Mesoscale eddies,which are mainly caused by baroclinic effects in the ocean,are common oceanic phenomena in the Northwest Pacific Ocean and play very important roles in ocean circulation,ocean dynamics and material en...Mesoscale eddies,which are mainly caused by baroclinic effects in the ocean,are common oceanic phenomena in the Northwest Pacific Ocean and play very important roles in ocean circulation,ocean dynamics and material energy transport.The temperature structure of mesoscale eddies will lead to variations in oceanic baroclinity,which can be reflected in the sea level anomaly(SLA).Deep learning can automatically extract different features of data at multiple levels without human intervention,and find the hidden relations of data.Therefore,combining satellite SLA data with deep learning is a good way to invert the temperature structure inside eddies.This paper proposes a deep learning algorithm,eddy convolution neural network(ECN),which can train the relationship between mesoscale eddy temperature anomalies and sea level anomalies(SLAs),relying on the powerful feature extraction and learning abilities of convolutional neural networks.After obtaining the temperature structure model through ECN,according to climatic temperature data,the temperature structure of mesoscale eddies in the Northwest Pacific is retrieved with a spatial resolution of 0.25°at depths of 0–1000 m.The overall accuracy of the ECN temperature structure is verified using Argo profiles at the locations of cyclonic and anticyclonic eddies during 2015–2016.Taking 10%error as the acceptable threshold of accuracy,89.64%and 87.25%of the cyclonic and anticyclonic eddy temperature structures obtained by ECN met the threshold,respectively.展开更多
This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A tempe...This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A temperature-indexed Concrete Damage Plasticity(CDP)framework incorporating bond–slip effects was developed in Abaqus to capture both global stress–strain responses and localized damage evolution.Uniaxial compression tests on thermally exposed cylinders provided residual strength data and failure observations for model calibration and validation.Results demonstrated a distinct two-stage degradation regime:moderate stiffness and strength reduction up to~400℃,followed by sharp deterioration beyond 500℃–600℃,with residual capacity at 700℃reduced to~20%–25%of the ambient value.Strain–damage analyses revealed the formation of a peripheral tensile strain band,which thickened and propagated inward with increasing temperature,governing crack initiation and cover spalling.Supplemental analyses highlighted that transverse reinforcement improved ductility and damage distribution at moderate temperatures(~300℃),but bond deterioration and steel softening beyond~600℃substantially diminished confinement effectiveness.The proposed CDP model accurately reproduced experimental stress–strain curves(R^(2)≈0.94–0.98 up to 600℃;≈0.90 at 700℃),with peak stress errors within 7%–10%and energy absorption captured within~12%.These findings confirm the robustness of the temperature-indexed CDP framework for simulating fire-damaged reinforced concrete and provide practical guidelines for post-fire assessment,spalling detection,and fire-resilient design of structural members.展开更多
Developing alloys with exceptional strength-ductility combinations across a broad temperature range is crucial for advanced structural applications.The emerging face-centered cubic medium-entropy alloys(MEAs)demonstra...Developing alloys with exceptional strength-ductility combinations across a broad temperature range is crucial for advanced structural applications.The emerging face-centered cubic medium-entropy alloys(MEAs)demonstrate outstanding mechanical properties at both ambient and cryogenic temperatures.They are anticipated to extend their applicability to elevated temperatures,owing to their inherent advantages in leveraging multiple strengthening and deformation mechanisms.Here,a dual heterostructure,comprising of heterogeneous grain structure with heterogeneous distribution of the micro-scale Nb-rich Laves phases,is introduced in a CrCoNi-based MEA through thermo-mechanical processing.Additionally,a high-density nano-coherentγ’phase is introduced within the grains through isothermal aging treatments.The superior thermal stability of the heterogeneously distributed precipitates enables the dual heterostructure to persist at temperatures up to 1073 K,allowing the MEA to maintain excellent mechanical properties across a wide temperature range.The yield strength of the dual-heterogeneous-structured MEA reaches up to 1.2 GPa,1.1 GPa,0.8 GPa,and 0.6 GPa,coupled with total elongation values of 28.6%,28.4%,12.6%,and 6.1%at 93 K,298 K,873 K,and 1073 K,respectively.The high yield strength primar-ily stems from precipitation strengthening and hetero-deformation-induced strengthening.The high flow stress and low stacking fault energy of the dual-heterogeneous-structured MEA promote the formation of high-density stacking faults and nanotwins during deformation from 93 K to 1073 K,and their density increase with decreasing deformation temperature.This greatly contributes to the enhanced strainhardening capability and ductility across a wide temperature range.This study offers a practical solution for designing dual-heterogeneous-structured MEAs with both high yield strength and large ductility across a wide temperature range.展开更多
In recent years,research investigations have focused on the substantial freshwater storage in the Beaufort Gyre(BG)region due to climate change.Despite active mesoscale eddies in the area,a notable gap in understandin...In recent years,research investigations have focused on the substantial freshwater storage in the Beaufort Gyre(BG)region due to climate change.Despite active mesoscale eddies in the area,a notable gap in understanding the three-dimensional structure and induced transport has been observed.This study concentrates on the Canada Basin in the western Arctic Ocean,specifically examining a subsurface anticyclonic eddy(SAE)sampled by a Mooring A in the BG region.Hybrid Coordinate Ocean Model(HYCOM)analysis data reveal its lifecycle from February 15 to March 15,2017,marked by initiation,development,maturity,decay,and termination stages.This work extends the finding of SAE passing through Mooring A by examining its overall effects,spatiotemporal variations,and swirl transport.SAE generation through baroclinic instability,which contributes to the westward tilt of the vertical axis,is also confirmed in this study.Swirl transport induced by SAE is predominantly eastward and downward due to its trajectory and background flow.SAE temporarily weakens stratification and extends the subsurface depth but demonstrates transient effects.Moreover,SAE transports upper-layer freshwater,Pacific Winter Water,and Atlantic Water downward,emphasizing its potential influence on freshwater redistribution in the Canadian Basin.This research provides valuable insights into mesoscale eddy dynamics,revealing their role in modulating the upper water mass in the BG region.展开更多
Using observations and models from phase 6 of the Coupled Model Intercomparison Project(CMIP6),this study analyzes the performance of CMIP6 models in simulating the vertical structure of the Quasi-Biennial Oscillation...Using observations and models from phase 6 of the Coupled Model Intercomparison Project(CMIP6),this study analyzes the performance of CMIP6 models in simulating the vertical structure of the Quasi-Biennial Oscillation(QBO)and its impacts on eastern China surface air temperature(SAT),with empirical orthogonal function(EOF)analysis.The first leading mode(EOF1)of the QBO leads to an overall cooling/warming over eastern China via the QBO’s subtropical path and Holton-Tan effect,while the second leading mode(EOF2)of the QBO tends to cause an east-west dipole of SAT anomalies between eastern and western China due to a strong Holton-Tan effect.Most models with a self-generated QBO can capture both westerly and easterly QBO anomalies in the mid-lower stratosphere in EOF1 and only westerly anomalies in EOF2.The multi-model ensemble mean can reproduce the eastern China SAT anomalies that are statistically significant and related to EOF1-like QBO events.However,the intensity of these anomalies is relatively weaker,attributable to the weak Pacific response to the subtropical effect of the QBO.In contrast,most models fail to induce a strong Holton-Tan effect and a Northern Annular Mode pattern in the polar region during the EOF2-like QBO events,resulting in weak and insignificant eastern China SAT anomalies on average.Overall,the models with a better representation of polar and Pacific responses to the QBO’s vertical structure exhibit a more reasonable eastern China SAT response,although such a response is weaker than observed.展开更多
