Elastic Green's Theorem Preprocesing for On-Shore Internal Multiple Attenuation - Arthur Weglein
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University of Houston Physic Professor Arthur Weglein Research Paper , Elastic Green's Theorem Preprocesing for On- Shore Multiple Attenuation
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Wavelet estimation for a multidimensional acoustic or elastic earth
A new and general wave theoretical wavelet estimation
method is derived. Knowing the seismic wavelet
is important both for processing seismic data and for
modeling the seismic response. To obtain the wavelet,
both statistical (e.g., Wiener-Levinson) and deterministic
(matching surface seismic to well-log data) methods
are generally used. In the marine case, a far-field
signature is often obtained with a deep-towed hydrophone.
The statistical methods do not allow obtaining
the phase of the wavelet, whereas the deterministic
method obviously requires data from a well. The
deep-towed hydrophone requires that the water be
deep enough for the hydrophone to be in the far field
and in addition that the reflections from the water
bottom and structure do not corrupt the measured
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array pattern, which is important for amplitude-versus-
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The inverse scattering series for tasks associated with primaries: direct non...
The inverse scattering series for tasks associated with primaries: direct non-linear inversion of 1D elastic media. In this paper, research on direct inversion for two pa-
rameter acoustic media (Zhang and Weglein, 2005) is
extended to the three parameter elastic case. We present
the first set of direct non-linear inversion equations for
1D elastic media (i.e., depth varying P-velocity, shear
velocity and density). The terms for moving mislocated
reflectors are shown to be separable from amplitude
correction terms. Although in principle this direct
inversion approach requires all four components of elastic
data, synthetic tests indicate that consistent value-added
results may be achieved given only ˆDPP measurements.
We can reasonably infer that further value would derive
from actually measuring ˆDPP , ˆD PS, ˆDSP and ˆDSS as
the method requires. The method is direct with neither
a model matching nor cost function minimization.
Coates weglein-1996
Internal multiple attenuation using inverse scattering: Results from prestack 1 & 2D acoustic and
elastic synthetics
R. T. Coates*, Schlumberger Cambridge Research, A. B. Weglein, Arco Exploration and Production Technology
Summary
The attenuation of internal multiples in a multidimensional
earth is an important and longstanding problem in exploration
seismics. In this paper we report the results of applying
an attenuation algorithm based on the inverse scattering
series to synthetic prestack data sets generated in on
and two dimensional earth models. The attenuation algorithm
requires no information about the subsurface structure
or the velocity field. However, detailed information about
the source wavelet is a prerequisite. An attractive feature of:
the attenuation algorithm is the preservation of the amplitude
(and phase) of primary events in the data; thus allowing for
subsequent AVO and other true amplitude processing.
Fu etal-2010
The document discusses the inverse scattering series (ISS) approach for eliminating internal multiples in land seismic data. ISS methods do not require information about the subsurface and can predict the traveltimes and amplitudes of all internal multiples. The authors apply 1D and 1.5D ISS algorithms to synthetic and field data from Saudi Arabia and achieve encouraging results, successfully attenuating most internal multiples while preserving primaries. However, further work is needed to more accurately predict multiples to handle interference between primaries and multiples.
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The document discusses (1) a new business model and IBM proposal for cost-effective seismic processing through cloud computing, (2) an invitation to participate in a pilot project using IBM cloud computing for multiple attenuation, (3) speedups of internal multiple attenuation achieved by ConocoPhillips, (4) upcoming deliverables from M-OSRP that address industry challenges and will benefit from IBM's cloud computing, and (5) an invitation to an upcoming technical review meeting.
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The significance of incorporating a 3D point source in the ISS internal multiple attenuator for a 1D subsurface - Xinglu Lin* and Arthur Weglein
Wavelet estimation for a multidimensional acoustic or elastic earth
A new and general wave theoretical wavelet estimation
method is derived. Knowing the seismic wavelet
is important both for processing seismic data and for
modeling the seismic response. To obtain the wavelet,
both statistical (e.g., Wiener-Levinson) and deterministic
(matching surface seismic to well-log data) methods
are generally used. In the marine case, a far-field
signature is often obtained with a deep-towed hydrophone.
