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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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Study consisted of an analytical approach, in which a mathematical model of existing printed circuit board component mounting techniques was analyzed, and an empirical investigation was performed to determine the extent of damage caused by temperature cycling of the printed circuit boards.
Lower bound for time required for group multiplication by logic circuits, using modified Winograd model for Abelian group
Studies were conducted to develop a real-time Arctic ice type identification system. Data obtained by NASA Mission 126, conducted at Pt. Barrow, Alaska (Site 93) in April 1970 was analyzed in detail to more clearly define the major mechanisms at work affecting the radar energy illuminating a terrain cell of sea ice. General techniques for reduction of the scatterometer data to a form suitable for application of ice type decision criteria were investigated, and the electronic circuit requirements for implementation of these techniques were determined. Also, consideration of circuit requirements are extended to include the electronics necessary for analog programming of ice type decision algorithms. After completing the basic circuit designs a laboratory model was constructed and a preliminary evaluation performed. Several system modifications for improved performance are suggested. (Modified author abstract)
Shuttle LRU (Line Replaceable Unit) Analysis Program (SLAP) aids in evaluation of LRU interface voltages in Shuttle orbiter electrical system. Slap includes reduced model of Shuttle LRU circuit. Although primarily intended for analysis of Shuttle LRU's SLAP could be adapted for voltage analysis in other situations.
A detailed experimental investigation of single-event upset (SEU) in static RAM (SRAM) chips fabricated using a family of high-performance NMOS (HMOS) depletion-mode-load process technologies, has been done. Empirical SEU models have been developed with the aid of heavy-ion data obtained with a three-stage tandem van de Graaff accelerator. The results of this work demonstrate a method by which SEU may be empirically modeled in NMOS integrated circuits.
In view of the potential impact of power electronics on power systems, there is need for a computer modeling/analysis tool to perform simulation studies on power systems with power electronic components as well as to educate engineering students about such systems. The modeling of the major power electronic components of the NASA Space Station Freedom Electric Power System is described along with ElectroMagnetic Transients Program (EMTP) and it is demonstrated that EMTP can serve as a very useful tool for teaching, design, analysis, and research in the area of power systems with power electronic components. EMTP modeling of power electronic circuits is described and simulation results are presented.
One of the major hurdles to developing a better understanding of the environmentally induced interactions in spacecraft systems (spacecraft charging) is the lack of simple tools to analyze the behavior of the spacecraft in a sub-storm environment. The available tool, NASA Charging Analyzer Program (NASCAP), is expensive to use and treats only half of the problem - surface effects only. In response to this need, we have developed, under our IRAD Program, a set of engineering tools that operate on personal computers and addresses both the surface and bulk charging aspects of the interactions. These engineering codes utilize circuit analysis techniques and model simplifications to allow rapid computations. The codes were compared to both NASCAP predictions and to bulk charging data with excellent agreement for both phenomena. The models used in our engineering codes are shown, and in the engineering codes, the models are defined in terms of plates or triangles in an unconfined space. The predictions are based upon current balances to each plate. The code has routines to allow interactions between the plates to simulate 'barrier' effects. The agreement for the predicted differential surface voltages for the model is given. In conducting the comparison of engineering codes to NASCAP predictions, it was found that some inconsistencies existed in the NASCAP code that are not obvious to the user. The use of the grid imposes constraints that voltage gradients exist between the grid points. This allows the existence of voltage gradients in conductors and influences surface resistivity predictions. These points are discussed along with the predictions for treating these inconsistencies properly. The model predictions for a variable intensity substorm is also presented.
A method is presented for simulating the coupled 'electromechanical' system to predict rotordynamic stability and unbalance response along with control system stability. The piezoelectric actuators and their amplifiers are represented as equivalent linear electrical circuits. The electromechanical system modeling approach is utilized to correlate test results from a double overhung rotor rig. The test results also show the effectiveness of the control system for suppressing the unbalance response of two modes using active stiffness and active damping.
A simple parameterization has been developed to simulate global lightning distributions. Convective cloud top height is used as the variable in the parameterization, with different formulations for continental and marine thunderstorms. The parameterization has been validated using two lightning data sets: one global and one regional. In both cases the simulated lightning distributions and frequencies are in very good agreement with the observed lightning data. This parameterization could be used for global studies of lightning climatology; the earth's electric circuit; in general circulation models for modeling global lightning activity, atmospheric NO(x) concentrations, and perhaps forest fire distributions for both the present and future climate; and, possibly, even as a short-term forecasting aid.
The integration of modern CAD tools with formal verification environments require translation from hardware description language to verification logic. A signal representation including both unknown state and a degree of strength indeterminacy is essential for the correct modeling of many VLSI circuit designs. A higher-order logic theory of indeterministic logic signals is presented.
We have designed, fabricated, and tested several novel microstrip-base YBa2Cu3O7-delta/SrTiO3/LaAlO3 (YBCO/STO/LAO) and Au/SrTiO3ALO3 (Au/STO/LAO) phase shifters. The first design consists of eight coupled microstrip phase shifters (CMPS) in series. This design using YBCO achieved a relative insertion phase shift (Delta f) of 484 degrees with a figure of merit of 80 degrees/dB at Vdc = 375 V, 16 GHz, and 40 K. A Delta f of 290 degrees was observed while maintaining the insertion loss below 4.5 dB. At 77 K, a Delta of 420 degrees was obtained for this phase shifter at the same bias and frequency. Both results correspond to an effective coupling length of 0.33 cm. A second compact design, consisting of an Au meander line and a CMPS section was also tested. Of the two samples tested, the best showed a figure of merit of 43 degrees/dB with Delta f = 290 degrees and 6.8 dB loss, at 40 K, 10 GHz and 400 V. Experimental and modeling results on these circuits will be discussed in the context of potential applications.
