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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.
141

Microscopie et spectroscopie de phase. Développements en diffusion Raman cohérente (CRS) et en thermo-plasmonique / Phase microscopy and spectroscopy for Coherent Raman Scattering (CRS) and Thermoplasmonics

Berto, Pascal 28 January 2013 (has links)
La microscopie par diffusion Raman cohérente anti-Stokes (CARS) est une technique de spectro-imagerie qui permet de cartographier les modes vibrationnels intra-moléculaires d'un échantillon biologique, sans nécessité de marquage préalable. La mesure CARS est cependant dégradée par un "fond non-résonant" qui détériore le contraste. Récemment, la microscopie par diffusion Raman stimulée (SRS) fut proposée comme une alternative à la microscopie CARS, permettant d'obtenir une imagerie "sur fond noir". Dans cette thèse, nous décrivons le développement d'un microscope SRS. Nous évaluons le caractère spécifique des contrastes CARS et SRS dans le cadre d'une application biomédicale concrète, à savoir la détection de mélanomes humains. Nous présentons une description exhaustive des phénomènes physiques pouvant conduire à des artéfacts de mesure en SRS. Nous proposons finalement une technique basée sur l'utilisation de trois faisceaux d'excitation à trois couleurs, permettant de supprimer ces artéfacts. Dans une seconde partie, nous nous intéressons à la microscopie CARS en configuration plein champ. Nous proposons une méthode permettant de supprimer le fond non-résonant. Celle-ci est basée sur une analyse de front d'onde du champ anti-Stokes. En guise d'ouverture, nous proposons une technique - toujours basée sur l'analyse de front d'onde - permettant de réaliser la spectroscopie d'absorption quantitative de nano-objets. Nous illustrons le potentiel de cette technique en réalisant des mesures sur des matrices de nanoparticules d'or et sur des nanoparticules uniques. / Coherent Anti-Stokes Raman Scattering (CARS) microscopy is a technique that can map the spatial distribution of intra-molecular vibrational modes of a biological sample. This method thus provides molecular specificity, without staining the sample. However, CARS signal is hampered by a "non-resonant background" which reduces the contrast. Recently, Stimulated Raman Scattering (SRS) microscopy has been proposed as an alternative to CARS microscopy because it is a background free method. In this thesis, we describe the development of a SRS microscope. We evaluate the specificity of CARS and SRS contrasts in a concrete biomedical application, the detection of human melanomas. We present a comprehensive description of the physical phenomena that can lead to artifacts in SRS microscopy. We show that the scattering properties of the sample can lead to artifacts. We propose a technique based on three excitation beams of different color which suppresses these artifacts. In the second part, we focus on CARS microscopy in a wide-field configuration. We implement a technique to remove the non-resonant background. This method is based on wavefront sensing of the anti-Stokes Field by quadriwave lateral sharing interferometry (QWLSI). We demonstrate that the measurement of the intensity and phase of the complex CARS field allows to retrieve the spontaneous Raman scattering spectrum. As a perspective, we propose a technique, still based on wavefront sensing by QWLSI, to achieve quantitative absorption spectroscopy of nano-objects. We illustrate the potential of this technique by performing measurements on arrays of gold nanoparticles and on single nanoparticles.
142

Template para elaboração de uma unidade didática na perspectiva dos estudos sociorretóricos de gênero / Template for the elaboration of a didactic unit in the perspective of the sociorhetorical studies of genre

