Dissertations / Theses on the topic 'Solids'
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1
Pradhan, Sulolit. "Solid state charge transfer in nanoparticle solids /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2008. http://uclibs.org/PID/11984.
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Liu, Weidong. "High density solids downflow gas-solids reactors." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0001/MQ42081.pdf.
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Pinto, Maria do Rosario. "Perfect solids." Thesis, University of Southampton, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358006.
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Tian, Jian Atwood J. L. "Molecular organic solids for gas adsorption and solid-gas interaction." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/6882.
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Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 24, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Dr. Jerry L. Atwood. Vita. Includes bibliographical references.
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Yang, Wei. "Solids phase chromatography." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505060.
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The present study focuses on the development of a novel technique, namely Solids Phase Chromatography (SPC), for particle classification and size analysis. SPC is a fractionation based technique and utilises a separation channel to fractionate the particle samples into sub-fractions according to their sizes. Subsequently, the products may be analysed by various detectors and recovered for other investigations.
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Mitchell, Martin R. "Investigation of structure and disorder in inorganic solids using solid-state NMR." Thesis, University of St Andrews, 2013. http://hdl.handle.net/10023/3367.
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The use of solid-state NMR and DFT calculations to study Y₂Sn[subscript(x)]Ti[subscript(2-x)]O₇, Y₂Sn[subscript(x)]Zr[subscript(2-x)]O₇ and Y₂Ti[subscript(x)]Zr[subscript(2-x)]O₇, materials with applications for the safe encapsulation of radioactive actinides is investigated. As a result of cation or anion disorder in these materials, NMR spectra are often complex and difficult to interpret. Therefore, an investigation using a range of NMR active nuclei and measurement of a variety of NMR parameters (isotropic chemical shift, δ[subscript(iso)]; span, Ω and quadrupolar coupling, C[subscript(Q)]) were used to provide a full and detailed picture of each material. The measurement of Ω in these disordered compounds with multiple resonances in the NMR spectra, required the use of 2D CSA-amplified PASS (CAPASS) experiments to enable the separation of each of the spinning sideband manifolds. An experimental assessment of the CAPASS experiment showed that although low ν₁/Ω[subscript(Hz)] ratios (as found in ⁸⁹Y NMR) resulted in distortions in the spectra obtained, a modified fitting procedure could be utilised to compensate for this fact, which allowed the accurate measurement of Ω. Despite the difficulties in acquiring the ⁸⁹Y NMR spectra, they were found to be the most informative of the NMR-active nuclei available. ¹¹⁹Sn NMR spectra, although much easier to acquire than ⁸⁹Y, were more complex and harder to analyse, owing to the overlapping resonances. Therefore, ¹¹⁹Sn NMR could only be used to confirm or support the results obtained using ⁸⁹Y NMR. Although ¹⁷O NMR was found to be useful, a full study could not be implemented due to the lack of ¹⁷O enriched samples; an area where future investigation may prove fruitful. Finally, [superscript(47/49)]Ti and ⁹¹Zr NMR spectra were found to be the most difficult to acquire due to their low receptivities and the quadrupolar broadened lineshapes, and as a result, little additional information was obtained. As a result of this analysis, for the Y₂Sn[subscript(x)]Ti[subscript(2-x)]O₇ pyrochlore solid solution, using primarily ⁸⁹Y δ[subscript(iso)] and Ω, and additionally confirmed with ¹¹⁹Sn δ[subscript(iso)], it was found that the Sn and Ti cations were randomly ordered throughout the B-sites. Additionally, ⁸⁹Y Ω could be used to obtain approximate Y-O[subscript(48f)] and Y-O[subscript(8b)] bond lengths for each type of Y environment. The study of Y₂Sn[subscript(x)]Zr[subscript(2-x)]O₇ using ⁸⁹Y NMR showed that although the end members were single phase, pyrochlore (Y₂Sn₂O₇) or defect fluorite (Y₂Zr₂O₇), the intermediate compositions were mostly two phase mixtures, consisting of an ordered pyrochlore (with an average formula of Y₂Sn₁.₈Zr₀.₂O₇) and a disordered phase, where the proportions of the pyrochlore and disordered phases decreased and increased, respectively, with the Zr content. Additionally, although the coordination states of the Y and Sn cations were easily determined using ⁸⁹Y and ¹¹⁹Sn NMR, respectively, the coordination states of the Zr cations could not be confirmed directly by ⁹¹Zr NMR. However, using indirect analysis from results obtained with ⁸⁹Y and ¹¹⁹Sn NMR, it was determined that 6 coordinate Zr was present in each composition, and it was always present in a greater proportion than 8 coordinate Zr. Finally, although ⁸⁹Y NMR spectra of Y₂Ti[subscript(x)]Zr[subscript(2-x)]O₇ were extremely difficult to analyse, it was tentatively proposed that they could be similar to Y₂Sn[subscript(x)]Zr[subscript(2-x)]O₇ due to some similarities observed between the spectra.
