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1
ASNAGHI, DONATA. "Supramolecular porous crystals: anesthetic vapors uptake and enantioselective recognition properties." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2018. http://hdl.handle.net/10281/199107.
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La mia tesi tratta di materiali cristallini microporosi e delle loro proprietà di adsorbimento di gas e liquidi. Mi sono occupata di cristalli dipeptidici e di metal-organic frameworks. Innanzittutto, ho analizzato i Valil-Alanina, Alanil-Isoleucina, Valil-Valina, Alanil-Isoleucina e Isoleucil-Valina e ho testato le loro capacità di assorbimento di anestetici volatili. Sono state condotte isoterme di adsorbimento di enflurano, isoflurano, alotano, desflurano e dietiletere a 298 e a 273 K. VA, VV e AI presentano un’affinità elevata per i guests, rappresentata da calori isosterici superiori a 30 kJ/mol e quantità assorbite fino a 20 cm3/g. Invece, IA e IV si sono dimostrate inefficaci, a causa delle ristrette dimensioni dei loro canali. Sono stati realizzati esperimenti nmr allo stato solido per i nuclei 13C, 1H e 19F. Gli spettri 1H a 30 kHz mostrano due tipologie di segnali: a ppm più bassi quelli dei guest assorbiti nelle matrici, mentre a ppm più elevati quelli dei guest presenti solo sulla superficie esterna, a dimostrazione del riempimento completo dei canali. I pattern di diffrazione confermano inoltre la stabilità dei dipeptidi anche in presenza di guests. Successivamente, si è proceduto con l’ottimizzazione dei minimi conformazionali di enflurano e isoflurano, di cui sono stati simulati i relativi spettri nmr. Dal confronto tra gli spettri simulati e quelli sperimentali è risultato che l’isoflurano viene assorbito nella VA in una sola delle sue due conformazioni. Il passo successivo è stata l’indagine delle proprietà di enantioselettività di metal-organic frameworks omochirali. Sono stati studiati quattro MOFs a base di Cu(ll), caratterizzati dallo stesso legante organico tetracarbossilato, a cui sono attaccate catene contenenti differenti centri chirali, direzionati all’interno dei nanocanali. Dei primi due MOFs, 1-Cu e 3-Cu, immersi in soluzioni acquose enantiopure di triptofano, è stato monitorato l’assorbimento dei due enantiomeri nel tempo tramite spettroscopia UV-visibile. Il reticolo 3-Cu possiede una buona selettività, preferendo l’L-triptofano all’enantiomero D in rapporto superiore a 3.3:1 dopo trenta minuti. Gli altri due MOFs, caratterizzati da gruppi ossidrilici legati allo stereocentro, sono stati studiati per la separazione di miscele racemiche. La sec-butilammina, l’etilbenzilammina e la sec-benzamide, precursori farmaceutici, sono stati fatti assorbire in soluzione in presenza dei MOFs e i prodotti benzoilati derivanti dall’assorbimento sono stati analizzati tramite HPLC. I cromatogrammi presentano picchi completamente risolti e brevi tempi di analisi. I bassi valori di enantioselettività sono dovuti in un caso alle ridotte dimensioni della butiliammina, e nell’altro alla scarsa affinità dei MOFs per le molecole aromatiche. Nonostante ciò, questi MOFs potrebbero risultare efficaci nella separazione di molecole alifatiche a lunga catena.Among the extensive family of supramolecular compounds, porous crystalline materials present appealing features: permanent porosity, good thermal and chemical stability, versatile functionalization, long-range order properties and multiple application branches. One of the latter is nanomedicine, which can spread from drug storage and delivery to enantioselective separation of pharmaceutical precursors. In my phD work I focused on two classes of crystalline microporous materials and their adsorption and enantioselective uptake properties. The porous dipeptides belonging to the Valyl-Alanine family result to be low density materials, with stable porosity and 1D chiral and hydrophobic channels. Five porous dipeptide matrixes, Valyl-Alanine, Alanyl-Isoleucine, Valyl-Valine, Isoleucyl-Alanine and Isoleucyl-Valine, were tested for the adsorption of volatile halogenated ethers used in general anesthesia, namely enflurane, isoflurane, halothane, desflurane and the common diethyl ether. Adsorption and desorption isotherms were performed at 273 and 298 K, showing the great affinity of the first three matrixes for the halogenated guests. The anesthetic molecules included in the dipeptide crystals were detected by 13C, 19F and fast- 1H MAS NMR spectroscopy. A conformational analysis on isoflurane and enflurane was conducted to determine the most stable energy minima and to simulate the relative NMR spectra, to be compared with the experimental ones. In the second part of the thesis, four new metal-organic frameworks (MOFs), characterized by alkyl moieties with enantiopure stereogenic centers lined inside the channels, are presented. The reaction between Cu(II) cations and organic tectons with methyl or hydroxyl groups bonded to the stereogenic carbons give tridimensional, stable and microporous structures, 1-Cu, 3-Cu, 1-Cu(OH) and 3-Cu(OH), respectively. First, the porosity of the homo-chiral MOFs was confirmed by N2 and CO2 adsorption isotherms. Then, the chiral and porous nature of these MOFs was explored for enantioselective uptake experiments. The first frameworks, 1-Cu and 3-Cu, thanks to their stability in water, were exploited for the adsorption in solution of the two enantiomers of tryptophan, monitored by UV-vis spectroscopy for 24 hours. The other two matrixes, 1-Cu(OH) and 3-Cu(OH), were employed for the resolution of racemic amines and amides by HPLC. After the soaking, the MOFs were carefully washed and on the remaining solutions a derivatization reaction was performed, in order to get aromatic compounds detectable by the UV-vis analyzer of the HPLC system. In conclusion, the first two MOFs showed a good selectivity, with 3-Cu preferentially adsorbing L-tryptophan in a ratio 3.3:1 compared to the D-isomer after just 30 minutes, while 1-Cu(OH) and 3-Cu(OH) presented negligible enantiomeric excess values.
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MANTRAVADI, NARESH VENKATA. "MEMS-BASED DEVELOPMENT OF A SILICON CPS WICK FOR LOOP HEAT PIPE APPLICATIONS." University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin978637264.
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Soutar, Monty. "Ngāti Porou leadership : Rāpata Wahawaha and the politics of conflict : "Kei te ora nei hoki tātou, me tō tātou whenua" /." Online version, 2000. http://bibpurl.oclc.org/web/20809.
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Silva, Gildivan dos Santos. "Qualidade fÃsica de um argissolo acinzentado do municÃpio de Pacajus (CE) apÃs a aplicaÃÃo de resÃduo de caju." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11089.
