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Acoustic cues of healthy reefs are known to support critical settlement behaviors for one reef-building coral, but acoustic responses have not been demonstrated in additional species. Settlement of Favia fragum larvae in response to replayed coral reef soundscapes were observed by exposing larvae in aquaria and reef settings to playback sound treatments for 24–72 h. Settlement increased under 24 h sound treatments in both experiments. The results add to growing knowledge that acoustically mediated settlement may be widespread among stony corals with species-specific attributes, suggesting sound could be one tool employed to rehabilitate and build resilience within imperiled reef communities. [ABSTRACT FROM AUTHOR]

In acoustic array signal processing, spatial spectrum estimation and the corresponding direction-of-arrival estimation are sometimes affected by stationary near-field interferences, presenting a considerable challenge for the target detection. To address the challenge, this paper proposes a beam-space spatial spectrum reconstruction algorithm. The proposed algorithm overcomes the limitations of common spatial spectrum estimation algorithms designed for near-field interference scenarios, which require knowledge of the near-field interference array manifold. The robustness and efficacy of the proposed algorithm under strong stationary near-field interference are confirmed through the analysis of simulated and real-life experimental data. [ABSTRACT FROM AUTHOR]

In this paper we study and characterise independence in near-vector spaces constructed using copies of finite fields. We show that for regular near-vector spaces of this nature, independence is equivalent to the notion of independence in the associated vector space. We prove that for the construction where the number of maximal regular subspaces coincides with the dimension, there are more elements outside of the quasi-kernel which can generate the entire space than previously thought. As a highlight, we completely characterise independence for this space and define matroids for finite field constructions and those using copies of a proper finite near-field. [ABSTRACT FROM AUTHOR]

In this paper we take a first look at hyper near-vector spaces. We define a hyper near-vector space having similar properties to Johannes André's near-vector space. We define important concepts including independence, the notion of a basis, regularity, subhyperspaces and as a highlight prove that there is a Decomposition Theorem for these spaces. [ABSTRACT FROM AUTHOR]

In this paper, we demonstrate that the realm of near-vector spaces enables us to address nonlinear problems while also providing access to most of the tools that linear algebra offers. We establish fundamental results for near-vector spaces, which serve to extend classical linear algebra into the realm of near-linear algebra. Within this paper, we finalize the algebraic proof that for a given scalar group F, any nonempty F-subspace that remains stable under addition and scalar multiplication constitutes an F-subspace. We prove that any quotient of a near-vector space by an F-subspace is itself a near-vector space, along with presenting the First Isomorphism Theorem for near-vector spaces. In doing so, we obtain comprehensive descriptions of the span. By defining linear independence outside the quasi-kernel, we introduce a new concept of basis. We also establish that near-vector spaces are characterized based on the presence of a scalar basis. [ABSTRACT FROM AUTHOR]

With the rapid advances in mobile communication technology, increase in mobile standards, and the consequent multiple applications of mobile phones in different fields, a higher risk of human exposure to radiofrequency (RF) radiation from the use of mobile phones is speculated. The study focused on the assessment of radiofrequency radiation levels in the near field of common mobile phones of different sizes used in Dutsin-Ma, Katsina State, Nigeria. Real-time measurements of power densities of 50 mobile phones of different sizes, types, and models at varying distances were done in isolated locations using a Cornet Electrosmog RF Meter. The power density was measured when each phone was in standby mode and when dialed at an interval of 10 cm between the RF meter and phone up to a maximum distance of 50 cm. The average power densities of investigated phones, in dialed mode, which range from 0.799 ± 0.11 mW/m² to 182.700 ± 10.91 mW/m², are below the reference level of exposure safety limit set by the International Commission on Non-Ionizing Radiation Protection for the general public. The RF radiation of the phones was found to be independent of the size of the phone. The data presented in this study can be used to promote user awareness, safety considerations, and informed decision-making regarding the safe usage of mobile devices. As long as a mobile phone is operated in the near field region, its power density does not necessarily decrease with distance. [ABSTRACT FROM AUTHOR]

Supersonic rectangular twin jets (SRTJ) are of interest for current and future generations of tactical aircraft. However, the adverse effects of screech-loop coupling have previously been documented to significantly increase the near-field (NF) pressure fluctuations. These high-amplitude pressure fluctuations have the potential to fatigue and damage nearby aft components of the aircraft. Previous studies have documented that theNF pressure fluctuation level depends on the coupling of the jets: in-phase coupling along the twin jets' minor axes produces stronger NF pressure fluctuations than that of out-of-phase coupling. The objective of thiswork is to further investigate the effects of coupling modes on NF pressure fluctuations in SRTJ and to mitigate the adverse effects of coupling using active flow control. Localized arc filament plasma actuators are employed to alter the SRTJs' coupling mode by leveraging natural flow instabilities with minimal power input. A NF microphone array is used for simultaneous coupling and NF pressure fluctuation measurements. Schlieren imaging and spectral proper orthogonal decomposition are used to assess the effects of control on the flow field. The effect of excitation at various frequencies and actuation patterns on coupling and NF pressure fluctuations in different flow regimes are explored and discussed. [ABSTRACT FROM AUTHOR]

