Function Of Azimuth Research Articles

Coupling Dynamics and Linear Polarization Phenomena in Codirectional Polariton Waveguide Couplers

AbstractIn this work, the previous studies investigating the potential of integrated devices using polariton waveguides that form codirectional couplers is extended. For suitable coupler parameters, a transfer of condensates between the arms of the coupler occurs leading to the observation of previously predicted Josephson‐like oscillations. The ability to tune the periodicity of these oscillations opens the way to the design of polaritonic circuits in which the directionality of the signal towards the output terminals can be controlled, for a fixed separation between the arms, varying the coupling length. The response of the devices to linearly polarized excitation is also investigated, delving into the dynamics of linear polarization at the output terminals of long couplers, providing valuable insights into their potential applications, including polariton switches and logic gates with efficient operation. The results are supported by numerical simulations based on the generalized Gross–Pitaevskii equation describing the dynamics of coherent polaritons in spatially non‐uniform systems, reproducing the polariton distribution on the output terminals and an oscillatory dependence of the corresponding emission as a function of the polarization azimuth. How the coupling and the controllable polarization degree of freedom in polariton couplers opens avenues for innovative optical architectures and functionalities is shown here.

Radial halo substructure in harmony with the Galactic bar

ABSTRACT Overdensities in the radial phase space $(r,v_{\rm r})$ of the Milky Way’s halo have previously been associated with the phase-mixed debris of a highly radial merger event such as Gaia Sausage–Enceladus. We present and test an alternative theory in which the overdense ‘chevrons’ are instead composed of stars trapped in resonances with the Galactic bar. We develop an analytic model of resonant orbits in the isochrone potential, and complement this with a test particle simulation of a stellar halo in a realistic barred Milky Way potential. These models are used to predict the appearance of action space $(J_\phi ,J_{\rm r})$ and radial phase space in the Solar neighbourhood. They are able to reproduce almost all salient features of the observed chevrons. In particular, both the analytic model and simulation predict that the chevrons are more prominent at $v_{\rm r}\ \lt\ 0$ when viewed near the Sun, as is observed by Gaia. This is inconsistent with formation by an ancient merger event. We also associate individual chevrons with specific resonances. At a bar pattern speed of $\Omega _\mathrm{b}=35$ km s$^{-1}$ kpc$^{-1}$, the two most prominent prograde chevrons align very closely with the corotation and outer Lindblad resonances. The former can be viewed as a highly eccentric extension of the Hercules stream. Finally, our model predicts that the $v_{\rm r}$ asymmetry changes sign as a function of Galactic radius and azimuth, and we find evidence that this is indeed the case in the Milky Way.

Empirical Green’s function analysis of some induced earthquake pairs from the Groningen gas field

We have applied the empirical Green’s function (EGF) method to 53 pairs of earthquakes, with magnitudes ranging from M = 0.4 to M = 3.4, induced by gas production from the Groningen field in the Netherlands. For a subset of the events processed, we find that the relative source time functions obtained by the EGF deconvolution show clear indications of a horizontal component of rupture propagation. The earthquake monitoring network used has dense azimuthal coverage for nearly all events such that wavelet duration times can be picked as a function of source-station azimuth and inverted using the usual Doppler broadening model to estimate rupture propagation strike, distance, and velocity. Average slip velocities have also been estimated and found to be in agreement with typical published values. We have used synthetic data, from both a simple convolutional model of the seismogram and more sophisticated finite difference rupture simulations, to validate our data processing workflow and develop kinematic models which can explain the observed characteristics of the field data. Using a measure based on the L1-norm to discriminate results of differing quality, we find that the highest quality results show very good alignment of the rupture propagation with directions of the detailed fault map, obtained from the full-field 3D seismic data. The dip direction rupture extents were estimated from the horizontal rupture propagation distances and catalogue magnitudes showing that, for all but the largest magnitude event (the M = 3.4 event of 8th January 2018), the dip-direction extent is sufficiently small to be contained wholly within the reservoir.

