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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

The perception of geometrical structure from congruence

The principle function of vision is to measure the environment. As demonstrated by the coordination of motor actions with the positions and trajectories of moving objects in cluttered environments and by rapid recognition of solid objects in varying contexts from changing perspectives, vision provides real-time information about the geometrical structure and location of environmental objects and events. The geometric information provided by 2-D spatial displays is examined. It is proposed that the geometry of this information is best understood not within the traditional framework of perspective trigonometry, but in terms of the structure of qualitative relations defined by congruences among intrinsic geometric relations in images of surfaces. The basic concepts of this geometrical theory are outlined.

Lappin, Joseph S.↗
NASA NTRS1997

Lignin Formation and the Effects of Gravity: A New Approach

Two aspects of considerable importance in the enigmatic processes associated with lignification have made excellent progress. The first is that, even in a microgravity environment, compression wood formation, and hence altered lignin deposition, can be induced upon mechanically bending the stems of woody gymnosperms. It now needs to be established if an organism reorientating its woody stem tissue will generate this tissue in microgravity, in the absence of externally applied pressure. If it does not, then gravity has no effect on its formation, and instead it results from alterations in the stress gradient experienced by the organism impacted. The second area of progress involves establishing how the biochemical pathway to lignin is regulated, particularly with respect to selective monolignol biosynthesis. This is an important question since individual monomer deposition occurs in a temporally and spatially specific manner. In this regard, the elusive metabolic switch between E-p-coumaryl alcohol and E-coniferyl alcohol synthesis has been detected, the significance of which now needs to be defined at the enzyme and gene level. Switching between monolignol synthesis is important, since it is viewed to be a consequence of different perceptions by plants in the gravitational load experienced, and thus in the control of the type of lignification response. Additional experiments also revealed the rate-limiting processes involved in monolignol synthesis, and suggest that a biological system (involving metabolite concentrations, as well as enzymatic and gene (in)activation processes) is involved, rather than a single rate-limiting step.

Lewis, Norman G.↗
NASA NTRS2022

Regression Bias in using Solar Wind Measurements

Simultaneous solar wind measurements from the solar wind monitors, WIND and ACE, differ due to the spatial and temporal structure of the solar wind. Correlation studies that use these measurements as input may infer an incorrect correlation due to uncertainties arising from this spatial and temporal structure, especially at extreme and rare solar wind values. In particular, regression analysis will lead to a regression function whose slope is biased towards the mean value of the measurement parameter. This article demonstrates this regression bias by comparing simultaneous ACE and WIND solar wind measurements. A non-linear regression analysis between them leads to a perception of underestimation of extreme values of one measurement on average over the other. Using numerical experiments, we show that popular regression analysis techniques such as linear least-squares, orthogonal least-squares, and non-linear regression are not immune to this bias. Hence while using solar wind parameters as an independent variable in a correlation or regression analysis, random uncertainty in the independent variable can create unintended biases in the response of the dependent variable. More generally, the regression to the mean effect can impact both event-based, statistical studies of magnetospheric response to solar wind forcing.

magnetosphere↗
NASA NTRSDate not supplied

Characterizing the Risk: Review of Sensorimotor Evidence and Research Roadmap

BACKGROUND: NASA’s Artemis program will take astronauts back to the lunar surface for the first time in almost 50 years. Despite the successes of the previous Apollo program, the Artemis missions will differ in duration, vehicle characteristics, and landing tasks that may exacerbate the risks to crew health/safety and mission objectives. NASA’s Human Research Program identifies the risk of altered sensorimotor/vestibular function impacting critical mission tasks as one of the top priority risks to lunar exploration missions. This session will review the existing evidence and remaining gaps in knowledge for the sensorimotor risk. DESCRIPTION: Alterations in sensorimotor processing during spaceflight can lead to motion sickness, spatial disorientation, and decrements in postural control, locomotion, and fine motor control during and following gravity-transitions. The risk of impairment is greatest during and soon after gravity-transitions, when performance decrements may have high operational impacts (e.g., manual landings, immediate egress following landing, and early extravehicular activities (EVAs)). Recent studies have specifically improved the risk characterization of changes in perception, motion sickness, postural and locomotor control, manual control, and fine-motor coordination. However, given the difficulty in obtaining measurements during and soon after gravity-transitions, evidence for initial decrements immediately following gravity-transitions remains limited. The most significant gaps in the risk include manual control ability around gravity-transitions, the incidence and severity of motion sickness during landings, and the ability to perform egress/EVAs soon after gravity-transition. To address these gaps, current research roadmaps leverage both spaceflight studies and ground-based analogs for risk characterization and countermeasure development/validation. DISCUSSION: This panel will further describe the current sensorimotor research strategies with an emphasis on the operational scenarios of manual control, crew egress, and EVA. The goal of this research is to accommodate the needs of the crew and facilitate human capabilities to ensure lunar mission success. This work will prepare NASA for successful Artemis missions and enable the next giant leap, the exploration of Mars.

