This work demonstrates experimentally the close relation between return currents from relativistic laser-driven target polarization and the quality of the relativistic laser–plasma interaction for laser-driven second...This work demonstrates experimentally the close relation between return currents from relativistic laser-driven target polarization and the quality of the relativistic laser–plasma interaction for laser-driven secondary sources,taking as an example ion acceleration by target normal sheath acceleration.The Pearson linear correlation of maximum return current amplitude and proton spectrum cutoff energy is found to be in the range from~0.70 to 0.94.kA-scale return currents rise in all interaction schemes where targets of any kind are charged by escaping laser-accelerated relativistic electrons.Their precise measurement is demonstrated using an inductive scheme that allows operation at high repetition rates.Thus,return currents can be used as a metrological online tool for the optimization of many laser-driven secondary sources and for diagnosing their stability.In particular,in two parametric studies of laser-driven ion acceleration,we carry out a noninvasive online measurement of return currents in a tape target system irradiated by the 1 PW VEGA-3 laser at Centro de Láseres Pulsados:first the size of the irradiated area is varied at best compression of the laser pulse;second,the pulse duration is varied by means of induced group delay dispersion at best focus.This work paves the way to the development of feedback systems that operate at the high repetition rates of PW-class lasers.展开更多
The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow ...The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow controller(CFC)are demanded to ensure the multiterminal DC grid to operates reliably and flexibly.However,since the CFC and the DCCB are all based on fully controlled semiconductor switches(e.g.,insulated gate bipolar transistor,integrated gate commutated thyristor,etc.),their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses.To solve these problems,integrated equipment with both current flow control and fault isolation abilities is proposed,which shares the expensive and duplicated components of CFCs and DCCBs among adjacent lines.In addition,the complicated coordination control of CFCs and DCCBs can be avoided by adopting the integrated equipment in themultiterminal DC grid.In order to examine the current flow control and fault isolation abilities of the integrated equipment,the simulation model of a specific meshed four-terminal DC grid is constructed in the PSCAD/EMTDC software.Finally,the comparison between the integrated equipment and the separate solution is presented a specific result or conclusion needs to be added to the abstract.展开更多
The rapid-cycling synchrotron(RCS)is a crucial device for proton beam acceleration at the China Spallation Neutron Source,operating at a repetition frequency of 25 Hz.The beam power was increased from 100 kW to 140 kW...The rapid-cycling synchrotron(RCS)is a crucial device for proton beam acceleration at the China Spallation Neutron Source,operating at a repetition frequency of 25 Hz.The beam power was increased from 100 kW to 140 kW.This increase makes the on-orbit beam more sensitive to disturbances in various parts of the accelerator,including the RCS magnet power supply system.This paper presents a method for reducing the high-order harmonic current error in resonant power supplies for dipole magnets and examines its impact on the horizontal orbit offset of the beam.It adopts a control scheme that combines high-order harmonic current compensation with PI double-loop control of the resonant power supply.By utilizing the existing digital controller hardware in the RCS power supply system,this study demonstrates how to achieve precise control of the 50 Hz harmonic current output in a cost-effective manner.Ultimately,it enhances performance by reducing the current error by up to 50%and provides methodological support for future upgrades to the power supply system.Such improvements enhance the stability of the RCS,reducing the beam horizontal orbit deviation by at least 19.8%.展开更多
This work proposes and fabricates the 4H-SiC power MOSFET with top oxide and double P-well(TODP-MOSFET)to enhance the single-event radiation tolerance of the gate oxide.Simulation results suggest that the proposed TOD...This work proposes and fabricates the 4H-SiC power MOSFET with top oxide and double P-well(TODP-MOSFET)to enhance the single-event radiation tolerance of the gate oxide.Simulation results suggest that the proposed TODP structure reduces the peak electric field within the oxide and minimizes the sensitive region by more than 70%compared to C-MOSFETs.Experimental results show that the gate degradation voltage of the TODP-MOSFET is higher than that of the C-MOSFET,and the gate leakage current is reduced by 95%compared to the C-MOSFET under heavy-ion irradiation with a linear energy transfer(LET)value exceeding 75 MeV·cm^(2)/mg.展开更多
The integration of large-scale new energy and high-capacity DC transmission leads to a reduction in system inertia.Grid-forming renewable energy sources(GF-RES)has a significant improvement effect on system inertia.Co...The integration of large-scale new energy and high-capacity DC transmission leads to a reduction in system inertia.Grid-forming renewable energy sources(GF-RES)has a significant improvement effect on system inertia.Commutation failure faults may cause a short-term reactive power surplus at the sending end and trigger transient overvoltage,threatening the safe and stable operation of the power grid.However,there is a lack of research on the calculation method of transient overvoltage caused by commutation failure in high-voltage DC transmission systems with grid-forming renewable energy sources integration.Based on the existing equivalent model of highvoltage DC transmission systems at the sending end,this paper proposes to construct a model of the high-voltage DC transmission system at the sending end with grid-forming renewable energy sources.The paper first clarifies the mechanism of overvoltage generation,then considers the reactive power droop control characteristics of GF-RES,and derives the transient voltage calculation model of theDC transmission system with GF-RES integration.It also proposes a calculation method for transient overvoltage at the sending-end converter bus with GF-RES integration.Based on the PSCAD/EMTDC simulation platform,this paper builds an experimental simulation model.By constructing three different experimental scenarios,the accuracy and effectiveness of the proposed transient overvoltage calculation method are verified,with a calculation error within 5%.At the same time,this paper quantitatively analyzes the impact of grid strength,new energy proportion,and rated transmission power on transient overvoltage from three different perspectives.展开更多
