The adsorptive denitrification performance of MIL-101(Cr)-0.5 toward pyridine,aniline or quinoline in simulated fuels with basic nitrogen content of 1732μg/g was evaluated separately.Furthermore,the effects of adsorp...The adsorptive denitrification performance of MIL-101(Cr)-0.5 toward pyridine,aniline or quinoline in simulated fuels with basic nitrogen content of 1732μg/g was evaluated separately.Furthermore,the effects of adsorption temperature,adsorption time and adsorbent dosage on their adsorptive denitrification performance were systematically investigated.The experimental results demonstrated that under a fixed adsorbent dosage of 0.05 g and a simulated fuel volume of 10 mL,the optimal removal efficiency for aniline was achieved at 30℃ within 30 min,whereas higher temperatures and longer times(40℃and 40 min)were required for effective removal of pyridine and quinoline.Density Functional Theory(DFT)calculations were conducted via Materials Studio(MS)software to study the adsorptive denitrification mechanism of MIL-101(Cr)toward these three basic nitrogen-containing compounds.The simulation calculation results revealed that the interaction between pyridine and MIL-101(Cr)primarily involved coordination adsorption.In contrast,the interaction between aniline or quinoline and MIL-101(Cr)proceeded mainly through coordination,with additional contributions fromπ-complexation and hydrogen bonding.The overall adsorption strength order is pyridine>aniline>quinoline.During the adsorption process,pyridine and quinoline transfer electrons to the MIL-101(Cr)surface through the H→C→N→Cr^(3+)pathway,while aniline transfers electrons to the MIL-101(Cr)surface through various pathways,including N→Cr^(3+),N→C→Cr^(3+)and N→H→O.Furthermore,adsorption kinetics studies indicated that the adsorption processes for all three basic nitrogen-containing compounds followed the quasi second order kinetic models.The experimental results on the effect of benzene on the adsorptive denitrification performance of MIL-101(Cr)-0.5 demonstrated that benzene exerted a more significant impact on the adsorption of aniline and quinoline.Finally,the adsorbent was regenerated using ethanol washing.It was found that MIL-101(Cr)-0.5 retained stable denitrification performance after two regeneration cycles.展开更多
To elucidate the effect of calcite-regulated activated carbon(AC)structure on low-temperature denitrification performance of SCR catalysts,this work prepared a series of Mn-Ce/De-AC-xCaCO_(3)(x is the calcite content ...To elucidate the effect of calcite-regulated activated carbon(AC)structure on low-temperature denitrification performance of SCR catalysts,this work prepared a series of Mn-Ce/De-AC-xCaCO_(3)(x is the calcite content in coal)catalysts were prepared by the incipient wetness impregnation method,followed by acid washing to remove calcium-containing minerals.Comprehensive characterization and low-temperature denitrification tests revealed that calcite-induced structural modulation of coal-derived AC significantly enhances catalytic activity.Specifically,NO conversion increased from 88.3%of Mn-Ce/De-AC to 91.7%of Mn-Ce/De-AC-1CaCO_(3)(210℃).The improved SCR denitrification activity results from the enhancement of physicochemical properties including higher Mn^(4+)content and Ce^(4+)/Ce^(3+)ratio,an abundance of chemisorbed oxygen and acidic sites,which could strengthen the SCR reaction pathways(richer NH_(3)activated species and bidentate nitrate active species).Therefore,NO removal is enhanced.展开更多
The rapid advancements in computer vision(CV)technology have transformed the traditional approaches to material microstructure analysis.This review outlines the history of CV and explores the applications of deep-lear...The rapid advancements in computer vision(CV)technology have transformed the traditional approaches to material microstructure analysis.This review outlines the history of CV and explores the applications of deep-learning(DL)-driven CV in four key areas of materials science:microstructure-based performance prediction,microstructure information generation,microstructure defect detection,and crystal structure-based property prediction.The CV has significantly reduced the cost of traditional experimental methods used in material performance prediction.Moreover,recent progress made in generating microstructure images and detecting microstructural defects using CV has led to increased efficiency and reliability in material performance assessments.The DL-driven CV models can accelerate the design of new materials with optimized performance by integrating predictions based on both crystal and microstructural data,thereby allowing for the discovery and innovation of next-generation materials.Finally,the review provides insights into the rapid interdisciplinary developments in the field of materials science and future prospects.展开更多
Purpose: Normobaric hypoxia(NH) is a frequent strategy for training under hypoxic conditions that can be administered through different equipment, including face masks or hypoxic chambers/tents. Nonetheless, the versa...Purpose: Normobaric hypoxia(NH) is a frequent strategy for training under hypoxic conditions that can be administered through different equipment, including face masks or hypoxic chambers/tents. Nonetheless, the versatility of administration methods may influence the outcomes.Methods: Web of Science, Scopus, SPORTDiscus and Pub Med/MEDLINE were searched to identify studies assessing the effect of NH administered by face mask or chamber/tent equipment on maximal oxygen uptake( VO2max) after a training period. An overall meta-analysis and sub-analysis of total program session volume(low, moderate, high), participants' training level(trained, active, sedentary), and the severity of hypoxia(moderate, severe) were conducted to explore the effects of the NH-administration system.Results: Eighteen studies were included. Compared with normoxia, NH showed a moderate global improvement in VO2max(standardized mean difference [SMD] = 0.74;p = 0.06), favoring the chamber/tent(SMD = 1.30;p< 0.01) over the face mask. Sub-analysis showed a very large effect in support of the hypoxic chamber/tent among sedentary individuals and training programs with a high volume of sessions. Severe hypoxia did not yield conclusive findings in VO2max improvements, although the chamber/tent proved more effective(SMD = 1.42;p< 0.01) than the face mask under moderate hypoxia.Conclusions: Chambers/tents may slightly accentuate the benefit of NH on aerobic performance, particularly in participants with limited training experience following a high volume of sessions under moderate hypoxia.However, the variability of sub-analysis factors(session volume, participants' training level, and methodological approaches) between studies using each type of hypoxia-generating equipment may influence this result.展开更多
Al/NH_(4)CoF_(3)-Φ(Φ=0.5,1.0,1.5,2.0,and 3.0)binary composites and Al-NH_(4)CoF_(3)@P(VDF-HFP)ternary composites are fabricated via ultrasonication-assisted blending and electrostatic spraying.The effect of equivale...Al/NH_(4)CoF_(3)-Φ(Φ=0.5,1.0,1.5,2.0,and 3.0)binary composites and Al-NH_(4)CoF_(3)@P(VDF-HFP)ternary composites are fabricated via ultrasonication-assisted blending and electrostatic spraying.The effect of equivalence ratio(Φ)on the reaction properties is systematically investigated in the binary Al/NH_(4)CoF_(3)system.For ternary systems,electrostatic spraying allows both components to be efficiently encapsulated by P(VDF-HFP)and to achieve structural stabilization and enhanced reactivity through synergistic interfacial interactions.Morphological analysis using SEM/TEM revealed that P(VDF-HFP)formed a protective layer on Al and NH_(4)CoF_(3)particles,improving dispersion,hydrophobicity(water contact angle increased by 80.5%compared to physically mixed composites),and corrosion resistance.Thermal decomposition of NH_(4)CoF_(3)occurred at 265℃,releasing NH_(3)and HF,which triggered exothermic reactions with Al.The ternary composites exhibited a narrowed main reaction temperature range and concentrated heat release,attributed to improved interfacial contact and polymer decomposition.Combustion tests demonstrated that Al-NH_(4)CoF_(3)@P(VDF-HFP)achieved self-sustaining combustion.In addition,a simple validation was done by replacing the Al component in the aluminium-containing propellant,demonstrating its potential application in the propellant field.This work establishes a novel strategy for designing stable,high-energy composites with potential applications in advanced propulsion systems.展开更多
