• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 106
  • 48
  • 18
  • 14
  • 14
  • 5
  • 3
  • 3
  • 2
  • 2
  • 2
  • 2
  • 1
  • 1
  • Tagged with
  • 226
  • 66
  • 62
  • 46
  • 43
  • 40
  • 39
  • 35
  • 34
  • 33
  • 33
  • 29
  • 25
  • 24
  • 18
  • 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.
41

Modèles d’intégration des designers créatifs dans les processus de conception industriels / Integration models for creative designers inside the industrial design process

Arrighi, Pierre-Antoine 26 March 2014 (has links)
De décisifs et puissants enjeux d'innovation ainsi que de renouvellement del'identité des objets bouleversent le monde industriel. De telles aptitudes créativessont usuellement associées aux designers industriels. Cependant, ces professionnelsne sont actuellement pas intégrés dans les processus numériques deconception.Afin de décrire ce paradoxe, nous formulons l'hypothèse que, l'omniprésencedans l'industrie de modèles de la conception de type séquentiel, qui juxtaposentcréativité et développement produit, entrave l'intégration des designers industrielsau sein des processus industriels. En effet, en compartimentant la conceptionen silos, ce type de modèles généralistes inhibe les méthodes spécifiquesdes concepteurs créatifs. Bien plus, les outils numériques adjoints au modèle séquentielétant calqués sur sa logique, ils reproduisent et les inconvénients d'unetelle structuration.En mobilisant quatre disciplines académiques qui traitent des outils numériques,à savoir les sciences informatiques, cognitives, de gestion et les théoriesde la conception, nous élaborons un nouveau modèle «dit stratifié». Ce dernierrévèle les modes de raisonnement empruntés par les concepteurs créatifs ainsique la nature des produits élaborés dans les environnements logiciels. A ce titre,l'entreprise Dassault Systèmes ainsi que la suite CATIA se sont révélés un substratde recherche idéal. Comme attendu, notre nouveau modèle propose desassertions inédites qui sont validées au cours de notre travail. Nous avons alorsdémontré que :1/ Certains ateliers de conception favorisent simultanément robustesse et générativité.Nous qualifions cette nouvelle propriété d'«originalité acquise».2/ Les avatars dans le logiciel ne résultent pas d'un raffinement progressif del'objet mais sont plutôt l'instanciation d'une base de règles paramétrée.3/ Les designers industriels requièrent des outils distincts de ceux employés parles artistes 3D ou les ingénieurs, de par la nature de leur conception. Plus exactement,ces professionnels génèrent des modèles conceptuels selon une logiquede singularité de masse.Ces résultats offrent ainsi la perspective engageante de l'émergence d'unenouvelle génération d'outils numériques de conception. Ces outils inédits serontaptes à intégrer les designers industriels et à proposer de l'innovation à la de / Many studies show that industrial design is key to triggering, fostering andsustaining innovation. However, the unique capacities of creation and innovationof industrial designers make it challenging for them to thrive within industrialenvironments.The challenge for companies is to create the optimal work environment forthose professionals, while ensuring their work can be integrated smoothly intothe existing industrial design processes. We assume this dilemma is partiallystemming from the intensive use of sequential design models in the industry.Design tools were developed on the assumption that creative front end andproduct development should be separated.We introduce here a new model, aiming at depicting accurately the reasoningmodes and the nature of the object being designed with the digital ComputerAided Design (CAD) suites. This model is the result of the joint mobilization offour academic fields : computer, cognitive and management science and designtheories. Dassault Systèmes and their CATIA software have proven to be an excellentresearch environment for such questions. As we have been thinking, thenew model (laminated) makes three new hypothesis. Those unheard assertionshave been suggested and validated with this thesis :1/ Some specific design workshops are able to provide simultaneously robust andgenerative design capacities. We call this characteristic «acquired originality».2/ The object representations within by the software are not the result of successiverefinements but derive directly from a parameterized set of rules.3/ Industrial designers have specific requirements for CAD tools, different fromtheir engineers and artists counterparts because what they design is fundamentallydifferent. IDs generate conceptual models using a mass singularity technique.Those results sketch the emergence of a new generation of CAD tools forindustrial designers and able to foster innovation.
42

