Electrostatic Field Theory Research Articles

Spiral tool path generation method for complex pocket machining based on electrostatic field theory

Spiral tool path generation method for complex pocket machining based on electrostatic field theory

Theoretical and experimental investigation on electrostatic field dynamics of Co3O4@NiPx electrocatalyst with core shell structure in overall water splitting reactions

Transition metal phosphides (TMPs) with platinum like electronic structures are becoming a potential choice to constructing bifunctional catalysts operated under alkaline conditions. Nevertheless, the instability of TMP prevents a further enhancement on its electrocatalytic activity. In this study, the Co3O4 core was first formed through thermal annealing in air, and then the outer NiPx layer was formed through the P-method, cleverly integrating the properties of the inner and outer materials and supplementing respective shortcomings, ultimately improving their water decomposition performance. When Co3O4@NiPx is used as a bifunctional electrocatalyst in 1 M KOH, the HER performance is determined to be 99 mV (η10). The electrocatalytic performance for oxygen evolution reaction (OER) is 249 mV (η50). For overall water decomposition, the bifunctional electrocatalysts Co3O4@NiPx coupled dual electrode alkaline battery only requires 1.51 V to obtain η50 and maintains its excellent electrocatalytic ability for 50 h. Finally, a combination of electrostatic field theory analysis and DFT calculations was used, the results indicated that the stability of core–shell materials can be significantly enhanced through Co3O4 core and internal electron redistribution by P atoms, thereby improving catalytic performance. The greatly improved electrochemical performance of Co3O4@NiPx indicates the rationality of the design and synthesis of the core–shell structure. The combination of electrostatic field theory analysis and DFT calculation also further reveals the rationality of its internal electrocatalytic mechanism.

Simulation Analysis and Optimization Design of Electromagnetic Fields in Coaxial Processing Cavities Based on the Theory of Electrostatic Fields

The coaxial processing cavity is an important component of high-frequency electromagnetic water treatment devices. Due to its easy installation, wide applicability, and excellent scale removal effect, it has been widely used in various factories. To study the influence of excitation source waveform, processing cavity length, and anode-cathode radius ratio on the intensity and distribution of the electromagnetic field in the coaxial processing cavity under time-varying fields, this paper derives the numerical calculation formula for electromagnetic energy in the coaxial processing cavity based on the theory of electrostatic fields. The finite element method is used to visualize the intensity and distribution of the electromagnetic field in the coaxial processing cavity. By optimizing the structure of the coaxial processing cavity, the optimal range of the anode-cathode radius ratio is determined. The research results show that, under the conditions of electrostatic field theory, square waves have the maximum electromagnetic energy, the length of the processing cavity does not affect the distribution of the electromagnetic field, and the optimal anode-cathode radius ratio range is 0.375-0.5.

Approximate Calculation and Feature Analysis of Electric Field in Space by Thunderclouds

The calculation of electric field in space excited by thunderclouds is an important basis for lightning warning and protection. In numerical calculation of the electromagnetic field, it is often necessary to perform multiple loop nesting calculations on several triple integrals, which consume a lot of computing resources. In order to shorten the calculation time and improve the calculation efficiency, the electric field excited by the charged thunderclouds in space is theoretically derived with the analytical method by the thundercloud cylindrical charge pile model and based on the electrostatic field theory. The complex integrand function is approximated, so that the analytic expression of electric field in space is obtained in this paper. Through simulation and comparison, it is found that the approximate solution and the exact solution are similar in size, the change trend is the same, and the approximate analytical expression can be used for the approximate calculation of the electric field in a short range. Under certain conditions, the approximate solution can be converted into an accurate solution, which can be used for the accurate calculation of the electric field. Approximate calculation not only simplifies theoretical derivation but also improves calculation efficiency. The calculation time has been shortened from tens of hours to less than one second by using different calculation methods, which is a difference of 7 orders of magnitude. With approximate analytical expression, the electric field excited by charge pile with typical structures in thunderclouds in space is calculated and the characteristics of that are analyzed in this paper. For lightning protection of mobile targets, approximate calculation is of great significance in shortening the lightning warning time and enhancing the protection effect.

Surface Charge Inversion Method on Cylindrical Insulators Based on Surface Potentials Measured Online

In this paper, a model of the Kelvin probe is established in COMSOL Multiphysics based on electrostatic field theory, and it is verified by measuring the surface potentials. The influence of the probe is also investigated. An improved charge inversion method based on surface potentials measured online is proposed. The surface charge density is directly obtained by the Gauss's theorem to avoid the calculation of the inversion matrix. The improved method is verified by comparing the surface charge density calculated by the analytical method. When considering the effect of the probe, the maximum difference in surface charge density is 0.3 μC/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> comparing to that when ignoring its effect, and the percentage of the difference is as high as 41%. The results indicate that the effects of the voltage of the probe under online measurement conditions must be considered.

