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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.
91

Corpus aligné bilingue français - russe : le cas de par / Aligned bilingual French - Russian corpus : the case of par

Kataeva, Olga 05 December 2014 (has links)
La thèse "Corpus aligné bilingue français - russe : le cas de par" présente une étude descriptive des emplois abstraits de la préposition par en français et de ses équivalents russes dans le cadre de la linguistique de corpus (J. Sinclair). L’exploration des exemples authentiques du corpus bilingue aligné constitué par nos soins, ainsi que des corpus existants permet, pour le français, d’esquisser des critères de distinction plus nette entre les sens "de cause à effet", "de fin à moyen", "de support à manière" de par, et, pour la perspective comparative, de construire un continuum de ses équivalents russes : cas morphologiques, prépositions, prépositions complexes, transformations sémantico - syntaxiques touchant à l’intégrité de la phrase. Compte tenu des particularités des prépositions en tant que catégorie lexico - grammaticale, on fait aussi appel aux instruments descriptifs élaborés dans le cadre de l’approche énonciative (J. J. Franckel, D. Paillard) : identité de la préposition, sa définition à l’aide du schéma X R (préposition) Y, distinction entre les prépositions de zonage et de discernement. / The thesis "Aligned bilingual French - Russian corpus : the case of par" presents a study describing several abstract meanings of the preposition par in French and of its Russian equivalents in the framework of Corpus Linguistics (J. Sinclair). Exploring authentic examples from our aligned bilingual corpus as well as from existing corpora allows us to propose criteria for distinguishing more clearly between "cause to effect", "aim to means", "support to manner" meanings of par in French, and to reveal a continuum of its equivalents in Russian language : morphologic cases, prepositions, complex prepositions, semantic and syntax transformations of the whole sentence. Taking into account particularities of prepositions as lexico -grammatical category, we also refer to descriptive tools proposed in the framework of enunciative linguistics (J. J. Franckel, D. Paillard) : identity of a preposition, its definition by the scheme X R (preposition) Y, distinction between the prepositions of zoning and of differentiation.
92

