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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.
561

Graphène et fluorographène par exfoliation de graphite fluoré : applications électrochimiques et propriétés de surface / Graphene and fluorographene by exfoliation of graphite fluorides : electrochemichal applications and surface properties

Herraiz, Michael 06 November 2018 (has links)
Sa conductivité électronique ou encore sa transparence optique sont autant de propriétés physico-chimiques singulières du graphène qui expliquent le nombre accru de méthodes d’exfoliation de précurseurs graphitiques développées pour l’obtention de ce matériau. Pour palier à l’utilisation d’un oxyde de graphite/graphène caractérisé par une chimie de surface mal maitrisée, des graphites fluorés, de cristallinité mais aussi de concentration en fluor variables, ont été préparés par fluoration de graphite sous fluor moléculaire pur après optimisation des paramètres. Les précurseurs, que ce soit par fluoration dynamique ou statique, ainsi obtenus ont été caractérisés finement : diffraction des rayons X, spectroscopies IR et Raman et leur texture sondée par Microscopie Electronique à Balayage et à Transmission. Suite à cela, trois méthodes d’exfoliation ont été mises en place, basées sur des mécanismes différents : i) une exfoliation par choc thermique, déjà connue mais dont les mécanismes de décomposition ont été affinés dans cette étude, ii) une exfoliation en voie liquide, avec l’utilisation pour la première fois d’un graphite fluoré pour la synthèse de graphène fluoré multi feuillets par voie électrochimique pulsée, et enfin iii) une méthode originale, peu conventionnelle, basée sur l’interaction laser femtoseconde/graphite hautement fluoré pour induire des mécanismes de réduction contrôlée, et surtout d’exfoliation de la matrice. Ces méthodes ont permis de mettre en évidence l’intérêt de la présence de fluor dans la course actuelle pour la synthèse de graphène, et ont montré l’obtention de matériaux graphéniques,possédant une fonction résiduelle fluorée intéressante pour certaines applications. / Its electronic conductivity or its optical transparency are unequaled physicochemicalproperties of graphene which explain the increased number of exfoliation methods based ongraphitic precursors to obtain this material. To overcome the use of a graphite/graphene oxidecharacterized by a poorly controlled surface chemistry, graphite fluorides, with variablecrystallinity and also fluorine concentration, were prepared by fluorination of graphite under puremolecular fluorine atmosphere after optimization of the process parameters. The obtainedprecursors, whether by dynamic or static fluorination, were characterized : X-Ray diffraction, FTIRand Raman spectroscopies for the structure, and their texture probed by Scanning andTransmission Electron Microscopy. After that, three methods of exfoliation were developed, basedon different mechanisms: i) a thermal shock, already known but decomposition mechanisms wererefined in this study, ii) an exfoliation within liquid medium by pulsed electrochemical treatment,using for the first time a fluorinated graphite for the synthesis of few-layered fluorinated grapheneand finally iii) an unconventional method, based on the interaction between femtosecond laser andhighly fluorinated graphite to induce mechanisms like controlled reduction, and especially for thisstudy exfoliation of the matrix. These methods have permit to highlight the interest of fluorine inthe current race for the synthesis of graphene, and have shown the production of graphenematerials, having an interesting fluorinated residual functionalization for some applications.
562

Propagation des ondes acoustiques dans une multicouche composée de couches viscoélastiques liquides, solides et poreuses / Acoustic wave propagation in a multilayer composed of fluid, solid, and porous viscoelastic layers

