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- American Institute of Physics
- Hindawi Publishing Corporation
- Massachusetts Institute of Technology
- University of Rochester.
- University of Rochester
- Monterey, California. Naval Postgraduate School
- Monterey California. Naval Postgraduate School
- Universidade Cornell
- American Geophysical Union
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## Invited Review Article: Review of centrifugal microfluidic and bio-optical disks

Fonte: American Institute of Physics
Publicador: American Institute of Physics

Tipo: Artigo de Revista Científica

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Spinning biodisks have advantages that make them attractive for specialized biochip applications. The two main classes of spinning biodisks are microfluidic disks and bio-optical compact disks (BioCD). Microfluidic biodisks take advantage of noninertial pumping for lab-on-a-chip devices using noninertial valves and switches under centrifugal and Coriolis forces to distribute fluids about the disks. BioCDs use spinning-disk interferometry, under the condition of common-path phase quadrature, to perform interferometric label-free detection of molecular recognition and binding. The optical detection of bound molecules on a disk is facilitated by rapid spinning that enables high-speed repetitive sampling to eliminate 1∕f noise through common-mode rejection of intensity fluctuations and extensive signal averaging. Multiple quadrature classes have been developed, such as microdiffraction, in-line, phase contrast, and holographic adaptive optics. Thin molecular films are detected through the surface dipole density with a surface height sensitivity for the detection of protein spots that is approximately 1 pm. This sensitivity easily resolves a submonolayer of solid-support immobilized antibodies and their antigen targets. Fluorescence and light scattering provide additional optical detection techniques on spinning disks. Immunoassays have been applied to haptoglobin using protein A∕G immobilization of antibodies and to prostate specific antigen. Small protein spots enable scalability to many spots per disk for high-throughput and highly multiplexed immonoassays.

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## Interferometric Dynamic Measurement: Techniques Based on High-Speed Imaging or a Single Photodetector

Fonte: Hindawi Publishing Corporation
Publicador: Hindawi Publishing Corporation

Tipo: Artigo de Revista Científica

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In recent years, optical interferometry-based techniques have been widely used to perform noncontact measurement of dynamic deformation in different industrial areas. In these applications, various physical quantities need to be measured in any instant and the Nyquist sampling theorem has to be satisfied along the time axis on each measurement point. Two types of techniques were developed for such measurements: one is based on high-speed cameras and the other uses a single photodetector. The limitation of the measurement range along the time axis in camera-based technology is mainly due to the low capturing rate, while the photodetector-based technology can only do the measurement on a single point. In this paper, several aspects of these two technologies are discussed. For the camera-based interferometry, the discussion includes the introduction of the carrier, the processing of the recorded images, the phase extraction algorithms in various domains, and how to increase the temporal measurement range by using multiwavelength techniques. For the detector-based interferometry, the discussion mainly focuses on the single-point and multipoint laser Doppler vibrometers and their applications for measurement under extreme conditions. The results show the effort done by researchers for the improvement of the measurement capabilities using interferometry-based techniques to cover the requirements needed for the industrial applications.

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## Synthetic Aperture Radar Interferometry with 3 satellites; InSAR with 3 satellites

Fonte: Massachusetts Institute of Technology
Publicador: Massachusetts Institute of Technology

Tipo: Tese de Doutorado
Formato: 128 p.; 6805700 bytes; 6811039 bytes; application/pdf; application/pdf

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Our study investigates interferometric SAR (InSAR) post-processing height retrieval techniques. We explore the possible improvements by adding a third satellite to the two already in orbit, and examine some potential uses of this setup. As such, we investigate three methods for height retrieval and compare their results with the original 2-satellite method. The first approach is data averaging; a simple method that extends from the results obtained using the 2-satellite method. The 3 sets of data obtained per sampling look are grouped into pairs, and the 2 statistical best pairs are selected to be averaged, producing a better estimate of the digital elevation map (DEM) height. The second approach is the unambiguous range magnification (URM) method, which seeks to ease the reliance on phase unwrapping steps often necessary in retrieving height. It does so by expanding the wrapped phase range without performing any phase unwrapping, through the use of different wrapping speeds of the 3 sets of satellite pairings. The third method is the maximum likelihood estimation technique, an asymptotically efficient method which employs the same phase expansion property as the URM to predict the closest phase estimate which best fits most (if not all) of the data sets provided.; (cont.) Results show that for a handful of flyover looks...

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## Phase diversity for segmented and multi-aperture systems

Fonte: University of Rochester.
Publicador: University of Rochester.

