Large Array Research Articles

Spectral Index Asymmetries in Double Radio Sources from the VLA Sky Survey

A sample of double radio sources was selected from the Very Large Array Sky Survey to investigate correlations of spectral asymmetries with lobe length ratios and jet-sidedness. The lobe length ratio informs us about the correlation between the lobe pressure and spectral index of FRII lobes from Active Galactic Nuclei. A second analysis was done on the subset with identifiable jets. The correlation of lobe length ratio with spectral index difference was weakly positive, although statistically insignificant. Similarly, there were no statistically significant trends of spectral index difference with jet-sidedness. Further testing with a larger data set may produce a more significant result.

MODELLING OF SOCIO-PSYCHOLOGICAL ADAPTATION OF AN INDIVIDUAL TO DIGITAL RISKS IN EDUCATION AND PROFESSIONAL SELF-DETERMINATION

Automated semantic analysis and topic modelling methods were first applied to a large corpus of public online communities and discussions to analyse strategies for responding to digital risks in modern society. A large array of public data on profiles of the social network “Vkontakte” and their subscriptions to online communities was used to train a predictive model of individual adaptation to risks in the field of education and professional self-determination. Based on the results of thematic modelling, three topics of subscriptions to online communities were identified as signs of psychological adaptation: preparation for exams, self-development and “popular” psychology, education and science. The developed version of the predictive model of psychological adaptation showed high accuracy and the importance of such factors as age, gender and place of residence for individual adaptation to digital risks in the field of education and professional self-determination.

Inflation, Fiscal Policy, and Inequality: The Impact of the Post‐Pandemic Price Surge and Fiscal Measures on European Households

AbstractFollowing the inflation surge in the aftermath of the pandemic crisis, Euro Area governments adopted a large array of fiscal measures to cushion its impact on households. The inflationary shock and related fiscal measures affected households differently depending on their country, their consumption patterns, and their position in the income distribution. This paper uncovers the aggregate and distributional impact of this inflationary shock, as well as the impact of the government measures aimed at supporting households and containing prices. The analysis is carried out for 2022 and includes Germany, France, Italy, Spain, Portugal, and Greece. Our work confirms that the purchasing power and welfare of low‐income households was more severely affected than that of high‐income households. Fiscal measures contributed significantly to closing this gap, though with country differences. However, most fiscal measures were not particularly targeted at low‐income households, implying a low cost‐effectiveness in protecting the poorest in some countries.

Large aperture microphone array measurement at operating airport for sound source model creation of J-FRAIN

In 2022, authors conducted microphone array measurements at an operating airport to create sound source models for commercial aircraft based on the noise prediction framework J-FRAIN. A similar measurement was also performed by our colleagues in 2019, but it was a trial to establish the concept of the framework and was done using a microphone array in which the number of microphones was reduced to about half. In order to improve the accuracy of the sound source models, the microphone array with a 30-meter diameter consisting of 195 microphones mounted on the ground was used in 2022. Recording-based simultaneous noise measurement using sound level meters was also performed around the airport to validate prediction results in terms of time histories of 1/3 octave band sound pressure levels. This paper describes an overview of the microphone array measurements conducted in 2022 and a case study of noise prediction around the airport using sound source models created from the data of microphone array measurements conducted in 2022. Predicted results are compared with 1/3 octave band data measured using sound level meters mounted at a height of 4 m above the ground at sites of noise monitoring stations around the airport.

An investigation of the performances of asynchronous measurements methods

In acoustical imaging and source localization, several methods for the exploitation of asynchronous array measurements have been proposed, based on covariance matrix completion, Bayesian estimation, fusion of beamforming maps, etc. The goal of asynchronous measurements is to reach the performance of large and dense arrays, with reduced experimental effort, by moving an array of limited size between experiments, and fuse the obtained data to produce an estimation of the distribution of acoustical sources. In this study, we consider the performances that one can expect from asynchronous measurements, and investigate the actual performances of several methods from the state of the art. In particular, the mean squared errors of the estimation of the position and power of an acoustical source are estimated using simulations and experimental measurements.

