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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Detection of Machining Chips by Pressure Reversal

Inaccessible interior spaces inspected acoustically. In acoustic inspection, inlet and outlet ports of component connected to pneumatic hoses of apparatus that rapidly reverses induced pressure differential. If loose particles inside this component, they will generate noise detected by series of contact microphones attached to component. Noise indicates general location of contaminants, and its characteristic helps in identifying particles from their acoustic signatures.

Wyett, L. M.↗
NASA NTRS1986

Static internal performance of a thrust vectoring and reversing two-dimensional convergent-divergent nozzle with an aft flap

The static internal performance of a multifunction nozzle having some of the geometric characteristics of both two-dimensional convergent-divergent and single expansion ramp nozzles has been investigated in the static-test facility of the Langley 16-Foot Transonic Tunnel. The internal expansion portion of the nozzle consisted of two symmetrical flat surfaces of equal length, and the external expansion portion of the nozzle consisted of a single aft flap. The aft flap could be varied in angle independently of the upper internal expansion surface to which it was attached. The effects of internal expansion ratio, nozzle thrust-vector angle (-30 deg. to 30 deg., aft flap shape, aft flap angle, and sidewall containment were determined for dry and afterburning power settings. In addition, a partial afterburning power setting nozzle, a fully deployed thrust reverser, and four vertical takeoff or landing nozzle, configurations were investigated. Nozzle pressure ratio was varied up to 10 for the dry power nozzles and 7 for the afterburning power nozzles.

Re, R. J.↗
NASA NTRS1986

Protobiological informatoin, bidirectional recognition and reverse translation

Emergence of protobiological information has been suggested by experiments in which heated mixtures of alpha-amino acids order themselves into a self limited array of thermal proteins. The polymers display selective catalytic, hormonal, and other activities. Interactions of varied cationic thermal proteins with polynucleotides indicate selective recognition in both directions. Reverse translation is partly a missing link in the molecular evolution flowsheet. The self ordering of amino acids serves conceptually as a deterministic evolutionary precursor of the modern coding mechanism. The possibility for the evolution of information at an early nontemplated protein stage is supported by findings of electrical signals from proteinoid microspheres prepared with no DNA/RNA in their history. The deposition of thermal copolyamino acids on lipid membranes in the Mueller-Rudin apparatus has here been found to produce electrical behavior like that evoked by bacterial EIM polypeptide. A new procedure is to make a film of membrane on the electrode; the results provide maximal repeatability. The principle of nonrandom biomacromolecular specificity identified by these studies in molecular evolution have been extrapolated to principles of evolution of advanced organisms.

Fox, S. W.↗
NASA NTRS1986

An auroral arc in the late evening plasma flow reversal

The late evening plasma flow reversal over Alaska on January 27, 1980 and changes associated with an auroral arc are examined on the basis of radar observations and rocket measurements. In particular, attention is given to changes in the plasma flow patterns resulting from a small substorm and to several effects associated with the auroral arc, such as an inverted V electron energy spectrum and, on the equatorial edge, an intense burst of auroral hiss and a very thin sheet of field-aligned electrons. Details of the experimental payload and geophysical conditions of the launch are included.

Cahill, L. J., Jr.↗
NASA NTRS1986

Interplanetary shock collisions - Forward with reverse shocks

When one interplanetary shock overtakes another, the structure that results depends upon the nature of the interacting shocks. The results of collisions of forward with reverse shocks, in two dimensions, are numerically examined, and it is shown that the results depend primarily upon shock strength. It is also noted that such interactions could explain why many energy outburst on the sun that would be expected to cause geomagnetic effects at the earth, do not.

Smith, Z. K.↗
NASA NTRS1986

Red/violet contrast reversal on Mars - Significance for eolian sediments

Viking Orbiter images of Mars are analyzed to define relationships between the observed contrast reversals (CR) and specific surface features. The link between CR phenomena and surface composition was first detected in contrast comparisons between UV and visible wavelength Mariner 9 data. Viking data, taken through red and violet filters, showed that the CRs occurred only with crater splotches and splotch-related streaks and in bright depositional and dark erosional streaks, both being low-albedo markings presumably caused by eolian forces. The splotch phenomena is confined mainly to the Oxia Palus region, although there are other regions where splotches and streaks commingle. Laboratory tests to mimic the CR characteristics showed that CRs are a common phenomena of different size fractions of iron oxides, e.g., goethite, where particles under 5 microns have been removed. The splotches, including dune formations, are therefore believed to indicate the presence of particles in the 100-800 microns diam range. Finer particles ride on the tops of the dust storms, and are continually removed from the surface by saltation.

