The remarkable ability of titanium alloys to preserve their superior physical and chemical characteristics when subjected to extreme conditions significantly enhances their importance in the aerospace,military,and med...The remarkable ability of titanium alloys to preserve their superior physical and chemical characteristics when subjected to extreme conditions significantly enhances their importance in the aerospace,military,and medical sectors.However,conventional machining of titanium alloys leads to elevated tool wear,development of surface defects,and reduced machining efficiency due to their low heat conductivity,and chemical affinity.These issues can be somewhat counteracted by integrating ultrasonic vibration in the conventional machining of titanium alloys and also enhance sustainability.This review article offers a holistic evaluation of the influence of ultrasonic vibration-assisted milling and turning on cutting forces,temperature,tool wear,and surface integrity,encompassing surface morphology,surface roughness,surface residual stress,surface hardness,and surface tribological properties during titanium alloys machining.Furthermore,it investigates the sustainability aspect that has not been previously examined.Studies on the performance of ultrasonic-assisted cutting revealed several advantages,including decreased cutting forces and cutting temperature,improved tool life,and a better-machined surface during machining.Consequently,the sustainability factor is improved due to minimized energy consumption and residual waste.In conclusion,the key challenges and future prospects in the ultrasonic-assisted cutting of titanium alloys are also discussed.This review article provides beneficial knowledge for manufactur-ers and researchers regarding ultrasonic vibration-assisted cutting of titanium alloy and will play an important role in achieving sustainability in the industry.展开更多
Minimum quantity lubrication(MQL),as a new sustainable and eco-friendly alternative cooling/lubrication technology that addresses the limitations of dry and wet machining,utilizes a small amount of lubricant or coolan...Minimum quantity lubrication(MQL),as a new sustainable and eco-friendly alternative cooling/lubrication technology that addresses the limitations of dry and wet machining,utilizes a small amount of lubricant or coolant to reduce friction,tool wear,and heat during cutting processes.MQL technique has witnessed significant developments in recent years,such as combining MQL with other sustainable techniques to achieve optimum results,using biodegradable lubricants,and innovations in nozzle designs and delivery methods.This review presents an in-depth analysis of machining characteristics(e.g.,cutting forces,temperature,tool wear,chip morphology and surface integrity,etc.)and sustainability characteristics(e.g.,energy consumption,carbon emissions,processing time,machining cost,etc.)of conventional MQL and hybrid MQL techniques like cryogenic MQL,Ranque-Hilsch vortex tube MQL,nanofluids MQL,hybrid nanofluid MQL and ultrasonic vibration assisted MQL in machining of aeronautical materials.Subsequently,the latest research and developments are analyzed and summarized in the field of MQL,and provide a detailed comparison between each technique,considering advantages,challenges,and limitations in practical implementation.In addition,this review serves as a valuable source for researchers and engineers to optimize machining processes while minimizing environmental impact and operational costs.Ultimately,the potential future aspects of MQL for research and industrial execution are discussed.展开更多
The T_(1)(Al_(2) CuLi)phase is one of the most effective strengthening nanoscale-precipitate in Al-Cu alloys with Li.However,its formation and evolution still need to be further clarified during aging due to the compl...The T_(1)(Al_(2) CuLi)phase is one of the most effective strengthening nanoscale-precipitate in Al-Cu alloys with Li.However,its formation and evolution still need to be further clarified during aging due to the complex precipitation sequences.Here,a detailed investigation has been carried out on the atomic struc-tural evolution of T_(1) precipitate in an aged Al-Cu-Li-Mg-Ag alloy using state-of-the-art Cs-corrected high-angle annular dark field(HAADF)-coupled with integrated differential phase contrast(iDPC)-scanning transmission electron microscopy(STEM)and energy-dispersive X-ray spectroscopy(EDXS)techniques.An intermediate T_(1)’phase between T_(1p) and T_(1) phase,with a crystal structure and orientation rela-tionship consistent with T_(1),but exhibiting different atomic occupancy and chemical composition was found.We observed the atomic structural transformation from T_(1p) to T_(1)’phase(fcc→hcp),involving only 1/12<112>Al shear component.DFT calculation results validated our proposed structural models and the precipitation sequence.Besides,the distributions of minor solute elements(Ag,Mg,and Zn)in the pre-cipitates exhibited significant differences.These findings may contribute to a further understanding of the nucleation mechanism of T_(1) precipitate.展开更多
Agrobacterium tumefaciens-mediated transformation has been widely adopted for plant genetic engineering and the study of gene function(Krenek et al.,2015).This method is prevalent in the genetic transformation of herb...Agrobacterium tumefaciens-mediated transformation has been widely adopted for plant genetic engineering and the study of gene function(Krenek et al.,2015).This method is prevalent in the genetic transformation of herbaceous plants,with notable applications in species such as Arabidopsis(Yin et al.,2024),soybean(Zhang et al.,2024),rice(Zhang et al.,2020),and Chinese cabbage(Li et al.,2021).However,its application in fruit trees is limited.This is primarily due to their long growth cycles and lack of rapid,efficient,and stable transgenic systems,which severely hinders foundational research involving plant genetic transformation(Mei et al.,2024).Furthermore,for subtropical fruit trees,the presence of recalcitrant seeds adds an extra layer of difficulty to genetic transformation(Umarani et al.,2015),as most methods rely on seed germination as a basis for transformation.展开更多
Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising techn...Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising technology to achieve high efficiency,because it has high machining flexibility and no machining tool wear.However,reports on the macro electrochemical jet machining of large size titanium alloy parts are very scarce,because it is difficult to achieve effective constraint of the flow field in macro electrochemical jet machining.In addition,titanium alloy is very sensitive to fluctuation of the flow field,and a turbulent flow field would lead to serious stray corrosion.This paper reports a series of investigations of the electrochemical jet machining of titanium alloy parts.Based on the flow analysis and experiments,the machining flow field was effectively constrained.TB6 titanium alloy part with a perimeter of one meter was machined.The machined surface was smooth with no obvious machining defects.The machining process was particularly stable with no obvious spark discharge.The research provides a reference for the application of electrochemical jet machining technology to achieve large allowance material removal in the machining of large titanium alloy parts.展开更多
