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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]

Inspired by recent experimental observations of anomalously large decay lengths in concentrated electrolytes, we revisit the Restricted Primitive Model (RPM) for an aqueous electrolyte. We investigate the asymptotic decay lengths of the one-body ionic density profiles for the RPM in contact with a planar electrode using classical Density Functional Theory (DFT) and compare these with the decay lengths of the corresponding two-body correlation functions in bulk systems, obtained in previous Integral Equation Theory (IET) studies. Extensive Molecular Dynamics (MD) simulations are employed to complement the DFT and IET predictions. Our DFT calculations incorporate electrostatic interactions between the ions using three different (existing) approaches: one is based on the simplest mean-field treatment of Coulomb interactions (MFC), while the other two employ the Mean Spherical Approximation (MSA). The MSAc invokes only the MSA bulk direct correlation function, whereas the MSAu also incorporates the MSA bulk internal energy. Although MSAu yields profiles that are in excellent agreement with MD simulations in the near field, in the far field, we observe that the decay lengths are consistent between IET, MSAc, and MD simulations, whereas those from MFC and MSAu deviate significantly. Using DFT, we calculated the solvation force, which relates directly to surface force experiments. We find that its decay length is neither qualitatively nor quantitatively close to the large decay lengths measured in experiments and conclude that the latter cannot be accounted for by the primitive model. The anomalously large decay lengths found in surface force measurements require an explanation that lies beyond primitive models. [ABSTRACT FROM AUTHOR]

Tip-enhanced Raman spectroscopy in combination with scanning tunneling microscopy could produce ultrahigh-resolution Raman spectra and images for single-molecule vibrations. Furthermore, a recent experimental study successfully decoupled the interaction between the molecule and the substrate/tip to investigate the intrinsic properties of molecules and their near-field interactions by Raman spectroscopy. In such a circumstance, more explicit treatments of the near field and molecular interactions beyond the dipole approximation would be desirable. Here, we propose a theoretical method based on the multipolar Hamiltonian that considers full spatial distribution of the electric field under the framework of real-time time-dependent density functional theory. This approach allows us to treat the on- and off-resonance Raman phenomena on the same footing. For demonstration, a model for the on- and off-resonance tip-enhanced Raman process in benzene was constructed. The obtained Raman spectra are well understood by considering both the spatial structure of the near field and the molecular vibration in the off-resonance condition. For the on-resonance condition, the Raman spectra are governed by the transition moment, in addition to the selection rule of off-resonance Raman. Interestingly, on-resonance Raman can be activated even when the near field forbids the π–π* transition at equilibrium geometry due to vibronic couplings originating from structural distortions. [ABSTRACT FROM AUTHOR]

A new scheme of near-field thermophotovoltaic devices is proposed by introducing the intermediate-band absorber. The two-step excitation via the intermediate band provides a large photogenerated current density and maintains a high voltage output for the thermal-electric conversion. Energy dissipation processes in devices are analyzed by using the detailed balance model. Results show that the powers and efficiencies of thermophotovoltaic devices with intermediate bands in appropriate positions are clearly larger than those of the conventional counterparts. Based on the optical properties observed in experiments, three types of absorber materials are compared, which indicates that InAs with low energy bandgap is more suitable as a high-temperature material for photon absorptions than GaSb and Si. Comparing the performance of our model with experiments, we show that the InAs based thermophotovoltaic device allows the enhancement of efficiency over a range of gap sizes. The proposed model may open a new field in the application of thermophotovoltaic devices. [ABSTRACT FROM AUTHOR]

We present a heat transfer model to obtain the temperature distribution within aligned nanorod arrays. The model includes thermal conduction along each nanorod in addition to a phenomenological treatment of near-field radiative energy exchange among the nanorods and allows us to investigate the interplay between these effects. The contribution of the near-field radiative energy exchange to overall heating is found to increase significantly with a decrease in inter-nanorod spacing and an increase in array size; the effect is also more prominent for nanorods with lower thermal conductivity and higher emissivity. [ABSTRACT FROM AUTHOR]

