首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 437 毫秒
1.
Christy Collis 《GeoJournal》2010,75(4):387-395
This is an article about the politics of territory in Antarctica. It revolves around what at first seems like a very simple geopolitical question: who owns Antarctica? As this article demonstrates, this seemingly simple question is far from easy to answer: it cannot be answered with a straightforward list of states, nor by conventional geopolitical understandings of territorial possession (Agnew and Corbridge, Mastering space: Hegemony, territory, and international political economy, 1995). Struggles between states for territorial possession has characterised much recent geopolitical history; struggles for Antarctica do not entirely follow this pattern, and revolve instead on the nature and the concept of territorial possession itself. The article focuses in particular on the debates about, and changes to, Antarctic legal and geopolitical territories triggered by the 1957–1958 International Geophysical Year: before the IGY Antarctica was an unstable composite of state claims, unclaimed terra nullius, and terra communis or land unavailable to state claim. By the 1959 Antarctic Treaty, this unstable composite legal and geopolitical geography emerged as a new form of territory, one in which the conventional global mode of territory—state possession—was no longer dominant. Understanding Antarctic legal geographies adds depth to critical geopolitical studies which focus on the ways in which space is actively constructed by specific discourses, understandings, and groups.  相似文献   

2.
This article examines young Peruvians’ aspirations and the role of migration in their imagined futures, from a generational perspective. The data come from Young Lives, a long-term study of childhood poverty combining survey and qualitative approaches with children and their parents. The paper uses a biographical approach that sees migration as part of individual biographies as well as social structures and life course processes. The aim is to deepen understanding of the social contexts in which aspirations for and by children are generated, paying close attention to family migration histories, dynamic household contexts, and children’s migration networks. The analysis focuses on the time-spaces of migration aspirations, showing the way past, present and future are interconnected. It also emplaces aspirations by focusing on the way aspirations by and for children are constituted in and through particular places. The conclusion reflects on the role of poverty and argues that ‘aspirations’ are about much more than abstract ‘futures’; they orient actions in the present and say a great deal about young people’s current realities and relationships.  相似文献   

3.
The dehydroxylation reactions of chrysotile Mg3Si2O5(OH)4 and brucite Mg(OH)2 were studied under inert nitrogen atmosphere using isothermal and non-isothermal approaches. The brucite decomposition was additionally studied under CO2 in order to check the influence of a competing dehydroxylation/carbonation/decarbonisation reaction on the reaction kinetics. Isothermal experiments were conducted using in situ high-temperature X-ray powder diffraction, whereas non-isothermal experiments were performed by thermogravimetric analyses. All data were treated by model-free, isoconversional approaches (‘time to a given fraction’ and Friedman method) to avoid the influence of kinetic misinterpretation caused by model-fitting techniques. All examined reactions are characterised by a dynamic, non-constant reaction-progress-resolved (‘α’-resolved) course of the apparent activation energy E a and indicate, therefore, multi-step reaction scenarios in case of the three studied reactions. The dehydroxylation kinetics of chrysotile can be subdivided into three different stages characterised by a steadily increasing E a (α ≤ 15 %, 240–300 kJ/mol), before coming down and forming a plateau (15 % ≤ α ≤ 60 %, 300–260 kJ/mol). The reaction ends with an increasing E a (α ≥ 60 %, 260–290 kJ/mol). The dehydroxylation of brucite under nitrogen shows a less dynamic, but generally decreasing trend in E a versus α (160–110 kJ/mol). In contrast to that, the decomposition of brucite under CO2 delivers a dynamic course with a much higher apparent E a characterised by an initial stage of around 290 kJ/mol. Afterwards, the apparent E a comes down to around 250 kJ/mol at α ~ 65 % before rising up to around 400 kJ/mol. The delivered kinetic data have been investigated by the z(α) master plot and generalised time master plot methods in order to discriminate the reaction mechanism. Resulting data verify the multi-step reaction scenarios (reactions governed by more than one rate-determining step) already visible in E a versus α plots.  相似文献   

4.
In this paper we suggest that a construct known as “possible selves”, which has been developed in psychological literature, holds conceptual merits that are of use to a growing body of literature on youth transitions, and within it, an increasing interest in imagined futures. We highlight several benefits of possible selves that have emerged from our empirical research with young men in two English towns, Luton and Swindon. Research and theorization about youth futures has suggested that young people’s values and their perceived positions in society can be elicited and seen in their projections of themselves in the future. We conclude that possible selves provides a useful addition to this literature by offering a theorization of the link between imagined possibilities in the future and motivation to act in the present. We suggest that this construct opens the scope of empirical and theoretical enquiry into youth transitions and trajectories toward future possibilities.  相似文献   

