The safety and durability of lithium-ion batteries under mechanical constraints depend significantly on electrochemical,thermal,and mechanical fields in applications.Characterizing and quantifying the multi-field coup...The safety and durability of lithium-ion batteries under mechanical constraints depend significantly on electrochemical,thermal,and mechanical fields in applications.Characterizing and quantifying the multi-field coupling behaviors requires interdisciplinary efforts.Here,we design experiments under mechanical constraints and introduce an in-situ analytical framework to clarify the complex interaction mechanisms and coupling degrees among multi-physics fields.The proposed analytical framework integrates the parameterization of equivalent models,in-situ mechanical analysis,and quantitative assessment of coupling behavior.The results indicate that the significant impact of pressure on impedance at low temperatures results from the diffusion-controlled step,enhancing kinetics when external pressure,like 180 to 240 k Pa at 10℃,is applied.The diversity in control steps for the electrochemical reaction accounts for the varying impact of pressure on battery performance across different temperatures.The thermal expansion rate suggests that the swelling force varies by less than 1.60%per unit of elevated temperature during the lithiation process.By introducing a composite metric,we quantify the coupling correlation and intensity between characteristic parameters and physical fields,uncovering the highest coupling degree in electrochemical-thermal fields.These results underscore the potential of analytical approaches in revealing the mechanisms of interaction among multi-fields,with the goal of enhancing battery performance and advancing battery management.展开更多
Minin-induced water inrush from a confined aquifer due to subsided floor karst collapse column(SKCC)is a type of serious disaster in the underground coal extraction.Karst collapse column(KCC)developed in a confined aq...Minin-induced water inrush from a confined aquifer due to subsided floor karst collapse column(SKCC)is a type of serious disaster in the underground coal extraction.Karst collapse column(KCC)developed in a confined aquifer occurs widely throughout northern China.A water inrush disaster from SKCC occurred in Taoyuan coal mine on February 3,2013.In order to analyze the effect of the KCC influence zone’s(KCCIZ)width and the entry driving distance of the water inrush through the fractured channels of the SKCC,the stress,seepage,and impact dynamics coupling equations were used tomodel the seepage rule,and a numerical FLAC3D model was created to determine the plastic zones,the vertical displacement development of the rockmass surrounding the entry driving working face(EDWF),and the seepage vector and water inflow development of the seepage field.The hysteretic mechanism of water inrush due to SKCC in Taoyuan coal mine was investigated.The results indicate that a water inrush disaster will occur when the width of the KCCIZ exceeds 16 m under a driving,which leads to the aquifer connecting with the fractured zones of the entry floor.Hysteretic water inrush disasters are related to the stress release rate of the surrounding rocks under the entry driving.When the entry driving exceeds about 10 m from the water inrush point,the stress release rate reaches about 100%,and a water inrush disaster occurs.展开更多
There were differences between real boundary and blast hole controlling boundary of irregular mined-out area in underground metal mines. There were errors in numerical analysis of stability for goaf, if it was analyze...There were differences between real boundary and blast hole controlling boundary of irregular mined-out area in underground metal mines. There were errors in numerical analysis of stability for goaf, if it was analyzed as regular 3D mined-out area and the influence of coupling stress-seepage-disturbance was not considered adequately. Taking a lead zinc mine as the background, the model was built by the coupling of Surpac and Midas-Gts based on the goaf model precisely measured by CMS.According to seepage stress fundamental equations based on the equivalent continuum mechanical and the theory about equivalent load of dynamic disturbance in deep-hole blasting, the stability of mined-out area under multi-field coupling of stress-seepage-dynamic disturbance was numerically analyzed. The results show that it is more consistent between the numerical analysis model based on the real model of irregular 3D shape goaf and the real situation, which could faithfully reappear the change rule of stress–strain about the surrounding rock under synthetic action of blasting dynamic loading and the seepage pressure. The mined-out area multi-field coupling formed by blasting excavation is stable. Based on combination of the advantages of the CMS,Surpac and Midas-Gts, and fully consideration of the effects of multi-field coupling, the accurate and effective way could be provided for numerical analysis of stability for mined-out area.展开更多
Human activities, such as blasting excavation, bolting, grouting and impounding of reservoirs, will lead to disturbances to rock masses and variations in their structural features and material properties. These engine...Human activities, such as blasting excavation, bolting, grouting and impounding of reservoirs, will lead to disturbances to rock masses and variations in their structural features and material properties. These engineering disturbances are important factors that would alter the natural evolutionary processes or change the multi-field interactions in the rock masses from their initial equilibrium states. The concept of generalized multi-field couplings was proposed by placing particular emphasis on the role of engineering disturbances in traditional multi-field couplings in rock masses. A mathematical model was then developed, in which the effects of engineering disturbances on the coupling-processes were described with changes in boundary conditions and evolutions in thermo-hydro-mechanical （THM） properties of the rocks. A parameter, d, which is similar to damage variables but has a broader physical meaning, was conceptually introduced to represent the degree of engineering disturbances and the couplings among the material properties. The effects of blasting excavation, bolting and grouting in rock engineering were illustrated with various field observations or theoretical results, on which the degree of disturbances and the variations in elastic moduli and permeabilities were particularly focused. The influences of excavation and groundwater drainage on the seepage flow and stability of the slopes were demonstrated with numerical simulations. The proposed approach was further employed to investigate the coupled hydro-mechanical responses of a high rock slope to excavation, bolting and impounding of the reservoir in the dam left abutment of Jinping I hydropower station. The impacts of engineering disturbances on the deformation and stability of the slope during construction and operation were demonstrated.展开更多
In order to study the multi-field coupling mechanical behavior of the simply-supported conductive rectangular thin plate under the condition of an externally lateral strong impulsive magnetic field, that is the dynami...In order to study the multi-field coupling mechanical behavior of the simply-supported conductive rectangular thin plate under the condition of an externally lateral strong impulsive magnetic field, that is the dynamic buckling phenomenon of the thin plates in the effect of the magnetic volume forces produced by the interaction between the eddy current and the magnetic fields, a FEM analysis program is developed to characterize the phenomena of magnetoelastic buckling and instability of the plates. The critical values of magnetic field for the three different initial vibrating modes are obtained, with a detailed discussion made on the effects of the lengththickness ratio a/h of the plate and the length-width ratio a/b as well as the impulse parameter on the critical value BOcr of the applied magnetic field.展开更多
