397 research outputs found
The importance of real-world experience in student learning
A core module for the computer science and computing degree courses at the University of North London provided a vehicle for developing an innovative approach in teaching and learning. It served as a means of bridging the gap between real-world business information systems (BIS) development practice and that which is normally simulated in academia. We also show how students can be encouraged to be proactive in creating their own real-world learning experience within an academic environment
Outsourcing network management
The paper analyses the current situation in
outsourcing of IT and network management
through the literature review and examples in
industry. We have focused on trends, benefits
and risks in outsourcing network management
and made proposals to address the problems
through a carefully managed network
outsourcing relationship. The available statistics
and the the survey of six UK companies has
revealed that the upfront negotiation of service
level agreements should be one of the most
important aspects of conducting the outsourcing
of network management
On the origin of eccentricities among extrasolar planets
Most observed extrasolar planets have masses similar to, but orbits very
different from, the gas giants of our solar system. Many are much closer to
their parent stars than would have been expected and their orbits are often
rather eccentric. We show that some of these planets might have formed in
systems much like our solar system, i.e. in systems where the gas giants were
originally on orbits with a semi-major axis of several au, but where the masses
of the gas giants were all rather similar. If such a system is perturbed by
another star, strong planet-planet interactions follow, causing the ejection of
several planets while leaving those remaining on much tighter and more
eccentric orbits. The eccentricity distribution of these perturbed systems is
very similar to that of the observed extrasolar planets with semi-major axis
between 1 and 6 au.Comment: Accepted for publication in MNRAS Letter
Radio Astronomy in LSST Era
A community meeting on the topic of "Radio Astronomy in the LSST Era" was
hosted by the National Radio Astronomy Observatory in Charlottesville, VA (2013
May 6--8). The focus of the workshop was on time domain radio astronomy and sky
surveys. For the time domain, the extent to which radio and visible wavelength
observations are required to understand several classes of transients was
stressed, but there are also classes of radio transients for which no visible
wavelength counterpart is yet known, providing an opportunity for discovery.
From the LSST perspective, the LSST is expected to generate as many as 1
million alerts nightly, which will require even more selective specification
and identification of the classes and characteristics of transients that can
warrant follow up, at radio or any wavelength. The LSST will also conduct a
deep survey of the sky, producing a catalog expected to contain over 38 billion
objects in it. Deep radio wavelength sky surveys will also be conducted on a
comparable time scale, and radio and visible wavelength observations are part
of the multi-wavelength approach needed to classify and understand these
objects. Radio wavelengths are valuable because they are unaffected by dust
obscuration and, for galaxies, contain contributions both from star formation
and from active galactic nuclei. The workshop touched on several other topics,
on which there was consensus including the placement of other LSST "Deep
Drilling Fields," inter-operability of software tools, and the challenge of
filtering and exploiting the LSST data stream. There were also topics for which
there was insufficient time for full discussion or for which no consensus was
reached, which included the procedures for following up on LSST observations
and the nature for future support of researchers desiring to use LSST data
products.Comment: Conference summary, 29 pages, 1 figure; to be published in the Publ.
Astron. Soc. Pacific; full science program and presentations available at
http://science.nrao.edu/science/event/RALSST201
Neutron Rich Hypernuclei in Chiral Soliton Model
The binding energies of neutron rich strangeness hypernuclei are
estimated in the chiral soliton approach using the bound state rigid oscillator
version of the SU(3) quantization model. Additional binding of strange
hypernuclei in comparison with nonstrange neutron rich nuclei takes place at
not large values of atomic (baryon) numbers, . This effect
becomes stronger with increasing isospin of nuclides, and for "nuclear variant"
of the model with rescaled Skyrme constant . Total binding energies of
(Lambda)He-8 and recently discovered (Lambda)H-6 satisfactorily agree with
experimental data. Hypernuclei (Lambda)H-7, (Lambda)He-9 are predicted to be
bound stronger in comparison with their nonstrange analogues H-7, He-9;
hypernuclei (Lambda)Li-10, (Lambda)Li-11, (Lambda)Be-12, (Lambda)Be-13, etc.
