Although the Mg-air battery with high theoretical energy density is desirable for the energy supply of marine engineering equipment,its applications remain limited due to the low actual discharge voltage and inferior ...Although the Mg-air battery with high theoretical energy density is desirable for the energy supply of marine engineering equipment,its applications remain limited due to the low actual discharge voltage and inferior Mg anode utilization rate.In addition to the microstructure of Mg alloy anodes,the properties of discharge product films are of great importance to the discharge performance.Herein,the discharge behaviors of Mg-Y-Zn alloys are first studied mainly from the perspective of film properties.Through contrastive analysis,it is found that the sufficient Y^(3+) produced during the discharge process can substitute Mg^(2+) in Mg(OH)_(2) to introduce effective cation vacancies.The Mg-Y-Zn anode with profuse cation vacancies in the product film shows a synergy of potential and efficiency,and this can be attributed to an increase in the migration pathway for Mg^(2+),reducing the diffusion over-potential caused by the protective product film.This study is expected to provide a new strategy from the perspective of cation vacancy design of discharge film for developing high-performance Mg-air batteries.展开更多
The ocean holds abundant petroleum,natural gas,and mineral resources that form an essential material foundation for the sustainable development of modern society.The safe and efficient exploitation of these resources ...The ocean holds abundant petroleum,natural gas,and mineral resources that form an essential material foundation for the sustainable development of modern society.The safe and efficient exploitation of these resources depends heavily on various slender,composite,flexible structures,including umbilical cables,dynamic power cables for offshore wind turbines,petroleum pipelines(both bonded and unbonded),deep-sea mining risers,and LNG cryogenic flexible hoses.These structures feature highly complex configurations and incur substantial design and manufacturing costs,while operating in environments far more severe and variable than those of onshore pipelines.They must withstand multisource stochastic loads generated by the combined action of wind,waves,currents,and tides,and maintain robustness under extreme conditions such as typhoons,earthquakes,and explosions.展开更多
Magnetic absorbers with high permeability have significant advantages in lowfrequency and broadband electromagnetic wave(EMW)absorption.However,the insufficient magnetic loss and inherent high conductivity of existing...Magnetic absorbers with high permeability have significant advantages in lowfrequency and broadband electromagnetic wave(EMW)absorption.However,the insufficient magnetic loss and inherent high conductivity of existing magnetic absorbers limit the further expansion of EMW absorption bandwidth.Herein,the spinel(FeCoNiCrCu)_(3)O_(4) high-entropy oxides(HEO)are successfully constructed on the surface of FeCoNiCr_(0.4)Cu_(0.2) high-entropy alloys(HEA)through low-temperature oxygen bath treatment.On the one hand,HEO and HEA have different magnetocrystalline anisotropies,which is conducive to achieving continuous natural resonance to improve magnetic loss.On the other hand,HEO with low conductivity can serve as an impedance matching layer,achieving magneto-electric co-modulation.When the thickness is 5 mm,the minimum reflection loss(RL)value and absorption bandwidth(RL<−5 dB)of bi-phase high-entropy composites(BPHEC)can reach−12.8 dB and 633 MHz,respectively.The RCS reduction value of multilayer sample with impedance gradient characteristic can reach 18.34 dB m^(2).In addition,the BPHEC also exhibits temperaturestable EMW absorption performance,high Curie temperature,and oxidation resistance.The absorption bandwidth maintains between 593 and 691 MHz from−50 to 150℃.This work offers a new and tunable strategy toward modulating the electromagnetic genes for temperature-stable ultra-broadband megahertz EMW absorption.展开更多
Transition metal phosphides(TMPs),with tunable electronic structures and diverse compositions,are promising candidates for electrocatalytic water splitting.However,their unsatisfactory electrical conductivity and tend...Transition metal phosphides(TMPs),with tunable electronic structures and diverse compositions,are promising candidates for electrocatalytic water splitting.However,their unsatisfactory electrical conductivity and tendency to aggregate during reactions result in structural instability,ultimately hindering further improvement of their electrocatalytic performance.To address these issues,a bamboo-leaf-like FeCoP/MXene heterojunction was synthesized by hydrothermal and thermal treatments,utilizing highly conductive MXene as the substrate.Density functional theory(DFT)calculations and experimental characterization reveal that strong Ti-O-Co/Fe covalent bond are formed between MXene and FeCoP through hybridization of O 2p and Co/Fe 3d orbitals,which enhance the structural stability of the interface and facilitate the effective anchoring of FeCoP on the MXene surface.Consequently,the structural stability and electrical conductivity of the catalyst are improved simultaneously.Additionally,interfacial charge redistribution optimizes the Gibbs free energy of hydrogen adsorption at the Co,Fe,and Ti sites while promoting the adsorption and activation of water molecules.These factors interact synergistically,leading to enhanced bi-functional electrocatalytic performance for both the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).In a FeCoP/MXene(+‖-)two-electrode system,the catalyst achieves a current density of 10 mA cm^(-2)at a potential of 1.5 V,which is superior to the RuO_(2)(+)‖Pt/C(-)system.The assembled water splitting device exhibits long-term stability for up to 100 h at a current density of 100 mA cm^(-2).Furthermore,an anion exchange membrane water electrolyzer(AEMWE)equipped with FeCoP/MXene as both anode and cathode achieves an industrial-grade current density of 500 mA cm^(-2)at 1.83 V.These results highlight the critical role of interfacial engineering in enhancing the electrocatalytic performance of TMPs for water splitting and provide valuable insights for the design of novel bifunctional TMP catalysts.展开更多
This study investigates how to pedagogically integrate ideological education with competency development in the Intercultural Communication course,a challenge arising from China’s dual reform contexts of the New Libe...This study investigates how to pedagogically integrate ideological education with competency development in the Intercultural Communication course,a challenge arising from China’s dual reform contexts of the New Liberal Arts initiative and the national curriculum ideology policy.As global interactions intensify,cultivating foreign language professionals who possess both firm cultural confidence and sophisticated intercultural competence have become a critical educational imperative.This exploratory study investigates how a three-dimensional“Value-Knowledge-Competency”framework can guide the redesign of course content,task design,and assessment to achieve organic fusion.Drawing on qualitative data from a case study,it analyzes specific implementation pathways,synthesizes teacher and student feedback,and discusses the resultant challenges and broader implications for foreign language curriculum reform.The findings suggest that such an integrated approach can effectively synergize value guidance with skill cultivation,though its success hinges on overcoming issues related to pedagogical naturalness,resource allocation,and standardized evaluation.展开更多
