High Frequency Electric Field Research Articles

Effect of Dy2O3 doping on microstructure and electrical characteristics of ZnO linear resistors

ZnO linear resistors, due to its excellent performance, are widely used in numerous industries and gradually replacing traditional conductive resistors, presenting a broad prospect for application. To study the effects of lanthanide oxides on the microstructure and electrical properties of ZnO-based linear resistors, this paper prepared Dy2O3-doped ZnO-Al2O3-TiO2-NiO based linear resistors using a solid-state sintering method. The results showed that proper doping of Dy2O3 could inhibit the growth of ZnO grains, leading to more uniform grain growth. Additionally, doped with appropriate amount of Dy2O3 could enhance the linear performance of ZnO linear resistors, reduce the grain boundary barrier height (φb), and decrease dielectric loss. Linear resistors with nonlinearity coefficient (α) of 1.07, grain boundary barrier height (φb) of 0.0934 eV and resistance-temperature coefficient (αT) of −5.39 × 10−3/°C were obtained. The doping of Dy2O3 could improve the comprehensive performance of ZnO linear resistors, making the fabricated ZnO linear resistors are more suitable for working in high frequency electric fields. The study and analysis of Dy2O3 doped ZnO linear resistors are of significant importance for the preparation of high performance ZnO linear resistors.

Ferroelectric Transformer Using High Frequency Electric Field for Switching Polarization to Get Multiple Levels of DC Voltage and for Fault Protection

Abstract: The fundamental understanding of negative capacitance is not fully complete. Ferroelectrics are like ferromagnetics in that the different areas of ferroelectrics get polarized in different directions based on the charge density and finally the net charge of the material, as a whole gives the resultant polarization in a particular direction. The negative permitivity results in opposite polarization and it can be further explained in multidomain ferroelectrics. The application model as a static DC transformer based on magnetic capacitor model is discussed here.

In Situ Self-Fluorescence 3D Imaging of Micro/Nano Damage in Silicone Gel for Understanding Insulation Failure under High-Frequency Electric Fields.

Strong electromagnetic and heat flux stresses can induce severe damage to solid insulation materials, leading to faults in power equipment and power electronics devices. However, in the absence of suitable in situ imaging methods for observing the development and morphology of electrical damage within insulation materials, the mechanism of insulation failure under high-frequency electric fields has remained elusive. In this work, a recently discovered fluorescence self-excitation phenomenon in electrical damage channels of polymers is used as the basis for a laser confocal imaging method that is able to realize three-dimensional (3D) in situ imaging of electrical tree channels in silicone gel through nondestructive means. Based on the reconstructed morphology of the damaged area, a spatial equivalent calculation model is proposed for analysis of the 3D geometric features of electrical trees. The insulation failure mechanism of silicone gel under electric fields of different frequencies is analyzed through ReaxFF molecular dynamics simulations of the thermal cracking process. This work provides a new method for in situ nondestructive 3D imaging of micro/nanoscale damage structures within polymers with potential applications to material analysis and defect diagnosis.

Bent-core liquid crystals joining the ethylene-oxide/lithium ion tandem: Ionic conductivity and dielectric response towards new electrolytes for energy applications

We report the dielectric and conductivity response of three materials containing bent-core and tetra(ethylene-oxide) moieties, and their complexes doped with lithium triflate salts, as new potential nanostructured electrolytes. Whilst the pristine bent-core compounds do not show mesomorphism, the doped materials display smectic mesophases inside indium tin oxide cells assisted by the selective solvation of the lithium ions in the ethylene-oxide blocks. The dielectric response of the materials in the high-frequency range is controlled by the chemical composition of the bent-core structure, and the presence of lithium ions promotes direct current conductivity at low frequencies, in the σdc ∼ 10-5 S cm−1 range, which can be enhanced to σdc ∼ 10-4 S cm−1 via trans-to-cis photoisomerization of azobenzene groups. The dynamic and dual character of these materials (responding to low and high frequency electrical fields), the formation of ferroelectric crystals capable to store energy, and their interactions with light, will be applied to develop new energy devices.