Thomas, P.↗
NASA NTRS1986

Turbulent relaxation to a force-free field-reversed state

The evolution of nonequilibrium initial conditions of an incompressible magnetohydrodynamic Z pinch is described by a three-dimensional, pseudospectral numerical code. Magnetohydrodynamic turbulence develops in the resistive, nonviscous magnetofluid, resulting in the selective decay of the energy relative to the magnetic helicity, at Lundquist numbers of only a few hundred. An interior force-free region grows with time and achieves spontaneous reversal of the toroidal magnetic field at the wall, without the necessity of an external electric field.

Dahlburg, J. P.↗
NASA NTRS1987

Measured pressure distributions inside nonaxisymmetric nozzles with partially deployed thrust reversers

An investigation was conducted in the Langley 16-Foot Transonic Tunnel at static conditions to measure the pressure distributions inside a nonaxisymmetric nozzle with simultaneous partial thrust reversing (50-percent deployment) and thrust vectoring of the primary (forward-thrust) nozzle flow. Geometric forward-thrust-vector angles of 0 and 15 deg. were tested. Test data were obtained at static conditions while nozzle pressure ratio was varied from 2.0 to 4.0. Results indicate that, unlike the 0 deg. vector angle nozzle, a complicated, asymmetric exhaust flow pattern exists in the primary-flow exhaust duct of the 15 deg. vectored nozzle.

Green, Robert S.↗
NASA NTRS1988

Aerodynamics in ground effect and predicted landing ground roll of a fighter configuration with a secondary-nozzle thrust reverser

An experimental investigation of the in-ground effect aerodynamic characteristics and predicted landing-ground-roll performance of wing-canard fighter configuration with a secondary nozzle thrust reverser was completed. These tests were conducted in the Langley 14 by 22 foot Subsonic Wind Tunnel using a model equipped with a pneumatic jet for thrust simulation of nozzle pressure ratios up to 4.0. The model was tested in the landing rollout configuration at approx. wheel touchdown height for a range of decreasing dynamic pressure from 50 psf down to 10 psf. Landing-ground-roll predictions of the configuration were calculated using the wind tunnel results.

Banks, Daniel W.↗
NASA NTRS1987

Do slow orbital periodicities appear in the record of earth's magnetic reversals?

Time-series spectral analysis has been performed on the dates of geomagnetic reversals of the last 20 Myr BP and earlier. Possible evidence is found from the presence of high spectral peaks for two very long periodicities, 0.4 Myr and 1.3 Myr, that may be associated with slow variations of the earth's orbital eccentricity as predicted by Berger. However, statistical significance tests and a number of other arguments do not confirm the two detections.

Stothers, Richard B.↗
NASA NTRS1988

The phase reversal phenomenon at flow separation and reattachment

Tests were conducted on two different airfoils, one of them in a low-turbulence tunnel, to detect laminar separation and turbulent reattachment locations. A 'nonintrusive' multielement sensor consisting of a large number of closely spaced individual nickel films was vacuum deposited on a thin substrate and bonded to the airfoil model surface. Each sensor element was a part of an independent constant temperature anemometer system. Time history as well as spectral analysis of signals from surface film gauges were used to determine the surface shear flow characteristics. A major breakthrough was achieved with the discovery of phase reversal in low-frequency dynamic shear stress signals across regions of flow separation and reattachment.

