Electric Charge Distribution Research Articles

Visuo-Haptic Simulations to Understand the Dependence of Electric Forces on Distance

In this paper, the potential of visuo-haptic simulators to help engineering students to understand the nature of electric forces between different electric charge distributions is addressed. Three visuo-haptic simulators were designed to perceive the attractive–repulsive behavior as well as the dependence on distance of electrical forces for: (a) point charge, (b) line charge, and (c) plane charge. Design elements were incorporated to improve the 3D perception of the simulators. A sample of N = 111 engineering students practiced with the simulators: 87 enrolled in an Electricity and Magnetism course and 24 enrolled in a more advanced Electromagnetic Fields course. Pre-test and Post-test were applied before and after working with the simulators and average learning gains were obtained. t-tests were performed to determine the statistical significance of the results. Significant learning gains were obtained for the comprehension of the force dependence in the case of line charge and plane charge, but not for the point charge, due to the fact that most students started with very high Pre-test scores in this last case. These results suggest that the use of visuo-haptic simulators may help students to better identify the dependence of electric forces on distance. It was also observed that the potential effect of improving the recognition of electric interactions was higher among students with lower previous familiarity with these topics, as compared to more advanced students. Through exit surveys, it was found that the students liked very much the haptic activity and that it sparked their interest in learning new physical concepts.

Electric field measurement in electric-field modified flames

The application of an electric field to a flame modifies the flame characteristics due to the collective motion of charged particles generated within the flame. The applied field mobilises electrons and ions depending on their polarity, leading to localised regions of space charge with sufficient density to either locally amplify or shield the applied electric field. A fundamental understanding of the local electric field is essential for both electrically and plasma-assisted combustion, because it determines electric body force as well as electron temperature. In this work, we propose a method, which is independent of gas composition and temperature, to measure the local electric field using electric field induced second harmonic generation (E-FISH). We successfully apply this method to a laminar nonpremixed counterflow flame by applying modulated direct current (DC) electric field with a microsecond duration zero volt pulse. Electric potential and space charge distribution are also deduced from the measured electric field. Furthermore, we show the importance of electron attachment to O2 forming O2− by changing the polarity of the applied DC electric field. When the anode is in the oxygen stream, a region of negative charge is obtained near the anode, whereas, when the anode is in the fuel stream, no region of negative charge is found. We also find the qualitative trends of the measured electric fields reasonably agree with previously reported one-dimensional modelling results. The limitations of the methodology are addressed, and we show that the ability to modulate the DC voltage on sub-microsecond timescales is required for accurate quantitative measurements.

Charged charm stars

The study of the general properties and stability of charm stars with a net electric charge is performed within the MIT bag model framework. We consider two different models for the electric charge distribution and demonstrate that both imply stellar configurations with larger masses and that satisfy the equilibrium condition. The dynamical stability against radial oscillations is investigated. Our results demonstrate that the eigenfrequencies are modified by the presence of a net electric charge, but the instability, previously demonstrated for the electrically neutral case, is also present in charged charm stars.

MOF Induces 2D GO to Assemble into 3D Accordion-Like Composites for Tunable and Optimized Microwave Absorption Performance.

Three-dimensional (3D) materials assembled by 2D layered lamella can provide abundant interfaces which are greatly advantageous for high-performance microwave absorbers. Herein, accordion-like CeO2- x /reduced graphene oxide (CeO2- x /RGO) hybrid materials can be successfully synthesized by a solvothermal and hydrothermal method, which are composed of laminated RGO sheets and confined CeO2- x nanoparticles (NPs). The multilayer structure is attributed to the process of Ce-MOF dissolving into NPs, then the NPs combining with graphene oxide (GO) to induce the 2D GO assembled into 3D accordion-like composites. The 3D accordion-like CeO2- x /RGO simultaneously utilizes the insulated CeO2- x and highly conductive RGO to assemble into the laminated structure with moderate electromagnetic parameters. The 3D-laminated lightweight CeO2- x /RGO composite exhibits excellent attenuation ability of an ultrabroad bandwidth (5.84 GHz) and a maximum reflection loss (-50.6 dB) which can be ascribed from the glorious impedance matching, synergistic effect between RGO sheets and the embedded CeO2- x NPs. An off-axis electron holography is carried out to visualize the spatial electrical potential and charge distribution around the CeO2- x /RGO heterojunction, which clarifies the dipole polarization and interfacial polarization. This work enlightens a simple strategy to fabricate an excellent 3D laminated RGO-based microwave absorber.

