SEARCH · Engineering Papers

Results for “rebound effect”

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.

SourceResearch connectionFrom yearThrough year

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

At least 109 records · Page 6

All sources NASA NTRS DOE OSTI

DOE OSTI2021

A Taxonomic Classification Approach for Global Spatio-temporal Data

The World Bank, World Health Organization, and other major vendors collectively provide thousands of global time series datasets that focus on issues of the environment, public health, economics, violence, education, and national security. Sorting these data into meaningful information requires the use of data mining techniques to cluster trends into an orderly and manageable number of cases. The World SpatioTemporal Analytics and Mapping (WSTAMP) project database (wstamp.ornl.gov) was developed to spatiotemporally harmonize global vendor data (23,300+ attributes, 200+ locations, 50+ years). Within the WSTAMP analytical environment, Dynamic Time Warping (DTW) has been a highly effective data-driven approach for clustering and mapping these time series into national spatiotemporal behavior maps. Two significant properties have surfaced from this work. First, several recognizable cluster patterns have emerged and persist across a range of locations, attributes, and time frames (e.g., increasing, decreasing, rebounding, peak, oscillating). Secondly, practitioners engaging WSTAMP have noted the explanatory and anticipatory value of these patterns and articulated particular interest in detecting them within the spatiotemporal cube. This need was addressed by shifting DTW-based clustering from an open ended, data-driven implementation to a taxonomic pattern matching approach. This paper presents the method including implementation strategies for visualization and human computer interaction and applies the approach to a sample data set and concludes with next steps.

Stewart, Robert↗

NASA NTRSDate not supplied

Oblique Eccentric Gaze Holding Evokes Larger Horizontal than Vertical Rebound Nystagmus

Rebound nystagmus (RN) has been used to probe the adaptation mechanisms of the gaze holding system. This type of nystagmus is invoked upon returning to central gaze after prolonged fixation at an eccentric point and it is thought to reflect a set-point adaptation of the neural integrator circuit. Previous studies have only observed horizontal RN after horizontal eccentric gaze holding, reflecting adaptation of the horizontal neural integrator. The current study seeks to elucidate how eccentric gaze at oblique target locations, where there are equal horizontal and vertical components, affects the characteristics of the resulting RN. For a given trial, subjects were instructed to fixate a central flashing target for 5 seconds, then fixate an eccentric continuous target for 30 seconds at one of six possible locations (4 oblique and 2 horizontal targets), and finally fixate centrally at a flashing target for 15 seconds where RN is assessed. Binocular eye-tracking data were collected at 250 Hz. Slow-phase velocity (SPV) or the slow drift part of the nystagmus was used to quantify the magnitude of RN. Subjects showed elevated SPV in the horizontal component (2.3 deg/s), but less in the vertical component (1.4 deg/s) after oblique eccentric gaze holding, reflecting an oblique RN. The smaller vertical RN may reflect a different behavior of the horizontal and vertical neural integrators which are anatomically separated. Under the current paradigm, oblique gaze holding would appear to have a smaller effect on adaptation of the vertical integrator than in the horizontal integrator. Further investigation is needed to establish the reference frame of this distinction between the horizontal and vertical integrator circuits.

gaze holding↗

NASA NTRSDate not supplied

Results for the Subjective Habitability Acceptability Questionnaire From HERA C5 and C6

