Η διαμόρφωση με πολύπλεξη συχνότητας ορθογωνίων φερουσών (Orthogonal Frequency Division Multiplexing - OFDM) έχει εδραιωθεί ως μία από τις επικρατέστερες μεθόδους διαμόρφωσης για την υψηλού ρυθμού μετάδοση πληροφορίας μέσω ασύρματων μέσων. Σε ένα σύστημα OFDM, ένα από τα βασικότερα και υπολογιστικά πολυπλοκότερα τμήματα είναι ο υπολογισμούς του Ταχύ Μετασχηματισμού Fourier. Αντικείμενο της εργασίας αυτής είναι η μελέτη της χρήσης εναλλακτικής αριθμητικής για την υλοποίηση κυκλωμάτων FFT. Τυπικά, τέτοιου είδους κυκλώματα υλοποιούνται χρησιμοποιώντας κάποια γραμμική αναπαράσταση σταθερής υποδιαστολής. Στη βιβλιογραφία έχουν προταθεί υλοποιήσεις του FFT με χρήση του Λογαριθμικού Συστήματος Αρίθμησης (Logarithmic Numbering System – LNS) και έχουν αναφερθεί κέρδη για συγκεκριμένους παράγοντες όπως το σφάλμα κβαντισμού, η επιφάνεια ολοκλήρωσης και η κατανάλωση ισχύος. Η αποδοτικότητα αυτών των λύσεων ερευνάται για τη συγκεκριμένη περίπτωση της εφαρμογής του FFT σε OFDM modems. Εστιάζοντας στην περίπτωση του FFT 64 σημείων για OFDM modem για ασύρματα δίκτυα 802.11a, μία από τις πλέον επιτυχημένες αρχιτεκτονικές που έχουν προταθεί για την υλοποίηση του, στηρίζεται στη λογική του FFT γραμμής – στήλης και παρουσιάζει έναν τρόπο πραγματοποίησης του υπολογισμού χωρίς κανένα ψηφιακό πολλαπλασιαστή. Με το βασικό πλεονέκτημα της λογαριθμικής αναπαράστασης να είναι η απλοποίηση των κυκλωμάτων πολλαπλασιασμού (με ταυτόχρονη όμως αύξηση του κόστους για την πραγματοποίηση προσθέσεων), δείχνεται ότι τελικά η υλοποίηση ενός FFT αμιγώς σε LNS δεν είναι προτιμητέα. Αν και η αρχιτεκτονική του FFT γραμμής – στήλης μπορεί να προσφέρει υψηλή απόδοση με χαμηλό κόστος υλοποίησης, παρουσιάζει μια σειρά από αδυναμίες, που σχετίζονται κυρίως με τη χρήση ειδικών κυκλωμάτων για την εκτέλεση των πολλαπλασιασμών με τις σταθερές που εμφανίζονται στον FFT (twiddle factors). Για την αντιμετώπιση αυτών των περιορισμών προτείνεται η εισαγωγή του LNS σε κάποια τμήματα του κυκλώματος του FFT, οδηγώντας έτσι στη δημιουργία ενός συστήματος μικτής αναπαράστασης. Σε τέτοιου είδους υβριδικά συστήματα τίθενται δύο βασικά ζητήματα. Το πρώτο αφορά τον ορισμό της ισοδυναμίας μεταξύ των διαφορετικών αναπαραστάσεων και το δεύτερο τον αποδοτικό τρόπο υλοποίησης των κυκλωμάτων μετατροπής από το ένα αριθμητικό σύστημα στο άλλο. Τυπικά, τα κριτήρια ισοδυναμίας που επιλέγονται είναι αυστηρά μαθηματικά ορισμένα, όπως για παράδειγμα ο Λόγος Σήματος προς Θόρυβο (Signal-to-Noise Ratio - SNR) ή το Μέσο Σχετικό Σφάλμα Αναπαράστασης (Average Relative Representation Error – ARRE). Στη συγκεκριμένη εργασία ακολουθείται μια λιγότερο δεσμευτική προσέγγιση, ορίζοντας την ισοδυναμία δύο αναπαραστάσεων με βάση την τελική απόδοση του συστήματος OFDM όσον αφορά το ρυθμό λαθών στο δέκτη (Bit Error Rate - BER). Με βάση αυτή τη λογική, αποδεικνύεται ότι μπορούν να χρησιμοποιηθούν αναπαραστάσεις πολύ μικρού μεγέθους λέξης και οι προσεγγίσεις που χρειάζεται να γίνουν κατά τις μετατροπές μεταξύ των δύο συστημάτων δεν είναι ανάγκη να είναι ιδιαίτερα ακριβείς. Έτσι, τα σχετικά κυκλώματα μπορούν να υλοποιηθούν αποδοτικά και με μικρό κόστος. Η υλοποίηση δύο συστημάτων για τον FFT 64 σημείων, ένα βασισμένο αποκλειστικά σε γραμμική αναπαράσταση σταθερής υποδιαστολής και ένα υβριδικό που χρησιμοποιεί γραμμική και λογαριθμική αναπαράσταση, δείχνει ότι χωρίς διαφορές όσον αφορά το BER και την καθυστέρηση (delay), η