102 research outputs found
Prediction of huge X-ray Faraday rotation at the Gd N_4,5 threshold
X-ray absorption spectra in a wide energy range around the 4d-4f excitation
threshold of Gd were recorded by total electron yield from in-plane magnetized
Gd metal films. Matching the experimental spectra to tabulated absorption data
reveals unprecedented short light absorption lengths down to 3 nm. The
associated real parts of the refractive index for circularly polarized light
propagating parallel or antiparallel to the Gd magnetization, determined
through the Kramers-Kronig transformation, correspond to a magneto-optical
Faraday rotation of 0.7 degrees per atomic layer. This finding shall allow the
study of magnetic structure and magnetization dynamics of lanthanide elements
in nanosize systems and dilute alloys.Comment: 4 pages, 2 figures, final version resubmitted to Phys. Rev. B, Brief
Reports. Minor change
Powder Bed Layer Characteristics: The Overseen First-Order Process Input
A discrete element powder model is used in conjunction with a finite volume melting model on the first layer of a powder bed selective laser melting process
Dynamic Acoustic Control of Individual Optically Active Quantum Dot-like Emission Centers in Heterostructure Nanowires
We probe and control the optical properties of emission centers forming in
radial het- erostructure GaAs-Al0.3Ga0.7As nanowires and show that these
emitters, located in Al0.3Ga0.7As layers, can exhibit quantum-dot like
characteristics. We employ a radio frequency surface acoustic wave to
dynamically control their emission energy and occupancy state on a nanosec- ond
timescale. In the spectral oscillations we identify unambiguous signatures
arising from both the mechanical and electrical component of the surface
acoustic wave. In addition, differ- ent emission lines of a single quantum dot
exhibit pronounced anti-correlated intensity oscilla- tions during the acoustic
cycle. These arise from a dynamically triggered carrier extraction out of the
quantum dot to a continuum in the radial heterostructure. Using finite element
modeling and Wentzel-Kramers-Brillouin theory we identify quantum tunneling as
the underlying mech- anism. These simulation results quantitatively reproduce
the observed switching and show that in our systems these quantum dots are
spatially separated from the continuum by > 10.5 nm.Comment: This document is the unedited Author's version of a Submitted Work
that was subsequently accepted for publication in Nano Letters, copyright
\c{copyright} American Chemical Society after peer review. To access the
final edited and published work see
http://pubs.acs.org/doi/abs/10.1021/nl404043
Real-Time Monitoring of Powder Mixing Dynamics with Spectroscopic PAT-Tools
The aim of Process Analytical Technology (PAT) is to gain deeper insight in pharmaceutical manufacturing processes, [...
Evaluation of API-Distribution and Coating Thickness by NIR Spectroscopy and Raman Chemical Mapping
Spray coating is an important unit operation in the pharmaceutical industry. [...
Coupling ground penetrating radar and fluid flow modeling for oilfield monitoring applications
The recent introduction of smart well technology allows for new geophysical monitoring opportunities. Smart wells, which allow zonal production control, combined with monitoring techniques capable of capturing the arrival of undesired fluids, have the potential to significantly increase the oil recovery. We consider borehole radar as a valuable technology for monitoring of the near-well region. By coupling a drainage process of a bottom water-drive reservoir with electromagnetic simulations, we find that radar sensors located in the production well can successfully map the fluid saturation evolution. In low-conductivity reservoirs (<0.02 S/m), a system performance above 80 dB is necessary to record reflections in the range of 10 m. Higher conductivity values strongly reduce the radar investigation depth. Despite the technical challenges to implement a permanent down-hole radar system, the potential semi-continuous acquisition would make 4D ground-penetrating radar a promising technology in capturing the near-well fluid dynamics. Suitable environments are bottom water-drive reservoirs with thin oil layer and heavy oil reservoirs exploited by steam-assisted gravity drainage processes.Geoscience & EngineeringCivil Engineering and Geoscience
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