18 research outputs found

    Explanation for the Resistivity Law in Quantum Hall System

    Full text link
    We consider a 2D electron system in a strong magnetic field, where the local Hall resistivity ρxy(r)\rho_{xy}(\vec r) is a function of position and ρxx(r)\rho_{xx}(\vec r) is small compared to ρxy\rho_{xy}. Particularly if the correlations fall off slowly with distance, or if fluctuations exist on several length scales, one finds that the macroscopic longitudinal resistivity RxxR_{xx} is only weakly dependent on ρxx\rho_{xx} and is approximately proportional to the magnitude of fluctuations in ρxy\rho_{xy}. This may provide an explanation of the empirical law RxxBdRxydBR_{xx} \propto B \frac{dR_{xy}}{dB} where RxyR_{xy} is the Hall resistance, and BB is the magnetic field.Comment: 11 pages (REVTeX 3.0). Revised Version. Complete postscript file for this paper is available on the World Wide Web at http://cmtw.harvard.edu/~simon/ ; Preprint number HU-CMT-94S0

    Reduction of the environmental impact of aviation via optimisation of aircraft size/range and flight network

    Get PDF
    REIVON is a Clean Sky 2 Technology Evaluator project that investigates to what extent CO2 emissions of global aviation can be reduced via optimisation of aircraft size/range and flight network. Three alternative global flight networks are created, considering (1) splitting long-haul flights into shorter legs (intermediate stop operations, ISO), (2) reducing frequency to the necessary minimum on busy routes using larger aircraft, and (3) a combination of 1 and 2. In all cases, the use of aircraft optimised for specific combinations of range and seating capacity not existing today will be considered. For the first time, REIVON will carry out a holistic analysis of the impact of an optimised flight network on global air transport system stakeholders, such as passengers, aircraft manufacturers, airlines and airports, and of potential measures to support the implementation of such an alternative network
    corecore