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The effects of plasma and electrostatic field on the growth and nutrient content of Chinese cabbage have been investigated. The parameters of height, dry weight, content of vitamin C (VC), soluble sugar (SS), and total amino acids (TAAs) are used to characterize the growth speed and quality of Chinese cabbage. The results show that both plasma and electrostatic field can promote the growth, increase the dry weight, and improve the quality of Chinese cabbage. In addition, the appropriate combination of plasma and electrostatic field can produce better effects than using one of them alone. [ABSTRACT FROM AUTHOR]

Despite the importance of the electric treeing phenomenon, a detailed understanding of the mechanisms is still lacking. Therefore, in this study, we analyze electrical trees as composites of very thin 3D tubes between a treeing needle and a plate electrode and calculate the energy-release rate to estimate the prerequisite force required for crack propagation. This study implements a new method using an analogy between concepts of fracture mechanics and Maxwell stress to calculate the energy-release rate of line-shape elements. We obtain the energy-release rate around a volume near the treeing needle and electrical trees and compare it before and after tree growth. To verify the results, path independence is tested, and it is found to be conserved only when the path does not include the inside surface of the treeing needle. In addition, the results show that the 1D-growth of the tree has little effect on the value of the energy-release rate, and therefore, it is necessary to predetermine the order and an adequate calculation area. Moreover, the value of the energy-release rate is found to be proportional to the square of the applied voltage. These results imply that calculating the energy-release rate exhibits a potential to mathematically evaluate the growth of electrical trees. [ABSTRACT FROM AUTHOR]

In this article, an electrostatic precipitators (ESP) with high electric field, which does not use corona discharge, was investigated. The ESP had a parallel plate configuration composed of a high voltage application plate electrode and grounded plate electrode with a gap of 5 mm. The electrode length was between 150 and 450 mm. The air was flowed at the gas velocity between 0.5 and 5 m/s in the ESP by a fan. A voltage up to 12.5 kV was applied to the high voltage application electrode, whereby the electric field intensity of 25 kV/cm was generated between the electrodes. The particle concentration in the air for the particle size between 0.3 and 5 μm was measured to calculate the collection efficiency. The collection efficiency in a conventional two-stage type ESP was also measured, and compared to the result in the ESP with high electric field. As a result, the collection efficiency at the electrode length of 450 mm was 77.6% at 12.5 kV, when the ratio of the input power was lower than 0.33 W/(m3/s), in the ESP with high electric field. On the other hand, the collection efficiency in the conventional ESP was 65.6% or 82.0% at the input power of 14.2 W/(m3/s) or 24.8 W/(m3/s). Therefore, it is revealed that the ESP with high electric field is effective for energy saving. [ABSTRACT FROM AUTHOR]

In this study, the charge polarity on a dielectric surface and the effect of initial charge on the multipactor threshold in a parallel-plate dielectric-loaded waveguide are investigated through 1-D particle-in-cell (PIC) simulation. The numerical results show that owing to different dielectric materials, two kinds of multipactor mechanisms exist on the dielectric multipactor. For analyzing the effect of charged dielectrics on the multipactor threshold, the single-sided (SS) and double-sided (DS) impacts on metal and dielectric surfaces are considered. As a result, the multipactor threshold could be suppressed by adding some initial charges on the dielectric surface, satisfying a certain condition. [ABSTRACT FROM AUTHOR]

A new version of the biogeography-based optimization algorithm is proposed in order to consider multiple objectives. In fact, by exploiting non-dominated sorting of habitats, it is possible to approximate Pareto-optimal solutions in the objective space. The optimal shape design of an electrostatic micromotor, which is a benchmark in the Micro Electro-Mechanical Systems design, is considered as the case study. [ABSTRACT FROM AUTHOR]

The performance of an electrical capacitance tomography (ECT) sensor is usually evaluated by static experiment with solid material(s) for some typical distributions encountered in two-phase flows. Considering the soft-field effect of an ECT sensor, the existing evaluation method is not appropriate for evaluating the performance of ECT for the real complex two-phase flows. In this paper, a new simulation model is proposed by coupling two physical fields: fluid field and electrostatic field, based on a mixture model and an electrostatic model. The mixture model is based on the diffusive flux model, which is suitable for liquid–solid mixtures with high concentration of solid particles. An ECT sensor with 12 electrodes is modeled based on an electrostatic model with a periodic excitation signal. The two models are coupled by an additional electric force in the momentum conservation equation in the mixture model. The time-varying permittivity distributions and capacitance data are obtained from the computational simulation based on the coupling model to investigate the performance of the ECT sensor and image reconstruction. Linear backprojection and Landweber iteration with different parameters are used to reconstruct images. Experiment was carried out using a rotation device with a 12-electrode ECT sensor to validate the simulation results. Both simulation and experimental results verify that the proposed coupling model is valid for evaluating the performance of ECT sensors and image reconstruction algorithms. [ABSTRACT FROM PUBLISHER]

