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.
In this paper we discuss the speckle reduction in images with the recently proposed Wavelet Embedded Anisotropic Diffusion (WEAD) and Wavelet Embedded Complex Diffusion (WECD). Both these methods are improvements over anisotropic and complex diffusion by adding wavelet based bayes shrink in its second stage. Both WEAD and WECD produce excellent results when compared with the existing speckle reduction filters.
Segmentation Based Multilevel Wide Band Compression for SAR Images Using Coif...CSCJournals
Synthetic aperture radar (SAR) data represents a significant resource of information for a large variety of researchers. Thus, there is a strong interest in developing data encoding and decoding algorithms which can obtain higher compression ratios while keeping image quality to an acceptable level. In this work, results of different wavelet-based image compression and segmentation based wavelet image compression are assessed through controlled experiments on synthetic SAR images. The effects of dissimilar wavelet functions, number of decompositions are examined in order to find optimal family for SAR images. The choice of optimal wavelets in segmentation based wavelet image compression is coiflet for low frequency and high frequency component. The results presented here is a good reference for SAR application developers to choose the wavelet families and also it concludes that wavelets transform is rapid, robust and reliable tool for SAR image compression. Numerical results confirm the potency of this approach.
Internal multiple attenuation using inverse scattering: Results from prestack...Arthur Weglein
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.
Boosting ced using robust orientation estimationijma
In this paper, Coherence Enhancement Diffusion (CED) is boosted feeding external orientation using new
robust orientation estimation. In CED, proper scale selection is very important as the gradient vector at
that scale reflects the orientation of local ridge. For this purpose a new scheme is proposed in which pre
calculated orientation, by using local and integration scales. From the experiments it is found the proposed
scheme is working much better in noisy environment as compared to the traditional Coherence
Enhancement Diffusion
In this paper we discuss the speckle reduction in images with the recently proposed Wavelet Embedded Anisotropic Diffusion (WEAD) and Wavelet Embedded Complex Diffusion (WECD). Both these methods are improvements over anisotropic and complex diffusion by adding wavelet based bayes shrink in its second stage. Both WEAD and WECD produce excellent results when compared with the existing speckle reduction filters.
Segmentation Based Multilevel Wide Band Compression for SAR Images Using Coif...CSCJournals
Synthetic aperture radar (SAR) data represents a significant resource of information for a large variety of researchers. Thus, there is a strong interest in developing data encoding and decoding algorithms which can obtain higher compression ratios while keeping image quality to an acceptable level. In this work, results of different wavelet-based image compression and segmentation based wavelet image compression are assessed through controlled experiments on synthetic SAR images. The effects of dissimilar wavelet functions, number of decompositions are examined in order to find optimal family for SAR images. The choice of optimal wavelets in segmentation based wavelet image compression is coiflet for low frequency and high frequency component. The results presented here is a good reference for SAR application developers to choose the wavelet families and also it concludes that wavelets transform is rapid, robust and reliable tool for SAR image compression. Numerical results confirm the potency of this approach.
Internal multiple attenuation using inverse scattering: Results from prestack...Arthur Weglein
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.
Boosting ced using robust orientation estimationijma
In this paper, Coherence Enhancement Diffusion (CED) is boosted feeding external orientation using new
robust orientation estimation. In CED, proper scale selection is very important as the gradient vector at
that scale reflects the orientation of local ridge. For this purpose a new scheme is proposed in which pre
calculated orientation, by using local and integration scales. From the experiments it is found the proposed
scheme is working much better in noisy environment as compared to the traditional Coherence
Enhancement Diffusion
OPTIMIZATION OF MANUFACTURE OF FIELDEFFECT HETEROTRANSISTORS WITHOUT P-NJUNCT...ijrap
It has been recently shown, that manufacturing p-n-junctions, field-effect and bipolar transistors, thyristors
in a multilayer structure by diffusion or ion implantation under condition of optimization of dopant and/or
radiation defects leads to increasing of sharpness of p-n-junctions (both single p-n-junctions and p-njunctions,
which include into their system). In this situation one can also obtain increasing of homogeneity
of dopant in doped area. In this paper we consider manufacturing a field-effect heterotransistor without pn-
junction. Optimization of technological process with using inhomogeneity of heterostructure give us
possibility to manufacture the transistors as more compact.
