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K. B. P. N. Jinadasa C. B. Dissanayake S. V. R. Weerasooriya A. Senaratne 《Environmental Geology》1993,21(4):251-255
Fluoride ion interaction with synthetically prepared goethite has been investigated over a range of pH values (4–9) and F– concentrations (10–3–10–5 M). The amount of F– retained by goethite suspensions was found to be a function of pH, media ionic strength, F– concentration, and goethite concentration. The lowest ionic strength (0.001 M KNO3) gave the highest adsorption medium. Uptake was minimal at pH >7 and increased with decreasing pH. Thermodynamic properties for fluoride adsorption at 298 K and 323 K were investigated. The isosteric heat of adsorption (H
r) was calculated and the heterogeneity and homogeneity of the surface examined for goethite. In view of the importance of fluoride in dental health, the interaction of fluoride on goethite in the physical environment has important implications on dental epidemiology. 相似文献
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Hansi Senaratne Amin Mobasheri Ahmed Loai Ali Cristina Capineri Mordechai Haklay 《International journal of geographical information science》2017,31(1):139-167
With the ubiquity of advanced web technologies and location-sensing hand held devices, citizens regardless of their knowledge or expertise, are able to produce spatial information. This phenomenon is known as volunteered geographic information (VGI). During the past decade VGI has been used as a data source supporting a wide range of services, such as environmental monitoring, events reporting, human movement analysis, disaster management, etc. However, these volunteer-contributed data also come with varying quality. Reasons for this are: data is produced by heterogeneous contributors, using various technologies and tools, having different level of details and precision, serving heterogeneous purposes, and a lack of gatekeepers. Crowd-sourcing, social, and geographic approaches have been proposed and later followed to develop appropriate methods to assess the quality measures and indicators of VGI. In this article, we review various quality measures and indicators for selected types of VGI and existing quality assessment methods. As an outcome, the article presents a classification of VGI with current methods utilized to assess the quality of selected types of VGI. Through these findings, we introduce data mining as an additional approach for quality handling in VGI. 相似文献
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Using Reverse Viewshed Analysis to Assess the Location Correctness of Visually Generated VGI 总被引：2，自引：1，他引：1
With the increased availability of user generated data, assessing the quality and credibility of such data becomes important. In this article, we propose to assess the location correctness of visually generated Volunteered Geographic Information (VGI) as a quality reference measure. The location correctness is determined by checking the visibility of the point of interest from the position of the visually generated VGI (observer point); as an example we utilize Flickr photographs. Therefore we first collect all Flickr photographs that conform to a certain point of interest through their textual labelling. Then we conduct a reverse viewshed analysis for the point of interest to determine if it lies within the area of visibility of the observer points. If the point of interest lies outside the visibility of a given observer point, the respective geotagged image is considered to be incorrectly geotagged. In this way, we analyze sample datasets of photographs and make observations regarding the dependency of certain user/photo metadata and (in)correct geotags and labels. In future the dependency relationship between the location correctness and user/photo metadata can be used to automatically infer user credibility. In other words, attributes such as profile completeness, together with location correctness, can serve as a weighted score to assess credibility. 相似文献
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Organic constituents present in the Muthurajawela peat deposit of Sri Lanka, have been investigated. Here, we report the variations with depth of sitosterol and sitostane (stigmastane), which were found to be major constituents of extracts and, hence, were selected to study the process of diagenesis.These two compounds were present in anomalous concentrations in the middle horizon of the depth profile.Considering the stratigraphy and sterol concentrations, it can be concluded that the middle horizon resulted from a sudden terrestrial input, which could have been due to a Pleistocene or Quaternary environmental change. 相似文献
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