23,852 research outputs found
Statistical Studies of Fading in Underwater Wireless Optical Channels in the Presence of Air Bubble, Temperature, and Salinity Random Variations (Long Version)
Optical signal propagation through underwater channels is affected by three
main degrading phenomena, namely absorption, scattering, and fading. In this
paper, we experimentally study the statistical distribution of intensity
fluctuations in underwater wireless optical channels with random temperature
and salinity variations as well as the presence of air bubbles. In particular,
we define different scenarios to produce random fluctuations on the water
refractive index across the propagation path, and then examine the accuracy of
various statistical distributions in terms of their goodness of fit to the
experimental data. We also obtain the channel coherence time to address the
average period of fading temporal variations. The scenarios under consideration
cover a wide range of scintillation index from weak to strong turbulence.
Moreover, the effects of beam-collimator at the transmitter side and aperture
averaging lens at the receiver side are experimentally investigated. We show
that the use of a transmitter beam-collimator and/or a receiver aperture
averaging lens suits single-lobe distributions such that the generalized Gamma
and exponential Weibull distributions can excellently match the histograms of
the acquired data. Our experimental results further reveal that the channel
coherence time is on the order of seconds and larger which implies to
the slow fading turbulent channels
Stochastic Dynamics for Video Infilling
In this paper, we introduce a stochastic dynamics video infilling (SDVI)
framework to generate frames between long intervals in a video. Our task
differs from video interpolation which aims to produce transitional frames for
a short interval between every two frames and increase the temporal resolution.
Our task, namely video infilling, however, aims to infill long intervals with
plausible frame sequences. Our framework models the infilling as a constrained
stochastic generation process and sequentially samples dynamics from the
inferred distribution. SDVI consists of two parts: (1) a bi-directional
constraint propagation module to guarantee the spatial-temporal coherence among
frames, (2) a stochastic sampling process to generate dynamics from the
inferred distributions. Experimental results show that SDVI can generate clear
frame sequences with varying contents. Moreover, motions in the generated
sequence are realistic and able to transfer smoothly from the given start frame
to the terminal frame. Our project site is
https://xharlie.github.io/projects/project_sites/SDVI/video_results.htmlComment: Winter Conference on Applications of Computer Vision (WACV 2020
Automated segmentation on the entire cardiac cycle using a deep learning work-flow
The segmentation of the left ventricle (LV) from CINE MRI images is essential
to infer important clinical parameters. Typically, machine learning algorithms
for automated LV segmentation use annotated contours from only two cardiac
phases, diastole, and systole. In this work, we present an analysis work-flow
for fully-automated LV segmentation that learns from images acquired through
the cardiac cycle. The workflow consists of three components: first, for each
image in the sequence, we perform an automated localization and subsequent
cropping of the bounding box containing the cardiac silhouette. Second, we
identify the LV contours using a Temporal Fully Convolutional Neural Network
(T-FCNN), which extends Fully Convolutional Neural Networks (FCNN) through a
recurrent mechanism enforcing temporal coherence across consecutive frames.
Finally, we further defined the boundaries using either one of two components:
fully-connected Conditional Random Fields (CRFs) with Gaussian edge potentials
and Semantic Flow. Our initial experiments suggest that significant improvement
in performance can potentially be achieved by using a recurrent neural network
component that explicitly learns cardiac motion patterns whilst performing LV
segmentation.Comment: 6 pages, 2 figures, published on IEEE Xplor
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