Coherence enhancement diffusion using robust orientation estimationcsandit
In this paper, a new robust orientation estimation for Coherence Enhancement Diffusion (CED)
is proposed. In CED, proper scale selection is very important as the gradient vector at that
scale reflects the orientation of local ridge. For this purpose, a new scheme is proposed in
which pre calculated orientation, by using orientation diffusion, is used to find the correct true
local scale. From the experiments it is found that the proposed scheme is working much better
in noisy environment as compared to the traditional Coherence Enhancement Diffusion.
Automatic Relative Radiometric Normalization for Change Detection of Satellit...IDES Editor
Several relative radiometric normalization (RRN)
techniques have been proposed till date most of which involve
selection of pseudo invariant features whose reflectance are
nearly invariant from image to image and are independent of
seasonal cycles. Extraction of such points is quiet tedious and
human operator has to provide mutual correspondence by
choosing easily recognizable and time invariant points. In
this paper, we intend to propose a new automatic radiometric
normalization technique to select PIFs in panchromatic
images known as Bin-Division Method. For multispectral
images, MAD (Multivariate Alteration Detection) has been
employed for selecting PIFs based on the assumption that
MAD components are invariant to affine transformation. This,
followed by robust linear regression constitutes the whole
automatic radiometric normalization procedure.
EDGE DETECTION IN RADAR IMAGES USING WEIBULL DISTRIBUTIONcsitconf
Radar images can reveal information about the shape of the surface terrain as well as its
physical and biophysical properties. Radar images have long been used in geological studies to
map structural features that are revealed by the shape of the landscape. Radar imagery also has
applications in vegetation and crop type mapping, landscape ecology, hydrology, and
volcanology. Image processing is using for detecting for objects in radar images. Edge
detection; which is a method of determining the discontinuities in gray level images; is a very
important initial step in Image processing. Many classical edge detectors have been developed
over time. Some of the well-known edge detection operators based on the first derivative of the
image are Roberts, Prewitt, Sobel which is traditionally implemented by convolving the image
with masks. Also Gaussian distribution has been used to build masks for the first and second
derivative. However, this distribution has limit to only symmetric shape. This paper will use to
construct the masks, the Weibull distribution which was more general than Gaussian because it
has symmetric and asymmetric shape. The constructed masks are applied to images and we
obtained good results.
EDGE DETECTION IN RADAR IMAGES USING WEIBULL DISTRIBUTIONcscpconf
Radar images can reveal information about the shape of the surface terrain as well as its physical and biophysical properties. Radar images have long been used in geological studies to
map structural features that are revealed by the shape of the landscape. Radar imagery also has applications in vegetation and crop type mapping, landscape ecology, hydrology, and
volcanology. Image processing is using for detecting for objects in radar images. Edge detection; which is a method of determining the discontinuities in gray level images; is a very
important initial step in Image processing. Many classical edge detectors have been developed over time. Some of the well-known edge detection operators based on the first derivative of the image are Roberts, Prewitt, Sobel which is traditionally implemented by convolving the image with masks. Also Gaussian distribution has been used to build masks for the first and second derivative. However, this distribution has limit to only symmetric shape. This paper will use to construct the masks, the Weibull distribution which was more general than Gaussian because it has symmetric and asymmetric shape. The constructed masks are applied to images and we obtained good results.
ANALYSIS OF LAND SURFACE DEFORMATION GRADIENT BY DINSAR cscpconf
The progressive development of Synthetic Aperture Radar (SAR) systems diversify the exploitation of the generated images by these systems in different applications of geoscience. Detection and monitoring surface deformations, procreated by various phenomena had benefited from this evolution and had been realized by interferometry (InSAR) and differential interferometry (DInSAR) techniques. Nevertheless, spatial and temporal decorrelations of the interferometric couples used, limit strongly the precision of analysis results by these techniques. In this context, we propose, in this work, a methodological approach of surface deformation detection and analysis by differential interferograms to show the limits of this technique according to noise quality and level. The detectability model is generated from the deformation signatures, by simulating a linear fault merged to the images couples of ERS1 / ERS2 sensors acquired in a region of the Algerian south.
