An adaptive 2 D nonhydrostatic dynamical core is proposed by using the multi-moment constrained finite-volume(MCV) scheme and the Berger-Oliger adaptive mesh refinement(AMR) algorithm. The MCV scheme takes several poi...An adaptive 2 D nonhydrostatic dynamical core is proposed by using the multi-moment constrained finite-volume(MCV) scheme and the Berger-Oliger adaptive mesh refinement(AMR) algorithm. The MCV scheme takes several pointwise values within each computational cell as the predicted variables to build high-order schemes based on single-cell reconstruction. Two types of moments, such as the volume-integrated average(VIA) and point value(PV), are defined as constraint conditions to derive the updating formulations of the unknowns, and the constraint condition on VIA guarantees the rigorous conservation of the proposed model. In this study, the MCV scheme is implemented on a height-based, terrainfollowing grid with variable resolution to solve the nonhydrostatic governing equations of atmospheric dynamics. The AMR grid of Berger-Oliger consists of several groups of blocks with different resolutions, where the MCV model developed on a fixed structured mesh can be used directly. Numerical formulations are designed to implement the coarsefine interpolation and the flux correction for properly exchanging the solution information among different blocks. Widely used benchmark tests are carried out to evaluate the proposed model. The numerical experiments on uniform and AMR grids indicate that the adaptive model has promising potential for improving computational efficiency without losing accuracy.展开更多
Dirac's method which itself is for constrained Boson fields and particle systems is followed and developed to treat Dirac fields in light-front coordinates.
Resolvent methods are presented for generating systematically iterative numerical algorithms for constrained problems in mechanics.The abstract framework corresponds to a general mixed finite element subdif-ferential ...Resolvent methods are presented for generating systematically iterative numerical algorithms for constrained problems in mechanics.The abstract framework corresponds to a general mixed finite element subdif-ferential model,with dual and primal evolution versions,which is shown to apply to problems of fluid dynamics,transport phenomena and solid mechanics,among others.In this manner,Uzawa's type methods and penalization-duality schemes,as well as macro-hybrid formulations,are generalized to non necessarily potential nanlinear mechanical problems.展开更多
In this paper,we consider the following logarithmic Schrödinger equation:−Δu+ωu=u log|u|^(2),u∈H^(1)(R^(N)),where N≥3,and ω>0 is a constant.With an auxiliary equation,we obtain the existence of normalized...In this paper,we consider the following logarithmic Schrödinger equation:−Δu+ωu=u log|u|^(2),u∈H^(1)(R^(N)),where N≥3,and ω>0 is a constant.With an auxiliary equation,we obtain the existence of normalized solutions by using the constrained variational method.展开更多
Effective constrained optimization algorithms have been proposed for engineering problems recently.It is common to consider constraint violation and optimization algorithm as two separate parts.In this study,a pbest s...Effective constrained optimization algorithms have been proposed for engineering problems recently.It is common to consider constraint violation and optimization algorithm as two separate parts.In this study,a pbest selection mechanism is proposed to integrate the current mutation strategy in constrained optimization problems.Based on the improved pbest selection method,an adaptive differential evolution approach is proposed,which helps the population jump out of the infeasible region.If all the individuals are infeasible,the top 5%of infeasible individuals are selected.In addition,a modified truncatedε-level method is proposed to avoid trapping in infeasible regions.The proposed adaptive differential evolution approach with an improvedεconstraint processmechanism(IεJADE)is examined on CEC 2006 and CEC 2010 constrained benchmark function series.Besides,a standard IEEE-30 bus test system is studied on the efficiency of the IεJADE.The numerical analysis verifies the IεJADE algorithm is effective in comparisonwith other effective algorithms.展开更多
This paper constructs a concentric ellipsoid torso-heart model by boundary element method and investigates the impacts of model structures on the cardiac magnetic fields generated by both equivalent primary source--a ...This paper constructs a concentric ellipsoid torso-heart model by boundary element method and investigates the impacts of model structures on the cardiac magnetic fields generated by both equivalent primary source--a current dipole and volume currents. Then by using the simulated magnetic fields based on torso-heart model as input, the cardiac current sources--an array of current dipoles by optimal constrained linear inverse method are constructed. Next, the current dipole array reconstruction considering boundaries is compared with that in an unbounded homogeneous medium. Furthermore, the influence of random noise on reconstruction is also considered and the reconstructing effect is judged by several reconstructing parameters.展开更多