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Cockroft, Nigel J. "Solid state spectroscopy : laser selective excitation of erbium ions in crystalline solids." Thesis, University of Canterbury. Physics, 1987. http://hdl.handle.net/10092/8056.
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Optical absorption and laser selective excitation (l.s.e.) spectroscopy have been used to study Er³⁺ ions in the CsCdBr₃ and hydrogenated CaF₂ and SrF₂ crystalline lattices. Sixteen hydrogenic charge compensation sites for both the H- and D- isotopes were found in CaF₂:0.05%Er³⁺, and nine new D- ion sites in SrF₂ :0.05%Er3³⁺. The relative occurrence of these sites can be controlled by variation of the duration of hydrogenation. For SrF₂:Er³⁺, this results in a change of the principal D- ion charge compensation arrangement. Classification of local-mode vibronic fluorescence transitions and consideration of isotope shifts of electronic transitions enabled the assignment of model configurations to several sites. Most hydrogenic sites were classified into one of two distinct families. A new effect, reversible polarised bleaching was observed, whereby hydrogenic ion migration in Er³⁺ ion site configurations can be controlled by l.s.e. with polarised light in oriented crystals. One hydrogenic site was found to consist of two photo-induced interconvertible components. Five new fluoride ion sites in CaF₂:Er³⁺ and nine in SrF₂:Er³⁺ were also determined. For <100> and <111> oriented crystals, the fluorescence spectra of several sites exhibited well defined polarisation which may be used to determine the Er³⁺ ion symmetry. Trigonal symmetry of the F- B site of CaF₂:Er³⁺ was confirmed by this means. Crystal field analysis of tetragonal and trigonal symmetry sites is also reported. An infra-red study revealed local mode lines of seven new sites in hydrogenated CaF₂:Er³⁺ and enabled correlation of some sites to those observed in the optical spectra. Reduction of Er³⁺ ions by the short range beta decay of tritium in the lattice was identified by local mode absorption. Erbium ions in CsCdBr₃ exhibited efficient upconverted fluorescence consistent with the formation of a dominant dimer site. Detailed spectroscopy resulted in the assignment of energy levels from twelve groups of transitions. Several of these transitions, studied by absorption and l.s.e., were found to consist of two components.
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Mujaji, Marjorie. "Solid state spectroscopy : laser selective excitation of holmium ions in crystalline solids." Thesis, University of Canterbury. Physics, 1992. http://hdl.handle.net/10092/8145.
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The technique of laser selective excitation has been used to study the spectra of 23 Ho³⁺centres present in CaF₂ and SrF₂ crystals, in mixed Ca₀.₉₉Sr₀.₀₁F₂ and Ca₀.₉₉Ba₀.₀₁F₂ crystals and in CsCdBr₃ crystals.
The polarisation of the fluorescence from < 100> and < 111> oriented crystals has been used to assign specific Ho³⁺ site symmetries to the various centres and to label the crystal-field energy levels of each centre by their group irreps.
The two principal Ho³⁺ centres (A and B) observed in both CaF2:Ho³⁺and SrF2:Ho³⁺ crystals have been shown to be of C₄ᵥ and C₃ᵥ symmetry respectively. The four new centres identified in Ca₀.₉₉Sr₀.₀₁F₂:Ho3³⁺ and Ca₀.₉₉Ba₀.₀₁F₂:Ho³⁺ crystals, are derived from the parent CaF₂ C₄ᵥ symmetry (A) centre by an on-axis and an off-axis placement of a dopant cation, Sr²⁺+ or Ba²⁺, in the vicinity of the Ho³⁺ - F- pair. The three additional centres found in SrF₂:Ho³⁺ crystals are from similar Ca²⁺and Ba²⁺ substitutions in the SrF₂ lattice.
