Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into...Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into the new β phase during the pulsed current-assisted aging process,and then the newly formed β phase is mainly transformed into the β_(t) phase,with occasional transition to new α_(p) phase,leading to a remarkable grain refinement,especially for the lamellarαs phases.In comparison to conventional aging treatment,the pulsed current-assisted aging approach achieves a significant enhancement in strength without degrading ductility,yielding an excellent mechanical property combination:a yield strength of 932 MPa,a tensile strength of 1042 MPa,and an elongation of 12.2%.It is primarily ascribed to the increased fraction of β_(t) phases,the obvious grain refinement effect,and the slip block effect induced by the multiple-variantαs colonies distributed within β_(t) phases.展开更多
Irradiating hard rocks by a high-power laser can reduce localized hardness in the rocks;however,continuous lasers produce a large amount of melt that inhibits further heat absorption.Pulsed lasers allow rocks to absor...Irradiating hard rocks by a high-power laser can reduce localized hardness in the rocks;however,continuous lasers produce a large amount of melt that inhibits further heat absorption.Pulsed lasers allow rocks to absorb and dissipate energy and avoid melt formation.In this study,200 W nanosecond pulsed laser was used to irradiate granite.The effects of laser parameters on the thermal cracking morphology,temperature field,warming pattern,and Leeb hardness of the granite surface were analyzed.The optimal laser parameters for softening granite were determined by performing objective optimization in MATLAB using granite's melting point as the reference.Nanoindentation techniques were employed to assess the softening characteristics of the granite surface along the longitudinal direction.The results showed that three main forms of thermal damage occurred on the granite surface:oxidative decomposition,spalling,and melting.The damage state was affected by the average laser power,with the pulse width and repetition frequency affecting surface damage differently.Appropriate laser parameters effectively controlled the melt damage on the granite surface,and irradiation with nanosecond pulsed lasers effectively reduced surface hardness.However,excessive power can generate large amounts of hard melts and weaken the softening effect.展开更多
The capture zones of the continuous and pulsed guidance laws in the pursuit-evasion game are analytically discussed in this paper to provide deep insights into the capturability distinction between the continuous guid...The capture zones of the continuous and pulsed guidance laws in the pursuit-evasion game are analytically discussed in this paper to provide deep insights into the capturability distinction between the continuous guidance law and the pulsed guidance law.Specifically,first,in the pursuit-evasion game,various capture cases are defined regarding the Zero-Effort Miss distance(ZEM)to facilitate the capturability analysis.Then,for both the evader and the pursuer,the Linear-Quadratic Differential Game(LQDG)guidance laws concerning the continuous acceleration and the pulsed acceleration are converted into a unified form.In each capture case,the optimal solution existence conditions are derived,and the corresponding capture zones are formulated.The discussion on the capture zones shows that if the optimal solution exists,the distinction between the pulsed guidance law and the continuous guidance law can be neglected under small guidance effort weight.However,the capture zone of the continuous guidance law is larger than that of the pulsed guidance law with large pursuer guidance effort weight,but smaller with large evader guidance effort weight.Finally,various simulations are conducted to illustrate the distinction of the continuous and pulsed guidance laws,as well as the impact of the acceleration ratio and the time constant ratio on the capturability.展开更多
Pulsed dynamic electrolysis(PDE),driven by renewable energy,has emerged as an innovative electrocatalytic conversion method,demonstrating significant potential in addressing global energy challenges and promoting sust...Pulsed dynamic electrolysis(PDE),driven by renewable energy,has emerged as an innovative electrocatalytic conversion method,demonstrating significant potential in addressing global energy challenges and promoting sustainable development.Despite significant progress in various electrochemical systems,the regulatory mechanisms of PDE in energy and mass transfer and the lifespan extension of electrolysis systems,particularly in water electrolysis(WE)for hydrogen production,remain insufficiently explored.Therefore,there is an urgent need for a deeper understanding of the unique contributions of PDE in mass transfer enhancement,microenvironment regulation,and hydrogen production optimization,aiming to achieve low-energy consumption,high catalytic activity,and long-term stability in the generation of target products.Here,this review critically examines the microenvironmental effects of PDE on energy and mass transfer,the electrode degradation mechanisms in the lifespan extension of electrolysis systems,and the key factors in enhancing WE for hydrogen production,providing a comprehensive summary of current research progress.The review focuses on the complex regulatory mechanisms of frequency,duty cycle,amplitude,and other factors in hydrogen evolution reaction(HER)performance within PDE strategies,revealing the interrelationships among them.Finally,the potential future directions and challenges for transitioning from laboratory studies to industrial applications are proposed.展开更多
BaFe_(12)O_(19)(BaM)thin films with thicknesses ranging from 15 nm–200 nm were deposited on Al_(2)O_(3)(0001)substrates by pulsed laser deposition(PLD).X-ray diffraction patterns show that a buffer layer with a thick...BaFe_(12)O_(19)(BaM)thin films with thicknesses ranging from 15 nm–200 nm were deposited on Al_(2)O_(3)(0001)substrates by pulsed laser deposition(PLD).X-ray diffraction patterns show that a buffer layer with a thickness of nearly 60 nm forms on the substrate,and then a c-axis perpendicularly oriented Ba M thin film grows on the buffer layer.Atomic force microscopy results indicate that the Ba M thin film exhibits a spiral island growth mode on the buffer layer.Magnetic hysteresis loop results confirm that the buffer layer exhibits no significant magnetic anisotropy,while the Ba M thin film exhibits perpendicular magnetic anisotropy.The out-of-plane coercivity decreases with increasing Ba M thin-film thickness due to the combined effect of grain size growth and lattice strain relaxation.The 200 nm thick film exhibits optimum magnetic properties with M_(s)=319 emu/cm^(3) and H_(c)=1546 Oe.展开更多
Pulsed magnet technology is the only way to generate ultra-strong magnetic fields higher than 45 T so far.However,the inherently fast-changing field strength(typically on the order of 1000 T/s)poses significant challe...Pulsed magnet technology is the only way to generate ultra-strong magnetic fields higher than 45 T so far.However,the inherently fast-changing field strength(typically on the order of 1000 T/s)poses significant challenges for spectroscopic measurements which rely on time integration of signals to improve spectral qualities.In this work,we report high-sensitivity spectroscopic measurements under pulsed high magnetic fields employing the long flat-top pulsed magnetic field technique.By means of a multiple-capacitor power supply,we were able to generate pulsed high magnetic fields with controllable flat-top pulse width and field stabilities.By synchronizing spectroscopic measurements with the waveform of the flattop magnetic field,the integration time of each spectrum can be increased by up to 100 times compared with that of the conventional spectroscopic measurements under pulsed magnetic fields,thus enabling high-sensitivity spectroscopic measurements under ultra-strong pulsed magnetic fields.These findings promise an efficient way to significantly improve the performance and extend the application of optical measurements under pulsed high magnetic fields.展开更多
