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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Enhanced TCAS 2/CDTI traffic Sensor digital simulation model and program description

Digital simulation models of enhanced TCAS 2/CDTI traffic sensors are developed, based on actual or projected operational and performance characteristics. Two enhanced Traffic (or Threat) Alert and Collision Avoidance Systems are considered. A digital simulation program is developed in FORTRAN. The program contains an executive with a semireal time batch processing capability. The simulation program can be interfaced with other modules with a minimum requirement. Both the traffic sensor and CAS logic modules are validated by means of extensive simulation runs. Selected validation cases are discussed in detail, and capabilities and limitations of the actual and simulated systems are noted. The TCAS systems are not specifically intended for Cockpit Display of Traffic Information (CDTI) applications. These systems are sufficiently general to allow implementation of CDTI functions within the real systems' constraints.

Goka, T.↗
NASA NTRS1985

Analysis of estimation algorithms for CDTI and CAS applications

Estimation algorithms for Cockpit Display of Traffic Information (CDTI) and Collision Avoidance System (CAS) applications were analyzed and/or developed. The algorithms are based on actual or projected operational and performance characteristics of an Enhanced TCAS II traffic sensor developed by Bendix and the Federal Aviation Administration. Three algorithm areas are examined and discussed. These are horizontal x and y, range and altitude estimation algorithms. Raw estimation errors are quantified using Monte Carlo simulations developed for each application; the raw errors are then used to infer impacts on the CDTI and CAS applications. Applications of smoothing algorithms to CDTI problems are also discussed briefly. Technical conclusions are summarized based on the analysis of simulation results.

Goka, T.↗
NASA NTRS1986

University participation via UNIDATA, part 1

The UNIDATA Project is a cooperative university project, operated by the University Corporation for Atmospheric Research (UCAR) with National Science Foundation (NSF) funding, aimed at providing interactive communication and computations to the university community in the atmospheric and oceanic sciences. The initial focus has been on providing access to data for weather analysis and prediction. However, UNIDATA is in the process of expanding and possibly providing access to the Pilot Climate Data System (PCDS) through the UNIDATA system in an effort to develop prototypes for an Earth science information system. The notion of an Earth science information system evolved from discussions within NASA and several advisory committees in anticipation of receiving data from the many Earth observing instruments on the space station complex (Earth Observing System).

Dutton, J.↗
NASA NTRS1986

van der Waals force between positronium and hydrogenic atoms Finite-mass corrections

The Feshbach projection-operator formalism is used to derive the asymptotic effective interaction potential between two atoms. Beyond the usual van der Waals potential, falling like x exp -6, three x exp -8 terms are also obtained: an attractive dipole-quadrupole term (absent in the positronium-positronium case because of symmetry), a repulsive energy-dependent term, and a repulsive mass-dependent but energy-independent one. This last term was not obtained by Manson and Ritchie (1985) using an independent method.

Au, C. K.↗
NASA NTRS1986

A spectral element method for the simulation of unsteady incompressible flows with heat transfer

The spectral element method is a high-order finite element technique for solution of the Navier-Stokes and energy equations. In the isoparametric spectral element discretization, the domain is broken up into general brick elements, and the dependent and independent variables represented as high-order tensor-product Lagrangian interpolants through Chebyshev collocation points. The nonlinear and convective terms in the governing equations are treated with explicit collocation, while the pressure and diffusive contributions are handled implicitly using variational projection operators. The method is applied to flow past a cylinder, flow in grooved channels, and natural convection in an enclosure.

Karniadakis, George E.↗
NASA NTRS1987

Isotropic probability measures in infinite dimensional spaces: Inverse problems/prior information/stochastic inversion

Let R be the real numbers, R(n) the linear space of all real n-tuples, and R(infinity) the linear space of all infinite real sequences x = (x sub 1, x sub 2,...). Let P sub n :R(infinity) approaches R(n) be the projection operator with P sub n (x) = (x sub 1,...,x sub n). Let p(infinity) be a probability measure on the smallest sigma-ring of subsets of R(infinity) which includes all of the cylinder sets P sub n(-1) (B sub n), where B sub n is an arbitrary Borel subset of R(n). Let p sub n be the marginal distribution of p(infinity) on R(n), so p sub n(B sub n) = p(infinity)(P sub n to the -1(B sub n)) for each B sub n. A measure on R(n) is isotropic if it is invariant under all orthogonal transformations of R(n). All members of the set of all isotropic probability distributions on R(n) are described. The result calls into question both stochastic inversion and Bayesian inference, as currently used in many geophysical inverse problems.