Optimized Design of Wind Turbine Blade Receptors Based on Electrostatic Field Theory

Lightning protection for blades is one of the most important factors for the safe operation of wind turbines. In view of the differences in the designs of blade receptors, a full-scale blade receptor model was constructed on the basis of the scaling experiment of the wind turbine and electrostatic field theory. By combining the electromagnetic finite element analysis with leader discharge theory, this study analyzed and discussed the influence of the protruding height of receptors and the design of receptor types on the lightning receiving effect of the blade, and the optimum design scheme of blade receptors was proposed. According to the results of this study, the field intensity distribution on the surface of the receptor was a high-boundary and low-middle structure. The receptor easily produced an upward connection leader as the lighting junction. The electric field intensity around the receptor was substantially distorted after 4 mm protrusion, which was approximately twice the electric field intensity of a flat right-angle receptor. The convex chamfer had multiple centralized lightning stroke points compared with the convex right-angle design, thereby exhibiting better solidification and reliability at the lightning stroke area, which are conducive to protecting the blade from lightning damage. The electric field intensity of the convex fillet was similar to the chamfer, but the radius of the electric field intensity of the convex fillet was small, and the attenuation of the electric field intensity with the radius was evident. This study provides a reference for further optimization design of blade receptors.

Electrostatic field theoretic approach to analyze the partial discharge phenomenon pertaining to insulation degradation

This paper elucidates the application of electrostatic field theory to analyze partial discharge due to the void formation inside the insulating material. Formation of voids leads to accumulation of static charges leading to capacitance build-up. The most probable cause of insulation failure is due to the subjection of high voltage. Prolonged high voltage poses a threat and leads to insulation failure. Failures occur in the tip gap between the conductor and insulating material’s inner periphery. Probable causes of such failures are corona discharge, surface discharge and treeing, leading to formation of Lichtenberger figures in the material and cavity discharge. This paper presents a way of fabricating the inner lining of the insulator with a semiconductor layer obeying avalanche breakdown at breakdown voltage or voltages at which partial discharge is likely to occur. With the onset of high voltage which can cause a discharge, the semiconductor experiences avalanche breakdown giving out a single photon ejection by Geiger mode (principle). A superior prevention method of using Teflon for insulation instead of XLPE/PILC has been suggested and simulated using COMSOL. Detection using Avalanche photo-detector(LiDAR) may enable us to track the probable location of the occurrence of partial discharge and isolate the system.

Linear relation between surface roughness and work function of light alloys

The correlation between surface structures and material properties is rather complicated, and how to understand and clarify the relationship is of much significance for revealing related physical, chemical and mechanical mechanisms. In this study, the effect of surface roughness on the work function (WF) of Mg and Al alloys was investigated by scanning Kelvin probe and theoretical analysis. With the increase of surface roughness, the WF of AZ31 Mg alloy and 2198 Al alloy increased to 4.67 eV and 3.97 eV from initial 4.3 eV and 3.77 eV, respectively. Based on the least-square fitting method and the electrostatic field theory, the linear relationship between the WF and the surface roughness of the alloys was found. Owing to the effect of the surface electrostatic field, the rougher the surface of the alloys was, the larger the electrostatic potential near the rough surface was. Accordingly, the movement and transfer of the electrons were trapped and the required energy escaping from the surface was increased, resulting in the linear increase of the WF with the increase of the surface roughness.

Equivalent-Circuit Expression of Environmental Noise Electric Fields in Intrabody Communication Channels

In the development of intrabody communication systems, the most challenging goal is to protect against noise due to other electronic devices. In this paper, the equivalent-circuit expression of environmental noise electric fields (the so-called radiated noise) in intrabody communication channels are derived based on the theory of electrostatic fields. In addition, numerical examples are shown by means of electrostatic analysis based on the method of moments, and the results agree with those by full-wave analysis based on the finite-difference time-domain method and those by measurements. Therefore, it is concluded that the proposed circuit model can properly express the contribution of environmental noise electric fields.

A Deployment Algorithm for Mobile Wireless Sensor Networks based on the Electrostatic Field Theory

Abstract This paper proposes a deployment algorithm based on the electrostatic field theory for mobile wireless sensor networks. The nodes and obstacles in the deployment area are taken as the charged particles; and the particles will move due to the Coulomb’s force from other particles or obstacles. Finally, the nodes automatically spread to the whole area by the resultant action and complete the deployment. Four metrics, including coverage, uniformity, deployment time and average displacement distance, are used to evaluate the performance of the algorithm. The simulation results show that the proposed algorithm can give full play to its self-adaptive advantages and achieve the desired deployment effect; it is a kind of deployment algorithm with self-adaptive characteristics.

