Download or read book Conception d une m thode de d convolution pour l estimation des angles d arriv e sur une antenne written by Oussama Akhdar and published by . This book was released on 2009 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ce mémoire a porté sur l’étude et la mise en oeuvre d’un sondeur spatio-temporel pour la caractérisation du canal radio. Tout d'abord, une étude bibliographique a été dédiée à la caractérisation du milieu de propagation et aux différentes techniques de mesure spatio-temporelle envisageables, en citant les méthodes de traitements associées. Une méthode originale pour la caractérisation spatiale a été conçue mettant en oeuvre un nouvel algorithme basé sur la rotation d’une antenne et en utilisant un procédé de déconvolution associé. La mise en place de cette méthode a permis d’effectuer un sondage spatial du canal de propagation avec une simple antenne patch présentant une ouverture angulaire à -3 dB de 70°. Par la suite, cette méthode de caractérisation spatiale développée a été couplée à une technique de mesure temporelle (corrélation glissante) permettant ainsi le sondage spatio-temporel du canal de propagation. Les mesures effectuées ont ensuite permis d’intégrer la réponse spatio-temporelle sur des simulateurs de transmission numérique afin de réaliser des simulations réalistes du canal de propagation. L’ensemble des résultats obtenus lors des sondages effectués constitue le point de départ d’autres campagnes de mesures plus exhaustives afin d’aboutir à des modèles de canaux spatiotemporels réalistes.
Download or read book Etudes en traitement d antenne pour la prise de son written by WOLFGANG.. TAGER and published by . This book was released on 1998 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: CETTE THESE PORTE SUR LE TRAITEMENT D'ANTENNE PAR UN RESEAU DE MICROPHONES. ON CONSTATE UNE GRANDE SIMILITUDE DES EQUATIONS DANS LE DOMAINE FREQUENTIEL ET DANS LE DOMAINE TEMPOREL LARGE BANDE. AINSI, IL EST POSSIBLE D'UTILISER LES MEMES ALGORITHMES DANS LES DEUX DOMAINES. ON UTILISE CETTE PROPRIETE POUR LA LOCALISATION (MAXIMUM DE VRAISEMBLANCE DETERMINISTE ET METHODE DU PROPAGATEUR) ET POUR L'ESTIMATION DU CANAL. UNE METHODE GENERIQUE EST DERIVEE SUR LA BASE DU TRAITEMENT SUPERDIRECTIF. AU LIEU DE S'APPUYER UNIQUEMENT SUR LES DIFFERENCES DE PHASE, ON UTILISE AUSSI LES DIFFERENCES D'AMPLITUDE, CE QUI PERMET D'OBTENIR UN FACTEUR DE DIRECTIVITE ELEVE AUX FREQUENCES POUR LESQUELLES LA TAILLE DE L'ANTENNE DEVIENT PETITE COMPAREE A LA LONGUEUR D'ONDE. AINSI, LE FACTEUR DE DIRECTIVITE PEUT MEME TENDRE VERS L'INFINI POUR F 0, ET CECI AVEC UNE ROBUSTESSE RAISONNABLE. EN PROFITANT DES RESULTATS DE CE TRAITEMENT FIXE, DEUX TRAITEMENTS ADAPTATIFS SONT PROPOSES. LE PREMIER REPOSE SUR UNE GENERALISATION DE LA METHODE LCMV. AU LIEU D'UN CRITERE DE COUT BASE UNIQUEMENT SUR LA PUISSANCE A LA SORTIE, DEUX TERMES SUPPLEMENTAIRES SONT AJOUTES QUI EXPRIMENT LE FACTEUR DE DIRECTIVITE ET LA ROBUSTESSE. LE DEUXIEME TRAITEMENT ADAPTATIF EST BASE SUR L'ALGORITHME DE FROST. AU LIEU D'AVOIR UNE CONTRAINTE DURE POUR PROTEGER LE SIGNAL UTILE, UN SIGNAL FICTIF EST INJECTE, QUI S'AJOUTE VIRTUELLEMENT AU SIGNAL UTILE, MAIS QUI A L'AVANTAGE D'ETRE CONNU. LE SIGNAL DESIRE A LA SORTIE DE L'ANTENNE EST CE SIGNAL FICTIF. UNE VARIATION DE LA PUISSANCE DE CE SIGNAL SELON UN CRITERE DE DETECTION D'ACTIVITE VOCALE PERMET DE RELACHER LA CONTRAINTE PENDANT L'ABSENCE DU SIGNAL UTILE AFIN DE REDUIRE EN MEME TEMPS LES SIGNAUX PERTURBATEURS. POUR REDUIRE DAVANTAGE LES PERTURBATIONS