Seven centres associated with n- charge compensation were observed in deuterated CaF₂:Ho³⁺ and SrF₂:Ho³⁺ crystals, with no C₄ᵥ symmetry centre being apparent.
For the CsCdBr3:Ho³⁺ system, spectra of the principal dimer centre and three other minority centres are reported. Strong upconversion fluorescence was observed for the principal dimer centre, enabling crystal-field energy levels for 18 Ho³⁺ multiplets to be determined. Low symmetry crystal-field splittings and pair splittings were observed on some of the sharper transitions.
Crystal-field analyses performed for all the C₄ᵥ and C₃ᵥ symmetry centres in CaF2:Ho³⁺, SrF2:Ho³⁺ and CsCdBr3:Ho³⁺ crystals are reported and the resulting crystal-field parameters discussed. Fluorescence lifetimes determined for the major Ho³⁺ centres are also presented.
The high resolution and ODNMR results for the C₄ᵥ symmetry A and SB1 centres in SrF2:Ho³⁺ crystals confirm the centre symmetry assignments and the model configurations proposed on the basis of the polarisation ratio measurements. The superhyperfine ODNMR frequencies correlate well with the changes in the crystal-field parameters between the two centres.
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Zatari, Taha Mohammed. "High solids anaerobic digestion of the putrescible fraction of municipal solid waste." Thesis, University of Newcastle Upon Tyne, 1996. http://hdl.handle.net/10443/389.
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Anaerobic digestion is increasingly becoming essential for treating the organic fraction of municipal solid waste (MSW) according to the growing 'energy from waste' recycle concept. Over the last decade, efforts have been made to control the anaerobic digestion of the putrescible fraction of municipal solid waste in engineered reactors, rather than continuing with 'free' digestion in landfill sites. This way of increasing treatment efficiency can be achieved with significantly reduced retention time (days rather than years) and enables the recovery of valuable energy from waste without biogas emissions into the atmosphere, which cause adverse greenhouse effects. Three basic approaches have been explored for the anaerobic treatment of MSW: (a) conventional 'low solids' slurry digestion; (b) two-phase digestion; and (c) high solids 'dry and semi-dry' digestion. The advantages of high solids digestion processes include high loading rates, and high yields of biogas and methane. Anaerobic digestion at high solids content is also reported to reduce capital and operating costs through smaller reactor volume. Different reactor design configurations have been applied at full-scale and their performance evaluated. Commercial plants which use a high solids digestion process, recycle a portion of the digested solids residue in addition to the liquid from the digested residue. However, the exact recycling ratio and data concerning the recycling impact on the stability and performance of the digestion process, are not well documented in the literature. Also, it is recognised that mixing is important to enhance anaerobic digestion but little research has concentrated on the impact of mixing on continuous or semi-continuous high solids anaerobic digestion systems. The main aim of this research was to evaluate the potential methane production in the stabilisation of the putrescible fraction of MSW using two novel reactor designs. A vertical sequential reactor (VSR) was used to assess the effects of digested recycle ratio (DRR) and leachate recycling (LR) and a horizontal rotary reactor (I-IRR) was used to evaluate the impact of mixing on the digestion of the PFMSW. Experiments were conducted in both batch and semi-continuous mode using three 70 1 reactors, under mesophilic conditions (3 5°C) and high total solids content. Process performance was assessed using various waste parameters for solid waste and leachate treatment. Regarding solid waste treatment, VS removal, biogas and methane production and yields were the main parameters used for assessment, among several others. Accordingly, COD, VFA, pH, alkalinity, N1H3-N, TKN etc. have been some of the parameters used to monitor leachate quality. Furthermore, internal biological activity in the VSR was assessed using the observed VFA concentrations and degradation under different operational conditions (DRR and LR). Initially, batch experiments were carried out in order to evaluate the first start-up of high solids digestion. Furthermore, they provided seed digested residues for the subsequent semi-continuous studies, in addition to providing essential information regarding ultimate process efficiency in terms of methane yield and VS removal. Also, rapid start-up batch experiments were used to determine the required RT for semi-continuous studies. Optimum DRR and LR were determined with the use of the VSR semicontinuous process. A DRR of 0.5 was found to be optimum in terms of volumetric methane production, while LR2 (3.5 £ leachate recycle) provided a desirable economical option, because of its lower liquid requirements. I-IRR gave limited indicatory results expressing high treatment potential for high solids anaerobic digestion of the putrescible fraction of MSW. Finally, a mathematical model was developed for optimising the VSR operational conditions, utilising data produced under semi-continuous conditions.
