Coal mining generates significant adverse environmental impacts. Historically, coal mining has been a very dangerous activity and the list of historical coal mining disasters is a long one. Underground mining hazards include suffocation, gas poisoning, roof collapse and gas explosions.
The term 'OVD' (Optically Variable Device) is used to describe both laser generated hologram images and electron beam generated images. These optically variable devices are created in highly-secure facilities and are at the forefront of overt asset and brand protection programmes.
OVA is the abbreviation for âOriginal Video Animation.â Normally in the anime world, an OVA is telling a story of a longer anime series. The series Magic Knight Rayearth is a good example of this. The tv series ran for two seasons. The OVA is a short retelling of the tv series season one.