Anode-free lithium metal batteries are prone to capacity degradation and safety hazards due to the formation and growth of lithium dendrites.The interface between the current collector and deposited lithium plays a cr...Anode-free lithium metal batteries are prone to capacity degradation and safety hazards due to the formation and growth of lithium dendrites.The interface between the current collector and deposited lithium plays a critical role in preventing dendrite formation by regulating the thermodynamics and kinetics of lithium deposition.In this study,we develop a phase field model to investigate the influence of the current collector’s surface energy on lithium deposition morphology and its effect on the quality of the lithium metal film.It is demonstrated that a higher surface energy of the current collector promotes the growth of lithium metal along the surface of the current collector.Further,our simulation results show that a higher surface energy accelerates the formation of the lithium metal film while simultaneously reducing its surface roughness.By examining different contact angles and applied potentials,we construct a phase diagram of deposition morphology,illustrating that increased surface energy facilitates the dense and uniform deposition of lithium metal by preventing the formation of lithium filaments and voids.These findings provide new insights into the development and application of anode-free lithium metal batteries.展开更多
A mathematical model combined projection algorithm with phase-field method was applied. The adaptive finite element method was adopted to solve the model based on the non-uniform grid, and the behavior of dendritic gr...A mathematical model combined projection algorithm with phase-field method was applied. The adaptive finite element method was adopted to solve the model based on the non-uniform grid, and the behavior of dendritic growth was simulated from undercooled nickel melt under the forced flow. The simulation results show that the asymmetry behavior of the dendritic growth is caused by the forced flow. When the flow velocity is less than the critical value, the asymmetry of dendrite is little influenced by the forced flow. Once the flow velocity reaches or exceeds the critical value, the controlling factor of dendrite growth gradually changes from thermal diffusion to convection. With the increase of the flow velocity, the deflection angle towards upstream direction of the primary dendrite stem becomes larger. The effect of the dendrite growth on the flow field of the melt is apparent. With the increase of the dendrite size, the vortex is present in the downstream regions, and the vortex region is gradually enlarged. Dendrite tips appear to remelt. In addition, the adaptive finite element method can reduce CPU running time by one order of magnitude compared with uniform grid method, and the speed-up ratio is proportional to the size of computational domain.展开更多
Flexoelectricity is a two-way coupling effect between the strain gradient and electric field that exists in all dielectrics,regardless of point group symmetry.However,the high-order derivatives of displacements involv...Flexoelectricity is a two-way coupling effect between the strain gradient and electric field that exists in all dielectrics,regardless of point group symmetry.However,the high-order derivatives of displacements involved in the strain gradient pose challenges in solving electromechanical coupling problems incorporating the flexoelectric effect.In this study,we formulate a phase-field model for ferroelectric materials considering the flexoelectric effect.A four-node quadrilateral element with 20 degrees of freedom is constructed without introducing high-order shape functions.The microstructure evolution of domains is described by an independent order parameter,namely the spontaneous polarization governed by the time-dependent Ginzburg–Landau theory.The model is developed based on a thermodynamic framework,in which a set of microforces is introduced to construct the constitutive relation and evolution equation.For the flexoelectric part of electric enthalpy,the strain gradient is determined by interpolating the mechanical strain at the node via the values of Gaussian integration points in the isoparametric space.The model is shown to be capable of reproducing the classic analytical solution of dielectric materials incorporating the flexoelectric contribution.The model is verified by duplicating some typical phenomena in flexoelectricity in cylindrical tubes and truncated pyramids.A comparison is made between the polarization distribution in dielectrics and ferroelectrics.The model can reproduce the solution to the boundary value problem of the cylindrical flexoelectric tube,and demonstrate domain twisting at domain walls in ferroelectrics considering the flexoelectric effect.展开更多