Background and Objectives: Cylindrical scanning technique is a well-established indirect measurement method to characterize a wide range of antenna patterns such as fan-beam antennas and phased array antennas with versatile radiation patterns. Methods: Cylindrical scanning technique which is based on the nearfield-to-farfield transformation based on cylindrical mode coefficients (CMCs), cannot predict the antenna radiation pattern with a very narrow beamwidth in the azimuth plane accurately, because a remarkable error occurs during the calculation of the derivative of high-order Hankel functions in the CMCs extraction. We aim to address this issue and introduce a simple yet rigorous technique namely the sequential sampling method (SSM) in conjunction with the two-dimensional Fast Fourier Transform (2D-FFT) to efficiently calculate the far-field radiation pattern of a super-directive antenna with a very narrow beamwidth in the azimuth plane. Briefly, the SSM offers several sequences of progressive azimuth angles and the corresponding order of Hankel functions in such a way that CMCs fully span 360 degrees of azimuth angles (φ) in the cylindrical coordinate system in each sequence. Afterward, by putting the farfield obtained by these sequences together, the final radiation pattern will have a high angular resolution. This technique can also be applied to determine the necessary criteria in the data acquisition step which should be satisfied to precisely measure the radiation pattern of super-directive antennas. These criteria are the maximum acceptable sampling resolution and the minimum value of the required azimuth angle (φ) in the data acquisition step if the far-field pattern is merely desired on the front side of the antenna. Results: For verifications, the far-field radiation pattern of an electrically large slot array antenna including 81x15 slots is calculated at 8.75 GHz by the proposed technique and the results are compared with the array theory. The results show that the azimuth pattern can accurately be measured as small as 0.1° resolution by the SSM. Conclusion: By comparing the results obtained by the proposed method and the traditional cylindrical scanning method, it can be inferred that the far-field pattern of an antenna with narrow beamwidth in the azimuth plane can easily be characterized by a cylindrical scanning system without any huge computational burden. [ABSTRACT FROM AUTHOR]

This paper is concerned with the inverse problem of determining an obstacle and the corresponding incident point sources in the Helmholtz equation from near-field scattering data. An optimization method is proposed to simultaneously recover both the obstacle and source locations. Moreover, a two-step sampling scheme with novel indicator functions is proposed to produce a good initial guess for solving the optimization problem. Theoretically, we analyze the convergence properties of the optimization method and the behaviors of the indicator functions. Several numerical examples are presented to show the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

In this study, the spectral control of near-field radiation transfer between a metal-insulator-metal (MIM)-structured emitter and a metal-semiconductor-metal (MSM)-structured cell was studied for advanced nanogap thermophotovoltaic (TPV) power generation systems using the finite-difference time-domain method. Moreover, the mechanism of spectral control was investigated by the visualization of magnetic condition through the emitter/vacuum gap/cell. For the emitter side, an MIM emitter consisting of nickel and silicon dioxide was used for the spectral enhancement of near-field radiation. For the cell side, an MSM cell consisting of gold, as the electrode, and gallium antimonide, for the photovoltaic semiconductor, was proposed considering a thin-layered TPV cell. The simulation results demonstrated that by the adjustment of the size of the MIM and MSM structures, the near-field radiation can be transferred selectively aiming the target wavelength for the bandgap of GaSb, and those effects can be shown based on the comparison to the blackbody radiation transfer at the same temperatures of the emitter (1000 K). In addition, a unique magnetic resonance condition was appeared when sharper radiation spectral control with enhanced near-field radiation flux can be obtained by optimizing the surface electrode structure of the cell (300 K). Furthermore, the evaluation results show that the spectral efficiency and power ratio increase when the structured emitter and cell was applied. Consequently, using a thin semiconductor layer cell with a p-n junction, similar to conventional cells, an energy conversion system with higher power density can be developed through spectral-controlled radiation transfer between the MIM emitter and MSM cell. These results provide greater flexibility for the control and design of the emitter and cell for nano-gap TPV generation systems. [ABSTRACT FROM AUTHOR]