Matta, Sandrine 07 December 2018 (has links)
Cette thèse propose un formalisme général pour modéliser la propagation des ondes acoustiques dans une multicouche composée de toute combinaison de couches liquides, solides élastiques isotropes et poro-élastiques isotropes, la méthode ayant la flexibilité d'être développée pour inclure d'autres natures de couches. Dans un premier lieu, un algorithme stable est développé, basé sur l'approche récursive de la matrice de rigidité, pour modéliser la propagation d'une onde plane incidente sur la multicouche en fonction de son angle d'incidence et de sa fréquence. Cet algorithme fusionne de manière récursive les matrices de rigidité des couches individuelles de la structure en une matrice de rigidité totale et permet ensuite le calcul des coefficients de réflexion et de transmission, ainsi que les composantes de déplacement et de contrainte à l'intérieur de la multicouche pour chaque direction d'incidence des ondes planes. Deuxièmement, pour modéliser la propagation d'un faisceau délimité d'ondes incidentes, la technique du spectre angulaire est utilisée, basée sur la décomposition de ce faisceau en un spectre d'ondes planes se propageant dans des directions différentes. Par la suite, le faisceau d'onde réfléchi dans le milieu d'incidence et le faisceau d'onde transmis dans le milieu de transmission, ainsi que la distribution des champs (composantes de déplacement et de contrainte) à l'intérieur de la multicouche sont obtenus en superposant la contribution de toutes les ondes planes se propageant dans les différentes directions. Comme application numérique, une tri-couche solide-poreuse-solide immergée dans l'eau est simulée. La réflexion et la transmission qui en résultent, ainsi que les composantes de déplacement et de contrainte dans la multicouche, correspondants à l’onde plane incidente et au faisceau limité incident, révèlent la stabilité du procédé et la continuité des déplacements et des contraintes aux interfaces. / This thesis proposes a general formalism to model the acoustic wave propagation in a multilayer consisting of any combination of fluid, isotropic elastic solid, and isotropic poroelastic layers, the method having the flexibility to be extended to include other layer-natures. At a first stage, a stable algorithm is developed, based on the recursive stiffness matrix approach, to model the propagation of a plane wave incident on the multilayer as a function of its incidence angle and frequency. This algorithm merges recursively the structureindividual layers stiffness matrices into one total stiffness matrix and allows then the calculation of the reflection and transmission coefficients, as well as the displacement and stress components inside the multilayer for every incident plane wave direction. Secondly, to model the propagation of a bounded incident wave beam, the angular spectrum technique is used which is based on the decomposition of this beam into a spectrum of plane waves traveling in different directions. The corresponding reflected wave beam in the incidence medium, and the transmitted wave beam in the transmission medium, as well as the fields distributions (displacement and stress components) inside the multilayer are obtained by summing the contribution of all the plane waves traveling in different directions. As a numerical application, a three-layered solid-porous-solid structure immersed in water is simulated. The resulting reflection and transmission as well as the displacement and stress components in the multilayer corresponding to both, the incident plane wave in different directions and the incident bounded beam reveal the stability of the method and the continuity of the displacements and stresses at the interfaces.
563

Processing, structure property relationships in polymer layer double hydroxide multifunctional nanocomposites

Ogbomo, Sunny Minister 08 1900 (has links)
Dan Beaty (1937-2002) was a prolific composer, pianist, researcher, educator, and writer. His large compositional output included chamber works, choral works, songs, orchestral pieces, electronic music, and keyboard works. Beaty was well versed in traditional Western music as well as the more avant-garde and perplexing idioms of the twentieth century. Beaty's compositions reflect the many fascinating, if not always popular, musical trends of his time. His music encompasses styles from serial to jazz, shows compositional influences from Arnold Schoenberg to Indonesian music, and demonstrates thought-provoking and highly intellectual craftsmanship. This document explores several of Beaty's songs through a discussion of the composer's life and compositional process. Songs included in this document are Three Weeks Songs, October, November, A Sappho Lyric, Love Song, That Night When Joy Began, and War Lyrics. This document was written to accompany the author's DMA Lecture-Recital at the University of North Texas. Unfortunately, Beaty's vocal music was never published and is mostly unknown. One goal of the project was to initiate interest in Beaty's songs. Through this document, Lecture-Recital, and additional performances, considerable strides have been made to bring Beaty's songs to new audiences throughout the United States. In addition, the author has received permission from the Beaty family to publish Dan Beaty's songs.
564

Elastomer based composites filled with layered fillers and ionic liquids / Composites élastomères chargés avec des charges lamellaires et des liquides ioniques

