In the context of modern software development characterized by increasing complexity and compressed development cycles,traditional static vulnerability detection methods face prominent challenges including high false ...In the context of modern software development characterized by increasing complexity and compressed development cycles,traditional static vulnerability detection methods face prominent challenges including high false positive rates and missed detections of complex logic due to their over-reliance on rule templates.This paper proposes a Syntax-Aware Hierarchical Attention Network(SAHAN)model,which achieves high-precision vulnerability detection through grammar-rule-driven multi-granularity code slicing and hierarchical semantic fusion mechanisms.The SAHAN model first generates Syntax Independent Units(SIUs),which slices the code based on Abstract Syntax Tree(AST)and predefined grammar rules,retaining vulnerability-sensitive contexts.Following this,through a hierarchical attention mechanism,the local syntax-aware layer encodes fine-grained patterns within SIUs,while the global semantic correlation layer captures vulnerability chains across SIUs,achieving synergistic modeling of syntax and semantics.Experiments show that on benchmark datasets like QEMU,SAHAN significantly improves detection performance by 4.8%to 13.1%on average compared to baseline models such as Devign and VulDeePecker.展开更多
A group optimal penetration strategy in complex attack and defense confrontation situation is proposed in this paper to solve the coordinated penetration decision-making problem of endo-atmospheric gliding simultaneou...A group optimal penetration strategy in complex attack and defense confrontation situation is proposed in this paper to solve the coordinated penetration decision-making problem of endo-atmospheric gliding simultaneous multi-missile penetration of interceptors.First,the problem of large search space of multi-missile coordinated penetration maneuvers is fully considered,and the flight corridor of multi-missile coordinated penetration is designed to constrain search space of multi-agent coordinated strategy,comprehensively considering path constraints and anticollision constraints of gliding multi-missile flight.Then,a multi-missile hierarchical coordinated decision-making mechanism based on confrontation situation is proposed,and the swarm penetration strategy is optimized with the goal of maximizing swarm penetration effectiveness.The upper layer plans the swarm penetration formation according to confrontation situation,and generates the swarm coordinated penetration trajectory based on Multi-Agent Deep Deterministic Policy Gradient(MADDPG)method.The lower layer interpolates and smooths penetration trajectory,and generates the penetration guidance command based on Soft Actor-Critic and Extended Proportional Guidance(SAC-EPG)method.Simulation results verify that the proposed multi-missile cooperative penetration method based on hierarchical reinforcement learning converges faster than the penetration method based on MADDPG,and can quickly learn multi-missile cooperative penetration skills.In addition,multi-missile coordination can give full play to the group's detection and maneuverability,and occupy favorable penetration time and space through coordinated ballistic maneuvers.Thus the success rate of group penetration can be improved.展开更多
Dear Editor,This letter presents a new secure hierarchical control strategy for steering tracking of in-wheel motor driven(IWMD)electric vehicle(EV)subject to limited network resources,hybrid cyber-attacks,model nonli...Dear Editor,This letter presents a new secure hierarchical control strategy for steering tracking of in-wheel motor driven(IWMD)electric vehicle(EV)subject to limited network resources,hybrid cyber-attacks,model nonlinearities,actuator redundancy and airflow disturbance.A hierarchical control architecture is proposed specifically for solving the problems of nonlinear system modeling and actuator redundancy.By utilizing the advantages of fully actuated system(FAS)approach,a nonlinear virtual controller against airflow disturbance is constructed in upper layer system and an event-triggered nonlinear distributed controller is proposed in lower layer system under stochastic hybrid cyber-attacks.A case study of overtaking task is carried out to validate the FAS-based hierarchical control strategy.展开更多
Partial Differential Equations(PDEs)are model candidates of soft sensing for aero-engine health management units.The existing Physics-Informed Neural Networks(PINNs)have made achievements.However,unmeasurable aero-eng...Partial Differential Equations(PDEs)are model candidates of soft sensing for aero-engine health management units.The existing Physics-Informed Neural Networks(PINNs)have made achievements.However,unmeasurable aero-engine driving sources lead to unknown PDE driving terms,which weaken PINNs feasibility.To this end,Physically Informed Hierarchical Learning followed by Recurrent-Prediction Term(PIHL-RPT)is proposed.First,PIHL is proposed for learning nonhomogeneous PDE solutions,in which two networks NetU and NetG are constructed.NetU is for learning solutions satisfying PDEs;NetG is for learning driving terms to regularize NetU training.Then,we propose a hierarchical learning strategy to optimize and couple NetU and NetG,which are integrated into a data-physics-hybrid loss function.Besides,we prove PIHL-RPT can iteratively generate a series of networks converging to a function,which can approximate a solution to well-posed PDE.Furthermore,RPT is proposed for prediction improvement of PIHL,in which network NetU-RP is constructed to compensate for information loss caused by data sampling and driving sources’immeasurability.Finally,artificial datasets and practical vibration process datasets from our wear experiment platform are used to verify the feasibility and effectiveness of PIHL-RPT based soft sensing.Meanwhile,comparisons with relevant methods,discussions,and PIHL-RPT based health monitoring example are given.展开更多
In global navigation satellite system denial environment,cross-view geo-localization based on image retrieval presents an exceedingly critical visual localization solution for Unmanned Aerial Vehicle(UAV)systems.The e...In global navigation satellite system denial environment,cross-view geo-localization based on image retrieval presents an exceedingly critical visual localization solution for Unmanned Aerial Vehicle(UAV)systems.The essence of cross-view geo-localization resides in matching images containing the same geographical targets from disparate platforms,such as UAV-view and satellite-view images.However,images of the same geographical targets may suffer from occlusions and geometric distortions due to variations in the capturing platform,view,and timing.The existing methods predominantly extract features by segmenting feature maps,which overlook the holistic semantic distribution and structural information of objects,resulting in loss of image information.To address these challenges,dilated neighborhood attention Transformer is employed as the feature extraction backbone,and Multi-feature representations based on Multi-scale Hierarchical Contextual Aggregation(MMHCA)is proposed.In the proposed MMHCA method,the multiscale hierarchical contextual aggregation method is utilized to extract contextual information from local to global across various granularity levels,establishing feature associations of contextual information with global and local information in the image.Subsequently,the multi-feature representations method is utilized to obtain rich discriminative feature information,bolstering the robustness of model in scenarios characterized by positional shifts,varying distances,and scale ambiguities.Comprehensive experiments conducted on the extensively utilized University-1652 and SUES-200 benchmarks indicate that the MMHCA method surpasses the existing techniques.showing outstanding results in UAV localization and navigation.展开更多
K–Se batteries have been identified as promising energy storage systems owing to their high energy density and cost-effectiveness.However,challenges such as substantial volume changes and low Se utilization require f...K–Se batteries have been identified as promising energy storage systems owing to their high energy density and cost-effectiveness.However,challenges such as substantial volume changes and low Se utilization require further investigation.In this study,novel N-doped multichannel carbon nanofibers(h-NMCNFs)with hierarchical porous structures were successfully synthesized as efficient cathode hosts for K–Se batteries through the carbonization of two electrospun immiscible polymer nanofibers and subsequent chemical activation.Mesopores originated from the decomposition of the polymer embedded in the carbon nanofibers,and micropores were introduced via KOH activation.During the activation step,hierarchical porous carbon nanofibers with enhanced pore volumes were formed because of the micropores in the carbon nanofibers.Owing to the mesopores that enabled easy access to the electrolyte and the high utilization of chain-like Se within the micropores,the Se-loaded hierarchical porous carbon nanofibers(60 wt%Se)exhibited a high discharge capacity and excellent rate performance.The discharge capacity of the nanofibers at the 1,000th cycle was 210.8 mA.h.g^(-1)at a current density of 0.5C.The capacity retention after the initial activation was 64%.In addition,a discharge capacity of 165 mA.h.g^(-1)was obtained at an extremely high current density of 3.0C.展开更多