Backus, George↗
NASA NTRS1987

Isotropic probability measures in infinite-dimensional spaces

Let R be the real numbers, R(n) the linear space of all real n-tuples, and R(infinity) the linear space of all infinite real sequences x = (x sub 1, x sub 2,...). Let P sub in :R(infinity) approaches R(n) be the projection operator with P sub n (x) = (x sub 1,...,x sub n). Let p(infinity) be a probability measure on the smallest sigma-ring of subsets of R(infinity) which includes all of the cylinder sets P sub n(-1) (B sub n), where B sub n is an arbitrary Borel subset of R(n). Let p sub n be the marginal distribution of p(infinity) on R(n), so p sub n(B sub n) = p(infinity) (P sub n to the -1 (B sub n)) for each B sub n. A measure on R(n) is isotropic if it is invariant under all orthogonal transformations of R(n). All members of the set of all isotropic probability distributions on R(n) are described. The result calls into question both stochastic inversion and Bayesian inference, as currently used in many geophysical inverse problems.

Backus, George↗
NASA NTRS1988

An efficient approach for statistical calculations with globally gridded filtered time series

The formulas for performing several statistical calculations based on Fourier coefficients are presented for use in atmospheric observational studies. The calculations discussed include a method for estimating the degree of temporal freedoms of two correlated time series and a method for performing seasonal analyses using a half-year summer/winter projection operator in the frequency domain. A modified lag-correlation calculation is proposed for obtaining lag correlations in the frequency domain. Also, a spectral approach for Empirical Orthogonal Function (EOF) and Extended EOF analysis is given which reduces the size of the matrix to be solved in the eigenproblem.

Gao, X. H.↗
NASA NTRS1988

Science and applications on the space station: A strategic vision

The central themes relating to science and applications on the Space Station for fiscal year 1989 are discussed. Materials science research is proposed in a wide variety of subfields including protein crystal growth, metallurgy, and properties of fluids. Also proposed are the U.S. Polar Platform, an Extended Duration Crew Operations Project, and a long-range Space Biology Research Project to investigate plant and animal physiology, gravitational biology, life support systems, and exobiology. The exterior of the Space Station will provide attachment points for payloads to study subjects such as the earth and its environment, the sun, other bodies in the solar system, and cosmic objects. Examples of such attached payloads are given. They include a plasma interaction monitoring system, observation of solar features and properties, studies of particle radiation from the sun, cosmic dust collection and analysis, surveys of various cosmic and solar rays, measurements of rainfall and wind and the study of global changes on earth.

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NASA NTRS1989

Coded-aperture imaging in nuclear medicine

Coded-aperture imaging is a technique for imaging sources that emit high-energy radiation. This type of imaging involves shadow casting and not reflection or refraction. High-energy sources exist in x ray and gamma-ray astronomy, nuclear reactor fuel-rod imaging, and nuclear medicine. Of these three areas nuclear medicine is perhaps the most challenging because of the limited amount of radiation available and because a three-dimensional source distribution is to be determined. In nuclear medicine a radioactive pharmaceutical is administered to a patient. The pharmaceutical is designed to be taken up by a particular organ of interest, and its distribution provides clinical information about the function of the organ, or the presence of lesions within the organ. This distribution is determined from spatial measurements of the radiation emitted by the radiopharmaceutical. The principles of imaging radiopharmaceutical distributions with coded apertures are reviewed. Included is a discussion of linear shift-variant projection operators and the associated inverse problem. A system developed at the University of Arizona in Tucson consisting of small modular gamma-ray cameras fitted with coded apertures is described.

Smith, Warren E.↗
NASA NTRS1990

A time-dependent wave packet approach to atom-diatom reactive collision probabilities - Theory and application to the H + H2(J = 0) system

This paper describes a new approach to the study of atom-diatom reactive collisions in three dimensions employing wave packets and the time-dependent Schroedinger equation. The method uses a projection operator approach to couple the inelastic and reactive portions of the total wave function and optical potentials to circumvent the necessity of using product arrangement coordinates. Reactive transition probabilities are calculated from the state resolved flux of the wave packet as it leaves the interaction region in the direction of the reactive arrangement channel. The present approach is used to obtain such vibrationally resolved probabilities for the three-dimensional H + H2 (J = 0) hydrogen exchange reaction, using a body-fixed system of coordinates.

Neuhauser, Daniel↗
NASA NTRS1992

Using microsoft excel applications in the graduate intern program at Goddard Space Flight Center

An outline of the Project Operations Branch at Goddard Space Flight Center is presented that describes the management of the division and each subgroup's responsibility. The paper further describes the development of software tools for the Macintosh personal computer, and their impending implementation. A detailed step by step procedure is given for using these software tools.