Synthesis, Characterization and Electrical Transport In Carbon Nanotubes

Mahanandia, Pitamber 01 1900 (has links) (PDF)
In this thesis, synthesis, characterization and electrical transport of Carbon nanotubes (CNTs) have been discussed. The first chapter contains a brief introduction of various forms of carbon including CNT. The CNTs are currently the materials of intense research interest due to their remarkable mechanical and electrical properties. CNTs can be visualized as a graphene sheet that has been rolled into a seamless tube. CNTs are either single-walled carbon nanotubes (SWCNT) or multi-walled carbon nanotubes (MWCNT). SWCNT is a tube with only one wall and MWCNT has many coaxial tubes and weak Van der Waal forces hold them together. The properties depend on chirality, diameter and length of the tubes. Chirality is defined by the symmetry and the chiral angle formed between the carbon bonds. The atomic structure of CNTs is described in terms of the tube chirality, which is defined by the chiral vector Ch and the chiral angle . The chiral vector is Ch = na1 + ma2, where the integers (n, m) are the number of steps along the zig-zag carbon. Depending on the tube chirality the electrical properties of the CNTs differ; they can be metallic or semiconducting. When n-m = 3p, where p is an integer, the CNTs are metallic and when n-m  3p, the CNTs are semiconducting. Due to the high anisotropy and high aspect ratio, CNTs have many potential applications with great technological importance such as functionalized molecules, conductive wires, bearings of rotational motors, field emitters, hydrogen storage, sensors, polymer composites, nanotube yarn and nanotube filters, X-ray generator, electron sources for microscopy and lithography, gas discharge tubes and vacuum microwave amplifiers, etc. The first chapter gives a brief introduction about various forms of carbon and their properties, particularly of CNTs. The nature of the CNTs depends on the method of production, which controls the degree of graphitization, the tube diameter and the chirality. Most synthesis methods originate from the idea of obtaining adequately active carbon atomic species or clusters from carbon sources and assembling them into CNTs without or with catalysts. The commonly used methods for the synthesis of carbon nanotubes are arc-discharge, Laser ablation, high-pressure catalytic decomposition of carbon monoxide (HiPCO), electrophoretic deposition (EPD), flame synthesis, pyrolysis, chemical vapour deposition (CVD), hot-filament CVD, plasma enhanced chemical vapour deposition (PECVD) using DC, RF, and micro wave power sources, hot-filament dc (HF-dc PECVD), inductively coupled plasma (ICPECVD) and electron cyclotron resonance (ECR PECVD). Although many efforts have been made to develop various synthesis methods, most of them require many steps. Moreover, the complicated and rigorous control of parameters and expensive materials are unavoidable that has put limitation in reproducing the same in large scale. In this chapter, a simple method for the synthesis of CNTs on a large scale that eliminates nearly the entire complex and expensive machinery associated with widely used growth techniques has been discussed. In Chapter 2, the synthesis and characterization of entangled CNTs are discussed. It is shown that entangled CNTs can be synthesized in one step by using double stage furnace. Tetrahydrofuran as carbon source material and nickelocene as catalyst source material have been used to synthesize CNTs. With this method CNTs can be synthesized at a temperature as low as at 600 0C. In this technique the self-developed pressure carries the vapours to the hot zone of the furnace. This has led to think in modifying the double stage furnace. A single stage furnace having temperature gradient is made to synthesize CNTs. The vapours are carried from low temperature zone to hot zone where the carbon species and catalysts react to form CNTs. The advantage of this furnace is that it is one-step process. Using another carbon source material such as Diethyl Ether and nickelocene as catalyst source material CNTs are synthesized. The as synthesized and purified CNTs are characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), transmission electron microscope (TEM), high resolution TEM (HRTEM) and Raman spectroscopy. The CNTs are multi-walled in nature as observed by HRTEM. In Chapter 3, the synthesis of aligned CNTs is discussed by using benzene as carbon source and ferrocene as catalyst source materials. Aligned MWCNTs were synthesized in the temperature range between 650 - 1100 0C in a single stage furnace without the need for carrier gas nor predeposited metal catalyst substrate. The essential need of CNTs are (1) to obtain aligned nanotubes with millimeter lengths to enable the formation of novel nanotube-polymer composites that incorporate continuous nanotubes throughout their thickness for highly anisotropic thermal and electrical conductivities; and (2) to provide samples for detailed physical characterization - tensile strength, thermal, electrical conductivity, field emission etc. SEM observation reveals the increase in length of nanotubes from 85 m to 1.4 mm with the increase of preparation temperature. The diameter as investigated by high-resolution transmission electron microscopy (HRTEM) remains almost constant 70-80 nm (75-85 layers). Once nanotube formation is established, the growth continues in the same direction and may well be reinforced by the presence of surrounding CNTs i.e. almost every particle produces a nanotube and bundling of neighboring tubes lead to collective vertical growth. The increase in length is due to the enhanced diffusion of active carbon with increasing preparation temperatures. The alignment of CNTs is also observed to the lateral side of the substrate. In Chapter 4, the synthesis and characterization of carbon nanoribbon and singled crystal iron filled CNTs is discussed. Particularly interesting are those CNTs filled with magnetic nanowires, which can provide an effective barrier against oxidation and consequently ensure a long-term stability in the core. The filling of metals within carbon nanotubes has extended the potential application base of these materials to quantum memory elements, high density magnetic storage media, semiconducting devices, field electron emitters, high resolution magnetic atomic force microscopy tips, magnetic field sensors and scanning probe microscopes etc. Tetrahydrofuran as carbon source material and ferrocene as catalyst materials has been used to synthesize mixture of carbon nanoribbons and iron filled CNTs. The techniques used to characterize the materials are XRD, SEM, HRTEM and superconducting quantum interference device (SQUID). The powder XRD pattern shows that the bcc -Fe phase of iron is present. HRTEM studies reveal the presence of multi-walled carbon nanotubes and well-crystallized -Fe phase filled inside the core region. Closer inspection of the HRTEM images indicated that the bcc structure -Fe nanowires are monocrystalline and Fe (110) plane is indeed perpendicular to the G (002) plane. Large coercivity (i.e. 1037 Oe at 300 K and 2023 Oe at 10 K) in the iron filled CNTs and carbon nanoribbons have been observed. The high coercivity is mainly attributed to the following two factors. Firstly, it is known that due to the uniaxial magnetic anisotropy of the nano size iron in the core region of the carbon nanotubes. Secondly, ferromagnetic behavior exhibited by the localized states at the edges of the carbon nanoribbons. The anisotropic electrical transport property of MWCNTs has been discussed in the chapter 5. The activated diffusive nature of transport along axial direction of CNT is explained. The transport perpendicular to the tube direction is explained in terms of a hopping mechanism. The anisotropic resistivity (N/P) value obtained is 3. The temperature dependent magnetoresistance (MR) is studied in magnetic fields up to 11 Tesla at low temperatures both in the parallel and perpendicular direction of an aligned MWCNT mat. In both cases a negative MR is observed. Chapter 6 discusses the preparation of CNT-polymer composites. The temperature dependence of the conductivity and magnetoresistance (MR) has been studied making four-point contact method on the carbon nanotubes polymer composites as result of increasing CNT content. The conductivity increases with increasing carbon nanotube weight percentage. The increase in conductivity as a function of the CNT weight percent is attributed to the introduction of conducting CNT paths in the polymer matrix. With the increasing CNT content the number of interconnections present in a random system is found to vary. Electrical conduction in nanotube mat or nanotube composites is explained by a variable range hopping (VRH) conduction mechanism. The negative magnetoresistance has been observed for the polymer composites. It is consistent with the report on CNTs bundles and polymer composites. Finally a brief summary of the work presented in this dissertation is discussed along with future directions in this research.
93