RESIDUELLES, DES POST-TRAITEMENTS PEUVENT ETRE APPLIQUES EN SORTIE D'ANTENNE. DEUX NOUVELLES METHODES DE POST-FILTRAGE SONT PROPOSEES. FINALEMENT, DEUX METHODES SONT PROPOSEES POUR REDUIRE LA CHARGE DE CALCUL. LA PREMIERE METHODE SERT A IMPLANTER EFFICACEMENT DES RETARDS FRACTIONNAIRES EN UTILISANT UNE FACTORISATION DES FILTRES. LA DEUXIEME METHODE EST UTILE POUR DES TRAITEMENTS DANS LE DOMAINE FREQUENTIEL QUI RESPECTENT APPROXIMATIVEMENT LA CONTRAINTE DE CONVOLUTION OU CORRELATION LINEAIRE. IL S'AGIT D'UN LISSAGE OU D'UNE INTERPOLATION DANS LE DOMAINE FREQUENTIEL.
Download or read book Convolution et d convolution lin aire 3 D appliqu es l holographie acoustique temporelle written by Jean-Michel Attendu and published by . This book was released on 2017 with total page 226 pages. Available in PDF, EPUB and Kindle. Book excerpt: L'holographie acoustique en champ proche est une methode permettant de calculer l'amplitude d'un champ sonore dans l'espace tridimensionnel et dans le temps. Son principe repose sur l'utilisation d'une antenne microphonique placee dans le champ proche de la source, qui permet d'obtenir une condition frontiere suffisante a la resolution de l'equation d'onde avec le formalisme de Green. La formulation standard permet de determiner le champ de sources stationnaires. Il est alors suppose que la source rayonne de maniere periodique dans le temps : le champ reconstruit est consequemment represente dans le domaine frequentiel. Lorsque la source est non-stationnaire, le champ doit etre represente dans le domaine temporel et le formalisme standard ne s'applique pas, car la nature finie et discrete du champ mesure introduit plusieurs erreurs de traitement du signal, notamment a cause de l'utilisation de la transformee de Fourier discrete qui suppose la periodicite. Les principales erreurs engendrees sont dues aux fuites spectrales (leakage) et au phenomene de recouvrement (wrap-around). Dans cette these, nous proposons un formalisme permettant de supprimer ces erreurs en utilisant un operateur de convolution lineaire tridimensionnel de meme que l'utilisation d'une fonction de Green echantillonnee dans le domaine temps-espace. Cette formulation ameliore significativement la reconstruction du champ sonore tant pour le probleme direct (propagation) que le probleme inverse (retro-propagation). En propagation, l'erreur obtenue avec la methode proposee est environ dix fois moindre qu'avec les methodes competitrices dans les cas etudies. De plus, on peut controler le niveau de l'erreur en choisissant un fenetrage et une discretisation adequate. On etablit egalement un lien entre l'erreur de troncature de la fonction de Green et la distance entre le plan de mesure et le plan de propagation. On valide la methode developpee en l'appliquant a des signaux simules a partir d'un modele de piston baffle, ainsi qu'a des signaux experimentaux obtenus dans un environnement anechoique. En retro-propagation, on obtient une reduction de l'erreur allant jusqu'a un facteur trois en comparaison a la methode standard basee sur l'utilisation de la convolution circulaire. L'erreur reste significative puisque le probleme inverse est mathematiquement mal pose. Par consequent, on analyse la performance de la methode de Tikhonov pour regulariser le probleme selon le niveau de bruit ajoute et la distance de propagation. Trois differentes methodes sont utilisees pour determiner le parametre de regularisation optimal, soient la methode de la courbe en L, la validation croisee generalisee et une approche Bayesienne.
