Automated composite ellipsoid modelling for high frequency GTD analysis

The preliminary results of a scheme currently being developed to fit a composite ellipsoid to the fuselage of a helicopter in the vicinity of the antenna location are discussed under the assumption that the antenna is mounted on the fuselage. The parameters of the close-fit composite ellipsoid would then be utilized as inputs into NEWAIR3, a code programmed in FORTRAN 77 for high frequency Geometrical Theory of Diffraction (GTD) Analysis of the radiation of airborne antennas

Description des captures au filet tramail sur le cours supérieur du Sinnamary (Guyane Française)

Le Sinnamary est un fleuve de Guyane Française, de moyenne importance (6565 km2). Il peut être divisé en trois zones : l'estuaire, le cours inférieur et le cours supérieur. Une série de pêches expérimentales a été réalisée dans le cours supérieur de ce fleuve, à l'aide de filets tramails de maille comprise entre 10 et 65 mm. La sélectivité des filets utilisés s'est avérée très forte, et la composition des captures fort différente selon la taille de la maille. Quatre espèces représentent 68% des prises #(Leporinus friderici, Curimata cyprinoides, Triporteus rotundadus, Myleus ternetzy)$ et l'analyse des captures montre que le nombre d'individus capturés par unité d'effort est supérieur en saison des pluies. L'origine de ces variations saisonnières de captures est discutée. (Résumé d'auteur

Zonation longitudinale du peuplement ichtyque du fleuve Sinnamary (Guyane Française)

Le Sinnamary est un fleuve de moyenne importance (bassin de 6565 km2) de la Guyane Française. A l'aide de divers critères d'ordre géologique, pédologique, hydrologique et phytosociologique, nous avons pu diviser le fleuve en 3 zones distinctes : la partie haute, le cours inférieur et l'estuaire. Un important effort d'échantillonnage, réparti dans le temps et mettant en jeu plusieurs techniques de pêche, a été consenti dans chacune de ces 3 zones. A l'aide de ce travail, le peuplement ichtyologique a pu être décrit : il s'avère très différent, tant du point de vue de la richesse spécifique, que dans sa composition, entre les différentes zones. (Résumé d'auteur

The Helicopter Antenna Radiation Prediction Code (HARP)

The first nine months effort in the development of a user oriented computer code, referred to as the HARP code, for analyzing the radiation from helicopter antennas is described. The HARP code uses modern computer graphics to aid in the description and display of the helicopter geometry. At low frequencies the helicopter is modeled by polygonal plates, and the method of moments is used to compute the desired patterns. At high frequencies the helicopter is modeled by a composite ellipsoid and flat plates, and computations are made using the geometrical theory of diffraction. The HARP code will provide a user friendly interface, employing modern computer graphics, to aid the user to describe the helicopter geometry, select the method of computation, construct the desired high or low frequency model, and display the results

Ostrogradski approach for the Regge-Teitelboim type cosmology

We present an alternative geometric inspired derivation of the quantum cosmology arising from a brane universe in the context of {\it geodetic gravity}. We set up the Regge-Teitelboim model to describe our universe, and we recover its original dynamics by thinking of such field theory as a second-order derivative theory. We refer to an Ostrogradski Hamiltonian formalism to prepare the system to its quantization. Our analysis highlights the second-order derivative nature of the RT model and the inherited geometrical aspect of the theory. A canonical transformation brings us to the internal physical geometry of the theory and induces its quantization straightforwardly. By using the Dirac canonical quantization method our approach comprises the management of both first- and second-class constraints where the counting of degrees of freedom follows accordingly. At the quantum level our Wheeler-De Witt Wheeler equation agrees with previous results recently found. On these lines, we also comment upon the compatibility of our approach with the Hamiltonian approach proposed by Davidson and coworkers.Comment: 11 pages, 2 figures, accepted for publication in Phys. Rev.

Operation of the helicopter antenna radiation prediction code

HARP is a front end as well as a back end for the AMC and NEWAIR computer codes. These codes use the Method of Moments (MM) and the Uniform Geometrical Theory of Diffraction (UTD), respectively, to calculate the electromagnetic radiation patterns for antennas on aircraft. The major difficulty in using these codes is in the creation of proper input files for particular aircraft and in verifying that these files are, in fact, what is intended. HARP creates these input files in a consistent manner and allows the user to verify them for correctness using sophisticated 2 and 3D graphics. After antenna field patterns are calculated using either MM or UTD, HARP can display the results on the user's screen or provide hardcopy output. Because the process of collecting data, building the 3D models, and obtaining the calculated field patterns was completely automated by HARP, the researcher's productivity can be many times what it could be if these operations had to be done by hand. A complete, step by step, guide is provided so that the researcher can quickly learn to make use of all the capabilities of HARP

Synthesis of a metal oxide by forming solvate eutectic mixtures and study of their synthetic performance under hyper- and hypo-eutectic conditions

The synthesis of YBa2Cu3O7−x (YBCO or 123) superconductor was carried out under hyper- and hypo-eutectic conditions with different ammonium compounds, i.e., ammonium nitrate, formate, acetate, carbonate, bicarbonate, and tetramethylammonium nitrate. The aim was to find more affordable synthetic pathways using highly available and cheaper compounds, as well as to study the crystal formation under no-carbon conditions when ammonium nitrate was employed. Best results were obtained when eutectic conditions were achieved, namely by ammonium nitrate and YBaCu nitrates in a 5:1 molar ratio (81% of the superconductor). Ammonium formate, acetate, carbonate, and bicarbonate did not produce eutectic mixes. Temperature analysis of the reaction carried out by ammonium nitrate/YBaCu nitrates indicated the formation of barium carbonate, despite no carbon source being used in this reaction. This phenomenon is further discussed in this work. Consequently, tetramethylammonium nitrate, as a chelator and carbon source, was used, providing >96% of the superconductor