Dissertations / Theses on the topic 'Energy functional'

In modelling the energetics of molecules and solids, the need for practical electron density functionals that seamlessly include the van der Waals interaction is growing. Such functionals are still in their infancy, and there is yet much experimentation to be performed in the formulation and numerical testing of the requisite approximations. A ground-state density functional approach that uses the exact relations of the adiabatic connection formula and the fluctuation-dissipation theorem to obtain the xc energy from the density-density response function seems promising, though a direct local density approximation for the interacting susceptibility will fail to yield the vdW interaction. Significant nonlocality can be built into the interacting susceptibility by screening a 'bare' susceptibility, for which a carefully chosen constraint-obeying local approximation is sufficient to yield a non-trivial van der Waals energy [6]. The constraints of charge conservation, and no response to a constant potential, are guaranteed by expressing the bare susceptibility in terms of the double gradients of a nonlocal bare polarisability. for which it should be easier to make an approximation based on physical principles than it would be for the susceptibility. The 'no-flow' condition is also deemed important. In this work, a simple delta-function approximation for the nonlocal polarisability is fully constrained by a new version of a recently-discovered force theorem (sum rule), requiring the additional input of the independent-electron Kohn-Sham potential. This constrained polarisability cannot be used as input for the seamless vdW scheme, which requires a non-delta-function bare polarisability, and is instead applied to systems containing spherical fragments in a perturbative/asymptotic fashion for calculation of the widely-separated van der Waals interaction. The main thrust of this work is an investigation of the efficacy of the force theorem to constrain simple approximations for response quantities. Many recent perturbative vdW density functionals are based on response functions that are electron-hydrodynamical approximations to the response of the uniform electron gas. These schemes require their response functions to be 'cut off' at low density and high density-gradient, where the approximation overestimates the true response. The imposition of the cut-off is crucial to the success of such schemes. Here, we replace the cut-off with an exact theorem (the force theorem) which naturally 'ties down' the response, based on the potential- and density-functions of the system. This is the first time that the force theorem has been directly applied as a constraint upon a model response function (its original use, by Vignale and Kohn (7), was as an exact identity in time-dependent DFT). Also new in this work is the orbital-by-orbital Kohn-Sham version of the force theorem, and its proof (differing significantly from Vignale's original derivation (8) of the interacting theorem) by directly appealing to the Kohn-Sham orbitals makes its first appearance here. For quantum dots, our constrained response-approximation exactly recovers the net linear dipole response, due mainly to the force theorem's ideal applicability to harmonically confined systems. For angularly-averaged atoms, reasonable static dipole polarisabilities are obtained for the independent-electron Kohn-Sham (bare) case. The results are poor for the fully-interacting case, attributable to the local nature of the approximation. This lends weight to the assertion that it is better to approximate a bare quantity, then screen it, than it is to directly approximate a fully-interacting quantity. Dynamic net polarisabilities constrained by the force theorem are guaranteed to have the correct high-frequency asymptotic convergence to the free electron response. It is seen that the calculated dynamic polarisabilities for atoms are too small at intermediate frequencies, since the calculated vdW C6 coefficients (Hamaker constants) of atomic dimers are up to an order of magnitude too small, even without the use of a low-density cutoff. It is seen that our constrained local model response is non-analytic along the imaginary-frequency axis, and this is very detrimental to the C6 calculations, even though the integrated net polarisability is analytic. Improvement of the polarisability ansatz is indicated, perhaps to a non-deltafunction uniform-gas-based approximation. The use of pseudopotentials may improve the force theorem results, by softening the extreme nature of the bare Coulomb potential.

Nanostructuring functional materials can lead to a variety of enhanced intrinsic material properties. In particular, nanowires (NWs) have large surface-to-volume ratio and large aspect ratio (length / diameter), which makes them sensitive to low-amplitude vibrations and have increased flexibility compared to the bulk form of the material. In this thesis, piezoelectric, ferroelectric, ferromagnetic and magnetoelectric (ME) NWs have been explored in the context of vibrational energy harvesting and magnetic energy harvesting and sensing; because of their increased piezoelectric coefficients and ME coupling compared to bulk. Low-temperature, solution-processable and hence scalable fabrication techniques have been used throughout this work. Electrochemical deposition or electrodeposition (ED) in conjunction with nanoporous templates i.e. template-assisted electrodeposition (TAED) have been used to grow piezoelectric zinc oxide (ZnO) and ferromagnetic nickel (Ni) NWs and three template-wetting based techniques have been used to grow ferroelectric poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) NWs and nanotubes (NTs). Both techniques have been optimised and subsequently combined to synthesise core-shell or (1-1) Ni - P(VDF-TrFE) composite NWs. The structural and crystalline properties of each type of nanostructure has been studied using a variety of techniques including: scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM) and all of the NWs have been shown to be polycrystalline. The energy harvesting performance of vertically aligned ZnO NW arrays embedded in flexible, polycarbonate (PC) templates when incorporated into a flexible nanocomposite nanogenerator (NG), has been tested via periodic impacting and flexing of the NG at different frequencies. The voltage ($V$), current ($I$) and power were recorded during testing and measured across a range of external load resistances. The aligned nature of the embedded NWs ensures good piezoelectric performance across the entire device under impacting, while the PC template ensures mechanical stability and longevity of the device, confirmed by good fatigue performance over 24 hours of continuous testing, which is rarely studied in this field. The power density ($P_\mathrm{d}$) was found to be 151 mW m$^{-3}$ for low-amplitude (0.68 mm) and low-frequency (5 Hz) impacting, resulting in energy conversion efficiencies ($\chi$) and device efficiencies ($\chi$') of $\approx$ 4.2 \% and $\approx$ 3.76 x 10$^{-3}$ \% respectively. The nanoscale or surface piezoelectric charge coefficient ($d_{33}$) was measured to be $\approx$ 12.5 pm V$^{-1}$ on an individual ZnO NW, using a combination of Kelvin probe force microscopy (KPFM) and non--destructive piezoresponse force microscopy (ND-PFM). Both nanoscale and bulk ME measurements have been performed on Ni - P(VDF-TrFE) ME composite (1-1) NWs, nanocomposite (1-3) films and (2-2) laminates. The latter two structures have been fabricated using TAED and ED for the Ni NW and film respectively, in combination with drop-casting and spin-coating for the P(VDF-TrFE) films. The scanning probe microscopy (SPM) measurements used here include atomic force microscopy (AFM), KPFM, magnetic force microscopy (MFM) and piezoresponse force microscopy (PFM) and it has been found that the ME coupling in the (1-1) composites NWs is enhanced compared to the other structures, confirmed by approximating the converse ME coupling coefficient ($\alpha^\mathrm{C}$) of each composite. Additionally, vibrating sample magnetometry (VSM) has been used to confirm the ferromagnetic nature of the Ni phases in the composite structures. ME composite devices based on (2-2) and (1-3) composite materials and have been fabricated and preliminary bulk ME measurements of the ME coupling coefficient ($\alpha^\mathrm{E}$) plus energy harvesting measurements have also been performed as a proof of concept that the nanoscale ME coupling translates to the bulk, to some extent.

La nature intermittente de l'énergie solaire est souvent résolue par un couplage entre le PV et une batterie. Notre approche plus fondamentale vise à développer des matériaux capables de combiner ces deux fonctions à l'échelle moléculaire. Des nanocristaux de TiO2 de 5 nm ont été synthétisés dans notre groupe, ce qui a permis une réaction quantitative de photorecharge sous illumination standard. Nous présentons ici une étude originale portant sur l'évolution des propriétés optoélectroniques et de la dynamique du transfert de charge dans une électrode de TiO2 à l'aide d'expériences spectroscopiques in operando effectuées pendant le fonctionnement de la batterie. L'augmentation de la valeur de la bande interdite et de l'absorbance a été observée lors de l'insertion du lithium dans TiO2. Un décalage négatif en énergie de la bande de conduction indique un potentiel plus oxydant des trous photogénérés dans le Li0.6TiO2 par rapport au TiO2 initial. En analysant les processus de recombinaison dans Li0.6TiO2, nous avons établi une compétition entre les processus ultra-rapides (gamme ps) de recombinaison directe et de transfert de charge vers Ti3+ dans Li0.6TiO2, ce qui limite potentiellement le rendement de la réaction de photorécharge. Cette étude a été étendue à d'autres matériaux d'insertion généralement utilisés dans les batteries lithium-ion (Li4Ti5O12, LiCoO2, LiFePO4, MoO3, etc.). Les positions de bord de bande, la bande interdite, le type de porteurs de charge et leur concentration ont été mesurées et rassemblées dans une base de données. Basé sur ces résultats, la possibilité de photorécharge induite par la lumière a été évaluée et les premiers résultats discutés
The problem of intermittent nature of solar energy is often addressed by the traditional coupling of the PV and battery units. Our more fundamental approach targets the development of materials able to combine solar energy conversion and storage at the molecular level. The 5 nm anatase TiO2 nanocrystals were synthesized in our group affording a quantitative photorecharge reaction by a sole contribution of illumination. Here, we present a study of the evolution of the optoelectronic properties and dynamics of charge transfer in TiO2 electrode using in situ / in operando experiments performed during the battery functioning (UV-visible, Mott-Schottky, fluorescence spectroscopy). The increase of the bandgap value and the rise of absorbance are observed upon lithium insertion into TiO2. A negative shift of the conduction band indicates a more oxidizing potential of the photogenerated holes in Li0.6TiO2 compared to TiO2. By analysis of the recombination processes in TiO2 upon lithium insertion, we established a competition of the ultra-fast (ps range) processes of direct recombination and charge transfer towards Ti3+ in Li0.6TiO2, potentially limiting the yield of the photorecharge reaction. This study was extended to other insertion materials typically used in lithium-ion batteries (Li4Ti5O12, LiCoO2, LiFePO4, MoO3, etc.). The measured band edge positions, band gap, charge carrier type and concentration were gathered into a database, based on which the fundamental evaluation of the possibility of the light-induced photorecharge was conducted. The first results of the photoelectrochemical study of chosen materials are also discussed

Density Functional Theory (DFT) is an important tool in the treatment of quantum many-body problems. In spite of being exact in principle, the application of DFT requires the use of approximations, because it involves an unknown universal functional called the exchange-correlation energy. In this thesis we describe an accurate and efficient extension of Chawla and Voth's planewave based algorithm for calculating exchange energies, exchange energy densities, and exchange energy gradients with respect to wave function parameters in systems of electrons subject to periodic boundary conditions. The theory and numerical results show that the computational effort scales almost linearly with the number of plane waves and quadratically with the number of k vectors. To obtain high accuracy with relatively few k vectors, we use an adaptation of Gygi and Baldereschi's method for reducing Brillouin zone integration errors. We then generate a large database of highly accurate exchange energy densities in 106 artificial but realistic solid-state systems. We use the database not only to examine the accuracy of some important existing exchange functionals, but also to show that there exists a smooth function of the local electron density, its gradient and Laplacian that fits our data well. We also study the effects of twist-averaging on the finite-size errors in the exchange energy of a uniform electron gas, using the Ewald, model periodic Coulomb (MPC) and screened Coulomb interactions. In the case of the Ewald interaction, this investigation is carried out in both the canonical (fixed particle number) and grand-canonical (fixed Fermi wave vector) ensembles. Finally, we study the new reciprocal-space approach to the . Coulomb finite-size errors introduced by Chiesa et al. and find that it is almost equivalent to the use of the MPC interaction.

