Charging Current Research Articles

Enhanced interlayer electron transfer by surface treatments in mixed-dimensional van der Waals semiconductor heterostructures

We investigate the excitonic species in WS2 monolayers transferred onto III–V semiconductor substrates with different surface treatments. When the III–V substrates were covered with amorphous native oxides, negatively charged excitons dominated the spectral weight in low-temperature near-resonance photoluminescence (PL) measurements. However, when the native oxides of the III–V substrates were reduced, neutral excitons began to dominate the spectral weight, indicating a reduction in the electron density in the WS2 monolayers. The removal of the native oxides enhanced the electron transfer from the WS2 monolayer to the III–V substrate. In addition, an additional shoulder-like PL feature appeared ∼50 meV below the emission of neutral excitons, which can be attributed to the emission of localized excitons. When the III–V substrate surface was passivated by sulfur after the reduction of the native oxides, neutral excitons still dominated the spectral weight. However, the low-energy PL shoulder disappeared again, suggesting the effective delocalization of excitons through substrate surface passivation. Surface engineering of the semiconductor substrates for two-dimensional (2D) materials can provide a novel approach to control the carrier density of the 2D materials, implement deterministic carrier localization or delocalization for the 2D materials, and facilitate the interlayer transfer of charge, spin, and valley currents. These findings open the avenue for novel device concepts and phenomena in mixed-dimensional semiconductor heterostructures.

Comparing costs and climate impacts of various electric vehicle charging systems across the United States

The seamless adoption of electric vehicles (EVs) in the United States necessitates the development of extensive and effective charging infrastructure. Various charging systems have been proposed, including Direct Current Fast Charging, Battery Swapping, and Dynamic Wireless Power Transfer. While many studies have evaluated the charging costs and greenhouse gas (GHG) intensity of EVs, a comprehensive analysis comparing these systems and their implications across vehicle categories remains unexplored. This study compares the total cost of ownership (TCO) and GHG-intensity of EVs using these charging systems. Based on nationwide infrastructure deployment simulations, the change to TCO from adopting EVs varies by scenario, vehicle category, and location, with local fuel prices, electricity prices, and traffic volumes dramatically impacting results. Further, EV GHG-intensity depends on local electricity mixes and infrastructure utilizations. This research highlights the responsiveness of EV benefits resulting from technology advancements, deployment decisions, and policymaking.

Analysis and Design of Wireless Charging Systems Without Extra Components for Load-Independent Constant Current and Voltage Battery Charging

Analysis and Design of Wireless Charging Systems Without Extra Components for Load-Independent Constant Current and Voltage Battery Charging

A Li-ion battery charger based on LDO regulator with pre-charge mode in 180 nm CMOS technology

This paper presents a novel Li-Ion battery charger that utilizes a low-dropout (LDO) regulator and incorporates four control modes: low constant current mode, pre-charge current mode, fast constant current mode, and constant voltage mode. The charger aims to meet specific criteria such as high precision, high efficiency, and small form factor. Through simulation results, the following specifications were obtained using a 1.8 V supply in a 0.18 μm complementary metal–oxide–semiconductor (CMOS) technology: a trickle current of 124.7 mA, a pre-charge current of 466.94 mA, a maximum charge current of 1.06 A, and a charge voltage of 4.21 V. The proposed charger demonstrates an efficiency of 92%.

Optimal Bivariate Control Strategy of Multistage Constant Current Charging for IPT-Based Wireless Electric Vehicle Charging

Optimal Bivariate Control Strategy of Multistage Constant Current Charging for IPT-Based Wireless Electric Vehicle Charging

Hybrid Topology with Reconfigurable Rectifier for Enable CC and CV Output Characteristics in Wireless Power Transfer Systems

To achieve simple and reliable conversion from constant current (CC) charging mode to constant voltage (CV) charging mode in wireless power transfer systems, this paper proposes a hybrid topology equipped with a reconfigurable rectifier. An AC switch is adapted to simultaneously realize the change from half-bridge rectification to full-bridge rectification and achieve the shift from a topology with capacitors in the series compensated primary and secondary sides to a topology with capacitors in the series compensated primary side and the inductor-capacitor-inductor (LCL) compensated secondary side. Notably, communication between the transmitter and receiver sides is not necessary in the proposed method. Furthermore, the zero phase angle characteristic is successfully maintained in both charging modes. The experimental results obtained using the 48 V/0.7 A experimental prototype, which was built to validate the relevant theoretical analysis, show that output current/voltage can be achieved in CC/CV charging mode independent of load resistance. Notably, the maximum power transfer efficiency of the system during the charging process reached 95.33%.