The influence of the helical twisting power on the bistable electro-optical performance of the liquid crystalline epoxide/mercaptan /negative-dielectric-anisotropy cholesteric liquid crystal composite films

Bistable electro-optical devices have been successfully prepared by thermal curing of the liquid crystalline epoxide, mercaptan and the cholesteric liquid crystals (N-ChLCs) with negative-dielectric-anisotropy. In order to study the influence of helical twisting power (HTP), an important parameter of the chiral dopant, on the bistable electro-optical properties of the liquid crystalline epoxide/mercaptan/N-ChLC composite films, four samples A1-A4 were prepared. Among them, four different N-ChLCs with the same Bragg reflect wavelength were prepared via blending the negative dielectric anisotropy nematic liquid crystal and the chiral dopant R811, R1011, R2011, as well as R5011, respectively. Results indicated that as the HTP increased, the transmittance in the wavelength range of 400–2500 nm became lower under the low-frequency (LF) electric field and after removing the LF electric field, which resulted from the smaller polymer microspheres. Meanwhile, samples with large HTP showed their large transmittance states under the high-frequency (HF) electric field (10 KHz, 90V) and after removing the HF electric field. Moreover, the sample A4 possessing the chiral dopant R5011 with a large HTP exhibited good bistability, and its large- and low-transmittance states can be maintained for a long time (>30 days) in the absence of electric fields.

High-frequency electric field intensity measurement based on frequency shift with high gain and wide frequency range

For the safe operation of equipment and personal safety protection in high-voltage environments, the precise measurement of the high-frequency electric field is of paramount importance. Optical electric field sensor (OES) is a current research trend for high-frequency electric field measurement but is generally limited by low sensitivity and the need for high-speed acquisition modules. Here, we propose a high-frequency electric field intensity measurement approach based on frequency shift with a high gain and a wide frequency range. We used two different frequency shift methods, i.e., stimulated Brillouin scattering and down-conversion. Based on the former method, an amplification module is designed to enhance the OES signal with a frequency range from 11 GHz to 20 GHz and a noise-suppressed gain of up to 63 dB, and based on the latter one, the high-frequency OES signal is down-converted to a sub-MHz intermediate frequency signal. The frequency shift approach shows the potential to detect and analyze high-frequency electric fields with low cost and a small footprint, which is valuable for their applications in electronic warfare, high-voltage engineering, space exploration, etc.

Combined removal experiment of multiple impurities from W/O emulsions under high frequency pulsed electric field: Study on laws of desalination, decalcification, and deacidification

AbstractElectrocoalescence is widely used to dehydrate crude oil, but impurities in crude oil are extremely complex, which greatly weaken the effect of dehydration. To understand the coupling law of various impurities, a static demulsification experiment was conducted under a high frequency and high voltage pulsed electric field to investigate the effects of electric field parameters (voltage, frequency, pulse width ratio), emulsification strength, electrocoalescence time, water content, acid value, injection alkali ratio, calcium content, decalcification agent concentration and removal process on desalination, decalcification, and deacidification. The results showed that the desalination and decalcification rates varied synchronously with the electric field parameters and water content. Additionally, the desalination and decalcification rates decreased with the emulsification strength, alkali injection ratio, acid value, and calcium content. Further, they increased first and then decreased with decalcifier concentration. The deacidification rate did not vary with the electric field parameters, but it strengthened with the water content and alkali injection ratio. Conversely, it decreased with the acid value, calcium content, and decalcifier concentration. Additionally, it increased first and then decreased with the emulsification intensity. The best removal procedure is deacidification followed by decalcification. These findings are helpful to achieve the combined removal of various impurities in crude oil.

