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The Muzhailing Tunnel, Gansu Province, China, runs for most (84.5%) of its length through layered slate. To study the mechanical properties of rock masses containing interbedded soft and hard layers, mechanical tests were conducted in the laboratory on hard limestone and soft carbonaceous slate. To simplify the application of mechanical analysis, an equivalent alternative strength model for soft and hard media was derived based on the strain energy equivalence criterion and the Mohr–Coulomb strength theory, and expressions for calculating the ultimate equilibrium stress point and failure azimuth were obtained. Based on the strength differences between soft- and hard-rock layers, an equivalent substitution calculation model was established for different thickness ratios and stress conditions with a strength ratio of 4:1. The influence of the thickness ratio and stress state on the ultimate stress curve was analyzed. [ABSTRACT FROM AUTHOR]

Considering the constraints in the costs and efficiency of seismic exploration acquisition, marine hydrocarbon exploration mainly relies on towed-streamer acquisition. However, the seismic data obtained from streamers have limited azimuthal coverage, posing significant challenges for the prediction of complex fractured reservoirs using azimuthal anisotropy features. To address this issue, we proposed a workflow for conventional offshore narrow-azimuth streamer data, including the local angle domain migration imaging and prestack anisotropy inversion methods based on the Rüger approximation equation. First, the local angle domain full-azimuth migration imaging method is used to perform prestack imaging processing on narrow-azimuth streamer seismic data, thus obtaining prestack gather data with azimuth information. The prestack anisotropy parameter inversion method is then used to predict the fracture intensity distribution. Finally, the method and technical process proposed in this paper are applied to the fractured reservoir description of buried hills reservoirs in the deepwater area of the northern South China Sea. The practical results demonstrate that the proposed workflow, which combines full-azimuth migration imaging processing and prestack azimuthal anisotropy parameter inversion, can accurately predict fractured reservoirs using narrow-azimuth seismic data acquired through marine towed-streamer surveys. This technical workflow is also applicable to fracture predictions and reservoir evaluations in similar seismic survey areas. [ABSTRACT FROM AUTHOR]

We propose a new definition of oblique plate convergence. Our model considers arc-trench curvature on a spherical Earth, and defines obliquity as the angle between the direction of plate convergence and the azimuth from the central point along the arc to the center of curvature of the arcuate trench. We also show how this model may be extended to multiple-arc trenches. We apply this definition to the Western Sunda Arc, which has been traditionally considered the prime example of oblique plate convergence, particularly the segment corresponding to Sumatra. We define eight arc-like segments along this arc-trench system. Obliquity angles on these arc-like segments vary from 92° in the northernmost (Burmese) arc to 7° offshore the Sunda strait (between Sumatra and Java). The angle of obliquity offshore Sumatra is 31°, almost within the definition of slightly oblique convergence. Given the low angle of obliquity, partitioning along the Sumatran fault, in the southern portion of the Western Sunda Arc, is difficult to explain by oblique plate convergence alone. We suggest that the entire segment (or forearc) inboard of the Western Sunda Arc be dragged from the Burmese arc, where overriding and subducting plates are completely coupled and oblique plate convergence is high. [ABSTRACT FROM AUTHOR]

Location of damage sources is an important aspect of structural health monitoring research. Acoustic emission (AE) technology is broadly concerned due to its potential advantages in damage monitoring and source localization. However, the traditional positioning method is based on the arrival of P wave, and the non-uniformity of concrete materials is not considered, resulting in poor accuracy at large distances. This paper describes a non-contact AE localization method using leaky Rayleigh waves via a new air-coupled MEMS microphones array unit. Compared with traditional contact detection, this method is convenient for rapid setup and monitoring in a wider range. The feasibility of the non-contact AE localization method was verified by numerical simulation and experiments. Azimuth (direction of arrival) of AE source is a key source parameter for damage location. The research shows that this method can determine the azimuth of AE source at different positions, the results are close to the actual coordinates. Non-contact monitoring method proposed in this paper is the basis for further research on the failure prediction of concrete plate-like structures such as tunnel lining and bridge deck. [ABSTRACT FROM AUTHOR]

Barite mineralization is visible as veins in the Kuik‒Qureq area, southern part of Sanandaj zone, Western Iran. Geological and structural maps of the area were prepared using remote sensing data and field achievements. Statistical analysis of fractures included the ratio of distance and length to abundance, and also the calculation of the fractal dimension of fractures. This analysis indicates the role of structural controls on the barite mineralization in the region. Petro-fabrics were used to determine displacement and contribution of faults in barite mineralization. Geometric analysis using rose diagrams determined that the trends of the dominant fractures are N‒S and NN‒S, NNW‒SSE, WNW‒ESE and NNE‒SSW, and the main barite mineralization was formed along these faults. A tectonic model is presented for the region based on classifying fractures by azimuth and features observed in thin section. According to the proposed model, at least four stages of tectonic deformation affected the region and during these the direction of the σ1 axis changed in a clockwise direction. Barite mineralization mainly occurred in two stages: the first and main stage when first order fractures formed with the N‒S trend, and during the third deformation stage when secondary barite was deposited in third order fractures with an E‒W trend. [ABSTRACT FROM AUTHOR]

Linear arrays are popularly used for passive surface wave imaging due to their high efficiency and convenience, especially in urban applications. The unknown characteristics such as azimuth of noise sources, however, make it challenging to extract accurate phase-velocity dispersion information by employing a 1-D linear array. To solve this problem, we proposed an alternative passive surface wave method to capture the dominant azimuth of noise sources and retrieve the phase-velocity dispersion curve by polarization analysis with multicomponent ambient noise records. We verified the proposed method using synthetic data sets under various source distributions. According to the calculated dominant azimuth, it is deduced that noise sources are mainly classified as either inline or offline distribution. For inline noise source distribution, we are able to directly obtain the unbiased phase-velocity measurements; for offline noise source distribution, we should correct the velocity overestimation due to azimuthal effects using the proposed method. Results from two field examples show that the distributions of noise sources are predominantly offline. We eliminated the velocity bias caused by offline source distribution and picked phase velocities following higher amplitude peaks along the trend. After the azimuthal correction, the picked phase-velocity dispersion curves in dispersion images generated from passive source data match well with those from active source data, demonstrating the practicability of the proposed technique. [ABSTRACT FROM AUTHOR]

On March 5, 2022, a 12 kg meteoroid crossed the sky above Central Italy and was observed by three different observational systems: the PRISMA all-sky camera network (10 stations), the Italian national seismic network (61 stations), and a 4-element infrasound array. The corresponding datasets, each with its own resolution, provided three independent assessments of the trajectory, size and speed of the meteoroid. The bolide traveled across central Italy with an azimuth of 102 degrees, becoming visible at about 91 km above sea level with a velocity of about 15.4 km/s. Its visible trajectory lasted about 15 s. Reasonably, the residual portion of the ablated bolide terminated its path in the Adriatic Sea and could not be recovered. Seismic and infrasound data well match optical observations detecting the bolide Mach cone at 68 km above sea level with a back azimuth of 25 degrees with respect to the array. By comparing results from the three different systems, discrepancies are within the estimated uncertainties, thus confirming the mutual consistency of the adopted methodologies. Therefore, this study shows that different approaches can be integrated to improve the detection capability for bolide crossing the sky in monitored regions. [ABSTRACT FROM AUTHOR]