A comparison of SIFT, PCA-SIFT and SURFCSCJournals
This paper compares three robust feature detection methods, they are, Scale Invariant Feature Transform (SIFT), Principal Component Analysis (PCA) -SIFT and Speeded Up Robust Features (SURF). Lowe presented SIFT [1], which was successfully used in recognition, stitching and many other applications because of its robustness. Yan Ke [2] gave a change of SIFT by using PCA to normalize the gradient patch instead of histogram. H. Bay [3] presented a faster method for SURF, which used Fast-Hessian detector. The performance of the three methods is compared for scale changes, rotation , blur, illumination changes and affine transformations, all of which uses repeatability as an evaluation measurement. Additionally, RANSAC is used to reject the inconsistent matches [4]. SIFT presents its stability in most situation except rotation and illumination changes. SURF is the fastest one with good performance as the same as SIFT, PCA-SIFT shows its advantages in rotation, blur and illumination changes.
Performance of cognitive radio networks with maximal ratio combining over cor...Polytechnique Montreal
In this paper, we apply the maximal ratio combining (MRC) technique to achieve higher detection probability in cognitive radio networks over correlated Rayleigh fading channels. We present a simple approach to derive the probability of detection in closed-form expression. The numerical results reveal that the detection performance is a monotonically increasing function with respect to the number of antennas. Moreover, we provide sets of complementary receiver operating characteristic (ROC) curves to illustrate the effect of antenna correlation on the sensing performance of cognitive radio networks employing MRC schemes in some respective scenarios.
OPTIMIZATION OF MANUFACTURE OF FIELDEFFECT HETEROTRANSISTORS WITHOUT P-NJUNCT...ijrap
It has been recently shown, that manufacturing p-n-junctions, field-effect and bipolar transistors, thyristors
in a multilayer structure by diffusion or ion implantation under condition of optimization of dopant and/or
radiation defects leads to increasing of sharpness of p-n-junctions (both single p-n-junctions and p-njunctions,
which include into their system). In this situation one can also obtain increasing of homogeneity
of dopant in doped area. In this paper we consider manufacturing a field-effect heterotransistor without pn-
junction. Optimization of technological process with using inhomogeneity of heterostructure give us
possibility to manufacture the transistors as more compact.
Coherence enhancement diffusion using robust orientation estimationcsandit
In this paper, a new robust orientation estimation for Coherence Enhancement Diffusion (CED)
is proposed. In CED, proper scale selection is very important as the gradient vector at that
scale reflects the orientation of local ridge. For this purpose, a new scheme is proposed in
which pre calculated orientation, by using orientation diffusion, is used to find the correct true
local scale. From the experiments it is found that the proposed scheme is working much better
in noisy environment as compared to the traditional Coherence Enhancement Diffusion.
Automatic Relative Radiometric Normalization for Change Detection of Satellit...IDES Editor
Several relative radiometric normalization (RRN)
techniques have been proposed till date most of which involve
selection of pseudo invariant features whose reflectance are
nearly invariant from image to image and are independent of
seasonal cycles. Extraction of such points is quiet tedious and
human operator has to provide mutual correspondence by
choosing easily recognizable and time invariant points. In
this paper, we intend to propose a new automatic radiometric
normalization technique to select PIFs in panchromatic
images known as Bin-Division Method. For multispectral
images, MAD (Multivariate Alteration Detection) has been
employed for selecting PIFs based on the assumption that
MAD components are invariant to affine transformation. This,
followed by robust linear regression constitutes the whole
automatic radiometric normalization procedure.
EDGE DETECTION IN RADAR IMAGES USING WEIBULL DISTRIBUTIONcsitconf
Radar images can reveal information about the shape of the surface terrain as well as its
physical and biophysical properties. Radar images have long been used in geological studies to
map structural features that are revealed by the shape of the landscape. Radar imagery also has
applications in vegetation and crop type mapping, landscape ecology, hydrology, and
volcanology. Image processing is using for detecting for objects in radar images. Edge
detection; which is a method of determining the discontinuities in gray level images; is a very
important initial step in Image processing. Many classical edge detectors have been developed
over time. Some of the well-known edge detection operators based on the first derivative of the
image are Roberts, Prewitt, Sobel which is traditionally implemented by convolving the image
with masks. Also Gaussian distribution has been used to build masks for the first and second
derivative. However, this distribution has limit to only symmetric shape. This paper will use to
construct the masks, the Weibull distribution which was more general than Gaussian because it
has symmetric and asymmetric shape. The constructed masks are applied to images and we
obtained good results.
