Uniform Charge Research Articles

General formulation of Coulomb explosion dynamics of highly symmetric charge distributions

We present a theoretical approach to study the dynamics of spherical, cylindrical and ellipsoidal charge distributions under their self-Coulomb field and a stochastic force due to collisions and random motions of charged particles. The approach is based on finding the current density of the charge distribution from the charge-current continuity equation and determining the drift velocities of the particles. The latter can be used either to derive the Lagrangian of the system, or to write Newton’s equation of motion with the Lorentz force. We develop a kinetic theory to include the stochastic force due to random motions of electrons in our model. To demonstrate the efficacy of our method, we apply it to various charge distributions and compare our results to N-body simulations. We show that our method reproduces the well-known emittance term in the envelope equation of uniform spherical and cylindrical charge distributions with correct coefficients. We use our model for the gravitational collapse of an ideal gas as well as the cyclotron dynamics of a cylindrical charge distribution in a uniform magnetic field and propose a method to measure the emittance of electron beams.

Systematically-optimized charge transport properties in cumulatively solution-coated zinc tin oxide and applications for complementary inverter circuits combining organic p-type transistors

Zinc-tin-oxide (ZTO) is considered as a promising alternative thin-film semiconductors due to its merits of Earth-abundant materials, non-toxicity, and solution-processable low-cost manufacturing. However, there is still insufficient effort to implement a ZTO-based practical applications such as integrated circuits due to the lack of desirable switching behavior for circuit operation. In this context, we systematically investigate a solution processed ZTO film through a comprehensive analysis including scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission line method (TLM), and X-ray photoelectron spectroscopy (XPS). We also fabricate the synthesized ZTO-based transistors, and characteristics of the transistors are evaluated depending on annealing temperature and number of coatings. Through the systematic investigation, this study obtains the suitable turn-on voltage of V TO = 0.15 V as well as uniform charge transport property of 2.14 cm 2 /V∙s ± 5.14%. Furthermore, we apply the ZTO transistor optimized for the circuit to the complementary inverter logic, and the measured inverter circuit provides an excellent voltage gain of 141.18 V/V and improved noise margin as high as 71.4% of half the supply voltage. • ZTO films were characterized by scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. • Thickness-dependent ZTO TFT characteristics were investigated. • Morphological and chemical composition variations by annealing temperature were studied. • A complementary inverter using ZTO, DNTT TFTs with a voltage gain of 141.18 V/V and a noise margin of 71.4% was demonstrated.

Scaling Challenges in High Power Photonic Crystal Surface-Emitting Lasers

Since the initial proposal in 1999 by Noda <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> , photonic crystal surface emitting lasers (PCSELs) have shown to achieve large area, coherent lasing with a narrow, single mode beam. Owing to their unique orthogonal electrical/optical cavity scheme, PCSELs have emerged as one of the most promising platforms for high power diode lasers. In this paper, we report the performance trade-offs and challenges in power scaling, modal competition, and charge injection control. To address these challenges, we investigate the electrical and optical performances of PCSELs under high-power operation. Heterostructure designs with electron block layers were incorporated for efficient and balanced electrical charge injection. Symmetry breaking strategy was introduced in the photonic crystal design to engineer the in-plane momentum dependent quality factor (Q(k)) for mode discrimination and single mode operation. The impact of electrode designs was also investigated to achieve large area uniform charge injection. Simulation results of these designs indicate promising solutions and improved performances for large-area high-power and single-mode PCSEL operations.

Effect of exchange-correlation functionals on the estimation of migration barriers in battery materials

Facile ionic mobility within host frameworks is crucial to the design of high-energy-density batteries with high-power-densities, where the migration barrier (Em) is the governing factor. Here, we assess the accuracy and computational performance of generalized gradient approximation (GGA), the strongly constrained and appropriately normed (SCAN), and their Hubbard U corrections, GGA+U and SCAN+U, within the density functional theory-nudged elastic band framework, in the prediction of Em as benchmarked against experimental data. Importantly, we observe SCAN to be more accurate than other frameworks, on average, albeit with higher computational costs and convergence difficulties, while GGA is a feasible choice for “quick” and “qualitative” Em predictions. Further, we quantify the sensitivity of Em with adding uniform background charge and/or the climbing image approximation in solid electrolytes, and the Hubbard U correction in electrodes. Our findings will improve the quality of Em predictions which will enable identifying better materials for energy storage applications.

