Dissertations / Theses on the topic 'Carrier capture'

This thesis’s main focus is a CO2 capture technology known as chemical looping combustion (CLC). The technology is a novel form of combustion and fuel processing that can be applied to gas, solid and liquid fuels. By using two interconnected fluidised-bed reactors, with a bed material capable of transferring oxygen from air to the fuel, a stream of almost pure CO2 can be produced. This stream is undiluted with nitrogen and is produced without any direct process efficiency loss from the overall combustion process. The heart of the process is the oxygen carrier bed material, which transfers oxygen from an air to fuel reactor for the conversion of the fuel. Oxygen carrier materials and their production should be of low relative cost for use in large-scale systems. The first part of this research centres on development and investigative studies conducted to assess the use of low-cost materials as oxygen carriers and as supports. Mixed-oxide oxygen carriers of modified manganese ore and iron ore were produced by impregnation. While copper (II) oxide supported on alumina cement and CaO have been produced by pelletisation. These oxygen carriers were investigated for their ability to convert gaseous fuels in a lab-scale fluidised bed, and characterised for their mechanical and chemical suitability in the CLC process. The modified ores and pelletised copper-based oxygen carriers’ mechanical properties were enhanced by their production methods and in the case of the modified iron ore, significant oxygen uncoupling was observed. The copper-based oxygen carriers particularly those containing alumina cement showed high conversion rates of gaseous fuels and improved mechanical stability. The second part of this research thesis focuses on the design philosophy, commissioning and operation of a dual-fast bed chemical looping pilot reactor. Based on the operational experience, recommendations for modifications to the CLC system are discussed. In support, a parallel hydrodynamic investigation has been conducted to validate control and operational strategies for the newlydesigned reactor system. It was determined that the two fast bed risers share similar density and pressure profiles. Stable global circulation rate is flexible and could be maintained despite being pneumatically controlled. Reactor-reactor leakage via the loop-seals is sensitive to loop seal bed-height, and inlet fluid velocity but can be maintained as such to ensure no leakage is encountered.

This work aims to develop fundamental insights about the underlying surface and bulk chemical processes instrumental to the efficiency of chemical looping combustion (CLC). CLC, which uses a solid-state oxygen carrier (e.g., metal oxides) to drive hydrocarbon combustion, is a promising combustion alternative that minimizes byproduct formation and facilities capture of CO2. In this work, we compare the performance of different transition metal oxides, namely iron, copper, cobalt, manganese, and nickel oxides, as oxygen carriers in CLC using CH4 as the reducing agent. Experiments used a continuous flow reactor across temperatures ranging from 500 to 800 oC and feed flowrates from 12.5 to 250 h-1. In addition to monitoring size-, temperature- and flow rate-dependent performance trends for CH4 conversion to CO2, microscopic and spectroscopic techniques were used to investigate the solid-state mechanism of oxygen carrier reduction and the coupled surface chemical and bulk material processes influencing performance. Bulk (XRD) and surface (XPS) analysis reveal that oxygen carrier reduction can be generally represented by two models, the unreacted shrinking core model (USCM) and the nuclei growth model (NNGM). The reduction of some metal oxides can also proceed via a two-stage solid-state mechanism; for example, hematite reduction to magnetite follows USCM, while the subsequent reductions of magnetite to wustite and wustite to iron metal follow NNGM. Furthermore, our results reveal that minimizing the particle size promotes oxygen carrier performance, but only for metal oxides reduced according to the USCM, where metal oxide reduction initiates on the particle surface. In contrast, no benefit of decreasing particle size was observed for materials reduced according to the NNGM because the reaction initiates in the particle bulk, such that a more critical determinant of reactivity may be the available oxygen carrier volume rather than surface area. Beyond these fundamental insights, cycling experiments were also performed to provide more practical information about the effect of oxygen carrier particle size on their long-term performance in CLC applications.

The major obstacle many promising drugs struggle to overcome is the barrier imposed by the outer cell membrane. In addition to technologies such as liposomes and cell-penetrating peptides, more attention is being given to the class of proteins known as lectins to deliver therapeutic and antigenic proteins to the interiors of cells. Lectins bind to but do not modify sugars, and provide an efficient route to endocytosis. The galactose/N-acetyl-galactosamine specific lectin ricin B-chain (RTB) is especially attractive in possibly fulfilling a carrier role due to its well-characterized endocytotic trafficking and its efficacy over a wide range of cell types. By producing RTB recombinantly in plants it is possible to create a fully active, non-toxic carrier that does not rely on the processing of large amounts of toxic material (e.g. castor bean). Payload molecules such as small molecules and proteins can be attached to RTB via chemical conjugation at primary amine groups, without the loss of lectin or uptake activities. The biotin/streptavidin interaction and direct genetic fusion of polypeptides also provide efficient mechanisms for the attachment of payload proteins to RTB. An immunoglobulin domain-based scaffolding mechanism bridges modified RTB and payload proteins when co-expressed in Agrobacterium-infiltrated plant leaves. Carrier and payload proteins expressed in plants and E. coli, respectively, and purified independently are not able to assemble into an efficient carrier/payload arrangement. These findings show that plant cells are able to correctly produce the two components of the carrier/payload system and assemble them into an efficient and flexible capture and carry technology.
Ph. D.

