The electric field at a water surface stressed by an AC voltage

Oscillating projections can develop on the surface of a conductive liquid stressed by a perpendicular, alternating electric field. In this work, a water surface was confined in a narrow channel, resulting in a single row of projections, allowing good observations of the projection shapes. This paper discusses the experimentally observed development of the projections, and the resulting electric field at their tips. The row of projections behaves as a standing wave at the frequency of the applied AC voltage. It was seen that the formation of the projections, and hence the maximum electric field, lags the applied voltage. The normally rounded projections can become conical if the voltage is high enough for sparking to occur. Sparking was observed to occur as the applied voltage declined from its peak, corresponding to the time of the calculated maximum electric field     

Charge and mass flux in the radial electric field of an evaporatingcharged water droplet: an experimental analysis

In the electrostatic application of pesticide sprays, charge retention by evaporating droplets in transit to deposit surfaces is a limiting problem. The possible charge loss via evaporative mass transfer and the possible alteration of evaporation rate caused by the presence of the droplet surface charge were experimentally investigated. For studies of evaporation from a charged 3 mm diameter water droplet conducted as a function of droplet potential (-1, -2, and -3 kV) and atmospheric relative humidity (22, 64, and 100%), the current flowing in the radial electric field of the charged evaporating was compared with that flowing in the radial field of a nonevaporating metal sphere to determine if the departing water vapor was electrified. It is concluded that electric charge on evaporating liquid droplets comprising agricultural chemical sprays neither alters the mass transfer rate nor is dissipated by the evaporation     

Induction charging of granular materials in an electric field

It is well known that particles can be freely levitated in an electric field due to the charge induced on the particles by the external field. The charge depends upon the electric field strength and particle properties. This paper studies some of these factors to investigate the fundamentals of induction charging for granular materials. An experimental apparatus was set up to collect the levitated particles in a filter contained in a Faraday pail and the charge-to-mass (Q/M) ratio was obtained based on the charge and mass measurements for the samples in the filter. Furthermore, the particle size distribution was measured and analyzed by laser diffraction and microscopy and the surface mean diameter (D/sub s/) and volume mean diameter (D/sub v/) were obtained. In these experiments irregular shaped Al/sub 2/O/sub 3/ particles and spherical glass beads with a size range of 42-390 /spl mu/m were used and tested at different electric field strengths. By combining the results of Q/M, D/sub s/ and D/sub v/, the charge per particle was calculated and the results compared with theoretical values. It was confirmed that the particle charge is dependent upon the electric field strength and the particle properties of size, shape, density, resistivity, and adhesive force.     

The control of mechanical strength by an electric field in ceramic composites dispersed with piezoelectric particles

The control of mechanical strength in structural ceramic composite has been proposed and demonstrated by dispersing piezoelectric particles. The change in strength of barium titanate/zirconia composite on polarization treatment was evaluated, and the mechanism of this phenomenon is discussed based on the previously proposed mechanism for monolithic piezoelectric ceramics. The bending strength of BT/8YSZ composite increased upon longitudinal poling and decreased upon transverse poling compared to the untreated samples. Both the strengthened and weakened specimens tended to return almost to their original strength by heating over the T _c of barium titanate. Scanning electron microscopy was then used to examine the crack propagation after the polarization treatment, and cracks going in the poling direction were found to detour around the barium titanate grains, which was attributable to the increase in strength in the poling direction.     

Ultrafast control of hole spin by electric field in semiconductors

Ultrafast and coherent transitions induced by electric field between spin states of the valence band in semiconductors are considered. It is shown that using optimized femtosecond electric fields one can, in principle, control a selected component of the hole spin. The feasibility of hole spin switching is illustrated using the well-known Luttinger-Kohn Hamiltonian for valence bands of tetrahedral and zinc-blende semiconductors. The presented results may be useful in the development of the ultrafast semiconductor spintronics.     

基于激光光电池供电的脉冲电场传感器设计

为了解决脉冲电场传感器电光调制部分的供电问题,设计研制了一种基于激光光电池供电的脉冲电场传感器,该传感 器由激光光电池供电电路、电光调制电路和感应天线构成。 设计制作了由供能激光器、锂电池、激光光电池、锂电池充电电路、 锂电池保护电路、锂电池升压放电电路构成的激光光电池供电电路。 测试结果表明,供电电路输出电压精度为 1. 04 %,纹波系 数为 0. 3 %,并且 48 h 持续工作输出电压波动为±0. 035 V。 设计制作了由单极子天线、场效应管型集成运放构成的传感器电光 调制电路。 实验结果表明,研制的脉冲电场传感器测量带宽在 39. 8 Hz~ 1 050 MHz,动态范围 0. 256 kV/ m ~ 13. 79 kV/ m。     

Analytical formula of induced electric fields in a spherical conductor by an ELF dipole magnetic field source

An analytical formula of induced electric field E in a spherical conductor by an ELF dipole magnetic field source is mathematically derived in vector form based on the equivalent mutlipole moment method with reexpansion technique (RE‐EMMM), where M _‖ and are parallel and perpendicular components of M , respectively. The validity of the formula is confirmed in the following three ways: (i) the derivation of the formula from the Sarvas equation with the reciprocity theorem derived by Eaton; (ii) the convergence of the formula to that of homogeneous magnetic field when M _‖ is located at the infinite distance; (iii) comparison of the analytical solutions with numerical solutions by RE‐EMMM. Furthermore, a formula for the trajectory, which satisfies E = 0 , is derived for the field by M _‖. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(3): 8– 17, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20739     

电蓄热水地暖系统

随着采暖费由职工单位缴纳改为单位补贴个人缴纳制度改革的深入,尤其是即将实行的集中供热采暖按量收费、节约归己、不足自补制度之后,人们对建筑节能的关注度日益提高。选用节约型的采暖方式,已渐成为建房和购房者的热点之一,故有必要对一些采暖方式作出分析与比较,以资参考。现将电蓄热水地热采暖技术简述如下。     

A trainer-simulator for improving and assessing the professional skill of the personnel of heat-supply networks

Considered are the technique of creating for the first time a computer trainer-simulator for dispatchers of heat-supply networks and the experience gained from its application in the regional and first all-Russia competitions in the professional skill of the personal servicing heat-supply networks.     

