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991.
SWAT(Soil and Water Assessment Tool)水文模型是近几年国内外使用最广泛的分布式水文模型,因其良好的精度、广泛的适应度得到了众多水文工作者的欢迎。但由于其参数率定部分过高的计算量,给水文工作者建模调参过程中造成了大量的不便。为了提高SWAT参数率定的运行效率,本文基于克里金插值理论,对于SWAT原有的优化算法进行改进,提出了一种基于随机过程的参数率定方法,通过一种“期望优化”的方式对拟合曲面进行寻优。并通过Intel MKL和一个对等式并行框架加以并行实现。大大提高了SWAT参数寻优的计算效率以及参数精度,并通过天山北坡流域的模拟验证了此并行模型的有效性,说明了克里金优化方法在水文模拟参数寻优的过程中能够达到良好的精度。 相似文献
992.
993.
本文针对传统图像角点特征匹配算法的匹配速度慢且准确率低等问题,提出一种基于空间纹理相似性的图像角点特征匹配算法。首先,计算图像目标上角点对应的空间距离矩阵;然后,通过计算图像角点的空间距离矩阵在对应角点邻域LBP特征向量上的瑞利商,将角点在图像灰度特征空间内的度量问题转换为纹理特征空间内幅值的度量问题;最后,根据角点对应的瑞利商的大小,实现不同图像间的角点特征匹配。对不同条件下采集的图像进行角点特征匹配,得到的匹配结果表明本文算法不仅能够很好的适应图像光照、几何变化,得到的匹配正确率较高,同时与传统算法相比本文算法在运行时间上也有大幅度的降低,当处理特征数量较小时平均降低48ms,而匹配特征数量较多时能够降低2408ms。 相似文献
994.
Zhi Qiao Meiyan Zhao Fang Wang Luo Liu 《International journal of remote sensing》2016,37(10):2433-2450
Forests account for more than 23% of China’s total area. As the most important terrestrial ecosystem, forests have tremendous ecological value. However, it remains difficult to classify forest subcategories at the national scale. In this study, a newly developed binary division procedure was used to categorize forest areas, including their spatiotemporal dynamics, during the period 2000–2010. Time-series images acquired using the Moderate Resolution Imaging Spectroradiometer (MODIS), together with auxiliary data on land use, climate zoning, and topography, were utilized. Hierarchical classification and zoning were combined with remote-sensing auto-classification. Based on the forest extent mask, the state-level forest system was divided into four classes and 18 subcategories. The method achieved an acceptable overall accuracy of 73.1%, based on a comparison to the sample points of China’s fourth forest general survey data set. In 2010, the total forest area was 1.755 × 106 km2, and the total area of and shrubs was 4.885 × 105 km2. The total area of woodland increased by 2536.25 km2 during the decade 2000–2010. The shrub subcategories exhibited almost no change during this time period; however, significant changes in forest area occurred in the mountainous region of Northeast China as well as in the hilly regions of Southern China. The main transformations took place in cold-temperate and temperate mountainous deciduous coniferous forest, subtropical deciduous coniferous forest, subtropical evergreen coniferous forest, and temperate and subtropical deciduous broadleaved mixed forests. The binary division procedure proposed herein can be used not only to rapidly classify more forest subcategories and monitor their dynamic changes, but also to improve the classification accuracy compared with global and national land-cover maps. 相似文献
995.
Huan Xie Xin Luo Xiong Xu Haiyan Pan Xiaohua Tong 《International journal of remote sensing》2016,37(8):1826-1844
The successful launch of the Landsat 8 satellite continues the Earth observation of the Landsat series, which has been taking place for nearly 40 years. With the increase in the band number and the improved spectral range compared with the previous Landsat imagery, it will be possible to expand the application of the new Landsat 8 imagery. The purpose of this study is to explore water extraction based on the new Landsat 8 Operational Land Imager (OLI) imagery. According to the specific inland water conditions (clear water, turbid water, and eutrophic water), a number of highly adaptable water indices are assessed for water extraction using Landsat OLI imagery. The results show that clear water is the easiest to extract among the different types of waterbodies, with the highest average accuracy of 97%. The highest-accuracy methods are the automated water extraction index for shadow pixels (AWEIsh), the normalized difference water index using bands 4 and 7 (NDWI47), and the normalized difference water index using bands 3 and 7 (NDWI37), with accuracies of 98.55%, 95.50%, and 96.61%, corresponding to clear water, turbid water, and eutrophic water, respectively. Through the analysis of the different methods for optimal band selection, the seventh band OLI7 (shortwave infrared 2, SWIR-2) of Landsat OLI shows the best performance in water identification. When applying the water indices to water extraction, Otsu’s algorithm has been used to automatically select the water threshold. Using extensive experiments with Otsu’s algorithm and a manual method, it was found that Otsu’s algorithm can replace manual selection and has the ability to select an accurate threshold for water extraction. 相似文献
996.
