Charge Flux Research Articles

Magnetospheric response on impact of solar wind diamagnetic structures borne by eruptive prominence

We address the sequence of Sun-to-Earth phenomena, that enables to study the mechanism for geoefficiency of eruptive prominences propagating from the Sun inside coronal mass ejections (CMEs). An eruptive prominence ejected in the solar wind (SW) moves at the SW velocity Earthward like adiamagnetic structure of eruptive prominence (DSEP).The key feature of the latter is a largesharp plasma concentration jump N inside the DSEP at a simultaneous sharp drop in the interplanetary magnetic field (IMF) modulus B. It is the anti-correlation between the N and B profiles in DSEP, due to which its contact with the magnetosphere may lead not only to magnetosphere compression, but also to penetration of DSEP substance into the magnetosphere. The duration of the magnetospheric disturbance (in the form of dayside auroras), global increase in the current systems, charged particle flux enhancement in the radiation belts, and generation of the irregular Pi2-3 oscillations aredetermined by the DSEP size. We present statistical investigations into DSEPs observed in different years of solar activity and builta qualitative modelfor DSEP geoefficiency.

Simulation of the effect of temperature on space charge transport in LDPE under DC electric field stress

Polymers are considered essential materials used in high-voltage direct current (HVDC) applications due to their excellent insulating properties. They are widely employed in various electrical equipment such as cables, transformers, and station insulators, providing effective protection against high currents and voltages. One of the main challenges in these applications is the effect of temperature on the performance of these insulators, as elevated temperatures can alter the electrical properties of polymers, potentially impacting the dynamics of electric charges within the material. In this work, bipolar charge transport (BCT) was used to study the effect of temperature on the dynamics of space charge in LDPE under a DC electric field. The model includes processes such as injection, migration, trapping, detrapping, and recombination. We applied a DC electric field of 50 kV/mm to low-density polyethylene (LDPE) films for 2 hours under different temperatures. The results indicate that higher temperatures significantly enhance charge mobility, leading to improved charge flux, reduced trapping, and increased detrapping of charges. This results in a more uniform distribution of the electric field within the material and a quicker transition to a steady-state condition. The increase in temperature within the applied electric field created a relative balance between trapped charge and mobile charge, indicating a positive effect of higher temperatures on the electrical insulation properties of LDPE.

High-temperature Brown-Zak oscillations in graphene/hBN moiré field effect transistor fabricated using molecular beam epitaxy

Graphene placed on hexagonal boron nitride (hBN) has received significant interest due to its excellent electrical performance and physics phenomena, such as superlattice Dirac points. Direct molecular beam epitaxy growth of graphene on hBN offers an alternative fabrication route for hBN/graphene devices. Here, we investigate the electronic transport of moiré field effect transistors (FETs) in which the conducting channel is monolayer graphene grown on hexagonal boron nitride by high temperature molecular beam epitaxy (HT-MBE). Alignment between hBN and HT-MBE graphene crystal lattices gives rise to a moiré-fringed hexagonal superlattice pattern. Its electronic band structure takes the form of a “Hofstadter butterfly”. When a strong magnetic field B is applied perpendicular to the graphene layer, the electrical conductance displays magneto-oscillations, periodic in B−1, over a wide range of gate voltages and temperatures up to 350 K. We attribute this behaviour to the quantisation of electronic charge and magnetic flux within each unit cell of the superlattice, which gives rise to so-called Brown-Zak oscillations, previously reported only in high-mobility exfoliated graphene. Thus, this HT-MBE graphene/hBN heterostructure provides a platform for observation of room temperature quantum effects and device applications.

