6,254 research outputs found
Space based topographic mapping experiment using Seasat synthetic aperture radar and LANDSAT 3 return beam vidicon imagery
A technique for producing topographic information is described which is based on same side/same time viewing using a dissimilar combination of radar imagery and photographic images. Common geographic areas viewed from similar space reference locations produce scene elevation displacements in opposite direction and proper use of this characteristic can yield the perspective information necessary for determination of base to height ratios. These base to height ratios can in turn be used to produce a topographic map. A test area covering the Harrisburg, Pennsylvania region was observed by synthetic aperture radar on the Seasat satellite and by return beam vidicon on by the LANDSAT - 3 satellite. The techniques developed for the scaling re-orientation and common registration of the two images are presented along with the topographic determination data. Topographic determination based exclusively on the images content is compared to the map information which is used as a performance calibration base
Verifying the distributed real-time network protocol RTnet using Uppaal
RTnet is a distributed real-time network protocol for fully-connected local area networks with a broadcast capability. It supports streaming real-time and non-realtime traffic and on-the-fly addition and removal of network nodes. This paper presents a formal analysis of RTnet using the model checker Uppaal. Besides normal protocol behaviour, the analysis focuses on the fault-handling properties of RTnet, in particular recovery after packet loss. Both qualitative and quantitative properties are presented, together with the verification results and conclusions about the robustness of RTnet
Three-dimensional foam flow resolved by fast X-ray tomographic microscopy
Thanks to ultra fast and high resolution X-ray tomography, we managed to
capture the evolution of the local structure of the bubble network of a 3D foam
flowing around a sphere. As for the 2D foam flow around a circular obstacle, we
observed an axisymmetric velocity field with a recirculation zone, and
indications of a negative wake downstream the obstacle. The bubble
deformations, quantified by a shape tensor, are smaller than in 2D, due to a
purely 3D feature: the azimuthal bubble shape variation. Moreover, we were able
to detect plastic rearrangements, characterized by the neighbor-swapping of
four bubbles. Their spatial structure suggest that rearrangements are triggered
when films faces get smaller than a characteristic area.Comment: 5 pages, 5 figure
Hydrodynamic lift of vesicles under shear flow in microgravity
The dynamics of a vesicle suspension in a shear flow between parallel plates
has been investigated under microgravity conditions, where vesicles are only
submitted to hydrodynamic effects such as lift forces due to the presence of
walls and drag forces. The temporal evolution of the spatial distribution of
the vesicles has been recorded thanks to digital holographic microscopy, during
parabolic flights and under normal gravity conditions. The collected data
demonstrates that vesicles are pushed away from the walls with a lift velocity
proportional to where is the shear rate,
the vesicle radius and its distance from the wall. This scaling as well
as the dependence of the lift velocity upon vesicle aspect ratio are consistent
with theoretical predictions by Olla [J. Phys. II France {\bf 7}, 1533--1540
(1997)].Comment: 6 pages, 8 figure
The Design and Operation of The Keck Observatory Archive
The Infrared Processing and Analysis Center (IPAC) and the W. M. Keck
Observatory (WMKO) operate an archive for the Keck Observatory. At the end of
2013, KOA completed the ingestion of data from all eight active observatory
instruments. KOA will continue to ingest all newly obtained observations, at an
anticipated volume of 4 TB per year. The data are transmitted electronically
from WMKO to IPAC for storage and curation. Access to data is governed by a
data use policy, and approximately two-thirds of the data in the archive are
public.Comment: 12 pages, 4 figs, 4 tables. Presented at Software and
Cyberinfrastructure for Astronomy III, SPIE Astronomical Telescopes +
Instrumentation 2014. June 2014, Montreal, Canad
Introducing Multi-Core at Automotive Engine Systems
International audienceWith the introduction of the new Euro 6, and Euro 7 emission standards for passenger cars, the combustion process of Engine Management Systems (EMS) needs to be controlled with an increased precision.In addition, new vehicle architectures are introduced (increased integration of functions inside an Engine Management System), as well as new SW architectures concepts like AUTOSAR or the support of ISO26262
Herbig-Haro flows in L1641N
We have used the 2.56m Nordic Optical Telescope (NOT) to observe two deep
fields in L1641N, selected on the basis of previous shock studies, using the
2.12 micron transition of H2 (and a Ks filter to sample the continuum) for a
total exposure time of 4.6 h (72 min Ks) in the overlapping region. The
resulting high-resolution mosaic shows numerous new shocks and resolves many
known shocks into multiple components. Using previous observations taken 9
years earlier we calculate a proper motion map and combine this with Spitzer 24
micron observations of the embedded young stars. The combined H2 mosaic shows
many new shocks and faint structures in the HH flows. From the proper motion
map we find that most HH objects belong to two major bi-polar HH flows, the
large-scale roughly North-South oriented flow from central L1641N and a
previously unseen HH flow in eastern L1641N. Combining the tangential velocity
map with the mid-IR Spitzer images, two very likely outflow sources are found.