Recent various experiments have provided evidence supporting the emergence of loop-current order in kagome metals. Particularly superconductivity in AV_(3)Sb_(5) is significantly enhanced when this charge order is sup...Recent various experiments have provided evidence supporting the emergence of loop-current order in kagome metals. Particularly superconductivity in AV_(3)Sb_(5) is significantly enhanced when this charge order is suppressed by pressure or doping. Distinct from magnetic order, loop-current order does not couple directly to spin and thus whether such fluctuations can enhance superconductivity remains elusive. We design a sign problem-free bilayer kagome model coupled to quantum Ising spins through bond currents and perform determinant quantum Monte Carlo simulations to explore single-particle properties and superconductivity arising from 2 × 2 loopcurrent fluctuations. We find that this loop-current order induces intriguing band folding, band broadening,and gap opening around saddle points. Remarkably, our pairing susceptibility analysis identifies a dominant enhancement of superconductivity due to loop-current fluctuations, with the dominant pairing being the chiral d-wave channel. This pairing primarily occurs within the intra-sublattice channel and involves third nearestneighbor sites, attributed to the unique sublattice texture associated with van Hove singularities. We also discuss potential experimental implications for kagome superconductors.展开更多
Background Pain sensitivity is critical for preventing non-suicidal self-injury(NSSI)behaviours;however,individuals engaging in such behaviours often exhibit decreased pain sensitivity,which may undermine this natural...Background Pain sensitivity is critical for preventing non-suicidal self-injury(NSSI)behaviours;however,individuals engaging in such behaviours often exhibit decreased pain sensitivity,which may undermine this natural safeguard.The dorsolateral prefrontal cortex(DLPFC)is a key region involved in pain regulation,and recent approaches using transcranial direct current stimulation(tDCS)to target the DLPFC have shown potential for modulating pain processing and restoring normal pain perception for individuals engaging in NSSI behaviours.Aims This study aimed to explore the immediate and short-term effects of a single session of tDCS on pain sensitivity in individuals with NSSI,as well as its secondary effects on mood and NSSI-related factors.Methods In this randomised,double-blind,parallel,sham-controlled clinical trial,participants with a history of NSSI were randomly assigned to receive either active or sham tDCS.The intervention consisted of a single 20 min tDCS session targeting the left DLPFC.The primary outcome was pain sensitivity,measured by the pressure pain threshold(PPT)and heat pain score(HPS).Secondary and additional outcomes included NSSI urges,NSSI resistance,self-efficacy in resisting NSSI,mood-related variables and exploratory cognitive-affective processes such as rumination,self-criticism and self-perceived pain sensitivity,assessed at baseline,immediately post-intervention,and at 24 hours,1 week and 2 weeks follow-ups.Results For the primary outcomes,no significant differences between groups were observed for pain sensitivity(PPT,padj=0.812;HPS,padj=0.608).However,an exploratory sensitivity analysis treating each trial as an individual observation revealed a significant effect on HPS(padj=0.036).For the secondary and additional outcomes,although there were initial improvements in joyful feelings and reductions in negative affect at 2 weeks post-intervention,these effects did not remain significant after multiple comparison corrections.Notably,reductions in rumination were statistically significant at both 1-week and 2-week follow-ups(1 week,p_(adj)=0.040;2 weeks,p_(adj)=0.042).There were no significant effects on NSSI urges,NSSI resistance,self-efficacy in resisting NSSI or self-criticism.Conclusions A single session of tDCS over the left DLPFC did not produce significant changes in pain sensitivity in individuals with NSSI.A sensitivity analysis indicated an effect on heat pain sensitivity,possibly reflecting changes in brain activity,warranting confirmation through neuroimaging.These findings suggest that tDCS warrants further investigation for its potential to influence pain-related cognitive-affective processes in individuals with NSSI.展开更多
Hepatocellular carcinoma(HCC)remains one of the commonest cancers world-wide with an overall poor prognosis and survival rates.The rising incidence of liver disease,in particular non-alcoholic fatty liver disease,will...Hepatocellular carcinoma(HCC)remains one of the commonest cancers world-wide with an overall poor prognosis and survival rates.The rising incidence of liver disease,in particular non-alcoholic fatty liver disease,will account for a continued increase in the rates of liver cancer.The recurrence of HCC has been reported across the different etiologies of liver disease.Unlike primary HCC,there is no agreed consensus or guidance as to the optimum management of re-current HCC(RHCC).Furthermore,the management of RHCC may prove more challenging compared to primary liver cancer,given the smaller residual liver volume and functions in settings following surgery or transplantation.Various modalities exist for the treatment of primary HCC including resection,liver transplantation,loco-regional and systemic therapies.Nevertheless,the role of such modalities remains unclear in the management of RHCC.In this article,we aim to review the different approaches of the current standards for the mana-gement of RHCC.We will also shed some light on the future perspectives in this field.展开更多
A commentary on an anode-free cell design with electrochemically stable sodium borohydride solid electrolyte and pelletized aluminium current collector for sodium all-solid-state batteries is presented.First,the viabl...A commentary on an anode-free cell design with electrochemically stable sodium borohydride solid electrolyte and pelletized aluminium current collector for sodium all-solid-state batteries is presented.First,the viable strategies for implementing anode-free configuration utilizing solid-state electrolytes are briefly reviewed.Then,the remarkable work of Meng et al.on designing an anode-free sodium all-solid-state battery is elucidated.Finally,the significance of Meng’s work is discussed.展开更多
