Evaluation of discharge behavior of lithium ion cells

This paper presents a mathematical model based on a porous-electrode theory to describe the discharge of a lithium ion cell. The expression for the electrostatic cell potential has been obtained by subtracting the overpotential at the front of the anode from the overpotential at the back of the cathode plus the integral of the solution phase electrostatic potential in the cathode and the separator. The resulting expression is used to plot the cell potential against time and is compared with experimental results using parameter values from the literature. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Design and fabrication of electrostatic micro-cantilever array as audible frequency generator

In assistive technologies involving voice communication, an audio signal with specific shape is needed. In this regard, the design and fabrication of an electrostatic cantilever array is proposed. An array of four metallic micro-cantilevers with dimensions 650 μm × 200 μm × 0.3 μm is fabricated on the silicon substrate. The working principle is based on the electrostatic effect generated due to a conductive path applied between the electrodes. The results are taken from zinc oxide (ZnO) piezoelectric thin film that allows making contact with the vibrating cantilevers on a specified applied input impulse signals. The results demonstrated the switching action of the cantilevers that depends on the polarity of the input pulses. The results obtained are compared with the FEM based (COMSOL Multiphysics) model that is designed and analyzed prior to the experiment. Further, the experimental results showed a good agreement with the predicted values calculated by the simulated model for the input impulse signal applied synchronously to all the micro-cantilevers. However, for asynchronous actuation mode, the result of the as-fabricated device showed a variation than the simulated results. The vibrations are generated periodically from all the cantilevers and the output shows the resultant signals that are very much in the audible frequency range.     

Coulombic potential lattice sums

An expression is derived for the electrostatic potential in an ellipsoidal crystalline system of point charges. The potential consists of two components: one, the intrinsic potential, is a periodic function of position and is independent of the shape and size of the ellipsoid; the other, the extrinsic potential, is a quadratic function of position and is a function of the shape and size of the ellipsoid. If the charge repetition unit is electrically neutral, the size dependence vanishes and the quadratic dependence reduces to a linear dependence.An infinite lattice electrostatic potential is defined and existence conditions obtained. It is shown that Madelung's and Evjen's potentials are special cases of the infinite lattice electrostatic potential whearas Ewald's potential is equal to the intrinsic potential. The relationship between these three potentials is discussed.     

Multiple polarization of geodesic curvature induced modes

Dispersion relations for geodesic acoustic modes are derived by using the Grad hydrodynamic equations thereby reconciling long known but not previously explained discrepancy between the results of kinetic and fluid calculations. Extended fluid theory allows a simple analysis of mode polarization and coupling. A new type of electromagnetic modes induced by geodesic compressibility is predicted. These modes are related to Alfvén and geodesic acoustic modes. While a standard geodesic acoustic mode involves poloidally and toroidally symmetric perturbations of electrostatic potential (m=n=0) and the first poloidal side-bands of plasma pressure, new modes involve side-bands of the electrostatic and vector potential as well as pressure perturbations at zeroth and second harmonics. It is shown that there exist two different values of the adiabatic constant depending on the mode polarization. Both standard (electrostatic) geodesic acoustic modes and new electromagnetic modes involve finite perturbations of parallel viscosity, which modify an effective adiabatic (compressibility) index for a toroidal plasma.     

The polarization tensor of neutral gluons in external fields at high temperature

The one-loop polarization operator of neutral gluons in the background constant Abelian isotopic, H ₃, and hypercharge, H ₈, chromomagnetic fields combined with A ₀ electrostatic potential at high temperature is calculated. The case when A ₀ = 0 is investigated separately. The proper time method is applied. It is found that neutral gluons do not acquire magnetic masses in the background fields, in contrast to the charged ones. The application of the results are discussed.Received: 6 October 2004, Revised: 13 December 2004, Published online: 9 February 2005A.V. Strelchenko: Permanent address: Dniepropetrovsk National University, Naukova 13 Str., Dniepropetrovsk 49050, Ukraine.     

Friction behavior of monolayer molybdenum diselenide nanosheet under normal electric field

The friction behavior of monolayer molybdenum diselenide (MoSe₂) under normal electric field was studied by the atomic force microscope. The friction coefficients of MoSe₂ are increasing with bias voltage applied on the Si substrate. The results show that the adhesion and electrostatic forces increase with bias and approximately follow a parabolic law. The friction force and surface potential are of the same tendency with bias application time, and the contribution of charges accumulation to friction is considerable. The mechanisms of the friction behavior under external normal electric field were explained with electrostatic force and adsorption. This study reveals a possibility of electronically controlling friction in two-dimensional MoSe₂ system, with potential applications in solid lubricant and moving parts for MEMS devices.     

