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
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
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
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
We study the trimer state in a three-body system,where two of the atoms are subject to Rashba-type spin-orbit coupling and spin-dependent loss while interacting spin-selectively with the third atom.The short-time cond...We study the trimer state in a three-body system,where two of the atoms are subject to Rashba-type spin-orbit coupling and spin-dependent loss while interacting spin-selectively with the third atom.The short-time conditional dynamics of the three-body system is effectively governed by a non-Hermitian Hamiltonian with an imaginary Zeeman field.Remarkably,the interplay of non-Hermitian single particle dispersion and the spin-selective interaction results in a Borromean state and an enlarged trimer phase.The stability of trimer state can be reflected by the imaginary part of trimer energy and the momentum distribution of trimer wave function.We also show the phase diagram of the three-body system under both real and imaginary Zeeman fields.Our results illustrate the interesting consequence of non-Hermitian spectral symmetry on the few-body level,which may be readily observable in current cold-atom experiments.展开更多
The direct deoxygenative homo-coupling of benzyl alcohols holds great promise to build up bibenzyl motifs in organic synthesis,yet it remains a grand challenge in selectivity and activity control.Herein,we first disco...The direct deoxygenative homo-coupling of benzyl alcohols holds great promise to build up bibenzyl motifs in organic synthesis,yet it remains a grand challenge in selectivity and activity control.Herein,we first discovered that iron carbide catalysts displayed high efficiency and selectivity in the catalytic deoxygenative homo-coupling of benzyl alcohols into bibenzyls using H_(2)as the reductant.Ir-promoted Fe0@Fe_(5)C_(2)gave the best performance among the investigated catalysts,and a broad scope of substrates with diverse functional groups could be smoothly converted into bibenzyls,with the yield up to 85%.In addition,in the presence of alkenes,three-component coupling reactions between alcohols and alkenes were also for the first time achieved to construct more complex multi-ring molecules.The radical-trapping experiment and FTIR measurements revealed the radical nature of the reaction and the significantly promoted C–O bond activation after carbonization,respectively.This work will provide guidelines for the rational design of efficient and selective catalysts for the alcohol-involved carbon-carbon coupling reactions.展开更多
In this study,a series of triaxial tests are conducted on sandstone specimens to investigate the evolution of their mechanics and permeability characteristics under the combined action of immersion corrosion and seepa...In this study,a series of triaxial tests are conducted on sandstone specimens to investigate the evolution of their mechanics and permeability characteristics under the combined action of immersion corrosion and seepage of different chemical solutions.It is observed that with the increase of confining pressure,the peak stress,dilatancy stress,dilatancy stress ratio,peak strain,and elastic modulus of the sandstone increase while the Poisson ratio decreases and less secondary cracks are produced when the samples are broken.The pore pressure and confining pressure have opposite influences on the mechanical properties.With the increase of the applied axial stress,three stages are clearly identified in the permeability evolution curves:initial compaction stage,linear elasticity stage and plastic deformation stage.The permeability reaches the maximum value when the highest volumetric dilatancy is obtained.In addition,the hydrochemical action of salt solution with pH=7 and 4 has an obvious deteriorating effect on the mechanical properties and induces the increase of permeability.The obtained results will be useful in engineering to understand the mechanical and seepage properties of sandstone under the coupled chemical-seepage-stress multiple fields.展开更多
Land–atmosphere coupling and sea surface temperature(SST)anomalies both have essential impacts on weather and climate extremes.Based on the ERA5 reanalysis dataset and the CESM1.2.2 model,this study investigates the ...Land–atmosphere coupling and sea surface temperature(SST)anomalies both have essential impacts on weather and climate extremes.Based on the ERA5 reanalysis dataset and the CESM1.2.2 model,this study investigates the influence of land–atmosphere coupling on summer extreme hot-humid events(EHHE)over southern Eurasia under different SST backgrounds.The results suggest that coupling causes near-surface air temperature increases that exceed 0.5℃.From 1961 to 2020,the frequency of EHHE has continuously increased,and is closely related to soil moisture anomalies in the northern Indian Peninsula(IDP)and the middle and lower reaches of the Yangtze River(YRB).Numerical simulations further demonstrate that land–atmosphere coupling raises the risk of EHHE by 25.4%.In a typical El Niño SST background state,intensified land–atmosphere coupling tends to produce notable increases in the frequency