Accurate time delay estimation of target echo signals is a critical component of underwater target localization.In active sonar systems,echo signal processing is vulnerable to the effects of reverberation and noise in...Accurate time delay estimation of target echo signals is a critical component of underwater target localization.In active sonar systems,echo signal processing is vulnerable to the effects of reverberation and noise in the maritime environment.This paper proposes a novel method for estimating target time delay using multi-bright spot echoes,assuming the target’s size and depth are known.Aiming to effectively enhance the extraction of geometric features from the target echoes and mitigate the impact of reverberation and noise,the proposed approach employs the fractional order Fourier transform-frequency sliced wavelet transform to extract multi-bright spot echoes.Using the highlighting model theory and the target size information,an observation matrix is constructed to represent multi-angle incident signals and obtain the theoretical scattered echo signals from different angles.Aiming to accurately estimate the target’s time delay,waveform similarity coefficients and mean square error values between the theoretical return signals and received signals are computed across various incident angles and time delays.Simulation results show that,compared to the conventional matched filter,the proposed algorithm reduces the relative error by 65.9%-91.5%at a signal-to noise ratio of-25 dB,and by 66.7%-88.9%at a signal-to-reverberation ratio of−10 dB.This algorithm provides a new approach for the precise localization of submerged targets in shallow water environments.展开更多
Studies of wave-current interactions are vital for the safe design of structures.Regular waves in the presence of uniform,linear shear,and quadratic shear currents are explored by the High-Level Green-Naghdi model in ...Studies of wave-current interactions are vital for the safe design of structures.Regular waves in the presence of uniform,linear shear,and quadratic shear currents are explored by the High-Level Green-Naghdi model in this paper.The five-point central difference method is used for spatial discretization,and the fourth-order Adams predictor-corrector scheme is employed for marching in time.The domain-decomposition method is applied for the wave-current generation and absorption.The effects of currents on the wave profile and velocity field are examined under two conditions:the same velocity of currents at the still-water level and the constant flow volume of currents.Wave profiles and velocity fields demonstrate substantial differences in three types of currents owing to the diverse vertical distribution of current velocity and vorticity.Then,loads on small-scale vertical cylinders subjected to regular waves and three types of background currents with the same flow volume are investigated.The maximum load intensity and load fluctuation amplitude in uniform,linear shear,and quadratic shear currents increase sequentially.The stretched superposition method overestimates the maximum load intensity and load fluctuation amplitude in opposing currents and underestimates these values in following currents.The stretched superposition method obtains a poor approximation for strong nonlinear waves,particularly in the case of the opposing quadratic shear current.展开更多
A surface pyrolysis and gas-phase combustion of the Ammonium Perchlorate(AP)/Hydroxy Terminated Polybutadiene(HTPB)composite propellant reaction kinetic mechanism with five-step chemical reaction is adopted.The effect...A surface pyrolysis and gas-phase combustion of the Ammonium Perchlorate(AP)/Hydroxy Terminated Polybutadiene(HTPB)composite propellant reaction kinetic mechanism with five-step chemical reaction is adopted.The effects of helium injection on the burning rate and combustion of AP/HTPB propellant are analyzed in details,and the characteristics of motor performance are obtained.The numerical simulation results demonstrate that helium injection enhances the combustion chamber pressure,thereby increasing the burning rate of propellant.However,the primary combustion reaction of the AP/HTPB propellant takes place within a thin layer on the burning surface,so the low-temperature helium has minimal impact on the gasphase combustion.Ultimately,the helium not only elevates the nozzle exit velocity,resulting in specific impulse gain,but also reduces the exhaust plume temperature.With an increase of helium mass flow rate,the area of the velocity increase zone at the nozzle exit continuously decreases,but the average velocity in the motor exit continuously increases.Overall,when the helium flow rate is 2.5 kg/s,the specific impulse can reach 10.5%.Reducing the helium injection hole diameter enhances mixing of helium and combustion gas and expands the velocity increase zone,thereby maximizing the exit velocity gain in average velocity at the nozzle exit.When the injection hole diameter is reduced from 100 mm to 20 mm,the specific impulse gain increases from 3.1%to 10.6%.Furthermore,increasing helium injection temperature greatly boosts the velocity of the mixed gas with the same helium mass fraction ultimately improving specific impulse.展开更多
This study investigates the effects of ocean boundaries on modal shapes in very-low-frequency(VLF,1–10 Hz)sound propagation through the deep ocean.Utilizing a normal mode solution formulated in terms of parabolic cyl...This study investigates the effects of ocean boundaries on modal shapes in very-low-frequency(VLF,1–10 Hz)sound propagation through the deep ocean.Utilizing a normal mode solution formulated in terms of parabolic cylinder functions(PCF),we demonstrate that boundary interactions induce a phase change reduction below-πat frequencies of several hertz.This reduction,in turn,forces a key transition in the solution,shifting the order of the PCF from integer to non-integer values.Analysis of the characteristic shape of the PCF versus its order reveals that these boundary-influenced modes exhibit an energy shift toward deeper regions and a weakened axial convergence of the underwater sound field.展开更多
Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The t...Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.展开更多
Underwater gas-liquid two-phase propulsion technology is an emerging propulsion method that offers high efficiency and unrestricted navigation speed.The integration of this technology into water ramjet engines can sig...Underwater gas-liquid two-phase propulsion technology is an emerging propulsion method that offers high efficiency and unrestricted navigation speed.The integration of this technology into water ramjet engines can significantly enhance propulsion efficiency and holds substantial potential for broad applications.However,forming a gas-liquid two-phase flow within the nozzle requires introducing a large amount of rammed seawater.At this time,there is a complex phase transition problem of combustion products in the combustion chamber,which makes the thermodynamic calculation for gas-liquid two-phase water ramjet engines particularly challenging.This paper proposes a thermodynamic calculation method for gas-liquid two-phase water ramjet engines,based on the energy equation for gas-liquid two-phase flow and traditional thermodynamic principles,enabling thermodynamic calculations under conditions of ultra-high water-fuel ratios.Additionally,ground ignition tests of the gas-liquid two-phase engine were conducted,yielding critical engine test parameters.The results demonstrate that the gas-liquid two-phase water ramjet engine achieves a high specific impulse,with a theoretical maximum specific impulse of up to 7000(N s)/kg.The multiphase flow effects significantly impact engine performance,with specific impulse losses reaching up to 25.86%.The error between the thrust and specific impulse in the ground test and the theoretical values is within 10%,validating the proposed thermodynamic calculation method as a reliable reference for further research on gas-liquid two-phase water ramjet engines.展开更多