Chemical looping combustion (CLC) is a technique for separating pure carbon dioxide from the combustion of fuels. The oxygen to burn the fuel comes from the lattice oxygen contained in solid particles of an inorganic oxide (the 'oxygen carrier'), instead of from oxygen in the air. Thus only CO2 and water leave the combustor, or fuel reactor. Next, the water is condensed, leaving pure CO2. The oxygen carrier is regenerated by oxidising it in air in a second reactor, called the air reactor. Accordingly, a stream of pure carbon dioxide can be produced, uncontaminated with gases such as nitrogen, normally present when the fuel burns in air. This intrinsic separation with CLC enables CO2 to be separated more efficiently than with other techniques, such as post-combustion scrubbing of carbon dioxide from stack gases with amine-based solvents. The design of a CLC system and its performance within an electricity system represents a multi-scale problem, ranging from the behaviour of single particles of oxygen carrier within a reactor to how a CLC-based power plant would perform in an electricity grid. To date, these scales have been studied in isolation, with little regard for the vital interactions and dependences amongst them. This Dissertation addresses this problem by considering CLC holistically for the first time, using a multi-scale approach. A stochastic model was developed, combining the particle-and reactor-scales of CLC. It included an appropriate particle model and can be coupled to a detailed reactor model. The combination represented a significant change from existing approaches, uniquely accounting for all the important factors affecting the assemblage of particles performing in the CLC reactors. It was used to determine the regimes of operation in which CLC is sensitive to factors such as the manner in which the particles are reacting, the residence time distribution of particles in the two reactors, the particle size distribution and the reaction history of particles. To demonstrate that the approach could simulate specific configurations of CLC, as well as a general system, the model was compared with results from experiments in which CLC with methane was conducted in a laboratory-scale circulating fluidised bed. The long-term performance of oxygen carrier materials is important, because, in an industrial process, they would be expected to function satisfactorily for many thousands of hours of operation. Long-term experiments were conducted to evaluate the resistance of different oxygen carrier materials to physical and chemical attrition. The evolution of their chemical kinetics was also determined. The results were used to evaluate the impact of different oxygen carrier materials in a fuel reactor at industrial-scale. Finally, a theoretical approach was developed to simulate how a fleet of CLC-based power plants would perform within the UK's national grid. By understanding how different parameters such as capital cost, operating cost and measures of efficiency, compared with other methods of generation offering carbon reduction, desirable design modifications and needs for improvement for CLC were identified by utilising the theoretical and experimental work conducted at the particle- and reactor-scales.

Impulsionados pela busca de fontes limpas de energia, surgem os processos de combustao com recirculacao quimica (CLC), e reforma com recirculacao quimica (CLR). CLC e CLR sao processos quimicos para oxidacao de hidrocarbonetos gasosos. E utilizada a acao de transportadores de oxigenio (TO), para transferir oxigenio do ar para o combustivel (neste caso o metano), evitando-se o contato direto entre ar atmosferico e metano por diversos motivos. Os TOs, compostos por oxidos metalicos na forma de po fino, circulam continuamente entre dois reatores de leito fluidizado (reator de ar e de combustivel), sofrendo sucessivos ciclos de reducao e oxidacao. Os processos se diferenciam com relacao aos produtos, em CLC objetiva-se a geracao de energia, atraves da oxidacao completa do combustivel, resultando em uma mistura de CO2 e H2O, podendo ser facilmente separada por condensacao. No caso do CLR a oxidacao ocorre de maneira parcial, dando origem a uma mistura de gas de sintese (H2 + CO). O CLC apresenta vantagens com relacao aos processos tradicionais de captura de CO2, pois nao se faz necessaria a utilizacao de processos secundarios para separacao gasosa, economizando assim energia, alem do fato de nao gerar gases do tipo NOx. O presente trabalho apresenta a preparacao de duas series de materiais, via impregnacao seca, uma com composicao 2, 4 e 8% m/m de oxido de niquel e outra com os mesmo teores de oxido de niobio, suportados sobre alumina comercial de alta area superficial especifica. Os materiais foram caracterizados pelas tecnicas de picnometria a helio, volumetria de nitrogenio, porosimetria por intrusao de mercurio, DRX, MEV, TPR 5%H2/N2 analisado com TCD em ChemBet, TPR 5%CH4/Ar e TPO 5%O2/Ar sendo a variacao de massa analisada em termobalanca (TGA/DSC), alem de se utilizar de espectrometria de massas para analise dos gases gerados. Os diferentes transportadores de oxigenio foram testados em reator de leito fixo, sendo avaliados em diferentes condicoes experimentais tais como: temperaturas de operacao, vazoes de reagentes gasosos, concentracoes de metano, adicao de CO2 e H2O ao combustivel. Os produtos da reacao no reator de leito fixo foram analisados por cromatografia gasosa e espectrometria de massa. Os resultados mostraram que; o deposito de carbono sobre o catalisador pode ser drasticamente reduzido com a adicao de mistura oxidante junto ao combustivel e que estes oxidos estudados tem potencial aplicacao industrial, mostrando-se seletivos para reforma do metano com consecutiva producao de gas de sintese.
Driven by the demand for clean energy sources, arise chemical-looping combustion - CLC, and chemical-looping reforming - CLR. CLC and CLR are chemical processes for oxidation of gaseous hydrocarbons. Both of them use the action of catalysts, here called oxygen carriers (OC), which transfers oxygen from the air to the fuel (in this case methane), avoiding the direct contact between the two gases for various reasons. The OC\'s are composed of metal oxides in the form of fine power, circle continuously between two fluidized bed reactors (fuel reactor and air reactor), suffering successive cycles of reduction and oxidation. The two processes differ in relation to the products; the aim of CLC is generation of energy (heat), through the complete oxidation of the fuel, resulting in a mixture of CO2 and H2O, which can be easily separated by condensation. In the case of CLR, the oxidation occurs partially, resulting in synthesis gas, a mixture of H2 and CO. The CLC processes shows advantages when compared to other traditional processes for capture of CO2, because it is not necessary to use secondary processes for gas separation, saving energy, besides the fact of no NOx is generated. This work describes the preparation of two series of materials via dry impregnation, which are composed of 2, 4 and 8% w/w niobium oxide or nickel oxide, supported on commercial alumina, with high specific surface area. The materials were characterized by the techniques of helium pycnometry, nitrogen volumetry, mercury intrusion porosimetry, DRX, MEV, TPR 5% H2/N2 analyzed with TCD in ChemBet, TPR 5% CH4/Ar and TPO 5% O2/Ar, being the changes in mass and heat analyzed in a thermogravimetric balance (TGA/DSC) coupled to a mass spectrometer permitting the analysis of the generated gases. The different oxygen carriers were tested in a fixed bed reactor, evaluated in different experimental conditions, such as operation temperature, flow rate of gaseous reactants, methane concentrations, addition of CO2 and H2O to the fuel. The products of the reaction in the fixed bed reactor were analyzed by gas chromatography and mass spectrometry. The results show that: the carbon deposits over the catalysts can be drastically reduced by addition of oxidizing mixture together to the fuel and these studied oxides have a potential industrial application, showing selectivity to reforming of methane with consecutive synthesis gas production.

