Horizontal Electric Field Research Articles

Is short-offset frequency-domain controlled-source electromagnetic survey using an equatorial configuration a good choice on land?

The frequency-domain controlled-source electromagnetic (FD-CSEM) method can be used to collect data in both the large-offset plane-wave zones and the short-offset zone using an axial configuration within conductive marine environments. In contrast, the equatorial configuration is more commonly adopted for field surveys on land. However, selecting a suitable offset using an equatorial configuration on land remains a challenge. Therefore, the primary objective of this study was to choose a reasonable offset using an equatorial configuration on land. To this end, we compared the distribution and decay characteristics of the horizontal electric field. Additionally, we analyzed the detectability of the horizontal electric field to targets based on the root mean square (RMS) misfit and three-dimensional (3D) simulation at different offsets. The 3D simulation results show that the maximum normalized response at different offsets is similar, indicating that electric fields at different offsets share similar resolution limits. However, the horizontal electric field at small offsets (less than 3 times the target depth) only have the detectability for the target resistivity and are unable to make more precise distinctions on the target thickness. The detectability for the target thickness at very small offsets (about one time the target depth) is limited, as frequency sounding cannot be effectively established. A larger offset distance (larger than 4 to 6 times the target depth) is required when observing the vertical magnetic field compared to the horizontal electric field. Finally, we observed the electric field data at different offsets in the Kalatongke nickel–copper deposit in Xinjiang, China, which verifies our theoretical analysis.

Insights into the Effect of a Microwave Field on the Properties of Modified γ-Alumina: A DFT Study

γ-Alumina is often used as a support for hydrodesulfurization catalysts due to its excellent performance. During the catalytic reaction, the strong surface acidity of γ-alumina can induce a strong interaction between the active phase and the support. The reaction activity of the catalyst can be affected by changing the present mode of the active phase on the surface of the support. The (110) crystal plane, acting as the strongest acidity plane of γ-alumina, was selected for modification. The supports modified with boron and phosphorus were successfully constructed, and the acid strengths were quantified by simulating the adsorption of the relevant probe molecules: pyridine in correlation with surface electronic properties via density functional theory. The surface adsorption energy calculation shows that the boron-modified surface is able to moderately reduce the adsorption capacity of alumina, while that of the surface modified by phosphorus is found to be enhanced over the sites of a tetrahedral coordination structure; however, at the other unsaturated Al sites, this is obviously reduced. The results of introducing electric fields imply that applying horizontal electric fields changes the surface acidity of alumina under the premise of a stable structure. With the enhancement of the horizontal electric fields, the adsorption capacity of tetra-coordination sites on the original surface gradually decreases, while those of the others gradually increases. However, for the boron-modified surface, introducing horizontal electric fields can reduce the adsorption capacity of all sites. Hence, microwave-electric-field-assisted modification of B further reduces the surface acidity of alumina, making it beneficial for deep hydrodesulfurization reactions.

Flow structure beneath periodic waves with constant vorticity under strong horizontal electric fields

While several articles have been written on Electrohydrodynamics (EHD) flows or flows with constant vorticity separately, little is known about the extent to which the combined effects of EHD and constant vorticity affect the flow. This study aims to shed light on this topic by investigating the combined influence of a horizontal electric field and constant vorticity on the free surface and the emergence of stagnation points. Using the Euler equations framework, we employ conformal mapping and pseudo-spectral numerical methods. Our findings reveal that increasing the electric field intensity eliminates stagnation points and smoothen the wave profile. This implies that a horizontal electric field acts as a mechanism for the elimination of stagnation points within the fluid body. Besides, we have identified regimes where three stagnation points appear on the free surface — something that cannot occur in purely gravity rotational waves.