In this paper, the shallow water problem is discussed. By treating the incompressible condition as the constraint, a constrained Hamilton variational principle is presented for the shallow water problem. Based on the ...In this paper, the shallow water problem is discussed. By treating the incompressible condition as the constraint, a constrained Hamilton variational principle is presented for the shallow water problem. Based on the constrained Hamilton variational principle, a shallow water equation based on displacement and pressure （SWE-DP） is developed. A hybrid numerical method combining the finite element method for spa- tial discretization and the Zu-class method for time integration is created for the SWE- DP. The correctness of the proposed SWE-DP is verified by numerical comparisons with two existing shallow water equations （SWEs）. The effectiveness of the hybrid numerical method proposed for the SWE-DP is also verified by numerical experiments. Moreover, the numerical experiments demonstrate that the Zu-class method shows excellent perfor- mance with respect to simulating the long time evolution of the shallow water.展开更多
As a new type of marine structure,floating breakwater can provide suitable water area for coastal residents.In this paper,a multi-module floating breakwater with three cylinders was designed.According to the character...As a new type of marine structure,floating breakwater can provide suitable water area for coastal residents.In this paper,a multi-module floating breakwater with three cylinders was designed.According to the characteristics of each module,the elastic connector was created.The cabins with functions such as living,generating electricity and entertainment were arranged.A linear spring constrained design wave(LSCDW)method for strength analysis of floating marine structures with multi-module elastic connections was proposed.The numerical model was verified by 1:50 similarity ratio in the test tank.According to the analysis of design wave and extreme wave conditions,considering the mooring loads and environmental loads and connector loads,the overall strength of breakwater was analyzed by LSCDW method.These studies can provide new insights and theoretical guidance for the design of multi-module floating structures.展开更多
This paper is devoted to studying the existence of solutions for the following logarithmic Schrödinger problem: −div(a(x)∇u)+V(x)u=ulogu2+k(x)| u |q1−2u+h(x)| u |q2−2u, x∈ℝN.(1)We first prove that the correspon...This paper is devoted to studying the existence of solutions for the following logarithmic Schrödinger problem: −div(a(x)∇u)+V(x)u=ulogu2+k(x)| u |q1−2u+h(x)| u |q2−2u, x∈ℝN.(1)We first prove that the corresponding functional I belongs to C1(HV1(ℝN),ℝ). Furthermore, by using the variational method, we prove the existence of a sigh-changing solution to problem (1).展开更多
Triangulation is widely used in scientific research, such as finite element mesh generation, surface reconstruction and the reconstruction of the density field data. This paper proposes a new method combining image pr...Triangulation is widely used in scientific research, such as finite element mesh generation, surface reconstruction and the reconstruction of the density field data. This paper proposes a new method combining image processing and density-controlled Centroidal Voronoi tessellations to quickly generate a density-controlled constrained Delaunay triangulation lbr 2D sea area. Firstly, preprocess digital images of the sea area and extract the boundary of seawater region by eight-neighbor searching algorithm. Then, 1 use Odd-Even Testing＂ method to check if one random vertex is inside the boundary and insert random vertices into the boundary. Finally, we get the CDT of random vertices by density-controlled CVT-Lloyd method. We also give some comparisons with existing methods, and our method performs better in final restllt of triangulation.展开更多