5.
The mafic–ultramafic complex of Sikhoran presents a long geological history, marked out by various magmatic, metamorphic and tectonic events. This history is much more complex than a simple ophiolite obduction over a continental margin. As early as the Upper Permian, following a mantle uprise in a Tethysian supra-subduction zone, the opening of a (back-arc?) basin in extensional/transtensional conditions provoked the intrusion of multiple gabbroic dykes, veins and plutons charged with fluids, through a mafic/ultramafic complex and its metamorphic cover. Several basins, characterised by abundant submarine basaltic volcanism developed during Jurassic, whose feeding dykes may be represented by the diabase dyke swarms intruding the whole Sikhoran complex and its metamorphic cover. To cite this article: H. Ghasemi et al., C. R. Geoscience 334 (2002) 431–438.  相似文献   

6.
High-resolution paleoenvironmental data from a peat profile with a small pollen source area are used to reconstruct the impacts of landnám on vegetation and soils at a Norse farm complex (∅2 at Tasiusaq) comprising two farms in the Eastern Settlement of Greenland. Analyses include the AMS 14C dating of plant macrofossil samples and the use of Bayesian radiocarbon calibration to construct improved age-depth models for Norse cultural horizons. The onset of a regional landnám may be indicated by the clearance of Betula pubescens woodland immediately prior to local settlement. The latter is dated to AD 950-1020 (2σ) and is characterised by possible burning of Betula glandulosa scrub to provide grassland pasture for domestic stock. Clearance and grazing resulted in accelerated levels of soil erosion at a westerly farm. This was followed by an easterly migration of settlement and agriculture. Site constraints prevent an assessment of the demise of the easterly farm, but pressures of overgrazing and land degradation may have been the major factors responsible for the abandonment of the earlier farm.  相似文献   

7.
A systematic analysis of the abundance and isotopic composition of ten REE (and Ba) in a sample from the reactor zone at the Oklo (Gabon) ore deposit is presented. From this analysis some constraints on the behavior of the REE group during and after the reaction time are determined. Taking into account the complex state of this sample, the main characteristics of the reactor are deduced.From the abundances of isotopes with large neutron capture cross sections the amount of REE (supposed to be natural) added after the reaction time is calculated first. The comparison of the fluence values obtained respectively from the analysis of the Nd and Dy isotopic spectrum indicates a rather good stability of the REE group during the reaction time. The total number (235U)f of 235U nuclei that fissioned during the reaction calculated from different elements of the REE group provides an indication on the relative migration of these elements since the reaction time. Results of these computations suggest a migration of the heavy REE relative to the light REE to outside the reaction zone. As a consequence of these deductions on the behavior of the REE in the Oklo ore, the light REE appear the most appropriate to study the characteristics of the reactor. The reactor characteristics we deduced from this sample (fluence, epithermal index, proportion of nuclides that fissioned, duration of the reactor) are within the range of the ones determined in other studies dealing with REE analysis.  相似文献   

8.
An internal isochron determined for a gabbro from the Stillwater complex by the Sm-Nd method yields a precise age of 2701 ± 8 Myr and initial 143Nd/144Nd = 0.508248 ± 12. The initial is close to the CHUR evolution curve but clearly displaced below it by ?Nd = ?2.8 ± 0.2. A spectrum of total rocks in the Stillwater complex ranging from anorthosite to pyroxenite were found to lie on the same isochron to within experimental error indicating the same age and initial. These data demonstrate that some ancient mantle-derived rocks have initial 143Nd/144Nd which deviate substantially from the CHUR evolution curve at the time of their formation. This implies that there was early layering in the mantle with substantial REE fractionation (~6–12% Nd/Sm enrichment) or that the Stillwater complex was highly contaminated with REE from much older continental crust during emplacement. The results show the necessity of high-precision ages and initial 143Nd/144Nd values in order to properly describe REE fractionation in the mantle. While the Sm-Nd age results show no indication of any irregularities, we have confirmed that the Rb-Sr data for the Stillwater are highly disturbed. This comparison indicates that the Sm-Nd parent-daughter system may be much less susceptible to element redistribution during metamorphism, therefore permitting wide application of this technique to rocks of complex histories.  相似文献   

