Computational solid mechanics has become an indispensable approach in engineering,and numerical investigation of fracturing in composites is essential,as composites are widely used in structural applications.Crack evo...Computational solid mechanics has become an indispensable approach in engineering,and numerical investigation of fracturing in composites is essential,as composites are widely used in structural applications.Crack evolution in composites is the path to elucidating the relationship between microstructures and fracture performance,but crack-based finite-element methods are computationally expensive and time-consuming,which limits their application in computation-intensive scenarios.Consequently,this study proposes a deep learning framework called Crack-Net for instant prediction of the dynamic crack growth process,as well as its strain-stress curve.Specifically,Crack-Net introduces an implicit constraint technique,which incorporates the relationship between crack evolution and stress response into the network architecture.This technique substantially reduces data requirements while improving predictive accuracy.The transfer learning technique enables Crack-Net to handle composite materials with reinforcements of different strengths.Trained on high-accuracy fracture development datasets from phase field simulations,the proposed framework is capable of tackling intricate scenarios,involving materials with diverse interfaces,varying initial conditions,and the intricate elastoplastic fracture process.The proposed Crack-Net holds great promise for practical applications in engineering and materials science,in which accurate and efficient fracture prediction is crucial for optimizing material performance and microstructural design.展开更多
As a critical component of pulse solid rocket motors(SRMs),the soft pulse separation device(PSD)is vital in enabling multi-pulse propulsion and has become a breakthrough in SRM engineering applications.To investigate ...As a critical component of pulse solid rocket motors(SRMs),the soft pulse separation device(PSD)is vital in enabling multi-pulse propulsion and has become a breakthrough in SRM engineering applications.To investigate the opening performance of the PSD,an axial PSD incorporating a star-shaped prefabricated defect was designed.The opening process was simulated using peridynamics,yielding the strain field distribution and the corresponding failure mode.A single-opening verification test was conducted.The simulation results showed good agreement with the experimental data,demonstrating the reliability of the peridynamic modeling approach.Furthermore,the effects of the prefabricated defect shape and depth on the opening performance of the PSD were analyzed through simulation.The research results indicate that the established constitutive model and failure criteria based on peridynamics can reasonably predict the failure location and the opening pressure of the soft PSD.Under the impact loading,the weak zone of the soft PSD firstly ruptures,and the damaged area gradually propagates along with the prefabricated defect,eventually leading to complete separation.A smaller prefabricated defect depth or a wider prefabricated defect distribution can cause a reduction in opening pressure.These research results provide valuable guidance for the preliminary design and optimization of PSDs in pulse solid rocket motors.展开更多
The acidity of atmospheric aerosols influences fundamental physicochemical processes that affect climate and human health.We recently developed a novel and facilewater-probebased method for directly measuring of the p...The acidity of atmospheric aerosols influences fundamental physicochemical processes that affect climate and human health.We recently developed a novel and facilewater-probebased method for directly measuring of the pH for micrometer-size droplets,providing a promising technique to better understand aerosol acidity in the atmosphere.The complex chemical composition of fine particles in the ambient air,however,poses certain challenges to using a water-probe for pH measurement,including interference from interactions between compositions and the influence of similar compositions on water structure.To explore the universality of our method,it was employed to measure the pH of ammonium,nitrate,carbonate,sulfate,and chloride particles.The pH of particles covering a broad range(0–14)were accurately determined,thereby demonstrating that our method can be generally applied,even to alkaline particles.Furthermore,a standard spectral library was developed by integrating the standard spectra of common hydrated ions extracted through the waterprobe.The library can be employed to identify particle composition and overcome the spectral overlap problem resulting from similar effects.Using the spectral library,all ions were identified and their concentrations were determined,in turn allowing successful pH measurement of multicomponent(ammonium-sulfate-nitrate-chloride)particles.Insights into the synergistic effect of Cl^(–),NO_(3)^(–),and NH_(4)^(+)depletion obtained with our approach revealed the interplay between pH and volatile partitioning.Given the ubiquity of component partitioning and pH variation in particles,the water probemay provide a new perspective on the underlying mechanisms of aerosol aging and aerosol–cloud interaction.展开更多