The demand for ^(238)Pu(nuclear battery heat source)drives the separation of its precursor,^(237)Np,from spent nuclear fuel(SNF).However,the co-existence of multi-valence states(IV/V/VI)of Np and similar redox behavio...The demand for ^(238)Pu(nuclear battery heat source)drives the separation of its precursor,^(237)Np,from spent nuclear fuel(SNF).However,the co-existence of multi-valence states(IV/V/VI)of Np and similar redox behavior with Pu(IV)hinder the effective separation of Np.N-Butyraldehyde(n-C_(3)H_(7)CHO)selectively reduces Np(VI)to Np(V)without reducing Pu(IV).Herein,we examined the reduction mechanisms of Np(VI)and Pu(IV)by n-C_(3)H_(7)CHO using relativistic density functional theory.Based on the results of the potential energy profiles,the reductions of both Np(VI)and Pu(IV)by n-C_(3)H_(7)CHO are thermodynamically feasible,whereas only the former is kinetically achievable.It uncovers that n-C_(3)H_(7)CHO can only reduce Np(VI)to Np(V)owing to kinetically controlled selective reduction.The analyses of spin density and bond distance indicate that the reduction nature for the first Np(VI)/Pu(IV)belongs to hydrogen atom transfer,whereas that for the second one involves outer-sphere electron transfer.Localized molecular orbitals(LMOs)analysis discloses the bonding evolution during the reduction process of Np(VI)/Pu(IV).This study elucidates the reason behind the kinetically controlled selective reduction of Np(VI)/Pu(IV)by n-C_(3)H_(7)CHO at the molecular level and offers in-depth perspectives on the isolation of specific metal ions from the view of kinetic control.展开更多
Designing a heterogeneous interface to improve the kinetics of electrocatalysts represents an effective yet challenging approach for enhancing the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).Herei...Designing a heterogeneous interface to improve the kinetics of electrocatalysts represents an effective yet challenging approach for enhancing the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).Herein,a simple MOF-assisted etching-pyrolysis strategy is proposed to fabricate an advanced Mott-Schottky(M–S)electrocatalyst composed of Co/CeO_(2)hetero-nanoparticles embedded within N-doped hollow carbon nanoboxes(H-Co/CeO_(2)@NCBs).Notably,the interfacial Co–O–Ce bond bridging productively facilitates the electron transfer and modulates the charge distribution of the active center,thereby contributing to the ORR/OER kinetics.As expected,the optimal M–S H-Co/CeO_(2)@NCBs catalyst exhibits promising bifunctional electrocatalytic activity with a small potential discrepancy of 0.65 V.Theoretical calculations reveal that the built-in electric field in the M–S heterojunction promotes electron transfer in oxygen electrocatalysis and the interfacial bridge-induced electron redistribution optimizes the adsorption/desorption of the oxygen intermediates,leading to reduced activation energy for the bifunctional ORR/OER reactions.Importantly,H-Co/CeO_(2)@NCBs-assembled Zn-air battery(ZAB)delivers high power density(179.8 mW cm^(−2))and long-term stability(400 h).Furthermore,the assembled flexible solid-state ZAB with H-Co/CeO_(2)@NCBs cathode also exhibits excellent charge–discharge reversibility and flexibility at various bending angles.This work provides a novel perspective on developing efficient and stable M–S bifunctional oxygen electrocatalysts.展开更多
The microstructural evolution and mechanical properties of a vacuum electron beam welded aerospace 5B70 aluminum alloy joint were studied.Quantitative analyses of the phase composition,microstructural evolution,grain ...The microstructural evolution and mechanical properties of a vacuum electron beam welded aerospace 5B70 aluminum alloy joint were studied.Quantitative analyses of the phase composition,microstructural evolution,grain size,grain boundary density,and texture changes were performed by X-ray diffraction,scanning electron microscopy,and electron backscatter diffraction.The fusion zone(FZ)comprises equiaxed cellular crystals,and a fine~20μm-thick crystal layer forms in the transition zone(TZ)between the FZ and heat affected zone(HAZ).The HAZ closely resembles the base material(BM),retaining the original rolling microstructure.Mechanical property testing shows that the fine-grained layer in the TZ exhibits the highest nanohardness,with the FZ corresponding to the lowest microhardness.The welded-joint sample has lower yield strength,ultimate tensile strength,and elongation after fracture than the BM.These reductions of mechanical properties are primarily influenced by the grain size and distribution of the precipitated phases.展开更多
Flexible materials with perovskite quantum dots(PQDs)are widely used in the field of photonics and opto-electronics due to their unique properties.Development of new materials based on these nanoparticles,incorporated...Flexible materials with perovskite quantum dots(PQDs)are widely used in the field of photonics and opto-electronics due to their unique properties.Development of new materials based on these nanoparticles,incorporated into flexible and lightweight nonwoven fabrics,demonstrated high photoconductivity and efficient light energy conversion.In this work,we propose a method for creating a stable luminescent nonwoven material using electrospinning,in which inorganic salt precursors are used without the need for additional stabilizers.Equimolar solutions of cesium and lead(Ⅱ)bromide were mixed with a fluoroplast,resulting in a series of samples.Luminescent materials were obtained containing PQDs with a composition of CsPbBr_(3),with emission peaks ranging from 507 to 517 nm under 365-nm excitation.We have experimentally established and theoretically confirmed that the peak position is related to the size of the particles formed in the fiber during electrospinning and depends on processing time.Developed materials exhibited stable luminescent properties for up to 2.5 years,making them a promising candidate for the development of new flexible optoelectronic devices based on PQDs.展开更多
