Dissertations / Theses on the topic 'Theoretical'

Ab initio Molecular Orbital and Valence-Bond methods and the semiempidcal, AM1 method are applied in the studies of: 1. The proton affinity of diacetylene The gas-phase ion-molecule reaction between diacetylene and a proton was studied theoretically at the MP4SDQ/6-311G** level. The geometries, calculated harmonic vibrational frequencies and the proton affinity of the most stable structures are compared. The results from this study are supported by selected ion flow tube measurements and are compared with other calculations 2. The gas-phase reaction of CH₃CN and CH₃⁺. The reaction between CH₃CN and CH₃⁺ was studied at the MP4SDQ/6-31G* level of theory in order to determine the products and establish the multistep dissociation pathway of the reaction. The location and height of the transition states in the process is used as a criteria for the feasibility of the proposed pathway. The result is compared with the expediential and theoretical studies of the same system done by Wincel and coworkers [146]. 3. The geometries and force constants of small-sized organotin compounds The calculations on 12 small-sized organotin compounds were done at the HF/3- 21G* level of theory. The objective of this study was to provide the force constants of SnX and X-Sn-Y types for the use in Molecular Mechanic calculations of organotin compounds. The calculated geometries and harmonic vibrational frequencies of stannane and methyl stannane are compared with experimental results in order to measure the reliability of the calculations. 4. The chemical properties of CnO, CnO⁺, CnHO⁺, CnS, CnS⁺ and CnHS⁺ species in the instellar clouds CnO and CnS when n = 2 and 3 have been reported to be found in some interstellar clouds. These species in such environments are subjected to ionization and protonation processes. Theoretical studies of these species were done at the MP4SDQ/6-311G** level of theory. The calculations suggest that these species are more stable in protonated forms and could be intermediates of some steady state processes. 5. Theoretical study of C₆H₄+ formation in acetylenic flames C₆H₄⁺ has been detected as an intermediate in acetylenic flames. The semiempirical AM1 method was used to determine the most stable products and to establish a chemical mechanism of the reaction between C₄H₂⁺ and C₂H₂. The results from AM1 method were refined by ab initio calculations at the HF/4-31G andMP4SDQ/6-31G* level. From this study, only chemical pathways involved acyclic structure isomers are feasible. 6. A Valence-Bond study of BH2 radical In this study a Valence-Bond program was used on IBM PC/AT microcomputer to study the correlation between the nuclear bond angle and the angle of hybrid orbitals of BH₂. The energies of BH₂ from the Valence-Bond calculations were also compared with the energies from the Molecular Orbital method at the HF, MP4SDQ and CI level with best orbital energy basis sets, 10s6p/2s1p for boron atom and 6s/1s for hydrogen atoms. GAUSSIAN series programs, the MICROMOL package, the GAMESS program, a Valence-Bond program and the MOPAC program were used to perform the calculations.

Theoretical You is a collection of autobiographical queer love poems told from the perspective of a single speaker. These love poems speak not only to lovers and exes, but also to lust and sex and desire, to the speaker's father (they do not reciprocate the cruelty he has shown her--they are neither malicious nor vindictive), and perhaps most importantly, to the speaker herself--she recognizes herself as a lesbian, as a human, who deserves to love and be loved. While love is the crux of these poems, the collection is just as much about heartbreak (which is, of course, inevitably tied to love, is the consequence of love), heartbreak others have inflicted on the speaker and heartbreak she has inflicted on herself, having walked out on many of the women she addresses in the collection. The poems work to navigate the challenges of heartbreak by confronting homophobia, familial rejection, gender binaries and the appearance norms tied to them, as well as the grief that comes with simply being unable to stop missing someone. Here is a young woman who still loves every woman she has ever been with, who has so much love to give, who has a father who refuses to accept her, in a world that is often cruel. All of this together creates the complicated situation of being perpetually heartbroken, even when the speaker is happily in a relationship, even though she has learned to love herself.
Master of Fine Arts

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Linguistics and Philosophy, 2002.
Includes bibliographical references (v. 2, leaves 230-241).
The issue of non-configurationality is fundamental in determining the possible range of variation in Universal Grammar. This dissertation investigates this issue in the context of Warlpiri, the prototypical non-configurational language. I argue that positing a macroparameter, a single parameter that distinguishes configurational languages from non-configurational, requires variation on a magnitude not permitted by Universal Grammar. After refuting in detail previous macroparametric approaches, I propose a microparametric analysis: non-configurational languages are fully configurational and analysed through fine-grained parameters with independent motivation. I develop this approach for Warlpiri,partially on the basis of new data collected through work with Warlpiri consultants and analysis of Warlpiri texts. Beginning with A-syntax, I show that Warlpiri exhibits short-distance A-scrambling through binding and WCO data. I present an analysis of split ergativity in Warlpiri (ergative-/absolutive case-marking, nominative/accusative agreement), deriving the split from a dissociation of case and agreement, and the inherent nature of ergative case, rather than from non-configurationality. Extending the analysis to applicative constructions in Warlpiri, I identify both symmetric and asymmetric applicatives. I argue that the principled distinctions between them are explained structurally rather than lexically; therefore the applicative data provide evidence for a hierarchical verb phrase in Warlpiri. The analysis reveals the first reported distinction between unaccusative and unergative verbs in the language.
(cont.) Turning to A'-syntax, I argue that word order is not free in Warlpiri; rather Warlpiri displays an articulated left peripheral structure. Thus, word order variations are largely determined by positioning of elements in ordered functional projections based on their status in the discourse. Furthermore, I present evidence from WCO and island effects that elements appear in these projections through movement. Finally, I investigate the wh-scope marking construction, arguing for an indirect dependency approach. In developing the analysis, I argue, contrary to standard assumptions, that the dependent clauses related with verbs of saying in Warlpiri are embedded rather than adjoined. On the basis of a poverty of the stimulus argument, I conclude the construction must follow from independent properties of the language. I propose that it follows from the discontinuous constituent construction, which I equate with split DPs/PPs in Germanic and Slavic languages. The syntactic structure of Warlpiri that emerges from the dissertation strongly supports a configurational analysis of the language, and thereby the microparameter approach to nonconfigurationality.
by Julie Anne Legate.
Ph.D.

Deep learning has long been criticised as a black-box model for lacking sound theoretical explanation. During the PhD course, I explore and establish theoretical foundations for deep learning. In this thesis, I present my contributions positioned upon existing literature: (1) analysing the generalizability of the neural networks with residual connections via complexity and capacity-based hypothesis complexity measures; (2) modeling stochastic gradient descent (SGD) by stochastic differential equations (SDEs) and their dynamics, and further characterizing the generalizability of deep learning; (3) understanding the geometrical structures of the loss landscape that drives the trajectories of the dynamic systems, which sheds light in reconciling the over-representation and excellent generalizability of deep learning; and (4) discovering the interplay between generalization, privacy preservation, and adversarial robustness, which have seen rising concerns in deep learning deployment.

