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1
Kumar, Hemant, University of Western Sydney e of Science Technology and Environment College. "Software analytical tool for assessing cardiac blood flow parameters". THESIS_FSTA_XXX_Kumar_H.xml, 2001. http://handle.uws.edu.au:8081/1959.7/392.
Testo completoAbstract (sommario):
Introduction of Doppler ultrasound techniques into the Intensive Care setting has revolutionised the way haemodynamic status is monitored in the critically ill. However, in order to increase the usefulness of these techniques, the Doppler signal and its spectrum need to be further analysed in ways to facilitate a better clinical response. Extensive processing of the Doppler spectrum on Diagnostic ultrasound machines is limited by the real time performance considerations. It was therefore proposed that the spectral information from these systems be extracted off-line and full set of analytical tools be made available to evaluate this information. This was achieved by creating an integrated and modular software tool called Spectron, which was intended as an aid in the overall management of the patients. The modular nature of Spectron was intended to ensure that new analytical tools and techniques could be easily added and tested. The software provides its users with considerable latitude in choosing various data acquisition and analysis parameters to suit various clinical situations and patient requirements. Spectron was developed under the Windows environment to provide a user friendly interface and to address a range of programming problems such as memory management and the size of the colour palettes. Spectron is able to detect the maximal velocities and compute the mean and median velocities. Relative increases in maximal velocities in cardiac blood flows after the administration of inotropic drugs have been shown in the pilot studies that were conducted. Spectron is able to help in obtaining estimates of the aortic blood flows and in other applications such measuring vascular impedance. Stenotic blood flows can be detected by using the spectral broadening index and blood flow characteristics can be studied by using various blood flow indices. Thus, this project attempted to help in patient management by providing clinicians with a range of blood flow parameters and has succeeded in meeting its objective to a large extentMaster of Engineering (Hons)
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Mohan, Anusha. "Neural Correlates of Spectral, Temporal and Spectro-temporal Modulation". Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5078.
Testo completoAbstract (sommario):
Natural sounds are characterized by the distribution of acoustic power over different frequency regions and/or time. This is termed spectral, temporal or spectro-temporal modulation. The auditory system is equipped with banks of filters tuned to different spectral, temporal and spectro-temporal modulation frequencies (SM, TM, STM). The sensitivity of the peripheral system to these modulations can be measured by undertaking a linear systems approach. In addition to understanding the psychophysical sensitivity, studying the neural patterns of their processing is also critical. The current study is an attempt to understand the relationship between the behavioral and neural correlates of spectral, temporal and spectro-temporal processing in ten normal hearing subjects (age range 21-27 years; mean = 23.7 years). In the behavioral experiment, sensitivity to SM, TM and STM frequencies was estimated using a 3-interval, 3-alternative, forced-choice paradigm with a 3-down-1-up tracking algorithm. In the electrophysiological experiment, Electroencephalographs (EEGs) were recorded in a change-detection paradigm in response to the same set of modulation stimuli used in the behavioral experiment presented at 20 dB sensation level (SL). The EEG data were analyzed to determine the global field power and latencies of the N1and P2 components and the amplitude of the N1-P2 complex. Although an overall parietal dominance was observed for all of the components, the N1-P2 complex was strongly lateralized to the right hemisphere in the frontal region, but the hemispheric asymmetry decreased at central and parietal regions. A highly significant but weak to moderate negative correlation between individual behavioral thresholds and N1-P2 amplitudes was observed, and this relationship also was observed when behavioral spectro-temporal transfer functions and N1-P2 amplitude transfer functions were examined together. Thus the current project reveals that a relationship exists between the behavioral measures and neural correlates and gives us hope to work towards establishing this relationship.
3
Régnier, David. "Contribution à l'étude des gammas prompts de fission". Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENI065.
Testo completoAbstract (sommario):
Cette thèse a essentiellement été motivée par la montée en puissance de la thématique des échauffements nucléaires en réacteurs. Elle avait pour objectif la mise en place de méthodes permettant la simulation de l'émission des gammas prompts de fission. Pour répondre à cette attente, différents algorithmes de désexcitation d'un noyau ont été implémentés. Ils ont été testés avec succès via plusieurs calculs d'application (rapport d'embranchement isomérique, largeur radiative totale, etc). Ces méthodes ont ensuite été mises en oeuvre dans le cadre du code de fission FIFRELIN. L'outil qui en résulte, permet la détermination d'un grand nombre d'observables de fission, dans le cadre d'un modèle unique. Une étude de sensibilité des résultats à différents éléments du calcul a été réalisée. Enfin, des simulations de la fission spontanée du 252Cf, et des fissions induites par neutrons thermiques sur l' 235U et le 239Pu ont été menées. Les spectres des gammas prompts pour ces trois systèmes fissionnants ont pu être déterminés. Les résultats obtenus sont en très bon accord avec les données expérimentales disponibles, dont certaines ont été publiées récemment (2012 et 2013)This PhD thesis has essentially been motivated by the nuclear heating problematic in reactors. The main goal of this work was the production of methods capable of simulating the prompt gamma emission from fission. First of all, several algorithms for the treatment of the nucleus deexcitation were implemented. They have been succesfully tested through various calculations (isomeric branching ratio, total radiative width, etc). These methods were then incorporated in the frame of the fission code FIFRELIN. The tool which results from this work, enables the determination of numerous fission observables in the frame of a single consistent model. A sensitivity study of the results to several numerical and nuclear models has been realized. At last, calculation have been lead for the 252Cf spontaneous fission and the thermal neutron induced fission of 235U and 239Pu. The prompt gamma spectra obtained for those three fissionning systems have been determined. The results are in good agreement with available experimental data, including recent measurements published in 2012 and 2013
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Martin, Alexandre. "Théorie de Mourre et opérateurs de Schrödinger : De nouvelles classes d'opérateurs conjugués". Thesis, Cergy-Pontoise, 2018. http://www.theses.fr/2018CERG0978/document.
Testo completoAbstract (sommario):
Dans cette thèse, nous nous intéressons à l’étude du spectre essentiel d’opérateurs de Schrödinger et tout particulièrement à l’obtention d’un Principe d’Absorption Limite pour ces opérateurs. Ce Principe d’Absorption Limite consiste en l’existence d’une limite de l’opérateur résolvante lorsque le paramètre spectral se rapproche du spectre essentiel et permet de connaitre des informations sur le groupe engendré par l’Hamiltonien de Schrödinger. Une méthode pour montrer ce Principe d’Absorption Limite est d’utiliser la théorie de Mourre. Cette théorie nécessite l’utilisation d’un autre opérateur appellé opérateur conjugué. Lorsqu’on veut appliquer la théorie de Mourre aux opérateurs de Schrödinger, on utilise habituellement un opérateur conjugué nommé le générateur des dilatations. Cet opérateur implique que les dérivées du potentiel doivent avoir une certaine décroissance ce qui peut être gênant dans certains cas.Dans cette thèse, nous appliquerons le théorème de Mourre avec d’autres types d’opérateurs conjugués, dont certains n’impliquent pas de conditions de dérivabilité. Dans une première partie, nous nous intéresserons aux opérateurs de Schrödinger sur l’espace euclidienpour lesquels nous montrerons un Principe d’Absorption Limite à énergie strictement positive, un Principe d’Absorption Limite à énergie nulle et l’absence de valeurs propres plongées dans le spectre essentiel. Dans une seconde partie, nous nous intéresserons aux opérateurs de Schrödinger sur des guides d’ondes pour lesquels nous montrerons un Principe d’Absorption Limite loin des seuils et un Principe d’Absorption Limite près des seuilsIn this thesis, we are interested in the study of the essential spectrum of Schrödinger operators and more particulary in the obtention of a Limiting Absorption Principle for these operators. This Limiting Absorption Principle consists on the existence of a limit for the resolvent operator when the spectral parameter is near the essential spectrum and permits to know some properties about the group generated by the Schrödinger Hamiltonian we study. A technique to prove this Limiting Absorption Principle is to use the Mourre theory. This theory needs to use an other operator called the conjugate operator. When we want to apply the Mourre theory to Schrödinger operators, we usually used a conjugate operatornamed the generator of dilations. This operator implies some conditions of decay on the derivatives of the potentials which can be a problem in certain cases. In this thesis, we will apply the Mourre theory with other types of conjugate operators wich, for some of them, does not imply any conditions on the derivatives of the potential.In a first part, we will be interested in Schrödinger operators on the euclidian space. We will show a Limiting Absorption Principle at positive energy, a Limiting Absorption principle at zero energy and the absence of eigenvalue embedded in the essential spectrum. In a second part, we will be interested in Schrödinger operators on wave guides for which we will prove a Limiting Absorption Principle far thresholds and near thresholds
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Rozario, Hoimonti Immaculata. "Spectroscopic study of acetylene and hydrogen cyanide". Thesis, Lethbridge, Alta. : University of Lethbridge, Dept. of Physics and Astronomy, c2012, 2012. http://hdl.handle.net/10133/3415.
Testo completoAbstract (sommario):
High-resolution molecular spectroscopy has been used to study acetylene line parameters and emission spectra of hydrogen cyanide. All acetylene spectra were recorded in our laboratory at the University of Lethbridge using a 3-channel tuneable diode laser spectrometer. N2-broadened line widths and N2-pressure induced line shifts have been measured for transitions in the v1+v3 band of acetylene at seven temperatures in the range 213–333K to obtain the temperature dependences of broadening and shift coefficients. The Voigt and hard-collision line profile models were used to retrieve the line parameters.
The line-broadening and line-shift coefficients as well as their temperature-dependent parameters have been also evaluated theoretically, in the frame work of a semi-classical approach based on an exponential representation of the scattering operator, an intermolecular potential composed of electrostatic quadrupole–quadrupole and pairwise atom–atom interactions as well as on exact trajectories driven by an effective isotropic potential. The experimental results for both N2-broadening and shifting show good agreement with the theoretical results.
We have studied the line intensities of the 1νl20←0νl20 band system from the HCN emission spectrum. The infrared emission spectrum of H12C14N was measured at the Justus-Liebig University, Giessen, Germany. The emission spectrum was analyzed with the spectrum analysis software Symath running using Mathematica as a platform. This approach allowed us to retrieve information on band intensity parameters.viii, 112 leaves : ill. ; 29 cm
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Dahl, Jason F. "Time Aliasing Methods of Spectrum Estimation". Diss., CLICK HERE for online access, 2003. http://contentdm.lib.byu.edu/ETD/image/etd157.pdf.