The statistical methods do not allow obtaining
the phase of the wavelet, whereas the deterministic
method obviously requires data from a well. The
deep-towed hydrophone requires that the water be
deep enough for the hydrophone to be in the far field
and in addition that the reflections from the water
bottom and structure do not corrupt the measured
wavelet. None of the methods address the source
array pattern, which is important for amplitude-versus-
offset (AVO) studies.
The inverse scattering series for tasks associated with primaries: direct non...
The inverse scattering series for tasks associated with primaries: direct non-linear inversion of 1D elastic media. In this paper, research on direct inversion for two pa-
rameter acoustic media (Zhang and Weglein, 2005) is
extended to the three parameter elastic case. We present
the first set of direct non-linear inversion equations for
1D elastic media (i.e., depth varying P-velocity, shear
velocity and density). The terms for moving mislocated
reflectors are shown to be separable from amplitude
correction terms. Although in principle this direct
inversion approach requires all four components of elastic
data, synthetic tests indicate that consistent value-added
results may be achieved given only ˆDPP measurements.
We can reasonably infer that further value would derive
from actually measuring ˆDPP , ˆD PS, ˆDSP and ˆDSS as
the method requires. The method is direct with neither
a model matching nor cost function minimization.
Coates weglein-1996
Internal multiple attenuation using inverse scattering: Results from prestack 1 & 2D acoustic and
elastic synthetics
R. T. Coates*, Schlumberger Cambridge Research, A. B. Weglein, Arco Exploration and Production Technology
Summary
The attenuation of internal multiples in a multidimensional
earth is an important and longstanding problem in exploration
seismics. In this paper we report the results of applying
an attenuation algorithm based on the inverse scattering
series to synthetic prestack data sets generated in on
and two dimensional earth models. The attenuation algorithm
requires no information about the subsurface structure
or the velocity field. However, detailed information about
the source wavelet is a prerequisite. An attractive feature of:
the attenuation algorithm is the preservation of the amplitude
(and phase) of primary events in the data; thus allowing for
subsequent AVO and other true amplitude processing.
Fu etal-2010
The document discusses the inverse scattering series (ISS) approach for eliminating internal multiples in land seismic data. ISS methods do not require information about the subsurface and can predict the traveltimes and amplitudes of all internal multiples. The authors apply 1D and 1.5D ISS algorithms to synthetic and field data from Saudi Arabia and achieve encouraging results, successfully attenuating most internal multiples while preserving primaries. However, further work is needed to more accurately predict multiples to handle interference between primaries and multiples.
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This article provides an alternative perspective on full-waveform inversion (FWI) methods, arguing that current FWI approaches are indirect model-matching methods rather than direct inversion. The article aims to 1) caution against claims that FWI is a final solution, 2) propose a direct inverse approach, and 3) provide an overview comparing indirect FWI and direct inversion methods. Indirect FWI methods incorrectly use modeling equations run backwards rather than true direct inversion, limiting the understanding and effectiveness of the solutions.
Ayadi weglein-2013
The Inverse Scattering Series (ISS) is a direct inversion method
for a multidimensional acoustic, elastic and anelastic earth. It
communicates that all inversion processing goals are able to
be achieved directly and without any subsurface information.
This task is reached through a task-specific subseries of the
ISS. Using primaries in the data as subevents of the first-order
internal multiples, the leading-order attenuator can predict the
time of all the first-order internal multiples and is able to attenuate
them.
However, the ISS internal multiple attenuation algorithm can
be a computationally demanding method specially in a complex
earth. By using an approach that is based on two angular
quantities and that was proposed in Terenghi et al. (2012), the
cost of the algorithm can be controlled. The idea is to use the
two angles as key-control parameters, by limiting their variation,
to disregard some calculated contributions of the algorithm
that are negligible. Moreover, the range of integration
can be chosen as a compromise of the required degree of accuracy
and the computational time saving.
This time-saving approach is presented
An Extension of Linear Inverse Scattering Methods for Absorptive Media to the...
An Extension of Linear Inverse Scattering
Methods for Absorptive Media to the Case of an
Absorptive Reference
Inverse scattering series for multiple attenuation: An example with surface a...
A multiple attenuation method derived from an inverse scattering
series is described. The inversion series approach allows a
separation of multiple attenuation subseries from the full series.
