17,644 research outputs found
Explicit towers of Drinfeld modular curves
We give explicit equations for the simplest towers of Drinfeld modular curves
over any finite field, and observe that they coincide with the asymptotically
optimal towers of curves constructed by Garcia and Stichtenoth.Comment: 10 pages. For mini-symposium on "curves over finite fields and codes"
at the 3rd European Congress in Barcelona 7/2000 Revised to correct minor
typographical and grammatical error
A modular approach for assessing the effect of radiation environments on man in operational systems. The radiobiological vulnerability of man during task performance
A modular approach for assessing the affects of radiation environments on man in operational systems has been developed. The feasibility of the model has been proved and the practicality has been assessed. It has been applied to one operational system to date and information obtained has been submitted to systems analysts and mission planners for the assessment of man's vulnerability and impact on systems survivability. In addition, the model has been developed so that the radiobiological data can be input to a sophisticated man-machine interface model to properly relate the radiobiological stress with other mission stresses including the effects of a degraded system
Transitive and self-dual codes attaining the Tsfasman-Vladut-Zink bound
A major problem in coding theory is the question of whether the class of cyclic codes is asymptotically good. In this correspondence-as a generalization of cyclic codes-the notion of transitive codes is introduced (see Definition 1.4 in Section I), and it is shown that the class of transitive codes is asymptotically good. Even more, transitive codes attain the Tsfasman-Vladut-Zink bound over F-q, for all squares q = l(2). It is also shown that self-orthogonal and self-dual codes attain the Tsfasman-Vladut-Zink bound, thus improving previous results about self-dual codes attaining the Gilbert-Varshamov bound. The main tool is a new asymptotically optimal tower E-0 subset of E-1 subset of E-2 subset of center dot center dot center dot of function fields over F-q (with q = l(2)), where all extensions E-n/E-0 are Galois
A GPU-based survey for millisecond radio transients using ARTEMIS
Astrophysical radio transients are excellent probes of extreme physical
processes originating from compact sources within our Galaxy and beyond. Radio
frequency signals emitted from these objects provide a means to study the
intervening medium through which they travel. Next generation radio telescopes
are designed to explore the vast unexplored parameter space of high time
resolution astronomy, but require High Performance Computing (HPC) solutions to
process the enormous volumes of data that are produced by these telescopes. We
have developed a combined software /hardware solution (code named ARTEMIS) for
real-time searches for millisecond radio transients, which uses GPU technology
to remove interstellar dispersion and detect millisecond radio bursts from
astronomical sources in real-time. Here we present an introduction to ARTEMIS.
We give a brief overview of the software pipeline, then focus specifically on
the intricacies of performing incoherent de-dispersion. We present results from
two brute-force algorithms. The first is a GPU based algorithm, designed to
exploit the L1 cache of the NVIDIA Fermi GPU. Our second algorithm is CPU based
and exploits the new AVX units in Intel Sandy Bridge CPUs.Comment: 4 pages, 7 figures. To appear in the proceedings of ADASS XXI, ed.
P.Ballester and D.Egret, ASP Conf. Se
HYPERION: An open-source parallelized three-dimensional dust continuum radiative transfer code
HYPERION is a new three-dimensional dust continuum Monte-Carlo radiative
transfer code that is designed to be as generic as possible, allowing radiative
transfer to be computed through a variety of three-dimensional grids. The main
part of the code is problem-independent, and only requires an arbitrary
three-dimensional density structure, dust properties, the position and
properties of the illuminating sources, and parameters controlling the running
and output of the code. HYPERION is parallelized, and is shown to scale well to
thousands of processes. Two common benchmark models for protoplanetary disks
were computed, and the results are found to be in excellent agreement with
those from other codes. Finally, to demonstrate the capabilities of the code,
dust temperatures, SEDs, and synthetic multi-wavelength images were computed
for a dynamical simulation of a low-mass star formation region. HYPERION is
being actively developed to include new features, and is publicly available
(http://www.hyperion-rt.org).Comment: Accepted for publication in Astronomy & Astrophysics. HYPERION is
being prepared for release at the start of 2012, but you can already sign up
to the mailing list at http://www.hyperion-rt.org to be informed once it is
available for downloa
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