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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.
1

Taiwanese Auto-tronic Industry Development Network Structure in Global Commodity Chain

Lin, Zheng-kuo 13 July 2006 (has links)
With the maturity of the semiconductor and communication technology, and vehicle technology is unable to break through obviously, therefore automobile corporations begins to try to apply the electronic product to the field of the vehicle in order to separate the difference district of the products, besides offering and is different from the function that machinery displays, its range of application is not only products, such as engine, transmission or chassis, but march toward with voluntarily safe, driving convenience, functional intelligence, relevant products of taking comfortableness and high dependability gradually, so involving the new industry in relevant technology, such as car making, electron, photoelectricity, communication, the auto-electron is attracted attention by the world. In global capitalism, economic activity is not only international in scope, it is also global in organization. 'Internationalization' refers to the geographic spread of economic activities across national boundaries. As such, it is not a new phenomenon. Indeed, it has been a prominent feature of the world economy since at least the seventeenth century when colonial empires began to carve up the globe in search of raw materials and new markets for their manufactured exports. 'Globalization' is much more recent than internationalization because it implies functional integration between internationally dispersed activities. So synthesize above-mentioned, I am going to use this regard globalizing the concept as theory 'Global commodity chain' of foundation, to inspect the electronic industry of the automobile of Taiwan, and plus the policies of automobile electron like 'IA completed vehicle plan' and its network structure. This research, in order to obtain each other's network inter-dynamic relation among industry, manufacturer, adopt the depth interview. The result of study is found, one of two kinds of driven ways derived out for the global commodity chain of the electronic industry mode of production of the automobile of Taiwan is 'buyer driven', the main reason is to urge the strength of industry's technology and products trend is coming from automobile corporation as 'branded manufacturers', and is absorbed in belonging to the roles of 'the factory' in the electronic manufacturer of Taiwan of the production field; And this industry is new industries derived out after combining with the electronic industry by the automobile, so the automobile and electron are on the inter-dynamic relation, and cooperative through 'security regardless parts', 'system software', 'call-center service¡¦; However government policies can actually drive the industry to develop, and combine the energy of the automobile and electronic industry, but government should offer more encourage policies to replace managing, restricted ones.
2

Разработка стратегии развития экспорта товаров для регионов России в современной мировой экономике (на примере Свердловской области) : магистерская диссертация / Working out of a strategy for the development of exports of goods for the regions of Russia in the modern world economy (on the example of the Sverdlovsk region)

Ананьина, А. А., Ananina, A. A. January 2017 (has links)
The paper reviewed the existing methodological approaches to the assessment of the export business of industrial regions of Russia. On their basis, we proposed the author's methodology for researching the working-out and development of the region's commodity export strategy, which consists in a comparative analysis of the potential of the industrial regions of Russia in the system of indicators, on exports of different countries and the Sverdlovsk region, on the commodity structure of regional exports; in the context analysis of the concepts and strategies of foreign economic activity of the regions; in determining the orientation of foreign economic relations of the Sverdlovsk region; in determining the level of internationalization of the largest exporters of Sverdlovsk region and their integration into the World Economic System; in the calculation of deferred dividends. The result of this methodology is the development of analysis findings and direction to increase the attractiveness of territories and increase exports, the national share in the global value chains, incl. mechanisms, methods, ways, etc. Next, we conducted an approbation of the proposed author's methodology, based on it, developed a new strategy for the development of exports of goods in the Sverdlovsk region and showed that the existing export development strategy for Sverdlovsk region's products implies an increase in exports in the standard way, that is, through the search for new markets, increase production of intermediate goods, the creation of a single commodity by different enterprises and the maintenance of relations with already existing trading and strategic partners. The new model of the strategy is based on combining of the maximum efforts of enterprises to create a large finished product and the output with this product in a new economic space, as well as an increase in the output of goods with high added value. In addition, it is proposed to conclude not only a classical contract of sale, but also a profit sharing agreement. In other words, our strategy is based on the geo-economic approach, which implies the creation of long internationalized investment-reproduction cycles. The new approach should not just increase exports, create new finished goods, but also increase the competitiveness and investment attractiveness of the region. / В работе были рассмотрены существующие методические подходы к оценке экспортной деятельности индустриальных регионов России. На их основании мы предложили авторскую методику исследования развития и разработки стратегии товарного экспорта регионов, которая заключается в сравнительном анализе потенциала индустриальных регионов России по системе показателей, по экспорту разных стран и СО, по товарной структуре экспорта регионов; в контен-анализе концепций и стратегий внешнеэкономической деятельности регионов; в определении ориентированности внешнеэкономических связей Свердловской области; в определении уровня интернационализации курпнейших экспортеров СО и их интеграции в МЭС; в расчете отложенных дивидендов. Итогом такой методики является разработка выводов анализа и направления для повышения привлекательности территорий и увеличение объемов экспорта, национальной доли в ГЦДС, в т.ч. механизмы, методы, способы и т.д. Далее мы провели апробацию предложенной авторской методики, на ее основании разработали новую стратегию развития экспорта товаров Свердловской области и показали , что существующая стратегия развития экспорта товаров Свердловской области подразумевает увеличение объемов экспорта стандартным путем, то есть через поиск новых рынков сбыта, увеличение производства промежуточных товаров, создание единичного товара разными предприятиями и поддержание отношений с уже существующими торговыми и стратегическими партнерами. Новая же модель стратегии основана на объединении максимальных усилий предприятий для создания крупного готового продукта и выход с этим продуктом в новое экономическое пространство, а также увеличение выпуска товара с высокой добавленной стоимостью. Кроме того, предлагается заключать не только классический договор купли-продажи, но и договор участия в прибылях. Другими словами наша стратегия основана на геоэкономическом подходе, который подразумевает создание длинных интернационализированных инвестиционно-воспроизводственных циклов. Новый подход должен не просто увеличить объемы экспорта, создать новыt готовые товары, но также повысить конкурентоспособность и инвестиционную привлекательность региона.
3