Effects of Eccentricity and Horizontal Electric Field on the Characteristics and Outcomes of Binary Collisions of Water Drops

AbstractEffects of eccentricity and horizontal electric field (EH) on the binary‐collision outcomes of water drops are examined using numerically calculated collision characteristics from previous studies and results of simulation experiment conducted by the authors. For a fixed collision kinetic energy (CKE), filament breakups can occur at all values of eccentricity but events of coalescence decrease, and that of sheet breakup increase with increasing eccentricity in absence of EH. However, as EH increases to ∼300 kVm−1 it opposes the variability of the coalescence and sheet breakup events with eccentricity. When EH exceeds ∼300 kVm−1 the collision outcomes might be determined only by the CKE and EH. The calculated value of coalescence efficiency and total number of fragments after a binary collision decreases with an increase in EH. It is argued that an electric field can significantly modify drop size distribution in thunderclouds and needs to be considered for development of precipitation.

Theoretical study of tip-enhanced photoluminescence of single molecule in nanocavity formed by apex protrusion and substrate

Tip-enhanced photoluminescence techniques, characterized by ultra-high detection sensitivity and spatial resolution, have exhibited unprecedented capabilities in exploring optoelectronic phenomena and unraveling intrinsic physical mechanism at the single-molecule level. To suppress the quenching of molecular luminescence and achieve high-resolution optical imaging, a rational design of the tip-substrate configuration is required. In this paper, we systematically investigate the tip-enhanced photoluminescence characteristics of single molecules located within the plasmonic nanocavity formed by the tip protrusion and the substrate from a theoretical perspective. The impacts of electron tunneling and electron-hole pair creation on localized electric field and quantum yield are discussed using the quantum correction model and nonlocal dielectric theory, respectively. The crucial roles of atomic-scale protrusion at the tip apex and the decoupling layer on the substrate in enhancing vertical and horizontal electric fields as well as quantum yields have been emphasized. The results indicate that in smaller sub-nanometer cavities, electron tunneling and nonlocal dielectric effects greatly weaken the electric field intensity and fluorescence quantum yield. Meanwhile, due to the sharp lightning rod effect, the presence of atomic-level protrusion at the tip apex can provide a strong and highly localized plasmonic field. We find that the added NaCl layer not only blocks charge transfer between molecules and the substrate but also effectively prevents fluorescence quenching. The maximum fluorescence and Raman enhancement factors near the tip apex approach up to 5 and 12 orders of magnitude, respectively, achieving sub-nanometer spatial resolution. Finally, compared to vertical electric field and dipole, sharp protrusion can excite a stronger horizontal electric field and couple with horizontal dipoles to yield a higher quantum yield, resulting in a three orders of magnitude higher in the fluorescence enhancement of horizontal dipole compared to the tip without protrusion. Our theoretical research not only confirms the experimental results of spectral enhancement with the proximity of the tip to the molecule in tip-enhanced photoluminescence, but also provides effective guidance for a deeper understanding of the mechanism of tip-enhanced fluorescence and Raman spectroscopy, as well as optimizing the experimental system.

Natural source-field induced polarisation exploration of an iron-oxide copper-gold (IOCG) deposit under thick cover

Induced polarisation (IP) is a common geophysical method of exploration for disseminated sulphides. However, in areas with deep (>200 m) and conductive (10 Ωm or less) cover, the technique is less successful as it requires a significant transmitter source and large-offset dipoles. An alternative approach is to use natural-variations in Earth’s external magnetic field as the polarising source of the signal, known as natural-field IP. This paper presents a study of extracting IP information from electrical dipole observations during a broadband magnetotelluric (MT) program with a 9 km by 9 km grid of 100 sites above the Vulcan IOCG deposit beneath 750 m of cover, ∼40 km north of the Olympic Dam IOCG mine in South Australia. Inter-site transfer functions between 95 sites and five reference sites at the southeast and southwest corners of the grid were computed to determine a phase shift between horizontal electric fields in the bandwidth of 1–100 s period. Phase shifts of up to – 5 degrees were centred on a region of brecciated hematite where drill holes intersected pyrite, and an inferred fault-zone from passive seismics that marks the boundary between upper crust that is resistive (>100 Ω.m) with high magnetic susceptibility to the south of the fault, and a region of conductive crust (<10 Ω.m) which is low magnetic susceptibility. Our study suggests that the natural-field IP method can identify regions of polarizable minerals beneath deep cover where artificial power sources cannot be feasibly deployed. Such surveys are cheaper, safer, and easier to deploy as only receivers are required, and 3D coverage can be obtained as the source-field is of much larger dimension than the survey array. In addition, the natural-field IP signals are observed as part of the MT program so that both electrical resistivity and polarisation parameters can be determined.

