10,035 research outputs found
Nonextensive aspects of self-organized scale-free gas-like networks
We explore the possibility to interpret as a 'gas' the dynamical
self-organized scale-free network recently introduced by Kim et al (2005). The
role of 'momentum' of individual nodes is played by the degree of the node, the
'configuration space' (metric defining distance between nodes) being determined
by the dynamically evolving adjacency matrix. In a constant-size network
process, 'inelastic' interactions occur between pairs of nodes, which are
realized by the merger of a pair of two nodes into one. The resulting node
possesses the union of all links of the previously separate nodes. We consider
chemostat conditions, i.e., for each merger there will be a newly created node
which is then linked to the existing network randomly. We also introduce an
interaction 'potential' (node-merging probability) which decays with distance
d_ij as 1/d_ij^alpha; alpha >= 0). We numerically exhibit that this system
exhibits nonextensive statistics in the degree distribution, and calculate how
the entropic index q depends on alpha. The particular cases alpha=0 and alpha
to infinity recover the two models introduced by Kim et al.Comment: 7 pages, 5 figure
Controlling a quantum system via its boundary conditions
We numerically study a particle in a box with moving walls. In the case where the walls are oscillating sinusoidally with a small amplitude, we show that states up to the fourth state can be populated with more than 80 percent population, while higher lying states can also be selectively excited. This work introduces a way of controlling quantum systems which does not rely on (dipole) selection rules
The petrology, mineralogy and geochemistry of the large Fen Carbonatite Complex (Norway) REE-Nb resource
Near-infrared observations of water-ice in OH/IR stars
A search for the near-infrared water-ice absorption band was made in a number
of very red OH/IR stars which are known to exhibit the 10um silicate
absorption. As a by-product, accurate positions of these highly reddened
objects are obtained. We derived a dust mass loss rate for each object by
modelling the spectral energy distribution and the gas mass loss rate by
solving the equation of motion for the dust drag wind. The derived mass loss
rates show a strong correlation with the silicate optical depth as well as that
of the water-ice. The stars have a high mass loss rate (> 1.0E-4 Msun/yr) with
an average gas-to-dust mass ratio of 110. In objects which show the 3.1um
water-ice absorption, the near-IR slope is much steeper than those with no
water-ice. Comparison between our calculated mass loss rates and those derived
from OH and CO observations indicates that these stars have recently increased
their mass loss rates.Comment: 10 pages, 6 figures : accepted for publication in A&
Non-Equilibrium Surface Tension of the Vapour-Liquid Interface of Active Lennard-Jones Particles
We study a three-dimensional system of self-propelled Brownian particles
interacting via the Lennard-Jones potential. Using Brownian Dynamics
simulations in an elongated simulation box, we investigate the steady states of
vapour-liquid phase coexistence of active Lennard-Jones particles with planar
interfaces. We measure the normal and tangential components of the pressure
tensor along the direction perpendicular to the interface and verify mechanical
equilibrium of the two coexisting phases. In addition, we determine the
non-equilibrium interfacial tension by integrating the difference of the normal
and tangential component of the pressure tensor, and show that the surface
tension as a function of strength of particle attractions is well-fitted by
simple power laws. Finally, we measure the interfacial stiffness using
capillary wave theory and the equipartition theorem, and find a simple linear
relation between surface tension and interfacial stiffness with a
proportionality constant characterized by an effective temperature.Comment: 12 pages, 5 figures (Corrected typos and References
Het veranderen van opvattingen van chemiedocenten door partici-patie in een ontwikkelnetwerk
Opvattingen over leren en onderwijzen spelen bij het handelen van docenten een grote rol. Omdat opvattingen diep geworteld zijn in de ervaringen van docenten blijken ze moeilijk te veranderen. Wil een curriculumverandering succesvol zijn dan moeten de opvattingen van docenten erbij worden betrokken.\ud
Het invoeren van een vernieuwing kan gezien worden als een leerproces van docenten, waarin aandacht is voor vakinhoud en didactiek maar ook voor opvattingen. Een van de manieren om dit leerproces vorm en inhoud te geven is door het opzetten van netwerken van docenten. De netwerken ontwikkelen leermaterialen voor leerlingen en de deelnemers gebruiken deze materialen in hun onderwijs. Het netwerk kan worden gezien als een leergemeenschap.\ud
De vraag in dit onderzoek is hoe de opvattingen van docenten door participatie in een ontwikkelnetwerk veranderen. De opvattingen van de docenten zijn daarvoor op drie momenten tijdens het ontwikkelproces vastgelegd, waarbij gebruik gemaakt is van meerdere instrumenten
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