υβριδική προσέγγιση απαιτεί μικρότερη επιφάνεια ολοκλήρωσης και παρουσιάζει σημαντικά χαμηλότερη κατανάλωση ισχύος. / Orthogonal Frequency Division Multiplexing (OFDM) has been established as one of the most prevalent methods for high data rate transmission through wireless channels. In an OFDM communication system, one of the fundamental and most computationally intensive parts is the computation of the Fast Fourier Transform (FFT). The subject of this thesis is to investigate the use of alternative arithmetic representation systems for the implementation of FFT circuits. Typically, these circuits are implemented using linear fixed-point representations. In literature, implementations of the FFT using the Logarithmic Numbering System (LNS) have been proposed and significant gains in quantization errors, chip area and power consumption have been reported. The effectiveness of these proposals in the case of the FFT for OFDM systems is investigated. Focusing on the case of the 64-point FFT for an OFDM modem for an 802.11a wireless network, one of the most efficient architectures proposed is based on the concept of row-column FFT and presents a way of implementing the computation without using any digital (non-fixed input) multiplier. The most important feature of the LNS representation is the fact that multiplication operations turn to mere additions, thus there are significant implementation gains. On the downside though, addition in LNS is very expensive. Combining the aforementioned, it is shown that the implementation of the whole FFT computation in LNS is not a preferable solution. Although the row-column FFT architecture may offer high performance and low implementation cost, it presents a number of deficiencies mainly due to the fact that special purpose circuits are used to perform the multiplications with the complex constants (twiddle factors) that appear in the computation. In order to alleviate these deficiencies, it is proposed to use the LNS representation in some parts of the FFT circuit, thus forming a hybrid-representation system. In hybrid-representation systems two major issues are raised. The first one is how to define equivalence between the arithmetic representation systems used and the second one is related to the cost of the circuits required to perform the conversions between the numbers of the different arithmetic systems. Typically, the equivalence criterion used is mathematically defined and metrics like the Signal-to-Noise Ratio (SNR) or Average Relative Representation Error (ARRE) are commonly used. In this report, a less restrictive metric is used: two arithmetic representations are defined to be equal if the Bit Error Rate (BER) performance of the overall OFDM system is equal. Using this approach, it is shown that short word-length representations may be used and the conversions between the linear and logarithmic systems need not be very accurate. This results in great simplification of the conversion process and the respected circuits can be implemented with low cost. For comparison, two 64-point FFT systems have been implemented, one using a linear fixed-point 2’s complement representation and one using both linear and LNS representation. Without any differences in BER performance and circuit delay, the hybrid-representation system requires less chip area and consumes significantly lower power.