The Agulhas Current is a major western boundary current flowing polewards on the southeast coast of South Africa.This analysis assesses its characteristics and suitability to generate power as a source of clean renewa...The Agulhas Current is a major western boundary current flowing polewards on the southeast coast of South Africa.This analysis assesses its characteristics and suitability to generate power as a source of clean renewable energy.On a section of coastline some 400 km long,over a period spanning more than 5 years an extensive set of current measurements was obtained.These data confirmed that south-westward currents with a speed greater than 1.2 m s^(-1)occurred over more than 60%of the recorded time;such ocean current speeds compare very favourably to winds required for energy generation.These currents occurred at the continental shelf break in water depths around 100 m,in the upper 50 m of the water column.Occasional current slowdowns and reversals did occur,with the major influence coming from‘Natal Pulses’,which are large-scale meanders in the Current that temporarily reversed the currents at the measurement sites.However,because of the surface temperature structure of the relevant water masses,such meanders can be identified in satellite imagery giving a few days advance warning of such current reversals.The characteristics of western boundary currents have been known for many years,but at Present,there is no operational system where this source of power is being utilised.It has tremendous potential for renewable energy generation,but is symptomatic of the many engineering challenges that still have to be solved to make such generation economically viable.展开更多
Accurate modeling of Earth's ionospheric F-region currents is essential for refining geomagnetic field models and understanding magnetosphere-ionosphere coupling.In this study,we develop averaged models to charact...Accurate modeling of Earth's ionospheric F-region currents is essential for refining geomagnetic field models and understanding magnetosphere-ionosphere coupling.In this study,we develop averaged models to characterize F-region currents using magnetic data from the MSS-1(Macao Science Satellite-1) and Swarm satellite missions.Our approach employs a toroidal field representation,utilizing spherical harmonics to capture spatial variations and Fourier series to represent temporal dynamics.Two models,Model-A and Model-B,derived from distinct datasets,are constructed to represent current patterns at altitudes of 450 km and 512 km,respectively.Our models successfully capture the primary spatial structures and seasonal variations of polar field-aligned currents.Additionally,they accurately reproduce the localized inter-hemispheric field-aligned currents observed in mid and low latitudes during solstices,particularly between 14:00 and 16:00 magnetic local times.These findings enhance our understanding of ionospheric F-region currents and contribute to more precise geomagnetic field modeling.展开更多
The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-...The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.展开更多
Purpose–This study summarizes the overall situation of the resources of the national science and technology innovation platform in the railway industry,including the distribution of platform types,supporting institut...Purpose–This study summarizes the overall situation of the resources of the national science and technology innovation platform in the railway industry,including the distribution of platform types,supporting institutions,construction sites,professional fields,etc.,to provide a reference for the further improvement and optimization of the national science and technology innovation platform system in the railway industry.Design/methodology/approach–Through literature review,field investigation,expert consultation and other methods,this paper systematically investigates and analyzes the development status of the national science and technology innovation platform in the railway industry.Findings–Taking the national science and technology innovation platform of the railway industry as the research object,this paper investigates and analyzes the construction,development and distribution of the national science and technology innovation platform of railway industry over the years.And the National Engineering Research Center of High-speed Railway and Urban Rail Transit System Technology was taken as an example to introduce its operation effect.Originality/value–China Railway has made great development achievements,with the construction and development of national science and technology innovation platform in the railway industry.In recent years,a large number of national science and technology innovation platforms have been built in the railway industry,which play an important role in railway technological innovation,standard setting and commodification,and Railway Sciences provide strong support for railway technology development.展开更多
In this study, we examined variability of sun-related energies, auroral electrojet current, ring current, and magnetopause current during solar cycles 23 and 24. The study revealed a dependence of sun-related energies...In this study, we examined variability of sun-related energies, auroral electrojet current, ring current, and magnetopause current during solar cycles 23 and 24. The study revealed a dependence of sun-related energies to the Sun and Earth currents systems with solar activity from 1996 to 2019. A decrease in the correlation between sun-related energies and sunspot number was observed over solar cycles 23 and 24 (0.88 for the solar cycle 23 and 0.66 for the solar cycle 24), with a drop in the speed of magnetic disturbances in the solar wind. These results could be attributed to the decrease in Sun’s magnetic field toroidal component magnitude induced by a weak in sunspots number and solar flares during the solar cycle 24. A weak in the Earth currents systems (auroral electrojet current, ring current, and magnetopause current) is also observed. During the decrease in the Earth currents, several peaks are observed, indicating a nonlinear dependence in the Earth currents variation (ring current, auroral electrojet current, and magnetopause current) from solar cycle 23 to solar cycle 24. This could be attributed to the Corotating Interaction Regions (CIRs) observed during the declining phase of solar cycle 23 and the deep minimum preceding solar cycle 24.展开更多
This paper investigates and analyzes the general situation of the tomato seed production industry in Lintong District,Xi'an City.Development strategies and suggestions are proposed to address existing problems.The...This paper investigates and analyzes the general situation of the tomato seed production industry in Lintong District,Xi'an City.Development strategies and suggestions are proposed to address existing problems.These include strengthening technological innovation and variety R&D,promoting industrial standardization and intelligent upgrading,enhancing brand building and market expansion,improving policy support and industrial chain coordination,strengthening intellectual property protection and talent cultivation,and expanding sales channels to promote industrial transformation and upgrading.展开更多
