Solid oxide fuel cells (SOFCs) are solid-state ceramic cells, typically operating between 1073 K and 1273 K. Because of high operating temperature, SOFCs are mostly applicable in stationary power generation. Among various configurations in which SOFCs exist, the planar configuration of solid oxide fuel cell (SOFC) has the potential to offer high power density due to shorter current path. Moreover, the planar configuration of SOFC is simple to stack and closely resemble the stacking arrangement of polymer electrolyte membrane (PEM) fuel cells. However, due to high operating temperature, there are problems associated with the development and commercialization of planar SOFCs, such as requirement of high temperature gas seals, internal stresses in cell components, and high material and manufacturing costs. Mathematical modeling is an essential tool for the advancement of SOFC technology. Mathematical models can help in gaining insights on the processes occurring inside the fuel cell, and can also aid in the design and optimization of fuel cells by examining the effect of various operating and design conditions on performance. A multi-component and multi-dimensional mathematical model of SOFCs has been developed in this thesis research. One of the novelties of the present model is its treatment of electrodes. An electrode in the present model is treated as two distinct layers referred to as the backing layer and the reaction zone layer. Reaction zone layers are thin layers in the vicinity of the electrolyte layer where electrochemical reactions occur to produce oxide ions, electrons and water vapor. The other important feature of the present model is its flexibility in fuel choice, which implies not only pure hydrogen but also any reformate composition can be used as a fuel. The modified Stefan-Maxwell equations incorporating Knudsen diffusion are used to model multi-component diffusion in the porous backing and reaction zone layers. The coupled governing equations of species, charge and energy along with the constitutive equations in different layers of the cell are solved for numerical solution using the finite volume method and developed code written in the computer language of C++. In addition, the developed numerical model is validated with various experimental data sets published in the open literature. Moreover, it is verified that the electrode in an SOFC can be treated as two distinct layers referred to as the backing layer and the reaction zone layer. The numerical model not only predicts SOFC performance at different operating and design conditions but also provides insight on the phenomena occurring within the fuel cell. In an anode-supported SOFC, the ohmic overpotential is the single largest contributor to the cell potential loss. Also, the cathode and electrolyte overpotentials are not negligible even though their thicknesses are negligible relative to the anode thickness. Moreover, methane reforming and water-gas shift reactions aid in significantly reducing the anode concentration overpotential in the thick anode of an anode-supported SOFC. A worthwhile comparison of performance between anode-supported and self-supported SOFCs reveals that anode-supported design of SOFCs is the potential design for operating at reduced temperatures. A parametric study has also been carried out to investigate the effect of various key operating and design parameters on the performance of an anode-supported SOFC. Reducing the operating temperature below 1073 K results in a significant drop in the performance of an anode-supported SOFC; hence ionic conductivity of the ion-conducting particles in the reaction zone layers and electrolyte needs to be enhanced to operate anode-supported SOFCs below 1073 K. Further, increasing the anode reaction zone layer beyond certain thickness has no significant effect on the performance of an anode-supported SOFC. Moreover, there is a spatial limitation to the transport of oxide ions in the reaction zone layer, thereby reflecting the influence of reaction zone thickness on cell performance.

