Presence Of Complex Structure Research Articles

CHANDRA X-Ray Observations of A119: Cold Fronts and a Shock in an Evolved Off-axis Merger

We present Chandra X-ray observations of the dynamically complex galaxy cluster A119 (z = 0.044). A119 is host to two narrow-angle-tail (NAT) radio sources (0053-015 and 0053-016), whose tails are oriented parallel to each other, despite orthogonally oriented jet axes. Imaging and spectral analysis reveal X-ray emission elongated along the NE–SW axis, along with the presence of complex structures, including surface brightness discontinuities, which suggest possible merger activity along this axis. From radial profiles of the X-ray surface brightness, temperature, pressure, and density, we identify two surface brightness edges that are found to be cold fronts, possibly associated with large-scale sloshing of intracluster medium gas. We also identify a brightness edge to the S that is found to be a shock front with Mach number M = 1.21 ± 0.11, consistent with a merger shock. In addition, previous optical studies show the alignment of optical substructures along the N–S direction. The elongated X-ray emission, orientations of the NAT tails, and alignment of the optical substructure all suggest recent or ongoing merger activity in the NE–SW direction.

The effect of geologic structure on fracture characterization using azimuthal vertical seismic profiles

Azimuthal vertical seismic profile (AzVSP) surveys have commonly been used for fracture characterization by analyzing the P-to-S converted wave response across fractured zones. Fractured media produce characteristic two-cycle patterns on AzVSP gathers that are disrupted in the presence of complex structures. Aiming to characterize the complexity of the AzVSP response in the presence of geologic structures, we have derived anisotropy parameters for effective horizontal transverse isotropic media, generated AzVSP signatures for the flat-interface case as the baseline, and compared the baseline signatures with AzVSP signatures for the dipping-interface cases. The fracture fill and fracture intensity are varied to capture the effect of the intrinsic fracture parameters on the AzVSP signatures. We find that dry fractures produce a stronger response compared with fluid-filled fractures for the same fracture density. The structural response on AzVSP signatures is isolated by generating synthetic seismograms across structurally equivalent isotropic models. Transverse energy, resulting from structures, could be misinterpreted as evidence for fracturing. The AzVSP signatures for a fractured dipping-interface two-layer model show significant distortion of the fracture response for the 10° dip case compared with the flat-interface signatures. As a possible solution to the structural problem, we use the arrival azimuths of the transmitted P-to-S event in synthetic signatures generated with the isotropic structural model, to orient the radial and transverse components parallel and perpendicular to the isotropic P-to-S event, respectively. Such structurally consistent orientation negates the effect of structure on AzVSP gathers and uncovers the underlying fracture response. This methodology can be extended to complex overburdens that are structurally well constrained.

AGE-SPECIFIC ADJUSTMENT OF GRADUATED MORTALITY

AbstractRecently, there has been an increasing interest from life insurers to assess their portfolios' mortality risks. The new European prudential regulation, namely Solvency II, emphasized the need to use mortality and life tables that best capture and reflect the experienced mortality, and thus policyholders' actual risk profiles, in order to adequately quantify the underlying risk. Therefore, building a mortality table based on the experience of the portfolio is highly recommended and, for this purpose, various approaches have been introduced into actuarial literature. Although such approaches succeed in capturing the main features, it remains difficult to assess the mortality when the underlying portfolio lacks sufficient exposure. In this paper, we propose graduating the mortality curve using an adaptive procedure based on the local likelihood. The latter has the ability to model the mortality patterns even in presence of complex structures and avoids relying on expert opinions. However, such a technique fails to offer a consistent yet regular structure for portfolios with limited deaths. Although the technique borrows the information from the adjacent ages, it is sometimes not sufficient to produce a robust life table. In the presence of such a bias, we propose adjusting the corresponding curve, at the age level, based on a credibility approach. This consists in reviewing the assumption of the mortality curve as new observations arrive. We derive the updating procedure and investigate its benefits of using the latter instead of a sole graduation based on real datasets. Moreover, we look at the divergences in the mortality forecasts generated by the classic credibility approaches including Hardy–Panjer, the Poisson–Gamma model and the Makeham framework on portfolios originating from various French insurance companies.

