Search NASA⌕ Search

SEARCH · Search NASA

Results for “relevancy”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Laboratory Studies of Chemical and Photochemical Processes Relevant to Stratospheric Ozone

This is the final report for this project. Its purpose is to reduce the uncertainty in rate coefficients for key gas-phase kinetic processes which impact our understanding of stratospheric ozone. The main emphasis of this work is on measuring the rate coefficients for the reactions of HO2 + O3, and HO2 + NO2 in the temperature range (200-240 K) relevant to the lower stratosphere. In order to accomplish this, a high pressure turbulent flow tube reactor was built and its flow characteristics were quantified. The instrument was coupled with tunable diode laser spectroscopy for HO2 detection. Room temperature measurements of the HO2 + NO2 rate coefficients over the pressure range of 50-300 torr agree well with previous measurements. Preliminary measurements of the HO2 + O, rate coefficients at 50 - 300 Torr over the temperature range of 208-294 K agree with the NASA evaluation from 294-225 K but deviate significantly (50 % higher) at approximately 210 K.

Villalta, P. W.↗
NASA NTRS2000

The Biological Relevance of Artificial Life: Lessons from Artificial Intelligence

There is no fundamental reason why A-life couldn't simply be a branch of computer science that deals with algorithms that are inspired by, or emulate biological phenomena. However, if these are the limits we place on this field, we miss the opportunity to help advance Theoretical Biology and to contribute to a deeper understanding of the nature of life. The history of Artificial Intelligence provides a good example, in that early interest in the nature of cognition quickly was lost to the process of building tools, such as "expert systems" that, were certainly useful, but provided little insight in the nature of cognition. Based on this lesson, I will discuss criteria for increasing the biological relevance of A-life and the probability that this field may provide a theoretical foundation for Biology.

Colombano, Silvano↗
NASA NTRS2001

Thermal Desorption/GCMS Analysis of Astrobiologically Relevant Organic Materials

Several macromolecular organic materials, both biologically-derived (type II kerogen and humic acid) and abiotic in origin (Murchison insoluble organic material, cyanide polymer, and Titan tholin) were subjected to thermal desorption using a Chromatoprobe attachment on a Varian Saturn 2000 GCMS system. Each sample was heated sequentially at 100, 200, and 300 C to release volatile components. The evolved compounds were then separated on a Supelco EC-1 dimethylsilica GC column and detected by the Saturn 2000 ion trap mass spectrometer. The various types of macromolecular organic material subjected to thermal desorption produced distinctly different GCMS chromatograms at each temperature, containing fractions of both low and high chromatographic mobility. The relative amounts of detectable volatiles released at each temperature also differed, with type II kerogen and cyanide polymer containing the highest percentage of low-temperature components. In all the samples, the highest yield of released compounds occurred at 300 C. Only cyanide polymer evolved a homologous hydrocarbon series, suggesting that it is the only material among those examined that contains a truly polymeric structure. Pyrolysis/gas chromatography/mass spectrometry has been used extensively for analysis of terrestrial organic macromolecular materials, and was also part of the instrument package on the Viking landers. Thorough analysis by pyrolysis usually employs temperatures of 500 C or higher, which for in situ analyses can be problematic given spacecraft power and materials constraints. This study demonstrates that heating of organic materials of astrobiological relevance to temperatures as low as 200-300 C for short periods releases volatile components that can be analyzed by gas chromatography and mass spectrometry. Even in the absence of full pyrolysis, useful chemical information on samples can be obtained, and materials from different biological and abiological sources can be distinguished. The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

McDonald, Gene D.↗
NASA NTRS2003

Progress Towards the Investigation of Technical Issues Relevant to the Design of an Aircraft Wake Vortex Advisory System (WakeVAS)

Wake vortex separations applied to aircraft during instrument operations have been shown to potentially introduce inefficiencies in air traffic operations during certain weather conditions conducive to short duration wake hazards between pairs of landing aircraft. NASA Langley Research Center (LaRC) demonstrated an integration of technologies that provided real-time observations and predictions of aircraft wake behavior, from which reduced wake spacing from the current criteria was derived. In order to take this proof of concept to an operational prototype system, NASA has been working in cooperation with the FAA and other government and industry members to design operational concepts for a Wake Vortex Advisory System (WakeVAS). In addition to concept development, open research issues are being addressed and activities to quantify system requirements and specifications are currently underway. This paper describes the technological issues relevant to WakeVAS development and current NASA efforts to address these issues.

