Total Electric Field Strength Research Articles

The evolution characteristics of surface charge on the gas–solid interface under the long-time co-action of DC-temperature gradient

The charge accumulation phenomenon at the gas–solid interface under the co-action of DC electric field and temperature gradient is of great significance, but its long-time evolution characteristics are still unclear. In this work, the accumulation and dissipation characteristics of the surface charge on the epoxy-SF6 interface within 216 h were obtained, indicating that, (a) the normal surface electric field is increased by the temperature gradient along the gas–solid interface, which results in a prominent increase in the surface charge density; (b) there are different evolution processes of surface charge in high and low temperature regions under the co-action of DC-temperature gradient, and the increase of the charge trap density caused by the degradation of solid material is considered to be an important reason for the charge evolution; (c) the total charge dissipation ratio within 600 s decreases with the increase of charging time in DC electric field, and the surface charge dissipates mainly to the gas side of the interface; (d) the large amount of charge accumulated at the interface distorts the surface electric field at the triple junction points. The total electric field strength at the low-temperature tri-junction point increases by 35.5%, while the direction of the tangential field at the high-temperature tri-junction point reverses during the long-time co-action of the DC-temperature gradient. The results of this work may be helpful to understand the long-time charge evolution characteristics of the gas–solid interface under the DC-temperature gradient and to reveal the failure mechanism of the gas–solid interface.

Multi-target microwave energy focusing optimization method based on genetic algorithm

Aiming at the application requirements of multi-target microwave energy transmission, this paper proposes a multi-target microwave energy focusing method based on the genetic algorithm. This method optimizes the feeding phase first and then optimizes the feeding amplitude. By optimizing the feeding phase, the microwaves radiated by the antenna array unit tend to be superimposed in phase at each target point; furthermore, the energy distribution on the focal plane is optimized by optimizing the feeding amplitude. Two-target and three-target focusing methods are taken as examples to conduct microwave energy focusing simulation research. The results show that by using optimized-phase optimized-amplitude feeding, the total electric field strength at the two target points and the three target points is increased by 13% and 8.7%, respectively, compared with the optimized-phase constant-amplitude feeding. A 6 × 6 microstrip antenna array working at 5.8 GHz is designed to conduct two-target and three-target microwave energy focusing experiments. The experimental results verify the effectiveness of the multi-target focusing method proposed in this paper.

ASSESSING THE RISK ASSOCIATED WITH SIMULTANEOUS EXPOSURE TO MOBILE COMMUNICATION SIGNALS WITHIN 900–2500 MHZ IN NIGERIA

In this study, the total exposure due to signals within GSM 900, GSM 1800, CDMA-1900 and 3G-2100 frequency bands at 200 m from the foot of 120, 100 and 80 base station masts in the Nigerian cities of Lagos, Ibadan and Abuja, respectively, was assessed. A calibrated hand-held spectrum analyser was used to measure the level of power (in dBm) of each signal within the mobile frequency bands. The exposure quotient associated with the combine electric field strengths from the various frequency bands in each city was estimated. The maximum value of total electric field strength at each point in Lagos, Ibadan and Abuja was 0.83V/m, 0.53V/m and 1.63V/m, respectively. This study shows that the exposure quotient due to the simultaneous exposure to the four bands of mobile communication signals in each city is far less than one, as recommend by International Commission on Non-Ionizing Radiation Protection.

Electromagnetic Field Exposure Assessment in a Multi Source Telecommunication Environment

RF-EMF exposure assessment carried out in an observatory open for general public visits, where there are multiple RF sources in the surrounding area. Fields at some points of interest have exceeded the ICNIRP exposure limits for the general public and, to comply with normative limits, relevant stations reduced their radiated power. Nevertheless, the total electric field strength in the vicinity of the observatory’s metallic parapet still exceeds exposure limits due to re-radiation. Thus, the main broadcast stations reduced even more their transmitted power to comply with the regulatory limits throughout the observatory area. A detailed evaluation is carried out close to metallic objects to assess the re-radiation phenomenon. Additionally, laboratory experiments were carried out to confirm the influence of re-radiation from the metallic parapet.