Application of sorption-enhanced catalysis to ethanol reforming / Användning av katalys förbättrad med sorption för etanolreformering

Ho, Jacky January 2016 (has links)
Lithium orthosilicate (Li4SiO4) is known to be a high temperature CO2 capture material. This work was focused on comparing Li4SiO4 to the extensively studied CaO as an adsorbent in sorption enhanced catalysis. Thermogravimetric analysis was used to study the effects of sorption temperature and compaction on Li4SiO4 using 15vol% CO2 in N2. After 2 hours of CO2 adsorption at 550°C the powder reached 35wt% uptake of CO2, corresponding to 93.6% of maximum efficiency and complete regeneration was possible at 700°C. Pressing Li4SiO4 to granular forms greatly decreased CO2 adsorption rates. Efforts to impregnate -Al2O3 with the suspended SiO2 solution from aqueous based sol-gel synthesis to produce nanodispersed Li4SiO4 failed due to the inability to form the targeted Li4SiO4 complex. X-ray diffraction analysis indicated the formation of the gel is crucial for the formation of the crystalline Li4SiO4 phase. A microreactor was used to study the steam reforming of ethanol over a series of 1% Pt on -Al2O3 catalyst composite impregnated over a range of nanodispersed CaO loading at S/C=1.5 in dilution. At 400°C enhancement could be observed with the presence of CaO sorbent compared to only 1% Pt/Al2O3. However, production quickly diminished due to high carbon deposition. For 1% Pt/Al2O3 tested at 400°C, ethylene production was 5 times higher than for hydrogen. Above 550°C the ethylene production was reduced to 0.18vol% and gas production stability was greatly improved for 1% Pt/Al2O3 and even more so with the addition of impregnated CaO sorbent. Hydrogen yields from homogeneous mixtures of 1%Pt/Al2O3 with Li4SiO4 powder in a microreactor were about 20% higher than those achievable of the same mixture with CaO powder. However, the composite 1%Pt/Al2O3 with 7.02wt% dispersed CaO gave 100% higher hydrogen production under similar conditions despite Li4SiO4 being a superior carbon capture material. / Litiumortosilikat (Li4SiO4) är ett känt CO2 adsorptionsmaterial vid höga temperaturer. Fokuset i detta arbete var att jämföra Li4SiO4 med det välstuderade CaO som adsorbent i adsorptionsförbättrad katalys. Termogravimetrisk analys användes för att studera effekten av temperatur och kompaktering på Li4SiO4 med 15vol% CO2 i balanserad N2. Efter 2 timmars CO2 adsorption vid 550°C hade pulvret nått 35vikt% ökning av CO2, vilket korresponderar till 93.6% av den maximala verkningsgraden. Dessutom var fullständig regenerering möjlig vid 700°C. Pressad Li4SiO4 i grynig form sänkte CO2 adsorptionshastigheten signifikant. Försök att impregnera -Al2O3 med suspenderad SiO2 från en vattenbaserad sol-gel metod för att bilda nanodispergerad Li4SiO4 misslyckades på grund av oförmågan att bilda önskade Li4SiO4 komplex. Röntgendiffraktions analys tydde på att bildningen av gelen var avgörande för bildningen av en kristallin Li4SiO4 fas. En mikroreaktor användes för att studera ångreformeringen av etanol hos 1% Pt på - Al2O3 katalysator komposit impregnerad med ett varierande tillskott av nanodispergerad CaO i utspädd S/C=1.5. Vid 400°C kunde en förbättring observeras då CaO var närvarande jämfört med endast 1% Pt/Al2O3. Dock minskade gasproduktionen kraftigt på grund av hög koksning. Tester på 1% Pt/Al2O3 vid 400°C visade att eten produktionen var 5 gånger högre än för vätgasproduktionen. Över 550°C sjunkte eten produktionen till 0.18vol% och gas produktionsstabiliteten förbättrades signifikant för 1% Pt/Al2O3 och även bättre i närvaro av nanodispergerad CaO. Vätgasutbytet från en homogen blandning av 1% Pt/Al2O3 med Li4SiO4 pulver i en mikroreaktor var 20% högre än det som åstadkoms för samma blandning med med CaO pulver. Dock visade 1%Pt/Al2O3 med 7.02vikt% dispergerad CaO 100% högre vätgasproduktion under liknande förhållanden trots att Li4SiO4 är en överlägsen koluppfångar material.
43

