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多层卫星网络中的管理策略研究 被引量:4
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作者 张承 郭薇 赵艳彬 《计算机技术与发展》 2015年第7期1-4,10,共5页
多层卫星网络已逐渐成为人们研究的重点,而其中一个重要的主题就是如何降低网络管理的复杂度和成本。对此,文中提出了一种分轨分簇的管理策略,即每个轨道上选择一个簇头管理该轨道上的卫星,而高层管理卫星只需管理每个轨道上的簇头。与... 多层卫星网络已逐渐成为人们研究的重点,而其中一个重要的主题就是如何降低网络管理的复杂度和成本。对此,文中提出了一种分轨分簇的管理策略,即每个轨道上选择一个簇头管理该轨道上的卫星,而高层管理卫星只需管理每个轨道上的簇头。与传统的覆盖分域策略相比,这种分轨分簇方式减少了管理卫星数目,并且降低了管理层星座的复杂度。此外,通过仿真分析还发现,分轨分簇的管理策略降低了管理卫星管理域变化的频度,而路由收敛时间并没有受到很大影响。 展开更多
关键词 管理策略 覆盖分域 卫星数目 管理效率
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Spatial Distribution of Land Cover and Vegetation Activity along Topographic Gradient in an Arid River Valley, SW China 被引量:2
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作者 LIU Wen XU Xianli +2 位作者 LUO Jiancheng SHEN Zhanfeng ZHONG Qiuhai 《Journal of Mountain Science》 SCIE CSCD 2009年第3期274-285,共12页
Anthropogenic activities have become more and more important in characterizing the landscape, but their impacts are still restricted by natural environments. This paper discusses the interactions of anthropogenic acti... Anthropogenic activities have become more and more important in characterizing the landscape, but their impacts are still restricted by natural environments. This paper discusses the interactions of anthropogenic activity, vegetation activity and topography through describing the spatial distribution of land cover and vegetation activity (represented by Normalized Difference Vegetation Index, NDVI) along topographic gradient in a mountainous area of southwestern China. Our results indicate that the existing landscape pattern is controlled by anthropogenic activities as well as topographic factors. Intensive anthropogenic activities mainly occur in areas with relatively low elevation, gentle and concave slopes, as these areas are easy and convenient to attain for human. Because of the destruction by human, some land cover types (mainly grassland and shrub) are only found in relatively harsher environments. This study also finds that topographic wetness index (W) used in other places only reflects runoff generation capacity, but not indicate the real spatial pattern of soil water content in this area. The relationships between NDVI and W, and NDVI and length slope factor (LSF) show that runoff and erosion have complex effects on vegetation activity. Greater values of W and LSF will lead to stronger capacity to produce runoff and transport sediment, and thereby increase soil water content and soil deposition, whereas beyond a certain threshold runoff and erosion are so strong that they would destruct vegetation growth. This study provides information needed to successfully restore native vegetation, improve land management, and promote sustainable development in mountainous areas, especially for developing regions. 展开更多
关键词 Vertical distribution of land cover Anthropogenic activity Vegetation activity Environmental variability China
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Spatial distribution rules and affecting factors of BIF in Anshan-Benxi area
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作者 WANG Wenqi ZHANG Wei +2 位作者 PENG Chong ZHU Ming XUE Linfu 《Global Geology》 2015年第2期109-116,121,共9页
A detailed investigation on 3D spatial distribution rules of Banded Iron-bearing Formation(BIF) with methods of gravity-magnetic inversion and 3D modeling of iron mine is presented based on the former analysis in the ... A detailed investigation on 3D spatial distribution rules of Banded Iron-bearing Formation(BIF) with methods of gravity-magnetic inversion and 3D modeling of iron mine is presented based on the former analysis in the Anshan-Benxi area.Three dimension spatial distribution types of BIF are concluded as hook-like,tabularlike and "W"-like.BIF was mainly developed in three types of space including(1) the syncline cores,(2)cover coverage area,and(3) the deeper buried area where the range of tectonic uplift is small.The influences of tectonism,magmatic intrusion and uplift-erosion on the spatial distribution shapes of BIF are clarified. 展开更多
关键词 Anshan-Benxi area BIF geometric types iron ore bodies affecting factors
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Predicting wild boar damages to croplands in a mosaic of agricultural and natural areas 被引量:1
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作者 Gentile Francesco FICETOLA Anna BONARDI +2 位作者 Paola MAIROTA Vincenzo LERONNI Emilio PADOA-SCHIOPPA 《Current Zoology》 SCIE CAS CSCD 2014年第2期170-179,共10页
Crop damages by wildlife is a frequent form of human-wildlife conflict. Identifying areas where the risk of crop damages is highest is pivotal to set up preventive measures and reduce conflict. Species distribution mo... Crop damages by wildlife is a frequent form of human-wildlife conflict. Identifying areas where the risk of crop damages is highest is pivotal to set up preventive measures and reduce conflict. Species distribution models are routinely used to predict species distribution in response of environmental changes. The aim of this paper was assessing whether species distribution models can allow to identify the areas most at risk of crop damages, helping to set up management strategies aimed at the mitigation of human-wildlife conflicts. We obtained data on wild boar Sus scrofa damages to crops in the Alta Murgia National Park, Southern Italy, and related them to landscape features, to identify areas where the risk of wild boar damages is highest. We used MaxEnt to build species distribution models. We identified the spatial scale at which landscape mostly affects the distribution damages, and optimized the regularization parameter of models, through an information-theoretic approach based on AIC. Wild boar damages quickly increased in the period 2007-2011; cereals and legtmaes were the crops more affected. Large areas of the park have a high risk of wild boar damages. The risk of damages was related to low cover of urban areas or olive grows, intermediate values of forest cover, and high values of shrubland cover within a 2-km radius. Temporally independent validation data demonstrated that models can successfully predict damages in the future. Species distribution models can accurately identify the areas most at risk of wildlife damages, as models calibrated on data collected during only a subset of years correctly predicted damages in the subsequent year [Current Zoology 60 (2): 170-179, 2014]. 展开更多
关键词 Environmental heterogeneity Human-wildlife conflict Landscape composition Predictive distribution model Protected areas Spatial scale Sus scrofa
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