Antoine, Lisa↗
NASA NTRS1993

Analysis of the anisotropic viscoplastic-damage response of composite laminates - Continuum basis and computational algorithms

The mathematical structure underlying the rate equations of a recently-developed constitutive model for the coupled viscoplastic-damage response of anisotropic composites is critically examined. In this regard, a number of tensor projection operators have been identified, and their properties were exploited to enable the development of a general computational framework for their numerical implementation using the Euler fully-implicit integration method. In particular, this facilitated (i) the derivation of explicit expressions of the (consistent) material tangent stiffnesses that are valid for both three-dimensional as well as subspace (e.g. plane stress) formulations, (ii) the implications of the symmetry or unsymmetry properties of these tangent operators from a thermodynamic standpoint, and (iii) the development of an effective time-step control strategy to ensure accuracy and convergence of the solution. In addition, the special limiting case of inviscid elastoplasticity is treated. The results of several numerical simulations are given to demonstrate the effectiveness of the schemes developed.

Saleeb, A. F.↗
NASA NTRS1993

Advanced cargo aircraft may offer a potential renaissance in freight transportation

The increasing demand for air freight transportation has prompted studies of large, aerodynamically efficient cargo-optimized aircraft capable of carrying intermodal containers, which are typically 8 x 8 x 20 ft. Studies have accordingly been conducted within NASA to ascertain the specifications and projected operating costs of such a vehicle, as well as to identify critical, development-pacing technologies. Attention is here given not only to the rather conventional, 10-turbofan engined configuration thus arrived at, but numerous innovative configurations featuring such concepts as spanloading, removable cargo pods, and ground effect.

Morris, Shelby J.↗
NASA NTRS1993

Network command processing system overview

The Network Command Processing System (NCPS) developed for the National Aeronautics and Space Administration (NASA) Ground Network (GN) stations is a spacecraft command system utilizing a MULTIBUS I/68030 microprocessor. This system was developed and implemented at ground stations worldwide to provide a Project Operations Control Center (POCC) with command capability for support of spacecraft operations such as the LANDSAT, Shuttle, Tracking and Data Relay Satellite, and Nimbus-7. The NCPS consolidates multiple modulation schemes for supporting various manned/unmanned orbital platforms. The NCPS interacts with the POCC and a local operator to process configuration requests, generate modulated uplink sequences, and inform users of the ground command link status. This paper presents the system functional description, hardware description, and the software design.

Nam, Yon-Woo↗
NASA NTRS1993

Preparing the DSN operations concepts

Operations concepts are prepared to support a specific application and can, therefore, be classified accordingly. Studies of NASA and military operations concepts suggest three major types: data services, customer services, and systems oriented. Data services concepts concentrate on data types (e.g., telemetry and command) and how these data are processed and delivered to the user. Such concepts are normally used by data-processing centers to describe data-coding schemes and data formats. Customer services concepts concentrate on the customers' requirements and describe how these requirements are met using the systems available to the operation. Project centers use such concepts to describe the various types of data as they flow from the source (e.g., a spacecraft) to the end user (i.e., the customer). Systems oriented concepts concentrate on the use of systems for processing and delivering customer data. This paper examines the latter type and the 'concepts' that are inherent within them.

Salazar, A. J.↗
NASA NTRS1993

Discrimination of poorly exposed lithologies in AVIRIS data

One of the advantages afforded by imaging spectrometers such as AVIRIS is the capability to detect target materials at a sub-pixel scale. This paper presents several examples of the identification of poorly exposed geologic materials - materials which are either subpixel in scale or which, while having some surface expression over several pixels, are partially covered by vegetation or other materials. Sabol et al. (1992) noted that a primary factor in the ability to distinguish sub-pixel targets is the spectral contrast between the target and its surroundings. In most cases, this contrast is best expressed as an absorption feature or features present in the target but absent in the surroundings. Under such circumstances, techniques such as band depth mapping (Clark et al., 1992) are feasible. However, the only difference between a target material and its surroundings is often expressed solely in the continuum. We define the 'continuum' as the reflectance or radiance spanning spectral space between spectral features. Differences in continuum slope and shape can only be determined by reduction techniques which considers the entire spectral range; i.e., techniques such as spectral mixture analysis (Adams et al., 1989) and recently developed techniques which utilize an orthogonal subspace projection operator (Harsanyi, 1993). Two of the three examples considered herein deal with cases where the target material differs from its surroundings only by such a subtle continuum change.

Farrand, William H.↗
NASA NTRS1995

Space Shuttle Orbiter corrosion history, 1981-1993: A review and analysis of issues involving structures and subsystems

This report summarizes past corrosion issues experienced by the NASA space shuttle orbiter fleet. Design considerations for corrosion prevention and inspection methods are reviewed. Significant corrosion issues involving structures and subsystems are analyzed, including corrective actions taken. Notable successes and failures of corrosion mitigation systems and procedures are discussed. The projected operating environment used for design is contrasted with current conditions in flight and conditions during ground processing.

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