Download or read book ORIGINE DES PERTES OPTIQUES DANS LES FIBRES A BASE SILICE written by Philippe Guenot and published by . This book was released on 1997 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: CETTE THESE PORTE SUR L'ETUDE DES PHENOMENES D'ATTENUATION DANS LES FIBRES OPTIQUES MONOMODES A BASE SILICE. DANS LE PROCHE INFRA ROUGE, LES PERTES OPTIQUES D'UNE FIBRE A BASE SILICE RESULTENT D'UN ENSEMBLE DE CONTRIBUTIONS DE DIFFUSION OPTIQUE, D'ABSORPTIONS, ET D'IMPERFECTIONS DE GUIDAGE. MALGRE LES NOMBREUSES ETUDES QUI ONT ETE REALISEES DEPUIS ENVIRON TRENTE ANS SUR CE SUJET, LA PART PRECISE DE CHACUNE DE CES CONTRIBUTIONS DANS LE COEFFICIENT D'ATTENUATION GLOBAL, LA LIMITE THEORIQUE DE TRANSPARENCE, AINSI QUE LES RAISONS QUI LIMITENT L'OBTENTION DE CE MINIMUM THEORIQUE, DEMEURENT SUJETTES A DISCUSSION. DANS LE CADRE DE CE TRAVAIL DE THESE, NOUS AVONS MIS AU POINT DES MOYENS EXPERIMENTAUX PERFORMANTS POUR ETUDIER LES PERTES OPTIQUES DES PREFORMES ET DES FIBRES ; LES CARACTERISATIONS ONT PORTE SUR UN LARGE EVENTAIL DE MATERIAUX CLEFS ENTRANT DANS L'ELABORATION DES PREFORMES, ET SUR DIFFERENTES STRUCTURES DE FIBRES. LES RESULTATS OBTENUS APPORTENT DES ELEMENTS DE REFLEXION COMPLEMENTAIRES AUX TRAVAUX DEJA PUBLIES DANS CE DOMAINE, ET NOUS ONT PERMIS : (I) DE MIEUX CERNER LES PROPRIETES INTRINSEQUES DE TRANSMISSION DES VERRES DE SILICE EN FONCTION DES COMPOSITIONS EMPLOYEES, (II) DE TRANCHER ENTRE LES DIVERS MODELES COMPORTEMENTAUX PUBLIES EXPLIQUANT LA GENERATION D'EXCES DE PERTES EN FONCTION DES CONDITIONS D'ELABORATION, ET D'EN PROPOSER UN NOUVEAU. CETTE ETUDE QUANTITATIVE MARQUE UNE AVANCEE SIGNIFICATIVE DANS LA COMPREHENSION DE L'ORIGINE DES PERTES OPTIQUES DANS LES FIBRES DE LIGNE. LA METHODOLOGIE EMPLOYEE EST APPLICABLE A TOUT TYPE DE FIBRE, AUSSI BIEN A BASE SILICE QU'A D'AUTRES BASES ; ELLE N'EST PAS SPECIFIQUE AUX FIBRES DE LIGNE MAIS GENERALE.
Download or read book D veloppement et caract risation de fibres optiques mutimat riaux verre silice ou verre air silice r alis es par un proc d bas sur l utilisation de poudre de verres written by Stéphanie Leparmentier and published by . This book was released on 2010 with total page 221 pages. Available in PDF, EPUB and Kindle. Book excerpt: La réalisation de guides d’onde ou de sources pour l’infrarouge moyen nécessite l’utilisation de verres optiques autres que la silice qui sont souvent fragiles, chers et difficiles à mettre en oeuvre, surtout pour la conception de PCF. Nous avons proposé de développer la géométrie inédite des fibres optiques multimatériaux dont seule la zone active est composée du verre performant. Une gaine en silice protège le coeur d’attaque mécanique ou chimique possible. Certains verres optiques permettent la réalisation de fibres verre/silice à forts Δn et des coefficients NL similaires à ceux de PCF air/verre. Un procédé, basé sur l’utilisation de poudres, a été développé pour la réalisation de FOM et de fibres plus conventionnelles dont les pertes optiques sont de l’ordre des pertes intrinsèques au matériau. Cette méthode peut être adaptée à tout type de verre sous forme de poudre et est compatible aux procédés Rod-in- Tube et Stack-and-Draw pour la conception de fibres multimatériaux microstructurées. Une méthode interférométrique a également été développée pour caractériser l’indice de réfraction de verres originaux présents dans le coeur de ces fibres sur une large bande spectrale.