Développement et étude de la synthèse par CVD à basse température de nanotubes de carbone alignés sur substrat d’aluminium / Development and study of CVD synthesis at low temperaturre of aligned carbon nanotubes on aluminium substrate

Nassoy, Fabien 13 April 2018 (has links)
Les supercondensateurs, basés sur des cycles rapides de charge/décharge d’ions, sont une solution intéressante pour répondre à la problématique du stockage d’énergie. Les nanomatériaux carbonés, couplés ou non à des matériaux actifs, présentent des potentialités en tant qu’électrode comparativement au carbone activé couramment utilisé. Dans le cadre d’un laboratoire commun, le CEA, Nawatechnologies et les universités de Tours et Cergy, cherchent à développer des électrodes plus efficaces mettant en œuvre des tapis de nanotubes de carbone verticalement alignés (VACNT) sur collecteur d’aluminium. C’est dans ce contexte que se situe ma thèse CIFRE avec comme objectif le développement et la compréhension de la croissance de nanotubes alignés sur feuille d’aluminium par une méthode de dépôt chimique en phase vapeur (Chemical Vapor Deposition (CVD)) assistée par aérosol. Au démarrage de ma thèse, cette technique était maîtrisée par le LEDNA (UMR-NIMBE), mais seulement pour des températures relativement élevées (>800°C). L’enjeu était donc d’étendre cette méthode pour répondre à l’utilisation de l’aluminium comme substrat, ce qui nécessité un abaissement de la température de croissance des VACNT au-dessous du point de fusion de l’Al (660°C). Dans ce cas, les précurseurs catalytiques et carbonés utilisés à plus haute température ne se décompose pas efficacement, c’est pourquoi il a été nécessaire d’ajouter deux composés : l’hydrogène qui favorise la décomposition du précurseur catalytique et l’acétylène dont la décomposition thermique et catalytique est plus favorable à basse température. La thèse est structurée autour de trois axes : l’optimisation du procédé de synthèse, la compréhension des mécanismes de croissances et une étude visant à remplacer l’acétylène par des précurseurs biosourcés. / Supercapacitors, with fast charge / discharge cycles, represent an interest for energy storage. Carbon nanomaterial have a great potential as electrode as compared to common activated carbon based electrodes. CEA, Nawatechnologies, university Tours and Cergy develop electrodes based on vertically aligned carbon nanotubes (VACNT) on aluminium substrate in a joint laboratory. In this context, the aim of my thesis is to develop and understand the growth of VACNT on aluminum foil by aerosol assisted Chemical Vapor Deposition (CVD). At the beginning of my thesis, this technique was mastered by the LEDNA (UMR-NIMBE), but only for relatively high temperatures (>800°C). The challenge was therefore to extend this method to respond to the use of aluminium as a substrate, which necessitated a lowering of the growth temperature of VACNT below the melting point of Al (660°C). In this case, the catalytic and carbonaceous precursors used at higher temperatures do not decompose effectively, so it was necessary to add two compounds : hydrogen which increases decomposition of the catalyst precursor [3] and acetylene with a catalytic and thermal decomposition more favorable around 600° C [5]. Therefore, the approach in this work is first to identify the most relevant synthesis parameters to reach VACNT growth at such a low temperature by varying them and analyzing subsequently the products obtained. Moreover, attention is paid on study of Al surface before growth or during the initial steps of VACNT growth, and of CNT / Al interface to understand VACNT formation mechanisms at lower temperatures.
94

