We introduce two improvements in the numerical scheme to simulate collision and slow shearing of irregular particles. First, we propose an alternative approach based on simple relations to compute the frictional conta...We introduce two improvements in the numerical scheme to simulate collision and slow shearing of irregular particles. First, we propose an alternative approach based on simple relations to compute the frictional contact forces. The approach improves efficiency and accuracy of the Discrete Element Method （DEM） when modeling the dynamics of the granular packing. We determine the proper upper limit for the integration step in the standard numerical scheme using a wide range of material parameters. To this end, we study the kinetic energy decay in a stress controlled test between two particles. Second, we show that the usual way of defining the contact plane between two polygonal particles is, in general, not unique which leads to discontinuities in the direction of the contact plane while particles move. To solve this drawback, we introduce an accurate definition for the contact plane based on the shape of the overlap area between touching particles, which evolves continuously in time.展开更多
In this study,perovskite-type La_(0.7)Ca_(0.3)Co_(0.3)Fe_(0.6)M_(0.1)O_(3-δ)(M=Cu,Zn)powders were synthesized using a scalable reverse co-precipitation method,presenting them as novel materials for oxygen transport m...In this study,perovskite-type La_(0.7)Ca_(0.3)Co_(0.3)Fe_(0.6)M_(0.1)O_(3-δ)(M=Cu,Zn)powders were synthesized using a scalable reverse co-precipitation method,presenting them as novel materials for oxygen transport membranes.The comprehensive study covered various aspects including oxygen permeability,crystal structure,conductivity,morphology,CO_(2) tolerance,and long-term regenerative durability with a focus on phase structure and composition.The membrane La_(0.7)Ca_(0.3)Co_(0.3)Fe_(0.6)M_(0.1)O_(3-δ)exhibited high oxygen permeation fluxes,reaching up to 0.88 and 0.64 mL·min^(−1)·cm^(−2) under air/He and air/CO_(2) gradients at 1173 K,respectively.After 1600 h of CO_(2) exposure,the perovskite structure remained intact,showcasing superior CO_(2) resistance.A combination of first principles simulations and experimental measurements was employed to deepen the understanding of Cu/Zn substitution effects on the structure,oxygen vacancy formation,and transport behavior of the membranes.These findings underscore the potential of this highly CO_(2)-tolerant membrane for applications in high-temperature oxygen separation.The enhanced insights into the oxygen transport mechanism contribute to the advancement of next-generation membrane materials.展开更多
Lattice-Boltzmann(LB)simulations are a common tool to numerically estimate the permeability of porous media.For valuable results,the porous structure has to be well resolved resulting in a large computational effort a...Lattice-Boltzmann(LB)simulations are a common tool to numerically estimate the permeability of porous media.For valuable results,the porous structure has to be well resolved resulting in a large computational effort as well as high memory demands.In order to estimate the permeability of realistic samples,it is of importance to not only implement very efficient codes,but also to choose the most appropriate simulation setup to achieve accurate results.With the focus on accuracy and computational effort,we present a comparison between different methods to apply an effective pressure gradient,efficient boundary conditions,as well as two LB implementations based on pore-matrix and pore-list data structures.展开更多
We propose an active learning scheme for automatically sampling a minimum number of uncorrelated configurations for fitting the Gaussian Approximation Potential(GAP).Our active learning scheme consists of an unsupervi...We propose an active learning scheme for automatically sampling a minimum number of uncorrelated configurations for fitting the Gaussian Approximation Potential(GAP).Our active learning scheme consists of an unsupervised machine learning(ML)scheme coupled with a Bayesian optimization technique that evaluates the GAP model.We apply this scheme to a Hafnium dioxide(HfO2)dataset generated from a“melt-quench”ab initio molecular dynamics(AIMD)protocol.Our results show that the active learning scheme,with no prior knowledge of the dataset,is able to extract a configuration that reaches the required energy fit tolerance.Further,molecular dynamics(MD)simulations performed using this active learned GAP model on 6144 atom systems of amorphous and liquid state elucidate the structural properties of HfO2 with near ab initio precision and quench rates(i.e.,1.0 K/ps)not accessible via AIMD.The melt and amorphous X-ray structural factors generated from our simulation are in good agreement with experiment.In addition,the calculated diffusion constants are in good agreement with previous ab initio studies.展开更多
Droplets on hydrophobic surfaces are ubiquitous in microfluidic applications and there exists a number of commonly used multicomponent and multiphase lattice Boltzmann schemes to study such systems.In this paper we fo...Droplets on hydrophobic surfaces are ubiquitous in microfluidic applications and there exists a number of commonly used multicomponent and multiphase lattice Boltzmann schemes to study such systems.In this paper we focus on a popular implementation of a multicomponent model as introduced by Shan and Chen.Here,interactions between different components are implemented as repulsive forces whose strength is determined by model parameters.In this paper we present simulations of a droplet on a hydrophobic surface.We investigate the dependence of the contact angle on the simulation parameters and quantitatively compare different approaches to determine it.Results show that the method is capable of modelling the whole range of contact angles.We find that the a priori determination of the contact angle is depending on the simulation parameters with an uncertainty of 10%to 20%.展开更多
基金GermanIsraeli Foundation Deutsche Forschungsgemeinschaft,under the project HE 2732781support by Deutsche Forschungsgemeinschaft, under the project LI 1599/1-1
文摘We introduce two improvements in the numerical scheme to simulate collision and slow shearing of irregular particles. First, we propose an alternative approach based on simple relations to compute the frictional contact forces. The approach improves efficiency and accuracy of the Discrete Element Method （DEM） when modeling the dynamics of the granular packing. We determine the proper upper limit for the integration step in the standard numerical scheme using a wide range of material parameters. To this end, we study the kinetic energy decay in a stress controlled test between two particles. Second, we show that the usual way of defining the contact plane between two polygonal particles is, in general, not unique which leads to discontinuities in the direction of the contact plane while particles move. To solve this drawback, we introduce an accurate definition for the contact plane based on the shape of the overlap area between touching particles, which evolves continuously in time.