Silva, Rosa Lídia da 28 June 2018 (has links)
Submitted by Filipe dos Santos (fsantos@pucsp.br) on 2018-08-17T13:19:52Z No. of bitstreams: 1 Rosa Lídia da Silva.pdf: 47760667 bytes, checksum: d80910ea86dadb29eb499036da193a43 (MD5) / Made available in DSpace on 2018-08-17T13:19:52Z (GMT). No. of bitstreams: 1 Rosa Lídia da Silva.pdf: 47760667 bytes, checksum: d80910ea86dadb29eb499036da193a43 (MD5) Previous issue date: 2018-06-28 / This dissertation is inserted in the Research Line: Text and speech in the oral and written modalities of the Program of Postgraduate Studies in Portuguese Language. It is the study of a model whose purpose is to guide the writing process of the didactic unit document, by teachers authors or experts in the disciplines. We use the nomenclature didactic unit as a series of teaching and learning activities assembled and organized for learning purposes (LIBÂNEO; FREITAS, [2009]). This model, named didactic unit template, is built with the components of a didactic unit, and may contain autoforming features, which facilitate the production of the final document, even by less experienced authors. Our main objective was to better understand the template, its composition and socio-rhetorical organization, to reflect if and in what way it affects the quality of the material it supports, contributing to the teaching and learning process. We use as theoretical foundation the socio-rhetorical studies of gender. The authors consulted were Swales (1990; 2004); Miller (1984, 2014); Bhatia (1993, 2001, 2012); Bazerman (2000); Bazerman and Miller (2011); Aguiar (2011); Biasi-Rodrigues and Bezerra (2012); Campos (2014); Crescitelli and Campos (2015) and Motta-Roth (1998; 2004). Being restricted the access to templates, for reasons of copyright, we began our study by textbooks, in view of being a type of text whose components are included in didactic units and for having their use recognized in the support of educational activities. We analysed ten books and, of these, we selected two to present the more detailed analysis. Having obtained a template of allowed use, named as Template COL, we were able to analyse it and reproduce it here. This model was created by the Commonwealth of Learning (COL), an international organization supporting education, especially in less developed countries. For a second example, we describe the items of a didactic unit template, based on our experience working with this type of model. In these models, we identify rhetorical moves and steps, according to Swales' (1990) CARS Model, to better understand the organization and interrelationship of its elements. In the course of research, we have a contact with a case study of a researcher active in the development of education in Namibia (FRÖHLICH, 2008), which shows the practical use of the template to support authors, even with less experience. The contact with the Template COL and the reality in which it is used has shown us that – in addition to helping in the quality of the final document, as we have seen previously because of our professional experience – the application of templates can be a valuable resource, including in less favored regions. Analysis by socio-rhetorical principles allowed us to see the text through more than one approach, considering its objectives, its functioning and the people affected by it. For us, it has been evident that the careful planning of the didactic unit and the construction of its final document in an organized way are important so that it fulfills its purpose with students and teachers. In this composition, the author can be aided by the template, which also requires planning and constitutes a tool to support the preparation of documents for educational purposes / Esta dissertação insere-se na Linha de Pesquisa: Texto e discurso nas modalidades oral e escrita do Programa de Estudos Pós-Graduados em Língua Portuguesa. Trata-se do estudo de um modelo cuja finalidade é guiar o processo de escrita do documento unidade didática, por autores professores ou especialistas nas disciplinas. Empregamos a nomenclatura unidade didática como sendo uma série de atividades de ensino e aprendizagem reunidas e organizadas com propósitos de aprendizagem (LIBÂNEO; FREITAS, [2009]). Esse modelo, nomeado template de unidade didática, é construído com os componentes de uma unidade didática, podendo conter recursos de autoformatação, que facilitam a produção do documento final, mesmo por autores menos experientes. Nosso objetivo principal foi conhecer melhor o template, sua composição e organização sociorretórica, para refletir se e de que maneira ele afeta a qualidade do material a que dá suporte, contribuindo com o processo de ensino e aprendizagem. Utilizamos como fundamentação teórica os estudos sociorretóricos de gênero. Os autores consultados foram Swales (1990; 2004); Miller (1984; 2015); Bhatia (1993; 2001; 2012); Bazerman (2000); Bazerman e Miller (2011); Aguiar (2011); Biasi-Rodrigues e Bezerra (2012); Crescitelli e Campos (2015) e Motta-Roth (1998; 2004). Sendo restrito o acesso a templates, por questões autorais, iniciamos nosso estudo por livros didáticos, tendo em vista serem um tipo de texto cujos componentes figuram em unidades didáticas e por terem seu uso consagrado no apoio a atividades educacionais. Analisamos dez livros e, desses, selecionamos dois para apresentar a análise mais detalhada. Tendo obtido um template de uso permitido, nomeado como Template COL, pudemos analisá-lo e reproduzi-lo aqui. Esse modelo foi criado pela Commonwealth of Learning (COL), organização internacional de apoio à educação, principalmente em países menos desenvolvidos. Para uma segunda exemplificação, descrevemos os itens de um template de unidade didática, baseadas em nossa experiência de trabalho com esse tipo de modelo. Identificamos, nesses modelos, os movimentos retóricos e passos, conforme o Modelo CARS, de Swales (1990), para entender melhor a organização e a inter-relação de seus elementos. No percurso de pesquisa, conhecemos um estudo de caso de uma pesquisadora atuante no desenvolvimento da educação na Namíbia (Fröhlich, 2008), que evidencia a utilidade prática do template para apoiar autores, mesmo com menor experiência. O contato com o Template COL e com a realidade em que é utilizado mostrou-nos que – além de auxiliar na qualidade do documento final, como já havíamos constatado anteriormente em razão de nossa experiência profissional – a aplicação de templates pode ser um valioso recurso, inclusive em regiões menos favorecidas. A análise por princípios sociorretóricos permitiu-nos ver o texto por mais de um enfoque, considerando seus objetivos, seu funcionamento e as pessoas que por ele são afetadas. Evidenciou-se, para nós, ser relevante o planejamento criterioso da unidade didática e a construção de seu documento final de maneira organizada, para que cumpra seu propósito junto a estudantes e professores. Nessa composição, o autor pode ser auxiliado pelo template, que requer, igualmente, planejamento e constitui uma ferramenta de apoio à elaboração de documentos com fins didáticos
143