Sandwiched functionally-graded piezoelectric semiconductor(FGPS)plates possess high strength and excellent piezoelectric and semiconductor properties,and have significant potential applications in micro-electro-mechan...Sandwiched functionally-graded piezoelectric semiconductor(FGPS)plates possess high strength and excellent piezoelectric and semiconductor properties,and have significant potential applications in micro-electro-mechanical systems.The multi-field coupling and free vibration of a sandwiched FGPS plate are studied,and the governing equation and natural frequency are derived with the consideration of electron movement.The material properties in the functionally-graded layers are assumed to vary smoothly,and the first-order shear deformation theory is introduced to derive the multi-field coupling in the plate.The total strain energy of the plate is obtained,and the governing equations are presented by using Hamilton’s principle.By introducing the boundary conditions,the coupling physical fields are solved.In numerical examples,the natural frequencies of sandwiched FGPS plates under different geometrical and physical parameters are discussed.It is found that the initial electron density can be used to modulate the natural frequencies and vibrational displacement of sandwiched FGPS plates in the case of nano-size.The effects of the material properties of FGPS layers on the natural frequencies are also examined in detail.展开更多
The fault caused by a pantograph-catenary arc is the main factor that threatens the stability of high-speed railway energy transmission.Pantograph-catenary arc vertical drift is more severe than the case under normal ...The fault caused by a pantograph-catenary arc is the main factor that threatens the stability of high-speed railway energy transmission.Pantograph-catenary arc vertical drift is more severe than the case under normal pressure,as it is easy to develop the rigid busbar,which may lead to the flashover occurring around the support insulators.We establish a pantograph-catenary arc experiment and diagnosis platform to simulate low pressure and strong airflow environment.Meanwhile,the variation law of arc drift height with time under different air pressures and airflow velocities is analyzed.Moreover,arc drift characteristics and influencing factors are explored.The physical process of the arc column drifting to the rigid busbar with the jumping mechanism of the arc root on the rigid busbar is summarized.In order to further explore the mechanism of the above physical process,a multi-field stress coupling model is built,as the multi-stress variation law of arc is quantitatively evaluated.The dynamic action mechanism of multi-field stress on arc drifting characteristics is explored,as the physical mechanism of arc drifting under low pressure is theoretically explained.The research results provide theoretical support for arc suppression in high-altitude areas.展开更多
Permafrost regions of Qilian Mountains in China are rich in gas hydrate resources.Once greenhouse gases in deep frozen layer are released into the atmosphere during hydrate mining,a series of negative consequences occ...Permafrost regions of Qilian Mountains in China are rich in gas hydrate resources.Once greenhouse gases in deep frozen layer are released into the atmosphere during hydrate mining,a series of negative consequences occur.This study aims to evaluate the impact of hydrate thermal exploitation on regional permafrost and carbon budgets based on a multi-physical field coupling simulation.The results indicate that the permeability of the frozen soil is anisotropic,and the low permeability frozen layer can seal the methane gas in the natural state.Heat injection mining of hydrates causes the continuous melting of permafrost and the escape of methane gas,which transforms the regional permafrost from a carbon sink to a carbon source.A higher injection temperature concentrates the heat and causes uneven melting of the upper frozen layer,which provides a dominant channel for methane gas and results in increased methane emissions.However,dense heat injection wells cause more uniform melting of the lower permafrost layer,and the melting zone does not extend to the upper low permeability formation,which cannot provide advantageous channels for methane gas.Therefore,a reasonable and dense number of heat injection wells can reduce the risk of greenhouse gas emissions during hydrate exploitation.展开更多
In recent years,the development of ultrafast transmission electron microscopy(UTEM)has created new opportunities for studying dynamic processes at the nanoscale with unprecedented temporal resolution.~([1–3])The sign...In recent years,the development of ultrafast transmission electron microscopy(UTEM)has created new opportunities for studying dynamic processes at the nanoscale with unprecedented temporal resolution.~([1–3])The significant advances in femtosecond and even attosecond temporal resolution are achieved through the integration of the pump-probe principle with transmission electron microscopy(TEM).展开更多
Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies,as well as veiled dielectric-responsive character,are instrumental in electromagnetic dissipation.Conventional methods,how...Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies,as well as veiled dielectric-responsive character,are instrumental in electromagnetic dissipation.Conventional methods,however,constrain their delicate constructions.Herein,an innovative alternative is proposed:carrageenan-assistant cations-regulated(CACR)strategy,which induces a series of sulfides nanoparticles rooted in situ on the surface of carbon matrix.This unique configuration originates from strategic vacancy formation energy of sulfides and strong sulfides-carbon support interaction,benefiting the delicate construction of defects-rich heterostructures in M_(x)S_(y)/carbon composites(M-CAs).Impressively,these generated sulfur vacancies are firstly found to strengthen electron accumulation/consumption ability at heterointerfaces and,simultaneously,induct local asymmetry of electronic structure to evoke large dipole moment,ultimately leading to polarization coupling,i.e.,defect-type interfacial polarization.Such“Janus effect”(Janus effect means versatility,as in the Greek two-headed Janus)of interfacial sulfur vacancies is intuitively confirmed by both theoretical and experimental investigations for the first time.Consequently,the sulfur vacancies-rich heterostructured Co/Ni-CAs displays broad absorption bandwidth of 6.76 GHz at only 1.8 mm,compared to sulfur vacancies-free CAs without any dielectric response.Harnessing defects-rich heterostructures,this one-pot CACR strategy may steer the design and development of advanced nanomaterials,boosting functionality across diverse application domains beyond electromagnetic response.展开更多
Because DC conductivities of oil-paper materials can be easily affected by electric field and temperature,the electrical properties under electro-thermal coupling of oil-paper materials should be considered when optim...Because DC conductivities of oil-paper materials can be easily affected by electric field and temperature,the electrical properties under electro-thermal coupling of oil-paper materials should be considered when optimising the insulation structure of valve-side winding of the converter transformer.Based on the finite element multi-physical field coupling simulation,the multi-objective optimisation of main insulation structure of valve-side winding is carried out.In view of the high time consuming of multi-physical field calculation and the actual needs of an insulation structure optimisation,the Kriging method and technique for order preference by similarity to the ideal solution(TOPSIS)method are introduced,and combines them with NSGA-II to obtain a joint algorithm that can be used for the optimisation of insulation structure of the converter transformer.By using the joint algorithm of multi-objective optimisation,the insulation structure configuration scheme of valve-side winding is optimised.It can be seen from the experiment result that,on the one hand,the joint algorithm adopted can obtain the insulation structure configuration scheme that meets the design requirements.On the other hand,when facing the configuration scheme optimisation under multi-field coupling,the computational time required by this method is only 0.15%of that required by original genetic algorithm.展开更多
