Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The concept of broadband coherent supercontinuum (SC) generation in all-normal dispersion (ANDi) fibers in the near-infrared, visible and ultraviolet (UV) spectral regions is introduced and investigated in detail. In numerical studies, explicit design criteria are established for ANDi photonic crystal fiber (PCF) designs that allow the generation of flat and smooth ultrabroad spectral profiles without significant fine structure and with excellent stability and coherence properties. The key benefit of SC generation in ANDi fibers is the conservation of a single ultrashort pulse in the time domain with smooth and recompressible phase distribution. In the numerical investigation of the SC generation dynamics self-phase modulation and optical wave breaking are identified as the dominant nonlinear effects responsible for the nonlinear spectral broadening. It is further demonstrated that coherence properties, spectral bandwidth and temporal compressibility are independent of input pulse duration for constant peak power. The numerical predictions are in excellent agreement with experimental results obtained in two realizations of ANDi PCF optimized for the near-infrared and visible spectral region. In these experiments, the broadest SC spectrum generated in the normal dispersion regime of an optical fiber to date is achieved. The exceptional temporal properties of the generated SC pulses are verified experimentally and their applicability for the time-resolved study of molecular dynamics in ultrafast transient absorption spectroscopy is demonstrated. In an additional nonlinear pulse compression experiment, the SC pulses obtained in a short piece of ANDi PCF could be temporally recompressed to sub-two cycle durations by linear chirp compensation. Numerical simulations show that even shorter pulse durations with excellent quality can be achieved by full phase compensation. The concept is further extended into the UV spectral regime by considering tapered optical fibers with submicron waist diameter. It is shown that coherent SC spectra with considerable spectral power densities in the usually hard to reach wavelength region below 300 nm can be generated using these freestanding photonic nanowires. Although technological difficulties currently prevent the fabrication of adequate nanofibers, the concept could be experimentally verified by coherent visible octave-spanning SC generation in tapered suspended core fibers with ANDi profile. The work contained in this thesis therefore makes important contributions to the availability and applicability of fiber-based broadband coherent SC sources with numerous high-impact applications in fundamental science and modern technology. / AFRIKAANSE OPSOMMING: Die konsep van breëband koherente superkontinuum (SK) in alles-normaal dispersiewe (ANDi) vesels in die naby-infrarooi, sigbare en ultraviolet (UV) spektrale gebiede word voorgestel en in detail ondersoek. In numeriese studies word eksplisiete ontwerpskriteria vasgestel vir ANDi fotoniese kristal vesel (FKV) ontwerpe wat dit moontlik maak om plat en gladde ultra-breë spektrale profiele te genereer sonder noemenswaardige fynstruktuur en met uitstekende stabiliteit en koherensie eienskappe. Die sleutel voordeel van SK genering in ANDi vesels is die behoud van ’n enkele ultrakort puls in tyd met ’n gladde en saamdrukbare fase distribusie. In die numeriese ondersoek van die SK generering is die dinamika van fase selfmodulering geïdentifiseer as die dominante nie-lineêre effek wat verantwoordelik is vir die nie-lineêre spektrale verbreding. Daar word voorts aangetoon dat die koherensie eienskappe, spektrale bandwydte en saamdrukbaarheid in tyd onafhanklik is van die inset pulsduur vir konstante drywing. Die numeriese voorspellings stem uitstekend ooreen met die eksperimentele resultate wat verkry is met twee ANDi FKVÕs wat optimeer is vir die naby-infrarooi en sigbare spektrale gebied. In hierdie eksperimente is die breedste SK spektrum gegenereer wat tot hede in die normaal dispersiewe regime met ’n optiese vesel behaal is. Die besondere eienskappe van die genereerde SK pulse is eksperimenteel bevestig en die toepasbaarheid vir tyd opgelosde studie van molekulêre dinamika is gedemonstreer. In ’n addisionele nie-lineêre puls kompressie eksperiment is SK pulse verkry in ’n kort stuk ANDi FKV wat in tyd saamgedruk kon word tot sub-twee siklus tydsduur deur liniêre tjirp kompensering. Numeriese simulasies toon aan dat selfs korter pulse met uitstekende kwaliteit behaalbaar is met volledige fase kompensasie. Die konsep is verder uitgebrei na die UV spektrale gebied deur ’n koniese vesel te beskou met sub-mikron diameter. Daar is aangetoon dat koherente SK spektra met noemenswaardige spektrale drywing in die golflengte gebied onder 300 nm, wat gewoonlik as moeilik toeganklik beskou word, bereik kan word deur hierdie vrystaande fotoniese nano-vesels aan te wend. Alhoewel tegnologiese probleme die vervaardiging van voldoende nano-vesels verhinder, kon die konsep eksperimenteel bewys word deur koherente sigbare oktaafspannende SK te genereer in koniese gesuspendeerde kern vesels met ’n ANDi profiel aan te wend. Die werk wat in die tesis vervat is, maak dus belangrike bydraes tot die beskikbaarheid en toepasbaarheid van vesel gebaseerde breëband koherente SK bronne met verskeie hoë impak toepassings in fundamentele wetenskap en moderne tegnologie.