A phase-field model for growth of iron whiskers that includes convection around a particle was investigated during the process of fluidized pre-reduction. In the simulations, the phase-field method was coupled with fl...A phase-field model for growth of iron whiskers that includes convection around a particle was investigated during the process of fluidized pre-reduction. In the simulations, the phase-field method was coupled with flow field and reduction of iron oxide particles. The results showed that the reduction rate at local place had significant effects on the iron ions diffusion and the iron whiskers were more easily grown on the area containing low mole fraction of oxygen. The growth of iron whiskers in the model was investigated in two important simple situations: a velocity change flow and a CO concentration change flow. Because of high reduction rate and low surface energy, iron whiskers were more easily grown on the windward surface and the length of iron whiskers increased with gas velocity increasing. However, both the length and numbers of iron whiskers increased with CO concentration increasing due to the more nucleation site of iron whiskers created by CO adsorbed. When the gas velocity is higher than 0.3 m/s or CO mole fraction is high than 0.6, the nucleation incubation time would be rapidly decreased, which could give suggestions to control the operational parameters in the fluidized pre-reduction process.展开更多
K4Ce2Nb10O30 ultrafine powders were prepared by stearic acid method (SAM). The obtained products were analyzed by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning ele...K4Ce2Nb10O30 ultrafine powders were prepared by stearic acid method (SAM). The obtained products were analyzed by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy and UV-visible absorption spectra. XRD patterns revealed that K4Ce2Nb10O30 powders treated at 900 oC for 2 h presented tetragonal structure without the presence of deleterious phases. Furthermore, the K4Ce2Nb10O30 prepared by SAM had considerable activity under visible light irradiation.展开更多
In order to identify the day and night pollution sources of PM10 in ambient air in Longyan City,the authors analyzed the elemental composition of respirable particulate matters in the day and night ambient air samples...In order to identify the day and night pollution sources of PM10 in ambient air in Longyan City,the authors analyzed the elemental composition of respirable particulate matters in the day and night ambient air samples and various pollution sources which were collected in January 2010 in Longyan with inductivity coupled plasma-mass spectrometry（ICP-MS）.Then chemical mass balance（CMB） model and factor analysis（FA） method were applied to comparatively study the inorganic components in the sources and receptor samples.The results of factor analysis show that the major sources were road dust,waste incineration and mixed sources which contained automobile exhaust,soil dust/secondary dust and coal dust during the daytime in Longyan City,China.There are two major sources of pollution which are soil dust and mixture sources of automobile exhaust and secondary dust during the night in Longyan.The results of CMB show that the major sources are secondary dust,automobile exhaust and road dust during the daytime in Longyan.The major sources are secondary dust,soil dust and automobile exhaust during the night in Longyan.The results of the two methods are similar to each other and the results will guide us to plan to control the PM10 pollution sources in Longyan.展开更多
In the process of preparation of semi-solid metal materials, a variety of factors would influence the preparing time and the morphology of non-dendritic microstructure. The aim of this work is using phase-field method...In the process of preparation of semi-solid metal materials, a variety of factors would influence the preparing time and the morphology of non-dendritic microstructure. The aim of this work is using phase-field method to simulate non-dendritic growth during preparation of AI-4Cu-Mg semi-solid alloy by electromagnetic stirring method （EMS method）. Several factors such as the disturbance intensity, anisotropy, the thickness of the interface and the ratio of diffusivity in solid and liquid were considered. It is shown that decreasing the thickness of the interface results in more circular outline of particles, and increasing the diffusivity in solid can reduce degree of microsegregation. The disturbance intensity in the model can be connected with current intensity of stator or magnetic induction density impressed. Simulation results show that the larger the disturbance intensity or magnetic induction density, the more globular morphology the original phase in the matrix.展开更多
The present method gives a detailed description for the development and validation of a simple stability indicating reverse phase liquid chromatographic method for 10-hydroxycamptothecin(10-HCTN) in the presence of it...The present method gives a detailed description for the development and validation of a simple stability indicating reverse phase liquid chromatographic method for 10-hydroxycamptothecin(10-HCTN) in the presence of its impurities namely Imp A and Imp B along with degradation products generated from forced degradation studies. The drug was subjected to stress conditions of hydrolysis (acid, base and neutral), oxidative, photolytic and thermal stress degradation. Degradation was observed when subjected to treatment with peroxides or under conditions normally used for typical acid and base hydrolysis. The drug was found to be stable under other stress conditions attempted such as photolytic and thermal. Successful separation and isolation of the drug from related impurities and degradation products formed under stress conditions was achieved on an Inertsil ODS-3V (250 mm × 4.6 mm, 5 μm) column using a phosphate buffer, acetonitrile, methanol and Nanopure water. The developed HPLC method was validated with respect to specificity, linearity, accuracy, precision, sensitivity, robustness and solution stability. The assay method was found to be linear in the range of 0.16 mg/mL to 0.24 mg/mL with a correlation coefficient of 0.999 and the linearity of the impurities was established from 0.02% (LOQ) to 0.3%. Recoveries of assay and impurities were found between 99.4% and 100.3%. The developed HPLC method can be used to determine the related substances and assay determinations of 10-HCTN and also to evaluate the quality and long term stability of production samples.展开更多