With the accelerating urbanization process,issues related to the urban ecological environment have become increasingly prominent.Among these,greenway optimization is regarded as one of the key approaches to improving ...With the accelerating urbanization process,issues related to the urban ecological environment have become increasingly prominent.Among these,greenway optimization is regarded as one of the key approaches to improving urban ecological quality.As the capital of Anhui Province,Hefei is striving to build a comprehensive greenway network in line with its“Park City”strategy.However,the current development of Hefei’s greenways faces challenges such as delayed planning,limited functions,inadequate facilities,and weak operation and maintenance management.In this study,comparative analysis and literature review were combined to comprehensively summarize the current characteristics of greenway development in Hefei,and improvement suggestions were proposed in areas such as ecological restoration,functional expansion,facility establishment,and long-term management.It is suggested that Hefei should enhance the systematic and synergistic nature of its greenway system,create a city green space network with regional characteristics,and optimize the city’s environmental carrying capacity,so as to meet the diverse needs of the public and thereby provide theoretical support and practical guidance for the sustainable development of Hefei’s greenway system.展开更多
As a new dynamic reactive power compensator,the grid-forming Static Var Generator(GF-SVG)can not only provide reactive power-voltage support,but also has inertial support capability.It has been experimentally deployed...As a new dynamic reactive power compensator,the grid-forming Static Var Generator(GF-SVG)can not only provide reactive power-voltage support,but also has inertial support capability.It has been experimentally deployed in many wind farms.However,studies have shown that when the three-phase short-circuit fault occurs in the wind farm,the transient overcurrent during the fault occurrence and fault clearance is suppressed,making it difficult for GF-SVG to use traditional fixed virtual impedance.Aiming at the problem,firstly,the influence of virtual reactance on control stability is analyzed using the GF-SVG’s current open-loop transfer function.Secondly,based on the existing current limitation strategies of GF-SVG,an adaptive virtual reactance current limitation strategy suitable for symmetrical faults of the power grid is proposed,which limits GF-SVG’s transient overcurrent during fault occurrence and fault clearance stage to the tolerance range of GF-SVG’s power devices.Based on the GF-SVG’s active power loop and reactive power loop small signal models,the availability of the proposed adaptive virtual reactance in suppressing the DC voltage drop of GF-SVG is analyzed,and shortening the transient overvoltage recovery time of the wind farm after the fault clearance is also discussed.Finally,electromagnetic simulation proves the effectiveness and correctness of the proposed adaptive current limitation method.展开更多
With the increase of global climate change and extreme weather events,more and more attention has been paid to the protection of China's meteorological cultural heritage.Meteorological cultural heritage is an impo...With the increase of global climate change and extreme weather events,more and more attention has been paid to the protection of China's meteorological cultural heritage.Meteorological cultural heritage is an important part of China's cultural heritage,which is unique and non renewable.It is of great significance to the inheritance of China's excellent traditional culture and the construction of a meteorological power.Because it is more special than water conservancy cultural heritage in China's historical development,it is not only a national context,but also mixed with foreign activities.This paper focuses on the protection and research of China's meteorological cultural heritage.Based on the current situation of the protection and utilization of China's meteorological cultural heritage,it analyzes the problems and shortcomings in the current protection work.In response to these problems,some targeted protection measures are proposed,including strengthening the construction of laws and regulations,improving the level of protection technology,enhancing public participation,and promoting the protection and sustainable development of meteorological cultural heritage.The aim is to provide useful references for the protection of China's meteorological cultural heritage in the future.展开更多
Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate at...Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate atomic diffusion to achieve ultra-fast spheroidization of carbides.However,the understanding of the mechanism by which different pulse current parameters regulate the dissolution behavior of carbides requires a large amount of experimental data to support,which limits the application of pulse current technology in the field of heat treatment.Based on this,quantify the obtained pulse current processing data to create an important dataset that could be applied to machine learning.Through machine learning,the mechanism of mutual influence between carbide regulation and various factors was elucidated,and the optimal spheroidization process parameters were determined.Compared to the 20 h required for traditional heat treatment,the application of pulsed electric current technology achieved ultra-fast spheroidization of GCr15 bearing steel within 90 min.展开更多
基金funding from the European Union’s Horizon 2020 research and innovation program through the European IMPULSE project under Grant Agreement No.871161from LASERLAB-EUROPE V under Grant Agreement No.871124+6 种基金from the Grant Agency of the Czech Republic(Grant No.GM23-05027M)Grant No.PDC2021120933-I00 funded by MCIN/AEI/10.13039/501100011033by the European Union Next Generation EU/PRTRsupported by funding from the Ministerio de Ciencia,Innovación y Universidades in Spain through ICTS Equipment Grant No.EQC2018-005230-Pfrom Grant No.PID2021-125389O A-I00 funded by MCIN/AEI/10.13039/501100011033/FEDER,UEby“ERDF A Way of Making Europe”by the European Unionfrom grants of the Junta de Castilla y León with Grant Nos.CLP263P20 and CLP087U16。
文摘This work demonstrates experimentally the close relation between return currents from relativistic laser-driven target polarization and the quality of the relativistic laser–plasma interaction for laser-driven secondary sources,taking as an example ion acceleration by target normal sheath acceleration.The Pearson linear correlation of maximum return current amplitude and proton spectrum cutoff energy is found to be in the range from~0.70 to 0.94.kA-scale return currents rise in all interaction schemes where targets of any kind are charged by escaping laser-accelerated relativistic electrons.Their precise measurement is demonstrated using an inductive scheme that allows operation at high repetition rates.Thus,return currents can be used as a metrological online tool for the optimization of many laser-driven secondary sources and for diagnosing their stability.In particular,in two parametric studies of laser-driven ion acceleration,we carry out a noninvasive online measurement of return currents in a tape target system irradiated by the 1 PW VEGA-3 laser at Centro de Láseres Pulsados:first the size of the irradiated area is varied at best compression of the laser pulse;second,the pulse duration is varied by means of induced group delay dispersion at best focus.This work paves the way to the development of feedback systems that operate at the high repetition rates of PW-class lasers.
