SEGO - A computer code for unfolding experimental pulse-height distributions
SEGO, computer code for unfolding scintillation pulse height spectra to get incident energy spectra
Burrus, W. R.↗
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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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Binary to binary-coded-decimal converter Patent
Binary to binary-coded decimal converter using single set of logic circuits notwithstanding number of shift register decades
Imlay, E. H.↗
A system for analysis and classification of voice communications
A method for analysis and classification of verbal communications typically associated with manned space missions or simulations was developed. The study was carried out in two phases. Phase 1 was devoted to identification of crew tasks and activities which require voice communication for accomplishment or reporting. Phase 2 entailed development of a message classification system and a preliminary test of its feasibility. The classification system permits voice communications to be analyzed to three progressively more specific levels of detail and to be described in terms of message content, purpose, and the participants in the information exchange. A coding technique was devised to allow messages to be recorded by an eight-digit number.
Older, H. J.↗
Steady and unsteady transonic flow
An investigation of the transonic flow over a circular arc airfoil was conducted to obtain basic information for turbulence modeling of shock-induced separated flows and to verify numerical computer codes which are being developed to simulate such flows. The investigation included the employment of a laser velocimeter to obtain data concerning the mean velocity, the shear stress, and the turbulent kinetic energy profiles in the flowfield downstream of the airfoil midchord where the flow features are more complex. Depending on the free-stream Mach number, the flowfield developed was either steady with shock-wave-induced separation extending from the foot of the shock wave to beyond the trailing edge or unsteady with a periodic motion also undergoing shock-induced separation. The experimental data were compared with the results of numerical simulations in which a computer code was employed that solved the time-dependent Reynolds' averaged compressible Navier-Stokes equations.
Seegmiller, H. L.↗
Trophic classification of selected Colorado lakes
Multispectral scanner data, acquired over several Colorado lakes using LANDSAT-1 and aircraft, were used in conjunction with contact-sensed water quality data to determine the feasibility of assessing lacustrine trophic levels. A trophic state index was developed using contact-sensed data for several trophic indicators. Relationships between the digitally processed multispectral scanner data, several trophic indicators, and the trophic index were examined using a supervised multispectral classification technique and regression techniques. Statistically significant correlations exist between spectral bands, several of the trophic indicators and the trophic state index. Color-coded photomaps were generated which depict the spectral aspects of trophic state.
Blackwell, R. J.↗
PLASIM: A computer code for simulating charge exchange plasma propagation
The propagation of the charge exchange plasma for an electrostatic ion thruster is crucial in determining the interaction of that plasma with the associated spacecraft. A model that describes this plasma and its propagation is described, together with a computer code based on this model. The structure and calling sequence of the code, named PLASIM, is described. An explanation of the program's input and output is included, together with samples of both. The code is written in ANSI Standard FORTRAN.
Robinson, R. S.↗
Ablation of carbonaceous materials in a hydrogen-helium arc-jet flow
The stagnation-point ablation rates of a graphite, a carbon-carbon composite, and four carbon-phenolic materials are measured in an arc-jet wind tunnel with a 50% hydrogen-50% helium mixture as the test gas. Flow environments are determined through measurements of static and impact pressures, heat-transfer rates to a calorimeter, and radiation spectra, and through numerical calculation of the flow through the wind tunnel, spectra, and heat-transfer rates. The environments so determined are: impact pressure approx. 3 atm, Mach number approx. 2.1, convective heat-transfer rate approx. 14 kw/sq cm, and radiative heat-transfer rate approx. 7 kw/sq cm in the absence of ablation. Ablation rates are determined from the measured rates of mass loss and recession of the ablation specimens. Compared with the predicted ablation rates obtained by running RASLE and CMA codes, the measured rates are higher by about 15% for all tested materials.
Park, C.↗
A fast, time-accurate unsteady full potential scheme
The unsteady form of the full potential equation is solved in conservation form by an implicit method based on approximate factorization. At each time level, internal Newton iterations are performed to achieve time accuracy and computational efficiency. A local time linearization procedure is introduced to provide a good initial guess for the Newton iteration. A novel flux-biasing technique is applied to generate proper forms of the artificial viscosity to treat hyperbolic regions with shocks and sonic lines present. The wake is properly modeled by accounting not only for jumps in phi, but also for jumps in higher derivatives of phi, obtained by imposing the density to be continuous across the wake. The far field is modeled using the Riemann invariants to simulate nonreflecting boundary conditions. The resulting unsteady method performs well which, even at low reduced frequency levels of 0.1 or less, requires fewer than 100 time steps per cycle at transonic Mach numbers. The code is fully vectorized for the CRAY-XMP and the VPS-32 computers.