Optical properties of c-Plane InGaN/GaN single quantum wells as a function of total electric field strength

We present low temperature photoluminescence spectra from four InGaN/GaN single quantum well structures where the total electric field across the quantum wells was varied by the manipulation of the surface polarization field, which is of opposite sign to the electrostatic built-in field originating from spontaneous and piezoelectric polarization intrinsic to the material. We find that, overall, the photoluminescence peak emission energy increases and its full width at half maximum decreases with decreasing total internal electric field. Using an atomistic tight-binding model of a quantum well with different total internal electric fields, we find that the calculated mean and standard deviation ground state transition energies follow the same trends with field as our experimentally determined spectral peak energies and widths. Overall, we attribute this behavior to a reduction in the quantum confined Stark effect and a connected reduction in the variation of ground state transition energies with decreasing electric field, respectively.

Measurement and evaluation of occupational exposure to electromagnetic field in the vicinity of FM/TV broadcast radiation

This paper involves the measurement and evaluation of electromagnetic field exposure levels at Kamarkouh FM/TV transmitter station at Qom province with multiple-frequency sources. Electromagnetic radiation levels were measured at 34 points for 6 min by Strength Meter Probe which is a broadband meter. The measured electromagnetic radiation levels were then compared to the International Commission of Non-Ionizing Radiation Protection standard. In addition, the theoretical electric field strength values at these same 34 points as above were estimated based on a free-space modeling calculation. The measurement results show that the maximum electromagnetic radiation level was 13.45 V/m, and this is far below the International Commission of Non-Ionizing Radiation Protection limits. The analysis of the comparison between calculated and measured electromagnetic radiation levels showed that there were other sources that contributed to increases in the electric field intensity. The source contributions to the total electric field strength were measured in a practical way. It means that by switching of the transmitters, the electric field strength measured in each state. The results showed that FM frequency band sources provided the highest contributions to the overall electromagnetic radiation level.

Research on Electric Field Simulation of GTEM Cell Based on UHF Sensor Calibration

In this paper, the GTEM cell electric field using to UHF sensor calibration is simulated by HFSS software. According to the simulation results, the field uniformity of the total electric field strength in the “1/3 area” of the GTEM cell can meet the requirements before being placed in the UHF sensor. However, the field uniformity of the total electric field strength has been greatly changed after the UHF sensor is placed. In addition, the maximum amplitude of the field strength change in the UHF sensor test area exceeds 10 dB compared to that before the UHF sensor is placed. It has a great influence on the calibration accuracy of UHF sensors. Through the simulation study of the electric field of GTEM cell, it provides a reference for further improving the calibration accuracy of UHF sensor.

Calculation and Analysis of Electromagnetic Environment Indexes and Influence Factors of ±1100 kV UHVDC Transmission Lines

In order to study the influence of electromagnetic environment of ±1100 kV Changji-Guquan the UHVDC lines, the ground total electric field and ion current density of the HVDC line is studied in this paper by using the charge simulation method and Deutsch’s hypothesis-based analytical method. And the correctness of the method is verified by the measured results. The EPRI formula and CISPR formula are applied to study the audible noise and radio interference. At last, the influence of UHVDC transmission line parameters on the electromagnetic environment is analyzed, and the influence factors that restrict the construction of the UHVDC transmission lines are also studied. The results show that the minimum height of the pole is limited by the total electric field strength, and the influence of the roughness coefficient should also be taken into account when calculating the minimum height of the wire, while the selection of the diameter of the wire is constrained by both the ground total electric field and the audible noise.

Analysis of Electromagnetic Environment and Influencing Factors of Yihua DC Transmission Lines

The electromagnetic environment of transmission lines is one of the major constraints to the design and construction of HVDC transmission lines. In this paper, the charge simulation method and the analytic method based on the Deutsch hypothesis are used to calculate the total electric field strength and ion current density of the 500 kV Yihua DC transmission lines, and the correctness of the calculation is verified by the actual measurement results. Then the EPRI formula and CISPR formula are applied to analyse the audible noise and radio interference of HVDC transmission lines. At last, the influence of factors such as the pole spacing of HVDC lines, the conductor height to the ground, the splitting spacing and the roughness coefficient on the electromagnetic environment of HVDC transmission lines are analysed. Among them, the height of conductor has effective impact on the total electric field strength, while the control of polar spacing is limited. The height of the conductor and the distance between the poles affect the level of audible noise and radio interference mostly, but the control effect of the two is opposite.