The surface multiple attenuation subseries was described and illustrated
in Carvalho et al. (1991, 1992). The internal multiple
attenuation method consists of selecting the parts of the odd
terms that are associated with removing only multiply reflected
energy. The method, for both types of multiples, is multidimensional
and does not rely on periodicity or differential moveout,
nor does it require a model of the reflectors generating the multiples.
An example with internal and surface multiples will be
presented.
Araujo etal-1994b
In this paper we present a multidimensional method for attenuating internal multiples that derives from
an inverse scattering series . The method doesn't depend on periodicity or differential moveout, nor does it
require a model for the multiple generating reflectors.
Verschuur etal-1999
Summary
Methods for removal of free-surface and internal multiples have been developed from bath a feedback model approach and inverse scatterin g theory. White these two formulations derive from different mathematica) viewpoints,
the resulting algorithm s for free-surface multiple are very similar. By contrast , the feedback and inverse scattering
method for internal multiple are totally different and have different requirements for sub surface information or
interpretive intervention . The former removes all multiple related to a certain boundary with the a of a surface
integral along this boundary ; the alter wilt predict and attenuate a ll internal multiple a t the same time . In this paper, we continue our comparison study of these internal multiple attenuation method ; specifically , we examine two
different realizations of the feedback method and the inverse scattering technique .
Internal multiple attenuation using inverse scattering: Results from prestack...
The attenuation of internal multiples in a multidimensional
earth is an important and longstanding problem in exploration
seismics. In this paper we report the results of applying
an attenuation algorithm based on the inverse scattering
series to synthetic prestack data sets generated in on
and two dimensional earth models. The attenuation algorithm
requires no information about the subsurface structure
or the velocity field. However, detailed information about
the source wavelet is a prerequisite. An attractive feature of:
the attenuation algorithm is the preservation of the amplitude
(and phase) of primary events in the data; thus allowing for
subsequent AVO and other true amplitude processing.
Wavelet estimation for a multidimensional acoustic or elastic earth- Arthur W...
A new and general wave theoretical wavelet estimation
method is derived. Knowing the seismic wavelet
is important both for processing seismic data and for
modeling the seismic response. To obtain the wavelet,
both statistical (e.g., Wiener-Levinson) and deterministic
(matching surface seismic to well-log data) methods
are generally used. In the marine case, a far-field
signature is often obtained with a deep-towed hydrophone.
The statistical methods do not allow obtaining
the phase of the wavelet, whereas the deterministic
method obviously requires data from a well. The
deep-towed hydrophone requires that the water be
deep enough for the hydrophone to be in the far field
and in addition that the reflections from the water
bottom and structure do not corrupt the measured
wavelet. None of the methods address the source
array pattern, which is important for amplitude-versus-
offset (AVO) studies
Hsu etal-2009
The document analyzes the reference velocity sensitivity of an elastic internal multiple attenuation algorithm. It first provides background on internal multiples and inverse scattering series methods for their attenuation. It then presents a 1.5D layered earth model and uses it to show that the elastic internal multiple algorithm can correctly predict arrival times without requiring an accurate reference velocity model, similarly to the acoustic case. The analysis involves deriving expressions for predicted internal multiples in the frequency-wavenumber domain and showing they depend only on the traveltimes of the primary reflections involved, not the reference velocities.
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This document summarizes finite difference modeling methods used at M-OSRP. It discusses:
1) The second order time and fourth order space finite difference schemes used to model acoustic wave propagation.
2) How boundary conditions like Dirichlet/Neumann generate strong spurious reflections that can mask true events.
3) The importance of accurate source fields for modeling - better source fields lead to more accurate linear inversions and the ability to observe phenomena like polarity reversals in modeled data.
Inverse scattering series for multiple attenuation: An example with surface a...
A multiple attenuation method derived from an inverse scattering
series is described. The inversion series approach allows a
separation of multiple attenuation subseries from the full series.
The surface multiple attenuation subseries was described and illustrated
in Carvalho et al. (1991, 1992). The internal multiple
attenuation method consists of selecting the parts of the odd
terms that are associated with removing only multiply reflected
energy. The method, for both types of multiples, is multidimensional
and does not rely on periodicity or differential moveout,
nor does it require a model of the reflectors generating the multiples.
