Results for “observable behavior” — Page 45

NASA NTRS2000

Metastable Eutectic Equilibrium in Natural Environments: Recent Developments and Research Opportunities

Chemical ordering at metastable eutectics was recognized in non-equilibrium gas-to- solid condensation experiments to constrain 'silicate' dust formation in O-rich circumstellar environments. The predictable metastable eutectic behavior successfully predicted the observed ferromagnesiosilica, compositions of circumstellar dust, presolar and solar nebula grains in the matrix of the collected aggregate IDPs. Many of the experimentally determined metastable eutectic solids match the fundamental building blocks of common rock-forming layer silicates: this could have implications for the origin of Life. The physical conditions conducive to metastable eutectic behavior, i.e. high temperature and (ultra)fast quenching, lead to unique amorphous, typically nano- to micrometer-sized, materials. The new paradigm of metastable eutectic behavior opens the door to new and exciting research opportunities in uncovering the many implications of these unique amorphous and typically nano- to micrometer-sized, metastable eutectic materials.

Rietmeijer, Fans J. M.↗

NASA NTRS2000

Metastable Eutectic Equilibrium in Natural Environments: Recent Development and Research Opportunities

Chemical ordering at metastable eutectics was recognized in non-equilibrium gas-to- solid condensation experiments to constrain 'silicate' dust formation in O-rich circumstellar environments. The predictable metastable eutectic behavior successfully predicted the observed ferromagnesiosilica compositions of circumstellar dust presolar and solar nebula grains in the matrix of the collected aggregate IDPs (Interplanetary Dust Particles). Many of the experimentally determined metastable eutectic solids match the fundamental building blocks of common rock-forming layer silicates: this could have implications for the origin of Life. The physical conditions conducive to metastable eutectic behavior, i.e. high temperature and (ultra) fast quenching, lead to unique amorphous, typically nano- to micrometer-sized, materials. The new paradigm of metastable eutectic behavior opens the door to new and exciting research opportunities in uncovering the many implications of these unique amorphous, and typically nano-to micrometer-sized, metastable eutectic materials.

Rietmeijer, Frans J. M.↗

NASA NTRS2016

Physics of the Cosmos: Program Annual Technology Report

From ancient times, humans have looked up at the night sky and wondered: Are we alone? How did the universe come to be? How does the universe work? PCOS focuses on that last question. Scientists investigating this broad theme use the universe itself as their laboratory, investigating its fundamental laws and properties. They test Einstein's General Theory of Relativity to see if our current understanding of space-time is borne out by observations. They examine the behavior of the most extreme environments - supermassive black holes, active galactic nuclei, and others - and the farthest reaches of the universe, to expand our understanding. With instruments sensitive across the spectrum, from radio, through infrared (IR), visible light, ultraviolet (UV), to X rays and gamma rays, as well as gravitational waves (GWs), they peer across billions of light-years, observing echoes of events that occurred instants after the Big Bang. The Laser Interferometer Gravitational-Wave Observatory (LIGO) recently recorded the first direct measurement of long-theorized GWs. Another surprising recent discovery is that the universe is expanding at an ever-accelerating rate, the first hint of so-called "dark energy," estimated to account for 75% of mass-energy in the universe. Dark matter, so called because we can only observe its effects on regular matter, accounts for another 20%, leaving only 5% for regular matter and energy. Scientists now also search for special polarization in the cosmic microwave background to support the notion that in the split-second after the Big Bang, the universe inflated faster than the speed of light! The most exciting aspect of this grand enterprise today is that we can finally develop the tools needed for such discoveries.