INFORME FINAL
"Alguns importants descobriments de la ciència són accidentals. Això fou, certament, el cas del ful·lerè C60. Quan ara fa quatre anys, l'any 2000, vaig iniciar el treball d'investigació sobre els metal·loful·lerens m'havien arribat veus de la importància mediàtica d'aquestes noves estructures però no de la intensa història del seu descobriment. Aquesta m'ha fascinat. Sobretot quan l'any 2003 vaig tenir la possibilitat de fer una estada al grup del professor Kroto de la universitat de Sussex (Gran Bretanya). Llavors els textos, sorprenents però inerts, que havia llegit sobre la història del descobriment dels ful·lerens prenien forma en espais coneguts i personatges propers". Aquest és el prefaci de la meva tesi. Segurament aquesta estada a Sussex al grup d'un dels descobridors dels ful·lerens ha estat el moment més entranyable en aquesta carrera científica per l'estudi dels metal·loful·lerens.
A partir de la síntesi de la molècula de C60 en quantitats apreciables la química dels ful·lerens en general, i en particular amb metalls de transició, ha experimentat un increment espectacular. L'objectiu d'aquesta tesi és l'estudi de l'estructura i la reactivitat de diferents derivats organometàl·lics de ful·lerens o metal·loful·lerens. El treball d'investigació usa les eines de la química computacional (Teoria del funcional de la densitat, DFT) per tal de modelar els metal·loful·lerens més interessants apareguts entre el 1999 i el 2005. Tot i que els metal·loful·lerens presenten una varietat d'estructures formidable, podem classificar-los en tres grans famílies des del punt de vista estructural: un primer grup són els metal·loful·lerens exoèdrics on els metalls es situen fora de la caixa, en un segon grup tenim els metal·loful·lerens heteroèdrics o heteroful·lerens on les caixes de carbonis han estat dopades (certes posicions han estat substituïdes) amb altres elements com ara: N, B, Si, Fe i altres metalls i finalment l'últim grup són els metal·loful·lerens endoèdrics on la derivatització metàl·lica es dóna a l'interior de la caixa. Així l'estudi teòric dels compostos més novedosos i novells de cadascuna de les tres famílies de metal·loful·lerens és el puntal de la present tesi doctoral. Per cadascuna de les famílies hem desgranat l'estructura electrònica i geomètrica, hem descrit el tipus d'enllaç metall-ful·lerè, hem avaluat els factors que intervenen en l'estabilitat relativa dels possibles isòmers, hem també predit la reactivitat davant de reaccions d'addició i finalment els hem caracteritzat des d'un punt de vista físic (càlcul del potencial d'ionització i afinitat electrònica). L'estructura electrònica ens ha permès seleccionar quins metal·loful·lerens endoèdrics seran estables avançant-nos als experimentalistes en la seva cerca de nous complexos. La diversitat de tipologies d'enllaç ha sigut tant gran com famílies de metal·loful·lerens. Hem descrit un enllaç iònic pels metal·loful·lerens endoèdrics, un enllaç covalent en el cas dels metal·loful·lerens heteroèdrics i un enllaç coordinatiu pels metal·loful·lerens exoèdrics. Hem aplicat noves metodologies per l'estudi de l'isomerisme. Les tècniques d'anàlisi multivariant de dades ens han permès esbrinar quins factors són importants per l'estabilitat relativa dels isòmers i a la vegada construir models de predicció per altres isòmers. Així doncs, l'acoblament de la química teòrica i la quimiometria ha estat sens dubte l'aportació més rellevant del present treball d'investigació.

Tarragona, 28 de novembre de 2004
Josep Maria Campanera Alsina


FINAL REPORT

The characterisation of the most novel metallofullerenes up to 2004 has been theoretically and systematically discussed in this study. From the structural point of view, metallofullerenes can be divided into three main groups, all of which have been discussed in this study: endohedral, heterohedral and exohedral metallofullerenes. The main families of compounds studied are Sc3-nMnN@Ck (n = 0-3, M = Y, La; k = 68, 78, 80) (endohedral), CxMn (x = 56, 57, 58, 59; M = Pt, Ir, Os; n = 1, 2) (heterohedral) and (-Ck){M(PH3)2}n (k = 60, 70, 84; M = Pt, Pd, Ni; n = 1, 2, 4, 6) (exohedral). The present study is a step forward in our knowledge of each of these families of compounds, and in particular, in our understanding of the metal-carbon bond, isomerism and reactivity. The DFT method proved to be an excellent computational tool for providing good geometries, for solving the intricacies of the different metal-carbon bonds, for producing experimental data (ionization potentials and electron affinities) and also for making predictions about isomerism stability and reactivity. The principal conclusions drawn about the species studied here are:
Different types of structures, different types of metal-carbon bonds. The metal units in each family of compounds are located differently in relation to the fullerene carbon framework: inside the cage, within the carbon framework and outside the cage. The encapsulation of a trimetallic nitride template unit (TNT, Sc3-nMnN; n = 0-3; M = Y, La) inside the carbon cage to produce TNT endohedral metallofullerenes is explained by an ionic pair (cage-metal) model in which the TNT unit formally transfers six electrons to the cage. On the other hand, in heterohedral metallofullerenes, metals establish a covalent metal-carbon bond without causing oxidation to the metal. Finally, the (MPH3)2 metal units situated exohedrally to the fullerene are only coordinated in a  mode to the CC bond.
Chemometric tools applied to isomerism studies. The regioisomers of heterohedral metallofullerenes are numerous: for example, the stoichiometry C57Pt2 has 47 distinct regioisomers. Thus, chemometric techniques which can manage considerable amounts of data must be used if we want to understand regioisomerism in heterohedral metallofullerenes. These tools have also been very useful for drawing conclusions from the considerable quantities of data provided by the factors which affect the stability of regioisomers. These tools have been used not only for analysing data but also for predicting the stability of other heterofullerenes.
TNT encapsulation stabilizes fullerene isomers that are not available as free fullerenes. TNT endohedral metallofullerenes are formed by the encapsulation of a metallic nitride template inside the following cages: D3-C68:6140, D3h'-C78:5, D5h-C80:6 and Ih-C80:7. Any of these cages have never been detected experimentally.So, endohedral metallofullerenes can make non-classical fullerene isomers available for study. Furthermore, on the basis of the electronic structure we predicted that no other IPR fullerenes between C60 and C84 will be capable of encapsulating a TNT unit, apart from the fullerene isomers that are already known.
Stability of the carbon skeleton is the principal factor that determines the regioisomer stability of the heterofullerenes. Metal atoms occupy neighbouring positions in the most stable structures of C57Pt2 and C56Pt2. Metal substitution deforms the carbon framework and partially destroys the fullerene aromaticity. This is the key factor in determining the stability of these disubstituted clusters. Indeed, it is much easier to make a big hole that permits the incorporation of two Pt atoms in the carbon cage than two smaller holes in two opposite sites of the fullerene.
Prediction of the exohedral reactivity taking into account the full characterization of the different CC bond types. We first performed a full characterization of all CC bond types of the fullerenes Ih-C60:1, D3-C68:6140, D5h-C70:1, D3h'-C78:5, Ih-C80:7, D2-C84:22 and D2d-C84:23. Each CC bond type is characterized by its topology, length, pyramidalization angle and Mayer bond order. This systematization enabled us to identify which sites were most reactive to a nucleophilic addition to free fullerenes or a [4 + 2] cycloaddition to TNT endohedral metallofullerenes.

