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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.
21

Synthesis and Characterization of Silica Coated CdSe/CdS Core/Shell Quantum Dots

Xu, Yang 14 December 2005 (has links)
A great deal of interest has been dawn on the colloidal chemistry based semiconductor nanocrysallites, also known as quantum dots (QDs). Because of the strong quantum confinement, quantum dots have unique size-dependent optical properties, which are much more superior to the conventional organic fluorescence materials. In addition, strong chemical resistant makes inorganic semiconductor QDs ideal candidate for next-generation of bio-labels and drug delivery vehicles. This report presents a user friendly approach to synthesize high quality biocompatible CdSe QDs in aqueous solution. Size of the dots can be controlled by adjusting the temperature, pH of the solution, and ratio of the precursors. A thin CdS layer was grown on CdSe QDs, forming a CdSe/CdS core/shell structure, to improve the photoluminescence. In order to use these QDs in-vivo, a more chemically robust coating, silica, was grown on the core/shell structure QD. The optical properties of the QDs were characterized by absorption and photoluminescence spectra. X-ray diffraction and transmission electron microscopy were conducted to verify the QDs composition and structure. / Ph. D.
22

Croissance et physique de structures photovoltaïques CuInSe2 / Growth and Physics of CuInSe2 Photovoltaic Structures

Robin, Yoann 23 September 2014 (has links)
Ce travail porte sur l'élaboration de cellules solaires CuInSe2 (CIS) en couches minces. Différentes techniques de croissance ont été mises en œuvre pour concevoir les matériaux composant la structure photovoltaïque. Ainsi, l'absorbeur CuInSe2 a été déposé par coévaporation sous vide (PVD) sur un substrat de verre recouvert de molybdène. Un système de détection de la lumière diffusée (SLS) par l'échantillon a été développé pour permettre le suivi in situ des transitions de phases pauvres/riches en cuivre. Cela a permis la croissance de couches de CuInSe2 à larges grains ainsi que le contrôle de leurs propriétés électro-optiques. La couche tampon de CdS a été obtenue par bain chimique (CBD) et son épaiseur optimisée par un procédé original où le substrat est directement chauffé par conduction. Enfin, la couche fenêtre de ZnO a été élaborée par divers procédés de croissance tels que l'électrodéposition (ED) et le dépôt par couches atomiques (ALD). Les propriétés structurales, optiques et électriques des différentes couches minces sont étudiées et mises en relation avec les performances photovoltaïques des cellules élaborées. / The aim of this work is the design of thin film CuInSe2 solar cells. Different growth techniques have been used to elaborate the layers involved in this photovoltaic stack. Thus, the absorber CuInSe2 has been deposited by coevaporation under vacuum (PVD) onto a molybdenum coated glass substrate. A scattered light monitoring system (SLS) has been designed in order to follow in situ the copper poor/rich phases transitions. It has led to the growth of CuInSe2 layers made of large crystalline grains with both high optical and electrical properties. The CdS buffer layer has been elaborated by chemical bath deposition (CBD) and its thickness has been tuned by an original process involving a conduction heated holder. Finally, the ZnO window layer has been grown by various techniques such as electrodeposition (ED) and atomic layer deposition (ALD). Structural, optical and electrical properties of all these thin films have been studied and correlated with the photovoltaic parameters of the solar cells elaborated.
23

Fabrication and Characterization of CIS/CdS and Cu2S/CdS Devices for Applications in Nano Structured Solar Cells

Jayaraman, Visweswaran 01 January 2005 (has links)
Nano structured solar cells provide an opportunity for increased open circuit voltages and and short circuit currents in solar cells due to quantum confinement of the window and absorber materials and an increase in the optical path length for the incident light. In this study, both bulk and nano heterojunctions of CIS/CdS and Cu2S/CdS devices have been fabricated and studied on plain glass substrates and inside porous alumina templates to compare their performance. The devices have also been characterized SEM, XRD and JV measurements. The J-V curves have also been analyzed for series resistance, diode ideality factor and reverse saturation current density.
24

Optimisation de la mesure de travail de sortie par microscopie à sonde locale sous vide : application aux dispositifs avancés / Optimization of the work function measurement by local probe microscopy under vacuum : application to advanced devices

