses varies at the Doppler frequency. A novel system has been demonstrated which uses a single laser diode source and a single detector. The distribution of the pulses to each channel and the delay between each channel is carried out using a optical fibre network with fibre delay lines, with a consequent reduction in 'electronic complexity. The characteristics of the optoelectronic components used in the system are tested, and two signal processing schemes are investigated. A two-dimensional Doppler difference fibre-linked probe was constructed to demonstrate the technique. Hybrid instruments using two Doppler difference channels and a reference beam channel to measure orthogonal velocity components offer the possibility of avoiding the errors introduced by non-orthogonal systems. A pulsed-diode reference beam anemometer based on optical fibres and suitable for inclusion in a time-division multiplexed hybrid instrument was tested.

Ce travail de thèse rassemble nos résultats d’étude sur l’utilisation des modes de résonance acoustique pour réaliser des capteurs distribués à base des fibres à cristaux photoniques (Photonic Crystal Fibres : PCF).Tout d’abord, nous avons démontré qu’à l’heure actuelle, il est difficile voire impossible de mesurer en rétrodiffusion les modes acoustiques transverses dans une fibre optique. Ces modes dont la fréquence est inférieure à 2 GHz, ont été mesurés dans une boucle non linéaire sur une PCF, une fibre conventionnelle et une fibre à dispersion décalée. Les différents spectres montrent une dépendance à la structure transverse des fibres.Ensuite, nous avons mis au point un réflectomètre Brillouin (Brillouin Optical Time Domain Reflectometer : BOTDR) permettant de suivre en temps réel le spectre Brillouin le long d’une fibre avec une résolution spatiale de l’ordre d’une dizaine de mètres. Il est particulièrement capable de discriminer différents modes présents dans le spectre Brillouin.La comparaison des spectrogrammes obtenus sur différentes structures transverses de fibres, confirme que l’existence de multipics Brillouin dans les PCF est liée au très petit coeur (dont le diamètre est de l’ordre de la longueur d’onde de mesure) de la fibre.Enfin, toujours dans l’optique de mieux observer le spectre Brillouin distribué, nous avons développé un outil d’analyse Brillouin vectorielle permettant de cartographier avec précision les modes Brillouin hybrides grâce à la complémentarité du spectrogramme de phase. Les mesures réalisées sur une PCF dont le diamètre varie linéairement de 3,5 µm à 2,6 µm montrent un second mode Brillouin dont la fréquence varie à raison de -118,2 MHz/µm. / This thesis deals with the results of our study on the use of acoustic resonance modesto achieve distributed sensors based on photonic crystal fibres (Photonic Crystal Fibres :PCF).First, we demonstrated that at present it is difficult to measure backscattered transverseacoustic modes in an optical fibre. These modes whose frequency is below 2 GHzhave been measured in a loop on a nonlinear PCF, a conventional fibre and a dispersionshifted fibre. The different spectra show a dependence on the fibres cross section structure.Then we developed a Brillouin reflectometer (Brillouin Optical Time Domain Reflectometer: BOTDR) to monitor in real time the Brillouin spectrum along a fibre witha spatial resolution of about a dozen meters. It is particularly capable of discriminatingbetween different modes present in the Brillouin spectrum. Comparison of spectrogramsobtained on different transverse structures, confirms that the existence of Brillouin multipeakon PCF is linked to the very small core (with a diameter of about the wavelengthof measurement) of the fibre.Finally, in order to better observe the distributed Brillouin spectrum, we have developeda vector Brillouin optical time domain analyzer for high-order acoustic modes toaccurately map the Brillouin hybrid modes with the complementary phase of the spectrogram.The measurements taken on a PCF whose diameter varies linearly from 3.5 micronsto 2.6 microns show a second Brillouin mode whose frequency varies as -118.2 MHz / um.