A novel carbon quantum dots modified potassium titanate nanotubes(CQDs/K2 Ti6 O13)composite photocatalyst was synthesized by hydrothermal treatment combined with calcination.X-ray diffraction(XRD)pattern and transmiss...A novel carbon quantum dots modified potassium titanate nanotubes(CQDs/K2 Ti6 O13)composite photocatalyst was synthesized by hydrothermal treatment combined with calcination.X-ray diffraction(XRD)pattern and transmission electron microscopy(TEM)indicated formation of potassium titanate nanotubes and successful deposition of CQDs onto K2 Ti6 O13.The photocatalytic performance of CQDs/K2 Ti6 O13 composite was evaluated by degradation of amoxicillin(AMX)under the irradiation of visible light and lights with the wavelengths of 365,385,420,450,485,520,595 and 630 nm.The results showed that the photocatalytic activity of CQDs/K2 Ti6 O13 hybrid material was greatly enhanced compared with the neat K2 Ti6 O13 calcined at 300℃.The narrowed band gap energy(Eg)and transfer of photo-excited electron by CQDs inhibited the immediate combination of electron-hole pairs,thus promoting photocatalytic activity.Moreover,CQ,Ds/K2 Ti6 O13 exhibited a broad spectrum of photocatalytic ability and it was interesting that the photocatalytic activity decreased with the increase of the irradiation wavelength.Reactive oxygen species(ROS)quenching tests suggested the hole(h^+)and hydroxyl radical(^·OH)played the primary roles in photocatalytic degradation of AMX.Moreover,CQ.Ds/K2 Ti6 O13 showed good reusability for AMX photocatalytic degradation after five successive runs.This study proposed an available method for titanate nanomaterials modification,and the developed novel CQDs/K2 Ti6 O13hyb rid material is p ro mising fo r potential application on antibiotics removal fro m water and wastewater.展开更多
In this work fingering double diffusive convection,i.e.the buoyancy-driven flow with fluid density being affected by two different scalar components,is investigated numerically with special efforts on the influences o...In this work fingering double diffusive convection,i.e.the buoyancy-driven flow with fluid density being affected by two different scalar components,is investigated numerically with special efforts on the influences of the physical properties of two scalar components.We show that different scalar properties can affect the global transport behaviors.The concentration flux exhibits different exponents in their power-law scalings for different combinations of scalar components.The scaling exponents of heat flux,however,depend mainly on the ratio of the diffusivities of two scalars.If one uses the local parameters of the finger layer in the bulk,the behaviors are very similar to those found in the fully periodic simulations.The horizontal width of the fingers is consistent with the wavelength of the fast growing mode.For one case we observe evidences of the thermohaline staircase,namely,the typical width of the flow structures changes significantly in different layers within the flow domain.展开更多
Metal halide perovskites are emerging as the most promising candidate for the next-generation Photovoltaics(PV)materials,due to their superior optoelectronic properties and low cost.However,the resulting Perovskite so...Metal halide perovskites are emerging as the most promising candidate for the next-generation Photovoltaics(PV)materials,due to their superior optoelectronic properties and low cost.However,the resulting Perovskite solar cells(PSCs)suffer from poor stability.In particular,the temperature and light activated ionic defects within the perovskite lattice,as well as electric-field-induced migration of ionic defects,make the PSCs unstable at operating condition,even with device encapsulation.There is no doubt that the investigation of ion migration is crucial for the development of PSCs with high intrinsic stability.In this review,we first briefly introduce the origin and pathways of ion migration,and also the essential characterization methods to identify ion migration.Next,we discuss the impact of ion migration on the perovskite films and cells with respect to photoelectric properties and stability.Then,several representative strategies to suppress ion migration are systematically summarized in the context of composition engineering,additive engineering and interface engineering,with an in-depth understanding on the underlying mechanisms which may provide more clues for further fabrication of PSCs with improved stability.Finally,a perspective with some suggestion on future research directions and chemical approaches are provided to alleviate ion migration in perovskite materials and the entire devices.展开更多
The desire for practical utilization of rechargeable lithium batteries with high energy density has motivated attempts to develop new electrode materials and battery systems. Here, without additional binders we presen...The desire for practical utilization of rechargeable lithium batteries with high energy density has motivated attempts to develop new electrode materials and battery systems. Here, without additional binders we present a simple vacuum filtration method to synthesize nitrogen and sulfur codoped graphene(N,S-G) blocking layer, which is ultra-lightweight, conductive, and free standing. When the N,S-G membrane was inserted between the catholyte and separator, the lithium–selenium(Li–Se)batteries exhibited a high reversible discharge capacity of 330.7 mAh g^(-1) at 1 C(1 C = 675 mA g^(-1)) after 500 cycles and high rate performance(over 310 mAh g^(-1) at 4 C) even at an active material loading as high as ～5 mg cm^(-2). This excellent performance can be ascribed to homogenous dispersion of the liquid active material in the electrode, good Li^+-ion conductivity, fast electronic transport in the conductive graphene framework, andstrong chemical confinement of polyselenides by nitrogen and sulfur atoms. More importantly, it is a promising strategy for enhancing the energy density of Li–Se batteries by using the catholyte with a lightweight heteroatom doping carbon matrix.展开更多
基金supported and partially funded by the National Natural Science Foundation of China(52288101)the China Postdoctoral Science Foundation(2024M761535)supported by the High Performance Computing Centers at Eastern Institute of Technology,Ningbo,and Ningbo Institute of Digital Twin.
