CE TRAVAIL EST UNE CONTRIBUTION A L'ETUDE DU RAYONNEMENT ACOUSTIQUE DES OBSTACLES DE REVOLUTION EN INCIDENCE QUELCONQUE ET A BASSE FREQUENCE. LA PREMIERE PARTIE DECRIT NOTRE ETUDE EXPERIMENTALE DES EFFETS DE DIFFRACTION SUR LA MESURE DE L'INTENSITE ACOUSTIQUE. CETTE ETUDE CONFIRME QUE L'INFLUENCE DE LA DIFFRACTION PEUT ETRE PRISE EN COMPTE EN REMPLACANT DANS L'EXPRESSION DE L'INTENSITE ACOUSTIQUE, LA SEPARATION GEOMETRIQUE PAR UNE SEPARATION APPARENTE. DANS UN DEUXIEME TEMPS, A PARTIR DE CONFIGURATIONS GEOMETRIQUES DONT LES SOLUTIONS EXACTES SONT CONNUES, NOUS CALCULONS LES CARACTERISTIQUES PROPRES A L'ONDE RAYONNEE ET SOULIGNONS LES RAISOS POUR LESQUELLES CETTE SEPARATION GEOMETRIQUE DOIT ETRE REMPLACEE PAR UNE SEPARATION APPARENTE. PUIS, AUX BASSES FREQUENCES, EN INCIDENCE QUELCONQUE ET POUR UN OBSTACLE A SYMETRIE DE REVOLUTION AUTOUR D'UN AXE, NOUS ETABLISSONS LA VALEUR DE LA PRESSION RAYONNEE SUR LA SURFACE DE L'OBSTACLE, AVEC UNE DEPENDANCE EXPLICITE EN (ANGLE D'INCIDENCE) ET (ANGLE POLIARE CLASSIQUE). LA RESOLUTION NUMERIQUE COMPLETE CONSISTE, AUX BASSES FREQUENCES, EN LA RESOLUTION D'UN NOMBRE FINI D'EQUATIONS INTEGRALES SUR UN DOMAINE UNIDIMENSIONNEL. LES RESULTATS NUMERIQUES, DANS LE CAS D'UN CYLINDRE DE LONGUEUR FINIE, SONT COMPARES AUX RESULTATS EXACTS D'UNE FORME GEOMETRIQUE VOISINE, LE SPHEROIDE

La premiere partie decrit l'etude experimentale des effets de diffraction sur la mesure de l'intensite acoustique. Cette etude confirme que l'influence de la diffraction peut etre prise en compte en remplacant, dans l'expression de l'intensite acoustique, la separation geometrique, dx, par une separation apparente, ' app Dans un deuxieme temps, a partir de configurations geometriques dont les solutions exactes sont connues nous calculons les caracteristiques propres a l'onde rayonnee et soulignons les raisons pour lesquelles cette separation geometrique doit etre remplacee par une separation apparente. Puis, aux basses frequences, en incidence quelconque et pour un obstacle a symetrie de revolution autour d'un axe, nous etablissons la valeur de la pression rayonnee sur la surface de l'obstacle, avec une dependance explicite en a (angle d'incidence) et 9 (angle polaire classique). La resolution numerique complete consiste, aux basses frequences, en la resolution d'un nombre fini d'equations integrales sur un domaine unidimensionnel. Les resultats numeriques, dans le cas d'un cylindre de longueur finie, sont compares aux resultats exacts d'une forme geometrique voisine, le spheroide."

ON ETUDIE LE RAYONNEMENT ACOUSTIQUE ENGENDRE PAR UN ECOULEMENT SUBSONIQUE AUTOUR DE CYLINDRES DE SECTION CIRCULAIRE. DANS UNE PREMIERE PARTIE, DES METHODES DE MESURE BIDIMENSIONNELLES DE L'INTENSITE ACOUSTIQUE SONT UTILISEES POUR CARACTERISER LE CHAMP SONORE DU A UN CYLINDRE ISOLE, A SURFACE LISSE OU A RUGOSITE FINE ALEATOIRE. LA SECONDE PARTIE EST UNE DETERMINATION EXPERIMENTALE DES PRESSIONS PARIETALES SUR UN OU DEUX CYLINDRES CONSIDERES COMME DES MAQUETTES DE CABLES DE TRANSPORT ELECTRIQUE, ET AYANT EN CONSEQUENCE UNE STRUCTURE DE SURFACE A RUGOSITE FORTE ET PERIODIQUE. LES LOIS DE COHERENCE DANS UNE SECTION OU EN ENVERGURE, AINSI QUE LES FONCTIONS DE REPONSE EN FREQUENCE DES PRESSIONS INSTATIONNAIRES ENTRE LES DEUX CYLINDRES SONT DONNEES. DANS LA TROISIEME PARTIE EST PROPOSE UN MODELE NUMERIQUE PLAN DE RAYONNEMENT ACOUSTIQUE D'UN ENSEMBLE DE MONOPOLES PLACES DANS CE PLAN. EN INTRODUISANT LES PARAMETRES ISSUS DES EXPERIENCES CI-DESSUS, UN MODELE DE CALCUL DU BRUIT DU, A UN OU DEUX CABLES DE TRANSPORT ELECTRIQUES PLACES L'UN DERRIERE L'AUTRE, EST ENFIN PRESENTE