The mean activity coefficient of 5, 10,15 , 20-tetrakis (P-methoxyl-O-sulfophenyl)porphyrin sodium in dilute aqueous solution has been determined in the modality range 0. 00547-0. 08871 mol · kg-1at 273. 2 K by t...The mean activity coefficient of 5, 10,15 , 20-tetrakis (P-methoxyl-O-sulfophenyl)porphyrin sodium in dilute aqueous solution has been determined in the modality range 0. 00547-0. 08871 mol · kg-1at 273. 2 K by the freezing-point depression method . The results of γ± are 0. 9945-0. 7695, it is in close agreement with that by isopiestic method.展开更多
A salt-assistant stearic acid method （SAM） capable of forming ultrafine K4Ce2Nb10O30 products was described. XRD pattern re-vealed that tetragonal K4Ce2Nb10O30 products could be obtained by heat treatment at 900 ℃ ...A salt-assistant stearic acid method （SAM） capable of forming ultrafine K4Ce2Nb10O30 products was described. XRD pattern re-vealed that tetragonal K4Ce2Nb10O30 products could be obtained by heat treatment at 900 ℃ for 2 h. Transmission electron microscopy （TEM） observations indicated the introduction of KCl could lead to the formation of rod-like K4Ce2Nb10O30 products. The species of salts played a crucial role in fine tuning the shapes and sizes of K4Ce2Nb10O30 products. Furthermore, the K4Ce2Nb10O30 prepared by salt-assistant SAM had considerable activity under visible light irradiation.展开更多
A coupled thermal-hydro-mechanical cohesive phase-field model for hydraulic fracturing in deep coal seams is presented.Heat exchange between the cold fluid and the hot rock is considered,and the thermal contribution t...A coupled thermal-hydro-mechanical cohesive phase-field model for hydraulic fracturing in deep coal seams is presented.Heat exchange between the cold fluid and the hot rock is considered,and the thermal contribution terms between the cold fluid and the hot rock are derived.Heat transfer obeys Fourier's law,and porosity is used to relate the thermodynamic parameters of the fracture and matrix domains.The net pressure difference between the fracture and the matrix is neglected,and thus the fluid flow is modeled by the unified fluid-governing equations.The evolution equations of porosity and Biot's coefficient during hydraulic fracturing are derived from their definitions.The effect of coal cleats is considered and modeled by Voronoi polygons,and this approach is shown to have high accuracy.The accuracy of the proposed model is verified by two sets of fracturing experiments in multilayer coal seams.Subsequently,the differences in fracture morphology,fluid pressure response,and fluid pressure distribution between direct fracturing of coal seams and indirect fracturing of shale interlayers are explored,and the effects of the cluster number and cluster spacing on fracture morphology for multi-cluster fracturing are also examined.The numerical results show that the proposed model is expected to be a powerful tool for the fracturing design and optimization of deep coalbed methane.展开更多
To enhance the computational efficiency of spatio-temporally discretized phase-field models,we present a high-speed solver specifically designed for the Poisson equations,a component frequently used in the numerical c...To enhance the computational efficiency of spatio-temporally discretized phase-field models,we present a high-speed solver specifically designed for the Poisson equations,a component frequently used in the numerical computation of such models.This efficient solver employs algorithms based on discrete cosine transformations(DCT)or discrete sine transformations(DST)and is not restricted by any spatio-temporal schemes.Our proposed methodology is appropriate for a variety of phase-field models and is especially efficient when combined with flow field systems.Meanwhile,this study has conducted an extensive numerical comparison and found that employing DCT and DST techniques not only yields results comparable to those obtained via the Multigrid(MG)method,a conventional approach used in the resolution of the Poisson equations,but also enhances computational efficiency by over 90%.展开更多
The internal pressure within fission gas bubbles(FGBs)in irradiated nuclear fuels drives mechanical interactions with the surrounding fuel skeleton.To investigate the micromechanical stress fields in irradiated nuclea...The internal pressure within fission gas bubbles(FGBs)in irradiated nuclear fuels drives mechanical interactions with the surrounding fuel skeleton.To investigate the micromechanical stress fields in irradiated nuclear fuels containing pressurized FGBs,a mechanical constitutive model for the equivalent solid of FGBs was developed and validated.This model was based on the modified Van der Waals equation,incorporating the effects of surface tension.Using this model,the micromechanical fields in irradiated U-10Mo fuels with randomly distributed FGBs were calculated during uniaxial tensile testing via the finite element(FE)method.The macroscopic elastic constants of the irradiated U-10Mo fuels were then derived using homogenization theory,and the influences of bubble pressure,bubble size,and porosity on these constants were examined.Results show that adjacent FGBs exhibit mechanical interactions,which leads to distinct stress concentrations in the surrounding fuel skeleton.The macroscopic elastic constants of irradiated U-10Mo fuels decrease with increasing the macroscopic porosity,which can be quantitatively described by the Mori-Tanaka model.In contrast,bubble pressure and size have negligible effects on these constants.展开更多