An example with internal and surface multiples will be
presented.
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All of the perturbative approaches to multidimensional wave
equation processing. for example. wave equation migration (see,
e.g., Claerbout, 1971; French, 1975: Schneider, 1978; Stolt, 1978;
Sattlegger et al, 1980), or Born approximation inversion (see,
e.g., Cohen and Bleistein, 1979; Raz, 1981: Clayton and Stolt,
1981) require some input velocity information. In the Born approximation
to inversion, a reference or background velocity is
chosena nd a perturbationa boutt his velocity is determined.S imilarly,
a velocity model is a required input to all wave equation
migration techniques.
The Inverse Source Problem in The Presence of External Sources- Dr. Arthur B....
This paper presents a brief review of the various integral equation formuiations that have been employed
for the inverse source problem for the inhomogeneous scalar Heimhoitz equation. It is shown that these
formulations apply only in cases where either the data are prescribed on a closed surface surrounding the
unknown source or where the unknown source lies entirely on one side of an open measurement surface.
A generalized integral equation is derived that applies to the more general case where unknown sources
can exist on both sides of an open measurement surface. This latter problem arises in geophysical remote
sensing and the derived integral equation offers an approach to this class of problems not offered by
currently employed techniques.
Direct non-linear inversion of multi-parameter 1D elastic media using the inv...
In this paper, we present the first non-linear direct target identification method and algorithm
for 1D elastic media (P velocity, shear velocity and density vary in depth) from the inverse
scattering series. Direct non-linear means that we provide explicit formulas that: (1) input data
and directly output changes in material properties, without the use or need for any indirect procedures
such as model matching, searching, optimization or other assumed aligned objectives or
proxies, and (2) the algorithms recognize and directly invert the intrinsic non-linear relationship
between changes in material properties and changes in the concomitant wave-field. The results
clearly demonstrate that, in order to achieve full elastic inversion, all four components of data
(ˆD PP , ˆDPS, ˆD SP and ˆDSS) are needed. The method assumes that only data and reference
medium properties are input, and terms in the inverse series for moving mislocated reflectors
resulting from the linear inverse term, are separated from amplitude correction terms. Although
in principle this direct inversion approach requires all four components of elastic data, synthetic
tests indicate that a consistent value-added result may be achieved given only ˆDPP measurements,
as long as the ˆD PP were used to approximately synthesize the ˆD PS, ˆDSP and ˆD SS
components. We can reasonably infer that further value would derive from actually measuring
ˆD
PP , ˆDPS, ˆDSP and ˆD SS as the method requires. For the case that all four components of
data are available, we give one consistent method to solve for all of the second terms (the first
terms beyond linear). The method’s nonlinearity and directness provides this unambiguous data
requirement message, and that unique clarity, and the explicit non-linear formulas casts doubts
and reasonable concerns for indirect methods, in general, and their assumed aligned goals, e.g.,
using model matching objectives, that would never recognize the fundamental inadequacy from
a basic physics point of view of using only PP data to perform elastic inversion. There are important
conceptual and practical implications for the link between data acquisition and target
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This article provides an alternative perspective on full-waveform inversion (FWI) methods, arguing that current FWI approaches are indirect model-matching methods rather than direct inversion. The article aims to 1) caution against claims that FWI is a final solution, 2) propose a direct inverse approach, and 3) provide an overview comparing indirect FWI and direct inversion methods. Indirect FWI methods incorrectly use modeling equations run backwards rather than true direct inversion, limiting the understanding and effectiveness of the solutions.
Ayadi weglein-2013
The Inverse Scattering Series (ISS) is a direct inversion method
for a multidimensional acoustic, elastic and anelastic earth. It
communicates that all inversion processing goals are able to
be achieved directly and without any subsurface information.
This task is reached through a task-specific subseries of the
ISS. Using primaries in the data as subevents of the first-order
internal multiples, the leading-order attenuator can predict the
time of all the first-order internal multiples and is able to attenuate
them.
