Linear Transformation of Electromagnetic Waves in Large-Scale Axially Symmetric Trap

2020 ◽  
Vol 46 (10) ◽  
pp. 992-1003
Author(s):  
T. A. Khusainov ◽  
E. D. Gospodchikov
Keyword(s):  
Linear Transformation ◽  
Electromagnetic Waves ◽  
Large Scale ◽  
Axially Symmetric

A PARALLEL SOLVER FOR REACTION–DIFFUSION SYSTEMS IN COMPUTATIONAL ELECTROCARDIOLOGY

2004 ◽  
Vol 14 (06) ◽  
pp. 883-911 ◽  
Author(s):  
PIERO COLLI FRANZONE ◽  
LUCA F. PAVARINO
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Reaction Diffusion ◽  
Ionic Currents ◽  
Reaction Diffusion Equations ◽  
Reaction Diffusion Equation ◽  
Fiber Direction ◽  
Axially Symmetric ◽  
Reaction Diffusion Systems ◽  
Cardiac Model

In this work, a parallel three-dimensional solver for numerical simulations in computational electrocardiology is introduced and studied. The solver is based on the anisotropic Bidomain cardiac model, consisting of a system of two degenerate parabolic reaction–diffusion equations describing the intra and extracellular potentials of the myocardial tissue. This model includes intramural fiber rotation and anisotropic conductivity coefficients that can be fully orthotropic or axially symmetric around the fiber direction. The solver also includes the simpler anisotropic Monodomain model, consisting of only one reaction–diffusion equation. These cardiac models are coupled with a membrane model for the ionic currents, consisting of a system of ordinary differential equations that can vary from the simple FitzHugh–Nagumo (FHN) model to the more complex phase-I Luo–Rudy model (LR1). The solver employs structured isoparametric Q1finite elements in space and a semi-implicit adaptive method in time. Parallelization and portability are based on the PETSc parallel library. Large-scale computations with up to O(107) unknowns have been run on parallel computers, simulating excitation and repolarization phenomena in three-dimensional domains.

scholarly journals The relationship between small-scale and large-scale ionospheric electron density irregularities generated by powerful HF electromagnetic waves at high latitudes

2006 ◽  
Vol 24 (11) ◽  
pp. 2901-2909 ◽  
Author(s):  
E. D. Tereshchenko ◽  
B. Z. Khudukon ◽  
M. T. Rietveld ◽  
B. Isham ◽  
T. Hagfors ◽  
...  
Keyword(s):  
Geomagnetic Field ◽  
Electromagnetic Waves ◽  
Large Scale ◽  
Small Scale ◽  
Direction Parallel ◽  
Model Calculations ◽  
Amplitude Fluctuations ◽  
Field Lines ◽  
Experimental Values ◽  
Magnetic Zenith

Abstract. Satellite radio beacons were used in June 2001 to probe the ionosphere modified by a radio beam produced by the EISCAT high-power, high-frequency (HF) transmitter located near Tromsø (Norway). Amplitude scintillations and variations of the phase of 150- and 400-MHz signals from Russian navigational satellites passing over the modified region were observed at three receiver sites. In several papers it has been stressed that in the polar ionosphere the thermal self-focusing on striations during ionospheric modification is the main mechanism resulting in the formation of large-scale (hundreds of meters to kilometers) nonlinear structures aligned along the geomagnetic field (magnetic zenith effect). It has also been claimed that the maximum effects caused by small-scale (tens of meters) irregularities detected in satellite signals are also observed in the direction parallel to the magnetic field. Contrary to those studies, the present paper shows that the maximum in amplitude scintillations does not correspond strictly to the magnetic zenith direction because high latitude drifts typically cause a considerable anisotropy of small-scale irregularities in a plane perpendicular to the geomagnetic field resulting in a deviation of the amplitude-scintillation peak relative to the minimum angle between the line-of-sight to the satellite and direction of the geomagnetic field lines. The variance of the logarithmic relative amplitude fluctuations is considered here, which is a useful quantity in such studies. The experimental values of the variance are compared with model calculations and good agreement has been found. It is also shown from the experimental data that in most of the satellite passes a variance maximum occurs at a minimum in the phase fluctuations indicating that the artificial excitation of large-scale irregularities is minimum when the excitation of small-scale irregularities is maximum.

WAVE PROPAGATION IN A CYLINDRICAL WAVE GUIDE CONTAINING INHOMOGENEOUS PLASMA INVOLVING A TURNING POINT

1963 ◽  
Vol 41 (1) ◽  
pp. 113-131 ◽  
Author(s):  
S. N. Samaddar
Keyword(s):  
Electric Fields ◽  
Electromagnetic Waves ◽  
Turning Point ◽  
Boundary Effect ◽  
Inhomogeneous Plasma ◽  
Simple Zero ◽  
Wave Guide ◽  
Wave Number ◽  
Axially Symmetric ◽  
Radial Wave