Timothy Ryan Macaulay↗
NASA NTRS1992

Human speed perception is contrast dependent

When two parallel gratings moving at the same speed are presented simultaneously, the lower-contrast grating appears slower. This misperception is evident across a wide range of contrasts (2.5-50 percent) and does not appear to saturate. On average, a 70 percent contrast grating must be slowed by 35 percent to match a 10 percent contrast grating moving at 2 deg/sec (N = 6). Furthermore, the effect is largely independent of the absolute contrast level and is a quasilinear function of log contrast ratio. A preliminary parametric study shows that, although spatial frequency has little effect, relative orientation is important. Finally, the misperception of relative speed appears lessened when the stimuli to be matched are presented sequentially.

Stone, Leland S.↗
NASA NTRS1996

Otolith-Canal Convergence in Vestibular Nuclei Neurons

During manned spaceflight, acute vestibular disturbances often occur, leading to physical duress and a loss of performance. Vestibular adaptation to the weightless environment follows within two to three days yet the mechanisms responsible for the disturbance and subsequent adaptation are still unknown In order to understand vestibular system function in space and normal earth conditions the basic physiological mechanisms of vestibular information co coding must be determined. Information processing regarding head movement and head position with respect to gravity takes place in the vestibular nuclei neurons that receive signals From the semicircular canals and otolith organs in the vestibular labyrinth. These neurons must synthesize the information into a coded output signal that provides for the head and eye movement reflexes as well as the conscious perception of the body in three-dimensional space The current investigation will for the first time. determine how the vestibular nuclei neurons quantitatively synthesize afferent information from the different linear and angular acceleration receptors in the vestibular labyrinths into an integrated output signal. During the second year of funding, progress on the current project has been focused on the anatomical orientation of semicircular canals and the spatial orientation of the innervating afferent responses. This information is necessary in order to understand how vestibular nuclei neurons process the incoming afferent spatial signals particularly with the convergent otolith afferent signals that are also spatially distributed Since information from the vestibular nuclei is presented to different brain regions associated with differing reflexive and sensory functions it is important to understand the computational mechanisms used by vestibular neurons to produce the appropriate output signal.

Dickman, J. David↗
NASA NTRS2008

Ambiguous Tilt and Translation Motion Cues in Astronauts after Space Flight

Adaptive changes during space flight in how the brain integrates vestibular cues with visual, proprioceptive, and somatosensory information can lead to impaired movement coordination, vertigo, spatial disorientation, and perceptual illusions following transitions between gravity levels. This joint ESA-NASA pre- and post-flight experiment is designed to examine both the physiological basis and operational implications for disorientation and tilt-translation disturbances in astronauts following short-duration space flights. The first specific aim is to examine the effects of stimulus frequency on adaptive changes in eye movements and motion perception during independent tilt and translation motion profiles. Roll motion is provided by a variable radius centrifuge. Pitch motion is provided by NASA's Tilt-Translation Sled in which the resultant gravitoinertial vector remains aligned with the body longitudinal axis during tilt motion (referred to as the Z-axis gravitoinertial or ZAG paradigm). We hypothesize that the adaptation of otolith-mediated responses to these stimuli will have specific frequency characteristics, being greatest in the mid-frequency range where there is a crossover of tilt and translation. The second specific aim is to employ a closed-loop nulling task in which subjects are tasked to use a joystick to null-out tilt motion disturbances on these two devices. The stimuli consist of random steps or sum-of-sinusoids stimuli, including the ZAG profiles on the Tilt-Translation Sled. We hypothesize that the ability to control tilt orientation will be compromised following space flight, with increased control errors corresponding to changes in self-motion perception. The third specific aim is to evaluate how sensory substitution aids can be used to improve manual control performance. During the closed-loop nulling task on both devices, small tactors placed around the torso vibrate according to the actual body tilt angle relative to gravity. We hypothesize that performance on the closed-loop tilt control task will be improved with this tactile display feedback of tilt orientation. The current plans include testing on eight crewmembers following Space Shuttle missions or short stay onboard the International Space Station. Measurements are obtained pre-flight at L-120 (plus or minus 30), L-90 (plus or minus 30), and L-30, (plus or minus 10) days and post-flight at R+0, R+1, R+2 or 3, R+4 or 5, and R+8 days. Pre-and post-flight testing (from R+1 on) is performed in the Neuroscience Laboratory at the NASA Johnson Space Center on both the Tilt-Translation Device and a variable radius centrifuge. A second variable radius centrifuge, provided by DLR for another joint ESA-NASA project, has been installed at the Baseline Data Collection Facility at Kennedy Space Center to collect data immediately after landing. ZAG was initiated with STS-122/1E and the first post-flight testing will take place after STS-123/1JA landing.

