• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 5
  • 5
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 2
  • 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

Adhezivní a reologické vlastnosti směsí na bázi chitosanu v médiích různého pH / Adhesive and rheological properties of chitosan-based mixtures in media of different pH

Omar, Alaa Abdel Gawad Ahmed Osman January 2020 (has links)
Title of thesis: Adhesive and rheological properties of chitosan-based mixtures in media of different pH Author: Alaa Omar Supervisor: PharmDr. Eva Šnejdrová, Ph.D. Consultant: Mgr. Juraj Martiška The aim of the diploma thesis is the study of rheological and adhesive properties of tableting materials for matrix tablets based on chitosan. The theoretical part describes in detail the materials used to prepare the matrix tablets, which were chitosan, sodium alginate and hypromellose. The experimental section was focused on the flow and adhesive properties of the chitosan-based mixtures after exposing them to a media of different pH. The flow tests were done on an absolute rotational rheometer. Obtained viscosity curves were analysed by Power law model. Viscosity at 10 s-1 and Power Law model coefficients were used to evaluate and compare the flow behaviour of dispersions with different concentrations of retarding component in different media. The test of adhesion was carried out using a pull away test on a rotational rheometer and evaluated as maximal detachment force. The remarkably high viscosity of 5% dispersions at pH 1.2 is due to the dissolution of chitosan, as sodium alginate is not soluble in acidic media. The increase in viscosity with the concentration of the retarding component is insured...
2

Compactação e compressibilidade de resíduos sólidos urbanos / Compaction and compressibility of municipal solid waste

Marques, Afonso Celso Moruzzi 17 July 2001 (has links)
Os objetivos desta pesquisa incluem: (i) estudar as características de compactação dos resíduos sólidos urbanos (RSU); (ii) avaliar os mecanismos de compressão dos RSU e o efeito de sobrecarga (aterro experimental) em maciço sanitário existente; (iii) desenvolver programa computacional para previsão de recalques em aterros sanitários. Um aterro experimental com cerca de 24.400 \'M POT.3\' de RSU e altura de até 4 m, distribuído em área aproximada de 8.400 \'M POT.2\', foi construído em São Paulo para estudar os procedimentos de compactação de aterros sanitários. Ensaios in situ de grande dimensão foram executados para avaliar o peso específico do resíduo, após a compactação, em diferentes posições e camadas do experimento. Ensaios de umidade e composição dos resíduos foram realizados, assim como o levantamento das espessuras das camadas para cada etapa construtiva. O aterro experimental foi construído sobre aterro existente, criando a oportunidade para estudar a compressão do resíduo novo e antigo. Rigoroso programa de monitoração de recalques foi implantado, de forma que as deformações do aterro experimental pudessem ser isoladas das do aterro existente. Marcos superficiais foram posicionados interna e externamente à área do experimento, e placas de recalque instaladas na base do aterro experimental. O período de monitoramento envolveu cerca de 3 anos de medidas. A pesquisa resultou em: (i) novos subsídios e relações para a compactação dos RSU, incluindo as influências do equipamento de compactação, número de passadas, espessura das camadas, plano de compactação e teor de umidade, mostrando ser este último o parâmetro de maior impacto no processo de compactação; (ii) dados de peso específico e de sua relação com a profundidade, assim como do efeito da compactação na compressibilidade dos RSU e na geração de líquidos percolados em aterros sanitários; (iii) avaliação do desempenho de modelos de compressibilidade existentes na literatura; (iv) desenvolvimento de modelo compósito para compressibilidade dos RSU, considerando a compressão mecânica primária e secundária e a parcela devido a biodegradação dos resíduos; (v) desenvolvimento do programa MSWSET usando o modelo compósito para cálculo dos recalques de aterros como função do tempo. O modelo e programa desenvolvidos apresentaram elevado desempenho, constituindo importante ferramenta para previsão de recalques de aterros sanitários. / The objectives of this research were to: (i) study the compaction characteristics of municipal solid waste (MSW); (ii) evaluate the compression mechanisms of MSW and its response to a surcharge (waste test fill) over an existing landfill; (iii) develop a computer program for landfill settlement predictions. A waste test fill with a volume of about 24,400 \'M POT.3\' and a height up to 4 m, distributed over an area of approximately 8,400 \'M POT.2\', was constructed in Sao Paulo, to study compaction procedures for sanitary landfills. Large in situ tests were performed to evaluate the unit weight of waste immediately after compaction at several locations for each lift. Water content measurements and composition determinations were carried out, as well as thickness measurements of the waste layers after each construction (compaction) phase. The test fill was constructed over an existing landfill. Thus, the test fill provided opportunities to study the compression of the new and the old waste. A rigorous program of deformation monitoring was implemented in order to separate compression of the test fill from settlement of the underlying landfill. Benchmarks were located inside and outside of the experimental area, and settlement plates were installed at the bottom of the test fill. The monitoring period encompasses around 3 years of measurements. The research provided: (i) new guidelines and relationships for compaction of municipal solid waste, including the influences of compaction equipment, number of passes, lift thickness, water content, and compaction plane. The water content has presented larger response on the compaction process than the other variables; (ii) quantitative data regarding unit weight, the influence of depth on unit weight, water content, compressibility of MSW, and leachate generation; (iii) assessment of the performance of existing MSW compressibility models described in the literature; (iv) development of a composite model of MSW compressibility that considers primary compression, secondary mechanical compression, and compression from biodegradation; (v) development of the computer program MSWSET using the composite model of MSW compressibility to calculate landfill settlement as a function of time. The developed model and program has presented a high performance, being a powerful tool for landfill settlement prediction.
3

