External Electromagnetic Radiation Research Articles

Multistable dynamics in a Hopfield neural network under electromagnetic radiation and dual bias currents

This paper investigates a Hopfield neural network under the simulation of external electromagnetic radiation and dual bias currents, in which the fluctuation of magnetic flux across the neuron membrane is used to emulate the influence of electromagnetic radiation. Utilizing conventional analytical methods, the basic properties of the proposed Hopfield neural network are discussed. Due to the addition of electromagnetic radiation and dual bias currents, the Hopfield neural network shows high sensitivity to system parameters and initial conditions. The proposed Hopfield neural network possesses multistability with periodic attractor, quasi-periodic attractor, chaotic attractor and transient chaotic attractor, and all of the attractors are hidden attractors because there is no equilibrium point in the system. In particular, when the neuron membrane magnetic flux is different, the system can present transient chaos with different chaotic times. More interestingly, with the change of system parameters, the proposed Hopfield neural network can exhibit parallel bifurcation behaviors. Finally, the Multisim simulation and hardware experiment results based on discrete electronic components are conducted to support the numerical ones. These results could give useful information to the study of nonlinear dynamic characteristics of the Hopfield neural network.

Isomers as a bridge between nuclear and atomic physics

The year 2021 marks exactly 100 years since Otto Hahn discovered the first example of nuclear isomerism. The existence of long-lived nuclear excited states opens a window on nuclear structure and applications. From isomers, the availability of electromagnetic decay pathways enables coupling to the atomic electrons, such that nuclear and atomic transitions become interdependent. The nuclear decay process of internal conversion is the most well known. However, observation of its inverse, nuclear excitation by free electron capture, is controversial and requires further research. In this work, the relationship between nuclear and atomic transitions is outlined, and examples are discussed of the use of external electromagnetic radiation to manipulate nuclear transitions associated with isomers.

Stimulation of Waves and Instabilities in Response to Irradiation of Electromagnetic Fields into Plasmas

Plasma is a unique phase of matter constituting positively or negatively charged atoms, excited atoms, neutral atoms, electrons, radicals, etcetera displaying a unique role in the nuclear fusion research besides studying electrical discharges in the domain of switching devices and biomedical applications lately. We discuss in this extensive proposition the fundamental plasma characteristics such as Debye length, plasma oscillations, plasma sheath and condition for sustainability and confinement of plasmas, besides examining the elementary waves in plasmas namely zero waves, electron plasma wave and ion plasma wave. The inherent electron plasma wave and ion plasma wave is associated with the driving of plasma currents which in turn depends upon the density perturbation and thermal velocities of the electrons and ions. The application of external electromagnetic radiation such as laser (pump wave) into the plasma modifies the dispersion relations of electron and ion plasma wave, respectively. The laser stimulates a plethora of waves in the plasma and undergoes remarkable physical phenomena such as self-focusing and filamentation of laser beams. The excitation of sideband waves of the laser beams into the plasma plays a key role in imparting ponderomotive force on the electron plasma waves leading to turbulence in the plasmas due to coupling of the waves. The oscillatory velocity of the electron due to pump wave, plasma density perturbation, ponderomotive force and current densities are associated with the excitation of instabilities in the plasma. Conclusively, such waves and instabilities in unmagnetized and magnetized plasma is comprehensively studied and concluded by proposing the investigation of unexplored twisted electromagnetic wave-plasma interaction.

Cyclotron resonance overtones and near-field magnetoabsorption via terahertz Bernstein modes in graphene

Two-dimensional electron systems subjected to a perpendicular magnetic field absorb electromagnetic radiation via cyclotron resonance (CR). Here we report a qualitative deviation from this well-known behaviour in graphene. Our measurements of the terahertz photoresponse reveal a resonant burst at the main overtone of the CR that exceeds the signal detected at the position of the ordinary CR. The dependencies of photoresponse on the magnetic field, doping level and sample geometry suggest that the origin of this anomaly lies in the near-field magnetoabsorption facilitated by the Bernstein modes—ultraslow magnetoplasmonic excitations reshaped by non-local electron dynamics. Close to CR harmonics, these modes are characterized by a flat dispersion and diverging plasmonic density of states that amplify radiation absorption. Besides carrying fundamental interest, our results show that radiation absorption via non-local collective modes can facilitate a strong photoresponse—a behaviour potentially useful for infrared and terahertz technology. Electrons in an external magnetic field absorb electromagnetic radiation via cyclotron resonance. Deviations from this behaviour in the form of overtone resonances due to ultraslow magnetoplasmonic excitations are now reported for graphene.