Electrically charged strange stars with an interacting quark matter equation of state

The properties of electrically charged strange quark stars predicted by an interacting quark matter equation of state (EoS) based on cold and dense perturbative quantum chromodynamics (pQCD) are investigated. The stability of strange stars is analyzed considering different models for the electric charge distribution inside the star as well as for distinct values for the total electric charge. A comparison with the predictions derived using the MIT bag model is also presented. We show that the presence of a net electric charge inside strange stars implies in a larger maximum mass in comparison to their neutral counterparts. Moreover, we demonstrate that the pQCD EoS implies larger values for the maximum mass of charged strange stars, with very heavy charged stars being stable systems against radial oscillations. For an electric charge distribution given by $q(r) = \beta r^3$, the pQCD EoS implies unstable configurations for large values of the renormalization scale as well as for large values of $\beta$, in contrast to the MIT bag model predictions.

Quantum aspects of the Lorentz symmetry violation on an electron in a nonuniform electric field

By focusing on the interface between quantum field theory and nonrelativistic quantum mechanics, based on a theory that goes beyond the Standard Model, we consider the hypothesis of having a privileged direction in the space-time. This hypothesis is made by considering a background of the Lorentz symmetry violation determined by a fixed space-like vector field. Then, we analyse quantum effects of this background on the interaction of a nonrelativistic electron with a nonuniform electric field produced by a uniform electric charge distribution.

A Quantum Model of the Distribution of Prime Numbers and the Riemann Hypothesis

After proving that numerical sequences such as Fibonacci numbers and prime numbers, can be generated as sequences of equilibrium points of an ideal half-infinite one-dimensional distribution of electric charges, a model of the distribution of primes on the x-axis is proposed, where primes ρ(n) are considered as quantum particles oscillating around the sequence of stationary points r(n) of the Lennard-Jones-like potential of the single-particle Hamiltonian. A particle-counting function πQ(x) is defined over the many-particle system, in the same way as the prime-counting function π(x). Through the application of the Hellmann-Feynman theorem, the existence of a solution n(x) ≈ li(x), coinciding asymptotically with the logarithmic integral function, is proved for the counting function of stationary points, together with the quantum equivalent of the Prime Number Theorem for the particle-counting function πQ(x). The conditions on the sequence of energy eigenvalues E(n) of the system, so that the Riemann hypothesis holds for the function πQ(x), are derived, thus proving the quantum theory results in the same bound of the position of the prime-particle in the n-th quantum state as that derived through analytical methods for the n-th prime. The model suggests new conjectures and statistical procedures which are applied to study the sign of the difference π(x)-li(x) and to explore the region beyond the Skewes number. The data predicted by the theory find confirmation when compared with those known in the literature. A new statistical local test of the Riemann hypothesis, based on the difference π(x)-li(x), is proposed.

Numerical investigation of the periodical complementary dielectric-barrier discharge equipped with double-ring electrodes in atmospheric helium

A two-dimensional fluid model was used to investigate the characteristics of helium dielectric-barrier discharge (DBD) equipped with double-ring electrodes at atmospheric pressure. Simulation results show that although the temporal evolutions of discharge current and current density at different radial positions exhibit the same or similar characteristics to those in traditional DBD, a distinctive spatial discharge structure is observed during the discharge process. The spatial distribution of electron density at current peak moments exhibits a periodical complementary feature between the center-advantage and the periphery-advantage with the inner ring electrode covering the radial axis from 0.5 to 1.0 mm. When the inner ring electrode covers the radial axis from 1.0 to 1.5 mm, the spatial distribution of electron density satisfies another periodical complementary behavior between the electrode-center-advantage and the coexistence of periphery-advantage and center-advantage. These complementary discharge features mainly result from non-uniform electric field and surface charge distribution at the end of the previous discharge. The difference of the discharge structure between the two cases is attributed to the fact that Laplacian field distributions are largely dependent on the arrangement of double-ring electrodes. Our observations show that electrode geometry plays an important role in the formation of the discharge structure.