As modern communication and detection technologies advance at a swift pace,multifunctional electromagnetic interference(EMI)shielding materials with active/positive infrared stealth,hydrophobicity,and electric-thermal...As modern communication and detection technologies advance at a swift pace,multifunctional electromagnetic interference(EMI)shielding materials with active/positive infrared stealth,hydrophobicity,and electric-thermal conversion ability have received extensive attention.Meeting the aforesaid requirements simultaneously remains a huge challenge.In this research,the melamine foam(MF)/polypyrrole(PPy)nanowire arrays(MF@PPy)were fabricated via one-step electrochemical polymerization.The hierarchical MF@PPy foam was composed of three-dimensional PPy micro-skeleton and ordered PPy nanowire arrays.Due to the upwardly grown PPy nanowire arrays,the MF@PPy foam possessed good hydrophobicity ability with a water contact angle of 142.00°and outstanding stability under various harsh environments.Meanwhile,the MF@PPy foam showed excellent thermal insulation property on account of the low thermal conductivity and elongated ligament characteristic of PPy nanowire arrays.Furthermore,taking advantage of the high conductivity(128.2 S m^(-1)),the MF@PPy foam exhibited rapid Joule heating under 3 V,resulting in dynamic infrared stealth and thermal camouflage effects.More importantly,the MF@PPy foam exhibited remarkable EMI shielding effectiveness values of 55.77 dB and 19,928.57 dB cm^(2)g^(-1).Strong EMI shielding was put down to the hierarchically porous PPy structure,which offered outstanding impedance matching,conduction loss,and multiple attenuations.This innovative approach provides significant insights to the development of advanced multifunctional EMI shielding foams by constructing PPy nanowire arrays,showing great applications in both military and civilian fields.展开更多
Accurate prediction of molecular properties is crucial for selecting compounds with ideal properties and reducing the costs and risks of trials.Traditional methods based on manually crafted features and graph-based me...Accurate prediction of molecular properties is crucial for selecting compounds with ideal properties and reducing the costs and risks of trials.Traditional methods based on manually crafted features and graph-based methods have shown promising results in molecular property prediction.However,traditional methods rely on expert knowledge and often fail to capture the complex structures and interactions within molecules.Similarly,graph-based methods typically overlook the chemical structure and function hidden in molecular motifs and struggle to effectively integrate global and local molecular information.To address these limitations,we propose a novel fingerprint-enhanced hierarchical graph neural network(FH-GNN)for molecular property prediction that simultaneously learns information from hierarchical molecular graphs and fingerprints.The FH-GNN captures diverse hierarchical chemical information by applying directed message-passing neural networks(D-MPNN)on a hierarchical molecular graph that integrates atomic-level,motif-level,and graph-level information along with their relationships.Addi-tionally,we used an adaptive attention mechanism to balance the importance of hierarchical graphs and fingerprint features,creating a comprehensive molecular embedding that integrated hierarchical mo-lecular structures with domain knowledge.Experiments on eight benchmark datasets from MoleculeNet showed that FH-GNN outperformed the baseline models in both classification and regression tasks for molecular property prediction,validating its capability to comprehensively capture molecular informa-tion.By integrating molecular structure and chemical knowledge,FH-GNN provides a powerful tool for the accurate prediction of molecular properties and aids in the discovery of potential drug candidates.展开更多
Exo-atmospheric vehicles are constrained by limited maneuverability,which leads to the contradiction between evasive maneuver and precision strike.To address the problem of Integrated Evasion and Impact(IEI)decision u...Exo-atmospheric vehicles are constrained by limited maneuverability,which leads to the contradiction between evasive maneuver and precision strike.To address the problem of Integrated Evasion and Impact(IEI)decision under multi-constraint conditions,a hierarchical intelligent decision-making method based on Deep Reinforcement Learning(DRL)was proposed.First,an intelligent decision-making framework of“DRL evasion decision”+“impact prediction guidance decision”was established:it takes the impact point deviation correction ability as the constraint and the maximum miss distance as the objective,and effectively solves the problem of poor decisionmaking effect caused by the large IEI decision space.Second,to solve the sparse reward problem faced by evasion decision-making,a hierarchical decision-making method consisting of maneuver timing decision and maneuver duration decision was proposed,and the corresponding Markov Decision Process(MDP)was designed.A detailed simulation experiment was designed to analyze the advantages and computational complexity of the proposed method.Simulation results show that the proposed model has good performance and low computational resource requirement.The minimum miss distance is 21.3 m under the condition of guaranteeing the impact point accuracy,and the single decision-making time is 4.086 ms on an STM32F407 single-chip microcomputer,which has engineering application value.展开更多
The increase in the utilization of infrared heat detection technology in military applications necessitates research on composites with improved thermal transmission performance and microwave absorption capabilities.T...The increase in the utilization of infrared heat detection technology in military applications necessitates research on composites with improved thermal transmission performance and microwave absorption capabilities.This study satisfactorily fabricated a series of MoS_(2)/BN-xyz composites(which were characterized by the weight ratio of MoS_(2)to BN,denoted by xy:z)through chemical vapor depos-ition,which resulted in their improved thermal stability and thermal transmission performance.The results show that the remaining mass of MoS_(2)/BN-101 was as high as 69.25wt%at 800℃under air atmosphere,and a temperature difference of 31.7℃was maintained between the surface temperature and the heating source at a heating temperature of 200℃.Furthermore,MoS_(2)/BN-301 exhibited an im-pressive minimum reflection loss value of-32.21 dB at 4.0 mm and a wide effective attenuation bandwidth ranging from 9.32 to 18.00 GHz(8.68 GHz).Therefore,these simplified synthesized MoS_(2)/BN-xyz composites demonstrate great potential as highly efficient con-tenders for the enhancement of microwave absorption performance and thermal conductance.展开更多
Listeria monocytogenes(LM)is a dangerous foodborne pathogen for humans.One emerging and validated method of indirectly assessing LM in food is detecting 3-hydroxy-2-butanone(3H2B)gas.In this study,the synthesis of 3-(...Listeria monocytogenes(LM)is a dangerous foodborne pathogen for humans.One emerging and validated method of indirectly assessing LM in food is detecting 3-hydroxy-2-butanone(3H2B)gas.In this study,the synthesis of 3-(2-aminoethylamino)propyltrimethoxysilane(AAPTMS)functionalized hierarchical hollow TiO_(2)nanospheres was achieved via precise controlling of solvothermal reaction temperature and post-grafting route.The sensors based on as-prepared materials exhibited excellent sensitivity(480 Hz@50 ppm),low detection limit(100 ppb),and outstanding selectivity.Moreover,the evaluation of LM with high sensitivity and specificity was achieved using the sensors.Such stable three-dimensional spheres,whose distinctive hierarchical and hollow nanostructure simultaneously improved both sensitivity and response/recovery speed dramatically,were spontaneously assembled by nanosheets.Meanwhile,the moderate loadings of AAPTMS significantly improved the selectivity of sensors.Then,the gas-sensing mechanism was explored by utilizing thermodynamic investigation,Gaussian 16 software,and in situ diffuse reflectance infrared transform spectroscopy,illustrating the weak chemisorption between the-NHgroup and 3H2B molecules.These portable sensors are promising for real-time assessment of LM at room temperature,which will make a magnificent contribution to food safety.展开更多