Particle Size Dependence on the Luminescence Spectra of Eu3+:Y2O3 and Eu3+:CaO

Williams, Diane Keith 26 November 2002 (has links)
Since the Eu3+ ion can occupy different cation sites in a host material, it can serve as a useful probe of nanocrystalline structures to gain more insight into the structural changes that can occur when the particle size is reduced from the bulk to nanometer regime. The use of laser spectroscopy to probe two nanocrystalline structures, Eu3+:Y2O3 and Eu3+:CaO, was investigated. The nanocrystalline structures were prepared by the laser-vaporization-gas-phase condensation of the bulk oxides. The particle size distribution and dominant particle diameters of the nanocrystals were determined by transmission electron microscopy. The particle size dependency results of Eu3+:Y2O3 revealed three distinct phases: (1) the sharp lines of the monoclinic Y2O3 were dominant in the larger particles; (2) the C2 site of the cubic phase, which appears in the smaller particles; and (3) the amorphous phase that increases in intensity as the particle size decreases. The observation of distinct spectral lines from the monoclinic phase confirms the presence of a crystalline phase for all of particle sizes studied. The site-selective results of various concentrations of 13-nm Eu3+:CaO showed that the laser-vaporization-gas-phase condensation method of preparation produced two europium-containing phases at most concentrations: cubic CaO and monoclinic Eu2O3. Results showed that the monoclinic Eu2O3 phase could be reduced by 95% by annealing at 800 0C for 30 minutes without particle growth. Since the Eu3+ ion and the Y3+ ion are isovalent, the substitution of a Eu3+ ion into Y2O3 is considered a trivial case of extrinsic disorder since the impurity is neutral relative to a perfect crystal1. As a result, it is not necessary to have any other defects present in the crystals to maintain charge neutrality. With Eu3+:CaO, the dopant and host cation charges are different and therefore the dopant distribution can be investigated by site-selective spectroscopy. Since the experimental dopant distribution results for nanocrystalline Eu3+:CaO were inconclusive, a model to predict the theoretical change in the dopant distribution in Eu3+:CaO as a function of particle size was developed. The model predicts that the defect chemistry is affected when the particle size is approximately 50 nm and smaller. / Ph. D.
44

Síntese e caracterização de pós vitrocerâmicos no sistema CaO-MgO-SiO2 utilizando sol-gel combinado a coprecipitação / Synthesis and characterization of glass-ceramic powders in the system CaO-MgO-SiO2 using sol-gel combined with coprecipitation