Tarragona, 8th Novembre 2004
Josep Maria Campanera Alsina

Theoretical strength of solids is defined as the ultimate strength beyond which plastic deformation, fracture, or decohesion would occur. Understanding the microscopic origin from quantum mechanics and thermoelastic formulation is of great importance to mechanical properties and engineering design of various solids. While quite a few theory models have been made in the past century by several generations of scientists, including Frankel and Born, a general and convincing framework has not been fully established. We study this issue from three respects: (1) Unify various elastic stability criteria for solids that determine an upper bound of theoretical strength; (2) with ab initio method, we test the elastic stability conditions of crystal Au. The phenomenon of bifurcation is observed: under hydrostatic expansion, the rhombohedral modulus reaches zero first of all; while under uniaxial tensile stress, the tetragonal shear modulus first reaches zero; (3) propose a nonlinear theoretical formulation of stability criterion. As an analytic method, this scheme is quite simple, in the mean time, it saves computation resource.

Magnetic flux emergence is the subject of how magnetic fields from the solar interior can rise and expand into the atmosphere to produce active regions. It is the link that joins dynamics in the convection zone with dynamics in the atmosphere. In this thesis, we study many aspects of magnetic flux emergence through mathematical modelling and computer simulations. Our primary aim is to understand the key physical processes that lie behind emergence. The first chapter introduces flux emergence and the theoretical framework, magnetohydrodynamics (MHD), that describes it. In the second chapter, we discuss the numerical techniques used to solve the highly non-linear problems that arise from flux emergence. The third chapter summarizes the current literature. In the fourth chapter, we consider how changing the geometry and parameter values of the initial magnetic field can affect the dynamic evolution of the emerging magnetic field. For an initial toroidal magnetic field, it is found that its axis can emerge to the corona if the tube’s initial field strength is large enough. The fifth chapter describes how flux emergence models can produce large-scale solar eruptions. A 2.5D model of the breakout model, using only dynamic flux emergence, fails to produce any large scale eruptions. A 3D model of toroidal emergence with an overlying magnetic field does, however, produce multiple large-scale eruptions and the form of these is related to the breakout model. The sixth chapter is concerned with signatures of flux emergence and how to identify emerging twisted magnetic structures correctly. Here, a flux emergence model produces signatures found in observations. The signatures from the model, however, have different underlying physical mechanisms to the original interpretations of the observations. The thesis concludes with some final thoughts on current trends in theoretical magnetic flux emergence and possible future directions.

Category theory has been advocated as a replacement for set theory as the foundation for mathematics. It is claimed that as a foundation set theory is both inadequate and inappropriate. Set theory is considered inadequate because it cannot produce all of the mathematical objects of interest. Set theory is considered inappropriate because it provides a poor framework for mathematical research. In this dissertation, I argue that category theory is subject to exactly the same objections by considering the use of category theory for work in graph theory.

Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 2008.
Includes bibliographical references.
In this thesis, we have developed an extensive study to evaluate image restoration from a single image, colored or monochromatic. Using a mixture of Gaussian and Poisson noise process, we derived an objective function to estimate the unknown object and point spread function (psf) parameters. We have found that, without constraint enforcement, this blind deconvolution algorithm tended to converge to the trivial solution: delta function as the estimated psf and the detected image as the estimated object. We were able to avoid this solution set by enforcing a priori knowledge about the characteristics of the solution, which included the constraints on object sharpness, energy conservation, impulse response point spread function solution, and object gradient statistics. Applying theses constraints resulted in significantly improved solutions, as evaluated visually and quantitatively using the distance of the estimated to the true function. We have found that the distance of the estimated psf was correlated better with visual observation than the distance metric using the estimated object. Further research needs to be done in this area. To better pose the problem, we expressed the point spread function as a series of Gaussian basis functions, instead of the pixel basis function formalism used above. This procedure has reduced the dimensionality of the parameter space and has resulted in improved results, as expected. We determined a set of weights that yielded optimum algorithm performance.
(cont.) Additional research needs to be done to include the weight set as optimization parameters. This will free the user from having to adjust the weights manually. Of course, if certain knowledge of a weight is available, then it may be better to start with that as an initial guess and optimize from there. With the knowledge that the gradient of the object obeys long-tailed distribution, we have incorporated a constraint using the first two moments, mean and variance, of the gradient of the object in the objective function. Additional research should be done to incorporate the entire distribution in the objective and gradient functions and evaluate the performance.
by Jean J. Dolne.
S.M.

The first chapter proposes an alternative (`dual regression') to the quantile regression process for the global estimation of conditional distribution functions. Dual regression provides all the interpretational power of the quantile regression process while largely avoiding the need for `rearrangement' to repair the intersecting conditional quantile surfaces that quantile regression often produces in practice. The method can be appropriately modified to provide full structural distribution function estimates of the single equation instrumental variables model. In the second chapter, I consider nonparametric identification in nonseparable triangular models. I construct a conditional independence representation which coincides with a normalized version of the structural function in the outcome equation. I illustrate the methodology by estimating a semiparametric nonseparable triangular model with an endogenous regressor. An empirical application to the estimation of gasoline demand functions in the United States is given, and I find that the estimated demand functions are mostly downward-sloping once endogeneity of prices has been accounted for. In the third chapter, I give a falsifiable characterization of a conditional exogeneity restriction imposed upon a vector of instruments given the first stage disturbance in a nonseparable triangular model. I assume that at least two instrumental variables are available, one continuous and one binary or discrete, and use exogenous shifts in their values to generate sets of transformations under which the distribution of observables is invariant. This invariance property is shown to be equivalent to the conditional exogeneity restriction. This result can be used for testing the validity of the available instruments. The fourth and final chapter describes the set of overidentifying restrictions generated by nonmonotonicity of the relationship between the endogenous variable and a continuous instrument in a nonseparable triangular model. The graph of `inverse' functions of a nonmonotone conditional quantile function with respect to the instrument is shown to identify observationally equivalent subpopulations. A procedure for constructing such `inverse' functions is proposed and illustrated with an empirical example.

