Some effects of the electrostatic interaction of water drops in the atmosphere

The electric field at the surface of two conducting spherical charged particles and their interaction force are calculated. It is shown that as particles carrying like charge approach each other, the force changes sign and becomes attractive. The case where the charge on each particle varies as the square of its radius is an exception (repulsion at any distance between the particles). Self-similar asymptotic solutions for the interaction force and energy are found for particles of identical size. For a pair of charged water drops falling simultaneously in the atmosphere, a numerical simulation shows that a drop formed by coalescence of the pair may be subject to the Rayleigh instability. Zh. Tekh. Fiz. 69, 12–17 (December 1999)     

Force between charged particles with ion condensation

We have numerically calculated the interaction forces between two highly charged spherical particles embedded in a cloud of small ions with or without charge redistribution on the particle surfaces. Ion condensation near the charged particles leads to reduced electrostatic interaction between the particles, and we find that the effective two-particle interaction is significantly smaller than the values expected from considering only effective single-particle potentials.     

Attraction of dust particles in current-carrying recombination plasma: influence of the space charge and recombination processes

We consider the problem about interaction of two conducting particles located in a weakly ionized collisional plasma with an external electric field. It is shown that the regions of the space charge, which are formed as a result of electrodynamical and recombination processes can lead to the attraction of “large particle–space charge” systems for similarly charged large particles. Thedependencies of the energy of interaction of the system on their mutual position are found and the conditions under which the interaction energy corresponds to the attraction of the systems are determined.     

Full Action for an Electromagnetic Field with Electrical and Magnetic Charges

The paper offers the full action for an electromagnetic field with electrical and magnetic charges; Feynman laws are formulated for the calculation of the interaction cross-sections for electrically and magnetically charged particles on the base of offered action within relativistic quantum field theory. Derived with formulated Feynman rules cross-section of the interaction between an elementary particle with magnetic charge and an elementary particle with electrical charge proves to be equal zero.     

Elastic charge density representation of the interaction via the nematic director field

The interaction between particle-like sources of the nematic director distortions (e.g., colloids, point defects, macromolecules in nematic emulsions) allows for a useful analogy with the electrostatic multipole interaction between charged bodies. In this paper we develop this analogy to the level corresponding to the charge density and consider the general status of the pairwise approach to the nematic emulsions with finite-size colloids. It is shown that the elastic analog of the surface electric charge density is represented by the two transverse director components on the surface imposing the director distortions. The elastic multipoles of a particle are expressed as integrals over the charge density distribution on this surface. Because of the difference between the scalar electrostatics and vector nematostatics, the number of elastic multipoles of each order is doubled compared to that in the electrostatics: there are two elastic charges, two vectors of dipole moments, two quadrupolar tensors, and so on. The two-component elastic charge is expressed via the vector of external mechanical torque applied on the particle. As a result, the elastic Coulomb-like coupling between two particles is found to be proportional to the scalar product of the two external torques and does not directly depend on the particles' form and anchoring. The real-space Green function method is used to develop the pairwise approach to nematic emulsions and determine its form and restrictions. The pairwise potentials are obtained in the familiar form, but, in contrast to the electrostatics, they describe the interaction between pairs (dyads) of the elastic multipole moments. The multipole moments are shown to be uniquely determined by the single-particle director field, unperturbed by other particles. The pairwise approximation is applicable only in the leading order in the small ratio particle size-to-interparticle distance as the next order contains irreducible three-body terms.     

