Дисертації з теми "Dense and porous structure"
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1
Singh, Kamaljit Engineering & Information Technology Australian Defence Force Academy UNSW. "Dynamics of residual non-aqueous phase liquids in porous media subject to freeze-thaw." Awarded by:University of New South Wales - Australian Defence Force Academy. Engineering & Information Technology, 2009. http://handle.unsw.edu.au/1959.4/44875.
Повний текст джерелаАнотація:
This project concerns the effect of freeze-thaw cycles on the pore-scale structure of nonaqueous phase liquid (NAPL) contaminants in water-saturated porous media. This problem is of critical importance to the entrapment of such contaminants in cold temperate, polar and high altitude regions, and has not been examined in the literature to date. This research work is conducted in three stages: (i) two-dimensional nondestructive visualisation of residual light non-aqueous phase liquid (LNAPL), and dense non-aqueous phase liquid (DNAPL), in porous media subject to successive freeze-thaw cycles; (ii) three-dimensional experiments on LNAPL in porous media subject to freeze-thaw, with quantification of phase volumes by X-ray micro-computed tomography (micro-CT); and (iii) the explanation of results by several pore scale mathematical and conceptual models. The two-dimensional cell experiments (using a monolayer of 0.5 mm diameter glass beads held between two glass sheets), and three-dimensional X-ray micro-CT experiments reveal a substantial mobilisation and rupture of ganglia during successive freeze-thaw cycles; this includes the detachment of smaller ganglia from larger ganglia and the mobilisation of NAPL in the direction of freezing front. The experiments also reveal significant shedding of numerous single/sub-singlet ganglia along narrow pore corridors, their entrapment in growing polycrystalline ice, and the coalescence of such small ganglia during thawing to form larger singlets. These changes were more predominant where the freezing commenced. The results of the experimental studies were interpreted by developing several mathematical and conceptual models, including freezing-induced pressure model, Darcy's law model, multipore ganglia model (rupture coefficient) and ice-snap off model.
2
Füldner, Gerrit, and Andreas Velte. "Water adsorption kinetics and diffusion in dense SAPO-34 layers on porous aluminium fibre structures – macroscopic measurements by a Volumetric Differential Pressure Step Method." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-198145.
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Füldner, Gerrit, and Andreas Velte. "Water adsorption kinetics and diffusion in dense SAPO-34 layers on porous aluminium fibre structures – macroscopic measurements by a Volumetric Differential Pressure Step Method: Water adsorption kinetics and diffusion in dense SAPO-34 layers on porousaluminium fibre structures – macroscopic measurements by a VolumetricDifferential Pressure Step Method." Diffusion fundamentals 24 (2015) 15, S. 1, 2015. https://ul.qucosa.de/id/qucosa%3A14529.
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Tazi, Bouchra. "Élaboration et caractérisation d'une nouvelle membrane minérale conductrice ionique à structures dense et microporeuse." Montpellier 2, 1988. http://www.theses.fr/1988MON20138.
Повний текст джерелаАнотація:
Ce travail presente l'elaboration d'une nouvelle membrane conductrice ionique en nasicon (na::(3)zr::(2)si::(2)po::(61)). Les tests d'echanges ioniques montrent la possibilite d'echange entre des ions na**(+) et des cations ag**(+), k**(+), li**(+) et na**(+))
5
Chan, Wing Nin. "Comparison of the wearing of porous and dense NiTi shape memory alloy." access abstract and table of contents access full-text, 2006. http://libweb.cityu.edu.hk/cgi-bin/ezdb/dissert.pl?msc-ap-b21458406a.pdf.
Повний текст джерелаАнотація:
Thesis (M.Sc.)--City University of Hong Kong, 2006."Master of Science in Materials Engineering & Nanotechnology dissertation." Title from title screen (viewed on Nov. 23, 2006) Includes bibliographical references.
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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.
Повний текст джерелаАнотація:
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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He, Xing. "Processing of porous and dense ceramics using natural polymer binders for biomedical applications." Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503879.
Повний текст джерелаАнотація:
Ceramics have long been used in different biomedical applications. Examples include biodegradable porous ceramic scaffolds and bioactive dense ceramic implants and prostheses. For the fabrication of different forms of ceramics, polymer binders, organic solvents and hazardous processing aids have often been used. Some of them, e.g. acrylamide monomers used in the conventional gelcasting processing. are even toxic. There is a compelling need to develop eco-friendly processing of ceramics. In this work, an environmentally-friendly protein system - egg white protein - has been employed to fabricate porous and dense ceramics to take the advantage of the well-known foaming and gelling capabilities of egg white protein.
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Şimşek, Deniz Çiftçioğlu Muhsin. "Preparation and characterization of HA powders-dense and porous HA based composite materials/." [s.l.: [s.n.], 2002. http://library.iyte.edu.tr/tezler/master/malzemebilimivemuh/T000326.pdf.
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Marangoni, Mauro. "Dense and porous glass and glass ceramics from natural and waste raw materials." Doctoral thesis, Università degli studi di Padova, 2016. http://hdl.handle.net/11577/3424468.
Повний текст джерелаАнотація:
The main goal of the herewith presented research activities was to develop innovative processes and materials for building applications adapted to the needs of Saudi Arabia according to the information exchanged with the partners from KACST (King Abdulaziz City of Science and Technology).
The research activity focused on the development of a wide range of ceramic components via sinter-crystallization of glasses produced from waste (fly ash, slag, sludge) with or without the addition of vitrification aids, such as cullet or silicates. The raw materials have been mixed in the appropriate ratios to yield ceramic compositions that could be used in the building industry (e.g glass ceramic tiles, porous panels, lightweight aggregates). Monolithic, porous or dense, sintered glass ceramics and ceramics were manufactured as substitutes for natural stones or traditional ceramics. Dense glass ceramics have outstanding properties (hardness, mechanical strength, durability), while porous glass ceramics provide low density and thermal conductivity. Furthermore highly reflective glazes, also matching the whiteness of Thassos marble, were manufacture sintering glass frits.
All the developed materials are based on the use of natural resources or waste materials from Saudi Arabia. Moreover, several techniques for direct foaming of glass ceramics have been developed, leading to highly porous ceramics with mainly closed cells. Alternative techniques have been developed for the production of open-celled ceramics.Il principale obiettivo delle attività di ricerca qui presentate riguardano lo sviluppo di nuovi processi e materiali per applicazioni in edilizia adattate alle esigenze dell'Arabia Saudita in base alle informazioni scambiate con i partner di KACST (King Abdulaziz City of Science and Technology). L'attività di ricerca è stata focalizzata sullo sviluppo di una vasta gamma di componenti ceramici mediante sintercristallizzazione di vetri prodotti da rifiuti (ceneri volanti e scorie) con o senza l'aggiunta di fondenti come rottame di vetro o silicati. Le materie prime sono state miscelate in rapporti adeguati alla produzione di composizioni ceramiche adatte all’utilizzo in edilizia; ad esempio piastrelle vetroceramiche, pannelli alleggeriti e aggregati leggeri. Vetroceramiche e ceramiche, dense e porose, sono state realizzate come sostituti alle pietre naturali e ai ceramici tradizionali. Vetroceramici densi presentano proprietà eccezionali (durezza, resistenza meccanica, durabilità), mentre vetroceramiche porose presentano ridotte densità e conducibilità termica. Inoltre sinterizzando fritte vetrose sono stati ottenuti smalti altamente riflettenti con bianchezza corrispondente al marmo di Thassos. Tutti i materiali sviluppati sono basati sull'utilizzo di risorse naturali o materiali di scarto provenienti dall’Arabia Saudita. Inoltre, sono state sviluppate diverse tecniche per la schiumatura diretta di vetroceramiche, portando alla realizzazione di materiali altamente porosi con celle principalmente chiuse. Utilizzando tecniche alternative sono state invece sviluppate vetroceramiche con una prevalenza di celle aperte.