Near-field radiative heat transfer can significantly improve the output power of thermophotovoltaic (TPV) systems. Therefore, it is crucial to explore how to increase the energy conversion efficiencies of near-field TPV systems. In this study, based on the fluctuation–dissipation theorem with the effective medium theory, we evaluate the performance of a near-field TPV system from the formulation of thermodynamics. It is found that a near-field TPV system consisting of InAs or GaSb cell can achieve higher heat flux or efficiency limit, respectively. Moreover, the TPV system with a hyperbolic metamaterial (HMM) emitter composed of nanowire or nanohole arrays can achieve higher heat flux and efficiency limit compared to that of the bulk reference. This is attributable to the HMMs being able to support hyperbolic modes, and the radiation with the HMM emitter exhibits a favorable entropy content for the energy conversion efficiency. This work provides an approach to determine the efficiency limit and establish a target for efficiency of the near-field TPV system without considering how the system works. The results of this study will facilitate the design and application of the HMM emitter and material of the TPV cell to improve the efficiency of near-field TPV systems. [ABSTRACT FROM AUTHOR]

Nanoscale plasmonic field enhancement at sub-wavelength metallic particles is crucial for surface sensitive spectroscopy, ultrafast microscopy, and nanoscale energy transduction. Here, we demonstrate control of the spatial distribution of localized surface plasmon modes at sub-optical-wavelength crystalline silver (Ag) micropyramids grown on a Si(001) surface. We employ multiphoton photoemission electron microscopy (mP-PEEM) to image how the plasmonic field distributions vary with the photon energy, light polarization, and phase in coherent two-pulse excitation. For photon energy hυ > 2.0 eV, the mP-PEEM images show single photoemission locus, which splits into a dipolar pattern that straddles the Ag crystal at a lower energy. We attribute the variation to the migration of plasmon resonances from the Ag/vacuum to the Ag/Si interfaces by choice of the photon energy. Furthermore, the dipolar response of the Ag/Si interface follows the polarization state of light: for linearly polarized excitations, the plasmon dipole follows the in-plane electric field vector, while for circularly polarized excitations, it tilts in the direction of the handedness due to the conversion of spin angular momentum of light into orbital angular momentum of the plasmons excited in the sample. Finally, we show the coherent control of the spatial plasmon distribution by exciting the sample with two identical circularly polarized light pulses with delay defined with attosecond precision. The near field distribution wobbles at the pyramid base as the pump–probe delay is advanced due to interferences among the contributing fields. We illustrate how the frequency, polarization, and pulse structure can be used to design and control plasmon fields on the nanofemto scale for applications in chemistry and physics. [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]

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]

The present work has elaborated the roles of near- and far-field lattice resonances (LRs) in the performance of one-dimensional metalattices composed of magneto-optically (MO) coated cylinders. By taking advantage of LR effects and MO-modified multipolar interferences, it is feasible to alter transmission or reflection with unity efficiency by turning on or off external magnetic fields. In the far field, multipolar LRs near Rayleigh anomaly (RA) can be acquired, leading to transmission suppression or enhancement for different multipolar interference mechanisms. Meanwhile, thanks to exciting degeneracy-broken multipoles, asymmetric diffractive patterns are observed despite normal incidence. However, in the diffractionless region with strong near-field couplings, we find that LR effects are capable of not only modifying scattering amplitude (> --> 1) but also introducing phase change or even inversion. Specifically, owing to the appearance of π /2-phase rotated electric dipoles, the first and second Kerker conditions are achieved simultaneously in this work. In addition, the coupling mechanism of RA-associated LRs and MO-influenced Mie modes supported by an individual cylinder is also unveiled. Besides, a proof-of-concept example using realistic Si@InSb metalattices has also been demonstrated, showing reconfigurable performance as expected. The revealed far/near-field mechanism of interplay between LRs and MO-modified multipoles will shed new light on wavefront engineering with diffracted effects and reconfigurable features. [ABSTRACT FROM AUTHOR]

Optical properties are numerically studied of a plasmonic planar 2D noble metal nanostructure with the design inspired by Babinet's principle. We stack a 2D array of nanodisks and a complementary screen—2D periodically perforated film—so that they are separated by a dielectric spacer. Near-field interaction between electric and magnetic dipoles induced in metal metasurfaces results in increased reflectance and suppressed absorption, canceling out initial resonances in the individual nanostructures. The proposed metasurface has polarization- and angle of incidence-independent response in a wide frequency range as compared to the resonance bandwidth. The proposed design is robust to possible structural imperfections. [ABSTRACT FROM AUTHOR]

