We study a Dirichlet optimal design problem for a quasi-linear monotone p-biharmonic equation with control and state constraints. We take the coefficient of the p-biharmonic operator as a design variable in . In this ...We study a Dirichlet optimal design problem for a quasi-linear monotone p-biharmonic equation with control and state constraints. We take the coefficient of the p-biharmonic operator as a design variable in . In this article, we discuss the relaxation of such problem.展开更多
In a vacuum spacetime equipped with the Bondi’s radiating metric which is asymptotically flat at spatial infinity including gravitational radiation (Condition D),we establish the relation between the ADM total energy...In a vacuum spacetime equipped with the Bondi’s radiating metric which is asymptotically flat at spatial infinity including gravitational radiation (Condition D),we establish the relation between the ADM total energy-momentum and the Bondi energy-momentum for perturbed radiative spatial infinity.The perturbation is given by defining the"real"time as the sum of the retarded time,the Euclidean distance and certain function f.展开更多
This paper considers dynamical systems under feedback with control actions limited toswitching.The authors wish to understand the closed-loop systems as approximating multi-scale problemsin which the implementation of...This paper considers dynamical systems under feedback with control actions limited toswitching.The authors wish to understand the closed-loop systems as approximating multi-scale problemsin which the implementation of switching merely acts on a fast scale.Such hybrid dynamicalsystems are extensively studied in the literature,but not much so far for feedback with partial stateobservation.This becomes in particular relevant when the dynamical systems are governed by partialdifferential equations.The authors introduce an augmented BV setting which permits recognition ofcertain fast scale effects and give a corresponding well-posedness result for observations with such minimalregularity.As an application for this setting,the authors show existence of solutions for systemsof semilinear hyperbolic equations under such feedback with pointwise observations.展开更多
Let G be a complex connected reductive group. Losev has shown that a smooth affine spherical G-variety X is uniquely determined by its weight monoid, which is the set of irreducible representations of G that occur in ...Let G be a complex connected reductive group. Losev has shown that a smooth affine spherical G-variety X is uniquely determined by its weight monoid, which is the set of irreducible representations of G that occur in the coordinate ring of X. In this paper we use a combinatorial characterization of the weight monoids of smooth affine spherical varieties to classify：（a） all such varieties for G = SL（2） × C~×and（b） all such varieties for G simple which have a G-saturated weight monoid of full rank. We also use the characterization and Knop＇s classification theorem for multiplicity free Hamiltonian manifolds to give a new proof of Woodward＇s result that every reflective Delzant polytope is the moment polytope of such a manifold.展开更多
The present article is concerned with the numerical solution of boundary integral e- quations by an adaptive wavelet boundary element method. This method approximates the solution with a computational complexity that ...The present article is concerned with the numerical solution of boundary integral e- quations by an adaptive wavelet boundary element method. This method approximates the solution with a computational complexity that is proportional to the solution＇s best N-term approximation. The focus of this article is on algorithmic issues which includes the crucial building blocks and details about the efficient implementation. By numerical examples for the Laplace equation and the Helmholtz equation, solved for different geome- tries and right-hand sides, we validate the feasibility and efficiency of the adaptive wavelet boundary element method.展开更多
Nearly all inf-sup stable mixed finite elements for the incompressible Stokes equations relax the divergence constraint. The price to pay is that a priori estimates for the ve- locity error become pressure-dependent, ...Nearly all inf-sup stable mixed finite elements for the incompressible Stokes equations relax the divergence constraint. The price to pay is that a priori estimates for the ve- locity error become pressure-dependent, while divergence-free mixed finite elements de- liver pressure-independent estimates. A recently introduced new variational crime using lowest-order Raviart-Thomas velocity reconstructions delivers a much more robust modi- fied Crouzeix-Raviart element, obeying an optimal pressure-independent discrete H1 ve- locity estimate. Refining this approach, a more sophisticated variational crime employing the lowest-order BDM element is proposed, which also allows proving an optimal pressure- independent L2 velocity error. Numerical examples confirm the analysis and demonstrate the improved robustness in the Navier-Stokes case.展开更多
