In wind power transmission via modular multilevel converter based high voltage direct current(MMCHVDC)systems,under traditional control strategies,MMC-HVDCcannot provide inertia support to the receiving-end grid(REG)d...In wind power transmission via modular multilevel converter based high voltage direct current(MMCHVDC)systems,under traditional control strategies,MMC-HVDCcannot provide inertia support to the receiving-end grid(REG)during disturbances.Moreover,due to the frequency decoupling between the two ends of the MMCHVDC,the sending-end wind farm(SEWF)cannot obtain the frequency variation information of the REG to provide inertia response.Therefore,this paper proposes a novel coordinated source-network-storage inertia control strategy based on wind power transmission via MMC-HVDC system.First,the grid-side MMC station(GS-MMC)maps the frequency variations of the REG to direct current(DC)voltage variations through the frequency mapping control,and uses submodule capacitor energy to provide inertial power.Then,the wind farm-side MMC station(WF-MMC)restores the DC voltage variations to frequency variations through the frequency restoration control and power loss compensation,providing real-time frequency information for the wind farm.Finally,based on real-time frequency information,thewind farmutilizes the rotor kinetic energy and energy storage to provide fast and lasting power support through the wind-storage coordinated inertia control strategy.Meanwhile,when the wind turbines withdraw from the inertia response phase,the energy storage can increase the power output to compensate for the power deficit,preventing secondary frequency drops.Furthermore,this paper uses small-signal analysis to determine the appropriate values for the key parameters of the proposed control strategy.A simulation model of the wind power transmission via MMCHVDC system is built in MATLAB/Simulink environment to validate and evaluate the proposed method.The results show that the proposed coordinated control strategy can effectively improve the system inertia level and avoid the secondary frequency drop under the load sudden increase condition.展开更多
Grid-Forming(GFM)converters are prone to fault-induced overcurrent and power angle instability during grid fault-induced voltage sags.To address this,this paper develops a multi-loop coordinated fault ridethrough(FRT)...Grid-Forming(GFM)converters are prone to fault-induced overcurrent and power angle instability during grid fault-induced voltage sags.To address this,this paper develops a multi-loop coordinated fault ridethrough(FRT)control strategy based on a power outer loop and voltage-current inner loops,aiming to enhance the stability and current-limiting capability of GFM converters during grid fault conditions.During voltage sags,the GFM converter’s voltage source behavior is maintained by dynamically adjusting the reactive power reference to provide voltage support,thereby effectively suppressing the steady-state component of the fault current.To address the active power imbalance induced by voltage sags,a dynamic active power reference correction method based on apparent power is designed to mitigate power angle oscillations and limit transient current.Moreover,an adaptive virtual impedance loop is implemented to enhance dynamic transient current-limiting performance during the fault initiation phase.This approach improves the responsiveness of the inner loop and ensures safe system operation under various fault severities.Under asymmetric fault conditions,a negative-sequence reactive current compensation strategy is incorporated to further suppress negative-sequence voltage and improve voltage symmetry.The proposed control scheme enables coordinated operation of multiple control objectives,including voltage support,current suppression,and power angle stability,across different fault scenarios.Finally,MATLAB/Simulink simulation results validate the effectiveness of the proposed strategy,showcasing its superior performance in current limiting and power angle stability,thereby significantly enhancing the system’s fault ride-through capability.展开更多
A novel algorithm, the immune genetic algorithm based on multi-agent, isproposed for the path planning of tightly coordinated two-robot manipulators, which constructsmainly immune operators accomplished by three steps...A novel algorithm, the immune genetic algorithm based on multi-agent, isproposed for the path planning of tightly coordinated two-robot manipulators, which constructsmainly immune operators accomplished by three steps: defining strategies and methods of multi-agent,calculating virtual forces acting on an agent, and constructing immune operators and performingimmunization during the evolutionary process. It is illustrated to be able to restrain thedegenerate phenomenon effectively and improve the searching ability with high converging speed.展开更多
As the development of new power systems accelerates and the impacts of high renewable energy integration and extreme weather intensify,grid-alternative energy storage is garnering increasing attention for its grid-int...As the development of new power systems accelerates and the impacts of high renewable energy integration and extreme weather intensify,grid-alternative energy storage is garnering increasing attention for its grid-interaction benefits and clear business models.Consequently,assessing the value of grid-alternative energy storage in the systemtransition has become critically important.Considering the performance characteristics of storage,we propose a value assessment frame-work for grid-alternative energy storage,quantifying its non-wires-alternative effects from both cost and benefit perspectives.Building on this,we developed a collaborative planning model for energy storage and transmission grids,aimed at maximizing the economic benefits of storage systems while balancing investment and operational costs.The model considers regional grid interconnections and their interactions with system operation.By participating in system operations,grid-alternative energy storage not only maximizes its own economic benefits but also generates social welfare transfer effects.Furthermore,based on multi-regional interconnected planning,grid-alternative energy storage can reduce system costs by approximately 35%,with the most significant changes observed in generation costs.Multi-regional coordinated planning significantly enhances the sys-tem’s flexibility in regulation.However,when the load factor of interconnection lines between regions remains constant,system operational flexibility tends to decrease,leading to a roughly 28.9%increase in storage investment.Additionally,under regional coordinated planning,the greater the disparity in wind power integration across interconnected regions,the more noticeable the reduction in system costs.展开更多
This paper presents an investigation on the target-guided coordinated control(TACC)of unmanned surface vehicles(USVs).In the scenario of tracking non-cooperative targets,the status information of the target can only b...This paper presents an investigation on the target-guided coordinated control(TACC)of unmanned surface vehicles(USVs).In the scenario of tracking non-cooperative targets,the status information of the target can only be obtained by some USVs.In order to achieve semi-encirclement tracking of noncooperative targets under maritime security conditions,a fixed-time tracking control method based on dynamic surface control(DSC)is proposed in this paper.Firstly,a novel TACC architecture with decoupled kinematic control law and decoupled kinetic control law was designed to reduce the complexity of control system design.Secondly,the proposed DSC-based target-guided kinematic control law including tracking points pre-allocation strategy and sigmoid artificial potential functions(SigAPFs)can avoid collisions during tracking process and optimize kinematic control output.Finally,a fixed-time TACC system was proposed to achieve fast convergence of kinematic and kinetics errors.The effectiveness of the proposed TACC approach in improving target tracking safety and reducing control output chattering was verified by simulation comparison results.展开更多
