4,656 research outputs found
Water rights, conflict and policy: Proceedings of a workshop held in Kathmandu, Nepal, January 22-24, 1996
IrrigationIrrigation managementWater rightsWater lawConflictFarmers' associations
The role of learning in complex problem solving using MicroDYN
It is still an open question which cognitive and non-cognitive personality traits are useful for describing and explaining behaviour and performance in complex problems. During complex problem solving (CPS), problem solvers have to interact with the task in a way in which learning ability might be beneficial for successful task completion. By investigating the relationship between learning ability and CPS, while accounting for interactions between complex system characteristics and person characteristics, this paper aims to understand the role of learning processes in CPS more closely. In a sample of N = 241 participants, we performed a preregistered analysis to investigate the relationship between knowledge acquisition performance in a CPS test (MicroDYN) and learning test performance (ADAFI) with a multilevel modeling approach across 10 CPS systems with various characteristics. In line with our expectations, we replicated previous findings on a relationship between learning test and MicroDYN performance and found this relationship to be more pronounced in systems with (vs. without) autonomous changes. Further system and person characteristics also showed effects as expected, with better performance in systems with lower complexity, with more experience with the task, and with more strategic exploration behaviour. Our results provide further evidence for the notion that learning is an important component for the successful completion of CPS tasks
Long-term variability of AGN at hard X-rays
Variability at all observed wavelengths is a distinctive property of AGN.
Hard X-rays provide us with a view of the innermost regions of AGN, mostly
unbiased by absorption along the line of sight. Swift/BAT offers the unique
opportunity to follow, on time scales of days to years and with a regular
sampling, the 14-195 keV emission of the largest AGN sample available up to
date for this kind of investigation. We study the amplitude of the variations,
and their dependence on sub-class and on energy, for a sample of 110 radio
quiet and radio loud AGN selected from the BAT 58-month survey. About 80% of
the AGN in the sample are found to exhibit significant variability on months to
years time scales, radio loud sources being the most variable. The amplitude of
the variations and their energy dependence are incompatible with variability
being driven at hard X-rays by changes of the absorption column density. In
general, the variations in the 14-24 and 35-100 keV bands are well correlated,
suggesting a common origin of the variability across the BAT energy band.
However, radio quiet AGN display on average 10% larger variations at 14-24 keV
than at 35-100 keV and a softer-when-brighter behavior for most of the Seyfert
galaxies with detectable spectral variability on month time scale. In addition,
sources with harder spectra are found to be more variable than softer ones.
These properties are generally consistent with a variable power law continuum,
in flux and shape, pivoting at energies >~ 50 keV, to which a constant
reflection component is superposed. When the same time scales are considered,
the timing properties of AGN at hard X-rays are comparable to those at lower
energies, with at least some of the differences possibly ascribable to
components contributing differently in the two energy domains (e.g.,
reflection, absorption).Comment: 17 pages, 11 figures, accepted for publication in A&
In-flight calibration of the INTEGRAL/IBIS mask
Since the release of the INTEGRAL Offline Scientific Analysis (OSA) software
version 9.0, the ghost busters module has been introduced in the INTEGRAL/IBIS
imaging procedure, leading to an improvement of the sensitivity around bright
sources up to a factor of 7. This module excludes in the deconvolution process
the IBIS/ISGRI detector pixels corresponding to the projection of a bright
source through mask elements affected by some defects. These defects are most
likely associated with screws and glue fixing the IBIS mask to its support.
Following these major improvements introduced in OSA 9, a second order
correction is still required to further remove the residual noise, now at a
level of 0.2-1% of the brightest source in the field of view. In order to
improve our knowledge of the IBIS mask transparency, a calibration campaign has
been carried out during 2010-2012. We present here the analysis of these data,
together with archival observations of the Crab and Cyg X-1, that allowed us to
build a composite image of the mask defects and to investigate the origin of
the residual noise in the IBIS/ISGRI images. Thanks to this study, we were able
to point out a simple modification of the ISGRI analysis software that allows
to significantly improve the quality of the images in which bright sources are
detected at the edge of the field of view. Moreover, a refinement of the area
excluded by the ghost busters module is considered, and preliminary results
show improvements to be further tested. Finally, this study indicates further
directions to be investigated for improving the ISGRI sensitivity, such as
taking into account the thickness of the screws in the mask model or studying
the possible discrepancy between the modeled and actual mask element bridges.Comment: accepted for publication in the proceedings of "An INTEGRAL view of
the high-energy sky (the first 10 years)" 9th INTEGRAL Workshop, October
15-19, 2012, Paris, France, in Proceedings of Science (INTEGRAL 2012), Eds.
A. Goldwurm, F. Lebrun and C. Winkler,
(http://pos.sissa.it/cgi-bin/reader/conf.cgi?confid=176), id 154; 6 pages, 4
figures, see the PoS website for the full resolution versio
- âŠ