Academic literature on the topic 'Impedance contrasts'
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Journal articles on the topic "Impedance contrasts"
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Cao, D., W. B. Beydoun, S. C. Singh, and A. Tarantola. "A simultaneous inversion for background velocity and impedance maps." GEOPHYSICS 55, no. 4 (April 1990): 458–69. http://dx.doi.org/10.1190/1.1442855.
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Full‐waveform inversion of seismic reflection data is highly nonlinear because of the irregular form of the function measuring the misfit between the observed and the synthetic data. Since the nonlinearity results mainly from the parameters describing seismic velocities, an alternative to the full nonlinear inversion is to have an inversion method which remains nonlinear with respect to velocities but linear with respect to impedance contrasts. The traditional approach is to decouple the nonlinear and linear parts by first estimating the background velocity from traveltimes, using either traveltime inversion or velocity analysis, and then estimating impedance contrasts from waveforms, using either waveform inversion or conventional migration. A more sophisticated strategy is to obtain both the subsurface background velocities and impedance contrasts simultaneously by using a single least‐squares norm waveform‐fit criterion. The background velocity that adequately represents the gross features of the medium is parameterized using a sparse grid, whereas the impedance contrasts use a dense grid. For each updated velocity model, the impedance contrasts are computed using a linearized inversion algorithm. For a 1-D velocity background, it is very efficient to perform inversion in the f-k domain by using the WKBJ and Born approximations. The method performs well both with synthetic and field data.
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Morozov, Igor B. "Exact elastic P/SV impedance." GEOPHYSICS 75, no. 2 (March 2010): C7—C13. http://dx.doi.org/10.1190/1.3318268.
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Several extensions of the concept of acoustic impedance (AI) to oblique incidence exist and are known as elastic impedances (EI). These quantities are constructed by heuristic integrations of reflectivity series but still involve approximations and do not represent a unique medium property. Nevertheless, for unambiguous interpretation, it is desirable to have an EI that would (1) be a mechanical property of the medium and (2) yield exact reflection coefficients at all angles of incidence. Here, such a definition is given for P- and/or SV-wave propagation in an arbitrary isotropic medium. The exact elastic P/SV impedance is a matrix quantity and represents the differential operator relating the stress and strain boundary conditions. With the use of the matrix form of the reflectivity problem, no approximations are required for accurate modeling of reflection (P/P and SV/SV) and mode-conversion (P/SV and SV/P) coefficients at all angles and for any contrasts in elastic properties. The matrix EI can be computed from real well logs and inverted from ray-parameter-dependent seismic reflectivity. Known limiting cases of P- and S-wave acoustic impedances are accurately reproduced and the approach also allows the extension of the concept of impedance to an attenuative medium. The matrix impedance readily lends itself to inversion with uncertainties typical of the standard acoustic-impedance inversion problem.
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Kiyashchenko, Denis, René-Edouard Plessix, and Boris Kashtan. "Modified imaging principle: An alternative to preserved-amplitude least-squares wave-equation migration." GEOPHYSICS 72, no. 6 (November 2007): S221—S230. http://dx.doi.org/10.1190/1.2786867.
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Impedance contrast images can result from a least-squares migration or from a modified imaging principle. Theoretically, the two approaches should give similar results, but in practice they lead to different estimates of the impedance contrasts because of limited acquisition geometry, difficulty in computing exact weights for least-squares migration, and small contrast approximation. To analyze those differences, we compare the two approaches based on 2D synthetics. Forward modeling is either a finite-difference solver of the full acoustic wave equation or a one-way wave-equation solver that correctly models the amplitudes. The modified imaging principle provides better amplitude estimates of the impedance contrasts and does not suffer from the artifacts at-tributable to diving waves, which can be seen in two-way, least-squares migrated sections. However, because of the shot-based formulation, artifacts appear in the modified imaging principle results in shadow zones where energy is defocused. Those artifacts do not exist with the least-squares migration algorithm because all shots are processed simultane-ously.
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Cho, Yongchae, Richard L. Gibson Jr., and Dehan Zhu. "Quasi 3D transdimensional Markov-chain Monte Carlo for seismic impedance inversion and uncertainty analysis." Interpretation 6, no. 3 (August 1, 2018): T613—T624. http://dx.doi.org/10.1190/int-2017-0136.1.