Polymer-based piezoelectric and triboelectric generators form the basis of well-known energy harvesting methods that are capable of transforming ambient vibrational energy into electrical energy via electrical polarization changes in a material and contact electrification, respectively. However, the low energy conversion efficiency and limited thermal stability of polymeric materials hinder practical application. While nanostructured polymers and polymer-based nanocomposites have been widely studied to overcome these limitations, the performance improvement has not been satisfactory due to limitations pertaining to long-standing problems associated with polymeric materials; such as low crystallinity of nanostructured polymers, and in the case of nanocomposites, poor dispersion and distribution of nanoparticles in the polymer matrix. In this thesis, novel functional polymeric nanomaterials, for stable and physically robust energy harvesting applications, are proposed by developing advanced nanofabrication methods. The focus is on ferroelectric polymeric nanomaterials, as this class of materials is particularly well-suited for both piezoelectric and triboelectric energy harvesting. The thesis is broadly divided into two parts. The first part focuses on Nylon-11 nanowires grown by a template-wetting method. Nylon-11 was chosen due to its reasonably good ferroelectric properties and high thermal stability, relative to more commonly studied ferroelectric polymers such as polyvinylidene fluoride (PVDF) and polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)). However, limitations in thin-film fabrication of Nylon-11 have led to poor control over crystallinity, and thus investigation of this material for practical applications had been mostly discontinued, and its energy harvesting potential never fully realised. The work in this thesis shows that these problems can be overcome by adopting nanoporous template-wetting as a versatile tool to grow Nylon-11 nanowires with controlled crystallinity. Since the template-grown Nylon-11 nanowires exhibit a polarisation without any additional electrical poling process by exploiting the nanoconfinement effect, they have been directly incorporated into nano-piezoelectric generators, exhibiting high temperature stability and excellent fatigue performance. To further enhance the energy harvesting capability of Nylon-11 nanowires, a gas -flow assisted nano-template (GANT) infiltration method has been developed, whereby rapid crystallisation induced by gas-flow leads to the formation of the ferroelectric δʹ-phase. The well-defined crystallisation conditions resulting from the GANT method not only lead to self-polarization but also increases average crystallinity from 29 % to 38 %. δʹ-phase Nylon-11 nanowires introduced into a prototype triboelectric generator are shown to give rise to a six-fold increase in output power density as observed relative to the δʹ-phase film-based device. Interestingly, based on the accumulated understanding of the template-wetting method, Nylon-11, and energy harvesting devices, it was found that thermodynamically stable α-phase Nylon-11 nanowires are most suitable for triboelectric energy generators, but not piezoelectric generators. Notably, definitive dipole alignment of α-phase nanowires is shown to have been achieved for the first time via a novel thermally assisted nano-template infiltration (TANI) method, resulting in exceptionally strong and thermally stable spontaneous polarization, as confirmed by molecular structure simulations. The output power density of a triboelectric generator based on α-phase nanowires is shown to be enhanced by 328 % compared to a δʹ-phase nanowire-based device under the same mechanical excitation. The second part of the thesis presents recent progress on polymer-based multi-layered nanocomposites for energy harvesting applications. To solve the existing issues related to poor dispersion and distribution of nanoparticles in the polymer matrix, a dual aerosol-jet printing method has been developed and applied. As a result, outstanding dispersion and distribution. Furthermore, this method allows precise control of the various physical properties of interest, including the dielectric permittivity. The resulting nanocomposite contributes to an overall enhancement of the device capacitance, which also leads to high-performance triboelectric generators. This thesis therefore presents advances in novel functional polymeric nanomaterials for energy harvesting applications, with improved performance and thermal stability. It further offers insight regarding the long-standing issues in the field of Nylon-11, template-wetting, and polymer-based nanocomposites.

Porous materials are useful in various energy and environmental applications such as electrodes for supercapacitive energy storage, gas storage media, and sieves for the removal of toxic chemicals. Carbonaceous materials derived from biomass have been widely used, but the properties obtained are variable as a result of the variation in the composition of the biomass often used to form them. The use of functionalised polymers as carbonisation precursors allows greater control of the structure and heteroatom doping in the resulting carbon. This thesis examines the largely unexplored route of carbonising porous organic networks, which have multiple advantages over non-porous and pre-carbonised analogues. This yields interesting properties for energy and gas storage applications. Only a few papers had been published in this area prior to the start of this PhD project, and there were no reports of carbonisation for the polymer networks investigated here. Thus, a range of methods and conditions were tested to prepare materials with excellent performance in their respective applications. This project also tackles the problem of toxic mercury contamination in water by developing microporous materials synthesised from low-cost, waste by-products.

Ce travail intitulé « Systèmes Conjugués Fonctionnelle pour la Conversion et le Stockage de l'Energie » porte sur la conception et la synthèse de nouvelles classes de systems π-conjugués fonctionnels pour la conversion photovoltaïque et le développement de nouveaux matériaux microporeux. Après une présentation générales de la structure et des propriétés électroniques des principales classes de systèmes conjugués et plus particulièrement des molécules conjuguées utilisées comme matériaux donneur dans les cellules solaires organiques (CSO), le second chapitre décrit la synthèse et l'étude d'une série de donneurs moléculaires obtenus par greffage de groupes dicyanovinle sur trois types de blocs conjugués rigides : carbazole cyclopentadithiophène et dithiénopyrrole (DTP). L'évaluation de ce systèmes dans des CSOs de type hétérojonction donneur-accepteur bicouche montre que le DTP conduit aux meilleurs résultats. Une étude de l'évolution des propriétés électroniques d'une série d'oligo-DTPs avec la longueur de la chaîne confirme par ailleurs l'intérêt de ce bloc donneur pour la conception de systèmes conjugués à faible bande interdite. Le chapitre suivant traite de la synthèse d'une série de molécules conjuguées de type donneur-accepteur-donneur (D-A-D) construites autour d'un cœur isoindigo ou alcoxy-cyanobithiophène et décrit une première anlyse de leurs potentialités comme matériaux donneurs dans les CSOs. Le quatrième chapitre porte sur la synhtèse d'une séries de molécules 3D issues du greffage de groupes donneurs sur une cœur quaterthiophène de géométrie quasi-tétraédrique engendrée par effet stérique et étudie les relations entre la structure des molécules la mobilité des charges positives dans les matériaux correspondants et les performances dans des CSOs. Enfin le cinquième et dernier chapitre décrit les premières étapes vers la conception et l'utilisation de molécules conjuguées 3D en vue de développer de nouvelles classes de matériaux électroactifs microporeux par polymérisation de systèmes moléculaires 3D munis de groupes terminaux réactifs
This work entitled « Functional Conjugated Systems for Energy Conversion and Storage » involves the design and synthesis of new classes of functional π-conjugated systems for photovoltaic conversion and the development of new microporous materials. After a general introduction to the structure and electronic properties of the major classes of conjugated systems and more particularly conjugated molecules used as donor material in organic solar cells (OSC), the second chapter describes the synthesis and study of a series of molecular donors obtained by grafting dicyanovinylene on three types of conjugated rigid blocks : carbazole, cyclopentadithiophene and dithienopyrrole (DTP). The evaluation of these systems in donor-acceptor bilayer heterojunction OSCs shows that the DTP leads to best results. A study of the evolution of the electronic properties, of a series of oligo-DTPs, with the chain length further confirms the interest of the donor block for low band gap conjugated systems. The next chapter deals with the synthesis of a series of conjugated molecules of donor-acceptor-donor (D-A-D) type, built around a core of isoindigo, and describes a first evaluation of their potential as donor materials in OSCs. The fourth chapter deals with the synthesis of a series of 3D molecules derived from the grafting of donor groupas on a quaterthiophene core with a quasi-tetrehedral geometry caused by steric effect, and examine the relationship between the structure of the molecules, the mobility of positive charges in these materials and their performance in OSCs. Finally the fift and last chapter describes the first steps towards the design and use of 3D conjugated molecules in order to develop new classes of electro-active materials by polymerization of microporous 3D molecular systems provided with reactive end groups

Windows are the least insulated components in the modern buildings envelopes. The energy-efficiency glazing units have been developed and used to reduce the heat loss from windows. As a type of most common glass product, insulating glass units (IGUs) have been widely adopted in the residential and commercial buildings. A type of new design of glazing units, vacuum glazing units (VGUs), has also been developed to further enhance the insulation performance. Research on the structural/durability behaviours of such new insulating glazing units is relatively limited, although the structural behaviours and safety of monolithic or laminated glass panels have been abundantly studied. This thesis intends to fill in this gap by performing thorough assessments on the structural performance of IGUs and VGUs under various environmental actions.

The focus of this doctoral thesis is the atomic level design of photocatalysts and gas sensing materials. The band gap narrowing in the metal oxides for the visible-light driven photocatalyst as well as the interaction of water and gas molecules on the reactive surfaces of metal oxides and the electronic structure of kaolinite has been studied by the state-of-art calculations. Present thesis is organized into three sections. The first section discusses the possibility of converting UV active photocatalysts (such as Sr2Nb2O7, NaTaO3, SrTiO3, BiTaO4 and BiNbO4) into a visible active photocatalysts by their band gap engineering. Foreign elements doping in wide band gap semiconductors is an important strategy to reduce their band gap. Therefore, we have investigated the importance of mono- and co-anionic/cationic doping on UV active photocatalysts. The semiconductor's band edge position is calculated with respect to the water oxidation/reduction potential for various doping. Moreover, the tuning of valence and conduction band edge position is discussed on the basis of dopant's p/d orbital energy. In the second section of thesis the energetic, electronic and optical properties of TiO2, NiO and β-Si3N4 have been discussed to describe the adsorption mechanism of gas molecules at the surfaces. The dissociation of water into H+ or OH- occurs on the O-vacancy site of the (001)-surface of rutile TiO2 nanowire, which is due to the charge transfer from Ti atom to water molecule. The dissociation of water into OH- and imino (NH) groups is also observed on the β-Si3N4 (0001)-surface due to the dangling bonds of the lower coordinated N and Si surface atoms. Fixation of the SO2 molecules on the anatase TiO2 surfaces with O-deficiency have been investigated by Density Functional Theory (DFT) simulation and Fourier Transform Infrared (FTIR) spectroscopy. DFT calculations have been employed to explore the gas-sensing mechanism of NiO (100)-surface on the basis of energetic and electronic properties. In the final section the focus is to describe the optical band gap of pristine kaolinite using the hybrid functional method and GW approach. Different possible intrinsic defects in the kaolinite (001) basal surface have been studied and their effect on the electronic structure has been explained. The detailed electronic structure of natural kaolinite has been determined by the combined efforts of first principles calculations and Near Edge X-ray Absorption Fine Structure (NEXAFS).

