Search

In the paper, a surface curvature of an odd-shaped solid conductor is under investigation. The correlation between the surface charge density and the surface curvature along the surface is analysed theoretically. The key result is that the surface charge density reaches a maximum at a location that is different from where the surface curvature is maximum. This new result has implications for scanning tunnel microscopy development and field-ion microscopy. • The specific features of the charge distribution on the surface and the mean curvature of the surface are investigated. • The analytical expressions for the principal curvatures of the odd-shaped surface of revolution are obtained. • Maximum curvature values are not obtained in the same points where the surface charge density peaks are obtained [ABSTRACT FROM AUTHOR]

Relaxation process of surface charge owing to dielectric barrier discharge (DBD) in “needle – air gap – polyethylene terephthalate film – plane” configuration is considered. Experimental data of the surface charge relaxation (SCR) are obtained by means of the rotating capacitive probe. Taking into account Gaussian radial distribution of accumulated charge density, effective surface and volume electrical conductivities of a barrier dielectric, phenomenological model of SCR for any dielectric thickness is proposed and exact solutions are obtained. The adequacy of the model is confirmed by the numerical computation. There is a good agreement between the experimental results and the model calculations. [ABSTRACT FROM AUTHOR]

The purpose of this study is to gain insights on the nature of the electrostatic energy of interaction between two uniformly charged hemispherical surfaces with constant surface charge density. The present system of these two interacting bodies represents a very difficult problem to solve since hemispherical surfaces lack the spherical symmetry of a uniformly charged spherical surface or a solid sphere counterpart. For this reason, an exact analytical calculation of the electrostatic interaction energy is not possible for an arbitrary orientation. However, this work shows that analytical results are possible for scenarios where the system of the two interacting hemispherical surfaces manifests some form of inherent symmetry. We identify such situations where combination of suitable mathematical tools appropriate for the axial symmetry together with transformations that apply to a spherical system of coordinates can reduce the difficulty of the problem. We show that there are some special cases where this very difficult integral problem can be reduced to a simpler one of summation of an infinite series. The approach is illustrated by showing explicitly the calculation of the interaction energy between the two uniformly charged hemispherical surfaces when they are brought together so that they are touching each other across the "equator". [ABSTRACT FROM AUTHOR]

The article deals with the transmission of electromagnetic radiation through a selected building element. Measurements were made to determine the shielding effectiveness of the electromagnetic field. In order to increase the shielding effectiveness, shielding coatings were applied to the selected building element, some of which were concentrated with a laboratory-generated powder to improve the shielding effectiveness of the electromagnetic field. It has been found that a spatial charge occurs when an electromagnetic field impinging on the surface of shielding coatings. The size and polarity of the surface charge depends on the type of shielding coating, the frequency and duration of the electromagnetic field. Measurements were performed for the frequency range from 0.9 to 7 GHz. [ABSTRACT FROM AUTHOR]

This study exploits conductive nickel/copper nonwoven polyester as a new triboelectric material and proves its effectiveness in improving the electrical characteristics of triboelectric energy harvesters and reducing production costs. The tribo-surface charge density as another influencing factor in the triboelectric nanogenerators (TENGs) output performance has also been addressed via pre-implanting charges into the surface of polytetrafluoroethylene (PTFE) film using a compact, small, and inexpensive boost step-up power module as an innovative tool. The open-circuit voltage and short-circuit current of eight TENGs are examined to assess the effect of the triboelectric materials, surface morphology, and charge-implantation process on the TENG performance. Sandpaper is used as a stamp to induce micro/nanostructures on the PTFE surface, and its surface charge density is improved using the proposed boost step-up power module. The main purpose of this study is not to provide a new structure for the TENG; this study provides a feasible way to reduce fabrication costs and increase the output performance of triboelectric energy harvesters. • Employing a novel, low-cost, and high-performance functional material for TENG. • Introducing a novel and low-cost module for charge pre-implanting into PTFE electrets. • Investigating the effect of the proposed methods on the output performance of TENG. [ABSTRACT FROM AUTHOR]

We report an exact result for the electrostatic potential energy stored in a hemispherical surface with uniform surface charge density. This system lacks the spherical symmetry of a uniformly charged spherical surface or its solid sphere counterpart. Consequently, a hemispherical surface with all its charge uniformly spread on its surface represents an interesting case study in electrostatics. In this work we combine the fact that the body has axial symmetry with clever mathematical tools to obtain an outcome that is remarkably simple. The final exact expression obtained for the electrostatic potential energy stored in a hemispherical surface with uniform surface charge density answers a long-standing question. Though the bulk of the treatment is analytical, the accuracy of the findings can also be ascertained by using symbolic computation software or numerical recipes. Hence, the present analytical results can be compared to ones obtained with various powerful numerical methods which nowadays are routinely used to check the correctness of analytical and semi-analytical calculations. • Hemispherical surface with uniform surface charge density. • Exact analytic result for the value of the electrostatic self-energy. • Method can be generalized to other similar systems with reduced symmetry. [ABSTRACT FROM AUTHOR]

Most studies on corona-charged nonwoven filters have used grounded electrodes during charging and surface potential measurements but not during filtration experiments. This study was focused on the investigation of a grounded metal grid effect on the filtration efficiency. The results showed that the filtration outcome strongly depends on the filter–grid distance. Moreover, the electric charge was maintained for a considerably long duration when the ground electrode was used, which led to an increase in the filtration efficiency. The efficiency exceeded 90% at a voltage of 10 kV with the grid and was <70% at 30 kV without the grid. • Potential decay and filtration performance of corona charged filters were investigated. • The effect of a grounded metal grid on the filtration efficiency was investigated. • The "filter–grid" distance affects both potential decay and filtration efficiency. • Electric charges are kept longer on the filter surface with the grid electrode. • The filtration performance was significantly improved with the grid electrode. [ABSTRACT FROM AUTHOR]