Windows of opportunities and knowledge networks: implications for the catch-up in developing countries

Melo, Marne Santos de 15 April 2016 (has links)
This document represents a doctoral thesis held under the Brazilian School of Public and Business Administration of Getulio Vargas Foundation (EBAPE/FGV), developed through the elaboration of three articles. The research that resulted in the articles is within the scope of the project entitled 'Windows of opportunities and knowledge networks: implications for catch-up in developing countries', funded by Support Programme for Research and Academic Production of Faculty (ProPesquisa) of Brazilian School of Public and Business Administration (EBAPE) of Getulio Vargas Foundation. / Submitted by Marne Santos de Melo (marne.melo@gmail.com) on 2016-05-03T22:11:34Z No. of bitstreams: 1 PhD Dissertation_MarneMelo_Final_Version.pdf: 2457125 bytes, checksum: 159e5ecfb2ba7a58c8f0bf57741590b7 (MD5) / Rejected by Marcia Bacha (marcia.bacha@fgv.br), reason: Aluna irá submeter novamente com o arquivo certo. Márcia Bacha on 2016-05-04T13:07:55Z (GMT) / Submitted by Marne Santos de Melo (marne.melo@gmail.com) on 2016-05-04T22:38:35Z No. of bitstreams: 1 PhD Dissertation_MarneMelo_Final_Version.pdf: 2754297 bytes, checksum: 00edcb7f67f2dec68188195feee49ba2 (MD5) / Rejected by Marcia Bacha (marcia.bacha@fgv.br), reason: A aluna irá submeter novamente. on 2016-05-05T18:36:20Z (GMT) / Submitted by Marne Santos de Melo (marne.melo@gmail.com) on 2016-05-05T21:20:52Z No. of bitstreams: 1 PhD Dissertation_MarneMelo_Final_Version_05052016.pdf: 2534725 bytes, checksum: f6d42a161060acc546b6d30458d2a77e (MD5) / Approved for entry into archive by ÁUREA CORRÊA DA FONSECA CORRÊA DA FONSECA (aurea.fonseca@fgv.br) on 2016-05-09T14:38:57Z (GMT) No. of bitstreams: 1 PhD Dissertation_MarneMelo_Final_Version_05052016.pdf: 2534725 bytes, checksum: f6d42a161060acc546b6d30458d2a77e (MD5) / Approved for entry into archive by Maria Almeida (maria.socorro@fgv.br) on 2016-05-16T17:05:04Z (GMT) No. of bitstreams: 1 PhD Dissertation_MarneMelo_Final_Version_05052016.pdf: 2534725 bytes, checksum: f6d42a161060acc546b6d30458d2a77e (MD5) / Made available in DSpace on 2016-05-16T17:05:21Z (GMT). No. of bitstreams: 1 PhD Dissertation_MarneMelo_Final_Version_05052016.pdf: 2534725 bytes, checksum: f6d42a161060acc546b6d30458d2a77e (MD5) Previous issue date: 2016-04-15 / This study aims to investigate the theory of catch-up cycles in the setting of developing countries. We chose the Brazilian seeds sector as the locus of investigation. In order to explain catching up and industrial leadership, as suggested by the authors, we confront changes at the global level and windows of opportunities that emerged with responses from the main company of the sector - Embrapa. In our empirical study, we made use of in-depth interviews with historical and longitudinal analysis. We found evidence that changes in key dimensions alter in importance over time, but that institutions/public policy seem to be the forces that most contribute to strong dominance of transnational companies nowadays. Moreover, differently than suggested by some authors (although they are mainly focused in the Argentinean seeds sector), we find evidence that transnational companies – particularly the Gene Giants – do are driven the process of seeds innovation in the industry. In addition, the highest amount of launching of new varieties each year is not synonymous of more (or bigger) innovation; dominant positions in the market is not directly associated with higher levels of technological innovation. In fact, market innovation – e. g., commercial approach of transnational companies, which includes financing of producers and sales distribution - seems to be, at least, as relevant as technological innovation in the setting of seeds industry. / Esse estudo busca investigar a teoria de ciclos de 'catch-up' no contexto de países em desenvolvimento. O setor de sementes agrícolas brasileiro foi escolhido como locus de investigação. A fim de explicar catching up e lideranças na indústria, foram confrontadas mudanças e janelas de oportunidades ocorridas no nível global com as respostas da principal empresa do setor – Embrapa. No estudo empírico, fizemos uso de entrevistas em profundidade e análise histórica e longitudinal. Foram encontradas evidências de que mudanças em