1,185 research outputs found
Gradient-index Solar Sail and its Optimal Orbital Control
Solar sails with the capability of generating a tangential radiation pressure
at the sun-pointing attitude, such as refractive sails can provide more
efficient methods for attitude and orbital control of sailcraft. This paper
presents the concept of gradient-index sail as an advanced class of refractive
sail, which operates by guiding the solar radiation through a structure made of
graded refractive index material. The design of the sail's refractive index
distribution is performed by transformation optics, and the resultant index
realized by the effective refractive index of non-resonant bulk metamaterials
made of silica. The performance of the sail was evaluated by using ray tracing
for a broad spectrum of solar radiation under the normal incidence angle, which
showed an efficiency of 90.5% for generation of a tangential radiation
pressure. We also studied the orbital control of the
tangential-radiation-pressure-generating sails, and showed that the full
orbital control, including the modification of orbital axes, eccentricity, and
inclination can be applied by changing the attitude of the sail merely around
the sun-sail axis, while the sail keeps the sun-pointing attitude at every
point of the orbit
Deep Networks for Compressed Image Sensing
The compressed sensing (CS) theory has been successfully applied to image
compression in the past few years as most image signals are sparse in a certain
domain. Several CS reconstruction models have been recently proposed and
obtained superior performance. However, there still exist two important
challenges within the CS theory. The first one is how to design a sampling
mechanism to achieve an optimal sampling efficiency, and the second one is how
to perform the reconstruction to get the highest quality to achieve an optimal
signal recovery. In this paper, we try to deal with these two problems with a
deep network. First of all, we train a sampling matrix via the network training
instead of using a traditional manually designed one, which is much appropriate
for our deep network based reconstruct process. Then, we propose a deep network
to recover the image, which imitates traditional compressed sensing
reconstruction processes. Experimental results demonstrate that our deep
networks based CS reconstruction method offers a very significant quality
improvement compared against state of the art ones.Comment: This paper has been accepted by the IEEE International Conference on
Multimedia and Expo (ICME) 201
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