10
Anderson, Michael Robert. "The dissolution and transport of dense non-aqueous phase liquids in saturated porous media /." Full text open access at:, 1988. http://content.ohsu.edu/u?/etd,171.
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Saedi, Soheil. "Shape Memory Behavior of Dense and Porous NiTi Alloys Fabricated by Selective Laser Melting." UKnowledge, 2017. http://uknowledge.uky.edu/me_etds/90.
Повний текст джерелаАнотація:
Selective Laser Melting (SLM) of Additive Manufacturing is an attractive fabrication method that employs CAD data to selectively melt the metal powder layer by layer via a laser beam and produce a 3D part. This method not only opens a new window in overcoming traditional NiTi fabrication problems but also for producing porous or complex shaped structures. The combination of SLM fabrication advantages with the unique properties of NiTi alloys, such as shape memory effect, superelasticity, high ductility, work output, corrosion, biocompatibility, etc. makes SLM NiTi alloys extremely promising for numerous applications.
The SLM process parameters such as laser power, scanning speed, spacing, and strategy used during the fabrication are determinant factors in composition, microstructural features and functional properties of the SLM NiTi alloy. Therefore, a comprehensive and systematic study has been conducted over Ni50.8 Ti49.2 (at%) alloy to understand the influence of each parameter individually. It was found that a sharp [001] texture is formed as a result of SLM fabrication which leads to improvements in the superelastic response of the alloy. It was perceived that transformation temperatures, microstructure, hardness, the intensity of formed texture and the correlated thermo-mechanical response are changed substantially with alteration of each parameter. The provided knowledge will allow choosing optimized parameters for tailoring the functional features of SLM fabricated NiTi alloys. Without going through any heat treatments, 5.77% superelasticity with more than 95% recovery ratio was obtained in as-fabricated condition only with the selection of right process parameters.
Additionally, thermal treatments can be utilized to form precipitates in Ni-rich SLM NiTi alloys fabricated by low energy density. Precipitation could significantly alter the matrix composition, transformation temperatures and strain, critical stress for transformation, and shape memory response of the alloy. Therefore, a systematic aging study has been performed to reveal the effects of aging time and temperature. It was found that although SLM fabricated samples show lower strength than the initial ingot, heat treatments can be employed to make significant improvements in shape memory response of SLM NiTi. Up to 5.5% superelastic response and perfect shape memory effect at stress levels up to 500 MPa was observed in solutionized Ni-rich SLM NiTi after 18h aging at 350ºC. For practical application, transformation temperatures were even adjusted without solution annealing and superelastic response of 5.5% was achieved at room temperature for 600C-1.5hr aged Ni-rich SLM NiTi.
The effect of porosity on strength and cyclic response of porous SLM Ni50.1 Ti49.9 (at%) were investigated for potential bone implant applications. It is shown that mechanical properties of samples such as elastic modulus, yield strength, and ductility of samples are highly porosity level and pore structure dependent. It is shown that it is feasible to decrease Young’s modulus of the SLM NiTi up to 86% by adding porosity to reduce the mismatch with that of a bone and still retain the shape memory response of SLM fabricated NiTi. The shape memory effect, as well as superelastic response of porous SLM Ni50.8Ti49.2,were also investigated at body temperature. 32 and 45% porous samples with similar behaviors, recovered 3.5% of 4% deformation at first cycle. The stabilized superelastic response was obtained after clicking experiments.
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Müller, Matthias H. "The structure of dense polymer systems : geometry, algorithms, software /." [S.l.] : [s.n.], 1999. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13096.
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Al-Khuzaee, Jafar Hameed. "X-ray absorption edge structure in hot dense plasmas." Thesis, University of Essex, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424128.
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Sadykova, Saltanat. "Electric microfield distributions and structure factors in dense plasmas." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2011. http://dx.doi.org/10.18452/16316.
Повний текст джерелаАнотація:
Die elektrischen Mikrofeldverteilungen (EMDs) und ihre Auswüchse wurden in einkomponentiger (OCP) Elektron-, zweikomponentigen (TCP) Elektron-Positron-, Wasserstoff- und einwertig ionisierten Alkaliplasmen im Rahmen verschiedener Pseudopotentialmodelle (PM) untersucht und mit sowohl Molekulardynamik (MD) und Monte-Carlo Simulationen als auch mit Experimenten vergliechen. Die verwendeten theoretischen Verfahren zur Berechnung von EMDs gehen zurück auf die von C. A. Iglesias entwickelte Kopplungsparameter Integrationstechnik (KPIT) für OCP und die von J. Ortner et al. vorgeschlagene verallgemeinerte KPIT für TCP. EMDs wurden im Rahmen der abgeschirmten Kelbg-, Deutsch-, Hellmann-Gurskii-Krasko(HGK)-PM untersucht, welche quantenmechanische Effekte, Abschirmungseffekte und die Struktur der Ionenrümpfe (HGK) berücksichtigen. Die Abschirmungseffekte wurden auf Grundlage der Bogoljubov-Born-Green-Kirkwood-Yvon- Methode eingeführt. Wir haben das abgeschirmte HGK-Pseudopotential in der Debye-Näherung sowie in einer mäßig gekoppelten Plasma-Näherung verwendet. Wir haben verschiedene Typen vom asymptotischen Verhalten der Verteilungsauswüchse in Abhangigheit von Plasmaparameter, Plasmatypen und Strahler bestimmt. Der Vergleich der experimentell gewonnenen Daten mit sowohl einem synthetischen Li2+-Lyman-Spektrum als auch mit einer synthetischen Li II 548 nm Linie lassen den Schluss zu, daß die EMD, welche auf der Grundlage der Iglesias-Methode für OCP im HGK-PM und der MD erhalten wurde, eine gute Übereinstimmung mit den experimentellen Werten liefert. Die statischen partiellen und Ladung-Ladung-Strukturfaktoren (SSF) wurden für Alkali- und Be2+-Plasmen unter Verwendung der von G. Gregori et al. beschriebenen Methode berechnet. Die dynamischen Strukturfaktoren (DSF) für Alkaliplasmen wurden unter Verwendung der durch V. M. Adamyan et al. entwickelten Methode der Momente berechnet. Bei beiden Methoden wurde das abgeschirmte HGK-Pseudopotential verwendet.The electric microfield distributions (EMDs) and its tails have been studied for electron one-component plasma (OCP), electron-positron, hydrogen and single-ionized alkali two-component plasmas (TCP) in a frame of different pseudopotential models (PM) and compared with Molecular Dynamics (MD) and Monte-Carlo simulations as well as with experiments. The theoretical methods used for calculation of EMDs are a coupling-parameter integration technique (CPIT) developed by C. A. Iglesias for OCP and the generalized CPIT proposed by J. Ortner et al. for TCP. We studied the EMDs in a frame of the screened Kelbg, Deutsch, Hellmann-Gurskii-Krasko (HGK) PMs which take into account quantum-mechanical, screening effects and the ion shell structure (HGK) due to the Pauli exclusion principle. The screening effects were introduced on a base of Bogoljubov-Born-Green-Kirkwood-Yvon method. We used the screened HGK pseudopotential in the Debye approximation as well as in a moderately coupled plasma approximation. The influence of the plasma coupling parameter on the EMD along with the ion shell structure was investigated. We determined different types of asymptotic behaviour of EMD tails in dependence on the plasma type, parameters and radiator. Comparison of a synthetic Li2+ Lyman spectrum as well as comparison of a synthetic Li II 548 nm line with experimental data allows us to conclude that the EMD, obtained on a base of the CPIT method for OCP within the HGK PM and MD, provides a good agreement with the experiment. We have calculated the partial and charge-charge static structure factors (SSF) for alkali and Be2+ plasmas using the method described by G. Gregori et al.. We have calculated the dynamic structure factors (DSF) for alkali plasmas using the method of moments developed by V. M. Adamyan et al. In both methods the screened HGK pseudopotential has been used.
