点状地图符号数据结构同化研究

从点状地图符号的构建和共享角度出发,分析了基于TrueType、图元法以及CAD图块符号等点状地图符号数据结构的优缺点。针对地图符号的图形特征,提出了一种基于路径的点状符号数据结构,给出了TrueType符号、图元符号、信息块符号到基于路径的点状符号同化方法。实验验证了基于路径的点状符号数据结构具有较强的描述能力和较强的扩展性。     

高分辨率遥感影像的建筑物自动提取

文章结合结构图分析方法,提出一种针对高分辨率遥感影像中建筑物自动提取方法.该方法利用几何限制对线基元进行初连接,解决由于边缘检测无法完整提取建筑外边缘问题;通过构造结构图确立线基元之间连接关系,搜索结构图中闭合路径,建立高级别特征,对过于散列的线基元进行整合;在此基础上,综合考虑建筑物的几何结构、光谱特征等图像信息筛选闭合路径,实现对建筑物的提取.最后通过对天绘一号高分辨率遥感影像进行建筑物自动提取验证了该方法的有效性.     

A graph edit dictionary for correcting errors in roof topology graphs reconstructed from point clouds

In the task of 3D building model reconstruction from point clouds we face the problem of recovering a roof topology graph in the presence of noise, small roof faces and low point densities. Errors in roof topology graphs will seriously affect the final modelling results. The aim of this research is to automatically correct these errors. We define the graph correction as a graph-to-graph problem, similar to the spelling correction problem (also called the string-to-string problem). The graph correction is more complex than string correction, as the graphs are 2D while strings are only 1D. We design a strategy based on a dictionary of graph edit operations to automatically identify and correct the errors in the input graph. For each type of error the graph edit dictionary stores a representative erroneous subgraph as well as the corrected version. As an erroneous roof topology graph may contain several errors, a heuristic search is applied to find the optimum sequence of graph edits to correct the errors one by one. The graph edit dictionary can be expanded to include entries needed to cope with errors that were previously not encountered. Experiments show that the dictionary with only fifteen entries already properly corrects one quarter of erroneous graphs in about 4500 buildings, and even half of the erroneous graphs in one test area, achieving as high as a 95% acceptance rate of the reconstructed models.     

The evolution of legal instruments and the sustainability of the Peruvian anchovy fishery

Landings statistics of the Peruvian anchovy fishery show that the fishery went through a phase of explosive and uncontrolled growth from its establishment in the mid-fifties until its collapse in 1972. After the collapse, a second phase from 1973 to 1984 was characterized by unfavorable warm ocean conditions and low catches. A third phase, from 1984 to the present, with propitious ocean-environmental conditions and modern governance, can be further divided into a controlled growth period (1985-1994) and a sustainable landings' period (1995 to present). The most recent period of the third phase has enabled the fishery to maintain its catches and be labeled as one of the most sustainable fisheries worldwide. This article highlights the evolution of the legal system that provides for the current sustainable landings and governance of this fishery. Results show that General Fisheries Acts were enacted independently of failures to sustain anchovy landings. The three Peruvian Fisheries Acts were a reflection of broader national socio-political changes and were enacted mainly to define the role of the state and private investment and to delimit foreign involvement in the fishery industry. By contrast, the enactment of secondary legislation to control quotas and fishing seasons increased as the fishery moved towards stable landings. During this phase, enacted secondary legislation showed also a clear peak during strong positive sea surface anomalies driven by the El Niño Southern Oscillation (ENSO) 1997-1998, providing evidence of rapid adaptive management. The role of Fisheries Acts in defining access rights at the national level from a multilevel governance approach is discussed and further key elements that contributed to the transition towards sustainability are suggested.     