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Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgicoDesde que o homem descobriu na agricultura uma forma de obter alimentos, a natureza passou a ser modificada. AlteraÃÃes foram causadas no ecossistema e com elas vieram as perdas na qualidade do solo. Com isso, sentiu-se a necessidade da implantaÃÃo de sistemas que preconizam pela conservaÃÃo do solo e, dessa forma, os resÃduos que antes eram queimados ou retirados da Ãrea agrÃcola comeÃam a ser deixados na superfÃcie do solo com o intuito de protegÃ-lo e promover melhorias na sua qualidade. Nesse contexto, a aplicaÃÃo de resÃduo orgÃnico no solo, como o bagaÃo de caju, pode trazer benefÃcios à qualidade fÃsica do mesmo. Diante do exposto, o objetivo da pesquisa foi avaliar o efeito da aplicaÃÃo de resÃduo de caju sobre a qualidade fÃsica do solo por meio de indicadores. Foram coletadas amostras de solo com estrutura preservada e nÃo preservada. As anÃlises foram determinadas em campo (infiltraÃÃo e condutividade hidrÃulica) e em laboratÃrio (Ãndice S e permeabilidade do solo ao ar). O delineamento empregado foi o de blocos ao acaso, composto por 5 tratamentos (cinco nÃveis de aplicaÃÃo â 0, 1, 2, 3, 4, que corresponde, respectivamente a: testemunha, 16, 32, 48, 64 t ha-1 de resÃduo orgÃnico) e quatro blocos. Para a anÃlise estatÃstica, verificou-se a normalidade dos dados a partir do teste de Kolmogorov-Smirnov e, em seguida, realizou-se a anÃlise de variÃncia e o teste Tukey a 5 % de probabilidade. Os valores condutividade hidrÃulica em solo saturado (K0) estiveram na faixa que variou de alta a muito alta, reduzindo a possibilidade de escoamento superficial. O resÃduo nÃo influenciou na retenÃÃo de Ãgua no solo, mesmo em doses elevadas. O Ãndice S mostrou valores acima dos considerados pela literatura (>0,035), sugerindo um bom indicador na qualidade estrutural do solo em estudo. A permeabilidade do solo ao ar (Kar) tambÃm demonstrou valores muito acima daquele considerado crÃtico (> 1Âm2), nÃo sendo, portanto, restritivo ao crescimento das plantas. à possÃvel afirmar que os resultados elevados K0, Ãndice S e Kar estiveram intimamente relacionados com a macroporosidade, caracterÃstica inerente ao solo utilizado nessa pesquisa. As doses crescentes de resÃduo de caju nÃo influenciaram significativamente nos resultados supracitados.
Since man discovered agriculture as a way to get food, nature has been modified. Changes were caused in the ecosystem and with them came the losses in soil quality. Therefore, it was presumed the need to implement systems that imply on the conservation of soil and thus the plant residues that were burned or removed from the agricultural area started to be left on the soil surface in order to protect the soil and to promote improvements in their quality. In this context, the application of plant residues on the soil, such as cashew residues, can bring benefits to physical quality of the soil. Given this, the present research objective was to evaluate the effect of cashew residue on soil physical quality measured through indicators. Samples were collected from both undisturbed not preserved soil. The analyzes were determined in the field (infiltration and hydraulic conductivity) and in the laboratory (index S and soil air permeability). The experimental design was randomized blocks, consisting of 5 treatments (five application rates: 0, 1, 2, 3, 4, which correspond, respectively, to: control, 16, 32, 48, 64 t ha-1 organic waste) and four blocks. For statistical analysis, it was verified the normality of data from the Kolmogorov-Smirnov and, then, followed by the analysis of variance and Tukey test at 5% probability. The values for saturated hydraulic conductivity (K0) was found to be in the range varying from high to very high, with reducing the possibility of superficial runoff. The residue did not affect the soil water content, even at high rate applications. The S index showed values above those shown in the literature (> 0.035), suggesting a good indicator of the soil quality under study. The soil air permeability (Kar) also had values above that considered critical (> 1μm2), being, therefore, limiting to plant growth. It can be argued that the high results K0, S and Kar were closely related to macroporosity, inherent characteristic of the soil used in this research. Increasing application rates of cashew residues did not significantly influence the above results.
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Vathylakis, Alexandros. "Reduction of broadband trailing edge noise by serrations." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/11554.
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This thesis aims to investigate and reduce the aerodynamic noise source known as trailing edge noise, or airfoil self-noise, by using passive flow control techniques. Airfoil self-noise is produced when a turbulent boundary layer generated on an airfoil surface is scattered by the airfoil’s trailing edge. The investigation is of experimental nature, conducted in the aeroacoustic as well as aerodynamic wind tunnel facilities at Brunel University London and the Institute of Sound and Vibration (ISVR) at the University of Southampton. The research is relevant for any application in which airfoil blades encounter a smooth non-turbulent inflow and hence where trailing edge noise is a dominant noise source. Potential applications can therefore be fan or rotor blades in aero-engines, wind turbine blades or industrial cooling fans. The approach taken for the reduction of trailing edge noise utilises passive flow control techniques through the use of trailing edge serrations and the additional support of porous materials. Both of the aforementioned are inspired by the owl’s silent flight due to its unique wing structure. The research presented here can be divided in three parts: The first part comprises an extensive assessment of the performance of non-flat plate trailing edge serrations for airfoil broadband noise and their aerodynamic performance in terms of lift and drag. It is found that serrations can realistically achieve noteworthy broadband airfoil self-noise reductions, however due to the fact that non-flat plate serrations are directly cut into the airfoil body, the blunt sections in the serration root produce an additional noise source of vortex shedding tonal noise. The second part investigates the two flow mechanisms involved. Regarding the mechanism responsible for broadband noise and the subsequent reductions by the serration geometry, the turbulent boundary layer structures are studied in depth on a serrated trailing edge of a flat plate. Experimental techniques such as hot wire anemometry, liquid crystal flow visualisation, unsteady surface pressure measurements and noise measurements are used. A redistribution of the momentum and turbulent energy near the sawtooth tip and side edges appears to reduce the trailing edge noise scattering-efficiency of the hydrodynamic pressure waves. For the study of the flow mechanism responsible for the vortex shedding tonal noise increase, noise and velocity measurements along with flow visualisation techniques are used for the identification and further understanding of this noise source. A highly three-dimensional wake-flow could be identified in the wake past the serration gap, which differs from the longitudinal vortices shed from a straight blunt serration root. The third part presents the concept of poro-serrated trailing edges as a novel method to substantially improve the overall noise performance of the non-flat plate trailing edge serration type. The use of porous metal foams or thin brush bundles which fill the interstices between adjacent members of the sawtooth can completely suppress the bluntness-induced vortex shedding noise. Most importantly a turbulent broadband noise reduction of up to 7 dB can be achieved without compromising the aerodynamic performances in lift and drag. The new serrated trailing edges do not cause any noise increase throughout the frequency range investigated here. Through noise and velocity measurements near the trailing edge of an airfoil, the reduction of the broadband noise is found to be primarily caused by the sawtooth geometry. The new serrated trailing edges have the potential to improve the industrial worthiness of the serration technology in achieving low noise radiation.
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Chen, Xiaohui. "Unsaturated hydro-chemo-mechanical modelling based on modified mixture theory." Thesis, University of Manchester, 2010. https://www.research.manchester.ac.uk/portal/en/theses/unsaturated-hydrochemomechanical-modelling-based-on-modified-mixture-theory(64ec76bb-1379-4e87-b9a7-562fa9267404).html.