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Tsuboi, Takashi. "Structure and Properties of Porous Silicon Surface." Kyoto University, 1999. http://hdl.handle.net/2433/181681.
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Feng, Yuping. "Design and characterization of dense and porous Fe-based alloys for biomedical and environmental applications." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/460679.
Повний текст джерелаАнотація:
Aquesta tesi doctoral comprèn la síntesi d’aliatges basats en ferro mitjançant diversos mètodes de fabricació. Aquests aliatges s’han dissenyat amb la intenció de ser utilitzats en biomedicina o en aplicacions mediambientals. S’ha donat especial èmfasi a dissenyar una composició adequada i a estudiar la morfologia i les propietats estructurals per tal d’optimitzar tant les propietats mecàniques com les propietats magnètiques dels materials resultants.
En primer lloc es va utilitzar la tècnica de fusió per arc i colada per succió amb motlle de coure per fabricar dos aliatges densos: un aliatge ferromagnètic amb composició en pes Fe-10Mn6Si1Pd i un aliatge paramagnètic amb memòria de forma amb composició en pes Fe-30Mn6Si1Pd. L’evolució de la microestructura, les propietats mecàniques i magnètiques, així com també la degradació, la citotoxicitat i la proliferació de cèl·lules en solució Hanks es van estudiar de forma sistemática en funció del temps d’immersió.
Per tal de millorar la biocompatibilitat de l’aliatge Fe-10Mn6Si1Pd, aquest aliatge es va recobrir amb fosfat de calci (brushita o hidroxilapatita) mitjançant la tècnica d’electrodeposició per corrent polsant. A conseqüència de la morfologia porosa d’aquests recobriments (per exemple: en forma d’agulles, cilindres o plaques), el mòdul de Young i la duresa mesurades foren inferiors als valors obtinguts en recobriments anàlegs no porosos.
Seguidament, amb l’objectiu d’incrementar la velocitat de degradació i reduir el mòdul de Young d’aquests aliatges compactes, es van fabricar aliatges porosos de Fe-30Mn6Si1Pd mitjançant un procés de premsa i sinterització de Fe, Si, Mn i Pd en pols prèviament mòlta i barrejada amb un 10, un 20 o un 40% en pes de NaCl en un molí de boles. Cal destacar, que després de submergir els aliatges porosos durant un període llarg de temps, el mòdul de Young reduït que es va mesurar en tots ells va ser d’uns 20 GPa (essent aquest valor similar al mòdul de Young de l’os humà, entre 3-27 GPa). Aquest fet afavoriria una bona compatibilitat biomecànica entre l’implant i el teixit ossi veí.
Per altra banda, es van fabricar escumes de Fe i Fe-Mn de cèl·la oberta utilitzant matrius de poliuretà poroses pel mètode de rèplica. Es va observar que la resposta magnètica d’aquestes escumes, des de pràcticament no magnètica a ferrimagnètica, es podia controlar ajustant el contingut de Mn i el flux de N2. També, en el marc de propietats magnètiques, es va utilitzar la tècnica d’irradiació amb làser polsat de femtosegon per crear patrons magnètics periòdics a la superfície d'un aliatge amorf no ferromagnètic basat en Fe.
Finalment, es va preparar un aliatge nanoporós ric en Fe per dissolució selectiva de cintes de Fe43.5Cu56.5 fabricades per tornejat en estat de fusió. Es va observar que els materials nanoporosos eren un excel·lent catalitzador heterogeni de la reacció de Fenton per la degradació del taronja de metil en solució aquosa.This Thesis dissertation covers different synthetic approaches to obtain Fe-based alloys to be used for biomedical and environmental applications. Special emphasis has been placed to design a proper composition and to study the morphology and structural properties to tailor both the mechanical and magnetic properties of the resulting materials. Firstly, ferromagnetic Fe-10Mn6Si1Pd (wt.%) and shape memory, paramagnetic Fe-30Mn6Si1Pd (wt.%) compact alloys were prepared by arc-melting followed by copper mold suction casting. The evolution of microstructure, mechanical and magnetic properties, as well as the assessment of degradation, cytotoxicity and cell proliferation in Hank’s solution as a function of the immersion time were systermatically studied. With the aim to improve the biocompatibility of the Fe-10Mn6Si1Pd alloy, calcium phosphate coatings (CaP) (i.e., brushite and hydroxyapatite) were electrodeposited on the alloy by pulsed current electrodeposition. Due to porous structures resulting from needle-, rod- or plate-like morphologies, the measured Young’s modulus and hardness of these coatings were lower than those of fully-dense CaP layers with analogous compositions. Then, to increase the degradation rate and to reduce the Young’s modulus of the fully bulk alloys, porous Fe-30Mn6Si1Pd (wt.%) alloys were prepared by a simple press and sinter process from ball-milled Fe, Mn, Si and Pd powders blended with 10 wt.%, 20 wt.% and 40 wt.% NaCl. Remarkably, the reduced Young’s modulus of all the porous alloys reached values close to 20 GPa after long-term immersion, a value which is close to the Young’s modulus of human bones (3–27 GPa), hence favoring good biomechanical compatibility between an eventual implant and the neighboring bone tissue. Meanwhile, open cell Fe and Fe-Mn oxides foams were prepared by the replication method using porous polyurethane templates. The magnetic response of the foams, from virtually non-magnetic to ferrimagnetic, could be tailored by controllably adjusting the Mn content as well as the N2 flow rate. Still dealing with magnetic properties, femtosecond pulsed laser irradiation was used to create periodic magnetic patterns at the surface of a non-ferromagnetic amorphous Fe-based alloy. Finally, a nanoporous Fe-rich alloy was prepared by selective dissolution of melt-spun Fe43.5Cu56.5 ribbons. The nanoporous ribbons were found to be an excellent heterogeneous Fenton catalyst towards the degradation of methyl orange in aqueous solution.
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Wu, Jeremy Po-Wei. "Reuse of silicate wastes : process development and property measurements of dense and porous glass-ceramics." Thesis, Imperial College London, 2006. http://hdl.handle.net/10044/1/11374.