Application of tracer studies results for adaptation of hydrodynamic models of oil fields

To date, a large array of tracer results has been accumulated, which are mainly processed analytically without further use in numerical hydrodynamic modelling, despite the fact that most commercial hydrodynamic simulators have modules for tracer modelling, which is undoubtedly an omission. Using the results of tracer studies makes it possible to select a filtration model, to specify both filtration-capacitance properties of productive sediments of the interwell space and the type of void space, which can serve as valuable factual material for analyses and development design.

SPH modelling of AGB wind morphology in hierarchical triple systems and a comparison to observation of R Aql

Complex asymmetric 3D structures are observed in the outflows of evolved low- and intermediate-mass stars, and are believed to be shaped through the interaction of companions that remain hidden within the dense wind. One example is the AGB star R Aql, for which ALMA (Atacama Large Millimeter Array) observations have revealed complex wind structures that might originate from a higher-order stellar system. We investigate how triple systems can shape the outflow of asymptotic giant branch (AGB) stars and characterise the different wind structures that form. For simplicity, we solely focus on co-planar systems in a hierarchical, stable orbit, consisting of an AGB star with one relatively close companion, and another one at a large orbital separation. We modelled a grid of hierarchical triple systems including a wind-launching AGB star, with the smoothed-particle-hydrodynamic Phantom code. We varied the outer companion mass, the AGB wind velocity, and the orbital eccentricities to study the impact of these parameters on the wind morphology. To study the impact of adding a triple companion, we additionally modelled and analysed a small grid of binary sub-systems, for comparison. To investigate if R Aql could be shaped by a triple system, we post-processed one of our triple models with a radiative transfer routine, and compared this to data of the ALMA ATOMIUM programme. The characteristic wind structures resulting from a hierarchical triple system are the following. A large two-edged spiral wake results behind the outer companion star. This structure lies on top of the spiral structure formed by the close binary, which is itself affected by the orbital motion around the system's centre of mass, such that it resembles a snail-shell pattern. This dense inner spiral pattern interacts with, and strongly impacts, the spiral wake of the outer companion, resulting in a wave pattern on the outer edge of this spiral wake. The higher the mass of the outer companion, the larger the density enhancement and the more radially compressed the outer spiral. Lowering the wind velocity has a similar effect, and additionally results in an elongation of the global wind morphology. Introducing eccentricity in the inner and outer orbit of the hierarchical system results in complex phase-dependent wind-companion interactions, and consequently in asymmetries in the inner part of the wind and the global morphology, respectively. From the comparison of our models to the observations of R Aql, we conclude that this circumstellar environment might be shaped by a similar system to the ones modelled in this work, but an elaborate study of the observational data is needed to better determine the orbital parameters and characteristics of the central system. The modelled outflow of an AGB star in a co-planar hierarchical systems is characterised by a large-scale spiral wake with a wavey outer edge, attached to the outer companion, on top of a compact inner spiral pattern that resembles a snail-shell pattern.

A radar array expansion design method based on modular subarray layout

Abstract This paper introduces a design method for expandable subarray structures used in phased array radar arrays. Based on the structural characteristics of modular subarray layout for large radar arrays, this paper analyzes the assembly dimension chain tolerance based on subarray expansion. One third of the allowable deviation of the radar array is used as the subarray design tolerance, and the size tolerance of each installation surface of the subarray is designed according to the design tolerance. Finally, the subarray array is assembled into any size of radar array, and the probability of the radar array assembly accuracy meeting the allowable deviation is 99.73%. For large radar arrays, adopting this design method can significantly reduce the tolerance span between the sub array and the area array, greatly reducing the difficulty of design and processing. This paper provides a fundamental design method for the expansion design of radar arrays with similar systems, which has universal applicability.

