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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Finite element method applied to heat conduction in solids with temperature dependent thermal conductivity, using nonlinear constitutive equation for heat ABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGHIABCDEFGH
Numerical solution of nonlinear Vlasov equation for collisionless plasma problems, discussing initial value problems, external electric fields, magnetic fields, etc
Nonlinear Vlasov equation treatment by Fourier- Hermite expansion techniques for plasma problems
Parameter plane method of stability analysis applied to spacecraft attitude control system with two nonlinearities related by nonlinear differential equation
Liquid propellant rocket engine combustion instabilities, describing unsteady combustor flow by single nonlinear wave equation with stable and unstable finite amplitude limit cycles
Nonlinear differential equations describing stability of fast nuclear reactor with incore thermionic converters and reactivity feedback
Nonlinear optimization techniques in dynamic programming and solution of ordinary nonlinear differential equations by Runge-Kutta method
Optimal vacuum rocket trajectories over spherical earth, deriving nonlinear differential equations for position and velocity
Magnetic field effects on collisionless plasma sheath near planar electrode, solving electric and magnetic potentials nonlinear differential equations by numerical scheme
Ar arc plasma thermochemical nonequilibrium, using finite difference techniques for nonlinear integrodifferential equations
Compressible transonic flow about two dimensional airfoils, developing inviscid nonlinear potential equations by relaxation procedures
Digital phase locked loop for FM signals demodulation, considering system nonlinear difference equation
Bounded integral manifolds existence for perturbed system of nonlinear differential equations near critical point, periodic orbit or periodic surface
Computer program is described for numerical solution of chemical equilibria in complex systems by using nonlinear algebraic equations. Free-energy minimization technique is used.
A procedure cast in a form appropriate to the finite element method is presented for geometrically nonlinear prebuckling and postbuckling structural analysis, including the identification of snap-through type of buckling. The principal features of this procedure are the use of direct iteration for solution of the nonlinear algebraic equations in the prebuckling range, an interpolation scheme for determination of the initial bifurcation point, a perturbation method in definition of the load-displacement behavior through the postbuckling regime, and extrapolation in determination of the limit point for snap-through buckling. Three numerical examples are presented in illustration of the procedure and in comparison with alternative approaches.
The problem of controlling a time-invariant system with parameter uncertainty is considered with incomplete state feedback. The controller is designed by minimaximizing a quadratic performance criterion and a sensitivity (or loss) criterion, involving the state of the system, the control, and the uncertainty vector. The resulting optimal controller is linear and optimal feedback gain matrix must satisfy a set of nonlinear algebraic equations. some algorithms for algebraic minimax problems are presented.
A general formulation of the dynamical problems associated with powered flight of a two stage flexible, variable-mass missile with internal flow, discrete masses, and aerodynamic forces is presented. The formulation comprises six ordinary differential equations for the rigid body motion, 3n ordinary differential equations for the n discrete masses and three partial differential equations with the appropriate boundary conditions for the elastic motion. This set of equations is modified to represent a single stage flexible, variable-mass missile with internal flow and aerodynamic forces. The rigid-body motion consists then of three translations and three rotations, whereas the elastic motion is defined by one longitudinal and two flexural displacements, the latter about two orthogonal transverse axes. The differential equations are nonlinear and, in addition, they possess time-dependent coefficients due to the mass variation.
The influence of a small parameter at the higher derivatives in the differential equations describing nonlinear systems of the Lur'e-Postnikov class on absolute stability in the parameter space is investigated. The conditions leading to singular perturbations of absolute stability are examined.