Testo completo
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Deepak, G. C. "Spectrum sharing systems for improving spectral efficiency in cognitive cellular network". Thesis, Lancaster University, 2017. http://eprints.lancs.ac.uk/85771/.
Testo completoAbstract (sommario):
Since spectrum is the invisible infrastructure that powers the wireless communication, the demand has been exceptionally increasing in recent years after the implementation of 4G and immense data requirements of 5G due to the applications, such as Internet-of-Things (IoT). Therefore, the effective optimization of the use of spectrum is immediately needed than ever before. The spectrum sensing is the prerequisite for optimal resource allocation in cognitive radio networks (CRN). Therefore, the spectrum sensing in wireless system with lower latency requirements is proposed first. In such systems with high spatial density of the base stations and users/objects, spectrum sharing enables spectrum reuse across very small regions. The proposed method in this Thesis is a multi-channel cooperative spectrum sensing technique, in which an independent network of sensors, namely, spectrum monitoring network, detects the spectrum availability. The locally aggregated decision in each zone associated with the zone aggregator (ZA) location is then passed to a decision fusion centre (DFC). The secondary base station (SBS) accordingly allocates the available channels to secondary users to maximize the spectral efficiency. The function of the DFC is formulated as an optimization problem with the objective of maximizing the spectral efficiency. The optimal detection threshold is obtained for different cases with various spatial densities of ZAs and SBSs. It is further shown that the proposed method reduces the spectrum sensing latency and results in a higher spectrum efficiency. Furthermore, a novel power allocation scheme for multicell CRN is proposed where the subchannel power allocation is performed by incorporating network-wide primary system communication activity. A collaborative subchannel monitoring scheme is proposed to evaluate the aggregated subchannel activity index (ASAI) to indicate the activity levels of primary users. Two utility functions are then defined to characterize the spectral efficiency (SE) and energy efficiency (EE) as a function of ASAI to formulate a utility maximization problem. The optimal transmit power allocation is then obtained with the objective of maximizing the total utility at the SBS, subject to maximum SBS transmit power and collision probability constraint at the primary receivers. Since optimal EE and SE are two contradicting objectives to obtain the transmit power allocation, the design approach to handle both EE and SE as a function of common network parameter, i.e., ASAI, is provided which ultimately proves the quantitative insights on efficient system design. Extensive simulation results confirm the analytical results and indicate a significant improvement in sensing latency and accuracy and a significant gain against the benchmark models on the rate performance, despite the proposed methods perform with lower signalling overhead.
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Bandeira, Nuno Filipe Cabrita. "Spectral networks algorithms for de novo interpretation of tandem mass spectra". Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3274510.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of California, San Diego, 2007.Title from first page of PDF file (viewed October 2, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 141-152).
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Filion, Côté Sandrine. "Spectro-angular optical biosensor based on surface plasmon resonance operating in the visible spectrum". Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=106424.
Testo completoAbstract (sommario):
Surface plasmon resonance (SPR) is one of the most widely used methods to implement biosensors because of its label-free and sensitive detection. Surface plasmon resonance allows the change in the refractive index of a sample to be measured accurately by the analysis of the light reflecting at a metal-dielectric interface. A way to increase the sensitivity of SPR biosensors was found in fabricating a spectro-angular SPR biosensor and using of a newly developed data processing method called the Double Projection Method. The objective of the work presented in this thesis is to improve further the detection limit of the spectro-angular biosensor by upgrading the cameras used for the data acquisition. Simulations have shown that the spatial resolution and the data precision have a significant impact on the accuracy of the refractive index change measurement. In this thesis, simulation results are presented to justify the modifications of the experimental system and to estimate the expected improvement in the detection limit of the spectro-angular biosensor by the use of higher spatial resolution and higher data precision cameras. The new design as well as the components purchased for the experimental set-up are detailed.La résonance plasmonique de surface (SPR) est une méthode très utilisée pour la réalisation de biocapteurs grâce à sa détection très sensible et sans marqueur. La résonance plasmonique de surface permet une mesure précise du changement de l'indice de réfraction d'un échantillon par l'analyse de la lumière reflétant sur l'interface entre un métal et un diélectrique. Il a été démontré que la sensibilité des biocapteurs SPR puisse être accrue par la fabrication d'un biocapteur SPR spectro-angulaire utilisant une nouvelle méthode de traitement des données appelée Double Projection Method (la méthode par double projection). L'objectif du travail présenté dans cette thèse est d'améliorer la limite de détection du biocapteur spectro-angulaire grâce à l'utilisation de caméras plus performantes pour la cueillette de données. Des simulations ont démontré que la résolution spatiale et la précision des données ont un impact significatif sur la précision de la mesure du changement dans l'indice de réfraction. Dans cette thèse, des résultats de simulations seront présentés afin de justifier les modifications à apporter au système expérimental et de démontrer l'amélioration prévue de la limite de détection du biocapteur spectro-angulaire par l'utilisation de caméras plus performantes. La nouvelle conception ainsi que les composantes choisis pour le système expérimental seront détaillées.
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Kharroubi, Hassane. "Étude du pouvoir réflecteur de monocristaux uniaxes et biaxes dans l'infrarouge lointain". Nancy 1, 1994. http://www.theses.fr/1994NAN10108.
Testo completoAbstract (sommario):
L'étude du pouvoir réflecteur (r) et de la transmission (t) des milieux anisotropes et absorbants dans l'infrarouge lointain nous a conduit a présenter des expressions directement programmables des relations permettant la détermination des constantes optiques, l'indice de réfraction n et l'indice d'absorption k à partir des mesures expérimentales de r et de t. Nous avons établi les expressions des facteurs de réflexion et de transmission pour les deux polarisations possibles de l'onde, en fonction de l'angle d'incidence. L'étude est limitée au cas de la propagation d'une onde plane dans les plans principaux du cristal. Nous abordons ensuite le cas de la lame à faces parallèles qui représente physiquement nos échantillons. Les facteurs de réflexion et de transmission sont mesurés dans l'infrarouge lointain de 10 à 600 cm##1 en lumière polarisée pour des températures comprises entre 7 et 300 k. Pour cette étude nous avons choisi un cristal biaxe, le nitrite de sodium et deux cristaux uniaxes, la cassitérite et le quartz. La comparaison des résultats expérimentaux et des valeurs calculées nécessite la connaissance de la fonction diélectrique. Nous utilisons la forme factorisée de la fonction diélectrique. Les valeurs initiales des paramètres d'ajustage sont déterminées par une analyse de Kramers-Kronig du spectre de réflexion sous incidence normale. La mesure simultanée du pouvoir réflecteur et de la transmission de la lame nous permet d'apporter une correction pour déterminer la valeur vraie du pouvoir réflecteur des cristaux, valeur nécessaire pour les calculs de physique du solide
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Mekler, A. A., Christine Böckmann e N. Sokolovskaia. "Particle distribution from spectral Mie-scattering: kernel representation and singular-value spectrum". Universität Potsdam, 2000. http://opus.kobv.de/ubp/volltexte/2007/1494/.
Testo completoAbstract (sommario):
This paper deals with the Mie scattering kernels for multi-spectral data. The kernels may be represented in form of power series. Furthermore, the
singular-value spectrum and the degree of ill-posedness in dependence on the refractive index of the particles are numerically approximated. A special hybrid
regularization technique allows us to determine via inversion the particle distributions of different types.
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鄧愛紅 e Aihong Deng. "Some studies towards improving positron lifetime spectroscopy for semiconductors". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B31214083.
Testo completo
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Bing, Zhou. "Crosshole resistivity and acoustic velocity imaging : S.5-D helmholtz equation modeling and inversion /". Title page, contents and abstract only, 1998. http://web4.library.adelaide.edu.au/theses/09PH/09phb613.pdf.
Testo completo
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Berge, Léonie. "Contribution à la modélisation des spectres de neutrons prompts de fission .Propagation d'incertitudes sur un calul de fluence cuve". Thesis, Université Grenoble Alpes (ComUE), 2015. http://www.theses.fr/2015GREAI039/document.