Based on the concept of covalent capture of supramolecular assemblies, the idea of mechanical encapsulation is exploited for the protection and delivery of peptidebased molecules. This thesis aims to establish a general method for the encapsulation of peptides within a rotaxane structure, as well as studying their mode of release under specific stimuli. The synthesis of such structures, relying on the elongation of short peptido[2]rotaxanes, is applied to the design of rotaxane peptide carriers whose function is to protect against biological degradation and release peptides under a biological stimulus. These molecules are composed of a rotaxane-encapsulated peptide bearing a biodegradable stopper, the enzyme-specific cleavage of which triggers peptide release, via ‘dethreading’. The synthesis and in vitro assessment of rotaxane carriers as agents for anti-cancer therapy will be described in detail. The future challenges and potential applications of the proposed systems will be addressed.

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This study analyzes profiles and career paths of directors and counselors from the following federal agencies: ANEEL, ANATEL, ANP, ANVISA, ANS, ANA, ANCINE, ANTAQ, ANTT e ANAC. We observe dimensions relating with conditions which, in theory, allow more decision-making autonomy to Brazilian federal regulators: 1) regulator’s level of expertise and skilled knowledge, watching his trainig area, level of education and previous experience in the regulated sector; 2) the existence of party affiliation before his appointment to the post at the agency; 3) the existence of cases of renewal regulators, beyond the government mandates of different presidents; 4) the professional origin of regulators and destination after their performance in regulatory agencies. At the same time, it is observed the institutional design of these Brazilian agencies and how some aspects of its structure and process can interfere with the outcome of the regulatory process, specially in regard to how regulators are indicated. Among the main results of this work, we highlight the strong connection between the training area of regulators and the playing field of regulatory agencies; the recovery of post-graduate courses in qualifying a candidate for a federal regulatory agency; and the proof of previous professional experience in the regulated sector, indicating that Brazilian regulators have relevant indicators of specialization and expertise in the sector. There have also been cases of indicated and reappointed regulators by different presidents, reinforcing the hypothesis that value expertise. Regarding political capture, stands out that just under a third of tregulators had previous party affiliation before their appointments. Most regulators are selected within the public service, but most of them will work in the private industry sphere, reinforcing the evidence that there may have been capture during their mandates in the agency. It is clear, also, a trend of strengthening of agencies’ bureaucracy from the end of the first term of President Lula, movement wich has increased in President Dilma Rousseff’s first term.
Este trabalho analisa o perfil e as trajetórias de carreira dos diretores e conselheiros das se-guintes agências federais: ANEEL, ANATEL, ANP, ANVISA, ANS, ANA, ANCINE, AN-TAQ, ANTT e ANAC. São observadas algumas dimensões que se relacionam com condicio-nantes que, em tese, permitiriam uma maior autonomia decisória do regulador brasileiro federal: 1) o nível de expertise e conhecimento especializado do regulador, observando sua área de formação, nível de escolaridade e sua experiência prévia no setor regulado; 2) a existência ou não de filiação partidária antes de sua indicação para o cargo na agência; 3) a existência ou não de casos de recondução de reguladores, além dos mandados governamentais de diferentes presidentes; e 4) a origem e o destino profissional do regulador após sua atuação na agência reguladora. Paralelamente, observa-se como foi elaborado o desenho institucional destas agências brasileiras e como algumas características de sua estrutura e processo podem interferir com o resultado do processo regulatório, especialmente no que se refere à forma como os reguladores são indicados. Entre os principais resultados do trabalho, destacam-se a forte co-nexão entre a área de formação dos reguladores e o campo de atuação das agências reguladores; a valorização de cursos de pós-graduação na qualificação de um candidato para uma agência reguladora federal; e a comprovação de experiência profissional prévia no setor regulado, indicando que os reguladores brasileiros apresentam indicadores relevantes de especialização e expertise no setor. Também ocorreram casos de reguladores indicados e reconduzidos por presidentes diferentes, reforçando a hipótese de valorização da especialização. Com relação a captura política, se destaca que pouco menos de um terço dos indicados possuía filiação partidária anterior à nomeação. A maioria dos reguladores é selecionada dentro do serviço público, mas boa parte deles vai trabalhar na esfera privada do setor, reforçando os indícios de que pode ter havido captura durante os mandatos na agência. Percebe-se, ainda, uma forte tendência de fortalecimento da burocracia das agências a partir do final do primeiro mandato do presidente Lula, movimento acentuado no primeiro mandato da presidente Dilma Rousseff.

