Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “total 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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Bond Valences and Anharmonicity in Vacancy-Ordered Double Perovskite Halides

We report that anharmonic lattice dynamics are intimately linked with optical and electronic properties in perovskite halides semiconductors. Vacancy-ordered double perovskites are a subset of the perovskite halide family containing isolated octahedral units. The absence of polyhedral connectivity engenders the vacancy-ordered double perovskites with additional degrees of dynamic freedom, which presents an ideal structural framework to study dynamic-property relationships in perovskite halide semiconductors. In the present study, we examine the structure and bonding origins of anharmonicity in the vacancy-ordered double perovskites Cs 2 Sn 1-x Te x I 6 . While X-ray diffraction indicates that all members adopt the cubic vacancy-ordered double perovskite structure, the local coordination environment probed by X-ray pair distribution function (XPDF) analysis reveals asymmetry of the Cs–I/I–I pair correlation that smoothly decreases with increasing tellurium content. Temperature-dependent neutron total scattering suggests that this asymmetry in the PDF occurs due to anharmonic lattice dynamics arising from octahedral tilting and Cs + displacements, as supported by Reverse Monte Carlo simulations of the Cs 2 SnI 6 and Cs 2 TeI 6 end members. We further correlate the trends in asymmetry and anharmonicity with the bond valence sum of the Cs + ion, and find that the anharmonicity vanishes when the bonding preferences of the Cs + are satisfied by the size of the cuboctahedral void. Lastly, this study presents a simple and effective approach for understanding the origin of anharmonicity in vacancy-ordered double perovskite materials.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Combining field and remote sensing data to estimate forest canopy damage and recovery following tropical cyclones across tropical regions

Abstract As tropical forests cycle the most water and carbon, it is crucial to understand the short- and long-term effects of intensifying cyclones on these ecosystems. Soil nutrient status has been shown to moderate forest cyclone responses using field litterfall measurements, but litterfall is one of the multiple cyclone impact metrtics, which may or may not be correlated with one another or with site nutrients. We used remotely sensed vegetation indices to quantify immediate damage and two-year recovery for 42 cases across nine tropical forests in Hawaii, Puerto Rico, Mexico, Australia, and Taiwan affected by 12 cyclones between 2004 and 2017. We tested whether changes in leaf area index (LAI) and enhanced vegetation index (EVI) correlated with changes in litterfall observations and how changes varied with total soil phosphorus (P) concentrations across regions. We compared cyclone-induced changes and recovery of LAI and EVI to litterfall observations compiled in a pantropical meta-analysis. We found large variation in changes in LAI and EVI across forests, with the greatest reductions in LAI (−77%) and EVI (−77%) in Mexico (Jalisco) and Puerto Rico, respectively. LAI ( r = −0.52) and EVI ( r = −0.60) changes correlated with those in litterfall across cases. Post-cyclone data showed recovery of LAI by four months, EVI by two months, and litterfall by ten months. We detected larger changes in LAI and EVI in forests with higher soil P, but these relationships were not significant when accounting for cyclone and site as random effects. Principal component analyses indicated a regional clustering of cases related to their contrasting cyclone regimes, with the frequency and intensity of cyclone events negatively correlated. Overall, remote sensing observations complement but do not substitute for ground observations that reveal cyclone damage and post-cyclone recovery in tropical forests, and soil phosphorus moderates some but not all metrics of stability in response to cyclones.

Bloom, Dellena E. (ORCID:0000000205981747)↗
DOE OSTI2019

Association Between Preoperative Muscle Mass and Intraoperative Bacterial Translocation in Patients Undergoing Hepatectomy, Pancreatoduodenectomy, and Esophagectomy

