To see the other types of publications on this topic, follow the link: Spectral inversion.
Dissertations / Theses on the topic 'Spectral inversion'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Spectral inversion.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Orozco, M. Catalina (Maria Catalina). "Inversion Method for Spectral Analysis of Surface Waves (SASW)." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5124.
Full textAbstract:
This research focuses on estimating the shear wave velocity (Vs) profile based on the dispersion curve obtained from SASW field test data (i.e., inversion of SASW data). It is common for the person performing the inversion to assume the prior information required to constrain the problem based on his/her own judgment. Additionally, the Vs profile is usually shown as unique without giving a range of possible solutions. For these reasons, this work focuses on: (i) studying the non-uniqueness of the solution to the inverse problem; (ii) implementing an inversion procedure that presents the estimated model parameters in a way that reflects their uncertainties; and (iii) evaluating tools that help choose the appropriate prior information.
One global and one local search procedures were chosen to accomplish these purposes: a pure Monte Carlo method and the maximum likelihood method, respectively. The pure Monte Carlo method was chosen to study the non-uniqueness by looking at the range of acceptable solutions (i.e., Vs profiles) obtained with as few constraints as possible. The maximum likelihood method was chosen because it is a statistical approach, which enables us to estimate the uncertainties of the resulting model parameters and to apply tools such as the Bayesian criterion to help select the prior information objectively.
The above inversion methods were implemented for synthetic data, which was produced with the same forward algorithm used during inversion. This implies that all uncertainties were caused by the nature of the SASW inversion problem (i.e., there were no uncertainties added by experimental errors in data collection, analysis of the data to create the dispersion curve, layered model to represent a real 3-D soil stratification, or wave propagation theory). At the end of the research, the maximum likelihood method of inversion and the tools for the selection of prior information were successfully used with real experimental data obtained in Memphis, Tennessee.
2
Set, Sze Yun. "Dispersion compensation in high bit rate transmission systems using midspan spectral inversion." Thesis, University of Southampton, 1998. https://eprints.soton.ac.uk/394393/.
Full textAbstract:
This thesis presents experimental and theoretical work on optical fibre communication systems covering dispersion compensation, short pulse generation and high speed transmission. The focus of this thesis is on dispersion compensation using the midspan spectral inversion (MSSI) technique. Experimental investigation and theoretical studies on an MSSI system suggest potential compensation of both fibre chromatic dispersion as well as fibre nonlinearity. The performance of MSSI systems is found to be limited by a few effects that cannot be compensated for by phase conjugation and a different approach has to be employed in order to overcome these factors. Optical phase conjugators are essential elements of MSSI transmission systems. Dispersion shifted fibre (DSF) and semiconductor optical amplifiers (SOA) are two of the most important nonlinear media for phase conjugation. A comparison of these two types of phase conjugator has been carried out. By using fibre Bragg grating based filters, the noise performance of the conjugators could be optimised. Computer numerical models of various optical components have been developed which could simulate the basic function of erbium-doped fibre amplifiers, optical band pass filters, optical fibres and fibre gratings. Signal transmission in single mode fibre is modelled using the split-step Fourier method to solve the nonlinear Schrödinger equation (NLSE). These numerical models can be programmed to suit different experimental setups and allow the study of various system experiment configurations. The theoretical results help to explain and provide estimated limitations to the experimental results. Experiments carried out in the laboratories have finally culminated in a 10 Gbit/s MSSI field trial in Italy. Successful transmission of 6 picosecond pulses at 10 Gbit/s over 140 km of standard installed fibre was demonstrated. The field trial proved not only the feasibility of 40 Gbit/s MSSI transmission in the final field trial but also an implication on upgradability of currently installed links around the world. A novel polarisation insensitive optical phase conjugation configuration is proposed and demonstrated. With the use of all-fibre DFB lasers as FWM pumps, the first all fibre optical phase conjugator is realised. This configuration can achieve polarisation insensitive operation with great simplicity compared to conventional methods, which are complex and of high component count. Moreover, the same configuration can be applied to an SOA with equally good performance. We have demonstrated wideband and polarisation independent phase conjugation using a highly nonlinear DSF and a long SOA. High bit-rate operation up to 40 Gbit/s and MSSI transmission over 204 km of standard fibre using these devices has also been experimentally investigated.
3
Deng, Mo Ph D. Massachusetts Institute of Technology. "Deep learning with physical and power-spectral priors for robust image inversion." Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127013.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 169-182).
Computational imaging is the class of imaging systems that utilizes inverse algorithms to recover unknown objects of interest from physical measurements. Deep learning has been used in computational imaging, typically in the supervised mode and in an End-to-End fashion. However, treating the machine learning algorithm as a mere black-box is not the most efficient, as the measurement formation process (a.k.a. the forward operator), which depends on the optical apparatus, is known to us. Therefore, it is inefficient to let the neural network to explain, at least partly, the system physics. Also, some prior knowledge of the class of objects of interest can be leveraged to make the training more efficient. The main theme of this thesis is to design more efficient deep learning algorithms with the help of physical and power-spectral priors.
We first propose the learning to synthesize by DNN (LS-DNN) scheme, where we propose a dual-channel DNN architecture, each designated to low and high frequency band, respectively, to split, process, and subsequently, learns to recombine low and high frequencies for better inverse conversion. Results show that the LS-DNN scheme largely improves reconstruction quality in many applications, especially in the most severely ill-posed case. In this application, we have implicitly incorporated the system physics through data pre-processing; and the power-spectral prior through the design of the band-splitting configuration. We then propose to use the Phase Extraction Neural Networks (PhENN) trained with perceptual loss, that is based on extracted feature maps from pre-trained classification neural networks, to tackle the problem of low-light phase retrieval under low-light conditions.
This essentially transfer the knowledge, or features relevant to classifications, and thus corresponding to human perceptual quality, to the image-transformation network (such as PhENN). We find that the commonly defined perceptual loss need to be refined for the low-light applications, to avoid the strengthened "grid-like" artifacts and achieve superior reconstruction quality. Moreover, we investigate empirically the interplay between the physical and con-tent prior in using deep learning for computational imaging. More specifically, we investigate the effect of training examples to the learning of the underlying physical map and find that using training datasets with higher Shannon entropy is more beneficial to guide the training to correspond better to the system physics and thus the trained mode generalizes better to test examples disjoint from the training set.
Conversely, if more restricted examples are used as training examples, the training can be guided to undesirably "remember" to produce the ones similar as those in training, making the cross-domain generalization problematic. Next, we also propose to use deep learning to greatly accelerate the optical diffraction tomography algorithm. Unlike previous algorithms that involve iterative optimization algorithms, we present significant progresses towards 3D refractive index (RI) maps from a single-shot angle-multiplexing interferogram. Last but not least, we propose to use cascaded neural networks to incorporate the system physics directly into the machine learning algorithms, while leaving the trainable architectures to learn to function as the ideal Proximal mapping associated with the efficient regularization of the data. We show that this unrolled scheme significantly outperforms the End-to-End scheme, in low-light imaging applications.
by Mo Deng.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science
4
Pappalardo, Cirino, Bernd Vollmer, and Ariane Lancon. "The star formation history of Virgo spiral galaxies. Combined spectral and photometric inversion." Phd thesis, Université de Strasbourg, 2010. http://tel.archives-ouvertes.fr/tel-00483128.
Full textAbstract:
Cette these etudie l'influence du balayage par pression dynamique sur l'histoire de la formation stellaire des galaxies spirales qui se trouvent dans des amas. Le balayage par pression dynamique est l'interaction hydrodynamique entre le milieu interstellaire (ISM) d'une galaxie spirale qui evolue dans le puits de potentiel d'un amas, et le milieu intra-amas (ICM). Si la pression dynamique exercee par l'ICM excede la force d'attraction gravitationnelle due au potentiel galactique, la galaxie perd du gaz de sa partie externe. L'amas de la Vierge constitue un laboratoire ideal pour etudier les effets de l'environnement sur l'evolution des galaxies. En effet, cet amas est riche en spirales et dynamiquement jeune. Des observations nous montrent que la quantite de gaz atomique qui se trouve dans les spirales de la Vierge est moins importante que celle des galaxies du champ. En particulier, les spirales des amas presentent des disques HI tronques. Pour celles des galaxies qui presentent aussi une distribution stellaire symetrique, le balayage par pression dynamique semblerait etre l'origine la plus probable de la troncature du gaz du disque.
5
Pappalardo, Cirino. "The star formation history of Virgo spiral galaxies : combined spectral and photometric inversion." Strasbourg, 2010. https://publication-theses.unistra.fr/public/theses_doctorat/2010/PAPPALARDO_Cirino_2010.pdf.
Full textAbstract:
Cette thèse étudie l'influence du balayage par pression dynamique sur l'histoire de la formation stellaire des galaxies spirales qui se trouvent dans des amas. Le balayage par pression dynamique est l'interaction hydrodynamique entre le milieu interstellaire (ISM) d'une galaxie spirale qui évolue dans le puits de potentiel d'un amas, et le milieu intra-amas (ICM). Si la pression dynamique exercée par l'ICM excède la force d'attraction gravitationnelle due au potentiel galactique, la galaxie perd du gaz de sa partie externe. L'amas de la Vierge constitue un laboratoire idéal pour étudier les effets de l'environnement sur l'évolution des galaxies. En effet, cet amas est riche en spirales et dynamiquement jeune. Des observations nous montrent que la quantité de gaz atomique qui se trouve dans les spirales de la Vierge est moins importante que celle des galaxies du champ. En particulier, les spirales de la Vierge est moins importante que celle des galaxies du champ. En particulier, les spirales des amas présentent des disques HI tronqués (Giovanelli & Haynes 1983). Pour celles des galaxies qui présentent aussi une distribution stellaire symétrique, le balayage par pression dynamique semblerait être l'origine la plus probable de la troncature du gaz du disqueThis thesis investigates the influence of ram pressure stripping on the star formation history of cluster spiral galaxies. Ram pressure stripping is the hydrodynamical interaction between the interstellar medium (ISM) of a spiral galaxy that is moving inside the potential well of a cluster, and the intracluster medium (ICM). If the dynamical pressure exerted by the ICM is larger than the restoring force due to the galactic potential, the galaxy loses gas from the outer disk. The Virgo cluster is an ideal laboratory to study environmental effects on galaxy evolution, because it is rich in spirals and dynamically young. From observations we know that the amount of atomic gas in Virgo spirals is less than that of galaxies in the field. In particular cluster spirals show truncated HI disks (Giovanelli & Haynes 1983, Cayatte et al. 1990). For those galaxies that also show a symmetrical stellar distribution, ram pressure stripping is the most probably origin of the gas-disk truncation
6
OLIVEIRA, OTAVIO KAMINSKI DE. "INVERSION OF NONLINEAR PERTURBATIONS OF THE LAPLACIAN IN GENERAL DOMAINS WITH FINITE SPECTRAL INTERACTION." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=27930@1.
Full textAbstract:
PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCOORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO
Consideramos a análise numérica de perturbações não lineares do Laplaciano definido em regiões limitadas tratáveis pelo Método de Elementos Finitos. Supomos que as não linearidades interagem com k autovalores do Laplaciano livre. Apresentamos uma redução do problema à inversão de uma função de k variáveis e delineamos uma técnica para tal. O texto é uma extensão dos trabalhos de Cal Neto, Malta, Saldanha e Tomei.
We consider the numerical analysis of nonlinear perturbations of the Laplacian defined in limited regions amenable to the Finite Element Method. The nonlinearities are supposed to interact only with k eigenvalues of the free Laplacian. We present a reduction of the problem to the inversion of a function of k variables and indicate a technique to do so. The text extends the works by Cal Neto, Malta, Saldanha and Tomei.
7
Reine, Carl Andrew. "A robust prestack Q-Inversion in the T-p Domain using variable-window spectral estimates." Thesis, University of Leeds, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511145.
Full text
8
Fernandez, Cesar Aaron Moya. "Two alternative inversion techniques for the determination of seismic site response and propagation-path velocity structure : spectral inversion with reference events and neural networks." 京都大学 (Kyoto University), 2004. http://hdl.handle.net/2433/147831.
Full text
9
Markusson, Ola. "Model and System Inversion with Applications in Nonlinear System Identification and Control." Doctoral thesis, KTH, Signals, Sensors and Systems, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3287.
Full text
10
Ghorbani, Ahmad. "Contribution au développement de la résistivité complexe et à ses applications en environnement." Paris 6, 2007. http://www.theses.fr/2007PA066607.