Quantifying the High Early Solar Cosmic-Ray Flux with Cosmogenic Neon Isotopes in Refractory Minerals

An enhancement in the activity of the early young Sun resulting in a high charged particle flux has been invoked to explain excesses in spallation-induced nuclides in primitive planetary materials. Astronomical observations of energetic outbursts of young stellar objects (YSOs) also support the idea of an active young Sun. However, the early solar cosmic-ray (SCR) flux has not been well constrained. Here we use measured concentrations of SCR-produced nuclides that formed and are preserved in meteoritical hibonite and spinel, some of the solar system’s oldest solids, and physical models for dust transport in the early protoplanetary disk to determine the magnitude of the early SCR flux. We focus our attention on cosmogenic neon, which cannot have been inherited from precursors and can only be produced in situ in solids. Our modeled effective exposure time to SCRs for these solids is very short, on the order of years. This indicates that the young Sun’s SCR flux recorded in refractory mineral hibonite was up to ∼7 orders of magnitude higher than the contemporary level. Our flux estimate is consistent with the >105× enhanced flux inferred from astronomical observations of greatly enhanced flare activities of YSOs.

Photoluminescence Tuning of Stable CaYGaO4: Bi/Eu via Compositional Modulation and Crystallographic Site Engineering for nUV wLEDs.

The olivine-based gallate CaYGaO4 (CYG) with unique cationic ordering, rich lattice sites, and self-photoluminescence (PL) is suitable for application as a host of phosphor. However, research in this area is still in its early stages, especially in high-quality full-spectrum white lighting. Herein, novel CYG: Bi3+/Eu3+ with a controllable PL property is designed based on energy transfer and superposition of emissions from blue self-PL, blue PL of Bi3+, and red-PL of Eu3+. Intriguingly, PL intensity and quantum efficiency could be enhanced via codoping Li+/Zn2+ separately/simultaneously because of their two intentional functions as both charge balancer and flux. Unlike self- and Eu3+ PL, Bi3+ PL is quite sensitive to the lattice environment owing to its exposed 6s2 electronic configuration and is tuned via codoping Sr2+ to regulate the nephelauxetic effect and crystal field splitting concurrently around Bi3+. Meanwhile, for further regulating the PL of Bi3+ and obtaining "warm" white light, La3+ is codoped into the phosphor via crystallographic site engineering to control the substitution trends of Bi3+ at distinct lattice sites. Finally, as a proof-of-concept, a full-spectrum phosphor-converted white-light-emitting diode device under nUV pumping with remarkable color rendering index (Ra), high luminous efficiency, and chemical/thermal stability is achieved by utilizing the individual CYG:Bi/Eu/Li/Zn/Sr/La phosphor via a remote "capping" packaging method.

Intercalation of GO-Ag nanoparticles in cellulose acetate nanofiltration mixed matrix membrane for efficient removal of chromium and cobalt ions from wastewater

Cellulose acetate (CA)/Polyethylene glycol (PEG) blended composite nanofiltration (NF) membrane encompassing graphene oxide-silver (GO-Ag) nanoparticles (NPs) has been successfully synthesized by dissolution casting techniques. The effect of different NP loadings on membrane morphology, surface roughness, hydrophilicity surface charge and permeation flux were evaluated. Owing to Donnon exclusion, steric hindrance, and solution diffusion mechanism, the synthesized modified membranes exhibited excellent rejection rates in the order of Co (II) (99 %) > Cr (VI) (91 %). Furthermore, pure water flux (PWF) of the modified membrane was obtained 660.56 L/m2h which is 78.45 % greater than pristine membrane. Due to its high surface hydrophilicity, surface roughness, and porosity, modified membrane exhibited good antifouling characteristics. The results indicated that the intercalation of GO-Ag NPs with a loading ratio of 0.8 wt% leads to the optimum membrane for Cr (VI) and Co (II) removal. The present work demonstrates the potential application of GO-Ag/CA modified NF mixed matrix membrane for serving as a promising platform for eliminating heavy metal ions in wastewater.