Background: The tricuspid annular plane systolic excursion (TAPSE) and pulmonary artery systolic pressure (PASP) is an indirect estimate of right ventricular-pulmonary arterial (RV-PA) coupling that has been shown to ...Background: The tricuspid annular plane systolic excursion (TAPSE) and pulmonary artery systolic pressure (PASP) is an indirect estimate of right ventricular-pulmonary arterial (RV-PA) coupling that has been shown to correlate with invasive measures. We aimed to assess the ability of the tricuspid annular plane systolic excursion/pulmonary systolic pressure ratio (TAPSE/PASP) as a measure for RV-PA coupling to predict the development of RV dysfunction after cardiac surgery. Methods: This prospective study was conducted on 100 patients with ischemic heart disease and undergoing cardiac surgery (coronary artery bypass graft (CABG)) with normal preoperative right ventricular function, classified according to RV function outcomes into 2 groups: Normal RV group (65 patients) and RV dysfunction group (35 patients). All cases underwent per and postoperative transthoracic echocardiography. Results: By using receiver operating characteristic curve analysis, pre-operative TAPSE/PASP ratio could significantly predict the RV dysfunction (P 0.58, with AUC of 94%, 88.6% sensitivity, and 89.2% specificity. Post-operative TAPSE/PASP Ratio could significantly predict the RV dysfunction (P 0.39, with AUC of 84%, 100% sensitivity, and 76.9% specificity. Pre-operative TAPSE/PASP ratio could significantly predict mortality (P Conclusion: The TAPSE/PASP ratio is an excellent tool for CABG patients for its ability to detect and predict the development of RV dysfunction after cardiac surgery, along with the prediction of mortality in post-operative CABG patients.展开更多
Electrochemical conversion of lignin for the production of high-value heterocyclic aromatic compounds has great potential.We demonstrate the targeted synthesis and cation modulation of NiCo_(2)O_(4)spinel nanoboxes,sy...Electrochemical conversion of lignin for the production of high-value heterocyclic aromatic compounds has great potential.We demonstrate the targeted synthesis and cation modulation of NiCo_(2)O_(4)spinel nanoboxes,synthesized via cation exchange and calcination oxidation.These catalysts exhibit excellent efficacy in the electrocatalytic conversion of lignin model compounds,specifically 2-phenoxy-1-phenylethanol,into nitrogen-containing aromatics,achieving high conversion rates and selectivities.These catalysts were synthesized via a cation exchange and calcination oxidation process,using Prussian blue nanocubes as precursors.The porous architecture and polymetallic composition of the NiCo_(2)O_(4)spinel demonstrated superior performance in electrocatalytic oxidative coupling,achieving a 99.2 wt%conversion rate of the 2-phenoxy-1-phenylethanol with selectivities of 37.5 wt%for quinoline derivatives and 31.5 wt%for phenol.Key innovations include the development of a sustainable one-pot synthesis method for quinoline derivatives,the elucidation of a multistage reaction pathway involving CAO bond cleavage,hydroxyaldol condensation,and CAN bond formation,and a deeper mechanistic understanding derived from DFT simulations.This work establishes a new strategy for lignin valorization,offering a sustainable route to produce high-value nitrogen-containing aromatics from renewable biomass under mild conditions,without the need for additional reagents.展开更多
Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression an...Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression and permeability tests to investigate the mechanical and seepage properties of tight sandstone.A digital core of tight sandstone was built using Computed Tomography(CT)scanning,which was divided into matrix and pore phases by a pore equivalent diameter threshold.A fluid-solid coupling model was established to investigate the seepage characteristics at micro-scale.The results showed that increasing the confining pressure decreased porosity,permeability,and flow velocity,with the pore phase becoming the dominant seepage channel.Cracks and large pores closed first under increasing pressure,resulted in a steep drop in permeability.However,permeability slightly decreased under high confining pressure,which followed a first-order exponential function.Flow velocity increased with seepage pressure.And the damage mainly occurred in stress-concentration regions under low seepage pressure.Seepage behavior followed linear Darcy flow,the damage emerged at seepage entrances under high pressure,which decreased rock elastic modulus and significantly increased permeability.展开更多
Photoelectrocatalytic coupling CO_(2)and volatile organic compounds (VOCs) is a promising green strategy for the synergistic conversion of the two carbon-containing resources to C2products.The catalytic efficiency is ...Photoelectrocatalytic coupling CO_(2)and volatile organic compounds (VOCs) is a promising green strategy for the synergistic conversion of the two carbon-containing resources to C2products.The catalytic efficiency is always at the mercy of chemical inertness of CO_(2)and the competitive hydrogen evolution of H2O.Herein,a modified g-C_(3)N_(4)/ZnAl-LDH Z-scheme heterojunction catalyst with dual reaction site was rationally designed and precisely constructed.The Faraday efficiency of ethanol reached 68.67%with a corresponding formation rate of 227.3μmol g^(-1)h^(-1).As revealed by in-situ characterizations and density functional theory calculations,CO_(2)and HCHO were absorbed at Zn site and N site,respectively.Then,*CO generated from CO_(2)and HCHO was converted to*CH_(3)O and*CHO on the dual-active-site heterojunction.The detailed reaction mechanism experiments indicated that C–C coupling only occurred between*CO and*CH_(3)O in electrocatalysis process.Apart from the“*CO+*CH_(3)O”path,another“*CO+*CHO”coupling path was also detected in photoelectrocatalytic process.The selectivity of ethanol was significantly enhanced due to the synthesis of dual-site catalyst and the dual-path coupling path between CO_(2)and HCHO simultaneously driven by light and electricity.展开更多
To address the issue of extensive deformation in the Tabaiyi Tunnel caused by the fault zone,nuclear magnetic resonance(NMR)technology was employed to analyze the physical and mechanical properties of waterabsorbing m...To address the issue of extensive deformation in the Tabaiyi Tunnel caused by the fault zone,nuclear magnetic resonance(NMR)technology was employed to analyze the physical and mechanical properties of waterabsorbing mudstone.This analysis aimed to understand the mechanism behind the significant deformations.Drawing from the principle of excavation stress compensation,a support scheme featuring NPR anchorcables and an asymmetric truss support system was devised.To validate the scheme,numerical analysis using a combination of the Discrete Element Method(DEM)-Finite Element Method(FEM)was conducted.Additionally,similar material model tests and engineering measurements were carried out.Field experiments were also performed to evaluate the NPR anchor-cable and truss support system,focusing on anchor cable forces,pressures between the truss and surrounding rock,pressures between the initial support and secondary lining,as well as the magnitude of settlement and convergence deformation in the surrounding rock.The results indicate that the waterinduced expansion of clay minerals,resulting from damage caused by fissure water,accelerated the softening of the mudstone's internal structure,leading to significant deformations in the Tabaiyi Tunnel under high tectonic stress.The original support design fell short as the length of the anchor rods was smaller than the expansion depth of the plastic zone.As a result,the initial support structure bore the entire load from the surrounding rock,and a non-coupled deformation contact was observed between the double-arch truss and the surrounding rock.The adoption of NPR asymmetric anchor-cable support effectively restrained the expansion and asymmetric distribution characteristics of the plastic zone.Considering the mechanical degradation caused by water absorption in mudstone,the rigid constraint provided by the truss proved crucial for controlling the stability of the surrounding rock.These research findings hold significant implications for managing large deformations in soft rock tunnels situated within fractured zones under high tectonic stress conditions.展开更多
Piezoelectric semiconductors(PSs)have widespread applications in semiconductor devices due to the coexistence of piezoelec-tricity and semiconducting properties.It is very important to conduct a theoretical analysis o...Piezoelectric semiconductors(PSs)have widespread applications in semiconductor devices due to the coexistence of piezoelec-tricity and semiconducting properties.It is very important to conduct a theoretical analysis of PS structures.However,the present of nonlinearity in the partial differential equations(PDEs)that describe those multi-feld coupling mechanical behaviors of PSs poses a significant mathematical challenge when studying these PS structures.In this paper,we present a novel approach based on machine learning for solving multi-field coupling problems in PS structures.A physics-informed neural networks(PINNs)is constructed for predicting the multi-field coupling behaviors of PS rods with extensional deforma-tion.By utilizing the proposed PINNs,we evaluate the multi-field coupling responses of a ZnO rod under static and dynamic axial forces.Numerical results demonstrate that the proposed PINNs exhibit high accuracy in solving both static and dynamic problems associated with Ps structures.It provides an effective approach to predicting the nonlinear multi-feld coupling phe-nomena in PS structures.展开更多
