Azimuthal Orientation Research Articles

A practical approach to develop a proper anisotropic rock physics model for media comprising of multiple fracture sets in the absence of sophisticated laboratory/wireline data

For economical production from a fractured reservoir, a characteristic analysis of the fracture parameters like its density and orientation within the reservoir is essential to improve the fluid flow during extraction. This study deals with the development of a proper anisotropic rock physics model for a media with multiple fracture sets to study the spatial distribution of important fracture parameters i.e., fracture density and orientation in the absence of sophisticated laboratory/wireline and pre-stack seismic data. The crest of hydrocarbon producing fault-bounded Balkassar Anticline in Northern Potwar, Upper Indus Basin, Pakistan is selected as a case study representing a potential zone for development of fractures at reservoir level (Sakesar Limestone). The methodology consists of the interpretation of 3D post-stack seismic and conventional wireline log data to demarcate the reservoir containing fractures. The Ant-tracking discrete fracture network (DFN) attribute is applied on 3D post-stack seismic data to obtain an initial estimate about the presence of fracture corridors and their orientations. Based on this initial estimate, a proper rock physics model has been developed utilizing inverse Gassmann relations, T-matrix approximation, and Brown and Korringa relations. The output from the developed rock physics model has been displayed in the form of 13 effective independent elastic stiffness constants (monoclinic symmetry–representing media comprising of multiple fracture sets) as a function of fracture densities and azimuthal fracture orientations. A clear decreasing trend in effective elastic stiffness constants with increasing fracture densities can be observed. Similarly, a periodic trend of effective elastic stiffness constants with fracture orientations can be observed. These trends are more or less expected, but they would have been difficult to quantify without a proper rock physics model. The use of independent effective elastic constants for the generation of synthetic seismic amplitude versus angle and azimuth (AVAZ) data and its correlation with observed seismic AVAZ data in a geostatistical sense has been discussed.

Performance Analysis of WDM in LoS Communications With Arbitrary Orientation and Position

This letter considers the wavenumber-division-multiplexing (WDM) scheme that was recently presented by Sanguinetti <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> (2022) line-of-sight communications between parallel (i.e., side-by-side) spatially-continuous electromagnetic segments. Our aim is to analyze the performance of WDM, combined with different digital processing architectures, when the electromagnetic segments have an arbitrary orientation and position. To this end, we first show how the general electromagnetic MIMO (multiple-input multiple-output) model from Sanguinetti <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> (2022) can be particularized to the case of interest and then use numerical results to evaluate the impact of geometric parameters (e.g., horizontal and vertical distances, azimuth and elevation orientations). It turns out that WDM performs satisfactorily also when the transmit and receive segments are not in boresight direction to each other.

Probing Copper and Copper-Gold Alloy Surfaces with Space-Quantized Oxygen Molecular Beam.

The orientation and motion of reactants play important roles in reactions. The small rotational excitations involved render the reactants susceptible to dynamical steering, making direct comparison between experiments and theory rather challenging. Using space-quantized molecular beams, we directly probed the (polar and azimuthal) orientation dependence of O2 chemisorption on Cu(110) and Cu3Au(110). We observed polar and azimuthal anisotropies on both surfaces. Chemisorption proceeded rather favorably with the O–O bond axis oriented parallel (vs perpendicular) to the surface and rather favorably with the O–O bond axis oriented along [001] (vs along [1̅10]). The presence of Au hindered the surface from further oxidation, introducing a higher activation barrier to chemisorption and rendering an almost negligible azimuthal anisotropy. The presence of Au also prevented the cartwheel-like rotations of O2.

Determination of Borehole Seismic Sensor Orientation Using Microseisms

ABSTRACT We introduce a novel method to determine the azimuthal orientation of borehole seismometer using microseisms that are ubiquitously present in seismic records. The microseisms are dominantly composed of Rayleigh waves that construct plane wavefronts over local stations. We determine the borehole seismometer orientation by comparing the polarization directions of Rayleigh waves in microseisms between borehole and surface stations. The Rayleigh wave polarization directions are determined using the nature of Rayleigh wave ground motions that present a 90° phase difference between the radial and vertical components. The azimuthal differences in apparent Rayleigh wave polarization directions between borehole seismometer and local surface seismometer provide information on the misorientation angle of borehole seismometer. Both the primary and secondary microseisms can be used. The method is applied to determine the misorientation angles of two deep borehole seismometers in the Yonsei Earth Observatory in Seoul, South Korea. The misorientation angles of borehole seismometers are determined stably using 18-hour-long ambient noise records, suggesting instant determination of borehole seismometer orientation based on short-time ambient noise records. Regional-event seismic waveforms at borehole seismometers match well with those at collocated surface station, supporting the correct determination of borehole seismometer orientation. The proposed method does not require information on seismic source locations and ray paths unlike conventional methods, allowing prompt determination of borehole seismometer orientation with high precision.

