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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
231

Process flowsheet development for recovering antimony from Sb-bearing copper concentrates / Processflödesschemautveckling för utvinning av antimon från Sb-haltiga kopparkoncentrat

Wu, Xian January 2023 (has links)
Mitt i Europas växande beroende av extern antimonproduktion har Europeiska kommissionen konsekvent betonat ett växande gap mellan utbud och efterfrågan sedan 2014. Som svar på denna utmaning riktade sig denna studie mot sekundära antimonkällor från underutnyttjade rester av guld, koppar och blymalm, som för närvarande utgör ett miljöproblem. Genom noggranna experiment, fastställde vi att optimal antimonurlakning uppnås vid 120 °C inom 2 timmar med en 250 g/L Na2S och 60 g/L NaOH-blandning. Detta tillvägagångssätt accentuerar selektiv extraktion, förbättrar antimonåtervinningen och minimerar kopparinterferens. En innovativ aspekt av denna studie var användandet utav mikrovågsassisterad urlakning, vilket visar fördelar i både utvinningseffektivitet och bevarande av mineralstrukturer jämfört med traditionella metoder. Våra resultat stöds av flera analytiska verktyg och ger en första förståelse, även om detaljerna kring mikrovågsassisterad urlakning och dess skalbarhet motiverar ytterligare utforskning. Denna studie introducerar en metod för urlakning av antimon från koppargruvavfall och föreslår ett motsvarande återvinningssystem som kan vara ekonomiskt lönsamt. Sådana ansträngningar kan ge ett blygsamt bidrag till att lindra den nuvarande situationen. / Amid Europe's growing reliance on external antimony production, the European Commission has consistently emphasized an expanding supply-demand gap since 2014. Responding to this challenge, our research targeted secondary antimony sources from underutilized residues of gold, copper, and lead ore processing, which currently pose environmental concerns. Through meticulous experimentation, we determined that optimal antimony leaching is achieved at 120°C within 2 hours, using a 250 g/L Na2S and 60 g/L NaOH mixture. This approach accentuates selective extraction, enhancing antimony recovery and minimizing copper interference. An innovative facet of this study was the adoption of microwave-assisted leaching, demonstrating advantages in both extraction efficiency and mineral structure conservation over traditional methods. Our results, backed by multiple analytical tools, provide an initial understanding, though areas like the specifics of microwave-assisted leaching and its scalability warrant further exploration. This study introduces a method for leaching antimony from copper mining waste and suggests a corresponding recycling system that may be economically viable. Such endeavors might offer a modest contribution to alleviating the present situation.
232

Full-wave characterization of bi-dimensional cavities and its application to the design of waveguide filters and multiplexers