This paper concerns a system of equations describing the vibrations of a planar network of nonlinear Timoshenko beams. The authors derive the equations and appropriate nodal conditions, determine equilibrium solutions...This paper concerns a system of equations describing the vibrations of a planar network of nonlinear Timoshenko beams. The authors derive the equations and appropriate nodal conditions, determine equilibrium solutions and, using the methods of quasilinear hyperbolic systems, prove that for tree-like networks the natural initial-boundary value problem admits semi-global classical solutions in the sense of Li [Li, T. T., Controllability and Observability for Quasilinear Hyperbolic Systems, AIMS Ser. Appl. Math., vol 3,American Institute of Mathematical Sciences and Higher Education Press, 2010] existing in a neighborhood of the equilibrium solution. The authors then prove the local exact controllability of such networks near such equilibrium configurations in a certain specified time interval depending on the speed of propagation in the individual beams.展开更多
In recent years,convolutional neural networks(CNNs)have demonstrated their effectiveness in predicting bulk parameters,such as effective diffusion,directly from pore-space geometries.CNNs offer significant computation...In recent years,convolutional neural networks(CNNs)have demonstrated their effectiveness in predicting bulk parameters,such as effective diffusion,directly from pore-space geometries.CNNs offer significant computational advantages over traditional methods,making them particularly appealing.However,the current literature primarily focuses on fully saturated porous media,while the partially saturated case is also of high interest for various applications.Partially saturated conditions present more complex geometries for diffusive transport,making the prediction task more challenging.Traditional CNNs tend to lose robustness and accuracy with lower saturation rates.In this paper,we overcome this limitation by introducing a CNN,which conveniently fuses diffusion prediction and a well-established morphological model that describes phase distributions in partially saturated porous media.We demonstrate the ability of our CNN to perform accurate predictions of relative diffusion directly from full pore-space geometries.Finally,we compare our predictions with well-established relations such as the one by Millington–Quirk.展开更多
文摘We study a Dirichlet optimal design problem for a quasi-linear monotone p-biharmonic equation with control and state constraints. We take the coefficient of the p-biharmonic operator as a design variable in . In this article, we discuss the relaxation of such problem.
基金partially supported by the National Natural Science Foundation of China(Grant Nos.10231050,10421001)the National Key Basic Research Project of China(Grant No.2006CB805905)the Innovation Project of Chinese Academy of Sciences
文摘In a vacuum spacetime equipped with the Bondi’s radiating metric which is asymptotically flat at spatial infinity including gravitational radiation (Condition D),we establish the relation between the ADM total energy-momentum and the Bondi energy-momentum for perturbed radiative spatial infinity.The perturbation is given by defining the"real"time as the sum of the retarded time,the Euclidean distance and certain function f.
基金support of the Elite Network of Bavaria under the grant #K-NW-2004-143
文摘This paper considers dynamical systems under feedback with control actions limited toswitching.The authors wish to understand the closed-loop systems as approximating multi-scale problemsin which the implementation of switching merely acts on a fast scale.Such hybrid dynamicalsystems are extensively studied in the literature,but not much so far for feedback with partial stateobservation.This becomes in particular relevant when the dynamical systems are governed by partialdifferential equations.The authors introduce an augmented BV setting which permits recognition ofcertain fast scale effects and give a corresponding well-posedness result for observations with such minimalregularity.As an application for this setting,the authors show existence of solutions for systemsof semilinear hyperbolic equations under such feedback with pointwise observations.