You, Lin 01 June 2012 (has links)
La compréhension des propriétés électriques de nano-objets est essentielle pour le développement s des nanotechnologies. La microscopie à force Kelvin (KFM) est une des techniques les plus utiles pour cartographier simultanément la topographie et la différence de potentiel de contact (CPD) à l'échelle nanométrique. Après 20 ans de développement, la KFM est principalement utilisé dans des conditions normales de pression et de température, permettant d'effectuer, de manière simple, de multiples analyses comparatives. Toutefois, sous ultra-vide (UHV), comme la surface est contrôlée et que la sensibilité est meilleure, des mesures plus précises et plus fiables sont réalisables. Dans la première partie, la mesure KFM sous atmosphère ambiante est améliorée en développant la technique simple-passage à la fois en modulation de fréquence (FM) et en modulation d'amplitude (AM). Une électronique externe Nanonis a été adaptée sur les AFMs commerciaux (Dimension 3100 et MultiMode, Bruker). Une étude comparative avec le mode Lift a été réalisée sur des couches de graphène épitaxié sur échantillon de SiC. L'effet de la distance pointe-échantillon sur le contraste et la résolution est décrit ainsi que l'influence des paramètres expérimentaux. Une amélioration significative du contraste et de la résolution est clairement observée sur les résultats obtenus par la technique simple passage en modulation de fréquence, indépendamment de la distance pointe-échantillon. Dans une deuxième partie, la technique KFM est développée sous vide secondaire. Le travail instrumental est réalisé sur un AFM EnviroScope de chez Bruker, qui a été équipé d'une électronique externe Nanonis, permettant de mesurer simultanément la topographie en mode non-contact et la CPD en modulation d'amplitude ou de fréquence. Les résultats montrent que la CPD mesurée est comparable à celle obtenue avec une mesure sous ultravide. Enfin, après avoir posé les bases à la fois expérimentale et théorique de la KFM, cette technique est utilisée pour caractériser les hétérostructures CdTe/CdS en films minces utilisés pour les applications de cellules solaires. Un protocole de préparation d'échantillon sur la tranche a été spécialement développé. L'hétérojonction CdTe/CdS est étudiée sous polarisation à la fois dans l'obscurité et sous éclairement. L'influence de l'épaisseur de la couche de CdS est également étudiée pour comprendre son effet dramatique sur le rendement des cellules solaires. / The development of nanoscience makes the understanding of the electrical properties of nano-objects essential. The Kelvin Force Microscopy (KFM) is one of the most useful techniques to map at the nanoscale and simultaneously both the topography and contact potential difference (CPD). After 20 years of development, KFM is mainly operated under air at normal pressure, allowing to perform, in an easy way, multiple comparative analyses. However, under UHV, as the surface is controlled and the sensitivity improved, more accurate and reliable measurements can be achieved. In the first part, KFM under ambient atmosphere is improved by developing the single-scan method using either a frequency modulation (FM) or an amplitude modulation (AM) mode. An external Nanonis electronic has been implemented on commercial AFMs (Dimension 3100 and MultiMode, Bruker). A comparative study with the common Lift-mode is done by imaging epitaxial graphene layers on SiC sample. The tip-sample separation effect on the CPD contrast and resolution is described as well as experimental settings. It is shown that higher contrasts are obtained using single-scan frequency modulation KFM regardless the tip-sample operating distance. In a second part, the KFM technique under secondary vacuum is developed. The instrumental work is carried out with an EnviroScope AFM from Bruker. We outfitted our Veeco's AFMs with an external Nanonis electronic to perform simultaneously the acquisition of topography and CPD using either the amplitude or the frequency modulation mode. The upgrade of the electronic has raised compatibility issues. Our results show that the comparable results are obtained with KFM under UHV. Finally, having laid down both the experimental and theoretical groundwork of the KFM, this technique is used to characterize CdTe/CdS heterostructures used in thin films solar cell application. A protocol for the cross section sample preparation has been specifically developed. The CdTe/CdS heterojunction is studied under polarization both in dark and under illumination. The influence of the CdS layer thickness is also studied to understand its dramatic effect on the solar cell efficiency.
25

Bank Disclosure and Financial Stability / Transparence des banques et stabilité financière

