• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 82
  • 29
  • 20
  • 5
  • 4
  • 4
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 180
  • 180
  • 36
  • 26
  • 23
  • 21
  • 20
  • 18
  • 18
  • 16
  • 15
  • 15
  • 15
  • 13
  • 13
  • 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

Temperature Dependent Size Exclusion Chromatography for Investigating Thermoreversibly Bonding Polymer Systems

Brandt, Josef 11 July 2016 (has links)
Polymers capable of thermally controlled reversible bonding reactions are promising candidates for stimuli responsive materials, as required for self-healing or drug delivery materials. In order to investigate how the dynamic reactions can be controlled, effective analytical tools are demanded that are capable of analyzing not only the polymers but can also monitor the respective bonding reactions. Herein, we employ size exclusion chromatography in a newly developed temperature dependent mode (TD SEC) for the in situ characterization of polymers that undergo retro Diels-Alder (rDA) reaction at temperatures higher than 60 °C. Monitoring the evolution of the molar mass distribution of the polymers during the rDA reaction and evaluating the data quantitatively gives detailed information about the extent of the reaction and allows elucidating structural parameters that can be used for controlling the polymers debonding behavior. In contrast to spectroscopic techniques, TD SEC analyzes only the size of the polymers, hence the polymers do not need to fulfill any particular requirements (e.g. presence of detectable functional groups) but only need to be soluble in the TD SEC, which makes the method universally applicable. Side effects that might bias the results are minimized by using a high temperature chromatograph that allows performing the analysis in a broad temperature range (60 – 200 °C) and in different solvents. Thus, the analysis can be performed under the exact conditions that are required for the bonding reactions and an in situ image is provided.
142

Die Selbstheilungskräfte von Wirtschaftssystemen aus geistes- und evolutionswissenschaftlicher Sicht

Stephan, Ulrich, Thießen, Friedrich 23 September 2013 (has links)
Es heißt, moderne Marktwirtschaften seien sich selbst regulierende Systeme. Dies gelte auch für die Moral der Akteure. Die Finanzkrisen der letzten Jahre haben die Frage nach der Stärke der Selbstheilungskräfte aufgeworfen. Dies wird im Aufsatz untersucht. Dazu werden zunächst die geisteswissenschaftlichen Konzeptionen des Liberalismus, des Ordoliberalismus und der Zentralverwaltungswirtschaft vorgestellt. Dann wird eine evolutionswissenschaftliche Konzeption dagegengestellt. Es zeigt sich, dass die geisteswissenschaftlichen Konzeptionen das „eigentliche“ Zielsystem der Akteure nur unvollkommen berücksichtigen. Sie über- oder unterschätzen daher das Vermögen der Systeme zur Selbstheilung. Die größte Übereinstimmung finden wir beim Ordoliberalismus, der mit seiner Skepsis in die Selbstheilungskräfte freier Märkte Recht hat: Es muss einen institutionellen Ordnungsrahmen geben, der mit der wünschenswerten gesellschaftlichen Moral besser als bisher zu verknüpfen ist. Für die weitere Forschung sehen wir die wichtige Aufgabe, die Selbstheilungskräfte der Gesellschaft in Bezug auf moralisches Verhalten genauer zu erforschen. / It has been said, modern market economies are self-regulating systems. This would also be true for the moral standards of its actors. The financial crises of recent years have put the strength of self-healing capacities in question. This will be investigated in the following paper. In order to do so, concepts of social sciences such as liberalism, ordoliberalism and central command economy will be presented. Subsequently, evolution theory will oppose these concepts. The analysis shows that social sciences only imperfectly recognize the essential objectives of actors. They over- or underestimate the self-healing capabilities of the economy systems. The largest conformity was found in the ordoliberalism, whose skeptics in self-healing capacities of free markets have been upheld. An institutional framework has to be put in place, which is more strongly linked to the morals of civil society as has been the case so far. In the future, one important task for research will be to further investigate self-healing capacities of societies in light of moral behavior.
143

Towards a sustainable road infrastructure in an age of digitization: opportunities and challenges