Isolation technology can reduce the type of structural damage that earthquakes cause.A new type of composite sliding-rolling friction composite seismic isolation bearing(SRF)with composite sliding friction and rolling...Isolation technology can reduce the type of structural damage that earthquakes cause.A new type of composite sliding-rolling friction composite seismic isolation bearing(SRF)with composite sliding friction and rolling friction is proposed.SRF is capable of realizing a parallel arrangement of sliding friction and rolling friction,and the coefficient of dynamic friction shows variability.The proposed static tests on composite bearings were conducted to investigate the effects of the number of shims,loading speed and vertical pressure on the dynamic friction factor.Test results show that the coefficient of dynamic friction first generally decreases and then increases with an increase in sliding speed,prior to again decreasing with an increase in vertical pressure.The dynamic friction factor increases and then decreases with an increase in the number of shims for a four-roll ball.It decreases and then increases with an increase in the number of shims for a five-roll ball.Based on finite element analysis,modeling and analyzing the effects of the coefficient of friction,the number of balls and the number of shims on the hysteresis performance of the support and derive its skeleton curve.The SRF hysteretic performance,dynamic friction factor and the number of rolling balls and shims show significant correlation.展开更多
The core components of an aircraft and the source of its lift are its wings,but lift generation is disrupted by the high temperature and pressure generated on the wing surface when an aircraft gun is fired.Here,to inv...The core components of an aircraft and the source of its lift are its wings,but lift generation is disrupted by the high temperature and pressure generated on the wing surface when an aircraft gun is fired.Here,to investigate how this process influences the aerodynamic parameters of aircraft wings,the k-ωshearstress-transport turbulence model and the nested dynamic grid technique are used to analyze numerically the transient process of the muzzle jet of a 30-mm small-caliber aircraft gun in highaltitude(10 km)flight with an incoming Mach number of Ma=0.8.For comparison,two other models are established,one with no projectile and the other with no wing.The results indicate that when the aircraft gun is fired,the muzzle jet acts on the wing,creating a pressure field thereon.The uneven distribution of high pressure greatly reduces the lift of the aircraft,causing oscillations in its drag and disrupting its dynamic balance,thereby affecting its flight speed and attitude.Meanwhile,the muzzle jet is obstructed by the wing,and its flow field is distorted and deformed,developing upward toward the wing.Because of the influence of the incoming flow,the shockwave front of the projectile changes from a smooth spherical shape to an irregular one,and the motion parameters of the projectile are also greatly affected by oscillations.The present results provide an important theoretical basis for how the guns of fighter aircraft influence the aerodynamic performance of the wings.展开更多
Under earthquake action, different site conditions have a notable impact on the dynamic response of high-speed railway bridges after earthquakes, which in turn poses a threat to the running stability of trains in the ...Under earthquake action, different site conditions have a notable impact on the dynamic response of high-speed railway bridges after earthquakes, which in turn poses a threat to the running stability of trains in the post-earthquake period. Therefore, establishing a calculation method for the post-earthquake train speed threshold that considers the influence of different site characteristics is of great engineering significance. Taking the CRTS Ⅲ slab track as the research object, this study is based on the track irregularity root mean square rate(TRR), which the authors proposed earlier to quantify the track regularity level. Using the nonlinear least squares fitting method, the mapping relationship between the TRR and the postearthquake train running performance indicators on bridges is established. Furthermore, the influence of laws governing site categories and train speeds on post-earthquake train running performance on bridges is analyzed, and a train speed threshold for bridges based on running performance under random site conditions is proposed. The research results indicate that all train running performance indicators increase significantly with the increase of train operating speed;different site categories have a significant impact on post-earthquake track residual deformation and train running stability. The greater the amplitude of postearthquake track alignment residual deformation, the lower the threshold for the stable running speed of trains after the earthquake, with the speed threshold decreasing by up to 20%. The research outcomes can provide technical references for the post-earthquake safe operation and maintenance of high-speed railway bridges under complex site conditions, as well as the formulation of targeted train speed control schemes.展开更多
The low-pressure and low-density conditions encountered at high altitudes significantly reduce the operating Reynolds number of micro radial-flow turbines,frequently bringing it below the self-similarity critical thre...The low-pressure and low-density conditions encountered at high altitudes significantly reduce the operating Reynolds number of micro radial-flow turbines,frequently bringing it below the self-similarity critical threshold of 3.5×10^(4).This departure undermines the applicability of conventional similarity-based design approaches.In this study,micro radial-flow turbines with rotor diameters below 50 mm are investigated through a combined approach integrating high-fidelity numerical simulations with experimental validation,aiming to elucidate the mechanisms by which low Reynolds numbers influence aerodynamic and thermodynamic performance.The results demonstrate that decreasing Reynolds number leads to boundary-layer thickening on blade surfaces,enhanced flow separation on the suction side,and increased secondary-flow losses within the blade passages.These effects jointly produce a pronounced and non-linear deterioration of turbine efficiency.Geometric scaling analysis further indicates that efficiency losses intensify with decreasing turbine size,and become particularly severe at low rotational speeds and high expansion ratios.Detailed flow-field analyses reveal a direct link between the degradation of blade loading distribution and the amplification of transverse pressure gradients under low-Reynolds-number conditions,providing physical insight into the observed performance decline.展开更多
The negative Poisson’s ratio(NPR)bolt is an innovative support element distinguished by its high strength,elongation,and a slightly negative Poisson’s ratio.Unlike conventional prestressed(PR)bolts with a positive P...The negative Poisson’s ratio(NPR)bolt is an innovative support element distinguished by its high strength,elongation,and a slightly negative Poisson’s ratio.Unlike conventional prestressed(PR)bolts with a positive Poisson’s ratio,the NPR bolt exhibits a quasi-ideal plastic response without a prominent yield platform,enabling it to sustain high prestress with a substantial safety margin,which is particularly advantageous for jointed rock masses.However,investigations into the shear resistance mechanisms of NPR bolts under varying prestress levels remain limited.This study conducted full-scale double shear tests to assess the shear strength,deformation behavior,energy absorption,and failure mechanisms of NPR bolts under different prestress conditions.To ensure a fair comparison with PR bolts,a prestress utilization coefficient(PUC)was introduced.The results reveal that at a PUC of 0.25,the NPR bolt achieved peak axial force,shear displacement,and peak shear force values that are 2.41,1.88,and 2.13 times greater than those of the PR bolt,respectively.Shear performance was optimized at a prestress level of 100 kN,with energy absorption reaching 47.1 kJ,which is 2.8 times that of the PR bolt.Furthermore,the necking ratio was significantly reduced,indicating more distributed plastic deformation and delayed failure.Field applications verified the superior performance,resulting in a 27.4%reduction in roof settlement and enhanced structural integrity.These findings confirm that NPR bolts possess excellent shear resistance,energy absorption,and deformation adaptability,and optimizing prestress significantly enhances their support performance,providing a strong basis for geotechnical engineering applications.展开更多
Lithium-sulfur(Li-S)batteries boast a theoretical energy density as high as 2600 Wh·kg^(−1),positioning them as a highly attractive option for future advanced energy storage systems.Challenges such as slow transf...Lithium-sulfur(Li-S)batteries boast a theoretical energy density as high as 2600 Wh·kg^(−1),positioning them as a highly attractive option for future advanced energy storage systems.Challenges such as slow transformation kinetics and shuttle effects associated with lithium polysulfides(LiPSs)have seriously hindered their practical applications.In this paper,we present a new method for the synthesis of hollow carbon-sphere-supported Co monatomic catalysts(Co-N-C).This new synthesis method achieves pyrolytic coordination using a precursor rich in imide(-RC=N-)polymers.This synthesis method not only improves the adsorbability and catalytic activity of LiPS but also significantly weakens the shuttle effect and generates Co-N-C with superior conductivity,abundant hollow structures,and a high specific surface area,thus efficiently capturing and restricting the movement of LiPS intermediates.The dispersed Co monoatomic catalysts(Co SACs)were anchored to a highly conductive nitrogen-doped carbon framework and exhibited symmetric N-coordination active sites(Co-N_(4))to ensure fast redox kinetics of LiPS and Li_(2)S_(2)/Li_(2)S solid-state products.The lithium-sulfur battery with Co-N-C as the sulfur carrier showed excellent discharging capacity of 1146.6 mAh·g^(−1) at a discharge rate of 0.5 C and maintained excellent performance at a high discharge rate of 2 C.The capacity decay rate in 500 cycles was only 0.086%per cycle,reflecting excellent long-term cycle stability.This study highlights the key role of the synergistic effect between single-atom cobalt catalysts and hollow carbon spheres in enhancing the efficiency of lithium-sulfur(Li-S)batteries.It also provides valuable insights into the construction and fabrication of highly active monatomic catalysts.The catalytic conversion efficiency of lithium polysulfides is significantly enhanced when embedded in hollow carbon architectures,which serves as a critical strategy for optimizing the electrochemical behavior of next-generation Li-S batteries.展开更多
