Despite their attractive features of high energy density,low cost,and safety,polysulfide/iodide flow batteries(SIFBs)are hampered by the sluggish kinetics of the iodide redox couple,which restricts overall performance...Despite their attractive features of high energy density,low cost,and safety,polysulfide/iodide flow batteries(SIFBs)are hampered by the sluggish kinetics of the iodide redox couple,which restricts overall performance.Multicomponent sulfides are demonstrated as promising catalysts for accelerating I^(-)/I_(3)^(-) redox reactions.Concurrently,the enhanced configurational entropy arising from multinary compositions drives synergistic effects among constituent elements,establishing a viable pathway to optimize catalytic performance.Building on these foundations,this work introduces a targeted orbital hybridization-optimized electron density strategy to enhance the catalytic activity.Implementing this concept,we developed an in-situ solvothermal synthesis process for an entropy-enhanced AgCuZnSnS_(4) loaded graphite felt(ACZTS/GF)electrode.The engineered electrode demonstrates exceptional electrocatalytic performance with improved bulk conductivity and interfacial charge transfer kinetics within a SIFB.The cell achieves a high energy efficiency of 88.5%at 20 mA·cm^(−2) with 10%state-of-charge.Furthermore,the battery delivers a maximum power density of 119.8 mW·cm^(−2) and exhibits excellent long-term cycling stability.These significant results stem from orbital hybridization-driven electronic state optimization and entropy effect-induced synergistic catalysis.展开更多
Flow boiling in open microchannels offers highly efficient heat transfer performance and has attracted increasing attention in the fields of heat transfer and thermalmanagement of electronic devices in recent years.Ho...Flow boiling in open microchannels offers highly efficient heat transfer performance and has attracted increasing attention in the fields of heat transfer and thermalmanagement of electronic devices in recent years.However,the continuous rise in power density of electronic components imposesmore stringent requirements on the heat transfer capability of microchannel flow boiling.HFE-7100,a dielectric coolant with favorable thermophysical properties,has become a focal point of research for enhancing flow boiling performance in open microchannels.The flow boiling heat transfer performance ofHFE-7100 was investigated in this study by fabricating micro-nano composite structures on the bottom surface of open microchannels using laser ablation technology.Based on visualization results,a comparative analysis was conducted on the bubble dynamics and flow pattern characteristics of HFE-7100 flow boiling in micronano structured open microchannels(MNSOMC)and smooth-surface open microchannels(SSOMC),to elucidate the enhancement mechanism of micro-nano structures on flow boiling heat transfer in open microchannels.The results indicate that the surface structures and strong wettability of MNSOMC accelerated bubble nucleation and departure.Moreover,bubbles in the channel tended to coalesce along the flow direction,forming elongated slug bubbles with high aspect ratios,which enabled efficient thin film evaporation in conjunction with intense nucleate boiling,thereby significantly enhancing flow boiling heat transfer.Under the experimental conditions of this study,the maximum enhancements in the heat transfer coefficient(HTC)and critical heat flux(CHF)of HFE-7100 inMNSOMC were 33.4%and 133.1%,respectively,with the CHF reaching up to 1542.3 kW⋅m^(−2).Furthermore,due to the superior wettability and capillary wicking capability of the micro-nano composite structures,the significant enhancement in flow boiling heat transfer was achieved without incurring a noticeable pressure drop penalty.展开更多
Poly(_(L)-lactide)(PLLA),a leading biodegradable polyester,has demonstrated potential as a sustainable alternative,owing to its excellent biodegradability and rigidity.However,their slow crystallization kinetics and p...Poly(_(L)-lactide)(PLLA),a leading biodegradable polyester,has demonstrated potential as a sustainable alternative,owing to its excellent biodegradability and rigidity.However,their slow crystallization kinetics and poor heat resistance limit their application scope.Recent advances have highlighted that the combination of extensional flow and thermal fields can achieve toughness–stiffness balance,high transparency,and good heat resistance.However,the effect of extensional flow on the post-non-isothermal crystallization of PLLA during heating and the resulting crystalline texture remains unclear.In this study,PLLA with a heterogeneous amorphous structure and oriented polymorph was prepared by extensional flow.The effect of heterogeneous amorphous structures on non-isothermal crystallization kinetics during the heating process was studied by thermal analysis,polarized optical microscopy,infrared spectroscopy,and ex situ/in situ X-ray characterization.These results clearly illustrate that extensional flow enhances the formation of oriented crystalline structures,accelerates non-isothermal crystallization,and modulates the polymorphic composition of PLLA.Moreover,an unexpected dual cold-crystallization behavior is identified in ordered PLLA samples upon extensional flow,which is from the extensional flow-induced heterogeneous amorphous phase into α' phase(low-temperature peak)and the pristine amorphous phase intoαphase(high-temperature peak).The extensional flow primarily promotes the formation of the more perfectαandα'phases,but has a negative effect on the final content ofαphase formed after cold crystallization andα'-to-αphase transformation.The findings of this work advance the understanding of PLLA non-isothermal crystallization after extensional flow and offer valuable guidance for high-performance PLLA upon heat treatment in practical processing.展开更多
The sluggish electrochemical catalytic activity of the graphite felt electrodes for anode reaction is still a barrier for achieving high-performance vanadium redox flow battery(VRFB).It is significant to leverage the ...The sluggish electrochemical catalytic activity of the graphite felt electrodes for anode reaction is still a barrier for achieving high-performance vanadium redox flow battery(VRFB).It is significant to leverage the exceptional conductivity,excellent electrocatalytic activity,and structural tunability of MXene to address this issue.Herein,this work introduces nitrogen atoms to modulate the carbon layer structure of Ti_(3)C_(2)T_(x)MXene,inducing a reconfiguration of the local electronic structure,which enhances the anode interface activity and thereby improves the performance of VRFB.Ti_(3)C_(2)T_(x)exhibits high conductivity,excellent hydrophilicity,and a large specific surface area,providing excellent interface characteristics for V^(3+)/V^(2+)redox reaction.Moreover,interlayer treatment to modulate the mesoporous structure of MXene further increases the reactive surface area.Importantly,doping nitrogen atoms at carbon layer induces lattice distortions in Ti_(3)C_(2)T_(x),which enhances the charge transfer processes of the V^(3+)/V^(2+)redox reaction.The catalysis mechanism is also validated through density functional theory.Furthermore,the modified graphite felt electrode,as the anode of VRFB,relieves a higher energy efficiency of 68%at 250 mA cm^(-2),while the pristine electrode cannot operate at this current density.In addition,at 150 mA cm^(-2),the modified battery maintains energy efficiency at 75%without degradation after 500 cycles.This study utilizes rational atomic-level engineering for effective structural modulation to significantly enhance the catalytic activity of electrode reaction,offering a unique perspective for developing high-performance MXene electrocatalysts of VRFB.展开更多
