Browsing Computational and Applied Mathematics by Title
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Variationally Constrained Numerical Solution of Electrical Impedance Tomography
(200210)We propose a novel, variational inversion methodology for the electrical impedance tomography problem, where we seek electrical conductivity σ inside a bounded, simply connected domain Ω, given simultaneous measurements ... 
Variations of Structured Broyden Families for Nonlinear Least Squares Problems
(199206)In this paper, we consider structured quasiNewton methods for finding a local solution to nonlinear least squares problems. This paper is concerned with the line search globalization method. Recently, factorized versions ... 
Velocity Analysis in the Presence of Uncertainty
(200606)Velocity analysis resolves relatively long scales of earth structure, on the order of 1 km. Migration produces images with length scales (wavelengths) on the order of 10's of m. In between these two scale regimes lies ... 
Velocity Inversion by Coherency Optimization
(198804)We introduce an approach to velocity and reflectivity estimation based on optimizing the coherence of multiple shotgather inversions of reflection seismograms. The resulting algorithm appears to avoid the severe convergence ... 
Velocity Inversion by Coherency Optimization
(198908)We introduce an approach to velocity and reflectivity estimation based on optimizing the coherence of multiple shotgather inversions of reflection seismograms. The resulting algorithm appears to avoid the severe convergence ... 
Velocity Inversion by Differential Semblance Optimization for 2D Common Source Data
(199204)Differential Semblance Optimization ("DSO") is a variant of datafitting (leastsquares) inversion of reflection seismograms. The misfit functions used in other implementations of leastsquares inversion (for example ... 
Velocity Inversion: A Case Study in InfiniteDimensional Optimization
(198807)The goal of seismic velocity inversion is the estimation of seismic wave velocities inside the earth by attempting to predict, in a leasterror sense, seismic waveforms measured at its surface. We present velocity inversion ... 
Verifying A RungeKutta Solver Using ADOLC
(200311)This report describes our effort to verify differential equation solvers using automatic differentiation (AD). In particular, the report describes the AD verification technique in general, as well as the application of the ... 
Very LargeScale Linear Programming: A Case Study in Combining Interior Point and Simplex Methods
(199105)Experience with solving a 12,753,313 variable linear program is described. This problem is the linear programming relaxation of a set partitioning problem arising from an airline crew scheduling application. A scheme is ... 
Viscoelastic Finite Difference Modeling
(199302)Real earth media disperse and attenuate propagating waves. This anelastic behavior can be well described by a viscoelastic model. We have developed a finite difference simulator to model wave propagation in viscoelastic ... 
Viscoelastic Finite Difference Modeling II
(199305)Real earth media disperse and attenuate propagating mechanical waves. This anelastic behavior can be described well by a viscoelastic model. We have developed a finite difference simulator to model wave propagation in ... 
Wavefield Splitting and Extrapolation of the Two Dimensional Plasma Wave Equation
(199208)Wave splitting is an important technique in a great variety of studies concerning wave propagation. It is a class of methods of splitting the wave equation under consideration into one way wave equations, or physically ... 
Weighted Least Squares Estimators on the Frequency Domain for the Parameters of a Time Series
(198609)A procedure for estimating the parameters of a time series is proposed. The estimate minimizes a criterion function which is the weighted sum of squares of the distances between the periodograms and the spectrum of the ... 
Weighting Schemes and Objective Functions in SubSurface Flow and Transport Parameter Identification via Inverse Simulation
(199510)We propose a number of different weighting schemes (piecewise linear, quadratic, sine and narrowbase sine) based on data magnitude for leastsquares minimization of concentration data for parameter estimation for groundwater ... 
Weight‐adjusted discontinuous Galerkin methods: Matrix‐valued weights and elastic wave propagation in heterogeneous media
(2018)Weight‐adjusted inner products are easily invertible approximations to weighted L2 inner products. These approximations can be paired with a discontinuous Galerkin (DG) discretization to produce a time‐domain method for ... 
Wellposedness of Initial/Boundary Value Problems for Hyperbolic Integrodifferential Systems with Nonsmooth Coefficients
(200810)In the late 1960's, J.L. Lions and collaborators showed that energy estimates could be used to establish existence, uniqueness, and continuous dependence on initial data for finite energy solutions of initial/boundary ... 
What Happens When We Trust a Region That is a Line?
(199504)Line searches and trust regions are two techniques to globalize nonlinear optimization algorithms. We claim that the trustregion technique has builtin an appropriate regularization of illconditioned secondorder ... 
What is Simulated Annealing?
(200002)Beginning in 1983, simulated annealing was marketed as a global optimization methodology that mimics the physical annealing process by which molten substances cool to crystalline lattices of minimal energy. This marketing ... 
When is Missing Data Recoverable?
(200610)Suppose a nonrandom portion of a data vector is missing. With some minimal prior knowledge about the data vector, can we recover the missing portion from the available one? In this paper, we consider a linear programming ... 
ønix: A Unix Emulator for VAX/VMS
(198708)