Full textAbstract:
Ce mémoire est divisé en deux chapitres. Le premier chapitre présente une synthèse bibliographique sur la méthode de Polarisation Provoquée (PP). Il passe en revue les derniers résultats théoriques et expérimentaux et insiste sur les applications environnementales de la méthode Polarisation Provoquée Spectrale (PPS ou Spectral Induced Polarization ou SIP en anglais), encore souvent appelée résistivité complexe. Le deuxième chapitre comprend cinq sous-chapitres. Dans un premier sous-chapitre, l'approche bayésienne est développée pour inverser les paramètres du modèle de Cole-Cole dans les domaines temporel et fréquentiel. Nous avons évalué la pertinence et la robustesse de la méthode des moindres carrés pour l’inversion des données issues de la méthode PP. Les résultats montrent que l'approche classique dans le domaine temporel ne peut pas mener à une évaluation appropriée des paramètres Cole-Cole. L'emploi harmonique de signal carré injecté à fin d’obtenir un plus large spectre n’est pas non plus satisfaisant. À l'opposé, les paramètres Cole-Cole sont mieux inversés dans le domaine fréquentiel. Dans un deuxième sous-chapitre, nous avons conçu un algorithme d'inversion 1D par homotopie pour récupérer les paramètres du modèle Cole-Cole à partir des données de PPS. Cet algorithme permet de découpler les effets associés à la seule PP de ceux issus de couplages électromagnétiques parasites se produisant dans une large bande de fréquences. Nous avons employé le code numérique, CR1Dmod, développé initialement par Ingeman-Nielsen et Baumgartner (2006), résout le problème direct. L’interface utilisateur graphique, que nous avons conçue, facilite les entrées des données et des paramètres du modèle a priori, ainsi que la définition de la configuration géométrique du dispositif (géométrie des câbles). Nous présentons deux exemples synthétiques pour illustrer la récupération des paramètres spectraux à partir de données de résistivités complexes. Dans un troisième sous-chapitre, la PPS est appliquée pour le suivi de l'infiltration d'eau dans un sol limoneux-argileux. L’infiltration a été réalisée à partir d’une pluie artificielle (à débit de pluie quasi-constant) et au cours de deux expérimentations, l’une menée in situ et l’autre sur une colonne de sol. Les expériences ont été basées sur l'acquisition couplée de données de tensiomètres et de spectres de PPS durant l’infiltration. Cette approche a confirmé l'existence d'une baisse significative de la phase (ou de la conductivité imaginaire) dans la partie haute fréquence du spectre (typiquement, 1-12 kHz) qui a été corrélée avec le remplissage d’eau dans des pores de diamètres compris dans la gamme de [30-85] m. Ces baisses de phase sont interprétées comme un effet de type Maxwell-Wagner. Les résultats de cette étude suggèrent que la méthode PPS serait en mesure de fournir des informations sur le remplissage par l'eau des plus gros pores et ainsi d’estimer indirectement des propriétés structurales. Dans un quatrième sous-chapitre, la mesure de la résistivité complexe est employée pour le suivi de la teneur en eau et des microfissures induites thermiquement sur des échantillons quasi-saturés d'argillite. Les mesures de PPS ont été enregistrées durant deux trajets consécutifs en dessiccation: (a) le premier trajet a consisté en une phase de désaturation à l'air ambiant et (b) durant le deuxième trajet, les échantillons ont été soumis à quatre paliers de chauffe (température égale à 70, 80, 90 et 105 °C). Durant la phase de désaturation, l'amplitude de la résistivité complexe a été extrêmement sensible au changement de teneur en eau (un facteur de 3 à 5). Pendant la phase de chauffage, la résistivité a augmenté de deux ordres de grandeur comparativement à l'état initial. Les modèles Cole-Cole et Cole-Cole Généralisé sont les meilleurs modèles pour inverser respectivement les données de PPS pour la phase de désaturation et la phase de chauffage. Cependant, les résultats prouvent que le développement de l'anisotropie et les changements par conséquent de texture peuvent induire différentes signatures spectrales et processus de polarisation. Dans le dernier sous-chapitre, le modèle empirique de Cole-Cole qui est très largement utilisé dans les études PP est employé pour l'étude de la compaction par dissolution sous contrainte de formations sédimentaires. Notre contribution dans cette étude a consisté à écrire l'algorithme nécessaire à l’application du modèle de Cole-Cole dans le domaine temporel.
11
Cureton, Geoffrey Patrick. "Retrieval of nonlinear spectral information from ocean sunglint." Thesis, Curtin University, 2010. http://hdl.handle.net/20.500.11937/1549.
Full textAbstract:
In this thesis we develop an inversion procedure which allows the retrieval of nonlinear characteristics of the ocean wave surface from observations of specularly reflected visible solar radiation, or sunglint. Knowledge of the higher order statistical properties of the wave surface enables us to gain an improved understanding of wave generation processes, to determine the degree of energy transfer between wave components, and to make statements about the likelihood of extreme or unlikely wave events. Apart from its scientific value, this information should be useful for the engineering of maritime structures, where account must be made of conditions occasionally exceeding what a structure is normally expected to withstand.Previous attempts at retrieving information about the ocean surface from sunglint data (Alvarez-Borrego, 1993) have used second order statistical descriptors, such as the variance and autocorrelation, to provide the connection between the slope and sunglint data. This approach results in the loss of phase information from the slope and sunglint statistical descriptors, which prevents the retrieval of the phase correlations between the wave components arising from nonlinear interactions.In order to address this deficiency, we derive the relationship between the slope and the sunglint data in terms of their respective third order cumulant functions. The glint function in this case is defined in terms of the corresponding joint slope probability density. This density function is developed using a perturbative approach, and consists of a Gaussian function (which characterises the second order statistical descriptors of the slope), and corrections which parameterise the higher order correlations between the slope variables. A consequence of this approach to synthesising the required slope density is a dependence on higher order, or Multidimensional Hermite Polynomials (MDHP). Accordingly, the differential and integral properties of these orthogonal polynomials are investigated with respect to their utility in formulating the slope density function.Using these tools, we develop an inversion procedure which exploits the generalised relationship connecting the statistical descriptors of the slope and glint to retrieve the slope descriptors, namely the slope cumulants and third order cumulant function. This technique is validated using synthetic ocean wave slope datasets with controlled phase correlations imposed on a subset of the wave spectrum components.
12
Levy, Robert Carroll. "Retrieval of troposheric aerosol properties over land from inversion of visible and near-infrared spectral reflectance application over Maryland /." College Park, Md. : University of Maryland, 2007. http://hdl.handle.net/1903/6822.
Full textAbstract:
Thesis (Ph. D.) -- University of Maryland, College Park, 2007.Thesis research directed by: Atmospheric and Oceanic Sciences. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
13
Qin, Yilong. "SPICE benchmark pour méthodes tomographiques globaux et test des modèles tomographiques globaux." Paris, Institut de physique du globe, 2007. http://www.theses.fr/2007GLOB0016.
Full textAbstract:
Au cours des deux dernières décennies, de nombreux modèles de vitesse globaux ont été obtenus en utilisant différents types des mesures sismologiques (temps de parcours des ondes volumiques, vitesse de phase des ondes de surface et forme d'onde) et différentes hypothèse théoriques (isotropie, anisotropie et anélasticite��). Selon le choix de l'algorithme d'inversion, la régularisation, la paramétrisation et le type de données, les modèles tomographiques sont généralement différents. Parallèlement, de nouvelles méthodes tomographiques de type fréquence finies ont été développes. Dans le cadre de cette thèse, nous avons réalise le banc d'essai (Blind test en anglais) pour méthodes tomographiques globaux. Et nous avons aussi vérifié les modèles tomographiques globaux existantsOver the last two decades, a lot of global-scale or regional-scale seismic models of the Earth's interiors have been constructed from different types of seismological measurements (body-wave traveltime, surface-wave phase velocity or full waveforms) and with different theoretical assumptions of seismic wave propagation (ray theory, Born approximation or wave equation) and with different inversion techniques (iterative least-square inversion, Monte-Carlo or Neighborhood algorithm) and different parameterizations (spherical harmonics up to a variable degree or blocks or adaptive triangles). Generally these different tomographic methods generate different tomographic models. To calibrate these different tomographic methods and test these different tomographic models, we decided to perform a global-scale benchmark for seismic tomography and test different global-scale tomographic models. So this thesis is divided into two parts
14
Benzerhouni, Kaddour. "Spectroscopie d'absorption de l'ammoniac et étude du laser (¹⁵NH₃+ N₂) à inversion de population." Paris 11, 1988. http://www.theses.fr/1988PA112097.
Full textAbstract:
Ce travail présente une étude sur la molécule d'ammoniac dans sa forme naturelle ( ¹⁴ NH₃ ) et l'une de ses formes isotopiques ( ¹⁵NH₃ ) selon deux grandes directions :• D'une part, on traite de l'aspect spectroscopique de la molécule d'ammoniac en étudiant le profil spectral des raies d'absorption. • D'autre part, on utilise le gaz d'ammoniac pour réaliser un laser moléculaire dans le moyen-infrarouge pompé optiquement par un laser CO2. Dans le chapitre 1, on rappelle les données spectroscopiques sur la molécule d'ammoniac. En particulier, on présente la bande parallèle -√2 située dans la région de 10,5 µm, qui donne lieu à des coïncidences entre les raies d'émissions du laser C02 et les raies d'absorption de ¹⁴ NH₃ et ¹⁵NH₃. Dans le chapitre Il, on s'intéresse à l'étude des profils de raies de la molécule d'ammoniac pour la mesure des largeurs et des intensités. Ces mesures sont réalisées à partir de spectres enregistrés par un spectromètre à diode laser à haute résolution. La méthode de détermination de la largeur collisionnelle est décrite. Pour la mesure de l'intensité d'une raie, les différentes méthodes utilisées sont exposées brièvement. Dans chaque cas, on discute des avantages et des inconvénients de la méthode. Les résultats expérimentaux sont décrits et discutés ensuite. Dans le chapitre III, on rappelle les différents travaux antérieurs sur le laser à ammoniac, en particulier, le pompage optique hors résonance et le développement des sources Raman de puissance. L'utilisation du laser "Raman" à 12,08 µm pour des mesures d'absorption sur la raie sP(7,0) est exposée. Les résultats expérimentaux dans le cas de ¹⁴ NH₃pur et en présence de gaz tampon (N₂, He) sont décrits et discutés ensuite. Dans le chapitre IV, on s'intéresse au pompage optique en résonance de la molécule ¹⁵NH₃. L'étude, la réalisation et l'optimisation du laser à inversion de population (¹⁵NH₃ + N₂) en anneau, émettant en continu à 11,76 µm sont décrites. Les principaux résultats expérimentaux du laser à 11. 76 µm et les performances en puissance sont reportés. Un modèle à taux de population du gain à faible signal est établi. Une analyse du gain en fonction des principaux paramètres est décrite pour interpréter les résultats expérimentauxThis work is a study of the ammonia molecule under its two isotopic species ¹⁴ NH₃ and ¹⁵NH₃. The two following topics are developed:On one hand, the spectroscopic aspect of the molecule is studied related to the spectral profile of the absorption tine. On the other hand, we perform ammonia laser working in mid infrared by optical pumping with a CO2 laser. In chapter I all spectroscopic data about this ammonia molecule are reported, especially the -√2 absorption band in the 10,5 µm spectral range. This band gives rise to a lot of quasi coïncidences with the emission lines of the C02 for the two isotopic species ¹⁴ NH₃ and ¹⁵NH₃. In chapter ll, the profile of the absorption lines is studied. The intensities and line-width of some tines have been measured using a diode laser spectrometer. The way to determine collisional line-width is described. Several methods are used to determine intensities. Advantages and disadvantages of each method are discussed. In chapter Ill, ail previous works about the ammonia laser are recalled, especially the off-resonant optical pumping giving rise to the powerful Raman laser. We report the work made with this "Raman laser" at 12,08 μm, in order to study the absorption profile of the sP(7,0) line of ammonia. The results obtained with ¹⁴ NH₃ specie self-broadened, or with buffer gases, N₂ or He, are reported and discussed. In chapter IV, we describe our work about the resonant optical pumping on ¹⁵NH₃ in a ring configuration. The study, realization and optimization for the population inversion laser (¹⁵NH₃+ N₂) giving a laser line at 11,76 μm, is developed. The main experimental results about the properties of this laser are reported. A rate equation model is established for the small signal gain. An analysis of the gain according to the different parameters of the laser gives a good comparison with experimental results
15
Boumaaza, Bouharket. "3D seismic attributes analysis and inversions for prospect evaluation and characterization of Cherokee sandstone reservoir in the Wierman field, Ness County, Kansas." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/35510.
Full textAbstract:
Master of ScienceDepartment of Geology
Abdelmoneam Raef
Matthew W. Totten
This work focuses on the use of advanced seismically driven technologies to estimate the distribution of key reservoir properties which mainly includes porosity and hydrocarbon reservoir pay. These reservoir properties were estimated by using a multitude of seismic attributes derived from post-stack high resolution inversions, spectral imaging and volumetric curvature. A pay model of the reservoir in the Wierman field in Ness County, Kansas is proposed. The proposed geological model is validated based on comparison with findings of one blind well. The model will be useful in determining future drilling prospects, which should improve the drilling success over previous efforts, which resulted in only few of the 14 wells in the area being productive. The rock properties that were modeled were porosity and Gamma ray. Water saturation and permeability were considered, but the data needed were not available. Sequential geological modeling approach uses multiple seismic attributes as a building block to estimate in a sequential manner dependent petrophysical properties such as gamma ray, and porosity. The sequential modelling first determines the reservoir property that has the ability to be the primary property controlling most of the other subsequent reservoir properties. In this study, the gamma ray was chosen as the primary reservoir property. Hence, the first geologic model built using neural networks was a volume of gamma ray constrained by all the available seismic attributes. The geological modeling included post-stack seismic data and the five wells with available well logs. The post-stack seismic data was enhanced by spectral whitening to gain as much resolution as possible. Volumetric curvature was then calculated to determine where major faults were located. Several inversions for acoustic impedance were then applied to the post-stack seismic data to gain as much information as possible about the acoustic impedance. Spectral attributes were also extracted from the post-stack seismic data. After the most appropriate gamma ray and porosity models were chosen, pay zone maps were constructed, which were based on the overlap of a certain range of gamma ray values with a certain range of porosity values. These pay zone maps coupled with the porosity and gamma ray models explain the performance of previously drilled wells.