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Accurate estimation of subsurface properties plays an important role in successful hydrocarbon exploration, and a variety of different types of inversion schemes are used to infer earth properties such as velocity or density by analyzing the surface seismic. The Markov-chain Monte Carlo (MCMC) stochastic approach is widely used to estimate subsurface properties. We have used a transdimensional form of MCMC, reversible jump MCMC (RJMCMC), to estimate seismic impedance, which allows the inference of the number of interfaces as well as the interface location and layer impedances. Estimating the uncertainty quantitatively is also very important when performing stochastic inversion. Therefore, the goal of this paper is to apply the transdimensional method to obtain a 3D seismic impedance model and to quantify uncertainty in impedance and interface locations. We also measured the speedup of the proposed algorithm by applying data and task parallelism. To demonstrate the performance and reliability of the proposed RJMCMC impedance inversion, we used seismic data from the E-segment of the Norne field in Norwegian Sea. The results of the quasi 3D transdimensional MCMC approach, which independently inverts data from each common-depth-point location, indicate high velocity contrasts near gas-oil contacts and high uncertainty in impedance near discontinuities. Also, the cross section of the impedance uncertainty volume helps to identify the location of a high-contrast boundary corresponding to the location of the possible gas reservoir. The proposed uncertainty measure can serve as an attribute to identify important reservoir features.
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Tobias, Steve. "Interpreters and near-field exploration: The role of leadership, culture, and organizational impedance contrasts." Interpretation 6, no. 2 (May 1, 2018): 5M—12M. http://dx.doi.org/10.1190/int-2018-0214-ps.1.
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Four years ago, several visionaries from SEG and AAPG collaborated to create Interpretation, a journal that serves the unique community of integrated interpretation. As the late R. Randy Ray wrote at the time, “It marks a historic recognition that geology and geophysics are intertwined at the core.” Indeed, this core community drives the exploration engine that powers the oil and gas industry through the multidisciplinary study of the petroleum system. The time has come for this same community to apply its considerable intellectual and operational acumen to optimizing another system that is rarely recognized as such: near-field exploration. Unlike “pure” conventional exploration, near-field exploration tends to be much more organizationally complex. Exploration functions need to deal with producing assets. Offices set in different cultures and separated by many time zones need to work together flawlessly. Engineering-centric dynamic geocellular models need to mesh with map-based static descriptions of the earth. Most importantly, a culture of value assurance needs to be balanced with a spirit of exploration that demands a culture of creativity and risk taking. These compartmentalized and layered oil and gas organizations share one important characteristic with the heterogeneous earth: each component can be considered to have its own unique impedance. As all interpreters know, elastic impedance contrasts associated with geological heterogeneity give rise to reflected seismic signals, the acquisition, processing, and interpretation of which are our bread and butter. Yet while organizational boundaries also impede the free flow of energy (in the form of knowledge/information, processes, workflows, etc.), there is little awareness that signals reflected from organizational impedance contrasts can be studied and ultimately inverted to understand and optimize various organizational components. Taken together, the heterogeneous environment known as near-field exploration can be modeled as a complex arrangement of different types of impedances, with (usually unmonitored) signals emanating from the many impedance contrasts. The monitoring, processing, and interpretation of these organizational signals are shown to fit well into the Shewhart cycle of plan-do-check-act, something that our engineering colleagues use regularly in their lean manufacturing processes. This paper introduces what for many will be a new paradigm for the organizational development of companies focused on near-infrastructure exploration. And yet for most interpreters reading this, it will seem “old hat.” Our community has been unmasking the geology associated with boundary reflections for almost a century. The time has come to improve the organizations within which we toil by applying our skills to the study of organizational impedance contrasts.
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Schmitt, Susanne, and Andreas Kirsch. "A factorization scheme for determining conductivity contrasts in impedance tomography." Inverse Problems 27, no. 9 (August 8, 2011): 095005. http://dx.doi.org/10.1088/0266-5611/27/9/095005.
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Niccoli, Matteo. "Mapping and validating lineaments." Leading Edge 34, no. 8 (August 2015): 948–50. http://dx.doi.org/10.1190/tle34080948.1.