To explore the non-linear relationship between risk sources and the hazard degree levels of accidents,and to precisely predict the hazard impact of metro operation accidents,we pro-pose the ordered constraint Apriori-...To explore the non-linear relationship between risk sources and the hazard degree levels of accidents,and to precisely predict the hazard impact of metro operation accidents,we pro-pose the ordered constraint Apriori-RF method for forecasting metro operation accident hazard degree levels.First,the hazard degree of metro operation accidents is quantified from three dimensions:casualties,train delays,and facility damages.K-means clustering is then applied to categorize hazard degree levels.Second,the ordered constraint Apriori algorithm is employed to mine valid association rules between metro operation risk sources and accident hazard degree levels.These valid association rules are subsequently employed in the random forest(RF)algorithm for training,establishing a reliable and accu-rate prediction model.Finally,the method is validated using metro accident data from a city in China.The research results indicate that the ordered constraint Apriori-RF method enhances the effectiveness of association rule mining by 74.9%and exhibits higher compu-tational efficiency.The predicted values of the ordered constraint Apriori-RF method have small errors.Compared to traditional RF algorithms,the root mean square error(RMSE)is reduced by 14%,and the weighted root mean square error(WRMSE)is reduced by 36%,demonstrating the higher accuracy of the ordered constraint Apriori-RF method and its clear advantages.The research findings provide a precise and effective method for quanti-tatively predicting the hazard degree levels of metro operation accidents,holding signifi-cant theoretical and practical value in ensuring metro operation safety and implementing accident mitigation and prevention measures.展开更多
The Taylor dispersion method was used to measure diffusion coefficients of three-component liquid systems. An improved constrained nonlinear least-square method was used to evaluate the ternary diffusion coefficients ...The Taylor dispersion method was used to measure diffusion coefficients of three-component liquid systems. An improved constrained nonlinear least-square method was used to evaluate the ternary diffusion coefficients directly by fitting the mathematical solutions of the dispersion equation to eluted solute peaks detected using a differential refractometer. Diffusion coefficients of the three-component system of acetone-benzene-CCl4, determined at 25℃, were used to test the procedure. The measured diffusion coefficients were compared with values obtained by optical interferometry and the diaphragm cell method. Ternary diffusion coefficients are also determinated for solutions of 1-hexanol-hexane-toluene and 1-propanol- water-ethylene glycol at 25℃, with an accuracy of approximately 0.05 m^2·s^- 1.展开更多
In this paper, a truncated hybrid method is proposed and developed for solving sparse large-scale nonlinear programming problems. In the hybrid method, a symmetric system of linear equations, instead of the usual quad...In this paper, a truncated hybrid method is proposed and developed for solving sparse large-scale nonlinear programming problems. In the hybrid method, a symmetric system of linear equations, instead of the usual quadratic programming subproblems, is solved at iterative process. In order to ensure the global convergence, a method of multiplier is inserted in iterative process. A truncated solution is determined for the system of linear equations and the unconstrained subproblems are solved by the limited memory BFGS algorithm such that the hybrid algorithm is suitable to the large-scale problems. The local convergence of the hybrid algorithm is proved and some numerical tests for medium-sized truss problem are given.展开更多
Combining robustness and high accuracy is one of the primary challenges in the magnetohydrodynamics(MHD)field of numerical methods.This paper investigates two critical physical constraints:wave order and positivity-pr...Combining robustness and high accuracy is one of the primary challenges in the magnetohydrodynamics(MHD)field of numerical methods.This paper investigates two critical physical constraints:wave order and positivity-preserving(PP)properties of the high-resolution HLLD Riemann solver,which ensures the positivity of density,pressure,and internal energy.This method’s distinctiveness lies in its ability to ensure that the wave characteristic speeds of the HLLD Riemann solver are strictly ordered.A provably PP HLLD Riemann solver based on the Lagrangian setting is established,which can be viewed as an extension of the PP Lagrangianmethod in hydrodynamics but with more and stronger constraint condition.In addition,the above two properties are ensured on moving grid method by employing the Lagrange-to-Euler transform.Meanwhile,a novel multi-moment constrained finite volume method is introduced to acquire third order accuracy,and practical limiters are applied to avoid numerical oscillations.Selected numerical benchmarks demonstrate the robustness and accuracy of our methods.展开更多