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New unsaturated coupled models have been developed for fluid transport in deformable rock by using modified mixture theory rather than a fully mechanics-based approach. These models include the following: an unsaturated hydro-mechanical coupled model for both non-swelling and swelling materials, in which a new coupled formulation for hydration swelling rock has been included; and an unsaturated hydro-mechanical-chemo coupled model, incorporating a new coupled formulation including osmosis flow and an unsaturated version of Darcy's law which has been extended by including osmosis effects.Modified mixture theory is mainly based on non-equilibrium thermodynamics. Helmholtz free energy is used to give the energy relationship between the fluids and solid and, by using the Gibbs-Duhem equation, the interactions between different fluids such as gas, water and chemical can be obtained. In this research, general coupled formulations for both large small and deformations have been obtained. For swelling rocks, the water between the clay platelets can be modeled by including the difference between the free energy of whole domain and that of the pore water plus the solid skeleton. By assuming small deformations, the final equations can be compared with those derived using the mechanics approach.The new coupled models have been tested by carrying out simple benchmark numerical simulations using finite elements. Problems analyzed include: (1) the consolidation of saturated swelling rocks in which the hydration swelling effects on consolidation have been analysed in detail; (2) the desaturation and resaturation of seasonally affected rocks around tunnels; (3) the desaturation stage for swelling rocks used in the containment of nuclear waste disposal; (4) chemical transport in very low permeability rock used for nuclear waste disposal, in which particular attention has been focused on osmosis flow and chemical consolidation. In summary, this thesis extends modified mixture theory and develops new coupled formulations which can be applied to deep nuclear waste disposal, including tunnelling, drilling and chemical transport in low permeability host rock.
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Najmi, Hussain. "Selectivity of Porous Composite Materials for Multispecies mixtures : Application to Fuel Cells." Thesis, Bourges, INSA Centre Val de Loire, 2018. http://www.theses.fr/2018ISAB0001/document.
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L'utilisation de pile à combustible à bord d'un avion impose d'extraire des espèces légères (telles que l'hydrogène et les hydrocarbures légers) du combustible liquide qui est stocké et utilisé, éventuellement à des températures où se produit une pyrolyse du carburant. La porosité d’un matériau composite pourrait être utilisée pour filtrer les espèces sélectionnées. L'efficacité de séparation d’un matériau poreux dépend de deux facteurs qui sont: la perméance et la sélectivité.Ces facteurs sont souvent déterminés avec une configuration classique utilisant un échantillon en forme d’un disque d’un matériau poreux. Cependant, cette configuration est loin de la réalité qui est composée de tubes. Par conséquent, une étude est réalisée en considérant les deux configurations en utilisant différents types de disques poreux et un tube composite poreux. Ensuite, les résultats obtenus sont comparés et les différents facteurs affectant le processus de perméation sont étudiés.Après cela, un banc d'essai innovant est développé et utilisé afin de déterminer la distribution axiale des deux propriétés d'un tube poreux en acier inoxydable (c'est-à-dire la perméance et la sélectivité). Les effets des conditions opératoires (débit massique d'entrée et pression d'entrée) ont été étudiés. Une nouvelle forme radiale de l'équation de perméabilité aux gaz a été développée pour ce travail et sa relation avec la perméabilité de Darcy est établie. La variation de pression le long de l'axe central du tube est déterminée. Les effets de cette variation de pression sur les propriétés physiques des gaz tels que la densité et la viscosité sont déterminés et leur influence sur la sélectivité est étudiée en utilisant différents gaz tels que l'azote, le dioxyde de carbone, le méthane et l'hélium.Plus tard, un mélange binaire de dioxyde de carbone (CO2) et d'Azote (N2) est considéré sous trois compositions volumétriques différentes (50/50%, 60/40% et 70/30%) afin d'évaluer la propriété de séparation de gaz d’un tube poreux (effet de membrane). La perméabilité au gaz pur, la perméabilité du mélange, la sélectivité idéale et la sélectivité de séparation de ce tube sont déterminées pour un débit massique et une pression d'entrée différents. Les facteurs affectant les distributions de CO2 et de N2 à l'intérieur du tube poreux sont étudiés.Les résultats obtenus peuvent être utiles pour comprendre les facteurs affectant la séparation des gaz dans le cas d'un tube poreux pour des processus industriels continusUsing Fuel Cell on board of aircraft imposes to extract light species (such as Hydrogen and light hydrocarbons) from the liquid fuel which is stored and used, possibly at temperatures where a fuel pyrolysis occurs. Porosity of a composite material could be used to filtrate the selected species. The separation efficiency of a porous material depends upon two factors which are: Permeance and Selectivity.These factors are often determined with a classical configuration using a porous disk sample. However, this configuration is far from the realistic one consisting of tubes. Therefore, a study is performed considering both configurations using different types of porous disks and a porous composite tube. Then, the obtained results are compared and the different factors affecting the permeation process are studied.After that, an innovative permselectivity test bench is developed and used in order to determine the axial distribution of the two properties of a stainless steel porous tube (i.e. permeance and selectivity). The effects of the operating conditions (inlet mass flowrate and inlet pressure) have been studied. A new radial form of the gas permeability equation has been developed for this work and its relationship with Darcy‘s permeability is established. The pressure variation along the centre axis of the tube is determined. The effects of this pressure variation on the physical properties of gases such as density and viscosity are determined and their influence on the selectivity is studied using different gases such as Nitrogen, Carbon dioxide, Methane, and Helium. Later, a binary mixture of Carbon Dioxide (CO2) and of Nitrogen (N2) is considered under three different volumetric compositions (50/50%, 60/40% and 70/30%) in order to evaluate the separation property of the porous stainless steel tube (membrane effect). The pure gas permeability, the mixture permeability, the ideal selectivity and the separation selectivity of this tube are determined for a different mass flowrate and inlet pressure. The factors affecting the distributions of CO2 and N2 inside the porous tube are investigated. The obtained results can be useful to understand the factors affecting gas separation in case of a porous tube for continuous industrial processes
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Farid, Mohammad Hosseini. "Mechanical Characterization and Constitutive Modeling of Rate-dependent Viscoelastic Brain Tissue under High Rate Loadings." Diss., North Dakota State University, 2019. https://hdl.handle.net/10365/29786.
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In this dissertation, theoretical, computational, and experimental methodologies are introduced to determine the rate-dependent material properties of the brain tissue. Experiments have shown that the brain tissue is significantly rate-dependent. To examine the range of strain rates at which trauma might happen, a validated finite element (FE) human head model was initially employed to examine the biomechanics and dynamic behavior of the head and brain under impact and blast loads. The strain rates to cause traumatic brain injury (TBI) were found to be in the range of 36 to 241 1/s, under these types of loadings. These findings provided a good estimation prior to exploring the required experiments for characterizing the brain tissue.
The brain samples were tested by employing unconfined compression tests at three different deformation rates of 10 (n= 10 brain samples), 100 (n=8), and 1000 mm/sec (n=12). It was found that the tissue exhibited a significant rate-dependent behavior with various compression rates. Two different material characterization approaches were proposed to evaluate the rate-dependent mechanical responses of the brain. In the first approach, based on the parallel rheological framework, a single-phase viscoelastic model which captures the key aspects of the rate-dependency in large strain behavior was introduced. The extracted material parameters showed an excellent constitutive representation of tissue response in comparison with the experimental test results (R^2=0.999). The obtained material parameters were employed in the FE simulations of the brain tissue and successfully verified by the experimental results. In the second approach, the brain tissue is modeled as a biphasic continuum, consisting of a compressible solid matrix fully saturated with an incompressible interstitial fluid. The governing equations based on conservation of mass and momentum are used to describe the solid-fluid interactions. This viscoelastic biphasic model can effectively estimate the rate-dependent tissue deformations, the hydrostatic pressure as well as fluid diffusion through the tissue.
