Dissertations / Theses on the topic 'Long Column'

Long-duration blast waves are typically defined by positive pressure durations in excess of 100ms and are characteristic of very large explosive events. Such blasts generate substantial impulse and dynamic pressures (blast winds) that considerably exceed shorter duration blasts with the same peak overpressures, which are particularly damaging to drag-sensitive structural elements such as steel columns. A number of recent large-scale industrial accidents have highlighted the potential for multiple detonations to occur that can cause long-duration blasts to successively interact with structures, and constituent column elements from different axes. This research investigates and quantifies blast loading, structural dynamic response and resulting damage states of steel column elements subjected to both single and multiple (successive) long-duration blasts. Primarily, this research examines the influence of multi-axis interaction and the effect of prior column damage on subsequent structural response, given the case of multiple detonations. Ten full-scale long-duration blast trials were conducted, testing steel I-section and square hollow section (SHS) columns aligned at different orientations to the blast to examine the influence of multi-axis interaction. Six trials also investigated the effect of prior column damage on subsequent structural response and damage accumulation by subjecting SHS columns to three successive blasts. Analysis of results revealed a clear relationship between blast loading, column mechanical properties and magnitude of structural response as a function of section orientation to the blast, thus demonstrating that multi-axis interaction has significant influence. Columns aligned at oblique orientations to the blast exhibited larger structural responses and higher loading due to increased projected area and drag coefficient providing evidence to question the validity of existing simplified blast loading characterisation methods. Column response to multiple blasts generally exhibited reduced structural resistance, with damage accumulation influenced by local residual stress states, load direction symmetry and sequencing. This research also examined uncoupled computational models of multi-axis blast loading and structural dynamic response of steel columns using computational fluid dynamics (CFD) and finite element analysis (FEA) respectively. Comparisons with experimental data have shown reasonable levels of agreement, indicating potential to provide future predictive capacity.

Aquesta tesi s'adreça al problema de planificació de la generació elèctrica a llarg termini per a una companyia específica (SGC) que participa en un mercat liberalitzat organitzat en un pool. Els objectius de la tesi són: modelitzar aquest problema, i desenvolupar i implementar tècniques apropiades i eficients que el resolguin.

Un planificació òptima a llarg termini és important, per exemple, per a la confecció de pressupostos, o per a la gestió de compres/consum de combustibles. Una altra aplicació és la de guiar la planificació a curt termini perquè aquesta tingui en compte decisions preses sota una òptica de llarg termini.

La nostra proposta per a fer la planificació de la generació és optimitzar la generació esperada de cada unitat (o la unió de diverses unitats de característiques semblants) del pool per a cada interval en que dividim el llarg termini.

El model bàsic per la planificació de la generació a llarg termini (LTGP) maximitza el benefici de totes les unitats del pool. La constricció més important és la satisfacció de la demanda, ja que el sistema està sempre balancejat. Utilitzem la formulació de Bloom i Gallant, la qual modela la càrrega a través d'una monòtona de càrrega per cada interval i requereix un número exponencial de constriccions lineals de desigualtat, anomenades LMCs. Altres constriccions (lineals) incloses en el model són: garantia de potència, límits en la disponibilitat de combustibles, emissions màximes de CO2 o una quota de mercat mínima per a la SGC.

Una extensió d'aquest model és la planificació conjunta de l'assignació de manteniments de les unitats tèrmiques d'una SGC amb la planificació de la generació. El model conjunt és un problema quadràtic amb variables binàries i contínues. Per resoldre aquest model es proposa un parell d'heurístiques i s'ha implementat un prototipus de branch and bound en AMPL.

Aquesta tesi també proposa una manera per coordinar el model LTGP proposat amb una planificació a curt termini. Es desenvolupa un model de curt que inclou els resultats de llarg termini.

Donat que el model de planificació a llarg termini s'ha de resoldre sovint (principalment per passar informació acurada al model de curt), les tècniques emprades per a resoldre'l han de donar resultats fiables en un espai de temps curt. Les tècniques aplicades han estat:
· Donat que les constriccions de recobriment i les fites de no negativitat defineixen un políedre convex els vèrtexs del qual són fàcils de trobar el model es transforma i les variables esdevenen els coeficients convexos que defineixen un punt. Aquest nou problema es resolt amb l'algoritme de Murtagh i Saunders, que és un procediment òptim. Aquest algoritme s'aplica sota un esquema de generació de columnes donat que el número de vèrtexs del políedre és comparable al número de constriccions. L'avantatge d'aquest mètode és que els vèrtexs es van generant a mesura que es necessiten.
· L'aplicació de mètodes directes és computacionalment costós donat el número exponencial de LMCs. De totes maneres, a l'òptim només un conjunt reduït de constriccions de recobriment seran actives. Hem desenvolupat una heurística, anomenada heurística GP, la qual genera un subconjunt de constriccions, entre les quals hi ha les LMCs que són actives a l'òptim. L'heurística resol una seqüència de problemes quadràtics, els quals incrementen el número de LMCs considerades a cada iteració. Els problemes es resolen amb mètodes de punt interior que s'inicialitzen amb tècniques de warm start per tal d'accelerar la convergència cap a la nova solució. Aquest procediment resulta ser molt més eficient que el de generació de columnes.