dimensões-chave alteram em importância ao longo do tempo, mas que instituições/políticas públicas parecem ser as forças que mais tem contribuído para a forte dominância das empresas transnacionais atualmente. Além disso, diferentemente do que tem sido sugerido por alguns autores (embora eles estivessem focados principalmente no setor de sementes da Argentina), encontramos evidências de que as empresas transnacionais - em particular as 'Gene Giants' - realmente tem direcionado o processo de inovação na indústria de sementes. Além disso, a maior quantidade de lançamento de novas variedades a cada ano não é sinónimo de mais (ou de maior) inovação; posições dominantes no mercado também não estão diretamente associadas a níveis mais elevados de inovação tecnológica. Na verdade, a inovação no mercado - e. g, abordagem comercial das empresas transnacionais, o que inclui o financiamento de produtores e de distribuição de vendas - parecem ser, pelo menos, tão relevantes quanto a inovação tecnológica no cenário da indústria de sementes. RESUMO 2 - UNDERSTANDING THE DYNAMICS OF NETWORK STRUCTURES: ALLYING THE GROUNDED-THEORY TO SOCIAL NETWORK APPROACH APPLIED TO THE BRAZILIAN SEEDS SECTOR O objetivo deste trabalho é lançar luz sobre uma lacuna previamente identificada em Powell et al. (2005) e posteriormente explorada em Ahuja, Soda e Zaheer (2012): a compreensão das origens e evolução das estruturas de rede intensivas em conhecimento; em outras palavras, seu dinamismo. Especificamente, essa pesquisa examinou como e por que redes centradas em uma empresa pública de P&D de um país em desenvolvimento têm evoluído para assumir as formas que elas possuem. No processo de examinar a questão de pesquisa, especial atenção foi dada para as várias razões pelas quais os setores público e privado buscam estabelecer parcerias. O contexto empírico escolhido foi o setor de sementes agrícolas do Brasil, mas nos focamos especificamente no programa de melhoramento de soja da Embrapa, a principal empresa representativa do setor. A lógica subjacente utilizada para desenvolver nosso arcabouço teórico foi a 'grounded theory'. O desenho de pesquisa é um estudo de caso único longitudinal, estudo indutivo, mas também foi feito uso da abordagem de rede social. Com base nos achados de pesquisa, nós desenvolvemos um arcabouço teórico para compreender o dinamismo das redes. Nós constatamos diferentes interesses entre as empresas, que mudaram ao longo do tempo, e diferentes efeitos para cada tipo de rede. Além disso, foi confirmada a crescente relevância da interação entre atores organizacionais e importantes 'trade-offs' entre organizações públicas e privadas. RESUMO 3 - TECHNOLOGICAL TRAJECTORY OF EMBRAPA AND THE CONQUEST OF CERRADO Apesar da existência de inúmeros estudos dedicados a investigar a trajetória tecnológica das empresas, pouca atenção tem sido dada a algumas características dessa trajetória. Como exemplo, podem ser citados o tempo que as empresas levam para avançar tecnologicamente e a influência de fatores, tais como as redes de conhecimento e mecanismos de aprendizagem na capacidade tecnológica das firmas. Na verdade, a relação redes-capacidades é considerada por muitos autores uma das mais importantes interações, que tem sido negligenciada. Esse artigo busca minimizar esses 'gaps' na literatura. Especificamente, nós examinamos a trajetória tecnológica da principal empresa brasileira do setor de sementes agrícolas – Embrapa – incluindo o tempo para avançar tecnologicamente e a relação redes de conhecimento-capacidades tecnológicas. No processo de examinar a trajetória tecnológica da Embrapa, nós examinamos como a Embrapa conquistou o Cerrado e mensuramos alguns importantes resultados de inovações tecnológicas – produção e exportação. Por meio de um estudo de caso longitudinal, nós concluímos que a Embrapa adotou diferentes trajetórias ao longo do tempo. Inicialmente a empresa adotou a trajetória 'path-following', em seguida a trajetória 'path-skipping' e, posteriormente, a trajetória 'path-creating'. A Embrapa também mudou seus parceiros ao longo do tempo (ou eles tiveram seus papeis adaptados às condições da época). Com a ajuda de parceiros, a Embrapa foi capaz de rapidamente alcançar o nível de liderança mundial. Ademais, indicadores de produção e exportação provaram ser relevantes para mensurar resultados de esforços de inovação.
4