Le point de départ de cette thèse est la conjecture de Bieberbach : sa démonstration par De Branges utilise deux ingrédients, à savoir la théorie de Loewner des domaines plans croissants et une inégalité de Milin qui concerne les coefficients logarithmiques. Nous commençons par étudier les coefficients logarithmiques du whole-plane SLE en utilisant une méthode combinatoire, assistée par ordinateur. Nous retrouvons les résultats en utilisant une équation aux dérivées partielles analogue à celle obtenue par Beliaev et Smirnov. Nous généralisons ces résultats en définissant le spectre généralisé du whole-plane SLE, que nous calculons par la même méthode, à savoir en dérivant, par le calcul d’Itô, une EDP parabolique satisfaite par les quantités que nous moyennons. Cette famille à deux paramètres d’EDP admet une riche structure algébrique que nous étudions en détail. La dernière partie de la thèse concerne l’opérateur de Grunsky et ses généralisations. Plus expérimentale, nous y mettons à jour, grâce à un logiciel de calcul formel, une structure assez complexe dont nous avons commencé l’exploration. / The starting point of this thesis is Bieberbach’s conjecture: its proof, given by De Branges, uses two ingredients, namely Loewner’s theory of increasing plane domains and an inequality from Milin about the logarithmic coefficients. We start with a study of the logarithmic coefficients of the whole-plane SLE by using a combinatorial method, assisted by computer. We find the results by using a partial differential equation similar to that obtained by Beliaev and Smirnov. We generalize these results by defining the generalized spectrum of the whole-plane SLE, that we calculate by the same method, namely by deriving, thanks to Itô calculus, a parabolic PDE satisfied by the quantities of which we take the average. This two-parameter family of PDEs admits a rich algebraic structure that we study in detail. The last part of this thesis is about the Grunsky operator and its generalizations. In this part that is more experimental we update, thanks to a computer algebra system, a rather complex structure of which we began the exploration.

Soit f une instance du whole-plane $\SLE_\kappa$ : on sait que pour certaines valeurs de κ, p les moments dérivés $\mathbb{E}(\vert f'(z) \vert^p)$ peuvent être écrits sous une forme fermée, étude qui a permis de mettre au jour une nouvelle phase du spectre des moyennes intégrales. Le but de cette thèse est une étude des moments généralisés $\frac{\vert f'(z) \vert^p}{\vert f(z) \vert^q}$ : cette étude permet de confirmer la structure algébrique riche du whole-plane SLE. On montre que les formes fermées des moments mixtes $\mathbb{E}\big(\frac{\vert f'(z) \vert^p}{\vert f(z) \vert^q}\big)$ apparaissent sur une famille dénombrable de paraboles du plan (p, q), en étendant les équations de Beliaev-Smirnov à ce cas. Nous introduisons également le spectre généralisé β(p, q; κ), correspondant au comportement asymptotiques des moyennes intégrales mixtes. Le spectre généralisé moyen du whole-plane SLE prend quatre formes possibles, séparés par cinq séparatrices dans $\R^2$. Nous proposons également une approche semblable pour la dérivée Schwarziene S(f)(z) de l’application de SLE. Les calculs sur les équations de Beliaev-Smirnov d’une certaine générale forme de moment mène à une formulation explicite de $\mathbb{E}(S(f)(z))$ . Nous étudions finalement la variance asymptotique de McMullen et démontrons une relation entre la croissance infinitésimale du spectre de la moyenne intégrale et la variance asymptotique pour SLE₂. / Let f an instance of the whole-plane $\SLE_\kappa$ conformal map from the unit disk D to the slit plane: We know that for certain values of κ, p the derivative moments $\mathbb{E}(\vert f'(z) \vert^p)$ can be written in a closed form, study that has updated a new phase of the integral means spectrum. The goal of this thesis is a study on generalized moments $\frac{\vert f'(z) \vert^p}{\vert f(z) \vert^q}$ : ΒββThis study permit confirm the rich algebraic structure of the whole-plane version of SLE. It will be showed that closed forms of the mixed moments E mixtes $\mathbb{E}\big(\frac{\vert f'(z) \vert^p}{\vert f(z) \vert^q}\big)$ can be obtained on a countable family of parabolas in the moment plane (p, q), by extending the so-called Beliaev–Smirnov equation to this case. We also introduce the generalized integral means spectrum, β(p, q; κ), corresponding to the singular behavior of the mixed moments. The average generalized spectrum of whole-plane SLE takes four possible forms, separated by five phase transition lines in $\R^2$. We also propose a similar approach for the Schwarzian derivative S(f)(z) of SLE maps. Computations on the Beliaev–Smirnov equation of a certain general form of moment lead to an explicit formula of $\mathbb{E}(S(f)(z))$ . We finally study the McMullen asymptotic variance and prove a relation between the infinitesimal growth of the integral mean spectrum and the asymptotic variance in an expectation sense for SLE₂.