Повний текст джерелаАнотація:
Vitrification is a well-established waste treatment method that has been used for silicate based wastes to achieve waste volume reduction and improve chemical stability before further use. However, the poor mechanical strength of the vitrified products has led to a low commercial value and thus an unjustifiable use of energy-intensive thermal technology over the cheaper, although environmentally unsatisfactory, land disposal option. To overcome this issue, the emphasis of this work lies in demonstrating the feasibility of fabricating dense glass-ceramics from several types of waste and combination of wastes, which are generally superior to their parent glasses in their mechanical performance, as well as highly porous glassceramics to be used in building industries as an alternative to conventional waste disposal. The first part of the research work demonstrated the ease of production of an array of relatively dense glass-ceramic material from coal ash from thermal power plants using powder sintering technology. These products had robust physical and mechanical properties suitable to compete against commercially available building materials such as granite and marble for the floor and wall covering applications. A fully-dense, fine-grained, high-strength glass-ceramic was also fabricated from Feslag using an economically viable single-stage melt heat-treatment route. The ironslag derived glass-ceramic material had a unique composition, with an associated microstructure containing a high content of titanium-rich compounds, and has the potential for non-critical load-bearing applications. Finally, the thesis provides the results of an experimental study concerning with the production of highly porous glass-ceramic foams from a mixture of coal ash and waste glass with the addition of an inorganic foaming agent. The correlations between physical, thermal, and mechanical properties were carried out based on results from practical experiments, physical model studies and numerical simulations using X-ray microtomography and finite element analysis. It was concluded that, these waste-derived materials have the potential to be used in building applications where there can be a large demand to meet the large volumes of wastes available.
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Bagul, Ruchita D. "Preparation of dense barium cerate film on a planar porous support for hydrogen separation membranes." [Gainesville, Fla.] : University of Florida, 2004. http://purl.fcla.edu/fcla/etd/UFE0005383.
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Villerot, Sophie. "Structure microscopique et dynamique des vortex dans un superfluide dense." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2012. http://tel.archives-ouvertes.fr/tel-00775920.
Повний текст джерелаАнотація:
L'étude des vortex trouve sa justification dans le rôle que ces derniers jouent dans la turbulence quantique. L'équation de Gross-Pitaevskii ne peut pas nous permettre de modéliser convenablement l'Hélium superfluide, mais on peut l'utiliser pour obtenir le paramètre d'ordre d'un superfluide modèle, ayant le maximum de propriétés en commun avec l'Hélium, notamment une courbe de dispersion identique, par la modification du terme d'interactions.En supposant que le minimum roton influence l'essentiel de la physique, on détermine la forme du paramètre d'ordre loin de la perturbation créée par le vortex rectilinéaire axisymétrique par deux approches différentes - il apparaît alors que seuls deux paramètres sont nécessaires pour caractériser entièrement le profil.Le modèle proposé par Pomeau-Rica, qui offre la possibilité d'étudier le superfluide près de la cristallisation, met en lumière l'impact de la profondeur du minimum roton sur l'amplitude des oscillations. Par comparaison avec les résultats obtenus ab initio par Reatto, les résultats donnés par le modèle de Berloff-Roberts exhibent un déphasage marqué, qui semble être une conséquence non-physique de la forme du spectre d'excitation. Les calculs énergétiques laissent à penser que les oscillations portent une faible fraction de l'énergie du vortex, l'énergie cinétique dominant.Le calcul du paramètre d'ordre est effectué pour un anneau de grande taille par rapport à la distance interatomique, à vitesse nulle et à vitesse non-nulle. La détermination des énergies potentielle et cinétique permet d'accéder à la vitesse maximale atteinte par l'anneau en fonction de son rayon et de la comparer à la vitesse critique de Landau.
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Algarra, Nicolas Pierre. "Pénétration d'une fibre flexible dans un milieu granulaire dense." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066500/document.
Повний текст джерелаАнотація:
Nous étudions de manière expérimentale un cas d’interaction fluide/structure entre une fibre élastique et un milieu granulaire dense proche du jamming. Dans notre dispositif expérimental horinzontal, un milieu granulaire bidimensionnel, aléatoire et dense est en interaction avec une fibre élastique encastrée. L'extrémité encastrée de cette fibre est en translation par rapport aux grains tandis que son extrémité libre fait initialement face au flux de grains dans une géométrie de pénétration, avant de se défléchir par interaction avec les grains. Les paramètres de contrôle de notre système sont la compacité du milieu granulaire, la longueur et la rigidité de la fibre. Notre dispositif nous permet de mesurer la déformée de la fibre, les efforts que les grains exercent sur la fibre, notamment la force de traînée et de suivre les réorganisation du milieu granulaire. Sous certaines conditions expérimentales, nous avons observé que ce système présente plusieurs régimes d'évolution. A faible et à forte déflexions de la fibre, le système connaît une évolution stochastique, liée à la nature aléatoire du milieu granulaire : respectivement de petites fluctuations de la fibre autour de sa position d'équilibre et des événements brusques de balayage de la fibre en flexion associés à des avalanches granulaires. La transition entre ces deux régimes est associée à une brisure de symétrie qui affecte tant la fibre que le milieu granulaire. Dans une première partie, nous étudions comment la déflexion de la fibre est influencée par les paramètres de contrôle, en particulier par l'écart au jamming. Dans une seconde partie, nous montrons qu'une asymétrie de densité se développe dans le milieu granulaire lorsque la fibre est suffisamment défléchie. Dans une troisième partie, nous tentons de comprendre l'évolution des forces mesurées à l'aide de simulations numériques de l'Elastica sur une poutre sous chargement. Enfin, nous proposons un modèle de compaction des grains par la fibre qui est en bon accord avec l'évolution expérimentale du système. Une application de cette thèse est la compréhension des mécanismes de pénétration d'une racine ou d'une tige dans un sol granulaireWe study experimentally a fluid/structure interaction between an elastic fiber and a dense granular medium near the jamming transition. In our horizontal setup, a bidimensionnal and dense random packing is interacting with a clamped elastic fiber. The clamped end of the fiber is in translation relative to the the grains while the free end faces initially the grain flux in a penetration geometry before being deflected by grain/fiber interactions. The control parameters of our system are the packing fraction of the medium, the length and the rigidity of the fiber. Our setup allows us to measure the deflected shape of the fiber, the forces exerted by the grains on the fiber (including the drag force) and to follow the reorganizations of the granular medium. Under some experimental conditions, we observed that this system exhibits several regimes of evolution. For low and large fiber deflections, the system evolves stochastically as a consequence of the random nature of the granular medium : respectively small fluctuations of the fiber around its equilibrium position and sudden events of unlozding of the fiber in flexion associated to granular avalanches. The transition between those two regimes is associated with a symmetry breaking that affects the granular medium as well as the fiber. In a first part, we study how the fiber deflection is influenced by the control parameters, particularly by the distance to jamming. In a second part, we show that a packing fraction asymmetry appears in the granular medium when the fiber is deflected enough. In a third part, we try to understand the evolution of the measured forces using numerical simulations of the Elastica on a constrained beam. Finally, we propose a model of compaction of the grains by the fiber that is in a good aggreement with the experimental evolution of the system. An application of this thesis is the understanding of the mechanisms involved in the penetration of a root or a beam in a granular soil
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Hawkins, Jared B. "Effect of Hydraulic Conductivity Heterogeneity on the Movement of Dense and Viscous Fluids in Porous Media." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1321978016.
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Arnold, Donna Claire. "Structure and electronic properties of porous manganese oxides." Thesis, University College London (University of London), 2004. http://discovery.ucl.ac.uk/1446478/.