Introduction It is necessary for an ideal bioceramic scaffold to have a suitable structure.The structure can affect the mechanical properties of the scaffold(i.e.,elastic modulus and compressive strength)and the biolo...Introduction It is necessary for an ideal bioceramic scaffold to have a suitable structure.The structure can affect the mechanical properties of the scaffold(i.e.,elastic modulus and compressive strength)and the biological properties of the scaffold(i.e.,degradability and cell growth rate).Lattice structure is a kind of periodic porous structure,which has some advantages of light weight and high strength,and is widely used in the preparation of bioceramic scaffolders.For the structure of the scaffold,high porosity and large pore size are important for bone growth,bone integration and promoting good mechanical interlocking between neighboring bones and the scaffold.However,scaffolds with a high porosity often lack mechanical strength.In addition,different parts of the bone have different structural requirements.In this paper,scaffolds with a non-uniform structure or a hierarchical structure were designed,with loose and porous exterior to facilitate cell adhesion,osteogenic differentiation and vascularization as well as relatively dense interior to provide sufficient mechanical support for bone repair.Methods In this work,composite ceramics scaffolds with 10%akermanite content were prepared by DLP technology.The scaffold had a high porosity outside to promote the growth of bone tissue,and a low porosity inside to withstand external forces.The compressive strength,fracture form,in-vitro degradation performance and bioactivity of graded bioceramic scaffolds were investigated.The models of scaffolds were imported into the DLP printer with a 405 nm light.The samples were printed with the intensity of 8 mJ/cm^(2)and a layer thickness of 50μm.Finally,the ceramic samples were sintered at 1100℃.The degradability of the hierarchical gyroid bioceramic scaffolds was evaluated through immersion in Tris-HCl solution and SBF solution at a ratio of 200 mL/g.The bioactivity of bioceramic was obtained via immersing them in SBF solution for two weeks.The concentrations of calcium,phosphate,silicon,and magnesium ions in the soaking solution were determined by an inductively coupled plasma optical emission spectrometer.Results and discussion In this work,a hierarchical Gyroid structure HA-AK10 scaffold(sintered at 1100℃)with a radial internal porosity of 50%and an external porosity of 70%is prepared,and the influence of structural form on the compressive strength and degradation performance of the scaffold is investigated.The biological activity of the bioceramics in vitro is also verified.The mechanical simulation results show that the stress distribution corresponds to the porosity distribution of the structure,and the low porosity is larger and the overall stress concentration phenomenon does not appear.After soaking in SBF solution,Si—OH is firstly formed on the surface of bioceramics,and then silicon gel layer is produced due to the presence of calcium and silicon ions.The silicon gel layer is dissociated into negatively charged groups under alkaline environment secondary adsorption of calcium ions and phosphate ions,forming amorphous calcium phosphate,and finally amorphous calcium phosphate crystals and adsorption of carbonate ions,forming carbonate hydroxyapatite.This indicates that the composite bioceramics have a good biological activity in-vitro and can provide a good environment for the growth of bone cells.A hierarchical Gyroid ceramic scaffold with a bone geometry is prepared via applying the hierarchical structure to the bone contour scaffold.The maximum load capacity of the hierarchical Gyroid ceramic scaffold is 8 times that of the uniform structure.Conclusions The hierarchical structure scaffold designed had good overall compressive performance,good degradation performance,and still maintained a good mechanical stability during degradation.In addition,in-vitro biological experimental results showed that the surface graded composite scaffold could have a good in-vitro biological activity and provide a good environment for bone cells.Compared to the heterosexual structure,the graded scaffold had greater mechanical properties.展开更多
In this paper,we propose hierarchical attention dual network(DNet)for fine-grained image classification.The DNet can randomly select pairs of inputs from the dataset and compare the differences between them through hi...In this paper,we propose hierarchical attention dual network(DNet)for fine-grained image classification.The DNet can randomly select pairs of inputs from the dataset and compare the differences between them through hierarchical attention feature learning,which are used simultaneously to remove noise and retain salient features.In the loss function,it considers the losses of difference in paired images according to the intra-variance and inter-variance.In addition,we also collect the disaster scene dataset from remote sensing images and apply the proposed method to disaster scene classification,which contains complex scenes and multiple types of disasters.Compared to other methods,experimental results show that the DNet with hierarchical attention is robust to different datasets and performs better.展开更多
Endowing stimuli-responsive materials with micro-nano structures is an intriguing strategy for the fabrication of superwetting surfaces;however,its application is limited by poor chemical/mechanical stability.Herein,a...Endowing stimuli-responsive materials with micro-nano structures is an intriguing strategy for the fabrication of superwetting surfaces;however,its application is limited by poor chemical/mechanical stability.Herein,a simple and versatile strategy was developed to fabricate durable polymeric superwetting surfaces with photoswitchable wettability on hierarchically structured metallic substrates.Inspired by nature,a novel functional terpolymer incorporating mussel-inspired catechol groups,photoresponsive azobenzene groups,and low-surface-energy fluorine-containing groups was synthesized via solution radical polymerization.The azobenzene-containing terpolymer possesses outstanding photoresponsiveness in both the solution and film states because of the trans-cis isomerization of the azobenzene moieties.After dip-coating with the mussel-inspired azo-copolymer,the as-prepared smart surfaces exhibited a photo-triggered change in wettability between high hydrophobicity and superhydrophilicity.More importantly,these superwetting surfaces with enhanced adhesion properties can tolerate harsh environmental conditions and repeated abrasion tests,thereby demonstrating excellent chemical robustness and mechanical durability.This study paves a new avenue for the convenient and large-scale fabrication of robust smart surfaces that could find widespread potential applications in microfluidic devices,water treatment,and functional coatings.展开更多
The development and deployment of aluminum conductor have been significantly hampered by the contradiction of yield strength,uniform elongation,and electrical conductivity.Herein,we successfully fabricated a pure alum...The development and deployment of aluminum conductor have been significantly hampered by the contradiction of yield strength,uniform elongation,and electrical conductivity.Herein,we successfully fabricated a pure aluminum(Al)clad aluminum alloy(AA)rod with hierarchical compositions and microstructures.The proposed pure Al clad AA rod showcases an optimized combination of yield strength,uniform elongation,and electrical conductivity,i.e.,easing the restriction on improving yield strength,uniform elongation,and electrical conductivity.Compared to existing experiments,uniform elongation improved fourfold,while yield strength increased by 13%and electrical conductivity improved by 2%in terms of the international annealed copper standard(IACS).Microstructural characterizations and theoretical analyses revealed that the optimal performance of the Al clad AA arose from low-density low-angle grain boundaries(LAGBs)in the outer Al and high-density LAGBs with nanoscale precipitations in the inner AA.Our findings offer a compelling strategy for fabricating high-performance aluminum conductors,thereby laying a solid technical foundation for their wide application in power delivery systems.展开更多