This study aims to clarify the mechanisms for the grain boundary(GB)segregation through investigating the absorption of excess solute atoms at GBs in Al−Cu alloys by using the hybrid molecular dynamics/Monte Carlo sim...This study aims to clarify the mechanisms for the grain boundary(GB)segregation through investigating the absorption of excess solute atoms at GBs in Al−Cu alloys by using the hybrid molecular dynamics/Monte Carlo simulations.Two segregation mechanisms,substitutional and interstitial mechanisms,are observed.The intergranular defects,including dislocations,steps and vacancies,and the intervals in structural units are conductive to the prevalence of interstitial mechanism.And substitutional mechanism is favored by the highly ordered twin GBs.Furthermore,the two mechanisms affect the GB structure differently.It is quantified that interstitial mechanism is less destructive to GB structure than substitutional one,and often leads to a segregation level being up to about 6 times higher than the latter.These findings contribute to atomic scale insights into the microscopic mechanisms about how solute atoms are absorbed by GB structures,and clarify the correlation among intergranular structures,segregation mechanisms and kinetics.展开更多
Alzheimer's disease,a progressively degenerative neurological disorder,is the most common cause of dementia in the elderly.While its precise etiology remains unclear,researchers have identified diverse pathologica...Alzheimer's disease,a progressively degenerative neurological disorder,is the most common cause of dementia in the elderly.While its precise etiology remains unclear,researchers have identified diverse pathological characteristics and molecular pathways associated with its progression.Advances in scientific research have increasingly highlighted the crucial role of non-coding RNAs in the progression of Alzheimer's disease.These non-coding RNAs regulate several biological processes critical to the advancement of the disease,offering promising potential as therapeutic targets and diagnostic biomarkers.Therefore,this review aims to investigate the underlying mechanisms of Alzheimer's disease onset,with a particular focus on microRNAs,long non-coding RNAs,and circular RNAs associated with the disease.The review elucidates the potential pathogenic processes of Alzheimer's disease and provides a detailed description of the synthesis mechanisms of the three aforementioned non-coding RNAs.It comprehensively summarizes the various non-coding RNAs that have been identified to play key regulatory roles in Alzheimer's disease,as well as how these noncoding RNAs influence the disease's progression by regulating gene expression and protein functions.For example,miR-9 targets the UBE4B gene,promoting autophagy-mediated degradation of Tau protein,thereby reducing Tau accumulation and delaying Alzheimer's disease progression.Conversely,the long non-coding RNA BACE1-AS stabilizes BACE1 mRNA,promoting the generation of amyloid-βand accelerating Alzheimer's disease development.Additionally,circular RNAs play significant roles in regulating neuroinflammatory responses.By integrating insights from these regulatory mechanisms,there is potential to discover new therapeutic targets and potential biomarkers for early detection and management of Alzheimer's disease.This review aims to enhance the understanding of the relationship between Alzheimer's disease and non-coding RNAs,potentially paving the way for early detection and novel treatment strategies.展开更多
In this work,a novel surface strengthening strategy for Mg-Li alloys was proposed,called cold spraying assisted high-speed laser cladding.CuAl9 aluminum bronze coating was firstly deposited on Mg-Li alloy by cold spra...In this work,a novel surface strengthening strategy for Mg-Li alloys was proposed,called cold spraying assisted high-speed laser cladding.CuAl9 aluminum bronze coating was firstly deposited on Mg-Li alloy by cold spraying,and then CoCrFe_(0.5)Ni_(1.5)Mo_(0.1)Nb_(0.68)eutectic highentropy alloy(EHEA)coating was prepared on the CuAl9 coating utilizing high-speed laser cladding.A gradient coating consisted of in-situ transition region and EHEA layer formed by bidirectional diffusion.The in-situ transition region was composed ofβ-Li,Cu_(2)Mg and Cu_(3)Al_(2)phases.TEM analysis indicated that Cu_(2)Mg and Cu_(3)Al_(2)phases were well matched with theβ-Li matrix phase.The EHEA coating had a nano-lamellar eutectic microstructure with relatively small lamellar-spacing(<100 nm).Metallurgical bonding interfaces formed between the EHEA coating,transition region and Mg-Li substrate.The evolution mechanism of the coating was revealed from the perspectives of mixing enthalpy,atomic radius difference and laser energy distribution.In 3.5 wt.%NaCl solution,the corrosion potential of the EHEA coating(-24 m VSHE)was 1345 m VSHEhigher than that of Mg-Li alloy(-1369 m VSHE),while the corrosion current density of the EHEA coating(3.13×10^(-7)A·cm^(-2))was almost three orders of magnitude lower than that of Mg-Li alloy(1.25×10^(-4)A·cm^(-2)).The wear rate of Mg-Li alloy(1.11×10^(-3)mm^(3)/N·m)was about 36 times higher than that of the EHEA coating(3.05×10^(-5)mm^(3)/N·m).展开更多
During high-speed rotation,the surface of aeronautic spiral bevel gears will generate significant pressure and viscous forces,which will cause a certain amount of windage power loss and reduce the efficiency of the tr...During high-speed rotation,the surface of aeronautic spiral bevel gears will generate significant pressure and viscous forces,which will cause a certain amount of windage power loss and reduce the efficiency of the transmission system.Based on the computational fluid dynamics,this paper analyzes the windage power loss of a single spiral bevel gear and a spiral bevel gear pair under oil injection lubrication.In addition,the shroud is used to suppress gear windage loss,and the clearance size and opening angle of the designed shroud are optimized.Finally,by comparing and analyzing the experimental results,the following conclusions were obtained:(1)For a single gear,the speed is the most important factor affecting windage loss,followed by the hand of spiral,and rotation direction;(2)For gear pairs,under oil injection lubrication,the input speed has the greatest impact on windage power loss,followed by the influence of oil injection port speed,temperature and oil injection port pressure;(3)Installing a shroud is an effective method to reduce windage power loss;(4)In the pure air phase,the smaller the clearance between the shroud and the gear surface,and the smaller the radial direction between the shroud and the shaft,the better the effect of reducing windage;(5)In the two-phase flow of oil and gas,it is necessary to design oil drainage holes on the shroud to ensure the smooth discharge of lubricating oil and improve the drag reduction effect.展开更多
In the last decade,space solar power satellites(SSPSs)have been conceived to support net-zero carbon emissions and have attracted considerable attention.Electric energy is transmitted to the ground via a microwave pow...In the last decade,space solar power satellites(SSPSs)have been conceived to support net-zero carbon emissions and have attracted considerable attention.Electric energy is transmitted to the ground via a microwave power beam,a technology known as microwave power transmission(MPT).Due to the vast transmission distance of tens of thousands of kilometers,the power transmitting antenna array must span up to 1 kilometer in diameter.At the same time,the size of the rectifying array on the ground should extend over a few kilometers.This makes the MPT system of SSPSs significantly larger than the existing aerospace engineering system.To design and operate a rational MPT system,comprehensive optimization is required.Taking the space MPT system engineering into consideration,a novel multi-objective optimization function is proposed and further analyzed.The multi-objective optimization problem is modeled mathematically.Beam collection efficiency(BCE)is the primary factor,followed by the thermal management capability.Some tapers,designed to solve the conflict between BCE and the thermal problem,are reviewed.In addition to these two factors,rectenna design complexity is included as a functional factor in the optimization objective.Weight coefficients are assigned to these factors to prioritize them.Radiating planar arrays with different aperture illumination fields are studied,and their performances are compared using the multi-objective optimization function.Transmitting array size,rectifying array size,transmission distance,and transmitted power remaine constant in various cases,ensuring fair comparisons.The analysis results show that the proposed optimization function is effective in optimizing and selecting the MPT system architecture.It is also noted that the multi-objective optimization function can be expanded to include other factors in the future.展开更多
