A three-dimensional(3D)electromagnetic(EM)inversion algorithm based on the nonlinear conjugate gradient(NLCG)method and a two-color plane Gauss-Seidel(GS)multigrid(MG)forward solver is developed to improve inversion e...A three-dimensional(3D)electromagnetic(EM)inversion algorithm based on the nonlinear conjugate gradient(NLCG)method and a two-color plane Gauss-Seidel(GS)multigrid(MG)forward solver is developed to improve inversion efficiency.The results indicate that the computational efficiency of each inversion can be improved by approximately a factor of three by using the proposed MG solver.First,the accuracy of the MG solver is validated through a test on a synthetic model.Next,the numerical performance of the inversion algorithm is evaluated using this model.Finally,the inversion algorithm is applied to a field EM data collected at the Beiya gold polymetallic ore district.A 3D resistivity model is obtained,and the formation process of the metal ore is analyzed.展开更多
As key equipment in medium voltage DC(MVDC)systems,modular multilevel AC/DC and DC/DC converters(MM-AC/DC,MM-DC/DC)have drawn marvelous attractions.However,research on DC fault ride-through focuses on MM-AC/DC,and the...As key equipment in medium voltage DC(MVDC)systems,modular multilevel AC/DC and DC/DC converters(MM-AC/DC,MM-DC/DC)have drawn marvelous attractions.However,research on DC fault ride-through focuses on MM-AC/DC,and the fault current elimination for MM-DC/DC remains a research gap,which limits the wide application of the MVDC system.To fulfil this research gap,the contribution of this paper is revealing the fault current characteristics of MM-DC/DC based on half-bridge and full-bridge submodules(HBSM and FBSM)and proposing a novel MM-DC/DC based on hybrid HBSM and thyristor-diode module(TDM).By integrating TDM in the upper bridge arm of one phase and the down bridge arm of the other phase in MM-DC/DC,the MM-DC/DC achieves self-elimination of fault currents.The basic concept is using the energy at the healthy side to modulate a reverse voltage source(RVS)at the faulty side of MM-DC/DC,forcing fault current through TDM pass across zero.TDM can extinguish the resulting fault current.The parameter design and control strategy of the novel MM-DC/DC are discussed.Simulation is carried out for verification,and the results show that fault current can be eliminated within several milliseconds without causing excessive operating losses and costs.展开更多
Conventional multilevel inverters often suffer from high harmonic distortion and increased design complexity due to the need for numerous power semiconductor components,particularly at elevated voltage levels.Addressi...Conventional multilevel inverters often suffer from high harmonic distortion and increased design complexity due to the need for numerous power semiconductor components,particularly at elevated voltage levels.Addressing these shortcomings,thiswork presents a robust 15-level PackedUCell(PUC)inverter topology designed for renewable energy and grid-connected applications.The proposed systemintegrates a sensor less proportional-resonant(PR)controller with an advanced carrier-based pulse width modulation scheme.This approach efficiently balances capacitor voltage,minimizes steady-state error,and strongly suppresses both zero and third-order harmonics resulting in reduced total harmonic distortion and enhanced voltage regulation.Additionally,a novel switching algorithm simplifies the design and implementation,further lowering voltage stress across switches.Extensive simulation results validate the performance under various resistive and resistive-inductive load conditions,demonstrating compliance with IEEE-519 THD standards and robust operation under dynamic changes.The proposed sensorless PR-controlled 15-PUC inverter thus offers a compelling,cost-effective solution for efficient power conversion in next-generation renewable energy systems.展开更多
Peripheral nerve injury is a common neurological condition that often leads to severe functional limitations and disabilities.Research on the pathogenesis of peripheral nerve injury has focused on pathological changes...Peripheral nerve injury is a common neurological condition that often leads to severe functional limitations and disabilities.Research on the pathogenesis of peripheral nerve injury has focused on pathological changes at individual injury sites,neglecting multilevel pathological analysis of the overall nervous system and target organs.This has led to restrictions on current therapeutic approaches.In this paper,we first summarize the potential mechanisms of peripheral nerve injury from a holistic perspective,covering the central nervous system,peripheral nervous system,and target organs.After peripheral nerve injury,the cortical plasticity of the brain is altered due to damage to and regeneration of peripheral nerves;changes such as neuronal apoptosis and axonal demyelination occur in the spinal cord.The nerve will undergo axonal regeneration,activation of Schwann cells,inflammatory response,and vascular system regeneration at the injury