13,572 research outputs found
Real-Time Reinforcement Learning for Vision-Based Robotics Utilizing Local and Remote Computers
Real-time learning is crucial for robotic agents adapting to ever-changing,
non-stationary environments. A common setup for a robotic agent is to have two
different computers simultaneously: a resource-limited local computer tethered
to the robot and a powerful remote computer connected wirelessly. Given such a
setup, it is unclear to what extent the performance of a learning system can be
affected by resource limitations and how to efficiently use the wirelessly
connected powerful computer to compensate for any performance loss. In this
paper, we implement a real-time learning system called the Remote-Local
Distributed (ReLoD) system to distribute computations of two deep reinforcement
learning (RL) algorithms, Soft Actor-Critic (SAC) and Proximal Policy
Optimization (PPO), between a local and a remote computer. The performance of
the system is evaluated on two vision-based control tasks developed using a
robotic arm and a mobile robot. Our results show that SAC's performance
degrades heavily on a resource-limited local computer. Strikingly, when all
computations of the learning system are deployed on a remote workstation, SAC
fails to compensate for the performance loss, indicating that, without careful
consideration, using a powerful remote computer may not result in performance
improvement. However, a carefully chosen distribution of computations of SAC
consistently and substantially improves its performance on both tasks. On the
other hand, the performance of PPO remains largely unaffected by the
distribution of computations. In addition, when all computations happen solely
on a powerful tethered computer, the performance of our system remains on par
with an existing system that is well-tuned for using a single machine. ReLoD is
the only publicly available system for real-time RL that applies to multiple
robots for vision-based tasks.Comment: Appears in Proceedings of the 2023 International Conference on
Robotics and Automation (ICRA). Source code at
https://github.com/rlai-lab/relod and companion video at
https://youtu.be/7iZKryi1xS
The metal-weak Milky Way stellar disk hidden in the Gaia-Sausage-Enceladus debris: the APOGEE DR17 view
We have for the first time identified the early stellar disk in the Milky Way
by using a combination of elemental abundances and kinematics. Using data from
APOGEE DR17 and Gaia we select stars in the Mg-Mn-Al-Fe plane with elemental
abundances indicative of accreted origin and find stars with both halo-like and
disk-like kinematics. The stars with halo-like kinematics lie along a lower
sequence in [Mg/Fe], while the stars with disk-like kinematics lie along a
higher sequence. Through with asteroseismic observations, we determine the
stars with halo-like kinematics are old, 9-11 Gyr and that the more evolved
stellar disk is about 1-2 Gyr younger. We show that the in situ fraction of
stars on deeply bound orbits is not small, in fact the inner Galaxy likely
harbours a genuine in-situ population together with an accreted one. In
addition, we show that the selection of Gaia-Sausage-Enceladus in the En-Lz
plane is not very robust. In fact, radically different selection criteria give
almost identical elemental abundance signatures for the accreted stars.Comment: 32 pages, 19 figures, accepted to Ap
SignReLU neural network and its approximation ability
Deep neural networks (DNNs) have garnered significant attention in various
fields of science and technology in recent years. Activation functions define
how neurons in DNNs process incoming signals for them. They are essential for
learning non-linear transformations and for performing diverse computations
among successive neuron layers. In the last few years, researchers have
investigated the approximation ability of DNNs to explain their power and
success. In this paper, we explore the approximation ability of DNNs using a
different activation function, called SignReLU. Our theoretical results
demonstrate that SignReLU networks outperform rational and ReLU networks in
terms of approximation performance. Numerical experiments are conducted
comparing SignReLU with the existing activations such as ReLU, Leaky ReLU, and
ELU, which illustrate the competitive practical performance of SignReLU
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Intensive and comprehensive aphasia therapy—a survey of the definitions, practices and views of speech and language therapists in the United Kingdom
Background
Research evidence suggests aphasia therapy must be delivered at high intensity to effect change. Comprehensive therapy, addressing all domains of the International Classification of Functioning, Disability and Health, is also called for by people with aphasia and their families. However, aphasia therapy is rarely intense or comprehensive. Intensive Comprehensive Aphasia Programmes (ICAPs) were designed to address this challenge, but such programmes are not widely implemented.