The presence of a surface oxide film(B_(2)O_(3))on boron(B)particles significantly compromises their combustion efficiency and kinetic performance in fuel-rich solid propellants.This study proposes an innovative conti...The presence of a surface oxide film(B_(2)O_(3))on boron(B)particles significantly compromises their combustion efficiency and kinetic performance in fuel-rich solid propellants.This study proposes an innovative continuous modification strategy combining non-thermal plasma(NTP)etching with fluorocarbon passivation.Characterization and kinetic analysis revealed that reactive plasma species—including atomic hydrogen(H),electronically excited molecular hydrogen(H_(2)^(*)),vibrationally excited molecular hydrogen(H_(2)v),and hydrogen ions(H^(+))—dominate the reduction of B_(2)O_(3)through lowering the transition energy barrier and shifting the reaction spontaneity.Subsequent argon plasma fragmentation of C_(8)F_(18)generates fluorocarbon radicals that form conformal passivation coatings(thickness:7 nm)on purified boron surfaces.The modified boron particles exhibit 37.5℃lower exothermic peak temperature and 27.2%higher heat release(14.8 kJ/g vs.11.6 kJ/g)compared to untreated counterparts.Combustion diagnostics reveal 194%increase in maximum flame height(135.10 mm vs.46.03 mm)and 134%enhancement in flame propagation rate(4.44 cm/s vs.1.90 cm/s).This NTP-based surface engineering approach establishes a scalable pathway for developing highperformance boron-based energetic composites.展开更多
Porous ionic liquid electrospray thrusters are the ideal propulsion technology for CubeSats because of their structural simplicity,high thrust accuracy and plume self-neutralization.The electrowetting technology can r...Porous ionic liquid electrospray thrusters are the ideal propulsion technology for CubeSats because of their structural simplicity,high thrust accuracy and plume self-neutralization.The electrowetting technology can replenish the propellant for the emitter online,thus prolonging the lifetime of the thruster.In order to gain a deeper understanding of its operating characteristics,the changes in thruster performance before and after propellant replenishment deserve to be scrutinized.In this study,the performance changes of a porous electrowetting ionic liquid electrospray thruster are tested by voltage-current test and time-of-flight mass spectrometry over a long operating time.The experimental results show that asymmetric operation with a negative current less than positive current for a long period of time causes anions to compensate for the emission after accumulation at the emitter,resulting in a phenomenon that the negative current is much larger than positive current.The reason for the difference in emission characteristics between the positive and negative modes is that the plume in the positive mode is quite ionized while the plume in the negative mode contains liquid droplets.This study provides a reference for the selection of operating conditions for ionic liquid electrospray thrusters.展开更多
This work examines the microstructure and corrosion properties of fine-grained Al 7075 across different regions under varying cooling conditions during friction stir welding.The findings demonstrate that forced coolin...This work examines the microstructure and corrosion properties of fine-grained Al 7075 across different regions under varying cooling conditions during friction stir welding.The findings demonstrate that forced cooling significantly improves the corrosion resistance of the welded joints.Specifically,the corrosion resistance was the highest in the stir zone,followed by the thermo-mechanical affected zone,and then the heat affected zone.Forced cooling mitigates grain growth by controlling the welding thermal effects,thereby increasing the proportion ofΣ3 grain boundaries.The modification of these microstructural characteristics promotes the formation of a dense oxide layer,thereby enhancing the corrosion resistance.Furthermore,forced cooling mitigates the precipitation and coarsening of the anodic phase in the stir zone,which in turn reduces the susceptibility of the joint to pitting corrosion.Additionally,the lower recrystallization texture content in the joint,resulting from forced cooling,contributes to a reduction in the number of corrosion-active sites,thereby further improving the corrosion performance of the welded joint.展开更多
Electrical and electronic devices face significant challenges in heatmanagement due to their compact size and high heat flux,which negatively impact performance and reliability.Conventional coolingmethods,such as forc...Electrical and electronic devices face significant challenges in heatmanagement due to their compact size and high heat flux,which negatively impact performance and reliability.Conventional coolingmethods,such as forced air cooling,often struggle to transfer heat efficiently.In contrast,thermoelectric coolers(TECs)provide an innovative active cooling solution to meet growing thermal management demands.In this research,a refrigerant based on mono ethylene glycol and distilled water was used instead of using gases,in addition to using thermoelectric cooling units instead of using a compressor in traditional refrigeration systems.This study evaluates the performance of a Peltierbased thermalmanagement systemby analyzing the effects of using two,three,and four Peltiermodules on cooling rates,power consumption,temperature reduction,and system efficiency.Experimental results indicate that increasing the number of Peltier modules significantly enhances cooling performance.The four-module system achieved an optimal balance between cooling speed and energy efficiency,reducing the temperature of a liquidmixture(30% mono ethylene glycol+70% distilled water plus laser dyes)to 8℃ in just 17 min.It demonstrated a cooling rate of 0.794℃/min and a high coefficient of performance(COP)of 1.2 while consuming less energy than the two-and three-module systems.Furthermore,the study revealed that increasing the number of modules led to faster air cooling and improved temperature reduction.These findings highlight the importance of selecting the optimal number of Peltier modules to enhance efficiency and cooling speed whileminimizing energy consumption.This makes TEC technology a sustainable and effective solution for applications requiring rapid and reliable thermal management.展开更多
Rechargeable magnesium batteries(RMBs)possess the merits of greater theoretical capacity,cheaper magnesium metal and not easily producing branched crystals,and greater safety.Therefore,the current researches mainly co...Rechargeable magnesium batteries(RMBs)possess the merits of greater theoretical capacity,cheaper magnesium metal and not easily producing branched crystals,and greater safety.Therefore,the current researches mainly concentrate on the exploration of high-performance RMBs in the initial stage,but still face many gigantic challenges.Herein,petal-shaped nanorods CoS/CuS materials are successfully synthesized as RMBs cathode materials through a two-step metal sulfide template-free solvent-thermal synthesis method,which can effectively improve the reaction kinetics due to the petal-like nano-structure and provide rich electrochemically active sites to decrease the transport barrier of Mg^(2+),thus contributing to the enhancement of the reaction kinetics of magnesium storage in RMBs.The electrochemical performance test illustrates that CoS/CuS composite nanomaterials can considerably improve the charging and discharging specific capacity of the batteries as well as the voltage of the batteries due to the existing synergistic effect between them.The specific capacity of CoS/CuS cathode still can still be maintained as high as 62.8 mAh g^(−1)after 300 cycles at 200 mA g^(−1).And the specific capacity of this electrode material changes from 180.6 mAh g^(−1)to 30 mAh g^(−1)at the current densities from 100 mA g^(−1)to 1000 mA g^(−1),and when the current density is restored to 100 mA g^(−1),the specific capacity gradually recovered to 178.6 mAh g^(−1),which showed better rate performance and ultra-high cycling stability.This work highlights how the introduction of CuS into CoS nanostructures can benefit the reversibility and cyclicity of the magnesium storage reaction and offers an original and practical route for the modification of RMBs electrode materials with good electrochemical properties.展开更多