of EHHE.The dominant processes that land–atmosphere coupling affects the EHHE variations are evidently different between these two regions.Land surface thermal anomalies predominate in the IDP,while moisture conditions are more critical in the YRB.When warm SST anomalies exist,dry soil anomalies in the IDP are prominent,and evaporation is constrained,increasing sensible heat flux.Positive geopotential height anomalies are significant,combined with adiabatic warming induced by descending motion and a noticeable warm center in the near-surface atmosphere.The southward shift of the westerly jet enhances divergence over YRB.The anticyclonic circulation anomalies over the western Pacific are conducive to guiding moisture transport to the YRB,providing a favorable circulation background for the development of summer EHHE.展开更多
Granite residual soil (GRS) is a type of weathering soil that can decompose upon contact with water, potentially causing geological hazards. In this study, cement, an alkaline solution, and glass fiber were used to re...Granite residual soil (GRS) is a type of weathering soil that can decompose upon contact with water, potentially causing geological hazards. In this study, cement, an alkaline solution, and glass fiber were used to reinforce GRS. The effects of cement content and SiO_(2)/Na2O ratio of the alkaline solution on the static and dynamic strengths of GRS were discussed. Microscopically, the reinforcement mechanism and coupling effect were examined using X-ray diffraction (XRD), micro-computed tomography (micro-CT), and scanning electron microscopy (SEM). The results indicated that the addition of 2% cement and an alkaline solution with an SiO_(2)/Na2O ratio of 0.5 led to the densest matrix, lowest porosity, and highest static compressive strength, which was 4994 kPa with a dynamic impact resistance of 75.4 kN after adding glass fiber. The compressive strength and dynamic impact resistance were a result of the coupling effect of cement hydration, a pozzolanic reaction of clay minerals in the GRS, and the alkali activation of clay minerals. Excessive cement addition or an excessively high SiO_(2)/Na2O ratio in the alkaline solution can have negative effects, such as the destruction of C-(A)-S-H gels by the alkaline solution and hindering the production of N-A-S-H gels. This can result in damage to the matrix of reinforced GRS, leading to a decrease in both static and dynamic strengths. This study suggests that further research is required to gain a more precise understanding of the effects of this mixture in terms of reducing our carbon footprint and optimizing its properties. The findings indicate that cement and alkaline solution are appropriate for GRS and that the reinforced GRS can be used for high-strength foundation and embankment construction. The study provides an analysis of strategies for mitigating and managing GRS slope failures, as well as enhancing roadbed performance.展开更多
In Earth system modeling,the land surface is coupled with the atmosphere through surface turbulent fluxes.These fluxes are computed using mean meteorological variables between the surface and a reference height in the...In Earth system modeling,the land surface is coupled with the atmosphere through surface turbulent fluxes.These fluxes are computed using mean meteorological variables between the surface and a reference height in the atmosphere.However,the dependence of flux computation on the reference height,which is usually set as the lowest level in the atmosphere in Earth system models,has not received much attention.Based on high-resolution large-eddy simulation(LES)data under unstable conditions,we find the setting of reference height is not trivial within the framework of current surface layer theory.With a reasonable prescription of aerodynamic roughness length(following the setting in LESs),reference heights near the top of the surface layer tend to provide the best estimate of surface fluxes,especially for the momentum flux.Furthermore,this conclusion for the sensible heat flux is insensitive to the ratio of roughness length for momentum versus heat.These results are robust,whether using the classical or revised surface layer theory.They provide a potential guide for setting the proper reference heights for Earth system modeling and can be further tested in the near future using observational data from land–atmosphere feedback observatories.展开更多
Purpose:In this paper,we use author clustering based on journal coupling(i.e.,shared academic journals)to determine researchers who have the same scientific interests and similar conceptual frameworks.The basic assump...Purpose:In this paper,we use author clustering based on journal coupling(i.e.,shared academic journals)to determine researchers who have the same scientific interests and similar conceptual frameworks.The basic assumption is that authors who publish in the same academic journals are more likely to share similar conceptual frameworks and interests than those who never publish in the same venues.Therefore,they are more likely to be part of the same invisible college(i.e.,authors in this subgroup contribute materially to research on the same topic and often publish their work in similar publication venues).Design/methodology/approach:Test in a controlled