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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Comments on the effect of adopting new precession and equinox corrections

It is shown that the derived terrestrial longitude zero point and UT1 rate will be different when determined by classical optical and space techniques so long as the precession constant and equinox offset and drift are imperfectly known. For the uncertainty of the new IAU precession constant, this inconsistency is expected to be nearly 0.04 arcsec in longitude and 0.1 ms/yr in UT1 rate. The consistency of constants does not guarantee consistent results. The classical practice of defining Greenwich Mean Sidereal Time (GMST) as invariant with respect to a fixed equinox if the longitude and UT1 results from the inertial techniques are to be stable against changes in the precession constant. One form for GMST is given.

Williams, J. G.↗
NASA NTRS1985

The evolution of adopted values for precession

The history of astronomical longitude precession determination is reviewed. Consideration is given to the work of Hipparchus and Ptolemy, the definition of rotation axes, the major 19th-century determinations, and 20th-century studies (using the data of Newcomb; based on PGC, GC, and McCormick/Cape catalogs; using FK3, FK4, and AGK3; involving galaxies; and using the dynamical method). Laser ranging and VLBI are seen as the most promising techniques for future precession measurements. Diagrams, graphs, and tables of numerical data are provided.

Lieske, J. H.↗
NASA NTRS1989

Atmospheric density remote sensing of mesosphere and thermosphere to be used for spacecraft design by adopting VHF radar and HF Doppler sounder at low latitude west Pacific site during winter time

Simultaneous observations of VHF radar and HF Doppler array systems located at Chung Li (Taiwan) are used to observe three-dimensional wind speeds and gravity waves. The density perturbations are determined at different altitudes of the mesosphere and thermosphere during weak convective motions of the cold front in the winter. The present observations are believed to be valuable for space projects dealing with the low-latitude atmosphere.

Hung, R. J.↗
NASA NTRS1939

Preliminary Report on Laminar-Flow Airfoils and New Methods Adopted for Airfoil and Boundary-Layer Investigations

Recent developments in airfoil-testing methods and fundamental air-flow investigations, as applied to airfoils, are discussed. Preliminary test results, obtained under conditions relatively free from stream turbulence and other disturbances, are presented. Suitable airfoils and airfoil-design principles were developed to take advantage of the unusually extensive laminar boundary layers that may be maintained under the improved testing conditions. The results are of interest mainly in range of below 6,000,000.

AIRFOILS - NACA 27-209-CHAR , A C , MOMENTS, C P &↗
NASA NTRS1995

Wormgear geometry adopted for implementing hydrostatic lubrication and formulation of the lubrication problem

The geometrical parameters for a wormgear intended to be used as the transmission in advanced helicopters are finalized. The resulting contact pattern of the meshing tooth surfaces is suitable for the implementation of hydrostatic lubrication Fluid film lubrication of the contact is formulated considering external pressurization as well as hydrodynamic wedge and squeeze actions. The lubrication analysis is aimed at obtaining the oil supply pressure needed to separate the worm and gear surfaces by a prescribed minimum film thickness. The procedure of solving the mathematical problem is outlined.

Sun, D. C.↗
NASA NTRS2001

On Quality Control Procedures Being Adopted for TRMM LBA and KWAJEX Soundings Data Sets

During NASA's Tropical Rainfall Measuring Mission (TRMM) field campaigns Large Scale Biosphere Atmosphere (LBA) held in Amazonia (Brazil) in the period January- February, 1999, and the Kwajalein Experiment (KWAJEX) held in the Republic of Marshall Islands in the period between August-September, 1999, extensive radiosonde observations (raob) were collected using VIZ and Vaisala sondes which have different response characteristics. In all, 320 raob for LBA and 972 fixed raob for KWAJEX have been obtained and are being processed. Most atmospheric sensible heat source (Q1) and apparent moisture sink (Q2) budget studies are based on sounding data, and the accuracy of the raob is important especially in regions of deep moist convection. A data quality control (QC) project has been initiated at GSFC by the principal investigator (JBH), and this paper addresses some of the quantitative findings for the level I and II QC procedures. Based on these quantitative assessment of sensor (or system) biases associated with each type of sonde, the initial data repair work will be started. Evidence of moisture biases between the two different sondes (VIZ and Vaisala) has been shown earlier by Halverson et al. (2000). Vaisala humidity sensors are found to have a low-level dry bias in the boundary layer, whereas above 600 mb the VIZ sensor tends to register a dryer atmosphere. All raob data were subjected to a limit check based on an algorithm already well tested for the raob data obtained during the Tropical Ocean Global Atmosphere (TOGA-COARE).

Roy, B.↗
NASA NTRS2003

Hosted Services for Advanced V and V Technologies: An Approach to Achieving Adoption without the Woes of Usage

Attempts to achieve widespread use of software verification tools have been notably unsuccessful. Even 'straightforward', classic, and potentially effective verification tools such as lint-like tools face limits on their acceptance. These limits are imposed by the expertise required applying the tools and interpreting the results, the high false positive rate of many verification tools, and the need to integrate the tools into development environments. The barriers are even greater for more complex advanced technologies such as model checking. Web-hosted services for advanced verification technologies may mitigate these problems by centralizing tool expertise. The possible benefits of this approach include eliminating the need for software developer expertise in tool application and results filtering, and improving integration with other development tools.

