ICESat-2（Ice, Cloud, and land Elevation Satellite-2）是美国NASA（National Aeronautics and Space Administration）在2018年发射的激光测高卫星,其上搭载的激光测高系统ATLAS（Advanced Topographic Laser Altimeter System）采用微脉冲多波束光子计数激光雷达系统,因其低能耗、高探测灵敏度、高重复频率的特性极大改善了沿轨采样密度,但也使获取的数据中包含大量的噪声,如何有效实现光子点云去噪分类成为后续应用的关键,也是当前研究的热点和难点,为此本文提出一种基于卷积神经网络的光子点云去噪和分类算法。首先将光子点云按照沿轨和高程方向划分格网,去除明显的噪声光子,并将每个粗信号光子点栅格化为影像;然后基于少量样本构建的卷积神经网络分类模型实现光子点云精去噪和分类;最后利用机载激光雷达数据进行验证,并与ATL08产品的去噪分类结果进行对比。结果表明,对于裸地和森林区域,卷积神经网络算法均能有效去除噪声光子,特别对于森林区域,可同时实现去噪和分类;其中,裸地区域地表计算的R2和RMSE分别为1.0和0.72 m,森林区域地表和树冠计算的R2分别为1.0和0.70, RMSE分别为1.11 m和4.99 m。本文利用深度学习算法实现光子点云去噪分类,在裸地和森林区域均取得了较好的结果,为后续光子点云数据处理提供了参考。 相似文献
Labile organic carbon （LOC） is a fraction of soil organic carbon （SOC） with rapid turnover time and is affected by soil fertilization. This investigation characterized the SOC content, LOC content and LOC distribution in the treatment plots of surface soil erosion at five levels （0-, 5-, 10-, 20- and 30-cm erosion）. The soil had received contrasting fertilizer treatments （i.e., chemical fertilizer or chemical fertilizer ＋ manure） for 6 years. This study demonstrated that both SOC and various LOC fractions contents were higher in the plots with fertilizer ＋ manure than in those with fertilizer alone under the same erosion conditions. The SOC and LOC contents de- creased as the erosion depth increased. Light fraction organic carbon, particulate organic carbon, easily oxidizable organic carbon （KMnO4-oxydizable organic carbon）, and microbial biomass carbon were 27% 57%, 37%-7%, 20%-25%, and 29%-33% higher respectively in the fertilizer ＋ manure plots, than in the fertilizer alone plots. Positive correlations （p 〈 0.05） between SOC content and different fractions contents were observed in all plots except the correlation between total SOC content and water-soluble organic carbon content in the different fertilization treatments. Obviously, fertilizer ＋ manure treatments would be conducive to the accumulation of LOC and SOC in the Black soil of Northeast China. 相似文献
Simultaneous measurements of the vertical magnetic field (VMF), three-dimensional electric field, ambient temperature, ambient relative humidity, particle mass concentration, and three-dimensional velocity are conducted during dust, haze, rain, snow, and thunderstorms. The hourly VMF variation (the rate of VMF increment and time increment with a 1-h time interval) is used to evaluate the disturbance level of the atmospheric magnetic field during the abovementioned weather conditions. There is no significant difference in the hourly VMF variations between hazy days and fair weather. However, the hourly VMF variations on dusty, rainy, snowy, and thunderstorm days differ from those in fair weather, implying that these weather conditions significantly affect the atmospheric magnetic field. On hazy days, although the haze particles are charged, the VMF does not change compared with in fair weather, which suggests that the horizontal electric field generated by haze particles is an irrotational field. On dusty and snowy days, the heterogeneity of the charge distribution forms a rotational horizontal electric field, which can induce the VMF to disturb the atmospheric magnetic field. During rain and thunderstorms, the hourly variation in the VMF is larger than in dust and snow, which can be attributed to the rotational horizontal electric field generated by raindrops and clouds. In addition, the hourly variation in the VMF in thunderstorms is one order of magnitude larger than that during days without thunderstorms, indicating that the VMF induced by the cumulonimbus cloud electric field is more significant than that in other weather conditions.
The breeding habitat selection by houbara bustards in Mori, Xinjiang, China during the breeding seasons from April to June 1998–2000 was studied. Most of habitats chosen for breeding were short sub-shrubby and open areas close to high bushy patches. The nesting females clearly prefer low covered areas and avoid densely covered and high vegetation sites. The number of herb species was significantly smaller at nest sites than at randomly selected sites. Only the distance to the closest fox den contributed the most to discrimination between successful and predated nests. The average distance to the closest fox den was significantly longer at successful nests than at depredated nests. Vegetative density, plant species richness, topography and distance to the closest fox den are possibly the most important factors that determined the nest sites selection of houbara bustard. The displaying males clearly prefer low covered areas and avoid densely covered and high vegetation sites. The vegetation density and number of plant species at display sites was significantly lower than that at randomly selected sites. The average distance to the closest bushy patch was significantly shorter at display sites than at random sites. Plant species richness, vegetative density, vegetative cover and distance to the bushy patches are possibly the most important factors for the display sites selection of houbara bustard
The protoliths of mafic-ultramafic plutons in the northern Dabie Mts. (NDM) (Hubei) include pyroxenite and gabbro. The zircon
U-Pb dating for a gabbro suggests that emplacement of mafic magma took place in the post-collisional setting at the age of
122.9±0.6 Ma. It is difficult to obtain a reliable Sm-Nd isochron age, due to disequilibrium of the Sm-Nd isotopic system.
Two hornblende40Ar/39Ar ages of 116.1±1.1 Ma and 106.6±0.8 Ma may record cooling of metamorphism in the mafic-ultramafic plutons in Hubei below
500°C. The hornblende40Ar/39Ar ages for the mafic-ultramafic rocks in Hubei are evidently 15–25 Ma younger than those for the same rocks in Anhui, indicating
that there is a diversity of the cooling rates for the mafic-ultramafic rocks in Hubei and Anhui. The difference in their
cooling rates may be controlled by the north-dipping normal faults in the NDM. The intense metamorphism occurring in the mafic-ultramafic
rocks in Hubei may result from the Yanshanian magmatic reheating and thermal fluid action induced by the Cretaceous migmatization.
The geochemical similarity of these mafic-ultramafic rocks wherever in Hubei and Anhui may be attributed to the same tectonic
setting via an identical genetic mechanism. 相似文献
