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Hiding an isolated object in free space using a transmissive invisibility cloak has become a significant research area, propelled by advancements in metamaterials and transformation optics over the past decade. Despite the availability of various simplified methods for implementing transmissive cloaks, issues such as impedance mismatches and narrow working bandwidths often arise, posing challenges. Achieving a broadband transmissive cloak in free space has proven to be particularly arduous. This study presents a near‐perfect one‐directional broadband transmissive cloak constructed from multilayer metasurfaces of arbitrary shapes, showcasing superior performance across a broadband frequency range. The phase distribution of the metasurfaces and the efficacy of the transmissive cloak are assessed using the generalized Snell's law. An experimental near‐perfect broadband transmissive cloak is successfully demonstrated to operate within the frequency range of 8.5 to 11.2 GHz. This study contributes to reducing the density and mass of cloaks, thereby facilitating the expansion of cloaking capabilities in various directions and across different frequency bands. [ABSTRACT FROM AUTHOR]

This study examines how the substrate temperature affects the electrical characteristics of the Zr-doped HfO2/Al/Zr-doped HfO2 (HZO/Al/HZO) tri-layer stack. Tri-layer stack is deposited by a simultaneous use of RF magnetron sputtering for HfO2 and DC magnetron sputtering for Zr and Al targets. During deposition, the substrate temperature is varied from 25 to 300°C. The observed hysteresis loop is prominent for the stack deposited at room temperature, while it becomes minute at higher temperatures. Interface trap density and oxide charge density of the tri-layer stack are minimum at 300°C and maximum at room temperatures. Frequency dispersion is detected in the stack deposited at room temperature, but it disappears in stacks deposited at 300°C. In addition, compared to other tri-layer stacks, the stack deposited at 300°C shows good conductivity. Therefore, compared to other samples, the tri-layer stack deposited at 300°C has improved electrical characteristics. It is shown that the substrate temperature has a significant impact on the electrical properties of the stack. [ABSTRACT FROM AUTHOR]

We summarize the method of hydrodynamic approximation for weakly ionized plasmas developed with Klimontovich in 1962 and give a generalization to many—component systems using Onsagers matrix theory and including dispersion effects. We develop the conductivity theory of complex plasma and electrolyte mixtures based on the model of charged hard spheres with given non‐additive contact distances, including frequency‐dependent electric fields. These generalizations are made with the aim to allow applications to complex natural systems as atmospheric plasmas and seawater. Finally, we give as an example a numerical calculation of the single ion conductivities of a six‐component seawater model. [ABSTRACT FROM AUTHOR]

Lignin is one of the most common biopolymers. The application of the electrophysical properties of the polymer is one of the directions of its use. The effect of impurities potassium bromide with an ionic crystal lattice on the electrophysical properties of lignin has been shown. The study of the frequency dependences of the specific electrical conductivity and the components of the complex dielectric permittivity in the frequency range from 6 × 10−2 to 6 × 107 rad s−1 was carried out. The nonadditivity of the electrophysical properties of the lignin‐potassium bromide system has been shown. It is established that the relaxation time of the π‐electrons of the aromatic rings of lignin depends on the content of potassium bromide in the mixture and varies from 1.6 × 10−7 (100% lignin) to 7.5 × 10−4 s (1% of KBr in mixture). The orientation of the positive charge of potassium atom of the KBr dipole atom to the π‐electrons of the benzene ring of lignin leads to change of high‐frequency relaxation time. This effect can be used in frequency filter to eliminate electronic polarization in the high‐frequency region. Thus, the polarization of ionic impurities has a significant effect on the dielectric properties of lignin in the region of medium and high frequencies of alternating electric field. [ABSTRACT FROM AUTHOR]

To design and develop efficient microwave absorbents via phase engineering is still less studied. The unique properties caused by constructing heterophase structure hold the potential to strengthen absorbing capability toward microwave radiation. Herein, amorphous/crystalline γ‐Fe2O3 nanosheets (Fe‐H) are carefully fabricated through a controlled annealing process. The matched Fermi levels formed on both sides of the heterophase interface not only provides efficient interfacial polarizations but also facilitates the transport of electrons with less scattering over the whole Fe‐H nanosheets. Thereby, both of the conduction loss and dielectric polarization relaxation are promoted, leading to a strengthened attenuation toward electromagnetic wave radiation. The as‐synthesized Fe‐H sample exhibited a minimum reflection loss of ‐89.5 dB centered at a thickness of 2.00 mm, associated with an effective absorption bandwidth (reflection loss ≤ ‐10 dB) reaching 6.45 GHz. All of these behaviors are superior to its pure amorphous absorbent and bare crystalline counterpart. Furthermore, this heterophase engineering strategy is valid when extended to Co and Ni based oxides, suggesting its universality and generality for promoting microwave absorption. Henceforth, this study indicates a favorable potential of the synthesis and application of amorphous/crystalline materials as heterophase microwave absorbents. [ABSTRACT FROM AUTHOR]