Carceller Candau, Carlos 16 May 2016 (has links)
[EN] Modern communications systems impose stringent requirements on the equipment that operates at microwave frequency, especially in the case of wireless communications. The design of passive components for these applications is contingent upon the availability of accurate electromagnetic (EM) modeling tools that can efficiently handle the complex geometry of these components. Despite the widespread use of mesh-based general-purpose computer-aided engineering (CAE) tools to perform final design verifications, their application during the optimization process is limited. Optimum designs require a large number of simulations, which are computationally expensive when performed by general purpose tools. Instead, microwave designers prefer to employ faster software tools tailored to specific geometries, such as waveguide components, multilayered structures, etc. Therefore, the development of faster and more efficient specialized EM tools has a direct impact on the design of microwave components, both quantitatively and qualitatively. Increasingly complex geometries are modeled more accurately, and may be incorporated into novel designs without penalizing development time and its associated costs. By doing so, passive components become more advanced and are able to fulfill stricter requirements. At the same time, new research and development opportunities arise in order to address the challenges posed by these advanced structures. The present thesis is focused on a specific type of waveguide cavity geometry: bi-dimensional structures of arbitrary shape. Most microwave components based on rectangular waveguides include these elements (bends, T-junctions, tapers, power-dividers, etc.), thus the scope of this work is wide. To characterize these structures, an efficient full-wave modal formulation is developed. Taking into account common properties of bi-dimensional structures, such as its electromagnetic symmetry, the resulting technique is very efficient and accurate. Thanks to the integration of this formulation into a CAE tool, a designer is able to solve complex systems that combine this type of element with components of vastly different shapes. The developed formulation is first applied to the analysis and design of passive components, such as filters, multiplexers and orthomode transducers. These examples are employed to validate the results, as well as to demonstrate the improvement that the proposed analysis technique represents over well-known commercial EM packages. Likewise, this formulation is combined with the tool SPARK3D to predict RF breakdown (multipactor and corona) in selected bi-dimensional structures. Then, novel implementations of waveguide quasi-elliptic filters, based on the interconnection of bi-dimensional cavities, are proposed. Special attention is paid to the realization of multiple transmission zeros (TZs) with tuning-less compact structures. First, a novel family of filters, known as hybrid-folded rectangular waveguide structures, is studied. Simple and flexible methods to prescribe the location of the transmission zeros realized by these structures are presented. Practical aspects related to their physical implementation are also discussed. Secondly, a compact and purely capacitive obstacle, capable of realizing multiple TZs, is presented and discussed. In both cases, multiple examples are given to illustrate the step-by-step process involved in the design of these structures. Finally, a systematic procedure for the design of wideband manifold-coupled multiplexers is proposed. To preven the generation of undesired resonances, stubs that connect the filters to the manifold are removed. Likewise, the manifold length is kept as short as possible. Following a simple procedure, based on analytical formulas and EM simulations, a good starting point for the final optimization of these structures is obtained. It has been applied to a wideband quadruplexer for passive intermodulation measurement at C-band. / [ES] Actualmente, los sistemas de comunicaciones imponen unos requisitos muy estrictos sobre el equipamiento en la banda de microondas. El diseño de estos componentes está supeditado, frecuentemente, a la disponibilidad de herramientas de modelado electromagnético (EM) que sean capaces de analizar geometrías complejas. A pesar del amplio uso de herramientas CAE (computer-aided engineering) de propósito general para la verificación final de prototipos, su potencial aplicación durante el proceso de diseño es limitada. Los diseños óptimos exigen realizar una gran cantidad de simulaciones EM. Dado que las simulaciones con estas técnicas tienen un alto coste computacional, los diseñadores suelen optar por emplear herramientas software especializadas en las estructuras que diseñan. Por tanto, el desarrollo de nuevas herramientas más precisas y eficientes ayudará a reducir el tiempo de diseño de estos productos, y con ello los costes asociados. Además, permitirá abrir nuevas líneas de investigación para responder a los retos que plantean geometrías cada vez más complejas. Esta tesis se centra en el desarrollo de una herramienta de análisis EM para un tipo concreto de estructuras: cavidades bidimensionales de sección arbitraria. Es habitual encontrar este tipo de estructuras en la mayoría de componentes implementados en guía rectangular. Por tanto, el rango de aplicación de la teoría desarrollada en esta tesis es muy amplio. En concreto, se ha desarrollado una nueva formulación basada en métodos modales que permite realizar una caracterización de onda completa de estas estructuras de forma eficiente y precisa. Al aprovechar su simetría geométrica y electromagnética, la herramienta desarrollada puede minimizar los cálculos a realizar, consiguiendo grandes velocidades de computación pero manteniendo una alta precisión. Gracias a la integración de esta formulación dentro de una herramienta CAE basada en métodos modales, se ofrece la posibilidad a los diseñadores de resolver sistemas muy