Les supernovæ à effondrement de cœur sont l’un des phénomènes connus les plus puissants de l’univers. Elles résultent de l’explosion d’étoiles très massives, ayant brûlé tout leur combustible. Le résidu chaud et compact, appelée proto-étoile à neutrons, se refroidit pour devenir une étoile à neutrons, objet inerte. La dynamique et la structure des étoiles compactes, c’est-à-dire les supernovæ à effondrement de cœur, les proto-étoiles à neutrons et les étoiles à neutrons, ne sont pas encore complètement connues, et sont aujourd’hui au cœur d’intenses recherches, en association avec les observations astrophysiques et les expériences nucléaires. L’un des ingrédients clés de la modélisation d’étoile compacte concerne l’équation d’état. La difficulté de l’obtention d’une équation d’état réaliste et consistante pour tous ces objets stellaires réside dans le fait que l’on doit considérer une large variété de conditions thermodynamiques, c’est-à-dire des valeurs de densités, de fractions de protons et de températures, très différentes. Le travail de cette thèse consiste à modéliser, à partir des degrés de libertés nucléoniques, la structure microscopique ainsi que la composition interne de la matière baryonique des étoiles compactes, afin d’obtenir une équation d’état réaliste et unifiée. En particulier, on est intéressé à utiliser un formalisme qui peut s’appliquer à des densités aussi bien sous-saturées que sur-saturées, et qui, à la limite thermodynamique de température nulle, est compatible avec les interactions effectives modernes et réalistes données par la théorie microscopique d’Hartree-Fock-Bogoliubov et contraintes par les expériences nucléaires. Pour atteindre cet objectif, on présente, pour la matière sous-saturée, un modèle en équilibre statistique nucléaire, qui correspond à une superposition statistique de configurations finies, appelées cellules de Wigner-Seitz. Chaque cellule contient un noyau, ou agrégat, baignant dans un gaz homogène d’électrons ainsi que dans un gaz homogène de neutrons et de protons. Au sein de chaque cellule, on étudie les différentes composantes de l’énergie nucléaire des agrégats en interaction avec les gaz. L’utilisation de la théorie nucléaire de champ moyen pour la description des agrégats ainsi que du gaz de nucléons permet de traiter de façon consistante la matière sous-saturée et la matière sur-saturée. À des densités de plus de deux-trois fois la densité de saturation, l’apparition de degrés de liberté supplémentaires pose de nouveau des problèmes de consitance théorique qui ne sont pas traités dans cette thèse. La thèse est organisée selon trois parties. Dans la partie I, on présente le modèle en équilibre statistique nucléaire, basé sur l’ensemble grand canonique et sur les interactions non relativistes de Skyrme. Des résultats en équilibre β sont présentés, et l’importance de la distribution en masse d’agrégats d’une part, et d’un traitement réaliste de l’énergie libre d’autre part, est discutée. Dans la partie II, on étudie le comportement fonctionnel de l’énergie baryonique des cellules de Wigner-Seitz, en utilisant l’approximation de Thomas-Fermi étendue. En particulier, les effets de volume et de surface dus au milieu stellaire sont étudiés, et leur dépendance en termes de taille et d’asymétrie du noyau, ainsi que de densité et d’asymétrie du gaz de nucléons est analysée. Des résultats préliminaires de l’effet de l’interaction de surface du milieu sont présentés, sous hypothèse de certaines approximations et dans le cas de l’équilibre β. Dans la partie III, on développe des approximations afin d’obtenir une expression analytique fiable de formule de masse, directement reliée à la forme fonctionnelle et aux paramètres de l’interaction de Skyrme. Dans cette partie, on se concentre principalement sur les noyaux dans le vide, et l’on analyse les différentes composantes de l’énergie de liaison en termes de propriétés de volume et de surface, ainsi que de propriétés isoscalaire et isovecteur
The core collapse supernova is one of the most powerful known phenomena in the universe. It results from the explosion of very massive stars after they have burnt all their fuel. The hot compact remnant, the so-called proto-neutron star, cools down to become an inert catalyzed neutron star. The dynamics and structure of compact stars, that is core collapse supernovae, proto-neutron stars and neutron stars, are still not fully understood and are currently under active research, in association with astrophysical observations and nuclear experiments. One of the key components for modelling compact stars concerns the Equation of State. The task of computing a complete realistic consistent Equation of State for all such stars is challenging because a wide range of densities, proton fractions and temperatures is spanned. This thesis deals with the icroscopic modelling of the structure and internal composition of baryonic matter with nucleonic degrees of freedom in compact stars, in order to obtain a realistic unified Equation of State. In particular, we are interesting in a formalism which can be applied both at sub-saturation and super-saturation densities, and which gives in the zero temperature limit results compatible with the microscopic Hartree-Fock-Bogoliubov theory with modern realistic effective in- teractions constrained on experimental nuclear data. For this purpose, we present, for sub-saturated matter, a Nuclear Statistical Equilibrium model which corresponds to a statistical superposition of finite configurations, the so-called Wigner-Seitz cells. Each cell contains a nucleus, or cluster, embedded in a homogeneous electron gas as well as a homogeneous neutron and proton gas. Within each cell, we investigate the different components of the nuclear energy of clusters in interaction with gases. The use of the nuclear mean-field theory for the description of both the clusters and the nucleon gas allows a theoretical consistency with the treatment at saturation and beyond. At densities above two-three times saturation, other degrees of freedom are expected to appear, which potentially lead to other consistency problems but this issue will not be treated in this thesis. The thesis is divided into three parts. In part I, we present the Nuclear Statistical Equilibrium model based on the grand canonical statistics and non-relativistic Skyrme interactions. Results at β-equilibrium are shown and the importance of the clusters distribution as well as a realistic treatment for the free energy model is discussed. Part II investigates the functional behavior of the baryonic energy in the Wigner-Seitz cell within the Extended-Thomas-Fermi approximation. In particular, both bulk and surface in-medium effects are studied, and their dependence on cluster size and asymmetry as well as gas densities and asymmetry is investigated. A preliminary result of in-medium surface effects is presented within some approximations in the case of β-equilibrated matter

The main aim of this thesis is the development of $^{17}$O solid-state nuclear magnetic resonance (NMR) spectroscopic techniques to study the local structure and ion dynamics of functional oxide materials for applications in energy conversion, in particular as electrodes and electrolytes in solid oxide fuel cells (SOFCs). Broadly, the work comprises two related areas: (1) application of a combined experimental and computational methodology to enable the first $^{17}$O solid-state NMR studies of paramagnetic oxides, in particular a class of perovskite-derived structures used as mixed ionic-electronic conductors (MIECs) for SOFC cathodes, and (2) further uses of multinuclear variable-temperature NMR spectroscopy, with emphasis on $^{17}$O NMR results, to elucidate mechanistic details of oxide-ion motion and sublattice exchange in a novel family of promising SOFC electrolyte materials based on $\delta$-Bi$_{2}$O$_{3}$. In the first section, $^{17}$O magic-angle spinning (MAS) NMR spectra of the paramagnetic MIEC, La$_{2}$NiO$_{4+\delta}$, are presented and rationalized with the aid of periodic DFT calculations. Advanced NMR pulse programming and quadrupolar filtering techniques are coupled to extract high-resolution spectra. In particular, these data reveal local structural distortions in La$_{2}$NiO$_{4+\delta}$ that arise from incorporation of interstitial oxide defects. Moreover, variable-temperature spectra indicate the onset of oxide-ion motion involving the interstitials at 130 °C, which is linked to an orthorhombic$-$tetragonal phase transition. By analyzing the ion dynamics on the spectral timescale, specific motional mechanisms are elucidated that prove relevant to understanding the functionality and conductivity of this phase. Next, a similar methodology is applied to the Sr-doped analogues, La$_{2-x}$Sr$_{x}$NiO$_{4+\delta}$, in an exploration of the defect chemistry and electronic structure of these phases (0 $\leq {x} \leq$ 1). By following the doping-induced evolution of spectral features assigned to interstitial and equatorial oxygen environments, changes in the ionic and electronic conductivity, respectively, are rationalized. This approach has been extended to the acquisition and assignment of $^{17}$O NMR spectra of isostructural Sm$_{2-x}$Sr$_{x}$NiO$_{4+\delta}$ and Pr$_{2-x}$Sr$_{x}$NiO$_{4+\delta}$ phases, promising SOFC cathode materials that exhibit paramagnetism on the A site (A = Sm, Pr). The final section details the characterization of oxide-ion motion in the fluorite-type phases Bi$_{1-x}$V$_{x}$O$_{1.5+x}$ and Bi$_{1-x}$P$_{x}$O$_{1.5+x}$ ($x$ = 0.087 and 0.148) developed as SOFC electrolytes. Variable-temperature NMR experiments between room temperature and 923 K reveal two distinct mechanisms. For the V-doped phases, an oxide-ion conduction mechanism is observed that involves oxygen exchange between the Bi-O sublattice and rapidly rotating VO$_{4}$ tetrahedral units. The more poorly conducting P-doped phase exhibits only vacancy conduction with no evidence of sublattice exchange, a result ascribed to the differing propensities of the dopants to undergo variable oxygen coordination. These initial insights suggest chemical design rules to improve the next generation of oxide-ion conducting materials.

The microstructure of the lung is complex, containing many branching airways and alveolar sacs for optimal gas exchange. Lung diseases such as cystic fibrosis (CF), asthma, and emphysema lead to a destruction of this microstructure. As such, there is a growing interest in the early identification and assessment of lung disease using non invasive imaging techniques. Pulmonary function tests such as spirometry and plethysmography are currently used for this purpose but can only provide quantitative lung function measurements rather than direct measurements of lung physiology and disease. Computed tomography (CT) has also been used but due to risk of cell damage and mutation from the ionising radiation, long term monitoring of the lungs is severely constrained. Recently, new methods based on magnetic resonance imaging (MRI) have been developed to provide diagnostic imaging of the lung. Conventional MRI is not very well suited for lung imaging due to the very low proton density of the pulmonary airspaces. This problem can be overcome by making the patient inspire noble gases such as 3He whose polarisations have been vastly increased through optical pumping. Therefore 3He MRI permits a non-invasive determination of lung function. The high diffusion coefficient of 3He can be exploited to probe the microstructure of the lung. By measuring how fast 3He diffuses within the lung, the size of the lung microstructure can be assessed. Normally, the airspace walls impede the diffusion of the gas but for diseased lungs where microstructure has been destroyed, diffusion is less restricted and a higher apparent diffusion coefficient (ADC) is observed. The research conducted for this thesis focused on the measurement of ADC using three different MRI pulse sequences with each sequence being designed to assess the peripheral airspaces over different length scales. These sequences were then implemented on three different subject study groups.

Diels-Alder chemistry was utilized to manipulate the surface energy of glass substrates in reversible manner. Glass slides and capillaries were functionalized with hydrophobic dieneophiles resulting in a non-wetting surface. A retro Diels-Alder reaction facilitated by the thermal treatment of the surface’s function to cleave the hydrophobic dieneophile and resulted in the fabrication of a hydrophilic surface. Contact angle (CA) measurements were used as preliminary measurements for monitoring the changes in surface energy exhibited during the initial hydrophobic state (CA - 70±3°), after attachment of the dieneophile creating a hydrophobic state (CA - 101±9°) followed by reestablishment of the hydrophilic state (CA - 70±6°) upon cleavage of the Diels-Alder adduct. The treatments developed on flat glass surfaces were transferred to glass capillaries, with effective treatment confirmed by fluid column measurements. Effective flow gating was developed in the capillaries via patterning of the surface with hydrophilic/hydrophobic regions. Finally, attempts to create self-pressurizing capillaries were unsuccessful due to pronounced contact angle hysteresis for the hydrophobic surface treatment. Indium-tin oxide (ITO) substrates were functionalized with successive surface intiated atom transfer radical polymerization (SI-ATRP) and electropolymerization. A novel hybrid styrenic/thiophene monomer (ProDOT-Sty) was synthesized and employed in the polymerization events. This unique monomer and combination of polymerization methods allowed for the templation of electropolymerized poly(3,4-alkyleneoxythiophene) brushes by first creating a poly(styrene) backbone via SI-ATRP. An ITO electrode functionalized with poly(ProDOT-Sty) brushes grafted from the ITO surface via SI-ATRP was analyzed via cyclic voltammetry which clearly indicated the electropolymerization event beginning at approximately +0.7 V vs Fc/Fc+. Photo patterning of the phosphonic acid ATRP initiator immobilized on the ITO surface was undertaken in order to create a surface that would limit growth of the polymer species to a patterned area for facile film brush thickness characterization via atomic force microscopy (AFM) at a later time. This was accomplished via lithography with ultraviolet radiation (UV) and was confirmed via scanning electron microscopy (SEM). A nanohetero structure composed of platinum tipped cadmium selenide seeded, cadium sulfide nanorods (CdSe@CdS-Pt NRs). CdSe quantum dots (QDs) with variable sizes were prepared by adjusting reaction temperatures and times. CdS nanorods were then grown utilizing the CdSe QDs as seeds. Various lengths of the CdSe@CdS NRs were produced that ranged from ~25 nm to ~135 nm. Investigation of the influence of the various synthetic conditions of the nanorod synthesis led to the conclusion that the ratio of CdSe seeds to Cd and S precursors could be manipulated in order to influence the length to which the nanorods grew. Pt tips were attached to an end of the CdSe@CdS nanorods as photocatalytic hydrogen production sites. TEM was utilized to characterize the different types of nanoparticles at each stage of assembly.