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Kwetkus, Bernhard Andreas. "Contact electrification of solids /." [S.l.] : [s.n.], 1992. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=9788.
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Wang, Hao. "Theoretical strength of solids." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42747.
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Theoretical strength of solids is defined as the ultimate strength beyond which plastic deformation, fracture, or decohesion would occur. Understanding the microscopic origin from quantum mechanics and thermoelastic formulation is of great importance to mechanical properties and engineering design of various solids. While quite a few theory models have been made in the past century by several generations of scientists, including Frankel and Born, a general and convincing framework has not been fully established. We study this issue from three respects: (1) Unify various elastic stability criteria for solids that determine an upper bound of theoretical strength; (2) with ab initio method, we test the elastic stability conditions of crystal Au. The phenomenon of bifurcation is observed: under hydrostatic expansion, the rhombohedral modulus reaches zero first of all; while under uniaxial tensile stress, the tetragonal shear modulus first reaches zero; (3) propose a nonlinear theoretical formulation of stability criterion. As an analytic method, this scheme is quite simple, in the mean time, it saves computation resource.
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Pronk, Sander. "Disorder in entropic solids." [S.l : Amsterdam : s.n] ; Universiteit van Amsterdam [Host], 2003. http://dare.uva.nl/document/86583.
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Foulkes, William Matthew Colwyn. "Interatomic forces in solids." Thesis, University of Cambridge, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328669.
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Pattenden, Paul Adam. "Muon studies of solids." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361930.
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Nichol, A. C. "Infrared spectroscopy of solids." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308601.
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Cook, M. I. "Magnetic resonance in solids." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253004.
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O'Connell, Andrew John. "Magnetic resonance in solids." Thesis, University of Oxford, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305439.
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Madden, Timo Michael. "Regular and perfect solids." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240612.
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Hou, Hang-sheng. "Cavitation instability in solids." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13697.
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Chadwick, Alan V. "Diffusion in nanocrystalline solids." Universitätsbibliothek Leipzig, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-195769.
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Enhanced atomic migration was an early observation from experimental studies into nanocrystalline solids. This contribution presents an overview of the available diffusion data for simple metals and ionic materials in nanocrystalline form. It will be shown that
enhanced diffusion can be interpreted in terms of atomic transport along the interfaces, which are comparable to grain boundaries in coarse-grained analogues. However, the method of sample preparation is seen to play a major role in the experiments and there are still many gaps in understanding the detailed mechanisms of diffusion in these systems.
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Chadwick, Alan V. "Diffusion in nanocrystalline solids." Diffusion fundamentals 2 (2005) 44, S. 1-22, 2005. https://ul.qucosa.de/id/qucosa%3A14377.
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Enhanced atomic migration was an early observation from experimental studies into nanocrystalline solids. This contribution presents an overview of the available diffusion data for simple metals and ionic materials in nanocrystalline form. It will be shown that
enhanced diffusion can be interpreted in terms of atomic transport along the interfaces, which are comparable to grain boundaries in coarse-grained analogues. However, the method of sample preparation is seen to play a major role in the experiments and there are still many gaps in understanding the detailed mechanisms of diffusion in these systems.
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Rayner, Anton. "Laser cooling of solids /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16448.pdf.
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Olusanmi, Oludolapo Janet. "Milling of organic solids." Thesis, University of Leeds, 2009. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509852.
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SUN, YONGTAO. "Multifunctional Hierarchical Cellular Solids." Doctoral thesis, Politecnico di Torino, 2013. http://hdl.handle.net/11583/2507349.
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Due to their peculiar low density properties, cellular solids are widely used in industries and play a very important role in our daily life. Two of the most studied celluar solids are honeycombs and foams. With the development of nanotechnology, another kind of cellular solids - carbon based materials are drawing more and more attentions nowadays, e.g., the carbon nanotube related researches. The other very hot research field is the bio-inspired materials. Many efforts have been made by the scientists all over the world and a lot of insightful results are obtained. No matter the well studied celluar solids or the newly studied natural and artificial materials, what we care about them are not only their mechicanl properties but also the multifunctionality they may display, in order that they could serve the human being more effectively and more conveniently. Therefore, in this thesis we have focused on the multifunctional hierarchical cellular solids.
