A pseudo random-access synchronous meteorological satellite system

Communications satellite system uses pseudo-random time frequency multiplexing technique for extracting real-time meteorological data from great number of isolated weather stations /data collection platforms/ situated randomly throughout the world

Explosions and Outflows during Galaxy Formation

We consider an explosion at the center of a halo which forms at the intersection of filaments inside a cosmological pancake, a convenient test-bed model for galaxy formation. ASPH/P3M simulations reveal that such explosions are anisotropic. The energy and metals are channeled into the low density regions, away from the pancake. The pancake remains essentially undisturbed, even if the explosion is strong enough to blow away all the gas located inside the halo and reheat the IGM surrounding the pancake. Infall quickly replenishes this ejected gas and gradually restores the gas fraction as the halo continues to grow. Estimates of the collapse epoch and SN energy-release for galaxies of different mass in the CDM model can relate these results to scale-dependent questions of blow-out and blow-away and their implication for early IGM heating and metal enrichment and the creation of gas-poor dwarf galaxies.Comment: To appear in "The 20th Texas Symposium on Relativistic Astrophysics", eds. H. Martel and J.C. Wheeler, AIP, in press (2001) (3 pages, 2 figures

A Convenient Set of Comoving Cosmological Variables and Their Application

We present a set of cosmological variables, called "supercomoving variables," which are particularly useful for describing the gas dynamics of cosmic structure formation. For ideal gas with gamma=5/3, the supercomoving position, velocity, density, temperature, and pressure are constant in time in a uniform, isotropic, adiabatically expanding universe. Expressed in terms of these supercomoving variables, the cosmological fluid conservation equations and the Poisson equation closely resemble their noncosmological counterparts. This makes it possible to generalize noncosmological results and techniques to cosmological problems, for a wide range of cosmological models. These variables were initially introduced by Shandarin for matter-dominated models only. We generalize supercomoving variables to models with a uniform component corresponding to a nonzero cosmological constant, domain walls, cosmic strings, a nonclumping form of nonrelativistic matter (e.g. massive nettrinos), or radiation. Each model is characterized by the value of the density parameter Omega0 of the nonrelativistic matter component in which density fluctuation is possible, and the density parameter OmegaX of the additional, nonclumping component. For each type of nonclumping background, we identify FAMILIES within which different values of Omega0 and OmegaX lead to fluid equations and solutions in supercomoving variables which are independent of Omega0 and OmegaX. We also include the effects of heating, radiative cooling, thermal conduction, viscosity, and magnetic fields. As an illustration, we describe 3 familiar cosmological problems in supercomoving variables: the growth of linear density fluctuations, the nonlinear collapse of a 1D plane-wave density fluctuation leading to pancake formation, and the Zel'dovich approximation.Comment: 38 pages (AAS latex) + 2 figures (postscript) combined in one gzip-ed tar file. Identical to original posted version, except for addition of 2 references. Monthly Notices of the R.A.S., in pres