Wave Radiation Research Articles

REMOVING RESIDUAL OIL BY INJECTING A SOLUTION-AIR COMPOSITION THROUGH A NEW INJECTOR INTO THE WETTED FORM

In the literature, the physical mechanism of the method of increasing the oil yield of the formation by means of elastic waves is indicated by various terms: vibrating, acoustic, elastic, pulsed, seismoacoustic, etc. We will talk about a general term that illuminates them in their physical essence - the method of wave action. Until now, some industrial-experimental application of the wavy impact method has been carried out in the fields of the former USSR and foreign countries. The wave field is divided into two parts according to the value of the generation frequency - the low-frequency effect of the method (up to 1 kHz) and the high-frequency effect of the method (higher than 1 kHz). The conversion of the first generated energy, the vibrating wave, into elastic energy is divided into mechanical, hydraulic, gas-pneumatic, electromechanical, etc. The use of this and other modifiers is chosen depending on the type of determined method of influence (increasing oil yield, intensification of filtration and reception), the geological and technical condition of the field and individual wells, and most importantly, the expected technical and economic effect. The wave effect is carried out near the selected area of the formation from the ground surface and the wellhead, using special vibration and impulse sources. The main issue of the acceptance of the wave effect method is the understanding of the physical process of elastic wave radiation in a porous medium saturated with formation fluids. Abasov MT, Hadiyev SM, Mirzajanzade AX, Krylov AP, Khavkin AY, etc., are the main works of this issue. carried out by the authors, it was possible to reveal the physical meaning of the processes taking place in the layer. Many modern oil recovery methods, such as the wave effect method, help to reduce the influence of some factors that make oil extraction difficult. However, they do not take into account the fact that they are not applied in time and that natural hydrocarbon fluids move under the influence of gravitational effects and capillary forces, which leads to a decrease in technical and economic indicators. Keywords: injector, diffuser, elastic waves, generation, frequency effect.

On the initial spin periods of magnetars born in weak supernova explosions and their gravitational wave radiation

The initial spin periods of newborn magnetars are strongly associated with the origin of their strong magnetic fields, both of which can affect the electromagnetic radiation and gravitational waves (GWs) emitted at their birth. Combining the upper limit ESNR≲1051\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$E_{\ extrm{SNR}}\\lesssim 10^{51}$$\\end{document} erg on the explosion energies of the supernova (SN) remnants around slowly-spinning magnetars with a detailed investigation on the evolution of newborn magnetars, we set constraints on the initial spin periods of magnetars born in weak SN explosions. Depending on the conversion efficiency η\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\eta $$\\end{document} of the electromagnetic energy of these newborn magnetars into the kinetic energy of SN ejecta, the minimum initial spin periods of these newborn magnetars are Pi, min≃5\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$P_{\ extrm{i, min}}\\simeq 5$$\\end{document}–6 ms for an ideal efficiency η=1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\eta =1$$\\end{document}, Pi, min≃3\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$P_{\ extrm{i, min}}\\simeq 3$$\\end{document}–4 ms for a possible efficiency η=0.4\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\eta =0.4$$\\end{document}, and Pi, min≃1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$P_{\ extrm{i, min}}\\simeq 1$$\\end{document}–2 ms for a relatively low efficiency η=0.1\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\eta =0.1$$\\end{document}. Based on these constraints and adopting reasonable values for the physical parameters of the newborn magnetars, we find that their GW radiation at νe,1=ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u _{\ extrm{e,1}}=\ u $$\\end{document} may be undetectable by the Einstein Telescope (ET) since the maximum signal-to-noise ratio (S/N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm{S/N}$$\\end{document}) is only 2.41 even the sources are located at a very close distance of 5 Mpc, where ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u $$\\end{document} are the spin frequencies of the magnetars. At such a distance, the GWs emitted at νe,2=2ν\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\ u _{\ extrm{e,2}}=2\ u $$\\end{document} from the newborn magnetars with dipole fields Bd=5×1014\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$B_{\ extrm{d}}=5\ imes 10^{14}$$\\end{document} and 1015\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{15}$$\\end{document} G may be detectable by the ET because S/N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm{S/N}$$\\end{document} are 10.01 and 19.85, respectively. However, if these newborn magnetars are located at 20 Mpc away in the Virgo supercluster, no GWs could be detected by the ET due to low S/N\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\mathrm{S/N}$$\\end{document}.