基金supported in part by Natural Science Foundation of Jiangsu Province under Grant BK20230255Natural Science Foundation of Shandong Province under Grant ZR2023QE281.
文摘The multi-terminal direct current(DC)grid has extinctive superiorities over the traditional alternating current system in integrating large-scale renewable energy.Both the DC circuit breaker(DCCB)and the current flow controller(CFC)are demanded to ensure the multiterminal DC grid to operates reliably and flexibly.However,since the CFC and the DCCB are all based on fully controlled semiconductor switches(e.g.,insulated gate bipolar transistor,integrated gate commutated thyristor,etc.),their separation configuration in the multiterminal DC grid will lead to unaffordable implementation costs and conduction power losses.To solve these problems,integrated equipment with both current flow control and fault isolation abilities is proposed,which shares the expensive and duplicated components of CFCs and DCCBs among adjacent lines.In addition,the complicated coordination control of CFCs and DCCBs can be avoided by adopting the integrated equipment in themultiterminal DC grid.In order to examine the current flow control and fault isolation abilities of the integrated equipment,the simulation model of a specific meshed four-terminal DC grid is constructed in the PSCAD/EMTDC software.Finally,the comparison between the integrated equipment and the separate solution is presented a specific result or conclusion needs to be added to the abstract.
基金supported by the Guangdong Basic and Applied Basic Research Foundation(No.2023B1515120030).
文摘The rapid-cycling synchrotron(RCS)is a crucial device for proton beam acceleration at the China Spallation Neutron Source,operating at a repetition frequency of 25 Hz.The beam power was increased from 100 kW to 140 kW.This increase makes the on-orbit beam more sensitive to disturbances in various parts of the accelerator,including the RCS magnet power supply system.This paper presents a method for reducing the high-order harmonic current error in resonant power supplies for dipole magnets and examines its impact on the horizontal orbit offset of the beam.It adopts a control scheme that combines high-order harmonic current compensation with PI double-loop control of the resonant power supply.By utilizing the existing digital controller hardware in the RCS power supply system,this study demonstrates how to achieve precise control of the 50 Hz harmonic current output in a cost-effective manner.Ultimately,it enhances performance by reducing the current error by up to 50%and provides methodological support for future upgrades to the power supply system.Such improvements enhance the stability of the RCS,reducing the beam horizontal orbit deviation by at least 19.8%.
基金supported by the Joint Funds of the National Natural Science Foundation of China(Grant No.U2341220)the Hefei Comprehensive National Science Center。
文摘This work proposes and fabricates the 4H-SiC power MOSFET with top oxide and double P-well(TODP-MOSFET)to enhance the single-event radiation tolerance of the gate oxide.Simulation results suggest that the proposed TODP structure reduces the peak electric field within the oxide and minimizes the sensitive region by more than 70%compared to C-MOSFETs.Experimental results show that the gate degradation voltage of the TODP-MOSFET is higher than that of the C-MOSFET,and the gate leakage current is reduced by 95%compared to the C-MOSFET under heavy-ion irradiation with a linear energy transfer(LET)value exceeding 75 MeV·cm^(2)/mg.
基金supported by Key Natural Science Research Projects of Colleges and Universities in Anhui Province(2022AH051831).
文摘The integration of large-scale new energy and high-capacity DC transmission leads to a reduction in system inertia.Grid-forming renewable energy sources(GF-RES)has a significant improvement effect on system inertia.Commutation failure faults may cause a short-term reactive power surplus at the sending end and trigger transient overvoltage,threatening the safe and stable operation of the power grid.However,there is a lack of research on the calculation method of transient overvoltage caused by commutation failure in high-voltage DC transmission systems with grid-forming renewable energy sources integration.Based on the existing equivalent model of highvoltage DC transmission systems at the sending end,this paper proposes to construct a model of the high-voltage DC transmission system at the sending end with grid-forming renewable energy sources.The paper first clarifies the mechanism of overvoltage generation,then considers the reactive power droop control characteristics of GF-RES,and derives the transient voltage calculation model of theDC transmission system with GF-RES integration.It also proposes a calculation method for transient overvoltage at the sending-end converter bus with GF-RES integration.Based on the PSCAD/EMTDC simulation platform,this paper builds an experimental simulation model.By constructing three different experimental scenarios,the accuracy and effectiveness of the proposed transient overvoltage calculation method are verified,with a calculation error within 5%.At the same time,this paper quantitatively analyzes the impact of grid strength,new energy proportion,and rated transmission power on transient overvoltage from three different perspectives.
