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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS2007

Mobile Collection and Automated Interpretation of EEG Data

A system that would comprise mobile and stationary electronic hardware and software subsystems has been proposed for collection and automated interpretation of electroencephalographic (EEG) data from subjects in everyday activities in a variety of environments. By enabling collection of EEG data from mobile subjects engaged in ordinary activities (in contradistinction to collection from immobilized subjects in clinical settings), the system would expand the range of options and capabilities for performing diagnoses. Each subject would be equipped with one of the mobile subsystems, which would include a helmet that would hold floating electrodes (see figure) in those positions on the patient s head that are required in classical EEG data-collection techniques. A bundle of wires would couple the EEG signals from the electrodes to a multi-channel transmitter also located in the helmet. Electronic circuitry in the helmet transmitter would digitize the EEG signals and transmit the resulting data via a multidirectional RF patch antenna to a remote location. At the remote location, the subject s EEG data would be processed and stored in a database that would be auto-administered by a newly designed relational database management system (RDBMS). In this RDBMS, in nearly real time, the newly stored data would be subjected to automated interpretation that would involve comparison with other EEG data and concomitant peer-reviewed diagnoses stored in international brain data bases administered by other similar RDBMSs.

Mintz, Frederick↗
NASA NTRS2010

Electrical Capacitance Volume Tomography with High-Contrast Dielectrics

The Electrical Capacitance Volume Tomography (ECVT) system has been designed to complement the tools created to sense the presence of water in nonconductive spacecraft materials, by helping to not only find the approximate location of moisture but also its quantity and depth. The ECVT system has been created for use with a new image reconstruction algorithm capable of imaging high-contrast dielectric distributions. Rather than relying solely on mutual capacitance readings as is done in traditional electrical capacitance tomography applications, this method reconstructs high-resolution images using only the self-capacitance measurements. The image reconstruction method assumes that the material under inspection consists of a binary dielectric distribution, with either a high relative dielectric value representing the water or a low dielectric value for the background material. By constraining the unknown dielectric material to one of two values, the inverse math problem that must be solved to generate the image is no longer ill-determined. The image resolution becomes limited only by the accuracy and resolution of the measurement circuitry. Images were reconstructed using this method with both synthetic and real data acquired using an aluminum structure inserted at different positions within the sensing region. The cuboid geometry of the system has two parallel planes of 16 conductors arranged in a 4 4 pattern. The electrode geometry consists of parallel planes of copper conductors, connected through custom-built switch electronics, to a commercially available capacitance to digital converter. The figure shows two 4 4 arrays of electrodes milled from square sections of copper-clad circuit-board material and mounted on two pieces of glass-filled plastic backing, which were cut to approximately square shapes, 10 cm on a side. Each electrode is placed on 2.0-cm centers. The parallel arrays were mounted with the electrode arrays approximately 3 cm apart. The open ends were surrounded by a metal guard to reduce the sensitivity of the electrodes to outside interference and to help maintain the spacing between the arrays. Other uses for this innovation potentially include quantifying the amount of commodity remaining in the fuel and oxidizer tanks while on-orbit without having to fire spacecraft engines. Another orbit application is moisture sensing in plant-growth experiments because microgravity causes moisture in soil to distribute itself in unusual ways. At the moment, the hardware and image reconstruction technique may only be of interest to people involved in nondestructive evaluation. The reconstructed image takes almost a full week to reproduce with existing computer power. However, because computer power and speeds follows Moore s Law, execution times are likely to become acceptable within the next five to eight years. The code was written in Mathematica for dedicated use with the ECVT system. In its present form, it is not suitable to be used directly as a consumer product. However, the code could be likely improved by rewriting it in a compiled language such as C or Fortran.