Comportement thermomécanique du sel gemme : Application au dimensionnement des cavités / Thermomechanical behavior of rock salt : Application to cavern design

Labaune, Paule 09 October 2018 (has links)
Les cavités salines représentent une technique prometteuse de stockage massif d’énergie, notamment pour les énergies renouvelables dont la production est par nature intermittente et imprévisible. Historiquement utilisées pour le stockage saisonnier d’hydrocarbures (méthane, pétrole...), les cavités salines sont aujourd’hui sollicitées pour le stockage de nouveaux fluides (hydrogène, dioxyde de carbone...) avec des scenarii plus exigeants. Les méthodes de dimensionnement des cavités doivent être mises à jour pour répondre aux nouveaux défis de la transition énergétique.Cette thèse propose une nouvelle méthodologie de dimensionnement des cavités salines, basée sur le développement d’un nouveau modèle constitutif pour le sel gemme incluant des critères de dilatance et de traction. Ce nouveau modèle permet d’ajuster avec un unique jeu de paramètres de nombreux essais de laboratoire différents, en particulier courts et longs.Des simulations couplées thermo-mécaniques de cavités, remplies de méthane ou d’hydrogène, et du sel gemme environnant sont réalisées pour différents scenarii d’exploitation, classiques ou se rapprochant des nouveaux besoins liés à la transition énergétique. On étudie en particulier les effets de la durée et de l’amplitude des cycles, du débit d’injection ou de soutirage. Les résultats obtenus avec la nouvelle méthodologie sont comparés avec ceux de la méthodologie classique. / Salt caverns are a promising technique for massive energy storage, especially in the case of the intermittent and unpredictable renewable energy. Historically used for seasonal storage of hydrocarbons (methane, oil...), they are potentially operated with increasingly demanding scenarios for the storage of other fluids (hydrogen, carbon dioxide...). Design methods need to be updated to rise to the new challenges of the energy transition.This thesis proposes a new methodology for salt cavern design, based on the development of a new rheological model including a dilatancy and a tensile criteria. This new model allows to fit numerous different laboratory tests with a single parameter set, in particular short- and long-term tests.Thermo-mechanical numerical simulations of caverns, filled with either methane or hydrogen, and the surrounding rock salt are performed under various cycling scenarios which are classical or closer to the needs associated with the energy transition. Effects of cycle duration, amplitude and mass flow are especially investigated. Results obtained with the new and the classical methodologies are compared.
4

Compactação e compressibilidade de resíduos sólidos urbanos / Compaction and compressibility of municipal solid waste