Response characteristics and detectability of pegmatitic rare-metal deposits using different grounded-wire configurations

The differential electrical dipole (DED) and differentially normalized electromagnetic method (DNME) have a stronger transverse magnetic field than the horizontal electric dipole (HED) and, thus, have been successfully used for resource exploration in conductive ocean environments. However, which of these two is more suitable for the exploration of resistive targets on land, such as pegmatite veins and ore-related mafic and ultramafic intrusions in mineral deposits, remains unknown. Thus, we conduct a comparative study of the DED, DNME, and HED based on forward modeling and application to a field survey. The signal amplitude of the horizontal electric field measured using the DED and DNME is substantially weaker than that obtained via the HED with the same source length and transmitting current. The lateral variation in the horizontal electric field response observed via the DNME reflects the change in the shallow electrical structure, indicating the spatial distribution of pegmatite veins, as verified by the 3D simulation results and data obtained in a field survey of pegmatitic rare-metal deposits in Lushi County, China. The DED and DNME exhibit similar abilities for detecting resistive targets. Both methods show higher detectability than HED based on 3D synthetic modeling. Our results indicate that the DNME, with its higher responses and better lateral resolution, is a better choice in field surveys on land than the DED.

Study on the single-event burnout mechanism of p-GaN gate AlGaN/GaN HEMTs

In this work, the single-event burnout (SEB) mechanism of p-GaN gate AlGaN/GaN HEMTs has been studied systematically. The irradiation experiment was carried out based on Ta ions with high linear energy transfer of 75.4 MeV/(mg/cm2), a standard criterion for commercial space applications. It is clearly observed that both the drain current and gate current increase during the irradiation. With the increasing drain bias, the device burns out eventually. Technology computer-aided design simulation was used to explore the possible burnout mechanism. The local high electric field peak induced by the electron and hole redistribution was proposed to explain the permanent damage. When heavy ions impact the device, electron–hole pairs are formed. With the aid of a horizontal electric field across the channel, electrons and holes move toward the drain and gate, respectively. The accumulation of electrons and holes around the drain edge and gate edge induces the local high electric field, which is even higher than the intrinsic breakdown electric field of GaN and AlGaN. The scanning electron microscope results verified the proposed SEB mechanism. This research offers significant theoretical and experimental insights for evaluating the reliability of GaN power devices against high-energy single-event burnout in aerospace applications.

The Indirect Effect of Lightning Electromagnetic Pulses on Electrostatic, Electromagnetic Fields and Induced Voltages in Overhead Energy Transmission Lines

The impact of a lightning electromagnetic pulse (LEMP) on a power line or power station produces an effect similar to that of switching between a significant power source and a power line circuit. This switch closure causes a sudden change in routing conditions, creating a transient state. This situation has been studied in terms of electrostatic and electromagnetic induction, as well as overvoltage changes. Appropriate mathematical models were used to analyze these changes. While vertical electric field analysis has been carried out in a few studies, magnetic field and horizontal electric field vectors have not been studied. In this study, the Rusck formulation and the Heidler current formulation are combined at the current level, developed and analyzed. This is because the Rusck expression can sometimes give incorrect results at the current level. Also, in the analysis, electromagnetic field formulations based on accelerating charges are used instead of the dipole approximation to eliminate the need for interpolation in the graphical results. In contrast to other studies in the literature, this study proposes the use of moving and accelerating load techniques to better understand the effects of LEMPs on power transmission lines. Also, in this study, the double exponential problem of the current form in Rusck’s formulation is addressed in order to obtain a close approximation of the physical form of the LEMP. Additionally, the field–line (coupling) relationship is studied according to a unique closed formulation, leading to important determinations about the overvoltages generated on a line depending on the propagation speed of the LEMP sprout and the electrical changes in the area where the LEMP first occurs.