COR↗

NASA NTRS2017

Program Annual Technology Report: Physics of the Cosmos Program Office

From ancient times, humans have looked up at the night sky and wondered: Are we alone? How did the universe come to be? How does the universe work? PCOS focuses on that last question. Scientists investigating this broad theme use the universe as their laboratory, investigating its fundamental laws and properties. They test Einstein’s General Theory of Relativity to see if our current understanding of space-time is borne out by observations. They examine the behavior of the most extreme environments – supermassive black holes, active galactic nuclei, and others – and the farthest reaches of the universe, to expand our understanding. With instruments sensitive across the spectrum, from radio, through infrared (IR), visible light, ultraviolet (UV), to X rays and gamma rays, as well as gravitational waves (GWs), they peer across billions of light-years, observing echoes of events that occurred instants after the Big Bang. Last year, the LISA Pathfinder (LPF) mission exceeded expectations in proving the maturity of technologies needed for the Laser Interferometer Space Antenna (LISA) mission, and the Laser Interferometer Gravitational-Wave Observatory (LIGO) recorded the first direct measurements of long-theorized GWs. Another surprising recent discovery is that the universe is expanding at an ever-accelerating rate, the first hint of so-called “dark energy,” estimated to account for 75% of mass-energy in the universe. Dark matter, so called because we can only observe its effects on regular matter, is thought to account for another20%, leaving only 5% for regular matter and energy. Scientists now also search for special polarization in the cosmic microwave background to support the notion that in the split-second after the Big Bang, the universe inflated faster than the speed of light! The most exciting aspect of this grand enterprise today is the extraordinary rate at which we can harness technologies to enable these key discoveries.

COR↗

NASA NTRS2011

Evaluation of Global Observations-Based Evapotranspiration Datasets and IPCC AR4 Simulations

Quantification of global land evapotranspiration (ET) has long been associated with large uncertainties due to the lack of reference observations. Several recently developed products now provide the capacity to estimate ET at global scales. These products, partly based on observational data, include satellite ]based products, land surface model (LSM) simulations, atmospheric reanalysis output, estimates based on empirical upscaling of eddycovariance flux measurements, and atmospheric water balance datasets. The LandFlux-EVAL project aims to evaluate and compare these newly developed datasets. Additionally, an evaluation of IPCC AR4 global climate model (GCM) simulations is presented, providing an assessment of their capacity to reproduce flux behavior relative to the observations ]based products. Though differently constrained with observations, the analyzed reference datasets display similar large-scale ET patterns. ET from the IPCC AR4 simulations was significantly smaller than that from the other products for India (up to 1 mm/d) and parts of eastern South America, and larger in the western USA, Australia and China. The inter-product variance is lower across the IPCC AR4 simulations than across the reference datasets in several regions, which indicates that uncertainties may be underestimated in the IPCC AR4 models due to shared biases of these simulations.

Mueller, B.↗

NASA NTRS1984

Magnetic buoyancy and the escape of magnetic fields from stars

A loss of magnetic flux through the free surface of a star into the surrounding space has important implications for the generation of the field within the star. The present investigation is concerned with the physics of the escape of net azimuthal flux from a star. The obtained results are used as a basis for the interpretation of some recent observations of the detailed behavior of magnetic fields emerging through the surface of the sun. The buoyancy of an isolated horizontal magnetic flux tube beneath the surface of a star causes the tube to rise at a rate comparable to the Alfven speed. The necessary conditions for escape of the flux are considered along with aspects of magnetic buoyancy, and the conditions on the sun. It appears that the observed retraction of bipolar magnetic fields at the end of their life at the surface is the one phenomenon which requires dynamical intervention. Attention is given to known dynamical effects which suppress the buoyant rise of an azimuthal magnetic field.

Parker, E. N.↗

NASA NTRS1987

Correlation between spectral state and quasi-periodic oscillation parameters in GX 5-1

In a series of seven Exosat observations, the bimodal spectral behavior and the quasi-periodic oscillation (QPO)/red noise properties of GX 5-1 show a strict correlation. In one of the two spectral states (characterized by a 'horizontal branch' in the hardness-intensity diagram), strong 20-40 Hz QPO and red noise below about 60 Hz were always present. In the other ('normal branch'), no QPO between 6 and 60 Hz or red noise above 1 Hz were detected, but there was an indication for weak QPO near 5 Hz. In both states 'very low frequency noise' (VLFN) is detected below 0.1 Hz which has a power-law shape and and which extends down to the lowest observed frequencies (0.0001 Hz). The VLFN is probably not directly related to the QPO. The results are compared to those on Sco X-1 and Cyg X-2 and it is concluded that, although all three sources show bimodal spectral and QPO/red noise behavior, there is a qualitative difference between GX 5-1 and Cyg X-2 on one hand and Sco X-1 on the other.