Polymer dielectrics are required to maintain high energy density at elevated temperatures for advanced power and electronic systems.Herein,we report a novel solution-processed core-shell structured poly-imide(PI)nanoc...Polymer dielectrics are required to maintain high energy density at elevated temperatures for advanced power and electronic systems.Herein,we report a novel solution-processed core-shell structured poly-imide(PI)nanocomposite with moderate dielectric constant HfO_(2)core and wide-bandgap Al_(2)O_(3)shell,ef-fectively addressing the typical trade-off between dielectric constant and breakdown strength in dielectric nanocomposites predominant at elevated temperatures.The formation of improved dielectrically match-ing interfaces by the rationally designed dielectric constant gradient from core-shell-matrix remarkably mitigates the distortion of the electric field around the interfaces,resulting in a high breakdown strength.Wide band gap Al_(2)O_(3)shell also introduces deeper traps to impede the conduction loss.The validity of Al_(2)O_(3)shell has been proved via experiments and simulations.Accordingly,HfO_(2)@Al_(2)O_(3)/PI nanocompos-ite exhibits an excellent charge-discharge efficiency of 91.7%at 300 MV/m and a maximum discharged energy density of 2.94 J/cm^(3)at 150℃,demonstrating its potential for high-temperature energy storage.展开更多
Sodium metal batteries(SMBs)are expected to become an alternative solution for energy storage and power systems in the future due to their abundant resources,substantial energy–density,and all-climate performance.How...Sodium metal batteries(SMBs)are expected to become an alternative solution for energy storage and power systems in the future due to their abundant resources,substantial energy–density,and all-climate performance.However,uneven Na deposition and slow charge transfer kinetics still significantly impair their low temperature and rate performance.Herein,we report a non-solvating trifluoromethoxy benzene(PhOCF_(3))that modulates dipole–dipole interactions in the solvation structure.This modulation effectively reduces the affinity between Na+and solvents,promoting an anion-rich solvation sheath formation and significantly enhancing room temperature electrochemical performance in SMBs.Furthermore,temperature-dependent spectroscopic characterizations and molecular dynamics simulations reveal that these dipole–dipole interactions thermodynamically exclude solvent molecules from inner Na^(+)solvation sphere at low temperatures,which endows the electrolyte with exceptional temperature adaptability,leading to remarkable improvement in low temperature SMB performance.Consequently,Na||Vanadium phosphate sodium(NVP)cells with the optimized electrolyte achieve 10,000 cycles at 10 C with capacity retention of 90.2%at 25℃and over 650 cycles at 0.5 C with a capacity of 92.1 mA h g^(−1)at−40℃.This work probed the temperature-responsive property of Na+solvation structure and designed the temperature-adaptive electrolyte by regulating solvation structure via dipole–dipole interactions,offering a valuable guidance for low temperature electrolytes design for SMBs.展开更多
Three-dimensional ocean subsurface temperature and salinity structures(OST/OSS)in the South China Sea(SCS)play crucial roles in oceanic climate research and disaster mitigation.Traditionally,real-time OST and OSS are ...Three-dimensional ocean subsurface temperature and salinity structures(OST/OSS)in the South China Sea(SCS)play crucial roles in oceanic climate research and disaster mitigation.Traditionally,real-time OST and OSS are mainly obtained through in-situ ocean observations and simulation by ocean circulation models,which are usually challenging and costly.Recently,dynamical,statistical,or machine learning models have been proposed to invert the OST/OSS from sea surface information;however,these models mainly focused on the inversion of monthly OST and OSS.To address this issue,we apply clustering algorithms and employ a stacking strategy to ensemble three models(XGBoost,Random Forest,and LightGBM)to invert the real-time OST/OSS based on satellite-derived data and the Argo dataset.Subsequently,a fusion of temperature and salinity is employed to reconstruct OST and OSS.In the validation dataset,the depth-averaged Correlation(Corr)of the estimated OST(OSS)is 0.919(0.83),and the average Root-Mean-Square Error(RMSE)is0.639°C(0.087 psu),with a depth-averaged coefficient of determination(R~2)of 0.84(0.68).Notably,at the thermocline where the base models exhibit their maximum error,the stacking-based fusion model exhibited significant performance enhancement,with a maximum enhancement in OST and OSS inversion exceeding 10%.We further found that the estimated OST and OSS exhibit good agreement with the HYbrid Coordinate Ocean Model(HYCOM)data and BOA_Argo dataset during the passage of a mesoscale eddy.This study shows that the proposed model can effectively invert the real-time OST and OSS,potentially enhancing the understanding of multi-scale oceanic processes in the SCS.展开更多
Magnesium(Mg)alloys typically suffer from cold brittleness at cryogenic temperatures(CT),where strength significantly increases and ductility decreases with decreasing temperature.This study investigates the improveme...Magnesium(Mg)alloys typically suffer from cold brittleness at cryogenic temperatures(CT),where strength significantly increases and ductility decreases with decreasing temperature.This study investigates the improvement of the strength-ductility balance at CT in Mg-3.6Y(wt.%)alloys with a bimodal grain structure,consisting of fine dynamically recrystallized(DRXed)grains and elongated unDRXed grains.The results demonstrate that the sample with∼50%DRXed region fraction achieves a remarkable strength-ductility synergy at CT.Dislocation strengthening in the unDRXed regions and grain boundary strengthening in the DRXed regions increase the tensile yield strength(TYS)by 1.6 times at CT compared to room temperature(RT).Concurrently,activation of{10¯12}tensile twinning and non-basal slip systems in DRXed regions,including prismatic a and pyramidal I c+a slips,along with abnormal pyramidal slip within unDRXed grains,reduces fracture elongation by only 1%relative to RT.Furthermore,the bimodal grain structure effectively alleviates strain localization through strain partitioning between DRXed and unDRXed grains,leading to the formation of interface-affected zones(IAZs)that promote the accumulation of geometrically necessary dislocations(GNDs)and enhance hetero-deformation-induced(HDI)hardening.At CT,the IAZs become wider and more pronounced,indicating enhanced GND accumulation that promotes stronger strain partitioning and more effective HDI strengthening.This work demonstrates that the bimodal grain structure is an effective approach to overcoming the low-temperature brittleness of Mg alloys,providing valuable insights for the design of high-performance materials for cryogenic applications.展开更多
Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence ...Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence of the martensitic transformation temperature span on Co content was observed.Before training,quite a narrow temperature span of the martensitic transformation,nearly independent of the Co content,was observed in all single crystals.After training the temperature span was still narrow for 8≤x≤10.9 but was obviously expanded for 10.9<x≤12.High-resolution transmission electron microscopy revealed that at the atomic scale,there exists incommensurate modulated structure in the single phase single crystals,as evidenced by nonperiodic satellite spots in the selected area electronic diffraction patterns.Moreover,the modulated wave vector of the satellite spots was increased by higher Co contents.Combining first principal calculations it was considered that the incommensurate modulated structure originates from the formation of Co-Co pairs.After training arrays of ordered dislocations with the same Burgers vector were introduced for 8≤x≤10.9 but the network of dislocations was formed for 10.9<x≤12.Based on analysis of transmission electron microscopy,geometric phase,thermodynamics,and Landau theory,it was considered that the austenite/martensite phase interface was pinned by the network of dislocations,expanding the temperature span of the martensitic transformation.This work supplies new insights for understanding the microstructure and martensitic transformation of Ni-Mn-Ga-based alloys.展开更多
The internal hotspot temperature rise prediction in nanocrystalline high-frequency transformers(nanoHFTs) is essential to ensure reliable operation. This paper presents a three-dimensional thermal network(3DTN) model ...The internal hotspot temperature rise prediction in nanocrystalline high-frequency transformers(nanoHFTs) is essential to ensure reliable operation. This paper presents a three-dimensional thermal network(3DTN) model for epoxy resin encapsulated nano HFTs, which aims to precisely predict the temperature distribution inside the transformer in combination with the finite element method(FEM). A magnetothermal bidirectional coupling 3DTN model is established by analyzing the thermal conduction between the core, windings, and epoxy resin, while also considering the convection and radiation heat transfer mechanisms on the surface of the epoxy resin. The model considers the impact of loss distribution in the core and windings on the temperature field and adopts a simplified 1/2 thermal network model to reduce computational complexity. Furthermore, the results of FEM are compared with experimental results to verify the accuracy of the 3DTN model in predicting the temperature rise of nano HFT. The results show that the 3DTN model reduces errors by an average of 5.25% over the traditional two-dimensional thermal network(2DTN) model, particularly for temperature distributions in the windings and core. This paper provides a temperature rise prediction method for the thermal design and offers a theoretical basis and engineering guidance for the optimization of their thermal management systems.展开更多
Sodium-ion hybrid capacitors(SICs),which combine the high energy density of batteries with the high power density and long cycle life of capacitors,are considered promising next-generation energy storage devices.Ensur...Sodium-ion hybrid capacitors(SICs),which combine the high energy density of batteries with the high power density and long cycle life of capacitors,are considered promising next-generation energy storage devices.Ensuring the performance of SICs in low-temperature environments is crucial for applications in high-altitude cold regions,where the desolvation process of Na+and the transport process in the solid electrolyte interphase(SEI)are determinant.In this paper,we proposed a multi-ether modulation strategy to construct a solvation sheath with multi-ether participation by modulating the coordination of Na+and solvents.This unique solvation sheath not only reduces the desolvation energy barrier of Na+,but more importantly forms a Na_(2)O-rich inorganic SEI and enhances the ionic dynamics of Na+.Benefiting from the excellent solvation structure design,SICs prepared with this electrolyte can achieve energy density of up to 178 Wh·kg^(-1) and ultra-high power density of 42390 W·kg^(-1) at room temperature.Notably,this SIC delivers record-high energy densities of 149 Wh·kg^(-1) and 119 Wh·kg^(-1) as well as power densities of up to 25200 W·kg^(-1) and 24591 W·kg^(-1) at−20℃ and−40℃,respectively.This work provides new ideas for the development of high-performance SICs for low-temperature operating environments.展开更多
We proposed a fiber optic high temperature sensor based on the Mach-Zehnder interference(MZI)structure,which is composed of two lengths of multi-mode fibers(MMFs),a length of few-mode fiber(FMF)and two sections of sin...We proposed a fiber optic high temperature sensor based on the Mach-Zehnder interference(MZI)structure,which is composed of two lengths of multi-mode fibers(MMFs),a length of few-mode fiber(FMF)and two sections of single-mode fibers(SMFs).Firstly,the two sections of MMFs were spliced with two sections of SMFs.Then,the MMFs were fused to two ends of FMF to form a symmetrically structured fiber-optic MZI structure.In this structure,the MMF served as the optical mode field coupling element,and the cladding and core of the FMF are the interference arm and the reference arm of the MZI structure,respectively.We investigated the sensor's response characteristics of the temperature and strain.The experimental results indicate that the sensor is sensitive to temperature variation,and the temperature response sensitivity is up to 61.4 pm/℃ in the range of 40-250℃,while the sensor has weak strain sensitivity,its strain sensitivity is only-0.72 pm/μe in the strain range of 0-1400μe.Moreover,the sensor has good stability and repeatability.In brief,the proposed fiber optic high temperature sensor has good properties,such as high sensitivity,compact structure,good stability and repeatability,which can be used for monitoring the temperature of submerged oil electric pump units under oil wells.展开更多
We study the influences of the temperature on the energy-band structure for the Holstein molecular-crystal model. We show that the energy-band width and the energy-gap width of a solid are relevant to both the interac...We study the influences of the temperature on the energy-band structure for the Holstein molecular-crystal model. We show that the energy-band width and the energy-gap width of a solid are relevant to both the interaction between an electron and thermal phonons and to thermal expansion. For a one-dimensional Li atom lattice chain, under the chosen parameters,the width of the ls and 2s energy bands narrows as the temperature increases and the energy-gap width between the two bands widens. These results agree qualitatively with those observed experimentally. Studying temperature dependence of the energy-band structure is of great importance for understanding optical and transporting characteristics of a solid.展开更多
A two-step method is proposed for detection and identification of invisible impact damage in composite structure under temperature changes using Lamb waves.First,a statistical outlier analysis is employed to distingui...A two-step method is proposed for detection and identification of invisible impact damage in composite structure under temperature changes using Lamb waves.First,a statistical outlier analysis is employed to distinguish whether the changes of Lamb wave signals are induced by damage within a monitoring area or are only affected by temperature changes.Damage indices are defined after the Lamb wave signals are processed by Fourier transform,and a Monte Carlo procedure is used to obtain the damage threshold value for the damage indices at the undamaged state.If the damage indices in the operation state exceed the threshold value,the presence of damage is determined.Then,a probabilistic damage imaging algorithm displaying probabilities of the presence of damage within the monitoring area is adopted to fuse information collected from multiple actuator-sensor paths to identify the location of damage.Damage indices under damaged state are used to generate the diagnostic image.Experimental study on a stiffened composite panel with random temperature changes is performed to demonstrate the effectiveness of the proposed method.展开更多