基金supported by the National Natural Science Foundation of China (Grant No. 12447103)financial support from the MERIT-WINGS course provided by the University of Tokyo+10 种基金the Fellowship for Integrated Materials Science and Career Development provided by the Japan Science and Technology Agencysupport from the computational resource of Wisteria/BDEC-01 provided by Information Technology Center, the University of Tokyo, for the Monte Carlo simulationthe support by the National Natural Science Foundation of China (Grant No. 12404275)the Fundamental Research Program of Shanxi Province (Grant No. 202403021212015)support from the Würzburg-Dresden Cluster of Excellence on Complexity and Topology in Quantum Matter-ct.qmat (EXC 2147, Project No. 390858490)supported by the National Natural Science Foundation of China (Grant No. 12274289)the National Key R&D Program of China (Grant Nos. 2022YFA1402702 and 2021YFA1401400)the Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0301902)Yangyang Development Fund, and Startup Funds from SJTUsupported by the National Key R&D Program of China (Grant No. 2023YFA1407300)the National Natural Science Foundation of China (Grant No. 12047503)。
文摘Recent various experiments have provided evidence supporting the emergence of loop-current order in kagome metals. Particularly superconductivity in AV_(3)Sb_(5) is significantly enhanced when this charge order is suppressed by pressure or doping. Distinct from magnetic order, loop-current order does not couple directly to spin and thus whether such fluctuations can enhance superconductivity remains elusive. We design a sign problem-free bilayer kagome model coupled to quantum Ising spins through bond currents and perform determinant quantum Monte Carlo simulations to explore single-particle properties and superconductivity arising from 2 × 2 loopcurrent fluctuations. We find that this loop-current order induces intriguing band folding, band broadening,and gap opening around saddle points. Remarkably, our pairing susceptibility analysis identifies a dominant enhancement of superconductivity due to loop-current fluctuations, with the dominant pairing being the chiral d-wave channel. This pairing primarily occurs within the intra-sublattice channel and involves third nearestneighbor sites, attributed to the unique sublattice texture associated with van Hove singularities. We also discuss potential experimental implications for kagome superconductors.
基金supported by National Natural Science Foundation of China(82471564)YT is supported by National Natural Science Foundation of China(32322035,32171078).
文摘Background Pain sensitivity is critical for preventing non-suicidal self-injury(NSSI)behaviours;however,individuals engaging in such behaviours often exhibit decreased pain sensitivity,which may undermine this natural safeguard.The dorsolateral prefrontal cortex(DLPFC)is a key region involved in pain regulation,and recent approaches using transcranial direct current stimulation(tDCS)to target the DLPFC have shown potential for modulating pain processing and restoring normal pain perception for individuals engaging in NSSI behaviours.Aims This study aimed to explore the immediate and short-term effects of a single session of tDCS on pain sensitivity in individuals with NSSI,as well as its secondary effects on mood and NSSI-related factors.Methods In this randomised,double-blind,parallel,sham-controlled clinical trial,participants with a history of NSSI were randomly assigned to receive either active or sham tDCS.The intervention consisted of a single 20 min tDCS session targeting the left DLPFC.The primary outcome was pain sensitivity,measured by the pressure pain threshold(PPT)and heat pain score(HPS).Secondary and additional outcomes included NSSI urges,NSSI resistance,self-efficacy in resisting NSSI,mood-related variables and exploratory cognitive-affective processes such as rumination,self-criticism and self-perceived pain sensitivity,assessed at baseline,immediately post-intervention,and at 24 hours,1 week and 2 weeks follow-ups.Results For the primary outcomes,no significant differences between groups were observed for pain sensitivity(PPT,padj=0.812;HPS,padj=0.608).However,an exploratory sensitivity analysis treating each trial as an individual observation revealed a significant effect on HPS(padj=0.036).For the secondary and additional outcomes,although there were initial improvements in joyful feelings and reductions in negative affect at 2 weeks post-intervention,these effects did not remain significant after multiple comparison corrections.Notably,reductions in rumination were statistically significant at both 1-week and 2-week follow-ups(1 week,p_(adj)=0.040;2 weeks,p_(adj)=0.042).There were no significant effects on NSSI urges,NSSI resistance,self-efficacy in resisting NSSI or self-criticism.Conclusions A single session of tDCS over the left DLPFC did not produce significant changes in pain sensitivity in individuals with NSSI.A sensitivity analysis indicated an effect on heat pain sensitivity,possibly reflecting changes in brain activity,warranting confirmation through neuroimaging.These findings suggest that tDCS warrants further investigation for its potential to influence pain-related cognitive-affective processes in individuals with NSSI.
文摘Hepatocellular carcinoma(HCC)remains one of the commonest cancers world-wide with an overall poor prognosis and survival rates.The rising incidence of liver disease,in particular non-alcoholic fatty liver disease,will account for a continued increase in the rates of liver cancer.The recurrence of HCC has been reported across the different etiologies of liver disease.Unlike primary HCC,there is no agreed consensus or guidance as to the optimum management of re-current HCC(RHCC).Furthermore,the management of RHCC may prove more challenging compared to primary liver cancer,given the smaller residual liver volume and functions in settings following surgery or transplantation.Various modalities exist for the treatment of primary HCC including resection,liver transplantation,loco-regional and systemic therapies.Nevertheless,the role of such modalities remains unclear in the management of RHCC.In this article,we aim to review the different approaches of the current standards for the mana-gement of RHCC.We will also shed some light on the future perspectives in this field.