9.
Biosecurity, in broad terms, aims to reduce the impact and incidence of threats to life through regulatory means. For reasons we raise in this paper, such regulation can often lead to the specification of disease free processes within the food and farming industry, with biosecurity success measured in terms of the degree of compliance with and allegiance to modern farming practice. We counter this progressive narrative in three ways. First we draw on UK-based qualitative fieldwork with vets, farmers and pigs to demonstrate how biosecure farming and disease freedom are translated and qualified, in practice, to pathogen free, pathogen management and ultimately to configuring health through immunity management. Second, these translations demonstrate how building health is dependent on spatial and microbiological diversity rather than uniformity. Crucially, health involves patch-work and situated knowledge practices that are under threat within an industry increasingly marked by control and homogeneity. Third, in conceptual terms, we argue that while pig farming is organised through both biosecurity and a biopolitical regulation of life, immunity opens up political space for exploring an alternative politics of life, one where farmers and others are not so much made responsible for disease prevention, but make valued contributions to understandings of animal health and food security.  相似文献   

10.
People living in the northeast of Thailand interchangeably label themselves and are labelled by others as Isan, Thai Isan, Lao Isan, Thai or Lao, depending on the ethnic, political, social or familial nuances of any given situation. I use the term Lao Isan to refer specifically to Isan people of Lao origin or ethnicity. Lao Isan are subject to complex and often competing notions of Isan-ness, Lao-ness and Thai-ness by insiders and outsiders. Using data derived from an ethnographic study of popular Thai television and Lao Isan youth (aged 17–25) living in the city of Khon Kaen and the town of Mahasarakham in northeast Thailand in 2002, this paper explores contemporary and co-existing interpretations of Isan identity or Khwampenisan among Lao Isan youth in relation to self-image and connections with national understandings of physical beauty as they are perpetuated in Thai-produced television programs.
Catherine Hesse-SwainEmail:
  相似文献   

11.
The numerical simulation of reactive mass transport processes in complex geochemical environments is an important tool for the performance assessment of future waste repositories. A new combination of the multi-component mass transport code GeoSys/RockFlow and the Gibbs Energy Minimization (GEM) equilibrium solver GEM-Selektor is used to calculate the accurate equilibrium of multiple non-ideal solid solutions which are important for the immobilization of radionuclides such as Ra. The coupled code is verified by a widely used benchmark of dissolution–precipitation in a calcite–dolomite system. A more complex application shown in this paper is the transport of Ra in the near-field of a nuclear waste repository. Depending on the initial inventories of Sr, Ba and sulfate, non-ideal sulfate and carbonate solid solutions can fix mobile Ra cations. Due to the complex geochemical interactions, the reactive transport simulations can describe the migration of Ra in a much more realistic way than using the traditional linear KD approach only.  相似文献   

12.
Washington State’s coastal estuaries are productive shallow water environments that support commercial fisheries for Dungeness crabs (Cancer magister) and English sole (Parophrys vetulus) by providing 0+(settlement to age l) populations with critical refuge and foraging habitats until subadults migrate to the nearshore coast. Intertidalmudflats also constitute prime areas for commercial oyster (Crassostrea gigas) culture, an, important industry for the coastal communities of Willapa Bay and Grays Harbor that supply much of the nation's oysters. Conflicts over natural resources and estuarine utilization have arisen over the last 37 yr due to the use of carbaryl (an organo carbamate pesticide) by oyster growers on their grounds to control populations of burrowing thalassinidean shrimp (Neotrypaea californiensis and Upogebia pugettensis). Burrowing shrimp, which have an indirect negative effect on oyster survival and growth through bioturbation and sediment destabilization, are killed by carbaryl, as are 0+ and subadult Dungeness crabs, 0+English sole, and other non-target species prsent on the tideflats at the time of application. The pesticide is delivered at 9 kg ha?1 directly to the mudflat as a wetable powder during low tides in July and August. Commercial crabbers and other groups who have economic, recreational, and environmental interests in the estuaries have generally opposed use of the chemical that oyster growers maintain is essential to sustain production levels. For years, government natural resource agencies that regulate the use of carbaryl lacked critical information needed to effectively manage the program. An Environmental Impact Statement (EIS) and Supplemental EIS have provided much of that data and helped shape management decisions with regard to establishing carbaryl concentration rates and total allowable spray area. Additional research is needed to develop more economically and environmentally sound policies for shrimp control based on burrowing shrimp-oyster interactions on an estuarine-wide scale. In this paper we review issues pertaining to oyster culture, the use of carbaryl to control burrowing shrimp populations, and effects on non-target species, drawing upon research from, published articles as well as unpublished data collected by the authors. We also discuss what is known of burrowing shrimp life history and ecology and emphasize the importance of integrating information on shrimp, such as timing of recruitment, variability in year class strength, and patterns of habitat use, into carbaryl control policies or alternative strategies that may be developed in the future. We recommend controlled experimentation be done to examine the ecological effects of delaying carbaryl application to some ghost shrimp beds until October after peak recruitment of 0+ ghost shrimp has occurred, allowing the number of hectares treated each year to vary based on fluctuations in pest population densities, and modifying the substrate by applying a dense layer of oyster shell to the mudflat (shell pavement) to reduce recruitment of ghost shrimp.  相似文献   