Subduction zones may be characterised by deep-seated tectonic structures whose effects propagate to the upper plate through faulting and magmatism. The overall geodynamic framework, as well as the roots of the many active faults affecting such regions, can be investigated by the study of the upper mantle anisotropic patterns, through the analysis of core-transiting teleseismic phases. Here, we discuss the results of XKS waves splitting observed in the central Mediterranean, particularly in southern Italy, which is characterised by the Adriatic-Ionian subduction system. Azimuths of polarisation of the fast wave (fast directions) were found to be generally trench-parallel, as an effect of the subducting slab, albeit a change to a perpendicular direction, in central Italy and Sicily, suggests discontinuities in the structure of the slab itself. However, while in central Italy a gradual rotation of fast directions points to a toroidal upper mantle flow through a tear in the Apenninic slab, in central-eastern Sicily, the splitting parameters show an abrupt change that matches well with the main crustal tectonic structures. There, the rapid trench migration, taking place at the transition between the subduction and continental collision domains, produced a rather complex Subduction Transform Edge Propagator fault system. The sharp variation in the pattern of the upper mantle anisotropy marks the main element of such a fault system and suggests its primary role in the segmentation process of the collisional margin. Our findings further show that the study of seismic anisotropy may be fundamental in investigating whether tectonic structures only involve the crust or extend down to the upper mantle. [ABSTRACT FROM AUTHOR]

In order to address the low azimuth imaging problem of traditional Range Doppler (RD) algorithm, a high-resolution imaging algorithm with optimal azimuth sampling sequence length (SSL) constraints is hereby proposed. According to this algorithm, efforts are made to design a formula for the calculation of the initial azimuth SSL on the basis of SAR azimuth imaging parameters. Having obtained the initial SSL and the criteria for the evaluation of SAR imaging performance, we continue to figure out the extreme values of the curve within a reasonable range of variation. On the basis of these values, the optimal azimuth SSL can be determined to provide data support for global azimuth imaging. Measurement data from imaging experiments on airborne and spaceborne SARs show that, compared with traditional RD algorithm, the proposed algorithm reveals outstanding advantages as indicated by a number of factors critical for the evaluation of imaging performance, such as resolution, peak sidelobe ratio (PSLR) and integral sidelobe ratio (ISLR). Compared with reference methods with local optimal imaging performance, the proposed algorithm can help to obtain global optimal SAR imaging data. [ABSTRACT FROM AUTHOR]

In this paper, an unambiguous two-dimensional (2D) direction of arrival (DOA) estimation algorithm based on a large-space L-shaped array is proposed. The proposed L-shaped array is composed of two large-space linear arrays. Each linear array consists of two uniform linear arrays with internal element spacing being larger than half wavelength of incident signal. Firstly, an unambiguous modified estimation of signal parameter via rotational invariance techniques (ESPRIT) algorithm is proposed to estimate the elevation angles. Then, using the estimated elevation angles, automatically matched azimuth angles can be estimated. On account of the adjustable element spacing, the proposed array is robust to mutual coupling effect. Moreover, simulation results can prove that the proposed algorithm has higher estimation accuracy than many similar 2D DOA estimation algorithms based on L-shaped array. [ABSTRACT FROM AUTHOR]

We design an all-dielectric silicon metasurface adopting an elliptical-cylindrical unit structure. In the case of circularly polarized light incidence, we can obtain terahertz vector Bessel beams with radial or azimuthal polarization characteristics. We demonstrate that the spatial position polarization control of the beam can be achieved by rotating the unit structure with quarter-wave plate function. In addition, the transmission phase is used to offset the extra phase brought by the polarization control, and the function of converting the left-handed or right-handed circularly polarized incident light into a radially or azimuthally polarized Bessel beam is successfully realized at the frequency of 0.71 THz. This research provides feasibility for the generation of vector Bessel beams in the terahertz band. [ABSTRACT FROM AUTHOR]

Performance of a solar reflector depends upon the topology of the reflector unit. Curved reflector certainly performs better but it has high-cost, high manufacturing complexity and sometimes even requires non-indigenous technology for its production. Besides, the flat plate solar reflecting unit (FSRU) offers low cost, are widely available and are indigenous in nature. The present work attempts to give a simple methodology to test different combinations of a large-scale FSRU under azimuthal sun alignment. The obtained result is validated with corresponding CAD model and previously performed experimental results. The FSRU is a funnel-type solar reflector in the form of an inverted frustum of a square pyramid. The path followed by the in the unit is classified in different categories, based on their interaction with reflectors. The results show that there is a good agreement between path of rays observed during experiment and path of rays predicted by a CAD software. The maximum deviation ( δ max ) in path for optical performance is 2.1%. On other hand the maximum uncertainty (χ) in path is 2.96% considering ± 1° error of manufacturing of FSRU. Thermal efficiency of FSRU is 69% considering reflectivity of 97% for the reflectors. The final output of the present study predicts that (a) amount of errors ( δ max and χ) are under control for large size of FSRU and (b) azimuthal alignment improves the FSRU's thermal performance. [ABSTRACT FROM AUTHOR]

This paper presents a new model for the generation of axisymmetric concentrated vortices. The solution of a nonlinear equation for internal gravity waves in an unstable stratified atmosphere is obtained and analyzed within the framework of ideal hydrodynamics. The corresponding expressions describing the dependences on the radius for the radial and vertical velocity components in the inner and outer regions of the vortex include combinations of Bessel functions and modified Bessel functions. The proposed new nonlinear analytical model makes it possible to study the structure and nonlinear dynamics of vortices in the radial and vertical regions. The vortex is limited in height. The maximum vertical velocity component is reached at a certain height. Below this height, radial flows converge towards the axis, and above it, an outflow occurs. The resulting instability in the stratified atmosphere leads to an increase in the radial and vertical velocity components according to the hyperbolic sine law, which turns into exponential growth. The characteristic growth time is determined by the inverse growth rate of the instability. The formation of vortices with finite velocity components, which increase with time, is analyzed. The radial structure of the azimuthal velocity is determined by the structure of the initial perturbation and can change with height. The maximum rotation is reached at a certain height. The growth of the azimuth velocity occurs according to a super-exponential law. [ABSTRACT FROM AUTHOR]

The reduction in longitudinal drag and increase in rate of penetration have recently been a hot topic in the drilling field. In this study, a motor-fully-rotating directional drilling system was proposed. Compared to the conventional system of motor/MWD (measurement while drilling), the advantage of the new system is that all drill string except the guiding bent housing rotates during slide drilling, which meets the two requirements of reducing longitudinal drag and increasing the rate of penetration. The stability of the toolface is the premise for the new proposed system to realize its working principle. Lateral force between the guiding bent housing and wellbore under different well conditions was evaluated by a model established by the continuous beam method. On this basis, combined with the principle of rolling friction, and through indoor experiments, it was shown that when the wellbore curvature is less than 6°/30 m and friction coefficient between the guiding bent housing and wellbore is bigger than 0.2, the toolface can be kept stable. Field tests showed that the well deviation angle continued to increase, while the azimuth remained unchanged in the well section where the tool was used, and the maximum change rate of inclination angle was 7.886°/30 m, verified the toolface stability of the proposed system during slide drilling. [ABSTRACT FROM AUTHOR]