Accurate TMS Head Modeling: Interfacing SimNIBS and BEM-FMM in a MATLAB-Based Module.

We interface the head modelling, coil models, Graphical User Interface (GUI), and post-processing capabilities of the SimNIBS package with the boundary element fast multipole method (BEM-FMM), implemented in a MATLAB-based module. The resulting pipeline combines the best of both worlds: the individualized head modelling and ease-of-use of SimNIBS with the numerical accuracy of BEM-FMM. The corresponding TMS (transcranial magnetic stimulation) modeling package is developed and made available online. It imports a SimNIBS surface segmentation and a coil field, and then exports electric-field values in selected surfaces or volumes. Additional information is also made available, such as discontinuous compartment surface electric fields and associated surface electric charge distributions.

Broad range electric field enhancement of a plasmonic nanosphere heterodimer

Interaction between metallic nanoparticles has been widely investigated due to the rise of the enhanced local electric field inside the gap. We numerically present the broadband near- and far-field spectra from the near-ultraviolet (UV) through the visible wavelength range using plasmonic heterodimers. Both near- and far-field resonances can be manipulated by the composition of heterodimers. They show strong dependencies on gap width and particle size. Compared with Al-Au and Al-Ag heterodimers, the dipole-mode resonant peak has a redshift for the Au-Ag heterodimer. In the near-UV range, the Al-Ag heterodimer gains the strongest optical enhancement. This is due to the robust optical resonance of Al and Ag particles in the near-UV range. On the other hand, the heterodimers with Au particles exhibit a better field enhancement at longer wavelengths. The physical origin of plasmonic resonances of the bonding dipole modes and higher-order modes are revealed by the simulated mappings of local electric fields and 3D surface charge distributions. Moreover, our simulations also reveal the suitability of the plasmon ruler equation and the power law enhancement equation to quantify the optical response of heterodimers.

Broad range electric field enhancement of a plasmonic nanosphere heterodimer

Interaction between metallic nanoparticles has been widely investigated due to the rise of the enhanced local electric field inside the gap. We numerically present the broadband near- and far-field spectra from the near-ultraviolet (UV) through the visible wavelength range using plasmonic heterodimers. Both near- and far-field resonances can be manipulated by the composition of heterodimers. They show strong dependencies on gap width and particle size. Compared with Al-Au and Al-Ag heterodimers, the dipole-mode resonant peak has a redshift for the Au-Ag heterodimer. In the near-UV range, the Al-Ag heterodimer gains the strongest optical enhancement. This is due to the robust optical resonance of Al and Ag particles in the near-UV range. On the other hand, the heterodimers with Au particles exhibit a better field enhancement at longer wavelengths. The physical origin of plasmonic resonances of the bonding dipole modes and higher-order modes are revealed by the simulated mappings of local electric fields and 3D surface charge distributions. Moreover, our simulations also reveal the suitability of the plasmon ruler equation and the power law enhancement equation to quantify the optical response of heterodimers.

Terahertz composite plasmonic slabs based on double-layer metallic gratings.

One composite plasmonic slab with a broad bandgap (40%) is experimentally and numerically demonstrated in the terahertz (THz) region. The composite slab consists of double-layer metallic gratings and a dielectric film, which supports two resonant modes. Electric field vectors and charge distributions proved that the low-frequency resonant mode originates from the symmetric plasmonic mode, while the high-frequency resonant mode is induced by the hybrid mode of plasmonic and dielectric modes. Compared with the double-layer metallic grating, the inserted dielectric film significantly enhances the transmission of the transverse magnetic (TM) waves and induces Fano resonances. The near-field coupling between metal gratings and dielectric film can be manipulated by changing the thickness and the refractive index of dielectric films. We further demonstrated that the plasmonic bandgap can be manipulated by tuning the grating width. These results suggest that this composite plasmonic slab is promising in terahertz integrated components development such as a filter, polarizer, or sensor.