A phase-field model integrated with the thermodynamic databases was constructed to investigate the impact of Ni content on the precipitation kinetics and phase transformation of the Cu-rich phase in Fe-Cu-Ni alloy at ...A phase-field model integrated with the thermodynamic databases was constructed to investigate the impact of Ni content on the precipitation kinetics and phase transformation of the Cu-rich phase in Fe-Cu-Ni alloy at 773 K.The results demonstrated that the Cu core-Ni shell structures form via the decomposition of Cu-Ni co-clusters,which is consistent with previous experimental results.As the Ni content increases,both the volume fraction and number density of Cu-rich precipitates increase,while their size decreases.With the increase in Ni content,the transformation from a Cu to 9R Cu is accelerated,which is the opposite to the result of increasing Mn content.Magnetic energy can increase the nucleation rate of the Cu-rich phase,but it does not affect the phase transformation driving force required for its crystal structure transformation.展开更多
Viscoelastic solids,such as composite propellants,exhibit significant time and rate dependencies,and their fracture processes display high levels of nonlinearity.However,the correlation between crack propagation and v...Viscoelastic solids,such as composite propellants,exhibit significant time and rate dependencies,and their fracture processes display high levels of nonlinearity.However,the correlation between crack propagation and viscoelastic energy dissipation in these materials remains unclear.Therefore,accurately modeling and understanding of their fracture behavior is crucial for relevant engineering applications.This study proposes a novel viscoelastic phase-field model.In the numerical implementation,the adopted adaptive time-stepping iterative strategy effectively accelerates the coupling iteration efficiency between the phase-field and the displacement field.Moreover,all unknown parameters in the model,including the form of the phase-field degradation function,are identified through fitting against experimental data.Based on an introduced scaling factor,themechanical response behaviors of solid propellant dogbone specimens under cyclic loading,relaxation,and tension are analyzed,and the predictive capacity of the model is demonstrated by comparing the experimental data with the simulation results.Finally,modeling results for Mode-I and Mode-II crack propagation in single-edge-notched specimens indicate that the reduction of viscous energy dissipation will significantly increase the fracture growth rate,but under the same boundary conditions,the crack path remains unchanged.展开更多
Magnesium is distinguished by its highly anisotropic inelastic deformation involving a profuse activity of deformation twinning.Instrumented micro/nano-indentation technique has been widely applied to characterize the...Magnesium is distinguished by its highly anisotropic inelastic deformation involving a profuse activity of deformation twinning.Instrumented micro/nano-indentation technique has been widely applied to characterize the mechanical properties of magnesium,typically through the analysis of the indentation load-depth response,surface topography,and less commonly,the post-mortem microstructure within the bulk material.However,experimental limitations prevent the real-time observation of the evolving microstructure.To bridge this gap,we employ a recently-developed finite-strain model that couples the phase-field method and conventional crystal plasticity to simulate the evolution of the indentation-induced twin microstructure and its interaction with plastic slip in a magnesium single-crystal.Particular emphasis is placed on two aspects:orientation-dependent inelastic deformation and indentation size effects.Several outcomes of our 2D computational study are consistent with prior experimental observations.Chief among them is the intricate morphology of twin microstructure obtained at large spatial scales,which,to our knowledge,represents a level of detail that has not been captured in previous modeling studies.To further elucidate on size effects,we extend the model by incorporating gradient-enhanced crystal plasticity,and re-examine the notion of‘smaller is stronger’.The corresponding results underscore the dominant influence of gradient plasticity over the interfacial energy of twin boundaries in governing the size-dependent mechanical response.展开更多
基金supported by the National Key Research and Development Program of China(2022YFA1203602)the National Natural Science Foundation of China(Grant No.12025206)+1 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0620101)the National Natural Science Foundations of China(Grant No.12202366).