Post-auricular orientation of auditory attention in sound field versus virtual sound space

The post-auricular muscle in many species’ changes orientation of external ears to improve hearing for biologically relevant sounds. The muscle exists in humans but cannot similarly change direction of their ears. Objectives focused on measuring activity of muscle during speech-in-noise task where orientations of speaker and noise were controlled experimentally to determine how signal-to-noise varies as function of presentation mode and azimuth (target speech and noise co-localized, 45°, or spatially separated, 135° and 45°, respectively). It was hypothesized that activity would be elicited in same proportion of subjects when evoked via earphones compared to speakers; there would be no significant differences in magnitude between conditions; maximum engagement would be observed with speech 135°, noise 45°. Activity was recorded with electrodes affixed around ears, outer canthi and neck, while listeners completed a spatialized listening test (locations of speaker/noise controlled experimentally). There was significant main effect of channel; significant interaction between presentation mode and channel; no significant differences between presentation modes for other muscles; no significant effect of azimuth. Engagement in virtual sound-space suggests that muscle activation occurs consequently of spatially directed attention, even when changes in pinna orientation are unlikely to have effect on sound heard.

CVPCNN: Conditionally variational parameterized convolution neural network for HRRP target recognition with imperfect side information

Radar target recognition tasks often incorporate valuable side information (SI) that aids in the recognition task. The effectiveness of SI has been fully verified in traditional statistical modeling approaches. Its full potential remains untapped in deep learning-based high-resolution range profile (HRRP) target recognition tasks. Taking into account the azimuth sensitivity of HRRP, azimuth is chosen as the SI of the proposed model. To integrate SI into deep neural networks, we propose two novel parameterized convolution methods, namely variational parameterized convolution (VPCONV) and the extended conditionally VPCONV (CVPCONV). Specifically, VPCONV makes the convolutional kernel weights as the function of the auxiliary azimuth, which gives the network the capability of adaptively adjusting to changes in azimuth. Acknowledging the challenge of estimating HRRP azimuth accurately in practical scenarios, VPCONV employs a heteroscedastic Gaussian distribution, featuring varying mean and variance, to generalize the estimation error of SI through variational encoding. Moreover, CVPCONV incorporates the properties of the HRRP samples themselves by kernel attention module. Finally, we present a lightweight SI-based network. The experimental results based on the measured HRRPs validate the effectiveness of proposed method across various extended recognition tasks, underscoring the potential of fusing SI via parameterized convolution in advancing target recognition systems.

RAM‐SCB Runs on Request at CCMC

AbstractThe Ring current–Atmosphere interactions Model (RAM) with Self‐Consistent magnetic (B) field (SCB) combines a large‐scale kinetic model of ring current plasma with a three‐dimensional (3‐D) force‐balanced model of the terrestrial magnetic field. RAM‐SCB simulates the evolution of major ion species (H+, O+, and He+ by default) and electrons as a function of azimuth, radial distance, energy, and pitch angle. Simulation outputs include the Dst index, and pressure and differential flux of the modeled species, thus providing benefit as a science code and to inform surface charging hazard within the model domain. Version 2.2 of this open‐source simulation code has now—as of 8 August 2023—been made available for Runs‐On‐Request via the Community Coordinated Modeling Center.

S Hmax orientation in the Alpine region from observations of stress-induced anisotropy of nonlinear elasticity

SUMMARY The orientation of SHmax is commonly estimated from in situ borehole breakouts and earthquake focal mechanisms. Borehole measurements are expensive, and therefore sparse, and earthquake measurements can only be made in regions with many well-characterized earthquakes. Here, we derive the stress-field orientation using stress-induced anisotropy in nonlinear elasticity. In this method, we measure the strain derivative of velocity as a function of azimuth. We use a natural pump-probe (NPP) approach which consists of measuring elastic wave speed using empirical Green’s functions (probe) at different points of the earth tidal strain cycle (pump). The approach is validated using a larger data set in the Northern Alpine Foreland region where the orientation of maximum horizontal compressive stress is known from borehole breakouts and drilling-induced fractures. The technique resolves NNW-SSW to N-S directed SHmax which is in good agreement with conventional methods and the recent crustal stress model. We confirm that the NPP method can be applied to dense large-scale seismic arrays. The technique is then applied to the Southern Alps to understand the contemporary stress pattern associated with the ongoing deformation due to counterclockwise rotation of the Adriatic plate with respect to the European plate. Our results explain why the two major faults in Northeastern Italy, the Giudicarie Fault and the Periadriatic Line (Pustertal–Gailtal Fault) are currently inactive, while the currently acting stress field allows faults in Slovenia to deform actively. We have demonstrated that the pump-probe method has the potential to fill in the measurement gap left by conventional approaches, both in terms of regional coverage and in depth.