Magnetic Field of the Quasar 1604+159 from Parsec to Kiloparsec Scale

Abstract We present a multifrequency polarimetric study for the quasar 1604+159. The source was observed at the L band with the American Very Long Baseline Array and the L, X, and U bands with the Very Large Array. These observations provide different resolutions from mas to arcsec, enabling us to probe the morphology and magnetic field from tens of parsec to hundreds of kiloparsec scale. We detect a symmetrical Fanaroff–Riley Class I–like structure. The source has several lobes and bulges, forming a cocoon shape. The polarization is normal to the edges of the structure with high fractional polarization up to ∼60%. Two hotspots are observed at the eastern and western sides of the source, located symmetrically relative to the core. The flux density ratio (>1.5) between the two hotspots suggests the Doppler beaming effect exists at a large scale. The polarized emission in the hotspots also shows a symmetrical structure with an oblique direction from the jet direction. In general, the jet propagates in a collimating structure with several bends. Polarization is also detected perpendicular to the local jet from ∼100 mas to ∼1″. The jet shows strong polarized intensity and high fractional polarization at the bending edges. We discuss the possible origins of the observed structure and magnetic field.

Multiwavelength identification of millisecond pulsar candidates in the Galactic bulge

Context. The existence of a population of millisecond pulsars in the Galactic bulge is supported, along with other evidence, by the Fermi GeV excess, an anomalous γ-ray emission detected almost 15 years ago in the direction of the Galactic center. However, radio surveys searching for pulsations have not yet revealed bulge millisecond pulsars. Aims. Identifying promising bulge millisecond pulsar candidates is key to motivating pointed radio pulsation searches. Candidates are often selected among steep-spectrum or polarized radio sources, but multiwavelength information can also be exploited: The aim of this work is to pinpoint strong candidates among the yet unidentified X-ray sources. Methods. We investigated the multiwavelength counterparts of sources detected by the Chandra X-ray observatory that have spectral properties expected for millisecond pulsars in the Galactic bulge. We considered that ultraviolet, optical, and strong infrared counterparts indicate that an X-ray source is not a bulge pulsar, while a radio or a faint infrared counterpart makes it a promising candidate. Results. We identify a large population of more than a thousand X-ray sources without optical, ultraviolet, or strong infrared counterparts. Among them, five are seen for the first time in unpublished radio imaging data from the Very Large Array. We provide the list of promising candidates, for most of which follow-up pulsation searches are ongoing.

Surface Properties of the Kalliope–Linus System from ALMA and VLA Data

The abundance and distribution of metal in asteroid surfaces can be constrained from thermal emission measurements at radio wavelengths, informing our understanding of planetesimal differentiation processes. We observed the M-type asteroid (22) Kalliope and its moon Linus in thermal emission at 1.3, 9, and 20 mm with the Atacama Large Millimeter/submillimeter Array and the Karl G. Jansky Very Large Array over most of Kalliope's rotation period. The 1.3 mm data provide ∼30 km resolution on the surface of Kalliope, while both the 1.3 and 9 mm data resolve Linus from Kalliope. We find a thermal inertia for Kalliope of 116−91+326 J m−2 s−0.5 K−1 and emissivities of 0.65 ± 0.02 at 1.3 mm, 0.56 ± 0.03 at 9 mm, and 0.77 ± 0.02 at 20 mm. Kalliope's millimeter wavelength emission is suppressed compared to its centimeter wavelength emission, and is also depolarized. We measure emissivities for Linus of 0.73 ± 0.04 and 0.85 ± 0.17 at 1.3 and 9 mm, respectively, indicating a less metal-rich surface composition for Linus. Spatial variability in Kalliope’s emissivity reveals a region in the northern hemisphere with a high dielectric constant, suggestive of enhanced metal content. These results are together consistent with a scenario in which Linus formed from reaggregated ejecta from an impact onto a differentiated Kalliope, leaving Kalliope with a higher surface metal content than Linus, which is distributed heterogeneously across its surface. The low emissivity and lack of polarization suggest a reduced regolith composition where iron is in the form of metallic grains and constitutes ∼25% of the surface composition.