Lithium-air batteries(LABs)are regarded as a next-generation energy storage option due to their relatively high energy density.The cyclic stability and lifespan of LABs are mainly influenced by the formation and decom...Lithium-air batteries(LABs)are regarded as a next-generation energy storage option due to their relatively high energy density.The cyclic stability and lifespan of LABs are mainly influenced by the formation and decomposition of lithium-based oxides at the air cathode,which not only lead to a low cathode catalytic efficiency but also restrict the electrochemical reversibility and cause side reaction problems.Carbon materials are considered key to solving these problems due to their conductivity,functional flexibility,and adjustable pore structure.This paper considers the research progress on carbon materials as air cathode catalytic materials for LABs,focusing on their structural characteristics,electrochemical behavior,and reaction mechanisms.Besides being used as air cathodes,carbon materials also show potential for being used as protective layers for metal anodes or as anode materials for LABs.展开更多
The strength improvement in the heat-treatable Al-Zn-Mg-Cu alloys is generally achieved by increasing the volume fraction of nanoprecipitates and reducing the grain size.However,utilizing one of them usu-ally leads to...The strength improvement in the heat-treatable Al-Zn-Mg-Cu alloys is generally achieved by increasing the volume fraction of nanoprecipitates and reducing the grain size.However,utilizing one of them usu-ally leads to a drastic decrease in ductility.Herein,we architect a hierarchical microstructure integrating bimodal grain structures,nanoprecipitates,and hard-brittle coarse particles wrapped by ductility coarse grain(CG)bands via conventional cold rolling(CR)deformation and heat treatment methods to break the strength-ductility dilemma in the Al-8.89Zn-1.98Mg-2.06Cu-0.12Zr-0.05Sc-0.05Hf(wt.%)alloy.The results reveal that the coupling of high-volume fraction(∼1.2%)nanoprecipitates,∼52%narrow CG bands,and most coarse particles encapsulated by CG bands contribute to the 45%CR sample with outstanding over-all mechanical properties(a tensile strength of 655 MPa,a yield strength of 620 MPa,and an elongation of 15.5%).Microstructure-based strength analysis confirms that the high strength relates to a trade-offbetween the hierarchical features,namely high-volume fraction nanoprecipitates to counterbalance the strength loss caused by grain coarsening.The excellent ductility is due to the introduction of medium CG content with a narrow width that can trigger a cross-scale strain distribution during plastic deforma-tion,suppressing the catastrophic failure in the fine grain(FG)regions and facilitating the dimple fracture along the CG bands.This study proposes a feasible approach for tailoring hierarchical microstructures in Al-Zn-Mg-Cu alloys to achieve a superior strength-ductility combination.展开更多
Continuous Fiber-reinforced Metal Matrix Composites(CFMMCs),such as Si C fiberreinforced TC17 matrix composites(SiC_(f)/TC17),are renowned for their exceptional mechanical properties.However,their heterogeneous compos...Continuous Fiber-reinforced Metal Matrix Composites(CFMMCs),such as Si C fiberreinforced TC17 matrix composites(SiC_(f)/TC17),are renowned for their exceptional mechanical properties.However,their heterogeneous compositions present significant machining challenges,including fiber pullout,matrix cracking,and accelerated tool wear.Ultrasonic Vibration-Assisted Grinding(UVAG)has proven to be an effective technique for overcoming these challenges.The material removal mechanisms in UVAG,especially in composites with both ductile and brittle phases,remain poorly understood.To explore these issues,UVAG and Conventional Grinding(CG)experiments were conducted on SiC_(f)/TC17 along two grinding directions:fiber's transverse direction(FT)and fiber's longitudinal direction(FL).This paper aims to provide a new dynamic mechanical model and shed light on the complex removal mechanisms in CFMMCs,which are characterized by a near one-to-one alternation of ductile and brittle phases.The findings reveal that UVAG reduces fiber damage and surface roughness compared to CG,especially when grinding along FT.UVAG lowers normal(F_(n))and tangential grinding forces(F_(t))by 15.3%and 12.3%,respectively.This highlights UVAG's potential for improving the machinability of complex materials like CFMMCs.The proposed grinding force model closely matches the experimental results.This paper hopes to support the precision abrasive machining of CFMMCs,a kind of complex and highly anisotropic composite material,and promote their application in the fields such as aerospace.展开更多
With the upgrade of armor protection materials,higher requirements are put forward for the penetration performance of tungsten alloy kinetic energy armor-piercing projectiles,and the penetration performance is closely...With the upgrade of armor protection materials,higher requirements are put forward for the penetration performance of tungsten alloy kinetic energy armor-piercing projectiles,and the penetration performance is closely related to the adiabatic shear band under extreme stress conditions.Here,the detailed analysis of the adiabatic shear band microstructure evolution of a dual-phase 90W-Ni-Fe alloy under a high strain rate was conducted by combining advanced electron microscopic characterization,while discussing shear fracture from a mechanical perspective under thermoplastic instability.The high temperature and high stress environment inside the adiabatic shear band led to the refinement of the W phase andγ-(Ni,Fe)phase grains to the submicron level,and induced the elements redistribution of W,Ni,and Fe to precipitate W nanocrystalline with hardness as high as 11.7 GPa along the recrystallization grain boundaries of theγ-(Ni,Fe)phase.Mechanical incompatibility caused by the hardness difference between W nanocrystalline andγ-(Ni,Fe)phases led to a strain gradient at the interface.The microvoids preferentially nucleated at the W nanocrystalline/γ-(Ni,Fe)phase interface,then merged to form microcracks and grew further,leading to shear failure.展开更多
Dyeing wastewater poses a serious threat to environmental protection and industrial development.The piezoelectric effect can be used to optimize the band structure of semiconductors and improve the photon efficiency o...Dyeing wastewater poses a serious threat to environmental protection and industrial development.The piezoelectric effect can be used to optimize the band structure of semiconductors and improve the photon efficiency of photocatalysts.Bi_(2)Fe_(4)O_(9),a narrow gap semiconductor with piezoelectric effect,was prepared by a hydrothermal synthesis method for the degradation of reactive dye KN-R.The results show that the degradation efficiency of KN-R can be significantly improved by piezo-photocatalysis,and the degradation rate constant of piezo-photocatalysis k_(pi-ph)is about 3.4 times as large as the degradation rate constant of piezoelectric catalysis k_(pi)and about 2.6 times as large as the degradation rate constant of photocatalysis k_(ph).At a pH value of 3 and a lower KN-R mass concentration(60 mg/L),a higher degradation efficiency(98.5%)is achieved.CO_(3)^(2-)and cationic surfactant(CTAB)inhibit the degradation of KN-R.It is proved that the contributions of different active species to the degradation of KN-R follow the order:·OH,·O_(2)^(-),h^(+),and^(1)O_(2).The possible mechanism of piezo-photocatalytic degradation of KN-R was discussed.The photoexcitation generates a large amount of free charges,and the piezoelectric effect modulates the energy band structure of Bi_(2)Fe_(4)O_(9)and promotes the separation of photogenerated electron-hole pairs.The synergistic effect of the two factors significantly improves the degradation efficiency of KN-R.展开更多
