Phase Transitions in the Brominated Ferroelectric Tris‐Sarcosine Calcium Chloride
paraelectrics SrTiO 3 and KTaO 3 . [ 9 ] However, the ultra-weak nature of the dipole moment in TSCC referred to below may reduce the effects of such long-range dipole interactions to a narrow temperature region around the critical point. This would mean that more conventional classical or quantum critical behaviour would be expected over a wider range of temperatures and tuning parameters. TSCC is hydrogen bonded and was characterized in the past as order-disorder albeit with no direct supporting evidence. [ 16,17 ] Since the time of these studies TSCC has come to be a prototypical displacive ferroelectrics, [ 18 ] as demonstrated by the existence of an under-damped soft mode. This mode can be followed into the GHz frequency regime [ 19 ] from highT values of ca 630 GHz = 21 cm −1 . Deuteration [ 20 ] produces little change in T C , implying that the transition is not controlled by the N-Cl-hydrogen bonds, a result compatible with the soft-mode mechanism operating in TSCC. [ 2 ]
Thermodynamic Relations between Anomalous Quantities near a Lambda Transition in Anisotropic Dielectrics
The thermodynamic treatment of the λ transition in liquid helium developed by Buchingham and Fairbank is generalized for transitions in anisotropic dielectrics. Tensor relations between the heat capcity cσ,E, the elastic compliances sμνT,E, the thermal expansion coefficients αμσ,E, the pyroelectric coefficients piσ,E and the piezoelectric coefficients diμT,E are derived, and a connection established between the symmetry and the coupling of anomalous quantities. It is shown that the asymptotic forms of the general equations lead to the Pippard—Garland equations with specified electric boundary conditions and, in addition, to a new set of equations that relate pyroelectric and piezoelectric coefficients in the transition region. Experimental data for triglycine sulfate near the ferroelectric phase transition are analyzed, and it is shown that the anomalous quantities cσ,E, sμνE, αμσ, and piσ,E, diμE are linearly related within the temperature interval (Tc—T) <16°, where the constants of proportionality give...
DEM generation from new VIR sensors: IKONOS, ASTER and Landsat-7
DEM generation is a living R&D topic since new-launched satellite images can be used to generate stereoscopic images. Using a coplanarity equation model developed at CCRS and an automatic matching method developed at PCI, DEMs are generated with new VIR stereo data. Accuracy of 4.9 m with high-resolution IKONOS images, and 33 m and 101 m with medium-resolution ASTER and Landsat-7 ETM/sup +/ images respectively are obtained. The same matching accuracy of one-pixel is translated into worse results with Landsat due to a small B/H ratio of 0.15.