EDGE DETECTION IN RADAR IMAGES USING WEIBULL DISTRIBUTIONcscpconf
Radar images can reveal information about the shape of the surface terrain as well as its physical and biophysical properties. Radar images have long been used in geological studies to
map structural features that are revealed by the shape of the landscape. Radar imagery also has applications in vegetation and crop type mapping, landscape ecology, hydrology, and
volcanology. Image processing is using for detecting for objects in radar images. Edge detection; which is a method of determining the discontinuities in gray level images; is a very
important initial step in Image processing. Many classical edge detectors have been developed over time. Some of the well-known edge detection operators based on the first derivative of the image are Roberts, Prewitt, Sobel which is traditionally implemented by convolving the image with masks. Also Gaussian distribution has been used to build masks for the first and second derivative. However, this distribution has limit to only symmetric shape. This paper will use to construct the masks, the Weibull distribution which was more general than Gaussian because it has symmetric and asymmetric shape. The constructed masks are applied to images and we obtained good results.
ANALYSIS OF LAND SURFACE DEFORMATION GRADIENT BY DINSAR cscpconf
The progressive development of Synthetic Aperture Radar (SAR) systems diversify the exploitation of the generated images by these systems in different applications of geoscience. Detection and monitoring surface deformations, procreated by various phenomena had benefited from this evolution and had been realized by interferometry (InSAR) and differential interferometry (DInSAR) techniques. Nevertheless, spatial and temporal decorrelations of the interferometric couples used, limit strongly the precision of analysis results by these techniques. In this context, we propose, in this work, a methodological approach of surface deformation detection and analysis by differential interferograms to show the limits of this technique according to noise quality and level. The detectability model is generated from the deformation signatures, by simulating a linear fault merged to the images couples of ERS1 / ERS2 sensors acquired in a region of the Algerian south.
A comparison of SIFT, PCA-SIFT and SURFCSCJournals
This paper compares three robust feature detection methods, they are, Scale Invariant Feature Transform (SIFT), Principal Component Analysis (PCA) -SIFT and Speeded Up Robust Features (SURF). Lowe presented SIFT [1], which was successfully used in recognition, stitching and many other applications because of its robustness. Yan Ke [2] gave a change of SIFT by using PCA to normalize the gradient patch instead of histogram. H. Bay [3] presented a faster method for SURF, which used Fast-Hessian detector. The performance of the three methods is compared for scale changes, rotation , blur, illumination changes and affine transformations, all of which uses repeatability as an evaluation measurement. Additionally, RANSAC is used to reject the inconsistent matches [4]. SIFT presents its stability in most situation except rotation and illumination changes. SURF is the fastest one with good performance as the same as SIFT, PCA-SIFT shows its advantages in rotation, blur and illumination changes.
Performance of cognitive radio networks with maximal ratio combining over cor...Polytechnique Montreal
In this paper, we apply the maximal ratio combining (MRC) technique to achieve higher detection probability in cognitive radio networks over correlated Rayleigh fading channels. We present a simple approach to derive the probability of detection in closed-form expression. The numerical results reveal that the detection performance is a monotonically increasing function with respect to the number of antennas. Moreover, we provide sets of complementary receiver operating characteristic (ROC) curves to illustrate the effect of antenna correlation on the sensing performance of cognitive radio networks employing MRC schemes in some respective scenarios.
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.
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 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.
Ultrasonic guided wave techniques have great potential for structural health monitoring applications. Appropriate mode and frequency selection is the basis for achieving optimised damage monitoring performance.
In this paper, several important guided wave mode attributes are
introduced in addition to the commonly used phase velocity and group velocity dispersion curves while using the general corrosion problem as an example. We first derive a simple and generic wave excitability function based on the theory of normal mode expansion and the reciprocity theorem. A sensitivity dispersion curve is formulated based on the group velocity dispersion curve. Both excitability and sensitivity dispersion curves are verified with finite element simulations. Finally, a
goodness dispersion curve concept is introduced to evaluate the tradeoffs between multiple mode selection objectives based on the wave velocity, excitability and sensitivity.