BACKGROUND The impact of habitability on psychological and performance outcomes is recognized as an important factor in habitat and vehicle design—especially as missions increase in length. Formal evaluation of habitability’s impact is possible using the Spaceflight Habitability Acceptability Questionnaire (SHAQ), which was psychometrically validated by Roma et al. in 2022 [1]. The SHAQ survey systematically quantifies the relationships between habitat areas (e.g., bedroom, kitchen, hygiene area, office, etc.) and behavioral health and performance (BHP) outcomes (i.e., individual and team performance, mood, stress, sleep, social interaction), and considers the moderating effects of key habitability aspects (i.e., privacy, control, convenience, efficiency, comfort, social density) on that relationship. METHOD Respondents were HERA participants from Campaign 5 and 6 (n = 32). Data from three environments were used in our SHAQ analyses: SHAQ in HERA (in-mission), SHAQ at Home (pre-mission), and SHAQ in Hotel (pre- and post-mission for C6, just pre-mission for C5). For each habitat area, respondents are asked how that area layout impacts six BHP outcomes on a 201-point visual analog scale with the anchors: impairs, has no effect, and facilitates. They also had the option to respond “Not Applicable”. Follow up questions asked why six key habitability aspects (e.g., privacy) influenced the way the habitat area affected a given outcome. Participants indicated whether a habitat area’s habitability aspects were inadequate (low score) to adequate (midpoint) to ideal (high score), using a 201-point visual analog scale as well but were binned to a 7-point scale for analyses. RESULTS AND CONCLUSION When comparing across environments, ratings of BHP outcomes were worse in HERA compared to home and pre-mission hotel, but rebounded for the post-mission hotel such that post-mission hotel rating were often higher than all previous ratings. Within HERA, ratings of how a habitat area impacted an outcome skewed towards facilitation with communal areas (i.e., galley and office) rated most facilitating. The follow up questions about why six key aspects related to habitability moderated outcomes indicated that most habitat areas were rated as having “adequate” habitability characteristics. Privacy was the only moderator with average scores below adequate for all habitat areas. The office had the most moderators scoring above adequate for all habitat areas. Ratings indicated small to moderate effects of layouts on BHP outcomes: with facilitating layouts averaging between 4 and 5, and impairing layouts averaging between 2 and 4. The sleeping module layout facilitated sleep, with ratings indicating adequate comfort but inadequate privacy. The galley layout facilitated social interaction and mood, with ratings indicating adequate efficiency and convenience. The office layout facilitated social interaction, team and individual performance, with ratings similarly indicating adequate efficiency and convenience. The hygiene module worsened individual performance, mood and stress, with ratings indicating less than adequate privacy and social density. Our findings suggest there is value in having dedicated team and individual spaces. REFERENCES [1] Roma, P. G., Landon, L.B., Spencer, C. A., Whitmire, A. M., & Williams, T. J. (2022). SHAQ: Development and Validation. Human Factors: Special Issue on Spaceflight, 65(6), 1074-1104. ACKNOWLEDGEMENTS This project was funded by the NASA Human Research Program directed task Human Factors and Behavioral Performance in HERA (PI = S. Bell) to the BHP Lab. KBR Inc. and JES Tech authors were supported by KBR’s Human Health and Performance Contract NNJ15HK11B with NASA.

behavioral health↗

DOE OSTI2024

A model for oblique impacts on material surfaces

Many practical situations of material damage, wear, and erosion involve collisions between small particles and surfaces at inclined angles. While there are many well-validated models of normal incidence impact situations, elastic-plastic models for oblique incidence impact events are lacking. Here the finite element method is used to predict the normal and tangential coefficient of restitution in oblique impacts for hard, elastic spheres impacting an elastic-perfectly plastic material surface. The proposed model covers various impact angles ranging from 0° to 45°, within a limiting impact velocity below which the effects of heating are negligible. The normal coefficient of restitution follows power-laws with respect to normalized values of the impact velocity. Interestingly, the tangential coefficient of restitution follows a linear relationship with impact velocity. Together, these results provide a semi-empirical set of equations predicting oblique impact rebounds (both velocity and trajectory) for a wide range of conditions and material properties, with which experimental results can be rapidly interpreted. As a result, Laser-Induced Particle Impact Test (LIPIT) data are also presented for aluminum particles impacting aluminum substrates, at impact angles of 25° and 40°; the results compare favorably with the model and validate the general use of such models for the analysis of experimental data.

Coefficient of restitution↗

NASA NTRS1992

Postglacial rebound with a non-Newtonian upper mantle and a Newtonian lower mantle rheology

A composite rheology is employed consisting of both linear and nonlinear creep mechanisms which are connected by a 'transition' stress. Background stress due to geodynamical processes is included. For models with a non-Newtonian upper-mantle overlying a Newtonian lower-mantle, the temporal responses of the displacements can reproduce those of Newtonian models. The average effective viscosity profile under the ice-load at the end of deglaciation turns out to be the crucial factor governing mantle relaxation. This can explain why simple Newtonian rheology has been successful in fitting the uplift data over formerly glaciated regions.

