Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “specific correlation”

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 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Serum bile acid and unsaturated fatty acid profiles of non-alcoholic fatty liver disease in type 2 diabetic patients

The understanding of bile acid (BA) and unsaturated fatty acid (UFA) profiles, as well as their dysregulation, remains elusive in individuals with type 2 diabetes mellitus (T2DM) coexisting with non-alcoholic fatty liver disease (NAFLD). Investigating these metabolites could offer valuable insights into the pathophy-siology of NAFLD in T2DM. Our aim is to identify potential metabolite biomarkers capable of distinguishing between NAFLD and T2DM. A training model was developed involving 399 participants, comprising 113 healthy controls (HCs), 134 individuals with T2DM without NAFLD, and 152 individuals with T2DM and NAFLD. External validation encompassed 172 participants. NAFLD patients were divided based on liver fibrosis scores. The analytical approach employed univariate testing, orthogonal partial least squares-discriminant analysis, logistic regression, receiver operating characteristic curve analysis, and decision curve analysis to pinpoint and assess the diagnostic value of serum biomarkers. Compared to HCs, both T2DM and NAFLD groups exhibited diminished levels of specific BAs. In UFAs, particular acids exhibited a positive correlation with NAFLD risk in T2DM, while the ω-6:ω-3 UFA ratio demonstrated a negative correlation. Levels of α-linolenic acid and γ-linolenic acid were linked to significant liver fibrosis in NAFLD. The validation cohort substantiated the predictive efficacy of these biomarkers for assessing NAFLD risk in T2DM patients. This study underscores the connection between altered BA and UFA profiles and the presence of NAFLD in individuals with T2DM, proposing their potential as biomarkers in the pathogenesis of NAFLD.

60 APPLIED LIFE SCIENCES↗
NASA NTRS1973

Monopropellant hydrazine resistojet: Flight application design

The design, development, and testing of an engineering model nominal 20-millipound thrust monopropellant hydrazine resistojet program is directed toward the advanced development of an electrothermal hydrazine thruster (EHT). The EHT decomposes hydrazine thermally and expands the decomposition products through a nozzle to provide the impulse necessary to fulfill spacecraft propulsive requirements. The thruster is capable of operation at pulse widths from 0.050 second to steady state and delivers specific impulse values up to about 230 seconds depending on the duty cycle. The program is comprised of six tasks including analyses, the generation of specifications and other documentation, design, fabrication and test, data correlation, and recommendations for the design of flight units.

Kurch, C. K.↗
NASA NTRS1974

Interpretation of columnar content measurements of the solar-wind turbulence

The temporal spectrum of measurements of the integrated electron columnar content between the earth and a distant source are considered. The relation between this spectrum and the three-dimensional wavenumber spectrum of the solar-wind density is derived under the assumption that the correlation scale is the smallest scale of interest. The specific case of round-trip measurements to a spacecraft is investigated for a power-law solar-wind density spectrum. The resulting spectrum has a power-law envelope one power less steep than the solar-wind density spectrum with several deep minima superposed.

Callahan, P. S.↗
NASA NTRS1974

Compositional studies of the lunar regolith at the Apollo 17 site

Major-, minor-, and trace-element abundance data are presented for twenty-two Apollo 17 samples, twelve Apollo 16 samples, and one Apollo 15 basalt. The data were obtained by INAA employing a 14 MeV neutron generator, a Cf-252 isotopic neutron source and nuclear reactor thermal neutrons. Abundance summations for the twenty-four samples analyzed for major and minor abundance elements averaged 98.8 plus or minus 0.3%. Similarities between the Apollo 17 and the Apollo 11 mare basalts are discussed. Abundances in 13 Apollo 17 soils exhibit the greatest compositional range we have observed for soils from a specific landing site. A strong inverse Fe-Al correlation in all lunar materials we have analyzed with the exception of most Apollo 16 samples is defined by the equation: %Fe = -1.36 %Al + 21.5. A strong direct Mn-Fe correlation is defined by the equation: %Fe = 75.9 %Mn + 0.08. Both regression lines appear to have the mare basalts, as one end-member and an unspecified Al-rich component at the other end. Comparisons of the data from direct O determinations and calculated O abundances based on normal stoichiometry are presented.

