Modification of the copper slab surface submicrorelief by applying high-density electric current

The modification of the copper slab surface submicrorelief by applying a current pulse of density higher than J _thr. The passage of a high-density current is shown to change the pattern of the copper slab polished surface, resulting in the formation of regular periodic structures. These structures are produced when moving dislocations emerge on the specimen surface.     

Non-linear effects of an alternating electric field on the non-metallic part of current in a two-dimensional random system

We present a calculation of the non-metallic part of current in the presence of an alternating electric field with finite strengths. The current exhibits interesting cross-over behaviours as a function of frequency. We study the generation of the high harmonics in the current.     

Effect of the electric current on the Casimir force between graphene sheets

The dependence of the thermal component of the Casimir force and Casimir friction between graphene sheets on the drift velocity of charge carriers in one of the sheets has been analyzed. It has been shown that the drift motion results in the measurable change in the thermal Casimir force owing to the Doppler effect. The thermal Casimir force, as well as Casimir friction, increases strongly in the case of resonant photon tunneling, when the energy of an emitted photon coincides with the excitation energy of an electron-hole pair. In the case of resonant photon tunneling, the dominant contribution to the Casimir friction even at temperatures above room temperature comes from quantum friction caused by quantum fluctuations. Quantum friction can be detected in an experiment on the friction drag between graphene sheets in a high electric field.     

椭圆交流磁滞回线和交流磁参量的测定

用霍尔元件做探头,用示波器测量和研究了铁磁材料的椭圆交流磁滞回线的性质和参量。     

非对称电极表面微观形貌对交流电渗流速的影响

经典交流电渗理论是利用电场进行非机械式微流体驱动的基础.传统理论交流电渗理论以双电层理论为基础,通过耦合电场方程以及流场方程得到微电极表面交流电渗流速表达式,通常与实验流速相差较大. 以电极表面微观形貌对交流电渗流速的影响为研究目标,定义微电极表面粗糙度为微观形貌特征参数,建立了等效双电层模型,并对传统交流电渗流速公式进行了修正.理论并仿真分析了表面粗糙度对于交流电渗流速的影响,利用非对称电极对交流电渗微流体驱动进行了实验研究,并进行对比分析.结果表明,理论分析与实验结果具有较好的一致性. 关键词： 交流电渗 电极表面粗糙度 等效双电层     

直流和交流Josephson效应的研究

基于Feynman模型得到的Josephson方程,在求解过程中采取了ρ1=ρ2的假设,但这个假设在数学处理上并不严格。为了得到严格的结果,未进行上述假设,通过解微分方程得到了严格的Josephson方程,结果显示在一定条件下才能得到通常所说的Josephson方程。     

Magnetic resonance imaging of alternating electric currents

Electric Current Density Imaging (CDI) is a new modality of magnetic resonance imaging that enables electric current distribution imaging in conductive samples containing water. So far, two CDI techniques have been in use: DC-CDI operating at zero frequency and RF-CDI operating at the RF Larmor frequency. In this paper we present a new CDI technique, which extends the CDI frequency range to alternating electric currents (AC-CDI). First, a theoretical model for the electric current response to the alternating voltage is presented. Later, this model is used for the frequency analysis of the AC-CDI sequence. Additionally, the effect of off-resonance spins and imperfect refocusing RF pulses on the stability of the AC-CDI sequence and the echo formation is studied. The new theory is verified by experiments on a model system and compared to the other two methods: DC-CDI and RF-CDI. Finally, an application of the AC-CDI sequence to biological systems is demonstrated by an experiment on a wood twig in which an increase of approximately 30% was obtained at AC as compared to DC electric current.     

演示电感和电容对交变电流影响的装置

将电源、电容、电感、电阻及小灯泡安装在电路演示板上,连接不同的电路,通过灯泡的明暗,可以分别直观地展示出电感和电容对交变电流的影响,同时也可以探究影响电感感抗大小的因素.     

Effect of electric current on the magnetic and magnetoelastic properties of amorphous ferromagnetic alloys

The magnetic and magnetoelastic parameters of Fe₆₄Co₂₁B₁₅ and Fe_81.5B_13.5Si₃C₂ amorphous ferromagnetic alloys treated by direct electric current in air are studied as functions of the applied magnetic field and current density. The samples of the alloy have the form of narrow strips with different lengths. It is found that the magnetoelastic parameters of the dc-treated alloys depend on the magnetic field in a qualitatively different way. From the behavior of the magnetic and magnetoelastic parameters of the alloys in the magnetic field a model of magnetization nonuniform distribution in amorphous ferromagnetic alloys subjected to dc treatment is proposed.     