Tipo: Tese de Doutorado
Formato: Number of Pages:xxx, 180 leaves

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Thesis (Ph. D.)--University of Rochester. Institute of Optics, 2009.; As telescopes become larger, segmented and multi-aperture designs are being implemented to meet cost, size and weight constraints. These systems require alignment of the segments or sub-apertures to within fractions of a wavelength. We investigate the performance of phase diversity, a technique of image-based wavefront sensing, for characterizing and aligning segmented and multi-aperture systems. Supporting work developing the core phase-diversity algorithm is also presented. The modification of phase diversity to incorporate a broadband object model is discussed. Through digital simulation, we show a benefit to using a broadband, gray-world algorithm, as opposed to the conventional monochromatic algorithm, when bandwidths greater than 20% are used for imaging. We further demonstrate that knowledge of the gray-world object spectrum is not required to achieve improved performance. Using digital simulation, three regularization techniques for phase-diversity metrics are compared to the conventional phase-diversity algorithm. For low signal-to-noise ratio (SNR), we demonstrate an improvement in both the phase estimation accuracy and convergence properties of the algorithm when a regularization based on the object and noise power spectra is used. We present a novel implementation of phase diversity unique to segmented and multi-aperture systems that utilizes individual sub-aperture piston phases in the pupil. Through digital simulation...

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## Robust image-based wavefront sensing

Fonte: University of Rochester
Publicador: University of Rochester

Tipo: Tese de Doutorado
Formato: Number of Pages:xxii, 171 leaves; Illustrations:ill. (some col.)

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Thesis (Ph. D.)--University of Rochester. Institute of Optics, 2011.; Several planned future optical systems, such as the James Webb Space Telescope (JWST), rely on image-based wavefront sensing for alignment, testing, and control of optical surfaces during operation. The focus of this work is on characterizing the effects of various non-idealities on the performance of image-based wavefront sensing algorithms, developing techniques to mitigate those effects, and demonstrating these techniques in computer simulations and in the lab. Two new techniques for algorithmically determining the proper sampling factor for optical propagation are presented and tested against experimental data collected in the lab and during JWST ground-based testing. A new method for mitigating against the effects of vibration on phase retrieval is discussed, implemented, and tested in simulation. The use of an alternative type of diversity, called transverse translation, is explored for use in the JWST and shown to be a promising technique through simulation. A method for extending the capture range of phase retrieval algorithms is presented and tested both in simulation and with experimental data collected in the lab. A benchmark of a phase retrieval algorithm running on a graphics card is presented and the practical implications for JWST testing are discussed. Finally...

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## Design of a phase sampled interferometry antenna using the robust symmetrical number system

Fonte: Monterey, California. Naval Postgraduate School
Publicador: Monterey, California. Naval Postgraduate School

Tipo: Tese de Doutorado

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This research has examined the benefits of using the Robust Symmetrical Number System (RSNS) to resolve ambiguities in phase sampling interferometry. A compact, high resolution direction finding antenna architecture based on the RSNS was developed to demonstrate experimentally the elimination of phase errors using a minimum amount of hardware. Previous work has determined that phase errors in the system will degrade the system performance. Several improvements were made to the original RSNS prototype antenna to provide enhanced performance. Adding isolators and supplementing the ground plane with copper tape (between the antenna elements), a reduction in the mutual coupling effects was accomplished. Mounting the microwave components on a brass plate also reduced errors contributed by vibrations and temperature. Tailor cutting all semi-rigid coaxial lines also helped reduce the number of connectors required to assemble the microwave circuit, also a source of phase errors. Matching the front-end amplifiers in each amplification stage rather than matching the characteristics of two cascaded amplifiers in each signal line has reduced relative phase errors between channels as well as matching the power outputs of the amplifiers. Two printed circuit boards were designed and built for the RSNS signal processor. The printed circuit boards provide a decrease in the electrical noise floor over the original design (assembled on breadboards). The new design has reduced the phase errors that were present in the first prototype system. The RSNS signal processing technique is able to provide a high-resolution phase sampled direction finding capability with an angular resolution of 1.9 degrees by using only three receiving elements (two interferometers)

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## Application of the robust symmetrical number system to high resolution direction finding interferometry

Fonte: Monterey, California. Naval Postgraduate School
Publicador: Monterey, California. Naval Postgraduate School