Two‐Step Photoalignment with High Resolution for the Alignment of Blue Phase Liquid Crystal

AbstractThe self‐assembling properties of liquid crystal (LC) are ideal for realizing switchable optical components. The director organization is strongly determined by the alignment at the substrate interfaces and photoalignment is a versatile method based on linearly polarized UV light. In this work, a two‐step photoalignment procedure is proposed to pattern the alignment at the surface. Illumination with uniform polarization or with an interference pattern is combined to obtain stripe patterns or square patterns of photoalignment. It can indeed be confirmed that the nematic director follows the varying azimuthal orientation. By increasing the angle between the two interfering beams, photoalignment with sub‐micrometer resolution is obtained, compatible with the dimensions of blue phase (BP) LC unit cell. Homogeneous domains of BP II with (100) or (110) crystal orientation are obtained and their Kossel patterns are recorded. The two‐step photoalignment technique allows to create patterns with high resolution and to control the orientation of BP LC, which is promising for photonic applications that require single domains.

Radar Characterization of Ice Crystal Orientation Fabric and Anisotropic Viscosity Within an Antarctic Ice Stream

AbstractWe use polarimetric radar sounding to investigate ice crystal orientation fabric and its impact on ice viscosity within the near surface of Rutford Ice Stream, West Antarctica. The technique retrieves lateral and depth variations in the horizontal components of ice fabric but no direct information on the vertical fabric component. In the shallowest ice (depths 40–100 m), the fabric is consistent with flow‐induced development and correlates with the surface compression direction. Notably, toward the ice‐stream margin, the horizontal compression angle and azimuthal fabric orientation tend toward 45° relative to ice flow which is consistent with the early stages of flow‐induced fabric under simple shear. The fabric orientation in deeper ice (depths 100–300 m) is, in places, significantly misaligned with shallower ice and the surface compression direction due to sharp depth transitions in orientation. We then use a rheological model to bound effective anisotropic viscosities (directional hardness) of ice that are consistent with the radar measurements. Toward the shear margin, we show that the shallow‐ice fabric does not appreciably soften the ice to lateral shear although this may happen in deeper ice. In the center of the ice stream, we show that lateral and depth variations in the fabric alignment relative to ice flow result in corresponding changes in uniaxial ice viscosities relative to ice flow. Our results indicate that spatial variability in the fabric translates to variability in viscosity that widely used isotropic ice‐flow models are unable to consider.

Multiple Reactivations of the Rennick Graben Fault System (Northern Victoria Land, Antarctica): New Evidence From Paleostress Analysis

AbstractThe dense fault network that separates the tectonic units of northern Victoria Land to the E from the East Antarctic Craton to the W represents a regionally sized, NNW‐SSE trending deformation zone that is also known as the Rennick Graben Fault system (RGF). This long‐lived deformation zone is characterized by great structural complexity, with the superposition and polyphasic reactivation of regional faults; it is known to have been active since the Cambrian‐Ordovician, when it formed as a suture zone between different terranes, up to the recent. Its complete framework and geodynamic evolution are still debated and have only been partially investigated. In this research, we explore the Meso‐Cenozoic tectonic framework of the RGF by investigating the paleostress fields that characterized the last geodynamic events in the area and their associated brittle deformation. We analyzed faults and fractures data collected at 89 sites during several PNRA ItaliAntartide expeditions and combined fault‐slip data inversion with the azimuthal orientation of faults and the spatial distribution of fracture intensities across the RGF. The results from this multi methodological approach confirm the existence of two geotectonic provinces (Bowers Mountains province to the E and Usarp Mountains to the W) characterized by different spatial distributions of brittle deformation, which are significantly more intense in the Bower Mountains domain. Here, the repeated reactivation of the RGF led to the superposition of two recent (Meso‐Cenozoic) major tectonic events, with prevalent strike‐slip kinematics and characterized by fault reactivation with right‐lateral movement overprinting the previous left‐lateral event.