Miller, M. D.↗
NASA NTRS1976

Effects of surface temperature and Reynolds number on heat transfer to the Shuttle Orbiter leeward fuselage

Heat-transfer data obtained at hypersonic shock tunnel conditions and three-dimensional flow field computations were used to study the influence of surface temperature and Reynolds number on the heating experienced by the leeward fuselage area of the Space Shuttle Orbiter configuration. The basic results of this study indicate that systematic variations in the average total enthalpy within a boundary layer (as obtained through controlled nonadiabatic processes) has an influence on the heat transfer to downstream areas which can be correlated; even in three-dimensional separated flow areas. Specifically, the average separated-flow Stanton number for the fuselage leeward surface is shown to be moderately dependent on the windward-wall to free-stream total temperature ratio.

Bertin, J. J.↗
NASA NTRS1981

Multivariable closed loop control analysis and synthesis for complex flight systems

A flight control system analysis and synthesis method is presented that is intended to be especially suitable for application to vehicles exhibiting complex dynamic characteristics. For such vehicles quantitative handling qualities specifications are not usually available. Howver, handling qualities objectives are specifically introduced in this method via the hypothesis of correlation between pilot ratings and the objective function of an optimal control model of the human pilot. Further, since augmentation and pilot operate in parallel, simultaneous determination of the augmentation and pilot model gains is required. Desirable augmented dynamics are obtained for a variety of complex systems and the method is experimentally verified in the case of simple pilot damper gain selection for optimum pitch tracking performance.

Schmidt, D. K.↗
NASA NTRS1982

Effects of unsteady free-stream velocity and free-stream turbulence at a stagnation point

The combined effects of transient free stream velocity and turbulence at a stagnation point on a cylinder situated in a crossflow is investigated analytically, and a model is formulated for the eddy diffusivity induced by free-stream turbulence. The steepest descent method is used to integrate the governing momentum expression, and numerical solutions are given for the unsteady wall shear stress function for specific free-stream transients. It is found after correlation of the results by means of a new turbulence parameter that wall friction increases with increasing free-stream turbulence intensity, and that the friction factor increases with increasing reduced frequency of oscillation values.

Gorla, R. S. R.↗
NASA NTRS1984

Venus: Global distribution of Pioneer-Venus radar roughness and reflectivity and global correlation of altimetry, roughness and reflectivity observations

An improved version of the Pionner-Venus orbital data was used for a statistical analysis of global radar roughness and (alpha(0)) (rho) reflectivity. Classification maps of the venusian surface are produced in a supervised manner on the basis of statistical and empirical studies of the individual data sets. The primary objective is to assess the degree of homogeneity of surface radar properties within topographic provinces in order to map possible geologic boundaries. Maps were produced by correlating two data sets at a time. Classification of specific regions, such as Ishtar, has demonstrated that distinct geological units can be identified.

Head, J. W.↗
NASA NTRS1989

Space Propulsion Hazards Analysis Manual (SPHAM), volume 1

The Space Propulsion Hazards Analysis Manual (SPHAM) is a compilation of methods and data directed at hazards analysis and safety for space propulsion and associated vehicles, but broadly applicable to other environments and systems. Methods are described of compiling relevant regulatory documentation, deriving design requirements and specifications, modeling accident scenarios in formal risk assessments, and correlation real-time data to risk probability modeling. Also, SPHAM provides methods for predicting post-accident blast, fragmentation, thermal, and environmental damage. Included in the appendices are an exhaustive bibliography, hazardous properties information on selected space propulsion commodities, and system descriptions of various launch vehicles, upper stages, and spacecrafts.

Becker, Dorothy L.↗
NASA NTRS1992

Estimation and enhancement of real-time software reliability through mutation analysis

A simulation-based technique for obtaining numerical estimates of the reliability of N-version, real-time software is presented. An extended stochastic Petri net is employed to represent the synchronization structure of N versions of the software, where dependencies among versions are modeled through correlated sampling of module execution times. Test results utilizing specifications for NASA's planetary lander control software indicate that mutation-based testing could hold greater potential for enhancing reliability than the desirable but perhaps unachievable goal of independence among N versions.

Geist, Robert↗
NASA NTRS1993

Cosmological perturbations of quantum-mechanical origin and anisotropy of the microwave background

Cosmological perturbations generated quantum mechanically (as a particular case, during inflation) possess statistical properties of squeezed quantum states. The power spectra of the perturbations are modulated and the angular distribution of the produced temperature fluctuations of the cosmic microwave background radiation is quite specific. An exact formula is derived for the angular correlation function of the temperature fluctuations caused by squeezed gravitational waves. The predicted angular pattern can, in principle, be revealed by observations like those by the Cosmic Background Explorer.