Climate change brings new challenges to the sustainable development of agriculture in the new era.Accurately grasping the patterns of climate change impacts on agricultural systems is crucial for ensuring agricultural...Climate change brings new challenges to the sustainable development of agriculture in the new era.Accurately grasping the patterns of climate change impacts on agricultural systems is crucial for ensuring agricultural sustainability and food security.Taking the Loess Plateau(LP),China as an example,this study used a coupling coordination degree model and spatial autocorrelation analysis to portray the spatial and temporal features of crop-cropland coupling relationship from 2000 to 2020 and explored the impact law of climate change through geographically and temporally weighted regression(GTWR).The results were as follows:1)the crop-cropland coupling coordination degree of the LP showed a gradual upward trend from 2000 to 2020,forming a spatial pattern with lower values in the central region and higher values in the surrounding areas.2)There was a positive correlation in the spatial distribution of cropcropland coupling coordination degree in the LP from 2000 to 2020,and the high value-low value(H-L)and low value-low value(L-L)agglomerations continued to expand eastward,while the spatial and temporal evolution of the high value-high value(H-H)and low value-high value(L-H)agglomerations was not obvious.3)The impacts of climatic elements on crop-cropland coupling coordination degree in the LP showed strong heterogeneity in time scales.The inhibitory impacts of summer days(SU)and frost days(FD)accounted for a higher proportion,while the annual average temperature(TEM)had both promoting and inhibiting impacts.The impacts proportion and intensity of extreme heavy precipitation day(R25),continuous drought days(CDD),and annual precipitation(PRE)all experienced significant changes.4)In space,the impacts of SU and FD on the crop-cropland coupling coordination degree varied with latitude and altitude.The adaptability of the LP to R25 gradually strengthened,and the extensions of CDD and increase of PRE led to the increasing inhibition beyond the eastern region of LP,and TEM showed a promoting impact in the Fenwei Plain.As an important grainproducing area in China,the LP should actively deal with the impacts of climate change on the crop-cropland coupling relationship,vigorously safeguard food security,and promote sustainable agricultural development.展开更多
Dual atomic catalysts(DAC),particularly copper(Cu_(2))-based nitrogen(N)doped graphene,show great potential to effectively convert CO_(2)and nitrate(NO_(3)-)into important industrial chemicals such as ethylene,glycol,...Dual atomic catalysts(DAC),particularly copper(Cu_(2))-based nitrogen(N)doped graphene,show great potential to effectively convert CO_(2)and nitrate(NO_(3)-)into important industrial chemicals such as ethylene,glycol,acetamide,and urea through an efficient catalytical process that involves C–C and C–N coupling.However,the origin of the coupling activity remained unclear,which substantially hinders the rational design of Cu-based catalysts for the N-integrated CO_(2)reduction reaction(CO_(2)RR).To address this challenge,this work performed advanced density functional theory calculations incorporating explicit solvation based on a Cu_(2)-based N-doped carbon(Cu_(2)N_(6)C_(10))catalyst for CO_(2)RR.These calculations are aimed to gain insight into the reaction mechanisms for the synthesis of ethylene,acetamide,and urea via coupling in the interfacial reaction micro-environment.Due to the sluggishness of CO_(2),the formation of a solvation electric layer by anions(F^(-),Cl^(-),Br^(-),and I^(-))and cations(Na+,Mg^(2+),K+,and Ca^(2+))leads to electron transfer towards the Cu surface.This process significantly accelerates the reduction of CO_(2).These results reveal that*CO intermediates play a pivotal role in N-integrated CO_(2)RR.Remarkably,the Cu_(2)-based N-doped carbon catalyst examined in this study has demonstrated the most potential for C–N coupling to date.Our findings reveal that through the process of a condensation reaction between*CO and NH_(2)OH for urea synthesis,*NO_(3)-is reduced to*NH_(3),and*CO_(2)to*CCO at dual Cu atom sites.This dual-site reduction facilitates the synthesis of acetamide through a nucleophilic reaction between NH_(3)and the ketene intermediate.Furthermore,we found that the I-and Mg^(2+)ions,influenced by pH,were highly effective for acetamide and ammonia synthesis,except when F-and Ca^(2+)were present.Furthermore,the mechanisms of C–N bond formation were investigated via ab-initio molecular dynamics simulations,and we found that adjusting the micro-environment can change the dominant side reaction,shifting from hydrogen production in acidic conditions to water reduction in alkaline ones.This study introduces a novel approach using ion-H_(2)O cages to significantly enhance the efficiency of C–N coupling reactions.展开更多
A conduction-cooled superconducting magnet producing a transverse field of 4 T has been designed for a new generation multi-field coupling measurement system, which will be used to study the mechanical behavior of sup...A conduction-cooled superconducting magnet producing a transverse field of 4 T has been designed for a new generation multi-field coupling measurement system, which will be used to study the mechanical behavior of superconducting samples at cryogenic temperatures and intense magnetic fields. A compact cryostat with a two-stage GM cryocooler is designed and manufactured for the superconducting magnet. The magnet is composed of a pair of flat racetrack coils wound by NbTi/Cu superconducting composite wires, a copper and stainless steel combinational former and two Bi2Sr2CaCu20~ superconducting current leads. The two coils are connected in series and can be powered with a single power supply. In order to support the high stress and attain uniform thermal distribution in the superconducting magnet, a detailed finite element （FE） analysis has been performed. The results indicate that in the operating status the designed magnet system can sufficiently bear the electromagnetic forces and has a uniform temperature distribution.展开更多
基金supported by the National Science Fund for Excellent Youth Scholars of China(52222708)the National Natural Science Foundation of China(51977007)。
文摘The safety and durability of lithium-ion batteries under mechanical constraints depend significantly on electrochemical,thermal,and mechanical fields in applications.Characterizing and quantifying the multi-field coupling behaviors requires interdisciplinary efforts.Here,we design experiments under mechanical constraints and introduce an in-situ analytical framework to clarify the complex interaction mechanisms and coupling degrees among multi-physics fields.The proposed analytical framework integrates the parameterization of equivalent models,in-situ mechanical analysis,and quantitative assessment of coupling behavior.The results indicate that the significant impact of pressure on impedance at low temperatures results from the diffusion-controlled step,enhancing kinetics when external pressure,like 180 to 240 k Pa at 10℃,is applied.The diversity in control steps for the electrochemical reaction accounts for the varying impact of pressure on battery performance across different temperatures.The thermal expansion rate suggests that the swelling force varies by less than 1.60%per unit of elevated temperature during the lithiation process.By introducing a composite metric,we quantify the coupling correlation and intensity between characteristic parameters and physical fields,uncovering the highest coupling degree in electrochemical-thermal fields.These results underscore the potential of analytical approaches in revealing the mechanisms of interaction among multi-fields,with the goal of enhancing battery performance and advancing battery management.