Gasperini, Paolo↗

NASA NTRS1994

A singularity free approach to post glacial rebound calculations

Calculating the post glacial response of a viscoelastic Earth model using the exponential decay normal mode technique leads to intrinsic singularities if viscosity varies continuously as a function of radius. We develop a numerical implementation of the Complex Real Fourier transform (CRFT) method as an accurate and stable procedure to avoid these singularities. Using CRFT, we investigate the response of a set of Maxwell Earth models to surface loading. We find that the effect of expanding a layered viscosity structure into a continuously varying structure is to destroy the modes associated with the boundary between layers. Horizontal motion is more sensitive than vertical motion to the viscosity structure just below the lithosphere. Horizontal motion is less sensitive to the viscosity of the lower mantle than the vertical motion is. When the viscosity increases at 670 km depth by a factor of about 60, the response of the lower mantle is close to its elastic limit. Any further increase of the viscosity contrast at 670 km depth or further increase of viscosity as a continuous function of depth starting from 670 km depth is unlikely to be resolved.

Fang, Ming↗

NASA NTRS1995

VLBI data, acquisition, environmental effects

During this quadrennium, very long baseline interferometry (VLBI) data acquisition and system development has focused on improving the accuracy of the system sufficiently to allow the determination of reliable estimates of height variations. Associated with this aim has been improvements in the determinations of horizontal velocity fields, monitoring water vapor delay using interferometric methods, and improvements to Earth rotation measurements. The primary aims of the improvements to height measurement accuracy have been to directly measure the contemporary magnitudes of post glacial rebound, and to determine a height reference system for measuring global sea level rise. High frequency Earth rotation studies have been carried out to better define the transformation parameters from an inertial coordinate system to an Earth fixed one, and to better understand the coupling between the components of the atmosphere-ocean-solid Earth system. Two major VLBI campaigns were carried out in support of these studies: (1) Epoch-92 in July 1992 and (2) Cont-94 in January 1994. Each of these campaigns lasted approximately two weeks and involved multiple VLBI networks operating simultaneously in addition to other space geodetic systems operating during these periods. Two major compilations of the VLBI results (and results from other space geodetic systems) have been published during this quadrennium.

Herring, Thomas A.↗

NASA NTRS1992

Asteroids and Archaean crustal evolution: Tests of possible genetic links between major mantle/crust melting events and clustered extraterrestrial bombardments

Since the oldest intact terrestrial rocks of ca. 4.0 Ga and oldest zircon xenocrysts of ca. 4.3 Ga measured to date overlap with the lunar late heavy bombardment, the early Precambrian record requires close reexamination vis a vis the effects of megaimpacts. The identification of microtektite-bearing horizons containing spinals of chondritic chemistry and Ir anomalies in 3.5-3.4-Ga greenstone belts provides the first direct evidence for large-scale Archaean impacts. The Archaean crustal record contains evidence for several major greenstone-granite-forming episodes where deep upwelling and adiabatic fusion of the mantle was accompanied by contemporaneous crustal anatexis. Isotopic age studies suggest evidence for principal age clusters about 3.5, 3.0, and 2.7 (+/- 0.8) Ga, relics of a ca. 3.8-Ga event, and several less well defined episodes. These peak events were accompanied and followed by protracted thermal fluctuations in intracrustal high-grade metamorphic zones. Interpretations of these events in terms of internal dynamics of the Earth are difficult to reconcile with the thermal behavior of silicate rheologies in a continuously convecting mantle regime. A triggering of these episodes by mantle rebound response to intermittent extraterrestrial asteroid impacts is supported by (1) identification of major Archaean impacts from microtektite and distal ejecta horizons marked by Ir anomalies; (2) geochemical and experimental evidence for mantle upwelling, possibly from levels as deep as the transition zone; and (3) catastrophic adiabatic melting required to generate peridotitic komatites. Episodic differentiation/accretion growth of sial consequent on these events is capable of resolving the volume problem that arises from comparisons between modern continental crust and the estimated sial produced by continuous two-stage mantle melting processes. The volume problem is exacerbated by projected high accretion rates under Archaean geotherms. It is suggested that impact shock effects have been largely obscured by (1) outpouring of voluminous basic/ultrabasic lavas, inundating shock-deformed crust and extending beyond the perimeters of impact excavated basins; (2) gravity subsidence and downfaulting of terrestrial maria, accounting for the burial and anatexis of subgreenstone basement; and (3) extensive shearing and recrystallization at elevated temperatures of impact structure, breccias, and mineral deformation features beneath impact-excavated basins, relics of which may be retained in structural windows in high-grade metamorphic terranes.