exercise the grouping of authors based on journal coupling to determine invisible colleges in a research field using a case study of 302 authors who had published in the Information Science and Library Science(IS&LS)category of the Web of Science Core Collection.For each author,we retrieved all the scientific journals in which this author had published his/her articles.We then used the cosine measure to calculate the similarity between authors(both first and second order).Findings:In this paper,using journal coupling of IS&LS authors,we found four main invisible colleges:“Information Systems”,“Business and Information Management”,“Quantitative Information Science”and“Library Science.”The main journals that determine the existence of these invisible colleges were Inform Syst Res,Inform Syst J,J Bus Res,J Knowl Manage,J Informetr,Pro Int Conf Sci Inf,Int J Geogr Inf Sci,J Am Med Inform Assn,and Learn Publ.However,the main journals that demonstrate that IS&LS determine a field were J Am Soc Inf Sci Tec/J Assoc Inf Sci Tech,Scientometrics,Inform Process Manag,and J Inf Sci.Research limitations:The results shown in this article are from a controlled exercise.The analysis performed using journal coupling excludes books,book chapters,and conference papers.In this article,only academic journals were used for the representation of research results.Practical implications:Our results may be of interest to IS&LS scholars.This is because these results provide a new lens for grouping authors,making use of the authors’journal publication profile and journal coupling.Furthermore,extending our approach to the study of the structure of other disciplines would possibly be of interest to historians of science as well as scientometricians.Originality/value:This is a novel approach based on journal coupling to determine authors who are most likely to be part of the same invisible college.展开更多
The vehicle-road coupling dynamics problem is a prominent issue in transportation,drawing significant attention in recent years.These dynamic equations are characterized by high-dimensionality,coupling,and time-varyin...The vehicle-road coupling dynamics problem is a prominent issue in transportation,drawing significant attention in recent years.These dynamic equations are characterized by high-dimensionality,coupling,and time-varying dynamics,making the exact solutions challenging to obtain.As a result,numerical integration methods are typically employed.However,conventional methods often suffer from low computational efficiency.To address this,this paper explores the application of the parameter freezing precise exponential integrator to vehicle-road coupling models.The model accounts for road roughness irregularities,incorporating all terms unrelated to the linear part into the algorithm's inhomogeneous vector.The general construction process of the algorithm is detailed.The validity of numerical results is verified through approximate analytical solutions(AASs),and the advantages of this method over traditional numerical integration methods are demonstrated.Multiple parameter freezing precise exponential integrator schemes are constructed based on the Runge-Kutta framework,with the fourth-order four-stage scheme identified as the optimal one.The study indicates that this method can quickly and accurately capture the dynamic system's vibration response,offering a new,efficient approach for numerical studies of high-dimensional vehicle-road coupling systems.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
The electromagnetic wave propagations and their coupling characteristics in magnetized plasma near the antenna of ion cyclotron range of frequencies(ICRF)is studied based on self-developed 3DFEM-IA code.This code effe...The electromagnetic wave propagations and their coupling characteristics in magnetized plasma near the antenna of ion cyclotron range of frequencies(ICRF)is studied based on self-developed 3DFEM-IA code.This code effectively resolves the three-dimensional(3D)geometry and the electromagnetic field using the finite element method.Our findings reveal that the distributions of electromagnetic fields and energy flow density significantly depend on the antenna phases,surface current density on the antenna straps,and background plasma density.Notably,the non-uniform surface current density on the antenna straps,resulting from the presence of induced currents,contributes to a reduction in coupling power within the edge plasma.Furthermore,the calculated coupling impedance increases with plasma density,corroborating well with experimental measurements.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