Hierarchical lignin-derived ordered mesoporous carbon(HOMC)was significant for advanced supercapacitors.However,achieving controllable fabrication and optimizing electrochemical behavior were challenging.In this work,...Hierarchical lignin-derived ordered mesoporous carbon(HOMC)was significant for advanced supercapacitors.However,achieving controllable fabrication and optimizing electrochemical behavior were challenging.In this work,an eco-friendly HOMC was synthesized using lignin as carbon precursors and Zn^(2+)as cross-linking and pore-forming agents,followed by KHCO_(3)activation,eliminating the need for toxic phenolic resins and acid treatments for metal removal.Machine learning technology,specifically an Artificial Neural Network(ANN model,was utilized to assist the experimental design and prediction.The ANN model suggested an ideal hierarchical structure and optimized oxygen level,achieved through the adjustment of Zn^(2+)additive concentration,carbonization temperature,and subsequent KHCO_(3)activation to maximize capacitance.The HOMC electrode,with a micropore-to-mesopore ratio(S_(micro)/S_(meso))of 1.01 and an oxygen content of 8.81 at%,acquired a specific capacitance of 362 F·g^(-1)at 0.5 A·g^(-1)in 6 mol·L^(-1)KOH electrolyte.The assembled HOMC//HOMC supercapacitor could afford a high energy density of 33.38 Wh·kg^(-1)with a corresponding specific power density of 300 W·kg^(-1)in TEATFB PC electrolyte.Meanwhile,the long-term cycle stability of 94.33%was achieved after 20,000 cycles.This work provides an ANN assisted strategy for the synthesis of HOMC,highlighting its potential to valorize biomass and agricultural waste in sustainable energy storag solutions.展开更多
Hierarchical SAPO-11, featuring both micropore and mesopore channels, demonstrates an outstanding performance in high-octane gasoline production. In this work, we propose an economic and effective approach to directly...Hierarchical SAPO-11, featuring both micropore and mesopore channels, demonstrates an outstanding performance in high-octane gasoline production. In this work, we propose an economic and effective approach to directly fabricate hierarchical SAPO-11 molecular sieve from natural kaolin, eliminating the need for mesoporogens. The systematic characterization results show that the kaolin-derived SAPO-11 possesses abundant micro-mesoporous structure and more Brønsted (B) acid sites on the external surface in contrast with the conventional SAPO-11 prepared employing silica sol as silicon source as well as SAPO-11 synthesized with the assist with of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (F127). The analysis of the formation process reveals that the kaolin not only provides silicon source for the SAPO-11 crystal growth, but also offers confined environment for crystal growth along the preferential orientation, resulting in the generation of the microporous and mesoporous structure. Benefiting from these unique properties, the kaolin-derived Pt/SAPO-11 exhibits considerably improved selectivity for di-branched C8 isomers in n-octane hydroisomerization.展开更多
In aerospace,BBC-Nb alloys confront notable challenges in thermal stability and toughness under cyclic fatigue at varying temperatures.Insufficient thermal stability and expedited coalescence of precipitates substanti...In aerospace,BBC-Nb alloys confront notable challenges in thermal stability and toughness under cyclic fatigue at varying temperatures.Insufficient thermal stability and expedited coalescence of precipitates substantially accelerates the degradation of alloys at elevated temperatures.Here,a Nb alloy with impressive thermal stability and mechanical properties was designed using theoretical calculations and a two-step graded heat treatment process.The superlative properties of the Nb alloy are primarily associated with the NbC hierarchical structures,i.e.,stable nanoparticles in Nb-BCC grains and discontinuous microparticles at grain boundaries(GBs).The hierarchical carbides configuration avoids continuous precipitation of carbides at GBs and preferential coarsening within the grains.The process involves precipitating ZrC nanoparticles at 1350℃,then stabilizing NbC at 1800℃ by replacing Zr with Nb.Nb-FCC nanophases enveloping NbC prevent coarsening and have strong relationships with both NbC nanoparticles and matrix.The concept of fine-tuning NbC precipitation within grains and introducing NbC at GBs with a substitution method offers a strategy for high-strength,heat-resistant materials.展开更多
The wave-absorbing materials are kinds of special electromagnetic functional materials and have been widely used in electromagnetic pollution control and military fields.In-situ integrated hierarchical structure const...The wave-absorbing materials are kinds of special electromagnetic functional materials and have been widely used in electromagnetic pollution control and military fields.In-situ integrated hierarchical structure construction is thought as a promising route to improve the microwave absorption performance of the materials.In the present work,layer-structured Co-metal-organic frameworks(Co-MOFs)precursors were grown in-situ on the surface of carbon fibers with the hydrothermal method.After annealed at 500℃ under Ar atmosphere,a novel multiscale hierarchical composite(Co@C/CF)was obtained with the support of carbon fibers,keeping the flower-like structure.Scanning electron microscope,transmission electron microscope,X-ray diffraction,Raman,and X-ray photoelectron spectroscopy were performed to analyze the microstructure and composition of the hierarchical structure,and the microwave absorption performance of the Co@C/CF composites were investigated.The results showed that the growth of the flower-like structure on the surface of carbon fiber was closely related to the metal-to-ligand ratio.The optimized Co@C/CF flower-like composites achieved the best reflection loss of−55.7 dB in the low frequency band of 6–8 GHz at the thickness of 2.8 mm,with the corresponding effective absorption bandwidth(EAB)of 2.1 GHz.The EAB of 3.24 GHz was achieved in the high frequency range of 12–16 GHz when the thickness was 1.5 mm.The excellent microwave absorption performance was ascribed to the introduction of magnetic components and the construction of the unique structure.The flower-like structure not only balanced the impedance of the fibers themselves,but also extended the propagation path of the microwave and then increased the multiple reflection losses.This work provides a convenient method for the design and development of wave-absorbing composites with in-situ integrated structure.展开更多
By integrating photocatalytic H_(2)O_(2) production with furfuryl alcohol(FAL)oxidation,this coupled process establishes an atom-economical pathway for sustainable chemical synthesis,simultaneously achieving energy st...By integrating photocatalytic H_(2)O_(2) production with furfuryl alcohol(FAL)oxidation,this coupled process establishes an atom-economical pathway for sustainable chemical synthesis,simultaneously achieving energy storage and biomass valorization.This study introduces a meticulously engineered MOF@MOF hierarchical photocatalytic architecture,specifically the PCN-134@MOF-525(PM-X series)composite,designed for synergistic catalysis of these processes.By strategically integrating two distinct MOF materials,we circumvent the limitations of single-component systems,such as facile charge carrier recombination,and establish a redox dualactive site catalytic system.This rational design transcends simple additivity,yielding emergent catalytic behaviors driven by precise control over interfacial electric fields and dynamic structural modulation.The resultant hierarchical organization enhances light harvesting,promotes efficient charge separation,and accelerates charge transfer kinetics.Mechanistic insights,derived from photoelectrochemical,spectroscopic,and in-situ IR analyses,reveal a synergistic interplay that suppresses electron-hole recombination and spatially segregates redox processes.PM-3 demonstrates a significant enhancement in catalytic efficiency(the highest value reported),exhibiting a 4.5-fold increase in both H_(2)O_(2) production and FAL oxidation rates compared to the individual MOF components,achieving near-quantitative FAL conversion and exceptional selectivity.This work provides a potent design blueprint,emphasizing interfacial engineering and structural synergy for unprecedented efficiency and selectivity in sustainable chemical transformations.展开更多
基金supported by the research start-up funds for invited doctor of Lanzhou University of Technology under Grant 14/062402。
文摘In the context of modern software development characterized by increasing complexity and compressed development cycles,traditional static vulnerability detection methods face prominent challenges including high false positive rates and missed detections of complex logic due to their over-reliance on rule templates.This paper proposes a Syntax-Aware Hierarchical Attention Network(SAHAN)model,which achieves high-precision vulnerability detection through grammar-rule-driven multi-granularity code slicing and hierarchical semantic fusion mechanisms.The SAHAN model first generates Syntax Independent Units(SIUs),which slices the code based on Abstract Syntax Tree(AST)and predefined grammar rules,retaining vulnerability-sensitive contexts.Following this,through a hierarchical attention mechanism,the local syntax-aware layer encodes fine-grained patterns within SIUs,while the global semantic correlation layer captures vulnerability chains across SIUs,achieving synergistic modeling of syntax and semantics.Experiments show that on benchmark datasets like QEMU,SAHAN significantly improves detection performance by 4.8%to 13.1%on average compared to baseline models such as Devign and VulDeePecker.
