3,683 research outputs found
Reply to Proffitt, Stefanucci, Banton, and Epstein
In this reply, we acknowledge that methodological differences between the experiment of Proffitt et al. (2003) and ours might explain our failure to replicate their finding. However, we maintain that our results obtained with three different response measures point to a lack of robustness. In this reply, we acknowledge that methodological differences between the experiment of Proffitt et al. (2003) and ours might explain our failure to replicate their finding. However, we maintain that our results obtained with three different response measures point to a lack of robustness of their finding. In response to their criticism of using blind walking to measure perceived distance, we argue on theoretical grounds that blind walking, while involving post-perceptual processes, can nevertheless provide a measure of perceived distance, and then cite some of the evidence indicating that it does indeed provide such a measure.En esta réplica, los autores reconocen que las diferencias metodológicas respecto al experimento de Proffit et al. (2003) podrían explicar el fallo en la replicación. Sin embargo, se indica que la obtención de resultados negativos en tres medidas diferentes parece implicar una escasa fortaleza en el efecto. Por otra parte, y en respuesta a las críticas sobre el uso de caminar a ciegas para medir la distancia percibida, se argumenta teóricamente que esta conducta puede proporcionar una medida adecuada de la distancia percibida, aunque implique procesos posteriores a la percepción. También se cita alguna evidencia en apoyo de esta conclusión
Does Energy Expenditure Affect the Perception of Egocentric Distance? A Failure to Replicate Experiment 1 of Proffitt, Stefanucci, Banton, and Epstein (2003)
In a series of recent studies, Proffitt and his colleagues have reported that the perceived distance to a target is influenced by the energy expenditure associated with any action, such as walking or throwing, for spanning the distance to the target. In particular, Proffitt, Stefanucci, Banton, and Epstein (2003) reported that wearing a heavy backpack caused verbal reports of distance to increase. We conducted a study to determine whether three responses dependent on perceived distance (verbal report of distance, blind walking, and estimates of object size) are influenced by the backpack manipulation. In two experiments, one involving a between-participants design and the other involving a within participants design, we found that none of the three responses were influenced by the wearing of a heavy backpack.En una serie reciente de trabajos, Proffitt y sus colegas informaron de que la distancia a la que se percibe una estimulación diana se ve afectada por el gasto de energía asociado a la realización de cualquier acción, como andar o lanzar un objeto, que pueda realizarse para cubrir la distancia hasta la estimulación diana. Concretamente, Proffitt, Stefanucci, Banton y Epstein (2003) afirmaron que llevar una mochila pesada hizo que se incrementasen los informes verbales sobre la distancia. Realizamos un estudio para verificar si tres respuestas que dependen de la distancia percibida (informe verbal de distancia, andar a ciegas y estimaciones del tamaño de un objeto) son afectadas por el uso de la mochila. En dos experimentos, uno con un diseño inter-participantes y el otro con un diseño intra-participantes, encontramos que ninguna de las tres respuestas era afectada por llevar una mochila pesada
Functional Equivalence of Spatial Images from Touch and Vision: Evidence from Spatial Updating in Blind and Sighted Individuals
This research examined whether visual and haptic map learning yield functionally equivalent spatial images in working memory, as evidenced by similar encoding bias and updating performance. In 3 experiments, participants learned 4-point routes either by seeing or feeling the maps. At test, blindfolded participants made spatial judgments about the maps from imagined perspectives that were either aligned or misaligned with the maps as represented in working memory. Results from Experiments 1 and 2 revealed a highly similar pattern of latencies and errors between visual and haptic conditions. These findings extend the well-known alignment biases for visual map learning to haptic map learning, provide further evidence of haptic updating, and most important, show that learning from the 2 modalities yields very similar performance across all conditions. Experiment 3 found the same encoding biases and updating performance with blind individuals, demonstrating that functional equivalence cannot be due to visual recoding and is consistent with an amodal hypothesis of spatial images
Thermal, Radiation and Impact Protective Shields (TRIPS) for Robotic and Human Space Exploration Missions
New concepts for protective shields for NASA s Crew Exploration Vehicles (CEVs) and planetary probes offer improved mission safety and affordability. Hazards include radiation from cosmic rays and solar particle events, hypervelocity impacts from orbital debris/ micrometeorites, and the extreme heating environment experienced during entry into planetary atmospheres. The traditional approach for the design of protection systems for these hazards has been to create single-function shields, i.e. ablative and blanket-based heat shields for thermal protection systems (TPS), polymer or other low-molecular-weight materials for radiation shields, and multilayer, Whipple-type shields for protection from hypervelocity impacts. This paper introduces an approach for the development of a single, multifunctional protective shield, employing nanotechnology- based materials, to serve simultaneously as a TPS, an impact shield and as the first line of defense against radiation. The approach is first to choose low molecular weight ablative TPS materials, (existing and planned for development) and add functionalized carbon nanotubes. Together they provide both thermal and radiation (TR) shielding. Next, impact protection (IP) is furnished through a tough skin, consisting of hard, ceramic outer layers (to fracture the impactor) and sublayers of tough, nanostructured fabrics to contain the debris cloud from the impactor before it can penetrate the spacecraft s interior