Повний текст джерелаАнотація:
Manganese oxides with varying pore sizes from ~2 to ~7 have been prepared by standard solid-state techniques and by low temperature hydrothermal methods. These materials have an open framework composed exclusively of manganese oxide, which in simple tunnel and layered structures is built up exclusively of edge and corner shared MnO6 octahedra. In more complex structures, such as that exhibited by Na0.44MnO2, this framework is built up of MnO6 octahedra and MnO5 square pyramids, where Mn3+ and Mn4+ are ordered on crystallographically distinct sites. The size of the tunnels or layer gap is dependent on the size of the cation used as a template. This thesis shows that it is possible to remove the 'template' ion from within many framework materials without destroying the structural integrity, this is due primarily to the ready conversion between the various manganese oxidation states to maintain charge balance. This makes it possible to tune the properties by incorporating varying amounts of foreign cations and/or small molecules into the vacant pore sites. These intercalation reactions result in small changes in the average manganese oxidation state, which in turn leads to differences in the thermal stability, observed magnetic and transport properties. We have also shown that it is possible to intercalate conducting polymers into the framework of some layered materials. Whilst the mechanism is not known, it can be seen that the oxidation state of the framework plays an important part in the ordering of the monomer/polymer units within the layers. Incorporation of these polymers leads to large changes in the magnitude of the observed magnetic moment as well as in the magnetic ordering. This work shows that these materials have a versatile framework, which leads to the real possibility of tuning the properties of a material to achieve desired effects leading to many possible uses for these types of materials.
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Rühle, Bastian. "Structure, dynamics and interactions in porous host-guest systems." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-169902.
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Misawa, Masaki, Naoki Takada, Hiroshi Yamashita, Shingo Satake, and Kazuhiro Yamamoto. "Lattice Boltzmann simulation on porous structure and soot accumulation." Elsevier, 2006. http://hdl.handle.net/2237/20046.
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Hansen, Eddy W., and Hans Christian Gran. "Probing pore-structure within porous polymer particles by NMR." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-194852.
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Lundberg, Eva. "Micro-Structure Modelling of Acoustics of Open Porous Material." Licentiate thesis, KTH, Farkost och flyg, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-187322.
Повний текст джерелаАнотація:
Transportation is a large and growing part of the world’s energy consumption. This drives a need for reduced weight of rail vehicles, just as it does for road vehicles. In spite of weight reductions, the vehicle still has to provide the same level of acoustic comfort for the passengers. Porous materials, with more than 90% air, are often included in multi-layer vehicle panels, contributing to acoustic performance without adding much weight. Here the acoustic performance of open cell porous materials, with focus on flow resistivity, is evaluated based on simplified micro-structure models to investigate the effect of anisotropy on the performance In order to evaluate how the redistribution of material affects the flow resistivity, the porosity of the material is kept constant. Two micro-geometries are analysed and compared: the hexahedral model and the tetrakaidecahedron (Kelvin cell). For flow resistivity calculations the solid frame is assumed to be rigid. The models are elongated in one direction to study the influence of micro-structural anisotropy on the macro level flow resistivity. To keep porosity constant, two different approaches are investigated. The first approach is to let strut thickness be uniform and adjust the volume of the cell to a constant ratio compared to the isotropic case. The second approach is to let the strut volume, and cell volume, be constant. For an anisotropic hexahedral cell with uniform strut thickness, the flow resistivity increases substantially with increasing height to width ratio for the hexahedral model, while the flow resistivity for the tetrakaidecahedron model with uniform strut thickness decreases with increasing height to width ratio. For both geometries and constant strut volume, the average flow resistivity is close to the same constant value. For uniform strut thickness the relative volume of anisotropic to isotropic volume is very important.The work has been carried out within the Centre for ECO2 Vehicle Design.
QC 20160523
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Hansen, Eddy W., and Hans Christian Gran. "Probing pore-structure within porous polymer particles by NMR." Diffusion fundamentals 3 (2005) 21, S. 1-2, 2005. https://ul.qucosa.de/id/qucosa%3A14312.
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Baychev, Todor. "Pore space structure effects on flow in porous media." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/pore-space-structure-effects-on-flow-in-porous-media(5542173d-d6d1-4768-9f38-4b41254fa194).html.
Повний текст джерелаАнотація:
Fluid flow in porous media is important for a number of fields including nuclear waste disposal, oil and gas, fuel cells, water treatment and civil engineering. The aim of this work is to improve the current understanding of how the pore space governs the fluid flow in porous media in the context of nuclear waste disposal. The effects of biofilm formation on flow are also investigated. The thesis begins with a review of the current porous media characterisation techniques and the means for converting the pore space into pore network models and their existing applications. Further, I review the current understanding of biofilm lifecycle in the context of porous media and its interactions with fluid flow. The model porous media used in this project is Hollington sandstone. The pore space of the material is characterised by X-ray CT and the equivalent pore networks from two popular pore network extraction algorithms are compared comprehensively. The results indicate that different pore network extraction algorithms could interpret the same pore space rather differently. Despite these differences, the single-phase flow properties of the extracted networks are in good agreement with the estimates from a direct approach. However, it is recommended that any flow or transport study using pore network modelling should entail a sensitivity study aiming to determine if the model results are extraction method specific. Following these results, a pore merging algorithm is introduced aimed to improve the over segmentation of long throats and hence improve the quality of the extracted statistics. The improved model is used to study quantitatively the pore space evolution of shale rock during pyrolysis. Next, the extracted statistics from one of the algorithms is used to explore the potential of regular pore network models for up-scaling the flow properties of porous materials. Analysis showed that the anisotropic flow properties observed in the irregular models are due to the different number of red (critical) features present along the flow direction. This observation is used to construct large regular models that can mimic that behaviour and to discuss the potential of estimating the flow properties of porous media based on their isotropic and anisotropic properties. Finally, a long-term flow-through column experiment is conducted aiming to understand the effects of bacterial colonisation on flow in Hollington sandstone. The results show that such systems are quite complex and are susceptible to perturbations. The flow properties of the sandstone were reduced significantly during the course of the experiment. The possible mechanisms responsible for the observed reductions in permeability are discussed and the need for developing new imaging techniques that can allow examining biofilm development in-situ is underlined as necessary for drawing more definitive conclusions.
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Rapold, Roland Fritz. "Atomistic simulation of the structure and ring motion of dense, amorphous polystyrene /." [S.l.] : [s.n.], 1993. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=10308.
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Muñiz, Navarro José Alberto. "A hybrid data structure for dense keys in in-memory database systems." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/62662.
Повний текст джерелаАнотація:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 71-72).
This thesis presents a data structure which performs well for in-memory indexing of keys that are unevenly distributed into clusters with a high density of keys. This pattern is prevalent, for example, in systems that use tables with keys where one field is auto-incremented. These types of tables are widely used. The proposed data structure consists of a B+ Tree with intervals as keys, and arrays as values. Each array holds a cluster of values, while the clusters themselves are managed by the B+ Tree for space and cache efficiency. Using the H-Tree as an in-memory indexing structure for an implementation of the TPC-C benchmark sped up the transaction processing time by up to 50% compared to an implementation based on B+Trees, and showed even more dramatic performance gains in the presence of few and large clusters of data.
by José Alberto Muñiz Navarro.
M.Eng.
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Totten, Christian T. "Effect of porous media and fluid properties on dense Non-Aqueous Phase Liquid migration and dilution mass flux." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010044.
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NASCIMENTO, MARCELO DE MATTOS. "USING DENSE 3D RECONSTRUCTION FOR VISUAL ODOMETRY BASED ON STRUCTURE FROM MOTION TECHNIQUES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2015. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=26102@1.
