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In this work, the insulating layer with a weakly conductive layer on its surface is charged with a needle electrode. The quantities that are measured and calculated are the transients of charging current and transferred charge. In addition, we calculate charge distribution in the weakly conductive layer at various moments of time, and potential kinetics. By comparing the calculation results with measurement data, it is possible to determine sheet resistance of the investigated weakly conductive layer. This sheet resistance can be also determined experimentally: during charging of the weakly conductive layer (deposited onto the insulating layer), the charging current and the deposited charge increase with decreasing sheet resistance of the weakly conductive material, hence its sheet resistance can be related to the measured charging current or to the deposited charge. The proposed method can be applied for measuring sheet resistances from 10+8 Ω/sq to 10+12 Ω/sq, and those measurements can be done in a second. It is also possible to use the contact-free method proposed in this work to measure various properties of the medium related to the material sheet resistance, e. g. relative air humidity, illumination, sample thickness, intensity of ionizing radiation, etc. This method is also suitable for measuring sheet resistance of island-type (discontinuous) layers, which is difficult to measure using usual methods. Results of this work make it possible to determine potential of a two-layer system consisting of a charged low-conductance layer and an insulator, as well as the radius of an electrographically developed area, which is important, for example, when the image is created using a needle electrode. 相似文献
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A laboratory electrostatic precipitator (ESP) together with a bipolar pre-charger has been designed for studying charge-induced agglomeration and fine particle collection. In terms of particle numbers, the ESP collection efficiency drops to its minimum of near 90% for particles with diameters of near 0.2 μm and 3 μm. For other particles, its value is around 94%–95%. By using the bipolar pre-charger, the grade efficiency can be significantly increased for all particle sizes due to the charge-induced particle agglomeration. The grade collection efficiency rises to about 95%–98% for all size particles. 相似文献
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研制了一种基于直线变压器技术的脉冲功率系统,采用水介质脉冲形成线并联充电作为脉冲形成装置。分析了给形成线充电时泄漏电阻对充电电压效率和能量效率的影响,给出了泄露电阻的能量损耗率计算公式;结合实验参数计算了本实验中水介质形成线的泄漏电阻,介于8.2 kΩ与3 kΩ之间。根据泄露电阻取值范围,分析了双模块和四模块实验中水介质形成线充电过程中的电压效率与能量效率,结果表明水介质形成线的能量损失占其获得能量的5%~12%;计算结果同时表明:随着实验模块数增加,能量损失逐渐增大。 相似文献
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研制了一种基于直线变压器技术的脉冲功率系统,采用水介质脉冲形成线并联充电作为脉冲形成装置。分析了给形成线充电时泄漏电阻对充电电压效率和能量效率的影响,给出了泄露电阻的能量损耗率计算公式;结合实验参数计算了本实验中水介质形成线的泄漏电阻,介于8.2kΩ与3kΩ之间。根据泄露电阻取值范围,分析了双模块和四模块实验中水介质形成线充电过程中的电压效率与能量效率,结果表明水介质形成线的能量损失占其获得能量的5%~12%;计算结果同时表明:随着实验模块数增加,能量损失逐渐增大。 相似文献
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Thomas Traußnig Stefan Topolovec Kashif Nadeem Dorothée Vinga Szabó Heinz Krenn Roland Würschum 《固体物理学:研究快报》2011,5(4):150-152
Aiming at a voltage‐control of magnetism, the magnetization of a porous γ‐Fe2O3–Pt nanocomposite is studied under the influence of charging the surfaces of the porous structure in an electrolyte. Reversible variations of the magnetization of up to 10.4% could be achieved upon charging in the regime where electrochemical adsorption and desorption occurs. The observed variation of the magnetization with electrochemical charging is assigned to the γ‐Fe2O3 nanoparticles whereas the conductive network of Pt nanoparticles is necessary for charging. (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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It is well known that experiments of charging and later discharging of materials with gas ignition probes or hand-coulombmeters show that some insulating materials do exist that cannot be hazardously charged by manual rubbing in spite of their high surface resistance. In this work, effects of variations of physical and chemical properties as well as the structure of these materials have been systematically investigated. The results obtained help to explain this behavior and propose approaches to predict the charging behavior of such insulating materials without any charging test at all. 相似文献