The squirmer is a simple yet instructive model for microswimmers, which employs an effective slip velocity on the surface of a spherical swimmer to describe its self-propulsion. We solve the hydrodynamic flow problem with the lattice Boltzmann (LB) method, which is well-suited for time-dependent problems involving complex boundary conditions. Incorporating the squirmer into LB is relatively straightforward, but requires an unexpectedly fine grid resolution to capture the physical flow fields and behaviors accurately. We demonstrate this using four basic hydrodynamic tests: two for the far-field flow—accuracy of the hydrodynamic moments and squirmer-squirmer interactions—and two that require the near field to be accurately resolved—a squirmer confined to a tube and one scattering off a spherical obstacle—which LB is capable of doing down to the grid resolution. We find good agreement with (numerical) results obtained using other hydrodynamic solvers in the same geometries and identify a minimum required resolution to achieve this reproduction. We discuss our algorithm in the context of other hydrodynamic solvers and present an outlook on its application to multi-squirmer problems. [ABSTRACT FROM AUTHOR]

We propose a scheme to achieve a dual-band electromagnetically induced transparency (EIT) effect in a planar terahertz metamaterial (MM), comprising an inner circular split ring resonator (CSRR) concentrically coupled to an outer asymmetric two-gap circular split ring resonator (ASRR). The scheme is numerically and theoretically analyzed. The dual-band EIT effect occurs as a result of the near field coupling between the resonant modes of the resonators comprising the MM configuration. It is observed that the dual-band EIT effect in the MM structure could be modulated with an in-plane rotation of the CSRR structure. The dual-band EIT effect is also examined by varying the asymmetry of the ASRR and the size of the inner CSRR. A theoretical model based upon the four-level tripod-system provides an intuitive explanation about the underlying coupling mechanism responsible for the dual-band EIT effect in the proposed MM structure. Our study could be significant in the development of multi-band slow light devices, narrowband absorbers, etc., in the terahertz regime. [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]

We consider a near-field electroluminescent refrigeration device. The device uses a GaAs light emitting diode as the cold side, and a Si photovoltaic cell as the hot side. The two sides are brought in close proximity to each other across a vacuum gap. The cooling is achieved by applying a positive bias on the GaAs light emitting diode. We show that the choice of GaAs and Si here can suppress the non-idealities for electroluminescent cooling purposes: GaAs has a wide bandgap with low Auger recombination, and Si is a non-polar semiconductor which leads to significantly reduced sub-bandgap heat transfer. We show that by using this configuration in the near-field regime, the cooling power density can reach 105W=m2 even in the presence of realistic Auger recombination and Shockley-Read-Hall recombination. In addition, with photovoltaic power recovery from the Si cell, the efficiency of the device can be further improved. Our work points to the significant potential of combining near-field heat transfer with active semiconductor devices for the control of heat flow. [ABSTRACT FROM AUTHOR]

Thermoradiative (TR) device has recently been proposed for noncontact direct photon-electricity energy conversion. We investigate how the near-field effect can boost the performance of a TR device. For a near-field TR device, a heat sink is placed close to the TR cell, with the separation being small compared to the characteristic photon wavelength. It is demonstrated that the TR device, like the thermophotovoltaic device, can be formulated using the transmissivity and the generalized Planck distribution. We quantitatively show that δ-function transmissivity is a very good approximation (capturing up to 90% of total radiative energy transfer) when the radiative energy transfer is governed by resonances. Three practical types of heat sinks are considered, a metallic material described by the Drude model, a polar dielectric material described by the Lorentz oscillator model, and a semiconductor material that is identical to the TR cell. The blackbody heat sink serves as the far-field reference. By properly choosing the resonant frequencies supported by the heat sink, we show that the heat sink made of a Drude or Lorentz material can enhance the output power by about 60 and 20 times, respectively, as compared to the blackbody reference. Even with a heat sink made of the same material as the TR-cell, which does not support any resonant modes, the output power can be enhanced by about 10 times. The mechanisms can be elucidated from the impedance matching condition derived from the coupled-mode theory. [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]

In this paper, we proposed a novel nano-gap thermophotovoltaic (TPV) device made up of thinfilms including the radiator. The optical, electrical, and thermal responses and performance of the device were assessed using coupled opto-electro-thermal numerical simulation. The device design consists of a thin-film tungsten radiator which is paired with a thin-film silicon TPV cell across a nanometric vacuum gap. Results were simulated based on experimental properties available in the current literature database. It is discovered that the maximum electrical power output of the thin-film nano-gap TPV device increases with cell temperature up to a certain threshold value due to improvements in generated photocurrent. Thin-film tungsten as a radiator is shown to improve radiative heat transfer above the bandgap compared to conventional bulk tungsten. The effect of cell thickness on responses and performance was also analysed. A 1-μm cell produces better performance over thinner thicknesses at the cost of greater cooling requirements. However, the improvements in output power offset the cooling costs, allowing for consistently favourable efficiencies. Finally, it is shown that the temperature profile in silicon thin-films under convective cooling can be approximated as uniform, simplifying the heat transport modelling process. [ABSTRACT FROM AUTHOR]