Abstract In the petroleum sector, spectral-induced polarization (SIP) can detect low-frequency electrical characteristics in rocks without causing any damage. Measurements from 1 mHz to 100 kHz were conducted at ambient temperature for synthetic shale sand combinations from Gabel El-Galala, Cairo, Egypt. Because of an increase in the relative conductor (shale) concentration despite a reduction in the relative insulator (sand) concentration, and the effect of increasing saturation, this is the first study to explain the electrical impact of shale sand combination. We will also look into its saturation and frequency to further model and analyze shale with electrical characteristics. Both conductivity and impedance decrease regarding sand's presence. The dielectric constant increases with increasing shale level and saturation below the percolation threshold but drops beyond it. Material rich in shale has lower impedance than material rich in sand. Concentrating and saturating the shale in the synthetic sand enhanced its electrical conductivity. Ionized liquid and the conductive minerals present in shale also contribute to this improvement. The mixture's electrical characteristics improved significantly as the frequency rose. Low-frequency analysis shows that the samples have high conductive and dielectric constants. These investigations could improve oil and gas recovery by illuminating the electrical characteristics of the reservoir rock.

Injection-molded polyoxymethylene (POM) has molecular chains mainly oriented in the injection direction. We investigated the directional dependence of the polarized infrared reflection and attenuated total reflection spectra by rotating the anisotropic POM sample. Because of the strong absorption and large frequency dispersion of the C–O vibration in the main-chain direction, we found phenomena such as shoulder wing generation that resulted from the mixing of optical responses attributed to the vibration in the main chain and that in the direction perpendicular to the main chain. The spectra of the directional dependence can be explained qualitatively because of the anisotropy of the mode with large frequency dispersion. Graphical abstract This is a visual representation of the abstract. [ABSTRACT FROM AUTHOR]

Clays have considerable influence on the electrical properties of hydrate-bearing sediments. It is desirable to understand the electrical properties of hydrate-bearing clayey sediments and to build hydrate saturation (Sh) models for reservoir evaluation and monitoring. The electrical properties of tetrahydrofuran-hydrate-bearing sediments with montmorillonite are characterized by complex conductivity at frequencies from 0.01 Hz to 1 kHz. The effects of clay and Sh on the complex conductivity were analyzed. A decrease and increase in electrical conductance result from the clay-swelling-induced blockage and ion migration in the electrical double layer (EDL), respectively. The quadrature conductivity increases with the clay content up to 10% because of the increased surface site density of counterions in EDL. Both the in-phase conductivity and quadrature conductivity decrease consistently with increasing Sh from 0.50 to 0.90. Three sets of models for Sh evaluation were developed. The model based on the Simandoux equation outperforms Archie's formula, with a root-mean-square error (ERMS) of 1.8% and 3.9%, respectively, highlighting the clay effects on the in-phase conductivity. The frequency effect correlations based on in-phase and quadrature conductivities exhibit inferior performance (ERMS = 11.6% and 13.2%, respectively) due to the challenge of choosing an appropriate pair of frequencies and intrinsic uncertainties from two measurements. The second-order Cole-Cole formula can be used to fit the complex-conductivity spectra. One pair of inverted Cole-Cole parameters, i.e., characteristic time and chargeability, is employed to predict Sh with an ERMS of 5.05% and 9.05%, respectively. [ABSTRACT FROM AUTHOR]

A spatial-frequency thin-film filter with inclusions of nanoparticles operating in the visible range of the spectrum is investigated. The effect of nanoparticles embedded in the central and lateral layers of the frustrated total internal reflection filter on the spectral characteristics, considering the frequency dispersion, is investigated. It is shown that plasmonic effects cause the splitting of the filter bandwidth into a set of narrow-band spectral lines and the angular splitting of the incident beam into a set of output beams. It is demonstrated that due to the difference in the resonance conditions for s- and p-polarization waves, the spectral lines of transparency do not coincide, which indicates the possibility of using the filter as a polarizer. [ABSTRACT FROM AUTHOR]

Chronoamperometric curves for the oxidation of a ferrocenyl derivative via a potential step, calculated using the Cottrell equation, showed less diffusion-controlled currents on a platinum wire electrode. This lower deviation cannot be explained via Butler–Volmer heterogeneous kinetics, but was ascribed to the negatively capacitive current associated with a redox reaction. The deviation in fully oxidized electrical potential corresponds to the non-zero concentration at the electrode surface, which cannot be predicted using the Nernst equation. This equation expresses the relationship between the electrical potential and activity at the electrode surface rather than the concentration. The diffusion equation determines the relationship between the current and surface concentration rather than activity. Negative capacitance or a non-zero concentration may arise from structure formation on the electrode owing to dipole–dipole interactions, which are similar to the generation of double-layer capacitance, including frequency dispersion. Following this concept, we derive expressions for a lowered diffusion-controlled current and time-dependent surface concentration. The negatively capacitive current shows the time dependence of t−0.9, which is similar to the decay of double-layer capacitive currents. The surface concentration decays with t−0.4-dependence.