Intra-pulse difference frequency generation in ZnGeP2 for high-frequency terahertz radiation generation

The highly-nonlinear chalcopyrite crystal family has experienced remarkable success as source crystals in the mid-infrared spectral range, such that these crystals are primary candidates for producing high terahertz frequency (i.e., gtrsim 10 THz) electric fields. A phase-resolved terahertz electric field pulse is produced via intra-pulse difference frequency generation in a chalcopyrite (110) ZnGeP2 crystal, with phase-matching being satisfied by the excitation electric field pulse having polarizations along both the ordinary and extraordinary crystal axes. While maximum spectral power is observed at the frequency of 24.5 THz (in agreement with intra-pulse phase-matching calculations), generation nonetheless occurs across the wide spectral range of 23–30 THz. To our knowledge, this is the first time a chalcopyrite ZnGeP2 crystal has been used for the generation of phase-resolved high-frequency terahertz electric fields.

Электроакустические свойства различных типов кварца в мелкодисперсном состоянии

An electroacoustic echo method for studying the high-frequency (HF) electrical and elastic properties of piezoelectric materials in a finely dispersed state is described. The characteristics and relaxation time of electroacoustic echo for natural and artificial quartz powders are determined. Natural one is represented by the following types: smoky quartz, citrine, amethyst, recrystallized, granular and columnar. It is shown that natural quartz (especially citrine), has a higher electromechanical coupling coefficient than artificial quartz. The amplitudes of HF electric field are determined, at which the saturation mode of the echo signals is observed.

Novel High-Frequency Electric Field Sweeping Concept for High-Power Gyrotron Collectors

Future fusion power plants will require for plasma heating and noninductive current drive high-power gyrotrons, each of which generates 2 MW of continuous-wave microwave power, while another 2 MW in the spent electron beam is dissipated as heat on the collector wall. In today’s 1-MW continuous-wave gyrotrons, collector coils superimpose an ac (10–50 Hz) magnetic field to sweep the hot spots of spent electrons over a large area. However, to double today’s power, it will also be critical to reduce the hot spot dwell time preventing significant increase of material fatigue. This can be achieved by increasing the sweeping frequency. However, a higher frequency magnetic field would hardly penetrate the metallic collector vessel due to eddy currents. Instead of magnetic field, sweeping with electric fields is proposed for the first time. The presented mechanism is capable to apply several orders higher sweeping frequency to reduce the periodic variation of temperature, and thus, the device lifetime can be extended.

Modeling, Simulation, and Computer Control of a High-Frequency Wood Drying System

High-frequency wood drying is the modern method used in raw wood drying so that treated wood can be used further in various processes. Such systems are used because of the economy, energy efficiency, obtaining of good mechanical properties of the wood after treatment, as well as reducing time consumption. Therefore, it is extremely important to understand each component of such systems and processes. The mentioned systems are implemented using high-frequency generators based on vacuum tubes (VT). Their development and, in particular, optimization are by far more complex than the transistor systems; therefore, the development is now compelled to rely on computer modelling and simulation. In this research, a high-frequency (HF) generator of 20 kW output power and 1.5–15 MHz adjustable frequency based on VT was produced and then, with the corresponding model for VT itself and the rest of the developed circuit, was followed by computer simulation and real-system measurement. The model parameters were adjusted, which provided additional system optimization. An extra match of the results from the simulation and measurement was obtained; thus, the optimization was performed faster and more precisely. In addition, an easier and quicker way of adjusting parameters of the PID controller using a developed software-based control system was attained. The problems of cooling the VT anode under high DC voltage, as well as temperature measurement in the HF electric field, have been solved.

The Dielectric Properties of Worker Bee Homogenate in a High Frequency Electric Field

Biological tissues, including insect tissues, are among lossy dielectric materials. The permittivity properties of these materials are described by loss factor ε″ and loss tangent tgδ. The dielectric properties of the worker honeybee body homogenate are tested in the range of high frequencies from 1 MHz to 6 GHz. The homogenate is produced by mixing whole worker honeybees and tested with an epsilometer from Compass Technology and a Copper Mountain Technologies vector circuit analyser VNA. Due to their consistency, the homogenate samples are placed inside polyurethane sachets. The measured permittivity relates to two components of a sample: homogenate and polyurethane. For five samples, two extremes were specified for the permittivity, loss factor ε″, and the loss tangent tgδ, for the frequency range 20 ÷ 80 MHz and 3 GHz. Four techniques of testing permittivity in biological tissues were used to determine the dielectric properties of the homogenate. A calculation model was developed featuring a minimum measurement error of the loss factor ε″ and the loss tangent tgδ. The power absorbed per unit volume is described for the whole frequency range.