Leme, Daniel de Rezende 28 June 2019 (has links)
Materiais biocerâmicos são constituídos por elementos encontrados normalmente no organismo e por esse motivo são empregados na área médica, principalmente para a fabricação de implantes dentários e aplicação ortopédica. A partir do tipo de ligação realizada com o organismo, o biocerâmico é classificado em inerte, reabsorvível e bioativo, sendo esse último dividido em vidro bioativo, hidroxiapatita e vitrocerâmico. O material vitrocerâmico exibe propriedades únicas devido a sua microestrutura específica, variedade de composições e propriedades mecânicas adequadas. Entre as possíveis composições, o sistema CaO-MgO-SiO2 exibe bioatividade devido a concentração de cálcio e silício que podem estimular os genes responsáveis pela proliferação de osteoblastos. A presença de magnésio eleva as propriedades mecânicas e a osteointegração devido a interações na superfície da cerâmica com os osteoblastos, possibilitando a formação de hidroxiapatita (HA) e consequentemente ligações diretas com o tecido vivo. Para este trabalho foram realizadas sínteses empregando sol-gel combinado com coprecipitação e sol-gel convencional, para comparação dos produtos obtidos. Os pós cerâmicos sintetizados foram caracterizados por DRX, MEV, BET e as cerâmicas foram testadas para determinação de bioatividade e citotoxicidade in vitro. A formação de HA na superfície das cerâmicas confirmou a bioatividade e observou-se que as amostras não são citotóxicas. Portanto, pôde-se concluir que a partir das metodologias aplicadas foi possível sintetizar pós cerâmicos que exibiram propriedades semelhantes, com potencial aplicação na área médica. / Bioceramic materials are constituted by elements normally found in the body and are therefore used in the medical field, mainly for the manufacture of dental implants and orthopedic application. From the type of binding performed with the organism, the bioceramic is classified as inert, resorbable and bioactive, the latter being divided into bioactive glass, hydroxyapatite and glass-ceramic. The glassceramic material exhibits unique properties due to its specific microstructure, variety of compositions and suitable mechanical properties. Among the possible compositions, the CaO-MgO-SiO2 system exhibits bioactivity due to the concentration of calcium and silicon that can stimulate the genes responsible for the proliferation of osteoblasts. The presence of magnesium increases the mechanical properties and the osseointegration due to interactions on the surface of the ceramic with the osteoblasts, allowing the formation of hydroxyapatite (HA) and consequently direct connections with the living tissue. In this work, syntheses were performed using sol-gel combined with coprecipitation and conventional sol-gel methods for comparison of the obtained products. The synthesized ceramic powders were characterized by XRD, SEM and BET, and the ceramics were submitted for tests of in vitro bioactivity and cytotoxicity. The formation of HA on the surface of the ceramics confirmed the bioactivity and no cytotoxicity was observed in the samples. Therefore, it was possible to conclude that using proposed methodologies it was possible to synthesize ceramic powders that exhibited similar properties, with potential application in the medical area.
45

Méthodologie pour la construction de systèmes CAO : SIGMA-CAO : une méthode globale pour la spécification, la mise en œuvre et l'utilisation de systèmes intégrés pour la conception assistée par ordinateur

David, Bertrand 30 September 1981 (has links) (PDF)
.
46

Idéalisation d'assemblages CAO pour l'analyse EF de structures

Boussuge, Flavien 08 July 2014 (has links) (PDF)
Les entreprises aéronautiques ont un besoin continu de générer de grands et complexes modèles de simulation, en particulier pour simuler le comportement structurel de sous-systèmes de leurs produits. Actuellement, le pré-traitement des modèles de Conception Assistée par Ordinateur (CAO) issus des maquettes numériques de ces sous-systèmes en Modèles Eléments Finis (MEF), est une tâche qui demande de longues heures de travail de la part des ingénieurs de simulation, surtout lorsque des idéalisations géométriques sont nécessaires. L'objectif de ce travail de thèse consiste à définir les principes et les opérateurs constituant la chaîne numérique qui permettra, à partir de maquettes numériques complexes, de produire des géométries directement utilisables pour la génération de maillages éléments finis d'une simulation mécanique. A partir d'une maquette numérique enrichie d'information sur les interfaces géométriques entre composants et d'information sur les propriétés fonctionnelles de l'assemblage, l'approche proposée dans ce manuscrit est d'ajouter un niveau supplémentaire d'enrichissement en fournissant une représentation structurelle de haut niveau de la forme des composants CAO. Le principe de cet enrichissement est d'extraire un graphe de construction de modèles CAO B-Rep de sorte que les processus de génération de forme correspondants fournissent des primitives volumiques directement adaptées à un processus d'idéalisation. Ces primitives constituent la base d'une analyse morphologique qui identifie dans les formes des composants à la fois des sous-domaines candidats à l'idéalisation mais également les interfaces géométriques qui leurs sont associées. Ainsi, les modèles de composants et leurs représentations géométriques sont structurés. Ils sont intégrés dans la maquette numérique enrichie qui est ainsi contextualisée pour la simulation par EF. De cette maquette numérique enrichie, les objectifs de simulation peuvent être utilisés pour spécifier les opérateurs géométriques adaptant les composants et leurs interfaces lors de processus automatiques de préparation d'assemblages. Ainsi, un nouveau procédé d'idéalisation de composant unitaire est proposé. Il bénéficie de l'analyse morphologique faite sur le composant lui fournissant une décomposition en sous-domaines idéalisables et en interfaces. Cette décomposition est utilisée pour générer les modèles idéalisés de ces sous-domaines et les connecter à partir de l'analyse de leurs interfaces, ce qui conduit à l'idéalisation complète du composant. Enfin, le processus d'idéalisation est étendu au niveau de l'assemblage et évolue vers une méthodologie de pré-traitement automatique de maquettes numériques. Cette méthodologie vise à exploiter l'information fonctionnelle de l'assemblage et les informations morphologiques des composants afin de transformer à la fois des groupes de composants associés à une même fonction ainsi que de traiter les transformations d'idéalisation de l'assemblage. Pour démontrer la validité de la méthodologie, des opérateurs géométriques sont développés et testés sur des cas d'application industriels.
47