New Insights on Scale-dependent Surface-Groundwater Exchange from a Floating Self-potential Dipole

In south-central Texas the lower Guadalupe River has incised into the outcrop of the Carrizo-Wilcox aquifer. The river and the aquifer are hydraulically connected across the outcrop, although the connectivity is obscured at the surface by alluvium and surface-water and groundwater exchange dynamics are currently poorly understood. To investigate surface-water and groundwater exchange dynamics between the lower Guadalupe River and the Carrizo-Wilcox aquifer, a geophysical study was completed along a 14.86 km reach of the river by using water-borne gradient self-potential (SP) profiling and two-dimensional direct-current electric resistivity tomography. This paper explores the applicability of these water-borne geoelectric methods in delineating gaining and losing channel reaches, and demonstrates that geoelectric signals in the form of total electric field strength can be logged with an electric dipole and decomposed into component SP signals depicting regional and local groundwater flow patterns attributable to regional and localized hydraulic gradients. Localized SP anomalies of several tens of millivolts, indicative of hyporheic exchange flows, are observed and superimposed upon a 124 mV regional SP anomaly indicative of ambient groundwater exchange flows between the river and the aquifer. The observed SP signals are interpreted through two-dimensional finite-element modeling of streaming potentials attributable to ambient groundwater exchange and hyporheic exchange flow patterns. Variables of the channel environment such as temperature and concentration gradients, depth, and velocity are considered and subsequently eliminated as alternative sources of the SP signals that are presented.

Frequency-Selective Evaluation of Personal Exposure to Electromagnetic Fields of Wireless Communications and Broadcast Transmitters

We performed a frequency-selective measurement campaign using personal exposure meters with a three-axis E-field probe to assess the electric field strength and power density of wireless communication systems and broadcast transmitters in Kosovo. Mean exposure levels were compared among different microenvironments--outdoor urban, living room, office and bedroom microenvironments--in different geographical locations and different exposure time periods. Furthermore, typical exposure levels in European countries and Kosovo were compared. Measurement post-processing results show that the highest values of the mean power density in an outdoor urban microenvironment were 0.173 mW/m2 for Wi-Fi 5G, 0.137 mW/m2 for GSM 900 uplink, 0.128 mW/m2 for GSM 1800 uplink and 0.112 mW/m2 for Wi-Fi 2G. The maximal recorded value of the total electric field strength was 10.44 V/m. The highest exposure levels per frequency band in the living room were 0.042 mW/m2 for FM, 0.023 mW/m2 for GSM 900 uplink and 0.023 mW/m2 for GSM 900 downlink and Wi-Fi 2G. In office environments, the mean power density for 14 predefined frequency bands in the range 88---5850 MHz was 0.227 mW/m2 in total. The highest total electric field strength for office microenvironments was 5.439 V/m. Residential homes were mainly dominated by the GSM bands (GSM 900 downlink, 54 %; GSM 1800 downlink, 36 %). For the frequency bands FM, TETRA and TV4&5, the exposure was much higher on upper residential floors.

