655 research outputs found
Thermal Recovery of Multi-Limbed Robots with Electric Actuators
The problem of finding thermally minimizing configurations of a humanoid robot to recover its actuators from unsafe thermal states is addressed. A first-order, data-driven, effort based, thermal model of the robots actuators is devised, which is used to predict future thermal states. Given this predictive capability, a map between configurations and future temperatures is formulated to find what configurations, subject to valid contact constraints, can be taken now to minimize future thermal states. Effectively, this approach is a realization of a contact-constrained thermal inverse-kinematics (IK) process. Experimental validation of the proposed approach is performed on the NASA Valkyrie robot hardware
Modular Autonomous Systems Technology Framework: A Distributed Solution for System Monitoring and Control
The Modular Autonomous Systems Technology (MAST) framework is a tool for building distributed, hierarchical autonomous systems. Originally intended for the autonomous monitoring and control of spacecraft, this framework concept provides support for variable autonomy, assume-guarantee contracts, and efficient communication between subsystems and a centralized systems manager. MAST was developed at NASA's Johnson Space Center (JSC) and has been applied to an integrated spacecraft example scenario
Energy self-sufficient systems for monitoring sewer networks
Underground infrastructure networks form the backbone of vital supply and
disposal systems. However, they are under-monitored in comparison to their
value. This is due, in large part, to the lack of energy supply for monitoring
and data transmission. In this paper, we investigate a novel, energy harvesting
system used to power underground sewer infrastructure monitoring networks. The
system collects the required energy from ambient sources, such as temperature
differences or residual light in sewer networks. A prototype was developed that
could use either a thermoelectric generator (TEG) or a solar cell to capture
the energy needed to acquire and transmit ultrasonic water level data via
LoRaWAN. Real-world field trials were satisfactory and showed the potential
power output, as well as, possibilities to improve the system. Using an
extrapolation model, we proved that the developed solution could work reliably
throughout the year.Comment: To be published in proceedings of the conference "21. ITG/GMA-
Fachtagung Sensoren und Messsysteme 2022", 10.-11. Mai 2022, N\"urnberger
CongressCenter, Nuremberg, Germany, or IEEE explor
The accretion disc in the quasar SDSS J0924+0219
We present single-epoch multi-wavelength optical-NIR observations of the
"anomalous" lensed quasar SDSS J0924+0219, made using the Magellan 6.5-metre
Baade telescope at Las Campanas Observatory, Chile. The data clearly resolve
the anomalous bright image pair in the lensed system, and exhibit a strong
decrease in the anomalous flux ratio with decreasing wavelength. This is
interpreted as a result of microlensing of a source of decreasing size in the
core of the lensed quasar. We model the radius of the continuum emission
region, sigma, as a power-law in wavelength, sigma lambda^zeta. We place an
upper limit on the Gaussian radius of the u'-band emission region of 3.04E16
h70^{-1/2} (/M_sun)^{1/2} cm, and constrain the size-wavelength power-law
index to zeta<1.34 at 95% confidence. These observations rule out an alpha-disc
prescription for the accretion disc in SDSS J0924+0219 with 94% confidence.Comment: 8 pages, 5 figures. Accepted for publication in MNRA
Exploring the dust content of SDSS DR7 damped Lyman alpha systems at 2.155.2
We have studied a sample of 1084 intervening absorption systems with 2.155.2, having log(N) 20.0 in the spectra of QSOs in
Sloan Digital Sky Survey (SDSS) data release 7 (DR7), with the aim of
understanding the nature and abundance of the dust and the chemical abundances
in the DLA absorbers. Composite spectra were constructed for the full sample
and several subsamples, chosen on the basis of absorber and QSO properties.
Average extinction curves were obtained for the samples by comparing their
geometric mean composite spectra with those of two samples of QSOs, matching in
z and i magnitude with the DLA sample, one sample without any absorbers
along their lines of sight and the other without any DLAs along their lines of
sight irrespective of the presence of other absorption systems. While the
average reddening in the DLA sample is small, we find definite evidence for the
presence of dust in subsamples based on absorber properties, in particular the
strength of metal absorption lines. DLAs along lines of sight to QSOs which are
not colour selected are found to be more dusty compared to those along the
lines of sight to the more numerous colour selected QSOs. From these studies
and from the strengths of absorption lines in the composite spectra, we
conclude that 10% of the DLAs in SDSS DR7 cause significant reddening,
have stronger absorption lines and have higher abundances as compared to the
rest of the sample. The rest of the sample shows little reddening. Due to the
dominant color selection method used to target QSOs in the SDSS DR7, this
fraction of 10% likely represents a lower limit for the global fraction of
dusty DLAs at high-z.Comment: 12 pages, 9 figures. To appear in MNRA
La(, ) cross sections constrained with statistical decay properties of La nuclei
The nuclear level densities and -ray strength functions of
La were measured using the La(He, ),
La(He, He) and La(d, p) reactions. The
particle- coincidences were recorded with the silicon particle
telescope (SiRi) and NaI(Tl) (CACTUS) arrays. In the context of these
experimental results, the low-energy enhancement in the A140 region is
discussed. The La( cross sections were calculated
at - and -process temperatures using the experimentally measured nuclear
level densities and -ray strength functions. Good agreement is found
between La( calculated cross sections and previous
measurements
Perspectives in machine learning for wildlife conservation
Data acquisition in animal ecology is rapidly accelerating due to inexpensive
and accessible sensors such as smartphones, drones, satellites, audio recorders
and bio-logging devices. These new technologies and the data they generate hold
great potential for large-scale environmental monitoring and understanding, but
are limited by current data processing approaches which are inefficient in how
they ingest, digest, and distill data into relevant information. We argue that
machine learning, and especially deep learning approaches, can meet this
analytic challenge to enhance our understanding, monitoring capacity, and
conservation of wildlife species. Incorporating machine learning into
ecological workflows could improve inputs for population and behavior models
and eventually lead to integrated hybrid modeling tools, with ecological models
acting as constraints for machine learning models and the latter providing
data-supported insights. In essence, by combining new machine learning
approaches with ecological domain knowledge, animal ecologists can capitalize
on the abundance of data generated by modern sensor technologies in order to
reliably estimate population abundances, study animal behavior and mitigate
human/wildlife conflicts. To succeed, this approach will require close
collaboration and cross-disciplinary education between the computer science and
animal ecology communities in order to ensure the quality of machine learning
approaches and train a new generation of data scientists in ecology and
conservation
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