16
Traforti, Anna. "Reactivated fault zones: kinematic complexity and fault rock spectral characterization." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3421819.
Full textAbstract:
In the present work three main factors contributing to the overall complexity of reactivated fault zones have been investigated: i) the problematic reconstruction of polyphase brittle tectonic evolution accommodated by fault zones dissecting lithologically heterogeneous rock domains; ii) the estimate of the mechanical anisotropy associated with pre-existing planar discontinuities (i.e., metamorphic foliations and inherited faults) steering their brittle reactivation process; iii) the spectral characterization of fault zone rocks in complex fault architectures aimed at inferring the distribution of fault zone domains by means of remote sensing techniques.
In order to achieve the goal of improving current understanding of these factors defining reactivated fault zone complexity, different methodologies have been applied: i) a paleostress inversion analysis that carefully considers each analyzed fault zones and the different mechanical behavior of the lithological domains they deform; ii) a bootstrapping statistical approach aimed at evaluating the homogeneity between the resulting stress tensors and identifying possible local stress perturbations; iii) a normalised slip tendency analysis that, integrated with paleostress reconstructions and detailed meso- and micro-structural observations, allows constraining the mechanical properties of pre-existing planar discontinuities; iv) a spectral features analysis of fault zone rock reflectance spectra, aimed at highlighting the correlation between variations in fault rock spectral signatures and grain size reduction related to fault comminution processes.
The main results of this work highlighted that: i) polyphase brittle tectonics within lithologically heterogeneous rock domains can be efficiently unrevealed by applying a paleostress inversion combined with bootstrapping statistical analysis of the resulting reduced stress tensors; ii) normalised slip tendency analysis can be considered a reliable method to investigate and constrain the weakness of pre-existing anisotropies at a regional scale (104-103 m); iii) the grain size reduction resulting from fault-related comminution processes on mineralogically homogenous bedrocks (carbonates in this case) influences the spectral signatures of fault rock samples, which absorption feature parameters vary systematically with the grain size in the VNIR and SWIR wavelength ranges; iv) consequently, remote sensing analysis, based on fault rock reflectance spectrum variabilities due to comminution processes, has a good potential in the identification of the spatial distribution and extent of fault core and damage zone domains (i.e., characterized by different grain sizes) on mineralogically homogenous bedrocks (carbonates in this case).Nel presente lavoro sono stati investigati tre fattori che contribuiscono alla definizione della complessità delle zone di faglia riattivate: i) la ricostruzione dell’evoluzione tettonica polifasica accomodata da zone di faglia che interessano litologie eterogenee; ii) la stima del grado di anisotropia meccanica associata alla presenza di discontinuità planari pre-esistenti (i.e., foliazioni metamorfiche e faglie), il quale influenza i meccanismi di riattivazione lungo tali piani; iii) la caratterizzazione spettrale delle rocce di faglia, finalizzata all’ identificazione della distribuzione delle zone di danno e di core tramite tecniche di remote sensing, con particolare riguardo a zone di faglie mature aventi un’architettura complessa. Al fine di dare un nuovo contributo alla comprensione dei fattori che definiscono le complessità insite nelle zone di faglia riattivate, sono state applicate diverse metodologie che comprendono: i) l’inversione del campo di paleostress, applicata considerando il comportamento meccanico dei domini litologici interessati da ogni differente zona di faglia; ii) l’approccio statistico di tipo ‘bootstrapping’ applicato al fine di valutare l’omogeneità tra i tensori di stress ricavati e di identificare possibili perturbazioni locali del campo di paleostress; iii) la ‘normalised slip tendensy analysis’ che, integrata alla ricostruzione del campo di paleostress e ad una caratterizzazione di tipo micro- e meso-strutturale, permette di stimare quantitativamente le proprietà meccaniche di discontinuità planari pre-esistenti; iv) l’analisi delle bande di assorbimento osservate negli spettri di riflettenza di diverse rocce di faglia, al fine di evidenziare il rapporto esistente tra le variazioni osservate nei parametri spettrali e i processi di comminuzione dovuti all’evolversi della zona di faglia stessa. I principali risultati di questo lavoro evidenziano come: i) tettoniche polifasiche che si sviluppano in domini rocciosi altamente eterogenei possono essere efficacemente ricostruite applicando in maniera integrata l’inversione del campo di paleostress e l’analisi statistica di tipo ‘bootstrapping’; ii) la ‘normalised slip tendency analysis’ permette di investigare la debolezza di anisotropie pre-esistenti a scala regionale (104-103 m); iii) la riduzione granulometrica connessa ai processi di comminuzione dovuti all’evolversi di una zona di faglia in rocce incassanti omogenee dal punto di vista mineralogico (carbonati in questo caso) influenza la firma spettrale delle rocce di faglia, le cui bande di assorbimento hanno caratteristiche che variano sistematicamente con la diminuzione della granulometria; iv) di conseguenza, l’analisi in remoto, basata sugli effetti della comminuzione sulle firme spettrali delle rocce di faglia, dimostra un buon potenziale nell’identificazione della distribuzione spaziale delle zone di danno e di core di una faglia in rocce incassanti omogenee dal punto di vista mineralogico.
17
Nassif, Moussa Daou David. "Caractérisation des aérosols par inversion des données combinées des photomètres et lidars au sol." Thèse, Université de Sherbrooke, 2012. http://hdl.handle.net/11143/6058.
Full textAbstract:
Aerosols are small, micrometer-sized particles, whose optical effects coupled with their impact on cloud properties is a source of large uncertainty in climate models. While their radiative forcing impact is largely of a cooling nature, there can be significant variations in the degree of their impact, depending on the size and the nature of the aerosols.
The radiative and optical impact of aerosols are, first and foremost, dependent on their concentration or number density (an extensive parameter) and secondly on the size and nature of the aerosols (intensive, per particle, parameters). We employed passive (sunphotmetry) and active (backscatter lidar) measurements to retrieve extensive optical signals (aerosol optical depth or AOD and backscatter coefficient respectively) and semi-intensive optical signals (fine and coarse mode OD and fine and coarse mode backscatter coefficient respectively) and compared the optical coherency of these retrievals over a variety of aerosol and thin cloud events (pollution, dust, volcanic, smoke, thin cloud dominated). The retrievals were performed using an existing spectral deconvolution method applied to the sunphotometry data (SDA) and a new retrieval technique for the lidar based on a colour ratio thresholding technique.
The validation of the lidar retrieval was accomplished by comparing the vertical integrations of the fine mode, coarse mode and total backscatter coefficients of the lidar with their sunphotometry analogues where lidar ratios (the intensive parameter required to transform backscatter coefficients into extinction coefficients) were (a) computed independently using the SDA retrievals for fine mode aerosols or prescribed for coarse mode aerosols and clouds or (b) computed by forcing the computed (fine, coarse and total) lidar ODs to be equal to their analog sunphotometry ODs. Comparisons between cases (a) and (b) as well as the semi-qualitative verification of the derived fine and coarse mode vertical profiles with the expected backscatter coefficient behavior of fine and coarse mode aerosols yielded satisfactory agreement (notably that the fine, coarse and total OD errors were <~ sunphotometry instrument errors). Comparisons between cases (a) and (b) also showed a degree of optical coherency between the fine mode lidar ratios.
18
Eremenko, Maxim. "Inversion des spectres infrarouges à haute résolution spectrale enregistrés en absorption à partir de ballons stratosphériques : ajustement global de grands domaines spectraux : inversion multi-paramètres (espèces moléculaires)." Paris 6, 2003. http://www.theses.fr/2003PA066109.
Full text
19
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.
Full text
20
Gao, Guochao. "Contribution to seismic modeling and imaging in the presence of reflector roughness." Thesis, Ecole centrale de Marseille, 2020. http://www.theses.fr/2020ECDM0010.
Full textAbstract:
En raison de divers processus géologiques et de mouvements crustaux, les interfaces rugueuses existent largement dans la Terre. Une interface rugueuse peut affecter fortement la propagation des ondes sismiques par des changements d'amplitude, de phase, d'angle de diffusion, du contenu en fréquence et même de conversion de type d'onde. Inévitablement, la qualité de l'imagerie sismique ou de l'inversion en est fortement influencée. Malgré les nombreux travaux consacrés à l'interaction des ondes avec des interfaces rugueuses, cette interaction est loin d’être comprise, car il est encore difficile de modéliser la propagation des ondes sismiques dans un tel contexte et par conséquent de reconstruire correctement le sous-sol. Cette thèse étudie l'effet des interfaces rugueuses sur la modélisation et l'imagerie des ondes sismiques et explore le potentiel d'une méthode électromagnétique pour s’affranchir de cet effet et ainsi mieux imager le sous-sol.Nous utilisons une méthode numérique basée sur les éléments finis spectraux, et plus précisément le code SPECFEM2D, qui permet de modéliser la propagation des ondes acoustiques dans le domaine temporel. Tout d'abord, nous considérons un réseau sinusoïdal et illustrons numériquement les conséquences de l'équation de réseau sur les signaux temporels. Ensuite, en utilisant l'analyse f-k, nous montrons le positionnement des différents ordres de diffraction dans le domaine fréquence-nombre d'onde. Après une analyse de sensibilité, nous sélectionnons une configuration appropriée qui permet la séparation des ordres de diffraction à partir d’un shot gather. Enfin, il est montré que la hauteur de rugosité et la longueur de corrélation influencent manifestement l'apparence du champ d'onde diffracté. Cependant, la longueur de corrélation a moins d'effet sur l'énergie des ondes diffractées que la rugosité d'interface.Nous utilisons un schéma d'inversion de forme d'onde complète (FWI) basé sur le logiciel DENISE afin d’étudier l'influence de la hauteur de rugosité et de la longueur de corrélation sur les résultats d'imagerie sismique. Lorsque la hauteur de rugosité augmente jusqu'à atteindre la longueur d'onde dominante ou plus, le bruit aléatoire domine dans les données sismiques, et les résultats FWI se détériorent considérablement, en particulier pour la reconstruction d'un réflecteur horizontal situé sous l'interface rugueuse. En revanche, la longueur de corrélation a un effet beaucoup plus faible sur le bruit aléatoire et la qualité des résultats inversés.Comme démontré dans ce travail, la rugosité de l'interface a un impact majeur sur la propagation et l'imagerie des ondes sismiques. Lorsqu'une interface rugueuse est présente dans le sous-sol, son effet doit être examiné de manière critique dans le cadre de la FWI, afin de reconstruire correctement les réflecteurs éventuellement situés en dessous, puis d'interpréter correctement les images du sous-sol. Dans ce contexte, nous effectuons des tests préliminaires sur l'utilisation d'une méthode d'extinction sélective visant à enlever l'impact de la rugosité sur les champs d'ondes. Les résultats sont prometteurs et montrent le potentiel de la méthode pour une meilleure imagerie. De plus, l'écart type de l'amplitude des données traitées semble pouvoir être utilisé pour évaluer les caractéristiques de l'interface rugueuse, ce qui présenterait également un intérêt important pour les géophysiciens et les géologuesDue to various geological processes and crustal movements, rough interfaces widely exist within the Earth. The rough interface can strongly affect seismic wave propagation, manifested as changes in the amplitude, phase, scattering angle, frequency content, and even the wave-type conversion. Inevitably, the quality of seismic imaging or inversion is also greatly influenced. Despite the numerous works devoted to the interaction of waves with rough interfaces, this interaction remains to be better understood, as it is still quite challenging to model the seismic wave propagation and to properly reconstruct the subsurface. The thesis investigates the effect of rough interfaces on seismic wave modeling and imaging, and explores the potential of an electromagnetic method to remove this effect and to better image the subsurface.We use a spectral-element method, and more specifically the code SPECFEM2D, for modeling acoustic wave propagation in the time domain. First, we consider a sinusoidal grating and illustrate numerically the consequences of the grating equation on the temporal signals. Then, using f-k analysis, we show the location of the different diffraction orders in the frequency-wavenumber domain. After a sensitivity analysis, we select an appropriate configuration that allows for the separation of diffraction orders from a shot gather. Last, both roughness height and correlation length are shown to obviously influence the appearance of the diffracted wavefield. However, the correlation length has less effect on the energy of the diffracted waves than the interface roughness.We adopt a full-waveform inversion (FWI) scheme based on the software package DENISE to study the influence of different roughness heights and correlation lengths on seismic imaging results. When the roughness height increases up to the dominant wavelength or is greater, the random noise dominates in the seismic data, and the FWI results significantly deteriorate, especially for the reconstruction of a horizontal reflector located below the rough interface. In contrast, the correlation length has a much smaller effect on both random noise and quality of the inverted results than the roughness height. As shown here, the interface roughness has a major impact on both seismic wave propagation and imaging. When a rough interface is expected to be present in the subsurface, its effect should be critically considered in FWI, in order to properly reconstruct reflectors possibly located below, and then to properly interpret images of the subsurface. In this context, we perform some preliminary tests on the use of a selective extinction method to remove the impact of the roughness on the wavefields. The results are promising and show the potential of the method for better imaging. In addition, the standard deviation of the amplitude of the processed data may be used to evaluate the characteristics of the rough interface, which is also of interest for geophysicists and geologists
21
Benavides, Iglesias Alfonso. "Experimental time-domain controlled source electromagnetic induction for highly conductive targets detection and discrimination." Texas A&M University, 2003. http://hdl.handle.net/1969.1/5810.