L'étude concerne les couches limites turbulentes dans le cas d'écoulements à surface libre sur fond rugueux homogène. Afin de réaliser cette étude, deux dispositifs de mesure PIV par stéréoscopie (PIV 2D-3C) ont été mis en place avec comme double objectif de fournir les lignes directrices au design d'un système stéréoscopique PIV in situ et d'étudier l'influence de la faible submersion des éléments rugueux sur la structure universelle de la couche limite sur fond rugueux, i.e. pour des submersions h/D comprises entre 0,33 et 0,66 (avec h la hauteur des rugosités et D la hauteur d'eau). Pour le premier objectif, le dispositif de mesure a permis un accès optique facilité par un point de vue incliné des caméras à la zone proche des rugosités dans des conditions naturelles d'écoulement (turbidité et éclairement naturels). Les mesures de vitesse ont été faites dans un canal hydraulique de petite dimension (12 m x 0,5 m x 0,25 m) rempli d'hémisphères positionnées en quinconce. Une étude paramétrique de l'influence de l'inclinaison des caméras ainsi que de la turbidité de l'eau sur la qualité des mesures de vitesse a été entreprise suivie par une nouvelle méthodologie basée sur l'analyse de l'intensité lumineuse dans le système. Il a été montré que l'écoulement est correctement résolu jusqu'à une turbidité d'environ 25 NTU avec un angle d'inclinaison par rapport au plan vertical de mesure de 25°. Pour le second objectif, les investigations expérimentales ont été réalisées dans une veine hydraulique de plus grande dimension (26 m x 1,10 m x 0,50 m), dont le fond rugueux est constitué par des cubes en PVC de 2 cm de côté comme dans l'étude de Florens et al. (2013). Les résultats mettent en évidence que l'étendue de la sous-couche rugueuse augmente avec la submersion pour finalement occuper toute la colonne d'eau dans le cas de la plus faible submersion (h/D=0,66). Malgré cela, une loi logarithmique est tout de même observée, et ce, quelle que soit la submersion étudiée. / This work deals with turbulent boundary layers in open-channel flows over rough homogeneous beds. The objectives of this work are, first, to provide some guidance for the design of an efficient in situ stereoscopic PIV measurements system (SPIV), and, second, to assess the effect of the relative submergence on the universal turbulent boundary layer structure for very high relative submergence ratios, i:e: 0.33 < h/D <0.66 (where h is the roughness height and D the water depth). For the first objective, a stereoscopic PIV configuration was set-up with steeply inclined camera viewpoints in order to improve the image quality and the optical access into the bed canopy under naturally occurring turbid conditions. Velocity measurements were undertaken in a 12 m x 0.5 m x 0.25 m open-channel flume filled with staggered hemispheres as surrogates for bed river peebles. A parametric study was then carried out to both analyze how the turbidity and camera angle impact the quality of PIV measurements. An innovative light intensity-based methodology was developed and applied to perform data analysis. The latter shows good PIV results up to 25 NTU with an optimal camera angle with respect to the vertical PIV measurements plane of 25. The SPIV measurements for the second objective were performed in a 26-m-long, 1.10-m-wide and 0.50-m-deep steep open channel filled with 2-cm cubes as in Florens et al. (2013). The results show that the extent of the roughness sublayer increases with the relative submergence to fill the entire water column for the highest relative submergence investigated. Despite this, the logarithmic law is still observed even for the highest relative submergence studied (h/D=0.66).