Redox-active organic compounds have received much attention as high-capacity electrodes for rechargeable batteries.However,the high solubility in organic electrolytes during charge and discharge processes hinders the ...Redox-active organic compounds have received much attention as high-capacity electrodes for rechargeable batteries.However,the high solubility in organic electrolytes during charge and discharge processes hinders the practical exploitation of organic compounds.This study presents a cobalt-based metal–organic coordination compound with bifunctional coordinated water(Co-MOC-H_(2)O)for sodium-ion storage.The coordinated water enhances interactions between sodium ions and nitrogen atoms in organic ligands through chelation,activating the inert sodium-ion storage sites(C=N).Moreover,the stable hydrogen bonded framework formed by the coordinated water molecules prevents the active organic compounds from dissolving into the electrolyte,thereby enhancing cycling stability.With the bifunctional coordinated water molecules,the Co-MOC-H_(2)O electrode delivers a high capacity of 403 mAh g^(-1)at 0.2 A g^(-1)over 600 cycles and exhibits a capacity retention of 77.9%at 2 A g^(-1)after 1100 cycles.This work highlights the crucial role of the coordinated water molecules in constructing high capacity and long-life sodium-ion storage materials.展开更多
The coordinated regional development strategy,recognized as one of China’s seven development strategies,plays a crucial role in reducing regional development disparities,optimizing resource allocation,and facilitatin...The coordinated regional development strategy,recognized as one of China’s seven development strategies,plays a crucial role in reducing regional development disparities,optimizing resource allocation,and facilitating high-quality development.This study analyzes a total of 418 relevant publications from China spanning the years 1998 to 2022.Utilizing CiteSpace software,a visualization analysis of keyword cooccurrence,mutation,and other bibliometric characteristics was conducted.The findings indicate that the number of publications during the specified period exhibited a fluctuating upward trend,with a notable increase observed after 2018.Furthermore,the research demonstrated a weak interdisciplinary crossover and a low intensity of collaboration among authors.The primary thematic areas of focus were identified as follows:connotation,mechanisms,countermeasure and suggestion,and evaluation.展开更多
Dear Editor,This letter is concerned with a coordinated path following control method for multiple unmanned underwater vehicles(UUVs)to carry out maritime search and rescue(MSR)missions.The kinetic model parameters of...Dear Editor,This letter is concerned with a coordinated path following control method for multiple unmanned underwater vehicles(UUVs)to carry out maritime search and rescue(MSR)missions.The kinetic model parameters of each UUV is totally unknown.Firstly,a kinematic control law is constructed by designing a vertical line-of-sight(LOS)guidance scheme.展开更多
In oil and gas exploration,small-scale karst cavities and faults are important targets.The former often serve as reservoir space for carbonate reservoirs,while the latter often provide migration pathways for oil and g...In oil and gas exploration,small-scale karst cavities and faults are important targets.The former often serve as reservoir space for carbonate reservoirs,while the latter often provide migration pathways for oil and gas.Due to these differences,the classification and identification of karst cavities and faults are of great significance for reservoir development.Traditional seismic attributes and diffraction imaging techniques can effectively identify discontinuities in seismic images,but these techniques do not distinguish whether these discontinuities are karst cavities,faults,or other structures.It poses a challenge for seismic interpretation to accurately locate and classify karst cavities or faults within the seismic attribute maps and diffraction imaging profiles.In seismic data,the scattering waves are associated with small-scale scatters like karst cavities,while diffracted waves are seismic responses from discontinuous structures such as faults,reflector edges and fractures.In order to achieve classification and identification of small-scale karst cavities and faults in seismic images,we propose a diffraction classification imaging method which classifies diffracted and scattered waves in the azimuth-dip angle image matrix using a modified DenseNet.We introduce a coordinate attention module into DenseNet,enabling more precise extraction of dynamic and azimuthal features of diffracted and scattered waves in the azimuth-dip angle image matrix.Leveraging these extracted features,the modified DenseNet can produce reliable probabilities for diffracted/scattered waves,achieving high-accuracy automatic classification of cavities and faults based on diffraction imaging.The proposed method achieves 96%classification accuracy on the synthetic dataset.The field data experiment demonstrates that the proposed method can accurately classify small-scale faults and scatterers,further enhancing the resolution of diffraction imaging in complex geologic structures,and contributing to the localization of karstic fracture-cavern reservoirs.展开更多
Conventional coordinated control strategies for DC bus voltage signal(DBS)in islanded DC microgrids(IDCMGs)struggle with coordinating multiple distributed generators(DGs)and cannot effectively incorporate state of cha...Conventional coordinated control strategies for DC bus voltage signal(DBS)in islanded DC microgrids(IDCMGs)struggle with coordinating multiple distributed generators(DGs)and cannot effectively incorporate state of charge(SOC)information of the energy storage system,thereby reducing the system flexibility.In this study,we propose an adaptive coordinated control strategy that employs a two-layer fuzzy neural network controller(FNNC)to adapt to varying operating conditions in an IDCMG with multiple PV and battery energy storage system(BESS)units.The first-layer FNNC generates optimal operating mode commands for each DG,thereby avoiding the requirement for complex operating modes based on SOC segmentation.An optimal switching sequence logic prioritizes the most appropriate units during mode transitions.The second-layer FNNC dynamically adjusts the droop power to overcome power distribution challenges among DG groups.This helps in preventing the PV power from exceeding the limits and mitigating the risk of BESS overcharging or over-discharging.The simulation results indicate that the proposed strategy enhances the coordinated operation of multi-DG IDCMGs,thereby ensuring the efficient and safe utilization of PV and BESS.展开更多
