Este trabalho propõe uma metodologia para enumerar soluções, que indiquem a barra e a compensação de potência reativa necessária para o sistema elétrico sob análise, que atendam aos requisitos avaliados pela função objetivo e as restrições. Nessa alocação de compensação ótima de potência reativa, obtemos as melhores barras e configurações de potências e tecnologias de dispositivos de compensação, minimizando as perdas totais de potência ativa da rede. Em redes fracas com conversores de frequência (por exemplo, para conexão de fontes renováveis, ou interligações utilizando conversores HVDC), esta metodologia proposta busca a melhor relação de curto-circuito trifásico (SCR) no ponto de conexão do conversor de frequência, melhorando a conexão da barra de interesse. O método busca soluções para alocar um único dispositivo de compensação, e soluções alocando simultaneamente dois dispositivos. A metodologia proposta baseia-se na enumeração exaustiva das soluções, e o estudo de caso nos sistemas de 14 e 30 barras do IEEE mostrou a aplicabilidade e funcionalidade da metodologia proposta. / This work proposes a methodology to enumerate solutions, which indicate the bar and the reactive power compensation required for the electrical system under analysis, that meet the requirements evaluated by the objective function and the constraints. In this allocation of optimal compensation of reactive power, we obtain the optimal bars and technologies of compensation devices, minimizing the total losses of active power of the network. In weak networks with frequency converters (e.g. for connection of renewable sources, or interconnections using HVDC converters), the proposed methodology seeks the best threephase short-circuit (SCR) relation at the connection point, improving the connection of the new generation. The method looks for solutions to allocate a single compensation device, and solutions to allocate two devices simultaneously. The proposed methodology is based on the exhaustive enumeration of the solutions. A case study carried out in the IEEE 14 and 30 bus systems shows the applicability and performance of the proposed methodology.

Dans cette thèse, nous étudions les écoulements de fluides compressibles décrits par les équations de Navier-Stokes-Fourier dans les cas stationnaire et instationnaire et avec des conditions de bord assurant l’isolation thermique et mécanique du fluide. On commence par le cas stationnaire barotrope et des conditions de Navier à la frontière du domaine. La pression est donc de la forme p(%) = % où est appelé coefficient adiabatique et nous arrivons à montrer l’existence de solutions faibles pour > 1.On généralise ensuite ce résultat aux équations de Navier-Stokes-Fourier avec conduction de la chaleur et glissement (partiel ou total) au bord, toujours dans le cas stationnaire. On montre cette fois-ci l’existence de solutions faibles particulières appelées solutions entropiques variationnelles respectant l’inégalité d’entropie pour > 1 et l’existence de solutions faibles respectant le bilan de l’énergie totale au sens faible pour > 5/4. On travaille ensuite sur les écoulements instationnaires décrits par les équations de Navier-Stokes-Fourier sur une large variété de domaines non bornés, tout d’abord pour des conditions de bord d’adhérence puis pour des conditions de Navier à la frontière (ce qui restreintquelque peu la diversité des domaines non bornés admissibles). On arrive à montrer l’existence de solutions faibles particulières respectant l’inégalité d’entropie et une inégalité de dissipation remplaçant l’égalité de conservation d’énergie totale dans le volume qui n’a plus de sens dans les domaines non bornés. Par après, on met en place une inégalité dite d’entropie relative dont on montre qu’elle est respectée par certaines des solutions faibles exhibées auparavant. Ces solutions sont appelées solutions dissipatives. On parvient à prouver que pour chaque donnée initiale, il existe au moins une solution dissipative. Cette inégalité d’entropie relative nous permet de démontrer le principe d’unicité forte-faiblepour nos solutions dissipatives. Précisément, cela signifie qu’une solution dissipative et une solution forte issues des mêmes données initiales coïncident sur le temps maximal d’existence de la solution forte. La propriété d’unicité forte-faible donne un fondement à la notion de solution dissipative pour les domaines non bornés. / In this thesis, we study the Navier-Stokes-Fourier system describing the flow of compressible fluids both in the steady and unsteady case and we suppose that the fluid is thermally and mechanically isolated. We start with the case of a steady barotropic fluid and Navier boundary conditions. In this situation, the pressure law considered is of the form p(%) = %, where is called the adiabatic constant. We show the existence of weak solutions for > 1. We then extend this result to the complete Navier-Stokes-Fourier system with heat conductivity and slip or partially slip boundary conditions, once again in thesteady case. In this setup, we prove the existence of a specific type of weak solutions, called variationnal entropy solutions, which satisfy the entropy inequality for > 1 and the existence of weak solutions satisfying the conservation of total energy in its weak formulation for > 5/4. We then treat the unsteady flows described by the complete Navier-Stokes-Fourier system on a large class of unbouded domains, first with no-slip boundary conditions and then with the Navier boundary conditions which reduce the class of the admissible unbounded domains. We manage to prove the existence of a specific type of weak solutions verifying the entropy inequality and a dissipation inequality instead of the global conservation of total energy which is no more relevant in the unbounded domains. Afterwards, we establish a new inequality called relative entropy inequality and we show that it is satisfied by some of the weak solutions presented previously. These are called dissipative solutions. Next we show that for any given initial data there exists at least one dissipative solution. This observation allows us toperform the proof of the weak-strong uniqueness principle in the class of dissipative solutions. Precisely, it means that a dissipative solution and a classical one emanating from the same initial data coincide as long as the latter exists. The weak-strong uniqueness property justifies the concept of dissipative solutions in the situation of unbounded domains.

