Friday, April 16, 2010

Around the blogs in 80 hours, a presentation and a conference.




The only way we can avoid a K-T level extinction event is to better know asteroids. Yesterday wasn't just tax day 2010, yesterday we've been told that we should be ready to land on an asteroid starting 2025, woohoo! That speech reminded of the other one made at that little institution from Texas we keep on hearing about (Compressed Sensing: Why does Rice Play Texas or How is CS a disruptive technology ? Part I).



The week-end is coming up, here are a list of blog entries of potential interest, but first let me mention two items related to Texas: a conference in Beijing (which site is hosted at UTA) and a presentation at Rice.

CSCN2010 The First Workshop on Compressive Sensing for Communications and Networking on Aug 15, 2010 in Beijing, China

Today will also see this presentation at Rice: Terahertz imaging with compressive sensing, Electrical and Computer Engineering, Speaker: Wai Lam Chan, Friday, April 16, 2010, 11:00 AM to 12:30 PM, A227 Abercrombie Engineering Laboratory. The abstract of the talk reads:

Most existing terahertz imaging systems are generally limited by slow image acquisition due to mechanical raster scanning. Other systems using focal plane detector arrays can acquire images in real time, but are either too costly or limited by low sensitivity in the terahertz frequency range.

To design faster and more cost-effective terahertz imaging systems, the first part of this thesis proposes two new terahertz imaging schemes based on compressive sensing (CS). Both schemes can acquire amplitude and phase-contrast images efficiently with a single-pixel detector, thanks to the powerful CS algorithms which enable the reconstruction of N-by-N pixel images with much fewer than N^2 measurements. The first CS Fourier imaging approach successfully reconstructs a 64x64 image of an object with pixel size 1.4 mm using a randomly chosen subset of the 4096 pixels which defines the image in the Fourier plane. Only about 12% of the pixels are required for reassembling the image of a selected object, equivalent to a 3/4 reduction in acquisition time. In combination with phase retrieval, the system also has the capability
to reconstruct images with only a small subset of Fourier amplitude measurements. The second single-pixel CS imaging approach uses a series of random masks for acquisition. Besides speeding up acquisition with a reduced number of measurements, the single-pixel system can further cut down acquisition time by electrical or optical spatial modulation of random patterns.

The speed of the second single-pixel CS imaging system is currently limited by the mechanical moving parts when modulating the random patterns. In order to switch between random patterns at high speed, the second part of this thesis implements a multi-pixel electrical spatial modulator for terahertz beams using active terahertz metamaterials. The first generation of this device consists of a 4x4 pixel array, where each pixel is an array of sub-wavelength-sized split-ring resonator elements fabricated on a semiconductor substrate, and is independently controlled by applying an external voltage. The results of terahertz transmission experiments show that the spatial modulator has a uniform modulation depth of around 40 percent across all pixels, and negligible crosstalk, at the resonant frequency. The second-generation spatial terahertz modulator, also based on metamaterials with a higher resolution (32x32), is under development. While a FPGA-based circuit is designed to independently control the large number of modulator pixels, certain challenges still exist in the fabrication and packaging of the modulator chip. Once fully implemented, this second-generation device will enable fast terahertz imaging with both pulsed and continuous-wave terahertz sources.


So here we are here is a selection of blog entries that deal with subjects somehow related to Compressive Sensing, here is what I found this past week, enjoy:

Gonzalo Vazquez Vilar in
I note a flurry of comments in the last entry I mentioned earlier last week ( CVX hackers? ). More specifically, one of the good things of being featured on Nuit Blanche is the ability to rise pretty high on Google search.

Andrew Gelman in
A Fast Hybrid Algorithm for Large Scale L1-Regularized Logistic Regression, hum...

Sarah in
Further reading includes: Random Matrix Theory.
K O'Rourke in
The AMD blog announced that we did not win a 48 processor machine, bummer.


My entry was here. I'll come back to that later.

Laurent Duval in





Credit: President Barack Obama delivers a speech at the Operations and Checkout Building at NASA Kennedy Space Center in Cape Canaveral, Fla. on Thursday, April 15, 2010. Obama visited Kennedy Space Center to deliver remarks on the bold new course the Administration is charting for NASA and the future of U.S. leadership in human space flight. Photo Credit: (NASA/Paul Alers)

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