Nurge, Mark↗
NASA NTRS2012

In-Flight Boundary-Layer Transition on a Large Flat Plate at Supersonic Speeds

A flight experiment was conducted to investigate the pressure distribution, local flow conditions, and boundary-layer transition characteristics on a large flat plate in flight at supersonic speeds up to Mach 2.0. The primary objective of the test was to characterize the local flow field in preparation for future tests of a high Reynolds number natural laminar flow test article. The tests used a F-15B testbed aircraft with a bottom centerline mounted test fixture. A second objective was to determine the boundary-layer transition characteristics on the flat plate and the effectiveness of using a simplified surface coating for future laminar flow flight tests employing infrared thermography. Boundary-layer transition was captured using an onboard infrared imaging system. The infrared imagery was captured in both analog and digital formats. Surface pressures were measured with electronically scanned pressure modules connected to 60 surface-mounted pressure orifices. The local flow field was measured with five 5-hole conical probes mounted near the leading edge of the test fixture. Flow field measurements revealed the local flow characteristics including downwash, sidewash, and local Mach number. Results also indicated that the simplified surface coating did not provide sufficient insulation from the metallic structure, which likely had a substantial effect on boundary-layer transition compared with that of an adiabatic surface. Cold wall conditions were predominant during the acceleration to maximum Mach number, and warm wall conditions were evident during the subsequent deceleration. The infrared imaging system was able to capture shock wave impingement on the surface of the flat plate in addition to indicating laminar-to-turbulent boundary-layer transition.

Banks, Daniel W.↗
NASA NTRS2002

Preliminary Design and Evaluation of Portable Electronic Flight Progress Strips

There has been growing interest in using electronic alternatives to the paper Flight Progress Strip (FPS) for air traffic control. However, most research has been centered on radar-based control environments, and has not considered the unique operational needs of the airport air traffic control tower. Based on an analysis of the human factors issues for control tower Decision Support Tool (DST) interfaces, a requirement has been identified for an interaction mechanism which replicates the advantages of the paper FPS (e.g., head-up operation, portability) but also enables input and output with DSTs. An approach has been developed which uses a Portable Electronic FPS that has attributes of both a paper strip and an electronic strip. The prototype flight strip system uses Personal Digital Assistants (PDAs) to replace individual paper strips in addition to a central management interface which is displayed on a desktop computer. Each PDA is connected to the management interface via a wireless local area network. The Portable Electronic FPSs replicate the core functionality of paper flight strips and have additional features which provide a heads-up interface to a DST. A departure DST is used as a motivating example. The central management interface is used for aircraft scheduling and sequencing and provides an overview of airport departure operations. This paper will present the design of the Portable Electronic FPS system as well as preliminary evaluation results.

Doble, Nathan A.↗
NASA NTRS1980

Mark 3 wideband digital recorder in perspective

The tape recorder used for the Mark 3 data acquisition and processing system is compared with earlier very long baseline interferometry recorders. Wideband 33-1/3 kbpi digital channel characteristics of instrumentation recorders and of a modern video cassette recorder are illustrated. Factors which influenced selection of the three major commercial components (transport, heads, and tape) are discussed. A brief functional description and the reasons for development of efficient signal electronics and necessary auxiliary control electronics are given. The design and operation of a digital bit synchronizer is illustrated as an example of the high degree of simplicity achieved.

Hinteregger, H. F.↗
NASA NTRS2010

Transition in Gas Turbine Control System Architecture: Modular, Distributed, and Embedded

Controls systems are an increasingly important component of turbine-engine system technology. However, as engines become more capable, the control system itself becomes ever more constrained by the inherent environmental conditions of the engine; a relationship forced by the continued reliance on commercial electronics technology. A revolutionary change in the architecture of turbine-engine control systems will change this paradigm and result in fully distributed engine control systems. Initially, the revolution will begin with the physical decoupling of the control law processor from the hostile engine environment using a digital communications network and engine-mounted high temperature electronics requiring little or no thermal control. The vision for the evolution of distributed control capability from this initial implementation to fully distributed and embedded control is described in a roadmap and implementation plan. The development of this plan is the result of discussions with government and industry stakeholders

Culley, Dennis↗
NASA NTRS1991

Compensated digital readout family

ISC has completed test on an IC which has 32 channels of amplifiers, low pass anti-aliasing filters, 13-bit analog-to-digital (A/D) converters with non-uniformity correction per channel and a digital multiplexer. The single slope class of A/D conversion is described, as are the unique variations required for incorporation of this technique for use with on-focal plane detector readout electronics. This paper describes the architecture used to implement the digital on-focal plane signal processing functions. Results from measured data on a test IC are presented for a circuit containing these functions operating at a sensor frame rate of 1000 hertz.

