34 research outputs found
Affordance-Aware Handovers With Human Arm Mobility Constraints
Reasoning about object handover configurations allows an assistive agent to
estimate the appropriateness of handover for a receiver with different arm
mobility capacities. While there are existing approaches for estimating the
effectiveness of handovers, their findings are limited to users without arm
mobility impairments and to specific objects. Therefore, current
state-of-the-art approaches are unable to hand over novel objects to receivers
with different arm mobility capacities. We propose a method that generalises
handover behaviours to previously unseen objects, subject to the constraint of
a user's arm mobility levels and the task context. We propose a
heuristic-guided hierarchically optimised cost whose optimisation adapts object
configurations for receivers with low arm mobility. This also ensures that the
robot grasps consider the context of the user's upcoming task, i.e., the usage
of the object. To understand preferences over handover configurations, we
report on the findings of an online study, wherein we presented different
handover methods, including ours, to users with different levels of arm
mobility. We find that people's preferences over handover methods are
correlated to their arm mobility capacities. We encapsulate these preferences
in a statistical relational model (SRL) that is able to reason about the most
suitable handover configuration given a receiver's arm mobility and upcoming
task. Using our SRL model, we obtained an average handover accuracy of
when generalising handovers to novel objects.Comment: Accepted for RA-L 202
Phosphorus retention in a lowland Neotropical stream following an eight-year enrichment experiment
Human alteration of the global P cycle has led to widespread P loading in freshwater ecosystems. Much research has been devoted to the capacity of wetlands and lakes to serve as long-term sinks for P inputs from the watershed, but we know much less about the potential of headwater streams to serve in this role. We assessed storage and retention of P in biotic and abiotic compartments after an 8-y experimental P addition to a 1st-order stream in a Neotropical wet forest. Sediment P extractions indicated that nearly all P storage was in the form of Fe- and Al-bound P (∼700 μg P/g dry sediment), similar to nearby naturally high-P streams. At the end of the enrichment, ∼25% of the total P added over the 8-y study was still present in sediments within 200 m of the injection site, consistent with water-column measurements showing sustained levels of high net P uptake throughout the experiment. Sediment P declined to baseline levels (∼100 μg P/g dry sediment) over 4 y after the enrichment ended. Leaf-litter P content increased nearly 2× over background levels during P enrichment and was associated with a 3× increase in microbial respiration rates, although these biotic responses were low compared to nearby naturally high- P streams. Biotic storage accounted for \u3c0.03% of retention of the added P. Our results suggest that the high sorption capacity of these sediments dampened the biotic effects of P loading and altered the timing and quantity of P exported downstream
Reasoning on Grasp-Action Affordances
Artificial intelligence is essential to succeed in challenging activities
that involve dynamic environments, such as object manipulation tasks in indoor
scenes. Most of the state-of-the-art literature explores robotic grasping
methods by focusing exclusively on attributes of the target object. When it
comes to human perceptual learning approaches, these physical qualities are not
only inferred from the object, but also from the characteristics of the
surroundings. This work proposes a method that includes environmental context
to reason on an object affordance to then deduce its grasping regions. This
affordance is reasoned using a ranked association of visual semantic attributes
harvested in a knowledge base graph representation. The framework is assessed
using standard learning evaluation metrics and the zero-shot affordance
prediction scenario. The resulting grasping areas are compared with unseen
labelled data to asses their accuracy matching percentage. The outcome of this
evaluation suggest the autonomy capabilities of the proposed method for object
interaction applications in indoor environments.Comment: Annual Conference Towards Autonomous Robotic Systems (TAROS19
Large-scale climatic phenomena drive fluctuations in macroinvertebrate assemblages in lowland tropical streams, Costa Rica: The importance of ENSO events in determining long-term (15y) patterns