Creating detailed subsurface models using predictive image-guided well-log interpolation

Integration of well-log data and seismic data to predict rock properties is an essential but challenging task in reservoir characterization. The standard methods commonly used to create subsurface model do not fully honor the importance of seismic reflectors and detailed structural information in guiding the spatial distribution of rock properties in the presence of complex structures, which can make these methods inaccurate. To overcome initial model accuracy limitations in structurally complex regimes, we have developed a method that uses the seismic image structures to accurately constrain the interpolation of well properties between well locations. A geologically consistent framework provides a more robust initial model that, when inverted with seismic data, delivers a highly detailed yet accurate subsurface model. An application to field data from the North Sea demonstrates the effectiveness of our method, which proves that incorporating the seismic structural framework when interpolating rock properties between wells culminates in the increased accuracy of the final inverted result compared with the standard inversion workflows.

Classification of breast lesions using segmented quantitative ultrasound maps of homodyned K distribution parameters.

Statistical modeling of an ultrasound backscattered echo envelope is used for tissue characterization. However, in the presence of complex structures within the analyzed area, estimation of parameters is disturbed and unreliable, e.g., in the case of breast tumor classification. In order to improve the differentiation of breast lesions, the authors proposed a method based on the segmentation of homodyned K distribution parameter maps. Regions within lesions of different scattering properties were extracted and analyzed. In order to improve the classification, the best-performing features were selected from various regions and then combined. A radio-frequency data set consisting of 103 breast lesions was used in the authors' analysis. Maps of homodyned K distribution parameters were created using an algorithm based on signal-to-noise ratio, kurtosis, and skewness of fractional-order envelope moments. A Markov random field model was used to segment parametric maps. Features of different segments were extracted and evaluated based on bootstrapping and the receiver operating characteristic curve. To determine the best-performing feature subset, the authors applied the joint mutual information criterion. It was found that there were individual features which performed better than the ones commonly used for lesion characterization, like the parameter obtained through averaging of values over the whole lesion. The authors selected and discussed the best-performing features. Properties of different extracted regions were important and improved the distinction between benign and malignant tumors. The best performance was obtained by combining four features with the area under the receiver operating curve of 0.84. The study showed that the analysis of internal changes in lesion parametric maps leads to a better classification of breast tumors. The authors recommend combining multiple features for characterization, instead of using only one parameter, especially in the case of heterogeneous lesions.

Evolution analysis of miocene channels and faults in offshore area of Strait of Hormuz (Eastern part of Persian Gulf) using seismic meta-attributes

Tectonic movement of Oman Orogeny and Zagros Orogeny and Hormuz Salt triggering are accompanied with presence of complex structures in Strait of Hormuz sedimentary basin. Geological model Obtained via multi-attribute analysis and the extracted geobodies are used to define type and relative age of channels and faults in offshore area of Strait of Hormuz (Eastern part of Persian Gulf). In this study, channels and faults were mapped using meta-attributes by a neural network. The probability volume helps more accurate extraction of channel bodies and fault planes. The channel bodies and fault planes can be revealed more continuous with dominant edges and subtle flexures as obtained results based on meta-attributes. Considering this approach, three distinct channel types (small (S), median (M) and large (L)) are illustrious in different substrates based on various flow powers that extended from West to East. Normal fault band with the NorthEast-SouthWest trend and few dip toward the East, whereas faulting may occur during late Mid Miocene- Early Upper Miocene. The main channels (M) and (L) are located on both sides of the fault in lower and upper deeps within Mid Miocene Mishan Formation sediments, while channels (S) located away from the fault within Upper Miocene-Pliocene Aghajari Formation sediments. Processes of sediment transport are very different in Miocene Aghajari and Mishan Formations as form of meandering channels and their slopes are dissimilar. Sediment supply has led to changing geometry of meandering channel due to effects of sea-level change. Based on seismic attribute study, slope and form of channel (M) has been affected by later faulting, whereas slope and form of channel (L) operated independently. Presence of meandering channel (M) with lower slope and higher sinuosity ratio in comparison with meandering channel (L) suggests that channels located in upper horizons of sedimentary basin could be consider as an appropriate place for hydrocarbon accumulation in intra Mid Miocene Mishan Formation. Furthermore, revealed channels within Mid Miocene Mishan Formation sediments are bigger than the channels within Upper Miocene-Pliocene Aghajari Formation. Reservoir properties study suggests that channel filled sediments are relatively porous than their backgrounds, producing relatively higher reservoir potential based on the integrated analysis of acoustic impedance and frequency content.