Experimental study of a turnstile aperiodic HF-band antenna with a terminal load in the form of a near ground four-arm spiral antenna

It is known that the energy characteristics of four-arm spiral near ground antennas with internal power supply (at the geometric center) vary significantly depending on the order of excitation of their inputs. When excitation of the arms of such antennas in the cross-polarization mode, their efficiency of radiating electromagnetic waves decreases by an order of magnitude or more; the article proposes an excitation method that is free of this drawback. The aim of the article is an experimental study of the comparative effectiveness of a near ground four-arm spiral antenna of the HF-band and the antenna system it is part of, when changing its excitation type (from internal to external) and mode (main and cross-polarization). A detailed description of the design of the antenna system and the method of implementing the excitation of its emitters are proposed. The proposed design of a phase-shifting device based on a Butler matrix can be used for effective electromagnetic waves radiation or reception by an antenna system of both right and left circular polarization. The results of the analysis of methods for excitation of a near ground four-arm spiral antenna presented in the article can be used in the design or modernization of antenna systems of ionosondes or radio centers with increasing their efficiency.

Basalt Fiber Reinforced Polymers: A Recent Approach to Electromagnetic Interference (EMI) Shielding

ABSTRACTElectromagnetic wave (EMW) radiation pollution is getting more severe as result of the advancement of electronic technology. Researching shielding materials with superior EMI (electromagnetic interference) shielding characteristics is therefore crucial. Basalt fibers (BFs) have been an emerging candidate in the fiber‐reinforced polymer (FRP) category due to their favorable mechanical and chemical properties, along with being favorites in sustainability and having low production costs. Therefore, due to the rising need for cheaper and efficient alternatives in the EMI shielding industry, the EMI shielding is covered in terms of BF composite materials and their properties in this review, starting with the EMI shielding mechanism and followed by how BF composites affect the EMI properties. This review then covers the post‐treatments of BF composites and, finally, the factors of the composites that affect the EMI properties. Moreover, the EMI shielding applications in which BFRPs are used are comprehensively discussed as well. This review aspires to bridge an understanding between EMI shielding as a material property and the BF composites that are developed to aid in the EMI shielding application.

Correction: Performance Evaluation of INSAT‑3D Derived Outgoing Long Wave Radiation Over India Using Remotely Sensed Observations

Correction: Performance Evaluation of INSAT‑3D Derived Outgoing Long Wave Radiation Over India Using Remotely Sensed Observations

A wideband dual-circularly polarized traveling wave dielectric resonator antenna array

ABSTRACT In order to meet the demand of high capacity and high speed transmission of satellite communication system, a wideband dual-circularly polarized dielectric resonator antenna (DRA) array is proposed based on the traveling wave principle. Four DRA elements with slot-coupling excitation are sequentially placed on the ground, and the feeding network is designed to realize the two orthogonal circular polarization radiation waves. A notched copper loop (NCL) around the antenna array is adopted to improve the radiation performance. Depending on the operation of the two ports, the NCL generates the induced currents which rotates clockwise/counterclockwise, increasing the axial ratio bandwidth. In order to further improve the gain stability, the copper sheets are embedded on the top surface of each radiation element, and the copper cylinders perturb the internal field distribution of the DRA to introduce higher-order modes. The measurement results show that the left-hand circular polarization and the right-hand circular polarization operating bandwidths are 11.8% (14.97–16.85 GHz) and 12% (14.91–16.82 GHz). The antenna gain achieves 9.0 dBic. This DRA array can be applied for the vehicle mounted RF terminals in satellite communication.