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Data enhancement can help to emphasize edges that correspond to contrasts in acoustic impedance, magnetic susceptibility, or bulk density. Such contrasts often indicate the presence of important geologic boundaries. Emphasizing the edges can help with mapping and interpretation of those boundaries.
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Douma, Huub, David Yingst, Ivan Vasconcelos, and Jeroen Tromp. "On the connection between artifact filtering in reverse-time migration and adjoint tomography." GEOPHYSICS 75, no. 6 (November 2010): S219—S223. http://dx.doi.org/10.1190/1.3505124.
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Finite-frequency sensitivity kernels in seismic tomography define the volumes inside the earth that influence seismic waves as they traverse through it. It has recently been numerically observed that an image obtained using the impedance kernel is much less contaminated by low-frequency artifacts due to the presence of sharp wave-speed contrasts in the background model, than is an image obtained using reverse-time migration. In practical reverse-time migration, these artifacts are routinely heuristically dampened by Laplacian filtering of the image. Here we show analytically that, for an isotropic acoustic medium with constant density, away from sources and receivers and in a smooth background medium, Laplacian image filtering is identical to imaging with the impedance kernel. Therefore, when imaging is pushed toward using background models with sharp wave-speed contrasts, the impedance kernel image is less prone to develop low-frequency artifacts than is the reverse-time migration image, due to the implicit action of the Laplacian that amplifies the higher-frequency reflectors relative to the low-frequency artifacts. Thus, the heuristic Laplacian filtering commonly used in practical reverse-time migration is fundamentally rooted in adjoint tomography and, in particular, closely connected to the impedance kernel.
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Amundsen, Lasse, Bjørn Ursin, and Martin Landrø. "The plane-wave primary reflection response from an impedance gradient interface." Journal of the Acoustical Society of America 152, no. 1 (July 2022): 659–66. http://dx.doi.org/10.1121/10.0012885.
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A weak scattering model that allows prediction of the one-dimensional acoustic plane wave primary reflection response from an impedance gradient interface is described. The velocity and density gradient profiles are represented by a smooth approximation to the Heaviside function of the Fermi–Dirac distribution type. The profiles are described by the velocities and densities at minus and plus infinity, the reference depth of the gradient interface, and its smoothness. The primary response is derived by using the Bremmer series to reduce a generally complex reflection problem to the simpler one of the primary reflections which is a valid solution for small impedance contrasts. The reflection response can be expressed in terms of the Appellian hypergeometric functions of two variables of the first kind and Gaussian hypergeometric functions. When the reflection response is evaluated at sufficiently large distance above the reference depth, the Appellian functions are reduced to Gaussian hypergeometric functions. In the Born approximation, the reflection response simplifies. In the limit of zero frequency, the reflection coefficient in the small impedance contrast approximation can be related to the classic reflection coefficient for two impedance layers in welded contact.
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Samore, Andrea, Marco Guermandi, Silvio Placati, and Roberto Guerrieri. "Parametric Detection and Classification of Compact Conductivity Contrasts With Electrical Impedance Tomography." IEEE Transactions on Instrumentation and Measurement 66, no. 10 (October 2017): 2666–79. http://dx.doi.org/10.1109/tim.2017.2711818.
Full textDissertations / Theses on the topic "Impedance contrasts"
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Kneeshaw, Peter John. "The role of dynamic contrast enhanced magnetic resonance imaging and electrical impedance mammography in the management of breast microcalcification." Thesis, University of Hull, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411899.
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Ronneburg, Arne. "Electrochemical Storage of Lithium in Silicon - Morphological Analysis from the Atomistic Scale to the Macroscale." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22866.
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Silizium-Elektroden werden aufgrund ihrer um eine Gröÿenordnung höheren Kapazität als mögliches Elektrodenmaterial in Lithium-Ionen-Batterien betrachtet. Diese Kapazität geht jedoch mit einer Volumenausdehnung von bis zu 310 % einher. Dies begünstigt einen schnellen Kapazitätsabfall und ein kontinuierliches Wachstum der SEI-Schicht. Ziel dieser Arbeit ist es daher, die Morphologie-Änderung der Siliziumelektrode während des Lithiierungs-Prozesses besser zu verstehen unter Nutzung von operando-Methoden
Im ersten Teil wurde Neutronenreflektometrie (NR) genutzt, um die Morphologie-Änderung auf der Nanometerskala einer Siliziumelektrode zu untersuchen. Das Wachsen/Schrumpfen der lithiierten Zone im Silizium wurde beobachtet. Auf der Oberfläche der Elektrode wächst im delithiierten Zustand eine Grenzschicht, welche die Lithiierung verhindert. Nachdem diese Schicht aufgelöst ist, kann Lithium eingelagert werden.
