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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.

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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Patterns and rates of soil movement and shallow failures across several small watersheds on the Seward Peninsula, Alaska

Abstract. Thawing permafrost can alter topography, ecosystems, and sediment and carbon fluxes, but predicting landscape evolution of permafrost-influenced watersheds in response to warming and/or hydrological changes remains an unsolved challenge. Sediment flux and slope instability in sloping saturated soils have been commonly predicted from topographic metrics (e.g., slope, drainage area). In addition to topographic factors, cohesion imparted by soil and vegetation and melting ground ice may also control spatial trends in slope stability, but the distribution of ground ice is poorly constrained and hard to predict. To address whether slope stability and surface displacements follow topographic-based predictions, we document recent drivers of permafrost sediment flux present on a landscape in western Alaska that include creep, solifluction, gullying, and catastrophic hillslope failures ranging in size from a few meters to tens of meters, and we find evidence of rapid and substantial landscape change on an annual timescale. We quantify the timing and rate of surface movements using a multi-pronged, multi-scalar dataset including aerial surveys, interannual GPS surveys, synthetic aperture radar interferometry (InSAR), and climate data. Despite clear visual evidence of downslope soil transport of solifluction lobes, we find that the interannual downslope surface displacement of these features does not outpace downslope displacement of soil in locations where lobes are absent (downslope movement means: 7 cm yr−1 for lobes over 2 years vs. 10 cm yr−1 in landscape positions without lobes over 1 year). Annual displacements do not appear related to slope, drainage area, or modeled total solar radiation but are likely related to soil thickness, and volumetric sediment fluxes are high compared to temperate landscapes of comparable bedrock lithology. Time series of InSAR displacements show accelerated movement in late summer, associated with intense rainfall and/or deep thaw. While mapped slope failures do cluster at slope–area thresholds, a simple slope stability model driven with hydraulic conductivities representative of throughflow in mineral and organic soil drastically overpredicts the occurrence of slope failures. This mismatch implies permafrost hillslopes have unaccounted-for cohesion and/or throughflow pathways, perhaps modulated by vegetation, which stabilize slopes against high rainfall. Our results highlight the breadth and complexity of soil transport processes in Arctic landscapes and demonstrate the utility of using a range of synergistic data collection methods to observe multiple scales of landscape change, which can aid in predicting periglacial landscape evolution.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2021

Random sub-diffusion and capture of genes by the nuclear pore reduces dynamics and coordinates inter-chromosomal movement

Hundreds of genes interact with the yeast nuclear pore complex (NPC), localizing at the nuclear periphery and clustering with co-regulated genes. Dynamic tracking of peripheral genes shows that they cycle on and off the NPC and that interaction with the NPC slows their sub-diffusive movement. Furthermore, NPC-dependent inter-chromosomal clustering leads to coordinated movement of pairs of loci separated by hundreds of nanometers. We developed fractional Brownian motion simulations for chromosomal loci in the nucleoplasm and interacting with NPCs. These simulations predict the rate and nature of random sub-diffusion during repositioning from nucleoplasm to periphery and match measurements from two different experimental models, arguing that recruitment to the nuclear periphery is due to random sub-diffusion and transient capture by NPCs. Finally, the simulations do not lead to inter-chromosomal clustering or coordinated movement, suggesting that interaction with the NPC is necessary, but not sufficient, to cause clustering.

59 BASIC BIOLOGICAL SCIENCES↗
NASA NTRS1974

Measuring ground movement in geothermal areas of Imperial Valley, California

Significant ground movement may accompany the extraction of large quantities of fluids from the subsurface. In Imperial Valley, California, one of the potential hazards of geothermal development is the threat of both subsidence and horizontal movement of the land surface. Regional and local survey nets are being monitored to detect and measure possible ground movement caused by future geothermal developments. Precise measurement of surface and subsurface changes will be required to differentiate man-induced changes from natural processes in this tectonically active region.

