An Empirical Study of Price Correlations: 2. The Decrease in Price Correlation with Distance and the Concept of Correlation Length
The dependence of the correlation between wheat price fluctuations on different markets with respect to the distance between those markets is investigated. It is shown that the decrease in the correlation is exponential and is governed by a characteristic distance which is called the correlation length for wheat prices. This is a measure of the level of market integration in a given area. The magnitude of the correlation length is compared for different cereals: wheat, rye, and oats, and the evolution of the correlation length during the 19th century is studied. In particular, it is observed that subsistence crises are characterised by a collective behaviour of the economy which results in a sudden peak in the correlation length. Last, the part played by the spatial correlation between precipitations is investigated. It appears to be rather small; consequently, the price-correlation length is primarily the result of economic factors.
Map pattern and friction of distance parameters: a comment
This note maintains that a recent paper by Cliff, Martin and Ord is incorrect in its conclusions relevant to a paper by Johnston, as shown by data fitted to their hypothetical spatial system.
Integration of Optically Generated Impulse Radio UWB Signals Into Baseband WDM-PON
We propose a compact integration system to simultaneously provide wireline and wireless [baseband and ultra-wideband (UWB)] services to end-users in a wavelength-division-multiplexed-passive optical network (WDM-PON). A 1-Gb/s UWB signal is optically generated and shares the same wavelength with the baseband signal. Error-free performance was achieved after 23-km single-mode-fiber (SMF) transmission for both signals and additional 0.4-m wireless transmission for the UWB signal. The low complexity and high spectrum efficiency of this system makes it attractive for deployment of in wireline/wireless converged gigabit optical access networks.