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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Analysis and synthesis of abstract data types through generalization from examples

The discovery of general patterns of behavior from a set of input/output examples can be a useful technique in the automated analysis and synthesis of software systems. These generalized descriptions of the behavior form a set of assertions which can be used for validation, program synthesis, program testing, and run-time monitoring. Describing the behavior is characterized as a learning process in which the set of inputs is mapped into an appropriate transform space such that general patterns can be easily characterized. The learning algorithm must chose a transform function and define a subset of the transform space which is related to equivalence classes of behavior in the original domain. An algorithm for analyzing the behavior of abstract data types is presented and several examples are given. The use of the analysis for purposes of program synthesis is also discussed.

Wild, Christian↗
NASA NTRS2019

ESD Reviews: Model Dependence in Multi-Model Climate Ensembles: Weighting, Sub-Selection and Out-Of-Sample Testing

The rationale for using multi-model ensembles in climate change projections and impacts research is often based on the expectation that different models constitute independent estimates; therefore, a range of models allows a better characterisation of the uncertainties in the representation of the climate system than a single model. However, it is known that research groups share literature, ideas for representations of processes, parameterisations, evaluation data sets and even sections of model code. Thus, nominally different models might have similar biases because of similarities in the way they represent a subset of processes, or even be near-duplicates of others, weakening the assumption that they constitute independent estimates. If there are near-replicates of some models, then treating all models equally is likely to bias the inferences made using these ensembles. The challenge is to establish the degree to which this might be true for any given application. While this issue is recognised by many in the community, quantifying and accounting for model dependence in anything other than an ad-hoc way is challenging. Here we present a synthesis of the range of disparate attempts to define, quantify and address model dependence in multi-model climate ensembles in a common conceptual framework, and provide guidance on how users can test the efficacy of approaches that move beyond the equally weighted ensemble. In the upcoming Coupled Model Intercomparison Project phase 6 (CMIP6), several new models that are closely related to existing models are anticipated, as well as large ensembles from some models. We argue that quantitatively accounting for dependence in addition to model performance, and thoroughly testing the effectiveness of the approach used will be key to a sound interpretation of the CMIP ensembles in future scientific studies.

Abramowitz, Gab↗
NASA NTRS2012

Directed Design of Experiments for Validating Probability of Detection Capability of a Testing System

A method of validating a probability of detection (POD) testing system using directed design of experiments (DOE) includes recording an input data set of observed hit and miss or analog data for sample components as a function of size of a flaw in the components. The method also includes processing the input data set to generate an output data set having an optimal class width, assigning a case number to the output data set, and generating validation instructions based on the assigned case number. An apparatus includes a host machine for receiving the input data set from the testing system and an algorithm for executing DOE to validate the test system. The algorithm applies DOE to the input data set to determine a data set having an optimal class width, assigns a case number to that data set, and generates validation instructions based on the case number.

Generazio, Edward R.↗
NASA NTRS1987

Algorithm Sorts Groups Of Data

For efficient sorting, algorithm finds set containing minimum or maximum most significant data. Sets of data sorted as desired. Sorting process simplified by reduction of each multielement set of data to single representative number. First, each set of data expressed as polynomial with suitably chosen base, using elements of set as coefficients. Most significant element placed in term containing largest exponent. Base selected by examining range in value of data elements. Resulting series summed to yield single representative number. Numbers easily sorted, and each such number converted back to original set of data by successive division. Program written in BASIC.

Evans, J. D.↗
NASA NTRS1995

Observations in the vicinity of substorm onset: Implications for the substrom process