Thesis (Ph.D.)--University of California, San Diego, 2005.
Title from p. 1 of PDF file (viewed October 21, 2005) Vita. Includes bibliographical references (p. 170-175 ). Available online via UMI ProQuest Digital Dissertations.

The theoretical tool of choice for the microscopic description of all medium- and heavy-mass nuclei is the Energy Density Functional (EDF) method. Such a method relies on the concept of spontaneous symmetry breaking and restoration. In that sense, it is intrinsically a two-step approach. However, the symmetry restoration procedure is only well-defined in the particular case where the energy functional derives from a pseudo-potential. Thereby and as it has been recently shown, existing parameterizations of the energy functional provides unphysical results. Such a problem as well as the lack of predictive power call for developing new families of functionals. The first part of the present work is devoted to a study of the symmetry restoration problem and to the identification of properties that could constrain the analytic form of energy functionals that do not derive from a pseudo-potential. The second part deals with the construction of an energy functional that derives from a pseudo potential. The difficulties of such work are (i) the identification of the minimal complexity of the pseudo-potential necessary to obtain an energy functional that is flexible enough to provide high-quality EDF parameterizations, (ii) the tedious analytical derivation of the functional and of the associated one-body fields, (iii) the implementation of the latter in existing codes, and (iv) the development of an efficient fitting procedure. Eventually, it seems possible to generate a parameterization that strictly derives from a pseudo-potential and that provides as good results as state-of-the-art (quasi) bilinear functionals.

The solid oxide fuel cell (SOFC) is a potential high efficient electrochemical device for vehicles, auxiliary power units and large-scale stationary power plants combined heat and power application. The main challenges of this technology for market acceptance are associated with cost and lifetime due to the high temperature (700-1000 oC) operation and complex cell structure, i.e. the conventional membrane electrode assemblies. Therefore, it has become a top R&D goal to develop SOFCs for lower temperatures, preferably below 600 oC. To address those above problems, within the framework of this thesis, two kinds of innovative approaches are adopted. One is developing functional composite materials with desirable electrical properties at the reduced temperature, which results of the research on ceria-based composite based low temperature ceramic fuel cell (LTCFC). The other one is discovering novel energy conversion technology - Single-component/ electrolyte-free fuel cell (EFFC), in which the electrolyte layer of conventional SOFC is physically removed while this device still exhibits the fuel cell function. Thus, the focus of this thesis is then put on the characterization of materials physical and electrochemical properties for those advanced energy conversion applications. The major scientific content and contribution to this challenging field are divided into four aspects except the Introduction, Experiments and Conclusions parts. They are: Continuous developments and optimizations of advanced electrolyte materials, ceria-carbonate composite, for LTCFC. An electrolysis study has been carried out on ceria-carbonate composite based LTCFC with cheap Ni-based electrodes. Both oxygen ion and proton conductance in electrolysis mode are observed. High current outputs have been achieved at the given electrolysis voltage below 600 oC. This study also provides alternative manner for high efficient hydrogen production.  Compatible and high active electrode development for ceria-carbonate composite electrolyte based LTCFC. A symmetrical fuel cell configuration is intentionally employed. The electro-catalytic activities of novel symmetrical transition metal oxide composite electrode toward hydrogen oxidation reaction and oxygen reduction reaction have been experimentally investigated. In addition, the origin of high activity of transition metal oxide composite electrode is studied, which is believed to relate to the hydration effect of the composite oxide. A novel all-nanocomposite fuel cell (ANFC) concept proposal and feasibility demonstration. The ANFC is successfully constructed by Ni/Fe-SDC anode, SDC-carbonate electrolyte and lithiated NiO/ZnO cathode at an extremely low in-situ sintering temperature, 600 oC. The ANFC manifests excellent fuel cell performance (over 550 mWcm-2 at 600 oC) and a good short-term operation as well as thermo-cycling stability. All results demonstrated its feasibility and potential for energy conversion. Fundamental study results on breakthrough research Single-Component/Electrolyte-Free Fuel Cell (EFFC) based on above nanocomposite materials (ion and semi-conductive composite) research activities. This is also the key innovation point of this thesis. Compared with classic three-layer fuel cells, EFFC with an electrolyte layer shows a much simpler but more efficient way for energy conversion. The physical-electrical properties of composite, the effects of cell configuration and parameters on cell performance, materials composition and cell fabrication process optimization, micro electrochemical reaction process and possible working principle were systematically investigated and discussed. Besides, the EFFC, joining solar cell and fuel cell working principle, is suggested to provide a research platform for integrating multi-energy-related device and technology application, such as fuel cell, electrolysis, solar cell and micro-reactor etc. This thesis provides a new methodology for materials and system innovation for the fuel cell community, which is expected to accelerate the wide implementation of this high efficient and green fuel cell technology and open new horizons for other related research fields.

QC 20131122

La méthode dite de la fonctionnelle de la densité d'énergie (EDF) est l'outil théorique de référence pour l'étude systématique de la structure des noyaux atomiques de masse A>20. La méthode EDF est formulée en deux étapes successives consistant à briser puis à restaurer les symétries du Hamiltonien nucléaire sous-jacent. La technique de restauration des symétries n'est cependant rigoureusement formulée que si la fonctionnelle d'énergie dérive explicitement d'une interaction effective, i.e. d'un pseudo-potentiel, ce qui constitue un cas particulier de la méthode EDF plus générale. Ainsi, et comme cela a été démontré récemment, l'utilisation des paramétrisations existantes des fonctionnelles d'énergie conduit à l'obtention de résultats non physiques. Le pouvoir prédictif limité des fonctionnelles d'énergie existantes et leur inocuité relative à la restauration des symétries, nécessitent aujourd'hui de repenser leur méthode de construction. La première partie de ce travail a été dédié à l'analyse approfondie du problème associé à la restauration de symétrie et à l'identification de pistes permettant de contraindre la forme analytique des fonctionnelles d'énergie ne dérivant pas d'un pseudo-potentiel indépendant du système. La seconde partie a consisté à développer un pseudo-potentiel rendant la restauration des symétries automatiquement bien définie. Les difficultés de ce travail ont résidé dans (i) l'identification de la complexité minimale du pseudo-potentiel nécessaire à l'obtention d'une fonctionnelle d'énergie assez flexible pour égaler, et si possible améliorer, les performances des paramétrisations existantes, (ii) la dérivation analytique de la fonctionnelle et des champs à un corps découlant de celle ci, (iii) l'implémentation de ces derniers dans les codes de calculs, et dans (iv) le développement d'un protocole d'ajustement des paramètres adapté à la nouvelle fonctionnelle d'énergie ainsi développée. Les premiers résultats obtenus ont permis de valider l'approche en démontrant la flexibilité suffisante du pseudo-potentiel au niveau des calculs réalisés sans restauration des symétries
The theoretical tool of choice for the microscopic description of all medium- and heavy-mass nuclei is the Energy Density Functional (EDF) method. Such a method relies on the concept of spontaneous symmetry breaking and restoration. In that sense, it is intrinsically a two-step approach. However, the symmetry restoration procedure is only well-defined in the particular case where the energy functional derives from a pseudo-potential. Thereby and as it has been recently shown, existing parameterizations of the energy functional provides unphysical results. Such a problem as well as the lack of predictive power call for developing new families of functionals. The first part of the present work is devoted to a study of the symmetry restoration problem and to the identification of properties that could constrain the analytic form of energy functionals that do not derive from a pseudo-potential. The second part deals with the construction of an energy functional that derives from a pseudo potential. The difficulties of such work are (i) the identification of the minimal complexity of the pseudo-potential necessary to obtain an energy functional that is flexible enough to provide high-quality EDF parameterizations, (ii) the tedious analytical derivation of the functional and of the associated one-body fields, (iii) the implementation of the latter in existing codes, and (iv) the development of an efficient fitting procedure. Eventually, it seems possible to generate a parameterization that strictly derives from a pseudo-potential and that provides as good results as state-of-the-art (quasi) bilinear functionals

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Economics, 2007.
Includes bibliographical references (p. 138-140).
This paper offers a set of explicit functional relationships that link energy and the economy. Despite the reliance on energy permeating the whole economy, no such complete relationships had been presented before. How related are energy and the economy? What role does energy play in the economic growth? Motivated to seek an explicit functional answer, I theorize the role of energy and then test it with economic models, using data for 16 OECD countries from 1980 to 2001. First, I find that energy is a cross-country representative good whose prices are equalized when converted to a reference currency. Thus, energy prices satisfy the purchasing power parity. For all but one country, the half life of the real energy exchange rate is less than a year and as low as six months, shorter than those derived by other real exchange rate measures. Second, considering energy a cross-time representative good, I obtain that a country's utility function is inversely proportional to both its income share of energy and its energy price. I also obtain an explicit, unified two-dimensional (cross countries and time) production function with energy and non-energy as the two inputs. Third, I conclude a cross-country parity relationship for income shares of energy, similar to that for energy prices.
(cont.) Further, I provide an intertemporal connection between the trajectory of the income share of energy and the productivity growth of the economy. Lastly, I demonstrate the tradeoffs between energy efficiency and economic wellbeing, with the energy price being the medium for the tradeoffs. One may apply the functional roles of energy offered in this paper to help frame the current global-scale issues that are energy relevant.
by Vincent H. Chang.
Ph.D.