However, the ISS internal multiple attenuation algorithm can
be a computationally demanding method specially in a complex
earth. By using an approach that is based on two angular
quantities and that was proposed in Terenghi et al. (2012), the
cost of the algorithm can be controlled. The idea is to use the
two angles as key-control parameters, by limiting their variation,
to disregard some calculated contributions of the algorithm
that are negligible. Moreover, the range of integration
can be chosen as a compromise of the required degree of accuracy
and the computational time saving.
This time-saving approach is presented
An Extension of Linear Inverse Scattering Methods for Absorptive Media to the...
An Extension of Linear Inverse Scattering
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A multiple attenuation method derived from an inverse scattering
series is described. The inversion series approach allows a
separation of multiple attenuation subseries from the full series.
The surface multiple attenuation subseries was described and illustrated
in Carvalho et al. (1991, 1992). The internal multiple
attenuation method consists of selecting the parts of the odd
terms that are associated with removing only multiply reflected
energy. The method, for both types of multiples, is multidimensional
and does not rely on periodicity or differential moveout,
nor does it require a model of the reflectors generating the multiples.
An example with internal and surface multiples will be
presented.
Araujo etal-1994b
In this paper we present a multidimensional method for attenuating internal multiples that derives from
an inverse scattering series . The method doesn't depend on periodicity or differential moveout, nor does it
require a model for the multiple generating reflectors.
Verschuur etal-1999
Summary
Methods for removal of free-surface and internal multiples have been developed from bath a feedback model approach and inverse scatterin g theory. White these two formulations derive from different mathematica) viewpoints,
the resulting algorithm s for free-surface multiple are very similar. By contrast , the feedback and inverse scattering
method for internal multiple are totally different and have different requirements for sub surface information or
interpretive intervention . The former removes all multiple related to a certain boundary with the a of a surface
integral along this boundary ; the alter wilt predict and attenuate a ll internal multiple a t the same time . In this paper, we continue our comparison study of these internal multiple attenuation method ; specifically , we examine two
different realizations of the feedback method and the inverse scattering technique .
Internal multiple attenuation using inverse scattering: Results from prestack...
The attenuation of internal multiples in a multidimensional
earth is an important and longstanding problem in exploration
seismics. In this paper we report the results of applying
an attenuation algorithm based on the inverse scattering
series to synthetic prestack data sets generated in on
and two dimensional earth models. The attenuation algorithm
requires no information about the subsurface structure
or the velocity field. However, detailed information about
the source wavelet is a prerequisite. An attractive feature of:
the attenuation algorithm is the preservation of the amplitude
(and phase) of primary events in the data; thus allowing for
subsequent AVO and other true amplitude processing.
Wavelet estimation for a multidimensional acoustic or elastic earth- Arthur W...
A new and general wave theoretical wavelet estimation
method is derived. Knowing the seismic wavelet
is important both for processing seismic data and for
modeling the seismic response. To obtain the wavelet,
both statistical (e.g., Wiener-Levinson) and deterministic
(matching surface seismic to well-log data) methods
are generally used. In the marine case, a far-field
signature is often obtained with a deep-towed hydrophone.
The statistical methods do not allow obtaining
the phase of the wavelet, whereas the deterministic
method obviously requires data from a well. The
deep-towed hydrophone requires that the water be
deep enough for the hydrophone to be in the far field
and in addition that the reflections from the water
bottom and structure do not corrupt the measured
wavelet. None of the methods address the source
array pattern, which is important for amplitude-versus-
offset (AVO) studies
Hsu etal-2009
The document analyzes the reference velocity sensitivity of an elastic internal multiple attenuation algorithm. It first provides background on internal multiples and inverse scattering series methods for their attenuation. It then presents a 1.5D layered earth model and uses it to show that the elastic internal multiple algorithm can correctly predict arrival times without requiring an accurate reference velocity model, similarly to the acoustic case. The analysis involves deriving expressions for predicted internal multiples in the frequency-wavenumber domain and showing they depend only on the traveltimes of the primary reflections involved, not the reference velocities.
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This document summarizes finite difference modeling methods used at M-OSRP. It discusses:
1) The second order time and fourth order space finite difference schemes used to model acoustic wave propagation.
2) How boundary conditions like Dirichlet/Neumann generate strong spurious reflections that can mask true events.
3) The importance of accurate source fields for modeling - better source fields lead to more accurate linear inversions and the ability to observe phenomena like polarity reversals in modeled data.