The transition of hydrogen sourcing from carbon-intensive to water-based methodologies is underway,with renewable energy-powered proton exchange membrane water electrolysis(PEMWE)emerging as the preeminent pathway for...The transition of hydrogen sourcing from carbon-intensive to water-based methodologies is underway,with renewable energy-powered proton exchange membrane water electrolysis(PEMWE)emerging as the preeminent pathway for hydrogen production.Despite remarkable advancements in this field,confronting the sluggish electrochemical kinetics and inherent high-energy consumption arising from deteriorated mass transport within PEMWE systems remains a formidable obstacle.This impediment stems primarily from the hindered protons mass transfer and the untimely hydrogen bubbles detachment.To address these challenges,we harness the inherent variability of electrical energy and introduce an innovative pulsed dynamic water electrolysis system.Compared to constant voltage electrolysis(hydrogen production rate:51.6 m L h^(-1),energy consumption:5.37 kWh Nm-^(3)H_(2)),this strategy(hydrogen production rate:66 m L h^(-1),energy consumption:3.83 kWh Nm-^(3)H_(2))increases the hydrogen production rate by approximately 27%and reduces the energy consumption by about 28%.Furthermore,we demonstrate the practicality of this system by integrating it with an off-grid photovoltaic(PV)system designed for outdoor operation,successfully driving a hydrogen production current of up to 500 mA under an average voltage of approximately 2 V.The combined results of in-situ characterization and finite element analysis reveal the performance enhancement mechanism:pulsed dynamic electrolysis(PDE)dramatically accelerates the enrichment of protons at the electrode/solution interface and facilitates the release of bubbles on the electrode surface.As such,PDE-enhanced PEMWE represents a synergistic advancement,concurrently enhancing both the hydrogen generation reaction and associated transport processes.This promising technology not only redefines the landscape of electrolysis-based hydrogen production but also holds immense potential for broadening its application across a diverse spectrum of electrocatalytic endeavors.展开更多
Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,...Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,including bubble,electromagnetic stirring,filtration separation,fluid flow,and sedimentation,often struggle with the removal of fine inclusions.Apart from these known methods,pulsed electric current(PEC),as an emerging technology,has demonstrated immense potential and environmental advantages.PEC offers adjustable current parameters and simple equipment,making it an attractive alternative to traditional methods.Its green energy-saving features and excellent results in regulating inclusion morphology and migration,as well as inhibiting submerged entry nozzle(SEN)clogging,make it a promising technology.In comparison to continuous current technology,PEC has shown significant advantages in regulating inclusions,not only improving purification efficiency but also demonstrating outstanding performance in flow stability and energy consumption.The ability of PEC to efficiently reduce inclusion numbers enhances the purity and quality of molten steel,improving its mechanical properties.Currently,the theoretical basis for controlling the movement of inclusions by current is mainly composed of three major theories:the double electric layer theory,electromagnetic force reverse separation theory,and electric free energy drive theory.These theories together form an important framework for researchers to understand and optimize the behavior of impurity movement controlled by electric current.Looking ahead,PEC is expected to pave the way for new solutions in directional regulation of inclusion migration,efficient inclusion removal,SEN clogging prevention,and the purification of molten steel.展开更多
In a pulsed plasma thruster,the voltage distribution between the electrodes is a key factor that influences the ionization process.However,few researchers have conducted in-depth studies of this phenomenon in the past...In a pulsed plasma thruster,the voltage distribution between the electrodes is a key factor that influences the ionization process.However,few researchers have conducted in-depth studies of this phenomenon in the past.Reported here are measurements of the voltage distribution between the plates of a parallel-plate pulsed plasma thruster under different discharge voltages,based on which the variations in the total circuit inductance and resistance as well as those between the plates are calculated.The results show that the time-averaged voltage across the plates accounts for 28.7%-50.4%of the capacitor voltage.As the capacitor initial voltage increases from 1250 V to 2000 V,the voltage across the plates rises,but its proportion relative to the capacitor voltage decreases.For every 250 V increase in the capacitor initial voltage,the average voltage proportion across the plates decreases by approximately 2%-3%.Additionally,the voltage proportion decreases gradually from the end near the propellant outward.The voltage distribution ratio between the plates is correlated with the proportions of the resistance and inductance between the plates relative to the total circuit.展开更多
To enhance the reliability of aluminum alloy welding quality,this study investigates the effects of gas pulse parameters on the arc characteristics and weld quality in pulsed plasma gas variable polarity plasma arc we...To enhance the reliability of aluminum alloy welding quality,this study investigates the effects of gas pulse parameters on the arc characteristics and weld quality in pulsed plasma gas variable polarity plasma arc welding(PPG-VPPAW)of 5051 aluminum alloy.Results showed that increasing the gas duty cycle enhanced arc pressure fluctuation but reduced average arc pressure.When the duty cycle exceeded 1/2,excessive pressure fluctuations destabilized the weld pool.Arc voltage fluctuations also intensified with larger duty cycles,reducing arc heat input and stability.Severe variations in arc divergence and high-temperature area were observed at duty cycles above 1/2,leading to poor heat transfer.Weld morphology confirmed these findings:duty cycles of 1/5 and 2/5 produced uniform surfaces with dense fish-scale ripples,while 3/5 and 4/5 introduced defects such as humping and undercut.Mechanical testing showed that conventional variable polarity plasma arc welding(VPPAW)joints reached 262 MPa tensile strength and 18.3%elongation,corresponding to 79.8%and 85.1%of base metal values.At a duty cycle of 2/5,the tensile strength increased to 297 MPa and the elongation to 21.5%,representing the best overall performance.Variations in the gas pulse frequency did not significantly affect the average arc pressure or arc voltage.However,as the gas pulse frequency decreased,the fluctuation frequency of the arc pressure and arc voltage also decreased,while the fluctuation amplitude of the arc voltage increased.At 8 Hz,the tensile strength and elongation increased by 13.4%and 17.5%,respectively,compared with lower frequencies(4 and 2.6 Hz).展开更多
Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate at...Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate atomic diffusion to achieve ultra-fast spheroidization of carbides.However,the understanding of the mechanism by which different pulse current parameters regulate the dissolution behavior of carbides requires a large amount of experimental data to support,which limits the application of pulse current technology in the field of heat treatment.Based on this,quantify the obtained pulse current processing data to create an important dataset that could be applied to machine learning.Through machine learning,the mechanism of mutual influence between carbide regulation and various factors was elucidated,and the optimal spheroidization process parameters were determined.Compared to the 20 h required for traditional heat treatment,the application of pulsed electric current technology achieved ultra-fast spheroidization of GCr15 bearing steel within 90 min.展开更多