Investigating the IBEX Ribbon Structure a Solar Cycle Apart

A “Ribbon” of enhanced energetic neutral atom (ENA) emissions was discovered by the Interstellar Boundary Explorer in 2009, redefining our understanding of the heliosphere boundaries and the physical processes occurring at the interstellar interface. The Ribbon signal is intertwined with that of a globally distributed flux (GDF) that spans the entire sky. To a certain extent, Ribbon separation methods enabled examining its evolution independent of the underlying GDF. Observations over a full solar cycle revealed the Ribbon’s evolving nature, with intensity variations closely tracking those of the solar wind (SW) structure after a few years delay, accounting for the SW–ENA recycling process. In this work, we examine the Ribbon structure, namely its ENA fluxes, angular extent, width, and circularity properties for two years, 2009 and 2019, representative of the declining phases of two adjacent solar cycles. We find that, (i) the Ribbon ENA fluxes have recovered in the nose direction and south of it down to ∼25° (for energies below 1.7 keV) and not at mid and high ecliptic latitudes; (ii) the Ribbon width exhibits significant variability as a function of azimuthal angle; (iii) circularity analysis suggests that the 2019 Ribbon exhibits a statistically consistent radius with that in 2009. The Ribbon’s partial recovery is aligned with the consensus of a heliosphere with its closest point being southward of the nose region. The large variability of the Ribbon width as a function of azimuth in 2019 compared to 2009 is likely indicative of small-scale processes within the Ribbon.

Wave interference at the contralateral ear helps explain non-monotonic envelope interaural time differences as a function of azimuth.

Interaural time differences (ITDs), an important acoustic cue for perceptual sound-source localization, are conventionally modeled as monotonic functions of azimuth. However, recent literature and publicly available databases from binaural manikins demonstrated ITDs conveyed by the envelopes (ENV-ITDs) of high-frequency (≥2 kHz) signals that were non-monotonic functions of azimuth. This study demonstrates using a simple, time-dependent geometric model of an elliptic head that the back-traveling (longer) sound path around the head, delayed and added to the conventionally treated front-traveling path, can account for non-monotonic ENV-ITDs. These findings have implications for spatial-hearing models in acoustic and electric (cochlear-implant) hearing.

Wavelength‐Dependent Photocurrent Generation Efficiency in the Carbon Nanowall Films

Herein, the efficiency of generation of unipolar photocurrent pulses under action of obliquely incident nanosecond laser pulses is studied in carbon nanowall (CNW) films on silicon substrate depending on the direction of the wave vector and polarization of the laser radiation. The films consist of flake‐like graphite crystallites of nanometer thickness. Each of the crystallites comprises stacked graphene atomic sheets oriented mostly perpendicular to the substrate surface with random orientation in other directions. The angular and polarization dependencies of the longitudinal and transverse photocurrents at wavelengths of 266, 354.7, 532, and 1064 nm are measured. The longitudinal and transverse photocurrents are odd functions of the incidence angle, and, for a given angle of incidence, they are even and odd functions of the polarization azimuth, respectively. It is noteworthy that with the decrease in exciting radiation wavelength, the conversion coefficients of laser pulse power into longitudinal and transverse photocurrents increase and decrease, respectively. At wavelength of 266 nm, the transverse photocurrent changes its polarity, and the longitudinal photocurrent generated by s‐polarized radiation exceeds the p‐polarized radiation photocurrent. The obtained results are explained by morphology peculiarities of the CNW films and the surface photogalvanic effect photocurrent generation.

