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  • Mechanical Engineering  (76)
  • Computer Programming and Software  (61)
  • Geophysics  (51)
  • 2000-2004  (188)
  • 1
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    Stratospheric Analysis and Forecasting in the Northern Winter of 1999/2000: The NASA DAO's GEOS-3 System (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: An evaluation is presented of the performance in the northern winter 1999/2000 of the GEOS-3 troposphere-stratosphere data assimilation system (DAS). The impacts of the two main input data types are assessed: upper-air soundings (sondes) provide wind and temperature information and satellite-based (Tiros Operational Vertical Sounders: TOVS) give estimates of the thermal structure. It is shown that in the low stratosphere (300-70hPa) the analyses are generally slightly warmer than the sonde data, but colder than the TOVS data; this relationship reverses between 70 and 10 hPa. There are geographical biases, related to the spatial and temporal coverage of the observation types and to the statistical weights assigned to them in the DAS. Forecasts show a tendency to reduce zonal asymmetries in the atmospheric flow and to suppress stratospheric temperature minima. In the DAS, the analysis increments compensate for this, but it leads to important biases in the multi-day forecasts. The analysis increments are as large as the diabatic forcing in the lower polar stratosphere, indicating a substantial model bias. The results provide important insights into the roles of different data types and the circulation model in producing accurate analyses for studies of polar chemistry and physical processes.
    Keywords: Geophysics
    Format: application/pdf
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  • 2
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    Air Mass Factor Formulation for Spectroscopic Measurements from Satellites: Application to Formaldehyde Retrievals from the Global Ozone Monitoring Experiment (2004)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We present a new formulation for the air mass factor (AMF) to convert slant column measurements of optically thin atmospheric species from space into total vertical columns. Because of atmospheric scattering, the AMF depends on the vertical distribution of the species. We formulate the AMF as the integral of the relative vertical distribution (shape factor) of the species over the depth of the atmosphere, weighted by altitude-dependent coefficients (scattering weights) computed independently from a radiative transfer model. The scattering weights are readily tabulated, and one can then obtain the AMF for any observation scene by using shape factors from a three dimensional (3-D) atmospheric chemistry model for the period of observation. This approach subsequently allows objective evaluation of the 3-D model with the observed vertical columns, since the shape factor and the vertical column in the model represent two independent pieces of information. We demonstrate the AMF method by using slant column measurements of formaldehyde at 346 nm from the Global Ozone Monitoring Experiment satellite instrument over North America during July 1996. Shape factors are cumputed with the Global Earth Observing System CHEMistry (GEOS-CHEM) global 3-D model and are checked for consistency with the few available aircraft measurements. Scattering weights increase by an order of magnitude from the surface to the upper troposphere. The AMFs are typically 20-40% less over continents than over the oceans and are approximately half the values calculated in the absence of scattering. Model-induced errors in the AMF are estimated to be approximately 10%. The GEOS-CHEM model captures 50% and 60% of the variances in the observed slant and vertical columns, respectively. Comparison of the simulated and observed vertical columns allows assessment of model bias.
    Keywords: Geophysics
    Type: Paper-2000JD900772. , Journal of Geophysical Research (ISSN 0148-0227); 106; D13; 14,539 - 14,440
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  • 3
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    Friction Stir Welding Development at National Aeronautics and Space Administration-Marshall Space Flight Center (2001)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: This paper presents an over-view of friction stir welding (FSW) process development and applications at Marshall Space Flight Center (MSFC). FSW process development started as a laboratory curiosity but soon found support from many users. The FSW process advanced very quickly and has found many applications both within and outside the aerospace industry. It is currently being adapted for joining key elements of the Space Shuttle External Tank for improved producibility and reliability. FSW process modeling is done to better understand and improve the process. Special tools have been developed to weld variable thickness materials including very thin and very thick materials. FSW is now being applied to higher temperature materials such as copper and to advanced materials such as metal matrix composites. FSW technology is being successfully transferred from MSFC laboratory to shop floors of many commercial companies.
    Keywords: Mechanical Engineering
    Type: TMS Conference; Nov 01, 2001; Indianapolis, IN; United States
    Format: text
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  • 4
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    Friction Stir Welding Development at NASA-Marshall Space Flight Center (2001)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper presents an overview of friction stir welding (FSW) process development and applications at Marshall Space Flight Center (MSFC). FSW process development started as a laboratory curiosity but soon found support from many users. The FSW process advanced very quickly and has found many applications both within and outside the aerospace industry. It is currently being adapted for joining key elements of the Space Shuttle External Tank for improved producibility and reliability. FSW process modeling is done to better understand and improve the process. Special tools have been developed to weld variable thickness materials including thin and thick materials. FSW is now being applied to higher temperature materials such as copper and to advanced materials such as metal matrix composites. FSW technology is being successfully transferred from MSFC laboratory to shop floors of many commercial companies.