Narrowband frequency-selective up-link and down-link evaluation of daily personal-exposure induced by wireless operating networks

The aim of the study is to present a frequency-selective evaluation of personal exposure induced by wireless operating networks in typical daily environments, derived by analysis of 1,905,162 samples of electric field strength, taken at a 5-s sampling interval. Measurements were collected with calibrated isotropic three-axial electric field probe personal exposure meters operating in the frequency range 88---5850 MHz. `' To estimate the electric field distribution below the measurement equipment detection limit, the robust regression on order statistics method was applied, enabling determination of mean values of electric field strength per wireless technology for: home, office, transport, outdoor, and leisure environments. The highest value of total electric field strength exposure is obtained on public transport (buses) followed by coffee shops and outdoor environments, whereas the lowest values are captured in home and office environments. Most of the mean values of the electric field were less than 0.06 V/m. Furthermore, the analyses between the contribution of uplink and downlink exposures for operating wireless cellular networks are given, including a comparison of uplink and downlink electric field levels from other countries. Readings of the 24-h personal-exposure pattern, reveal the GSM + UMTS downlink and Wi-Fi as dominant exposure contributors. The results of this study show that spatial and temporal exposure levels in Kosovo are comparable to those reported for other European countries and far below the international safety guidelines and exposure limits.

Statistical analysis of electromagnetic radiation measurements in the vicinity of GSM/UMTS base station installed on buildings in Serbia.

As a result of dense deployment of public mobile base stations, additional electromagnetic (EM) radiation occurs in the modern human environment. At the same time, public concern about the exposure to EM radiation emitted by such sources has increased. In order to determine the level of radio frequency radiation generated by base stations, extensive EM field strength measurements were carried out for 664 base station locations, from which 276 locations refer to the case of base stations with antenna system installed on buildings. Having in mind the large percentage (42 %) of locations with installations on buildings, as well as the inevitable presence of people in their vicinity, a detailed analysis of this location category was performed. Measurement results showed that the maximum recorded value of total electric field strength has exceeded International Commission on Non-Ionizing Radiation Protection general public exposure reference levels at 2.5 % of locations and Serbian national reference levels at 15.6 % of locations. It should be emphasised that the values exceeding the reference levels were observed only outdoor, while in indoor total electric field strength in no case exceeded the defined reference levels.

Conversion from mono-axial to isotropic measurements for assessing human exposure to electromagnetic fields of GSM/DCS/UMTS base stations

This paper proposes a way to assess total electric field strength by using mono-axial probe (instead of isotropic, tri-axial probe). When mono-axial probe is used, additional conversion factor should be applied. Consequently, the usage of mono-axial probe causes additional uncertainty in measurement results that should be taken into account. Measurement results for seven different environments show that the additional multiplicative conversion factor value of 1.95 should be applied and additional uncertainty in measurement results of 33.07 % should be taken into account.

Simple algorithm for calculating the total electric field of high‐voltage direct current transmission lines

The basic equations of high-voltage direct current transmission lines’ ion current field are consisted of electric field Poisson equation, ion current density equation and the current continuity equation, hence, the key to calculating total electric field is to solve the non-linear differential equations, but the calculation process is very complicated. A simple algorithm is proposed to solve the problem in this study. First, the charge simulation method, an accurate numerical method, is employed to calculate the distribution of the electrical fields of a conductor. Then, the thought of emission charge is referred to calculate total electric field strength, this method does not need to adopt Deutsch hypothesis, and it avoids solving complex differential equations; hence, the calculation process can be greatly simplified. Finally, it is found that the calculated values agree satisfactorily with data measured on laboratory models and full-scale test lines.

Statistical analysis of electromagnetic radiation measurements in the vicinity of GSM/UMTS base station antenna masts

As a result of dense installations of public mobile base station, additional electromagnetic radiation occurs in the living environment. In order to determine the level of radio-frequency radiation generated by base stations, extensive electromagnetic field strength measurements were carried out for 664 base station locations. Base station locations were classified into three categories: indoor, masts and locations with installations on buildings. Having in mind the large percentage (47 %) of sites with antenna masts, a detailed analysis of this location category was performed, and the measurement results were presented. It was concluded that the total electric field strength in the vicinity of base station antenna masts in no case exceeded 10 V m(-1), which is quite below the International Commission on Non-Ionizing Radiation Protection reference levels. At horizontal distances >50 m from the mast bottom, the median and maximum values were <1 and 2 V m(-1), respectively.