This study focused on improving the cathode performance of Ba_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.15)O_(3-δ)(BSCN)-based perovskite materials through molybdenum(Mo)doping.Pure BSCN and Mo-modified-BSCN—Ea_(0.6)Sr_(0.4)Co_(0...This study focused on improving the cathode performance of Ba_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.15)O_(3-δ)(BSCN)-based perovskite materials through molybdenum(Mo)doping.Pure BSCN and Mo-modified-BSCN—Ea_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.1)Mo_(0.05)O_(3-δ)(B S CNM_(0.05)),Ba_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.05)Mo_(0.1)O_(3-δ)(BSCNM_(0.1)),and Ba_(0.6)Sr_(0.4)Co_(0.85)Mo_(0.15)O_(3-δ)(BSCM)—with Mo doping contents of 5mol%,10mol%,and15mol%,respectively,were successfully prepared using the sol-gel method.The effects of Mo doping on the crystal structure,conductivity,thermal expansion coefficient,oxygen reduction reaction(ORR)activity,and electrochemical performance were systematically evaluated using X-ray diffraction analysis,thermally induced characterization,electrochemical impedance spectroscopy,and single-cell performance tests.The results revealed that Mo doping could improve the conductivity of the materials,suppress their thermal expansion effects,and significantly improve the electrochemical performance.Surface chemical state analysis using X-ray photoelectron spectroscopy revealed that 5mol%Mo doping could facilitate a high adsorbed oxygen concentration leading to enhanced ORR activity in the materials.Density functional theory calculations confirmed that Mo doping promoted the ORR activity in the materials.At an operating temperature of 600℃,the BSCNM_(0.05)cathode material exhibited significantly enhanced electrochemical impedance characteristics,with a reduced area specific resistance of 0.048Ω·cm~2,which was lower than that of the undoped BSCN matrix material by 32.39%.At the same operating temperature,an anode-supported single cell using a BSCNM_(0.05)cathode achieved a peak power density of 1477 mW·cm^(-2),which was 30.71%,56.30%,and 171.50%higher than those of BSCN,BSCNM_(0.1),and B SCM,respectively.The improved ORR activity and electrochemical performance of BSCNM_(0.05)indicate that it can be used as a cathode material in low-temperature solid oxide fuel cells.展开更多
A performance improvement model of research and development(R&D)institutions based on evolutionary game and Bayesian network is proposed.First,the nature and performance factors of new R&D institutions are sys...A performance improvement model of research and development(R&D)institutions based on evolutionary game and Bayesian network is proposed.First,the nature and performance factors of new R&D institutions are systematically analyzed,the appropriate factor model is found,and the sharing of performance benefits between institutions and employees,the change in distribution proportion,and the risk of institutional improvement and employee cooperation are considered.Second,based on the mechanism improvement and employee cooperation,the payment matrix is given and evolutionary game analysis is carried out to obtain a stable and balanced institutional improvement probability and employee cooperation probability.These two probability values are substituted into the Bayesian network model of performance improvement of new R&D institutions,and the posterior probability of performance improvement is predicted by Bayesian network reasoning and diagnosis to find effective improvement measures.Finally,practical case analysis is given to verify the effectiveness and practicability of the proposed method.展开更多
Magnesium-based anode materials have attracted significant attention in the energy storage domain because of their high theoretical capacities and low electrochemical potentials.However,in conventional electrolyte sys...Magnesium-based anode materials have attracted significant attention in the energy storage domain because of their high theoretical capacities and low electrochemical potentials.However,in conventional electrolyte systems,magnesium metal electrodes dynamically generate an ion-blocking surface layer,resulting in prominent voltage polarization,which severely limits their practical applications.In this study,ZIF-8/carbon nanotubes(CNTs)coatings were used to modify the anodes of magnesium batteries.Compared with the unaltered magnesium battery,the voltage lag time of the ZIF-8/CNTs coating was shortened from 4 s before modification to 0.26 s,and the battery impedance was lowered by two orders of magnitude.The duration of the discharge platform was increased from 4 h before modification to 6-10 h,the anode utilization rate was more than doubled,and the specific energy density was significantly enhanced compared with the battery before modification.The mechanism indicates that the ZIF-8/CNTs coating can limit the infiltration of corrosive substances,extend their transmission path,and offer more effective protection to the magnesium anode.The incorporation of CNTs improves the conductivity of the battery,and it significantly improves the electrochemical performance of the magnesium battery.展开更多
In composite solid propellants with high aluminum(Al)content and low burning rate,incomplete combustion of the Al powder may occur.In this study,varying lithium(Li)content in Al-Li alloy powder was utilized instead of...In composite solid propellants with high aluminum(Al)content and low burning rate,incomplete combustion of the Al powder may occur.In this study,varying lithium(Li)content in Al-Li alloy powder was utilized instead of pure aluminum particles to mitigate agglomeration and enhance the combustion efficiency of solid propellants(Combustion efficiency herein refers to the completeness of metallic fuel oxidation,quantified as the ratio of actual-to-theoretical energy released during combustion)with high Al content and low burning rates.The impact of Al-Li alloy with different Li contents on combustion and agglomeration of solid propellant was investigated using explosion heat,combustion heat,differential thermal analysis(DTA),thermos-gravimetric analysis(TG),dynamic high-pressure combustion test,ignition experiment of small solid rocket motor(SRM)tests,condensation combustion product collection,and X-ray diffraction techniques(XRD).Compared with pure Al,Al-Li alloys exhibit higher combustion heat,which contributes to improved combustion efficiency in Al-Li alloy-containing propellants.DTA and TG analyses demonstrated higher reactivity and lower ignition temperatures for Al-Li alloys.High-pressure combustion experiments at 5 MPa showed that Al-Li alloy fuel significantly decreases combustion agglomeration.The results from theφ75 mm andφ165 mm SRM and XRD tests further support this finding.This study provides novel insights into the combustion and agglomeration behaviors of high-Al,low-burning-rate composite solid propellants and supports the potential application of Al-Li alloys in advanced propellant formulations.展开更多
基金Supported by Basic Scientific Research Project of the Liaoning Provincial Department of Education Has Been Unveiled to Facilitate Local Project Funding (JYTMS20230835)Enhanced Scientific Research Project Funded by the Departmentof Higher Education in Liaoning Province (General program)(JYTMS20230852)。
文摘The adsorptive denitrification performance of MIL-101(Cr)-0.5 toward pyridine,aniline or quinoline in simulated fuels with basic nitrogen content of 1732μg/g was evaluated separately.Furthermore,the effects of adsorption temperature,adsorption time and adsorbent dosage on their adsorptive denitrification performance were systematically investigated.The experimental results demonstrated that under a fixed adsorbent dosage of 0.05 g and a simulated fuel volume of 10 mL,the optimal removal efficiency for aniline was achieved at 30℃ within 30 min,whereas higher temperatures and longer times(40℃and 40 min)were required for effective removal of pyridine and quinoline.Density Functional Theory(DFT)calculations were conducted via Materials Studio(MS)software to study the adsorptive denitrification mechanism of MIL-101(Cr)toward these three basic nitrogen-containing compounds.The simulation calculation results revealed that the interaction between pyridine and MIL-101(Cr)primarily involved coordination adsorption.In contrast,the interaction between aniline or quinoline and MIL-101(Cr)proceeded mainly through coordination,with additional contributions fromπ-complexation and hydrogen bonding.The overall adsorption strength order is pyridine>aniline>quinoline.During the adsorption process,pyridine and quinoline transfer electrons to the MIL-101(Cr)surface through the H→C→N→Cr^(3+)pathway,while aniline transfers electrons to the MIL-101(Cr)surface through various pathways,including N→Cr^(3+),N→C→Cr^(3+)and N→H→O.Furthermore,adsorption kinetics studies indicated that the adsorption processes for all three basic nitrogen-containing compounds followed the quasi second order kinetic models.The experimental results on the effect of benzene on the adsorptive denitrification performance of MIL-101(Cr)-0.5 demonstrated that benzene exerted a more significant impact on the adsorption of aniline and quinoline.Finally,the adsorbent was regenerated using ethanol washing.It was found that MIL-101(Cr)-0.5 retained stable denitrification performance after two regeneration cycles.