Modeling of Errors in Nakagami Imaging: Illustration on Breast Mass Characterization

Nakagami imaging is an attractive tissue characterization method, as the parameter estimated at each location is related to properties of the tissues. The application to clinical ultrasound images is problematic, as the estimation of the parameters is disturbed by the presence of complex structures. We propose to consider separately the different aspects potentially affecting the value of the Nakagami parameters and quantify their effects on the estimation. This framework is applied to the classification of breast masses. Quantitative parameters are computed on two groups of ultrasound images of benign and malignant tumors. A statistical analysis of the result indicated that the previously observed difference between average values of the Nakagami parameters is explained mostly by estimation errors. In the future, new methods for reliable computation of Nakagami parameters need to be developed, and factors of error should be considered in studies using Nakagami parameters.

Domain transform: A tool for imaging and interpreting geomorphology and stratigraphy in seismic volumes

The presence of complex structure on seismic data often makes it difficult to recognize and interpret depositional systems in the volume. A number of techniques, under the broad topic of chronostratigraphy, have been developed in recent years to address this problem and enable more complete imaging and interpretation of seismic geomorphology and stratigraphy. A “domain transform” (DT) is an interpretation-guided process designed to remove some or all structural deformation from a seismic volume. It improves the imaging of paleo-depositional systems by creating a volume that consists of approximations of paleo-depositional surfaces. Such volumes are ideal for imaging, analysis, and interpretation of seismic geomorphology and stratigraphy.

Seismically-generated hydroplastic deformation structures in the Late Miocene lacustrine deposits of the Malatya Basin, eastern Turkey

The Late Miocene succession of continental deposits in the Malatya Basin, eastern Anatolia, comprises alluvial-fan, lacustrine and fluvial facies associations. This fault-bounded basin formed in a tectonically active region, notorious for strong earthquakes still today. The lacustrine deposits in the northern part of the basin show several isolated horizons of soft-sediment deformation, including such structures as slump folds, load and flame features, sand dikes and small-scale synsedimentary reverse faults with associated folds. There is no direct evidence supporting instabilities due to unequal loading or overloading, wave-induced cyclical and/or impulsive stresses, sudden changes in groundwater level or bioturbation capable of producing these deformation structures. The soft-sediment deformation structures described in the lacustrine deposits are interpreted as having developed as a result of seismic activity taking place along the Malatya fault zone, based on the tectonic setting of the basin, the lateral extent of the soft-sediment deformation structures over hundreds of metres, their confinement by undeformed layers, the presence of complex structures, and similarities with structures interpreted as being seismically induced in other areas and those obtained experimentally.

Wavelet-based compression/denoising of coronary X-ray images

Compression of angiographic images has been shown to be difficult when compared with other medical imaging modalities. The factors partially responsible for this are the presence of complex structures that are only apparent by subtle changes in the contrast and the significant amount of acquisition noise. In this work, we propose a Comp?Denoiser adapted to coronary X-ray images. For this purpose, Wavelet-based Trellis Coded Quantisation (WTCQ) algorithm is extended to incorporate a bivariate thresholding that considers dependencies between wavelet coefficients and their parents in coarser sub-bands. Experimental results show that despite its simplicity our method yields high compression performance.

High-Power EMI on RF Amplifier and Digital Modulation Schemes

We present the performance of an RF amplifier and digital modulation techniques in the presence of high-power electromagnetic interference (EMI) to provide existing and next generation communication systems with critical information. An advanced measurement setup comprised of a large-signal network analyzer is used to characterize the adverse effects of EMI on the device characteristics of an RF power amplifier and the performance of digital modulation schemes. Furthermore, our analysis incorporated hybrid numerical tools, such as the hybrid S-parameter method to carry out an extensive EMI analysis of digital modulation schemes in the presence of complex structures, such as cylindrical cavities. Our studies yield critical information for the communication systems. For instance, our analysis suggests that digital modulation schemes are more susceptible to EMI than the RF power amplifier that processes the modulated signals. Power levels of the order of megawatts are required to have a notable impact on the device characteristics of an RF amplifier in the presence of a missile-like body, whereas, much lower power levels are sufficient to degrade the performance of a digital modulation scheme as long as it is within the bandwidth of the modulated signal. Our analysis further indicates that nonconstant envelope digital modulation schemes are more susceptible to EMI.

