Many authors have assumed that motor actions required for collision avoidance and for collision achievement (for example, in driving a car or hitting a ball) are guided by monitoring the time to collision (TTC), and that this is done on the basis of moment-to-moment values of the optical variable tau [1] [2] [3]. This assumption has also motivated the search for single neurons that fire when ta...

The approach of an object can be monitored from its optic flow. More specifically, it has been postulated that time-to-collision at constant velocity is perceived by relating visual angle theta to its rate of change theta, time-to-collision being theta/theta. This hypothesis is reappraised, and an alternative based on the parameters theta and angular acceleration theta is proposed. The expressi...

The survival of many animals hinges upon their ability to avoid collisions with other animals or objects, or to precisely control the timing of collisions. Optical expansion provides a compelling impression of object approach and in principle can provide the basis for judgments of time to collision (TTC) [1]. It has been demonstrated that pigeons [2] and houseflies [3] have neural systems that ...

a modified model has been analytically developed to describe the induction time of an elliptic air bubble in contact with an elliptic hydrophobic oil droplet. the role of hydrophobicity was revealed in the slippage of liquid over the surfaces of bubble and droplet. in this condition, the analytical relationships for pressure distribution and consequently hydrodynamic resistance force through th...

We measured the precision (i.e. Weber fraction) and the accuracy with which the time to collision (TTC) with a simulated approaching object is estimated. We simulated a rigid spherical object and a rigid nonspherical object (an oblate spheroid whose longer axis was vertical). We used the following viewing conditions: that the available information about TTC was only monocular (M), only binocula...

One of the factors which are usually difficult to be measured in mills is the grindability and distribution of feed under real situation and in a short time. In the condition of achieving a fast and convenient way to determine these parameters, the proper relationship between energy, hardness and particle size distribution can be obtained. Feed hardness is one of the most important factors in g...

The τ-function and the η-function are phenomenological models that are widely used in the context of timing interceptive actions and collision avoidance, respectively. Both models were previously considered to be unrelated to each other: τ is a decreasing function that provides an estimation of time-to-contact (ttc) in the early phase of an object approach; in contrast, g has a maximum before t...