Similarity-based approaches in hydrogeology: proposal of a new concept for data-scarce groundwater resource characterization and prediction

Hydrogeology Journal - A new concept is proposed for describing, analysing and predicting the dynamic behaviour of groundwater resources based on classification and similarity. The concept makes...     

Comparison of F-region electron density observations by satellite radio tomography and incoherent scatter methods

In November 1995 a campaign of satellite radiotomography supported by the EISCAT incoherent scatter radar and several other instruments was arranged in Scandinavia. A chain of four satellite receivers extending from the north of Norway to the south of Finland was installed approximately along a geomagnetic meridian. The receivers carried out difference Doppler measurements using signals from satellites flying along the chain. The EISCAT UHF radar was simultaneously operational with its beam swinging either in geomagnetic or in geographic meridional plane. With this experimental set-up latitudinal scans of F-region electron density are obtained both from the radar observations and by tomographic inversion of the phase observations given by the difference Doppler experiment. This paper shows the first results of the campaign and compares the electron densities given by the two methods.     

High-temperature study and thermal expansion of phlogopite

 Unit-cell dimensions of a natural phlogopite from Pargas, Finland, have been determined in the temperature interval of 27–1050 °C by X-ray powder diffraction technique. Expansion rates vary discontinuously with temperature with a break at 412 °C. Below this temperature, the linear expansions (α) for a, b and c axis lengths are 3.74 × 10⁻⁵ K⁻¹, 1.09 × 10⁻⁵ K⁻¹, and 1.19 × 10⁻⁵ K⁻¹, respectively, and above that they are 0.86 × 10⁻⁵ K⁻¹, 0.80 × 10⁻⁵ K⁻¹, and 1.93 × 10⁻⁵ K⁻¹. The volume thermal expansion coefficients are 6.26 × 10⁻⁵ K⁻¹ and 3.71 × 10⁻⁵ K⁻¹ for low-temperature and high-temperature intervals, respectively. The observed kink in the rate of thermal expansions with temperature could be due to the different mode of structural changes. Thermogravimetric analysis of the sample indicates the oxidation of iron in the temperature range of 500–600 °C and dehydroxylation as well as decomposition of phlogopite in the temperature range of 900–1200 °C. Received: 8 September 1998 / Accepted: 28 February 2000