Transient nonlocal heat flux in simple metals at low excitations

In this paper we discuss the ultrafast transfer of charge and energy in a metal in the kinetic approximation. An exact solution of the Boltzmann transport equation for the electron distribution function in the relaxation time approximation is obtained, which is used to calculate transport coefficients for charge and heat fluxes. Different regimes of energy transfer under conditions of significant spatial dispersion and non-equilibrity of the electron distribution function are discussed.

Recent Functionalized Strategies of Metal-Organic Frameworks for Anode Protection of Aqueous Zinc-Ion Battery.

The inherent benefits of aqueous Zn-ion batteries (ZIBs), such as environmental friendliness, affordability, and high theoretical capacity, render them promising candidates for energy storage systems. Nevertheless, the Zn anodes of ZIBs encounter severe challenges, including dendrite formation, hydrogen evolution reaction, corrosion, and surface passivation. These would result in the infeasibility of ZIBs in practical situations. To this end, artificial interfaces with functionalized materials are crafted to protect the Zn anode. They have the capability to modulate the zinc ion flux in proximity to the electrode surface and shield it from aqueous electrolytes by leveraging either size effects or charge effects. Considering metal-organic frameworks (MOFs) with tunable pore size, chemical composition, and stable framework structures, they have emerged as effective materials for building artificial interfaces, prolonging the lifespan, and improving the unitization of Zn anode. In this review, the contributions of MOFs for protecting Zn anode, which mainly involves facilitating homogeneous nucleation, manipulating selective deposition, regulating ion and charge flux, accelerating Zn desolvation, and shielding against free water and anions are comprehensively summarized. Importantly, the future research trajectories of MOFs for the protection of the Zn anode are underscored, which may propose new perspectives on the practical Zn anode and endow the MOFs with high-value applications.

Microbursts of the UV atmospheric emission in the auroral zone

In this paper we present data on the UV-microburst (300–400 nm flashes with a duration less than 1 s) measurements in the auroral zone. Measurements were performed during the period 09.2021–04.2022 by the highly sensitive imaging photometer installed at the Verkhnetulomsky observatory of the Polar Geophysical Institute. It is shown that microbursts are grouped in a series with a duration from 10 s to 10 min. They were observed in relatively quiet geomagnetic conditions (KP < 3) at the southern boundary of the auroral oval in the evening magnetic local time (MLT) sector. UV-microbursts are observed in different observational conditions (clouds, transparent clouds and clear sky) and spatially represent various patterns: uniform diffuse illumination, local spots. Joint analyses of the optical measurements and satellite data on charged particle fluxes demonstrates that an auroral oval, characterized by a plasma, is placed to the north of the observatory. At the same time increased flux of electrons with energy more than 100 keV is observed at the same L-shell and MLT sector. The possible origin of the UV-microbursts is a precipitation of energetic electrons from a poleward boundary of the outer radiation belt in a form of relativistic electron microbursts is discussed.

Modeling of the Hydrogen Bond-Induced Frequency Shifts of the HOH and HOD Bending Modes of Water.

The intramolecular bending mode of water is a possible useful probe of the hydrogen-bond situations in aqueous systems, but the behavior of its frequency and intensity should be further elucidated for better understanding on its nature and, hence, for its better utilization as a probe. Here, an analysis toward this goal is conducted by doing theoretical calculations on molecular clusters of normal isotopic and deuterated species of water and examining the correlations among the vibrational, structural, and electrostatic properties. It is shown that electrostatic interactions, particularly both of the in-plane components of the electric field along the OH bond and perpendicular to it, play a major role in controlling the hydrogen bond-induced shifts of the force constant, but additional factors, including the intermolecular structural and/or charge-transfer properties, are also important. Models of the hydrogen bond-induced shifts of the force constant are presented in a form that may be combined with classical molecular dynamics. With regard to the infrared intensity changes, it is shown on the basis of the electron density analysis that the intermolecular charge flux and polarization effect play an important role, depending on the angular characteristics of the hydrogen bond.