Download or read book Cr ation et caract risation d une susceptibilit non lin aire d ordre deux dans les verres massifs et dans les fibres optiques base de silice written by Yves Quiquempois and published by . This book was released on 1999 with total page 628 pages. Available in PDF, EPUB and Kindle. Book excerpt: La nature amorphe des verres de silice entraîne l'absence de susceptibilité non-linéaire d'ordre deux Chi( 2 ). Néanmoins, la possibilité de créer une susceptibilité Chi( 2 ) par la méthode de polarisation thermique a été démontrée en 1991. Cette méthode consiste à chauffer à une température optimale le matériau soumis à un champ électrique. Ce résultat est expliqué par l'apparition d'un champ électrique statique permanent dans le verre et par l'orientation d'entités hyperpolarisables durant la polarisation. Partant d'un modèle de conduction ionique, nous avons calculé les variations des susceptibilités Chi( 1 ) et Chi( 2 ) induites dans le matériau polarisé. Pour vérifier la validité de ce modèle, nous avons réalisé des expériences sur des lames de verre de compositions différentes (InfrasilTM 301, SuprasilTM I, verres germanosilicates) et dans des fibres optiques à structure évidée. Dans les échantillons massifs, nous avons utilisé la méthode des franges de Maker spatiales afin de caractériser la susceptibilité Chi( 2 ) créée. Cette méthode consiste à mesurer la puissance harmonique générée dans le verre en fonction de l'angle d'incidence d'un faisceau pompe sur l'échantillon. Nous avons amélioré les performances de cette méthode en mettant au point un montage original. Deux lentilles hémisphériques, placées de chaque coté de la lame polarisée, permettent d'atteindre des angles de propagation interne proche de 90°. Ainsi, nous avons montré que, dans les verres en InfrasilTM 301, la susceptibilité Chi( 2 ) créée est localisée dans une fine couche située près de la surface anodique, alors qu'elle existe dans tout le volume d'un verre de SuprasilTM I. L'étude de la polarisation thermique des fibres optiques a permis de déduire le sens du champ électrique créé dans le matériau. Le dispositif utilisé pour les mesures préfigure le commutateur ou le modulateur tout fibre qui pourrait s'appliquer à la technologie des télécommunications optiques.
Download or read book Etude et mise en oeuvre de proc d s de fabrication de pr formes et fibres optiques unimodales en verres fluor s written by Chantal Falcou and published by . This book was released on 1988 with total page 134 pages. Available in PDF, EPUB and Kindle. Book excerpt: LES VERRES FLUORES FONT L'OBJET D'UN GRAND INTERET DANS LES TELECOMMUNICATIONS GRANDE DISTANCE ETANT DONNE LEUR FAIBLE ATTENUATION THEORIQUE QUI EST DE 0.01 DB/KM DANS LA REGION DE 2.5 M, CE QUI AUTORISERAIT UN GAIN D'UN FACTEUR 10 PAR RAPPORT AUX PERFORMANCES ACTUELLES DES FIBRES OPTIQUES EN SILICE. CEPENDANT, DE NOMBREUX PHENOMENES EXTRINSEQUES, LIES ENTRE AUTRES A L'ELABORATION DU MATERIAU, COMPROMETTENT L'OBTENTION DE CETTE ATTENUATION. AUSSI EST-IL INTERESSANT DE DETERMINER L'ORIGINE DES PERTES DANS LES FIBRES OPTIQUES EN VERRES FLUORES AFIN D'AMENER LES AMELIORATIONS NECESSAIRES A LA REALISATION DES VERRES, DES PREFORMES ET DES FIBRES OPTIQUES. NOTRE ETUDE EST AXEE SUR LA MISE EN OEUVRE DE NOUVEAUX PROCEDES D'ELABORATION DE PREFORMES POUR FIBRES OPTIQUES UNIMODALES. LES DEUX PROCEDES EXPOSES SONT DONC BASES SUR LA RECHERCHE DE TECHNIQUES PERMETTANT D'OBTENIR UN DIAMETRE DE COEUR FAIBLE, CE QUI CONSTITUE UN CRITERE ESSENTIEL POUR L'OBTENTION DU REGIME UNIMODAL. IL S'AGIT D'UNE PART, DE LA DIFFUSION DU PLOMB A L'INTERIEUR DE LA MATRICE FLUOREE AFIN D'AUGMENTER SON INDICE DE REFRACTION SUR UNE PROFONDEUR SUFFISANTE, ET D'AUTRE PART, DU CHEMISAGE D'UNE PREFORME MULTIMODALE PREALABLEMENT ETIREE. QUE L'ON PROCEDE A LA DIFFUSION OU AU CHEMISAGE, CES DEUX TECHNIQUES FONT APPEL AU RETREINT DANS LA MESURE OU IL CONSTITUE LA PHASE ULTIME DE L'ELABORATION DE LA PREFORME. AUSSI, UNE ETUDE EST CONSACREE A LA REALISATION ET A LA FAISABILITE DU RETREINT D'UN TUBE EN VERRE FLUORE. L'ETUDE DE LA DIFFUSION DU PLOMB S'ACCOMPAGNE D'UNE EXPERIMENTATION ET D'UNE INTERPRETATION THEORIQUE QUI PERMETTENT LE CALCUL DU COEFFICIENT DE DIFFUSION DU PLOMB AUX TEMPERATURES DE 305 ET 295C. LE CHEMISAGE FAIT L'OBJET D'UNE EXPERIMENTATION QUI PROUVE SA FAISABILITE ET QUI CONDUIT A LA DETERMINATION DE L'ATTENUATION SPECTRALE D'UNE FIBRE OPTIQUE UNIMODALE.