Este trabalho propõe estudos de casos em sistemas de energia elétrica por meio do Fluxo de Potência Ótimo (FPO) e da Análise de Sensibilidade em diferentes cenários de operação. Para isso, foram obtidos dados teóricos, a partir de levantamento bibliográfico, que explicitaram os conceitos de otimização aplicados ao sistema estático de energia elétrica. A pesquisa fundamentou-se metodologicamente no método primal-dual barreira logarítmica e nas condições necessárias de primeira-ordem de Karush-Kuhn-Tucker (KKT) para o problema de FPO, e no teorema proposto por Fiacco (1976) para a Análise de Sensibilidade. Os sistemas de equações resultantes das condições de estacionaridade, da função Lagrangiana, foram resolvidos pelo método de Newton. Na implementação computacional foram usadas técnicas de esparsidade. Estudos de casos foram realizados nos sistemas 3, IEEE 14, 30, 118, 300 barras e no equivalente CESP 440 kV com 53 barras, em que foi verificada a eficiência das técnicas apresentadas. / This work proposes a study of cases in power systems by Optimal Power Flow (OPF) and Sensitivity Analysis in different operation scenarios. For this purpose, theoretical data were obtained, starting from a bibliographical review, which enlightened the optimization concepts applied to the static system of electrical energy. The research was methodologically based on the primal-dual logarithmic barrier method and in the first-order necessary Karush-Kuhn-Tucker conditions to the OPF problem and in the theorem proposed by Fiacco (1976) to the Sensitivity Analysis. The equation sets generated by the first-order necessary conditions of the Lagrangian function, were solved by Newton\'s method. In the computational implementation, sparsity techniques were used. Studies of cases were carried out in the 3, IEEE 14, 30, 118, 300 buses and in the equivalent CESP 440 kV 53 bus, where the efficiency of the presented techniques was verified.

Submitted by Rafael Ramos de Souza null (rr.souza@live.com) on 2016-08-09T15:45:13Z No. of bitstreams: 1 VERSÃO_ENTREGUE.pdf: 1452852 bytes, checksum: ae6aa21d2282113ac3abaade8414218e (MD5) / Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-08-11T12:16:39Z (GMT) No. of bitstreams: 1 souza_rr_me_bauru.pdf: 1452852 bytes, checksum: ae6aa21d2282113ac3abaade8414218e (MD5) / Made available in DSpace on 2016-08-11T12:16:39Z (GMT). No. of bitstreams: 1 souza_rr_me_bauru.pdf: 1452852 bytes, checksum: ae6aa21d2282113ac3abaade8414218e (MD5) Previous issue date: 2016-06-10 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O problema de Fluxo de Potência Ótimo tem por objetivo a otimização de um critério de desempenho elétrico sujeito ao atendimento das demandas de potência ativa e reativa em cada barra e de restrições técnico-operacionais dos sistemas de geração e transmissão. É um problema de otimização, não-linear, não-convexo e de grande porte. Neste trabalho é explorado o problema de Fluxo de Potência Ótimo Reativo com o objetivo de minimizar as perdas de potência ativa na transmissão e para resolvê-lo é proposto um método primal-dual de pontos interiores/exteriores barreira logarítmica modificada com estratégias de teste quadrático e determinação de direções de busca combinadas. O teste quadrático é proposto como alternativa ao procedimento de Cholesky na verificação da positividade da matriz hessiana do problema, que, se definida positiva, garante direções de descida para o método. As novas direções de busca são determinadas através de combinações das direções dos procedimentos previsor e corretor, determinadas através da análise das condições de complementaridade das variáveis primais e duais do problema. O método proposto foi implementado em Matlab e aplicado aos sistemas elétricos 9 e 39 barras e aos sistemas IEEE 14, 30, 57 e 118 barras. O desempenho do método com as estratégias propostas é avaliado em termos do número de iterações e do tempo computacional. Os resultados são promissores e permitem a aplicação do presente método, com as estratégias propostas, para resolver o problema de Fluxo de Potência Ótimo Reativo com maior dimensão do que os sistemas testados. / The reactive optimal power flow problem is concerned with the optimization of a specific criterion associated with the transmission system while enforcing the power balance in each transmission bus, as well as operational and physical constraints associated with generation and transmission systems. It is a nonlinear, non-convex and large optimization problem. In this work we consider the active losses minimization in the transmission system as a criterion for the optimal power flow problem. The solution of the problem is investigated by proposing a modified log-barrier primal-dual interior/exterior point method with a quadratic test strategy and new search direction procedures. The quadratic test is proposed as an alternative strategy to the Cholesky procedure for calculating the positivity of the Hessian matrix of the problem.The new search directions investigated in the paper are determined by combining the search directions calculated in the predictor and corrector steps, respectively, and also by using information associated with the complementarity conditions. The method proposed is implemented in Matlab and applied to solving the reactive optimal power flow problem for 9 and 39-bus systems, as well as for the IEEE 14, 30, 57 and 118-bus test systems. The performance of the method with the proposed strategies for search directions is evaluated in terms of the number of iterations and computational times. The results are promising and allow the application of the present method with the proposed search strategies for solving problems of larger dimensions.

