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At least 235 records · Page 13

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NASA NTRS1982

Initial stages of cavitation damage and erosion on copper and brass tested in a rotating disk device

In view of the differences in flow and experimental conditions, there has been a continuing debate as to whether or not the ultrasonic method of producing cavitation damage is similar to the damage occurring in cavitating flow systems, namely, venturi and rotating disk devices. In this paper, the progress of cavitation damage during incubation periods on polycrystalline copper and brass tested in a rotating disk device is presented. The results indicate several similarities and differences in the damage mechanism encountered in a rotating disk device (which simulates field rotary devices) and a magnetostriction apparatus. The macroscopic erosion appears similar to that in the vibratory device except for nonuniform erosion and apparent plastic flow during the initial damage phase.

Rao, P. V.↗

NASA NTRS1982

Deep impurity trapping concepts for power semiconductor devices

High voltage semiconductor switches using deep impurity doped silicon now appear feasible for high voltage (1-100 kV), high power (10 Kw) switching and protection functions for future space power applications. Recent discoveries have demonstrated several practical ways of gating deep impurity doped silicon devices in planar configurations and of electrically controlling their characteristics, leading to a vast array of possible circuit applications. A new family of semiconductor switching devices and transducers are possible based on this technology. New deep impurity devices could be simpler than conventional p-n junction devices and yet use the same basic materials and processing techniques. In addition, multiple functions may be possible on a single device as well as increased ratings.

Sundberg, G. R.↗

NASA NTRS1982

Single event upset sensitivity of low power Schottky devices

Data taken from tests involving heavy ions in the Berkeley 88 in. cyclotron being directed at low power Schottky barrier devices are reported. The tests also included trials in the Harvard cyclotron with 130 MeV protons, and at the U.C. Davis cyclotron using 56 MeV protons. The experiments were performed to study the single event upsets in MSI logic devices containing flip-flops. Results are presented of single-event upsets (SEU) causing functional degradation observed in post-exposure tests of six different devices. The effectiveness of the particles in producing SEUs in logic device functioning was found to be directly proportional to the proton energy. Shielding was determined to offer negligible protection from the particle bombardment. The results are considered significant for the design and fabrication of LS devices for space applications.

Price, W. E.↗

NASA NTRS1984

Impacting device for testing insulation

An electro-mechanical impacting device for testing the bonding of foam insulation to metal is descirbed. The device lightly impacts foam insulation attached to metal to determine whether the insulation is properly bonded to the metal and to determine the quality of the bond. A force measuring device, preferably a load cell mounted on the impacting device, measures the force of the impact and the duration of the time the hammer head is actually in contact with the insulation. The impactor is designed in the form of a handgun having a driving spring which can propel a plunger forward to cause a hammer head to impact the insulation. The device utilizes a trigger mechanism which provides precise adjustements, allowing fireproof operation.

Redmon, J. W.↗

NASA NTRS1983

Single event upset (SEU) of semiconductor devices - A summary of JPL test data

The data summarized describe single event upset (bit-flips) for 60 device types having data storage elements. The data are from 15 acceleration tests with both protons and heavier ions. Tables are included summarizing the upset threshold data and listing the devices tested for heavy ion induced bit-flip and the devices tested with protons. With regard to the proton data, it is noted that the data are often limited to one proton energy, since the tests were usually motivated by the engineering requirement of comparing similar candidate devices for a system. It is noted that many of the devices exhibited no upset for the given test conditions (the maximum fluence and the maximum proton energy Ep are given for these cases). It is believed, however, that some possibility of upset usually exists because there is a slight chance that the recoil atom may receive up to 10 to 20 MeV of recoil energy (with more energy at higher Ep).

Nichols, D. K.↗

NASA NTRS1985

The performance of smooth-wall drag reducing outer-layer devices in rough-wall boundary layers

The boundary layer drag on a 0.28 m x 0.91 m flat-plate was measured to evaluate the performance of smooth-wall drag reducing outer-layer devices in rough-wall boundary layers up to a chord Reynolds number, Re(c) of 17,000. The devices were a pair of thin flat ribbons placed in tandem. The wall conditions examined were smooth, transverse-groove roughnesses having cavity width/depth ratios of 0.7 (d-type) and 3 (k-type), and sandpaper roughness (k-type) of grit sizes 180, 50 and 36. The area-averaged wall-drag was reduced compared to the respective normal levels for all wall conditions. All k-type rough walls exhibited a comparable level of drag reduction (about 7 percent) which was lower than that in the smooth-wall. The d-type rough-wall exhibited a transitional behavior in that the drag reduction dropped from the smooth-wall level to that of the k-type roughnesses with increase in the flow speed. In further experiments on a 6 meter long sandpaper roughened wall and with a pair of symmetric airfoil devices in tandem at an Re(c) of 77,500, it was possible to recover the device drag penalty fully, but no net drag reduction was achieved. The apparent loss of performance of the devices in a rough-wall is explained in terms of their inability to alter the pressure component of the drag in a significant way.

