Now showing items 12-23 of 23

    • 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, ...