Although both single-phasic, as well as bi-phasic models, can successfully capture the key aspects of the rate-dependency in large strain deformation, it was shown the biphasic model can demystify more phenomenological behavior of this tissue that could not be perceived with yet established, single-phasic approaches.
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Kunik, Serguei. "Étude numérique et expérimentale du mécanisme de lubrification eX-Poro-HydroDynamique (XPHD)." Thesis, Poitiers, 2018. http://www.theses.fr/2018POIT2264/document.
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La lubrification eX-Poro-HydroDynamique (XPHD) est un mécanisme de lubrification d’inspiration biomimétique. Il s’agit principalement d’un écoulement dans un milieu poreux, dont la phase solide représentée par des fibres, induit des forces élastiques de compression considérées comme négligeables par rapport aux forces hydrodynamiques générées à l’intérieur du milieu poreux. L’idée essentielle de la lubrification XPHD consiste en remplacement du matériau antifriction et du film de fluide mince, traditionnellement utilisé dans les solutions classiques, par une couche poreuse imbibée d’un fluide qui fournit plus grande capacité de charge. Ce type de lubrification représente une solution technologique totalement nouvelle (en rupture avec la solution classique) qui peut permettre de remplacer les lubrifiants pétroliers, de créer des systèmes tribologiques autolubrifiants et donc plus écologiques et moins coûteux. Ce travail de recherche est donc focalisé sur l’évolution des performances de la lubrification XPHD dans le cadre d’un mouvement tangentiel, adapté à l’étude de butées pour faible et moyenne vitesses de rotation. Dans ce contexte scientifique, une étude approfondie d’un matériau poreux présélectionné (mousse en polyuréthane) fut réalisée avec le but de déterminer les caractéristiques physiques et les paramètres cruciaux pour la lubrification XPHD: la porosité et la perméabilité du matériau poreux. Les modèles théorique et numérique de lubrification XPHD proposés se basent sur l’équation de Darcy-Brinkman et les hypothèses de la lubrification classique, ainsi que l’écoulement à l’intérieur du milieu poreux sont prédit avec une nouvelle forme de l’équation de Reynolds. Le banc d’essais spécialement développé permet d’étudier expérimentalement le mécanisme de lubrification XPHD pour des différents types de dislocateur en combinaison avec des liquides newtoniens et nonnewtoniens. Une description détaillée du banc d’essais et de tous les dispositifs expérimentaux utilisés ainsi que la comparaison des résultats de modélisation et des résultats expérimentaux sont présentésThe eX-Poro-HydroDynamic (XPHD) lubrication is a new biomimetic inspired lubrication mechanism. It consists of self-sustained fluid films generated within highly compressible porous layers imbibed with liquids, whose solid phase represented by fibers, induces compressive elastic forces considered negligible compared to the hydrodynamic forces generated inside the porous medium. The essential idea of XPHD lubrication is to replace the antifriction material and the thin fluid film, traditionally used for classical sliding motion, with a porous layer imbibed with a fluid that provides a greater load capacity. This type of lubrication represents a completely new technological solution (in rupture with the classical one) that can replace petroleum lubricants, create self-lubricating and therefore more ecological and less expensive tribological systems. This research work is focused on the evolution of XPHD lubrication performances in the context of a tangential movement, adapted to the study of thrust bearing for low and medium rotation speeds. In this scientific context, a thorough study of a preselected porous material (polyurethane foam) was carried out with the aim of determining the physical characteristics and the crucial parameters for XPHD lubrication: the porosity and the permeability of the porous material. The theoretical and numerical models of the XPHD lubrication proposed are based on the Darcy-Brinkman equation and the classical lubrication hypothesis, as well as the flow within the porous media is predicted with a new form of the Reynolds equation. The specially developed test rig is used to investigate experimentally the mechanism of the XPHD lubrication for different types of thrust bearing in combination with Newtonian and non-Newtonian liquids. A detailed description of the test rig and all used experimental devices, as well the comparison between the experimental and numerical results are presented
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Henselwood, Fred William. "Porous and non-porous water soluble polymer nanospheres." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp02/NQ31033.pdf.
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Rane, Mahendra. "Porous Membrane." Doctoral thesis, Universitätsbibliothek Chemnitz, 2010. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-201000336.
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Membrane processes can cover a wide range of separation problems [with a
specific membrane (membrane structure) required for every problem]. Thus,
there are membranes available that differ in their structure and consequently in
the functionality. Therefore membrane characterization is necessary to ascertain,
which membrane may be used for a certain separation. Membranes of pore size
ranging from 100nm to 1μm with a uniform pore size are very important in
membrane technology. An optimum performance is achieved when the
membrane is as thin as possible having a uniform pore size.
Here in this thesis, membranes were synthesized by particle assisted wetting
using mono-layers of silica colloids as templates for pores along with
polymerizable organic liquids on water surface. The pore size reflects the
original shape of the particles. Thus it is possible to tune the pore size by
varying the particle size. This method is effective to control pore sizes of
membranes by choosing silica particles of suitable size.
This approach gives a porous structure that is very thin, but unfortunately
limited in mechanical stability. Thus there is a need for support which is robust
and can withstand the various mechanical stresses. A small change in the
membrane or defect in the layered structure during the membrane formation can
have drastic effect on the assembly. Lateral homogeneity of the layer generated
by the particle assisted wetting can be judged by examination of its reflectivity,
but once it is transferred on any solid support this option is no more.
So a method is needed to detect the cracks or the inhomogenity of the
membrane which can be detected even after the transfer. To tackle this problem
a very simple and novel technique for characterizing the membrane by
fluorescence labeling and optical inspection was developed in this thesis. The
idea was to add a fluorescent dye which is poorly water soluble to the spreading
solution comprising of the particles and the monomer. If the dye survived the
photo-cross linking, then it would be embedded in the cross-linked polymer and
would serve as a marker. Defects and inhomogenity would show up as cracks
and spots. By the method that we have developed, we can detect our membrane
from the support and spot defects.
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Xie, Mengying. "Porous City." Thesis, KTH, Arkitektur, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-281399.
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My project is about the growing problem of relations between humans and wildlife in cities. The more we built, the less space of habitat for wildlife to survive. I choose to work in Beijing, a megacity with a population of tens of millions, also home to many wildlife. I investigated the issue about coexistence of humans and wild animals in Beijing. I choose to design something for birds. Birds, along humans, are the most powerful biological force of globalization on the planet. I mainly studied one type of birds in Beijing called Beijing Swift. The purpose is to create a new mode in which people and birds could coexist in the city by exploring the concept of territory for birds. I use activeness and passiveness to define the concept of territory in terms of time, vertical space and horizontal space. Humans have dominance in the city where animals may be disturbed by people's behavior at any time or any place. Therefore I want to improve birds’ active dominance in their territory by providing bird-specific architecture, restricting human’s behavior and hiding human’s behavior in birds’ habitat.
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Cocchini, Ugo. "Mass transfer phenomena through porous and non-porous membranes." Thesis, Imperial College London, 2001. http://hdl.handle.net/10044/1/8024.
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Deng, Hailin. "Upscaling reactive transport parameters for porous and fractured porous media." Tallahassee, Florida : Florida State University, 2009. http://etd.lib.fsu.edu/theses/available/etd-10292009-103844/.