We study the light emission from a quantum emitter and double metallic nanoshell hybrid systems. Quantum emitters act as local sources which transmit their light efficiently due to a double nanoshell near field. The double nanoshell consists of a dielectric core and two outer nanoshells. The first nanoshell is made of a metal, and the second spacer nanoshell is made of a dielectric material or human serum albumin. We have calculated the fluorescence emission for a quantum emitter-double nanoshell hybrid when it is injected in an animal or a human body. Surface plasmon polariton resonances in the double nanoshell are calculated using Maxwell's equations in the quasistatic approximation, and the fluorescence emission is evaluated using the density matrix method in the presence of dipole-dipole interactions. We have compared our theory with two fluorescence experiments in hybrid systems in which the quantum emitter is Indocyanine Green or infrared fluorescent molecules. The outer spacer nanoshell of double metallic nanoshells consists of silica and human serum albumin with variable thicknesses. Our theory explains the enhancement of fluorescence spectra in both experiments. We find that the thickness of the spacer nanoshell layer increases the enhancement when the fluorescence decreases. The enhancement of the fluorescence depends on the type of quantum emitter, spacer layer, and double nanoshell. We also found that the peak of the fluorescence spectrum can be shifted by changing the shape and the size of the nanoshell. The fluorescence spectra can be switched from one peak to two peaks by removing the degeneracy of excitonic states in the quantum emitter. Hence, using these properties, one can use these hybrids as sensing and switching devices for applications in medicine. [ABSTRACT FROM AUTHOR]

We theoretically study the impact of quantum coherence on the states of polarization of the plasmonic fields of a quantum dot-metallic nanoparticle system. Via tracing Stokes parameters we predict that, depending on the refractive index of the environment, such a system can pass through different states of polarization with certain ellipticity and handedness. We demonstrate that this allows the nanoparticle system to act as a quantum sensor, wherein ultrasmall changes in the refractive index can lead to distinct changes in the time-dependent evolution of states of polarization (Stokes vector) of the plasmonic fields. Our numerical analysis also shows how these states can become strongly dependent on the intensity and frequency of the laser field responsible for the generation of quantum coherence. Possible applications for high resolution investigation of conformational dynamics and structures of biological molecules are discussed. [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]

In this paper, we investigate the impact of bending a multi-wire endoscope in the context of subwavelength imaging and near-field transport. To this end, we study the reflection and transmission by a "bent" wire medium in different configurations and demonstrate that the structure can be quite robust to the effect of bending provided the total length of the bent wires satisfies the Fabry-Pérot condition. The study is carried out relying on an analytical homogenization theory and using two additional boundary conditions obtained with physical arguments. It is proven that a structure formed by two connected sets of tilted metallic wires can allow for the near field transport with a deeply subwavelength resolution. To illustrate the applications and potentials of the results, the performance of bent multi-wire endoscopes is characterized using full wave numerical simulations. [ABSTRACT FROM AUTHOR]

Wefelscheid (Untersuchungen über Fastkörper und Fastbereiche, Habilitationsschrift, Hamburg, 1971) generalised the well-known Theorem of Artin/Schreier about the characterization of formally real fields and the fundamental result of Baer/Krull to near-fields. In the last fifty years arose from the Theorem of Baer/Krull a theory, which analyses the entirety of the orderings of a field (E. Becker, L. Bröcker, M. Marshall et al.), as presented e.g. in the book by Lam (Orderings, valuations and quadratic forms, American Mathematical Society, Providence, 1983). At the centre of this theory are preorders and their compatibility with valuations or places. We develop some essential results of this theory for the near-field case. In particular, we derive the Brown/Marshall's inequalities and Bröcker's Theorem on the trivialisation of fans in the near-field case. [ABSTRACT FROM AUTHOR]