The flow control at low Reynolds numbers is one of the most promising technologies in the field of aerodynamics,and it is also an important source of the innovation for novel aircraft.In this study,a new way of nonlin...The flow control at low Reynolds numbers is one of the most promising technologies in the field of aerodynamics,and it is also an important source of the innovation for novel aircraft.In this study,a new way of nonlinear flow control by interaction between two flexible flaps is proposed,and their flow control mechanism is studied employing the self-constructed immersed boundary-lattice Boltzmann-finite element method(IB-LB-FEM).The effects of the difference in material properties and flap length between the two flexible flaps on the nonlinear flow control of the airfoil are discussed.It is suggested that the relationship between the deformation of the two flexible flaps and the evolution of the vortex under the fluid-structure interaction(FSI).It is shown that the upstream flexible flap plays a key role in the flow control of the two flexible flaps.The FSI effect of the upstream flexible flap will change the unsteady flow behind it and affect the deformation of the downstream flexible flap.Two flexible flaps with different material properties and different lengths will change their own FSI characteristics by the induced vortex,effectively suppressing the flow separation on the airfoil’s upper surface.The interaction of two flexible flaps plays an extremely important role in improving the autonomy and adjustability of flow control.The numerical results will provide a theoretical basis and technical guidance for the development and application of a new flap passive control technology.展开更多
The formation,evolution,and dynamics of flow structures in wall-bounded turbulence have long been central themes in fluid-mechanics research.Over the past three decades,Soliton-like Coherent Structures(SCSs)have emerg...The formation,evolution,and dynamics of flow structures in wall-bounded turbulence have long been central themes in fluid-mechanics research.Over the past three decades,Soliton-like Coherent Structures(SCSs)have emerged as a ubiquitous and unifying feature across a wide range of shear flows,including K-type,O-type,N-type,and bypass transitional boundary layers,as well as fully developed turbulent boundary layers,mixing layers,and pipe flows.This paper presents a systematic review of the fundamental properties of SCSs and highlights their fundamental role in multiple transition scenarios.The analysis further explores the connection between SCSs and low-speed streaks,offering insight into their coupled dynamics.The phenomenon of turbulent bursting is also examined within the context of SCS dynamics.Together,these studies underscore the potential of SCSs to serve as a coherent dynamical framework for understanding turbulence generation mechanisms in wall-bounded flows.Finally,the review extends to the manifestation of SCSs in other canonical flows,including mixing layers,stratified shear flows,and jets,confirming their universality and significance in fluid dynamics.These findings not only advance our understanding of turbulence generation but also offer a promising theoretical foundation for future research in transitional and turbulent flows.展开更多
This paper investigates the uniaxial tensile mechanical properties and flow behavior of Ti-6Al-4V alloys with equiaxed microstructure at cryogenic temperatures ranging from 77 K to298 K and strain rates from 10^(-4)/s...This paper investigates the uniaxial tensile mechanical properties and flow behavior of Ti-6Al-4V alloys with equiaxed microstructure at cryogenic temperatures ranging from 77 K to298 K and strain rates from 10^(-4)/s to 10^(-2)/s.Scanning electron microscopy is utilized to analyze the fracture morphology,aiming to reveal the fracture behavior at various temperatures.The applicability of the Zener-Hollomon parameter and the Johnson-Cook model in describing the flow stress of Ti-6Al-4V at cryogenic temperatures is analyzed.Moreover,a constitutive relationship modeling method based on the variational recurrent networks is proposed.Mechanical test results show a significant increase in the strength of equiaxed Ti-6Al-4V alloy under cryogenic conditions while the plastic deformation process is shortened.However,the fracture analysis indicates that even at 77 K,the fracture process is still dominated by ductile fracture,and brittle fracture does not occur within the range of 77 K to 298 K.The fitting results validate the performance of the Zener-Hollomon parameter and the Johnson-Cook model in describing the deformation flow stress of Ti-6Al-4V alloy at cryogenic temperatures.The results also indicate that the proposed constitutive relationship modeling method based on the variational recurrent network performs better,making it a potential method for widespread applications.展开更多
This study sheds light on how pore structure characteristics and varying dynamic pressure conditions influence the permeability of tight sandstone reservoirs,with a particular focus on the Paleozoic reservoirs in the ...This study sheds light on how pore structure characteristics and varying dynamic pressure conditions influence the permeability of tight sandstone reservoirs,with a particular focus on the Paleozoic reservoirs in the Qingshimao Gas Field.Using CT scans of natural core samples,a three-dimensional digital core was constructed.The maximum ball method was applied to extract a related pore network model,and the pore structure characteristics of the core samples,such as pore radius,throat radius,pore volume,and coordination number,were quantitatively evaluated.The analysis revealed a normally distributed pore radius,suggesting a high degree of reservoir homogeneity and favorable conditions for a connected pore system.However,it was found that the majority of throat radii measured less than 1μm,which severely restricted fluid flow and diminished permeability.Over 50%of the pores measured under 100μm^(3),further constraining fluid movement.Additionally,30%-50%of the pore network was composed of isolated and blind-end pores,which significantly impaired formation connectivity and reduced permeability.Based on this,the lattice Boltzmann method(LBM)was used for pore-scale flow simulation to investigate the influence mechanism of pore structure characteristics and dynamic-static parameters such as displacement pressure difference on the permeability performance of the considered tight sandstone reservoirs for various pressure gradients(0.1,1,and 10 MPa).The simulations revealed a strong relationship between pressure differential and both the number of streamlines and flow path tortuosity.When the pressure differential increased to 1 MPa,30 streamlines were observed,with a tortuosity factor of 1.5,indicating the opening of additional seepage channels and the creation of increasingly winding flow paths.展开更多
Pinus koraiensis(Sieb.et Zucc.) is a coniferous tree species naturally distributed in northeastern China.However,the effects of gene flow on its genetic diversity and structure remain unclear.This study investigates t...Pinus koraiensis(Sieb.et Zucc.) is a coniferous tree species naturally distributed in northeastern China.However,the effects of gene flow on its genetic diversity and structure remain unclear.This study investigates these dynamics in seven populations using ten microsatellite markers.The results show a high level of genetic diversity within the populations(Ho=0.633,He=0.746).In addition,molecular analysis of variance(AMOVA) shows that 98% of genetic diversity occurs within populations,with minimal differentiation between populations(Fst=0.009-0.033).Gene flow analysis shows significant migration rates between specific population pairs,particularly C-TH(87%),LS-Y(69%) and TH-LS(69%),suggesting genetic homogenization.Bayesian clustering(STRUCTURE) supports admixture and weak population differentiation.Environmental factors,especially temperature-related variables,significantly influence genetic patterns.Partial Mantel tests and multiple matrix regression show strong correlations between genetic distance and adaptations to cold temperatures(bio6 and bio11).Overall,this study emphasizes the robust genetic diversification and high migration rates in the populations of P.koraiensis and highlights their resilience.These results emphasize the importance of incorporating genetic and ecological factors into conservation strategies for sustainable forest management.This research provides valuable insights into the complex interplay of genetic variation,gene flow and environmental influences in forest tree species and improves our understanding of their adaptive mechanisms.展开更多
Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5...Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5)CoCrFeNi high-entropy alloy(HEA)under electrically assisted compression(EAC)were investigated.The results showed that the flow stress decreased with increasing current density in the EAC.Specifically,the flow curves exhibited S-shaped softening at a higher current density,which was dominated by the non-uniform distribution of the Joule heating temperature during EAC.When the flow stress was fixed at 500 MPa and 80 A·mm^(−2),compressible deformation amounts of 63.7%were observed at a strain rate of 1 s−1,indicating full compression of Al_(0.5)CoCrFeNi HEA at low-stress levels.Based on the microstructure,the flowability of Al_(0.5)CoCrFeNi HEA was improved during EAC,and the flow direction shifted from 45°to the horizontal direction.The current density,which influences the Joule heating temperature and strain rate,synergistically affects the stacking fault energy(SFE)and critical resolved shear stress(CRSS),which affect the tendency for twinning behavior.Thererfore,deformation nanoscale twins(DTs)were observed,indicating a shift in the deformation mechanisms from dislocation slip domination to a mixed pattern of dislocation slip and twinning.This study confirmed the deformability of Al_(0.5)CoCrFeNi HEA during EAC and provided an experimental foundation and theoretical support for the formation of HEAs.展开更多