Cette thèse s’intéresse à la topologie des lissages des singularités non-isoléesde surfaces complexes. La question est celle de la description de la topologie de la variété,appelée fibre de Milnor, qui survient lors de ce procédé de lissage. Devant la difficulté dedécrire la totalité de cette topologie, beaucoup de recherches se sont concentrées sur le bordde la fibre de Milnor. Dans le cas des singularités isolées, il est connu depuis les travaux deMumford (1961), que ce bord est une variété graphée, isomorphe au bord de la singularité.Différents résultats (Michel & Pichon 2003, 2014, Némethi & Szilárd 2012) ont par lasuite prouvé que dans le cas des singularités réduites non-isolées, le bord de la fibre de Milnorest encore une variété graphée, en imposant à l’espace total du lissage d’être lui-mêmelisse. Fernández de Bobadilla & Menegon-Neto (2014) ont quant à eux élargi le contexte,considérant le cas d’une surface non réduite dans un espace total à singularité isolée. Dansce travail, on poursuit l’extension de ce résultat à un plus large contexte, autorisant l’espacetotal du lissage à présenter des singularités non-isolées, tout en imposant à la surface d’êtreréduite. Notre preuve s’inspire de celle de Némethi et Szilard, permettant comme chez euxde produire une méthode pour le calcul de cette variété. Ceci rend praticable le calcul effectifd’une grande quantité d’exemples, représentant un progrès dans la quête de la compréhensiondes variétés pouvant apparaître comme bords de fibres de Milnor.Nous appliquons en particulier la méthode aux singularités Newton-non-dégénéréesdéfinies sur des germes toriques tridimensionnels quelconques. Nous généralisons de cettemanière un théorème de Oka (1986), en exprimant le bord de la fibre de Milnor en termesdu polyèdre de Newton de la singularité. / This thesis is dedicated to the study of the topology of smoothings of non-isolated singularities of complex surfaces. The question is to describe the topology of themanifold, called Milnor fiber, which appears during this process of smoothing. Consideringthe great difficulty of a description of the whole of this topology, many researches havefocused on the study of the boundary of the Milnor fiber. In the case of isolated singularities,it is known since the work of Mumford (1961) that this boundary is a graph manifold,isomorphic to the link of the singularity.Different results (Michel & Pichon 2003, 2014, Némethi & Szilárd 2012) have then provedthat, in the case of reduced non-isolated singularities, the boundary of the Milnor fiber isagain a graph manifold, while restraining to the case of a smooth total space of smoothing.Fernández de Bobadilla & Menegon-Neto (2014) have widened the context, consideringnon-reduced surfaces, and allowing the total space to have an isolated singularity. In thiswork, we pursue the extension of this result to a larger context, allowing the total spaceto present non-isolated singularities, while restraining ourselves to the study of reducedsurface singularities. Our proof is inspired by the one of Némethi and Szilard, and allows usfurthermore to provide a method for the computation of this manifold. This makes possiblethe actual computation of a large number of examples, representing a step forward in thequest for the comprehension of the manifolds that can actually appear as boundaries ofMilnor fibers.We apply in particular the method to Newton non-degenerate singularities defined on3-dimensional toric germs. This is a generalization of a theorem of Oka (1986), expressingthe boundary of the Milnor fiber in terms of the Newton polyhedron of the singularity.

Le lin (Linum usitatissimum) fait partie des premières plantes cultivées dans le monde. Depuis toujours il est une source de fibres (périphloèmiennes) de très grande qualité pour l'industrie textile et connait actuellement un nouvel intérêt dans l'industrie des matériaux composites. Les fibres périphloèmiennes de lin possèdent des propriétés mécaniques remarquables grâce à la structure et la composition chimique de leurs parois cellulaires. Afin d'approfondir nos connaissances concernant la mise en place de la paroi cellulaire des fibres de lin, nous avons généré des ESTs à partir de tissus externes riches en fibres. La classification fonctionnelle des ESTs a permis l'identification de séquences codant une beta xylosidase potentielle (LuBXL1). La caractérisation fonctionnelle de plantes sous-exprimant (stratégie IR-PTGS) LuBXL1 n'as pas pu permettre la mise en évidence d'un phénotype macroscopique. En revanche, des analyses microscopiques ont suggéré des modifications éventuelles de la paroi des cellules xylèmiennes. La technique d'empreinte enzymatique a démontré une augmentation relative de l'oligoxyloglucanes XXXG dans les tissus internes de lignées sousexprimant LuBX1, associée une diminution dans la quantité relative de certains oligoxylanes. Ces observations suggèrent que chez le lin la sous-expression de LuBXL1 est associée à des modifications des hémicelluloses pariétales. / Flax (Linum usitatissimum) has been a source of high quality fibers (bast fibers) for several thousand years. The fibers are currently used in the textile industry but also increasingly in the fabrication of composites. The interesting mechanical properties of these bast fibers depend upon the structure and chemical composition of their cell walls. ln order to improve our knowledge about the mechanisms underlying cell wall formation in flax fibers we produced ESTs from outer tissues, rich in fibers. Functional classification of ESTs allowed the identification of sequences coding a potential beta-xylosidase (LuBXL1). LuBXL1 down-regulated (IR-PTGS) plants did not show any visible phenotype. However, microscopie analysis suggested that down-regulation could have affected xylem cell wall structure. Enzymatic Fingerprinting indicated a relative increase in the relative quantity of the XXXG oligoxyloglucans in stem inner tissues of down-regulated lines, together with a relative decrease in the quantity of certain oligoxylans. These observations suggest that the down-regulation of LuBXL1 in flax is associated with modifications in cell wall hemicelluloses.

<p>The purpose of work was to show properties of concrete modified with wooden fibres and to compare whem with unmodified concrete in order to show influence of these wooden fibres on chosen properties and to check if using of these types of admixtures is benificial in economical and technical point of view.</p>