文摘Anode-free lithium metal batteries are prone to capacity degradation and safety hazards due to the formation and growth of lithium dendrites.The interface between the current collector and deposited lithium plays a critical role in preventing dendrite formation by regulating the thermodynamics and kinetics of lithium deposition.In this study,we develop a phase field model to investigate the influence of the current collector’s surface energy on lithium deposition morphology and its effect on the quality of the lithium metal film.It is demonstrated that a higher surface energy of the current collector promotes the growth of lithium metal along the surface of the current collector.Further,our simulation results show that a higher surface energy accelerates the formation of the lithium metal film while simultaneously reducing its surface roughness.By examining different contact angles and applied potentials,we construct a phase diagram of deposition morphology,illustrating that increased surface energy facilitates the dense and uniform deposition of lithium metal by preventing the formation of lithium filaments and voids.These findings provide new insights into the development and application of anode-free lithium metal batteries.
基金Projects(51161011,11364024)supported by the National Natural Science Foundation of ChinaProject(1204GKCA065)supported by the Key Technology R&D Program of Gansu Province,China+1 种基金Project(201210)supported by the Fundamental Research Funds for the Universities of Gansu Province,ChinaProject(J201304)supported by the Funds for Distinguished Young Scientists of Lanzhou University of Technology,China
文摘A mathematical model combined projection algorithm with phase-field method was applied. The adaptive finite element method was adopted to solve the model based on the non-uniform grid, and the behavior of dendritic growth was simulated from undercooled nickel melt under the forced flow. The simulation results show that the asymmetry behavior of the dendritic growth is caused by the forced flow. When the flow velocity is less than the critical value, the asymmetry of dendrite is little influenced by the forced flow. Once the flow velocity reaches or exceeds the critical value, the controlling factor of dendrite growth gradually changes from thermal diffusion to convection. With the increase of the flow velocity, the deflection angle towards upstream direction of the primary dendrite stem becomes larger. The effect of the dendrite growth on the flow field of the melt is apparent. With the increase of the dendrite size, the vortex is present in the downstream regions, and the vortex region is gradually enlarged. Dendrite tips appear to remelt. In addition, the adaptive finite element method can reduce CPU running time by one order of magnitude compared with uniform grid method, and the speed-up ratio is proportional to the size of computational domain.
基金funded by the National Natural Science Foundation of China(Grant No.12272020)Beijing Natural Science Foundation(Grant No.JQ21001)+1 种基金S.W.acknowledges support from the Fundamental Research Funds for the Central Universities(Grant No.YWF-23-SDHK-L-019)M.Y.acknowledges support from the National Natural Science Foundation of China(Grant Nos.12302134,12272173,and 11902150).
文摘Flexoelectricity is a two-way coupling effect between the strain gradient and electric field that exists in all dielectrics,regardless of point group symmetry.However,the high-order derivatives of displacements involved in the strain gradient pose challenges in solving electromechanical coupling problems incorporating the flexoelectric effect.In this study,we formulate a phase-field model for ferroelectric materials considering the flexoelectric effect.A four-node quadrilateral element with 20 degrees of freedom is constructed without introducing high-order shape functions.The microstructure evolution of domains is described by an independent order parameter,namely the spontaneous polarization governed by the time-dependent Ginzburg–Landau theory.The model is developed based on a thermodynamic framework,in which a set of microforces is introduced to construct the constitutive relation and evolution equation.For the flexoelectric part of electric enthalpy,the strain gradient is determined by interpolating the mechanical strain at the node via the values of Gaussian integration points in the isoparametric space.The model is shown to be capable of reproducing the classic analytical solution of dielectric materials incorporating the flexoelectric contribution.The model is verified by duplicating some typical phenomena in flexoelectricity in cylindrical tubes and truncated pyramids.A comparison is made between the polarization distribution in dielectrics and ferroelectrics.The model can reproduce the solution to the boundary value problem of the cylindrical flexoelectric tube,and demonstrate domain twisting at domain walls in ferroelectrics considering the flexoelectric effect.