Gain enhancement of compact CPW‐Fed ultra‐wideband antenna using an FSS reflector

AbstractIn this paper, an enhancement gain of compact CPW‐Fed antenna using a single layer frequency selective surfaces (FSSs) reflector for ultra‐wideband (UWB) applications is presented. A hexagonal CPW‐Fed antenna with a size of 30 × 30 mm2 is realized to provide a UWB bandwidth operation. In this study, a novel design of an FSS unit cell with reduction and a small size of 8 × 8 mm2 is proposed. It allows one to achieve a UWB band‐stop response between 3 and 11.5 GHz. The FSS reflector has 7 × 7 units with a total size of 56 × 56 mm2. This reflector is placed below the antenna at a distance of 20 mm. The main objective of this contribution is to improve the gain level of the antenna, where the proposed antenna achieves an improvement of realized gain of 6.2 dBi with increasing from 2.2 to 8.4 dBi. The antenna became more directive after the integration of the FSS reflector with a directional radiation pattern. The numerical and experimental results are in good concordance with the simulated one. This study is performed in terms of voltage standing wave ratio, radiation pattern, realized gain, and radiation efficiency.

Cylindrical micro-pressure wave radiation from tunnel portals in deep cuttings

Cylindrical micro-pressure wave radiation from tunnel portals in deep cuttings

Fabrication and Evaluation of an Electromagnetic Shielding Material Made of Randomly Chopped Tape Carbon Fiber/Polyamide 6 Composites

Abstract Environmental pollution generated by electromagnetic wave radiation has significantly increased including in automotive applications. Thus, material technology, including polymer composite, has attracted a reduction of the negative effect of electromagnetic radiation. In this study, carbon fiber reinforced polyamide thermoplastic (PA-6/CF) made of carbon fiber with polyamide 6 tape, in the shape of a half-box, was produced using the hot compression method with different tape-length, and then the electrical conductivity and electromagnetic shielding performance were evaluated. The electrical conductivity was obtained from the resistivity measured by using a digital multimeter. Whilst the effectiveness of electromagnetic interference shielding (EMI-SE) was investigated using two methods, calculation, and actual measurement. The result shows that there is a different electrical conductivity between base and slope area of the PA-6/CF box composite. It also was observed that the actual EMI shielding performance shows a corresponding increase with the length of chopped carbon fiber tape and has a higher value compared to the calculated EMI-SE. Then, the highest value obtained for actual EMI-SE was 54 dB for the PA6/CF composite with 20-mm tape length, in the frequency range 0.3 – 1 GHz, and on horizontal antenna polarization. Whereas the composite with 10-mm and 15-mm tape length was the lowest EMI- SE (38 dB) on vertical antenna polarization, in the same frequency range. Furthermore, the microscopy analysis depicted that there are more voids exist in the slope area compared with the base area of the PA-6/CF composites. Finally, the molded PA-6/CF composites can be used as the battery enclosures of electrical vehicles in automobiles.

Local heating at the running crack tip in bcc iron according to molecular dynamics

Abstract This study presents estimates of a possible temperature rise at the crack tip from three dimensional (3D) atomistic simulations of fracture via molecular dynamics (MD) technique. Simulations start from an initial temperature of 0 K. The pre-existing edge crack was loaded in tension mode I. Crack initiation in MD is accompanied by surface dislocation emissions and later by a cross slip of the emitted dislocations into other slip systems. This leads both to stress waves radiation and to local heating in the plastic zone created by these dislocations. The local heating at the crack tip in the surface layers reaches a level of 480–500 K at some atoms, but an average temperature in the plastic zone is lower and depends on a chosen crack tip zone size. In the bulk crystal, where no dislocation emission (i.e. no plastic zone) has been realized, no significant heating is observed at the crack tip. MD results at the free sample surface comply with experimental data for ferritic steels with a pre-existing notch, loaded (quasi-statically) in mode I, as well as with some continuum predictions.