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Thesis (Ph. D.)--Florida State University, 2009.Advisor: Ming Ye, Zhenxue Dai, Florida State University, College of Arts and Sciences, Dept. of Geological Sciences. Title and description from dissertation home page (viewed on Apr. 26, 2010). Document formatted into pages; contains xxii, 167 pages. Includes bibliographical references.
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Vasiliev, Petr. "Functionalization and processing of porous powders into hierarchically porous monoliths." Doctoral thesis, Stockholms universitet, Institutionen för fysikalisk kemi, oorganisk kemi och strukturkemi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-27496.
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Inorganic porous materials are widely used in a number of applications, where is a need to functionalize and produce materials with a multiscale porosity. The first part of the thesis describes how a novel and facile powder processing approach, using pulsed current processing (PCP) or, as it is commonly called, spark plasma sintering (SPS), has been employed to produce mechanically stable, hierarchically porous bodies from different porous powders. Surfactant-templated mesoporous spheres were PCP-treated to yield meso/macro porous monoliths. The bimodal pore size can be tailored by choice of templating molecules in the aerosol-assisted synthesis process and by the particle size of the spheres. Diatomite powders were used to produce macro/macroporous monoliths. The densification behaviour of this inexpensive and renewable macroporous raw material was evaluated in detail, and an optimum temperature range was identified where the PCP process yields mechanically strong monoliths. Binder-less, hierarchically porous zeolite monoliths were produced from various zeolite powders, e.g. silicalite-1, ZSM-5 and zeolite Y. Line-broadening analysis of X-ray powder diffraction data by the Rietveld method and electron microscopy showed that the formation of strong interparticle bonds during the PCP process is associated with a local amorphization reaction that is induced by the high contact stress and temperature. Xylene isomerisation studies showed that binder-less ZSM-5 monoliths display a high catalytic selectivity. Direct (in-situ) nanoparticle functionalization of surfactant templated mesoporous silica particles has also been demonstrated. Pre-synthesized TiO2 nanoparticles were dispersed in a precursor solution, containing surfactant and silica source, and processed in an aerosol-generator to produce spherical nanoparticle-functionalized mesoporous particles.
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Kecht, Johann. "Colloidal Porous Nanoparticles." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-88441.
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Chow, Hon-nin. "Computer aided modelling of porous structures." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B39848929.
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Harter, Thomas. "Unconditional and conditional simulation of flow and transport in heterogeneous, variably saturated porous media." Diss., The University of Arizona, 1994. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1994_36_sip1_w.pdf&type=application/pdf.
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Huang, Po-Chuan. "Investigation and modeling of complex interfacial effects for porous/non-porous configurations /." The Ohio State University, 1993. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487843688957013.
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Plikk, Peter. "Porous degradable polyester scaffolds /." Stockholm : Royal Institute of Technology, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3960.
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Robert, Geneviève. "Rheology of porous rhyolite." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2738.
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I describe an experimental apparatus used to perform deformation experiments
relevant to volcanology. The apparatus supports low-load, high-temperature deformation
experiments under dry and wet conditions on natural and synthetic samples. The
experiments recover the transient rheology of complex (melt ± porosity ± solids) volcanic
materials during uniaxial deformation. The key component to this apparatus is a steel
cell designed for high-temperature deformation experiments under controlled water
pressure. Experiments are run under constant displacement rates or constant loads; the
range of accessible experimental conditions include: 25 - 1100 °C, load stresses 0 to 150
MPa, strain rates 10⁻⁶ to 10⁻² s⁻¹, and fluid pressures 0-150 MPa.
I present a suite of high-temperature, uniaxial deformation experiments performed
on 25 by 50 mm unjacketed cores of porous Φ∼0.8) sintered rhyolitic ash. The
experiments were performed at, both, atmospheric (dry) and elevated water pressure
conditions (wet). Dry experiments were conducted mainly at 900 °C, but also included a
suite of lower temperature experiments at 850, 800 and 750 °C. Wet experiments were
performed at ∼650 °C under water pressures of 1, 2.5, 3, and 5 MPa, and at a fixed PH2O
of ∼2.5 MPa for temperatures of ∼385, 450, and 550 °C. During deformation, strain is
manifest by shortening of the cores, reduction of porosity, flattening of ash particles, and
radial bulging of the cores. The continuous reduction of porosity leads to a dynamic
transient strain-dependent rheology and requires strain to be partitioned between a
volume (porosity loss) and a shear (radial bulging) component. The effect of increasing
porosity is to expand the window for viscous deformation for dry melts by delaying the
onset of brittle deformation by ∼50 °C (875 °C to 825 °C). The effect is more
pronounced in hydrous melts (∼0.67 — 0.78 wt. % H₂0) where the viscous to brittle
transition is depressed by ∼140 to 150 °C. Increasing water pressure also delays the onset
of strain hardening due to compaction-driven porosity reduction. These rheological data
are pertinent to volcanic processes where high-temperature porous magmas I liquids are
encountered (e.g., magma flow in conduits, welding of pyroclastic materials).
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Hollewand, Michael Paul. "Transport in porous catalysts." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.281985.
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Lawson, D. A. "Combustion in porous media." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.354839.
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Su, Zixue. "Porous anodic metal oxides." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/1019.
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An equifield strength model has been established to elucidate the formation mechanism for the highly ordered alumina pore arrays and titanium oxide nanotubular arrays prepared via a common electrochemical methodology, anodisation. The fundamentals of the equifield strength model was the equilibrium between the electric field driven oxidation rate of the metal and electric field enhanced dissolution rate of oxide. During the anodic oxidation of metal, pore initiation was believed to generate based on dissolution rate difference caused by inhomogeneity near the metal/oxide interface. The ionic nanoconvection driven by the electric force exerted on the space charge layer in the vicinity of electrolyte/oxide interface is established to be the main driving force of the pore ordering at the early stage of the anodisation. While the equifield strength requirement governs the following formation of the single pore and the self-ordering of random distributed pore arrays during the anodisation process. Hexagonal patterned Al2O3 nanopore arrays and TiO2 nanotubular arrays have been achieved by anodisation of corresponding metal substrates in proper electrolytes. The two characteristic microstructural features of anodic aluminium oxide (AAO) and anodic titanium oxide (ATO) were investigated using scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). The observations of the hemispherical electrolyte/oxide and oxide/metal interfaces, uniform thickness of the oxide layer, as well as self-adjustment of the pore size and pore ordering can be well explained by the equifield strength model. Field enhanced dissociation of water is extremely important in determination of the porosity of anodic metal oxide. The porosity of AAO and ATO films was found to be governed by the relative dissociation rate of water which is dependent on anodisation conditions, such as electrolyte, applied voltage, current density and electric field strength. Using an empirical method, the relations between the porosity of the AAO (ATO) films and the anodisation parameters, such as electric field strength, current density and applied voltage, have been established. Besides, the extent that an external electric field can facilitate the heterolytic dissociation of water molecule has been estimated using quantum-chemical model computations combined with the experimental aspect. With these achievements, the fabrication of anodic metal oxide films can be understood and controlled more precisely. Additionally, the impacts of other factors such as the electrolyte type and the temperature effect on the morphology of the anodic products were also investigated. Some important experimental evidences on the pore diameters variation with applied voltage in the anodisation of aluminium and the titanium were obtained for future investigation of the anodic metal oxide formation processes.