Purpose: This study investigated the correlation between the fecal profile and muscle mass, which has not been elucidated before. Methods: This study included patients who underwent hepatectomy, pancreatoduodenectomy, or esophagectomy and had fecal samples collected preoperatively and mesenteric lymph nodes (MLNs) harvested intraoperatively to determine the fecal profile and presence of bacteria in the MLNs. Total psoas area (TPA) was measured at the third lumbar vertebra using preoperative computed tomography images. TPA was standardized by body surface area (BSA) using the following equation: standardized TPA (mm{sup 2}/m{sup 2}) (stTPA) = TPA (mm{sup 2})/BSA (m{sup 2}). The fecal concentrations of representative microorganisms and organic acids also were measured. Results: A total of 127 patients undergoing hepatectomy (n = 48), pancreatoduodenectomy (n = 44), and esophagectomy (n = 35) were included. The fecal levels of predominant obligate anaerobes showed a positive correlation with stTPA, whereas that of pathogenic microorganisms showed a negative correlation with stTPA. The fecal concentrations of total short chain fatty acids (the sum of acetic acid, propionic acid, and butyric acid) also showed a positive correlation with stTPA. The stTPA was significantly lower in patients with positive microorganisms in the MLNs (patients with bacterial translocation) compared to those without microorganisms in the MLNs (p = 0.047). Conclusions: This study was the first to demonstrate the association between muscle mass and the fecal profile, as well as their association with bacterial translocation.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2020

Transverse momentum fluctuations and their correlation with elliptic flow in nuclear collision

In this article, we propose observables v 0 and v 0 (p T ) which quantify the relative fluctuations in the total transverse momentum at fixed multiplicity. We first study the factorization of the fixed multiplicity momentum dependent two particle correlation function into a product of v 0 ($p^{a}_{T}$) and v 0 ($p^{b}_{T}$) within realistic hydrodynamic simulations. Then we present computations of v 0 (p T ) for different particle types. We determine the relation between the integrated v 0 and previously measured observables, and compare results from a hybrid hydrodynamics based model to experimental data. The effects of bulk viscosity and an initial pre-equilibrium stage on the results are quantified. We find that v 0 is strongly correlated with the initial state entropy per elliptic area, S/A. Using this result, we explain how the observed correlations between the elliptic flow and the transverse momentum (both in simulations and experiment) reflect the initial state correlations between 1/A and ellipticity ε 2 at fixed multiplicity. Furthermore, we argue that the systematic experimental study of v 0 , with the same sophistication as used for the other v n , can contribute significantly to our understanding of quark gluon plasma properties.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2020

Uncertainty analysis of steady-state measurements with a hot-filament type calorimetric emissometer

Calorimetric emissometers measure total hemispherical emissivity by measuring the heat transferred from a heated sample to its surroundings under a vacuum. The accuracy of emissometers standardized by the ASTM C835-06 are well understood. This work uses the Guide to the Evaluation of Uncertainty in Measurement (GUM) for the propagation uncertainties for an ASTM compliant emissometer. The GUM method was able to develop a measurement model and expressions to determine the uncertainty for other emissometers of this type. Data on ‘as-received’ Hastelloy X was used to develop a detailed uncertainty analysis of the emissivity measurement. Data on ‘as-received’ SS 347 and sandblasted A387 Gr. 91 and previous data by the group on A508/A533B were used to determine uncertainty over the ranges 0.16 to 0.81. For all samples, relative uncertainties in emissivities varied from 0.77% to 2.5% when using a fluxgate magnetometer sensor (FMS) to measure the DC heating current. Data on Hastelloy X using a Hall-effect sensor for DC current and low alloy steel showed the DC current and voltage across the test section to be dominate sources of uncertainty. When these sources were reduced, the specimen temperature and the surface area of the test sections were main sources of uncertainty in the emissivity, especially at higher temperatures. As thermal expansion of the surface was considered in the calculations, correlation between specimen temperature and surface area was examined. It was found to be a small contribution to emissivity's uncertainty despite the differences in linear CTE and its uncertainty for the materials analyzed in this study. For low temperatures, the chamber temperature can be a significant source of uncertainty if not sufficiently cooled. The GUM was also briefly compared to uncertainty from the 2nd and 3rd expansions of the Taylor series. We found that the results were the same when rounding to two significant figures.

