ABSTRACT:In this study, the spatial distribution of the potential drought hazard areas in Korea was estimated by conducting frequency analysis with the Standardized Precipitation Index (SPI), and the changes in potential drought hazard areas that appeared because of climate changes were predicted. In an attempt to estimate the changes in the spatial distribution of potential drought hazard areas, past observed data (1976-2010) from 54 automated weather stations under the Korea Meteorological Administration (KMA) and projected precipitation data by four global climate models (GCMs). CNRM:CM3, CSIRO:MK3, CONS:ECHOG and UKMO:HADCM, were used. The severity-duration-frequency (SDF) curves were derived for the 54 weather stations in order to estimate the potential drought hazard areas by employing the potential drought hazard mapping approach. The spatial distribution analysis for the potential drought hazard areas showed that the drought in the Nakdong River basin, which was a frequent drought hazard area in the past, was more aggravated, and more severe droughts were predicted for the future in the Han River basin (Han River, Anseong Stream, West of Han River), which is located in the middle part of the country. From the analysis results of the four GCMs, more severe drought is expected throughout the Korean Peninsula in the future, by using the CONS:ECHOG model compared with the projected data from the four GCMs. Additionally, potential drought areas would shift from the south toward the east and central parts of the country, as projected by the UKMO:HADCM model.
The tensile properties of Cu-9Ni-6Sn alloys with different swaging amounts of 64, 77, and 95 pct, either solutionized and aged (S/A) or directly aged (D/A), were examined as a function of aging time. It was found that the aging response of Cu-9Ni-6Sn alloys varied greatly depending on the prior solution heat treatment before aging and/or different swaging amounts. The swaged S/A Cu-9Ni-6Sn alloys showed a multistage increase in tensile strength with respect to aging time, probably due to the sequential occurrence of spinodal decomposition, formation of metastable ␥и precipitates, and recrystallization. The effect of different swaging amounts, ranging from 64 to 95 pct, was minimal on the aging response of S/A specimens. The prior cold working, however, appeared to favor the spinodal strengthening, comparing unswaged and swaged S/A Cu-9Ni-6Sn alloys. In 95 pct swaged D/A Cu-9Ni-6Sn alloys, the level of hardening was much less sensitive to aging time. A complex interaction between the reduction in dislocation density, the formation of equilibrium precipitates, and the reduction of Sn content in the Sn-rich segregates during an aging process is believed to be responsible for such a lean sensitivity. The increases in tensile strength of 64 and 77 pct swaged D/A Cu-9Ni-6Sn alloys were found to be much steeper than that in the 95 pct counterparts in the early and intermediate stages of aging, which is believed to be related to the relative contribution from work hardening and precipitation hardening to the strength level of D/A specimens.
The texture evolution of cold rolled tough pitch copper foils could be changed by altering the initial texture and microstructure before cold rolling. The development of -fiber texture was substantially suppressed even after 92% reduction for the case of abnormally coarse initial grain structure and extremely strong initial cube texture. Instead, the intensity of cube and RD (rolling direction)-rotated cube texture components was increased continuously by increasing the intensity of the initial cube texture.
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