Osteoarthritis is one of the most common joint diseases,leading to joint pain,dysfunction,and a reduced quality of life for patients.Therefore,it is particularly important to explore more effective prevention,treatmen...Osteoarthritis is one of the most common joint diseases,leading to joint pain,dysfunction,and a reduced quality of life for patients.Therefore,it is particularly important to explore more effective prevention,treatment and management methods to relieve patients'pain and enhance their quality of life.Among physical therapies,pulsed electrical stimulation(PES)is considered to be a promising treatment method due to its high safety and ease-of-use features.PES provides a non-invasive,safe and effective option for patients.However,there are fewer studies on the biomechanical changes of PES in periarticular tissues,and its effects on the biological behavior of chondrocytes remain unknown.This study investigated the effects of PES on the biomechanical properties of osteoarthritic joints and the biological behavior of chondrocytes.The results showed that PES with an intensity of 10 mA and a frequency of 4 Hz increased the cross-sectional area of muscle fibers,prevented muscle atrophy and loss of function,and restored the mechanical properties of muscle tissue.PES also effectively increases the resistivity of knee osteoarthritis cartilage tissue,as well as the elastic modulus of cartilage,which can enhance the bio-mechanical characteristics of cartilage tissue.PES also promoted the metabolic activity of chondrocytes and increased cartilage matrix synthesis,thereby improving the overall structure and mechanical properties of cartilage tissue.Additionally,cellular experiments showed that 5 consecutive days of 800 mV PES significantly increased the expression level of Piezol gene in chondrocytes.At the same time,the expression of type II collagen and transforming growth factor beta increased,while the expression of matrix metallopeptidase 13 decreased.These changes favored the promotion of cartilage matrix synthesis.This has a positive effect on protecting and improving joint health and reducing the impact of osteoarthritis,and is important for understanding the mechanism of action of PES on chondrocytes and the development of related therapeutic strategies.展开更多
BACKGROUND Atrial fibrillation,affecting approximately 33 million people globally,is the most common sustained arrhythmia,increasing risks of stroke,heart failure,and mortality.Pulmonary vein isolation via catheter ab...BACKGROUND Atrial fibrillation,affecting approximately 33 million people globally,is the most common sustained arrhythmia,increasing risks of stroke,heart failure,and mortality.Pulmonary vein isolation via catheter ablation is a key rhythm control strategy,with cryoballoon ablation(CBA)being a standard thermal method but associated with risks like phrenic nerve palsy(5%-10%),esophageal injury,and vein stenosis.Pulsed field ablation(PFA),a non-thermal technique using electrical pulses for selective electroporation,offers potential for shorter procedures and improved safety.Limited direct comparisons between PFA and CBA necessitate a systematic evaluation of their efficacy and safety.AIM To compare the procedural success,safety,and 1-year arrhythmia-free survival of PFA vs CBA for first-time pulmonary vein isolation in adults with paroxysmal or persistent atrial fibrillation.METHODS A Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant systematic review and metaanalysis was conducted,searching PubMed,EMBASE,Web of Science,and other databases up to August 2025 for comparative studies.Pooled mean difference for continuous outcomes and odds ratio(OR)for dichotomous outcomes were calculated using random-effects models.Study quality was assessed with the Newcastle-Ottawa Scale,heterogeneity with I2,and publication bias with funnel plots.RESULTS Seven studies(six cohorts,one randomized controlled trial)were included,with a mean age of approximately 66 years,59%-78%male,and high prevalence of hypertension and diabetes.PFA significantly reduced procedure time(mean difference=-15.24 minutes,95%CI:-16.63 to-13.85,P<0.00001;I2=89%),improved arrhythmia-free survival(OR=1.27,95%CI:1.04-1.55,P=0.02;I2=45%),and lowered phrenic nerve palsy risk(OR=0.17,95%CI:0.04-0.63,P=0.008;I2=0%).No significant differences were found in fluoroscopy time,cardiac tamponade,repeat ablation,or vascular complications.CONCLUSION PFA demonstrates shorter procedure times,reduced phrenic nerve palsy,and better arrhythmia control compared to CBA,with comparable safety profiles.However,evidence is limited by observational study designs,heterogeneity,and potential bias.Large-scale randomized controlled trials with extended follow-up are needed to confirm these findings and guide clinical practice.展开更多
Low-intensity pulsed ultrasound(LIPUS)is a non-invasive sonodynamic therapy that has been approved by the U.S.Food and Drug Administration for clinical use.Clinical trials have demonstrated that LIPUS ameliorates mild...Low-intensity pulsed ultrasound(LIPUS)is a non-invasive sonodynamic therapy that has been approved by the U.S.Food and Drug Administration for clinical use.Clinical trials have demonstrated that LIPUS ameliorates mild-to-moderate erectile dysfunction without adverse events.Histological analysis of the corpus cavernosum suggests that the therapeutic benefits of LIPUS may be attributed to alleviation of fibrosis,enhanced neovascularization,and promotion of innervation.Further investigations have revealed that LIPUS facilitates cavernous tissue repair through non-thermal mechanisms,including a cavitation effect,acoustic streaming,mass transfer enhancement,and direct mechanical stimulation.Mechanobiological transduction triggers molecular signaling cascades within endogenous cavernous cells,thereby stimulating cell proliferation,angiogenesis,extracellular matrix remodeling,and stem cell differentiation.Although LIPUS has the potential to induce cavernous rehabilitation in the treatment of erectile dysfunction,further investigations are necessary to elucidate the mechanisms via which LIPUS regulates each type of cavernous cell to determine the optimal parameters for this innovative therapy.展开更多
The kinetic characteristics of plasma-assisted oxidative pyrolysis of ammonia are studied by using the global/fluid models hybrid solution method.Firstly,the stable products of plasma-assisted oxidative pyrolysis of a...The kinetic characteristics of plasma-assisted oxidative pyrolysis of ammonia are studied by using the global/fluid models hybrid solution method.Firstly,the stable products of plasma-assisted oxidative pyrolysis of ammonia are measured.The results show that the consumption of NH_(3)/O_(2)and the production of N_(2)/H_(2)change linearly with the increase of voltage,which indicates the decoupling of nonequilibrium molecular excitation and oxidative pyrolysis of ammonia at low temperatures.Secondly,the detailed reaction kinetics mechanism of ammonia oxidative pyrolysis stimulated by a nanosecond pulse voltage at low pressure and room temperature is established.Based on the reaction path analysis,the simplified mechanism is obtained.The detailed and simplified mechanism simulation results are compared with experimental data to verify the accuracy of the simplified mechanism.Finally,based on the simplified mechanism,the fluid model of ammonia oxidative pyrolysis stimulated by the nanosecond pulse plasma is established to study the pre-sheath/sheath behavior and the resultant consumption and formation of key species.The results show that the generation,development,and propagation of the pre-sheath have a great influence on the formation and consumption of species.The consumption of NH_(3)by the cathode pre-sheath is greater than that by the anode pre-sheath,but the opposite is true for OH and O(1S).However,within the sheath,almost all reactions do not occur.Further,by changing the parameters of nanosecond pulse power supply voltage,it is found that the electron number density,electron current density,and applied peak voltages are not the direct reasons for the structural changes of the sheath and pre-sheath.Furthermore,the discharge interval has little effect on the sheath structure and gas mixture breakdown.The research results of this paper not only help to understand the kinetic promotion of non-equilibrium excitation in the process of oxidative pyrolysis but also help to explore the influence of transport and chemical reaction kinetics on the oxidative pyrolysis of ammonia.展开更多