Multi-scroll hidden attractor in memristive HR neuron model under electromagnetic radiation and its applications.

This paper aims to propose a novel no-equilibrium Hindmarsh-Rose (HR) neuron model with memristive electromagnetic radiation effect. Compared with other memristor-based HR neuron models, the uniqueness of this memristive HR neuron model is that it can generate multi-scroll hidden attractors with sophisticated topological structures and the parity of the scrolls can be controlled conveniently with changing the internal parameters of the memristor. In particular, the number of scrolls of the multi-scroll hidden attractors is also associated with the intensity of external electromagnetic radiation stimuli. The complex dynamics is numerically studied through phase portraits, bifurcation diagrams, Lyapunov exponents, and a two-parameter diagram. Furthermore, hardware circuit experiments are carried out to demonstrate theoretical analyses and numerical simulations. From the perspective of engineering application, a pseudo-random number generator is designed. Besides, an image encryption application and security analysis are also performed. The obtained results show that the memristive HR neuron model possesses excellent randomness and high security, which is suitable for chaos-based real-world applications.

Thermal radiation ofsubwavelengthparticles

A method is proposed for calculating the dependences of the emissivity of subwavelength parti-cles (SP) from various materials in the form of disks, spheres, cubes and cylinders on their sizes (D) and temperature (T), for cases when external electromagnetic radiation practically does not affect their temperature. For all the listed types of particles, the cutoff wavelengths λcutoffdepending on the size of the SP and the particle shape coefficients ξare determined. With a decrease in the particle size, from the radiation spectrum, which was originally described by Planck's law, wavelengths exceeding λcutoffare gradually excluded. This leads to a decrease in the integral radiation, a decrease in the emissivity and a shift of the radiation spectrum to the blue region. A simple scheme is also proposed for determining ε -the emission coefficients of the midrange according to the calculated graph ε (U), where: U = (ξ × D × T) / B; B is the con-stant of the Wien displacement formula.

Effect of external electromagnetic radiation on the anomalous metallic behavior in superconducting Ta thin films

We investigated transport characteristics of superconducting Ta thin films with three configurations in rf radiation filters; no filter, only room-temperature filters, and low-temperature filters in addition to room-temperature filters. The transport properties near the transition temperature are strongly dependent on whether the room-temperature filter is installed or not. The entire transition is shifted to higher temperature with loading layers of the room-temperature filters. Once the zero-resistance state is achieved at B=0, no strong radiation effect is observed even with low-temperature filters installed. When magnetic field is turned on, the nonzero-resistance saturation at low temperatures is revealed without low-temperature filters, which has been considered to be magnetic-field-induced quantum metallic phase. However, the insertion of the additional low-temperature filter weakens the saturation of the resistance, the signature of the metallic behavior. This observation suggests that the previously reported anomalous metallic state in Ta films is mainly induced by the unfiltered radiation and, thus, the intrinsic metallic ground state should be limited to the narrow range of magnetic fields near the critical point, if exists.