A thoroughly mechanistic understanding of the electrochemical CO reduction reaction(eCORR)at the interface is significant for guiding the design of high-performance electrocatalysts.However,unintentionally ignored fac...A thoroughly mechanistic understanding of the electrochemical CO reduction reaction(eCORR)at the interface is significant for guiding the design of high-performance electrocatalysts.However,unintentionally ignored factors or unreasonable settings during mechanism simulations will result in false positive results between theory and experiment.Herein,we computationally identified the dynamic site preference change of CO adsorption with potentials on Cu(100),which was a previously unnoticed factor but significant to potential-dependent mechanistic studies.Combined with the different lateral interactions among adsorbates,we proposed a new C–C coupling mechanism on Cu(100),better explaining the product distribution at different potentials in experimental eCORR.At low potentials(from–0.4 to–0.6 V_(RHE)),the CO forms dominant adsorption on the bridge site,which couples with another attractively aggregated CO to form a C–C bond.At medium potentials(from–0.6 to–0.8 VRHE),the hollow-bound CO becomes dominant but tends to isolate with another adsorbate due to the repulsion,thereby blocking the coupling process.At high potentials(above–0.8 VRHE),the CHO intermediate is produced from the electroreduction of hollow-CO and favors the attraction with another bridge-CO to trigger C–C coupling,making CHO the major common intermediate for C–C bond formation and methane production.We anticipate that our computationally identified dynamic change in site preference of adsorbates with potentials will bring new opportunities for a better understanding of the potential-dependent electrochemical processes.展开更多
Electrochemical carbon dioxide reduction reaction(CO_(2)RR)produces valuable chemicals by consuming gaseous CO_(2)as well as protons from the electrolyte.Protons,produced by water dissociation in alkaline electrolyte,...Electrochemical carbon dioxide reduction reaction(CO_(2)RR)produces valuable chemicals by consuming gaseous CO_(2)as well as protons from the electrolyte.Protons,produced by water dissociation in alkaline electrolyte,are critical for the reaction kinetics which involves multiple proton coupled electron transfer steps.Herein,we demonstrate that the two key steps(CO_(2)-^(*)COOH and^(*)CO-^(*)COH)efficiency can be precisely tuned by introducing proper amount of water dissociation center,i.e.,Fe single atoms,locally surrounding the Cu catalysts.In alkaline electrolyte,the Faradaic efficiency(FE)of multi-carbon(C^(2+))products exhibited a volcano type plot depending on the density of water dissociation center.A maximum FE for C^(2+)products of 73.2%could be reached on Cu nanoparticles supported on N-doped Carbon nanofibers with moderate Fe single atom sites,at a current density of 300 mA cm^(–2).Experimental and theoretical calculation results reveal that the Fe sites facilitate water dissociation kinetics,and the locally generated protons contribute significantly to the CO_(2)activation and^(*)CO protonation process.On the one hand,in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy(in-situ ATR-SEIRAS)clearly shows that the^(*)COOH intermediate can be observed at a lower potential.This phenomenon fully demonstrates that the optimized local water dissociation kinetics has a unique advantage in guiding the hydrogenation reaction pathway of CO₂molecules and can effectively reduce the reaction energy barrier.On the other hand,abundant^(*)CO and^(*)COH intermediates create favorable conditions for the asymmetric^(*)CO-^(*)COH coupling,significantly increasing the selectivity of the reaction for C^(2+)products and providing strong support for the efficient conversion of related reactions to the target products.This work provides a promising strategy for the design of a dual sites catalyst to achieve high FE of C^(2+)products through the optimized local water dissociation kinetics.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
Light-driven CO_(2) reduction reaction(CO_(2)RR)to value-added ethylene(C2H4)holds significant promise for addressing energy and environmental challenges.While the high energy barriers for*CO intermediates hydrogenati...Light-driven CO_(2) reduction reaction(CO_(2)RR)to value-added ethylene(C2H4)holds significant promise for addressing energy and environmental challenges.While the high energy barriers for*CO intermediates hydrogenation and C–C coupling limit the C_(2)H_(4)generation.Herein,CuxP/g-C_(3)N_(4) heterojunction prepared by an in-situ phosphating technique,achieved collaborative photocatalytic CO_(2) and H2O,producing CO and C_(2)H_(4)as the main products.Notably,the selectivity of C_(2)H_(4)produced by CuxP/g-C_(3)N_(4) attained to 64.25%,which was 9.85 times that of CuxP(6.52%).Detailed time-resolution photoluminescence spectra,femtosecond transient absorption spectroscopy tests and density functional theory(DFT)calculation validate the ultra-fast interfacial electron transfer mechanism in CuxP/g-C_(3)N_(4) heterojunction.Successive*H on P sites caused by adsorbed H2O splitting with moderate hydrogenation ability enables the multi-step hydrogenation during CO_(2)RR process over CuxP/g-C_(3)N_(4).With the aid of mediated asymmetric Cu and P dual sites by g-C_(3)N_(4) nanosheet,the produced*CHO shows an energetically favorable for C–C coupling.The coupling formed*CHOCHO further accepts photoexcited efficient e–and*H to deeply produce C_(2)H_(4)according to the C^(2+)intermediates,which has been detected by in-situ diffuse reflectance infrared Fourier transform spectroscopy and interpreted by DFT calculation.The novel insight mechanism offers an essential understanding for the development of CuxP-based heterojunctions for photocatalytic CO_(2) to C^(2+)value-added fuels.展开更多
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.