Study on space charge accumulation characteristics of silicone elastomer under DC voltage

AbstractThe electric field distortion caused by the accumulation of space charge in the insulating dielectric is easy to lead to accelerated ageing and even breakdown. In this paper, the space charge characteristics and the interfacial electric field change with time of silicone elastomer under different polarity DC voltages are studied. The results show that the homopolar charge injection is dominant in the silicone elastomer, and the electric field threshold is less than 4 kV/mm. The accumulation of homopolar charge weakens the interfacial electric field, resulting in the reduction of charge injection, and the interfacial electric field and spatial charge distribution gradually stabilise over time. In addition, the electric field at the interface does not decrease to the charge injection field threshold when it reaches stability. A time‐varying electric field model of the metal‐dielectric interface under a direct current field is derived and a calculation method for the time of charge accumulation to stabilise is proposed, based on the Schottky injection model and the relation between current density and volume charge density. The accuracy of the model is verified by comparing it with the experimental results of the stability time of silicone elastomer. This model is used to estimate the time when space charge accumulation reaches stability by means of the electric field threshold and the interface barrier, which can provide reference for the experimental measurement of space charge.

Indirect search of heavy neutral leptons using the DUNE near detector

We evaluate the potential of the DUNE near detector (DUNEND) for establishing bounds for heavy neutral leptons (HNLs). This is achieved by studying how the presence of HNLs affects the production rates of active neutrinos, therefore creating a deficit in the neutrino charged current (CC) events at the LArTPC of the DUNEND. The estimated bounds on HNLs are calculated for masses between 1 eV and 500 MeV. We consider 10 years of operation (five in neutrino and antineutrino modes) and obtain limits of |Uμ4|2 < 9 × 10−3 (4 × 10−2) and |Ue4|2 < 7 × 10−3 (3 × 10−2) for masses below 10 MeV and a 5% (20%) overall normalization uncertainty in the neutrino charged current event rate prediction. These limits, within the region of masses below 2 (10) MeV, are better than those that can be achieved by DUNE direct searches for the case of a 5% (20%) uncertainty. When a conservative 20% uncertainty is present, our limits can only improve current constraints on |Ue4|2 by up to a factor of 3 in a small region of approximately 5 eV and set limits on |Uμ4|2 in a mass region free of constraints (40 eV–1 MeV).

From Fundamental Interfacial Reaction Kinetics to Macroscopic Current–Voltage Characteristics: Case Study of Solid Acid Fuel Cell Limitations and Possibilities

AbstractThe unique properties of solid acid electrolytes, in particular CsH2PO4, are in many ways ideal for fuel cell operation. However, the technology is constrained by high cathode overpotentials. Here a simplified cathode geometry is employed to obtain the fundamental electrochemical parameters (exchange current density and charge transfer coefficient) describing the oxygen reduction reaction (ORR) at the CsH2PO4‐Pt‐gas interface. The parameters are incorporated into a 1D model of the voltage–current characteristics of realistic SAFC cathodes, which reproduced the measured polarization behavior of such cathodes without recourse to fitting adjustable parameters. Following this validation, the model is utilized to evaluate the impact of changes to cathode properties, microstructure, and operating conditions. Of these, the charge transfer coefficient, measured to have a value of ≈0.6 for ORR on Pt in the SAFC cathode environment, is found to have the greatest impact on power output. Nevertheless, even without material modifications, a combination of microstructural and operational modifications are identified with projected performance metrics meeting Department of Energy targets (0.8 V at 300 mA cm−2, and peak power density of 1 W cm−2), albeit at high Pt loadings. However, the analysis indicates that truly meaningful advances will likely necessitate the discovery of alternative ORR catalysts.

First Measurement of R(Xτ/ℓ) as an Inclusive Test of the b→cτν Anomaly

We measure the tau-to-light-lepton ratio of inclusive B-meson branching fractions R(Xτ/ℓ)≡B(B→Xτν)/B(B→Xℓν), where ℓ indicates an electron or muon, and thereby test the universality of charged-current weak interactions. We select events that have one fully reconstructed B meson and a charged lepton candidate from 189 fb−1 of electron-positron collision data collected with the Belle II detector. We find R(Xτ/ℓ)=0.228±0.016(stat)±0.036(syst), in agreement with standard-model expectations. This is the first direct measurement of R(Xτ/ℓ). Published by the American Physical Society 2024

Demonstration of Controlled Skyrmion Injection Across a Thickness Step.