文摘A group optimal penetration strategy in complex attack and defense confrontation situation is proposed in this paper to solve the coordinated penetration decision-making problem of endo-atmospheric gliding simultaneous multi-missile penetration of interceptors.First,the problem of large search space of multi-missile coordinated penetration maneuvers is fully considered,and the flight corridor of multi-missile coordinated penetration is designed to constrain search space of multi-agent coordinated strategy,comprehensively considering path constraints and anticollision constraints of gliding multi-missile flight.Then,a multi-missile hierarchical coordinated decision-making mechanism based on confrontation situation is proposed,and the swarm penetration strategy is optimized with the goal of maximizing swarm penetration effectiveness.The upper layer plans the swarm penetration formation according to confrontation situation,and generates the swarm coordinated penetration trajectory based on Multi-Agent Deep Deterministic Policy Gradient(MADDPG)method.The lower layer interpolates and smooths penetration trajectory,and generates the penetration guidance command based on Soft Actor-Critic and Extended Proportional Guidance(SAC-EPG)method.Simulation results verify that the proposed multi-missile cooperative penetration method based on hierarchical reinforcement learning converges faster than the penetration method based on MADDPG,and can quickly learn multi-missile cooperative penetration skills.In addition,multi-missile coordination can give full play to the group's detection and maneuverability,and occupy favorable penetration time and space through coordinated ballistic maneuvers.Thus the success rate of group penetration can be improved.
基金supported by the National Natural Science Foundation of China(62173209,61773238)the Science Center Program of National Natural Science Foundation of China(62188101).
文摘Dear Editor,This letter presents a new secure hierarchical control strategy for steering tracking of in-wheel motor driven(IWMD)electric vehicle(EV)subject to limited network resources,hybrid cyber-attacks,model nonlinearities,actuator redundancy and airflow disturbance.A hierarchical control architecture is proposed specifically for solving the problems of nonlinear system modeling and actuator redundancy.By utilizing the advantages of fully actuated system(FAS)approach,a nonlinear virtual controller against airflow disturbance is constructed in upper layer system and an event-triggered nonlinear distributed controller is proposed in lower layer system under stochastic hybrid cyber-attacks.A case study of overtaking task is carried out to validate the FAS-based hierarchical control strategy.
基金supported in part by the National Science and Technology Major Project of China(No.2019-I-0019-0018)the National Natural Science Foundation of China(Nos.61890920,61890921,12302065 and 12172073).
文摘Partial Differential Equations(PDEs)are model candidates of soft sensing for aero-engine health management units.The existing Physics-Informed Neural Networks(PINNs)have made achievements.However,unmeasurable aero-engine driving sources lead to unknown PDE driving terms,which weaken PINNs feasibility.To this end,Physically Informed Hierarchical Learning followed by Recurrent-Prediction Term(PIHL-RPT)is proposed.First,PIHL is proposed for learning nonhomogeneous PDE solutions,in which two networks NetU and NetG are constructed.NetU is for learning solutions satisfying PDEs;NetG is for learning driving terms to regularize NetU training.Then,we propose a hierarchical learning strategy to optimize and couple NetU and NetG,which are integrated into a data-physics-hybrid loss function.Besides,we prove PIHL-RPT can iteratively generate a series of networks converging to a function,which can approximate a solution to well-posed PDE.Furthermore,RPT is proposed for prediction improvement of PIHL,in which network NetU-RP is constructed to compensate for information loss caused by data sampling and driving sources’immeasurability.Finally,artificial datasets and practical vibration process datasets from our wear experiment platform are used to verify the feasibility and effectiveness of PIHL-RPT based soft sensing.Meanwhile,comparisons with relevant methods,discussions,and PIHL-RPT based health monitoring example are given.
基金supported by the National Natural Science Foundation of China(Nos.12072027,62103052,61603346 and 62103379)the Henan Key Laboratory of General Aviation Technology,China(No.ZHKF-230201)+3 种基金the Funding for the Open Research Project of the Rotor Aerodynamics Key Laboratory,China(No.RAL20200101)the Key Research and Development Program of Henan Province,China(Nos.241111222000 and 241111222900)the Key Science and Technology Program of Henan Province,China(No.232102220067)the Scholarship Funding from the China Scholarship Council(No.202206030079).
文摘In global navigation satellite system denial environment,cross-view geo-localization based on image retrieval presents an exceedingly critical visual localization solution for Unmanned Aerial Vehicle(UAV)systems.The essence of cross-view geo-localization resides in matching images containing the same geographical targets from disparate platforms,such as UAV-view and satellite-view images.However,images of the same geographical targets may suffer from occlusions and geometric distortions due to variations in the capturing platform,view,and timing.The existing methods predominantly extract features by segmenting feature maps,which overlook the holistic semantic distribution and structural information of objects,resulting in loss of image information.To address these challenges,dilated neighborhood attention Transformer is employed as the feature extraction backbone,and Multi-feature representations based on Multi-scale Hierarchical Contextual Aggregation(MMHCA)is proposed.In the proposed MMHCA method,the multiscale hierarchical contextual aggregation method is utilized to extract contextual information from local to global across various granularity levels,establishing feature associations of contextual information with global and local information in the image.Subsequently,the multi-feature representations method is utilized to obtain rich discriminative feature information,bolstering the robustness of model in scenarios characterized by positional shifts,varying distances,and scale ambiguities.Comprehensive experiments conducted on the extensively utilized University-1652 and SUES-200 benchmarks indicate that the MMHCA method surpasses the existing techniques.showing outstanding results in UAV localization and navigation.
基金financially supported by the Materials/Parts Technology Development Program(No.RS-202400456324)funded by the Ministry of Trade,Industry&Energy(MOTIE,Korea)by the National Research Foundation(NRF)of Korea grant(No.RS-2024-00454367)funded by the Ministry of Science and ICT(MSIT,Korea)。
文摘K–Se batteries have been identified as promising energy storage systems owing to their high energy density and cost-effectiveness.However,challenges such as substantial volume changes and low Se utilization require further investigation.In this study,novel N-doped multichannel carbon nanofibers(h-NMCNFs)with hierarchical porous structures were successfully synthesized as efficient cathode hosts for K–Se batteries through the carbonization of two electrospun immiscible polymer nanofibers and subsequent chemical activation.Mesopores originated from the decomposition of the polymer embedded in the carbon nanofibers,and micropores were introduced via KOH activation.During the activation step,hierarchical porous carbon nanofibers with enhanced pore volumes were formed because of the micropores in the carbon nanofibers.Owing to the mesopores that enabled easy access to the electrolyte and the high utilization of chain-like Se within the micropores,the Se-loaded hierarchical porous carbon nanofibers(60 wt%Se)exhibited a high discharge capacity and excellent rate performance.The discharge capacity of the nanofibers at the 1,000th cycle was 210.8 mA.h.g^(-1)at a current density of 0.5C.The capacity retention after the initial activation was 64%.In addition,a discharge capacity of 165 mA.h.g^(-1)was obtained at an extremely high current density of 3.0C.