Solid oxide fuel cells (SOFCs) are solid-state ceramic cells, typically operating between 1073 K and 1273 K. Because of high operating temperature, SOFCs are mostly applicable in stationary power generation. Among various configurations in which SOFCs exist, the planar configuration of solid oxide fuel cell (SOFC) has the potential to offer high power density due to shorter current path. Moreover, the planar configuration of SOFC is simple to stack and closely resemble the stacking arrangement of polymer electrolyte membrane (PEM) fuel cells. However, due to high operating temperature, there are problems associated with the development and commercialization of planar SOFCs, such as requirement of high temperature gas seals, internal stresses in cell components, and high material and manufacturing costs. Mathematical modeling is an essential tool for the advancement of SOFC technology. Mathematical models can help in gaining insights on the processes occurring inside the fuel cell, and can also aid in the design and optimization of fuel cells by examining the effect of various operating and design conditions on performance. A multi-component and multi-dimensional mathematical model of SOFCs has been developed in this thesis research. One of the novelties of the present model is its treatment of electrodes. An electrode in the present model is treated as two distinct layers referred to as the backing layer and the reaction zone layer. Reaction zone layers are thin layers in the vicinity of the electrolyte layer where electrochemical reactions occur to produce oxide ions, electrons and water vapor. The other important feature of the present model is its flexibility in fuel choice, which implies not only pure hydrogen but also any reformate composition can be used as a fuel. The modified Stefan-Maxwell equations incorporating Knudsen diffusion are used to model multi-component diffusion in the porous backing and reaction zone layers. The coupled governing equations of species, charge and energy along with the constitutive equations in different layers of the cell are solved for numerical solution using the finite volume method and developed code written in the computer language of C++. In addition, the developed numerical model is validated with various experimental data sets published in the open literature. Moreover, it is verified that the electrode in an SOFC can be treated as two distinct layers referred to as the backing layer and the reaction zone layer. The numerical model not only predicts SOFC performance at different operating and design conditions but also provides insight on the phenomena occurring within the fuel cell. In an anode-supported SOFC, the ohmic overpotential is the single largest contributor to the cell potential loss. Also, the cathode and electrolyte overpotentials are not negligible even though their thicknesses are negligible relative to the anode thickness. Moreover, methane reforming and water-gas shift reactions aid in significantly reducing the anode concentration overpotential in the thick anode of an anode-supported SOFC. A worthwhile comparison of performance between anode-supported and self-supported SOFCs reveals that anode-supported design of SOFCs is the potential design for operating at reduced temperatures. A parametric study has also been carried out to investigate the effect of various key operating and design parameters on the performance of an anode-supported SOFC. Reducing the operating temperature below 1073 K results in a significant drop in the performance of an anode-supported SOFC; hence ionic conductivity of the ion-conducting particles in the reaction zone layers and electrolyte needs to be enhanced to operate anode-supported SOFCs below 1073 K. Further, increasing the anode reaction zone layer beyond certain thickness has no significant effect on the performance of an anode-supported SOFC. Moreover, there is a spatial limitation to the transport of oxide ions in the reaction zone layer, thereby reflecting the influence of reaction zone thickness on cell performance.

Denna uppsats undersöker hur argument som bygger på statistik kan förstås utifrån den klassiska retoriken. Utgångspunkten är den vanligt förekommande uppdelningen av bevismedel som antingen tillhörande konsten eller inte, där statistik ofta placeras i den senare kategorin. Denna uppdelning undersöks kritiskt genom en nyläsning av Aristoteles, Cicero och Quintilianus. Uppsatsen visar att Cicero ger ett bättre retoriskt perspektiv än Aristoteles eller Quintilianus för att förstå hur statistikargumentation fungerar. Därför används just Ciceros topiker (loci) såsom de är systematiserade i verket Topica för att analysera två debatter om jobbfrågan mellan Fredrik Reinfeldt och Stefan Löfvén under valåret 2014. Analysen finner främst 9 loci i debatterna, och belyser därmed flera olika sätt som statistik kan användas för att skapa argument i retoriska syften.