Cutting-edge research has primarily focused on flow synthesis of linear block copolymers,lacking the ability for manipulating chain architectures for more extensive applications.Herein,we develop a flow chemistry plat...Cutting-edge research has primarily focused on flow synthesis of linear block copolymers,lacking the ability for manipulating chain architectures for more extensive applications.Herein,we develop a flow chemistry platform for the continuous microflow synthesis of bottlebrush block copolymers(BBCPs)using a grafting-through method.This involves performing ring-opening metathesis polymerization(ROMP)of two different macromonomers within two microfluidic reactors connected in series.The microflow environment allows for complete monomer conversion within a few tens of seconds,benefiting from the superior mixing efficiency achieved in Z-shaped channels as indicated by both theoretical simulations and experimental results.Consequently,a library of well-defined BBCPs of up to 528 distinct samples can be produced within one day through automation of the continuous procedure,while keeping precise control on degree of polymerization(DP<4)and polydispersity indices(PDI<1.2).The synthetic method is generally applicable to different macromonomers with different compositions and contour lengths,yielding libraries of branched block copolymers with great diversity in physiochemical properties and chain architectures.This work presents a powerful platform for high-throughput production of branched copolymers,significantly lowering the costs of the materials for real applications.展开更多
Recently,significant progress has been made in conceptually describing the dynamic aspects of coarse particle entrainment,which has been explored experimentally for open channel flows.The aim of this study is to exten...Recently,significant progress has been made in conceptually describing the dynamic aspects of coarse particle entrainment,which has been explored experimentally for open channel flows.The aim of this study is to extend the application of energy criterion to the low mobility aeolian transport of solids(including both natural sediment and anthropogenic debris such as plastics),ranging from incomplete(rocking)to full(rolling)entrainments.This is achieved by linking particle movements to energetic flow events,which are defined as flow structures with the ability to work on particles,setting them into motion.It is hypothesized that such events should impart sufficient energy to the particles,above a certain threshold value.The concept’s validity is demonstrated experimentally,using a wind tunnel and laser distance sensor to capture the dynamics of an individual target particle,exposed on a rough bed surface.Measurements are acquired at a high spatiotemporal resolution,and synchronously with the instantaneous air velocity at an appropriate distance upwind of the target particle,using a hot film anemometer.This enables the association of flow events with rocking and rolling entrainments.Furthermore,it is shown that rocking and rolling may have distinct energy thresholds.Estimates of the energy transfer efficiency,normalized by the drag coefficient,range over an order of magnitude(from about 0.001 to 0.0048 for rocking,up to about 0.01,for incipient rolling).The proposed event-based theoretical framework is a novel approach to characterizing the energy imparted from the wind to the soil surface and could have potential implications for modelling intermittent creep transport of coarse particles and related aeolian bedforms.展开更多
Currently,the Al_(2)O_(3)content in the high-alumina slag systems within blast furnaces is generally limited to 16wt%–18.5wt%,making it challenging to overcome this limitation.Unlike most studies that concentrated on...Currently,the Al_(2)O_(3)content in the high-alumina slag systems within blast furnaces is generally limited to 16wt%–18.5wt%,making it challenging to overcome this limitation.Unlike most studies that concentrated on managing the MgO/Al_(2)O_(3)ratio or basicity,this paper explored the effect of equimolar substitution of MgO for CaO on the viscosity and structure of a high-alumina CaO-MgO-Al_(2)O_(3)-SiO_(2)slag system,providing theoretical guidance and data to facilitate the application of high-alumina ores.The results revealed that the viscosity first decreased and then increased with higher MgO substitution,reaching a minimum at 15mol%MgO concentration.Fourier transform infrared spectroscopy(FTIR)results found that the depths of the troughs representing[SiO_(4)]tetrahedra,[AlO_(4)]tetrahedra,and Si-O-Al bending became progressively deeper with increased MgO substitution.Deconvolution of the Raman spectra showed that the average number of bridging oxygens per Si atom and the X_(Q^(3))/X_(Q^(2))(X_(Q^(i))is the molar fraction of Q^(i) unit,and i is the number of bridging oxygens in a[SiO_(4)]tetrahedral unit)ratio increased from 2.30 and 1.02 to 2.52 and 2.14,respectively,indicating a progressive polymerization of the silicate structure.X-ray photoelectron spectroscopy(XPS)results highlighted that non-bridging oxygen content decreased from 77.97mol% to 63.41mol% with increasing MgO concentration,whereas bridging oxygen and free oxygen contents increased.Structural analysis demonstrated a gradual increase in the polymerization degree of the tetrahedral structure with the increase in MgO substitution.However,bond strength is another important factor affecting the slag viscosity.The occurrence of a viscosity minimum can be attributed to the complex evolution of bond strengths of non-bridging oxygens generated during depolymerization of the[SiO_(4)]and[AlO_(4)]tetrahedral structures by CaO and MgO.展开更多
With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite h...With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity.The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires(SiC_(nws))grown in situ,while boron nitride(BN)interfacial structure is introduced on graphene nanoplates.The unique composite structure forces multiple scattering of incident EMWs,ensuring the combined effects of interfacial polarization,conduction networks,and magnetic-dielectric synergy.Therefore,the as-prepared composites present a minimum reflection loss value of−37.8 dB and a wide effective absorption bandwidth(EAB)of 9.2 GHz(from 8.8 to 18.0 GHz)at 2.5 mm.Besides,relying on the intrinsic high-temperature resistance of SiC_(nws) and BN,the EAB also remains above 5.0 GHz after annealing in air environment at 600℃ for 10 h.展开更多
To expand the study on the structures and biological activities of the anthracyclines anticancer drugs and reduce their toxic side effects,the new anthraquinone derivatives,9‑pyridylanthrahydrazone(9‑PAH)and 9,10‑bisp...To expand the study on the structures and biological activities of the anthracyclines anticancer drugs and reduce their toxic side effects,the new anthraquinone derivatives,9‑pyridylanthrahydrazone(9‑PAH)and 9,10‑bispyridylanthrahydrazone(9,10‑PAH)were designed and synthesized.Utilizing 9‑PAH and 9,10‑PAH as promising anticancer ligands,their respective copper complexes,namely[Cu(L1)Cl_(2)]Cl(1)and{[Cu_(4)(μ_(2)‑Cl)_(3)Cl_(4)(9,10‑PAH)_(2)(DMSO)_(2)]Cl_(2)}_(n)(2),were subsequently synthesized,where the new ligand L1 is formed by coupling two 9‑PAH ligands in the coordination reaction.The chemical and crystal structures of 1 and 2 were elucidated by IR,MS,elemental analysis,and single‑crystal X‑ray diffraction.Complex 1 forms a mononuclear structure.L1 coordinates with Cu through its three N atoms,together with two Cl atoms,to form a five‑coordinated square pyramidal geometry.Complex 2 constitutes a polymeric structure,wherein each structural unit centrosymmetrically encompasses two five‑coordinated binuclear copper complexes(Cu1,Cu2)of 9,10‑PAH,with similar square pyramidal geometry.A chlorine atom(Cl_(2)),located at the symmetry center,bridges Cu1 and Cu1A to connect the two binuclear copper structures.Meanwhile,the two five‑coordinated Cu2 atoms symmetrically bridge the adjacent structural units via one coordinated Cl atom,respectively,thus forming a 1D chain‑like polymeric structure.In vitro anticancer activity assessments revealed that 1 and 2 showed significant cytotoxicity even higher than cisplatin.Specifically,the IC_(50)values of 2 against HeLa‑229 and SK‑OV‑3 cancer cell lines were determined to be(5.92±0.32)μmol·L^(-1)and(6.48±0.39)μmol·L^(-1),respectively.2 could also block the proliferation of HeLa‑229 cells in S phase and significantly induce cell apoptosis.In addition,fluorescence quenching competition experiments suggested that 2 might interact with DNA by an intercalative binding mode,offering insights into its underlying anticancer mechanism.CCDC:2388918,1;2388919,2.展开更多