42 ENGINEERING↗
NASA NTRS1988

Systematic properties of CO emission from galaxies. II - Weighted correlations

The dependence of molecular gas emission on various global galaxy properties is tested by examining a series of correlations. CO luminosities of entire galaxies are correlated with their H I content, blue luminosity, disk area, far-infrared luminosity, Hubble type, Elmegreen arm type, DDO luminosity class, total B-V color, disk B-V color, and H-alpha emission. A weighted correlation test is derived and applied to correct for the strong Malmquist bias in the available CO observations of galaxies. The relative strengths of the correlations indicate that molecular emission has a strong dependence on galaxy scale, a weak dependence on galaxy form, and is closely linked to tracers of star forming regions.

Verter, Frances↗
NASA NTRS1973

Cross-correlation analysis of the AE index and the interplanetary magnetic field Bz component.

A cross-correlation study between magnetospheric activity (the AE index) and the southward-directed component of the interplanetary magnetic field (IMF) is made for a total of 792 hours (33 days) with a time resolution of about 5.5 min. The peak correlation tends to occur when the interplanetary data are shifted approximately 40 min later with respect to the AE index data. Cross-correlation analysis is conducted on some idealized wave forms to illustrate that this delay between southward turning of the IMF and the AE index should not be interpreted as being the duration of the growth phase.

Meng, C.-I.↗
NASA NTRS1986

Spatial characteristics of observed precipitation fields: A catalog of summer storms in Arizona, Volume 2

The parameters of the conceptual model are evaluated from the analysis of eight years of summer rainstorm data from the dense raingage network in the Walnut Gulch catchment near Tucson, Arizona. The occurrence of measurable rain at any one of the 93 gages during a noon to noon day defined a storm. The total rainfall at each of the gages during a storm day constituted the data set for a single storm. The data are interpolated onto a fine grid and analyzed to obtain: an isohyetal plot at 2 mm intervals, the first three moments of point storm depth, the spatial correlation function, the spatial variance function, and the spatial distribution of the total storm depth. The description of the data analysis and the computer programs necessary to read the associated data tapes are presented.

Fennessey, N. M.↗
NASA NTRS2001

The Effects of Hypergravity and Adrenalectomy on Bone Mineral Content, Urine Calcium and Body Mass in Rats

The effects of 14 days of increased gravitational load, and the absence of adrenal stress hormones on total body bone mineral content (BMC) were examined in male Sprague-Dawley rats. Centrifugation at 2 Gs (2G) was used to increase the gravitational load, and bilateral adrenalectomy (ADX) was used to eliminate the production of adrenal stress hormones. Stationary groups at 1 G (1G) and sham operated (SHAM) animals served as controls. Thirty rats (n=6 or 8) made up the four experimental groups (1G SHAM, 1G ADX, 2G SHAM and 2G ADX). BMC was assessed by dual energy x-ray absorptiometry (DXA) which was performed to determine the total body bone mineral content, and also through bone ashing of the left femur and the left humerus. Activity was determined through biotelemetry, also body mass and food intake were measured. Multi-factorial analysis of variance (MANCOVA) and Newman Keuls post hoc tests were used to analyze significant effects (p is less than 0.05) for the primary variables. Results from both DXA and the ashed femur indicated that BMC decreased significantly with increased G for both the SHAM and ADX groups. The BMC determined by DXA for the 1G ADX group was also significantly lower than the 1G SHAM group, however the 2G SHAM and 2G ADX groups were not significantly different. However, the bone ashing results showed the femur differed significantly only between the rates of centrifugation and not between the ADX and SHAM. The humerus showed no significant difference between any of the groups. There was a significant decrease in body mass with increased G and there was no ADX effect on body mass. When DXA BMC was normalized for body mass changes, there were no significant group differences. However, with bone ashing, the femur BMC/BW still showed significant difference between rates of centrifugation, with the 2G group being lower. Activity level decreased with body mass, and food intake data showed there was significant hypophagia during the first few days of centrifugation. Urine calcium was measured and was found decrease at the start of centrifugation for the 2G groups and rise to a level higher than that of the stationary groups. Finally, the correlation between BW and BMC was determined to be highly correlated (r = .71). These results suggest that the decrease in total body BMC seen with hypergravity may be based to a large extent on the differences in body mass induced by the 2G load.