On-chip multifunctional metasurfaces with full-parametric multiplexed Jones matrix

On-chip metasurface for guided wave radiation works as an upgrade of conventional grating couplers, enriching the interconnection between guided wave and free-space optical field. However, the number of controllable parameters in equivalent Jones matrix of on-chip metasurface is limited that restricts the channels for multiplexing. Here, a supercell design based on detour phase and geometric phase has been proposed to reach full-parametric modulation of Jones matrix. As proof of concept, four independent sets of amplitude-phase channels have been experimentally demonstrated through a single on-chip metasurface. Moreover, through joint modulation of three phase mechanisms including detour phase, geometric phase and propagation phase, the Jones matrix could be decoupled from forward- and backward-propagating guided waves for direction multiplexing. This work paves the way for guided wave radiation towards high-capacity multiplexing and may further extend its application in optical communications, optical displays and augmented/virtual reality.

Exploiting Axisymmetry to Optimize CFD Simulations—Heave Motion and Wave Radiation of a Spherical Buoy

Simulating the free decay motion and wave radiation from a heaving semi-submerged sphere poses significant computational challenges due to its three-dimensional complexity. By leveraging axisymmetry, we reduce the problem to a two-dimensional simulation, significantly decreasing computational demands while maintaining accuracy. In this paper, we exploit axisymmetry to perform a large ensemble of Computational Fluid Dynamics (CFDs) simulations, aiming to evaluate and maximize both accuracy and efficiency, using the Reynolds Averaged Navier–Stokes (RANS) solver interFOAM, in the opensource finite volume CFD software OpenFOAM. Validated against highly accurate experimental data, extensive parametric studies are conducted, previously limited by computational constraints, which facilitate the refinement of simulation setups. More than 50 iterations of the same heaving sphere simulation are performed, informing efficient trade-offs between computational cost and accuracy across various simulation parameters and mesh configurations. Ultimately, by employing axisymmetry, this research contributes to the development of more accurate and efficient numerical modeling in ocean engineering.

Effects of nucleon-nucleon short-range correlation and symmetry energy on the evolution of newly born magnetars

Abstract Millisecond magnetars are widely suggested as the central engines powering hydrogen-poor superluminous supernovae (SLSNe). These magnetars primarily lose huge rotational energy through gravitational wave radiation (GWR) and magnetic dipole radiation (MDR), with MDR serving as an energy source for SLSNe. We study the evolution of the magnetar spin, magnetic inclination angle, and the resulting thermal radiative luminosity of the SLSNe, where the impacts of the nucleon-nucleon short-range correlation, the mass and initial spin of the magnetar, and the density-dependent symmetry energy of the dense nuclear matter on the evolution are discussed. The relativistic mean-field theory is employed to calculate the nuclear matter properties, and we particularly concentrate on the time- and space-dependent bulk viscosity which is crucial for the magnetic inclination angle evolution. It is found that the nucleon-nucleon short-range correlation weakens the damping of bulk viscosity of dense matter and therefore inhibits the growth of magnetic inclination angle, and it reduces the MDR (GWR) peak luminosity of a canonical magnetar by several times while it raises the peak thermal radiation luminosity of SLSNe by several times. For magnetars with nonrotating mass obviously lower than the $1.4 \, \rm M_\odot$ with slow initial rotation, the magnetic inclination angle is more likely to evolve towards 0 degrees quickly, and these magnetars are not suitable as the central engine for SLSNe. Within the ‘family’ of FSUGarnet interaction, a stiffer symmetry energy gives a lower threshold of direct Urca process and hence gives a much larger bulk viscosity coefficient, and thus it promotes the growth of the magnetic inclination angle and the GWR for canonical stars but reduces the peak brightness of SLSNe significantly.