Evaluation of the Sensitivity of Seismic Inversion Algorithms to Different St...IJERA Editor
Seismic wavelet estimation is an important step in processing and analysis of seismic data. Inversion methods as Narrow-Band and theConstrained Sparse-Spike ones require information about it so that the inversion solution, once it is not a unique problem, may be restricted by comparing the real seismic trace with the synthetic generated by convolution of the estimated reflectivity and wavelet. Besides helping in seismic inversion, a good estimate of the wavelet enables an inverse filter with less uncertainty to be computed in the deconvolution step and while tying well logs, a better correlation between the seismic trace and well log can be achieved. Depending on the use or not of well log information, the methods of wavelet estimation can be divided into two classes: statistical and deterministic. This work aimed to test the sensitivity of acoustic post-stack seismic inversion algorithms to wavelets statistically estimated by two distinct methods
Direct non-linear inversion of multi-parameter 1D elastic media using the inv...Arthur Weglein
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.
Boosting CED Using Robust Orientation Estimationijma
n this paper, Coherence Enhancement Diffusion (CED) is boosted feeding external orientation using new
robust orientation estimation. In CED, proper scale selection is very important as the gradient vector at
that scale reflects the orientation of local ridge. For this purpose a new scheme is proposed in which pre
calculated orientation, by using local and integration scales. From the experiments it is found the proposed
scheme is working much better in noisy environment as compared to the traditional Coherence
Enhancement Diffusion
Wavelet estimation for a multidimensional acoustic or elastic earthArthur Weglein
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...Arthur Weglein
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.
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
Wavelet estimation for a multidimensional acoustic or elastic earth- Arthur W...Arthur Weglein
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
Inverse scattering series for multiple attenuation: An example with surface a...Arthur Weglein
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.
Deghosting is a longstanding seismic objective and problem that has received considerable renewed attention due to : (1). an interest in so-called "broadband seismology" and the low frequency /low vertical wave number.
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....Arthur Weglein
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.
Linear inversion of absorptive/dispersive wave field measurements: theory and...Arthur Weglein
The use of inverse scattering theory for the inversion of viscoacoustic wave field
measurements, namely for a set of parameters that includes Q, is by its nature very
different from most current approaches for Q estimation. In particular, it involves an
analysis of the angle- and frequency-dependence of amplitudes of viscoacoustic data
events, rather than the measurement of temporal changes in the spectral nature of
events. We consider the linear inversion for these parameters theoretically and with
synthetic tests. The output is expected to be useful in two ways: (1) on its own it
provides an approximate distribution of Q with depth, and (2) higher order terms in
the inverse scattering series as it would be developed for the viscoacoustic case would
take the linear inverse as input.
We will begin, following Innanen (2003) by casting and manipulating the linear
inversion problem to deal with absorption for a problem with arbitrary variation of
wavespeed and Q in depth, given a single shot record as input. Having done this, we
will numerically and analytically develop a simplified instance of the 1D problem. This
simplified case will be instructive in a number of ways, first of all in demonstrating
that this type of direct inversion technique relies on reflectivity, and has no interest in
or ability to analyse propagation effects as a means to estimate Q. Secondly, through
a set of examples of slightly increasing complexity, we will demonstrate how and where
the linear approximation causes more than the usual levels of error. We show how
these errors may be mitigated through use of specific frequencies in the input data,
or, alternatively, through a layer-stripping based, or bootstrap, correction. In either
case the linear results are encouraging, and suggest the viscoacoustic inverse Born
approximation may have value as a standalone inversion procedure.
Initial study and implementation of the convolutional Perfectly Matched Layer...Arthur Weglein
In this report, first steps and results of the implementation of the Convolutional Perfectly
Matched Layer (CPML), for the modeling of the 2D acoustic heterogeneous wave equation
are presented. We also compare the conditions to set to zero, for all angles of incidence, the
reflection coefficient at the interface between two PML media, with the analogous conditions
for the reflection coefficient at an interface between two acoustic media. A side product of the
present work for the M-OSRP is a code to create synthetic data, using Finite-Difference (FD)
methods with PML BCs.