基金This work is supported by the National Natural Science Foundation of China (51374263, 51674052)The authors are grateful for the Chongqing Research Program of Basic Research and Frontier Technology (cstc2018jcyjAX0003)National Natural Science Foundation of China (91634106, 51704048) is also acknowledged.
文摘A phase-field model for growth of iron whiskers that includes convection around a particle was investigated during the process of fluidized pre-reduction. In the simulations, the phase-field method was coupled with flow field and reduction of iron oxide particles. The results showed that the reduction rate at local place had significant effects on the iron ions diffusion and the iron whiskers were more easily grown on the area containing low mole fraction of oxygen. The growth of iron whiskers in the model was investigated in two important simple situations: a velocity change flow and a CO concentration change flow. Because of high reduction rate and low surface energy, iron whiskers were more easily grown on the windward surface and the length of iron whiskers increased with gas velocity increasing. However, both the length and numbers of iron whiskers increased with CO concentration increasing due to the more nucleation site of iron whiskers created by CO adsorbed. When the gas velocity is higher than 0.3 m/s or CO mole fraction is high than 0.6, the nucleation incubation time would be rapidly decreased, which could give suggestions to control the operational parameters in the fluidized pre-reduction process.
基金Project supported by the National Natural Science Foundation of China (20872051) "Zijin Star" of NJUST
文摘K4Ce2Nb10O30 ultrafine powders were prepared by stearic acid method (SAM). The obtained products were analyzed by X-ray diffraction, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy and UV-visible absorption spectra. XRD patterns revealed that K4Ce2Nb10O30 powders treated at 900 oC for 2 h presented tetragonal structure without the presence of deleterious phases. Furthermore, the K4Ce2Nb10O30 prepared by SAM had considerable activity under visible light irradiation.
基金Supported by the Natural Basic Research Program of China(No.2005CB422207)the Fund of Eco-enviromental Impacts and Protection in Devoloping and Utilizing of Oil-shale Resources(No.OSR-01-06)
文摘In order to identify the day and night pollution sources of PM10 in ambient air in Longyan City,the authors analyzed the elemental composition of respirable particulate matters in the day and night ambient air samples and various pollution sources which were collected in January 2010 in Longyan with inductivity coupled plasma-mass spectrometry（ICP-MS）.Then chemical mass balance（CMB） model and factor analysis（FA） method were applied to comparatively study the inorganic components in the sources and receptor samples.The results of factor analysis show that the major sources were road dust,waste incineration and mixed sources which contained automobile exhaust,soil dust/secondary dust and coal dust during the daytime in Longyan City,China.There are two major sources of pollution which are soil dust and mixture sources of automobile exhaust and secondary dust during the night in Longyan.The results of CMB show that the major sources are secondary dust,automobile exhaust and road dust during the daytime in Longyan.The major sources are secondary dust,soil dust and automobile exhaust during the night in Longyan.The results of the two methods are similar to each other and the results will guide us to plan to control the PM10 pollution sources in Longyan.
文摘In the process of preparation of semi-solid metal materials, a variety of factors would influence the preparing time and the morphology of non-dendritic microstructure. The aim of this work is using phase-field method to simulate non-dendritic growth during preparation of AI-4Cu-Mg semi-solid alloy by electromagnetic stirring method （EMS method）. Several factors such as the disturbance intensity, anisotropy, the thickness of the interface and the ratio of diffusivity in solid and liquid were considered. It is shown that decreasing the thickness of the interface results in more circular outline of particles, and increasing the diffusivity in solid can reduce degree of microsegregation. The disturbance intensity in the model can be connected with current intensity of stator or magnetic induction density impressed. Simulation results show that the larger the disturbance intensity or magnetic induction density, the more globular morphology the original phase in the matrix.
