587 research outputs found
Human-Centered Autonomy for UAS Target Search
Current methods of deploying robots that operate in dynamic, uncertain
environments, such as Uncrewed Aerial Systems in search \& rescue missions,
require nearly continuous human supervision for vehicle guidance and operation.
These methods do not consider high-level mission context resulting in
cumbersome manual operation or inefficient exhaustive search patterns. We
present a human-centered autonomous framework that infers geospatial mission
context through dynamic feature sets, which then guides a probabilistic target
search planner. Operators provide a set of diverse inputs, including priority
definition, spatial semantic information about ad-hoc geographical areas, and
reference waypoints, which are probabilistically fused with geographical
database information and condensed into a geospatial distribution representing
an operator's preferences over an area. An online, POMDP-based planner,
optimized for target searching, is augmented with this reward map to generate
an operator-constrained policy. Our results, simulated based on input from five
professional rescuers, display effective task mental model alignment, 18\% more
victim finds, and 15 times more efficient guidance plans then current
operational methods.Comment: Extended version to ICRA conference submission. 9 pages, 5 figure
HARPS: An Online POMDP Framework for Human-Assisted Robotic Planning and Sensing
Autonomous robots can benefit greatly from human-provided semantic
characterizations of uncertain task environments and states. However, the
development of integrated strategies which let robots model, communicate, and
act on such 'soft data' remains challenging. Here, the Human Assisted Robotic
Planning and Sensing (HARPS) framework is presented for active semantic sensing
and planning in human-robot teams to address these gaps by formally combining
the benefits of online sampling-based POMDP policies, multimodal semantic
interaction, and Bayesian data fusion. This approach lets humans
opportunistically impose model structure and extend the range of semantic soft
data in uncertain environments by sketching and labeling arbitrary landmarks
across the environment. Dynamic updating of the environment model while during
search allows robotic agents to actively query humans for novel and relevant
semantic data, thereby improving beliefs of unknown environments and states for
improved online planning. Simulations of a UAV-enabled target search
application in a large-scale partially structured environment show significant
improvements in time and belief state estimates required for interception
versus conventional planning based solely on robotic sensing. Human subject
studies in the same environment (n = 36) demonstrate an average doubling in
dynamic target capture rate compared to the lone robot case, and highlight the
robustness of active probabilistic reasoning and semantic sensing over a range
of user characteristics and interaction modalities
Measuring and Correcting Wind-Induced Pointing Errors of the Green Bank Telescope Using an Optical Quadrant Detector
Wind-induced pointing errors are a serious concern for large-aperture
high-frequency radio telescopes. In this paper, we describe the implementation
of an optical quadrant detector instrument that can detect and provide a
correction signal for wind-induced pointing errors on the 100m diameter Green
Bank Telescope (GBT). The instrument was calibrated using a combination of
astronomical measurements and metrology. We find that the main wind-induced
pointing errors on time scales of minutes are caused by the feedarm being blown
along the direction of the wind vector. We also find that wind-induced
structural excitation is virtually non-existent. We have implemented offline
software to apply pointing corrections to the data from imaging instruments
such as the MUSTANG 3.3 mm bolometer array, which can recover ~70% of
sensitivity lost due to wind-induced pointing errors. We have also performed
preliminary tests that show great promise for correcting these pointing errors
in real-time using the telescope's subreflector servo system in combination
with the quadrant detector signal.Comment: 17 pages, 11 figures; accepted for publication in PAS
Cytonuclear discordance in the Florida Everglades invasive Burmese python (Python bivittatus) population reveals possible hybridization with the Indian python (P. molurus)
The invasive Burmese python (Python bivittatus) has been reproducing in the Florida Everglades since the 1980s. These giant constrictor snakes have caused a precipitous decline in small mammal populations in southern Florida following escapes or releases from the commercial pet trade. To better understand the invasion pathway and genetic composition of the population, two mitochondrial (mtDNA) loci across 1,398 base pairs were sequenced on 426 snakes and 22 microsatellites were assessed on 389 snakes. Concatenated mtDNA sequences produced six haplotypes with an average nucleotide and haplotype diversity of π = 0.002 and h = 0.097, respectively. Samples collected in Florida from morphologically identified P. bivittatus snakes were similar to published cytochrome oxidase 1 and cytochrome b sequences from both P. bivittatus and Python molurus and were highly divergent (genetic distances of 5.4% and 4.3%, respectively). The average number of microsatellite alleles and expected heterozygosity were NA = 5.50 and HE = 0.60, respectively. Nuclear Bayesian assignment tests supported two genetically distinct groups and an admixed group, not geographically differentiated. The effective population size (NE = 315.1) was lower than expected for a population this large, but reflected the low genetic diversity overall. The patterns of genetic diversity between mtDNA and microsatellites were disparate, indicating nuclear introgression of separate mtDNA lineages corresponding to cytonuclear discordance. The introgression likely occurred prior to the invasion, but genetic information on the native range and commercial trade is needed for verification. Our finding that the Florida python population is comprised of distinct lineages suggests greater standing variation for adaptation and the potential for broader areas of suitable habitat in the invaded range