Effect of direct electric current on phase formation in Pb-Sn liquid-solid alloys

The effect of a constant electric current on the phase state of alloys of the lead-tin system in the liquid-solid state was investigated. It was shown that solid inclusions are displaced to one of the electrodes according to the effective charge (particles Z* > 0 are transferred to the cathode, while particles Z* < 0 are transported to the anode).     

Polaron in a strong alternating electric field

The solution is found for the transport equation for a Feynman polaron having arbitrary coupling interacting with the acoustic oscillations in an alternating electric field. In the low-frequency case, this solution cannot be normalized — there are runaway polarons. For high frequencies, this effect is absent. Equations are obtained for the electrical conductivity of polaron semiconductors for various particular cases, including the runaway regime.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 45–49, April, 1979.     

Electroviscous effect in an alternating electric field

Experimental dependence of the relative dynamic viscosities of liquid dielectrics on the applied alternating voltage amplitude and frequency is presented. The voltage frequency was varied from 20 Hz to 2 kHz. The variation of viscosity can be attributed to a change in the liquid structure, with ion-molecule complexes centered at the ions produced as a result of charge injection from an electrode. A change in the injection regime leads to a change in viscosity.     

Effect of sample tilt on nanoindentation behaviour of materials

Analysis of nanoindentation is based on the elastic solution of a rigid indenter perpendicularly penetrating a flat contact surface. In reality, nanoindentation is often performed on a tilt sample surface due to sample tilt mounting or the existing roughness of a polished or raw surface. In this study, finite element simulations as well as nanoindentation experiments on a fused-quartz sample with different tilt angles were carried out to investigate the influence of sample tilt on nanoindentation behaviour of materials. It was found that sample tilt results in increases in the indentation load, contact area and contact stiffness at the same penetration depth. The contact area increase caused by sample tilt cannot be accounted for by Sneddon's equation, commonly used in nanoindentation analysis. This results in a significant underestimation of indentation projected contact area, which in turn leads to an overestimation of the mechanical properties measured by nanoindentation.     

Effect of electric fields on the ion current signals in a constant volume combustion chamber

Ion current sensing has the potential to become a promising combustion diagnostic technique for mass productive engines. In this paper, the effect of electric fields on ion current signals measured from a series of methane/air flames in a constant volume combustion chamber (CVCC) is investigated both experimentally and numerically. Based on simultaneous flame Schlieren imaging and ion current measurement, the relation between the flame/electrodes contact area and the ion current signal waveform is explored under different electric field configurations. A CFD model, which incorporates flame plasma hydrodynamics, neutral/charged species reaction kinetics and ion-electric field interactions, is constructed. The effect of the electric field on the ion distribution and the charged species flux are analyzed, and the signal amplitude and timing are well predicted under the equivalence ratio range of Ф?=?0.7–1.1. Besides, the behavior of electrons, which is normally neglected in previous studies, is also analyzed in this work. The results show that it will affect the signal as well. The electron produced in the flame front zone can hardly diffuse into the pre-flame zone (<?350?K) even its mobility is 3-4 order higher than those of the positive ions. Therefore, the anode of the ion probe, which placed in the pre-flame zone, cannot detect the ion current signal until it contacts the flame front.     

Particle production in a slowly alternating electric field

The spectral density of particles produced in a slowly alternating electric field E(t) is calculated. At m²/|eE|?1 the field can be considered as constant, provided |?/E| ? m(|eE|/m²)^{$\text{3}\text{2}$}.     

Induced soap-film flow by non-uniform alternating electric field

Fluid flows generated on soap films by non-uniform alternating electric fields are studied. Two parallel metal rods subjected to an AC voltage are placed perpendicular to the soap film, which is anchored in a dielectric frame. The fluid flow is generated by electrohydrodynamic induction. At very low signal frequencies there is induced surface charge, but there is no tangential electric field at the surface, so there is no force and no flow. Fluid flow is observed increasing the frequency, when there are both surface charge and tangential electric field. The flow velocity increases with decreasing thickness of the soap film.     

"电感和电容对交变电流的影响"演示实验的改进

"电感和电容对交变电流的影响"演示实验的操作难度大且现象不明显,为此介绍了2种演示该实验的方法,一是通过将电灯分别与电感(电容)和电阻串联对比进行实验来演示电感和电容对交变电流的影响;二是通过信号发生器和示波器来研究交流电对电感(电容)的影响.2种方法演示效果均较好.