Flower-like tin oxide-supported platinum（Pt/SnOx） with a hierarchical structure was synthesized by a hydrothermal method and characterized by XRD,SEM,TEM,high resolution TEM,XPS and nitrogen adsorption.The flower-li...Flower-like tin oxide-supported platinum（Pt/SnOx） with a hierarchical structure was synthesized by a hydrothermal method and characterized by XRD,SEM,TEM,high resolution TEM,XPS and nitrogen adsorption.The flower-like Pt/SnOx microspheres of 1 μm in diameter were composed of staggered petal-like nanosheets with a thickness of 20 nm.Pt nanoparticles（NPs） of 2-3 nm were well dispersed on the SnOx nanosheets.The catalyst was tested in the catalytic oxidation of gaseous formaldehyde（HCHO） at room temperature,and exhibited enhanced activity compared to Pt NPs supported on commercial SnO and ground SnOx.HCHO removal of 87%was achieved over the hierarchical Pt/SnOx after 1 h of reaction,which was 1.5 times that over the ground SnOx-supported Pt（Pt/g-SnOx）,and the high activity was maintained after six recycles,showing the high stability of this catalyst.HCHO decomposition kinetics was modeled as a second order reaction.The reaction rate constant for Pt/SnOx was 5.6 times higher than Pt/g-SnOx.The hierarchical pore structure was beneficial for the diffusion and adsorption of HCHO molecules,and the highly dispersed Pt NPs on the SnOx nanosheets were the active sites for the oxidative decomposition of HCHO into CO2 and H2O.This study provided a promising approach for designing efficient catalysts for indoor HCHO removal at ambient temperature.展开更多
High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increa...High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increased conduction loss often leads to a significant decline in electromagnetic wave absorp-tion(EMWA)performance at elevated temperatures,which severely restricts their practical application.In this study,we propose a novel approach for efficient electromagnetic wave absorption across a wide temperature range using reduced graphene oxide(RGO)/epoxy resin(EP)metacomposites that integrate both electromagnetic parameters and metamaterial design concepts.Due to the discrete distribution of the units,electromagnetic waves can more easily penetrate the interior of materials,thereby exhibiting stable microwave absorption(MA)performance and impedance-matching characteristics suitable across a wide temperature range.Consequently,exceptional MA properties can be achieved within the tem-perature range from 298 to 473 K.Furthermore,by carefully controlling the structural parameters in RGO metacomposites,both the resonant frequency and effective absorption bandwidth(EAB)can be optimized based on precise manipulation of equivalent electromagnetic parameters.This study not only provides an effective approach for the rational design of MA performance but also offers novel insights into achieving super metamaterials with outstanding performance across a wide temperature spectrum.展开更多
Commercial carbonate electrolytes suffer from ion transport difficulty in bulk electrolytes and interphase at low temperatures,bringing challenges to the application of lithium-ion batteries(LIBs)at low temperatures.H...Commercial carbonate electrolytes suffer from ion transport difficulty in bulk electrolytes and interphase at low temperatures,bringing challenges to the application of lithium-ion batteries(LIBs)at low temperatures.Herein,the ester solvent of methyl propionate(MP)with low melting point and low viscosity was used to tackle ion transport difficulty in electrolytes.Fluorinated ester was further added to accelerate interfacial transport through intermolecular interactions.The influence of fluorinated esters with different fluorination degrees on the solvation structure of electrolytes and the performance of batteries was further studied.As a result,methyl pentafluoropropionate(M5F)with five fluorine atoms was selected for its optimal interactions with both Li+and MP solvent in the primary solvation structure,contributing to desired solvation structure for fast interfacial transport.The LiFePO4(LFP)||graphite cell with LiFSI-MP-M5F electrolyte exhibited a high cyclability of 85.8%after 120 cycles and retained 81.2%of room-temperature capacity when charged and discharged at−30℃.1 Ah LFP||graphite pouch cell with high cathode loading(20 mg/cm^(2))in LiFSI-MP-M5F electrolyte exhibited 0.85 Ah capacity when charged and discharged at−20℃.This work provides a guidance for electrolyte design by synergistic fluorinated and non-fluorinated solvents for LIBs at low-temperature application.展开更多
This article aims to develop a head pursuit （HP） guidance law for three-dimensional hypervelocity interception, so that the effect of the perturbation induced by seeker detection can be reduced. On the basis of a no...This article aims to develop a head pursuit （HP） guidance law for three-dimensional hypervelocity interception, so that the effect of the perturbation induced by seeker detection can be reduced. On the basis of a novel HP three-dimensional guidance model, a nonlinear variable structure guidance law is presented by using Lyapunov stability theory. The guidance law positions the interceptor ahead of the target on its tlight trajectory, and the speed of the interceptor is required to be lower than that of the target, A numerical example of maneuvering ballistic target interception verifies the rightness of the guidance model and the effectiveness of the proposed method.展开更多
Microseismic/acoustic emission(MS/AE)source localization method is crucial for predicting and controlling of potentially dangerous sources of complex structures.However,the locating errors induced by both the irregula...Microseismic/acoustic emission(MS/AE)source localization method is crucial for predicting and controlling of potentially dangerous sources of complex structures.However,the locating errors induced by both the irregular structure and pre-measured velocity are poorly understood in existing methods.To meet the high-accuracy locating requirements in complex three-dimensional hole-containing structures,a velocity-free MS/AE source location method is developed in this paper.It avoids manual repetitive training by using equidistant grid points to search the path,which introduces A*search algorithm and uses grid points to accommodate complex structures with irregular holes.It also takes advantage of the velocity-free source location method.To verify the validity of the proposed method,lead-breaking tests were performed on a cubic concrete test specimen with a size of 10 cm10 cm10 cm.It was cut out into a cylindrical empty space with a size of/6cm10 cm.Based on the arrivals,the classical Geiger method and the proposed method are used to locate lead-breaking sources.Results show that the locating error of the proposed method is 1.20 cm,which is less than 2.02 cm of the Geiger method.Hence,the proposed method can effectively locate sources in the complex three-dimensional structure with holes and achieve higher precision requirements.展开更多
基金The National Key Research and Development Program of China under contract Nos 2016YFC1402608,2016YFC1400904,2016YFC1400900 and 2019YFD0901000。
文摘Mesoscale eddies,which are mainly caused by baroclinic effects in the ocean,are common oceanic phenomena in the Northwest Pacific Ocean and play very important roles in ocean circulation,ocean dynamics and material energy transport.The temperature structure of mesoscale eddies will lead to variations in oceanic baroclinity,which can be reflected in the sea level anomaly(SLA).Deep learning can automatically extract different features of data at multiple levels without human intervention,and find the hidden relations of data.Therefore,combining satellite SLA data with deep learning is a good way to invert the temperature structure inside eddies.This paper proposes a deep learning algorithm,eddy convolution neural network(ECN),which can train the relationship between mesoscale eddy temperature anomalies and sea level anomalies(SLAs),relying on the powerful feature extraction and learning abilities of convolutional neural networks.After obtaining the temperature structure model through ECN,according to climatic temperature data,the temperature structure of mesoscale eddies in the Northwest Pacific is retrieved with a spatial resolution of 0.25°at depths of 0–1000 m.The overall accuracy of the ECN temperature structure is verified using Argo profiles at the locations of cyclonic and anticyclonic eddies during 2015–2016.Taking 10%error as the acceptable threshold of accuracy,89.64%and 87.25%of the cyclonic and anticyclonic eddy temperature structures obtained by ECN met the threshold,respectively.
