Bipolar charged aerosol agglomeration and collection by a two-zone agglomerator

ＩｎｔｒｏｄｕｃｔｉｏｎＢｅｃａｕｓｅｏｆｔｈｅｌｏｗｅｆｆｉｃｉｅｎｃｙｏｆｔｈｅｅｌｅｃｔｒｏｓｔａｔｉｃｐｒｅｃｉｐｉｔａｔｏｒ (ＥＳＰ)ｆｏｒｃｏｌｌｅｃｔｉｎｇｔｈｅｓｕｂｍｉｃｒｏｎｐａｒｔｉｃｌｅｓ ,ｔｈｅｅｌｅｃｔｒｉｃａｌａｇｇｌｏｍｅｒａｔｉｏｎｍｅｔｈｏｄｈａｓｌｅｄｔｏａｎｉｎｃｒｅａｓｉｎｇｉｎｔｅｒｅｓｔｉｎｒｅｄｕｃｉｎｇｔｈｅｅｍｉｓｓｉｏｎｏｆｔｈｅｆｉｎｅｐａｒｔｉｃｌｅｓ .Ｍａｎｙａｕｔｈｏｒｓｈａｖｅｓｔｕｄｉｅｄｅｌｅｃｔｒｉｃａｌａｇｇｌｏｍｅｒａｔｉ…     

博茨瓦纳欧科范果湿地1972～2000年泛滥方式

欧科范果三角洲地区泛滥范围年年在变化.这种变化与安哥拉高地集水区的区域性降水及当地降雨量有关.我们采用了1972～2000年的3000多幅卫星图像来描绘湿地的格局,其中从1985～2000年的图像几乎是NOAAAVHRR每日连续传送的,1972年以来的其它图像是从Landsat传感器上传下来的,其连续性次之.对AVHRR图像每10天为一期,用无监督分类方法分成陆地和水体.对LandsatTM和ERS2-ATSR数据进行分析的结果,与测算的淹没区域89%相吻合.结果显示欧科范果湿地近期30年期间的变化约在2450～11400km2之间.     

Differential N uptake by maize cultivars and soil nitrate dynamics under N fertilization in West Africa

Nitrate is prone to leaching in the sandy soils of the West African moist savannas. Better management of nitrogen (N) resources and maize cultivars with enhanced genetic capacity to capture and utilize soil and fertilizer N are strategies that could improve N-use efficiency. In two field experiments conducted at Zaria, northern Nigeria, five maize (Zea mays L.) cultivars planted early in the season were assessed under various N levels for differences in N uptake, soil N dynamics, and related N losses. Cultivar TZB-SR accumulated more N in the aboveground plant parts in both years than the other cultivars. All, except the semi-prolific late (SPL) variety, met about 50–60% of their N demand by the time of silking (64–69 DAP). In both years, SPL had the greatest capacity to take up N during the grain filling period, and it had the highest grain-N concentration and the least apparent N loss through leaching in the second year. There were no significant differences in soil N dynamics among cultivars in both years. At harvest, the residual N in the upper 90 cm of the profile under all the cultivars ranged from 56 to 72 kg ha⁻¹ in the first year and from 73 to 83 kg ha⁻¹ in the second year. Apparent N loss from 0 to 90 cm soil profile through leaching ranged from 35 to 122 kg ha⁻¹ in both years. N application significantly increased N uptake by more than 30% at all sampling dates in the second year of the experiment, but had no effect on apparent N loss. Results indicate that the use of maize cultivars with high N uptake capacity during the grain filling period when maximum leaching losses occur could enhance N recovery and may be effective in reducing leaching losses of mineral N in the moist savanna soils.