Bandyopadhyay, P. R.↗

NASA NTRS1985

Development and testing of tip devices for horizontal axis wind turbines

A theoretical and field experimental program has been carried out to investigate the use of tip devices on horizontal axis wind turbine rotors. The objective was to improve performance by the reduction of tip losses. While power output can always be increased by a simple radial tip extension, such a modification also results in an increased gale load both because of the extra projected area and longer moment arm. Tip devices have the potential to increase power output without such a structural penalty. A vortex lattice computer model was used to optimize three basic tip configuration types for a 25 kW stall limited commercial wind turbine. The types were a change in tip planform, and a single-element and double-element nonplanar tip extension (winglets). A complete data acquisition system was developed which recorded three wind speed components, ambient pressure, temperature, and turbine output. The system operated unattended and could perform real-time processing of the data, displaying the measured power curve as data accumulated in either a bin sort mode or polynomial curve fit. Approximately 270 hr of perormance data were collected over a three-month period. The sampling interval was 2.4 sec; thrus over 400,000 raw data points were logged. Results for each of the three new tip devices, compared with the original tip, showed a small decrease (of the order of 1 kW) in power output over the measured range of wind speeds from cut-in at about 4 m/s to over 20 m/s, well into the stall limiting region. Changes in orientation and angle-of-attack of the winglets were not made. For aircraft wing tip devices, favorable tip shapes have been reported and it is likely that the tip devices tested in this program did not improve rotor performance because they were not optimally adjusted.

Gyatt, G. W.↗

NASA NTRS1986

Theoretical and material studies on thin-film electroluminescent devices

Electroluminescent materials and device technology were assessed. The evaluation strongly suggests the need for a comprehensive theoretical and experimental study of both materials and device structures, particularly in the following areas: carrier generation and multiplication; radiative and nonradiative processes of luminescent centers; device modeling; new device concepts; and single crystal materials growth and characterization. Modeling of transport properties of hot electrons in ZnSe and the generation of device concepts were initiated.

Summers, C. J.↗

NASA NTRS1986

A class of optically controlled millimeter wave devices

Three specific devices were investigated: the sheet resistance device, the Schottky-barrier diode and the PIN diode. Several sheet resistance devices were fabricated and tested. Based on the encouraging results from these devices, a mask was designed and sent to a vendor and is expected to be received very soon. A set of masks for fabricating transparent cathode Schottky-barrier diodes was designed. These masks were given to NASA Goddard Space Flight Center for fabrication of the diodes. A mask set was designed to fabricate PIN diodes with transparent electrodes. With slight modifications, the same mask set also can be used to fabricate other devices, such as MESFET and the IMPATT diode.

Chowdhary, R.↗

NASA NTRS1987

Detection of radio-frequency modulated optical signals by two and three terminal microwave devices

An interdigitated photoconductor (two terminal device) on GaAlAs/GaAs heterostructure was fabricated and tested by an electro-optical sampling technique. Further, the photoresponse of GaAlAs/GaAs HEMT (three terminal device) was obtained by illuminating the device with an optical signal modulated up to 8 GHz. Gain-bandwidth product, response time, and noise properties of photoconductor and HEMT devices were obtained. Monolithic integration of these photodetectors with GaAs microwave devices for optically controlled phased array antenna applications is discussed.

Bhasin, K. B.↗

NASA NTRS1987

CONFIG: Qualitative simulation tool for analyzing behavior of engineering devices

To design failure management expert systems, engineers mentally analyze the effects of failures and procedures as they propagate through device configurations. CONFIG is a generic device modeling tool for use in discrete event simulation, to support such analyses. CONFIG permits graphical modeling of device configurations and qualitative specification of local operating modes of device components. Computation requirements are reduced by focussing the level of component description on operating modes and failure modes, and specifying qualitative ranges of variables relative to mode transition boundaries. Simulation processing occurs only when modes change or variables cross qualitative boundaries. Device models are built graphically, using components from libraries. Components are connected at ports by graphical relations that define data flow. The core of a component model is its state transition diagram, which specifies modes of operation and transitions among them.