La modelització i els casos de prova estan basats en dades d'un sistema de pool pur i de mercat com ha estat a Espanya fins el juliol de 2006.
This thesis presents an approach to the long-term planning of power generation for a company (SGC) participating in a liberalized market organized as a pool. The goal of this thesis is two-fold: to model the problem and to develop and implement appropriate and efficient techniques for solving it.

The optimization of the long-term generation planning is important for budgeting and planning fuel acquisitions, and to give a frame where to fit short-term generation planning.

Our proposal for planning long-term generation is to optimize the expected generation of each unit (or the merger of several units of the same type) in the power pool over each interval into which the long-term horizon is split.

The basic model for long-term generation planning (LTGP) maximizes the profit for all the units participating in the pool. The most important constraint is matching demand, since the market always clears. The Bloom and Gallant formulation is used, which models the load with a load-duration curve for each interval and requires an exponential number of linear inequality constraints, called herein LMCs. Other (linear) constraints included in the model are: minimum generation time, limits on the availability of fuel, maximum CO2 emission limits or the market share of the SGC.

This thesis also proposes the way in which coordination between the LTGP model developed and a short-term plan should be considered and provides a model for short-term electrical power planning adapted to the LTGP proposed and which includes the long-term results.

Another decision that needs to be taken from a long-term point of view is the joint scheduling of thermal unit maintenances with the generation planning of a particular SGC. The results of a prototype of a Branch and Bound implemented in AMPL are included in this thesis.

Long-term planning needs to be considered before short-term planning and whenever the real situation deviates from the forecasted parameters, so the techniques implemented must be efficient so as to provide reliable solutions in a short time. Two methods for handling the LMCs are proposed and compared:

● A decomposition technique exploits the fact that the LMCs plus the non-negativity bounds define a convex polyhedron for each interval whose vertices are easy to find. Thus, the problem is transformed and the variables become the coefficients of a convex combination of the vertices. The transformed problem is quadratic with linear constraints, making it suitable to be solved with the Murtagh & Saunders algorithm, which gives an optimal solution. A column-generation approach is used because the number of vertices of the polyhedron is comparable to the number of LMCs. The advantage of this method is that it does not require previous computation of all of the vertices, but rather computes them as the algorithm iterates.

● The application of direct methods is computationally difficult because of the exponential number of inequality LMCs. However, only a reduced subset of LMCs will be active at the optimizer. A heuristic, named GP heuristic, has been devised which is able to find a reduced set of LMCs including those that are active at the optimizer. It solves a sequence of quadratic problems in which the set of LMCs considered is enlarged at each iteration. The quadratic problems are solved with an interior point method, and warm starts are employed to accelerate the solution of the successively enlarged quadratic problems. This procedure is more efficient than the column generation one.

The modeling and tests of this thesis are based on the pure pool system and market data from the Spanish system up to July 2006.

Thin-walled steel sections made from high strength thin cold-reduced G550 steel to Australian Standard AS 1397-1993 under compression are investigated experimentally and theoretically in this thesis. This thesis describes three series of compression tests performed on box-section stub columns, box-section long columns and lipped channel section columns cold-formed from high strength steel plates in 0.42 mm or 0.60 mm thickness with nominal yield stress of 550 MPa. The tests presented in this thesis formed part of an Australian Research Council research project entitled: Compression Stability of High Strength Steel Sections with Low Strain-Hardening. For the fix-ended stub column tests, a total of 94 lipped-square and hexagonal section stub columns were tested to study the influence of low strain hardening of G550 steel on the compressive section capacities of the column members. For the pin-ended long column tests, a total of 28 box-section columns were tested to study the stability of members with sections which undergo local instability at loads significantly less than the ultimate loads. For the fix-ended lipped channel section columns, a total of 21 stub and long columns were tested to study the failure resulting from local and distortional buckling with interaction between the modes. A numerical simulation on the three series of tests using the commercial finite element computer program ABAQUS is also presented as part of this thesis. The post-buckling behaviour of thin-walled compression members is investigated. The effect of changing variables, such as geometric imperfections and end boundary conditions is also investigated. The ABAQUS analysis gives accurate simulations of the tests and is in good agreement to the experimental results. Theoretical studies using finite strip methods are presented in this thesis to investigate the buckling behaviour of cold-formed members in compression. The theoretical studies provide valuable information on the local and distortional buckling stresses for use in the interaction buckling studies. The finite strip models used are the semi-analytical and spline models. As expected for the stub columns tests, the greatest effect of low strain hardening was for the stockier sections where material properties play an important role. For the more slender sections where elastic local buckling and post-local buckling are more important, the effect of low strain hardening does not appear to be as significant. The pin-ended and fix-ended long column tests show that interaction, which is between local and overall buckling in the box sections, and between local and distortional buckling in the open channel sections, has a significant effect on their member capacities. The results of the successful column tests and ABAQUS simulation have been compared with the design procedures in the Australian & New Zealand Standard for Cold-Formed Steel Structures AS&NZS 4600 and the North American Specification for Cold-Formed Steel Structural Members prepared by the American Iron and Steel Institute. The stub column tests show that the current design rules give too conservative predictions on the compressive section capacities of the column members; whereas the long column tests show that the current column design rules are unconservative if used in their current form for G550 steel. Three design proposals are presented in this thesis to account for the effects of high strength thin steels on the section and member capacities.