Propagation of axially symmetric E-type and H-type modes of electromagnetic waves in a radially inhomogeneous plasma inside a wave guide is considered. For E-type modes conditions for the propagation of slow surface waves along the plasma–dielectric interface have been obtained. Approximate expressions for fields for wavelengths much smaller than the ratio of the gradient of the permittivity to the permittivity of the plasma are also given.It is also shown that if the dielectric constant ε(r) of the plasma vanishes along a particular surface r = r0, the electromagnetic fields for E-type modes behave singularly along this surface. In particular, if ε(r) has a simple zero at r0 ≠ 0, the radial and the longitudinal electric fields become singular as 1/ε(r0) and log ε(r0) respectively at r0. On the other hand, if ε(r) has a multiple zero at r0, the singularities of the above-mentioned fields will be as strong as a multiple pole at r0.Turning-point phenomena are also observed when the radial wave number [Formula: see text] vanishes along a surface. It is shown that the fields are oscillatory in the region [Formula: see text] and evanescent in the region [Formula: see text] for both E-type and H-type modes. The treatment of the singular behavior of the fields at ε(r) = 0, and of the turning-point phenomena at [Formula: see text], does not consider any boundary effect; therefore the results obtained here will be valid also for an inhomogeneous plasma column in free space.

scholarly journals RIS-Assisted Space-Air-Ground Integrated Networks: New Horizons for Flexible Access and Connectivity

2021 ◽  
Author(s):  
Lina Bariah ◽  
Lina Mohjazi ◽  
Hanaa Abumarshoud ◽  
Bassant Selim ◽  
sami muhaidat ◽  
...  
Keyword(s):  
Electromagnetic Waves ◽  
Large Scale ◽  
Low Cost ◽  
High Rate ◽  
Time Variability ◽  
Disruptive Technology ◽  
Efficient Manner ◽  
Integrated Network ◽  
Integrated Networks ◽  
Research Issues

Space-air-ground integrated network (SAGIN) has emerged as a paradigm shifting architecture that offers large-scale, flexible wireless coverage and seamless, high-rate connectivity to complement terrestrial communications. Nonetheless, unlocking the potentials of SAGIN is subject to addressing non-trivial challenges associated with their inherent time-variability, self-organization, and heterogeneity. Meanwhile, the concept of reconfigurable intelligent surfaces (RISs) is recognized as a disruptive technology that supports an unprecedented control of electromagnetic waves propagation and potentially offers significant enhancements in spectral efficiency, coverage expansion, and security, all achieved in a low-cost and energy-efficient manner. We anticipate that the integration of RISs into SAGIN will not only play a fundamental role in improving the quality of inter- and intra- layer communications, but will also provide complex interactions among the three network segments, and hence, opens the horizons for a new breed of applications across all industries. In this article, we explore the underlying opportunities and challenges of integrating RIS-enabled communications into SAGIN, and present a forward-looking overview of the cross-layer operational elements supported by RISs. Finally, we outline major enabling technologies and present a look ahead toward addressing open research issues.

scholarly journals Multispectral electromagnetic shielding using ultra-thin metal-metal oxide decorated hybrid nanofiber membranes

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Dayong He ◽  
Nan Zhang ◽  
Aamir Iqbal ◽  
Yuying Ma ◽  
Xiaofeng Lu ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Electromagnetic Interference ◽  
Electromagnetic Waves ◽  
Large Scale ◽  
High Surface ◽  
Electromagnetic Shielding ◽  
X Rays ◽  
Frequency Range ◽  
Practical Applications ◽  
Metal Metal

AbstractLightweight shielding materials that can protect devices against undesirable multispectral electromagnetic waves are critical in electronic, medical, military, and aerospace applications. However, the existing shielding materials are heavyweight and work only in a narrow frequency-range. In this work, we developed metal–metal oxide Ag-WO3 decorated polymeric nanofiber hybrid membranes with versatile multispectral electromagnetic shielding abilities for practical applications. The Ag-WO3 hybrid provides multiple functions, such as excellent metallic conductivity provided by silver, high photoelectric effect and low thermal conductivity arising from the high atomic number in WO3, and strong infrared energy absorbing capability caused by a designed Schottky barrier interface between Ag and WO3. Additionally, the nanofibrous hybrid membrane structure provides high surface area, good air permeability, and robust mechanical strength and durability. These highly conductive, lightweight, ultrathin, and flexible membranes exhibit efficient microwave electromagnetic interference shielding of 92.3 dB at a thickness of ~42 μm in 8–26.5 GHz frequency range, 0.75–0.5 emissivity for near- to far-field infrared bands, and 32.03% attenuation for X-rays of 30 keV at 0.24 mm thickness, indicating their potential for shielding against large-scale multispectral electromagnetic waves from low-frequency microwaves to high-frequency X-rays.

scholarly journals On the new modes of planetary-scale electromagnetic waves in the ionosphere

2004 ◽  
Vol 22 (4) ◽  
pp. 1203-1211 ◽  
Author(s):  
G. D. Aburjania ◽  
K. Z. Chargazia ◽  
G. V. Jandieri ◽  
A. G. Khantadze ◽  
O. A. Kharshiladze
Keyword(s):  
Electromagnetic Waves ◽  
Large Scale ◽  
Low Frequency ◽  
Planetary Scale ◽  
Phase Velocities ◽  
F Region ◽  
E Region ◽  
General Dispersion ◽  
Fast Waves ◽  
The Waves