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Zhang, Jin. "Shakedown of porous materials." Thesis, Lille 1, 2018. http://www.theses.fr/2018LIL1I044/document.
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Cette thèse est consacrée à la détermination des états limites de l'adaptation des matériaux ductiles poreux sur la base du théorème de Melan et en considérant le modèle de la sphère creuse. Dans un premier temps, nous proposons le critère analytique macroscopique d'adaptation avec la matrice de von Mises sous deux charges particuliers, alterné et pulsé. Le critère analytique dépend des première et seconde invariants des contraintes macroscopiques, du signe du troisième et du coefficient de Poisson. Ensuite, ce critère est étendu aux charges cycliques répétées générales par la construction d'un champ de contraintes résiduelles d'essai plus approprié permettant simultanément des calculs analytiques et l'amélioration du modèle précédent. De plus, il est également utilisé pour les matériaux ductiles poreux avec une matrice de Drucker-Prager.L'idée repose d'abord sur la solution exacte pour le charge purement hydrostatique. Il s'avère que la ruine se produit par fatigue. Ensuite, des champs de contrainte d'essai appropriés sont construits avec des termes supplémentaires pour capter les effets de cisaillement. Le domaine de sécurité, défini par l'intersection du domaine d'adaptationet celui d'analyse limite (la ruine survenant brusquement par formation d'un mécanisme au premier cycle), est entièrement comparé avec des simulations élasto-plastique incrémentales et des calculs directs simplifiés.Enfin, nous fournissons une méthode numérique directe pour prédire le domaine de sécurité de l'adaptation des matériaux poreux soumis à des charges variant de manière indépendante en considérant le chemin critique du domaine de chargement au lieu de l'histoire entière. Le problème de l'adaptation est transformé en un problème d'optimisation de grande taille, qui peut être résolu efficacement par l'optimiseur non-linéaire IPOPT pour donner non seulement le facteur de charge limite, mais aussi le champ de contrainte résiduelle correspondant à l'état d'adaptationThis thesis is devoted to the determination of shakedown limit states of porous ductile materials based on Melan's static theorem by considering the hollow sphere model, analytically and numerically. First of all, we determine the analytical macroscopic shakedown criterion of the considered unit cell with von Mises matrix under alternating and pulsating special loading cases. The proposed macroscopic analytical criterion depends on the first and second macroscopic stresses invariants, the sign of the third one and Poisson's ratio. Then, the procedure is extended to the general cyclically repeated loads by the construction of a more appropriate trial residual stress field allowing analytical computations and the improvement of the previous model simultaneously. Moreover, this approach is applied to porous materials with dilatant Drucker-Prager matrix.The idea relies firstly on the exact solution for the pure hydrostatic loading condition. It turns out that the collapse occurs by fatigue. Next, suitable trial stress fields are built with additional terms to capture the shear effects. The safety domain, defined by the intersection of the shakedown limit domain and the limit analysis domain corresponding to the sudden collapse by development of a mechanism at the first cycle, is fully compared with step-by-step incremental elastic-plastic simulations and simplified direct computations. At last, we provide a direct numerical method to predict the shakedown safety domain of porous materials subjected to multi-varying independent loadings by considering the critical loading path of the load domain instead of the whole history. The shakedown problem is transformed into a large-size optimization problem, which can be solved efficiently by the non-linear optimizer IPOPT to give out not only the limit load factor, but also the corresponding residual stress field for the shakedown state
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Tucker, Julie. "Porous perfluorocarbon chromatographic supports." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627206.
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Ruthven, Douglas M. "Diffusion through porous media." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-188922.
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This paper considers permeation through microporous or nanoporous inorganic membranes under the influence of an applied pressure gradient. In general membrane permeation may be considered as a diffusive process, driven by the gradient of chemical potential (which depends on both composition and pressure). The relative importance of these two factors varies greatly for different types of system. The general features of such processes are reviewed and the diffusional behavior of selected systems is examined.
(membrane permeation, osmosis, diffusion, zeolite membrane, DDR-3, SAPO-34)
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Gong, Xuehui. "POROUS POLYMERIC FUNCTIONAL MATERIALS." Case Western Reserve University School of Graduate Studies / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=case1595256175834586.
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Harwin, Damien Anthony. "Flows in porous channels." Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437726.
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Bai, Chengying. "Highly porous geopolymer components." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3427257.
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The geopolymers, semi-crystalline three-dimensional silico-aluminate inorganic polymers, have attracted increasing attention from a wide range of scientific interests. The topic of this study deals with the synthesis, the characterization and the potential applications of porous geopolymers (PGs) or geopolymer foams (GFs, total porosity > 70 vol%), realized through different processing routes. Firstly, the processes are divided into five categories: (i) direct foaming, (ii) replica method, (iii) sacrificial template, (iv) the 3D printing, and (v) others. The microstructure, porosity, and properties of porous geopolymers also compared and discussed. Secondly, K-based porous geopolymers were produced by direct foaming using hydrogen peroxide as chemical pore-forming agent (PFA) combined with three types of stabilizing agent (SA, egg white, Tween 80, vegetable oils), and by direct foaming plus reactive emulsion templating. Furthermore, open-celled phosphate-based porous geopolymers were obtained by a simple direct foaming method (using Triton X-100 as physical pore-forming agent). The porosity, pore morphology, high temperature performance, adsorption, mechanical, and insulating properties of PGs were investigated. High strength PGs with tailored porosity and controlled macro-porous structure were fabricated by different processes. The results suggest that the porous geopolymers are promising low-cost highly porous candidates for potential applications such as catalyst or membrane supports (high open porosity and high strength), adsorption (high removal efficiency and adsorption capacity with high open porosity) and insulating (low thermal conductivity, high porosity, and acceptable strength) materials.I geopolimeri, polimeri inorganici silicoalluminati tridimensionali semi-cristallini, hanno attirato crescente attenzione da una vasta gamma di interessi scientifici. L'argomento di questo studio riguarda la sintesi, la caratterizzazione e le potenziali applicazioni di geopolimeri porosi (PG) o schiume di geopolimeri (GF, porosità totale> 70% vol), realizzati attraverso diversi percorsi di lavorazione. In primo luogo, i processi sono suddivisi in cinque categorie: (i) schiumatura diretta, (ii) metodo di replica, (iii) modello sacrificale, (iv) stampa 3D e (v) altri. Anche la microstruttura, la porosità e le proprietà dei geopolimeri porosi sono state confrontate e discusse. In secondo luogo, i geopolimeri porosi basati su K sono stati prodotti mediante schiumatura diretta utilizzando perossido di idrogeno come agente chimico di formazione dei pori (PFA) combinato con tre tipi di agente stabilizzante (SA, bianco d'uovo, Tween 80, oli vegetali) e mediante schiumatura diretta più reattivo emulsione che modella. Inoltre, geopolimeri porosi a base di fosfato a cellule aperte sono stati ottenuti con un semplice metodo di schiumatura diretta (usando Triton X-100 come agente fisico di formazione dei pori). Sono state studiate la porosità, la morfologia dei pori, le prestazioni ad alte temperature, l'adsorbimento, le proprietà meccaniche e isolanti delle PG. I PG ad alta resistenza con porosità adattata e struttura macroporosa controllata sono stati fabbricati con diversi processi. I risultati suggeriscono che i geopolimeri porosi promettono candidati altamente porosi a basso costo per potenziali applicazioni come catalizzatori o supporti a membrana (elevata porosità aperta e alta resistenza), adsorbimento (alta efficienza di rimozione e capacità di adsorbimento con elevata porosità aperta) e isolanti (basso materiali di conducibilità termica, elevata porosità e resistenza accettabile).