Tipo: Tese de Doutorado

Português

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To reduce the number of phase sampling comparators in a direction finding (DF) interferometer antenna, a new array based on a robust symmetrical number system (RSNS) is described. The RSNS is used to decompose the spatial filtering operation into a number of parallel sub-operations that are of smaller computational complexity. Each sub-operation (interferometer) symmetrically folds the phase with folding period equal to 2Nm(i) where N is the number of channels that are used and n(i) the channel modulus. A small comparator ladder mid-level quantizes each folded phase response. Each sub-operation only requires a precision in accordance with that modulus. A much higher DF resolution is achieved after the N different RSNS moduli are used and the results of these low precision sub-operations are recombined. The parallel use of phase waveforms increases the antenna resolution without increasing the folding rate of the system. The new antenna is constructed and tested in an anechoic chamber, and the results are compared with the experimental results of a previously tested optimum symmetrical number system (OSNS) array. Although the dynamic range of the RSNS is somewhat less than the OSNS, the inherent Gray code properties make it attractive for error control in phase sampling interferometry.

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## Mixed signal processor for a robust symmetrical number system direction finding antenna

Fonte: Monterey California. Naval Postgraduate School
Publicador: Monterey California. Naval Postgraduate School

Formato: xvi, 100 p. : ill. (some col.) ; 28 cm.

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#Antennas (Electronics)#Robust symmetrical number system#Phase sampling interferometry#Direction finding#Ambiguity resolution#antennas.#

Approved for public release; distribution is unlimited.; Approved for public release; distribution is unlimited.; This applied research project has designed, simulated, constructed and tested the performance of a processing system for a prototype direction finding antenna. A mixed signal architecture to derive the direction of arrival from a Robust Symmetrical Number System (RSNS) encoded direction finding array is based on a new phase sampling interferometer approach that can be easily incorporated into established techniques to provide a high resolution, small-baseline array with few number of phase sampling comparators. The approach is based on preprocessing the received signal using the RSNS. The preprocessing is used to decompose the spatial filtering operation into a number of parallel suboperations (moduli) that are of smaller computational complexity. A much higher direction finding spatial resolution is achieved after the N different moduli are used and the results of the low precision suboperations are recombined, in addition to the reduction of the number of possible encoding errors due to the RSNS' inherent Gray-coding properties. This has resulted in a four inch antenna array being able to attain an angular resolution of less than 1.8 degrees with a continuous field of view of 120 degrees. The accompanying electronics occupy two 6 inch by 8 inch printed circuit boards...

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## The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 21/05/2010
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Recent high resolution observations of the Galactic center black hole allow
for direct comparison with accretion disk simulations. We compare
two-temperature synchrotron emission models from three dimensional, general
relativistic magnetohydrodynamic simulations to millimeter observations of Sgr
A*. Fits to very long baseline interferometry and spectral index measurements
disfavor the monochromatic face-on black hole shadow models from our previous
work. Inclination angles \le 20 degrees are ruled out to 3 \sigma. We estimate
the inclination and position angles of the black hole, as well as the electron
temperature of the accretion flow and the accretion rate, to be i=50+35-15
degrees, \xi=-23+97-22 degrees, T_e=(5.4 +/- 3.0)x10^10 K and
Mdot=(5+15-2)x10^-9 M_sun / yr respectively, with 90% confidence. The black
hole shadow is unobscured in all best fit models, and may be detected by
observations on baselines between Chile and California, Arizona or Mexico at
1.3mm or .87mm either through direct sampling of the visibility amplitude or
using closure phase information. Millimeter flaring behavior consistent with
the observations is present in all viable models, and is caused by magnetic
turbulence in the inner radii of the accretion flow. The variability at
optically thin frequencies is strongly correlated with that in the accretion
rate. The simulations provide a universal picture of the 1.3mm emission region
as a small region near the midplane in the inner radii of the accretion flow...

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## Near and mid-IR sub-arcsecond structure of the dusty symbiotic star R Aqr

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 10/03/2000
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The results of a high-resolution interferometric campaign targeting the
symbiotic long-period variable (LPV) R~Aqr are reported. With both
near-infrared measurements on baselines out to 10m and mid-infrared data
extending to 32m, we have been able to measure the characteristic sizes of
regions from the photosphere of the LPV and its extended molecular atmosphere,
out to the cooler circumstellar dust shell. The near-infrared data were taken
using aperture masking interferometry on the Keck-I telescope and show R~Aqr to
be partially resolved for wavelengths out to 2.2 microns but with a marked
enlargement, possibly due to molecular opacity, at 3.1 microns. Mid-infrared
interferometric measurements were obtained with the U.C. Berkeley Infrared
Spatial Interferometer (ISI) operating at 11.15 microns from 1992 to 1999.
Although this dataset is somewhat heterogeneous with incomplete coverage of the
Fourier plane and sampling of the pulsation cycle, clear changes in the
mid-infrared brightness distribution were observed, both as a function of
position angle on the sky and as a function of pulsation phase. Spherically
symmetric radiative transfer calculations of uniform-outflow dust shell models
produce brightness distributions and spectra which partially explain the data...