Full textAbstract:
The response of geological materials at the scale of meters and the response
of buried targets of different shapes and sizes using controlled-source electromagnetic
induction (CSEM) is investigated. This dissertation focuses on three topics; i) frac-
tal properties on electric conductivity data from near-surface geology and processing
techniques for enhancing man-made target responses, ii) non-linear inversion of spa-
tiotemporal data using continuation method, and iii) classification of CSEM transient
and spatiotemporal data.
In the first topic, apparent conductivity profiles and maps were studied to de-
termine self-affine properties of the geological noise and the effects of man-made con-
ductive metal targets. 2-D Fourier transform and omnidirectional variograms showed
that variations in apparent conductivity exhibit self-affinity, corresponding to frac-
tional Brownian motion. Self-affinity no longer holds when targets are buried in the
near-surface, making feasible the use of spectral methods to determine their pres-
ence. The difference between the geology and target responses can be exploited using
wavelet decomposition. A series of experiments showed that wavelet filtering is able
to separate target responses from the geological background.
In the second topic, a continuation-based inversion method approach is adopted,
based on path-tracking in model space, to solve the non-linear least squares prob-
lem for unexploded ordnance (UXO) data. The model corresponds to a stretched-
exponential decay of eddy currents induced in a magnetic spheroid. The fast inversion of actual field multi-receiver CSEM responses of inert, buried ordnance is also shown.
Software based on the continuation method could be installed within a multi-receiver
CSEM sensor and used for near-real-time UXO decision.
In the third topic, unsupervised self-organizing maps (SOM) were adapted for
data clustering and classification. The use of self-organizing maps (SOM) for central-
loop CSEM transients shows potential capability to perform classification, discrimi-
nating background and non-dangerous items (clutter) data from, for instance, unex-
ploded ordnance. Implementation of a merge SOM algorithm showed that clustering
and classification of spatiotemporal CSEM data is possible. The ability to extract tar-
get signals from a background-contaminated pattern is desired to avoid dealing with
forward models containing subsurface response or to implement processing algorithm
to remove, to some degree, the effects of background response and the target-host
interactions.
22
Pike, Brian Henry. "Functionalism, qualia and spectrum inversion." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293880.
Full text
23
Peiponen, K. E. (Kai-Erik). "Optical spectra analysis of turbid liquids." Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514291685.
Full textAbstract:
Abstract
This thesis is devoted to methods of analyzing optical spectra obtained from turbid liquids, i.e., liquids that are optically very thick and/or scatter light. Data for spectral analysis were obtained with a new, multifunction spectrophotometer developed for industrial liquid samples. One characteristic of the spectrophotometer is that spectral analysis methods can be implemented into the software. Here, the emphasis was on data inversion methods, particularly the Kramers-Kronig analysis and the maximum entropy method, which can be used to gain information on the wavelength-dependent complex refractive index of liquid samples. Relating to such characteristics as density and colour, the complex refractive index also helps to identify the species that form a liquid. The methods were applied to study the internal reflection of light from the prism-liquid interface of the probe and to analyze surface plasmon resonance spectra. This study provided new methods of investigating the optical properties of relatively difficult objects, like offset inks, and of assessing adhesion forces between ink and the substrate system. Another important part of the thesis was the exploration of spectral analysis methods to obtain optical properties of nanoparticles in a liquid matrix. Bounds for the optical properties of multi-component structures in a liquid were considered with the aid of Wiener bounds.
24
Mahieux, Arnaud. "Inversion des spectres infrarouges enregistrés par l'instrument SOIR à bord de la sonde Venus Express." Doctoral thesis, Universite Libre de Bruxelles, 2011. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209957.
Full textAbstract:
Vénus, deuxième planète du système solaire, souvent appelée sœur de la Terre, car présentant des caractéristiques de taille et de masse similaires, est fort différente de notre planète. En effet, son atmosphère est beaucoup plus dense et dynamiquement active que celle de la Terre. Dans ce travail, nous nous concentrerons sur la région s'étendant de 70 km à 180~km d'altitude :la mésosphère et la basse thermosphère.SOIR, acronyme de Solar Occultation in the InfraRed, est un instrument russo-franco-belge embarqué à bord de la mission Venus Express de l'Agence Spatiale Européenne. Il utilise un réseau à échelle comme élément diffractant. La plage de nombre d'onde mesurable par SOIR s'étend de 2200 cm-1 à 4400 cm-1, ou 4.3 µm à 2.2 µm en longueur d'onde. Les ordres de diffraction utiles varient de 101 à 194. Un filtre acousto-optique - AOTF - est utilisé comme passe-bande pour sélectionner les ordres de diffraction. La résolution de l'instrument varie de 0.13 à 0.24 cm-1.
Du fait d'un temps de développement raccourci, presque toutes les calibrations de l'instrument ont dû être réalisées en vol. Elles comprennent les calibrations relatives au réseau à échelle (angle exact de Blaze et fonction de Blaze), au détecteur (non-uniformité pixel à pixel, courbe de sensibilité spectrale, relation entre les pixels et les nombres d'onde, résolution de l'instrument, intervalle d'échantillonnage spectral, rapport signal sur bruit, background thermique) et à l'AOTF (relation entre la radio-fréquence d'excitation de l'AOTF et les nombres d'onde, fonction de transfert de l'AOTF). L'approche et la réalisation de ces différentes calibrations sont présentées dans le présent travail. Les caractéristiques de l'instrument y sont également décrites.
Un algorithme d'inversion spectrale a été développé pour le cas spécifique de SOIR. Tenant compte du mode de mesure, l'occultation solaire, la méthode de la pelure d'oignons a été implémentée dans un algorithme dit de l'Estimation Optimale. Cette méthode permet d'inverser l'ensemble des mesures spectrales en une fois, et également d'en tirer d'autres informations, comme l'amélioration de certaines caractéristiques instrumentales. Les paramètres qui sont ajustés au sein de l'algorithme sont la densité de la ou des espèces absorbant dans la région spectrale concernée, la température, les paramètres de la ligne de base, qui permettent de déterminer les caractéristiques des aérosols, le déplacement Doppler des raies qui trouve principalement son origine dans la vitesse de déplacement du satellite, et l'amélioration de certaines calibrations. Une étude de sensibilité des différents paramètres de l'algorithme est également présentée, ainsi qu'une évaluation des erreurs instrumentales systématiques.
Dans l'ensemble des spectres enregistrés durant les 4 premières années de la mission, des profils verticaux de CO2, CO, H2O, HDO, SO2, H2SO4, HCl et HF ont été obtenus. Des valeurs limites de densité de OCS, H2CO, O3 et CH4 ont également été calculées.
Les résultats concernant le dioxyde de carbone sont développés dans le texte. Des profils verticaux de CO2 s'étendant de 70 km à 180 km d'altitude sont analysés en profondeur. Ils sont comparés aux profils dits hydrostatiques, et des hypothèses quant à la dynamique agissant au niveau des deux terminateurs de Vénus sont formulées.
/
Venus, second planet of the solar system, is often seen as the sister planet of the Earth. In terms of size and mass, they are indeed very similar, but the Venus atmosphere is much thicker and active. The altitude region extending from 70 km to 180~km is studied in this thesis, namely the mesosphere and the lower thermosphere.
SOIR, which stands for Solar Occultation in the InfraRed, is a Russian / French / Belgian instrument flying on board of the Venus Express (VEX) spacecraft of the European Space Agency. The diffracting device of SOIR is an echelle grating. The wavenumber region studied ranges from 2200 cm-1 to 4400 cm-1, or 4.3 µm to 2.2 µm in wavelength. The diffraction orders used with SOIR vary from 101 to 194. To select the required echelle grating diffraction order, an Acousto-Optical Tunable Filter - AOTF - is located after the entrance slit of the instrument. The instrument resolution varies from 0.13 to 0.24 cm-1.
SOIR was developed in a very short time. Thus, virtually all the calibrations had to be made in-flight. These concern the echelle grating (exact Blaze angle computation, Blaze function), the detector (pixel-to-pixel non-uniformity, spectral sensitivity curve, pixel-to-wavenumber relationship, instrument resolution, spectral sampling interval, signal-to-noise ratio, thermal background) and the AOTF (wavenumber to AOTF frequency relation, AOTF transfer function). The procedure for and the computation of these calibrations are described in this work, as well as the instrument characteristics.
A spectral inversion algorithm was developed specifically for the SOIR measurement technique: the solar occultation. The onion peeling method is implemented using the Optimal Estimation Method. It allows the inversion of the spectral data in one go, and also the enhancement of some instrumental characteristics. The algorithm variables are the densities of the species absorbing in the diffraction order, the temperature of the atmosphere under study, the spectral background parameters, that allow the determination of the Venus aerosols characteristics, the Doppler shift (mainly linked to the shift induced by the satellite displacement), and the improvement of some instrumental calibrations. A sensitivity study on the algorithm parameters is also presented, and the instrumental systematic errors are investigated.
Vertical profiles of CO2, CO, H2O, HDO, SO2, H2SO4, HCl and HF are derived from the spectra measured during the first 4 mission years. Upper limits on OCS, H2CO, O3 and CH4 have also been calculated.
We focus on the carbon dioxide results in the present study. A selection of vertical profiles extending from 70 km to 180 km are analyzed in details. They are compared to the hydrostatic profiles, and propositions concerning the terminators' dynamics are formulated.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
25
吳子傑 and Tsz-kit Victor Ng. "Inversion of low energy electron diffraction IV spectra of reconstructed structure of SiC (0001)." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31225007.
Full text
26
Ng, Tsz-kit Victor. "Inversion of low energy electron diffraction IV spectra of reconstructed structure of SiC (0001)." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B23234283.
Full text
27
Nagayama, Taisuke. "A new inversion method for the spectroscopic analysis of image data." abstract and full text PDF (free order & download UNR users only), 2006. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1433297.
Full text
28
Wilson, Adam. "Theory and methods of frequency-dependent AVO Inversion." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/4740.
Full textAbstract:
Amplitude-versus-offset, AVO, approximations allow the estimation of various properties from pre-stack seismic gathers. Recently it has been suggested that fluid mobility is a controlling factor in pore pressure equalisation and can result in anomalous velocity dispersion in the seismic bandwidth. However, current approximations all assume an elastic subsurface and are unable to account for velocity dispersion. I have applied existing methodologies to a real dataset to qualitatively detect and interpret spectral amplitude anomalies. Three areas had AVO and spectral signature consistent with frequency-dependent AVO theory. The results suggest that it is feasible to measure such effects on real data in the presence of random noise. It would imply that the relaxation parameter, tau, is larger in the field than has been measured in water-saturated real and synthetic sandstones in the laboratory. I extended a two-term AVO approximation by accounting for velocity dispersion and showed how the resultant reflection coefficient becomes frequency-dependent. I then used this to measure P- and S-wave reflectivity dispersion using spectrally-balanced amplitudes. The inversion was able to quantify the affect of the P-wave velocity dispersion as an instantaneous effect on the reflection. NMO stretch was an issue at the far offsets and I limited myself to the near offsets and effectively measured only the P-wave reflectivity dispersion. I showed how the P-wave reflectivity dispersion signs depend on the AVO classification of the reflection whilst the magnitude depends on the crack density of my model. I showed how the effect of noise and thin-bed tuning can enter uncertainties into the interpretation of spectral anomalies. Whilst it is possible to detect frequency-dependent AVO signatures on pre-stack gathers, the interpretation remains non-unique. I have quantitatively measured a new physical property, reflectivity dispersion, from pre-stack seismic data. I have presented a method of detecting and measuring velocity dispersion in pre-stack gathers but there remain ambiguities in the interpretation of such results. The approach incorporates spectrally decomposed data in an extended AVO inversion scheme. Future work should investigate the application of the methodology to a real seismic dataset.