Suplementação oral de glicosaminoglicanos e expressão de pequenos proteoglicanos ricos em leucina após cistotomia em bexigas saudáveis versus parcialmente obstruídas.

Castro, Natália Caroline Nalesso de. January 2018 (has links)
Orientador: Juliany Gomes Quitzan / Resumo: A diminuição da complacência da bexiga está relacionada com modificações no equilíbrio dos componentes da matriz extracelular e na concentração das fibras de colágeno, acarretando em espessamento da parede vesical e fibrose. O objetivo do estudo é analisar a relação entre suplementação oral dos glicosaminogicanos (GAGs), distribuição de pequenos proteoglicanos ricos em leucina (SRLPs) e síntese de colágeno em bexigas saudáveis e fibrosadas por obstrução parcial submetidas a cistotomia. Foram utilizados 56 ratos da linhagem Wistar, fêmeas, divididos em cinco grupos experimentais- G1 (8) – controle, sem procedimento, G2 (12) – animais não suplementados, submetidos ao procedimento de obstrução vesical e posterior cistotomia, G3 (12) – animais suplementados e submetidos ao procedimento de obstrução vesical e posterior cistotomia, G4 (12) – animais não suplementados e submetidos ao procedimento de cistotomia e G5 (12) animais suplementados e submetidos ao procedimento de cistotomia. A suplementação de glicosaminoglicanos foi realizada a cada 24 horas por via oral durante 28 dias pós cistotomia, quando então os animais foram eutanasiados. O colágeno foi avaliado pela Microscopia Cars e biglican, decorina, lumican e fibromodulina pelo método de imunofluorescência. Para análise estatística foi utilizado o teste ANOVA e T-STUDENT, com nível de significância p <0,05. Os animais dos grupos G2 e 3 foram os que apresentaram diferença estatística na seguinte constante: peso bexiga final /p... (Resumo completo, clicar acesso eletrônico abaixo) / Mestre
144

Human skin investigations using nonlinear spectroscopy and microscopy / Développements en spectroscopie et microscopie non linéaire pour l'étude morphologique et fonctionnelle de la peau humaine