site.Corresponding damage to target organs can occur,including skeletal muscle atrophy and sensory receptor disruption.We then provide a brief review of the research advances in therapeutic approaches to peripheral nerve injury.The main current treatments are conducted passively and include physical factor rehabilitation,pharmacological treatments,cell-based therapies,and physical exercise.However,most treatments only partially address the problem and cannot complete the systematic recovery of the entire central nervous system-peripheral nervous system-target organ pathway.Therefore,we should further explore multilevel treatment options that produce effective,long-lasting results,perhaps requiring a combination of passive(traditional)and active(novel)treatment methods to stimulate rehabilitation at the central-peripheral-target organ levels to achieve better functional recovery.展开更多
The use of electronic currency for transactions,denoting a cashless paradigm,has become increasingly common.However,this financial innovation is not prevalent in all countries.This study aims to explain the discrepanc...The use of electronic currency for transactions,denoting a cashless paradigm,has become increasingly common.However,this financial innovation is not prevalent in all countries.This study aims to explain the discrepancies across countries,including individual and country factors.It may be superficially posited that this lag in development stems from individual or microlevel usage challenges.However,the application of the Technology Acceptance Model highlights the presence of overarching characteristics conducive to extensive adoption.Thus,an additional stratum,the multilevel perspective,needs to be examined.This analytical framework incorporates not only individual attributes but also the sociotechnical framework or mesolevel factors in which they operate.A multilevel econometric model is used.The results of these analyses show that the impact on the adoption of cashless payments extends beyond individual factors(attitude to technology use,perceived usefulness,and perceived ease of use).Our primary contribution,conceptually and empirically,is to broaden the analysis vision.A comprehensive multilevel analysis revealed that broader contextual elements,such as infrastructure and national skills,exert a significant influence on the adoption of cashless transactions.Consequently,the widespread acceptance of cashless payment methods is not only contingent on individual choices but is also a collective phenomenon in which the surrounding environment plays a crucial role as a catalyst for the end users in the cashless economy.展开更多
Hydrogen production coupled with small molecule oxidation derived by renewable energy power has been widely studied as an effective method to reduce energy consumption and prepare added value production.Here,the coppe...Hydrogen production coupled with small molecule oxidation derived by renewable energy power has been widely studied as an effective method to reduce energy consumption and prepare added value production.Here,the copper-cobalt phosphide with a multilevel structure has been designed based on the hard and soft acids and bases theory.The nanocone composed of lamellas presented a sharp tip,which a positive effect on the mass transfer enhanced by a local electric field,and the nanolamellas contain CoP/Cu_(3)P interface provide the highly selective active site for the gluconic acid(GNA)synthesis and hydrogen evolution.The catalyst can drive hydrogen evolution at 5 A·cm^(-2)up to 437 h without active decay,and the electrocatalytic glucose oxidation at anode presents high efficiency due to Cu(I)introduction and the synergetic effect between interfaces.Density functional theory(DFT)calculation shows that water splitting more readily occurs at the CoP,which provides adsorbed H and-OH for hydrogen evolution and glucose oxidation,respectively,and glucose adsorption more readily occurs at the Cu_(3)P,which presents lower conversion energy for high value-added GNA.Efficient hydrogen evolution and glucose conversion indicate its high intrinsic activity and synergetic effect.This work provides a special interface construction strategy for the catalytic conversion of hydrogen and small molecules.展开更多
In this study,we used an extensive sampling network established in central Romania to develop tree height and crown length models.Our analysis included more than 18,000 tree measurements from five different species.In...In this study,we used an extensive sampling network established in central Romania to develop tree height and crown length models.Our analysis included more than 18,000 tree measurements from five different species.Instead of building univariate models for each response variable,we employed a multivariate approach using seemingly unrelated mixed-effects models.These models incorporated variables related to species mixture,tree and stand size,competition,and stand structure.With the inclusion of additional variables in the multivariate seemingly unrelated mixed-effects models,the accuracy of the height