Modeling and Validating the Optimal Routes of a Sensor Network Using the Electrostatic Field Equations

In this paper, the analogy between the optimal routes within a sensor network and the electrostatic field lines is utilized successfully. In other words, partial differential equations similar to those of the electrostatic field theory are solved using Finite Difference Method (FDM) to find the optimal routes of the network. For the purpose of validation, an Opnet program based on the generated optimal routes is written to find the throughput and delay of the sensor network, a similar program is then applied to some arbitrary routing scenarios. The results show that the throughput and delay performance of the proposed method is better than that of the chosen arbitrary routing scenarios. It is also found from the results that the throughput of some scenarios is 50 % lower than that of the proposed method.

Dielectric Analysis of Dynamic Fouling Behavior on Surface of Polyethersulfone Composite Ultrafiltration Membrane

A dielectric analysis model for the fouling layer on the polyethersulfone composite ultrafiltration (UF) membrane and solution system, which consists of the solution, concentration polarization layer (CPL), and cake layer, was established by virtue of the interfacial polarization and the electrostatic field theory. The effect of some important parameters, such as the depth, conductivity of CPL, and cake layer, on the dielectric spectroscopy (or dielectric relaxation properties) of the UF system was discussed by the parameter sensitivity analysis and the dielectric measurement. The simulations indicate that the CPL can be created rapidly and the cake layer formation is the dynamic balance process of growth and erosion in the process of UF. The key factor affecting on the dielectric spectrum of UF system is the electrical properties of the CPL and the cake layer. In comparison to the results of dielectric measurement, the simulations indicate that the model proposed in this work is valid and reliable to some degree for describing and explaining the dielectric relaxation phenomenon in UF system. It is very important to further understand the fouling behavior of membrane surface and optimize the controlling techniques of membrane fouling in the process of UF.

ELECTROSTATIC FIELD IN SUPERCONDUCTORS AT EQUILIBRIUM

The theory of electrostatic fields in superconductors at equilibrium is reviewed. We start from the simple Bernoulli potential balancing the Lorentz and inertial forces. Then we add interaction of superconducting and normal electrons and forces due to gradients of the condensation energy. Nonlocal relation between perturbing forces and the induced electrostatic field is formulated within the extended Ginzburg-Landau theory.

Electrostatic field theory and circuit analysis in the design of coalescers with pulsed dc voltage

This paper presents a mathematical analysis of the electric field and interfacial free charge experienced by the emulsion in an electrostatic coalescer that is subjected to a pulsed dc voltage. Previous work in this area is re-assessed, but the analysis is expanded. A novel static analysis of the system is presented, giving valuable physical insight. It becomes obvious that there must be a limited range of frequencies that are effective in a pulsed dc scheme. Thereafter, analytical expressions for the steady-state solution, where both the switching frequency and duty ratio (or mark space ratio) can be varied, are presented for the first time. These expressions are used to derive voltage and charge profiles for a specific example under various circumstances. In addition, a previously found criterion for optimum switching frequency is analyzed, and it is found that there are actually three physical parameters that all would show the same correlation with coalescer performance, not only charge as previously found, but also voltage and current. An analytical expression for the correlation quantity is derived, and the numerical example indicates that there is a narrow range of frequencies and duty ratios that are effective.

Research on electrostatic deformation of space membrane mirror

薄膜反射镜将解决反射镜孔径与重量相互制约的问题. 采用静电拉伸法控制薄膜反射镜面形, 具有结构简单、反射镜面形易于控制等优点, 其原理为利用静电场上库仑力作用使薄膜产生面形变化, 生成所需的光学曲面. 由于薄膜变形力学, 以及静电场理论的复杂性, 目前薄膜成形及其面形控制在理论分析上仍未有定量的结果. 本文主要以单电极静电场中的薄膜反射镜面形为考察因素, 通过数值计算的方法得到薄膜反射镜上的静电力分布, 运用有限元分析获得该分布下的反射镜面形, 并将其与理想面形进行比较. 提出采用多电极闭环控制可获得更高的控制精度, 对静电拉伸薄膜的研究具有一定的指导意义.