First-Spike-Latency Codes : Significance, Relation to Neuronal Network Structure and Application to Physiological Recordings

Raghavan, Mohan January 2013 (has links) (PDF)
Over the last decade advances in multineuron simultaneous recording techniques have produced huge amounts of data. This has led to the investigation of probable temporal relationships between spike times of neurons as manifestations of the underlying network structure. But the huge dimensionality of data makes the search for patterns difficult. Although this difficulty may be surpassed by employing massive computing resources, understanding the significance and relation of these temporal patterns to the underlying network structure and the causative activity is still difficult. To find such relationships in networks of excitatory neurons, a simplified network structure of feedforward chains called "Synfire chains" has been frequently employed. But in a recurrently connected network where activity from feedback connections is comparable to the feedforward chain, the basic assumptions underlying synfire chains are violated. In the first part of this thesis we propose the first-spike-latency based analysis as a low complexity method of studying the temporal relationships between neurons. Firstly, spike latencies being temporal delays measured at a particular epoch of time (onset of activity after a quiescent period) are a small subset of all the temporal information available in spike trains, thereby hugely reducing the amount of data that needs to be analyzed. We also define for the first time, "Synconset waves and chains" as a sequence of first-spike-times and the causative neuron chain. Using simulations, we show the efficacy of the synconset paradigm in unraveling feedforward chains of excitatory neurons even in a recurrent network. We further create a framework for going back and forth between network structure and the observed first-spike-latency patterns. To quantify these associations between network structure and dynamics we propose a likelihood measure based on Bayesian reasoning. This quantification is agnostic to the methods of association used and as such can be used with any of the existing approaches. We also show the benefits of such an analysis when the recorded data is subsampled, as is the case with most physiological recordings. In the subsequent part of our thesis we show two sample applications of first-spike-latency analysis on data acquired from multielectrode arrays. Our first application dwells on the intricacies of extracting first-spike-latency patterns from multineuron recordings using recordings of glutamate injured cultures. We study the significance of these patterns extracted vis-a-vis patterns that may be obtained from exponential spike latency distributions and show the differences between patterns obtained in injured and control cultures. In a subsequent application, we study the evolution of latency patterns over several days during the lifetime of a dissociated hippocampal culture.
5