In this paper, a near field focusing transmission metasurface (MS) based on polarization sensitivity is developed at microwave frequency. The MS unit cell has only three metal layers, which is less than the published dual‐polarized transmission structure. And the phase shifting range can cover 320° for x‐ and y‐polarized waves. The biggest bright spot of the focusing MS made of the proposed units is its changeable focus point by rotating the horn 0°–90° round its central axis: focusing switching between one and two focusing points. In addition, the developed MS has the following advantages: multifunctional, low sidelobe, high focusing efficiency, small size, wideband, and less layer number. The focusing relative bandwidth is 9.7%, and the maximum focusing efficiency is 30% at center frequency 15.5 GHz. The efficiency is higher than that of published results in transmission orthogonal polarization mode. The proposed MS has potential applications in medical treatment, noncontact sensing system. [ABSTRACT FROM AUTHOR]

The relationship between velocity and pressure fluctuations in the near field of a subsonic turbulent jet and at its axis is investigated. The data of the measurements of the velocity fluctuations at the jet axis and the pressure fluctuations in the jet near-field are analyzed. It is shown that the spectral characteristics of the velocity fluctuations at the axis can be converted to the spectra of the axisymmetric mode of the pressure fluctuations outside the jet. The conversion is based on the use of the eigenfunctions of the pressure fluctuations obtained in solving the stability problem for a cylindrical mixing layer of finite thickness in the locally-parallel approximation. [ABSTRACT FROM AUTHOR]

Combined effects of polarization, split gap, and rod width on the resonance hybridization and near field properties of strongly coupled gold dimer-rod nanosystem are comparatively investigated in the light of the constituent nanostructures. By aligning polarization of the incident light parallel to the long axis of the nanorod, introducing small split gaps to the dimer walls, and varying width of the nanorod, we have simultaneously achieved resonance mode coupling, huge near field enhancement, and prolonged plasmon lifetime. As a result of strong coupling between the nanostructures and due to an intense confinement of near fields at the split and dimer-rod gaps, the extinction spectrum of the coupled nanosystem shows an increase in intensity and blueshift in wavelength. Consequently, the near field lifespan of the split-nanosystem is prolonged in contrast to the constituent nanostructures and unsplit-nanosystem. On the other hand, for polarization of the light perpendicular to the long axis of the nanorod, the effect of split gap on the optical responses of the coupled nanosystem is found to be insignificant compared to the parallel polarization. These findings and such geometries suggest that coupling an array of metallic split-ring dimer with long nanorod can resolve the huge radiative loss problem of plasmonic waveguide. In addition, the Fano-like resonances and immense near field enhancements at the split and dimer-rod gaps imply the potentials of the nanosystem for practical applications in localized surface plasmon resonance spectroscopy and sensing. [ABSTRACT FROM AUTHOR]

We characterize the translational and rotational dynamics of birefringent spherical colloidal particles by depolarized light scattering in the far- and near-field regimes. For this purpose, we use depolarized dynamic light scattering and propose an extension of dynamic heterodyne near-field light scattering that takes into account the polarization state of the light. Such a combination of methods allows to access colloidal dynamics in an extended q-range and permits to evaluate different modes of particles motion in suspension. Furthermore, we obtain a good agreement between results from the far- and near-field approaches thus validating our proposal and opening the possibility to investigate simultaneously the subtle interplay between translational and rotational motions of anisotropic colloidal particles in length-scales from the order of the particle size to several interparticle distances. [ABSTRACT FROM AUTHOR]

One of the obstacles preventing wireless power transfer from becoming ubiquitous is their leakage of power: high-amplitude electromagnetic fields that can interfere with other electronic devices, increase health concerns, or hinder power metering. In this paper, we present near-field plates (NFPs) as a novel method to tailor the electromagnetic fields generated by a wireless power transfer system while maintaining high efficiency. NFPs are modulated arrays or surfaces designed to form prescribed near-field patterns. The NFP proposed in this paper consists of an array of loaded loops that are designed to confine the electromagnetic fields of a resonant transmitting loop to the desired direction (receiving loop) while suppressing fields in other directions. The step-by-step design procedure for this device is outlined. Two NFPs are designed and examined in full-wave simulation. Their performance is shown to be in close agreement with the design predictions, thereby verifying the proposed design and operation. A NFP is also fabricated and experimentally shown to form a unidirectional wireless power transfer link with high efficiency. [ABSTRACT FROM AUTHOR]