Context: Quantum mechanical calculations involving electron correlation, frequency dispersion, and solvent effects were carried out to examine the second-order nonlinear optical response of various acceptor, X (-CF3, -CN, -NO2) substituted in N,N-dimethylaniline (DMA) and julolidine(JLD). Here, both DMA and JLD acts as donor and the three substituted groups, X (-CF3, -CN and -NO2) at the para position of both the ring systems as acceptor. The NLO response (βHRS) of -CF3 and -CN substituted DMA and JLD is relatively lower compared to DMA-NO2 and JLD-NO2. The charge distribution is found higher in case of -NO2 substituted DMA and JLD (±443 and ±449) compared to their -CF3 or –CN substitution. Electronic characteristics such as UV-Vis absorption spectra, crucial excited state parameters and charge transfer contribution to βHRS have been used to explain the NLO parameter of DMA-X and JLD-X. Variation of the incident optical frequency of light shows fluctuation of βHRS value and highest values of βHRS are obtain at the λmax frequency of each compound. Solvent polarity variation study on βHRS shows that βHRS varies linearly with the Kirkwood-Onsagar dielectric factor (D). Methods: All computational studies have been carried out using density functional theory (DFT) based method. Since CAM-B3LYP based hybrid functional improves the asymptotic behavior of the exchange interaction by dividing into short-range and long-range components, first hyperpolarizability values in the present study were computed using DFT/ CAM-B3LYP/ 6-31G+(d,p) level of theory. [ABSTRACT FROM AUTHOR]

In the petroleum sector, spectral-induced polarization (SIP) can detect low-frequency electrical characteristics in rocks without causing any damage. Measurements from 1 mHz to 100 kHz were conducted at ambient temperature for synthetic shale sand combinations from Gabel El-Galala, Cairo, Egypt. Because of an increase in the relative conductor (shale) concentration despite a reduction in the relative insulator (sand) concentration, and the effect of increasing saturation, this is the first study to explain the electrical impact of shale sand combination. We will also look into its saturation and frequency to further model and analyze shale with electrical characteristics. Both conductivity and impedance decrease regarding sand's presence. The dielectric constant increases with increasing shale level and saturation below the percolation threshold but drops beyond it. Material rich in shale has lower impedance than material rich in sand. Concentrating and saturating the shale in the synthetic sand enhanced its electrical conductivity. Ionized liquid and the conductive minerals present in shale also contribute to this improvement. The mixture's electrical characteristics improved significantly as the frequency rose. Low-frequency analysis shows that the samples have high conductive and dielectric constants. These investigations could improve oil and gas recovery by illuminating the electrical characteristics of the reservoir rock. [ABSTRACT FROM AUTHOR]

The last decade has seen the rapid emergence of nonhydrostatic modeling as an advanced tool for studies of tsunami processes and source mechanisms that warrants a critical assessment of the state of the art and value-added features in relation to contemporary approaches. Inclusion of depth-averaged vertical velocity and nonhydrostatic pressure in the nonlinear shallow-water equations enables description of long-wave dynamics in quasi three-dimensional flows. The governing equations involve first-order derivatives, but retain higher-order properties, as in the Boussinesq-type approach. The commonly-used staggered finite difference scheme continues to provide the surface elevation and horizontal velocity, which in turn are updated by the nonhydrostatic pressure evaluated from a Poisson-type equation. In addition to having dispersion properties complementary to the governing equations, the numerical framework allows implementation of time-varying seafloor excitation from earthquake rupture, a shock-capturing scheme for discontinuous flows, and a multilevel two-way nested grid system for dispersive and shock waves. A series of numerical and laboratory benchmarks as well as a case study of the 2011 Tohoku tsunami illustrate the model capabilities in describing tsunami generation, dispersion, shoaling, bore formation, and separation-driven currents with high precision across a wide range of temporal and spatial scales for general application. These capabilities have an important role in resolving effects of detailed earthquake rupture patterns and providing accurate tsunami impact predictions with implications for warning guidance, hazard assessment, and seismological research. [ABSTRACT FROM AUTHOR]

At the moment, there is a scientific and technical problem of developing adequate methods and models of conformal radiating structures with chiral filling based on spiral elements, taking into account the frequency dispersion of macroscopic parameters, allowing for high accuracy of calculations with small computational resources. The paper shows a mathematical model of conformal radiating structures with chiral filling based on spiral elements, taking into account the frequency dispersion of macroscopic parameters. A singular integral equation is obtained with respect to an unknown function of the longitudinal distribution of the current density. The advantage of the developed method is the possibility of correct calculation of the characteristics of conformal radiating structures with filling from chiral metamaterials. The results obtained can be used to create conformal antennas based on chiral metamaterials consisting of spiral elements for mobile radio communication systems. [ABSTRACT FROM AUTHOR]