The study chronologically maps the argumentations concerning migration and refugee policy made by Stefan Löfvén, chairman of the Swedish Social Democratic Party as of January 27, 2012, and Prime Minister of Sweden as of October 3, 2014. It examines how and why the reasoning coming from Löfvén in the subject has changed during his time as a political leader and that is done with the help of two guiding independent variables. To do so the study answers the following primary research question: - How has the mediated image and reasoning coming from Stefan Löfvén on migration – and refugee policy changed and why? The two independent variables consist of two big happenings for Stefan Löfvén as a political leader. The first variable “from party leader in opposition to prime minister” tells us how his reasoning is affected by becoming prime minster. The second variable “the increasing amount of asylum applications” tells us how his reasoning is affected by an increasing amount of filed asylum applications. These two independent variables create the following two précised research questions: - How has the mediated reasoning, its theses and arguments, coming from Stefan Löfvén been affected by going from being “only” a party leader in opposition to becoming the country’s prime minister? - How has the mediated reasoning, its theses and arguments, coming from Stefan Löfvén been affected by the increasing amount of asylum applications? The result of the study shows that both independent variables and the happenings characterizing them has affected the generally mediated image and reasoning coming from Stefan Löfvén in the subject of migration and refugee policy. The results also shows that the “subject” of migration – and refugee policy is a bit more complex and two sub-categories besides the more general subject were identified and the mediated reasoning in these were in some cases affected in a different way.

Abstract The aim of this work was to formulate separation process models with both predictive capabilities and robust solution strategies. Although all separation process models should have predictive capabilities, the current literature still has multiple applications in which predictive models having the combination of a clear phenomenon base and robust solving strategy are not available. The separation process models investigated in this work were liquid-liquid phase separation and membrane separation models. The robust solving of a liquid-liquid phase separation model typically demands the solution of a phase stability analysis problem. In addition, predicting the liquid-liquid phase compositions reliably depends on robust phase stability analysis. A phase stability analysis problem has multiple feasible solutions, all of which have to be sought to ensure both the robust solving of the model and predictive process model. Finding all the solutions with a local solving method is difficult and generally inexact. Therefore, the modified bounded homotopy methods, a global solving method, were further developed to solve the problem robustly. Robust solving demanded the application of both variables and homotopy parameter bounding features and the usage of the trivial solution in the solving strategy. This was shown in multiple liquid-liquid equilibrium cases. In the context of membrane separation models, predictive capabilities are achieved with the application of a Maxwell-Stefan based model. With the Maxwell-Stefan approach, multicomponent separation can be predicted based on pure component permeation data alone. On the other hand, the solving of the model demands a robust solving strategy with application-dependent knowledge. These issues were illustrated in the separation of a H2/CO2 mixture with a high-silica MFI zeolite membrane at high pressure and low temperature. Similarly, the prediction of mixture adsorption based on pure component adsorption data alone was successfully demonstrated. In the context of membrane separation models, predictive capabilities are achieved with the application of a Maxwell-Stefan based model. With the Maxwell-Stefan approach, multicomponent separation can be predicted based on pure component permeation data alone. On the other hand, the solving of the model demands a robust solving strategy with application-dependent knowledge. These issues were illustrated in the separation of a H2/CO2 mixture with a high-silica MFI zeolite membrane at high pressure and low temperature. Similarly, the prediction of mixture adsorption