In the first chapter, by reviewing some recent developments of the cellular solids, honeycombs and carbon nanotube networks, we summarized the potential multifunctionality they show and thus the significance they may be of for practical applications. Based on this simple review, the motivation of this thesis is introduced, which is to explore the multifunctionalities of these two kinds of cellular solids more widely and deeply.
In chapter 2, through the effective media model, the thermal and thermomechanical performances of the two-dimensional metal honeycombs (with relative density less than 0.3), hexagonal, triangular, square and Kagome honeycombs, are systematically studied.
To improve the in-plane stiffness of the regular hexagonal honeycombs, in chapters 3 and 4 we proposed the multifunctional hierarchical honeycombs (MHH). The MHH is constructed by substituting the cell wall of an original regular honeycomb with five different equal mass lattices, hexagonal, triangular, Kagome, re-entrant hexagonal and chiral honeycombs, respectivley. Elastic and transport properties of the MHH with hexagonal, triangular and Kagome substructures are studied. In-plane stiffnesses of the MHH with re-entrant hexagonal and chiral honeycombs are analyzed.
Chapter 5 involves the cellular solids, super carbon nanotubes (STs). To avoid the diameter shrinkage that the normal STs under uniaxial tension show, a new kind of hierarchical fibers with a negative Poisson’s ratio for tougher composites is proposed and their equivalent elastic parameters are calculated. Chapter 6 reported an application of the hierarchical fibers in bridged crack model.
Chapter 7 provides conclusions and an outlook for the future work.
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Rovnyak, David S. (Davis Sherman) 1971. "Solid-state nuclear magnetic resonance of quadrupolar nuclei with applications to biological solids." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/85294.
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Klanner, Catharina. "Evaluation of descriptors for solids." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=97123941X.
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Martínez, García Julio César. "Dynamics in orientationally disordered solids." Doctoral thesis, Universitat Politècnica de Catalunya, 2011. http://hdl.handle.net/10803/35856.
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The key features of dynamics of ultraslowing glass forming systems are their universality in diversity. Its
origin is recognized as one of the greatest challenges of condensed matter physics and materials
engineering in the XXI century. Similar phenomena are observed on approaching the glass transition in
low molecular weight supercooled liquids, polymers, colloidal fluids as well as in solids, for instance in
orientationally disordered crystals, spin glass-like magnetic, vortex glasses. Pre-vitreous dynamics is also
proposed as a general reference for the category of complex liquids/soft matter systems.
The upsurge of the primary relaxation time or related dynamical properties is the basic physical
phenomena of the still mysterious previtreous behavior. This means a much more pronounced slowing
down than the Arrhenius pattern observed far above the glass transition temperature. Portraying this
behavior constitutes one of key checkpoints for theoretical models developed to unwind the glass
transition puzzle. However, none of the aforementioned features can answer the understanding that
governs the increase of relaxation time in liquids upon cooling.
In this thesis we focus on the above questions studying the dynamics of some materials for which their
molecules can retain a translational order being orientationally disordered between them upon cooling,
which are referred to plastic phases or orientationally disordered (OD) crystalline phases. The work
presented in this thesis potentially extends the knowledge of dynamics of OD phases and orientationally
glasses (OG), a research topic which has gained interest during the last decades.
Through this study, especial attention has been devoted to the phenomenological equations accounting
to the temperature dependence of the mean relaxation time describing the orientational dynamics .The
study was carried out by the use of BDS as well as two complementary experimental techniques. We
show distortion-sensitive and derivative-based empirical analysis of the validity of leading equations for
portraying the previtreous evolution of primary relaxation time. A new method for studying the dynamics of
glass forming systems is introduced and the minimization procedure is validated and discussed.
We present the results divided in two topics, the dynamics of the pure compounds and mixed crystals and
the derivative analysis through different existing models.
In the first topic we focus on the dynamics of the pure compounds and mixed crystals formed between
cycloheptanol and cyclooctanol as well as the a-relaxation dynamics of 1-cyano-adamantane and its
mixtures with 1-chloro-adamantane. The second topic is divided in two groups of models, linearized and
non-linearized models. In the linearized models we show the application of the derivative based,
distortion-sensitive analysis to liquid crystals (LC) and OD phases. We also discuss the results concerning
to the cases of the olygomeric liquid epoxy resin (EPON828), neopentylalcohol and neopentylglycol
mixture, isooctylcyanobiphenyl and propylene carbonate. The possible empirical correlations between one
of the linearized models with the universal pattern for the high frequency wing of the loss curve for primary
relaxation time for LCs and OD phases is also shown.