13.
The characterisation of relative copper isotope amount ratios (δ65Cu) helps constrain a variety of geochemical processes occurring in the geosphere, biosphere and hydrosphere. The accurate and precise determination of δ65Cu in matrix reference materials is crucial in the effort to validate measurement methods. With the goal of expanding the number and variety of available geological and biological materials, we have characterised the δ65Cu values of ten reference materials by MC‐ICP‐MS using C‐SSBIN model for mass bias correction. SGR‐1b (Green River shale), DOLT‐5 (dogfish liver), DORM‐4 (fish protein), TORT‐3 (lobster hepatopancreas), MESS‐4 (marine sediment) and PACS‐3 (marine sediment) have for the first time been characterised for δ65Cu. Additionally, four reference materials (with published δ65Cu values) have been characterised: BHVO‐1 (Hawaiian basalt), BIR‐1 (Icelandic basalt), W‐2a (diabase) and Seronorm? Trace Elements Serum L‐1 (human serum). The reference materials measured in this study possess complex and varied matrices with copper mass fractions ranging from 1.2 µg g?1 to 497 µg g?1 and δ65Cu values ranging from ?0.20‰ to 0.52‰ with a mean expanded uncertainty of ± 0.07‰ (U, k = 2), covering much of the natural copper isotope variability observed in the environment.  相似文献   

14.
Neoproterozoic tectonic geography was dominated by the formation of the supercontinent Rodinia, its break-up and the subsequent amalgamation of Gondwana. The Neoproterozoic was a tumultuous time of Earth history, with large climatic variations, the emergence of complex life and a series of continent-building orogenies of a scale not repeated until the Cenozoic. Here we synthesise available geological and palaeomagnetic data and build the first full-plate, topological model of the Neoproterozoic that maps the evolution of the tectonic plate configurations during this time. Topological models trace evolving plate boundaries and facilitate the evaluation of “plate tectonic rules” such as subduction zone migration through time when building plate models. There is a rich history of subduction zone proxies preserved in the Neoproterozoic geological record, providing good evidence for the existence of continent-margin and intra-oceanic subduction zones through time. These are preserved either as volcanic arc protoliths accreted in continent-continent, or continent-arc collisions, or as the detritus of these volcanic arcs preserved in successor basins. Despite this, we find that the model presented here still predicts less subduction (ca. 90%) than on the modern earth, suggesting that we have produced a conservative model and are likely underestimating the amount of subduction, either due to a simplification of tectonically complex areas, or because of the absence of preservation in the geological record (e.g. ocean-ocean convergence). Furthermore, the reconstruction of plate boundary geometries provides constraints for global-scale earth system parameters, such as the role of volcanism or ridge production on the planet's icehouse climatic excursion during the Cryogenian. Besides modelling plate boundaries, our model presents some notable departures from previous Rodinia models. We omit India and South China from Rodinia completely, due to long-lived subduction preserved on margins of India and conflicting palaeomagnetic data for the Cryogenian, such that these two cratons act as ‘lonely wanderers’ for much of the Neoproterozoic. We also introduce a Tonian-Cryogenian aged rotation of the Congo-São Francisco Craton relative to Rodinia to better fit palaeomagnetic data and account for thick passive margin sediments along its southern margin during the Tonian. The GPlates files of the model are released to the public and it is our expectation that this model can act as a foundation for future model refinements, the testing of alternative models, as well as providing constraints for both geodynamic and palaeoclimate models.  相似文献   

