Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 26 for “"finite difference approximation"”.
-
A provably stable and high-order accurate finite difference approximation for the incompressible boundary layer equations
A Provably Stable and High-Order Accurate Finite Difference Approximation for the Incompressible Boundary Layer Equations Mojalefa Prince Nchupang In recent years, there has been considerable interest in numerical simulations of incompress-ible flows due to their numerous industrial applications. …
-
Lie group invariant finite-difference schemes for the neutron diffusion equation
Finite difference techniques are used to solve a variety of differential equations. For the neutron diffusion equation, the typical local truncation error for standard finite difference approximation is on the order of the mesh spacing squared. To improve the accuracy of the finite difference …
-
Quasi-Newton and Multigrid Methods for Semiconductor Device Simulation
A finite difference approximation to the semiconductor device equations using the Bernoulli function approximation to the exponential function is described, and the robustness of this approximation is demonstrated. Sheikh's convergence analysis of Gummel's method and quasi-Newton methods is …
-
Prediction of erosion in cementitious materials subject to high thermal and pressure loading
… using a constant jet temperature with a standard finite difference approximation and the thermal properties of concrete which varied with respect to temperature. The properties of concrete were measured with an initial free moisture content of either 0% or 100%. The finite difference approximation …
-
Vibrações e estabilidade paramétrica de cascas axissimétricas
… transient responses are then obtained through a finite difference approximation in the time domain anda finite element discretization in the longitudinal direction. The steady-state periodic solution is determined. Its infinitesimal stability is studied and the first approximation of parametric …
-
ΕΠΙΔΡΑΣΗ ΑΝΟΜΟΙΟΜΟΡΦΗΣ ΑΝΑΔΡΑΣΗΣ ΣΤΟ ΟΠΤΙΚΟ ΠΕΔΙΟ ΑΝΙΧΝΕΥΤΗ
… ARE SOLVED NUMERICALLY WITH THE METHOD OF FINITE DIFFERENCE APPROXIMATION TO DERIVATIVES. IT WAS FOUND THAT FEEDBACK WILL, IN GENERAL, REDUCE THE DETECTOR FIELD OF VIEW AT LOW FREQUENCIES, IN AGREEMENT WITH PREVIOUS INVESTIGATIONS, BUT THE COUPLING OF DIFFERENT FEEDBACK MECHANISMS MAY …
-
Forward modeling the gravitational field using a direct solution of Poisson's equation
… of the density function. We first use a finite-difference approximation to obtain the numerical solution, which we later compare to a finite-volume solution approximation. The accuracy of this method is demonstrated through applications to synthetic models and comparisons with integral …
-
The direct determination of nonlinear displacements of arbitrarily supported shallow shells using mathematical programming techniques
… obtain the displacement set which minimizes the finite-difference approximation of the shell potential energy by using mathematical programing techniques. In order to determine the mathematical programing technique which is most suitable for minimizing the shell potential several methods which …
-
Numerical simulation of microwave heating of a target with temperature dependent electrical properties in a single-mode cavity
… the time-dependent Maxwell's equations with the finite-difference time domain method (FDTD) until a time-harmonic steady state is obtained. Here we replace this technique with a more direct solution of a finite-difference approximation of the Helmholtz equation. The system of equations produced …
-
An implicit numerical solution of the turbulent three-dimensional incompressible boundary-layer equations
… was developed using a Crank-Nicholson implicit finite-difference technique, with the turbulent stress terms modeled with an eddy-viscosity model obtained from mixing length theory. The method was applied to two three-dimensional flow geometries for which experimental data exists and a comparison …
-
Shape sensitivity analysis of flutter response of a laminated wing
… of the eigenvalue. The first method is purely a finite difference calculation of the eigenvalue derivative directly from the solution of the flutter problem corresponding to the two different values of the shape parameters. The second method uses an analytic expression for the eigenvalue …
-
Comparison of Two Vortex-in-cell Schemes Implemented to a Three-dimensional Temporal Mixing Layer
… the vorticity field is discretized into a finite set of Lagrangian elements (particles) and the computational domain is covered by Eulerian mesh. Velocity field is computed on the mesh by solving Poisson equation. The solution proceeds in time by advecting the particles with the flow. …
-
Electrical analogs for plate equations and their applications in mechanical vibration suppression by P.Z.T. actuators
… their circuital analogs are derived using their finite-difference approximation. Afterwards, the coupling between the two structures is modelled considering piezoelectric actuators uniformly distributed on the mechanical system and connected to the nodes of the electric circuit. Then the …
-
The application of wave based techniques to intensity measurement in beams and plates
… of these spatial derivatives. Commonly a finite difference approximation is used, however alternative techniques based on the decomposition of the motion into wave components can offer improved versatility and accuracy, along with greater insight into the dynamics of the system. These …
-
Computational aspects of sensitivity calculations in linear transient structural analysis
… calculation techniques suitable for large-order finite element analyses. Accordingly, approximation vectors such as vibration mode shapes are used to reduce the dimensionality of the finite element model. Much of the research focused on the accuracy of both response quantities and sensitivities …
-
The extrusion processing of instant coffee for the purposes of creating a pressurised microstructure
… and the surrounding fluid was calculated using a finite difference approximation of the governing partial differential equations. The model was written in MATLAB and initial validation was carried out by comparison with existing models for bubble dynamics. Experimental observations of bubble …
-
Wheel Speed Distribution Control and its Effect on Vehicle
… trigonometry, Cartesian coordinates and finite difference approximation in the time domain to facilitate development of high speed models. The model has been built using the BASIC'O programming code in the DOS'O environment and optimised to meet the novel Model Predictive Control (MPC) …
-
A Mathematical Model of the Dynamics of an Optically Pumped Four-Level Solid State Laser System
… are compared to those obtained by using a stable finite difference approximation. The results of the comparison demonstrate that the implicit integration scheme is viable as well as efficient for numerically solving the system of partial differential equations and can be considered a useful …
-
Ring-polymer approaches to instanton theory
… It is explained why this conical form is a good approximation to the optimal dividing surface and therefore why centroid-based quantum transition-state theories are inaccurate for asymmetric barriers at low temperatures. The geometry of the ring-polymer transition state is found to describe a …
-
Hydrologic-economic modeling of irrigated agriculture in the Lower Murrumbidgee Catchment : investigations into sustainability
… using a linear state-space model derived from a finite-difference approximation of the groundwater flow equation. The number of groundwater states is substantially reduced using balanced truncation, a technique used in control engineering. A simple representation of the salinization process is …
Page 1 of 2