Im zweiten Teil wurde operando Röntgen- Phasenkontrast-Radiographie genutzt. Ein rechteckiges Riss-Gitter wurde dabei im delithiierten Zustand beobachtet, welches sich während der Lithiierung schließt. Dieses Gitter ist entlang der Kristallachsen des Siliziums orientiert. Im nächsten Zyklus entsteht das Gitter am selben Ort wieder, und breitet sich mit steigender Zyklenzahl über die Elektrode aus.
Im dritten Teil wurde der Einfluss einer künstlichen Grenzschicht auf die Lithiierung untersucht. Erneut wurde NR genutzt. Die künstliche Schicht verringert das Wachstum der SEI-Schicht, unterdrückt es jedoch nicht komplett. Nach 2 Zyklen ist die Grenzschicht degradiert, und Seitenreaktionen können beobachtet werden.Silicon electrodes receive great interest as potential electrode material in lithium-based batteries due to their one order of magnitude higher capacity. This is accompanied by a volume expansion of up to 310 %, leading to an accelerated capacity loss of the electrodes. The volume expansion creates mechanical stress, leading to fracturization of the electrode and the continuous growth of the solid-electrolyte-interphase (SEI) layer under the consumption of active material. The aim of this thesis is to investigate the morphological changes of silicon electrodes during lithiation/ delithiation. Especially operando-techniques are well-suited to investigate these morphological changes since they allow us to precisely link structural data and the electrochemical state. The first project uses operando neutron reflectometry (NR) and in-situ electrochemical impedance spectroscopy (EIS) to analyze the morphology change of the silicon surface on the nanometer-scale. The growth and shrinkage of the lithiated layers within the electrode as well as the lithium concentration was determined with this method. An SEI-layer forms on top of the silicon electrode in the delithiated state, which hinders the lithium uptake in the initial part of the subsequent lithiation. The second project analyzes the morphology-change of the electrode on the µm-scale. Here the fracturization of the silicon electrode is investigated by operando X-ray phase-contrast radiography. A rectangular fracturization pattern was observed during the second half of the delithiation, which vanished again during the lithiation. The third project investigates the influence of an artificial coating layer on the lithiation process. Again operando NR was chosen as analysis tool. The artificial coating decreased the formation of the SEI-layer within the first cycles, but did not suppress it completely. However, this layer degraded already in an early stage of cycling, resulting in the occurrence of side reactions afterward.
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Setiawan, Bambang. "Quantifying the seismic site amplification characteristics of Adelaide’s regolith." Thesis, 2018. http://hdl.handle.net/2440/120417.
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The historical seismic events have clearly indicated that site amplification has played a principal role in defining the damage to structures founded on the regolith in the city of Adelaide, South Australia. An amplification factor of up to 3.7 is suggested. Thus, a seismic site amplification study in Adelaide city is needed. The use of the ambient noise method for quantifying seismic site amplification of Adelaide’s regolith was selected because of its advantages (non-destructive and affordable). The application of ambient noise analysis for the study of site effects at regolith locations was carried out as it is underdeveloped and requires further attention. A case study is examined which explores Adelaide’s regolith and incorporates 10 in situ ambient noise measurements carried out across the city of Adelaide for seismically classifying the site, estimating bedrock depth and obtaining the shear wave velocity profile. Seismic site classification was investigated using the horizontal vertical spectral ratio (HVSR) technique. The results show that Adelaide’s regolith varies from classes D to C (NEHRP classification system), classes D to B (Australian Standard classification system) or classes D/DE to C (regolith case classification system) and are in a good agreement with several previous studies. The depth of bedrock is crucial in seismic hazard studies because the basin geometry has been shown to play an important role in the altering of seismic waves. Both the generic function (GF) of the classic HVSR method and the spatial autocorrelation (SPAC) technique were used to estimate the depth to bedrock. The bedrock depth predictions from the seismic methods were validated against boreholes drilled in close proximity to the measured sites. The comparison demonstrates that the SPAC method provides better estimates, especially to those obtained from another approach. In the general framework of seismic hazard analysis for quantifying site amplification, the knowledge of near surface shear wave velocity profile is crucial. New constraints by means of shear wave velocities for the study case site were developed and proposed. The proposed shear wave velocity models were compared and validated against previous studies and forward modelling techniques. On the basis of these validation results, the applicability of the array SPAC method at regolith sites is justified.Thesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental & Mining Engineering, 2018
Books on the topic "Impedance contrasts"
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Galiuto, L., R. Senior, and H. Becher. Contrast echocardiography. Oxford University Press, 2011. http://dx.doi.org/10.1093/med/9780199599639.003.0007.