Chen, Xueqin 11 December 2014 (has links)
La peau est un organe qui enveloppe le corps, elle est une barrière naturelle importante et efficace contre différents envahisseurs. Pour le traitement des maladies dermatologiques ainsi que dans l'industrie cosmétique, les applications topiques sur la peau sont largement utilisées. Ainsi beaucoup d'efforts ont été investis dans la recherche sur la peau visant à comprendre l'absorption moléculaire et les mécanismes rendant efficace la pénétration. Cependant, il reste difficile d'obtenir une visualisation 3D de haute résolution combinée à une information chimique- ment spécifique et quantitative dans la recherche sur la peau. La spectroscopie et la microscopie non-linéaire, incluant la fluorescence excitée à 2-photon (TPEF), la diffusion Raman spontanée, la diffusion Raman cohérente anti-Stokes (CARS) et la diffusion Raman stimulée (SRS), sont introduits dans ce travail pour l'identification sans ambiguïté de la morphologique de la peau et la détection de molécules appliquées de façon topique. Plusieurs méthodes quantitatives basées sur la spectroscopie et la microscopie non-linéaire sont proposées pour l'analyse chimique en3D sur la peau artificielle, ex vivo et in vivo sur la peau humaine. De plus, afin de s'adapter aux applications cliniques à venir, un design endoscopique est étudié pour permettre l'imagerie non-linéaires dans les endoscopes flexibles. / Skin is an organ that envelops the entire body, acts as a pivotal, efficient natural barrier to- wards various invaders. For the treatment of major dermatological diseases and in the cosmetic industry, topical applications on skin are widely used, thus many efforts in skin research have been aimed at understanding detailed molecular absorption and efficient penetration mechanisms. However, it remains difficult to obtain high-resolution visualization in 3D together with chemical selectivity and quantification in skin research. Nonlinear spectroscopy and microscopy, including two-photon excited fluorescence (TPEF), spontaneous Raman scattering, coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS), are introduced in this work for unambiguous skin morphological identification and topical applied molecules detection. Sev- eral quantitative methods based on nonlinear spectroscopy and microscopy are designed for 3D chemical analysis in reconstructed skin, ex vivo and in vivo on human skin. Furthermore, to adapt to forthcoming clinical applications, an endoscopic design is investigated to bring nonlin- ear imaging in flexible endoscopes.
145

"Goodness is the only investment that never fails" : En studie om hur Volvo Cars kommunicerar CSR på sin webbplats / "Goodness is the only investment that never fails" : A study about how Volvo Cars communicate CSR on their website