Abstract. Using an analogy method the frequencies of new modes of the electromagnetic planetary-scale waves (with a wavelength of 103 km or more), having a weather forming nature, are found at different ionospheric altitudes. This method gives the possibility to determine spectra of ionospheric electromagnetic perturbations directly from the dynamic equations without solving the general dispersion equation. It is shown that the permanently acting factor-latitude variation of the geomagnetic field generates fast and slow weakly damping planetary electromagnetic waves in both the E- and F-layers of the ionosphere. The waves propagate eastward and westward along the parallels. The fast waves have phase velocities (1–5)km s–1 and frequencies (10–1–10–4), and the slow waves propagate with velocities of the local winds with frequencies (10–4–10–6)s–1 and are generated in the E-region of the ionosphere. Fast waves having phase velocities (10-1500)km s–1 and frequencies (1–10–3)s–1 are generated in the F-region of the ionosphere. The waves generate the geomagnetic pulsations of the order of one hundred nanoTesla by magnitude. The properties and parameters of the theoretically studied electromagnetic waves agree with those of large-scale ultra-low frequency perturbations observed experimentally in the ionosphere. Key words. Ionosphere (ionospheric disturbances; waves propagation; ionosphere atmosphere interactions)

Eutectic Microbonding of Composite Materials Using Microwave Technology

2021 ◽  
Vol 1164 ◽  
pp. 17-23
Author(s):  
Robert Cristian Marin ◽  
Iulian Ştefan ◽  
Răzvan Ionuţ Iacobici ◽  
Sorin Vasile Savu
Keyword(s):  
Magnetic Materials ◽  
Electromagnetic Waves ◽  
Large Scale ◽  
Input Power ◽  
Thermal Source ◽  
Microwave Generator ◽  
Eutectic Alloys ◽  
Ball Mills ◽  
Load Impedance ◽  
Base Materials

The paper aims to report researches in microbonding process of composite magnetic materials using as thermal source the heat produced in base materials by the conversion of the electromagnetic waves with high frequency into thermal energy. This technology can be applied by targeting the base materials with microwaves and taking into account that composite magnetic materials based on ferrites, present good absorbance and conversion properties of the microwaves into heat. For experimental research, the base materials were sintered sampled of raw products obtained from stoichiometric mixtures of 6Fe2O3 + BaCO3. The raw products were obtained by milling and alloying processes using planetary ball mills. The milling and alloying processes have been perfomed in dry environement for homogeneous mixtures and wet environment for mixtures obtained using mechanical alloying. In terms of eutectic alloys used for microbonding, there have been used lead free Sn96,5%+Ag3%+Cu0,5% with melting point around 2170 C. The microbonding process have been perfomed in two steps: first step was focused on prepairing the base materials by cleaning and deposition of eutectic alloys on their surfaces; the second step was the heating of the base materials in microwave field. A microwave generator with adjustable input power from 0 W to 6000 W with a WR340 waveguide have been used as thermal sources. The researches have shown that the base materials were bonded using less than 10 % of microwave power and the eutectic alloys reached the melting temperature în less than 3 seconds when the magnetron was set to full power. A matching load impedance automatic tuner up to 6000 W have been used for increasing the level of absorbed power from nicrowave generator to samples and decreasing the level of rejected power from composite magnetic material to microwave generator. The temperature have been measured using IR pyrometers with range measurement between 0 and 7000 C. The process can be succesfully applied to a large scale for small parts of electrical engines with permanent cermic magnets.

scholarly journals Output feedback disturbance rejection control for building structure systems subject seismic excitations

2020 ◽  
pp. 002029402095974
Author(s):  
Qixun Lan ◽  
Xiaoguo Zhang ◽  
Yajie Li ◽  
Jingjing Mu ◽  
Weiping Zhu ◽  
...  
Keyword(s):  
Linear Transformation ◽  
Output Feedback ◽  
Disturbance Rejection ◽  
Large Scale ◽  
Inverse Transformation ◽  
Building Structure ◽  
Seismic Excitations ◽  
Structure System ◽  
Disturbance Rejection Control ◽  
Mild Assumption

In this paper, the output feedback disturbance rejection control (OFDRC) problem is considered for buildings structures subject seismic excitations. First, based on a mild assumption and a linear transformation, the addressed problem of building structure system is translated into the output feedback disturbance rejection control problem large-scale system with disturbances. Then, by utilizing generalized-proportional-integral observer (GPIO) technique and output feedback domination approach, an output feedback decentralized disturbance rejection control law is derived via a systematic design manner. The multi-overlapping output feedback disturbance rejection controller is obtained according to the inverse transformation of a linear transformation. Strict theory analysis demonstrates that the states of the structure system will be stabilized to a small bounded region. Finally, an 8-story structure system is employed to evaluate the effectiveness of the proposed control strategy. Simulation results demonstrate that the proposed OFDRC exhibits better seismic loads attenuation ability and strong robustness against model uncertainties.

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