流形上的空间密度聚类算法研究     

刘峰  刘希玉  刘弘 《中国海洋大学学报(自然科学版)》2007,37(4):681-684,626

研究流形上的聚类分析，针对基于密度的空间聚类引入了流形概念，提出1种基于流形的密度聚类算法，该方法将流形的概念与聚类相结合，可以适用于样本为复杂分布的聚类。文中通过实例证明此算法的有效性。  相似文献   

Eastern English Channel fish assemblages: measuring the structuring effect of habitats on distinct sub-communities   总被引：1，自引：0，他引：1  

Vaz  S.; Carpentier  A.; Coppin  F. 《ICES Journal of Marine Science》2007,64(2):271-287

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Biological processes and environmental factors regulating the dynamics of the Norwegian Skagerrak cod populations since 1919   总被引：1，自引：1，他引：1  

Fromentin  Jean-Marc; Gjosaeter  Jakob; Bjornstad  Ottar N.; Stenseth  N. Chr. 《ICES Journal of Marine Science》2000,57(2):330-338

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Spatial patterns of pollock and zooplankton distribution in the Pribilof Islands, Alaska nursery area and their relationship to pollock recruitment   总被引：2，自引：1，他引：2  

Swartzman  Gordon; Napp  Jeffrey; Brodeur  Richard; Winter  Andreas; Ciannelli  Lorenzo 《ICES Journal of Marine Science》2002,59(6):1167-1186

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Abundance of the introduced seastar, Asterias amurensis, and spatial variability in soft sediment assemblages in SE Tasmania: Clear correlations but complex interpretation     

D. Jeff Ross  Craig R. Johnson  Chad L. Hewitt   《Estuarine, Coastal and Shelf Science》2006,67(4):695-707

The northern Pacific seastar, Asterias amurensis, was first collected in southeast Tasmania in 1986. Mistaken for the endemic asteroid Uniophora granifera, its true identity was not realised until 1992. It is now a conspicuous predator in soft sediment habitats in this region, and is considered a major threat to native assemblages and commercial species. We examined the structure of soft sediment assemblages at different spatial scales in southeast Tasmania, and correlated spatial variation in community composition with seastar abundances. We found that the structure of soft sediment assemblages is highly variable at a range of spatial scales from metres to tens of kilometres. Clear differences in the composition of assemblages and abundances of major taxa were detected between areas with and without seastars and between areas with low and high seastar densities. However, the nature of these patterns suggests that they are more likely due to differences in sediment characteristics than due to impacts of the seastar. Thus, spatial differences in soft sediment assemblages might have been erroneously attributed to seastars without detailed information on important physical factors such as sediment characteristics. A second survey, using larger sampling units (1 m²) but across a more limited spatial extent, targeted bivalves and heart urchins that were identified as important prey of the seastar in observations of feeding and in experimental studies. Large-scale patterns of abundance and size structure were consistent with seastar effects anticipated from small-scale experimental and feeding studies for some, but not all, species. While the field survey ultimately provided evidence about the presence or absence of seastar impacts at large-scales, the identification of key ecological variables in experimental and feeding studies proved crucial to both the design and interpretation of patterns observed in the large-scale surveys. Overall, this work highlighted the necessity to consider multiple lines of evidence rather than relying on a single ‘inferential’ test, in the absence of pre-impact data.  相似文献   

Habitat characteristics and spatial arrangement affecting the diversity of fish and decapod assemblages of seagrass (Zostera marina) beds around the coast of Jersey (English Channel)     

Emma L. Jackson  Martin J. Attrill  Malcolm B. Jones 《Estuarine, Coastal and Shelf Science》2006,68(3-4):421

Recent research and management plans for seagrass habitats have called for landscape level approaches. The present study examines the spatial utilisation of subtidal seagrass beds by fish and decapods around the coast of Jersey (49°N 02° W). A hierarchical scale of landscape configuration and the plant characteristics of eight seagrass beds were measured and the contributions of these variables as predictors of the properties of the fish and decapod assemblages were evaluated using multiple linear regression models. The results indicated that total diversity had a negative relationship with transect heterogeneity and total species number had a weak negative association with increasing fragmentation. Both total diversity and total species number showed a positive relationship with depth. In fact, in all models of species number and densities, values were higher in deeper seagrass beds. Total decapod density increased with aggregation of seagrass patches within a landscape. In addition to landscape configuration, smaller-scale structural changes in both canopy height and epiphyte load appeared to influence densities of decapod crustaceans. At night, fewer patterns could be explained by the independent variables in the model.  相似文献   