Multi-instrument data sets from the ground and satellites at both low and high altitude have provided new results concerning substorm onset and its source region in the magnetosphere. Twenty-six out of 37 substorm onset events showed evidence of azimuthally spaced auroral forms (AAFs) prior to the explosive poleward motion associated with optical substorm onset. AAFs can span 8 hours of local time prior to onset and generally propagate eastward in the morning sector. Onset itself is, however, more localized spanning only about 1 hour local time. AAF onset occur during time periods when the solar wind pressure is relatively high. AAFs brighten in conjunction with substorm onset leading to the conclusion that they are a growth phase activity casually related to substorm onset. Precursor activity associated with these AAFs is also seen near geosynchronous orbit altitude and examples show the relationship between the various instrumental definitions of substorm onset. The implied mode number (30 to 135) derived from this work is inconsistent with cavity mode resonances but is consistent with a modified flute/ballooning instability which requires azimuthal pressure gradients. The extended source region and the distance to the open-closed field line region constrain reconnection theory and local mechanisms for substorm onset. It is demonstrated that multiple onset substorms can exist for which localized dipolarizations and the Pi 2 occur simultaneously with tail stretching existing elsewhere. These pseudobreakups can be initiated by auroral streamers which originate at the most poleward set of arc systems and drift to the more equatorward main UV oval. Observations are presented of these AAFs in conjunction with low- and high-altitutde particle and magnetic field data. These place the activations at the interface between dipolar and taillike field lines probably near the peak in the cross-tail current. These onsets are put in the context of a new scenario for substorm morphology which employs individual modules which operate independently or couple together. This allows particular substorm events to be more accurately described and investigated.

Elphinstone, R. D.↗
NASA NTRS1974

An evaluation of machine processing techniques of ERTS-1 data for user applications

A broad study is described to evaluate a set of machine analysis and processing techniques applied to ERTS-1 data. Based on the analysis results in urban land use analysis and soil association mapping together with previously reported results in general earth surface feature identification and crop species classification, a profile of general applicability of this procedure is beginning to emerge. Put in the hands of a user who knows well the information needed from the data and also is familiar with the region to be analyzed it appears that significantly useful information can be generated by these methods. When supported by preprocessing techniques such as the geometric correction and temporal registration capabilities, final products readily useable by user agencies appear possible. In parallel with application, through further research, there is much potential for further development of these techniques both with regard to providing higher performance and in new situations not yet studied.

Landgrebe, D.↗
NASA NTRS1982

Stress constraints in optimality criteria design

Procedures described emphasize the processing of stress constraints within optimality criteria designs for low structural weight with stress and compliance constraints. Prescreening criteria are used to partition stress constraints into either potentially active primary sets or passive secondary sets that require minimal processing. Side constraint boundaries for passive constraints are derived by projections from design histories to modify conventional stress-ratio boundaries. Other procedures described apply partial structural modification reanalysis to design variable groups to correct stress constraint violations of unfeasible designs. Sample problem results show effective design convergence and, in particular, advantages for reanalysis in obtaining lower feasible design weights.

Levy, R.↗
NASA NTRS1988

A representational framework and user-interface for an image understanding workstation

Problems in image understanding involve a wide variety of data (e.g., image arrays, edge maps, 3-D shape models) and processes or algorithms (e.g., convolution, feature extraction, rendering). The underlying structure of an Image Understanding Workstation designed to support mulitple levels and types of representations for both data and processes is described, also the user-interface. The Image Understanding Workstation consists of two parts: the Image Understanding (IU) Framework, and the user-interface. The IU Framework is the set of data and process representations. It includes multiple levels of representation for data such as images (2-D), sketches (2-D), surfaces (2 1/2 D), and models (3-D). The representation scheme for processes characterizes their inputs, outputs, and parameters. Data and processes may reside on different classes of machines. The user-interface to the IU Workstation gives the user convenient access for creating, manipulating, transforming, and displaying image data. The user-interface follows the structure of the IU Framework and gives the user control over multiple types of data and processes. Both the IU Framework and user-interface are implemented on a LISP machine.