Liu, Zhuhuan January 2022 (has links)
Pavement system plays an indispensable role in the socio-economic and sustainable development of every modern society. Yet, pavement construction and maintenance is also responsible for a significant fraction of the GHG emissions from the whole transport sector. At the same time, the extensive global pavement network entails continual investment in maintenance and rehabilitation activities. Given the evidence from previous studies, pavement maintenance has a great potential in reducing pavement-induced GHG emissions and fuel consumption. To assist the transition towards a future sustainable road infrastructure, this thesis has marked the theoretical basis of sustainable pavement maintenance management. Two approaches are discussed to offer a multi-dimensional view for future sustainability improvement in pavement maintenance practices. With the still-evolving concept of sustainability in road infrastructure, it is necessary to recognize where we are and what we need to do to develop a comprehensive management framework with the opportunities and challenges. Based on a systematic literature review, this project identifies the current stage of sustainable road infrastructure management and guides to sustainability-oriented maintenance optimization for designing top-down strategies. Meanwhile, it is not enough to only optimize the decision-making process; more bottom-up knowledge of pavement materials is required to inform better maintenance design. This thesis has focused on the self-healing property of asphalt material due to the non-negligible sustainability indications it implies. By applying neutron tomography and image processing technique, the microstructural changes during the self-healing process are analyzed with its 7-hour time-series volumetric data. The experiment has shown that different filler content has a great influence on self-healing efficiency in asphalt mastics. The results will give us the possibility to optimize asphalt self-repair, shedding a light on a new generation of sustainable asphalt pavement. The two approaches presented in this thesis offer valuable insights into sustainable road infrastructure optimization from different aspects. / I varje modernt samhälle spelar vägarna en viktig roll för socioekonomisk och hållbar utveckling. Vägnätet, med byggande och underhåll, bidrar också med en betydande del av växthusgasutsläppen från hela transportsektorn. Vägnätet kräver kontinuerliga investeringar på grund av behovet av underhåll . Tidigare studier har visat att det finns en stor potential för minskning av utsläppen av växthusgaser från vägunderhåll. Vägarnas kvalitet spelar också roll för trafikens bränsleförbrukning.  Fokus för denna avhandling är att underlätta för framtida hållbar väginfrastruktur. När det gäller den teoretiska grunden för hållbar förvaltning av vägar och underhåll av vägbeläggningar är det nödvändigt att förstå vad som är dagens aktuella teknik, och också att veta vad vi behöver utveckla för att få ett heltäckande ledningsramverk för vägunderhåll. Här finns både möjligheter och utmaningar. Baserat på en systematisk litteraturgenomgång identifierar detta projekt det aktuella läget när det gäller praktik för förvaltning av väginfrastruktur. Som ett resultat av detta presenteras olika metoder som tillämpas för en målorienterad underhållsoptimering, som måste göras top-down från den som har övergripande ansvar för vägnätet. Samtidigt räcker det inte att bara optimera beslutsprocessen, det krävs mer bottom-up kunskap i fråga om beläggningsmaterial för att förbättra metoderna för underhåll. Denna avhandling har därför också fokuserat på den självläkande egenskapen hos asfaltmaterial. Här fanns en unik möjlighet att tillämpa neutrontomografi och bildbehandlingsteknik för analyser av de mikrostrukturella förändringarna under självläkningsprocessen i asfaltmaterial, med 7-timmars tidsserievolymetriska data. Experimentet har visat att olika innehåll av fyllmedel i asfaltmastixen  har stor inverkan på självläkandets effektivitet. De två tillvägagångssätten som presenteras i denna avhandling ger värdefulla insikter om hållbar väginfrastrukturoptimering ur olika aspekter. / <p>QC 220309</p>
144

Élaboration d'élastomères silicones supramoléculaires auto-cicatrisants / Design of self-healing supramolecular silicone elastomers

