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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Tele-autonomous systems: New methods for projecting and coordinating intelligent action at a distance

There is a growing need for humans to perform complex remote operations and to extend the intelligence and experience of experts to distant applications. It is asserted that a blending of human intelligence, modern information technology, remote control, and intelligent autonomous systems is required, and have coined the term tele-autonomous technology, or tele-automation, for methods producing intelligent action at a distance. Tele-automation goes beyond autonomous control by blending in human intelligence. It goes beyond tele-operation by incorporating as much autonomy as possible and/or reasonable. A new approach is discussed for solving one of the fundamental problems facing tele-autonomous systems: The need to overcome time delays due to telemetry and signal propagation. New concepts are introduced called time and position clutches, that allow the time and position frames between the local user control and the remote device being controlled, to be desynchronized respectively. The design and implementation of these mechanisms are described in detail. It is demonstrated that these mechanisms lead to substantial telemanipulation performance improvements, including the result of improvements even in the absence of time delays. The new controls also yield a simple protocol for control handoffs of manipulation tasks between local operators and remote systems.

Conway, Lynn↗
NASA NTRS1990

Effective actions for bosonic topological defects

A gauge field theory is considered which admits p-dimensional topological defects, expanding the equations of motion in powers of the defect thickness. In this way an effective action and effective equation of motion is derived for the defect in terms of the coordinates of the p-dimensional worldsurface defined by the history of the core of the defect.

Gregory, Ruth↗
NASA NTRS1990

Symmetrical jet action in the R Aquarii binary system

Collimated mass flow in opposite directions is detected in the R Aqr binary-system jet by means of high-resolution long-slit spectroscopy of several optical emission lines. Also presented are images of the jet structure in the forbidden line of O III, which clearly show bipolar symmetry extending to distances of about 2750 AU on either side of the central Mira variable. The Mira light was greatly reduced by utilization of a vignetting disk on the window of the imaging CCD. This result confirms the recent report of morphological evidence for an R Aqr jet from the detection of bipolar radio continuum emission at 6 cm, and provides the necessary kinematical evidence to show that jet action is actually taking place.

Hollis, J. M.↗
NASA NTRS1990

Summary data on all NASA procurement actions

Summary data on all NASA procurement actions and detailed information on contracts, grants, agreements, and other procurements over $25,000 awarded by NASA during the first six months on fiscal year 1990 are presented. Areas addressed include competition in NASA awards, awards to business firms, awards to educational and other nonprofit institutions, contract for operation of Jet Propulsion Laboratory, and awards through other government agencies. Other topics covered are the U.S. geographical distribution of awards, awards placed outside the U.S., and procurement activity by installation.

Source record↗
NASA NTRS1991

Quick action clamp

A quick release toggle clamp that utilizes a spring that requires a deliberate positive action for disengagement is presented. The clamp has a sliding bolt that provides a latching mechanism. The bolt is moved by a handle that tends to remain in an engaged position while under tension.

Calco, Frank S.↗
NASA NTRS1991

Computations involving differential operators and their actions on functions

The algorithms derived by Grossmann and Larson (1989) are further developed for rewriting expressions involving differential operators. The differential operators involved arise in the local analysis of nonlinear dynamical systems. These algorithms are extended in two different directions: the algorithms are generalized so that they apply to differential operators on groups and the data structures and algorithms are developed to compute symbolically the action of differential operators on functions. Both of these generalizations are needed for applications.

Crouch, Peter E.↗
NASA NTRS1990

Evidence for fast dynamo action in a chaotic web

The evolution of a magnetic field in a chaotic web is studied. The model flow possessing the web is closely related to the nearly integrable ABC flow with A = B and C much less than 1. The magnetic diffusivity is taken to be zero and the field is followed using the Cauchy solution. It is found that the flow folds the magnetic field constructively, in the sense that the average magnetic field in a chaotic region grows exponentially in time. This is suggestive of fast dynamo action, although the effect of diffusion of the strong streamwise magnetic field remains to be assessed.

Gilbert, A. D.↗
NASA NTRS1992

Science in action: An interdisciplinary science education program

Science in Action is an education outreach program for pre-collegiate students. It is based on the concept that, in order to interest students in science, they must see science and scientists at work. The program encompasses the full range of scientific disciplines - the core sciences, engineering, and mathematics. A unique aspect of the program is the involvement and support of scientists and engineers representing local professional societies, industries, business, and academic institutions. An outline of the program is given.

Horton, Linda L.↗
NASA NTRS1992

Dynamo action in stratified convection with overshoot

Results are presented from direct simulations of turbulent compressible hydromagnetic convection above a stable overshoot layer. Spontaneous dynamo action occurs followed by saturation, with most of the generated magnetic field appearing as coherent flux tubes in the vicinity of strong downdrafts, where both the generation and destruction of magnetic field is most vigorous. Whether or not this field is amplified depends on the sizes of the magnetic Reynolds and magnetic Prandtl numbers. Joule dissipation is balanced mainly by the work done against the magnetic curvature force. It is this curvature force which is also responsible for the saturation of the dynamo.

Nordlund, Ake↗
NASA NTRS1992

Nonlinear restrictions on dynamo action

Astrophysical dynamos operate in the limit of small magnetic diffusivity. In order for magnetic reconnection to occur, very small magnetic structures must form so that diffusion becomes effective. The formation of small-scale fields is accompanied by the stretching of the field lines and therefore by an amplification of the magnetic field strength. The back reaction of the magnetic field on the motions leads to the eventual saturation of the dynamo process, thus posing a constraint on the amount of magnetic flux that can be generated by dynamo action, It is argued that in the limit of small diffusivity only a small amount of flux, many orders of magnitude less than the observed fluxes, can be created by dynamo processes.