On the Dendrite‐Suppressing Effect of Laser‐Processed Polylactic Acid‐Derived Carbon Coated Zinc Anode in Aqueous Zinc Ion Batteries

AbstractA major bottleneck limiting the commercialization of aqueous zinc ion batteries (AZIBs) is dendrite formation on the zinc (Zn) anode during the plating/stripping process, which leads to rapid deterioration in performance and, consequently to the device failure. In this regard, researchers are trying to design more stable anodes toward suppressing dendrite formation. One possible solution to tackle this problem and to extend the cycling life of AZIBs is to modify the zinc anode surface by coating carbonaceous materials, enabling more controlled charge flux and uniform ion distribution. This work reports sustainable and bio‐derived polylactic acid (PLA) as a coating layer on the zinc anode. Carbonizing this polymer under ambient conditions using a high‐power nanosecond laser forms a carbon‐coated zinc foil, which was directly utilized as the anode in aqueous zinc ion batteries. The fabricated laser‐processed PLA‐derived carbon‐coated zinc anode demonstrated an extended cycling life of almost 1600 hours, significantly outperforming the bare zinc anode. A full aqueous zinc ion battery assembled from as‐modified anode and as‐prepared V2O5 nanofibers as cathode was able to deliver a specific capacity of 238 mAh g−1 at 1.0 A g−1 with a capacity retention of 70 % after 1000 cycles.

On the Dendrite-Suppressing Effect of Laser-Processed Polylactic Acid-Derived Carbon Coated Zinc Anode in Aqueous Zinc Ion Batteries.

A major bottleneck limiting the commercialization of aqueous zinc ion batteries (AZIBs) is dendrite formation on the zinc (Zn) anode during the plating/stripping process, which leads to rapid deterioration in performance and, consequently to the device failure. In this regard, researchers are trying to design more stable anodes toward suppressing dendrite formation. One possible solution to tackle this problem and to extend the cycling life of AZIBs is to modify the zinc anode surface by coating carbonaceous materials, enabling more controlled charge flux and uniform ion distribution. This work reports sustainable and bio-derived polylactic acid (PLA) as a coating layer on the zinc anode. Carbonizing this polymer under ambient conditions using a high-power nanosecond laser forms a carbon-coated zinc foil, which was directly utilized as the anode in aqueous zinc ion batteries. The fabricated laser-processed PLA-derived carbon-coated zinc anode demonstrated an extended cycling life of almost 1600 hours, significantly outperforming the bare zinc anode. A full aqueous zinc ion battery assembled from as-modified anode and as-prepared V2O5 nanofibers as cathode was able to deliver a specific capacity of 238 mAh g-1 at 1.0 A g-1 with a capacity retention of 70 % after 1000 cycles.

Observations of GRB 221009A by the MAVEN-SEP Instrument at Mars

We report on the detection of the Brightest Of All Time (the BOAT) gamma-ray burst (GRB) 221009A by the MAVEN Solar Energetic Particle (SEP) silicon (Si) detectors. The SEP instrument on board the MAVEN spacecraft at Mars is designed to measure charged particle fluxes and energies. In this work, we show that the SEP Si detectors have detected populations of secondary charged particles and low-energy primary photons from the GRB. Our analysis relies on a series of simplified Geant4 Monte Carlo simulations. We show that electromagnetic and hadronic interactions between the GRB photons and the spacecraft’s passive material and Si detectors produced the detected secondary particles.