基金supported by the National Natural Science Foundation of China(Project Nos.51708185,41807209 and 51778215,SC,http://www.nsfc.gov.cn)the Young Teacher Foundation of HPU(Project No.2019XQG-19,SC,http://www6.hpu.edu.cn/rsc)+1 种基金the Henan Provincial Youth Talent Promotion Program(Project No.2020HYTP003,SC,http://www.hast.net.cn:82)the Doctor Foundation of Henan Polytechnic University(Project No.B2017-51 and B2017-53,SC,http://kxc.hpu.edu.cn).
文摘Minin-induced water inrush from a confined aquifer due to subsided floor karst collapse column(SKCC)is a type of serious disaster in the underground coal extraction.Karst collapse column(KCC)developed in a confined aquifer occurs widely throughout northern China.A water inrush disaster from SKCC occurred in Taoyuan coal mine on February 3,2013.In order to analyze the effect of the KCC influence zone’s(KCCIZ)width and the entry driving distance of the water inrush through the fractured channels of the SKCC,the stress,seepage,and impact dynamics coupling equations were used tomodel the seepage rule,and a numerical FLAC3D model was created to determine the plastic zones,the vertical displacement development of the rockmass surrounding the entry driving working face(EDWF),and the seepage vector and water inflow development of the seepage field.The hysteretic mechanism of water inrush due to SKCC in Taoyuan coal mine was investigated.The results indicate that a water inrush disaster will occur when the width of the KCCIZ exceeds 16 m under a driving,which leads to the aquifer connecting with the fractured zones of the entry floor.Hysteretic water inrush disasters are related to the stress release rate of the surrounding rocks under the entry driving.When the entry driving exceeds about 10 m from the water inrush point,the stress release rate reaches about 100%,and a water inrush disaster occurs.
基金Project(2012BAK09B02-05)supported by the National"Twelfth Five"Science and Technology Support Program,ChinaProject(51274250)supported by the National Natural Science Foundation of China+2 种基金Project(2013zzts057)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(11KF02)supported by the Research Fund of the State Key Laboratory of Coal Resources and Mine safety,CUMT,ChinaProject(2012M511417)supported by China Postdoctoral Science Foundation
文摘There were differences between real boundary and blast hole controlling boundary of irregular mined-out area in underground metal mines. There were errors in numerical analysis of stability for goaf, if it was analyzed as regular 3D mined-out area and the influence of coupling stress-seepage-disturbance was not considered adequately. Taking a lead zinc mine as the background, the model was built by the coupling of Surpac and Midas-Gts based on the goaf model precisely measured by CMS.According to seepage stress fundamental equations based on the equivalent continuum mechanical and the theory about equivalent load of dynamic disturbance in deep-hole blasting, the stability of mined-out area under multi-field coupling of stress-seepage-dynamic disturbance was numerically analyzed. The results show that it is more consistent between the numerical analysis model based on the real model of irregular 3D shape goaf and the real situation, which could faithfully reappear the change rule of stress–strain about the surrounding rock under synthetic action of blasting dynamic loading and the seepage pressure. The mined-out area multi-field coupling formed by blasting excavation is stable. Based on combination of the advantages of the CMS,Surpac and Midas-Gts, and fully consideration of the effects of multi-field coupling, the accurate and effective way could be provided for numerical analysis of stability for mined-out area.
基金Supported by the National Natural Science Fund for Distinguished Young Scholars of China(50725931)the National Natural Science Foundation of China(50839004,51079107)the Supporting Program of the "Eleventh Five-year Plan" for Sci & Tech Research of China(2008BAB29B01)
文摘Human activities, such as blasting excavation, bolting, grouting and impounding of reservoirs, will lead to disturbances to rock masses and variations in their structural features and material properties. These engineering disturbances are important factors that would alter the natural evolutionary processes or change the multi-field interactions in the rock masses from their initial equilibrium states. The concept of generalized multi-field couplings was proposed by placing particular emphasis on the role of engineering disturbances in traditional multi-field couplings in rock masses. A mathematical model was then developed, in which the effects of engineering disturbances on the coupling-processes were described with changes in boundary conditions and evolutions in thermo-hydro-mechanical （THM） properties of the rocks. A parameter, d, which is similar to damage variables but has a broader physical meaning, was conceptually introduced to represent the degree of engineering disturbances and the couplings among the material properties. The effects of blasting excavation, bolting and grouting in rock engineering were illustrated with various field observations or theoretical results, on which the degree of disturbances and the variations in elastic moduli and permeabilities were particularly focused. The influences of excavation and groundwater drainage on the seepage flow and stability of the slopes were demonstrated with numerical simulations. The proposed approach was further employed to investigate the coupled hydro-mechanical responses of a high rock slope to excavation, bolting and impounding of the reservoir in the dam left abutment of Jinping I hydropower station. The impacts of engineering disturbances on the deformation and stability of the slope during construction and operation were demonstrated.
基金Project supported by the National Natural Sciences Foundation of China (Nos. 10132010 and 90405005).
文摘In order to study the multi-field coupling mechanical behavior of the simply-supported conductive rectangular thin plate under the condition of an externally lateral strong impulsive magnetic field, that is the dynamic buckling phenomenon of the thin plates in the effect of the magnetic volume forces produced by the interaction between the eddy current and the magnetic fields, a FEM analysis program is developed to characterize the phenomena of magnetoelastic buckling and instability of the plates. The critical values of magnetic field for the three different initial vibrating modes are obtained, with a detailed discussion made on the effects of the lengththickness ratio a/h of the plate and the length-width ratio a/b as well as the impulse parameter on the critical value BOcr of the applied magnetic field.