Schroeder, Joyce D.↗
NASA NTRS2015

Managing Large Datasets for Atmospheric Research

Since the mid-1980s, airborne and ground measurements have been widely used to provide comprehensive characterization of atmospheric composition and processes. Field campaigns have generated a wealth of insitu data and have grown considerably over the years in terms of both the number of measured parameters and the data volume. This can largely be attributed to the rapid advances in instrument development and computing power. The users of field data may face a number of challenges spanning data access, understanding, and proper use in scientific analysis. This tutorial is designed to provide an introduction to using data sets, with a focus on airborne measurements, for atmospheric research. The first part of the tutorial provides an overview of airborne measurements and data discovery. This will be followed by a discussion on the understanding of airborne data files. An actual data file will be used to illustrate how data are reported, including the use of data flags to indicate missing data and limits of detection. Retrieving information from the file header will be discussed, which is essential to properly interpreting the data. Field measurements are typically reported as a function of sampling time, but different instruments often have different sampling intervals. To create a combined data set, the data merge process (interpolation of all data to a common time base) will be discussed in terms of the algorithm, data merge products available from airborne studies, and their application in research. Statistical treatment of missing data and data flagged for limit of detection will also be covered in this section. These basic data processing techniques are applicable to both airborne and ground-based observational data sets. Finally, the recently developed Toolsets for Airborne Data (TAD) will be introduced. TAD (tad.larc.nasa.gov) is an airborne data portal offering tools to create user defined merged data products with the capability to provide descriptive statistics and the option to treat measurement uncertainty.

Chen, Gao↗
NASA NTRS1992

Sites of fine-scale electron density turbulence in the interstellar medium

Observations of radio-wave scattering effects probe interstellar electron-density turbulence. But with limited use of complementary data sets only broad conclusions have been obtained. The locations of this turbulence are unknown (phases, objects, etc.), as is the mechanism for its production, although it could play a role in various galactic processes. The IRAS data set was used to search for correlations between scattering and structures traced by infrared emitting dust. The existent HI (21-cm line emission), and 408-MHz radio-continuum all-sky surveys were used to search for correlations between scattering and structures traced by these emissions. Only lines of sight outside the galactic plane were considered (to better delimit the structures which might be causing scattering). No correlation is apparent between 21-cm line emission, or infrared continuum emission and interstellar scattering. However, a correlation exists between the scattering toward extragalactic radio sources and 408-MHz continuum emission.

Simonetti, John H.↗
NASA NTRS2012

The Effect of Geocenter Motion on Jason-2 and Jason-1 Orbits and the Mean Sea Level

We have investigated the impact of geocenter motion on Jason-2 orbits. This was accomplished by computing a series of Jason-1, Jason-2 GPS-based and SLR/DORIS-based orbits using ITRF2008 and the IGS repro1 framework based on the most recent GSFC standards. From these orbits, we extract the Jason-2 orbit frame translational parameters per cycle by the means of a Helmert transformation between a set of reference orbits and a set of test orbits. The fitted annual and seasonal terms of these time-series are compared to two different geocenter motion models. Subsequently, we included the geocenter motion corrections in the POD process as a degree-1 loading displacement correction to the tracking network. The analysis suggested that the GSFC's Jason-2 std0905 GPS-based orbits are closely tied to the center of mass (CM) of the Earth whereas the SLR/DORIS std0905 orbits are tied to the center of figure (CF) of the ITRF2005 (Melachroinos et al., 2012). In this study we extend the investigation to the centering of the GPS constellation and the way those are tied in the Jason-1 and Jason-2 POD process. With a new set of standards, we quantify the GPS and SLR/DORIS-based orbit centering during the Jason-1 and Jason-2 inter-calibration period and how this impacts the orbit radial error over the globe, which is assimilated into mean sea level (MSL) error, from the omission of the full term of the geocenter motion correction.

Melachroinos, Stavros A.↗
NASA NTRS1979

A correlation

The paper reports on some correlative features of two sets of space-based atmospheric measurements which are globally distributed with good statistical coverage. One set of data, pertaining to tropospheric processes, is lightning occurrence frequency derived from measurements aboard the DMSP satellite. The second set of data, pertaining to thermospheric processes, is the occurrence frequency of wavelike structures in neutral atmospheric density profiles derived from measurements aboard AE-C and AE-D. A significant correlation was found between the occurrence patterns of dawn lightning, which is indicative of massive long-lived tropospheric convective activity, and the occurrence patterns of wavelike structures in the thermosphere.