Brazing filler metals are widely applied,which serve as an industrial adhesive in the joining of dissimilar structures.With the continuous emergence of new structures and materials,the demand for novel brazing filler ...Brazing filler metals are widely applied,which serve as an industrial adhesive in the joining of dissimilar structures.With the continuous emergence of new structures and materials,the demand for novel brazing filler metals is ever-increasing.It is of great significance to investigate the optimized composition design methods and to establish systematic design guidelines for brazing filler metals.This study elucidated the fundamental rules for the composition design of brazing filler metals from a three-dimensional perspective encompassing the basic properties of applied brazing filler metals,formability and processability,and overall cost.The basic properties of brazing filler metals refer to their mechanical properties,physicochemical properties,electromagnetic properties,corrosion resistance,and the wettability and fluidity during brazing.The formability and processability of brazing filler metals include the processes of smelting and casting,extrusion,rolling,drawing and ring-making,as well as the processes of granulation,powder production,and the molding of amorphous and microcrystalline structures.The cost of brazing filler metals corresponds to the sum of materials value and manufacturing cost.Improving the comprehensive properties of brazing filler metals requires a comprehensive and systematic consideration of design indicators.Highlighting the unique characteristics of brazing filler metals should focus on relevant technical indicators.Binary or ternary eutectic structures can effectively enhance the flow spreading ability of brazing filler metals,and solid solution structures contribute to the formability.By employing the proposed design guidelines,typical Ag based,Cu based,Zn based brazing filler metals,and Sn based solders were designed and successfully applied in major scientific and engineering projects.展开更多
As-forged WSTi6421 titanium alloy billet afterβannealing was investigated.Abnormally coarse grains larger than adjacent grains could be observed in the microstructures,forming abnormal grain structures with uneven si...As-forged WSTi6421 titanium alloy billet afterβannealing was investigated.Abnormally coarse grains larger than adjacent grains could be observed in the microstructures,forming abnormal grain structures with uneven size distribution.Through electron backscattered diffraction(EBSD),the forged microstructure at various locations of as-forged WSTi6421 titanium alloy billet was analyzed,revealing that the strength of theβphase cubic texture generated by forging significantly influences the grain size afterβannealing.Heat treatment experiments were conducted within the temperature range from T_(β)−50°C to T_(β)+10°C to observe the macro-and micro-morphologies.Results show that the cubic texture ofβphase caused by forging impacts the texture of the secondaryαphase,which subsequently influences theβphase formed during the post-βannealing process.Moreover,the pinning effect of the residual primaryαphase plays a crucial role in the growth ofβgrains during theβannealing process.EBSD analysis results suggest that the strength ofβphase with cubic texture formed during forging process impacts the orientation distribution differences ofβgrains afterβannealing.Additionally,the development of grains with large orientations within the cubic texture shows a certain degree of selectivity duringβannealing,which is affected by various factors,including the pinning effect of the primaryαphase,the strength of the matrix cubic texture,and the orientation relationship betweenβgrain and matrix.Comprehensively,the stronger the texture in a certain region,the less likely the large misoriented grains suffering secondary growth,thereby aggregating the difference in microstructure and grain orientation distribution across different regions afterβannealing.展开更多
The simulation of the ground effect has always been a technical difficulty in wind tunnel tests of high-speed trains.In this paper,large eddy simulation and the curl acoustic integral equation were used to simulate th...The simulation of the ground effect has always been a technical difficulty in wind tunnel tests of high-speed trains.In this paper,large eddy simulation and the curl acoustic integral equation were used to simulate the flow-acoustic field results of high-speed trains under four ground simulation systems(GSSs):“moving ground+rotating wheel”,“stationary ground+rotating wheel”,“moving ground+stationary wheel”,and“stationary ground+stationary wheel”.By comparing the fluid-acoustic field results of the four GSSs,the influence laws of different GSSs on the flow field structure,aero-acoustic source,and far-field radiation noise characteristics were investigated,providing guidance for the acoustic wind tunnel testing of high-speed trains.The calculation results of the aerodynamic noise of a 350 km/h high-speed train show that the moving ground and rotating wheel affect mainly the aero-acoustic performance under the train bottom.The influence of the rotating wheel on the equivalent sound source power of the whole vehicle was not more than 5%,but that of the moving ground slip was more than 15%.The average influence of the rotating wheel on the sound pressure level radiated by the whole vehicle was 0.3 dBA,while that of the moving ground was 1.8 dBA.展开更多
As the proportion of composite materials used in aircraft continues to increase, the electromagnetic Shielding Effectiveness (SE) of these materials becomes a critical factor in the electromagnetic safety design of ai...As the proportion of composite materials used in aircraft continues to increase, the electromagnetic Shielding Effectiveness (SE) of these materials becomes a critical factor in the electromagnetic safety design of aircraft structures. The assessment of electromagnetic SE for Slotted Composite Structures(SCSs) is particularly challenging due to their complex geometries and there remains a lack of suitable models for accurately predicting the SE performance of these intricate configurations. To address this issue, this paper introduces SCS-Net, a Deep Neural Network (DNN) method designed to accurately predict the SE of SCS. This method considers the impacts of various structural parameters, material properties and incident wave parameters on the SE of SCSs. In order to better model the SCS, an improved Nicolson-Ross-Weir (NRW) method is introduced in this paper to provide an equivalent flat structure for the SCS and to calculate the electromagnetic parameters of the equivalent structure. Additionally, the prediction of SE via DNNs is limited by insufficient test data, which hinders support for large-sample training. To address the issue of limited measured data, this paper develops a Measurement-Computation Fusion (MCF) dataset construction method. The predictions based on the simulation results show that the proposed method maintains an error of less than 0.07 dB within the 8–10 GHz frequency range. Furthermore, a new loss function based on the weighted L1-norm is established to improve the prediction accuracy for these parameters. Compared with traditional loss functions, the new loss function reduces the maximum prediction error for equivalent electromagnetic parameters by 47%. This method significantly improves the prediction accuracy of SCS-Net for measured data, with a maximum improvement of 23.88%. These findings demonstrate that the proposed method enables precise SE prediction and design for composite structures while reducing the number of test samples needed.展开更多
The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-...The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.展开更多
基金supported by the National Natural Science Foundation of China(Nos.22171180,22461142137,and 22478242)the Shanghai Municipal Science and Technology Major Project,China.