In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 21...In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 2117.38 HV30,a 9.60%rise in fracture toughness from 9.06 to 9.93 MPa·m^(1/2),while the friction coefficient decreases from 0.63 to 0.47.Through the residual stress evolution,WC orientation change and the martensitic transformation of Co,and the internal enhancement mechanism of cryogenic combined with pulsed electric field treatment are revealed.The electron wind generated by the pulsed electric field can efficiently reduce the residual stress induced by cryogenic process.The evolution of residual stress promotes the base slip of WC,increasing the degree of{0001}orientation.In addition,the degree of martensitic transformation of Co intensifies,with the hcp-Co/fcc-Co ratio rising from 0.41%to 17.86%.The enhanced WC{0001}orientation and increased hcp-Co content contribute to significant improvements in hardness and wear resistance.This work provides a novel efficient enhancement strategy for ceramics and alloys,with the potential to be a mainstream strengthening method in the future.展开更多
In recent years,the effect of pulsed magnetic fields on improving the solidification structure of alloys has attracted significant attention.A GH4738 nickel-based alloy smelted using a self-designed 20-kg electromagne...In recent years,the effect of pulsed magnetic fields on improving the solidification structure of alloys has attracted significant attention.A GH4738 nickel-based alloy smelted using a self-designed 20-kg electromagnetic casting system was taken as the research object.Finite element software was used to numerically simulate the magnetic field intensity,distribution,and temperature field of the casting device.The effect of the pulsed magnetic field on the solidification process of the GH4738 alloy was studied by means of low-magnification microstructural analysis.The measured magnetic field shows that when the duty cycle is 20%,the pulse frequency is 50 Hz,the output current is in the range of 150–250 A,and the peak magnetic field intensity of the crucible center is 68–116 mT.The crucible temperature is heated to 600℃and the melt center solidification time is 12.844 s.The microstructural analysis of the ingot shows that its shrinkage hole is reduced from 130 to 100 mm,and the equiaxed crystal area is increased from 2275 to 3150 mm^(2).The solidification angle of the dendrite is changed under the action of the pulsed magnetic field,and the tilt angle is 45°.The results show that the pulsed magnetic field promotes the primary crystal core of the GH4738 alloy,improves the nucleation rate of the melt,reduces the size difference of the solidification structure between the center and the edge of the ingot,and improves the uniformity of the solidification structure.展开更多
The corrosion resistance of cobalt-based alloy cladding layers is crucial for the long-term reliability of materials in the nuclear power industry,where they are exposed to highly aggressive environmental conditions.A...The corrosion resistance of cobalt-based alloy cladding layers is crucial for the long-term reliability of materials in the nuclear power industry,where they are exposed to highly aggressive environmental conditions.A major challenge to their performance is the corrosion occurring at phase boundaries under harsh operating conditions.This study investigates the effects of pulsed magnetic field treatment(PMT)on improving corrosion resistance at phase boundaries,specifically at the carbide/matrix Co interface,and seeks to clarify the underlying mechanisms.Advanced characterization techniques,including scanning electron microscopy(SEM),in situ transmission electron microscopy(TEM),in situ scanning kelvin probe force microscopy(SKPFM),and density functional theory(DFT)calculations,were employed.PMT samples exhibited no interface corrosion cracking or carbide spalling and showed a significant reduction in corrosion depth.TEM analysis revealed reduced lattice distortion at phase boundaries and a partial transformation of face-centered cubic(FCC)Co to hexagonal closepacked(HCP)Co.The enhanced corrosion resistance at phase boundaries is attributed to changes in the electronic work function(EWF),as determined by SKPFM measurements and DFT calculations.展开更多
This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow condition...This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow conditions of 2.9 MPa stagnation pressure,1900 K stagnation temperature,and Mach number of 3.0.It has been observed that,at the same equivalence ratio,the combustion mode and flow field structure undergo irreversible changes from a weak combustion state to a strong combustion state at a specific pulsed jet frequency compared to steady jet.For steady jet,the combustion mode is dual-mode.As the frequency of the unsteady jet changes,the combustion mode also changes:it becomes a transition mode at frequencies of 171 Hz and 260 Hz,and a ramjet mode at 216 Hz.Combustion instability under steady jet manifests as a transition in flame stabilization mode.In contrast,under pulsed jet,combustion instability appears either as a transition in flame stabilization mode or as flame blow-off and flashback.The flow field oscillation frequency in the non-reacting flow is 171 Hz,which may resonate with the 171 Hz pulsed jet frequency,making the combustion oscillations most pronounced at this frequency.When the jet frequency is increased to 216 Hz,the combustion intensity significantly increases,and the combustion mode transfers to the ramjet mode.However,further increasing the frequency to 260 Hz results in a decrease in combustion intensity,returning to the transition mode.The frequency of the flow field oscillations varies with the coupling of the pulsed injection frequency,shock wave,and flame,and if the system reaches an unstable state,that is,pre-combustion shock train moves far upstream of the isolator during the pulsed jet period,strong combustion state can be achieved,and this process is irreversible.展开更多
Capacitor-based pulsed power supply(PPS)is widely used in fields related to electromagnetic launch,plasma,and materials'synthesis,modification and processing.As industrial applications place higher requirements on...Capacitor-based pulsed power supply(PPS)is widely used in fields related to electromagnetic launch,plasma,and materials'synthesis,modification and processing.As industrial applications place higher requirements on compact and portable pulsed power supplies,the National Key Laboratory of Transient Physics(NKLTP)recently developed a pulsed power supply consisting of a set of compact pulse-forming units(PFU),each with a capacitor energy storage of 220 kJ.This integrated PPS comes with a complete system configuration,a miniature compact structure,a high rate of repetition,and high power,with energy storage density exceeding 1.2 MJ/m^(3).This paper describes the device-level design of the unit,the system layout,the control system,the thermal management system,and the experimental results of the pulsed power supply.The experimental results verified the good reliability of the PPS at high repetition rates with each unit module delivering an output current of more than 100 kA.Additionally,flexible current pulse shapes can be formed by setting the charging voltage and the trigger sequence of the PFUs.The pulse forming network(PFN)developed from these PFUs was successfully applied to electromagnetic launch.展开更多
基金National Key Research and Development Program of China(2021YFB3700801)。
文摘Low-density short-duration pulsed current-assisted aging treatment was applied to the Ti-6Al-4V-0.5Mo-0.5Zr alloy subjected to different solution treatments.The results show that numerous α_(p) phases redissolve into the new β phase during the pulsed current-assisted aging process,and then the newly formed β phase is mainly transformed into the β_(t) phase,with occasional transition to new α_(p) phase,leading to a remarkable grain refinement,especially for the lamellarαs phases.In comparison to conventional aging treatment,the pulsed current-assisted aging approach achieves a significant enhancement in strength without degrading ductility,yielding an excellent mechanical property combination:a yield strength of 932 MPa,a tensile strength of 1042 MPa,and an elongation of 12.2%.It is primarily ascribed to the increased fraction of β_(t) phases,the obvious grain refinement effect,and the slip block effect induced by the multiple-variantαs colonies distributed within β_(t) phases.