Radiofrequency identification (RFID), particularly passive RFID, is extensively employed in industrial applications to track and trace products, assets, and material flows. The ongoing trend toward increasingly miniaturized RFID sensor tags is likely to continue as technology advances, although miniaturization presents a challenge with regard to the communication coverage area. Recently, efforts in applying metamaterials in RFID technology to increase power transfer efficiency through their unique capacity for electromagnetic wave manipulation have been reported. In particular, metamaterials are being increasingly applied in far-field RFID system applications. Here, we report the development of a magnetic metamaterial and local field enhancement package enabling a marked boost in near-field magnetic strength, ultimately yielding a dramatic increase in the power transfer efficiency between reader and tag antennas. The application of the proposed magnetic metamaterial and local field enhancement package to near-field RFID technology, by offering high power transfer efficiency and a larger communication coverage area, yields new opportunities in the rapidly emerging Internet of Things (IoT) era. [ABSTRACT FROM AUTHOR]

This paper develops an active magnetic near field probe (H‐field probe) by using a four‐layer printed circuit board (PCB) technique. Two‐turn detection structure and a low noise amplifier are used to improve probe's frequency response. The two‐turn detection structure can maximize the use of PCB stack resources, and a 14.5 dB gain amplifier can increase signal output capability. The probe can then be used for electromagnetic compatibility (EMC) test from 150 kHz to 3 GHz. Compared with traditional active shielded‐loop H‐field probe (TAHP) with loop area of 500 μm2, the frequency response of the proposed probe can improve 20 dB at 0.5 GHz. Different from the method of comparing the sensitivity of the probe only through the frequency response, this paper measures and analyzes the real sensitivity of the probing device composed of the proposed probe. Under the condition of the same receiver parameter setting, the sensitivity at 0.5 GHz is increased by 11.7 dB compared with commercial passive probing device and 20.2 dB at 0.5 GHz compared with the probing device with TAHP device. It reaches −32.4 dB μA. In addition, the proposed probe has acceptable spatial resolution of 1.28 mm at 1 GHz, which is more suitable for printed circuit board level EMI analysis. [ABSTRACT FROM AUTHOR]

Tip-enhanced Raman spectroscopy (TERS) is a valuable method for surface analysis with nanometer to angstrom-scale resolution; however, the accurate simulation of particular TERS signals remains a computational challenge. We approach this challenge by combining the two main contributors to plasmon-enhanced Raman spectroscopy and to the high resolution in TERS, in particular, the electromagnetic and the chemical effect, into one quantum mechanical simulation. The electromagnetic effect describes the sample's interaction with the strong, highly localized, and inhomogeneous electric fields associated with the plasmonic tip and is typically the thematic focus for most mechanistic studies. On the other hand, the chemical effect covers the different responses to the extremely close-range and highly position-sensitive chemical interaction between the apex tip atom(s) and the sample, and, as we could show in previous works, plays an often underestimated role. Starting from a (time-dependent) density functional theory description of the chemical model system, comprised of a tin(II) phthalocyanine sample molecule and a single silver atom as the tip, we introduce the electromagnetic effect through a series of static point charges that recreate the electric field in the vicinity of the plasmonic Ag nanoparticle. By scanning the tip over the molecule along a 3D grid, we can investigate the system's Raman response on each position for nonresonant and resonant illumination. Simulating both effects on their own already hints at the achievable signal enhancement and resolution, but the combination of both creates even stronger evidence that TERS is capable of resolving submolecular features.

• 7 cubature methods are tested against analytical orientation-averaging formulas. • Cubature performance is tested for far-field cross-sections and circular dichroism. • Cubature performance on far-field and near-field properties is compared. • Cubature accuracy is linked to the size parameter of the particle cluster. • The angular complexity of the integrand is quantified by a spherical harmonic decomposition. • The multipole truncation parameter is found not to affect the cubature performance. The optical properties of nanoparticles can be substantially affected by their assembly in compact aggregates. This is a common situation notably for nanoparticles synthesised and self-assembled into rigid clusters in colloidal form, where they may be further characterised or used in spectroscopic applications. The theoretical description of such experiments generally requires averaging the optical response over all possible cluster orientations, as they randomly orient themselves over the course of a measurement. This averaging is often done numerically by simulating the optical response for several directions of incidence, using a spherical cubature method. The simulation time increases with the number of directions and can become prohibitive, yet few studies have examined the trade-off between averaging accuracy and computational cost. We benchmark seven commonly-used spherical cubature methods for both far-field and near-field optical responses for a few paradigmatic cluster geometries: dimers of nanospheres and of nanorods, and a helix. The relative error is rigorously evaluated in comparison to analytical results obtained with the superposition T -matrix method. Accurate orientation averaging is especially important for quantities relating to optical activity, the differential response to left and right circularly polarised light, and our example calculations include in particular far-field circular dichroism and near-field local degree of optical chirality. [ABSTRACT FROM AUTHOR]