El sector pesquero a lo largo de los años ha tenido fases de expansión y crisis que evidencian la problemática de la industria, la cual es el sobredimensionamiento de flota y planta; esto conllevó a la sobre explotación de la biomasa anchovetera y la ineficiencia de los agentes económicos en sus operaciones. Es por eso que en el año 2008, se promulga el Decreto Legislativo 1084, a través del cual se estableció el nuevo sistema de Límites Máximos de Captura por Embarcación (LMCE), este nuevo régimen entra en vigencia la primera temporada del 2009 y rige sólo para la anchoveta que se destina al consumo humano indirecto (CHI), es decir, para la anchoveta que es utilizada para la elaboración de harina y aceite de pescado. Esta norma introdujo cuotas individuales de pesca de anchoveta y se las asignó a las embarcaciones que ya operaban en esta pesquería, con la cual se eliminó el sistema anterior que se basaba en las cuotas globales de capturas, las cuales incentivaba a que se dé la “Carrera Olímpica” (pesca desmedida) para obtener la mayor cantidad del recurso posible. Para analizar la repercusión del Decreto Legislativo 1084, el presente trabajo propone evaluar el comportamiento pre y post reforma del sector de los años 2005 hasta 2014, con la finalidad de demostrar la eliminación de la pesca desmedida y mejora de calidad en los desembarques de anchoveta. Los resultados obtenidos después de la investigación realzan lo importante que fue la implementación del Decreto Legislativo 1084 en el sector pesquero, presentando mejoras en el ordenamiento del sector que se ve reflejado en el desarrollo de la industria pesquera.
The fishing sector over the years has had phases of expansion and crisis that show that the problem of the industry is the oversizing of the fleet and plant, this led to the over exploitation of anchovy biomass and that the economic agents are less efficient in their operations. That is why, in 2008, Legislative Decree 1084 is enacted, through which it was established the new system of Maximum Limits of Capture by Vessel (MLCV), this regime comes into force in the first season of 2009 and which governs only anchovy intended for indirect human consumption (IHC), that is, for the anchovy that is used for the production of fish meal and fish oil. This standard introduced individual anchovy fishing quotas and allocated it to vessels already operating in this fishery, thereby eliminating the previous system, which set a global catch quota, which encouraged the "Olympic Race" to get as much of the resource as possible. In order to analyze the impact of Legislative Decree 1084, the present research proposes to evaluate the pre and post reform behavior of the sector, in order to demonstrate that overfishing was eliminated and that a better quality of the anchovy landings was generated. The results obtained after the investigation highlight the importance of the implementation of Legislative Decree 1084 in the fishing sector, presenting improvements in the ordering of the sector that is reflected in the development of the fishing industry
Trabajo de Suficiencia Profesional