Breakup of large water droplets by electric fields

The results are presented of an experimental study of the processes that lead to the breakup of a large water droplet doped with alcohol to approach the density of oil and immersed in an oil dielectric medium to which a strong electric field is applied. The study, which was carried out by means of photography, showed that the deformation of the droplets prior to breakup involves distinct characteristic stages of importance to the induction charging and to the ultimate charge separation phenomena. The experimental results show the conditions and the phenomena that lead to the breakup of an initially uncharged water droplet when subjected to an electric field that is not perfectly uniform and in a gravity field     

Experiment of an electric water heater with autonomous frequency regulation

Integration of wind power generation into power systems has been limited because of the problem of frequency regulation during light‐load periods at night in some areas in Japan. As a solution, autonomous frequency regulation by electric water heaters (EWHs) has been proposed. A control board to control the power consumption of an EWH is fabricated. It measures both the power system frequency and thermal energy stored in a hot‐water tank, and then turns on/off a heating element according to a control algorithm. It is confirmed that the board can measure power system frequency every 1 s with a resolution of better than 0.01 Hz and that it can measure the vertical temperature distribution in the storage tank with an acceptable accuracy to calculate the future power consumption ratio, which is a parameter that decides the turn on/off of the heating element while considering end‐user comfort. Then, an EWH with autonomous frequency regulation is fabricated by embedding the board, and the EWH is operated to investigate the performance. © 2013 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Increasing the reliability of electric networks

A review of Russian and American periodicals on the reliability of electric networks is carried out. New measures to increase the reliability of electric power supply of consumers are described.     

Breakdown of air over a water surface stressed by a perpendicularalternating electric field, in the presence of a dielectric barrier

Distortion of the surface of a water layer serving as the ground electrode of an experimental ozone generator has a strong influence on the generator's performance. The distortion is highly affected by the frequency, as well as the magnitude, of the applied electric field. In turn, the resultant field is affected by the distortion. Over the frequency range tested (20-300 Hz), the applied field required to initiate electrical breakdown of the air over the water surface was found to be less than that required for breakdown over a flat metallic electrode. This reduction in applied field for breakdown is attributed to a reduction of the air-gap height due to an upward bulge of the water surface, and to field intensification by sharply pointed cones. The cones are most predominant at lower frequencies     

Production of oil/water type uniformly sized droplets using aconvergent AC electric field

The authors proposed a new method to produce uniformly sized insulating liquid droplets (such as kerosene or plastic monomer) in immiscible liquid media (distilled water) by means of an applied convergent electric field generated using AC or pulsed voltage. The disintegration mechanism of the liquid column was observed precisely using video images and still photographs. Kerosene droplets with an essentially uniform diameter ranging from 100 to 250 μm were produced synchronously with the applied AC frequency using a nozzle diameter of 100 μm. When the flow rate of the co-flowing liquid surrounding the oil-phase liquid jet was increased, the synchronous frequency became higher and the size of the resulting droplets was decreased due to the elongation of the liquid jet. The disintegration mechanism is most likely the forced oscillation of the liquid jet stimulated by each cycle change of the applied voltage. The droplet size can be widely controlled by varying the AC frequency, nozzle diameter, liquid flow rate and velocity ratio between the oil-phase and co-flowing water     

基于模拟电荷和边界元法的变电站工频电场分布仿真研究

本文提出了一种模拟电荷法和边界元法相结合的方法,将变电站内设备的影响考虑进去,可更加准确地确定变电站内工频电场分布,并且本文采用了合理简化剖分的方法,减少了冗长的叠加过程,在保证了计算精度的同时,大大缩短了计算时间,为变电站内工频电场计算提供了一种快速有效的方法。本文仿真结果与变电站实测结果基本一致,证明该方法能够用于变电站工频电场分布的预测。     

一种基于矢量电场的多电极电场梯度计算优化方法研究

通过对变电站中电气设备电场梯度信息检测计算方法进行研究,结合矢量电场多电极梯度信息,使用压缩感知贪婪重构算法对电场检测计算方法进行优化,对电场梯度信息进行有效识别,提高电压等级检测判断的准确率。该方法通过分析带电体周围电场信息,能够准确地计算出高电压导体周围的电场分布和电压等级。通过在110 k V变电站复杂工频电场环境中进行试验,获取带电载体一个间隔的场强分布。实验分析表明,该方法可以有效提高带电载体电压等级的检测能力和对带电体周围电场信息的响应速度,提高了工作人员在复杂工频电场环境下工作的安全性。     

Development of three-dimensional electric field computation system by surface charge method

This paper describes development of three-dimensional electric field computation system by surface charge method. Using this system, both potential and electric field in the case which includes resistance or true electric charge can be calculated. And this system is able to be connected to the pre-post processors, which is useful for us to make arbitrary shape and to display results of analysis.