Synthesis and Transformation of AuCu Intermetallic Nanoparticles

Sinha, Shyam Kanta January 2013 (has links) (PDF)
Investigations on size dependent phase stability and transformations in isolated nanoparticles have gained momentum in recent times. Size dependent phase stability generates size specific particle microstructure which consequently yields size specific functionality. One important prerequisite for conducting studies on nanoparticles is their synthesis. A substantial amount of research effort has therefore been focused on devising methodologies for synthesizing nanoparticles with controlled shapes and sizes. The present thesis deals with both these two aspects: (a) synthesis of nanoparticles and (b) phase transformations in nanoparticles. The system chosen in this study is AuCu intermetallic nanoparticles. The choice of AuCu nanoparticle was due to the fact that the literature contains abundance of structural and thermodynamic data on Au–Cu system which makes it a model system for investigating size dependence of phase transformations. With respect to synthesis, the present thesis provides methodologies for synthesizing alloyed Au–Cu nanoparticles of different sizes, Au–Cu nano-chain network structures and uniform Au–Cu2S hybrid nanoparticles. For every type, results are obtained from a detailed investigation of their formation mechanisms which are also presented in the thesis. With respect to phase transformation, the thesis presents results on the size dependence of fcc to L10 transformation onset in Au–Cu nanoparticles under isothermal annealing conditions. The present thesis is divided into eight chapters. A summary of results and key conclusions of work presented in each chapter are as follows. The ‘introduction’ chapter (chapter I) describes the organization of the thesis. Chapter II (literature study) presents a review of the research work reported in the literature on the various methodologies used for synthesizing Au–Cu based nanoparticles of different shapes and sizes and on ordering transformation in AuCu nanoparticles. The chapter also presents a brief discussion on the reaction variables that control the process of nucleation and growth of the nanoparticles in solution. Chapter III titled ‘experimental details and instrumentation’ describes the synthesis procedures that were used for producing various nanoparticles in the present work. The chapter also briefly describes the various characterization techniques that were used to investigate the nanoparticles. The fourth chapter titled ‘synthesis and mechanistic study of different sizes of AuCu nanoparticles’ provides two different methodologies for synthesis, referred as ‘two-stage process’ and ‘two-step process’ that have been used for producing alloyed AuCu nanoparticles of different sizes (5, 7, 10, 14, 17, 25 nm). The ‘two-stage’ process involved sequential reduction of Au and Cu precursors in a one pot synthesis process. Whereas, the ‘two-step’ process involved a two-pot synthesis in which separately synthesized Au nanoparticles were coated with Cu to generate alloyed AuCu nanoparticles. In the two-stage synthesis process it was observed that by changing the total surfactant-to-metal precursor molar ratio, sizes of the alloyed AuCu nanoparticles can be varied. ‘Total surfactants’ here include equal molar amounts of oleic acid and oleylamine surfactants. Interestingly, it was observed that there exists a limitation with respect to the minimum nanoparticle size that can be achieved by using the two-stage process. The minimum AuCu nanoparticle size achieved using the two-stage synthesis process was 14 nm. Mechanism of formation of AuCu nanoparticles in the two-stage synthesis process was investigated to find out the reason for this size limitation and also to determine how the synthesis process can be engineered to synthesize alloyed AuCu nanoparticles with smaller (<14nm) sizes. Studies to evaluate mechanism of synthesis were conducted by investigating phase and size of nanoparticles present in the reaction mixture extracted at various stages of the synthesis process. Their studies revealed that (a) the nanoparticle formation mechanism in the two-stage synthesis process involves initial formation of Au nanoparticles followed by a heterogeneous nucleation and diffusion of Cu atoms into these Au rich seeds to form Au–Cu intermetallic nanoparticles and (b) by increasing the relative molar amount of the oleylamine surfactant, size of the initial Au seed nanoparticles can be further reduced from the minimum size that can be achieved in the case when equal molar amounts of oleylamine and oleic acid surfactants are used. The information obtained from the mechanistic study was then utilized to design the two-step synthesis process. In the two-step process, Au nanoparticles were synthesized in a reaction mixture containing only the oleylamine surfactant. Use of only oleylamine resulted in production of pure Au nanoparticles with sizes that were well below 10 