36,129 research outputs found
Weakly-Supervised Action Segmentation with Iterative Soft Boundary Assignment
In this work, we address the task of weakly-supervised human action
segmentation in long, untrimmed videos. Recent methods have relied on expensive
learning models, such as Recurrent Neural Networks (RNN) and Hidden Markov
Models (HMM). However, these methods suffer from expensive computational cost,
thus are unable to be deployed in large scale. To overcome the limitations, the
keys to our design are efficiency and scalability. We propose a novel action
modeling framework, which consists of a new temporal convolutional network,
named Temporal Convolutional Feature Pyramid Network (TCFPN), for predicting
frame-wise action labels, and a novel training strategy for weakly-supervised
sequence modeling, named Iterative Soft Boundary Assignment (ISBA), to align
action sequences and update the network in an iterative fashion. The proposed
framework is evaluated on two benchmark datasets, Breakfast and Hollywood
Extended, with four different evaluation metrics. Extensive experimental
results show that our methods achieve competitive or superior performance to
state-of-the-art methods.Comment: CVPR 201
Power Allocation for Energy-Harvesting-based Fading Cognitive Multiple Access Channels: with or without Successive Interference Cancellation
This paper considers a fading cognitive multiple access channel (CMAC), where multiple secondary users (SUs), who share the spectrum with a primary user (PU), transmit to a cognitive base station (CBS). A power station is assumed to harvest energy from the nature and then provide power to the SUs. We investigate the power allocation problems for such a CMAC to maximize the SU sum rate under the interference power constraint, the sum transmit power constraint and the peak transmit power constraint of each individual SU. In particular, two scenarios are considered: with successive interference cancellation (SIC) and without SIC. For the first scenario, the optimal power allocation algorithm is derived. For the second scenario, a heuristic algorithm is proposed. We show that the proposed algorithm with SIC outperforms the algorithm without SIC in terms of the SU sum rate, while the algorithm without SIC outperforms the algorithm with SIC in terms of the number of admitted SUs for a high sum transmit power limit and a low peak transmit power limit of each individual SU
Strongly lensed repeating Fast Radio Bursts as precision probes of the universe
Fast Radio bursts (FRBs), bright transients with millisecond durations at
GHz and typical redshifts probably , are likely to be
gravitationally lensed by intervening galaxies. Since the time delay between
images of strongly lensed FRB can be measured to extremely high precision
because of the large ratio between the typical galaxy-lensing delay
time (10 days) and the width of bursts (ms),
we propose strongly lensed FRBs as precision probes of the universe. We show
that, within the flat CDM model, the Hubble constant can be
constrained with a uncertainty from 10 such systems probably
observed with the Square Kilometer Array (SKA) in 30 years. More
importantly, the cosmic curvature can be model-independently constrained to a
precision of . This constraint can directly test the validity of the
cosmological principle and break the intractable degeneracy between the cosmic
curvature and dark energy.Comment: 8 pages, 6 figure
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