基金supported by the Key Research and Development Program of Sichuan Province(Grant No.2023ZHCG0050)the Fundamental Research Funds for the Central Universities of China(Grant No.2682024QZ006 and 2682024ZTPY042)the Analytic and Testing Center of Southwest Jiaotong University.
文摘As modern communication and detection technologies advance at a swift pace,multifunctional electromagnetic interference(EMI)shielding materials with active/positive infrared stealth,hydrophobicity,and electric-thermal conversion ability have received extensive attention.Meeting the aforesaid requirements simultaneously remains a huge challenge.In this research,the melamine foam(MF)/polypyrrole(PPy)nanowire arrays(MF@PPy)were fabricated via one-step electrochemical polymerization.The hierarchical MF@PPy foam was composed of three-dimensional PPy micro-skeleton and ordered PPy nanowire arrays.Due to the upwardly grown PPy nanowire arrays,the MF@PPy foam possessed good hydrophobicity ability with a water contact angle of 142.00°and outstanding stability under various harsh environments.Meanwhile,the MF@PPy foam showed excellent thermal insulation property on account of the low thermal conductivity and elongated ligament characteristic of PPy nanowire arrays.Furthermore,taking advantage of the high conductivity(128.2 S m^(-1)),the MF@PPy foam exhibited rapid Joule heating under 3 V,resulting in dynamic infrared stealth and thermal camouflage effects.More importantly,the MF@PPy foam exhibited remarkable EMI shielding effectiveness values of 55.77 dB and 19,928.57 dB cm^(2)g^(-1).Strong EMI shielding was put down to the hierarchically porous PPy structure,which offered outstanding impedance matching,conduction loss,and multiple attenuations.This innovative approach provides significant insights to the development of advanced multifunctional EMI shielding foams by constructing PPy nanowire arrays,showing great applications in both military and civilian fields.
基金supported by Macao Science and Technology Development Fund,Macao SAR,China(Grant No.:0043/2023/AFJ)the National Natural Science Foundation of China(Grant No.:22173038)Macao Polytechnic University,Macao SAR,China(Grant No.:RP/FCA-01/2022).
文摘Accurate prediction of molecular properties is crucial for selecting compounds with ideal properties and reducing the costs and risks of trials.Traditional methods based on manually crafted features and graph-based methods have shown promising results in molecular property prediction.However,traditional methods rely on expert knowledge and often fail to capture the complex structures and interactions within molecules.Similarly,graph-based methods typically overlook the chemical structure and function hidden in molecular motifs and struggle to effectively integrate global and local molecular information.To address these limitations,we propose a novel fingerprint-enhanced hierarchical graph neural network(FH-GNN)for molecular property prediction that simultaneously learns information from hierarchical molecular graphs and fingerprints.The FH-GNN captures diverse hierarchical chemical information by applying directed message-passing neural networks(D-MPNN)on a hierarchical molecular graph that integrates atomic-level,motif-level,and graph-level information along with their relationships.Addi-tionally,we used an adaptive attention mechanism to balance the importance of hierarchical graphs and fingerprint features,creating a comprehensive molecular embedding that integrated hierarchical mo-lecular structures with domain knowledge.Experiments on eight benchmark datasets from MoleculeNet showed that FH-GNN outperformed the baseline models in both classification and regression tasks for molecular property prediction,validating its capability to comprehensively capture molecular informa-tion.By integrating molecular structure and chemical knowledge,FH-GNN provides a powerful tool for the accurate prediction of molecular properties and aids in the discovery of potential drug candidates.
基金co-supported by the National Natural Science Foundation of China(No.62103432)the China Postdoctoral Science Foundation(No.284881)the Young Talent fund of University Association for Science and Technology in Shaanxi,China(No.20210108)。
文摘Exo-atmospheric vehicles are constrained by limited maneuverability,which leads to the contradiction between evasive maneuver and precision strike.To address the problem of Integrated Evasion and Impact(IEI)decision under multi-constraint conditions,a hierarchical intelligent decision-making method based on Deep Reinforcement Learning(DRL)was proposed.First,an intelligent decision-making framework of“DRL evasion decision”+“impact prediction guidance decision”was established:it takes the impact point deviation correction ability as the constraint and the maximum miss distance as the objective,and effectively solves the problem of poor decisionmaking effect caused by the large IEI decision space.Second,to solve the sparse reward problem faced by evasion decision-making,a hierarchical decision-making method consisting of maneuver timing decision and maneuver duration decision was proposed,and the corresponding Markov Decision Process(MDP)was designed.A detailed simulation experiment was designed to analyze the advantages and computational complexity of the proposed method.Simulation results show that the proposed model has good performance and low computational resource requirement.The minimum miss distance is 21.3 m under the condition of guaranteeing the impact point accuracy,and the single decision-making time is 4.086 ms on an STM32F407 single-chip microcomputer,which has engineering application value.
基金supported by the Science and Technology Department of Qinghai Province,China(No.2022-ZJ-932Q).
文摘The increase in the utilization of infrared heat detection technology in military applications necessitates research on composites with improved thermal transmission performance and microwave absorption capabilities.This study satisfactorily fabricated a series of MoS_(2)/BN-xyz composites(which were characterized by the weight ratio of MoS_(2)to BN,denoted by xy:z)through chemical vapor depos-ition,which resulted in their improved thermal stability and thermal transmission performance.The results show that the remaining mass of MoS_(2)/BN-101 was as high as 69.25wt%at 800℃under air atmosphere,and a temperature difference of 31.7℃was maintained between the surface temperature and the heating source at a heating temperature of 200℃.Furthermore,MoS_(2)/BN-301 exhibited an im-pressive minimum reflection loss value of-32.21 dB at 4.0 mm and a wide effective attenuation bandwidth ranging from 9.32 to 18.00 GHz(8.68 GHz).Therefore,these simplified synthesized MoS_(2)/BN-xyz composites demonstrate great potential as highly efficient con-tenders for the enhancement of microwave absorption performance and thermal conductance.
基金supported by the National Natural Science Foundation of China(No.32272399)the Shanghai Natural Science Foundation(No.21ZR1427500).
文摘Listeria monocytogenes(LM)is a dangerous foodborne pathogen for humans.One emerging and validated method of indirectly assessing LM in food is detecting 3-hydroxy-2-butanone(3H2B)gas.In this study,the synthesis of 3-(2-aminoethylamino)propyltrimethoxysilane(AAPTMS)functionalized hierarchical hollow TiO_(2)nanospheres was achieved via precise controlling of solvothermal reaction temperature and post-grafting route.The sensors based on as-prepared materials exhibited excellent sensitivity(480 Hz@50 ppm),low detection limit(100 ppb),and outstanding selectivity.Moreover,the evaluation of LM with high sensitivity and specificity was achieved using the sensors.Such stable three-dimensional spheres,whose distinctive hierarchical and hollow nanostructure simultaneously improved both sensitivity and response/recovery speed dramatically,were spontaneously assembled by nanosheets.Meanwhile,the moderate loadings of AAPTMS significantly improved the selectivity of sensors.Then,the gas-sensing mechanism was explored by utilizing thermodynamic investigation,Gaussian 16 software,and in situ diffuse reflectance infrared transform spectroscopy,illustrating the weak chemisorption between the-NHgroup and 3H2B molecules.These portable sensors are promising for real-time assessment of LM at room temperature,which will make a magnificent contribution to food safety.