We propose a hybrid method based on the finite-difference time-domain (FDTD) algorithm and analytical methods to solve the elastic scattering of 3-D objects outside a borehole. In the proposed method, the FDTD algorithm containing the incident waves generated by a borehole acoustic source is first used to calculate the wave fields inside a rectangular volume enclosing the object. Then, the reciprocity theorem for the wave fields in the fluid/solid configurations is employed to transform the near fields around the object into the far fields inside the borehole. This method uses the regional domain which tightly encloses the object, thus avoiding the simulation for the whole domain and leading to high efficiency for the large-scale and multiscale problems containing both the borehole and far-field objects. The validations with both analytical solutions and independent numerical methods demonstrate the accuracy and efficiency of the hybrid method. [ABSTRACT FROM AUTHOR]

A planar metamaterial structure has been designed to obtain surface plasmon-induced-transparency (PIT) effect, which is composed of a nanodisk sandwiched between double rods. From theoretical perspective, the three-level plasmonic system has been utilized to analyze the near-field coupling mechanism. Besides, the simulation results show that PIT resonance can be tailored by structure parameters. Particularly, when the length of the rods is more than twice of the diameter of the disk, two PIT windows are generated simultaneously, based on the coupling between the bright mode of the nanodisk and two multipole dark modes of rods. Furthermore, a metamaterial structure, composed by a disk and two pairs of nanorods, is suggested to achieve the polarization-independent plasmon-induced-transparency effect. As a result, this work shows great application prospect in the area of compact optical devices, such as multiband tunable filters, plasmonic switches, and slow light devices. [ABSTRACT FROM AUTHOR]

Magnetic metamaterials exhibit extraordinary electromagnetic properties and have shown great potential in low-frequency near-field electromagnetic applications. A near-field device or system is consisted of different natural media and low-frequency metamaterials, and it is essential to develop a numerical methodology to compute the transient response of such a device or system. However, most existing works are dedicated to high-frequency metamaterials and wave propagation problems, whereas the study of numerical methodology for low-frequency metamaterials in magnetoquasistatic (MQS) fields is still blank and challenging. In this regard, a time-domain finite-element method (TDFEM) is first derived for MQS field applications of low-frequency metamaterials. The metamaterials are modeled as continuous media and approximated by a nonstandard Lorentz dispersion equation. The formulas to handle dispersive media in near field are derived based on the auxiliary equation method. The proposed method is validated in a 2-D axisymmetric case study by comparing its results with those of frequency-domain computations. [ABSTRACT FROM AUTHOR]

In this paper, the arc array for squint-less near-field focusing is used, theoretically analyzed, and verified. The arc array is designed to overcome the squint phenomenon in the near-field and transfers the maximum power at a focused distance. The implemented transmitter is composed of 16 × 1 vivaldi antennas with a 0.7 λ spacing and operates at a frequency of 5.8 GHz. In addition, the design method of the arc array is proposed, considering the focused distances. In the experiments, the bending degree of the arc array is 4.14 ∘ when the focused distance is 0.5 m. At a fractional bandwidth of 27.5%, the focus position is shifted 32%. On the other hand, in the arc array, the focus position is not shifted. Experimental results from the implemented arc array show good agreement with the proposed theory. [ABSTRACT FROM AUTHOR]

We establish local C 1 , α estimates for one source near field refractors under structural assumptions on the target, and with no assumptions on the smoothness of the densities. [ABSTRACT FROM AUTHOR]

Electromagnetic (EM) metasurfaces are essential in a wide range of EM engineering applications, from incorporated into antenna designs to separate devices like radome. Near-field manipulators are a class of metasurfaces engineered to tailor an EM source's radiation patterns by manipulating its near-field components. They can be made of all-dielectric, hybrid, or all-metal materials; however, simultaneously delivering a set of desired specifications by an all-metal structure is more challenging due to limitations of a substrate-less configuration. The existing near-field phase manipulators have at least one of the following limitations; expensive dielectric-based prototyping, subject to ray tracing approximation and conditions, narrowband performance, costly manufacturing, and polarization dependence. In contrast, we propose an all-metal wideband phase correcting structure (AWPCS) with none of these limitations and is designed based on the relative phase error extracted by post-processing the actual near-field distributions of any EM sources. Hence, it is applicable to any antennas, including those that cannot be accurately analyzed with ray-tracing, particularly for near-field analysis. To experimentally verify the wideband performance of the AWPCS, a shortened horn antenna with a large apex angle and a non-uniform near-field phase distribution is used as an EM source for the AWPCS. The measured results verify a significant improvement in the antenna's aperture phase distribution in a large frequency band of 25%. [ABSTRACT FROM AUTHOR]