Estudou-se o emprego da Cromatografia a Líquido por Injeção Seqüencial (SIC) explorando o uso de uma cela de longo caminho óptico com guia de onda (LCW) de 100 cm para a melhora dos limites de detecção (LOD) e quantificação (LOQ) na determinação de atrazina (ATR), propazina (PRO) e simazina (SIM). Para isto, utilizou-se uma fase móvel com composição de 44:56 (v v-1) metanol : tampão acetato de amônio 1,25 mM, pH 4,7, coluna monolítica e a detecção espectrofotométrica em 238 nm. Obtiveram-se valores de LOD e LOQ, respectivamente, de 1,76 e 5,86 µg L-1 para ATR, 4,51 e 15 µg L-1 para PRO e 2,25 e 7,5 µg L-1 para SIM. Com o emprego da cela de longo caminho óptico os valores de LOD ficaram abaixo dos recomendados pela US-EPA, que permite para águas potáveis uma concentração de 3 µg L-1 para ATR, 4 µg L-1 para SIM e 10 µg L-1 para PRO. Realizaram-se estudos de adsorção de SIM, PRO e ATR e seus metabólitos desisopropilatrazina (DIA), desetilatrazina (DEA) e 2-hidroxiatrazina (HAT) em solo, ácido húmico e solo modificado com ácido húmico. Para isso foi utilizado um sistema de monitoramento on-line composto por um filtro tangencial e uma bomba peristáltica para circulação da suspensão. Foram realizados estudos cinéticos em duas etapas e, em ambas, foi utilizado um mix dos compostos com concentração inicial de 1,0 mg L-1 e gradiente de eluição passo a passo para a separação dos compostos utilizando três fases móveis com composições de 15 ou 28, 40 e 50% (v v-1) metanol : tampão acetato de amônio 1,25 mM pH 4,7. Na primeira etapa o tempo de contato entre triazinas e adsorventes foi de 90 min. Na segunda etapa foi utilizado apenas o solo como adsorvente e o tempo de contato foi de 24 h. Para a primeira etapa do estudo só foi possível aplicar modelo cinético de pseudo-segunda ordem, o qual permitiu estimar os valores de massa adsorvida de triazina por massa de adsorvente, sendo que o ácido húmico é o material com maior capacidade adsortiva (1470 ± 43µg g-1 para DIA a 2380 ± 51 µg g-1 para PRO). O composto mais adsorvido em solo é PRO (26,5 ± 0,1 µg g-1). A presença de ácido húmico no solo aumentou a adsorção de ATR (de 19,4 ± 0,7 para 23 ± 2 µg g-1), de HAT (10,9 ± 0,7 para 18 ± 2 µg g-1) e de PRO (26,5 ± 0,7 para 29,8 ±0,2 µg g-1), mas diminuiu a adsorção de SIM e não afetou DIA e DEA. No estudo com tempo de contato de 24 h foi possível aplicar modelos de pseudo-primeira e segunda ordem. Os resultados obtidos confirmaram a maior adsorção de PRO, seguidos da ATR. HAT, SIM, DEA e DIA apresentaram as menores taxas de adsorção em solo, sendo que os dois últimos apresentaram uma tendência de dessorção após 4 h de contato, tendo maior potencial de lixiviação para corpos d\'água próximos aos locais de aplicação.
This work describes the use of Sequential Injection Liquid Chromatography (SIC) coupled to a long path length optical flow cell with 100 cm long Liquid Core Waveguide (LCW) to improve the limits of detection (LOD) and quantification (LOQ) for determination of atrazine (ATR), propazine (PRO) and simazine (SIM). Separation was achieved with a mobile phase composition of 44:56 (v v-1) methanol:1.25 mM ammonium acetate buffer, pH 4.7, monolithic column and spectrophotometric detection at 238 nm. The values of LOD and LOQ were, respectively, 1.76 and 5.86 µg L-1 for ATR, 4.51 and 15 µg L-1 for PRO and 2.25 and 7.5 µg L-1 for SIM. The LOD values achieved with the employment of long optical path cell were lower than those recommended by US-EPA, which allows for drinking water, maximum concentration levels of 3 µg L-1 for ATR, 4 µg L-1 for SIM and 10 µg L-1 for PRO. Adsorption of SIM, PRO and ATR, as well as their metabolites desisopropylatrazine (DIA), desethylatrazine (DEA) and 2-hidroxyatrazine (HAT) on soil, humic acid and soil modified with humic acidic was studied. An on-line monitoring system was assembled, composed of a tangential filter and a peristaltic pump for circulation of the suspension. Kinetic studies were carried out in two steps, and in both, it was used a mix of compounds with initial concentration of 1,0 mg L-1 and a stepwise gradient elution for separation of the compounds using three mobile phases with compositions of 15 or 28, 40 and 50% (v v-1) methanol: 1.25 mM ammonium acetate buffer, pH 4.7. In the first step the contact time between triazines and adsorbents was 90 minutes. In a second study made only with soil, the contact time was 24 h. Data obtained in the first stage of the study was only fitted to pseudo-second order kinetic equation, which allowed one to estimate the values of the adsorbed mass of triazine per mass of adsorbent. Humic acid was the material with higher adsorptive capacity (from 1470 ± 43 µg g-1 for DIA to 2380 ± 50 µg g-1 for PRO). In soil, PRO exhibited the highest adsorption (26.5 ± 0.1 µg g-1). The presence of humic acid in the soil increased adsorption of ATR (19.4±0.7 to 23±2 µg g-1), HAT (10.9 ± 0.7 to 18 ± 2 µg g-1) and PRO (26.5 ± 0.7 to 29.8 ± 0.2 µg g-1), but decreased adsorption of SIM, not affecting DIA and DEA. In the study with contact time of 24 h, it was possible apply pseudo-first and pseudo-second order equations for SIM, ATR and PRO. The results confirmed the greatest adsorption of PRO, followed by ATR. HAT, SIM, DEA and DIA had low rates of adsorption on soil, the latter two showed a trend of desorption after 4 h of contact, having the greatest potential for leaching to water bodies near to the places of application.