complejos que combinan este tipo de cavidades con otros componentes de geometrías distintas. Esta formulación se aplica, en primer lugar, al análisis y diseño de componentes pasivos comunes, tales como filtros, multiplexores y OMTs. Estos ejemplo validan la herramienta desarrollada, y demuestran la significativa mejora que supone el uso de esta nueva técnica con respecto a otros paquetes software de análisis electromagnético. Asimismo, al combinar esta formulación con la herramienta SPARK3D se abre la posibilidad de predecir la aparición de fenómenos de descarga de alta potencia en determinadas estructuras bidimensionales. A continuación, se proponen nuevas formas de implementar filtros cuasi-elípticos basados en la interconexión de cavidades bi-dimensionales. Se hace especial hincapié en la realización de múltiples ceros de transmisión mediante estructuras compactas que no requieran sintonía. Por una parte se estudian los filtros hybrid-folded rectangular waveguide. Este trabajo incluye una discusión en profundidad sobre distintas implementaciones de este tipo de filtros. En ella se consideran aspectos prácticos relacionados con su uso e implementación física, que ofrecen al diseñador unos criterios claros para elegir la estructura que más se ajuste a sus especificaciones. Por otra parte se presenta un nuevo obstáculo de naturaleza capacitiva muy compacto, que permite la realización de múltiples ceros de transmisión incluso en estructuras en línea. En ambos casos se incluyen ejemplos de aplicación y se describe la metodología seguida para su diseño. Finalmente, se expone un procedimiento sistemático para diseñar multiplexores de banda ancha. Para prevenir la generación de resonancias indeseadas se evitan, en la medida de lo posible, las interconexiones mediante tramos cortos de guía. Siguiendo una metodología simple se consigue un excelente punto inicial para su optimización. La te / [CA] Els actuals sistemes de comunicacions sense fils imposen uns requisits molt estrictes sobre l'equipament de la banda de microones. El disseny d'aquests components està supeditat, frequentment, a la disponibilitat de ferramentes de modelatge electromagèntic (EM) que siguen capaços de gestionar geometries complexes. Tot i l'ampli ús de ferramentes CAE (computer-aided engineering) de propòsit general per a la verificació final de prototips, la seua aplicació durant el procés de disseny és limitada. Els dissenys òptims exigeixen realitzar una gran quantitat de simulacions. Les simulacions amb aquestes tècniques tenen un alt cost computacional, per tant els dissenyadors solen optar per utilitzar ferramentes software especialitzades en les estructures que dissenyen. Per tant, el desenvolupament de noves tècniques d'anàlisi més precises i eficients ajudarà a reduir el temps de desenvolupament d'aquests productes, i dels seus costos associats. A més permetrà obrir noves línies d'investigació per respondre els reptes que plantegen geometries cada vegada més complexes. Aquesta tesi es centra en el desenvolupament d'una ferramenta d'anàlisi EM per a un tipus concret d'estructures: cavitats bidimensionals de forma arbitraria. És habitual trobar aquestes estructures en la majoria de components implementats en guia rectangular. Per tant, l'àmbit d'aplicació de la teoria presentada en esta tesi és molt ampli. En concret, s'ha desenvolupat una nova formulació basada en mètodes modals que permet realitzar una caracterització d'ona completa d'aquestes estructures de forma eficient i precisa. Aprofitant la seua simetria geomètrica i electromagnètica, la ferramenta desenvolupada pot minimitzar els càlculs a realitzar, aconseguint grans velocitats de càlcul mantenint una alta precisió. Gràcies a la integració d'aquesta formulació dins d'una ferramenta CAE basada en mètodes modals, s'ofereix la possibilitat als dissenyadors de resoldre sistemes molt complexos que combinen aquest tipus de cavitats amb altres components de diferent geometria. Aquesta formulació s'aplica, en primer lloc, a l'anàlisi i disseny de components passius comuns: filtres, multiplexors i OMTs. Aquests exemples serveixen per a validar la ferramenta desenvolupada, així com demostrar la significativa millora que suposa l'ús d'aquesta nova tècnica respecte d'altres paquets software d'anàlisi electromagnètic. Així mateix, mitjançant la combinació d'aquesta formulació amb la ferramenta SPARK3D s'obri la possibilitat de predir l'aparició de fenòmens de descàrrega d'alta potència en estructures bidimensionals. A continuació, es proposen noves formes d'implementar filtres quasi el-líptics en guia d'ona basats en la interconnexió de cavitats bidimensionals. Es fa especial èmfasi en la realització de múltiples zeros de transmissió mitjançant estructures compactes que no requereixen de sintonia. D'una banda s'estudien els filtres hybrid folded rectangular waveguide. Aquest treball inclou una discussió en profunditat sobre diferents implementacions d'aquest tipus de filtres. S'hi consideren aspectes pràctics relacionats amb el seu ús i implementació física, que ofereixen al dissenyador uns criteris clars per triar l'estructura que més s'ajuste a les seues especificacions. D'altra banda es presenta un nou obstacle de naturalesa capacitiva extremadament compacte, que permet la realització de múltiples zeros de transmissió fins i tot en estructures en línia. En els dos casos s'inclouen exemples d'aplicació i es descriu la metodologia seguida per al seu disseny. Finalment, s'exposa un procediment sistemàtic per dissenyar multiplexors de banda ampla. Per prevenir la generació de ressonàncies no desitjades s'eviten les interconnexions amb trams de guia curts. Seguint una metodologia simple, basada en fórmules analítiques i simulacions electromagnètiques, s'aconsegueix un excel-lent punt inicial per a l'optimització. / Carceller Candau, C. (2016). Full-wave characterization of bi-dimensional cavities and its application to the design of waveguide filters and multiplexers [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/64089
233