Ce travail porte sur la conception, la fabrication et la caractérisation d’une photodiode très haut débit (UTC PD) et son intégration avec un préamplificateur optique à semi-conducteur (SOA) pour les liaisons optiques à courte distance à 100 Gbit/s en bandes C et O. Il porte également sur la conception d'un duplexeur (Tx / Rx) avec liaison montante en bande C et liaison descendante en bande O. L'intégration monolithique d’un SOA avec une photodiode haut débit sans filtre optique entre les deux présente des avantages majeurs parmi lesquels: - Augmentation de la distance de transmission. - Augmentation du nombre d'utilisateurs connectés. - Diminution des coûts globaux de fabrication incluant l’assemblage. La première partie de cette étude porte sur l'optimisation SOA pour un fonctionnement à forte puissance (Psat). Un faible facteur de bruit (NF) et une faible dépendance à la polarisation (PDL) sont requis pour les récepteurs préamplifiés. De plus, un fonctionnement du et opérer en régime linéaire est nécessaire pour les schémas de modulation complexes. Le SOA actuel possède un gain de 18 dB avec un facteur de bruit de 8 dB, une faible PDL (<2 dB), et une bonne puissance de saturation en entrée (-8 dBm). Grâce à l’optimisation de la structure verticale du SOA et de son couplage avec la fibre les performances attendues sont améliores : Psat >-5 dBm, NF <8 dB, PDL et gain similaire. D'autre part, les interconnexions électriques de la photodiode ont été optimisées ce qui a permis de démontrer des photodiodes avec une bande passante supérieure à 100 GHz. Les photodiodes présentent un fort coefficient de réponse (R) (0,6 A/W à 1,3 μm et 0,55 A/W à 1,55 μm) et une faible PDL <1 dB. Un fort courant de saturation de 14 mA à 100 GHz a aussi été démonté. Enfin, la caractérisation des SOA-UTC réalisés a montré simultanément une très forte responsivité (95 A/W), une faible dépendance à la polarisation PDL (<2 dB), un faible NF (8 dB) et une large bande passante à 3 dB (> 95 GHz), qui placent nos composants au meilleur niveau de l’état de l’art avec un produit gain-bande record de 6,1 THz. Les Mesures numériques à 64 Gbit/s montrent que notre récepteur atteint une sensibilité de -17 dBm pour un taux d'erreur de 10-9, et la sensibilité attendue à 100 Gbit/s est de -14 dBm
This work focuses on the design, fabrication and measurements of a uni-travelling carrier high speed photodiode (UTC PD) and its integration with a semiconductor optical preamplifier (SOA) for short reach 100 Gbit/s optical links, in O- and C- bands. This work also focuses on the design of a duplexer (Tx/Rx) with downstream in O-band and upstream in C-band. The SOA monolithic integration with a high speed PD without an optical filter in between yields major benefits among which: - Increase in the transmission distance. - Increase in the split ratio correlated to the number of connected users. - Decrease of the overall fabrication and assembling cost. The first part of this work is dedicated to optimizing the SOA for high power operation (Psat). The low noise figure (NF), and polarization dependence loss (PDL) are critical parameters for a preamplified receiver. Also complex modulation formats require linear gain regime of the SOA. The current SOA presents 18 dB gain with NF (8 dB), low PDL (<2 dB), and good input power saturation (-8 dBm). Thanks to further optimization of the SOA vertical structure and coupling with the optical fiber, the expected SOA performance is higher Psat >-5 dBm, NF <8 dB, similar PDL and gain. Secondly, the electrical interconnects of the photodiode is optimized to increase the photodiodes’ bandwidth, which allows to demonstrate photodiode with >100 GHz bandwidth. The PD presents high responsivity (R) (0,6 A/W at 1,3 μm and 0.55 A/W at 1,55 μm) and low PDL <1 dB. Also the saturation photocurrent is high (14 mA at 100 GHz). Finally, the SOA-UTC demonstrates high responsivity (95 A/W), low PDL (<2 dB), low NF (8 dB) and a wide 3 dB bandwidth (>95 GHz), which yields a record gain-bandwidth product of 6.1 THz. Large signal measurements at 64 Gbit/s show that our receiver reaches a low sensitivity of -17 dBm for a bit error rate of 10-9, and is expected to reach -14 dBm at 100 Gbit/s