Lee and Zhou introduced the clean index of rings in 2004. Motivated by this work, Basnet and Bhattacharyya introduced both the weak clean index of rings and the nil clean index of rings and Cimpean and Danchev introduced the weakly nil clean index of rings. In this work, we calculate each of these indices for the rings ℤ/nℤ and matrix rings with entries in ℤ/nℤ. A generalized index is also introduced.

This study examines the determinants of the use of uncertain and weak modal words in 10-K filings and the effect of these words on analyst forecast attributes. I find that the use of uncertain and weak modal words in 10-K filings is positively (negatively) associated with firm size, volatility of business and operations (firm age and number of business segments). More importantly, after controlling for readability and management tone, I find that the use of uncertain and weak modal words in 10-K filings is associated with greater analyst following, lower forecast dispersion, greater forecast accuracy, and lower uncertainty in analysts’ overall and common information environment. The results of this study provide more insights into why management uses uncertain and weak modal words in 10-K filings and how these words in 10-K filings affect analysts’ behavior and their forecast outcomes.

Weak bonds such as hydrogen bond, pi-pi stacking and van der Waals interaction are much weaker in the strength but play a more important role for the existence of various lives. For example, they are the major intermolecular interactions in the liquid and solid structure of water and determine the 3 dimensional structure of protein and DNA, which are the crucial organic molecules in lives. As a result, studying these weak bonds can lead to the better understanding of fundamental knowledge of lives. Kohn-Sham (K-S) Density Functional Theory (DFT) is an accurate and effect way to investigate the fundamental properties for many-body systems, in which, only the exchange-correlation energy as a functional of electron density need to be approximated. However, weak interaction system is still a challenge problem for KS-DFT. In this dissertation work, several standard density functionals are used to study these weak interactions in the solid state structure ice as long as nucleic bases molecules in the biologic system. It is found that the hydrogen bond can be well described by most semilocal functionals: the mismatch problem of ice Ih and AgI for GGA functional can be solved by using the higher level meta-GGA functionals and the binding length and energy between nucleic bases in DNA can be well described. However, the more accurate dispersion correction is strongly needed for van der Waals interactions and pi stacking for super-high pressure ice phases and large size biologic molecules, where van der Waals interaction takes major role. Finally, the basic structural properties of various phases of ice and DNA can be understood based on the investigation with appropriate functionals. / acase@tulane.edu

The present study examined the relationships between anxiety, cognitive functioning, weak central coherence, and social skills in a group of 102 children diagnosed with an Autism Spectrum Disorder (ASD; Autistic disorder, Asperger's disorder, and PDD-NOS). The results indicated that children diagnosed with Asperger's disorder had significantly higher cognitive functioning and Block Design scores (i.e., weaker central coherence) compared to those diagnosed with autism or PDD-NOS. Regression analyses results showed that anxiety and cognitive functioning moderated the association between weak central coherence and social skills. For children with low cognitive functioning and high anxiety, weak central coherence was associated with poorer social skills than those with low cognitive functioning, high anxiety, and strong central coherence. For children with high cognitive functioning and high anxiety, weak central coherence was associated with better social skills than those with high cognitive functioning and strong central coherence. Implications of these findings are discussed. / acase@tulane.edu

