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Dissertations / Theses on the topic 'Homogeneous'
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1
Garg, Akanksha. "Homogeneous Dislocation Nucleation." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/401.
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Pekson, Oemer. "Homogeneous exact fillings." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236334.
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Alnuaimi, Nasser Abdullah. "Modeling ultrasonic transducer in homogeneous and non-homogeneous media using DPSM method." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280583.
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Modeling ultrasonic transducers is an important aspect of research in nondestructive evaluation and testing. In most nondestructive evaluation applications, the ultrasonic transducers are traditionally modeled as: (1) point sources generating spherical wave fronts (2) line sources generating cylindrical wave fronts, or (3) planar surfaces generating plane wave fronts. In reality, the transducer front face has finite dimensions; it is neither point source nor planar source because the ultrasound that emits from a piezoelectric transducer does not originate from a point or an infinite plane, but instead originates from the finite surface of the piezoelectric element with flat or curved front face. Analytically modeling the fields radiated by ultrasonic transducers is a very difficult task because of the large number of possible transducer types, sizes and configurations that are used in practice. In this study, a semi analytical technique the Distributed Point Source Method (DPSM) is adapted to model ultrasonic transducers. The DPSM discretizes the transducer surface into a finite number of elemental surfaces. As a result, the complexity associated with the discretization of the three-dimensional problem geometry as done in the finite element technique is reduced. In the DPSM technique, the fundamental governing equations for elastic wave propagation in a fluid and in a solid are solved. For this reason, the DPSM technique is called a semi-analytical technique. In this research, computer codes for computing the ultrasonic field in a three dimensional inhomogeneous medium in front of a transducer of finite dimension have been written in MatLab. Two different cases are considered in this study, nonhomogeneous fluid and fluid-solid interface. Both normal and inclined incidence cases are investigated. This investigation shows that DPSM is an efficient technique for modeling ultrasonic transducers in nonhomogeneous media.
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Craythorne, Steven James. "Heterogenizing homogeneous hydrogenation catalysts." Thesis, Queen's University Belfast, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486059.
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Catalysts frequently used in the fine chemical industries are qften homogeneous, therefore requiring expensive and time consuming methods of catalyst regeneration. The loss of expensive transition metals used in most homogeneous catalysts is significant, and further tests must be conducted to measure levels of contamination of the final product, a critical consideration in the phannaceutical and foodstuffs industries. This thesis reports the synthesis, material preparation and testing of three methods of entrapping active catalysts. The methods described have been developed to fulfill the conditions suitable for the individual catalyst. Acidic, basic and fast gelling sol-gel techniques are discussed in which silica based glasses, ionogels and organogels are functionalized with active catalyst species. These cat~lysts have undergone the hydrogenation of styrene, the enantioselective hydrogenation of geraniol and the transfer hydrogenation ofacetophenone. We report the results of catalytic reactions employing these heterogenized homogenous catalysts comparable in selectivity and conversion to their homogeneous counterparts, yet having ease of separation. and effortless handling conditions equivalent to and (in some cases) better than corresponding heterogeneous catalysts. We also report the negligible metal leaching in our catalyst systems.
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Yang, Dan-Hui. "Homogeneous and heterogeneous sonochemistry." Doctoral thesis, Universite Libre de Bruxelles, 1992. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/212940.
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Skorniakov, Viktor. "Asymptotically homogeneous Markov chains." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20101223_152954-43357.
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In the dissertation there is investigated a class of Markov chains defined by iterations of a function possessing a property of asymptotical homogeneity. Two problems are solved: 1) there are established rather general conditions under which the chain has unique stationary distribution; 2) for the chains evolving in a real line there are established conditions under which the stationary distribution of the chain is heavy-tailed.Disertacijoje tirta Markovo grandinių klasė, kurios iteracijos nusakomos atsitiktinėmis asimptotiškai homogeninėmis funkcijomis, ir išspręsti du uždaviniai: 1) surastos bendros sąlygos, kurios garantuoja vienintelio stacionaraus skirstinio egzistavimą; 2) vienmatėms grandinėms surastos sąlygos, kurioms esant stacionarus skirstinys turi "sunkias" uodegas.
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Adams, Nicholas James. "Studies in homogeneous catalysis." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.312264.
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Araujo, Fatima. "Einstein homogeneous Riemannian fibrations." Thesis, University of Edinburgh, 2008. http://hdl.handle.net/1842/4375.
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This thesis is dedicated to the study of the existence of homogeneous Einstein metrics on the total space of homogeneous fibrations such that the fibers are totally geodesic manifolds. We obtain the Ricci curvature of an invariant metric with totally geodesic fibers and some necessary conditions for the existence of Einstein metrics with totally geodesic fibers in terms of Casimir operators. Some particular cases are studied, for instance, for normal base or fiber, symmetric fiber, Einstein base or fiber, for which the Einstein equations are manageable. We investigate the existence of such Einstein metrics for invariant bisymmetric fibrations of maximal rank, i.e., when both the base and the fiber are symmetric spaces and the base is an isotropy irreducible space of maximal rank. We find this way new Einstein metrics. For such spaces we describe explicitly the isotropy representation in terms subsets of roots and compute the eigenvalues of the Casimir operators of the fiber along the horizontal direction. Results for compact simply connected 4-symmetric spaces of maximal rank follow from this. Also, new invariant Einstein metrics are found on Kowalski n-symmetric spaces.