The initial stresses widely exist in elastic materials.While achieving a continuum stress-free configuration through compatible unloading is desirable,mechanical unloading alone frequently proves insufficient,posing c...The initial stresses widely exist in elastic materials.While achieving a continuum stress-free configuration through compatible unloading is desirable,mechanical unloading alone frequently proves insufficient,posing challenges in avoiding virtual stress-free configurations.In this paper,we introduce a novel concept of equivalent temperature variation to counteract the incompatible initial strain.Our focus is on initially stressed cylindrical and spherical elastomers,where we first derive the Saint-Venant,Beltrami-Michell,and Volterra integral conditions in orthogonal curvilinear coordinates using the exterior differential form theory.It is shown that for any given axially or spherically distributed initial stress,an equivalent temperature variation always exists.Furthermore,we propose two innovative initial stress forms based on the steady-state heat conduction.By introducing an equivalent temperature variation,the initial stress can be released through a compatible thermo-mechanical unloading process,offering valuable insights into the constitutive theory of initially stressed elastic materials.展开更多
The disorganized lithium dendrites and unstable solid electrolyte interphase(SEI)severely impede the practical application of lithium metal batteries(LMBs).Herein,the N-Zn-F coordinated triazine-based covalent organic...The disorganized lithium dendrites and unstable solid electrolyte interphase(SEI)severely impede the practical application of lithium metal batteries(LMBs).Herein,the N-Zn-F coordinated triazine-based covalent organic framework(TTA-COF-ZnF_(2))is fabricated for the first time as an artificial SEI layer on the surface of lithium metal anodes(LMAs)to handle these issues.Zn-N coordination in onedimensional(1D)ordered COF can increase lithiophilic sites,reduce the Li-nucleation barrier,and regulate the Li+local coordination environment by optimizing surface charge density around the Zn metal.The electron-rich state induced by strong electron-withdrawing F-groups constructs electronegative nanochannels,which trigger efficient Li+desolvation.These beneficial attributes boost Li^(+)transfer,and homogenize Li^(+)flux,leading to uniform Li deposition.Besides,the lithiophilic triazine ring polar groups in TTA-COF-ZnF_(2)further facilitate the Li^(+)migration.The latent working mechanism of adjusting Li deposition behaviors and stabilizing LMAs for TTA-COF-ZnF_(2)is illustrated by detailed in-situ/ex-situ characterizations and density functional theory(DFT)calculations.As expected,TTA-COF-ZnF_(2)-modified Li|Cu half cells deliver a higher Coulombic efficiency(CE)of 98.4% over 250 cycles and lower nucleation overpotential(11 mV)at 1 mA cm^(-2),while TTA-COF-ZnF_(2)@Li symmetric cells display a long lifespan over3785 h at 2 mA cm^(-2).The TTA-COF-ZnF_(2)@Li|S full cells exert ultra high capacity retention of 81%(837 mA h g^(-1))after 600 cycles at 1C.Besides,the TTA-COF-ZnF_(2)@Li|LFP full cells with a high loading of 7.1 mg cm^(-2)exert ultrahigh capacity retention of 89%(108 mAh g^(-1))after 700 cycles at 5C.This synergistic strategy in N-Zn-F coordinated triazine-based COF provides a new insight to regulate the uniform platins/stripping behaviors for developing ultra-stable and dendrite-free LMBs.展开更多
Agricultural insurance plays a key role in promoting the coordinated development of green agriculture and farmers’income growth,which is crucial for China’s high-quality agricultural development.Using the coupling c...Agricultural insurance plays a key role in promoting the coordinated development of green agriculture and farmers’income growth,which is crucial for China’s high-quality agricultural development.Using the coupling coordination degree model,this study empirically demonstrates that the development of agricultural insurance significantly promotes the coordinated development of green agriculture and farmers’income growth once a certain threshold is exceeded.This effect is more pronounced in the major grain-producing regions and the central provinces.Expanding the scale of agricultural production and increasing investment in agricultural technology are the key mechanisms through which agricultural insurance supports the dual goals of green agriculture and income growth in China.In conclusion,this study proposes several policy recommendations,which include increasing investment in agricultural insurance infrastructure,strengthening the policy guidance for agricultural insurance,and designing differentiated agricultural insurance policies.展开更多
This paper concerns the exponential attitude-orbit coordinated control problems for gravitational-wave detection formation spacecraft systems.Notably,the large-scale communication delays resulting from oversized inter...This paper concerns the exponential attitude-orbit coordinated control problems for gravitational-wave detection formation spacecraft systems.Notably,the large-scale communication delays resulting from oversized inter-satellite distance of space-based laser interferometers are first modeled.Subject to the delayed communication behaviors,a new delay-dependent attitude-orbit coordinated controller is designed.Moreover,by reconstructing the less conservative Lyapunov-Krasovskii functional and free-weight matrices,sufficient criteria are derived to ensure the exponential stability of the closed-loop relative translation and attitude error system.Finally,a simulation example is employed to illustrate the numerical validity of the proposed controller for in-orbit detection missions.展开更多
The exploration of the coupling and coordination between urban innovation capability(IC)and industrial transformation(IF)serves as a novel perspective for interpreting the increasingly severe phenomenon of population ...The exploration of the coupling and coordination between urban innovation capability(IC)and industrial transformation(IF)serves as a novel perspective for interpreting the increasingly severe phenomenon of population shrinkage during the industrialization process.This study investigated the evolutionary characteristics of IC and IF in shrinking and growing cities in Northeast China from 2010 to 2020.It uses entropy weighted model,coupling coordination degree,the Dagum Gini coefficient,and geographic detectors to analyze the coordinated development of IC and IF in the context of population shrinkage.The study analyzed the spatiotemporal patterns and driving mechanisms for their coordinated development.The results show that:1)both urban IC and IF exhibited an overall positive trend during the study period.Shrinking cities depend more on IF to address the challenges of population shrinkage,while growing cities mainly rely on innovation-driven development.2)The coupling gap between IC and IF in shrinking and growing cities has widened over time,with the coordination level of shrinking cities steadily decreasing.Cities with serious disorder are concentrated in northern Heilongjiang Province,while most cities in Jilin Province experience moderate disorder.Liaoning Province,however,shows generally good coupling coordination.3)Human capital is the key factor driving coupling coordination in both types of cities.Shrinking cities rely on economic and financial development,with the‘repair-type’logic that emphasizes short-term economic growth and resource compensation.In contrast,the coupling of growing cities relies on basic support capabilities,with the‘optimization-type’logic focused on enhancing endogenous resilience and systemic coordination.Exploring the coordination between urban innovation capabilities and industrial transformation can provide a new perspective for research on population shrinkage,which holds certain theoretical and practical significance for implementing the new round of revitalization strategy in Northeast China.展开更多