29
Furtado, Neto Alexandre [UNESP]. "O potêncial de poço duplo e a molécula de amônia." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/91817.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:25:29Z (GMT). No. of bitstreams: 0
Previous issue date: 2011-12-12Bitstream added on 2014-06-13T20:33:08Z : No. of bitstreams: 1
furtadoneto_a_me_guara.pdf: 575510 bytes, checksum: 6a1a49e71ce6fbc8113435f66d99a240 (MD5)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O foco deste trabalho é o espectro de inversão da molécula de amônia, resultado do fenômeno do tunelamento quântico. Para isso, usamos um modelo simpli cado, uni- dimensional, suscetível a uma análise teórica rigorosa usando a mecânica quântica não- relativística. Dentre as diversas funções hamiltonianas já estudadas para este modelo, zemos uma rápida apreciação dos trabalhos de Cohen, Dennison-Uhlenbeck, Manning, Merzbacher e Rosen-Morse. Para um estudo mais profundo, usamos o potencial do poço duplo nito que, posteriormente, descobrimos já fora analisado por Peacock-López. Re- zemos a análise deste potencial usando um caminho diferente do realizado por aquele autor. Analisamos os casos limites para este potencial e notamos que realmente, nesses regimes, ele tende para um poço nito único ou dois poços nitos separados. Então, de- senvolvemos um software grá co centrado no pacote MINUIT, desenvolvido pelo CERN, para analisar e ajustar os parâmetros aos dados experimentais da amônia e, ao nal, comparamos os resultados obtidos com aqueles encontrados na literatura. No ajuste dos parâmetros à amônia, houve uma melhoria acentuada quando passamos de uma fórmula mais simples da massa reduzida para outra mais so sticada. No caso especí co do po- tencial de Peacock-López, a comparação revela que os nossos resultados, de uma maneira geral, são mais precisos. Nossa análise se soma àquelas que contêm uma discussão quan- titativa do potencial de poço duplo. Como parte integrante deste trabalho, uma versão unidimensional simétrica do potencial de Morse foi exatamente resolvida em termos de funções de Kummer e um par de equações transcendentes para as autoenergias. A tentativa de ajustar este resultado à molécula de amônia, porém, mostrou que os padrões de poço duplo deste potencial...
The focus of this work is the inversion spectrum of the ammonia molecule, a result of the phenomenon of quantum tunneling. For this, we use a simpli ed, one-dimensional model, amenable to a rigorous theoretical analysis using the non-relativistic quantum me- chanics. Among the various Hamiltonian functions previously studied for this model, we made a quick appraisal of the work of Cohen, Dennison-Uhlenbeck, Manning, Merzbacher and Rosen-Morse. For a deeper study, we used the nite double-well potential which, as we later discovered, had been considered by Peacock-López. We redid the analysis of this potential using a di¤erent path made by that author. We analyze the limiting cases for this potential and actually noticed that in these schemes, it tends to one nite well or two separate nite wells. So, we developed a graphical software centered on the MINUIT pack- age, developed by CERN, to analyze and adjust the parameters to the experimental data of ammonia and at the end, we compared the results with those found in the literature. In setting the parameters of ammonia, there was a marked improvement when we move from a simpler formula for the reduced mass to a more sophisticated one. In the speci c case of the potential of Peacock-López, the comparison shows that our results, in general, are more accurate and precise. Our analysis adds to those that contain a quantitative discussion of the double-well potential. As part of this work, a symmetric one-dimensional version of the Morse potential is exactly solved in terms of the Kummer functions and a pair of transcendental equations for the eigenenergies. Attempting to adjust this result to the ammonia molecule, however, showed that the double-well patterns of this potential well are irreconcilable with the energy spectrum of ammonia: Close pairs separated by long intervals
30
Lachérade, Sophie. "Caractérisation des propriétés optiques des matériaux urbains à partir d'images de télédétection à très hautes résolutions spatiale et spectrale." Toulouse, ENSAE, 2006. http://www.theses.fr/2006ESAE0008.
Full textAbstract:
Le signal reçu par un système optique de télédétection observant des milieux urbains est particulièrement complexe, en raison des particularités de ces derniers : occultations, ombres, éclairements réfléchis par les façades ou encore effets directionnels des matériaux urbains. Ces phénomènes rendent difficile la détermination automatique des matériaux directement à partir des luminances mesurées en entrée du capteur. L’objectif de cette thèse est de développer une méthode de transfert radiatif inverse, ICARE, permettant de déterminer la réflectance spectrale des matériaux urbains à partir d'images aéroportées très hautes résolutions spatiale et spectrale dans le domaine réflectif (0,4 µm ‒ 2,5 µm) en prenant simultanément en compte le relief en trois dimensions de la scène, sa forte hétérogénéité spatiale ainsi que les effets atmosphériques mis en jeu. La première partie de cette étude a été consacrée à une étude phénoménologique du signal sur un profil de rue typique de façon à analyser en détail les différents contributeurs radiatifs d’une telle scène. Cette étude nous a permis de mettre à jour les difficultés de la modélisation inverse notamment dans les zones d’ombre où les effets d'environnement sont prépondérants. Dans un second temps, des solutions physiques sont proposées pour modéliser chacun des termes intervenant dans l'équation de transfert radiatif et une approche itérative est mise en place pour résoudre le problème inverse. Dans un troisième temps, l'étude aborde la validation numérique et expérimentale du modèle. La validation numérique a été effectuée sur une image simulée par le code de transfert radiatif direct Amartis sur différents types de reliefs urbains, afin de vérifier la robustesse du modèle. La validation expérimentale a été effectuée avec succès à partir des données et images acquises pendant la campagne Capitoul qui s'est déroulée à Toulouse en avril 2004.
31
Liu, Qinya Stock J. M. "Spectral-element simulations of 3-D seismic wave propagation and applications to source and structural inversions /." Diss., Pasadena, Calif. : Caltech, 2006. http://resolver.caltech.edu/CaltechETD:etd-05262006-172954.
Full text
32
Rinkel, Jean-Marc. "Inverses et propriétés spectrales des matrices de Toeplitz à symbole singulier." Paris 11, 2001. http://www.theses.fr/2001PA112187.
Full text
33
Fiorucci, Irene <1980>. "Development of the optimal estimation method for inversion of stratospheric emission spectra and validation of HNO3 profiles." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2933/1/fiorucci_irene_tesi.pdf.
Full textAbstract:
This doctoral thesis focuses on ground-based measurements of stratospheric nitric acid (HNO3)concentrations obtained by means of the Ground-Based Millimeter-wave Spectrometer (GBMS). Pressure broadened HNO3 emission spectra are analyzed using a new inversion algorithm developed as part of this thesis work and the retrieved vertical profiles are extensively compared to satellite-based data. This comparison effort I carried out has a key role in establishing a long-term (1991-2010), global data record of stratospheric HNO3, with an expected impact on studies concerning ozone decline and recovery. The first part of this work is focused on the development of an ad hoc version of the Optimal Estimation Method (Rodgers, 2000) in order to retrieve HNO3 spectra observed by means of GBMS. I also performed a comparison between HNO3 vertical profiles retrieved with the OEM and those obtained with the old iterative Matrix Inversion method. Results show no significant differences in retrieved profiles and error estimates, with the OEM providing however additional information needed to better characterize the retrievals. A final section of this first part of the work is dedicated to a brief review on the application of the OEM to
other trace gases observed by GBMS, namely O3 and N2O. The second part of this study deals with the validation of HNO3 profiles obtained with the new inversion method. The first step has been the validation of GBMS measurements of tropospheric opacity, which is a necessary tool in the
calibration of any GBMS spectra. This was achieved by means of comparisons among correlative measurements of water vapor column content (or Precipitable Water Vapor, PWV) since, in the spectral region observed by GBMS, the tropospheric opacity is almost entirely due to water vapor
absorption. In particular, I compared GBMS PWV measurements collected during the primary field campaign of the ECOWAR project (Bhawar et al., 2008) with simultaneous PWV observations obtained with Vaisala RS92k radiosondes, a Raman lidar, and an IR Fourier transform spectrometer. I found that GBMS PWV measurements are in good agreement with the other three data sets exhibiting a mean difference between observations of ~9%. After this initial validation,
GBMS HNO3 retrievals have been compared to two sets of satellite data produced by the two NASA/JPL Microwave Limb Sounder (MLS) experiments (aboard the Upper Atmosphere Research Satellite (UARS) from 1991 to 1999, and on the Earth Observing System (EOS) Aura mission from 2004 to date). This part of my thesis is inserted in GOZCARDS (Global Ozone Chemistry and Related Trace gas Data Records for the Stratosphere), a multi-year project, aimed at developing a long-term data record of stratospheric constituents relevant to the issues of ozone decline and
expected recovery. This data record will be based mainly on satellite-derived measurements but ground-based observations will be pivotal for assessing offsets between satellite data sets. Since the GBMS has been operated for more than 15 years, its nitric acid data record offers a unique opportunity for cross-calibrating HNO3 measurements from the two MLS experiments. I compare GBMS HNO3 measurements obtained from the Italian Alpine station of Testa Grigia (45.9° N, 7.7° E, elev. 3500 m), during the period February 2004 - March 2007, and from Thule Air Base,
Greenland (76.5°N 68.8°W), during polar winter 2008/09, and Aura MLS observations. A similar intercomparison is made between UARS MLS HNO3 measurements with those carried out from the GBMS at South Pole, Antarctica (90°S), during the most part of 1993 and 1995. I assess systematic
differences between GBMS and both UARS and Aura HNO3 data sets at seven potential temperature levels. Results show that, except for measurements carried out at Thule, ground based and satellite data sets are consistent within the errors, at all potential temperature levels.
34
Fiorucci, Irene <1980>. "Development of the optimal estimation method for inversion of stratospheric emission spectra and validation of HNO3 profiles." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2010. http://amsdottorato.unibo.it/2933/.
Full textAbstract:
This doctoral thesis focuses on ground-based measurements of stratospheric nitric acid (HNO3)concentrations obtained by means of the Ground-Based Millimeter-wave Spectrometer (GBMS). Pressure broadened HNO3 emission spectra are analyzed using a new inversion algorithm developed as part of this thesis work and the retrieved vertical profiles are extensively compared to satellite-based data. This comparison effort I carried out has a key role in establishing a long-term (1991-2010), global data record of stratospheric HNO3, with an expected impact on studies concerning ozone decline and recovery. The first part of this work is focused on the development of an ad hoc version of the Optimal Estimation Method (Rodgers, 2000) in order to retrieve HNO3 spectra observed by means of GBMS. I also performed a comparison between HNO3 vertical profiles retrieved with the OEM and those obtained with the old iterative Matrix Inversion method. Results show no significant differences in retrieved profiles and error estimates, with the OEM providing however additional information needed to better characterize the retrievals. A final section of this first part of the work is dedicated to a brief review on the application of the OEM to
other trace gases observed by GBMS, namely O3 and N2O. The second part of this study deals with the validation of HNO3 profiles obtained with the new inversion method. The first step has been the validation of GBMS measurements of tropospheric opacity, which is a necessary tool in the
calibration of any GBMS spectra. This was achieved by means of comparisons among correlative measurements of water vapor column content (or Precipitable Water Vapor, PWV) since, in the spectral region observed by GBMS, the tropospheric opacity is almost entirely due to water vapor
absorption. In particular, I compared GBMS PWV measurements collected during the primary field campaign of the ECOWAR project (Bhawar et al., 2008) with simultaneous PWV observations obtained with Vaisala RS92k radiosondes, a Raman lidar, and an IR Fourier transform spectrometer. I found that GBMS PWV measurements are in good agreement with the other three data sets exhibiting a mean difference between observations of ~9%. After this initial validation,
GBMS HNO3 retrievals have been compared to two sets of satellite data produced by the two NASA/JPL Microwave Limb Sounder (MLS) experiments (aboard the Upper Atmosphere Research Satellite (UARS) from 1991 to 1999, and on the Earth Observing System (EOS) Aura mission from 2004 to date). This part of my thesis is inserted in GOZCARDS (Global Ozone Chemistry and Related Trace gas Data Records for the Stratosphere), a multi-year project, aimed at developing a long-term data record of stratospheric constituents relevant to the issues of ozone decline and
expected recovery. This data record will be based mainly on satellite-derived measurements but ground-based observations will be pivotal for assessing offsets between satellite data sets. Since the GBMS has been operated for more than 15 years, its nitric acid data record offers a unique opportunity for cross-calibrating HNO3 measurements from the two MLS experiments. I compare GBMS HNO3 measurements obtained from the Italian Alpine station of Testa Grigia (45.9° N, 7.7° E, elev. 3500 m), during the period February 2004 - March 2007, and from Thule Air Base,
Greenland (76.5°N 68.8°W), during polar winter 2008/09, and Aura MLS observations. A similar intercomparison is made between UARS MLS HNO3 measurements with those carried out from the GBMS at South Pole, Antarctica (90°S), during the most part of 1993 and 1995. I assess systematic
differences between GBMS and both UARS and Aura HNO3 data sets at seven potential temperature levels. Results show that, except for measurements carried out at Thule, ground based and satellite data sets are consistent within the errors, at all potential temperature levels.
35
Ullah, Irfan. "Caracterização da subsuperfície rasa através da curva da razão espectral H/V e da inversão conjunta das curvas de dispersão e elipticidade." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/14/14132/tde-04062018-101840/.