Inverse scattering series for multiple attenuation: An example with surface a...
A multiple attenuation method derived from an inverse scattering
series is described. The inversion series approach allows a
separation of multiple attenuation subseries from the full series.
The surface multiple attenuation subseries was described and illustrated
in Carvalho et al. (1991, 1992). The internal multiple
attenuation method consists of selecting the parts of the odd
terms that are associated with removing only multiply reflected
energy. The method, for both types of multiples, is multidimensional
and does not rely on periodicity or differential moveout,
nor does it require a model of the reflectors generating the multiples.
An example with internal and surface multiples will be
presented.
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The document discusses the benefits of exercise for mental health. Regular physical activity can help reduce anxiety and depression and improve mood and cognitive functioning. Exercise boosts blood flow and levels of neurotransmitters and endorphins which elevate and stabilize mood.
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All of the perturbative approaches to multidimensional wave
equation processing. for example. wave equation migration (see,
e.g., Claerbout, 1971; French, 1975: Schneider, 1978; Stolt, 1978;
Sattlegger et al, 1980), or Born approximation inversion (see,
e.g., Cohen and Bleistein, 1979; Raz, 1981: Clayton and Stolt,
1981) require some input velocity information. In the Born approximation
to inversion, a reference or background velocity is
chosena nd a perturbationa boutt his velocity is determined.S imilarly,
a velocity model is a required input to all wave equation
migration techniques.
The Inverse Source Problem in The Presence of External Sources- Dr. Arthur B....
This paper presents a brief review of the various integral equation formuiations that have been employed
for the inverse source problem for the inhomogeneous scalar Heimhoitz equation. It is shown that these
formulations apply only in cases where either the data are prescribed on a closed surface surrounding the
unknown source or where the unknown source lies entirely on one side of an open measurement surface.
A generalized integral equation is derived that applies to the more general case where unknown sources
can exist on both sides of an open measurement surface. This latter problem arises in geophysical remote
sensing and the derived integral equation offers an approach to this class of problems not offered by
currently employed techniques.
Direct non-linear inversion of multi-parameter 1D elastic media using the inv...
In this paper, we present the first non-linear direct target identification method and algorithm
for 1D elastic media (P velocity, shear velocity and density vary in depth) from the inverse
scattering series. Direct non-linear means that we provide explicit formulas that: (1) input data
and directly output changes in material properties, without the use or need for any indirect procedures
such as model matching, searching, optimization or other assumed aligned objectives or
proxies, and (2) the algorithms recognize and directly invert the intrinsic non-linear relationship
between changes in material properties and changes in the concomitant wave-field. The results
clearly demonstrate that, in order to achieve full elastic inversion, all four components of data
(ˆD PP , ˆDPS, ˆD SP and ˆDSS) are needed. The method assumes that only data and reference
medium properties are input, and terms in the inverse series for moving mislocated reflectors
resulting from the linear inverse term, are separated from amplitude correction terms. Although
in principle this direct inversion approach requires all four components of elastic data, synthetic
tests indicate that a consistent value-added result may be achieved given only ˆDPP measurements,
as long as the ˆD PP were used to approximately synthesize the ˆD PS, ˆDSP and ˆD SS
components. We can reasonably infer that further value would derive from actually measuring
ˆD
PP , ˆDPS, ˆDSP and ˆD SS as the method requires. For the case that all four components of
data are available, we give one consistent method to solve for all of the second terms (the first
terms beyond linear). The method’s nonlinearity and directness provides this unambiguous data
requirement message, and that unique clarity, and the explicit non-linear formulas casts doubts
and reasonable concerns for indirect methods, in general, and their assumed aligned goals, e.g.,
using model matching objectives, that would never recognize the fundamental inadequacy from
a basic physics point of view of using only PP data to perform elastic inversion. There are important
conceptual and practical implications for the link between data acquisition and target
identification goals and objectives.
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An Extension of Linear Inverse Scattering Methods for Absorptive Media to the...
An Extension of Linear Inverse Scattering Methods for Absorptive Media to the...
Inverse scattering series for multiple attenuation: An example with surface a...
Inverse scattering series for multiple attenuation: An example with surface a...