Le CO₂ est l’un des principaux gaz à effet de serre qui participe activement au réchauffement du système climatique. La capture et le stockage géologique du carbone permettent de limiter les impacts des augmentations de concentration en CO₂ dans l’atmosphère. La principale qualité d’un site de stockage est de présenter une probabilité de fuite minimale. Il est donc essentiel de développer des outils de surveillance afin d’évaluer leur importance et de prévoir des actions correctives. Ce travail de thèse a pour objectif d’étudier les processus physicochimiques et les impacts d’une fuite de CO₂ sur les hydrosystèmes proches surface (zone vadose (ZV) et nappe) dans un système carbonaté réservoir d’âge Oligocène situé au sein du bassin aquitain. Cette étude a suivi : i) une approche expérimentale sur le site pilote de Saint-Emilion (Gironde, France) où une injection de CO₂ a eu lieu dans l’aquifère à partir d’un puits de forage ; ii) une approche en laboratoire à l’échelle de la carotte afin d’étudier les interactions du système CO₂-H₂O-CaCO₃. Ce travail apporte une démarche expérimentale nouvelle en couplant des méthodes géochimiques et géophysiques sur les deux échelles d’investigation. La ligne de base, réalisée à travers la ZV l’année précédant l’expérience d’injection, a étudié l’évolution naturelle du CO₂ lors d’un cycle hydrogéologique. Après l’injection dans la nappe et au regard de nos résultats, la conductivité électrique (σ), le pH, les concentrations en Ca²⁺, HCO₃- et CO₂ se sont avérés être de bons indicateurs, suffisamment sensibles et réactifs, pouvant être utilisés sur un site de stockage de CO₂ afin de suivre toutes perturbations physicochimiques. Des simulations numériques ont permis de mieux appréhender les processus de réaction et de transport. Les expériences à l’échelle de la carotte ont quantifié l’influence des effets du CO₂ sur le comportement électrique de la roche carbonatée. Une meilleure définition de la relation entre les concentrations en CO₂, la σ et le pH permet de passer de l’échelle de la carotte à l’échelle du site pilote et vice versa. L’ensemble des résultats de ce travail de thèse met en avant l’importance de la caractérisation de l’hétérogénéité pétrophysique du réservoir. Il est également essentiel d’établir une ligne de base, permettant de distinguer les variations naturelles en CO₂ de celles induites par une fuite. Le couplage des observations sur le terrain et des démonstrations en laboratoire permet d’augmenter les chances de détection d’une fuite de CO₂ sur un site de stockage géologique
CO₂ is one of the main greenhouse gases that actively contributes to the global warming. The carbon capture and geological storage can limit the impacts of increases in CO₂ concentration in the atmosphere. The main quality of a storage site is to present a minimum probability of leakage. Therefore, it is essential to develop monitoring tools in order to assess their importance and plan corrective actions. The objective of this thesis is to study the physicochemical processes and the impacts of a CO₂ leak on near-surface hydrosystems (vadose zone (VZ) and aquifer) in a carbonate reservoir system of Oligocene age located within the Aquitaine basin. This study followed: i) an experimental approach at the Saint-Emilion pilot site (Gironde, France) where CO₂ injection took place into the aquifer from a borehole; ii) a core-scale laboratory approach to study the interactions of the CO₂-H₂O-CaCO₃ system. This work brings a new experimental approach by coupling geochemical and geophysical methods on the two scales of investigation. The baseline, carried out through the VZ the year before the injection experiment, studied the natural evolution of CO₂ during a hydrogeological cycle. After injection into the aquifer and according to our results, the electrical conductivity (σ), the pH, the concentrations of Ca²⁺, HCO₃- and CO₂ turned out to be good indicators, sufficiently sensitive and reactive, which can be used on a CO₂ storage site to monitor any physicochemical disturbances. Numerical simulations have made it possible to better understand the reaction and transport processes. Core-scale experiments quantified the influence of CO₂ effects on the electrical behavior of carbonate rock. Better definition of the relationship between the concentrations of CO₂, σ and pH makes it possible to pass from the core scale to the pilot site scale and vice versa. All the results of this thesis work highlight the importance of characterizing the petrophysical heterogeneity of the reservoir. It is also essential to establish a baseline, making it possible to distinguish natural variations in CO₂ from those induced by a leak. Coupling field observations and laboratory demonstrations increases the chances of detecting a CO₂ leak at a geological storage site

碩士
國立東華大學
應用物理研究所
93
Abstract We have investigated the carrier capture and relaxation processes in InAs/GaAs self-assembled quantum dots at room temperature by time-resolved photoluminescence techniques with a high time resolution of ~ 150 fsec. We have observed rising processes in time-resolved PL intensity at the energies of quantum dot confined states and the wetting layer. The rising processes are assigned to the carrier capture from the barriers into the wetting layer and confined states in InAs dots and subsequent relaxation in each detected energy level. We found that the carrier capture rate is faster than the intra-dot relaxation within the range of excitation densities that we investigated. Under high excitation intensity, the electronic states in the dots were populated mainly by carriers directly captured from the barrier. However, at low excitation densities, the PL rise times were influenced by the carrier diffusion.

碩士
國立臺灣大學
光電(科學)研究所
84
Carrier capture times in intrinsic multiple quantum well waveguides are measured using the pump-probe technique. To prepare the pump and probe pulses, the pulse spectrum from a mode-locked Ti:sapphire laser is first broadened with a piece of fiber. With appropriate selections of wavelengths and pulse recompression, sub-picosecond pulses at various wavelengths can be used for both nondegenerate and degenerate pump-probe experiments. Two samples with different quantum well structures are used: one has weak coupling of wavefunctions between the neighboring wells; the other has strong coupling. The experimental data show that the capture times are always between 10 and 30 psec in our samples. Since our barrier thicknesses are quite thin, the drift of carriers in barrier layers does not contribute much in capture time. The measured capture time should be basically spent for quantum capture. Based on a three-level model, we have numerically shown that a semiconductor gain medium with a structure consisting of two different quantum wells may lead to dual-wavelength laser operation if the balance of carrier capture competition between the two wells can be reached. The major controlling parameters for the operation are the ratio of the carrier quantum capture times of the two wells and the absorption constant of the short- wavelength photons by the long-wavelength quantum well. It is shown that there exists a large parameter space for dual- wavelength operation.

碩士
國立臺灣大學
光電工程學研究所
101
The Heterojunction Bipolar Light-Emitting Transistors (HBLETs) have become one of the best candidate of next generation optical communication light source because of it’s extremely fast carrier recombination lifetime (~ tens ps) and the characteristics of transistors after its’ invention in 2004. Compared with the Light-Emitting Diode (LED) and Diode Laser (DL), the key to the extremely short lifetime of the LET is the transistor structure. LETs have been improved both in carriers recombination ability and optical emission characteristics by incorporating single or multiple quantum wells (QWs) in the p-type base region. The material, number, and structure of QWs will affect both the electrical and optical performance of LETs evidently. In the case of LEDs or DLs, carrier capture and escape processes in QWs have been studied intensively due to their influence on limiting the optical modulation bandwidth. Due to the short base effect of “tilted” charge population in transistors, the effective minority carrier lifetime in the base region of the LET can be progressively reduced to sub-100 ps since the slow carriers will be swept to the collector by the electrical field of base-collector junction and become collector current. As a result, the electron transportation and diffusion in LET are affected by QWs but are different with the LED and DL. The purpose of this thesis is to investigate the QWs carrier capture and escape characteristics of LET and thus provide the design principle in the future. In the experiment, we utilize the microwave measurement followed by small-signal analysis to obtain the base transit time of LET and the small-signal model. The base transit time of the reference heterojunction bipolar transistor (HBT) are also measured and compared in order to obtain carrier capture and escape time caused by the QWs. The carrier capture and escape time are further explained by the thermionic emission theory where the carrier effective barrier height is obtained by QWs energy states calculation and electroluminescence (EL) spectrum measurement.