史傳所見之曹操、劉備、孫權之研究

吳玉蓮, WU, YU-LIAN Unknown Date (has links)
三國人物經過多年的傳說,難免為後人踵事增華,以訛傳訛而混淆了他們在歷史中真 正扮演的角色。 漢末三國人禾最盛,尤以曹操、劉備、孫權能嶄露頭角。本論文為揭開三國之主的真 相,以正史三國志及裴注為依據,各按年代,細分節目,逐一剖析三者的出身背景、 人格形成及創業過程,試從三者者的一生動靜語默間,較客觀的掌握他們的形相。正 文由導論開始,以下分四章,第一章曹操的形相,共分兩節,先討論史家筆下的曹操 ,再由問題的澄清進而分析曹操的內心世界,包括曹操的笑、哭、令及文學。第二章 劉備的形相。共分兩節,先討論史家筆下的劉備,進而強調劉備情深義重的人格及時 勢造英雄的機運。第三章孫權的形相。共分兩節,先討論史家筆下的孫權,再敘述孫 權承父兄遺蔭的貴冑習性及平凡中見情的美德。第四章結論,分三節,先從思想上比 較,再由才德上比較三者的異同,最後為結語。
48

Caracterização e aproveitamento de resíduos gerados na produção de etanol de segunda geração / Characterization and benefit of wastes generated during ethanol production of second generation