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A scanning electron microscope (SEM) is employed to investigate the temperature effect on the charging behaviour of alkali-silicate glasses under electron beam irradiation using electrostatic influence method (EIM). A modified special arrangement adapted to the SEM allows to study charging mechanisms and charge transport characteristics of these glasses using the simultaneous measurement of displacement and leakage currents. The trapping process during continuous electron irradiation can be directly determined by the EIM. The experimental results reveal that the charging ability of glasses decreases with increasing temperature. The variation of charge process has been confirmed by measuring the surface potential in response to the sample temperature. In this report, we introduce also the secondary electron emission (SEE) yield. It was found the strong dependence of the SEE yield on the temperature variation. The higher is the temperature and the lower is the SEE yield. The trapping ability is analyzed taking into account the regulation mechanisms involved under electron irradiation. 相似文献
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设计了一种输出电压为4 MV的超前触发型Marx发生器,为了进一步优化采用电阻充电的Marx发生器输出特性,提高系统的充电效率并且减小级间充电电压不均匀性,对Marx发生器恒流充电过程进行了解析求解。结果表明:各级间充电电压差为与充电电阻、电容和充电速率成正比,与时间无关的定值,充电时间越长电压效率越高,且与电压变化率无关 。该结论具有普遍适用性。结合我们设计的4 MV超前触发型Marx发生器回路,利用PSpice对Marx发生器的恒流充电过程进行了模拟,得到了自洽的结果,并且与恒压充电进行了对比。当充电电阻为10 k,各级电容为400 nF,充电速率为10 kV/s时,恒流充电能量效率达到90%,约为恒压充电能量效率的2倍,充电时间为恒压充电的1/3。 相似文献
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空间辐射环境中,聚合物介质的深层充放电效应是威胁航天器安全的重要因素之一.文中在Chudleigh和von Berlepsch所发展的电位衰减模型基础上引入传输电流项,考虑了电子入射引起的感应电导率和感应电场的影响,提出了新的分析研究介质材料深层充电规律和特征的模型.通过该模型,分析了不同辐射条件下介质的表面电位、内部电荷与电场分布的变化,并设计实验及援引其他实验数据对模型分析结果进行验证.分析和实验结果表明,聚合物介质在深层充电过程中的平衡电位随着入射电子束流强度和介质电阻率的增加而增大,决定深层充电平
关键词:
深层充电
电荷传输模型
电子束
聚合物 相似文献
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The present paper describes an extension of the Maier-Saupe theory of liquid crystals to a system of charged interacting rods and shows that nematic to isotropic transitions can also be induced by increasing the charge on the rods. The effects of length of rod, concentration of salt and the volume fraction on the phase diagram are described. The concept of the charge-induced isotropic phase is described, and it is argued that the structure is expected to be glassy. Evidence to support these conclusions from the existing literature is presented. 相似文献
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The dynamic characteristics of harvesting energy from mechanical vibration via piezoelectric conversion 下载免费PDF全文
As an alternative power solution for low-power devices, harvesting energy from the ambient mechanical vibration has received increasing research interest in recent years. In this paper we study the transient dynamic characteristics of a piezoelectric energy harvesting system including a piezoelectric energy harvester, a bridge rectifier, and a storage capacitor. To accomplish this, this energy harvesting system is modeled, and the charging process of the storage capacitor is investigated by employing the in-phase assumption The results indicate that the charging voltage across the storage capacitor and the gathered power increase gradually as the charging process proceeds, whereas the charging rate slows down over time as the charging voltage