Bridge faults, especially in CMOS circuits, have unique characteristics which make them difficult to detect during testing. This paper presents a technique for detecting bridge faults which have an effect on the output of CMOS Domino logic circuits. The faults are modeled at the transistor level and this technique is based on analyzing the off-set of the function during off-line testing.
We hypothesized that an electric field (inductance) produced by charged blood components passing through the many branches of arteries and veins could assess total blood volume (TBV) or plasma volume (PV). Individual (N = 29) electrical circuits (inductors, two resistors, and a capacitor) were determined from bioelectrical response spectroscopy (BERS) using a Hewlett Packard 4284A Precision LCR Meter. Inductance, capacitance, and resistance from the circuits of 19 subjects modeled TBV (sum of PV and computed red cell volume) and PV (based on 125I-albumin). Each model (N = 10, cross validation group) had good validity based on 1) mean differences (-2.3 to 1.5%) between the methods that were not significant and less than the propagated errors (+/- 5.2% for TBV and PV), 2) high correlations (r > 0.92) with low SEE (< 7.7%) between dilution and BERS assessments, and 3) Bland-Altman pairwise comparisons that indicated "clinical equivalency" between the methods. Given the limitation of this study (10 validity subjects), we concluded that BERS models accurately assessed TBV and PV. Further evaluations of the models' validities are needed before they are used in clinical or research settings.
Modern aircraft rely heavily on dependable operation of many safety-critical software components. Despite careful design, verification and validation (V&V), on-board software can fail with disastrous consequences if it encounters problematic software/hardware interaction or must operate in an unexpected environment. We are using a Bayesian approach to monitor the software and its behavior during operation and provide up-to-date information about the health of the software and its components. The powerful reasoning mechanism provided by our model-based Bayesian approach makes reliable diagnosis of the root causes possible and minimizes the number of false alarms. Compilation of the Bayesian model into compact arithmetic circuits makes SWHM feasible even on platforms with limited CPU power. We show initial results of SWHM on a small simulator of an embedded aircraft software system, where software and sensor faults can be injected.
DNA is an ideal template for a biological nanowire-it has a linear structure several atoms thick; it possesses addressable nucleobase geometry that can be precisely defined; and it is massively scalable into branched networks. Until now, the drawback of DNA as a conducting nanowire been, simply put, its low conductance. To address this deficiency, we extensively characterize a chemical variant of canonical DNA that exploits the affinity of natural cytosine bases for silver ions. We successfully construct chains of single silver ions inside double-stranded DNA, confirm the basic dC-Ag+-dC bond geometry and kinetics, and show length-tunability dependent on mismatch distribution, ion availability and enzyme activity. An analysis of the absorbance spectra of natural DNA and silver-binding, poly-cytosine DNA demonstrates the heightened thermostability of the ion chain and its resistance to aqueous stresses such as precipitation, dialysis and forced reduction. These chemically critical traits lend themselves to an increase in electrical conductivity of over an order of magnitude for 11-base silver-paired duplexes over natural strands when assayed by STM break junction. We further construct and implement a genetic pathway in the E. coli bacterium for the biosynthesis of highly ionizable DNA sequences. Toward future circuits, we construct a model of transcription network architectures to determine the most efficient and robust connectivity for cell-based fabrication, and we perform sequence optimization with a genetic algorithm to identify oligonucleotides robust to changes in the base-pairing energy landscape. We propose that this system will serve as a synthetic biological fabrication platform for more complex DNA nanotechnology and nanoelectronics with applications to deep space and low resource environments.
Electrical systems with high power and high power density are integral to many aerospace and energy applications. These systems, enabled by power electronics with wide bandgap semiconductor devices, require management of both efficiency/thermal aspects and electromagnetic interference that are problems specific to high power and high frequency applications, respectively. In addition to advanced active components, these applications also require passive components (inductors, capacitors, conductors) capable of operation under challenging conditions. This work surveys the state of the art of magnetic components and soft magnetic materials used as inductive cores. The wide variety of motor and converter topologies translates to a variety of requirements in the magnetics including mechanical properties, permeabilities, and frequency response. The scaling impact of material properties will be surveyed with respect to component performance and sizing, using both data from experiment and the published literature. Variations on simulations, both in lumped circuits and finite element models, will also be discussed as these are important aspects of the design phase of modern power electronics.
We have demonstrated advances in mosaic hybridization that will enable very large format far-infrared detectors. Specifically we have produced electrical detector models via mosaic hybridization yielding superconducting circuit paths by hybridizing separately fabricated sub-units onto a single detector unit. The detector model was made on a 100mm diameter wafer while four model readout quadrant chips were made from a separate 100mm wafer. The individually fabricated parts were hybridized using a flip-chip bonder to assemble the detector-readout stack. Once all of the hybridized readouts were in place, a single, large and thick silicon substrate was placed on the stack and attached with permanent epoxy to provide strength and a Coefficient of Thermal Expansion match to the silicon components underneath. Wirebond pads on the readout chips connect circuits to warm readout electronics; and were used to validate the successful superconducting electrical interconnection of the model mosaic-hybrid detector. This demonstration is directly scalable to 150 mm diameter wafers, enabling pixel areas over ten times the area currently available.