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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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At least 451 records · Page 25

All sources NASA NTRS DOE OSTI

NASA NTRS1976

State-plane trajectories used to observe and control the behavior of a voltage step-up dc-to-dc converter

State-plane analysis techniques are employed to study the voltage step up energy storage dc-to-dc converter. Within this framework, an example converter operating under the influence of a constant on time and a constant frequency controller is examined. Qualitative insight gained through this approach is used to develop a conceptual free running control law for the voltage step up converter which can achieve steady state operation in one on/off cycle of control. Digital computer simulation data is presented to illustrate and verify the theoretical discussions presented.

Burns, W. W., III↗

NASA NTRS1977

Optimum step design for centering of pistons moving in an incompressible fluid

Hydrodynamic effects are analyzed for a stepped piston moving within a tight clearance tube filled with an incompressible fluid. Together with the hydrostatic effects that were analyzed in an earlier paper, a complete solution is obtained and an optimum step design for centering of the piston is suggested. The axial speed resulting from an axial driving force is calculated, and some experimental results for pistons falling in a water filled tube are presented.

Etsion, I.↗

NASA NTRS1978

A finite-step method for estimating the spanwise lift distribution of wings in symmetric, yawed, and rotary flight at low speeds

The finite-step method was programmed for computing the span loading and stability derivatives of trapezoidal shaped wings in symmetric, yawed, and rotary flight. Calculations were made for a series of different wing planforms and the results compared with several available methods for estimating these derivatives in the linear angle of attack range. The agreement shown was generally good except in a few cases. An attempt was made to estimate the nonlinear variation of lift with angle of attack in the high alpha range by introducing the measured airfoil section data into the finite-step method. The numerical procedure was found to be stable only at low angles of attack.

Krenkel, A. R.↗

NASA NTRS1978

Origin of the stepped topography of the Martian poles

Ablation and condensation of water vapor are suggested as the principal factors responsible for the circumpolar layered and stepped terrain found at the North and South Poles of Mars. A metastable erosion rate due to decreasing albedo and increasing radiation input caused by dust deposits on the steeper slopes of the ablating layered deposits provides a mechanism for the development of the stepped topography. Loose excess dust accumulated during scarp ablation may then be removed by wind erosion.

Howard, A. D.↗

NASA NTRS1978

Prediction, evaluation, and specification of flying qualities by means of step target tracking

A new approach to flying qualities specification and evaluation is presented which coordinates current research in the areas of pilot ratings, pilot-aircraft modeling techniques, and simulation and flight test procedures. A time-domain pilot model is described which can model discontinuous and nonlinear pilot behavior in conjunction with completely general time-varying nonlinear aircraft models to simulate discrete maneuvers. This pilot-aircraft model is applied to an existing set of in-flight simulation data, and calculates tracking error and time-on-target statistics for step target tracking that directly relate to the reported pilot comments and ratings. Predicted step target tracking data for eighteen F-5E flight conditions are presented, and the use of the method for control system design is demonstrated using the YF-17.

Onstott, E. D.↗

NASA NTRS1979

Transistor step stress testing program for JANTX2N2905A

The effect of power/temperature step stress when applied to the transistor JANTX2N2905A manufactured by Texas Instruments and Motorola is reported. A total of 48 samples from each manufacturer was submitted to the process outlined. In addition, two control sample units were maintained for verification of the electrical parametric testing. All test samples were subjected to the electrical tests outlined in Table 2 after completing the prior power/temperature step stress point.

Source record↗

NASA NTRS1979

Transistor step stress program for JANTX2N4150

Reliability analysis of the transistor JANTX2N4150 manufactured by General Semiconductor and Transitron is reported. The discrete devices were subjected to power and temperature step stress tests and then to electrical tests after completing the power/temperature step stress point. Control sample units were maintained for verification of the electrical parametric testing. Results are presented.

Source record↗

NASA NTRS1979

Transistor step stress program for JANTX2N2432A

Power/temperature step stress was applied to the transistor JANTX2N2432A manufactured by Crystalonics and Texas Instruments. A total of 48 samples from each manufacturer were submitted to the process outlined. In addition, two control sample units were maintained for verification of the electrical parametric testing. All test samples were subjected to the electrical tests after completing the prior power/temperature step stress point.

Source record↗

NASA NTRS1979

Diode step stress program for JANTX1N5615

The effect of power/temperature step stress when applied to the switching diode JANTX1N5615 manufactured by Semtech and Micro semiconductor was examined. A total of 48 samples from each manufacturer were submitted to the process. In addition, two control sample units were maintained for verification of the electrical parametric testing. All test samples were subjected to the electrical tests after completing the prior power/temperature step stress point. Results are presented.

Source record↗

NASA NTRS1979

Diode step stress program for JANTX1N1202A

Power/temperature step stress was applied to the switching diode JANTX1N1202A manufactured by General Electric and International Rectifier. A total of 48 samples from each manufacturer was submitted to the process. In addition, two control sample units were maintained for verification of the electrical parametric testing. All test samples were subjected to the electrical tests after completing the prior power/temperature step stress point. Results are given.

