In the present study, a modified Hall-Petch correlation on the basis of dislocation pile-up model was used to estimate the yield strength of SiCp/AI composites. The experimental results show that the modified Hall-Pet...In the present study, a modified Hall-Petch correlation on the basis of dislocation pile-up model was used to estimate the yield strength of SiCp/AI composites. The experimental results show that the modified Hall-Petch correlation expressed as σcy=244+371λ-1/2 fits very well with the experimental data, which indicated that the strength increase of SiCp/AI composites might be due to the direct blocking of dislocation motion by the particulate-matrix interface, namely, the dislocation pile-up is the most possible strengthening mechanism for SiCp/AI composites.展开更多
A 9.25-m-long sediment core from Bosten Lake, Xinjiang, provides detailed information about changes in the water budget and biological acticity over the last 8400 calendar years. The chronology is constructed from six...A 9.25-m-long sediment core from Bosten Lake, Xinjiang, provides detailed information about changes in the water budget and biological acticity over the last 8400 calendar years. The chronology is constructed from six AMS radiocarbon dates on the terrestrial plant remains. Based on analyses of TOC, CO3, detrital compounds and biogenic SiO2, lake level fluctuations and periods of remarkably-negative water budget appeared at 8.4—8.2 cal ka, 7.38—7.25 cal ka, 5.7—5.5 cal ka, 3.7—3.4 cal ka and 3.3—2.9 cal ka, respectively. As they are in-phase with low lake levels at Sumxi Co and Bangong Co in western Tibet Plateau and with paleolakes in Inner Mongolia, a climate-induced change to somewhat drier and warmer conditions is inferred. A further drop in lake level after 1320 AD of about 200 yr duration may be attributed to a negative water balance prior to the main phase of the Little Ice Age. Deep and stable lake phases of 1500 yr and 1800 yr duration at 7.2—5.7 cal ka and 5.5—3.7 cal ka coincide with maximum moisture during the Holocene Megathermal in China. The long term trend towards aridity since about 4.3 cal ka can clearly be recognised. The reduced water budget of Bosten Lake from 640—1200 AD may be attributed to local effects.展开更多
文摘In the present study, a modified Hall-Petch correlation on the basis of dislocation pile-up model was used to estimate the yield strength of SiCp/AI composites. The experimental results show that the modified Hall-Petch correlation expressed as σcy=244+371λ-1/2 fits very well with the experimental data, which indicated that the strength increase of SiCp/AI composites might be due to the direct blocking of dislocation motion by the particulate-matrix interface, namely, the dislocation pile-up is the most possible strengthening mechanism for SiCp/AI composites.
基金partly supported by China National Cooperation Project(Grant No.2002CB714004).
文摘A 9.25-m-long sediment core from Bosten Lake, Xinjiang, provides detailed information about changes in the water budget and biological acticity over the last 8400 calendar years. The chronology is constructed from six AMS radiocarbon dates on the terrestrial plant remains. Based on analyses of TOC, CO3, detrital compounds and biogenic SiO2, lake level fluctuations and periods of remarkably-negative water budget appeared at 8.4—8.2 cal ka, 7.38—7.25 cal ka, 5.7—5.5 cal ka, 3.7—3.4 cal ka and 3.3—2.9 cal ka, respectively. As they are in-phase with low lake levels at Sumxi Co and Bangong Co in western Tibet Plateau and with paleolakes in Inner Mongolia, a climate-induced change to somewhat drier and warmer conditions is inferred. A further drop in lake level after 1320 AD of about 200 yr duration may be attributed to a negative water balance prior to the main phase of the Little Ice Age. Deep and stable lake phases of 1500 yr and 1800 yr duration at 7.2—5.7 cal ka and 5.5—3.7 cal ka coincide with maximum moisture during the Holocene Megathermal in China. The long term trend towards aridity since about 4.3 cal ka can clearly be recognised. The reduced water budget of Bosten Lake from 640—1200 AD may be attributed to local effects.