15.
The combination of cathodoluminescence (CL) analysis, temperature and temperature–time calculations, and microstructural numerical modelling offers the possibility to derive the time-resolved evolution of a metamorphic rock. This combination of techniques is applied to a natural laboratory, namely the Ballachulish contact aureole, Scotland. Analysis of the Appin Quartzite reveals that the aureole was produced by two distinct magmatic events and infiltrated by associated fluids. Developing microstructures allow us to divide the aureole into three distinct regions. Region A (0–400?m, 663°C?<?T max?<?714°C) exhibits a three-stage grain boundary migration (GBM) evolution associated with heating, fluid I and fluid II. GBM in region B (400–700?m, 630°C?<?T max?<?663°C) is associated with fluid II only. Region C (>700?m of contact, T max?<?630°C) is characterised by healed intragranular cracks. The combination of CL signature analysis and numerical modelling enables us to recognise whether grain size increase occurred mainly by surface energy-driven grain growth (GG) or strain-induced grain boundary migration (SIGBM). GG and SIGBM result in either straight bands strongly associated with present-day boundaries or highly curved irregular bands that often fill entire grains, respectively. At a temperature of ~620°C, evidence for GBM is observed in the initially dry, largely undeformed quartzite samples. At this temperature, evidence for GG is sparse, whereas at ~663°C, CL signatures typical for GG are commonplace. The grain boundary network approached energy equilibrium in samples that were at least 5?ka above 620°C.  相似文献   

16.
Fossil pollen identified in the earliest sediments of three cushion bogs in the Cordillera Pelada (40°10′S, 73°30′W) dated 10,425 14C yr B.P. includes the subantarctic species Dacrydium fonckii, Tetroncium magellanicum, Astelia pumila, Gaimardia australis, Donatia fascicularis, and Drosera uniflora. All grow today in the Cordillera Pelada and range poleward to the southernmost Province of Magallanes; one species, Drapetes muscosa, included with the pollen of these plants in the earliest record, is no longer a constituent of the flora but is limited only to subantarctic Chile. Available evidence indicates that plants survived the last glaciation north of the glacial border with the course of postglacial migration southward following the wastage of the glacier complex. Holocene climatic and vegetational changes in the Cordillera Pelada are interpreted in the context of regional reconstructions which show maximum warmth about 9000 yr ago with a pronounced dry period lasting from 9000 to 6500 yr B.P. Maximum precipitation was later reached around 4000 yr ago but has decreased overall since then. The regional decline of the endemic gymnosperm Fitzroya cupressoides, which today is extensively destroyed in the Cordillera Pelada, follows this decrease in precipitation. These climatic data suggest a net south ward shift in the zone of westerly winds that bring rainfall to the region over the past 4000 yr.  相似文献   

17.
To understand the evolution of a disaster, we propose a Framework for Assessing Crisis in a System Environment (FACSE). FACSE is set in a multi-system environment, containing the human system as well as the various natural and technological systems that interact with people. We take a lifecycle perspective, via which we quantify rhythms of life exhibited in multiple systems, across different scales, at different times. The lifecycle perspective also implies a relative approach in that rhythms of life during time t can be compared against those during t-1. We illustrate how rhythms of life in the human system can be measured at different scales. We propose a new concept??the degree of disaster, which is a composite score that encompasses the various measurements of rhythms of life from multiple systems, across different scales. We conclude the paper by discussing the potential offered by FACSE in disaster research as well as the limitations.  相似文献   

18.
Nancy Worth 《Geoforum》2009,40(6):1050-1060
Drawing on recent work in psychology, philosophy, and youth geographies, this article responds to calls for theoretical rigour in children’s geographies by developing the concept of becoming for youth transitions research. Becoming has been used by psychologist Gordon Allport (1955) in his work on the processual nature of personal identity, while Elizabeth Grosz (1999) has used the concept of becoming to explore conceptions of time as a lived experience, focusing on the dynamics of time as duration. This article uses the unifying concept of futurity to tie together the works of Allport and Grosz, exploring how the concept of becoming can be used to consider the inherent complexities of contemporary youth transitions. To demonstrate the value of working with these reconceptualizations, examples of becoming will be explored through research with visually impaired young people. This research productively uses narrative and a life mapping technique to capture the messiness of becoming, seeing transition through the scale of a life and important life events.  相似文献   

