4,505 research outputs found
Subminiature micropower digital recorder
High-density digital data, collected periodically or randomly from multiplicity of sensors, are recorded by subminiature recorder. Magnetic recording head is energized with suitable pulsatile signals to reverse polarization on magnetically-sensitive tape while tape is immobilized at recording head. Prior to next recording, set tape so new area of tape is at recording head
Probability laws related to the Jacobi theta and Riemann zeta function and Brownian excursions
This paper reviews known results which connect Riemann's integral
representations of his zeta function, involving Jacobi's theta function and its
derivatives, to some particular probability laws governing sums of independent
exponential variables. These laws are related to one-dimensional Brownian
motion and to higher dimensional Bessel processes. We present some
characterizations of these probability laws, and some approximations of
Riemann's zeta function which are related to these laws.Comment: LaTeX; 40 pages; review pape
EuropeanaTravel
EuropeanaTravel is an EU-funded initiative to digitise cultural heritage treasures on the themes of
travel, tourism, trade routes and exploration from Europe’s national and leading research libraries
Growth of the Brownian forest
Trees in Brownian excursions have been studied since the late 1980s. Forests
in excursions of Brownian motion above its past minimum are a natural extension
of this notion. In this paper we study a forest-valued Markov process which
describes the growth of the Brownian forest. The key result is a composition
rule for binary Galton--Watson forests with i.i.d. exponential branch lengths.
We give elementary proofs of this composition rule and explain how it is
intimately linked with Williams' decomposition for Brownian motion with drift.Comment: Published at http://dx.doi.org/10.1214/009117905000000422 in the
Annals of Probability (http://www.imstat.org/aop/) by the Institute of
Mathematical Statistics (http://www.imstat.org
Optical properties of silicon carbide for astrophysical applications I. New laboratory infrared reflectance spectra and optical constants
Silicon Carbide (SiC) optical constants are fundamental inputs for radiative
transfer models of astrophysical dust environments. However, previously
published values contain errors and do not adequately represent the bulk
physical properties of the cubic (beta) SiC polytype usually found around
carbon stars. We provide new, uncompromised optical constants for beta- and
alpha-SiC derived from single-crystal reflectance spectra and investigate
quantitatively whether there is any difference between alpha- and beta-SiC that
can be seen in infrared spectra and optical functions.
Previous optical constants for SiC do not reflect the true bulk properties,
and they are only valid for a narrow grain size range. The new optical
constants presented here will allow narrow constraints to be placed on the
grain size and shape distribution that dominate in astrophysical environments.
In addition, our calculated absorption coefficients are much higher than
laboratory measurements, which has an impact on the use of previous data to
constrain abundances of these dust grains.Comment: 12 pages; 10 figures; laboratory optical constants available from
CDS. Accepted by Astronomy & Astrophysic
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