Long-term observations of the turbid outflow plume from the Russian River, California

Understanding the mechanisms that spread freshwater away from small river systems and form turbid, low-salinity coastal plumes is crucial for assessing water quality in coastal waters. We present an analysis of 15 years (January 2004 to December 2018) of daily MODIS Aqua satellite data and in situ instrument data on the turbid freshwater plume that forms off the Russian River (California, USA), a prototypical Mediterranean-climate, small mountainous river system (SMRS). We present per-pixel statistical metrics and regression analyses to identify and quantify the controls on the extent and configuration of the plume exerted by river discharge, waves, winds, and tides. While freshwater outflow exhibits a persistent signal in nearshore waters, a large-scale plume only extends offshore into coastal waters during high river flow, when plume turbidity can be detected more than 10 km offshore from the river mouth. Our results show times when wave radiation stress exceeds outflow inertia, confining the plume within the surf zone and leading to an absence of detectable plume turbidity in coastal waters. Although tidal currents significantly influence the plume near the inlet, wind forcing is the primary control on plume shape and extent in coastal waters, deflecting the turbid outflow more than 30 km upcoast or downcoast of the river mouth with respective wind directions. Coriolis forcing is also significant and observed most clearly during periods of high river discharge and low wind forcing. In addition to introducing novel remote sensing methodology for SMRS plume analyses, these findings highlight the complex interplay of forcing related to tides, river discharge, winds, and waves in shaping the behavior of SMRS plumes. New insights include the impact of tides on larger discharges, the role of Coriolis forcing in SMRS plumes, and the effect of cross-shore winds on plume compression. Further, by considering the Russian River as a model for SMRS, this study can be used to ground-truth existing numerical models of small river plumes and to contribute to understanding critical for managing coastal water quality and nearshore ecosystems.

New algorithm of measuring gravitational wave radiation from rotating binary system

In order to investigate the gravitational wave (GW) radiation, without resorting to the traceless transverse gauge approach to the GW formalism of the linearized general relativity, we formulate the so-called modified linearized general relativity (MLGR). As an application of the MLGR, we construct a novel paradigm of measuring the GW radiation from a binary system of compact objects, to theoretically interpret its phenomenology. To accomplish this, we formulate the mass scalar and mass vector potentials for the merging binary compact objects, from which we construct the mass magnetic field in addition to the mass electric one which also includes the mass vector potential effect. Next, defining the mass Poyinting vector in terms of the mass electric and mass magnetic fields in the MLGR, we find the GW radiation intensity profile possessing a prolate ellipsoid geometry due to the merging binary compact objects source. At a given radial distance from the binary compact objects, the GW radiation intensity on the revolution axis of the binary compact objects is shown to be twice that on the equatorial plane. Moreover, we explicitly obtain the total radiation power of the GW, which has the same characteristic as that of the electromagnetic wave in the rotating charge electric dipole moment. We also find that, in no distorting limit of the merging binary compact objects, the compact objects in the MLGR do not yield the total GW radiation power, consistent with the result of the traceless transverse gauge algorithm in the linearized general relativity.

Relationship Between Short and Long Wave Radiation with Cloud Cover in Baghdad City