Aims
This study surveyed the views of UK-based speech and language therapists (SLTs) regarding intensive and comprehensive aphasia therapy. It explored definitions of intensive and comprehensive therapy, patterns of provision, views about candidacy and barriers/facilitators. It also investigated awareness of ICAPs and perceived potential of this service model. Differences across UK regions and workplace settings were explored.
Methods & Procedures
An e-survey ran for 5 months. Quantitative data were analysed using descriptive and inferential statistics. Qualitative free text comments were analysed using content analysis.
Outcomes & Results
Two hundred twenty-seven respondents engaged in the e-survey. Definitions of intensive aphasia therapy did not reach UK clinical guideline/research-level thresholds for most of the sample. Those providing more therapy provided definitions with higher standards of intensity. Mean therapy delivered was 128 min/week. Geographical location and workplace setting influenced the amount of therapy delivered. The most frequently delivered therapy approaches were functional language therapy and impairment-based therapy. Cognitive disability and fatigue were concerns for therapy candidacy. Barriers included lack of resources and low levels of optimism that issues could be solved. 50% of respondents were aware of ICAPs and 15 had been involved in ICAP provision. Only 16.5% felt their service could be reconfigured to deliver an ICAP.
Conclusions & Implications
This e-survey evidences a mismatch between an SLT's concept of intensity and that espoused by clinical guidelines/research. Geographical variations in intensity are concerning. Although a wide range of therapy approaches are offered, certain aphasia therapies are delivered more frequently. Awareness of ICAPs was relatively high, but few respondents had experience of this model or felt it could be executed in their context. Further initiatives are needed if services are to move from a low-dose or non-comprehensive model of delivery. Such initiatives might include but not be confined to wider uptake of ICAPs. Pragmatic research might also explore which treatments are efficacious with a low-dose model of delivery, given that this model is dominant in the United Kingdom. These clinical and research implications are raised in the discussion.
What this paper adds
What is already known on this subject
There is a gap between the high intensity of aphasia treatment provided in research versus mainstream clinical settings. A lower standard of 45 min/day set by UK clinical guidelines is also not achieved. Although speech and language therapists (SLTs) provide a wide range of therapies, they typically focus on impairment-based approaches.
What this study adds
This is the first survey of UK SLTs asking about their concept of intensity in aphasia therapy and what types of aphasia therapy they provide. It explores geographical and workplace variations and barriers and facilitators to aphasia therapy provision. It investigates Intensive Comprehensive Aphasia Programmes (ICAPs) in a UK context.
What are the clinical implications of this work?
There are barriers to the provision of intensive and comprehensive therapy in the United Kingdom and reservations about the feasibility of ICAPs in a mainstream UK context. However, there are also facilitators to aphasia therapy provision and evidence that a small proportion of UK SLTs are providing intensive/comprehensive aphasia therapy). Dissemination of good practice is necessary and suggestions for increasing intensity of service provision are listed in the discussion
Quantum speed limit from a quantum-state-diffusion method
Characterizing the most efficient evolution, the quantum speed limit (QSL)
plays a significant role in quantum technology. How to generalize the
well-established QSL from closed systems to open systems has attracted much
attention. In contrast to the previous schemes to derive the QSL from the
reduced dynamics of open system, we propose a QSL bound from the point of view
of the total system consisting of the open system and its environment using a
quantum-state-diffusion method. The application of our scheme to a two-level
system reveals that the system possesses an infinite speedup capacity in the
noiseless case, which is destroyed by the environment under the Born-Markovian
approximation. It is interesting to find that the capacity in the noiseless
case is recovered in the non-Markovian dynamics as long as a bound state is
formed in the energy spectrum of the total system. Enriching the
characterization schemes of the QSL, our result provides an efficient way to
control the QSL of open systems
Weak localization in radiative transfer of acoustic waves in a randomly-fluctuating slab
This paper concerns the derivation of radiative transfer equations for
acoustic waves propagating in a randomly fluctuating slab (between two parallel
planes) in the weak-scattering regime, and the study of boundary effects
through an asymptotic analysis of the Wigner transform of the wave solution.