Automatic Registration of TOBI Side-Scan Sonar and Multi-Beam Bathymetry Images for Improved Data Fusion   总被引：1，自引：0，他引：1  

Le Bas  T. P.  Mason  D. C. 《Marine Geophysical Researches》1997,19(2):163-176

Deep towed side-scan sonar vehicles such as TOBI acquire high quality imagery of the seafloor with very high spatial resolution but poor locational accuracy. Fusion of the side-scan sonar data with bathymetry data from an independent source is often desirable to reduce ambiguity in geological interpretations, to aid in slant-range correction and to enhance seafloor representation. The main obstacle to fusion is accurate registration of the two datasets.The application of hierarchical chamfer matching to the registration of TOBI side-scan sonar images and multi-beam swath bathymetry is described. This matches low level features such as edges in the TOBI image, with corresponding features in a synthetic TOBI image created by simulating the flight of the TOBI vehicle through the bathymetry. The method is completely automatic, relatively fast and robust, and much easier than manual registration. It allows accurate positioning of the TOBI vehicle, enhancing its usefulness as a research tool. The method is illustrated by automatic registration of TOBI and multi-beam bathymetry data from the Mid-Atlantic Ridge.  相似文献   

1980-2000年中国耕作土壤有机碳的动态变化   总被引：12，自引：0，他引：12  

于严严  郭正堂  吴海斌 《海洋地质与第四纪地质》2006,26(6):123-130

通过分析我国1980年来耕作土壤有机质的实测数据,对比研究了90年代末和80年代初两个时段土壤有机碳密度的变化特征,并对变化的原因和未来发展趋势进行了探讨。结果表明,总体上我国实测点位(或区域)耕作土壤平均有机碳密度在此期间略有增加。其中,华北黄淮海潮土和褐土区、下辽河平原棕壤农业区和长江以南的水稻土区增幅分别达19%(0.24 kg/m2)、14%(0.29 kg/m2)和16%(0.29 kg/m2);相反,云南砖红壤区、东北和内蒙的黑土和黑钙土区有机碳损失,下降幅度分别达27%(1.01 kg/m2)和3%(0.11 kg/m2)。黄土高原的黑垆土和黄绵土区,山西北部的褐土区、新疆西北部的灌耕土区没有明显变化。两时段有机碳密度的空间分布与气候带总体一致,但20年间有机碳含量变化与80年代初的初始含量呈显著负相关。有机碳含量在低值区增加与近年来农田轮作、施肥和灌溉面积增加等农作措施的改善有关,而高值区的下降则与耕作时间短、强度大和初始含量高有关。根据现有耕作土壤与未耕作状态的碳损失状况估算,如果能在未来30~50年通过合理的农业措施使土壤有机碳损失量恢复50%,则华北、西北、华中南、西南和东北地区分别可能具有约51%、26%、7%、17%和30%的增长空间,指示我国耕作土壤具有较大的碳汇潜力。  相似文献   

SPOT遥感影像处理技术以及在青岛市海洋功能区划中的应用   总被引：2，自引：0，他引：2  

乔磊  杨荣民  李广雪  刘勇  马妍妍 《海洋湖沼通报》2005,(2):8-12,28

青岛市海洋功能区划中，大范围采用了法国高分辨率陆地卫星SPOT-5HRG 1A级遥感数据。利用Geoimage遥感影像处理软件对数据进行了处理．包括：遥感影像的正射纠正、辐射处理和不同分辨率影像地融合等，获得了高空间分辨率和良好的光谱分辨率的遥感图像。很好的识别出青岛海岸带地区地物分布特征。为海洋功能区划底图补充了真实而丰富的信息．  相似文献   

杭州湾海域水体悬沙粒度统计分析     

茹荣忠 《海洋学研究》2002,20(4):13-18

利用2000年9月在杭州湾进行的原型水文泥沙测验所获取的648个悬沙粒度样品,进行了样品粒度统计分析,结果表明:在杭州湾测验区域,粒径为4.00～20.20μm的悬沙出现频率最高;悬沙的中值粒径值自东向西迅速增大;北岸海域悬沙的中值粒径值大于南岸海域悬沙的中值粒径值。  相似文献