Simple and strong: twisted silver painted nylon artificial muscle actuated by Joule heating
Highly oriented nylon and polyethylene fibres shrink in length when heated and expand in diameter. By twisting and then coiling monofilaments of these materials to form helical springs, the anisotropic thermal expansion has recently been shown to enable tensile actuation of up to 49% upon heating. Joule heating, by passing a current through a conductive coating on the surface of the filament, is a convenient method of controlling actuation. In previously reported work this has been done using highly flexible carbon nanotube sheets or commercially available silver coated fibres. In this work silver paint is used as the Joule heating element at the surface of the muscle. Up to 29% linear actuation is observed with energy and power densities reaching 840 kJ m[superscript -3] (528 J kg[superscript -1]) and 1.1 kW kg[superscript -1] (operating at 0.1 Hz, 4% strain, 1.4 kg load). This simple coating method is readily accessible and can be applied to any polymer filament. Effective use of this technique relies on uniform coating to avoid temperature gradients
Entangled-State Cycles of Atomic Collective-Spin States
We study quantum trajectories of collective atomic spin states of
effective two-level atoms driven with laser and cavity fields. We show that
interesting ``entangled-state cycles'' arise probabilistically when the (Raman)
transition rates between the two atomic levels are set equal. For odd (even)
, there are () possible cycles. During each cycle the
-qubit state switches, with each cavity photon emission, between the states
, where is a Dicke state in a rotated
collective basis. The quantum number (), which distinguishes the
particular cycle, is determined by the photon counting record and varies
randomly from one trajectory to the next. For even it is also possible,
under the same conditions, to prepare probabilistically (but in steady state)
the Dicke state , i.e., an -qubit state with excitations,
which is of particular interest in the context of multipartite entanglement.Comment: 10 pages, 9 figure
Nuclear receptor REVERBα is a state-dependent regulator of liver energy metabolism
The nuclear receptor REVERBα is a core component of the circadian clock and proposed to be a dominant regulator of hepatic lipid metabolism. Using antibody-independent ChIP-sequencing of REVERBα in mouse liver, we reveal a high-confidence cistrome and define direct target genes. REVERBα-binding sites are highly enriched for consensus RORE or RevDR2 motifs and overlap with corepressor complex binding. We find no evidence for transcription factor tethering and DNA-binding domain-independent action. Moreover, hepatocyte-specific deletion of Reverbα drives only modest physiological and transcriptional dysregulation, with derepressed target gene enrichment limited to circadian processes. Thus, contrary to previous reports, hepatic REVERBα does not repress lipogenesis under basal conditions. REVERBα control of a more extensive transcriptional program is only revealed under conditions of metabolic perturbation (including mistimed feeding, which is a feature of the global Reverbα -/- mouse). Repressive action of REVERBα in the liver therefore serves to buffer against metabolic challenge, rather than drive basal rhythmicity in metabolic activity
Calcific myofibrosis due to pentazocine abuse: a case report
<p>Abstract</p> <p>Introduction</p> <p>Pentazocine, a synthetic narcotic analgesic, is commonly used for the relief of moderate to severe pain secondary to various conditions. It is usually well tolerated; however, adverse effects are not uncommon, especially when higher doses are used and when it is used in a dependent fashion. There have been reports of various complications associated with its use, including skin fibrosis, skin ulceration, abnormal skin pigmentation and symmetrical myopathy with fibrous myopathy. Fibrosis has usually been reported in the muscles at the site of injection of the drug. Being opioid in nature, it has a high abuse potential.</p> <p>Case presentation</p> <p>Here we report a case of pentazocine-induced calcific myofibrosis in a 42-year-old man involving muscles which were not injected with pentazocine.</p> <p>Conclusion</p> <p>This case highlights the care that needs to be taken when prescribing opioid analgesics, such as pentazocine, as routine painkillers. Patients who have history of substance abuse are more likely to abuse other agents, including prescription drugs. Rare consequences such as calcific myofibrosis are devastating and can cause significant lifelong disability.</p
Combined distributed turbo coding and space frequency block coding techniques
The distributed space-time (frequency) coding and distributed channel turbo coding used independently represent two cooperative techniques that can provide increased throughput and spectral efficiency at an imposed maximum Bit Error Rate (BER) and delay required from the new generation of cellular networks. This paper proposes two cooperative algorithms that employ jointly the two types of techniques, analyzes their BER and spectral efficiency performances versus the qualities of the channels involved, and presents some conclusions regarding the adaptive employment of these algorithms. © 2010 V. Bota et al.FP7/ICT/2007/21547
Combined distributed turbo coding and space frequency block coding techniques
The distributed space-time (frequency) coding and distributed channel turbo coding used independently represent two cooperative techniques that can provide increased throughput and spectral efficiency at an imposed maximum Bit Error Rate (BER) and delay required from the new generation of cellular networks. This paper proposes two cooperative algorithms that employ jointly the two types of techniques, analyzes their BER and spectral efficiency performances versus the qualities of the channels involved, and presents some conclusions regarding the adaptive employment of these algorithms. © 2010 V. Bota et al.FP7/ICT/2007/21547
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