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NEGRONI, MATTIA. "Dynamics in Porous Materials." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2020. http://hdl.handle.net/10281/263115.
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Il mio lavoro di tesi si è basato sulla caratterizzazione dei materiali porosi rivolgendo particolare attenzione alla ricerca di elementi dinamici all’interno delle strutture e allo studio dei gas adsorbiti. Sono riuscito a rilevare la presenza di rotori parafenilenici ultraveloci sia in cristalli molecolari porosi che in metal-organic framework (MOF). Uno studio più approfondito ha inoltre rivelato come questi moti siano influenzati dal gas adsorbito. Nello specifico l’energia di attivazione della rotazione aumenta in funzione della quantità di gas nei pori. Per meglio capire questa interazione è però fondamentale la conoscenza del comportamento dei gas nei materiali porosi. Ho pertanto rivolto la mia attenzione allo studio del moto di xeno e CO2 in diversi materiali. L’utilizzo combinato di NMR e calcoli ab initio si è rivelato fondamentale per la comprensione di questi fenomeni ed è stato possibile rivelare particolari caratteristiche tanto dei gas quanto dei materiali stessi. La complessità della diffusione all’interno dei canali si è anche presentata in modi insoliti come il moto elicoidale dell’anidride carbonica imposto dal potenziale elettrostatico. Volendo continuare lo studio dei gas nei pori, ho caratterizzato diversi porous aromatic framework (PAF) con la tecnica dello xeno iperpolarizzato. Questo non mi ha consentito solo di misurare con accuratezza le dimensioni dei pori ma anche calcolare l’energia di interazione tra lo xeno e le pareti dei canali. Desiderando espandere le mie conoscenze sull’iperpolarizzazione come tecnica NMR, ho passato sei mesi presso il gruppo del Prof. L. Emsley a Losanna imparando la dynamic nuclear polarization (DNP) nonché la sua applicazione a diversi materiali.My thesis work was based on the characterization of porous materials, paying particular attention to the research of dynamic elements within the structures and to the study of adsorbed gases. I was able to detect the presence of ultrafast paraphenylenic rotors in both porous molecular crystals and metal-organic frameworks (MOFs). A more detailed study has also revealed how these motions are influenced by the adsorbed gas. Specifically, the activation energy of the rotation increases as a function of the quantity of gas in the pores. To better understand this interaction, the knowledge of the behavior of gases in porous materials is fundamental. I turned my attention to the study of xenon and CO2 motion in different materials. The combined use of NMR and ab initio calculations proved to be fundamental for understanding these phenomena and it was possible to reveal particular characteristics both of the gases and of the materials. The complexity of the diffusion within the channels has also been presented in unusual ways as the helicoidal motion of carbon dioxide imposed by the electrostatic potential. To continue the study of pore gases, I characterized several porous aromatic frameworks (PAFs) with the hyperpolarized xenon technique. This not only allowed me to accurately measure the pore size but also to calculate the interaction energy between the xenon and the channel walls. To expand my knowledge on hyperpolarization as an NMR technique, I spent six months at the group of Prof. L. Emsley in Lausanne learning dynamic nuclear polarization (DNP) as well as its application to different materials.
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Kodumuri, Pradeep. "IN-SITU GROWTH OF POROUS ALUMINO-SILICATES AND FABRICATION OF NANO-POROUS MEMBRANES." Cleveland State University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=csu1243304850.
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Rioux, Ran Wei. "The Rate of Fluid Absorption in Porous Media." Fogler Library, University of Maine, 2003. http://www.library.umaine.edu/theses/pdf/RiouxRW2003.pdf.
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Tran, Kien Nguyen. "Modelling of vapour-liquid phase equilibrium and adsorptions on non-porous and porous carbon /." St. Lucia, Qld., 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17383.pdf.
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Appleby, Susan. "Macroscopic stress analysis and microscopic continuum modelling for porous and non porous elastic solids." Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284319.
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Alvarez, Sara D. "Stability and biocompatability of porous silicon and porous alumina for cell and biomolecular sensing." Diss., [La Jolla, Calif.] : University of California, San Diego, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3338847.
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Thesis (Ph. D.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed Jan. 13, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 126-141).
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Alvarez, Martinez José Manuel. "Foam-flow behavior in porous media : effects of flow regime and porous-medium heterogeneity /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.
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Crimm, Robert Prentiss. "Experimental apparatus for measuring moisture transfer in porous materials subject to relative humidity and temperature differences." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-01122010-020146/.
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Sun, Ssu-Hsueh. "Finite element analyses of coupled heat and moisture transport in cylindrical porous media and coal logs /." free to MU campus, to others for purchase, 1997. http://wwwlib.umi.com/cr/mo/fullcit?p9841186.
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Kobler, Johannes. "Thin Films from Porous Nanoparticles." Diss., lmu, 2008. http://nbn-resolving.de/urn:nbn:de:bvb:19-98694.
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Koumoto, K., W. S. Seo, and S. Ozawa. "Huge thermopower of porous Y_2O_3." American Institute of Physics, 1997. http://hdl.handle.net/2237/6986.
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Jiang, Tong. "Porous tin(IV) sulfide materials." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape10/PQDD_0007/NQ41557.pdf.
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Karlsson, Linda. "Biomolecular interactions with porous silicon /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/tek804s.pdf.
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Stol, Remco. "Capillary electrochromatography with porous particles." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2002. http://dare.uva.nl/document/61674.
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Little, Sylvia Bandy. "Multiphase flow through porous media." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/11779.
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Booth, Richard J. S. "Miscible flow through porous media." Thesis, University of Oxford, 2008. http://ora.ox.ac.uk/objects/uuid:542d3ec1-2894-4a34-9b93-94bc639720c9.
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This thesis is concerned with the modelling of miscible fluid flow through porous media, with the intended application being the displacement of oil from a reservoir by a solvent with which the oil is miscible. The primary difficulty that we encounter with such modelling is the existence of a fingering instability that arises from the viscosity and the density differences between the oil and solvent. We take as our basic model the Peaceman model, which we derive from first principles as the combination of Darcy’s law with the mass transport of solvent by advection and hydrodynamic dispersion. In the oil industry, advection is usually dominant, so that the Péclet number, Pe, is large. We begin by neglecting the effect of density differences between the two fluids and concentrate only on the viscous fingering instability. A stability analysis and numerical simulations are used to show that the wavelength of the instability is proportional to Pe^−1/2, and hence that a large number of fingers will be formed. We next apply homogenisation theory to investigate the evolution of the average concentration of solvent when the mean flow is one-dimensional, and discuss the rationale behind the Koval model. We then attempt to explain why the mixing zone in which fingering is present grows at the observed rate, which is different from that predicted by a naive version of the Koval model. We associate the shocks that appear in our homogenised model with the tips and roots of the fingers, the tip-regions being modelled by Saffman-Taylor finger solutions. We then extend our model to consider flow through porous media that are heterogeneous at the macroscopic scale, and where the mean flow is not one dimensional. We compare our model with that of Todd & Longstaff and also models for immiscible flow through porous media. Finally, we extend our work to consider miscible displacements in which both density and viscosity differences between the two fluids are relevant.