Van Der Klis, M.↗

NASA NTRSDate not supplied

An Approach to Identifying Aspects of Positive Pilot Behavior within the Aviation Safety Reporting System

The National Airspace System (NAS) is constantly evolving as air traffic continues to ramp up to pre-pandemic numbers and projected to grow to unprecedented levels in the coming years. As well as increasing demand to the current system, emerging operations such as Unmanned Autonomous Systems are also expected to add to complexity in the airspace. To address these issues, the industry and government agencies supporting the NAS will need to rely upon additional automation and new technologies to address future operational requirements, while continuing to be a world-leading safe transportation system. As these new technologies are implemented, the system continues to rely on human pilots and controllers in the loop to monitor the system and intervene in situations the automation cannot handle. The goal of proactively addressing safety is of foremost concern to ensure passenger confidence. The industry has implemented various Safety Monitoring Systems to identify safety risks and proactively address them before they result in a serious incident or accident. One such program is the Aviation Safety Reporting System (ASRS). ASRS is a long-established system where pilots and controllers voluntarily and anonymously report safety incidents they experienced and observed during line operations by providing rich text narratives describing the events, the environment, and conditions leading to the safety event of concern. These narratives provide insight and context around events of interest and can be used to identify emerging problems. They can trigger investigations within Flight Operational Quality Assurance or Flight Data Monitoring programs. However, this process typically focuses on the adverse events and the unsafe aspects of the operations surrounding the reported or detected events. This perspective of investigating factors that went wrong around an adverse event is commonly referred to as Safety I. Alternatively, characterizing successful actions that operators perform every day under varying conditions that keep the system within safe operating bounds is a concept referred to as Safety II. The benefit of the Safety II view is that the scope is much larger than that of Safety I since a vast majority of the operations result in successful flights. Many of the successful techniques used to manage operational threats are not documented in standard operating procedures or taught during training. They are typically acquired over time by working with experienced pilots during line operations or in many cases after experiencing a problem for the first time and reacting to it in situ, drawing from years of experience to manage the threat. In an attempt to quantify these positive actions, we are proposing an approach to extracting key behaviors within ASRS reports that can support the Safety II concept. Our analysis assumes that ASRS reports contain some descriptions of corrective actions that operators performed to prevent a situation from leading to an accident. Leveraging recent advances in Natural Language Process modeling, we have developed an approach to extract positive sentiment from reports, embed these positive statements in a vector space where they can be numerically analyzed, and clustering these statements into similar contextual categories. From these contextualized categories we can attempt to summarized and distilled aspects of the positive behavior. The goal is to identify categories of behavior that describe consistent operator techniques that supports the Safety II concept. With this information, airlines may enable learning from these positive actions, or address procedures that need to be changed to avoid having pilots implement a workaround. These insights can provide a lens into what is “going right” in the operations that may otherwise not be known widely within the community. It is envisioned that this approach can be extended to other narrative programs such as Line Operation Safety Audit or Learning Improvement Team reports where similar observed behavior can be analyzed to extract positive actions and inform the overall operations.

NLP↗

NASA NTRSDate not supplied

An Approach to Identifying Aspects of Positive Pilot Behavior within the Aviation Safety Reporting System