Applying man-machine-environment system engineering(MMESE)in vessels is a method to improve the effectiveness of the interaction between equipment, environment, and humans for the purpose of advancing operating effici...Applying man-machine-environment system engineering(MMESE)in vessels is a method to improve the effectiveness of the interaction between equipment, environment, and humans for the purpose of advancing operating efficiency, performance, safety, and habitability of a vessel and its subsystems. In the following research, the life cycle of vessels was divided into 9 phases, and 15 research subjects were also identified from among these phases. The 15 subjects were systemized, and then the man-machine-environment engineering system application model for vessels was developed using the ICAM definition method 0 (IDEF0), which is a systematical modeling method. This system model bridges the gap between the data and information flow of every two associated subjects with the major basic research methods and approaches included, which brings the formerly relatively independent subjects together as a whole. The application of this systematic model should facilitate the application of man-machine-environment system engineering in vessels, especially at the conceptual and embodiment design phases. The managers and designers can deal with detailed tasks quickly and efficiently while reducing repetitive work.展开更多
Sustainable development for our life is important task,which is driven by key materials and technologies.In this roadmap,we discuss three main aspects in addressing environmental questions,green chemical processes and...Sustainable development for our life is important task,which is driven by key materials and technologies.In this roadmap,we discuss three main aspects in addressing environmental questions,green chemical processes and energy challenges.They are included,such as gas treatment and separation,wastewater treatment,waste gas treatment,solid waste treatment,lithium extraction,hydrogen production,water splitting,CO_(2) reduction,photocatalytic clean technologies,plastic degradation,fuel cells,lithium batteries,sodium batteries,aqueous batteries,solid state batteries,metal air batteries and supercapacitors.Their status,challenges,progress and future perspectives are also discussed.We hope that this paper can give clear views on sustainable development in materials and technologies.展开更多
With the arrival of the intelligence era of Industry 4.0,social development has shown complex and diversified characteristics,gradually forming an innovation ecological environment constructed by vertical interaction ...With the arrival of the intelligence era of Industry 4.0,social development has shown complex and diversified characteristics,gradually forming an innovation ecological environment constructed by vertical interaction of multi-layer innovation systems and horizontal collaboration of multiple organizations and departments,which has posed extremely challenging requirements for higher engineering education to cultivate engineering talents with comprehensive engineering qualities who can solve complex engineering problems.However,practical engineering problems may involve a complex knowledge chain of interdisciplinary and multi-disciplinary cross-coupling.Therefore,higher engineering education needs to form a new interdisciplinary and multi-disciplinary integrated engineering innovation talent training system.Based on the characteristics of the mechanical and electronic engineering major,we will reshape and reconstruct the core courses of the mechanical and electronic engineering major.Two core courses are formed:Drive and Measurement and Control I and Drive and Measurement and Control II,with information flow and energy flow as the main lines,following up with the comprehensive practical curriculum system based on the unity of knowledge and practice and ability-oriented thinking,supporting teaching objectives,promoting students’individual development,and providing guidelines for relevant curriculum reforms.展开更多
The paper took SPOC teaching in University Computer Foundation for example, discussed how to make online education meet the basic objectives and requirements of traditional teaching, meanwhile fulfilling the potential...The paper took SPOC teaching in University Computer Foundation for example, discussed how to make online education meet the basic objectives and requirements of traditional teaching, meanwhile fulfilling the potential applications of MOOCs to meet the needs of all walks in computer application. Based on the sharing of resources in many application-oriented universities,from the perspective of teaching reform around innovation and entrepreneurship in the era of internet, the paper focused on the exploitation and significance of MOOCs. By discussing the means to develop and build the MOOCs University Computer Foundation, which was based on curriculum sharing, the paper demonstrated the work flow. It underlined that, in the educational circumstances nowadays, it was necessary to introduce and spread MOOCs. At the same time, it elaborated on the problems existing in the construction of MOOCs University Computer Foundation, and proposed some concrete methods on further development of MOOCs to meet the requirements of students in application-oriented universities.展开更多
Under the background of new engineering,the reform of the comprehensive practical course system for mechanical and electronic engineering majors actively responds to the challenges posed by the new round of technologi...Under the background of new engineering,the reform of the comprehensive practical course system for mechanical and electronic engineering majors actively responds to the challenges posed by the new round of technological revolution and industrial transformation to higher education,cultivating top-notch innovative intellectuals with comprehensive engineering qualities,meeting the requirements of being able to solve complex engineering problems rather than just cognitive capabilities,forming two core courses through reconstructing and reshaping the core courses of the major.The core courses include Drive,Measurement,and Control I and Drive,Measurement,and Control II,which highlight the comprehensive framework of mechanical and electronic engineering professional knowledge,continuing the comprehensive practical course system based on the unity of knowledge and practice,following the trend of new engineering,highlighting the practicality of professional innovation,assisting engineering education reform,and promoting high-quality development of new engineering professionals cultivation.展开更多
基金support of the Natural Science Foundation of Heilongjiang Province of China(No.LH2023E059)the National Natural Science Foundation of China(No.52071093)the Opening Project of Jiangsu Key Laboratory of Advanced Structural Materials and Application Technology(No.ASMA202205).
文摘Although the Mg-air battery with high theoretical energy density is desirable for the energy supply of marine engineering equipment,its applications remain limited due to the low actual discharge voltage and inferior Mg anode utilization rate.In addition to the microstructure of Mg alloy anodes,the properties of discharge product films are of great importance to the discharge performance.Herein,the discharge behaviors of Mg-Y-Zn alloys are first studied mainly from the perspective of film properties.Through contrastive analysis,it is found that the sufficient Y^(3+) produced during the discharge process can substitute Mg^(2+) in Mg(OH)_(2) to introduce effective cation vacancies.The Mg-Y-Zn anode with profuse cation vacancies in the product film shows a synergy of potential and efficiency,and this can be attributed to an increase in the migration pathway for Mg^(2+),reducing the diffusion over-potential caused by the protective product film.This study is expected to provide a new strategy from the perspective of cation vacancy design of discharge film for developing high-performance Mg-air batteries.