基金Project(52378425)supported by the National Natural Science Foundation of ChinaProject(1053320221044)supported by the Fundamental Research Funds for the Central Universities,China。
文摘Irradiating hard rocks by a high-power laser can reduce localized hardness in the rocks;however,continuous lasers produce a large amount of melt that inhibits further heat absorption.Pulsed lasers allow rocks to absorb and dissipate energy and avoid melt formation.In this study,200 W nanosecond pulsed laser was used to irradiate granite.The effects of laser parameters on the thermal cracking morphology,temperature field,warming pattern,and Leeb hardness of the granite surface were analyzed.The optimal laser parameters for softening granite were determined by performing objective optimization in MATLAB using granite's melting point as the reference.Nanoindentation techniques were employed to assess the softening characteristics of the granite surface along the longitudinal direction.The results showed that three main forms of thermal damage occurred on the granite surface:oxidative decomposition,spalling,and melting.The damage state was affected by the average laser power,with the pulse width and repetition frequency affecting surface damage differently.Appropriate laser parameters effectively controlled the melt damage on the granite surface,and irradiation with nanosecond pulsed lasers effectively reduced surface hardness.However,excessive power can generate large amounts of hard melts and weaken the softening effect.
基金co-supported by the National Natural Science Foundation of China(Nos.U24B20157,62203031)the Natural Science Foundation of Beijing Municipality,China(No.4242041)+2 种基金the Natural Science Foundation of Zhejiang Province,China(No.LY24F030002)the Aeronautical ScienceFoundation of China(No.2024Z066051001)the Fundamental Research Funds for the Central Universities of China。
文摘The capture zones of the continuous and pulsed guidance laws in the pursuit-evasion game are analytically discussed in this paper to provide deep insights into the capturability distinction between the continuous guidance law and the pulsed guidance law.Specifically,first,in the pursuit-evasion game,various capture cases are defined regarding the Zero-Effort Miss distance(ZEM)to facilitate the capturability analysis.Then,for both the evader and the pursuer,the Linear-Quadratic Differential Game(LQDG)guidance laws concerning the continuous acceleration and the pulsed acceleration are converted into a unified form.In each capture case,the optimal solution existence conditions are derived,and the corresponding capture zones are formulated.The discussion on the capture zones shows that if the optimal solution exists,the distinction between the pulsed guidance law and the continuous guidance law can be neglected under small guidance effort weight.However,the capture zone of the continuous guidance law is larger than that of the pulsed guidance law with large pursuer guidance effort weight,but smaller with large evader guidance effort weight.Finally,various simulations are conducted to illustrate the distinction of the continuous and pulsed guidance laws,as well as the impact of the acceleration ratio and the time constant ratio on the capturability.
基金financially supported by the Key Research and Development Program of Heilongjiang Province(No.2024ZXJ03C06)National Natural Science Foundation of China(No.52476192,No.52106237)+1 种基金Natural Science Foundation of Heilongjiang Province(No.YQ2022E027)Technology Project of China Datang Technology Innovation Co.,Ltd(No.DTKC-2024-20610).
文摘Pulsed dynamic electrolysis(PDE),driven by renewable energy,has emerged as an innovative electrocatalytic conversion method,demonstrating significant potential in addressing global energy challenges and promoting sustainable development.Despite significant progress in various electrochemical systems,the regulatory mechanisms of PDE in energy and mass transfer and the lifespan extension of electrolysis systems,particularly in water electrolysis(WE)for hydrogen production,remain insufficiently explored.Therefore,there is an urgent need for a deeper understanding of the unique contributions of PDE in mass transfer enhancement,microenvironment regulation,and hydrogen production optimization,aiming to achieve low-energy consumption,high catalytic activity,and long-term stability in the generation of target products.Here,this review critically examines the microenvironmental effects of PDE on energy and mass transfer,the electrode degradation mechanisms in the lifespan extension of electrolysis systems,and the key factors in enhancing WE for hydrogen production,providing a comprehensive summary of current research progress.The review focuses on the complex regulatory mechanisms of frequency,duty cycle,amplitude,and other factors in hydrogen evolution reaction(HER)performance within PDE strategies,revealing the interrelationships among them.Finally,the potential future directions and challenges for transitioning from laboratory studies to industrial applications are proposed.
文摘BaFe_(12)O_(19)(BaM)thin films with thicknesses ranging from 15 nm–200 nm were deposited on Al_(2)O_(3)(0001)substrates by pulsed laser deposition(PLD).X-ray diffraction patterns show that a buffer layer with a thickness of nearly 60 nm forms on the substrate,and then a c-axis perpendicularly oriented Ba M thin film grows on the buffer layer.Atomic force microscopy results indicate that the Ba M thin film exhibits a spiral island growth mode on the buffer layer.Magnetic hysteresis loop results confirm that the buffer layer exhibits no significant magnetic anisotropy,while the Ba M thin film exhibits perpendicular magnetic anisotropy.The out-of-plane coercivity decreases with increasing Ba M thin-film thickness due to the combined effect of grain size growth and lattice strain relaxation.The 200 nm thick film exhibits optimum magnetic properties with M_(s)=319 emu/cm^(3) and H_(c)=1546 Oe.
基金financially supported by the National Key Research and Development Program of China(Grant No.2022YFA1602700)the National Natural Science Foundation of China(Grant No.12274159)。
文摘Pulsed magnet technology is the only way to generate ultra-strong magnetic fields higher than 45 T so far.However,the inherently fast-changing field strength(typically on the order of 1000 T/s)poses significant challenges for spectroscopic measurements which rely on time integration of signals to improve spectral qualities.In this work,we report high-sensitivity spectroscopic measurements under pulsed high magnetic fields employing the long flat-top pulsed magnetic field technique.By means of a multiple-capacitor power supply,we were able to generate pulsed high magnetic fields with controllable flat-top pulse width and field stabilities.By synchronizing spectroscopic measurements with the waveform of the flattop magnetic field,the integration time of each spectrum can be increased by up to 100 times compared with that of the conventional spectroscopic measurements under pulsed magnetic fields,thus enabling high-sensitivity spectroscopic measurements under ultra-strong pulsed magnetic fields.These findings promise an efficient way to significantly improve the performance and extend the application of optical measurements under pulsed high magnetic fields.