Ludwig, David E.↗
NASA NTRS1995

Ozone absorption spectroscopy in search of low-lying electronic states

A spectrometer capable of detecting ozone absorption features 9 orders of magnitude weaker than the Hartley band has been employed to investigate the molecule's near-infrared absorption spectrum. At this sensitivity a wealth of information on the low-lying electronically excited states often believed to play a role in atmospheric chemistry is available in the form of vibrational and rotational structure. We have analyzed these spectra using a combination of digital filtering and isotope substitution and find evidence for three electronically excited states below 1.5 eV. The lowest of these states is metastable, bound by approximately 0.1 eV and probably the (3)A2 rather than the (3)B2 state. Its adiabatic electronic energy is 1.24 +/- 0.01 eV, slightly above the dissociation energy of the ground state. Two higher states, at 1.29 +/- 0.03 and 1.48 +/- 0.03 eV are identified as the (3)B2 and the (3)B1, respectively. Combined with other recent theoretical and experimental data on the low-lying electronic states of ozone, these results imply that these are, in fact, the lowest three excited states; that is, there are no electronically excited states of ozone lying below the energy of O(3P) + O2((3)Sigma(-), v = 0). Some of the implications for atmospheric chemistry are considered.

Anderson, S. M.↗
NASA NTRS1994

Optoelectronic Receiver For Communication And Control

Many operational and diagnostic features integrated into circuit chip. GaAs-based integrated circuit designed to serve as optoelectronic interface in phased-array antenna. Intended function to receive digital control signals transmitted on optical fiber and to convert signals to electronic control signals, which then applied to monolithic microwave integrated circuit (MMIC). Also used in reception of high-rate optical digital communications within computers, between computers, and in signal-distribution systems in aircraft, automobiles, and ships. Interface circuit represents significant improvement over preexisting interface circuits in that its clock-signal-recovery subcircuit requires little or no preamble for immediate synchronization.

Kunath, Richard↗
NASA NTRS2003

A Radar/Radiometer Instrument for Mapping Soil Moisture and Ocean Salinity

The RadSTAR instrument combines an L-band, digital beam-forming radar with an L-band synthetic aperture, thinned array (STAR) radiometer. The RadSTAR development will support NASA Earth science goals by developing a novel, L-band scatterometer/ radiometer that measures Earth surface bulk material properties (surface emissions and backscatter) as well as surface characteristics (backscatter). Present, real aperture airborne L-Band active/passive measurement systems such as the JPUPALS (Wilson, et al, 2000) provide excellent sampling characteristics, but have no scanning capabilities, and are extremely large; the huge JPUPALS horn requires a the C-130 airborne platform, operated with the aft loading door open during flight operation. The approach used for the upcoming Aquarius ocean salinity mission or the proposed Hydros soil mission use real apertures with multiple fixed beams or scanning beams. For real aperture instruments, there is no upgrade path to scanning over a broad swath, except rotation of the whole aperture, which is an approach with obvious difficulties as aperture size increases. RadSTAR will provide polarimetric scatterometer and radiometer measurements over a wide swath, in a highly space-efficient configuration. The electronic scanning approaches provided through STAR technology and digital beam forming will enable the large L-band aperture to scan efficiently over a very wide swath. RadSTAR technology development, which merges an interferometric radiometer with a digital beam forming scatterometer, is an important step in the path to space for an L-band scatterometer/radiometer. RadSTAR couples a patch array antenna with a 1.26 GHz digital beam forming radar scatterometer and a 1.4 GHz STAR radiometer to provide Earth surface backscatter and emission measurements in a compact, cross-track scanning instrument with no moving parts. This technology will provide the first L-band, emission and backscatter measurements in a compact aircraft instrument and will be ideally suited to large apertures, possibly at GEO, and could possibly be implemented on a swarm of micro-satellites. This instrument will have wide application for validation studies, and will have application for other microwave frequencies.