Rutishauser, David K.↗
NASA NTRS2003

Spectra and Photochemistry of Relevance to Icy Outer Solar System Objects

The Astrochemistry Lab at NASA Ames (www.astrochem.org) has an interest in the organic photochemistry of extraterrestrial ices, having traditionally performed experiments under interstellar conditions. We have recently embarked on projects for PG\&G to measure spectra and elucidate the photochemistry of ices relevant to outer Solar System objects. 1) We will report on the determination of real and imaginary indicies of refraction of H2O and N2 dominated ices containing simple, common, extraterrestrial molecules such as NH3, HCN, formaldehyde, \& methanol. 2) We will compare and contrast the photochemistry of H2O ices containing organic molecules at 100 K with previously reported work at 15 K.

Bernstein, M. P.↗
NASA NTRS2004

Measuring Questions: Relevance and its Relation to Entropy

The Boolean lattice of logical statements induces the free distributive lattice of questions. Inclusion on this lattice is based on whether one question answers another. Generalizing the zeta function of the question lattice leads to a valuation called relevance or bearing, which is a measure of the degree to which one question answers another. Richard Cox conjectured that this degree can be expressed as a generalized entropy. With the assistance of yet another important result from Janos Acz6l, I show that this is indeed the case; and that the resulting inquiry calculus is a natural generalization of information theory. This approach provides a new perspective of the Principle of Maximum Entropy.

Knuth, Kevin H.↗
NASA NTRS2003

Nitric oxide in microgravity-induced orthostatic intolerance: relevance to spinal cord injury

Prolonged exposure to microgravity results in cardiovascular deconditioning which is marked by orthostatic intolerance in the returning astronauts and recovering bed-ridden patients. Recent studies conducted in our laboratories at University of California, Irvine have revealed marked elevation of nitric oxide (NO) production in the kidney, heart, brain, and systemic arteries coupled with significant reduction of NO production in the cerebral arteries of microgravity-adapted animals. We have further demonstrated that the observed alteration of NO metabolism is primarily responsible for the associated cardiovascular deconditioning. Recovery from acute spinal cord injury (SCI) is frequently complicated by orthostatic intolerance that is due to the combined effects of the disruption of efferent sympathetic pathway and cardiovascular deconditioning occasioned by prolonged confinement to bed. In this presentation, I will review the nature of altered NO metabolism and its role in the pathogenesis of microgravity-induced cardiovascular deconditioning. The possible relevance of the new findings to orthostatic intolerance in patients with acute SCI and its potential therapeutic implications will be discussed.

Review↗
NASA NTRS2003

The effects of study-task relevance on perceptual repetition priming

Repetition priming is easily elicited in many traditional paradigms, and the possibility that perceptual priming may be other than an automatic consequence of perception has received little consideration. This issue is explored in two experiments. In Experiment 1, participants named the target from a four-item category search study task more quickly than the nontarget study items at a later naming test. Experiment 2 extended this finding to conditions in which stimuli were individually presented at study. In three different study tasks, stimuli relevant to study-task completion elicited priming on a later test, but stimuli presented outside the context of a task did not. In both experiments, recognition was above chance for nonrelevant stimuli, suggesting that participants explicitly remembered stimuli that did not elicit priming. Results suggest that priming is sensitive to study-task demands and may reflect a more adaptive and flexible mechanism for modification of perceptual processing than previously appreciated.

