1,019 research outputs found
Levy distribution and long correlation times in supermarket sales
Sales data in a commodity market (supermarket sales to consumers) has been
analysed by studying the fluctuation spectrum and noise correlations. Three
related products (ketchup, mayonnaise and curry sauce) have been analysed. Most
noise in sales is caused by promotions, but here we focus on the fluctuations
in baseline sales. These characterise the dynamics of the market. Four hitherto
unnoticed effects have been found that are difficult to explain from simple
econometric models. These effects are: (1) the noise level in baseline sales is
much higher than can be expected for uncorrelated sales events; (2) weekly
baseline sales differences are distributed according to a broad non-Gaussian
function with fat tails; (3) these fluctuations follow a Levy distribution of
exponent alpha = 1.4, similar to financial exchange markets and in stock
markets; and (4) this noise is correlated over a period of 10 to 11 weeks, or
shows an apparent power law spectrum. The similarity to stock markets suggests
that models developed to describe these markets may be applied to describe the
collective behaviour of consumers.Comment: 19 pages, 7 figures, accepted for publication in Physica
Deploying correct fault loop in distance protection of multiple-circuit shared tower transmission lines with different voltages
Distance protection of multiple-circuit shared tower transmission lines with different voltages:Part II: Fault loop impedance
Distance protection of multiple-circuit shared tower transmission lines with different voltages:Part I: Fault current magnitude
Adaptive Tuning of Frequency Thresholds Using Voltage Drop Data in Decentralized Load Shedding
Testing of ground fault relay response during the energisation of megawatt range electric boilers in thermal power plants
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