Lofgren, B. E.↗
NASA NTRS1975

Verification by Remote Sensing of an Oil Slick Movement Prediction Model

The author has identified the following significant results. LANDSAT, aircraft, ships, and air-dropped current drogues were deployed to determine current circulation and to track oil slick movement on four different dates in Delaware Bay. Results were used to verify a predictive model for oil slick movement and dispersion. The model predicts the behavior of oil slicks given their size, location, tidal stage (current), weather (wind), and nature of crude. Both LANDSAT satellites provided valuable data on gross circulation patterns and convergent coastal fronts which by capturing oil slicks significantly influence their movement and dispersion.

Klemas, V.↗
NASA NTRS1977

A relationship between eye movement patterns and performance in a precognitive tracking task

Eye movements made by various subjects in the performance of a precognitive tracking task are studied. The tracking task persented by an antiaircraft artillery (AAA) simulator has an input forcing function represented by a deterministic aircraft fly-by. The performance of subjects is ranked by two metrics. Good, mediocre, and poor trackers are selected for analysis based on performance during the difficult segment of the tracking task and over replications. Using phase planes to characterize both the eye movement patterns and the displayed error signal, a simple metric is developed to study these patterns. Two characterizations of eye movement strategies are defined and quantified. Using these two types of eye strategies, two conclusions are obtained about good, mediocre, and poor trackers. First, the eye tracker who used a fixed strategy will consistently perform better. Secondly, the best fixed strategy is defined as a Crosshair Fixator.

Repperger, D. W.↗
NASA NTRS1980

Instrument scanning and controlling: Using eye movement data to understand pilot behavior and strategies

Eye movement data and other parameters including instrument readings, aircraft state and position variables, and control maneuvers were recorded while pilots flew ILS simulations in a B 737. The experiment itself employed seven airline pilots, each of whom flew approximately 40 approach/landing sequences. The simulator was equipped with a night visual scene but the scene was fogged out down to approximately 60 meters (200 ft). The instrument scanning appeared to follow aircraft parameters not physical position of instruments. One important implication of the results is: pilots look for categories or packets of information. Control inputs were tabulated according to throttle, wheel position, column, and pitch trim changes. Three seconds of eye movements before and after the control input were then obtained. Analysis of the eye movement data for the controlling periods showed clear patterns. The results suggest a set of miniscan patterns which are used according to the specific details of the situation. A model is developed which integrates scanning and controlling. Differentiations are made between monitoring and controlling scans.

Dick, A. O.↗
NASA NTRS1980

Downslope movement of material on Deimos

Viking Orbiter images have shown downslope movement of loose material to be an important surface process on Deimos. Loose surface material moves downslope from prominent ridges and accumulates in topographic lows. In some areas, up to 10 m of surface material have been removed; in others, craters up to 200 m in diameter have been filled completely by material moving downslope. Brighter material associated with, and probably derived from crater rims, also moves downslope and forms tapered streamers up to 3 km in length which appear as prominent features on the satellite. The mechanism for downslope movement is uncertain, but thermal creep, micrometeroroid bombardment and impact-related seismic shaking may be involved. Certain craters show conspicuous infilling even though their prominent rims should prevent material moving downslope from reaching their interiors. Such fill must have been emplaced ballistically - the amounts of sediment suggest that over half of all ejecta produced on Deimos are retained on the satellite. Phobos appears to retain little ejecta and shows little evidence of downslope movement of debris.

Thomas, P.↗
NASA NTRS1981

The guidance of saccadic eye movements to perceptually mislocalized visual and non-visual targets

The present experiment examined whether saccadic eye movements to visual targets are dependent on the perceived directions of the targets or on their retinally specified directions. Perceptual mislocations of visual targets were induced by having the target light attached to a subject's stationary hand while his biceps or triceps muscle was vibrated. Such vibration leads to apparent extension or flexion of the subject's restrained forearm and perceived visual motion of the stationary target light. Subjects always made accurate saccadic eye movements to a visual target, even when the target was perceptually mislocalized by as much as 20 deg. By contrast, when subjects made saccadic eye movements to a nonvisual target, the location of their hand in the dark, they always looked to the perceived direction of the target even though it did not necessarily correspond to the true direction. These findings indicate that a distinction is maintained between 'reflexive aspects' of oculomotor control related to foveation and the computation of perceived visual direction.

