Electric Field Changes Research Articles

Influence of Sintering Additives on Modified (Ba,Sr)(Sn,Ti)O3 for Electrocaloric Application

This paper reports on the influence of sintering additives CuO and MgO on the recently developed lead-free electrocaloric (EC) material Ba0.82Sr0.18Sn0.065Ti0.935O3 (BSSnT-18-6.5). Details on the sintering behavior and the resulting microstructure of bulk ceramic samples prepared through solid-state synthesis and their dielectric, ferroelectric, and electrocaloric properties are presented. On the one hand, the addition of CuO (xCuO = 2%) significantly reduced the sintering temperature from 1400 °C to 1150 °C. On the other hand, the addition of MgO (xMgO = 1%) dramatically reduced the average grain size from 40 µm to 0.4 µm, leading to an increase in dielectric breakdown strength from 4.4 V µm−1 to 7.7 V µm−1. Thus, BSSnT-18-6.5 with the addition of MgO to bulk ceramic samples could achieve maximum EC temperature changes (|ΔTEC|) of 0.27 K around 30 °C with almost no aberration within a broad temperature range from 5 °C to 50 °C under an applied electric field change of 5 V µm−1. The results show the potential of this material for the fabrication of multilayer ceramic (MLC) components for future electrocaloric applications.

Scientific discovery – electrodynamic induction

This article presents experimental evidence and a description of the scientific discovery «The phenomenon of electric current excitation in a conductor moving in an electrostatic field». The first class of effects I will show you are those caused by the electrostatic force. It is the force that controls the movement of atoms, collides, and generates heat and light energy. This force also causes atoms to combine in an infinite number of ways according to nature's fantastic designs, and to form all the amazing structures we see around us. According to Maxwell's theory, an eddy magnetic field should always appear when the electric field changes. In our work, we will study relatively low-frequency changes in the magnetic field, which are negligible compared to its theoretical calculation. In addition, there is every reason to believe that in practice no magnetic field occurs inside the capacitor. The conclusions of these works can be confirmed by the operation of the Tesla transformer, whose high-voltage end is connected to a single capacitor, which in turn forms a capacitor with the surface of the Earth. Due to the quarter-wave distribution, we can only observe the electric field around this capacitor, and the magnetic field appears in the current (ground) part of this transformer.

Methane coupling in nanosecond pulsed plasmas: Correlation between temperature and pressure and effects on product selectivity

We present a zero-dimensional kinetic model to characterise specifically the gas-phase dynamics of methane conversion in a nanosecond pulsed discharge (NPD) plasma reactor. The model includes a systematic approach to capture the nanoscale power discharges and the rapid ensuing changes in electric field, gas and electron temperature, as well as species densities. The effects of gas temperature and reactor pressure on gas conversion and product selectivity are extensively investigated and validated against experimental work. We discuss the important reaction pathways and provide an analysis of the dynamics of the heating and cooling mechanisms. H radicals are found to be the most populous plasma species and they participate in hydrogenation and dehydrogenation reactions, which are the dominant recombination reactions leading to C2H4 and C2H2 as main products (depending on the pressure).

Analysis of 5G channel loss and its influencing factors in substation based on ray tracing algorithm

Abstract5G (fifth generation) signals have small coverage and poor stability, and 5G channels are prone to loss in substations densely populated with metal equipment. Due to the particularity of the spatial layout in the substation, traditional physical or statistical channel models cannot accurately calculate the 5G channel loss in the substation. Therefore, this paper introduces the basic idea of ray tracing algorithm for studying ray propagation. Based on the geometric optics theory of ray propagation, the effective channel path of 5G signal in substation is found. Through the electromagnetic reflection theory and consistent diffraction theory, the energy loss caused by signal reflection and diffraction is calculated. Combined with the relationship between the free space loss of 5G signal on the transceiver path and the change of electric field, the solution method of 5G channel loss in substation is deduced. According to this method, (the influence of signal receiver height, 5G antenna height and its spatial position in horizontal and vertical directions on 5G channel loss of substation is studied in turn. By optimizing the layout of communication facilities according to the influence law, the reliability of 5G channel in substation can be realized).