Fiber amplifiers with high power and high pulse energy are strongly in demand for both scientific research and industrial applications. Ytterbium-doped fiber has been an outstanding choice for its broad-gain bandwidth and excellent power conversion efficiencies. In this dissertation, we introduced a compact high power high pulsed energy laser system with chirally coupled core (3C) Yb-doped fibers as the gain media. Traditional standard fibers and photonic crystal fibers are not suitable for compact high power high pulse energy laser systems because of poor higher order modes (HOMs) management and complicated air-hole structure. Newly invented 3C silica fibers solve these problems. A helical side-core around the Yb-doped central core extracts the HOMs from the central core. By adjusting this chirally structure, the core of the 3C fiber can be enlarged and the transverse mode of the fiber can be single mode at certain wavelengths. To simulate the amplification process with high power high pulse energy better, a new modeling method based on a combination of the rate equations and the nonlinear Schrödinger equations is invented. The gain was calculated from rate equations and the pulse evolution was analyzed using nonlinear Schrödinger equation. The simulation provided a good guidance for building compact high power high pulse energy laser systems. To achieve high power and high pulse energy, the system is designed as a two-stage structure. The laser

The goal of this study is to further advance the state of the art in developing self-sufficient methods to predict the performance of an aerosol filter. The simulation methods developed in this study are based on first principles and consequently, they do not rely on empirical correction factors. These simulation methods can be used to predict the instantaneous collection efficiency and pressure drop of a filter under dust-loading conditions. In the current study, 3-D micro- and macroscale CFD models are developed to simulate the service life of flat-sheet and pleated filters. These CFD micro- and macroscale models are also used to quantify the effects of a fiber’s cross-sectional shape on the performance of the resulting filter. As fiber manufacturing methods are rapidly advancing, these fibers are becoming more accessible. The filtration performance of trilobal fibers is compared with their circular counterparts under dust-loading conditions. Our results show that trilobal fibers do not outperform circular ones except in very limited conditions, revealing no advantage over circular fibers. In addition, a fast but approximate 2-D model is developed to predict the filtration performance of flat and circular pleated filters. The predictions of the model are compared with predictions from the more sophisticated CFD models, as well as with experimental work in the literature. Our 2-D model developed in this study is aimed at providing the aerosol filtration industry with a fast but fairly accurate method of designing pleated filters. With a CPU-time of practically zero, the developed model allows one to conduct a broad parameter study, altering the parameters that affect the filtration performance of pleated filters. Using this model, predictive correlations for dust-loaded pleated filters are presented. These correlations allow one to estimate the instantaneous pressure drop and collection efficiency of pleated filters effectively.

The thesis evaluates the influence of the addition of polypropylene fibers on the properties of concrete. One of the major elements is to compare different finishes polypropylene fibers without static functions, including low temperature plasma treatment plasma. The main work is to test the knowledge of the properties of fresh concrete with these fibers, as well as testing volume changes and finally testing these concretes on physical and mechanical properties