基金grateful for support from the National Natural Science Foundation of China(Nos.52472247,52172229,21401145)Fundamental Research Funds for the Central Universities(No.104972024KFYjc0079).
文摘A commentary on an anode-free cell design with electrochemically stable sodium borohydride solid electrolyte and pelletized aluminium current collector for sodium all-solid-state batteries is presented.First,the viable strategies for implementing anode-free configuration utilizing solid-state electrolytes are briefly reviewed.Then,the remarkable work of Meng et al.on designing an anode-free sodium all-solid-state battery is elucidated.Finally,the significance of Meng’s work is discussed.
文摘The Agulhas Current is a major western boundary current flowing polewards on the southeast coast of South Africa.This analysis assesses its characteristics and suitability to generate power as a source of clean renewable energy.On a section of coastline some 400 km long,over a period spanning more than 5 years an extensive set of current measurements was obtained.These data confirmed that south-westward currents with a speed greater than 1.2 m s^(-1)occurred over more than 60%of the recorded time;such ocean current speeds compare very favourably to winds required for energy generation.These currents occurred at the continental shelf break in water depths around 100 m,in the upper 50 m of the water column.Occasional current slowdowns and reversals did occur,with the major influence coming from‘Natal Pulses’,which are large-scale meanders in the Current that temporarily reversed the currents at the measurement sites.However,because of the surface temperature structure of the relevant water masses,such meanders can be identified in satellite imagery giving a few days advance warning of such current reversals.The characteristics of western boundary currents have been known for many years,but at Present,there is no operational system where this source of power is being utilised.It has tremendous potential for renewable energy generation,but is symptomatic of the many engineering challenges that still have to be solved to make such generation economically viable.
基金supported by the National Natural Science Foundation of China (42250101)the Macao Foundation. The computation made use of the high-performance computing resources at the center of the MSS data processing and analysis。
文摘Accurate modeling of Earth's ionospheric F-region currents is essential for refining geomagnetic field models and understanding magnetosphere-ionosphere coupling.In this study,we develop averaged models to characterize F-region currents using magnetic data from the MSS-1(Macao Science Satellite-1) and Swarm satellite missions.Our approach employs a toroidal field representation,utilizing spherical harmonics to capture spatial variations and Fourier series to represent temporal dynamics.Two models,Model-A and Model-B,derived from distinct datasets,are constructed to represent current patterns at altitudes of 450 km and 512 km,respectively.Our models successfully capture the primary spatial structures and seasonal variations of polar field-aligned currents.Additionally,they accurately reproduce the localized inter-hemispheric field-aligned currents observed in mid and low latitudes during solstices,particularly between 14:00 and 16:00 magnetic local times.These findings enhance our understanding of ionospheric F-region currents and contribute to more precise geomagnetic field modeling.
基金sponsored by the National Natural Science Foundation of China(Nos.5210125 and 52375422)the Science Research Project of Hebei Education Department(No.BJK2023058)the Natural Science Foundation of Hebei Province(Nos.E2020208069,B2020208083 and E202320801).
文摘The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.
文摘Purpose–This study summarizes the overall situation of the resources of the national science and technology innovation platform in the railway industry,including the distribution of platform types,supporting institutions,construction sites,professional fields,etc.,to provide a reference for the further improvement and optimization of the national science and technology innovation platform system in the railway industry.Design/methodology/approach–Through literature review,field investigation,expert consultation and other methods,this paper systematically investigates and analyzes the development status of the national science and technology innovation platform in the railway industry.Findings–Taking the national science and technology innovation platform of the railway industry as the research object,this paper investigates and analyzes the construction,development and distribution of the national science and technology innovation platform of railway industry over the years.And the National Engineering Research Center of High-speed Railway and Urban Rail Transit System Technology was taken as an example to introduce its operation effect.Originality/value–China Railway has made great development achievements,with the construction and development of national science and technology innovation platform in the railway industry.In recent years,a large number of national science and technology innovation platforms have been built in the railway industry,which play an important role in railway technological innovation,standard setting and commodification,and Railway Sciences provide strong support for railway technology development.
文摘In this study, we examined variability of sun-related energies, auroral electrojet current, ring current, and magnetopause current during solar cycles 23 and 24. The study revealed a dependence of sun-related energies to the Sun and Earth currents systems with solar activity from 1996 to 2019. A decrease in the correlation between sun-related energies and sunspot number was observed over solar cycles 23 and 24 (0.88 for the solar cycle 23 and 0.66 for the solar cycle 24), with a drop in the speed of magnetic disturbances in the solar wind. These results could be attributed to the decrease in Sun’s magnetic field toroidal component magnitude induced by a weak in sunspots number and solar flares during the solar cycle 24. A weak in the Earth currents systems (auroral electrojet current, ring current, and magnetopause current) is also observed. During the decrease in the Earth currents, several peaks are observed, indicating a nonlinear dependence in the Earth currents variation (ring current, auroral electrojet current, and magnetopause current) from solar cycle 23 to solar cycle 24. This could be attributed to the Corotating Interaction Regions (CIRs) observed during the declining phase of solar cycle 23 and the deep minimum preceding solar cycle 24.