Повний текст джерелаАнотація:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROAlvo de intenso estudo da visão computacional, a reconstrução densa 3D teve um importante marco com os primeiros sistemas em tempo real a alcançarem precisão milimétrica com uso de câmeras RGBD e GPUs. Entretanto estes métodos não são aplicáveis a dispositivos de menor poder computacional. Tendo a limitação de recursos computacionais como requisito, o objetivo deste trabalho é apresentar um método de odometria visual utilizando câmeras comuns e sem a necessidade de GPU, baseado em técnicas de Structure from Motion (SFM) com features esparsos, utilizando as informações de uma reconstrução densa. A Odometria visual é o processo de estimar a orientação e posição de um agente (um robô, por exemplo), a partir das imagens. Esta dissertação fornece uma comparação entre a precisão da odometria calculada pelo método proposto e pela reconstrução densa utilizando o Kinect Fusion. O resultado desta pesquisa é diretamente aplicável na área de realidade aumentada, tanto pelas informações da odometria que podem ser usadas para definir a posição de uma câmera, como pela reconstrução densa, que pode tratar aspectos como oclusão dos objetos virtuais com reais.
Aim of intense research in the field computational vision, dense 3D reconstruction achieves an important landmark with first methods running in real time with millimetric precision, using RGBD cameras and GPUs. However these methods are not suitable for low computational resources. Having low computational resources as requirement, the goal of this work is to show a method of visual odometry using regular cameras, without using a GPU. The proposed method is based on technics of sparse Structure From Motion (SFM), using data provided by dense 3D reconstruction. Visual odometry is the process of estimating the position and orientation of an agent (a robot, for instance), based on images. This dissertation compares the proposed method with the odometry calculated by Kinect Fusion. Results of this research are applicable in augmented reality. Odometry provided by this work can be used to model a camera and the data from dense 3D reconstruction, can be used to handle occlusion between virtual and real objects.
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Heptner, Nils. "Dynamics and non-equilibrium structure of colloidal dumbbell-shaped particles in dense suspensions." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät, 2016. http://dx.doi.org/10.18452/17518.
Повний текст джерелаАнотація:
Neben ihrer Bedeutung in industriellen Anwendungen dienen Kolloide als Modellsysteme in Experimenten und in der Theorie, um die Struktur und Dynamik von kondensierter Materie zu untersuchen. Kürzlich wurde experimentell gezeigt, dass eine kleine Anisotropie ausreicht, um die viskoelastische Antwort im Vergleich zu harten Kugeln drastisch zu ändern. Die mikroskopischen Ursachen hierfür sind bisher nicht verstanden. In dieser Arbeit werden daher Nichtgleichgewichts-Brownsche-Dynamik-Simulationen (NEBD) von harten kolloidalen Dumbbells in oszillatorischen Scherfeldern entwickelt und eingesetzt, um diese Resultate mit Verbindung zu Rheologie- und Neutronenstreuexperimenten zu erklären. Weiterhin wird die Bedeutung der Anisotropie für Struktur und Dynamik von solchen Suspensionen im Gleichgewicht mit Hilfe von "Linear-Response"-Theorie und Brownsche-Dynamik-Simulationen analysiert. Im linearen Limit zeigt die Scherviskosität bei hohen Packungsdichten einen dramatischen Anstieg jenseits eines kritischen Anisotropieparameters. Dies weist darauf hin, dass schon bei den kleinen Anisotropien kollektive Rotations-Translations-Kopplungen für langsame Zeitskalen verantwortlich sind. Weiterhin wird ein Nichtgleichgewichtsübergang mittels NEBD-Simulationen von Suspensionen harter Dumbbells im PC unter oszillatorischer Scherung ersichtlich. Es wird gezeigt, dass der kontinuierliche Übergang nur für sehr kleine Aspektverhältnisse erhalten bleibt. Oberhalb eines bestimmten Aspektverhältnisses wird der Übergang durch einen ungeordneten Zustand vermittelt. Außerdem wird ein Sliding-Layer Zustand mit kollektiver Ordnung der Teilchenausrichtung bei hohen Scheramplituden beobachtet. Somit zeigt diese Arbeit, dass die NEBD-Simulationen Phänomene in Rheologie- und Streuexperimenten erklären. Angesichts dieser Experimente wird gezeigt, dass der Orientierungsfreiheitsgrad einen starken Einfluss auf den strukturellen Übergang bei steigenden Amplituden hat.Besides being important for industrial applications, colloidal suspensions have long served as model systems for investigating the structure and dynamics of condensed matter. Recently, it has been demonstrated experimentally that apparently a small particle anisotropy is sufficient to dramatically change the viscoelastic response under external shearing fields, of which the microscopic mechanisms are not yet sufficiently understood. In the present work, NEBD simulations of colloidal hard dumbbells in oscillatory shear fields are developed and employed to elucidate the novel findings in close connection with comprehensive rheology and SANS experiments. Furthermore, by utilising BD simulations and linear response theory, the impact of anisotropy on structure and dynamics of such suspensions in equilibrium is analysed. In the linear response limit, the shear viscosity exhibits a dramatic increase at high packing fractions beyond a critical anisotropy of the particles. This indicates that newly occurring, collective rotational-translational couplings must be made responsible for slow time scales appearing in the PC. Moreover, a non-equilibrium transition emerging at moderate aspect ratios is revealed by NEBD of plastic crystalline suspensions under oscillatory shear. This transition behaviour is systematically studied. It is demonstrated that the continuous nature of the transition is retained for very low aspect ratios only. Above a certain aspect ratio, the transition is mediated by an intermediate disordered state. Furthermore, a partially oriented sliding layer state featuring a finite collective order in the particles'' orientations is observed at high strains. Hence, this thesis demonstrates that the NEBD simulations explain novel phenomena in rheology and scattering experiments. In the light of these experiments, it is shown that the orientational degree of freedom has a vigorous impact on the structural transition under increasing oscillatory shear.
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Dvoyashkin, Muslim, Alexey Khokhlov, Rustem Valiullin, Jörg Kärger, and Matthias Thommes. "Fluid behavior in porous silicon channels with complex pore structure." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-190953.
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Dvoyashkin, Muslim, Alexey Khokhlov, Rustem Valiullin, Jörg Kärger, and Matthias Thommes. "Fluid behavior in porous silicon channels with complex pore structure." Diffusion fundamentals 11 (2009) 80, S. 1-2, 2009. https://ul.qucosa.de/id/qucosa%3A14045.
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Klym, H. I., and I. V. Hadzama. "Evolution of Porous Structure in Technologically Modified MgO-Al2O3 ceramics." Thesis, Sumy State University, 2013. http://essuir.sumdu.edu.ua/handle/123456789/35403.
Повний текст джерелаАнотація:
Evolution of porous structure in technologically modified spinel MgO-Al2O3 ceramics sintered at differ-ent temperature are studies. It is shown that increasing of sintering temperature from 1200 to 1400 ·C re-sult in transformation of pore size distribution in ceramics from tri- to bi-modal. It is established that in-creasing of humidity sensitivity in ceramics sintered at 1300 ·C are related to achievement near to opti-mum pore size distribution and their quantity in the higher indicated region. Prolonged degradation trans-formation at higher temperature and relative humidity result in lose sensitivity up to 40%.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35403
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Marshall, Andrew J. "Porous hydrogels with well-defined pore structure for biomaterials applications /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/8559.
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Mugerwa, M. N. "Stochastic network modelling of porous media in two dimensions." Thesis, University of Manchester, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.378652.