The outflow source of the eastern flow, L1641N-172, is found to be the
currently brightest mid-IR source in L1641N and seem to have brightened
considerably during the past 20 years. We make the first detection of this
source in the near-IR (Ks) and also find a near-IR reflection nebula pointing
at the source, probably the illuminated walls of a cone-shaped cavity cleared
out by the eastern lobe of the outflow. Extending a line from the eastern
outflow source along the proper motion vector we find that HH 301 and HH 302
(almost 1 pc away) belong to this new HH flow.Comment: 10 pages, 4 figures, Accepted for publication by A &
How universal is the fractional-quantum-Hall edge Luttinger liquid?
This article reports on our microscopic investigations of the edge of the
fractional quantum Hall state at filling factor . We show that the
interaction dependence of the wave function is well described in an
approximation that includes mixing with higher composite-fermion Landau levels
in the lowest order. We then proceed to calculate the equal time edge Green
function, which provides evidence that the Luttinger exponent characterizing
the decay of the Green function at long distances is interaction dependent. The
relevance of this result to tunneling experiments is discussed.Comment: 5 page
Discrimination and anatomical mapping of PET-positive lesions: comparison of CT attenuation-corrected PET images with coregistered MR and CT images in the abdomen
Purpose: PET/MR has the potential to become a powerful tool in clinical oncological imaging. The purpose of this prospective study was to evaluate the performance of a single T1-weighted (T1w) fat-suppressed unenhanced MR pulse sequence of the abdomen in comparison with unenhanced low-dose CT images to characterize PET-positive lesions. Methods: A total of 100 oncological patients underwent sequential whole-body 18F-FDG PET with CT-based attenuation correction (AC), 40mAs low-dose CT and two-point Dixon-based T1w 3D MRI of the abdomen in a trimodality PET/CT-MR system. PET-positive lesions were assessed by CT and MRI with regard to their anatomical location, conspicuity and additional relevant information for characterization. Results: From among 66 patients with at least one PET-positive lesion, 147 lesions were evaluated. No significant difference between MRI and CT was found regarding anatomical lesion localization. The MR pulse sequence used performed significantly better than CT regarding conspicuity of liver lesions (p < 0.001, Wilcoxon signed ranks test), whereas no difference was noted for extrahepatic lesions. For overall lesion characterization, MRI was considered superior to CT in 40% of lesions, equal to CT in 49%, and inferior to CT in 11%. Conclusion: Fast Dixon-based T1w MRI outperformed low-dose CT in terms of conspicuity and characterization of PET-positive liver lesions and performed similarly in extrahepatic tumour manifestations. Hence, under the assumption that the technical issue of MR AC for whole-body PET examinations is solved, in abdominal PET/MR imaging the replacement of low-dose CT by a single Dixon-based MR pulse sequence for anatomical lesion correlation appears to be valid and robus
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