16,244 research outputs found
Geographical catch distribution of yellowfin and skipjack tuna in the Eastern Pacific Ocean, 1967-1970, and fleet and total catch statistics, 1962-1970
ENGLISH: Logbook records of tuna vessels fishing in the eastern Pacific Ocean were used to prepare charts showing the distribution of yellowfin tuna and skipjack catches by i-degree area, by quarter of the year, and by gear, for the years 1967-1970. Recent changes in the geographical distribution of yellowfin catch are illustrated. Also given are annual catch statistics and the composition of the international tuna fishing fleets which operated in the Commission's Yellowfin Regulatory Area each year, 1962-1970. SPANISH: Los registros de los cuadernos de bitácora de los barcos pesqueros de atún en el Océano Pacífico oriental se usaron para preparar gráficos que presentan para los años de 1967-1970, la distribución de captura del atún aleta amarilla y barrilete por área de 1 grado, trimestre del año y, por las artes. Se ilustran los recientes cambios en la distribución geográfica de la captura del atún aleta amarilla. Se presentan también las estadísticas de captura anual y la composición de la flota internacional de pesca, que explota cada año el Area Reglamentaria de la Comisión, 1962-1970.
(PDF contains 95 pages.
Geographical distribution of yellowfin tuna and skipjack catches in the Eastern Pacific Ocean, by quarters of the year, 1963-1966
ENGLISH: Logbook records of tuna vessels fishing in the eastern Pacific Ocean were used to prepare charts showing the distribution of yellowfin and skipjack tuna catches by 1-degree area, by quarter of the year, and by gear for the years 1963-1966. Recent changes in the geographical distribution of yellowfin catches are illustrated. The size composition of the U. S. tuna fleet is given, and recent changes are discussed. SPANISH: Los registros de los cuadernos de bitácora de los barcos atuneros que pescan en el Océano Pacifico oriental, se emplearon para preparar los gráficos que indican la distribuci6n de las capturas de atún aleta amarilla y de barrilete por área de 1 grado, por trimestre del ano y por aparejo de pesca para los anos de 1963-1966. Se ilustran los cambios recientes en la distribucion geográfica de las capturas de atún aleta amarilla. Se da la composición de tamaño de la flota atunera de los E. U. y se discuten los cambios recientes.
(PDF contains 76 pages.
Emission from Very Small Grains and PAH Molecules in Monte Carlo Radiation Transfer Codes: Application to the Edge-On Disk of Gomez's Hamburger
We have modeled optical to far infrared images, photometry, and spectroscopy
of the object known as Gomez's Hamburger. We reproduce the images and spectrum
with an edge-on disk of mass 0.3M_sun and radius 1600AU, surrounding an A0 III
star at a distance of 280pc. Our mass estimate is in excellent agreement with
recent CO observations. However, our distance determination is more than an
order of magnitude smaller than previous analyses which inaccurately
interpreted the optical spectrum. To accurately model the infrared spectrum we
have extended our Monte Carlo radiation transfer codes to include emission from
polycyclic aromatic hydrocarbon (PAH) molecules and very small grains (VSG). We
do this using pre-computed PAH/VSG emissivity files for a wide range of values
of the mean intensity of the exciting radiation field. When Monte Carlo energy
packets are absorbed by PAHs/VSGs we reprocess them to other wavelengths by
sampling from the emissivity files, thus simulating the absorption and
re-emission process without reproducing lengthy computations of statistical
equilibrium, excitation and de-excitation in the complex many level molecules.
Using emissivity lookup tables in our Monte Carlo codes gives the flexibility
to use the latest grain physics calculations of PAH/VSG emissivity and opacity
that are being continually updated in the light of higher resolution infrared
spectra. We find our approach gives a good representation of the observed PAH
spectrum from the disk of Gomez's Hamburger. Our models also indicate the
PAHs/VSGs in the disk have a larger scaleheight than larger radiative
equilibrium grains, providing evidence for dust coagulation and settling to the
midplane.Comment: ApJ accepte
Development of a figure-of-merit for space missions
The concept of a quantitative figure-of-merit (FOM) to evaluate different and competing options for space missions is further developed. Over six hundred individual factors are considered. These range from mission orbital mechanics to in-situ resource utilization (ISRU/ISMU) plants. The program utilizes a commercial software package for synthesis and visual display; the details are completely developed in-house. Historical FOM's are derived for successful space missions such as the Surveyor, Voyager, Apollo, etc. A cost FOM is also mentioned. The bulk of this work is devoted to one specific example of Mars Sample Return (MSR). The program is flexible enough to accommodate a variety of evolving technologies. Initial results show that the FOM for sample return is a function of the mass returned to LEO, and that missions utilizing ISRU/ISMU are far more cost effective than those that rely on all earth-transported resources
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