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We investigate the 1/f noise properties of epitaxial graphene devices at low temperatures as a function of temperature, current, and magnetic flux density. At low currents, an exponential decay of the 1/f noise power spectral density with increasing temperature is observed that indicates mesoscopic conductance fluctuations as the origin of 1/f noise at temperatures below 50 K. At higher currents, deviations from the typical quadratic current dependence and the exponential temperature dependence occur as a result of nonequilibrium conditions due to current heating. By applying the Kubakaddi theory [S. S. Kubakaddi, Phys. Rev. B 79, 075417 (2009)10.1103/PhysRevB.79.075417], a model describing the 1/f noise power spectral density of nonequilibrium mesoscopic conductance fluctuations in epitaxial graphene is developed and used to determine the energy loss rate per carrier. In the regime of Shubnikov-de Haas oscillations, a strong increase of 1/f noise is observed, which we attribute to an additional conductance fluctuation mechanism due to localized states in quantizing magnetic fields. When the device enters the regime of quantized Hall resistance, the 1/f noise vanishes. It reappears if the current is increased and quantum Hall breakdown sets in. © 2016 American Physical Society.

With current sonar technology the operator must handle large quantities of data. The primary medium for displaying these data is the CRT. Because of the limited space available on the CRT, the operator must scan multiple pages of data rapidly if he or she is to monitor all of the information. Thus, signal visibility is critical. To ensure good visibility, it is necessary to understand the impact of display characteristics on the detectability of signals on a display. This study examined two factors that could influence the detection of lines on a frequency-time-intensity (Fr') display. The first was type of monitor - multichrome or monochrome. Current systems use a monochrome monitor because its resolution is believed to be superior to a multichrome monitor. The second was orientation of the signals relative to the orientation of the CRT raster. Currently, the signals on an Fr' display are perpendicular to the CRT raster. The study examined the advantage of having signal lines on the Fr' display fall along the scan lines of the CRT. Two experiments were carried out to assess the effect of these factors on the detection of signals of varying strength presented on a simulated FYI display. Performance was similar on the monochrome and multichrome monitors. However, there was a slight advantage, about 1 dB, to using a display format in which the signals fell along the scan lines of the CRT. This improvement increased to 2 dB for signals that were separated by one pixel from a stronger signal. It was concluded that detection was not impaired on a multichrome display and that there could be an advantage to designing the interface for a passive sonar display so that the signals fall along the scan lines of the CRT.