The mechanism of morphology change at the first (western) entrance of lake Saroma were investigated with the 20 years bathymetric survey data set. It shows that the volume around the entrance decreased after the east jetty construction started and the major morphology changes were erosion along the channel and movement of ebb shoal. A numerical model which aimed to predict the morphology change for several years was developed based on the sediment transport characteristics. The simulation result shows that this model can quantitatively reconstruct the observed morphological changes for 3-4 years.
The effect of equal-channel angular pressing (ECAP) on the pitting corrosion resistance of Al and Al-Mg alloy was investigated by means of polarization curves in solutions containing 300 ppm of Cl- and by surface analysis. The potentials for pitting corrosion of Al and Al-Mg alloy were evidently shifted to the noble direction by ECAP process, indicating that this process improves resistance to pitting corrosion. SEM observation revealed that the pitting corrosion occurred near the impurity precipitates and the size of impurity precipitated decreased with ECAP process. The time-dependence of corrosion potential and the polarization resistance determined by AC impedance technique suggested that the formation rate of Al oxide films was increased with ECAP process. The improvement in pitting corrosion resistance of Al and Al-Mg by ECAP seems to be attributable to the decrease in the size of impurity precipitates and the increase in the formation rate of Al oxide films.