nm. These Au nanoparticles were washed and dispersed in a solution containing Cu precursor. Introduction of a reducing agent into this reaction mixture led to the heterogeneous nucleation of Cu onto the Au seed particles and their subsequent diffusion into them to form alloyed AuCu nanoparticles with sizes of ~5, 7 and 10 nm. The study present in this chapter essentially signified that the surfactants used in the reaction mixture not only prevent nanoparticles from agglomerating in the final dispersion but also control their nucleation and growth and therefore can be used as a tool to tune nanoparticle sizes. The fifth chapter titled ‘size dependent onset of FCC-to-L10 transformations in AuCu alloy nanoparticles’ illustrates the effect of AuCu nanoparticle size on the onset of ordering under isothermal annealing conditions. Nanoparticles in this study were annealed in-situ in a transmission electron microscope. Samples were prepared by drop drying a highly dilute dispersion of as-synthesized nanoparticles onto an electron transparent TEM grid. Nanoparticles sitting on the TEM grid were well separated from each other to minimize particle sintering during the annealing operation. It was however observed that during the isothermal annealing, particle coarsening due to atomic diffusion was appreciable for 5 nm particles but negligible for 7 and 10 nm particles. Therefore for this study only 7 nm and 10 nm sized particles were considered. Onset of ordering was determined from the time when first sign of the diffraction spot, corresponding to the ordered phase, appears in the selected area electron diffraction pattern from a region containing large number of AuCu nanoparticles. Through a series of isothermal experiments it was observed that the time for onset of ordering increased with decrease in size of the nanoparticles. It is speculated that the delay in onset of ordering may be due to the fact that with a decrease in nanoparticle size the probability of a nanoparticle containing a fluctuation that shall generate a thermodynamically stable nuclei of the ordered phase decreases. A sharp interface between the ordered and the disordered phase inside the particle was also observed which suggested that the ordering transformation in as-synthesized fcc AuCu nanoparticles is a first order transformation. The sixth chapter titled ‘synthesis and characterization of Au1-xCux–Cu2S hybrid nanostructures: morphology control by reaction engineering’ provides a modified polyol method based synthesis strategy for producing uniform Au–Cu2S hybrid nanoparticles. Detailed compositional and structural characterization revealed that the hybrid nanoparticles are composed of cube shaped Au-rich, Au–Cu solid solution phase and hemispherical shaped Cu2S phase. Interestingly, the hemispherical Cu2S phase was attached to only one facet of the cube shaped phase. A study on the formation mechanism of hybrid nanoparticles was also conducted by characterizing specimens extracted from the reaction mixture at different stages of the synthesis process. The study revealed that the mechanism of formation of hybrid nanoparticles involved initial formation of isolated cube shaped pure Au nanoparticles and Cu–thiolate complex with a sheet morphology. With increase in time at 180°C, the Cu–thiolate complex decomposed and one part of the Cu atoms that were produced from the decomposition were utilized in forming the spherical Cu2S and other part diffused into the Au nanoparticles to form Au–Cu solid solution phase. The chapter also presents a study on the effect of dodecanethiol (DDT) on achieving the hemisphere-on-cube hybrid morphology. In this study it is illustrated that an optimum concentration of dodecanethiol is required both for achieving size and morphological uniformity of the participating phases and for their attachment to form a hybrid nanoparticle. The seventh chapter titled ‘synthesis of Au–Cu nano-chains network and effect of temperature on morphological evolution’ provides methodology for synthesizing fcc Au– Cu nano-chain network structures using polyvinylprrolidone (PVP) surfactant. It was observed that with increase in the molar amount of PVP in the reaction mixture, morphology of the as-synthesized product gradually changed from isolated nanoparticles to branched nano-chain like. The nano-chains contained twins which indicated an absence of continuous growth and possibility of growth by oriented attachment of initially formed Au–Cu nanoparticles. Both in-situ and ex-situ annealing of the nano-chains led to their decomposition into isolated nanoparticles of varying sizes. Annealing also caused fcc-to¬L10 phase transformation. Investigation of the wave length of perturbation leading to breaking of a nano-chain into particles indicated that the surface energy anisotropy affects the splitting of nano-chain network structure into nano-sized particles. The thesis ends with a last chapter where we have presented possible future extension of current work.
6