Beamforming is one of the most important techniques for multibeam echo sounder (MBES) for engineering applications, such as seafloor topographic survey and underwater target detection. However, due to the Rayleigh limit in the conventional beamforming (CBF) algorithm, the output of the beamforming is often limited by the aperture and the number of elements, thus leading to low resolution and signal-to-noise ratio (SNR). To further improve the resolution and array gain (AG) of the beamforming algorithm for MBES, a dynamic background suppression deconvolved multiple signal classification (DBSD–MUSIC) algorithm is proposed in this work. The dynamic variable point scattering function (PSF) is constructed using the signal characteristics of the signal covariance matrix for each moment. The MUSIC azimuth spectrum is deconvolved using the dynamic PSF and Richardson–Lucy (R–L) iterative algorithm. Thus, the azimuth spectrum of DBSD–MUSIC algorithm is obtained. Based on the analysis and comparison of the simulation results and experimental multibeam data, we show that the resolution of the proposed algorithm is better than the traditional MUSIC algorithm. In addition, it also has a better AG and the direction of arrival (DOA) estimation performance. [ABSTRACT FROM AUTHOR]

A geological model related to coal-rock electromagnetic parameters is constructed in this work using coal-rock media and coal-rock interfaces as the research objects for electromagnetic wave propagation response. An in-depth analysis was conducted to examine the response characteristics of the electromagnetic wave detection technology for coal and rock geological orientations while drilling in coal mines. We also studied the detection and identification methods and applicability of coal and rock interfaces. Next, we simulated the response characteristics of the instrument in the coal seam and established a calculation method for the orientation of the interface between the roof and floor of the coal seam and the distance between the instrument and the coal seam's interface. The quasi-Newton method was used to perform inversion calculations on the theoretical model of the response of the borehole-while-drilling azimuth electromagnetic wave resistivity tool, and the simulation data were inverted in real time, thereby reducing the number of calculations of the Jacobian matrix, improving the inversion speed, and decreasing the level of dependence on the initial value. Furthermore, we obtained the signal response law of electromagnetic wave detection in low-resistivity aquifers and abnormal geological bodies (e.g., collapse columns and gangue interlayers) based on forward and inversion numerical simulation. Finally, by investigating the directional electromotive force simulation imaging method of the orthogonal coil, we verified the feasibility of the application of azimuth electromagnetic wave resistivity in high-resistivity coal seams. In this way, we can provide the basis for the detection of coal seam interface, geological anomaly body, and geological guidance application. [ABSTRACT FROM AUTHOR]

GNSS measurement-based geodetic studies have led to researchers explaining the regional deformation in the Himalaya in terms of arc-parallel shearing and arc-normal compression. Arc-parallel extension is caused by an increase in the shearing rate, which is reflected in the increasing arc-parallel velocities as one moves along-arc away from the arc-center. This has prompted many to recognize the significance of arc-parallel shearing and extension in the Himalayan orogeny. Several researchers have proposed that the arc-parallel deformation is taken up almost entirely by the Karakoram fault system through slip transfer from the Himalayan foothills, though recent studies have provided some evidence of dextral faulting within the Northwest (NW) Himalayan accretionary wedge. In this paper we address this issue by providing topography-derived evidence such as the deviation of the maximum gradient azimuth from the arc-normal along the Himalayan arc to show that obliquity in convergence is a significant controlling factor in shaping the morphology of the Himalayan slopes. Approximately 4 ± 3 mm/year of arc-parallel dextral shear is being accommodated within the accretionary wedge spanning the NW Himalaya (particularly the part in Himachal and Garhwal), which is approximately 55% of the total arc-parallel dextral shear resulting from the ongoing convergence between southern Tibet and the Indian Plate in this portion of the Himalaya. The study further suggests consistency of the observed Himalayan deformation with the oblique convergence model and the significant role that the underthrusting ridges inherited from the Indian Plate are playing in the strain accommodation pattern in the overlying Himalaya. [ABSTRACT FROM AUTHOR]

Potential field filters are widely used in exploration and interpretation of geologic structures, archaeological sites, hazards assessment, and in engineering and environmental studies. There are countless filters and attributes and their number keeps growing: directional, horizontal and vertical derivatives; analytic, monogenic and direct analytic signals; modules; local phase; tilt angle; azimuth; local (horizontal, vertical and total) wavenumbers; theta function; high order derivatives; enhancements; normalizations. Furthermore, almost all of these filters can be applied to other filters—often named with overwhelming acronym combinations making it almost impossible to keep up with the particular and general development of this field. In this work, we present a review of more than 200 publications and compile more than 50 proposed methods in a unified mathematical framework, and an easy-to-follow notation. We asses all the methods, their definitions, connections, variations, redundancies and limitations, including a vast list of references and some historical notes. We improve and amend some points—regarding not only its mathematical applications but also the attributions that correspond to each method. We also establish connections with other fields of research—seismics, mathematics, image analysis—in which the same or similar techniques are used, but have remained isolated and unknown to each other. [ABSTRACT FROM AUTHOR]

With the rapid growth of the construction industry, precise and efficient monitoring of building deformation has become a crucial factor in ensuring their secure construction and stable operation. The frequent occurrence of occlusion and diffraction errors in satellite signals caused by high-rise buildings has emerged as a primary challenge that constrains the accuracy of positioning in deformation monitoring by BeiDou Navigation Satellite (BDS). To solve the problems, this study proposes an elevation mask angle modeling method of satellite signal occlusion based on azimuth rounding and applies it to real-time BDS building deformation monitoring and positioning algorithm. The proposed approach involves defining a particular subset of integer azimuth and elevation angles, followed by utilizing the minimum elevation angle from this subset to develop a model for the azimuth-dependent elevation mask angle. We aimed to develop an elevation angle mask model using a conventional approach, and the model can be utilized to focus on non-line-of-sight (NLOS) and multipath signals and attenuate their impact on positioning accuracy by reducing their weight. The experimental results show that the elevation angle mask model can be easily completed by using the observation data of BDS satellites in a single day, and its use can make the number of effective satellites involved in the calculation of real-time deformation monitoring of BDS more accurate and reliable. The root mean square (RMS) of positioning results including float solutions was increased respectively by 91.1%, 93.3%, and 72.7% in the direction of East-North-Up (ENU), and the RMS of results with fixed ambiguity was increased by 6.9%, 10.0%, and 29.5%, respectively. Therefore, it can be concluded that the elevation mask angle modeling algorithm is convenient to realize and can significantly improve the performance of deformation monitoring results by BDS. [ABSTRACT FROM AUTHOR]