Chronoamperometric curves for the oxidation of a ferrocenyl derivative via a potential step, calculated using the Cottrell equation, showed less diffusion-controlled currents on a platinum wire electrode. This lower deviation cannot be explained via Butler–Volmer heterogeneous kinetics, but was ascribed to the negatively capacitive current associated with a redox reaction. The deviation in fully oxidized electrical potential corresponds to the non-zero concentration at the electrode surface, which cannot be predicted using the Nernst equation. This equation expresses the relationship between the electrical potential and activity at the electrode surface rather than the concentration. The diffusion equation determines the relationship between the current and surface concentration rather than activity. Negative capacitance or a non-zero concentration may arise from structure formation on the electrode owing to dipole–dipole interactions, which are similar to the generation of double-layer capacitance, including frequency dispersion. Following this concept, we derive expressions for a lowered diffusion-controlled current and time-dependent surface concentration. The negatively capacitive current shows the time dependence of t−0.9, which is similar to the decay of double-layer capacitive currents. The surface concentration decays with t−0.4-dependence. [ABSTRACT FROM AUTHOR]

A mathematical model of the electromagnetic wave propagation in 3D gratings of oriented ferromagnetic nanowires (FMNWs) has been developed based on the solution of a 3D boundary value problem of diffraction for Maxwell's equations supplemented with the Landau–Lifshitz equation. Mathematical modeling of the controllability of frequency dispersion of electromagnetic waves in reconfigurable periodic 3D gratings of oriented FMNWs is performed by the method of autonomous blocks with Floquet channels depending on the direction and magnitude of the bias field under ferromagnetic resonance (FMR) conditions in the millimeter wave range with a change in the periodicity (packing density) of the gratings. [ABSTRACT FROM AUTHOR]

Abstract—The paper describes the ideas about the sources of induced polarization fields generated by external forces of non-electrical origin. Layered polarizable media are considered, over which a change in the sign of induced polarization can be observed for an axial electrical installation. Numerical model experiments substantiate the conclusion that the induced polarization is caused by galvanic currents and is not related to the induction component in this case. [ABSTRACT FROM AUTHOR]

Square steel tube, which is widely used in civil engineering, can suffer from a wide variety of damages and aging defects, thus its nondestructive testing (NDT) has attracted wide attention. This work proposes an ultrasonic guided wave (UGW)-based damage detection method for square steel tubes using structure symmetry. Firstly, the dispersion characteristics of square steel tubes are obtained using the semi-analytical finite element (SAFE) method, after which the optimal guided wave modes for damage located on the long and short edges of the steel tube are selected by modal analysis. Then, using the symmetry of the square steel tube's section, the symmetric layout scheme of the transmitters and the receivers is designed; on this basis, a signal processing strategy for damage detection is proposed by subtracting the receiving signals obtained from symmetric positions. Finally, the effectiveness of the proposed damage detection method is verified by numerical simulations and laboratory experiments. The results show that the proposed method has good inspection accuracy for crack and hole damages on both the long and short edges of square steel tube because the dispersion effect and clutters can be reduced utilizing structure symmetry. It is worth mentioning that the inspection effect for corner holes can be enhanced by modifying the position of the receivers. [ABSTRACT FROM AUTHOR]

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A spatial-frequency thin-film filter with inclusions of nanoparticles operating in the visible range of the spectrum is investigated. The effect of nanoparticles embedded in the central and lateral layers of the frustrated total internal reflection filter on the spectral characteristics, considering the frequency dispersion, is investigated. It is shown that plasmonic effects cause the splitting of the filter bandwidth into a set of narrow-band spectral lines and the angular splitting of the incident beam into a set of output beams. It is demonstrated that due to the difference in the resonance conditions for s- and p-polarization waves, the spectral lines of transparency do not coincide, which indicates the possibility of using the filter as a polarizer.

The results of geophysical surveys at five hydraulic structures of the Middle Urals are presented. The main purpose was to use induction sounding to study the polarization-frequency properties of earth-fill dams for safety assessment. [ABSTRACT FROM AUTHOR]

This paper presents the design and processing of the SAR acquisition technique named frequency scanning (f-SCAN), aimed to obtain high sensitivity to targets with low backscattering and to improve the signal-to-noise ratio (SNR) in wide-swath systems. The f-SCAN is an interesting alternative to the scanning on receive method (SCORE), which needs multiple phase centres achieved using the digital beam forming (DBF) technique. f-SCAN requires less hardware complexity than SCORE; at the same time, it improves the sidelobes and ambiguities' suppression. The elements used in f-SCAN to generate the pencil beam are the true time delay lines (TTDLs) and the phase shifters (PSs). The general methodology to design an f-SCAN spaceborne SAR high-resolution wide-swath (HRWS) system is introduced; emphasis is put on the mathematical definition of the timing parameters and on a novel method of using TTDLs to achieve the full spanning of wide swaths. The processing of f-SCAN data is also considered: we introduce a novel algorithm to limit the data volume and to guarantee an almost invariant slant range impulse response function (IRF) by removing spectral distortions. Eventually, new definitions, specific for f-SCAN, of the well-known SAR performance parameters, are provided. Simulation results and performances are presented. The advantages and disadvantages with respect to SCORE are discussed using the design of a real case system. [ABSTRACT FROM AUTHOR]