Plasmon-enhanced luminescence of rare-earth ions by gold and silver nanoparticles in PMMA

In this work plasmon resonances in gold and silver nanoparticles to enhance luminescent properties of PMMA doped with different rare-earth ions densities are investigated. For this purpose, a rate equation model based on the Förster theory is used. This model describes the luminescent dynamics between donor and acceptor rare earth ions and considers the electric field changes due to metallic nanoparticles. The MNPBEM Matlab toolbox is used to calculate the electric field in our system, including the electric field of the excitation and the electric field induced by the nanoparticle. The results show that rare earth luminescence can be increased in the proximity of spherical gold and silver nanoparticles due to the change in the optical field and the transition rates. Accordingly, the rate equation model proposed here explains the increase in luminescent emission when the dopants interact with the metal nanoparticles. Additionally, the calculations allow to find the optimal conditions of nanoparticle size and excitation wavelength to achieve the maximum amplification of optical field and, therefore, the maximum amplification of the emission of rare earth ions.

Chemical modification of the GaP(0 0 1) surface electric field with sulfide solutions

The surface electric field in GaP(001) passivated with aqueous and alcoholic sulfide solutions is studied by reflectance anisotropy spectroscopy using data on the surface chemical and electronic structure obtained by synchrotron-radiation X-ray photoelectron spectroscopy. Treatment of n-GaP(001) surface with a sulfide solution decreases the surface electric field depending on sulfide solution composition. In particular, passivation with the solution of ammonium sulfide in 2-propyl alcohol turns the total surface electric field almost to zero, while passivation with the aqueous ammonium sulfide solution reduces the surface electric field in a lesser extent. On the other hand, sulfide treatment of p-GaP(001) surface enhances the surface electric field dramatically and this enhancement is nearly independent of the sulfide solution composition. Such changes in the surface electric field can be related to the modification of the dipole associated with chemical bonds in the passivating layer.

Further studies of positive Narrow Bipolar Events detected at close range

Using electric field change data and VHF data of 201 positive Narrow Bipolar Events (+NBEs) detected at close range (< 80 km) at seven sensor sites, three aspects of +NBEs are investigated: the VHF “Development Time” (∆T0), the detailed VHF waveform, and the VHF “Major Trailing Pulses” (MTPs) that follow some +NBEs. The +NBE Development Time study used 137 + NBEs divided into two groups: 72 INBEs (+NBEs that initiate a full lightning flash) and 65 Not-INBEs. These 137 + NBEs had VHF peak powers ranging from 0.1 to 66 kW and ∆T0 values ranging from <1 μs to 23.4 μs with an average of 4.2 μs. The +NBEs with higher peak power (> 20 kW) were all found to have short ∆T0 (< 4 μs), while lower power NBEs (< 7 kW) exhibit the full range of ∆T0 values. The detailed study of VHF waveforms of 201 + NBEs shows that the shape of each +NBE is significantly different at the multiple sensors sites. This finding supports mechanisms in which an NBE is caused by numerous streamers occurring within a few μs. Among 201 + NBEs, 67 + NBEs (with VHF powers of 400–37,500 W) were followed, within 30 μs, by at least one MTP; 39 of these 67 NBEs had a second MTP and 16 of those 39 NBEs had a third MTP. All but one MTP had VHF peak power between 5 W and 270 W; the exceptional case, a single MTP occurring after an NBE with peak VHF power of 6.5 kW, had VHF power of 3.3 kW. MTPs were found to occur from 4.9 to 32 μs after the +NBE or preceding MTP, and they are hypothesized to be evidence of re-radiation in the previously ionized NBE region that is (repeatedly) excited by reflection from an above-cloud ion layer.

Lightning Prediction Using Electric Field Measurements Associated with Convective Events at a Tropical Location

Nowcasting of lightning occurrences is essential in tropical locations as lightening causes severe damage to life and property. This study attempts to nowcast lightning events during convective phenomena using an electric field monitor (EFM) at a tropical urban location, Kolkata (22.65°N, 88.45°E). Before the onset of heavy lightning occurrences, definite changes in the atmospheric electric field (EF) are observed, which in turn are associated with high cloud liquid water content (LWC) and low cloud base height (CBH). A model has been proposed to nowcast lightning strikes within about 17.5 km radius of the present location based on the EF standard deviation (EFSD) values. The proposed technique is tested with the lightning data provided by a collocated lightning detector, which yields a prediction efficiency of ~ 0.91 (~ 0.86), a false alarm rate of ~ 0.23 (~ 0.18), and a critical success index of ~ 0.71 (~ 0.72) with an optimal range of other performance parameters during the monsoon (pre-monsoon) periods, thereby generating an alarm 45 min before lightning events.