From 100 MHz to 10 GHz: Unveiling the spectral evolution of the X-shaped radio galaxy in Abell 3670

Context. X-shaped radio galaxies (XRGs) are characterised by two pairs of misaligned lobes: active lobes hosting radio jets and the wings. None of the formation mechanisms proposed thus far are able to exhaustively reproduce the diverse features observed among XRGs. Emerging evidence has proposed the existence of sub-populations of XRGs forming via different processes. Aims. The brightest cluster galaxy (BCG) in Abell 3670 (A3670) is a dumbbell system hosting the XRG MRC 2011-298. The morphological and spectral properties of this interesting XRG were first characterised based on Karl G. Jansky Very Large Array (JVLA) data at 1–10 GHz. In the present work, we follow up on MRC 2011-298 with the upgraded Giant Metrewave Radio Telescope (uGMRT) at 120–800 MHz to further constrain its properties and origin. Methods. We carried out a detailed spectral analysis sampling different spatial scales. Integrated radio spectra, spectral index maps, radio colour-colour diagrams, and radiative age maps of both the active lobes and prominent wings were employed to test the origin of the source. Results. We confirm a progressive spectral steepening from the lobes to the wings. The maximum radiative age of the source is ~80 Myr, with the wings being older than the lobes by ≳30 Myr in their outermost regions. Conclusions. The observed properties are in line with an abrupt reorientation of the jets by ~90 deg from the direction of the wings to their present position. This formation mechanism is further supported by the comparison with numerical simulations in the literature, which additionally highlight the role of hydrodynamic processes in the evolution of large wings such as those of MRC 2011-298. It is plausible that the coalescence of supermassive black holes could have triggered the spin-flip of the jets. Moreover, we show that the S-shape of the radio jets is likely driven by precession with a period of P ~ 10 Myr.

New readout system of the FATIMA detectors based on Silicon Photomultipliers arrays

We present a new readout system based on large area Silicon Photomultipliers arrays coupled with cylindrical 1.5 × 2” LaBr3(Ce) FATIMA-type crystals. This achieves the fast-timing capabilities of such crystals coupled to the usual Photomultiplier Tubes. Energy calibration was measured with 137Cs and 152Eu standard radioactive sources, while the timing performances were investigated with a 60Co radioactive source. We benchmark our results against the corresponding results obtained with the fast R9779 Photomultiplier tubes and highlight the importance of achieving similar energy and timing performances for nuclear structure experiments. The FWHM energy resolution for the 1.5 × 2” LaBr3(Ce) crystal coupled with the SiPM and PMT was found to be 3.31(2)% and 3.85(1)%, respectively, for the 661.6 keV transition of the 137Cs source. The timing resolution was measured between a conical crystal known for its fast response and a cylindrical crystal coupled to a SiPM or PMT readout. We obtain values of FWHM = 230(1) ps and 232(1) ps, respectively, between the 1173.2-1332.5 keV transitions of the 60Co source. In addition, a temperature effect compensation circuit was developed to maintain a good stability of the gain during long measurements, typical for in-beam/off-beam experiments in nuclear physics.

Optical pump magnetometers parametric correction method based on three-axis coil arrays

Optical pump magnetometers (OPMs), based on the SERF principle, are increasingly prevalent in biomagnetic field detection and localization studies. However, cross-axis crosstalk is an unavoidable consequence of the non-ideal factors introduced during the development of the sensor array, whether during the initial design or manufacturing process. This study introduce a novel method to compensate for cross-axis crosstalk by a set of three-axis coils.The gain matrix of each sensor in an OPM array is calibrated by the magnetic field generated by the activation of the three-axis coils. The results showed that the correlation coefficients between the corrected coil distribution field measurements and the true values improved substantially, exceeding 0.99. Similarly, the similarity between the forward-field simulation and the measured results for the localization of a physical model of a current dipole improved significantly, from 0.78 to 0.96. This work presents the first report of the simultaneous calibration of a large OPM array comprising 64 OPMs. The suppression of cross-axis crosstalk errors improves the sensor measurement accuracy and the consistency of the array. This method is expected to further improve the accuracy of OPM array-based source localization.