基金Supported by the Science and Technology Cooperation and Exchange special project of Cooperation of Shanxi Province(202404041101014)the Fundamental Research Program of Shanxi Province(202403021212333)+3 种基金the Joint Funds of the National Natural Science Foundation of China(U24A20555)the Lvliang Key R&D of University-Local Cooperation(2023XDHZ10)the Initiation Fund for Doctoral Research of Taiyuan University of Science and Technology(20242026)the Outstanding Doctor Funding Award of Shanxi Province(20242080).
文摘To elucidate the effect of calcite-regulated activated carbon(AC)structure on low-temperature denitrification performance of SCR catalysts,this work prepared a series of Mn-Ce/De-AC-xCaCO_(3)(x is the calcite content in coal)catalysts were prepared by the incipient wetness impregnation method,followed by acid washing to remove calcium-containing minerals.Comprehensive characterization and low-temperature denitrification tests revealed that calcite-induced structural modulation of coal-derived AC significantly enhances catalytic activity.Specifically,NO conversion increased from 88.3%of Mn-Ce/De-AC to 91.7%of Mn-Ce/De-AC-1CaCO_(3)(210℃).The improved SCR denitrification activity results from the enhancement of physicochemical properties including higher Mn^(4+)content and Ce^(4+)/Ce^(3+)ratio,an abundance of chemisorbed oxygen and acidic sites,which could strengthen the SCR reaction pathways(richer NH_(3)activated species and bidentate nitrate active species).Therefore,NO removal is enhanced.
基金financially supported by the National Science Fund for Distinguished Young Scholars,China(No.52025041)the National Natural Science Foundation of China(Nos.52450003,U2341267,and 52174294)+1 种基金the National Postdoctoral Program for Innovative Talents,China(No.BX20240437)the Fundamental Research Funds for the Central Universities,China(Nos.FRF-IDRY-23-037 and FRF-TP-20-02C2)。
文摘The rapid advancements in computer vision(CV)technology have transformed the traditional approaches to material microstructure analysis.This review outlines the history of CV and explores the applications of deep-learning(DL)-driven CV in four key areas of materials science:microstructure-based performance prediction,microstructure information generation,microstructure defect detection,and crystal structure-based property prediction.The CV has significantly reduced the cost of traditional experimental methods used in material performance prediction.Moreover,recent progress made in generating microstructure images and detecting microstructural defects using CV has led to increased efficiency and reliability in material performance assessments.The DL-driven CV models can accelerate the design of new materials with optimized performance by integrating predictions based on both crystal and microstructural data,thereby allowing for the discovery and innovation of next-generation materials.Finally,the review provides insights into the rapid interdisciplinary developments in the field of materials science and future prospects.
基金supported by the Andalusian FEDER Operational Program [B-CTS-374-UGR20 and C-SEJ-015-UGR23]the Spanish Ministry of Science,Innovation and Universities [PGC2018-097388-BI00-MCI/AEI/FEDER,UE]。
文摘Purpose: Normobaric hypoxia(NH) is a frequent strategy for training under hypoxic conditions that can be administered through different equipment, including face masks or hypoxic chambers/tents. Nonetheless, the versatility of administration methods may influence the outcomes.Methods: Web of Science, Scopus, SPORTDiscus and Pub Med/MEDLINE were searched to identify studies assessing the effect of NH administered by face mask or chamber/tent equipment on maximal oxygen uptake( VO2max) after a training period. An overall meta-analysis and sub-analysis of total program session volume(low, moderate, high), participants' training level(trained, active, sedentary), and the severity of hypoxia(moderate, severe) were conducted to explore the effects of the NH-administration system.Results: Eighteen studies were included. Compared with normoxia, NH showed a moderate global improvement in VO2max(standardized mean difference [SMD] = 0.74;p = 0.06), favoring the chamber/tent(SMD = 1.30;p< 0.01) over the face mask. Sub-analysis showed a very large effect in support of the hypoxic chamber/tent among sedentary individuals and training programs with a high volume of sessions. Severe hypoxia did not yield conclusive findings in VO2max improvements, although the chamber/tent proved more effective(SMD = 1.42;p< 0.01) than the face mask under moderate hypoxia.Conclusions: Chambers/tents may slightly accentuate the benefit of NH on aerobic performance, particularly in participants with limited training experience following a high volume of sessions under moderate hypoxia.However, the variability of sub-analysis factors(session volume, participants' training level, and methodological approaches) between studies using each type of hypoxia-generating equipment may influence this result.
基金supported by the National Natural Science Foundation of China(No.51706105)。
文摘Al/NH_(4)CoF_(3)-Φ(Φ=0.5,1.0,1.5,2.0,and 3.0)binary composites and Al-NH_(4)CoF_(3)@P(VDF-HFP)ternary composites are fabricated via ultrasonication-assisted blending and electrostatic spraying.The effect of equivalence ratio(Φ)on the reaction properties is systematically investigated in the binary Al/NH_(4)CoF_(3)system.For ternary systems,electrostatic spraying allows both components to be efficiently encapsulated by P(VDF-HFP)and to achieve structural stabilization and enhanced reactivity through synergistic interfacial interactions.Morphological analysis using SEM/TEM revealed that P(VDF-HFP)formed a protective layer on Al and NH_(4)CoF_(3)particles,improving dispersion,hydrophobicity(water contact angle increased by 80.5%compared to physically mixed composites),and corrosion resistance.Thermal decomposition of NH_(4)CoF_(3)occurred at 265℃,releasing NH_(3)and HF,which triggered exothermic reactions with Al.The ternary composites exhibited a narrowed main reaction temperature range and concentrated heat release,attributed to improved interfacial contact and polymer decomposition.Combustion tests demonstrated that Al-NH_(4)CoF_(3)@P(VDF-HFP)achieved self-sustaining combustion.In addition,a simple validation was done by replacing the Al component in the aluminium-containing propellant,demonstrating its potential application in the propellant field.This work establishes a novel strategy for designing stable,high-energy composites with potential applications in advanced propulsion systems.
