4,244 research outputs found
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
The 1 keV to 200 keV X-ray Spectrum of NGC 2992 and NGC 3081
The Seyfert 2 galaxies NGC 2992 and NGC 3081 have been observed by INTEGRAL
and Swift. We report about the results and the comparison of the spectrum above
10 keV based on INTEGRAL IBIS/ISGRI, Swift/BAT, and BeppoSAX/PDS. A spectrum
can be extracted in the X-ray energy band ranging from 1 keV up to 200 keV.
Although NGC 2992 shows a complex spectrum below 10 keV, the hard tail observed
by various missions exhibits a slope with photon index = 2, independent on the
flux level during the observation. No cut-off is detectable up to the detection
limit around 200 keV. In addition, NGC 3081 is detected in the INTEGRAL and
Swift observation and also shows an unbroken Gamma = 1.8 spectrum up to 150
keV. These two Seyfert galaxies give further evidence that a high-energy
cut-off in the hard X-ray spectra is often located at energies E_C >> 100 keV.
In NGC 2992 a constant spectral shape is observed over a hard X-ray luminosity
variation by a factor of 11. This might indicate that the physical conditions
of the emitting hot plasma are constant, while the amount of plasma varies, due
to long-term flaring activity.Comment: 8 pages, 4 figures, accepted for publication in Ap
The Haupt Effect: Coupled rotational and dipolar relaxation of methyl groups
A theory is described for the dynamic proton dipolar polarization observed by Haupt (1972) in 4-methylpyridine following a sudden temperature change. The theory differs from that of Haupt in assuming that transitions which change the rotational quantum number of the 4-methyl group by +or-3 occur very rapidly, maintaining thermal equilibrium within each of the three subsets of rotational levels corresponding to the three methyl group proton spin symmetry species A, Ea and Eb. The difference of A and E species populations approaches the new equilibrium value slowly and exponentially, following the temperature jump, and generates dipolar polarization in the process. Transitions between Ea and Eb species lead to destruction of the polarization, whose evolution from zero due to these competing processes has the simple form C(exp(-at)-exp(-bt)). This is checked by a modified version of Haupt\u27s experiment in which the initial temperature jump is followed by a later burst of RF pulses which reduces the dipolar polarization to zero
The Haupt Effect: Coupled rotational and dipolar relaxation of methyl groups
A theory is described for the dynamic proton dipolar polarization observed by Haupt (1972) in 4-methylpyridine following a sudden temperature change. The theory differs from that of Haupt in assuming that transitions which change the rotational quantum number of the 4-methyl group by +or-3 occur very rapidly, maintaining thermal equilibrium within each of the three subsets of rotational levels corresponding to the three methyl group proton spin symmetry species A, Ea and Eb. The difference of A and E species populations approaches the new equilibrium value slowly and exponentially, following the temperature jump, and generates dipolar polarization in the process. Transitions between Ea and Eb species lead to destruction of the polarization, whose evolution from zero due to these competing processes has the simple form C(exp(-at)-exp(-bt)). This is checked by a modified version of Haupt\u27s experiment in which the initial temperature jump is followed by a later burst of RF pulses which reduces the dipolar polarization to zero
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&
Atom cooling and trapping by disorder
We demonstrate the possibility of three-dimensional cooling of neutral atoms
by illuminating them with two counterpropagating laser beams of mutually
orthogonal linear polarization, where one of the lasers is a speckle field,
i.e. a highly disordered but stationary coherent light field. This
configuration gives rise to atom cooling in the transverse plane via a Sisyphus
cooling mechanism similar to the one known in standard two-dimensional optical
lattices formed by several plane laser waves. However, striking differences
occur in the spatial diffusion coefficients as well as in local properties of
the trapped atoms.Comment: 11 figures (postscript
Chiral model for dense, hot and strange hadronic matter
An extended chiral SU(3) model is applied to the description of dense, hot
and strange hadronic matter. The degrees of freedom are the baryon octet and
decuplet and the spin-0 and spin-1 meson multiplets. The parameters of the
model are fitted to the hadron masses in vacumm, infinite nuclear matter
properties and soft pion theorems. At high densities the appearance of density
isomers cannot be ruled out and extrapolation to finite temperature exhibits a
first order phase transition at . The predicted dropping
baryon masses lead to drastically changed particle ratios compared to ideal gas
calculations.Comment: 4 pages, 3 figures, Contribution to the Proceedings of the 15th
Particles and Nuclei International Conference (PANIC 99), Uppsala, Sweden,
June 10-16, 199
A new class of semiclassical wave function uniformizations
We present a new semiclassical technique which relies on replacing
complicated classical manifold structure with simpler manifolds, which are then
evaluated by the usual semiclassical rules. Under circumstances where the
original manifold structure gives poor or useless results semiclassically the
replacement manifolds can yield remarkable accuracy. We give several working
examples to illustrate the theory presented here.Comment: 12 pages (incl. 12 figures
Whirlpool: Improving Dynamic Cache Management with Static Data Classification
Cache hierarchies are increasingly non-uniform and difficult to manage. Several techniques, such as scratchpads or reuse hints, use static information about how programs access data to manage the memory hierarchy. Static techniques are effective on regular programs, but because they set fixed policies, they are vulnerable to changes in program behavior or available cache space. Instead, most systems rely on dynamic caching policies that adapt to observed program behavior. Unfortunately, dynamic policies spend significant resources trying to learn how programs use memory, and yet they often perform worse than a static policy. We present Whirlpool, a novel approach that combines static information with dynamic policies to reap the benefits of each. Whirlpool statically classifies data into pools based on how the program uses memory. Whirlpool then uses dynamic policies to tune the cache to each pool. Hence, rather than setting policies statically, Whirlpool uses static analysis to guide dynamic policies. We present both an API that lets programmers specify pools manually and a profiling tool that discovers pools automatically in unmodified binaries.
We evaluate Whirlpool on a state-of-the-art NUCA cache. Whirlpool significantly outperforms prior approaches: on sequential programs, Whirlpool improves performance by up to 38% and reduces data movement energy by up to 53%; on parallel programs, Whirlpool improves performance by up to 67% and reduces data movement energy by up to 2.6x.National Science Foundation (U.S.) (grant CCF-1318384)National Science Foundation (U.S.) (CAREER-1452994)Samsung (Firm) (GRO award
Comparing alkylresorcinols and mammalian lignans as biomarkers of wholegrain wheat or wholegrain rye intake in a dose-response intervention trial: the Grain Mark Study
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