排序方式: 共有5条查询结果,搜索用时 0 毫秒
1
1.
2.
选取青藏高原典型多年冻土区风火山小流域高寒草甸和沼泽化草甸典型样地进行人工降雨截留试验,综合运用统计分析、模型回归分析等方法,对两种草甸类型截留特征及其影响因子进行分析。结果表明:两种草甸类型对降雨的截留能力是不同的,高寒草甸最大截留量0.61mm,沼泽化草甸为0.18mm;高寒草甸的最大截留率为12.4%,沼泽化草甸为3.8%。通过分析各因子对截留的影响,得出高寒草甸截留量与降雨量呈对数函数关系,沼泽化草甸截留量与降雨量呈二次多项式关系;两种草甸截留量与降雨强度都呈幂函数关系,与植被盖度均呈线性相关关系。 相似文献
3.
北斗三号全球卫星导航系统现已提供4个频率以上的观测数据,支持多频组合定位理论和方法的研究。基于此,文中提出一种短基线下的北斗四频组合定位解算方法,利用北斗B1I,B3I,B1C,B2a 4个频率的观测数据两两组合形成独立不相关的窄巷观测值联立,以位置参数和双差模糊度组成状态向量,结合卡尔曼滤波估计进行定位解算。基于该方法,文中针对两组不同长度的短基线进行测试,结果显示:在17 m短基线中,该方法平面精度优于2 mm,高程方向精度优于4 mm;在3 km的短基线中,平面精度优于4.5 mm,高程精度优于6 mm。测试结果表明,在短基线情况下,该方法的定位精度相较于北斗单频及三频方法在平面和高程方向均有不同程度的提高。 相似文献
5.
Oxidative stress responses of submerged macrophyte Vallisneria asiatica to different concentrations of cyanobacteria 总被引:1,自引:0,他引:1
In a 10-day aquarium experiment,this investigation examines macrophyte restoration in eutrophic Lake Taihu,the physiological effects of different plant biomass levels and of increasing natural cyanobacterial concentrations on a submerged macrophyte,Vallisneria asiatica. Cyanobacterial stress suppressed the superoxide dismutase(SOD) activity of the plant's leaves and induced the catalase(CAT) and peroxidase(POD) activities of its roots. The soluble protein content in V. asiatica decreased with an increase in natural cyanobacterial concentrations,whereas the malonaldehyde(MDA) increased significantly at chlorophylla(Chl a) concentrations of 222 and 262 μg/L in water. V. asiatica adapted to the stress caused by cyanobacterial concentrations by adjusting its antioxidant defense system to remove the excessive reactive oxygen species when the algal Chl a concentration was 109 μg/L. Additionally,high biomass of V. asiatica(2 222 g FW/m 2) can inhibit the reproduction of cyanobacteria more significantly than low biomass(1 111 g FW/m2). High biomass of V. asiatica increased the oxidative stress in an individual plant when the initial Chl a concentration in the water reached 222 and 262 μg/L,as expressed by the increased MDA in leaves,compared with low biomass of V. asiatica. This provides a basis for controlling cyanobacterial concentrations and V. asiatica biomass for the recovery of V. asiatica in eutrophic Lake Taihu. 相似文献
1