Impact of pulsed electric field on cell disintegration and mass transfer in sugar beet

This study investigated the effects of pulsed electric field (PEF) treatments on sugar beet tissues. A PEF system was used to vary field strength, pulse number and capacitance in respective range of 0.5–6kVcm−1; 1–100 pulses; 0.5–32μF. It was observed that tissue damage in sugar beet was most influenced by total energy input and electric field strength. Furthermore, the energy consumption for cell disintegration by PEF treatment was significantly lower compared to thermal treatment indicating average values of about 8kJkg−1 and 156kJkg−1 respectively. The transfer of solids at room temperature from PEF pretreated sugar beet (1 or 2kVcm−1, 8μF, and 20 pulses) was higher than the untreated and thermal treated samples at 75°C. The overall results showed that the optimization of PEF treatment conditions is very important to achieve high cell disintegration and sugar beet yield.

Electrokinetically driven concentration of particles and cells by dielectrophoresis with DC-offset AC electric field

Insulator-based dielectrophoresis (iDEP) has been successfully used for on-chip manipulations of biological samples. Despite its effectiveness, iDEP typically requires high DC voltages to achieve sufficient electric field; this is mainly due to the coupled phenomena among linear electrokinetics: electroosmosis (EO) and electrophoresis (EP) and nonlinear electrokinetics: dielectrophoresis (DEP). This paper presents a microfluidic technique using DC-offset AC electric field for electrokinetic concentration of particles and cells by repulsive iDEP. This technique introduces AC electric field for producing iDEP which is decoupled from electroosmosis (EO) and electrophoresis (EP). The repulsive iDEP is generated in a PDMS tapered contraction channel that induces non-uniform electric field. The benefits of introducing AC electric field component are threefold: (i) it contributes to DEP force acting on particles, (ii) it suppresses EO flow and (iii) it does not cause any EP motion. As a result, the required DC field component that is mainly used to transport particles on the basis of EO and EP can be significantly reduced. Experimental results supported by numerical simulations showed that the total DC-offset AC electric field strength required to concentrate 15-μm particles is significantly reduced up to 85.9% as compared to using sole DC electric field. Parametric experimental studies showed that the higher buffer concentration, larger particle size and higher ratio of AC-to-DC electric field are favorable for particle concentration. In addition, the proposed technique was demonstrated for concentration of yeast cells.

Reply to comment by R. Dhanya and S. Gurubaran on “Initial results from SKiYMET meteor radar at Thumba (8.5°N, 77°E): 1. Comparison of wind measurements with MF spaced antenna radar system”

Reply to comment by R. Dhanya and S. Gurubaran on “Initial results from SKiYMET meteor radar at Thumba (8.5°N, 77°E): 1. Comparison of wind measurements with MF spaced antenna radar system”

A statistical study of large‐amplitude parallel electric fields in the upward current region of the auroral acceleration region

We present a survey of 64 direct observations of large‐amplitude parallel electric fields E∥ in the upward current region of the southern auroral acceleration zone, obtained by the three‐axis electric field experiment on Polar. These E∥ events range in amplitude from about 25 to 300 mV/m and represent a significant fraction of the total electric field strength (E∥/E⟂ ranges from ∼0.25 to O(10)). The E∥ structures, which tend to occur at the edges of oppositely directed (converging) pairs of perpendicular electric field structures (electrostatic shocks), have transverse (to the magnetic field) widths of ∼1.0–20 km at altitudes ranging from 0.8RE to 1.5RE, assuming the structures are stationary. The parallel potential drops associated with these large‐amplitude parallel electric fields are highly localized in altitude (e.g., tens of kilometers as opposed to thousands of kilometers). The amplitude of the parallel electric field shows a strong anticorrelation with the plasma density inferred from spacecraft potential measurements. We find no apparent correlation between the amplitude of the parallel electric field and altitudes sampled (between 0.8RE and 1.5RE), current density, and Kp, though there is a suggestion that the largest E∥/E⟂ ratios are confined to lower altitudes. Taking sampling biases into consideration, we find that the large parallel electric fields occur preferentially at higher values of Kp and within a thin layer centered about 1.28RE. A detailed analysis favors ambipolar effects over electron inertial effects as an explanation for the parallel electric field signatures.