19.
In interpreting the inception and demise of different carbonate depositional systems, climatic-oceanographic variations together with sea-level oscillations are commonly considered key elements. However, local tectonic controls cannot be ruled out. In attempts to discriminate among the main factors controlling the evolution of the southern Apennine mid-Cretaceous carbonate system, detailed facies analyses have been performed on Aptian–Albian carbonate successions in the Matese Group (southern Apennines). Since the mid Aptian, the analysed successions testify to a tectonically-driven topography, replacing the previous large tropical shallow-water domain with subdomains characterised by diversified sedimentological trends. Nevertheless, around the middle part of the Aptian, the studied successions register palaeoecological signals that cannot be linked exclusively with tectonic disturbance because of the coeval appearance of analogous signals at a global scale, including a significant change in biological assemblages and an outbreak of organisms indicative of stressful conditions in the water mass.Upper Bedoulian strata clearly record open marine settings characterised by a significant richness of the benthic communities. The biota included rudists, gastropods and echinoids plus many different benthic foraminifers and green algae. Rudists considered to be typically “tropical” forms (the caprinid Offneria nicolinae (Mainelli) and Offneria murgensis Masse, the requieniid Lovetchenia Masse and the monopleurid Agriopleura Kühn) characterise thick subtidally deposited strata in which large coral colonies and mollusc shells contributed to occasional storm-related skeletal concentrations.The analysed Gargasian strata show impoverished biota: caprinids totally disappear, both as in situ and storm-related layer components, and hermatypic corals are drastically reduced. Muddy lithofacies prevail in intertidal metric cycles in which cyanobacterial consortia, both in the form of dense laminae and coalescent oncoids, orbitolinids and small gastropods (cerithiids) suggest restricted, nutrient-rich water. Large oncoids of Bacinella irregularis/Lithocodium aggregatum and mollusc (mostly chondrodontids and gastropods) shell fragments significantly contribute to storm-related coarse skeletal intercalations, in which oligotrophic condition-adapted forms (e.g., hermatypic corals) are reduced or absent. This pattern suggests generalised conditions of stress in the water mass and in more marginal open areas.During the mid-Aptian interval, characterised by the flourishing of assemblages adapted to mesotrophic–eutrophic conditions, the southern Apennines shallow-water domain shows a progressive reduction of the previous mainly aragonite-dominated chlorozoan assemblages and an increase of calcite-dominated skeletal components, including rudists with thickened calcitic outer shell layers. Cyanobacteria and polychaetes characteristically marked the first phases of recovery in the shallow-water domains, rapidly evolving into more complex and differentiated assemblages. The outbreak of nerineid and acteonid gastropods seems to be related to a flourishing of cyanobacterial mats and related microphytae and also to the presence of polychaetes tubes (Thartarella cocumeriformis (Wahlman)). Moreover, the grazing activity of the nerineids favoured the flourishing of oyster-like bivalves. Among the rudists, the persistence and radiation of species adapted to a wide range of temperatures, such as Requieniidae and Monopleuridae as well as the first elevator Radiolitidae suggests some kind of oceanographic change (e.g., seawater chemistry and/or temperature).On the basis of the features described above, we propose the existence of a complex environmental scenario in which cooler conditions, presumably coupled with meso/eutrophic and locally oligophotic conditions, related to climatic/oceanographic global changes, cooperated in modifying the carbonate factory characterisation in a tectonically controlled setting.  相似文献   

20.
Cross validation of kriging in a unique neighborhood   总被引：1，自引：0，他引：1  
Cross validation is an appropriate tool for testing interpolation methods: it consists of leaving out one data point at a time, and determining how well this point can be estimated from the other data. Cross validation is often used for testing “moving neighborhood” kriging models; in this case, each unknown value is predicted from a small number of surrounding data. In “unique neighborhood” kriging algorithms, each estimation uses all the available data; as a result, cross validation would spend much computer time. For instance, with ndata points it would cost at least the resolution of nsystems of n × nlinear equations (each with a different matrix).Here, we present a much faster method for cross validation in a unique neighborhood. Instead of solving nsystems n × n,it only requires the inversion of one n × nmatrix. We also generalized this method to leaving out several points instead of one.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号