Testo completoAbstract (sommario):
Le spectre des neutrons prompts de fission (PFNS) est une donnée très importante pour diverses applications de la physique nucléaire. Cependant, en dehors du spectre de la fission spontanée du 252Cf, qui est reconnu comme un standard international et est utilisé pour la métrologie, le PFNS reste mal connu pour la plupart des noyaux fissionnants. En particulier, pour la fission rapide (induite par un neutron de plus de 100 keV environ), il existe peu de mesures, et les évaluations internationales présentent de fortes contradictions. De plus, il existe très peu de données sur les covariances associées aux diverses évaluations du spectre. Dans cette thèse, trois aspects de l'évaluation du PFNS sont abordés. Le premier aspect est la modélisation du spectre via le code FIFRELIN, développé au CEA Cadarache, qui simule la chaine de désexcitation des fragments de fission par émissions successives de neutrons et gammas prompts par la méthode de Monte-Carlo. Ce code a pour vocation de calculer les observables de fission dans un même calcul cohérent, à partir des distributions en masse, en énergie cinétique et en spin des fragments de fission. FIFRELIN a donc un caractère prédictif que n'ont pas les modèles analytiques utilisés pour décrire le PFNS. Une étude des paramètres de modèle influents, notamment le paramètre de densité de niveaux, est mené afin de tenter de mieux reproduire le spectre. Le deuxième aspect de la thèse concerne l'évaluation du PFNS et de sa matrice de covariance. On propose une méthodologie pour évaluer le spectre et sa matrice de covariance de manière rigoureuse, à travers l'outil CONRAD du CEA Cadarache. Ceci implique la modélisation du spectre à travers des modèles simples, notamment celui de Madland-Nix qui est le plus utilisé dans les évaluations, en ajustant les paramètres de ces modèles afin de reproduire les données expérimentales. La matrice de covariance provient de la propagation rigoureuse des sources d'incertitude qui interviennent dans le calcul. En particulier, les incertitudes systématiques liées au dispositif expérimental sont propagées par des techniques de marginalisation. La marginalisation permet de propager ces incertitudes sur le spectre calculé, en obtenant des incertitudes réalistes sans besoin d'être artificiellement rehaussées comme c'est souvent le cas dans le cadre d'ajustements bayésiens. La propagation de ces incertitudes expérimentales impacte aussi la matrice de corrélation du spectre calculé. On présente les résultats pour la fission induite par neutron thermique de l'235U et du 239Pu. Pour le modèle de Madland-Nix avec section inverse constante, l'énergie moyenne des neutrons prompts obtenue est de 1.979 MeV pour l'235U, et de 2.087 MeV pour le 239Pu. Le dernier aspect de la thèse est l'étude de l'impact du PFNS et de ses covariances sur le calcul du flux neutronique sur la cuve d'un réacteur. L'enjeu est de taille, car l'estimation de la fluence au niveau de la cuve d'un réacteur détermine l'intégrité de celle-ci, et donc la durée de vie du réacteur. On observe l'importance des termes de corrélations du spectre pour calculer notamment l'incertitude sur le flux intégré au-dessus de 1 MeV, de l'ordre de 6% (incertitude due seulement au spectre)The prompt fission neutron spectrum (PFNS) is very important for various nuclear physics applications. Yet, except for the 252Cf spontaneous fission spectrum which is an international standard and is used for metrology purposes, the PFNS is still poorly known for most of the fissionning nuclides. In particular, few measurements exist for the fast fission spectrum (induced by a neutron whose energy exceeds about 100 keV), and the international evaluations show strong discrepancies. There are also very few data about covariances associated to the various PFNS evaluations. In this work we present three aspects of the PFNS evaluation. The first aspect is about the spectrum modeling with the FIFRELIN code, developed at CEA Cadarache, which simulates the fission fragment de-excitation by successive emissions of prompt neutrons and gammas, via the Monte-Carlo method. This code aims at calculating all fission observables in a single consistent calculation, starting from fission fragment distributions (mass, kinetic energy and spin). FIFRELIN is therefore more predictive than the analytical models used to describe the spectrum. A study of model parameters which impact the spectrum, like the fragment level density parameter, is presented in order to better reproduce the spectrum. The second aspect of this work is about the evaluation of the PFNS and its covariance matrix. We present a methodology to produce this evaluation in a rigorous way, with the CONRAD code, developed at CEA Cadarache. This implies modeling the spectrum through simple models, like the Madland-Nix model which is the most commonly used in the evaluations, by adjusting the model parameters to reproduce experimental data. The covariance matrix arises from the rigorous propagation of the sources of uncertainty involved in the calculation. In particular, the systematic uncertainties arising from the experimental set-up are propagated via a marginalization technique. The marginalization allows propagating these uncertainties on the calculated spectrum, and obtaining realistic uncertainties without having to artificially raise them, as it is sometimes necessary in Bayesian adjustments. The experimental uncertainty propagation also impacts the spectrum correlation matrix. We present the result for thermal neutron-induced fission of 235U and 239Pu. For the Madland-Nix model with constant inverse cross-section, the prompt neutron mean energy is 1.979 MeV for 235U and 2.087 MeV for 239Pu. The last aspect of this work is the calculation of the impact of the PFNS and its covariance matrix on a reactor vessel flux. This calculation is of major importance, since the vessel fluence estimation determines the vessel integrity, and therefore determines the reactor lifetime. We observe the importance of the PFNS correlation terms, to compute in particular the vessel flux uncertainty above 1 MeV, which is of the order of 6% (uncertainty only due to PFNS)
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Lu, Lu. "Spectral-efficient design in modern wireless communications networks". Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/53902.
Testo completoAbstract (sommario):
We investigate spectral-efficient design and develop novel schemes to improve spectral efficiency of the modern wireless communications networks. Nowadays, more and more spectrum resources are required to support various high-data-rate applications while spectrum resources are limited. Moreover, static allocation and exclusive access in current spectrum assignment policy caused a lot of licensed spectrum bands to be underutilized. To deal with the problem, cognitive radio (CR) has been developed, which allows unlicensed/secondary users to transmit with licensed/primary users as long as the former ones do not generate intolerable interference to the latter ones. The coexistence of users and networks requires careful and dynamic planning to mitigate interference. Otherwise, the network performance will be severely undermined. We study both spectrum sensing and spectrum access techniques and propose several transmit schemes for different types of cognitive ratio networks, including spectrum overlay and spectrum underlay systems. The proposed algorithms can improve spectral efficiency of the networks efficiently and have potentials to be used in future wireless communications networks.
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Harvey, Pierre Dominique. "Applications of vibrational spectroscopy and NMR spin-lattice relaxation time measurements to organometallic and organic molecular crystals". Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=73986.
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Akkouche, Sofiane. "Sur la theorie spectrale des opérateurs de Schrödinger discrets". Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14098/document.
Testo completoAbstract (sommario):
Cette thèse traite de la théorie spectrale des opérateurs de Schrödinger discrets H(λ) := - Δ + b sur Zd et plus généralement sur des graphes pondérés infinis. Plus précisément, nous étudions le comportement des fonctions spectrales qui représentent les bornes du spectre de ces opérateurs. Un des principaux résultats est l'obtention d'une condition nécessaire et suffisante sur le potentiel b pour que le bas du spectre soit strictement positif. L'étude du haut du spectre est également considérée.Nous étudions tout d'abord ces questions pour les opérateurs de Schrödinger discrets sur Zd. La régularité de cet espace permet alors d'obtenir des résultats spécifiques dans ce cas particulier. Nous généralisons ensuite nos travaux au cas des graphes infinis pondérés. Les techniques développées dans ce cadre nous permettent également d'étudier le comportement asymptotique du bas du spectre pour les grandes valeurs de λThis thesis deals with the spectral theory of discrete Schrödinger operators H(λ) := - Δ + b on Zd and more generally on in#nite weighted graphs. Precisely, we study the behavior of the spectral functions which represent the spectral bounds of these operators. One of the main results is the obtention of a necessary and sufficient condition on the potential b such that the bottom of the spectrum is stricly positive.The study of the top of the spectrum is also treated.We first study these questions for discrete Schrödinger operators on Zd. The regularity of this space provides specific results in this particular case. Then we extend our work to the case of infinite weighted graphs. Moreover, the technics developed in this framework allow us to study the asymptotic behavior of the bottom of the spectrum for large values of λ
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Borde, Arnaud. "One-Dimensional Power Spectrum and Neutrino Mass in the Spectra of BOSS". Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01023004.
Testo completoAbstract (sommario):
The framework of the studies presented in this thesis is the one-dimensional power spectrum of the transmitted flux in the Lyman-alpha forests. The Lyman-alpha forest is an an absorption pattern seen in the spectra of high redshift quasars corresponding to the absorption of the quasar light by the hydrogen clouds along the line of sight. It is a powerful cosmological tool as it probes relatively small scales, of the order of a few Mpc. It is also sensible to small non-linear effects such as the one induced by massive neutrinos.First, we have developed two independent methods to measure the one-dimensional power spectrum of the transmitted flux in the Lyman-alpha forest. The first method is based on a Fourier transform, and the second on a maximum likelihood estimator. The two methods are independent and have different systematic uncertainties. The determination of the noise level in the data spectra was subject to a novel treatment, because of its significant impact on the derived power spectrum. We applied the two methods to 13,821 quasar spectra from SDSS-III/BOSS DR9 selected from a larger sample of over 60,000 spectra on the basis of their high quality, large signal-to-noise ratio, and good spectral resolution. The power spectra measured using either approach are in good agreement over all twelve redshift bins from =2.2 to =4.4, and scales from 0.001 (km/s)^−1 to 0.02 (km/s)^−1. We carefully determined the methodological and instrumental systematic uncertainties of our measurements.Then, we present a suite of cosmological N-body simulations with cold dark matter, baryons and neutrinos aiming at modeling the low-density regions of the IGM as probed by the Lyman-alpha forests at high redshift. The simulations are designed to match the requirements imposed by the quality of BOSS and eBOSS data. They are made using either 768^3 or 192^3 particles of each type, spanning volumes ranging from (25 Mpc/h)^3 for high-resolution simulations to (100 Mpc/h)^3 for large-volume ones. Using a splicing technique, the resolution is further enhanced to reach the equivalent of simulations with 3072^3 = 29 billion particles of each type in a (100 Mpc/h)^3 box size, i.e. a mean mass per gas particle of 1.2x10^5 solar masses. We show that the resulting power spectrum is accurate at the 2% level over the full range from a few Mpc to several tens of Mpc. We explore the effect on the one-dimensional transmitted-flux power spectrum of 4 cosmological parameters (n_s, sigma_8, Omega_m ,H_0), 2 astrophysical parameters (T_0, gamma) related to the heating rate of the IGM and the sum of the neutrino masses. By varying the input parameters around a central model chosen to be in agreement with the latest Planck results, we built a grid of simulations that allows the study of the impact on the flux power spectrum of these seven relevant parameters. We improve upon previous studies by not only measuring the effect of each parameter individually, but also probing the impact of the simultaneous variation of each pair of parameters. We thus provide a full second-order expansion, including cross-terms, around our central model. We check the validity of the second-order expansion with independent simulations obtained either with different cosmological parameters or different seeds for the initial condition generation. Finally, a comparison to the one-dimensional Lyman-alpha forest power spectrum obtained in the first part with BOSS data shows an excellent agreement.Eventually, even if there are still some potential biases and systematic errors that need to be studied in our simulation, we performed cosmological fits combining our measurement of the one-dimensional power spectrum and other cosmological probes such as the CMB results provided by Planck. These preliminary results are very encouraging as they lead to some of the tighest cosmological constraints as of today, especially on the sum of the neutrino masses with an upper limit of 0.1 eV.
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Brett, Caroline. "Spectral theory using linear systems and sampling from the spectrum of Hill's equation". Thesis, Lancaster University, 2015. http://eprints.lancs.ac.uk/79286/.