文摘The present method gives a detailed description for the development and validation of a simple stability indicating reverse phase liquid chromatographic method for 10-hydroxycamptothecin(10-HCTN) in the presence of its impurities namely Imp A and Imp B along with degradation products generated from forced degradation studies. The drug was subjected to stress conditions of hydrolysis (acid, base and neutral), oxidative, photolytic and thermal stress degradation. Degradation was observed when subjected to treatment with peroxides or under conditions normally used for typical acid and base hydrolysis. The drug was found to be stable under other stress conditions attempted such as photolytic and thermal. Successful separation and isolation of the drug from related impurities and degradation products formed under stress conditions was achieved on an Inertsil ODS-3V (250 mm × 4.6 mm, 5 μm) column using a phosphate buffer, acetonitrile, methanol and Nanopure water. The developed HPLC method was validated with respect to specificity, linearity, accuracy, precision, sensitivity, robustness and solution stability. The assay method was found to be linear in the range of 0.16 mg/mL to 0.24 mg/mL with a correlation coefficient of 0.999 and the linearity of the impurities was established from 0.02% (LOQ) to 0.3%. Recoveries of assay and impurities were found between 99.4% and 100.3%. The developed HPLC method can be used to determine the related substances and assay determinations of 10-HCTN and also to evaluate the quality and long term stability of production samples.
文摘The mean activity coefficient of 5, 10,15 , 20-tetrakis (P-methoxyl-O-sulfophenyl)porphyrin sodium in dilute aqueous solution has been determined in the modality range 0. 00547-0. 08871 mol · kg-1at 273. 2 K by the freezing-point depression method . The results of γ± are 0. 9945-0. 7695, it is in close agreement with that by isopiestic method.
基金supported by the National Natural Science Foundation of China (50902070)the Natural Science Foundation of Jiangsu province (BK2009391)+1 种基金the Research Fund for the Doctoral Program of Higher Education of China (20093219120011)NUST Research Funding (ZDJH07)
文摘A salt-assistant stearic acid method （SAM） capable of forming ultrafine K4Ce2Nb10O30 products was described. XRD pattern re-vealed that tetragonal K4Ce2Nb10O30 products could be obtained by heat treatment at 900 ℃ for 2 h. Transmission electron microscopy （TEM） observations indicated the introduction of KCl could lead to the formation of rod-like K4Ce2Nb10O30 products. The species of salts played a crucial role in fine tuning the shapes and sizes of K4Ce2Nb10O30 products. Furthermore, the K4Ce2Nb10O30 prepared by salt-assistant SAM had considerable activity under visible light irradiation.
基金Project supported by the National Natural Science Foundation of China(No.42202314)。
文摘A coupled thermal-hydro-mechanical cohesive phase-field model for hydraulic fracturing in deep coal seams is presented.Heat exchange between the cold fluid and the hot rock is considered,and the thermal contribution terms between the cold fluid and the hot rock are derived.Heat transfer obeys Fourier's law,and porosity is used to relate the thermodynamic parameters of the fracture and matrix domains.The net pressure difference between the fracture and the matrix is neglected,and thus the fluid flow is modeled by the unified fluid-governing equations.The evolution equations of porosity and Biot's coefficient during hydraulic fracturing are derived from their definitions.The effect of coal cleats is considered and modeled by Voronoi polygons,and this approach is shown to have high accuracy.The accuracy of the proposed model is verified by two sets of fracturing experiments in multilayer coal seams.Subsequently,the differences in fracture morphology,fluid pressure response,and fluid pressure distribution between direct fracturing of coal seams and indirect fracturing of shale interlayers are explored,and the effects of the cluster number and cluster spacing on fracture morphology for multi-cluster fracturing are also examined.The numerical results show that the proposed model is expected to be a powerful tool for the fracturing design and optimization of deep coalbed methane.
基金Supported by Shanxi Province Natural Science Research(202203021212249)Special/Youth Foundation of Taiyuan University of Technology(2022QN101)+3 种基金National Natural Science Foundation of China(12301556)Research Project Supported by Shanxi Scholarship Council of China(2021-029)International Cooperation Base and Platform Project of Shanxi Province(202104041101019)Basic Research Plan of Shanxi Province(202203021211129)。
文摘To enhance the computational efficiency of spatio-temporally discretized phase-field models,we present a high-speed solver specifically designed for the Poisson equations,a component frequently used in the numerical computation of such models.This efficient solver employs algorithms based on discrete cosine transformations(DCT)or discrete sine transformations(DST)and is not restricted by any spatio-temporal schemes.Our proposed methodology is appropriate for a variety of phase-field models and is especially efficient when combined with flow field systems.Meanwhile,this study has conducted an extensive numerical comparison and found that employing DCT and DST techniques not only yields results comparable to those obtained via the Multigrid(MG)method,a conventional approach used in the resolution of the Poisson equations,but also enhances computational efficiency by over 90%.