文摘Introduction It is necessary for an ideal bioceramic scaffold to have a suitable structure.The structure can affect the mechanical properties of the scaffold(i.e.,elastic modulus and compressive strength)and the biological properties of the scaffold(i.e.,degradability and cell growth rate).Lattice structure is a kind of periodic porous structure,which has some advantages of light weight and high strength,and is widely used in the preparation of bioceramic scaffolders.For the structure of the scaffold,high porosity and large pore size are important for bone growth,bone integration and promoting good mechanical interlocking between neighboring bones and the scaffold.However,scaffolds with a high porosity often lack mechanical strength.In addition,different parts of the bone have different structural requirements.In this paper,scaffolds with a non-uniform structure or a hierarchical structure were designed,with loose and porous exterior to facilitate cell adhesion,osteogenic differentiation and vascularization as well as relatively dense interior to provide sufficient mechanical support for bone repair.Methods In this work,composite ceramics scaffolds with 10%akermanite content were prepared by DLP technology.The scaffold had a high porosity outside to promote the growth of bone tissue,and a low porosity inside to withstand external forces.The compressive strength,fracture form,in-vitro degradation performance and bioactivity of graded bioceramic scaffolds were investigated.The models of scaffolds were imported into the DLP printer with a 405 nm light.The samples were printed with the intensity of 8 mJ/cm^(2)and a layer thickness of 50μm.Finally,the ceramic samples were sintered at 1100℃.The degradability of the hierarchical gyroid bioceramic scaffolds was evaluated through immersion in Tris-HCl solution and SBF solution at a ratio of 200 mL/g.The bioactivity of bioceramic was obtained via immersing them in SBF solution for two weeks.The concentrations of calcium,phosphate,silicon,and magnesium ions in the soaking solution were determined by an inductively coupled plasma optical emission spectrometer.Results and discussion In this work,a hierarchical Gyroid structure HA-AK10 scaffold(sintered at 1100℃)with a radial internal porosity of 50%and an external porosity of 70%is prepared,and the influence of structural form on the compressive strength and degradation performance of the scaffold is investigated.The biological activity of the bioceramics in vitro is also verified.The mechanical simulation results show that the stress distribution corresponds to the porosity distribution of the structure,and the low porosity is larger and the overall stress concentration phenomenon does not appear.After soaking in SBF solution,Si—OH is firstly formed on the surface of bioceramics,and then silicon gel layer is produced due to the presence of calcium and silicon ions.The silicon gel layer is dissociated into negatively charged groups under alkaline environment secondary adsorption of calcium ions and phosphate ions,forming amorphous calcium phosphate,and finally amorphous calcium phosphate crystals and adsorption of carbonate ions,forming carbonate hydroxyapatite.This indicates that the composite bioceramics have a good biological activity in-vitro and can provide a good environment for the growth of bone cells.A hierarchical Gyroid ceramic scaffold with a bone geometry is prepared via applying the hierarchical structure to the bone contour scaffold.The maximum load capacity of the hierarchical Gyroid ceramic scaffold is 8 times that of the uniform structure.Conclusions The hierarchical structure scaffold designed had good overall compressive performance,good degradation performance,and still maintained a good mechanical stability during degradation.In addition,in-vitro biological experimental results showed that the surface graded composite scaffold could have a good in-vitro biological activity and provide a good environment for bone cells.Compared to the heterosexual structure,the graded scaffold had greater mechanical properties.
基金Supported by the National Natural Science Foundation of China(61601176)。
文摘In this paper,we propose hierarchical attention dual network(DNet)for fine-grained image classification.The DNet can randomly select pairs of inputs from the dataset and compare the differences between them through hierarchical attention feature learning,which are used simultaneously to remove noise and retain salient features.In the loss function,it considers the losses of difference in paired images according to the intra-variance and inter-variance.In addition,we also collect the disaster scene dataset from remote sensing images and apply the proposed method to disaster scene classification,which contains complex scenes and multiple types of disasters.Compared to other methods,experimental results show that the DNet with hierarchical attention is robust to different datasets and performs better.
基金supported by the Natural Science Foundation of Shandong Province(No.ZR2022MB034)the Development Program Project of the Young Innovation Team of Institutions of Higher Learning in Shandong Province。
文摘Endowing stimuli-responsive materials with micro-nano structures is an intriguing strategy for the fabrication of superwetting surfaces;however,its application is limited by poor chemical/mechanical stability.Herein,a simple and versatile strategy was developed to fabricate durable polymeric superwetting surfaces with photoswitchable wettability on hierarchically structured metallic substrates.Inspired by nature,a novel functional terpolymer incorporating mussel-inspired catechol groups,photoresponsive azobenzene groups,and low-surface-energy fluorine-containing groups was synthesized via solution radical polymerization.The azobenzene-containing terpolymer possesses outstanding photoresponsiveness in both the solution and film states because of the trans-cis isomerization of the azobenzene moieties.After dip-coating with the mussel-inspired azo-copolymer,the as-prepared smart surfaces exhibited a photo-triggered change in wettability between high hydrophobicity and superhydrophilicity.More importantly,these superwetting surfaces with enhanced adhesion properties can tolerate harsh environmental conditions and repeated abrasion tests,thereby demonstrating excellent chemical robustness and mechanical durability.This study paves a new avenue for the convenient and large-scale fabrication of robust smart surfaces that could find widespread potential applications in microfluidic devices,water treatment,and functional coatings.
基金supported by the National Natural Science Foundation of China(Nos.12072327,12302497)the National Outstanding Youth Science Fund Project(No.12125206)+2 种基金Major International Joint Research Project(No.W2411003)Fund raised by China Electric Power Research Institute(No.GC80-21-002)CAS Project for Young Scientists in Basic Research(YSBR-096).
文摘The development and deployment of aluminum conductor have been significantly hampered by the contradiction of yield strength,uniform elongation,and electrical conductivity.Herein,we successfully fabricated a pure aluminum(Al)clad aluminum alloy(AA)rod with hierarchical compositions and microstructures.The proposed pure Al clad AA rod showcases an optimized combination of yield strength,uniform elongation,and electrical conductivity,i.e.,easing the restriction on improving yield strength,uniform elongation,and electrical conductivity.Compared to existing experiments,uniform elongation improved fourfold,while yield strength increased by 13%and electrical conductivity improved by 2%in terms of the international annealed copper standard(IACS).Microstructural characterizations and theoretical analyses revealed that the optimal performance of the Al clad AA arose from low-density low-angle grain boundaries(LAGBs)in the outer Al and high-density LAGBs with nanoscale precipitations in the inner AA.Our findings offer a compelling strategy for fabricating high-performance aluminum conductors,thereby laying a solid technical foundation for their wide application in power delivery systems.