文摘This study investigates the thermo–mechanical behavior of C40 concrete and reinforced concrete subjected to elevated temperatures up to 700℃by integrating experimental testing and advanced numerical modeling.A temperature-indexed Concrete Damage Plasticity(CDP)framework incorporating bond–slip effects was developed in Abaqus to capture both global stress–strain responses and localized damage evolution.Uniaxial compression tests on thermally exposed cylinders provided residual strength data and failure observations for model calibration and validation.Results demonstrated a distinct two-stage degradation regime:moderate stiffness and strength reduction up to~400℃,followed by sharp deterioration beyond 500℃–600℃,with residual capacity at 700℃reduced to~20%–25%of the ambient value.Strain–damage analyses revealed the formation of a peripheral tensile strain band,which thickened and propagated inward with increasing temperature,governing crack initiation and cover spalling.Supplemental analyses highlighted that transverse reinforcement improved ductility and damage distribution at moderate temperatures(~300℃),but bond deterioration and steel softening beyond~600℃substantially diminished confinement effectiveness.The proposed CDP model accurately reproduced experimental stress–strain curves(R^(2)≈0.94–0.98 up to 600℃;≈0.90 at 700℃),with peak stress errors within 7%–10%and energy absorption captured within~12%.These findings confirm the robustness of the temperature-indexed CDP framework for simulating fire-damaged reinforced concrete and provide practical guidelines for post-fire assessment,spalling detection,and fire-resilient design of structural members.
基金supported by the Tianjin Science and Technology Plan Project(No.22JCQNJC01280)the Central Funds Guiding the Local Science and Technology Development of Hebei Province(Nos.226Z1001G and 226Z1012G)+1 种基金the National Natural Science Foundation of China(No.52002109,52071124)the Young Elite Scientists Sponsorship Program by CAST(No.2022QNRC001).
文摘Developing alloys with exceptional strength-ductility combinations across a broad temperature range is crucial for advanced structural applications.The emerging face-centered cubic medium-entropy alloys(MEAs)demonstrate outstanding mechanical properties at both ambient and cryogenic temperatures.They are anticipated to extend their applicability to elevated temperatures,owing to their inherent advantages in leveraging multiple strengthening and deformation mechanisms.Here,a dual heterostructure,comprising of heterogeneous grain structure with heterogeneous distribution of the micro-scale Nb-rich Laves phases,is introduced in a CrCoNi-based MEA through thermo-mechanical processing.Additionally,a high-density nano-coherentγ’phase is introduced within the grains through isothermal aging treatments.The superior thermal stability of the heterogeneously distributed precipitates enables the dual heterostructure to persist at temperatures up to 1073 K,allowing the MEA to maintain excellent mechanical properties across a wide temperature range.The yield strength of the dual-heterogeneous-structured MEA reaches up to 1.2 GPa,1.1 GPa,0.8 GPa,and 0.6 GPa,coupled with total elongation values of 28.6%,28.4%,12.6%,and 6.1%at 93 K,298 K,873 K,and 1073 K,respectively.The high yield strength primar-ily stems from precipitation strengthening and hetero-deformation-induced strengthening.The high flow stress and low stacking fault energy of the dual-heterogeneous-structured MEA promote the formation of high-density stacking faults and nanotwins during deformation from 93 K to 1073 K,and their density increase with decreasing deformation temperature.This greatly contributes to the enhanced strainhardening capability and ductility across a wide temperature range.This study offers a practical solution for designing dual-heterogeneous-structured MEAs with both high yield strength and large ductility across a wide temperature range.
基金support of the Fundamental Research Funds for the Central Universities(No.E2ET0411X2).
文摘In recent years,research investigations have focused on the substantial freshwater storage in the Beaufort Gyre(BG)region due to climate change.Despite active mesoscale eddies in the area,a notable gap in understanding the three-dimensional structure and induced transport has been observed.This study concentrates on the Canada Basin in the western Arctic Ocean,specifically examining a subsurface anticyclonic eddy(SAE)sampled by a Mooring A in the BG region.Hybrid Coordinate Ocean Model(HYCOM)analysis data reveal its lifecycle from February 15 to March 15,2017,marked by initiation,development,maturity,decay,and termination stages.This work extends the finding of SAE passing through Mooring A by examining its overall effects,spatiotemporal variations,and swirl transport.SAE generation through baroclinic instability,which contributes to the westward tilt of the vertical axis,is also confirmed in this study.Swirl transport induced by SAE is predominantly eastward and downward due to its trajectory and background flow.SAE temporarily weakens stratification and extends the subsurface depth but demonstrates transient effects.Moreover,SAE transports upper-layer freshwater,Pacific Winter Water,and Atlantic Water downward,emphasizing its potential influence on freshwater redistribution in the Canadian Basin.This research provides valuable insights into mesoscale eddy dynamics,revealing their role in modulating the upper water mass in the BG region.
基金supported by the National Natural Science Foundation of China(Grant Nos.42120104001,42192563 and 42005010)the Shanghai Sailing Program(Grant No.23YF1401400).
文摘Using observations and models from phase 6 of the Coupled Model Intercomparison Project(CMIP6),this study analyzes the performance of CMIP6 models in simulating the vertical structure of the Quasi-Biennial Oscillation(QBO)and its impacts on eastern China surface air temperature(SAT),with empirical orthogonal function(EOF)analysis.The first leading mode(EOF1)of the QBO leads to an overall cooling/warming over eastern China via the QBO’s subtropical path and Holton-Tan effect,while the second leading mode(EOF2)of the QBO tends to cause an east-west dipole of SAT anomalies between eastern and western China due to a strong Holton-Tan effect.Most models with a self-generated QBO can capture both westerly and easterly QBO anomalies in the mid-lower stratosphere in EOF1 and only westerly anomalies in EOF2.The multi-model ensemble mean can reproduce the eastern China SAT anomalies that are statistically significant and related to EOF1-like QBO events.However,the intensity of these anomalies is relatively weaker,attributable to the weak Pacific response to the subtropical effect of the QBO.In contrast,most models fail to induce a strong Holton-Tan effect and a Northern Annular Mode pattern in the polar region during the EOF2-like QBO events,resulting in weak and insignificant eastern China SAT anomalies on average.Overall,the models with a better representation of polar and Pacific responses to the QBO’s vertical structure exhibit a more reasonable eastern China SAT response,although such a response is weaker than observed.