Este trabalho descreve uma abordagem do método primal-dual barreira logarítmica (MPDBL) associado ao método de Newton modificado para a resolução do problema de fluxo barreira logarítmica e nas condições de primeira ordem de Karush-Kuhn-Tucker (KKT). O sistema de equações resultantes das condições de estacionaridade, da função Lagrangiana, foi resolvido pelo método de Newton modificado. Na implementação computacional foram usadas as técnicas de esparsidade. Os resultados numéricos dos testes realizados em 5 sistemas (3, 14, 30, 57 e 118 barras) evidenciam o potencial desta metodologia na solução do problema de FPO. / This work describes an approach on primal-dual logarithmic barrier for solving the optimal power flow problem (OPF). The investigation was based on the logarithmic barrier function and Karush-Kuhn-Tucker (KKT) first-order necessary conditions. The equation system, obtained from the stationary conditions of the Lagrangian function, was solved using the Newton\'s modified method. The implementation was performed using sparsity techniques. The numerical results, carried out in five systems (3, 14,30, 57 and 118 bus), demonstrate the reliability of this approach in the solution OPF problem.

Este trabalho descreve uma abordagem do método primal-dual barreira logarítmica (MPDBL) associado ao método de Newton modificado para a resolução do problema de fluxo de potência para sistemas de distribuição radial. Também foi realizado um estudo comparativo com duas técnicas clássicas de solução do problema de fluxo potência para redes de distribuição radial. São os métodos: Backward/Forward Sweep e o método proposto por M. Baran e F. Wu, que é baseado na técnica de Newton-Raphson. Este método utiliza uma matriz Jacobiana modificada que atende a característica radial dos sistemas de distribuição. Nos testes comparativos serão considerados todos os parâmetros do sistema. Os algoritmos de solução serão analisados em suas propriedades de convergência e será realizado um teste de robustez. Os resultados dos testes realizados em 4 sistemas (4, 10, 34 e 70 barras) e o teste comparativo entre os métodos evidenciam a melhor metodologia na solução do problema de fluxo de potência para sistemas radiais / This work describes an approach on primal-dual logarithmic barrier method (PDLBM) associate to the method of Newton modified for the resolution of the problem of power flow for radial distribution systems. Also a comparative study with two classic techniques of solution of the flow problem was carried through power for nets of radial distribution. They are the methods: Backward/Forward Sweep and the method considered for M. Baran and F. Wu, that is based on the technique of Newton-Raphson. This method uses modified Jacobiana matrix that takes care of the radial characteristic of the distribution systems. In the comparative tests all will be considered the parameters of the system. The solution algorithms will be analyzed in its properties of convergence and will be carried through a robustness test. The results of the tests carried through in 4 systems (4, 10, 34 and 70 bus) and the comparative test between the methods evidence the best methodology in the solution of the problem of power flow for radial systems

Este trabalho apresenta uma abordagem do método da função barreira logarítmica (MFBL) para a resolução do problema de fluxo de potência ótimo (FPO). A pesquisa fundamenta-se metodologicamente na função barreira logarítmica e nas condições de primeira ordem de Karush-Kuhn-Tucker (KKT). Para a solução do sistema de equações resultantes das condições de estacionaridade, da função Lagrangiana, utiliza-se o método de Newton. Na implementação computacional utiliza-se técnicas de esparsidade. Através dos resultados numéricos dos testes realizados em 5 sistemas (3, 8, 14, 30 e 118 barras) evidencia-se o potencial desta metodologia na solução do problema de FPO. / This work describes an approach on logarithmic barrier function method to solving the optimal power flow (OPF) problem. Search was based on the logarithmic barrier function and first order conditions of Karush-Kuhn-Tucker (KKT). To solve the equation system, obtained from the stationary conditions of the Lagrangian function, is used the Newton method. Implementation is performed using sparsity techniques. The numerical results, carried out in five systems (3, 8, 14, 30 and 118 bus), demonstrate the reliability of this approach in the solution OPF problem.

