Now showing items 11-23 of 23

    • Fast Wavelet Transforms for Matrices Arising from Boundary Element Methods 

      Bond, David M.; Vavasis, Stephen A. (Cornell University, 1994-03)
      (The following contains mathematical formulae and symbols that may become distorted in ASCII text.) For many boundary element methods applied to Laplace's equation in two dimensions, the resulting integral equation has ...
    • Nested Dissection for Sparse Nullspace Bases 

      Stern, Julio M.; Vavasis, Stephen A. (Cornell University, 1990-12)
      We propose a nested dissection approach to finding a fundamental cycle basis in a planar graph. the cycle basis corresponds to a fundamental nullspace basis of the adjacency matrix. This problem is meant to model sparse ...
    • A Note on Wavelet Bases for Two-Dimensional Surfaces 

      Vavasis, Stephen A. (Cornell University, 1990-09)
      Recent work by Beylkin, Coifman and Rokhlin has demonstrated that integral equations for functions on $IR$ can be solved rapidly by expressing the integrands in a wavelet basis. Boundary element methods for solving partial ...
    • Numerical Conformal Mapping Using Cross-ratios and Delaunay Triangulation 

      Driscoll, Tobin; Vavasis, Stephen A. (Cornell University, 1996-02)
      We propose a new algorithm for computing the Riemann mapping of the unit disk to a polygon, also known as the Schwarz-Christoffel transformation. The new algorithm, CRDT, is based on cross-ratios of the prevertices, and ...
    • Preconditioning for Boundary Integral Equations (Preliminary Version) 

      Vavasis, Stephen A. (Cornell University, 1990-02)
      We propose new classes of preconditioners for the linear systems arising from a boundary integral equation method. The problem under consideration is Laplace's equation in three dimensions. The system arising in this context ...
    • Proving Polynomial-Time for Sphere-Constrained Quadratic Programming 

      Vavasis, Stephen A.; Zippel, Richard (Cornell University, 1990-12)
      Recently Ye and Karmarkar have proposed similar algorithms for minimizing a nonconvex quadratic function on a sphere. These algorithms are based on trust-region work going back to Levenberg and Marquardt. Although both ...
    • Quadratic Programming is in NP 

      Vavasis, Stephen A. (Cornell University, 1990-02)
      Quadratic programming is an important example of optimization with applications to engineering design, coombinatorical optimization, game theory, and economics. Garey and Johnson [1979] state that quadratic programming ...
    • Quality Mesh Generation in Higher Dimensions 

      Mitchell, Scott A.; Vavasis, Stephen A. (Cornell University, 1996-12)
      We consider the problem of triangulating a d-dimensional region. Our mesh generation algorithm, called QMG, is a qradtree-based algorithm that can triangulate any polyhedral region including nonconvexregions with holes. ...
    • Quality Mesh Generation in Three Dimensions 

      Mitchell, Scott A.; Vavasis, Stephen A. (Cornell University, 1992-02)
      We show how to triangulate a three dimensional polyhedral region with holes. Our triangulation is optimal in the following two senses: First, our triangulation achieves the best possible aspect ratio up to a constant. ...
    • Quality Mesh Generation in Three Dimensions 

      Mitchell, Scott A.; Vavasis, Stephen A. (Cornell University, 1992-09)
      We show how to triangulate a three dimensional polyhedral region with holes. Our triangulation is optimal in the following two senses. First, our triangulation achieves the best possible aspect ratio up to a constant. ...
    • Stable Finite Elements for Problems With Wild Coefficients 

      Vavasis, Stephen A. (Cornell University, 1993-06)
      We consider solving an elliptic boundary value problem in the case that the coefficients vary by many orders of magnitude over the domain. A linear finite element method is used. It is shown that the standard method for ...
    • Stable Numerical Algorithms for Equilibrium 

      Vavasis, Stephen A. (Cornell University, 1992-09)
      An equilibrium system (also known as a KKT system, a saddle- point system, or a sparse tableau) is a square linear system with a certain structure. G. Strang has observed that equilibrium systems arise in optimization, ...
    • Stable Numerical Algorithms for Equilibrium Systems 

      Vavasis, Stephen A. (Cornell University, 1992-04)
      An equilibrium system (also known as a KKT system, a saddlepoint system or a sparse tableau) is a square linear system with a certain structure. G. Strang has observed that equilibrium systems arise in optimization, ...