Uniaxial models are commonly used to describe the change in magnitude of horizontal principal stresses in depleted reservoirs and consequently to analyze the stability of infill wellbores. The accuracy of these models is assessed in this paper through a three-dimensional axisymmetric stress solution for a depleted disk-shaped reservoir embedded within an infinite and homogenous model of the subsurface rock. The solution is used to obtain the limits of mud weight window that would not cause wellbore breakout or fracturing, as well as the safest trajectory of wellbores that are drilled in general vicinity of depleted reservoirs. Inside and outside of a reservoir subjected to different faulting regimes are considered for wellbore stress analysis. Results indicate that despite their common use, the uniaxial models may return significantly erroneous predictions of the change in the in-situ stress state around and about a depleted reservoir. In particular, the stress change is found to strongly depend on the geological azimuth and radial distance from the reservoir center point. Consequently, the uniaxial models may fall short in accurate prediction of the tensile or shear failure gradients of infill wells. These errors would be more substantial for wells that are closer to the reservoir boundaries. Highlights: Stability analysis of infill wellbores requires a 3D stress solution at reservoir scale. Reservoir depletion alters the vertical component of in-situ stress, as well. Uniaxial models produce conservative estimates of tensile failure gradient inside depleted reservoirs. Reservoir depletion causes a reduction in wellbore shear failure gradient outside the reservoir. [ABSTRACT FROM AUTHOR]

In this work, the tunable dual-band split ring terahertz (THz) polarization converter is proposed based on Weyl semimetals (WSMs). By changing the chemical potential of the WSMs, the polarization converter can realize the frequency-dependent linear–linear and circular–circular cross-polarization conversion in the two bands of 1.21–1.29 THz and 1.97–2.04 THz, respectively. The achieved polarization converter ratio (PCR) is higher than 99% for the two types of cross polarizations. Besides, the WSM-based polarization conversion also shows 2π phase shift and amplitude modulation by rotating the azimuth angles of the split ring. Furthermore, the 3-bit coding metasurfaces can achieve tunable linear–linear, circular–circular, and linear–circular beam modulation by adjusting the chemical potential of the WSMs. The proposed tunable metasurface would have wide applications in multiband cross-polarizations and different types of wave modulation with linear–linear, circular–circular, and linear–circular. [ABSTRACT FROM AUTHOR]

A receiver system and azimuth estimation method for non-cooperative underwater acoustic frequency hopping (FH) signal are proposed. Using single acoustic vector sensor as receiver, the time–frequency information and spatial information are combined by constructing space–time–frequency distribution matrix. Then the time–frequency ridge line is extracted by neural network, and the energy extracted from the time–frequency ridge line is integrated with time. Finally, the target azimuth is estimated based on the principle of complex acoustic intensity method. Simulation analysis and experimental results show that the proposed method can effectively estimate the azimuth of the non-cooperative underwater acoustic FH signal under the condition of low signal-to-noise ratio (SNR). The root mean square error of azimuth estimation is less than 1° under the condition SNR > –10 dB, which improves the azimuth estimation performance of the traditional complex acoustic intensity method. [ABSTRACT FROM AUTHOR]

This work presents a 12-element 360° azimuth plane scanning planar circular antenna array for compact THz wireless devices. Proposed array comprises of 12 bow-tie Yagi-Uda directional antennas, operating within 0.235–0.322 THz band where each antenna achieves a maximum radiation beam for an angle of around 30°, arranged in a circular fashion to cover 360°. Individual antennas are stamped on a silicon dioxide (SiO2) dielectric substrate having compact dimensions of 1.35 mm × 1 mm × 0.06 mm and employ gold material of thickness 5 µm as a conducting material in the top and bottom planes. Maximum peak gain of each antenna is found to be 10.4 dBi at 0.322 THz within the operating band. Three parasitic elements are employed as directors to enhance the directional properties. Initially, a single element bow-tie Yagi-Uda antenna design is presented and then followed by a 6-element and 12-element circular antenna array design. Exhibiting compact dimensions, higher directivity, better performance and simple design lead to a suitable module for smart THz wireless scanning devices in the range of IEEE 802.15.3d (0.252–0.325 THz) standard and H-band (0.22–0.32 THz). [ABSTRACT FROM AUTHOR]

In the direction-of-arrival (DOA) estimation methods for uniform circular arrays (UCAs) with directional sensors, the high computational complexity arises when achieving the estimation accuracy by leveraging all the sensors in the element space. We present a low-complexity sectorized DOA estimation scheme for directional UCAs. It models the radiation pattern within half-power bandwidth in a closed mathematical expression and thereby constructs reconfigurable sectorized steering vectors of an arbitrary angular sector by using the Hadamard cyclic vector with the Vandermonde structure. The DOA estimation over the azimuth plane throughout the element space is transformed to DOA estimates within multiple individual angular sectors. The new scheme comprises three stages, i.e., submatrix extraction, sectorized weighted beamforming and sector DOA estimation. The feasibility and effectiveness of the proposed scheme are validated by numerical simulations. The simulation results demonstrate that, compared to the previous sector-free DOA estimation methods based on the entire azimuth plane, our scheme has a low hardware and computational complexity under an acceptable estimation error. [ABSTRACT FROM AUTHOR]

Fracture orientation and in particular the fracture strike play an important role in guiding the accurate estimation of the orientation of in situ stress fields. Fracture strike can be extracted based on the azimuthal seismic reflection responses. Thus, the characteristics of seismic reflection responses varying with fracture strike are critical for fracture strike estimation. In this work, a set of vertical fractures with different strikes is introduced into an isotropic host matrix based on the Schoenberg linear-slip theory, and the azimuthal seismic reflection response is modeled based on the reflection/transmission analysis at a plane interface. The effect of fracture parameters, i.e., fracture density, fracture aspect ratio, and fluid infill on the seismic reflection response, is analyzed. The influences of fracture strike on the stiffness matrix are simulated, and we further discuss the impacts on the P- and S-wave velocities. The influences of fracture strike on the reflection coefficient are depicted using the rose diagram method. The proposed workflow is applied to real seismic reflection data. The method is used to estimate the fracture strike with the seismic data in the Sichuan Basin work area by assuming that all fractures are vertically oriented, and the rose diagram is obtained close to the target layer. The results show that the fracture strike predicted by the method is in good agreement with the estimation based on the well-bore imaging data. [ABSTRACT FROM AUTHOR]

Coordinate–time measurements are considered as one of the most common types of measurements in various radio navigation and radar systems in the field of geodesy and radio communications. It is shown that the increase in the number of coordinate–time measuring instruments, as well as the increased level of requirements for the accuracy of determining user coordinates, stipulated the relevance of the development of the State Primary Special Standard of Location Coordinates. The composition of the State primary special standard of location coordinates GET 218-2022, developed at VNIIFTRI, is presented, which will ensure the uniformity of measurements of coordinates and azimuth, satellite geodetic and navigation equipment using signals from global navigation satellite systems GLONASS, GPS, Galileo, BeiDou and ground augmentations. The metrological characteristics of GET 218-2022 in terms of storing absolute coordinates, reproducing/measuring the unsolicited range in phases of the ranging code and carrier frequency, reproducing the coordinates of the consumer of global navigation satellite systems, measuring increments of coordinates in coordinate systems are studied. The results of studies of the metrological characteristics of GET 218-2022 in terms of storing absolute coordinates and measuring increments of user coordinates showed a comparable level of accuracy with the characteristics of the international ITRS system. With the use of GET 218-2022, it is possible to test such promising measuring instruments as high-precision unsolicited measurement systems, precision receivers of global navigation satellite systems in the mode of absolute/relative phase measurements. [ABSTRACT FROM AUTHOR]