The National Airspace System (NAS) is constantly evolving as air traffic continues to ramp up to pre-pandemic numbers and projected to grow to unprecedented levels in the coming years. As well as increasing demand to the current system, emerging operations such as Unmanned Autonomous Systems are also expected to add to complexity in the airspace. To address these issues, the industry and government agencies supporting the NAS will need to rely upon additional automation and new technologies to address future operational requirements, while continuing to be a world-leading safe transportation system. As these new technologies are implemented, the system continues to rely on human pilots and controllers in the loop to monitor the system and intervene in situations the automation cannot handle. The goal of proactively addressing safety is of foremost concern to ensure passenger confidence. The industry has implemented various Safety Monitoring Systems to identify safety risks and proactively address them before they result in a serious incident or accident. One such program is the Aviation Safety Reporting System (ASRS). ASRS is a long-established system where pilots and controllers voluntarily and anonymously report safety incidents they experienced and observed during line operations by providing rich text narratives describing the events, the environment, and conditions leading to the safety event of concern. These narratives provide insight and context around events of interest and can be used to identify emerging problems. They can trigger investigations within Flight Operational Quality Assurance or Flight Data Monitoring programs. However, this process typically focuses on the adverse events and the unsafe aspects of the operations surrounding the reported or detected events. This perspective of investigating factors that went wrong around an adverse event is commonly referred to as Safety I. Alternatively, characterizing successful actions that operators perform every day under varying conditions that keep the system within safe operating bounds is a concept referred to as Safety II. The benefit of the Safety II view is that the scope is much larger than that of Safety I since a vast majority of the operations result in successful flights. Many of the successful techniques used to manage operational threats are not documented in standard operating procedures or taught during training. They are typically acquired over time by working with experienced pilots during line operations or in many cases after experiencing a problem for the first time and reacting to it in situ, drawing from years of experience to manage the threat. In an attempt to quantify these positive actions, we are proposing an approach to extracting key behaviors within ASRS reports that can support the Safety II concept. Our analysis assumes that ASRS reports contain some descriptions of corrective actions that operators performed to prevent a situation from leading to an accident. Leveraging recent advances in Natural Language Process modeling, we have developed an approach to extract positive sentiment from reports, embed these positive statements in a vector space where they can be numerically analyzed, and clustering these statements into similar contextual categories. From these contextualized categories we can attempt to summarized and distilled aspects of the positive behavior. The goal is to identify categories of behavior that describe consistent operator techniques that supports the Safety II concept. With this information, airlines may enable learning from these positive actions, or address procedures that need to be changed to avoid having pilots implement a workaround. These insights can provide a lens into what is “going right” in the operations that may otherwise not be known widely within the community. It is envisioned that this approach can be extended to other narrative programs such as Line Operation Safety Audit or Learning Improvement Team reports where similar observed behavior can be analyzed to extract positive actions and inform the overall operations.

NLP↗

NASA NTRSDate not supplied

An Approach to Identifying Aspects of Positive Pilot Behavior within the Aviation Safety Reporting System

The National Airspace System (NAS) is constantly evolving as air traffic continues to ramp up to pre-pandemic numbers and projected to grow to unprecedented levels in the coming years. As well as increasing demand to the current system, emerging operations such as Unmanned Autonomous Systems are also expected to add to complexity in the airspace. To address these issues, the industry and government agencies supporting the NAS will need to rely upon additional automation and new technologies to address future operational requirements, while continuing to be a world-leading safe transportation system. As these new technologies are implemented, the system continues to rely on human pilots and controllers in the loop to monitor the system and intervene in situations the automation cannot handle. The goal of proactively addressing safety is of foremost concern to ensure passenger confidence. The industry has implemented various Safety Monitoring Systems to identify safety risks and proactively address them before they result in a serious incident or accident. One such program is the Aviation Safety Reporting System (ASRS). ASRS is a long-established system where pilots and controllers voluntarily and anonymously report safety incidents they experienced and observed during line operations by providing rich text narratives describing the events, the environment, and conditions leading to the safety event of concern. These narratives provide insight and context around events of interest and can be used to identify emerging problems. They can trigger investigations within Flight Operational Quality Assurance or Flight Data Monitoring programs. However, this process typically focuses on the adverse events and the unsafe aspects of the operations surrounding the reported or detected events. This perspective of investigating factors that went wrong around an adverse event is commonly referred to as Safety I. Alternatively, characterizing successful actions that operators perform every day under varying conditions that keep the system within safe operating bounds is a concept referred to as Safety II. The benefit of the Safety II view is that the scope is much larger than that of Safety I since a vast majority of the operations result in successful flights. Many of the successful techniques used to manage operational threats are not documented in standard operating procedures or taught during training. They are typically acquired over time by working with experienced pilots during line operations or in many cases after experiencing a problem for the first time and reacting to it in situ, drawing from years of experience to manage the threat. In an attempt to quantify these positive actions, we are proposing an approach to extracting key behaviors within ASRS reports that can support the Safety II concept. Our analysis assumes that ASRS reports contain some descriptions of corrective actions that operators performed to prevent a situation from leading to an accident. Leveraging recent advances in Natural Language Process modeling, we have developed an approach to extract positive sentiment from reports, embed these positive statements in a vector space where they can be numerically analyzed, and clustering these statements into similar contextual categories. From these contextualized categories we can attempt to summarized and distilled aspects of the positive behavior. The goal is to identify categories of behavior that describe consistent operator techniques that supports the Safety II concept. With this information, airlines may enable learning from these positive actions, or address procedures that need to be changed to avoid having pilots implement a workaround. These insights can provide a lens into what is “going right” in the operations that may otherwise not be known widely within the community. It is envisioned that this approach can be extended to other narrative programs such as Line Operation Safety Audit or Learning Improvement Team reports where similar observed behavior can be analyzed to extract positive actions and inform the overall operations.

