Haloxylon ammodendron, a typical desert shrub with C4 pathway of photosynthesis, possessing a strong ability to adapt to an extreme drought environment, has a rapid growth rate in sandy lands and is widely used in san...Haloxylon ammodendron, a typical desert shrub with C4 pathway of photosynthesis, possessing a strong ability to adapt to an extreme drought environment, has a rapid growth rate in sandy lands and is widely used in sand-fixing shelter-forest systems in oasis-desert ecotones. To assess the effects of H. ammodendron plantation on the soil, we measured soil properties and herbaceous characteristics along a nearly 40-year chronosequence after H. ammodendron was planted in shifting sand dunes in an oasis-desert ecotone. Results showed that silt and clay fractions increased significantly in the topsoil. The accumulation rates of soil organic carbon （SOC）, total nitrogen （TN） and total phosphorus （TP） were faster in the early stages （0-9 years） and slower in the late stages （9-39 years）. The soil pH and electrical conductivity （EC） were higher than those in the non-vegetation dunes. Moreover, the soil properties in the topsoil （0-5 cm） showed larger variation scope than those in the deeper soil layers （5-20 cm）. The significant relationships of the soil silt＋clay content with the chemical properties mainly appeared in the topsoil. The wind erosion susceptibility of the soil, evaluated by erodible fraction （EF）, decreased significantly with increasing H. ammodendron plantation age. Additionally, the annual pioneer herb, Agriophyllum squarrosum, was gradually substituted by the annual salt-tolerant herb, Bassia dasyphylla, with increasing plantation age. These results showed beneficial effects of H. ammodendron plantation on improving soil conditions. However, the dynamics of the herbaceous species also reminded us that the long- term effects of H. ammodendron plantation, especially on changes in vegetation composition, still need further evaluation.展开更多
车辆检测是智能交通系统的关键技术之一,对实时性和准确性有较高的要求。对此,文章提出了一种基于You Only Look Once(YOLO)v3改进的车辆检测算法,该算法能够确保实时检测的前提下,大幅度提高检测准确率。首先,改进了YOLOv3的特征提取网...车辆检测是智能交通系统的关键技术之一,对实时性和准确性有较高的要求。对此,文章提出了一种基于You Only Look Once(YOLO)v3改进的车辆检测算法,该算法能够确保实时检测的前提下,大幅度提高检测准确率。首先,改进了YOLOv3的特征提取网络,使用跨阶段残差模块替换原有残差模块。该结构的特征重用特性可以有效提高提取特征的效率;其次,设计了一种新的特征融合网络,通过融合不同深度网络层的特征信息,进一步提高了算法的检测准确性。实验结果表明,与原YOLOv3相比,该算法既满足检测实时性,平均精确率(mean Average Precision,mAP)又提高了8.7%。展开更多
基金funded by the National Natural Science Foundation of China(41401337)
文摘Haloxylon ammodendron, a typical desert shrub with C4 pathway of photosynthesis, possessing a strong ability to adapt to an extreme drought environment, has a rapid growth rate in sandy lands and is widely used in sand-fixing shelter-forest systems in oasis-desert ecotones. To assess the effects of H. ammodendron plantation on the soil, we measured soil properties and herbaceous characteristics along a nearly 40-year chronosequence after H. ammodendron was planted in shifting sand dunes in an oasis-desert ecotone. Results showed that silt and clay fractions increased significantly in the topsoil. The accumulation rates of soil organic carbon （SOC）, total nitrogen （TN） and total phosphorus （TP） were faster in the early stages （0-9 years） and slower in the late stages （9-39 years）. The soil pH and electrical conductivity （EC） were higher than those in the non-vegetation dunes. Moreover, the soil properties in the topsoil （0-5 cm） showed larger variation scope than those in the deeper soil layers （5-20 cm）. The significant relationships of the soil silt＋clay content with the chemical properties mainly appeared in the topsoil. The wind erosion susceptibility of the soil, evaluated by erodible fraction （EF）, decreased significantly with increasing H. ammodendron plantation age. Additionally, the annual pioneer herb, Agriophyllum squarrosum, was gradually substituted by the annual salt-tolerant herb, Bassia dasyphylla, with increasing plantation age. These results showed beneficial effects of H. ammodendron plantation on improving soil conditions. However, the dynamics of the herbaceous species also reminded us that the long- term effects of H. ammodendron plantation, especially on changes in vegetation composition, still need further evaluation.
文摘车辆检测是智能交通系统的关键技术之一,对实时性和准确性有较高的要求。对此,文章提出了一种基于You Only Look Once(YOLO)v3改进的车辆检测算法,该算法能够确保实时检测的前提下,大幅度提高检测准确率。首先,改进了YOLOv3的特征提取网络,使用跨阶段残差模块替换原有残差模块。该结构的特征重用特性可以有效提高提取特征的效率;其次,设计了一种新的特征融合网络,通过融合不同深度网络层的特征信息,进一步提高了算法的检测准确性。实验结果表明,与原YOLOv3相比,该算法既满足检测实时性,平均精确率(mean Average Precision,mAP)又提高了8.7%。