Shankar, V.↗
Peacekeeper tank slosh model
Information on a tank slosh model for Peacekeeper missiles is given in viewgraph form. Allowable vehicle errors for nose cone ejection clearance, vehicle maneuver sloshing problems, slosh/moment prediction, slosh surface specification, code validation, experimental model-computational model comparison and the propellant storage assembly are covered.
Schwartz, Sidney H.↗
Propfan test assessment testbed aircraft stability and control/performance 1/9-scale wind tunnel tests
One-ninth scale wind tunnel model tests of the Propfan Test Assessment (PTA) aircraft were performed in three different NASA facilities. Wing and propfan nacelle static pressures, model forces and moments, and flow field at the propfan plane were measured in these tests. Tests started in June 1985 and were completed in January 1987. These data were needed to assure PTA safety of flight, predict PTA performance, and validate analytical codes that will be used to predict flow fields in which the propfan will operate.
Little, B. H., Jr.↗
Old and new observations of V523 Saggitarii
The history of V523 Sgr is reviewed. New photoelectric timings of minimum light are used to improve the period of apsidal rotation and the orbital eccentricity. UBV photometry indicates that the mean spectral type is F0, and not A5. Blue and yellow light curves described here are the first photelectric ones ever obtained. Within satisfactory limits, the light curves have been solved for consistent stellar parameters with the code EBOP. With significant qualifications, a mean value of the stellar structural constant is given.
Koch, Robert H.↗
Thermodynamic and fluid mechanic analysis of rapid pressurization in a dead-end tube
Three models have been applied to very rapid compression of oxygen in a dead-ended tube. Pressures as high as 41 MPa (6000 psi) leading to peak temperatures of 1400 K are predicted. These temperatures are well in excess of the autoignition temperature (750 K) of teflon, a frequently used material for lining hoses employed in oxygen service. These findings are in accord with experiments that have resulted in ignition and combustion of the teflon, leading to the combustion of the stainless steel braiding and catastrophic failure. The system analyzed was representative of a capped off-high-pressure oxygen line, which could be part of a larger system. Pressurization of the larger system would lead to compression in the dead-end line, and possible ignition of the teflon liner. The model consists of a large plenum containing oxygen at the desired pressure (500 to 6000 psi). The plenum is connected via a fast acting valve to a stainless steel tube 2 cm inside diameter. Opening times are on the order of 15 ms. Downstream of the valve is an orifice sized to increase filling times to around 100 ms. The total length from the valve to the dead-end is 150 cm. The distance from the valve to the orifice is 95 cm. The models describe the fluid mechanics and thermodynamics of the flow, and do not include any combustion phenomena. A purely thermodynamic model assumes filling to be complete upstream of the orifice before any gas passes through the orifice. This simplification is reasonable based on experiment and computer modeling. Results show that peak temperatures as high as 4800 K can result from recompression of the gas after expanding through the orifice. An approximate transient model without an orifice was developed assuming an isentropic compression process. An analytical solution was obtained. Results indicated that fill times can be considerably shorter than valve opening times. The third model was a finite difference, 1-D transient compressible flow model. Results from the code show the recompression effect but predict much lower peak temperatures than the thermodynamic model.
Leslie, Ian H.↗
Statistical properties of ideal three-dimensional magnetohydrodynamics
Classical Gibbs ensemble methods are used to study the spectral structure of three-dimensional ideal MHD in periodic geometry. In this paper the equilibrium ensemble incorporates constraints of total energy, magnetic helicity, and cross helicity. Several new results are proven for ensemble averages, including the constraint that magnetic energy equal or exceed kinetic energy, and that cross helicity represents a constant fraction of magnetic energy across the spectral domain, for arbitrary size systems. Two zero-temperature limits are considered in detail, emphasizing the role of complete and partial condensaiton of spectral quantities to the longest wavelength states. The ensemble predictions are compared to direct numerical solution using a low-order truncation Galerkin spectral code. Implications for spectral transfer of nonequilibrium, dissipative turbulent MHD systems are discussed.
Stribling, T.↗
CFD Simulations Of Sonic Booms In Near And Mid Fields
Report discusses computational fluid dynamics (CFD) to simulate generation and propagation of sonic booms in near- and mid-field regions of supersonic flows about simplified bodies representative of advanced airplanes. Parabolized Navier-Stokes equations integrated by implicit, approximate-factorization, finite-volume algorithm in which crossflow inviscid fluxes evaluated by Roe's flux-difference-splitting scheme. Near-field solutions obtained by applying algorithm to flows immediately surrounding bodies. Solutions transferred to computer codes based on Whitham"s F-function theory for extrapolation to far-field.