A Generalized MoM-SPICE Iterative Technique for Field Coupling to Multiconductor Transmission Lines in Presence of Complex Structures

A generalized method of moments (MoM)-SPICE iterative technique for field coupling analysis of multiconductor transmission lines (MTLs) in the vicinity of complex structures is presented. Telegrapher's coupling equations are modified with additional distributed voltage and current sources for more accurate analysis of the total current induced onto transmission line bundles in the presence of complex structures. These additional voltage and current sources are introduced to enforce the electric field boundary condition and continuity equation on MTLs beyond the quasi-static regime. The surrounding structure is modeled via the MoM and a SPICE-like simulator is used to simulate equivalent circuit model of the MTLs extracted via the partial element equivalent circuit method. The proposed technique is based on perturbation theory with the quasi-static current distributions on the transmission lines still assumed to be dominant. Validation examples for single and MTLs are given in the presence of complex structures.

Direct and Ultimate Ownership Structures in the UK: an intertemporal perspective over the last decade

In this paper we analyse the evolution of the direct and ultimate ownership structure of a large sample of UK non-financial listed firms over the last decade. Our data show that while outsider ownership is relatively stable over time, managerial ownership shows a sharp decreasing trend and it is significantly lower in the presence of a large outside controller. Nonetheless, while average shareholding by executives confirms the decreasing trend, the opposite holds for non-executive directors. In addition, while average board size is rather constant in time, the proportion of non-executives is steadily increasing in time. As far as ultimate ownership is concerned, our data show that the existence of complex ownership structures in the UK is far from being negligible. We document that more than 10 per cent of the firms are owned via a complex structure and the degree of divergence between cash flow and control rights for these firms is around 11 per cent at the 10 per cent cut-off. Our data also suggest that the presence of complex structures is decreasing in time at any cut-off level. In addition, we report a decreasing trend over time of “widely held” firms. Finally, we show preliminary evidence of a negative impact of the divergence between cash flow and control rights on firm value.

3D angle‐domain common‐image gathers for migration velocity analysis

ABSTRACTAngle‐domain common‐image gathers (ADCIGs) are an essential tool for migration velocity analysis (MVA). We present a method for computing ADCIGs in 3D from the results of wavefield‐continuation migration. The proposed methodology can be applied before or after the imaging step in a migration procedure. When computed before imaging, 3D ADCIGs are functions of the offset ray parameters (p, p); we derive the geometric relationship that links the offset ray parameters to the aperture angle γ and the reflection azimuth φ. When computed after imaging, 3D ADCIGs are directly produced as functions of γ and φ.The mapping of the offset ray parameters (p, p) into the angles (γ, φ) depends on both the local dips and the local interval velocity; therefore, the transformation of ADCIGs computed before imaging into ADCIGs that are functions of the actual angles is difficult in complex structure. By contrast, the computation of ADCIGs after imaging is efficient and accurate even in the presence of complex structure and a heterogeneous velocity function. On the other hand, the estimation of the offset ray parameters (p, p) is less sensitive to velocity errors than the estimation of the angles (γ, φ). When ADCIGs that are functions of the offset ray parameters (p, p) are adequate for the application of interest (e.g. ray‐based tomography), the computation of ADCIGs before imaging might be preferable.Errors in the migration velocity cause the image point in the angle domain to shift along the normal to the apparent geological dip. By assuming stationary rays (i.e. small velocity errors), we derive a quantitative relationship between this normal shift and the traveltime perturbation caused by velocity errors. This relationship can be directly used in an MVA procedure to invert depth errors measured from ADCIGs into migration velocity updates. In this paper, we use it to derive an approximate 3D residual moveout (RMO) function for measuring inconsistencies between the migrated images at different γ and φ. We tested the accuracy of our kinematic analysis on a 3D synthetic data set with steeply dipping reflectors and a vertically varying propagation velocity. The tests confirm the accuracy of our analysis and illustrate the limitations of the straight‐ray approximation underlying our derivation of the 3D RMO function.