Contactless ultrasonic power transfer (UPT), using piezoelectric transducers, is based on transferring energy using acoustic waves, in which the waves are generated by an acoustic source or transmitter and then transferred through an acoustic medium such as water or human tissue to a sensor or receiver. The receiver then converts the mechanical strain induced by the incident acoustic waves to electricity and delivers to an electrical load, in which the electrical power output of the system can be determined. The execution and efficiency of this technology can be significantly enhanced through patterning, focusing, and localization of the transmitted acoustic energy in space to simultaneously power pre-determined distributed sensors or devices. A passive 3D-printed acoustic hologram plate alongside a single transducer can generate arbitrary and pre-designed ultrasound fields in a particular distance from the hologram mounted on the transmitter, i.e., a target plane. This dissertation presents the use of these simple, cost-effective, and high-fidelity acoustic holograms in UPT systems to selectively enhance and pattern the electrical power output from the receivers. Different holograms are numerically designed to create single and multi-focal pressure patterns in a target plane where an array of receivers are placed. The incident sound wave from a transmitter, after passing through the hologram, is manipulated, hence, the output field is the desired pressure field, which excites the receivers located at the pre-determined focal points more significantly. Furthermore, multi-functional holograms are designed to generate multiple images at different target planes and driving frequencies, called, respectively, multi-image-plane and multi-frequency patterning holograms. The multiple desired pressure distributions are encoded on the single hologram plate and each is reconstructed by changing the axial distance and by switching the frequency. Several proof-of-concept experiments are performed to verify the functionality of the computationally designed holograms, which are fabricated using modern 3D-printers, i.e., the desired wavefronts are encoded in the hologram plates' thickness profile, being input to the 3D-printer. The experiments include measurement of output pressure fields in water using needle hydrophones and acquisition of receivers' voltage output in UPT systems. Another technique investigated in this dissertation is the implementation of acoustic impedance matching layers deposited on the front leading surface of the transmitter and receiver transducers. Current UPT systems suffer from significant acoustic losses through the transmission line from a piezoelectric transmitter to an acoustic medium and then to a piezoelectric receiver. This is due to the unfavorable acoustic impedance mismatch between the transducers and the medium, which causes a narrow transducer bandwidth and a considerable reflection of the acoustic pressure waves at the boundary layers. Using matching layers enhance the acoustic power transmission into the medium and then reinforce the input as an excitation into the receiver. Experiments are performed to identify the input acoustic pressure from a cylindrical transmitter to a receiver disk operating in the 33-mode of piezoelectricity. Significant enhancements are obtained in terms of the receiver's electrical power output when implementing a two-layer matching structure. A design platform is also developed that can facilitate the construction of high-fidelity acoustically matched transducers, that is, the material layers' selection and determination of their thicknesses. Furthermore, this dissertation presents a numerical analysis for the dynamical motions of a high-intensity focused ultrasound (HIFU)-excited microbubble or stable acoustic cavitation, which includes the effects of acoustic nonlinearity, diffraction, and absorption of the medium, and entails the problem of several biomedical ultrasound applications. Finally, the design and use of acoustic holograms in microfluidic channels are addressed which opens the door of acoustic patterning in particle and cell sorting for medical ultrasound systems.
Doctor of Philosophy
This dissertation presents several techniques to enhance the wireless transfer of ultrasonic energy in which the sound wave is generated by an acoustic source or transmitter, transferred through an acoustic medium such as water or human tissue to a sensor or receiver. The receiver transducer then converts the vibrational energy into electricity and delivers to an electrical load in which the electrical power output from the system can be determined. The first enhancement technique presented in this dissertation is using a pre-designed and simple structured plate called an acoustic hologram in conjunction with a transmitter transducer to arbitrarily pattern and shape ultrasound fields at a particular distance from the hologram mounted on the transmitter. The desired wavefront such as single or multi-focal pressure fields or an arbitrary image such as a VT image pattern can simply be encoded in the thickness profile of this hologram plate by removing some of the hologram material based on the desired shape. When the sound wave from the transmitter passes this structured plate, it is locally delayed in proportion to the hologram thickness due to the different speed of sound in the hologram material compared to water. In this dissertation, various hologram types are designed numerically to implement in the ultrasonic power transfer (UPT) systems for powering receivers located at the predetermined focal points more significantly and finally, their functionality and performances are verified in several experiments. Current UPT systems suffer from significant acoustic losses through the transmission from a transmitter to an acoustic medium and then to a receiver due to the different acoustic impedance (defined as the product of density and sound speed) between the medium and transducers material, which reflects most of the incident pressure wave at the boundary layers. The second enhancement technology addressed in this dissertation is using intermediate materials, called acoustic impedance matching layers, bonded to the front side of the transmitter and receiver face to alleviate the acoustic impedance mismatch. Experiments are performed to identify the input acoustic pressure from a transmitter to a receiver. Using a two-layer matching structure, significant enhancements are observed in terms of the receiver's electrical power output. A design platform is also developed that can facilitate the construction of high-fidelity acoustically matched transducers, that is, the material layers' selection and determination of their thicknesses. Furthermore, this dissertation presents a numerical analysis for the dynamical motions of a microbubble exposed to a high-intensity focused ultrasound (HIFU) field, which entails the problem of several biomedical ultrasound applications such as microbubble-mediated ultrasound therapy or targeted drug delivery. Finally, an enhancement technique involving the design and use of acoustic holograms in microfluidic channels is addressed which opens the door of acoustic patterning in particle and cell sorting for medical ultrasound systems.

Heavily-selected livestock production traits rarely come without compromise; altered physiology arising from intensive selection often gives rise to concern of a welfare trade-off. A particularly clear example of welfare challenge caused by genetic selection in chickens is the ‘broiler-breeder paradox’, wherein breeding populations of broiler-type birds selected for fast growth are feed-restricted in order to reduce growth and maintain reproductive viability at sexual maturity. In order to better-inform management and breeding strategies for alleviating reproductive problems resulting from genetic selection for growth, it is essential to develop a better understanding of the physiological processes underpinning growth. Whereas the molecular mechanisms governing energy balance in mammals have been relatively welldescribed, analogous avian systems have not received as much research attention and remain somewhat poorly understood. The broad aim of this doctoral project was to contribute to understanding of avian energy balance, particularly in the context of selection for high growth. Using an advanced broiler-layer intercross chicken line (AIL), high- and low-growth haplotypes at the locus encoding the cholecystokinin A receptor (CCKAR), underlying the most significant QTL for growth in chickens, were characterised. Of over 300 variations detected, a select panel spaced across the CCKAR locus were tested for prediction of bodyweight in a diverse cohort of chicken populations. One intronic SNP was found to be significant (p < 0.05) and proximal to transcription factor binding sites. The effect of this locus on gross bodyweight remained significant into the 20th AIL generation (~20% at 10wk, p < 0.05). In this otherwise effectively genetically homogeneous population, several specific physiological traits were predicted by CCKAR haplotype alone, yielding some clues as to the significance of perturbed cholecystokinin (CCK) signalling in broiler strains. While birds with high-growth CCKAR haplotype (HG) did not appear to consume more, feed conversion efficiency (FCE) was improved, at least for males, compared to low-growth (LG) (p < 0.05). Visceral organ anatomies were morphologically disparate, with HG individuals exhibiting ~1/3 less gallbladder mass (p < 0.01), and ~10% shorter GI tract (p < 0.01) and metatarsal bone (p < 0.05). Further gaps in knowledge of the expression of peripheral satiety hormones in chicken are addressed in this thesis. Tissue distributions for expression of CCK, gastrin, pancreatic polypeptide (PPY) and peptide YY (PYY), were mapped and their respective dynamic responses to nutritive state examined. CCK was found to be most highly expressed in the brain, whereas PYY, PPY and gastrin were far more abundant in distinct regions of the periphery. Interestingly, peripheral CCK was not responsive to short-term (< 10h) satiety in experimental populations where PYY and gastrin were. PYY expression was found to be greatest in the pancreas and consistently upregulated within hours after feeding (p < 0.01), whereas gastrin expression was confined to the gastric antrum and paradoxically highest in fasting birds (p < 0.01). PPY expression is strictly limited to the pancreas and appears dependent on longerterm energy state. These results highlight similarities and differences to mammalian systems; notably, the avian pancreas seems to fulfil an exceptional role as a site of signal integration, perhaps unsurprising considering its disproportionate size compared to mammals. Indeed, pancreatic PYY appears to act as a primary peripheral short-term satiety hormone in birds. This body of work contributes to the understanding of avian energy balance and growth. An invaluable foundation for future research is formed by the identification of the major locations of production, and basic nutrient-responsive trends, for several peripheral avian hormones. Information on the growth role of CCKAR is consolidated and expanded upon, demonstrating a clear genetic contribution to maintenance organ morphology and overall growth. Such knowledge can be used to reliably assess and advise on selection and management of chickens to stem welfare concerns without compromising production. Comparisons between avian and other vertebrate endocrine systems make for interesting insight into the adaptive role of energy homeostatic mechanisms in divergent evolution of mammals and non-mammalian vertebrates. In some aspects, birds might better represent the ancestral phenotype from which each vertebrate clade arose.

In the past decade, the use of nanotechnology as a tool to develop and fabricate new structures and devices for biological sensing and energy applications has become increasingly widespread. In this work, a systematic study has been performed on one-dimensional nanomaterials, with a focus on the development of miniaturized devices with a "bottom up" approach. First, members of the nano - carbon family are utilized for biosensing applications; in particular, carbon nanotubes as well as nitrogen - doped and boron - doped nanocrystalline diamond (NCD) films. These carbon - based materials possess several unique electrochemical properties over other conductive materials which make them suitable for biosensing applications. Single walled carbon nanotubes were deposited on a glass carbon electrode and modified for the detection of Salmonella DNA hybridization. Electrochemical impedance spectroscopy (EIS) was used as the method of detection and a detection limit of 10-9 M was achieved. Nanocrystalline diamond was grown using a microwave enhanced plasma chemical vapor deposition method. The diamond electrodes were doped with either boron or nitrogen to provide substrates and characterization was performed using scanning electron microscopy, atomic force microscopy, Raman spectroscopy, Fourier transform infrared spectroscopy, UV-vis spectroscopy, as well as by electrochemical methods. Modified boron - doped NCD was able to detect Salmonella DNA hybridization via EIS and fluorescent microscopy. The detection limit for these genosensors was found to be 0.4 micrometer complementary DNA. Boron - doped and nitrogen - incorporated nanocrystalline diamond also served as functionalized electrodes for lactic acid detection. It was found that the boron - doped electrodes could detect 0.5 mM lactic acid in a phosphate buffer solution. Second, bismuth antimony nanowires were grown in an anodized alumina template for the fabrication of a thermoelectric cooling device. Bismuth antimony nanowires were chosen due to their high thermoelectric efficiency compared to their bulk material counterpart. The development of a successful anodized template was achieved and EIS was used to diagnose the optimal etch parameters of the barrier oxide layer for nanowire growth. Bismuth antimony nanowires were grown directly on a silicon substrate and a thermoelectric cooling device was fabricated. The nanowires exhibited a thermoelectric efficiency of 0.18 at room temperature.

Energy efficiency is gaining more and more importance, since well-known ecological reasons lead to rising energy costs. In consequence, energy consumption is now also an important economical criterion. Energy consumption of single hardware resources has been thoroughly optimized for years. Now software becomes the major target of energy optimization. In this paper we introduce an approach called energy auto tuning(EAT), which optimizes energy efficiency of software systems running on multiple resources. The optimization of more than one resource leads to higher energy savings, because communication costs can be taken into account. E.g., if two components run on the same resource, the communication costs are likely to be less, compared to be running on different resources. The best results can be achieved in heterogeneous environments as different resource characteristics enlarge the synergy effects gainable by our optimization technique. EAT software systems derive all possible distributions of themselves on a given set of hardware resources and reconfigure themselves to achieve the lowest energy consumption possible at any time. In this paper we describe our software architecture to implement EAT.