文摘In this study,perovskite-type La_(0.7)Ca_(0.3)Co_(0.3)Fe_(0.6)M_(0.1)O_(3-δ)(M=Cu,Zn)powders were synthesized using a scalable reverse co-precipitation method,presenting them as novel materials for oxygen transport membranes.The comprehensive study covered various aspects including oxygen permeability,crystal structure,conductivity,morphology,CO_(2) tolerance,and long-term regenerative durability with a focus on phase structure and composition.The membrane La_(0.7)Ca_(0.3)Co_(0.3)Fe_(0.6)M_(0.1)O_(3-δ)exhibited high oxygen permeation fluxes,reaching up to 0.88 and 0.64 mL·min^(−1)·cm^(−2) under air/He and air/CO_(2) gradients at 1173 K,respectively.After 1600 h of CO_(2) exposure,the perovskite structure remained intact,showcasing superior CO_(2) resistance.A combination of first principles simulations and experimental measurements was employed to deepen the understanding of Cu/Zn substitution effects on the structure,oxygen vacancy formation,and transport behavior of the membranes.These findings underscore the potential of this highly CO_(2)-tolerant membrane for applications in high-temperature oxygen separation.The enhanced insights into the oxygen transport mechanism contribute to the advancement of next-generation membrane materials.
文摘Lattice-Boltzmann(LB)simulations are a common tool to numerically estimate the permeability of porous media.For valuable results,the porous structure has to be well resolved resulting in a large computational effort as well as high memory demands.In order to estimate the permeability of realistic samples,it is of importance to not only implement very efficient codes,but also to choose the most appropriate simulation setup to achieve accurate results.With the focus on accuracy and computational effort,we present a comparison between different methods to apply an effective pressure gradient,efficient boundary conditions,as well as two LB implementations based on pore-matrix and pore-list data structures.
基金This material is based upon work supported by Laboratory Directed Research and Development funding from Argonne National Laboratory,provided by the Director,Office of Science,of the U.S.Department of Energy(DOE)under Contract No.DEAC02-06CH11357This research used resources of the Argonne Leadership Computing Facility,which is a DOE Office of Science User Facility supported under Contract DE-AC02-06CH11357+3 种基金Argonne National Laboratory’s work was supported by the U.S.DOE,Office of Science,under contract DE-AC02-06CH11357This research used resources of the Advanced Photon Source,a U.S.DOE Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No.DE-AC02-06CH11357Use of the Center for Nanoscale Materials,an Office of Science user facility,was supported by the U.S.DOE,Office of Science,Office of Basic Energy Sciences,under Contract No.DE-AC02-06CH11357C.H.and A.N.K gratefully acknowledges useful discussions with Dr.Jens Smiatek,Dr.Frank Uhlig,and financial support from the German Funding Agency(Deutsche Forschungsgemeinschaft-DFG)under Germany’s Excellence Strategy—EXC 2075—390740016.
文摘We propose an active learning scheme for automatically sampling a minimum number of uncorrelated configurations for fitting the Gaussian Approximation Potential(GAP).Our active learning scheme consists of an unsupervised machine learning(ML)scheme coupled with a Bayesian optimization technique that evaluates the GAP model.We apply this scheme to a Hafnium dioxide(HfO2)dataset generated from a“melt-quench”ab initio molecular dynamics(AIMD)protocol.Our results show that the active learning scheme,with no prior knowledge of the dataset,is able to extract a configuration that reaches the required energy fit tolerance.Further,molecular dynamics(MD)simulations performed using this active learned GAP model on 6144 atom systems of amorphous and liquid state elucidate the structural properties of HfO2 with near ab initio precision and quench rates(i.e.,1.0 K/ps)not accessible via AIMD.The melt and amorphous X-ray structural factors generated from our simulation are in good agreement with experiment.In addition,the calculated diffusion constants are in good agreement with previous ab initio studies.
基金This work was supported by the DFG priority program“nano-and microfluidics”and the Collaborative Research Centre(SFB)716The computations were performed at the Jülich Supercomputing Centre and the Scientific Supercomputing Centre Karlsruhe.
文摘Droplets on hydrophobic surfaces are ubiquitous in microfluidic applications and there exists a number of commonly used multicomponent and multiphase lattice Boltzmann schemes to study such systems.In this paper we focus on a popular implementation of a multicomponent model as introduced by Shan and Chen.Here,interactions between different components are implemented as repulsive forces whose strength is determined by model parameters.In this paper we present simulations of a droplet on a hydrophobic surface.We investigate the dependence of the contact angle on the simulation parameters and quantitatively compare different approaches to determine it.Results show that the method is capable of modelling the whole range of contact angles.We find that the a priori determination of the contact angle is depending on the simulation parameters with an uncertainty of 10%to 20%.