NLP↗

NASA NTRS1995

RE J1255+266: Detection of an extremely bright EUV transient

During a pointed ROSAT observation in the direction of the Coma cluster of galaxies an exceptionally bright EUV source, RE J1255+266, was detected serendipitously. The source is located close to the Galactic North Pole, at b(sub II) is approximately or equal to 89 deg. Its observed EUV flux (62 - 110 eV) at the time of the detection was of order 7 x 10(exp -9) ergs/sq cm, making RE J1255+266 temporarily one of the brightest EUV sources on the sky. The EUV flare of RE J1255+266 has a light curve with a decay time of about 0.86 days. With respect to earlier non-detections, the source brightened by a factor of approximately 7000. Such a behavior has not been observed before. Thus, it is unclear what type of source RE J1255+266 might be. Up to now no positive identification with any known source could be obtained. Emission at the position of the source was previously only detected in the 1987 Green Bank radio continuum survey. Simultaneous observations with Compton Gamma Ray Observatory/Burst and Transient Source Experiment (CGRO/BATSE) resulted in non-detections of the source in the 8 - 50 keV energy range.

Dahlem, M.↗

NASA NTRS1980

The behavior of ozone near the stratopause from two years of BUC observations

Two years of Nimbus 4 backscattered ultraviolet data have been recalibrated and reprocessed. A Laplace transform inversion was applied to radiances at 2876 A and below for 560,000 individual scans for the period April 1970-May 1972. The behavior of ozone near 50 km as a function of time, latitude, and longitude is presented. The high-latitude 1-mbar ozone mixing ratio is maximum at the winter solstice, about 10 microgram/g and is minimum at the summer solstice, about 4 microgram/g. Below 30 deg latitude the ozone is fairly constant at 4 microgram/g. Ozone variability is large in winter and spring and small in summer and fall.

Mcpeters, R. D.↗

NASA NTRS1994

Modeling of stress/strain behavior of fiber-reinforced ceramic matrix composites including stress redistribution

A computational simulation procedure is presented for nonlinear analyses which incorporates microstress redistribution due to progressive fracture in ceramic matrix composites. This procedure facilitates an accurate simulation of the stress-strain behavior of ceramic matrix composites up to failure. The nonlinearity in the material behavior is accounted for at the constituent (fiber/matrix/interphase) level. This computational procedure is a part of recent upgrades to CEMCAN (Ceramic Matrix Composite Analyzer) computer code. The fiber substructuring technique in CEMCAN is used to monitor the damage initiation and progression as the load increases. The room-temperature tensile stress-strain curves for SiC fiber reinforced reaction-bonded silicon nitride (RBSN) matrix unidirectional and angle-ply laminates are simulated and compared with experimentally observed stress-strain behavior. Comparison between the predicted stress/strain behavior and experimental stress/strain curves is good. Collectively the results demonstrate that CEMCAN computer code provides the user with an effective computational tool to simulate the behavior of ceramic matrix composites.

Mital, Subodh K.↗

NASA NTRS1975

Observations of low energy interplanetary electrons

Observations of the temporal behavior of low energy (0.16-6 MeV) at 1 AU are reported. The electron intensity is found to vary by a factor of more than five from one quiet time to another, including short-term enhancements of the type reported at higher electron energies. Over a period of about four months, beginning with the time at which the interplanetary field line first connects earth and Jupiter, the magnitude and frequency of the increases grow abruptly and remain high. The observed longitudinal distribution of Jovian electrons could be the result of the interconnection of the interplanetary field with an extended Jovian magnetotail.

