Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Aging analysis”

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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS2018

Detrital Shocked Zircon Provides First Radiometric Age Constraint of <1472 Ma for the Santa Fe Impact Structure, New Mexico, USA

Impact structures are prone to erosion, burial and tectonic deformation. The Santa Fe impact structure in New Mexico contains shatter cones and shocked quartz, but is highly tectonized and eroded; estimates of the impact age (1200-300 Ma) and size (6-13 km) are poorly constrained. Here we report the first occurrence of shock-twinned zircon identified both in modern sediments and bedrock at the Santa Fe impact structure. Zircon {112} twin lamellae are considered diagnostic evidence of shock deformation and have been identified at several impact structures including Vredefort, Sudbury, Ries, Rock Elm, and in lunar impact breccia. A total of 6619 grains from fifteen sediment samples and two rock samples were surveyed; seven shocked grains were identified (7/6619 = 0.1%). One shocked zircon was identified in a biotite schist shatter cone. Five of seven shocked zircon grains were EBSD mapped; three were analyzed with multiple SIMS spots. EBSD mapping revealed {112} deformation twin lamellae in each of the five zircon grains. U-Pb geochronology for three of the shocked zircon grains yield crystallization ages from 1715+/-22 to 1472+/-35 Ma. LA-ICPMS U-Th-Pb analysis of detrital zircon grains from five samples yielded Paleoproterozoic (1800-1600 Ma) and Mesoproterozoic (1500-1300 Ma) ages. We reveal the first confirmed shocked zircon at the Santa Fe structure. Zircon is the third shocked mineral identified at this site, in addition to xenotime and quartz]; the {112} twin lamellae indicate that exposed bedrock may have experienced shock pressures up to ~20 GPa. The 1472+/-35 Ma age determined from a shock-twinned zircon is the first reliable maximum impact age constraint based on analysis of shocked material and extends the window for the Santa Fe impact event into the Mesoproterozoic.

Montalvo, Pedro E.↗
NASA NTRS2000

Holter monitoring: are two days better than one?

The optimal duration of Holter monitoring (HM) to minimize costs and maximize yield is unknown. In a retrospective review of 164 patients referred to a tertiary care center for evaluation with 2 days of HM, we found that 48 hours was not cost effective when compared with the traditional 24-hour period.

NASA Discipline Cardiopulmonary↗
NASA NTRS1988

Detecting a periodic signal in the terrestrial cratering record

A time-series analysis of model periodic data, where the period and phase are known, has been performed in order to investigate whether a significant period can be detected consistently from a mix of random and periodic impacts. Special attention is given to the effect of age uncertainties and random ages in the detection of a periodic signal. An equivalent analysis is performed with observed data on crater ages and compared with the model data, and the effects of the temporal distribution of crater ages on the results from the time-series analysis are studied. Evidence for a consistent 30-m.y. period is found to be weak.

Grieve, Richard A. F.↗
NASA NTRS1982

Tharsis volcanoes - Separation distances, relative ages, sizes, morphologies, and depths of burial

Network analysis indicates the separation distances of the Tharsis volcanoes to be 700 to 900 km; this is considered to be the thickness of the Tharsis thermal lithosphere or 'tectosphere' which has thickened with time. Although as a whole the Tharsis volcanoes exhibit a random distribution, preferential alignments emerge when the history of the region is divided into separate periods. The preferential alignments mimic those of fractures in the surrounding terrain. Photogeologic and morphometric data indicate that the volcanoes fall into four distinct classes: montes, tholi, paterae, and a class whose sole representative is Alba Patera. The volcanoes have been buried by lava up to about 4 km in thickness. The sizes of the volcanoes directly correlate with their separation distances from their nearest neighbors. It is concluded that the greater the lithosphere thickness, the larger will be the volcano and the greater its separation distance from its nearest neighbor.

Whitford-Stark, J. L.↗
NASA NTRS1972

Technique for rapid determination of relative ages of lunar areas from orbital photography.