Ultrafast protein response in the Pfr state of Cph1 phytochrome

Photoisomerization is a fundamental process in several classes of photoreceptors. Phytochromes sense red and far-red light in their Pr and Pfr states, respectively. Upon light absorption, these states react via individual photoreactions to the other state. Cph1 phytochrome shows a photoisomerization of its phycocyanobilin (PCB) chromophore in the Pfr state with a time constant of 0.7 ps. The dynamics of the PCB chromophore has been described, but whether or not the apoprotein exhibits an ultrafast response too, is not known. Here, we compare the photoreaction of 13C/15N labeled apoprotein with unlabeled apoprotein to unravel ultrafast apoprotein dynamics in Cph1. In the spectral range from 1750 to 1620 cm−1 we assigned several signals due to ultrafast apoprotein dynamics. A bleaching signal at 1724 cm−1 is tentatively assigned to deprotonation of a carboxylic acid, probably Asp207, and signals around 1670 cm−1 are assigned to amide I vibrations of the capping helix close to the chromophore. These signals remain after photoisomerization. The apoprotein dynamics appear upon photoexcitation or concomitant with chromophore isomerization. Thus, apoprotein dynamics occur prior to and after photoisomerization on an ultrafast time-scale. We discuss the origin of the ultrafast apoprotein response with the ‘Coulomb hammer’ mechanism, i.e. an impulsive change of electric field and Coulombic force around the chromophore upon excitation.Graphical abstract

Acupoints sensitization in people with and without chronic low back pain:A matched-sample cross-sectional study.

Acupoints are considered a dynamic functional area, which can reflect the internal condition of the body. In pathological states, disease-related acupoints are believed to be activated, which is known as acupoint sensitization. This study aimed to investigate the major manifestations of acupoint sensitization in patients with chronic low back pain (cLBP) to provide better understanding of acupoint sensitization phenomena in the context of cLBP. This study was a matched-sample cross-sectional study 16 participants diagnosed with cLBP and 16 healthy controls matched in age, sex, and ethnicity were included. The following aspects of sensitization phenomena of targeted points were compared: pressure pain threshold (PPT), skin temperature, surface electrical conductance, receptive field, and morphological change of skin. PPT at points of interest were significantly lower in cLBP participants compared with healthy controls (P< 0.05); in addition, receptive field was found to be larger at left BL 23 in cLBP participants (P< 0.05). There was no statistically significant difference in skin temperature, electrical conductance, or morphology between the two groups. Reduced PPT at all detected points and enlarged receptive field at left BL 23 were found in cLBP participants. These two features appear key in defining acupoint sensitization in cLBP, and provide evidence for selecting and locating acupuncture points in future clinical studies.

Automatic trajectory control of single cells using dielectrophoresis based on visual feedback.

This paper deals with the automatic control of the trajectory of T-lymphocytes using dielectrophoretic (DEP) actuation. Dielectrophoresis is a physical phenomenon induced by a non-uniform electric field enabling application of a force on a dielectric object. In most of the cases, it is used in a passive way. The electric field is in a steady state and the force applied on the cells depends on the cell's characteristics and position inside the channel. These systems are limited as cells with similar characteristics will undergo the same forces. To overcome this issue, active devices where the electric field changes over time were developed. However, the voltages that should be applied to generate the desired electric field are mostly computed offline using finite element methods. Thus, there is a low number of devices using automatic approaches with dielectrophoretic actuation where the electric field is computed and updated in real time based on the current position of the cell. We propose here an experimental bench used to study the automatic trajectory control of cells by dielectrophoresis. The computation of the dielectrophoretic force is done online with a model based on the Fourier series depending on the cell's characteristics, position and electric field. This model allows the use of a controller based on visual feedback running at 120 Hz to control the position of cells inside a microfluidic chip. As cells are sensitive to the electric field, the controller limits the norm of the electric field while maximizing the gradient to maximize the DEP force. Experiments have been performed and T-lymphocytes were successfully steered along several types of trajectories at a speed of five times their size per second. The mean error along those trajectories is below 2 μm. The viability of the cells has been checked after the experiments and confirms that this active DEP actuation does not harm the cells.

Endogenous electric field accelerates phenol degradation in bioelectrochemical systems with reduced electrode spacing.

Reducing the electrode spacing in bioelectrochemical systems (BESs) are widely reported to improve power output, which was mainly attributed to the decrease of ohmic resistance (Rohm) for a long time. Here we found the change of endogenous electric field (EF) intensity was the key to improve electroactivity in response to a reduced electrode spacing, which also accelerated phenol biodegradation. Correlation and principal components analysis revealed that the microbial community of electroactive biofilm (EAB) was independent of Rohm, while the EF intensity was found closely related to most of predominant genera. A strong EF selectively enriched phenol-degrading bacteria Comamonas in suspension and Geobacter in EAB, contributed to the improvement of degradation efficiency. EF also induced the secretion of extracellular polymeric substances, protected EAB from being inactivated by phenol. Our findings highlighted the importance of EF intensity on BESs performance, providing new insights into the design and application of BESs in wastewater treatment.