Degree reduction of parametric curves and surfaces is an important process in the exchange of product model data between various CAD systems. In this paper the degenerate conditions of triangular Bezier surface patch...Degree reduction of parametric curves and surfaces is an important process in the exchange of product model data between various CAD systems. In this paper the degenerate conditions of triangular Bezier surface patches are derived. The degenerate conditions and constrained optimization methods are used to develop a degree reduction method for triangular Bezier surface patches. The error in the degree reduction of a triangular Bezier surface is also shown to depend on some geometric invariants which decrease exponentially in the subdivision process. Therefore, the degree reduction method can be combined with a subdivision algorithm to generate lower degree approximations which are within some preset error tolerance.展开更多
We investigate the critical nucleus and equilibrium morphologies duringprecipitation of a second-phase particle in a solid. We show that a combination ofdiffuse-interface description and a constrained string method is...We investigate the critical nucleus and equilibrium morphologies duringprecipitation of a second-phase particle in a solid. We show that a combination ofdiffuse-interface description and a constrained string method is able to predict boththe critical nucleus and equilibrium precipitate morphologies simultaneously without a priori assumptions. Using the cubic to cubic transformation as an example, it isdemonstrated that the maximum composition within a critical nucleus can be eitherhigher or lower than that of equilibrium precipitate while the morphology of an equilibrium precipitate may exhibit lower symmetry than the critical nucleus resulted fromelastic interactions.展开更多
A well-balanced second order finite volume central scheme for the magnetohydrodynamic(MHD)equations with gravitational source term is developed in this paper.The scheme is an unstaggered central scheme that evolves th...A well-balanced second order finite volume central scheme for the magnetohydrodynamic(MHD)equations with gravitational source term is developed in this paper.The scheme is an unstaggered central scheme that evolves the numerical solution on a single grid and avoids solving Riemann problems at the cell interfaces using ghost staggered cells.A subtraction technique is used on the conservative variables with the support of a known steady state in order to manifest the well-balanced property of the scheme.The divergence-free constraint of themagnetic field is satisfied after applying the constrained transport method(CTM)for unstaggered central schemes at the end of each time-step by correcting the components of the magnetic field.The robustness of the proposed scheme is verified on a list of numerical test cases from the literature.展开更多
In this study,a computational framework in the field of artificial intelligence was applied in computational fluid dynamics(CFD)field.This Framework,which was initially proposed by Google Al department,is called"...In this study,a computational framework in the field of artificial intelligence was applied in computational fluid dynamics(CFD)field.This Framework,which was initially proposed by Google Al department,is called"TensorFlow".An improved CFD model based on this framework was developed with a high-order difference method,which is a constrained interpolation profile(CIP)scheme for the base flow solver of the advection term in the Navier-Stokes equations,and preconditioned conjugate gradient(PCG)method was implemented in the model to solve the Poisson equation.Some new features including the convolution,vectorization,and graphics processing unit(GPU)acceleration were implemented to raise the computational efficiency.The model was tested with several benchmark cases and shows good performance.Compared with our former CIP-based model,the present Tensor Flow-based model also shows significantly higher computational efficiency in large-scale computation.The results indicate TensorFlow could be a promising framework for CFD models due to its ability in the computational acceleration and convenience for programming.展开更多
Feasible,smooth,and time-jerk optimal trajectory is essential for manipulators utilized in manufacturing process.A novel technique to generate trajectories in the joint space for robotic manipulators based on quintic ...Feasible,smooth,and time-jerk optimal trajectory is essential for manipulators utilized in manufacturing process.A novel technique to generate trajectories in the joint space for robotic manipulators based on quintic B-spline and constrained multi-objective student psychology based optimization(CMOSPBO)is proposed in this paper.In order to obtain the optimal trajectories,two objective functions including the total travelling time and the integral of the squared jerk along the whole trajectories are considered.The whole trajectories are interpolated by quintic B-spline and then optimized by CMOSPBO,while taking into account kinematic constraints of