Afonso Celso Moruzzi Marques 17 July 2001 (has links)
Os objetivos desta pesquisa incluem: (i) estudar as características de compactação dos resíduos sólidos urbanos (RSU); (ii) avaliar os mecanismos de compressão dos RSU e o efeito de sobrecarga (aterro experimental) em maciço sanitário existente; (iii) desenvolver programa computacional para previsão de recalques em aterros sanitários. Um aterro experimental com cerca de 24.400 \'M POT.3\' de RSU e altura de até 4 m, distribuído em área aproximada de 8.400 \'M POT.2\', foi construído em São Paulo para estudar os procedimentos de compactação de aterros sanitários. Ensaios in situ de grande dimensão foram executados para avaliar o peso específico do resíduo, após a compactação, em diferentes posições e camadas do experimento. Ensaios de umidade e composição dos resíduos foram realizados, assim como o levantamento das espessuras das camadas para cada etapa construtiva. O aterro experimental foi construído sobre aterro existente, criando a oportunidade para estudar a compressão do resíduo novo e antigo. Rigoroso programa de monitoração de recalques foi implantado, de forma que as deformações do aterro experimental pudessem ser isoladas das do aterro existente. Marcos superficiais foram posicionados interna e externamente à área do experimento, e placas de recalque instaladas na base do aterro experimental. O período de monitoramento envolveu cerca de 3 anos de medidas. A pesquisa resultou em: (i) novos subsídios e relações para a compactação dos RSU, incluindo as influências do equipamento de compactação, número de passadas, espessura das camadas, plano de compactação e teor de umidade, mostrando ser este último o parâmetro de maior impacto no processo de compactação; (ii) dados de peso específico e de sua relação com a profundidade, assim como do efeito da compactação na compressibilidade dos RSU e na geração de líquidos percolados em aterros sanitários; (iii) avaliação do desempenho de modelos de compressibilidade existentes na literatura; (iv) desenvolvimento de modelo compósito para compressibilidade dos RSU, considerando a compressão mecânica primária e secundária e a parcela devido a biodegradação dos resíduos; (v) desenvolvimento do programa MSWSET usando o modelo compósito para cálculo dos recalques de aterros como função do tempo. O modelo e programa desenvolvidos apresentaram elevado desempenho, constituindo importante ferramenta para previsão de recalques de aterros sanitários. / The objectives of this research were to: (i) study the compaction characteristics of municipal solid waste (MSW); (ii) evaluate the compression mechanisms of MSW and its response to a surcharge (waste test fill) over an existing landfill; (iii) develop a computer program for landfill settlement predictions. A waste test fill with a volume of about 24,400 \'M POT.3\' and a height up to 4 m, distributed over an area of approximately 8,400 \'M POT.2\', was constructed in Sao Paulo, to study compaction procedures for sanitary landfills. Large in situ tests were performed to evaluate the unit weight of waste immediately after compaction at several locations for each lift. Water content measurements and composition determinations were carried out, as well as thickness measurements of the waste layers after each construction (compaction) phase. The test fill was constructed over an existing landfill. Thus, the test fill provided opportunities to study the compression of the new and the old waste. A rigorous program of deformation monitoring was implemented in order to separate compression of the test fill from settlement of the underlying landfill. Benchmarks were located inside and outside of the experimental area, and settlement plates were installed at the bottom of the test fill. The monitoring period encompasses around 3 years of measurements. The research provided: (i) new guidelines and relationships for compaction of municipal solid waste, including the influences of compaction equipment, number of passes, lift thickness, water content, and compaction plane. The water content has presented larger response on the compaction process than the other variables; (ii) quantitative data regarding unit weight, the influence of depth on unit weight, water content, compressibility of MSW, and leachate generation; (iii) assessment of the performance of existing MSW compressibility models described in the literature; (iv) development of a composite model of MSW compressibility that considers primary compression, secondary mechanical compression, and compression from biodegradation; (v) development of the computer program MSWSET using the composite model of MSW compressibility to calculate landfill settlement as a function of time. The developed model and program has presented a high performance, being a powerful tool for landfill settlement prediction.
5