Godoi, Isamara 15 February 2016 (has links)
Made available in DSpace on 2017-07-10T19:24:09Z (GMT). No. of bitstreams: 1 Isamara_ Godoi.pdf: 2059512 bytes, checksum: c7f04b4bfb9d29047a6d89e02a8418e1 (MD5) Previous issue date: 2016-02-15 / Researches concerning the use of biomass lignocellulosic composition for second-generation ethanol production have received special attention as a possible contribution to energy sustainability. Although such activity has mainly used waste from the agricultural industry, it also generates other impactful solid and liquid wastes to the environment because they contain high concentrations of acids, alkaline and toxic elements. Thus, this trial aimed registering chemical characterization and recovering wastes generated in order to obtain a second-generation ethanol, particularly the precipitate produced during detoxification process by overliming hydrolyzed hemicellulose from sugarcane bagasse and liquid waste produced during cellulignin delignification phase in the pre-treatment to make the process of enzymatic saccharification of cellulose easier. Initially, the solid residue was submitted to physical and chemical analyses such as granulometric, analysis of metal compounds, content of inhibitory compounds to microbial activity such as acetic acid, furfural, hydroxymethylfurfural and phenols, sugars and moisture content. Waste potential determination as corrective of soil acidity was carried out by analyzing the attributes of corrective quality in soil (PN, PRNT), Ca and Mg and granulometry). Solid residue was also evaluated for its influence on bacterial communities by traditional microbiological techniques, bioassays with worms and lettuce seed germination. Liquid waste was characterized based on its metal contents present and inhibitory compounds. The lignin present in such liquor was precipitated with sulfuric acid and, after its characterization by infrared spectroscopy, was used as a biosorbent on lead ions adsorption in aqueous solution. The results have suggested that the waste generated during second-generation ethanol obtainment have some potential to become by-products to be applied in agricultural and environmental area. Lastly, the present trial has contributed to the production of bioethanol to be implemented in industry according to lignocellulosic biorefinery concept from an integrated model for a full biomass use in a sustainable management and correct disposal of the generated waste. / Pesquisas sobre o aproveitamento de biomassas de composição lignocelulósica para produção de etanol de segunda geração têm recebido atenção especial como possível contribuição para a sustentabilidade energética. Embora tal atividade utilize principalmente resíduos da agroindústria, gera outros resíduos sólidos e líquidos impactantes para o meio ambiente por conterem alta concentração de elementos ácidos, alcalinos e tóxicos. Por conseguinte, este trabalho visou à caracterização química e ao aproveitamento dos resíduos gerados na obtenção de etanol de segunda geração, em particular o precipitado formado no processo de destoxificação por overliming do hidrolisado hemicelulósico de bagaço de cana-de-açúcar e o resíduo líquido gerado na etapa de deslignificação da celulignina durante o pré-tratamento para facilitar o processo de sacarificação enzimática da celulose. Inicialmente o resíduo sólido foi submetido a análises físico-químicas, granulométrica, análise de metais, ao teor de compostos inibidores para a atividade microbiana, tais como ácido acético, furfural, hidroximetilfurfural e fenóis, açúcares e teor de umidade. A determinação do potencial do resíduo como corretivo da acidez do solo foi realizada através da análise dos atributos da qualidade dos corretivos do solo (PN, PRNT, teores de Ca e Mg e granulometria). O resíduo sólido foi também avaliado quanto à sua influência nas comunidades bacterianas através de técnicas microbiológicas tradicionais, bioensaios com minhocas e testes de germinação de sementes de alface. O resíduo líquido foi caracterizado quanto aos teores de metais presentes e compostos inibidores. A lignina presente no licor foi precipitada com ácido sulfúrico e, após caracterização por espectrometria de infravermelho, utilizada como biossorvente na adsorção de íons chumbo em solução aquosa. Os resultados indicam que os resíduos gerados na obtenção de etanol de segunda geração possuem potencial para se tornarem subprodutos com aplicação na área agrícola e ambiental. Desta forma, o presente trabalho vem a contribuir para a implementação industrial da produção de bioetanol dentro do conceito de biorrefinaria lignocelulósica, a partir de um modelo integrado para completo aproveitamento da biomassa, de forma sustentável e com adequada destinação dos resíduos gerados.
49

Caracterização e aproveitamento de resíduos gerados na produção de etanol de segunda geração / Characterization and benefit of wastes generated during ethanol production of second generation