文摘Despite their attractive features of high energy density,low cost,and safety,polysulfide/iodide flow batteries(SIFBs)are hampered by the sluggish kinetics of the iodide redox couple,which restricts overall performance.Multicomponent sulfides are demonstrated as promising catalysts for accelerating I^(-)/I_(3)^(-) redox reactions.Concurrently,the enhanced configurational entropy arising from multinary compositions drives synergistic effects among constituent elements,establishing a viable pathway to optimize catalytic performance.Building on these foundations,this work introduces a targeted orbital hybridization-optimized electron density strategy to enhance the catalytic activity.Implementing this concept,we developed an in-situ solvothermal synthesis process for an entropy-enhanced AgCuZnSnS_(4) loaded graphite felt(ACZTS/GF)electrode.The engineered electrode demonstrates exceptional electrocatalytic performance with improved bulk conductivity and interfacial charge transfer kinetics within a SIFB.The cell achieves a high energy efficiency of 88.5%at 20 mA·cm^(−2) with 10%state-of-charge.Furthermore,the battery delivers a maximum power density of 119.8 mW·cm^(−2) and exhibits excellent long-term cycling stability.These significant results stem from orbital hybridization-driven electronic state optimization and entropy effect-induced synergistic catalysis.
基金funded by the National Natural Science Foundation of China(Grant No.52276047)the Open Fund of NationalKey Laboratory of SpacecraftThermal Control(Grant No.NKLST-JJ-202401011)the Beijing Municipal Science&Technology Commission(Grant No.Z231100006123010).
文摘Flow boiling in open microchannels offers highly efficient heat transfer performance and has attracted increasing attention in the fields of heat transfer and thermalmanagement of electronic devices in recent years.However,the continuous rise in power density of electronic components imposesmore stringent requirements on the heat transfer capability of microchannel flow boiling.HFE-7100,a dielectric coolant with favorable thermophysical properties,has become a focal point of research for enhancing flow boiling performance in open microchannels.The flow boiling heat transfer performance ofHFE-7100 was investigated in this study by fabricating micro-nano composite structures on the bottom surface of open microchannels using laser ablation technology.Based on visualization results,a comparative analysis was conducted on the bubble dynamics and flow pattern characteristics of HFE-7100 flow boiling in micronano structured open microchannels(MNSOMC)and smooth-surface open microchannels(SSOMC),to elucidate the enhancement mechanism of micro-nano structures on flow boiling heat transfer in open microchannels.The results indicate that the surface structures and strong wettability of MNSOMC accelerated bubble nucleation and departure.Moreover,bubbles in the channel tended to coalesce along the flow direction,forming elongated slug bubbles with high aspect ratios,which enabled efficient thin film evaporation in conjunction with intense nucleate boiling,thereby significantly enhancing flow boiling heat transfer.Under the experimental conditions of this study,the maximum enhancements in the heat transfer coefficient(HTC)and critical heat flux(CHF)of HFE-7100 inMNSOMC were 33.4%and 133.1%,respectively,with the CHF reaching up to 1542.3 kW⋅m^(−2).Furthermore,due to the superior wettability and capillary wicking capability of the micro-nano composite structures,the significant enhancement in flow boiling heat transfer was achieved without incurring a noticeable pressure drop penalty.
基金supported by the National Natural Science Foundation of China(Nos.U23A20583,52033005,U21A2090,and 52173040)Department of Science and Technology of Sichuan Province(No.2024NSFTD0003)。
文摘Poly(_(L)-lactide)(PLLA),a leading biodegradable polyester,has demonstrated potential as a sustainable alternative,owing to its excellent biodegradability and rigidity.However,their slow crystallization kinetics and poor heat resistance limit their application scope.Recent advances have highlighted that the combination of extensional flow and thermal fields can achieve toughness–stiffness balance,high transparency,and good heat resistance.However,the effect of extensional flow on the post-non-isothermal crystallization of PLLA during heating and the resulting crystalline texture remains unclear.In this study,PLLA with a heterogeneous amorphous structure and oriented polymorph was prepared by extensional flow.The effect of heterogeneous amorphous structures on non-isothermal crystallization kinetics during the heating process was studied by thermal analysis,polarized optical microscopy,infrared spectroscopy,and ex situ/in situ X-ray characterization.These results clearly illustrate that extensional flow enhances the formation of oriented crystalline structures,accelerates non-isothermal crystallization,and modulates the polymorphic composition of PLLA.Moreover,an unexpected dual cold-crystallization behavior is identified in ordered PLLA samples upon extensional flow,which is from the extensional flow-induced heterogeneous amorphous phase into α' phase(low-temperature peak)and the pristine amorphous phase intoαphase(high-temperature peak).The extensional flow primarily promotes the formation of the more perfectαandα'phases,but has a negative effect on the final content ofαphase formed after cold crystallization andα'-to-αphase transformation.The findings of this work advance the understanding of PLLA non-isothermal crystallization after extensional flow and offer valuable guidance for high-performance PLLA upon heat treatment in practical processing.
基金financially supported by the National Natural Science Foundation of China(51872090,51772097)Hebei Natural Science Fund for Distinguished Young Scholar(E2019209433)+3 种基金Youth Talent Program of Hebei Provincial Education Department(BJ2018020)Natural Science Foundation of Hebei Province(E2020209151,E2024209029)National Key R&D Plan Project(2022YFB4200305)Research Projects of China National Petroleum Corporation(2024ZG50,2023DQ03-04)。
文摘The sluggish electrochemical catalytic activity of the graphite felt electrodes for anode reaction is still a barrier for achieving high-performance vanadium redox flow battery(VRFB).It is significant to leverage the exceptional conductivity,excellent electrocatalytic activity,and structural tunability of MXene to address this issue.Herein,this work introduces nitrogen atoms to modulate the carbon layer structure of Ti_(3)C_(2)T_(x)MXene,inducing a reconfiguration of the local electronic structure,which enhances the anode interface activity and thereby improves the performance of VRFB.Ti_(3)C_(2)T_(x)exhibits high conductivity,excellent hydrophilicity,and a large specific surface area,providing excellent interface characteristics for V^(3+)/V^(2+)redox reaction.Moreover,interlayer treatment to modulate the mesoporous structure of MXene further increases the reactive surface area.Importantly,doping nitrogen atoms at carbon layer induces lattice distortions in Ti_(3)C_(2)T_(x),which enhances the charge transfer processes of the V^(3+)/V^(2+)redox reaction.The catalysis mechanism is also validated through density functional theory.Furthermore,the modified graphite felt electrode,as the anode of VRFB,relieves a higher energy efficiency of 68%at 250 mA cm^(-2),while the pristine electrode cannot operate at this current density.In addition,at 150 mA cm^(-2),the modified battery maintains energy efficiency at 75%without degradation after 500 cycles.This study utilizes rational atomic-level engineering for effective structural modulation to significantly enhance the catalytic activity of electrode reaction,offering a unique perspective for developing high-performance MXene electrocatalysts of VRFB.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.92371201,52192633,11872293,and 92152301)the Natural Science Basic Research Program of Shaanxi(Grant Nos.2024JC-YBQN-0008,and 2022JC-03)+1 种基金Shaanxi Key Research and Development Program(Grant No.2022ZDLGY02-07)the Joint Natural Science Foundation of China with Guangdong Province for TianHe-II Supercomputer Resources,and the Research Start-up Foundation of Xi’an University of Science and Technology for the High-Level Talent.