Grishchuk, L. P.↗
NASA NTRS1996

Southern Hemisphere In Situ Observations of OH, HO2, CIO and BrO from the ER-2 Aircraft for the 1994 ASHOE Mission

A summary of the first order scientific conclusions that emerged from the research done under this grant are as follows: (1) For the first time, the concentration of the key hydrogen and halogen radicals OH, H02, ClO and BrO were determined on a global scale extending from the arctic circle to the antarctic circle, over the altitude domain of the ER-2. That domain extends from 15-20 km altitude, covering a critical part of the lower stratosphere; (2) Simultaneous, in situ measurements of the concentrations of OH, H02, ClO, BrO, NO and NO2 demonstrate the predominance of odd-hydrogen and halogen free radical catalysis in determining the rate of removal of ozone in the lower stratosphere over the complete ASHOE mission. This extends to the global scale the "first look" data obtained during the NASA Stratospheric Photochemistry and Dynamics Experiment (SPADE), executed out of Ames Research Center in June 1993. This represents a major rearrangement of our understanding with respect to the hierarchy of dominant catalytic cycles controlling ozone loss in the lower stratosphere. For the past twenty years, it has been assumed that nitrogen radicals dominate the destruction rate of ozone in the lower stratosphere; (3) Throughout the altitude and latitude range covered by ASHOE, it was determined that a single catalytic cycle, HO2 + O3 yields OH + 2O2, accounted for one half of the total O3 removal in this region of the atmosphere. Halogen radical catalytic cycles were found to account for one third of the ozone loss, and nitrogen radicals were found to account for 20% of the loss; (4) Simultaneous observations of the full complement of radicals, tracers, ozone, and water vapor during ASHOE demonstrated quantitatively the coupling that exists between the rate limiting radicals and other reactive species in the photochemical reaction network. Specifically, the concentrations of ClO and HO2 are inversely correlated with the concentration of NOx. This carries the implication that the NOx effluent from the proposed High Speed Civil Transport may be less destructive to stratospheric ozone than had previously been thought. ASHOE brought this conclusion forward for the first time on a global basis; and (5) The density of BrO was measured on a global scale during ASHOE in the lower stratosphere. It was found that bromine is responsible for 55-65% of the local rate of catalytic destruction of ozone by reactions involving bromine and chlorine. Normalizing calculated loss rates to total available inorganic bromine and chlorine explicitly demonstrates that bromine is 60-80 times more efficient than chlorine in removing ozone in the lower stratosphere. An inferred value of total inorganic bromine is in excellent agreement with measurements of their source species, organic bromine compounds in the troposphere.

Anderson, James G.↗
NASA NTRS1997

Penetration Electric Fields and Inner Magnetosphere Dynamics: A Model and Data Comparison

The initial substorm interval to be studied has been selected to be the magnetic storm of June 4, 1991, and following. The CRRES electric and magnetic field data has been processed. We have added DMSP ion drift and energetic particle data and further refined the CRRES data for intercomparison. The DMSP data increase the frequency of monitoring of the temporal response of the penetration electric fields to every 100 min. Energy is seen to flow between the ionosphere and magnetosphere at low L values during the main phase of the magnetic storm in the form of field-aligned Poynting flux. This indicates electrodynamic coupling of the regions with Alfven waves. The first comparisons of the data with outputs of the Rice Magnetospheric Specification Model (MSM) were made. Both positive and negative correlation were seen as might be expected. Differences were especially evident in the time constants of the processes. Comparisons with the more physically self-consistent Rice Convection Model (RCM) with both electric fields and particle data are in progress to suggest physical constraints for our understanding of the phenomena.

Maynard, Nelson C.↗
NASA NTRS1996

Studies of Tidal and Planetary Wave Variability in the Middle Atmosphere using UARS and Correlative MF Radar Data

The goals of this research effort have been to use MF radar and UARS/HRDI wind measurements for correlative studies of large-scale atmospheric dynamics, focusing specifically on the tidal and various planetary wave structures occurring in the middle atmosphere. We believed that the two data sets together would provide the potential for much more comprehensive studies than either by itself, since they jointly would allow the removal of ambiguities in wave structure that are difficult to resolve with either data set alone. The joint data were to be used for studies of wave structure, variability, and the coupling of these motions to mean and higher-frequency motions.