Testo completoAbstract (sommario):
This thesis, entitled Spectral Theory Using Linear Systems and Sampling from the Spectrum of Hill’s Equation is submitted by Caroline Brett, Master of Science for the degree of Doctor of Philosophy, September 2015. It uses linear systems to solve various problems connected with Hill’s equation, −f + qf = λf for q ∈ C2, real-valued and π-periodic. Introducing a new operator, Rx constructed from a linear system, (−A, B, C) allows us to solve Hill’s equation and the inverse spectral problem. We use Rx to construct a function, T(x, y) that satisfies a Gelfand–Levitan integral equation and then derive a PDE for T(x, y). Solving this PDE recovers q. Extending Hill’s work in [28], we show that there exist Hilbert–Schmidt operators, Rp and Rc analogous to Rx, such that the roots of their Carleman determinants are elements of the periodic spectrum of Hill’s equation. The latter half concerns sampling from entire functions in Paley–Wiener space. From the periodic spectrum of Hill’s equation we derive a sampling sequence, (tn)n∈Z. Whittaker, Kotel’nikov and Shannon give a sampling result for (n)n∈Z where samples occur at a constant rate. Samples taken from the periodic spectrum do not occur at a constant rate, nevertheless we provide analogous results for this case. From (tn)n∈Z we also construct Riesz bases for L2[0, π] and L2[−π, π], the Fourier transform space of PW(π). In L2[0, π] we construct the dual Riesz basis using linear systems. Furthermore, we show that the determinant of the Gram matrix associated with the Riesz basis is a Lipschitz continuous function of (tn)n∈Z. Finally, we look at an integral, Ia associated with Ramanujan and use it to create a basis for PW π2. We conclude with an evaluation of various determinants associated with Ia.
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Stark, Anthony. "Phase Spectrum Based Speech Processing and Spectral Energy Estimation for Robust Speech Recognition". Thesis, Griffith University, 2011. http://hdl.handle.net/10072/366490.
Testo completoAbstract (sommario):
Speech is the dominant mode of communication between humans; simple to learn, easy to use and integral for modern life. Given the importance of speech, development of a human-machine speech interface has been greatly anticipated. This challenging task is encapsulated in the digital speech processing research field. In this dissertation, two specific areas of research are considered: 1) the use of short-time Fourier spectral phase in digital speech processing and 2) use of the minimum mean square error spectral energy estimator for environment-robust automatic speech recognition. In speech processing and modelling, the short-time Fourier spectral phase has been considered of minor importance. This is because classic psychoacoustic experiments have shown speech intelligibility to be closely related to short-time Fourier spectral magnitude. Given this result, it is unsurprising that the majority of speech processing literature has involved exploitation of the short-time magnitude spectrum. Despite this, recent studies have shown useful information can be extracted from the spectral phase of speech. As a result, it is now known that spectral phase possesses much of the same intelligibility information as spectral magnitude. It is this avenue of research that is explored in greater detail within this dissertation. In particular, we investigate two phase derived quantities – the short-time instantaneous frequency spectrum and the short-time group delay spectrum. The properties of both spectra are investigated mathematically and empirically, identifying the relationship between known speech features and the underlying phase spectrum. We continue the investigation by examining two related quantities – the instantaneous frequency deviation and the group delay deviation. As a result of this research, two novel phase-based spectral representations are proposed, both of which show a high degree information applicable to speech processing.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
Full Text
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Rosenmann, Laurence. "Etudes théorique et expérimentale de l'élargissement par collisions des raies de CO2 perturbé par CO2, H2O, N2 et O2 : constitution d'une base de données infrarouge et Raman appliquée aux transferts thermiques et à la combustion". Châtenay-Malabry, Ecole centrale de Paris, 1988. http://www.theses.fr/1988ECAP0071.
Testo completoAbstract (sommario):
Etude systématique des coefficients d'élargissement par collisions des raies infrarouge et Raman de dioxyde de carbone perturbé par dioxyde de carbone, eau, diazote et dioxygène. Les résultats obtenus dans la gamme de température 300-3000 K sont utiles pour modéliser les transferts radiatifs en particulier dans les systèmes de combustion, et pour les diagnostics infrarouge et Raman.
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Mambrini, Thomas. "Caractérisation de panneaux solaires photovoltaïques en conditions réelles d’implantation et en fonction des différentes technologies". Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112380/document.
Testo completoAbstract (sommario):
Dans un contexte de fort déploiement du Photovoltaïque (PV), de plus en plus de recherches sont menées pour assurer une certaine fiabilité et prédictibilité de la production provenant du PV. Les investisseurs se plaignent d’un manque de visibilité dans cette filière et hésitent à investir dans le PV (surtout avec les baisses régulières des tarifs de rachats). Il est donc nécessaire pour le développement de la filière PV de faire des efforts pour étudier, comprendre les systèmes PV en fonctionnement et ainsi donner plus de visibilité pour l’amélioration des systèmes, leur monitoring, une plus grande fiabilité et pouvoir prédire plus précisément le productible PV en améliorant les modèles de prédiction du productible PV déjà existants.C’est dans ce cadre que s’inscrit cette thèse qui a pour but de caractériser les modules PV en conditions réelles d’utilisation en fonction des différentes technologies. Nous étudions, dans cette thèse, les facteurs extérieurs qui influent sur le comportement des modules de différentes filières, pour tenter de rendre le PV plus fiable et prédictible. C’est donc un axe de recherche qui vient en complément de la caractérisation en laboratoire qui a pour objectif l’amélioration des rendements des cellules.Pour y parvenir il est nécessaire, dans un premier temps, de connaitre les paramètres extérieurs qui influent sur le fonctionnement du module et savoir comment les étudier. Une partie de la thèse est par conséquent consacrée à l'étude des facteurs météorologiques et atmosphériques ayant un impact sur le comportement électrique du module ainsi que la mise en place d'instruments et méthodes pour les mesurer. On présente également les avantages et inconvénients de la caractérisation en extérieur.Après avoir exposé tous les paramètres à prendre en compte, on décrit l'installation de plusieurs plateformes de caractérisation de modules PV entièrement automatisées que l'on a monté au cours de cette thèse au LGEP ainsi qu'à l'École Polytechnique et qui ont toutes un objectif particulier.Ce manuscrit montre par la suite les différentes applications et utilités que peuvent avoir de telles plateformes en analysant les données enregistrées régulièrement (toutes les minutes en moyenne) sur des périodes allant de quelques jours à plusieurs mois. On compare, par la même occasion, les données constructeur prises en conditions standard de test et les performances mesurées dans de nombreuses conditions de modules PV. Les résultats obtenus peuvent servir à la fois pour la recherche, l'aide à la compréhension du comportement des modules, par conséquent aide à la prévision du productible d'installation PV et peuvent avoir un rôle pédagogique dans l'enseignement du PV.Enfin, une dernière partie est dédiée à la description et à la démonstration de faisabilité d'une carte qui permet d'obtenir les caractéristiques principales de n'importe quel module PV en les extrayant de la courbe I(V) mesurée. Cette carte, développée au LGEP, a d'autres utilités telles que la recherche du point de fonctionnement maximale du module (MPPT)Nowadays, photovoltaic (PV) keeps growing fast and an increasing number of studies is require in order to assure the reliability and predictability of the PV-produced electricity. The lack of visibility concerning this field is a continuous source of complaints from the investors who hesitate to commit to PV projects (especially after the decrease of buying prices in Europe). Therefore, to assure the successful increase of PV energy, it is necessary to provide studies aiming at better understanding PV systems in real operations conditions, that means in outdoor conditions.The goal of this doctoral work has been to characterize different PV module technologies in their real use conditions. The outdoor parameters that influence the behavior of different module technologies have been investigated. The goal was to obtain useful information which could make PV-produced electricity more reliable. Therefore, these studies can efficiently complete standard laboratory characterization tests made under a single condition, the purpose of which is usually to determine the efficiency of the different solar cells technologies.To achieve this goal, first it has been necessary to define the outdoor parameters that mainly influence the modules and the most suitable methods to be used for their investigation. For this reason, part of this doctoral work has been devoted to the study of weather and atmospheric factors affecting the electrical behavior of the modules, as well as setting up instruments and methods to measure them. Additionally, advantages and disadvantages of outdoors characterizations have been addressed.Then, after multiple fully automated PV platforms, mounted at the LGEP and at Ecole Polytechnique, thanks to a collaboration with the Laboratoire de Méteorologie Dynamique (LMD). The different applications and uses of these platforms have been highlighted by analyzing data recorded periodically (every minute on average) over periods ranging from days to several months. Manufacturer data, which are acquired in standard test conditions, and the performance measured in several conditions are compared. These results can be used for both research, understanding the behavior of the modules, help in predicting the energy yield of PV system and also to stress the educational role in teaching PV.Finally, the feasibility of an electric card that provides the main characteristics of any PV module by extracting the measured I(V) curve is described. Such electric card, developed at the LGEP, has other uses such as the determination of the maximum operating point
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Clayton, Michael J. "Analysis of the ultraviolet emissions of nitric oxide from mid-latitude rocket observations". Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA237340.
Testo completoAbstract (sommario):
Thesis (M.S. in Physics)--Naval Postgraduate School, June 1990.Thesis Advisor(s): Cleary, David D. "June 1990." Description based on signature page. as viewed on October 19, 2009. DTIC Identifiers: Dayglow, emission spectra, ultraviolet spectra, theses. Author(s) subject terms: Ultraviolet spectra, dayglow, nitric oxide. Includes bibliographical references (p. 57-58). Also available in print.
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Ajohani, Maha. "SPECTRAL PHASOR ANALYSIS ON ABSORBANCE SPECTRA FOR QUANTIFYING THE CONTENT OF DYE MIXTURES". Miami University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=miami1464191406.
Testo completo
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Baldoni, Riccardo. "Investigation of spectral stability of X-ray tubes by simulations and experimental spectrum measurements". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10574/.
Testo completoAbstract (sommario):
L'obiettivo di questo lavoro è quello di analizzare la stabilità di uno spettro raggi X emesso da un tubo usurato per analisi cardiovascolari, in modo da verificare il suo comportamento. Successivamente questo tipo di analisi sarà effettuata su tubi CT. Per raggiungere questo scopo è stato assemblato un particolare set-up con un rivelatore al germanio criogenico in modo da avere la miglior risoluzione energetica possibile ed alcuni particolari collimatori così da ridurre il flusso fotonico per evitare effetti di pile-up. Il set-up è stato costruito in modo da avere il miglior allineamento possibile nel modo più veloce possibile, e con l'obiettivo di rendere l'intero sistema portabile. Il tubo usato è un SRM Philips tube per analisi cardiovascolari; questa scelta è stata fatta in modo da ridurre al minimo i fattori esterni (ottica elettromagnetica, emettitori) e concentrare l'attenzione solo sugli effetti, causati dalle varie esposizioni, sull'anodo (roughness e bending) e sul comportamento di essi durante il surriscaldamento e successivo raffreddamento del tubo. I risultati mostrano come durante un'esposizione alcuni fattori di usura del tubo possono influire in maniera sostanziale sullo spettro ottenuto e quindi alterare il risultato. Successivamente, nell'elaborato, mediante il software Philips di ricostruzione e simulazione dello spettro si è cercato di riprodurre, variando alcuni parametri, la differenza riscontrata sperimentalmente in modo da poter simulare l'instabilità e correggere i fattori che la causano. I risultati sono interessanti non solo per questo esperimento ma anche in ottica futura, per lo sviluppo di applicazioni come la spectral CT. Il passo successivo sarà quello di spostare l'attenzione su un CT tube e verificare se l'instabilità riscontrata in questo lavoro è persiste anche in una analisi più complessa come quella CT.