Godoi, Isamara 15 February 2016 (has links)
Made available in DSpace on 2017-05-12T14:47:26Z (GMT). No. of bitstreams: 1 Isamara_ Godoi.pdf: 2059512 bytes, checksum: c7f04b4bfb9d29047a6d89e02a8418e1 (MD5) Previous issue date: 2016-02-15 / Researches concerning the use of biomass lignocellulosic composition for second-generation ethanol production have received special attention as a possible contribution to energy sustainability. Although such activity has mainly used waste from the agricultural industry, it also generates other impactful solid and liquid wastes to the environment because they contain high concentrations of acids, alkaline and toxic elements. Thus, this trial aimed registering chemical characterization and recovering wastes generated in order to obtain a second-generation ethanol, particularly the precipitate produced during detoxification process by overliming hydrolyzed hemicellulose from sugarcane bagasse and liquid waste produced during cellulignin delignification phase in the pre-treatment to make the process of enzymatic saccharification of cellulose easier. Initially, the solid residue was submitted to physical and chemical analyses such as granulometric, analysis of metal compounds, content of inhibitory compounds to microbial activity such as acetic acid, furfural, hydroxymethylfurfural and phenols, sugars and moisture content. Waste potential determination as corrective of soil acidity was carried out by analyzing the attributes of corrective quality in soil (PN, PRNT), Ca and Mg and granulometry). Solid residue was also evaluated for its influence on bacterial communities by traditional microbiological techniques, bioassays with worms and lettuce seed germination. Liquid waste was characterized based on its metal contents present and inhibitory compounds. The lignin present in such liquor was precipitated with sulfuric acid and, after its characterization by infrared spectroscopy, was used as a biosorbent on lead ions adsorption in aqueous solution. The results have suggested that the waste generated during second-generation ethanol obtainment have some potential to become by-products to be applied in agricultural and environmental area. Lastly, the present trial has contributed to the production of bioethanol to be implemented in industry according to lignocellulosic biorefinery concept from an integrated model for a full biomass use in a sustainable management and correct disposal of the generated waste. / Pesquisas sobre o aproveitamento de biomassas de composição lignocelulósica para produção de etanol de segunda geração têm recebido atenção especial como possível contribuição para a sustentabilidade energética. Embora tal atividade utilize principalmente resíduos da agroindústria, gera outros resíduos sólidos e líquidos impactantes para o meio ambiente por conterem alta concentração de elementos ácidos, alcalinos e tóxicos. Por conseguinte, este trabalho visou à caracterização química e ao aproveitamento dos resíduos gerados na obtenção de etanol de segunda geração, em particular o precipitado formado no processo de destoxificação por overliming do hidrolisado hemicelulósico de bagaço de cana-de-açúcar e o resíduo líquido gerado na etapa de deslignificação da celulignina durante o pré-tratamento para facilitar o processo de sacarificação enzimática da celulose. Inicialmente o resíduo sólido foi submetido a análises físico-químicas, granulométrica, análise de metais, ao teor de compostos inibidores para a atividade microbiana, tais como ácido acético, furfural, hidroximetilfurfural e fenóis, açúcares e teor de umidade. A determinação do potencial do resíduo como corretivo da acidez do solo foi realizada através da análise dos atributos da qualidade dos corretivos do solo (PN, PRNT, teores de Ca e Mg e granulometria). O resíduo sólido foi também avaliado quanto à sua influência nas comunidades bacterianas através de técnicas microbiológicas tradicionais, bioensaios com minhocas e testes de germinação de sementes de alface. O resíduo líquido foi caracterizado quanto aos teores de metais presentes e compostos inibidores. A lignina presente no licor foi precipitada com ácido sulfúrico e, após caracterização por espectrometria de infravermelho, utilizada como biossorvente na adsorção de íons chumbo em solução aquosa. Os resultados indicam que os resíduos gerados na obtenção de etanol de segunda geração possuem potencial para se tornarem subprodutos com aplicação na área agrícola e ambiental. Desta forma, o presente trabalho vem a contribuir para a implementação industrial da produção de bioetanol dentro do conceito de biorrefinaria lignocelulósica, a partir de um modelo integrado para completo aproveitamento da biomassa, de forma sustentável e com adequada destinação dos resíduos gerados.
50

Idéalisation d'assemblages CAO pour l'analyse EF de structures / Idealization of CAD assemblies for FE structural analyses

