54,765 research outputs found
Role of Sorption Isotherms in the Analysis of Coupled Heat and Mass Fluxes in Porous Media
The aim of this work is to show the importance of the sorption isotherms
in the study of the heat and mass fluxes in unsaturated porous media. General forms of the heat and mass fluxes are presented in terms of experimentally accessible quantities. The role of the isotherm slope in the coupling of heat and mass fluxes and its influence on the effective permeability are shown. Separate relations for vapor and liquid fluxes through the porous medium are presented as functions of the temperature and the isotherm slopes. Nonstationary isothermal mass flux is also analyzed, a relaxation time for this process is identifled, and its relation to the isotherm slope is also discussed
Tracing the Dynamics of Disk Galaxies with Optical and IR Surface Photometry: Color Gradients in M99
We present optical and IR surface photometry of M99 (NGC 4254) at g, r_S i, J
and K'. We also present a K' image of M51 (NGC 5194) for comparison. Fourier
decomposition of the disk light reveals that the radial distribution of power
depends on wavelength, which in turn implies that the spiral structure traced
in the visual (i.e. young population I and dust) is different from the one
detected at 2 microns (i.e. old stellar disk). We observe radial modulation of
the power and a dependency of power with wavelength that are consistent with
modal theory of spiral structure.
A central motivation for our research is the fundamental idea of density wave
theory that the passage of a spiral density wave triggers star formation. We
have found a stellar population age gradient consistent with this scenario in a
reddening-free, red supergiant-sensitive, Q-like photometric parameter at 6 kpc
galactocentric distance across one of the arms of M99. We rule out that the
change in this parameter, Q(r_SJgi), across the arm is mainly due to dust. The
difference in Q(r_SJgi) going from the interarm regions to the arms also
indicates that arms cannot be due exclusively to crowding of stellar orbits.
We present the first measurement of Omega_p, the angular speed of the spiral
pattern, and of the location of the corotation radius, derived from the drift
velocity of the young stars away from their birth site. The measured Q(r_SJgi)
implies a star formation rate for M99 within the range of 10-20 M_odot/yr; a
disk stellar mass surface density of ~80 M_odot/pc^2; and a maximum
contribution of ~20 percent from red supergiants to the K' light in a small
region, and much smaller on average. We measure a K' arm--interarm contrast of
2-3, too high for M99 to be a truly isolated galaxy.Comment: 25 pages of uuencoded, compressed Postscript (text only). To appear
in 1 April 1996 issue of The Astrophysical Journal. Also available, together
with 2 uuencoded, compressed PostScript files with 10 figures each, at
http://astro.berkeley.edu/preprints.htm
Eccentric geophysical-observatory satellite S-49 with interpretation of the radio- beacon experiment Technical report no. 1
Evaluation of radio beacon data from satellite observation of earth exosphere - data scaling technique
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