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Neville, Joshua T. "Direct-sequence spread spectrum system designs for future aviation data links using spectral overlay". Ohio : Ohio University, 2004. http://www.ohiolink.edu/etd/view.cgi?ohiou1176923782.
Testo completo
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Hieber, Matthias, e Elmar Schrohe. "Lρ spectral independence of elliptic operators via commutator estimates". Universität Potsdam, 1997. http://opus.kobv.de/ubp/volltexte/2008/2504/.
Testo completoAbstract (sommario):
Let {Tsub(p) : q1 ≤ p ≤ q2} be a family of consistent Csub(0) semigroups on Lφ(Ω) with q1, q2 ∈ [1, ∞)and Ω ⊆ IRn open. We show that certain commutator conditions on Tφ and on the resolvent of its generator Aφ ensure the φ independence of the spectrum of Aφ for φ ∈ [q1, q2].
Applications include the case of Petrovskij correct systems with Hölder continuous coeffcients, Schrödinger operators, and certain elliptic operators in divergence form with real, but not necessarily symmetric, or complex coeffcients.
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Faulkner, Sean (Sean Anthony) Carleton University Dissertation Engineering Electrical. "Composite sequences for rapid acquisition of direct-sequence spread spectrum signals". Ottawa, 1992.
Cerca il testo completo
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Isbiliroglu, Levent. "Strategy for Selecting Input Ground Motion for Structural Seismic Demand Analysis". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAU009/document.
Testo completoAbstract (sommario):
Les signaux accélérométriques enregistrés lors de l’occurrence d’un événement sismique est très large présentent une forte variabilité, par conséquent ils ne sont pas utilisé dans les analyse dynamiques de tenue sismique des structures. En effet, l’utilisation des accélérogrammes réels, pour les analyses dynamiques non linéaires, s’avère couteuse en termes de temps de calcul. La pratique courante prévoit la minimisation (voir suppression) de telle variabilité, mais les conséquences d’une telle opération sur la réponse des structures ne sont pas clairement indiquées. L’étude ci-présente a pour scope la quantification de l’impact des méthodes de sélection qui gardent la variabilité du signal sur les résultats de l’analyse de la réponse des structures (exprimée en termes d’engineering demand parameters EDPs). En particulier les questions suivantes seront investiguées :Quel est le niveau de variabilité des accélérogrammes réels et comment ce niveau est modifié par les techniques couramment utilisées ?Quelle est l’impact de la variabilité sur la réponse de plusieurs types de structures ?Pour un scénario sismique donné, un spectre cible est défini à partir de plusieurs équation de prédiction du mouvement sismique, sélection parmi celles disponibles en littérature. Les accélérogrammes sont sélectionnés à partir de quatre familles d’accélérogrammes, chacune relative à une méthode de modification : réels (enregistrés); mise à l’échelle (multiplication, par un facteur) ; calés aux spectres cibles avec large tolérance ; calés aux spectres cibles dans une plage de tolérance étroite.Chaque jeu de signaux est composé de cinq accélérogrammes et la sélection des signaux est faite en tenant compte de deux sources de variabilité : la variabilité au sein de chaque jeu de données (intraset), et la variabilité entre les différents jeux de données (interset) tous compatibles avec le même spectre cible. Les tests sur les EDPs menés sur les signaux accélérométriques réels mènent à la quantification de la variabilité naturelle (pour le scénario considéré). Les analyses basées sur les signaux réels sont utilisés comme benchmark afin d’évaluer non seulement de combien la distribution des EDPs (en termes de valeur moyenne et variabilité) est réduite par les différentes méthodes testées, mais aussi d’évaluer l’impact des choix de l’équation de prédiction du mouvement, des plages de tolérance, du nombre d’accélérogrammes constituant chaque jeu, du nombre de jeux, de le scope de l’analyse structurale et le modèle de structure.Ce travaille nous conduit à conclure que un seul jeu d’accélérogramme, tel qu’utilisé dans la pratique courante, est insuffisant pour assurer le niveau d’EDPs indépendamment de la méthode de modification utilisés, cela est lié à la variabilité des signaux et entre les jeux d’accélérogrammes. Les signaux réels, compatibles avec le spectre définis pour le scénario sismique, are l’option plus réaliste pour l’analyse dynamique non-linéaire ; si une méthode de modification du signal est nécessaire, la plus adaptées dépend du scope de l’analyse spectrale et du modèle. Le choix de l’équation de prédiction du mouvement sismique utilisée pour définir le spectre cible impacte significativement les caractéristiques des mouvements sismiques et des EDPs. Cette observation ne dépend pas de la stratégie de de modification du signalThe observed variability is very large among natural earthquake records, which are not consolidated in the engineering applications due to the cost and the duration. In the current practice with the nonlinear dynamic analysis, the input variability is minimized, yet without clear indications of its consequences on the output seismic behavior of structures. The study, herein, aims at quantifying the impact of ground motion selection with large variability on the distribution of engineering demand parameters (EDPs) by investigating the following questions:What is the level of variability in natural and modified ground motions?What is the impact of input variability on the EDPs of various structural types?For a given earthquake scenario, target spectra are defined by ground motion prediction equations (GMPEs). Four ground motion modification and selection methods such as (1) the unscaled earthquake records, (2) the linearly scaled real records, (3) the loosely matched spectrum waveforms, and (4) the tightly matched waveforms are utilized. The tests on the EDPs are performed on a record basis to quantify the natural variability in unscaled earthquake records and the relative changes triggered by the ground motion modifications.Each dataset is composed by five accelerograms; the response spectrum compatible selection is then performed by considering the impact of set variability. The intraset variability relates to the spectral amplitude dispersion in a given set, and the interset variability relates to the existence of multiple sets compatible with the target.The tests on the EDPs are performed on a record basis to quantify the natural variability in unscaled earthquake records and the relative changes triggered by the ground motion modifications. The distributions of EDPs obtained by the modified ground motions are compared to the observed distribution by the unscaled earthquake records as a function of ground motion prediction equations, objective of structural analysis, and structural models.This thesis demonstrates that a single ground motion set, commonly used in the practice, is not sufficient to obtain an assuring level of the EDPs regardless of the GMSM methods, which is due to the record and set variability. The unscaled real records compatible with the scenario are discussed to be the most realistic option to use in the nonlinear dynamic analyses, and the ‘best’ ground motion modification method is demonstrated to be based on the EDP, the objective of the seismic analysis, and the structural model. It is pointed out that the choice of a GMPE can provoke significant differences in the ground motion characteristics and the EDPs, and it can overshadow the differences in the EDPs obtained by the GMSM methods
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Le, Gall Eva. "Exploration neurocognitive des liens entre les troubles du spectre schizophrénique et les troubles du spectre autistique : Profils communs et différences fonctionnelles dans les domaines du fonctionnement cognitif général, du langage figuré et de la cognition sociale". Thesis, Nice, 2016. http://www.theses.fr/2016NICE2004/document.
Testo completoAbstract (sommario):
Les troubles schizophréniques et les troubles du spectre autistique (TSA) ont en commun des troubles de la communication, des interactions sociales, des affects et des émotions. Dans le domaine de la cognition sociale, ces similitudes suscitent des questions sur la similarité ou les différences des processus neurocognitifs sous-jacents. Cependant, à l’heure actuelle, très peu d’études expérimentales comparent directement les personnes avec un trouble schizophrénique et les personnes avec un TSA dans les différents domaines de la cognition. Dans cette thèse, ces questions seront abordées à travers 3 domaines : le profil cognitif (évaluation du fonctionnement cognitif général et analyse qualitative de la fluence verbale), le domaine du langage pragmatique : (compréhension du langage figuré en contexte et des métaphores) et le domaine de la cognition sociale (reconnaissance des émotions faciales et style d’attribution). Ainsi, il sera examiné, si les similitudes apparentes entre les troubles schizophréniques et les TSA à ces différents domaines se matérialisent par des performances similaires et si des comportements et des performances similaires résultent de mécanismes neurocognitifs communs, différents, ou diamétralement opposés. Nos résultats ont montré que malgré des similitudes apparentes, le fonctionnement neurocognitif observé dans les troubles du spectre schizophrénique et autistique se caractérise par des différences qualitatives importantes que nous discutons dans le contexte de la littérature internationale et des perspectives cliniques de ces recherchesSchizophrenia Spectrum Disorders and Autism Spectrum Disorders (ASD) have similar difficulties in communication, social interaction, affects and emotions. These apparent similarities raise the question whether similar or different neurocognitive processes might underlie similar symptoms and cognitive profiles. However, currently, very few experimental studies directly compare individuals with autism and schizophrenia in different cognition areas.The major aim of the present Doctoral Dissertation was to address these issues by exploring three areas: cognitive profile (the assessment of general cognitive functioning and the quantitative and the qualitative analysis of verbal fluency), pragmatic language (idiom comprehension in context and novels metaphors’ comprehension) and social cognition (facial affect recognition and attributional style). In each of these areas, the major results showed that despite apparent cognitive similarities, neurocognitive functioning observed in patients with schizophrenic disorders and autism were characterized by significant qualitative differences that were examined and discussed in the context of the international literature and in relation to the possible clinical perspectives
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Tatsiankou, Viktar. "Instrumentation Development for Site-Specific Prediction of Spectral Effects on Concentrated Photovoltaic System Performance". Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31222.