Visual Perception↗
NASA NTRS2002

Ocular input for human melatonin regulation: relevance to breast cancer

The impact of breast cancer on women across the world has been extensive and severe. As prevalence of breast cancer is greatest in industrialized regions, exposure to light at night has been proposed as a potential risk factor. This theory is supported by the epidemiological observations of decreased breast cancer in blind women and increased breast cancer in women who do shift-work. In addition, human, animal and in vitro studies which have investigated the melatonin-cancer dynamic indicate an apparent relationship between light, melatonin and cancer, albeit complex. Recent developments in understanding melatonin regulation by light in humans are examined, with particular attention to factors that contribute to the sensitivity of the light-induced melatonin suppression response. Specifically, the role of spectral characteristics of light is addressed, and recent relevant action spectrum studies in humans and other mammalian species are discussed. Across five action spectra for circadian and other non-visual responses, a peak sensitivity between 446-484 nm was identified. Under highly controlled exposure circumstances, less than 1 lux of monochromatic light elicited a significant suppression of nocturnal melatonin. In view of the possible link between light exposure, melatonin suppression and cancer risk, it is important to continue to identify the basic related ocular physiology. Visual performance, rather than circadian function, has been the primary focus of architectural lighting systems. It is now necessary to reevaluate lighting strategies, with consideration of circadian influences, in an effort to maximize physiological homeostasis and health.

Review↗
NASA NTRS2006

Time Relevance of Convective Weather Forecast for Air Traffic Automation

The Federal Aviation Administration (FAA) is handling nearly 120,000 flights a day through its Air Traffic Management (ATM) system and air traffic congestion is expected to increse substantially over the next 20 years. Weather-induced impacts to throughput and efficiency are the leading cause of flight delays accounting for 70% of all delays with convective weather accounting for 60% of all weather related delays. To support the Next Generation Air Traffic System goal of operating at 3X current capacity in the NAS, ATC decision support tools are being developed to create advisories to assist controllers in all weather constraints. Initial development of these decision support tools did not integrate information regarding weather constraints such as thunderstorms and relied on an additional system to provide that information. Future Decision Support Tools should move towards an integrated system where weather constraints are factored into the advisory of a Decision Support Tool (DST). Several groups such at NASA-Ames, Lincoln Laboratories, and MITRE are integrating convective weather data with DSTs. A survey of current convective weather forecast and observation data show they span a wide range of temporal and spatial resolutions. Short range convective observations can be obtained every 5 mins with longer range forecasts out to several days updated every 6 hrs. Today, the short range forecasts of less than 2 hours have a temporal resolution of 5 mins. Beyond 2 hours, forecasts have much lower temporal. resolution of typically 1 hour. Spatial resolutions vary from 1km for short range to 40km for longer range forecasts. Improving the accuracy of long range convective forecasts is a major challenge. A report published by the National Research Council states improvements for convective forecasts for the 2 to 6 hour time frame will only be achieved for a limited set of convective phenomena in the next 5 to 10 years. Improved longer range forecasts will be probabilistic as opposed to the deterministic shorter range forecasts. Despite the known low level of confidence with respect to long range convective forecasts, these data are still useful to a DST routing algorithm. It is better to develop an aircraft route using the best information available than no information. The temporally coarse long range forecast data needs to be interpolated to be useful to a DST. A DST uses aircraft trajectory predictions that need to be evaluated for impacts by convective storms. Each time-step of a trajectory prediction n&s to be checked against weather data. For the case of coarse temporal data, there needs to be a method fill in weather data where there is none. Simply using the coarse weather data without any interpolation can result in DST routes that are impacted by regions of strong convection. Increasing the temporal resolution of these data can be achieved but result in a large dataset that may prove to be an operational challenge in transmission and loading by a DST. Currently, it takes about 7mins retrieve a 7mb RUC2 forecast file from NOAA at NASA-Ames Research Center. A prototype NCWF6 1 hour forecast is about 3mb in size. A Six hour NCWFG forecast with a 1hr forecast time-step will be about l8mb (6 x 3mb). A 6 hour NCWF6 forecast with a l5min forecast time-step will be about 7mb (24 x 3mb). Based on the time it takes to retrieve a 7mb RUC2 forecast, it will take approximately 70mins to retrieve a 6 hour NCWF forecast with 15min time steps. Until those issues are addressed, there is a need to develop an algorithm that interpolates between these temporally coarse long range forecasts. This paper describes a method of how to use low temporal resolution probabilistic weather forecasts in a DST. The beginning of this paper is a description of some convective weather forecast and observation products followed by an example of how weather data are used by a DST. The subsequent sections will describe probabilistic forecasts followed by a descrtion of a method to use low temporal resolution probabilistic weather forecasts by providing a relevance value to these data outside of their valid times.

