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91.
92.
Seamless integration of spatial statistics and GIS: The S-PLUS for ArcView and the S+Grassland Links
Shuming Bao Luc Anselin Doug Martin Diana Stralberg 《Journal of Geographical Systems》2000,2(3):287-306
The extension of the functional capacity of geographic information systems (GIS) with tools for statistical analysis in general
and exploratory spatial data analysis (ESDA) in particular has been an increasingly active area of research in recent years.
In this paper, two operational implementations that combine the functionality of spatial data analysis software with a GIS
are considered more closely. They consist of linkages between the S-PLUS software for data analysis and two different GIS implementations, the ArcView desktop system, which is mostly vector-oriented, and the primarily raster-based Grassland open GIS environment. We emphasize conceptual and technical issues related to the software implementation of these approaches
and suggest future directions for linking spatial statistics and GIS.
Received: 14 January 1999 / Accepted: 11 May 1999 相似文献
93.
Luc?AnselinEmail author Yong Wook?Kim Ibnu?Syabri 《Journal of Geographical Systems》2004,6(2):197-218
This paper deals with the extension of internet-based geographic information systems with functionality for exploratory spatial data analysis (esda). The specific focus is on methods to identify and visualize outliers in maps for rates or proportions. Three sets of methods are included: extreme value maps, smoothed rate maps and the Moran scatterplot. The implementation is carried out by means of a collection of Java classes to extend the Geotools open source mapping software toolkit. The web based spatial analysis tools are illustrated with applications to the study of homicide rates and cancer rates in U.S. counties.This research was supported in part by a number of grants from the US National Science Foundation: NSF Grant SBR-9410612, BCS-9978058, to the Center for Spatially Integrated Social Science (csiss), and a grant from the National Consortium on Violence Research (ncovr is supported under grant SBR-9513040 from the National Science Foundation). In addition, support was provided by grant RO1 CA 95949-01 from the National Cancer Institute. Special thanks to Dr. Eugene J. Lengerich of the Pennsylvania State Cancer Institute for providing the data on colon cancer diagnoses. 相似文献
94.
We present a comparison between several methods used to reconstruct fluxes and vertical profiles of wind, temperature and
humidity from measurements at two levels in the atmospheric surface layer for different practical applications. An analytical
method and an iterative method are tested by evaluating the quality of estimations of surface fluxes from detailed field measurements
obtained during a campaign on the site of Lannemezan in the south-west of France. The iterative method yields better results,
but the analytical one can give results of the same level of accuracy provided that specific constants in its formulation
are modified. Then these techniques are applied to wind and temperature reconstruction for an experiment dedicated to wind
power estimates over flat terrain. If turbulent fluxes are not needed, a simple power law appears to be sufficient, as the
method based on Monin–Obukhov theory does not improve the accuracy of the vertical profile reconstruction. 相似文献
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97.
Luc Bernier 《Geochimica et cosmochimica acta》2007,71(23):5684-5697
Coupled S speciation and acid generation resulting from S processing associated with five different microbial treatments, all primarily Acidithiobacillus spp. (i.e. autotrophic S-oxidizers) were evaluated in batch laboratory experiments. Microbial treatments included two culture-adapted strains, Acidithiobacillus ferrooxidans and Acidithiobacillus thiooxidans, their consortia and two environmental enrichments from a mine tailings lake that were determined to be >95% Acidithiobacillus spp., by whole-cell fluorescent hybridization. Using batch experiments simulating acidic mine waters with no carbon amendments, acid generation, and S speciation associated with the oxidation of three S substrates (thiosulfate, tetrathionate, and elemental S) were evaluated. Aseptic controls showed no observable pH decrease over the experimental time course (1 month) for all three S compounds examined. In contrast, pH decreased in all microbial treatments from starting pH values of 4 to 2 or less for all three S substrates. Results show a non-linear relationship between the pH dynamics of the batch cultures and their corresponding sulfate concentrations, and indicate how known microbial S processing pathways have opposite impacts, ultimately on pH dynamics. Associated geochemical modeling indicated negligible abiogenic processes contributing to the observed results, indicating strong microbial control of acid generation extending over pH ranges from 4 to less than 2. However, the observed acid generation rates and associated S speciation were both microbial treatment and substrate-specific. Results reveal a number of novel insights regarding microbial catalysis of S oxidation: (1) metabolic diversity in S processing, as evidenced by the observed geochemical signatures in S chemical speciation and rates of acid generation amongst phylogenetically similar organisms (to the genus level); (2) consortial impacts differ from those of individual strain members; (3) environmental enrichments of Acidithiobacillus spp. catalyze different S reaction arrays than pure strain Acidithiobacillus spp.; and (4) microbial catalysis of S reactions involves significant disproportionation tied to substantial H+ consumption, with the formation of as yet, poorly characterized intermediate S species, most likely polythionates and polysulfane monosulfonic acids that are thought to be involved in microbial S storage mechanisms. 相似文献
98.