Integrals of Legendre polynomials over half range and their relation to the electrostatic potential in hemispherical geometry

Spherical symmetry is often encountered in many problems in mathematics and physical sciences. On the other hand, cases that involve hemispherical geometry lead to much less studied mathematical situations. In this work, we consider a case study that arises from potential theory where absence of a full spherical symmetry gives rise to expressions involving Legendre polynomials constrained in an interval that is different from the usual range in which they are orthogonal. We use exact mathematical results for the integrals of Legendre polynomials of arbitrary order over half range to obtain analytic expressions for the electrostatic potential created by a solid hemisphere with uniform volume charge density.

Highly efficient separation of benzene + cyclohexane mixtures by extraction combined extractive distillation using imidazolium-based dicationic ionic liquids

Benzene (BEN) and cyclohexane (CYH), which have very close boiling points and a binary azeotrope, are the most difficult binary components in the separation of aromatic and non-aromatic hydrocarbons. This study further explored the separation mechanism and industrial application prospects of BEN ​+ ​CYH mixtures separated by a dicationic ionic liquid (DIL) [C5(MIM)2][NTf2]2 based on experimental research. The calculation results of the Conductor-like Screening model Segment Activity Coefficient (COSMO-SAC) model show that selectivity and solvent capacity of the DIL are significantly improved. The effects of different anions and cations on the microstructure distribution and diffusion behavior of BEN ​+ ​CYH system were investigated by quantum chemistry (QC) calculations and molecular dynamics (MD) simulations. The results indicate that the anion [NTf2]− has low polarity, uniform charge distribution, and a dual role of hydrogen bonding and π-π bonding, and the cation [C5(MIM)2]2+ has stronger interaction with BEN and higher selectivity than conventional cations. The liquid-liquid extraction and extractive distillation (LLE-ED) process using an optimized 65 mol/mol DIL ​+ ​35 mol/mol H2O mixed solution as the extractant was proposed, which solved the problem of low product purity in the LLE process and high energy consumption in the ED process. Under the best operating conditions, the purity of CYH product was 99.9%, the purity of BEN product was 99.6%, the recovery rate of BEN reached 99.9%, and the recovery rate of DIL reached 99.9%. The heat-integrated LLE-ED process reduced total annual cost by 21.6%, and reduced CO2 emissions by 48.0%, which has broad industrial application prospects.

Effects of Electrostatic Interactions on Kapitza Resistance in Hexagonal Boron Nitride–Water Interfaces

Electrostatic interactions in nanoscale systems can influence the heat transfer mechanism and interfacial properties. This study uses molecular dynamics simulations to investigate the impact of various electrostatic interactions on the Kapitza resistance (Rk) on a hexagonal boron nitride-water system. The Kapitza resistance at hexagonal boron nitride nanotube (hBNNT)-water interface reduces with an increase in diameter of the nanotube due to more aggregation of water molecules per unit surface area. An increase in the partial charges on boron and nitride caused the reduction in Rk. With the increase in partial charge, a better hydrogen bonding between hBNNT and water was observed, whereas the structure and order of the water molecules remain the same. Nevertheless, the addition of NaCl salt into water does not have any influence on interfacial thermal transport. Rk remains unchanged with electrolyte concentration because the cumulative Coulombic interaction between the ions and the hBNNT is significantly less when compared with water molecules. Furthermore, the effect of electric field strength on interfacial heat transfer is also investigated by providing uniform positive and negative surface charges on the outermost hBN layers. Rk is nearly independent of the practical range of applied electric fields and decreases with an increasing electric field for extreme field strengths until the electrofreezing phenomenon occurs. The ordering of water molecules toward the charged surface leads to an increase in the layering effect, causing the reduction in Rk in the presence of an electric field.

Thermodynamic and dynamical signatures of a quantum spin Hall insulator to superconductor transition

Thermodynamic and dynamical properties of a model of Dirac fermions with a deconfined quantum critical point (DQCP) separating an interaction-generated quantum spin-Hall insulator from an s-wave superconductor [Nature Comm.~{\bf 10}, 2658 (2019)] are studied by quantum Monte Carlo simulations. Inside the deconfined quantum critical region bound by the single-particle gap, spinons and spinless charge-2e skyrmions emerge. Since the model conserves total spin and charge, and has a single length scale, these excitations lead to a characteristic linear temperature dependence of the uniform spin and charge susceptibilities. At the DQCP, the order parameter dynamic structure factors show remarkable similarities that support emergent Lorentz symmetry. Above a critical temperature, superconductivity is destroyed by the proliferation of spin-1/2 vortices.