Chan, William N.↗
NASA NTRS2009

A Study of Ablation-Flowfield Coupling Relevant to the Orion Heatshield

The coupled interaction between an ablating surface and the surrounding aerothermal environment is studied. An equilibrium ablation model is coupled to the LAURA flowfield solver, which allows the char ablation rate (m-dot(sub c)) to be computed as part of the flowfield solution. The wall temperature (T(sub w)) and pyrolysis ablation rate (m-dot(sub g)) may be specified by the user, obtained from the steady-state ablation approximation, or computed from a a material response code. A 32 species thermochemical nonequilibrium flowfield model is applied, which permits the treatment of C, H, O, N, and Si containing species. Coupled ablation cases relevant to the Orion heatshield are studied. These consist of diffusion-limited oxidation cases with Avcoat as the ablation material. The m-dot(sub c) values predicted from the developed coupled ablation analysis were compared with those obtained from a typical uncoupled ablation analysis. The coupled results were found to be as much as 50% greater than the uncoupled values. This is shown to be a result of the cumulative effect of the two fundamental approximations inherent in the uncoupled analysis.

Johnston, Christopher O.↗
NASA NTRS2009

Laboratory Studies of Ethane Ice Relevant to Outer Solar System Surfaces

Oort Cloud comets, as well as TNOs Makemake (2045 FYg), Quaoar, and Pluto, are known to contain ethane. However, even though this molecule is found on several outer Solar System objects relatively little information is available about its amorphous and crystalline phases. In new experiments, we have prepared ethane ices at temperatures applicable to the outer Solar System, and have heated and ion-irradiated these ices to study phase changes and ethane's radiation chemistry using mid-IR spectroscopy (2.2 - 16.6 microns). Included in our work is the meta-stable phase that exists at 35 - 55 K. These results, including newly obtained optical constants, are relevant to ground-based observational campaigns, the New Horizons mission, and supporting laboratory work. An improved understanding of solid-phase ethane may contribute to future searches for this and other hydrocarbons in the outer Solar System.

Moore, Marla H.↗
NASA NTRS2010

Infrared Spectra, Index of Refraction, and Optical Constants of Nitrile Ices Relevant to Titan's Atmosphere

Spectra and optical constants of nitrite ices known or suspected to be in Titan's atmosphere are presented from 2.5 to 200 microns (4000 to 50 per cm ). These results are relevant to the ongoing modeling of Cassini CIRS observations of Titan's winter pole. Ices studied include: HCN, hydrogen cyanide; C2N2, cyanogen; CH3CN, acetonitrile; C 2H5CN, propionitrile; and HC3N, cyanoacetylene. For each of these molecules we report new measurements of the index of refraction, n, determined in both the amorphous- and crystallinephase at 670 nm. Spectra were measured and optical constants were calculated for each nitrite at a variety of temperatures including 20, 35, 50, 75, 95, and 110 K, in the amorphous- and crystalline-phase. This laboratory effort uses a dedicated FTIR spectrometer to record transmission spectra of thin-film ice samples. Laser interference is used to measure film thickness during condensation onto a transparent cold window attached to the tail section of a closed-cycle helium cryostat. Optical constants, real (n) and imaginary (k) refractive indices, are determined using Kramers-Kronig (K-K) analysis. Our calculation reproduces the complete spectrum, including all interference effects. Index of refraction measurements are made in a separate dedicated FTIR spectrometer where interference deposit fringes are measured using two 670 nm lasers at different angles to the ice substrate. A survey of these new measurements will be presented along with a discussion of their validation, errors, and application to Titan data.