文摘The flow control at low Reynolds numbers is one of the most promising technologies in the field of aerodynamics,and it is also an important source of the innovation for novel aircraft.In this study,a new way of nonlinear flow control by interaction between two flexible flaps is proposed,and their flow control mechanism is studied employing the self-constructed immersed boundary-lattice Boltzmann-finite element method(IB-LB-FEM).The effects of the difference in material properties and flap length between the two flexible flaps on the nonlinear flow control of the airfoil are discussed.It is suggested that the relationship between the deformation of the two flexible flaps and the evolution of the vortex under the fluid-structure interaction(FSI).It is shown that the upstream flexible flap plays a key role in the flow control of the two flexible flaps.The FSI effect of the upstream flexible flap will change the unsteady flow behind it and affect the deformation of the downstream flexible flap.Two flexible flaps with different material properties and different lengths will change their own FSI characteristics by the induced vortex,effectively suppressing the flow separation on the airfoil’s upper surface.The interaction of two flexible flaps plays an extremely important role in improving the autonomy and adjustability of flow control.The numerical results will provide a theoretical basis and technical guidance for the development and application of a new flap passive control technology.
基金supported by the National Key Project(GJXM92579).
文摘The formation,evolution,and dynamics of flow structures in wall-bounded turbulence have long been central themes in fluid-mechanics research.Over the past three decades,Soliton-like Coherent Structures(SCSs)have emerged as a ubiquitous and unifying feature across a wide range of shear flows,including K-type,O-type,N-type,and bypass transitional boundary layers,as well as fully developed turbulent boundary layers,mixing layers,and pipe flows.This paper presents a systematic review of the fundamental properties of SCSs and highlights their fundamental role in multiple transition scenarios.The analysis further explores the connection between SCSs and low-speed streaks,offering insight into their coupled dynamics.The phenomenon of turbulent bursting is also examined within the context of SCS dynamics.Together,these studies underscore the potential of SCSs to serve as a coherent dynamical framework for understanding turbulence generation mechanisms in wall-bounded flows.Finally,the review extends to the manifestation of SCSs in other canonical flows,including mixing layers,stratified shear flows,and jets,confirming their universality and significance in fluid dynamics.These findings not only advance our understanding of turbulence generation but also offer a promising theoretical foundation for future research in transitional and turbulent flows.
基金supported by the National Natural Science Foundation of China(No.52275116)。
文摘This paper investigates the uniaxial tensile mechanical properties and flow behavior of Ti-6Al-4V alloys with equiaxed microstructure at cryogenic temperatures ranging from 77 K to298 K and strain rates from 10^(-4)/s to 10^(-2)/s.Scanning electron microscopy is utilized to analyze the fracture morphology,aiming to reveal the fracture behavior at various temperatures.The applicability of the Zener-Hollomon parameter and the Johnson-Cook model in describing the flow stress of Ti-6Al-4V at cryogenic temperatures is analyzed.Moreover,a constitutive relationship modeling method based on the variational recurrent networks is proposed.Mechanical test results show a significant increase in the strength of equiaxed Ti-6Al-4V alloy under cryogenic conditions while the plastic deformation process is shortened.However,the fracture analysis indicates that even at 77 K,the fracture process is still dominated by ductile fracture,and brittle fracture does not occur within the range of 77 K to 298 K.The fitting results validate the performance of the Zener-Hollomon parameter and the Johnson-Cook model in describing the deformation flow stress of Ti-6Al-4V alloy at cryogenic temperatures.The results also indicate that the proposed constitutive relationship modeling method based on the variational recurrent network performs better,making it a potential method for widespread applications.
文摘This study sheds light on how pore structure characteristics and varying dynamic pressure conditions influence the permeability of tight sandstone reservoirs,with a particular focus on the Paleozoic reservoirs in the Qingshimao Gas Field.Using CT scans of natural core samples,a three-dimensional digital core was constructed.The maximum ball method was applied to extract a related pore network model,and the pore structure characteristics of the core samples,such as pore radius,throat radius,pore volume,and coordination number,were quantitatively evaluated.The analysis revealed a normally distributed pore radius,suggesting a high degree of reservoir homogeneity and favorable conditions for a connected pore system.However,it was found that the majority of throat radii measured less than 1μm,which severely restricted fluid flow and diminished permeability.Over 50%of the pores measured under 100μm^(3),further constraining fluid movement.Additionally,30%-50%of the pore network was composed of isolated and blind-end pores,which significantly impaired formation connectivity and reduced permeability.Based on this,the lattice Boltzmann method(LBM)was used for pore-scale flow simulation to investigate the influence mechanism of pore structure characteristics and dynamic-static parameters such as displacement pressure difference on the permeability performance of the considered tight sandstone reservoirs for various pressure gradients(0.1,1,and 10 MPa).The simulations revealed a strong relationship between pressure differential and both the number of streamlines and flow path tortuosity.When the pressure differential increased to 1 MPa,30 streamlines were observed,with a tortuosity factor of 1.5,indicating the opening of additional seepage channels and the creation of increasingly winding flow paths.
基金funded by grants from the Innovation Project of the State Key Laboratory of Tree Genetics and Breeding(2021B01).
文摘Pinus koraiensis(Sieb.et Zucc.) is a coniferous tree species naturally distributed in northeastern China.However,the effects of gene flow on its genetic diversity and structure remain unclear.This study investigates these dynamics in seven populations using ten microsatellite markers.The results show a high level of genetic diversity within the populations(Ho=0.633,He=0.746).In addition,molecular analysis of variance(AMOVA) shows that 98% of genetic diversity occurs within populations,with minimal differentiation between populations(Fst=0.009-0.033).Gene flow analysis shows significant migration rates between specific population pairs,particularly C-TH(87%),LS-Y(69%) and TH-LS(69%),suggesting genetic homogenization.Bayesian clustering(STRUCTURE) supports admixture and weak population differentiation.Environmental factors,especially temperature-related variables,significantly influence genetic patterns.Partial Mantel tests and multiple matrix regression show strong correlations between genetic distance and adaptations to cold temperatures(bio6 and bio11).Overall,this study emphasizes the robust genetic diversification and high migration rates in the populations of P.koraiensis and highlights their resilience.These results emphasize the importance of incorporating genetic and ecological factors into conservation strategies for sustainable forest management.This research provides valuable insights into the complex interplay of genetic variation,gene flow and environmental influences in forest tree species and improves our understanding of their adaptive mechanisms.
基金supported by the National Natural Science Foundation of China(Nos.52305349,52305423 and 51635005)CGN-HIT Advanced Nuclear and New Energy Research Institute(No.CGN-HIT202305).
文摘Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5)CoCrFeNi high-entropy alloy(HEA)under electrically assisted compression(EAC)were investigated.The results showed that the flow stress decreased with increasing current density in the EAC.Specifically,the flow curves exhibited S-shaped softening at a higher current density,which was dominated by the non-uniform distribution of the Joule heating temperature during EAC.When the flow stress was fixed at 500 MPa and 80 A·mm^(−2),compressible deformation amounts of 63.7%were observed at a strain rate of 1 s−1,indicating full compression of Al_(0.5)CoCrFeNi HEA at low-stress levels.Based on the microstructure,the flowability of Al_(0.5)CoCrFeNi HEA was improved during EAC,and the flow direction shifted from 45°to the horizontal direction.The current density,which influences the Joule heating temperature and strain rate,synergistically affects the stacking fault energy(SFE)and critical resolved shear stress(CRSS),which affect the tendency for twinning behavior.Thererfore,deformation nanoscale twins(DTs)were observed,indicating a shift in the deformation mechanisms from dislocation slip domination to a mixed pattern of dislocation slip and twinning.This study confirmed the deformability of Al_(0.5)CoCrFeNi HEA during EAC and provided an experimental foundation and theoretical support for the formation of HEAs.
