Types Of Charge Distributions Research Articles

Reduced-order Abraham-Lorentz-Dirac equation and the consistency of classical electromagnetism

It is widely believed that classical electromagnetism is either unphysical or inconsistent, owing to pathological behavior when self-force and radiation reaction are non-negligible. We argue that there is no inconsistency as long as it is recognized that certain types of charge distribution are simply impossible, such as, for example, a point particle with finite charge and finite inertia. This is owing to the fact that negative inertial mass is an unphysical concept in classical physics. It remains useful to obtain an equation of motion for small charged objects that describes their motion to good approximation without requiring knowledge of the charge distribution within the object. We give a simple method to achieve this, leading to a reduced-order form of the Abraham-Lorentz-Dirac equation, essentially as proposed by Eliezer, Landau, and Lifshitz and derived by Ford and O'Connell.

Charge distribution in thin mesoscopic superconducting rings with enhanced surface superconductivity

The charge distribution in a thin mesoscopic superconducting ring with enhanced surface superconductivity (of a negative surface extrapolation length $b$) is investigated by the phenomenological Ginzburg-Landau theory. The nature of charge distribution is considerably influenced by the extrapolation length $b$, the inner and outer radius, and the applied magnetic field. We find a complete negative charge distribution besides the conventional charge distributions of charging vortex states in the Meissner state and the giant vortex state. In addition, one type of charge distribution that only exists in a giant vortex state can also be found in the Meissner state for a ring with a small inner radius. For the multivortex state, we find that the stable multivortex state can exist in small mesoscopic superconducting rings that we studied. The charge distributions for different kinds of multivortex states are given.

Charge distributions and molecular electrostatic potentials around amino acids: Usefulness of hybridization displacement charge

Molecular electrostatic potential (MEP) values on the van der Waals surfaces of 20 amino acids were computed using experimental geometries and four different types of charge distributions, that is, (i) potential-derived (CHelpG) charges obtained from ab initio SCF calculations using the 3-21G basis set, (ii) hybridization displacement charges (HDC) combined with Löwdin charges obtained using the AM1 method, (iii) Clementi charges obtained from a simulation of the interaction of a water molecule with each of the amino acids, and (iv) Clementi–Fraga (CF) charges obtained using a classification scheme of atom types due to Clementi and coworkers and a normalization scheme due to Fraga. Taking the MEP values obtained using the CHelpG charges as a standard, it has been shown that HDC describe MEP patterns of the molecules much better than do the Clementi and CF charge distributions and with an accuracy comparable to that of the ab initio method. Thus, HDC can be employed to study the electrostatic properties of proteins reliably and with a great computational economy. ©1999 John Wiley & Sons, Inc. Int J Quant Chem 74: 271–289, 1999

Charging effect on the HRTEM imaging of small MgO crystals

It is reported that lattice fringes appearing in the profile image of the (100) surface of a small MgO crystal observed from the [001] or [011] direction by a high-resolution conventional transmission electron microscope show strange bending at the corners of the crystal. In order to interpret this bending of fringes on the surface, a charging effect is introduced into the contrast simulation with the multi-slice method. Contrasts simulated on the assumption of three types of charge distribution are compared with actual micrographs. It is found that the bending of fringes can be explained by the charging effect, that is, lattice fringes are observed as being bent even if the atomic arrangement is not distorted. The seriousness of the effect of charging on imaging does not depend on the density of charge, but on the total amount of additive charges in the whole of the crystal. The calculated images that include the effects of defocus and aberrations of the electron lenses are much more sensitive to the charging effects than the calculated intensity distributions at the exit surface of the crystal.

垂直磁気ヘッドの三次元磁界解析モデル

We previously described a simple, analytical, 3 dimensional head field model for a perpendicular recording head with a soft magnetic underlayer. In that model, we assumed two magnetically charged planes to obtain the head field at the region close to the head surface and under the pole tip. For simplicity of calculation, the charge distribution was approximated by a step function. However, it was found that the field can be analytically obtained from the a+1/(b-cx2) type of charge distribution more accurately than from a step function approximation. In this paper, the derivation of the modified method is explained, and the head fields obtained by the modified model are compared with those of the previous model and large-scale experimental results. The modified model gives smoother head fields and better agreement with large-scale experimental results than the previous model.

Determination of circular microstrip disc by Noble's variational method

In the paper, Noble's variational method is applied to the calculation of the static capacitance of a circular microstrip disc by using a linear combination of two types of charge distributions, namely, a uniform charge distribution, or gate function, and the classical form of the charge distribution for the infinitely thick slab, or Maxwell's function. The variational method reduces the dual equations describing the microstrip problem to the evaluation of three similar integrals, which can then be evaluated efficiently and accurately by the Gauss-Laguerre quadrature. It is found, as a rule, that the method gives a more accurate representation of the charge distributions on the disc, yields values of capacitance which are within better than 0.4% of the values obtained from a numerically accurate method and is capable of being implemented on a programmable calculator, e.g. the HP —41C.

The Booth theory of electrophoresis of liquid drops

Summary The Booth electrophoresis equation for liquid drops has been considered in detail. Illustrative numerical calculations of the mobility function, 6πη 1 U/E e1ξ, for different values of η a have been made for two different types of charge distribution in the fluid of the drop ( viz. , the interfacial layer and the diffuse double layer types for certain limiting values of fluid viscosity, and different values of the conductance parameter, λ. The mobility equations for these two types of charge distribution have also been applied to some experimental data of Mooney .

The booth theory of electrophoresis of liquid drops

The Booth electrophoresis equation for liquid drops has been considered in detail. Illustrative numerical calculations of the mobility function, 6πη 1 U/E ε1ξ, for different values of η a have been made for two different types of charge distribution in the fluid of the drop ( viz. , the interfacial layer and the diffuse double layer types for certain limiting values of fluid viscosity, and different values of the conductance parameter, λ. The mobility equations for these two types of charge distribution have also been applied to some experimental data of Mooney .

An Electron Beam Technique for Visualization of Charge Distribution

An Electron-optical apparatus for visualizing the distribution of surface charge on a solid sample is described. By the deflection of electron beam which is scanned near the charge, a characteristic pattern corresponding to the charge distribution is obtained on a screen as a track of the end points of the beam. The tracks are analyzed theoretically from the interaction between electric charges and electron beams. Experiments are performed on various types of charge distributions. It is shown that the theoretical curves agree well with the observed tracks.