FIELD IONIZATION OF MOLECULES IN AN INTENSE LASER FIELD

In order to predict the field ionization probabilities, the accurate ab initio electrostatic potential of molecules has to be calculated. However, the calculation of the full ab initio electrostatic potential of molecules is complicated, even impossible for some larger molecules with low symmetry. Here, we present a semi-empirical model to treat the field ionization of molecules in an intense laser field. In this model, a modified Coulomb potential is used to take the place of the complicated ab initio electrostatic potential of molecules. The analytic equations of the Keldysh adiabatic parameter using the Coulomb potential and the modified Coulomb potential have first been given. Using our semi-empirical model, we have calculated the field ionization probabilities and the Keldysh adiabatic parameters of O₂, N₂, SO₂, C₂H₄, CH₃CN and C₆H₆ in an intense laser field. The results agree excellently with the calculations using the ab initio electrostatic potential of molecules. As the modified parameter for the Coulomb potential can be found from experimental measurements, the field ionization mechanism of molecules can be immediately predicted with our semi-empirical model.     

Collective Electrostatic Interaction of Particles in a Complex Plasma with Ion Flow

Linearized electrostatic potential of a test charge in a complex (dusty) plasma with ion flow is found. Dust component is treated as a continuous medium. Positions of dust particles are assumed to be fixed (unperturbed by the test charge). Calculations are performed using the static dielectric response function found in the framework of the fluid model. The model includes ion loss and ion creation caused respectively by absorption on dust particles and ionization. Dust charge variations and friction force on ions (ion‐neutral and ion‐dust friction) are also present in the model. The main point of the paper is the potential distribution in the plane containing the test charge and oriented perpendicular to the ion flow. The possibility of the electrostatic attraction of two same sign charges in the plane perpendicular to the ion flow is investigated. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

圆形面偶极层的静电势

讨论了圆形面偶极层静电势问题的正确解法,阐明了对于延拓法的正确理解,给出了有限间距时圆形平行板（分别带有异性面电荷）的静电势问题。     

Comparison of the Monte Carlo estimation of surface electrostatic potential at the hematite (0 0 0 1)/electrolyte interface with the experiment

The Monte Carlo simulations of the surface electrostatic potential are presented for the hematite (0 0 0 1) crystal plane. According to the ab initio calculations, the Fe-terminated (0 0 0 1) plane contains only one type of surface groups. The charge of this surface group is predicted using quantum population analyses, and the result is very close to this of the 1-pK model assumption. The surface topology and topography were constructed using the relaxed crystal plane structure. The Monte Carlo simulations for the reduced (including only hydrogen ions) and the extended (containing also electrolyte) models give the linear non-Nernstian pH-profile of surface potential. The simulation results are in agreement with the experimental measurements carried out by Kallay et al. [N. Kallay, Z. Dojnovi?, A. Cop, J. Colloid Interface Sci. 286 (2005) 610-614.] in the point of zero charge vicinity. This suggests that in this pH-region the surface properties are basically governed by the H⁺ ions uptake/release and the electrolyte ions complexations. The discrepancy for strongly acidic and basic regions suggests that some additional processes take place in the single-crystal electrode measurement, which results in the non-linear ψ₀=f(pH) profile.     

The mean spherical model for charged hard spheres

The reduced mean electrostatic potential v(r) and the radial distribution functions gij(r) for a system of charged hard spheres of equal diameter are calculated from the solution of the mean spherical model equation given by Waisman and Lebowitz. An analytical solution is given for v(r) and the gij(r) are shown to be the sum of the Percus-Yevick uncharged hard-sphere distribution function and an electrostatic term. The correct qualitative behaviour of the mean potential is predicted at high concentrations but the radial distribution functions are only accurate for low valency electrolytes at high concentrations.     

Darboux Transformation of the Nonstationary Dirac Equation

The method of differential transformation operators is applied to the Dirac equation with the generalized form of the time-dependent potential. It is demonstrated that the transformation operator and the transformed potential are solutions of the initial equation. It is established that under certain conditions, an integral expression can be retrieved for the transformed potential. Examples of new potentials expressed through elementary functions are presented for which the Dirac equation can be solved exactly.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 34–41, April, 2005.     

Application of the electrostatic mean value theorem to electrostatic sensor electrodes

We present a method for approximating the potential of conducting objects due to a known electrostatic source. The method involves averaging the incident potential over the conductor surface or volume region, which is known to give the exact value for a perfectly conducting sphere. The method is extended to spheroidal geometries, both prolate and oblate, to study the error incurred for deviations from the spherical case. Exact values for the spheroid potentials are derived and compared with those obtained by the mean value approximations. The result for the oblate spheroid is extended to the case of a two-dimensional electrostatic disk. The approximations are proposed as a method for predicting the potential of conducting electrodes used with electrostatic sensors for the measurement of electrostatic field disturbances. In this regard, the mean value approximation is applied to determine the source to electrode mutual capacitance, which is implemented in the model for the sensor system. Electrostatic disk electrodes are used with an electrostatic disturbance sensor to experimentally validate the application of the mean value approximation.     

