353 research outputs found
Blind Compressed Sensing Over a Structured Union of Subspaces
This paper addresses the problem of simultaneous signal recovery and
dictionary learning based on compressive measurements. Multiple signals are
analyzed jointly, with multiple sensing matrices, under the assumption that the
unknown signals come from a union of a small number of disjoint subspaces. This
problem is important, for instance, in image inpainting applications, in which
the multiple signals are constituted by (incomplete) image patches taken from
the overall image. This work extends standard dictionary learning and
block-sparse dictionary optimization, by considering compressive measurements,
e.g., incomplete data). Previous work on blind compressed sensing is also
generalized by using multiple sensing matrices and relaxing some of the
restrictions on the learned dictionary. Drawing on results developed in the
context of matrix completion, it is proven that both the dictionary and signals
can be recovered with high probability from compressed measurements. The
solution is unique up to block permutations and invertible linear
transformations of the dictionary atoms. The recovery is contingent on the
number of measurements per signal and the number of signals being sufficiently
large; bounds are derived for these quantities. In addition, this paper
presents a computationally practical algorithm that performs dictionary
learning and signal recovery, and establishes conditions for its convergence to
a local optimum. Experimental results for image inpainting demonstrate the
capabilities of the method
Recommended from our members
Electrodeposition of Diamond-like Carbon Films
Electrodeposition of diamond-like carbon (DLC) films was studied on different substrates using two different electrochemical methods. The first electrochemical method using a three-electrode system was studied to successfully deposit hydrogenated DLC films on Nickel, Copper and Brass substrates. The as-deposited films were characterized by scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), fourier transform infrared spectroscopy (FTIR) and cyclic voltammetry (CV). A variety of experimental parameters were shown to affect the deposition process. The second electrochemical method was developed for the first time to deposit hydrogen free DLC films on Ni substrates through a two-electrode system. The as-deposited films were characterized by Raman spectroscopy and FTIR. According to Raman spectra, a high fraction of diamond nanocrystals were found to form in the films. Several possible mechanisms were discussed for each deposition method. An electrochemical method was proposed to deposit boron-doped diamond films for future work
Minimum superlattice thermal conductivity from molecular dynamics
The dependence of superlattice thermal conductivity on period length is investigated by molecular dynamics simulation. For perfectly lattice matched superlattices, a minimum is observed when the period length is of the order of the effective phonon mean free path. As temperature decreases and interatomic potential strength increases, the position of the minimum shifts to larger period lengths. The depth of the minimum is strongly enhanced as mass and interatomic potential ratios of the constituent materials increase. The simulation results are consistent with phonon transmission coefficient calculations, which indicate increased stop bandwidth and thus strongly enhanced Bragg scattering for the same conditions under which strong reductions in thermal conductivity are found. When nonideal interfaces are created by introducing a 4% lattice mismatch, the minimum disappears and thermal conductivity increases monotonically with period length. This result may explain why minimum thermal conductivity has not been observed in a large number of experimental studies
Communications-Inspired Projection Design with Application to Compressive Sensing
We consider the recovery of an underlying signal x \in C^m based on
projection measurements of the form y=Mx+w, where y \in C^l and w is
measurement noise; we are interested in the case l < m. It is assumed that the
signal model p(x) is known, and w CN(w;0,S_w), for known S_W. The objective is
to design a projection matrix M \in C^(l x m) to maximize key
information-theoretic quantities with operational significance, including the
mutual information between the signal and the projections I(x;y) or the Renyi
entropy of the projections h_a(y) (Shannon entropy is a special case). By
capitalizing on explicit characterizations of the gradients of the information
measures with respect to the projections matrix, where we also partially extend
the well-known results of Palomar and Verdu from the mutual information to the
Renyi entropy domain, we unveil the key operations carried out by the optimal
projections designs: mode exposure and mode alignment. Experiments are
considered for the case of compressive sensing (CS) applied to imagery. In this
context, we provide a demonstration of the performance improvement possible
through the application of the novel projection designs in relation to
conventional ones, as well as justification for a fast online projections
design method with which state-of-the-art adaptive CS signal recovery is
achieved.Comment: 25 pages, 7 figures, parts of material published in IEEE ICASSP 2012,
submitted to SIIM
Proteomic Analysis of Serum in Lung Cancer Induced by 3-Methylcholanthrene
Lung cancer remains the leading cause of cancer-related mortality worldwide. Early detection of lung cancer is problematic due to the lack of a marker with high diagnosis sensitivity and specificity. To determine the differently expressed proteins in the serum of lung cancer and figure out the function of the proteins, two-dimensional electrophoresis (2DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) were used to screen the serum proteins of lung cancer model induced by 3-methylcholanthrene (MCA). From optimized 2DE image, 455 spots in the normal sera and 716 spots in the lung cancers sera were detected. Among them, 141 protein spots were differentially expressed when comparing the serum from normal rat and serum from lung cancer model, including 82 overexpressed proteins and 59 underexpressed proteins. Changes of haptoglobin, transthyretin, and TNF superfamily member 8 (TNFRS8) were confirmed in sera from lung cancer by MALDI-TOF-MS. Proteomics technology leads to identify changes of haptoglobin, transthyretin, and TNFRS8 in serum of rat lung cancer model and represents a powerful tool in searching for candidate proteins as biomarkers
- …