Laskowska, Anna 02 December 2014 (has links)
Cette thèse se concentre sur la préparation et l'étude des composites élastomères chargés avec des particules lamellaires et des liquides ioniques. Ces composites sont caractérisés par des propriétés mécaniques améliorées, une diminution du gonflement par les solvants, une faible perméabilité aux gaz ainsi que par une amélioration de la conductivité ionique. Les propriétés de structure et de surface différentes des charges lamellaires, telles que le rapport d'aspect des particules, la surface spécifique et l'activité de surface ont été analysées comme les facteurs impactant le renforcement du caoutchouc nitrile (NBR) et du caoutchouc nitrile carboxylé (XNBR). Une attention particulière a été portée aux systèmes XNBR contenant des hydroxydes doubles lamellaires (MgAI-HDL), qui varient en fonction du rapport Mg / Al et de morphologie de particules. L'application simultanée de MgAI-HDL en tant que charge et en tant qu'agent de réticulation dans XNBR ne fournit pas uniquement un produit écologique sans oxyde de zinc mais également un composite élastomère ionique avec de meilleures propriétés mécaniques, de barrière et de transparence. Cette thèse considère également les applications potentielles des liquides ioniques en tant qu'additifs multifonctionnels dans les composites élastomères afin d'obtenir une bonne dispersion des charges minérales dans une matrice polymère ainsi qu'une amélioration de la conductivité ionique des matériaux composites. La concentration optimale et le type de liquides ioniques ont été sélectionnés pour obtenir un bon compromis entre les propriétés mécaniques et la conductivité des matériaux composites de caoutchouc / This thesis focused on the preparation and the study of elastomer composites filled with layered fillers with improved mechanical properties, decreased swelling in solvents, increased UV stability and reduced gas permeability. The layered minerals were investigated not only in terms of their use as reinforcing fillers for rubbers but also as crosslinking agents, gas barrier and UV stability enhancers. The layered fillers tested belong to a class of cationic clays (natural and synthetic hectorite), anionic clays (hydrotalcites or magnesium aluminum layered double hydroxides MgAI-LDHs) and graphene-based materials. Different structural and surface properties of layered fillers were investigated as factors impacting the reinforcement of acrylonitrile-butadiene rubber (NBR) and carboxylated acrylonitrile-butadiene rubber (XNBR). Special attention has been devoted to the XNBR systems containing MgAI-LDHs varying in Mg / AI ratios, layers aspect ratios and particles morphologies. It was reported that the simultaneous application of MgAI-LDH as a filler and as a crosslinking agent in XNBR provides not only environmentally friendly, zinc-oxide free product but also ionic elastomer composite with improved mechanical, barrier and transparent properties. This thesis considers also the potential application of imidazolium ionic liquids as dispersing agents in rubber matrix, plasticizers and ionic conductivity enhancers. The optimal concentration and type of ionic liquids were selected for obtaining a good compromise between mechanical and conductivity properties of rubber composites
565

Multi-Stage Cellular Manufacturing System Design under Certain and Uncertain Conditions

Almasarwah, Najat E., MASARWAH January 2020 (has links)
No description available.
566

Sustainable Effects of Technological Innovation on Business Models : A Case Study on AR in the Grocery Industry / Hållbara Effekter av Teknisk Innovation på Affärsmodeller : En fallstudie om AR i dagligvarubranschen

Bolos, Raphael, Grujcic, Vlado January 2023 (has links)
In the growing digitalization of the grocery industry, it is necessary for traditional grocery retailers to adapt their business models to the new digital era. Augmented reality (AR) and other digital tools have proven to have the ability to transform the grocery business, and it is crucial for traditional grocers to act in order to remain competitive. AR technology has been used in a number of different retail industries, such as the clothing industry and the furniture industry. The purpose of this paper is to investigate how the implementation of AR can affectthe business model of a traditional grocery retailer. A case study has been conducted with a food company in Sweden, at the request of our commissioner working in the field of digitalization of different industries. Furthermore, the Triple Layered Business Model Canvas, has been used as a tool to identify the current business model, and to give suggestions on how the future business model can look like, after an implementation of AR. The results show a change on the canvas of the three different sustainability factors, but also an identification of the different challenges a grocery retailer can face. The results show an increased collaboration with external partners and the implementation of new activities for the case company. Furthermore, the study emphasizes the impact on distribution and suppliers, as well as the social consequences. Preparation for the technology is further presented in the study.  The study contributes to increased knowledge of business model change in the grocery industry. Previous research on the impact of AR on the grocery industry has been confirmed, and this paper contributes new research investigating the impact of technological innovations on the business model of traditional grocery retailers. This study also adds knowledge on theuse of the Triple Layered Business Model Canvas as an analytical tool for sustainability and business model change. / I den växande digitaliseringen av livsmedelsbranschen är det nödvändigt för traditionella livsmedelshandlare att anpassa sina affärsmodeller till den nya digitala eran. Förstärkt verklighet (AR) och andra digitala verktyg har visat sig ha förmågan att omvälva livsmedelshandeln, och det är avgörande för traditionella livsmedelshandlare att agera för att behålla sin konkurrenskraft. AR-tekniken har använts inom ett flertal olika industrier inom detaljhandeln, såsom klädindustrin och möbelindustrin. Den här uppsatsens syfte är att undersöka hur implementeringen av AR kan påverka en traditionell livsmedelshandlarnas affärsmodell. En fallstudie har gjorts på ett livsmedelsföretag i Sverige, på begäran av vår kommissarie som arbetar inom digitalisering av olika branscher. Vidare har Triple Layered Business Model Canvas använts som ett verktyg för att identifiera den nuvarande affärsmodellen, och för att ge förslag på hur den framtida affärsmodellen kan se ut, efter en implementering av förstärkt verklighet (AR). Resultaten visar en förändring av canvasen med tre olika hållbarhetsfaktorerna, men även en identifiering över de olika utmaningarna en livsmedelshandlare kan stå inför. Resultatet visar ett ökat samarbete med externa partners samt implementering av nya aktiviteter för fallföretaget. Dessutom belyses påverkan på distribution och leverantörer, samt de sociala konsekvenserna. Vidare i studien presenteras även olika relevanta och betydelsefulla förberedelser för en implementation av AR tekniken. Studien bidrar till ökad kunskap inom förändring av affärsmodeller inom livsmedelsindustrin. Tidigare forskning om förstärkt verklighets påverkan på livsmedelsbranschen har bekräftats, och denna uppsats bidrar med ny forskning som undersöker effekten av teknologiska innovationer på affärsmodellen för traditionella livsmedelshandlare. Denna studie tillför även kunskap om användningen av Triple Layered Business Model Canvas som analysverktyg för hållbarhet och förändring av affärsmodeller.
567