Hildebrand, Peter H.↗
NASA NTRS1987

Properties of low-energy electron precipitation in the cleft during periods of unusually high ambient electron temperatures

A recently developed automated fitting procedure for Dynamics Explorer 2 electron energy spectra represents each auroral electron spectrum as a superposition of several Maxwellian and several Gaussian components. The fitting parameters give a digital representation which uniquely describes each spectrum. It is shown that unusually high ambient electron temperatures (of the order of 10,000 K) in the cleft are strongly correlated with the intensity parameters of the lowest-temperature Maxwellian components of the precipitation. The collisional heat input into the ambient electrons by these Maxwellian components of the precipitation fluxes is shown to be more than an order of magnitude higher in the high-temperature storm time cases than it is in a control set of 'normal temperature' quiet time cases. The heating effect of the solar flux is shown to be nearly the same for both sets of cases. As a result it is concluded that electron precipitation is the chief mechanism responsible for those high ambient temperatures.

Fontheim, Ernest G.↗
NASA NTRS1982

Electronically Calibratable Clock

Calibration circuit corrects apparent clock rate (ACR) of digital clock without altering oscillator frequency. Calibration circuit does not require iterative adjustments to reference frequency or rate, and correction to ACR is controlled by pushbuttons. Technique is applicable to any timer or counter that counts up to predetermined number then outputs a pulse to a readout register or to control another device.

Davidson, J. R.↗
NASA NTRS1995

CMOS Image Sensors: Electronic Camera On A Chip

Recent advancements in CMOS image sensor technology are reviewed, including both passive pixel sensors and active pixel sensors. On- chip analog to digital converters and on-chip timing and control circuits permit realization of an electronic camera-on-a-chip. Highly miniaturized imaging systems based on CMOS image sensor technology are emerging as a competitor to charge-coupled devices for low cost uses.

Space Microelectronics Image Sensors APS Digital I↗
NASA NTRS1993

Solar Anomalous and Magnetospheric Particle Explorer attitude control electronics box design and performance

The attitude Control Electronics (ACE) Box is the center of the Attitude Control Subsystem (ACS) for the Solar Anomalous and Magnetospheric Particle Explorer (SAMPEX) satellite. This unit is the single point interface for all of the Attitude Control Subsystem (ACS) related sensors and actuators. Commands and telemetry between the SAMPEX flight computer and the ACE Box are routed via a MIL-STD-1773 bus interface, through the use of an 80C85 processor. The ACE Box consists of the flowing electronic elements: power supply, momentum wheel driver, electromagnet driver, coarse sun sensor interface, digital sun sensor interface, magnetometer interface, and satellite computer interface. In addition, the ACE Box also contains an independent Safehold electronics package capable of keeping the satellite pitch axis pointing towards the sun. The ACE Box has dimensions of 24 x 31 x 8 cm, a mass of 4.3 kg, and an average power consumption of 10.5 W. This set of electronics was completely designed, developed, integrated, and tested by personnel at NASA GSFC. SAMPEX was launched on July 3, 1992, and the initial attitude acquisition was successfully accomplished via the analog Safehold electronics in the ACE Box. This acquisition scenario removed the excess body rates via magnetic control and precessed the satellite pitch axis to within 10 deg of the sun line. The performance of the SAMPEX ACS in general and the ACE Box in particular has been quite satisfactory.

Chamberlin, K.↗
NASA NTRS1995

Electronic Photography

The main objective was to assist in the production of electronic images in the Electronic Photography Lab (EPL). The EPL is a new facility serving the electronic photographic needs of the Langley community. The purpose of the Electronic Photography lab is to provide Langley with access to digital imaging technology. Although the EPL has been in operation for less than one year, almost 1,000 images have been produced. The decision to establish the lab was made after careful determination of the centers needs for electronic photography. The LaRC community requires electronic photography for the production of electronic printing, Web sites, desktop publications, and its increased enhancement capabilities. In addition to general use, other considerations went into the planning of the EPL. For example, electronic photography is much less of a burden on the environment compared to conventional photography. Also, the possibilities of an on-line database and retrieval system could make locating past work more efficient. Finally, information in an electronic image is quantified, making measurements and calculations easier for the researcher.

Payne, Meredith Lindsay↗