Glikson, A. Y.↗

DOE OSTI2021

Mechanistic basis of post-treatment control of SIV after anti-α4β7 antibody therapy

Treating macaques with an anti-α4β7 antibody under the umbrella of combination antiretroviral therapy (cART) during early SIV infection can lead to viral remission, with viral loads maintained at < 50 SIV RNA copies/ml after removal of all treatment in a subset of animals. Depletion of CD8+ lymphocytes in controllers resulted in transient recrudescence of viremia, suggesting that the combination of cART and anti-α4β7 antibody treatment led to a state where ongoing immune responses kept the virus undetectable in the absence of treatment. A previous mathematical model of HIV infection and cART incorporates immune effector cell responses and exhibits the property of two different viral load set-points. While the lower set-point could correspond to the attainment of long-term viral remission, attaining the higher set-point may be the result of viral rebound. Here we expand that model to include possible mechanisms of action of an anti-α4β7 antibody operating in these treated animals. We show that the model can fit the longitudinal viral load data from both IgG control and anti-α4β7 antibody treated macaques, suggesting explanations for the viral control associated with cART and an anti-α4β7 antibody treatment. This effective perturbation to the virus-host interaction can also explain observations in other nonhuman primate experiments in which cART and immunotherapy have led to post-treatment control or resetting of the viral load set-point. Interestingly, because the viral kinetics in the various treated animals differed—some animals exhibited large fluctuations in viral load after cART cessation—the model suggests that anti-α4β7 treatment could act by different primary mechanisms in different animals and still lead to post-treatment viral control. This outcome is nonetheless in accordance with a model with two stable viral load set-points, in which therapy can perturb the system from one set-point to a lower one through different biological mechanisms.

60 APPLIED LIFE SCIENCES↗

NASA NTRS1999

Viscoelastic Postseismic Rebound to Strike-Slip Earthquakes in Regions of Oblique Plate Convergence

According to the slip partitioning concept, the trench parallel component of relative plate motion in regions of oblique convergence is accommodated by strike-slip faulting in the overriding continental lithosphere. The pattern of postseismic surface deformation due to viscoelastic flow in the lower crust and asthenosphere following a major earthquake on such a fault is modified from that predicted from the conventual elastic layer over viscoelastic halfspace model by the presence of the subducting slab. The predicted effects, such as a partial suppression of the postseismic velocities by 1 cm/yr or more immediately following a moderate to great earthquake, are potentially detectable using contemporary geodetic techniques.

Cohen, Steven C.↗

NASA NTRS2004

Time-Variable Gravity from Satellite Laser-Ranging: The Low-Degree Components and Their Connections with Geophysical/Climatic Changes

Satellite laser-ranging (SLR) has been observing the tiny variations in Earth s global gravity for over 2 decades. The oblateness of the Earth's gravity field, J2, has been observed to undergo a secular decrease of J2 due mainly to the post-glacial rebound of the mantle. Sometime around 1998 this trend reversed quite suddenly. This reversal persisted until 2001, at which point the atmosphere-corrected time series appears to have reversed yet again towards normal. This anomaly signifies a large interannual change in global mass distribution. A number of possible causes have been considered, with oceanic mass redistribution as the leading candidate although other effects, such as glacial melting and core effects may be contributing. In fact, a strong correlation has been found between the J2 variability and the Pacific decadal oscillation. It is relatively more difficult to solve for corresponding signals in the shorter wavelength harmonics from the existing SLR-derived time variable gravity results, although it appears that geophysical fluid mass transport is being observed. For example, the recovered J3 time series shows remarkable agreement with NCEP-derived estimates of atmospheric gravity variations. Likewise, some of the non-zonal harmonic components have significant interannual signal that appears to be related to mass transport related to climatic effects such as El Nino Southern Oscillation. We will present recent updates on the J2 evolution, as well as a monthly time sequence of low-degree component map of the time-variable gravity complete through degree 4, and examine possible geophysical/climatic causes.