Pricing regime choices for international airports: A rationale for the non-discrimination principle

This study investigates whether airports should be prohibited from charging differential charges to airlines. Two countries’ (publicly owned) airports and airlines interlink, and passengers travel round-trips. Each country may choose pricing regimes (uniform versus discriminatory charges) and charge levels, sequentially or simultaneously, to maximize local welfare. Surprisingly, we find that each country choosing uniform charges achieves unique equilibrium in the sequential game, in which countries may commit to a particular pricing regime before setting charge levels. However, in the simultaneous game without the commitment effect, each country choosing discriminatory charges achieves the unique equilibrium. The total welfare achieved under the former equilibrium is larger than (equal to) that under the latter for asymmetric (symmetric) airline competition. These findings provide the economic rationale for the prevalent non-discriminatory principles for international airports from a local and global welfare perspective.

Fabrication of positively charged nanofiltration membrane with uniform charge distribution by reversed interfacial polymerization for Mg2+/Li+ separation

Nanofiltration is considered a promising technology for separation of multivalent/monovalent ions such as extracting lithium from Salt Lake brine with high Mg2+/Li+ ratio. However, the nanofiltration membranes fabricated via conventional interfacial polymerization process generally possess negatively charged surface and have low Mg2+/Li+ selectivity. Herein, we proposed a new and facile method, i.e., reversed interfacial polymerization (RIP), to prepare nanofiltration membranes with positively charged surface and uniform charge distribution. The sequence of amine (polyethyleneimine, PEI) and acyl chloride (trimesoyl chloride, TMC) monomers on polysulfone support was reversed compared to the conventional interfacial polymerization (IP) process. Moreover, the solvent of amine monomer was acetone instead of water. The nanofiltration membranes fabricated by this method exhibited higher water flux (from 4.88 to 22.25 Lm−2h−1) and MgCl2 rejection (from 84.36% to 97.71%). Meanwhile, LiCl/MgCl2 separation factor in single salt solution reached up to 13.93, which was almost quadruple compared to the conventional control membrane. In addition, the developed nanofiltration membrane also exhibited an excellent separation selectivity (SLi, Mg = 9.22) in mixture system (Mg2+/Li+ mass ratio of 20), which had good application potential in extracting lithium resources from Salt Lake brine.

Motion of a charged particle in the static fields of an infinite straight wire

The nonrelativistic trajectory of a point charge q in the magnetic field of a steady line current I is characterized by the three components of its initial velocity. The motion is periodic in the cylindrical coordinates s, ϕ̇, and ż, describing, in the generic case, a kind of “double helix,” with one helix serving as a guide while the other winds around it. A positive charge “drifts” in the direction of the current (a negative charge goes the other way). The inclusion of a uniform line charge λ (coinciding with the current) does not alter the motion qualitatively, but it does change the drift velocity, and can even reduce it to zero, collapsing the trajectory to the surface of a toroid. The relativistic treatment modifies and illuminates these results.

Modeling and optimization of a rotational symmetric spherical triboelectric generator

Triboelectric nanogenerators (TENGs) are superb candidates to harvest low-frequency energy from water waves, wind, and ambient vibrations. They consist of triboelectrically-charged dielectric materials in relative motion and have been realized experimentally in several configurations and geometries. In this work, we provide a detailed mathematical analysis and fast computational method for designing spherical TENG devices to realize optimal performance. The method provides a self-consistent analysis to determine the charge distribution on spherical electrodes in compliance with the physical constraint of uniform potentials over the electrode surfaces. It is shown that the difference between the assumptions of a uniform potential vs. uniform charge density on electrodes for spherical TENG model parameters increases with the spatial dimensions of the electrodes relative to other characteristic dimensions of the TENG. For typical spherical TENGs the difference in harvested energy can be several percentages. A major benefit of the present model of a spherical TENG is its applicability to design large TENG network systems for which 3D methods, such as the finite element method, are computationally far too demanding.

Construction of multistage porous carbon materials for the hydrochlorination of acetylene: Impact of nitrogen incorporation

The benchmark carbon-based catalyst, activated carbon (AC), has a low catalytic activity due to its uniform surface charge distribution and stable structure. To overcome these problems, melamine-phenol-formaldehyde (MPF) resin, which is rich in pyridinic N and pyrrolic N, multi-porous C-N materials rich with defect sites were synthesized in situ by heat treatment using silica sol as the template and phenol, melamine, and formaldehyde as the carbon and nitrogen sources. The experimental results and characterization techniques revealed that carbon materials with abundant hierarchical pores and local C-N active sites were constructed by incorporating heteroatom-containing groups. Hydrogen chloride and acetylene molecules were activated due to the high electronegativity of defective sites, and the synergistic interactions between pyridinic N and π-containing functional groups (C=C, triazine ring, etc.). The structure-performance relationship was also clarified using DFT calculations. In addition, the strong interactions between heteroatomic sites and metal species also made MPF-800 an admirable metal catalyst support. Overall, the disadvantages of acetylene hydrochlorination catalyzed by benchmark AC were resolved.

