213 research outputs found
Dynamical Modelling and a Decentralized Adaptive Controller for a 12-Tetrahedral Rolling Robot
The 12-tetrahedral robot is an addressable reconfigurable technology (ART)-based variable geometry truss mechanism with twenty-six extensible struts and nine nodes arranged in a tetrahedral mesh. The robot has the capability of reconfiguring shape and dimension for environment sensing requirements, which makes it suitable for space exploration and environmental perception. In this paper, we have derived a dynamics model and presented a decentralized adaptive controller for a 12-tetrahedral robot. First, the robot is divided into the node and the strut subsystems, and the kinetic and the potential energy are calculated for the two subsystems. Then, the dynamics model is achieved by applying the Lagrangian formalism on the total energy of the robot. Since the dynamics is too complicated for implementing model-based controllers, a two-layer controller is presented to control the robot, in which the planning layer determines gait and trajectory of the robot, and the executive layer adopts the decentralized adaptive control strategy and consists of twenty-six strut controllers. Each strut controller regulates the movement of the corresponding strut without information exchange with other struts. Co-simulations based on ADAMS and Matlab have been conducted to verify the feasibility and effectiveness of the proposed controller
THE INFLUENCE OF CHROMATIC ABERRATION ON DEMOSAICKING
International audienceThe wide deployment of colour imaging devices owes much to the use of colour filter array (CFA). A CFA produces a mosaic image, and normally a subsequent CFA demosaick-ing algorithm interpolates the mosaic image and estimates the full-resolution colour image. Among various types of optical aberrations from which a mosaic image may suffer, chromatic aberration (CA) influences the spatial and spectral correlation through the artefacts such as blur and mis-registration, which demosaicking also relies on. In this paper we propose a simulation framework aimed at an investigation of the influence of CA on demosaicking. Results show that CA benefits de-mosaicking to some extent, however CA lowers the quality of resulting images by any means
Programmed Design of a LithiumâSulfur Battery Cathode by Integrating Functional Units
Sulfur is considered to be one of the most promising cathode materials due to its high theoretical specific capacity and low cost. However, the insulating nature of sulfur and notorious âshuttle effectâ of lithium polysulfides (LiPSs) lead to severe loss of active sulfur, poor redox kinetics, and rapid capacity fade. Herein, a hierarchical electrode design is proposed to address these issues synchronously, which integrates multiple building blocks with specialized functions into an ensemble to construct a selfâsupported versatile cathode for lithiumâsulfur batteries. Nickel foam acts as a robust conductive scaffold. The heteroatomâdoped host carbon with desired lithiophilicity and electronic conductivity serving as a reservoir for loading sulfur can trap LiPSs and promote electron transfer to interfacial adsorbed LiPSs and Ni3S2 sites. The sulfurized carbon nanofiber forest can facilitate the Liâion and electron transport and retard the LiPSs diffusion as a barrier layer. Sulfiphilic Ni3S2 acts as both a chemical anchor with strong adsorption affinity to LiPSs and an efficient electrocatalyst for accelerating kinetics for redox conversion reactions. Synergistically, all functional units promote the lithium ion coupled electron transfer for binding and redox conversion of LiPSs, resulting in high reversible capacities, remarkable cycle stability, and excellent rate capability
Coherent manipulation of spin wave vector for polarization of photons in an atomic ensemble
We experimentally demonstrate the manipulation of two-orthogonal components
of a spin wave in an atomic ensemble. Based on Raman two-photon transition and
Larmor spin precession induced by magnetic field pulses, the coherent rotations
between the two components of the spin wave is controllably achieved.