Chao, Benjamin F.↗

NASA NTRS1988

The effect of a shallow low-viscosity zone on the mantle flow, the geoid anomalies and the geoid and depth-age relationships at fracture zones

A two-dimensional FEM is used to investigate the flow driven by the horizontal temperature gradient at a fracture zone and to calculate the resulting geoid and topography anomalies. Using a three-layered viscosity structure for the upper mantle, results are presented for the effects of varying: (1) the viscosity contrast between the fluid layers: (2) the Rayleigh number based on the viscosity of the bottom layer; and (3) the thickness of the low-viscosity channel. Good agreement is obtained with the results of geoid anomalies over the Udintsev fracture zone when the viscosity of the top layer is greater than one order of magnitude less than post-glacial rebound values.

Robinson, Elizabeth M.↗

NASA NTRS1982

Optical pulse evolution in the Stanford free-electron laser and in a tapered wiggler

The Stanford free electron laser (FEL) oscillator is driven by a series of electron pulses from a high-quality superconducting linear accelerator (LINAC). The electrons pass through a transverse and nearly periodic magnetic field, a 'wiggler', to oscillate and amplify a superimposed optical pulse. The rebounding optical pulse must be closely synchronized with the succession of electron pulses from the accelerator, and can take on a range of structures depending on the precise degree of synchronism. Small adjustments in desynchronism can make the optical pulse either much shorter or longer than the electron pulse, and can cause significant subpulse structure. The oscillator start-up from low level incoherent fields is discussed. The effects of desynchronism on coherent pulse propagation are presented and compared with recent Stanford experiments. The same pulse propagation effects are studied for a magnet design with a tapered wavelength in which electrons are trapped in the ponderomotive potential.

Colson, W. B.↗

DOE OSTI2024

A generalized analytical energy balance model for evaluating agglomeration from a binary collision of wet particles

Agglomeration of wet particles, i.e., particles coated with a thin liquid layer, is a common phenomenon in many processes like fluidized bed combustion of low rank fuels. The availability of an agglomeration model that can evaluate the outcome of a binary collision between wet particles differing in solid particle properties, liquid layer thicknesses, and initial collision (impact) speeds is essential for obtaining a comprehensive understanding on the existing processes experiencing wet particle agglomeration or for a successful development of new processes with high chances of wet particle agglomeration. This study presents a generalized agglomeration model on the basis of energy conservation before and after collision when colliding wet particles may differ in solid particle properties, liquid layer thicknesses, and impact speeds. The model was established based on the approximate values of energy losses that may happen during the collision. It incorporates body forces, solid-solid contacting, liquid capillary, and viscous contributions, as well as the liquid bridge volume effect. Predictions of the new model for collision outcomes of identical wet particles were like those from an analytical energy balance model developed recently by the group for identical wet particles. We also validated the new model by experimental data from literature. The results of a collision direction analysis indicated that the direction often has a minimal effect on the collision outcome in many practical scenarios. The results of Monte Carlo uncertainty analyses with the new model revealed that proper estimations of impact speed, under capillary limiting conditions, and thickness of coating layers and asperity heights, under viscous limiting conditions, are critical for the realistic prediction of collision outcomes at impact speeds close to critical impact speed, i.e., the minimum particle speed required for the particles to rebound.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