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Lockett, Deborah Carol. "Homomorphism-Homogeneous relational structures." Thesis, Queen Mary, University of London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.509701.
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Arzhantsev, I. V., D. A. Timashev, and Andreas Cap@esi ac at. "Affine Embeddings of Homogeneous Spaces." ESI preprints, 2000. ftp://ftp.esi.ac.at/pub/Preprints/esi929.ps.
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Semenov, Nikita. "Motives of projective homogeneous varieties." Diss., lmu, 2007. http://nbn-resolving.de/urn:nbn:de:bvb:19-70866.
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Aizenberg, Lev, and Nikolai Tarkhanov. "Stable expansions in homogeneous polynomials." Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2009/2992/.
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An expansion for a class of functions is called stable if the partial sums are bounded uniformly in the class. Stable expansions are of key importance in numerical analysis where functions are given up to certain error. We show that expansions in homogeneous functions are always stable on a small ball around the origin, and evaluate the radius of the largest ball with this property.
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Södergren, Anders. "Asymptotic Problems on Homogeneous Spaces." Doctoral thesis, Uppsala universitet, Matematiska institutionen, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-132645.
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This PhD thesis consists of a summary and five papers which all deal with asymptotic problems on certain homogeneous spaces. In Paper I we prove asymptotic equidistribution results for pieces of large closed horospheres in cofinite hyperbolic manifolds of arbitrary dimension. All our results are given with precise estimates on the rates of convergence to equidistribution. Papers II and III are concerned with statistical problems on the space of n-dimensional lattices of covolume one. In Paper II we study the distribution of lengths of non-zero lattice vectors in a random lattice of large dimension. We prove that these lengths, when properly normalized, determine a stochastic process that, as the dimension n tends to infinity, converges weakly to a Poisson process on the positive real line with intensity 1/2. In Paper III we complement this result by proving that the asymptotic distribution of the angles between the shortest non-zero vectors in a random lattice is that of a family of independent Gaussians. In Papers IV and V we investigate the value distribution of the Epstein zeta function along the real axis. In Paper IV we determine the asymptotic value distribution and moments of the Epstein zeta function to the right of the critical strip as the dimension of the underlying space of lattices tends to infinity. In Paper V we determine the asymptotic value distribution of the Epstein zeta function also in the critical strip. As a special case we deduce a result on the asymptotic value distribution of the height function for flat tori. Furthermore, applying our results we discuss a question posed by Sarnak and Strömbergsson as to whether there in large dimensions exist lattices for which the Epstein zeta function has no zeros on the positive real line.
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Dunn, Corey. "Curvature homogeneous pseudo-Riemannian manifolds /." view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1188874491&sid=3&Fmt=2&clientId=11238&RQT=309&VName=PQD.
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Thesis (Ph. D.)--University of Oregon, 2006.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 146-147). Also available for download via the World Wide Web; free to University of Oregon users.
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Hallbom, Donald John. "Pipe flow of homogeneous slurry." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2399.
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The objective of this Thesis is to devise a system for the "rheology-based design" of non-settling (homogeneous) slurry pipelines that is more conducive to application by practicing engineers without impairing its accuracy or utility for research purposes. The cornerstone is the development of a new rheological model and constitutive equation for homogeneous slurry based on the aggregation/deaggregation of the suspended mineral particles. This “yield plastic” model is shown to describe a family of models that includes the Newtonian, Bingham plastic and Casson models as special cases. It also closely approximates the results of many consistency models, including power law, yield power law, Cross and Carreau-Yasuda.
The yield plastic model is then used to develop design equations to determine the pressure-gradient of laminar and turbulent pipe flow. A relative energy dissipation criterion is proposed for the laminar-turbulent transition and shown to be consistent with currently used transition models for Newtonian and Bingham fluids. Finally, a new dimensionless group (the “stress number”) is proposed that is directly proportional to the pressure-gradient and independent of the velocity. When the design equations are presented graphically in terms of the stress number and the plastic Reynolds number, the resulting “design curve diagram” is shown to be a dimensionless (pressure-gradient vs. velocity) pipe flow curve.
The net result is that the hydraulic design of homogeneous slurry systems only requires the use of a single constitutive equation and three engineering design equations. The results are presented in a conceptually easy form that will foster an intuitive understanding of non-Newtonian pipe flow. This will assist engineers to understand the impact of slurry rheology when designing, operating and troubleshooting slurry pipelines and, in the future, other slurry related processes.
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Thiffault, Johanne. "Estimation for homogeneous Poisson processes." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=63370.
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Maddox, P. J. "Oxidative addition on homogeneous catalysis." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379910.