In the final part we show that the form of the equation recently introduced by Mauro et al. does not allow a
similar straightforward linearization procedure. Unlike the previous models, the involved parameters are
not correlated with the slope and the intercept of a linear function. In order to solve this problem, we have
introduced the concept of the enthalpy space.
The evidences of the existence of crossovers as well as quantitative descriptions are discussed. We show
also a new procedure for detecting the crossover in a very easy way. A new kind of crossovers which
seems to be impossible to be detected by the classical Stickel transformation is presented.La principal característica de la dinámica de sistemas vítreos viscosos, es su universalidad en la diversidad. Su origen es uno de los mayores desafíos de la física de la materia condensada y de la ingeniería de materiales en el siglo XXI. La fenomenología típica de las fases vítreas se observan cerca de la transición vítrea en líquidos subenfriados de bajo peso molecular, polímeros, fluidos coloidales, así como en los sólidos con fases orientacionalmente desordenadas. La imposibilidad de explicar las causas del gran aumento del tiempo de relajación al enfriar un líquido, constituye uno de los problemas más importantes no resueltos en materia condensada. Con el objetivo de dar respuesta a dicha interrogante, se han propuesto modelos termodinámicos y dinámicos que han resultado inconsistentes. En esta tesis nos centramos en dicha problemática, estudiando la dinámica orientacional de algunos materiales que al ser enfriados pueden conservar un orden traslacional mientras que se conserva el desorden orientacional de las moléculas que los forman. Dichas fases se conocen como fases plásticas u orientacionalmente desordenadas (OD). El trabajo presentado en esta tesis amplía el conocimiento de la dinámica de dichas fases, un tema de investigación cuyo interés ha aumentado durante las últimas décadas. Se ha dedicado una atención especial a las ecuaciones fenomenológicas que describen la dependencia del tiempo de relajación con la temperatura. El estudio se ha llevado a cabo mediante el uso de espectroscopía dieléctrica de banda ancha, así como mediante el uso de técnicas experimentales complementarias. Se ha introducido un nuevo método para el estudio de la dinámica de los sistemas que dan lugar a fases vítreas. El método ha sido validado y discutido. Los resultados de esta tesis se presentan divididos en dos temas, por un lado, la dinámica de compuestos puros y de los cristales mixtos y, por otro, el análisis mediante el método derivativo aplicado a los diferentes modelos físicos existentes. En el primer tema nos centramos en la dinámica de los compuestos puros y los cristales mixtos formados por cicloheptanol y ciclooctanol, así como la dinámica de la relajación alfa en 1-ciano-adamantano y sus mezclas con 1-cloro-adamantano. El segundo tema se divide en dos grupos de modelos, los modelos lineales y no lineales. En los modelos lineales se muestra la aplicación del procedimiento de derivativo en los cristales líquidos (CL) y las fases OD. También se discuten los resultados relativos a los casos de la resina líquida (EPON828), la mezcla neopentil-alcohol y neopentil-glicol, el carbonato de propileno, así como el CL isooctilcianobifenil. Se discute también la existencia de posibles correlaciones empíricas entre uno de los modelos lineales con el patrón universal para la parte de alta frecuencia de la curva de pérdidas dieléctricas de la relajación primaria para las fases CL y OD. En la parte final se muestra que la forma de la ecuación introducida recientemente por Mauro et al. no permite la linearización mediante el método derivativo. A diferencia de los modelos anteriores, los diferentes parámetros no están correlacionados con la pendiente y el origen de coordenadas de una función lineal. Para resolver este problema, hemos introducido el concepto del espacio entálpico. Se analiza también la existencia de cambios de comportamiento dinámicos y se aportan descripciones cuantitativas. Se muestra también un nuevo procedimiento para detectar los cambios dinámicos de una manera fácil, que permite incluso detectar aquéllos que son obviados mediante el método clásico de Stickel.
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Mostoufi, Navid. "Solids behaviour in fluidized beds." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0017/NQ53540.pdf.
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Tekoğlu, Cihan. "Size effects in cellular solids." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 2006. http://irs.ub.rug.nl/ppn/298794977.
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Fagas, Georgios. "Vibrational properties of complex solids." Thesis, Lancaster University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.321898.