The benefits of using a walking interface to navigate virtual environments
Navigation is the most common interactive task performed in three-dimensional virtual environments (VEs), but it is also a task that users often find difficult. We investigated how body-based information about the translational and rotational components of movement helped participants to perform a navigational search task (finding targets hidden inside boxes in a room-sized space). When participants physically walked around the VE while viewing it on a head-mounted display (HMD), they then performed 90% of trials perfectly, comparable to participants who had performed an equivalent task in the real world during a previous study. By contrast, participants performed less than 50% of trials perfectly if they used a tethered HMD (move by physically turning but pressing a button to translate) or a desktop display (no body-based information). This is the most complex navigational task in which a real-world level of performance has been achieved in a VE. Behavioral data indicates that both translational and rotational body-based information are required to accurately update one's position during navigation, and participants who walked tended to avoid obstacles, even though collision detection was not implemented and feedback not provided. A walking interface would bring immediate benefits to a number of VE applications
Increased HCO production in the outer disk around HD 163296
Three formaldehyde lines were observed (HCO 3--2, HCO
3--2, and HCO 3--2) in the protoplanetary disk
around the Herbig Ae star HD 163296 with ALMA at 0.5 arcsecond (60 AU) spatial
resolution. HCO 3--2 was readily detected via imaging, while
the weaker HCO 3--2 and HCO 3--2 lines
required matched filter analysis to detect. HCO is present throughout most
of the gaseous disk, extending out to 550 AU. An apparent 50 AU inner radius of
the HCO emission is likely caused by an optically thick dust continuum. The
HCO radial intensity profile shows a peak at 100 AU and a secondary bump at
around 300 AU, suggesting increased production in the outer disk. Different
parameterizations of the HCO abundance were compared to the observed
visibilities with minimization, using either a characteristic
temperature, a characteristic radius or a radial power law index to describe
the HCO chemistry. Similar models were applied to ALMA Science Verification
data of CO. In all modeling scenarios, fits to the HCO data show an
increased abundance in the outer disk. The overall best-fit HCO model shows
a factor of two enhancement beyond a radius of 27020 AU, with an inner
abundance of . The HCO emitting region has a lower
limit on the kinetic temperature of K. The CO modeling suggests
an order of magnitude depletion in the outer disk and an abundance of in the inner disk. The increase in HCO outer disk emission
could be a result of hydrogenation of CO ices on dust grains that are then
sublimated via thermal desorption or UV photodesorption, or more efficient
gas-phase production beyond about 300 AU if CO is photodisocciated in this
region
Effects of Heavy-Ion Irradiation on Microstructure of V-4Cr-4Ti Alloy at Moderate Temperatures
V-4Cr-4Ti is promising for first-wall and structural applications in magnetic fusion reactors. Fast neutron sources were used to evaluate postirradiation properties of fusion candidate materials, but FFTF and EBR-II have been shutdown. Under these circumstances, heavy-ion irradiation is an attractive alternative. We used 3-MeV V{sup +} and 4.5-MeV Ni{sup 2+} ions to investigate effects of irradiation on microstructure of V-4Cr-4Ti at 200-420 C. This paper report results of ion irradiation experiments and compare with fast-neutron irradiation data. From TEM, the dominant feature of postirradiation microstructure was a high density of dislocation loops and point- defect clusters. Density and defect size depend on irradiation dose and temperature. Precipitates and voids/bubbles were not observed, even in specimens simultaneous injected with he and exposed to heavy ions. Increased transport of point defects to internal interfaces was observed, as manifested by defect denuded zones along grain boundaries. Defect denuded zones along grain boundaries could lead to segregation of impurities and solutes and formation of precipitates on grain boundaries
Active localization of virtual sounds
We describe a virtual sound display built around a 12 MHz 80286 microcomputer and special purpose analog hardware. The display implements most of the primary cues for sound localization in the ear-level plane. Static information about direction is conveyed by interaural time differences and, for frequencies above 1800 Hz, by head sound shadow (interaural intensity differences) and pinna sound shadow. Static information about distance is conveyed by variation in sound pressure (first power law) for all frequencies, by additional attenuation in the higher frequencies (simulating atmospheric absorption), and by the proportion of direct to reverberant sound. When the user actively locomotes, the changing angular position of the source occasioned by head rotations provides further information about direction and the changing angular velocity produced by head translations (motion parallax) provides further information about distance. Judging both from informal observations by users and from objective data obtained in an experiment on homing to virtual and real sounds, we conclude that simple displays such as this are effective in creating the perception of external sounds to which subjects can home with accuracy and ease
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