236 research outputs found
The Effects of Separating Visual and Motor Workspaces on the Generalization of Visuomotor Adaptation across Movement Conditions
Separating visual and proprioceptive information in terms of workspace locations during reaching movement has been shown to disturb transfer of visuomotor adaptation across the arms. Here, we investigated whether separating visual and motor workspaces would also disturb generalization of visuomotor adaptation across movement conditions within the same arm. In our behavioral study, subjects were divided into four experimental groups (plus three control groups). The first two groups adapted to a visual rotation under a dissociation condition in which the targets for reaching movement were presented in midline while their arm performed reaching movement laterally. Following that, they were tested in an association condition in which the visual and motor workspaces were combined in midline or laterally. The other two groups first adapted to the rotation in one association condition (medial or lateral), then were tested in the other association condition. The latter groups demonstrated complete transfer from the training to the generalization session, whereas the former groups demonstrated substantially limited transfer. In our fMRI study, we examined brain activity while subjects learned a visuomotor adaptation task in a condition in which visual and motor workspaces were either dissociated or associated with each other, and subsequently performed the same visuomotor task with the same hand in a condition in which visual and motor workspace were associated. Our main results showed that the neural involvement is similar between the early training and the early generalization phases in the `dissociation-to-association\u27 conditions; while that is similar between the late adaptation and the early generalization phases in the `association-to-association\u27 condition. These findings suggest that a visual-proprioceptive conflict in terms of workspace locations disrupts the development of a neural representation, or an internal model, that is associated with novel visuomotor adaptation, thus resulting in limited generalization of visuomotor adaptation
Maximizing the Effects of Passive Training on Visuomotor Adaptation By Incorporating Other Motor Learning Strategies
Passive training has been shown to be an effective rehabilitation approach for stroke survivors, especially for those who suffer from severe control loss or complete paralysis. However, the effectiveness of the treatments that utilize passive assist training is still low. The goal of this dissertation was to develop a training condition that can maximize the effects of passive training on motor learning by combining its effect with other motor learning strategies. To achieve this goal, two specific aims were pursued: one aim was to determine the effects of passive training on learning a visuomotor adaptation task; and the other aim was to determine the effects of passive training in combination with other strategies on learning a visuomotor adaptation task. Experimental results indicated that passive training has a positive effect on visuomotor learning. Furthermore, it was confirmed that a training condition consisting of action observation and passive training leads to significant performance gains beyond what either intervention alone can do. This suggests that passive training could elicit motor representational changes, inducing instance-reliant learning process (use-dependent plasticity) that encodes motor instances associated with specific effectors and task conditions. The findings from this study show great potential for developing specific rehabilitation protocols that utilize passive training and action observation together for severely impaired stroke patients in the future
Separation of Visual and Motor Workspaces During Targeted Reaching Results in Limited Generalization of Visuomotor Adaptation
Separating visual and proprioceptive information in terms of workspace locations during reaching movement has been shown to disturb transfer of visuomotor adaptation across the arms. Here, we investigated whether separating visual and motor workspaces would also disturb generalization of visuomotor adaptation across movement conditions within the same arm. Subjects were divided into four experimental groups (plus three control groups). The first two groups adapted to a visual rotation under a “dissociation” condition in which the targets for reaching movement were presented in midline while their arm performed reaching movement laterally. Following that, they were tested in an “association” condition in which the visual and motor workspaces were combined in midline or laterally. The other two groups first adapted to the rotation in one association condition (medial or lateral), then were tested in the other association condition. The latter groups demonstrated complete transfer from the training to the generalization session, whereas the former groups demonstrated substantially limited transfer. These findings suggest that when visual and motor workspaces are separated, two internal models (vision-based one, proprioception-based one) are formed, and that a conflict between the two disrupts the development of an overall representation that underlies adaptation to a novel visuomotor transform
Why does the apparent mass of a coronal mass ejection increase?
