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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRSDate not supplied

Passenger Aggregation Network with Very Efficient Listing (PANVEL) Ridesharing Model for Urban Air Mobility

This paper introduces a ridesharing model useful for examining the role of ridesharing in advancing Urban Air Mobility (UAM) operations. Although the success of UAM will likely require a host of new technologies in aircraft design, airspace management, autonomy, and more, operational innovations like ridesharing may also be key, especially to lower operating costs and attract a broader market. The ridesharing algorithm introduced, termed the Passenger Aggregation Network with Very Efficient Listing (PANVEL) model, estimates trip numbers and passenger occupancy aboard particular aircraft within a UAM network in a metropolitan area. This algorithm is applied within a transportation computational framework to determine the impact of ridesharing on mode choice, passenger travel patterns, and transportation costs. The algorithm aggregates passengers traveling between identical origin-destination pairs, factoring in individual-specific metrics, such as value of time and alternative mode options, to generate high load factors on UAM aircraft. The computational framework simulates passenger mode-choice selections using an effective-cost approach to determine the number of ridesharing UAM-preferred trips, and results with ridesharing are representative of a rough upper bound on UAM ridership potential for a given metro area. A case study in the Cleveland metro area is presented to demonstrate the algorithm and assess ridesharing potential.

advanced air mobility↗
NASA NTRSDate not supplied

Passenger Aggregation Network with Very Efficient Listing (PANVEL) Ridesharing Model for Urban Air Mobility

This presentation introduces a ridesharing model useful for examining the role of ridesharing in advancing Urban Air Mobility (UAM) operations. Although the success of UAM will likely require a host of new technologies in aircraft design, airspace management, autonomy, and more, operational innovations like ridesharing may also be key, especially to lower operating costs and attract a broader market. The ridesharing algorithm introduced, termed the Passenger Aggregation Network with Very Efficient Listing (PANVEL) model, estimates trip numbers and passenger occupancy aboard particular aircraft within a UAM network in a metropolitan area. This algorithm is applied within a transportation computational framework to determine the impact of ridesharing on mode choice, passenger travel patterns, and transportation costs. The algorithm aggregates passengers traveling between identical origin-destination pairs, factoring in individual-specific metrics, such as value of time and alternative mode options, to generate high load factors on UAM aircraft. The computational framework simulates passenger mode-choice selections using an effective-cost approach to determine the number of ridesharing UAM-preferred trips, and results with ridesharing are representative of a rough upper bound on UAM ridership potential for a given metro area. A case study in the Cleveland metro area is presented to demonstrate the algorithm and assess ridesharing potential.

advanced air mobility↗
NASA NTRS2023

Coronal Heating as Determined by the Solar Flare Frequency Distribution Obtained by Aggregating Case Studies

Flare frequency distributions represent a key approach to addressing one of the largest problems in solar and stellar physics: determining the mechanism that counterintuitively heats coronae to temperatures that are orders of magnitude hotter than the corresponding photospheres. It is widely accepted that the magnetic field is responsible for the heating, but there are two competing mechanisms that could explain it: nanoflares or Alfvén waves. To date, neither can be directly observed. Nanoflares are, by definition, extremely small, but their aggregate energy release could represent a substantial heating mechanism, presuming they are sufficiently abundant. One way to test this presumption is via the flare frequency distribution, which describes how often flares of various energies occur. If the slope of the power law fitting the flare frequency distribution is above a critical threshold, α = 2 as established in prior literature, then there should be a sufficient abundance of nanoflares to explain coronal heating. We performed >600 case studies of solar flares, made possible by an unprecedented number of data analysts via three semesters of an undergraduate physics laboratory course. This allowed us to include two crucial, but nontrivial, analysis methods: preflare baseline subtraction and computation of the flare energy, which requires determining flare start and stop times. We aggregated the results of these analyses into a statistical study to determine that α = 1.63 ± 0.03. This is below the critical threshold, suggesting that Alfvén waves are an important driver of coronal heating.

