12,856 research outputs found
Implementing a Business Process Management System Using ADEPT: A Real-World Case Study
This article describes how the agent-based design of ADEPT (advanced decision environment for processed tasks) and implementation philosophy was used to prototype a business process management system for a real-world application. The application illustrated is based on the British Telecom (BT) business process of providing a quote to a customer for installing a network to deliver a specified type of telecommunication service. Particular emphasis is placed upon the techniques developed for specifying services, allowing heterogeneous information models to interoperate, allowing rich and flexible interagent negotiation to occur, and on the issues related to interfacing agent-based systems and humans. This article builds upon the companion article (Applied Artificial Intelligence Vol.14, no 2, pgs. 145-189) that provides details of the rationale and design of the ADEPT technology deployed in this application
An XMM-Newton observation of the Narrow Line Seyfert 1 Galaxy, Markarian 896
XMM-Newton observations of the NLS1 Markarian 896 are presented. Over the
2-10 keV band, an iron emission line, close to 6.4 keV, is seen. The line is
just resolved and has an equivalent width of ~170 eV. The broad-band spectrum
is well modelled by a power law slope of gamma ~ 2.03, together with two
blackbody components to fit the soft X-ray excess. Using a more physical
two-temperature Comptonisation model, a good fit is obtained for an input
photon distribution of kT ~ 60eV and Comptonising electron temperatures of ~0.3
and 200 keV. The soft excess cannot be explained purely through the
reprocessing of a hard X-ray continuum by an ionised disc reflector.Comment: 6 pages, 4 figures, accepted by MNRA
Resolving the large scale spectral variability of the luminous Seyfert 1 galaxy 1H 0419-577: Evidence for a new emission component and absorption by cold dense matter
An XMM-Newton observation of the luminous Seyfert 1 galaxy 1H 0419-577 in
September 2002, when the source was in an extreme low-flux state, found a very
hard X-ray spectrum at 1-10 keV with a strong soft excess below ~1 keV.
Comparison with an earlier XMM-Newton observation when 1H 0419-577 was `X-ray
bright' indicated the dominant spectral variability was due to a steep power
law or cool Comptonised thermal emission. Four further XMM-Newton observations,
with 1H 0419-577 in intermediate flux states, now support that conclusion,
while we also find the variable emission component in intermediate state
difference spectra to be strongly modified by absorption in low ionisation
matter. The variable `soft excess' then appears to be an artefact of absorption
of the underlying continuum while the `core' soft emission can be attributed to
recombination in an extended region of more highly ionised gas. We note the
wider implications of finding substantial cold dense matter overlying (or
embedded in) the X-ray continuum source in a luminous Seyfert 1 galaxy.Comment: 34 pages, 15 figures, submitted to Ap
A universal GRB photon energy-peak luminosity relation
The energetics and emission mechanism of GRBs are not well understood. Here
we demonstrate that the instantaneous peak flux or equivalent isotropic peak
luminosity, L_iso ergs s^-1, rather than the integrated fluence or equivalent
isotropic energy, E_iso ergs, underpins the known high-energy correlations.