Clement, G.↗
NASA NTRS1997

Root cytoskeleton: its role in perception of and response to gravity

We have critically evaluated the possible functions of the plant cytoskeleton in root gravisensing and graviresponse and discussed the evidence that microtubules (MTs) and actin microfilaments (MFs) do not control differential cell growth during bending of roots. On the other hand, MF and MT networks are envisaged to participate in gravisensing because of the mechanical properties of the cytoskeletal structures that interconnect plant cell organelles with the plasma membrane. In restrained gravisensing, forces are suggested to be transmitted to membranes because large-scale gravity-dependent repositioning of organelles is effectively prevented due to the cytoskeleton-mediated anchorage of their envelopes at the plasma membrane. From the cytoskeletal point of view, we can also envisage an unrestrained gravity sensing when cytoskeletal tethers are not strong enough to preserve the tight control over distribution of organelles and the latter, if heavy enough, are allowed to sediment towards the physical bottom of cells. This situation obviously occurs in root cap statocytes because these uniquely organized cells are depleted of prominent actin MF bundles, endoplasmic MT arrays, and ER elements in their internal cytoplasm. Nevertheless, indirect evidence clearly indicates that sedimented root cap statoliths are enmeshed within fine but dynamic MF networks and that their behaviour is obviously under, at least partial, cytoskeletal control. The actomyosin-enriched domain among and around amyloplasts is proposed to increase the perception of gravity due to the grouping effect of sedimenting statoliths. Cytoskeletal links between myosin-rich statoliths, and cell peripheries well equipped with dense cortical MTs, membrane-associated cytoskeleton, as well as with ER elements, would allow efficient restrained gravisensing only at the statocyte cell cortex. As a consequence of cytoskeletal depletion in the internal statocyte cytoplasm and bulk sedimentation of large amyloplasts, restrained gravisensing is spatially restricted to the bottom of the statocyte irrespective of whether roots are vertical or horizontal. This spatial aspect allows for efficient gravisensing via amplification of gravity-induced impacts on the cellular architecture, a phenomenon which is unique to root cap statocytes.

NASA Discipline Plant Biology↗
NASA NTRS1990

Process and representation in graphical displays

How people comprehend graphics is examined. Graphical comprehension involves the cognitive representation of information from a graphic display and the processing strategies that people apply to answer questions about graphics. Research on representation has examined both the features present in a graphic display and the cognitive representation of the graphic. The key features include the physical components of a graph, the relation between the figure and its axes, and the information in the graph. Tests of people's memory for graphs indicate that both the physical and informational aspect of a graph are important in the cognitive representation of a graph. However, the physical (or perceptual) features overshadow the information to a large degree. Processing strategies also involve a perception-information distinction. In order to answer simple questions (e.g., determining the value of a variable, comparing several variables, and determining the mean of a set of variables), people switch between two information processing strategies: (1) an arithmetic, look-up strategy in which they use a graph much like a table, looking up values and performing arithmetic calculations; and (2) a perceptual strategy in which they use the spatial characteristics of the graph to make comparisons and estimations. The user's choice of strategies depends on the task and the characteristics of the graph. A theory of graphic comprehension is presented.