文摘Isolation technology can reduce the type of structural damage that earthquakes cause.A new type of composite sliding-rolling friction composite seismic isolation bearing(SRF)with composite sliding friction and rolling friction is proposed.SRF is capable of realizing a parallel arrangement of sliding friction and rolling friction,and the coefficient of dynamic friction shows variability.The proposed static tests on composite bearings were conducted to investigate the effects of the number of shims,loading speed and vertical pressure on the dynamic friction factor.Test results show that the coefficient of dynamic friction first generally decreases and then increases with an increase in sliding speed,prior to again decreasing with an increase in vertical pressure.The dynamic friction factor increases and then decreases with an increase in the number of shims for a four-roll ball.It decreases and then increases with an increase in the number of shims for a five-roll ball.Based on finite element analysis,modeling and analyzing the effects of the coefficient of friction,the number of balls and the number of shims on the hysteresis performance of the support and derive its skeleton curve.The SRF hysteretic performance,dynamic friction factor and the number of rolling balls and shims show significant correlation.
基金supported by the National Natural Science Foundation of China(Grant No.12402268)the Fundamental Research Funds for the Central Universities(Grant No.30925010410)。
文摘The core components of an aircraft and the source of its lift are its wings,but lift generation is disrupted by the high temperature and pressure generated on the wing surface when an aircraft gun is fired.Here,to investigate how this process influences the aerodynamic parameters of aircraft wings,the k-ωshearstress-transport turbulence model and the nested dynamic grid technique are used to analyze numerically the transient process of the muzzle jet of a 30-mm small-caliber aircraft gun in highaltitude(10 km)flight with an incoming Mach number of Ma=0.8.For comparison,two other models are established,one with no projectile and the other with no wing.The results indicate that when the aircraft gun is fired,the muzzle jet acts on the wing,creating a pressure field thereon.The uneven distribution of high pressure greatly reduces the lift of the aircraft,causing oscillations in its drag and disrupting its dynamic balance,thereby affecting its flight speed and attitude.Meanwhile,the muzzle jet is obstructed by the wing,and its flow field is distorted and deformed,developing upward toward the wing.Because of the influence of the incoming flow,the shockwave front of the projectile changes from a smooth spherical shape to an irregular one,and the motion parameters of the projectile are also greatly affected by oscillations.The present results provide an important theoretical basis for how the guns of fighter aircraft influence the aerodynamic performance of the wings.
基金supported by the Science and Technology Research and Development Program Project of China Railway Group Limited (Grant No.2022-Major-17)the National Natural Science Foundation of China (Grant Nos.52578619,52178180)+2 种基金the National Key Research and Development Program of China (Grant No.2022YFC3004304)the Frontier Cross Research Project of Central South University (Grant No.2023QYJC006)the Natural Science Foundation of Hunan Province Funding Project (Grant No.2023JJ40724)。
文摘Under earthquake action, different site conditions have a notable impact on the dynamic response of high-speed railway bridges after earthquakes, which in turn poses a threat to the running stability of trains in the post-earthquake period. Therefore, establishing a calculation method for the post-earthquake train speed threshold that considers the influence of different site characteristics is of great engineering significance. Taking the CRTS Ⅲ slab track as the research object, this study is based on the track irregularity root mean square rate(TRR), which the authors proposed earlier to quantify the track regularity level. Using the nonlinear least squares fitting method, the mapping relationship between the TRR and the postearthquake train running performance indicators on bridges is established. Furthermore, the influence of laws governing site categories and train speeds on post-earthquake train running performance on bridges is analyzed, and a train speed threshold for bridges based on running performance under random site conditions is proposed. The research results indicate that all train running performance indicators increase significantly with the increase of train operating speed;different site categories have a significant impact on post-earthquake track residual deformation and train running stability. The greater the amplitude of postearthquake track alignment residual deformation, the lower the threshold for the stable running speed of trains after the earthquake, with the speed threshold decreasing by up to 20%. The research outcomes can provide technical references for the post-earthquake safe operation and maintenance of high-speed railway bridges under complex site conditions, as well as the formulation of targeted train speed control schemes.
基金supported by the Tiangsu Association for Science and Technology(Grant No.JSKX 0225089).
文摘The low-pressure and low-density conditions encountered at high altitudes significantly reduce the operating Reynolds number of micro radial-flow turbines,frequently bringing it below the self-similarity critical threshold of 3.5×10^(4).This departure undermines the applicability of conventional similarity-based design approaches.In this study,micro radial-flow turbines with rotor diameters below 50 mm are investigated through a combined approach integrating high-fidelity numerical simulations with experimental validation,aiming to elucidate the mechanisms by which low Reynolds numbers influence aerodynamic and thermodynamic performance.The results demonstrate that decreasing Reynolds number leads to boundary-layer thickening on blade surfaces,enhanced flow separation on the suction side,and increased secondary-flow losses within the blade passages.These effects jointly produce a pronounced and non-linear deterioration of turbine efficiency.Geometric scaling analysis further indicates that efficiency losses intensify with decreasing turbine size,and become particularly severe at low rotational speeds and high expansion ratios.Detailed flow-field analyses reveal a direct link between the degradation of blade loading distribution and the amplification of transverse pressure gradients under low-Reynolds-number conditions,providing physical insight into the observed performance decline.
基金supported by the State Key Laboratory of Intelligent Construction and Healthy Operation and Maintenance of Deep Underground Engineering(Grant No.SDGZ2505)the Postdoctoral Fellowship Program of the China Postdoctoral Science Foundation(Grant No.GZB20250742)the General Program of the China Postdoctoral Science Foundation(Grant No.2025M773213).
文摘The negative Poisson’s ratio(NPR)bolt is an innovative support element distinguished by its high strength,elongation,and a slightly negative Poisson’s ratio.Unlike conventional prestressed(PR)bolts with a positive Poisson’s ratio,the NPR bolt exhibits a quasi-ideal plastic response without a prominent yield platform,enabling it to sustain high prestress with a substantial safety margin,which is particularly advantageous for jointed rock masses.However,investigations into the shear resistance mechanisms of NPR bolts under varying prestress levels remain limited.This study conducted full-scale double shear tests to assess the shear strength,deformation behavior,energy absorption,and failure mechanisms of NPR bolts under different prestress conditions.To ensure a fair comparison with PR bolts,a prestress utilization coefficient(PUC)was introduced.The results reveal that at a PUC of 0.25,the NPR bolt achieved peak axial force,shear displacement,and peak shear force values that are 2.41,1.88,and 2.13 times greater than those of the PR bolt,respectively.Shear performance was optimized at a prestress level of 100 kN,with energy absorption reaching 47.1 kJ,which is 2.8 times that of the PR bolt.Furthermore,the necking ratio was significantly reduced,indicating more distributed plastic deformation and delayed failure.Field applications verified the superior performance,resulting in a 27.4%reduction in roof settlement and enhanced structural integrity.These findings confirm that NPR bolts possess excellent shear resistance,energy absorption,and deformation adaptability,and optimizing prestress significantly enhances their support performance,providing a strong basis for geotechnical engineering applications.
基金supported by the National Natural Science Foundation of China(No.52064035)the Key Research and Development Program of Gansu Province,China(No.25YFGA024)the Natural Science Foundation of Zhejiang Province,China(No.LGG22E020003).