碩士
國立交通大學
電子物理系所
92
In this study, we have investigated the InAs/InGaAs (dots-in-a -well) structure with different InAs thickness . Red shift of Photoluminescence (PL) spectroscopy is observed from 1238nm to 1310nm as the InAs thickness increases from 1.97 to 2.7 ML. A significant reduction of the PL intensity is accompanied with a blue shift for 3.06 ML and 3.33 ML samples, indicating that there is a critical thickness in the InAs growth. The capacitance-voltage (C-V) measurement shows a carrier confinement for 2.34 ML sample. With increasing the InAs thickness to 3.06 and 3.33 ML, a significant carrier depletion caused by relaxation is observed near the bottom InAs/GaAs interface. Traps at 0.37eV and 0.41eV are measured by DLTS in 3.06 ML and 3.33 ML samples, respectively. These two traps are suggested to cause the carrier depletion. DLTS measurements have also provided an evidence of the capture barriers Eσ=0.1eV and Eσ=0.22eV for 3.06 ML and 3.33 ML samples, respectively.

Dissertação de mestrado em Industrial and Firm Economics
This dissertation aims to investigate the entry decision of a Low-Cost Carrier (LCC) in a market where the incumbent firm, the Full-Cost Carrier (FCC), has a competitive advantage due to the existence of captive loyal consumers, who are only willing to fly with this company. As the LCC is more efficient than the FCC in terms of operation costs, this dissertation investigates under which conditions for cost differences and dimension of FCC’s captive segment, will the LCC entrance occur. With this goal in mind, a theoretical model of price competition is proposed and solved, using game theoretical tools. We conclude that, as expected, the entry of the LCC will be more likely in markets with a lower proportion of captive consumers to the FCC, which translates into a greater potential demand (selective market) for the LCC. The entry will also be more likely the greater the cost advantage of LCC compared to the FCC. Regarding the impact on profits, we conclude that the FCC will face greater losses if its initial competitive advantage (proportion of captive consumers) is less significant and faces the actual entry of a very efficient LCC. With regard to the LCC, we show that the entry becomes more likely the greater the lower is its cost in comparison to the incumbent company. With these results, we conclude that if the FCC wants to smooth price competition with a cost-efficient LCC, it should devote resources to increasing passenger loyalty. On the other hand, LCCs interested in entering a market should guarantee cost levels low enough to address the disadvantages of competing with a FCC with captive consumers.
Esta dissertação tem como objetivo investigar em que medida a existência de consumidores leais cativos a uma companhia aérea incumbente, a Full-Cost Carrier (FCC), bem como a eficiência em custos, pode condicionar a decisão de entrada de uma companhia Low-Cost Carrier (LCC) num mercado inicialmente monopolizado. Com este objetivo é proposto um modelo teórico de concorrência em preços, resolvido com base na teoria dos jogos. Examinamos os lucros da FCC após a entrada bem-sucedida da LCC, bem como os impactos ao nível da decisão de entrada da LCC. Com este modelo, conclui-se que, como esperado, a entrada da LCC será mais provável em mercados com uma proporção menor de consumidores cativos à FCC, o que se traduz numa maior procura potencial (mercado seletivo) para a LCC. A entrada será também mais provável quanto maior a vantagem de custos da LCC comparativamente à FCC. No que diz respeito ao impacto nos lucros, conclui-se que a FCC enfrentará maiores perdas se a sua vantagem competitiva inicial (proporção de consumidores cativos) for pouco significativa e se deparar com a entrada efetiva de uma LCC muito eficiente. No que diz respeito à LCC conclui-se que existindo custo exógeno de entrada, a sua entrada é mais provável quanto maior a sua eficiência em custos em comparação com a FCC (i.e., quanto menos eficiente for a incumbente). Com estes resultados, conclui-se que se as FCC quiserem suavizar a concorrência em preços com uma LCC agressiva em custos, devem dedicar recursos a aumentar a lealdade dos passageiros. Por outro lado, as LCC interessadas em entrar num mercado devem garantir níveis de custos suficientemente baixos para colmatarem as desvantagens em concorrer com uma FCC com consumidores cativos.