A leaching study was undertaken with $ sp{14}$C radio-labelled atrazine in long, intact, soil columns to investigate the fate and transport of atrazine in a Quebec sandy loam soil and to test two contaminant transport models, namely PRZM and LEACHMP.
Results indicated a large variation in atrazine concentration. The maximum levels in the leachate of the soil columns ranged from 0 to 11.2 $ mu$g/L. Deisopropyl-atrazine, the principal metabolite in the soil columns, was detected near the soil surface and did not leach beyond 15 cm depth. The adsorptive and desorptive capacity of atrazine in the soil columns was mainly attributed to organic matter and moisture content.
LEACHMP was found to be superior in predicting hydrologic characteristics in the soil columns as compared to PRZM which required calibration. Both models underestimated levels of atrazine near the soil surface and in the leachate (115 cm depth). The results from first and second order analysis for PRZM and LEACHMP showed considerable uncertainty in atrazine fate and transport. First and second order analyses were found to be useful tools in indicating where efforts to reduce uncertainty can best be directed.

Para melhor aproveitamento da resistência do concreto, utiliza-se concreto de maior resistência à compressão em pilares e concreto de resistência inferior em vigas e lajes. Considerando o método construtivo adotado tradicionalmente no Brasil, a região do pilar que cruza o nível do pavimento é moldada com a utilização do mesmo material que é lançado no pavimento. Essa mistura de materiais no mesmo pilar gera dúvida em relação ao seu dimensionamento. Dado que essa região está confinada pelo pavimento pode-se considerar, no caso em que uma laje lisa circunda o pilar, dentro de determinados limites, que esse pilar se comportará como tendo resistência uniforme. Este trabalho levantou pesquisas anteriores e normas vigentes com o objetivo de saber o que já foi estudado e quais são as recomendações atuais para a situação em que se tem laje apoiada sobre vigas e não uma laje lisa, isto é, uma situação menos confinada. Com base nessa pesquisa, formularam-se modelos a serem ensaiados em escala reduzida no laboratório e modelos de elementos finitos com a finalidade de aprofundar o estudo dessa situação.
Aiming the better use of the concrete strength a high-performance concrete is use in columns and a less resistant concrete in slabs and beams. Considering the constructive method adopted in Brazil, the region of the column that crosses the floor is executed using the same material that is used at the pavement. When used in columns, it is blended with a less resistant concrete in the floors, which is not considered during the column design. Is it possible that this less resistant concrete can confine the column to the point that its strength turns out to be the same of the rest of the members? This paper has studied earlier researches and up-to-date standards with the goal of know what have been studied and the actual recommendations for situations that the floor has beams and slabs instead of only slabs, in other words, a less confined region. Based in this research was formulated models to be tested in the laboratory and models in Finite Element Models to studie further the stresses.

