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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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Random walk theory applied to electron motion in early stage of He breakdown in electric field, based on integral and differential cross section data
Reliability prediction of narrow band structures under random excitations, considering catastrophic and fatigue failure modes
Structural dynamic responses as nonstationary narrow band random process, establishing peak values distribution functions with frequency interpretation
Random images transmission rates, comparing line- by-line and two dimensional encoding
Buckling of axially compressed circular cylindrical shells with localized or random axisymmetric imperfections, deriving asymptotic approximation formulas for stress calculation
Heisenberg ferromagnet magnetic and thermodynamic properties in random phase approximation, determining magnetization and susceptibility with Green function theory
Cosmic ray transport in random magnetic fields, deriving coupled integrodifferential equations for radiant intensity and flux
Material fatigue failure under narrow band random vibration effects, deriving fatigue life prediction equation based on composite experimental design and statistical tests
Stochastic, random and ordinary Green function relations for two point correlation functions in mathematical physics
Wave equations for motion in stochastic medium, using linear random operator theory
Random fluctuating longitudinal pressure gradient effect on steady incompressible channel flow for arbitrary power spectrum and probability density
Point source average signal reflection from conductive plane in random oscillation
The pseudoisotropic laminate analogy is used in conjunction with fiber composite micro and macromechanics to predict the thermal and mechanical properties of planar randomly reinforced fiber composites (PRRFC). Theoretical results are presented for boron/epoxy, Thornel-50/epoxy, and S-glass/epoxy PRRFC. The results show that the thermal and elastic properties depend on both constituent materials and the fiber volume ratio. The strength depends also on the type of applied stress.
A summary is presented of the generation and testing of random numbers on the IBM 360/44 computer. Various generators and statistical tests are considered.
The fatigue life of material under multifactor influence of broad band random excitations has been investigated. Parameters which affect the fatigue life are postulated to be peak stress, variance of stress and the natural frequency of the system. Experimental data were processed by the hybrid computer. Based on the experimental results and regression analysis a best predicting model has been found. All values of the experimental fatigue lives are within the 95% confidence intervals of the predicting equation.
Methods are presented for the generation of random numbers with uniform and normal distributions. Subprogram listings of Fortran generators for the Univac 1108, SDS 930, and CDC 3200 digital computers are also included. The generators are of the mixed multiplicative type, and the mathematical method employed is that of Marsaglia and Bray.
The pseudoisotropic-laminate analogy is used in conjunction with fiber composite micro- and macromechanics to predict the thermal and mechanical properties of planar randomly reinforced fiber composites (PRRFC). Theoretical results are presented for boron/aluminum, boron/epoxy, Thornel-50/epoxy, and S-glass/epoxy PRRFC. The results show that the thermal and elastic properties depend on both constituent materials and the fiber volume ratio. The strength depends also on the type of applied stress. In general, no simple ratio exists between the properties of unidirectional fiber composites and those of PRRFC. The data are presented in convenient graphical form to serve as an aid for design and/or analysis and also for further research in PRRFC. The residual stresses and the impact resistance are also theoretically examined.
An analysis is made of steady-state and non-steady-state methods for the measurement of panel damping. Particular emphasis is placed on the use of random process techniques in conjunction with digital data reduction methods. The steady-state methods considered use the response power spectral density, response autocorrelation, excitation-response crosspower spectral density, or single-sided Fourier transform (SSFT) of the response autocorrelation function. Non-steady-state methods are associated mainly with the use of rapid frequency sweep excitation. Problems associated with the practical application of each method are evaluated with specific reference to the case of a panel exposed to a turbulent airflow, and two methods, the power spectral density and the single-sided Fourier transform methods, are selected as being the most suitable. These two methods are demonstrated experimentally, and it is shown that the power spectral density method is satisfactory under most conditions, provided that appropriate corrections are applied to account for filter bandwidth and background noise errors. Thus, the response power spectral density method is recommended for the measurement of the damping of panels exposed to a moving airflow.