Hultén, Manne, Rommel Benedikt, Lukas January 2018 (has links)
Idag implementerar allt fler företag CSR-strategier i sina verksamheter. Trots att många konsumenter tycker att det är viktigt att företag engagerar sig i hållbarhetsfrågor är det ändå inte speciellt många som är medvetna om vilka som engagerar sig och hur de engagerar sig. Att kommunicera kring sitt engagemang blir därför en avgörande faktor för organisationer som vill skapa trovärdighet och förstärka sitt varumärke. Tidigare forskning pekar på att det är en svår och komplicerad uppgift att kommunicera kring CSR. Syftet med denna uppsats är att få en ökad förståelse för hur biltillverkaren Volvo Cars kommunicerar CSR på sin webbplats. Studien undersöker både hur kommunikationen är uppbyggd utifrån textens stil och meddelandets innehåll men också hur frekvent företaget kommunicerar sitt ekonomiska, sociala och miljömässiga engagemang samt hur kommunikationen är inramad mot företagets primära intressentgrupper utifrån de tre motiven från triple bottom line-teorin. Volvo Cars är intressant att undersöka i detta sammanhang eftersom företaget är en del av en bransch som har en stor inverkan på miljön. Dessutom beskriver företaget sig själv som aktiv deltagare i hållbarhetsfrågor. Studien har genomförts genom en tillämpning av två kvalitativa innehållsanalyser och en kvantitativ innehållsanalys. Data har hämtats från Volvo Cars landningssida för hållbarhet och från företagets hållbarhetsrapport från 2015. Materialet har analyserats utifrån triple bottom line-teorin, intressentmodellen och ett konceptuellt ramverk för CSR-kommunikation. Uppsatsens resultat visar att Volvo Cars CSR-kommunikation är relationsbyggande och innehåller ett förhållandevis komplicerat och “tungt” språk. Företaget kommunicerar sitt engagemang kring miljö mest frekvent och kommunikationen är inramad väldigt olika till de respektive intressentgrupperna. / Today, more and more companies are implementing CSR-strategies into their businesses. Although many consumers find it important that companies engage in sustainability issues, there are still not that many who are aware of who engages and how they engage. Therefore, it is essential for organizations to communicate about their CSR engagement in order to create credibility and maximize business returns. Previous research show that communicating CSR is a difficult and complicated task. The purpose of this thesis is to create an increased understanding in how the car manufacturer Volvo Cars communicates its CSR commitment on their corporate website. The study examines how the communication is structured based on style and message content, how often Volvo Cars communicate their economic, social and environmental commitments and how the communication is framed to various stakeholder groups based on the three motives from the triple bottom line theory. Volvo Cars is interesting to investigate in this context since the company is part of an industry that has a major impact on the environment. In addition, the company also describes itself as an active participant in sustainability-issues. The study has been conducted by using two qualitative and one quantitative content analysis. The data was collected from Volvo Cars landing page of sustainability and from the company's sustainability report from 2015. The data has been analyzed based on the triple bottom line-theory, the stakeholder model and a conceptual framework for CSR-communication. The findings of this thesis show that Volvo Cars CSR-communication is relationship building and contains a relatively complicated and “heavy” language. The company communicates its commitment about environment most often and the communication is framed very differently to various stakeholder groups.
146

Resan mot den virtuella verkligheten : En multipel fallstudie av den virtuella verklighetens påverkan på varumärkesimagen inom bilindustrin / The Journey Towards the Virtual Reality

Jehrlander, Niklas, Pettersson, Max January 2017 (has links)
Purpose The purpose of this study is to investigate how companies can use VR-commercials and commercials to influence brand image. Furthermore, the purpose is to identify which factors in these medias that affect brand image as well as account for the differences between these two medias. Research questions How can companies use VR-commercials and commercials to influence brand image? Which factors affect brand image through VR-commercials and commercials and what is the differences between these two medias? Result VR-commercials and commercials make it possible to influence the brand image. The essay also mentions the identified factors that affect the brand image which are environment, telepresence, memories and associations, noise and disturbances, barriers and music. Contribution The study describes how companies can use VR-commercials and commercials to influence an individual's brand image. The study clarifies the differences between the two medias and the factors that influence the brand image of the interviewees. An analysis model is presented since a gap in the existing knowledge in communications theory was discovered / Problemställning Kommer dagens reklamfilmer vara tillräckliga för att få kunden att lyssna till företag eller kommer det krävas mer av deras marknadsföring för att företag ska lyckas nå ut till sina kunder? Syfte Syftet med denna studie är att undersöka hur företag kan använda VR-reklam och reklamfilm för att påverka varumärkesimagen. Vidare är syftet att identifiera vilka faktorer i dessa medier som påverkar en individs varumärkesimage samt redogöra för eventuella skillnader de två medierna sinsemellan. Frågeställningar Hur kan företag använda VR-reklam respektive reklamfilm för att påverka varumärkesimagen? Vilka faktorer påverkar varumärkesimagen via VR-reklam respektive reklamfilm och vad skiljer dessa medier åt? Resultat Genom VR-reklam och reklamfilm går det att påverka varumärkesimagen. I uppsatsen nämns även de identifierade faktorer som har påverkan på denna vilka är miljö, telenärvaro, minnen och associationer, brus och störningar, barriärer och musik. Kunskapsbidrag I studien beskrivs hur företag kan använda VR-reklam och reklamfilm för att påverka en individs varumärkesimage. I studien klargörs de skillnader som finns mellan medierna och vilka faktorer som har påverkat intervjupersonernas varumärkesimage. En egen analysmodell presenteras då en lucka i den befintliga kommunikationsteorin upptäcktes.
147