Malin, Jane T.↗

NASA NTRS1988

Application of copper-carbon fiber composites to power semiconductor devices

Copper-carbon composite electrodes are used in a series of power semiconductor devices, i.e., resin molded diodes, button-type diodes, stud-type diodes, power modules, and integrated circuit igniter modules. The properties of these power semiconductor devices compare favorably with those conventional devices using Mo or W electrodes. In thermal fatigue tests, no degradation in the electrical and mechanical characteristics of these devices are observed. The new composite electrode with carbon fibers satisfies all of the major requirements for the electrodes in power semiconductor devices.

Kuniya, Keiichi↗

NASA NTRS1986

A dual plate thermoplastic recording device for holographic interferometry

The development of a dual plate holographic interferometer using thermoplastic recording devices is described. The operational characteristics of the thermoplastic devices are investigated and optimized for fringe contrast and signal-to-noise ratio. The dual plate device was demonstrated in a transonic wind tunnel at NASA Ames Research Center. The interferograms derived from the thermoplastic device are compared with those derived from conventional photographic emulsions. The fringe contrast achieved with the optimized thermoplastic device is equivalent to the contrast achieved with conventional techniques.

Umstatter, Holly L.↗

NASA NTRS1987

Detection of radio-frequency modulated optical signals by two and three terminal microwave devices

Bhasin, K. B.↗

NASA NTRS1990

Solid-state reprogrammable analog resistive devices for electronic neural networks

The fabrication and performance of WO3-based, solid-state, three-terminal device configurations as programmable analog memory elements are reported. These transistorlike device structures exhibit good resistance progammability with a remarkable resolution of a few percent of the resistive strength over a four orders of magnitude dynamic range. The most critical component of these devices is an insulating layer between the active WO3 and the cation donor layer. The progamming characteristics and operation mechanisms of the device are described, and probable reaction mechanisms critical to the device stability are discussed.

Ramesham, R.↗

NASA NTRS1990

X ray sensitive area detection device

A radiation sensitive area detection device is disclosed which comprises a phosphor-containing film capable of receiving and storing an image formed by a pattern of incoming x rays, UV, or other radiation falling on the film. The device is capable of fluorescing in response to stimulation by a light source in a manner directly proportional to the stored radiation pattern. The device includes: (1) a light source capable of projecting light or other appropriate electromagnetic wave on the film so as to cause it to fluoresce; (2) a means to focus the fluoresced light coming from the phosphor-containing film after light stimulation; and (3) at least one charged coupled detector or other detecting element capable of receiving and digitizing the pattern of fluoresced light coming from the phosphor-containing film. The device will be able to generate superior x ray images of high resolution from a crystal or other sample and will be particularly advantageous in that instantaneous near-real-time images of rapidly deteriorating samples can be obtained. Furthermore, the device can be made compact and sturdy, thus capable of carrying out x ray or other radiation imaging under a variety of conditions, including those experienced in space.

Carter, Daniel C.↗

NASA NTRS1991

Silicon device performance measurements to support temperature range enhancement

Semiconductor power devices are typically rated for operation below 150 C. Little data is known for power semiconductors over 150 C. In most cases, the device is derated to zero operating power at 175 C. At the high temperature end of the temperature range, the intrinsic carrier concentration increases to equal the doping concentration level and the silicon behaves as an intrinsic semiconductor. The increase in intrinsic carrier concentration results in a shift of the Fermi level toward mid-bandgap at elevated temperatures. This produces a shift in devices characteristics as a function of temperature. By increasing the doping concentration higher operating temperatures can be achieved. This technique was used to fabricate low power analog and digital devices in silicon with junction operating temperatures in excess of 300 C. Additional temperature effects include increased p-n junction leakage with increasing temperature, resulting in increased resistivity. The temperature dependency of physical properties results in variations in device characteristics. These must be quantified and understood in order to develop extended temperature range operation.

Bromstead, James↗

NASA NTRS1990

Heat tube device

The present invention discloses a heat tube device through which a working fluid can be circulated to transfer heat to air in a conventional air conditioning system. The heat tube device is disposable about a conventional cooling coil of the air conditioning system and includes a plurality of substantially U-shaped tubes connected to a support structure. The support structure includes members for allowing the heat tube device to be readily positioned about the cooling coil. An actuatable adjustment device is connected to the U-shaped tubes for allowing, upon actuation thereof, for the heat tubes to be simultaneously rotated relative to the cooling coil for allowing the heat transfer from the heat tube device to air in the air conditioning system to be selectively varied.

Khattar, Mukesh K.↗