The longitudinal electric current in Maxwellian collisional plasma generated by a transverse electromagnetic wave

Allowance for nonlinearity leads to the appearance of the longitudinal electric current directed along a wave vector. This longitudinal current is orthogonal to the known transverse classical current at linear analysis. The kinetic Vlasov equation for collisional Maxwellian plasma is used upon the determination of the longitudinal electric current. The Bhatnagar–Gross–Krook collision integral is applied. The electron distribution function is taken from the Vlasov equation in the approximation quadratic over an electromagnetic field. The formula for the calculation of the electric current is derived. When the collision frequency tends to zero, all results for collisional plasma transfer into a corresponding known formula for collisionless plasma. The case of small wave numbers is considered. The value of the longitudinal current when the collision frequency tends to zero also transfers into the known expression for the current in collisionless plasma. The dependence of the dimensionless current on the wave number, frequency of electromagnetic field oscillations, and the collision frequency of electrons with plasma particles is studied.     

Influence of magnetic field on electromagnetic instabilities in semiconductor superlattices

Electromagnetic instability criteria in semiconductor superlattices (SL) in the region of a negative differential conductivity (NDC) are studied in the presence of a static transverse field. The regimes with vertical constant electric field in a "short" plate of SL and with vertical current density vector in a "long" plate are considered. The effective differential conductivity tensors for both these regimes are derived and the influence of the magnetic field on the NDC threshold and the growth increment is investigated. The frequencies of the excited waves and the dependence of the growth increment on the direction of propagation for the extraordinary waves are determined.     

New Standard of Electric Field Strength

A new technique is presented for establishing a standard of electric field strength using a highly conducting sphere. An analysis is made to determine the current on the sphere as a function of the electric field strength of an incident plane wave. A method of measuring that current using electronic circuitry and an optical indicator within the sphere is described, and an intercomparison is made with an independent field-strength standard. This technique is a significant improvement over previous ones in that it permits the absolute determination of field strength with a maximum uncertainty of 1 percent or less at 30 MHz and is applicable to a broad range of frequencies and field strengths.     

The electric conductivity of a laser plasma excited at a ceramic surface

The electric conductivity of a laser plasma, excited at the surface of a 22KhS ceramics by a pulsed laser radiation, was studied in the presence of an external electric field oriented perpendicularly to the laser beam direction. Depending on the output laser power density, there are three characteristic regimes: (i) the absence of a laser plasma possessing electric conductivity; (ii) the formation of a conducting plasma in which the current is proportional to the laser power density and to the square of the applied electric field strength; (iii) the formation of a conducting plasma in which the current depends linearly both on the laser power density and on the applied electric field strength.     

微型大气电场监测装置的设计与实现

针对户外场磨式地面电场仪存在的输入阻抗高、感应电流信号弱、易受外界电磁波干扰、功耗大且无市电供电等问题,设计一种光伏发电加蓄电池储能供电的低功耗大气电场监测装置。为减小系统功耗,提高测量精度,设计微型低速双定子差分式电场传感器,传感器感应到的两路微弱电流信号经过T型反馈网络实现I/U变换。通过减法器和4 Hz低通滤波器消除共模干扰和工频干扰,提高信号的信噪比。利用光传感器采集同步感应信号,与AD630锁相放大器配合对信号进行处理,得到与场强成正比例关系的直流电压。经实验验证,系统在–50~50 kV/m的模拟电场强度范围内,测量分辨力可达到10 V/m,测量线性度<1%。所设计系统能够在光伏供电的情况下独立运行,实时测量大气电场强度并将测量结果传输到上位机,为雷电监测预警提供必要的数据支持。     

A Contribution to the Problem of Correct Description of Electromagnetic Waves in Layered Media with Magnetic Properties

To model electromagnetic phenomena in layered media when we have a spatial charge distribution and an electric double layer at the boundary of contact it is proposed that the equation of telegraphy for the vector of the electric field strength and 12 conditions at the boundary of contact which reflect the laws of conservation of charge and energy without separating explicitly the surface charge for the multidimensional case be employed. An example of solution of the problem of propagation of a plane monochromatic wave for two media with dissimilar electrophysical properties is given for the one-dimensional case.     