Astrostatistics distributions↗
NASA NTRS2016

Advancing the Power and Utility of Server-Side Aggregation

During the upcoming Summer 2016 meeting of the ESIP Federation (July 19-22), OpenDAP will hold a Developers and Users Workshop. While a broad set of topics will be covered, a key focus is capitalizing on recent EOSDIS-sponsored advances in Hyrax, OPeNDAPs own software for server-side realization of the DAP2 and DAP4 protocols. These Hyrax advances are as important to data users as to data providers, and the workshop will include hands-on experiences of value to both. Specifically, a balanced set of presentations and hands-on tutorials will address advances in1.server installation,2.server configuration,3.Hyrax aggregation capabilities,4.support for data-access from clients that are HTTP-based, JSON-based or OGC-compliant (especially WCS and WMS),5.support for DAP4,6.use and extension of server-side computational capabilities, and7.several performance-affecting matters.Topics 2 through 7 will be relevant to data consumers, data providers andnotably, due to the open-source nature of all OPeNDAP softwareto developers wishing to extend Hyrax, to build compatible clients and servers, andor to employ Hyrax as middleware that enables interoperability across a variety of end-user and source-data contexts. A session for contributed talks will elaborate the topics listed above and embrace additional ones.

aggregation↗
NASA NTRS2019

OPeNDAP Clients, Aggregation and S3

In this talk, we will discuss our work for testing OPeNDAP client access of data stored in the Amazon S3 cloud storage using a set of common analysis tools including Panoply, Jupyter Notebooks with Python xarray, NCO command line tool package, ArcGIS, and GDAL. We will also discuss our ongoing work on improving performance in Hyrax aggregation functionality.

Amazon S3↗
NASA NTRSDate not supplied

Statistical Descriptors of Composite Fiber Aggregation

This study introduces a method of characterizing fiber aggregation and resin rich regions in composite microstructures. Microscale models of representative elements (RVE) need to be indicative of the extend of clustering (i.e. close fiber-to-fiber interaction) and resin rich “pools” which may impact the overall strength and performance of a composite structure. This algorithm was used to evaluate different unidirectional 2-D microstructure scans, which will be compared to their manufacturing method or any special treatment processes. These cluster and pool scan statistics can be used as criteria to judge statistical equivalency of artificially constructed microstructures.

Statistics↗
NASA NTRS2022

A Record of Low-Temperature Asteroidal Processes of Amoeboid Olivine Aggregates from the Kainsaz Co3.2 Chondrite

Amoeboid olivine aggregates (AOAs) from the Kainsaz CO3.2 chondrite were analyzed using transmission electron microscopy in order to gain a more complete understanding of thermal metamorphism on the parent body and the role of fluids during metamorphic heating. The Kainsaz AOAs are dominated by strongly zoned, fine-grained, olivine grains (Fa2-31) with heterogeneous Fe enrichments along the grain boundaries, which are interpreted as the result of 26Fe2+-Mg2+ interdiffusion with the matrix during thermal metamorphism. However, our diffusion calculations show that such AOA olivine zoning and compositions cannot be produced by a simple diffusional exchange during metamorphic heating, unlike chondrule olivine zoning and compositions. In addition, fine-grained ferroan olivine overgrowths occur heterogeneously in crystallographic continuity with olivines on the AOA exteriors. The overgrowths (Fa33-36) are compositionally distinct from the underlying AOA olivines and are not fully equilibrated with the matrix olivines (Fa~20-55).The ferroan olivine overgrowths likely formed by precipitation from fluids in an epitaxial relationship with forsteritic olivine on the edges of AOAs. Texturally and compositionally diverse chromite grains are also observed along olivine grain boundaries, in olivine grains, and in pore spaces between olivine grains. They share a similar crystallographic orientation relationships with adjacent olivine, suggestive of their formation by exsolution and/or epitaxial growth. Collectively, these observations provide evidence for the mobilization of Fe, Mg, Si, Cr, and Al in the presence of fluids along olivine grain boundaries and into olivine grains during thermal metamorphism. We conclude that in Kainsaz AOAs, the strong zonation development in individual olivine grains and the formation of ferroan olivine overgrowths and chromite grains were a fluid-driven process that occurred at relatively low temperatures (<500°C), during the cooling history of the CO3 chondrite parent body, following the peak of thermal metamorphism.

Amoeboid olivine aggregates↗
NASA NTRS2022

Assessment of Aggregate Risk for JWST

This presentation communicates the aggregate assessment of risk performed for the James Webb Space Telescope prior to shipping the observatory to the launch site.

JWST↗
NASA NTRSDate not supplied

Characteristics of Extreme Precipitation Events (EPE) in the Tropics and Association with Convective Aggregation

Extreme precipitation (EP) has become increasingly frequent and is causing more devastating impacts on society in recent years. EP is traditionally measured by the maximum or threshold-exceeding gridded precipitation of a given duration. We have developed an extreme precipitation event (EPE) algorithm that tracks entire precipitation life cycle across space and time, which enables us to characterize properties of the entire EPE, such as duration (from sub-daily to multi-day), areal coverage, and total rain volume of the event. These EPE characteristics are critical in understanding precipitation development and their interaction with large-scale meteorology, in addition, providing more comprehensive matrix for disaster management. This study examines the EPE characteristics from the tropics derived from high-resolution Integrated Multi-satellitE Retrievals fro GPM (IMERG) product. The difference between EPE characteristics between tropical land and ocean will be discussed. Large-scale meteorological control as well as convective aggregation will be studied on the impact of EPE characteristics in tropics.