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## Quantum dynamics in ultra-cold atomic physics

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 01/12/2011
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We review recent developments in the theory of quantum dynamics in ultra-cold
atomic physics, including exact techniques, but focusing on methods based on
phase-space mappings that are appli- cable when the complexity becomes
exponentially large. These phase-space representations include the truncated
Wigner, positive-P and general Gaussian operator representations which can
treat both bosons and fermions. These phase-space methods include both
traditional approaches using a phase-space of classical dimension, and more
recent methods that use a non-classical phase-space of increased
dimensionality. Examples used include quantum EPR entanglement of a four-mode
BEC, time-reversal tests of dephasing in single-mode traps, BEC quantum
collisions with up to 106 modes and 105 interacting particles, quantum
interferometry in a multi-mode trap with nonlinear absorp- tion, and the theory
of quantum entropy in phase-space. We also treat the approach of variational
optimization of the sampling error, giving an elementary example of a nonlinear
oscillator.

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## Detection noise bias and variance in the power spectrum and bispectrum in optical interferometry

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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Long-baseline optical interferometry uses the power spectrum and bispectrum
constructs as fundamental observables. Noise arising in the detection of the
fringe pattern gives rise to both variance and biases in the power spectrum and
bispectrum. Previous work on correcting the biases and estimating the variances
for these quantities typically includes restrictive assumptions about the
sampling of the interferogram and/or about the relative importance of Poisson
and Gaussian noise sources. Until now it has been difficult to accurately
compensate for systematic biases in data which violates these assumptions. We
seek a formalism to allow the construction of bias-free estimators of the
bispectrum and power spectrum, and to estimate their variances, under less
restrictive conditions which include both unevenly-sampled data and
measurements affected by a combination of noise sources with Poisson and
Gaussian statistics. We used a method based on the moments of the noise
distributions to derive formulae for the biases introduced to the power
spectrum and bispectrum when the complex fringe amplitude is derived from an
arbitrary linear combinations of a set of discrete interferogram measurements.
We simulated interferograms with different combinations of photon noise and
read noise and with different fringe encoding schemes to illustrate the effects
of these biases. We have derived formulae for bias-free estimators of the power
spectrum and bispectrum which can be used with any linear estimator of the
fringe complex amplitude. We have demonstrated the importance of bias-free
estimators for the case of the detection of faint companions (for example
exoplanets) using closure phase nulling. We have derived formulae for the
variance of the power spectrum and have shown how the variance of the
bispectrum could be calculated.; Comment: 9 pages...

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## An image-plane algorithm for JWST's non-redundant aperture mask data

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 12/11/2014
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The high angular resolution technique of non-redundant masking (NRM) or
aperture masking interferometry (AMI) has yielded images of faint
protoplanetary companions of nearby stars from the ground. AMI on James Webb
Space Telescope (JWST)'s Near Infrared Imager and Slitless Spectrograph
(NIRISS) has a lower thermal background than ground-based facilites and does
not suffer from atmospheric instability. NIRISS AMI images are likely to have
90 - 95% Strehl ratio between 2.77 and 4.8 micron. In this paper we quantify
factors that limit the raw point source contrast of JWST NRM. We develop an
analytic model of the NRM point spread function which includes different
optical path delays (pistons) between mask holes and fit the model parameters
with image plane data. It enables a straightforward way to exclude bad pixels,
is suited to limited fields of view, and can incorporate effects such as
intra-pixel sensitivity variations. We simulate various sources of noise to
estimate their effect on the standard deviation of closure phase, sigma_CP (a
proxy for binary point source contrast). If sigma_CP < 10^-4 radians --- a
contrast ratio of 10 magnitudes --- young accreting gas giant planets (e.g. in
the nearby Taurus star-forming region) could be imaged with JWST NIRISS. We
show the feasibility of using NIRISS' NRM with the sub-Nyquist sampled F277W...