velocity,acceleration,and jerk.CMOSPBO mainly includes improved student psychology based optimization,archive management,and an adaptiveε-constraint handling method.Lévyflights and differential mutation are adopted to enhance the global exploration capacity of the improved SPBO.Theεvalue is varied with iterations and feasible solutions to prevent the premature convergence of CMOSPBO.Solution density estimation corresponding to the solution distribution in decision space and objective space is proposed to increase the diversity of solutions.The experimental results show that CMOSPBO outperforms than SQP,and NSGA-II in terms of the motion efficiency and jerk.The comparison results demonstrate the effectiveness of the proposed method to generate time-jerk optimal and jerk-continuous trajectories for manipulators.展开更多
基金supported by The National Key Research and Development Program of China(Grants Nos.2017YFA0603901 and 2017YFC1501901)The National Natural Science Foundation of China(Grant No.41522504)。
文摘An adaptive 2 D nonhydrostatic dynamical core is proposed by using the multi-moment constrained finite-volume(MCV) scheme and the Berger-Oliger adaptive mesh refinement(AMR) algorithm. The MCV scheme takes several pointwise values within each computational cell as the predicted variables to build high-order schemes based on single-cell reconstruction. Two types of moments, such as the volume-integrated average(VIA) and point value(PV), are defined as constraint conditions to derive the updating formulations of the unknowns, and the constraint condition on VIA guarantees the rigorous conservation of the proposed model. In this study, the MCV scheme is implemented on a height-based, terrainfollowing grid with variable resolution to solve the nonhydrostatic governing equations of atmospheric dynamics. The AMR grid of Berger-Oliger consists of several groups of blocks with different resolutions, where the MCV model developed on a fixed structured mesh can be used directly. Numerical formulations are designed to implement the coarsefine interpolation and the flux correction for properly exchanging the solution information among different blocks. Widely used benchmark tests are carried out to evaluate the proposed model. The numerical experiments on uniform and AMR grids indicate that the adaptive model has promising potential for improving computational efficiency without losing accuracy.
文摘Dirac's method which itself is for constrained Boson fields and particle systems is followed and developed to treat Dirac fields in light-front coordinates.
文摘Resolvent methods are presented for generating systematically iterative numerical algorithms for constrained problems in mechanics.The abstract framework corresponds to a general mixed finite element subdif-ferential model,with dual and primal evolution versions,which is shown to apply to problems of fluid dynamics,transport phenomena and solid mechanics,among others.In this manner,Uzawa's type methods and penalization-duality schemes,as well as macro-hybrid formulations,are generalized to non necessarily potential nanlinear mechanical problems.
基金supported by the Natural Science Research Project of Department of Education of Guizhou Province(No.QJJ2023062)the National Natural Science Foundation of China(No.52174184)。
文摘In this paper,we consider the following logarithmic Schrödinger equation:−Δu+ωu=u log|u|^(2),u∈H^(1)(R^(N)),where N≥3,and ω>0 is a constant.With an auxiliary equation,we obtain the existence of normalized solutions by using the constrained variational method.
基金supported by National Natural Science Foundation of China under Grant Nos.52005447,72271222,71371170,71871203,L1924063Zhejiang Provincial Natural Science Foundation of China underGrant No.LQ21E050014Foundation of Zhejiang Education Committee under Grant No.Y201840056.
文摘Effective constrained optimization algorithms have been proposed for engineering problems recently.It is common to consider constraint violation and optimization algorithm as two separate parts.In this study,a pbest selection mechanism is proposed to integrate the current mutation strategy in constrained optimization problems.Based on the improved pbest selection method,an adaptive differential evolution approach is proposed,which helps the population jump out of the infeasible region.If all the individuals are infeasible,the top 5%of infeasible individuals are selected.In addition,a modified truncatedε-level method is proposed to avoid trapping in infeasible regions.The proposed adaptive differential evolution approach with an improvedεconstraint processmechanism(IεJADE)is examined on CEC 2006 and CEC 2010 constrained benchmark function series.Besides,a standard IEEE-30 bus test system is studied on the efficiency of the IεJADE.The numerical analysis verifies the IεJADE algorithm is effective in comparisonwith other effective algorithms.