Internal multiple attenuation using inverse scattering: Results from prestack...
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Wavelet estimation for a multidimensional acoustic or elastic earth- Arthur W...
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Robustnesosf a New Source-Signature Estimation Method Under Realistic Data Co...
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Examples of a Nonlinear Inversion Method Based on the T Matrix of ScatteringT...
Examples of a Nonlinear Inversion Method Based on the T Matrix of ScatteringT...
Inverse scattering series for multiple attenuation: An example with surface a...
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Reverse Time Migration and Green's Theorem- Professor. Arthur B. Weglein
Reverse Time Migration and Green's Theorem- Professor. Arthur B. Weglein
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The Inverse Source Problem in The Presence of External Sources- Dr. Arthur B....
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Direct non-linear inversion of multi-parameter 1D elastic media using the inv...
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Mechanisms and Applications of Antiviral Neutralizing Antibodies - Creative B...
Neutralizing antibodies, pivotal in immune defense, specifically bind and inhibit viral pathogens, thereby playing a crucial role in protecting against and mitigating infectious diseases. In this slide, we will introduce what antibodies and neutralizing antibodies are, the production and regulation of neutralizing antibodies, their mechanisms of action, classification and applications, as well as the challenges they face.
Synopsis presentation VDR gene polymorphism and anemia (2).pptx
I am the PhD scholar of FND department, Assam down town University
Evidence of Jet Activity from the Secondary Black Hole in the OJ 287 Binary S...
Wereport the study of a huge optical intraday flare on 2021 November 12 at 2 a.m. UT in the blazar OJ287. In the binary black hole model, it is associated with an impact of the secondary black hole on the accretion disk of the primary. Our multifrequency observing campaign was set up to search for such a signature of the impact based on a prediction made 8 yr earlier. The first I-band results of the flare have already been reported by Kishore et al. (2024). Here we combine these data with our monitoring in the R-band. There is a big change in the R–I spectral index by 1.0 ±0.1 between the normal background and the flare, suggesting a new component of radiation. The polarization variation during the rise of the flare suggests the same. The limits on the source size place it most reasonably in the jet of the secondary BH. We then ask why we have not seen this phenomenon before. We show that OJ287 was never before observed with sufficient sensitivity on the night when the flare should have happened according to the binary model. We also study the probability that this flare is just an oversized example of intraday variability using the Krakow data set of intense monitoring between 2015 and 2023. We find that the occurrence of a flare of this size and rapidity is unlikely. In machine-readable Tables 1 and 2, we give the full orbit-linked historical light curve of OJ287 as well as the dense monitoring sample of Krakow.
Quality assurance B.pharm 6th semester BP606T UNIT 5
Warehousing
Good warehousing practices
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Reaching the age of Adolescence- Class 8
This is a presentation on understanding the age of adolescence.
fermented food science of sauerkraut.pptx
This ppt contains the production of a fermented food name - sauerkraut
Embracing Deep Variability For Reproducibility and Replicability
Embracing Deep Variability For Reproducibility and ReplicabilityUniversity of Rennes, INSA Rennes, Inria/IRISA, CNRS
Embracing Deep Variability For Reproducibility and Replicability
Abstract: Reproducibility (aka determinism in some cases) constitutes a fundamental aspect in various fields of computer science, such as floating-point computations in numerical analysis and simulation, concurrency models in parallelism, reproducible builds for third parties integration and packaging, and containerization for execution environments. These concepts, while pervasive across diverse concerns, often exhibit intricate inter-dependencies, making it challenging to achieve a comprehensive understanding. In this short and vision paper we delve into the application of software engineering techniques, specifically variability management, to systematically identify and explicit points of variability that may give rise to reproducibility issues (eg language, libraries, compiler, virtual machine, OS, environment variables, etc). The primary objectives are: i) gaining insights into the variability layers and their possible interactions, ii) capturing and documenting configurations for the sake of reproducibility, and iii) exploring diverse configurations to replicate, and hence validate and ensure the robustness of results. By adopting these methodologies, we aim to address the complexities associated with reproducibility and replicability in modern software systems and environments, facilitating a more comprehensive and nuanced perspective on these critical aspects.
https://hal.science/hal-04582287
HUMAN EYE By-R.M Class 10 phy best digital notes.pdf
Class 10 human eye notes physics
Handwritten best quality
Sexuality - Issues, Attitude and Behaviour - Applied Social Psychology - Psyc...