Lackner, J. R.↗
NASA NTRS1984

Fitts' Law? a Test of the Relationship Between Information Load and Movement Precision

The independence of information load (Hick's Law) and movement precision (Fitts' Law) was tested using additive factors methodology. Subjects were required to classify stimuli according to a decision rule with a variable entropy. The stimuli were presented in the center of the CRT screen. In response, subjects had to move a cursor from a starting point near the stimulus to the appropriate target. The precision of the response movement was varied by manipulating the ratio of the radius of the annulus to the width of the target area. The dependent measure was elapsed time between onset of the stimulus and completion of the response movement. Independence of the Hick's Law and Fitts' Law components of the reaction time was tested with an analysis of variance. Presence of an interaction would suggest that a decision stage and a response stage are dependent, and cannot be considered discrete steps in a serial process.

Zalaski, M.↗
NASA NTRS1984

New Uses for Sensitivity Analysis: How Different Movement Tasks Effect Limb Model Parameter Sensitivity

Original results for a newly developed eight-order nonlinear limb antagonistic muscle model of elbow flexion and extension are presented. A wider variety of sensitivity analysis techniques are used and a systematic protocol is established that shows how the different methods can be used efficiently to complement one another for maximum insight into model sensitivity. It is explicitly shown how the sensitivity of output behaviors to model parameters is a function of the controller input sequence, i.e., of the movement task. When the task is changed (for instance, from an input sequence that results in the usual fast movement task to a slower movement that may also involve external loading, etc.) the set of parameters with high sensitivity will in general also change. Such task-specific use of sensitivity analysis techniques identifies the set of parameters most important for a given task, and even suggests task-specific model reduction possibilities.

Winters, J. M.↗
NASA NTRS1986

Hitts Law? A test of the relationship between information load and movement precision

Recent technological developments have made viable a man-machine interface heavily dependent on graphics and pointing devices. This has led to new interest in classical reaction and movement time work by Human Factors specialists. Two experiments were designed and run to test the dependence of target capture time on information load (Hitt's Law) and movement precision (Fitts' Law). The proposed model linearly combines Hitt's and Fitts' results into a combination law which then might be called Hitts' Law. Subjects were required to react to stimuli by manipulating a joystick so as to cause a cursor to capture a target on a CRT screen. Response entropy and the relative precision of the capture movement were crossed in a factorial design and data obtained that were found to support the model.

Zaleski, M.↗
NASA NTRS1986

Adapted head- and eye-movement responses to added-head inertia

Adaptation to inertia added to the head was studied in men by mounting masses on a rigidly attached helmet until two- to ten-fold increases of inertia were produced, while an overhead suspension compensated for the weights. The observed changes in the eye and head movement coordination included increased head movement latencies, as well as changes in the eye movement amplitude, and later stabilizing alternate contractions of the neck muscles. Oscillopsia, or continual displacement or instability of the visual world, which is a symptom of a breakdown of space constancy, was prominent and consistent in the perceptual reports of the subjects. Although adaptation resulting from adding inertia to the head occurred much faster than that induced by adding prisms or lenses, it has similar perceptual and motor components that may be objectively studied in detail.

Gauthier, G. M.↗
NASA NTRS1986

Short time Fourier analysis of the electromyogram - Fast movements and constant contraction

Short-time Fourier analysis was applied to surface electromyograms (EMG) recorded during rapid movements, and during isometric contractions at constant forces. A portion of the data to be transformed by multiplying the signal by a Hamming window was selected, and then the discrete Fourier transform was computed. Shifting the window along the data record, a new spectrum was computed each 10 ms. The transformed data were displayed in spectograms or 'voiceprints'. This short-time technique made it possible to see time-dependencies in the EMG that are normally averaged in the Fourier analysis of these signals. Spectra of EMGs during isometric contractions at constant force vary in the short (10-20 ms) term. Short-time spectra from EMGs recorded during rapid movements were much less variable. The windowing technique picked out the typical 'three-burst pattern' in EMG's from both wrist and head movements. Spectra during the bursts were more consistent than those during isometric contractions. Furthermore, there was a consistent shift in spectral statistics in the course of the three bursts. Both the center frequency and the variance of the spectral energy distribution grew from the first burst to the second burst in the same muscle. The analogy between EMGs and speech signals is extended to argue for future applicability of short-time spectral analysis of EMG.

