Ce travail présente une évaluation des performances des transistors à effet de champ à base de graphène (GFET) grâce à des simulations électriques des modèles compact dédiés à des applications à haute fréquence. Les transistors à base de graphène sont parmi les nouvelles technologies et sont des candidats prometteurs pour de futures applications à hautes performances dans le cadre du plan d’action « au-delà du transistor CMOS ». Dans ce contexte, cette thèse présente une évaluation complète des transistors à base de graphène tant au niveau du dispositif que du circuit grâce au développement de modèles compacts précis pour des GFETs, de l’analyse de la fiabilité, en étudiant les mécanismes critiques de dégradation des GFETs, et de la conception des architectures de circuits basés sur des GFETs.Dans cette thèse nous présentons, à l’aide de certaines notions bien particulières de la physique, un modèle compact grand signal des transistors FET à double grille à base de graphène monocouche. Ainsi, en y incluant une description précise des capacités de grille et de l’environnement électromagnétique (EM), ce travail étend également les aptitudes de ce modèle à la simulation RF. Sa précision est évaluée en le comparant à la fois avec un modèle numérique et avec des mesures de différentes technologies GFET. Par extension, un modèle grand signal pour les transistors FET à double grille à base de graphène bicouche est présenté. Ce modèle considère la modélisation de l’ouverture et de la modulation de la bande interdite (bandgap) dues à la polarisation de la grille. La polyvalence et l’applicabilité de ces modèles compacts des GFETs monocouches et bicouches ont été évalués en étudiant les GFETs avec des altérations structurelles.Les aptitudes du modèle compact sont encore étendues en incluant des lois de vieillissement qui décrivent le piégeage de charges et la génération d’états d’interface qui sont responsables de la dégradation induite par les contraintes de polarisation. Enfin, pour évaluer les aptitudes du modèle compact grand signal développé, il a été implémenté au niveau de différents circuits afin de prédire les performances par simulations. Les trois architectures de circuits utilisées étaient un amplificateur triple mode, un circuit amplificateur et une architecture de circuit « balun ». / This work presents an evaluation of the performances of graphene-based Field-Effect Transistors (GFETs) through electrical compact model simulation for high-frequency applications. Graphene-based transistors are one of the novel technologies and promising candidates for future high performance applications in the beyond CMOS roadmap. In that context, this thesis presents a comprehensive evaluation of graphene FETs at both device and circuit level through development of accurate compact models for GFETs, reliability analysis by studying critical degradation mechanisms of GFETs and design of GFET-based circuit architectures.In this thesis, an accurate physics-based large-signal compact model for dual-gate monolayer graphene FET is presented. This work also extends the model capabilities to RF simulation by including an accurate description of the gate capacitances and the electro-magnetic environment. The accuracy of the developed compact model is assessed by comparison with a numerical model and with measurements from different GFET technologies.In continuation, an accurate large-signal model for dual-gate bilayer GFETs is presented. As a key modeling feature, the opening and modulation of an energy bandgap through gate biasing is included to the model. The versatility and applicability of the monolayer and bilayer GFET compact models are assessed by studying GFETs with structural alterations.The compact model capabilities are further extended by including aging laws describing the charge trapping and the interface state generation responsible for bias-stress induced degradation.Lastly, the developed large-signal compact model has been used along with EM simulations at circuit level for further assessment of its capabilities in the prediction of the performances of three circuit architectures: a triple-mode amplifier, an amplifier circuit and a balun circuit architecture.