Ce travail de thèse comporte l'étude des invariants logarithmiques le long des $l^{d}$-extensions et se compose de trois parties étroitement reliées. La première partie est un compendium sur les divers approches à l'arithmétique algorithmique, c'est à dire l'étude générale des invariants logarithmiques. En particulier on y présente quatre définitions équivalentes du groupe de classes logarithmiques et on y démontre leur équivalence. On donne aussi une preuve alternative d'un théorème d'Iwasawa de type logarithmique. La deuxième partie s'interprète comme un addendum historique sur l'étude du groupe de classes logarithmiques le long des $l$-extensions. On démontre que sous la conjecture de Gross-Kuz'min la théorie d'Iwasawa peut être bien employée pour l'étude du cas non-cyclotomique. Ainsi, on démontre des relations entre les invariants $mu$ et $lambda$ correspondant au $ell$-groupe de classes avec les invariants $ilde{mu}$ et $ilde{lambda}$ attachés aux groupes de classes logarithmiques. La troisième partie comporte l'étude du module d'Iwasawa logarithmique pour des $l^{d}$-extensions, c'est à dire du groupe de Galois $X=Gal(L_{d}/K_{d})$ de la $ell$-extension maximale abélienne logarithmiquement non-ramifiée du compositum $K_{d}$ des différentes $l$-extensions d'un corps de nombres $K$. On démontre sous la conjecture de Gross-Kuz'min, de façon analogue au cas classique, que $X$ est bien un module noethérien et de torsion sous l'algèbre d'Iwasawa de $K_{d}$. Ainsi, on déduit des relations entre les invariants logarithmiques $ilde{mu}$ et $ilde{lambda}$ des $l$-extensions de $K$ qui satisfont une hypothèse de décomposition. / This work is concerned with the study of logarithmic invariants on $l^{d}$-extensions and is subdivided in three pieces, which are closely related to each other. The first part is a compendium of the different approaches to logarithmic arithmetic, that is the study of the logarithmic invariants. In particular we show the equivalence between the four definitions of the logarithmic class group existing in the literature. Also we give an alternative proof of an Iwasawa logarithmic result. The second part can be thought as an historic addendum on the study of the logarithmic class group over $l$-extensions. Assuming the Gross-Kuz'min conjecture we show that the logarithmic class group can be studied in the Iwasawa setting for non-cyclotomic extensions. We also give relations between the classical $mu$ and $lambda$ invariants and the logarithmic invariants $ilde{mu}$ and $ilde{lambda}$ attached to the logarithmic class groups. The third part studies the properties of the Iwasawa logarithmic module for $l^{d}$-extensions, that is the Galois group $X=Gal(L_{d}/K_{d})$ of the maximal abelian $ell$-extension logarithmically unramified of the compositum $K_{d}$ of the different $l$-extensions of a number field $K$. Assuming the Gross-Kuz'min conjecture we show that $X$ is a noetherian torsion module over the Iwasawa algebra of $K_{d}$. We also deduce relations between the logarithmic invariants $ilde{mu}$ and $ilde{lambda}$ of the $l$-extensions of $K$ which satisfy a splitting condition.