Development of a technique for determining relative ages of regions of the lunar surface from orbital photography using a model of small-impact erosion. The erosion model relates the shape of a crater to the integrated flux of debris that has impacted the surface since that crater was fresh. The shape of the most modified crater of a particular diameter is thereby related to the relative age of the surface. Application of this analysis to orbital photography reveals that the major mare units vary in the accumulation of impacts by more than a factor of 3. Comparison of these data with crystallization ages determined from samples collected during the Apollo 11 and 12 missions indicates that the impact fluxes were decreasing during the stages of mare formation. An exponentially decaying flux for the last 3.5 b.y. with a half-life of 0.6 to 1.4 b.y. is compatible with the data.

Soderblom, L. A.↗
NASA NTRS1979

I-Xe dating of silicate and troilite from IAB iron meteorites

Silicate and troilite inclusions from IAB iron meteorites were dated by the I-Xe technique. Silicate samples from inclusions in the Copiapo, Landes, Woodbine, Pitts and Mundrabilla meteorites and troilite samples from Pitts and Mundrabilla were subjected to neutron irradiation and the xenon isotope ratios produced were determined. Well-defined I-Xe ages were obtained for Woodbine, Copiapo, Landes and Mundrabilla and are found to be within 3.7 million years of the Bjurbole meteorite, suggesting a close relationship to the stone chondrites. The analysis of troilite from Pitts suggests an age of 17 million years older than Bjurbole, while Mundrabilla troilite is observed to predate Mundrabilla silicate. The abundances of Ga, Ge and Ni are found to be correlated with I-Xe ages, supporting the validity of the I-Xe dating method. The results are considered to favor a nebular model of meteorite formation.

Niemeyer, S.↗
NASA NTRS2007

Strain Measurement Using FBG on COPV in Stress Rupture Test

White Sands Test Facility (WSTF) was requested to perform ambient temperature hydrostatic pressurization testing of a Space Transportation System (STS) 40-in. Kevlar Composite Overwrapped Pressure Vessel (COPV). The 40-in. vessel was of the same design and approximate age as the STS Main Propulsion System (MPS) and Orbiter Maneuvering System (OMS) vessels. The NASA Engineering Safety Center (NESC) assembled a team of experts and conducted an assessment that involved a review of national Kevlar COPY data. During the review, the STS COPVs were found to be beyond their original certification of ten years. The team observed that the likelihood of STS COPV Stress rupture, a catastrophic burst before leak failure mode, was greater than previously believed. Consequently, a detailed assessment of remaining stress rupture life became necessary. Prior to STS-114, a certification deviation was written for two flights of OV-103 (Discovery) and OV-104 (Atlantis) per rationale that was based on an extensive review of the Lawrence Livermore National Laboratories, COPV data, and revisions to the STS COPV stress levels. In order to obtain flight rationale to extend the certification deviation through the end of the Program, the Orbiter Project Office has directed an interagency COPV team to conduct further testing and analysis to investigate conservatism in the stress rupture model and evaluate material age degradation. Additional analysis of stress rupture life requires understanding the fiber stresses including stress that occurs due to thru-wall composite compression in COPV components. Data must be obtained at both zero gauge pressure (pre-stress) and at the component operating pressure so that this phenomenon can be properly evaluated. The zero gauge pressure stresses are predominantly a result of the autofrettage process used during vessel manufacture. Determining these pre-stresses and the constitutive behavior of the overwrap at pressure will provide necessary information to better predict the remaining life of the STS COPVs. The primary test objective is obtaining data to verify the hypothesis of a radially oriented thru-thickness stress-riser in the COPV composite whose magnitude is a function of the applied pressure and the load history. The anticipated load dependent response follows from the constitutive behavior of the composite overwrap so data to quantify its nonlinear and time dependent response will be sought. The objective of the Fiber Braggs Gratings (FBGs) were to advance the state-of-the-art by developing techniques using FBG sensors that are capable of assessing stress-rupture degradation in Kevlar COPVs in a health monitoring mode (1). Moreover, they sought to answer questions of how embedded sensors affect overall integrity of the structure. And lastly, they sought to provide an important link in the overall stress rupture study that will help close the loop on the COPV fabrication process. NDE inspection methods will be used from start to finish and FBG will be an integral link within the overall chain.