The in-situ stress information underground is of crucial importance for drilling and reservoir development. As the cost of direct stress measurements is high and only limited information can be obtained, the application of wellbore imaging devices made it possible to interpret the local stress state more economical. Breakout azimuths revealed by well logs are widely used to determine principal stress directions in traditional method, however strength anisotropic related to bedding planes may greatly affect breakout azimuth, width and depth, which can result in misleading for in-situ stress interpretations. Based on weak-plane borehole stability model and Mogi-Coulomb matrix strength criterion, we analyzed the relationship between in-situ stress and breakout geometry (azimuth, width and depth) both in isotropic and anisotropic formation. The results show that the azimuth of breakout is controlled by weak plane's azimuth, while steep dipping bedding plane widen the breakout and make it extending into rocks. For specific strata with determined property, breakout geometry will change regularly with the increase of the principal stress ratio. A breakout accident observed in well WFSD-2 help to illustrate the method and the magnitude of the maximum horizontal principal stress is determined. [ABSTRACT FROM AUTHOR]

This paper presents the design and validation of a slot-patch-hybrid circularly polarized antenna array for 28 GHz millimeter (mm) wave (mm-wave) applications. The proposed design has a simple geometry that facilitates the fabrication process, which is otherwise a challenging task due to the sub-mm dimensions of the circuit in the mm-wave band. In the proposed structure, aperture-coupled series slot-fed array is utilized to excite the 45° inclined pair of patches. The feeding array aperture is designed by printing a straight microstrip feed line with a matching stub at the open end. Further, a coupling slot is etched underneath the feed line in the conventional horizontal position, and two vertical slots are merged toward each end of the slot. For realization of the series phased array of (1 × (4 × 2)) elements, the slots are placed half guided wavelength away extending the array network along the feed line. A pair of the radiating patches are loaded on the top of the vertical slots. To ensure excitation of the 90° phase-shifted orthogonal field components of equal magnitude, the loaded patches are rotated by 45° in the azimuth plane. The produced circularly polarized (CP) fields are further refined by an additional diagonal radiating slot etched in the middle of the pair of radiating patches parallel to the non-radiating edges. With the combination of radiating patches and the slots, a wide axial ratio bandwidth of 27.5–28.5 GHz, broad impedance bandwidth, a highly directional beam, and a peak realized CP gain of 15.15 dBic is achieved. For realizing omnidirectional radiation pattern necessary for the base station applications, 3-dimentional hexagonal/octagonal topology is utilized in six- and eight-antenna configurations. A detailed theoretical and numerical analysis and the corresponding results shows that the adjacent beams could be merged together constructively to form omnidirectional radiation patterns. The advantage of the proposed technique is the ease of implementation without affecting the major performance figures. [ABSTRACT FROM AUTHOR]

The polarization plane of a diffracted wave in the transmitted diffraction orders is shown by us to be significantly rotated, which is absent in the reflected diffraction orders, for anisotropic Bragg light diffraction on volume phase holographic gratings for significant perturbation amplitudes of the medium refractive index. Periodic changes in the transmission coefficients of diffracted waves with a change in the azimuth of incident light polarization are shown to be due to a significant difference in the Fresnel reflection coefficients at the layer boundaries for the s- and p-components of the incident light. These periodic changes are absent in the reflected diffraction orders. [ABSTRACT FROM AUTHOR]

Due to different sedimentary environments, the realistic formation always presents different electrical anisotropic characteristics. Multicomponent induction logging technology is an efficient method to solve complicated electrical anisotropy problems. However, because of the mathematical complexity, the investigation of unconventional electrical anisotropy in borehole geophysics is still insufficient. Additional situations, such as the classification of electrical anisotropy and the corresponding solution, need to be considered. For convenience, we introduce a universal algorithm to solve arbitrary electrical anisotropic problems. Uniaxial and biaxial anisotropic resistivity media are studied. In addition, the anisotropic dip and azimuth angles are used to further characterize the complex electrical anisotropy conditions. Numerical simulations confirm the robustness of the algorithm, and illustrate the tool responses under different electrical anisotropic situations. It can be concluded that anisotropic dip and azimuth can exert a great influence on triaxial induction logging responses. Some important phenomena can be observed; for example, critical borehole and critical anisotropic dip exist in the rotated uniaxial and biaxial media. Different monotonic rules can be found before and after these critical angles. Cross-coupling magnetic components, Hxy (Hyx) and Hyz (Hzy), are closely related to the anisotropic azimuth. The proposed algorithm can effectively overcome the deficiency of the traditional method and reduce the uncertainties in resistivity interpretation. [ABSTRACT FROM AUTHOR]

Using a motion-capture system and custom head-calibration methods, we reconstructed the head-centric view of freely behaving pigeons and examined how they orient their head when presented with various types of attention-getting objects at various relative locations. Pigeons predominantly employed their retinal specializations to view a visual target, namely their foveas projecting laterally (at an azimuth of ± 75°) into the horizon, and their visually-sensitive "red areas" projecting broadly into the lower-frontal visual field. Pigeons used their foveas to view any distant object while they used their red areas to view a nearby object on the ground (< 50 cm). Pigeons "fixated" a visual target with their foveas; the intervals between head-saccades were longer when the visual target was viewed by birds' foveas compared to when it was viewed by any other region. Furthermore, pigeons showed a weak preference to use their right eye to examine small objects distinctive in detailed features and their left eye to view threat-related or social stimuli. Despite the known difficulty in identifying where a bird is attending, we show that it is possible to estimate the visual attention of freely-behaving birds by tracking the projections of their retinal specializations in their visual field with cutting-edge methods. [ABSTRACT FROM AUTHOR]

We analyzed the seismological characteristics of a microearthquake sequence that occurred from September 2009 to August 2020 with epicenters concentrated within a small area, ∼10 km WNW of downtown Suncheon, South Korea. During the study period, 33 events with a local magnitude (ML) < 2.0 were cataloged by the Korea Meteorological Administration. We identified 101 uncataloged events in the source region by using the matched filter method and estimated magnitudes based on amplitude ratios measured with a reference event. The focal mechanism solutions of 16 events were obtained with P-wave polarities and S-wave to P-wave amplitude ratios, which were used in iterative stress inversion to estimate the current stress orientation. The hypocenters of this sequence were relocated using the double-difference method. A total of 133 relocated microearthquakes were aligned at ∼11 km depth along a 500 m long lineation with an azimuth of N80°E and a dip of 84°N. This matched very well with the principal focal mechanism from the stress inversion of 16 focal mechanism solutions, striking N77°E with a dip of 88°N. The maximum principal stress direction of the Suncheon microearthquake sequence was a trend of NE-SW, slightly different from the regional tectonic stress in the eastern Eurasian plate, which may imply the existence of local stress perturbations in the study area. [ABSTRACT FROM AUTHOR]