The pronounced anisotropy in mechanical properties presents a major obstacle to the extensive application of aluminum-lithium(Al-Li)alloys,primarily attributed to heterogeneous precipitate distribution,grain structure...The pronounced anisotropy in mechanical properties presents a major obstacle to the extensive application of aluminum-lithium(Al-Li)alloys,primarily attributed to heterogeneous precipitate distribution,grain structure variations,and crystallographic texture.This study investigates the impact of pre-thermal treatment prior to hot rolling and aging treatment on the anisotropy of mechanical properties of 2195 alloy sheet fabricated by gas atomization,hot pressing and hot rolling.The results demonstrate that pre-treatment at 450℃for 4 h promotes finer and more uniform distribution of precipitates,effectively mitigating mechanical anisotropy of the alloy sheet.Additionally,this treatment facilitates recrystallization during hot rolling,further reducing mechanical anisotropy.The in-plane anisotropy(IPA)factors for ultimate tensile strength(UTS)and yield strength(YS)are 1.15%and 0.77%,respectively.Subsequent aging treatment enhances grain refinement and the uniformity of the T_(1) phase,suppresses the formation of precipitation-free zones(PFZs),significantly improving the strength and toughness of the alloy sheet.After peak aging at 165℃for 48 h,the alloy sheet exhibits YS of 547 MPa,UTS of 590 MPa,and elongation(EL)of 7.7%.展开更多
Flapping-Wing Micro Air Vehicles(FMAVs)are compact and agile,capable of accessing narrow spaces that conventional vehicles struggle to reach,such as ruins,caves,or the interiors of complex structures,making them ideal...Flapping-Wing Micro Air Vehicles(FMAVs)are compact and agile,capable of accessing narrow spaces that conventional vehicles struggle to reach,such as ruins,caves,or the interiors of complex structures,making them ideal tools for reconnaissance and rescue missions.1 However,the operation of FMAVs relies on coordinating multiple forces with different scaling effects,posing challenges to miniaturization design.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
The direct deoxygenative homo-coupling of benzyl alcohols holds great promise to build up bibenzyl motifs in organic synthesis,yet it remains a grand challenge in selectivity and activity control.Herein,we first disco...The direct deoxygenative homo-coupling of benzyl alcohols holds great promise to build up bibenzyl motifs in organic synthesis,yet it remains a grand challenge in selectivity and activity control.Herein,we first discovered that iron carbide catalysts displayed high efficiency and selectivity in the catalytic deoxygenative homo-coupling of benzyl alcohols into bibenzyls using H_(2)as the reductant.Ir-promoted Fe0@Fe_(5)C_(2)gave the best performance among the investigated catalysts,and a broad scope of substrates with diverse functional groups could be smoothly converted into bibenzyls,with the yield up to 85%.In addition,in the presence of alkenes,three-component coupling reactions between alcohols and alkenes were also for the first time achieved to construct more complex multi-ring molecules.The radical-trapping experiment and FTIR measurements revealed the radical nature of the reaction and the significantly promoted C–O bond activation after carbonization,respectively.This work will provide guidelines for the rational design of efficient and selective catalysts for the alcohol-involved carbon-carbon coupling reactions.展开更多
High-energy-density(HED)fuel(e.g.widely used JP-10 and RJ-4),featuring compact 3D polycyclic structure with high strain,is of critical importance for volume-limited military aircraft,since their high density and combu...High-energy-density(HED)fuel(e.g.widely used JP-10 and RJ-4),featuring compact 3D polycyclic structure with high strain,is of critical importance for volume-limited military aircraft,since their high density and combustion heat can provide more propulsion energy.To reduce the reliance on petroleum source,it is highly desirable to develop renewable alternatives for the production of strained polycyclic HED fuel,but which remains a big challenge because of the inaccessibility caused by the high strain,We herein demonstrate a three-step catalytic route towards highly strained C_(17)and C_(18)spirofuel with biomass feedstocks.The process includes catalytic aldol condensation of renewable cyclohexanone/cyclopentanone with benzaldehyde,catalytic spiro Diels-Alder(D-A)reaction of aldol adduct with isoprene,and catalytic hydrodeoxygenation.The key spiro D-A reaction is enabled by the catalysis of heterogeneous Lewis acidic ionic liquid.The chloroaluminate IL,formed by benign urea and AICl3,exhibits good catalytic performance and reusability for this step.An eventual hydrodeoxygenation(HDO)over Pd/C and H-Y produces strained tricyclic spirofuel with density>0.93 g/mL,combustion heat>41 MJ/L and freezing point<-40℃,which are better than the properties of tactical fuel RJ-4.Therefore,it is anticipated that the as-prepared renewable fuels have the potential to replace traditional petroleum-derived HED fuels.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415 and 52205475)the Science Center for Gas Turbine Project(No.P2023-B-IV-003-001)+1 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Huaqiao University Engineering Research Center of Brittle Materials Machining(MOE,2023IME-001)。
文摘The remarkable ability of titanium alloys to preserve their superior physical and chemical characteristics when subjected to extreme conditions significantly enhances their importance in the aerospace,military,and medical sectors.However,conventional machining of titanium alloys leads to elevated tool wear,development of surface defects,and reduced machining efficiency due to their low heat conductivity,and chemical affinity.These issues can be somewhat counteracted by integrating ultrasonic vibration in the conventional machining of titanium alloys and also enhance sustainability.This review article offers a holistic evaluation of the influence of ultrasonic vibration-assisted milling and turning on cutting forces,temperature,tool wear,and surface integrity,encompassing surface morphology,surface roughness,surface residual stress,surface hardness,and surface tribological properties during titanium alloys machining.Furthermore,it investigates the sustainability aspect that has not been previously examined.Studies on the performance of ultrasonic-assisted cutting revealed several advantages,including decreased cutting forces and cutting temperature,improved tool life,and a better-machined surface during machining.Consequently,the sustainability factor is improved due to minimized energy consumption and residual waste.In conclusion,the key challenges and future prospects in the ultrasonic-assisted cutting of titanium alloys are also discussed.This review article provides beneficial knowledge for manufactur-ers and researchers regarding ultrasonic vibration-assisted cutting of titanium alloy and will play an important role in achieving sustainability in the industry.