Download or read book Artificial Intelligence and Industrial Applications written by Tawfik Masrour and published by Springer Nature. This book was released on 2020-09-01 with total page 442 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book gathers the refereed proceedings of the Artificial Intelligence and Industrial Applications (A2IA’2020), the first installment of an annual international conference organized by the ENSAM-Meknes at Moulay Ismail University, Morocco. The 30 papers presented here were carefully reviewed and selected from 141 submissions by an international scientific committee. They address various aspects of artificial intelligence such as smart manufacturing, smart maintenance, smart supply chain management, supervised learning, unsupervised learning, reinforcement learning, graph-based and semi-supervised learning, neural networks, deep learning, planning and optimization, and other AI applications. The book is intended for AI experts, offering them a valuable overview of the status quo and a global outlook for the future, with many new and innovative ideas and recent important developments in AI applications, both of a foundational and practical nature. It will also appeal to non-experts who are curious about this timely and important subject.
Download or read book Space Systems as Contributors to the NATO Defence Mission written by North Atlantic Treaty Organization. Advisory Group for Aerospace Research and Development. Mission Systems Panel. Symposium and published by . This book was released on 1997 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Principles of Radar and Sonar Signal Processing written by Chevalier François Le and published by Artech House. This book was released on 2002 with total page 422 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Monitoring soils in the environment with remote sensing and gis written by Richard Escadafal and published by IRD Orstom. This book was released on 1996 with total page 674 pages. Available in PDF, EPUB and Kindle. Book excerpt: ISSS congress remote sensing
Download or read book Quantum Communications and Cryptography written by Alexander V. Sergienko and published by CRC Press. This book was released on 2018-10-03 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: All current methods of secure communication such as public-key cryptography can eventually be broken by faster computing. At the interface of physics and computer science lies a powerful solution for secure communications: quantum cryptography. Because eavesdropping changes the physical nature of the information, users in a quantum exchange can easily detect eavesdroppers. This allows for totally secure random key distribution, a central requirement for use of the one-time pad. Since the one-time pad is theoretically proven to be undecipherable, quantum cryptography is the key to perfect secrecy. Quantum Communications and Cryptography is the first comprehensive review of the past, present, and potential developments in this dynamic field. Leading expert contributors from around the world discuss the scientific foundations, experimental and theoretical developments, and cutting-edge technical and engineering advances in quantum communications and cryptography. The book describes the engineering principles and practical implementations in a real-world metropolitan network as well as physical principles and experimental results of such technologies as entanglement swapping and quantum teleportation. It also offers the first detailed treatment of quantum information processing with continuous variables. Technologies include both free-space and fiber-based communications systems along with the necessary protocols and information processing approaches. Bridging the gap between physics and engineering, Quantum Communications and Cryptography supplies a springboard for further developments and breakthroughs in this rapidly growing area.
Download or read book Extraterrestrial Seismology written by Vincent C. H. Tong and published by Cambridge University Press. This book was released on 2015-06-25 with total page 467 pages. Available in PDF, EPUB and Kindle. Book excerpt: Taking a transdisciplinary approach to seismology, this unique book reviews the most recent developments in planetary seismology, helioseismology, and asteroseismology.
Download or read book Modern Radar Detection Theory written by Antonio De Maio and published by IET. This book was released on 2015-11-25 with total page 395 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modern radar detection is the new frontier for advanced radar systems capable of operating in challenging scenarios with a plurality of interference sources, both manmade and natural. Written by top researchers and recognized leaders in the field, this is the first book to provide a comprehensive understanding of the current research trends in modern radar detection. It updates readers with the latest radar signal processing algorithms now capable with high-speed computer chips and sophisticated programs. It also includes examples and applications from real systems. This is essential reading for radar systems design engineers within aerospace companies, military radar engineers, and aerospace contractors/consultants.