Anomalous Josephson effect

Abstract This review is devoted to one of the most relevant areas of modern condensed matter physics, the anomalous Josephson effect (AJE), which consists of the appearance of a phase shift in a hybrid structure, leading to a finite superconducting current at zero phase difference. AJE reflects the joint manifestation of superconductivity, spin-orbit interaction, and magnetism, and the study of such structures allows progress in understanding their mutual influence, while also opening up promising applications in superconducting spintronics. This review describes the physics of the φ 0 junction, the control of the magnetic properties of the barrier by means of a superconducting current, and, in turn, the effect of the magnetic moment of the barrier on the Josephson current. A discussion of new effective methods of magnetic moment reversal in the φ 0 junction, in particular, by a superconducting current pulse, as well as studies of the quantum properties of Josephson nanostructures with magnetic and topologically nontrivial barriers for the creation of new superconducting spintronic devices, is presented. The experimental realization of the φ 0 junction, which has recently been demonstrated in a number of studies by direct measurement of the current-phase relation, allows the magnitude of the spin-orbit coupling to be measured and opens up new possibilities for the phase control of Josephson devices. This research helps in understanding fundamental spin-dependent phenomena and developing applications for computer technology. In particular, control of the magnetic state by superconductivity opens up new possibilities for the development of ultrafast cryogenic memory. This review presents the results of studying the magnetic dynamics along the current–voltage characteristic of the φ 0 junction and analysis of the spin dynamics in this junction. The question of the possibility of controlling the magnetic precession by the appearance of higher harmonics in the current–phase relation, as well as the DC component of the current, which significantly increase near ferromagnetic resonance, is considered. Interesting phenomena in the φ 0 junction occur under the influence of external electromagnetic radiation. Thus, the review presents an analysis of the main theoretical and experimental work devoted to AJE, gives examples of the manifestation of AJE in various systems, indicates the prospects for research in this area, and discusses unsolved problems.

Wireless Data Collecting Device with RF Energy Harvester for Aircraft

The paper considers the problems of developing the wireless devices for monitoring the parameters of aircraft units and assemblies and the wireless data transmission providing the low energy consumption and eliminating the external electromagnetic radiation influence on the data link. A structural diagram of the device is presented, a solution for the problem of the external electromagnetic field influence on the data link is proposed, and the energy consumption calculations for the device are presented.

An inertial model of vortices to explain the extreme sensitivity of hexatic vortex fluid to low frequency ac excitation

Recently, it has been demonstrated that the Hexatic vortex fluid realized in 2-dimensional vortex state of a very weakly pinned amorphous MoGe thin film is extremely sensitive to external ac excitation. A large amplification of resistance is observed when the sample is exposed to external electromagnetic radiation or a small ac current is superimposed with the subcritical measuring dc current. The observed resistance strongly depends on both amplitude and frequency of the ac excitation. In this paper, we develop an inertial model of vortex lattice subjected to a small amplitude of ac current, by extending the flux creep theory. We show that the resistance increases exponentially with both amplitude and frequency of the ac current and explain quantitatively the variation of resistance with the amplitude and frequency of ac current using the presented model.

Effects of aging level on induced heating-healing properties of asphalt mixes

This research investigates the effects of asphalt mixture aging on induced heating-healing processes. Induced healing of asphalt mixes, performed through applying external electromagnetic radiation, is an innovative preventive maintenance technique for repairing cracks in asphalt mixture. The fluidity and crack filling capability of asphalt binders play a pivotal role in induced healing characteristics. In this paper, activated carbon was used to enhance electromagnetic sensitivity of mixes. In order to impose various levels of aging, asphalt concrete specimens were aged in the oven for 3, 5, 7, and 9 days at 85 ℃. The indirect tensile and semicircular bending tests were conducted to evaluate the healing capability of mixes under the cyclic breaking-healing scenario. The evolution of various aging levels, under various loading cycles, crack lengths, and breaking temperatures, indicates the adverse effect of the aging on the induced healing process. It was concluded that the efficiency of induced heating-healing in asphalt mixes decreases as the aging level is increased. Moreover, it was deduced that induced healing efficiency of asphalt mixes fractured at low temperatures is more than that of asphalt mixes fractured at intermediate temperatures. In addition, statistical analysis was conducted to evaluate the statistical significance of different parameters, such as aging level, notch length, modification, and their interactions, in the induced healing process of asphalt mixes. The results indicate the necessity of considering the aging level of asphalt mixes in analyzing induced heating-healing processes under the external electromagnetic field.