基金financially supported by the National Natural Science Foundation of China(Nos.92160301,92060203,52175415,and 52205475)the Science Center for Gas Turbine Project(Nos.P2022-AB-IV-002-001 and P2023-B-IV-003-001)+2 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Superior Postdoctoral Project of Jiangsu Province(No.2022ZB215)the National Key Laboratory of Science and Technology on Helicopter Transmission in NUAA(No.HTL-A-22G12).
文摘Minimum quantity lubrication(MQL),as a new sustainable and eco-friendly alternative cooling/lubrication technology that addresses the limitations of dry and wet machining,utilizes a small amount of lubricant or coolant to reduce friction,tool wear,and heat during cutting processes.MQL technique has witnessed significant developments in recent years,such as combining MQL with other sustainable techniques to achieve optimum results,using biodegradable lubricants,and innovations in nozzle designs and delivery methods.This review presents an in-depth analysis of machining characteristics(e.g.,cutting forces,temperature,tool wear,chip morphology and surface integrity,etc.)and sustainability characteristics(e.g.,energy consumption,carbon emissions,processing time,machining cost,etc.)of conventional MQL and hybrid MQL techniques like cryogenic MQL,Ranque-Hilsch vortex tube MQL,nanofluids MQL,hybrid nanofluid MQL and ultrasonic vibration assisted MQL in machining of aeronautical materials.Subsequently,the latest research and developments are analyzed and summarized in the field of MQL,and provide a detailed comparison between each technique,considering advantages,challenges,and limitations in practical implementation.In addition,this review serves as a valuable source for researchers and engineers to optimize machining processes while minimizing environmental impact and operational costs.Ultimately,the potential future aspects of MQL for research and industrial execution are discussed.
基金supported by the Pre-research fund(No.412130024).
文摘The T_(1)(Al_(2) CuLi)phase is one of the most effective strengthening nanoscale-precipitate in Al-Cu alloys with Li.However,its formation and evolution still need to be further clarified during aging due to the complex precipitation sequences.Here,a detailed investigation has been carried out on the atomic struc-tural evolution of T_(1) precipitate in an aged Al-Cu-Li-Mg-Ag alloy using state-of-the-art Cs-corrected high-angle annular dark field(HAADF)-coupled with integrated differential phase contrast(iDPC)-scanning transmission electron microscopy(STEM)and energy-dispersive X-ray spectroscopy(EDXS)techniques.An intermediate T_(1)’phase between T_(1p) and T_(1) phase,with a crystal structure and orientation rela-tionship consistent with T_(1),but exhibiting different atomic occupancy and chemical composition was found.We observed the atomic structural transformation from T_(1p) to T_(1)’phase(fcc→hcp),involving only 1/12<112>Al shear component.DFT calculation results validated our proposed structural models and the precipitation sequence.Besides,the distributions of minor solute elements(Ag,Mg,and Zn)in the pre-cipitates exhibited significant differences.These findings may contribute to a further understanding of the nucleation mechanism of T_(1) precipitate.
基金funded by the Key-Area Research and Development Program of Guangdong Province(Grant No.2022B0202070002)the Guangxi Science and Technology Major Program(Grant No.GuikeAA23023007-2)+1 种基金the Guangdong Province Modern Agricultural Industry Technology System Innovation Team Construction Project(2024CXTD19)Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515010303)。
文摘Agrobacterium tumefaciens-mediated transformation has been widely adopted for plant genetic engineering and the study of gene function(Krenek et al.,2015).This method is prevalent in the genetic transformation of herbaceous plants,with notable applications in species such as Arabidopsis(Yin et al.,2024),soybean(Zhang et al.,2024),rice(Zhang et al.,2020),and Chinese cabbage(Li et al.,2021).However,its application in fruit trees is limited.This is primarily due to their long growth cycles and lack of rapid,efficient,and stable transgenic systems,which severely hinders foundational research involving plant genetic transformation(Mei et al.,2024).Furthermore,for subtropical fruit trees,the presence of recalcitrant seeds adds an extra layer of difficulty to genetic transformation(Umarani et al.,2015),as most methods rely on seed germination as a basis for transformation.
基金the National Natural Science Foundation of China(No.52205468)China Postdoctoral Science Foundation(No.2022M710061 and No.2023T160277)Natural Science Foundation of Jiangsu Province(No.BK20210755)。
文摘Large size titanium alloy parts are widely used in aerospace.However,they are difficult to manufacture using mechanical cutting technology because of severe tool wear.Electrochemical jet machining is a promising technology to achieve high efficiency,because it has high machining flexibility and no machining tool wear.However,reports on the macro electrochemical jet machining of large size titanium alloy parts are very scarce,because it is difficult to achieve effective constraint of the flow field in macro electrochemical jet machining.In addition,titanium alloy is very sensitive to fluctuation of the flow field,and a turbulent flow field would lead to serious stray corrosion.This paper reports a series of investigations of the electrochemical jet machining of titanium alloy parts.Based on the flow analysis and experiments,the machining flow field was effectively constrained.TB6 titanium alloy part with a perimeter of one meter was machined.The machined surface was smooth with no obvious machining defects.The machining process was particularly stable with no obvious spark discharge.The research provides a reference for the application of electrochemical jet machining technology to achieve large allowance material removal in the machining of large titanium alloy parts.
