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991.
Tao Pei Stanislav Sobolevsky Carlo Ratti Alexander Amini Chenghu Zhou 《Transactions in GIS》2014,18(Z1):126-142
The aggregated mobile phone network (AMPN) (i.e. the calling time or numbers are aggregated at every vertex), which records the call volume between different places over time, has been studied extensively to reveal the mobility patterns of residents, etc. Nevertheless, most previous works were implemented based on the non‐directionality of the network model. This simplification may overlook some important characteristics of AMPN. To explore the AMPN as a directional network model, we introduce the concept of directional heterogeneity in the study of AMPN data. The heterogeneity is twofold: (1) the imbalance of vertex (difference between outgoing and incoming calls of the vertex); and (2) the reciprocity of each edge (difference between the directed weights of the same edge). Taking the data of Singapore as an example, we systematically analyze the directional heterogeneity of AMPN. Our findings include three aspects. First, the AMPN shows as more unbalanced in the night‐time than in the daytime, and its imbalance decreases as vertex granularity increases. Second, the directional heterogeneity varied with locations. Specifically, the residential area is dominated by deficits and others by surpluses. Third, the trajectories of incoming and outgoing calls follow a similar geographical pattern (i.e. southeast‐north‐south‐north‐southeast), indicating the calling behavior and routine mobility of users over time and space. 相似文献
992.
通过理论分析与实地调研,构建人口就地城镇化模型,分析推进人口就地迁移的影响因素、就业模式和居住模式。理论模型与甘肃省敦煌市的实证结果都表明:人们在就地能找到理想的工作及农业生产有利可图的前提下,通过居住成本、就业成本、家庭、农业与乡土情结等因素的综合影响选择就地迁移。就地迁移的就业模式有农业模式、农-工业模式、农-服务业模式3种,不同的就业模式形成合居式、分居式和季节性迁移3种居住模式。通过深度访谈及问卷调研发现,敦煌人口基于地方农-服务业的资源优势就地流动,呈就地城镇化模式。青年人和老年人在该模式影响下形成了以城乡分离为主的分居式居住模式。 相似文献
993.
????IGS??????????????????????Allan???????????????????????????????????????????????????????????????????????????????о????????????1??GPS???????????GLONASS???????????4??????????????????????????????1??1/2??1/3??1/4???2???????????????GPS????????Allan????????????仯????GLONASS????????Allan????????????????仯??????GPS????????д???????????GLONASS???????????????????????????????仯??????С??3????????ε?????????????????仯??? 相似文献
994.
Fu-Ping Pei Wen-Liang Xu De-Bin Yang Yang Yu Wei Wang Quan-Guo Zhao 《Journal of Asian Earth Sciences》2011,40(2):636-650
LA–ICP–MS zircon U–Pb ages, geochemical and Sr–Nd–Pb isotope data are presented for mafic–ultramafic complexes from the southern Liaoning–southern Jilin area with the aim of determining the nature of the Mesozoic lithospheric mantle and to further constrain the spatial extent of destruction of the North China Craton (NCC). The complexes consist of olivine-websterite, gabbro, dolerite, and gabbro-diorite. Zircons from the complexes show typical zoning absorption, are euhedral–subhedral in shape, and yield high Th/U ratios (1.23–2.87), indicating a magmatic origin. Zircon U–Pb age data indicate that they formed in the Early Cretaceous (129–137 Ma). Geochemically, they have SiO2 = 44.3–49.8%, MgO = 6.8–26.5%, Cr = 102–3578 ppm, and Ni = 31–1308 ppm, and are characterized by enrichment in large ion lithophile elements (LILEs) and light rare earth elements (LREEs), and depletion in high field strength elements (HFSEs) and heavy rare earth elements (HREEs), as well as a wide range of Sr–Nd–Pb isotopic compositions [(87Sr/86Sr)i = 0.70557–0.71119; εNd (t) = ?5.4 to ?20.1; (206Pb/204Pb)i = 15.13–17.85; Δ7/4 = ?11.49 to 16.00; Δ8/4 = 102.64–203.48]. Compared with the southern Liaoning mafic–ultramafic rocks, the southern Jilin mafic–ultramafic rocks have high TiO2 and Al2O3 contents, high εNd (t) values, low (La/Yb)N values, low initial 87Sr/86Sr ratios, and low radiogenic Pb isotopic compositions. These findings indicate that the primary magmas of the southern Jilin complexes were derived from lithospheric mantle that was previously metasomatized by a melt derived from the delaminated ancient lower crust, whereas the primary magmas of the southern Liaoning complexes originated from partial melting of a lithospheric mantle source that was previously modified by melt derived from the broken-off Yangtze slab. Therefore, the lateral extent of the NCC destruction should include the southern Liaoning–southern Jilin area. 相似文献
995.