Maximum energy yield of PV surfaces in France and Italy from climate based equations for optimum tilt at different azimuth angles

In the present paper, the problem of the determination of yearly maximum energy producibility in terms of optimum tilt angle for solar surfaces is addressed with reference to 216 locations in France and Italy. Original correlations are proposed to calculate the optimal surface slope as a correction parameter to be applied to the local latitude angle. The correction factor formulas are based on local climate conditions and have been inferred from local monthly insolation data (12-year global and diffuse irradiance, PV-GIS-SARAH platform). An optimization problem is solved aimed at maximizing the yearly collectable energy by a sloped surface, in a range of azimuth values (from South Facing to East Facing), for all the selected locations. Different equation forms have been investigated and compact and accurate formulas have been developed able to provide the optimal tilt as a function of latitude, surface azimuth and clearness parameters. The accuracy of the proposed formulas resulted in a correlation coefficient with respect to the “exact” tilt angles higher than 0.93 for azimuth angles till 60°. Proposed formulas allow up to a 4% increase in collectable solar energy, corresponding, as an example, to a virtual increase in PV module efficiency from 21% to 21.8%.

A Source Study of the Mw 7.0 Acapulco, Mexico, Earthquake of 8 September 2021

AbstractThe Acapulco earthquake of 2021 broke a segment of the southeast Guerrero seismic gap along the Mexican subduction thrust. The rupture initiated offshore Acapulco (16.770° N, 99.942° W) and propagated down-dip toward northeast. This source directivity is confirmed from both (1) an analysis of local and regional recordings as a function of azimuth and (2) kinematic inversion of near-source, band-pass filtered (0.025–0.5 Hz) displacement seismograms and Global Positioning System static coseismic displacement vectors. The inversion reveals little slip near the hypocenter (<0.5 m) and significant slip distributed over an area of ∼184 km2, with the large slip patches in the northeast part of the fault. The estimated average slip and static stress drop are 260 cm and 18.6 MPa, respectively. Moment rate function reported by National Earthquake Information Center–U.S. Geological Survey from finite-fault modeling is simple, and it resembles other Mexican subduction earthquakes in the 7.0 ≤ M ≤ 7.5 range. Moment rate spectrum is well fit by the Brune ω−2 source model. Radiated seismic energy from teleseismic P waves is 7.5×1014 J, and ER/M0 is 2.1×10−5. Radiated energy enhancement factor—a measure of source complexity—is small, 5.8, similar to other Mexican subduction thrust earthquakes. Seismograms at DeBilt of the 2021 and the 11 May 1962 Acapulco earthquakes show an extraordinary similarity, seldom seen at M 7.0 level. The 2021 earthquake seems a repeat of the 1962 earthquake. The slip deficit since 1962 corresponding to a plate convergence rate of 6.2 cm/yr and perfect coupling is 366 cm. Thus, the seismic slip of 260 cm during that 2021 earthquake suggests a coupling ratio of 0.7, greater than 0.3 and 0.5 reported from geodetic measurements. Large moment release in the southeast seismic gap appears to have a periodicity of ~60 yr. Because 60 yr have elapsed since the last sequence earthquakes (1957 MS 7.5; 1962 MS 7.0 and 6.8), a renewal of large earthquakes in the region may be expected.

Performance investigation of SUNTRAP module for different locations: An energy and exergy analysis

Concentrating Photovoltaic/Thermal (CPV/T) systems can harness the freely available solar energy to simultaneously generate electricity and sensible heat. Using the principles of optical concentration, they can generate more electrical energy per unit area of solar cells and provide a better quality of thermal energy. In this work, we have developed an analytical model to simulate and predict the performance of a dense array hybrid CPV/T collector called “SUNTRAP.” The concentration of incident radiation is achieved using a reflective type three-dimensional cross-compound parabolic concentrator (3DCCPC) with a geometric concentration ratio of 3.6 × . The extraction of heat from the solar cells is achieved by allowing water to flow through the copper cooling duct on which the solar cells with CCPC are bonded. Using previously developed algorithms, the optical efficiency of the CCPC is calculated as a function of solar azimuth and altitude angle. The obtained optical efficiency is coupled to the thermal model to obtain the temperature distribution in the collector. The numerical results are in good agreement with the experimental measurements obtained at the outdoor solar laboratory at Penryn Campus, Cornwall. The average deviation in outlet water temperature between the numerical and experimental ones is 1.9%. The total electrical and thermal energy obtained from the CCPC-PV/T module on an experimental day is 1.21 kWh/m2 and 46.46 kWh/m2. A parametric study was done to obtain the effect of flow rate and external wind velocity on the performance of the collector. The solar cell temperature is found to decrease with an increasing flow rate. The performance prediction of the CCPC-PV/T module at Penryn shows that the module produced maximum energy in August, producing 7.51 kWh/m2 of useful energy. An economic analysis was performed to obtain the Levelized cost of electricity (LCOE) that the CCPC-PV/T module can deliver, and the LCOE was found to be £1.08/kWh. The coupled model is also utilised to predict the performance of the system for five different geographical locations, including Chennai, Rome, Alice Springs, Montreal, and Barrow. The model considers optimum panel tilt and time-dependent optical efficiency of the concentrator while estimating the energy output. Based on the results, the overall performance of the collector was found to be good in Chennai, with an annual electrical energy gain of 51.95 kWh/m2 and an annual thermal energy gain of 1164 kWh/m2.