Modeling analysis of patch antenna efficiency considering impedance matching characteristics of cable feed end

The small size of patch antenna makes its application scenarios diverse, and its research is quite extensive. However, the calculation of the influence of the applied excitation source and operating band on the overall operation of the antenna is very complicated, and the related modeling is less. Therefore, a patch antenna model with dual input feed is constructed by COMSOL based on the finite element analysis method. After considering the reasonableness of the coaxial cable insulation medium setting, the geometry structure of the patch antenna with dual input end feeding is constructed. The balanced antenna uses two input feeds, so in the balanced system, the operational performance of the antenna is changed by adjusting the two input signal excitation, so the spatial electric field distribution of the patch antenna under different operating frequencies is explored by applying different external applied excitation sources. Finally, the electric field change law of patch antenna under different operating working conditions is compared and analyzed, and the way to analyze the antenna operating performance is summarized.

Numerical Investigation on the Effects of Wind and Shielding Conductor on the Ion Flow Fields of HVDC Transmission Lines

Ion flow field is an important aspect of high voltage direct current (HVDC) transmission lines. In this paper, we apply the upwind finite volume method for solving the ion flow field of three HVDC configurations to clarify the effect of the wind and the role of shielding conductors. For the monopolar configuration installation, the ground current distribution with underbuilt shield wires was studied numerically and experimentally. For the ±250 kV bipolar configuration, the calculated peak electric field and current density are verified with the values in a reference. The ±500 kV bipolar configuration is used to investigate the change in electric field and ion current within the same corridors of the existing HVAC lines. We analyze the ion flow field with and without the dedicated metallic return conductor (DMRC). In the absence of wind, the maximum of the electric field is lower than that of the HVAC lines and the current density is very low on the ground. In the presence of wind, the electric field and the current distribution become unsymmetrical on the ground level. The peak current density increases significantly on the downwind side. The HVDC line without DMRC has the electric field peak higher than that of the HVAC lines. With the higher wind shear coefficient, the peak of the electric field and the current density increases on the downwind side. Overall investigations summarize that DMRC can effectively reduce the peak of the electric field to be lower than that of the existing 500 kV HVAC lines under all wind conditions.

Stable and decoupled schemes for an electrohydrodynamics model

In this paper, we study numerical solutions of an electrohydrodynamics model. The considered model appears in the description of electric convection dynamics arising from unipolar charge injection on the boundary of insulating liquid, which is a coupling of the Navier–Stokes equations, charge transfer equation, and potential energy equation. A class of stable numerical schemes is proposed and analysed for this coupled equation system. The advantage of the proposed schemes is twofold: (1) they are unconditionally stable, consequently the choice of time step size only concerns the accuracy requirement; (2) they decouple the charge density and potential energy from the Navier–Stokes equations, and therefore can be implemented efficiently. The numerical examples provided in the paper show that the proposed schemes achieve the expected convergence rate, and can be used to accurately simulate the changes of flow field and electric field induced by the electrical convection. We first consider the case of constant density, then extend the construction, analysis, and validation of the schemes to the case of variable density.

Observation and Modeling of Dart Leader Development in an Altitude‐Triggered Lightning Flash

AbstractThe dart leader development process of an altitude‐triggered lightning flash with eight return strokes was analyzed. The analysis, based on the high‐speed camera and electric field data, revealed three different processes of dart leaders: (a) normal dart leader process; (b) dart leader process with chasing leader; and (c) dart leader process with bidirectional leader. These dart leaders are very different in terms of the average 2‐D speed and the electric field change. Moreover, in the bidirectional leader process, the 2‐D speed of the upward positive leader is greater than that of the downward negative leader. A piecewise‐speed source‐charge model was used to simulate the electric field change of the normal dart leader. The superposition of downward positive leader was used to simulate the fading and decaying process of the leader tail, which appeared in the chasing leader and bidirectional leader. The bidirectional leader model was used to simulate the bidirectional leader process, and the final simulation results are in good agreement with the measured electric field.

Theoretical study of a four-level EIT-type system in the presence of structured coupling light for microwave field detection.

In this work, we have theoretically studied the four-level atomic system for the measurement of a microwave (MW) field. We employed the electromagnetically induced transparency (EIT) technique for finding the MW field in the presence of a Laguerre-Gaussian (LG) beam as a coupling light. We have shown that, by the application of LG modes, narrower dips for the probe absorption spectrum can be generated, which can be easily identified and gives better resolution compared with the Gaussian mode. An exact location of dips in the probe absorption spectrum is found, and it is useful in the measurement of MW fields. We have estimated the FWHM of the probe absorption spectrum for Gaussian and LG coupling cases as 3.74×105 H z and 1.07×105 H z, respectively. Based on FWHM, we have found that minimum change in MW electric field in the order of 3.32µV c m -1 will be detectable in the case of the LG mode as a coupling beam.