Next-Generation Metasurface Applications Powered by Empirical Designs and Machine Learning

Huang, Xiaoyan January 2024 (has links)
Metasurfaces have presented themselves as next generation optical platforms with an unprecedented capability to exert designer amplitude, phase, and polarization control on incoming electromagnetic (EM) waves. Existing works have focused on demonstrating simple optical functionalities (lensing, beam steering, holography) at longer wavelengths (microwave, infrared), and the design methodology has largely been empirical. In this work, we demonstrate next generation metasurface applications in near infrared and visible wavelengths. The purpose of such applications evolves from imaging to complex machine vision applications, and as such calls for a updated design paradigm that combines traditional, empirical based methods with modern inverse design tools based on machine learning. We expand the potential of metasurfaces by demonstrating their interdisciplinary applications in complex imaging, quantum optics and optical computation. A homebrew fabrication and testing pipeline is developed to support the challenging mission of near infrared and visible frequency usage. Furthermore, we propose a new design paradigm that combines physics informed intuitions with modern machine learning to simulate and design metasurface in an accurate and time-efficient way. In conclusion, I will discuss the outlook of metasurfaces in real-world applications, whose unique combination of performance and form factor make them ideal candidates for next-generation optical devices.
234

Novel Methods for Co-crystallisation

Pagire, Sudhir K. January 2014 (has links)
The research described in this dissertation mainly covers the development of novel technologies for co-crystallisation along with the discovering of plumbagin co-crystal and thermodynamic interrelationship between the co-crystal polymorphs. Co-crystallisation is a fast growing field in the area of crystal design and has shown potential advantages in the field of pharmaceutical. Currently, many research groups are working on the development of new technologies for the synthesis of pure and stoichiometrically controlled co-crystals. In present study, three novel technologies have been developed for co-crystallisation, which include microwave assisted co-crystallisation, spherical crystallisation and microwave assisted sub-critical water processing. The microwave assisted co-crystallisation is a slurry based technology where, effects of drug solubility and dielectric properties of the solvent were investigated using caffeine / maleic acid as a model co-crystal pair. The mechanism of co-crystallisation under microwave irradiation has been proposed. The co-crystals of plumbagin with improved solubility were obtained with the coformers such as hydroquinone, resorcinol and urea using microwave assisted co-crystallisation technique. The spherical crystallisation technology was developed for co-crystallisation of carbamazepine / saccharin co-crystal pair and demonstrated its application for polymorphic control and as a potential technique for the purification of desired crystal form through surface energetic based separation. The thermodynamic interrelationship between Form I and Form II of carbamazepine / saccharin co-crystal was studied using different thermodynamic tests. The results obtained suggest that the carbamazepine / saccharin co-crystal polymorphs are monotropic. Microwave assisted sub-critical water processing has been explored as a green technology for the synthesis of co-crystals. Carbamazepine / saccharin co-crystal pair has been used as a model pair and effects of processing variables on the resulting crystal form and degradation of an API have been studied.
235

Microwave-Assisted Synthesis and Photophysical Properties of Poly-Imine Ambipolar Ligands and Their Rhenium(I) Carbonyl Complexes

Salazar Garza, Gustavo Adolfo 08 1900 (has links)
The phenomenon luminescence rigidochromism has been reported since the 1970s in tricarbonyldiimine complexes with a general formula [R(CO)3LX] using conventional unipolar diimine ligands such as 2,2;-bipyridine or 1,10-phenanthroline as L, and halogens or simple solvents as X. As a major part of this dissertation, microwave-assisted synthesis, purification, characterization and detailed photoluminescence studies of the complex fac-[ReCl(CO)3L], 1, where L = 4-[4,6-bis(3,5-dimethyl-1H-pyrazol-1-yl]-N,N-diethylbenzenamine are reported. The employment of microwaves in the preparation of 1 decreased the reaction time from 48 to 2 hours compared to the conventional reflux method. Stoichiometry variations allows for selective preparation of either a mononuclear, 1, or binuclear, fac-[Re2Cl2(CO)6], 2, complex. The photophysical properties of 1 were analyzed finding that it possesses significant luminescence rigidochromism. The steady state photoluminescence emission spectra of 1 in solution shift from 550 nm in frozen media to 610 nm when the matrix becomes fluid. Moreover, a very sensitive emission spectral analysis of 0.1 K temperatures steps shows a smooth transition through the glass transition temperature of the solvent host. Furthermore, synthetic modifications to L have attained a family of ambipolar compounds that have tunable photophysical, thermophysical and other material properties that render them promising candidates for potential applications in organic electronics and/or sensors - either as is or for their future complexes with various transition metals and lanthanides.
236