There has been an increasing interest in uncovering smuggled nuclear materials associated with the War on Terror. Detection of special nuclear materials hidden in cargo containers is a major challenge in national and international security. We propose a new physics-based method to determine the presence of the spectral signature of one or more nuclides from a poorly resolved spectra with weak signatures. The method is different from traditional methods that rely primarily on peak finding algorithms. The new approach considers each of the signatures in the library to be a linear combination of subspectra. These subspectra are obtained by assuming a signature consisting of just one of the unique gamma rays emitted by the nuclei. We propose a Poisson regression model for deducing which nuclei are present in the observed spectrum. In recognition that a radiation source generally comprises few nuclear materials, the underlying Poisson model is sparse, i.e. most of the regression coefficients are zero (positive coefficients correspond to the presence of nuclear materials). We develop an iterative algorithm for a penalized likelihood estimation that prompts sparsity. We illustrate the efficacy of the proposed method by simulations using a variety of poorly resolved, low signal-to-noise ratio (SNR) situations, which show that the proposed approach enjoys excellent empirical performance even with SNR as low as to -15db. The proposed method is shown to be variable-selection consistent, in the framework of increasing detection time and under mild regularity conditions. We study the problem of testing for shielding, i.e. the presence of intervening materials that attenuate the gamma ray signal. We show that, as detection time increases to infinity, the Lagrange multiplier test, the likelihood ratio test and Wald test are asymptotically equivalent, under the null hypothesis, and their asymptotic null distribution is Chi-square. We also derived the local power of these tests. We also develop a nonparametric approach for detecting spectra indicative of the presence of SNM. This approach characterizes the shape change in a spectrum from background radiation. We do this by proposing a dissimilarity function that characterizes the complete shape change of a spectrum from the background, over all energy channels. We derive the null asymptotic test distributions in terms of functionals of the Brownian bridge. Simulation results show that the proposed approach is very powerful and promising for detecting weak signals. It is able to accurately detect weak signals with SNR as low as -37db.

Noncovalent interactions have a long history and have received huge attention since their discovery almost a century ago. The prevalence of noncovalent interactions can be seen in the formation of simple dimers to structural and functional modification of large biomolecules. Even though plenty of experimental and theoretical studies are performed to understand various noncovalent interactions, the nature and variety of those interactions are still subject of study. And still they are receiving tremendous attention due to their significant role in the stability and conformation of biomolecules, catalysis of organic and inorganic reactions, crystal packing and material design. This dissertation explores various new sorts of noncovalent interactions, compares them with existing ones, and extensively studies the relevance of noncovalent interactions to various biological systems of interest by applying quantum mechanical tools. A new sort of noncovalent interaction has been identified where two electronegative atoms interact directly with each other with no intervening hydrogen or halogen atoms. These interactions are found to be surprisingly strong, even stronger than regular OH···O and NH···O hydrogen bonds in some cases, and are stabilized by the charge transfer from electron donor to electron acceptor. The major portion of this dissertation deals with the rigorous investigation of new sorts of interactions like P···N, S···N, Cl···N and several other charge transfer types of interactions with side by side comparison with hydrogen and halogen bonds. Similarly, a new carbonyl-carbonyl stacking geometry in peptide-peptide interactions is explored. These stacking geometries are energetically close to stronger NH···O hydrogen bonds, and get some assistance from CH···O hydrogen bonds. Carbon is considered one of the potent H-bond donors, albeit weaker, due to its ubiquitous presence in biomolecules. So, another portion of this dissertation is focused on the study of neutral and charged CH hydrogen bonds simulating various interpeptide interactions and enzyme catalysis. And the last part of this dissertation deals with the putative H-bonds that might be present in tip functionalized carbon nanotubes.

The cochlea is an organ which extracts frequency information from the input sound wave. It also produces nerve signals, which are further analysed by the brain and ultimately lead to perception of the sound. An existing model of the cochlea by Fragni`ere is first analysed by simulation. This passive model is found to have the properties that the living cochlea does in terms of the frequency response. An analog VLSI circuit implementation of this cochlear model in CMOS weak inversion is proposed, using log-domain filters in current domain. It is fabricated on a chip and a measurement of a basilar membrane section is performed. The measurement shows a reasonable agreement to the model. However, the circuit is found to have a problem related to transistor mismatch, causing different behaviour in identical circuit blocks. An active cochlear model is proposed to overcome this problem. The model incorporates the effect of the outer hair cells in the living cochlea, which controls the quality factor of the basilar membrane filters. The outer hair cells are incorporated as an extra voltage source in series with the basilar membrane resonator. Its value saturates as the input signal becomes larger, making the behaviour rather closer to that of a passive model. The simulation results show this nonlinear phenomenon, which is also seen in the living cochlea. The contribution of this thesis is summarised as follows: a) the first CMOS weak inversion current domain basilar membrane resonator is designed and fabricated, and b) the first active two-dimensional cochlear model for analog VLSI implementation is developed.

In this work I used a code of galaxy formation (GALICS) to explore three different points that are relevant to the the problem of galaxy formation. The first deals with the method of simulation itself, the second considers the simulation of infrared galaxies within GALICS and the third investigated the role of galaxy formation in measurements of weak gravitational lensing.<br /><br />I examined the predictability of models such as GALICS, using an exploratory test, based on the response of the model to variations in the parameters controlling star formation. I have also proposed a new description, in the astrophysical context, of merger trees.<br /><br />I helped to implement new physical prescriptions into GALICS to bring the model into better agreement with the available observations of infrared galaxies. <br /><br />I wrote a code (LEMOMAF) to simulate the weak lensing effect, taking advantage of the coevolution of galaxies and dark matter included in GALICS.