Moore, Marla↗
NASA NTRS2011

Infrared Spectra and Optical Constants of Nitrile Ices Relevant to Titan's Atmosphere

Spectra and optical constants of nitrile ices known or suspected to be in Titan?s atmosphere have been determined from 2.0 to 333.3 microns (approx.5000 to 30/cm). These results are relevant to the ongoing modeling of Cassini CIRS observations of Titan?s winter pole. Ices studied were: HCN, hydrogen cyanide; C2N2, cyanogen; CH3CN, acetonitrile; C2H5CN, propionitrile; and HC3N, cyanoacetylene. Optical constants were calculated, using Kramers-Kronig analysis, for each nitrile ice?s spectrum measured at a variety of temperatures, in both the amorphous- and crystalline phases. Spectra were also measured for many of the nitriles after quenching at the annealing temperature and compared with those of annealed ices. For each of these molecules we also measured the real component, n, of the refractive index for amorphous and crystalline phases at 670 nm. Several examples of the information contained in these new data sets and their usefulness in modeling Titan?s observed features will be presented (e.g., the broad emission feature at 160/cm; Anderson and Samuelson, 2011).

Anderson, Carrie↗
NASA NTRS2011

Statistical Models of Fracture Relevant to Nuclear-Grade Graphite: Review and Recommendations

The nuclear-grade (low-impurity) graphite needed for the fuel element and moderator material for next-generation (Gen IV) reactors displays large scatter in strength and a nonlinear stress-strain response from damage accumulation. This response can be characterized as quasi-brittle. In this expanded review, relevant statistical failure models for various brittle and quasi-brittle material systems are discussed with regard to strength distribution, size effect, multiaxial strength, and damage accumulation. This includes descriptions of the Weibull, Batdorf, and Burchell models as well as models that describe the strength response of composite materials, which involves distributed damage. Results from lattice simulations are included for a physics-based description of material breakdown. Consideration is given to the predicted transition between brittle and quasi-brittle damage behavior versus the density of damage (level of disorder) within the material system. The literature indicates that weakest-link-based failure modeling approaches appear to be reasonably robust in that they can be applied to materials that display distributed damage, provided that the level of disorder in the material is not too large. The Weibull distribution is argued to be the most appropriate statistical distribution to model the stochastic-strength response of graphite.

Nemeth, Noel N.↗
NASA NTRS2011

Thermal Reactions Between Sulfur Dioxide and H202 and Their Relevance to the Jovian Icy Satellites and Other Small Bodies

Laboratory experiments have demonstrated that magnetospheric radiation in the Jovian system drives reaction chemistry in ices at temperatures relevant to Europa and other icy satellites. Here we present new results on thermally-induced reactions occurring between 50 and 130 K in solid H2O + H2O2 + SO2 samples. In our studies, we find that warming our three component mixtures induces a thermal reaction that produces SO4(2-), and this reaction appears to consume equal amounts of H2O2 and SO2. We suspect that the results may explain some of the observations related to the presence and distribution H2O2 across Europa's surface as well as the lack of H2O2 on Ganymede and Callisto. If other molecules prove to be reactive with H2O2 at these or at even lower temperatures, then it may also explain why H2O2 has been absent from surfaces of many of the small icy bodies that are known to be exposed to ionizing radiation.

Loefler, Mark J.↗