Download or read book Influence des effets thermiques et m caniques sur la relaxation des pr formes et des fibres optiques base de silice written by Valérie Martinez and published by . This book was released on 2004 with total page 150 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cette thèse est consacrée à l'étude de l'influence des effets thermiques et mécaniques sur les modifications structurales des verres de silice et de silice dopée. La première partie de ce travail concerne l'étude des paramètres structuraux qui régissent l'atténuation dans les fibres optiques de télécommunication. Les mesures de diffusion Raman, Rayleigh, Brillouin et des rayons X aux petits angles ont montré que des traitements thermiques appropriés qui abaissent la température fictive des fibres, peuvent diminuer les fluctuations de densité et ainsi améliorer la transmission. La seconde partie de ce travail concerne l'impact de l'indentation sur la structure d'un verre de silice pure et de deux échantillons dopés GeO2. Une cartographie Raman de l'indent a été effectuée et l'évolution des signatures spectroscopiques (bande principale, D1 et D2) a mis en évidence différentes modifications structurales caractéristiques d'une densification
Download or read book Journal de physique written by and published by . This book was released on 2003 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Terra 2008 written by Leslie Rainer and published by Getty Publications. This book was released on 2011-06-14 with total page 438 pages. Available in PDF, EPUB and Kindle. Book excerpt: Earthen architecture constitutes one of the most diverse forms of cultural heritage and one of the most challenging to preserve. It dates from all periods and is found on all continents but is particularly prevalent in Africa, where it has been a building tradition for centuries. Sites range from ancestral cities in Mali to the palaces of Abomey in Benin, from monuments and mosques in Iran and Buddhist temples on the Silk Road to Spanish missions in California. This volume's sixty-four papers address such themes as earthen architecture in Mali, the conservation of living sites, local knowledge systems and intangible aspects, seismic and other natural forces, the conservation and management of archaeological sites, research advances, and training.
Download or read book Adhesion Between Polymers and Concrete Adh sion Entre Polym res Et B ton written by H. R. Sasse and published by Springer. This book was released on 1986 with total page 792 pages. Available in PDF, EPUB and Kindle. Book excerpt: Preface Adhesion is a phenomenon architects and civil engineers are not very familiar with. In other disciplines knowledge about surface properties and the background of bonding energies is also far from satisfactory; nevertheless there are many important· applications in concrete engineering, where adhesion is necessary for success and durability. These include: - coating and painting - repair of concrete surfaces - bonding of fresh to old concrete - crack injection - glueing of precast elements - glueing of steel to concrete, etc. In 1981 RILEM established the technical committee 52-RAC 'Resin Adherence to Concrete'. The main aims of the committee's work were - to collect research results and practical experiences - to initiate and coordinate research programs - to develop, on a scientific base, test methods for field and for laboratory purposes. One of the results of the committee's work is a state-of-the-art report, which will be presented orally as a General Report at the International Symposium ISAP '86, and will be printed either in the RILEM journal Materials and Structures or separately. Several test recommendations have been elaborated and will be prepared as drafts for the participants ofISAP '86. These are: - direct tensile test - pull-off test - direct shear test - slant shear test - four-point bending test - dynamic loading test - thermal compatibility test (two versions) - injectibility test.
Download or read book Dictionary of Building and Civil Engineering written by Don Montague and published by Taylor & Francis. This book was released on 1996 with total page 472 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dual-language dictionary lists over 20,000 specialist terms in both French and English, covering architecture, building, engineering and property terms. It meets the needs of all building professionals working on projects overseas. It has been comprehensively researched and compiled to provide an invaluable reference source in an increasingly European marketplace.