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Contrast echocardiography is a non-invasive, well tolerated echocardiographic technique which employs ultrasound contrast agent in order to improve the quality of echocardiographic images, by enhancing blood flow signal.Clinical usefulness of this echocardiographic imaging modality resides in the possibility of providing better acoustic signal in cases of poor quality images, with additional important information related to assessment of myocardial perfusion. Indeed, about one-third of echocardiographic images are affected by poor quality due to high acoustic impedance of the chest wall of the patients secondary to obesity or pulmonary diseases, not allowing detection of left ventricular endocardial border. Moreover, in patients with low ejection fraction and apical left ventricular aneurysm, intraventricular thrombus could be undetectable with standard echocardiography. Furthermore, coronary microcirculation cannot be assessed by standard echocardiography. Contrast echocardiography can be performed in all such conditions to improve diagnostic power of echocardiography.The adjunctive role of contrast echocardiography is well defined in both rest and stress echocardiography in order to detect the endocardial border and intraventricular thrombi, to accurately measure ejection fraction, wall motion, and to assess myocardial perfusion.The purpose of this chapter is to explain basic principles, feasibility, safety, major clinical applications, current indications, and further developments of contrast echocardiography.
Book chapters on the topic "Impedance contrasts"
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Polydorides, Nick. "High Contrast Electrical Impedance Imaging." In Progress in Industrial Mathematics at ECMI 2006, 608–12. Berlin, Heidelberg: Springer Berlin Heidelberg, 2008. http://dx.doi.org/10.1007/978-3-540-71992-2_101.
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Magee, Patrick, and Mark Tooley. "Gas pressure, Volume and Flow Measurement." In The Physics, Clinical Measurement and Equipment of Anaesthetic Practice for the FRCA. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199595150.003.0018.
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The physics of pressure, flow and the gas laws have been discussed in Chapter 7 in relation to the behaviour of gas and vapour. This section will focus on the physical principles of the measurement of gas pressure, volume and flow. Unlike a liquid, a gas is compressible and the relationship between pressure, volume and flow depends on the resistance to gas flow (or impedance if there is a frequency dependence between pressure and flow in alternating flow, see Chapter 4 for the electrical analogy of this) in conduits (bronchi, anaesthetic tubing); it also depends on the compliance of structures being filled and emptied (alveoli, reservoir bags, tubing or bellows). Normal breathing occurs by muscular expansion of the thorax, thus lowering the intrathoracic pressure, allowing air or anaesthetic gas to flow towards the alveoli down a pressure gradient from atmospheric pressure. When positive pressure ventilation occurs, gas is ‘pushed’ under pressure into the alveoli. Depending on the exact relationship between the ventilator and the lungs, different relationships exist between airway pressure (rather than alveolar pressure, which cannot easily be measured) and gas flow and volume. Gas pressure measurement devices were traditionally in the form of an aneroid barometer, a hollow metal bellows calibrated for pressure and temperature, which contracts when the external pressure on it increases, and expands when it decreases. The movement is linked to a pointer and indicator dial. It is often more convenient to make the device in the shape of part of a circular section, but the principle is the same. This is what the Bourdon gauge, which commonly measures pressure in gas cylinders, looks like. The detection of movement of the diaphragm of an aneroid barometer can take several forms. The movement can either be linked via a direct mechanical linkage to a pointer, or diaphragm movement can be linked to a capacitative or inductive element in an electrical circuit, such as a Wheatstone bridge. Airway pressure during spontaneous breathing or artificial ventilation is low. The preferred units of measurement are cm H2O and the range of values is between −20 and +20 cmH2O. The aneroid barometer to measure this will therefore be of light construction, using thin copper for the bellows material.
