2,388 research outputs found
The role of terminators and occlusion cues in motion integration and segmentation: a neural network model
The perceptual interaction of terminators and occlusion cues with the functional processes of motion integration and segmentation is examined using a computational model. Inte-gration is necessary to overcome noise and the inherent ambiguity in locally measured motion direction (the aperture problem). Segmentation is required to detect the presence of motion discontinuities and to prevent spurious integration of motion signals between objects with different trajectories. Terminators are used for motion disambiguation, while occlusion cues are used to suppress motion noise at points where objects intersect. The model illustrates how competitive and cooperative interactions among cells carrying out these functions can account for a number of perceptual effects, including the chopsticks illusion and the occluded diamond illusion. Possible links to the neurophysiology of the middle temporal visual area (MT) are suggested
Solar array flight experiment/dynamic augmentation experiment
This report presents the objectives, design, testing, and data analyses of the Solar Array Flight Experiment/Dynamic Augmentation Experiment (SAFE/DAE) that was tested aboard Shuttle in September 1984. The SAFE was a lightweight, flat-fold array that employed a thin polyimide film (Kapton) as a substrate for the solar cells. Extension/retraction, dynamics, electrical and thermal tests, were performed. Of particular interest is the dynamic behavior of such a large lightweight structure in space. Three techniques for measuring and analyzing this behavior were employed. The methodology for performing these tests, gathering data, and data analyses are presented. The report shows that the SAFE solar array technology is ready for application and that new methods are available to assess the dynamics of large structures in space
Low-distortion slow light using two absorption resonances
We consider group delay and broadening using two strongly absorbing and
widely spaced resonances. We derive relations which show that very large pulse
bandwidths coupled with large group delays and small broadening can be
achieved. Unlike single resonance systems, the dispersive broadening dominates
the absorptive broadening which leads to a dramatic increase in the possible
group delay. We show that the double resonance systems are excellent candidates
for realizing all-optical delay lines. We report on an experiment which
achieved up to 50 pulse delays with 40% broadening.Comment: 4 pages 4 figure
Computer control study for a manned centrifuge Final technical report
Analog simulation of manned centrifuge capability for production of various gravity levels - centrifuge control syste
Hands-On Universe: A Global Program for Education and Public Outreach in Astronomy
Hands-On Universe (HOU) is an educational program that enables students to
investigate the Universe while applying tools and concepts from science, math,
and technology. Using the Internet, HOU participants around the world request
observations from an automated telescope, download images from a large image
archive, and analyze them with the aid of user-friendly image processing
software. This program is developing now in many countries, including the USA,
France, Germany, Sweden, Japan, Australia, and others. A network of telescopes
has been established among these countries, many of them remotely operated, as
shown in the accompanying demo. Using this feature, students in the classroom
are able to make night observations during the day, using a telescope placed in
another country. An archive of images taken on large telescopes is also
accessible, as well as resources for teachers. Students are also dealing with
real research projects, e.g. the search for asteroids, which resulted in the
discovery of a Kuiper Belt object by high-school students. Not only Hands-On
Universe gives the general public an access to professional astronomy, but it
is also a more general tool to demonstrate the use of a complex automated
system, the techniques of data processing and automation. Last but not least,
through the use of telescopes located in many countries over the globe, a form
of powerful and genuine cooperation between teachers and children from various
countries is promoted, with a clear educational goal.Comment: 4 pages, 1 figure, to appear in the proceedings of the ADASS X
conference, Boston, October 2000, ASP conf. pro
Variation reduction in a continuous web process
Thesis (S.M.)--Massachusetts Institute of Technology, Sloan School of Management; and, Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1998.Includes bibliographical references (p. 71).by William C. Pack.S.M
The role of executive function in bridging the intention-behaviour gap for binge-drinking in university students
Background: Alcohol consumption contributes to a significant proportion of disease and the high prevalence amongst young adults is a worldwide health concern. Purpose: To determine which aspects of executive function (EF) distinguish binge-drinkers from non binge-drinkers and to establish the role of EF in predicting behaviour. Methods: Self-report questionnaires, four tests of self-regulation and a behaviour measure were administered to 153 students. Results: The Theory of Planned Behaviour model was significant in predicting both intentions and behaviour. Although binge-drinkers and non binge-drinkers were found to differ on three of the four measures of EF,none predicted additional variance in behaviour. Planning ability and inhibition control moderated the relationship between intention and behaviour such that for individuals who intended to binge-drink, those with high planning ability or high inhibitory control were more likely to avoid doing so.Conclusions: Interventions targeting binge-drinking behaviour should aim to develop planning skills and inhibitory control
Tree-Based Overlay Networks for Scalable Applications
The increasing availability of high-performance computing systems with thousands, tens of thousands, and even hundreds of thousands of computational nodes is driving the demand for programming models and infrastructures that allow effective use of such large-scale environments. Tree-based Overlay Networks (TBĹŚNs) have proven to provide such a model for distributed tools like performance profilers, parallel debuggers, system monitors and system administration tools. We demonstrate that the extensibility and flexibility of the TBĹŚN distributed computing model, along with its performance characteristics, make it surprisingly general, particularly for applications outside the tool domain. We describe many interesting applications and commonly-used algorithms for which TBĹŚNs are well-suited and provide a new (non-tool) case study, a distributed implementation of the mean-shift algorithm commonly used in computer vision to delineate arbitrarily shaped clusters in complex, multi-modal feature spaces. 1
Local field potentials reflect multiple spatial scales in V4
Local field potentials (LFP) reflect the properties of neuronal circuits or columns recorded in a volume around a microelectrode (Buzsáki et al., 2012). The extent of this integration volume has been a subject of some debate, with estimates ranging from a few hundred microns (Katzner et al., 2009; Xing et al., 2009) to several millimeters (Kreiman et al., 2006). We estimated receptive fields (RFs) of multi-unit activity (MUA) and LFPs at an intermediate level of visual processing, in area V4 of two macaques. The spatial structure of LFP receptive fields varied greatly as a function of time lag following stimulus onset, with the retinotopy of LFPs matching that of MUAs at a restricted set of time lags. A model-based analysis of the LFPs allowed us to recover two distinct stimulus-triggered components: an MUA-like retinotopic component that originated in a small volume around the microelectrodes (~350 μm), and a second component that was shared across the entire V4 region; this second component had tuning properties unrelated to those of the MUAs. Our results suggest that the LFP reflects neural activity across multiple spatial scales, which both complicates its interpretation and offers new opportunities for investigating the large-scale structure of network processing
- …