based on pure component adsorption data alone was successfully demonstrated. / Tiivistelmä Työn tavoitteena oli muotoilla prosessin käyttäytymisen ennustamiseen kykeneviä erotusprosessimalleja ja niiden ratkaisuun käytettäviä luotettavia strategioita. Vaikka kaikkien erotusprosessimallien tulisi olla ennustavia, on tällä hetkellä useita kohteita, joissa prosessin käyttäytymistä ei voida ennustaa siten, että käytettävissä olisi sekä ilmiöpohjainen malli että ratkaisuun soveltuva luotettava strategia. Tässä työssä erotusprosessimalleista kohteina tarkasteltiin neste-neste-erotuksen ja membraanierotuksen kuvaukseen käytettäviä malleja. Neste-neste-erotusmallien luotettava ratkaisu vaatii yleensä faasistabiilisuusongelman ratkaisua. Lisäksi faasien koostumusten luotettava ennustaminen pohjautuu faasistabiilisuusanalyysiin. Faasistabiilisuusongelmalla on useita mahdollisia ratkaisuja, jotka kaikki tulee löytää, jotta voitaisiin varmistaa luotettava mallin ratkaisu sekä prosessimallin ennustuskyvyn säilyminen. Kaikkien ratkaisujen löytäminen on sekä vaikeaa että epätarkkaa paikallisesti konvergoituvilla ratkaisumenetelmillä. Tämän vuoksi globaaleihin ratkaisumenetelmiin kuuluvia modifioituja rajoitettuja homotopiamenetelmiä kehitettiin edelleen, jotta faasistabiilisuusongelma saataisiin ratkaistua luotettavasti. Ratkaisun luotettavuus vaati sekä muuttujien että homotopiaparametrin rajoittamista ja ongelman triviaalin ratkaisun käyttöä ratkaisustrategiassa. Tämä käyttäytyminen todennettiin useissa neste-nestetasa-painoa kuvaavissa esimerkeissä. Membraanierotusta tarkasteltaessa ennustava malli voidaan muotoilla käyttämällä Maxwell-Stefan pohjaista mallia. Maxwell-Stefan lähestymistavalla voidaan ennustaa monikomponenttiseosten erotusta perustuen puhtaiden komponenttien membraanin läpäisystä saatuun mittausaineistoon. Toisaalta mallin ratkaisu vaatii luotettavan ratkaisustrategian, jossa hyötykäytetään kohteesta riippuvaa tietoa. Näitä kysymyksiä havainnollistettiin H2/CO2 seoksen erotuksessa MFI-zeoliitti-membraanilla korkeassa paineessa. Samoin seosten adsorboitumiskäyttäytymistä ennustettiin onnistuneesti pelkästään puhtaiden komponenttien adsorptiodatan pohjalta. Kokonaisuutena voidaan todeta, että tarkasteltujen erotusprosessimallien ennustavuutta voidaan parantaa yhdistämällä malli, jolla on selkeä ilmiöpohja ja luotettava ratkaisustrategia. Lisäksi mallien käytettävyys erotusprosessien suunnittelussa on parantunut työn tulosten pohjalta.

In den letzten Jahren hat der Europagedanke Stefan Zweigs erneut Interesse geweckt, sowohl in der Forschung als auch in den Medien und in der Politik in einer Zeit, in der Beobachter Parallelen zu der Gegenwart suchen und versuchen einen Zeitgeist der Instabilität und Negativität in Europa und im Westen zu erklären. Zweigs Memoiren Die Welt von Gestern (1942) stellen ein bekanntes, frühes Beispiel eines entwickelten Europagedankens dar, obwohl sein Wert oft debattiert wird. In dieser literaturwissenschaftlichen Arbeit wird der Text derMemoiren und der Europagedanke, der darin ausgedrückt wird, analysiert. Der Fokus der Analyse liegt auf drei Motiven: Der Flucht ins Geistige, dem idealen Habsburger Mythos und dem Sieg in der Niederlage. Zweig benutzt diese Motive, um einen Europagedanken vorzulegen, der kulturelle und geistige Gemeinsamkeiten betont und der auch eine utopische Vision der Konzilianz und Freiheit fördert, die im scharfen Kontrast zu Europas damaligen Zusammenbruch in den 1930er und 40er Jahren steht. Obwohl sich diese Europavision zu Zweigs Lebzeiten als unerreichbar erwies, umfasst Zweigs Europagedanke auch einen moralischen Heroismus, und verspricht seinen Befürwortern, darunter Zweig, eine geistige Permanenz und die Hoffnung auf eine bessere Zukunft. / Stefan Zweigs Europatanke har under senare år blivit föremål för förnyat intresse i såväl akademin som i medier och i politiken i en tid då man sökt historiska paralleller till vår samtid och försökt förklara en tidsanda som kännetecknas av instabilitet och negativitet i Europa och i västvärlden i stort. Zweigs memoarer Die Welt von Gestern (1942) utgör ett välkänt, tidigt exempel på en gedigen reflektion kring Europatanken. Dock är meriterna hos Zweigs Europatanke omdebatterade. Denna litteraturvetenskapliga studie analyserar texten i Zweigs memoarer och den Europatanke som ges uttryck för däri med fokus på tre motiv: den s.k. Flucht ins Geistige, den idealistiska, habsburgska myten, och idén om segern i nederlaget. Zweiganvänder dessa motiv på ett