The site locations of real-time Global navigation satellite system (GNSS) monitoring are usually located in a canyon environment, where the signals are frequently affected by multipath, diffraction, and even non-line-of-sight (NLOS) reception, etc. How to establish an accurate mathematical model is crucial at this time. In this paper, a composite stochastic model based on elevation, azimuth, and carrier-to-noise-power-density ratio (C/N0) is proposed, which can reflect the terrain topography of the monitoring station. Specifically, according to a mapping function of azimuth, a so-called geographic cut-off elevation is introduced to detect and exclude the NLOS reception and even outlier, then a constrained elevation is obtained. Besides, based on the template functions of C/N0 and its precision, a procedure is implemented to determine the equivalent elevation, where the contamination of multipath and diffraction are considered properly. To validate the effectiveness of the proposed method, a designed experiment and real deformation monitoring in canyon environments are tested. The results show that the real terrain topography can be reflected to a great extent after using the proposed method. The positioning precision and reliability have been improved, and the performance of ambiguity resolution is also enhanced compared with the other traditional approaches. In real-time kinematic positioning, single-epoch centimeter-level and even millimeter-level accuracies can be obtained under these challenging conditions. [ABSTRACT FROM AUTHOR]

Geodetic and seismological observations have shown discrepancies between azimuths of maximum contraction (strain rate) and maximum compression (stress). These discrepancies can be the results of the superposition of localized or transient mechanical processes such as fault coupling during seismic cycles. Rich sets of recent geophysical data allow us to conduct spatiotemporal imaging of the discrepancies. Here, we estimate the spatiotemporal evolution in the strain-rate fields of the Japanese Islands with optimized smoothing distances from 1997 to 2021 using Global Navigation Satellite System (GNSS) data, and investigate how the maximum contraction axes of horizontal strain rates differ from those of horizontal stress based on earthquake focal mechanisms. Several characteristic results are observed for each region within the Japanese Islands. Both azimuths of the strain rates and stress differ by more than 60° over hundreds of kilometers from the Kanto region to along the Nankai Trough, related to seismotectonics due to the dual subduction of the Philippine Sea plate and the Pacific plate beneath the Japanese Islands. The differences in the azimuths imply the effect of the very long-term stable subduction of the Pacific plate. We find that the azimuthal differences tend to be small along tectonic zones with active inland earthquakes and high strain rates on the back-arc sides. We also find that the 2011 off the Pacific coast of Tohoku earthquake caused notable azimuthal differences in the strain rates and the stress in the Tohoku region. The strength of fault may cause lower response sensitivity of seismological stress to major earthquakes than geodetic strain rate. Our dataset has wide spatiotemporal coverage and can serve as a basis for further research, for example, to estimate the current fault conditions during seismic cycles. [ABSTRACT FROM AUTHOR]

In this paper, a novel planar and wideband metal-only retroreflector is proposed that efficiently reflects the obliquely incident electromagnetic wave along its incident direction in omnidirectional angle range. The means of omnidirectional is the capability of retroreflectivity in all azimuth angles (φ i) and in a wide elevation angle (θ i) range. The proposed structure consists of a symmetrical transmitarray structure with beam scanning capability in which a metal plate is placed instead of the feed. The transmitarray is designed by using the generalized multifocal approach in which the beam scanning capability is possible via feed displacement and the phase of the elements has azimuthal symmetry that causes omnidirectional property. Now by placing a metal plate at the location of feed displacement and provided that the focused waves are nearly perpendicular to the metal plate, the plane wave is reflected back along its incident direction i.e. the retroreflectivity property is obtained. The proposed retroreflector simulated by CST STUDIO software and fabricated with laser cut technology. The results of measurement show an omnidirectional retroreflectivity with half-power (3-dB RCS level) elevation field of view of 60° (− 30° to 30°) in the frequency range of 8.5–10 GHz (approximately 17%) for both TE and TM polarization. [ABSTRACT FROM AUTHOR]

Phenotypic plasticity (PP) is the ability of an organism to produce multiple phenotypes in response to environmental changes. In cultivated species, such as maize (Zea mays L.), the PP of plant architecture traits will play an important role in the adaptation of genotypes to unpredictable scenarios given by climate change, marginal areas, and seeding with variable plant density (D). We bring information to improve the understanding of the environmental modulation of PPs of plant architecture traits of maize, untangling their genetic bases, and testing the hypothesis of independent genetic control of the traits per se and their PPs. The PP of traits related to leaf area, spatial distribution of leaf area and stem architecture [(leaf area, maximum leaf width, maximum leaf length (LL), leaf orientation value, vertical leaf angle, leaf length to the flagging point (LF), LF/LL relationship (LFLL), azimuthal leaf orientation, ear height (EH), plant eight (PH), EH/PH relatioship (EHPH) and stem diameter] were estimated using 160 RILs from the IBM B73 × Mo17 Syn4 population, cultivated under two contrasting D (5 and 10 pl m−2) during two growing seasons that determined different environmental conditions. Data were phenotypically analyzed and quantitative traits loci (QTLs) were mapped. For leaf area and stem architecture related traits, high mean values of traits per se were related with high PPs values at low intraspecific competition while low mean values were observed at high intraspecific competition. The opposite response was found on leaf orientation related traits, with the exception of AZ. Forty-eight QTLs were detected for PP of plant architecture related traits on all chromosomes with exception of chromosome 7. There was no phenotypic correlation and no co-located QTLs for traits per se and their PPs. This independent genetic control for traits per se and their PPs would allow breeders to develop genotypes adapted to specific environments selecting for high or low PP in combination with high or low values for relevant agronomic traits. [ABSTRACT FROM AUTHOR]

Geological and geophysical data acquired from naturally fractured hydrocarbon reservoirs usually exhibit the presence of multiple sets of fractures. Two different nonorthorhombic sets of fractures embedded in isotropic background rocks can reveal the anisotropic characteristics of monoclinic symmetry with a horizontal symmetry plane. Here, we focus on the modeling and inversion of the effective elastic properties in fractured reservoirs with monoclinic symmetry induced by a set of horizontal fractures and a set of tilted fractures with rotationally invariant properties embedded in purely isotropic host rock. To facilitate the seismic characterization of fractured reservoirs with monoclinic symmetry, we introduce two sets of fracture weakness parameters to replace the Thomsen-type anisotropic parameters and describe these two nonorthogonal sets of rotationally invariant fractures. With the incident and reflected P wave in such a monoclinic anisotropic medium, we perform the seismic characterization of two nonorthogonal sets of rotationally invariant fractures based on the reflected amplitudes variation with offset and azimuth (AVOAz). Using the linear-slip theory, we first derive the effective elastic stiffness tensor as a function of background isotropic elastic moduli, normal and shear weakness parameters of horizontal and tilted fractures, and the dip angle. We then derive the first-order perturbations in elastic stiffness tensor and formulate the linearized PP-wave reflection coefficient based on the seismic scattering theory. Next, we propose a robust AVOAz inversion approach to characterize these two nonorthogonal fractures with rotationally invariant fractures. Finally, synthetic and real data examples are used to demonstrate that the background elastic moduli and fracture properties can be reasonably estimated using the azimuthal seismic reflected amplitudes. The new formulation and inversion approach may provide us a useful tool to characterize the naturally fractured reservoirs with monoclinic symmetry induced by horizontal and tilted fractures in a more reasonable manner than previous method. [ABSTRACT FROM AUTHOR]

Terrestrial lidar scanning (TLS) has become a widely accepted expert tool for monitoring geohazards on bare or sparsely vegetated slopes through change detection. While trees can be an important indicator of landslide activity at a slope, vegetation is often removed or ignored when monitoring landslides with TLS. This paper explores the use of multi-temporal terrestrial lidar scanning at a slope in the Peace River valley of British Columbia to test the author's hypothesis that tree stems in TLS data can be used to track landslide displacement and provide insight into the landslide mechanism. Six TLS datasets, each collected approximately 6 months apart, are used, and roto-translation methods are employed to determine the azimuth, plunge, and toppling angle of trees between each TLS scan. The tree displacement patterns are compared to TLS change detection results on bare-ground, and to single-point tracking techniques for extracting displacement vectors. Considerations for future applications are discussed. [ABSTRACT FROM AUTHOR]