We also provide a short description of the main stages involved in the original Reverse Time
Migration (RTM) algorithm, with focus on the 2D acoustic heterogeneous wave equation. We
include a derivation of the equations of the CPML for the backward propagation of the data,
which is part of the RTM. As far as the authors knowledge, these equations and derivations
have not been reported in the literature. The reason we include the RTM is because the present
report can be considered part of a broader research project whose objective is to compare the
RTM with PML BCs with the Green’s theorem based RTM, developed within the M-OSRP.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
This pdf is about the Schizophrenia.
For more details visit on YouTube; @SELF-EXPLANATORY;
https://www.youtube.com/channel/UCAiarMZDNhe1A3Rnpr_WkzA/videos
Thanks...!
Introduction:
RNA interference (RNAi) or Post-Transcriptional Gene Silencing (PTGS) is an important biological process for modulating eukaryotic gene expression.
It is highly conserved process of posttranscriptional gene silencing by which double stranded RNA (dsRNA) causes sequence-specific degradation of mRNA sequences.
dsRNA-induced gene silencing (RNAi) is reported in a wide range of eukaryotes ranging from worms, insects, mammals and plants.
This process mediates resistance to both endogenous parasitic and exogenous pathogenic nucleic acids, and regulates the expression of protein-coding genes.
What are small ncRNAs?
micro RNA (miRNA)
short interfering RNA (siRNA)
Properties of small non-coding RNA:
Involved in silencing mRNA transcripts.
Called “small” because they are usually only about 21-24 nucleotides long.
Synthesized by first cutting up longer precursor sequences (like the 61nt one that Lee discovered).
Silence an mRNA by base pairing with some sequence on the mRNA.
Discovery of siRNA?
The first small RNA:
In 1993 Rosalind Lee (Victor Ambros lab) was studying a non- coding gene in C. elegans, lin-4, that was involved in silencing of another gene, lin-14, at the appropriate time in the
development of the worm C. elegans.
Two small transcripts of lin-4 (22nt and 61nt) were found to be complementary to a sequence in the 3' UTR of lin-14.
Because lin-4 encoded no protein, she deduced that it must be these transcripts that are causing the silencing by RNA-RNA interactions.
Types of RNAi ( non coding RNA)
MiRNA
Length (23-25 nt)
Trans acting
Binds with target MRNA in mismatch
Translation inhibition
Si RNA
Length 21 nt.
Cis acting
Bind with target Mrna in perfect complementary sequence
Piwi-RNA
Length ; 25 to 36 nt.
Expressed in Germ Cells
Regulates trnasposomes activity
MECHANISM OF RNAI:
First the double-stranded RNA teams up with a protein complex named Dicer, which cuts the long RNA into short pieces.
Then another protein complex called RISC (RNA-induced silencing complex) discards one of the two RNA strands.
The RISC-docked, single-stranded RNA then pairs with the homologous mRNA and destroys it.
THE RISC COMPLEX:
RISC is large(>500kD) RNA multi- protein Binding complex which triggers MRNA degradation in response to MRNA
Unwinding of double stranded Si RNA by ATP independent Helicase
Active component of RISC is Ago proteins( ENDONUCLEASE) which cleave target MRNA.
DICER: endonuclease (RNase Family III)
Argonaute: Central Component of the RNA-Induced Silencing Complex (RISC)
One strand of the dsRNA produced by Dicer is retained in the RISC complex in association with Argonaute
ARGONAUTE PROTEIN :
1.PAZ(PIWI/Argonaute/ Zwille)- Recognition of target MRNA
2.PIWI (p-element induced wimpy Testis)- breaks Phosphodiester bond of mRNA.)RNAse H activity.
MiRNA:
The Double-stranded RNAs are naturally produced in eukaryotic cells during development, and they have a key role in regulating gene expression .
Inverse scattering series for multiple attenuation: An example with surface and internal multiples
1. Inverse scattering series for multiple attenuation: An example with surface
and internal multiples
Fernanda V. PPPG/Federal University of Bahia; Arthur B. Weglein, Schlumberger
Cambridge Research; Paulo Marcus Carvalho, SA; and R.H. Stolt, Conoco S14.4
SUMMARY
A multiple attenuation method derived from an inverse scatter-
ing 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 il-
lustrated 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 multidimen-
sional and does not rely on periodicity or differential moveout,
nor does it require a model of the reflectors generating the mul-
tiples. An example with internal and surface multiples will be
presented.