approaches to the peak value of the piezoelectric voltage across the piezoelectric materials. In addition, due to the added electrical damping and the change of the system natural frequency when the charging process is initiated, a sudden drop in the vibration amplitude is observed, which in turn affects the charging rate. However, the vibration amplitude begins to increase as the charging process continues, which is caused by the decrease in the electrical damping (i.e., the decrease in the energy removed from the mechanical vibration). This electromechanical coupling characteristic is also revealed by the variation of the vibration amplitude with the charging voltage. 相似文献
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从T模型等效电路出发,在等效电路中磁化电感两端的电压在形成线等效电容充电到第一个峰值之前变化较小这一假设之下,推导了电容器通过变压器对脉冲形成线充电的解析表达式,给出了考虑回路存在电阻和杂散电感下的表达式。最后利用电路模拟来验证解析表达式,结果表明:给出的解析表达式能够较好地分析电容器通过变压器对脉冲形成线充电过程;在形成线充电的第一个半周期内,解析理论得到的结果与模拟结果比较吻合,在原边电容和形成线等效电容可比较的情况下,从变压器耦合系数较低(不超过0.7)到耦合系数接近于1的情况都适用。 相似文献
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We present a theory for the phase behaviour of mixtures of charge-stabilised colloidal spheres plus interacting polymer chains
in good and θ -solvents within the framework of free-volume theory. We use simple but accurate combination rules for the depletion
thickness around a colloidal particle and for the osmotic pressure up to the semi-dilute concentration regime. Hence, we obtain
expressions for the free energy for mixtures of charged colloidal particles and non-adsorbing interacting polymers. From that,
we calculate the phase behaviour, and discuss its topology in dependence on the competition between the charge-induced repulsion
and the polymer-induced attraction. The homogeneous mixture of colloids and polymers becomes more stabilised against demixing
when increasing the electrostatic repulsion. This charge-induced stabilisation is strongest for small polymer-to-colloid size
ratios and is more pronounced for charged colloids mixed with polymers in a good solvent than for polymers in a θ -solvent.
For the weakly charged regime we find that the phase diagram becomes salt-concentration-independent in the protein limit for
charged colloids plus polymers in a θ -solvent. The liquid window, i.e., the concentration regimes where a colloidal liquid exists, is narrowed down upon increasing the charge-induced repulsion.
Also this effect is more pronounced when charged colloids are mixed with polymer chains in a good solvent. In summary, we
demonstrate that the solvent quality significantly influences the phase behaviour of mixtures of charged colloids plus non-adsorbing
polymers if the range of the screened electrostatic repulsion becomes of the order of the range of the depletion-induced attraction. 相似文献
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基于高功率重复频率脉冲功率源的需求,开展了高功率脉冲充电电源的重复频率特性研究,分析了基于全桥串联谐振充电原理的恒流充电技术。根据高功率Marx型脉冲功率源的工作要求,计算了串联谐振充电的各个关键参数。研制的紧凑型高功率脉冲充电电源,最大输出电压±50 kV,充电电流2.5 A,重复频率1~50 Hz连续可调,可在重复频率条件下长时间稳定运行。该充电电源体积小、质量轻、抗干扰能力和抗负载短路能力强,已经应用于高功率重复频率脉冲功率源技术研究,实现了10万次重复频率无故障运行。 相似文献
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In this study, a nonlinear integro-differential equation is derived to express the charging kinetics of stationary and rotational cylindrical dielectric particle in unipolar corona field. An algorithm is developed to solve the derived equation numerically by using Euler method. The variation of charge on the dielectric cylindrical particle is presented and evaluated by considering the variable parameters of the particle, medium and field. Assessments of the numerical results demonstrate that the limit charge value on stationary cylindrical dielectric particle during the charging process in unipolar corona field is less in comparison with the rotational cylindrical particle in identical conditions. Also this is an important factor for electron–ion technology in the aspect of charging kinetic problems. 相似文献