Este trabalho aborda o comportamento de dois solos (uma argila e uma areia), reforçados com fibras plásticas de polipropileno. Os solos foram compactados no teor de umidade ótimo e peso específico seco máximo e foram misturados com fibras de diferentes teores e comprimentos. Os resultados dos ensaios de compressão simples foram usados para selecionar os teores e comprimentos ótimos de fibras. Os resultados mostraram que a resistência do solo arenoso cresceu com o aumento do teor e comprimento das fibras e o solo argiloso apresentou acréscimo de resistência, com o aumento do teor até o comprimento de fibra de 10 mm. As curvas tensão-deformação dos ensaios triaxiais, para solos com e sem reforço foram similares, com uma resistência de pico definida e pequena redução de queda de tensão pós pico. As amostras de solo arenoso apresentaram considerável aumento de resistência, com o aumento do teor e comprimento das fibras. Pequenos painéis, fabricados com o solo argiloso (300 x 300 x 100) mm, mostraram que a presença da fibra pode reduzir a magnitude das trincas quando comparados com o solo sem reforço. / This work presents the behavior of two soils (clay and sandy) reinforced with polypropylene plastic fibers. The soils were compacted at the optimum moisture content and maximum dry unit weight and were mixed with fibers of different lengths and contents. Unconfined compressive tests results were used to select the optimum fiber length and content. The results showed that the granular soil strength increased with increasing fiber length and content. The cohesive soil, on the other hand, showed strength up to fiber length of 10 mm. Stress - strain curves from triaxial tests for both reinforced and unreinforced cohesive soil were similar with a defined peak strength and small post peak reduction. Granular soil samples presented considerable strength increases with the increases of length and fiber content. Small panels fabricated with the reinforced cohesive soil (300 x 300 x 100) mm, showed that the presence of fiber can reduce crack magnitude when compared with the unreinforced soil.

O Brasil necessita de uma ampla implantação de sistemas de saneamento básico, como os de águas pluviais e, principalmente, coleta e tratamento de esgoto. Para resolver este problema pode ser interessante o emprego de tubos de concreto. Apesar de recente, o estudo de tubos de concreto reforçados com fibras já possibilitou a revisão da norma brasileira NBR 8890:2007 que prevê a utilização das fibras como único reforço do componente. No entanto, apenas fibras de aço são permitidas. Apesar de terem um potencial de durabilidade maior do que os tubos convencionalmente armados, ainda há a possibilidade de ampliar sua vida útil se forem utilizadas macrofibras poliméricas, que são resistentes à corrosão eletrolítica e hoje se encontram disponibilizadas no mercado Nacional. A dúvida que permanece é se essas fibras conseguem apresentar o mesmo desempenho mecânico das fibras de aço. Assim, esta dissertação de mestrado tem por objetivo principal realizar uma avaliação comparativa de desempenho mecânico das macrofibras poliméricas e das fibras de aço destinadas ao reforço de tubos de concreto para obras de saneamento básico. De forma a possibilitar estas avaliações foi feita uma verificação de desempenho por meio do ensaio de compressão diametral, com controle de deslocamentos, em tubos de concreto reforçados com fibras. Complementarmente, foram feitos o ensaio de absorção de água, a determinação do teor de fibra incorporado ao concreto por meio de testemunhos extraídos dos tubos e o ensaio de compressão axial em corpos-de-prova moldados. Os resultados demonstraram que as macrofibras poliméricas não obtiveram desempenho mecânico satisfatório, principalmente no que se refere à resistência residual pós-fissuração do tubo. Tal desempenho só foi obtido com a utilização de fibras de aço, o qual apresentou o dobro da capacidade resistente residual das macrofibras poliméricas para o mesmo teor em volume. Dessa forma, os tubos de concreto de 1 m de diâmetro reforçado com fibras, analisados neste estudo, apresentaram dificuldade de obtenção do desempenho pós-fissuração, o que dificultou a aprovação nos critérios da NBR 8890:2007. Assim, para que estes tubos pudessem atingir as cargas especificadas nesta norma seria preciso aumentar o teor ou o comprimento das fibras, o que iria dificultar a moldagem dos tubos. / Brazil requires a wide deployment of systems for drainage and, especially, sewage collection and treatment. To resolve this issue may be interesting the use of concrete pipes. Although recent, the study of fiber reinforced concrete pipes has already enabled the revision of the Brazilian standard NBR 8890:2007. This standard allows the use of fibers as the sole reinforcement for the components. However, only steel fibers are allowed. Despite the possibility that fibers can provide a potential higher durability compared to the conventionally reinforced concrete pipes, there is also the possibility of extension of the pipe lifetime by the use of polymeric fibers. This kind of fiber is resistant to electrolytic corrosion and, nowadays, is available in the Brazilian market. The remaining doubt is if these fibers can provide the same mechanical performance of steel fibers. Thus, this work has the main objective of carried out a comparative evaluation of the mechanical performance of polymeric fibers and steel fibers reinforcement for drainage concrete pipes. In order to enable these assessments, a verification of mechanical performance was made through the crushing test, where the diametric displacement of the pipes was also measured. In addition, tests were made in order to measure the concrete water absorption, the fiber actual consumption determination in cores extracted from the pipes, and compressive strength determination. The results showed that the polymeric macrofibers did not reach satisfactory performance, especially regarding to the residual post-crack strength. Only the steel fiber reinforced concrete pipes were able to fit the requirements, which had twice the post-crack residual strength presented by the polymeric fibers with the same content by volume. Thus, the fibers reinforced concrete pipes with diameter of one meter, used in this experimental program, showed difficult to obtaining the post-cracking behavior, which turns difficult the approval in the Brazilian standard criteria. So, the pipes reinforced with polymeric fibers could only possibly reach the load levels specified for post-crack strength by the use of a higher content or an increased length of fibers, which would turns much more difficult the concrete pipes production.

