14,504 research outputs found
Une nouvelle classe d'opérateurs de Teager-Kaiser multidimensionnels basée sur les dérivées directionnelles d'ordre supérieur
This work aims at introducing some energy operators linked to Teager-Kaiser energy operator and its associated higher order versions and expand them to multidimensional signals. These operators are very useful for analyzing oscillatory signals with time-varying amplitude and frequency (AM-FM). We prove that gradient tensors combined with Kronecker powers allow to express these operators by directional derivatives along any n-D vector. In particular, we show that the construction of a large class of non linear operators for AM-FM multidimensional signal demodulation is possible. Also, a new scalar function using the directional derivative along a vector giving the ”sign” of the frequency components is introduced. An application of this model to local n-D AM-FM signal is presented and related demodulation error rates estimates. To show the effectiveness and the robustness of our method in term of envelope and frequency components extraction, results obtained on synthetic and real data are compared to multi-dimensional energy separation algorithm and to our recently introduced n-D operator
Quantum Image Processing and Its Application to Edge Detection: Theory and Experiment
Processing of digital images is continuously gaining in volume and relevance,
with concomitant demands on data storage, transmission and processing power.
Encoding the image information in quantum-mechanical systems instead of
classical ones and replacing classical with quantum information processing may
alleviate some of these challenges. By encoding and processing the image
information in quantum-mechanical systems, we here demonstrate the framework of
quantum image processing, where a pure quantum state encodes the image
information: we encode the pixel values in the probability amplitudes and the
pixel positions in the computational basis states. Our quantum image
representation reduces the required number of qubits compared to existing
implementations, and we present image processing algorithms that provide
exponential speed-up over their classical counterparts. For the commonly used
task of detecting the edge of an image, we propose and implement a quantum
algorithm that completes the task with only one single-qubit operation,
independent of the size of the image. This demonstrates the potential of
quantum image processing for highly efficient image and video processing in the
big data era.Comment: 13 pages, including 9 figures and 5 appendixe
2-D Prony-Huang Transform: A New Tool for 2-D Spectral Analysis
This work proposes an extension of the 1-D Hilbert Huang transform for the
analysis of images. The proposed method consists in (i) adaptively decomposing
an image into oscillating parts called intrinsic mode functions (IMFs) using a
mode decomposition procedure, and (ii) providing a local spectral analysis of
the obtained IMFs in order to get the local amplitudes, frequencies, and
orientations. For the decomposition step, we propose two robust 2-D mode
decompositions based on non-smooth convex optimization: a "Genuine 2-D"
approach, that constrains the local extrema of the IMFs, and a "Pseudo 2-D"
approach, which constrains separately the extrema of lines, columns, and
diagonals. The spectral analysis step is based on Prony annihilation property
that is applied on small square patches of the IMFs. The resulting 2-D
Prony-Huang transform is validated on simulated and real data.Comment: 24 pages, 7 figure
HBT pion interferometry with phenomenological mean field interaction
To extract information on hadron production dynamics in the ultrarelativistic
heavy ion collision, the space-time structure of the hadron source has been
measured using Hanbury Brown and Twiss interferometry. We study the distortion
of the source images due to the effect of a final state interaction. We
describe the interaction, taking place during penetrating through a cloud
formed by evaporating particles, in terms of a one-body mean field potential
localized in the vicinity of the source region. By adopting the semiclassical
method, the modification of the propagation of an emitted particle is examined.
In analogy to the optical model applied to nuclear reactions, our
phenomenological model has an imaginary part of the potential, which describes
the absorption in the cloud. In this work, we focus on the pion interferometry
and mean field interaction obtained using a phenomenological forward
scattering amplitude in the elastic channels. The p-wave scattering with
meson resonance leads to an attractive mean field interaction, and the presence
of the absorptive part is mainly attributed to the formation of this resonance.