基金supported by grants from the National Natural Science Foundation of China(Nos.52031017,51801237)the National Key Laboratory of Science and Technology on High-strength Structural Materials in Central South University,China(No.6142912200106).
文摘This study aims to clarify the mechanisms for the grain boundary(GB)segregation through investigating the absorption of excess solute atoms at GBs in Al−Cu alloys by using the hybrid molecular dynamics/Monte Carlo simulations.Two segregation mechanisms,substitutional and interstitial mechanisms,are observed.The intergranular defects,including dislocations,steps and vacancies,and the intervals in structural units are conductive to the prevalence of interstitial mechanism.And substitutional mechanism is favored by the highly ordered twin GBs.Furthermore,the two mechanisms affect the GB structure differently.It is quantified that interstitial mechanism is less destructive to GB structure than substitutional one,and often leads to a segregation level being up to about 6 times higher than the latter.These findings contribute to atomic scale insights into the microscopic mechanisms about how solute atoms are absorbed by GB structures,and clarify the correlation among intergranular structures,segregation mechanisms and kinetics.
文摘Alzheimer's disease,a progressively degenerative neurological disorder,is the most common cause of dementia in the elderly.While its precise etiology remains unclear,researchers have identified diverse pathological characteristics and molecular pathways associated with its progression.Advances in scientific research have increasingly highlighted the crucial role of non-coding RNAs in the progression of Alzheimer's disease.These non-coding RNAs regulate several biological processes critical to the advancement of the disease,offering promising potential as therapeutic targets and diagnostic biomarkers.Therefore,this review aims to investigate the underlying mechanisms of Alzheimer's disease onset,with a particular focus on microRNAs,long non-coding RNAs,and circular RNAs associated with the disease.The review elucidates the potential pathogenic processes of Alzheimer's disease and provides a detailed description of the synthesis mechanisms of the three aforementioned non-coding RNAs.It comprehensively summarizes the various non-coding RNAs that have been identified to play key regulatory roles in Alzheimer's disease,as well as how these noncoding RNAs influence the disease's progression by regulating gene expression and protein functions.For example,miR-9 targets the UBE4B gene,promoting autophagy-mediated degradation of Tau protein,thereby reducing Tau accumulation and delaying Alzheimer's disease progression.Conversely,the long non-coding RNA BACE1-AS stabilizes BACE1 mRNA,promoting the generation of amyloid-βand accelerating Alzheimer's disease development.Additionally,circular RNAs play significant roles in regulating neuroinflammatory responses.By integrating insights from these regulatory mechanisms,there is potential to discover new therapeutic targets and potential biomarkers for early detection and management of Alzheimer's disease.This review aims to enhance the understanding of the relationship between Alzheimer's disease and non-coding RNAs,potentially paving the way for early detection and novel treatment strategies.
基金financially supported by the National Natural Science Foundation of China(No.51975137,52205189)。
文摘In this work,a novel surface strengthening strategy for Mg-Li alloys was proposed,called cold spraying assisted high-speed laser cladding.CuAl9 aluminum bronze coating was firstly deposited on Mg-Li alloy by cold spraying,and then CoCrFe_(0.5)Ni_(1.5)Mo_(0.1)Nb_(0.68)eutectic highentropy alloy(EHEA)coating was prepared on the CuAl9 coating utilizing high-speed laser cladding.A gradient coating consisted of in-situ transition region and EHEA layer formed by bidirectional diffusion.The in-situ transition region was composed ofβ-Li,Cu_(2)Mg and Cu_(3)Al_(2)phases.TEM analysis indicated that Cu_(2)Mg and Cu_(3)Al_(2)phases were well matched with theβ-Li matrix phase.The EHEA coating had a nano-lamellar eutectic microstructure with relatively small lamellar-spacing(<100 nm).Metallurgical bonding interfaces formed between the EHEA coating,transition region and Mg-Li substrate.The evolution mechanism of the coating was revealed from the perspectives of mixing enthalpy,atomic radius difference and laser energy distribution.In 3.5 wt.%NaCl solution,the corrosion potential of the EHEA coating(-24 m VSHE)was 1345 m VSHEhigher than that of Mg-Li alloy(-1369 m VSHE),while the corrosion current density of the EHEA coating(3.13×10^(-7)A·cm^(-2))was almost three orders of magnitude lower than that of Mg-Li alloy(1.25×10^(-4)A·cm^(-2)).The wear rate of Mg-Li alloy(1.11×10^(-3)mm^(3)/N·m)was about 36 times higher than that of the EHEA coating(3.05×10^(-5)mm^(3)/N·m).
基金Supported by National Natural Science Foundation of China(Grant Nos.51175422,61973011)Shaanxi Provincial Natural Science Basic Research Plan of China(Grant No.2022JM-195)+1 种基金Fundamental Research Funds for the Central Universities of Chinathe Research Start-up Funds of Hangzhou International Innovation Institute of Beihang University(Grant No.2024KQ036)。
文摘During high-speed rotation,the surface of aeronautic spiral bevel gears will generate significant pressure and viscous forces,which will cause a certain amount of windage power loss and reduce the efficiency of the transmission system.Based on the computational fluid dynamics,this paper analyzes the windage power loss of a single spiral bevel gear and a spiral bevel gear pair under oil injection lubrication.In addition,the shroud is used to suppress gear windage loss,and the clearance size and opening angle of the designed shroud are optimized.Finally,by comparing and analyzing the experimental results,the following conclusions were obtained:(1)For a single gear,the speed is the most important factor affecting windage loss,followed by the hand of spiral,and rotation direction;(2)For gear pairs,under oil injection lubrication,the input speed has the greatest impact on windage power loss,followed by the influence of oil injection port speed,temperature and oil injection port pressure;(3)Installing a shroud is an effective method to reduce windage power loss;(4)In the pure air phase,the smaller the clearance between the shroud and the gear surface,and the smaller the radial direction between the shroud and the shaft,the better the effect of reducing windage;(5)In the two-phase flow of oil and gas,it is necessary to design oil drainage holes on the shroud to ensure the smooth discharge of lubricating oil and improve the drag reduction effect.