Convective aggregation↗
NASA NTRS1973

Contact thermal conductivity in lunar aggregates.

The contribution of the contact conductivity to the thermal conductivity in aggregates is found to depend on pressure with an exponent greater than 1/3 and, for a specific model with an exponent of 3/5, when the particle packing is irregular. A lunar thermal conductivity profile near the surface, including a term involving depth to the 3/5 power, is considered.

Pilbeam, C. C.↗
NASA NTRS1973

Elastic properties of plagioclase aggregates and seismic velocities in the moon

The compressional velocities of Apollo 16 gabbroic anorthosites in which the cracks have been closed match the seismic velocity of 7 km/sec in the 25 to 65 km depth region of the moon beneath the Imbrium Basin. The intrinsic velocities of plagioclase aggregates indicate that a velocity of 7 km/sec in a highly calcic gabbroic anorthosite is consistent only with a very small pyroxene component. Because mare basalts and gabbroic-anorthosites both have intrinsic velocities of 7 km/sec, the laboratory velocity data do not require a compositional change from basalt to anorthosite at the 25 km discontinuity. The laboratory velocity data only imply that the 25 km seismic discontinuity is one of microcrack density. The physical rather than the chemical or mineralogical state is constrained.

Wang, H.↗
NASA NTRS1973

Origin and characteristics of excess Fe metal in lunar glass welded aggregates

We show that the characteristic features of lunar glass welded aggregates including their irregular shapes, vesicularity, and content of submicron Fe metal in the welding glass can be explained by a model in which they are predominantly formed by micrometeorite impacts into the solar wind saturated topmost surface of the regolith. The Fe metal is reduced from silicates by the solar wind gases. Other possible mechanisms of Fe metal formation are discussed and shown to play at most minor roles. It is shown that surface tension forces control vesicularity and that the low gravity and high vacuum conditions prevailing on the moon are unimportant. Consequences of this surface tension control to possible lunar eruptive volcanism and to the Ar-40/Ar-39 dating of impact events are discussed.

Housley, R. M.↗
NASA NTRS1974

Decomposition-aggregation stability analysis of the spinning Skylab

Stability of an 11-th order linear model of the spinning Skylab is determined by the decomposition-aggregation method based upon the comparison principle and vector Liapunov functions. To reduce the inherent conservativeness of the method an optimization problem is formulated and resolved producing the optimum comparison system. The system provides the best estimate of the stability region of the important structural parameter - asymmetry in the boom settings.

Cuk, S. M.↗
NASA NTRS1975

Compartmentalization of amino acids in surfactant aggregates - Partitioning between water and aqueous micellar sodium dodecanoate and between hexane and dodecylammonium propionate trapped water in hexane

The partitioning of amino acids (glycine, alanine, leucine, phenylalanine, histidine, aspartic acid, glutamic acid, lysine, isoleucine, threonine, serine, valine, proline, arginine) in aqueous and nonaqueous micellar systems was studied experimentally. Partitioning from neat hexane into dodecylammonium propionate trapped water in hexane was found to be dependent on both electrostatic and hydrophobic interactions, which implies that the interior of dodecylammonium propionate aggregates is negatively charged and is capable of hydrogen bonding in addition to providing a hydrophobic environment. Unitary free energies of transfer of amino acid side chains from hexane to water were determined and solubilities of amino acids in neat hexane substantiated the amino acid hydrophobicity scale. The relevance of the experiments to prebiotic chemistry was examined.

Fendler, J. H.↗
NASA NTRS1980

Swarms: Optimum aggregations of spacecraft

Swarms are aggregations of spacecraft or elements of a space system which are cooperative in function, but physically isolated or only loosely connected. For some missions the swarm configuration may be optimum compared to a group of completely independent spacecraft or a complex rigidly integrated spacecraft or space platform. General features of swarms are induced by considering an ensemble of 26 swarms, examples ranging from Earth centered swarms for commercial application to swarms for exploring minor planets. A concept for a low altitude swarm as a substitute for a space platform is proposed and a preliminary design studied. The salient design feature is the web of tethers holding the 30 km swarm in a rigid two dimensional array in the orbital plane. A mathematical discussion and tutorial in tether technology and in some aspects of the distribution of services (mass, energy, and information to swarm elements) are included.

Mayer, H. L.↗