A new method for deriving atomic charges and dipoles for n, -alkanes: investigation of transferability and geometry dependence

Atomic charge models are known to be unsatisfactory for representing the ab initio electrostatic potential (ESP) of n, -alkanes. A new method for deriving atomic charges and dipoles is proposed and applied to n-alkanes ranging from C₄ to C₁₀. Electrostatic parameters found by this method reproduce accurately the ab initio ESP. The issues of transferability and conformational dependence are also addressed by introducing charges and dipoles taken from a truncated distributed multipole analysis, in the same spirit as the restrained electrostatic potential method. A transferable model is proposed for larger alkanes (>C₁₀). We also estimate the error made when using a set of Boltzmann-weighted electrostatic parameters for all conformers. The reduced number of electrostatic sites considered in our model makes it suitable for computer simulation of liquid n-alkanes.     

Parabolic oxidation of metals in homogeneous electric fields

A previously proposed thin film parabolic growth law (Fromhold, 1963) is extended to include film growth due to any number of diffusing defect species of arbitrary valence, and an analysis is made of the effects of applying external electrostatic potentials during oxidation. The total electrical conductivity and the partial conductivities are markedly position-dependent in the protective film, varying by orders of magnitude from one interface to the other. The built in electrostatic potential across the film is independent of thickness of the film and is a function of the partial conductivities of the diffusing ionic and electronic defect species. Effects of electrical shorting of the oxide film by external circuitry are analyzed. Depending on polarity, a constant applied potential can increase or decrease the rate constant but does not alter the kinetics from the parabolic form, in accordance with published experimental data. The net electrostatic potential required to stop metal oxidation is derived for the model in question. For growth by a single ionic species, the stopping potential is that electrostatic potential which gives an equal electrochemical potential at the metal-oxide and the oxideoxygen interfaces. For growth by multiple ionic species, the stopping potential is a function of the ionic partial conductivities.     

A second-order accurate finite volume method for the computation of electrical conditions inside a wire-plate electrostatic precipitator on unstructured meshes

In this paper, an unstructured cell-centered second-order accurate finite volume method is presented for the computation of electrical conditions inside wire-plate electrostatic precipitators. The potential equation was discretized using a second-order accurate scheme by invoking a new type of special line-structure. The space–charge density equation was discretized using a second-order upwind scheme, and solved using a new direct method. The local gradients are reconstructed by a weighted least-square reconstruction method. The method can deal with complex geometries by using unstructured meshes. Numerical experiments show that the predicted results agree well with the existing experimental data.     

Metal surface dipole moment and work function in the linear potential model

Summary Jellium metal surface properties such as the surface dipole barrier and work function are studied in the linear potential approximation to the effective potential at the surface. The metal surface position and field strength are determined respectively by the requirement of overall charge neutrality and the constraintst on the electrostatic potential by the Budd-Vannimenus theorem. The calculations are primarily analytic and these properties are given in terms of the universal function of the field strength. The results obtained employing the Ceperley-Alder expression for the correlation energy closely approximate those of Lang and Kohn.     

等离子体环境下孤立导体表面充电时域特性研究

航天器在等离子体环境下的表面充放电受到多种因素影响, 其中充电时间是影响静电放电频次的一个重要因素. 本文从等离子体的微观结构出发, 同时考虑材料参数特性, 在对每个粒子运用力学原理的基础上, 以统计方法 推导出孤立导体球表面充电电位时域表达式. 利用电位时域表达式推导出孤立导体球净电荷量时域表达式及静电场能量时域表达式. 以较低非极地地球轨道和较高地球同步轨道为例对孤立导体球电位、 净电荷量及静电场能量的时域特性进行了讨论, 分析了空间环境参数和导体球半径大小对表面充电的影响, 总结出等离子体环境下孤立导体表面充电时域特性规律. 关键词： 等离子体 孤立导体 表面带电 时域     

Concise presentation of the Coulomb electrostatic potential of a uniformly charged cube

We use a novel method to calculate in closed form the Coulomb electrostatic potential created by a uniformly charged cube at an arbitrary point in space. We apply a suitable transformation of variables that allows us to obtain a simple presentation of the electrostatic potential in one-dimensional integral form. The final concise closed form expression of the Coulomb electrostatic potential of the uniformly charged cube is obtained after completing the calculation of the resulting one-dimensional integrals. Such integrals consist of combinations of products of error functions and power functions that can be solved exactly despite their intimidating appearance. The exact analytic formula for the Coulomb electrostatic potential that we derive reflects the symmetry of the cube and is easy to implement. We illustrate its use by calculating the exact values of the electrostatic potential at some points of symmetry such as the center of cube, center of face of cube, center of edge of cube and corner of cube.