A presente pesquisa trata da investigação experimental do comportamento de pilares por meio de encamisamento com concreto de alta resistência. Os principais objetivos da pesquisa são estudar o comportamento ao longo do tempo e o efeito de précarregamento nos pilares reforçados. Foram ensaiados vinte modelos experimentais, variando-se a forma da seção transversal (circular e quadrada), a taxa de armadura transversal da camisa de reforço e a existência ou não de pré-carregamento. Foram também realizados ensaios complementares sobre pilares curtos de seção circular para observação dos efeitos de confinamento. Ensaios de caracterização dos concretos utilizados sob ações de longa duração foram realizados. Para estudar a influência da deformação lenta, simulou-se nesta pesquisa pilares de concreto armado submetidos a pré-carregamento, os quais foram mantidos durante um certo período de tempo numa câmara climatizada. Estes pilares foram reforçados sem que fosse retirada a força de pré-carregamento.Todos os pilares foram submetidos ensaios à compressão axial de curta duração por meio de uma máquina universal de ensaios servo-hidráulica, em modo de controle de deslocamento. Na análise dos resultados foram aplicados modelos de cálculo do efeito de confinamento, análise numérica pelo Método dos Elementos Finitos e outras formulações teóricas, para efeito de confrontação de resultados teóricos e experimentais. As principais conclusões são de que, no reforço por encamisamento de pilares, uma vez garantidas adequadas condições de confinamento: a capacidade resistente do pilar original pode ser totalmente considerada na avaliação da resistência do elemento reforçado; o efeito de pré-carregamento de um pilar reforçado não afeta a resistência última do elemento reforçado, mas pode afetar a sua deformabilidade. Além disso, na análise do comportamento dos pilares ao longo do tempo, pôde-se perceber que houve transferência de esforços entre o pilar original e a camisa de reforço, mas seu efeito foi pouco significativo em termos de alteração da capacidade resistente
The thesis presents an experimental investigation on the behavior of RC columns strengthened by high-performance concrete jackets. The main objectives are to analyze the immediate and time-dependant behavior of the elements and the preloading effect in its load capacity and deformability. Twenty columns were tested varying the transversal section shape (circular and square), transversal reinforcement ratio of the jacket and the preloading condition. Also complimentary tests were made on short circular section columns to observe confinement effects. A set of long-term tests was made to characterize the concrete immediate and time-dependant properties. To analyze the influence of time-dependant deformations, original columns were submitted to preloading forces and they were kept in a weather-controlled chamber during a certain period. The high-performance concrete jackets were applied to the original columns without removing the preloading forces. Every column was subjected to a monotonic axial compression test in a servohydraulic universal machine, in the displacement-controlled mode. In the analysis of the results theoretical models of concrete confinement, Finite Element Method simulations and other formulations were applied to examine the experimental results. The main conclusions are that, if adequate confinement conditions are maintained in the strengthened columns: the load capacity of the original column can be totally considered in strength evaluation; the preloading effect does not affect the ultimate load of the rehabilitated member, but it may affect the column deformability. Moreover, in the long-term behavior analysis, load transfer between the original column and jacket was observed. However, its effect was not significant in the load capacity of the strengthened member

Liquid crystalline materials forming columnar mesophases are of importance for both the fundamental research and technological applications due to their supramolecular architecture allowing for one-dimensional charge transport. The potential applications of these materials include light emitting diodes, solar cells, field effect transistors and photovoltaic cells. However, to design a LC material suitable for a particular application, a fundamental understanding of the structure-property relationships is needed.

In the present thesis, a variety of systems forming columnar mesophases have been explored. They include small molecular weight compounds (triphenylene, phthalocyanine derivatives and star-shaped mesogens) and polymer materials. The research was focused on the study of the influence of the molecular architecture and specific interactions such as hydrogen bonding on the supramolecular organization in the mesophase, as well as on the influence of columnar mesophase on crystal growth. The main results of the thesis are summarized below.

The influence of hydrogen bonding on the structure and charge carrier mobility was investigated for a triphenylene derivative, hexaazatriphenylene, having lateral alkyl chains linked to the core via amide groups. These linking groups provide the possibility to form inter- and intra-molecular hydrogen bonds. Acting as “clamps”, the inter-molecular hydrogen bonds are found to enforce the attractive interactions between the molecules in the column. Thus, the columnar mesophase formed by this system is characterized by the smallest inter-disk distance ever found in columnar mesophases (3.18 Å). The improved intra-columnar order brings about a higher charge carrier mobility (0.02 cm2/Vs) as compared to other triphenylene derivatives without hydrogen bonds.

Phthalocyanine derivatives, which are liquid crystalline at ambient temperature, could be suitable for opto-electronic applications due to their improved processibility and self-healing of structural defects. Our interest in these systems was inspired by the fact that, in spite of numerous studies performed to date, only very a few phthalocyanine derivatives were found to exhibit columnar mesophases at ambient temperature. We observed that by introducing branches in alkyl chains close to the core, we were able to render the material LC at ambient temperature. Analysis of X-ray diffraction patterns measured on oriented samples showed that these systems form hexagonal and rectangular ordered columnar mesophases. This finding is in contradiction with the general view stating that non-hexagonal mesophases can be only disordered. Since the absolute majority of applications require fabrication of films, it was very important to achieve the visualization of the organization of the phthalocyanine derivatives at the nanometer scale. AFM images on thick spin-coated films with columnar resolution are presented for the first time. They allowed the examination of columnar curvatures and breaks at the boundaries between different single crystal-like domains.