Banks, Curtis↗
NASA NTRS2000

Vascular mechanics of the coronary artery

This paper describes our research into the vascular mechanics of the coronary artery and plaque. The three sections describe the determination of arterial mechanical properties using intravascular ultrasound (IVUS), a constitutive relation for the arterial wall, and finite element method (FEM) models of the arterial wall and atheroma. METHODS: Inflation testing of porcine left anterior descending coronary arteries was conducted. The changes in the vessel geometry were monitored using IVUS, and intracoronary pressure was recorded using a pressure transducer. The creep and quasistatic stress/strain responses were determined. A Standard Linear Solid (SLS) was modified to reproduce the non-linear elastic behavior of the arterial wall. This Standard Non-linear Solid (SNS) was implemented into an axisymetric thick-walled cylinder numerical model. Finite element analysis models were created for five age groups and four levels of stenosis using the Pathobiological Determinants of Atherosclerosis Youth (PDAY) database. RESULTS: The arteries exhibited non-linear elastic behavior. The total tissue creep strain was epsilon creep = 0.082 +/- 0.018 mm/mm. The numerical model could reproduce both the non-linearity of the porcine data and time dependent behavior of the arterial wall found in the literature with a correlation coefficient of 0.985. Increasing age had a strong positive correlation with the shoulder stress level, (r = 0.95). The 30% stenosis had the highest shoulder stress due to the combination of a fully formed lipid pool and a thin cap. CONCLUSIONS: Studying the solid mechanics of the arterial wall and the atheroma provide important insights into the mechanisms involved in plaque rupture.

NASA Program Biomedical Research and Countermeasur↗
NASA NTRSDate not supplied

Characterizing Martian Volcanic Provinces’ Magmatic Evolution and Chemistry through Equations of State Modeling Initial Study

Here we discuss a novel interdisciplinary approach to investigating igneous compositions of large volcanic provinces on Mars using remote sensing data sets (Mars Odyssey Gamma Ray and neutron Spectrometer suite--GRS, and gravity) to inform petrologic and thermoelastic modeling. Martian volcanic provinces, starting from Noachian to Amazonian age, including Elysium (EVP), are locations of great geologic interest which have been active over long time scales from Hesperian to Amazonian. Regional scale change in eruptive processes are poorly understood. Compared to large igneous provinces on Earth, the martian volcanic activity has persisted for orders of magnitude longer. Therefore, changes in mantle chemistry, pressure, and temperature during lithospheric cooling are expected to produce significant changes in the conditions of magma production, storage and ascent, affecting the degree of fractional crystallization and crustal contamination. In this study, we perform a detailed modeling to test the hypothesis that compositional variability within volcanic provinces resulted from spatiotemporal changes in the depth of magma formation and present initial results. Our methods include constraining the pressure and temperature conditions of EVP as a case study of geologically recent magmatic evolution on Mars using GRS informed surface chemistry constraints and pMELTS modeling. Second, we place constraints on the density and seismic velocities of the EVP melt through thermoelastic modeling with a local gravity analysis. This analysis is also extended to Noachian aged volcanic provinces on Mars initial results estimates mantle pressure for each sub-region is 16 kbar pressure, whereas, degree of partial melting is low and varies between 10 to 12. This study aims to validate our theoretical model and develop a perspective view of spatiotemporal changes at the interior of Mars throughout the time.

Martian science, Mars, geology, geophysics↗
NASA NTRS1998

Diagnostic yield and optimal duration of continuous-loop event monitoring for the diagnosis of palpitations. A cost-effectiveness analysis

BACKGROUND: Continuous-loop event recorders are widely used for the evaluation of palpitations, but the optimal duration of monitoring is unknown. OBJECTIVE: To determine the yield, timing, and incremental cost-effectiveness of each week of event monitoring for palpitations. DESIGN: Prospective cohort study. PATIENTS: 105 consecutive outpatients referred for the placement of a continuous-loop event recorder for the evaluation of palpitations. MEASUREMENTS: Diagnostic yield, incremental cost, and cost-effectiveness for each week of monitoring. RESULTS: The diagnostic yield of continuous-loop event recorders was 1.04 diagnoses per patient in week 1, 0.15 diagnoses per patient in week 2, and 0.01 diagnoses per patient in week 3 and beyond. Over time, the cost-effectiveness ratio increased from $98 per new diagnosis in week 1 to $576 per new diagnosis in week 2 and $5832 per new diagnosis in week 3. CONCLUSIONS: In patients referred for evaluation of palpitations, the diagnostic yield of continuous-loop event recording decreases rapidly after 2 weeks of monitoring. A 2-week monitoring period is reasonably cost-effective for most patients and should be the standard period for continuous-loop event recording for the evaluation of palpitations.