文摘In the last decade,space solar power satellites(SSPSs)have been conceived to support net-zero carbon emissions and have attracted considerable attention.Electric energy is transmitted to the ground via a microwave power beam,a technology known as microwave power transmission(MPT).Due to the vast transmission distance of tens of thousands of kilometers,the power transmitting antenna array must span up to 1 kilometer in diameter.At the same time,the size of the rectifying array on the ground should extend over a few kilometers.This makes the MPT system of SSPSs significantly larger than the existing aerospace engineering system.To design and operate a rational MPT system,comprehensive optimization is required.Taking the space MPT system engineering into consideration,a novel multi-objective optimization function is proposed and further analyzed.The multi-objective optimization problem is modeled mathematically.Beam collection efficiency(BCE)is the primary factor,followed by the thermal management capability.Some tapers,designed to solve the conflict between BCE and the thermal problem,are reviewed.In addition to these two factors,rectenna design complexity is included as a functional factor in the optimization objective.Weight coefficients are assigned to these factors to prioritize them.Radiating planar arrays with different aperture illumination fields are studied,and their performances are compared using the multi-objective optimization function.Transmitting array size,rectifying array size,transmission distance,and transmitted power remaine constant in various cases,ensuring fair comparisons.The analysis results show that the proposed optimization function is effective in optimizing and selecting the MPT system architecture.It is also noted that the multi-objective optimization function can be expanded to include other factors in the future.
文摘Lithium-air batteries(LABs)are regarded as a next-generation energy storage option due to their relatively high energy density.The cyclic stability and lifespan of LABs are mainly influenced by the formation and decomposition of lithium-based oxides at the air cathode,which not only lead to a low cathode catalytic efficiency but also restrict the electrochemical reversibility and cause side reaction problems.Carbon materials are considered key to solving these problems due to their conductivity,functional flexibility,and adjustable pore structure.This paper considers the research progress on carbon materials as air cathode catalytic materials for LABs,focusing on their structural characteristics,electrochemical behavior,and reaction mechanisms.Besides being used as air cathodes,carbon materials also show potential for being used as protective layers for metal anodes or as anode materials for LABs.
基金supported by the Key Laboratory Fund of National Key Laboratory of Science and Technology on High-strength Structural Materials(Nos.412130024,623020031)the Pre-research Fund(No.412130024).
文摘The strength improvement in the heat-treatable Al-Zn-Mg-Cu alloys is generally achieved by increasing the volume fraction of nanoprecipitates and reducing the grain size.However,utilizing one of them usu-ally leads to a drastic decrease in ductility.Herein,we architect a hierarchical microstructure integrating bimodal grain structures,nanoprecipitates,and hard-brittle coarse particles wrapped by ductility coarse grain(CG)bands via conventional cold rolling(CR)deformation and heat treatment methods to break the strength-ductility dilemma in the Al-8.89Zn-1.98Mg-2.06Cu-0.12Zr-0.05Sc-0.05Hf(wt.%)alloy.The results reveal that the coupling of high-volume fraction(∼1.2%)nanoprecipitates,∼52%narrow CG bands,and most coarse particles encapsulated by CG bands contribute to the 45%CR sample with outstanding over-all mechanical properties(a tensile strength of 655 MPa,a yield strength of 620 MPa,and an elongation of 15.5%).Microstructure-based strength analysis confirms that the high strength relates to a trade-offbetween the hierarchical features,namely high-volume fraction nanoprecipitates to counterbalance the strength loss caused by grain coarsening.The excellent ductility is due to the introduction of medium CG content with a narrow width that can trigger a cross-scale strain distribution during plastic deforma-tion,suppressing the catastrophic failure in the fine grain(FG)regions and facilitating the dimple fracture along the CG bands.This study proposes a feasible approach for tailoring hierarchical microstructures in Al-Zn-Mg-Cu alloys to achieve a superior strength-ductility combination.
基金financially supported by the National Natural Science Foundation of China(Nos.92160301,52175415,and 52205475)the Science Center for Gas Turbine Project(No.P2023-B-Ⅳ-003-001)+2 种基金the Natural Science Foundation of Jiangsu Province(No.BK20210295)the Fundamental Research Funds for the Central Universities(Nos.NG2024015 and NS2023028)the State Key Laboratory of Mechanics and Control for Aerospace Structures(Nanjing University of Aeronautics and Astronautics)(No.MCAS-S-0423G02)。
文摘Continuous Fiber-reinforced Metal Matrix Composites(CFMMCs),such as Si C fiberreinforced TC17 matrix composites(SiC_(f)/TC17),are renowned for their exceptional mechanical properties.However,their heterogeneous compositions present significant machining challenges,including fiber pullout,matrix cracking,and accelerated tool wear.Ultrasonic Vibration-Assisted Grinding(UVAG)has proven to be an effective technique for overcoming these challenges.The material removal mechanisms in UVAG,especially in composites with both ductile and brittle phases,remain poorly understood.To explore these issues,UVAG and Conventional Grinding(CG)experiments were conducted on SiC_(f)/TC17 along two grinding directions:fiber's transverse direction(FT)and fiber's longitudinal direction(FL).This paper aims to provide a new dynamic mechanical model and shed light on the complex removal mechanisms in CFMMCs,which are characterized by a near one-to-one alternation of ductile and brittle phases.The findings reveal that UVAG reduces fiber damage and surface roughness compared to CG,especially when grinding along FT.UVAG lowers normal(F_(n))and tangential grinding forces(F_(t))by 15.3%and 12.3%,respectively.This highlights UVAG's potential for improving the machinability of complex materials like CFMMCs.The proposed grinding force model closely matches the experimental results.This paper hopes to support the precision abrasive machining of CFMMCs,a kind of complex and highly anisotropic composite material,and promote their application in the fields such as aerospace.
基金supported by the National Natural Science Foundation of China(No.51931012)the Science and Technology Innovation Program of Hunan Province(No.2023RC3068).
文摘With the upgrade of armor protection materials,higher requirements are put forward for the penetration performance of tungsten alloy kinetic energy armor-piercing projectiles,and the penetration performance is closely related to the adiabatic shear band under extreme stress conditions.Here,the detailed analysis of the adiabatic shear band microstructure evolution of a dual-phase 90W-Ni-Fe alloy under a high strain rate was conducted by combining advanced electron microscopic characterization,while discussing shear fracture from a mechanical perspective under thermoplastic instability.The high temperature and high stress environment inside the adiabatic shear band led to the refinement of the W phase andγ-(Ni,Fe)phase grains to the submicron level,and induced the elements redistribution of W,Ni,and Fe to precipitate W nanocrystalline with hardness as high as 11.7 GPa along the recrystallization grain boundaries of theγ-(Ni,Fe)phase.Mechanical incompatibility caused by the hardness difference between W nanocrystalline andγ-(Ni,Fe)phases led to a strain gradient at the interface.The microvoids preferentially nucleated at the W nanocrystalline/γ-(Ni,Fe)phase interface,then merged to form microcracks and grew further,leading to shear failure.