Multiphysics Modeling of Volcanic Unrest at Mt. Ruapehu (New Zealand)

AbstractPre‐eruptive signals at the crater lake‐bearing Mt. Ruapehu (New Zealand) are either absent or hard to identify. Here, we report on geophysical anomalies arising from hydrothermal unrest (HTU) and magmatic unrest (MU) using multiphysics numerical modeling. Distinct spatio‐temporal anomalies are revealed when jointly solving for ground displacements and changes in gravitational and electrical potential fields for a set of subsurface disturbances including magma recharge and anomalous hydrothermal flow. Protracted hydrothermal injections induce measurable surface displacements (&gt;0.5 cm) at Ruapehu's summit plateau, while magmatic pressurization (5–20 MPa) results in ground displacements below detection limits. Source density changes of 10 kg/m3 (MU simulations) and CO2 fluxes between 2,150 and 3,600 t/d (HTU simulations) induce resolvable residual gravity changes between +8 and −8 μGal at the plateau. Absolute self‐potential (SP) anomalies are predicted to vary between 0.3 and 2.5 mV for all unrest simulations and exceed the detection limit of conventional electric surveying. Parameter space exploration indicates that variations of up to 400% in the Biot‐Willis coefficient produce negligible differences in surface displacement in MU simulations, but strongly impact surface displacement in HTU simulations. Our interpretation of the findings is that monitoring of changes in SP and gravity should permit insights into MU at Ruapehu, while HTU is best characterized using ground displacements, residual gravity changes and SP anomalies. Our findings are useful to inform multiparameter monitoring strategies at Ruapehu and other volcanoes hosting crater lakes.

Characterization of the initial stage in upward lightning at the Gaisberg Tower: 2. Electric field signatures

• Near and far electric field signatures of IS current pulses were analyzed. • Electric field signatures of early-stage-IS bipolar current pulses were characterized. • Such bipolar pulses could be associated with upward leader inception. We examined the characteristics of electric field signatures occurring during the initial stage of 58 flashes measured simultaneously at near (170 m) and far (79 or 109 km) distances from the Gaisberg Tower located near Salzburg, Austria. Of the 340 field signatures measured at the near station, 68 (20%) were associated with current pulses occurring during the initiation and propagation phase (IPP) of the upward leader, and 272 (80%) were associated with pulses that occurred during the mature phase (MP) of the upward leader. Of the 68 field signatures of IPP pulses, 40 were associated with bipolar (IPP-B type) current pulses and 28 were associated with unipolar (IPP-U type) current pulses. Field signatures of IPP-B pulses were only detected at the near measurement station and appear to be associated with currents in relatively short (meter-scale) channel segments formed during the upward leader inception. At the far stations, field signatures of 84 IS pulses were recorded and analyzed. There was modest correlation between the background-to-peak current of IS pulses and near and far electric radiation field changes as well as between radiation field changes recorded at near and far distances.

Surface trap characteristics of polyimide and effect of surface charge accumulation on surface flashover

Charge accumulation on the surface of insulation dielectric used in high voltage DC equipment is one of the important causes of surface flashover. Surface charge accumulation is closely related to surface trap characteristics. In this paper, the surface trap energy level distribution of polyimide (PI) was calculated and analyzed by the corona charging method and surface potential decay method. Besides, electron and hole trap characteristics were studied by changing the polarity and amplitude of the charging voltage. Furthermore, the influence of surface charge polarity and quantity on the flashover voltage was researched. Experimental results indicate that the energy level of traps corresponding to the maximum trapped charge density ranges around 0.94 eV. In addition, the energy level of the hole trap is slightly higher than that of the electron trap. The maximum charge density captured by the electron trap and hole trap is about 1.17 × 1021 and 1.03 × 1021 eV−1 m−3, respectively. The polarity of the surface charge can influence the conductivity characteristics of PI, the surface heterocharge reduces the volume conductivity by about 80% while the surface homocharge improves the volume conductivity of PI by about 6.4 times. Besides, both negative and positive surface charges can improve surface conductivity. The polarity of surface charge influences the flashover characteristics of PI, the flashover voltage increases by about 37.8% with the increase of homocharge density and decreases by about 23.8% with the increase of heterocharge density, which is related to the change of electric field near the cathode caused by surface charge accumulation.