Characteristics of Collagen Changes in Small Intestine Anastomoses Induced by High-Frequency Electric Field Welding.

High-frequency electric field welding-induced tissue fusion has been explored as an advanced surgical method for intestinal anastomoses; however, intrinsic mechanisms remain unclear. The aim of this study was to investigate microcosmic changes of collagen within the fusion area, with various parameters. Ex vivo small intestine was fused with mucosa-mucosa. Four levels of compressive pressure (100 kPa, 150 kPa, 200 kPa, 250 kPa) were applied for 10 s in order to fuse the colons under a power level of 140 W. Then, collagen fibers of the fusion area were examined by fibrillar collagen alignment and TEM. Three levels of power (90 W, 110 W, 140 W) and three levels of time (5 s, 10 s, 20 s) were applied in order to fuse colons at 250 kPa, and then collagen within the fusion area was examined by Raman spectroscopy. Fibrillar collagen alignment analysis showed that with the increase in compression pressure, alignment of the collagen in the fusion area gradually increased, and the arrangement of collagen fibers tended to be consistent, which was conducive to the adhesion of collagen fibers. TEM showed that pressure changed the distribution and morphology of collagen fibers. Raman spectroscopy showed that increased power and time within a certain range contributed to collagen cross linking. Peak positions of amide I band and amide III band changed. These results suggested that higher power and a longer amount of time resulted in a decrease in non-reducible cross links and an increase in reducible cross links. Compression pressure, power, and time can affect the state of collagen, but the mechanisms are different. Compressive pressure affected the state of collagen by changing its orientation; power and time denatured collagen by increasing temperature and improved the reducible cross linking of collagen to promote tissue fusion.

Evaporation investigation of nanofluid droplet affected by electrical field with periodically changed direction

The droplet evaporation phenomenon is very important for the development of droplet microfluidic technology. The existing studies have shown that high frequency and high electrical field strength have great effects on droplet evaporation and wetting characteristics respectively. However, the effects of high frequency together with high voltage on nanofluid droplet evaporation and wetting characteristics have not been studied and the mechanism is not clear. Therefore, the evaporation characteristics of nanofluid droplets at high voltage and high frequency were experimentally investigated to improve its evaporation rate and reveal its evaporation mechanism. The results show that the evaporation rates increase first and then decrease with the increase of voltage frequency (0–2 kHz), and the frequency at the high voltage obtained the maximum evaporation rate increases (90 Hz) when compared with the low voltage condition. Besides, the effect of electrical field on nanoparticles using the deposition surface was also explored, and the results show that the motion of the particles manipulated by the electrical field forces together with the oscillatory fluctuations of the droplets result in the enhancement of the evaporation rate of the nanofluid. • Frequency obtained maximum evaporation rate increases when compared to low voltage. • Evaporation rate of nanofluids increases with improvement of concentration and voltage. • Oscillatory fluctuations combined nanoparticle motion result in evaporation enhancement.

FireFly: An Insect-Scale Aerial Robot Powered by Electroluminescent Soft Artificial Muscles

Light production in natural fireflies represents an effective and unique method for communication and mating. Inspired by bioluminescence, we develop a 650 mg aerial robot powered by four electroluminescent (EL) dielectric elastomer actuators (DEAs) that have distinct colors and patterns. To enable simultaneous actuation and light emission, we embed EL particles in a DEA that has highly transparent electrodes. During robot flight, a strong ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula> 40 V/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mu$</tex-math></inline-formula> m) and high frequency (400 Hz) electric field is generated within the DEA, exciting the EL particles to emit light. Compared to a regular DEA, our new design and fabrication methods require small additional weight (2.4%) and actuation power (3.2%) without adversely impacting the DEA’s output power or lifetime. We further develop a position and attitude tracking method using vision-based color detection. We demonstrate a series of closed-loop flights and compare camera-tracked results with that of the state-of-the-art Vicon motion tracking system. The root-mean-square (rms) position and attitude errors are 2.55 mm and 2.60 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> , respectively. This work illustrates a novel and effective design for communication and motion tracking in extreme payload-constrained microscale aerial systems, and it further shows the potential of achieving coordinated swarm flights without using well-calibrated in door tracking systems.