prediction models improved by over 10% for all species,whereas the improvement in the crown length models was considerably smaller.Our findings indicate that trees in mixed stands tend to have shorter heights but longer crowns than those in pure stands.We also observed that trees in homogeneous stand structures have shorter crown lengths than those in heterogeneous stands.By employing a multivariate mixed-effects modelling framework,we were able to perform cross-model random-effect predictions,leading to a significant increase in accuracy when both responses were used to calibrate the model.In contrast,the improvement in accuracy was marginal when only height was used for calibration.We demonstrate how multivariate mixed-effects models can be effectively used to develop multi-response allometric models that can be easily calibrated with a limited number of observations while simultaneously achieving better-aligned projections.展开更多
In the quest for high-efficiency and cost-effective catalysts for the oxygen evolution reaction(OER),a novel biomass-driven strategy is developed to fabricate a unique one-dimensional rod-arrays@two-dimensional interl...In the quest for high-efficiency and cost-effective catalysts for the oxygen evolution reaction(OER),a novel biomass-driven strategy is developed to fabricate a unique one-dimensional rod-arrays@two-dimensional interlaced-sheets(C_(1D@2D))network.A groundbreaking chemical fermentation(CF)pore-generation mechanism,proposed for the first time for creating nanopores within carbon structures,is based on the optimal balance between gasification and solidification.This mechanism not only results in a distinctive C_(1D@2D) multilevel network with nanoscale,intersecting and freely flowing channels but also introduces a novel concept for in situ,extensive and hierarchical pore formation.The unique architecture,combined with the homogeneous dispersion of Ni-Fe nanoparticles,facilitates easy electrolyte penetration and provides abundant active sites for the anchoring and dispersion of reactive molecules or ions.Consequently,the Ni-Fe@C_(1D@2D) porous network demonstrates an exceptional OER electrocatalytic performance,achieving a record-low overpotential of 165 mV at 10 mA cm^(−2)and maintaining long-term stability for over 90 h.Theoretical calculations reveal that the porous structure markedly strengthens the interaction between alloy nanoparticles and the carbon matrix,thereby significantly boosting their electrocatalytic activity and stability.These findings unequivocally validate the CF pore-generation mechanism as a powerful and innovative strategy for designing highly efficient functional nanostructures.展开更多
基金financially supported by the National Science and Technology Major Project,China(No.2024ZD1002100)the National Natural Science Foundation of China(Nos.42330801,42474112,42504062)+1 种基金the China Postdoctoral Science Foundation(No.2024M761704)Shuimu Tsinghua Scholar Program of Tsinghua University,China(No.2024SM114)。
文摘A three-dimensional(3D)electromagnetic(EM)inversion algorithm based on the nonlinear conjugate gradient(NLCG)method and a two-color plane Gauss-Seidel(GS)multigrid(MG)forward solver is developed to improve inversion efficiency.The results indicate that the computational efficiency of each inversion can be improved by approximately a factor of three by using the proposed MG solver.First,the accuracy of the MG solver is validated through a test on a synthetic model.Next,the numerical performance of the inversion algorithm is evaluated using this model.Finally,the inversion algorithm is applied to a field EM data collected at the Beiya gold polymetallic ore district.A 3D resistivity model is obtained,and the formation process of the metal ore is analyzed.
基金supported by Science and Technology Project of SGCC(5108-202218280A-2-370-XG).
文摘As key equipment in medium voltage DC(MVDC)systems,modular multilevel AC/DC and DC/DC converters(MM-AC/DC,MM-DC/DC)have drawn marvelous attractions.However,research on DC fault ride-through focuses on MM-AC/DC,and the fault current elimination for MM-DC/DC remains a research gap,which limits the wide application of the MVDC system.To fulfil this research gap,the contribution of this paper is revealing the fault current characteristics of MM-DC/DC based on half-bridge and full-bridge submodules(HBSM and FBSM)and proposing a novel MM-DC/DC based on hybrid HBSM and thyristor-diode module(TDM).By integrating TDM in the upper bridge arm of one phase and the down bridge arm of the other phase in MM-DC/DC,the MM-DC/DC achieves self-elimination of fault currents.The basic concept is using the energy at the healthy side to modulate a reverse voltage source(RVS)at the faulty side of MM-DC/DC,forcing fault current through TDM pass across zero.TDM can extinguish the resulting fault current.The parameter design and control strategy of the novel MM-DC/DC are discussed.Simulation is carried out for verification,and the results show that fault current can be eliminated within several milliseconds without causing excessive operating losses and costs.