Download or read book UNESCO General History of Africa Vol I Abridged Edition written by Jacqueline Ki-Zerbo and published by Univ of California Press. This book was released on 1990 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This volume covers the period from the end of the Neolithic era to the beginning of the seventh century of our era. This lengthy period includes the civilization of Ancient Egypt, the history of Nubia, Ethiopia, North Africa and the Sahara, as well as of the other regions of the continent and its islands."--Publisher's description
Download or read book Basic Technics in Ecological Farming Techniques de Base en Agriculture Biologique Grunds tzliche Verfahren der kologischen Landwirtschaft Le Maintien de la Fertilit des Sols The Maintenance of Soil Fertility Die Erhaltung der Bodenfruchtbarkeit written by Stuart Hill and published by Birkhäuser. This book was released on 2013-12-14 with total page 364 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Analytical Methods in the Nuclear Fuel Cycle written by and published by . This book was released on 1972 with total page 610 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Livestock Policy Analysis written by International Livestock Research Institute and published by ILRI (aka ILCA and ILRAD). This book was released on 1995-01-01 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: Policy concepts; Identification of policy issues; Production systems, supply and demand; Market, price and trade policies; Marketing and distribution systems; Budget and manpower planning; Land tenure police for the livestock sector; Policy analysis report writing and communication; Livestock production and marketing in alphabeta - a case study.
Download or read book Guidelines for Soil Description written by Food and Agriculture Organization of the United Nations and published by Food & Agriculture Org.. This book was released on 2006 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: Soils are affected by human activities, such as industrial, municipal and agriculture, that often result in soil degradation and loss. In order to prevent soil degradation and to rehabilitate the potentials of degraded soils, reliable soil data are the most important prerequisites for the design of appropriate land-use systems and soil management practices as well as for a better understanding of the environment. The availability of reliable information on soil morphology and other characteristics obtained through examination and description of the soil in the field is essential, and the use of a common language is of prime importance. These guidelines, based on the latest internationally accepted systems and classifications, provide a complete procedure for soil description and for collecting field data. To help beginners, some explanatory notes are included as well as keys based on simple test and observations.--Publisher's description.
Download or read book Experimental Chaos written by Stefano Boccaletti and published by A I P Press. This book was released on 2004-12-14 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt: The 8th Experimental Chaos Conference again demonstrated the broad spectrum of areas where nonlinear dynamics plays an important role, such as circuits, hydrodynamics, optics, chemistry, fracture dynamics, neuroscience, and cognitive science. Additional contributions outline the trends for development and application of concepts and techniques of nonlinear dynamics.
Download or read book An Introduction To Plasmonics written by Olivier Pluchery and published by World Scientific. This book was released on 2023-08-28 with total page 356 pages. Available in PDF, EPUB and Kindle. Book excerpt: What is a plasmon? Is it a particle, like a photon or a wave? Plasmonics stands at the frontier of condensed matter physics, which is the world of electrons, optics and of photons. Plasmonics is one of the most active fields in nanophotonics. This book begins by exploring the concepts behind waves, and the electromagnetic description of light when it interacts with metals; it dedicates every chapter thereafter to all aspects of plasmonics. In particular, the surface plasmon polariton wave is explained in full detail, as well as the localized surface plasmon resonance of metallic nanoparticles. The active research area opened by plasmonics, as well as its applications, are also briefly explained, such as advanced biosensing, subwavelength waveguiding, quantum plasmonics, nanoparticle-based cancer therapies, optical nano-antenna and high-efficiency photovoltaic cells.The book is adapted for graduate students and places a special emphasis on providing complete explanations of the fundamental concepts of plasmonics. Further, each of these concepts is illustrated with examples drawn from the most recent scientific literature. Each chapter ends with a set of exercises that will help the reader revise the concepts and go deeper into the world of plasmonics. More than 70 exercises are included.
Download or read book Imitation and Illusion written by Ingrid Geelen and published by Royal Institute for Cultural Heritage. This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the late Middle Ages luxurious textiles were among the most highly prized indicators of status and wealth and an essential requirement of prestigious secular and ecclesiastical life. The depiction of these sumptuous silks and gold brocades was a crucial element in the visual arts, and their realistic and recognizable representation was a challenge to every artist. Painters and polychromers strove to imitate the fashionable fabrics by using applied brocade, a highly sophisticated form of relief decoration that adhered to panel paintings, murals and sculpture and through the play of light and shadow evoked the dazzling illusion of gold-brocaded cloths. Imitation and Illusion is the result of a detailed study of applied brocade in the art of the Low Countries. Eleven fascinating and innovative chapters offer an in-depth examination of the historical, geographical, morphological and technical aspects of this cast tin relief technique. New light is also shed on artistic collaboration and workshop practice in the fifteenth and early sixteenth century. The catalogue includes 86 well known and lesser known panel and wall paintings, sculptures, altarpieces, and architectural elements produced between 1420 and 1540, decorated with applied brocade and providing stunning testimony to the visual variety and material magnificence of late-medieval art. Abundantly illustrated, Imitation and Illusion investigates the artistic production of the fifteenth- and sixteenth-century Low Countries from an intriguing and original perspective. It represents a significant contribution to our understanding of medieval polychromy and will appeal to everyone whose curiosity is aroused by the illusionistic ingenuity of the medieval artist.