Multilevel modeling of NPP change and impacts of water resources in the Lower Heihe River Basin

Net primary productivity (NPP) lays the foundation for provision of various ecosystem services, and understanding the impacts of potential influencing factors on NPP is of great significance to formulating appropriate management measures to guarantee the sustainable provision of essential ecosystem services. This study analyzed the impacts of potential influencing factors on NPP in the lower Heihe River Basin, a typical arid and semi-arid region in China. First, NPP was estimated with the C-FIX model, and then the multilevel model was used to analyze the impacts of potential influencing factors on NPP during 2000–2008. Finally decomposition analysis was used to further analyze the contribution of influencing factors to NPP change during 2000–2008. The average NPP increased by approximately 9.07% during 2000–2008, and results of the multilevel model indicate that both the socioeconomic variables and demographic variables are useful in explaining NPP change. In particular, coefficients of rainfall and evapotranspiration which represent the water availability reached 0.0456 and 0.2956, respectively. Results of decomposition analysis suggested that the water availability played an important role in increasing NPP, with a contribution rate of 44.17%, and it is necessary to carry out some policies that can promote the water use efficiency to increase NPP under the background of climate change and intensified human activities. There are some uncertainties in the results of this study, but these results still can provide valuable reference information for the water resource management to increase the ecosystem service supply in the lower Heihe River Basin.     

面向空间要素基元对象--关系模式的新型GIS软件技术研究

面向图层处理单元的GIS数据模型、数据处理模式已不再适应大规模海量空间数据组织、处理以及网络分发的需要。文章提出以空间要素基元处理取代传统的面向图层处理的模式,并在对象-关系数据库(ORDBMS)统一框架下构筑、组织、存储、处理空间数据,最终形成基于ORDBMS的GIS应用。     

中国古代治水的科学思想

根据农业发源于山区的考古结论,指出中国古代存在一个近两千年的治水过程,也是农业由山区转移到平原的过程,同中国古代文化的形成过程有着十分密切的联系.中国古代治水也是有别于其它文明古国的特殊气候与地理条件下的重大事件.进而论证治水在中国古代物质与精神文明形成过程中的促进作用,并指出现代人水关系的基本原理可在古代治水中找到借鉴.     

Geochemistry of Adakites from the Philippines: Constraints on Their Origins

Abstract. We have identified in the Philippine Archipelago 230 samples of Late Miocene to Quaternary intermediate and evolved magmatic rocks or glasses, the compositions of which plot within the adakitic field defined by Defant and Drum-mond (1990) using Sr/Y ratios versus Y contents. These rocks belong to four different subductions, along the Manila Trench (Batan, Northern Luzon, Central Luzon), the Negros and Sulu Trenches (Negros and Western Mindano), the Cotobato Trench (Southern Mindanao) and the Philippine Trench (Eastern Mindanao). Lavas from Central Mindanao overlie the deep remnants of the Molucca Sea Plate, and were emplaced in a post-collision setting.
All these samples show a significant depletion in Y and HREE with respect to their "normal" calc-alkaline equivalents, suggesting that garnet was either a residual phase during partial melting or a fractionating mineral during differentiation or assimilation coupled with fractional crystallisation (AFC). However, only 19 samples out of our set (i.e., 8 %) display very high Sr/Y ratios (100–250). Our preferred model for the genesis of these "typical adakites" is ca. 20 % partial melting of subducted altered oceanic metabasalts converted to eclogite. This melting process could have been triggered by water from the underlying serpentinites. Most of the samples, termed "intermediate adakites", display major and trace element chemical features intermediate between those of the former group and those of normal calc-alkaline lavas. We show that magma mixing between slab-derived adakitic magmas and mafic mantle-derived melts accounts for most of the trends linking typical and intermediate adakites, although an additional contribution of mantle is required in some cases.     

马尔柯夫转移概率矩阵序列的收敛性

在数学地质中,一般计算马尔柯夫转移概率矩阵序列极限时,都是用升高矩阵乘幂的方法,所以计算量是很大的。本文用解线性方程组的方法,求出了它的极限概率矩阵,并以实例对两种方法进行比较。