Hannaford, Blake↗
NASA NTRS1987

Time-locked time-histories - A new way of examining eye-movement data

A problem often encountered when eye-movement measurement is conducted is the choice of 'indices' or 'statistics' available to present such information. The present study reports the use of the Time-Locked Time-History as a technique of value in the examination and presentation of eye-movement data. Plots created using this technique are labeled time-locked time-histories as they illustrate subject eye lookpoint during a period of time before and after a certain time-locking event. Events that occur with some degree of repetition, such as the onset or termination of control activities, warning signals, or changes in indicator positions may be utilized as time-locking events. The present study reports the use of this technique in an eye-movement study using a secondary task in which the subject must discriminate specific types of information in the display.

Comstock, J. Raymond, Jr.↗
NASA NTRS1989

Outputs of paired Gabor filters summed across the background frame of reference predict the direction of movement

A cortical neural network that computes the visibility of shifts in the direction of movement is proposed. The network computes: (1) the magnitude of the position difference between the test and background patterns, (2) localized contrast differences at different spatial scales analyzed by computing temporal gradients of the difference and sum of the outputs of paired even- and odd-symmetric bandpass filters convolved with the input pattern, and (3) using global processes that pool the output from paired even- and odd-symmetric simple and complex cells across the spatial extent of the background frame of reference the direction a test pattern moved relative to a textured background. Evidence that magnocellular pathways are used to discriminate the direction of movement is presented. Since magnocellular pathways are used to discriminate the direction of movement, this task is not affected by small pattern changes such as jitter, short presentations, blurring, and different background contrasts that result when the veiling illumination in a scene changes.

Lawton, Teri B.↗
NASA NTRS1989

Time optimal movement of cooperating robots

The maximization of the speed of movement along a prescribed path, of the system formed by a set of robot arms and the object they hold is examined. The actuator torques that maximize the acceleration of the system are shown to be determined by the solution to a standard linear programming problem. The combination of this result with the known control strategy for time optimal movement of a single robot arm yields an algorithm for time optimal movement of multiple robot arms holding the same workpiece.

Mccarthy, J. M.↗
NASA NTRS1992

Fixed Or Controlled-Movement Foot Restraint

Foot restraint gives user three options: holds user's feet in fixed position, allows them to slide sideways, or allows them to pivot independently about axis through ball of foot, as user chooses. Selects degree of restraint to suit task at hand. Movements to enter and leave foot restraint simple and direct. Simply forces each cleat lightly into space between rails until spring force of movable rail secures it. Body movements for sliding and rotation equally straightforward. Designed for use in absence of gravitation, restraint useful on Earth, underwater or in some hazardous locations where movements restricted.

Reilly, Gloria B.↗
NASA NTRS1992

A spaceflight experiment to investigate the effects of a range of unilateral blue light phototropic stimulations on the movements of wheat coleoptiles (6-IML-1)

In 1978, in response to an announcement of opportunity by NASA, two independent groups proposed related investigations to study the response of seedling plants to photostimulations at microgravity. The spaceflight experiment is known by its NASA acronym, FOTRAN. The scientific objectives behind the experiment are outlined, and a brief description of the spaceflight equipment and the experimental procedures developed to accomplish the aims of the experiment are presented. By reference to the results of ground-based studies, the likely scientific returns of the FOTRAN experiment will be assessed. The experiment is designed to investigate the effects of a range of blue light stimulations on the movements of wheat coleoptiles at zero-g. The seedlings will be dark-grown, and their movements assessed from infrared time-lapse video recordings made during flight. The photostimulus may be expected to modulate circumnutations of the coleoptiles, by synchronizing, initiating or amplifying these rhythmic movements, and to initiate the classic phototropic response.

Heathcote, David G.↗