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At least 1,495 records · Page 83
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

SPECTRUM - A system for the analysis of imaging spectrometer data

This paper examines several design issues related to the development of SPECTRUM, a knowledge-based system for the geological interpretation of imaging spectrometer data. SPECTRUM is implemented using a combination of the programming languages STAR and C, which are coupled both at the level of procedures - involving function calls between the two languages - and at the level of data structures - involving the formation of a hybrid knowledge base shared by the two languages. Aspects of the coupling relating to each level of the implementation are described, followed by a listing of general observations regarding the coupling of symbolic and numerical techniques as extracted from the SPECTRUM project.

Borchardt, Gary C.↗
NASA NTRS1992

ASpect: A new spectrum and line analysis package for IRAF

We examined several publicly available spectral analysis software packages looking for one with enough functionality and versatility to meet the analysis needs of astronomers during the next decade. None of those examined can satisfactorily support the wide variety of panchromatic science programs that are now becoming possible. Furthermore, we concluded that none of these packages can be simply modified to include critical functions because of their original (limited) designs. During the next two years we will write a new spectral analysis package, ASpect, that will incorporate the latest analysis techniques for astronomical spectra in all wavelength domains. The ASpect package has several functional requirements. It must operate on spectra from a wide variety of ground-based and space-based instruments spanning wavelengths from radio to gamma rays. It must accommodate non-linear dispersion relations. It must provide a variety of functions, individually or in combination, with which to fit spectral features and the continuum. It is vitally important that known bad data be masked and that, uncertainties be propagated throughout the calculations in order for astronomers to evaluate the reliability of results. Finally, this new package must provide a powerful, intuitive graphical user interface to handle the burden of data input/output (I/O), on-line 'help,' selection of relevant features for analysis, plotting and graphical interaction, and data base management--all in a comprehensible environment. We anticipate that ASpect will take the form of an external package in IRAF (such as the NOAO and STSDAS packages) and will be layered upon the IRAF virtual Operating System to make it available on as many platforms as possible, while making it resistant to changes in operating systems and compilers. Our choice of IRAF is motivated by its portability, its wide use within the astronomical community, and its rich set of existing user applications.

Hulbert, S. J.↗
NASA NTRS2018

Vehicle Design Data Format and Process for a Complete TARIS and OLTARIS Radiation Analysis for Designers and Engineers

Protecting astronauts from space radiation is a complex task when it comes to modeling and simulation. This document shows what information is needed from a spacecraft designer using CAD (Computer-Assisted Design) at each phase of the design to enable the engineers to evaluate the design phase against space radiation limits to determine the suitability of the design for space flight. The current personal exposure limits are listed in NASA STD-3001. A proxy to determine the REID (Radiation Exposure Induced Death) in NASA STD-3001 is the whole body effective dose equivalent (E or effective dose). For short-term tissue effects, organ-averaged gray equivalent (G (sub T)) is used. The TARIS (Tool for the Assessment of Radiation In Space - for LaRC (Langley Research Center) engineers) and OLTARIS (On-Line TARIS) - for designers) systems are used to generate these response functions. The E can use ICRP60 or NASA Q-values. A possible space radiation design basis environment for short-term tissue effects is described and used in all analyses. A single space vehicle was designed with three astronaut configurations and two of those configurations were used in a storm shelter thickness perturbation analysis. Conversion of the data from the CAD model to input necessary for TARIS and OLTARIS is also discussed in detail with relevant examples.

Singleterry, Robert C.↗
NASA NTRS2002

A statistical model for interpreting computerized dynamic posturography data

Computerized dynamic posturography (CDP) is widely used for assessment of altered balance control. CDP trials are quantified using the equilibrium score (ES), which ranges from zero to 100, as a decreasing function of peak sway angle. The problem of how best to model and analyze ESs from a controlled study is considered. The ES often exhibits a skewed distribution in repeated trials, which can lead to incorrect inference when applying standard regression or analysis of variance models. Furthermore, CDP trials are terminated when a patient loses balance. In these situations, the ES is not observable, but is assigned the lowest possible score--zero. As a result, the response variable has a mixed discrete-continuous distribution, further compromising inference obtained by standard statistical methods. Here, we develop alternative methodology for analyzing ESs under a stochastic model extending the ES to a continuous latent random variable that always exists, but is unobserved in the event of a fall. Loss of balance occurs conditionally, with probability depending on the realized latent ES. After fitting the model by a form of quasi-maximum-likelihood, one may perform statistical inference to assess the effects of explanatory variables. An example is provided, using data from the NIH/NIA Baltimore Longitudinal Study on Aging.