INTRODUCTION
Multiple suppression is a long-standing problem in exploration
seismology. The conventional techniques used today for attenu-
ating multiples are moveout based methods such as NMO-stack,
f-k and p-r filtering, predictive methods based on periodicity as-
sumptions, wave equation modeling and subtraction methods,
and surface multiple removal methods. There are many cases
where these procedures are effective. However, there are also
many instances where multiples remain a serious problem. The
reason is that the available procedures make assumptions about
the nature of the earth that are often violated in practice. Those
methods based on moveout and on periodicity assume that the
earth is one dimensional with horizontal uniform layers’. Curved
or dipping reflectors and variations in the overburden can cause
serious problems for these 1D methods. Wave equation modeling
methods and surface removal methods can accomodate a multi-
dimensional earth. However, the method based on wave equation
modeling requires precise knowledge of the reflectors causing the
upward and downward reflections (Wiggins, 1988). The surface
removal method requires knowledge of the reflector causing the
downward reflection. It removes all downward reflections that
occur at the referred surface (e.g., Riley and Claerbout, 1976,
Dragoset, 1992, Verschuur et al., 1992).
The internal multiple attenuation method that we describe is de-
rived from an inverse scattering series. In contrast with methods
for attenuating internal multiples that require a repeated applica-
tion of surface removal and downward continuation, this inverse
scattering series approach does not require knowledge of the re-
flectors that generate the multiples, nor does it require a model
of the medium properties needed for downward continuation.
INVERSE SCATTERING SERIES
The scattered field, can be written in terms of the Lippmann-
Schwinger equation as
I
=
where is the Green function for the homogeneous half-space
and V is the model perturbation. G represents the total field
and can be written as G = G,. Substituting the latter
expression in the L-S equation you obtain the series:
= (I
+ . . . .
Expanding V as a power series in the measured data as V =
(Moses, 1956, Prosser, 1969, Razavy, 1975),
=
=
= .
The linear term is obtained directly from the measured values
of G,. The terms of higher orders and so on, are obtained
recursively. A data free of multiples is given by
D =
= . . . .
In the process of going from data to model properties, multiples
are removed and primaries are mapped from data-like events in
time to model properties in space. The full inversion series, whose
purpose is to determine model properties in space, only converges
for very small contrasts in medium properties. An idea presented
in Weglein and Stolt (1993) was to separate this full inversion se-
ries into subseries that perform separately the task of surface and
internal multiple suppression from the task of primary alteration.
The Green function for a homogeneous background with a free-
surface can be written as a sum, where is the free
space Green function and is the added term due to the free-
surface, Figure 1. A free-surface multiple suppression method
was developed by Carvalho (1992) and brief reports of that work
appear in Carvalho et al. (1991, 1992). The method was derived
by ignoring the direct interactions and substituting in the full
series by This method will eliminate all events with at
least one reflection at the free-surface. All other events, including
internal multiples, will remain in the data.
1039
Downloaded03/20/15to129.7.0.94.RedistributionsubjecttoSEGlicenseorcopyright;seeTermsofUseathttp://library.seg.org/
2. 2 Multiple attenuation
Internal Multiple Attenuation
A brief description of an internal multiple attenuation subseries
is presented in Araujo et al. (1994a) with a more complete de-
velopment given in Araujo (1994b) and Araujo et al. (1994c). In
that work, it is assumed that either free-surface multiples have
been removed or that they do not represent a problem in the
data. is substituted for in the full series. The problem
is that the series with is responsible not only for attenuating
internal multiples but also for performing the alteration of the
primaries. The separation between these two tasks is done by
selecting from the series only portions of the odd terms that are
responsible for removing multiply reflected energy, Weglein and
Stolt (1993). These pieces of the odd terms will form a subseries
for attenuating internal multiples. All other terms and pieces of
terms are omitted.
Results
The reflection data shown in the examples are for a plane wave
normal incident on a acoustic medium.
Figure 2 shows the combined free-surface multiple suppression
and the internal multiple attenuation methods. Figure 2a presents
the results for the free-surface multiple suppression (Carvalho et
al., 1991) and Figure 2b uses the output generated by the exam-
ple in Figure 2a as the input for the internal multiple attenuation
method. Trace 1 is the data and trace 2 is the data after mul-
tiple attenuation. The primaries are labeled P, the free-surface
multiples SM, and the internal multiples IM.