Doping amino acids with classical gas hydrate inhibitors to facilitate the hydrate inhibition effect at low dosages

AbstractThe formation of gas hydrates in offshore subsea lines is a major flow assurance concern for the oil and gas industry. In this work, the thermodynamic hydrate inhibition (THI) effect of doping amino acids (AA) such as glycine (Gly), l‐alanine (Ala), and histidine (His) with classical gas hydrate inhibitors (CHI) such as methanol (Me), ethylene glycol (EG), and sodium chloride (NaCl) have been examined at diverse operating conditions. The experimental tests were carried out using rocking cell assembly [RC‐5] on pure methane gas at different pressure conditions (40–120 bars) using an equal ratio mixture (1:1) of AA and CHI at a low dosage (2 wt%). The computational three‐dimensional molecular models of AA and CHI were generated to examine electric charge distribution within these molecules and cognize the interaction mechanism between methane hydrates and AA. The experimental results indicate that Me and EG can synergize the THI effect of AA at a low dosage of 1 wt%. The AA doped with Me tend to provide better THI effect compared to AA doped with EG and NaCl. The experimental results also show that the doped AA Ala mixtures provide THI effect similar to pure CHI such as Me, EG, and NaCl at low dosage (2 wt%). © 2020 Society of Chemical Industry and John Wiley & Sons, Ltd.

Mapping the surface potential, charge density and adhesion of cellulose nanocrystals using advanced scanning probe microscopy

Cellulose nanocrystals (CNC) are the focus of significant attention in the broad area of sustainable technologies for possessing many desirable properties such as a large surface area, high strength and stiffness, outstanding colloidal stability, excellent biocompatibility and biodegradability, low weight and abundance in nature. Yet, a fundamental understanding of the micro- and nanoscale electrical charge distribution on nanocellulose still remains elusive. Here we present direct quantification and mapping of surface charges on CNCs at ambient condition using advanced surface probe microscopy techniques such as Kelvin probe force microscopy (KPFM), electrostatic force microscopy (EFM) and force-distance (F–D) curve measurements. We show by EFM measurements that the surface charge in the solid-state (as contrasted with liquid dispersions) present at ambient condition on CNCs provided by Innotech Alberta is intrinsically negative and the charge density is estimated to be 13 μC/cm2. These charges also result in CNCs having two times the adhesive force exhibited by SiO2 substrates in adhesion mapping studies. The origin of negative surface charge is likely due to the formation of CNCs through sulfuric acid hydrolysis where sulfate half esters groups remained on the surface (Johnston et al., 2018).

Study of charged stellar models in f(𝒢) gravity with Tolman–Kuchowicz space–time

In the context of modified [Formula: see text] gravity model, the current study highlights the effect of electric charge for static spherically symmetric stellar models in presence of anisotropic matter distribution. For this purpose, we specifically consider the metric potentials of Tolman–Kuchowicz space–time, which are singularity free and satisfy the stability criteria. The possible existence of charge and a strong electric field, inside the stars is due to the higher values of energy density of matter, pressure distribution and gravitational fields. For the solution of Einstein–Maxwell field equations, the simplified phenomenological MIT bag equation of state, i.e. [Formula: see text] and a specific form of electrical charge distribution [Formula: see text] are to be considered. Further, to derive the values of unknown parameters of the stellar objects, we match interior Tolman–Kuchowicz space–time to exterior Reissner–Nordström metric, at the surface of stellar system. In addition to this, for the physical validity and stability of our suggested model, we conduct several physical tests such as effective energy density, effective pressures, energy conditions, stability against equilibrium of the forces, mass-radius relation, surface redshift, Herrera’s cracking concept and electric charge for well-known compact stellar objects viz., SAX J 1808.4-3658 and PSR 1937+21. It is observed that all these tests follow the physically accepted pattern and the influence of charge leads to more stable and viable stellar structures of compact objects in [Formula: see text] gravity.

Analytical model for homocharge accumulation in LDPE — role of conduction, injection and diffusion

Homocharge, particularly, positive charge near anode has been observed inside low-density polyethylene (LDPE) by many researchers. However, the phenomenon is yet to be understood theoretically and mathematical analysis is pending, although, simulations have been reported. Simulation of evolution of space charge in LDPE, with time and space, using bipolar charge transport model considered only drift component of charge carriers inside the dielectric. The experimental results suggest significant concentration gradient in space charge distribution. The authors derived a comprehensive drift and diffusion based analytical models, for the time/space evolution of space charge and electric field in dielectrics using Maxwell's equations, current continuity equation, conduction and injection mechanisms. The proposed analytic models of electric field and space charge distribution entwines charge injection at electrodes and charge transport inside the medium, which seem to have not been reported until now. Remarkable, believed to be unprecedented, agreement between the analytical and experimental results has been observed. Using the model, the role of conduction, injection, diffusion on homocharge accumulation has been investigated. Pulsed electroacoustic method is used for the measurements of the space charge dynamics.