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Broomfield, Seth Emlyn. "Picosecond optical studies of solids." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.253303.
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Ruiz-Diaz, J. E. "Fast ion transport in solids." Thesis, University of Oxford, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355773.
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Tronconi, Alvaro Luiz. "Magnetic resonance in crystalline solids." Thesis, University of Oxford, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329981.
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Clark, Robert Andrew. "Studies on novel molecular solids." Thesis, Bangor University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252653.
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Wilkes, Philip John. "NMR of phosphorus-containing solids." Thesis, Durham University, 1987. http://etheses.dur.ac.uk/6666/.
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The purpose of this work has been the determination of structure in solids using the technique of solid-state nuclear magnetic resonance spectroscopy. High-resolution (^31) p NMR spectra have been obtained for a range of phosphate species. A number of techniques have been applied to these systems including cross-polarization, magic angle spinning, and high power proton decoupling. Characterisation using additional NMR techniques such as (^1) H cramps has been carried out wherever possible. The results obtained yield molecular and crystallographic information consistent with data from X-ray diffraction when known. Shielding tensor components were determined from static and/or spinning spectra wherever possible. The phosphate species studied include a series of precipitated calcium phosphates. A particular model for the structure of amorphous calcium phosphate is favoured in the light of (^31) p NMR measurements. One sample showed NMR evidence for changes in composition whilst in the solid state. The origins of (^31) p NMR line widths in high-resolution solid-state spectra have been considered in some detail. Variation of (^31) p NMR linewidth as function of spinning rate has been noted for a number phosphate compounds. Multiple pulse techniques have been applied on the phosphorus channel with pleasing improvements in spectral resolution. Five solid binary phosphorus sulphides have also been studied using phosphorus MAS NMR, and the results compared to solution state data wherever possible. A number of anomalies between solution and solid-state data have been noted and discussed.
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McBride, Hugh Joseph. "Wave propagation in elastic solids." Thesis, Monterey, California. Naval Postgraduate School, 1992. http://hdl.handle.net/10945/24107.
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Zhang, Zhichao. "Impact attrition of particulate solids." Thesis, University of Surrey, 1994. http://epubs.surrey.ac.uk/2945/.
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Papadopoulos, Dimitris G. "Impact breakage of particulate solids." Thesis, University of Surrey, 1998. http://epubs.surrey.ac.uk/804878/.
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Gutschke, Siegfried O. H. "Solvothermal synthesis of coordination solids." Thesis, University of East Anglia, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327491.
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Stone, Cora Emma. "Neutron studies of amorphous solids." Thesis, University of Reading, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396244.
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Peirson, Neil Francis. "'1'9F NMR studies in solids." Thesis, Open University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305064.
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Bidgood, Christopher M. "Safe storage of combustible solids." Thesis, London South Bank University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357171.
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Kerr, Noel Clark. "Laser radiation interactions with solids." Thesis, Loughborough University, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329727.
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Klintworth, John Wilhelm. "Dynamic crushing of cellular solids." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304395.
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BOTTI, TALITA COFFLER. "SOLIDS TRANSPORT IN LAMINAR FLOW." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24700@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
Após a década de 80 tornou-se frequente a utilização de poços direcionais, tanto poços horizontais quanto os de longo alcance, nas operações de desenvolvimentos de campos petrolíferos, os quais permitiram grande avanço na exploração. Este cenário, porém, traz grandes desafios para operações de perfuração relacionadas à limpeza de poços. A limpeza de poços consiste na remoção dos cascalhos de dentro do anular do poço através da circulação do fluido de perfuração. Devido à inclinação do poço, os cascalhos sofrem a ação da gravidade sendo empurrados para o fundo do canal, já que possuem densidade maior que a da fase líquida, assim, transportados a uma velocidade menor que a velocidade do escoamento. Ao se depositarem no fundo do canal, formam um leito estacionário, obstruindo parte do anular e diminuindo a vazão, o que gera problemas, como por exemplo, redução da taxa de penetração, desgaste prematuro da broca, elevação do torque e arraste, aprisionamento da coluna, perda de circulação, dentre outros, podendo gerar a perda do poço. Desta forma, o perfeito entendimento do processo de sedimentação e transporte de partículas sólidas suspensas em fluido é fundamental para a otimização do processo de perfuração de poços. Este trabalho analisa o escoamento laminar bidimensional de suspensões de partículas sólidas devido a um gradiente de pressão entre duas placas paralelas, representando uma descrição simplificada do escoamento que ocorre em um anular de poço durante o processo de perfuração. O perfil do leito de partículas ao longo do canal e a relação vazão-diferença de pressão para diferentes condições de escoamento são determinados pela solução numérica das equações que descrevem o problema. A formulação matemática leva a um sistema acoplado de três equações diferenciais: conservação de massa e de quantidade de movimento e a equação de transporte, que engloba os efeitos de difusão de partículas devido à frequência de interação entre as partículas, ao gradiente de viscosidade e à diferença de densidade entre o líquido e as partículas. O sistema é resolvido pela técnica de Elementos Finitos, através do método de Galerkin. Os resultados obtidos serão de extrema importância no desenvolvimento de modelos mais precisos que descrevam o processo de transporte de sólidos em anulares de poços.