基金supported by the National Natural Science Foundation of China(Nos.12172236 and 12202289)。
文摘Sandwiched functionally-graded piezoelectric semiconductor(FGPS)plates possess high strength and excellent piezoelectric and semiconductor properties,and have significant potential applications in micro-electro-mechanical systems.The multi-field coupling and free vibration of a sandwiched FGPS plate are studied,and the governing equation and natural frequency are derived with the consideration of electron movement.The material properties in the functionally-graded layers are assumed to vary smoothly,and the first-order shear deformation theory is introduced to derive the multi-field coupling in the plate.The total strain energy of the plate is obtained,and the governing equations are presented by using Hamilton’s principle.By introducing the boundary conditions,the coupling physical fields are solved.In numerical examples,the natural frequencies of sandwiched FGPS plates under different geometrical and physical parameters are discussed.It is found that the initial electron density can be used to modulate the natural frequencies and vibrational displacement of sandwiched FGPS plates in the case of nano-size.The effects of the material properties of FGPS layers on the natural frequencies are also examined in detail.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51707166,51922090,U1966602,and U19A20105)the Sichuan Science and Technology General Project(Grant Nos.2019YJ0213 and2019JDJQ0019)。
文摘The fault caused by a pantograph-catenary arc is the main factor that threatens the stability of high-speed railway energy transmission.Pantograph-catenary arc vertical drift is more severe than the case under normal pressure,as it is easy to develop the rigid busbar,which may lead to the flashover occurring around the support insulators.We establish a pantograph-catenary arc experiment and diagnosis platform to simulate low pressure and strong airflow environment.Meanwhile,the variation law of arc drift height with time under different air pressures and airflow velocities is analyzed.Moreover,arc drift characteristics and influencing factors are explored.The physical process of the arc column drifting to the rigid busbar with the jumping mechanism of the arc root on the rigid busbar is summarized.In order to further explore the mechanism of the above physical process,a multi-field stress coupling model is built,as the multi-stress variation law of arc is quantitatively evaluated.The dynamic action mechanism of multi-field stress on arc drifting characteristics is explored,as the physical mechanism of arc drifting under low pressure is theoretically explained.The research results provide theoretical support for arc suppression in high-altitude areas.
基金supported by the Second Tibetan Plateau Scientific Expedition and Research Program(STEP)(No.2019QZKK0904)the National Natural Science Foundation of China(Nos.42107190,41972287 and 42277144)。
文摘Permafrost regions of Qilian Mountains in China are rich in gas hydrate resources.Once greenhouse gases in deep frozen layer are released into the atmosphere during hydrate mining,a series of negative consequences occur.This study aims to evaluate the impact of hydrate thermal exploitation on regional permafrost and carbon budgets based on a multi-physical field coupling simulation.The results indicate that the permeability of the frozen soil is anisotropic,and the low permeability frozen layer can seal the methane gas in the natural state.Heat injection mining of hydrates causes the continuous melting of permafrost and the escape of methane gas,which transforms the regional permafrost from a carbon sink to a carbon source.A higher injection temperature concentrates the heat and causes uneven melting of the upper frozen layer,which provides a dominant channel for methane gas and results in increased methane emissions.However,dense heat injection wells cause more uniform melting of the lower permafrost layer,and the melting zone does not extend to the upper low permeability formation,which cannot provide advantageous channels for methane gas.Therefore,a reasonable and dense number of heat injection wells can reduce the risk of greenhouse gas emissions during hydrate exploitation.
文摘In recent years,the development of ultrafast transmission electron microscopy(UTEM)has created new opportunities for studying dynamic processes at the nanoscale with unprecedented temporal resolution.~([1–3])The significant advances in femtosecond and even attosecond temporal resolution are achieved through the integration of the pump-probe principle with transmission electron microscopy(TEM).
基金financially supported by the National Natural Science Foundation of China(Grants nos.62201411,62371378,22205168,52302150 and 62304171)the China Postdoctoral Science Foundation(2022M722500)+1 种基金the Fundamental Research Funds for the Central Universities(Grants nos.ZYTS2308 and 20103237929)Startup Foundation of Xidian University(10251220001).
文摘Defects-rich heterointerfaces integrated with adjustable crystalline phases and atom vacancies,as well as veiled dielectric-responsive character,are instrumental in electromagnetic dissipation.Conventional methods,however,constrain their delicate constructions.Herein,an innovative alternative is proposed:carrageenan-assistant cations-regulated(CACR)strategy,which induces a series of sulfides nanoparticles rooted in situ on the surface of carbon matrix.This unique configuration originates from strategic vacancy formation energy of sulfides and strong sulfides-carbon support interaction,benefiting the delicate construction of defects-rich heterostructures in M_(x)S_(y)/carbon composites(M-CAs).Impressively,these generated sulfur vacancies are firstly found to strengthen electron accumulation/consumption ability at heterointerfaces and,simultaneously,induct local asymmetry of electronic structure to evoke large dipole moment,ultimately leading to polarization coupling,i.e.,defect-type interfacial polarization.Such“Janus effect”(Janus effect means versatility,as in the Greek two-headed Janus)of interfacial sulfur vacancies is intuitively confirmed by both theoretical and experimental investigations for the first time.Consequently,the sulfur vacancies-rich heterostructured Co/Ni-CAs displays broad absorption bandwidth of 6.76 GHz at only 1.8 mm,compared to sulfur vacancies-free CAs without any dielectric response.Harnessing defects-rich heterostructures,this one-pot CACR strategy may steer the design and development of advanced nanomaterials,boosting functionality across diverse application domains beyond electromagnetic response.
基金National Key R&D Program of China,Grant/Award Number:2021YFB2401705。
文摘Because DC conductivities of oil-paper materials can be easily affected by electric field and temperature,the electrical properties under electro-thermal coupling of oil-paper materials should be considered when optimising the insulation structure of valve-side winding of the converter transformer.Based on the finite element multi-physical field coupling simulation,the multi-objective optimisation of main insulation structure of valve-side winding is carried out.In view of the high time consuming of multi-physical field calculation and the actual needs of an insulation structure optimisation,the Kriging method and technique for order preference by similarity to the ideal solution(TOPSIS)method are introduced,and combines them with NSGA-II to obtain a joint algorithm that can be used for the optimisation of insulation structure of the converter transformer.By using the joint algorithm of multi-objective optimisation,the insulation structure configuration scheme of valve-side winding is optimised.It can be seen from the experiment result that,on the one hand,the joint algorithm adopted can obtain the insulation structure configuration scheme that meets the design requirements.On the other hand,when facing the configuration scheme optimisation under multi-field coupling,the computational time required by this method is only 0.15%of that required by original genetic algorithm.