基金National Natural Science Foundation of China(No.52476192,No.52106237)Natural Science Foundation of Heilongjiang Province(No.YQ2022E027)。
文摘The transition of hydrogen sourcing from carbon-intensive to water-based methodologies is underway,with renewable energy-powered proton exchange membrane water electrolysis(PEMWE)emerging as the preeminent pathway for hydrogen production.Despite remarkable advancements in this field,confronting the sluggish electrochemical kinetics and inherent high-energy consumption arising from deteriorated mass transport within PEMWE systems remains a formidable obstacle.This impediment stems primarily from the hindered protons mass transfer and the untimely hydrogen bubbles detachment.To address these challenges,we harness the inherent variability of electrical energy and introduce an innovative pulsed dynamic water electrolysis system.Compared to constant voltage electrolysis(hydrogen production rate:51.6 m L h^(-1),energy consumption:5.37 kWh Nm-^(3)H_(2)),this strategy(hydrogen production rate:66 m L h^(-1),energy consumption:3.83 kWh Nm-^(3)H_(2))increases the hydrogen production rate by approximately 27%and reduces the energy consumption by about 28%.Furthermore,we demonstrate the practicality of this system by integrating it with an off-grid photovoltaic(PV)system designed for outdoor operation,successfully driving a hydrogen production current of up to 500 mA under an average voltage of approximately 2 V.The combined results of in-situ characterization and finite element analysis reveal the performance enhancement mechanism:pulsed dynamic electrolysis(PDE)dramatically accelerates the enrichment of protons at the electrode/solution interface and facilitates the release of bubbles on the electrode surface.As such,PDE-enhanced PEMWE represents a synergistic advancement,concurrently enhancing both the hydrogen generation reaction and associated transport processes.This promising technology not only redefines the landscape of electrolysis-based hydrogen production but also holds immense potential for broadening its application across a diverse spectrum of electrocatalytic endeavors.
基金supported by the Fundamental Research Funds for the Central Universities(No.FRF-BD-23-01).
文摘Non-metallic inclusions in steel are a significant challenge,affecting material properties and leading to issues such as stress concentration,cracking,and accelerated corrosion.Current methods for removing inclusions,including bubble,electromagnetic stirring,filtration separation,fluid flow,and sedimentation,often struggle with the removal of fine inclusions.Apart from these known methods,pulsed electric current(PEC),as an emerging technology,has demonstrated immense potential and environmental advantages.PEC offers adjustable current parameters and simple equipment,making it an attractive alternative to traditional methods.Its green energy-saving features and excellent results in regulating inclusion morphology and migration,as well as inhibiting submerged entry nozzle(SEN)clogging,make it a promising technology.In comparison to continuous current technology,PEC has shown significant advantages in regulating inclusions,not only improving purification efficiency but also demonstrating outstanding performance in flow stability and energy consumption.The ability of PEC to efficiently reduce inclusion numbers enhances the purity and quality of molten steel,improving its mechanical properties.Currently,the theoretical basis for controlling the movement of inclusions by current is mainly composed of three major theories:the double electric layer theory,electromagnetic force reverse separation theory,and electric free energy drive theory.These theories together form an important framework for researchers to understand and optimize the behavior of impurity movement controlled by electric current.Looking ahead,PEC is expected to pave the way for new solutions in directional regulation of inclusion migration,efficient inclusion removal,SEN clogging prevention,and the purification of molten steel.
基金supported by the Beijing Natural Science Foundation(No.QY24166).
文摘In a pulsed plasma thruster,the voltage distribution between the electrodes is a key factor that influences the ionization process.However,few researchers have conducted in-depth studies of this phenomenon in the past.Reported here are measurements of the voltage distribution between the plates of a parallel-plate pulsed plasma thruster under different discharge voltages,based on which the variations in the total circuit inductance and resistance as well as those between the plates are calculated.The results show that the time-averaged voltage across the plates accounts for 28.7%-50.4%of the capacitor voltage.As the capacitor initial voltage increases from 1250 V to 2000 V,the voltage across the plates rises,but its proportion relative to the capacitor voltage decreases.For every 250 V increase in the capacitor initial voltage,the average voltage proportion across the plates decreases by approximately 2%-3%.Additionally,the voltage proportion decreases gradually from the end near the propellant outward.The voltage distribution ratio between the plates is correlated with the proportions of the resistance and inductance between the plates relative to the total circuit.
基金supported by the National Natural Science Foundation of China(Grant No.52275302 and 52322508)the R&D Program of Beijing Municipal Education Commission(Grant No.KZ20231000519)。
文摘To enhance the reliability of aluminum alloy welding quality,this study investigates the effects of gas pulse parameters on the arc characteristics and weld quality in pulsed plasma gas variable polarity plasma arc welding(PPG-VPPAW)of 5051 aluminum alloy.Results showed that increasing the gas duty cycle enhanced arc pressure fluctuation but reduced average arc pressure.When the duty cycle exceeded 1/2,excessive pressure fluctuations destabilized the weld pool.Arc voltage fluctuations also intensified with larger duty cycles,reducing arc heat input and stability.Severe variations in arc divergence and high-temperature area were observed at duty cycles above 1/2,leading to poor heat transfer.Weld morphology confirmed these findings:duty cycles of 1/5 and 2/5 produced uniform surfaces with dense fish-scale ripples,while 3/5 and 4/5 introduced defects such as humping and undercut.Mechanical testing showed that conventional variable polarity plasma arc welding(VPPAW)joints reached 262 MPa tensile strength and 18.3%elongation,corresponding to 79.8%and 85.1%of base metal values.At a duty cycle of 2/5,the tensile strength increased to 297 MPa and the elongation to 21.5%,representing the best overall performance.Variations in the gas pulse frequency did not significantly affect the average arc pressure or arc voltage.However,as the gas pulse frequency decreased,the fluctuation frequency of the arc pressure and arc voltage also decreased,while the fluctuation amplitude of the arc voltage increased.At 8 Hz,the tensile strength and elongation increased by 13.4%and 17.5%,respectively,compared with lower frequencies(4 and 2.6 Hz).
基金supported by the National Key R&D Program of China(2020YFA0714900,2023YFB3709903)the National Natural Science Foundation of China(U21B2082,52474410)+6 种基金the Key R&D Program of Shandong Province,China(2023CXGC010406)the Scientific Research Special Project for First-Class Disciplines in Inner Mongolia Autonomous Region(YLXKZX-NKD-001)the International Science and Technology Cooperation Project of Higher Education Institutions in Inner Mongolia Autonomous Region(GHXM-002)the Natural Science Foundation of Inner Mongolia Autonomous Region of China(2024ZD06)the Technology Support Project for the Construction of Major Innovation Platforms in Inner Mongolia Autonomous Region(XM2024XTGXQ16)the Beijing Municipal Natural Science Foundation(2222065)the Fundamental Research Funds for the Central Universities(FRF-TP-22-02C2).
文摘Traditional heat treatment methods require a significant amount of time and energy to affect atomic diffusion and enhance the spheroidization process of carbides in bearing steel,while pulsed current can accelerate atomic diffusion to achieve ultra-fast spheroidization of carbides.However,the understanding of the mechanism by which different pulse current parameters regulate the dissolution behavior of carbides requires a large amount of experimental data to support,which limits the application of pulse current technology in the field of heat treatment.Based on this,quantify the obtained pulse current processing data to create an important dataset that could be applied to machine learning.Through machine learning,the mechanism of mutual influence between carbide regulation and various factors was elucidated,and the optimal spheroidization process parameters were determined.Compared to the 20 h required for traditional heat treatment,the application of pulsed electric current technology achieved ultra-fast spheroidization of GCr15 bearing steel within 90 min.