Using new spectral/temporal parameters calculated for 101 bursts with redshifts
from BATSE, BeppoSAX, HETE-II and Swift we describe a parameter space which
characterises the apparently diverse properties of the prompt emission. We show
that a source frame characteristic-photon-energy/peak luminosity ratio, K_z,
can be constructed which is constant within a factor of 2 for all bursts
whatever their duration, spectrum, luminosity and the instrumentation used to
detect them. The new parameterization embodies the Amati relation but indicates
that some correlation between E_peak and E_iso follows as a direct mathematical
inference from the Band function and that a simple transformation of E_iso to
L_iso yields a universal high energy correlation for GRBs. The existence of K_z
indicates that the mechanism responsible for the prompt emission from all GRBs
is probably predominantly thermal.Comment: Submitted to Ap
A-STAR: The All-Sky Transient Astrophysics Reporter
The small mission A-STAR (All-Sky Transient Astrophysics Reporter) aims to
locate the X-ray counterparts to ALIGO and other gravitational wave detector
sources, to study the poorly-understood low luminosity gamma-ray bursts, and to
find a wide variety of transient high-energy source types, A-STAR will survey
the entire available sky twice per 24 hours. The payload consists of a coded
mask instrument, Owl, operating in the novel low energy band 4-150 keV, and a
sensitive wide-field focussing soft X-ray instrument, Lobster, working over
0.15-5 keV. A-STAR will trigger on ~100 GRBs/yr, rapidly distributing their
locations.Comment: Accepted for the European Astronomical Society Publications Series:
Proceedings of the Fall 2012 Gamma-Ray Burst Symposium held in Marbella,
Spain, 8-12 Oct 201
Violation of the Leggett-Garg inequality with weak measurements of photons
By weakly measuring the polarization of a photon between two strong
polarization measurements, we experimentally investigate the correlation
between the appearance of anomalous values in quantum weak measurements, and
the violation of realism and non-intrusiveness of measurements. A quantitative
formulation of the latter concept is expressed in terms of a Leggett-Garg
inequality for the outcomes of subsequent measurements of an individual quantum
system. We experimentally violate the Leggett-Garg inequality for several
measurement strengths. Furthermore, we experimentally demonstrate that there is
a one-to-one correlation between achieving strange weak values and violating
the Leggett-Garg inequality.Comment: 5 pages, 4 figure
Fe K emission and absorption features in XMM-Newton spectra of Mkn 766 - evidence for reprocessing in flare ejecta
We report on the analysis of a long XMM-Newton EPIC observation in 2001 May
of the Narrow Line Seyfert 1 galaxy Mkn 766. The 3-11 keV spectrum exhibits a
moderately steep power law continuum, with a broad emission line at ~6.7 keV,
probably blended with a narrow line at ~6.4 keV, and a broad absorption trough
above ~8.7 keV. We identify both broad spectral features with reprocessing in
He-like Fe. An earlier XMM-Newton observation of Mkn 766 in 2000 May, when the
source was a factor ~2 fainter, shows a similar broad emission line, but with a
slightly flatter power law and absorption at a lower energy. In neither
observation do we find a requirement for the previously reported broad 'red
wing' to the line and hence of reflection from the innermost accretion disc.
More detailed examination of the longer XMM-Newton observation reveals evidence
for rapid spectral variability in the Fe K band, apparently linked with the
occurrence of X-ray 'flares'. A reduction in the emission line strength and
increased high energy absorption during the X-ray flaring suggests that these
transient effects are due to highly ionised ejecta associated with the flares.
Simple scaling from the flare avalanche model proposed for the luminous QSO PDS
456 (Reeves etal. 2002) confirms the feasibility of coherent flaring being the
cause of the strong peaks seen in the X-ray light curve of \mkn.Comment: 9 pages, 11 figures, submitted to MNRA
A Construction of Solutions to Reflection Equations for Interaction-Round-a-Face Models
We present a procedure in which known solutions to reflection equations for
interaction-round-a-face lattice models are used to construct new solutions.
The procedure is particularly well-suited to models which have a known fusion
hierarchy and which are based on graphs containing a node of valency . Among
such models are the Andrews-Baxter-Forrester models, for which we construct
reflection equation solutions for fixed and free boundary conditions.Comment: 9 pages, LaTe
Boson Sampling from Gaussian States
We pose a generalized Boson Sampling problem. Strong evidence exists that
such a problem becomes intractable on a classical computer as a function of the
number of Bosons. We describe a quantum optical processor that can solve this
problem efficiently based on Gaussian input states, a linear optical network
and non-adaptive photon counting measurements. All the elements required to
build such a processor currently exist. The demonstration of such a device
would provide the first empirical evidence that quantum computers can indeed
outperform classical computers and could lead to applications
- …