Source record↗

NASA NTRS1979

Transistor step stress program for JANTX2N2060

The effect of power/temperature step stress when applied to the dual transistor JANTX2N2060 manufactured by Raytheon and Motorola is reported. A total of 48 samples from each manufacturer were submitted to the process. In addition, two control sample units were maintained for verification of the electrical parametric testing. All test samples were subjected to the electrical tests after completing the prior power/temperature step stress point. Results are given.

Source record↗

NASA NTRS1979

Diode step stress program for JANTX1N645-1

The diode JANTX1N645-1 manufactured by Semtech and Micro Semiconductor was subjected to power/temperature step stress in order to assess its reliability. All test samples were subjected to electrical tests after completing the power/temperature step stress point. Control sample units were maintained for verification of the electrical parametric testing. Results are presented in tabular form.

Source record↗

NASA NTRS1979

Transistor step stress program for JANTX2N2219A

Power/temperature step stress was applied to the dual transistor JANTX2N2219A manufactured by Texas Instruments and National Semiconductor. A total of 48 samples from each manufacturer were submitted to the process outlined. In addition, two control sample units were maintained for verification of the electrical parametric testing. All test samples were subjected to electrical tests after completing the prior power/temperature step stress point.

Source record↗

NASA NTRS1979

Rapid, single-step most-probable-number method for enumerating fecal coliforms in effluents from sewage treatment plants

A single-step most-probable-number method for determining the number of fecal coliform bacteria present in sewage treatment plant effluents is discussed. A single growth medium based on that of Reasoner et al. (1976) and consisting of 5.0 gr. proteose peptone, 3.0 gr. yeast extract, 10.0 gr. lactose, 7.5 gr. NaCl, 0.2 gr. sodium lauryl sulfate, and 0.1 gr. sodium desoxycholate per liter is used. The pH is adjusted to 6.5, and samples are incubated at 44.5 deg C. Bacterial growth is detected either by measuring the increase with time in the electrical impedance ratio between the innoculated sample vial and an uninnoculated reference vial or by visual examination for turbidity. Results obtained by the single-step method for chlorinated and unchlorinated effluent samples are in excellent agreement with those obtained by the standard method. It is suggested that in automated treatment plants impedance ratio data could be automatically matched by computer programs with the appropriate dilution factors and most probable number tables already in the computer memory, with the corresponding result displayed as fecal coliforms per 100 ml of effluent.

Munoz, E. F.↗

NASA NTRS1979

Explicit large time-step schemes for the shallow water equations

Modifications to explicit finite difference schemes for solving the shallow water equations for meteorological applications by increasing the time step for the fast gravity waves are analyzed. Terms associated with the gravity waves in the shallow water equations are treated on a coarser grid than those associated with the slow Rossby waves, which contain much more of the available energy and must be treated with higher accuracy, enabling a several-fold increase in time step without degrading the accuracy of the solution. The method is presented in Cartesian and spherical coordinates for a rotating earth, using generalized leapfrog, frozen coefficient, and Fourier filtering finite difference schemes. Computational results verify the numerical stability of the approach.

Turkel, E.↗

NASA NTRS1982

Phenomenological study of subsonic turbulent flow over a swept rearward-facing step

The phenomenology of turbulent, subsonic flow over a swept, rearward-facing step was studied. Effects of variations in step height, sweep angle, base geometry, and end conditions on the 3-D separated flow were examined. The separated flow was visualized using smoke wire, oil drop, and surface tuft techniques. Measurements include surface pressure, reattachment distance and swirl angle. Results indicate: (1) model/test section coupling affects the structure of the separated flow, but spanwise end conditions do not; (2) the independence principle is evidently valid for sweep angles up to 38 deg; (3) a sweep angle/swirl angle correlation exists; and (4) base modifications can significantly reduce the reattachment distance.

Selby, G. V.↗

NASA NTRS1982

The digital step edge

The facet model was used to accomplish step edge detection. The essence of the facet model is that any analysis made on the basis of the pixel values in some neighborhood has its final authoritative interpretation relative to the underlying grey tone intensity surface of which the neighborhood pixel values are observed noisy samples. Pixels which are part of regions have simple grey tone intensity surfaces over their areas. Pixels which have an edge in them have complex grey tone intensity surfaces over their areas. Specially, an edge moves through a pixel only if there is some point in the pixel's area having a zero crossing of the second directional derivative taken in the direction of a non-zero gradient at the pixel's center. To determine whether or not a pixel should be marked as a step edge pixel, its underlying grey tone intensity surface was estimated on the basis of the pixels in its neighborhood.

Haralick, R. M.↗

NASA NTRS1982

A numerical solution of the supersonic flow over a rearward facing step with transverse non-reacting hydrogen injection

The present investigation represents an application of computational fluid dynamics to a problem associated with the flow in the combustor region of a supersonic combustion ramjet engine (scramjet). The governing equations are considered, taking into account the Navier-Stokes equations, a molecular viscosity calculation, the molecular thermal conductivity, molecular diffusion, and a turbulence model. The employed numerical solution is patterned after the explicit, time-dependent, unsplit, predictor-corrector, finite-difference method given by MacCormack (1969). The calculation is concerned with the supersonic flow over a rearward-facing step with transverse H2 injection at conditions germane to the combustor region of a scramjet engine. The H2 jet acts as an effective body which essentially shields the primary flow from the rearward-facing step, thus substantially changing the wave pattern in the primary flow.

Berman, H. A.↗