Testo completoAbstract (sommario):
The description of a novel device to measure the spectral direct normal irradiance is presented. The solar spectral irradiance meter (SSIM) was designed at the University of Ottawa
as a cost-effective alternative to a prohibitively expensive field spectroradiometer (FSR). The latter measures highly-varying and location-dependent solar spectrum, which is essential for accurate characterization of a concentrating photovoltaic system’s performance. The SSIM measures solar spectral irradiance in several narrow wavelength bands with a combination of photodiodes with integrated interference filters. This device performs spectral measurements at a fraction of the cost of a FSR, but additional post-processing is required to deduce the
solar spectrum. The model was developed to take the SSIM’s inputs and reconstruct the
solar spectrum in 280–4000 nm range. It resolves major atmospheric processes, such as air mass changes, Rayleigh scattering, aerosol extinction, ozone and water vapour absorptions.
The SSIM was installed at the University of Ottawa’s CPV testing facility in September,
2013. The device gathered six months of data from October, 2013 to March, 2014.
The mean difference between the SSIM and the Eppley pyrheliometer was within ±1.5%
for cloudless periods in October, 2013. However, interference filter degradation and condensation negatively affected the performance of the SSIM. Future design changes will improve the longterm reliability of the next generation SSIMs.
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Azeem, Muhammad Moazam. "Erasure Correcting Codes for Opportunistic Spectrum Access (OSA)". Thesis, Paris, CNAM, 2014. http://www.theses.fr/2014CNAM1002/document.
Testo completoAbstract (sommario):
Les années récentes ont vu l’explosion du trafic sur les réseaux mobiles depuis l’apparition de nouveaux terminaux (smartphones, tablettes) et des usages qu’ils permettent, en particulier les données multimédia, le trafic voix restant sensiblement constant. Une conséquence est le besoin de plus de spectre, ou la nécessité de mieux utiliser le spectre déjà alloué. Comme il n’y a pas de coordination entre les utilisateurs secondaire(s) et primaire, avant toute transmission les premiers doivent mettre en œuvre des traitements pour détecter les périodes dans lesquelles l’utilisateur primaire transmet, ce qui est le scénario considéré dans cette thèse. Nous considérons donc une autre approche, reposant sur l’utilisation de codes correcteurs d’effacements en mode paquet. La dernière partie de la thèse aborde un scénario dans lequel il n’y a plus d’utilisateur primaire, tous les utilisateurs ayant le même droit à transmettre dans le canal. Nous décrivons une modification de la couche MAC du 802.11 consistant à réduire les différents temps consacrés à attendre (SIFS, DIFS, backoff, . . .) afin d’accéder plus souvent au canal, au prix de quelques collisions supplémentaires qu’il est possible de récupérer en mettant en œuvre des codes correcteurs d’effacementsThe emergence of new devices especially the smartphones and tablets having a lot of new applications have rocketed the wireless traffic in recent years and this is the cause of main surge in the demand of radio spectrum. There is a need of either more spectrum or to use existing spectrum more efficiently due to dramatic increase in the demand of limited spectrum. Among the new dynamic access schemes designed to use the spectrum more efficiently opportunistic spectrum access (OSA) is currently addressed when one or more secondary users (SU) are allowed to access the channel when the PU is not transmitting. The erasure correcting codes are therefore envisioned to recover the lost data due to sensing impairments. We define the parameter efficiency of SU and optimize it in-terms of spectrum utilization keeping into account sensing impairments, code parameters and the activity of PU. Finally, the spectrum access for multiple secondary users is addressed when there is no primary and each user has equal right to access the channel. The interesting scenarios are Cognitive radio networks and WiFi where 802.11 protocol gives the specification for MAC layer. The throughput curvesachieved by retransmission and using various erasure correcting codes are compared. This modification in MAC layer will reduce the long waiting time to access the channel, as the number of users are increased
33
Kumar, Hemant. "Software analytical tool for assessing cardiac blood flow parameters". Thesis, View thesis, 2001. http://handle.uws.edu.au:8081/1959.7/392.
Testo completoAbstract (sommario):
Introduction of Doppler ultrasound techniques into the Intensive Care setting has revolutionised the way haemodynamic status is monitored in the critically ill. However, in order to increase the usefulness of these techniques, the Doppler signal and its spectrum need to be further analysed in ways to facilitate a better clinical response. Extensive processing of the Doppler spectrum on Diagnostic ultrasound machines is limited by the real time performance considerations. It was therefore proposed that the spectral information from these systems be extracted off-line and full set of analytical tools be made available to evaluate this information. This was achieved by creating an integrated and modular software tool called Spectron, which was intended as an aid in the overall management of the patients. The modular nature of Spectron was intended to ensure that new analytical tools and techniques could be easily added and tested. The software provides its users with considerable latitude in choosing various data acquisition and analysis parameters to suit various clinical situations and patient requirements. Spectron was developed under the Windows environment to provide a user friendly interface and to address a range of programming problems such as memory management and the size of the colour palettes. Spectron is able to detect the maximal velocities and compute the mean and median velocities. Relative increases in maximal velocities in cardiac blood flows after the administration of inotropic drugs have been shown in the pilot studies that were conducted. Spectron is able to help in obtaining estimates of the aortic blood flows and in other applications such measuring vascular impedance. Stenotic blood flows can be detected by using the spectral broadening index and blood flow characteristics can be studied by using various blood flow indices. Thus, this project attempted to help in patient management by providing clinicians with a range of blood flow parameters and has succeeded in meeting its objective to a large extent
34
Baliga, Shankar B. "Infrared spectrum of solid D̳2 and Raman spectra of solid H̳2, D̳2 and HD /". The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487264603218894.
Testo completo
35
Daigle, J. A. Bernard. "Development of an ion trap mass spectrometer for elemental analysis". Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/30688.
Testo completoAbstract (sommario):
Mass spectrometry is a widely used technique for the performance of elemental analysis: not only does it provides excellent limits of detection for a large number of elements, but it is also able to provide information about the isotopic distribution of the analyte. The radio-frequency quadrupole ion trap is a relatively new design of mass spectrometer, which offers the ability to confine charged particles for extended periods of time in a well defined volume by applying a radio-frequency oscillating voltage to an arrangement of three electrodes. A mass analysis of the trapped ions can be obtained by selectively extracting the ions from the cavity of the trap, where they can be detected by an electron multiplier. Despite its unique capabilities, to date the applications of the ion trap mass spectrometer have mostly been restricted to gas chromatography detection. Until recently, there have been very few attempts to use it for any other types of routine analysis.
Our interest lies in the development of an instrument capable of performing a complete mass spectrometric elemental analysis of small volume liquid samples (a few (μL) at trace or ultra-trace concentration levels. The ability of the ion trap to accumulate ions in its cavity and to provide an entire mass spectrum of these ions in a single scan of the radio-frequency oscillating voltage applied between the electrodes, makes it a very interesting candidate for the ultra-trace analysis of small size samples. However, to perform an analysis on a sample with the ion trap the sample must first be vaporized; and if an elemental analysis is required, the sample will also have to be atomized. The graphite furnace atomizer used in atomic absorption spectroscopy offers a number of advantages which make it potentially useful for this purpose: it has a high transport efficiency of the analyte from liquid or solid state to the vapour phase, the ionization of the analyte in the furnace is very low (as required by the ion trap) and it handles small volume samples very well. A graphite furnace ion
trap mass spectrometer was designed to fulfil the need of having instrumentation capable of multielemental mass spectrometric analysis of small volume samples containing traces of the analytes of interest.
This document contains a description of the principles of operation of the ion trap as well as a detailed description of the instrument actually built. Data are presented in order to assess the capabilities of the instrument, as well as some of the problems encountered with it. The results obtained with the graphite furnace ion trap mass spectrometer allow us to conclude that the proposed design is not appropriate for the performance of elemental analysis, but is appropriate for mass spectrometric study of low boiling point compounds which can interfere with atomic absorption analysis: it is calculated that these compounds could be analysed at the ppm level.
Promising results obtained with a set up in which the analyte is vaporized directly into the cavity of the ion trap through laser ablation are also presented. These limited results show the potential of this methodology for direct elemental analysis of solid samples.Science, Faculty of
Chemistry, Department of
Graduate
36
Walsh, Penelope Jane, e n/a. "Modelling and spectroscopy of polypyridyl and porphyrin complexes for electroluminescence and solar cell applications". University of Otago. Department of Chemistry, 2007. http://adt.otago.ac.nz./public/adt-NZDU20070927.151236.
Testo completoAbstract (sommario):
This thesis reports the spectroscopic and computational studies of two classes of compounds, which have applications in new optoelectronic materials technology. Substituted ligands of dipyrido-[3,2a:2�,3�c]phenazine (dppz), and their Cu(I), Re(I) and Ru(II) complexes have utility in organic electroluminescent devices. A series of Zn(II) tetraphenylporphyrins with conjugated functional groups at the β-position have been used with success in liquid heterojunction dye-sensitized solar cells. The vibrational spectra and optoelectronic properties of the two classes were investigated using Raman, resonance Raman and transient resonance Raman spectroscopy, in conjunction with density functional theory methods.
Density functional theory frequency calculations were used to aid vibrational mode assignments for the dppz compounds, and show close agreement with the experimental non-resonance Raman spectra. The enhancement of modes which are localized on differing sections of the ligand was identified. The nature of the absorbing chromophores for the dppz ligands and complexes was established using resonance Raman spectroscopy in concert with vibrational assignments from calculations. Transient resonance Raman spectra of the ligands provided spectral signatures for the triplet ligand-centred state; these features were observed in the TR� spectra of the metal complexes, along with other features attributable to MLCT states.
Electroluminescent devices were fabricated using the dppz ligands and complexes as emissive dopants, and their properties investigated. The optoelectronic behaviour of the devices was found to be influenced by the mechanism of exciton formation on the dopant. The device properties were also dependent on the dopant concentration, the concentrations of other components and the driving voltage.
The electronic structure of the porphyrin compounds was investigated using time-dependent density functional theory methods. Comparison of calculated optical transitions with experimental data shows that the calculations predict trends in the optical absorption spectra with change of functional group and with increase in conjugation chain length. The calculations suggest that the electron-withdrawing substituent decreases the configuration interaction effect by breaking the degeneracy of the two lowest unoccupied MOs, and other configuration interaction effects come into play involving other frontier MOs. Interrupting the conjugation of the functional group is shown to mitigate the breakdown of the configuration interaction.
The perturbation of the normal electronic structure of the porphyrin by the substituent was also investigated using resonance Raman spectroscopy. Vibrational analysis identified bands due to the substituent, implying coupling between the porphyrin and substituent chromophores. Changes in frequency of porphyrin core modes due to the differing substituents and different metal centres were reproduced by density functional theory calculations.