基金Supported by Research Project on Food Detection Technology Innovation and Standard Integration 2024(YNXM-2024-FW-019).
文摘This paper investigates and analyzes the general situation of the tomato seed production industry in Lintong District,Xi'an City.Development strategies and suggestions are proposed to address existing problems.These include strengthening technological innovation and variety R&D,promoting industrial standardization and intelligent upgrading,enhancing brand building and market expansion,improving policy support and industrial chain coordination,strengthening intellectual property protection and talent cultivation,and expanding sales channels to promote industrial transformation and upgrading.
基金Sponsored by Research Team Project of Anhui Xinhua University(kytd202202)Anhui Provincial College Student Innovation Training Program Support Project(S202212216138,S202212216133,S202212216147)+1 种基金National College Student Innovation Training Program Support Project(AH202112216114)Key Project for Scientific Research in Anhui Higher Education Institutions(Natural Sciences Category)(2024AH050601).
文摘With the accelerating urbanization process,issues related to the urban ecological environment have become increasingly prominent.Among these,greenway optimization is regarded as one of the key approaches to improving urban ecological quality.As the capital of Anhui Province,Hefei is striving to build a comprehensive greenway network in line with its“Park City”strategy.However,the current development of Hefei’s greenways faces challenges such as delayed planning,limited functions,inadequate facilities,and weak operation and maintenance management.In this study,comparative analysis and literature review were combined to comprehensively summarize the current characteristics of greenway development in Hefei,and improvement suggestions were proposed in areas such as ecological restoration,functional expansion,facility establishment,and long-term management.It is suggested that Hefei should enhance the systematic and synergistic nature of its greenway system,create a city green space network with regional characteristics,and optimize the city’s environmental carrying capacity,so as to meet the diverse needs of the public and thereby provide theoretical support and practical guidance for the sustainable development of Hefei’s greenway system.
基金supported by the National Natural Science Foundation of China under Grant 52077030.
文摘As a new dynamic reactive power compensator,the grid-forming Static Var Generator(GF-SVG)can not only provide reactive power-voltage support,but also has inertial support capability.It has been experimentally deployed in many wind farms.However,studies have shown that when the three-phase short-circuit fault occurs in the wind farm,the transient overcurrent during the fault occurrence and fault clearance is suppressed,making it difficult for GF-SVG to use traditional fixed virtual impedance.Aiming at the problem,firstly,the influence of virtual reactance on control stability is analyzed using the GF-SVG’s current open-loop transfer function.Secondly,based on the existing current limitation strategies of GF-SVG,an adaptive virtual reactance current limitation strategy suitable for symmetrical faults of the power grid is proposed,which limits GF-SVG’s transient overcurrent during fault occurrence and fault clearance stage to the tolerance range of GF-SVG’s power devices.Based on the GF-SVG’s active power loop and reactive power loop small signal models,the availability of the proposed adaptive virtual reactance in suppressing the DC voltage drop of GF-SVG is analyzed,and shortening the transient overvoltage recovery time of the wind farm after the fault clearance is also discussed.Finally,electromagnetic simulation proves the effectiveness and correctness of the proposed adaptive current limitation method.
文摘With the increase of global climate change and extreme weather events,more and more attention has been paid to the protection of China's meteorological cultural heritage.Meteorological cultural heritage is an important part of China's cultural heritage,which is unique and non renewable.It is of great significance to the inheritance of China's excellent traditional culture and the construction of a meteorological power.Because it is more special than water conservancy cultural heritage in China's historical development,it is not only a national context,but also mixed with foreign activities.This paper focuses on the protection and research of China's meteorological cultural heritage.Based on the current situation of the protection and utilization of China's meteorological cultural heritage,it analyzes the problems and shortcomings in the current protection work.In response to these problems,some targeted protection measures are proposed,including strengthening the construction of laws and regulations,improving the level of protection technology,enhancing public participation,and promoting the protection and sustainable development of meteorological cultural heritage.The aim is to provide useful references for the protection of China's meteorological cultural heritage in the future.
基金supported by the National Key R&D Program of China(2020YFA0714900,2023YFB3709903)the National Natural Science Foundation of China(U21B2082,52474410)+6 种基金the Key R&D Program of Shandong Province,China(2023CXGC010406)the Scientific Research Special Project for First-Class Disciplines in Inner Mongolia Autonomous Region(YLXKZX-NKD-001)the International Science and Technology Cooperation Project of Higher Education Institutions in Inner Mongolia Autonomous Region(GHXM-002)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(2024ZD06)the Technology Support Project for the Construction of Major Innovation Platforms in Inner Mongolia Autonomous Region(XM2024XTGXQ16)the Beijing Municipal Natural Science Foundation(2222065)the Fundamental Research Funds for the Central Universities(FRF-TP-22-02C2).
文摘Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate atomic diffusion to achieve ultra-fast spheroidization of carbides.However,the understanding of the mechanism by which different pulse current parameters regulate the dissolution behavior of carbides requires a large amount of experimental data to support,which limits the application of pulse current technology in the field of heat treatment.Based on this,quantify the obtained pulse current processing data to create an important dataset that could be applied to machine learning.Through machine learning,the mechanism of mutual influence between carbide regulation and various factors was elucidated,and the optimal spheroidization process parameters were determined.Compared to the 20 h required for traditional heat treatment,the application of pulsed electric current technology achieved ultra-fast spheroidization of GCr15 bearing steel within 90 min.