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Huang, Yingqing. "Characterization of dense suspensions using frequency domain photon migration." Texas A&M University, 2003. http://hdl.handle.net/1969.1/2207.
Повний текст джерелаАнотація:
Interparticle interactions determine the microstructure, stability, rheology, and optical properties of concentrated colloidal suspensions involved in paint, paper, cosmetic, and pharmaceutical industries, etc. Frequency domain photon migration (FDPM) involves modeling the photon transport in a multiple scattering medium as a diffusion process in order to simultaneously determine isotropic scattering and absorption coefficients from measured amplitude attenuation and phase shift of the propagating photon density wave.
Using FDPM, we investigated the impact of electrostatic interaction upon the optical properties and structure of dense charged suspensions. We demonstrated that electrostatic interactions among charged polystyrene latex may significantly affect the light scattering properties and structure of dense suspensions at low ionic strength (<0.06 mM NaCl equivalent) by actual FDPM measurement. We showed that the structure factor models addressing electrostatic interaction can be used to describe the microstructure of charged suspensions and quenched scattering due to electrostatics, and demonstrated that FDPM has the potential to be a novel structure and surface charge probe for dense suspensions. We also showed that the FDPM measured isotropic scattering coefficients may respond to the change in effective particle surface charge, and displayed the potential of using FDPM for probing particle surface charge in concentrated suspensions. We presented that the interference approximation implies a linear relationship between the absorption coefficient and volume fraction of suspension. We illustrated that FDPM measured absorption coefficient varies linearly with suspension volume fraction and affirmed the interference approximation from a perspective of light absorption. The validation of the interference approximation enables us to develop the methodology for estimating absorption efficiencies and imaginary refractive indices for both particles and suspending fluid simultaneously using FDPM. We further demonstrated a novel application of FDPM measured absorption coefficients in determining pigment absorption spectra, and displayed the potential of using FDPM as a novel analytical tool in pigment and paint industry.
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Alat, Gokcen. "A Variable Structure - Autonomous - Interacting Multiple Model Ground Target Tracking Algorithm In Dense Clutter." Phd thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615512/index.pdf.
Повний текст джерелаАнотація:
Tracking of a single ground target using GMTI radar detections is considered. A Variable Structure-
Autonomous- Interactive Multiple Model (VS-A-IMM) structure is developed to address challenges
of ground target tracking, while maintaining an acceptable level computational complexity at the same
time. The following approach is used in this thesis: Use simple tracker structuresincorporate a priori information such as topographic constraints, road maps as much as possible
use enhanced gating techniques to minimize the eect of clutter
develop methods against stop-move motion and hide motion of the target
tackle on-road/o-road transitions and junction crossings
establish measures against non-detections caused by environment. The tracker structure is derived using a composite state estimation set-up that incorporate multi models and MAP and MMSE estimations. The root mean square position and velocity error performances of the VS-A-IMM algorithm are compared with respect to the baseline IMM and the VS-IMM methods found in the literature. It is observed that the newly developed VS-A-IMM algorithm performs better than the baseline methods in realistic conditions such as on-road/o-road transitions, tunnels, stops, junction crossings, non-detections.
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Marín, Aguilar Susana. "Local structure and dynamics of dense colloidal systems : from patchy particles to hard spheres." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP052.
Повний текст джерелаАнотація:
Le rôle de la structure dans la dynamique colloïdale vitreuse est encore un sujet de débat. Cependant, il existe des preuves d'un lien direct entre les changements de la dynamique et les propriétés structurelles du système. Nous explorons l'interaction de la structure et de la dynamique locales en utilisant des particules à patchs. Pour ce faire, nous utilisons des simulations de dynamique moléculaire. Nous montrons qu'en renforçant la géométrie icosaédrique, le dynamique du système présente un ralentissement extrême. Grâce à ces résultats, nous fournissons une voie pour contrôler la dynamique vitreuse par l'utilisation de particules à patchs. De plus, il est intéressant de savoir si nous pouvons extraire des informations sur la dynamique en utilisant uniquement des informations structurelles. Afin d'explorer ce point, nous simulons une grande variété de mélanges de sphères dures. Nous montrons que la dynamique globale de ces systèmes peut être prédite avec précision en introduisant un nouveau paramètre d'ordre appelé tétraédralité de la structure locale qui compte le nombre de tétraèdres auxquels chaque particule participe. Les prédictions de ce paramètre d'ordre restent valables pour dans une grande variété de densités, ce qui prouve son universalité dans cette famille de précurseurs de verre. De plus, il est également capable de saisir les changements sur la dynamique locale, car les régions à forte tétraédralité sont fortement corrélées avec les régions à dynamique lente. Enfin, nous explorons l'utilisation de techniques d'apprentissage machine non supervisé pour classer les particules ayant des environnements structurels différentsThe role played by the structure in determining the dynamics of glassy colloidal systems is still a subject of debate. However, there is compelling evidence of a direct link between changes in the local structure and the dynamical slowdown in glassy systems. Here, we explore the interplay between local structure and dynamics by using patchy particles as glass formers. This is done by making use of molecular dynamics simulations. We show that reinforcing icosahedral geometry causes, the system to exhibit an extreme slowdown in its dynamics. With these results, we provide a route for controlling glassy dynamics through the use of patchy particles. Additionally, an interesting point is whether we can extract information about dynamics from only structural information. In order to explore this point, we simulate a wide variety of hard-sphere mixtures. We show that global dynamics of these systems can be precisely predicted by quantifying the tetrahedrality of the local structure: an order parameter that consists of counting the number of tetrahedra each particle participates in. The predictions of this order parameter maintain their accuracy over a wide variety of densities proving its universality in this family of glass formers. Moreover, it is also capable of capturing the changes in the local dynamics, as regions with high tetrahedrality are strongly correlated with regions with slow dynamics. Finally, we demonstrate that unsupervised machine learning techniques can be used to classify particles with different structural environments, which are strongly correlated to local dynamics
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Hatchel, Jennifer M. "Structure and Function of the Electron-dense Core in Mycoplasma pneumoniae and its Relatives." Miami University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=miami1248183957.
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Tazi, Bouchra. "Elaboration et caractérisation d'une nouvelle membrane minérale conductrice ionique à structure dense et microporeuse." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb376188163.
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Nsir, Khalifa. "Experimental and numerical study of the migration of dense non-aqueous phase liquid in saturated porous medium at Darcy scale." Strasbourg, 2009. https://publication-theses.unistra.fr/public/theses_doctorat/2009/NSIR_Khalifa_2009.pdf.