Spintronic devices incorporating magnetic skyrmions have attracted significant interest recently. Such devices traditionally focus on controlling magnetic textures in 2D thin films. However, enhanced performance of spintronic properties through the exploitation of higher dimensionalities motivates the investigation of variable-thickness skyrmion devices. We report the demonstration of a skyrmion injection mechanism that utilizes charge currents to drive skyrmions across a thickness step and, consequently, a metastability barrier. Our measurements show that under certain temperature and field conditions skyrmions can be reversibly injected from a thin region of an FeGe lamella, where they exist as an equilibrium state, into a thicker region, where they can only persist as a metastable state. This injection is achieved with a current density of 3 × 108 A m-2, nearly 3 orders of magnitude lower than required to move magnetic domain walls. This highlights the possibility to use such an element as a skyrmion source/drain within future spintronic devices.

Antiferromagnetic magnonic charge current generation via ultrafast optical excitation

Néel spin-orbit torque allows a charge current pulse to efficiently manipulate the Néel vector in antiferromagnets, which offers a unique opportunity for ultrahigh density information storage with high speed. However, the reciprocal process of Néel spin-orbit torque, the generation of ultrafast charge current in antiferromagnets has not been demonstrated. Here, we show the experimental observation of charge current generation in antiferromagnetic metallic Mn2Au thin films using ultrafast optical excitation. The ultrafast laser pulse excites antiferromagnetic magnons, resulting in instantaneous non-equilibrium spin polarization at the antiferromagnetic spin sublattices with broken spatial symmetry. Then the charge current is generated directly via spin-orbit fields at the two sublattices, which is termed as the reciprocal phenomenon of Néel spin-orbit torque, and the associated THz emission can be detected at room temperature. Besides the fundamental significance on the Onsager reciprocity, the observed magnonic charge current generation in antiferromagnet would advance the development of antiferromagnetic THz emitter.

Selection of an Optimal Frequency for Offshore Wind Farms

Offshore wind power has attracted significant attention due to its high potential, capability for large-scale farms, and high capacity factor. However, it faces high investment costs and issues with subsea power transmission. Conventional high-voltage AC (HVAC) methods are limited by charging current, while high-voltage DC (HVDC) methods suffer from the high cost of power conversion stations. The low-frequency AC (LFAC) method mitigates the charging current through low-frequency operation and can reduce power conversion station costs. This paper aims to identify the economically optimal frequency by comparing the investment costs of LFAC systems at various frequencies. The components of LFAC, including transformers, offshore platforms, and cables, exhibit frequency-dependent characteristics. Lower frequencies result in an increased size and volume of transformers, leading to higher investment costs for offshore platforms. In contrast, cable charging currents and losses are proportional to frequency, causing the total cost to reach a minimum at a specific frequency. To determine the optimal frequency, simulations of investment costs for varying capacities and distances were conducted.

Experimental study of the effect of different pulse charging patterns on lithium-ion battery charging

This study aims to experimentally investigate the impact of different pulse charging patterns on the charging time and performance of lithium-ion batteries at room temperature. Experimental results indicate that most pulse charging protocols have a positive impact on shortening the total charging time compared to the CC-CV charging method with the same input charge capacity. This effect is observed not only in LFP batteries but also in NMC batteries. Three pulse charging patterns are studied: constant current charge (C–C), charge rest (C–R), and charge discharge (C-D). The C-D mode results in the shortest charging time and the smallest cell internal resistance. Compared to the 1C CC-CV baseline, the pulse C-D mode reduces the charging time by approximately 6.8 %, decreases the average pulse internal resistance by about 17.5 %, and increases the remaining discharge capacity ratio by 3.76 % after 800 cycles. Additionally, a pseudo-2D physics model is used to study the internal effects on the battery using the pulse C-D mode. The results show that using the pulse charging method (C-D) results in a more even distribution of electrolyte salt concentration and electrode particle lithium concentration across the cell, thereby improving battery performance.

Charged-current non-standard neutrino interactions at Daya Bay

The full data set of the Daya Bay reactor neutrino experiment is used to probe the effect of the charged current non-standard interactions (CC-NSI) on neutrino oscillation experiments. Two different approaches are applied and constraints on the corresponding CC-NSI parameters are obtained with the neutrino flux taken from the Huber-Mueller model with a 5% uncertainty. For the quantum mechanics-based approach (QM-NSI), the constraints on the CC-NSI parameters ϵeα and ϵeαs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\epsilon}_{e\\alpha}^s $$\\end{document} are extracted with and without the assumption that the effects of the new physics are the same in the production and detection processes, respectively. The approach based on the weak effective field theory (WEFT-NSI) deals with four types of CC-NSI represented by the parameters [εX]eα. For both approaches, the results for the CC-NSI parameters are shown for cases with various fixed values of the CC-NSI and the Dirac CP-violating phases, and when they are allowed to vary freely. We find that constraints on the QM-NSI parameters ϵeα and ϵeαs\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ {\\epsilon}_{e\\alpha}^s $$\\end{document} from the Daya Bay experiment alone can reach the order O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(0.01) for the former and O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(0.1) for the latter, while for WEFT-NSI parameters [εX]eα, we obtain O\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$ \\mathcal{O} $$\\end{document}(0.1) for both cases.

