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51.
An Exploration of Future Patterns of the Contributions to OpenStreetMap and Development of a Contribution Index 总被引:2,自引:0,他引:2
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Jamal Jokar Arsanjani Peter Mooney Marco Helbich Alexander Zipf 《Transactions in GIS》2015,19(6):896-914
OpenStreetMap (OSM) represents one of the most well‐known examples of a collaborative mapping project. Major research efforts have so far dealt with data quality analysis but the modality of OSM's evolution across space and time has barely been noted. This study aims to analyze spatio‐temporal patterns of contributions in OSM by proposing a contribution index (CI) in order to investigate the dynamism of OSM. The CI is based on a per cell analysis of the node quantity, interactivity, semantics, and attractivity (the ability to attract contributors). Additionally this research explores whether OSM has been constantly attracting new users and contributions or if OSM has experienced a decline in its ability to attract continued contributions. Using the Stuttgart region of Germany as a case study the empirical findings of the CI over time confirm that since 2007, OSM has been constantly attracting new users, who create new features, edit the existing spatial objects, and enrich them with attributes. This rate has been dramatically growing since 2011. The utilization of a Cellular Automata‐Markov (CA‐Markov) model provides evidence that by the end of 2016 and 2020, the rise of CI will spread out over the study area and only a few cells without OSM features will remain. 相似文献
52.
Shoreline variation and river deltas are among the most dynamic systems in marine environments. The related different variations in spatial and temporal scales play significant roles in land planning and different management applications. Modeling the dynamics of seashore of Boujagh National Park (BNP) which is located on the southern coast of the Caspian Sea in the Sefidrud Delta (SD), considering natural and anthropogenic factors, was the main objective of the current study. To achieve this goal, a combination of remote sensing data, historical data, and numerical simulations was utilized. The BNP covers an area of 3,270 ha and includes two international wetlands, Boujagh and Kiashahr. In earlier periods, this area faced severe morphological changes whereas recently its shoreline has experienced gradual variations. Accordingly, at the first stage, the shoreline variation from 2006 to 2017 was extracted by processing and classifying Operational Land Imager (OLI) and Thematic Mapper (TM) images from Landsat satellites using the Maximum Likelihood approach. In the second stage, the two dimensional MIKE21 model was utilized to identify wave and coastal current patterns and parameters for the year 2015. Morphologically, the results showed that, the shoreline of the BNP is affected by several natural and anthropogenic factors. Seaward advancement of the shoreline occurred in zones A (east zone) and C (west zone) due to Caspian Sea Level drop and sedimentation while retreating occurred at Zone B (north zone) influenced by wave and current patterns and reduction of the Sefidrud River flows. Also, the results imply that maintaining the existing conditions results in the disappearance of a considerable part of the ecological area in the BNP. Hence, to manage and preserve the coastline of the BNP complying with the current anthropogenic and natural factors, it is vital to take necessary management measures. 相似文献
53.
Zakari Arétouyap Njandjock Nouck Philippe Robert Nouayou William Teikeu Assatse Jamal Asfahani 《Environmental Earth Sciences》2017,76(3):134
Water scarcity is one of the major concerns that people are facing worldwide. Although the liquid is absolutely abundant through the globe, its availability poses too much problems specifically to each region. Those problems can result in one or a combination of three basic situations: declining water (drought), overabundance of surface water (floods) or degradation of the quality of water (pollution). All these situations are reflected in the scarcity of good quality water. Arid regions are particularly concerned. In such areas where groundwater contained in aquifers is usually perceived as providence, any project of groundwater exploration and exploitation must be preceded by prior careful and meticulous investigation, in order to avoid early and premature drying. This investigation is likely to predict the future behaviour of aquifers and to improve the groundwater resources management. Beside fundamental properties as hydraulic conductivity, the present paper that addresses the water sector in the semi-arid region of northern Cameroon emphasizes the importance of porosity on aquifer productivity and consequently on the groundwater resources management. The porosity of the local aquifer has then been determined using the Waxman and Smits model which establishes a reliable relationship between the apparent and corrected formation factors, F a and F c , taking the clay effects into consideration. This approach can be applied in other similar semi-arid regions through the world. 相似文献
54.
Jamal Bittar 《Astrophysics and Space Science》2000,273(1-4):65-72
We give a short definition of B[e] star and we show spectrocopicvariabilities obtained for the peculiar star HD 45677 especialy for the strong He I line at 5876 Å. We present also some photometric observations for this type of stars that show a important excess in thenear and mid infrared due to the presence of circumstellar dust. The modelingof these stars shows that a simple model with a spherical dust shell fits well the observations. High spatial resolution gives an additional constraint on the modeling. 相似文献
55.
Fractionation and risk assessment of heavy metals in soil samples collected along Zerqa River,Jordan 总被引:3,自引:0,他引:3
Habes A. Ghrefat Nigem Yusuf Ahmad Jamarh Jamal Nazzal 《Environmental Earth Sciences》2012,66(1):199-208
The objectives of the current study were to determine the chemical partitioning of Pb, Ni, Zn, Co, Cr, Mn, Fe and Cd using
sequential extraction procedure and to assess the environmental risk associated with these metals in the farming soils along
Zerqa River. Metal concentrations were measured by atomic absorption spectrophotometer. The study area demonstrated a wide
range for pH, organic matter, carbonate contents, and cation exchange capacity, and is polluted with Pb, Cd, Mn, and Cu. The
extensive use of fertilizers and pesticides in the agricultural activities, and discharge of treated and untreated wastewater
are the major sources of pollution in the study area. Principal component analysis coupled with Pearson’s correlation analysis
between the heavy metals revealed strong and positive correlation between these metals in the study area. According to the
Risk Assessment Code (RAC), major portions of Cd and Mn are contained in exchangeable and carbonates fractions and therefore
can easily enter the food chain. These metals pose a high to very high risk to the environment. Cu, Ni, Pb, and Zn pose medium
risk, while Cr poses a low environment risk. 相似文献
56.