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.
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supported by the National Natural Science Foundation of China(Grant No.11974331)。
文摘We study the trimer state in a three-body system,where two of the atoms are subject to Rashba-type spin-orbit coupling and spin-dependent loss while interacting spin-selectively with the third atom.The short-time conditional dynamics of the three-body system is effectively governed by a non-Hermitian Hamiltonian with an imaginary Zeeman field.Remarkably,the interplay of non-Hermitian single particle dispersion and the spin-selective interaction results in a Borromean state and an enlarged trimer phase.The stability of trimer state can be reflected by the imaginary part of trimer energy and the momentum distribution of trimer wave function.We also show the phase diagram of the three-body system under both real and imaginary Zeeman fields.Our results illustrate the interesting consequence of non-Hermitian spectral symmetry on the few-body level,which may be readily observable in current cold-atom experiments.
文摘The direct deoxygenative homo-coupling of benzyl alcohols holds great promise to build up bibenzyl motifs in organic synthesis,yet it remains a grand challenge in selectivity and activity control.Herein,we first discovered that iron carbide catalysts displayed high efficiency and selectivity in the catalytic deoxygenative homo-coupling of benzyl alcohols into bibenzyls using H_(2)as the reductant.Ir-promoted Fe0@Fe_(5)C_(2)gave the best performance among the investigated catalysts,and a broad scope of substrates with diverse functional groups could be smoothly converted into bibenzyls,with the yield up to 85%.In addition,in the presence of alkenes,three-component coupling reactions between alcohols and alkenes were also for the first time achieved to construct more complex multi-ring molecules.The radical-trapping experiment and FTIR measurements revealed the radical nature of the reaction and the significantly promoted C–O bond activation after carbonization,respectively.This work will provide guidelines for the rational design of efficient and selective catalysts for the alcohol-involved carbon-carbon coupling reactions.
基金Projects(12072102,12102129)supported by the National Natural Science Foundation of ChinaProject(DM2022B01)supported by the Key Laboratory of Safe Mining of Deep Metal Mines,Ministry of Education,ChinaProject(JZ-008)supported by the Six Talent Peaks Project in Jiangsu Province,China。
文摘In this study,a series of triaxial tests are conducted on sandstone specimens to investigate the evolution of their mechanics and permeability characteristics under the combined action of immersion corrosion and seepage of different chemical solutions.It is observed that with the increase of confining pressure,the peak stress,dilatancy stress,dilatancy stress ratio,peak strain,and elastic modulus of the sandstone increase while the Poisson ratio decreases and less secondary cracks are produced when the samples are broken.The pore pressure and confining pressure have opposite influences on the mechanical properties.With the increase of the applied axial stress,three stages are clearly identified in the permeability evolution curves:initial compaction stage,linear elasticity stage and plastic deformation stage.The permeability reaches the maximum value when the highest volumetric dilatancy is obtained.In addition,the hydrochemical action of salt solution with pH=7 and 4 has an obvious deteriorating effect on the mechanical properties and induces the increase of permeability.The obtained results will be useful in engineering to understand the mechanical and seepage properties of sandstone under the coupled chemical-seepage-stress multiple fields.
基金supported by the National Science Foundation of China(Grant Nos.42088101 and 42275172).
