2,313 research outputs found
On the possibility of measuring relativistic gravitational effects with a LAGEOS-LAGEOS II-OPTIS-mission
In this paper we wish to preliminary investigate if it would be possible to
use the orbital data from the proposed OPTIS mission together with those from
the existing geodetic passive SLR LAGEOS and LAGEOS II satellites in order to
perform precise measurements of some general relativistic
gravitoelectromagnetic effects, with particular emphasis on the Lense-Thirring
effect.Comment: Abridged version. 16 pages, no figures, 1 table. First results from
the GGM01C Earth gravity model. GRACE data include
Comparison of ultracold neutron sources for fundamental physics measurements
Ultracold neutrons (UCNs) are key for precision studies of fundamental
parameters of the neutron and in searches for new CP violating processes or
exotic interactions beyond the Standard Model of particle physics. The most
prominent example is the search for a permanent electric dipole moment of the
neutron (nEDM). We have performed an experimental comparison of the leading UCN
sources currently operating. We have used a 'standard' UCN storage bottle with
a volume of 32 liters, comparable in size to nEDM experiments, which allows us
to compare the UCN density available at a given beam port.Comment: 20 pages, 30 Figure
LAGEOS-type Satellites in Critical Supplementary Orbit Configuration and the Lense-Thirring Effect Detection
In this paper we analyze quantitatively the concept of LAGEOS--type
satellites in critical supplementary orbit configuration (CSOC) which has
proven capable of yielding various observables for many tests of General
Relativity in the terrestrial gravitational field, with particular emphasis on
the measurement of the Lense--Thirring effect.Comment: LaTex2e, 20 pages, 7 Tables, 6 Figures. Changes in Introduction,
Conclusions, reference added, accepted for publication in Classical and
Quantum Gravit
A new laser-ranged satellite for General Relativity and space geodesy: IV. Thermal drag and the LARES 2 space experiment
In three previous papers we presented the LARES 2 space experiment aimed at a
very accurate test of frame-dragging and at other tests of fundamental physics
and measurements of space geodesy and geodynamics. We presented the error
sources in the LARES 2 experiment, its error budget, Monte Carlo simulations
and covariance analyses confirming an accuracy of a few parts per thousand in
the test of frame-dragging, and we treated the error due to the uncertainty in
the de Sitter effect, a relativistic orbital perturbation. Here we discuss the
impact in the error budget of the LARES 2 frame-dragging experiment of the
orbital perturbation due to thermal drag or thermal thrust. We show that the
thermal drag induces an uncertainty of about one part per thousand in the LARES
2 frame-dragging test, consistent with the error estimates in our previous
papers.Comment: 17 pages, 9 figure
Strong relative intensity squeezing by 4-wave mixing in Rb vapor
We have measured -3.5 dB (-8.1 dB corrected for losses) relative intensity
squeezing between the probe and conjugate beams generated by stimulated,
nondegenerate four-wave mixing in hot rubidium vapor. Unlike early observations
of squeezing in atomic vapors based on saturation of a two-level system, our
scheme uses a resonant nonlinearity based on ground-state coherences in a
three-level system. Since this scheme produces narrowband, squeezed light near
an atomic resonance it is of interest for experiments involving cold atoms or
atomic ensembles.Comment: Submitted to Optics Letter
What influences the speed of prototyping? An empirical investigation of twenty software startups
It is essential for startups to quickly experiment business ideas by building
tangible prototypes and collecting user feedback on them. As prototyping is an
inevitable part of learning for early stage software startups, how fast
startups can learn depends on how fast they can prototype. Despite of the
importance, there is a lack of research about prototyping in software startups.
In this study, we aimed at understanding what are factors influencing different
types of prototyping activities. We conducted a multiple case study on twenty
European software startups. The results are two folds, firstly we propose a
prototype-centric learning model in early stage software startups. Secondly, we
identify factors occur as barriers but also facilitators for prototyping in
early stage software startups. The factors are grouped into (1) artifacts, (2)
team competence, (3) collaboration, (4) customer and (5) process dimensions. To
speed up a startups progress at the early stage, it is important to incorporate
the learning objective into a well-defined collaborative approach of
prototypingComment: This is the author's version of the work. Copyright owner's version
can be accessed at doi.org/10.1007/978-3-319-57633-6_2, XP2017, Cologne,
German
Discrimination of Overt, Mouthed, and Imagined Speech Activity using Stereotactic EEG
Recent studies have demonstrated that it is possible to decode and synthesize acoustic speech directly from intracranial measurements of brain activity. A current major challenge is to extend the efficacy of this decoding to imagined speech processes toward the development of a practical speech neuroprosthesis for the disabled. The present study used intracranial brain recordings from participants that performed a speaking task consisting of overt, mouthed, and imagined speech trials. In order to better elucidate the unique neural features that contribute to the discrepancies between overt and imagined model performance, rather than directly comparing the performance of speech decoding models trained on respective speaking modes, this study developed and trained models that use neural data to discriminate between pairs of speaking modes. The results further support that, while there exists a common neural substrate across speech modes, there are also unique neural processes that differentiate speech modes
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