基金National Natural Science Foundation of China(12135008,12132005)。
文摘The internal pressure within fission gas bubbles(FGBs)in irradiated nuclear fuels drives mechanical interactions with the surrounding fuel skeleton.To investigate the micromechanical stress fields in irradiated nuclear fuels containing pressurized FGBs,a mechanical constitutive model for the equivalent solid of FGBs was developed and validated.This model was based on the modified Van der Waals equation,incorporating the effects of surface tension.Using this model,the micromechanical fields in irradiated U-10Mo fuels with randomly distributed FGBs were calculated during uniaxial tensile testing via the finite element(FE)method.The macroscopic elastic constants of the irradiated U-10Mo fuels were then derived using homogenization theory,and the influences of bubble pressure,bubble size,and porosity on these constants were examined.Results show that adjacent FGBs exhibit mechanical interactions,which leads to distinct stress concentrations in the surrounding fuel skeleton.The macroscopic elastic constants of irradiated U-10Mo fuels decrease with increasing the macroscopic porosity,which can be quantitatively described by the Mori-Tanaka model.In contrast,bubble pressure and size have negligible effects on these constants.
基金supported by the National Natural Science Foundation of China(Grant No.51871086).
文摘A phase-field model integrated with the thermodynamic databases was constructed to investigate the impact of Ni content on the precipitation kinetics and phase transformation of the Cu-rich phase in Fe-Cu-Ni alloy at 773 K.The results demonstrated that the Cu core-Ni shell structures form via the decomposition of Cu-Ni co-clusters,which is consistent with previous experimental results.As the Ni content increases,both the volume fraction and number density of Cu-rich precipitates increase,while their size decreases.With the increase in Ni content,the transformation from a Cu to 9R Cu is accelerated,which is the opposite to the result of increasing Mn content.Magnetic energy can increase the nucleation rate of the Cu-rich phase,but it does not affect the phase transformation driving force required for its crystal structure transformation.
基金funded by National Natural Science Foundation of China(Grant No.11872372)Graduate Innovation Foundation of Hunan Province of China(Grant No.CX20230018).
文摘Viscoelastic solids,such as composite propellants,exhibit significant time and rate dependencies,and their fracture processes display high levels of nonlinearity.However,the correlation between crack propagation and viscoelastic energy dissipation in these materials remains unclear.Therefore,accurately modeling and understanding of their fracture behavior is crucial for relevant engineering applications.This study proposes a novel viscoelastic phase-field model.In the numerical implementation,the adopted adaptive time-stepping iterative strategy effectively accelerates the coupling iteration efficiency between the phase-field and the displacement field.Moreover,all unknown parameters in the model,including the form of the phase-field degradation function,are identified through fitting against experimental data.Based on an introduced scaling factor,themechanical response behaviors of solid propellant dogbone specimens under cyclic loading,relaxation,and tension are analyzed,and the predictive capacity of the model is demonstrated by comparing the experimental data with the simulation results.Finally,modeling results for Mode-I and Mode-II crack propagation in single-edge-notched specimens indicate that the reduction of viscous energy dissipation will significantly increase the fracture growth rate,but under the same boundary conditions,the crack path remains unchanged.
文摘Magnesium is distinguished by its highly anisotropic inelastic deformation involving a profuse activity of deformation twinning.Instrumented micro/nano-indentation technique has been widely applied to characterize the mechanical properties of magnesium,typically through the analysis of the indentation load-depth response,surface topography,and less commonly,the post-mortem microstructure within the bulk material.However,experimental limitations prevent the real-time observation of the evolving microstructure.To bridge this gap,we employ a recently-developed finite-strain model that couples the phase-field method and conventional crystal plasticity to simulate the evolution of the indentation-induced twin microstructure and its interaction with plastic slip in a magnesium single-crystal.Particular emphasis is placed on two aspects:orientation-dependent inelastic deformation and indentation size effects.Several outcomes of our 2D computational study are consistent with prior experimental observations.Chief among them is the intricate morphology of twin microstructure obtained at large spatial scales,which,to our knowledge,represents a level of detail that has not been captured in previous modeling studies.To further elucidate on size effects,we extend the model by incorporating gradient-enhanced crystal plasticity,and re-examine the notion of‘smaller is stronger’.The corresponding results underscore the dominant influence of gradient plasticity over the interfacial energy of twin boundaries in governing the size-dependent mechanical response.