文摘Background: The tricuspid annular plane systolic excursion (TAPSE) and pulmonary artery systolic pressure (PASP) is an indirect estimate of right ventricular-pulmonary arterial (RV-PA) coupling that has been shown to correlate with invasive measures. We aimed to assess the ability of the tricuspid annular plane systolic excursion/pulmonary systolic pressure ratio (TAPSE/PASP) as a measure for RV-PA coupling to predict the development of RV dysfunction after cardiac surgery. Methods: This prospective study was conducted on 100 patients with ischemic heart disease and undergoing cardiac surgery (coronary artery bypass graft (CABG)) with normal preoperative right ventricular function, classified according to RV function outcomes into 2 groups: Normal RV group (65 patients) and RV dysfunction group (35 patients). All cases underwent per and postoperative transthoracic echocardiography. Results: By using receiver operating characteristic curve analysis, pre-operative TAPSE/PASP ratio could significantly predict the RV dysfunction (P 0.58, with AUC of 94%, 88.6% sensitivity, and 89.2% specificity. Post-operative TAPSE/PASP Ratio could significantly predict the RV dysfunction (P 0.39, with AUC of 84%, 100% sensitivity, and 76.9% specificity. Pre-operative TAPSE/PASP ratio could significantly predict mortality (P Conclusion: The TAPSE/PASP ratio is an excellent tool for CABG patients for its ability to detect and predict the development of RV dysfunction after cardiac surgery, along with the prediction of mortality in post-operative CABG patients.
基金National Natural Science Foundation of China (U23A6005 and 22078069)Project funded by China Postdoctoral Science Foundation (GZB20230172 and 2023M740748)。
文摘Electrochemical conversion of lignin for the production of high-value heterocyclic aromatic compounds has great potential.We demonstrate the targeted synthesis and cation modulation of NiCo_(2)O_(4)spinel nanoboxes,synthesized via cation exchange and calcination oxidation.These catalysts exhibit excellent efficacy in the electrocatalytic conversion of lignin model compounds,specifically 2-phenoxy-1-phenylethanol,into nitrogen-containing aromatics,achieving high conversion rates and selectivities.These catalysts were synthesized via a cation exchange and calcination oxidation process,using Prussian blue nanocubes as precursors.The porous architecture and polymetallic composition of the NiCo_(2)O_(4)spinel demonstrated superior performance in electrocatalytic oxidative coupling,achieving a 99.2 wt%conversion rate of the 2-phenoxy-1-phenylethanol with selectivities of 37.5 wt%for quinoline derivatives and 31.5 wt%for phenol.Key innovations include the development of a sustainable one-pot synthesis method for quinoline derivatives,the elucidation of a multistage reaction pathway involving CAO bond cleavage,hydroxyaldol condensation,and CAN bond formation,and a deeper mechanistic understanding derived from DFT simulations.This work establishes a new strategy for lignin valorization,offering a sustainable route to produce high-value nitrogen-containing aromatics from renewable biomass under mild conditions,without the need for additional reagents.
基金financially supported by the National Natural Science Foundation of China(Nos.42272153 and 42472195)the Research Fund of PetroChina Tarim Oilfield Company(No.671023060003)the Research Fund of China National Petroleum Corporation Limited(No.2023ZZ16YJ04).
文摘Deep tight reservoirs exhibit complex stress and seepage fields due to varying pore structures,thus the seepage characteristics are significant for enhancing oil production.This study conducted triaxial compression and permeability tests to investigate the mechanical and seepage properties of tight sandstone.A digital core of tight sandstone was built using Computed Tomography(CT)scanning,which was divided into matrix and pore phases by a pore equivalent diameter threshold.A fluid-solid coupling model was established to investigate the seepage characteristics at micro-scale.The results showed that increasing the confining pressure decreased porosity,permeability,and flow velocity,with the pore phase becoming the dominant seepage channel.Cracks and large pores closed first under increasing pressure,resulted in a steep drop in permeability.However,permeability slightly decreased under high confining pressure,which followed a first-order exponential function.Flow velocity increased with seepage pressure.And the damage mainly occurred in stress-concentration regions under low seepage pressure.Seepage behavior followed linear Darcy flow,the damage emerged at seepage entrances under high pressure,which decreased rock elastic modulus and significantly increased permeability.
基金Natural Science Foundation of Shanxi Province,China (Grant No. 20210302123001)DNL Cooperation Fund,CAS (DNL202004),ICC CAS (Grant No. SCJCWRW-2023-21)Key Research and Development Program of Shanxi Province (202202090301020)。
文摘Photoelectrocatalytic coupling CO_(2)and volatile organic compounds (VOCs) is a promising green strategy for the synergistic conversion of the two carbon-containing resources to C2products.The catalytic efficiency is always at the mercy of chemical inertness of CO_(2)and the competitive hydrogen evolution of H2O.Herein,a modified g-C_(3)N_(4)/ZnAl-LDH Z-scheme heterojunction catalyst with dual reaction site was rationally designed and precisely constructed.The Faraday efficiency of ethanol reached 68.67%with a corresponding formation rate of 227.3μmol g^(-1)h^(-1).As revealed by in-situ characterizations and density functional theory calculations,CO_(2)and HCHO were absorbed at Zn site and N site,respectively.Then,*CO generated from CO_(2)and HCHO was converted to*CH_(3)O and*CHO on the dual-active-site heterojunction.The detailed reaction mechanism experiments indicated that C–C coupling only occurred between*CO and*CH_(3)O in electrocatalysis process.Apart from the“*CO+*CH_(3)O”path,another“*CO+*CHO”coupling path was also detected in photoelectrocatalytic process.The selectivity of ethanol was significantly enhanced due to the synthesis of dual-site catalyst and the dual-path coupling path between CO_(2)and HCHO simultaneously driven by light and electricity.
基金financially supported by the Innovation Fund Research Project of State Key Laboratory for Geomechanics and Deep Underground Engineering,China University of Mining and Technology(Grant No.SKLGDUEK202201)。
文摘To address the issue of extensive deformation in the Tabaiyi Tunnel caused by the fault zone,nuclear magnetic resonance(NMR)technology was employed to analyze the physical and mechanical properties of waterabsorbing mudstone.This analysis aimed to understand the mechanism behind the significant deformations.Drawing from the principle of excavation stress compensation,a support scheme featuring NPR anchorcables and an asymmetric truss support system was devised.To validate the scheme,numerical analysis using a combination of the Discrete Element Method(DEM)-Finite Element Method(FEM)was conducted.Additionally,similar material model tests and engineering measurements were carried out.Field experiments were also performed to evaluate the NPR anchor-cable and truss support system,focusing on anchor cable forces,pressures between the truss and surrounding rock,pressures between the initial support and secondary lining,as well as the magnitude of settlement and convergence deformation in the surrounding rock.The results indicate that the waterinduced expansion of clay minerals,resulting from damage caused by fissure water,accelerated the softening of the mudstone's internal structure,leading to significant deformations in the Tabaiyi Tunnel under high tectonic stress.The original support design fell short as the length of the anchor rods was smaller than the expansion depth of the plastic zone.As a result,the initial support structure bore the entire load from the surrounding rock,and a non-coupled deformation contact was observed between the double-arch truss and the surrounding rock.The adoption of NPR asymmetric anchor-cable support effectively restrained the expansion and asymmetric distribution characteristics of the plastic zone.Considering the mechanical degradation caused by water absorption in mudstone,the rigid constraint provided by the truss proved crucial for controlling the stability of the surrounding rock.These research findings hold significant implications for managing large deformations in soft rock tunnels situated within fractured zones under high tectonic stress conditions.