NASA Discipline Neuroscience↗
NASA NTRS1974

The application of natural science data to land management decision-making

A natural environmental analysis process which allows the decision maker to know the probable consequences of a decision prior to the act is developed. Emphasis is placed on the fit between the natural environment and the social, economic, and functional attributes of man's communities and the transition from nature in its present state to various forms and intensities of development. Applications of the analysis are examined. It is concluded that the analysis is a workable system for land use management.

Williams, D. L.↗
NASA NTRS1975

Zero-derivative boundary condition for pulsed distributed systems

To permit use of experimentally determined Peclet numbers in numerical simulations of pulsed distributed flow systems such as chromatograph columns, substitution of the zero-derivative boundary condition for the infinite boundary condition used in treating data is examined. Moment analysis shows that application of the zero-derivative condition external to the column will yield equivalent numerical results for the two boundary conditions. Criteria for locating this position are provided as a function of the Peclet number.

Lashmet, P. K.↗
NASA NTRS1976

System for analysis of LANDSAT agricultural data: Automatic computer-assisted proportion estimation of local areas

The author has identified the following significant results. A conceptual man machine system framework was created for a large scale agricultural remote sensing system. The system is based on and can grow out of the local recognition mode of LACIE, through a gradual transition wherein computer support functions supplement and replace AI functions. Local proportion estimation functions are broken into two broad classes: (1) organization of the data within the sample segment; and (2) identification of the fields or groups of fields in the sample segment.

Nalepka, R. F.↗
NASA NTRS1979

Voyager design and flight loads comparison

Estimates of flight loads for Voyager 1 and Voyager 2 are summarized. These member loads are obtained by using the measured flight accelerations at the launch vehicle/spacecraft interface as forcing functions for the Voyager mathematical model. The flight loads are compared to the Voyager design loads obtained from the shock spectra/impedance method and to the loads obtained using space vehicle transient loads analysis. Finally, based on these data, an assessment of the shock spectra/impedance loads method used for Voyager is presented.

Chen, J. C.↗
NASA NTRS1984

A comparison of several methods of calculating fracture toughness from composite laminate test data

Critical fracture toughness was determined by two different techniques for graphite/epoxy laminates of three stacking sequences and several thicknesses. Critical fracture toughness was determined by a finite element stress analysis of a center-cracked tension specimen which yielded the stress intensity factor as a function of specimen thickness and applied load. As an alternative approach the critical strain energy release rate was determined from the compliance calibration technique. Test results from both procedures are compared and discussed.

Harris, C. E.↗
NASA NTRS1985

Analysis of data from NASA B-57B gust gradient program

Statistical analysis of the turbulence measured in flight 6 of the NASA B-57B over Denver, Colorado, from July 7 to July 23, 1982 included the calculations of average turbulence parameters, integral length scales, probability density functions, single point autocorrelation coefficients, two point autocorrelation coefficients, normalized autospectra, normalized two point autospectra, and two point cross sectra for gust velocities. The single point autocorrelation coefficients were compared with the theoretical model developed by von Karman. Theoretical analyses were developed which address the effects spanwise gust distributions, using two point spatial turbulence correlations.

Frost, W.↗
NASA NTRS1986

Characterization of elastomeric materials with application to design

Redesign of the Space Shuttle Solid Booster has necessitated re-evaluation of the material used in the field joint O-ring seals. The viscoelastic characteristics of five candidate materials were determined. The five materials are: two fluorocarbon compounds, two nitrile compounds, and a silicon compound. The materials were tested in a uniaxial compression test to determine the characteristic relaxation functions. These tests were performed at five different temperatures. A master material curve was developed for each material from the experimental data. The results are compared to tensile relaxation tests. Application of these results to the design analysis is discussed in detail.

Bower, Mark V.↗
NASA NTRS1985

Development of ADOCS controllers and control laws. Volume 3: Simulation results and recommendations

The Advanced Cockpit Controls/Advanced Flight Control System (ACC/AFCS) study was conducted by the Boeing Vertol Company as part of the Army's Advanced Digital/Optical Control System (ADOCS) program. Specifically, the ACC/AFCS investigation was aimed at developing the flight control laws for the ADOCS demonstator aircraft which will provide satisfactory handling qualities for an attack helicopter mission. The three major elements of design considered are as follows: Pilot's integrated Side-Stick Controller (SSC) -- Number of axes controlled; force/displacement characteristics; ergonomic design. Stability and Control Augmentation System (SCAS)--Digital flight control laws for the various mission phases; SCAS mode switching logic. Pilot's Displays--For night/adverse weather conditions, the dynamics of the superimposed symbology presented to the pilot in a format similar to the Advanced Attack Helicopter (AAH) Pilot Night Vision System (PNVS) for each mission phase is a function of SCAS characteristics; display mode switching logic. Results of the five piloted simulations conducted at the Boeing Vertol and NASA-Ames simulation facilities are presented in Volume 3. Conclusions drawn from analysis of pilot rating data and commentary were used to formulate recommendations for the ADOCS demonstrator flight control system design. The ACC/AFCS simulation data also provide an extensive data base to aid the development of advanced flight control system design for future V/STOL aircraft.