NASA NTRS2003

Time-Variable Gravity and Ocean Connections

Any large mass transport in the Earth system produces changes in the gravity field. Low harmonic degree components of such gravity variations have been observed by the satellite-laser-ranging (SLR) technique for the past quarter century, particularly in 52, the Earth's dynamic oblateness. 52 undergoes a slight decrease due primarily to the post-glacial rebound of the mantle, but large interannual anomalies have been observed, notably during 1998-2002. Intriguing evidences for the cause of the latter have been found in the extratropical Pacific basins, especially related to the Pacific Decadal Oscillation, and perhaps in related land hydrology. We will examine the latest results based on ocean altimetry, sea-surface temperature, and ocean and hydrology model outputs. Without firm estimates for the steric effects (which have no gravity signal), we will point out possible underestimation of OGCMs with respect to temporal variabilities. Besides J2, SLR also derived time series for other low-degree gravity components. While the formal uncertainty of these terms is significantly higher, some of these series have significant signal that show correlation to various climatic signals. For example, there is a significant correlation of the sectoral S2,2 with the Southern Oscillation Index signifying the influence of El Nino/La Nina. Cases such as these demonstrate the utility of assessing the mass component of climate variations, and anticipate the utility of GRACE-type space gravity observations with much higher spatial resolution.

Chao, Benjamin F.↗

NASA NTRS1986

Microcirculatory fluid dynamics in weightlessness and simulated weightlessness

The method of Smith et al. (1985), which makes it possible to simultaneously measure the macrocirculation and microcirculation in an unanesthetized rat, was used to study the effect of acute hypokinesia on the rat microvascular system. The measurements yielded values of the length, diameter, and number of arteriolar and venular vessels; vascular patterns; branching ratios; and the amplitude and frequency of vasomotion. Early effects (30-60 min after the start of the head-down tilt) include a 10 percent increase in the diameter of arterioles, a slight increase of heart rate and mean arterial blood pressure, and an increase in the heart rate-pulse pressure product, with most of the changes returning to normal after 2-3 h. The baroreceptor reflex index was reduced by almost 50 percent for the first 2 h, but rebounded to almost 3 times the control value after 3 h. This indicates that, in spite of relatively small changes in gross hemodynamic parameters, the cardiovascular function is altered significantly during the acute phase of hypokinesia.

Hutchins, P. M.↗

NASA NTRS1989

Time-dependent convection with non-Newtonian viscosity

A numerical model of bottom-heated, two-dimensional convection in boxes of aspect ratios 2.5 and 4.0 was used to study the differences in time-dependent convection between Newtonian and stress-dependent viscosity. The onset of time dependence due to boundary layer instability is found at approximately the same effective Rayleigh number for both rheologies. However, with increasing Rayleigh number, the temporal and spatial fluctuations in the flow field become much more pronounced with non-Newtonian rheology; also, the tendency for breakup of long cells into smaller ones is stronger. The presence of stress-dependent rheology can cause long-wavelength lateral viscosity variations up to an order of magnitude; this result could have strong implications for the interpretation of mantle viscosity from postglacial rebound.

Christensen, Ulrich R.↗

NASA NTRS1994

Volatiles, rheology, and mantle convection: Comparing Earth, Venus, and Mars

Silicate rheology is controlled in part by volatile content. The variation of viscosity with position in the mantle will influence the nature of mantle convection; hence, modeling mantle convection and its effect on surface observables such as the geoid places constraints on the viscosity structure of a planet's mantle and may indirectly constrain the volatile distribution. Models of viscous mantle flow and the Earth's geoid indicate that there is roughly a two order of magnitude variation in viscosity between the upper and lower mantles, although there is some disagreement over the depth of the viscosity minimum in the upper mantle. Some studies of post-glacial rebound also support such a viscosity contrast between the upper and lower mantles. On Venus, several highland regions appear to be supported by mantle plumes. Modeling of the geoid and topography of these regions indicates that if these features are plume-related, then the mantle of Venus can not have an Earth-like low viscosity zone in its upper mantle. On Mars, the Tharsis volcanic province has alternatively been explained as supported either by mantle convection or by flexure of a thick lithosphere. If the convective model is correct, then the large geoid anomaly requires that Mars can not have a low viscosity zone in its upper mantle.

Kiefer, Walter S.↗