Kriging in a finite domain     

Clayton V. Deutsch 《Mathematical Geosciences》1993,25(1):41-52

Adopting a random function model {Z(u),u ε study areaA} and using the normal equations (kriging) for estimation amounts to assume that the study areaA is embedded within a infinite domain. At first glance, this assumption has no inherent limitations since all locations outsideA are of no interest and simply not considered. However, there is an interesting and practically important consequence that is reflected in the kriging weights assigned to data contiguously aligned along finite strings; the weights assigned to the end points of a string are large since the end points inform the infinite half-space beyond the string. These large weights are inappropriate when the finite string has been created by either stratigraphic/geological limits or a finite search neighborhood. This problem will be demonstrated with numerical examples and some partial solutions will be proposed.  相似文献   

Subaerial weathering of sedimentary organic matter     

Jerry L. Clayton  Paul J. Swetland 《Geochimica et cosmochimica acta》1978,42(3):305-312

Small diameter core samples were taken from outcrops of the Permian Phosphoria Formation and the Cretaceous Pierre Shale of the Western United States to determine the effects of weathering on organic matter in shale outcrops. While the Pierre Shale core showed no evidence of weathering, the Phosphoria Formation showed significant reduction of overall organic content and pronounced changes in organic composition over the near-surface interval of the core. Total organic carbon is lower by as much as 60% over the upper 2 ft of the core. Chloroform-soluble organic matter and total hydrocarbon (C₁₅₊) concentrations are 50% lower over this same interval. The ratio of saturated to aromatic hydrocarbons decreases steadily with core depth over the upper 2.6 ft of the core. Aromatic hydrocarbons are enriched in the stable carbon-13 isotope by an average of 1.7%. over this same interval. Shallow core samples also show a loss of n-paraffins relative to branched/cyclic compounds in the saturated C¹⁵⁺ fraction.Although the extent of weathering is variable, certain characteristic effects are recognizable and can be applied to the interpretation of outcrop data in organic geochemical studies.  相似文献   

Fieldwork and Tropicality in French Indochina: Reflections on Pierre Gourou's Les Paysans Du Delta Tonkinois, 1936     

Gavin Bowd  Daniel Clayton 《Singapore journal of tropical geography》2003,24(2):147-168

This paper examines the fieldwork undertaken by the distinguished French geographer Pierre Gourou (1900–99) in the Tonkin Delta (Red River Delta) of northern Vietnam in the 1920s and 1930s, and his wider configuration of “the tropical world” as a distinct space of knowledge and radical otherness. Gourou's fieldwork endeavours in French Indochina are interpreted in the light of recent work on “tropicality”: the idea that “the tropics” need to be understood as a western cultural construction and colonising discourse that essentialised the hot, wet regions of the world, and exalted the temperate world over its tropical counterpart. The paper focuses on Gourou's monumental 1936 study Les paysans du delta tonkinois, étude de géographie humaine. It is argued that in this study, and his later comparative work on the tropics, Gourou elaborated a distinct geographical variant of tropicality, but one that, ultimately, reinforced the essentialist logic and momentum of this discourse. Particular attention is paid to the geographical ideas, fieldwork techniques and discursive strategies that Gourou used in his 1936 study, and the French colonial context in which he worked. The article shows how Gourou appealed to western reason and science as tools of study, identified overpopulation as the key problem facing the Tonkin Delta, and suggested that colonial practices of modernisation had a limited place and ineffectual role in the rice plains of the region.  相似文献   

Multiple imputation framework for data assignment in truncated pluri-Gaussian simulation     

Diogo?S.?F.?SilvaEmail authorView author&#;s OrcID profile  Clayton?V.?Deutsch 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(9):2251-2263

Truncated pluri-Gaussian simulation (TPGS) is suitable for the simulation of categorical variables that show natural ordering as the TPGS technique can consider transition probabilities. The TPGS assumes that categorical variables are the result of the truncation of underlying latent variables. In practice, only the categorical variables are observed. This translates the practical application of TPGS into a missing data problem in which all latent variables are missing. Latent variables are required at data locations in order to condition categorical realizations to observed categorical data. The imputation of missing latent variables at data locations is often achieved by either assigning constant values or spatially simulating latent variables subject to categorical observations. Realizations of latent variables can be used to condition all model realizations. Using a single realization or a constant value to condition all realizations is the same as assuming that latent variables are known at the data locations and this assumption affects uncertainty near data locations. The techniques for imputation of latent variables in TPGS framework are investigated in this article and their impact on uncertainty of simulated categorical models and possible effects on factors affecting decision making are explored. It is shown that the use of single realization of latent variables leads to underestimation of uncertainty and overestimation of measured resources while the use constant values for latent variables may lead to considerable over or underestimation of measured resources. The results highlight the importance of multiple data imputation in the context of TPGS.  相似文献   

The use of selected pseudo-invariant targets for the application of atmospheric correction in multi-temporal studies using satellite remotely sensed imagery     

