The acquisition of precise soil data representative of the entire survey area, is a critical issue for many treatments such as irrigation or fertilization in precision agriculture. The aim of this study was to investi...The acquisition of precise soil data representative of the entire survey area, is a critical issue for many treatments such as irrigation or fertilization in precision agriculture. The aim of this study was to investigate the spatial variability of soil bulk electrical conductivity （ECb） in a coastal saline field and design an optimized spatial sampling scheme of ECb based on a sampling design algorithm, the variance quad-tree （VQT） method. Soil ECb data were collected from the field at 20 m interval in a regular grid scheme. The smooth contour map of the whole field was obtained by ordinary kriging interpolation, VQT algorithm was then used to split the smooth contour map into strata of different number desired, the sampling locations can be selected within each stratum in subsequent sampling. The result indicated that the probability of choosing representative sampling sites was increased significantly by using VQT method with the sampling number being greatly reduced compared to grid sampling design while retaining the same prediction accuracy. The advantage of the VQT method is that this scheme samples sparsely in fields where the spatial variability is relatively uniform and more intensive where the variability is large. Thus the sampling efficiency can be improved, hence facilitate an assessment methodology that can be applied in a rapid, practical and cost-effective manner.展开更多
用硅胶柱色谱及重结晶等方法,并根据理化性质和光谱数据从一株红树林共生真菌Paecilomycessp.Tree 1-7中分离鉴定了四个化合物,分别为secalon ic ac id A(1),tenellic ac id A(2),大黄素(3),大黄酚(4)。并首次对化合物1和2进行了抗人的...用硅胶柱色谱及重结晶等方法,并根据理化性质和光谱数据从一株红树林共生真菌Paecilomycessp.Tree 1-7中分离鉴定了四个化合物,分别为secalon ic ac id A(1),tenellic ac id A(2),大黄素(3),大黄酚(4)。并首次对化合物1和2进行了抗人的肝癌细胞hepG2的活性测试。结果显示,化合物1有很强的抗肿瘤活性,IC50=2.0μg/m l,化合物2的抗肿瘤活性IC50=62.1μg/m l。展开更多
基于特征的视觉同时定位与地图构建(Simultaneous Localization and Mapping,SLAM)存在实时性和鲁棒性差等问题,提出一种改进的基于四叉树的ORB特征提取方法,设计包含前后端及地图构建的机器人RGB-D SLAM算法。在前端使用四叉树方法完成...基于特征的视觉同时定位与地图构建(Simultaneous Localization and Mapping,SLAM)存在实时性和鲁棒性差等问题,提出一种改进的基于四叉树的ORB特征提取方法,设计包含前后端及地图构建的机器人RGB-D SLAM算法。在前端使用四叉树方法完成ORB特征的均匀提取,计算描述子间汉明距离实现特征匹配。根据随机采样一致性算法思想,结合EPNP(Efficient Perspective-N-Point)和迭代最近点法求解位姿,获取多次迭代后的准确位姿。采用关键帧进行回环检测,并且基于光速法平差优化位姿图,从而构建全局一致的3D地图,达到减少累积误差的目的。通过TUM数据集和多履带式全向移动机器人进行对比验证,实验结果满足实时性和稳定性要求,证明了算法的可行性和有效性。展开更多
基金We thank the financial support from the National Natural Science Foundation of China(40701007,40571066)the Postdoctoral Science Foundation of China(20060401048).
文摘The acquisition of precise soil data representative of the entire survey area, is a critical issue for many treatments such as irrigation or fertilization in precision agriculture. The aim of this study was to investigate the spatial variability of soil bulk electrical conductivity （ECb） in a coastal saline field and design an optimized spatial sampling scheme of ECb based on a sampling design algorithm, the variance quad-tree （VQT） method. Soil ECb data were collected from the field at 20 m interval in a regular grid scheme. The smooth contour map of the whole field was obtained by ordinary kriging interpolation, VQT algorithm was then used to split the smooth contour map into strata of different number desired, the sampling locations can be selected within each stratum in subsequent sampling. The result indicated that the probability of choosing representative sampling sites was increased significantly by using VQT method with the sampling number being greatly reduced compared to grid sampling design while retaining the same prediction accuracy. The advantage of the VQT method is that this scheme samples sparsely in fields where the spatial variability is relatively uniform and more intensive where the variability is large. Thus the sampling efficiency can be improved, hence facilitate an assessment methodology that can be applied in a rapid, practical and cost-effective manner.
文摘用硅胶柱色谱及重结晶等方法,并根据理化性质和光谱数据从一株红树林共生真菌Paecilomycessp.Tree 1-7中分离鉴定了四个化合物,分别为secalon ic ac id A(1),tenellic ac id A(2),大黄素(3),大黄酚(4)。并首次对化合物1和2进行了抗人的肝癌细胞hepG2的活性测试。结果显示,化合物1有很强的抗肿瘤活性,IC50=2.0μg/m l,化合物2的抗肿瘤活性IC50=62.1μg/m l。