In this thesis, we have studied the electronic and optical properties of solar energy m-terials. The studies are performed in the framework of density functional theory (DFT), GW, Bethe-Salpeter equation (BSE) approaches and Kinetic Monte Carlo (KMC). We present four sets of results. In the first part, we report our results on the band gap engineering issues for BiNbO4and NaTaO3, both of which are good photocatalysts. The band gap tuning is required for these materials in order to achieve the maximum solar to hydrogen conversion efficiency. The most common method for the band gap reduction is an introduction of foreign elements. The mono-doping in the system generates electrons or holes states near band edges, which reduce the efficiency of photocatalytic process. Co-doping with anion and cation or anion and anion can provide a clean band gap. We have shown that further band gap reduction can be achieved by double-hole mediated coupling between two anionic dopants. In the second part, the structure and optical properties of (CdSxSe1x)42nanoclusters have been studied. Within this study, the structures of the (CdS)42, (CdSe)42, Cd42Se32S10, Cd42Se22S20, and Cd42Se10S32 clusters have been determined using the simulated annealing method. Factors influencing the band gap value have been analyzed. We show that the gap is most significantly reduced when strongly under coordinated atoms are present on the surface of the nanoclusters. In addition, the band gap depends on the S concentration as well as on the distribution of the S and Se atoms in the clusters. We present the optical absorption spectra calculated with BSE and random phase approximation (RPA) methods based on the GW corrected quasiparticle energies. In the third part, we have employed the state-of-art computational methods to investigate the electronic structure and optical properties of TiO2high pressure polymorphs. GW and BSE methods have been used in these calculations. Our calculations suggest that the band gap of fluorite and pyrite phases have optimal values for the photocatalytic process of decomposing water in the visible light range. In the fourth part we have built a kinetic model of the first water monolayer growth on TiO2(110) using the kinetic Monte Carlo (KMC) method based on parameters describing water diffusion and dissociation obtained from first principle calculations. Our simulations reproduce the experimental trends and rationalize these observations in terms of a competition between different elementary processes. At high temperatures our simulation shows that the structure is well equilibrated, while at lower temperatures adsorbed water molecules are trapped in hydrogen-bonded chains around pairs of hydroxyl groups, causing the observed higher number of molecularly adsorbed species at lower temperature.

QC 20140603

Organic coatings are widely used to lower the corrosion rate of metallic structures. However, penetration of water, oxygen and corrosive ions through pores present in the coating results in corrosion initiation and propagation once these species reach the metal substrate. Considering the need for systems that offer active protection with self-healing functionality, composite coatings containing polyaniline (PANI) conducting polymer are proposed in this study. In the first phase of my work, PANI was synthesized by various methods and characterized. The rapid mixing synthesis method was chosen for the rest of this study, providing PANI with high electrical conductivity, molecular structure of emeraldine salt, and morphology of spherical nanoparticles. PANIs doped with phosphoric and methane sulfonic acid revealed hydrophilic nature, and I showed that by incorporating a long-chain alkylphosphonic acid a hydrophobic PANI could be prepared. The second phase of my project was dedicated to making homogenous dispersions of PANI in a UV-curable resin based on polyester acrylate (PEA). Interfacial energy studies revealed the highest affinity of PEA to PANI doped with phosphoric acid (PANI-PA), and no attractive or long-range repulsive forces were measured between the PANI-PA surfaces in PEA.This is ideal for making conductive composites as, along withno aggregation tendency, the PANI-PA particles might come close enough to form an electrically connected network. Highly stable PEA/PANI-PA dispersions were prepared by pretreatment of PANI-PA in acetone followed by mixing in PEA in small portions under pearl-milling. The third phase of my project dealt with kinetics of the free radical polymerization that was utilized to cure the PEA/PANI-PA mixture. UV-vis absorption studies suggested a maximum allowed PANI-PA content of around 4 wt.% in order not to affect the UV curing behavior in the UV-C region. Real-time FTIR spectroscopy studies, using a laboratory UV source, revealed longer initial retardation of the photocuring and lower rates of crosslinking reactions for dispersions containing PANI-PA of higher than 3 wt.%. The presence of PANI-PA also made the formulations more sensitive to changes in UV light intensity and oxygen inhibition during UV curing. Nevertheless, curing of the dispersions with high PANI-PA content, of up to 10 wt.%, was demonstrated to be possible at either low UV light intensities provided the oxygen replenishment into the system was prevented, or by increasing the UV light intensity to very high levels. In the last phase of my project, the PEA and PEA/PANI-PA coatings, cured under high intensity UV lamps, were characterized. SEM analysis showed small PANI-PA particles to be closely packed within the matrix, and the electrical conductivity of the composite films was measured to be in the range of semiconductors. This suggested the presence of a connected network of PANI-PA, as confirmed by investigations of mechanical and electrical variations at the nanoscale by PeakForce TUNA AFM. The data revealed the presence of a PEA-rich layer at the composite-air interface, and a much higher population of the conductive network within the polymer matrix. High current signal was correlated with a high elastic modulus, consistent with the level measured for PANI-PA, and current-voltage studies on the conductive network showed non-Ohmic characteristics. Finally, the long-term protective property of the coatings was characterized by OCP and impedance measurements. Short-term barrier-type corrosion protection provided by the insulating PEA coating was turned into a long-term and active protection by addition of as little as 1 wt.% PANI-PA. A large and stable ennoblement was induced by the coatings containing PANI-PA of up to 3 wt.%. Higher content of PANI-PA led to poorer protection, probably due to the hydrophilicity of PANI-PA facilitating water transport in the coating and the presence of potentially weaker spots in the film. An iron oxide layer was found to fully cover the metal surface beneath the coatings containing PANI-PA after final failure observed by electrochemical testing.

QC 20141103

Energy efficiency is gaining more and more importance, since well-known ecological reasons lead to rising energy costs. In consequence, energy consumption is now also an important economical criterion. Energy consumption of single hardware resources has been thoroughly optimized for years. Now software becomes the major target of energy optimization. In this paper we introduce an approach called energy auto tuning(EAT), which optimizes energy efficiency of software systems running on multiple resources. The optimization of more than one resource leads to higher energy savings, because communication costs can be taken into account. E.g., if two components run on the same resource, the communication costs are likely to be less, compared to be running on different resources. The best results can be achieved in heterogeneous environments as different resource characteristics enlarge the synergy effects gainable by our optimization technique. EAT software systems derive all possible distributions of themselves on a given set of hardware resources and reconfigure themselves to achieve the lowest energy consumption possible at any time. In this paper we describe our software architecture to implement EAT.

La síntesi d'òxids de metalls de transició per dipòsit de capes atòmiques (ALD) està contribuint al desenvolupament de nanomaterials, estructures i dispositius que són difícils d'aconseguir mitjançant tècniques de dipòsit tradicionals i tenen característiques prometedores per a diverses àrees d'aplicació com a energia, electrònica i salut. És important desenvolupar processos d'ALD més robustos per òxids de metalls de transició, ampliant la biblioteca de composicions i facilitant la seva integració amb altres materials. El principal objectiu d'aquesta tesi és contribuir al desenvolupament de processos d'ALD per fabricar capes primes basades en òxids de metalls de transició i recobriments conformals, i entendre la importància de la reactivitat entre els precursors metalorgànics i la superfície del substrat per guiar possibles aplicacions. En particular, els esforços s'han centrat en els següents aspectes: 1. Explorar un nou precursor de cobalt (β -heteroarilalquenolato de cobalt) per dipositar capes de Co3O4 per ALD. La introducció de lligands heteroarilo i grups CF3-, en comparació amb els precursors comercials, ofereix una major estabilitat del precursor i una manipulació segura en condicions ambientals. Les condicions de dipòsit d'ALD s'han investigat a fons optimitzant la durada del pols del precursor, la temperatura de dipòsit i la dependència de l'espessor de la capa amb el nombre de cicles d'ALD. Es mostra que aquesta química afavoreix la formació de capes primes d'ALD Co3O4 i recobriments conformals quan es combinen amb ozó com a oxidant. 2. Comparar la idoneitat d'un precursor heterobimetàl.lic de Gd-Fe versus fonts metalorgàniques separades de Gd i Fe per dipositar capes primes d'òxids ternaris magnètics de GdxFeyOz. El nou complex heterobimetàl.lic de Gd-Fe, que conté una relació estequiomètrica de 1Gd: 1Fe, facilita l'estabilització epitaxial de capes primes de GdFeO3 en substrats monocristal·lins de SrTiO3 quan es combina amb ozó. Alternativament, busquem l'oportunitat de sintetitzar òxids ternaris de GdxFeyOz utilitzant precursors separats de Gd i Fe sintetitzats a mida: un guanidinato de gadolini i un cetoiminato de ferro coordinat a N i O. El comportament del cetoiminat de ferro s'ha comparat amb el ferrocè, disponible comercialment. La reactivitat de cada precursor s'ha provat amb aigua i ozó com a agents oxidants. Es mostra que la química del precursor afecta tant la composició com a la cristal·linitat de les capes dipositades. S'han avaluat les propietats magnètiques dels sistemes d'òxid GdxFeyOz resultants. 3. Investigar la influència dels tractaments amb plasma (N2, H2O) en nanotubs de carboni (CNTs) en el posterior dipòsit de recobriments conformales de Fe2O3 per ALD. S'ha demostrat que la funcionalització de la superfície dels CNT és essencial per obtenir més llocs d'ancoratge per aconseguir la desitjada homogeneitat del recobriment. L'agent oxidant ozó també juga un paper clau. S'han dut a terme mesures electroquímiques en els nanocompòsits Fe2O3@CNTs per correlacionar la funcionalització de la superfície i la qualitat de la capa d'ALD Fe2O3 amb el rendiment electroquímic. Això obre noves oportunitats per a la fabricació d'ànodes més eficients per supercondensadors.
La síntesis de óxidos de metales de transición por depósito de capas atómicas (ALD) está contribuyendo al desarrollo de nanomateriales, estructuras y dispositivos que son difíciles de lograr mediante técnicas de depósito tradicionales y tienen características prometedoras para diversas áreas de aplicación como energía, electrónica y salud. Es importante desarrollar procesos de ALD más robustos para óxidos de metales de transición, ampliando la biblioteca de composiciones y facilitando su integración con otros materiales. El principal objetivo de esta tesis es contribuir al desarrollo de procesos de ALD para fabricar películas delgadas basades en óxidos de metales de transición y recubrimientos conformales, y arrojar luz sobre la reactividad entre los precursores metalorgánicos y la superficie del sustrato para guiar posibles aplicaciones. En particular, los esfuerzos se han centrado en los siguientes aspectos: 1. Explorar un nuevo precursor de cobalto (β -heteroarilalquenolato de cobalto) para depositar películas de Co3O4 por ALD. La introducción de ligandos heteroarilo y grupos CF3-, en comparación con los precursores comerciales, ofrece una mayor estabilidad del precursor y una manipulación segura en condiciones ambientales. Las condiciones de depósito de ALD se han investigado a fondo optimizando la duración del pulso del precursor, la temperatura de depósito y la dependencia del espesor de la película con el número de ciclos de ALD. Se muestra que esta química favorece la formación de películas delgadas de ALD Co3O4 y recubrimientos conformados cuando se combinan con ozono como oxidante. 2. Comparar la idoneidad de un precursor heterobimetálico de Gd-Fe versus fuentes metalorgánicas separadas de Gd y Fe para depositar películas delgadas de óxido ternario magnéticos de GdxFeyOz. El novedoso complejo heterobimetálico de Gd-Fe, que contiene una relación estequiométrica de 1Gd: 1Fe, facilita la estabilización epitaxial de películas delgadas de GdFeO3 en sustratos monocristalinos de SrTiO3 cuando se combina con ozono. Alternativamente, buscamos la oportunidad de sintetizar óxidos ternarios de GdxFeyOz utilizando precursores separados de Gd y Fe sintetizados a medida: un guanidinato de gadolinio y un cetoiminato de hierro coordinado con O, N. El comportamiento del cetoiminato de hierro se ha comparado con el ferroceno, disponible comercialmente. La reactividad de cada precursor se ha probado con agua y ozono como agentes oxidantes. Se muestra que la química del precursor afecta tanto a la composición como a la cristalinidad de las películas depositadas. Se han evaluado las propiedades magnéticas de los sistemas de óxido GdxFeyOz resultantes. 3. Investigar la influencia de los tratamientos con plasma (N2, H2O) en nanotubos de carbono (CNTs) en el posterior depósito de recubrimientos conformales de Fe2O3 por ALD. Se ha demostrado que la funcionalización de la superficie de los CNTs es esencial para obtener más sitios de anclaje para lograr la deseada homogeneidad del recubrimiento. El agente oxidante ozono también juega un papel clave. Se han llevado a cabo medidas electroquímicas en los nanocompuestos Fe2O3@CNTs para correlacionar la funcionalización de la superficie y la calidad de la capa de ALD Fe2O3 con el rendimiento electroquímico. Esto abre nuevas oportunidades para la fabricación de ánodos más eficientes para supercondensadores.
The synthesis of transition metal oxides by atomic layer deposition (ALD) is contributing to the development of nanomaterials, structures and devices that are difficult to achieve by traditional deposition techniques and hold promising characteristics for various application areas such as energy, electronics and health. Research on developing more robust ALD processes for transition metal oxides, expanding the library of compositions and facilitating their integration with other materials are thus of great relevance. The main objective of this thesis is to contribute to the development of ALD processes of transition metal oxide-based thin films and conformal coatings, and to shed light on the relevant reactivity between the metalorganic precursors and substrate surfaces to guide potential applications. In particular, the efforts have been focused on the following aspects: 1. Explore a novel cobalt precursor (β-heteroarylalkenolate Cobalt) to deposit ALD Co3O4 films. The introduction of heteroaryl moieties and CF3- groups, compared to commercial precursors, offers higher precursor stability and safe handling at ambient conditions. ALD deposition conditions have been thoroughly investigated by optimizing precursor pulse length, deposition temperature and film thickness dependence on the number of ALD cycles. It is shown that this chemistry favors the formation of ALD Co3O4 thin films and conformal coatings when combined with ozone as oxidant. 2. Compare the suitability of a heterobimetallic Gd-Fe precursor versus separate metalorganic sources of Gd and Fe to deposit magnetic GdxFeyOz ternary oxide thin films. The novel heterobimetallic single-source Gd-Fe complex which contains 1Gd:1Fe stoichiometric ratio, facilitates the epitaxial stabilization of GdFeO3 thin films on SrTiO3 single crystal substrates when combined with ozone. Alternatively, we seek the opportunity to synthesize GdxFeyOz ternary oxides from separate Gd and Fe precursors, with different precursor chemistries, via the supercycle approach. For that, it has been explored the use of two tailor-made precursors: a fully N-coordinated gadolinium guanidinate and a mixed O,N- coordinated iron ketoiminate. The behavior of the iron ketoiminate has been compared to the commercially available ferrocene. The reactivity of each precursor has been tested with water and ozone as co-reactants. It is shown that the precursor chemistry affects both the composition and crystallinity of the deposited films. Magnetic properties of the resultant GdxFeyOz oxide systems have been evaluated. 3. Investigate the influence of plasma treatments (N2, H2O) for carbon nanotubes (CNTs) on the subsequent deposition of conformal Fe2O3 coatings by ALD. It has been demonstrated that surface functionalization of the CNTs is essential to obtain more anchoring sites for achieving desirable coating homogeneity and that the ozone co-reactant plays a key role on it as well. Electrochemical measurements on the Fe2O3@CNTs nanocomposites have been carried out to correlate surface functionalization and ALD Fe2O3 layer quality with the electrochemical performance. This opens new opportunities for the fabrication of more efficient anodes for supercapacitors.