During aircraft ground steering,the nose landing gear(NLG)tires of large transport aircraft often experience excessive lateral loads,leading to sideslip.This compromises steering safety and accelerates tire wear.To ad...During aircraft ground steering,the nose landing gear(NLG)tires of large transport aircraft often experience excessive lateral loads,leading to sideslip.This compromises steering safety and accelerates tire wear.To address this issue,the rear landing gear is typically designed to steer in coordination with the nose wheels,reducing sideslip and improving maneuverability.This study examines how structural parameters and weight distribution affect the performance of coordinated steering in landing gear design for large transport aircraft.Using the C-5 transport aircraft as a case study,we develop a multi-wheel ground steering dynamics model,incorporating the main landing gear(MLG)deflection.A ground handling dynamics model is also established to evaluate the benefits of coordinated steering for rear MLG during steering.Additionally,the study analyzes the impact of structural parameters such as stiffness and damping on the steering performance of the C-5.It further investigates the effects of weight distribution,including the center-of-gravity(CG)height,the longitudinal CG position,and the mass asymmetry.Results show that when the C-5 employs coordinated steering for rear MLG,the lateral friction coefficients of the NLG tires decrease by 22%,24%,26%,and 27%.The steering radius is reduced by 29.7%,and the NLG steering moment decreases by 19%,significantly enhancing maneuverability.Therefore,in the design of landing gear for large transport aircraft,coordinated MLG steering,along with optimal structural and CG position parameters,should be primary design objectives.These results provide theoretical guidance for the design of multi-wheel landing gear systems in large transport aircraft.展开更多
This paper introduces a hybrid configuration design to enhance the precision of satellite antenna position measurement.By fixing the circular array antenna on the antenna mounting surface and integrating coordinate sy...This paper introduces a hybrid configuration design to enhance the precision of satellite antenna position measurement.By fixing the circular array antenna on the antenna mounting surface and integrating coordinate system transformation relationships with interferometric direction finding(DF)and positioning technology,accurate estimation of the antenna position is ensured.This method optimizes the quality and stability of data fusion by integrating pulse parameter characteristics,satellite orbit and attitude information,as well as the field of view information from observation stations,using techniques such as maximum-ratio-combining(MRC)and orbit extrapolation.Specifically,the sampling-importance resampling particle-filtering and Kalman-filtering(SIR-PF-KF)hybrid filtering prediction technology is employed to precisely predict and correct the three-dimensional(3D)position errors of the L-array antenna.Through data processing of five to nine orbits,accurate estimation of the antenna’s 3D position is achieved,achieving an estimation accuracy of 3μm,significantly improving the accuracy of on-orbit rapid calibration.Experimental results show that the interferometer positioning accuracy is improved from 7.9 km before antenna position correction to within 0.2 km after correction,verifying the effectiveness and practicability of this method,which aims to address issues with positioning accuracy.展开更多
In the context of national efforts to promote high-quality development of vocational education and deepen industry-education integration,private vocational undergraduate institutions serve as crucial platforms bridgin...In the context of national efforts to promote high-quality development of vocational education and deepen industry-education integration,private vocational undergraduate institutions serve as crucial platforms bridging the cultivation of high-level technical and skilled talents with regional industrial development.The alignment between their distinctive specialty clusters and regional industrial synergy directly impacts talent development quality and regional economic efficiency.This paper analyzes the inherent logic of coordinated development between specialty clusters and regional industries,leveraging the flexible operational mechanisms and direct industry connections of private vocational institutions.It identifies current challenges,including“inaccurate demand alignment,insufficient resource integration,and loose interest coordination,”and proposes four strategic dimensions:establishing collaborative research mechanisms,optimizing cluster layouts,deepening industry-education integration,and improving support systems.These recommendations provide actionable references for advancing high-quality coordinated development between private vocational institutions and regional industries.展开更多
Research has shown that when vehicles follow the Ackerman steering principle(ASP),the tire wear can be reduced and the path tracking performance can be improved.However,in the case of four-wheel independent steering(4...Research has shown that when vehicles follow the Ackerman steering principle(ASP),the tire wear can be reduced and the path tracking performance can be improved.However,in the case of four-wheel independent steering(4WIS)vehicles,the steering systems of the four wheels are relatively independent,and there are differences and uncertainties in individual steering dynamics,which lead to challenges for all four wheels in simultaneously satisfying the ASP and may deteriorate the vehicle path tracking performance.In response to this problem,this paper introduces a four-wheel consistent coordinated steering control for 4WIS vehicles.The algorithm innovatively reconfigures the Ackerman steering relationships as coupling constraints among the wheels,and utilizes the constraint-following method to design controller.The controller achieves uniform boundedness(UB)and uniform ultimate boundedness(UUB)of ASP constraint error.The Carsim/Simulink joint simulation results demonstrate that the algorithm guarantees the approximate satisfaction of ASP in both the transient and steady-state of the vehicle path tracking.Also,it significantly improves the path tracking performance.展开更多
We employed random distributions and gradient descent methods for the Generator Coordinate Method(GCM)to identify effective basis wave functions,taking halo nuclei ^(6)He and ^(6)Li as examples.By comparing the ground...We employed random distributions and gradient descent methods for the Generator Coordinate Method(GCM)to identify effective basis wave functions,taking halo nuclei ^(6)He and ^(6)Li as examples.By comparing the ground state(0^(+))energy of ^(6)He and the excited state(0^(+))energy of 6 Li calculated with various random distributions and manually selected generation coordinates,we found that the heavy tail characteristic of the logistic distribution better describes the features of the halo nuclei.Subsequently,the Adam algorithm from machine learning was applied to optimize the basis wave functions,indicating that a limited number of basis wave functions can approximate the converged values.These results offer some empirical insights for selecting basis wave functions and contribute to the broader application of machine learning methods in predicting effective basis wave functions.展开更多
基金funded by State Grid Corporation of China Central Branch Technology Project(52140024000C).