Near-orthogonal Orientation of Small-scale Magnetic Flux Ropes Relative to the Background Interplanetary Magnetic Field

Small-scale magnetic flux ropes (SMFRs) have been identified at a large range of heliospheric distances from the Sun. Their features are somewhat similar to those of larger-scale flux rope structures such as magnetic clouds (MCs), while their occurrence rate is far higher. In this work, we examined the orientations of a large number of SMFRs that were identified at 1 au by fitting to the force-free model. We find that, while most of the SMFRs lie mostly close to the ecliptic plane, as previously known, their azimuthal orientations relative to the Sun–Earth line are found largely at two specific angles (slightly less than 45° and 225°). This latter feature in turn leads to a strong statistical trend in which the axis of SMFRs lies at a large tilt angle relative to (most often nearly orthogonal to) the corresponding background interplanetary magnetic field directions in the ecliptic plane. This feature is different from previous reports on SMFRs—and in stark contrast to the cases of MCs. This is an important observational constraint that should be considered for understanding SMFR generation and propagation.

Ordering of copper phthalocyanine films on functionalized Si(111)

The adsorption and growth of copper phthalocyanine (CuPc) has been studied on passivated Si(111) surfaces. As passivating agents, Ga, Bi, and Ag were used, leading to a 3×3-R30∘ reconstruction of the surface in each case. X-ray photoemission spectra indicate a non-dissociative adsorption. The structure and morphology have been investigated with low-energy electron diffraction and scanning tunneling microscopy. For Ga-terminated substrates, ordered domains are observed with random azimuthal orientation. Upon further deposition, three-dimensional islands are found. In case of Bi-terminated Si(111), a rather smooth morphology with high structural disorder evolves, which is attributed to an inefficient surface diffusion. The CuPc films with best structural order, with a nearly square unit mesh, and with smooth morphology are achieved on Ag-terminated Si(111). The differences in structural and morphological evolution of the CuPc films for Ga, Bi, and Ag surface passivation are discussed in terms of interfacial interaction and occupied versus unoccupied local density of states.

S-duct flow distortion with non-uniform inlet conditions.

Convoluted aero-engine intakes are often required to enable closer integration between engine and airframe. Although the majority of previous research focused on the distortion of S-duct intakes with undistorted inlet conditions, there is a need to investigate the impact of more challenging inlet conditions at which the intake duct is expected to operate. The impact of inlet vortices and total pressure profiles on the inherent unsteady flow distortion of an S-duct intake was assessed with stereo particle image velocimetry. Inlet vortices disrupted the characteristic flow switching mode but had a modest impact on the peak levels and unsteady fluctuations. Non-uniform inlet total pressure profiles increased the peak swirl intensity and its unsteadiness. The frequency of swirl angle fluctuations was sensitive to the azimuthal orientation of the non-uniform total pressure distribution. The modelling of peak distortion with the extreme value theory revealed that although for some inlet configurations the measured peak swirl intensity was similar, the growth rate of the peak values beyond the experimental observations was substantially different and it was related with the measured flow unsteadiness. This highlights the need of unsteady swirl distortion measurements and the use of statistical models to assess the time-invariant peak distortion levels. Overall, the work shows it is vital to include the effect of the inlet flow conditions as it substantially alters the characteristics of the complex intake flow distortion.

Pore Ordering in Anodic Aluminum Oxide: Interplay between the Pattern of Pore Nuclei and the Crystallographic Orientation of Aluminum.

Anodization of aluminum with a pre-patterned surface is a promising approach for preparing anodic aluminum oxide (AAO) films with defect-free pore arrangement. Although pronounced effects of crystallographic orientation of Al on the AAO structure have been demonstrated, all current studies on the anodization of pre-patterned aluminum consider the substrate as an isotropic medium and, thus, do not consider the azimuthal orientation of the pattern relative to the basis vectors of the Al unit cell. Here, we investigate the interplay between the azimuthal alignment of the pore nuclei array and the crystallographic orientation of aluminum. Al(100) and Al(111) single-crystal substrates were pre-patterned by a Ga focused ion beam and then anodized under self-ordering conditions. The thickness-dependent degree of pore ordering in AAO was quantified using statistical analysis of scanning electron microscopy images. The observed trends demonstrate that the preferred azimuthal orientation of pore nuclei rows coincides with the <110> directions in the Al unit cell, which is favorable for creating AAO with a high degree of pore ordering. In the case of an unspecified azimuthal orientation of the pore nuclei array, crystallography-affected disorder within the AAO structure occurs with increasing film thickness. Our findings have important implications for preparing defect-free porous films over 100 µm in thickness that are crucial for a variety of AAO applications, e.g., creating metamaterials and 2D/3D photonic crystals.