Valence-electron energy loss near edges, truncated slabs, and junctions

Valence losses in electron microscopy can be conveniently computed using classical dielectric excitation theory. In many practical situations, the presence of complex structures gives rise to the possibility of coupling between interface modes, surface modes, and edge modes. In the nonrelativistic case, the losses in such geometries can be calculated by taking a distribution of surface and interface points, each of which is associated with an interface charge. These charges interact self-consistently with each other as well as with the charge of the incident electron. Here, we have applied this boundary charge method to provide scanning transmission electron microscopy energy loss spectra near-edged structures such as truncated slabs and junctions formed by several media. We find the dominant modes associated with such systems and study their contribution to the characteristic energy loss functions. The significance of these excitations compared with the planar interface peaks is discussed in terms of the sample geometry with illustrations for the cases of an MgO cube and an Si/SiO2 thin-film interface. @S0163-1829~99!00939-X#

Multiple elimination using a pattern‐recognition technique

Standard prestack multiple elimination techniques, such as predictive deconvolution or Radon transforms, fail in the presence of complex structures.

Lightning induced transient voltages in presence of complex structures and nonlinear loads

EMI induced in electronic circuits inside a building due to a lightning flash can be caused by either a direct strike to the lightning protection system or or by an indirect discharge in close proximity. This paper deals with the induced transient voltages on nonlinearly terminated metallic loops inside a building due to an indirect lightning strike. The conductive parts of the building (such as reinforcing bars in walls and floors, metallic beams), the lightning protection system, and the loops are simulated by an electric field integral equation in the time domain, with the nonlinear loads by a system of nodal equations. These two sets of equations allow a solution to be determined completely in the time domain. The proposed technique is validated by comparison with other referenced numerical techniques. Some results which show the effects of the conductive structural elements of the building on the induced transients are presented.

Velocity-Depth Model Estimation for a Subsalt Target from the Southern Gas Basin of the North Sea: ABSTRACT

The Southern Gas Basin of the North Sea has been subjected to extensional tectonics, primarily in the east-west direction. Subsequent occurrence of the salt diapirism gave rise to the presence of complex structures. By doing a depth-domain analysis of a 3-D seismic survey data from an area in the Southern Gas Basin, we delineated the structural geometry of the top Rotliegendes formation beneath the complex Zechstein diapiric formation. This required an accurate estimate of the velocity-depth model above the Zechstein diapiric formation and removal of its deleterious effect on the underlying Permian sands of Rotliegendes and deeper targets. We conducted a layer-by-layer depth-domain analysis, and used coherency inversion to estimate layer velocities and 3-D poststack depth migration to delineate reflector geometries down to top Zechstein. We verified the accuracy of the velocity-depth model for the overburden above Zechstein by analyzing image gathers from prestack depth migration. We then analyzed constant-half-space image-gather stacks to estimate velocities for the substratum including Zechstein and the underlying Carboniferous sequence. Finally, we performed 3-D prestack depth migration to delineate the base Zechstein - top Rotliegendes geometry. This study demonstrates the need for depth-domain analysis of seismic data to derive accurate structure maps for targets beneathmore » complex structures associated with salt and overthrust tectonics. The final output from depth-domain analysis -- a velocity-depth model, can then be used as a canvas for a reservoir model.« less

Energy transfer, up-conversion and nonequivalent crystal field effects in the KYP4O12:Pr3+ system

Under selective pulsed dye laser excitation in the 1D2 state fluorescence of Pr3+ ions in KYP4O12 has been studied. The presence of complex structures in the excitation and emission spectra associated with ion pairs and perturbed single ions is revealed. It is shown that in low concentration crystals most of the 1D2 fluorescence originates from the perturbed Pr3+ ions. The kinetics of the 1D2 decay is measured and discussed in terms of cross relaxation, energy transfer to traps and up-conversion processes. These results are in satisfactory agreement with the developed rate equation model. The contribution of short-range interaction, probably superexchange, in the quenching of 1D2 fluorescence in strongly concentrated crystals is examined. The first observations of 1D2 and up-converted 3P0 emissions in stoichiometric Pr3+ phosphate are reported.