Commercially available fitness trackers have been found to accurately measure steps and caloric expenditure during walking and running activities. Circuit-style, highintensity functional training (HIFT) has become increasingly popular because it is inexpensive and effective in improving muscular strength and cardiovascular fitness. PURPOSE: To evaluate the accuracy of five accelerometers (ActiGraph GT3X, Nike Fuelband, Fitbit One, Fitbit Charge HR, and Jawbone UP Move) in estimating energy expenditure while performing an acute bout of HIFT. METHODS: Participants (n = 47) underwent baseline testing and at least 48 hours later, each participant completed the main test: a 15-minute workout consisting of 12 repetitions each of 7 different exercises; performed circuit-style by completing as many rounds as possible. During the main test, each participant wore the Cosmed K4b2 portable metabolic analyzer (PMA) and five different accelerometers. RESULTS: Four of the five fitness trackers reported lower (p <0.01) total caloric expenditure values compared to the PMA during the acute bout of HIFT. The waist-mounted device (ActiGraph, 182.55 ± 37.93 kcals) most closely mimicked caloric expenditure compared to the PMA (Cosmed, 144.99 ± 37.13 kcals) as indicated by an insignificant p value (0.056). Systematic differences between the activity monitors were calculated using an Intraclass Correlation (ICC) with an ICC = -0.032. The ICC of F (46,235) = 0.812 (p = 0.799) was not significant at the predetermined 0.05 alpha level. A Repeated Measures ANOVA showed that when compared to the Cosmed, all activity monitors were significantly different at the 0.05 alpha level. The Fitbit One and the Fitbit Charge HR were the only two activity monitors that are not significantly different from one another (p = 0.985). The range of error based on mean absolute percentage errors (MAPE) was lowest for the ActiGraph (15.1%) and highest for the Fitbit Charge HR (22.1%). CONCLUSION: The wrist- and hip-mounted fitness trackers do not accurately assess energy expenditure during HIFT exercise. Supported by: WKU Graduate School, NIGMS 2P20 GM103436-14; Institutional Development Award (IDeA) from National Institute of General Medical Sciences, National Institutes of Health, 5P20GM103436 and the WKU RCAP Grant 14-8007.

Vector processors are a very promising solution for mobile devices and servers due to their inherently energy-efficient way of exploiting datalevel parallelism. While vector processors succeeded in the high performance market in the past, they need a re-tailoring for the mobile market that they are entering now. Functional units are a key components of computation intensive designs like vector architectures, and have significant impact on overall performance and power. Therefore, there is a need for novel, vector-specific, design space exploration and low power techniques of vector functional units. We present a design space exploration of vector adder (VA) and multiplier unit (VMU). We examine advantages and side effects of using multiple vector lanes and show how it performs across a broad frequency spectrum to achieve an energy-efficient speed-up. As the final results of our exploration, we derive Pareto optimal design points and present guidelines on the selection of the most appropriate VMU and VA for different types of vector processors according to different sets of metrics of interest. To reduce the power of vector floating-point fused multiply-add units (VFU), we comprehensively identify, propose, and evaluate the most suitable clock-gating techniques for it. These techniques ensure power savings without jeopardizing the performance. We focus on unexplored opportunities for clock-gating application to vector processors, especially in active operating mode. Using vector masking and vector multilane-aware clock-gating, we report power reductions of up to 52%, assuming active VFU operating at the peak performance. Among other findings, we observe that vector instruction-based clock-gating techniques achieve power savings for all vector floating-point instructions. Finally, when evaluating all techniques together, the power reductions are up to 80%. We propose a methodology that enables performing this research in a fully parameterizable and automated fashion using two kinds of benchmarks, synthetic and "real world" application based. For this interrelated circuit-architecture research, we present novel frameworks with both architectural- and circuit-level tools, simulators and generators (including ones that we developed). Our frameworks include both design(e.g. adder's family type) and vector architecture-related parameters (e.g. vector length). Additionally, to find the optimal estimation flow, we perform a comparative analysis, using a design space exploration as a case study, of the currently most used estimation flows: Physical layout Aware Synthesis (PAS) and Place and Route (PnR). We study and compare post-PAS and post-PnR estimations of the metrics of interest and the impact of various design parameters and input switching activity factor (aI).

The exponential increase in the demands of world’s energy and the devastating effects of current fossil fuels based sources has forced us to reduce our dependence on the current sources as well as finding cleaner, cheaper and renewable alternates. Being abundant, efficient and renewable, hydrogen can be opted as the best possible replacement of the diminishing and harmful fossil fuels. But the transformation towards the hydrogen-based economy is hindered by the unavailability of suitable storage medium for hydrogen. First principles calculations based on density functional theory has been employed in this thesis to investigate the structures modelling and thermodynamics of various efficient materials capable of storing hydrogen under chemisorption and physisorption mechanisms. Thanks to their high storage capacity, abundance and low cost, metal hydride (MgH2) has been considered as promising choice for hydrogen storage. However, the biggest drawback is their strong binding with the absorbed hydrogen under chemisorption, which make them inappropriate for operation at ambient conditions. Different strategies have been applied to improve the thermodynamics including doping with light and transitions metals in different phases of MgH2 in bulk form.  Application of mechanical strain along with Al, Si and Ti doping on MgH2 (001) and (100) surfaces has also been found very useful in lowering the dehydrogenation energies that ultimately improve adsorption/desorption temperatures. Secondly, in this thesis, two-dimensional materials with high surface area have been studied for the adsorption of hydrogen in molecular form (H2) under physisorption. The main disadvantage of this kind of storage is that the adsorption of H2 with these nanostructures likes graphane, silicene, silicane, BN-sheets, BC3 sheets are low and demand operation at cryogenic conditions. To enhance the H2 binding and attain high storage capacity the above-mentioned nanostructures have been functionalized with light metals (alkali, alkaline) and polylithiated species  (OLi2, CLi3, CLi4). The stabilities of the designed functional materials for H2 storage have been verified by means of molecular dynamics simulations.

In this work I present a constructive method for finding critical points of the Ginzburg-Landau energy functional using the method of Sobolev gradients. I give a description of the construction of the Sobolev gradient and obtain convergence results for continuous steepest descent with this gradient. I study the Ginzburg-Landau functional with magnetic field and the Ginzburg-Landau functional without magnetic field. I then present the numerical results I obtained by using steepest descent with the discretized Sobolev gradient.

Functional heterojunctions in organic electronic devices are interfaces formed either between a conducting electrode and an organic semiconductor or between two different organic semiconductors in blended and multilayered structures. This thesis is primarily concerned with the energy level alignment and the interfacial electronic structures at functional heterojunctions encountered in electronic devices made with solution-processable semiconducting polymers. Investigations on the electronic structures across these heterointerfaces are performed with the combined use of electromodulation and photoemission spectroscopic techniques. Electromodulation and ultraviolet photoemission spectroscopic techniques enable direct determination of the surface work functions of electrodes at the electrode/semiconducting polymer interfaces. We overcame the inherent problems faced by electromodulation spectroscopy, which undermine accurate determination of interfacial electronic structures, by performing electroabsorption (EA) measurements at reduced temperatures. We showed in this thesis that low-temperature EA spectroscopy is a surface sensitive technique that can determine the interface electronic structures in electrode/polymer semiconductor/electrode diodes. Using this technique, we demonstrated that the energy level alignments in these solution-processed organic electronic devices are determined by the surface work functions of passivated metals rather than by those of clean metals encountered in ultrahigh vacuum. This thesis also discloses our studies on the electronic structures in polymeric diodes with type II donor-acceptor heterojunctions using the EA spectroscopy. We showed that minimising meausurement temperature and attenuating EA illumination intensity enable accurate determinations of the electronic structures in these devices. We demonstrated that the electronic structures and the performance characteristics of multilayered polymer light-emitting diodes are also determined by the surface work functions of passivated metals. Our investigations confirm that electronic doping of the organic active layers, rather than minimisation of the Schottky barriers at electrode/polymer contacts, holds the key in realising high-performance organic light-emitting devices.