Let $T$ be a bounded disjointness preserving linear operator from $C_0(X)$ into $C_0(Y)$, where $X$ and $Y$ are locally compact Hausdorff spaces. We give several equivalent conditions for $T$ to be compact; they are: $T$ is weakly compact; $T$ is completely continuous; $T= sum_n delta_{x_n} otimes h_n$ for a sequence of distinct points ${x_n}_n$ in $X$ and a norm null mutually disjoint sequence ${h_n}_n$ in $C_0(Y)$. The structure of a graph with countably many vertices associated to such a compact operator $T$ gives rise to a new complete description of the spectrum of $T$. In particular, we show that a nonzero complex number $la$ is an eigenvalue of $T$ if and only if $lambda^k= h_1(x_k) h_2(x_1) cdots h_k(x_{k-1})$ for some positive integer $k$. We also give a decomposition of compact disjointness preserving operators $T$ from $C_0(X,E)$ into $C_0(Y,F)$, where $X$ and $Y$ are locally compact Hausdorff spaces, $E$ and $F$ are Banach spaces. That is, $T= sum_n de_{x_n} otimes h_n$ for a sequence of distinct points ${x_n}_n$ in $X$ and a norm null mutually disjoint sequence ${h_n}_n$, where $h_n: Y o B(E,F)$ is continuous and vanishes at infinity in the uniform operator topology and $h_n(y)$ is compact for each $y$ in $Y$. For completely continuous disjointness preserving linear operators, we get a similar decomposition. More precisely, completely continuous disjointness preserving operators $T$ have a countable sum decomposition of completely continuous atoms $de_{x_n} otimes h_n$, where $h_n: Y o B(E,F)$ is continuous, vanishes at infinity in the strong operator topology and $h_n$ is uniformly completely continuous. In case of weakly compact disjointness preserving linear operators, $T$ have a countable sum decomposition of weakly compact atoms whenever the Banach space $E$ is separable. A counterexample is given whenever $E$ in nonseparable.

In this thesis, we aim to study derivations from l^1(Z+) to its dual, l^\infty(Z+). We first characterize them as certain closed subspace of l^1(Z+). Then we present a necessary and sufficient condition, due to M. J. Heath, to make a bounded derivation on l^1(Z+) into l^\infty(Z+), a compact linear operator. After that base on the work in [6], we study weakly compact derivations from l^1(Z+) to its dual. We introduce T-sets and TF-sets and then state their relation with weakly compact operators on l^1(Z+). These results are originally due to Y. Choi and M. J. Heath, but we give simpler proofs. Finally, we will study certain classes of derivations from L^1(R+) to L^\infty(R+), and give an elementary proof that they are always mapped into C0(R+).

American automobile manufacturers experienced a bitter-sweet time during the 1980s. On one hand, they gained support from the government to prevent mass imports of small cars from Japan; while on the other hand, they still lost market share to their Japanese counterparts and ever since then, they have been facing fierce competition from the Japanese auto-makers. To better understand today s competition in the automobile market, it is crucial to study the industry in the 1980s when the scope of the market began to change. This paper focuses mainly on studying the compact car market in the 1980s, which was the primary competition field then. It first briefly introduces the rise of Japanese automobile industry, and the economic background of the decade. Then it examines the U.S. compact car segment in detail, and finally constructs a model to explain consumer decisions on purchasing compact cars. In the end, it gives suggestion to the Big Three companies according to the findings presented in this paper.

Thesis (Ph.D.)--York University, [2004]. Graduate Programme in [Mathematics]. / Typescript. Includes bibliographical references (leaves 163-166). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ99158

In recent years, the field of evolutionary dynamic optimisation has seen significant increase in scientific developments and contributions. This is as a result of its relevance in solving academic and real-world problems. Several techniques such as hyper-mutation, hyper-learning, hyper-selection, change detection and many more have been developed specifically for solving dynamic optimisation problems. However, the complex structure of algorithms employing these techniques make them unsuitable for real-world, real-time dynamic optimisation problem using embedded systems with limited memory. The work presented in this thesis focuses on a compact approach as an alternative to population based optimisation algorithm, suitable for solving real-time dynamic optimisation problems. Specifically, a novel compact dynamic optimisation algorithm suitable for embedded systems with limited memory is presented. Three novel dynamic approaches that augment and enhance the evolving properties of the compact genetic algorithm in dynamic environments are introduced. These are 1.) change detection scheme that measures the degree of dynamic change 2.) mutation schemes whereby the mutation rates is directly linked to the detected degree of change and 3.) change trend scheme the monitors change pattern exhibited by the system. The novel compact dynamic optimization algorithm outlined was applied to two differing dynamic optimization problems. This work evaluates the algorithm in the context of tuning a controller for a physical target system in a dynamic environment and solving a dynamic optimization problem using an artificial dynamic environment generator. The novel compact dynamic optimisation algorithm was compared to some existing dynamic optimisation techniques. Through a series of experiments, it was shown that maintaining diversity at a population level is more efficient than diversity at an individual level. Among the five variants of the novel compact dynamic optimization algorithm, the third variant showed the best performance in terms of response to dynamic changes and solution quality. Furthermore, it was demonstrated that information transfer based on dynamic change patterns can effectively minimize the exploration/exploitation dilemma in a dynamic environment.

