Collision-dominated positive column of a weakly ionized gas.
Collision dominated quiescent positive column of weakly ionized gas, examining validity of constant coefficient electron diffusion equation and boundary value problem
Blank, J. L.↗
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Results for “diffusion equation”
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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The dynamics of variable stars.
Cepheid variable stars dynamics, analyzing spherical hydrodynamics and radiation diffusion equations as initial value problem
Christy, R. F.↗
Displacement of rays in a turbulent medium.
Rays associated Fokker-Planck relation for isotropic turbulence diffusion equation, discussing logarithmic refractive index, moments and path length
Liu, C. H.↗
Convection electric fields and the diffusion of trapped magnetospheric radiation.
Time dependent convection electric fields as agents for diffusing trapped magnetospheric radiation inward toward earth, discussing one dimensional diffusion equation
Birmingham, T. J.↗
A study of the composition of the lower solar corona.
Lower solar corona composition changes due to pressure and thermal gradients calculated with multicomponent diffusion equations
Nakada, M. P.↗
Electrical conductivity of a collisionless magnetoplasma in a weakly turbulent magnetic field
Electrical conductivity of collisionless magnetoplasma in weakly turbulent magnetic field, using quasi-linear approach for diffusion equation for distribution function describing test particles
Newman, C. E.↗
Variation of the ion-temperature gradient along field lines in the outer plasmasphere
Ion temperature gradient along magnetic field lines in outer plasmasphere by thermal diffusion equations compared with electron temperature observations
Grebowsky, J. M.↗
Study of cosmic rays in the solar environment Final report, 12 Jan. 1968 - 11 Jan. 1971
Convection-diffusion equation for closed formulation of cosmic ray transport theory in solar environment
Klimas, A.↗
A study of the composition of the solar corona and solar wind
Solar corona and wind composition, accounting for He flux and heavy elements from diffusion equations solution
Nakada, M. P.↗
Two-dimensional inert accumulation in space hydrogen-oxygen fuel cells
Dead ended compartments concentration and current distributions calculation in space hydrogen-oxygen fuel cells, using mathematical model with convective diffusion equation
Gidaspow, D.↗
Variable boundary II heat conduction
Computer program for solving both transient and steady-state heat transfer problems is presented. Specific applications of computer program are described. Formulation for individual nodes of solid medium for heat balance is presented. Diffusion equation is solved for all nodes simultaneously at finite increments of time.
Gramer, J.↗
Behavior of nitric oxide formed by the space shuttle in the mesosphere
A numerical model of eddy diffusive transport of emitted gases from the space shuttle wake, including chemical reactions between the emitted constituents and the ambient atmosphere, has been constructed for 75 km altitude. The numerical methods involve explicit solution of the diffusion equation and Runge-Kutta method for the chemical reactions. The time required to reach background levels of nitric oxide concentration of 7 x 10 to the 7th power molecules/cc has been calculated. This relaxation time depends strongly on atmospheric conditions.
Eberstein, I. J.↗
Diffusion in a unidirectional filament reinforced metal composite.
A theoretical analysis has been developed to describe composition changes resulting from exposure of a unidirectional filament reinforced metal composite to an elevated temperature environment. The analysis was based on a simple superposition of finite-difference solutions of the diffusion equation, and was applicable to the case for which the filament and matrix metals comprised an isomorphous binary alloy system. The possibility of chemical reaction between filaments and matrix was excluded. Excellent agreement was obtained between calculated concentration profiles and results of quantitative electron microprobe analyses of nickel filament reinforced copper samples.
Herring, H. W.↗
Thermalization and transport of photoelectrons - A comparison of theoretical approaches.
Three methods of studying ionospheric photoelectron thermalization, in which transport effects are evaluated in different ways, are outlined and compared. One method uses a diffusion equation formulation, the second proceeds from a two-stream approximation to the general particle transfer equation, and the third employs a Monte Carlo technique to simulate electron paths. The methods are compared by applying them to identically prepared models. The methods are in close agreement for altitudes in the region of local energy loss, but higher altitudes reveal a discrepancy of as much as a factor of 2 in the net flux of photoelectrons. The discrepancy is removed by appropriately modifying the computational techniques.
Cicerone, R. J.↗
A study of the diffusional behavior of a two-phase metal matrix composite exposed to a high temperature environment
The progress of diffusion-controlled filament-matrix interaction in a metal matrix composite where the filaments and matrix comprise a two-phase binary alloy system was studied by mathematically modeling compositional changes resulting from prolonged elevated temperature exposure. The analysis treats a finite, diffusion-controlled, two-phase moving-interface problem by means of a variable-grid finite-difference technique. The Ni-W system was selected as an example system. Modeling was carried out for the 1000 to 1200 C temperature range for unidirectional composites containing from 6 to 40 volume percent tungsten filaments in a Ni matrix. The results are displayed to show both the change in filament diameter and matrix composition as a function of exposure time. Compositional profiles produced between first and second nearest neighbor filaments were calculated by superposition of finite-difference solutions of the diffusion equations.
Tenney, D. R.↗
Rigid format alter packets for the analysis of electromagnetic field problems
The computer program NASTRAN is used to solve electromagnetic field problems. The diffusion equation and the boundary conditions valid for problems of these kinds together with a replacing potential energy function are given. The extent to which an analogy with finite element displacement and temperature approaches holds is indicated. The outputting of complex quantities is made possible after adjustment of standard rigid format 1 input data blocks to module SDR2. The applications made involve the study of the proximity effect in a system of three parallel conductors and the analysis of the magnetic field in the vicinity of the points of contact in circuit breakers.
Spreeuw, E.↗
Monte Carlo analysis of uncertainty propagation in a stratospheric model. 1: Development of a concise stratospheric model
A concise model has been developed to analyze uncertainties in stratospheric perturbations, yet uses a minimum of computer time and is complete enough to represent the results of more complex models. The steady state model applies iteration to achieve coupling between interacting species. The species are determined from diffusion equations with appropriate sources and sinks. Diurnal effects due to chlorine nitrate formation are accounted for by analytic approximation. The model has been used to evaluate steady state perturbations due to injections of chlorine and NO(X).
Rundel, R. D.↗
Influence of two-dimensional hygrothermal gradients on interlaminar stresses near free edges
Interlaminar stresses are determined for mechanical loading, uniform hygrothermal loading, and gradient moisture loading through implementation of a finite element computer code. Nonuniform two-dimensional hygroscopic gradients are obtained from a finite difference solution of the diffusion equation. It is shown that hygroscopic induced stresses can be larger than those resulting from mechanical and thermal loading, and that the distribution of the interlaminar normal stress may be changed significantly in the presence of a two-dimensional moisture gradient in the boundary layer of a composite laminate.
Farley, G. L.↗