Subject and Purpose. In the context of growing anticipation of fundamentally new optical and radiophysical devices, the present study is concerned with the total electromagnetic wave tunneling through an asymmetric three-layer structure such that contains a conductive negative-permittivity layer. The aim of this work is to recognize how the asymmetry property of this three-layer structure acts on the effect of total wave tunneling with the frequency dispersion of the conductive negative-permittivity layer taken into account. Methods and Methodology. The frequency-dependent conditions of the total electromagnetic wave tunneling through an asymmetric three-layer structure are sought by numerical simulations. A universal approach based on the introduction of dimensionless frequencies and dimensionless layer thicknesses allows us to numerically investigate conditions of the total electromagnetic wave tunneling for any desired frequencies and geometric parameters of the asymmetric three-layer structure. Results. It has been shown that the asymmetry property of the three-layer structure can significantly change the total electromagnetic wave tunneling conditions. It has been demonstrated that parameters of the asymmetric three-layer structure can be selected in such a way as to modify the total electromagnetic wave tunneling conditions toward a desired practical application of the structure. It has been found that a proper choice of the parameters can minimize the action of the three-layer structure asymmetry on the electromagnetic wave tunneling effect. Conclusion. Asymmetric three-layer structures can be of use to effectively change conditions of the total electromagnetic wave tunneling in an effort to provide devices under development with desired characteristics.

Acoustic recordings of signals in the 1.5–4.0-kHz band were analyzed for information about the sound speed and attenuation frequency dispersion of a fine-grained sediment found in the New England Mudpatch. Analysis of piston cores established prior bounds for a geophysical parameterization of a seabed model that predicts Kramers–Kronig dispersion relations. Sediment layers are described by the Buckingham viscous grain shearing (VGS) model that accounts for the effects of overburden pressure of compressional and shear speeds and attenuations. A statistical inverse problem was solved by using multiple samples of received levels recorded on two vertical line arrays as a function time and hydrophone depth for six frequencies in the 1.5–4.0-kHz band. A statistical inference model that assumed both model parameters and data samples are random variables quantified information content from marginalization of a conditional posterior probability distribution for the geophysical parameters that characterize the mud layer. From the inferred geophysical parameter point estimates the sediment sound speed and attenuation frequency dispersion are predicted and compared to previously reported direct measurements. Also, the predicted sound-speed gradient in the mud sediment from the VGS model is compared to a previous inference that utilized explosive sources. [ABSTRACT FROM AUTHOR]

High-frequency dispersion of the AlGaN/GaN HEMT output resistance has been investigated. Using the electron momentum balance equation, we demonstrated that the deviation of the dynamic drift velocity from its static value could be considered as the main reason for the high-frequency dispersion of the transistor output resistance. Moreover, a new intrinsic small-signal equivalent circuit has been proposed to consider the output resistance dispersion. Comparison with measured s- parameters have validated the proposed approach.

To tackle the increasing electromagnetic pollution, broadband electromagnetic wave (EMW) absorption materials are urgently needed. Toward this goal, traditional strategies resort to the construction of multicomponent dielectric/magnetic hybrid materials, including ternary, quaternary, or even more complicated systems. However, they always suffer from many intrinsic drawbacks in practical applications. Herein, a theory‐directed strategy is presented to design plainified EMW absorption materials (binary hybrids) via amplified interface effects, which are based on well‐designed multilayer alternating core‐shell nanostructures by chemical vapor deposition (CVD). A defect‐engineered CVD graphene (DG) core composed of graphitic open edges and in‐plane defects is used as a lossy phase. Correspondingly, a CVD Si3N4 layer with nanometer thickness is used as an impedance matching shell. By optimizing the alternating numbers of DG/Si3N4 units, enhanced interface polarization and strong frequency dispersion behavior of permittivity (especially the real part, ε′) are obtained, which helps the plainified binary hybrids to reach an effective absorption bandwidth (EAB) of 8.0 GHz at a thickness of 2.7 mm. Moreover, these plainified hybrids show excellent thermal and pH stability. Even after 1000 °C oxidation, for example, an EAB of 7.44 GHz coupling with a minimum reflection coefficient of −77.3 dB is still achieved. [ABSTRACT FROM AUTHOR]

Stationary problems for the diffraction (tunneling) of a plane electromagnetic wave through a layer of matter with dielectric properties, as well as a quantum particle tunneling through a rectangular potential barrier are considered. It is shown that there are no superluminal motions, and the transit time is always longer when the wave passes the structure at the speed of light.

The notions of negative refraction and negative index, introduced by V. Veselago more than 50 years ago, have appeared beyond the frontiers of macroscopic electromagnetism and purely formal during 30 years, until the work of J. Pendry in the late 1990s. Since then, the negative index materials and the metamaterials displayed extraordinary properties and spectacular effects which have tested the domain of validity of macroscopic electromagnetism. In this article, several of these properties and phenomena are reviewed. First, mechanisms underlying the negative index and negative refraction are briefly presented. Then, it is shown that the frame of the time-harmonic Maxwell’s equations cannot describe the behavior of electromagnetic waves in the situations of the perfect flat lens and corner reflector due to the presence of essential spectrum at the perfect $-1$ index frequency. More generally, it is shown that simple corner structures filled with frequency dispersive permittivity have a whole interval of essential spectrum associated with an analog of “black hole” phenomenon. Finally, arguments are provided to support that, in passive media, the imaginary part of the magnetic permeability can take positive and negative values. These arguments are notably based on the exact expression, for all frequency and wave vector, of the spatially-dispersive effective permittivity tensor of a multilayered structure.