Dans cette thèse, nous étudions les décompositions arborescentes qui satisfont certaines contraintes supplémentaires et nous proposons des algorithmes pour les calculer dans certaines classes de graphes. Finalement, nous résolvons des problèmes liés au routage en utilisant ces décompositions ainsi que des propriétés structurelles des graphes. Cette thèse est divisée en deux parties. Dans la première partie, nous étudions les décompositions arborescentes satisfaisant des propriétés spécifiques. Dans le Chapitre 2, nous étudions les décompositions de taille minimum, c’est-À-Dire avec un nombre minimum de sacs. Etant donné une entier k 4 fixé, nous prouvons que le problème de calculer une décomposition arborescente de largeur au plus k et de taille minimum est NP-Complet dans les graphes de largeur arborescente au plus 4. Nous décrivons ensuite des algorithmes qui calculent des décompositions de taille minimum dans certaines classes de graphes de largeur arborescente au plus 3. Ces résultats ont été présentés au workshop international ICGT 2014. Dans le Chapitre 3, nous étudions la cordalité des graphes et nous introduisons la notion de k-Good décomposition arborescente. Nous étudions tout d’abord les jeux de Gendarmes et Voleur dans les graphes sans long cycle induit. Notre résultat principal est un algorithme polynomial qui, étant donné un graphe G, soit trouve un cycle induit de longueur au moins k+1, ou calcule une k-Good décomposition de G. Ces résultats ont été publiés à la conférence internationale ICALP’12 et dans la revue internationale Algorithmica. Dans la seconde partie de la thèse, nous nous concentrons sur des problèmes de routage. / A tree decomposition of a graph is a way to represent it as a tree by preserving some connectivity properties of the initial graph. Tree decompositions have been widely studied for their algorithmic applications, in particular using dynamic programming approach. In this thesis, we study tree decompositions satisfying various constraints and design algorithms to compute them in some graph classes. We then use tree decompositions or specific graph properties to solve several problems related to routing. The thesis is divided into two parts. In the first part, we study tree decompositions satisfying some properties. In Chapter 2, we investigate minimum size tree decompositions, i.e., with minimum number of bags. Given a fixed k 4, we prove it is NP-Hard to compute a minimum size decomposition with width at most k in the class of graphs with treewidth at least 4. We design polynomial time algorithms to compute minimum size tree decompositions in some classes of graphs with treewidth at most 3 (including trees). Part of these results will be presented in ICGT 2014. In Chapter 3, we study the chordality (longest induced cycle) of graphs and introduce the notion of good tree decomposition (where each bag must satisfy some particular structure). Precisely, we study the Cops and Robber games in graphs with no long induced cycles. Our main result is the design of a polynomial-Time algorithm that either returns an induced cycle of length at least k+1 of a graph G or compute a k-Good tree decomposition of G. These results have been published in ICALP 2012 and Algorithmica. In the second part of the thesis, we focus on routing problems.