Nicolas Camille Flammarion FRAS was a French astronomer and author. He was a prolific author of more than fifty titles, including popular science works about astronomy, several notable early science fiction novels, and works on psychical research and related topics.

This new, third volume of Cohen-Tannoudji's groundbreaking textbook covers advanced topics of quantum mechanics such as uncorrelated and correlated identical particles, the quantum theory of the electromagnetic field, absorption, emission and scattering of photons by atoms, and quantum entanglement. Written in a didactically unrivalled manner, the textbook explains the fundamental concepts in seven chapters which are elaborated in accompanying complements that provide more detailed discussions, examples and applications. * Completing the success story: the third and final volume of the quantum mechanics textbook written by 1997 Nobel laureate Claude Cohen-Tannoudji and his colleagues Bernard Diu and Franck Laloë * As easily comprehensible as possible: all steps of the physical background and its mathematical representation are spelled out explicitly * Comprehensive: in addition to the fundamentals themselves, the books comes with a wealth of elaborately explained examples and applications Claude Cohen-Tannoudji was a researcher at the Kastler-Brossel laboratory of the Ecole Normale Supérieure in Paris where he also studied and received his PhD in 1962. In 1973 he became Professor of atomic and molecular physics at the Collège des France. His main research interests were optical pumping, quantum optics and atom-photon interactions. In 1997, Claude Cohen-Tannoudji, together with Steven Chu and William D. Phillips, was awarded the Nobel Prize in Physics for his research on laser cooling and trapping of neutral atoms. Bernard Diu was Professor at the Denis Diderot University (Paris VII). He was engaged in research at the Laboratory of Theoretical Physics and High Energy where his focus was on strong interactions physics and statistical mechanics. Franck Laloë was a researcher at the Kastler-Brossel laboratory of the Ecole Normale Supérieure in Paris. His first assignment was with the University of Paris VI before he was appointed to the CNRS, the French National Research Center. His research was focused on optical pumping, statistical mechanics of quantum gases, musical acoustics and the foundations of quantum mechanics.

Proceedings from a conference "A global assessment of the 1989 recommendation on the safeguarding of traditional culture and folklore" held at the Smithsonian Institution June 27-30 1999. The purpose of the conference was to assess the implementation of the Recommendation (an international normative instrument adopted by UNESCO in 1989), to bring together points of view and perspectives on the Recommendaion from around the world, and suggest ways in which the Recommendation might develop in the future so that its purpose, the safeguarding of traditional culture and folklore, might be achieved.

This book addresses a broad range of topics on antennas for space applications. First, it introduces the fundamental methodologies of space antenna design, modelling and analysis as well as the state-of-the-art and anticipated future technological developments. Each of the topics discussed are specialized and contextualized to the space sector. Furthermore, case studies are also provided to demonstrate the design and implementation of antennas in actual applications. Second, the authors present a detailed review of antenna designs for some popular applications such as satellite communications, space-borne synthetic aperture radar (SAR), Global Navigation Satellite Systems (GNSS) receivers, science instruments, radio astronomy, small satellites, and deep-space applications. Finally it presents the reader with a comprehensive path from space antenna development basics to specific individual applications. Key Features: Presents a detailed review of antenna designs for applications such as satellite communications, space-borne SAR, GNSS receivers, science instruments, small satellites, radio astronomy, deep-space applications Addresses the space antenna development from different angles, including electromagnetic, thermal and mechanical design strategies required for space qualification Includes numerous case studies to demonstrate how to design and implement antennas in practical scenarios Offers both an introduction for students in the field and an in-depth reference for antenna engineers who develop space antennas This book serves as an excellent reference for researchers, professionals and graduate students in the fields of antennas and propagation, electromagnetics, RF/microwave/millimetrewave systems, satellite communications, radars, satellite remote sensing, satellite navigation and spacecraft system engineering, It also aids engineers technical managers and professionals working on antenna and RF designs. Marketing and business people in satellites, wireless, and electronics area who want to acquire a basic understanding of the technology will also find this book of interest.