In this letter, a high-performance graphene-based electrostatic field sensor is demonstrated. Combining the ultrahigh mobility of graphene and the long lifetime of carriers in SiO2/lightly doped Si substrate, our device achieves a fast response of \sim 2~\mu \texts and detection limit of electrostatic potential as low as ~5 V, which is improved by an order of magnitude as compared with commercial products. The proposed device structure opens a promising pathway to high-sensitive electrostatic detection, and also greatly facilitates the development of novel sensors. [ABSTRACT FROM AUTHOR]

The breakdown and triggering characteristics of triggered vacuum switch (TVS) are very important features, and they affect the operation reliability of TVS. Both of them mainly depend on the electrode material, electrode shape, gap distance, and surface condition. For an optimized electrode's geometry, finite-element method electrostatic field simulations were conducted to evaluate the effect of geometric parameters on the electrostatic field strength and distribution. The distribution of electrostatic field of the TVS with multirod system (MTVS) is calculated by the finite method. The simulation results show that the geometric enhancement factor (GEF) is decreased with the increase of the fillet radius of the edge of the rod. In case of the fillet radius for the side face of rod 3 mm and the fillet radius of the top face of the rod is 5 mm, the GEF is decrease to a minimum value of 3. The breakdown voltage of MTVS was measured by the high-voltage direct current generator after switch currents with amplitude of 63 kA and width of 13 ms with the interval time of 10–15 min. The influences of electrode materials and operation times on the breakdown voltage and trigger characteristics are also studied. The experimental results show that the breakdown voltage of the optimized MTVS is higher than that of the non-optimized MTVS. The breakdown voltage of CuCr30 is higher than that of oxygen-free copper. In addition to, the trigger characteristics of MTVS are influenced mainly by the electrode materials, the fillet radius of electrode has a little effect on the triggering characteristics of MTVS. [ABSTRACT FROM AUTHOR]

The polypropylene (PP) was corona charged using different grid voltage to prepare varies electrets with different polarities. The penetration and stability of the external electrostatic field of the PP electret through the excised fresh, stratum corneum (SC) stripped and dehydrated rat skin and the surface potential decay at the dermis side of the rat skin were investigated after application of different PP electrets onto the skin samples. The results indicated that the PP electrets could change the polarized state of the fresh and SC stripped skin. The change of the polarized state of the skin was closely related to the polarity and magnitude of the potential of the PP electret. The external electric field of the PP electret could penetrate through all skin samples and showed good stability as well. Besides, the electrostatic field of the PP electret could also form a stable potential difference between both sides of the SC to regulate the polarized state of the SC. [ABSTRACT FROM PUBLISHER]

The streak camera is one of the highest temporal resolution measurement devices for luminous phenomena, and the sampling streak camera is its advanced device for image measurements in time domain. In general, the temporal resolution of the sampling streak camera is less than that of the conventional streak camera due to complicated electron motion in the device. For improvement of the sampling streak camera for higher temporal resolution of order of pico-second, understanding of physical phenomena in this device is essential and then numerical analysis play an important role. This paper presents a numerical analysis method of the sampling streak camera based on self-consistent simulation of electrostatic field and relativistic electron beam motion by using particle-in-cell (PIC) method. It is predicted from the numerical simulation that higher temporal resolution operation of the sampling streak camera will cause serious inaccuracy in phase information due to the space charge effects. [ABSTRACT FROM PUBLISHER]

This paper presents a modified version of the hybrid FEM-DBCI (Finite Element Method-Dirichlet Boundary Condition Iteration) method to solve static and quasi-static electromagnetic field problems in open boundary domains. The modification consists of overlapping the fictitious truncation boundary with the integration one, as in the FEM-BEM (Boundary Element Method) method. The global algebraic system obtained is solved iteratively by means of the GMRES (Generalized Minimal Residual) solver, applied virtually to a reduced system in which the unknowns are those relative to the potential on the truncation boundary only. Some validation examples are provided. [ABSTRACT FROM AUTHOR]