Mass is one of the most fundamental parameters characterizing the dynamics of
a coronal mass ejection (CME). It has been found that CME apparent mass
measured from the brightness enhancement in coronagraph images shows an
increasing trend during its evolution in the corona. However, the physics
behind it is not clear. Does the apparent mass gain come from the mass outflow
from the dimming regions in the low corona, or from the pileup of the solar
wind plasma around the CME when it propagates outwards from the Sun? We
analyzed the mass evolution of six CME events. Their mass can increase by a
factor of 1.6 to 3.2 from 4 to 15 Rs in the field of view (FOV) of the
coronagraph on board the Solar Terrestrial Relations Observatory (STEREO). Over
the distance about 7 to 15 Rs, where the coronagraph occulting effect can be
negligible, the mass can increase by a factor of 1.3 to 1.7. We adopted the
`snow-plough' model to calculate the mass contribution of the piled-up solar
wind in the height range from about 7 to 15 Rs. For 2/3 of the events, the
solar wind pileup is not sufficient to explain the measured mass increase. In
the height range from about 7 to 15 Rs, the ratio of the modeled to the
measured mass increase is roughly larger than 0.55. Although the ratios are
believed to be overestimated, the result gives evidence that the solar wind
pileup probably makes a non-negligible contribution to the mass increase. It is
not clear yet whether the solar wind pileup is a major contributor to the final
mass derived from coronagraph observations. However, our study suggests that
the solar wind pileup plays increasingly important role in the mass increase as
a CME moves further away from the Sun.Comment: 27 pages, 2 tables, 9 figures, accepted by Ap
ARCH-COMP20 Category Report: Hybrid Systems with Piecewise Constant Dynamics and Bounded Model Checking
This report presents the results of a friendly competition for formal verification of continuous and hybrid systems with piecewise constant dynamics. The friendly competition took place as part of the workshop Applied Verification for Continuous and Hybrid Systems (ARCH) in 2020. In this fourth edition, five tools have been applied to solve six different benchmark problems in the category for piecewise constant dynamics: BACH, PHAVerLite, PHAVer/SX, TROPICAL, and XSpeed. Compared to last year, we combine the HBMC and HPWC categories of ARCH-COMP 2019 to a new category PCDB (hybrid systems with Piecewise Constant bounds on the Dynamics (HPCD) and Bounded model checking (BMC) of HPCD systems). The result is a snapshot of the current landscape of tools and the types of benchmarks they are particularly suited for. Due to the diversity of problems, we are not ranking tools, yet the presented results probably provide the most complete assessment of tools for the safety verification of continuous and hybrid systems with piecewise constant dynamics up to this date
ReliTalk: Relightable Talking Portrait Generation from a Single Video
Recent years have witnessed great progress in creating vivid audio-driven
portraits from monocular videos. However, how to seamlessly adapt the created
video avatars to other scenarios with different backgrounds and lighting
conditions remains unsolved. On the other hand, existing relighting studies
mostly rely on dynamically lighted or multi-view data, which are too expensive
for creating video portraits. To bridge this gap, we propose ReliTalk, a novel
framework for relightable audio-driven talking portrait generation from
monocular videos. Our key insight is to decompose the portrait's reflectance
from implicitly learned audio-driven facial normals and images. Specifically,
we involve 3D facial priors derived from audio features to predict delicate
normal maps through implicit functions. These initially predicted normals then
take a crucial part in reflectance decomposition by dynamically estimating the
lighting condition of the given video. Moreover, the stereoscopic face
representation is refined using the identity-consistent loss under simulated
multiple lighting conditions, addressing the ill-posed problem caused by
limited views available from a single monocular video. Extensive experiments
validate the superiority of our proposed framework on both real and synthetic
datasets. Our code is released in https://github.com/arthur-qiu/ReliTalk
A polybenzimidazole/graphite oxide based three layer membrane for intermediate temperature polymer electrolyte membrane fuel cells
A three layer membrane (TLM) of polybenzimidazole/graphite oxide/polybenzimidazole (PBI/GO/PBI) has been fabricated as an electrolyte for intermediate temperature polymer exchange membrane fuel cells (IT-PEMFCs). The membrane is prepared by encapsulating a GO layer with two single PBI membranes via a layer-by-layer procedure and subsequently imbibed with phosphoric acid (PA). The TLM exhibits a lower swelling ratio than that of the pristine PBI membrane at the same PA loading time. The mechanical strength of the TLM could reach 28.6 MPa at 150 °C, significantly higher than that of a PBI membrane (12.2 MPa). The TLM is loaded with a PA amount of 2.23H3PO4 molecules per repeat unit (PRU), which provides a proton conductivity of 0.0138 S cm−1 at 150 °C. The three layer structure promotes a membrane for PEMFCs with lower PA leakage and material corrosion. The fuel cell performance based on TLM exhibits a peak power density of 210 mW cm−2 at 150 °C
- …