Velocity, Distance and Purpose
On a vast landscape of mountains, bog and permafrost with no roads, what is the effect of the new high velocities made available by aviation, backed up by telecommunication? How do these intersect with the older, slower velocities of hunting and reindeer
review describes the two main sources of binocular information, namely, changing disparity over time and interocular velocity differences; this could be used for the perception of motion-in-depth. We discuss the evidence obtained in recent years on the extent to which each of them is used in human vision
). Visual stimuli were presented on a head-mounted display; meanwhile, the subjects rotated their heads back and forth (Fig. 1a). This new method allowed us to measure how head rotation in the horizontal plane affected the perceived velocity of the MAE. The perceived velocity has been considered to reflect
Measurements of xylem sap velocities have been used to assess the influence of atmospheric conditions and air pollutants on the transpiration of full-grown trees. For a period of four months sap velocities of oak, beech and Douglas fir were measured on an hourly basis using the heat-pulse technique. Simultaneously, concentrations of S02, NO, N02 and 03 were measured along with air temperature, light intensity, air humidity, precipitation, wind speed and wind direction. To analyse these time series, a technique is introduced which can handle time-dependent relations: the stochastic response model. This statistical model is a submodel of the class of structural models and is estimated by means of the Kalman filter. The influence of weather conditions on heat-pulse velocities (HPV) is prevailing: 80% of the variance is explained by the single variable vapour pressure deficit. No influence of gaseous pollutants on HPV could be assessed. Possible explanations are discussed.
This study investigates the relation of fibre length and ray dimensions to the sound propagation velocity in four commercial tropical hardwoods. The species used in the study were Doussié (Afzelia bipindensis Harms), Merbau (Intsia bijuga (Colebr.) Kuntze), Muiracatiara (Astronium graveolens Jacq.) and Wengé (Millettia laurentii De Wild.). The sound propagation velocity was established by the frequency-resonance method. A positive correlation was obtained between fibre length and sound velocity within species. The correlation was stronger in species with a higher proportion of libriform fibres. A trend analogous to fibre length within species was observed for ray ratio but, in contrast to fibre length, the correlation was strong also between species. The samples with higher and at the same time narrower rays (higher ray ratio) showed a higher velocity of sound propagation along the grain.
The interaction of luminance, velocity, and shape information in the perception of motion transparency, coherence, and non-rigid motion R. JASINSCHI*, A. ROSENFELD and H. J. ARAÚJO† Computer Vision Laboratory, Center for Automation Research, University of Maryland, College Park, MD 20742