Les novæ naines permettent, depuis presque 50 ans maintenant, de tester les modèles d’accrétion. Ces systèmes montrent des éruptions en optique d’une durée de l’ordre de la semaine avec des temps de récurrence de l’ordre du mois. Ces éruptions sont communément attribuées à une instabilité thermo-visqueuse au sein du disque d’accrétion entourant la naine blanche. Les temps caractéristiques de ces éruptions posent de fortes contraintes sur les mécanismes de transport de moment cinétique pilotant l’accrétion dans le disque, mécanismes qui constituent l’objet de cette thèse. Il est souvent admis que l’instabilité magnéto-rotationnelle (MRI) est responsable du transport de moment cinétique via la turbulence qu’elle produit. Cependant, je montre ici, à l’aide de simulations locales de disque d’accrétion avec transfert radiatif, que le transport turbulent produit par la MRI ne permet pas de reproduire les courbes de lumière. En quiescence, où le disque est peu ionisé, il est même peu probable que de la turbulence MRI puisse survivre. Un des résultats majeurs de cette thèse est d’avoir mis en lumière que la MRI ne participe pas qu’au transport turbulent mais peut également lancer des vents magnéto-hydrodynamiques (MHD) qui transportent également du moment cinétique, voire dominent le transport dans l’état quiescent. Ces vents MHD induisent un couple magnétique de surface sur le disque et ne peuvent être réduits à une turbulence effective, en partie car ceux-ci ne déposent pas d’énergie thermique localement mais en emportent contrairement au transport turbulent. Nous avons inclus le transport de moment cinétique dû au couple du vent MHD dans un modèle d’instabilité de disque, modèle classiquement utilisé pour reproduire les éruptions de novæ naines. Avec ce nouveau modèle, nous avons montré qu’il est possible de reproduire les courbes de lumière des éruptions de novæ naines, en utilisant un champ magnétique à la surface de la naine blanche compatible avec ce qui est attendu. C’est la première fois que les éruptions de novæ naines sont modélisées avec succès en utilisant des prescriptions pour le transport de moment cinétique basées sur des simulations MHD et non sur les observations. / Dwarf novæ have been used for almost 50 years now as a test for the theory of accretion. These systems exhibit eruptions in optical light lasting approximately a week with a recurrence time scale of a month. Eruptions are thought to be due to a thermal-viscous instability in the accretion disk surrounding the white dwarf. This model has long been known to put constraints on the mechanisms transporting angular momentum in the disk, which will be the subject of this thesis. Traditionally, transport is presumed to be turbulent where turbulence is due to the magneto-rotational instability (MRI). However, I show here, using local simulations of accretion disks with radiative transfer that there exists a discrepancy between observations and light curves obtained with MRI turbulence only. In quiescence, where the disk is poorly ionised, it is very unlikely that MRI can even survive. One of the key results of this thesis is that MRI do not participate to turbulent angular momentum transport only, but is also able to drive MHD outflows which extract angular momentum very efficiently, especially in quiescence. Wind-driven transport is, by nature, very different from turbulent transport, it induces a surface-torque on the disk and do not deposit thermal energy locally but extract energy from the disk instead. We included MHD wind-driven angular momentum transport in a disk instability model, model which is usually used to reproduce light curves of dwarf novæ. Using this new model, we were able to retrieve light curves looking alike observations, with a magnetic field consistent with what is expected from the dipolar magnetic field of a white dwarf. It is the first time that eruptions of dwarf novæ are modeled with success using prescriptions for angular momentum transport derived from first principles instead of ad hoc parameters.