Mewaldt, R. A.↗

NASA NTRS1976

The behavior of the Mg II doublet features near 2800 A observed in F, A, and B supergiants

The Mg II doublet features near 2800 A were recently observed in F-, A-, and B-type supergiants with a balloon-borne ultraviolet stellar spectrometer. The stars observed are Alpha UMi (F8 Ib), Alpha Per (F5 Ib), Eta Leo (A0 Ib), and Rho Leo (B1 Ib). The Mg II doublet features in Alpha UMi and Alpha Per show emission superposed on photospheric absorption. In the spectrum of Eta Leo, the Mg II lines are in absorption and show shortward-shifted components attributable to mass loss. In the spectrum of Rho Leo, the Mg II lines are primarily a composite of the photospheric and interstellar absorption features. The general behavior of the Mg II lines for supergiants of spectral types M through B are also discussed.

Kondo, Y.↗

NASA NTRS2009

Impulsive Reconnection in the Sun's Atmosphere

Recent high-resolution observations from the Hinode mission show dramatically that the Sun's atmosphere is filled with explosive activity ranging from chromospheric explosions that reach heights of Mm, to coronal jets that can extend to solar radii, to giant coronal mass ejections (CME) that reach the edge of the heliosphere. The driver for all this activity is believed to be 3D magnetic reconnection. From the large variation observed in the temporal behavior of solar activity, it is clear that reconnection in the corona must take on a variety of distinct forms. The explosive nature of jets and CMEs requires that the reconnection be impulsive in that it stays off until a substantial store of free energy has been accumulated, but then turns on abruptly and stays on until much of this free energy is released. The key question, therefore, is what determines whether the reconnection is impulsive or not. We present some of the latest observations and numerical models of explosive and non-explosive solar activity. We argue that, in order for the reconnection to be impulsive, it must be driven by a quasi-ideal instability. We discuss the generality of our results for understanding 31) reconnection in other contexts.

Antiochos, Spiro K.↗

NASA NTRS1988

Transparent metal model study of the use of a cellular growth front to form aligned monotectic composite materials

The purpose of this work was to resolve a scientific controversy in the understanding of how second phase particles become aligned during unidirectional growth of a monotectic alloy. A second aspect was to make the first systematic observations of the solidification behavior of a monotectic alloy during cellular growth in-situ. This research provides the first systematic transparent model study of cellular solidification. An interface stability diagram was developed for the planar to cellular transition of the succinonitrile glycerol (SNG) system. A method was developed utilizing Fourier Transform Infrared Spectroscopy which allows quantitative compositional analysis of directionally solidified SNG along the growth axis. To determine the influence of cellular growth front on alignment for directionally solidified monotectic alloys, the planar and cellular growth morphology was observed in-situ for SNG between 8 and 17 percent glycerol and for a range of over two orders of magnitude G/R.

Kaukler, William F.↗

NASA NTRS1996

Dust Coagulation in Protoplanetary Accretion Disks

The time evolution of dust particles in circumstellar disk-like structures around protostars and young stellar objects is discussed. In particular, we consider the coagulation of grains due to collisional aggregation. The coagulation of the particles is calculated by solving numerically the non-linear Smoluchowski equation. The different physical processes leading to relative velocities between the grains are investigated. The relative velocities may be induced by Brownian motion, turbulence and drift motion. Starting from different regimes which can be identified during the grain growth we also discuss the evolution of dust opacities. These opacities are important for both the derivation of the circumstellar dust mass from submillimeter/millimeter continuum observations and the dynamical behavior of the disks. We present results of our numerical studies of the coagulation of dust grains in a turbulent protoplanetary accretion disk described by a time-dependent one-dimensional (radial) alpha-model. For several periods and disk radii, mass distributions of coagulated grains have been calculated. From these mass spectra, we determined the corresponding Rosseland mean dust opacities. The influence of grain opacity changes due to dust coagulation on the dynamical evolution of a protostellar disk is considered. Significant changes in the thermal structure of the protoplanetary nebula are observed. A 'gap' in the accretion disk forms at the very frontier of the coagulation, i.e., behind the sublimation boundary in the region between 1 and 5 AU.

Schmitt, W.↗