sofistikerat sätt och lägger fram en Europatanke som betonar kulturella och konstnärliga gemensamheter och en utopisk vision som kännetecknas av försonlighet och frihet, och som står i stark kontrast med Europas pågående kollaps på 1930-och 40-talet. Zweigs Europatanke visade sig inte vara genomförbar under Zweigs livstid menden omfattade även en moralisk heroism och utlovade sina anhängare, däribland Zweig själv, ett löfte om intellektuell och andlig permanens. / Stefan Zweig’s idea of European unity has in recent years received renewed interest. This is true not just in academia, but also in media and politics, as observers have sought parallels to our own present day and to explain a Zeitgeist of instability and negativity in Europe and the Western world. Zweig’s memoirs Die Welt von Gestern (1942) provide a famous early example of an articulated reflection on European unity, however, its merits are often debated. This literary study analyses the text of Zweig’s memoirs and the idea of European unity expressed therein with a focus on three motifs: the Flucht ins Geistige, the idealistic Habsburg mythos, and the “victory in defeat”. Zweig employs these motifs in sophisticated ways to present an idea of European unity which emphasises cultural and artistic commonalities, a utopian vision of magnanimity and freedom in sharp contrast to Europe’s ongoing collapse in the 1930s and 40s and finally one which, although unattainable in Zweig’s lifetime, embodies a moral heroism and the promise of permanence for its supporters, Zweig among them.

Optimal control (motion planning) of the free interface in classical two-phase Stefan problems is considered. The evolution of the free interface is modeled by a level set function. The first-order optimality system is derived on a formal basis. It provides gradient information based on the adjoint temperature and adjoint level set function. Suitable discretization schemes for the forward and adjoint systems are described. Numerical examples verify the correctness and flexibility of the proposed scheme.:1 Introduction 2 Model Equations 3 The Optimal Control Problem and Optimality Conditions 4 Discretization of the Forward and Adjoint Systems 5 Numerical Results 6 Discussion and Conclusion A Formal Derivation of the Optimality Conditions B Transport Theorems and Shape Calculus

Syftet med undersökningen är att analysera och jämföra Carl XVI Gustafs och Stefan Löfvens tal till nationen angående covid-19 pandemin. De retoriska dragen jag har valt att grunda min undersökning på är ethos, pathos och logos, dispositio samt topikerna kausalitet och definition. De retoriska medlen används för att visa hur de används i en retorisk krissituation och vilka likheter eller skillnader det finns mellan talarna.            Resultatet visar att både Löfven och Carl Gustaf samspelar med ethos, pathos och logos. Skillnaden på dispositionen mellan talarna är att Löfven avviker från Renbergs standardposition medan Carl Gustaf följer den. Definitions- och kausalitetstopiker används av båda talare för att framställa logos och pathos och beskriva orsak och konsekvenser samt definiera vad de egentligen pratar om.            Slutsatsen utifrån resultatet visar att Löfven använder sig mest av pathos och logos medan Carl Gustaf fokuserar mest på ethos och pathos. Undersökningen visar att båda talare använder topiker men att defintionstopiker förekommer oftare än kausalitetstopiker i talen. I dispositionen använder både Löfven och Carl Gustaf två argument tillsammans med ett motargument.

This paper reports a numerical approach for modelling the thermal behavior and heat accumulation/liberation of sustainable cementitious composites made with Recycled Brick Aggregates (RBAs) employed as carriers for Phase-Change Materials (PCMs). In the framework of the further development of the fixed grid modelling method, classically employed for solving the well-known Stefan problem, an enthalpy-based approach and an apparent calorific capacity method have been proposed and validated. More specifically, the results of an experimental program, following an advanced incorporation and immobilization technique, developed at the Institut für Werkstoffe im Bauwesen for investigating the thermal responses of various combinations of PCM-RBAs, have been considered as the benchmark to calibrate/validate the numerical results. Promising numerical results have been obtained, and temperature simulations showed good agreement with the experimental data of the analyzed mixtures.