Short waves are waves that have a short wavelength and are characterised by high frequencies. Therefore, they propagate over short distances from the source and are used for wireless communications and radio broadcasting. As for long waves, they have a long wavelength characterised by low frequencies and usually extend far from the source easily. When the clouds prevent sunlight from reaching Earth, it reflects a large part of it and absorbs part of the radiation that passes through it, so that less radiation reaches the Earth’s surface as a result of the clouds. The daily data of the high, medium, and low cloud cover, as well as the daily and annual data of solar radiation (long and short-wave radiation) were extracted from satellite data collected by the European Center for Medium-Range Weather Forecasting (ECMWF) over the Baghdad station at 00:00 am and 12:00 pm for the period (2015-2019). The study aims to find the effect of cloud cover on long and short waves and to find the type of relationship between them. The results showed that. The High and medium clouds are more visible in winter and less in summer. The clouds of all kinds decrease at 00:00 am and can be observed at noon. The relationship between solar radiation and cloud cover is inverse. In 2015 different types of clouds appeared, including low-lying cumulus and cumulus-medium. The radiation of long waves increases in the spring and summer when the amount of solar radiation entering the atmosphere is greater, and therefore the atmosphere derives its heat from these long waves emanating from the surface of the earth, at a time when the air could not absorb the short waves that make up the sun’s rays when it penetrated it. Through the Pearson coefficient test, several results were obtained, including that the relationship between high, medium, and low cloud cover, as well as total solar radiation, showed an inverse association; the more clouds there are, the less solar radiation reaches the earth’s surface.

Radiation of Electromagnetic Waves by Regular and Biconical Dipoles with Variable Distributed Surface Impedance and Arbitrary Excitation

An approximate analytical solution of a problem concerning the radiation of electromagnetic waves by regular and biconical dipoles with constant and variable complex distributed surface impedance and arbitrary excitation is derived. Solution correctness is confirm by satisfactory agreement of experimental and numerical results from well-known literary sources. Numerical results are given for the input characteristics and radiation fields of the dipoles in the cases of its symmetric and asymmetric excitation by a point source.

Flow characteristics of the rip current system adjacent to a coastal vertical structure for irregular waves

Rip currents are common hazards found on many beaches around the world. The present research examines the rip current flow features adjacent to a coastal vertical structure with total reflection function to the incident waves. The laboratory experiments were conducted over the planar beach for both regular and irregular waves to explore the specific phenomenon for the irregular waves, and a higher-order Boussinesq equation model was adopted in the simulations to analyze the formation mechanism of the flow features. The study results show that, the standing wave pattern for the irregular wave is much weaker than that for the regular wave with inducing only one apparent node rip at the first node line in the reflection wave area. Moreover, the specific “single-vortex” flow pattern was formed in the crossing wave field for the irregular wave tests. This specific flow pattern is found essentially induced by the larger wave reflection rate of the vertical structure, which leads to the strong lateral flow against the downstream longshore current. This specific flow pattern prefers to present for the smaller wave incident angles and larger wave heights and periods, and leads to the feeding flow volume rates discharged more in the form of lateral flow. The C-shaped lateral flow is found mainly induced by the longshore gradient of the wave set-up instead of the non-uniform wave radiation stress nearshore.

Hydrodynamic analysis of an oscillating water column array in presence of variable bathymetry

In this study, hydrodynamic analysis of an oscillating water column (OWC) array in the presence of the variable bathymetry (seafloor depth) is performed by using a semi-analytical potential-flow solver. Within the framework of linear theory, the boundary-value problem associated with wave diffraction and radiation by an OWC array with variable bathymetry is formulated and the semi-analytical hydrodynamic model is developed using the matched eigenfunction expansion method. The fluid domain above variable bathymetry is mathematically discretized into multiple subdomains using the boundary approximation method. The Haskind relation and the energy flux conservation law are used to verify the semi-analytical model. The hydrodynamic performance of the OWC array in the presence of the ripple and coral reef bathymetries are investigated in further. Pronounced oscillations are observed for the curve of reflection coefficient Cr and hydrodynamic efficiency η for cases with ripple and coral reef bathymetries. Bragg resonance is identified as the triggering of the strong oscillations in Cr and η for case of ripple bathymetry. The primary frequency of Bragg resonance and the peaked value of Cr converge as the ripple number increases (i.e., Ns > 3). Particularly, for cases with coral reef bathymetry, the wave resonance modal in open-ended basins results in a significant wave amplification at the weather side of the OWC array.

Surface Wave and Back Radiation Suppression in Microwave Breast Screening

Surface Wave and Back Radiation Suppression in Microwave Breast Screening