Stair-Like Frequency Response of Single Neuron to External Electromagnetic Radiation and Onset of Chaotic Behaviors

The nonlinear response of neuron firing under external electromagnetic radiation as well as transmembrane current, as two kinds of external forces, are studied in an improved Fitzhugh–Nagumo (FHN) model. The control effects of external forces to neuron firing are measured by winding number [Formula: see text] during mode transition of motion types. The phenomenon of match and mismatch between the angular frequency [Formula: see text] and the angular frequency of external forcing can be explained by whether the winding number is [Formula: see text] or not. [Formula: see text] remains as constants like [Formula: see text], [Formula: see text] and [Formula: see text], etc. The amplitude of transmembrane current [Formula: see text] is increased so that it distributes in a stair-like structure in parameter space before the system enters chaotic state when [Formula: see text] is large enough. The scenarios of motion type switching are different between and beyond in the stairs. Besides, the occurrence and the disappearance of chaos are accompanied with the destruction of the orbit with the variation of parameters which temporarily spoils the toroidal topology and induces chaotic oscillation. Indeed, nonlinear response to external forces is pivotal to neuron firing and its control.

Landau–Kelly representation of statistical thermodynamics of a quantum plasma and electron emission from metals

We have investigated the influence of a strong magnetic field on various aspects of a quantum Fermi plasma. Due to the strong magnetic field, the distribution function becomes anisotropic. First, we consider non-degenerate quantum, Landau and Kelly distribution function. It was found that the adiabatic equation is similar to the adiabatic equation for a Maxwell distribution function, when we include the magnetic field in the energy expression. Using the Kelly distribution for a degenerate, quantum Fermi gas, parallel and perpendicular components of the pressure were derived. It was found that perpendicular component of pressure never becomes zero and three-dimensional system always stay three-dimensional. Lastly, we investigated electron emission from metals and have shown the influence of the magnetic field. We calculated thermionic emission, the so-called Richardson effect. In addition, we investigate the influence of external electromagnetic radiation on the electron current density (Hallwachs effect) from metals.

Arrays of Metal Nanostructures for Plasmon-enhanced Spectroscopy

We report on the study of localized surface plasmon resonances (LSPRs) arising in arrays of metal (Au) nanoclusters, dimers, and nanoantennas under the influence of external electromagnetic radiation. Using nanolithography, the plasmonic arrays with different morphologies including cylindrical nanoclusters and dimers, linear and H-type nanoantennas were fabricated. Their LSPR frequencies were determined from the analysis of optical reflection and IR spectra. LSPR frequency depends strongly on morphology of metal nanostructures and is varied from visible to terahertz spectral range with variation of the structures from cylindrical nanoclusters to the nanoantennas with a high aspect ratio. We established the interconnection between the structural parameters of the plasmonic arrays and their LSPR frequencies based on the results of 3D electrodynamic simulations.

Capturing and shunting energy in chaotic Chua circuit

Abstract Nonlinear electric devices are critical for building chaotic circuits and the outputs voltage from the capacitor are often detected for further analyzing the dynamics of the nonlinear circuits. Continuous exchange between the electric field energy in the capacitor and magnetic field energy in the induction coil is effective to keep continuous oscillation in the circuit. That is, energy encoding and transmission can regulate the dynamical behaviors in chaotic circuits. In this paper, a branch circuit, which is built by using a capacitor and induction coil, is paralleled with one output end of chaotic Chua circuit, and this external branch circuit is activated to control chaos by pumping energy from Chua circuit and capturing external electromagnetic radiation. From dynamical control view, it explains the mechanism for differential control via capacitor and integral control via induction coil. While in the view of energy encoding, the control branch of circuit built by using a capacitor connected with induction coil in series can capture some external field energy and thus the nonlinear behaviors are controlled by generating equivalent current in the branch of control circuit. The circuit equation and also the dimensionless dynamical system under energy control are obtained, and numerical studies are supplied to confirm the control mechanism from physical view. In the end, it gives possible suggestions to enhance the control effectiveness in experimental way.