Jue Wang Jun Wang Yong Wu Yun Zhu Zhen Luo Yaqi Deng 《International journal of remote sensing》2016,37(18):4460-4485
Multistatic passive radar imaging system (MPRIS) does not behave as well as traditional inverse synthetic aperture radar (ISAR) imaging system does on account of the limited illuminators of opportunity and relatively narrow bandwidth of the signals. Furthermore, in the MPRIS, limited by the unavoidable measurement errors of the positions of the illuminators or receivers, or the manoeuvrability of the moving target, the translation motion of the target cannot be compensated accurately, in which the echo will be contaminated by an error phase, resulting in the occurrence of serious image defocus and the degeneracy of the image quality. In this article, two nonparametric autofocusing techniques based on the principles of minimum entropy and maximum contrast, respectively, are proposed to deal with the undesired problems under the multistate geographical configuration consisting of one illuminator and several receivers distributed around a target. The error phase is corrected by introducing an adjustment phase in the frequency domain and the adjustment phase can be searched by iteratively solving an equation that is derived by optimizing the quality measure of the image. Since no assumption is made during the derivation, the proposed techniques could be used to compensate any form of the phase error. In addition, the influence of the multistatic configuration on the image resolution is analysed and an optimized configuration is obtained. The effectiveness of the proposed algorithms is verified via the theoretical derivations and simulations. 相似文献
997.
In this paper, we propose a new fast normal-based interpolating subdivision scheme for curve and surface design. Different from the 4-points interpolating subdivision scheme, it is based on cubic Bezier curves and the normal vectors are used to generate a circle. Both a convex edge and an inflexion edge can be subdivided into convex sub-edges and then generate smooth curves. Under proper angle conditions, this subdivision scheme converges and the limit curve will be \(\hbox {G}^{1}\) smoothness. When applying it to subdivide surface on triangle/quadrilateral meshes, we use the normal vectors and have no need to consider the meshes neighboring to the current surface elements. Such advantage leads to that the subdivision scheme has fast rendering speed without changing the topology of the meshes. Subdivision examples and results by our scheme are illustrated and meantime is compared with those generated by other well-known schemes. It shows that this scheme can generate a more smooth curve based on both a convex edge and an inflexion edge, and the limit surface has better smoothness than those of other interpolating schemes. 相似文献
998.
In order to realize accurate control of underwater vehicles, this paper proposed a fractal prediction model of surge. Firstly, we introduce the current state-of-the-art of fractal prediction; secondly, we complete a fractal analysis with the R_S method, calculating the fractal dimension of surge using the short-time dimension method; thirdly, we correct the vertical scaling factor of the Iterated Function System (IFS) using the fractal dimension. Then the predictive value can be calculated through anti-iteration according to the statistical significantly IFS and proposing a fractal prediction model. Finally, we complete a simulation analysis based on the actual data and a comparison to another prediction algorithm. The result shows that the fractal prediction algorithm of this article has better comprehensive performance. 相似文献
999.
Xin Fan Yuyao Feng Zhi Chai Xianfeng David Gu Zhongxuan Luo 《The Visual computer》2016,32(9):1191-1203
We address the issue of deforming an image of a source object to that of a target. Previous works including barycentric coordinates and functional maps can hardly enforce shape consistency, especially for the objects with complex nested shape components. We leverage the conformal welding theory that maps 2D shapes (planar contours) to the automorphisms of the unit circle, named shape signatures. Conformal welding enables us to apply the Laplacian constraint to deformations in the signature space (or unit circle domain), which renders efficiency and flexibility. Additionally, we are able to fully reconstruct complex shape contours from deformed signatures, and hence generate the morphed images for target shapes. The experiments on complex shape contours and facial images, where multiple components exist, validate the effectiveness of the proposed approach. 相似文献
1000.
Touchless interaction has received considerable attention in recent years with benefit of removing barriers of physical contact. Several approaches are available to achieve mid-air interactions. However, most of these techniques cause discomfort when the interaction method is not direct manipulation. In this paper, gestures based on unimanual and bimanual interactions with different tools for exploring CT volume dataset are designed to perform the similar tasks in realistic applications. Focus + context approach based on GPU volume ray casting by trapezoid-shaped transfer function is used for visualization and the level-of-detail technique is adopted for accelerating interactive rendering. Comparing the effectiveness and intuitiveness of interaction approach with others by experiments, ours has a better performance and superiority with less completion time. Moreover, the bimanual interaction with more advantages is timesaving when performing continuous exploration task. 相似文献