The improvement of device linearity in AlGaN/GaN HEMTs at millimeter-wave frequencies using dual-gate configuration

The linearity performance of the AlGaN/GaN high-electron-mobility-transistors (HEMTs) is critical for circuit applications especially at millimeter-wave frequencies. In this paper, we propose a new dual-gate (DG) configuration for linearity improvement at millimeter-wave frequencies. Using 2D simulation, we observed the improvement in device linearity by placing the additional DC gate in the source-gate access region. Adjusting the bias voltage of the DC gate modulates the horizontal electric field in the channel and controls the acceleration behavior of the channel electrons. Furthermore, such bias adjustment enhances the electron density in the channel to compensate for the transconductance (Gm) degradation. Both of these contribute to the flattening of the Gm profile for linearity improvement. The proposed DG configuration improves the C/I ratio by 10 dB compared to the conventional single gate (SG) device at 38 GHz. Additionally, a 60 % improvement in the cutoff frequency (fT) and maximum oscillation frequency (fmax) is obtained compared to the traditional DG configuration where the second gate is placed in the gate-drain drift region. This is mainly due to the reduction in gate capacitances from the redistribution of the electrons in the device. Such superior characteristics have shown great potential of the proposed device for high linearity applications at millimeter-wave frequencies.

Application and Parameter Optimization of Electro-Kinetic Geosynthetics Electrodes Based on the Wild Horse Optimizer in Horizontal Electric Field Sludge Dewatering

This study systematically compared the performance of five corrosion-resistant electrode materials for electro-dewatering. Through a comprehensive analysis of dewatering efficiency, energy consumption, and corrosion resistance, conductive plastic composite electrodes (EKG) were selected as the optimal electrode material for experimentation. Additionally, the impact of electric field strength and electrode spacing on the efficiency and energy consumption of electro-dewatering (EDW) was investigated. The results showed that the increase in electric field intensity could improve the solid content and dewatering efficiency of the sediments, but the corresponding energy consumption also increased. The increased spacing of the plates reduced the dehydration effect and increased the energy consumption. By employing the Wild Horse Optimization algorithm, empirical and multifactorial response models for the dewatering solidification process were established, aimed at predicting the dewatering performance and energy consumption. The study concludes that for the remediation of heavy metals, the electric field strength should not exceed 10 V/cm to avoid excessive heavy metal migration and potential adverse chemical reactions.

ОСОБЛИВОСТІ ПОСТАНОВКИ ТЕОРЕТИЧНИХ НАВЧАЛЬНО-ДОСЛІДНИЦЬКИХ ЗАВДАНЬ З ФІЗИКИ

The article considers the necessity of introducing theoretical methods of idealization and mode ling in educational research. A brief overview of the problem of involving talented students in educational research not on a competitive basis, but for the organic development of their creative potential is given. The importance of theoretical educational research tasks in teaching physics is analyzed. A possible direction for organizing educational research aimed at developing the creative potential of talented students in physics and other natural-mathematical disciplines is proposed. Since curious students often put forward technically unrealizable ideas due to lack of factual knowledge and experience, the article provides an example of using a pedagogical technique known as “Socratic dialogue”. Examples of setting purely theoretical educational research tasks aimed at implementing methods for measuring the electric charge of a small ball suspended on a thread are given. Possible solutions to such problems are indicated for the case: 1) static equilibrium of such a ball in a horizontal electric field; 2) harmonic oscillations of a pendulum with a charged ball in a vertical electric field. A theoretical assess ment of the order of magnitude of results obtained from the practical creation of proposed measuring devices is carried out. The article’s conclusions provide an author’s vision of recommendations for implementing theoretical educational research in physics.