Microscopie de mélange à quatre ondes résolue en polarisation pour sonder l’ordre moléculaire dans les milieux biologiques / Polarization resolved four-wave mixing microscopy : a tool to probe molecular order in biological media

Bioud, Fatma Zohra 28 November 2013 (has links)
Nous avons développé une méthodologie basée sur phénomène de mélange à quatre ondre polarimétrique « Four wave Mixing FWM » et son équivalen résonant la diffusion Raman cohérente anti-Stokes (CARS, Coherent Anti-Stokes Raman Scattering) polarimétrique et réalisé des mesures sur des systèmes cristallins, simili biologiques : les membranes cellulaires connues sous le nom de « Multilamellar Vesicles MLV » et des échantillons de biologiques : la myeline, et ce, en variant les polarisations des lasers excitateurs, Pompe et Stokes. Le signal anti-Stokes émis est ensuite analysé afin d’en extraire les ordres 2 et 4 de la fonction de distribution angulaire des molécules actives constituant l’échantillon. Pour cela, plusieurs approches sont explorées telles que des algorithmes d’optimisation ou par décomposition en série de fourrier du signal polarimétrique. Ces multiples approches en traitement du signal permettent d’obtenir de manière rapide les coefficients des fonctions de distribution angulaire recherchées, et ainsi d’avoir des informations sur la symétrie des échantillons imagés, allant jusqu’à l’observation d’une symétrie d’ordre 4. La capacité de la microscopie non linéaire résolue en polarisation à sonder des ordres moléculaires est clairement démontrée et ainsi son intérêt dans l’étude de la relation entre la structure et la fonction de systèmes biologiques. / The capacity to quantify molecular orientational order in tissues is of a great interest since pathologies (skin lesion, neurodegenerative diseases, etc) can induce strong modifications in proteins’ organization. While numerous studies have been undertaken using polarization resolved second order nonlinear optical microscopy which is only specific to non-centrosymmetric organizations, higher order effects have been less explored. Four-wave mixing (FWM) microscopy and its resonant counterpart coherent anti-Stokes Raman scattering (CARS) can be of a great utility as label free diagnosis tools benefiting from less constraining symmetry rules. In this work, we implement incident polarizations tuning in FWM and CARS microscopy to probe molecular order, using a generic method to read-out symmetry information.Fourier analysis of the polarization-resolved FWM/CARS signal processed with an analytical model provides a fast and direct determination of the symmetry orders of the distribution function of the probed molecules. This method does not require a priori knowledge of the organization structure and provides quantitatively its second and fourth order symmetries. We applied this technique on different systems, from crystalline to less organized (multilamellar vesicles and proteins aggregates). We show that this new approach brings additional and more refined information on supra-molecular structures in complex media.
148

En jämförelsestudie av risker och säkerhet mellan elbilar och vätgasbilar / A comparative study of risks and safety between electric cars and hydrogen cars