Comparative study of electron conduction in azulene and naphthalene

We have studied the feasibility of electron conduction in azulene molecule and compared with that in its isomer naphthalene. We have used non-equilibrium Green’s function formalism to measure the current in our systems as a response of the external electric field. Parallely we have performed the Gaussian calculations with electric field in the same bias window to observe the impact of external bias on the wave functions of the systems. We have found that the conduction of azulene is higher than that of naphthalene inspite of its intrinsic donor-acceptor property, which leads a system to more insulating state. Due to stabilization through charge transfer the azulene system can be fabricated as a very effective molecular wire. Our calculations show the possibility of huge device application of azulene in nano-scale instruments.     

Waves in elastic semiconductors in a bias electric field

Certain aspects of bulk and surface wave propagation are studied in elastic semiconductors on the basis of a previously given phenomenological, nonlinear, rotationally invariant, thermodynamically admissible theory of deformable semiconductors. More precisely, the paper aims at exhibiting the dynamical couplings between various elastic modes and electric properties when an elastic semiconductor has been subjected to an intense bias electric field which breaks the “natural” symmetry and thereby induces couplings (electromechanical couplings, elasto-resistance, influence of initial charges) which would be ignored, had the theory been linear from the start. Special attention is devoted to the coupling of bulk elastic and charge waves for both longitudinal and orthogonal settings of the bias field and to alterations brought by conduction and induced electromechanical couplings on surface modes when the bias field is set orthogonal to the sagittal plane. Then the influence of conduction on the main properties (dispersion, attenuation, penetration depth) of Bleustein-Gulyaev waves is exhibited. The study is analytical, using small characteristic parameters to study complex couplings when necessary. Numerical estimates, however, allow one to judge of the relative influence of conduction as compared to the more usual dielectric case.     

Quadratic electro-optic properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 transparent ceramics under both DC and AC bias

The basic quadratic electro-optic properties of Pb(Mg1/3Nb2/3)O3-PbTiO3 (PMN-PT) transparent ceramics have been studied under both DC and AC electric field bias. The contribution of piezoelectric resonance to electro-optic effect for this quadratic electro-optic ceramics material has been experimentally demonstrated and theoretically analyzed. It is found that, at the piezoelectric resonance frequencies, the piezoelectric induced electro-optic effect dominates and leads to a dramatically high sensitivity for weak electric signal detection. About 20 dB signal-to-noise ratio is attained when detecting AC electric field strength of 1 V/m with optimized DC bias. Besides, the effects of AC frequency and amplitude on halfwave voltage V(π) of PMN-PT are investigated.     

Calculation of piezoelectric transducers based on MIM structures

The conditions for optimal excitation of piezoceramic transducers are determined from the equality of the bias and conduction currents in a metal-polar insulator-metal (MIM) structure under an external electric field. Charge-carrier injection from the cathode is shown to affect the electric field strength distribution along the thickness of the insulator and the integral characteristic, i.e., the capacitance of thin-layer structures. Numerical computation indicates that in the case of piezoceramic plates 0.4&#x2013;0.5 mm thick electron emission from the cathode is possible at voltages of 5&#x2013;8 V.Translated from Izmeritel'naya Tekhnika, No. 2, pp. 50&#x2013;54, February, 1995.     

Influence of constant current on the formation of a neck in a porous bar subjected to tension

We study the conditions of neck formation in a thermoviscoplastic bar in tension for a broad range of strain rates and different modes of application of direct electric current. The proposed model takes into account complex determining relations for the material of the bar, the process of heat transfer, and the presence of discontinuities (pores). We determine the conditions of stability of uniform tension of the bar and evolution of perturbations of its uniform deformation for various values of the parameters. It is shown that (i) the critical level of strains for a bar in tension strongly depends on the wave number, especially within the range of its small values, (ii) the action of an electric current on the deformed bar weakens the conditions of neck initiation in the case where the current strength is constant (this effect is more pronounced in the mode of constant current strength than in the mode of constant voltage), (iii) as the porosity of the bar increases, the conditions of neck initiation are weakened for both modes of application of the electric current, (iv) the influence of the amplitude of perturbations and the Thomson effect on the stability of the deformed bar is weak, and (v) for small strain rates, the dependence of the level of strains on the wave number is insignificant. Scientific-Research Institute of Mechanics and Applied Mathematics at the Rostov State University, Rostov-on-Don, Russia. Translated from Problemy Prochnosti, No. 3, pp. 95–105, May–June, 2000.     

