Astron.Astrophys.426:353-365,2004 We have undertaken a thorough dynamical investigation of five extrasolar
planetary systems using extensive numerical experiments. The systems Gl 777 A,
HD 72659, Gl ...614, 47 Uma and HD 4208 were examined concerning the question of
whether they could host terrestrial like planets in their habitable zones
(=HZ). First we investigated the mean motion resonances between fictitious
terrestrial planets and the existing gas giants in these five extrasolar
systems. Then a fine grid of initial conditions for a potential terrestrial
planet within the HZ was chosen for each system, from which the stability of
orbits was then assessed by direct integrations over a time interval of 1
million years. The computations were carried out using a Lie-series integration
method with an adaptive step size control. This integration method achieves
machine precision accuracy in a highly efficient and robust way, requiring no
special adjustments when the orbits have large eccentricities. The stability of
orbits was examined with a determination of the Renyi entropy, estimated from
recurrence plots, and with a more straight forward method based on the maximum
eccentricity achieved by the planet over the 1 million year integration.
Additionally, the eccentricity is an indication of the habitability of a
terrestrial planet in the HZ; any value of e>0.2 produces a significant
temperature difference on a planet's surface between apoapse and periapse. The
results for possible stable orbits for terrestrial planets in habitable zones
for the five systems are summarized as follows: for Gl 777 A nearly the entire
HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive
for a sufficiently long time, while for Gl 614 our results exclude terrestrial
planets moving in stable orbits within the HZ.
We have undertaken a thorough dynamical investigation of five extrasolar planetary systems using extensive numerical experiments. The systems Gl 777 A, HD 72659, Gl 614, 47 Uma and HD 4208 were ...examined concerning the question of whether they could host terrestrial like planets in their habitable zones (=HZ). First we investigated the mean motion resonances between fictitious terrestrial planets and the existing gas giants in these five extrasolar systems. Then a fine grid of initial conditions for a potential terrestrial planet within the HZ was chosen for each system, from which the stability of orbits was then assessed by direct integrations over a time interval of 1 million years. The computations were carried out using a Lie-series integration method with an adaptive step size control. This integration method achieves machine precision accuracy in a highly efficient and robust way, requiring no special adjustments when the orbits have large eccentricities. The stability of orbits was examined with a determination of the Renyi entropy, estimated from recurrence plots, and with a more straight forward method based on the maximum eccentricity achieved by the planet over the 1 million year integration. Additionally, the eccentricity is an indication of the habitability of a terrestrial planet in the HZ; any value of e>0.2 produces a significant temperature difference on a planet's surface between apoapse and periapse. The results for possible stable orbits for terrestrial planets in habitable zones for the five systems are summarized as follows: for Gl 777 A nearly the entire HZ is stable, for 47 Uma, HD 72659 and HD 4208 terrestrial planets can survive for a sufficiently long time, while for Gl 614 our results exclude terrestrial planets moving in stable orbits within the HZ.
Se estudiaron durante 3 meses en forma interdisciplinaria a los sistemas de produccion del Mpio. de Tlapacoyan, Ver. para conocer la tipologia de los mismos, la racionalidad del productor e ...identificar problemas y su posible solucion mediante la investigacion. El area de trabajo se delimito mediante una apreciacion visual de la region y se entrevistaron a productores, instituciones y cooperativas con injerencia en el area, para entender sus objetivos y aspiraciones; se seleccionaron los criterios a usar en la clasificacion tipologica por medio de una encuesta a 24 productores, comerciantes y extensionistas; finalmente los tipos de productores se definieron a traves de una encuesta a 62 de 870 productores; los datos de las encuestas se procesaron mediante analisis estadisticos descriptivos y multifactoriales. El 7 % de los productores tiene ganado bovino de doble proposito (promedio 25 animales/finca), intercalado con agricultura mixta, la ganaderia bovina ocupo el 37 % de la superficie total y solamente el 5 % estuvo en pastos introducidos; los productores no practican la fertilizacion y las malezas se controlan con chapeo manual; el promedio de produccion de leche /vaca es de 3.7 lt y la comercializan 4 de los 8 productores; las medidas sanitarias son escasas y solamente 5 % ha recibido asesoria tecnica. Los caballos y burros son utilizados para carga en la epoca de cosecha y para transporte humano. La presencia de ganaderia de traspatio (cerdos, aves) es importante (70 % de los productores) ya que es fuente de alimento y dinero para la familia. Es importante senalar que la agricultura compite fuertemente con la ganaderia, por lo que los pastos son desplazados por cultivos perennes, para asegurar un mejor ingreso economico. Se concluye que el nivel tecnico es bajo, resultando que el ingreso economico por el sector pecuario es menor que el proveniente del sector agricola ocasionando el cambio de pastos hacia cultivos.
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