Browsing by Author "Kearsley, Anthony J."

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    An Infeasible Point Method for Minimizing the Lennard-Jones Potential
    (1993-10) Gockenbach, Mark S.; Kearsley, Anthony J.; Symes, William W.
    Minimizing the Lennard-Jones potential, the most-studied problem for molecular conformation, is an unconstrained global optimization problem. In this paper, the problem is reformulated as an equality constrained nonlinear program in such a way that the likelihood of finding a global minimizer is increased. Implementation of an algorithm for solving this nonlinear program is discussed, and results of numerical tests are presented.
  • Thumbnail Image
    Item
    Numerical Simulation and Optimal Shape for Viscous Flow by a Fictitious Domain Method
    (1994-08) Glowinski, Roland; Kearsley, Anthony J.; Pan, Tsorng-Whay; Periaux, Jacques
    In this article we discuss the fictitious domain solution of the Navier-Stokes equations modelling unsteady incompressible viscous flow. The method is based on a Lagrange multiplier treatment of the boundary conditions to be satisfied and is particularly well suited to the treatment of no-slip boundary conditions. This approach allows the use of structured meshes and fast specialized solvers for problems on complicated geometries. Another interesting feature of the fictitious domain approach is that it allows the solution of optimal shape problems without regriding. The resulting methodology is applied to the solution of flow problems including external incompressible viscous flow modelled by the Navier-Stokes equations and then to an optimal shape problem for Stokes and Navier-Stokes flow.
  • Thumbnail Image
    Item
    On the Simulation and Control of Some Friction Constrained Motions
    (1993-05) Glowinski, Roland; Kearsley, Anthony J.
    In this paper, some issues involved with numerical simulation and control of some elasto-dynamic systems are discussed. The motivation is the simulation of dry or Coulomb friction in the joints that link together remote manipulator systems used in aerospace operations (for example, space shuttle remote manipulator systems). The goal here is to develop numerical techniques to simulate and control these systems, while properly modeling the Coulomb friction. The numerical procedure described employs a finite difference time discretization in conjunction with a vector of multipliers that predicts the friction effect for all time. In addition to this discrete multiplier technique an associated regularization procedure that greatly improves the behavior of these multipliers is also presented. Numerical examples conclude the paper.
  • Thumbnail Image
    Item
    Optimal Signal Sets for Non-Gaussian Detectors
    (1995-05) Gockenbach, Mark S.; Kearsley, Anthony J.
    Identifying a maximally-separated set of signals is important in the design of modems.  The notion of optimality is dependent on the model chosen to describe noise in the measurements; while some analytic results can be derived under the assumption of Gaussian noise, no such techniques are known for choosing signal acts in the non-Gaussian case. To obtain numerical solutions for non-Gaussian detectors, minimax problems are transformed into nonlinear programs,resulting in a novel formulation yielding problems with relatively few variables and many inequality constraints. Using sequential quadratic programming, optimal signal sets are obtained for a variety of noise distributions.