Weighing the Galactic disk using phase-space spirals

We have applied our method to weigh the Galactic disk using phase-space spirals to the proper motion sample of Gaia’s early third release (EDR3). For stars in distant regions of the Galactic disk, the latitudinal proper motion has a close projection with vertical velocity, such that the phase-space spiral in the plane of vertical position and vertical velocity can be observed without requiring that all stars have available radial velocity information. We divided the Galactic plane into 360 separate data samples, each corresponding to an area cell in the Galactic plane in the distance range of 1.4–3.4 kpc, with an approximate cell length of 200–400 pc. Roughly half of our data samples were disqualified altogether due to severe selection effects, especially in the direction of the Galactic centre. In the remainder, we were able to infer the vertical gravitational potential by fitting an analytic model of the phase-space spiral to the data. This work is the first of its kind, in the sense that we are weighing distant regions of the Galactic disk with a high spatial resolution, without relying on the strong assumptions of axisymmetry. Post-inference, we fitted a thin disk scale length of 2.2 ± 0.1 kpc, although this value is sensitive to the considered spatial region. We see surface density variations as a function of azimuth of the order of 10–20%, which is roughly the size of our estimated sum of potential systematic biases. With this work, we have demonstrated that our method can be used to weigh distant regions of the Galactic disk despite strong selection effects. We expect to reach even greater distances and improve our accuracy with future Gaia data releases and further improvements to our method.

Wind-Direction Estimation from Single X-Band Marine Radar Image Improvement by Utilizing the DWT and Azimuth-Scale Expansion Method.

In this study, a method based on the discrete wavelet transform (DWT) and azimuth-scale expansion is presented to retrieve the sea-surface wind direction from a single X-band marine radar image. The algorithm first distinguishes rain-free and rain-contaminated radar images based on the occlusion zero-pixel percentage and then discards the rain-contaminated images. The radar image whose occlusion areas have been removed is decomposed into different low-frequency sub-images by the 2D DWT, and the appropriate low-frequency sub-image is selected. Images collected with a standard marine HH-polarized X-band radar operating at grazing incidence display a single intensity peak in the upwind direction. To overcome the influence of the occlusion area, before determining the wind direction, the data near the ship bow are shifted to expand the azimuth scale of the data. Finally, a harmonic function is least-square-fitted to the range-averaged radar return of the low-frequency sub-image as a function of the antenna look azimuth to determine the wind direction. Different from the wind-direction retrieval algorithms previously presented, this method is more suitable for sailing ships, as it functions well even if the radar data are heavily blocked. The results show that compared with the single-curve fitting algorithm, the algorithm based on DWT and azimuth-scale expansion can improve the wind-direction results in sailing ships, showing a reduction of 7.84° in the root-mean-square error with respect to the reference.

A creeping-wave elliptic-head model that explains non-monotonic envelope interaural time differences

Interaural time and level differences (ITDs and ILDs) created by interactions of impinging sound with the head facilitate horizontal-plane sound localization. ILDs are known to be non-monotonic functions of azimuth, resulting in predictable mislocalization of tonal sources at some frequencies, while ITDs are typically construed as monotonic functions of azimuth. However, recent measurements using a binaural mannequin revealed envelope ITDs (ENV-ITDs) that were non-monotonic functions of azimuth, with the extent of nonmonotonicity dependent on carrier frequency. This study proposes that delayed sound traveling around the back of the head causes this phenomenon. ENV-ITDs created by a time-dependent model of incident sound waves propagating around the front and back of an elliptical head were compared to ENV-ITDs computed using publicly available HRTF libraries for a broadband speech excitation signal. Results from the model align with data from the HRTF libraries, with nonmonotonicities in the ENV-ITD-azimuth functions occurring at nearly identical azimuths and frequencies. These data suggest the veracity of this phenomenon and may have implications for spatial hearing abilities. They also suggest that time-independent models of ITDs that only consider frequency and incident angle, such as spherical head or circular arc length models, could be updated to include such time dependence.