Theoretical and experimental studies of the spatial sensitivity of an electrostatic pulverised fuel meter

In coal-fired power plants, the coal is pulverised and pneumatically conveyed to the burners. It is essential to measure and control pulverised fuel (PF) to improve combustion efficiency, reduce pollution and lower operating costs. Unlike single-phase flow, where flow density is generally considered to be uniform, air–solids two-phase flow in pneumatic conveying systems can undergo inhomogeneous concentration distributions across a given pipe cross-sectional area, especially around bends and bifurcators or trifurcators. The “roping” flow regime is an extreme example of inhomogeneous solids distribution, where highly concentrated solids form a column-like (rope-like) flow. For such complex flow regimes, solids concentration or solids mass flow meters will give different outputs when inhomogeneous flow occurs at locations where these meters are installed if they are sensitive to the flow patterns. This problem can be solved in two ways. The first and simplest approach is to restrict the meter's installation to locations where solids are relatively uniformly distributed over the cross-sectional area of the pipe. Alternatively, it can be solved by using a meter having uniform spatial sensitivity, so that the measurement would not be affected by the flow regimes. Because the installation locations of PF meters must suit other requirements, such as accessibility for the convenience of maintenance, it is ideal if the meters have uniform spatial sensitivities. Electrostatic mass-flow meters are typically used to give a measure of the fuel mass flow rate. One design employs ring-shaped electrodes which have non-uniform sensitivity, resulting in variations in meter output for the same flow stream passing through the sensing volume at the different radii relative to the meter's central line. This paper presents a theoretical analysis of the spatial sensitivity of the electrostatic meter with ring-shaped electrodes in the time and frequency domains. One goal of the study is to improve its performance and to achieve uniform sensitivity. The experimental data presented in this paper support the overall mathematic modeling, based on electrostatic field theory, using the finite-element method (FEM). Although the FEM analysis provides useful results, a more rigorous investigation is recommended for future work.

2D director calculation for liquid crystal optical phased array

A practical numerical model for a liquid crystal cell is set up based on the geometrical structure of liquid crystal optical phased arrays. Model parameters include width and space of electrodes, thickness of liquid crystal layer, alignment layers and glass substrates, pre-tilted angles, dielectric constants, elastic constants and so on. According to electrostatic field theory and Frank-Oseen elastic continuum theory, 2D electric potential distribution and 2D director distribution are calculated by means of the finite difference method on non-uniform grids. The influence of cell sizes on director distribution is analyzed. The fringe field effect between electrodes is also discussed.

Skeletonisation: An electrostatic field-based approach

Skeleton representation of an object is a powerful shape descriptor that captures both boundary and region information of the object. The skeleton of a shape is a representation composed of idealized thin lines that preserve the connectivity or topology of the original shape. Although the literature contains a large number of skeletonisation algorithms, many open problems remain. In this paper, we present a new skeletonisation approach that relies on the Electrostatic Field Theory (EFT). Many problems associated with existing skeletonisation algorithms are solved using the proposed approach. In particular, connectivity, thinness and other desirable features of a skeleton are guaranteed. It also captures notions of corner detection, multiple scale, thinning, and skeletonisation all within one unified framework. The performance of the proposed EFT-based algorithm is studied extensively. Using the Hausdorf distance measure, the noise sensitivity of the algorithm is compared to two existing skeletonisation techniques. In addition, the experimental results also demonstrate the multiscale property of the proposed approach.

Calculation of vibronic coupling constants for tetrahedral and octahedral d electron systems via dynamic ligand field theory and application to optical spectra

A perturbative model for the calculation of electron-phonon coupling constants of tetrahedral transition metal complexes based on the electrostatic ligand field theory is presented. Orbital vibronic coupling constants are expressed in terms of common ligand field parameters, and linear many-electron coupling constants for all d2-d9 strong field states in tetrahedral and octahedral symmetry are reduced to orbital coupling constants, enabling comparisons of coupling strength and directions of nuclear distortions over a wide range of transition metal complexes in a general way. The usefulness of the model is demonstrated for well resolved optical spectra of tetrahedral [MnO4]2-, [CrO4]3-, [CoCl4]2- and octahedral [CrF6]3-, [Cr(NH3)6]3+, [VO6]8- complexes, revealing good correspondence. The method is especially valuable for the interpretation of such spectra because it is easy to apply and the prediction of band shapes does not require additional parameters to be fitted to experiment. Nuclear distortions from the cubic reference geometry and Jahn-Teller stabilization energies are calculated.

Transmission of polar effects: prediction by the Kirkwood–Westheimer electrostatic field effect model

The pKa values of four pseudo-substituted bromo- and unsubstituted 4-carboxy[2.2]paracyclophanes have been measured and Kirkwood–Westheimer calculations carried out; the substituent effects observed are both normal and reversed, the electrostatic field theory accounting for them both qualitatively and, for the pseudo ortho-, metal-, and para-isomers, quantitatively.