Transient dislocation emission from a crack tip in an anisotropic elastic material

The emission of a dislocation with a general Burgers vector from the tip of a stationary semi-infinite crack in an anisotropic elastic material is examined. The dislocation is assumed to leave the crack tip along the crack extension plane at constant speed. Explicit expressions for the transient shielding stress intensity factors at the crack tip and the drag forces on the dislocations are derived. Numerical results for a class of cubic materials and two hexagonal crystals, zinc and cobalt, are given. Dislocation emission under plane stress wave loading is discussed.     

Synchronous electrorotation of nanowires in fluid

We demonstrate electrorotation of metal nanowires phase-locked to a driving alternating current electric field. Field rotation was accomplished by a low-frequency signal that modulates the amplitude of the high-frequency field. Steady, synchronous rotation of the nanowires was observed for frequencies up to a maximum rotational frequency, which depends on the magnitude of the applied electric field. A locally two-dimensional nanowire fluid flow model was developed to calculate the viscous fluid drag torque, including drag contributions due to the proximity of the floor. Synchronicity and phase-lock angle predicted by equating the calculated fluid drag and electrical driving torques is in good agreement with experimentally determined values, which provides support for the model. Synchronous electrorotation allows for precise control of nanowire rotational speed and orientation for frequencies as low as a fraction of 1 Hz. Potential applications include reconfigurable polarization filters, microfluidic valves, and stirring devices.     

Transverse-electric/transverse-magnetic polarization converter using 1D finite biaxial photonic crystal

We show that by using a one-dimensional anisotropic photonic structure, it is possible to realize optical wave polarization conversion by reflection and transmission processes. Thus a single incident S(P) polarized plane wave can produce a single reflected P(S) polarized wave and a single transmitted P(S) polarized wave. This polarization conversion property can be fulfilled with a simple finite superlattice (SL) constituted of anisotropic dielectric materials. We discuss the appropriate choices of the material and geometrical properties to realize such structures. The transmission and reflection coefficients are calculated in the framework of the Green's function method. The amplitude and the polarization characteristics of reflected and transmitted waves are determined as functions of frequency, wave vector k(parallel) (parallel to the interface), and the orientations of the principal axes of the layers constituting the SL. Specific applications of these results are given for a SL consisting of alternating biaxial anisotropic layers NaNO(2)/SbSI sandwiched between two identical semi-infinite isotropic media.     

An electroacoustic method for measuring the intensity of high-powermicrowave pulses

A microwave electric field intensity meter for single high-power radiowave pulses is described. A surface acoustic wave (SAW) dielectric acoustic line is used which has nonlinear electroacoustic properties and is comprised of two transducers. The first (nonlinear) transducer is affected by a microwave electric field and provides the SAW excitation due to nonlinear effects. A delayed SAW signal, carrying information about the electric field strength, is received by a linear interdigital transducer     

Liquid metal flow through a thin walled elbow in a plane perpendicular to a uniform magnetic field

This paper presents analytical solutions for the liquid-metal flow through two straight pipes connected by a smooth elbow with the same inside radius. The pipes and the elbow lie in a plane which is perpendicular to a uniform, applied magnetic field. The strength of the magnetic field is assumed to be sufficiently strong that inertial and viscous effects are negligible. This assumption is appropriate for the liquid-lithium flow in the blanket of a magnetic confinement fusion reactor, such as a tokamak. The pipes and the elbow have thin metal walls.The flow tends toward the inside surface of the elbow, approaching a vortex about the center of curvature of the elbow. This flow migration away from the uniform fully developed flow in the pipes leads to voltage variations along the pipes. These voltage variations drive four electric current circulations in planes perpendicular to the magnetic field. These current circulations produce significant pressure variations in the cross sections of the pipes and elbow. A long length of pipe is required on both sides of the elbow for the completion of the circuits for these electric current circulations and for the decay of the disturbances to the fully developed flow in the straight pipes. All pressure drops and rises due to the three-dimensional electric current circulations cancel. The total pressure drop is the same as that for fully developed flow in a single straight pipe with the same length. While the analysis treats pipes and elbows with circular cross sections, the absence of a pressure drop in addition to that for fully developed flow is true for any smooth elbow.     