Hani Serhal Daniel Bernard Jamal El Khattabi Bastin-Lacherez Sabine Isam Shahrour 《Environmental Geology》2009,57(7):1579-1592
Since 1975, Europe sets up its policy to limit the degradation and the pollution of the aquatic environments through 30 directives
and regulations. In the north of France, the nitrate concentrations measured in the groundwater exceed the water drinking
limit fixed at 50 mg/L by the European framework directive in the field of water (2000/60/EC). This high concentration is
due to intensive agriculture, industrialization and demographic growth. Several programs were launched in order to resolve
this situation: “Ferti-better” or the use of fertilizer in moderation and installation and amelioration of wastewater collect
and treatment systems. In order to estimate the influence of the anthropic activities on the quality of groundwater in the
“Artois-Picardy” basin, a preliminary validation on parcel and district scale were necessary. The impact of these programs
in the “Cambrai district” was evaluated using an integrated approach, which is based on the use of four numerical models:
AgriFlux, VS2DT, Modflow and MT3D. The results illustrate an improvement due to the “Ferti-Better” program initiated in 1990
and punctual degradation under urbanized areas. Predictions (2015) show a spatial evolution of nitrates concentration varying
with the thickness of unsaturated layer. The integrated model constitutes an efficient tool for predicting the evolution of
the groundwater quality. This approach is important to control the application of the new European laws in the water field. 相似文献
57.
In an attempt to model regular variations of the ionosphere, the least-squares harmonic estimation is applied to the time
series of the total electron contents (TEC) provided by the JPL analysis center. Multivariate and modulated harmonic estimation
spectra are introduced and estimated for the series to detect the regular and modulated dominant frequencies of the periodic
patterns. Two significant periodic patterns are the diurnal and annual signals with periods of 24/n hours and 365.25/n days (n = 1, 2, …), which are the Fourier series decomposition of the regular daily and yearly periodic variations of the ionosphere.
The spectrum shows a cluster of periods near 27 days, thereby indicating irregularities at this solar cycle period. A series
of peaks, with periods close to the diurnal signal and its harmonics, are evident in the spectrum. In fact, the daily signal
harmonics of ω
i
= 2πi are modulated with the annual signal harmonics of ω
j
= 2πj/365.25 as ω
ijM
= 2πi(1 ± j/365.25i). Among them, at low and midlatitudes, the largest variations belong to the diurnal signal modulated to the semiannual signal.
Some preliminary results on the modulated part are presented. The maximum ranges of the modulated daily signal are ±15 TECU
and ±6 TECU at high and low solar periods, respectively. A model consisting of purely harmonic functions plus modulated ones
is capable of studying known regular anomalies of the ionosphere, which is currently in progress. 相似文献
58.
59.
In this paper, a novel approach based on multiobjective particle swarm optimization (MOPSO) is presented for panchromatic (Pan) sharpening of a multispectral (MS) image. This new method could transfer spatial details of the pan image into a high-resolution version of the MS image, while color information from the low-resolution MS image is well preserved. The pan and MS images are locally different because of different resolutions, and therefore we cannot directly combine them in the spatial domain. For this reason, we generate two initial results, which are more appropriate for a weighted combination. First, the pan and the MS images are histogram matched. Then we use the shiftable contourlet transform (SCT) to decompose the histogram-matched pan and MS images. The SCT is a new shiftable and modified version of the contourlet transform. In this step, an algorithm based on the SCT is used to generate two initial results of the high-resolution MS images. Our objective is to produce two modified high-resolution MS images, in which one has high spatial similarity to the pan image and the other one has high radiometric quality in each band. Therefore, we have used two different fusion rules to integrate the high-frequency contourlet coefficients of the pan and MS images to generate two initial results of high-resolution MS image or the pan-sharpened (PS) image. Finally, we can find the optimal PS image by applying the MOPSO algorithm and using the two initial PS results. Specifically, the PS image is obtained via a weighted combination of the two initial results, in which the weights are locally estimated via a multiobjective particle swarm optimization algorithm to generate a PS image with high spatial and radiometric qualities. Based on experimental results obtained, the produced pan-sharpened image also has good spectral quality. The efficiency of the proposed method is tested by performing pan-sharpening of high-resolution (Quickbird and Wordview2) and medium-resolution (Landsat-7 ETM +) datasets. Extensive comparisons with the state-of-the-art pan-sharpening algorithms indicate that our new method provides improved subjective and objective results. 相似文献
60.
Sarfarazi Vahab Fattahi Shahin Asgari Kaveh Bahrami Reza Wang Xiao 《Geotechnical and Geological Engineering》2022,40(6):2881-2896
Geotechnical and Geological Engineering - This paper investigates different configuration of the room and pillar under uniaxial loading using experimental and particle flow code in two dimension... 相似文献