Lau, A.↗
NASA NTRS1984

Analysis of a transport fuselage section drop test

Transport fuselage section drop tests provided useful information about the crash behavior of metal aircraft in preparation for a full-scale Boeing 720 controlled impact demonstration (CID). The fuselage sections have also provided an operational test environment for the data acquisition system designed for the CID test, and data for analysis and correlation with the DYCAST nonlinear finite-element program. The correlation of the DYCAST section model predictions was quite good for the total fuselage crushing deflection (22 to 24 inches predicted versus 24 to 26 inches measured), floor deformation, and accelerations for the floor and fuselage. The DYCAST seat and occupant model was adequate to approximate dynamic loading to the floor, but a more sophisticated model would be required for good correlation with dummy accelerations. Although a full-section model using only finite elements for the subfloor was desirable, constraints of time and computer resources limited the finite-element subfloor model to a two-frame model. Results from the two-frame model indicate that DYCAST can provide excellent correlation with experimental crash behavior of fuselage structure with a minimum of empirical force-deflection data representing structure in the analytical model.

E. L. Fasanella↗
DOE OSTI2018

Model-free reconstruction of magnetic correlations in frustrated magnets

Frustrated magnetic systems exhibit extraordinary physical properties, but quantification of their magnetic correlations poses a serious challenge to experiment and theory. Current insight into frustrated magnetic correlations relies on modelling techniques such as reverse Monte-Carlo methods, which require knowledge about the exact ordered atomic structure. Here, we present a method for direct reconstruction of magnetic correlations in frustrated magnets by three-dimensional difference pair distribution function analysis of neutron total scattering data. The methodology is applied to the disordered frustrated magnet bixbyite, (Mn 1– x Fe x ) 2 O 3 , which reveals nearest-neighbor antiferromagnetic correlations for the metal sites up to a range of approximately 15 Å. Pertinently, this technique allows for magnetic correlations to be determined directly from the experimental data without any assumption about the atomic structure.

36 MATERIALS SCIENCE↗
NASA NTRS2013

Tropical Atlantic Dust and Smoke Aerosol Variations Related to the Madden-Julian Oscillation in MODIS and MISR Observations

In this study, Moderate Resolution Imaging Spectroradiometer (MODIS) fine mode fraction and Multi-angle Imaging SpectroRadiometer (MISR) nonspherical fraction data are used to derive dust and smoke aerosol optical thickness (T(sub dust) and T(sub smoke)) over the tropical Atlantic in a complementary way: due to its wider swath, MODIS has 3-4 times greater sampling than MISR, but MISR dust discrimination is based on particle shape retrievals, whereas an empirical scheme is used for MODIS. MODIS and MISR show very similar dust and smoke winter climatologies. T(sub dust) is the dominant aerosol component over the tropical Atlantic, accounting for 40-70 percent of the total aerosol optical thickness (AOT), whereas T(sub smoke) is significantly smaller than T(sub dust). The consistency and high correlation between these climatologies and their daily variations lends confidence to their use for investigating the relative dust and smoke contributions to the total AOT variation associated with the Madden-Julian Oscillation (MJO). The temporal evolution and spatial patterns of the τdus anomalies associated with the MJO are consistent between MODIS and MISR: the magnitude of MJO-realted T(sub dust) anomalies is comparable to or even larger than that of the total T, while the T(sub smoke) anomaly represents about 15 percent compared to the total, which is quite different from their relative magnitudes to the total T on the climatological time scale. This suggests that dust and smoke are not influenced by the MJO in the same way. Based on correlation analysis, dust is strongly influenced by the MJO-modulated trade wind and precipitation anomalies, and can last as long as one MJO phase, whereas smoke is less affected.