We present a theoretical study of nanoscale radiative thermal transport between an overlapping pair of movable comb-like SiO2 gratings by an improved and more accurate near-field radiative heat transfer (NFRHT) method. This method does not rely on the effective medium theory (EMT) that does not take the geometric shape factors of nanostructures into account. Contrary to the EMT treating the grating structure as a homogeneous film, our improved NFRHT method can accurately predict the change of heat flux between the overlapping nanogratings for different scenarios considering surface pattern effects. The longitudinal and lateral movements of the comb-like overlapping nanogratings have been investigated to evaluate the dynamic control of NFRHT, which can be significantly modulated, resulting in heat flux ratios up to 23.5 and 5.5, respectively, for small-scale displacements. Furthermore, the NFRHT between overlapping non-contact metamaterials can exceed the intrinsic heat conduction limit for a contact mode by an order of magnitude while properly adjusting the period and relative position of the overlapping nanogratings. By taking advantage of movable metamaterials, the dynamic tuning of NFRHT and light manipulation can provide great benefit to the fields of energy harvesting and conversion, infrared sensing and detection, and thermal management technology. [ABSTRACT FROM AUTHOR]

Both multilayered (ML) and few-layered (FL) Ti3C2Tx nanosheets have been prepared through a typical etching and delaminating procedure. Various characterizations confirm that the dominant terminal groups on ML-Ti3C2Tx and FL-Ti3C2Tx are different, which have been assigned to O-related and hydroxyl groups, respectively. Such deviation of the dominant terminals results in the different physical and chemical performance and eventually makes the nanosheets have different potential applications. In particular, before coupling to Ag nanoparticles, ML-Ti3C2Tx can present stronger near-field enhancement effect; however, Ag/FL-Ti3C2Tx hybrid structure can confine stronger near-field due to the electron injection, which can be offered by the terminated hydroxyl groups. [ABSTRACT FROM AUTHOR]

Regarding wave scattering on a three-dimensional nonspherical obstacle, the Rayleigh hypothesis states that the scattered field can be expanded everywhere outside the obstacle using only outgoing eigensolutions of the underlying Helmholtz equation. However, the correctness of this assumption has not yet been finally clarified, although it is important for the near-field analysis of scattering processes and for multiple scattering. To circumvent this uncertainty, Waterman introduced the extended boundary condition to develop his T-matrix method. This approach leads to the restriction that, when modeling multiple scattering processes using this T-matrix, the smallest circumscribing spheres of the individual obstacles must not overlap. The purpose of this paper is to provide a justification of the correctness of Rayleigh's hypothesis and clarify its implications for modeling multiple scattering. We show that Waterman's T-matrix can in fact be used inside the critical region between the surface of the obstacle and its smallest circumscribing sphere to represent the near-field and that one does not necessarily have to exclude an overlap of these spheres in the multiple scattering modeling. The theoretical considerations in the first part of this paper are supplemented by a numerical study of a benchmark configuration for multiple scattering in the last part. [ABSTRACT FROM AUTHOR]

This article proposes and analyzes two possible methods to compensate the raw near-field data obtained with an array of near-field probes. The first method is based on the spatial compensation procedure for a single probe and is modified toward an array of probes. The second method is to use standard spectral (plane wave) single-probe compensation. To use the latter, guidelines on how to design an array and modify the overall measurement procedure such that mutual coupling and edge effects have less influence are given. The different methods are tested in simulation and compared with the performance of compensation on a single probe. It is shown that the standard spectral single-probe compensation, in combination with proper array design, will result in an error as low as the same compensation technique used on a single probe. It is also shown that the spatial compensation improves the results in comparison with regular calibration. However, the error is not low enough to be used for postprocessing due to ill-conditioning. This article shows the path to much needed, fast, and accurate near-field measurements. [ABSTRACT FROM AUTHOR]