Compton scattering of polarized radiation by a nondegenerate and unpolarized electron gas is examined. Two polarization bases are introduced for pulses of photons: external, connected with the geometry of the medium and internal, connected with a scattering event. Starting with a general relativistic kinetic equation describing the multiple effect of the mechanism taking induced processes into account, it is shown that for describing a stationary, azimuthally independent radiation field in a plane layer, two Stokes parameters for linear polarization are sufficient. The features of the redistribution functions (RF) in frequency and direction are clarified, as well as the rotation angles from internal bases to external ones, and back which arise with forward and backward scattering. An algorithm is proposed for eliminating singularities during azimuthal averaging. The azimuthal averages from the most singular term of the RF are expressed in terms of elliptical integrals of the first kind. [ABSTRACT FROM AUTHOR]

Due to the flexibility of the towed line array, shear currents caused by an internal solitary wave (ISW) distort the array shape. This will lead to a mismatch between the conventional target detection algorithm and the array shape, resulting in a significant decline in the performance of the towed line array gain, azimuth resolution, etc. Based on the improved motion model of towed cable constructed by Ablow and Schechter (Ocean Eng, 10: 443–457, 1983), we propose a motion model of the towed line array under an ISW according to the Korteweg-De Vries (KdV) equation and solve the model by finite difference method combined with the Newton iteration method. In addition, the DFT beamforming theory is used to detect the target signal after the array shape distortion compensation to verify the validity of the model. The data analysis shows that the array shape distortion caused by the ISW is mainly affected by the relative position between the array and the ISW, the amplitude of the ISW, the fluid layer density, the fluid layer depth, the towing velocity, the tangential/normal drag coefficient, the elastic modulus, and the towed cable density. The influence of elastic modulus and the towed cable density on array shape distortion can be ignored. The detection results show that the output signal power is about 6 dB higher than the output noise power, and the array gain and azimuth resolution are improved after array shape distortion compensation. [ABSTRACT FROM AUTHOR]

Values for Doppler center frequency are calculated from the echo signal at the satellite using the Doppler centroid method and so include the predicted Doppler frequency caused by the relative motion of the satellite and the Earth, which is the main component of Doppler center frequency and must be removed to obtain the Doppler frequency anomaly for ocean current measurement. In this paper, a new Doppler frequency anomaly algorithm was proposed when measuring surface currents with synthetic aperture radar (SAR). The key of the proposed algorithm involved mean filtering method in the range direction and linear fitting in the azimuth direction to remove the radial and the azimuthal component of predicted Doppler frequency from the Doppler center frequency, respectively. The basis is that the theoretical Doppler center frequency model of SAR exhibits an approximately linear characteristic in both the range direction and in the azimuth direction. With the help of the new algorithm for predicted Doppler frequency removal, the estimation error of Doppler frequency anomaly can be reduced by avoiding employing the theoretical antenna pattern and imperfect satellite attitude parameters in the conventional Doppler frequency method. SAR measurement results demonstrated that, compared to the conventional Doppler frequency with/without error correction method, the proposed algorithm allows for a pronounced improvement in the current measuring accuracy in comparison with the global ocean multi-observation (MOB) products. In addition, the effectiveness and robustness of the proposed Doppler algorithm has been demonstrated by its application in the high velocity current in the Kuroshio region. [ABSTRACT FROM AUTHOR]

The null ellipsometry technique of generalized ellipsometry based on using a compensator-free polarizer–sample–analyzer scheme for the case of incidence of an s- or p-polarized light on an anisotropic system is analyzed. Analytical expressions establishing a relation between measured angular quantity (analyzer azimuth at minimum intensity of detected radiation) and elements of the (2 × 2) anisotropic Jones matrix are derived. The dependence of this angular quantity on sample orientation (azimuth) is proposed to be used for determining optic-geometrical parameters of studied anisotropic systems. Sensitivity of the proposed method is estimated and is found to be comparable with that of the polarizer–compensator–sample–analyzer scheme. A comparative analysis of the discussed method with the well-known photometric method of generalized ellipsometry in the polarizer–sample–analyzer scheme based on measurement of the dependence of reflected-light intensity on sample azimuth at fixed polarizer and analyzer positions is presented. It is estimated that an error of a single arc minute in the proposed method and a relative error of determining the energy reflection coefficient of 0.05% in the photometric method of the generalized ellipsometry correspond to the same sensitivity. [ABSTRACT FROM AUTHOR]

In this paper, a two-dimensional direction-of-arrival (DOA) estimation algorithm based on nested acoustic vector-sensor (AVS) array is introduced. The minimum unit interval of the used nested AVS array is integral multiple of half-wavelength of signal. Firstly, four selection matrices are used to recombine four received vectors, by which four special cross-covariance matrices are obtained to form an extended block covariance matrix. Then, a set of parameters on elevation angles are estimated by traditional estimation of signal parameter via rotational invariance technique (ESPRIT) algorithm. Using these parameters, unambiguous elevation angles can be obtained without spectral peak search and added eigenvalue decomposition. At last, using the estimated elevation angles, the azimuth angles can be estimated by array manifold matching algorithm. The proposed algorithm can distinguish more signals than some existing ESPRIT algorithms. Many simulation results can prove the performance of the proposed algorithm in improving the accuracy of DOA estimation. Simulation results also show that the unit interval of optimal nested AVS array should be larger than half-wavelength of received signal. [ABSTRACT FROM AUTHOR]

A medium is called anisotropic when one or more of its physical properties change with the direction of measurement. The main anisotropy causes include presence of fracture, shale layers and induced stresses. Some conventional methods of anisotropy evaluation, are determination of Thomsens coefficients and the empirical relations. The high cost of coring and the lack of generalizability of empirical relations have led to turning to other methods of anisotropy estimation. In this research, considering the characteristic of shear wave splitting into two components in an anisotropic environment, the difference in the arrival time of shear wave components (fast and slow) is considered as a magnitude of anisotropy. Then, based on the anisotropy values obtained from the shear wave splitting, intelligent methods were used to estimate the anisotropy. By selecting the effective inputs with high correlation coefficient to anisotropy, the anisotropy values were predicted and compared by each of the stand-alone methods. Considering the high errors of each individual method, an ensemble of intelligent methods and meta-heuristic algorithms was used because of their high precision and generalizability. Also, the azimuth of the fast shear wave was used to determine the direction of the fractures and the principal stresses in the study area. A total of 42 data samples from one of the southwestern Iran oilfields was used to construct the Committee Machine with Intelligent System. Afterward, anisotropy was estimated utilizing four intelligent systems including: Artificial Neural-Network (ANN), Fuzzy Inference System (FIS), Adaptive Neuro-Fuzzy Inference System (ANFIS), Radial-basis Function (RBF) and two meta-heuristic algorithms including: Genetic Algorithm (GA) and Ant-Colony Optimization Routing (ACOR). The designed Committee Machine with Intelligent System (CMIS) includes four input parameters of porosity (φ)\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$(\mathrm{\varphi })$$\end{document}, clay volume (VClay)\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$({{\text{V}}}_{{\text{Clay}}})$$\end{document}, compressional wave velocity (VP)\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$({{\text{V}}}_{{\text{P}}})$$\end{document} and shear velocity (VS)\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$({{\text{V}}}_{{\text{S}}})$$\end{document}. The results show that among the estimator models, the ANN model has the highest correlation coefficient and the RBF model has the lowest Mean-Squared Error (MSE). Moreover, among the meta-heuristic algorithms, the GA model has the best optimization coefficient according to the values of correlation coefficient (≅\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\cong$$\end{document} 0.93) and minimum mean squared error (≅\documentclass[12pt]{minimal}\usepackage{amsmath}\usepackage{wasysym}\usepackage{amsfonts}\usepackage{amssymb}\usepackage{amsbsy}\usepackage{mathrsfs}\usepackage{upgreek}\setlength{\oddsidemargin}{-69pt}\begin{document}$$\cong$$\end{document} 0.0001). Finally, having the azimuth of the fast shear velocity (30°-50o North-East), the direction of the fracture and the principal-horizontal stress were identified. [ABSTRACT FROM AUTHOR]