Cheung, Samson H.↗
Gamma-ray spectroscopy: The diffuse galactic glow
The goal of this project is the development of a numerical code that provides statistical models of the sky distribution of gamma-ray lines due to the production of radioactive isotopes by ongoing Galactic nucleosynthesis. We are particularly interested in quasi-steady emission from novae, supernovae, and stellar winds, but continuum radiation and transient sources must also be considered. We have made significant progress during the first half period of this project and expect the timely completion of a code that can be applied to Oriented Scintillation Spectrometer Experiment (OSSE) Galactic plane survey data.
Hartmann, Dieter H.↗
The development of a program analysis environment for Ada: Reverse engineering tools for Ada
The Graphical Representations of Algorithms, Structures, and Processes for Ada (GRASP/Ada) has successfully created and prototyped a new algorithm level graphical representation for Ada software, the Control Structure Diagram (CSD). The primary impetus for creation of the CSD was to improve the comprehension efficiency of Ada software and thus improve reliability and reduce costs. The emphasis was on the automatic generation of the CSD from Ada source code to support reverse engineering and maintenance. The CSD has the potential to replace traditional prettyprinted Ada source code. In Phase 1 of the GRASP/Ada project, the CSD graphical constructs were created and applied manually to several small Ada programs. A prototype (Version 1) was designed and implemented using FLEX and BISON running under the Virtual Memory System (VMS) on a VAX 11-780. In Phase 2, the prototype was improved and ported to the Sun 4 platform under UNIX. A user interface was designed and partially implemented. The prototype was applied successfully to numerous Ada programs ranging in size from several hundred to several thousand lines of source code. In Phase 3 of the project, the prototype was prepared for limited distribution (GRASP/Ada Version 3.0) to facilitate evaluation. The user interface was extensively reworked. The current prototype provides the capability for the user to generate CSD from Ada source code in a reverse engineering mode with a level of flexibility suitable for practical application.
Cross, James H., II↗
Software engineering capability for Ada (GRASP/Ada Tool)
The GRASP/Ada project (Graphical Representations of Algorithms, Structures, and Processes for Ada) has successfully created and prototyped a new algorithmic level graphical representation for Ada software, the Control Structure Diagram (CSD). The primary impetus for creation of the CSD was to improve the comprehension efficiency of Ada software and, as a result, improve reliability and reduce costs. The emphasis has been on the automatic generation of the CSD from Ada PDL or source code to support reverse engineering and maintenance. The CSD has the potential to replace traditional prettyprinted Ada Source code. A new Motif compliant graphical user interface has been developed for the GRASP/Ada prototype.
Cross, James H., II↗
Regular Topologies for Gigabit Wide-Area Networks
In general terms, this project aimed at the analysis and design of techniques for very high-speed networking. The formal objectives of the project were to: (1) Identify switch and network technologies for wide-area networks that interconnect a large number of users and can provide individual data paths at gigabit/s rates; (2) Quantitatively evaluate and compare existing and proposed architectures and protocols, identify their strength and growth potentials, and ascertain the compatibility of competing technologies; and (3) Propose new approaches to existing architectures and protocols, and identify opportunities for research to overcome deficiencies and enhance performance. The project was organized into two parts: 1. The design, analysis, and specification of techniques and protocols for very-high-speed network environments. In this part, SRI has focused on several key high-speed networking areas, including Forward Error Control (FEC) for high-speed networks in which data distortion is the result of packet loss, and the distribution of broadband, real-time traffic in multiple user sessions. 2. Congestion Avoidance Testbed Experiment (CATE). This part of the project was done within the framework of the DARTnet experimental T1 national network. The aim of the work was to advance the state of the art in benchmarking DARTnet's performance and traffic control by developing support tools for network experimentation, by designing benchmarks that allow various algorithms to be meaningfully compared, and by investigating new queueing techniques that better satisfy the needs of best-effort and reserved-resource traffic. This document is the final technical report describing the results obtained by SRI under this project. The report consists of three volumes: Volume 1 contains a technical description of the network techniques developed by SRI in the areas of FEC and multicast of real-time traffic. Volume 2 describes the work performed under CATE. Volume 3 contains the source code of all software developed under CATE.
Shacham, Nachum↗