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Results for “Electrical techniques”

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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Development of a thin film solid state gaseous HCl sensor

The selection of materials to develop a thin film HCl sensor is discussed. Data were primarily concerned with chemical and physical properties of the film and with electrical properties which exhibit and enhance electrical response when HCl is absorbed on the film surface. Techniques investigated for enhancing electrical response include changing conditions for growing films, adding impurities to the film, changing ambient light intensity, and altering the ambient temperature of the sensing element.

Source record↗
NASA NTRS1991

Electric fields in the solar atmosphere - A review

A review is presented of remote sensing techniques which measure the electric field component transverse to the line of sight and achieve a sensitivity range of 5-10 V/cm. Three models are shown to predict quasistatic, macroscopic values of E(parallel), the electric field component parallel to the magnetic vector, beyond the sensitivity range considered. These processes are: the discharge model of flares; the models of return currents related to flare particle beams; and the models of neutral sheets related to two-ribbon flares and postflare loops. Time dependent electric fields related to MHD and plasma waves, and to plasma disturbance, may allow the detection of both E components (parallel and perpendicular). The uncertainty relating to the emission measures, time scales, volumes, and plasma conditions of these flares and electrified plasma volumes is emphasized. It is pointed out, however, that important information can be obtained by observing electric fields at existing sensitivity levels. By measuring these E-fields, the understanding of flares and related dynamic events can be improved.

Foukal, P.↗
NASA NTRS1984

Electrical self-calibration of nonideal bolometers

An analytical method for determining the absorbed energy calibration of an IR bolometer from purely electrical measurements is presented. The technique is targeted at detectors with purely electrical nonlinearities. It is shown that the responsivity can be derived from the I-V plot if the limiting high-frequency impedance is measured. The electrical nonlinearity is then the difference between the impedance and the dc resistance. The model is used for designing a circuit for measuring the relative impedance parameters. The results are applicable to studies of IR sources and the detection of energy pulses with bolometers.

Mather, J. C.↗
NASA NTRS1989

Low-speed flowfield characterization by infrared measurements of surface temperatures

An experimental program was aimed at identifying areas in low speed aerodynamic research where infrared imaging systems can make significant contributions. Implementing a new technique, a long electrically heated wire was placed across a laminar jet. By measuring the temperature distribution along the wire with the IR imaging camera, the flow behavior was identified. Furthermore, using Nusselt number correlations, the velocity distribution could be deduced. The same approach was used to survey wakes behind cylinders in a wind-tunnel. This method is suited to investigate flows with position dependent velocities, e.g., boundary layers, confined flows, jets, wakes, and shear layers. It was found that the IR imaging camera cannot accurately track high gradient temperature fields. A correlation procedure was devised to account for this limitation. Other wind-tunnel experiments included tracking the development of the laminar boundary layer over a warmed flat plate by measuring the chordwise temperature distribution. This technique was applied also to the flow downstream from a rearward facing step. Finally, the IR imaging system was used to study boundary layer behavior over an airfoil at angles of attack from zero up to separation. The results were confirmed with tufts observable both visually and with the IR imaging camera.

Gartenberg, E.↗
NASA NTRS1972

Electric fields in the ionosphere and magnetosphere.

Review of current techniques for measuring ionospheric and magnetospheric electric fields and existing measurements. Considerable progress in understanding electric fields has been made in the auroral regions where fields originating basically from convection patterns in the magnetosphere and modified by ionospheric interaction have been detected by both the barium ion cloud and double floating probe techniques and have been compared against predictions. The anticorrelation of electric fields and auroral arcs, the establishment of the auroral electrojet currents as Hall currents, the irregular nature of the electric fields, and the reversal of the electric fields between the eastward and westward electrojet regions have been some of the important observations. Recent barium ion cloud observations in the polar cap have indicated that the long assumed electrojet return current across the polar cap does not exist.

Maynard, N. C.↗
NASA NTRS1973

Investigation of substrate-mounted thin-film meteoroid sensors for use in large area impact experiments

Two types of sensor designs were investigated: (1)a polysulfone dielectric film with vapor-deposited aluminum and gold sensor plates, bonded to a relatively thick aluminum substrate, and (2) an aluminum oxide (A1203) dielectric layer prepared on an aluminum substrate by anodization, with a layer of vapor-deposited aluminum providing one sensor plate and the substrate serving as the other plate. In the first design, specimens were prepared which indicate the state of the art for application of this type of sensor for elements of a meteoroid detection system having an area as large as 10 sq M. Techniques were investigated for casting large-area polysulfone films on the surface of water and for transferring the films from the water. Methods of preparing sensors by layering of films, the deposition of capacitor plates, and sensor film-to-substrate bonding, as well as techniques for making electrical connections to the capacitor plates, were studied.

Carollo, S. F.↗
NASA NTRS1976

Review study and evaluation of possible flight experiments relating to cloud physics experiments in space

The general objectives of the Zero-Gravity Atmospheric Cloud Physics Laboratory Program are to improve the level of knowledge in atmospheric cloud research by placing at the disposal of the terrestrial-bound atmospheric cloud physicist a laboratory that can be operated in the environment of zero-gravity or near zero-gravity. This laboratory will allow studies to be performed without mechanical, aerodynamic, electrical, or other techniques to support the object under study. The inhouse analysis of the Skylab 3 and 4 experiments in dynamics of oscillations, rotations, collisions and coalescence of water droplets under low gravity-environment is presented.

Hunt, R. J.↗
NASA NTRS1978

A new look at performance capabilities of arc-driven shock tubes

High shock-tube velocities simulating Jovian entry have been achieved with arc-driver operation using a method of tailoring electrical circuit impedance to arc-plasma impedance. The concept of impedance matching also prescribes a requirement for minimum electrical capacitance. The technique of developing the strongest shock-generating capability for an arc-driver system with the least total energy is discussed. Several programs using the shock tube for developmental research in energy and industrial applications are outlined.

Dannenberg, R. E.↗
NASA NTRS1983

Low-Cost Electrically-Heated Glass Panels

Inexpensive process converts architectural reflective-coated glass into electrically heated panels. Technique utilizes reflective layer as heating element in ordinary glass. Panels have many applications, including automobile windows, home-heating panels, temperature-controlled windows or containers, and food warming trays.

Shlichta, P. J.↗
NASA NTRS1986

Measuring Resistivities of Small Fibers

Technique for measuring electrical resistivities of fibers of graphite, silicon carbide/silicon nitride mixture, and other materials used in composites simple, accurate, and reproducible. Suitable for monofilament fibers with diameters of about 10 to 50 micrometers. Also adapted to two fiber strands.

Daniels, J.↗
NASA NTRS1986

Detection of fiber damage in a graphite epoxy composite using current injection and magnetic field mapping

A novel NDE technique is reported for detecting fiber disruptions in graphite-epoxy composites. The technique involves injecting electric current along the graphite fibers of a composite and measuring the resulting magnetic fields. The disruptions in current paths, which occur in areas of fiber damage, are detectable as perturbations in the magnetic field. The experimental setup, the measurements, and the magnetic images of experimental samples are presented. A resistive model has been developed to be used in the modeling of two-dimensional conductivity patterns in graphite composites. Diagrams of the setup and the circuitry are included.

Blalock, T. N.↗