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## The radio remnant of SN1993J: an instrumental explanation for the evolving complex structure

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 28/10/2008
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We present simulated images of Supernova 1993J at 8.4 GHz using Very Long
Baseline Interferometry (VLBI) techniques. A spherically symmetric source model
is convolved with realistic uv-plane distributions, together with standard
imaging procedures, to assess the extent of instrumental effects on the
recovered brightness distribution. In order to facilitate direct comparisons
between the simulations and published VLBI images of SN1993J, the observed
uv-coverage is determined from actual VLBI observations made in the years
following its discovery.
The underlying source model only exhibits radial variation in its density
profile, with no azimuthal dependence and, even though this model is
morphologically simple, the simulated VLBI observations qualitatively reproduce
many of the azimuthal features of the reported VLBI observations, such as
appearance and evolution of complex azimuthal structure and apparent rotation
of the shell. We demonstrate that such features are inexorably coupled to the
uv-plane sampling.
The brightness contrast between the peaks and the surrounding shell material
are not as prominent in the simulations (which of course assume no antenna- or
baseline-based amplitude or phase errors, meaning no self-calibration
procedures will have incorporated any such features in models). It is
conclusive that incomplete uv-plane sampling has a drastic effect on the final
images for observations of this nature. Difference imaging reveals residual
emission up to the 8 sigma level. Extreme care should be taken when using
interferometric observations to directly infer the structure of objects such as
supernovae.; Comment: 14 pages...

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## Image Deblurring Using Derivative Compressed Sensing for Optical Imaging Application

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 28/07/2011
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Reconstruction of multidimensional signals from the samples of their partial
derivatives is known to be a standard problem in inverse theory. Such and
similar problems routinely arise in numerous areas of applied sciences,
including optical imaging, laser interferometry, computer vision, remote
sensing and control. Though being ill-posed in nature, the above problem can be
solved in a unique and stable manner, provided proper regularization and
relevant boundary conditions. In this paper, however, a more challenging setup
is addressed, in which one has to recover an image of interest from its noisy
and blurry version, while the only information available about the imaging
system at hand is the amplitude of the generalized pupil function (GPF) along
with partial observations of the gradient of GPF's phase. In this case, the
phase-related information is collected using a simplified version of the
Shack-Hartmann interferometer, followed by recovering the entire phase by means
of derivative compressed sensing. Subsequently, the estimated phase can be
combined with the amplitude of the GPF to produce an estimate of the point
spread function (PSF), whose knowledge is essential for subsequent image
deconvolution. In summary, the principal contribution of this work is twofold.
First...

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## Comparison of fringe-tracking algorithms for single-mode near-infrared long-baseline interferometers

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

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To enable optical long baseline interferometry toward faint objects, long
integrations are necessary despite atmospheric turbulence. Fringe trackers are
needed to stabilize the fringes and thus increase the fringe visibility and
phase signal-to-noise ratio (SNR), with efficient controllers robust to
instrumental vibrations, and to subsequent path fluctuations and flux
drop-outs.
We report on simulations, analysis and comparison of the performances of a
classical integrator controller and of a Kalman controller, both optimized to
track fringes under realistic observing conditions for different source
magnitudes, disturbance conditions, and sampling frequencies. The key
parameters of our simulations (instrument photometric performance, detection
noise, turbulence and vibrations statistics) are based on typical observing
conditions at the Very Large Telescope observatory and on the design of the
GRAVITY instrument, a 4-telescope single-mode long baseline interferometer in
the near-infrared, next in line to be installed at VLT Interferometer.
We find that both controller performances follow a two-regime law with the
star magnitude, a constant disturbance limited regime, and a diverging detector
and photon noise limited regime. Moreover...

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## Extracting seismic core phases with array interferometry

Fonte: American Geophysical Union
Publicador: American Geophysical Union

Tipo: Article; PeerReviewed
Formato: application/pdf; text/plain; application/msword

Publicado em 28/03/2013
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Seismic body waves that sample Earth's core are indispensable for studying the most remote regions of the planet. Traditional core phase studies rely on well-defined earthquake signals, which are spatially and temporally limited. We show that, by stacking ambient-noise cross-correlations between USArray seismometers, body wave phases reflected off the outer core (ScS), and twice refracted through the inner core (PKIKP^2) can be clearly extracted. Temporal correlation between the amplitude of these core phases and global seismicity suggests that the signals originate from distant earthquakes and emerge due to array interferometry. Similar results from a seismic array in New Zealand demonstrate that our approach is applicable in other regions and with fewer station pairs. Extraction of core phases by interferometry can significantly improve the spatial sampling of the deep Earth because the technique can be applied anywhere broadband seismic arrays exist.

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