In order to study vegetation evolution and environmental changes around 2.5 Ma B.P., a total of 146 pollen samples with an average time resolution of 7 000 years were analyzed in the deep-sea record at the depth of 13...In order to study vegetation evolution and environmental changes around 2.5 Ma B.P., a total of 146 pollen samples with an average time resolution of 7 000 years were analyzed in the deep-sea record at the depth of 135 - 95 m （in composition depth） from ODP Site 1143 （9° 22＇ N, 113° 17＇ E） in the southern South China Sea. The results show that the pollen influx has a distinct change. During 2.6 - 2.0 Ma B.P., the average value of pollen influx increased evidently compared with that of 3.0 - 2.6 Ma B.P. It shows that the sea level of SCS dropped dramatically around 2.6 Ma B.P., corresponding to the formation of the Northern Hemisphere ice-sheets and the enhancement of the East Asian Monsoon. The pollen influx variations reflect the glacial-interglacial cycles corresponding with the deep-sea oxygen isotope curve and indicate that the sea level of SCS rose and dropped many times after 2.6 Ma B.P. The spectrum analysis results of pollen influx show that there are cycles at 0.1Ma （eccentricity） and 46.9 ka （obliquity） during 3.0 - 2.0 Ma B.P.展开更多
以La 2O 3粉、Al_(2)O_(3)粉、Cr 2O 3粉、Fe 2O 3粉为原料,按照LaAl 1-x-y Cr x Fe y O 3(x=y=0,0.1,0.2,0.25)的化学计量比配料,依次经球磨、烘干、在1200℃预烧、再球磨、成型、1600℃保温2 h烧结后,制备了Cr 3+-Fe 3+共掺杂铝酸镧材...以La 2O 3粉、Al_(2)O_(3)粉、Cr 2O 3粉、Fe 2O 3粉为原料,按照LaAl 1-x-y Cr x Fe y O 3(x=y=0,0.1,0.2,0.25)的化学计量比配料,依次经球磨、烘干、在1200℃预烧、再球磨、成型、1600℃保温2 h烧结后,制备了Cr 3+-Fe 3+共掺杂铝酸镧材料,然后利用XRD、XPS、IR等手段进行分析表征。结果表明:掺杂后产物均为钙钛矿结构化合物。Cr 3+-Fe 3+共掺杂试样在近红外波段的辐射性较未掺杂的LaAlO 3大幅提高,试样LaAl 0.5 Cr 0.25 Fe 0.25 O 3在0.76~2.5μm波段的红外发射率从0.236提高到0.83。红外发射率提高的机制在于:Cr 3+-Fe 3+共掺杂后形成了跃迁激活能仅为0.1 eV的Fe 3+Fe 4+小极化子,并且带隙中引入了对应于Cr 5+和Cr 6+的杂质能级,增强了杂质吸收和自由载流子吸收,从而提高了材料在近红外的发射率。展开更多
基金the National Natural Science Foundation of China projects （40371116） the National Major Basic Research Program of China （G200078502）.
文摘In order to study vegetation evolution and environmental changes around 2.5 Ma B.P., a total of 146 pollen samples with an average time resolution of 7 000 years were analyzed in the deep-sea record at the depth of 135 - 95 m （in composition depth） from ODP Site 1143 （9° 22＇ N, 113° 17＇ E） in the southern South China Sea. The results show that the pollen influx has a distinct change. During 2.6 - 2.0 Ma B.P., the average value of pollen influx increased evidently compared with that of 3.0 - 2.6 Ma B.P. It shows that the sea level of SCS dropped dramatically around 2.6 Ma B.P., corresponding to the formation of the Northern Hemisphere ice-sheets and the enhancement of the East Asian Monsoon. The pollen influx variations reflect the glacial-interglacial cycles corresponding with the deep-sea oxygen isotope curve and indicate that the sea level of SCS rose and dropped many times after 2.6 Ma B.P. The spectrum analysis results of pollen influx show that there are cycles at 0.1Ma （eccentricity） and 46.9 ka （obliquity） during 3.0 - 2.0 Ma B.P.