Modellierung des mechanischen Verhaltens der Komponenten eines intrinsischen Hybridverbundes

Kießling, Robert 10 January 2020 (has links)
Durch die Kombination verschiedener Werkstoffklassen ermöglichen Hybridverbunde die Entwicklung von Strukturbauteilen, die sich beispielsweise durch eine hohe Festigkeit bei einem gleichzeitig geringen Gewicht auszeichnen. Trotz des großen Einsatzpotentials wurden Hybridverbunde, begründet durch eine kostenintensive und zeitaufwendige Fertigung, bislang nicht für Großserienbauteile vorgesehen. Mit der Konzeption intrinsischer, das heißt einstufiger, Produktionsprozesse wird es jedoch gelingen die Attraktivität zu steigern und damit die Anwendung von Hybridverbunden unter anderem auch in der Automobilindustrie zu etablieren. Exemplarisch soll im Rahmen dieser Arbeit die Entwicklung eines intrinsischen Hybridverbundes für crashbelastete Strukturbauteile simulativ begleitet werden. Der dabei betrachtete Hybridverbund besteht aus einem endlosfaserverstärktem Kunststoff, in den ein metallischer Einleger eingebracht ist. Zur Realisierung der Anbindung der Komponenten sieht das Konzept des Hybridverbundes die Kombination von Form- und Stoffschluss vor. Dabei resultiert der Stoffschluss aus der Beschichtung des metallischen Einlegers, die die Ausbildung eines Interface bewirkt. Zur Realisierung des Formschlusses werden während des überlagerten Umformprozesses lokal Formschlusselemente des metallischen Einlegers in den endlosfaserverstärkten Kunststoff gepresst. Dadurch weisen die resultierenden Bauteile eine komplexe innere Struktur auf, die die simulative Analyse und damit die Bauteilauslegung erschwert. Das Ziel der vorliegenden Arbeit besteht in der Modellierung und Simulation dieses intrinsischen Hybridverbundes. Dazu ist zunächst das Materialverhalten aller Komponenten durch adäquate Materialmodelle für große Deformationen abzubilden. Für deren Entwicklung wird ein Konzept zur Materialmodellierung aufgegriffen und erweitert, das die Formulierung auf der Basis direkt verschalteter rheologischer Elemente ermöglicht. Nach entsprechenden Parameteridentifikationen werden die Materialmodelle im Rahmen von Finite-Elemente-Simulationen eines aus dem Hybridverbund gefertigten Demonstratorbauteils angewendet. Dabei ermöglicht das Vorgehen zur Modellerstellung die Berücksichtigung und Bewertung von Einflüssen der intrinsischen Fertigung auf das Bauteilverhalten. / Hybrid parts, combining for example low weight with high strength, are based on the combination of different material classes. Despite an enormous potential for applications, hybrid composites are not well established for large series parts due to the expensive and complex production. To increase the number of applications, intrinsic, i.e. single-step, manufacturing processes are designed. Within this work, the development of an intrinsic hybrid composite for crash-relevant structural parts is supported by simulations. The considered hybrid composite is made up of a fibre-reinforced polymer, in which a metallic insert is integrated. The connection between these components is based on a combination of geometrical form fit and adhesive bonding. On one hand, adhesive bonds result from a coating of the metallic insert. On the other hand, local form fit elements are pressed into the fibre reinforced polymer during the global forming process. Consequently, the resulting parts, manufactured in just one step, show a complex inner structure, which make simulative analyses and dimensioning more difficult. Within the work at hand, the main research goal is the modelling and simulation of this intrinsic hybrid composite. To this end, the mechanical behaviour of all individual components has to be described by appropriate material models at large strains. For those developments, a concept of material modelling, which enables the formulation based on directly connected rheological elements, is adopted and extended. After identifying the according material parameters, these material models are applied within finite element simulations of a demonstrator made up of the hybrid composite. Thereby, the applied procedure for creating finite element models allows to consider and evaluate how the intrinsic manufacturing process affects the mechanical behaviour of the parts.

Page generated in 0.0969 seconds