基金supported by the National Natu-ral Science Foundation of China(Nos.52107232 and 52377026)China Postdoctoral Science Foundation(No.2021M702563)+2 种基金State Key Laboratory of Electrical Insulation and Power Equipment(No.EIPE22312)Taishan Scholars and Young Experts Program of Shan-dong Province(No.tsqn202103057)the Qingchuang Talents Induction Program of Shandong Higher Education Institution(Research and Innovation Team of Structural-Functional Polymer Composites)and Fundamental Research Funds for the Central Universities(No.xzy012024004).
文摘Polymer dielectrics are required to maintain high energy density at elevated temperatures for advanced power and electronic systems.Herein,we report a novel solution-processed core-shell structured poly-imide(PI)nanocomposite with moderate dielectric constant HfO_(2)core and wide-bandgap Al_(2)O_(3)shell,ef-fectively addressing the typical trade-off between dielectric constant and breakdown strength in dielectric nanocomposites predominant at elevated temperatures.The formation of improved dielectrically match-ing interfaces by the rationally designed dielectric constant gradient from core-shell-matrix remarkably mitigates the distortion of the electric field around the interfaces,resulting in a high breakdown strength.Wide band gap Al_(2)O_(3)shell also introduces deeper traps to impede the conduction loss.The validity of Al_(2)O_(3)shell has been proved via experiments and simulations.Accordingly,HfO_(2)@Al_(2)O_(3)/PI nanocompos-ite exhibits an excellent charge-discharge efficiency of 91.7%at 300 MV/m and a maximum discharged energy density of 2.94 J/cm^(3)at 150℃,demonstrating its potential for high-temperature energy storage.
基金the financial support of National Key Research and Development Program of China(2021YFB2400300)National Natural Science Foundation of China(21875198,21875195)+1 种基金the Fundamental Research Funds for the Central Universities(20720190040)the Key Project of Science and Technology of Xiamen(3502Z20201013)。
文摘Sodium metal batteries(SMBs)are expected to become an alternative solution for energy storage and power systems in the future due to their abundant resources,substantial energy–density,and all-climate performance.However,uneven Na deposition and slow charge transfer kinetics still significantly impair their low temperature and rate performance.Herein,we report a non-solvating trifluoromethoxy benzene(PhOCF_(3))that modulates dipole–dipole interactions in the solvation structure.This modulation effectively reduces the affinity between Na+and solvents,promoting an anion-rich solvation sheath formation and significantly enhancing room temperature electrochemical performance in SMBs.Furthermore,temperature-dependent spectroscopic characterizations and molecular dynamics simulations reveal that these dipole–dipole interactions thermodynamically exclude solvent molecules from inner Na^(+)solvation sphere at low temperatures,which endows the electrolyte with exceptional temperature adaptability,leading to remarkable improvement in low temperature SMB performance.Consequently,Na||Vanadium phosphate sodium(NVP)cells with the optimized electrolyte achieve 10,000 cycles at 10 C with capacity retention of 90.2%at 25℃and over 650 cycles at 0.5 C with a capacity of 92.1 mA h g^(−1)at−40℃.This work probed the temperature-responsive property of Na+solvation structure and designed the temperature-adaptive electrolyte by regulating solvation structure via dipole–dipole interactions,offering a valuable guidance for low temperature electrolytes design for SMBs.
基金jointly supported by the National Key Research and Development Program of China(2022YFC3104304)the National Natural Science Foundation of China(Grant No.41876011)+1 种基金the 2022 Research Program of Sanya Yazhou Bay Science and Technology City(SKJC-2022-01-001)the Hainan Province Science and Technology Special Fund(ZDYF2021SHFZ265)。
文摘Three-dimensional ocean subsurface temperature and salinity structures(OST/OSS)in the South China Sea(SCS)play crucial roles in oceanic climate research and disaster mitigation.Traditionally,real-time OST and OSS are mainly obtained through in-situ ocean observations and simulation by ocean circulation models,which are usually challenging and costly.Recently,dynamical,statistical,or machine learning models have been proposed to invert the OST/OSS from sea surface information;however,these models mainly focused on the inversion of monthly OST and OSS.To address this issue,we apply clustering algorithms and employ a stacking strategy to ensemble three models(XGBoost,Random Forest,and LightGBM)to invert the real-time OST/OSS based on satellite-derived data and the Argo dataset.Subsequently,a fusion of temperature and salinity is employed to reconstruct OST and OSS.In the validation dataset,the depth-averaged Correlation(Corr)of the estimated OST(OSS)is 0.919(0.83),and the average Root-Mean-Square Error(RMSE)is0.639°C(0.087 psu),with a depth-averaged coefficient of determination(R~2)of 0.84(0.68).Notably,at the thermocline where the base models exhibit their maximum error,the stacking-based fusion model exhibited significant performance enhancement,with a maximum enhancement in OST and OSS inversion exceeding 10%.We further found that the estimated OST and OSS exhibit good agreement with the HYbrid Coordinate Ocean Model(HYCOM)data and BOA_Argo dataset during the passage of a mesoscale eddy.This study shows that the proposed model can effectively invert the real-time OST and OSS,potentially enhancing the understanding of multi-scale oceanic processes in the SCS.
基金supported by National Key Research&Development Program of China[grant number 2022YFE0110600]National Natural Science Foundation[grant number 52220105003]the State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology[grant number XNDCQQ2910201124].
文摘Magnesium(Mg)alloys typically suffer from cold brittleness at cryogenic temperatures(CT),where strength significantly increases and ductility decreases with decreasing temperature.This study investigates the improvement of the strength-ductility balance at CT in Mg-3.6Y(wt.%)alloys with a bimodal grain structure,consisting of fine dynamically recrystallized(DRXed)grains and elongated unDRXed grains.The results demonstrate that the sample with∼50%DRXed region fraction achieves a remarkable strength-ductility synergy at CT.Dislocation strengthening in the unDRXed regions and grain boundary strengthening in the DRXed regions increase the tensile yield strength(TYS)by 1.6 times at CT compared to room temperature(RT).Concurrently,activation of{10¯12}tensile twinning and non-basal slip systems in DRXed regions,including prismatic a and pyramidal I c+a slips,along with abnormal pyramidal slip within unDRXed grains,reduces fracture elongation by only 1%relative to RT.Furthermore,the bimodal grain structure effectively alleviates strain localization through strain partitioning between DRXed and unDRXed grains,leading to the formation of interface-affected zones(IAZs)that promote the accumulation of geometrically necessary dislocations(GNDs)and enhance hetero-deformation-induced(HDI)hardening.At CT,the IAZs become wider and more pronounced,indicating enhanced GND accumulation that promotes stronger strain partitioning and more effective HDI strengthening.This work demonstrates that the bimodal grain structure is an effective approach to overcoming the low-temperature brittleness of Mg alloys,providing valuable insights for the design of high-performance materials for cryogenic applications.