Fritts, David C.↗
NASA NTRS2015

Functional Foods Baseline and Requirements Analysis

Current spaceflight foods were evaluated to determine if their nutrient profile supports positioning as a functional food and if the stability of the bioactive compound within the food matrix over an extended shelf-life correlated with the expected storage duration during the mission. Specifically, the research aims were: Aim A. To determine the amount of each nutrient in representative spaceflight foods immediately after processing and at predetermined storage time to establish the current nutritional state. Aim B. To identify the requirements to develop foods that stabilize these nutrients such that required concentrations are maintained in the space food system throughout long duration missions (up to five years). Aim C. To coordinate collaborations with health and performance groups that may require functional foods as a countermeasure.

Cooper, M. R.↗
NASA NTRS2015

Geomorphic and Geologic Controls of Geohazards induced by Nepal's 2015 Gorkha Earthquake

The Gorkha earthquake (Magnitude 7.8) on 25 April 2015 and later aftershocks struck South Asia, killing approx.9,000 and damaging a large region. Supported by a large campaign of responsive satellite data acquisitions over the earthquake disaster zone, our team undertook a satellite image survey of the earthquakes induced geohazards in Nepal and China and an assessment of the geomorphic, tectonic, and lithologic controls on quake-induced landslides. Timely analysis and communication aided response and recovery and informed decision makers. We mapped 4,312 co-seismic and post-seismic landslides. We also surveyed 491 glacier lakes for earthquake damage, but found only 9 landslide-impacted lakes and no visible satellite evidence of outbursts. Landslide densities correlate with slope, peak ground acceleration, surface downdrop, and specific metamorphic lithologies and large plutonic intrusions.

earthquake↗
NASA NTRS2018

Boundary of the Slow Solar Wind

This work argues that there are two fundamental states of the non-transient solar wind, and that these can be distinguished by a number of criteria. Here we define the states, which will be termed slow and fast, or SSW and FSW, for lack of better terms, by the level of velocity fluctuations, v, in them, with the slow wind having systematically lower fluctuations than the fast wind. Almost all winds with speeds less than 450 km s1 are in the slow class, and winds with speeds greater than 600 km s1 are fast, but we argue that in between, consistent with other work, the v classification is more fundamental than speed. We show that the fluctuation categorization coincides well with classes based on Alfvénicy, proton specific entropy, ion thermal speed, and ionic composition. This correlated behavior among these solar wind parameters exists regardless of it being associated with a heliospheric current sheet or a pseudostreamer. This work provides evidence that both the so-called SSW I and SSW II scenarios coexist for the SSW formation. In addition, that the dynamical properties (thermal, magnetic, and turbulence properties) correlate well with properties set at the inner corona (ion ionization states and FIP bias)implies that there exists a boundary layer on the Sun within which the SSW is formed. This boundary layer would set up the coronal conditions for the source and transport of the SSW.

Ko, Yuan-Kuen↗
NASA NTRS2017

Review of a Draft - Avoiding the Impossible: Re-focusing a Non-Feasible Mission 2-Hrs into a 3-Day Engineering Session

Concurrent engineering offers a great many benefits to engineers and mission designers throughout the world of aerospace. The only downside of concurrent engineering, and this is somewhat unavoidable, is that you don’t know the results of a design session until the end when it is completed. Usually, this is not a problem – you wouldn’t start building a spacecraft before the design is finished. However, within mass and cost constrained systems, you may end up with a final design that although technically sound – is not feasible due to mass or cost limits. Employing in-session mass and cost models with flexible inputs that refine their estimates and variance as more detailed information comes in throughout a design session allows major design changes to be made when the probability of breaching a mass or cost cap exceeds a threshold level. This enables mission designers to re-focus the study, and avoid spending 3-days with 15 engineers designing a non-feasible mission. By understanding key correlations and nested relationships within mass or cost, and specifically mass or cost allocations per mission element by mission type, it’s possible to get flexible-input, statistically based mass and cost estimates very early in the design process. Baseline models are seeded using mission characteristics and general parameters (outer planetary orbiter-probe mission, $500M cost cap for example) to provide a rough estimate of the expected mass or cost. As information gets solidified during the session, it gets added to the model and the estimates are updated. Continuing the orbiter-probe mission example, modeling probe heat shield cost as a percent of total probe cost, and probe cost as a percent of total flight system cost, and total flight system cost as a percent of total mission cost allows a design team to roll-up solidified information to estimate the probability of fitting within a mass or cost constraint early in a concurrent design session. When only the heat shield cost is known, the variance of the final estimate is higher, whereas when the full probe gets defined, naturally, the variance of the estimate decreases. A methodology, model, verification and demo implementation for cost limit breach are presented.

Hihn, Jairus M.↗