We also incorporate a simple time dependence of the potential reflecting the
dynamics of the evaporating source. Using the obtained potential, we examine
how and to what extent the so-called HBT Gaussian radius is varied by the
modification of the propagation
Transient Propagation and Scattering of Quasi-Rayleigh Waves in Plates: Quantitative comparison between Pulsed TV-Holography Measurements and FC(Gram) elastodynamic simulations
We study the scattering of transient, high-frequency, narrow-band
quasi-Rayleigh elastic waves by through-thickness holes in aluminum plates, in
the framework of ultrasonic nondestructive testing (NDT) based on full-field
optical detection. Sequences of the instantaneous two-dimensional (2-D)
out-of-plane displacement scattering maps are measured with a self-developed
PTVH system. The corresponding simulated sequences are obtained by means of an
FC(Gram) elastodynamic solver introduced recently, which implements a full
three-dimensional (3D) vector formulation of the direct linear-elasticity
scattering problem. A detailed quantitative comparison between these
experimental and numerical sequences, which is presented here for the first
time, shows very good agreement both in the amplitude and the phase of the
acoustic field in the forward, lateral and backscattering areas. It is thus
suggested that the combination of the PTVH system and the FC(Gram)
elastodynamic solver provides an effective ultrasonic inspection tool for
plate-like structures, with a significant potential for ultrasonic NDT
applications.Comment: 46 pages, 16 figures, corresponding author Jos\'e Carlos
L\'opez-V\'azquez, [email protected]. Changes: 1st, 4th, 5th paragraphs
(intro), 3rd, 4th paragraphs (sec. 4); [59-60] cited only in appendixes; old
ref. [52] removed; misprints corrected in the uncertainty of c_L (subsec.
3.1), citation to fig. 10 (sec. 4), size of images (caption fig.15);
reference to Lam\'e constants removed in subsec. 3.
Sexual pheromone modulates the frequency of cytosolic Ca2+ bursts in Saccharomyces cerevisiae
Transient and highly regulated elevations of cytosolic Ca2+ control a variety of cellular processes. Bulk measurements using radioactive Ca2+ and the luminescent sensor aequorin have shown that in response to pheromone, budding yeast cells experience a rise of cytosolic Ca2+ that is mediated by two import systems composed by the Mid1-Cch1-Ecm7 protein complex, and the Fig 1 protein. Although this response has been largely studied, there is no report on Ca2+ dynamics at the single cell level. Here, using protein calcium indicators we show that both vegetative and pheromone-treated yeast cells exhibit discrete and asynchronous Ca2+ bursts. Most bursts reach maximal amplitude in 1-10 secs, span between 7 and 30 secs and decay fitting a single exponential model. In vegetative cells bursts are scarce but preferentially occur when cells are transitioning G1 and S phase. Upon pheromone presence Ca2+ burst occurrence increases dramatically, persisting during cell growth polarization. Pheromone concentration modulates burst frequency in a mechanism that depends on Mid1, Fig 1 and a third, still unidentified, import system. We also show that the calcineurin-responsive transcription factor Crz1 experiences nuclear localization bursts during the pheromone response.Fil: Carbo, Natalia. Instituto Pasteur de Montevideo; UruguayFil: Tarkowski, Nahuel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas; ArgentinaFil: Perez Ipiña, Emiliano. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Ponce Dawson, Silvina Martha. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; ArgentinaFil: Aguilar, Pablo Sebastián. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; Argentin
A Survey of Ocean Simulation and Rendering Techniques in Computer Graphics
This paper presents a survey of ocean simulation and rendering methods in
computer graphics. To model and animate the ocean's surface, these methods
mainly rely on two main approaches: on the one hand, those which approximate
ocean dynamics with parametric, spectral or hybrid models and use empirical
laws from oceanographic research. We will see that this type of methods
essentially allows the simulation of ocean scenes in the deep water domain,
without breaking waves. On the other hand, physically-based methods use
Navier-Stokes Equations (NSE) to represent breaking waves and more generally
ocean surface near the shore. We also describe ocean rendering methods in
computer graphics, with a special interest in the simulation of phenomena such
as foam and spray, and light's interaction with the ocean surface
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