Guillemin, François 14 November 2016 (has links)
Cette thèse examine l'impact de la transparence informationnelle des banques sur la stabilité financière pendant la période 1990-2013. Elle est composée de deux essais empiriques, un essai théorique, ainsi que d'une revue de la littérature. Le premier chapitre met en lumière la littérature existante, théorique et empirique, qui servira comme tremplin pour le reste de la dissertation, Le chapitre 2 teste les effets de la transparence informationnelle des banques sur les prix des swaps de crédit pendant la crise de la dette souveraine européenne, sut- la période 2010-2013. Les banques les plus transparentes sont les banques qui souffrent le moins de la volatilité des prix des swaps de crédit au moment des annonces de dégradation des notes des états. La transparence, via la gouvernance des marchés financiers participent à améliorer la stabilité financière. Le chapitre 3 teste, théoriquement, les incitations à retirer des déposants en présence d'ambiguïté et dans le cas où l'information est imparfaite. Les résultats montrent que plus leur degré de pessimisme génère une incitation supérieure à retirer leurs dépôts de l'institution dans laquelle ils ont déposés. La combinaison de l'ambiguïté et de l'asymétrie d'information ouvre la porte à de nouvelles perspectives en termes de transparence informationnelle de la part des banques en direction des déposants et participant ainsi à l'amélioration de la stabilité financière en évitant les paniques bancaires. Le chapitre 4 teste empiriquement les résultats obtenus dans le chapitre précédent. Nous testons l'attractivité, pour les déposants, des banques les plus transparentes sur la période 1990-2013 tout en prenant en considération l'ambiguïté. Les résultats confirment que l' ambiguïté a un effet négatif sur le montant des dépôts totaux des banques et que la transparence informationnelle peut activer des incitations au retrait chez les déposants. / This thesis tries to understand the relationship between banking disclosure and financial stability for several actors of bank's governance. Disclosure has a positive impact on financial market participant made possible by a reduction of the information premium. Regarding depositors, we decided to partially reject the hypothesis of perfect rationality by introducing the ambiguity notion. We were able to show that a negative relationship exists between ambiguity and deposit levels bath theoretically and empirically. Disclosure policies have therefore a negative impact on European total deposit empirically.
26

Le rôle des Credit Default Swaps dans les crises de la dette souveraine. Une application au cas de la zone euro / The role of Credit Default Swaps in sovereign debt crisis. An application to the case of the euro area

El cheikh, Samah 16 July 2019 (has links)
Cette thèse porte sur l'étude des facteurs sous-jacents au risque du défaut souverain, tel que mesuré par les spreads des CDS souverains, au cours de la crise de la dette souveraine en Europe. En analysant les données mensuelles de janvier 2007 à septembre 2015 en utilisant un modèle à correction d'erreur (VECM), nous constatons que le risque de défaut souverain européen répond en partie à un environnement macroéconomique caractérisé par de mauvaises politiques budgétaires et une détérioration des facteurs économiques. Plus précisément, la hausse du taux de chômage, le niveau d'endettement et la réduction des soldes de la balance courante ont accru les spreads des CDS souverains. Ces résultats ne permettent pas de rejeter l’hypothèse selon laquelle le défaut souverain a été motivé par des fondamentaux économiques faibles. Mais l'importance relative de ces facteurs change avec le temps et le groupe de pays. La présence et l'absence de la Grèce ont joué un rôle clé dans l'évolution des spreads dans les pays de la zone euro. La dégradation des notations en Grèce et l'aversion accrue pour le risque de la part des Européens ont contribué à une augmentation significative des spreads de CDS des pays de la zone euro et des autres pays. Notre analyse VECM met en évidence des retombées directes de la Grèce vers la périphérie de la zone euro via des canaux non fondamentaux. Enfin, nos résultats suggèrent que l’émergence de la crise de la dette a été causée par des fondamentaux faibles, mais a également un caractère auto-réalisateur. / This thesis attempts to identify the factors behind the sovereign default risk, as measured by sovereign CDS spreads, during the sovereign debt crisis in Europe. By analyzing monthly data from January 2007 to September 2015 using vector error correction model with panel data, we find that European sovereign default risk is partly a response to a macroeconomic environment characterized by poor fiscal policies and deteriorating economic factors. Specifically, higher unemployment rate, debt levels and lower current account balances have increased the sovereign CDS spreads. These results do not allow us to reject the hypothesis that the sovereign default was driven by weak economic fundamentals. But the relative importance of these factors changes over time and group of countries. The presence and absence of Greece have played a key role in the developments of the spreads in the euro area countries. The rating downgrades in Greece and the higher European risk aversion had contributed to a significant rise in the CDS spreads of euro and non-euro area countries. Our VECM analysis does suggest direct spillovers from Greece to Euro area periphery via non-fundamental channels. Finally, our results suggest that the emergence of the debt crisis was caused by weak fundamentals but has also a self-fulfilling character.
27