Stack, J. Pete↗
NASA NTRS1987

'But Captain, I've been doing this a lot longer than you have' - The effects of 'role-reversal' on crew interaction

Legislation providing for airline deregulation has, among other things, created some ambiguity with respect to cockpit role structures. With the demise of some airlines, the absorption of others, the merging of seniority lists, and a new shortage of pilots, individuals with experience equivalent to or greater than that of the pilot in command may be placed in roles of lesser status. A formerly senior captain may be flying in the right seat as a first officer with an individual very much 'junior' in terms of both age and experience. Moreover, the mandatory retirement of airline pilots at age 60 does not apply to flight engineers, and some are 'down-grading' to fly in that capacity. The effects of this 'role-reversal' phenomenon on the crew coordination process have not been explored. The purpose of this study was to begin investigating this phenomenon using data obtained from a previous 'short-haul' full mission study conducted by Foushee, Lauber, Baetge, and Acomb (1986).

Lozito, Sandra C.↗
NASA NTRS1988

Analysis of microalloy precipitate reversion in steels

The influence of the ferrite to austenite allotropic transformation on the stability of MXn precipitates in an iron matrix is studied. In the MX phase, M is a group IVb or Vb transition metal, such as niobium, titanium, or vanadium. X is carbon or nitrogen and n is in the range of 0.75-1.0. The application of the present model to the case of vanadium carbide reversion in a microalloyed steel is discussed.

Michal, G. M.↗
NASA NTRS1989

Stiffness change of a graphite epoxy laminate under reverse fatigue loading

The stiffness of a flat specimen, made of graphite epoxy (T300/934), was measured during reverse fatigue loading. Laminates of basic layup, unidirectional cross-ply and angle-ply, as well as multidirectional (isotropic) layup, were tested. It was found that all the laminates exhibit rapid stiffness degradation on the last (third) fatigue stage. Except for the 0-deg unidirectional laminate, the last stage starts at about 70 to 80 percent of the fatigue life, regardless of the load level and the final mode of failure (tension or compression). It is shown that, for this material, stiffness degradation is a result of crack accumulation, mainly along the fibers, even for the fiber dominated laminates. This general phenomenon can serve to predict usable safe life of laminates under fatigue loading.

Rotem, Assa↗
NASA NTRS1988

Thermally reversible gels in electrophoresis. I - Matrix characterization

Two series of thermally reversible hydrogen-bonded gels have been characterized: (5 pct) PVA-(4 pct) PEG and (5 pct) PVA-(0.04 pct) borate gels. They both have extremely low melting points (16-17 C) and could be of potential interest for recovery of proteins after preparative electrophoresis. The PVA-borate gels can be exploited in the pH range 7-11 by progressively increasing the borate content in the pH interval 8 to 7 and concomitantly decreasing the borate levels in the pH zone 8 to 11. It is hypothesized that the low melting point of these gels is due to the fact that they are sparingly and sparsely hydrogen bonded along the PVA chain: on the average, 1 OH group out of 3 or 4 OH groups in the PVA polymer should be engaged in H-bond formation.

Righetti, Pier Giorgio↗
NASA NTRS1990

Plasma flow reversals at the dayside magnetopause and the origin of asymmetric polar cap convection

Events observed in a fast plasma experiment, where the y-component of the plasma flow within the low latitude boundary layer and magnetopause current layer was oppositely directed to that in the adjacent magnetosheath, are examined. The observations are shown to be qualitatively and quantitatively consistent with previous observations of accelerated flows at the magnetopause and with models of magnetic reconnection, with reconnection occurring at low latitudes near the GSE XY plane, independently of the magnitude or the sign of the y-component ot the local magnetosheath magnetic field. Local magnetic shears at the magnetopause for these events (in 60-180 deg range) and the fact that these events occur at low latitudes do not support the antiparallel merging hypothesis. The observations of B(y)-dependent flow reversals demonstrate how the asymmetric polar cap convection and related phenomena, such as the Svalgaard-Mansurov effect, originate in magnetic reconnection at the dayside magnetopause.

Gosling, J. T.↗
NASA NTRS1991

GRASP/Ada: Graphical Representations of Algorithms, Structures, and Processes for Ada. The development of a program analysis environment for Ada: Reverse engineering tools for Ada, task 2, phase 3

The main objective is the investigation, formulation, and generation of graphical representations of algorithms, structures, and processes for Ada (GRASP/Ada). The presented task, in which various graphical representations that can be extracted or generated from source code are described and categorized, is focused on reverse engineering. The following subject areas are covered: the system model; control structure diagram generator; object oriented design diagram generator; user interface; and the GRASP library.

Cross, James H., II↗