基金supported by the National Natural Science Foundation of China(Grant Nos.12272250 and 11972242)the Fundamental Research Program of Shanxi Province(Grant No.202203021212254)+2 种基金the Regional Joint Key Funding Program of the National Natural Science Foundation of China(Grant No.U21A20353)China Postdoctoral Science Foundation(Grant No.2020M680913)Shanxi Province Returned Overseas Foundation(Grant No.2022-081).
文摘Osteoarthritis is one of the most common joint diseases,leading to joint pain,dysfunction,and a reduced quality of life for patients.Therefore,it is particularly important to explore more effective prevention,treatment and management methods to relieve patients'pain and enhance their quality of life.Among physical therapies,pulsed electrical stimulation(PES)is considered to be a promising treatment method due to its high safety and ease-of-use features.PES provides a non-invasive,safe and effective option for patients.However,there are fewer studies on the biomechanical changes of PES in periarticular tissues,and its effects on the biological behavior of chondrocytes remain unknown.This study investigated the effects of PES on the biomechanical properties of osteoarthritic joints and the biological behavior of chondrocytes.The results showed that PES with an intensity of 10 mA and a frequency of 4 Hz increased the cross-sectional area of muscle fibers,prevented muscle atrophy and loss of function,and restored the mechanical properties of muscle tissue.PES also effectively increases the resistivity of knee osteoarthritis cartilage tissue,as well as the elastic modulus of cartilage,which can enhance the bio-mechanical characteristics of cartilage tissue.PES also promoted the metabolic activity of chondrocytes and increased cartilage matrix synthesis,thereby improving the overall structure and mechanical properties of cartilage tissue.Additionally,cellular experiments showed that 5 consecutive days of 800 mV PES significantly increased the expression level of Piezol gene in chondrocytes.At the same time,the expression of type II collagen and transforming growth factor beta increased,while the expression of matrix metallopeptidase 13 decreased.These changes favored the promotion of cartilage matrix synthesis.This has a positive effect on protecting and improving joint health and reducing the impact of osteoarthritis,and is important for understanding the mechanism of action of PES on chondrocytes and the development of related therapeutic strategies.
文摘BACKGROUND Atrial fibrillation,affecting approximately 33 million people globally,is the most common sustained arrhythmia,increasing risks of stroke,heart failure,and mortality.Pulmonary vein isolation via catheter ablation is a key rhythm control strategy,with cryoballoon ablation(CBA)being a standard thermal method but associated with risks like phrenic nerve palsy(5%-10%),esophageal injury,and vein stenosis.Pulsed field ablation(PFA),a non-thermal technique using electrical pulses for selective electroporation,offers potential for shorter procedures and improved safety.Limited direct comparisons between PFA and CBA necessitate a systematic evaluation of their efficacy and safety.AIM To compare the procedural success,safety,and 1-year arrhythmia-free survival of PFA vs CBA for first-time pulmonary vein isolation in adults with paroxysmal or persistent atrial fibrillation.METHODS A Preferred Reporting Items for Systematic Reviews and Meta-Analyses-compliant systematic review and metaanalysis was conducted,searching PubMed,EMBASE,Web of Science,and other databases up to August 2025 for comparative studies.Pooled mean difference for continuous outcomes and odds ratio(OR)for dichotomous outcomes were calculated using random-effects models.Study quality was assessed with the Newcastle-Ottawa Scale,heterogeneity with I2,and publication bias with funnel plots.RESULTS Seven studies(six cohorts,one randomized controlled trial)were included,with a mean age of approximately 66 years,59%-78%male,and high prevalence of hypertension and diabetes.PFA significantly reduced procedure time(mean difference=-15.24 minutes,95%CI:-16.63 to-13.85,P<0.00001;I2=89%),improved arrhythmia-free survival(OR=1.27,95%CI:1.04-1.55,P=0.02;I2=45%),and lowered phrenic nerve palsy risk(OR=0.17,95%CI:0.04-0.63,P=0.008;I2=0%).No significant differences were found in fluoroscopy time,cardiac tamponade,repeat ablation,or vascular complications.CONCLUSION PFA demonstrates shorter procedure times,reduced phrenic nerve palsy,and better arrhythmia control compared to CBA,with comparable safety profiles.However,evidence is limited by observational study designs,heterogeneity,and potential bias.Large-scale randomized controlled trials with extended follow-up are needed to confirm these findings and guide clinical practice.
文摘Low-intensity pulsed ultrasound(LIPUS)is a non-invasive sonodynamic therapy that has been approved by the U.S.Food and Drug Administration for clinical use.Clinical trials have demonstrated that LIPUS ameliorates mild-to-moderate erectile dysfunction without adverse events.Histological analysis of the corpus cavernosum suggests that the therapeutic benefits of LIPUS may be attributed to alleviation of fibrosis,enhanced neovascularization,and promotion of innervation.Further investigations have revealed that LIPUS facilitates cavernous tissue repair through non-thermal mechanisms,including a cavitation effect,acoustic streaming,mass transfer enhancement,and direct mechanical stimulation.Mechanobiological transduction triggers molecular signaling cascades within endogenous cavernous cells,thereby stimulating cell proliferation,angiogenesis,extracellular matrix remodeling,and stem cell differentiation.Although LIPUS has the potential to induce cavernous rehabilitation in the treatment of erectile dysfunction,further investigations are necessary to elucidate the mechanisms via which LIPUS regulates each type of cavernous cell to determine the optimal parameters for this innovative therapy.
基金Fundamental Research Funds for the Central Universities(M23JBZY00050)National Natural Science Foundation of China(22278032)。
文摘The kinetic characteristics of plasma-assisted oxidative pyrolysis of ammonia are studied by using the global/fluid models hybrid solution method.Firstly,the stable products of plasma-assisted oxidative pyrolysis of ammonia are measured.The results show that the consumption of NH_(3)/O_(2)and the production of N_(2)/H_(2)change linearly with the increase of voltage,which indicates the decoupling of nonequilibrium molecular excitation and oxidative pyrolysis of ammonia at low temperatures.Secondly,the detailed reaction kinetics mechanism of ammonia oxidative pyrolysis stimulated by a nanosecond pulse voltage at low pressure and room temperature is established.Based on the reaction path analysis,the simplified mechanism is obtained.The detailed and simplified mechanism simulation results are compared with experimental data to verify the accuracy of the simplified mechanism.Finally,based on the simplified mechanism,the fluid model of ammonia oxidative pyrolysis stimulated by the nanosecond pulse plasma is established to study the pre-sheath/sheath behavior and the resultant consumption and formation of key species.The results show that the generation,development,and propagation of the pre-sheath have a great influence on the formation and consumption of species.The consumption of NH_(3)by the cathode pre-sheath is greater than that by the anode pre-sheath,but the opposite is true for OH and O(1S).However,within the sheath,almost all reactions do not occur.Further,by changing the parameters of nanosecond pulse power supply voltage,it is found that the electron number density,electron current density,and applied peak voltages are not the direct reasons for the structural changes of the sheath and pre-sheath.Furthermore,the discharge interval has little effect on the sheath structure and gas mixture breakdown.The research results of this paper not only help to understand the kinetic promotion of non-equilibrium excitation in the process of oxidative pyrolysis but also help to explore the influence of transport and chemical reaction kinetics on the oxidative pyrolysis of ammonia.