Um neue Halbleiter-Bauelemente zu entwickeln und die Effizienz bereits existierender zu verbessern, müssen neue Materialien erkundet und untersucht werden. Für Anwendungen in Hochleistungselektronik und UV-Optoelektronik ist Ga2O3 mit seiner ultra-weiten Bandlücke von 4.8 eV ein vielversprechender Kandidat. Diese Anwendung haben zu wachsendem Interesse an seinen fundamentalen elektronischen und optischen Eigenschaften geführt. Diese Dissertation präsentiert eine umfassende ab initio-Untersuchung der elektronischen Anregungen in Ga2O3, um zu dem Verständnis dieser fundamentalen Eigenschaften beizutragen. Die Arbeit besteht aus zwei Teilen: Im ersten Teil präsentieren wir eine Vielteilchen-Störungstheorie Methode zur konsistenten Berechnung der neutralen Anregungen von Valenz- und Kernelektronen in kristallinen Halbleitern. Diese ermöglicht die präzise Berechnung von Absorptions- und Streuungsspektren vom optischen bis zum Röntgenbereich. Zusätzlich präsentieren wir einen neuartigen Ausdruck für resonante inelastische Röntgenstreuung (RIXS) innerhalb unseres Vielteilchen-Formalismus, der eine detaillierte Analyse dieser Streuung erlaubt. Mit ausgewählten Beispielen demonstrieren wir das Potential unserer Implementation, die Spektren dieser verschiedenen spektroskopischen Methoden zu berechnen, zu analysieren und zu interpretieren. Im zweiten Teil der Dissertation verwenden wir unsere Methode, um die Anregungen der Valenzelektronen, sowie der Ga 1s-, Ga 2p- und O 1s-Elektronen in Ga2O3 zu berechnen. Wir finden ausgeprägte Unterschiede in den diversen Röntgenabsorptionsspektren von Ga2O3 -Polymorphen, die von der unterschiedlichen lokalen elektronischen Struktur stammen. Wir bestimmen die Zusammensetzung der Valenz- und Kernanregungen und analysieren ihre Signatur in den verschiedenen Absorptions- und Streuungsspektren. Abschließend demonstrieren wir wie RIXS einen zusätzlichen Blickwinkel auf die Valenz- und Kernanregungen und deren Wechselwirkungen ermöglicht.
To develop new semiconductor devices and improve the performance of existing ones, the exploration and understanding of novel materials is required. With an ultra-wide band gap of around 4.8 eV, Ga2O3 is a promising candidate for applications in UV-optoelectronics and power electronics. These applications have led to an increasing interest in its fundamental electronic and optical properties. In this thesis, we present a comprehensive first-principles study of the electronic excitations of Ga2O3 to contribute to the understanding of these fundamental properties. The thesis consists of two parts: In the first part, we present an all-electron many-body perturbation theory (MBPT) approach for consistent calculations of neutral core and valence excitations. It enables accurate calculation of absorption and inelastic scattering spectra in the optical, UV, and x-ray region. While these spectroscopic techniques probe either the valence or core excitations, resonant inelastic x-ray scattering (RIXS) reveals the interplay between the two. We present a novel expression for the RIXS cross section within our all-electron many-body formalism that allows for a detailed analysis of this interplay. We demonstrate the capability of our implementation to compute, analyze, and interpret the different spectroscopic techniques with selected examples of prototypical insulators. In the second part, we apply our approach to study valence excitations, as well as excitations of various core states, i.e. the gallium 1s, gallium 2p, and oxygen 1s states in Ga2O3 . Comparing the core spectra of Ga2O3 polymorphs, we find distinct differences that originate from their local environments. We determine the composition of valence and core excitons, and analyze their signatures in the various absorption and scattering spectra. Finally, we demonstrate how RIXS can be employed to provide a different viewpoint on the core and valence excitations and unravel the interplay between them.

In this work we investigate the global symmetries of six-dimensional superconformal field theories (6D SCFTs) via their description in F-theory. We provide computer algebra system routines determining global symmetry maxima for all known 6D SCFTs while tracking the singularity types of the associated elliptic fibrations. We tabulate these bounds for many CFTs including every 0-link based theory. The approach we take provides explicit tracking of geometric information which has remained implicit in the classifications of 6D SCFTs to date. We derive a variety of new geometric restrictions on collections of singularity collisions in elliptically fibered Calabi-Yau varieties and collect data from local model analyses of these collisions. The resulting restrictions are sufficient to match the known gauge enhancement structure constraints for all 6D SCFTs without appeal to anomaly cancellation and enable our global symmetry computations for F-theory SCFT models to proceed similarly.

To design a cyclone abatement system for particulate control, it is necessary to accurately estimate cyclone performance. In this cyclone study, new theoretical methods for computing travel distance, numbers of turns and cyclone pressure drop have been developed. The flow pattern and cyclone dimensions determine the travel distance in a cyclone. The number of turns was calculated based on this travel distance. The new theoretical analysis of cyclone pressure drop was tested against measured data at different inlet velocities and gave excellent agreement. The results show that cyclone pressure drop varies with the inlet velocity, but not with cyclone diameter. Particle motion in the cyclone outer vortex was analyzed to establish a force balance differential equation. Barth??s "static particle" theory, particle (with diameter of d50) collection probability is 50% when the forces acting on it are balanced, combined with the force balance equation was applied in the theoretical analyses for the models of cyclone cut-point and collection probability distribution in the cyclone outer vortex. Cyclone cut-points for different dusts were traced from measured cyclone overall collection efficiencies and the theoretical model for calculating cyclone overall efficiency. The cut-point correction models (K) for 1D3D and 2D2D cyclones were developed through regression fit from traced and theoretical cut-points. The regression results indicate that cut-points are more sensitive to mass median diameter (MMD) than to geometric standard deviation (GSD) of PSD. The theoretical overall efficiency model developed in this research can be used for cyclone total efficiency calculation with the corrected d50 and PSD. 1D3D and 2D2D cyclones were tested at Amarillo, Texas (an altitude of 1128 m / 3700 ft), to evaluate the effect of air density on cyclone performance. Two sets of inlet design velocities determined by the different air densities were used for the tests. Experimental results indicate that optimal cyclone design velocities, which are 16 m/s (3200 ft/min) for 1D3D cyclones and 15 m/s (3000 ft/min) for 2D2D cyclones, should be determined based on standard air density. It is important to consider the air density effect on cyclone performance in the design of cyclone abatement systems.

This thesis presents four research papers. In the first three papers we have derived analytical results for the transport properties in unconventional superconductors and ferromagnetic systems with multiple broken symmetries. In Paper I and parts of Paper II we have studied tunneling transport between two non-unitary ferromagnetic spin-triplet superconductors, and found a novel interplay between ferromagnetism and superconductivity manifested in the Josephson effect as a spin- and charge-current in the absence of an applied voltage across the junction. The critical amplitudes of these currents can be adjusted by the relative magnetization direction on each side of the junction. Furthermore, in Paper II, we have found a way of controlling a spin-current between two ferromagnets with spin-orbit coupling. Paper III considers a junction consisting of a ferromagnet and a non-unitary ferromagnetic superconductor, and we show that the conductance spectra contains detailed information about the superconducting gaps and pairing symmetry of the Cooper-pairs.

In the last paper we present a Monte Carlo study of an effective Hamiltonian describing orbital currents in the CuO2 layers of high-temperature superconductive cuprates. The model features two intrinsically anisotropic Ising models, coupled through an anisotropic next-nearest neighbor interaction, and an Ashkin–Teller nearest neighbor fourth order coupling. We have studied the specific heat anomaly, as well as the anomaly in the staggered magnetization associated with the orbital currents and its susceptibility. We have found that in a limited parameter regime, the specific heat anomaly is substantially suppressed, while the susceptibility has a non-analytical peak across the order-disorder transition. The model is therefore a candidate for describing the breakup of hidden order when crossing the pseudo-gap line on the under-doped side in the phase diagram of high-temperature superconductors.