文摘The ocean holds abundant petroleum,natural gas,and mineral resources that form an essential material foundation for the sustainable development of modern society.The safe and efficient exploitation of these resources depends heavily on various slender,composite,flexible structures,including umbilical cables,dynamic power cables for offshore wind turbines,petroleum pipelines(both bonded and unbonded),deep-sea mining risers,and LNG cryogenic flexible hoses.These structures feature highly complex configurations and incur substantial design and manufacturing costs,while operating in environments far more severe and variable than those of onshore pipelines.They must withstand multisource stochastic loads generated by the combined action of wind,waves,currents,and tides,and maintain robustness under extreme conditions such as typhoons,earthquakes,and explosions.
基金Supported by Program for the National Natural Science Foundation of China(No.52071053,U1704253,52103334)the Fundamental Research Funds for the Central Universities(DUT24GF102)the Shandong Province Natural Science Youth Fund(ZR2024QA134)。
文摘Magnetic absorbers with high permeability have significant advantages in lowfrequency and broadband electromagnetic wave(EMW)absorption.However,the insufficient magnetic loss and inherent high conductivity of existing magnetic absorbers limit the further expansion of EMW absorption bandwidth.Herein,the spinel(FeCoNiCrCu)_(3)O_(4) high-entropy oxides(HEO)are successfully constructed on the surface of FeCoNiCr_(0.4)Cu_(0.2) high-entropy alloys(HEA)through low-temperature oxygen bath treatment.On the one hand,HEO and HEA have different magnetocrystalline anisotropies,which is conducive to achieving continuous natural resonance to improve magnetic loss.On the other hand,HEO with low conductivity can serve as an impedance matching layer,achieving magneto-electric co-modulation.When the thickness is 5 mm,the minimum reflection loss(RL)value and absorption bandwidth(RL<−5 dB)of bi-phase high-entropy composites(BPHEC)can reach−12.8 dB and 633 MHz,respectively.The RCS reduction value of multilayer sample with impedance gradient characteristic can reach 18.34 dB m^(2).In addition,the BPHEC also exhibits temperaturestable EMW absorption performance,high Curie temperature,and oxidation resistance.The absorption bandwidth maintains between 593 and 691 MHz from−50 to 150℃.This work offers a new and tunable strategy toward modulating the electromagnetic genes for temperature-stable ultra-broadband megahertz EMW absorption.
基金financially supported by the National Natural Science Foundation of China(No.22279030)the Natural Science Fund for Distinguished Young Scholars of Heilongjiang Province(No.JQ2024B003)+1 种基金Fundamental Research Funds for the Undergraduate Universities of Heilongjiang Province(No.2024-KYYWF-0122)the Project of Key Laboratory of Superlight Materials and Surface Technology of Harbin Engineering University
文摘Transition metal phosphides(TMPs),with tunable electronic structures and diverse compositions,are promising candidates for electrocatalytic water splitting.However,their unsatisfactory electrical conductivity and tendency to aggregate during reactions result in structural instability,ultimately hindering further improvement of their electrocatalytic performance.To address these issues,a bamboo-leaf-like FeCoP/MXene heterojunction was synthesized by hydrothermal and thermal treatments,utilizing highly conductive MXene as the substrate.Density functional theory(DFT)calculations and experimental characterization reveal that strong Ti-O-Co/Fe covalent bond are formed between MXene and FeCoP through hybridization of O 2p and Co/Fe 3d orbitals,which enhance the structural stability of the interface and facilitate the effective anchoring of FeCoP on the MXene surface.Consequently,the structural stability and electrical conductivity of the catalyst are improved simultaneously.Additionally,interfacial charge redistribution optimizes the Gibbs free energy of hydrogen adsorption at the Co,Fe,and Ti sites while promoting the adsorption and activation of water molecules.These factors interact synergistically,leading to enhanced bi-functional electrocatalytic performance for both the hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).In a FeCoP/MXene(+‖-)two-electrode system,the catalyst achieves a current density of 10 mA cm^(-2)at a potential of 1.5 V,which is superior to the RuO_(2)(+)‖Pt/C(-)system.The assembled water splitting device exhibits long-term stability for up to 100 h at a current density of 100 mA cm^(-2).Furthermore,an anion exchange membrane water electrolyzer(AEMWE)equipped with FeCoP/MXene as both anode and cathode achieves an industrial-grade current density of 500 mA cm^(-2)at 1.83 V.These results highlight the critical role of interfacial engineering in enhancing the electrocatalytic performance of TMPs for water splitting and provide valuable insights for the design of novel bifunctional TMP catalysts.
基金Funding Source:2024 Heilongjiang Province Higher Education Teaching Reform Key Research Project.Project Name:Practice and Exploration of Curriculum-Based Political Education in the Intercultural Communication Course Under the New Liberal Arts Framework(Grant No.SJGZB2024063).
文摘This study investigates how to pedagogically integrate ideological education with competency development in the Intercultural Communication course,a challenge arising from China’s dual reform contexts of the New Liberal Arts initiative and the national curriculum ideology policy.As global interactions intensify,cultivating foreign language professionals who possess both firm cultural confidence and sophisticated intercultural competence have become a critical educational imperative.This exploratory study investigates how a three-dimensional“Value-Knowledge-Competency”framework can guide the redesign of course content,task design,and assessment to achieve organic fusion.Drawing on qualitative data from a case study,it analyzes specific implementation pathways,synthesizes teacher and student feedback,and discusses the resultant challenges and broader implications for foreign language curriculum reform.The findings suggest that such an integrated approach can effectively synergize value guidance with skill cultivation,though its success hinges on overcoming issues related to pedagogical naturalness,resource allocation,and standardized evaluation.
基金Supported by the State Key Laboratory of Acoustics and Marine Information Chinese Academy of Sciences(SKL A202507).