Subject and Purpose. The effect of total electromagnetic wave tunneling through a three-layer structure containing a plasma-like negative-permittivity layer is important for both gaining a better insight into the high-frequency properties of layered solids and, hence, creating new types of high-frequency radio-physical devices. The main purpose is to study the influence the frequency dispersion of the negative-permittivity layer exerts on the electromagnetic wave tunneling through a three-layer structure with an asymmetric dielectric medium. Methods and Methodology. A new universal approach is used, based on introducing dimensionless frequencies and dimensionless layer thicknesses of a three-layer structure. It allows the frequency-dependent conditions of the effect of total electromagnetic wave tunneling to be examined for different frequency ranges and various three-layer structure parameters. Results. It has been shown that taking into account the frequency dispersion of the negative-permittivity layer makes it possible to observe the total tunneling of electromagnetic waves at different frequencies with an appropriate choice of the three-layer structure parameters. In various frequency ranges, the effect of two-frequency total tunneling of electromagnetic waves has been predicted. Conclusion. In the presence of a frequency dispersion of a negative-permittivity layer as part of a three-layer structure, the total electromagnetic wave tunneling conditions of this structure are softened and modified significantly. In this case, unique phenomena arise that can be used to create fundamentally new high-frequency devices in optics, radiophysics, and electronics.

Questions of the experimental determination of the electrical parameters of existing and newly synthesized materials and coatings for microwave frequencies are elucidated. Problems related to microwave measurements of the electrical and geometric parameters of dielectric and magnetodielectric coatings on metallic substrates are examined. An original radio method is proposed for combined measurements of the dependences of the complex dielectric and magnetic permeabilities, as well as the thickness of plane-layered samples of dielectric and magnetodielectric coatings on a metallic substrate. Determination of the electrical and geometric parameters of a coating reduces to minimizing a target function constructed on the basis of the discrepancy of between experimental and computed theoretical values of the field attenuation coefficients for a microwave surface model of the measurements on a grid of discrete frequencies. A simulation model model of the measurements based on the CST Microwave studio (Simulia Corp., USA) and the Matlab system is presented. A simulation model of the measurements is presented based on determining the frequency dependences of the electrical parameters and thickness of a sample of radio-absorbing coating on a metallic substrate. Errors in the estimates of the complex dielectric and magnetic permeabilities in the 9–13.5 GHz band of no more than 10% are found with a confidence level of 0.95 and a mean square deviation in the noise level of 0.006. The proposed method may be in demand in various science-based areas, e.g., microelectronics, aerospace, mechanical engineering, etc. [ABSTRACT FROM AUTHOR]

The permeability of saturated soils has great influence on the velocities and attenuation characteristics of fast compressional wave P1, low compressional wave P2, and shear wave S in saturated soils, respectively. In three different cases, namely zero, finite, and infinite permeability, the wave equations and theoretical velocities of P1, P2, and S wave in saturated soils are given based on the u-w-p equation, respectively. According to the solutions of the wave equations, the real velocities and attenuation coefficients of three waves are redefined, respectively. In different saturated soils, the influences of the permeability and the loading frequency on the wave velocities and attenuation are discussed, respectively. Moreover, the suitable application scope of the u-p equation is discussed based on different permeabilities and loading frequencies. [ABSTRACT FROM AUTHOR]

This paper presents the new version of the operational code used at the Tsunami Warning Centers in French Polynesia and in mainland France. This nested multigrid code solves either the nonlinear shallow water or the weakly nonlinear Boussinesq equations in a spherical or Cartesian coordinates system. The objective is to simulate the propagation of tsunamis both in the context of tsunami early warning and in the context of research. The originality of this code is to simulate the tsunami propagation through a series of nested grids in which the numerical scheme is specified by the user. Three standard finite-difference methods and two finite volume schemes are available to take into account the dispersive nature of waves or to capture flow discontinuities. The performance of the five numerical schemes has been assessed through idealized 1D and 2D test cases. The convergence rate with grid refinement is evaluated for three of these tests. Diffusion and dispersion of the five schemes are evaluated through the 1D far-field propagation in a channel of constant depth. Finally, two-dimensional simulations of the 2011 Japanese tsunami are performed considering a homogeneous tectonic source. Coastal inundation is simulated in the bay of Kamaishi where run-up heights reached 10 m. The ability of the five schemes to propagate trans-Pacific tsunamis is evaluated through comparisons of time series between simulations and observations at DART buoys. In the context of tsunami early warning, numerical results show that standard finite-difference methods reproduce most of the observed time gauges and that numerical errors associated to these schemes are acceptable. • Tsunami simulation is performed both in a research and an operational context. • Three finite-difference methods and two finite volume schemes are presented. • The five numerical schemes are assessed through 1D and 2D numerical experiments. • The trans-Pacific propagation of the 2011 Japanese tsunami is simulated. • Standard finite-difference methods are acceptable in an operational context. [ABSTRACT FROM AUTHOR]