文摘In wind power transmission via modular multilevel converter based high voltage direct current(MMCHVDC)systems,under traditional control strategies,MMC-HVDCcannot provide inertia support to the receiving-end grid(REG)during disturbances.Moreover,due to the frequency decoupling between the two ends of the MMCHVDC,the sending-end wind farm(SEWF)cannot obtain the frequency variation information of the REG to provide inertia response.Therefore,this paper proposes a novel coordinated source-network-storage inertia control strategy based on wind power transmission via MMC-HVDC system.First,the grid-side MMC station(GS-MMC)maps the frequency variations of the REG to direct current(DC)voltage variations through the frequency mapping control,and uses submodule capacitor energy to provide inertial power.Then,the wind farm-side MMC station(WF-MMC)restores the DC voltage variations to frequency variations through the frequency restoration control and power loss compensation,providing real-time frequency information for the wind farm.Finally,based on real-time frequency information,thewind farmutilizes the rotor kinetic energy and energy storage to provide fast and lasting power support through the wind-storage coordinated inertia control strategy.Meanwhile,when the wind turbines withdraw from the inertia response phase,the energy storage can increase the power output to compensate for the power deficit,preventing secondary frequency drops.Furthermore,this paper uses small-signal analysis to determine the appropriate values for the key parameters of the proposed control strategy.A simulation model of the wind power transmission via MMCHVDC system is built in MATLAB/Simulink environment to validate and evaluate the proposed method.The results show that the proposed coordinated control strategy can effectively improve the system inertia level and avoid the secondary frequency drop under the load sudden increase condition.
文摘Grid-Forming(GFM)converters are prone to fault-induced overcurrent and power angle instability during grid fault-induced voltage sags.To address this,this paper develops a multi-loop coordinated fault ridethrough(FRT)control strategy based on a power outer loop and voltage-current inner loops,aiming to enhance the stability and current-limiting capability of GFM converters during grid fault conditions.During voltage sags,the GFM converter’s voltage source behavior is maintained by dynamically adjusting the reactive power reference to provide voltage support,thereby effectively suppressing the steady-state component of the fault current.To address the active power imbalance induced by voltage sags,a dynamic active power reference correction method based on apparent power is designed to mitigate power angle oscillations and limit transient current.Moreover,an adaptive virtual impedance loop is implemented to enhance dynamic transient current-limiting performance during the fault initiation phase.This approach improves the responsiveness of the inner loop and ensures safe system operation under various fault severities.Under asymmetric fault conditions,a negative-sequence reactive current compensation strategy is incorporated to further suppress negative-sequence voltage and improve voltage symmetry.The proposed control scheme enables coordinated operation of multiple control objectives,including voltage support,current suppression,and power angle stability,across different fault scenarios.Finally,MATLAB/Simulink simulation results validate the effectiveness of the proposed strategy,showcasing its superior performance in current limiting and power angle stability,thereby significantly enhancing the system’s fault ride-through capability.
文摘A novel algorithm, the immune genetic algorithm based on multi-agent, isproposed for the path planning of tightly coordinated two-robot manipulators, which constructsmainly immune operators accomplished by three steps: defining strategies and methods of multi-agent,calculating virtual forces acting on an agent, and constructing immune operators and performingimmunization during the evolutionary process. It is illustrated to be able to restrain thedegenerate phenomenon effectively and improve the searching ability with high converging speed.
基金funded by the Technology Project of State Grid Jibei Electric Power Supply Co.,Ltd.(Grant Number:52018F240001).
文摘As the development of new power systems accelerates and the impacts of high renewable energy integration and extreme weather intensify,grid-alternative energy storage is garnering increasing attention for its grid-interaction benefits and clear business models.Consequently,assessing the value of grid-alternative energy storage in the systemtransition has become critically important.Considering the performance characteristics of storage,we propose a value assessment frame-work for grid-alternative energy storage,quantifying its non-wires-alternative effects from both cost and benefit perspectives.Building on this,we developed a collaborative planning model for energy storage and transmission grids,aimed at maximizing the economic benefits of storage systems while balancing investment and operational costs.The model considers regional grid interconnections and their interactions with system operation.By participating in system operations,grid-alternative energy storage not only maximizes its own economic benefits but also generates social welfare transfer effects.Furthermore,based on multi-regional interconnected planning,grid-alternative energy storage can reduce system costs by approximately 35%,with the most significant changes observed in generation costs.Multi-regional coordinated planning significantly enhances the sys-tem’s flexibility in regulation.However,when the load factor of interconnection lines between regions remains constant,system operational flexibility tends to decrease,leading to a roughly 28.9%increase in storage investment.Additionally,under regional coordinated planning,the greater the disparity in wind power integration across interconnected regions,the more noticeable the reduction in system costs.
文摘This paper presents an investigation on the target-guided coordinated control(TACC)of unmanned surface vehicles(USVs).In the scenario of tracking non-cooperative targets,the status information of the target can only be obtained by some USVs.In order to achieve semi-encirclement tracking of noncooperative targets under maritime security conditions,a fixed-time tracking control method based on dynamic surface control(DSC)is proposed in this paper.Firstly,a novel TACC architecture with decoupled kinematic control law and decoupled kinetic control law was designed to reduce the complexity of control system design.Secondly,the proposed DSC-based target-guided kinematic control law including tracking points pre-allocation strategy and sigmoid artificial potential functions(SigAPFs)can avoid collisions during tracking process and optimize kinematic control output.Finally,a fixed-time TACC system was proposed to achieve fast convergence of kinematic and kinetics errors.The effectiveness of the proposed TACC approach in improving target tracking safety and reducing control output chattering was verified by simulation comparison results.
基金supported by the National Natural Science Foundation of China(22121005,92372203,92372001,52072186,and 52301278)the National Key Research and Development Program of China(2022YFB2402200)+3 种基金the Science and Technology Plans of Tianjin(23JCYBJC00170)the Fundamental Research Funds for the Central Universities,Nankai University(63241206 and 9242000710)Shanghai Jiao Tong University Shaoxing Research Institute of Renewable Energy and Molecular Engineering(JDSX2023003)the Natural Science Foundation of Jiangsu Province(BK20230937).