基金Project supported by the State Key Development Program for Basic Research of China(Grant No.2006CB601007)the National Natural Science Foundation of China(Grant No.10674006)the National High Technology Research and Development Program of China(Grant No.2007AA03Z238)
文摘This paper constructs a concentric ellipsoid torso-heart model by boundary element method and investigates the impacts of model structures on the cardiac magnetic fields generated by both equivalent primary source--a current dipole and volume currents. Then by using the simulated magnetic fields based on torso-heart model as input, the cardiac current sources--an array of current dipoles by optimal constrained linear inverse method are constructed. Next, the current dipole array reconstruction considering boundaries is compared with that in an unbounded homogeneous medium. Furthermore, the influence of random noise on reconstruction is also considered and the reconstructing effect is judged by several reconstructing parameters.
基金Project supported by the National Natural Science Foundation of China(No.11472067)
文摘In this paper, the shallow water problem is discussed. By treating the incompressible condition as the constraint, a constrained Hamilton variational principle is presented for the shallow water problem. Based on the constrained Hamilton variational principle, a shallow water equation based on displacement and pressure （SWE-DP） is developed. A hybrid numerical method combining the finite element method for spa- tial discretization and the Zu-class method for time integration is created for the SWE- DP. The correctness of the proposed SWE-DP is verified by numerical comparisons with two existing shallow water equations （SWEs）. The effectiveness of the hybrid numerical method proposed for the SWE-DP is also verified by numerical experiments. Moreover, the numerical experiments demonstrate that the Zu-class method shows excellent perfor- mance with respect to simulating the long time evolution of the shallow water.
基金the National Natural Science Foundation of China(No.52071161)。
文摘As a new type of marine structure,floating breakwater can provide suitable water area for coastal residents.In this paper,a multi-module floating breakwater with three cylinders was designed.According to the characteristics of each module,the elastic connector was created.The cabins with functions such as living,generating electricity and entertainment were arranged.A linear spring constrained design wave(LSCDW)method for strength analysis of floating marine structures with multi-module elastic connections was proposed.The numerical model was verified by 1:50 similarity ratio in the test tank.According to the analysis of design wave and extreme wave conditions,considering the mooring loads and environmental loads and connector loads,the overall strength of breakwater was analyzed by LSCDW method.These studies can provide new insights and theoretical guidance for the design of multi-module floating structures.
文摘This paper is devoted to studying the existence of solutions for the following logarithmic Schrödinger problem: −div(a(x)∇u)+V(x)u=ulogu2+k(x)| u |q1−2u+h(x)| u |q2−2u, x∈ℝN.(1)We first prove that the corresponding functional I belongs to C1(HV1(ℝN),ℝ). Furthermore, by using the variational method, we prove the existence of a sigh-changing solution to problem (1).
基金Supported by National Natural Science Foundation of China(NSFC)(61572288,61373078)the Fundamental Research Funds of Shandong University(2015JC009)the Program for New Century Excellent Talents in University(NCET-13-0529)
文摘Triangulation is widely used in scientific research, such as finite element mesh generation, surface reconstruction and the reconstruction of the density field data. This paper proposes a new method combining image processing and density-controlled Centroidal Voronoi tessellations to quickly generate a density-controlled constrained Delaunay triangulation lbr 2D sea area. Firstly, preprocess digital images of the sea area and extract the boundary of seawater region by eight-neighbor searching algorithm. Then, 1 use Odd-Even Testing＂ method to check if one random vertex is inside the boundary and insert random vertices into the boundary. Finally, we get the CDT of random vertices by density-controlled CVT-Lloyd method. We also give some comparisons with existing methods, and our method performs better in final restllt of triangulation.
基金supported by"The Shanghai Philosophy and Social Science Planning Project"under Grant 2022BGL001.