The possibility of templating columnar crystal growth was studied for a star-shaped mesogen using a combination of direct- and reciprocal-space techniques. AFM images with columnar resolution showed that the crystal growth initiated in the monotropic columnar mesophase occurs almost in register with the mesomorphic template. In the final crystalline structure, the placement of the crystalline columns is controlled by the mesomorphic tracks at the scale of an individual column, i.e. at the scale of approximately 3.5 nm.

The mesophase-assisted crystallization was also studied for the case of a polymer material forming columnar mesophase, poly(di-n-propylsiloxane). X-ray diffraction on oriented fibers allowed us to correct the previous indexation and solve the structure of the unit cell. The crystallization process was studied on samples crystallized in different conditions. It was found that, depending on crystallization conditions, both folded-chain and extended-chain crystals can be obtained. Thus, crystallization of the material from the mesophase results in the formation of 100-150nm thick crystals, which corresponds to a nearly extended-chain conformation. By contrast, when crystallized from a dilute solution, folded-chain crystals result. The mechanisms of chain unfolding was studied by variable temperature atomic force microscopy on PDPS single crystals. It was found that crystals rapidly thicken above the initial melting point, up to 80 nm.
Doctorat en sciences, Spécialisation physique
info:eu-repo/semantics/nonPublished

Dans les puits de production d’eau, de pétrole, de gaz et de chaleur géothermique, ou dans les puits d’accès à un stockage d’hydrocarbures, il est précieux de connaître la perméabilité de la formation ou de sa couverture en fonction de la profondeur, soit pour améliorer le modèle de réservoir, soit pour choisir les zones dans lesquelles procéder à des opérations spéciales.On propose une technique qui consiste à balayer la hauteur du découvert par une interface entre deux liquides de viscosités très contrastées. Le débit total qui pénètre la formation à chaque instant est ainsi une fonction de la position de l’interface et de l’historique des pressions dans le puits. On doit alors résoudre un problème inverse : rechercher la perméabilité fonction de la profondeur à partir de l’historique des débits dans le temps. Dans la pratique, le puits est équipé d’un tube central. Le balayage est effectué par injection d’un liquide à pression d’entrée constante dans le tube central et soutirage d’un autre liquide par l’espace annulaire. On mesure les débits d’injection et de soutirage dont la différence est le débit qui entre dans la formation.Pour valider et améliorer cette technique, on a d’abord utilisé une maquette simulant un découvert multi-couches disponible au LMS. On a exploité aussi des essais en place réalisés dans la couverture peu perméable d’un stockage souterrain de gaz. Dans ces essais, un liquide visqueux placé dans le découvert était déplacé par un liquide moins visqueux (méthode dite « opening »). Les couches plus perméables étaient correctement identifiées (Manivannan et al. 2017), mais une estimation quantitative était un défi en raison des phénomènes transitoires qui affectent le voisinage immédiat des puits. De plus, le rayon investigué dans le massif était petit.La thèse a relevé ces défis en proposant un essai légèrement différent et une nouvelle technique d’interprétation. Les essais avec une maquette modifiée ont montré la supériorité d’une méthode « closing » dans laquelle le puits est d’abord rempli du liquide le moins visqueux. On ménage une période de stabilisation avant l’injection du liquide visqueux pour réduire les effets transitoires ; elle permet aussi d’estimer la perméabilité moyenne et l’influence de la zone endommagée à la paroi (le « skin »).Puis on conduit l’essai proprement dit. L’historique des débits mesurés en tête de puits constitue le profil d’injection dont on déduit le profil de perméabilité.. Cette estimation suppose un écoulement monophasique dans chaque couche et la même « skin » pour toute la formation. Les incertitudes principales portent sur les pressions de formation et les variations possibles du « skin ». Elles sont estimées au moyen d’un calcul analytique. On a vérifié sur la maquette que les profils de perméabilité estimés présentent une bonne concordance avec les perméabilités mesurées avant les essais.On a réalisé un essai sur un sondage de 1750 m de long atteignant une couche de sel dont on a correctement estimé la perméabilité moyenne pendant la période de stabilisation. Toutefois elle était si faible (4.0E-21 m²) que l’utilisation de deux fluides n’a pas permis de faire une différence entre les diverses parties du puits
In wells producing water, oil, gas or geothermal energy, or in access wells to hydrocarbon storage, it is critical to evaluate the permeability of the formation as a function of depth, to improve the reservoir model, and also to identify the zones where additional investigation or special completions are especially useful.A new technique is proposed, consisting of scanning the open hole (uncased section of the wellbore) with an interface between two fluids with a large viscosity contrast. The injection rate into the formation depends on interface location and well pressure history. An inverse problem should be solved: estimate permeability as a function of depth from the evolution of flow rates with time. The wells are usually equipped with a central tube. The scanning is done by injecting a liquid in the central tube at constant wellhead pressure. Injection and withdrawal rates are measured at the wellhead; the difference between these two rates is the formation injection rate.To validate and improve this technique, we used a laboratory model mimicking a multi-layer formation, already available at LMS. We also made use of in-situ tests performed on an ultra-low permeable cap rock above an underground gas storage reservoir. In these tests, a viscous fluid contained in the open hole was displaced by a less-viscous fluid (a method called opening WTLog). The more permeable layers were correctly identified (Manivannan et al. 2017), but a quantitative estimation was challenging due to transient phenomena in the vicinity of the wellbore (near-wellbore zone). In addition, the investigation radius was small.These challenges are addressed by proposing a slightly modified test procedure and a new interpretation workflow. Laboratory tests with a modified test setup showed the advantages of the ‘closing’ method in which the well is filled with a less-viscous fluid at the start of the test. We also added a stabilization period before the injection of viscous fluid to minimize the transient effects; this period is also used to estimate the average permeability of the open hole and the effect of near-wellbore damage (skin).Then the test proper is performed (closing WTLog). The injection profile of the less-viscous fluid is computed from the wellhead flow rate history. A permeability profile is estimated from the injection profile. The permeability estimation considers a monophasic flow in each layer and the same skin value for all the formation layers. Major uncertainties in the permeability estimates are caused by formation pressures and heterogeneities in skin values; they are estimated using an analytical formula. We have verified on the laboratory setup that the estimated permeability profiles are well correlated to the permeabilities measured before the tests.An attempt was made to perform a WTLog in a 1750-m long wellbore opening in a salt formation. The first phase was successful and the average permeability was correctly assessed. However, this permeability was so small (4.0E-21 m² or 4 nD) that the gauges and the flowmeters were not accurate enough to allow a clear distinction between the permeabilities of the various parts of the open hole