文摘Land–atmosphere coupling and sea surface temperature(SST)anomalies both have essential impacts on weather and climate extremes.Based on the ERA5 reanalysis dataset and the CESM1.2.2 model,this study investigates the influence of land–atmosphere coupling on summer extreme hot-humid events(EHHE)over southern Eurasia under different SST backgrounds.The results suggest that coupling causes near-surface air temperature increases that exceed 0.5℃.From 1961 to 2020,the frequency of EHHE has continuously increased,and is closely related to soil moisture anomalies in the northern Indian Peninsula(IDP)and the middle and lower reaches of the Yangtze River(YRB).Numerical simulations further demonstrate that land–atmosphere coupling raises the risk of EHHE by 25.4%.In a typical El Niño SST background state,intensified land–atmosphere coupling tends to produce notable increases in the frequency of EHHE.The dominant processes that land–atmosphere coupling affects the EHHE variations are evidently different between these two regions.Land surface thermal anomalies predominate in the IDP,while moisture conditions are more critical in the YRB.When warm SST anomalies exist,dry soil anomalies in the IDP are prominent,and evaporation is constrained,increasing sensible heat flux.Positive geopotential height anomalies are significant,combined with adiabatic warming induced by descending motion and a noticeable warm center in the near-surface atmosphere.The southward shift of the westerly jet enhances divergence over YRB.The anticyclonic circulation anomalies over the western Pacific are conducive to guiding moisture transport to the YRB,providing a favorable circulation background for the development of summer EHHE.
基金the support provided by the National Natural Science Foundation of China(Grant Nos.52278336 and 42302032)Guangdong Basic and Applied Research Foundation(Grant Nos.2023B1515020061).
文摘Granite residual soil (GRS) is a type of weathering soil that can decompose upon contact with water, potentially causing geological hazards. In this study, cement, an alkaline solution, and glass fiber were used to reinforce GRS. The effects of cement content and SiO_(2)/Na2O ratio of the alkaline solution on the static and dynamic strengths of GRS were discussed. Microscopically, the reinforcement mechanism and coupling effect were examined using X-ray diffraction (XRD), micro-computed tomography (micro-CT), and scanning electron microscopy (SEM). The results indicated that the addition of 2% cement and an alkaline solution with an SiO_(2)/Na2O ratio of 0.5 led to the densest matrix, lowest porosity, and highest static compressive strength, which was 4994 kPa with a dynamic impact resistance of 75.4 kN after adding glass fiber. The compressive strength and dynamic impact resistance were a result of the coupling effect of cement hydration, a pozzolanic reaction of clay minerals in the GRS, and the alkali activation of clay minerals. Excessive cement addition or an excessively high SiO_(2)/Na2O ratio in the alkaline solution can have negative effects, such as the destruction of C-(A)-S-H gels by the alkaline solution and hindering the production of N-A-S-H gels. This can result in damage to the matrix of reinforced GRS, leading to a decrease in both static and dynamic strengths. This study suggests that further research is required to gain a more precise understanding of the effects of this mixture in terms of reducing our carbon footprint and optimizing its properties. The findings indicate that cement and alkaline solution are appropriate for GRS and that the reinforced GRS can be used for high-strength foundation and embankment construction. The study provides an analysis of strategies for mitigating and managing GRS slope failures, as well as enhancing roadbed performance.
基金supported by the Natural Science Foundation of China(Grant Nos.42088101 and 42375163)the Guangdong Major Project of Basic and Applied Basic Research(Grant No.2021B0301030007)the specific research fund of The Innovation Platform for Academicians of Hainan Province(Grant No.YSPTZX202143)。
文摘In Earth system modeling,the land surface is coupled with the atmosphere through surface turbulent fluxes.These fluxes are computed using mean meteorological variables between the surface and a reference height in the atmosphere.However,the dependence of flux computation on the reference height,which is usually set as the lowest level in the atmosphere in Earth system models,has not received much attention.Based on high-resolution large-eddy simulation(LES)data under unstable conditions,we find the setting of reference height is not trivial within the framework of current surface layer theory.With a reasonable prescription of aerodynamic roughness length(following the setting in LESs),reference heights near the top of the surface layer tend to provide the best estimate of surface fluxes,especially for the momentum flux.Furthermore,this conclusion for the sensible heat flux is insensitive to the ratio of roughness length for momentum versus heat.These results are robust,whether using the classical or revised surface layer theory.They provide a potential guide for setting the proper reference heights for Earth system modeling and can be further tested in the near future using observational data from land–atmosphere feedback observatories.