Current displacement of a solid cylindrical conductor placed in a semiclosed slot, taking into account the leakage field in the gap

The field problem is solved assuming a constant magnetic field strength in the middle of the slot opening. Adapting the vector potential in gap and conductor, which has been expanded into Fourier series and described in different coordinate systems, one obtains a system of linear complex equations for the Fourier coefficients. The calculation of surface current density and surface field strength is checked by measuring the bar current and comparing it with a value deduced from the measurement of the voltage drop at the surface of the bar. This comparison becomes significant due to the fact that these quantities converge badly and determine the bar impedance by means of Poyntings's vector. Finally a comparison is made with the normal approach, which has high practical importance, and which takes the magnetic field strength on the surface of the conductor as a given boundary condition. This comparison shows the advantages of the analysis presented over the conventional approximation. At last a finite element (FE) solution for this problem is given.     

Using MBPE technique to accelerate solving the thin-wire EFIE used in numerical simulation of lightning

The antenna theory (AT) model is widely used to numerically simulate the propagation of current wave along lightning return-stroke channels and compute the radiated electromagnetic fields. In this model, the return stroke channel is considered as a vertical monopole antenna above perfectly conducting ground for which the numerical solution of the governing electric field integral equation (EFIE) in the frequency domain by the conventional method of moment (MoM) is prohibitively slow. In this paper, a model-based parameter estimation (MBPE) technique is proposed to reduce the number of frequency-domain calculation points required for the evaluation of space-time current distribution along a lightning return stroke channel. In applying this technique to a rational function model for the channel current distribution, a uniform-like sampling strategy is investigated. In order to accelerate the building of the moment impedance matrix, the reciprocal closed-form mutual impedance of sinusoidal electric dipoles and the symmetry of the model are used. The proposed technique is validated against the conventional inverse fast Fourier transform algorithm which uses a MoM solution for all frequencies within the channel base current spectrum. It is shown that considerable computation efficiency is achieved in terms of CPU time without losing accuracy.     

Polarization ellipse and Stokes parameters in geometric algebra

In this paper, we use geometric algebra to describe the polarization ellipse and Stokes parameters. We show that a solution to Maxwell's equation is a product of a complex basis vector in Jackson and a linear combination of plane wave functions. We convert both the amplitudes and the wave function arguments from complex scalars to complex vectors. This conversion allows us to separate the electric field vector and the imaginary magnetic field vector, because exponentials of imaginary scalars convert vectors to imaginary vectors and vice versa, while exponentials of imaginary vectors only rotate the vector or imaginary vector they are multiplied to. We convert this expression for polarized light into two other representations: the Cartesian representation and the rotated ellipse representation. We compute the conversion relations among the representation parameters and their corresponding Stokes parameters. And finally, we propose a set of geometric relations between the electric and magnetic fields that satisfy an equation similar to the Poincaré sphere equation.     

Wave propagation generated by piezoelectric actuators attached to elastic substrates

Summary Piezoelectric actuators can be used to generate high-frequency elastic waves for damage identification of materials. This paper provides a comprehensive theoretical study of the electromechanical behavior of surface-bonded or embedded piezoelectric actuators under inplane electric fields. A modified one-dimensional actuator model is introduced, from which arbitrarily distributed electric fields along the actuator can be considered. The model is used to simulate the dynamic load transfer between the actuator and the host medium and the resulting elastic wave propagation by using the integral transform method and solving the resulting singular integral equations. Of particular interest is the generated waveform away from the actuator under different electric fields. An asymptotic analysis is conducted to obtain the far-field solution of the wave field. The property of the resulting waveform is studied, and the simulation shows that the direction of wave propagation can be adjusted by controlling the phase distribution of the applied electric field along the actuator.