文摘Redox-active organic compounds have received much attention as high-capacity electrodes for rechargeable batteries.However,the high solubility in organic electrolytes during charge and discharge processes hinders the practical exploitation of organic compounds.This study presents a cobalt-based metal–organic coordination compound with bifunctional coordinated water(Co-MOC-H_(2)O)for sodium-ion storage.The coordinated water enhances interactions between sodium ions and nitrogen atoms in organic ligands through chelation,activating the inert sodium-ion storage sites(C=N).Moreover,the stable hydrogen bonded framework formed by the coordinated water molecules prevents the active organic compounds from dissolving into the electrolyte,thereby enhancing cycling stability.With the bifunctional coordinated water molecules,the Co-MOC-H_(2)O electrode delivers a high capacity of 403 mAh g^(-1)at 0.2 A g^(-1)over 600 cycles and exhibits a capacity retention of 77.9%at 2 A g^(-1)after 1100 cycles.This work highlights the crucial role of the coordinated water molecules in constructing high capacity and long-life sodium-ion storage materials.
文摘The coordinated regional development strategy,recognized as one of China’s seven development strategies,plays a crucial role in reducing regional development disparities,optimizing resource allocation,and facilitating high-quality development.This study analyzes a total of 418 relevant publications from China spanning the years 1998 to 2022.Utilizing CiteSpace software,a visualization analysis of keyword cooccurrence,mutation,and other bibliometric characteristics was conducted.The findings indicate that the number of publications during the specified period exhibited a fluctuating upward trend,with a notable increase observed after 2018.Furthermore,the research demonstrated a weak interdisciplinary crossover and a low intensity of collaboration among authors.The primary thematic areas of focus were identified as follows:connotation,mechanisms,countermeasure and suggestion,and evaluation.
基金supported by the National Science and Technology Major Project(2022ZD0119902)the Doctoral Scientific Research Foundation of Liaoning Province(2023-BS-077)+2 种基金the Postdoctoral Research Foundation of China(2024M751980)the Open Project of State Key Laboratory of Maritime Technology and Safety(SKLMTA-DMU2024Y3)Bolian Research Funds of Dalian Maritime University/Fundamental Research Funds for the Central Universities(3132023616).
文摘Dear Editor,This letter is concerned with a coordinated path following control method for multiple unmanned underwater vehicles(UUVs)to carry out maritime search and rescue(MSR)missions.The kinetic model parameters of each UUV is totally unknown.Firstly,a kinematic control law is constructed by designing a vertical line-of-sight(LOS)guidance scheme.
基金supported by Science Fund for Creative Research Groups of the National Natural Science Foundation of China,No.42321002。
文摘In oil and gas exploration,small-scale karst cavities and faults are important targets.The former often serve as reservoir space for carbonate reservoirs,while the latter often provide migration pathways for oil and gas.Due to these differences,the classification and identification of karst cavities and faults are of great significance for reservoir development.Traditional seismic attributes and diffraction imaging techniques can effectively identify discontinuities in seismic images,but these techniques do not distinguish whether these discontinuities are karst cavities,faults,or other structures.It poses a challenge for seismic interpretation to accurately locate and classify karst cavities or faults within the seismic attribute maps and diffraction imaging profiles.In seismic data,the scattering waves are associated with small-scale scatters like karst cavities,while diffracted waves are seismic responses from discontinuous structures such as faults,reflector edges and fractures.In order to achieve classification and identification of small-scale karst cavities and faults in seismic images,we propose a diffraction classification imaging method which classifies diffracted and scattered waves in the azimuth-dip angle image matrix using a modified DenseNet.We introduce a coordinate attention module into DenseNet,enabling more precise extraction of dynamic and azimuthal features of diffracted and scattered waves in the azimuth-dip angle image matrix.Leveraging these extracted features,the modified DenseNet can produce reliable probabilities for diffracted/scattered waves,achieving high-accuracy automatic classification of cavities and faults based on diffraction imaging.The proposed method achieves 96%classification accuracy on the synthetic dataset.The field data experiment demonstrates that the proposed method can accurately classify small-scale faults and scatterers,further enhancing the resolution of diffraction imaging in complex geologic structures,and contributing to the localization of karstic fracture-cavern reservoirs.
基金supported by National Key R&D Program of ChinaunderGrant,(2021YFB2601403).
文摘Conventional coordinated control strategies for DC bus voltage signal(DBS)in islanded DC microgrids(IDCMGs)struggle with coordinating multiple distributed generators(DGs)and cannot effectively incorporate state of charge(SOC)information of the energy storage system,thereby reducing the system flexibility.In this study,we propose an adaptive coordinated control strategy that employs a two-layer fuzzy neural network controller(FNNC)to adapt to varying operating conditions in an IDCMG with multiple PV and battery energy storage system(BESS)units.The first-layer FNNC generates optimal operating mode commands for each DG,thereby avoiding the requirement for complex operating modes based on SOC segmentation.An optimal switching sequence logic prioritizes the most appropriate units during mode transitions.The second-layer FNNC dynamically adjusts the droop power to overcome power distribution challenges among DG groups.This helps in preventing the PV power from exceeding the limits and mitigating the risk of BESS overcharging or over-discharging.The simulation results indicate that the proposed strategy enhances the coordinated operation of multi-DG IDCMGs,thereby ensuring the efficient and safe utilization of PV and BESS.
基金Project supported by the National Natural Science Foundation of China(Nos.12241205 and 12032019)the National Key Research and Development Program of China(No.2022YFA1203200)the Strategic Priority Research Program of Chinese Academy of Sciences(Nos.XDB0620101 and XDB0620103)。
文摘The initial stresses widely exist in elastic materials.While achieving a continuum stress-free configuration through compatible unloading is desirable,mechanical unloading alone frequently proves insufficient,posing challenges in avoiding virtual stress-free configurations.In this paper,we introduce a novel concept of equivalent temperature variation to counteract the incompatible initial strain.Our focus is on initially stressed cylindrical and spherical elastomers,where we first derive the Saint-Venant,Beltrami-Michell,and Volterra integral conditions in orthogonal curvilinear coordinates using the exterior differential form theory.It is shown that for any given axially or spherically distributed initial stress,an equivalent temperature variation always exists.Furthermore,we propose two innovative initial stress forms based on the steady-state heat conduction.By introducing an equivalent temperature variation,the initial stress can be released through a compatible thermo-mechanical unloading process,offering valuable insights into the constitutive theory of initially stressed elastic materials.