After the 80 s, the use of directional wells, both horizontal and long range wells, became frequent in the development of oil fields, which allowed great progress in exploration. This scenario, however, brings great challenges to operations related to wellbore cleaning. Wellbore cleaning consists in the removal of cuttings from within the annular through the circulation of drilling fluid. Due to the inclination of the well, the cuttings undergo the action of gravity and more to the bottom of the channel, as they have higher density than the liquid phase. They may be transported with a speed less than the speed of the liquid flow. When deposited on the channel, the cuttings form a stationary bed, blocking part of the annular and decreasing the flow rate that causes problems, such as reducing the rate of penetration, premature wear of the bit, high torque and drag, trapping column, loss of circulation and others, which may cause the loss of the well. Therefore, the fundamental understanding of particle sedimentation and transport in a suspending flowing liquid is necessary for drilling operation design and optimization. This research studies the laminar two-dimensional flow of solid particles suspended in a liquid due to a pressure gradient between two parallel plates, representing a simplified description of the flow that occurs in an annular during the drilling process. The profile of the particle bed along the channel and the flow rate pressure difference relationship for different flow conditions are determined. The mathematical formulation leads to a coupled system of three differential equations: mass and momentum conservation and transport equation, which includes the effects of particle diffusion due to the frequency of interaction between the particles, the gradient of viscosity and the difference density between the liquid and the particles. The system is solved by the finite element method Galerkin. The results will be of extreme importance in the development of more accurate models that describe the solids transport process in annular space.
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Kim, Kwon Hee. "Shear localization in viscoplastic solids." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14662.
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Liao, Bolin Ph D. Massachusetts Institute of Technology. "Practical electron cloaking in solids." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78239.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 71-72).
The design and experimental realization of "metamaterials" in the past decade has opened up new venues to obtain artificial materials with exotic properties that are desirable but not commonly encountered in the nature. Optical metamaterials have shown great potentials in applications such as optoelectronics, subwavelength imaging, and optical information processing etc. The invisibility effect, or "cloaking effect", is one of the most striking demonstrations of the unprecedented ability of manipulating light provided by optical metamaterials. As a natural extension, the cloaking effect of acoustic waves and quantum matter waves has also been discussed recently. Currently the main strategy of designing "cloaks" is the so-called transformation optics, and the resulting continuous distribution of material properties, such as the refractive index for optical metamaterials, the effective mass and the potential profile for matter-wave metamaterials, requires the artificial structures be much smaller than the wavelength of corresponding waves. In this thesis, the strategy of cloaking artificial scattering centers from conducting electrons in solids is discussed theoretically. The wavelength of conducting electrons in solids is of the order of a few nanometers, rendering the transformation optics technique impractical in this circumstance. Instead, a method based on the expansion of partial waves, analogous to the Mie theory for electromagnetic waves, is proposed. As an example, the design of "invisible" core-shell nanoparticles is demonstrated, and its application in thermoelectrics is discussed, where it is shown a simultaneous enhancement of the Seebeck coefficient and the electrical conductivity can be achieved. The corresponding formalism in 2D (both normal 2D electron gas system and graphene) is also derived, based on which novel electronic switches and filters can be constructed using properly designed gates to achieve desired potential profiles.
by Bolin Liao.
S.M.
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Liu, Shuangxi. "NMR studies of inorganic solids." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627317.
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Lee, Robert Frank. "Spin dependent transport in solids." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615695.
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Wang, Xiaolin. "Continuum modelling of cellular solids." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624856.
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