    Keywords: Mechanical Engineering
    Type: TMS Special Publication on Friction Stir Welding; Jan 01, 2001; Warrendale, PA; United States
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  • 5
    Electronic Resource
    Electronic Resource
    Geophysics For Slope Stability (2000)
    Springer
    Surveys in geophysics 21 (2000), S. 423-448 
    Details
    ISSN: 1573-0956
    Keywords: Geophysics ; seismic ; electromagnetic ; geo-electric ; resistivity ; self-potential ; gravity ; boundary ; property ; slope stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A pre-requisite in slope stability analyses is that the internal structure and the mechanical properties of the soil or rock mass of the slope, are known or can be estimated with a reasonable degree of certainty. Geophysical methods to determine the internal structure of a soil or rock mass may be used for this purpose. Various geophysical methods and their merits for slope stability analyses are discussed. Seismic methods are often the most suitable because the measurements depend on the mechanical properties that are also important in the mechanical calculation of slope stability analyses. Other geophysical methods, such as electromagnetic, electric resistivity, self-potential, and gravity methods, may be useful to determine the internal structure, but require a correlation of found boundaries with mechanical properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006797126800
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    Paper (German National Licenses)
    Fulltext
  • 6
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    A Software Architecture for Intelligent Synthesis Environments (2001)
    In:  Other Sources
    Details
    Publication Date: 2011-08-31
    Description: The NASA's Intelligent Synthesis Environment (ISE) program is a grand attempt to develop a system to transform the way complex artifacts are engineered. This paper discusses a "middleware" architecture for enabling the development of ISE. Desirable elements of such an Intelligent Synthesis Architecture (ISA) include remote invocation; plug-and-play applications; scripting of applications; management of design artifacts, tools, and artifact and tool attributes; common system services; system management; and systematic enforcement of policies. This paper argues that the ISA extend conventional distributed object technology (DOT) such as CORBA and Product Data Managers with flexible repositories of product and tool annotations and "plug-and-play" mechanisms for inserting "ility" or orthogonal concerns into the system. I describe the Object Infrastructure Framework, an Aspect Oriented Programming (AOP) environment for developing distributed systems that provides utility insertion and enables consistent annotation maintenance. This technology can be used to enforce policies such as maintaining the annotations of artifacts, particularly the provenance and access control rules of artifacts-, performing automatic datatype transformations between representations; supplying alternative servers of the same service; reporting on the status of jobs and the system; conveying privileges throughout an application; supporting long-lived transactions; maintaining version consistency; and providing software redundancy and mobility.
    Keywords: Computer Programming and Software
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  • 7
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    Overview of NASA's UEET Program (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: This paper presents a general overview of NASA's Ultra Efficient Engine Technology (UEET) Program. The program's vision is to develop and hand off revolutionary turbine engine propulsion technologies that will enable future generation vehicles over a wide range of flight speeds. The specific goals include: 1) Perform propulsion technologies to enable increases in system efficiency and, therefore, fuel burn reductions of up to 15% (equivalent reductions in CO2); and 2) Provide combustor technologies (configuration and materials) which will enable reductions in Landing/Take-off (LTO) NOx of 70% relative to 1996 ICAO standards.
    Keywords: Mechanical Engineering
    Type: 2001 NASA Seal/Secondary Air System Workshop; Volume 1; 53-67; NASA/CP-2002-211911/VOL1
    Format: text
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  • 8
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    Sun and Sky Radiance Measurements and Data Analysis Protocols (2001)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: This chapter is concerned with two types of radiometric measurements essential to verify atmospheric correction algorithms and to calibrate vicariously satellite ocean color sensors. The first type is a photometric measurement of the direct solar beam to determine the optical thickness of the atmosphere. The intensity of the solar beam can be measured directly, or obtained indirectly from measurements of diffuse global upper hemispheric irradiance. The second type is a measurement of the solar aureole and sky radiance distribution using a CCD camera, or a scanning radiometer viewing in and perpendicular to the solar principal plane. From the two types of measurements, the optical properties of aerosols, highly variable in space and time, can be derived. Because of the high variability, the aerosol properties should be known at the time of satellite overpass. Atmospheric optics measurements, however, are not easy to perform at sea, from a ship or any platform. This complicates the measurement protocols and data analysis. Some instrumentation cannot be deployed at sea, and is limited to island and coastal sites. In the following, measurement protocols are described for radiometers commonly used to measure direct atmospheric transmittance and sky radiance, namely standard sun photometers, fast-rotating shadow-band radiometers, automated sky scanning systems, and CCD cameras. Methods and procedures to analyze and quality control the data are discussed, as well as proper measurement strategies for evaluation of atmospheric correction algorithms and satellite-derived ocean color.
    Keywords: Geophysics
    Type: In Situ Aerosol Optical Thinkness Collected by the SIMBIOS Program (1997-2000): Protocols, and and Data QC and Analysis; 26-42; NASA/TM-2001-209982
    Format: text
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  • 9
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    Overview of NASA Glenn Seal Development Program (2001)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: NASA Glenn hosted the Seals/Secondary Air System Workshop on October 25-26, 2000. Each year NASA and our industry and university partners share their respective seal technology developments. We use these workshops as a technical forum to exchange recent advancements and 'lessons-learned' in advancing seal technology and solving problems of common interest. As in the past we are publishing two volumes. Volume I will be publicly available and individual papers will be made available online through the web page address listed at the end of this chapter.
    Keywords: Mechanical Engineering
    Type: 2000 NASA Seal/Secondary Air System Workshop; Volume 1; 1-21; NASA/CP-2001-211208/VOL1
    Format: text
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  • 10
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    Managing Distributed Systems with Smart Subscriptions (2000)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: We describe an event-based, publish-and-subscribe mechanism based on using 'smart subscriptions' to recognize weakly-structured events. We present a hierarchy of subscription languages (propositional, predicate, temporal and agent) and algorithms for efficiently recognizing event matches. This mechanism has been applied to the management of distributed applications.
    Keywords: Computer Programming and Software
    Type: Distributed Objects in Computational Science; Unknown
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