996.
The objective of this study was to investigate the effects of diurnal temperature fluctuation amplitude (DTFA) on the geothermal regime of the embankment on the Qinghai–Tibet plateau. The investigation was simulated by respectively denoting the diurnal temperatures at the embankment surface, embankment slope, and natural ground surface with sinusoidal waves. The amplitudes of the waves were denoted by 0°C, 5°C, 8°C, and 12°C, respectively. The numerical result shows that the DTFA cannot vary the frequency of the seasonal temperature fluctuation of the underlying soil, but can significantly change the magnitude of the soil’s temperature. The changes include: (1) The high DTFA, such as 12°C, can significantly lead to the warming of the soil under the embankment. (2) Interestingly, when the DTFA at ground surface is 5°C, the underlying soil is in a cooler stage compared to when such DTFA is 0°C, 8°C, or12°C. This interesting result means that the documented model which ignores the diurnal temperature rhythm overestimates the warming of the underlying soil at the low DTFA region and underestimates such warming at the high DTFA region. This result also suggests that the soil under the embankment can be cooled down if the DTFA on the ground surface was maintained at or approximately at 5°C. 相似文献
997.
Tao Pei 《Mathematical Geosciences》2011,43(3):345-362
The task of discriminating between heterogeneity and complete spatial randomness (CSR) for a given point process can be divided into three subtasks: the identification of the point pattern; the determination of the sizes of clusters; and the estimation of the numbers of events in dominant clusters. Many studies have been performed regarding the first and second subtasks. However, limited work has been done on the third aspect; hence, the determination of the number of events in each dominant cluster is still an unsolved problem. In this paper, we provide a solution by constructing a new index which is defined as the ratio between the variance of the (k+1)th nearest distance and that of the kth nearest distance. Our method can be divided into two phases: the detection of point pattern and the estimation of the numbers of events in dominant clusters. These phases can be estimated by the values at which the index abruptly decreases to be less than 1. A comparative study between the existing indices and our index shows the following: (i) our index can indicate the numbers of events in dominant clusters in a relatively objective way, which is different from the K-function revealing the sizes of clustered patterns; (ii) it is a nonparametric index and is easy to implement; and (iii) it demonstrates the highest detection power for differentiating between heterogeneity and CSR. The simulations and two seismic case studies also confirmed the correctness of our method. 相似文献
998.
999.
中国锰矿成矿规律初探-陈毓川院士八十华诞专辑 总被引:3,自引:0,他引:3
中国锰矿资源较丰富,资源量排名在世界上位列第5.中国锰矿种类多样,有海相沉积型、火山-沉积型、碳酸盐岩中热水沉积型(或“层控”型)、与岩浆作用有关的热液型、受变质型及表生型.其中,海相沉积型占资源量的71.4%,表生型占15.7%,是最主要的两种类型.中国锰矿广泛分布于“泛扬子区”、华北陆块的燕辽地区以及天山和祁连山部分地区,尤以“泛扬子区”为最,并具分布广泛又相对集中的总体特征.中国的成锰时代多,中—新元古代、早古生代(寒武纪、奥陶纪)、晚古生代—早中生代是中国锰矿形成的重要时代.中国锰矿时-空分布的主要特征是“北锰南迁”:中元古代锰矿主要产于华北陆块的燕辽裂谷带,新元古代—古生代锰矿主要产于“泛扬子区”的大陆边缘盆地或台内盆地中.大型、超大型锰矿床或锰矿田的形成,受控于非构造期盆地性质、古海洋结构、古海水性质及海平面升降等因素,其形成环境存在一定的相似性及同源性. 相似文献
1000.
桂西是我国最重要的锰矿富集地区之一。近年来在德保县荣华乡新发现了锰帽型矿床,锰矿体赋存于中三叠统百逢组碎屑岩系中。前人对该层位的锰矿研究很少,本文首次结合深部钻探工程,对矿床控矿因素及矿层空间展布进行了研究。钻探工程识别出了6个矿层,其中Ⅱ、Ⅲ、Ⅳ矿层稳定,空间上延续性较好。荣华锰矿床的形成是地层岩性、构造条件、地貌特征与古气候因素等多种因素综合作用的结果。矿体的空间展布、规模及其形态等主要受地层和构造因素控制,而该区持续的温暖潮湿气候和有利的地形地貌因素是后期氧化锰矿富集的重要条件。深部钻探工程揭示了原生碳酸锰矿(品位:6.65%~8.20%)的存在,该区深部碳酸锰矿具有较大找矿潜力。 相似文献