Fauvre, Lucile 13 December 2018 (has links)
Ces travaux de thèse concernent l’étude de matériaux supramoléculaires en vue de générer de nouveaux élastomères silicones auto-cicatrisants. Dans un premier temps, l’étude de la bibliographie a permis de recenser les différentes voies intégrant de la chimie supramoléculaire développées dans le domaine des silicones et basées sur les liaisons hydrogène. L’effet des groupements associatifs sur les propriétés rhéologiques et mécaniques des matériaux a été discuté, et les limitations de ces systèmes soulignées. La chimie développée par l’équipe du Dr. Leibler, adaptée par la suite aux silicones par le Pr. Zhang et son équipe, a particulièrement été analysée lors de notre étude de compréhension. Les relations structures/propriétés n’étaient pas clairement élucidées à l’issue de cette étude de la bibliographie. Des études modèles impliquant un PDMS téléchélique aminé ainsi que de l’urée ont donc été réalisées. La caractérisation précise des structures des produits de réaction a permis de mettre en exergue certaines corrélations entre structures (choix du groupement associant, masse molaire du copolymère, fonctionnalité) et propriétés (rhéologiques et mécaniques) qui n’avaient alors pas été démontrées pour ces systèmes. Il a aussi été montré que la force des groupements et les enchevêtrements jouent un rôle primordial. Une chimie différente, inspirée des travaux de Yilgör et al sur les copolymères segmentés, a par la suite été envisagée, en mettant en jeu cette fois la réaction d’aza-Michael. Cette synthèse se démarque du premier système par un meilleur contrôle de la structure macromoléculaire finale. Un silicone supramoléculaire élastomère et auto-cicatrisant a été obtenu en combinant une fonctionnalité importante et une masse molaire finale élevée. Les propriétés mécaniques de ce polymère ont été optimisées par l’ajout de charges plus ou moins renforçantes. L’impact d’un tel renfort sur les propriétés auto-cicatrisantes du système a été discuté. / This PhD thesis focused on the investigation of supramolecular materials in order to generate new self-healing supramolecular silicone elastomers. Firstly, a literature review on silicone materials was realized and we identified the different ways developed in the silicone domain that imply supramolecular chemistry and in particular hydrogen-bonds. The influence of associating groups on rheological and mechanical properties of these materials was discussed, and the restrictions of such systems were highlighted. The chemistry developed by Dr. Leibler and co-workers, later adapted to silicones by Pr Zhang and his team, was deeply investigated during our comprehension study. Relationships between structure and properties were nonetheless not fully elucidated in these studies. Model reactions involving telechelic amino-PDMS and urea were then carried out. The thorough characterization of the final structure of the reaction products highlighted few correlations between structural parameters (choice of the type of associating group, molecular weight of copolymer, functionality) and properties (rheological and mechanical) that had not been demonstrated yet for these systems. We showed that, among others, the strength of the associating groups as well as the entanglements play a fundamental role. A different chemistry, inspired by Yilgör and co-workers’ studies on segmented copolymers, was later considered by carrying out an aza-Michael reaction. This synthesis differs from the previous one by its better control of the final macromolecular structure. A supramolecular silicone elastomer with self-healing abilities was obtained by combining a large functionality together with a high final molecular weight. Mechanical properties of this material were further enhanced through the addition of more or less reinforcing fillers. The influence of such reinforcement on self-healing capacity of this system was discussed.
145

Bounded model checking v nástroji Java PathFinder / Bounded Model Checking Using Java PathFinder

Dudka, Vendula January 2008 (has links)
This thesis deals with the application of bounded model checking method for self-healing assurance of concurrency related problems. The self-healing is currently interested in the Java programming language. Therefore, it concetrate mainly on the model checker Java PathFinder which is built for handling Java programs. The verification method is implemented like the Record&Replay trace strategy for navigation through a state space and performance bounded model checking from reached state through the use of Record&Replay trace strategy. Java PathFinder was extended by new moduls and interfaces in order to perform the bounded model checking for self-healing assurance. Bounded model checking is applied at the neighbourhood of self-healing.
146

Polyurethane (PU) Nanocomposites; Interplay of Composition, Morphology, and Properties

Solouki Bonab, Vahab 01 February 2019 (has links)
No description available.
147

FACILE AND FAST FABRICATION OF FUNCTIONAL THIN FILMS VIA POLYELECTROLYTE LAYER-BY-LAYER ASSEMBLY

Cho, Szu-Hao 26 August 2020 (has links)
No description available.
148

Development and characterization of novel organic coatings based on biopolymer chitsan

Kumar, Girdhari 01 December 2006 (has links)
No description available.
149

[pt] ITINERÂNCIAS ZINE-FEMINISTAS: UM MERGULHAR EM DATILOGRAFIAS DE FÚRIA E SAUDADE / [en] ZINE-FEMINIST IS ON THE ROAD: A PLUNGE ON FURY AND LONGING