Henrik Svensen Gray Bebout Long Li Luc Chevallier 《Geochimica et cosmochimica acta》2008,72(20):4929-4947
We have investigated the N geochemistry of minerals and rocks from contact metamorphic aureoles and hydrothermal vent complexes (HVC) in the Karoo Basin in South Africa. The HVC formed during phreatic eruptions associated with rapid devolatilization and pressure build-up in contact aureoles around early Jurassic sill intrusions. By combining outcrop data from a HVC and core data from contact aureoles, we investigate the relationship between light element release during metamorphism and vertical fluid migration. Sandstone and breccia from the HVC contain early-diagenetic ammonium -bearing feldspar (buddingtonite) and illite. Ammonium occupies up to 95% of the A site in feldspar, corresponding to concentrations up to 5.2 wt% N. Bulk-rock N isotope data for rocks from inside and outside the hydrothermal vent complex fall into two distinct groups. Background samples have δ15Nair between +1.5‰ and +4.9‰, whereas minerals from the vent complex have δ15N in the range +7.5 to +10.6‰. The N geochemistry of contact metamorphic shale from the lower stratigraphic units of the Karoo Basin shows that the vitrinite reflectance and δ15N values are positively correlated. Shale with reflectivity values >4%Ro are enriched in 15N, with δ15N values between +6‰ and +14‰, implying the release of isotopically light N into metamorphic fluids (probably as N2). We suggest that the relatively high δ15N values of the early-diagenetic buddingtonite in the HVC reflect exchange of buddingtonite with N-bearing fluids ascending from greater depth after their release during contact metamorphism and dehydration. We present a qualitative model whereby hydrothermal vent complexes represent fluid flow structures after their formation, focusing N-bearing metamorphic fluids sourced in deeper levels of the basin. The release of organic N from sediments at depth in volcanic basins could play a role in the geochemical cycle of N, becoming particularly important during periods of intense volcanic activity. 相似文献
99.
Ftima Gonzlez Snchez Luc R. Van Loon Thomas Gimmi Andreas Jakob Martin A. Glaus Larryn W. Diamond 《Applied Geochemistry》2008,23(12):3840-3851
The effect of temperature and ionic strength on the diffusion of HTO parallel to the direction of compaction through 5 highly compacted clay minerals (bulk dry density, ρb,d = 1.90 ± 0.05 Mg/m3), namely montmorillonite (Na- and Ca-form), illite (Na- and Ca-form), and kaolinite, was studied. The diffusion experiments were carried out at temperatures between 0 °C and 60 °C and at ionic strengths of 0.01 M and 1 M NaCl for the Na-form clays and kaolinite, and of 0.005 M and 0.5 M CaCl2 for the Ca-form. The ionic strength had an insignificant influence on the values of the effective diffusion coefficient (variation by less than 10%) for the clays under study at this degree of compaction. The effective diffusion coefficients followed the order Na-montmorillonite < Ca-montmorillonite < Ca-illite < Na-illite kaolinite. It is thought that the differences between Na- and Ca-montmorillonite originate from the larger size particles, and thus the lower tortuosity of the latter; whereas the differences between Na- and Ca-illite are related to the different degree of solvation of the Na and Ca cations. The activation energies were successfully calculated using the Arrhenius law. Swelling clays (Na- and Ca-montmorillonite) had slightly larger activation energy values (20 kJ/mol) compared to bulk water (17 kJ/mol); Ca-illite (16 kJ/mol), Na-illite (13 kJ/mol) and kaolinite (14.4 kJ/mol) lower values than that of bulk water. The low activation energies of the last three clays may be related to weaker H-bonds between water and the clay surfaces compared to those in bulk water. 相似文献
100.