文摘Purpose:In this paper,we use author clustering based on journal coupling(i.e.,shared academic journals)to determine researchers who have the same scientific interests and similar conceptual frameworks.The basic assumption is that authors who publish in the same academic journals are more likely to share similar conceptual frameworks and interests than those who never publish in the same venues.Therefore,they are more likely to be part of the same invisible college(i.e.,authors in this subgroup contribute materially to research on the same topic and often publish their work in similar publication venues).Design/methodology/approach:Test in a controlled exercise the grouping of authors based on journal coupling to determine invisible colleges in a research field using a case study of 302 authors who had published in the Information Science and Library Science(IS&LS)category of the Web of Science Core Collection.For each author,we retrieved all the scientific journals in which this author had published his/her articles.We then used the cosine measure to calculate the similarity between authors(both first and second order).Findings:In this paper,using journal coupling of IS&LS authors,we found four main invisible colleges:“Information Systems”,“Business and Information Management”,“Quantitative Information Science”and“Library Science.”The main journals that determine the existence of these invisible colleges were Inform Syst Res,Inform Syst J,J Bus Res,J Knowl Manage,J Informetr,Pro Int Conf Sci Inf,Int J Geogr Inf Sci,J Am Med Inform Assn,and Learn Publ.However,the main journals that demonstrate that IS&LS determine a field were J Am Soc Inf Sci Tec/J Assoc Inf Sci Tech,Scientometrics,Inform Process Manag,and J Inf Sci.Research limitations:The results shown in this article are from a controlled exercise.The analysis performed using journal coupling excludes books,book chapters,and conference papers.In this article,only academic journals were used for the representation of research results.Practical implications:Our results may be of interest to IS&LS scholars.This is because these results provide a new lens for grouping authors,making use of the authors’journal publication profile and journal coupling.Furthermore,extending our approach to the study of the structure of other disciplines would possibly be of interest to historians of science as well as scientometricians.Originality/value:This is a novel approach based on journal coupling to determine authors who are most likely to be part of the same invisible college.
基金Supported by the National Natural Science Foundation of China(No.U22A20246)the Key Project of Natural Science Foundation of Hebei Province of China(Basic Research Base Project)(No.A2023210064)the Science and Technology Program of Hebei Province of China(Nos.246Z1904G and 225676162GH)。
文摘The vehicle-road coupling dynamics problem is a prominent issue in transportation,drawing significant attention in recent years.These dynamic equations are characterized by high-dimensionality,coupling,and time-varying dynamics,making the exact solutions challenging to obtain.As a result,numerical integration methods are typically employed.However,conventional methods often suffer from low computational efficiency.To address this,this paper explores the application of the parameter freezing precise exponential integrator to vehicle-road coupling models.The model accounts for road roughness irregularities,incorporating all terms unrelated to the linear part into the algorithm's inhomogeneous vector.The general construction process of the algorithm is detailed.The validity of numerical results is verified through approximate analytical solutions(AASs),and the advantages of this method over traditional numerical integration methods are demonstrated.Multiple parameter freezing precise exponential integrator schemes are constructed based on the Runge-Kutta framework,with the fourth-order four-stage scheme identified as the optimal one.The study indicates that this method can quickly and accurately capture the dynamic system's vibration response,offering a new,efficient approach for numerical studies of high-dimensional vehicle-road coupling systems.
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Project supported by the National MCF Energy Research and Development Program(Grant No.2022YFE03190100)the National Natural Science Foundation of China(Grant Nos.12422513,12105035,and U21A20438)the Xiaomi Young Talents Program。
文摘The electromagnetic wave propagations and their coupling characteristics in magnetized plasma near the antenna of ion cyclotron range of frequencies(ICRF)is studied based on self-developed 3DFEM-IA code.This code effectively resolves the three-dimensional(3D)geometry and the electromagnetic field using the finite element method.Our findings reveal that the distributions of electromagnetic fields and energy flow density significantly depend on the antenna phases,surface current density on the antenna straps,and background plasma density.Notably,the non-uniform surface current density on the antenna straps,resulting from the presence of induced currents,contributes to a reduction in coupling power within the edge plasma.Furthermore,the calculated coupling impedance increases with plasma density,corroborating well with experimental measurements.
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.