碩士
淡江大學
土木工程學系
91
For long-span bridges the aerodynamic stability and buffeting response become more significant due to their large flexibilities and relatively low structural dampings. Since the type of bridge is highly susceptible to wind excitations, it needs some devices to control the aerodynamic vibrations. The passive dampers that have been used in the engineering structures include tuned mass dampers (TMD), tuned liquid dampers (TLD), tuned liquid column dampers (TLCD), and so on. A numerical analysis is used to study the performance of tuned liquid column dampers (TLCD) on wind-induced vibrations of long-span bridges. The governing equations of the bridge-damper system in lift, drag, and torsional directions are formulated and both structural coupling and aerodynamic coupling effects are taken into account. The reduction of dynamic torsional response through the attachment of the damper to the bridge deck are investigated. The effects of torsional mass ratio, head loss, ratio of liquid horizontal length to its total length(B/L), and frequency of TLCD on the performance are also studied. Comparison between the numerical results and the experimental results indicate that they are in good agreement. The results also show that tuned liquid column dampers can effectively suppress torsional buffeting responses of bridges.

碩士
國立成功大學
土木工程學系
102
SUMMARY Prestressed concrete is usually used for bridge structures, and the prediction of prestress losses is one of the main factors considered in the design of bridge. As for bridge, the effect on the temperature is also can’t be overlook. This thesis aims at studying the long-term change and prestress losses of post-tensioning precast segmental pier column and box-girder after prestressing. The thermal deformation of box girder is also studied. In experimental study, the prestress losses in 5-span unit of Kaohsiung Port Viaduct and the displacement of the temperature effect to the bridge was monitored and compared with design code. In the evaluation of pretress losses, the pier columns had generated 1085~1340 kgf/cm2 prestress losses within 616 days after prestressing, which is 7.6~9.3% of the initial prestress. The box-girder in span B14 generated 910~1740 kgf/cm2 internal prestress losses, accounting for 5.6%~10.7% of the initial prestress and 960 kgf/cm2 external prestress losses, accounting for 6.7% of the initial prestress within 388 days. The average temperature change day and night in Spring and Summer has about 5 ℃, which is 45 ×10-6 concrete strain of box girder and 9.3mm longitudinal movement at LRB of the 5 span unit.