基金supported by the National Natural Science Foundation of China(Nos.U21A20399 and 52274407)Liaoning Province Applied Basic Research Program(No.2022JH2/101300212).
文摘In this work,we aim to develop a novel post-treatment process combining cryogenic and pulsed electric field treatment to enhance WC-Co cemented carbides.The results show a 15.62%increase in hardness from 1831.38 to 2117.38 HV30,a 9.60%rise in fracture toughness from 9.06 to 9.93 MPa·m^(1/2),while the friction coefficient decreases from 0.63 to 0.47.Through the residual stress evolution,WC orientation change and the martensitic transformation of Co,and the internal enhancement mechanism of cryogenic combined with pulsed electric field treatment are revealed.The electron wind generated by the pulsed electric field can efficiently reduce the residual stress induced by cryogenic process.The evolution of residual stress promotes the base slip of WC,increasing the degree of{0001}orientation.In addition,the degree of martensitic transformation of Co intensifies,with the hcp-Co/fcc-Co ratio rising from 0.41%to 17.86%.The enhanced WC{0001}orientation and increased hcp-Co content contribute to significant improvements in hardness and wear resistance.This work provides a novel efficient enhancement strategy for ceramics and alloys,with the potential to be a mainstream strengthening method in the future.
基金supported by National Natural Science Foundation of China(No.52074092)the Fundamental Research Funds for Inner Mongolia University of Science&Technology(No.2023QNJS007)+1 种基金Program for Young Talents of Science and Technology in Universities of Inner Mongolia Autonomous Region(No.NJYT23115)the Inner Mongolia Natural Science Foundation(No.2022MS05039).
文摘In recent years,the effect of pulsed magnetic fields on improving the solidification structure of alloys has attracted significant attention.A GH4738 nickel-based alloy smelted using a self-designed 20-kg electromagnetic casting system was taken as the research object.Finite element software was used to numerically simulate the magnetic field intensity,distribution,and temperature field of the casting device.The effect of the pulsed magnetic field on the solidification process of the GH4738 alloy was studied by means of low-magnification microstructural analysis.The measured magnetic field shows that when the duty cycle is 20%,the pulse frequency is 50 Hz,the output current is in the range of 150–250 A,and the peak magnetic field intensity of the crucible center is 68–116 mT.The crucible temperature is heated to 600℃and the melt center solidification time is 12.844 s.The microstructural analysis of the ingot shows that its shrinkage hole is reduced from 130 to 100 mm,and the equiaxed crystal area is increased from 2275 to 3150 mm^(2).The solidification angle of the dendrite is changed under the action of the pulsed magnetic field,and the tilt angle is 45°.The results show that the pulsed magnetic field promotes the primary crystal core of the GH4738 alloy,improves the nucleation rate of the melt,reduces the size difference of the solidification structure between the center and the edge of the ingot,and improves the uniformity of the solidification structure.
基金financially supported by the National Key Research and Development Program of China(No.2020YFA0714900)the Joint Fund of the Ministry of Education(No.8091B012201)
文摘The corrosion resistance of cobalt-based alloy cladding layers is crucial for the long-term reliability of materials in the nuclear power industry,where they are exposed to highly aggressive environmental conditions.A major challenge to their performance is the corrosion occurring at phase boundaries under harsh operating conditions.This study investigates the effects of pulsed magnetic field treatment(PMT)on improving corrosion resistance at phase boundaries,specifically at the carbide/matrix Co interface,and seeks to clarify the underlying mechanisms.Advanced characterization techniques,including scanning electron microscopy(SEM),in situ transmission electron microscopy(TEM),in situ scanning kelvin probe force microscopy(SKPFM),and density functional theory(DFT)calculations,were employed.PMT samples exhibited no interface corrosion cracking or carbide spalling and showed a significant reduction in corrosion depth.TEM analysis revealed reduced lattice distortion at phase boundaries and a partial transformation of face-centered cubic(FCC)Co to hexagonal closepacked(HCP)Co.The enhanced corrosion resistance at phase boundaries is attributed to changes in the electronic work function(EWF),as determined by SKPFM measurements and DFT calculations.
基金supported by the Program of Key Laboratory of Cross-Domain Flight Interdisciplinary Technology,China(No.2023-ZY0205)。
文摘This paper describes an experimental study investigating the effects of sinusoidal pulsed injection on the combustion mode transition in a dual-mode supersonic combustor.The results are obtained under inflow conditions of 2.9 MPa stagnation pressure,1900 K stagnation temperature,and Mach number of 3.0.It has been observed that,at the same equivalence ratio,the combustion mode and flow field structure undergo irreversible changes from a weak combustion state to a strong combustion state at a specific pulsed jet frequency compared to steady jet.For steady jet,the combustion mode is dual-mode.As the frequency of the unsteady jet changes,the combustion mode also changes:it becomes a transition mode at frequencies of 171 Hz and 260 Hz,and a ramjet mode at 216 Hz.Combustion instability under steady jet manifests as a transition in flame stabilization mode.In contrast,under pulsed jet,combustion instability appears either as a transition in flame stabilization mode or as flame blow-off and flashback.The flow field oscillation frequency in the non-reacting flow is 171 Hz,which may resonate with the 171 Hz pulsed jet frequency,making the combustion oscillations most pronounced at this frequency.When the jet frequency is increased to 216 Hz,the combustion intensity significantly increases,and the combustion mode transfers to the ramjet mode.However,further increasing the frequency to 260 Hz results in a decrease in combustion intensity,returning to the transition mode.The frequency of the flow field oscillations varies with the coupling of the pulsed injection frequency,shock wave,and flame,and if the system reaches an unstable state,that is,pre-combustion shock train moves far upstream of the isolator during the pulsed jet period,strong combustion state can be achieved,and this process is irreversible.
基金financial support from the National Key Laboratory of Transient Physics,Nanjing University of Science and Technology(Grant No.6142604230101)Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant Nos.KYCX20_0321 and KYCX20_0322).
文摘Capacitor-based pulsed power supply(PPS)is widely used in fields related to electromagnetic launch,plasma,and materials'synthesis,modification and processing.As industrial applications place higher requirements on compact and portable pulsed power supplies,the National Key Laboratory of Transient Physics(NKLTP)recently developed a pulsed power supply consisting of a set of compact pulse-forming units(PFU),each with a capacitor energy storage of 220 kJ.This integrated PPS comes with a complete system configuration,a miniature compact structure,a high rate of repetition,and high power,with energy storage density exceeding 1.2 MJ/m^(3).This paper describes the device-level design of the unit,the system layout,the control system,the thermal management system,and the experimental results of the pulsed power supply.The experimental results verified the good reliability of the PPS at high repetition rates with each unit module delivering an output current of more than 100 kA.Additionally,flexible current pulse shapes can be formed by setting the charging voltage and the trigger sequence of the PFUs.The pulse forming network(PFN)developed from these PFUs was successfully applied to electromagnetic launch.