文摘Accurate time delay estimation of target echo signals is a critical component of underwater target localization.In active sonar systems,echo signal processing is vulnerable to the effects of reverberation and noise in the maritime environment.This paper proposes a novel method for estimating target time delay using multi-bright spot echoes,assuming the target’s size and depth are known.Aiming to effectively enhance the extraction of geometric features from the target echoes and mitigate the impact of reverberation and noise,the proposed approach employs the fractional order Fourier transform-frequency sliced wavelet transform to extract multi-bright spot echoes.Using the highlighting model theory and the target size information,an observation matrix is constructed to represent multi-angle incident signals and obtain the theoretical scattered echo signals from different angles.Aiming to accurately estimate the target’s time delay,waveform similarity coefficients and mean square error values between the theoretical return signals and received signals are computed across various incident angles and time delays.Simulation results show that,compared to the conventional matched filter,the proposed algorithm reduces the relative error by 65.9%-91.5%at a signal-to noise ratio of-25 dB,and by 66.7%-88.9%at a signal-to-reverberation ratio of−10 dB.This algorithm provides a new approach for the precise localization of submerged targets in shallow water environments.
基金Supported by the Development and Application Project of Ship CAE Software.
文摘Studies of wave-current interactions are vital for the safe design of structures.Regular waves in the presence of uniform,linear shear,and quadratic shear currents are explored by the High-Level Green-Naghdi model in this paper.The five-point central difference method is used for spatial discretization,and the fourth-order Adams predictor-corrector scheme is employed for marching in time.The domain-decomposition method is applied for the wave-current generation and absorption.The effects of currents on the wave profile and velocity field are examined under two conditions:the same velocity of currents at the still-water level and the constant flow volume of currents.Wave profiles and velocity fields demonstrate substantial differences in three types of currents owing to the diverse vertical distribution of current velocity and vorticity.Then,loads on small-scale vertical cylinders subjected to regular waves and three types of background currents with the same flow volume are investigated.The maximum load intensity and load fluctuation amplitude in uniform,linear shear,and quadratic shear currents increase sequentially.The stretched superposition method overestimates the maximum load intensity and load fluctuation amplitude in opposing currents and underestimates these values in following currents.The stretched superposition method obtains a poor approximation for strong nonlinear waves,particularly in the case of the opposing quadratic shear current.
基金co-supported by the Fundamental Research Funds for Central Universities,China(No.3072024XX0206)the Natural Science Foundation of Heilongjiang Province,China(No.LH2024E069)。
文摘A surface pyrolysis and gas-phase combustion of the Ammonium Perchlorate(AP)/Hydroxy Terminated Polybutadiene(HTPB)composite propellant reaction kinetic mechanism with five-step chemical reaction is adopted.The effects of helium injection on the burning rate and combustion of AP/HTPB propellant are analyzed in details,and the characteristics of motor performance are obtained.The numerical simulation results demonstrate that helium injection enhances the combustion chamber pressure,thereby increasing the burning rate of propellant.However,the primary combustion reaction of the AP/HTPB propellant takes place within a thin layer on the burning surface,so the low-temperature helium has minimal impact on the gasphase combustion.Ultimately,the helium not only elevates the nozzle exit velocity,resulting in specific impulse gain,but also reduces the exhaust plume temperature.With an increase of helium mass flow rate,the area of the velocity increase zone at the nozzle exit continuously decreases,but the average velocity in the motor exit continuously increases.Overall,when the helium flow rate is 2.5 kg/s,the specific impulse can reach 10.5%.Reducing the helium injection hole diameter enhances mixing of helium and combustion gas and expands the velocity increase zone,thereby maximizing the exit velocity gain in average velocity at the nozzle exit.When the injection hole diameter is reduced from 100 mm to 20 mm,the specific impulse gain increases from 3.1%to 10.6%.Furthermore,increasing helium injection temperature greatly boosts the velocity of the mixed gas with the same helium mass fraction ultimately improving specific impulse.
基金Project supported by the National Natural Science Foundation of China(Grant No.12204128)。
文摘This study investigates the effects of ocean boundaries on modal shapes in very-low-frequency(VLF,1–10 Hz)sound propagation through the deep ocean.Utilizing a normal mode solution formulated in terms of parabolic cylinder functions(PCF),we demonstrate that boundary interactions induce a phase change reduction below-πat frequencies of several hertz.This reduction,in turn,forces a key transition in the solution,shifting the order of the PCF from integer to non-integer values.Analysis of the characteristic shape of the PCF versus its order reveals that these boundary-influenced modes exhibit an energy shift toward deeper regions and a weakened axial convergence of the underwater sound field.
基金Supported by the National Natural Science Foundation of China under Grant No.51975138the High-Tech Ship Scientific Research Project from the Ministry of Industry and Information Technology under Grant No.CJ05N20the National Defense Basic Research Project under Grant No.JCKY2023604C006.
文摘Marine thin plates are susceptible to welding deformation owing to their low structural stiffness.Therefore,the efficient and accurate prediction of welding deformation is essential for improving welding quality.The traditional thermal elastic-plastic finite element method(TEP-FEM)can accurately predict welding deformation.However,its efficiency is low because of the complex nonlinear transient computation,making it difficult to meet the needs of rapid engineering evaluation.To address this challenge,this study proposes an efficient prediction method for welding deformation in marine thin plate butt welds.This method is based on the coupled temperature gradient-thermal strain method(TG-TSM)that integrates inherent strain theory with a shell element finite element model.The proposed method first extracts the distribution pattern and characteristic value of welding-induced inherent strain through TEP-FEM analysis.This strain is then converted into the equivalent thermal load applied to the shell element model for rapid computation.The proposed method-particularly,the gradual temperature gradient-thermal strain method(GTG-TSM)-achieved improved computational efficiency and consistent precision.Furthermore,the proposed method required much less computation time than the traditional TEP-FEM.Thus,this study lays the foundation for future prediction of welding deformation in more complex marine thin plates.