A theoretical framework for interpretation and prediction of magneto-optical measurements

Frilén, Viktor January 2023 (has links)
The interplay of experiments and theory is essential to deepen our understanding of magnetization dynamics. This thesis aims to serve as a bridge between these two aspects by establishing a mathematical framework that enables the computation of optical observable quantities based on theoretical models. The equations are cast in a matrix representation that is well-suited for performing numerical simulations. Additionally, the generality of these methods enables their application to layered media with any geometry, regardless of whether they possess magnetic properties or not. Furthermore, it explores the various perspectives and physical mechanisms involved in magneto-optic measurements to provide the reader with a self consistent introduction to the subject matter. Numerical calculations are presented for bulk Fe, alternating layers of Fe/Au and Ni with a MgO coating and a SiO substrate for different energies, angle of incident and magnetization direction. The results demonstrate the effectiveness of the method in predicting measurable outcomes from theoretical considerations and enables the analysis of optimal experimental configurations. / Samverkan mellan experiment och teori är avgörande för fördjupa vår förståelse av magnetiska system och deras dynamik. Målet med denna uppsats är att etablera en koppling mellan dessa två aspekter genom att formulera ett matematiskt ramverk som möjliggör beräkningar av optiska observerbara storheter baserat på teoretiska modeller. Ekvationerna formuleras med matriser vilket är väl lämpat för att utföra numeriska simuleringar. Dessutom möjliggör metodens generella natur tillämpning på skiktade material av godtycklig geometri, oavsett om de har magnetiska egenskaper eller inte. Vidare utforskar uppsatsen olika perspektiv och fysikaliska mekanismer som är involverade i magneto-optiska mätningar för att ge läsaren en självständig introduktion till ämnet. Numeriska beräkningar presenteras för bulkjärn, växlande lager av Fe/Au och Ni med en MgO-beläggning och ett SiO-substrat för olika energier, infallsvinkel och magnetiseringsriktning. Resultaten visar på metodens förmåga att förutsäga mätbara resultat baserat på teoretiska överväganden och tillåter analys av optimala experimentella uppställningar.
568

Dilution effects of highly concentrated electrolyte with fluorinated solvents on charge/discharge characteristics of Ni-rich layered oxide positive electrode / 高ニッケル層状酸化物正極充放電特性に及ぼす濃厚電解液のフッ素系溶媒希釈効果 / コウニッケル ソウジョウ サンカブツ セイキョク ジュウホウデン トクセイ ニ オヨボス ノウコウ デンカイエキ ノ フッソケイ ヨウバイ キシャク コウカ

