22 research outputs found
Plan de comunicación y financiero de la franquicia venezolana juan chichero en el Ecuador para la ciudad de Guayaquil
EN ESTE PROYECTO LAS METAS ES INCREMENTAR LAS VENTAS DEL PRODUCTO JUAN CHICHERO ANALIZANDO EL PRODUCTO Y CONOCIENDO MAS ACERCA DE LA EMPRESA SUS ESTRATEGIAS. INVESTIGACION DE MERCADO LO QUE PIENSA LA POBLACION GUAYAQUILEÑA Y PARA MEJORARLAS.
DENTRO DE NUESTRO PROYECTO SE ENCUENTRAN ALGUNAS ACCIONES DE COMUNICACION QUE DEBIDO AL PRESUPUESTO NO SE PUDIERON REALIZAR EN EL TIEMPO DE LA PROYECCION
Protostellar collapse and fragmentation using an MHD GADGET
Although the influence of magnetic fields is regarded as vital in the star
formation process, only a few magnetohydrodynamics (MHD) simulations have been
performed on this subject within the smoothed particle hydrodynamics (SPH)
method. This is largely due to the unsatisfactory treatment of non-vanishing
divergence of the magnetic field. Recently smoothed particle
magnetohydrodynamics (SPMHD) simulations based on Euler potentials have proven
to be successful in treating MHD collapse and fragmentation problems, however
these methods are known to have some intrinsical difficulties. We have
performed SPMHD simulations based on a traditional approach evolving the
magnetic field itself using the induction equation. To account for the
numerical divergence, we have chosen an approach that subtracts the effects of
numerical divergence from the force equation, and additionally we employ
artificial magnetic dissipation as a regularization scheme. We apply this
realization of SPMHD to a widely known setup, a variation of the 'Boss &
Bodenheimer standard isothermal test case', to study the impact of the magnetic
fields on collapse and fragmentation. In our simulations, we concentrate on
setups, where the initial magnetic field is parallel to the rotation axis. We
examine different field strengths and compare our results to other findings
reported in the literature. We are able to confirm specific results found
elsewhere, namely the delayed onset of star formation for strong fields,
accompanied by the tendency to form only single stars. We also find that the
'magnetic cushioning effect', where the magnetic field is wound up to form a
'cushion' between the binary, aids binary fragmentation in a case, where
previously only formation of a single protostar was expected.Comment: 18 pages, 11 figures. Final version (with revisions). Accepted to
MNRA
SPH Simulations of Black Hole Accretion: A Step to Model Black Hole Feedback in Galaxies
(Abridged) We test how accurately the smoothed particle hydrodynamics (SPH)
numerical technique can follow spherically-symmetric Bondi accretion. Using the
3D SPH code GADGET-3, we perform simulations of gas accretion onto a central
supermassive black hole (SMBH) of mass 10^8 M_sun within the radial range of
0.1 - 200 pc. We carry out simulations without and with radiative heating by a
central X-ray corona and radiative cooling. For an adiabatic case, the radial
profiles of hydrodynamical properties match the Bondi solution, except near the
inner and outer radius of the computational domain. We find that adiabatic
Bondi accretion can be reproduced for durations of a few dynamical times at the
Bondi radius, and for longer times if the outer radius is increased. With
radiative heating and cooling included, the spherically accreting gas takes a
longer time to reach a steady-state than the adiabatic Bondi accretion runs,
and in some cases does not reach a steady-state even within several hundred
dynamical times. We find that artificial viscosity in the GADGET code causes
excessive heating near the inner radius, making the thermal properties of the
gas inconsistent with a physical solution. This overheating occurs typically
only in the supersonic part of the flow, so that it does not affect the mass
accretion rate. We see that increasing the X-ray luminosity produces a lower
central mass inflow rate, implying that feedback due to radiative heating is
operational in our simulations. With a sufficiently high X-ray luminosity, the
inflowing gas is radiatively heated up, and an outflow develops. We conclude
that the SPH simulations can capture the gas dynamics needed to study radiative
feedback provided artificial viscosity alters only highly supersonic part of
the inflow.Comment: 25 pages, 3 tables, and 16 figures. Version accepted for publication
in MNRAS. Sec. 3.1.5 extensively revised, results from new runs adde