Vertikálně uspořádaná pole CdS nanotyčinek pro aplikace v solárních článcích / Vertically aligned CdS nanorod arrays for solar cell applications

Hroch, Daniel January 2016 (has links)
This thesis describes the deposition of nanoparticles into nanoporous alumina templates. Nanoparticles of cadmium sulphide were chosen thanks to wide band gap of 2,45 eV. CdS is desired semiconductor promising better efficiency when comes to solar radiation conversion to useful energy. Theoretical part consists of explanation of photovoltaic principles, band-gap theory of materials, currently available technologies to manufacture solar cells and their efficiencies. Next part introduces the approaches of manufacturing nanoporous templates from aluminium (Anodized Aluminium Oxide, AAO) in details together with options to deposit cadmium sulphide into these structures. There is also brief description of deposition based on vacuum filtration. Experiments were made in Laboratory of Microsensors and Nanotechnologies at Faculty of Electrical Engineering and Communication in Brno University of. The experimental chapter describes manufacturing process of AAO and deposition via vacuum filtration. Samples were evaluated by Scanning Electron Microscopy.
28

我國筆記型電腦CTO/CDS生產模式創新與電腦化之研究

黃進成, Huang, Chin-Cheng Unknown Date (has links)
我國PC(個人電腦,Personal Computer)產業產值佔全球的60%以上,但幾乎97%以上都是為人作嫁,替他廠牌代工,在辛苦、薄利的製造領域鑽營7%不到的毛利。反觀一些品牌大廠卻能在買賣之間,獲得近乎製造兩倍以上的毛利,並且將庫存風險、交運、售後服務等煩瑣的業務要求製造者承擔。尤其筆記型電腦因體積小,CTO (Configure To Order)與CDS (China Direct Shipment)能力成為國際品牌大廠評核製造者能力的必要條件。 更因為市場競價的關係,品牌廠商以比價、競價、公開成本資訊的手法,遊走於我製造廠之間,把代工利潤壓到微乎其微的地步。製造廠只好移廠大陸,尋求更低廉的製造成本,並且擴大產能、執行垂直整合,意圖以規模經濟和範疇經濟來彌補獲利的不足。 本研究以Dorothy的企業核心能力與知識創造活動理論為依據,探討我國筆記型電腦業者發展CTO/CDS的知識創造活動和技術跨國移轉問題,並以價值鏈分析,探討我國筆記型電腦業者在產業國際分工移轉過程中所扮演的角色。全文分四大部份: 1. 文獻探討:以專家的理論作為本研究的基礎,一方面使本研究有所依據,快速進行;另一方面可驗證理論的實用性。 2. CTO/CDS實務研究:CTO/CDS的實現必須仰賴強大的資訊系統支援,本研究一方面提供CTO/CDS的電腦化實務經驗供產業參考;另一方面以CTO/CDS系統為例,探討我國筆記型電腦的實體系統和技術能力。 3. 知識創造活動研究:以一家公司為個案深入探討,再輔以其他四家公司訪談資訊相比對印證,研究筆記型電腦產業知識創造的過程和應用,以期提升活用知識的能力。 4. 價值鏈與創新模型分析:研究產業價值鏈各階段的附加價值貢獻,我國業者的能力、秉賦和扮演的角色,以期往高附加價值領域開拓。 最後希望能藉由結論,串連「實體系統、技術能力」→「活用知識」→「高附加價值」而建議出「贏的策略」。 本文僅研究者個人的意見,在有限的研究領域裡提出心得與建議,若能為產業所認同,實感榮幸。但產業環境複雜,要考慮的因素相當多,諾大疏漏的領域,祈望產業先進及專家學者多加批評指教! / Although the PC production value of Taiwan is beyond 60% to the world, most of them were made by term of OEM/ODM. Taiwan PC companies earned no more than 7% gross profit through their hard production routine. Not only the brand-named companies could earn double just by trade, but also they asked the makers to bear the risk of inventory, delivery and service jobs. Especially, because of the small size of notebook, CTO/CDS capability became the “must criteria” when the brand-named companies survey the producers for OEM/ODM. Due to the market price competition, brand-named companies strangulated the profit of makers by way of bidding and cost analysis. Taiwan makers had no choice but to move their works to Grand China for the purpose of lower cost. They enlarged the production capacity and diversified the PC production by vertical integration, in order to cover the shortage of profit by economic of scale and scope. This thesis was base on theory of Dorothy Leonard-Barton“ Wellsprings of Knowledge: Building and Sustaining the Sources of Innovation”, researched the issues of CTO/CDS knowledge development and cross-national shift of skill of Taiwan NB makers, and also studied the roles that Taiwan makers played at the value chain of NB industry. The article can be divided into the following four parts according to their different natures: 1. Review of academic papers: The basic theories that can make the study going smoothly and rapidly. 2. Study of CTO/CDS practice: To study the CTO/CDS information system and skill, and provide CTO/CDS practice for reference. 3. Study of knowledge creation activities: A deep case study plus the surveys of the other four companies describe the process of knowledge creation and skill innovation in order to enhance the application ability of knowledge. 4. Value chain and innovation model analysis: To study the added value of each segment in the NB value chain, and the industry innovation model to find out Taiwan NB makers’ ability and capability. Finally, I try to come out the “winner strategies” by integrating “ systems”, “abilities”, “capacities”, “knowledge” and “high value” in the ending. All deductive inferences of this limited research are my personal viewpoints only. I will be very proud if they can be recognized by others. Actually, the business environment is more complex than what we think. Any comments, views and opinions toward this paper are welcome and will be highly appreciated.
29