文摘Lithium-sulfur(Li-S)batteries boast a theoretical energy density as high as 2600 Wh·kg^(−1),positioning them as a highly attractive option for future advanced energy storage systems.Challenges such as slow transformation kinetics and shuttle effects associated with lithium polysulfides(LiPSs)have seriously hindered their practical applications.In this paper,we present a new method for the synthesis of hollow carbon-sphere-supported Co monatomic catalysts(Co-N-C).This new synthesis method achieves pyrolytic coordination using a precursor rich in imide(-RC=N-)polymers.This synthesis method not only improves the adsorbability and catalytic activity of LiPS but also significantly weakens the shuttle effect and generates Co-N-C with superior conductivity,abundant hollow structures,and a high specific surface area,thus efficiently capturing and restricting the movement of LiPS intermediates.The dispersed Co monoatomic catalysts(Co SACs)were anchored to a highly conductive nitrogen-doped carbon framework and exhibited symmetric N-coordination active sites(Co-N_(4))to ensure fast redox kinetics of LiPS and Li_(2)S_(2)/Li_(2)S solid-state products.The lithium-sulfur battery with Co-N-C as the sulfur carrier showed excellent discharging capacity of 1146.6 mAh·g^(−1) at a discharge rate of 0.5 C and maintained excellent performance at a high discharge rate of 2 C.The capacity decay rate in 500 cycles was only 0.086%per cycle,reflecting excellent long-term cycle stability.This study highlights the key role of the synergistic effect between single-atom cobalt catalysts and hollow carbon spheres in enhancing the efficiency of lithium-sulfur(Li-S)batteries.It also provides valuable insights into the construction and fabrication of highly active monatomic catalysts.The catalytic conversion efficiency of lithium polysulfides is significantly enhanced when embedded in hollow carbon architectures,which serves as a critical strategy for optimizing the electrochemical behavior of next-generation Li-S batteries.
基金supported by the National Natural Science Foundation of China(Nos.U2341249,12005076,22205112)the Fundamental Research Funds for the Central Universities(No.2025201012)。
文摘The presence of a surface oxide film(B_(2)O_(3))on boron(B)particles significantly compromises their combustion efficiency and kinetic performance in fuel-rich solid propellants.This study proposes an innovative continuous modification strategy combining non-thermal plasma(NTP)etching with fluorocarbon passivation.Characterization and kinetic analysis revealed that reactive plasma species—including atomic hydrogen(H),electronically excited molecular hydrogen(H_(2)^(*)),vibrationally excited molecular hydrogen(H_(2)v),and hydrogen ions(H^(+))—dominate the reduction of B_(2)O_(3)through lowering the transition energy barrier and shifting the reaction spontaneity.Subsequent argon plasma fragmentation of C_(8)F_(18)generates fluorocarbon radicals that form conformal passivation coatings(thickness:7 nm)on purified boron surfaces.The modified boron particles exhibit 37.5℃lower exothermic peak temperature and 27.2%higher heat release(14.8 kJ/g vs.11.6 kJ/g)compared to untreated counterparts.Combustion diagnostics reveal 194%increase in maximum flame height(135.10 mm vs.46.03 mm)and 134%enhancement in flame propagation rate(4.44 cm/s vs.1.90 cm/s).This NTP-based surface engineering approach establishes a scalable pathway for developing highperformance boron-based energetic composites.
基金co-supported by the National Key R&D Program of China(Nos.2020YFC2201103 and 2022YFB4601300)the National Natural Science Foundation of China(No.U22B20120)+1 种基金the Program of Beijing Engineering Research Center of Efficient and Green Aerospace Propulsion Technology,China(No.Lab ASP-2024-09)the Beijing Institute of Technology Research Fund Program for Young Scholars,China。
文摘Porous ionic liquid electrospray thrusters are the ideal propulsion technology for CubeSats because of their structural simplicity,high thrust accuracy and plume self-neutralization.The electrowetting technology can replenish the propellant for the emitter online,thus prolonging the lifetime of the thruster.In order to gain a deeper understanding of its operating characteristics,the changes in thruster performance before and after propellant replenishment deserve to be scrutinized.In this study,the performance changes of a porous electrowetting ionic liquid electrospray thruster are tested by voltage-current test and time-of-flight mass spectrometry over a long operating time.The experimental results show that asymmetric operation with a negative current less than positive current for a long period of time causes anions to compensate for the emission after accumulation at the emitter,resulting in a phenomenon that the negative current is much larger than positive current.The reason for the difference in emission characteristics between the positive and negative modes is that the plume in the positive mode is quite ionized while the plume in the negative mode contains liquid droplets.This study provides a reference for the selection of operating conditions for ionic liquid electrospray thrusters.
基金Project(ASM-20240)supported by the Key Laboratory of Advanced Structural Materials(Changchun University of Technology),Ministry of Education,ChinaProject(2022TD-30)supported by the Scientific and Technological Innovation Team Project of Shaanxi Innovation Capability Support Plan,China。
文摘This work examines the microstructure and corrosion properties of fine-grained Al 7075 across different regions under varying cooling conditions during friction stir welding.The findings demonstrate that forced cooling significantly improves the corrosion resistance of the welded joints.Specifically,the corrosion resistance was the highest in the stir zone,followed by the thermo-mechanical affected zone,and then the heat affected zone.Forced cooling mitigates grain growth by controlling the welding thermal effects,thereby increasing the proportion ofΣ3 grain boundaries.The modification of these microstructural characteristics promotes the formation of a dense oxide layer,thereby enhancing the corrosion resistance.Furthermore,forced cooling mitigates the precipitation and coarsening of the anodic phase in the stir zone,which in turn reduces the susceptibility of the joint to pitting corrosion.Additionally,the lower recrystallization texture content in the joint,resulting from forced cooling,contributes to a reduction in the number of corrosion-active sites,thereby further improving the corrosion performance of the welded joint.
文摘Electrical and electronic devices face significant challenges in heatmanagement due to their compact size and high heat flux,which negatively impact performance and reliability.Conventional coolingmethods,such as forced air cooling,often struggle to transfer heat efficiently.In contrast,thermoelectric coolers(TECs)provide an innovative active cooling solution to meet growing thermal management demands.In this research,a refrigerant based on mono ethylene glycol and distilled water was used instead of using gases,in addition to using thermoelectric cooling units instead of using a compressor in traditional refrigeration systems.This study evaluates the performance of a Peltierbased thermalmanagement systemby analyzing the effects of using two,three,and four Peltiermodules on cooling rates,power consumption,temperature reduction,and system efficiency.Experimental results indicate that increasing the number of Peltier modules significantly enhances cooling performance.The four-module system achieved an optimal balance between cooling speed and energy efficiency,reducing the temperature of a liquidmixture(30% mono ethylene glycol+70% distilled water plus laser dyes)to 8℃ in just 17 min.It demonstrated a cooling rate of 0.794℃/min and a high coefficient of performance(COP)of 1.2 while consuming less energy than the two-and three-module systems.Furthermore,the study revealed that increasing the number of modules led to faster air cooling and improved temperature reduction.These findings highlight the importance of selecting the optimal number of Peltier modules to enhance efficiency and cooling speed whileminimizing energy consumption.This makes TEC technology a sustainable and effective solution for applications requiring rapid and reliable thermal management.
基金financially supported by the National Natural Science Foundation of China(Nos.21804008,52102209)the International Technological Collaboration Project of Shanghai(No.17520710300)+1 种基金Anhui Provincial Natural Science Foundation(No.2108085QE197)Guangdong Basic and Applied Basic Research Foundation(Nos.2022A1515010834,2020A1515110221).