On the Critical Conditions for Realization of Instability of Azimuthal Modes of Conducting Liquid Jets Carrying Uniform and Nonuniform Induced Surface Charges and Their Electrodispersion

On the Critical Conditions for Realization of Instability of Azimuthal Modes of Conducting Liquid Jets Carrying Uniform and Nonuniform Induced Surface Charges and Their Electrodispersion

Magnetic N-doped partially graphitized carbon-loaded Pd-Co alloy nanoparticles for efficient hydrogen production

Liquid organic hydrogen carriers (LOHCs) are generally recognized as an important form of hydrogen storage. The low hydrogen release rate and high hydrogen release temperature limit the application of LOHCs. The PdCo alloy nanoparticles (NPs) loaded on magnetic N-doped partially graphitized carbon (PdCo/NGC) were prepared in an environmentally friendly manner by N2 glow discharge plasma method. Porous support carbon is prepared by calcining Zeolitic Imidazolate Frameworks-67 (ZIF-67) at 800 °C, which is not only magnetic but also N-doped and partially graphitized. PdCo NPs are uniformly dispersed on NGC with an average particle size of 4.0 nm. The plasma reduction method can effectively prevent the agglomeration of PdCo alloy NPs, which is an important guarantee for the small particle size of PdCo NPs. The uniform dispersion effect and charge transfer effect produced by the alloy structure of PdCo NPs improve the catalytic activity. PdCo/NGC shows excellent catalytic performance for dodecahydro-N-ethylcarbazole (H12-NEC) dehydrogenation. The complete conversion of H12-NEC is achieved at 180 °C for 6 h, the selectivity of N-ethylcarbazole is 97.87% and the dehydrogenation efficiency is as high as 98.79%. PdCo/NGC catalysts with a saturation magnetization of 25 emug−1 at room temperature can be effectively recovered under the action of an external magnetic field. They show superior catalytic stability, in which the dehydrogenation efficiency can still reach 93.60% after six cycles.

Probing the Contribution of Lateral Pathways to Out‐of‐Plane Charge Transport in Organic Bulk Heterojunctions

AbstractThe nanoscale interpenetrating electron donor–acceptor network in organic bulk heterojunction (BHJ) solar cells results in efficient charge photogeneration but creates complex 3D pathways for charge transport. At present, little is known about the extent to which out‐of‐plane charge flow relies on lateral electrical connectivity. In this work, a procedure, based on conductive atomic force microscopy, is introduced to quantify lateral current spreading during out‐of‐plane charge transport. Using the developed approach, the dependence of lateral spreading on BHJ phase separation, composition, and molecule type (small molecule vs polymer) is studied. In the small‐molecule BHJ, 7,7′‐(4,4‐bis(2‐ethylhexyl)‐4H‐silolo[3,2‐b:4,5‐b′]dithiophene‐2,6‐diyl)bis(6‐fluoro‐4‐(5′‐hexyl‐[2,2′‐bithiophen]‐5‐yl)benzo[c]‐[1,2,5]thiadiazole):(6,6)‐Phenyl‐C71‐butyric acid methyl ester (p‐DTS(FBTTh2)2:PC71BM), an increase is observed in lateral hole current spreading as the population of donor crystallites, bearing an edge‐on molecular orientation, is increased. When integrated into BHJs, the polymer donor poly(3‐hexylthiophene‐2,5‐diyl) (P3HT) leads to greater lateral hole current spreading and more spatially uniform charge transport than the small‐molecule donor, owing to in‐plane charge transport along the polymer backbone. Through the newly introduced electrical characterization scheme, these experiments bring to light the role of lateral electrical connectivity in assisting charge navigation across BHJs.