Landis, Kenneth H.↗
NASA NTRS1988

Photometry and polarimetry of Mercury

Information available on the photometric and polarimetric properties of Mercury's surface is discussed, with special consideration given to data concerning the nature of the Mercurial regolith and the comparison of the Mercury's photometric properties with those of the moon. The results from an analysis performed in terms of Hapke's (1981, 1984, 1986) photometric function confirm the remarkable similarity of photometric properties of the two celestial bodies. However, their highland/mare alabedo ratios differs considerably; while the ratio is about 2 on the moon, it is only about 1.4 on Mercury. Mercury also shows slightly lower values of the maximum positive polarization observed, a difference that is consistent with either a slightly higher average reflectance for Mercury, or with a difference in regolith texture, or both.

Veverka, J.↗
NASA NTRS1990

Surface Reorientation and Settling in Cylinders upon Step Reduction in Gravity

A large literature exists concerning the equilibrium configurations of free liquid/gas surfaces in reduced gravity environments. Such conditions generally yield surfaces of constant curvature contracting the container wall at a particular angle. The time required to reach and stabilize about this configuration is less studied for the case of sudden changes in gravity level; e.g., from normal- to low-gravity, as can occur in many drop tower experiments. The particular interest here was to determine the total reorientation time for such surfaces in cylinders, as a function primarily of contact angle and kinematic viscosity, in order to aid in the development of drop tower experiment design. A large parametric range of tests were performed and, based on an accompanying scale analysis, the complete data set was correlated. The results of other investigations are included for comparison.

Weislogel, Mark M.↗
NASA NTRS1990

Surface settling in partially filled containers upon step reduction in gravity

A large literature exists concerning the equilibrium configurations of free liquid/gas surfaces in reduced gravity environments. Such conditions generally yield surfaces of constant curvature meeting the container wall at a particular (contact) angle. The time required to reach and stabilize about this configuration is less studied for the case of sudden changes in gravity level, e.g. from normal- to low-gravity, as can occur in many drop tower experiments. The particular interest here was to determine the total reorientation time for such surfaces in cylinders (mainly), as a function primarily of contact angle and kinematic viscosity, in order to aid in the development of drop tower experiment design. A large parametric range of tests were performed and, based on an accompanying scale analysis, the complete data set was correlated. The results of other investigations are included for comparison.

Weislogel, Marl M.↗
NASA NTRS1991

LDEF contaminants analysis data

Modification of surface texture for Ram Facing FEP Teflon on the Long Duration Exposure Facility (LDEF) satellite is documented. Photos of changes in surface texture if thermal blanket material with position on tray C-08 are presented. Infrared spectra and photographic documentation of molecular film deposits on LDEF surfaces by location is reported. Results of a survey of the functional groups and elemental composition of the brown film found widely distributed on the surface of LDEF is shown. A partial photographic catalog of LDEF particulate contaminants is included. A set of photos of particles collected or photographed in place on the surface of LDEF is shown. Particle counts and surface obscuration data for the LDEF satellite are reported. The surface data in tables and charts is presented for the LDEF satellite by location.

Crutcher, E. Russ↗
NASA NTRS1991

Improved millimeter-wave mixer performance analysis at cryogenic temperatures

The results of a 600-GHz mixer performance analysis using an improved model for computing the Schottky diode capacitance-voltage (C-V) relationship are presented. The computed C-V data for a realistic submillimeter-waver mixer diode are given as a function of physical temperature and compared to the standard analytic expression based on a solution of Poisson's equation. Both C-V relationships are used to predict the performance of an ideally terminated 600 GHz mixer operating at 300, 140, 80, and 30 K. It is shown that the drift-diffusion model more accurately describes the mixer performance when the physical temperature is reduced below roughly 100 K.

Siegel, Peter H.↗
NASA NTRS1994

Graphical User Interface for the NASA FLOPS Aircraft Performance and Sizing Code

XFLOPS is an X-Windows/Motif graphical user interface for the aircraft performance and sizing code FLOPS. This new interface simplifies entering data and analyzing results, thereby reducing analysis time and errors. Data entry is simpler because input windows are used for each of the FLOPS namelists. These windows contain fields to input the variable's values along with help information describing the variable's function. Analyzing results is simpler because output data are displayed rapidly. This is accomplished in two ways. First, because the output file has been indexed, users can view particular sections with the click of a mouse button. Second, because menu picks have been created, users can plot engine and aircraft performance data. In addition, XFLOPS has a built-in help system and complete on-line documentation for FLOPS.

Lavelle, Thomas M.↗