Corruption is an important social and ethical problem
fight with it requires changes in values, norms and behavioral patterns of the society. This is usually a long and difficult process. Decades should pass to change deep values of a society. In the mean time, it is possible to combat corruption by changing incentive structures in the economy. If deep causes of the problem are analyzed carefully, a new system of governance can be established, such that, even most opportunist individuals do not find getting involved in corrupt practices profitable. Aim of this thesis is to examine characteristics of the system providing a fertile environment for corruption and to figure out factors stimulating corrupt transactions using game theoretical models. The first two models examine corruption as a kind of transaction between the briber and the bribee. In the models, it is shown that intermediaries sector occur from the profit maximization behavior of agents. This sector, by establishing long term, trust based relationships with bureaucrats, decreases risks occurring from the fact that the two parties involved in a corrupt transaction do not know each other perfectly. This sector, by reducing the likelihood of detection, serves corrupt transactions, and in return for the service it provided, takes commission, so gets benefit. Third model examines a strange type of corruption, a case of (spurious) middlemen obtaining bribe from the public service bureaucrats give, by pretending that he has influence on the acceptance or speed of it. The model tries to detect the characteristics of the environment making such a deception process persistent.

The use of high pressure as a tool to design new materials as well as to investigatematerials properties has become increasingly important during last one decade. The maingoal of the present thesis is to enhance the significance of the high pressure method as aquantitative tool in solid state investigations. Virtually all of the properties of solids aredirectly determined by their electronic structure. Similarly, the changes in the propertiesof solids under pressure are determined by the changes in the electronic structure underpressure. We have attempted to provide a comprehensive description of the resulting theoryin a electronic structure and the properties of condensed matter. The theoretical basis for these investigations is the density functional theory, in combinationwith ab initio method. The study of pressure induced phase transitions for thecompounds of CaF2, Cr2GeC, Ti3SiC2, as well as V at 0 K are presented. The latticeparameters, the phase transition pressures, the equation of states, the electronic structureshave been calculated and shown a good agreement with experimental results. A lattices dynamic study of the body center cubic (bcc) Fe under high pressure andhigh temperature is presented. The bcc iron could dynamical stabilize in the Earth innercore conditions. The unusual phase transition of bcc V under high pressure is investigatedand it is shown that the driving mechanism is electron-phonon interaction. Finally, a method based on the LDA+U approach has been applied to study spin statetransition in FeCO3. Our results show that magnetic entropy play a significant role in spinstate transition.
QC 20100920

Different theoretical approaches have been presented in this thesis to study the Raman scattering effect. The first one is response theory applied up to third order of polarization, where the determination of α, β and γ is used to calculate linear Raman scattering (resonance Raman scattering (RRS) and normal Raman scattering (NRS)), hyper Raman scattering (HRS) and coherent anti-Stokes Raman scattering (CARS), respectively. The response theory refers to adiabatic time-dependent density functional theory in the complex domain with applications on RRS and NRS, and to a recently developed methodology (Thorvaldsen et al. [105, 106]) for the analytic calculation of frequency-dependentpolarizability gradients of arbitrary order, here with applications on CARSand HRS. Various systems have been studied with the response theory, such as explosive substances (DNT, TNT, RDX and H2O2), optical power limiting materials (platinum(II) acetylide molecules), DNA bases (methylguanine-methylcytosine) and other systems (Trans-1,3,5-hexatriene and Pyridine). We have explored the dependency of the calculated spectra on parametrization in terms of exchange-correlation functionals and basis sets, and on geometrica loptimization. The second approach refers to time-dependent wave packet methodology for RRS and its time-independent counterpart in the Kramers-Heisenberg equation for the scattering cross section, which reduces the calculation of the RRS amplitude to computation of matrix elements of transition dipole moments between vibrational wave functions. The time-dependent theory has been used to examine RRS as a dynamical process where particular attention is paid to the notion of fast scattering in which the choice of photon frequency controls the scattering time and the nuclear dynamics. It is shown that a detuning from resonance causes a depletion of the RRS spectrum from overtones and combination bands, a situation which is verified in experimental spectra. The cross section of NRS has been predicted for the studied molecules to be in the order of 10−30 cm2/sr. A further increase in sensitivity with a signal enhancement up to 104 to 105 is predicted for the RRS technique, while CARS conditions imply an overall increase of the intensity by several orders of magnitude over NRS. In contrast to RRS and CARS, the HRS intensity is predicted to be considerably weaker than NRS, by about four orders of magnitude. However, silent modes in NRS can be detected by HRS which in turncan provide essential spectroscopic information and become complementary to NRS scattering. With the above mention methodological development for NRS, RRS, CARS and HRS, we have at our disposal a powerful set of modelling tools for the four different Raman techniques. They have complementary merits and limitations which facilitate the use of these spectroscopes in applications of Raman scattering for practical applications, for instance stand-off detection of foreign substances.
QC 20110112

This thesis deals with the phonology of Gitksan, a Tsimshianic language spoken in northern British Columbia, Canada. The claim of this thesis is that Gitksan exhibits several gradient phonological restrictions on consonantal cooccurrence that hold over the lexicon. There is a gradient restriction on homorganic consonants, and within homorganic pairs, there is a gradient restriction on major class and manner features. It is claimed that these restrictions are due to a generalized OCP effect in the grammar, and that this effect can be relativized to subsidiary features, such as place, manner, etc. It is argued that these types of effects are best analyzed with the system of weighted constraints employed in Harmonic Grammar (Legendre et al. 1990, Smolensky & Legendre 2006). It is also claimed that Gitksan exhibits a gradient assimilatory effect among specific consonants. This type of effect is rare, and is unexpected given the general conditions of dissimilation. One such effect is the frequency of both pulmonic pairs of consonants and ejective pairs of consonants, which occur at rates higher than expected by chance. Another is the occurrence of uvular-uvular and velar-velar pairs of consonants, which also occur at rates higher than chance. This pattern is somewhat surprising, as there is a gradient prohibition on cooccurring pairs of dorsal consonants. These assimilatory patterns are analyzed using the Agreement by Correspondence approach (Hansson 2001, Rose & Walker 2004), which mandates that output correspondents agree for some phonological feature. The general discussion of assimilation and dissimilation is continued in morphological contexts, such as reduplication. It is claimed there are differences in the gradient and categorical patterns of assimilation and dissimilation in Coast Tsimshian and Gitksan reduplicative contexts. A summary of the attested reduplicative patterns in the languages, as well as results from a nonce-probe task, supports this claim. This difference between Coast Tsimshian and Gitksan is indicative of a larger difference in the reduplicative patterns of the languages of the Tsimshianic family: each member of the family exhibits slightly different patterns of deglottalization. A typological study of these patterns suggests that glottalized sonorants and obstruents are fundamentally different segment types.
Arts, Faculty of
Linguistics, Department of
Graduate