碩士
國立成功大學
土木工程學系
103
The precast prestressed segmental pier column of Kaohsiung Port Viaduct this thesis studying for is an Innovative Technology Engineering. For investigate the deformation behavior of the precast prestressed segmental pier column, we embedded eight strain gauges at each of the segmental pier column in 5-span unit, monitor the deformation of the concrete and compared with prognosticated. Evaluate the effective prestress of the segmental pier column. The deformation of the pier column after shrinkage、prestressing、creep of concrete and relaxation of prestressing steel is almost stable. The deformation of the concrete at prestressing had generated 224 × 10-6 ~ 250 × 10-6 elastic strain, and generated 325 × 10-6~ 504 × 10-6 concrete strain, which is 1057~1413 kgf/cm2 external prestress losses, accounting for 7.4%~9.8% of the initial pretress within 800 days after prestressing. Due to the deformation of the pier column is almost stable, thermal deformation is the main affect for the change of the deformation. The average temperature change between winter and summer form a deformation of the concrete, which is 79 × 10-6 ~ 99 × 10-6 concrete strain. Also, the sunshine and the average temperature change day and night form a deformation of the concrete, which is 35 × 10-6 ~ 45 × 10-6 concrete strain.

碩士
國立臺灣科技大學
營建工程系
100
The objective of this research is to examine the seismic behavior of reinforced concrete bridge columns under long duration ground motions. In order to achieve this purpose, two typical reinforced concrete bridge columns designed per current seismic bridge design codes were tested. The first column (called CLC) was tested using the developed loading protocol. This protocol was developed to simulate the effects of long duration ground motions. The second column (called COC) was tested one cycle for each drift to represent short duration ground motions effects and to provide a baseline performance. Test results showed that the column under the long duration loading protocol exhibited significantly greater stiffness and strength degradation than those under the conventional cyclic loading protocol. Based on the test results, relationships between hysteretic parameters, hysteretic energy dissipation and maximum occurred displacement were discussed. The stiffness degradation is related to the hysteretic energy dissipation. The strength degradation is related to the hysteretic energy dissipation and maximum displacement. The pinching is related to maximum displacement. Furthermore, analytical model was proposed based on test results. This model is capable of considering the effects of hysteretic energy dissipation and maximum occurred displacement on the stiffness degradation, strength degradation and pinching. The model through calibrations can capture the response characteristics of reinforced concrete bridge columns tested under both loading protocols. Based on the observations of constant-R spectra, if above mentioned effects are not considered properly then ductility demand will be underestimated especially in long duration earthquakes. Note that the underestimation decreased as structural period increased. In addition, ground motion duration was found to be insignificant with respect to ductility demand. According to constant ductility analysis, it is suggested that when a structure is subjected under long duration ground motions, the proposed model is more preferably to be used to predict the response of structure. In contrast, the proposed model may be replaced with the commonly used modified Clough model if the structure is subjected to short duration and not located in short period region.

A reactive distillation column for the alkylation of benzene with long chain linear olefin was studied. The study involved design, construction, experimentation, and simulation of the column. Establishing the design required study of reaction rates, thermodynamic relationships, and packing structures. A heuristic was developed for the design of such columns. This heuristic involved estimating an amount of catalyst loading and subsequently determining the operating parameters for a column. This method is particularly applicable to systems with high concentrations of inert feeds. A column was constructed following the design. Data was collected from the column and compared to simulations. The simulations were performed with Aspen Plus RADFRAC. In this manner, the data was used to validate the commercial steady state models for reactive distillation. In addition, dynamic simulations of the system were performed. These dynamic simulations provided insight into more design considerations. For example, steady state simulations indicated an optimal feed stage based on steady state conversion of the olefin. However, the dynamic simulations showed a potential disadvantage to the utilization of the optimal feed stage. With some disturbances, a column configured with the feed stage with the highest steady state conversion also deviated from the steady state faster and with greater amplitude than other configurations. These considerations were further explored in developing a control scheme for reactive distillation columns. Control of reactive distillation differs from traditional distillation in that one control variable is conversion. Traditional distillation generally focuses on production rates and product purity. To this end, control schemes were analyzed and dynamic simulations were performed. These simulations showed an advantage to a variable pairing in which duty is paired with conversion. The conversion was inferred from a stage temperature in the reactive zone. In addition, distillate rate may be paired with product composition. In conclusion, the reactive distillation column design for long chain olefin alkylation of benzene requires careful estimation of catalyst requirements and valid simulation tools. In addition, dynamic response should be considered in the design. Finally, a simple inferential control scheme may be adequate.
text

碩士
中原大學
化學研究所
96
As-synthesized and calcined SBA-15 mesoporous sieves were surface-modified with long alkylsilanes by microwave thermal heating. Optimal temperatures and time of microwave heating were studied systematically. The mesoporous SBA-15 silicas are functionalized effectively using alkylsilanes with different carbon length. SBA-15 materials surface-modified with long alkylsilanes were used as HPLC stationary phase and show better separation effect than traditional calcined SBA-15 materials surface-modified with silanes. Silane-functionalized mesoporous silicas have been synthesized by co-condensation of variable alkylsilanes and tetraethoxysilane (TEOS) in acidic medium with the block copolymer Pluronic 123 as the structure directing agent. The influence of synthesis parameters, the molar ratio of X = silane /( silane + TEOS) was studied. SBA-15 materials surface-modified by co-condensation with long alkylsilanes were used as HPLC stationary phase show better separation effect than traditional calcined SBA-15 materials surface-modified with silanes.