MSCI Climate Paris Aligned Indices : A quantitative study comparing the performance of SR indices and their conventional benchmark indices

Casselryd, Linnéa, Lantto, Agnes, Zanic, Alicia Julienne January 2021 (has links)
There is no clear consensus about whether green investments perform better, worse orequal to conventional brown investments. With the rising popularity of socialinvestments, it becomes increasingly important to understand these investments. Therecent launch of the MSCI Climate Paris Aligned Indices (CPAI) aim to illustrate thedevelopment of an economy that is in line with the requirements and goals of the ParisAgreement from 2015. In this research we aim to find out whether the MSCI Europe,USA and EM Climate Paris Aligned Indices outperform their parent indices. We do thisby comparing performance measures such as the net return, standard deviation of netreturns and Sharpe ratio. We further conduct an ordinary least squares regression to testwhether the betas and Jensen´s alphas of the CPAI differ significantly from their parentindices.The results show that only the USA CPAI clearly outperforms its parent index. This isdue to it having a higher Sharpe Ratio and Jensen’s alpha as well as higher monthly netreturns and a lower standard deviation compared to its parent index. The regressionshows that it does perform better than the parent index. The results for the EM CPAIshow that it performs in a similar way as its parent index. It has a higher monthly netreturn but also slightly higher standard deviation which leads to an equally large Sharperatio. Neither the estimated Jensen’s alpha nor the beta are significantly different fromthose of its parent index and thus the hypothesis of it performing equally as well as itsparent index cannot not be rejected. Lastly, the Europe CPAI has a higher Sharpe ratio,Jensen’s alpha and monthly net returns than its parent index, but it also exhibits a higherstandard deviation. The regression indicated that it performs in a similar way as itsparent index, no difference could be proven. In conclusion, this means that all CPAIperform at least equally as well as their parent indices, if not better.
95

Finding George Bailey: Wonderful leaders, wonderful lives

Light, Mark 18 December 2007 (has links)
No description available.
96

<b>Effect of Film Thickness on CeO</b><sub><strong>2</strong></sub><b>/Au Vertically Aligned Nanocomposite Morphology and Properties</b>

Matteo T Moceri (18431868) 26 April 2024 (has links)
<p dir="ltr">The primary goal of this work is to gain a fundamental understanding on how growth conditions affect the morphology and crystallography orientation of CeO<sub>2</sub>/Au vertically aligned nanocomposite (VAN) thin films. Focus has been placed on how the changes in morphology and crystallography translate to tunable optical properties. The morphological effects have been observed and analyzed via two main approaches: the change in morphology was observed at multiple points along the film thickness, and the morphology at the film/substrate interface has been analyzed with respect to total film thickness. The changes in Au crystallography orientations have been observed by measuring peak shift in XRD patterns and determining the resulting in- and out-of-plane strain. To observe additional effects of this morphology change, optical measurements have been taken for films at the bottom, middle, and top of the thickness range. Strong trends in transmittance, plasmonic absorption peak shifts and hyperbolic permittivity behavior are correlated with the film thickness. This tunability of optical properties likely arises from changes in both Au pillar phase morphology and crystal orientation. These findings demonstrate that changing film thickness may be a desirable method to easily tune the morphology and optical properties of VAN thin films.</p>
97