Les gaz issus de la combustion des énergies fossiles dans les centrales électriques contiennent une grande variété de polluants tels que les gaz-acides et ne peuvent être rejetés directement dans l'atmosphère. Ces polluants gazeux doivent être traités par des méthodes de captage en post combustion dans des colonnes d'absorption utilisant des solvants chimiques. L'objectif est donc de concevoir une unité d'élimination sélective des gaz-acides tels que CO2, H2S et COS en utilisant des solvants de la famille des alcanolamines. Cette thèse développe dans un premier temps, un modèle de non-équilibre, adapté aux systèmes multiconstituants électrolytiques et réactifs, pour la représentation des colonnes d'absorption réactive. Le modèle comporte des modules pour représenter la thermodynamique en espèces vraies (espèces ioniques et moléculaires), le transfert simultané de masse et de chaleur, et les réactions chimiques. Les équations généralisées de Maxwell-Stefan sont utilisées pour quantifier les interactions multiconstituants lors de la diffusion. Le schéma réactionnel est intégralement pris en compte dans la phase liquide, et les réactions chimiques peuvent être cinétiquement contrôlées ou à l'équilibre chimique instantané. La séparation réactive en régime permanent est ainsi simulée avec une description rigoureuse des phénomènes de réaction-diffusion dans les films diffusionnels. Dans un deuxième temps, une installation pilote de captage du CO2 par une solution aqueuse de diéthanolamine est mise en fluvre pour la validation expérimentale du modèle. La diéthanolamine a une forte réactivité vis-à-vis du CO2; ceci engendre un profil important de concentration du soluté dans la colonne. Le pilote est dédié à la validation de modèle, il est donc équipé de plusieurs unités d'échantillonnage gaz et liquide à différentes hauteurs de garnissage. Les profils longitudinaux de la concentration du CO2 en gaz et en liquide, de l'humidité absolue et de la température liquide peuvent être établis expérimentalement et être comparés avec ceux provenant de la simulation. L'outil de simulation validé devient alors un outil de prédiction de l'efficacité des unités réelles de captage par l'absorption réactive. / The exhaust gases coming from the combustion of fossil fuels in power plants contain a wide variety of pollutants such as acid gases and can not be discharged directly into the atmosphere. These gaseous pollutants must be treated by postcombustion capture methods in absorption columns using chemical solvents. The objective is then to design a selective removal unit of acid-gases such as CO2, H2S and COS by using solvents of the alkanolamine family. This thesis develops as the first step, a non-equilibrium model, adapted to multicomponent electrolytic and reactive systems, for the representation of reactive absorption columns. The model includes modules to represent the thermodynamics on the basis of true species (ionic and molecular species), the simultaneous heat and mass transfer, and the chemical reactions. The generalized equations of Maxwell-Stefan are used to take into account the multicomponent interactions during diffusion. The reaction scheme is fully included in the liquid phase, and the chemical reactions can be kinetically controlled or at instantaneous equilibrium. The reactive separation at steady-state conditions is then simulated with a rigorous description of the reaction-diffusion phenomena in diffusional films. In the second step, a pilot plant of CO2 capture with an aqueous solution of diethanolamine is implemented for experimental validation of the model. Diethanolamine has high reactivity with respect to CO2; this generates an important concentration profile of solute in the column. The pilot plant is dedicated to model validation; it is equipped with several gas and liquid sampling units at different heights of packing. The longitudinal profiles of the gas and liquid CO2 concentration, the absolute humidity and the liquid temperature can be established experimentally and compared with those from the simulation. The validated simulation tool then becomes a tool to predict the effectiveness of real capture units by reactive absorption.