Source record↗
NASA NTRS2015

Sample Acquisition and Analytical Chemistry Challenges to Verifying Compliance to Aviators Breathing Oxygen (ABO) Purity Specification

NASA has been developing and testing two different types of oxygen separation systems. One type of oxygen separation system uses pressure swing technology, the other type uses a solid electrolyte electrochemical oxygen separation cell. Both development systems have been subjected to long term testing, and performance testing under a variety of environmental and operational conditions. Testing these two systems revealed that measuring the product purity of oxygen, and determining if an oxygen separation device meets Aviator's Breathing Oxygen (ABO) specifications is a subtle and sometimes difficult analytical chemistry job. Verifying product purity of cryogenically produced oxygen presents a different set of analytical chemistry challenges. This presentation will describe some of the sample acquisition and analytical chemistry challenges presented by verifying oxygen produced by an oxygen separator - and verifying oxygen produced by cryogenic separation processes. The primary contaminant that causes gas samples to fail to meet ABO requirements is water. The maximum amount of water vapor allowed is 7 ppmv. The principal challenge of verifying oxygen produced by an oxygen separator is that it is produced relatively slowly, and at comparatively low temperatures. A short term failure that occurs for just a few minutes in the course of a 1 week run could cause an entire tank to be rejected. Continuous monitoring of oxygen purity and water vapor could identify problems as soon as they occur. Long term oxygen separator tests were instrumented with an oxygen analyzer and with an hygrometer: a GE Moisture Monitor Series 35. This hygrometer uses an aluminum oxide sensor. The user's manual does not report this, but long term exposure to pure oxygen causes the aluminum oxide sensor head to bias dry. Oxygen product that exceeded the 7 ppm specification was improperly accepted, because the sensor had biased. The bias is permanent - exposure to air does not cause the sensor to return to its original response - but the bias can be accounted for by recalibrating the sensor. After this issue was found, continuous measurements of water vapor in the oxygen product were made using an FTIR. The FTIR cell is relatively large, so response time is slow - but moisture measurements were repeatable and accurate. Verifying ABO compliance for oxygen produced by commercial cryogenic processes has a different set of sample acquisition and analytical chemistry challenges. Customers want analytical chemists to conserve as much as possible. Hygrometers are not exposed to hours of continuous flow of oxygen, so they don't bias, but small amounts of contamination in valves can cause a "fail". K bottles are periodically cleaned and recertified - after cleaning residual moisture can cause a "fail". Operators let bottle pressure drop to room pressure, introduce outside air into the bottle, and the subsequent fill will "fail". Outside storage of K‐bottles has allowed enough in‐leakage, so contents will "fail".

Graf, John↗
NASA NTRS2016

Processing Device for High-Speed Execution of an Xrisc Computer Program

A processing device for high-speed execution of a computer program is provided. A memory module may store one or more computer programs. A sequencer may select one of the computer programs and controls execution of the selected program. A register module may store intermediate values associated with a current calculation set, a set of output values associated with a previous calculation set, and a set of input values associated with a subsequent calculation set. An external interface may receive the set of input values from a computing device and provides the set of output values to the computing device. A computation interface may provide a set of operands for computation during processing of the current calculation set. The set of input values are loaded into the register and the set of output values are unloaded from the register in parallel with processing of the current calculation set.

Ng, Tak-Kwong↗
NASA NTRS1984

Earth Observing System. Volume 1, Part 2: Science and Mission Requirements. Working Group Report Appendix

The Earth Observing System (EOS) is a planned NASA program, which will carry out multidisciplinary Earth science studies employing a variety of remote sensing techniques in the 1990's, as a prime mission, using the Space Station polar platform. Its primary goal is the generation of long term Earth science data sets of measurements and processes in the areas of agriculture, forestry, geology, hydrology, oceanography, snow and ice, troposphere and upper atmospheric chemistry, radiation and dynamics pertaining to global studies of Earth as a system, emphasizing the interactions and couplings of the atmospbere-ocean-land-cryosphere system. These results will provide the information needed to qualify our understanding of the global hydrological cycle, global biogeochemical cycles and global climate processes. This report provides the science rationale, recommended observational needs, the broad system configuration and a recommended implementation strategy to achieve the stated mission goals. The report is one volume of a proposed five volume set constituting the Phase A report as the Earth Observing System (EOS).