Enzyme-induced changes in skin and its implications

Surface charge of the skin matrix is an extremely important parameter in leather making process because effectivity of the chemicals largely depends on the surface charge of the skin matrix. In the present research work, isoelectric point (Ip) and point of zero charge (pzc) are used to predict the distribution of electric potential and charge at the skin tissue–liquid interface after chemical and enzymatic unhairing of the skin. In this study, the determination of zeta potential and isoelectric point for relimed tissues processed by chemical and enzymatic methods was performed using a zeta potential analyzer and a titrimetric method. These results indicate that enzyme-treated tissues had lower isoelectric point than the chemical-treated tissues, which has been explained by studying the amino acid composition of the tissues. The tissue samples were also characterized by FTIR–ATR and solid-state 13C NMR spectroscopy to understand the chemical/structural changes occurred due to enzymatic treatment. The lower Ip/pzc of the tissue obtained by enzymatic process ensured maximum uptake of chemicals, making it an eco-benign process.

A Molecular Dynamics Simulation of Polyampholytic Polypeptides Associated with Atomic Clusters on the Surfaces of Metal-Like Nanoobjects

Abstract—Electrically induced conformational changes of polyampholytic polypeptides associated with model metal atomic clusters on the surfaces of metal-like nanoparticle and substrate with uniform distribution of electric charge, as well as on the surface of a polarized nanoparticle, were studied using molecular dynamics simulations. The average distances between the atomic clusters bound to the polypeptide and the adsorbent under a change in the charge density on its surface were calculated. Electrically induced changes in the polyampholyte conformations led to a significant shift of the atomic clusters associated with the macrochain relative to the adsorbing surface of the nanoobject, which can be used in sensors based on the effects of surface plasmon resonance and surface-enhanced Raman scattering, as well as in nanoprobes with adjustable parameters or parameters switched under the influence of an electric field.

The study of bicyclic amidine-based ionic liquids as promising carbon dioxide capture agents

Abstract CO2 capture by ionic liquids has been successfully achieved, indicating that the adsorption of CO2 plays an important role in the activation and transformation of CO2. In this work, highly efficient capture of CO2 is investigated with several novel ILs, which were prepared from bicyclic amidine (DBN) with pyrazole derivatives. Among the kinds of DBN-based ILs, it is found that the optimal absorption capacity (0.93 mol CO2/mol IL) can be achieved by [DBNH][3-MethylPyr] at 40 °C and atmospheric pressure. In view of analysis, the significant increase in CO2 capacity was affected by the reactivity of activated nitrogen, steric hindrance and the type of substituents. On the basis of the spectroscopic investigation and Density Functional Theory (DFT) calculation, the absorption mechanism was illustrated, it was verified that anions can react with CO2 to form carbamates. Meanwhile, charge analysis reasonably elucidated the diversity of absorption capacity in various ILs. It suggested that electric-charge distribution of activated nitrogen in pyrazole ring system can play an important role in determining the reaction of ILs with CO2. Consequently, DBN-based ILs can be excellent candidates for CO2 capture.

Computational relaxation method for modeling electrostatic systems with non-trivial geometries

Through electrostatic potential, it is possible to analyze an electromagnetic system and find the generated electric field and charge distribution for a given setup. However, most boundary conditions prove to be impossible to solve analytically. In the following paper, we present a computational relaxation method for modeling the potential, electric field and charge density of 2D electromagnetic systems with non-trivial geometries. By performing the experimental realization of finite parallel plates, we find an astonishing agreement between experimental results and our model. We study the uncertainties introduced by the model by comparing our results with theoretical predictions in the specific case of infinite parallel wires, and show that the error rate drops exponentially as the system size increases. Finally, the number of iterations required to reach equilibrium has also been analyzed for different lattice-sweeping methods.