D.G. Hadjimitsis  C.R.I. Clayton  A. Retalis 《International Journal of Applied Earth Observation and Geoinformation》2009

Because atmospheric effects can have a significant impact on the data obtained from multi-spectral satellite remote sensing, it is frequently necessary to make corrections before any other image processing can be started. This paper describes a robust and relatively simple atmospheric correction method that uses pseudo-invariant targets (PITs) in conjunction with the empirical line method. The method is based on the selection of a number of suitable generic PITs, on the basis that they are large, distinctive in shape, and occur in many geographical areas. Whereas the multi-temporal normalization method corrects all images to a selected reference image, in this method images are simultaneously corrected using targets with a range of estimated surface reflectance values. The paper describes some applications of the method for a range of environmental studies involving water quality and air pollution monitoring, and mapping land-cover changes.  相似文献   

Lea County 001, an H5 chondrite,and Lea County 002, an ungrouped type 3 chondrite     

Michael E. Zolensky  Roberta Score  John W. Schutt  Robert N. Clayton  Toshiko K. Mayeda 《Meteoritics & planetary science》1989,24(4):227-232

Abstract— A search of active deflation basins near Jal, Lea County, New Mexico resulted in the discovery of two meteorites, Lea County 001 and 002. Lea County 001 has mean olivine and low-Ca pyroxene compositions of Fa₁₉ and Fs₁₇, respectively. These and all other mineralogical and petrological data collected indicate a classification of H5 for this stone. Lea County 002 has mean olivine and low-Ca pyroxene compositions of Fa₂ and Fs₄, and is unequilibrated. Although it is mineralogically most similar to Kakangari and chondritic clasts within Cumberland Falls, the high modal amount of forsterite makes Lea County a unique type 3 chondrite. Oxygen isotope data for Lea County 002 fall on an ¹⁶O-mixing line through those of the enstatite meteorites and IAB irons, a feature shared by Kakangari.  相似文献   

Thermally enhanced α-decay and thes-process     

Frank A. Perrone  Donald D. Clayton 《Astrophysics and Space Science》1971,11(3):451-462

In this paper temperature enhanced -decay at high stellar temperatures is investigated in conjunction withs-process nucleosynthesis. The temperature dependence of -decay is the result of more energetic, hence faster, decay from thermally excited nuclear states. A formula for the effective halflife is derived as a function of the atomic number and weight, temperature, and the -decayQ-value of the isotope. The effect of such enhanced -decay upons-process abundances is discussed, and information abouts-process neutron flux intensities is deduced based on the calculated -decay halflives of the isotopes Nd 144 and Sm 150. The neutron flux-temperature relationships are compared to specific constant temperature carbon-burning models of massive stars which are considered to be possible sources of solar systems-process abundances. Finally, information regarding the time betweens-process termination and final interstellar injection ofs-process material is derived using the decay calculations.  相似文献   

The deglaciation of southern Sweden 13,500-10,000 B.P.     

BJÖRN E. BERGLUND 《Boreas: An International Journal of Quaternary Research》1979,8(2):89-117

Because of its well-developed ice-marginal zones, SW Sweden is an important reference area for the study of deglaciation, chronology and palaeoclimate 13,500-10,000 B.P. The ice-marginal zones are described and defined. Earlier research and opinions concerning the deglaciation are summarized. Based on radiocarbon dates from shells, vertebrate bones and limnic sediments, a revised deglaciation chronology is presented. This chronology is supported by biostratigraphic transects of time-space diagrams. The radiocarbon and varve chronologies are compared. Some ice-marginal zones are supposed to be 400 to 900 years older than expected from the varve chronology. The deglaciation chronology is correlated within the southern margin of the Scandinavian inland ice. Various consequences for the interpretation of glacial dynamics, shoreline displacement, and the biological environment are mentioned.  相似文献   

On the development of infrared radiation from an expanding nova shell     

D. D. Clayton  N. C. Wickramasinghe 《Astrophysics and Space Science》1976,42(2):463-475

We discuss the precipitation and growth of grains in carbon-rich nova ejecta with a view to understanding the evolution of infrared luminosity of such objects. An initial phase of rapid grain growth is followed by an extended period of slower growth due to thinning out of the expanding gas. The period of rapid grain growth is attended by an equally rapid rise of infrared luminosity which reaches a maximum and thereafter declines more slowly after grains have grown to a significant fraction of their final radius. This behaviour of luminosity and also a rapid decline of grain temperature from 2000–900 K predicted in an optically thin model is shown to be in good agreement with data for Nova Serpentis 1970. Comparison of our model calculations with observations provide tentative estimates of various parameters of interest for dust grains condensing in Nova Serpentis 1970.  相似文献   

Apparent magnetic polarity reversals due to remagnetization resulting from late diagenetic growth of greigite from siderite     

Leonardo Sagnotti  rew P. Roberts  Richard Weaver  Kenneth L. Verosub  Fabio Florindo  Christopher R. Pike  Trevor Clayton  Gary S. Wilson 《Geophysical Journal International》2005,160(1):89-100

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