工业中粉体颗粒的荷电机理及数值模拟方法

工业过程中粉体颗粒不可避免地会相互摩擦碰撞而荷电. 荷电颗粒的存在可能会危害正常的工业生产过程, 也可能对工业过程起促进作用. 因此, 荷电粉体颗粒及其特性受到了广泛的关注, 但目前对粉体颗粒的荷电机理依然缺乏透彻的了解, 尤其是在气固两相流动中的粉体颗粒荷电现象. 事实上, 工业中存在的粉体颗粒的运动都受到流体的影响, 是典型的气固两相流系统, 流体对粉体颗粒的作用使粉体颗粒接触的荷电现象变得更为复杂, 因此从两相流动的观点来研究粉体颗粒荷电的物理本质就显得越来越重要. 本文介绍了工业过程中的几种不同类型的粉体颗粒荷电行为, 回顾了颗粒的荷电机理与描述颗粒荷电的数学模型. 对于工业过程中颗粒的荷电现象及颗粒在多相流体中的动力学行为, 介绍了研究颗粒受流体影响时荷电特性的数值模拟方法. 本文旨在对粉体颗粒的荷电机理、应用以及研究方法进行梳理与探讨, 为正确认识工业过程中粉体颗粒的荷电现象并加以控制利用提供理论借鉴.     

High Pressure as a Tool for Characterizing Charge Carriers in a Conducting Polymer

A characteristic feature of conducting polymers is the existence of localized charge carriers. The localization process is closely related to the charge carrier-phonon interaction, which is a function of local molecular properties of the polymer chain on which the carriers are localized. Depending on this interaction in conducting polymers with a non-degenerate ground state singly charged polarons or doubly charged bipolarons may exist. It will be shown that high pressure is a useful tool for studying charge carrier properties by influencing the local molecular conformation. A transition between both types of charge carriers is observed in polypyrrole.     

GaAs-Ga1-xAlxAs量子阱中极化子的结合能

本文应用微扰法,计算了GaAs-Ga1-xAlxAs量子阱内电子极化子,轻、重空穴极化子的基态束缚能,得到极化子束缚能随阱宽的变化曲线.     

Interactions between charges and metallic surfaces

We report numerical results for the potential of interaction between two charged particles on a metallic surface. The density functional formalism approach is utilized. The interaction is cast in the form of an image interaction with a correction parameter λ, which depends on the positions of the particles. We find that for molecular distances, λ for the metal mediated interaction, between two charges is approximately given by the average of λ for the self interaction of there charges with the surface. However, the derivatives of the two charges λ, with respect to the particle positions (needed for the evaluation of forces and force constants), cannot be simply expressed as a function of single charge parameters.     

Interaction of ions and electrons with nanoparticles in hydrocarbon combustion plasmas

The interaction of electrons and ions with a polydisperse ensemble of soot nanoparticles during the combustion of hydrocarbon fuels is studied. The dynamics of the particle charging is analyzed. It is shown that, in the initial stage, all the soot particles are charged negatively, the largest particles (100–150 nm) carrying up to 40–50 elementary charges. As time elapses, the negative charge is neutralized and the charge distribution becomes more symmetric. Finally, because of the interaction between ions (electrons) and soot particles, the total concentration of the positive ions becomes higher than that of the negative ones.     

Numerical simulation of particle size effects on contact electrification in granular systems

Based on the contact charge transfer model between two particles due to a single collision proposed by Apodaca, the contact charges carried on a particle is derived due to multiple collisions, including the repeat collisions between two particles and the collisions with different particles, in mixed-size granular system of identical material. The effect of the particle size on the charges carried on the particle is simulated. The results indicate that for a mixed-size granular system, due to multiple collisions among particles, there exists a threshold particle radius, the particles with radius higher than which and the particles with radius lower than which carry opposite charges. The threshold particle radius is equal to mean value of particle size in the mixed-size granular system. Basically, the polarity of the charges carried on the largest particle is same as the polarity of the transfer charge carrier, and in case of the positive charge transferred, the largest particle will be positively charged and the smallest particle will be negatively charged, and vice versa. In the same size region, the more dispersive the particle size is, the more the net charges can be produced. In normal-distributed granular system, the magnitude of contact charge is determined mainly by the particle size distribution, size region, total particle number and the relative impact velocity.     