Magnetic enhancement of the electrical asymmetry effect in capacitively coupled plasmas

The development of real-time control strategies for key discharge parameters, such as densities, fluxes, and energy distributions, is of fundamental interest to many plasma sources. Over the last decade, multi-harmonic ‘tailored’ voltage waveforms have been successfully employed to achieve enhanced control of key parameters in a wide range of radio-frequency (RF) plasma sources through application of the electrical asymmetry effect (EAE). More recently, the analogous magnetic asymmetry effect (MAE) has been numerically and experimentally demonstrated to achieve a notable degree of control in parallel plate RF plasma sources. The MAE is achieved via selectively magnetising the charged species adjacent to one electrode, altering the charge flux to the surface and enforcing a DC self-bias to maintain quasineutrality. This study addresses the degree of control achieved by the MAE in a non-planar geometry via 2D fluid/kinetic simulations of a magnetised RF capacitively coupled plasma source employing two different magnetic topologies. The simultaneous application of the EAE and MAE is then presented for the same geometry, demonstrating a degree of non-linear behaviour dependant upon the applied magnetic topology. Control of the DC self-bias voltage ηdc is demonstrated for a single 600 Vpp , 13.56 MHz discharge in both ‘convergent’ (maximum on-axis field strength) and ‘divergent’ (minimum on-axis field strength) magnetic topolgies. MAE induced modulations of ηdc = 0.13 Vpp and ηdc = 0.03 Vpp are achieved for each magnetic topology, respectively, for magnetic field strengths between 50 and 1000 G. Simultaneous application of an EAE and MAE is achieved through a multi-harmonic ‘peak’-type tailored voltage waveform employing varying harmonic phase offsets between 0∘ ⩽ θ ⩽ 360∘ . The degree to which the DC self-bias voltage is modulated by the applied EAE is mediated by the orientation and magnitude of the applied magnetic field. The EAE induced DC self-bias modulations exhibit non-linear behaviour in response to a superimposed MAE, such that the resulting DC self-bias differs from an additive combination of the two effects alone Simultaneous application of the electrical and MAEs offers the possibility of further decoupling ion and electron dynamics in RF plasma sources, and represents an improvement over each approach in isolation.

A finite-element method model for a ferromanganese and silicomanganese pilot furnace

We report on the development of a finite-element method model for a pilot furnace for the production of manganese alloys. The model is a multiphysics model that addresses material flow, electrical conditions, heat transfer, and physical and chemical transformations. It is capable of studying both quasi-steady and transient states in time-dependent simulations. The model includes common charge materials and fluxes and can simulate production of both ferromanganese and silicomanganese alloys with acid and basic slags, as well as changing charge compositions. The model output provides access to the material distribution in the furnace during furnace runs, temperature profiles, current paths, energy balances, and alloy and slag production rates and compositions.

Three Puzzles with Covariance and Supertranslation Invariance of Angular Momentum Flux and Their Solutions.

We describe and solve three puzzles arising in covariant and supertranslation-invariant formulas for the flux of angular momentum and other Lorentz charges in asymptotically flat spacetimes: (i)Supertranslation invariance and covariance imply invariance under spacetime translations; (ii)the flux depends on redundant auxiliary degrees of freedom that cannot be set to zero in all Lorentz frames without breaking Lorentz covariance; (iii)supertranslation-invariant Lorentz charges do not generate the transformations of the Bondi mass aspect implied by the isometries of the asymptotic metric. In this Letter, we solve the first two puzzles by presenting covariant formulas that unambiguously determine the auxiliary degrees of freedom and clarify the last puzzle by explaining the different roles played by covariant and canonical charges. Our construction makes explicit the choice of reference frame underpinning seemingly unambiguous results presented in the current literature.

Flux correlators and semiclassics

We consider correlators for the flux of energy and charge in the background of operators with large global U(1) charge in conformal field theory (CFT). It has recently been shown that the corresponding Euclidean correlators generically admit a semiclassical description in terms of the effective field theory (EFT) for a conformal superfluid. We adapt the semiclassical description to Lorentzian observables and compute the leading large charge behavior of the flux correlators in general U(1) symmetric CFTs. We discuss the regime of validity of the large charge EFT for these Lorentzian observables and the subtleties in extending the EFT approach to subleading corrections. We also consider the Wilson-Fisher fixed point in d = 4 − ϵ dimensions, which offers a specific weakly coupled realization of the general setup, where the subleading corrections can be systematically computed without relying on an EFT.