文摘To explore the non-linear relationship between risk sources and the hazard degree levels of accidents,and to precisely predict the hazard impact of metro operation accidents,we pro-pose the ordered constraint Apriori-RF method for forecasting metro operation accident hazard degree levels.First,the hazard degree of metro operation accidents is quantified from three dimensions:casualties,train delays,and facility damages.K-means clustering is then applied to categorize hazard degree levels.Second,the ordered constraint Apriori algorithm is employed to mine valid association rules between metro operation risk sources and accident hazard degree levels.These valid association rules are subsequently employed in the random forest(RF)algorithm for training,establishing a reliable and accu-rate prediction model.Finally,the method is validated using metro accident data from a city in China.The research results indicate that the ordered constraint Apriori-RF method enhances the effectiveness of association rule mining by 74.9%and exhibits higher compu-tational efficiency.The predicted values of the ordered constraint Apriori-RF method have small errors.Compared to traditional RF algorithms,the root mean square error(RMSE)is reduced by 14%,and the weighted root mean square error(WRMSE)is reduced by 36%,demonstrating the higher accuracy of the ordered constraint Apriori-RF method and its clear advantages.The research findings provide a precise and effective method for quanti-tatively predicting the hazard degree levels of metro operation accidents,holding signifi-cant theoretical and practical value in ensuring metro operation safety and implementing accident mitigation and prevention measures.
基金Supported by the National Natural Science Foundation of China (No. 29836130) and the German Research Foundation of Germany
文摘The Taylor dispersion method was used to measure diffusion coefficients of three-component liquid systems. An improved constrained nonlinear least-square method was used to evaluate the ternary diffusion coefficients directly by fitting the mathematical solutions of the dispersion equation to eluted solute peaks detected using a differential refractometer. Diffusion coefficients of the three-component system of acetone-benzene-CCl4, determined at 25℃, were used to test the procedure. The measured diffusion coefficients were compared with values obtained by optical interferometry and the diaphragm cell method. Ternary diffusion coefficients are also determinated for solutions of 1-hexanol-hexane-toluene and 1-propanol- water-ethylene glycol at 25℃, with an accuracy of approximately 0.05 m^2·s^- 1.
文摘In this paper, a truncated hybrid method is proposed and developed for solving sparse large-scale nonlinear programming problems. In the hybrid method, a symmetric system of linear equations, instead of the usual quadratic programming subproblems, is solved at iterative process. In order to ensure the global convergence, a method of multiplier is inserted in iterative process. A truncated solution is determined for the system of linear equations and the unconstrained subproblems are solved by the limited memory BFGS algorithm such that the hybrid algorithm is suitable to the large-scale problems. The local convergence of the hybrid algorithm is proved and some numerical tests for medium-sized truss problem are given.
基金supported by the National Natural Science Foundation of China(12131002,11971071,12288101)Foundation of National Key Laboratory of Computational Physics(6142A05220201)China Postdoctoral Science Foundation(2024M760059).
文摘Combining robustness and high accuracy is one of the primary challenges in the magnetohydrodynamics(MHD)field of numerical methods.This paper investigates two critical physical constraints:wave order and positivity-preserving(PP)properties of the high-resolution HLLD Riemann solver,which ensures the positivity of density,pressure,and internal energy.This method’s distinctiveness lies in its ability to ensure that the wave characteristic speeds of the HLLD Riemann solver are strictly ordered.A provably PP HLLD Riemann solver based on the Lagrangian setting is established,which can be viewed as an extension of the PP Lagrangianmethod in hydrodynamics but with more and stronger constraint condition.In addition,the above two properties are ensured on moving grid method by employing the Lagrange-to-Euler transform.Meanwhile,a novel multi-moment constrained finite volume method is introduced to acquire third order accuracy,and practical limiters are applied to avoid numerical oscillations.Selected numerical benchmarks demonstrate the robustness and accuracy of our methods.
文摘Degree reduction of parametric curves and surfaces is an important process in the exchange of product model data between various CAD systems. In this paper the degenerate conditions of triangular Bezier surface patches are derived. The degenerate conditions and constrained optimization methods are used to develop a degree reduction method for triangular Bezier surface patches. The error in the degree reduction of a triangular Bezier surface is also shown to depend on some geometric invariants which decrease exponentially in the subdivision process. Therefore, the degree reduction method can be combined with a subdivision algorithm to generate lower degree approximations which are within some preset error tolerance.