Effects of Spatial Nonlocality versus Nonlocal Causality for Bound Electrons in External Fields.

Using numerically exact solution of the time-dependent Schrödinger equation together with time-dependent quantum Monte Carlo (TDQMC) calculations, here we compare the effects of spatial nonlocality versus nonlocal causality for the ground state and for real-time evolution of two entangled electrons in parabolic potential in one spatial dimension. It was found that the spatial entanglement quantified by the linear quantum entropy is predicted with good accuracy using the spatial nonlocality, parameterized naturally within the TDQMC approach. At the same time, the nonlocal causality predicted by the exact solution leads to only small oscillations in the quantum trajectories which belong to the idler electron as the driven electron is subjected to a strong high frequency electric field, without interaction between the electrons.

Dynamic Impedance Analysis of Intestinal Anastomosis during High-Frequency Electric Field Welding Process.

The success rate of the electrosurgical high-frequency electric field welding technique lies in reasonable control of the welding time. However, the final impedance value used to control the welding time varies due to differences in tissue size and the welding method during the welding process. This study aims to introduce a new reference indicator not limited by impedance size from dynamic impedance to achieve an adequate weld strength with minimal thermal damage, providing feedback on the tissue welding effect in medical power supplies. End-to-end anastomosis experiments were conducted with porcine small intestine tissue under seven levels of compression pressure. The dynamic impedance changes were analyzed, combined with compression pressure, temperature, moisture, and collagen during welding. The welding process was divided into three stages according to the dynamic impedance, with impedance decreasing in Period Ⅰ and impedance increasing in Period Ⅲ. Period Ⅲ was the key to high-strength connections due to water evaporation and collagen reorganization. The dynamic impedance ratio is defined as the final impedance divided by the minimum impedance, and successful welding would be predicted when detecting the dynamic impedance ratio over 4 (n = 70, p < 0.001). Dynamic impedance monitoring can be used as a macroscopic real-time prediction of the anastomosis effect.

Measurement of the Intensity of a High-Frequency Electric Field: Application of a Ring Waveguide with Two Slots Filled with Electro-Optic Polymer

Measurement of the Intensity of a High-Frequency Electric Field: Application of a Ring Waveguide with Two Slots Filled with Electro-Optic Polymer

Hybrid receiving line for broadband electric field measurement

High-frequency electric field measurements with a regular receiving dipole characterized by poor electrode contact are greatly influenced by the capacitive currents arising between wires and ground. At the same time, making use of the non-contact receiving dipoles is not generally suitable for low-frequency electric field measurements.We introduce a novel hybrid galvanic-capacitive receiving dipole, which could be used for broadband electric field measurement even with high contact resistance of the grounded electrodes.

Contactless transport method of two-dimensional electron system studies

We introduce two contactless measurement methods at extremely low temperature: capacitances and surface acoustic waves. Both methods can be used to study the physical properties of the quantum system through the interaction between electrons and high frequency electric field. We first present preliminary results of high-mobility two-dimensional electron systems studied by a high-precision capacitance measurement method at extremely low temperature. Our setup can resolve &lt; 0.05% variation of a &lt; 1 pF capacitance at 10 mK–300 K and 0–14 T. Second, we also study two-dimensional electron systems using surface acoustic waves. We can use 0.1 nW excitation and obtain &lt; 10&lt;sup&gt;–5&lt;/sup&gt; sensitivity. These measurement methods may be widely applied to the study of two-dimensional systems, especially the materials without high quality contacts.