10,172 research outputs found
Visualizing Road Appearance Properties in Driving Video
With the increasing videos taken from driving recorders on thousands of cars, it is a challenging task to retrieve these videos and search for important information. The goal of this work is to mine certain critical road properties in a large scale driving video data set for traffic accident analysis, sensing algorithm development, and testing benchmark. Our aim is to condense video data to compact road profiles, which contain visual features of the road environment. By visualizing road edge and lane marks in the feature space with the reduced dimension, we will further explore the road edge models influenced by road and off-road materials, weather, lighting condition, etc
Experimental observation and computational analysis of striations in electronegative capacitively coupled radio-frequency plasmas
Self-organized spatial structures in the light emission from the ion-ion
capacitive RF plasma of a strongly electronegative gas (CF4) are observed
experimentally for the first time. Their formation is analyzed and understood
based on particle-based kinetic simulations. These "striations" are found to be
generated by the resonance between the driving radio-frequency and the
eigenfrequency of the ion-ion plasma (derived from an analytical model) that
establishes a modulation of the electric field, the ion densities, as well as
the energy gain and loss processes of electrons in the plasma. The growth of
the instability is followed by the numerical simulations
Predict Vehicle Collision by TTC From Motion Using a Single Video Camera
The objective of this paper is the instantaneous computation of time-to-collision (TTC) for potential collision only from the motion information captured with a vehicle borne camera. The contribution is the detection of dangerous events and degree directly from motion divergence in the driving video, which is also a clue used by human drivers. Both horizontal and vertical motion divergence are analyzed simultaneously in several collision sensitive zones. The video data are condensed to the motion profiles both horizontally and vertically in the lower half of the video to show motion trajectories directly as edge traces. Stable motion traces of linear feature components are obtained through filtering in the motion profiles. As a result, this avoids object recognition and sophisticated depth sensing in prior. The fine velocity computation yields reasonable TTC accuracy so that a video camera can achieve collision avoidance alone from the size changes of visual patterns. We have tested the algorithm for various roads, environments, and traffic, and shown results by visualization in the motion profiles for overall evaluation
Progressive Transient Photon Beams
In this work we introduce a novel algorithm for transient rendering in
participating media. Our method is consistent, robust, and is able to generate
animations of time-resolved light transport featuring complex caustic light
paths in media. We base our method on the observation that the spatial
continuity provides an increased coverage of the temporal domain, and
generalize photon beams to transient-state. We extend the beam steady-state
radiance estimates to include the temporal domain. Then, we develop a
progressive version of spatio-temporal density estimations, that converges to
the correct solution with finite memory requirements by iteratively averaging
several realizations of independent renders with a progressively reduced kernel
bandwidth. We derive the optimal convergence rates accounting for space and
time kernels, and demonstrate our method against previous consistent transient
rendering methods for participating media
Polarized cortical tension drives zebrafish epiboly movements
The principles underlying the biomechanics of morphogenesis are
largely unknown. Epiboly is an essential embryonic event in which
three tissues coordinate to direct the expansion of the blastoderm.
How and where forces are generated during epiboly, and how
these are globally coupled remains elusive. Here we developed a
method, hydrodynamic regression (HR), to infer 3D pressure fields,
mechanical power, and cortical surface tension profiles. HR is
based on velocity measurements retrieved from 2D+T microscopy
and their hydrodynamic modeling. We applied HR to identify
biomechanically active structures and changes in cortex local
tension during epiboly in zebrafish. Based on our results, we
propose a novel physical description for epiboly, where tissue
movements are directed by a polarized gradient of cortical tension.
We found that this gradient relies on local contractile forces at the
cortex, differences in elastic properties between cortex components
and the passive transmission of forces within the yolk cell.
All in all, our work identifies a novel way to physically regulate
concerted cellular movements that might be instrumental for the
mechanical control of many morphogenetic processes.Peer ReviewedPostprint (author's final draft
Direct Vehicle Collision Detection from Motion in Driving Video
The objective of this work is the instantaneous computation of Time-to-Collision (TTC) for potential collision only from motion information captured with a vehicle borne camera. The contribution is the detection of dangerous events and degree directly from motion divergence in the driving video, which is also a clue used by human drivers, without applying vehicle recognition and depth measuring in prior. Both horizontal and vertical motion divergence are analyzed simultaneously in several collision sensitive zones. Stable motion traces of linear feature components are obtained through filtering in the motion profiles. As a result, this avoids object recognition, and sophisticated depth sensing. The fine velocity computation yields reasonable TTC accuracy so that the video camera can achieve collision avoidance alone from size changes of visual patterns
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