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Georeferencing images is a laborious process so schemes for automating this process have been under investigation for some time. Among the most promising automatic registration algorithms are those based on the Fast Fourier Transform (FFT). The displacement between two given images can be determined by computing the ratio F 1 conj(F 2 )/|F 1 F 2 |, and then applying the inverse Fourier transform. The result is an impulse-like function, which is approximately zero everywhere except at the displacement that is necessary to optimally register the images. Converting from rectangular coordinates to log-polar coordinates, shifts representing rotation and scaling can also determined to complete the georectification process.Our FFT-based algorithm has been successfully implemented in IDL (Interactive Data Language) and added as two user functions to an image processing software package -ENVI (ENvironment for Visualizing Images) interface. ENVI handles all pre-processing and postprocessing work such as input, output, display, filter, analysis, and file management. To test this implementation, several dozen tests were conducted on both simulated and "real world" images. The results of these tests show advantages and limitations of this algorithm. In particular, our tests show that the accuracy of the resulting registration is quite good compared to current manual methods.

Removal of nitrate from water has been receiving growing attention in water treatment. In this study, we report the photocatalytic denitrification (PCDN) by nonlinear optical (NLO) material, i.e. lithium niobate (LiNbO). The hydrothermally synthesized LiNbO powder could achieve efficient denitrification in water, evidenced by 98.4% nitrate removal and 95.8% nitrogen selectivity at reaction time of 120 min and pH-neutral condition. Based on the first-order kinetics of PCDN, the kinetic constant for LiNbO is almost three times as that of conventional TiO (P25) under the same conditions. As suggested by the hole scavenger experiments, the LiNbO should proceed with photocatalytic reduction of nitrate through direct heterogeneous interaction with electrons at the conduction band of LiNbO. This may represent a different mechanism from P25, where nitrate is mainly reduced by CO radicals generated by the holes at the valence band. The unique second harmonic generation (SHG) effects of NLO materials enable them to produce more electrons and minimize the electron-hole recombination, which improves the efficiency and stability of the PCDN process. The current study provides a proof-of-concept demonstration of NLO photocatalytic material for more effective nitrate removal in water treatment.

Lightning discharges in winter thunderstorms in Japan exhibit many unique features. The most well known feature is the frequent production of positive cloud-to-ground (CG) lightning flashes (Brook et al., 1982;Takeuti et al., 1978). Exceptionally powerful and energetic positive CG flashes in winter thunderstorms have been observed and investigated extensively and are known to induce transient luminous events such as sprites and elves (

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