Electric field-dependent photoexcited spin-polarized electron transport in Bi2Se3 topological insulator

Three-dimensional (3D) topological insulators (TIs) exhibit spin-polarized surface states in which the spin of electrons is locked to their momentum. The helical surface states can be explored from circularly polarized light-induced spin photocurrent, a phenomenon called circular photogalvanic effect (CPGE). In this work, we fabricate a TI transistor with the Bi2Se3 channel layer synthesized using vapor deposition. The photocurrent response of Bi2Se3 TI is characterized under horizontal and longitudinal electric fields. CPGE and linear photogalvanic effect (LPGE) contribute to the surface state photocurrent at room temperature. The longitudinal electric field provides kinetic energy to the electrons so that the transition of electrons to higher energy bands in momentum space occurs. Under a photon excitation with the energy far above the TI bandgap, we observed a photocurrent difference between left and right circularly polarized light excitation. The photocurrent variation with gate voltage (longitudinal field) is also investigated. Adjusting the Fermi level with the gate bias leads to changes in the population of bulk state carriers and spin electrons in surface states. By shifting the gate bias toward negative, the CPGE current increases because of the reduced scattering with bulk carriers. Our work reveals that longitudinal and horizontal electric fields can manipulate the helical spin-polarized photocurrent of Bi2Se3. From the asymmetry of circularly polarized photoconductive differential current (CPDC) under the horizontal field, we found evidence of spin-polarized electron transition to other conduction band valleys at room temperature under a high-energy photon excitation.

The electronic properties of C2N/antimonene heterostructure regulated by the horizontal and vertical strain, external electric field and interlayer twist

The electronic properties of C2N/antimonene (Sb) van der Waals (vdW) heterostructure are investigated based on the density functional theory. The results show that the C2N/Sb vdW heterostructure behaves type-II band alignment with a direct Eg of 0.35 eV. The electronic structure can be adjusted by horizontal (vertical) strain, electric field, interlayer twist, and vertical strained-twisted cases, respectively. The horizontal strain shows a more extensive controlling range of Eg than the vertical strain, but the vertical strain adjusting shows better linear features than the horizontal strain. When applying an electric field, the maximum Eg can reach 1.4 eV with Type-I band alignment, which has potential in transistors, solar cells, Light Emitting Diode(LED), and other applications. The heterostructure keeps robust type-II band alignment with different twist angles between C2N and Sb monolayer, which contributes to efficient separation of photo-generated electron-hole pairs as photovoltaic and optical detector devices. When the vertical strain is applied on the twisted heterostructure, the band alignment, Eg, and energy states near the Fermi energy (EF) change obviously due to orbital hybridization strengthened. Our results suggest that there are various means to regulate the electronic properties of heterostructures.

Self-excited converging shock structure in a complex plasma medium.

We report the study of a self-excited converging shock structure observed in a complex plasma medium. A high-density dust cloud of melamine formaldehyde particles is created and horizontally confined by a circular ring in a dc glow discharge plasma at a particular discharge voltage and pressure. Later, as the discharge voltage is increased, a circular density crest is spontaneously generated around the outer boundary of the dust cloud. This nonlinear density structure is seen to propagate inward towards the center of the dust cloud. The properties of the excited structure are analyzed and found to follow the characteristics of a converging shock structure. A three-dimensional molecular dynamics simulation has also been performed in which a stable dust cloud is formed and levitated by the balance of forces due to gravity and an external electric field mimicking the cathode sheath electric field in the experiment. Particles are also horizontally confined by an external electric field, representing the sheath electric field of the circular ring present in the experiment. A circular shock structure has been excited by applying an external perturbation in the horizontal electric field around the outer boundary of the dust cloud. The characteristic properties of the shock are analyzed in the simulation and qualitatively compared with the experimental findings. This paper is not only of fundamental interest but has many implications concerning the study of converging shock waves excited in other media for various potential applications.

Fully Nonlinear Evolution of Free-Surface Waves with Constant Vorticity under Horizontal Electric Fields

This work presents the results of a direct numerical simulation of the nonlinear free surface evolution of a finite-depth fluid with a linear shear flow under the action of horizontal electric fields. The method of time-dependent conformal transformation for the description of the combined effects of the electric fields and constant vorticity is generalized for the first time. The simulation results show that strong shear flow co-directed in the wave propagation direction leads to the formation of large-amplitude surface waves, and, for some limiting vorticity value, a wave breaking process with the formation of an air bubble in the liquid is possible. The oppositely directed shear flow can cause the retrograde motion of a surface wave (wave propagation in the opposite direction to the linear wave speed). The simulations conducted taking into account the electro-hydrodynamic effects demonstrate that a high enough external horizontal electric field suppresses these strongly nonlinear processes, and the surface waves tend to preserve their shape.