In this paper we construct unstable shocks in the context of 2D isentropic compressible Euler in azimuthal symmetry. More specifically, we construct initial data that when viewed in self-similar coordinates, converges asymptotically to the unstable C 1 5 self-similar solution to the Burgers' equation. Moreover, we show the behavior is stable in C 8 modulo a two dimensional linear subspace. Under the azimuthal symmetry assumption, one cannot impose additional symmetry assumptions in order to isolate the corresponding manifold of initial data leading to stability: rather, we rely on modulation variable techniques in conjunction with a Newton scheme. [ABSTRACT FROM AUTHOR]

A general sliding block model for calculating permanent displacement of slope is presented. Ground shaking can be applied to base or block in a direction horizontal or parallel to the inclined plane, with or without a simultaneous vertical component of ground motion, and the azimuth of the examined slope can be considered in the model. The effects of the application of excitation, the vertical component of ground motions, and the slope azimuth on earthquake-induced permanent displacements of near-fault seismic slopes are investigated using the model. The results indicate that: (1) The application of excitation has significant influence on the permanent displacements. (2) The influence of the vertical component of ground motion on the permanent displacement depends more on the phase synchronization of the horizontal and vertical components than on the amplitude. (3) The computed displacements are found to be very sensitive to the azimuth of the slope. [ABSTRACT FROM AUTHOR]

Earthquakes of the 2015 Teresva series have been relocated using differential arrivals only of their P-waves at the same set of seismic stations and source-specific station terms. At least six distinct groups had been identified in the series as a result of single linkage clustering analysis of cross-correlations between their waveforms. Differential arrivals were estimated separately in each group, and not directly relative to the master event, but through the chains of events with the largest cross-correlations. Time drift at some Ukrainian stations had been detected by comparing intervals between the first P-waves from the same earthquakes at pairs of stations and taken into account, assuming a linear drift rate. The relocated epicenter of the main MSH3.5 earthquake was only ~ 2.3 km to the east of the macroseismic one and almost exactly at the intersection of the two major local faults, perpendicular and parallel to the Carpathians arc. The almost linear alignment of the other earthquakes in azimuth ~ 320° almost coincided with the parallel fault and with the nodal plane of the almost purely strike-slip focal mechanism estimated for the strongest earthquake from its first polarities at 26 stations, and by moment tensor inversion of the ground displacement amplitudes and duration of the first P-wave pulses at 18 stations. A very interesting oscillatory (cyclic) pattern of the epicenter migration along the SE–NW axis, obtained as a result of relocation, was also confirmed by variations in S-relative to P-wave delays: During the cycle, the epicenters gradually shifted to NW and at the beginning of the new cycle returned. [ABSTRACT FROM AUTHOR]

The diffraction of light by reflective holographic gratings in a layer placed between the coating and the substrate having refractive indices different from the average refractive index of the inserted layer is investigated. Significant differences between the reflection and transmission coefficients of the light diffracted on such a holographic grating with a change in the modulation amplitude of the refractive index of the layer, and the reflection and transmission coefficients of reflection gratings in matched structures are established. It is shown that at a large width of the layer in which the reflective holographic grating is located, there is a significant rotation of the plane of polarization of reflected and transmitted diffracted waves with a change in the modulation amplitude of the layer, caused by Fresnel reflection of light at the layer boundaries. [ABSTRACT FROM AUTHOR]

The influence of the detection direction on the quality of spectral data was not taken into account, which is catastrophic for some samples where the reflectivity direction was very different. To explore the directional characteristics of mixed pixels reflectivity, we used an ASD FieldSpec3 spectroradiometer to carry out multi-angle spectral measurement experiments in the laboratory, and the direction error model is established. As a result, the proportions of black area (PBA) and the observed azimuths (Φ) will affect the reflectivity of the mixed pixel in the visible light band. It is found that when the PBA is close to 0, the reflectivity distribution of mixed pixels is characterized by the reflected energy reflecting uniformly around the entire hemisphere space. When PBA is close to 1, there is a significant difference in the reflectivity of mixed pixels in 2π space. The direction error model better reflects the reflectivity changes caused by PBA and observed azimuth. The mean absolute error of the estimated reflectivity compared with the measured value is only 0.047. When the PBA is large, the estimation accuracy of the model is higher. When the PBA is small, and the observed azimuth is large, the accuracy of the model is slightly worse. The "two-block" mixed pixel is an ideal sample to satisfy the direction error model, while a dispersed "multi-block" mixed pixel is not applicable to the correction model. When conducting mixed pixel spectral measurement experiment, the influence of the detection azimuth on the spectral reflectivity should be fully considered, which is beneficial to improve the reliability of experiments on multi-angle spectral measurements of mixed pixels. [ABSTRACT FROM AUTHOR]

A solenoid magnetic field plays an important role in a non-line-of-sight azimuth transmission system based on polarization-maintaining fiber, which is directly related to the transmission accuracy of azimuth information. This research mainly studies the factors that affect the solenoid magnetic field according to the modulation signal from the direct current to the alternating current, as well as the hollow solenoid. First, the magnetic field components of the static solenoid are derived from the Biot–Savart law by using the uniform cylindrical current equivalent model. Then, the magnetic field of the near axial region is studied from the axial and radial directions, and the feasibility of calculating the magnetic field of the multi-layer solenoid with the superposition principle is verified by measuring the magnetic field of each position on the axis of the solenoid with a Gauss meter. Finally, the alternating electromagnetic field model is established using Maxwell's equations, and the magnetic and electric fields of the hollow solenoid are further solved. The results show that the magnetic field in the middle part of the magneto-optic glass is more stable, and the magnetic collecting ability of the solenoid is stronger. The magnetic field intensity at the center of the magneto-optic modulation solenoid of the system is the largest, and it decreases with the distance from the center. The alternating electromagnetic field is closely related to frequency. The results provide a reference for the study of the azimuth accuracy of a non-line-of-sight azimuth transmission system. [ABSTRACT FROM AUTHOR]