High-Speed Scanning Tunneling Microscopy on Thin Oxide Film Systems

Gura, Leonard Gordian 13 April 2023 (has links)
Dünne Silizium- und Germaniumdioxidfilme auf Ru(0001)-Kristallen werden hinsichtlich dynamischer Prozesse untersucht. Zwischen Oxidfilm und Substrat befinden sich Sauerstoffatome, die eine ent-scheidende Rolle in diesen Systemen spielen. Zunächst werden diese Sauerstofflagen auf Ru(0001) mittels Hochgeschwindigkeits-Rastertunnelmikroskopie (STM) analysiert. Daraufhin wird die GeO2-Monolage auf Ru(0001) bei hohen Bildraten mit einer selbstentwickelten halbautomatischen Netz-werkdetektion untersucht. Schließlich wird die SiO2-Bilage auf Ru(0001) mit konventionellen sowie mit schnellen STM-Messungen bei Raumtemperatur und bei 600 K abgebildet. Um schnelle Messungen bei hohen Temperaturen zu realisieren, wird ein Hochgeschwindigkeits-STM konstruiert, welches bei unterschiedlichen Temperaturen betrieben werden kann. Unkon-ventionelle Spiralgeometrien ermöglichen verzerrungsfreie Bilder in weniger als 10 ms aufzunehmen. Die adsorbierten Sauerstofflagen werden erstmals bei hohen Bildraten untersucht. Die experimen-tellen Ergebnisse werden durch extern durchgeführte Dichtefunktionaltheorie-Berechnungen ergänzt. In den auf Ru(0001) bei Raumtemperatur stabilen Sauerstofflagen O(2×2), O(2×1) und 3O(2×2) werden dynamische Prozesse beobachtet. Die Besetzung des Zwischenzustandes entlang des Diffusionspfades und schnelle "Umklapp"-Prozesse eindimensionaler Linien werden auf atomarer Ebene aufgelöst. Komplexe Domänengrenzen in der GeO2-Monolage auf Ru(0001) werden mit Hochgeschwindigkeits-STM abgebildet. Die Messungen an der SiO2-Bilage auf Ru(0001) zeigen dynamische Änderungen des Abbildungskontrasts, die mit den mobilen Sauertsoffatomen an der Grenzfläche zusammenhängen können. Messungen bei hohen Temperaturen zeigen dynamische Kontraständerungen von mesoskopischen Strukturen. Diese Messungen stellen die ersten schnellen Hochtemperatur-STM-Aufnahmen des Siliziumdioxidfilms dar und bilden die Grundlage für künftige Studien zu dynamischen Veränderungen in dünnen Oxidschichtsystemen. / Dynamics related to thin silicon- and germanium dioxide films that are grown on Ru(0001) crystals are investigated. Between the film and the metal support oxygen species are present that play a crucial role for these film systems. First, these oxygen adlayers on Ru(0001) are analyzed by high-speed scan-ning tunneling microscopy (STM) with the focus on dynamic processes. In a next step, the monolayer of germanium dioxide (germania) supported on Ru(0001) is studied at elevated frame rates and with a self-designed semi-automated network detection. Finally, the bilayer of silicon dioxide (silica) on Ru(0001) is studied by conventional and by high-speed STM both at room temperature and at 600 K. To realize fast STM measurements at elevated temperatures, a high-speed STM is designed that can operate at variable temperatures. Images are acquired in less than 10 ms with unconventional spiral scan patterns. The dynamics in oxygen adlayers are investigated for the first time at elevated frame rates. Experimental results are supported by density functional theory (DFT) calculations performed externally. Dynamic events are observed in the oxygen adlayers that are stable on Ru(0001) at room temperature, namely O(2×2), O(2×1), and 3O(2×2). The occupation of an intermediate state along the oxygen diffusion pathway and fast "flipping" events of atomic one-dimensional stripe patterns are observed. On the germania monolayer on Ru(0001), complex domain boundary structures are resolved with high-speed STM. In high-speed scans on the silica bilayer on Ru(0001), dynamic changes of the imaging contrast are observed that may relate to the mobile species in the oxygen interfacial layer. Measurements at elevated temperature reveal dynamic contrast changes of mesoscopic features. These measurements constitute the first high-speed STM scans on the silica film at elevated temperatures and form the basis for future studies with the focus on dynamic processes in thin oxide film systems.

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