Vainshtein, Samuel I.↗
NASA NTRS1993

Cam-Action Scribing Tool

Cam-action scribe designed for use on lathe produces continuous, constant-depth circumferential line on nominally cylindrical workpiece, even when workpiece somewhat out of round.

Malinzak, R. Michael↗
NASA NTRS1993

The development of a mixing layer under the action of weak streamwise vortices

The action of weak, streamwise vortices on a plane, incompressible, steady mixing layer is examined in the large Reynolds-number limit. The outer, inviscid region is bounded by a vortex sheet to which the viscous region is confined. It is shown that the local linear analysis becomes invalid at streamwise distances O(epsilon(sup -1)), where epsilon is much less than 1 is the cross flow amplitude, and a new nonlinear analysis is constructed for this region. Numerical solutions of the nonlinear problem show that the vortex sheet undergoes an O(1) change in position and that the solution is ultimately terminated by the appearance of a singularity. The corresponding viscous layer shows downstream thickening, but appears to remain well behaved up to the singular location.

Goldstein, Marvin E.↗
NASA NTRS1993

Crisis action planning and replanning using SIPE-2

Rome Laboratory and DARPA are jointly sponsoring an initiative to develop the next generation of AI planning and scheduling technology focused on military operations planning, especially for crisis situations. SRI International has demonstrated their knowledge-based planning technology in this domain with a system called SOCAP, System for Operations Crisis Action Planning. SOCAP's underlying power comes from SIPE-2, a hierarchical, domain-independent, nonlinear AI planner also developed at SRI. This paper discusses the features of SIPE-2 that made it an ideal choice for military operations planning and which contributed greatly to SOCAP's success.

Skidmore, Jennifer D.↗
NASA NTRS1993

The development of a mixing layer under the action of weak streamwise vortices

The action of weak, streamwise vortices on a plane, incompressible, steady mixing layer is examined in the large Reynolds number limit. The outer, inviscid region is bounded by a vortex sheet to which the viscous region is confined. It is shown that the local linear analysis becomes invalid at streamwise distances O(epsilon sup -1), where (epsilon much less than 1) is the crossflow amplitude, and a new nonlinear analysis is constructed for this region. Numerical solutions of the nonlinear problem show that the vortex sheet undergoes an O(1) change in position and that the solution is ultimately terminated by a breakdown in the numerical procedure. The corresponding viscous layer shows downstream thickening, but appears to remain well behaved up to the terminal location.

Goldstein, M. E.↗
NASA NTRS1992

Bubble migration under the combined action of buoyancy and thermocapillarity

The migration of a gas bubble under the combined action of buoyancy and a downward temperature gradient is analyzed. Inertial effects are considered negligible, but allowance is made for convective transport of energy in the model. Results from a numerical solution of the governing equations are presented and discussed.

Merritt, Randy M.↗
NASA NTRS1922

Testing airplanes in flight: determining position of resultant of action of air and longitudinal stability of an airplane at different angles of attack

Measurements made during flight with the triple recording device which gives the horizontal and vertical speeds of an airplane and the angle it makes with the horizon, render it possible to calculate its lift, its drag, and R the resultant of the action of the air both in magnitude and direction, but with these data alone, it is impossible to determine the position of this resultant in the plane of symmetry of the airplane. We will also see how we may determine the position of R during flight and then calculate the variations in the stability of an airplane.

STABILITY, LONGITUDINAL↗
NASA NTRS1955

Chemical Action of Halogenated Agents in Fire Extinguishing

The action of halogenated agents in preventing flame propagation in fuel-air mixtures in laboratory tests is discussed in terms of a possible chemical mechanism. The mechanism chosen is that of chain-breaking reactions between agent and active particles (hydrogen and oxygen atoms and hydroxyl radicsls). Data from the literature on the flammability peaks of n-heptane agent-air mixtures are treated. Ratings of agent effectiveness in terms of the fuel equivalent of the agent, based on both fuel and agent concentrations at the peak, are proposed as preferable to ratings in terms of agent concentration alone. These fuel-equivalent ratings are roughly correlated by reactivities assigned to halogen and hydrogen atoms in the agent molecules. It is concluded that the presence of hydrogen in agent need not reduce its fire-fighting ability, provided there is enough halogen to make the agent nonflammable. A method is presented for estimating from quenching-distance data a rate constant for the reaction of agent with active particles. A quantitative result is obtained for methyl bromide. This rate constant predicts the observed peak concentration of methyl bromide quite well. However, more data are needed to prove the validity of the method. The assumption that hal.ogenatedagents act mainly by chain-bresking reactions with active particles is consistent with the experimental facts and should help guide the selection of agents for further tests.

Belles, Frank E.↗
NASA NTRS1925

The Influence of the Form of a Wooden Beam on Its Stiffness and Strength III : Stresses in Wood Members Subjected to Combined Column and Beam Action

The general purpose in this study was to determine the stresses in a wooden member subjected to combined beam and column action. What may be considered the specific purpose, as it relates more directly to the problem of design, was to determine the particular stress that obtains at maximum load which, for combined loading, does not occur simultaneously with maximum stress.

Newlin, J A↗