Vertical and horizontal electric fields stimulate growth and physiological responses in lettuce

Vertical and horizontal electric fields stimulate growth and physiological responses in lettuce

Gas-solid photoelectrocatalytic CO2 reduction using solid planar photoelectrocatalytic device ITO/RGO/ITO

Photoelectric co-catalysis is a promising method for carbon dioxide (CO2) reduction due to its greater flexibility and higher reaction efficiency. However, the development of gas-phase photoelectrocatalysis is still in progress. Additionally, there is limited information available regarding the intrinsic photocatalytic capability of reduced graphene oxide (RGO) and its “structure-activity” relationship. In this study, solid planar photoelectrocatalytic (PEC) devices ITO/RGO/ITO were designed to enable gas-solid PEC CO2 reduction. The device consists of two strip electrodes functioning as the cathode and anode, biased to create a horizontal electric field that facilitates the separation of photogenerated electron-hole pairs. RGO-130 (heat treatment at 130 °C) presented the best PEC CO2 reduction efficiency, 2.2 times higher than photocatalysis under visible light irradiation. This enhancement can be attributed to its moderate oxygen content (48.8%), 001 crystal face and “layer upon layer” structure, all of which facilitate the separation and transfer of photogenerated carriers. Therefore, RGO is capable of acting as a stand-alone catalyst for the photocatalytic CO2 reduction, and the appropriate design of RGO in surface and structure can improve its activity. This work provides a new perspective on research and application of PEC CO2 reduction, in view of its environmentally safe and conducive to large-scale applications.

Propagation Characteristics of Lightning Radiation Field on Three-Layer Vertical Layered Ground Based on CPML Absorption Boundary

The perfectly matched layer absorbing boundary condition based on coordinate scaling transformation (CPML) has a good absorption effect in finite-difference time-domain method (FDTD) calculation. In this study, we derive the CPML update equations in the 2-D cylindrical coordinate system by setting an appropriate coordinate-stretching variable, which can more easily achieve CPML and obtain good results in the calculation of lightning electromagnetic field. Then, the propagation characteristics of the lightning return stroke radiation field on the three-layer vertical layered ground structure are studied. The results show the following: 1) at 10 m above the ground, the vertical electric field and azimuthal magnetic field are almost not affected by the vertically layered ground structure, while the horizontal electric field is slightly affected by the vertical layered ground structure and 2) at 3 m below the ground, the lightning radiation fields are all affected by the vertically layered ground structure, which the vertical electric field is the most affected, and it can also use two-layer vertical layered ground structure instead of three-layer vertical layered ground structure for FDTD calculation under certain conditions, which can simplify the calculation model. All the results are obtained at a close distance from the lighting channel.

Numerical Study of Free-Surface Electro-Hydrodynamic Wave Turbulence

Direct numerical simulation of threedimensional chaotic motion of a dielectric liquid with a free surface under the action of external horizontal electric field is carried out. The numerical model takes into account the effects of surface tension, viscosity, and external isotropic random forcing acting at large scales. A transition from dispersive capillary wave turbulence to quasi-isotropic nondispersive EHD surface turbulence with increase of the external electric field strength is numerically observed for the first time. At the regime of developed EHD wave turbulence, the total electrical energy is found to be much greater than the energy of capillary waves, i.e., electrohydrodynamic effects play a dominant role. At the same time, anisotropic effects are detected that lead to the generation of capillary wave packets traveling perpendicular to the external field direction. Despite the revealed anisotropy, the calculated spectrum of EHD wave turbulence is in very good agreement with the analytical spectrum obtained on the basis of dimensional analysis of weak turbulence spectra.