Повний текст джерелаАнотація:
Le processus de déplacement vertical d’un fluide non miscible et plus dense que l’eau (DNAPL) en milieu poreux saturé a été étudié à l’échelle de Darcy. Les expériences sur colonnes de laboratoire ont été conduites en utilisant deux modes d'écoulement : vertical ascendant et vertical descendant. Le milieu poreux utilisé est un sable homogène et le polluant considéré est un composé organo-chloré (Trichloréthylène, TCE), fréquemment trouvé dans des cas de pollutions industrielles de sols et d’eaux souterraines. Dans chaque essai, nous avons mesuré les temps d’arrivée du front eau/DNAPL dans une section de contrôle du dispositif expérimental au moyen des capteurs à fibres optiques. Nous avons aussi mesuré la pression du DNAPL à l’entrée et à la sortie de la colonne de milieu poreux. Une cartographie in situ du champ de saturations en DNAPL a été également effectuée. De ce fait, nous avons pu mettre en évidence une forte non uniformité de la répartition du polluant non miscible dans le milieu poreux saturé. De plus, nous avons pu quantifier d’une manière précise les instabilités de déplacement. A partir des résultats obtenus, il a été montré que les forces de poussée (ou de gravité) sont capables d’exercer des effets très significatifs à la fois sur la stabilité du processus de déplacement et sur l’efficacité de la récupération de la phase mobile du DNAPL. Concernant la simulation numérique, un modèle discret de pores et de capillaires a été développé. Une approche de calcul basée sur la théorie d’empilement des sphères a été élaborée pour évaluer les caractéristiques géométriques du réseau équivalent du milieu poreux utilisé dans l’expérimentation. Les résultats expérimentaux et numériques s'accordaient bien. Le modèle numérique s’est montré capable de reproduire l’évolution temporelle de la pression observée pour les différents régimes de déplacement stable et instableThe immiscible displacement processes of a dense non-aqueous phase liquid (DNAPL) were studied in a sand-filled column. The considered pollutant is the Trichloroethylene, volatile and soluble chlorinated solvent, usually found in soils and ground water industrial pollution. Experiments were performed using two flow modes, namely vertical-upwards and vertical- downwards. A Fibre optic sensors were developed to measuring the arrival times of water/DNAPL at a control section of experiment device. The DNAPL pressure at the inlet and outlet section of the system was also monitored. The experiment program also allowed for measuring the local DNAPL saturations. Thereby, permitting to quantify evolving fingering patterns of non aqueuse phase liquid in the saturated porous medium. It has also been shown that the distribution of the non aqueuse phase liquid in the porous medium is heterogeneous. Furthermore, the obtained results underline that buoyancy forces (gravity) can have significant effects on the stability of the displacement process and on the oil recovery efficiency during injection of water. Numerically, a pore-scale network model based on spherical pore bodies and cylindrical pore throats was developed to simulate laboratory experiment. A computational approach based on the theory of packing spheres has also been developed to assess the geometric characteristics of the equivalent network of the used porous medium in the experiment. Good agreement between the numerical and experimental results was obtained. An important feature of the model is its capability to reproduce the observed pressure behaviour for stable and unstable displacement regimes
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Ikeda, Noboru. "Quantitative comparison of osteoconduction of porous, dense A-W glass-ceramic and hydroxyapatite granules (effects of granule and pore size)." Kyoto University, 2000. http://hdl.handle.net/2433/180891.
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Rice, Johnathan Scott. "The Transition From Diffuse to Dense Molecular Clouds." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1534945134382193.
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Gurnagul, N. (Norayr). "Some effects of relative humidity on the porous structure of paper." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74013.
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Mathews, Tobias John. "Void structure, colloid and tracer transport properties of stratified porous media." Thesis, University of Plymouth, 1999. http://hdl.handle.net/10026.1/2794.
Повний текст джерелаАнотація:
The characterisation of the properties of porous materials is of great importance in the effective management of natural and manmade systems. A sophisticated network model, 'Pore-Cor', of some of these properties has been previously developed. The present study has significantly extended the scope of the model's predictive capabilities. Flow and transport behaviour was examined in laboratory sand columns of various depths. These experiments examined unsaturated flow of water and conservative solute tracer transport through homogeneous sand samples. Flow through these was not homogeneous or repeatable. Experimental observations found that this may have been due to subtle random variations in packing, and the network model was shown to be able to simulate these. Solute transport of bromide was studied, applied both uniformly and from a point source. Both scenarios were modelled using a convection-dispersion equation, and it was demonstrated that the lateral component of such transport was highly significant. It was shown how convection-dispersion equation predictions of uniformly applied tracer transport might be improved by the application of the network model and a method for improving predicted lateral solute transport was outlined. It has been shown that levels of correlation in the distribution of differently sized voids within porous material may be responsible for large variations in permeability. This can make accurate modelling of permeability very difficult. A technique was developed for assessing the degree and nature of such correlations. The new method was tested on a variety of artificial and real samples and demonstrated to provide a quantitative assessment of such correlations. A method by which this could be used to improve network model simulations of materials possessing such correlation was described.
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Evans, Nathan Timothy. "Processing-structure-property relationships of surface porous polymers for orthopaedic applications." Diss., Georgia Institute of Technology, 2016. http://hdl.handle.net/1853/55004.
Повний текст джерелаАнотація:
The use of polymers in orthopaedics is steadily increasing. In some markets, such as spinal fusion and soft tissue anchors, the polymer polyetheretherketone (PEEK) is already the material of choice in the majority of implants. Despite PEEK’s widespread use, it is often associated with poor osseointegration, which can lead to implant loosening and ultimately failure of the device. Many attempts have been explored to improve the osseointegration of PEEK but none have had widespread clinical success. In this dissertation, a novel surface porous structure has been created, where limiting the porosity to the surface maintains adequate mechanical properties for load bearing applications while providing a surface for improved osseointegration. Careful control of the processing parameters resulted in tunable porous microstructures optimized for bone ingrowth: highly interconnected 200-500µm pores with porosity ranging from 60-85% and pore layers from 300-6000µm thick. Mechanical characterization, including monotonic tensile and compression, tensile fatigue, shear, and abrasion tests, were used to probe the effects of the surface porosity on the relevant mechanical properties of the material. In addition, the effect of surface porosity and surface roughness on the mechanical properties of a range of thermoplastics with varying chemistries and crystallinities was explored. This research showed that there is a great disparity in the notch sensitivity of polymers that correlates to the polymers fracture toughness as well as trends in the monotonic stress-strain curve. The results illustrate that care must be taken in the design of polymeric implants, especially when introducing topographical changes to promote osseointegration, in order to ensure they maintain adequate load-bearing capacity. Finally, preliminary in vitro and in vivo data demonstrated the ability of surface porous PEEK (PEEK-SP) to promote osseointegration. Cells grown on PEEK-SP demonstrated enhanced mineralization and differentiation, suggesting the ability of PEEK-SP to facilitate bone ingrowth. The potential of PEEK-SP was further demonstrated by implantation in a rat femoral segmental defect model which demonstrated bone ingrowth and reduced formation of a fibrous capsule.
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Strömberg, Ella. "Characterizing the pore structure of porous matrices using SEQ-NMR spectroscopy." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-414081.
Повний текст джерелаАнотація:
Characterization of the pore structure is a crucial part in themanufacturing of porous media used for purification of biologicalpharmaceuticals. This project took place at Cytiva in Uppsala and aimedat optimizing a newly developed method in pore structurecharacterization called size-exclusion quantification NMR (SEQ-NMR). Bymeasuring with diffusion NMR on a polymer solution before and afterequilibration with a material of interest the pore structure of thematerial can be determined. This project aimed at reducing the durationof a SEQ-NMR experiment while examining the performance of the methodduring different conditions with the goal of making the methodapplicable for quality control procedures. The method was optimizedboth by simulations and by experimental diffusion NMR measurements. Itwas discovered that the performance of the method could be improved byhaving an optimal mixture of the polymer solution and duringexperiments distributing ten measurement points with linear spacing.With these parameters optimized the duration of the method could bereduced with 22 hours landing on a total duration of 8 hours. Theduration combined with the complexity of the method still makes themethod unsuitable for use in quality control of porous media. Despitethe small possibility of SEQ-NMR being a quality control method thisproject has proven the method to be both reproducible and sensitive.