Extreme sensitivity of the vortex state in a -MoGe films to radio-frequency electromagnetic perturbation

Recently, detailed real space imaging using scanning tunneling spectroscopy of the vortex lattice in a weakly pinned a-MoGe thin film revealed that the vortex lattice melts in two steps with temperature or magnetic field, going first from a vortex solid to a hexatic vortex fluid and then from a hexatic vortex fluid to an isotropic vortex liquid. In this paper, we show that the resistance in the vortex fluid states is extremely sensitive to radio-frequency electromagnetic perturbation. In the presence of very low-amplitude excitation above few kilohertz, the resistance increases by several orders of magnitude. On the other hand when the superconductor is well shielded from external electromagnetic radiation, the dissipation in the sample is very small and the resistance is below our detection limit.

Calculation of specific absorption rate (SAR) in human brain neurons using complex permittivity

The effect of the external electromagnetic radiation on the human brain has been investigated by the numerical calculation of the frequency-dependent complex permittivity. Using the Hodgkin–Huxley neuron model, an analytical method for the calculation of the electromagnetic power absorption in the brain neurons is proposed based on the complex permittivity of neuron membranes. The effect of the human head is considered through the calculation of forward and backward travelling electromagnetic waves. The modified time-dependent Hodgkin–Huxley equations have been used to obtain the reflectivity and transmissivity of the external stimulus at the membrane of the cell. The amount of absorbed energy by the human head is presented in the form of the electromagnetic absorption rate.

Diffusion-drift model of ion migration over interstitial sites of a two-dimensional lattice

An analytical and numerical modeling of the process of obtaining hydroxyl radicals OH0 and atomic hydrogen H0 from water molecules on a square lattice based on electrical neutralization of ions OH− on an anode and ions H+ on a cathode is conducted. The numerical solution of a system of equations describing a stationary migration of ions H+ and OH− over the interstitial sites of a square lattice located in an external electric field is considered. The ions H+ and OH− in the interstitial sites of a square lattice are generated as a result of dissociation of a water molecule under the action of external electromagnetic radiation and external constant (stationary) electric field. It is assumed that anode and cathode are unlimited ion sinks. The problem is solved using the finite difference approximation for the initial system of differential equations with the construction of an iterative process due to the nonlinearity of the constituent equations. It is shown by using calculation that the dependence of the ion current on a difference of electric potentials between anode and cathode is sublinear.

Stationary charge imbalance effect in a system of coupled Josephson junctions

We investigate the stationary charge imbalance effect in the system of coupled overdamped Josephson junctions. We show that the stationary charge imbalance in the resistive state brings to a decrease in the Josephson frequency in the junctions of the stack. The formed difference in frequencies leads to a nonuniform switch of junctions along the stack to the Shapiro step regime in the presence of external electromagnetic radiation. On the other hand, such nonuniform switching leads to the appearance of voltage spikes on the IV-characteristic of the stack. We show that the stationary charge imbalance is responsible for a slope in the Shapiro step due to the difference of the nonequilibrium potentials at the edges of the step. The obtained results have been compared with the voltage bias coupled Josephson junctions and experimental results.

Plasmonic Field Enhancement by Metallic Subwave Lattices on Silicon in the Near-Infrared Range

The enhancement of the electric field in plasmonic nanostructures on a Si substrate in the near-infrared range is studied theoretically. Two-dimensional square arrays of circular holes of various diameters in a gold film serve as metasurfaces allowing the conversion of the external electromagnetic radiation into surface plas-mon modes at the Au-Si interface. It is established that illumination of nanostructures from the side of the Si substrate provides a higher field enhancement compared to the case of frontal illumination, since the incident light wave in the former case reaches the gold interface without passage through subwavelength holes for which the transmittance is extremely low. The plasmonic field enhancement, as a function of the diameter of holes of the array, shows the maximum at which the Bloch plasmon polaritons propagating along the Au-Si interface are transformed to localized surface plasmon modes. Two types of localized plasmons are detected. The short-wavelength plasmon is excited along the array diagonals and exists at any angles of incidence of light on the structure. The long-wavelength plasmon occurs only at nonzero angles of incidence and is located along orthogonal directions parallel to the sides of the square array. These results are directly related to the problem of fabricating effective silicon photodetectors with quantum dots.