A proprietary approach developed by bringing together the best of learning theories from Psychology, design principles from the world of visualization, and pedagogical methods from over a decade of training experience, that enables you to: Learn better, faster!
JAMES WEBB STUDY THE MASSIVE BLACK HOLE SEEDS
The pathway(s) to seeding the massive black holes (MBHs) that exist at the heart of galaxies in the present and distant Universe remains an unsolved problem. Here we categorise, describe and quantitatively discuss the formation pathways of both light and heavy seeds. We emphasise that the most recent computational models suggest that rather than a bimodal-like mass spectrum between light and heavy seeds with light at one end and heavy at the other that instead a continuum exists. Light seeds being more ubiquitous and the heavier seeds becoming less and less abundant due the rarer environmental conditions required for their formation. We therefore examine the different mechanisms that give rise to different seed mass spectrums. We show how and why the mechanisms that produce the heaviest seeds are also among the rarest events in the Universe and are hence extremely unlikely to be the seeds for the vast majority of the MBH population. We quantify, within the limits of the current large uncertainties in the seeding processes, the expected number densities of the seed mass spectrum. We argue that light seeds must be at least 103 to 105 times more numerous than heavy seeds to explain the MBH population as a whole. Based on our current understanding of the seed population this makes heavy seeds (Mseed > 103 M⊙) a significantly more likely pathway given that heavy seeds have an abundance pattern than is close to and likely in excess of 10−4 compared to light seeds. Finally, we examine the current state-of-the-art in numerical calculations and recent observations and plot a path forward for near-future advances in both domains.
Candidate young stellar objects in the S-cluster: Kinematic analysis of a sub...
Context. The observation of several L-band emission sources in the S cluster has led to a rich discussion of their nature. However, a definitive answer to the classification of the dusty objects requires an explanation for the detection of compact Doppler-shifted Brγ emission. The ionized hydrogen in combination with the observation of mid-infrared L-band continuum emission suggests that most of these sources are embedded in a dusty envelope. These embedded sources are part of the S-cluster, and their relationship to the S-stars is still under debate. To date, the question of the origin of these two populations has been vague, although all explanations favor migration processes for the individual cluster members. Aims. This work revisits the S-cluster and its dusty members orbiting the supermassive black hole SgrA* on bound Keplerian orbits from a kinematic perspective. The aim is to explore the Keplerian parameters for patterns that might imply a nonrandom distribution of the sample. Additionally, various analytical aspects are considered to address the nature of the dusty sources. Methods. Based on the photometric analysis, we estimated the individual H−K and K−L colors for the source sample and compared the results to known cluster members. The classification revealed a noticeable contrast between the S-stars and the dusty sources. To fit the flux-density distribution, we utilized the radiative transfer code HYPERION and implemented a young stellar object Class I model. We obtained the position angle from the Keplerian fit results; additionally, we analyzed the distribution of the inclinations and the longitudes of the ascending node. Results. The colors of the dusty sources suggest a stellar nature consistent with the spectral energy distribution in the near and midinfrared domains. Furthermore, the evaporation timescales of dusty and gaseous clumps in the vicinity of SgrA* are much shorter ( 2yr) than the epochs covered by the observations (≈15yr). In addition to the strong evidence for the stellar classification of the D-sources, we also find a clear disk-like pattern following the arrangements of S-stars proposed in the literature. Furthermore, we find a global intrinsic inclination for all dusty sources of 60 ± 20◦, implying a common formation process. Conclusions. The pattern of the dusty sources manifested in the distribution of the position angles, inclinations, and longitudes of the ascending node strongly suggests two different scenarios: the main-sequence stars and the dusty stellar S-cluster sources share a common formation history or migrated with a similar formation channel in the vicinity of SgrA*. Alternatively, the gravitational influence of SgrA* in combination with a massive perturber, such as a putative intermediate mass black hole in the IRS 13 cluster, forces the dusty objects and S-stars to follow a particular orbital arrangement. Key words. stars: black holes– stars: formation– Galaxy: center– galaxies: star formation
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