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Mealey, Liam Robert. "Heat Transfer in Porous Media." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.494108.
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Kou, Shuting, and 寇舒婷. "Porous structure modeling with computers." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2014. http://hdl.handle.net/10722/206700.
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Porous structures are a particular type of solids, where a large number of pores exist in the geometric domain of interest. Research on porous structures have received increasingly keen interest in recent years and this is largely because of many unique and superior properties that porous structures possess. They can undertake special tasks which general solid materials are not competent to do.
In recent twenty years numerous representations are put forward for porous structure modeling. But the challenges in practical porous structure design still exist and the structure heterogeneity brings many difficulties. This thesis is motivated to propose new porous structure modeling strategies which are more accurate, flexible and easy for porous structure description.
An approach of porous structure modeling based on quadtree/octree and NURBS is proposed first. Quadtree and octree are tools for modeling domain partition. The pore size and pore distribution are controlled by the flexibility of quadtree and octree enumeration technique. Derived polygon and polyhedron are then introduced to assist the generation of NURBS curves and surfaces. These NURBS curves and surfaces form the boundaries of the porous structures.
However there are limitations of the above method. The accurate control of porosity is not easily achieved in 3D porous structure modeling and seemingly adopting quadtree/octree for the modeling domain partition is also less than satisfactory. Hence a new representation for porous structures based on Centroidal Voronoi tessellation (CVT) and pore-network is put forward. CVT is utilized for modeling domain partition because the CVT cells are approximate hexagons which is widely existent in plants, animals and other cellular structures in nature. The density distribution function used in CVT generation also helps to build functionally graded porous structures. Pore-network, which is a mature and commonly used model in the research of multiphase flow in porous media, is subsequently introduced to build the porous structures. This modeling approach results in porous structures that could mimic the geometry and performance of structures in nature.
To evaluate the object’s properties, finite element analysis (FEA) is conducted on the porous structure models represented by the two methods. The mechanics properties of the two types of models are analyzed. The stress-strain curve of each sample is plotted and the effective Young’s modulus is calculated. Comparison of these two types of models is also done. Besides, the contributions of the thesis and suggestions for future research are also discussed.published_or_final_version
Mechanical Engineering
Master
Master of Philosophy
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Tchang, Cervin Nicholas. "Porous Materials from Cellulose Nanofibrils." Doctoral thesis, KTH, Fiberteknologi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155065.
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In the first part of this work a novel type of low-density, sponge-like material for the separation of mixtures of oil and water has been prepared by vapour deposition of hydrophobic tri-chloro-silanes on ultra-porous cellulose nanofibril (CNF) aerogels. To achieve this, a highly porous (>99%) robust CNF aerogel with high structural flexibility is first formed by freeze-drying an aqueous suspension of the CNFs. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the CNF suspension before freeze-drying. The hydrophobic light-weight aerogels are almost instantly filled with the oil phase when they selectively absorb oil from water, with a capacity to absorb up to 45 times their own weight. The oil can subsequently be drained from the aerogel and the aerogel can then be subjected to a second absorption cycle. The second part is about aerogels with different pore structures and manufactured with freeze-drying and supercritical carbon dioxide for the preparation of super slippery surfaces. Tunable super slippery liquid-infused porous surfaces (SLIPS) were fabricated through fluorination of CNFsand subsequent infusion with perfluorinated liquid lubricants. CNF-based self-standing membranes repelled water and hexadecane with roll-off angles of only a few degrees. The lifetime of the slippery surface was controlled by the rate of evaporation of the lubricant, where the low roll-off angle could be regained with additional infusion. Moreover, adjusting the porosity of the membranes allowed the amount of infused lubricant to be tuned and thereby the lifetime. The CNF-based process permitted the expansion of the concept to coatings on glass, steel, paper and silicon. The lubricant-infused films and coatings are optically transparent and also feature self-cleaning and self-repairing abilities. The third part describes how porous structures from CNFs can be prepared in a new way by using a Pickering foam technique to create CNF-stabilized foams. This technique is promising for up-scaling to enable these porous nanostructured cellulose materials to be produced on a large scale. With this technique, a novel, lightweight and strong porous cellulose material has been prepared by drying aqueous foams stabilized with surface-modified CNFs. Confocal microscopy and high-speed video imaging show that the long-term stability of the wet foams can be attributed to the octylamine-coated, rod-shaped CNF nanoparticles residing at the air-liquid interface which prevent the air bubbles from collapsing or coalescing. Careful removal of the water yields a porous cellulose-based material with a porosity of 98 %, and measurements with an autoporosimeter (APVD) reveal that most pores have a radius in the range of 300 to 500 μm. In the fourth part, the aim was to clarify the mechanisms behind the stabilizing action of CNFs in wet-stable cellulose foams. Factors that have been investigated are the importance of the surface energy of the stabilizing CNF particles, their aspect ratio and charge density, and the concentration of CNF particles at the air-water interface. In order to investigate these parameters, the viscoelastic properties of the interface have been evaluated using the pendant drop method. The properties of the interface have also been compared by foam stability tests to clarify how the interface properties can be related to the foam stability over time. The most important results and conclusions are that CNFs can be used as stabilizing particles for aqueous foams already at a concentration as low as 5 g/L. The reasons for this are the high aspect ratio which is important for gel formation and the viscoelastic modulus of the air-water interface. Foams stabilized with CNFs are therefore much more stable than foams stabilized by cellulose nanocrystals (CNC). The charge density of the CNFs affects the level of liberation of the CNFs within large CNF aggregates and hence the number of contact points at the interface, and also the gel formation and viscoelastic modulus. The charges also lead to a disjoining pressure related to the long-range repulsive electrostatic interaction between the stabilized bubbles, and this contributes to foam stability. In the fifth part, the aim was to develop the drying procedure in order to producea dry porous CNF material using the wet foam as a precursor and to evaluate the dry foam properties. The wet foam was dried in an oven while placed on a liquid-filled porous ceramic frit to preserve and enhance the porous structure in the dried material and prevent the formation of larger cavities and disruptions. The cell structure has been studied by SEM microscopy and APVD (automatic pore volume distribution). The mechanical properties have been studied by a tensile tester (Instron 5566) and the liquid absorption ability with the aid of the APVD-equipment. By changing the charge density of the CNFs it is possible to prepare dry foams with different densities and the lowest density was found to be 6 kg m-3with a porosity of 99.6 %. The Young ́s modulus in compression was 50 MPa and the energy absorption was 2340kJ m-3 for foams with a density of 200 kg m-3. The liquid absorption of the foam with a density of 13 kg m-3 is 34 times its own weight. By chemically cross-linking the foam,it wasalso possible to empty the liquid-filled foams by compression and then to reabsorb the liquid to the same degree with maintained foam integrity. This new processing method also shows great promise for preparing low-density cellulose foams continuously and could be very suitable for industrial up-scaling.QC 20141103
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Murison, Julie Lynette. "Wetting heterogeneities in porous media." Doctoral thesis, Niedersächsische Staats- und Universitätsbibliothek Göttingen, 2014. http://hdl.handle.net/11858/00-1735-0000-0022-5E9C-2.
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