Gillan, Douglas J.↗
NASA NTRS1988

Perceived change in orientation from optic flow in the central visual field

The effects of internal depth within a simulation display on perceived changes in orientation have been studied. Subjects monocularly viewed displays simulating observer motion within a volume of randomly positioned points through a window which limited the field of view to 15 deg. Changes in perceived spatial orientation were measured by changes in posture. The extent of internal depth within the display, the presence or absence of visual information specifying change in orientation, and the frequency of motion supplied by the display were examined. It was found that increased sway occurred at frequencies equal to or below 0.375 Hz when motion at these frequencies was displayed. The extent of internal depth had no effect on the perception of changing orientation.

Dyre, Brian P.↗
NASA NTRS2013

Gesture-Based Robot Control with Variable Autonomy from the JPL Biosleeve

This paper presents a new gesture-based human interface for natural robot control. Detailed activity of the user's hand and arm is acquired via a novel device, called the BioSleeve, which packages dry-contact surface electromyography (EMG) and an inertial measurement unit (IMU) into a sleeve worn on the forearm. The BioSleeve's accompanying algorithms can reliably decode as many as sixteen discrete hand gestures and estimate the continuous orientation of the forearm. These gestures and positions are mapped to robot commands that, to varying degrees, integrate with the robot's perception of its environment and its ability to complete tasks autonomously. This flexible approach enables, for example, supervisory point-to-goal commands, virtual joystick for guarded teleoperation, and high degree of freedom mimicked manipulation, all from a single device. The BioSleeve is meant for portable field use; unlike other gesture recognition systems, use of the BioSleeve for robot control is invariant to lighting conditions, occlusions, and the human-robot spatial relationship and does not encumber the user's hands. The BioSleeve control approach has been implemented on three robot types, and we present proof-of-principle demonstrations with mobile ground robots, manipulation robots, and prosthetic hands.

BioSleeve↗
NASA NTRS1994

Multichannel spatial auditory display for speech communications

A spatial auditory display for multiple speech communications was developed at NASA/Ames Research Center. Input is spatialized by the use of simplified head-related transfer functions, adapted for FIR filtering on Motorola 56001 digital signal processors. Hardware and firmware design implementations are overviewed for the initial prototype developed for NASA-Kennedy Space Center. An adaptive staircase method was used to determine intelligibility levels of four-letter call signs used by launch personnel at NASA against diotic speech babble. Spatial positions at 30 degrees azimuth increments were evaluated. The results from eight subjects showed a maximum intelligibility improvement of about 6-7 dB when the signal was spatialized to 60 or 90 degrees azimuth positions.

NASA Discipline Space Human Factors↗
NASA NTRS1985

Detection of volcanic eruptions from space by their sulfur dioxide clouds

The capabilities of the total ozone mapping spectrometer (TOMS) on the Nimbus 7 satellite for tracking volcano plumes are assessed. TOMS was installed on the sun-synchronous polar orbiting satellite to measure spatial variations in the global total ozone field. Radiance absorption coefficients of the atmosphere for four near-UV wavelengths from 312.5-380.0 are measured. Data from the El Chichon eruption in March-April 1982 revealed that SO2 was an absorbing species at 312.5 and 317.5 nm. The near-UV absorption level differences between SO2 and O3 permit discriminating the atmospheric densities of each species. An examination of the data base generated by TOMS since 1978 showed the perceptible tracks of all known major eruptions in the 1978-1982 time period. A constellation of three of the polar orbiting TOMS would be sufficient to provide near-real time alerts of plumes to warn aircraft of the hazards.

Krueger, A. J.↗
NASA NTRS1992

Human speed perception is contrast dependent

When two parallel gratings moving at the same speed are presented simultaneously, the lower-contrast grating appears slower. This misperception is evident across a wide range of contrasts (2.5-50 percent) and does not appear to saturate (e.g. a 50 percent contrast grating appears slower than a 70 percent contrast grating moving at the same speed). On average, a 70 percent contrast grating must be slowed by 35 percent to match a 10 percent contrast grating moving at 2 deg/sec (N = 6). Furthermore, the effect is largely independent of the absolute contrast level and is a quasi-linear function of log contrast ratio. A preliminary parametric study shows that, although spatial frequency has little effect, relative orientation is important. Finally, the misperception of relative speed appears lessened when the stimuli to be matched are presented sequentially.