The widespread use of anisotropic composite dielectric coatings operating in the microwave range in various science-intensive areas has led to the search and selection of effective methods for radio wave nondestructive testing of their electrophysical parameters. The existing approaches based on estimating the reflection and transmission coefficients of electromagnetic waves have low accuracy and reliability in assessing the components of the complex permittivity tensor and the thickness of such coatings and fail to take into account the frequency dispersion of these coatings and their placement on a metal substrate. In this paper, we propose an original method for local evaluation of the components of the complex dielectric permittivity tensor taking into account their frequency dispersion, as well as the thickness of anisotropic dielectric coatings on a metal substrate using radial surface electromagnetic waves of the microwave range. The method is based on solving inverse problems to determine the components of the dielectric permittivity tensor and the thickness of the coatings from the frequency and angular dependences of the field attenuation coefficient of the radial surface electromagnetic wave excited in the sample under study. The numerical and field experiments have shown that for a measurement frequency band of 9–13.5 GHz, the errors in the estimates of anisotropy coefficients are no more than 10% with a confidence level of 0.95. The statistical limit of the resolution of the magnitude off anisotropy in the dielectric permittivity is introduced and substantiated; this makes it possible to evaluate the ability of the method to distinguish two close values of any pair of components of the dielectric constant tensor. Numerical and field experiments have shown that the method can ensure estimation of these values when the difference between them is 0.2–0.3% or less in the frequency range of 9–13.5 GHz. [ABSTRACT FROM AUTHOR]

An improved millimeter-wave nonlinear model for InP heterojunction bipolar transistor (HBT) is proposed in this letter. The frequency dispersion effect has been taken into account in the Agilent HBT model in Agilent ADS software. Model verification is carried out by comparison of measured and simulated dc and S-parameters up to 110 GHz. [ABSTRACT FROM AUTHOR]

The development of metamaterials has led to the search and selection of effective methods for radio wave nondestructive testing of their electrophysical parameters. The existing approaches to testing, based on the recovery of the effective electrophysical parameters of metamaterials from the reflection and transmission coefficients of an electromagnetic wave, have low reliability and do not provide the local inspection of the parameters. In this paper, we propose for the first time a radio-wave method for local inspection of complex dielectric and magnetic permeabilities, as well as the thickness of flat-layered samples of metamaterials on a metal substrate using surface electromagnetic waves of the microwave range. The method is based on solving the inverse problem of determining the effective electrophysical parameters of a metamaterial from the frequency dependence of the complex attenuation coefficient of the field of a surface electromagnetic wave excited in the sample under study. In this case, the electrophysical parameters of the metamaterial are represented in the form of parametric frequency functions in accordance with the Drude–Lorentz dispersion models, and the solution of the inverse problem is reduced to minimizing the objective function constructed from the discrepancy between the experimental and calculated theoretical values of the attenuation coefficients of the surface electromagnetic wave field on a grid of discrete frequencies. The structure of the measuring complex that implements the proposed inspection method is presented. A sample of a flat-layered metamaterial based on SRR elements with a region of negative refraction in the frequency range of 10.06–10.64 GHz was investigated for the numerical and experimental verification of the method. Experimental verification has shown that the local values of the effective electrophysical parameters of the studied metamaterial differ from the calculated ones by no more than 10%. [ABSTRACT FROM AUTHOR]

This paper presents a comparative analysis of the mixture models used in radio physics to describe the effective properties of composite materials and formulates the limits of their applicability and criteria for checking their correctness. Two of the most general models have been chosen, which take into account the transformation of the composite structure upon changes in its composition. The correspondence of the chosen model to the experimental results is considered. The effect of the composite structure on the frequency of the maximum and the shape of its dielectric absorption line is shown. The analysis shows that the complication of the models in comparison with those already known and an increase in the number of parameters determined from the experiment is inappropriate at the existing level of the composition and material parameters (permittivity and permeability) measuring error and due to a significant contribution of the size and surface effects, which is not taken into account in quasi-static mixture models. [ABSTRACT FROM AUTHOR]

We present the results of a study that confirms the high efficiency of using surface microwaves in assessing the extent of exfoliation of dielectric and magnetodielectric coatings from a metal base. The complex coefficient of attenuation of the field of a surface electromagnetic wave along the normal to the coating surface is used as a parameter for estimating the extent of exfoliation. In contrast to the existing approaches, the developed electrodynamic measurement model takes into account the real and imaginary parts of the complex dielectric permittivity and magnetic permeability of the coating with allowance for their frequency dispersion; this improves the accuracy and reliability of estimating the extent of exfoliation. An algorithm is developed for estimating the extent of coating exfoliation based on the search for the maximum joint probability density of the coefficient of attenuation of the field of a surface electromagnetic wave measured at a set of frequencies. We introduce and substantiate a statistical limit of the resolution of two values of exfoliation; this makes it possible to evaluate the possibility of discriminating between two close values of exfoliation depending on the bandwidth of attenuation coefficient measurements, their number, and the signal-to-noise ratio. The structure of a measuring complex that implements the proposed approaches to exfoliation assessment is provided. Numerical and field experiments have shown the fundamental possibility of estimating the value of recorded values of exfoliation of dielectric and magnetodielectric coatings from a metal substrate with a thickness of 20 μm or less in the frequency band of 9–13.5 GHz. [ABSTRACT FROM AUTHOR]