Madden-Julian Oscillation↗
NASA NTRS1981

Measurement of recovery temperature on an airfoil in the Langley 0.3-m transonic cryogenic tunnel

Experimental measurements of recovery temperature were made on an airfoil in the Langley 0.3-m Transonic Cryogenic Tunnel at Mach numbers of 0.60 and 0.84 over a Reynolds number per meter range from about 15,000,000 to about 335,000,000. The measured recovery temperatures were considerably below those associated with ideal-gas ambient temperature wind tunnels. This difference was accentuated as the stagnation pressure increased and the total temperature decreased. A boundary-layer code modified for use with cryogenic nitrogen adequately predicted the measured adiabatic wall temperature at all conditions. A quantitative, on-line assessment of the nonadiabatic condition of a model can be made during the operation of a cryogenic wind tunnel by using a correlation for the adiabatic wall temperature which is only a function of total temperature, total pressure, and local Mach number on the model.

Johnson, C. B.↗
DOE OSTI2019

Quantification of fat and skeletal muscle tissue at abdominal computed tomography: associations between single-slice measurements and total compartment volumes

Purpose: Body composition is of great prognostic value in several severe diseases, including different types of cancer as well as cardiometabolic disorders. We aimed to investigate the correlations of skeletal muscle mass and abdominal adipose tissue compartments between volumetric and single-slice measurements to study the usefulness of several anatomical landmarks for estimation of total compartment volumes using abdominal CT-scans. Methods: In this retrospective study volumetric quantifications of paraspinal skeletal muscles (SM) and adipose tissue compartments (visceral adipose tissue, VAT; subcutaneous adipose tissue, SAT) were performed in 50 consecutive patients (26 male; mean age, 63 ± 15 years) who underwent abdominal multislice-CT for diagnostic purposes using an in-house software. Associations between total volumes of SM, VAT, and SAT with single-slice measurements at eight predefined anatomical landmarks (median intervertebral disk spaces T12/L1 to L5/S1; level of the umbilicus (U); level of the radix of the superior mesenteric artery (SMA)) were studied using correlation coefficients. Results: Statistical analysis revealed a strong association between single-slice measurements of adipose tissue compartments with total VAT and SAT volume (VAT: all r > 0.89, P < 0.001; SAT: all r > 0.95, P < 0.001). The strongest associations with total SM volume were found for single-slice measurements obtained at L3/4 (r = 0.94, P < 0.001) and were further improved by normalization to height (r = 0.98, P < 0.001). Conclusions: Single-slice measurements of SM, VAT, and SAT at several anatomical landmarks are strongly associated with total compartment volumes and therefore allow for easy and simultaneous assessment of skeletal muscle mass and adipose tissue compartment volumes.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2023

Correlating chemistry and mass transport in sustainable iron production

Steelmaking contributes 8% to the total CO 2 emissions globally, primarily due to coal-based iron ore reduction. Clean hydrogen-based ironmaking has variable performance because the dominant gas–solid reduction mechanism is set by the defects and pores inside the mm- to nm-sized oxide particles that change significantly as the reaction progresses. While these governing dynamics are essential to establish continuous flow of iron and its ores through reactors, the direct link between agglomeration and chemistry is still contested due to missing measurements. In this work, we directly measure the connection between chemistry and agglomeration in the smallest iron oxides relevant to magnetite ores. Using synthesized spherical 10-nm magnetite particles reacting in H 2 , we resolve the formation and consumption of wüstite (Fe 1-x O)—the step most commonly attributed to whiskering. Using X-ray diffraction, we resolve crystallographic anisotropy in the rate of the initial reaction. Complementary imaging demonstrated how the particles self-assemble, subsequently react, and grow into elongated “whisker” structures. Our insights into how morphologically uniform iron oxide particles react and agglomerate in H 2 reduction enable future size-dependent models to effectively describe the multiscale aspects of iron ore reduction.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2007