A general method of analysis of a variety of stochastic processes in terms of probability density functions (PDFs) is developed and applied to several model as well as physically realistic systems. A model for diffusion in a bistable potential is the first system considered. The time dependence of the PDF for this system is described by a Fokker-Planck equation with non-linear coefficients. A numerical procedure is developed for finding the solution of this class of Fokker-Planck equations. The solution of the Fokker-Planck equation is obtained in terms of an eigenfunction expansion. The numerical procedure provides an efficient method of determining the eigenfunctions and eigenvalues of Fokker-Planck operators. The methods developed in the study of the model system are then applied to the trans-gauche isomerization of n-butane in CC1₄. This system is studied with the use of Kramers equation to describe the time evolution of the PDF. It is found that at room temperature the isomerization rate obeys a first order rate law. The rate constant for this system is sensitive to the collision frequency between the the n-butane and CC1₄ as has been previously suggested. It is also found that transition state theory underestimates the rate constant at all collision frequencies. However, the activation energy given by transition state theory is consistent with the activation energy obtained in this work. The problem of the escape of light constituents from planetary atmospheres is also considered. Here, the primary objective is to construct a collisional kinetic theory of planetary exospheres based on a rigorous solution of the Boltzmann equation. It is shown that this problem has many physical and mathematical similarities with the problems previously considered. The temperature and density profiles of light gases in the exosphere as well as their escape fluxes are calculated. In the present work, only a thermal escape mechanism was considered, although it is shown how non-thermal escape mechanisms may be included. In addition, these results are compared with various Monte-Carlo calculations of escape fluxes.
Science, Faculty of
Chemistry, Department of
Graduate

This analytical study describes, in a general way, via a select literature overview, the historical development of distant communications technology and information (computer) technology; and presents a theoretical construct for TELETECHNOLOGY signals and their manipulation. The visual, sound and binary signalling elements constitute and modulate the interactions of the radiant energy activity within the abstract influx model and relate these to the actual ethnotechnological world. A purview of representative technological terms is broached; implications for the use and management of communications and information technologies are presented; a measurement instrument framework is depicted; and a possible new world view is proposed.
Education, Faculty of
Graduate

In this thesis I present a reading of Hume's projectionism. Hume took very seriously our predicament of being in a position of making judgments about the external world, and about other minds, solely on the basis of our own beliefs. By "Hume's projectionism" I mean his answer to this predicament, namely, that our minds construct beliefs unaided by mind-independent events; that these beliefs are then projected upon the world; and that for us the world literally becomes the bearer of our notions. "Hume's projectionism" thus is an examination of the external world, or rather what we believe it to be, through the analysis of conceptual constructs that for us constitute its very nature. In my interpretation I place considerable emphasis upon the fact that Hume identifies three essentially different sets of conceptual tools that result in three theoretical standpoints---that of common sense, the theory of the false philosophy, and that of the true philosophy. Human beings are capable of constructing three incompatible and independent sets of beliefs. Hume believes that we have no independent and objective grounds that would warrant the evaluation of our projections. Consequently, our only hope to establish a normative evaluation of our beliefs lies in the analysis of the conceptual tools by which each of these projections is constructed. I develop three separate arguments to support my reading. First, I argue that Hume's arguments implicitly rely on his theory of theories, which I set out in chapter 2. This chapter considers the conceptual tools that Hume can use in normative evaluations of our beliefs. Secondly, in chapter 3 I seek to show that Hume should best be seen as attempting to reconcile the dispute between Locke's scientific realism and Berkeley's instrumentalism. By showing the historical roots of Hume's projectionism I hope to undermine any charge that my reading of Hume is anachronistic. Thirdly, in chapter 4 I examine Hume's account of probability, where I seek to illustrate Hume's attempt to assess the changes in philosophical problems that result from his considered belief that absolute truth and certainty are unattainable. In my thesis I hope to establish that Hume's philosophy is projectionism through and through. This is a highly controversial interpretation. By definition, if Hume is a projectionist, then his philosophical position cannot be defined solely as empiricism, or skepticism, or common-sense realism. I believe that if we focus upon Hume's implicit philosophical methodology, then we have no choice but to consider seriously the issue about the variety of his arguments. We then have to come to understand how it is possible for Hume to be an empiricist, a sceptic, and a realist---all at the same time? I argue that we can best understand this only if we view Hume's system as projectionism.

This thesis deals with the phonology of Gitksan, a Tsimshianic language spoken in northern British Columbia, Canada. The claim of this thesis is that Gitksan exhibits several gradient phonological restrictions on consonantal cooccurrence that hold over the lexicon. There is a gradient restriction on homorganic consonants, and within homorganic pairs, there is a gradient restriction on major class and manner features. It is claimed that these restrictions are due to a generalized OCP effect in the grammar, and that this effect can be relativized to subsidiary features, such as place, manner, etc. It is argued that these types of effects are best analyzed with the system of weighted constraints employed in Harmonic Grammar (Legendre et al. 1990, Smolensky & Legendre 2006). It is also claimed that Gitksan exhibits a gradient assimilatory effect among specific consonants. This type of effect is rare, and is unexpected given the general conditions of dissimilation. One such effect is the frequency of both pulmonic pairs of consonants and ejective pairs of consonants, which occur at rates higher than expected by chance. Another is the occurrence of uvular-uvular and velar-velar pairs of consonants, which also occur at rates higher than chance. This pattern is somewhat surprising, as there is a gradient prohibition on cooccurring pairs of dorsal consonants. These assimilatory patterns are analyzed using the Agreement by Correspondence approach (Hansson 2001, Rose & Walker 2004), which mandates that output correspondents agree for some phonological feature. The general discussion of assimilation and dissimilation is continued in morphological contexts, such as reduplication. It is claimed there are differences in the gradient and categorical patterns of assimilation and dissimilation in Coast Tsimshian and Gitksan reduplicative contexts. A summary of the attested reduplicative patterns in the languages, as well as results from a nonce-probe task, supports this claim. This difference between Coast Tsimshian and Gitksan is indicative of a larger difference in the reduplicative patterns of the languages of the Tsimshianic family: each member of the family exhibits slightly different patterns of deglottalization. A typological study of these patterns suggests that glottalized sonorants and obstruents are fundamentally different segment types.

In the past three decades, spintronic devices have played an important technological role. Half-metallic alloys have drawn much attention due to their special properties and promised spintronic applications. This dissertation describes some theoretical techniques used in first-principal calculations of alloys that may be useful for spintronic device applications with an emphasis on half-metallic ferromagnets. I consider three types of simple spintronic materials using a wide range of theoretical techniques. They are (a) transition metal based half-Heusler alloys, like CrMnSb, where the ordering of the two transition metal elements within the unit cell can cause the material to be ferromagnetic semiconductors or semiconductors with zero net magnetic moment, (b) half-Heusler alloys involving Li, like LiMnSi, where the Li stabilizes the structure and increases the magnetic moment of zinc blende half-metals by one Bohr magneton per formula unit, and (c) zinc blende alloys, like CrAs, where many-body techniques improve the fundamental gap by considering the physical effects of the local field. Also, I provide a survey of the theoretical models and numerical methods used to treat the above systems.