Leaf area index estimation of a row-planted eggplant canopy using wide-angle time-lapse photography divided according to view-zenith-angle contours

In year-round horticultural fruit production, the leaf area index (LAI; L) is a useful indicator for proper crop management. In this study, wide-angle time-lapse digital cameras were applied to estimate the L of a row-planted eggplant canopy throughout an entire growth period. Six wide-angle time-lapse cameras were placed above the canopy; three cameras pointed to the nadir, and the other three pointed at 57.5°-tilted angles from the nadir with different azimuthal orientations (i.e., along the row, at a 40° angle from the row, and perpendicular to the row). L was estimated based on the gap-fraction theory using three methods: (1) the crop method, in which only a part of each photograph was used to calculate L, (2) the whole-image method, in which the entirety of each photograph was used to calculate L, and (3) the contour method, in which each photograph was divided into zones according to the view-zenith-angle contours and L was estimated through weighted averaging of the zonal Ls. The L values estimated using the crop method were heavily biased depending on the camera position and orientation, whereas the values obtained with the other two methods were less affected by the camera position and orientation, indicating the advantage of a wide viewing angle. Compared to the whole-image method, the contour method improved the L estimation accuracy. Under the assumption of a spherical leaf-angle distribution, nadir-looking photography tended to overestimate L, whereas 57.5°-angled photography was more consistent with the allometrically obtained reference L value. The accuracy of the L estimations obtained using nadir-looking photography was improved considerably by applying the beta leaf-angle distribution function with optimized parameters. This study highlights the (1) applicability of wide-angle photography for estimating the L of a row-crop canopy, (2) advantage of the contour method, and (3) importance of using a proper leaf-angle distribution.

Effects of the azimuthal orientation on glancing angle deposited nanostructured surfaces for enhanced boiling heat transfer

Effects of the azimuthal orientation on glancing angle deposited nanostructured surfaces for enhanced boiling heat transfer

Polarization-Insensitive Unit Cells for a Cost-Effective Design of a 3-D-Printed Fresnel-Lens Antenna

A 3-D printed Fresnel-lens antenna formed by dielectric unit cells insensitive to polarization is presented in this article. The proposed unit cell can be implemented in any azimuth orientation, simplifying the design and the implementation of the Fresnel subzones, which is an advantage over the previous 3-D-printed Fresnel-lens designs. The unit cell exhibits a T-shaped geometry capable of providing no change in relative permittivity under TE polarizations orthogonal to each other. The novel design of the unit cell also provides robustness under oblique incidence and frequency. These features allow the radial arrangement of the unit cells to configure the subzones of the Fresnel lens, ensuring the desired relative permittivity. Additionally, the geometry of the printed unit cells enables self-supported subzones with the minimum number of unit cells per subzone. A 3-D-printed prototype of the proposed Fresnel lens was manufactured by stereolithography (SLA). The measurement results showed a good agreement with the simulated ones. The measured gain was 26.5 ± 0.5 dBi from 55 GHz to 65 GHz with a mean antenna efficiency of 79%.

Plasmonically Enhanced Superradiance of Broken-Symmetry Diamond Color Center Arrays Inside Core-Shell Nanoresonators.

Superradiance was demonstrated in broken-symmetry arrays of SiV diamond color centers embedded into concave plasmonic nanoresonators. The coupled configurations, including the diamond-silver (bare) and diamond-silver-diamond (coated) nanoresonators’ geometry parameters as well as the emitters’ azimuthal orientation and distance from the metal, were numerically optimized. An objective function consisting of the total fluorescence enhancement multiplied by the corrected emission quantum efficiency was used to design nanoresonators that promote superradiance. A larger total fluorescence enhancement was achieved via a larger number of emitters in both geometries, in coated spherical and in bare ellipsoidal nanoresonators. The superradiance performance was better in the case of a smaller number of emitters in bare spherical and coated ellipsoidal nanoresonators and in the case of a larger number of emitters in coated spherical and bare ellipsoidal nanoresonators. Ellipsoidal geometry is advantageous independent of composition and seeding. The configurations optimal for non-cooperative fluorescence enhancement and superradiance are coincidental. A radiative rate enhancement proportional to the number of emitters was found in wide spectral regions; therefore, superradiance implies N-fold enhancements coexist at excitation and emission. In ellipsoidal nanoresonators, the better superradiance achieved via a smaller quality-factor is accompanied by larger frequency pulling.