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Garland, Carl Sherman. "Redox promotion of homogeneous catalysis." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.257734.
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Núñez, Magro Ángel Alberto. "New reactions under homogeneous conditions." Thesis, University of St Andrews, 2007. http://hdl.handle.net/10023/482.
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BDTBPMB has been proven to be an essential ligand in carbonylation chemistry. Its two tert-butyl groups and wide bite angle give it the ideal characteristics for this kind of chemistry, and leads to high activity and selectivity with use of its complexes. During this work the group of reactions where this ligand has been proven to be active has been extended with two new protocols for hydroxycarbonylation and aminocarbonylation. In the hydroxycarbonylation process, a large variety of unsaturated compounds were studied. Dioxane was found to be the ideal solvent, due to its properties in terms of coordinability, and miscibility with water. Using this solvent as the medium, a BDTBPMB complex of palladium was found to be highly active and selective under mild conditions. Initial attempts to address the aminocarbonylation of alkenes catalysed by the Pd/BDTBPMB system did not give high activity. This problem was overcome by the addition of an arylalcohol. Under those conditions, high selectivity and conversion was obtained in a wide variety of amides. However, attempts to address the aminocarbonylation of alkenes with ammonia gas to generate primary amides did not result in any conversion. The generation of these primary amides was obtained with transamidation of N-phenylnonamides which can be prepared by aminocarbonylation. Amides have been successfully hydrogenated to amines catalysed by a Ru/Triphos system. This system has been proven to be highly active in this reaction. High selectivities have been obtained in the generation of secondary amine. However, initial results of the hydrogenation of primary amides resulted in no formation of primary amines. A careful analysis of the mechanism of the formation of various products from the hydrogenation of primary amides allows the selective formation of primary amines by the ruthenium/Triphos system in the presence of ammonia. The possibility of the generation of primary amides in situ from acids under hydrogenation conditions, giving primary amines was explored with high conversion and moderate selectivities. To complete this work, a system based on a palladium complex for the decarboxylation of benzoic acids was developed. Usually, the decarboxylation reactions catalysed by copper require high temperatures. However, palladium complexes of highly electron donating ligands such as BDTBPMB or P([superscript]tBu)₃ were found to be highly active under milder conditions. This catalytic system was proven to be active in desulfonation reactions giving high conversion.
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Torrezão, de Sousa Susana. "Countable homogeneous coloured partial orders." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.414166.
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Lovell, Stephen Christopher. "Automorphism groups of homogeneous structures." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435795.
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Shaikh, Muhammad. "Homogeneous to heterogeneous Face Recognition." Thesis, Northumbria University, 2015. http://nrl.northumbria.ac.uk/32283/.
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Face Recognition, a very challenging research area, is being studied for almost more than a decade to solve variety of problems associated with it e.g. PIE (pose, expression and illumination), occlusion, gesture, aging etc. Most of the time, these problems are considered in situations when images are captured from same sensors/cameras/modalities. The methods in this domain are termed as homogeneous face recognition. In reality face images are being captured from alternate modalities also e.g. near infrared (NIR), thermal, sketch, digital (high resolution), web-cam (low resolution) which further alleviates face recognition problem. So, matching faces from different modalities are categorized as heterogeneous face recognition (HFR). This dissertation has major contributions in heterogeneous face recognition as well as its homogeneous counterpart. The first contribution is related to multi-scale LBP, Sequential forward search and KCRC-RLS method. Multi scale approaches results in high dimensional feature vectors that increases computational cost of the proposed approach and overtraining problem. Sequential forward approach is adopted to analyze the effect of multi-scale. This study brings an interesting facts about the merging of features of individual scale that it results in significant reduction of the variance of recognition rates among individual scales. In second contribution, I extend the efficacy of PLDA to heterogeneous face recognition. Due to its probabilistic nature, information from different modalities can easily be combined and priors can be applied over the possible matching. To the best of author’s knowledge, this is first study that aims to apply PLDA for intermodality face recognition. The third contribution is about solving small sample size problem in HFR scenarios by using intensity based features. Bagging based TFA method is proposed to exhaustively test face databases in cross validation environment with leave one out strategy to report fair and comparable results. The fourth contribution is about the module which can identify the modality types is missing in face recognition pipeline. The identification of the modalities in heterogeneous face recognition is required to assist automation in HFR methods. The fifth contribution is an extension of PLDA used in my second contribuiton. Bagging based probabilistic linear discriminant analysis is proposed to tackle problem of biased results as it uses overlapping train and test sets. Histogram of gradient descriptors (HOG) are applied and recognition rates using this method outperform all the state-of-the-art methods with only HOG features.
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Witt, James David Samuel. "Superconductivity and non-homogeneous magnetism." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610601.
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Siniora, Daoud Nasri. "Automorphism groups of homogeneous structures." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/17156/.
