510 research outputs found
Effects of Depression on Nonconscious Perception: Affective Judgment and Affective Priming
Clinical Psycholog
Sense-making strategies in explorative intelligence analysis of network evolutions
Visualising how social networks evolve is important in intelligence analysis in order to detect and monitor issues, such as emerging crime patterns or rapidly growing groups of offenders. It remains an open research question how this type of information should be presented for visual exploration. To get a sense of how users work with different types of visualisations, we evaluate a matrix and a node-link diagram in a controlled thinking aloud study. We describe the sense-making strategies that users adopted during explorative and realistic tasks. Thereby, we focus on the user behaviour in switching between the two visualisations and propose a set of nine strategies. Based on a qualitative and quantitative content analysis we show which visualisation supports which strategy better. We find that the two visualisations clearly support intelligence tasks and that for some tasks the combined use is more advantageous than the use of an individual visualisation
Exploiting the sensitivity of two satellite cloud height retrievals to cloud vertical distribution
This work presents a study on the sensitivity of two satellite cloud height
retrievals to cloud vertical distribution. The difference in sensitivity is
exploited by relating the difference in the retrieved cloud heights to cloud
vertical extent. The two cloud height retrievals, performed within the Freie
Universität Berlin AATSR MERIS Cloud (FAME-C) algorithm, are based on
independent measurements and different retrieval techniques. First, cloud top
temperature (CTT) is retrieved from Advanced Along Track Scanning Radiometer
(AATSR) measurements in the thermal infrared. Second, cloud top pressure (CTP)
is retrieved from Medium Resolution Imaging Spectrometer (MERIS) measurements
in the oxygen-A absorption band. Both CTT and CTP are converted to cloud top
height (CTH) using atmospheric profiles from a numerical weather prediction
model. A sensitivity study using radiative transfer simulations in the near-
infrared and thermal infrared were performed to demonstrate the larger impact
of the assumed cloud vertical extinction profile on MERIS than on AATSR top-
of-atmosphere measurements. The difference in retrieved CTH (ΔCTH) from AATSR
and MERIS are related to cloud vertical extent (CVE) as observed by ground-
based lidar and radar at three ARM sites. To increase the impact of the cloud
vertical extinction profile on the MERIS-CTP retrievals, single-layer and
geometrically thin clouds are assumed in the forward model. The results of the
comparison to the ground-based observations were separated into single-layer
and multi-layer cloud cases. Analogous to previous findings, the MERIS-CTP
retrievals appear to be close to pressure levels in the middle of the cloud.
Assuming a linear relationship, the ΔCTH multiplied by 2.5 gives an estimate
on the CVE for single-layer clouds. The relationship is weaker for multi-layer
clouds. Due to large variations of cloud vertical extinction profiles
occurring in nature, a quantitative estimate of the cloud vertical extent is
accompanied with large uncertainties. Yet, estimates of the CVE can contribute
to the characterization of a cloudy scene. To demonstrate the plausibility of
the approach, an estimate of the CVE was applied to a case study. In light of
the follow-up mission Sentinel-3 with AATSR and MERIS like instruments, Sea
and Land Surface Temperature Radiometer (SLSTR) and (Ocean and Land Colour
Instrument) OLCI, respectively, for which the FAME-C algorithm can be easily
adapted, a more accurate estimate of the CVE can be expected. OLCI will have
three channels in the oxygen-A absorption band, thus providing more pieces of
information on the cloud vertical extinction profile
An Artificially Lattice Mismatched Graphene/Metal Interface: Graphene/Ni/Ir(111)
We report the structural and electronic properties of an artificial
graphene/Ni(111) system obtained by the intercalation of a monoatomic layer of
Ni in graphene/Ir(111). Upon intercalation, Ni grows epitaxially on Ir(111),
resulting in a lattice mismatched graphene/Ni system. By performing Scanning
Tunneling Microscopy (STM) measurements and Density Functional Theory (DFT)
calculations, we show that the intercalated Ni layer leads to a pronounced
buckling of the graphene film. At the same time an enhanced interaction is
measured by Angle-Resolved Photo-Emission Spectroscopy (ARPES), showing a clear
transition from a nearly-undisturbed to a strongly-hybridized graphene
-band. A comparison of the intercalation-like graphene system with flat
graphene on bulk Ni(111), and mildly corrugated graphene on Ir(111), allows to
disentangle the two key properties which lead to the observed increased
interaction, namely lattice matching and electronic interaction. Although the
latter determines the strength of the hybridization, we find an important
influence of the local carbon configuration resulting from the lattice
mismatch.Comment: 9 pages, 3 figures, Accepted for publication in Phys. Rev.
Vortex-forced-oscillations of thin flexible plates
Fluid-structure interaction of a slender flexible cantilevered-element and
vortices in an otherwise steady flow is considered here by investigating the
dynamics of thin low-density polyethylene sheets subject to periodic forcing
due to B\'enard-K\`arm\`an vortices in a -meter long narrow water channel.
The vortex shedding frequency is varied via the mean flow speed and
the cylinder diameter , and mm, while the structures'
bending resistance is properly controlled via its Young's modulus ,
thickness and length . Thereby, it is first shown that the
non-dimensional time-averaged sheet deflection, namely, the sheet
\textit{reconfiguration} and also, the
time-averaged \textit{drag force} ,
where is the well-known Vogel number for flexible
structures in a steady flow and is the Cauchy number
comparing the relative magnitude of the profile drag force over a typical
elastic restoring force, if the sheet were rigid. Measurements and a simple
model based on torsional-spring-mounted flat plate illustrate that the tip
amplitude is not only directly proportional to the characteristic
size of the eddies, say , but also to the sheet mechanical properties and
the vortex flow characteristics such that . Furthermore, a rich phenomenology
of structural dynamics including vortex-forced-vibration, lock-in with the
sheet natural frequency, flow-induced vibration due to the sheet wake,
multiple-frequency and modal response is reported
General description of quasi-adiabatic dynamical phenomena near exceptional points
The appearance of so-called exceptional points in the complex spectra of
non-Hermitian systems is often associated with phenomena that contradict our
physical intuition. One example of particular interest is the state-exchange
process predicted for an adiabatic encircling of an exceptional point. In this
work we analyse this and related processes for the generic system of two
coupled oscillator modes with loss or gain. We identify a characteristic system
evolution consisting of periods of quasi-stationarity interrupted by abrupt
non-adiabatic transitions, and we present a qualitative and quantitative
description of this switching behaviour by connecting the problem to the
phenomenon of stability loss delay. This approach makes accurate predictions
for the breakdown of the adiabatic theorem as well as the occurrence of chiral
behavior observed previously in this context, and provides a general framework
to model and understand quasi-adiabatic dynamical effects in non-Hermitian
systems.Comment: Main text: 9 pages; 5 figures. Appendix: 4 pages; 1 figur
Reflection resonances in surface-disordered waveguides: strong higher-order effects of the disorder
We study coherent wave scattering through waveguides with a step-like surface disorder and find distinct enhancements in the reflection coefficients at well-defined resonance values. Based on detailed numerical and analytical calculations, we can unambiguously identify the origin of these reflection resonances to be higher-order correlations in the surface disorder profile which are typically neglected in similar studies of the same system. A remarkable feature of this new effect is that it relies on the longitudinal correlations in the step profile, although individual step heights are random and thus completely uncorrelated. The corresponding resonances are very pronounced and robust with respect to ensemble averaging, and lead to an enhancement of wave reflection by more than one order of magnitude.Peer Reviewe
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