Uniform residence time in microreactor-assisted solution deposition of CdS thin-films for CIGS photovoltaic cells

Hires, Clayton Lamar 12 January 2011 (has links)
Photovoltaic (PV) cells have long been an attractive alternative for the consumption of fossil fuels but current manufacturing practices suffer from poor energy efficiency, large carbon footprints, low material utilization, high processing temperatures and high solvent usage. A critical step in PV production is the deposition of CdS as a thin film to serve as a "buffer layer" between the optically absorbent layer and the transparent conducting oxide (TCO) layer to complete an effective p-n junction. The development of an inexpensive, low temperature, constant flow deposition process for producing CdS films is investigated. Micro-assisted solution concepts are implemented to promote the selectivity of heterogeneous surface reactions over homogeneous bulk precipitation. Analytical models based off Hagen-Poiseuille equation for fluid flow are coupled with computational fluid dynamic simulations to produce uniform flow fields within the deposition step permitting uniform film coverage on large substrates. / Graduation date: 2011 / Access restricted to the OSU Community at author's request from Jan. 11, 2011-Jan. 11, 2012.
30

En beslöjad debatt : En jämförande diskursanalys mellan den mediala och den politiska diskursen av burka i Sverige utifrån Köpenhamnsskolan

Öman, Johanna January 2014 (has links)
The debate concerning face veiling has been brought in to view by several governments in Europe. Luca Mavelli studies the debate regarding the burqa using the concept of securitization and from that the objective of this study is to analyze the medial- and the political discourse in Sweden regarding the burqa. The formulated questions drawn from this is; who are the securitizing actors? According to the securitization actors, who can de defined as a referent object? Wherein is the threat according to the securitizing actors? Is it possible to recognize a difference between the medial and the political discourse? Furthermore the paper adopts the theoretical framework that is the concept of securitization, formulated by the Copenhagen School of security. The methodological foundation is based on a social constructivist approach and consequently uses Norman Faircloughs critical discourse analyzes as an analytical tool. Conclusions show that the two discourses often express similar results but a difference is apparent in how the debate is presented. Representatives of the political parties are defined as securitizing actors and to a certain degree so is the media. Furthermore, according to the securitizing actors the referent objects are Swedish traditions and culture, the threat lies in the values that are attached to the burqa.

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