文摘Rechargeable magnesium batteries(RMBs)possess the merits of greater theoretical capacity,cheaper magnesium metal and not easily producing branched crystals,and greater safety.Therefore,the current researches mainly concentrate on the exploration of high-performance RMBs in the initial stage,but still face many gigantic challenges.Herein,petal-shaped nanorods CoS/CuS materials are successfully synthesized as RMBs cathode materials through a two-step metal sulfide template-free solvent-thermal synthesis method,which can effectively improve the reaction kinetics due to the petal-like nano-structure and provide rich electrochemically active sites to decrease the transport barrier of Mg^(2+),thus contributing to the enhancement of the reaction kinetics of magnesium storage in RMBs.The electrochemical performance test illustrates that CoS/CuS composite nanomaterials can considerably improve the charging and discharging specific capacity of the batteries as well as the voltage of the batteries due to the existing synergistic effect between them.The specific capacity of CoS/CuS cathode still can still be maintained as high as 62.8 mAh g^(−1)after 300 cycles at 200 mA g^(−1).And the specific capacity of this electrode material changes from 180.6 mAh g^(−1)to 30 mAh g^(−1)at the current densities from 100 mA g^(−1)to 1000 mA g^(−1),and when the current density is restored to 100 mA g^(−1),the specific capacity gradually recovered to 178.6 mAh g^(−1),which showed better rate performance and ultra-high cycling stability.This work highlights how the introduction of CuS into CoS nanostructures can benefit the reversibility and cyclicity of the magnesium storage reaction and offers an original and practical route for the modification of RMBs electrode materials with good electrochemical properties.
基金financially supported by the National Natural Science Foundation of China(No.22309067)the Open Project Program of the State Key Laboratory of Materials-Oriented Chemical Engineering,China(No.KL21-05)the Marine Equipment and Technology Institute,Jiangsu University of Science and Technology,China(No.XTCX202404)。
文摘This study focused on improving the cathode performance of Ba_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.15)O_(3-δ)(BSCN)-based perovskite materials through molybdenum(Mo)doping.Pure BSCN and Mo-modified-BSCN—Ea_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.1)Mo_(0.05)O_(3-δ)(B S CNM_(0.05)),Ba_(0.6)Sr_(0.4)Co_(0.85)Nb_(0.05)Mo_(0.1)O_(3-δ)(BSCNM_(0.1)),and Ba_(0.6)Sr_(0.4)Co_(0.85)Mo_(0.15)O_(3-δ)(BSCM)—with Mo doping contents of 5mol%,10mol%,and15mol%,respectively,were successfully prepared using the sol-gel method.The effects of Mo doping on the crystal structure,conductivity,thermal expansion coefficient,oxygen reduction reaction(ORR)activity,and electrochemical performance were systematically evaluated using X-ray diffraction analysis,thermally induced characterization,electrochemical impedance spectroscopy,and single-cell performance tests.The results revealed that Mo doping could improve the conductivity of the materials,suppress their thermal expansion effects,and significantly improve the electrochemical performance.Surface chemical state analysis using X-ray photoelectron spectroscopy revealed that 5mol%Mo doping could facilitate a high adsorbed oxygen concentration leading to enhanced ORR activity in the materials.Density functional theory calculations confirmed that Mo doping promoted the ORR activity in the materials.At an operating temperature of 600℃,the BSCNM_(0.05)cathode material exhibited significantly enhanced electrochemical impedance characteristics,with a reduced area specific resistance of 0.048Ω·cm~2,which was lower than that of the undoped BSCN matrix material by 32.39%.At the same operating temperature,an anode-supported single cell using a BSCNM_(0.05)cathode achieved a peak power density of 1477 mW·cm^(-2),which was 30.71%,56.30%,and 171.50%higher than those of BSCN,BSCNM_(0.1),and B SCM,respectively.The improved ORR activity and electrochemical performance of BSCNM_(0.05)indicate that it can be used as a cathode material in low-temperature solid oxide fuel cells.
基金supported by the National Natural Science Foundation of China(72071106)Jiangsu Provincial Social Science Fund(23EYA001)+1 种基金Jiangsu Provincial Education Science Planning Fund(Ba/2024/08)Jiangsu Higher Education Association Fund(24FYHLX090)。
文摘A performance improvement model of research and development(R&D)institutions based on evolutionary game and Bayesian network is proposed.First,the nature and performance factors of new R&D institutions are systematically analyzed,the appropriate factor model is found,and the sharing of performance benefits between institutions and employees,the change in distribution proportion,and the risk of institutional improvement and employee cooperation are considered.Second,based on the mechanism improvement and employee cooperation,the payment matrix is given and evolutionary game analysis is carried out to obtain a stable and balanced institutional improvement probability and employee cooperation probability.These two probability values are substituted into the Bayesian network model of performance improvement of new R&D institutions,and the posterior probability of performance improvement is predicted by Bayesian network reasoning and diagnosis to find effective improvement measures.Finally,practical case analysis is given to verify the effectiveness and practicability of the proposed method.
基金supported by the Guangxi Natural Science Foundation,China(No.2020GXNSFAA 159011)the National Natural Science Foundation of China(No.51664011).
文摘Magnesium-based anode materials have attracted significant attention in the energy storage domain because of their high theoretical capacities and low electrochemical potentials.However,in conventional electrolyte systems,magnesium metal electrodes dynamically generate an ion-blocking surface layer,resulting in prominent voltage polarization,which severely limits their practical applications.In this study,ZIF-8/carbon nanotubes(CNTs)coatings were used to modify the anodes of magnesium batteries.Compared with the unaltered magnesium battery,the voltage lag time of the ZIF-8/CNTs coating was shortened from 4 s before modification to 0.26 s,and the battery impedance was lowered by two orders of magnitude.The duration of the discharge platform was increased from 4 h before modification to 6-10 h,the anode utilization rate was more than doubled,and the specific energy density was significantly enhanced compared with the battery before modification.The mechanism indicates that the ZIF-8/CNTs coating can limit the infiltration of corrosive substances,extend their transmission path,and offer more effective protection to the magnesium anode.The incorporation of CNTs improves the conductivity of the battery,and it significantly improves the electrochemical performance of the magnesium battery.
基金the National Natural Science Foundation of China(Grant No.U2441263)for financial support of this work。
文摘In composite solid propellants with high aluminum(Al)content and low burning rate,incomplete combustion of the Al powder may occur.In this study,varying lithium(Li)content in Al-Li alloy powder was utilized instead of pure aluminum particles to mitigate agglomeration and enhance the combustion efficiency of solid propellants(Combustion efficiency herein refers to the completeness of metallic fuel oxidation,quantified as the ratio of actual-to-theoretical energy released during combustion)with high Al content and low burning rates.The impact of Al-Li alloy with different Li contents on combustion and agglomeration of solid propellant was investigated using explosion heat,combustion heat,differential thermal analysis(DTA),thermos-gravimetric analysis(TG),dynamic high-pressure combustion test,ignition experiment of small solid rocket motor(SRM)tests,condensation combustion product collection,and X-ray diffraction techniques(XRD).Compared with pure Al,Al-Li alloys exhibit higher combustion heat,which contributes to improved combustion efficiency in Al-Li alloy-containing propellants.DTA and TG analyses demonstrated higher reactivity and lower ignition temperatures for Al-Li alloys.High-pressure combustion experiments at 5 MPa showed that Al-Li alloy fuel significantly decreases combustion agglomeration.The results from theφ75 mm andφ165 mm SRM and XRD tests further support this finding.This study provides novel insights into the combustion and agglomeration behaviors of high-Al,low-burning-rate composite solid propellants and supports the potential application of Al-Li alloys in advanced propellant formulations.
