Detection of linear ego-acceleration from optic flow.

Human observers are able to estimate various ego-motion parameters from optic flow, including rotation, translational heading, time-to-collision (TTC), time-to-passage (TTP), etc. The perception of linear ego-acceleration or deceleration, i.e.

[Investigation on occupational hazards of ultraviolet light, sunscreen awareness and behaviors in Wuhan city traffic police].

Objective: To understand the awareness of occupational hazards to ultraviolet (UV) and sunscreen awareness, protective measures in Wuhan City traffic police on duty outside.

Methods: The investigation included questionnaire survey in Wuhan City 367 traffic police on duty outside, talk with them face to face, fill in the questionnaires, and medical examine skin of exposed parts of body of them and 134 Wuhan City administration staffs.

Results: They understand UV harm to the human body and skin well (94.