曹 子揚, Ziyang Cao 22 March 2020 (has links)
高ニッケル三元系材料は商用のLiCoO2正極より高い容量を有するため、EVsで使用するリチウムイオン電池の正極材料の候補として有望である。本論文に、著者は濃厚電解液とフッ素化溶媒を用いた希釈電解液に着目し、高ニッケル三元系LiNi0.8Co0.1Mn0.1O2(NCM811)の充放電サイクル特性を向上させた。電解液中の溶媒化構造の観点から、濃厚電解液の希釈効果がNCM811の充放電特性に及ぼす影響を詳細に検討した。 / Ni-rich ternary materials have higher capacity than the commercial LiCoO2 positive electrode, and therefore they are promising candidates for the positive electrode material of lithium ion batteries for use in EVs. In this thesis, the author focused on highly concentrated electrolytes and their diluted electrolytes with fluorinated solvents to improve the cycling performance of a Ni-rich ternary LiNi0.8Co0.1Mn0.1O2 (NCM811) for practical application. Dilution effects of the concentrated electrolytes on the charge/discharge properties of NCM811 were discussed in detail from the viewpoint of the solvation structure in the electrolyte. / 博士(工学) / Doctor of Philosophy in Engineering / 同志社大学 / Doshisha University
569

Speaking of Myself: Independence, Self-Representation, and the Speeches of Rudyard Kipling

Wilkes, Jacob M. 25 March 2009 (has links) (PDF)
Rudyard Kipling is a man of immense diversity. He successfully managed to write for over half a century in a variety of genres: short story, travelogue, ballad, personal narrative, and news reporting, to name only a few. While doing so, Kipling readily interacted with a range of subjects and created a multitude of ideas. Likewise, on a personal level, Kipling led an immensely diverse life. He could easily claim four separate continents as home, living variously in India, the United States, England, and South Africa. By profession he was a writer, but as an observer he was so skilled that he learned by heart a variety of professions ranging from street beggar to statesman. Both before and after his life, this variety and complexity has been a subject of debate. Some ignore it, others focus on a particular side of it, but for all it represents an interesting challenge in both studying and classifying Kipling. This thesis seeks to address that challenge by focusing on how Kipling's varying and competing images and ideas work together to assert Kipling's independence. In doing so, this work will look specifically at how Kipling uses multifaceted techniques in his public speeches. In looking at the speeches, the thesis explores three ways in which multiplicity reinforces independence: the combination of privacy and creation, the refashioning of expert detail and self-image, and the fusion of simplistic structure and subtle complexity.
570

[en] BREAKUP OF TWO-LAYER LIQUID FILMS / [pt] QUEBRA DE UM FILME DE LÍQUIDO COMPOSTO POR DUAS CAMADAS

PEDRO HENRIQUE SOUZA CALDERANO 23 August 2021 (has links)
[pt] Filmes finos de líquido estão presentes em uma variedade de sistemas e aplicações. Estamos interessados em filmes compostos por duas camadas, que são comuns no processo de revestimento por cortina. No revestimento por cortina, o líquido cai de uma matriz formando uma cortina formada por um filme fino antes de molhar o substrato em movimento. Um dos limites mais importantes do processo é a ruptura da cortina, que define um limite inferior para a vazão do líquido de revestimento. Consequentemente, este limite inferior da vazão define a espessura mínima viável do filme depositado. Evidências experimentais mostraram que o uso de uma cortina compostas por duas camadas, com uma das camadas sendo mais fina e viscoelástica, pode atrasar a ruptura da cortina para taxas de fluxo mais baixas. A quebra de filmes líquidos de duas camadas, compostas por um líquido newtoniano e um viscoelástico, é estudado por meio da resolução das equações diferenciais que descrevem a evolução da configuração do filme até seu rompimento. O efeito de diferentes parâmetros no tempo de ruptura é determinado. Os resultados mostram o mesmo comportamento observado experimentalmente, a fina camada de líquido viscoelástico retarda o rompimento, estabilizando o filme líquido. / [en] Thin liquid sheets are present in a variety of systems and applications. Here, we are interested in double-layered sheets, which are common in the curtain coating process. In curtain coating, the liquid falls from a die forming a thin curtain before wetting the moving substrate. One of the most important process limits is the curtain breakup, which sets a lower limit for the coating liquid flow rate. Consequently, this flow rate lower limit defines the feasible minimum deposited film thickness. Experimental evidence have shown that using a two-layer curtain, with a viscoelastic thin layer, may delay the curtain breakup to lower flow ratios. The breakup of two-layer liquid sheets, composed of a Newtonian and a viscoelastic liquid, is studied by solving the differential equations that describe the evolution of the liquid sheet configuration until breakup. The effect of different parameters on the breakup time is determined. The results show the same behavior observed experimentally, thin viscoelastic liquid layer delays the breakup, stabilizing the liquid sheet.

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