基金partially supported by the DFG Schwerpunktprogramm 1388–Darstellungstheoriesupport from the National Science Foundation(USA)through grant DMS 1407394the PSC-CUNY Research Award Program
文摘Let G be a complex connected reductive group. Losev has shown that a smooth affine spherical G-variety X is uniquely determined by its weight monoid, which is the set of irreducible representations of G that occur in the coordinate ring of X. In this paper we use a combinatorial characterization of the weight monoids of smooth affine spherical varieties to classify：（a） all such varieties for G = SL（2） × C~×and（b） all such varieties for G simple which have a G-saturated weight monoid of full rank. We also use the characterization and Knop＇s classification theorem for multiplicity free Hamiltonian manifolds to give a new proof of Woodward＇s result that every reflective Delzant polytope is the moment polytope of such a manifold.
文摘The present article is concerned with the numerical solution of boundary integral e- quations by an adaptive wavelet boundary element method. This method approximates the solution with a computational complexity that is proportional to the solution＇s best N-term approximation. The focus of this article is on algorithmic issues which includes the crucial building blocks and details about the efficient implementation. By numerical examples for the Laplace equation and the Helmholtz equation, solved for different geome- tries and right-hand sides, we validate the feasibility and efficiency of the adaptive wavelet boundary element method.
文摘Nearly all inf-sup stable mixed finite elements for the incompressible Stokes equations relax the divergence constraint. The price to pay is that a priori estimates for the ve- locity error become pressure-dependent, while divergence-free mixed finite elements de- liver pressure-independent estimates. A recently introduced new variational crime using lowest-order Raviart-Thomas velocity reconstructions delivers a much more robust modi- fied Crouzeix-Raviart element, obeying an optimal pressure-independent discrete H1 ve- locity estimate. Refining this approach, a more sophisticated variational crime employing the lowest-order BDM element is proposed, which also allows proving an optimal pressure- independent L2 velocity error. Numerical examples confirm the analysis and demonstrate the improved robustness in the Navier-Stokes case.
基金supported by the National Basic Research Program of China(No.2103CB834100)the National Science Foundation of China(No.11121101)+1 种基金the National Natural Sciences Foundation of China(No.11101273)the DFG-Cluster of Excellence:Engineering of Advanced Materials
文摘This paper concerns a system of equations describing the vibrations of a planar network of nonlinear Timoshenko beams. The authors derive the equations and appropriate nodal conditions, determine equilibrium solutions and, using the methods of quasilinear hyperbolic systems, prove that for tree-like networks the natural initial-boundary value problem admits semi-global classical solutions in the sense of Li [Li, T. T., Controllability and Observability for Quasilinear Hyperbolic Systems, AIMS Ser. Appl. Math., vol 3,American Institute of Mathematical Sciences and Higher Education Press, 2010] existing in a neighborhood of the equilibrium solution. The authors then prove the local exact controllability of such networks near such equilibrium configurations in a certain specified time interval depending on the speed of propagation in the individual beams.
基金supported by the DFG Research Training Group 2339 Interfaces,Complex Structures,and Singular LimitsN.Ray was supported by the DFG Research Training Group 2339 Interfaces,Complex StructuresSingular Limits and the DFG Research Unit 2179 MadSoil.F.Frank and F.Woller received support from the Competence Network for Scientific High Performance Computing in Bavaria(KONWIHR).
文摘In recent years,convolutional neural networks(CNNs)have demonstrated their effectiveness in predicting bulk parameters,such as effective diffusion,directly from pore-space geometries.CNNs offer significant computational advantages over traditional methods,making them particularly appealing.However,the current literature primarily focuses on fully saturated porous media,while the partially saturated case is also of high interest for various applications.Partially saturated conditions present more complex geometries for diffusive transport,making the prediction task more challenging.Traditional CNNs tend to lose robustness and accuracy with lower saturation rates.In this paper,we overcome this limitation by introducing a CNN,which conveniently fuses diffusion prediction and a well-established morphological model that describes phase distributions in partially saturated porous media.We demonstrate the ability of our CNN to perform accurate predictions of relative diffusion directly from full pore-space geometries.Finally,we compare our predictions with well-established relations such as the one by Millington–Quirk.