Structural Health Monitoring using Vertically Aligned Carbon Nanotubes for Cryogenic Tanks / Övervakning av kompositstrukturers livslängd med hjälp av vertikalt riktade kolnanorör för kryotankar

Olanders, Martin January 2023 (has links)
By structural health monitoring (SHM) of composite structures, their sustainability, safety and economics can be improved. On one hand, it enables using components to their full life or having them replaced early before otherwise unforeseen failure. On the other hand, it may make structures lighter as designs with smaller safety margins would be possible. Cryogenic liquid hydrogen tanks for aircraft would need to become lighter to enable such fossil-free aviation, which could require SHM. Vertically aligned carbon nanotubes (VACNT) have been used as embedded sensors in composites for temperature and strain sensing while other architectures of nanotubes have been used to detect fatigue damage. In this work, VACNT embedded in carbon fibre/epoxy composites are cycled both thermally and mechanically to investigate their suitability to detect damage in composite cryogenic tanks. It was found VACNT retain their strain sensing ability after cycling to cryogenic temperatures and that a relationship of increasing electrical resistance to increased cycling and damage is possible. That indicates VACNT are suitable for SHM of cryogenic tanks, but more testing and better electrical insulation of the VACNT is needed to confirm this. / Genom att övervaka kompositstrukturers livslängd med structural health monitoring (SHM), kan miljöhållbarheten, säkerheten och ekonomin i att använda dem förbättras. Å ena sidan möjliggör det att komponenter används sin fulla livslängd eller ersätts innan annars oförutsedda skador leder till kollaps. Å andra sidan kan det göra strukturer lättare eftersom designer med mindre säkerhetsmarginaler vore möjliga. Kryotankar för flytande väte i flygplan behöver bli lättare för att möjliggöra sådant fossilfritt flygande, vilket skulle kunna kräva SHM. Vertikalt riktade kolnanorör (vertically aligned carbon nanotubes, VACNT) har använts som inbäddade temperatur- och töjningssensorer i kompositer och andra kolnanorörsmaterial har använts för att detektera utmattningsskador. I detta arbetet har VACNT inbäddat i kolfiber och epoxi cyklats både termiskt och mekaniskt för att undersöka dess lämplighet som sensorer för skadedetektering i kryotankar. Det konstaterades att VACNT behåller sin töjningsdetekteringsförmåga efter termisk cykling till kryotemperatur och att det är möjligt att ett förhållande om ökande resistans med ökande cykling och skada kan finnas. Det indikerar att VACNT vore lämpliga för SHM i kryotankar, men mer provning och bättre elektrisk isolering av VACNT behövs för att bekräfta det.
98

Alignment of various environmental authorisation processes for the mining industry / Wessel Johannes Oosthuizen

Oosthuizen, Wessel Johannes January 2012 (has links)
Mining contributes significantly to the economic development of South Africa, contributes to pollution and other negative environmental impacts. Section 24 of the Constitution of the Republic of South Africa, 1996 (Constitution) places a duty on government to, amongst others adopt legislative measures to protect the environment, prevent pollution and degradation, and secure sustainable development, while promoting justifiable economic and social development. Government responded with the introduction of new acts or the amendment of existing acts most of which require an authorisation process as a “command and control” tool to enforce environmental governance within the mining sector. The abovementioned legislative development will be discussed from a historical perspective up to the current developments. The research aims to attempt to align the authorisation process pertaining to mining. The mining life cycle will be illustrated and the authorisation requirements for each of the mining life cycle processes will be discussed alongside its challenges such as fragmentation, lack of capacity in government sectors, lack of communication and cooperative governance within government. The lack of focus within the authorisation requirements will be deliberated. To avoid the negative consequences of the current authorisation processes such as duplication, unnecessary time delays and the stifling of economic growth, an investigation into how the various fragmented authorisation processes can be aligned into a single streamlined authorisation process which will contribute to the sustainable development within South Africa will be made. / MPhil (Environmental Law and Governance), North-West University, Potchefstroom Campus, 2013
99