基金supported by the Stable Support Fund forBasic Disciplines,China(No.3072024WD0201)。
文摘Underwater gas-liquid two-phase propulsion technology is an emerging propulsion method that offers high efficiency and unrestricted navigation speed.The integration of this technology into water ramjet engines can significantly enhance propulsion efficiency and holds substantial potential for broad applications.However,forming a gas-liquid two-phase flow within the nozzle requires introducing a large amount of rammed seawater.At this time,there is a complex phase transition problem of combustion products in the combustion chamber,which makes the thermodynamic calculation for gas-liquid two-phase water ramjet engines particularly challenging.This paper proposes a thermodynamic calculation method for gas-liquid two-phase water ramjet engines,based on the energy equation for gas-liquid two-phase flow and traditional thermodynamic principles,enabling thermodynamic calculations under conditions of ultra-high water-fuel ratios.Additionally,ground ignition tests of the gas-liquid two-phase engine were conducted,yielding critical engine test parameters.The results demonstrate that the gas-liquid two-phase water ramjet engine achieves a high specific impulse,with a theoretical maximum specific impulse of up to 7000(N s)/kg.The multiphase flow effects significantly impact engine performance,with specific impulse losses reaching up to 25.86%.The error between the thrust and specific impulse in the ground test and the theoretical values is within 10%,validating the proposed thermodynamic calculation method as a reliable reference for further research on gas-liquid two-phase water ramjet engines.
基金supported by the National Natural Science Foundation of China(Nos.22376197,U2441225,22076188).
文摘The demand for ^(238)Pu(nuclear battery heat source)drives the separation of its precursor,^(237)Np,from spent nuclear fuel(SNF).However,the co-existence of multi-valence states(IV/V/VI)of Np and similar redox behavior with Pu(IV)hinder the effective separation of Np.N-Butyraldehyde(n-C_(3)H_(7)CHO)selectively reduces Np(VI)to Np(V)without reducing Pu(IV).Herein,we examined the reduction mechanisms of Np(VI)and Pu(IV)by n-C_(3)H_(7)CHO using relativistic density functional theory.Based on the results of the potential energy profiles,the reductions of both Np(VI)and Pu(IV)by n-C_(3)H_(7)CHO are thermodynamically feasible,whereas only the former is kinetically achievable.It uncovers that n-C_(3)H_(7)CHO can only reduce Np(VI)to Np(V)owing to kinetically controlled selective reduction.The analyses of spin density and bond distance indicate that the reduction nature for the first Np(VI)/Pu(IV)belongs to hydrogen atom transfer,whereas that for the second one involves outer-sphere electron transfer.Localized molecular orbitals(LMOs)analysis discloses the bonding evolution during the reduction process of Np(VI)/Pu(IV).This study elucidates the reason behind the kinetically controlled selective reduction of Np(VI)/Pu(IV)by n-C_(3)H_(7)CHO at the molecular level and offers in-depth perspectives on the isolation of specific metal ions from the view of kinetic control.
基金supported by the National Natural Science Foundation of China(U24A20550,52273264 and 52470073)the Key Project of the Heilongjiang Provincial Natural Science Foundation(ZD2024B001)Outstanding Youth Fund of Heilongjiang Province(JQ2022E005).
文摘Designing a heterogeneous interface to improve the kinetics of electrocatalysts represents an effective yet challenging approach for enhancing the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).Herein,a simple MOF-assisted etching-pyrolysis strategy is proposed to fabricate an advanced Mott-Schottky(M–S)electrocatalyst composed of Co/CeO_(2)hetero-nanoparticles embedded within N-doped hollow carbon nanoboxes(H-Co/CeO_(2)@NCBs).Notably,the interfacial Co–O–Ce bond bridging productively facilitates the electron transfer and modulates the charge distribution of the active center,thereby contributing to the ORR/OER kinetics.As expected,the optimal M–S H-Co/CeO_(2)@NCBs catalyst exhibits promising bifunctional electrocatalytic activity with a small potential discrepancy of 0.65 V.Theoretical calculations reveal that the built-in electric field in the M–S heterojunction promotes electron transfer in oxygen electrocatalysis and the interfacial bridge-induced electron redistribution optimizes the adsorption/desorption of the oxygen intermediates,leading to reduced activation energy for the bifunctional ORR/OER reactions.Importantly,H-Co/CeO_(2)@NCBs-assembled Zn-air battery(ZAB)delivers high power density(179.8 mW cm^(−2))and long-term stability(400 h).Furthermore,the assembled flexible solid-state ZAB with H-Co/CeO_(2)@NCBs cathode also exhibits excellent charge–discharge reversibility and flexibility at various bending angles.This work provides a novel perspective on developing efficient and stable M–S bifunctional oxygen electrocatalysts.
基金supported by the National Natural Science Foundation of China(Nos.52175206,52205187,52130509)the Science and Technology Planning Project of Guizhou Province,China(No.ZK[2022]013)。
文摘The microstructural evolution and mechanical properties of a vacuum electron beam welded aerospace 5B70 aluminum alloy joint were studied.Quantitative analyses of the phase composition,microstructural evolution,grain size,grain boundary density,and texture changes were performed by X-ray diffraction,scanning electron microscopy,and electron backscatter diffraction.The fusion zone(FZ)comprises equiaxed cellular crystals,and a fine~20μm-thick crystal layer forms in the transition zone(TZ)between the FZ and heat affected zone(HAZ).The HAZ closely resembles the base material(BM),retaining the original rolling microstructure.Mechanical property testing shows that the fine-grained layer in the TZ exhibits the highest nanohardness,with the FZ corresponding to the lowest microhardness.The welded-joint sample has lower yield strength,ultimate tensile strength,and elongation after fracture than the BM.These reductions of mechanical properties are primarily influenced by the grain size and distribution of the precipitated phases.
基金supported by the Russian Science Foundation grant number 24-23-00481,https://rscf.ru/project/24-2300481/.
文摘Flexible materials with perovskite quantum dots(PQDs)are widely used in the field of photonics and opto-electronics due to their unique properties.Development of new materials based on these nanoparticles,incorporated into flexible and lightweight nonwoven fabrics,demonstrated high photoconductivity and efficient light energy conversion.In this work,we propose a method for creating a stable luminescent nonwoven material using electrospinning,in which inorganic salt precursors are used without the need for additional stabilizers.Equimolar solutions of cesium and lead(Ⅱ)bromide were mixed with a fluoroplast,resulting in a series of samples.Luminescent materials were obtained containing PQDs with a composition of CsPbBr_(3),with emission peaks ranging from 507 to 517 nm under 365-nm excitation.We have experimentally established and theoretically confirmed that the peak position is related to the size of the particles formed in the fiber during electrospinning and depends on processing time.Developed materials exhibited stable luminescent properties for up to 2.5 years,making them a promising candidate for the development of new flexible optoelectronic devices based on PQDs.