Boussuge, Flavien 08 July 2014 (has links)
Les entreprises aéronautiques ont un besoin continu de générer de grands et complexes modèles de simulation, en particulier pour simuler le comportement structurel de sous-systèmes de leurs produits. Actuellement, le pré-traitement des modèles de Conception Assistée par Ordinateur (CAO) issus des maquettes numériques de ces sous-systèmes en Modèles Eléments Finis (MEF), est une tâche qui demande de longues heures de travail de la part des ingénieurs de simulation, surtout lorsque des idéalisations géométriques sont nécessaires. L'objectif de ce travail de thèse consiste à définir les principes et les opérateurs constituant la chaîne numérique qui permettra, à partir de maquettes numériques complexes, de produire des géométries directement utilisables pour la génération de maillages éléments finis d'une simulation mécanique. A partir d'une maquette numérique enrichie d'information sur les interfaces géométriques entre composants et d'information sur les propriétés fonctionnelles de l'assemblage, l'approche proposée dans ce manuscrit est d'ajouter un niveau supplémentaire d'enrichissement en fournissant une représentation structurelle de haut niveau de la forme des composants CAO. Le principe de cet enrichissement est d'extraire un graphe de construction de modèles CAO B-Rep de sorte que les processus de génération de forme correspondants fournissent des primitives volumiques directement adaptées à un processus d'idéalisation. Ces primitives constituent la base d'une analyse morphologique qui identifie dans les formes des composants à la fois des sous-domaines candidats à l'idéalisation mais également les interfaces géométriques qui leurs sont associées. Ainsi, les modèles de composants et leurs représentations géométriques sont structurés. Ils sont intégrés dans la maquette numérique enrichie qui est ainsi contextualisée pour la simulation par EF. De cette maquette numérique enrichie, les objectifs de simulation peuvent être utilisés pour spécifier les opérateurs géométriques adaptant les composants et leurs interfaces lors de processus automatiques de préparation d'assemblages. Ainsi, un nouveau procédé d'idéalisation de composant unitaire est proposé. Il bénéficie de l'analyse morphologique faite sur le composant lui fournissant une décomposition en sous-domaines idéalisables et en interfaces. Cette décomposition est utilisée pour générer les modèles idéalisés de ces sous-domaines et les connecter à partir de l'analyse de leurs interfaces, ce qui conduit à l'idéalisation complète du composant. Enfin, le processus d'idéalisation est étendu au niveau de l'assemblage et évolue vers une méthodologie de pré-traitement automatique de maquettes numériques. Cette méthodologie vise à exploiter l'information fonctionnelle de l'assemblage et les informations morphologiques des composants afin de transformer à la fois des groupes de composants associés à une même fonction ainsi que de traiter les transformations d'idéalisation de l'assemblage. Pour démontrer la validité de la méthodologie, des opérateurs géométriques sont développés et testés sur des cas d'application industriels. / Aeronautical companies face a significant increase in complexity and size of simulation models especially at the level of assemblies, sub-systems of their complex products. Pre-processing of Computer Aided Design (CAD) models derived from the digital representation of sub-systems, i.e., Digital Mock-Ups (DMUs), into Finite Elements Analysis (FEA) models requires usually many tedious manual tasks of model preparation and shape transformations, in particular when idealizations of components or assemblies have to be produced. Therefore, the purpose of this thesis is to make a contribution to the robust automation of the time-consuming sequences of assembly preparation processes. Starting from an enriched DMU with geometrical interfaces between components and functional properties, the proposed approach takes DMU enrichment to the next level by structuring components' shapes. This approach extracts a construction graph from B-Rep CAD models so that the corresponding generative processes provide meaningful volume primitives for idealization application. These primitives form the basis of a morphological analysis which identifies the sub-domains for idealization in the components' shapes and their associated geometric interfaces. Subsequently, models of components as well as their geometric representation get structured in an enriched DMU which is contextualized for FEA application. Based on this enriched DMU, simulation objectives can be used to specify geometric operators that can be robustly applied to automate components and interfaces shape transformations during an assembly preparation process. A new idealization process of standalone components is proposed while benefiting from the decomposition into sub-domains and their geometric interfaces provided by the morphological analysis of the component. Interfaces between sub-domains are evaluated to robustly process the connections between the idealized sub-domains leading to the complete idealization of the component. Finally, the scope of the idealization process is extended to shape transformations at the assembly level and evolves toward a methodology of assembly pre-processing. This methodology aims at exploiting the functional information of the assembly and interfaces between components to perform transformations of groups of components and assembly idealizations. In order to prove the applicability of the proposed methodology, corresponding operators are developed and successfully tested on industrial use-cases.

Page generated in 0.0278 seconds