文摘Conventional multilevel inverters often suffer from high harmonic distortion and increased design complexity due to the need for numerous power semiconductor components,particularly at elevated voltage levels.Addressing these shortcomings,thiswork presents a robust 15-level PackedUCell(PUC)inverter topology designed for renewable energy and grid-connected applications.The proposed systemintegrates a sensor less proportional-resonant(PR)controller with an advanced carrier-based pulse width modulation scheme.This approach efficiently balances capacitor voltage,minimizes steady-state error,and strongly suppresses both zero and third-order harmonics resulting in reduced total harmonic distortion and enhanced voltage regulation.Additionally,a novel switching algorithm simplifies the design and implementation,further lowering voltage stress across switches.Extensive simulation results validate the performance under various resistive and resistive-inductive load conditions,demonstrating compliance with IEEE-519 THD standards and robust operation under dynamic changes.The proposed sensorless PR-controlled 15-PUC inverter thus offers a compelling,cost-effective solution for efficient power conversion in next-generation renewable energy systems.
基金supported by grants from the Natural Science Foundation of Tianjin(General Program),Nos.23JCYBJC01390(to RL),22JCYBJC00220(to XC),and 22JCYBJC00210(to QL).
文摘Peripheral nerve injury is a common neurological condition that often leads to severe functional limitations and disabilities.Research on the pathogenesis of peripheral nerve injury has focused on pathological changes at individual injury sites,neglecting multilevel pathological analysis of the overall nervous system and target organs.This has led to restrictions on current therapeutic approaches.In this paper,we first summarize the potential mechanisms of peripheral nerve injury from a holistic perspective,covering the central nervous system,peripheral nervous system,and target organs.After peripheral nerve injury,the cortical plasticity of the brain is altered due to damage to and regeneration of peripheral nerves;changes such as neuronal apoptosis and axonal demyelination occur in the spinal cord.The nerve will undergo axonal regeneration,activation of Schwann cells,inflammatory response,and vascular system regeneration at the injury site.Corresponding damage to target organs can occur,including skeletal muscle atrophy and sensory receptor disruption.We then provide a brief review of the research advances in therapeutic approaches to peripheral nerve injury.The main current treatments are conducted passively and include physical factor rehabilitation,pharmacological treatments,cell-based therapies,and physical exercise.However,most treatments only partially address the problem and cannot complete the systematic recovery of the entire central nervous system-peripheral nervous system-target organ pathway.Therefore,we should further explore multilevel treatment options that produce effective,long-lasting results,perhaps requiring a combination of passive(traditional)and active(novel)treatment methods to stimulate rehabilitation at the central-peripheral-target organ levels to achieve better functional recovery.
基金Euskal Herriko Unibertsitatea(UPV/EHU)ECRI Ethics in Finance&Social Value GIU22/003Fundacion Emilio Soldevilla para la Investigacion y el Desarrollo en Economia de la Empresa(FESIDE)BOPV2020.
文摘The use of electronic currency for transactions,denoting a cashless paradigm,has become increasingly common.However,this financial innovation is not prevalent in all countries.This study aims to explain the discrepancies across countries,including individual and country factors.It may be superficially posited that this lag in development stems from individual or microlevel usage challenges.However,the application of the Technology Acceptance Model highlights the presence of overarching characteristics conducive to extensive adoption.Thus,an additional stratum,the multilevel perspective,needs to be examined.This analytical framework incorporates not only individual attributes but also the sociotechnical framework or mesolevel factors in which they operate.A multilevel econometric model is used.The results of these analyses show that the impact on the adoption of cashless payments extends beyond individual factors(attitude to technology use,perceived usefulness,and perceived ease of use).Our primary contribution,conceptually and empirically,is to broaden the analysis vision.A comprehensive multilevel analysis revealed that broader contextual elements,such as infrastructure and national skills,exert a significant influence on the adoption of cashless transactions.Consequently,the widespread acceptance of cashless payment methods is not only contingent on individual choices but is also a collective phenomenon in which the surrounding environment plays a crucial role as a catalyst for the end users in the cashless economy.
基金supported by the National Nature Science Foundation of China(No.22269021)Tianshan Talent Project of Xinjiang Uygur Autonomous Region(No.2023TSYCQNTJ0039)the Open project of Key Laboratory in Xinjiang Uygur Autonomous Region of China(No.2023D04027).