Thesis (MSc)--Stellenbosch University, 2012.
AFRIKAANSE OPSOMMING: Berekeninge met Density Functional Theory (DFT) is ’n nuttige tegniek om die dinamika van molekules op potensiële energievlakke te verstaan. Beginnende met ’n prototipe molekuul formaldimien, wat die kern vorm van die groter fotochromiese molekuul dithizonatophenyl kwik (DPM), word die modellering van die molekuul meer ingewikkeld tot laasgenoemde bestudeer kan word asook sy fotochromiese afgeleides wat vervanging van elektronryk en elektronarm radikale by orto, meta en para posisies van die phenyl ringe insluit. DFT berekeninge word met spektra van Absorpsiespektroskopie met UV en sigbare lig asook tyd opgeloste spektra, verkry dmv femtosekondespektroskopie, vergelyk. In pol^ere aprotiese, pol^ere protiese en nie-pol^ere oplosmiddels, isomeriseer die molekuul om die C=N dubbelbinding. Daar kan tussen die twee isomere onderskei word deur dat die een in oplossing in sy grondtoestand blou en die ander een oranje voorkom. Die isomerisering is’n fotogeinduseerde proses. Die optimering van die molekul^ere struktuur, absorpsiespektra, oplosmiddel-afhanklikheid, en potensiële energievlak metings van die molekuul word bestudeer. Die sterk/swak wisselwerking wat in pol^ere protiese/aprotiese oplosmiddels verskyn word geopenbaar deur die hoe/lae absorpsie van die sekond^ere bande van die molekules. Daar is gevind dat die absorpsiespektra van DPM bathochromies in oplosmiddels met hoë diëlektriese konstantes is. Vir die potensiële energievlak berekeninge van die grondtoestand word rigiede en ontspanne metodes gebruik waar laasgenoemde met gebroke simmetrie berekeninge verkry word. Van alle metodes wat vir berekeninge gebruik was, gee die B3LYP/CEP-31G metode die beste benadering aan eksperimentele data. Alle berekeninge word gedoen met twee bekende sagteware pakkette; Amsterdam Density Functional (ADF) en Gaussian, wat op twee verskillende DFT metodes gebaseer is.
ENGLISH ABSTRACT: Density functional theory is a useful computational tool in the understanding of molecular dynamics on potential energy surfaces. Starting with a prototype molecule formaldimine, the photochromic molecule dithizonatophenylmercury II (DPM) and a set of its photochromic derivatives, (involving substitutions of electron donating and electron withdrawing substituents at ortho, meta and para positions of the dithizonato phenyl rings), are studied through density functional calculation in comparison with steady state absorption spectra obtained from UV-Visible and femto second spectroscopy experiments. In polar aprotic, polar protic and non-polar solvents these molecules isomerise around C=N double bond chromophore, from orange electronic ground states to blue electronic ground states upon photo-excitation. We investigate the structural optimisations, the absorption spectra, the solvent dependence and the potential energy surface (PES) of these molecules. The strong (weak) interactions exhibited by the polar protic (aprotic) solvents used are revealed through high (low) absorbance in the secondary bands of these molecules. The absorption spectra of DPM are found to be bathochromic in solvents with high dielectric constants. For the ground state PES calculation we make use of rigid and relaxed methods, and the latter is obtained through broken symmetry calculation. Of all the methods used in calculation, B3LYP/CEP-31G method gives the best approximation to the experimental data. All calculations are done using the two renown software, Amsterdam Density Functional (ADF) and Gaussian, availing their different density functional methods.

This thesis analyzes the application of functional link-net (FLN) method in forecasting electricity demand in Turkey. Current official forecasting model (MAED), which is employed by Turkish Electricity Transmission Company (TEiAS) and other methods are discussed. An emprical investigation and evaluation of using functional link nets is provided.

The work in this thesis mainly focuses on the assessment of density functional methods for computing structures and energies of organic and bioorganic molecules. Previous studies found dramatic conformational and stability changes from B3LYP to MP2 geometry optimization for some Tyr-Gly conformers. Possible reasons could be large intramolecular basis set superposition errors (BSSEs) in the MP2 calculations and the lack of dispersion in the B3LYP calculations. The fragmentation method and three kinds of rotation methods were used to investigate intramolecular BSSE. It is concluded that the rotation method cannot be used to correct intramolecular BSSE along a rotation profile. Another methodology is to employ modern density functionals. We focused on M06-L with the Tyr-Gly conformer ‘book6’. Potential energy profiles were determined by computing the energy for geometries optimized at various fixed values of a distance that controls the degree of foldedness of the structure. M06-L manifested itself as a very promising method to investigate the potential energy surface of small peptides containing aromatic residues. To predict Tyr-Gly structures, 108 potential conformers were created with a Fortran program. The geometry optimizations were done using M06-L/6-31G(d) and M05-2X/6-31+G(d). Two schemes were employed and the most stable conformers were compared to the 20 stable conformers found by B3LYP. Both schemes found 10 conformers similar to one of the B3LYP stable conformers, as well as several newly found conformers. The study of a missing B3LYP stable conformer showed that the possible reason of missing conformers may be the lack in dispersion in B3LYP theory. To study the hydration effect, we studied the conformations of neutral and zwitterionic 3-fluoro-γ-aminobutyric acid (3F-GABA) in solution using different solvation models, mainly the explicit water molecule models. Zwitterionic forms of 3F-GABA are preferred in solution. M06-2X performs better in calculating transition energy profiles than MP2.

The production of hydrogen gas, through the process of water splitting,is one of the most promising concepts for the production of clean andrenewable fuel.The introduction of this thesis provides a brief overview of fossil fuelsand the need for an energy transition towards clean and renewable energy.Hydrogen gas is presented as a possible candidate fuel with its productionthrough artificial photosynthesis, being described. However, the highlykinetically demanding key reaction of the process – the water oxidationreaction – requires the use of a catalyst. Hence, a short presentation of differentmolecular water oxidation catalysts previously synthesized is also provided.The second part of the thesis focuses on ruthenium-based molecularcatalysis for water oxidation. Firstly, the design and the catalytic performancefor a new series of catalysts are presented. Secondly, a further study onelectron paramagnetic resonance of a catalyst shows the coordination of awater molecule to a ruthenium centre to generate a 7-coordinated complex atRuIII state. Finally, in an electrochemical study, coupled with nuclear magneticresonance analysis, mass spectrometry and X-ray diffraction spectroscopy, wedemonstrate the ability of a complex to perform an in situ dimerization of twounits in order to generate an active catalyst.The final part of this thesis focuses on immobilisation of first rowtransition metal catalysts on the surface of electrodes for electrochemical wateroxidation. Initially, a copper complex was designed and anchored on a goldsurface electrode. Water oxidation performance was studied byelectrochemistry, while deactivation of the electrode was investigated throughX-ray photoelectron spectroscopy, revealing the loss of the copper complexfrom the electrode during the reaction. Finally, we re-investigated cobaltporphyrin complexes on the surface of the electrode. Against the backgroundof previous report, we show that the decomposition of cobalt porphyrin intocobalt oxide adsorbed on the surface is responsible for the catalytic activity.This result is discussed with regard to the detection limit of various spectroscopic methods.

QC 20170529

Orientador também citado por: CASTOR FILHO, Fernando
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Energy-efficiency has concerned hardware and low-level software designers for years. However, the rapid proliferation of battery-powered mobile devices combined with the growing worldwide movement towards sustainability have caused developers and researchers to study the energy impact of application software in execution. Recent work has studied the effect that factors such as code obfuscation, object-oriented refactorings, and data types have on energy efficiency. In this work, we attempt to shed light on the energy behavior of concurrent programs written in a purely functional language, Haskell. We conducted an empirical study to assess the performance and energy behavior of three different thread management approaches and three primitives for concurrency control using nine different benchmarks with an experimental space exploration of more than 400 configurations. In this study, we found out that small changes can make a big difference in terms of energy consumption. For instance, in one of our benchmarks, under a specific configuration, choosing one concurrency control primitive (MVar) over another (TMVar) can yield 60% energy savings. Also, the relationship between energy consumption and performance is not always clear. We found scenarios where the configuration with the best performance also exhibited the worst energy consumption. To support developers in better understanding this complex relationship, we have extended two existing performance analysis tools also to collect and present data about energy consumption. In addition, based on the results of our empirical study, we provide a list of guidelines for developers with good practices for writing energy-efficient code in this environment.
Há anos eficiência energética é uma preocupação para designers de hardware e software baixonível. Entretanto, a rápida proliferação de dispositivos móveis alimentados por bateria combinado com o crescente movimento global em busca de sustentabilidade tem motivado desenvolvedores e pesquisadores a estudar o impacto energético de softwares de aplicação em execução. Trabalhos recentes tem estudado o efeito que fatores como obsfucação de código, refatorações em linguagem orientadas à objetos e tipos de dados tem em eficiência energética. Este trabalho tenta lançar luz sobre o comportamento energético de programas concorrentes escritos em uma linguagem puramente funcional, Haskell. Nós conduzimos um estudo empírico para avaliar o desempenho e o comportamento energético de três diferentes abordagens para gerenciamento de threads e três primitivas para controle de concorrência usando nove diferentes benchmarks com um espaço de exploração experimental de mais de 400 configurações. Neste estudo, descobrimos que pequenas mudanças podem fazer uma grande diferença em termos de consumo de energia. Por exemplo, em um dos benchmarks, sob uma configuração específica, escolher uma primitiva de controle de concorrência (MVar) ao invés de outra (TMVar) pode acarretar em uma economia de 60% em consumo de energia. Percebemos também que nem sempre a relação entre consumo de energia e desempenho é clara. Em alguns cenários analisados, a configuração com melhor desempenho também apresentou o pior consumo de energia. Para ajudar desenvolvedores a entender melhor essa complexa relação, nós estendemos duas ferramentas de análise de desempenho existentes para coletar e apresentar dados sobre consumo de energia. Adicionalmente, baseado nos resultados do nosso estudo empírico, listamos um conjunto de recomendações para desenvolvedores com boas práticas de como escrever código energeticamente eficiente nesse ambiente.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 204-211).
This thesis relates to the emerging field of high-throughput density functional theory (DFT) computation for materials design and optimization. Although highthroughput DFT is a promising new method for materials discovery, its practical implementation can be difficult. This thesis describes in detail a software infrastructure used to perform over 80,000 DFT computations. Accurately calculating total energies of diverse chemistries is an ongoing effort in the electronic structure community. We describe a method of mixing total energy calculations from different energy functionals (e.g., GGA and GGA+U) so that highthroughput calculations can be more accurately applied over a wide chemical space. Having described methods to perform accurate and rapid DFT calculations, we move next to applications. A first application relates to finding sorbents for Hg gas removal for Integrated Gas Combined Cycle (IGCC) power plants. We demonstrate that rapid computations of amalgamation and oxidation energies can identify the most promising metal sorbents from a candidate list. In the future, more extensive candidate lists might be tested. A second application relates to the design and understanding of Li ion battery cathodes. We compute some properties of about 15,000 virtual cathode materials to identify a new cathode chemistry, Li₉V₃(P₂O₇)₃(PO₄)₂ . This mixed diphosphate-phosphate material was recently synthesized by both our research group and by an outside group. We perform an in-depth computational study of Li₉V₃(P₂O₇)₃(PO₄)₂ and suggest Mo doping as an avenue for its improvement. A major concern for Li ion battery cathodes is safety with respect to 02 release. By examining our large data set of computations on cathode materials, we show that i) safety roughly decreases with increasing voltage and ii) for a given redox couple, polyanion groups reduce safety. These results suggest important limitations for researchers designing high-voltage cathodes. Finally, this thesis describes the beginnings of a highly collaborative 'Materials Genome' web resource to share our calculated results with the general materials community. Through the Materials Genome, we expect that the work presented in this thesis will not only contribute to the applications discussed herein, but help make high-throughput computations accessible to the broader materials community.
by Anubhav Jain.
Ph.D.