Conference papers on the topic "Impedance contrasts"
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Wu, Zedong, Zhiyuan Wei, Zhigang Zhang, Jiawei Mei, Rongxin Huang, and Ping Wang. "Elastic FWI for large impedance contrasts." In Second International Meeting for Applied Geoscience & Energy. Society of Exploration Geophysicists and American Association of Petroleum Geologists, 2022. http://dx.doi.org/10.1190/image2022-w17-02.1.
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Noble, Mark, Jonas Lindgren, and Albert Tarantola. "Large‐sized nonlinear inversion of a marine data set: Retrieving the source, background velocity, and impedance contrasts." In SEG Technical Program Expanded Abstracts 1991. Society of Exploration Geophysicists, 1991. http://dx.doi.org/10.1190/1.1888865.
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Sengupta, S. "Understanding The Mesozoics Beyond Basalt: A Case Study Of Sub-Basalt Imaging." In Digital Technical Conference. Indonesian Petroleum Association, 2020. http://dx.doi.org/10.29118/ipa20-g-434.
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The Deccan Volcanic Province of India is considered as one of the largest basalts-covered regions in the world, formed due to extensive outpouring of basaltic lavas during Deccan volcanism (∼65 Ma). The sedimentary sequence below the flood basalt is mainly characterized by Mesozoic strata with a varying thickness of 1000 m to 2500 m. It is considered that requisite heat generation due to Deccan Trap volcanism soon after the Cretaceous sedimentation may have acted as a catalyst in hydrocarbon potential in this area (Vardhan et al. 2008). However, it is essentially unexplored because of the limitations of conventional marine streamer P-wave seismic acquisition in imaging the structures both intra-basalt and sub-basalt. The major challenges can be considered as follows: Strong reflections due to high impedance contrasts at the top (and bottom) of the basalts leading to significant loss of transmitted seismic energy; Scattering of energy due to large acoustic impedance contrast at top and bottom of the basalt; Generation of multiples, both surface-related and interbed, from the top and bottom of the basalt, and intra-basalt boundaries, masking genuine primary reflections at the pre-basasediments; Significant attenuation of seismic energy in the basaltic sequences due to its complex internal structure generally causing weak sub-basasignal; Low signal-to-noise ratio creating ambiguity in estimating accurate velocity model of subsurface. This case study demonstrates that, even with legacy marine streamer surveys, an appropriate workflow of combining suitable advanced technologies can help to overcome the long-standing challenges of sub-basalt imaging. The reprocessed data show clear uplift in the sub-basalt imaging and the inversion results validate the quality of the new data in relation to the well logs.
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Guo, K., J. Li, X. Chen, G. Zhu, D. Liu, and X. Liu. "Acoustic Impedance Contrast Inversion with Multiplicative Regularization." In 82nd EAGE Annual Conference & Exhibition. European Association of Geoscientists & Engineers, 2021. http://dx.doi.org/10.3997/2214-4609.202112877.
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Porzi, C., A. Isomaki, M. Guina, and O. G. Okhotnikov. "Impedance-detuned high-contrast vertical cavity semiconductor switch." In 2005 Optical Fiber Communications Conference Technical Digest. IEEE, 2005. http://dx.doi.org/10.1109/ofc.2005.192974.
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A. Ribeiro, G., E. Ficanha, L. Knop, and M. Rastgaar. "Impedance of the Human Ankle During Standing for Posture Control." In 2018 Design of Medical Devices Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/dmd2018-6894.
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The stiffness and damping of anatomical joints can be modulated by muscle co-contraction, where antagonistic muscles contract simultaneously, increasing both the joint’s stiffness and damping. In a second order system, the mechanical impedance, or simply impedance, is a function of the system’s inertia, damping, and stiffness. The ankle impedance can be defined as the resultant force due to an external motion perturbation. The impedance modulation of the human ankle is required for stable walking. The estimation of the time-varying impedance modulation of the human ankle is the focus of research by different groups [1,2].