Download or read book Antennas and Propagation for Wireless Communication Systems written by Simon R. Saunders and published by John Wiley & Sons. This book was released on 2007-05-07 with total page 547 pages. Available in PDF, EPUB and Kindle. Book excerpt: Antennas and propagation are of fundamental importance to the coverage, capacity and quality of all wireless communication systems. This book provides a solid grounding in antennas and propagation, covering terrestrial and satellite radio systems in both mobile and fixed contexts. Building on the highly successful first edition, this fully updated text features significant new material and brand new exercises and supplementary materials to support course tutors. A vital source of information for practising and aspiring wireless communication engineers as well as for students at postgraduate and senior undergraduate levels, this book provides a fundamental grounding in the principles of antennas and propagation without excessive recourse to mathematics. It also equips the reader with practical prediction techniques for the design and analysis of a very wide range of common wireless communication systems. Including: Overview of the fundamental electromagnetic principles underlying propagation and antennas. Basic concepts of antennas and their application to specific wireless systems. Propagation measurement, modelling and prediction for fixed links, macrocells, microcells, picocells and megacells Narrowband and wideband channel modelling and the effect of the channel on communication system performance. Methods that overcome and transform channel impairments to enhance performance using diversity, adaptive antennas and equalisers. Key second edition updates: New chapters on Antennas for Mobile Systems and Channel Measurements for Mobile Radio Systems. Coverage of new technologies, including MIMO antenna systems, Ultra Wideband (UWB) and the OFDM technology used in Wi-Fi and WiMax systems. Many new propagation models for macrocells, microcells and picocells. Fully revised and expanded end-of-chapter exercises. The Solutions Manual can be requested from www.wiley.com/go/saunders_antennas_2e
Download or read book Global and National Soils and Terrain Digital Databases SOTER written by Food and Agriculture Organization of the United Nations. Land and Water Development Division and published by Food & Agriculture Org.. This book was released on 1993 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Annenbergs written by John E. Cooney and published by Simon & Schuster. This book was released on 1982 with total page 456 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This is the colorful and dramatic biography of two of America's most controversial entrepreneurs: Moses Louis Annenberg, 'the racing wire king, ' who built his fortune in racketeering, invested it in publishing, and lost much of it in the biggest tax evasion case in United States history; and his son, Walter, launcher of TV Guide and Seventeen magazines and former ambassador to Great Britain."--Jacket.
Download or read book Proof Theory and Automated Deduction written by Jean Goubault-Larrecq and published by Springer Science & Business Media. This book was released on 2001-11-30 with total page 448 pages. Available in PDF, EPUB and Kindle. Book excerpt: Interest in computer applications has led to a new attitude to applied logic in which researchers tailor a logic in the same way they define a computer language. In response to this attitude, this text for undergraduate and graduate students discusses major algorithmic methodologies, and tableaux and resolution methods. The authors focus on first-order logic, the use of proof theory, and the computer application of automated searches for proofs of mathematical propositions. Annotation copyrighted by Book News, Inc., Portland, OR
Download or read book Governance Regulation and Powers on the Internet written by Eric Brousseau and published by Cambridge University Press. This book was released on 2012-04-23 with total page 463 pages. Available in PDF, EPUB and Kindle. Book excerpt: An interdisciplinary survey of the issues surrounding the governance of the Internet.
Download or read book Philostratus written by Philostratus (the Athenian) and published by . This book was released on 1912 with total page 280 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Translating the Middle Ages written by Karen L. Fresco and published by Routledge. This book was released on 2016-02-17 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt: Drawing on approaches from literary studies, history, linguistics, and art history, and ranging from Late Antiquity to the sixteenth century, this collection views 'translation' broadly as the adaptation and transmission of cultural inheritance. The essays explore translation in a variety of sources from manuscript to print culture and the creation of lexical databases. Several essays look at the practice of textual translation across languages, including the vernacularization of Latin literature in England, France, and Italy; the translation of Greek and Hebrew scientific terms into Arabic; and the use of Hebrew terms in anti-Jewish and anti-Muslim polemics. Other essays examine medieval translators' views and performance of translation, looking at Lydgate's translation of Greek myths through mental images rendered through rhetorical figures or at how printing transformed the rhetoric of intervernacular translation of chivalric romances. This collection also demonstrates translation as a key element in the construction of cultural and political identity in the Fet des Romains and Chester Whitsun Plays, and in the papacy's efforts to compete with Byzantium by controlling the translation of Greek writings.