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A homogeneous structure is a countable (finite or countably infinite) first order structure such that every isomorphism between finitely generated substructures extends to an automorphism of the whole structure. Examples of homogeneous structures include any countable set, the pentagon graph, the random graph, and the linear ordering of the rationals. Countably infinite homogeneous structures are precisely the Fraisse limits of amalgamation classes of finitely generated structures. Homogeneous structures and their automorphism groups constitute the main theme of the thesis. The automorphism group of a countably infinite structure becomes a Polish group when endowed with the pointwise convergence topology. Thus, using Baire Category one can formulate the following notions. A Polish group has generic automorphisms if it contains a comeagre conjugacy class. A Polish group has ample generics if it has a comeagre diagonal conjugacy class in every dimension. To study automorphism groups of homogeneous structures as topological groups, we examine combinatorial properties of the corresponding amalgamation classes such as the extension property for partial automorphisms (EPPA), the amalgamation property with automorphisms (APA), and the weak amalgamation property. We also explain how these combinatorial properties yield the aforementioned topological properties in the context of homogeneous structures. The main results of this thesis are the following. In Chapter 3 we show that any free amalgamation class over a finite relational language has Gaifman clique faithful coherent EPPA. Consequently, the automorphism group of the corresponding free homogeneous structure contains a dense locally finite subgroup, and admits ample generics and the small index property. In Chapter 4 we show that the universal bowtie-free countably infinite graph admits generic automorphisms. In Chapter 5 we prove that Philip Hall's universal locally finite group admits ample generics. In Chapter 6 we show that the universal homogeneous ordered graph does not have locally generic automorphisms. Moreover we prove that the universal homogeneous tournament has ample generics if and only if the class of finite tournaments has EPPA.
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Black, Malcolm J. "Harmonic maps into homogeneous spaces." Thesis, University of Warwick, 1990. http://wrap.warwick.ac.uk/107838/.
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This thesis investigates harmonic maps into homogeneous spaces, principally flag manifolds. First we show that an f-holomorphic map of a Hermitian cosymplectic manifold is harmonic provided that the f-structure on the co-domain satisfies (d∇F)1,1 = 0, where ∇ is the Levi-Civita connection. We then characterize those invariant f-structures and metrics on homogeneous spaces which satisfy this condition. On a homogeneous space whose tangent bundle splits as a direct sum of mutually distinct isotropy spaces (e.g. a flag manifold), we see that an f-structure which is horizontal (i.e. [F+, F] ⊂ h) satisfies (d∇F)1,1 = 0 for any choice of invariant metric. Thus f-holomorphic maps are equi-harmonic (harmonic with respect to all invariant metrics). Equi-harmonic maps are seen to behave well in combination with homogeneous geometry. Next we classify horizontal f-structures on flag manifolds. The classification provides a unified framework for producing examples of flag manifolds fibring twistorially over homogeneous spaces. Another application of this classification is to find f-holomorphic orbits in full flag manifolds. Finally, we show that an equi-harmonic map of a Riemann surface which is also equi-weakly conformal is f-holomorphic with respect to a horizontal f-structure. Our classification theorem then allows a more concrete description of such maps bringing further examples to light.
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Buriak, Jillian M. "Homogeneous catalytichydrogenation in micellar media." Université Louis Pasteur (Strasbourg) (1971-2008), 1995. http://www.theses.fr/1995STR13037.
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Dans ce travail, nous avons examine l'application des micelles aqueuses et inverses comme milieux reactionnels pour l'hydrogenation asymetrique. Afin de montrer que la catalyse organometallique etait possible dans ces systemes, nous avons commence par etudier l'hydrogenation catalytique de dienes conjugues par une serie de catalyseurs cationiques de formule generale rh(diene)(p-p)x (p-p represente une diphosphine achirale, x un halogenure) dans diverses structures micellaires. Les resultats de ces experiences ont permis de mettre en evidence des effets importants sur la vitesse, le mecanisme et la composition des produits de la reaction. L'hydrogenation catalytique asymetrique des imines a ete realisee avec des complexes chiraux du type rh(nbd)(p-p)clo#4 (p-p represente une diphosphine chiral) en presence des micelles inverses de aot dans le benzene. Nous avons remarque une augmentation importante de l'enantioselectivite et de la duree de vie du catalyseur. L'ee, ainsi que la vitesse sont intimement dependants de la presence de co-additifs (tel que l'eau, l'anisole et l'ether couronne 15-5). Nombreuses etudes physiques et physico-chimiques ont permis d'etablir que l'amelioration de l'exces enantiomerique est du a une interaction entre le complexe metallique cationique et le groupement sulfonate du surfactant. L'effet positif de la coordination du sulfonate peut etre applique a l'hydrogenation asymetrique des olefines prochirales simples comme l'-ethylstyrene. Nous avons remarque de fortes augmentations de l'enantioselectivite lorsque celui-ci et des substrats similaires sont hydrogenes sous des conditions identiques. Dans la derniere partie de cette these, nous decrivons une nouvelle methode pour determiner l'exces enantiomerique de composees aromatiques
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Bradley-Williams, David Beowulf. "Jordan groups and homogeneous structures." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/9006/.