Figure 3 shows that the internal multiple attenuation method
works well with band-limited data. Trace 1 is the data (gen-
erated without free-surface multiples), traces 2, 3 and 4 are the
multiple attenuation operators, and trace 5 is the data after mul-
tiple attenuation, given by the sum of traces 1 to 4.
CONCLUSIONS
A multidimensional internal multiple attenuation method based
on an inverse scattering series is described and examples pre-
sented. The method does not depend on periodicity, differential
nor does it require previous knowledge of the subsurface
characteristics. The subseries for internal multiple attenuation is
rapidly convergent for all contrasts in medium properties. This
is in contrast to the full inversion series that only converges for
small changes in medium properties. The identified subseries for
internal multiple attenuation has, for the tests, resulted in a
slight increase in the amplitude of the primaries.
ACKNOWLEDGEMENTS
The authors thank
berger Cambridge Research, ARCO, and Conoco for supporting
different aspects of this project.
REFERENCES
Araujo, F.V., Weglein, A.B., Carvalho, P.M., and Stolt, R.H.,
1994a , Internal multiple attenuation, EAEG Abstracts.
Araujo, F.V., Linear and non-linear methods derived from
scattering theory: Backscattered tomography and internal mul-
tiple attenuation: Ph.D. Thesis, Universidade Federal da Bahia
(in Portuguese).
Araujo, F.V., Weglein, A.B., Carvalho, P.M., and Stolt , R.H.,
Inverse scattering series approach to internal multiple at-
tenuation, in preparation, to be submitted to Geophysics.
Carvalho, P.M., 1992, Free-surface multiple reflection elimination
method based on non-linear inversion of seismic data: Ph.D. The-
sis, Universidade Federal da Bahia (in Portuguese).
Carvalho, P.M., Weglein, A.B., and Stolt, R.H., 1991, Exam-
ples of a non-linear inversion method based on the T matrix of
scattering theory: application to multiple suppression, Expanded
abstracts SEG, v.2.
Carvalho, P.M., Weglein, A.B., and Stolt, R.H., 1992, Non-linear
inverse scattering for multiple suppression: application to real
data, Part I: Expanded abstracts SEG, v.2, 1093-1095.
Dragoset, W.H., 1992, Surface multiple attenuation theory,
practical issues, examples, EAEG Abstracts, B027.
Moses, H.E., 1956, Calculation of scattering potential from re-
flection coefficients: Phys. Rev., 102, 559-567.
Prosser, R.T., 1969, Formal solutions of inverse scattering prob-
lems, J. Math. Phys., 10, 1819-1822.
Razavy, M., 1975, Determination of the wave velocity in an
mogeneous medium from reflection data: J. Acoustic Am.,
58, 956-963.
Riley, D.C. and Claerbout, J.F., 1976, 2D multiple reflections:
Geophysics, 41, 592-620.
Verschuur, D.J., Berkhout, A.J. and Wapenaar, C.P.A., 1992,
Adapt ative surface-related multiple elimination: Geophysics, 57,
1166-1177.
Weglein, A.B. and Stolt, R.H., 1993, I. The wave physics of down-
ward continuation, estimation, and volume and surface
scattering. II. Approaches to linear and non-linear
inversion: Mathematical frontiers in reflection seismology, Ed.
W.W. Symes, SIAM/SEG.
Wiggins, J.W., 1988, Attenuation of complex water-bottom mul-
tiples by wave-equation based prediction and subtraction: Geo-
physics, 53, 15271539.
Downloaded03/20/15to129.7.0.94.RedistributionsubjecttoSEGlicenseorcopyright;seeTermsofUseathttp://library.seg.org/
3. Multiple attenuation 3
Fig.1 - Green function for a homogeneous medium with
a free-surface.
Fig.3 - Internal multiple attenuation with band-limited data.
Model: cl = = = =
= h2 = = 240m.
Band-pass filter (Hz): [10, 20, 90, 100].
Fig.2 - Combined a) free-surface and b) internal multiple attenuation
Model: cl = = =
hl = 80m, h2 = 72m. .
1041
Downloaded03/20/15to129.7.0.94.RedistributionsubjecttoSEGlicenseorcopyright;seeTermsofUseathttp://library.seg.org/