This thesis is centred on the analysis of how the different groups of specialist experts that make up theoretical physics at large communicate and transmit knowledge between themselves. The analysis is carried out using two sociological frameworks: the Studies in Expertise and Experience (SEE) approach Collins and Evans, and mechanisms of sociological and institutional trust in the general sociology of science literature. I argue that the communication process is carried out in two ways: through interactional expertise that is based on deep comprehension when the interaction is between micro-cultures that are sociologically closely connected, and through lower forms of knowledge relying on trust for the micro-cultures that are sociologically far apart. Because the SEE framework is strongly based on the transmission of tacit knowledge, an analysis of the importance of tacit knowledge in theoretical physics is carried out to support the SEE analysis, and specific types of tacit knowledge are closely examined to understand how they shape theoretical physics practice. I argue that `physical intuition', one of the guiding principles of all theoretical activity, is in fact a type of tacit knowledge -somatic tacit knowledge- that is well known within social studies of science. The end result is a description of physics that highlights the importance of sociological mechanisms that hold the discipline together, and that permit knowledge to flow from the empirical to the theoretical poles of physics practice. The thesis is supported by unstructured interview material and by the author's prolonged interaction within theoretical physics professional circles

This thesis develops a theoretical framework to evaluate XML retrieval. XML retrieval deals with retrieving those document parts that specifically answer a query. It is concerned with using the document structure to improve the retrieval of information from documents by only delivering those parts of a document an information need is about. We define a theoretical evaluation methodology based on the idea of `aboutness' and apply it to XML retrieval models. Situation Theory is used to express the aboutness proprieties of XML retrieval models. We develop a dedicated methodology for the evaluation of XML retrieval and apply this methodology to five XML retrieval models and other XML retrieval topics such as evaluation methodologies, filters and experimental results.

This thesis involves the computational study of uranium, neptunium, plutonium, and americium complexes in aqueous and non-aqueous solution. It seeks answers to specific experimental questions, to provide additional information to experiments, and to make predictions that experimentalists can use to design or abstain from new experiments. The work mainly uses density functional theory, as this method shows good scaling with system size. This is important because actinides have a large number of electrons, and the ligands in this work are often very large. The family of compounds with the formula U02(H2O) (OH)m 2 ,7 ( +w=5) are studied, to investigate how the changing equatorial ligand field affects the uranyl ion as hydroxide ligands replace water ligands. The investigation involves uranyl stretching vibrations, orbital analysis, charge analysis, and bond orders. I evaluate how solvent models affect the geometry and uranyl stretching vibrations. The cis and trans isomers of the U02Cl2(Cy3PNH)2 and U02Cl2(Cy3PO)2 (Cy = cyclohexyl) exist in equilibrium, even though one expects the bulky phosphinimine and phosphine oxide ligands to show large repulsion in a cis configuration. It is unknown experimentally whether the trans or the cis isomer is the major species. N-donor ligands displace O-donor ligands, when added to solution of U02Cl2(Cy3PO)2, i.e. the N-donor ligands form stronger bonds to uranium than the O-donor ligands. I investigate which isomer is the major species, and explain why the cis isomer exists at all. The origin of the stronger N-donor ligand bonds is studied by orbital analysis, energy decomposition, and electron densities. This study is extended to include all halide ligands, and uranium is substituted by neptunium, plutonium, and americium. I use the concepts of electron localisation and electron density differences on the systems above, to further study the actinyl axial and equatorial bonding in greater detail. I compare this analysis with the results from more traditional methods, e.g. charge analysis. I also investigate if it is possible to form stable c/s-uranyl compounds and neptunyl complexes with cation-cation interactions.

In recent years, magnetic separation has attracted considerable attention as a technique for the separation of paramagnetic particles from the media carrying them. Equipment may be at least approximately specified by theoretical formulae, or by analysis of the results of laboratory experiments. In general, and neglecting experimental errors, the two methods of predicting separator performance will not agree due to the physical approximations which are necessary to achieve analytical solutions of the resulting equations.

Acoustic noise problems are encountered in many fields and are very often undesirable. The localisation of sound sources is the first step 10 reducing noise problems. In this thesis, the ability and feasibility of an acoustic camera in this regard is demonstrated The acoustic camera deals with the problem of sound sources coming from different directions by estimating the sound contributions incident to the acoustic camera. One example of an aero-acoustic noise problem is an air plane with its air foil. These cause unwanted noise due 10 the flowed air. Or another example is the current collector on trains which causes unwanted noise as well as affecting driving. Another problem, dealt with later in this thesis, is a cylinder flowed by air in a wind tunnel. A practical case 0/ this problem is a car antenna in the form of a cylinder; this causes noise due to the driving wind Fans can be optimised for aero-acoustics as well - an example is a cooling fan in a computer, or larger fans for air conditioners that can transport the noise over the whole tunnel in which they are built. Some processing techniques are used and implemented in the acoustic camera. The first technique is the "classical" Delay-and-Sum Beam/arming technique and the improved orthogonal beamforming, with the ability to separate non-correlated sound sources in a Single measurement. The second technique is based on the decomposition of the Eigenvalues of the cross spectral matrix. In addition to the experimental section of this thesis, the results are compared to a simulation, where a flowed object measured with the acoustic camera is compared to a suitable simulation with the same parameters like dimensions and velocity. Here f/owed means that a suitable object, a cylinder for example, is placed in the wind tunnel and flowed by air. The outcome of this thesis is the analysing of a flow induced problem, a fan for example. First steps were done with 2D flow simulations of a cylinder to become familiar with the topic program and implementing MATLAB® code to process the points of interest. This analysing could be done with a simulation or with the acoustic camera. The aim of this work is concerned with sound sources and the mechanism behind it. Suitable aero-acoustic experiments were chosen that can be analysed with the acoustic camera and with numerical simulation as well. With the acoustic camera, these sound sources can be visualised using the beamforming method A similar procedure should be done to the numerical simulations. These simulations are done and the sound sources are visualised there as well by rebuilt an array of microphones, which acts as acoustic camera, in the numerical simulations.

This thesis describes the application of total energy pseudopotential calculations to the study of the mechanical deformation of diamond. It begins with a description of the theoretical basis for these calculations. Following this is an outline of the elements required for an implementation of the theory for periodic systems and using a basis set of plane waves. The simulations performed on the deformation of diamond approximate the system of interest to one in which the system is periodically repeated. The importance of this approximation is studied in detail and the errors introduced are found to be small enough to neglect. Next, a study of one of the most unusual aspects of the mechanical deformation of diamond is presented. Diamond polishing and in particular the very strong anisotropy between different polishing directions on the (110) surface is simulated. The experimental evidence regarding diamond polishing is presented and the approximations made in representing the polishing process by the simulations are discussed. Differences in the mechanism of material removal between polishing directions are related to processes of nanogroove formation and are shown to be consistent with the experimental findings. A preliminary study which investigates the resolution limit of Atomic Force Microscopy (AFM) in the contract mode is presented. A central problem in contact mode AFM has been whether or not tips which have a single atom at the apex can support the long range attractive van de Waals force. Two vertical scans of a single atom diamond tip into a diamond (111) surface are presented. These simulations indicate that, in this system, the single atom tip is resistant to force in the vertical direction but that lateral movement results in removal of the apex atom from the tip. The thesis concludes with a brief survey of the central results and a discussion of the likely future developments in the field.