基金supported by National Natural Science Foundation of China(52376104,52201158)Joint Funds of the National Natural Science Foundation of China(U20A20302)+3 种基金Innovative group projects in Hebei Province(E2021202006)the project of Science and Technology in the Universities of Hebei Province(JZX2023006)Natural Science Foundation of Hebei Province(C202202003)Hebei University of Technology Cross-disciplinary(XKJC-2024001)。
文摘Hierarchical lignin-derived ordered mesoporous carbon(HOMC)was significant for advanced supercapacitors.However,achieving controllable fabrication and optimizing electrochemical behavior were challenging.In this work,an eco-friendly HOMC was synthesized using lignin as carbon precursors and Zn^(2+)as cross-linking and pore-forming agents,followed by KHCO_(3)activation,eliminating the need for toxic phenolic resins and acid treatments for metal removal.Machine learning technology,specifically an Artificial Neural Network(ANN model,was utilized to assist the experimental design and prediction.The ANN model suggested an ideal hierarchical structure and optimized oxygen level,achieved through the adjustment of Zn^(2+)additive concentration,carbonization temperature,and subsequent KHCO_(3)activation to maximize capacitance.The HOMC electrode,with a micropore-to-mesopore ratio(S_(micro)/S_(meso))of 1.01 and an oxygen content of 8.81 at%,acquired a specific capacitance of 362 F·g^(-1)at 0.5 A·g^(-1)in 6 mol·L^(-1)KOH electrolyte.The assembled HOMC//HOMC supercapacitor could afford a high energy density of 33.38 Wh·kg^(-1)with a corresponding specific power density of 300 W·kg^(-1)in TEATFB PC electrolyte.Meanwhile,the long-term cycle stability of 94.33%was achieved after 20,000 cycles.This work provides an ANN assisted strategy for the synthesis of HOMC,highlighting its potential to valorize biomass and agricultural waste in sustainable energy storag solutions.
基金the National Natural Science Foundation of China(grant 22208054,22178059 and U23A20113)Natural Science Foundation of Fujian Province,China(grant 2022J01572)+1 种基金Sinochem Quanzhou Energy Technology Co.,Ltd.(grant ZHQZKJ-19-F-ZS-0076)Qingyuan Innovation Laboratory(grant 00121002 and 00523005)for their financial supports.
文摘Hierarchical SAPO-11, featuring both micropore and mesopore channels, demonstrates an outstanding performance in high-octane gasoline production. In this work, we propose an economic and effective approach to directly fabricate hierarchical SAPO-11 molecular sieve from natural kaolin, eliminating the need for mesoporogens. The systematic characterization results show that the kaolin-derived SAPO-11 possesses abundant micro-mesoporous structure and more Brønsted (B) acid sites on the external surface in contrast with the conventional SAPO-11 prepared employing silica sol as silicon source as well as SAPO-11 synthesized with the assist with of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (F127). The analysis of the formation process reveals that the kaolin not only provides silicon source for the SAPO-11 crystal growth, but also offers confined environment for crystal growth along the preferential orientation, resulting in the generation of the microporous and mesoporous structure. Benefiting from these unique properties, the kaolin-derived Pt/SAPO-11 exhibits considerably improved selectivity for di-branched C8 isomers in n-octane hydroisomerization.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52471025 and 51901252)the Natural Science Foundation of Hunan Province(Grant No.2023JJ30684)the Natural Science Foundation of Changsha Municipal(Grant No.kq2202091).
文摘In aerospace,BBC-Nb alloys confront notable challenges in thermal stability and toughness under cyclic fatigue at varying temperatures.Insufficient thermal stability and expedited coalescence of precipitates substantially accelerates the degradation of alloys at elevated temperatures.Here,a Nb alloy with impressive thermal stability and mechanical properties was designed using theoretical calculations and a two-step graded heat treatment process.The superlative properties of the Nb alloy are primarily associated with the NbC hierarchical structures,i.e.,stable nanoparticles in Nb-BCC grains and discontinuous microparticles at grain boundaries(GBs).The hierarchical carbides configuration avoids continuous precipitation of carbides at GBs and preferential coarsening within the grains.The process involves precipitating ZrC nanoparticles at 1350℃,then stabilizing NbC at 1800℃ by replacing Zr with Nb.Nb-FCC nanophases enveloping NbC prevent coarsening and have strong relationships with both NbC nanoparticles and matrix.The concept of fine-tuning NbC precipitation within grains and introducing NbC at GBs with a substitution method offers a strategy for high-strength,heat-resistant materials.
基金financially supported by the National Natural Science of Foundation of China(No.52371097)the Shenyang Unveiling and Leading Project,China(No.22-301-1-01)。
文摘The wave-absorbing materials are kinds of special electromagnetic functional materials and have been widely used in electromagnetic pollution control and military fields.In-situ integrated hierarchical structure construction is thought as a promising route to improve the microwave absorption performance of the materials.In the present work,layer-structured Co-metal-organic frameworks(Co-MOFs)precursors were grown in-situ on the surface of carbon fibers with the hydrothermal method.After annealed at 500℃ under Ar atmosphere,a novel multiscale hierarchical composite(Co@C/CF)was obtained with the support of carbon fibers,keeping the flower-like structure.Scanning electron microscope,transmission electron microscope,X-ray diffraction,Raman,and X-ray photoelectron spectroscopy were performed to analyze the microstructure and composition of the hierarchical structure,and the microwave absorption performance of the Co@C/CF composites were investigated.The results showed that the growth of the flower-like structure on the surface of carbon fiber was closely related to the metal-to-ligand ratio.The optimized Co@C/CF flower-like composites achieved the best reflection loss of−55.7 dB in the low frequency band of 6–8 GHz at the thickness of 2.8 mm,with the corresponding effective absorption bandwidth(EAB)of 2.1 GHz.The EAB of 3.24 GHz was achieved in the high frequency range of 12–16 GHz when the thickness was 1.5 mm.The excellent microwave absorption performance was ascribed to the introduction of magnetic components and the construction of the unique structure.The flower-like structure not only balanced the impedance of the fibers themselves,but also extended the propagation path of the microwave and then increased the multiple reflection losses.This work provides a convenient method for the design and development of wave-absorbing composites with in-situ integrated structure.
基金supported by National Natural Science Foundation of China(22378219)Project ZR2023QB173 supported by Shandong Provincial Natural Science Foundation and Postdoctoral Application Project of Qingdao(QHBSH20230102024)Prof.H.Tang gratefully acknowledges financial support from Taishan Youth Scholar Program of Shandong Province.
文摘By integrating photocatalytic H_(2)O_(2) production with furfuryl alcohol(FAL)oxidation,this coupled process establishes an atom-economical pathway for sustainable chemical synthesis,simultaneously achieving energy storage and biomass valorization.This study introduces a meticulously engineered MOF@MOF hierarchical photocatalytic architecture,specifically the PCN-134@MOF-525(PM-X series)composite,designed for synergistic catalysis of these processes.By strategically integrating two distinct MOF materials,we circumvent the limitations of single-component systems,such as facile charge carrier recombination,and establish a redox dualactive site catalytic system.This rational design transcends simple additivity,yielding emergent catalytic behaviors driven by precise control over interfacial electric fields and dynamic structural modulation.The resultant hierarchical organization enhances light harvesting,promotes efficient charge separation,and accelerates charge transfer kinetics.Mechanistic insights,derived from photoelectrochemical,spectroscopic,and in-situ IR analyses,reveal a synergistic interplay that suppresses electron-hole recombination and spatially segregates redox processes.PM-3 demonstrates a significant enhancement in catalytic efficiency(the highest value reported),exhibiting a 4.5-fold increase in both H_(2)O_(2) production and FAL oxidation rates compared to the individual MOF components,achieving near-quantitative FAL conversion and exceptional selectivity.This work provides a potent design blueprint,emphasizing interfacial engineering and structural synergy for unprecedented efficiency and selectivity in sustainable chemical transformations.