NASA Discipline Cardiopulmonary↗
NASA NTRS1991

Natural aging and reversion behavior of Al-Cu-Li-Ag-Mg alloy Weldalite (tm) 049

This study was initiated to understand the natural aging and reversion behavior of Weldalite (trademark) 049 in tempers without cold work. Of particular interest are: (1) the microstructural basis for the high strength in the T4 condition; (2) an explanation of the reversion phenomenon; and (3) the effect of re-aging at room temperature after a reversion treatment. Mechanical properties were measured and transmission electron microscopy (TEM) analysis performed at various stages of microstructural development during aging, reversion, and subsequent re-aging.

Gayle, Frank W.↗
NASA NTRS1996

Changes in aerobic power of women, ages 20-64 yr

This study quantified and compared the cross-sectional and longitudinal influence of age, self-report physical activity (SR-PA), and body composition (%fat) on the decline of maximal aerobic power (VO2peak) of women. The cross-sectional sample consisted of 409 healthy women, ages 20-64 yr. The 43 women of the longitudinal sample were from the same population and examined twice, the mean time between tests was 3.7 (+/-2.2) yr. Peak oxygen uptake was determined by indirect calorimetry during a maximal treadmill test. The zero-order correlation of -0.742 between VO2peak and %fat was significantly (P < 0.05) higher then the SR-PA (r = 0.626) and age correlations (r = -0.633). Linear regression defined the cross-sectional age-related decline in VO2peak at 0.537 ml.kg-1.min-1.yr-1. Multiple regression analysis (R = 0.851) showed that adding %fat and SR-PA and their interaction to the regression model reduced the age regression weight of -0.537, to -0.265 ml.kg-1.min-1.yr-1. Statistically controlling for time differences between tests, general linear models analysis showed that longitudinal changes in aerobic power were due to independent changes in %fat and SR-PA, confirming the cross-sectional results. These findings are consistent with men's data from the same lab showing that about 50% of the cross-sectional age-related decline in VO2peak was due to %fat and SR-PA.

Aging/physiology↗
NASA NTRS1983

Nature of the H chondrite parent body regolith - Evidence from the Dimmitt breccia

Meteorite regolith breccias are clastic rocks which formed by lithification of fragmental regolith material that once resided at the surface of a meteorite parent body. A study is reported of the matrix and 21 clasts of various sizes (0.2-24 mm) in the Dimmitt H chondrite regolith breccia using petrographic and electron microprobe techniques. In addition, oxygen isotope studies of three clasts and instrumental neutron activation analysis (INAA) and Ar-39/Ar-40 age dating of one clast are reported. The Dimmitt meteorite was found about 1942 near Dimmitt, Texas. Attention is given to analytical procedures, the clastic matrix, equilibrated clasts, poikilitic melt-rock clast, clasts of different chondrite groups, graphite-magnetite aggregates, the origin of exotic clasts, and the complexity of parent body surfaces processes.

Rubin, A. E.↗
NASA NTRS1986

The advanced X-ray Astrophysics Facility

The basic characteristics and capabilities of the Advanced X-ray Astrophysics Facility (AXAF) are described. The use of the AXAF to perform mass determinations in galaxies and in cluster of galaxies is discussed. The study of galaxy evolution, the interactions of galaxies with their environment, and the properties of galactic halos with the AXAF is proposed. The application of the facility to cosmological measurements, the estimation of the age of the universe, and the analysis of stars, galaxy clusters, and protogalaxies is examined.

Tananbaum, H.↗
NASA NTRS1991

Monitoring global snow cover

A snow model that supports the daily, operational analysis of global snow depth and age has been developed. It provides improved spatial interpolation of surface reports by incorporating digital elevation data, and by the application of regionalized variables (kriging) through the use of a global snow depth climatology. Where surface observations are inadequate, the model applies satellite remote sensing. Techniques for extrapolation into data-void mountain areas and a procedure to compute snow melt are also contained in the model.