Successively, the two manipulated spin-wave components are mapped into two
orthogonal polarized optical emissions, respectively. By measuring Ramsey
fringes of the retrieved optical signals, the \pi/2-pulse fidelity of ~96% is
obtained. The presented manipulation scheme can be used to build an arbitrary
rotation for qubit operations in quantum information processing based on atomic
ensembles
Discrete wavelet transform based multispectral filter array demosaicking
International audienceThe idea of colour filter array may be adapted to multi-spectral image acquisition by integrating more filter types into the array, and developing associated demosaicking algorithms. Several methods employing discrete wavelet transform (DWT) have been proposed for CFA demosaicking. In this work, we put forward an extended use of DWT for mul-tispectral filter array demosaicking. The extension seemed straightforward, however we observed striking results. This work contributes to better understanding of the issue by demonstrating that spectral correlation and spatial resolution of the images exerts a crucial influence on the performance of DWT based demosaicking
CommonsenseVIS: Visualizing and Understanding Commonsense Reasoning Capabilities of Natural Language Models
Recently, large pretrained language models have achieved compelling
performance on commonsense benchmarks. Nevertheless, it is unclear what
commonsense knowledge the models learn and whether they solely exploit spurious
patterns. Feature attributions are popular explainability techniques that
identify important input concepts for model outputs. However, commonsense
knowledge tends to be implicit and rarely explicitly presented in inputs. These
methods cannot infer models' implicit reasoning over mentioned concepts. We
present CommonsenseVIS, a visual explanatory system that utilizes external
commonsense knowledge bases to contextualize model behavior for commonsense
question-answering. Specifically, we extract relevant commonsense knowledge in
inputs as references to align model behavior with human knowledge. Our system
features multi-level visualization and interactive model probing and editing
for different concepts and their underlying relations. Through a user study, we
show that CommonsenseVIS helps NLP experts conduct a systematic and scalable
visual analysis of models' relational reasoning over concepts in different
situations.Comment: This paper is accepted by IEEE VIS, 2023. To appear in IEEE
Transactions on Visualization and Computer Graphics (IEEE TVCG). 14 pages, 11
figure
Quantum Interference of Stored Coherent Spin-wave Excitations in a Two-channel Memory
Quantum memories are essential elements in long-distance quantum networks and
quantum computation. Significant advances have been achieved in demonstrating
relative long-lived single-channel memory at single-photon level in cold atomic
media. However, the qubit memory corresponding to store two-channel spin-wave
excitations (SWEs) still faces challenges, including the limitations resulting
from Larmor procession, fluctuating ambient magnetic field, and
manipulation/measurement of the relative phase between the two channels. Here,
we demonstrate a two-channel memory scheme in an ideal tripod atomic system, in
which the total readout signal exhibits either constructive or destructive
interference when the two-channel SWEs are retrieved by two reading beams with
a controllable relative phase. Experimental result indicates quantum coherence
between the stored SWEs. Based on such phase-sensitive storage/retrieval
scheme, measurements of the relative phase between the two SWEs and Rabi
oscillation, as well as elimination of the collapse and revival of the readout
signal, are experimentally demonstrated
Anchorage: Visual Analysis of Satisfaction in Customer Service Videos via Anchor Events
Delivering customer services through video communications has brought new
opportunities to analyze customer satisfaction for quality management. However,
due to the lack of reliable self-reported responses, service providers are
troubled by the inadequate estimation of customer services and the tedious
investigation into multimodal video recordings. We introduce Anchorage, a
visual analytics system to evaluate customer satisfaction by summarizing
multimodal behavioral features in customer service videos and revealing
abnormal operations in the service process. We leverage the semantically
meaningful operations to introduce structured event understanding into videos
which help service providers quickly navigate to events of their interest.
Anchorage supports a comprehensive evaluation of customer satisfaction from the
service and operation levels and efficient analysis of customer behavioral
dynamics via multifaceted visualization views. We extensively evaluate
Anchorage through a case study and a carefully-designed user study. The results
demonstrate its effectiveness and usability in assessing customer satisfaction
using customer service videos. We found that introducing event contexts in
assessing customer satisfaction can enhance its performance without
compromising annotation precision. Our approach can be adapted in situations
where unlabelled and unstructured videos are collected along with sequential
records.Comment: 13 pages. A preprint version of a publication at IEEE Transactions on
Visualization and Computer Graphics (TVCG), 202
EmoCo: Visual analysis of emotion coherence in presentation videos
Emotions play a key role in human communication and public presentations.
Human emotions are usually expressed through multiple modalities. Therefore,
exploring multimodal emotions and their coherence is of great value for
understanding emotional expressions in presentations and improving presentation
skills. However, manually watching and studying presentation videos is often
tedious and time-consuming. There is a lack of tool support to help conduct an
efficient and in-depth multi-level analysis. Thus, in this paper, we introduce
EmoCo, an interactive visual analytics system to facilitate efficient analysis
of emotion coherence across facial, text, and audio modalities in presentation
videos. Our visualization system features a channel coherence view and a
sentence clustering view that together enable users to obtain a quick overview
of emotion coherence and its temporal evolution. In addition, a detail view and
word view enable detailed exploration and comparison from the sentence level
and word level, respectively. We thoroughly evaluate the proposed system and
visualization techniques through two usage scenarios based on TED Talk videos
and interviews with two domain experts. The results demonstrate the
effectiveness of our system in gaining insights into emotion coherence in
presentations.Comment: 11 pages, 8 figures. Accepted by IEEE VAST 201
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