基金financially supported by the National Natural Science Foundation of China(52472093,52176185)the Department of Science and Technology of Hubei Province of China(2022CFA069,2022BAA086)。
文摘The disorganized lithium dendrites and unstable solid electrolyte interphase(SEI)severely impede the practical application of lithium metal batteries(LMBs).Herein,the N-Zn-F coordinated triazine-based covalent organic framework(TTA-COF-ZnF_(2))is fabricated for the first time as an artificial SEI layer on the surface of lithium metal anodes(LMAs)to handle these issues.Zn-N coordination in onedimensional(1D)ordered COF can increase lithiophilic sites,reduce the Li-nucleation barrier,and regulate the Li+local coordination environment by optimizing surface charge density around the Zn metal.The electron-rich state induced by strong electron-withdrawing F-groups constructs electronegative nanochannels,which trigger efficient Li+desolvation.These beneficial attributes boost Li^(+)transfer,and homogenize Li^(+)flux,leading to uniform Li deposition.Besides,the lithiophilic triazine ring polar groups in TTA-COF-ZnF_(2)further facilitate the Li^(+)migration.The latent working mechanism of adjusting Li deposition behaviors and stabilizing LMAs for TTA-COF-ZnF_(2)is illustrated by detailed in-situ/ex-situ characterizations and density functional theory(DFT)calculations.As expected,TTA-COF-ZnF_(2)-modified Li|Cu half cells deliver a higher Coulombic efficiency(CE)of 98.4% over 250 cycles and lower nucleation overpotential(11 mV)at 1 mA cm^(-2),while TTA-COF-ZnF_(2)@Li symmetric cells display a long lifespan over3785 h at 2 mA cm^(-2).The TTA-COF-ZnF_(2)@Li|S full cells exert ultra high capacity retention of 81%(837 mA h g^(-1))after 600 cycles at 1C.Besides,the TTA-COF-ZnF_(2)@Li|LFP full cells with a high loading of 7.1 mg cm^(-2)exert ultrahigh capacity retention of 89%(108 mAh g^(-1))after 700 cycles at 5C.This synergistic strategy in N-Zn-F coordinated triazine-based COF provides a new insight to regulate the uniform platins/stripping behaviors for developing ultra-stable and dendrite-free LMBs.
基金This paper presents preliminary research findings from two projects:a major project funded by the National Social Science Fund of China,titled“Changes in the Nature of Rural Poverty in China in the New Era and Research on Post-2020 Anti-Poverty Policies”(Project No:19ZDA116)Doctoral Research Project under the Special Program for Talents in Shortage Areas Serving National Needs,Nanjing University of Finance and Economics,titled“The Impact of Policy-Based Agricultural Insurance on Farmers’Income and Welfare Levels”(Project No:BSZX2021-12).
文摘Agricultural insurance plays a key role in promoting the coordinated development of green agriculture and farmers’income growth,which is crucial for China’s high-quality agricultural development.Using the coupling coordination degree model,this study empirically demonstrates that the development of agricultural insurance significantly promotes the coordinated development of green agriculture and farmers’income growth once a certain threshold is exceeded.This effect is more pronounced in the major grain-producing regions and the central provinces.Expanding the scale of agricultural production and increasing investment in agricultural technology are the key mechanisms through which agricultural insurance supports the dual goals of green agriculture and income growth in China.In conclusion,this study proposes several policy recommendations,which include increasing investment in agricultural insurance infrastructure,strengthening the policy guidance for agricultural insurance,and designing differentiated agricultural insurance policies.
基金supported by the Na⁃tional Key R&D Program of China(No.2022YFC2204800)the Graduate Student Independent Exploration and Innovation Program of Central South University(No.2024ZZTS 0767).
文摘This paper concerns the exponential attitude-orbit coordinated control problems for gravitational-wave detection formation spacecraft systems.Notably,the large-scale communication delays resulting from oversized inter-satellite distance of space-based laser interferometers are first modeled.Subject to the delayed communication behaviors,a new delay-dependent attitude-orbit coordinated controller is designed.Moreover,by reconstructing the less conservative Lyapunov-Krasovskii functional and free-weight matrices,sufficient criteria are derived to ensure the exponential stability of the closed-loop relative translation and attitude error system.Finally,a simulation example is employed to illustrate the numerical validity of the proposed controller for in-orbit detection missions.
基金Under the auspices of National Natural Science Foundation of China(No.42471227,42171198)。
文摘The exploration of the coupling and coordination between urban innovation capability(IC)and industrial transformation(IF)serves as a novel perspective for interpreting the increasingly severe phenomenon of population shrinkage during the industrialization process.This study investigated the evolutionary characteristics of IC and IF in shrinking and growing cities in Northeast China from 2010 to 2020.It uses entropy weighted model,coupling coordination degree,the Dagum Gini coefficient,and geographic detectors to analyze the coordinated development of IC and IF in the context of population shrinkage.The study analyzed the spatiotemporal patterns and driving mechanisms for their coordinated development.The results show that:1)both urban IC and IF exhibited an overall positive trend during the study period.Shrinking cities depend more on IF to address the challenges of population shrinkage,while growing cities mainly rely on innovation-driven development.2)The coupling gap between IC and IF in shrinking and growing cities has widened over time,with the coordination level of shrinking cities steadily decreasing.Cities with serious disorder are concentrated in northern Heilongjiang Province,while most cities in Jilin Province experience moderate disorder.Liaoning Province,however,shows generally good coupling coordination.3)Human capital is the key factor driving coupling coordination in both types of cities.Shrinking cities rely on economic and financial development,with the‘repair-type’logic that emphasizes short-term economic growth and resource compensation.In contrast,the coupling of growing cities relies on basic support capabilities,with the‘optimization-type’logic focused on enhancing endogenous resilience and systemic coordination.Exploring the coordination between urban innovation capabilities and industrial transformation can provide a new perspective for research on population shrinkage,which holds certain theoretical and practical significance for implementing the new round of revitalization strategy in Northeast China.