Armstrong, Richard↗
NASA NTRS1996

Calcium kinetics with microgram stable isotope doses and saliva sampling

Studies of calcium kinetics require administration of tracer doses of calcium and subsequent repeated sampling of biological fluids. This study was designed to develop techniques that would allow estimation of calcium kinetics by using small (micrograms) doses of isotopes instead of the more common large (mg) doses to minimize tracer perturbation of the system and reduce cost, and to explore the use of saliva sampling as an alternative to blood sampling. Subjects received an oral dose (133 micrograms) of 43Ca and an i.v. dose (7.7 micrograms) of 46Ca. Isotopic enrichment in blood, urine, saliva and feces was well above thermal ionization mass spectrometry measurement precision up to 170 h after dosing. Fractional calcium absorptions determined from isotopic ratios in blood, urine and saliva were similar. Compartmental modeling revealed that kinetic parameters determined from serum or saliva data were similar, decreasing the necessity for blood samples. It is concluded from these results that calcium kinetics can be assessed with micrograms doses of stable isotopes, thereby reducing tracer costs and with saliva samples, thereby reducing the amount of blood needed.

Clinical Trial↗
NASA NTRS2010

Towards Prognostics of Power MOSFETs: Accelerated Aging and Precursors of Failure

This paper presents research results dealing with power MOSFETs (metal oxide semiconductor field effect transistor) within the prognostics and health management of electronics. Experimental results are presented for the identification of the on-resistance as a precursor to failure of devices with die-attach degradation as a failure mechanism. Devices are aged under power cycling in order to trigger die-attach damage. In situ measurements of key electrical and thermal parameters are collected throughout the aging process and further used for analysis and computation of the on-resistance parameter. Experimental results show that the devices experience die-attach damage and that the on-resistance captures the degradation process in such a way that it could be used for the development of prognostics algorithms (data-driven or physics-based).

Celaya, Jose R.↗
NASA NTRS2011

Increased Intracranial Pressure and Visual Impairment Associated with Long-Duration Spaceflight

Although humans have been flying in space since the 1960s, more recent missions have revealed a new suite of physiological adaptations and consequences of space flight. Notably, 60% of long-duration crewmembers (ISS/MIR) and >25% of short-duration (Shuttle) crewmembers have reported subjective degradation in vision (based on debrief comments) (Gibson 2011). Decreased near-visual acuity was demonstrated in 46% of ISS/Mir and 21% of Shuttle crewmembers, resulting in a shift of up to 1-2 diopters in their refractive correction. It is likely that the recently revealed ophthalmic changes have been present since the first days of human space flight, but have been overlooked or attributed to other causations. The reported changes in vision have occurred at various time points throughout missions, with ranging degrees of visual degradation. Although some cases resolved upon return to Earth, several astronauts have not regained preflight visual acuity, indicating that the damage may be permanent. While observing these changes over the years, without other overt symptomology and with the given age range of the flying population, this has largely been attributed to an expected hyperopic shift due to aging. However, the availability of onboard analysis techniques, including visual acuity assessments, retinal imagery, and ultrasounds of the eye and optic nerve tracts, along with more detailed post-flight techniques, has led to the recent recognition of a wider syndrome. Along with vision changes, findings include flattening of the globe, swelling of the optic disc (papilledema), choroidal folds in the retina, swelling of the optic nerve sheath, and visual field defects. It is widely hypothesized that this constellation of findings may be explained by an elevation of intracranial pressure (ICP). Out of the 60% of long-duration astronauts that have reported a subjective degradation in vision, a subset (currently 10 astronauts) have developed this syndrome. The National Aeronautics and Space Administration (NASA) has made it a high priority to understand this syndrome and provide mitigation techniques to protect crewmembers from visual impairment. While there are many possible factors that could contribute to intracranial hypertension associated with spaceflight, the relative contribution of these, as well as the processes by which eye damage occurs as a result of intracranial hypertension, are not fully understood. The observed pathophysiological phenomena are extremely complex and it is likely that multiple factors contribute to their incidence, rather than one simple mechanism. This paper will define and examine the findings in detail, and expound upon the potential contributing factors and their relative contribution to this syndrome.

Marshall-Bowman, Karina↗