文摘Dyeing wastewater poses a serious threat to environmental protection and industrial development.The piezoelectric effect can be used to optimize the band structure of semiconductors and improve the photon efficiency of photocatalysts.Bi_(2)Fe_(4)O_(9),a narrow gap semiconductor with piezoelectric effect,was prepared by a hydrothermal synthesis method for the degradation of reactive dye KN-R.The results show that the degradation efficiency of KN-R can be significantly improved by piezo-photocatalysis,and the degradation rate constant of piezo-photocatalysis k_(pi-ph)is about 3.4 times as large as the degradation rate constant of piezoelectric catalysis k_(pi)and about 2.6 times as large as the degradation rate constant of photocatalysis k_(ph).At a pH value of 3 and a lower KN-R mass concentration(60 mg/L),a higher degradation efficiency(98.5%)is achieved.CO_(3)^(2-)and cationic surfactant(CTAB)inhibit the degradation of KN-R.It is proved that the contributions of different active species to the degradation of KN-R follow the order:·OH,·O_(2)^(-),h^(+),and^(1)O_(2).The possible mechanism of piezo-photocatalytic degradation of KN-R was discussed.The photoexcitation generates a large amount of free charges,and the piezoelectric effect modulates the energy band structure of Bi_(2)Fe_(4)O_(9)and promotes the separation of photogenerated electron-hole pairs.The synergistic effect of the two factors significantly improves the degradation efficiency of KN-R.
基金Project(52274369)supported by the National Natural Science Foundation of ChinaProject(623020034)supported by the National Key Laboratory of Science and Technology on High-strength Structural Materials,China。
文摘The pronounced anisotropy in mechanical properties presents a major obstacle to the extensive application of aluminum-lithium(Al-Li)alloys,primarily attributed to heterogeneous precipitate distribution,grain structure variations,and crystallographic texture.This study investigates the impact of pre-thermal treatment prior to hot rolling and aging treatment on the anisotropy of mechanical properties of 2195 alloy sheet fabricated by gas atomization,hot pressing and hot rolling.The results demonstrate that pre-treatment at 450℃for 4 h promotes finer and more uniform distribution of precipitates,effectively mitigating mechanical anisotropy of the alloy sheet.Additionally,this treatment facilitates recrystallization during hot rolling,further reducing mechanical anisotropy.The in-plane anisotropy(IPA)factors for ultimate tensile strength(UTS)and yield strength(YS)are 1.15%and 0.77%,respectively.Subsequent aging treatment enhances grain refinement and the uniformity of the T_(1) phase,suppresses the formation of precipitation-free zones(PFZs),significantly improving the strength and toughness of the alloy sheet.After peak aging at 165℃for 48 h,the alloy sheet exhibits YS of 547 MPa,UTS of 590 MPa,and elongation(EL)of 7.7%.
基金supported by the Scientific Research Innovation Capability Support Project for Young Faculty,China(No.ZYGXQNJSKYCXNLZCXM-D1)the National Natural Science Foundation of China(No.52272384).
文摘Flapping-Wing Micro Air Vehicles(FMAVs)are compact and agile,capable of accessing narrow spaces that conventional vehicles struggle to reach,such as ruins,caves,or the interiors of complex structures,making them ideal tools for reconnaissance and rescue missions.1 However,the operation of FMAVs relies on coordinating multiple forces with different scaling effects,posing challenges to miniaturization design.
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The direct deoxygenative homo-coupling of benzyl alcohols holds great promise to build up bibenzyl motifs in organic synthesis,yet it remains a grand challenge in selectivity and activity control.Herein,we first discovered that iron carbide catalysts displayed high efficiency and selectivity in the catalytic deoxygenative homo-coupling of benzyl alcohols into bibenzyls using H_(2)as the reductant.Ir-promoted Fe0@Fe_(5)C_(2)gave the best performance among the investigated catalysts,and a broad scope of substrates with diverse functional groups could be smoothly converted into bibenzyls,with the yield up to 85%.In addition,in the presence of alkenes,three-component coupling reactions between alcohols and alkenes were also for the first time achieved to construct more complex multi-ring molecules.The radical-trapping experiment and FTIR measurements revealed the radical nature of the reaction and the significantly promoted C–O bond activation after carbonization,respectively.This work will provide guidelines for the rational design of efficient and selective catalysts for the alcohol-involved carbon-carbon coupling reactions.
基金supported by the Fundamental Research Funds for the Central Universities(2023QN1009)Xuzhou Basic Research Project(KC23018)+1 种基金China University of Mining and Technology(CUMT)Open Sharing Fund for Large-scale Instruments and Equipment(DYGX-2024-34)Priority Academic Program Development of Jiangsu Higher Education Institutions.
文摘High-energy-density(HED)fuel(e.g.widely used JP-10 and RJ-4),featuring compact 3D polycyclic structure with high strain,is of critical importance for volume-limited military aircraft,since their high density and combustion heat can provide more propulsion energy.To reduce the reliance on petroleum source,it is highly desirable to develop renewable alternatives for the production of strained polycyclic HED fuel,but which remains a big challenge because of the inaccessibility caused by the high strain,We herein demonstrate a three-step catalytic route towards highly strained C_(17)and C_(18)spirofuel with biomass feedstocks.The process includes catalytic aldol condensation of renewable cyclohexanone/cyclopentanone with benzaldehyde,catalytic spiro Diels-Alder(D-A)reaction of aldol adduct with isoprene,and catalytic hydrodeoxygenation.The key spiro D-A reaction is enabled by the catalysis of heterogeneous Lewis acidic ionic liquid.The chloroaluminate IL,formed by benign urea and AICl3,exhibits good catalytic performance and reusability for this step.An eventual hydrodeoxygenation(HDO)over Pd/C and H-Y produces strained tricyclic spirofuel with density>0.93 g/mL,combustion heat>41 MJ/L and freezing point<-40℃,which are better than the properties of tactical fuel RJ-4.Therefore,it is anticipated that the as-prepared renewable fuels have the potential to replace traditional petroleum-derived HED fuels.