Trabalho de Projeto do Mestrado Integrado em Engenharia Biomédica apresentado à Faculdade de Ciências e Tecnologia
O uso de lentes de contacto é um dos fatores com maior responsabilidade no crescimento do número de casos de hipóxia ocular nos últimos anos. Sendo a córnea um tecido avascular, a obtenção de oxigénio está dependente, quer da difusão direta com a atmosfera, quer do oxigénio dissolvido no fluido lacrimal.Vários investigadores apresentaram, como resposta a este problema, algumas propostas, como colírios que aliviam certos sintomas (como a síndrome do olho seco) ou lentes de contacto com maior permeabilidade ao oxigénio. Porém, nenhuma das soluções apresentada foi, ainda, capaz de resolver o problema.O objetivo desta dissertação passou pela criação de uma lente de contacto do tipo hidrogel modificada, de forma a que a sua capacidade de captação, retenção e libertação de oxigénio fosse superior quando comparada com uma lente controlo. Para, tal foi necessária a síntese de micro/nano cápsulas de sílica porosa, carregadas de perfluorodecalina (componente responsável pela elevada solubilidade do oxigénio).A síntese deste sistema de cápsulas foi conseguida através de uma emulsão, seguida da sua estabilização, através do método sol-gel em meio aquoso. De realçar que, para estabelecer a concentração de surfactantes a usar, calculou-se a concentração micelar crítica (método do anel de du Noüy). Por outro lado, para estabelecer os tempos de sonicação foram avaliados os diâmetros hidrodinâmicos, a cinética de formação e a cinética de degradação (método da dispersão dinâmica da luz – DLS).Paralelamente foram sintetizados filmes usados como controlo (HEMA reticulado), que permitiram definir alguns parâmetros, tais como tempos de agitação, desgaseificação e de fotopolimerização. Foram ainda estudadas propriedades como a espessura e a massa das lentes obtidas a partir dos filmes de HEMA, verificando-se a homogeneidade do material. Esta informação permitiu verificar que o molde para a polimerização era adequado, bem como a ferramenta usada no seu corte. Caracterizaram-se propriedades do polímero como a sua capacidade de absorver água, hidrofilicidade, transmitância, morfologia (Scanning Electron Microscopy - SEM), temperatura de degradação (TGA). Foi calculada a temperatura de transição vítrea (Differential Scanning Calorimetry - DSC) e, por fim, realizaram-se ensaios de oxigenação.Deste modo, fundiram-se os dois conceitos e, após síntese dos primeiros filmes (HEMA + micro/nano cápsulas de sílica, carregadas de PFD), procedeu-se à caracterização deste sistema.Com os dados obtidos foi possível concluir que a incorporação de micro/nano cápsulas de sílica, carregadas de PFD nos filmes de HEMA aumenta a capacidade de oxigenação em meio aquoso.
One of the main factors contributing to the increasing numbers of ocular hypoxia cases in the past years is the use of contact lenses. The fact that cornea is an avascular tissue, makes it dependent on the oxygen obtained by direct difusion from the atmosphere or by the oxygen existent in the tear film.Researchers presented already several proposals in order to solve this problem, such as eye drops, responsible for relieving dry eye syndrome symptoms, or contact lenses with improved oxygen permeability. Nonetheless, none of the present solutions are capable of solving the problem.This project had the aim of preparing a modified hydrogel contact lens, increasing its ability of collecting, stocking and releasing oxygen, compared with a control. It was necessary to synthesize micro/nano silica capsules, loaded with perfluorodecalin (responsible for the high oxygen solubility).This system was prepared by an emulsion technique followed by its stabilization with the sol-gel method in aqueous medium. In order to determine surfactant concentration to be used, critical micelle concentration was calculated (du Noüy method). On the other hand, to establish the sonication period, hydrodinamic diameter, formation kinetics and degradation kinetics were evaluated (Dynamic Light Scattering).Concurrently, control films were synthesized (cross-linked HEMA), which allowed to define several parameters, such as stirring, degas and photopolimerization periods. To assess lenses’ homogeneity polymer’s mass and thickness were determined. This information allowed to verify that the mold used for the polymerization and the cutting tool were adequated.Properties such as swelling, hidrophilicity, transmittance, morphology (SEM), degradation temperature (TGA) were also evaluated. At last, glass-transition temperature was calculated and oxygenation trials were conducted.Therefore, both concepts were merged and, after synthesis of the first modified film (HEMA + micro/nano silica capsules, loaded with PFD), it was characterized.Data obtained showed that combining micro/nano silica capsules, loaded with PFD, with hydrogel films, increases its oxygenation ability in aqueous medium.

El documental 1509 Operación Victoria, dirigido por Judith Vélez, profesora del curso Historia del Cine, se transmitirá el domingo 9 de setiembre a las 6:50 p.m. por América Televisión. A través de entrevistas inéditas y dramatizaciones, Vélez nos cuenta la verdadera historia de la captura del líder del grupo terrorista Sendero Luminoso, Abimael Guzmán. Es un documental que nos relata acerca de un puñado de jóvenes oficiales de la policía de investigaciones del Perú liderado por el Cmdte. Benedicto Jiménez, quienes asumieron la difícil tarea de capturar a Guzmán. Seguidor de Marx, Lenin y Mao propició la creación de una maquinaria de muerte y destrucción para la conquista del poder. El Grupo especial de inteligencia el GEIN, logró en 29 meses, lo que no se logró en 10 años de guerra interna: conocer el aparato partidario, el modus operandi de esta organización clandestina, así como, identificar las casas en las que vivió Abimael Guzmán, ubicadas en los barrios más residenciales de la ciudad de Lima.