by Chiu Chi-Wai. / Thesis (M.B.A.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 75-78). / ACKNOWLEDGMENT --- p.ii / ABSTRACT --- p.iii / TABLE OF CONTENTS --- p.iv / LIST OF FIGURES --- p.vi / LIST OF TABLES --- p.vii / Chapter / Chapter I. --- INTRODUCTION --- p.1 / Objective --- p.1 / Background --- p.1 / Outline of Subsequent Sections --- p.2 / Summary of Conclusions --- p.3 / Chapter II. --- METHODOLOGY --- p.4 / Chapter III. --- PTA GLOBAL AND REGIONAL OUTLOOK --- p.6 / The PTA - Polyester Chain --- p.6 / Polyester Products --- p.6 / Polyester Raw Material Outlook --- p.8 / Asian PTA Supply and Demand --- p.9 / Conclusion: Asian PTA Supply and Demand --- p.11 / Chapter IV. --- COUNTRY ANALYSIS --- p.12 / Macroeconomics Overview --- p.12 / Regulatory and Investment Environment --- p.15 / India vs. China --- p.18 / Chapter V. --- MARKET ANALYSIS --- p.20 / PET Market --- p.20 / PTA Market --- p.24 / India PTA Supply and Demand --- p.26 / Conclusion: India PTA Supply and Demand --- p.27 / Chapter VI. --- TECHNICAL ANALYSIS --- p.28 / Oxidation --- p.28 / Purification --- p.29 / Chapter VII. --- ECONOMIC ANALYSIS --- p.31 / Review of Petrochemical Industry in India --- p.31 / Project Economics and Assumptions --- p.34 / Conclusion --- p.43 / Chapter VIII. --- PROJECT FUNDING ANALYSIS --- p.49 / Risk Factors --- p.50 / Principle Terms of Bank Syndication --- p.56 / Chapter IX. --- CONCLUSION --- p.58 / Current Environment and Future Trends --- p.58 / Investment Opportunity --- p.60 / Summary of Economic Analysis --- p.60 / Factors for Future Success --- p.61 / APPENDIX --- p.62 / BIBLIOGRAPHY --- p.75