Anwer, Andri, Boujakly, Edward January 2021 (has links)
Rapporten är skriven för ett högskoleingenjörsexamensarbete på kungliga tekniska högskolan, inom programmet maskinteknik, med inriktning industriell ekonomi och produktion. Bakgrunden av detta arbete ska ge läsaren en grund för de olika modellerna, elbilar och vätgasbilar samt väcka ett intresse för att bevara säkerheten med valet av bil. Syftet och målet med denna studie har varit att presentera en jämförelsestudie, gällande elbilar och vätgasbilar, samt svara på frågeställningarna som arbetet tagit fram. Resultatet av arbetet bygger på både FMEA- analyser för vätgasbilar och elbilar, samt jämförelsematris som ger en förtydligad bild på skillnader mellan elbilar och vätgasbilar, ur vissa valda funktioner. En förtydligad bild av FMEA analysen har byggt, genom att tillämpa ett paretodiagram som beskriver de olika risker och prioritering som finns för respektive modell. Rekommendationer och ytterligare säkerhetsarbeten för att minimera dessa risker beskrivs i FMEA analysen, utifrån indata och beskrivningar från tidigare rapporter, samt kunskap från studier. Resultatet från FMEA- analysen, paretodiagrammet, samt jämförelsematrisen visar att vätgasbilar är en säkrare modell och har en framtid eftersom utvecklingsmöjligheterna fortfarande finns, då dessa är nya på marknaden. Vätgasbilen är även mindre riskbenägen modell jämfört med elbilar, detta kan man visa med hjälp av RPN-talet, som är lägre för vätgasbilar, i jämförelse med elbilarnas RPN-tal. / The background of this thesis will give the reader the basis for the models of electric and hydrogen fueled vehicles. The purpose and goal of this study has been to present a comparative study regarding electric and hydrogen vehicles, and to answer the questions that the study has raised. The results of the work are based on both FMEA analysis for hydrogen and electric vehicles, as well as a comparison matrix that provides a clarified picture of the differences between electric vehicles and hydrogen vehicles, through certain selected factors. A clarified picture of the FMEA analysis results has been built by applying a pareto diagram that describes the different risks of each model and also what their priorities are. Recommendations and additional safety work to minimize these risks are suggested and described in the FMEA analysis, based on input data and descriptions from previous reports, as well as gained knowledge from studies. The results from the FMEA analysis, pareto-diagram and the comparison matrix shows that hydrogen vehicles are a less risk-prone model compared to electric vehicles and have a bright future as development opportunities still exist, this due to the fact that they are still new in the automotive industry. This can be proved with the help of the RPN number for hydrogen vehicles, which is lower compared to the RPN number of electric vehicles.
149