Alignment of various environmental authorisation processes for the mining industry / Wessel Johannes Oosthuizen

Oosthuizen, Wessel Johannes January 2012 (has links)
Mining contributes significantly to the economic development of South Africa, contributes to pollution and other negative environmental impacts. Section 24 of the Constitution of the Republic of South Africa, 1996 (Constitution) places a duty on government to, amongst others adopt legislative measures to protect the environment, prevent pollution and degradation, and secure sustainable development, while promoting justifiable economic and social development. Government responded with the introduction of new acts or the amendment of existing acts most of which require an authorisation process as a “command and control” tool to enforce environmental governance within the mining sector. The abovementioned legislative development will be discussed from a historical perspective up to the current developments. The research aims to attempt to align the authorisation process pertaining to mining. The mining life cycle will be illustrated and the authorisation requirements for each of the mining life cycle processes will be discussed alongside its challenges such as fragmentation, lack of capacity in government sectors, lack of communication and cooperative governance within government. The lack of focus within the authorisation requirements will be deliberated. To avoid the negative consequences of the current authorisation processes such as duplication, unnecessary time delays and the stifling of economic growth, an investigation into how the various fragmented authorisation processes can be aligned into a single streamlined authorisation process which will contribute to the sustainable development within South Africa will be made. / MPhil (Environmental Law and Governance), North-West University, Potchefstroom Campus, 2013
100

Gemensamt mål eller gemensamma medel? : En komparativ textanalys av svensk och finsk säkerhetsstrategi efter kalla krigets slut och dess konsekvenser för det svensk-finska försvarssamarbetet. / Common ends or common means?

Anderssson, Linus, Karlberg, Fredrik January 2019 (has links)
COMMON ENDS OR COMMON MEANS? The Cold War is over and Sweden and Finland are starting to deal with the new security enviroment that has emerged. Grand Strategy in both countries is changing to meet the new Europe and surroundings. Both Sweden and Finland consider the risk of a direct attack in the near future to be highly unlikely and this has effects on the respective countries grand strategy. A broadened approach to security is applied and the military instrument is no longer the primary concern in the strategy. Both Sweden and Finland become members of the European Union in 1995 but neither is a member of NATO, the countries both consider themselves as military non-aligned, the only two countries with a coastline to the Baltic Sea with that stance. This makes for a logic choice to cooperate for the common security and a cooperation is formed to cover security policies to be relevant in peace, crisis and war. Even though the countries are existing in and interpret the new security enviroment in similar ways they approach the challanges in differing ways. This creates the differences that we identify and describe in this thesis. The purpose of this thesis is to identify and describe the differences between Sweden's and Finland's grand strategy, how this difference has changed from 1996 to 2018 and if these differences can have consequences for the cooperation between the two countries, mainly military and at the highest strategic level. The thesis is focused on the elements of the grand strategy that involves the armed forces of the respective countries. This comparative text analysis compares political policy documents within the grand strategy field from both Sweden and Finland. We will compare the period from 1996-2018. The comparison will be made by examining three occasions in the period, year 1996, Year 2004 and year 2018. The documents used have relevance against these years and are analyzed by applying Jacob Westberg's model; ends, means, ways and environment. The differences and the consequences that are the conclusions of this thesis are that cooperation are not always formed because it is the best possible option but sometimest the only possible options. Sweden and Finland's history differ in some parts and this has affected the respective country's security strategies. Finland has a history of coping for itself and has thus a national focus with focus on a stable national defense while Sweden has a history without war in modern times and a constant glance at military international engagement and the political benefits that can be achieved on the international scene.

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