Stone, Leland S.↗
NASA NTRS1988

Engineering Data Compendium. Human Perception and Performance, Volume 2

The concept underlying the Engineering Data Compendium was the product of a Research and Development program (Integrated Perceptual Information for Designers project) aimed at facilitating the application of basic research findings in human performance to the design of military crew systems. The principal objective was to develop a workable strategy for: (1) identifying and distilling information of potential value to system design from existing research literature, and (2) presenting this technical information in a way that would aid its accessibility, interpretability, and applicability by system designers. The present volumes of the Engineering Data Compendium represent the first implementation of this strategy. This is Volume 2, which contains sections on Information Storage and Retrieval, Spatial Awareness, Perceptual Organization, and Attention and Allocation of Resources.

Boff, Kenneth R.↗
NASA NTRS2008

Software Simulates Sight: Flat Panel Mura Detection

In the increasingly sophisticated world of high-definition flat screen monitors and television screens, image clarity and the elimination of distortion are paramount concerns. As the devices that reproduce images become more and more sophisticated, so do the technologies that verify their accuracy. By simulating the manner in which a human eye perceives and interprets a visual stimulus, NASA scientists have found ways to automatically and accurately test new monitors and displays. The Spatial Standard Observer (SSO) software metric, developed by Dr. Andrew B. Watson at Ames Research Center, measures visibility and defects in screens, displays, and interfaces. In the design of such a software tool, a central challenge is determining which aspects of visual function to include while accuracy and generality are important, relative simplicity of the software module is also a key virtue. Based on data collected in ModelFest, a large cooperative multi-lab project hosted by the Optical Society of America, the SSO simulates a simplified model of human spatial vision, operating on a pair of images that are viewed at a specific viewing distance with pixels having a known relation to luminance. The SSO measures the visibility of foveal spatial patterns, or the discriminability of two patterns, by incorporating only a few essential components of vision. These components include local contrast transformation, a contrast sensitivity function, local masking, and local pooling. By this construction, the SSO provides output in units of "just noticeable differences" (JND) a unit of measure based on the assumed smallest difference of sensory input detectable by a human being. Herein is the truly amazing ability of the SSO, while conventional methods can manipulate images, the SSO models human perception. This set of equations actually defines a mathematical way of working with an image that accurately reflects the way in which the human eye and mind behold a stimulus. The SSO is intended for a wide variety of applications, such as evaluating vision from unmanned aerial vehicles, measuring visibility of damage to aircraft and to the space shuttles, predicting outcomes of corrective laser eye surgery, inspecting displays during the manufacturing process, estimating the quality of compressed digital video, evaluating legibility of text, and predicting discriminability of icons or symbols in a graphical user interface.

Source record↗
NASA NTRS1990

Perception of interstellar structure - Facing complexity

Some orthodox notions concerning the structure and evolution of star-forming regions are challenged; it is proposed that they arise largely by a dual process in which conceptual models are fashioned after categories which are in great part reflections of observational limitations, and the models are projected onto interpretations of data. Several examples are discussed. The need for internal support of molecular clouds is questioned. It is suggested that the inverse density-size relation often claimed for clouds and accounted for by several theoretical models is an artifact caused by limited dynamic range column density detectability, selection bias, distance uncertainties, and internal density gradients, and is contradicted by several unbiased surveys. Column density structures mapped with a large spatial and column density dynamic range are found to be dominated by irregular, connected, and nested forms on all sides. These features and a technique for the quantification of the complex structure are illustrated with a densely-sampled column density image of the Taurus region constructed from IRAS data.

Scalo, John↗
NASA NTRS1996

What Perception Implies about Implementation of Interactive Acoustic Environments

Virtual acoustics, also known as 3-D sound and auralization, is the simulation of the complex acoustic field experienced by a listener within an environment. Going beyond the simple intensity panning of normal stereo techniques, the goal is to process sounds so that they appear to come from particular positions in three-dimensional space. Current techniques use digital signal processing to synthesize the acoustical properties that people use to localize a sound source. This paper briefly reviews these techniques as well as the results of a number of psychoacoustical studies designed to validate the synthesis. In particular, the relationship between the results of recent perceptual studies on the role of head motion to the implementation of interactive spatial audio systems is addressed.

Wenzel, Elizabeth M.↗