Radiation of a charge moving over the diffraction grating

The states of a charged particle with a finite free path are determined in the field of a resonant electromagnetic wave. The exact resonance conditions, the modulation and beam instability mechanisms, the charge and current densities (Ohm's law) are obtained for the collisionless beam of resonance particles. Quantum theory of radiation is developed for the resonant adiabatic interaction between a particle and a wave taking into account the interaction with a constant magnetic field induced at the grating surface by the charge and nonresonant waves. The radiation power, the spectrum, and the range of generated frequencies are determined. The results obtained can be used in the plasma and solid-state theories and in electronics.     

Investigation of electrostatic charge distribution within the reactor wall fouling and bulk regions of a gas–solid fluidized bed

The distribution of charge within the wall fouling region and bulk of a fluidized bed reactor was investigated. Experiments were conducted in a 0.1 m in diameter carbon steel fluidization column under atmospheric conditions. Polyethylene particles were fluidized with extra dry air at 1.5 the minimum fluidization velocity (bubbling flow regime) for 1 h. Using an online Faraday cup measurement technique, the net charge-to-mass ratio (q/m), as well as the size distribution of all particles adhered to the column wall and those in the bulk of the bed was determined. The wall particles were found to be predominantly negatively charged while those which did not adhere to the wall were predominantly positively charged. The charge distribution within each region was then investigated by a custom made charged particle separator that separated the particles according to their charge magnitude and polarity. It was determined that although the net charge of the wall layer particles was negative, a significant amount of positively charged particles existed within each sample and therefore the entire wall particle layer. This suggests that the wall layer was formed through layering between positively and negatively charged particles. Particles in the bulk of the bed also consisted of bipolarly charged particles.     

Kinetic equation with exact charge conservation.

A kinetic master equation for multiplicity distributions is formulated for charged particles which are created or destroyed only in pairs due to the conservation of their Abelian charge. It allows one to study time evolution of the multiplicity distributions in a relativistic many-body system with arbitrary average particle multiplicities. It is shown to reproduce the equilibrium results for both canonical (rare particles) and grand canonical (abundant particles) systems. For canonical systems, the equilibrium multiplicity is much lower and the relaxation time is much shorter than the naive extrapolation from grand canonical results. Implications for chemical equilibration in heavy-ion collisions are also discussed.     

Interaction of electromagnetic oscillations with charged particle flows in nonuniform plasma-like structures

A hydrodynamic theory is developed of the interaction of electromagnetic oscillations with a monoenergetic charged particle beam propagating through a structure consisting of plasma and dielectric layers bounded by perfectly conducting planes. It is shown that, in such a system, plasma oscillations are excited due to the transformation of space charge oscillations of the particle flow into plasma oscillations at the layer boundaries. The regions of generation and decay of plasma oscillations are determined.     

Screening by composite charged particles: the case of quantum well trions

We investigate the screening properties of a two-dimensional gas of charged excitons (trions). In a first approach to this complex problem, we determine the Hartree response of these composite charged particles within a random phase approximation, showing the effect of the trion internal structure. Only in the long wave-length limit, trions behave as point charges with mass equal to the sum of the three particle components. For finite wave-vectors, the trion screening strongly deviate from the point charge behavior and can even vanish completely at a nodal wave-vector, due to a compensation between the contribution of the two electrons and the hole within a trion. Predictions are presented for the screening of a Coulomb potential, the scattering by charged impurities and the properties of trionic plasmons.     

Formulae for the electrodynamic interaction of point particles with a substrate

A complete expression is derived for the force and energy of electrodynamic (van der Waals) interaction between a point particle and a planar semi-infinite substrate. The new result implicitly includes contributions from charge fluctuations at all frequencies, the role of finite temperature, of retardation due to finite light velocity and terms due to many-body interactions occurring in condensed media. The point particle may be in a vacuum or suspended in a condensed medium.

The required expressions are deduced from Dzyaloshinskii, Lifshitz and Pitaevskii's original formula for the interaction of two flat semi-infinite media; the method is checked by using it to derive an intuitive but complete form for the electrodynamic attraction between two point particles. Evaluation of these formulae for application to measurements of particle adhesion and of deflection of molecular beams can be computed from electromagnetic properties of component materials.