Goddard Space Flight Center↗
NASA NTRS1987

High resolution Viking Orbiter images: A useful data source for testing the viability of geomorphic processes attributed to Martian landforms

The diversity of landforms visible in the Viking images of Mars have led to a proliforation of geomorphic agents proposed to be active in shaping the Martian surface. While it is likely that numerous different processes have contributed to the geomorphology of Mars throughout Martian history, it is important that proposed Martian geomorphic agents be subjected to critical scrutiny by the scientific community. High resolution Viking Orbiter images represent a data set for investigating geomorphic processes on Mars. Geologic mapping of Mars can take place at a variety of scales, utilizing a variety of image resolutions, but an interpretation of the history of individual landforms is dependent upon the best available spatial resolution. These high resolution images provide the opportunity to examine proposed Martian geomorphic processes. It is clear that researchers may not interpret features in the same way but it is important that high resolution images of candidate features be made available to the scientific community so that a consensus can be reached. This procedure can provide a way to refine the understanding of geomorphic processes on Mars.

Zimbelman, James R.↗
NASA NTRS1994

Pinatubo Aerosol Evolution: Using Composite Data Sets to Build the Global- To Micro-Scale Picture and Assess Consistency of Different Measurements

This paper brings together experimental evidence required to build realistic models of the global evolution of physical, chemical, and optical properties of the aerosol resulting from the 1991 Pinatubo volcanic eruption. Such models are needed to compute the effects of the aerosol on atmospheric chemistry, dynamics, radiation, and temperature. Whereas there is now a large and crowing body of post-Pinatubo measurements by a variety of techniques, some results are in conflict, and a self-consistent, unified picture is needed, along with an assessment of remaining uncertainties. This paper examines, data from photometers, radiometers, impactors, optical counter/sizers, and lidars operated on the ground, aircraft, balloons, and spacecraft. Example data sources include: (1) Tracking sunphotometers and lidars at Mauna Loa Observatory (MLO) and on the DC-8. (2) Particle spectrometers and wire impactors on the ER-2 and DC-8. (3) Dustsondes (particle counter/sizers on balloons). and (3) SAGE II, SAM II, AVHRR, CLAES, and ISAMS sensors on a variety of satellites. We assess the mutual consistency of these disparate data sets and recommend 'consensus' properties and uncertainties in the process of developing a composite data set. Recommended properties include the spatial and temporal evolution of particle chemical composition, shape, wavelength-and temperature-dependent refractive index, size distribution, and optical depth spectra. Supporting references are cited and representative data shown.

Russell, Philip B.↗
NASA NTRS1994

Pinatubo Aerosol Evolution: Using Composite Data Sets to Build the Global- to Micro-Scale Picture and Assess Consistency of Different Measurements

This paper brings together experimental evidence required to build realistic models of the global evolution of physical, chemical, and optical properties of the aerosol resulting from the 1991 Pinatubo volcanic eruption. Such models are needed to compute the effects of the aerosol on atmospheric chemistry, dynamics, radiation, and temperature. Whereas there is now a large and growing body of post-Pinatubo measurements by a variety of techniques, some results are in conflict, and a self-consistent, unified picture is needed, along with an assessment of remaining uncertainties. This paper examines data from photometers, radiometers, impactors, optical counters/sizers, and lidars operated on the ground, aircraft, balloons, and spacecraft. Example data sources include: - Tracking sunphotometers and lidars at Mauna Loa Observatory (MLO) and on the DC-8 - Particle spectrometers and wire impactors on the ER-2 and DC-8 - Dustsondes (particle counters/sizers on balloons) - SAGE II, SAM II, AVHRR, CLAES, and ISAMS sensors on a variety of satellites. We assess the mutual consistency of these disparate data sets and recommend 'consensus" properties and uncertainties in the process of developing a composite data set. Recommended properties include the spatial and temporal evolution of particle chemical composition, shape, wavelength and temperature-dependent refractive index, size distribution, and optical depth spectra. Supporting references are cited and representative data shown.

Russell, P. B.↗