Overcoming the Low‐Surface‐Energy‐Induced Wettability Problem of Flexible and Transparent Electrodes for Large‐Area Organic Photovoltaic Modules over 500 cm2

AbstractTo realize the commercialization of nonfullerene acceptor‐based efficient organic solar cells, a low‐cost and indium‐tin‐oxide‐free (ITO‐free) flexible electrode‐based module that can be produced by roll‐to‐roll production should be developed. However, the low surface energy of ITO‐free electrodes hinders the formation of a uniform charge transport layer through solution processing; this is the main cause of the efficiency drop. Herein, the realization of a highly uniform ZnO bilayer on an ultrathin Ag film‐based transparent electrode that is suitable for flexible substrates and large‐area organic photovoltaic (OPV) module fabrication is demonstrated. Based on the sputtered ZnO and blade‐coated ZnO nanoparticle‐based electron transport bilayer, large OPV module areas of 528.5 and 108 cm2 with high efficiencies of 7.67% and 9.15%, respectively, are achieved.

An Energy Storage System Composed of Photovoltaic Arrays and Batteries with Uniform Charge/Discharge

The main purpose of this study was to develop a photovoltaic module array (PVMA) and an energy storage system (ESS) with charging and discharging control for batteries to apply in grid power supply regulation of high proportions of renewable energy. To control the flow of energy at the DC load and charge/discharge the battery uniformly, this work adapted a bidirectional buck–boost soft-switching converter and the maximum power point tracking (MPPT) technique of the photovoltaic module array. First, a boost converter is used with the perturb and observe (P&amp;O) method, so that the photovoltaic module array can work at the maximum power point (MPP) at any time. When the output power of the photovoltaic module array is greater than the load power, the excess power is used to charge the battery; on the contrary, if the output power of the photovoltaic module array is lower than the load power, the battery discharges for auxiliary power supply. This makes the voltage of the DC link maintain a constant value. The monitoring circuit sends the voltage and current signals to the TMS320F2809 digital signal processor (DSP) produced by Texas Instruments to control the battery charging/discharging voltage and current. The photovoltaic module array works at the MPP to improve the performance of the overall energy storage system. Finally, the actual test result shows that the soft-switching converter used in this work, when compared to the hard-switching converter, can improve efficiency by nearly 4% when the load power is above 125 W. When the photovoltaic power generation system operation is between 150 W and 400 W, the proposed uniform charging and discharging architecture can rapidly reach uniformity.

Self-Organized Space Charge Structure Formations in DC Glow Discharge

Experimental investigations of a hollow cathode discharge through the controlled variation of anode potential inside a hollow cylindrical cavity, in the absence and presence of the magnetic field, reveal the self-organization of uniform complex space charge structure formation around the spherical anode into concentrated localized anode spots. The discharge current&#x2013;voltage (<inline-formula> <tex-math notation="LaTeX">$I$ </tex-math></inline-formula>&#x2013;<inline-formula> <tex-math notation="LaTeX">$V$ </tex-math></inline-formula>) characteristic along with the electrostatic floating potential and discharge current fluctuations measured during the glow discharge regime suggest that the initial stable multiple sheath formation around the anode dissociates into intermittent multiple localized anode spot formations while passing through transient states during anode potential variation. On introducing a magnetic field, the localized concentrated anode spot formations on the anode surface undergo random distribution through self-organized criticality (SOC) and pronounced low-frequency oscillations (&#x007E;52.4 kHz). These oscillations gradually develop into harmonics of 100 kHz on further increasing the anode potential in the presence of the external magnetic field. Various discharge regimes are investigated through the time-resolved floating potential variation measurements using a cylindrical Langmuir probe (LP). We report on the relation between the discharge variations with the nonlinear time series analysis of the discharge current and floating potential fluctuations through the reconstructed phase space in different time domains to analyze the dynamics of complex structure formations and the existence of SOC behavior during the present hollow cathode discharge regime. The study of self-organized pattern formations and SOC behavior is vital for understanding the complex behavior of plasmas in the field of strongly coupled plasmas, plasma-based surface treatments, and thrusters for further development.

Radiation hardness and timing performance in MALTA monolithic pixel sensors in TowerJazz 180 nm

The MALTA family of depleted monolithic pixel sensors produced in TowerJazz 180 nm CMOS technology target radiation hard applications for the HL-LHC and beyond. Several process modifications and front-end improvements have resulted in radiation hardness >1015 1 MeV neq/cm2 and time resolution below 2 ns, with uniform charge collection and efficiency across the pixel of size 36.4 × 36.4 µm2 with small collection electrode. This contribution will present the comparison of samples produced on high-resistivity epitaxial silicon with Czochralski substrates, before and after neutron irradiation, and results from MALTA2 with a new cascoded front-end flavour that further reduces the RTS noise.