Modular, Vision-Based Control of Automated Charging Systems for Electric Vehicles

Contemporary vehicle fleets include a variety of both manually and automated operated vehicles. A significant shift involves the increasing use of electric powertrains. However, the current electric charging infrastructure predominantly relies on manual processes. There is an opportunity to automate the charging process for these cars, with the intent to enhance convenience, aid people with accessibility needs, to support MW charging where EV cables are heavy, and finally to enable autonomous driving. The charging standards are common but the mechanisms to access the charging ports are not i.e., lids and protectives. This could be a challenge in the automation process given the complexity of the manipulation task at hand. With the increasing variety of electric vehicle models, standardizing charging mechanisms becomes imperative to streamline the charging process and enable broader adoption. In summary, this paper presents a holistic approach to addressing the evolving needs of electric vehicle charging infrastructure, emphasizing the importance of automation in enabling efficient, accessible, and future-ready charging solutions.

Generation of charge current by the inverse Stern-Gerlach effect in semiconductors

Generation of charge current by the inverse Stern-Gerlach effect in semiconductors

Negative longitudinal resistance of monolayer graphene in the quantum Hall regime

In the quantum Hall regime, the charge current is carried by ideal one-dimensional edge channels where the backscattering is prohibited by topology. This results in the constant potential along the edge of the Hall bar leading to zero 4-terminal longitudinal resistance rxx. Finite scattering between the counter-propagating edge states, when the topological protection is broken, commonly results in rxx > 0. However, a local disorder, if allowing intersection of the edge states, can result in a counter-intuitive scenario when rxx < 0. In this work, we report the observation and a systematic study of such unconventional negative longitudinal resistance seen in an encapsulated monolayer graphene Hall bar device measured in the quantum Hall regime. We supplement our findings with the numerical calculations, which allow us to outline the conditions necessary for the appearance of negative rxx and to exclude the macroscopic disorder (contamination bubble) as the main origin of it.

Suppression of Initial Charging Torque for Electric Drive-Reconfigured On-Board Charger

This paper presents a new electric drive-reconfigured on-board charger and initial electromagnetic torque suppression method. This proposed reconfigured on-board charger does not need many components added to the original electric drive system: only a connector is needed, which is easy to add. Specifically, the inverter for propulsion is reconfigured as a buck chopper and a conduction path to match the reconfigured windings. Two of the machine phase windings serve as inductors, while the third phase winding is reutilized as a common-mode inductor. In addition, the initial charging torque is generated at the outset of the charging process, which may cause an instant shock or even rotational movement. In order to prevent vehicle movement, the reason for the charging torque and suppression method were analyzed. Further, predictive control of the model based on mutual inductance analysis was adopted, where the charging torque was directly used as a control object in the cost function. Finally, experimental performances were applied to verify the proposed reconfigured on-board charger under constant current and constant voltage charging.

Integrated on-board electric vehicle battery charger with multifunctional features

ABSTRACT Because of the continuous demand for reliable, efficient, small-size, light weighted, and low-cost Electric Vehicle (EV) battery charging systems, an integrated on-board charger is proposed with a high-power propulsion motor drive. It utilises stator windings of motor, the 6-leg Voltage Source Converter (VSC), DC-DC converter, and feedback sensors to facilitate vehicular battery charging. With this system, soft switching technique based bidirectional isolated DC-DC converter is proposed that offers the advantage of simple circuitry design due to no usage of extra passive or active components. This paper presents mathematical modelling, analysis, and controller design of this proposed configuration under various operating modes. The complete system is developed in Sim Power system toolbox of MATLAB software and tested in real-time environment. The performance investigations of proposed system are carried out for three operating modes like Grid-to-Vehicle (G2V), Vehicle-to-Grid (V2G), Vehicle-to-Vehicle (V2V) under Constant Current (CC) and Constant Voltage (CV) battery charging modes. Furthermore, the investigations ensure the system’s excellent efficiency, less THD, and nearly unity power factor operation under all operating conditions.