Large bandwidth array waveguide grating design for FBG interrogation system

The array waveguide grating (AWG) demodulation method has been widely used in recent years. However, the resolution and total measurement range of AWG-based Fiber Bragg Grating (FBG) interrogation systems are limited by the output characteristics of AWGs. We designed and fabricated a multi-channel SiO2-based AWG as a key component of FBG Interrogation. To increase the dynamic range of demodulation, a multimode interference coupler (MMI) structure is introduced in the middle of the input waveguide and the input slab waveguide. From the simulation results, the 3-dB bandwidth of the AWG is increased from 1.04 nm to 1.86 nm. We test the performance of the interrogation system based on this AWG. The results demonstrate that the system can achieve continuous demodulation in the C-band, with an interrogation accuracy better than 20.22 pm and a wavelength resolution of 1 pm.

Feasibility of a Fiber-Dispersive Raman Spectrometer for Biomarker Detection.

Raman spectroscopy is among the top analytical techniques for ultra-low-dense organic matter, crucial to the search for life and analysis of celestial body surfaces in space exploration missions. Achieving the ultimate sensitivity of in-situ Raman spectroscopy necessitates a breakthrough in detecting inelastically scattered light. Single-photon detectors (SPDs) operating in photon counting mode, which can differentiate between Raman and luminescence responses, are promising candidates for the challenging scientific requirements. Since large SPD arrays are not yet commercially available, a dispersive element can be adapted to a single-pixel detector. By exploiting chromatic dispersion in optical fibers and picosecond-pulsed excitation, we delay the arrivals of different spectral components onto a single-pixel SPD. This method also separates weak Raman signals from stronger luminescence through correlated time-domain measurements. We study the impact of fiber properties and the excitation wavelength of a pulsed laser on the spectral resolution of the fiber-dispersive Raman spectrometer (FDRS). Additionally, we demonstrate the FDRS's potential for studying biomarkers and discuss its feasibility for analyzing inclusions in ice matrices.

Narrow [O iii] Emission Lines as a Potential Proxy for the Evolutionary Stage of Quasars

Radio spectral shape of quasars can provide insight into the ages of quasars. We have compiled data for 1804 quasars with z ≲ 1 from the Sloan Digital Sky Survey (SDSS). Additionally, these quasars were also mapped by the Low-Frequency Array at 144 MHz and the Very Large Array Sky Survey at 3000 MHz. The radio spectral index, designated as α3000144 (with S(ν) ∝ ν α ), is analyzed between 144 and 3000 MHz as a proxy for the ages of quasars. We measure the [O III] λ5007 emission line in the SDSS spectra. A strong correlation was found between the equivalent width of the core component of the [O III] λ5007 emission line and α3000144 . This relationship suggests that the core component of the [O III] λ5007 emission line could potentially serve as a surrogate for the evolutionary stage of a quasar. The quasars at an early stage of evolutions tend to show weaker [O III] λ5007 emission, while older quasars exhibit stronger [O III] λ5007 emission.

Deciphering ovarian torsion: insights from CT imaging analysis.

