1,295 research outputs found
Dynamics of a solar pressure stabilized satellite
Dynamics of sun-pointing satellite in heliocentric orbit of nonzero eccentricit
Interactions of Ar(9+) and metastable Ar(8+) with a Si(100) surface at velocities near the image acceleration limit
Auger LMM spectra and preliminary model simulations of Ar(9+) and metastable
Ar(8+) ions interacting with a clean monocrystalline n-doped Si(100) surface
are presented. By varying the experimental parameters, several yet undiscovered
spectroscopic features have been observed providing valuable hints for the
development of an adequate interaction model. On our apparatus the ion beam
energy can be lowered to almost mere image charge attraction. High data
acquisition rates could still be maintained yielding an unprecedented
statistical quality of the Auger spectra.Comment: 34 pages, 11 figures, http://pikp28.uni-muenster.de/~ducree
Investeren in competenties; een onderzoek in de Greenports
Inventarisatie van de huidige en toekomstige vraag/behoeftes aan competenties bij ondernemers, managers en werknemers in het tuinbouwcluste
Magnetoelectrically driven catalytic degradation of organics
Here, we report the catalytic degradation of organic compounds by exploiting
the magnetoelectric (ME) nature of cobalt ferrite-bismuth ferrite (CFO-BFO)
core-shell nanoparticles. The combination of magnetostrictive CFO with the
multiferroic BFO gives rise to a magnetoelectric engine that purifies water
under wireless magnetic fields via advanced oxidation processes, without
involvement of any sacrificial molecules or co-catalysts. Magnetostrictive
CoFe2O4 nanoparticles are fabricated using hydrothermal synthesis, followed by
sol-gel synthesis to create the multiferroic BiFeO3 shell. We perform
theoretical modeling to study the magnetic field induced polarization on the
surface of magnetoelectric nanoparticles. The results obtained from these
simulations are consistent with the experimental findings of the piezo-force
microscopy analysis, where we observe changes in the piezoresponse of the
nanoparticles under magnetic fields. Next, we investigate the magnetoelectric
effect induced catalytic degradation of organic pollutants under AC magnetic
fields and obtained 97% removal efficiency for synthetic dyes and over 85%
removal efficiency for routinely used pharmaceuticals. Additionally, we perform
trapping experiments to elucidate the mechanism behind the magnetic field
induced catalytic degradation of organic pollutants by using scavengers for
each of the reactive species. Our results indicate that hydroxyl and superoxide
radicals are the main reactive species in the magnetoelectrically induced
catalytic degradation of organic compounds
Extended Classical Over-Barrier Model for Collisions of Highly Charged Ions with Conducting and Insulating Surfaces
We have extended the classical over-barrier model to simulate the
neutralization dynamics of highly charged ions interacting under grazing
incidence with conducting and insulating surfaces. Our calculations are based
on simple model rates for resonant and Auger transitions. We include effects
caused by the dielectric response of the target and, for insulators, localized
surface charges. Characteristic deviations regarding the charge transfer
processes from conducting and insulating targets to the ion are discussed. We
find good agreement with previously published experimental data for the image
energy gain of a variety of highly charged ions impinging on Au, Al, LiF and KI
crystals.Comment: 32 pages http://pikp28.uni-muenster.de/~ducree
Optimizing gamma-ray spectrometers for UAV-borne surveys with geophysical applications
Heavy duty unmanned aerial vehicles (UAVs) have made it possible to fly with large gamma-ray spectrometers that weigh several kilograms. Moreover, they can be purchased at an affordable price. These large UAV-borne gamma-ray detection systems are used to map the naturally occurring radionuclides 40K, 238U, 232Th. Such platforms have the advantage that they can be deployed over terrain that is difficult to access, while still maintaining a high spatial resolution. In contrast to UAV-borne radioactive pollution studies, the naturally occurring radionuclides have a much lower activity and therefore require longer integration time, slower flying speed or a larger detector, in order to effectively determine the spatial radionuclide distribution. Therefore, the question arises: what is the minimum practical detector size required to successfully map 40K, 238U and 232Th concentrations from UAV platforms. In this study an agricultural field has been mapped with three different scintillator-based gamma-ray spec-trometers: a 2000 ml, 1000 ml, and 350 ml detector. They were mounted together on the same UAV. At a flying height of 20 m and a speed of 5.6 m
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