This Thesis describes some theoretical studies on ligated and bare clusters. Chapter 1 gives a review of the two theoretical models, Tensor Surface Harmonic Theory (TSH) and Jellium Model, accounting for the electronic structures of ligated and bare clusters. The Polyhedral Skeletal Electron Pair Theory (PSEPT), which correlates the structures and electron counts (total number of valence electrons) of main group and transition metal ligated clusters, is briefly described. A structural jellium model is developed in Chapter 2 which accounts for the electronic structures of clusters using a crystal-field perturbation. The zero-order potential we derive is of central-field form, depends on the geometry of the cluster, and has a well-defined relationship to the full nuclear-electron potential. Qualitative arguments suggest that this potential produces different energy level orderings for clusters with a nucleus with large positive charge at the centre of the cluster, enabling the spherical jellium model to be applied to alkali metal clusters seeded with magnesium and zinc. Analysis of the effects of the non-spherical perturbation on the spherical jellium shell structures leads to the conclusion that for a cluster with a closed shell electronic structure a high symmetry arrangement which is approximately or precisely close packed will be preferred. It also provides a basis for rationalising those structures, which have been predicted using ab initio calculations, of clusters with incomplete shell electronic configurations In Chapter 3, the geometric conclusions derived in the structural jellium model are developed in more detail. Alkali metal clusters with closed shell electronic configurations according to the jellium model adopt geometries of high symmetry and based on the T_d , O_h and I_h point groups. For high nuclearity clusters alternative high symmetry structures can occur and those which are either the most close packed or spherical are predicted to be the most stable. When the jellium closed shell "magic numbers" coincides with one of these high symmetry structures then the cluster will be particularly stable. The group theoretical consequences of the Tensor Surface Harmonic Theory are developed in Chapter 4 for[ML₂]_n, [ML₄]_n and [ML₅]_n clusters where either the xz and yz or x²-y² and xy components to L^π_d and L^δ_d do not contribute equally to the bonding. The closed shell requirements for such clusters are defined and the orbital symmetry constraints pertaining to the interconversion of conformers of these clusters are described. In Chapter 5 Stone's Tensor Surface Harmonic methodology is applied to high nuclearity transition metal carbonyl cluster compounds with 13-44 metal atoms. Two limiting bonding situations are identified and represented in terms of general electron counting rules. If the radial bonding effects predominate the clusters are characterised by 12n_s+Δ_i valence electrons, where Δ_i is the characteristic electron count of the interstitial moiety. If radial and tangential bonding effects are important then the total number of valence electrons is 12n_s+2(s_s+s_i-l), where s_s and s_i are the number of skeletal bonding molecular orbitals associated with surface (s_s) and interstitial (s_i) moieties. Chapter 6 develops a new theoretical framework to account for the bonding in the high nuclearity ligated clusters with columnar topologies. The wave functions of columnar metal clusters can be expressed as an expansion based on the particle on the cylinder problem. This bonding analysis is applied to clusters containing columns of triangles and squares. In Chapter 7 the origin of non-bonding orbitals in molecular compounds is reviewed and analysed using general quantum mechanical considerations. A combination of the pairing theorem and a group theoretical analysis leads to a definition of the number of the non-bonding molecular orbitals in co-ordination, polyene and cluster compounds. The non-bonding molecular orbitals have been generated by defining the nodal characteristics of the relevant orbitals and evaluating the solutions under the appropriate boundary conditions. The stereochemical role of nonbonding molecular orbitals in co-ordination compounds is also discussed.

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This thesis argues that coercive counterinsurgency (COIN) has played a larger role historically than is currently recognized in todays FM 3-24 doctrine, which reflects the popular view of COIN as emphasizing protection of the population. The extent to which the essence of COIN has been misunderstood and misinterpreted, undermining the coercive gold standard is a central concern. While there has been some recognition of the utility of coercive action against insurgents, ethical concerns about proportionality and the indiscriminate use of force have imposed constraints. Where the gold standard represents deliberate, strict coercion against the population, FM 3-24 emphasizes a far more limited coercive approach, one that may be to the detriment of COIN operations as understood in historical perspective.

Optical metamaterials are artificial media that exhibit new properties from structuring on the nanometric scale. One of the main researches in metamaterials investigates materials with negative refractive index, which can allow the development of perfect lens and other exciting potential applications. In this thesis, we theoretically study the properties of negative-index optical fishnet metamaterials, especially the origin of their negative-valued refractive index, and also associated theoretical problems. The thesis can be divided into 4 parts. In the first part we study the light scattering at an interface between air and a semi-infinite fishnet metamaterial. With a fully-vectorial numerical method, we calculate the scattering coefficients of the interface and find that the energy transport inside the fishnet is due to a single Bloch mode, the fundamental one. Based on the single-interface scattering coefficients and the effective index of this Bloch mode we propose a new algorithm for retrieving effective optical parameters of the metamaterial. The approach emphasizes the key role played by the fundamental Bloch mode and provides retrieved parameters that are more accurate or stable than those obtained by classical methods based only on light reflection and transmission through finite-thickness metamaterial slabs. Due to the importance of the fundamental Bloch mode in the light transport in metamaterials, in the second part, based on the Bloch mode orthogonality we derive closed-form expressions for the scattering coefficients at an interface between two periodic media with slightly different geometrical parameters, which is a computationally demanding electromagnetic problem. We show that the analytical expressions are very accurate for various geometries, including dielectric waveguides and metallic metamaterials. Thus they can be useful for designing and engineering stacks of periodic structures. As shown in the first part, the fundamental Bloch mode is central to explain the negative refraction phenomenon in fishnet metamaterials. In the third part, we derive an accurate semi-analytical model for the complex propagation constant of the fishnet fundamental Bloch mode. This is achieved by analyzing light propagation and scattering inside the fishnet. The model shows that the origin of broad-band negative index of fishnets can be mainly understood as a plasmon resonance in the transversal metal-insulator-metal (MIM) channels. The plasmon resonance enhances the 'magnetic' response of fishnet and the losses associated to this resonance can be compensated by including gain in the dielectric layers of the fishnet. Furthermore, the model allows an easy and precise geometrical tailoring of fishnet metamaterials. As shown in the third part, it is the plasmon resonance in metal-insulator-metal (MIM) structures that induces the negative index of fishnet metamaterials. In the last part, we study the asymptotic behavior of 3D MIM nanoresonators, as the resonator size is shrunk below the diffraction limit. In particular we show that the quality factor increases from 10 to 100 when the resonator volume is scaled down from (λ/2n)3 to (λ/50)3. We provide a comprehensive study with a semi-analytical Fabry-Perot model. The model remains accurate over the whole size scale even in the quasi-static regime for which retardation effects are not expected. This important and counterintuitive result indicates that both localized plasmon resonances in nanoparticles and delocalized resonance in elongated plasmonic nanowires can be possibly understood as a wave-retardation based antenna problem.