基金financially supported by the National Natural Science Foundation of China(No.22071176)。
文摘Cutting-edge research has primarily focused on flow synthesis of linear block copolymers,lacking the ability for manipulating chain architectures for more extensive applications.Herein,we develop a flow chemistry platform for the continuous microflow synthesis of bottlebrush block copolymers(BBCPs)using a grafting-through method.This involves performing ring-opening metathesis polymerization(ROMP)of two different macromonomers within two microfluidic reactors connected in series.The microflow environment allows for complete monomer conversion within a few tens of seconds,benefiting from the superior mixing efficiency achieved in Z-shaped channels as indicated by both theoretical simulations and experimental results.Consequently,a library of well-defined BBCPs of up to 528 distinct samples can be produced within one day through automation of the continuous procedure,while keeping precise control on degree of polymerization(DP<4)and polydispersity indices(PDI<1.2).The synthetic method is generally applicable to different macromonomers with different compositions and contour lengths,yielding libraries of branched block copolymers with great diversity in physiochemical properties and chain architectures.This work presents a powerful platform for high-throughput production of branched copolymers,significantly lowering the costs of the materials for real applications.
基金supported by the National Natural Science Foundation of China (Grants Nos.41171005,41071005,12272344,and 12350710176)the Ministry of Science and Technology of the People’s Republic of China (Grant No.2013CB956000).
文摘Recently,significant progress has been made in conceptually describing the dynamic aspects of coarse particle entrainment,which has been explored experimentally for open channel flows.The aim of this study is to extend the application of energy criterion to the low mobility aeolian transport of solids(including both natural sediment and anthropogenic debris such as plastics),ranging from incomplete(rocking)to full(rolling)entrainments.This is achieved by linking particle movements to energetic flow events,which are defined as flow structures with the ability to work on particles,setting them into motion.It is hypothesized that such events should impart sufficient energy to the particles,above a certain threshold value.The concept’s validity is demonstrated experimentally,using a wind tunnel and laser distance sensor to capture the dynamics of an individual target particle,exposed on a rough bed surface.Measurements are acquired at a high spatiotemporal resolution,and synchronously with the instantaneous air velocity at an appropriate distance upwind of the target particle,using a hot film anemometer.This enables the association of flow events with rocking and rolling entrainments.Furthermore,it is shown that rocking and rolling may have distinct energy thresholds.Estimates of the energy transfer efficiency,normalized by the drag coefficient,range over an order of magnitude(from about 0.001 to 0.0048 for rocking,up to about 0.01,for incipient rolling).The proposed event-based theoretical framework is a novel approach to characterizing the energy imparted from the wind to the soil surface and could have potential implications for modelling intermittent creep transport of coarse particles and related aeolian bedforms.
基金financially supported by the National Natural Science Foundation of China(Nos.52425408 and 52304345)the Fundamental Research Funds for the Central Universities,China(No.2023CDJXY-016)the Postdoctoral Science Foundation of Chongqing(No.CSTB2023NSCQ-BHX0174)。
文摘Currently,the Al_(2)O_(3)content in the high-alumina slag systems within blast furnaces is generally limited to 16wt%–18.5wt%,making it challenging to overcome this limitation.Unlike most studies that concentrated on managing the MgO/Al_(2)O_(3)ratio or basicity,this paper explored the effect of equimolar substitution of MgO for CaO on the viscosity and structure of a high-alumina CaO-MgO-Al_(2)O_(3)-SiO_(2)slag system,providing theoretical guidance and data to facilitate the application of high-alumina ores.The results revealed that the viscosity first decreased and then increased with higher MgO substitution,reaching a minimum at 15mol%MgO concentration.Fourier transform infrared spectroscopy(FTIR)results found that the depths of the troughs representing[SiO_(4)]tetrahedra,[AlO_(4)]tetrahedra,and Si-O-Al bending became progressively deeper with increased MgO substitution.Deconvolution of the Raman spectra showed that the average number of bridging oxygens per Si atom and the X_(Q^(3))/X_(Q^(2))(X_(Q^(i))is the molar fraction of Q^(i) unit,and i is the number of bridging oxygens in a[SiO_(4)]tetrahedral unit)ratio increased from 2.30 and 1.02 to 2.52 and 2.14,respectively,indicating a progressive polymerization of the silicate structure.X-ray photoelectron spectroscopy(XPS)results highlighted that non-bridging oxygen content decreased from 77.97mol% to 63.41mol% with increasing MgO concentration,whereas bridging oxygen and free oxygen contents increased.Structural analysis demonstrated a gradual increase in the polymerization degree of the tetrahedral structure with the increase in MgO substitution.However,bond strength is another important factor affecting the slag viscosity.The occurrence of a viscosity minimum can be attributed to the complex evolution of bond strengths of non-bridging oxygens generated during depolymerization of the[SiO_(4)]and[AlO_(4)]tetrahedral structures by CaO and MgO.
基金sponsored by National Natural Science Foundation of China(No.52302121,No.52203386)Shanghai Sailing Program(No.23YF1454700)+1 种基金Shanghai Natural Science Foundation(No.23ZR1472700)Shanghai Post-doctoral Excellent Program(No.2022664).
文摘With vigorous developments in nanotechnology,the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers.Herein,a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity.The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires(SiC_(nws))grown in situ,while boron nitride(BN)interfacial structure is introduced on graphene nanoplates.The unique composite structure forces multiple scattering of incident EMWs,ensuring the combined effects of interfacial polarization,conduction networks,and magnetic-dielectric synergy.Therefore,the as-prepared composites present a minimum reflection loss value of−37.8 dB and a wide effective absorption bandwidth(EAB)of 9.2 GHz(from 8.8 to 18.0 GHz)at 2.5 mm.Besides,relying on the intrinsic high-temperature resistance of SiC_(nws) and BN,the EAB also remains above 5.0 GHz after annealing in air environment at 600℃ for 10 h.