Theoretical analysis and simulation of microwave-generation from a coaxial vircator

Hägg, Martin January 2017 (has links)
High-power microwave, HPM, systems can be used as non-lethal weapons with the ability to destroy or disturb electronics, by damaging internal circuits and inducing high currents. Today microwave sources are being developed with peak powers exceeding 1 GW, one of these devices is the vircator, a narrowband source which is unique to the HPM community. In order to understand and develop microwave sources like the vircator it is necessary to have computer models, as simulations gives an invaluable understanding of the mechanisms involved during operation, saving time and development costs.                                                                  This thesis presents the results from a theoretical analysis and a simulation study using a well known electromagnetic particle-in-cell code, Computer Simulation Technology Particle Studio. The results are then compared to measured data from a HPM system, the Bofors HPM Blackout. The results show that CST PS can be used to design and study the coaxial vircator with good results.
237

Suivi de la température de surface dans les zones de pergélisol arctique par l'utilisation de données de télédétection inversées dans le schéma de surface du modèle climatique canadien (CLASS)

Marchand, Nicolas January 2017 (has links)
Les régions de haute latitude sont actuellement les plus sensibles aux effets du réchauffement climatique, et avec des élévations de température pouvant atteindre les 3 à 8 ◦C au niveau du pôle sur les 100 prochaines années. Les pergélisols (sols présentant des températures négatives deux années consécutives) sont présents sur 25 % des terres émergées de l’hémisphère nord et contiennent de grandes quantités de carbone « gelé », estimées à 1400 Gt (40 % de la quantité de carbone terrestre global). Des études récentes ont montré qu’une partie non négligeable (50 %) des premiers mètres des pergélisols pourraient fondre d’ici 2050, et 90 % d’ici 2100. Le but de l’étude est donc d’améliorer les moyens de suivi de l’évolution des températures du sol dans les zones arctiques, et plus particulièrement dans les régions couvertes de neige. L’objectif est de décrire la température du sol tout au long de l’année y compris sous un manteau neigeux, et d’analyser l’évolution de l’épaisseur de la couche active des pergélisols en relation avec la variabilité du climat. Nous utilisons des données satellites (fusion de données de température dans l’infra-rouge thermique “LST” et de température de brillance micro-onde AMSR-E « Tb ») assimilées dans le schéma de surface du modèle climatique canadien (CLASS, V 3.6) couplé à un modèle simple de transfert radiatif (HUT). Cette approche bénéficie des avantages de chaque type de donnée de manière à réaliser deux objectifs spécifiques : 1-construire une méthodologie solide permettant de retrouver les températures du sol, avec et sans neige, en zone de toundra, et 2-à partir de ces températures du sol, dériver la durée de fonte estivale et l’épaisseur de la couche active du pergélisol. Nous décrivons le couplage des modèles ainsi que la méthodologie permettant l’ajustement des paramètres météorologiques d’entrée du modèle CLASS (essentiellement les températures de l’air et les précipitations issues de la base de données des réanalyses météorologiques NARR) de manière à minimiser les LST et Tb simulées en comparaison aux mesures satellites. Par rapport aux données de mesures de sol de stations météorologiques prises comme référence pour validation dans les zones de toundra d’Amérique du Nord, les résultats montrent que la méthode proposée améliore significativement la simulation des températures du sol lorsqu’on utilise les données LST MODIS et Tb à 10 et 19 GHz pour contraindre le modèle, en comparaison avec les sorties du modèle sans les données satellites. Dans ce processus d’inversion, la correction de l’évolution des conditions de neige au cours de l’hiver contrainte avec le rapport de polarisation à 11 GHz constitue une approche originale. Une analyse de l’erreur pour 4 sites de toundra et sur plusieurs années (18 cas) est effectuée pour la période estivale (1,7 -3,6 K) ainsi que pour la période hivernale couverte de neige (1,8 -3,5 K). L’indice des degrés-jours de fontes annuel, dérivé des températures du sol simulés par notre approche, permet de cartographier les zones de pergélisols continu en accord avec les cartes actuelles. Un meilleur suivi des processus d’évolution des pergélisols, et tout particulièrement de l’impact de la couverture de neige, devrait permettre une meilleure compréhension des effets du réchauffement climatique sur la fonte