Myotonometry as a Surrogate Measure of Muscle Strength

Space flight-induced muscle atrophy/neuromuscular degradation and the consequent decrements in crew-member performance are of increasing concern as mission duration lengthens, and planetary exploration after extended space flight is planned. Pre- to post-flight strength measures have demonstrated that specific countermeasures, such as resistive exercise, are effective at countering microgravity-induced muscle atrophy and preventing decrements in muscle strength. However, in-flight assessment/monitoring of exercise countermeasure effectiveness will be essential during exploration class missions due to their duration. The ability to modify an exercise countermeasure prescription based on such real-time information will allow each individual crew member to perform the optimal amount and type of exercise countermeasure to maintain performance. In addition, such measures can be used to determine if a crew member is physically capable of performing a particular mission-related task during exploration class missions. The challenges faced in acquiring such data are those common to all space operations, namely the requirement for light-weight, low power, mechanically reliable technologies that make valid measurements in microgravity, in this case of muscle strength/neuromuscular function. Here we describe a simple, light-weight, low power, non-invasive device, known as the Myotonometer, that measures tissue stiffness as an indirect measure of muscle contractile state and muscle force production. Repeat myotonometer measurements made at the same location on the surface of the rectis femoris muscle (as determined using a 3D locator device, SEM plus or minus 0.34 mm) were shown to be reproducible over time at both maximal voluntary contraction (MVC) and at rest in a total of 17 sedentary subjects assessed three times over a period of seven days. In addition, graded voluntary isometric force production (i.e. 20%, 40%, 60%, 80% & 100% of MVC) during knee extension was shown to be significantly (p less than 0.01) correlated with contemporaneous myotonometer measurements made on the rectis femoris muscle in a total of 16 healthy subjects (8 males, 8 females). Further-more, this device has been operationally tested during parabolic flight demonstrating its suitability for use in a microgravity environment. Our data indicates that the Myotonometer is a viable surrogate measure of muscle contractile state/tone and of muscle strength/force production. Additional studies are required to assess the suitability of this technique for assessing these measures in de-conditioned subjects such as crew-members.

Ang, B. S.↗
DOE OSTI2025

Post-Wildfire Mobilization of Organic Carbon

Wildfires significantly alter watershed functions, particularly the mobilization of organic carbon (OC). This study investigated OC mobility and the physicochemical characteristics of wildfire-impacted soils and ashes from the northern California and Nevada fires (Dixie, Beckworth, Caldor). Organic carbon in wildfire-derived ashes (9.2–57.3 mg/g) generally exceeded levels in the background soils (4.3–24.4 mg/g), except at the Dixie fire sites. The mobile OC fraction varied from 0.0093 to 0.029 in ashes and 0.010 to 0.065 in soils, though no consistent trend was observed between the ashes and soils. Notably, the ash samples displayed lower OC mobility compared with the soils beneath them. A negative correlation was found between the mobile OC fraction and bulk OC content. Wildfire increased the total amount of mobile OC substantially by 5.2–574% compared to the background soils. Electron paramagnetic resonance (EPR) spectra confirmed the presence of environmentally persistent free radicals (EPFRs), which correlated with observed redox reactivity. Additionally, X-ray absorption near edge structure (XANES) and X-ray fluorescence (XRF) imaging revealed that Fe(II) oxidation in soils beneath the ashes may have enhanced the OC mobility, likely driven by pyrogenic carbon and free radicals. These findings enhance our understanding of post-wildfire OC mobilization and the impact of ash–soil physicochemical properties on watershed health.

organic carbon↗
NASA NTRS1955

Aerodynamic Design of Axial-flow Compressors. VI - Experimental Flow in Two-Dimensional Cascades

Available experimental two-dimensional cascade data for conventional compressor blade sections are correlated at a reference incidence angle in the region of minimum loss. Variations of reference incidence angle, total-pressure loss, and deviation angle with cascade geometry, inlet Mach number, and Reynolds number are investigated. From the analysis and the correlations of the available data, rules and relations are evolved for the prediction of blade-profile performance. These relations are developed in simplified forms readily applicable to compressor design procedures.

Lieblein, Seymour↗