In this paper an improved placement of the integration surface for the integral equation in the hybrid finite element method--Dirichlet boundary condition iteration (FEM-DBCI) method is achieved by selecting it as lying in the middle of the tetrahedral or hexahedral finite elements. A better accuracy is obtained with respect to the case in which the integration surface lies along the element faces. Some numerical examples are provided. [ABSTRACT FROM AUTHOR]

This paper presents a novel family of nodal boundary elements to be used in the context of the hybrid FEM-BEM method to deal with unbounded static and quasi-static electromagnetic field problems. In this new type of boundary elements the scalar field is developed by means of classical polynomial shape functions of a given order, whereas its normal derivative is developed with lower-order shape functions. [ABSTRACT FROM AUTHOR]

This paper describes an iterative method to solve efficiently the global algebraic system of equations obtained by applying the hybrid finite element method-boundary element method (FEM-BEM) to the solution of open-boundary electrostatic problems. In the proposed approach, a conjugate gradient (CG) solver is used to solve the FEM equations, whereas the BEM equations are solved by making use of the direct LU solver. To do so, it is convenient to implement the BEM equations in a nonconventional way, by choosing the nodes of the potential as not coinciding with those of its normal derivative. [ABSTRACT FROM AUTHOR]

A novel, physically motivated deformable model for shape recovery and segmentation is presented. The model, referred to as the charged-particle model (CPM), is inspired by classical electrodynamics and is based on a simulation of charged particles moving in an electrostatic field. The charges are attracted towards the contours of the objects of interest by an electrostatic field, whose sources are computed based on the gradient-magnitude image. The electric field plays the same role as the potential forces in the snake model, while internal interactions are modeled by repulsive Coulomb forces. We demonstrate the flexibility and potential of the model in a wide variety of settings: shape recovery using manual initialization, automatic segmentation, and skeleton computation. We perform a comparative analysis of the proposed model with the active contour model and show that specific problems of the latter are surmounted by our model. The model is easily extendable to 3D and copes well with noisy images. [ABSTRACT FROM AUTHOR]

Pulsed intense electron beams with remarkable parameters are generated in transient hollow-cathode discharges (THCD). The channel spark is different from the other THCD configurations with respect to the low gas pressure and the tube geometry, which consists of a dielectric capillary tube and an anode mounted on its external surface. In this paper, the channel-spark discharge is systematically studied by electrical and fast shutter camera measurements. The buildup of electrostatic field and the equipotential lines are calculated by the numerical code Electrostatic Field (ElFi) 3.0. The influence of the gas pressure, breakdown voltage, and external capacitance on the discharge current and the beam current are outlined. Depending on the gas pressure, two different discharge modes are observed, i.e., the high resistive and the regular modes, which can be distinguished by the shape of the electrical signals. The plasma development in these modes is studied by electrical and fast shutter camera measurements, performed spectrally integrated and with interference filters to separate the emission of the ions originating from the working gas and capillary material. Compared to the pseudospark, the plasma development in channel spark presents similar as well as specific features due to the low gas pressure and to the capacitive anode-plasma coupling [ABSTRACT FROM PUBLISHER]

Effect of surface charges on dc flashover characteristics of a composite polymeric insulator is studied by means of experiments and theoretical calculations. The considered insulator consisted of a glass fiber reinforced epoxy core covered with a layer of silicone rubber and terminated by metallic electrodes with rounded smooth edges. In the experiments, the insulator surface was charged by external corona while keeping the electrodes grounded and different charging levels were realized by varying its intensity. A series of disruptive discharge tests were carried out on the charged insulator under negative dc voltages. It was revealed that negative deposited surface charges led to an enhancement of the flashover performance whereas positive ones reduced the flashover voltage level. A theoretical model has been developed and utilized for analyzing the experimental results. In the model, surface charge density profiles deduced from measured surface potential distributions were used as boundary conditions for calculations of electric fields. The measured and calculated flashover voltages were found to be in agreement indicating that the observed variations in the flashover characteristics could be attributed to the modifications of the electric field produced by the surface charges. [ABSTRACT FROM PUBLISHER]

Effect of pre-deposited surface charges on impulse flashover characteristics of a polymeric insulator is studied by means of computer simulations utilizing a model based on criteria for streamer inception, propagation and sustenance. A parametric study is performed to investigate the influences imposed by magnitude and polarity of the charge, its location on insulator surface and properties of insulator material on its flashover voltages. The obtained results are analyzed in terms of electric field distributions in the vicinity of the insulator surface and are compared with experimental data available in the literature. [ABSTRACT FROM AUTHOR]