9,207 research outputs found
Direction of Arrival with One Microphone, a few LEGOs, and Non-Negative Matrix Factorization
Conventional approaches to sound source localization require at least two
microphones. It is known, however, that people with unilateral hearing loss can
also localize sounds. Monaural localization is possible thanks to the
scattering by the head, though it hinges on learning the spectra of the various
sources. We take inspiration from this human ability to propose algorithms for
accurate sound source localization using a single microphone embedded in an
arbitrary scattering structure. The structure modifies the frequency response
of the microphone in a direction-dependent way giving each direction a
signature. While knowing those signatures is sufficient to localize sources of
white noise, localizing speech is much more challenging: it is an ill-posed
inverse problem which we regularize by prior knowledge in the form of learned
non-negative dictionaries. We demonstrate a monaural speech localization
algorithm based on non-negative matrix factorization that does not depend on
sophisticated, designed scatterers. In fact, we show experimental results with
ad hoc scatterers made of LEGO bricks. Even with these rudimentary structures
we can accurately localize arbitrary speakers; that is, we do not need to learn
the dictionary for the particular speaker to be localized. Finally, we discuss
multi-source localization and the related limitations of our approach.Comment: This article has been accepted for publication in IEEE/ACM
Transactions on Audio, Speech, and Language processing (TASLP
A sparse semi-blind source identification method and its application to Raman spectroscopy for explosives detection
Rapid and reliable detection and identification of unknown chemical substances are critical to homeland security. It is challenging to identify chemical components from a wide range of explosives. There are two key steps involved. One is a non-destructive and informative spectroscopic technique for data acquisition. The other is an associated library of reference features along with a computational method for feature matching and meaningful detection within or beyond the library. In this paper, we develop a new iterative method to identify unknown substances from mixture samples of Raman spectroscopy. In the first step, a constrained least squares method decomposes the data into a sum of linear combination of the known components and a non-negative residual. In the second step, a sparse and convex blind source separation method extracts components geometrically from the residuals. Verification based on the library templates or expert knowledge helps to confirm these components. If necessary, the confirmed meaningful components are fed back into step one to refine the residual and then step two extracts possibly more hidden components. The two steps may be iterated until no more components can be identified. We illustrate the proposed method in processing a set of the so called swept wavelength optical resonant Raman spectroscopy experimental data by a satisfactory blind extraction of a priori unknown chemical explosives from mixture samples. We also test the method on nuclear magnetic resonance (NMR) spectra for chemical compounds identification. © 2013 Published by Elsevier B.V
Sivers and Boer-Mulders observables from lattice QCD
We present a first calculation of transverse momentum dependent nucleon
observables in dynamical lattice QCD employing non-local operators with
staple-shaped, "process-dependent" Wilson lines. The use of staple-shaped
Wilson lines allows us to link lattice simulations to TMD effects determined
from experiment, and in particular to access non-universal, naively
time-reversal odd TMD observables. We present and discuss results for the
generalized Sivers and Boer-Mulders transverse momentum shifts for the SIDIS
and DY cases. The effect of staple-shaped Wilson lines on T-even observables is
studied for the generalized tensor charge and a generalized transverse shift
related to the worm gear function g_1T. We emphasize the dependence of these
observables on the staple extent and the Collins-Soper evolution parameter. Our
numerical calculations use an n_f = 2+1 mixed action scheme with domain wall
valence fermions on an Asqtad sea and pion masses 369 MeV as well as 518 MeV.Comment: 25 pages, 13 figures; version accepted by journal. Contains
additional section explaining and summarizing the methodolog
The Status of Parton Saturation and the CGC
This is a personal summary of the meeting "Saturation, the Color Glass
Condensate and Glasma: What Have we Learned from RHIC?" that took place at BNL
in May 2010. The purpose of the meeting was to discuss the status of high
density QCD and parton saturation, and to review the progress that RHIC has
allowed in the field.Comment: Summary talk of the workshop "Saturation, the Color Glass Condensate
and Glasma: What Have we Learned from RHIC?", BNL, May 2010. To be published
in Nucl. Phys.
Non-negative mixtures
This is the author's accepted pre-print of the article, first published as M. D. Plumbley, A. Cichocki and R. Bro. Non-negative mixtures. In P. Comon and C. Jutten (Ed), Handbook of Blind Source Separation: Independent Component Analysis and Applications. Chapter 13, pp. 515-547. Academic Press, Feb 2010. ISBN 978-0-12-374726-6 DOI: 10.1016/B978-0-12-374726-6.00018-7file: Proof:p\PlumbleyCichockiBro10-non-negative.pdf:PDF owner: markp timestamp: 2011.04.26file: Proof:p\PlumbleyCichockiBro10-non-negative.pdf:PDF owner: markp timestamp: 2011.04.2
Collinear factorization violation and effective field theory
The factorization of amplitudes into hard, soft and collinear parts is known
to be violated in situations where incoming particles are collinear to outgoing
ones. This result was first derived by studying limits where non-collinear
particles become collinear. We show that through an effective field theory
framework with Glauber operators, these factorization-violating effects can be
reproduced from an amplitude that is factorized before the splitting occurs. We
confirm results at one-loop, through single Glauber exchange, and at two-loops,
through double Glauber exchange. To approach the calculation, we begin by
reviewing the importance of Glauber scaling for factorization. We show that for
any situation where initial state and final state particles are not collinear,
the Glauber contribution is entirely contained in the soft contribution. The
contributions coming from Glauber operators are necessarily non-analytic
functions of external momentum, with the non-analyticity arising from the
rapidity regulator. The non-analyticity is critical so that Glauber operators
can both preserve factorization when it holds and produce
factorization-violating effects when they are present.Comment: 55 Pages, 5 figure
Spectral Separation of Quantum Dots within Tissue Equivalent Phantom Using Linear Unmixing Methods in Multispectral Fluorescence Reflectance Imaging
Introduction
Non-invasive Fluorescent Reflectance Imaging (FRI) is used for accessing physiological and molecular processes in biological media. The aim of this article is to separate the overlapping emission spectra of quantum dots within tissue-equivalent phantom using SVD, Jacobi SVD, and NMF methods in the FRI mode.
Materials and Methods
In this article, a tissue-like phantom and an optical setup in reflectance mode were developed. The algorithm of multispectral imaging method was then written in Matlab environment. The setup included the diode-pumped solid-state lasers at 479 nm, 533 nm, and 798 nm, achromatic telescopic, mirror, high pass and low pass filters, and EMCCD camera. The FRI images were acquired by a CCD camera using band pass filter centered at 600 nm and high pass max at 615 nm for the first region and high pass filter max at 810 nm for the second region. The SVD and Jacobi SVD algorithms were written in Matlab environment and compared with a Non-negative Matrix Factorization (NMF) and applied to the obtained images.
Results
PSNR, SNR, CNR of SVD, and NMF methods were obtained as 39 dB, 30.1 dB, and 0.7 dB, respectively. The results showed that the difference of Jacobi SVD PSNR with PSNR of NMF and modified NMF algorithm was significant (p<0.0001). The statistical results showed that the Jacobi SVD was more accurate than modified NMF.
Conclusion
In this study, the Jacobi SVD was introduced as a powerful method for obtaining the unmixed FRI images. An experimental evaluation of the algorithm will be done in the near future
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