1,800 research outputs found
An Investigation of Aircraft Heaters XXXV : Thermocouple Conduction Error Observed in Measuring Surface Temperatures
Incorporating Physical Knowledge into Machine Learning for Planetary Space Physics
Recent improvements in data collection volume from planetary and space
physics missions have allowed the application of novel data science techniques.
The Cassini mission for example collected over 600 gigabytes of scientific data
from 2004 to 2017. This represents a surge of data on the Saturn system.
Machine learning can help scientists work with data on this larger scale.
Unlike many applications of machine learning, a primary use in planetary space
physics applications is to infer behavior about the system itself. This raises
three concerns: first, the performance of the machine learning model, second,
the need for interpretable applications to answer scientific questions, and
third, how characteristics of spacecraft data change these applications. In
comparison to these concerns, uses of black box or un-interpretable machine
learning methods tend toward evaluations of performance only either ignoring
the underlying physical process or, less often, providing misleading
explanations for it. We build off a previous effort applying a semi-supervised
physics-based classification of plasma instabilities in Saturn's magnetosphere.
We then use this previous effort in comparison to other machine learning
classifiers with varying data size access, and physical information access. We
show that incorporating knowledge of these orbiting spacecraft data
characteristics improves the performance and interpretability of machine
learning methods, which is essential for deriving scientific meaning. Building
on these findings, we present a framework on incorporating physics knowledge
into machine learning problems targeting semi-supervised classification for
space physics data in planetary environments. These findings present a path
forward for incorporating physical knowledge into space physics and planetary
mission data analyses for scientific discovery.Comment: 25 pages, 7 figures, accepted for publication in Frontiers in
Astronomy and Space Sciences for the Research Topic of Machine Learning in
Heliophysics at https://www.frontiersin.org/articles/10.3389/fspas.2020.0003
Spectral and Spin Measurement of Two Small and Fast-Rotating Near-Earth Asteroids
In May 2012 two asteroids made near-miss "grazing" passes at distances of a
few Earth-radii: 2012 KP24 passed at nine Earth-radii and 2012 KT42 at only
three Earth-radii. The latter passed inside the orbital distance of
geosynchronous satellites. From spectral and imaging measurements using NASA's
3-m Infrared Telescope Facility (IRTF), we deduce taxonomic, rotational, and
physical properties. Their spectral characteristics are somewhat atypical among
near-Earth asteroids: C-complex for 2012 KP24 and B-type for 2012 KT42, from
which we interpret the albedos of both asteroids to be between 0.10 and 0.15
and effective diameters of 20+-2 and 6+-1 meters, respectively. Among B-type
asteroids, the spectrum of 2012 KT42 is most similar to 3200 Phaethon and 4015
Wilson-Harrington. Not only are these among the smallest asteroids spectrally
measured, we also find they are among the fastest-spinning: 2012 KP24 completes
a rotation in 2.5008+-0.0006 minutes and 2012 KT42 rotates in 3.634+-0.001
minutes.Comment: 4 pages, 3 figures, accepted for publication in Icaru
A Systematic Review on the Biomechanics of Breakfall Technique (Ukemi) in Relation to Injury in Judo within the Adult Judoka Population
Microfabrication of Optically Flat Silicon Micro-Mirrors for Fully Programmable Micro-Diffraction Gratings
AbstractWe have fabricated and characterized a Fully Programmable Micro-Diffraction Grating (FPMDG) with 64 silicon micro-mirrors for spectral shaping in the visible and near-infrared wavelength range. The FPMDG arrays of 50μm and 80μm wide and 700μm long silicon micro-mirrors have been fabricated in a process based on anodic bonding of an 8μm-SOI wafer and a borosilicate glass wafer. The detrimental bending of the micro-mirrors during electrostatic actuation has been minimized through separation of the mechanical and optical sections of the device. Flexures incorporating serpentine structures have been used to reduce the actuation dependence on length and thickness. Independent addressing of the micro-mirrors with negligible cross-talk and with bending of the micro-mirrors smaller than 0.14μm over 700μm have been demonstrated
Nonlinear software sensor for monitoring genetic regulation processes with noise and modeling errors
Nonlinear control techniques by means of a software sensor that are commonly
used in chemical engineering could be also applied to genetic regulation
processes. We provide here a realistic formulation of this procedure by
introducing an additive white Gaussian noise, which is usually found in
experimental data. Besides, we include model errors, meaning that we assume we
do not know the nonlinear regulation function of the process. In order to
illustrate this procedure, we employ the Goodwin dynamics of the concentrations
[B.C. Goodwin, Temporal Oscillations in Cells, (Academic Press, New York,
1963)] in the simple form recently applied to single gene systems and some
operon cases [H. De Jong, J. Comp. Biol. 9, 67 (2002)], which involves the
dynamics of the mRNA, given protein, and metabolite concentrations. Further, we
present results for a three gene case in co-regulated sets of transcription
units as they occur in prokaryotes. However, instead of considering their full
dynamics, we use only the data of the metabolites and a designed software
sensor. We also show, more generally, that it is possible to rebuild the
complete set of nonmeasured concentrations despite the uncertainties in the
regulation function or, even more, in the case of not knowing the mRNA
dynamics. In addition, the rebuilding of concentrations is not affected by the
perturbation due to the additive white Gaussian noise and also we managed to
filter the noisy output of the biological systemComment: 21 pages, 7 figures; also selected in vjbio of August 2005; this
version corrects a misorder in the last three references of the published
versio
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