基金Supported by the Fundamental Research Program of CSTIND under Grant No.GF2007004Harbin Engineering University Central Foundation under Grant No.HEUCF100718
文摘Applying man-machine-environment system engineering(MMESE)in vessels is a method to improve the effectiveness of the interaction between equipment, environment, and humans for the purpose of advancing operating efficiency, performance, safety, and habitability of a vessel and its subsystems. In the following research, the life cycle of vessels was divided into 9 phases, and 15 research subjects were also identified from among these phases. The 15 subjects were systemized, and then the man-machine-environment engineering system application model for vessels was developed using the ICAM definition method 0 (IDEF0), which is a systematical modeling method. This system model bridges the gap between the data and information flow of every two associated subjects with the major basic research methods and approaches included, which brings the formerly relatively independent subjects together as a whole. The application of this systematic model should facilitate the application of man-machine-environment system engineering in vessels, especially at the conceptual and embodiment design phases. The managers and designers can deal with detailed tasks quickly and efficiently while reducing repetitive work.
基金supported by the Russian Science Foundation(No.22-13-00035)the National Outstanding Young Scientists Fund(No.52125002)+14 种基金the National Key Research and Development Program of China(Nos.2023YFC3904800 and 2022YFB4002501)the National Natural Science Foundation of China(Nos.52400228,52300139,22308063,52103340,U22A20418,22578302,52202208,52400163,52205054,22075171,52177214,22405201,52371072,52171078,52377218)the Key Research and Development Project of Science and Technology Department of Zhejiang Province(No.2024C03284(SD2))the Research Development Fund of Zhejiang A&F University(No.2024LFR042)the President Research Funds from Xiamen University(No.ZK1111)Nanqiang Youth Scholar program of Xiamen University,the Young Elite Scientists Sponsorship Program by CAST(No.2023QNRC001)Natural Science Foundation of Xiamen(No.3502z202471037)Open Fund of the State Environmental Protection Key Laboratory of Urban Air Particulate Matter Pollution Prevention and Control,College of Environmental Science and Engineering,Nankai University(No.NKPMLF202409)the Key Project of Research and Development Plan of Jiangxi Province(No.20243BBI91001)Natural Science Foundation of Shanghai(No.23ZR1423400)the Postdoctoral Science Research Program of Shaanxi(No.2023BSHEDzZ159)Xidian University Specially Funded Project for Interdisciplinary Exploration(No.TZJH2024062)the Open Project of Yunnan Precious Metals Laboratory Co.,Ltd.(No.YPML-20240502058)the Fundamental Research Program of Shanxi Province(No.202303021212159)the Natural Science Foundation of Shanxi Normal University(No.JCYJ2024017).
文摘Sustainable development for our life is important task,which is driven by key materials and technologies.In this roadmap,we discuss three main aspects in addressing environmental questions,green chemical processes and energy challenges.They are included,such as gas treatment and separation,wastewater treatment,waste gas treatment,solid waste treatment,lithium extraction,hydrogen production,water splitting,CO_(2) reduction,photocatalytic clean technologies,plastic degradation,fuel cells,lithium batteries,sodium batteries,aqueous batteries,solid state batteries,metal air batteries and supercapacitors.Their status,challenges,progress and future perspectives are also discussed.We hope that this paper can give clear views on sustainable development in materials and technologies.
文摘With the arrival of the intelligence era of Industry 4.0,social development has shown complex and diversified characteristics,gradually forming an innovation ecological environment constructed by vertical interaction of multi-layer innovation systems and horizontal collaboration of multiple organizations and departments,which has posed extremely challenging requirements for higher engineering education to cultivate engineering talents with comprehensive engineering qualities who can solve complex engineering problems.However,practical engineering problems may involve a complex knowledge chain of interdisciplinary and multi-disciplinary cross-coupling.Therefore,higher engineering education needs to form a new interdisciplinary and multi-disciplinary integrated engineering innovation talent training system.Based on the characteristics of the mechanical and electronic engineering major,we will reshape and reconstruct the core courses of the mechanical and electronic engineering major.Two core courses are formed:Drive and Measurement and Control I and Drive and Measurement and Control II,with information flow and energy flow as the main lines,following up with the comprehensive practical curriculum system based on the unity of knowledge and practice and ability-oriented thinking,supporting teaching objectives,promoting students’individual development,and providing guidelines for relevant curriculum reforms.
文摘The paper took SPOC teaching in University Computer Foundation for example, discussed how to make online education meet the basic objectives and requirements of traditional teaching, meanwhile fulfilling the potential applications of MOOCs to meet the needs of all walks in computer application. Based on the sharing of resources in many application-oriented universities,from the perspective of teaching reform around innovation and entrepreneurship in the era of internet, the paper focused on the exploitation and significance of MOOCs. By discussing the means to develop and build the MOOCs University Computer Foundation, which was based on curriculum sharing, the paper demonstrated the work flow. It underlined that, in the educational circumstances nowadays, it was necessary to introduce and spread MOOCs. At the same time, it elaborated on the problems existing in the construction of MOOCs University Computer Foundation, and proposed some concrete methods on further development of MOOCs to meet the requirements of students in application-oriented universities.
文摘Under the background of new engineering,the reform of the comprehensive practical course system for mechanical and electronic engineering majors actively responds to the challenges posed by the new round of technological revolution and industrial transformation to higher education,cultivating top-notch innovative intellectuals with comprehensive engineering qualities,meeting the requirements of being able to solve complex engineering problems rather than just cognitive capabilities,forming two core courses through reconstructing and reshaping the core courses of the major.The core courses include Drive,Measurement,and Control I and Drive,Measurement,and Control II,which highlight the comprehensive framework of mechanical and electronic engineering professional knowledge,continuing the comprehensive practical course system based on the unity of knowledge and practice,following the trend of new engineering,highlighting the practicality of professional innovation,assisting engineering education reform,and promoting high-quality development of new engineering professionals cultivation.