文摘Computational solid mechanics has become an indispensable approach in engineering,and numerical investigation of fracturing in composites is essential,as composites are widely used in structural applications.Crack evolution in composites is the path to elucidating the relationship between microstructures and fracture performance,but crack-based finite-element methods are computationally expensive and time-consuming,which limits their application in computation-intensive scenarios.Consequently,this study proposes a deep learning framework called Crack-Net for instant prediction of the dynamic crack growth process,as well as its strain-stress curve.Specifically,Crack-Net introduces an implicit constraint technique,which incorporates the relationship between crack evolution and stress response into the network architecture.This technique substantially reduces data requirements while improving predictive accuracy.The transfer learning technique enables Crack-Net to handle composite materials with reinforcements of different strengths.Trained on high-accuracy fracture development datasets from phase field simulations,the proposed framework is capable of tackling intricate scenarios,involving materials with diverse interfaces,varying initial conditions,and the intricate elastoplastic fracture process.The proposed Crack-Net holds great promise for practical applications in engineering and materials science,in which accurate and efficient fracture prediction is crucial for optimizing material performance and microstructural design.
基金supported by the National Natural Science Foundation of China(No.12202011)the Youth Research fund of Shanghai Academy of Spaceflight Technology(KJW-KT-QNKYJJ-2022-25)China Postdoctoral Science Foundation(Nos.2024T170009,2022M710190).
文摘As a critical component of pulse solid rocket motors(SRMs),the soft pulse separation device(PSD)is vital in enabling multi-pulse propulsion and has become a breakthrough in SRM engineering applications.To investigate the opening performance of the PSD,an axial PSD incorporating a star-shaped prefabricated defect was designed.The opening process was simulated using peridynamics,yielding the strain field distribution and the corresponding failure mode.A single-opening verification test was conducted.The simulation results showed good agreement with the experimental data,demonstrating the reliability of the peridynamic modeling approach.Furthermore,the effects of the prefabricated defect shape and depth on the opening performance of the PSD were analyzed through simulation.The research results indicate that the established constitutive model and failure criteria based on peridynamics can reasonably predict the failure location and the opening pressure of the soft PSD.Under the impact loading,the weak zone of the soft PSD firstly ruptures,and the damaged area gradually propagates along with the prefabricated defect,eventually leading to complete separation.A smaller prefabricated defect depth or a wider prefabricated defect distribution can cause a reduction in opening pressure.These research results provide valuable guidance for the preliminary design and optimization of PSDs in pulse solid rocket motors.
基金supported by the National Natural Science Foundation of China(No.91844000)China Postdoctoral Science Foundation(No.2020M670048).
文摘The acidity of atmospheric aerosols influences fundamental physicochemical processes that affect climate and human health.We recently developed a novel and facilewater-probebased method for directly measuring of the pH for micrometer-size droplets,providing a promising technique to better understand aerosol acidity in the atmosphere.The complex chemical composition of fine particles in the ambient air,however,poses certain challenges to using a water-probe for pH measurement,including interference from interactions between compositions and the influence of similar compositions on water structure.To explore the universality of our method,it was employed to measure the pH of ammonium,nitrate,carbonate,sulfate,and chloride particles.The pH of particles covering a broad range(0–14)were accurately determined,thereby demonstrating that our method can be generally applied,even to alkaline particles.Furthermore,a standard spectral library was developed by integrating the standard spectra of common hydrated ions extracted through the waterprobe.The library can be employed to identify particle composition and overcome the spectral overlap problem resulting from similar effects.Using the spectral library,all ions were identified and their concentrations were determined,in turn allowing successful pH measurement of multicomponent(ammonium-sulfate-nitrate-chloride)particles.Insights into the synergistic effect of Cl^(–),NO_(3)^(–),and NH_(4)^(+)depletion obtained with our approach revealed the interplay between pH and volatile partitioning.Given the ubiquity of component partitioning and pH variation in particles,the water probemay provide a new perspective on the underlying mechanisms of aerosol aging and aerosol–cloud interaction.
