Vibrations are motions, usually unintentional, which occur frequently in rotating as well as stationary machines and structures. Prolonged exposure to vibration at a level well in excess of the threshold of perception (20-1000 Hz) leads to physiological disorders, and in some cases to occupational diseases (for example, as a result of using pneumatic drilling equipment or power saws). The very low-frequency vibrations (under 2 Hz) produced by various forms of transport can cause distress in some people. The disturbances originate in the central nervous system and are due to stimulation of the labyrinth. The degree of disturbance may vary with circumstances and particularly the weather. Low-frequency vibration (1.5-16 Hz) produced by vehicles is transmitted through the body to all the internal organs. The effects of such vibration are cumulative and include postural reactions, neurological symptoms, behavioural changes and problems of concentration. In addition to their effect on the human body, vibrations may cause damage to buildings, and in particular to buildings of historic interest which were not constructed in anticipation of such effects.
In all sectors of modern industry, machinery, equipment and power-driven tools can be encountered which generate intense vibration that may be transmitted to the workers who operate them.
The Encyclopedia of World Problems and Human Potential is a collaboration between UIA and Mankind 2000, started in 1972. It is the result of an ambitious effort to collect and present information on the problems with which humanity is confronted, as well as the challenges such problems pose to concept formation, values and development strategies. Problems included are those identified in international periodicals but especially in the documents of some 60,000 international non-profit organizations, profiled in the Yearbook of International Organizations.
The Encyclopedia includes problems which such groups choose to perceive and act upon, whether or not their existence is denied by others claiming greater expertise. Indeed such claims and counter-claims figure in many of the problem descriptions in order to reflect the often paralyzing dynamics of international debate. In the light of the interdependence demonstrated among world problems in every sector, emphasis is placed on the need for approaches which are sufficiently complex to encompass the factions, conflicts and rival worldviews that undermine collective initiative towards a promising future.
Non-profit, apolitical, independent, and non-governmental in nature, the UIA has been a pioneer in the research, monitoring and provision of information on international organizations, international associations and their global challenges since 1907.