Full textAbstract:
A destruição causada por um terremoto depende de muitos fatores, como características e profundidade da fonte, magnitude, distância epicentral e da configuração geológica da área. A destruição causada devido à configuração geológica da área é denominada como efeito local. A modelagem do efeito local implica na determinação do tempo e nível de vibração e do efeito de amplificação do deslocamento. As propriedades elásticas dos materiais geológicos (velocidade das ondas de compressão e de cisalhamento, densidade, espessura da camada de solo, etc.) podem ser obtidas por diversos métodos geofísicos. O conhecimento dessas propriedades elásticas ajuda a melhor projetar as infraestruturas e reduzir as chances de danos. Este procedimento é denominado de microzoneamento. Os parâmetros mais importantes para realizar o microzoneamento são as espessuras dos sedimentos que recobrem o embasamento e o perfil das velocidades das ondas S (cisalhamento). Esses dois parâmetros são adequadamente caracterizados pelo uso de várias técnicas geofísicas como perfilagens em furos de sondagem, reflexão e refração sísmica. Esses métodos geofísicos trazem algumas restrições como a necessidade da execução de um furo, emprego de fontes sísmicas artificiais que muitas vezes são dispendiosas e por vezes de uso restrito em áreas urbanas, além de muitas vezes estarem limitadas a investigações de apenas algumas dezenas de metros. Os métodos que substituíram esses métodos geofísicos convencionais nas últimas décadas são a análise do ruído sísmico produzido por fontes naturais e culturais. Este ruído sísmico ambiental pode ser registrado com menor custo e esforço e com boa cobertura lateral. Várias técnicas que se utilizam do ruído sísmico podem ser empregadas, no entanto, aquela que obteve maior atenção nos últimos anos é a técnica da razão do espectro horizontal sobre o espectro vertical da onda de superfície (H/V). A curva da razão espectral H/V é uma ferramenta rápida, fácil e de baixo custo para a caracterização da subsuperfície rasa. Existem vários estudos realizados sobre o tema que tentaram cobrir todos os aspectos e problemas associados ao método. Aqui neste estudo são aprofundados alguns aspectos ainda não avaliados em detalhe. Diferentes procedimentos para a modelagem e as associações entre os fenômenos físicos envolvidos e as características da curva H/V são discutidos e os resultados numéricos desses estudos são comparados com informações extraídas de perfis de sondagens de um dos locais estudados. O pico e a forma da curva H / V são modelados para encontrar o desvio na frequência de pico a partir da frequência de ressonância da onda de cisalhamento considerando diferentes campos de onda em torno do pico, assim como sua relação com a forma dominante da curva. A frequência de pico das curvas H/V é utilizada para estimar a relação entre a frequência a espessura através de análise de regressão. O estudo mostra que a curva de dispersão obtida a partir de um ensaio MASW pode ser usada para estimar a velocidade da onda S a um metro de profundidade e sua tendência de aumento com a profundidade. Esses valores podem ser usados para estimar a relação frequência-espessura para uma área. Esses resultados são comparados com a relação frequência-espessura derivada experimentalmente para a mesma área. A sensibilidade da forma da curva H/V à estrutura de velocidade do meio é analisada através de duas técnicas de modelagem (elipticidade da onda Rayleigh e campo difuso baseado na curva H/V). Diferentes partes da curva H/V são invertidas visando avaliar qual a parte da curva H/V contém as informações mais importantes sobre a estrutura subterrânea. As lições aprendidas dessas análises são aplicadas a três dados experimentais de locais distintos. As ondas Love podem contaminar o resultado da curva H/V. Duas técnicas diferentes para remover o efeito das ondas amorosas são discutidas. Em seguida, são discutidos os resultados da inversão conjunta das curvas de dispersão e da curva H/V após remoção do efeito da onda Love, ou seja, a curva de elipticidade. Alguns aspectos novos da técnica H/V são discutidos no final.The destruction caused by an earthquake at a site depends on many factors like source characteristics such as magnitude, epicentral distance from the site, depth of the source, and on the geological setting of the area. The destruction caused due to the geological setting of an area is termed as site effect. To model the site effect of an area is to determine the shaking level longevity and its displacement amplification. The elastic properties (shear and compressional wave velocities, density, thickness of soil layer, etc.) of the site are required to find out by employing various geophysical procedures. The knowledge of these elastic properties help in better designing the infrastructure, which reduces the chances of destruction caused by a local geological setting due to an earthquake occurrence. This procedure is widely termed as microzonation. The most important parameters for the microzonation are the thickness of soft sediments over the seismic bedrock and its shear wave velocity profile. These two parameters are properly characterized by employing various geophysical techniques like borehole measurement, seismic reflection and seismic refraction. The conventional geophysical methods bring some hindrance to the picture such as, the drilling of a borehole and artificial seismic sources deployment for the reflection and refraction survey, which are both expensive and time consuming, difficult or even in some case impossible to implement in urbanized environment, the investigation is depth limited to few tens of meter. The methods which replaced this conventional geophysical method from the last decades or so is the analysis of Earth vibration caused by the seismic noise which is produced by both natural and cultural sources. This ambient seismic noise can be recorded with less cost and effort with good lateral coverage. Various seismic noise techniques are employed for this job; however, the one which got the most attention in recent years is the horizontal over vertical spectral ratio (H/V) technique. The H/V spectral ratio curve is a fast easy and cheap tool for the near-subsurface characterization. There are various study performed on the topic which has tried to cover almost all the aspects and problems associated with the method. Here in this study, we try to detail the aspects of this technique, which are not been evaluated fully. The different modelling procedures presented to model and physically link the H/V curve with some physical phenomenon will be discussed and its numerical result with the experimental H/V curve will be compared for a borehole test site. The peak and the shape of the H/V curve will be modelled to find its peak frequency deviation from the shear wave resonance frequency by considering different wave-field around the peak. Similarly, the shape dominancy of the H/V curve linkage will be find out. The peak frequency of the H/V curve is used to estimate the thickness-frequency relation by regression analysis. Here we will show that the dispersion curve obtained from multi-channel analysis of surface waves (MASW) can be used to estimate the velocity at one meter and the shear wave velocity increase trend with depth. These values can be used to estimate the thickness frequency relation for an area and its result will be compared with the experimentally derived thickness-frequency relationship for the same area. The sensitivity of the H/V curve shape to the subsurface velocity structure will find out for two main modelling techniques (Rayleigh wave ellipticity and diffused field based H/V curve). The different parts of the H/V curve are inverted (back modelled) to find out the part of H/V curve which is carrying the most important information about the subsurface structure. The lesson learned from all this analysis will be applied to experimental data of three different sites. The Love waves might contaminate the result of the H/V curve. Two different techniques to remove their effects will be discussed. Then, the joint inversion result of the dispersion and this Love effect removed H/V for more precisely ellipticity curve is discussed. Some new aspects of the H/V curve technique are also discussed at the end.
36
Bezzeghoud, Mourad. "Inversion et analyse spectrale des ondes p : potentialite des donnees numeriques large bande : application a des seismes mediterraneens et chiliens." Paris 7, 1987. http://www.theses.fr/1987PA077249.
Full textAbstract:
Les donnees sismiques digitales sont utilisees pour une modelisation realiste des sources sismiques, en particulier avec les methodes d'inversion. Les principaux seismes etudies sont issus de reseaux sismologiques numeriques recents, ce qui permet de deconvoluer la reponse de l'appareil; a l'aide d'un filtre passe haut ou pourra elargir la bande de frequence a partir d'enregistrement courte periode. La dynamique du processus de rupture associe aux seismes est etudiee par la forme de l'onde sismique lb. Deux techniques sont utilisees (inversion iterative et deconvolution temporelle) afin d'extraire la fonction source et le moment sismique. L'etude du comportement de la structure spectrale haute frequence montre que le couplage entre l'amplitude des phases de profondeur, la duree et la profondeur de la source. On estimera la densite dun moment sismique moyen et la duree de la source a partir des ondes p
37
Bezzeghoud, Mourad. "Inversion et analyse spectrale des ondes P, potentialité des données numériques large bande application à des séismes méditerranéens et chiliens /." Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37602992t.
Full text
38
Noersomadi. "Characteristics of tropical tropopause and stratospheric gravity waves analyzed using high resolution temperature profiles from GNSS radio occultation." Kyoto University, 2019. http://hdl.handle.net/2433/242617.
Full text
39
Bureau, Jérôme. "Les raies moléculaires de l'atmosphère solaire dans l'infrarouge : spectroscopie, transfert radiatif et modélisation physico-chimique du CO et de ses isotopomères." Paris 6, 2009. http://www.theses.fr/2009PA066250.
Full textAbstract:
Pour déterminer l'abondance O/H et les rapports isotopiques de C et de O dans le soleil, nous avons développé un modèle chimique photosphérique, un modèle de transfert radiatif qui détermine le spectre émergent et un programme d'inversion qui restitue les abondances de CO et de ses isotopomères à partir de spectres solaires infrarouge. Dans le modèle thermochimique, nous avons sélectionné les espèces à prendre en compte pour modéliser l'abondance du CO et le fond continu dans l'infrarouge. Nous avons construit un modèle à trois composantes à partir de champs hydrodynamiques 3D. Nous avons modélisé les coefficients d'élargissement collisionnels CO-H jusqu'à J=150 et à haute température à partir des coefficients CO-He et CO-H2 à plus basse température pour de plus faibles J. L'inversion des largeurs équivalentes des raies de CO nous a permis d'obtenir un rapport O/H=575+/-30, des rapports isotopiques 12C/13C=85+/- 10, 16O/18O=485+/-75 et 16O/17O=1700. +/-700.
40
Dixneuf, Sophie. "Spectroscopie de diffusion de la lumière dans les mélanges de gaz atomiques." Angers, 2006. https://tel.archives-ouvertes.fr/tel-01773264.
Full textAbstract:
Cette thèse est une contribution à l'étude des polarisabilités induites dans les gaz rares, en représentation à la fois spatiale et fréquentielle. Pour la première fois, des spectres Raman collisionnels de mélanges gazeux ont été enregistrés, calculés quantiquement puis interprétés. Plus précisément, les ailes spectrales Stokes anisotrope et isotrope du systèmes Ne-Ar ont été explorées jusqu'à 300 cm-1 , à température ambiante, l'aile anisotrope du Kr-Xe jusqu'à 135 cm-1. Pour le Ne-Ar, les meilleurs accords entre théorie et expérience ont été obtenus pour des modèles de polarisabilité induite issus de calculs ab initio récents, du type "coupled-custer" ou perturbatif à symétrie adaptée associés à des bases orbitalaires étendues. Aucun modèle n'a cependant parfaitement reproduit l'aile spectrale anisotrope lointaine du Ne-Ar. Pour des systèmes plus lourds comme le Kr-Xe, une théorie Møller-Plesset d'ordre deux a offert une réponse spectrale très satisfaisante. Une nouvelle approche d'inversion des spectres a par ailleurs été développée comme base méthodologique afin d'accéder à des modèles de polarisabilité conformes à l'observation. L'inversion a été appliquée à l'argon et au néon purs, pour lesquels les larges intervalles Raman sondés par l'équipe assurent la convergence des moments spectraux utilisés comme entrée. Les modèles ainsi optimisés corrigent les défauts des résultats ab initio aux faibles séparations, essentiellement traduites par les ailes spectrales lointaines. Enfin, un modèle d'anisotropie (Ne)2 et Ne-Ar, dépourvu de singularité à l'origine, est ici proposé comme possible représentation physique de l'anisotropie des gaz raresThis thesis is a contribution to the study of the interaction-induced polarizabilities by rare gases, in both the coordinate and the frequency representation. For the first time, collision-induced Raman spectra by atomic gaseous mixtures were recorded, computed quantum mechanically, and interpreted. More specifically, anisotropic and isotropic Stokes spectral wings by room-temperature Ne-Ar were investigated up to 300 cm-1 , whereas the anisotropic wing of the Kr-Xe was explored up to 135 cm-1. For Ne-Ar, the best agreement between theory and experiment was found when modern ab initio interaction-induced polarizability input was used, i. E. Models obtained within coupled-custer or symmetry adapted perturbation theory associated to extended orbital basis sets. Nevertheless, none of those models was it able to satisfactorily reproduce the far anisotropic spectral wing of Ne-Ar. For heavier systems such as Ke-Xe, second order Møller-Plesset theory provided a very satisfactory spectral response. On the other hand, a new spectral inversion approach was developed as a device to access polarizability models consistent with experiment. The inversion was applied to pure argon and neon gases for which broad domains of detuning, probed by the group, ensured that the input spectral moments were properly converged. The optimized models were shown to correct the defects of the ab initio ones at short separations, essentially affecting the far wing of the spectra. Finally, a singurality-free anisotropy model for (Ne)2 and Ne-Ar was proposed as a simple but potential candidate to represent the physical anisotropy of atomic gases
41
Dufour, Gaëlle. "Spectroscopie moléculaire atmosphérique : mesures diode laser au laboratoire, inversion des spectres enregistrés sous ballon, modélisation photochimique et contribution à la validation satellitaire." Paris 6, 2004. http://www.theses.fr/2004PA066101.