We propose a thermal modulation structure made of two identical SiO2 slabs coated by Dirac semimetal (DSM) films and separated by a nanoscale vacuum gap. The energy transmission probability reveals that the coupled surface plasmon polaritons (SPPs) between the two DSM films, and the surface phonon polaritons (SPhPs) supported by the SiO2 substrate can vary sensitively with the Fermi level, the degenerate factor of 3D Dirac points and the thickness of the DSM film, thus providing the possibilities for modulating the radiative heat transfer by tuning these parameters. Based on Maxwell's equations incorporating fluctuational electrodynamics, the effects of these parameters on the heat transfer coefficient and the thermal modulation contrast are numerically analyzed. Under proper parameters, higher modulation contrasts are obtained by continuously tuning the Fermi level from 0.05 eV to 0.3 eV. The obtained results might be helpful in designing a DSM-based thermal modulator with higher modulation contrasts. [ABSTRACT FROM AUTHOR]

Investigation of the near field dynamics of a single and tandem array of three jets are provided by 2-D time-resolved particle image velocimetry (TR-PIV) measurements. Instantaneous velocity fields are examined in the transverse and spanwise planes with jet to crossflow velocity ratios in the range from 0.9 to 1.7. Previous studies have shown that for high ratios (≥ 2), the leading jet provides sufficient shielding to ensure that all jets downstream exhibit nearly identical flow characteristics. The current transverse plane measurements exhibit more unique and localized features as a result of the competing effects of pressure gradients and vortex mechanisms assessed via the jet exit profiles, first and second order turbulent statistics, streamline trajectories, recirculation areas and penetrations depths. Proper orthogonal decomposition (POD) is applied to the spanwise plane instantaneous velocity fields to determine the statistically dominant features of the single and tandem jet configurations at equivalent velocity ratios. The velocity fields are then reconstructed using the truncated POD modes to provide further insight into the shear layer and wake vortices that drive these configurations. Vortex identification algorithms are applied to the reconstructed velocity fields to determine the statistical characteristics of the vortices, including their centroids, populations, areas and strengths, each of which exhibit largely different dependencies on jet configuration and velocity ratio. Several of the investigated metrics are found to exhibit different behaviors below and above a velocity ratio of unity and also as a function of increasing velocity ratio between 1 and 2, implying that several transitions mechanisms are present in the low velocity ratio regime investigated herein. [ABSTRACT FROM AUTHOR]

We investigate the control mechanisms of the deep Pacific Ocean circulation by introducing updated methods for parameterizing tidal mixing. The column-integrated rates of dissipation in near- and far-fields are derived from the tidal energy conversion and dissipation rates estimated by a high resolution tide model. In the calculation of the far-field mixing, its dependency on stratification is taken into account based on theoretical and observational knowledge. Unlike previous studies that did not take the stratification dependence into account, the far-field mixing does not function to significantly enhance the deep Pacific Ocean circulation. The deep Pacific Ocean circulation is also found to be insensitive to the decay scale height of the near-field mixing. However, these factors affect the reproducibility of the radiocarbon distribution, especially its minimum in the upper deep layer, through their influence on the mixing with the shallower layers. [ABSTRACT FROM AUTHOR]

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We study how nanophotonic structures can be used for determining the position of a nearby nanoscale object with subwavelength accuracy. Through perturbing the near-field environment of a metasurface transducer consisting of nano-apertures in a metallic film, the location of the nanoscale object is transduced into the transducer's far-field optical response. By monitoring the scattering pattern of the nanophotonic near-field transducer and comparing it to measured reference data, we demonstrate the two-dimensional localization of the object accurate to 24 nm across an area of 2 × 2 μm. We find that adding complexity to the nanophotonic transducer allows localization over a larger area while maintaining resolution, as it enables encoding more information on the position of the object in the transducer's far-field response. [ABSTRACT FROM AUTHOR]

Excitation of novel graphene plasmons is examined using finite-element analysis via COMSOL RF module 5.6. The theoretical model is simulated with graphene grating on the glass substrate having fixed periodicity (Λ = 700 nm) by illumination with transverse magnetic (TM) polarized light through the substrate side. The effect of thickness variation on SPPs excitation has been acquired from transmission spectra while keeping the periodicity and slit width of grating structure constant via analyzing the trend followed by the resonance dips. The electric and magnetic field behavior has also been analyzed for each thickness, and a specific grating thickness of 10 nm was taken into consideration owing to the thickness constraints regarding graphene. Slit width variation of the grating structure has been investigated using far-field analysis to observe the formation of SPPs from transmission spectra and near-field analysis for understanding the underlying physics. These analyses resulted in SPP excitation more appreciable at slit widths in between 250 and 350 nm. The slit width range regarding the chosen periodicity supports the most efficient plasmonics mode and many applications of such devices are found in real life. [ABSTRACT FROM AUTHOR]