基金support from the National Key Research and Development Program of China(Grant No.2021YFB3501402)the National Natural Science Foundation of China(Grant Nos.52250313 and 52121001)Yang Liu and Chen Si acknowledge financial support from the National Natural Science Foundation of China(Grant No.12274013).
文摘Significant two-way shape memory effect(TWSME)was achieved in single crystals of single-phase multielement Ni42-x Cu8 Cox Mn37 Ga13(8≤x≤12)alloys by performing thermomechanical training.However,anomalous dependence of the martensitic transformation temperature span on Co content was observed.Before training,quite a narrow temperature span of the martensitic transformation,nearly independent of the Co content,was observed in all single crystals.After training the temperature span was still narrow for 8≤x≤10.9 but was obviously expanded for 10.9<x≤12.High-resolution transmission electron microscopy revealed that at the atomic scale,there exists incommensurate modulated structure in the single phase single crystals,as evidenced by nonperiodic satellite spots in the selected area electronic diffraction patterns.Moreover,the modulated wave vector of the satellite spots was increased by higher Co contents.Combining first principal calculations it was considered that the incommensurate modulated structure originates from the formation of Co-Co pairs.After training arrays of ordered dislocations with the same Burgers vector were introduced for 8≤x≤10.9 but the network of dislocations was formed for 10.9<x≤12.Based on analysis of transmission electron microscopy,geometric phase,thermodynamics,and Landau theory,it was considered that the austenite/martensite phase interface was pinned by the network of dislocations,expanding the temperature span of the martensitic transformation.This work supplies new insights for understanding the microstructure and martensitic transformation of Ni-Mn-Ga-based alloys.
基金supported by the Project of the National Key Research and Development Program of China under Grant 2022YFB2404100。
文摘The internal hotspot temperature rise prediction in nanocrystalline high-frequency transformers(nanoHFTs) is essential to ensure reliable operation. This paper presents a three-dimensional thermal network(3DTN) model for epoxy resin encapsulated nano HFTs, which aims to precisely predict the temperature distribution inside the transformer in combination with the finite element method(FEM). A magnetothermal bidirectional coupling 3DTN model is established by analyzing the thermal conduction between the core, windings, and epoxy resin, while also considering the convection and radiation heat transfer mechanisms on the surface of the epoxy resin. The model considers the impact of loss distribution in the core and windings on the temperature field and adopts a simplified 1/2 thermal network model to reduce computational complexity. Furthermore, the results of FEM are compared with experimental results to verify the accuracy of the 3DTN model in predicting the temperature rise of nano HFT. The results show that the 3DTN model reduces errors by an average of 5.25% over the traditional two-dimensional thermal network(2DTN) model, particularly for temperature distributions in the windings and core. This paper provides a temperature rise prediction method for the thermal design and offers a theoretical basis and engineering guidance for the optimization of their thermal management systems.
基金support from National Outstanding Youth Science Fund(52222314)Near Space Technology and Industry Guidance Fund Project(LKJJ-2023010-01)+3 种基金CNPC Innovation Found(2021DQ02-1001)Dalian Outstanding Youth Science and Technology Talent Project(2023RJ006)Dalian Science and Technology Innovation Project(2022JJ12GX022)Xinghai Talent Cultivation Plan(X20200303).
文摘Sodium-ion hybrid capacitors(SICs),which combine the high energy density of batteries with the high power density and long cycle life of capacitors,are considered promising next-generation energy storage devices.Ensuring the performance of SICs in low-temperature environments is crucial for applications in high-altitude cold regions,where the desolvation process of Na+and the transport process in the solid electrolyte interphase(SEI)are determinant.In this paper,we proposed a multi-ether modulation strategy to construct a solvation sheath with multi-ether participation by modulating the coordination of Na+and solvents.This unique solvation sheath not only reduces the desolvation energy barrier of Na+,but more importantly forms a Na_(2)O-rich inorganic SEI and enhances the ionic dynamics of Na+.Benefiting from the excellent solvation structure design,SICs prepared with this electrolyte can achieve energy density of up to 178 Wh·kg^(-1) and ultra-high power density of 42390 W·kg^(-1) at room temperature.Notably,this SIC delivers record-high energy densities of 149 Wh·kg^(-1) and 119 Wh·kg^(-1) as well as power densities of up to 25200 W·kg^(-1) and 24591 W·kg^(-1) at−20℃ and−40℃,respectively.This work provides new ideas for the development of high-performance SICs for low-temperature operating environments.
基金supported by the Scientific Research Program Funded by Shaanxi Provincial Education Department (No.15JK1573)the Postgraduate Innovation and Practice Ability Development Fund of Xi’an Shiyou University (No.YCS21211084)。
文摘We proposed a fiber optic high temperature sensor based on the Mach-Zehnder interference(MZI)structure,which is composed of two lengths of multi-mode fibers(MMFs),a length of few-mode fiber(FMF)and two sections of single-mode fibers(SMFs).Firstly,the two sections of MMFs were spliced with two sections of SMFs.Then,the MMFs were fused to two ends of FMF to form a symmetrically structured fiber-optic MZI structure.In this structure,the MMF served as the optical mode field coupling element,and the cladding and core of the FMF are the interference arm and the reference arm of the MZI structure,respectively.We investigated the sensor's response characteristics of the temperature and strain.The experimental results indicate that the sensor is sensitive to temperature variation,and the temperature response sensitivity is up to 61.4 pm/℃ in the range of 40-250℃,while the sensor has weak strain sensitivity,its strain sensitivity is only-0.72 pm/μe in the strain range of 0-1400μe.Moreover,the sensor has good stability and repeatability.In brief,the proposed fiber optic high temperature sensor has good properties,such as high sensitivity,compact structure,good stability and repeatability,which can be used for monitoring the temperature of submerged oil electric pump units under oil wells.
文摘We study the influences of the temperature on the energy-band structure for the Holstein molecular-crystal model. We show that the energy-band width and the energy-gap width of a solid are relevant to both the interaction between an electron and thermal phonons and to thermal expansion. For a one-dimensional Li atom lattice chain, under the chosen parameters,the width of the ls and 2s energy bands narrows as the temperature increases and the energy-gap width between the two bands widens. These results agree qualitatively with those observed experimentally. Studying temperature dependence of the energy-band structure is of great importance for understanding optical and transporting characteristics of a solid.
基金Supported by the Aeronautical Science Foundation of China(2008ZA52012)the Six Kinds of Excellent Talent Project in Jiangsu Province of China(2010JZ004)the Research Foundation of Nanjing University of Aeronautics and Astronautics(NS2010027)~~
文摘A two-step method is proposed for detection and identification of invisible impact damage in composite structure under temperature changes using Lamb waves.First,a statistical outlier analysis is employed to distinguish whether the changes of Lamb wave signals are induced by damage within a monitoring area or are only affected by temperature changes.Damage indices are defined after the Lamb wave signals are processed by Fourier transform,and a Monte Carlo procedure is used to obtain the damage threshold value for the damage indices at the undamaged state.If the damage indices in the operation state exceed the threshold value,the presence of damage is determined.Then,a probabilistic damage imaging algorithm displaying probabilities of the presence of damage within the monitoring area is adopted to fuse information collected from multiple actuator-sensor paths to identify the location of damage.Damage indices under damaged state are used to generate the diagnostic image.Experimental study on a stiffened composite panel with random temperature changes is performed to demonstrate the effectiveness of the proposed method.