Full text
42
Benna, Mehdi. "Génération et inversion de données de propagation d'ondes radio à travers un noyau cométaire (simulation de l'expérience CONSERT)." Toulouse 3, 2002. http://www.theses.fr/2002TOU30116.
Full text
43
Furtado, Neto Alexandre. "O potêncial de poço duplo e a molécula de amônia /." Guaratinguetá : [s.n.], 2012. http://hdl.handle.net/11449/91817.
Full textAbstract:
Orientador: Antonio Soares de CastroBanca: Denis Dalmazi
Banca: Manuel Bastos Malheiro de Oliveira
Resumo: O foco deste trabalho é o espectro de inversão da molécula de amônia, resultado do fenômeno do tunelamento quântico. Para isso, usamos um modelo simpli cado, uni- dimensional, suscetível a uma análise teórica rigorosa usando a mecânica quântica não- relativística. Dentre as diversas funções hamiltonianas já estudadas para este modelo, zemos uma rápida apreciação dos trabalhos de Cohen, Dennison-Uhlenbeck, Manning, Merzbacher e Rosen-Morse. Para um estudo mais profundo, usamos o potencial do poço duplo nito que, posteriormente, descobrimos já fora analisado por Peacock-López. Re- zemos a análise deste potencial usando um caminho diferente do realizado por aquele autor. Analisamos os casos limites para este potencial e notamos que realmente, nesses regimes, ele tende para um poço nito único ou dois poços nitos separados. Então, de- senvolvemos um software grá co centrado no pacote MINUIT, desenvolvido pelo CERN, para analisar e ajustar os parâmetros aos dados experimentais da amônia e, ao nal, comparamos os resultados obtidos com aqueles encontrados na literatura. No ajuste dos parâmetros à amônia, houve uma melhoria acentuada quando passamos de uma fórmula mais simples da massa reduzida para outra mais so sticada. No caso especí co do po- tencial de Peacock-López, a comparação revela que os nossos resultados, de uma maneira geral, são mais precisos. Nossa análise se soma àquelas que contêm uma discussão quan- titativa do potencial de poço duplo. Como parte integrante deste trabalho, uma versão unidimensional simétrica do potencial de Morse foi exatamente resolvida em termos de funções de Kummer e um par de equações transcendentes para as autoenergias. A tentativa de ajustar este resultado à molécula de amônia, porém, mostrou que os padrões de poço duplo deste potencial... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract:The focus of this work is the inversion spectrum of the ammonia molecule, a result of the phenomenon of quantum tunneling. For this, we use a simpli ed, one-dimensional model, amenable to a rigorous theoretical analysis using the non-relativistic quantum me- chanics. Among the various Hamiltonian functions previously studied for this model, we made a quick appraisal of the work of Cohen, Dennison-Uhlenbeck, Manning, Merzbacher and Rosen-Morse. For a deeper study, we used the nite double-well potential which, as we later discovered, had been considered by Peacock-López. We redid the analysis of this potential using a di¤erent path made by that author. We analyze the limiting cases for this potential and actually noticed that in these schemes, it tends to one nite well or two separate nite wells. So, we developed a graphical software centered on the MINUIT pack- age, developed by CERN, to analyze and adjust the parameters to the experimental data of ammonia and at the end, we compared the results with those found in the literature. In setting the parameters of ammonia, there was a marked improvement when we move from a simpler formula for the reduced mass to a more sophisticated one. In the speci c case of the potential of Peacock-López, the comparison shows that our results, in general, are more accurate and precise. Our analysis adds to those that contain a quantitative discussion of the double-well potential. As part of this work, a symmetric one-dimensional version of the Morse potential is exactly solved in terms of the Kummer functions and a pair of transcendental equations for the eigenenergies. Attempting to adjust this result to the ammonia molecule, however, showed that the double-well patterns of this potential well are irreconcilable with the energy spectrum of ammonia: Close pairs separated by long intervals
Mestre
44
Rakotomanga, Prisca. "Inversion de modèle et séparation de signaux de spectroscopie optique pour la caractérisation in vivo de tissus cutanés." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0329.
Full textAbstract:
La détection de tissus biologiques pré-cancéreux au cours d’un diagnostic clinique est rendue possible grâce au développement de méthodes spectroscopiques optiques, appelées également biopsie optique. Ces méthodes permettent de mettre en évidence les modifications du métabolisme et de la structure des tissus biologiques. Dans cette thèse, les mesures optiques sont réalisées sur les tissus cutanés à l’aide d’un instrument intégrant deux modalités : la réflectance diffuse résolue spatialement et l’autofluorescence. L’exploitation des spectres consiste à résoudre un problème inverse non-linéaire pour estimer les propriétés optiques du milieu sondé à l’aide d’un modèle d’interaction lumière-tissu. À partir de ces propriétés optiques, la caractérisation de l’état du tissu, sain ou anormal, est possible. La première contribution de la thèse est de proposer une méthode d'inversion qui intègre une simulation Monte Carlo rapide et une fonction coût gérant les deux modalités spectrales dans le but d’améliorer la précision de l’estimation des propriétés optiques, quelle que soit la géométrie de la sonde. La deuxième contribution de la thèse est d'étudier la cinétique des fluorophores présents dans les tissus par une approche de séparation de sources, qui ne nécessite pas le recours à une simulation Monte Carlo. Dans cette approche, une collection de spectres acquis au cours du temps est analysée conjointement, avec peu d'hypothèses a priori de la forme des signaux sources. La sensibilité de cette approche est validée par l’emploi d’agents de clarification optique qui augmentent la transparence des tissus en diminuant la diffusion et l’absorption des photons dans les tissus, et donnent ainsi accès à des informations plus précises en profondeurThe detection of pre-cancerous biological tissues during clinical diagnosis is made possible by the development of optical spectroscopic methods, also known as optical biopsy. These methods make it possible to identify changes in the metabolism and structure of biological tissues. In this thesis, optical measurements are performed on skin tissues using an optical device that integrates two modalities: spatially resolved diffuse reflectance and autofluorescence. Spectra exploitation involves solving a non-linear inverse problem to estimate the optical properties using a light-tissue interaction model. From these optical properties, it is possible to characterize the condition of the tissue, healthy or abnormal. The first contribution of the thesis is to propose an inversion method that integrates a fast Monte Carlo model and a cost function managing two spectral modalities in order to improve the accuracy of the estimation of optical properties, regardless of the geometry of the probe. The second contribution is to study the kinetics of fluorophores present in tissues by a source separation approach, which does not require the use of a Monte Carlo model. In this approach, a collection of spectra acquired over time is analyzed together, with few a priori assumptions about the shape of the source signals. The sensitivity of this approach is validated by the use of optical clearing that increase tissue transparency by decreasing photon diffusion and absorption in tissues, thus providing access to more accurate in-depth information
45
Muñoz, Ramirez Oscar Mauricio. "Contributions on spectral control for the asymmetrical full bridge multilevel inverter." Doctoral thesis, Universitat Rovira i Virgili, 2010. http://hdl.handle.net/10803/8476.
Full textAbstract:
Las topologías de circuitos inversores multinivel pueden trabajar a tensiones y potencias mayores que las alcanzadas por convertidores convencionales de dos niveles. Además, la conversión multinivel reduce la distorsión armónica de las variables de salida y en algunos casos, a pesar del aumento de elementos de conmutación, también reduce las pérdidas de conversión al incrementarse el número de niveles. La reducción de distorsión alcanzada por el número de niveles puede aprovecharse para reducir las pérdidas de conmutación disminuyendo la frecuencia de las señales portadoras. Para reducir aún más esta frecuencia sin degradar el espectro, nosotros controlamos las pendientes de las portadoras triangulares. Primero se han desarrollado dos modelos analíticos para predecir el espectro del voltage de salida, dependiendo de: el índice de modulación MA, la razón de distribución de voltaje K de las fuentes de alimentación , y las cuatro pendientes de las portadoras{r1, r2, r3, r4}. El primer modelo considera el Muestreo Natural y se basa en Series Dobles de Fourier (SDF) mientras que el segundo modelo, utiliza la Serie Sencilla de Fourier (SSF) introduciendo el concepto de Muestreo Pseudo-Natural, una aproximación digital de la modulación natural. Ambos modelos son programados en Matlab, verificados con Pspice y validados con un prototipo experimental que contiene un modulador digital implementado con DSP.
La concordancia entre las modulaciones natural y pseudo-natural, asi como entre sus respectivos modelos, es aprovechada por un algorítmo genético (AG) donde la THD es la función costo a reducir. Después de varios ensayos y de sintonizar el AG, se genera una matriz que contiene conjuntos de portadoras optimizadas dentro un rango específico de las variables {MA,K} y es probada con un segundo prototipo en lazo cerrado. Un lazo lento digital modifica las portadoras creadas por un dsPIC en modulaciones PWM; estas son demoduladas y sus amplitudes corregidas por un lazo de acción anticipada. Estas portadoras se comparan con una referencia sinusoidal que a su vez es modificada por variables de estado, generando finalmente la modulación multinivel en lazo cerrado. Los resultados finales demuestran la fiabilidad de la reducción de armónicos usando la programación de las pendientes de las portadoras.
Palabras claves: inversor multinivel, PWM, distorsión armónica, modelo espectral, pendiente de portadora, conjunto de portadoras, distribución de niveles, Serie Doble de Fourier, Serie Simple de Fourier, muestreo natural, muestreo regular, muestreo pseudo-natural , Algoritmos Genéticos.
Multilevel inverter (MI) topologies can work at higher voltage and higher power than conventional two-level converters. In addition, multilevel conversion reduces the output variables harmonic distortion and, sometimes, in spite of the devices-count increment, the conversion losses can also decrease by increasing the number of levels. The harmonic distortion reduction achieved by increasing the number of levels, can be used to further reducing the switching losses by decreasing the inverter carrier frequencies. To reduce even more the switching frequency without degrading output spectrum, we control the triangular carrier waveforms slopes.
First, to achieve this target, two analytical models have been created in order to predict the inverter output voltage spectrum, depending on diverse parameters: the amplitude modulation index MA, the voltage distribution K of the inverter input sources, and the four carrier slopes {r1, r2, r3, r4}. The first model considers Natural Sampling and is based on Double Fourier Series (DFS) whereas the second model based on Simple Fourier Series (SFS), introduces the concept of Pseudo-Natural Sampling, as a digital approximation of the natural modulation. Both models are programmed in Matlab, verified with Pspice simulations and validated with a first experimental prototype with a DSP digital modulator.
The good agreement between natural and pseudo-natural modulations, as well as their respective DFS and SFS models, is exploited by a Genetic Algorithm (GA) application where THD is the cost function to minimize. After testing and properly tuning the GA, a framework matrix containing the optimized carriers set for a specific range of variables {MA,K} is generated and then, tested with a second, closed-loop prototype. A slow digital loop modifies the carrier slopes created by dsPIC microcontroller as PWM modulations, whose amplitude, once demodulated, are affected by a feed-forward loop. These carriers, compared with a sinusoidal reference, state-feedback modified, generate finally the closed-loop multilevel modulation. The final results demonstrates the feasibility of harmonic reduction by means of carrier slopes programming.
Keywords: multilevel inverter, PWM, harmonic distortion, spectral modeling, carrier slope, carriers set, level distribution, Double Fourier Series, Simple Fourier Series, natural sampling, regular sampling, pseudo-natural sampling, Genetic Algorithms.
46
Matar, Christian. "Restitution des propriétés des nuages à partir des mesures multi-spectrales, multi-angulaires et polarisées du radiomètre aéroporté OSIRIS." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R041/document.
