11,491 research outputs found
Relative entropy minimizing noisy non-linear neural network to approximate stochastic processes
A method is provided for designing and training noise-driven recurrent neural
networks as models of stochastic processes. The method unifies and generalizes
two known separate modeling approaches, Echo State Networks (ESN) and Linear
Inverse Modeling (LIM), under the common principle of relative entropy
minimization. The power of the new method is demonstrated on a stochastic
approximation of the El Nino phenomenon studied in climate research
Numerical Tests of Rotational Mixing in Massive Stars with the new Population Synthesis Code BONNFIRES
We use our new population synthesis code BONNFIRES to test how surface
abundances predicted by rotating stellar models depend on the numerical
treatment of rotational mixing, such as spatial resolution, temporal resolution
and computation of mean molecular weight gradients. We find that even with
identical numerical prescriptions for calculating the rotational mixing
coefficients in the diffusion equation, different timesteps lead to a deviation
of the coefficients and hence surface abundances. We find the surface
abundances vary by 10-100% between the model sequences with short timestep of
0.001Myr to model sequences with longer timesteps. Model sequences with
stronger surface nitrogen enrichment also have longer main-sequence lifetimes
because more hydrogen is mixed to the burning cores. The deviations in
main-sequence lifetimes can be as large as 20%. Mathematically speaking, no
numerical scheme can give a perfect solution unless infinitesimally small
timesteps are used. However, we find that the surface abundances eventually
converge within 10% between modelling sequences with sufficiently small
timesteps below 0.1Myr. The efficiency of rotational mixing depends on the
implemented numerical scheme and critically on the computation of the mean
molecular weight gradient. A smoothing function for the mean molecular weight
gradient results in stronger rotational mixing. If the discretization scheme or
the computational recipe for calculating the mean molecular weight gradient is
altered, re-calibration of mixing parameters may be required to fit
observations. If we are to properly understand the fundamental physics of
rotation in stars, it is crucial that we minimize the uncertainty introduced
into stellar evolution models when numerically approximating rotational mixing
processes.Comment: 8 pages, 6 figures, accepted by A&
Thermodes and Theories
This brief outline reviews some of the important studies done with various types of thermodes employed for heating or cooling loci in the brain and discusses some sources of the findings relevant to our understanding of temperature regulation in mammals
MUNICIPAL CORPORATIONS-ZONING-RIGHT OF GRANTEE TO ACT ON VARIANCE ISSUED TO HIS GRANTOR
A zoning ordinance prohibited the erection of private garages within twenty feet of the street line. Because of the peculiar shape of the lot in question, a variance was granted to the then owner permitting the building of a garage closer to the street line. However, before the garage was built, the land was sold to the present owner who obtained a building permit and began construction. Plaintiffs, owners of the adjoining lot, objected to the granting of the permit and appealed to the zoning board of review which denied their appeal. On certiorari, held, present owner might act on the variance granted to his predecessor. Mastrati v. Strauss, (R.I. 1949) 67 A. (2d) 29
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