Understanding how environmental variables influence the distribution and density of organisms over relatively long temporal scales is a central question in ecology given increased climatic variability (e.g., precipitation, ENSO events). The primary goal of our study was to evaluate long-term (15y time span) patterns of climate, as well as environmental parameters in two Neotropical streams in lowland Costa Rica, to assess potential effects on aquatic macroinvertebrates. We also examined the relative effects of an 8y whole-stream P-enrichment experiment on macroinvertebrate assemblages against the backdrop of this long-term study. Climate, environmental variables and macroinvertebrate samples were measured monthly for 7y and then quarterly for an additional 8y in each stream. Temporal patterns in climatic and environmental variables showed high variability over time, without clear inter-annual or intra-annual patterns. Macroinvertebrate richness and abundance decreased with increasing discharge and was positively related to the number of days since the last high discharge event. Findings show that fluctuations in stream physicochemistry and macroinvertebrate assemblage structure are ultimately the result of large-scale climatic phenomena, such as ENSO events, while the 8y P-enrichment did not appear to affect macroinvertebrates. Our study demonstrates that Neotropical lowland streams are highly dynamic and not as stable as is commonly presumed, with high intra- and inter-annual variability in environmental parameters that change the structure and composition of freshwater macroinvertebrate assemblages.This study was financed by National Science Foundation (DEB 1122389) to Catherine M. Pringle. The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.UCR::Vicerrectoría de Investigación::Unidades de Investigación::Ciencias Básicas::Centro de Investigación en Ciencias del Mar y Limnología (CIMAR
Phosphorus retention in a lowland Neotropical stream following an eight-year enrichment experiment
Human alteration of the global P cycle has led to widespread P loading in freshwater ecosystems. Much research has been devoted to the capacity of wetlands and lakes to serve as long-term sinks for P inputs from the watershed, but we know much less about the potential of headwater streams to serve in this role. We assessed storage and retention of P in biotic and abiotic compartments after an 8-y experimental P addition to a 1st-order stream in a Neotropical wet forest. Sediment P extractions indicated that nearly all P storage was in the form of Fe- and Al-bound P (∼700 μg P/g dry sediment), similar to nearby naturally high-P streams. At the end of the enrichment, ∼25% of the total P added over the 8-y study was still present in sediments within 200 m of the injection site, consistent with water-column measurements showing sustained levels of high net P uptake throughout the experiment. Sediment P declined to baseline levels (∼100 μg P/g dry sediment) over 4 y after the enrichment ended. Leaf-litter P content increased nearly 2× over background levels during P enrichment and was associated with a 3× increase in microbial respiration rates, although these biotic responses were low compared to nearby naturally high- P streams. Biotic storage accounted for \u3c0.03% of retention of the added P. Our results suggest that the high sorption capacity of these sediments dampened the biotic effects of P loading and altered the timing and quantity of P exported downstream
Phosphorus retention in a lowland Neotropical stream following an eight-year enrichment experiment
Human alteration of the global P cycle has led to widespread P loading in freshwater ecosystems. Much research has been devoted to the capacity of wetlands and lakes to serve as long-term sinks for P inputs from the watershed, but we know much less about the potential of headwater streams to serve in this role. We assessed storage and retention of P in biotic and abiotic compartments after an 8-y experimental P addition to a 1st-order stream in a Neotropical wet forest. Sediment P extractions indicated that nearly all P storage was in the form of Fe- and Al-bound P (∼700 μg P/g dry sediment), similar to nearby naturally high-P streams. At the end of the enrichment, ∼25% of the total P added over the 8-y study was still present in sediments within 200 m of the injection site, consistent with water-column measurements showing sustained levels of high net P uptake throughout the experiment. Sediment P declined to baseline levels (∼100 μg P/g dry sediment) over 4 y after the enrichment ended. Leaf-litter P content increased nearly 2× over background levels during P enrichment and was associated with a 3× increase in microbial respiration rates, although these biotic responses were low compared to nearby naturally high- P streams. Biotic storage accounted for \u3c0.03% of retention of the added P. Our results suggest that the high sorption capacity of these sediments dampened the biotic effects of P loading and altered the timing and quantity of P exported downstream