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La, Sorella Giorgio <1987>. "Supramolecular approaches to Homogeneous catalysis." Doctoral thesis, Università Ca' Foscari Venezia, 2015. http://hdl.handle.net/10579/8319.
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The development of homogeneous systems capable to mimic the enzymes activity is a fundamental topic for catalysis. For that purpose, in this thesis we reported the employment of supramolecular resorcin[4]arene capsule in organic solvents and micelles in water.
The resorcin[4]arene capsule is a spherical hexamer. The high number of electron-rich aromatic rings on the surface of the capsule cause cation-π interactions that confer to the cavity the possibility to accommodate positively charged compounds. We demonstrated that the capsule is also capable to host formally neutral compounds with partial carbene-like electron poor character. In the presence of isocyanides, the empty capsule favoured the nucleophilic attack of either water leading to the formation of the corresponding N-formylamide or trimethylsilylazide leading to the corresponding 1H-tetrazole via the [3+2] cycloaddition. Similarly, in the presence of diazoacetate esters the cavity showed an interesting catalytic activity promoting the 1,3-dipolar cycloaddition with electron-poor alkenes forming N containing heterocyclic compounds.
The interaction of dipolar compounds with capsule was investigated as well using N-oxides as guests. The strong H-bonding acceptor character of N-oxides caused a strong interaction with the hydroxyl groups of the resorcin[4]arene moieties that completely changed the reactivity of the guest with electron-rich aryl isocyanides. The formation of the corresponding diazo-compound as main product in the absence of the capsule moved to the urea derivative with supramolecular host in the reaction solution.
The cation-π interactions within the cavity was exploited to catalyse certain reactions known to involve the formation of cationic intermediates, even though the substrates were not suitable gusts for the cavity. This was the case of the sulfoxidation reaction of thioethers with H2O2 as oxidant and the acid catalysed hydration of alkynes. In both cases the stabilization of the intermediate cationic species within the cavity turned out to be pivotal for the catalytic effect observed.
Micelles are obtained from surfactants that self-assemble in water developing apolar nano-environment in polar media. Micelles made of commercial anionic sulfonated surfactants were employed to stabilize Pd-nanoparticles catalytic systems through a facile, economical and eco-friendly procedure. The achieved catalytic activity showed modulable depending on the surfactant employed, proving effective in hydrogenation, hydro-dehydration and hydrodechlorination reactions in water.
An intensive study was realized in order to find a suitable micellar medium capable to promote the multicomponent synthesis of triazoles from organic bromides, sodium azide and alkynes in a single step reaction. The direct synthesis of triazoles was reached avoiding the employment of the preliminary preparation of dangerous organic azides.
Finally, both supramolecular systems based on micelles in water and resorcin[4]arene in organic solvents were employed to achieve substrate selectivity. Micellar media allowed the preferential conversion of more hydrophobic substrate during competitive Heck and hydrogenation reactions. Conversely, the confined space within the cavity of the resorcin[4]arene capsule was employed to reach the preferential conversion of smaller substrates in the competitive condensation reaction between series of acids and amines with different lengths.
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Calzi, Mattia. "Functional Calculus on Homogeneous Groups." Doctoral thesis, Scuola Normale Superiore, 2019. http://hdl.handle.net/11384/85740.
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In the first part of the thesis, we consider the following problem.
Let G be a homogeneous group, and let (L_1,...,L_n) be a jointly hypoelliptic commutative finite family of formally self-adjoint, homogeneous, left-invariant differential operators without constant terms.
Then, the operators L_j are essentially self-adjoint as operators on L^2(G) with domain C^infty_c(G), and their closures commute emph{as self-adjoint operators}.
Therefore, one may consider the joint functional calculus associated with the family (L_1,...,L_n).
More precisely, for every bounded Borel measurable function $m$ on $R^n$, the corresponding operator m(L_1,...,L_n) commutes with left translations, so that it admits a unique right convolution kernel K(m).
The so-defined kernel transform K then maps S(R^n) continuously into S(G), and L^2(eta) isometrically into L^2(G) for some uniquely determined positive Radon measure eta on R^n; this latter property can be considered as an analogue of the Plancherel isomorphism.
In addition, K maps L^1(eta) continuously into C_0(G), and this property can be considered as an analogue of the Riemann--Lebesgue lemma.
We focus on the following properties of K:
(RL) if K(m)in L^1(G), then m can be taken in C_0(R^n): this is again an analogue of the Riemann--Lebesgue lemma;
(S) if K(m)in S(G), then m can be taken in S(R^n).
We prove that properties (RL) and (S) are compatible with products, and we characterize the Rockland operators which satisfy property (S) when the underlying group G is abelian.
We then consider the case of 2-step stratified groups, and families whose elements are either sub-Laplacians or vector fields of homogeneous degree 2. In this setting, we prove several sufficient conditions, as well as some necessary ones, for properties (RL) and (S); we even characterize them in some more specific settings.
In addition, we study the case of general (that is, not necessarily homogeneous) sub-Laplacians on 2-step stratified groups, and prove that they always satisfy properties (RL) and (S).