文摘A thoroughly mechanistic understanding of the electrochemical CO reduction reaction(eCORR)at the interface is significant for guiding the design of high-performance electrocatalysts.However,unintentionally ignored factors or unreasonable settings during mechanism simulations will result in false positive results between theory and experiment.Herein,we computationally identified the dynamic site preference change of CO adsorption with potentials on Cu(100),which was a previously unnoticed factor but significant to potential-dependent mechanistic studies.Combined with the different lateral interactions among adsorbates,we proposed a new C–C coupling mechanism on Cu(100),better explaining the product distribution at different potentials in experimental eCORR.At low potentials(from–0.4 to–0.6 V_(RHE)),the CO forms dominant adsorption on the bridge site,which couples with another attractively aggregated CO to form a C–C bond.At medium potentials(from–0.6 to–0.8 VRHE),the hollow-bound CO becomes dominant but tends to isolate with another adsorbate due to the repulsion,thereby blocking the coupling process.At high potentials(above–0.8 VRHE),the CHO intermediate is produced from the electroreduction of hollow-CO and favors the attraction with another bridge-CO to trigger C–C coupling,making CHO the major common intermediate for C–C bond formation and methane production.We anticipate that our computationally identified dynamic change in site preference of adsorbates with potentials will bring new opportunities for a better understanding of the potential-dependent electrochemical processes.
文摘Electrochemical carbon dioxide reduction reaction(CO_(2)RR)produces valuable chemicals by consuming gaseous CO_(2)as well as protons from the electrolyte.Protons,produced by water dissociation in alkaline electrolyte,are critical for the reaction kinetics which involves multiple proton coupled electron transfer steps.Herein,we demonstrate that the two key steps(CO_(2)-^(*)COOH and^(*)CO-^(*)COH)efficiency can be precisely tuned by introducing proper amount of water dissociation center,i.e.,Fe single atoms,locally surrounding the Cu catalysts.In alkaline electrolyte,the Faradaic efficiency(FE)of multi-carbon(C^(2+))products exhibited a volcano type plot depending on the density of water dissociation center.A maximum FE for C^(2+)products of 73.2%could be reached on Cu nanoparticles supported on N-doped Carbon nanofibers with moderate Fe single atom sites,at a current density of 300 mA cm^(–2).Experimental and theoretical calculation results reveal that the Fe sites facilitate water dissociation kinetics,and the locally generated protons contribute significantly to the CO_(2)activation and^(*)CO protonation process.On the one hand,in-situ attenuated total reflection surface-enhanced infrared absorption spectroscopy(in-situ ATR-SEIRAS)clearly shows that the^(*)COOH intermediate can be observed at a lower potential.This phenomenon fully demonstrates that the optimized local water dissociation kinetics has a unique advantage in guiding the hydrogenation reaction pathway of CO₂molecules and can effectively reduce the reaction energy barrier.On the other hand,abundant^(*)CO and^(*)COH intermediates create favorable conditions for the asymmetric^(*)CO-^(*)COH coupling,significantly increasing the selectivity of the reaction for C^(2+)products and providing strong support for the efficient conversion of related reactions to the target products.This work provides a promising strategy for the design of a dual sites catalyst to achieve high FE of C^(2+)products through the optimized local water dissociation kinetics.
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.
文摘Light-driven CO_(2) reduction reaction(CO_(2)RR)to value-added ethylene(C2H4)holds significant promise for addressing energy and environmental challenges.While the high energy barriers for*CO intermediates hydrogenation and C–C coupling limit the C_(2)H_(4)generation.Herein,CuxP/g-C_(3)N_(4) heterojunction prepared by an in-situ phosphating technique,achieved collaborative photocatalytic CO_(2) and H2O,producing CO and C_(2)H_(4)as the main products.Notably,the selectivity of C_(2)H_(4)produced by CuxP/g-C_(3)N_(4) attained to 64.25%,which was 9.85 times that of CuxP(6.52%).Detailed time-resolution photoluminescence spectra,femtosecond transient absorption spectroscopy tests and density functional theory(DFT)calculation validate the ultra-fast interfacial electron transfer mechanism in CuxP/g-C_(3)N_(4) heterojunction.Successive*H on P sites caused by adsorbed H2O splitting with moderate hydrogenation ability enables the multi-step hydrogenation during CO_(2)RR process over CuxP/g-C_(3)N_(4).With the aid of mediated asymmetric Cu and P dual sites by g-C_(3)N_(4) nanosheet,the produced*CHO shows an energetically favorable for C–C coupling.The coupling formed*CHOCHO further accepts photoexcited efficient e–and*H to deeply produce C_(2)H_(4)according to the C^(2+)intermediates,which has been detected by in-situ diffuse reflectance infrared Fourier transform spectroscopy and interpreted by DFT calculation.The novel insight mechanism offers an essential understanding for the development of CuxP-based heterojunctions for photocatalytic CO_(2) to C^(2+)value-added fuels.