A Charge-Charge Flux-Dipole Flux Analysis of Simple Molecular Systems with Halogen Bonds.

The presence of halogen bonds (R-X···B; R = substituent group, X = halogen, and B = Lewis base) provides quite amazing molecular systems for electronic structure investigations, presenting unique characteristics of fundamental relevance to supramolecular chemistry among other areas. Here, we use a double-hybrid approach from Density Functional Theory and triple-ζ basis sets augmented with diffuse functions (B2PLYP/def2-TZVPD) to deal with a large group of simple molecular systems containing halogen bonds (XBs), focusing on geometrical structures, binding energies, harmonic vibrational frequencies, and fundamental infrared intensities. Next, the electron densities and their variations on vibrations are carefully studied with the Quantum Theory of Atoms in Molecules (QTAIM) formalism and the charge-charge flux-dipole flux (CCFDF) model. We notice that the R-X stretching mode usually shows vibrational frequency decrements and infrared intensifications during the XB formation. Such features were also observed in hydrogen bonds, although the explanation for the band strengthening is different. Surprisingly, the most important contribution to these intensity increments due to complexation is now the interaction term between the charge flux and dipole flux (CF × DF). Thus, the use of atomic dipoles is mandatory to fully understand this phenomenon. In fact, the huge charge flux contributions to changes in dipole moment derivatives of R-X stretchings on halogen bonding are no longer accompanied by opposite variations of similar magnitudes in polarizations described by atomic dipole fluxes, which provided nearly unaltered values during the XB formation. Thus, the electronic charge flux direction change that takes place in complexes (from B to R) now reinforces dipole moment derivative terms from such atomic polarizations (mainly from the X atom). This intermolecular charge flux seems to be responsible for the unusual features noticed in the R-X stretching mode with the CCDDF/QTAIM model.

A comprehensive review of different electric motors for electric vehicles application

Electric vehicles (EVs) offer several advantages over internal combustion engines (ICE), including high energy efficiency, noise reduction, low maintenance, and a wider speed range. This results in lower fuel consumption, reducing dependency on oil imports and enhancing energy security. The motor drive is a critical component of EVs, providing the necessary propulsion force. This paper presents a comprehensive comparison of state-of-the-art motors suitable for EV applications, including DC motors, induction motors (IM), brushless DC motors (BLDC), permanent magnet synchronous motors (PMSM), and switched reluctance motors (SRM). Various design aspects relevant to traction applications, such as cost, reliability, efficiency, torque, fault-tolerance ability, excitation arrangements, and power density are also addressed. The performance of an EV based on the SRM drive is analyzed using MATLAB Simulink, with a special focus on parameters like speed, torque, flux, and state of charge (SOC). The review highlights that SRM drives have significant potential in EVs due to their reliable structure, fault tolerance capability, and magnet-free design. However, their application in EVs is currently limited due to torque ripples, as evident from the simulations. This paper is expected to serve as a foundation for further enhancing the performance of SRM drives for EV applications.

An Expansion of Polarization Control Using Semiconductor-Liquid Junctions.

This report examines the concept of independent control over current and applied potential in electrocatalysis, as a means of improving control over product selectivity. Previous work, while permitting separate modulation of current and potentiostat bias, precluded independent control over the current flow and applied cell potential. This study seeks to resolve that limitation by exploiting the Schottky diode behavior inherent to semiconductor-electrolyte interfaces. Light is explored as a prospective second degree of freedom for controlling polarization in a suitably designed, photoelectrochemical (PEC) device, enabling the arbitrary selection of current with respect to an applied cell potential. In contrast to metal electrodes, the property of light-dependent carrier concentrations in semiconductors forms the operative means of controlling charge fluxes at some arbitrary applied potential in PEC devices featuring a semiconductor-liquid junction. This functionality enables exploration of polarization states distinct from those accessible with a dark cell, with implications for improved control over electrochemical reactions.