In this paper, we present a novel and efficient scheme for extracting, indexing and retrieving color images. Our motivation was to reduce the space overhead of partition-based approaches taking advantage of the fact t...In this paper, we present a novel and efficient scheme for extracting, indexing and retrieving color images. Our motivation was to reduce the space overhead of partition-based approaches taking advantage of the fact that only a relatively low number of distinct values of a particular visual feature is present in most images. To extract color feature and build indices into our image database we take into consideration factors such as human color perception and perceptual range, and the image is partitioned into a set of regions by using a simple classifying scheme. The compact color feature vector and the spatial color histogram, which are extracted from the seqmented image region, are used for representing the color and spatial information in the image. We have also developed the region-based distance measures to compare the similarity of two images. Extensive tests on a large image collection were conducted to demonstrate the effectiveness of the proposed approach.展开更多
针对静态和动态救援场景下的多无人机协同任务调度问题,提出基于密度的噪声应用空间聚类-一致性包算法(density-based spatial clustering of applications with noise-consensus-based bundle algorithm,DBSCAN-CBBA)。首先,针对任务...针对静态和动态救援场景下的多无人机协同任务调度问题,提出基于密度的噪声应用空间聚类-一致性包算法(density-based spatial clustering of applications with noise-consensus-based bundle algorithm,DBSCAN-CBBA)。首先,针对任务执行阶段存在的场景不确定以及无人机携带物资载荷限制等问题,建立了一种更为符合救援实际的多任务分配模型。然后,优化了一致性包算法的任务包构建结构以提高算法效率和搜索最优解的能力。第1阶段通过基于密度聚类算法生成候选任务集合,并通过随机方式构建非候选任务集合;第2阶段通过无人机之间的通信,消解它们因独立构建任务包而产生的冲突。最后,将该算法分别应用于静态和实时动态任务分配场景。仿真实验结果表明,该算法可较为高效地找到合理的任务分配方案。展开更多
Mid-troposphere CO2 data retrieved by the AIRS(atmospheric infrared sounder) were validated with five ground-based stations and aircraft measurements in the Northern Hemisphere.AIRS CO2 products show good agreement wi...Mid-troposphere CO2 data retrieved by the AIRS(atmospheric infrared sounder) were validated with five ground-based stations and aircraft measurements in the Northern Hemisphere.AIRS CO2 products show good agreement with ground and aircraft observations.The data had a monthly average accuracy better than 3 ppmv.In this study,the spatial and temporal distribution of mid-troposphere CO2 from January 2003 to December 2008 was analyzed based on this satellite product.The average concentration of atmospheric CO2 was higher in the Northern Hemisphere than in the Southern Hemisphere.The yearly average results show a gradual increase from 2003 to 2008.In China,the annual growth rate was about 2 ppmv/a,similar to the United States,Europe,Australia and India,but was slightly lower than Canada and Russia.Mid-troposphere CO2 concentrations were higher over northern China than over southern areas,due to differences in natural conditions and industrial layout.There were four centers of high CO2 concentration between 35° and 45°N over China,with low concentrations over Yunnan Province.There was a significant seasonal CO2 variation with peak concentration in spring and the lowest concentration in autumn.展开更多
文摘In this paper, we present a novel and efficient scheme for extracting, indexing and retrieving color images. Our motivation was to reduce the space overhead of partition-based approaches taking advantage of the fact that only a relatively low number of distinct values of a particular visual feature is present in most images. To extract color feature and build indices into our image database we take into consideration factors such as human color perception and perceptual range, and the image is partitioned into a set of regions by using a simple classifying scheme. The compact color feature vector and the spatial color histogram, which are extracted from the seqmented image region, are used for representing the color and spatial information in the image. We have also developed the region-based distance measures to compare the similarity of two images. Extensive tests on a large image collection were conducted to demonstrate the effectiveness of the proposed approach.
文摘针对静态和动态救援场景下的多无人机协同任务调度问题,提出基于密度的噪声应用空间聚类-一致性包算法(density-based spatial clustering of applications with noise-consensus-based bundle algorithm,DBSCAN-CBBA)。首先,针对任务执行阶段存在的场景不确定以及无人机携带物资载荷限制等问题,建立了一种更为符合救援实际的多任务分配模型。然后,优化了一致性包算法的任务包构建结构以提高算法效率和搜索最优解的能力。第1阶段通过基于密度聚类算法生成候选任务集合,并通过随机方式构建非候选任务集合;第2阶段通过无人机之间的通信,消解它们因独立构建任务包而产生的冲突。最后,将该算法分别应用于静态和实时动态任务分配场景。仿真实验结果表明,该算法可较为高效地找到合理的任务分配方案。
基金supported by the National Natural Science Foundation of China (40905056)the fund from State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry (LAPC-KF-2008-11)+2 种基金the key projects from the National Key Technology R&D Program of China (2008BAC34B04-2)the European Union project "AMFIC" (FP6-2005-Space)the National Basic Research Program of China (2005C-B422202 and 2006CB-403702)
文摘Mid-troposphere CO2 data retrieved by the AIRS(atmospheric infrared sounder) were validated with five ground-based stations and aircraft measurements in the Northern Hemisphere.AIRS CO2 products show good agreement with ground and aircraft observations.The data had a monthly average accuracy better than 3 ppmv.In this study,the spatial and temporal distribution of mid-troposphere CO2 from January 2003 to December 2008 was analyzed based on this satellite product.The average concentration of atmospheric CO2 was higher in the Northern Hemisphere than in the Southern Hemisphere.The yearly average results show a gradual increase from 2003 to 2008.In China,the annual growth rate was about 2 ppmv/a,similar to the United States,Europe,Australia and India,but was slightly lower than Canada and Russia.Mid-troposphere CO2 concentrations were higher over northern China than over southern areas,due to differences in natural conditions and industrial layout.There were four centers of high CO2 concentration between 35° and 45°N over China,with low concentrations over Yunnan Province.There was a significant seasonal CO2 variation with peak concentration in spring and the lowest concentration in autumn.