des pergélisols et l’avenir de leurs stocks de carbone. / Abstract : High latitude areas currently are the most sensitive to global warming effects. In the next 100 years, temperature could rise up to 3 to 8 ◦C at the North Pole. Permafrost (ground with negative temperatures two years in a row) represents 25% of northern hemisphere lands, and contains huge quantities of "frozen" carbon estimated at 1400 Gt (40 % of the global terrestrial carbon). Recent studies showed that a part (50 %) of the permafrost first few meters could melt by 2050, and 90 % by 2100. The goal of our study is to improve our understanding of ground temperature evolution in arctic areas, especially in snow covered regions. The objective is to discribe the ground temperature all year long with and without a snow cover, and to analyze the evolution of the permafrost’s active layer in relation with the climate variability. We use remote sensing data (fuzzed of MODIS "LST" surface temperatures and AMSR-E "Tb" brightness temperatures) assimilated in the canadian landscape surface scheme (CLASS) coupled to a simple radiative transfer model (HUT). This approach takes into account the advantages of each kind of data in order to achieve two objectives : 1 - build a solid methodology allowing to retrieve ground temperatures, with and without a snow cover, in tundra areas ; 2 - from those retrieved ground temperatures, derive the summer melting duration which can be linked to the permafrost active layer thickness. We describe the models coupling as well as the methodology allowing the adjustement of CLASS input meteorological parameters (essentially the air temperatures and precipitations from the NARR meteorological data base) in order to minimize the simulated LST and Tb in comparison to remote sensing data. By using meteorological station’s ground temperature measurments as a reference for validation in North America tundra areas, results show that the proposed method improves the simulation of ground temperatures when using LST MODIS and Tb at 10 and 19 GHz data to constrain the model, in comparison with model outputs without satellite data. Using the Tb polarization ratio H/V at 10 GHz allows an improvement of the constrain on winter period simulations. An analyze of the error is conducted for summer (1,7 - 3,6 K) and winter (1,8 - 3,5 K). We present climatic applications for future work that meets the second objective of the Ph.D. A better understanding of evolution processes of permafrost, and particularly of the impact of the snow cover, should allow us a better understanding of global warming effects on the permafrost’s melting and the future of their carbon stocks.
238

Vapo-diffusion assistée par micro-ondes : conception, optimisation et application / Microwave steam diffusion : conception, optimization and application

Farhat, Asma 05 November 2010 (has links)
Un nouveau procédé d'extraction des huiles essentielles a été développé, mis au point et optimisé nommé «Vapo-diffusion Assistée par Micro-ondes (MSDf)». Le procédé MSDf à été appliqué à l'extraction des huiles essentielles des peaux d'oranges et de fleurs de lavande. Ce procédé est basé sur la combinaison d'une technique d'extraction classique : l'hydro-diffusion et le chauffage micro-ondes comme technologie d'intensification. Une deuxième nouvelle approche pour l'extraction des huiles essentielles à partir de matrices aromatiques sèches et sans ajout de vapeur ni d'eau nommé «Diffusion à sec générée par micro-ondes (MDG)». Le procédé MDG à été appliqué à l'extraction des huiles essentielles des graines de carvi. Le MSDf et le MDG apparaissent comme des procédures «douces» permettant un gain de temps et d'énergie considérable et la diminution des rejets de CO2 dans l'atmosphère / Microwave steam diffusion (MSDf) was developed as a cleaner and new process design and operation for isolation of essentials oils and was compared to conventional steam diffusion (SDf). This green process has been applied and tested using two aromatic matrixes: fresh orange peels and dry lavender flowers. This process is based on the combination of a traditional technique of extraction: hydro-diffusion and the microwave irradiation energy. Without adding any steam or water, we proposed also a novel and green approach for extraction of secondary metabolites from dried plant materials. This “steam and water free” approach based on a simple principle involves the application of microwave irradiation and earth gravity to extract the essential oil from dried caraway seeds. MSDf and MDG were better than SDf in terms of energy saving, cleanliness and reduced waste water
239

Reciclagem de elastômeros via micro-ondas. / Recycling of elastomers via microwaves.