Modern Raman Spectroscopy Investigations of Lithium Niobate

Reitzig, Sven 22 April 2024 (has links)
The new generation of non-linear optical devices, based on periodically-poled lithium niobate thin film platforms, aims at achieving record-high conversion efficiencies and a formerly unknown capability for integration into modern quantum optical systems. It thus not only suits the demands of high-end telecommunication applications, but also provides striking potential for further performance enhancement. However, most of these record-setting new developments lack in in-depth analysis of their domain grid structures to determine whether the key requirements for efficient non-linear optical conversion are ideally fulfilled. Established analysis techniques for the exploration of bulk lithium niobate, like Raman spectroscopy, have not been adapted for these thin film structures, because the low interaction volumes require long acquisition times. In this work, the importance of Raman spectroscopy analysis for thin film lithium niobate device optimization is demonstrated in cross-correlated co-imaging with second-harmonic imaging and piezoresponse force microscopy. Key performance indicators of quasi-phase matching are identified and specifically investigated. The experiments show that Raman spectroscopy is capable of detecting all these indicators and is unique in its ability to identify performance-inhibiting mechanical and electrical stress fields. In an attempt to establish high-speed Raman imaging on lithium niobate structures, the coherent four-wave mixing method of broadband coherent anti-Stokes Raman scattering (B-CARS) is, for the first time, systematically introduced for fundamental solid state analysis by theoretically and experimentally addressing all special implications of crystalline material systems via the model material lithium niobate, e.g. phase matching conditions, phase retrieval, and complex selection rules. It is shown that the resonant B-CARS signal can be retrieved in post-processing and allows a direct comparison with spontaneous Raman spectroscopy. The predicted CARS selection rules are experimentally confirmed, and phonons are assigned to their respective B-CARS peaks. Furthermore, B-CARS signals are shown to be predominantly generated by scattering in forward direction. The insights of these fundamental investigations are applied for lithium niobate domain wall imaging via B-CARS. Hyperspectral spontaneous Raman spectroscopy and B-CARS images are compared with regard to imaging speed, signal-to-noise ratio, domain wall contrast mechanism, and signature width. The experiments prove that B-CARS allows at least a 20-fold speed increase with an improved signal-to-noise ratio as compared to spontaneous Raman spectroscopy. The domain wall signature is of similar nature for both techniques, and is not changed via phase retrieval, thus allowing high-speed B-CARS domain wall imaging in lithium niobate without post-processing. The massive B-CARS domain wall signal is attributed to a Čerenkov-like effect analogous to second-harmonic imaging. This is the first time that such an effect has been shown by a Raman scattering technique. These findings show the importance of Raman scattering investigations for the optimization of modern non-linear optical devices, and outline a way to massively increase the speed of Raman crystal analysis via B-CARS. Thus, with further studies that quantify the effects detailed qualitatively in this work and take B-CARS analyses to a broader range of crystalline samples, this work can form the basis towards establishing the high-speed and in-depth analysis of modern non-linear optical platforms via coherent Raman imaging.:1. Motivation .......... 1 2. Fundamentals .......... 4 2.1 Lithium Niobate .......... 4 2.1.1 Ferroelectric Structures .......... 4 2.1.2 Domain Engineering .......... 6 2.1.3 Thin Film Lithium Niobate (TFLN) .......... 8 2.2 Spontaneous Raman Spectroscopy .......... 10 2.2.1 Raman Spectroscopy of Lithium Niobate Crystals .......... 14 2.2.2 Domain Imaging with Spontaneous Raman Spectroscopy .......... 18 2.3 Coherent anti-Stokes Raman Scattering (CARS) .......... 20 2.3.1 Signal Generation .......... 21 2.3.2 Broadband Coherent anti-Stokes Raman Scattering (B-CARS) .......... 24 2.3.3 The Non-Resonant Background .......... 25 2.3.4 Selection Rules .......... 27 2.3.5 Phase Matching .......... 30 3. Experimental Methods .......... 32 3.1 Spontaneous Raman Spectroscopy (SR) Setup .......... 32 3.2 B-CARS Setup .......... 34 3.3 Raman Data Analysis .......... 35 3.4 B-CARS Phase Retrieval .......... 36 3.5 Second-Harmonic Generation Microscopy .......... 38 3.6 Piezoresponse Force Microscopy .......... 40 4. Thin Film Lithium Niobate Co-Imaging .......... 42 4.1 TFLN Sample and Co-Imaging Approach .......... 45 4.2 Piezoresponse Force Microscopy Imaging .......... 47 4.3 Second-Harmonic Generation Imaging .......... 49 4.4 Hyperspectral Raman Imaging .......... 53 4.5 Conclusions on Cross-Correlated Co-Imaging .......... 58 5. Fundamental Aspects of B-CARS on Lithium Niobate .......... 61 5.1 Phase Matching .......... 62 5.2 Phase Retrieval .......... 65 5.3 Selection Rules and Phonon Assignment .......... 67 5.4 Conclusions .......... 71 6. B-CARS Domain Wall Analysis in Lithium Niobate .......... 73 6.1 Preliminary Considerations .......... 73 6.2 Sample Preparation .......... 74 6.3 Spectral Analysis .......... 75 6.4 Determination of Acquisition Times .......... 78 6.5 Domain Wall Signatures .......... 79 6.6 Domain Imaging .......... 82 6.7 Conclusions .......... 83 7. Summary and Outlook .......... 85 Appendix .......... I References .......... XIII Own Publications .......... XXIV Acknowledgements .......... XXV
150

Design of a car utilization audit.

Nowicki, Victor. January 1978 (has links)
Thesis: M.S., Massachusetts Institute of Technology, Department of Civil Engineering, 1978 / Includes bibliographical references. / M.S. / M.S. Massachusetts Institute of Technology, Department of Civil Engineering

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