文摘To expand the study on the structures and biological activities of the anthracyclines anticancer drugs and reduce their toxic side effects,the new anthraquinone derivatives,9‑pyridylanthrahydrazone(9‑PAH)and 9,10‑bispyridylanthrahydrazone(9,10‑PAH)were designed and synthesized.Utilizing 9‑PAH and 9,10‑PAH as promising anticancer ligands,their respective copper complexes,namely[Cu(L1)Cl_(2)]Cl(1)and{[Cu_(4)(μ_(2)‑Cl)_(3)Cl_(4)(9,10‑PAH)_(2)(DMSO)_(2)]Cl_(2)}_(n)(2),were subsequently synthesized,where the new ligand L1 is formed by coupling two 9‑PAH ligands in the coordination reaction.The chemical and crystal structures of 1 and 2 were elucidated by IR,MS,elemental analysis,and single‑crystal X‑ray diffraction.Complex 1 forms a mononuclear structure.L1 coordinates with Cu through its three N atoms,together with two Cl atoms,to form a five‑coordinated square pyramidal geometry.Complex 2 constitutes a polymeric structure,wherein each structural unit centrosymmetrically encompasses two five‑coordinated binuclear copper complexes(Cu1,Cu2)of 9,10‑PAH,with similar square pyramidal geometry.A chlorine atom(Cl_(2)),located at the symmetry center,bridges Cu1 and Cu1A to connect the two binuclear copper structures.Meanwhile,the two five‑coordinated Cu2 atoms symmetrically bridge the adjacent structural units via one coordinated Cl atom,respectively,thus forming a 1D chain‑like polymeric structure.In vitro anticancer activity assessments revealed that 1 and 2 showed significant cytotoxicity even higher than cisplatin.Specifically,the IC_(50)values of 2 against HeLa‑229 and SK‑OV‑3 cancer cell lines were determined to be(5.92±0.32)μmol·L^(-1)and(6.48±0.39)μmol·L^(-1),respectively.2 could also block the proliferation of HeLa‑229 cells in S phase and significantly induce cell apoptosis.In addition,fluorescence quenching competition experiments suggested that 2 might interact with DNA by an intercalative binding mode,offering insights into its underlying anticancer mechanism.CCDC:2388918,1;2388919,2.
基金National Natural Science Foundation of China(U22A20191)。
文摘Brazing filler metals are widely applied,which serve as an industrial adhesive in the joining of dissimilar structures.With the continuous emergence of new structures and materials,the demand for novel brazing filler metals is ever-increasing.It is of great significance to investigate the optimized composition design methods and to establish systematic design guidelines for brazing filler metals.This study elucidated the fundamental rules for the composition design of brazing filler metals from a three-dimensional perspective encompassing the basic properties of applied brazing filler metals,formability and processability,and overall cost.The basic properties of brazing filler metals refer to their mechanical properties,physicochemical properties,electromagnetic properties,corrosion resistance,and the wettability and fluidity during brazing.The formability and processability of brazing filler metals include the processes of smelting and casting,extrusion,rolling,drawing and ring-making,as well as the processes of granulation,powder production,and the molding of amorphous and microcrystalline structures.The cost of brazing filler metals corresponds to the sum of materials value and manufacturing cost.Improving the comprehensive properties of brazing filler metals requires a comprehensive and systematic consideration of design indicators.Highlighting the unique characteristics of brazing filler metals should focus on relevant technical indicators.Binary or ternary eutectic structures can effectively enhance the flow spreading ability of brazing filler metals,and solid solution structures contribute to the formability.By employing the proposed design guidelines,typical Ag based,Cu based,Zn based brazing filler metals,and Sn based solders were designed and successfully applied in major scientific and engineering projects.
基金Key Research and Development Plan of Shaanxi Province(2023-YBGY-493)。
文摘As-forged WSTi6421 titanium alloy billet afterβannealing was investigated.Abnormally coarse grains larger than adjacent grains could be observed in the microstructures,forming abnormal grain structures with uneven size distribution.Through electron backscattered diffraction(EBSD),the forged microstructure at various locations of as-forged WSTi6421 titanium alloy billet was analyzed,revealing that the strength of theβphase cubic texture generated by forging significantly influences the grain size afterβannealing.Heat treatment experiments were conducted within the temperature range from T_(β)−50°C to T_(β)+10°C to observe the macro-and micro-morphologies.Results show that the cubic texture ofβphase caused by forging impacts the texture of the secondaryαphase,which subsequently influences theβphase formed during the post-βannealing process.Moreover,the pinning effect of the residual primaryαphase plays a crucial role in the growth ofβgrains during theβannealing process.EBSD analysis results suggest that the strength ofβphase with cubic texture formed during forging process impacts the orientation distribution differences ofβgrains afterβannealing.Additionally,the development of grains with large orientations within the cubic texture shows a certain degree of selectivity duringβannealing,which is affected by various factors,including the pinning effect of the primaryαphase,the strength of the matrix cubic texture,and the orientation relationship betweenβgrain and matrix.Comprehensively,the stronger the texture in a certain region,the less likely the large misoriented grains suffering secondary growth,thereby aggregating the difference in microstructure and grain orientation distribution across different regions afterβannealing.
基金This work is supported by the National Natural Science Foundation of China(No.52272363)the Foundation of the Key Laboratory of Aerodynamic Noise Control(No.ANCL20200302),China.
文摘The simulation of the ground effect has always been a technical difficulty in wind tunnel tests of high-speed trains.In this paper,large eddy simulation and the curl acoustic integral equation were used to simulate the flow-acoustic field results of high-speed trains under four ground simulation systems(GSSs):“moving ground+rotating wheel”,“stationary ground+rotating wheel”,“moving ground+stationary wheel”,and“stationary ground+stationary wheel”.By comparing the fluid-acoustic field results of the four GSSs,the influence laws of different GSSs on the flow field structure,aero-acoustic source,and far-field radiation noise characteristics were investigated,providing guidance for the acoustic wind tunnel testing of high-speed trains.The calculation results of the aerodynamic noise of a 350 km/h high-speed train show that the moving ground and rotating wheel affect mainly the aero-acoustic performance under the train bottom.The influence of the rotating wheel on the equivalent sound source power of the whole vehicle was not more than 5%,but that of the moving ground slip was more than 15%.The average influence of the rotating wheel on the sound pressure level radiated by the whole vehicle was 0.3 dBA,while that of the moving ground was 1.8 dBA.
基金supported by the National Natural Science Foundation of China(Nos.62101020 and 62141405)the Special Scientific Research Project of Civil Aircraft,China(No.MJZ5-2N22).
文摘As the proportion of composite materials used in aircraft continues to increase, the electromagnetic Shielding Effectiveness (SE) of these materials becomes a critical factor in the electromagnetic safety design of aircraft structures. The assessment of electromagnetic SE for Slotted Composite Structures(SCSs) is particularly challenging due to their complex geometries and there remains a lack of suitable models for accurately predicting the SE performance of these intricate configurations. To address this issue, this paper introduces SCS-Net, a Deep Neural Network (DNN) method designed to accurately predict the SE of SCS. This method considers the impacts of various structural parameters, material properties and incident wave parameters on the SE of SCSs. In order to better model the SCS, an improved Nicolson-Ross-Weir (NRW) method is introduced in this paper to provide an equivalent flat structure for the SCS and to calculate the electromagnetic parameters of the equivalent structure. Additionally, the prediction of SE via DNNs is limited by insufficient test data, which hinders support for large-sample training. To address the issue of limited measured data, this paper develops a Measurement-Computation Fusion (MCF) dataset construction method. The predictions based on the simulation results show that the proposed method maintains an error of less than 0.07 dB within the 8–10 GHz frequency range. Furthermore, a new loss function based on the weighted L1-norm is established to improve the prediction accuracy for these parameters. Compared with traditional loss functions, the new loss function reduces the maximum prediction error for equivalent electromagnetic parameters by 47%. This method significantly improves the prediction accuracy of SCS-Net for measured data, with a maximum improvement of 23.88%. These findings demonstrate that the proposed method enables precise SE prediction and design for composite structures while reducing the number of test samples needed.
基金sponsored by the National Natural Science Foundation of China(Nos.5210125 and 52375422)the Science Research Project of Hebei Education Department(No.BJK2023058)the Natural Science Foundation of Hebei Province(Nos.E2020208069,B2020208083 and E202320801).
文摘The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.