are bound stronger in the nuclear variant of the model.Comment: 8 pages, 4 tables; amendments made, data on binding energy of
(Lambda)He-8 and references added; prepared for the conferences Quarks-2012
and HYP201
Formation, Survival, and Detectability of Planets Beyond 100 AU
Direct imaging searches have begun to detect planetary and brown dwarf
companions and to place constraints on the presence of giant planets at large
separations from their host star. This work helps to motivate such planet
searches by predicting a population of young giant planets that could be
detectable by direct imaging campaigns. Both the classical core accretion and
the gravitational instability model for planet formation are hard-pressed to
form long-period planets in situ. Here, we show that dynamical instabilities
among planetary systems that originally formed multiple giant planets much
closer to the host star could produce a population of giant planets at large
(~100 AU - 100000 AU) separations. We estimate the limits within which these
planets may survive, quantify the efficiency of gravitational scattering into
both stable and unstable wide orbits, and demonstrate that population analyses
must take into account the age of the system. We predict that planet scattering
creates a population of detectable giant planets on wide orbits that decreases
in number on timescales of ~10 Myr. We demonstrate that several members of such
populations should be detectable with current technology, quantify the
prospects for future instruments, and suggest how they could place interesting
constraints on planet formation models.Comment: 13 pages (emulateapj format), 10 figures, accepted for publication in
Ap
Stellar atmosphere parameters with MAx, a MAssive compression of x^2 for spectral fitting
MAx is a new tool to estimate parameters from stellar spectra. It is based on
the maximum likelihood method, with the likelihood compressed in a way that the
information stored in the spectral fluxes is conserved. The compressed data are
given by the size of the number of parameters, rather than by the number of
flux points. The optimum speed-up reached by the compression is the ratio of
the data set to the number of parameters. The method has been tested on a
sample of low-resolution spectra from the Sloan Extension for Galactic
Understanding and Exploration (SEGUE) survey for the estimate of metallicity,
effective temperature and surface gravity, with accuracies of 0.24 dex, 130K
and 0.5 dex, respectively. Our stellar parameters and those recovered by the
SEGUE Stellar Parameter Pipeline agree reasonably well. A small sample of
high-resolution VLT-UVES spectra were also used to test the method and the
results have been compared to a more classical approach. The speed and
multi-resolution capability of MAx combined with its performance compared with
other methods indicates that it will be a useful tool for the analysis of
upcoming spectral surveys.Comment: 17 pages, 10 figures, minor changes after the chief language editor.
A&A, in pres
Swarm-NG: a CUDA Library for Parallel n-body Integrations with focus on Simulations of Planetary Systems
We present Swarm-NG, a C++ library for the efficient direct integration of
many n-body systems using highly-parallel Graphics Processing Unit (GPU), such
as NVIDIA's Tesla T10 and M2070 GPUs. While previous studies have demonstrated
the benefit of GPUs for n-body simulations with thousands to millions of
bodies, Swarm-NG focuses on many few-body systems, e.g., thousands of systems
with 3...15 bodies each, as is typical for the study of planetary systems.
Swarm-NG parallelizes the simulation, including both the numerical integration
of the equations of motion and the evaluation of forces using NVIDIA's "Compute
Unified Device Architecture" (CUDA) on the GPU. Swarm-NG includes optimized
implementations of 4th order time-symmetrized Hermite integration and mixed
variable symplectic integration, as well as several sample codes for other
algorithms to illustrate how non-CUDA-savvy users may themselves introduce
customized integrators into the Swarm-NG framework. To optimize performance, we
analyze the effect of GPU-specific parameters on performance under double
precision.
Applications of Swarm-NG include studying the late stages of planet
formation, testing the stability of planetary systems and evaluating the
goodness-of-fit between many planetary system models and observations of
extrasolar planet host stars (e.g., radial velocity, astrometry, transit
timing). While Swarm-NG focuses on the parallel integration of many planetary
systems,the underlying integrators could be applied to a wide variety of
problems that require repeatedly integrating a set of ordinary differential
equations many times using different initial conditions and/or parameter
values.Comment: Submitted to New Astronom
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