These radiative transfer equations allow to model the transport of wave energy
density, taking into account the scattering by random heterogeneities. The
approach builds on the method of images, where the slab is extended to a
full-space, with a periodic map of mechanical properties and a series of
sources located along a periodic pattern. Two types of boundary effects, both
on the (small) scale of the wavelength, are observed: one at the boundaries of
the slab, and one inside the domain. The former impact the entire energy
density (coherent as well as incoherent) and is also observed in half-spaces.
The latter, more specific to slabs, corresponds to the constructive
interference of waves that have reflected at least twice on the boundaries of
the slab and only impacts the coherent part of the energy density.Comment: 7 figure
Virtual reality check: a comparison of virtual reality, screen-based, and real world settings as research methods for HRI
To reduce costs and effort, experiments in human-robot interaction can be carried out in Virtual Reality (VR) or in screen-based (SB) formats. However, it is not well examined whether robots are perceived and experienced in the same way in VR and SB as they are in the physical world. This study addresses this topic in a between-subjects experiment, measuring trust and engagement of an interaction with a mobile service robot in a museum scenario. Measures were made in three different settings, either the real world, in VR or in a game-like SB and then compared with an ANOVA. The results indicate, that neither trust nor engagement differ dependent on the experimental setting. The results imply that both VR and SB are eligible ways to explore the interaction with a mobile service robot, if some peculiarities of each medium are taken into account
Distance education under oppression: The case of Palestinian higher education
© 2023 The Authors. Published by MDPI. This is an open access article available under a Creative Commons licence.
The published version can be accessed at the following link on the publisher’s website: https://doi.org/10.3390/educsci13070729This paper draws from both empirical research on an EU-funded project in Palestine and from the lived experiences of Palestinian HE educators. The geopolitical situation is precarious at the best of times in Palestine, where Israel monitors and controls the Palestinians’ right to travel, live and work—even more so if they wish to accomplish these activities abroad—and their access to the internet is never free from surveillance. In these circumstances and under these conditions, distance education has played a crucial role in supporting Palestinian students to develop a global voice. This paper captures some of the educational challenges encountered by Palestinian students and teachers generally in their daily contexts and, more specifically, in their experiences of learning and teaching, and the methods used to overcome these barriers. It draws on multiple sources and on studies re-cently carried out in the field by Palestinian colleagues and will discuss the challenging aspects of learning online from a range of perspectives in each of these studies before offering conclusions and recommendations/implications for other areas of study in situations of oppression. Initial findings indicate that distance education enables a form of continuity in regions exposed and accustomed to extreme and regular disruption. We were also inspired to see throughout responses the values at-tributed to pursuing education by Palestinian educators and their students. The persistence and perseverance reflect a determination that underlines the importance of education as a fundamental human right, national identity and sovereignty, personal source of hope and strength, and oppor-tunity to open one’s world. In our conclusions, we argue for the importance of digital literacy among educators to facilitate the continuity of distance education and finish with some recommendations as to how technologies can ease disruption to ordinary educational service.This research received no external funding
Information-Theoretic Limits on Compression of Semantic Information
As conventional communication systems based on classic information theory
have closely approached the limits of Shannon channel capacity, semantic
communication has been recognized as a key enabling technology for the further
improvement of communication performance. However, it is still unsettled on how
to represent semantic information and characterise the theoretical limits. In
this paper, we consider a semantic source which consists of a set of correlated
random variables whose joint probabilistic distribution can be described by a
Bayesian network. Then we give the information-theoretic limit on the lossless
compression of the semantic source and introduce a low complexity encoding
method by exploiting the conditional independence. We further characterise the
limits on lossy compression of the semantic source and the corresponding upper
and lower bounds of the rate-distortion function. We also investigate the lossy
compression of the semantic source with side information at both the encoder
and decoder, and obtain the rate distortion function. We prove that the optimal
code of the semantic source is the combination of the optimal codes of each
conditional independent set given the side information
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