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.
What is an LVDT? The letters LVDT are an acronym for Linear Variable Differential Transformer , a common type of electromechanical transducer. that can convert the rectilinear motion of an object to which it is coupled mechanically into a corresponding electrical signal. LVDT.