Includes photographs of project. / Digitized by Kansas Correctional Industries

Au cours des dernières années, le développement de matériaux composites avancés fabriqués à partir de fibres naturelles a été principalement axé sur l'obtention de matériaux à haut module et à haute résistance. Cependant, la résistance élevée n'est pas suffisante, car certains des matériaux possèdent une nature fragile (l'allongement à la rupture est faible), et l'un des critères de performance les plus importants devrait être la capacité à absorber l'énergie et à résister aux chocs. La manière dont un matériau composite se déforme et subit des endommagements dépend à la fois des propriétés chimiques et mécaniques de trois constituants de base : les fibres, la matrice et une fine région d'interphase (parfois appelée interface) chargée d'assurer le lien entre matrice et fibre. En raison de leurs propriétés uniques et de leur nature abondante, les fibres à base de cellulose émergent comme un choix privilégié pour les communautés scientifiques, techniques et commerciales qui recherchaient des matériaux durables dans diverses applications. Bien que ces fibres possèdent plusieurs avantages par rapport aux charges synthétiques, l'adhérence entre la fibre et la matrice, la sensibilité à l'humidité et les propriétés au feu restent des domaines difficiles à traiter. Dans ce contexte, une nouvelle technique basée sur la méthode par pulvérisation-séchage-durcissement a permis de fabriquer un revêtement sol-gel hydrophobe sur la surface de la fibre de coco lignocellulosique. La modification de surface des fibres de coco a été effectuée à l'aide d'un plasma oxygène à basse pression suivi d'un enduit sol-gel polymérisable à sec avec un siloxane à fonction fluoroalkyle (FAS). Le prétraitement par plasma a augmenté la concentration effective du réseau FAS sur les fibres de fibre de coco dans le but de créer la surface extrêmement hydrophobe. L'efficacité du traitement plasma et du sol gel FAS sur fibre de coco a été étudiée en utilisant différentes techniques de caractérisation telles que l'analyse de l'angle de contact, l'absorption d'eau, la microscopie électronique à balayage, la microscopie à force atomique et la spectroscopie photoélectronique. Les propriétés mécaniques, morphologiques, rhéologiques et thermiques de différentes formulations de mélanges PP/EPDM ont été étudiées pour trouver la composition optimale du mélange pour la préparation de composites. Les composites résultants à base de polypropylène, d'EPDM et de fibre de coco possèdent des propriétés de résistance aux chocs élevées et des propriétés de traction et de flexion comparables. Les propriétés mécaniques, morphologiques, rhéologiques et thermiques des composites PP/EPDM/Coir ont été étudiées en détail pour examiner la stabilité des composites. / In recent years, the development of advanced high performance composite materials made from natural fibers was mainly focussed on achieving high modulus and strength materials. However, the high strength is not sufficient, as some of the materials possess brittle nature (the overall elongation to fracture is small), and one of the more important performance criterion should be the ability to absorb energy and resist impact loadings. The manner in which a composite material deforms and subjected to fractures depends upon both the chemical and mechanical properties of three basic constituents: the fibers, the matrix and a fine interphase region (sometimes referred to as the interface) responsible for assuring the bond between the matrix and fiber. Due to its unique properties and abundant in nature, lignocellulose based fibers are emerging as a preferred choice for scientific, engineering and commercial communities who were looking for sustainable materials in various applications. Though these fibers possess several advantages over synthetic fillers, adhesion between the fiber and matrix, moisture repellence, flame retardant properties etc are still challenging areas to be addressed. In this context a novel technique based on spray-dry- cure method to establish a hydrophobic sol-gel coating on the lignocellulosic coir fiber surface. The surface modification of lignocellulosic coir fibers was done with the use of low-pressure oxygen plasma, followed by the application of a spray-dry-cure sol–gel coating with the water and oil repellent organic–inorganic hybrid precursor fluoroalkyl-functional siloxane (FAS), with the aim of creating the extremely hydrophobic coir fiber surface. The plasma pre-treatment increased the effective concentration of the FAS network on the lignocellulosic coir fibers. The effectiveness of plasma treatment and FAS sol gel coating on the coir fiber was studied using different characterisation techniques such as contact angle analysis, water absorption studies, scanning electron microscopy, atomic force microscopy and X-ray photoelectron spectroscopy. The mechanical, morphological, rheological and thermal properties of different PP/EPDM blend formulations were carried out to find out optimum blend composition for composite preparation. The resulting composites based on polypropylene, EPDM and coir possess high impact strength properties and comparable tensile and flexural properties. The mechanical, morphological, rheological and thermal properties of PP/EPDM/Coir composites were studied in detail to examine the stability of the composites.

The goal of the thesis is to incorporate materials with either fluorescent or conductive properties in silk fibers, by feeding silkworms with a diet containing these materials. To achieve this, one would have to breed (rear) silkworm from eggs into larvaes, then to feed the silkworms with this special diet containing fluorescent or conductive materials. Samples of silk were then collected either from spun cocoons or via removing the silk producing organs (silk glands) from the silkworms via dissection. The samples were then analyzed with absorbance spectrometer, spectrofluorometer or via photoluminesecent measurement to determine if any materials had been incorporated into the silk fibers.   Silkworms were successfully reared from eggs up to moths, once the silkworm larvae had grown enough in size their diet were switches from their regular food (silkworm chow) to food containing conjugated molecules or polymers with fluorescent or conductive properties. A total of 14 materials were tested. One material gave a clear positive result and that was from the fluorescent compound Rhodamine B. Other fluorescent materials, Nile red and POWT yielded some results indicating their presence in the silk but the results were not conclusive. The rest of the materials all failed with being incorporated within the silk fibers; this was due to their lethality, size, lack of zwitterionic properties and such.  The properties of the materials are of great importance for the uptake process, where a small zwitterionic molecule has a great change of being taken up and incorporated in the silk fibers. Whereas a big materials such as a polymer without any zwitterionic will in most cases just follow through the food in the digestive track without any uptake.