In Sweden and around the world, there has been a pandemic during the years 2020 and 2021. People who have been working in offices have, to a large extent, been encouraged to work from their homes and as a result, it has been noticed that working from home has a possibility to continue after thepandemic is over. With this in mind, the question how housing and working conditions should bedeveloped for this to be achievable in the long run is raised. The project has been carried out with the aim of investigating how housing can be designed to enable working from home and be a valid option even after the pandemic. The study has been carried out in four steps: • A literary study of working from home, different types of offices and housing development has been carried out. This was to get a clear picture of what is required of a workplace to be able to get good work result and how homes can be designed so working from home does not disturb the home life. • A survey to find out how working from home has been perceived by people during the pandemic and what would enable them to work from home in the future. • A site analysis, the site that is projected is located in Stockholm and will function as an interaction with the rest of the area. The area that has been chosen is Värtahamnen, which with an already planned block, is the basis for the location and design of the apartment building. • A design phase. Research by design shows what an apartment building adapted for home based work can look like. Three target groups were selected: singles, cohabitants and families The results of the study show that a majority of people are willing to have their working situation as a combination of working from home and going to an office. As the social part of pandemic and working from home has made people feel too isolated, they want to be able to get social interaction during the work week. After collecting information about, different types offices, housing design and Värtahamnens planned conditions, a program for an apartment building has been developed. Four apartments with different living spaces were chosen to show different conditions people have had when working from home. - 30 sqm Singel- 25 sqm Singel- 56 sqm Cohabitant- 83 sqm Family The building was developed with the aim that working from home should be a possible alternative for the residents. The neighborhood and the area should also be able to provide for the needs that theresidents have, within a reasonable distance. As the information from the questionnaire and the literature study can be interpreted differently depending on who is studying it, the way the building and apartments are developed will not be definitive but will work as a proposal from those who conducted the study, this makes the answers to the report one of several possibilities. / I Sverige och i världen har det under åren 2020 och 2021 pågått en pandemi. Personer som jobbat på kontor har i stort utsträckning blivit uppmuntrade att jobba hemifrån och som effekt ser man möjligheten med hemarbete även efter pandemin. Med detta i åtanke uppstår frågan hur bostäder och arbetsförhållanden ska utvecklas för att det ska vara görbart i längden.Examensarbetet har utförts i syfte att undersöka hur bostäder kan utformas för att underlätta hemarbete och vara en möjlighet även efter pandemin. Studien har utformats i fyra olika steg: En litteraturstudie, där en fördjupning kring hemarbete, kontor och bostadsutveckling har utförts. Detta för att få en tydlig bild över vad som krävs av en arbetsplats för att få ett bra arbetsresultat och hur bostäder kan utformas för att få en bra samvaro tillsammans med arbete. • En enkätundersökning för att få reda på hur hemarbetet har uppfattats av människor under pandemin och vad som skulle underlätta deras hemarbete i fortsättningen. • En platsanalys. Områdets som är valt är placerat i Värtahamnen, Stockholm. Området har redan ett planerat kvarter och står som grund för placeringen samt utformning av flerbostadshuset. • En gestaltning. Genom research by design visas det hur ett flerbostadshus anpassat för hemarbete kan se ut. Tre målgrupper valdes ut: ensamstående, sambo och familj. Resultatet av förundersökningen visar att en majoritet kan tänka sig att jobba med en kombination av hemarbete och kontor. Då den sociala delen i hemarbetet har gjort att människor känner sig för isolerade vill man ha en möjlighet att få socialt utbyte under arbetsveckan. Efter insamlad information om hemarbete, kontorsformer, bostadsutformning och Värtahamnens förutsättningar har förslagshandlingar till ett flerbostadshus för hemarbete tagits fram. Resultatet blev fyra lägenheter. - 30 kvm Singellägenhet- 35 kvm Singellägenhet- 56 kvm Sambo- 83 kvm Familj Byggnaden är framtagen i det syfte att hemarbete ska vara ett möjligt alternativ för de boende.Utformningen av lägenheterna är gjord så att hemarbete och samvaron i hemmet inte ska påverka varandra negativ. Som komplement till lägenheterna utformades också två kontorsvarianter, en privat för de boende och allmän. Detta gör att de boende kan arbete på tre sociala nivåer. Kvarteret och området ska erbjuda de vardagliga behov som de boende har inom rimliga avstånd. Då informationen från enkäten och litteraturstudien kan tolkas olika beroende på vem det är som tar del av den blir svaret på undersökningen inte definitiv utan ett förslag från dem som har genomfört undersökningen, detta gör att svaren på rapporten blir en av flera möjligheter.

In this essay we give an elementary introduction to topology so that we can prove Tychonoff’s theorem, and also its equivalence with the axiom of choice. / Denna uppsats tillhandahåller en grundläggande introduktion till topologi för att sedan bevisa Tychonoff’s theorem, samt dess ekvivalens med urvalsaxiomet.