We also prove that, under some mild assumptions, a multiplier m can be taken so as to satisfy Mihlin--Hormander conditions of order infinity if and only if the corresponding kernel K(m) satisfies Calderon--Zygmund conditions of order infinity.
In the second part of the thesis, we present some results which are joint work with T. Bruno.
We fix the standard sub-Laplacian on an H-type group, and consider its heat kernel (p_s)_{s>0}. We provide sharp asymptotic estimates at $infty$ for basically all the derivatives of p_1. Because of the homogeneity of the family (p_s), these estimates can also be considered as short-time asymptotics.
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Zimmerli, Urs. "Limit cycles in homogeneous azeotropic distillation." Zürich : ETH, Eidgenössische Technische Hochschule Zürich, 2001. http://e-collection.ethbib.ethz.ch/show?type=dipl&nr=15.
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Funes, Ardoiz Ignacio. "Computational Chemistry for Homogeneous Redox Catalysis." Doctoral thesis, Universitat Rovira i Virgili, 2017. http://hdl.handle.net/10803/456826.
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Aquesta Tesis Doctoral s'ha centrat en l'estudi computacional mitjançant metodologia DFT (Teoria del funcional de la densitat) de reaccions redox catalitzades en fase homogènia. La primera part recau en l'estudi computacional de dos cicles catalítics d'acoblament oxidatiu. Aquest estudi ha aconseguit desxifrar una de les claus d'aquest tipus de reaccions, l'efecte de l'oxidant extern. Demostrem que en totes dues reaccions, diferents metalls de transició poden col•laborar per a donar una reacció més eficient i selectiva. A més a més, descobrim els factors claus per a la regioselectivitat de les dues reaccions estudiades. La segona reacció va ser estudiada en col•laboració amb el grup experimental del Prof. Frederic Patureau (University of Kaiserslautern).
La segona part de la tesis es centra en canvi en l'estudi teòric de la reacció d'oxidació de l'aigua catalitzada per complexes de la primera serie de transició. S'ha desenvolupat una nova família de catalitzadors mononuclears de coure en col•laboració amb el grup del Prof. Antoni Llobet (ICIQ). S'ha descobert un nou mecanisme de formació de l'enllaç oxígen-oxígen que consisteix en l'atac nucleòfil de l'aigua mitjançant la transferència d'un electró (SET-WNA). Un cop descobert aquest mecanisme, es va veure que també operava sobre altres catalitzadors de coure i ruteni, redefinint així el context mecanístic d'aquesta reacció en catàlisis homogènia.
Aquesta tesis, per tant, proporciona una profunda base mecanística sobre importants reaccions redox mitjançant la química computacional a través dels mètodes DFT.Esta Tesis Doctoral se ha centrado en el estudio computacional mediante metodología DFT (Teoría del funcional de la densidad) de reacciones redox catalizadas en fase homogénea. La primera parte versa sobre el estudio computacional de dos ciclos catalíticos de acoplamiento oxidativo. Este estudio dio con una de las claves en este tipo de reacciones, el efecto del oxidante externo. Demostramos en ambas reacciones como diferentes metales de transición podían colaborar para dar una reacción más eficiente y selectiva. Además descubrimos las claves para la regioselectividad en ambas reacciones. La segunda reacción fue estudiada en colaboración con el grupo experimental del profesor Frederic Patureau (University of Kaiserslautern). Por otro lado, la segunda parte de esta tesis se centra en el estudio teórico de la reacción de oxidación de agua catalizada por complejos de la primera serie de transición. Desarrollamos una nueva familia de catalizadores mononucleares de cobre con la colaboración experimental del grupo del profesor Antoni Llobet (ICIQ), descubriendo un nuevo mecanismo en la formación de enlace oxígeno-oxígeno, el ataque nucleófilo del agua mediante la transferencia de un electrón (SET-WNA). Tras esto extendimos este mecanismo a otros sistemas de cobre y de rutenio, redefiniendo el contexto mecanístico para esta reacción en catálisis homogénea. Esta tesis, por tanto, proporciona una profunda base mecanística sobre el estudio de importantes reacciones redox mediante química computacional a través de los métodos DFT.
This Doctoral Thesis is focused on the computational study by DFT methodology (Density Functional Theory) of homogeneous redox catalized reactions. The first part describes successfully the mechanism of two different catalytic cycles of oxidative coupling reactions. This study found out the explanation about one of the challenging questions on the field, the key role of the external oxidant. We demonstrated the cooperation between different transition metals is essential to catalyze the reaction efficiently and with good selectivities. Additionally, we explained also the regioselectivity of both reactions, in very good agreement with the experimental results. The second reaction was studied in collaboration with the experimental group of professor Frederic Patureau (University of Kaiserslautern). On the other hand, the second part of the thesis is focused on the theoretical study of water oxidation reaction catalyzed by first-row transition metal complexes. Firstly, we developed a new family of mononuclear copper complexes in collaboration with the experimental group of professor Antoni Llobet (ICIQ), discovering a new mechanism for the oxygen-oxygen bond formation step, the water nucleophilic attack. single electron transfer (SET-WNA). From this point, we extended the new mechanism to other catalytic systems based on copper and ruthenium, redefining the mechanistic scenario for the homogeneous catalytic version of this reaction. Therefore, this thesis provides a deep theoretical knowledge abour the homogeneous redox catalysis mechanisms by DFT calculations.