This project has allowed the spectroscopic investigation of the active optical states in a number of polypyridyl and porphyrin compounds, and determined the efficacy of DFT and TDDFT calculations to predict the properties of these compounds.
37
Reiss, Boris. "Development of a two-tone frequency modulation tunable diode laser absorption spectrometer (TTFM-TDLAS) for measuring methane fluxes". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0016/MQ56199.pdf.
Testo completo
38
Medina, Gerardo Juan. "Ligand isotope vibrational spectroscopic and DFT studies of Pt(II) and Cu(I) complexes". Thesis, Rhodes University, 2005. http://hdl.handle.net/10962/d1004982.
Testo completoAbstract (sommario):
Ligand-isotope labelling studies were performed on Zeise’s salt derivatives with pyridine N-oxide and quinoline N-oxide, their perdeuterated and O-18 isotopomers, C₂D₄ and ¹³CO, and the results of the vibrational analyses are reported. The isotopomers are modelled utilizing DFT calculations at the B3LYP level with the 6-31 G** basis set, and a pseudopotential level for the Pt atom. The calculated and observed structure and vibrational spectra correlate well. The crystal structures of [Pt(C₂2H₄)(pyO)Cl₂] and [Pt(CO)(quinO)Br₂] are reported. The frequency for the νPt-O vibration, ambiguously assigned in the literature, is here assigned unequivocally at 400 cm⁻¹. Previously observed, but inadequately described phenomena are addressed: the νN-O vibration in substituted quinoline N-oxides has been assigned previously at significantly different frequencies, depending on the nature of the substituent. This suggests that there is no specific mid-ir band associated with a high N-O character. A suitable explanation is presented for this phenomenon, showing that in low symmetry systems (eg. quinO) the N-O stretch is dispersed among several modes, whereas in high symmetry systems (eg. pyO) only a few limited modes have a high N-O character. A theoretical study of Cu(I) carbonyl compounds with macrocyclic ligands is presented. Local and global HSAB parameters applied to the donor and Cu atoms are used to explain the observed reactivities and the available spectroscopic data. Extended to [Cu(CO){H₂N(CH₂)[subscript n]NH(CH₂)[subscript m] NH₂}] BPh₄ (where n = 2, m = 2, 3 and n =3, m = 3, 4) and their -d₅ and ¹³CO isotopomers, subtle differences obtained experimentally for the CO stretching frequency in this series have been reproduced in the DFT calculations at the B3LYP level, using the 6-31 G* and 6-31 G** basis sets. Several properties (ligand pK[subscript a] values, νCO frequencies, etc.) correlate with some HSAB descriptors. Vibrational analyses are presented of Cu(I) carbonyl Schiff-base derivatives of N-Benzylidene-N’-[2-(benzyilidene-amino)-ethyl]-ethane-1,2-diamine, {2,2N3(C₆H₄R)₂}, and their -d₅ and ¹³CO isotopomers. The crystal structure of [Cu(CO){2,2N3(C₆H₅)₂}]BPh₄ is reported. From geometry optimizations and the HSAB descriptors, spectroscopic trends ([n]Cu-N and [nu]CO) are related to calculated global hardness and the Hammett substituent parameters, and are discussed in terms of σ-donation and π-backbonding of Cu- CO.
39
Lacroix, Arthur. "Reconstruction, caractérisation et modélisation acoustiques des éclairs d'orages". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS428.
Testo completoAbstract (sommario):
Le tonnerre est le son produit par les éclairs. Bien qu’audible, il contient une importante composante infrasonore (f < 20Hz) dont l’origine est toujours en débat. Le tonnerre a été mesuré, dans le cadre de la campagne européenne HyMeX, pendant deux mois (septembre – octobre 2012), dans les Cévennes à partir de deux réseaux de capteurs couvrant la bande de fréquence [0.5–180] Hz. La participation à cette campagne a également permis d’obtenir des mesures électromagnétiques donnant la localisation au sol des décharges de foudre (réseau opérationnel EUCLID) et la reconstruction tridimensionnelle de la décharge orageuse (réseau de recherche HyLMA). De cette base de données, vingt-sept flashes ayant eu lieu à moins de 25 km de la station ont été sélectionnés. Une méthode acoustique originale, permettant la reconstruction et la séparation des différentes composantes d’un même flash a été développée, permettant d’isoler le contenu acoustique des arcs en retour et de montrer sans ambiguïté qu’ils émettent la majorité de l’énergie acoustique, en particulier les infrasons. Par ailleurs, une étude statistique a montré une forte dépendance de certains paramètres acoustiques, telle l’énergie acoustique, à la distance à l’éclair. Un nouveau modèle théorique a ensuite été développé et a montré que le caractère cylindrique de l’éclair favorise l’émanation des infrasons tandis que la tortuosité du canal de foudre apporte une très forte variabilité à champ proche. Les résultats statistiques sur la simulation montrent un très bon accord avec les mesures du terrain. Enfin, un lien entre l’énergie déposée à la source et l’énergie acoustique par longueur de l’éclair a été mis en évidenceThunder is the sound made by lightning. In addition to the audible content thunder also includes an important infrasound component (f < 20Hz). The origin of this component is still in debate. In the context of the European campaign HyMeX, thunder was recorded in the Cevennes through two sensors networks covering the frequency range [0.5–180.0] Hz). Electromagnetic measures were also obtained allowing to locate stroke impact location (EU- CLID operational network) and build 3D reconstruction of the storm cell (HyLMA research network). 27 flashes occurring less than 25 km from the station were selected. An original method allowing the separation, within the acoustical signal, of Cloud-to-Ground (CG) from Intra-Cloud (IC) parts of the discharge was developed. A total of 36 CG signals and associated spectra was obtained, along with IC signals and shows clearly that the main origin of infrasound is the CG. Moreover, a statistical study has shown a strong dependency of some acoustical parameters such as the acoustical energy and the distance to the lightning stroke. These new results cannot be explained by the two existing models. That is why a new one was developed. Many cases of simulated thunder have been carried out and have shown that the cylindrical and extended aspect of the lightning channel favors infrasound emission while the tortuous shape leads to a strong variability in the close field. Statistical analysis like the one lead on the experimental data was realized to compare the model to the field measures. Results show a good agreement between both. Finally, a link between source released energy and acoustic energy was shown
40
Xiao, Jun. "Contributions to nonstationary spectrum estimation and stationary tests in the time-frequency plane". Lyon, École normale supérieure (sciences), 2008. http://www.theses.fr/2008ENSL0460.
Testo completo
41
Youatt, Andrew Pierce. "Analyzing Edgard Varese's Ionisation Using Digital Spectral Analysis". Thesis, The University of Arizona, 2012. http://hdl.handle.net/10150/232473.
Testo completoAbstract (sommario):
Although Robert Cogan's New Images of Musical Sound won the Society of Music Theory's Outstanding Publication Award in 1987, his musical application of spectral analysis has seen little use over the past 25 years. Spectral images are most effective at illustrating the timbre of sound, and harmony, not timbre, is the key structural component of most Western music. There are, however, some compositions in which timbre plays a critical role. Chief among these is Edgard Varèse's Ionisation, an epic percussion ensemble piece built around 40 instruments and 13 musicians. Previous analyses by Jean-Charles François and Varèse protege Chou Wen-Chung have emphasized the importance of timbre to Ionisation's construction, but are limited in their exploration of timbral qualities. Modern digital spectral analysis allows for a more accurate picture of the individual timbres that make up Ionisation and define the broader textures and structures that give the piece meaning.
42
Yilmaz, Nihal. "Spectral Characteristics Of Wind Waves In The Eastern Black Sea". Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608614/index.pdf.
Testo completoAbstract (sommario):
Wind waves are highly complex, random phenomena. One way to describe the irregular nature of the sea surface is the use of wave energy spectrum. Spectral information for wind waves in the Black Sea is extremely limited. Knowledge on spectral characteristics of wind waves would contribute to scientific, engineering and operational coastal and marine activities in the Black Sea. The aim of the present thesis is to investigate characteristics of wind wave spectra for the Eastern Black Sea. This would allow detailed understanding of the nature of the waves occurring in this enclosed basin. Long-term wave measurements obtained by directional buoys deployed offshore at Sinop, Hopa and Gelendzhik were utilized as the three sets of wave data. Records were analyzed to identify them as uni-modal or multi-modal spectra, and occurrences of spectral peaks were computed. Single peaked spectra were studied as belonging to fully arisen or developing sea states. Model parameters of JONSWAP and PM spectra were estimated for the observed spectra by using a least square error method. The records of developing seas were further analyzed to select the ones belonging to stable wind conditions. Fetch dependencies of non-dimensional spectral variables, mean parameters of JONSWAP model spectrum and the envelop of dimensionless spectra were investigated for this data sub-set.
43
Luce, Quentin. "Etude des rayons cosmiques d'ultra-haute énergie avec l'Observatoire Pierre Auger : de l'extraction du signal à l'interprétation du spectre en énergie". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS253/document.
Testo completoAbstract (sommario):
L’origine et la composition des rayons cosmiques demeurent, presque un siècle après leur découverte, une question ouverte, certains résultats des expériences de détection des rayons cosmiques se contredisant même, aux énergies supérieures à 10¹⁸ eV. A ces énergies, le flux reçu sur Terre est si faible qu’une détection directe est impossible sur une échelle de temps raisonnable. La collaboration Pierre Auger a ainsi construit dans la Pampa argentine, un observatoire couvrant une surface de 3000 km² afin de déterminer les énergies, les masses et les directions d’arrivée des rayons cosmiques. Les techniques de détection déployées font de l’Observatoire Pierre Auger une référence dans le domaine des Ultra-Hautes Énergies. Durant les trois années de mon doctorat, il m’a été donné l’opportunité d’étudier les méthodes de détection déployées par cette expérience et de m’intéresser spécialement à son détecteur de surface dont l’extraction du signal jusqu’à la reconstruction des directions d’arrivée et des énergies des rayons cosmiques sont présentées dans ce manuscrit avec les optimisations développées, permettant l’établissement du spectre des rayons cosmiques. L’étude de ce spectre, combinée à celle des observables de composition, obtenues par le détecteur de fluorescence, permet son interprétation en terme de masse afin de contraindre les modèles d’accélération et de propagation dans le milieu Galactique ou extragalactiqueThe origin and the composition of the cosmic rays, almost one century after their discovery, remain an open question. Results of some experiments dedicated to their detection are even contradicting themselves at energies above 10¹⁸ eV. At these energies, the flux of the cosmic rays reaching the Earth is so low that direct detection is unthinkable in a reasonable time scale. The collaboration Pierre Auger has thus built, in the Argentine Pampa, an observatory covering an area of 3000 km² to determine the energies, masses and arrival directions of cosmic rays. Deployed detection techniques make the Pierre Auger Observatory a reference in the field of Ultra-High Energy. During the three years of my thesis, I had the chance to study the detection methods deployed by this experiment, focusing on its surface detector from the extraction of its signal to the reconstruction of the arrival direction and energy of the cosmic ray, which are presented in this manuscript along with the optimizations developed. The energy spectrum of cosmic rays is then reconstructed. The study of this spectrum, combined with the observables of composition, deduced from the fluorescence detector, allows its interpretation in term of mass. Acceleration and propagation models in Galactic or extragalactic environment can then be constrained by this combined study
44
Collard, Florian. "Etude et optimisation du protocole E-SSA, méthode d'accès multiples à haute efficacité spectrale pour système de communications par satellite". Thesis, Toulouse, ISAE, 2014. http://www.theses.fr/2014ESAE0028/document.