基金supported by the National Natural Science Foundation of China(51671003)the China Postdoctoral Science Foundation(2017M610022)+3 种基金the National Basic Research Program of China(2016YFB0100201)the Open Project Foundation of State Key Laboratory of Chemical Resource Engineeringthe start-up supports from Peking Universitythe Young Thousand Talented Program,China~~
基金Innovative Research Group of the National Natural Science Foundation of China(NFSC)(No.51721006)China Postdoctoral Science Foundation(No.2017M620132)
文摘A novel carbon quantum dots modified potassium titanate nanotubes(CQDs/K2 Ti6 O13)composite photocatalyst was synthesized by hydrothermal treatment combined with calcination.X-ray diffraction(XRD)pattern and transmission electron microscopy(TEM)indicated formation of potassium titanate nanotubes and successful deposition of CQDs onto K2 Ti6 O13.The photocatalytic performance of CQDs/K2 Ti6 O13 composite was evaluated by degradation of amoxicillin(AMX)under the irradiation of visible light and lights with the wavelengths of 365,385,420,450,485,520,595 and 630 nm.The results showed that the photocatalytic activity of CQDs/K2 Ti6 O13 hybrid material was greatly enhanced compared with the neat K2 Ti6 O13 calcined at 300℃.The narrowed band gap energy(Eg)and transfer of photo-excited electron by CQDs inhibited the immediate combination of electron-hole pairs,thus promoting photocatalytic activity.Moreover,CQ,Ds/K2 Ti6 O13 exhibited a broad spectrum of photocatalytic ability and it was interesting that the photocatalytic activity decreased with the increase of the irradiation wavelength.Reactive oxygen species(ROS)quenching tests suggested the hole(h^+)and hydroxyl radical(^·OH)played the primary roles in photocatalytic degradation of AMX.Moreover,CQ.Ds/K2 Ti6 O13 showed good reusability for AMX photocatalytic degradation after five successive runs.This study proposed an available method for titanate nanomaterials modification,and the developed novel CQDs/K2 Ti6 O13hyb rid material is p ro mising fo r potential application on antibiotics removal fro m water and wastewater.
基金supported by the Major Research Plan of National Natural and Science Foundation of China for Turbulent Structures(Grants 91852107 and 91752202).
文摘In this work fingering double diffusive convection,i.e.the buoyancy-driven flow with fluid density being affected by two different scalar components,is investigated numerically with special efforts on the influences of the physical properties of two scalar components.We show that different scalar properties can affect the global transport behaviors.The concentration flux exhibits different exponents in their power-law scalings for different combinations of scalar components.The scaling exponents of heat flux,however,depend mainly on the ratio of the diffusivities of two scalars.If one uses the local parameters of the finger layer in the bulk,the behaviors are very similar to those found in the fully periodic simulations.The horizontal width of the fingers is consistent with the wavelength of the fast growing mode.For one case we observe evidences of the thermohaline staircase,namely,the typical width of the flow structures changes significantly in different layers within the flow domain.
基金supported by the National Key Research and Development Program of China(2017YFA0206701,2020YFB1506400)the National Natural Science Foundation of China(51972004,21975028)the China Postdoctoral Science Foundation(2020M670040)。
文摘Metal halide perovskites are emerging as the most promising candidate for the next-generation Photovoltaics(PV)materials,due to their superior optoelectronic properties and low cost.However,the resulting Perovskite solar cells(PSCs)suffer from poor stability.In particular,the temperature and light activated ionic defects within the perovskite lattice,as well as electric-field-induced migration of ionic defects,make the PSCs unstable at operating condition,even with device encapsulation.There is no doubt that the investigation of ion migration is crucial for the development of PSCs with high intrinsic stability.In this review,we first briefly introduce the origin and pathways of ion migration,and also the essential characterization methods to identify ion migration.Next,we discuss the impact of ion migration on the perovskite films and cells with respect to photoelectric properties and stability.Then,several representative strategies to suppress ion migration are systematically summarized in the context of composition engineering,additive engineering and interface engineering,with an in-depth understanding on the underlying mechanisms which may provide more clues for further fabrication of PSCs with improved stability.Finally,a perspective with some suggestion on future research directions and chemical approaches are provided to alleviate ion migration in perovskite materials and the entire devices.
基金supported by the National Natural Science Foundation of China (51125001,51172005)the NSFCRGC Joint Research Scheme (51361165201)the Start-up Foundation of High-level Talents in Chongqing Technology and Business University (1856008)
文摘The desire for practical utilization of rechargeable lithium batteries with high energy density has motivated attempts to develop new electrode materials and battery systems. Here, without additional binders we present a simple vacuum filtration method to synthesize nitrogen and sulfur codoped graphene(N,S-G) blocking layer, which is ultra-lightweight, conductive, and free standing. When the N,S-G membrane was inserted between the catholyte and separator, the lithium–selenium(Li–Se)batteries exhibited a high reversible discharge capacity of 330.7 mAh g^(-1) at 1 C(1 C = 675 mA g^(-1)) after 500 cycles and high rate performance(over 310 mAh g^(-1) at 4 C) even at an active material loading as high as ～5 mg cm^(-2). This excellent performance can be ascribed to homogenous dispersion of the liquid active material in the electrode, good Li^+-ion conductivity, fast electronic transport in the conductive graphene framework, andstrong chemical confinement of polyselenides by nitrogen and sulfur atoms. More importantly, it is a promising strategy for enhancing the energy density of Li–Se batteries by using the catholyte with a lightweight heteroatom doping carbon matrix.