Koga, Dennis↗
NASA NTRS2003

Using CASE to Adopt Organizational Learning at NASA

The research direction was articulated in a statement of work created in collaboration between two program colleagues, an outside researcher and an internal user. The researcher was to deliver an implemented CASE tool (CasewiseTM) that was to be used to serve non-traditional (i.e., not software development related) organizational purposes. The explicitly stated functions of the tool were the support of 1) ISO-9000 compliance in the documentation of processes and 2) the management of process improvement. The collaborative team consisted of the researcher (GT), a full-time accompanying student (CRO), and the user (JD). The team originally focused on populating the CASE repository for the purpose of solving the two primary objectives. Consistent with the action research approach, several additional user requirements emerged as the project evolved, needs became apparent in discussions about how the tool would be used to solve organizational problems. These deliverables were contained within the CASE repository: 1) the creation of a paradigm diagram 2) the creation of a context diagram 3) the creation of child diagrams 4) the generation of 73 issues relating to organizational change 5) a compendium of stakeholder interview transcripts All record keeping was done manually and then keyed into the CASE interface. An issue is the difference between an organization s current situation (action) and its collective ideals.

Templeton, Gary F.↗
NASA NTRS2002

Adopting Industry Standards for Control Systems Within Advanced Life Support

This paper gives a description of OPC (Object Linking and Embedding for Process Control) standards for process control and outlines the experiences at JSC with using these standards to interface with I/O hardware from three independent vendors. The I/O hardware was integrated with a commercially available SCADA/HMI software package to make up the control and monitoring system for the Environmental Systems Test Stand (ESTS). OPC standards were utilized for communicating with I/O hardware and the software was used for implementing monitoring, PC-based distributed control, and redundant data storage over an Ethernet physical layer using an embedded din-rail mounted PC.

Young, James Scott↗
NASA NTRS2012

Cognitive Network Modeling as a Basis for Characterizing Human Communication Dynamics and Belief Contagion in Technology Adoption

Societal level macro models of social behavior do not sufficiently capture nuances needed to adequately represent the dynamics of person-to-person interactions. Likewise, individual agent level micro models have limited scalability - even minute parameter changes can drastically affect a model's response characteristics. This work presents an approach that uses agent-based modeling to represent detailed intra- and inter-personal interactions, as well as a system dynamics model to integrate societal-level influences via reciprocating functions. A Cognitive Network Model (CNM) is proposed as a method of quantitatively characterizing cognitive mechanisms at the intra-individual level. To capture the rich dynamics of interpersonal communication for the propagation of beliefs and attitudes, a Socio-Cognitive Network Model (SCNM) is presented. The SCNM uses socio-cognitive tie strength to regulate how agents influence--and are influenced by--one another's beliefs during social interactions. We then present experimental results which support the use of this network analytical approach, and we discuss its applicability towards characterizing and understanding human information processing.

Hutto, Clayton↗
NASA NTRS2014

Agent Based Modeling of Air Carrier Behavior for Evaluation of Technology Equipage and Adoption

As part of ongoing research, the National Aeronautics and Space Administration (NASA) and LMI developed a research framework to assist policymakers in identifying impacts on the U.S. air transportation system (ATS) of potential policies and technology related to the implementation of the Next Generation Air Transportation System (NextGen). This framework, called the Air Transportation System Evolutionary Simulation (ATS-EVOS), integrates multiple models into a single process flow to best simulate responses by U.S. commercial airlines and other ATS stakeholders to NextGen-related policies, and in turn, how those responses impact the ATS. Development of this framework required NASA and LMI to create an agent-based model of airline and passenger behavior. This Airline Evolutionary Simulation (AIRLINE-EVOS) models airline decisions about tactical airfare and schedule adjustments, and strategic decisions related to fleet assignments, market prices, and equipage. AIRLINE-EVOS models its own heterogeneous population of passenger agents that interact with airlines; this interaction allows the model to simulate the cycle of action-reaction as airlines compete with each other and engage passengers. We validated a baseline configuration of AIRLINE-EVOS against Airline Origin and Destination Survey (DB1B) data and subject matter expert opinion, and we verified the ATS-EVOS framework and agent behavior logic through scenario-based experiments. These experiments demonstrated AIRLINE-EVOS's capabilities in responding to an input price shock in fuel prices, and to equipage challenges in a series of analyses based on potential incentive policies for best equipped best served, optimal-wind routing, and traffic management initiative exemption concepts..

Horio, Brant M.↗
NASA NTRS2014

A Framework for Land Cover Classification Using Discrete Return LiDAR Data: Adopting Pseudo-Waveform and Hierarchical Segmentation

Acquiring current, accurate land-use information is critical for monitoring and understanding the impact of anthropogenic activities on natural environments.Remote sensing technologies are of increasing importance because of their capability to acquire information for large areas in a timely manner, enabling decision makers to be more effective in complex environments. Although optical imagery has demonstrated to be successful for land cover classification, active sensors, such as light detection and ranging (LiDAR), have distinct capabilities that can be exploited to improve classification results. However, utilization of LiDAR data for land cover classification has not been fully exploited. Moreover, spatial-spectral classification has recently gained significant attention since classification accuracy can be improved by extracting additional information from the neighboring pixels. Although spatial information has been widely used for spectral data, less attention has been given to LiDARdata. In this work, a new framework for land cover classification using discrete return LiDAR data is proposed. Pseudo-waveforms are generated from the LiDAR data and processed by hierarchical segmentation. Spatial featuresare extracted in a region-based way using a new unsupervised strategy for multiple pruning of the segmentation hierarchy. The proposed framework is validated experimentally on a real dataset acquired in an urban area. Better classification results are exhibited by the proposed framework compared to the cases in which basic LiDAR products such as digital surface model and intensity image are used. Moreover, the proposed region-based feature extraction strategy results in improved classification accuracies in comparison with a more traditional window-based approach.

Light Detection & Ranging (LIDAR)↗