Search results for "Noise abatement"
showing 2 items of 2 documents
Frequency influence on the hot-electron noise reduction in GaAs operating under periodic signals
2008
A Monte Carlo study of the role of the frequency on the hot-electron intrinsic noise reduction in an n-type GaAs bulk driven by two mixed cyclostationary electric fields is presented. Previous numerical results showed the possibility to reduce the diffusion noise under specific wave-mixing conditions. In this work the variations of the noise properties are investigated by computing and integrating the spectral density of the velocity fluctuations. We found that the effect of reduction of the noise level due to the addition of a second field at twice frequency is almost independent of the frequency.
Helicopter operations: the environmental impact and ground facilities. Procedures and operational standards for the system’s acceptance.
2012
The link between the heliports, environmental quality and safety is an important challenge in the field of helicopter transport. This challenge is especially crucial when the helicopter operations are carried out on densely urbanized areas. Often these areas have significant constraints and obstacles, particularly in terms of noise pollution. These constraints make the approach/takeoff maneuvers very complicated. The theme of the environmental sustainability of the rotorcraft is strongly felt in many countries. The production of noise is subjected to numerous rules and procedures, which tend to improve the acceptability of the helicopter by residents in neighboring areas to verti/heliports.…