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Onyumbe, Okitowamba. "Groupoids of homogeneous factorisations of graphs /." Online access, 2008. http://etd.uwc.ac.za/usrfiles/modules/etd/docs/etd_gen8Srv25Nme4_9246_1278010591.pdf.
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Cederholm, Alex. "Homogeneous models of anechoic rubber coatings." Doctoral thesis, KTH, Aeronautical and Vehicle Engineering, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3611.
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Donzelli, Fabrizio. "Algebraic Density Property of Homogeneous Spaces." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/209.
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Let X be an affine algebraic variety with a transitive action of the algebraic automorphism group. Suppose that X is equipped with several fixed point free non-degenerate SL_2-actions satisfying some mild additional assumption. Then we prove that the Lie algebra generated by completely integrable algebraic vector fields on X coincides with the set of all algebraic vector fields. In particular, we show that apart from a few exceptions this fact is true for any homogeneous space of form G/R where G is a linear algebraic group and R is a proper reductive subgroup of G.
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Bloomberg, Deborah M. "Pedophilia a heterogeneous or homogeneous phenomenon?" Thesis, University of Ottawa (Canada), 1986. http://hdl.handle.net/10393/4562.
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Koshan, Jeffrey W. "Finite covers of homogeneous directed graphs." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0026/NQ51884.pdf.
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Stemp, Michael C. "Homogeneous catalysis in alkaline water electrolysis." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0019/MQ45844.pdf.
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Zondervan, Charon. "Homogeneous catalytic oxidation a ligand approach /." [S.l. : [Groningen : s.n.] ; University Library Groningen] [Host], 1997. http://irs.ub.rug.nl/ppn/298195445.
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Koshkin, Sergiy. "Homogeneous spaces and Faddeev-Skyrme models." Diss., Manhattan, Kan. : Kansas State University, 2006. http://hdl.handle.net/2097/171.
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Groot, Debby de. "Dendrimers as homogeneous transition metal catalysts." [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2001. http://dare.uva.nl/document/58731.
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Clancy, Dominic. "Homogeneous and inhomogeneous superstring cosmological models." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249229.
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Ypma, Fonger. "Deformation quantisation and noncommutative homogeneous spaces." Thesis, University of Oxford, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444947.
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Robb, Lynzi M. "Kinetic analysis of homogeneous catalytic reactions." Thesis, University of St Andrews, 2011. http://hdl.handle.net/10023/2562.
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Reaction progress kinetic analysis (RPKA) is a powerful tool for determining kinetic parameters of catalytic reactions. Many of the published articles that have used RPKA have employed reaction calorimetry for obtaining sufficient data to be reliable. The use of gas uptake measurements, in place of calorimetry is explored in this Thesis. Chapter 2 details the use of gas uptake measurements in establishing the order with respect to substrate and gas for the rhodium catalysed hydrogenation of 1-octene. Previous studies have used initial rate measurements to establish these orders and the reaction cycle is well known. The use of RPKA allows the same information to be established in two reactions. Chapter 3 focuses on the rhodium catalysed hydroformylation of 1-octene as it involves the reaction of one substrate with two gases. Using RPKA it is possible to determine the order in substrate and the overall order in gas, but it was found difficult to determine the order with respect to the individual gases using RPKA alone. Chapter 4 shows the palladium catalysed methoxycarbonylation of vinyl acetate. The reaction has two substrate concentrations changing simultaneously as well as a gas. This chapter shows that by careful design of experiments the orders with respect to each of these substrates and CO can be determined in minimal numbers of experiments. Chapter 5 focuses on the methoxycarbonylation of alkynes, which uses RPKA in complex multistep reactions, to establish if RPKA can be used to determine the kinetics with respect to the individual reacting components for each step. This study focuses on the methoxycarbonylation of phenylacetylene to produce methyl cinnamate as well as the methoxycarbonylation of both terminal and internal linear alkynes. These linear alkynes carbonylate to produce an α,β-unsaturated ester. The double bond is isomerised from its conjugated position along the chain to the terminal position where it is trapped and carbonylated to produce an α,ω-dieter product.
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Hoyes, James Russell. "Homogeneous and Particle-Driven Gravity Currents." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.515344.
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Taylor, Russell Alan. "Hydrogen bonding effects in homogeneous catalysis." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500138.
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Bosquain, Sylvain S. "Homogeneous and heterogeneous oxidations of alkylbenzenes." Thesis, University of York, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.288594.
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Schmidutz, Tobias Fabian. "Studies of a homogeneous Bose gas." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708544.