CAMILA OLIVIA DE MELO 11 December 2019 (has links)
[pt] Em 2015, iniciei uma investigação etnográfica com o objetivo de mapear e participar de coletivos feministas que estivessem ativos politicamente por meio da mídia fanzine, ou zines. Entre 2015-2018, arquivamos 101 zines das regiões Centro-Sul do Brasil; circulamos por envelopes na troca de cartas, por eventos punkfeministas e, principalmente, por feiras de zines a céu aberto. A vertigem da cidade do Rio de Janeiro-RJ, nosso locus de pesquisa, nos afetou enquanto o país passava por uma série de tombamentos nas macroestruturas de poder. Neste cenário, as zineiras (quem faz zines) formavam alianças em gestos de resistência às violências cotidianas da metrópole e elaboravam relações políticas velcro-provisórias (Gloria Anzaldúa), sendo os zines a sua principal mídia de emissão e prática de si (Michel Foucault). Em nosso campo de pesquisa pudemos refletir sobre as práticas de escrita zinefeministas contemporâneas; os gestos de revide às violações de limites (dentro e fora de espaços contraculturais); e, com Judith Butler, enxergar os levantes como potência desses coletivos. Além disso, mergulhamos no trabalho da dadaísta Hannah Höch para analisar os zines de nosso recorte. A proposta desta tese foi problematizar as noções de comunidade, amizade e sabedorias consagradas; além das próprias experiências ocorridas na pesquisa dentro do que chamamos de campo zinefeminista. Observamos as dinâmicas, afetações políticas e relações entre as participantes dessa rede; aproximamo-nos de sua economia das trocas e, com as falas de zineiras não-heterossexuais, contamos uma história com impulsos de fúria e saudade. / [en] In 2015, I started an ethnographic research with the objective of mapping and attending feminist collectives that were politically active through self-publications (zines). Between the years 2015-2018 we have archived 101 zines from the Center- South regions of Brazil; we have checked envelopes in the exchange of letters, and we also have circulated through punk-feminist events and particularly open skies zine fairs. Rio de Janeiro city s vertigo, our research locus, affected us as the country underwent a series of toppling in the macro-structures of power. In this scenario, the zinesters formed alliances regarding gestures of resistances to the daily violence of the metropolis and elaborated political relations called velcro-alliance (Gloria Anzaldúa) being the zines their main medium and practice of the self (Michel Foucault). In our research field, we could reflect on contemporary zine-feminist writing practices; the gestures of retaliation to the limit violations (inside and outside the counter-cultural spaces); and with Judith Butler we were able to see the uprisings as the power of these feminist collectives. In addition, we have immersed in the Dadaist Hannah Höch s work so we could analyze the zines of our scope. The goal of this thesis was to problematize the notions of community, friendship and consecrated wisdom; besides the particular experiences that have occurred in the research within what we call the zine-feminist field. We have had the opportunity to observe the dynamics, political affectations and relationships among the participants of this network; we have approached ourselves to the economy of trade and, using the speeches of non-heterosexual zinesters, we have told a story with impulses of fury and longing (in Brazilian Portuguese, the feeling of missing someone).
150

Developing the Next Generation of Perovskite Solar Cells

Blake P Finkenauer (12879047) 15 June 2022 (has links)
<p>  </p> <p>Organic-inorganic halide perovskites are at the brink of commercialization as the next generation of light-absorbing materials for solar energy harvesting devices. Perovskites have large absorption coefficients, long charge-carrier lifetimes and diffusion lengths, and a tunable absorption spectrum. Furthermore, these materials can be low-temperature solution-processed, which transfers to low-cost manufacturing and cost-competitive products. The remarkable material properties of perovskites enable a broad product-market fit, encompassing traditional and new applications for solar technology. Perovskites can be deposited on flexible substrates for flexible solar cells, applied in thermochromic windows for power generation and building cooling, or tuned for tandem solar cell application to include in high-performance solar panels. However, perovskites are intrinsically unstable, which has so far prevented their commercialization. Despite large research efforts, including over two thousand publications per year, perovskite solar cells degrade in under one year of operation. In a saturated research field, new ideas are needed to inspire alternative approaches to solve the perovskite stability problem. In this dissertation, we detail research efforts surrounding the concept of a self-healing perovskite solar cell.</p> <p>     A self-healing perovskite solar cell can be classified with two distinctions: mechanically healing and molecularly healing. First, mechanically self-healing involves the material’s ability to recover its intrinsic properties after mechanical damage such as tares, lacerations, or cracking. This type of healing was unique to the organic polymer community and ultra-rare in semiconducting materials. By combining a self-healing polymer with perovskite material, we developed a self-healing semiconducting perovskite composite material which can heal using synergistic grain growth and solid-state diffusion processes at slightly elevated temperatures. The material is demonstrated in flexible solar cells with improved bending durability and a power conversion efficiency reaching 10%. The addition of fluidic polymer enables macroscopic perovskite material movement, which is otherwise brittle and rigid. The results inspire the use of polymer scaffolds for mechanically self-healing solar cells.</p> <p>     The second type of healing, molecular healing, involves healing defects within the rigid crystal domains resulting from ion migration. The same phenomenon which leads to device degradation, also assists the recovery of the device performance after resting the device in the dark. During device operation, perovskite ions diffuse in the perovskite lattice and accumulate at the device interfaces where they undergo chemical reactions or leave the perovskite layer, ultimately consuming the perovskite precursors. The photovoltaic performance can be recovered if irreversible degradation is limited. Ideally, degradation and recovery can match day and night cycling to dramatically extend the lifetime of perovskite solar cells. In this dissertation, we introduce the application of chalcogenide chemistry in the fabrication of perovskite solar cells to control the thin film crystallization process, ultimately to reduce defects in the perovskite bulk and introduce surface functionality which extends the device stability. This new strategy will help improve molecularly self-healing perovskite solar cell by reducing irreversible degradation. Lastly, we present a few other new ideas to inspire future research in perovskite solar cells and assist in the commercialization of the next generation of photovoltaics.</p>

Page generated in 0.0805 seconds