In the milieu of emergency medicine, pelvic and lower abdominal pain present recurrently, with ovarian torsion posing a formidable diagnostic quandary amid multifarious etiologies. Given the burgeoning reliance on CT in acute care settings, it invariably assumes primacy as the principal imaging modality. This study endeavors to elucidate the CT imaging manifestations encountered by surgically confirmed ovarian torsion patients and utilizing CT to differentiate necrosis. A retrospective analysis (January, 2015- April, 2019) utilizing hospital archives was conducted on patients diagnosed with ovarian torsion, post-surgery. Inclusion criteria encompassed patients who underwent CT examinations within one week of diagnosis. A large array of CT findings encompassing midline orientation, uterine deviation, intraovarian hematoma/mass, and multiple others were systematically documented. 90 patients were diagnosed with ovarian torsion- 53 (59%) had CT within one week of diagnosis, 41(77%) underwent a CT with IV contrast and 12 (23%) without IV contrast. Mean age was 43 years (range 19-77 years), with near equal distribution of involvement of each ovary. Mean maximum ovarian diameter was 11.7 ± 6.3cm (4.2-34.8cm). Most common imaging features include the presence of thickened pedicle (43/53, 81%), midline ovary (41/53, 77%), presence of thickened fallopian tube (31/49, 63%), and ipsilateral uterine deviation (33/53, 62%). Based on contemporaneous imaging report, torsion was diagnosed in 25/ 53 studies giving a sensitivity of 47%. Enlarged ovarian dimensions (> 3.0cm), thickened vascular pedicle or fallopian tube, midline ovarian disposition with ipsilateral uterine deviation, and the presence of a whirlpool sign emerged as predominant CT imaging features in surgically confirmed ovarian torsion cases, serving as pivotal diagnostic aides for radiologists. Concomitant pelvic free fluid and intraovarian hematoma signify necrotic changes, indicative of ischemic severity and disease progression.

Radio Scrutiny of the X-Ray-weak Tail of Low-mass Active Galactic Nuclei: A Novel Signature of High-Eddington Accretion?

The supermassive black holes (M BH ∼ 106–1010 M ⊙) that power luminous active galactic nuclei (AGNs), i.e., quasars, generally show a correlation between thermal disk emission in the ultraviolet (UV) and coronal emission in hard X-rays. In contrast, some “massive” black holes (mBHs; M BH ∼ 105–106 M ⊙) in low-mass galaxies present curious X-ray properties with coronal radiative output up to 100× weaker than expected. To examine this issue, we present a pilot study incorporating Very Large Array radio observations of a sample of 18 high-accretion-rate (Eddington ratios L bol/L Edd > 0.1), mBH-powered AGNs (M BH ∼ 106 M ⊙) with Chandra X-ray coverage. Empirical correlations previously revealed in samples of radio-quiet, high-Eddington AGNs indicate that the radio–X-ray luminosity ratio, L R/L X, is approximately constant. Through multiwavelength analysis, we instead find that the X-ray-weaker mBHs in our sample tend toward larger values of L R/L X even though they remain radio-quiet per their optical–UV properties. This trend results in a tentative but highly intriguing correlation between L R/L X and X-ray weakness, which we argue is consistent with a scenario in which X-rays may be preferentially obscured from our line of sight by a “slim” accretion disk. We compare this observation to weak emission-line quasars (AGNs with exceptionally weak broad-line emission and a significant X-ray-weak fraction) and conclude by suggesting that our results may offer a new observational signature for finding high-accretion-rate AGNs.

Layout Optimization of Wave Energy Park Based on Multi-Objective Optimization Algorithm

Abstract In this paper, both semi-analytical method and numerical simulation is applied to investigate the hydrodynamic behavior of large arrays of point-absorber wave energy converters (WECs). To analyze wave interactions among multiple WECs within an array, a semi-analytical model is developed based on the potential flow theory and the matched eigen-function expansions method. The fluid domain is divided into two kinds of regions: interior regions underneath the cylinders and an exterior region surrounding all the cylinders. The matched eigenfunction expansions method is employed to solve the radiation potential problem in each domain, and the hydrodynamic coefficients and motion response of the cylinders in the array are evaluated. To validate the accuracy of the semi-analytical method, WAMIT is adopted to simulate the wave energy park numerically and compared with the results by the semi-analytical model. The hydrodynamic characteristics and power absorption performance of the WECs within the wave energy park are analyzed. The power performance of a wave energy park is studied as functions of layout geometry, incident wave direction and separation distance between WECs respectively. Finally, MOPSO based on a surrogate model is used to optimize the layout of wave energy array.