基金supported in part by the Fundamental Research Funds for the Central Universi-ties(No.NP2022416)the Aeronautical Science Founda-tion of China(No.2022Z029052001).
文摘During aircraft ground steering,the nose landing gear(NLG)tires of large transport aircraft often experience excessive lateral loads,leading to sideslip.This compromises steering safety and accelerates tire wear.To address this issue,the rear landing gear is typically designed to steer in coordination with the nose wheels,reducing sideslip and improving maneuverability.This study examines how structural parameters and weight distribution affect the performance of coordinated steering in landing gear design for large transport aircraft.Using the C-5 transport aircraft as a case study,we develop a multi-wheel ground steering dynamics model,incorporating the main landing gear(MLG)deflection.A ground handling dynamics model is also established to evaluate the benefits of coordinated steering for rear MLG during steering.Additionally,the study analyzes the impact of structural parameters such as stiffness and damping on the steering performance of the C-5.It further investigates the effects of weight distribution,including the center-of-gravity(CG)height,the longitudinal CG position,and the mass asymmetry.Results show that when the C-5 employs coordinated steering for rear MLG,the lateral friction coefficients of the NLG tires decrease by 22%,24%,26%,and 27%.The steering radius is reduced by 29.7%,and the NLG steering moment decreases by 19%,significantly enhancing maneuverability.Therefore,in the design of landing gear for large transport aircraft,coordinated MLG steering,along with optimal structural and CG position parameters,should be primary design objectives.These results provide theoretical guidance for the design of multi-wheel landing gear systems in large transport aircraft.
文摘This paper introduces a hybrid configuration design to enhance the precision of satellite antenna position measurement.By fixing the circular array antenna on the antenna mounting surface and integrating coordinate system transformation relationships with interferometric direction finding(DF)and positioning technology,accurate estimation of the antenna position is ensured.This method optimizes the quality and stability of data fusion by integrating pulse parameter characteristics,satellite orbit and attitude information,as well as the field of view information from observation stations,using techniques such as maximum-ratio-combining(MRC)and orbit extrapolation.Specifically,the sampling-importance resampling particle-filtering and Kalman-filtering(SIR-PF-KF)hybrid filtering prediction technology is employed to precisely predict and correct the three-dimensional(3D)position errors of the L-array antenna.Through data processing of five to nine orbits,accurate estimation of the antenna’s 3D position is achieved,achieving an estimation accuracy of 3μm,significantly improving the accuracy of on-orbit rapid calibration.Experimental results show that the interferometer positioning accuracy is improved from 7.9 km before antenna position correction to within 0.2 km after correction,verifying the effectiveness and practicability of this method,which aims to address issues with positioning accuracy.
基金China Private Education Association 2025 Annual Planning Topic“Research on the Construction Path of Characteristic Specialty Groups in Private Vocational Undergraduate Colleges——Dynamic Adjustment Mechanism of Specialty at Hainan Science and Technology Vocational University Based on Regional Industrial Demand”(CANQN250302)。
文摘In the context of national efforts to promote high-quality development of vocational education and deepen industry-education integration,private vocational undergraduate institutions serve as crucial platforms bridging the cultivation of high-level technical and skilled talents with regional industrial development.The alignment between their distinctive specialty clusters and regional industrial synergy directly impacts talent development quality and regional economic efficiency.This paper analyzes the inherent logic of coordinated development between specialty clusters and regional industries,leveraging the flexible operational mechanisms and direct industry connections of private vocational institutions.It identifies current challenges,including“inaccurate demand alignment,insufficient resource integration,and loose interest coordination,”and proposes four strategic dimensions:establishing collaborative research mechanisms,optimizing cluster layouts,deepening industry-education integration,and improving support systems.These recommendations provide actionable references for advancing high-quality coordinated development between private vocational institutions and regional industries.
基金Supported by National Natural Science Foundation of China(Grant Nos.52222216,52202493,52202466,U24B20124)Hunan Provincial Natural Science Foundation of China(Grant No.2022JJ40059).
文摘Research has shown that when vehicles follow the Ackerman steering principle(ASP),the tire wear can be reduced and the path tracking performance can be improved.However,in the case of four-wheel independent steering(4WIS)vehicles,the steering systems of the four wheels are relatively independent,and there are differences and uncertainties in individual steering dynamics,which lead to challenges for all four wheels in simultaneously satisfying the ASP and may deteriorate the vehicle path tracking performance.In response to this problem,this paper introduces a four-wheel consistent coordinated steering control for 4WIS vehicles.The algorithm innovatively reconfigures the Ackerman steering relationships as coupling constraints among the wheels,and utilizes the constraint-following method to design controller.The controller achieves uniform boundedness(UB)and uniform ultimate boundedness(UUB)of ASP constraint error.The Carsim/Simulink joint simulation results demonstrate that the algorithm guarantees the approximate satisfaction of ASP in both the transient and steady-state of the vehicle path tracking.Also,it significantly improves the path tracking performance.
基金supported by the National Key R&D Program of China(No.2023YFA1606701)the National Natural Science Foundation of China(Nos.12175042,11890710,11890714,12047514,12147101,and 12347106)+1 种基金Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030008)China National Key R&D Program(No.2022YFA1602402).
文摘We employed random distributions and gradient descent methods for the Generator Coordinate Method(GCM)to identify effective basis wave functions,taking halo nuclei ^(6)He and ^(6)Li as examples.By comparing the ground state(0^(+))energy of ^(6)He and the excited state(0^(+))energy of 6 Li calculated with various random distributions and manually selected generation coordinates,we found that the heavy tail characteristic of the logistic distribution better describes the features of the halo nuclei.Subsequently,the Adam algorithm from machine learning was applied to optimize the basis wave functions,indicating that a limited number of basis wave functions can approximate the converged values.These results offer some empirical insights for selecting basis wave functions and contribute to the broader application of machine learning methods in predicting effective basis wave functions.