基金This research is supported in part by NSF-DMS 0712744,NSF DMR-0710483 and NSF-IIP 541674 Center for Computational Materials Design(CCMD).
文摘We investigate the critical nucleus and equilibrium morphologies duringprecipitation of a second-phase particle in a solid. We show that a combination ofdiffuse-interface description and a constrained string method is able to predict boththe critical nucleus and equilibrium precipitate morphologies simultaneously without a priori assumptions. Using the cubic to cubic transformation as an example, it isdemonstrated that the maximum composition within a critical nucleus can be eitherhigher or lower than that of equilibrium precipitate while the morphology of an equilibrium precipitate may exhibit lower symmetry than the critical nucleus resulted fromelastic interactions.
基金the National Council for Scientific Research of Lebanon(CNRS-L)for granting a doctoral fellowship to Farah Kanbarfunding by theQualification Programof the Julius Maximilians University Wurzburg.
文摘A well-balanced second order finite volume central scheme for the magnetohydrodynamic(MHD)equations with gravitational source term is developed in this paper.The scheme is an unstaggered central scheme that evolves the numerical solution on a single grid and avoids solving Riemann problems at the cell interfaces using ghost staggered cells.A subtraction technique is used on the conservative variables with the support of a known steady state in order to manifest the well-balanced property of the scheme.The divergence-free constraint of themagnetic field is satisfied after applying the constrained transport method(CTM)for unstaggered central schemes at the end of each time-step by correcting the components of the magnetic field.The robustness of the proposed scheme is verified on a list of numerical test cases from the literature.
基金Supported by the National Natural Science Foundation of China(Grant No.51679212,51979245).
文摘In this study,a computational framework in the field of artificial intelligence was applied in computational fluid dynamics(CFD)field.This Framework,which was initially proposed by Google Al department,is called"TensorFlow".An improved CFD model based on this framework was developed with a high-order difference method,which is a constrained interpolation profile(CIP)scheme for the base flow solver of the advection term in the Navier-Stokes equations,and preconditioned conjugate gradient(PCG)method was implemented in the model to solve the Poisson equation.Some new features including the convolution,vectorization,and graphics processing unit(GPU)acceleration were implemented to raise the computational efficiency.The model was tested with several benchmark cases and shows good performance.Compared with our former CIP-based model,the present Tensor Flow-based model also shows significantly higher computational efficiency in large-scale computation.The results indicate TensorFlow could be a promising framework for CFD models due to its ability in the computational acceleration and convenience for programming.
基金funded by Zhejiang Provincial Soft Science Project of China under Grant Number 2023C35088.
文摘Feasible,smooth,and time-jerk optimal trajectory is essential for manipulators utilized in manufacturing process.A novel technique to generate trajectories in the joint space for robotic manipulators based on quintic B-spline and constrained multi-objective student psychology based optimization(CMOSPBO)is proposed in this paper.In order to obtain the optimal trajectories,two objective functions including the total travelling time and the integral of the squared jerk along the whole trajectories are considered.The whole trajectories are interpolated by quintic B-spline and then optimized by CMOSPBO,while taking into account kinematic constraints of velocity,acceleration,and jerk.CMOSPBO mainly includes improved student psychology based optimization,archive management,and an adaptiveε-constraint handling method.Lévyflights and differential mutation are adopted to enhance the global exploration capacity of the improved SPBO.Theεvalue is varied with iterations and feasible solutions to prevent the premature convergence of CMOSPBO.Solution density estimation corresponding to the solution distribution in decision space and objective space is proposed to increase the diversity of solutions.The experimental results show that CMOSPBO outperforms than SQP,and NSGA-II in terms of the motion efficiency and jerk.The comparison results demonstrate the effectiveness of the proposed method to generate time-jerk optimal and jerk-continuous trajectories for manipulators.