Testo completoAbstract (sommario):
Le travail de recherche présenté dans cette thèse est basé sur l’étude du protocole de communication par satellite appelé « Enhanced Spread Spectrum Aloha » (E-SSA) et créé par l’Agence Spatiale Européenne (ESA) en 2009. Il s’agit d’une technique qui permet à un terminal d’envoyer des messages courts par satellite de manière totalement asynchrone. L’intérêt est de maximiser l’efficacité spectrale tout en gardant une complexité minimale du terminal grâce aux techniques d’étalement de spectre et d’annulation d’interférences (SIC). Alors qu’au départ le protocole E-SSA avait pour but d’apporter un support physique pour des applications destinées à des terminaux mobiles en bande S, les développements se sont récemment étendus à une gamme de terminaux fixes dans des bandes de fréquence différentes (C, Ku ou Ka). À partir de ces deux modèles d’utilisation de l’E-SSA, ce travail de recherche se concentre sur la mise en place de solutions techniques permettant d’augmenter significativement la capacité globale du système. Cela est possible à travers une optimisation des différents paramètres du protocole et la conception d’algorithmes de gestion des puissances des terminauxThe work presented in this thesis focuses on the satellite communication protocol named “Enhanced Spread Spectrum Aloha” (E-SSA) and developed in 2009 by the European Space Agency (ESA). The E-SSA structure, based on fully asynchronous random access, perfectly copes with low-duty cycle bursty transmissions adapted to satellite messaging. High performance in terms of spectral efficiency is possible by exploiting iterative successive interference cancellation (SIC) while keeping minimal complexity at the terminal side. If the first exploitation of the protocol concerned mobile applications in S-band, it has been extended to fleets of fixed terminals in other frequency bandwidths (C, Ku or Ka). Starting from these two scenarios, this thesis proposes different innovations to further boost the E-SSA global system capacity. These technical solutions particularly include a fine optimization of protocol parameters and new power control algorithms
45
Taraldsen, Gunnar. "Spectral theory of random operators : The energy spectrum of the quantum electron in a disordered solid". Doctoral thesis, Norwegian University of Science and Technology, Faculty of Information Technology, Mathematics and Electrical Engineering, 1992. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-670.
Testo completo
46
Bazkir, Ozcan. "Realization Of Detector Based Spectral Responsivity Scale From Ultraviolet To Near Infrared Regions Of Electromagnetic Spectrum". Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/2/12605148/index.pdf.
Testo completoAbstract (sommario):
Realization of spectral responsivity scale was studied in three stages. Firstly, absolute optical power measurements using Electrical Substitution Cryogenic Radiometer (ESCR) was studied. The absolute measurements were done at discrete laser wavelengths of tunable Ar+ (488 nm and 514.5 nm), Nd:YAG (532 nm) and fixed He-Ne (632.8 nm) laser sources. To increase measurement accuracy the method used for the stabilization of laser beams, transmittance measurements of optical windows, and minimization of scattered beams were discussed.
Secondly, realization of absolute responsivity scale between 350- 850 nm ranges was studied. The scale based on reflection type trap detectors consisting of three silicon photodiodes. Various measurement systems were established in order to make optical characterization of trap detectors like non-linearity, surface non-homogeneity, polarization dependency, reflectance, and internal quantum efficiency. The absolute responsivity was linked to the absolute optical power by measuring the current response of trap detectors to the absolute power measured by ESCR system at laser wavelengths. Using models for the trap detector&rsquos, reflectance and internal quantum efficiency the scale between 350- 850 nm ranges was realized with an uncertainty of 0.05 %. Finally, the spectral responsivity scale in ultraviolet (UV) and near-infrared (NIR) regions was realized using Electrically Calibrated Pyroelectric Radiometer (ECPR). Optically characterizing the spatial non-uniformity of pyroelectric detector and its surface reflectance, the spectral responsivity scale was established with uncertainties ±
0.5-1.0 % between 250 nm and 350 nm and ±
0.5-1.5 % between 850 and 2500 nm.
47
Kakar, Jaber Ahmad. "UAV Communications: Spectral Requirements, MAV and SUAV Channel Modeling, OFDM Waveform Parameters, Performance and Spectrum Management". Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/53512.
Testo completoAbstract (sommario):
Unmanned Aerial Vehicles (UAV) are expected to be deployed both by government and
industry. Rules for integrating commercial UAVs into a nation's airspace still need to be
defined, safety being the main concern. As part of this thesis, the communication needs of
UAVs as important requirement for UAV integration into the national airspace is considered.
Motivated by recent prediction of UAV quantities, revealing the importance of Micro UAVs
(MAV) and Small UAVs (SUAV), the thesis determines spectral requirements for control and
non-payload communication (CNPC). We show that spectral efficiency, particularly in the
downlink, is critical to the large-scale deployment of UAVs. Due to the limited range of small
SUAV and MAV systems, communication between air and ground elements of these UAVs is
established through radio Line-of-Sight (LoS) links. Ultimately, efficient LoS UAV systems
are based on a better understanding of channels in the downlink, i.e. air-to-ground (A2G)
channels, and also on efficient waveform as well as spectrum management implementation.
Because of limited research in wideband aeronautical channel modeling, we have derived
an A2G channel prototype applicable to SUAV and MAV. As part of the research at Wire-
less@VT in designing and prototyping Orthogonal Frequency Division Multiplexing (OFDM)
waveforms, this thesis derives the optimal parameters for SUAV and MAV A2G channels.
Finally, the thesis discusses concepts that relate flight route with spectrum management
as well as opportunities for a more dynamic spectrum allocation for UAV communication
systems.Master of Science
48
Van, Hecke Ria [Verfasser], Holger [Gutachter] Dette e Stanislav [Gutachter] Volgushev. "Novel methods for spectral analysis : \(\it U\)-spectral densities and integrated copula spectra / Ria Van Hecke ; Gutachter: Holger Dette, Stanislav Volgushev ; Fakultät für Mathematik". Bochum : Ruhr-Universität Bochum, 2018. http://d-nb.info/1154307786/34.
Testo completo
49
Rowe, Penny. "Measurements of the foreign-broadened continuum of water vapor in the 6.3 micron band at -30 celsius /". Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/8604.
Testo completo
50
Strachan, Clare, e n/a. "Spectroscopic investigation and quantitation of polymorphism and crystallinity of pharmaceutical compounds". University of Otago. School of Pharmacy, 2005. http://adt.otago.ac.nz./public/adt-NZDU20070427.141108.
Testo completoAbstract (sommario):
Spectroscopy is increasingly used to investigate and monitor the solid state forms of pharmaceutical materials and products. Spectroscopy�s speed, nondestructive sampling, compatibility with fibre optics and safety also make it attractive for in-line monitoring.
In this thesis, the spectroscopic techniques Fourier transform Raman spectroscopy, terahertz pulsed spectroscopy and second harmonic generation were used to characterise and quantify polymorphism and crystallinity of pharmaceutical compounds. Where possible, the multivariate analysis technique partial least squares was used for quantitative analysis. Fourier transform Raman spectroscopy detects polarisability changes mainly associated with molecular vibrations. Terahertz pulsed spectroscopy is a new spectroscopic technique that operates between the infrared and microwave regions of the electromagnetic spectrum and detects dipole moment changes mainly associated with crystalline phonon vibrations in the solid state. Second harmonic generation is a nonlinear optical phenomenon that depends on the dipole moment in crystals and crystal symmetry.
Several materials capable of existing in different solid state forms were used. FT-Raman spectroscopy was able to differentiate carbamazepine forms I and III, enalapril maleate forms I and II and γ-crystalline and amorphous indomethacin. Combined with partial least squares the technique could quantify binary mixtures of CBZ forms I and III with a limit of detection as low as 1%, and mixtures of enalapril maleate with a limit of detection of as low as 2%.
Terahertz pulsed spectroscopy obtained very different spectra for carbamazepine forms I and III, enalapril maleate forms I and II, γ-crystalline and amorphous indomethacin, crystalline and supercooled thermotropic liquid crystalline fenoprofen calcium, three forms of lactose, and five forms of sulphathiazole. At present the modes in the spectra cannot be attributed to specific phonon modes. Quantitation of binary mixtures of different forms of a compound using partial least squares analysis usually resulted in a limit of detection of about 1%.
Second harmonic generation was used to quantify binary mixtures of different forms of enalapril maleate and lactose, as well as binary mixtures of enalapril maleate form II and polyvinylpyrrolidone. A quantitative relationship was present for each of the mixtures, however the limits of detection were usually above 10%. The high value is probably due to the machine being a prototype and univariate analysis associated with a single output variable. Future improvements to the apparatus and measurement parameters are likely to reduce the limits of detection. Ranitidine hydrochloride polymorphs could also be differentiated using second harmonic generation, however γ-crystalline and amorphous indomethacin and forms I and III of carbamazepine could not.
The methods used in this thesis were successfully used for qualitative and quantitative analysis of polymorphism and crystallinity of pharmaceutical compounds. TPS and SHG are useful additions to the range of experimental techniques that can be used to investigate and monitor properties of pharmaceutical solids.