基金supported by the National Natural Science Foundation of China (51320105001, 51372190, 21573170, 51272199, 21433007)the National Basic Research Program of China (973 program, 2013CB632402)+2 种基金the Natural Science Foundation of Hubei Province (2015CFA001)the Fundamental Research Funds for the Central Universities (WUT: 2015-Ⅲ-034)Innovative Research Funds of SKLWUT (2015-ZD-1)~~
文摘Flower-like tin oxide-supported platinum（Pt/SnOx） with a hierarchical structure was synthesized by a hydrothermal method and characterized by XRD,SEM,TEM,high resolution TEM,XPS and nitrogen adsorption.The flower-like Pt/SnOx microspheres of 1 μm in diameter were composed of staggered petal-like nanosheets with a thickness of 20 nm.Pt nanoparticles（NPs） of 2-3 nm were well dispersed on the SnOx nanosheets.The catalyst was tested in the catalytic oxidation of gaseous formaldehyde（HCHO） at room temperature,and exhibited enhanced activity compared to Pt NPs supported on commercial SnO and ground SnOx.HCHO removal of 87%was achieved over the hierarchical Pt/SnOx after 1 h of reaction,which was 1.5 times that over the ground SnOx-supported Pt（Pt/g-SnOx）,and the high activity was maintained after six recycles,showing the high stability of this catalyst.HCHO decomposition kinetics was modeled as a second order reaction.The reaction rate constant for Pt/SnOx was 5.6 times higher than Pt/g-SnOx.The hierarchical pore structure was beneficial for the diffusion and adsorption of HCHO molecules,and the highly dispersed Pt NPs on the SnOx nanosheets were the active sites for the oxidative decomposition of HCHO into CO2 and H2O.This study provided a promising approach for designing efficient catalysts for indoor HCHO removal at ambient temperature.
基金supported by the National Nature Science Foundation of China(Nos.22305066 and 52372041).
文摘High-temperature microwave absorbing materials(MAMs)and structures are increasingly appealing due to their critical role in stealth applications under harsh environments.However,the impedance mismatch caused by increased conduction loss often leads to a significant decline in electromagnetic wave absorp-tion(EMWA)performance at elevated temperatures,which severely restricts their practical application.In this study,we propose a novel approach for efficient electromagnetic wave absorption across a wide temperature range using reduced graphene oxide(RGO)/epoxy resin(EP)metacomposites that integrate both electromagnetic parameters and metamaterial design concepts.Due to the discrete distribution of the units,electromagnetic waves can more easily penetrate the interior of materials,thereby exhibiting stable microwave absorption(MA)performance and impedance-matching characteristics suitable across a wide temperature range.Consequently,exceptional MA properties can be achieved within the tem-perature range from 298 to 473 K.Furthermore,by carefully controlling the structural parameters in RGO metacomposites,both the resonant frequency and effective absorption bandwidth(EAB)can be optimized based on precise manipulation of equivalent electromagnetic parameters.This study not only provides an effective approach for the rational design of MA performance but also offers novel insights into achieving super metamaterials with outstanding performance across a wide temperature spectrum.
基金supported by the National Key R&D Program of China(No.2022YFB3803400)National Natural Science Foundation of China(Nos.52102054,52020105010,51927803,52188101 and 52072378)+1 种基金Liaoning Province Science and Technology Planning Project(No.2022-BS-007)Fujian Science and Technology Program(No.2023T3025).
文摘Commercial carbonate electrolytes suffer from ion transport difficulty in bulk electrolytes and interphase at low temperatures,bringing challenges to the application of lithium-ion batteries(LIBs)at low temperatures.Herein,the ester solvent of methyl propionate(MP)with low melting point and low viscosity was used to tackle ion transport difficulty in electrolytes.Fluorinated ester was further added to accelerate interfacial transport through intermolecular interactions.The influence of fluorinated esters with different fluorination degrees on the solvation structure of electrolytes and the performance of batteries was further studied.As a result,methyl pentafluoropropionate(M5F)with five fluorine atoms was selected for its optimal interactions with both Li+and MP solvent in the primary solvation structure,contributing to desired solvation structure for fast interfacial transport.The LiFePO4(LFP)||graphite cell with LiFSI-MP-M5F electrolyte exhibited a high cyclability of 85.8%after 120 cycles and retained 81.2%of room-temperature capacity when charged and discharged at−30℃.1 Ah LFP||graphite pouch cell with high cathode loading(20 mg/cm^(2))in LiFSI-MP-M5F electrolyte exhibited 0.85 Ah capacity when charged and discharged at−20℃.This work provides a guidance for electrolyte design by synergistic fluorinated and non-fluorinated solvents for LIBs at low-temperature application.
文摘This article aims to develop a head pursuit （HP） guidance law for three-dimensional hypervelocity interception, so that the effect of the perturbation induced by seeker detection can be reduced. On the basis of a novel HP three-dimensional guidance model, a nonlinear variable structure guidance law is presented by using Lyapunov stability theory. The guidance law positions the interceptor ahead of the target on its tlight trajectory, and the speed of the interceptor is required to be lower than that of the target, A numerical example of maneuvering ballistic target interception verifies the rightness of the guidance model and the effectiveness of the proposed method.
基金The authors wish to acknowledge financial support from the National Natural Science Foundation of China(51822407 and 51774327)Natural Science Foundation of Hunan Province in China(2018JJ1037)Innovation Driven project of Central South University(2020CX014).
文摘Microseismic/acoustic emission(MS/AE)source localization method is crucial for predicting and controlling of potentially dangerous sources of complex structures.However,the locating errors induced by both the irregular structure and pre-measured velocity are poorly understood in existing methods.To meet the high-accuracy locating requirements in complex three-dimensional hole-containing structures,a velocity-free MS/AE source location method is developed in this paper.It avoids manual repetitive training by using equidistant grid points to search the path,which introduces A*search algorithm and uses grid points to accommodate complex structures with irregular holes.It also takes advantage of the velocity-free source location method.To verify the validity of the proposed method,lead-breaking tests were performed on a cubic concrete test specimen with a size of 10 cm10 cm10 cm.It was cut out into a cylindrical empty space with a size of/6cm10 cm.Based on the arrivals,the classical Geiger method and the proposed method are used to locate lead-breaking sources.Results show that the locating error of the proposed method is 1.20 cm,which is less than 2.02 cm of the Geiger method.Hence,the proposed method can effectively locate sources in the complex three-dimensional structure with holes and achieve higher precision requirements.