Pressure and Thermal Characterisation of Dynamic Instabilities During Flow Boiling in Micro/Mini-Channels at Different Azimuth Orientations

Pressure and Thermal Characterisation of Dynamic Instabilities During Flow Boiling in Micro/Mini-Channels at Different Azimuth Orientations

Crustal Structure Beneath the Northern Appalachians and the Eastern Grenville Province

AbstractSoutheastern Canada and the northeastern USA include terranes that were tectonized since the Archean, making this region an excellent place to investigate the evolution of continental crust. Our study area covers the Archean southeastern Superior Province, the Proterozoic eastern Grenville, and the Phanerozoic northern Appalachians comprising terranes with either Peri‐Laurentian or Peri‐Gondwanan heritage. Adopting a Rayleigh wave ambient noise tomography method, we used noise data recorded between 2013 and 2015, and obtained high resolution anisotropic tomographic images of the crust enabling us to discuss tectonic implications. The azimuthal anisotropy orientations follow a dominant NE‐SW trend across the study area, but some localized changes of anisotropy direction in the Bay of Fundy and across the Appalachian front are observed. The crust beneath the older Superior and Grenville provinces is generally fast, whereas the Appalachians include strong slow anomalies, especially at upper crustal depths, where they represent thick sedimentary basins beneath the St. Lawrence valley, the Gulf of St. Lawrence, and the Bay of Fundy. We suggest that the boundary between the Peri‐Laurentian and the Peri‐Gondwanan terranes at depth is marked by a Moho‐offset feature observable in our models. A generally similar crustal seismic signature for the two youngest easternmost tectonic domains suggest that they were never separated by a wide ocean basin. Our results provide important evidence for evolution of the continental crust during and after accretionary/collisional episodes in the study area.

Interactive web mapping tools and custom subsurface cross-sections for interdisciplinary geologic investigation

Using Python-based geospatial analytics, open-source web mapping technologies, geophysical data models, and subsurface stratigraphy models from the Regional Geology Geologic Framework Model database assembled by Los Alamos National Laboratory, we developed a suite of web-based geologic investigation tools to identify and understand subsurface structures and geophysical properties concerning salt and shale formations within the contiguous United States. Coupled with a web map interface, these tools allow for the interactive visualization of various geologic data and demonstrate the ability to quickly generate custom subsurface cross-sections, borehole charts, and diagrams for azimuthal orientation data. These capabilities were developed for stakeholder and researcher use to facilitate informed decision making for spent nuclear waste disposition. However, these capabilities provide a flexible model for a variety of subsurface investigation needs, and we have demonstrated this flexibility by adapting these tools to meet visualization needs for various subsurface models within a web-based platform.

Band Structure and Energy Level Alignment of Chiral Graphene Nanoribbons on Silver Surfaces.

Chiral graphene nanoribbons are extremely interesting structures due to their narrow band gaps and potential development of spin-polarized edge states. Here, we study their band structure on low work function silver surfaces. The use of a curved Ag single crystal provides, within the same sample, regions of disparate step structure and step density. Whereas the former leads to distinct azimuthal growth orientations of the graphene nanoribbons atop, the latter modulates the substrate’s work function and thereby the interface energy level alignment. In turn, we disclose the associated charge transfer from the substrate to the ribbon and assess its effect on the nanoribbon’s properties and the edge state magnetization.

A simplified approach for including the incidence angle effect in seismic risk assessment

AbstractA simplified procedure is developed to consider the azimuthal orientation of buildings when estimating seismic risk. Two square‐plan reinforced concrete building models are considered as a testbed, one with similar and one with dissimilar properties along the two principal horizontal axes. The fragility of both structures is analysed using a set of ground motion records rotated to multiple incidence angles to develop orientation‐dependent fragility functions. It has been observed that, re‐orienting all records so that these structures have the same azimuth vis‐à‐vis the corresponding epicentre leads to significant differences compared to assuming random orientations. Additional results stemming from single‐degree‐of‐freedom oscillators further confirm such findings, showing a dependence to the proximity to the faults and the level of dissimilarity in the principal horizontal axes of the structure. The end results point to a non‐negligible bias in assessment studies when a structure's orientation with respect to governing rupture scenarios is not taken into account. It is shown that the median of fragility curves calculated for un‐rotated incidence angles can be bias‐corrected through shifted by an amount that depends on the azimuthal orientation and level of axes‐dissimilarity of structures.