Canazza, Moisés Amorim 12 April 2019 (has links)
A reciclagem de materiais poliméricos tem sido objeto de estudos a fim de poupar recursos naturais, principalmente de fontes não renováveis, com objetivo de minimizar os impactos causados ao meio ambiente. Nesse cenário, aparecem os materiais elastoméricos, como a borracha, principalmente na utilizada da fabricação de pneus, uma vez que a indústria pneumática consome aproximadamente 60% da produção de borracha. Como a destinação final de forma ambientalmente correta do pneu é uma exigência devidamente amparada por normas e leis nacionais e internacionais, o objetivo desse trabalho é desenvolver um estudo sobre a eficácia das irradiações das micro-ondas no processo de desvulcanização do pó de pneu. Para esse estudo as amostras de pó de pneu foram submetidas a irradiações de micro-ondas, e posteriormente incorporadas às matrizes poliméricas de NR (borracha natural) e SBR (borracha de butadieno-estireno), e caracterizadas para verificação de suas propriedades. Para caracterização das amostras foram utilizados os seguintes ensaios: Espectroscopia no Infravermelho (FTIR), Dureza, Resistência à Tração e Alongamento, Reometria, Índice de Inchamento, Análise Termogravimétrica (TGA) e Microscopia Eletrônica de Varredura (MEV). Verificou-se viabilidade técnica da incorporação do pó de pneu nas matrizes de NR e SBR, uma vez que alguns resultados mostraram que a adição do pó de pneu irradiado via micro-ondas não ocasionou perdas significativas nas propriedades mecânicas e térmicas dos compostos. / The recycling of polymeric materials has been studied in order to save natural resources, mainly from non-renewable sources, in order to minimize the impacts caused to the environment. In this scenario, there are elastomeric materials, such as rubber, mainly used in tire manufacturing, since the pneumatic industry consumes approximately 60% of rubber production. As the final destination of an environmentally correct tire is a requirement, duly supported by national and international laws and regulations, the objective of this work is to develop a study on the efficiency of microwave irradiation in the process of tire powder devulcanization. For this study the tire powder samples were subjected to microwave irradiation, and later incorporated into the polymer matrices of NR (natural rubber) and SBR (butadiene-styrene rubber), and characterized for verification of their properties. For characterization of the samples the following tests were used: Infrared Spectroscopy (FTIR), Hardness, Tensile Strength and Stretching, Rheometry, Swell Index, Thermogravimetric Analysis (TGA) and Scanning Electron Microscopy (MEV). It was verified the technical feasibility of the incorporation of the tire powder in the NR and SBR matrices, since some results showed that the addition of the tire powder irradiated by microwave did not cause significant losses in the mechanical and thermal properties of the compounds.
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[en] MICROWAVE DEVICES USING CARBON NANOTUBES AND GRAPHENE / [pt] DISPOSITIVOS DE MICROONDAS UTILIZANDO NANOTUBOS DE CARBONO E GRAFENO

GELZA DE MOURA BARBOSA 10 October 2014 (has links)
[pt] Esta Tese consiste na pesquisa, dimensionamento e desenvolvimento de estruturas de microondas que utilizam grafeno e nanotubos de carbono como componente fundamental. São apresentadas aplicações em dispositivos de micro-ondas e no domínio óptico, tais como filtros, conversores de frequência, antenas de microondas, absorvedores de microondas etc. Também são apresentados os resultados dos testes realizados em todos os dispositivos desenvolvidos. Alguns dispositivos contém inovações ainda não reportadas na literatura. / [en] This Thesis consists inthe research, dimensioning and design of microwave structures that use graphene and carbon nanotubes as fundamental component. Applications are presented in microwave devices and in the optical domain, such as filters, frequency converters, microwave antennas, microwave absorber etc. Besides that, the results of the tests performed in all designed devices are presented. Some devices have innovations not yet reported in the literature.

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