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Tear, Gareth Richard. "Shock properties of homogeneous anisotropic dielectrics." Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/53828.
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Anisotropy, the directional dependence of a physical quantity, is present in numerous physical processes involved in the shock compression of solid materials. The effect that a particular property’s anisotropy has on the propagation of a shock wave is obscured by other effects such as those from strain rate and material heterogeneity. Recent studies have focussed on single- and bi-crystal metals to understand the effect of crystal anisotropy on the mechanics of shock wave propagation. This thesis extends this work to optically transparent non-metallic dielectric single crystals by developing an optical model for anisotropic dielectrics and performing experimental measurements to test the validity of that optical model. Current optical models for shock compressed materials use an isotropic Gladstone- Dale model or isotropic modifications of the Gladstone-Dale model. This thesis extends the isotropic Gladstone-Dale model to an anisotropic photoelastic model for the optical behaviour of linear anisotropic materials under shock compression in the elastic regime. The model uses static photoelastic tensor values available in the literature to predict material response under uniaxial strain in an arbitrary crystal orientation. The effect of varying photoelastic tensor values is studied using Monte Carlo techniques, and confidence intervals on dynamic predictions are presented. Polarimetry is applied to experimentally measure birefringence under shock compression delivered using plate impact on a single stage light gas gun. This method is used to validate the linear photoelastic model developed in this thesis. Experiments were performed on < 10-10 > (a-cut) sapphire up to 15 GPa longitudinal stress and < 10-10 > (a-cut) calcite up to 2 GPa longitudinal stress. It was found that the birefringence of a-cut sapphire under shock compression behaved in agreement with the model in the elastic regime for a 5% error on the photoelastic tensor. Furthermore it was found that birefringence predictions for a-cut calcite as given by the same model did not agree with experimentally measured results. The discrepancy was 0.3% at 1.2 GPa, in excess of 5 standard deviations. Possible reasons for the discrepancy are put forward. Current optical models for shock compressed materials use an isotropic Gladstone-Dale model or isotropic modifications of the Gladstone-Dale model. This thesis extends the isotropic Gladstone-Dale model to an anisotropic photoelastic model for the optical behaviour of linear anisotropic materials under shock compression. The model uses static photoelastic tensor values available in the literature to predict material response under uniaxial strain in an arbitrary crystal orientation. The effect of varying photoelastic tensor values is studied using Monte Carlo techniques, and confidence intervals on dynamic predictions are presented. Polarimetry is applied to experimentally measure birefringence under shock compression. This method is used to validate the linear photoelastic model developed in this thesis. Experiments were performed on ⟨1 0 1 0⟩ (a-cut) sapphire and ⟨1 0 1 0⟩ (a-cut) calcite. It was found that the birefringence of a-cut sapphire under shock compression behaved in agreement with the model. Furthermore it was found that birefringence predictions for a-cut calcite as given by the same model did not agree with experimentally measured results. Possible reasons for the discrepancy are put forward.
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Holm, Tara Suzanne 1975. "Equivariant cohomology, homogeneous spaces and graphs." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/8463.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2002.Includes bibliographical references (p. 97-100).
The focus of this thesis is manifolds with group actions, in particular symplectic manifolds with Hamiltonian torus actions. We investigate the relationship between the equivariant cohomology of the manifold M and the fixed point data of the torus action. We are interested in understanding the topology of the space of T-orbits in M. In particular, we explore aspects of this topology which are determined by data from the image of a moment map [Phi] : M [right arrow] t* associated to the Hamiltonian action. To better understand the orbit space, we apply the algebraic techniques of equivariant cohomology to the study these systems further. Equivariant cohomology associates to a manifold with a G-action a ring H*G(M). Much of the topology of the orbit space is encoded in the equivariant cohomology ring H*G(M). In 1998, Goresky, Kottwitz and MacPherson provided a new method for computing this ring. Their method associates to this orbit space a graph [Gamma] whose vertices are the zero-dimensional orbits and edges the connected components of the set of one-dimensional orbits. The ring H*G(M) can then be computed combinatorially in terms of the data incorporated in [Gamma]. The strength of this construction is that it makes the computation of equivariant cohomology into a combinatorial computation, rather than a topological one. In the projects described herein, we apply the GKM theory to the case of homogeneous spaces by studying the combinatorics of their associated graphs. We exploit this theory to understand the geometry of homogeneous spaces with non-zero Euler characteristic.
(cont.) Next, we describe how to weaken the hypotheses of the GKM theorem. The spaces to which the GKM theorem applies must satisfy certain dimension conditions; however, there are many manifolds M with naturally arising T-actions that do not satisfy these conditions. We allow a more general situation, which includes some of these cases. Finally, we find a theory identical to the GKM theory in a setting suggested by work of Duistermaat. As in the GKM situation, this theory applies only when the spaces involved satisfy certain dimension conditions.
by Tara Suzanne Holm.
Ph.D.
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Harris, Thomas Clive. "Homogeneous and particle-driven gravity currents." Thesis, University of Cambridge, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.624500.
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