The applicability of dispersive and nondispersive wave models for describing long-wave propagation and run-up on a beach in the case of composite bottom topography is investigated: a plane beach transforms into a zone of constant depth. Numerical simulations are performed in the framework of two models: (1) nonlinear shallow-water theory and (2) the dispersive model in the Boussinesq approximation based on modified Peregrine equations. Simulations are compared with the data of a laboratory experiment for different types of waves: regular waves, biharmonic signals, and "vessel-like" wave trains strongly modulated by frequency and amplitude. Conclusions about the applicability of the corresponding theories for describing considered types of waves are drawn based on this comparison. [ABSTRACT FROM AUTHOR]

In the presence of prominent gate oxide trapping, the conventional technique for channel mobility extraction in MOSFETs based on I – V/C – V measurements becomes inadequate. This is the consequence of two different effects associated with oxide traps: gate voltage stretch-out and electron trapping and detrapping in the oxide at the megahertz (MHz)-range frequencies that are commonly utilized. In thin-channel planar InGaAs MOSFETs, both effects are observed and found to result in a severe overestimation of mobile charge and subsequently an underestimation of mobility using I – V/C – V. To address this issue, we demonstrate a new mobility extraction technique (RF- ID) based on concurrent I – V and S-parameter measurement in the gigahertz (GHz) regime that is largely immune to oxide trapping. Excellent agreement with Hall measurements as well as with theoretical predictions from Poisson–Schrodinger simulations gives confidence to the new technique. Importantly, the new technique is not limited to InGaAs planar MOSFETs, but applies to any device geometry and any material system. Promising mobility ~1100 cm2/V⋅s is found in quantum-well planar InGaAs MOSFETs with a 4-nm-thick channel. [ABSTRACT FROM AUTHOR]

In this study, the temperature dependence of dielectric behaviours and the polarisation and electrostrain responses of 0.4Bi(Ni 1/2 Zr 1/2)O 3 –0.6PbTiO 3 (0.4BNZ–0.6PT) were studied to better understand their electrical performance. A Rietveld refinement analysis of the XRD pattern, supported by bright-field TEM images, suggests the coexistence of tetragonal and pseudocubic phases. Above 398 K, the normalised piezoelectric coefficient (d 33 ∗) increases due to heating, reaching 941 pm/V at 453 K. Most importantly, 0.4BNZ–0.6PT displays obvious frequency dispersion in the ferroelectric state. A low-temperature dielectric anomaly occurred at approximately 175 K that was related to the origin of the frequency dispersion. The planar electromechanical coupling constant (k p) also changed considerably after heating, increasing from 0.14 at 90 K to 0.43 at 300 K. This indicates an intrinsic relationship between the dielectric and piezoelectric behaviours. Our study demonstrates that there is a significant difference between typical ferroelectrics and the ferroelectric state of 0.4BNZ–0.6PT relaxor ferroelectrics. [ABSTRACT FROM AUTHOR]

The problem of calculating the reflection and transmission coefficients of elastic P-wave incident from a porous half-space onto a fluid-filled crack is solved. The influence of capillary effects arising at the interface between a crack and a porous matrix on these coefficients is analyzed. In the first-order (single-) scattering approximation, the wave number of the effective P-wave propagating in a porous-fractured medium is calculated. It is shown that the hydrodynamic effects associated with fluid filtration at cracks' boundaries in the field of an acoustic wave lead to significant frequency dispersion of the effective P-wave velocity. [ABSTRACT FROM AUTHOR]

Digital beamforming (DBF) with Scan-On-Receive (SCORE) in elevation is a powerful technique for spaceborne synthetic aperture radar (SAR) to achieve high-resolution wide-swath (HRWS) images. DBF in spaceborne SAR should be implemented in real-time to reduce the volume of the downloaded data. Current digital beamformers in SAR systems usually use phase shift instead of a time delay network to ensure real-time implementation. However, conventional phase shift DBF SAR with narrow array bandwidth is not applicable for broadband signals. The beam steering deviation as a function of frequency is obvious for signals with large fractional bandwidth, which appears as a phenomenon of frequency dispersion. If the signal bandwidth is wider than the array bandwidth, frequency dispersion can significantly deteriorate the signal-to-noise ratio (SNR) and must be well relieved. This article analyzes the frequency dispersion in DBF SAR and proposes an innovative DBF-SCORE scheme with specially designed scalloped beam. The proposed digital scalloped beamforming (DSBF) scheme is effective in relieving the influence of frequency dispersion in DBF SAR. Theoretical analysis and simulation results validate the effectiveness of the proposed scheme. The proposed DSBF scheme gives practical solution to the problem of frequency dispersion in broadband DBF SAR, which makes DBF-SCORE a more practical technique for future spaceborne HRWS SAR. [ABSTRACT FROM AUTHOR]