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Baumstein, Anatoly, Partha Routh, Kyle Basler-Reeder, Young Ho Cha, David Tang, Jay Barr, and Alex Martinez. "Elastic Full Wavefield Inversion: The Benefits and the Challenges in Clastic and Subsalt Setting." In ADIPEC. SPE, 2022. http://dx.doi.org/10.2118/211620-ms.
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Abstract The main focus of our work is application of visco-elastic Full Waveform Inversion (eFWI) to estimation of elastic parameters directly from seismic shot data. In particular, we aim to recover the ratio between pressure wave velocity Vp and shear wave velocity Vs, which can be indicative of the type of fluid present in a potential subsurface reservoir. The workflow we describe does not directly use well ties for wavelet control, as is typical in seismic inversion. We provide intuitive explanations for choices behind the proposed multi-stage hierarchical algorithm, outline its key steps, and present field data examples from a structurally simple clastic setting and a complex sub-salt environment. The latter, in particular, makes differentiating net versus non-net in pre-salt carbonate reservoirs a challenging problem when using narrow azimuth streamer data. The challenges include significant illumination variability caused by complex geometries of the evaporites, complex wave modes and scattering caused by strong property contrasts in the evaporites and carbonates, and layering of anhydrite and other salts within the evaporites causing complex transmission losses. The thick carbonate reservoir units beneath the salt further complicate the estimation process due to lack of low frequency signal recorded in streamer data. Our methodology shows that it is possible to directly invert shot data to obtain geologically meaningful elastic properties that can be useful in exploration and early development phases. However, challenges remain. We demonstrate that inverted acoustic impedance (Ip) from eFWI has higher fidelity and more reliable magnitude compared to the ratio between compressional and shear wave propagation speeds (Vp/Vs). In fact, the former is sufficiently accurate to be reliably used for porosity prediction. In turn, eFWI Vp/Vs inversion results are in qualitative agreement with well information (as a blind test) for the clastic example and able to discriminate the net versus non-net for the pre-salt example without well information. However, the quantitative match may be insufficient to determine the type of fluid via rock property inversion without any well control. Further research is needed to investigate the sensitivity of Vp/Vs and determine if the quality of the data is key a factor, in addition to stabilizing simultaneous extraction of several elastic parameters from seismic data via constrained inversion framework.
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AlJishi, Ali F., Mustafa A. Al-Marzooq, Mohammad I. Babli, and Mamadou S. Diallo. "AVO friendly seismic amplitude scaling in high impedance contrast surface conditions." In SEG Technical Program Expanded Abstracts 2019. Society of Exploration Geophysicists, 2019. http://dx.doi.org/10.1190/segam2019-3216402.1.
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Zhang, Shengnan, Yanbin Xu, and Feng Dong. "Ultrasound modulated electrical impedance tomography by contrast libraries of measurements variation." In 2017 29th Chinese Control And Decision Conference (CCDC). IEEE, 2017. http://dx.doi.org/10.1109/ccdc.2017.7978670.
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Dhruv, Neel, and Frank Tendick. "Frequency Dependence of Compliance Contrast Detection." In ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-2416.
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Abstract Psychophysical experiments were performed to investigate the haptic perception of objects with varying compliance over their surfaces. Perception of compliance contrast is important in interaction with soft environments, as in teleoperative surgery. Simulated surfaces were presented using a haptic interface in virtual environments. An adaptive 2–down, 1–up procedure was used to determine thresholds for compliance contrast detection at a range of spatial frequencies. The maximum effective temporal frequencies of compliance change, due to the subjects’ action of scanning the surfaces, were calculated. Force contrast detection thresholds were determined at a range of temporal frequencies to investigate the reliance of compliance contrast detection on force cues. Compliance and force discrimination thresholds were determined in order to compare with low frequency contrast thresholds. Compliance and force contrast detection thresholds were found to be 2% and 1% above 1/2 cyc/cm and 20 Hz, respectively. Both were significantly smaller than respective compliance and force discrimination thresholds and low frequency contrast detection thresholds. It appears that the improvement in compliance contrast detection sensitivity is due to subjects being more sensitive to force contrast at higher temporal frequencies. By changing environment exploration strategies or limb impedance, subjects may be able to change their sensitivity to object compliance contrast.