Full textAbstract:
La rétroaction des nuages demeure l’une des incertitudes majeures des modèles de prévision climatique, en particulier les interactions entre aérosols, nuages et rayonnement (IPCC - Boucher et al., 2013). Les nuages sont en effet difficiles à prendre en compte car ils présentent des variabilités spatiales et temporelles importantes. Les mesures de télédétection aéroportées avec une résolution de quelques dizaines de mètres sont très appropriées pour améliorer et affiner nos connaissances sur les propriétés des nuages et leurs variabilités à haute résolution spatiale. Dans ce contexte, nous exploitons les mesures multi-angulaires du nouveau radiomètre aéroporté OSIRIS (Observing System Including PolaRization in the Solar Infrared Spectrum), développé par le Laboratoire d'Optique Atmosphérique. Il est basé sur le concept POLDER et est un prototype du futur instrument spatial 3MI sur les plates-formes MetOp-SG de l’EUMETSAT-ESA à partir de 2022. En télédétection, les nuages sont généralement caractérisés par deux propriétés optiques: l'épaisseur optique des nuages (COT) et le rayon effectif des particules d'eau / de glace formant le nuage (Reff). Actuellement, la plupart des algorithmes de télédétection opérationnels utilisés pour extraire ces propriétés de nuage à partir de mesures passives sont basés sur la construction de tables pré-calculées (LUT) sous l'hypothèse d'une couche de nuage plan-parallèle. Cette méthode est très dépendante des conditions de simulations choisies pour la construction des LUT et rend difficile l'estimation des incertitudes qui en découlent. Au cours de cette thèse, nous utilisons le formalisme de la méthode d’estimation optimale (Rodgers, 2000) pour mettre au point une méthode d’inversion flexible permettant de restituer COT et Reff en utilisant les mesures multi-angulaires visibles et proche-infrarouges d’OSIRIS. Nous montrons que cela permet l'exploitation de l'ensemble des informations disponibles pour chaque pixel afin de s'affranchir des effets angulaires des radiances et d’inverser des propriétés plus cohérente avec l'ensemble des mesures. Nous avons, d’autre part, appliqué le cadre mathématique fourni par la méthode d’estimation optimale pour quantifier les incertitudes sur les paramètres restitués. Trois types d’erreurs ont été évaluées: (1) Les erreurs liées aux incertitudes de mesure, qui atteignent 10% pour les valeurs élevées de COT et de Reff. (2) Les erreurs de modèle liées à une estimation incorrecte des paramètres fixes du modèle (vent de surface de l'océan, altitude des nuages et variance effective de la distribution en taille des gouttelettes d'eau) qui restent inférieures à 0,5% quelles que soient les valeurs de COT et Reff restituées. (3) Les erreurs liées au modèle physique simplifié qui ne prend pas en compte les profils verticaux hétérogènes et utilise l'hypothèse du nuage plan-parallèle homogène et l'approximation du pixel indépendant. Ces deux dernières incertitudes s'avèrent être les plus importantesCloud feedbacks remain one of the major uncertainties of climate prediction models, particularly the interactions between aerosols, clouds and radiation (IPCC - Boucher et al., 2013). Clouds are indeed difficult to account for because they have significant spatial and temporal variability depending on a lot of meteorological variables and aerosol concentration. Airborne remote sensing measurements with tens of meters resolution are very suitable for improving and refining our knowledge of cloud properties and their high spatial variability. In this context, we exploit the multi-angular measurements of the new airborne radiometer OSIRIS (Observing System Including PolaRization in the Solar Infrared Spectrum), developed by the Laboratoire d'Optique Atmosphérique. It is based on the POLDER concept as a prototype of the future 3MI space instrument planned to be launched on the EUMETSAT-ESA MetOp-SG platform in 2022.In remote sensing applications, clouds are generally characterized by two optical properties: the Cloud Optical Thickness (COT) and the effective radius of the water/ice particles forming the cloud (Reff). Currently, most operational remote sensing algorithms used to extract these cloud properties from passive measurements are based on the construction of pre-computed lookup tables (LUT) under the assumption of a homogeneous plane-parallel cloud layer. The LUT method is very dependent on the simulation conditions chosen for their constructions and it is difficult to estimate the resulting uncertainties. In this thesis, we use the formalism of the optimal estimation method (Rodgers, 2000) to develop a flexible inversion method to retrieve COT and Reff using the visible and near-infrared multi-angular measurements of OSIRIS. We show that this method allows the exploitation of all available information for each pixel to overcome the angular effects of radiances and retrieve cloud properties more consistently using all measurements. We also applied the mathematical framework provided by the optimal estimation method to quantify the uncertainties on the retrieved parameters. Three types of errors were evaluated: (1) Errors related to measurement uncertainties, which reach 10% for high values of COT and Reff. (2) Model errors related to an incorrect estimation of the fixed parameters of the model (ocean surface wind, cloud altitude and effective variance of water droplet size distribution) that remain below 0.5% regardless of the values of retrieved COT and Reff. (3) Errors related to the simplified physical model that uses the classical homogeneous plan-parallel cloud assumption and the independent pixel approximation and hence does not take into account the heterogeneous vertical profiles and the 3D radiative transfer effects. These last two uncertainties turn out to be the most important
47
Bacour, Cédric. "Contribution à la détermination des paramètres biophysiques des couverts végétaux par inversion de modèles de réflectance : analyses de sensibilité comparatives et configurations optimales." Paris 7, 2001. http://www.theses.fr/2001PA077164.
Full text
48
Bazin, Cyrille. "L'interface photosphère solaire/chromosphère et couronne : apport des éclipses et des images EUV." Phd thesis, Aix-Marseille Université, 2013. http://tel.archives-ouvertes.fr/tel-00921889.
Full textAbstract:
Les régions d'interface du Soleil de la photosphère à la chromosphère et au delà de la basse couronne ont été étudiées depuis longtemps à partir des spectres éclairs obtenus durant les éclipses totales de Soleil. Les éclipses sont les plus adaptées à ce type d'observation, car l'occultation a lieu en dehors de l'atmosphère terrestre et sont exemptes de lumière parasite provenant du " disque occulteur " (c'est-à-dire la Lune), une propriété de grande importance lorsqu'on observe très près du limbe. La résolution temporelle des premiers spectres éclairs ne permettait pas de résoudre les basses couches de la région de transition et étaient dégradés par des effets non-linéaires qui affectaient les films photographiques. Les images Extrême-UV des régions du limbe obtenues récemment dans l'espace sont analysées avec des modèles hydrostatiques à une dimension, comme les modèles VAL, mais cette méthode ne tient pas compte du phénomène d'émergence du champ magnétique, associé au réseau chromosphérique qui est responsable de: i) les spicules et le milieu interspiculaire, ii) les jets coronaux et macrospicules, et iii) l'ovalisation de la chromosphère. Les composants de la région d'interface sont dynamiques et différents types d'ondes et de reconnexions magnétiques sont supposées agir. Un saut de température de 0.01 à 1 MK est observé autour de 2 Mm d'altitude plus loin, et produit plus loin le flot du vent solaire permanent. Le processus de chauffage responsable du saut de température et la source du vent solaire ne sont pas encore compris. Dans cette thèse, nous traitons ces problèmes à partir de spectres éclairs récents réalisés avec les technologies actuelles de détecteurs CCD rapides, images d'éclipse en lumière blanche et des images EUV obtenues avec des instruments de missions spatiales. Nous illustrons les mécanismes des émissions des raies à faible potentiel de première ionisation (FIP) présents dans les basses couches de l'atmosphère solaire. Nous identifions plus précisément les raies associées aux éléments low FIP à la fois à l'intérieur et en dehors des protubérances. Nous caractérisons en détail les enveloppes d'hélium dans les interfaces. Méthodes: 1) technique des spectres éclairs sans fente avec imagerie CCD rapide (éclipses 2006, 2008, 2009, 2010 et 2012). 2) Analyses des spectres du continu entre la myriade de raies d'émission au delà du limbe solaire et construction de courbes de lumière de quelques raies d'émission low FIP et high FIP. 3) Evaluations d'inversions d'intégrales d'Abel pour déduire des échelles de hauteurs et discussion de variations de température et de densité. 4) Analyse d'images EUV obtenues aux mêmes instants depuis AIA/SDO, SWAP, SOT/Hinode des missions spatiales, images en lumière blanche pour discuter des constituants de la couronne. Principaux résultats: i) Le bord du Soleil et la bifurcation de température : le vrai continu à partir du spectre observé aux altitudes de 400 à 600 km au dessus du limbe dans le contexte de de mesures de diamètre solaire et processus d'émission. ii) raies d'émission visibles dans les régions d'interface comprenant les raies He I et surtout la raie He II Pα visible à partir de 800 km au dessus du limbe, produite par photo-ionisation, montrant des enveloppes autour du Soleil et permettant le sondage de l'interface protubérance-couronne. iii) La contribution de structures de petite taille comme les spicules et macrospicules commençant à 1 Mm au dessus du limbe et montrant que les modèles hydrostatiques stratifiés 1D ne sont pas adaptés pour les couches supérieures. Nous montrons que les raies low FIP sont sur-abondantes dans l'interface photosphère-chromosphère, que la couronne solaire est alimentée en permanence par ces éléments. Le titane est un élément abondant dans le milieu interspiculaire, et une analogie sur les gradients de température entre les interfaces photosphère-chromosphère et protubérance-couronne peut être établie.
49
Buchard, Virginie. "Caractérisation du contenu atmosphérique en ozone et en aérosols au moyen de mesures spectrales dans l'UV : validation de l'instrument spatial OMI / AURA." Thesis, Lille 1, 2009. http://www.theses.fr/2009LIL10025/document.
Full textAbstract:
Depuis la découverte d'une diminution de la quantité d'ozone stratosphérique au milieu des années 1980, une surveillance de la couche d'ozone et de l'éclairement UV s'est mise en place à l'aide d'instruments au sol et spatiaux. Les mesures de rayonnement UV permettent d'une part de surveiller l'intensité de ce rayonnement arrivant au sol, et d'autre part de caractériser certains composés atmosphériques comme la quantité d'ozone et les aérosols. L'essentiel de ce travail concerne l'analyse et l'utilisation des mesures d'éclairement UV spectral effectuées sur deux sites de mesures au sol, à Villeneuve d'Ascq (VdA) et à Briançon. Nous avons poursuivi la restitution de la colonne totale d'ozone, ce qui nous a permis de disposer d'une série temporelle de plusieurs années. Nous avons également déterminé deux paramètres aérosols, l'épaisseur optique (AOT) et l'albédo de diffusion simple; les comparaisons avec les mesures photométriques du réseau AERONET/PHOTONS se sont révélées très satisfaisantes. Les données obtenues à partir de septembre 2004 nous ont permis de participer dans le cadre d'un projet de l'ESA, à la validation de l'instrument spatial OMI, destiné à effectuer une surveillance globale de l'ozone et de l'UV. Ce travail a permis d'établir que les produits ozone d'OMI sont bien restitués, alors que les éclairements UV spectral et érythémateux sont à utiliser avec précaution. A VdA, les comparaisons entre les AOT-OMI et les AOT restituées au sol sont peu satisfaisantes. De meilleurs accords ont été obtenus sur les sites photométriques impliqués dans la campagne AMMA en Afrique de l'Ouest, cette région étant sous l'influence de contenus élevés en aérosols absorbantsSince the discovery of the stratospheric ozone reduction in the middle of the 1980's, a monitoring of the ozone layer and UV irradiance was organized, using ground-based and satellite instruments. Measurements of UV radiation allow both to monitor the intensity of this radiation reaching the surface and to retrieve atmospheric compounds as content of ozone and aerosol characteristics. The main part of this work concerns the analysis and the use of UV spectral measurements performed at Villeneuve d'Ascq (VdA) and at Briançon. We continued the restitution of the total column of ozone that provides a multi-year record of this quantity. We determined two aerosol parameters, the aerosol optical thickness (AOT) and the single scattering albedo; comparisons with photometric measurements from the AERONET/PHOTONS network appeared very good. The data obtained from September 2004 enabled us to be involved within the framework of an ESA project in the validation of the OMI/AURA instrument, which is dedicated to a global monitoring of ozone and UV. We have established that the OMI ozone products are very well retrieved, whereas spectral and erythemal dose UV have to be used with caution. At VdA, the comparisons between OMI-AOT and those derived fram graund-based measurements are not satisfying. Better results were obtained at six sites located in WesternAfrica region during the AMMA campaign, this region being influenced by high loads of absorbing aerasols
50
Luo, Qiu. "L'étude et l'application des méthodes inverses aux problèmes vibro-acoustiques." Compiègne, 1997. http://www.theses.fr/1997COMP1075.
Full textAbstract:
Des méthodes existantes pour l'identification et la caractérisation des sources vibro-acoustiques y compris les techniques de cohérence et des spectres principaux, sont confrontées par des difficultés d'application lorsque les sources multiples sont fortement corrélées ou difficilement disponibles. L'objectif initial des recherches présentées dans ce mémoire était donc de développer des méthodes qui pourraient apporter une meilleure caractérisation des sources multiples et de les appliquer à des différents problèmes industriels et de recherches. Après un rappel des éléments mathématiques associés aux méthodes qui sont présentées dans ce mémoire, la décomposition en valeurs singulières et la pseudo-inverse des matrices, la méthode inverse MMS (Méthode de Matrice Spectrale) est systématiquement étudiée à l'aide des simulations numériques et des tests expérimentaux. Les résultats nous permettent d'évaluer qualitativement et quantitativement la précision de la méthode inverse MMS pour l'identification et la caractérisation des sources, indépendantes ou cohérentes. Plusieurs applications basées sur la méthode inverse MMS sont développées dans les domaines vibratoires et acoustiques. Chacune de ces applications est développée soit directement d'un projet industriel soit d'une extension de l'étude initiale couvrant un des sujets suivants : - Mesure d'intensimétrie vibratoire, en vue de l'amélioration de sa précision et le conditionnement des composants individuels lors des multiples sources, - Caractérisation des forces de coupe des machines-outils en usinage, en vue de l'établissement d'un modèle paramétrique des vibrations de la machine-outil, - Identification du bruit émis par les brûleurs de chaudière, en vue de sa modélisation et sa réduction, - Prévision des rayonnements acoustiques d'un panneau à partir des mesures vibratoires, en vue d'évaluer la sensibilité acoustique vis-à-vis de la vibration mécanique de différents matériaux. Dans l'annexe une nouvelle méthode de l'identification des propriétés dynamiques des joints mécaniques est présentée. Cette méthode est basée sur l'identification des ondes de flexion associée à la technique de pseudo-inverse de matrice.