Front-back reversals for tones heard in a room by moving listeners

The tone localization experiments reported by Macaulay and Hartmann [J. Acoust. Soc. Am. 149, 4159–4179 (2021)] were highly biased in favor of sources in front of the listener. Nevertheless, listeners sometimes localized tones in back, both when they were stationary and when they were required to move. The experiments provided extensive data relevant to the matter of in-back localization, because they measured head location and orientation as well as ear canal signals throughout each experiment trial. Because the experiments were done in a room, the data were irregular functions of source azimuth. Analysis revealed the following effects: For stationary trials, back responses were strongly correlated with weaker tone levels in the ear canals for 500, 2000, and 4000 Hz. Correlation was greatly reduced at 1000 Hz. That result is consistent with head-related transfer functions, where ear-canal intensity is greater for sounds in front except near 1000 Hz. For moving trials, back responses at 500 and 1000 Hz were strongly correlated with the slopes of interaural level differences and interaural time differences as functions of head-pointing direction, as naturally occur in free field. Correlations decreased dramatically at higher frequencies.

Development of an electromechanical test system and acoustical metrics to predict impacts of hearing protection devices on sound localization

Hearing protection devices (HPDs) such as earplugs and earmuffs can protect users from dangerously high acoustical pressures but also distort cues important for the spatial localization of sounds, likely through spectral distortions associated with occlusion of the pinnae. Evaluation of the degree to which an HPD distorts localization cues is essential for critical situations where users must be protected from high pressures but maintain spatial awareness. Automated testing offers several prospective advantages over human subject testing including cost, speed, and repeatability. In this paper, we describe an electromechanical system using a rotating manikin test fixture and a speaker on a track to simulate a hemispheric speaker array. The sound source localization impact of an HPD is estimated by comparing test signals recorded by the manikin with and without an HPD in place. Test results, as a function of sound source azimuth and elevation in the virtual speaker array, and as an average across locations, are shown for a variety of HPDs. Results are compared to an initial set of parallel measurements of sound localization during HPD use in human subjects.

Analysis of underwater sounds from impact pile driving at the Block Island Wind Farm

Impact pile driving creates intense, impulsive sound that radiates into the surrounding environment. Piles driven vertically into the seabed generate an azimuthally symmetric underwater sound field whereas piles driven on an angle will generate an azimuthally dependent sound field. Measurements were made during impact pile driving of raked piles to secure jacket foundation structures to the seabed at the Block Island Wind Farm at ranges between 500 m and 15 km. These measurements were analyzed to investigate variations in rise time, decay time, pulse duration, kurtosis, and sound received levels as a function of range and azimuth. Variations in the radiated sound field along opposing azimuths resulted in differences in measured sound exposure levels of up to 10 dB and greater due to the pile rake as the sound propagated in range. The raked pile configuration was modeled using an equivalent axisymmetric FEM model to describe the azimuthally dependent measured sound fields and compared to the measured data. These measurements made during wind farm construction will be presented and discussed. [Work supported by the Bureau of Ocean Energy Management.]

Making the Urban Sky View Factor With Numerical Models Consistent With Radiation Heat Transfer Theory

Abstract This work proposes a method for removing the inconsistency between the numerical models used for determining the sky view factor (SVF) in an urban environment and fundamental radiation heat transfer theory. For this purpose, a transformation of the coordinate system from global to surface was developed, which corrected the measurement of the angular coordinates of the elements in the discretized sky vault. The transformation was deployed in a published numerical model and was validated in a non-urban environment with a widely used analytical expression for the SVF, with which it was found to be in excellent agreement. The method was subsequently applied to an urban scenario, and the results were compared with the original numerical model. The proposed method provides a better determination of the SVF as a function of the surface azimuth and tilt angle.