基金supported by the National Natural Science Foundation of China[11972139]Natural Science Foundation of Zhejiang Province[LR21A020002]Specialized research projects of Huanjiang Laboratory。
文摘Piezoelectric semiconductors(PSs)have widespread applications in semiconductor devices due to the coexistence of piezoelec-tricity and semiconducting properties.It is very important to conduct a theoretical analysis of PS structures.However,the present of nonlinearity in the partial differential equations(PDEs)that describe those multi-feld coupling mechanical behaviors of PSs poses a significant mathematical challenge when studying these PS structures.In this paper,we present a novel approach based on machine learning for solving multi-field coupling problems in PS structures.A physics-informed neural networks(PINNs)is constructed for predicting the multi-field coupling behaviors of PS rods with extensional deforma-tion.By utilizing the proposed PINNs,we evaluate the multi-field coupling responses of a ZnO rod under static and dynamic axial forces.Numerical results demonstrate that the proposed PINNs exhibit high accuracy in solving both static and dynamic problems associated with Ps structures.It provides an effective approach to predicting the nonlinear multi-feld coupling phe-nomena in PS structures.
基金Under the auspices of Major Program of National Natural Science Foundation of China(No.42293271)Alliance of International Science Organizations(No.ANSO-PA-2023-16)。
文摘Climate change brings new challenges to the sustainable development of agriculture in the new era.Accurately grasping the patterns of climate change impacts on agricultural systems is crucial for ensuring agricultural sustainability and food security.Taking the Loess Plateau(LP),China as an example,this study used a coupling coordination degree model and spatial autocorrelation analysis to portray the spatial and temporal features of crop-cropland coupling relationship from 2000 to 2020 and explored the impact law of climate change through geographically and temporally weighted regression(GTWR).The results were as follows:1)the crop-cropland coupling coordination degree of the LP showed a gradual upward trend from 2000 to 2020,forming a spatial pattern with lower values in the central region and higher values in the surrounding areas.2)There was a positive correlation in the spatial distribution of cropcropland coupling coordination degree in the LP from 2000 to 2020,and the high value-low value(H-L)and low value-low value(L-L)agglomerations continued to expand eastward,while the spatial and temporal evolution of the high value-high value(H-H)and low value-high value(L-H)agglomerations was not obvious.3)The impacts of climatic elements on crop-cropland coupling coordination degree in the LP showed strong heterogeneity in time scales.The inhibitory impacts of summer days(SU)and frost days(FD)accounted for a higher proportion,while the annual average temperature(TEM)had both promoting and inhibiting impacts.The impacts proportion and intensity of extreme heavy precipitation day(R25),continuous drought days(CDD),and annual precipitation(PRE)all experienced significant changes.4)In space,the impacts of SU and FD on the crop-cropland coupling coordination degree varied with latitude and altitude.The adaptability of the LP to R25 gradually strengthened,and the extensions of CDD and increase of PRE led to the increasing inhibition beyond the eastern region of LP,and TEM showed a promoting impact in the Fenwei Plain.As an important grainproducing area in China,the LP should actively deal with the impacts of climate change on the crop-cropland coupling relationship,vigorously safeguard food security,and promote sustainable agricultural development.
基金National Natural Science Foundation of China(U22B20149,22308376)Outstanding Young Scholars Foundation of China University of Petroleum(Beijing)(2462023BJRC015)Foundation of United Institute for Carbon Neutrality(CNIF20230209)。
文摘Dual atomic catalysts(DAC),particularly copper(Cu_(2))-based nitrogen(N)doped graphene,show great potential to effectively convert CO_(2)and nitrate(NO_(3)-)into important industrial chemicals such as ethylene,glycol,acetamide,and urea through an efficient catalytical process that involves C–C and C–N coupling.However,the origin of the coupling activity remained unclear,which substantially hinders the rational design of Cu-based catalysts for the N-integrated CO_(2)reduction reaction(CO_(2)RR).To address this challenge,this work performed advanced density functional theory calculations incorporating explicit solvation based on a Cu_(2)-based N-doped carbon(Cu_(2)N_(6)C_(10))catalyst for CO_(2)RR.These calculations are aimed to gain insight into the reaction mechanisms for the synthesis of ethylene,acetamide,and urea via coupling in the interfacial reaction micro-environment.Due to the sluggishness of CO_(2),the formation of a solvation electric layer by anions(F^(-),Cl^(-),Br^(-),and I^(-))and cations(Na+,Mg^(2+),K+,and Ca^(2+))leads to electron transfer towards the Cu surface.This process significantly accelerates the reduction of CO_(2).These results reveal that*CO intermediates play a pivotal role in N-integrated CO_(2)RR.Remarkably,the Cu_(2)-based N-doped carbon catalyst examined in this study has demonstrated the most potential for C–N coupling to date.Our findings reveal that through the process of a condensation reaction between*CO and NH_(2)OH for urea synthesis,*NO_(3)-is reduced to*NH_(3),and*CO_(2)to*CCO at dual Cu atom sites.This dual-site reduction facilitates the synthesis of acetamide through a nucleophilic reaction between NH_(3)and the ketene intermediate.Furthermore,we found that the I-and Mg^(2+)ions,influenced by pH,were highly effective for acetamide and ammonia synthesis,except when F-and Ca^(2+)were present.Furthermore,the mechanisms of C–N bond formation were investigated via ab-initio molecular dynamics simulations,and we found that adjusting the micro-environment can change the dominant side reaction,shifting from hydrogen production in acidic conditions to water reduction in alkaline ones.This study introduces a novel approach using ion-H_(2)O cages to significantly enhance the efficiency of C–N coupling reactions.
基金Supported by National Natural Science Foundation of China(11327802,11302225)China Postdoctoral Science Foundation(2014M560820)National Scholarship Foundation of China(201404910172)
文摘A conduction-cooled superconducting magnet producing a transverse field of 4 T has been designed for a new generation multi-field coupling measurement system, which will be used to study the mechanical behavior of superconducting samples at cryogenic temperatures and intense magnetic fields. A compact cryostat with a two-stage GM cryocooler is designed and manufactured for the superconducting magnet. The magnet is composed of a pair of flat racetrack coils wound by NbTi/Cu superconducting composite wires, a copper and stainless steel combinational former and two Bi2Sr2CaCu20~ superconducting current leads. The two coils are connected in series and can be powered with a single power supply. In order to support the high stress and attain uniform thermal distribution in the superconducting magnet, a detailed finite element （FE） analysis has been performed. The results indicate that in the operating status the designed magnet system can sufficiently bear the electromagnetic forces and has a uniform temperature distribution.