文摘Hydrogen production coupled with small molecule oxidation derived by renewable energy power has been widely studied as an effective method to reduce energy consumption and prepare added value production.Here,the copper-cobalt phosphide with a multilevel structure has been designed based on the hard and soft acids and bases theory.The nanocone composed of lamellas presented a sharp tip,which a positive effect on the mass transfer enhanced by a local electric field,and the nanolamellas contain CoP/Cu_(3)P interface provide the highly selective active site for the gluconic acid(GNA)synthesis and hydrogen evolution.The catalyst can drive hydrogen evolution at 5 A·cm^(-2)up to 437 h without active decay,and the electrocatalytic glucose oxidation at anode presents high efficiency due to Cu(I)introduction and the synergetic effect between interfaces.Density functional theory(DFT)calculation shows that water splitting more readily occurs at the CoP,which provides adsorbed H and-OH for hydrogen evolution and glucose oxidation,respectively,and glucose adsorption more readily occurs at the Cu_(3)P,which presents lower conversion energy for high value-added GNA.Efficient hydrogen evolution and glucose conversion indicate its high intrinsic activity and synergetic effect.This work provides a special interface construction strategy for the catalytic conversion of hydrogen and small molecules.
基金supported by the European Union and the Romanian Government through the Competitiveness Operational Programme 2014–2020, under the project“Increasing the economic competitiveness of the forestry sector and the quality of life through knowledge transfer,technology and CDI skills”(CRESFORLIFE),ID P 40 380/105506, subsidiary contract no. 17/2020partially by the FORCLIMSOC Nucleu Programme (Contract 12N/2023)+2 种基金project PN 23090101CresPerfInst project (Contract 34PFE/December 30, 2021)“Increasing the institutional capacity and performance of INCDS ‘Marin Drǎcea’in RDI activities-CresPer”LM was financially supported by the Research Council of Finland's flagship ecosystem for Forest-Human-Machine Interplay–Building Resilience, Redefining Value Networks and Enabling Meaningful Experiences (UNITE)(decision number 357909)
文摘In this study,we used an extensive sampling network established in central Romania to develop tree height and crown length models.Our analysis included more than 18,000 tree measurements from five different species.Instead of building univariate models for each response variable,we employed a multivariate approach using seemingly unrelated mixed-effects models.These models incorporated variables related to species mixture,tree and stand size,competition,and stand structure.With the inclusion of additional variables in the multivariate seemingly unrelated mixed-effects models,the accuracy of the height prediction models improved by over 10% for all species,whereas the improvement in the crown length models was considerably smaller.Our findings indicate that trees in mixed stands tend to have shorter heights but longer crowns than those in pure stands.We also observed that trees in homogeneous stand structures have shorter crown lengths than those in heterogeneous stands.By employing a multivariate mixed-effects modelling framework,we were able to perform cross-model random-effect predictions,leading to a significant increase in accuracy when both responses were used to calibrate the model.In contrast,the improvement in accuracy was marginal when only height was used for calibration.We demonstrate how multivariate mixed-effects models can be effectively used to develop multi-response allometric models that can be easily calibrated with a limited number of observations while simultaneously achieving better-aligned projections.
基金supported by the National Natural Science Foundation of China(Grant No.22275082 and 22175084).
文摘In the quest for high-efficiency and cost-effective catalysts for the oxygen evolution reaction(OER),a novel biomass-driven strategy is developed to fabricate a unique one-dimensional rod-arrays@two-dimensional interlaced-sheets(C_(1D@2D))network.A groundbreaking chemical fermentation(CF)pore-generation mechanism,proposed for the first time for creating nanopores within carbon structures,is based on the optimal balance between gasification and solidification.This mechanism not only results in a distinctive C_(1D@2D) multilevel network with nanoscale,intersecting and freely flowing channels but also introduces a novel concept for in situ,extensive and hierarchical pore formation.The unique architecture,combined with the homogeneous dispersion of Ni-Fe nanoparticles,facilitates easy electrolyte penetration and provides abundant active sites for the anchoring and dispersion of reactive molecules or ions.Consequently,the Ni-Fe@C_(1D@2D) porous network demonstrates an exceptional OER electrocatalytic performance,achieving a record-low overpotential of 165 mV at 10 mA cm^(−2)and maintaining long-term stability for over 90 h.Theoretical calculations reveal that the porous structure markedly strengthens the interaction between alloy nanoparticles and the carbon matrix,thereby significantly boosting their electrocatalytic activity and stability.These findings unequivocally validate the CF pore-generation mechanism as a powerful and innovative strategy for designing highly efficient functional nanostructures.
